TECHNOLOGICAL FIELD

The invention generally concerns polymers, methods of manufacturing thereof and uses thereof.

BACKGROUND In the age of smart devices and electric vehicles, rechargeable lithium-ion batteries have become an imperative technology. The main idea of lithium batteries relies on the lithium intercalation electrochemistry of electrode materials.

In recent years, following the fast development of electronic devices, tremendous research efforts have been devoted to the pursuit of new generation lithium- ion batteries, in which batteries can store more power and run for longer periods of time before recharging, without any safety issues. Thus, most research focuses on developing electrode active materials. At the anode, graphite the material of choice is now replaced by silicon, tin, and titanium-based nanostructures, possessing higher energy capacity compared to graphite. Despite the fact that such materials store more lithium, they also exhibit larger volume expansion and contraction. Repeated variations in particle size (via contraction and expansion) induce cracking of the anode, which subsequently results in capacity loss. At the cathode, for reducing costs, L1C0O2 is substituted with materials having lower Co content.

Many of the problems associated with performance of an electrode originate from weak electrode interconnection, in which binders play a critical role. Good binders should maintain electrode integrity, especially in case of dramatic volume change. Notwithstanding that polyvinylidene fluoride (PVDF) is the most widely-used binder for conventional lithium batteries, it exhibits various limitations. These include: (1) the non-polar structure of PVDF is only able to form weak intermolecular interactions with active materials of the electrode, which, with time and cycling, disrupts the homogenous composite structure; (2) the insulating nature of PVDF requires the addition of carbon additives to increase the electrical conductivity and others. In traditional lithium-ion batteries, carbon additives are essential for providing electron-conducting networks within battery electrodes. In general, the “flawless” electrode matrix should enable the following: (a) form strong interactions with active materials and maintain adhesion; (b) enable a continuous conductive network within the electrode; (c) exhibit adequately high failure strain to adapt to volume changes during cycling (i.e., charging and discharging) without breaking; and (d) be electrochemically stable in the rough battery environment.

Although there are several binders on the market that can be applied for high energy density batteries, such as sodium carboxymethyl cellulose (CMC), sodium carboxymethyl chitosan (CCTS), sodium alginate (SA), styrene-butadiene rubber (SBR), or polytetrafluoroethylene (PTFE), there is still a need for a binder which provides or enables the characteristics described above.

Luo et al [1] discloses copolymer structures of poly(acrylic acid)-graft-methoxy poly(ethylene oxide), synthesized in the presence of dicyclohexyl dimethylcarbodiimide (DCC) and 4-dimethylaminopyridine (DMAP), resulting in up to 23% grafting yield in 168 hours of reaction time, at 50 °C. The approximate molecular weight of the polymers disclosed is about 240,000 gr/mol. The grafted polymers are proposed for use as dispersants in aqueous suspensions.

Publication [2] teaches structures of PAA-g-PEGs obtained by RAFT polymerization and subsequent condensation. The resulting materials were investigated as lubricants for treatment of osteoarthritis.

Unlike methacrylic acid and poly (oligoethylene glycol) methacrylate (PAA-co- PEGma) that are widely known and reported [3], copolymerization of acrylic acid and oligoethylene glycol acrylate (PAA-co-PEGa) reports are scarce and not explored well in a sense of application and their chemical behavior (monomer ratios and polymerization methodology) [4].

Electrical properties of PAA-g-PEGs copolymer structures have been reported in Zhou et al. [5]. In this paper, the authors demonstrate the influence of the type of PEG- based pendant group on PAA backbone on electrical properties of that polymer.

Nam et al [6] discloses the use of PAU-g-PEG polymer in energy storage devices, and particularly as a binder in pure silicon anodes. PAA-g-PEG and pure PAA exhibited an inferior electrode performance compared to PAU-g-PEG in pure silicon anodes. Nam also teaches that the grafting degree of the co-polymers is almost 100%, and the molecular weight is about 142,000 gr/mol. The grafting process in Nam involves radical polymerization of tert-butyl acrylate (tBA) and poly(ethylene glycol) methyl ether methacrylate (PEG-MEM A) monomers.

REFERENCES

[1] Luo, Y., Ran, Q., Wu, S. and Shen, J. (2008), Synthesis and characterization of a poly(acrylic acid)-graft-methoxy poly(ethylene oxide) comblike copolymer. J. Appl. Polym. Sci., 109: 3286-3291.

[2] Ming-Chee Tan. Synthesis, Characterization And Evaluation Of Poly(Acrylic Acid)-Graft-Poly(Ethylene Glycol)'S As Boundary Lubricants For Treatment Of Osteoarthritis. Cornell University, 2015. [3] Neugerbauer D., Graft copolymers with poly(ethylene oxide) segments,

Polymer International 2007, 56, 12, 1469-1498.

[4] Krieg A., Pietsch C., Baumgaertel A., Hager M. D.,Becer C. R. and Schubert S. U., Dual hydrophilic polymers based on (meth)acrylic acid and poly (ethylene glycol) - synthesis and water uptake behavior. Polym. Chem., 2010,1, 1669-1676.

[5] Zhou, Xinlu & Zhao, Kongshuang. (2017). How Side chains Affect Conformation and Electrical Properties of poly electrolyte in Solution. Phys. Chem. Chem. Phys., 2017, 19, 20559.

[6] Nam J, Kim E, K K R, Kim Y, Kim TH. A conductive self-healing polymeric binder using hydrogen bonding for Si anodes in lithium-ion batteries. Sci

Rep. 2020 Sep 11;10(1): 14966.

[7] Saindane P., Jagtap R. N., RAFT copolymerization of amphiphilic poly (ethyl acrylate -b-acrylic acid) as wetting and dispersing agents for water borne coating, Progress in Organic Coatings, 2015, 79, 106-114. [8] Benaglia M., Chiefari J., Chong Y. K., Moad G., Rizzardo E., Thang S.

H., Universal (Switchable) RAFT Agents, J. Am. Chem. Soc. 2009, 131, 20, 6914- 6915. GENERAL DESCRIPTION

The invention disclosed herein generally concerns a novel group of polymers or co-polymers which may be used in various electrical storage devices and components. As demonstrated herein, the novel class of polymers provides a superior alternative to available binders used in construction of electrodes and various electronic devices. The ability to produce the polymers in one-pot or one-step processes renders the polymers easily accessible, low cost and most importantly free of toxic materials.

Thus, in a first aspect of the invention, there is provided a polymer comprising a carbon backbone substituted with a plurality of glycol ester functionalities, at least a portion of said glycol ester functionalities being capped with an end group being or comprising a non-reactive (or unreactive) functionality different from a glycol.

In some embodiments, the carbon backbone being further substituted by a plurality of carboxylic acid functionalities. In some embodiments, the backbone is derived from a polymer having pendent carboxylic acid functionalities.

In some embodiments, the backbone is derived from poly (aery lie acid) (PAA) having a plurality of carboxylic acid groups, wherein a portion of said carboxylic acids groups is provided as esters of at least one glycol, such that the at least one glycol having a non-reactive end group is different from glycol or is different from a hydroxyl group (-OH).

The invention further provides a polymer comprising a poly(acrylic acid) (PAA) backbone, wherein a plurality (one or two or more) of glycol functionalities pendent from the backbone is capped with an end group being or comprising a non-reactive (or unreactive) functionality different from a glycol, the polymer excluding PAA-g-mPEG9 and PAA-g-mPEO.

Further provided is a polymer comprising a poly(acrylic acid) (PAA) backbone having (i) a plurality of glycol ester functionalities pendent from the backbone, wherein the glycol ester functionalities comprise each a non-reactive (or unreactive) end group functionality, and (ii) a plurality of carboxylic acid functionalities, the polymer excluding PAA-g-mPEG9 and PAA-g-mPEO. In some embodiments or in another aspect, the/a polymer has the general formula (I): wherein

EG is a non-reactive functionality (being the capping non-reactive end group), v is an integer designating the number of repeating units (along the PAA backbone), which may be between 1 and 7000, or between 6000 and 7000, or is 6244, n is an integer designating the number of repeating glycol (-CH2-CH2-O-) moieties in the graft, being n>2, m is an integer between 1 and 6, and

* designates point of connectivity or polymer terminus points.

In some embodiments, “*” designates an end group or a terminating group which may be an aliphatic group, i.e., -CH3 or a substituted -CH2- or -CH- group or a substituted carbon atom.

In some embodiments, the polymer further comprises bear carboxylic acid functionalities. In other words, where PAA constructs the main backbone of the polymer, a portion of the pendent carboxylic acid groups remain unsubstituted or non- esterified, namely in an acid form.

Thus, in some embodiments of the invention, the polymer is of a structure (II): wherein

EG is a non-reactive functionality (being the capping non-reactive end group), v is an integer designating the number of repeating units (along the backbone, e.g., the PAA backbone), may be an integer between 1 and 1000, and more specifically between 120 and 1000, n is an integer designating the number of repeating glycol (-CH2-CH2-O-) moieties in the polymer, n>2, m is an integer between 1 and 6, x is an integer designating the number of repeating units (along the backbone, e.g., the PAA backbone), may be an integer between 1 and 1000, and more specifically between 120 and 1000; and

* designates point of connectivity of polymer terminus points.

In some embodiments, the values of v and x combined is between 200 and 2500, or between 250 and 2000, or between 200 and 1000.

Where the polymer is derived from PAA, the number of carboxylic acid groups available for esterification as disclosed herein may be v+x or may be between 200 and 2500, or between 250 and 2000, or between 200 and 1000. Where the polymer is a product of polymerization of acrylic acid monomers, the number of monomers constituting both the bear carboxylic acids and the esterified carboxylic acids may be v+x or may be between 200 and 2500, or between 250 and 2000, or between 200 and 1000.

As noted herein, a polymer of the invention, being in some cases a copolymer, comprises a carbon backbone substituted with a plurality of glycol ester functionalities. The carbon backbone may be derived from a polymer backbone, such as that of PAA which comprises a plurality of carboxylic acid functionalities that may be converted to a plurality of glycol ester functionalities. In other words, some or all of the carboxylic acid groups may be esterified with a glycol functionality to provide the ester functionality. The end group (EG) or capping group is provided at the end of the glycol functionality.

Of the plurality of carboxylic acid functionalities, a portion is esterified to provide the glycol ester functionalities (in other words -COO-glycol-EG, as defined), while another portion of the carboxylic acid functionalities may remain unsubstituted or may remain bear carboxylic acid functionalities (-COOH). The ratio between the portion of the esterified carboxylic acid functionalities (integer v) and the portion of the bear carboxylic acid functionalities (integer x) may be between 1:0 and 1:0.3. In other words, in some embodiments where the ratio (esterified:bear) is 1:0, all carboxylic acid functionalities are esterified to provide glycol ester functionality or capped glycol esters. In other embodiments, the ratio (esterified:bear) is 1:0.2, 1:0.4, 1:0.5, 1:0.6 or 1:0.8.

In some embodiments, the number of bear functionalities is 10%, 20%, 30%, 40%, 50%, 60%, or 80% of the total number of carboxylic acid functionalities available for esterification. In some embodiments, the number of bear functionalities is 10%, 20%, or 30% of the total number of carboxylic acid functionalities available for esterification.

In some embodiments, the number of bear functionalities is between 10% and 30%, or between 10% and 20% or between 15% and 30%, or between 10% and 60%, or between 40% and 80%, between 10% and 30%, or between 50% and 80% of the total number of carboxylic acid functionalities available for esterification.

The “ glycol functionality ” or the glycol-type functionality is any glycol structure, as known in the art, having an oxygen atom bonded to an alkylene moiety, i.e., -0-(CEb)m-, wherein m is an integer defining the length of the alkylene. Typically, the glycol functionality may contain two or more alkylene glycol units, which may be the same or different. In some embodiments, the glycol functionality having the structure , as defined for polymers of structures (I) and

(II), or polymers of any structure defined herein, may comprise two or more identical alkylene glycol units. For example, in cases where m is 1 (providing ethylene) and n is 2 (providing two repeating glycol units in chain), the above glycol functionality may be -O-CH2-CH2-O-CH2-CH2-O-EG.

In some embodiments, the glycol functionality having the structure , as defined for polymers of structures (I) and (II) or any other structure of the invention, may comprise two or more different alkylene glycol units. For example, one alkylene may comprise 2 methylene groups (m=l), while another may comprise three methylene groups (m=2). Where n, for example, is 2, the glycol functionality having 2 different (or mixed) alkylene groups may be -O-CH2-CH2- O-CH2-CH2-CH2-O-EG, or -O-CH2-CH2-CH2-O-CH2-CH2-OEG. Similarly, where n is 3, the glycol functionality having 3 mixed alkylene groups may be -O-CH2-CH2-O- CH2-CH2-CH2-O-CH2-CH2-O-EG, or -O-CH2-CH2-CH2-O-CH2-CH2-O-CH2-CH2-CH2- O-EG and other combinations.

Thus, the glycol functionality , as depicted and defined for polymers of structures (I) and (II) or any other structure of the invention, may be a multi(alkylene glycol)-EG, wherein the alkylene glycol comprises one or more or a mixture or a combination of ethylene glycol, propylene glycol, butylene glycol, pentylene glycol and/or hexylene glycol.

In some embodiments, the alkylene glycol is ethylene glycol.

In some embodiments, the alkylene glycol is propylene glycol.

In some embodiments, where the alkylene glycol comprises two or more glycol units, one or more of said glycol units may be a methylene (-CH2-), provided that the alkylene glycol does not consist of methylene units.

In some embodiments, the glycol structure is a poly alkylene glycol.

In some embodiments, the poly alkylene glycol is a polyethylene glycol.

In some embodiments, the glycol structure is selected from diethylene glycol (DEG) and polyethylene glycol (PEG), wherein said PEG is further selected from PEG120, PEG 160, PEG350, PEG550 and PEG750. The numeric value provided following “PEG” designates the molecular weight of the PEG moiety.

The length of the glycol functionality is defined by the integer m in structure of the invention. For example, where m is 1, the glycol is an ethylene glycol and where m is 2, the glycol is propylene glycol and so forth. Integer n designates the number of repeating glycol moieties, e.g., ethylene glycol, in the polymer. Integer n may be 2 or any integer greater than 2. In some embodiments, n is an integer between 2 and 30. For example, where n is 2 and m is 1, the glycol functionality is a glycol comprising two ethylene glycol moieties. In other words, the glycol functionality is -O-CH2-CH2-O- CH2-CH2-.

In some embodiments, in a polymer of the invention having structure (I) or (II) or any other structure, m is 1, 2, 3, 4, 5 or 6.

In some embodiments, in a polymer of the invention having structure (I) or (II) or any other structure, n is 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10. In some embodiments, in a polymer of the invention having structure (I) or (II) or any other structure, n is between 10 and 30.

In some embodiments, in a polymer of the invention having structure (I) or (II) or any other structure, m is 1, 2, 3, 4, 5 or 6 and n is between 1 and 30.

In some embodiments, in a polymer of the invention having structure (I) or (II) or any other structure, m is 1 or 2 and n is between 1 and 5.

In some embodiments, the polymer of the invention is a copolymer.

In other embodiments, the polymer is a grafted polymer. Thus, in some embodiments, the invention provides a grafted co-polymer comprising a poly(acrylic acid) (PAA) backbone grafted with a plurality of glycol functionalities (to provide the glycol ester functionalities, as defined herein), each of said glycol functionalities being capped with an end group which is or which comprises a non-reactive (or unreactive) functionality that is different from the glycol structure. In some embodiments, grafting does not convert each and every carboxylic acid of the PAA backbone into a glycol ester functionality. In some embodiments, at least a portion of the carboxylic acid functionalities present on the PAA backbone are bear and the remaining are provided as capped glycol esters, as defined herein.

Copolymers of the invention are structured to prevent crosslinking via the glycol ester functionalities. Crosslinking is prevented by capping the glycol units with end groups (EG) or a capping end group which protects the branch from crosslinking with other branch segments or other polymers or copolymers during utilization of said polymers or during the polymer constructions, grafting or polymerization process which are also provided in the herein invention. The “ capping group ” or “ end group (EG)” is a non-glycol group, namely a group different from glycol or a group that is not -OH. The capping group is a non-reactive group protecting the branch and selected from any unreactive group containing at least one carbon atom. In some embodiments, the capping group may be selected from any aliphatic, cyclic, polycyclic and aromatic groups. Non-limiting examples of such groups include methyl, ethyl, propyl, n-butyl and pentyl. Other examples include groups comprising at least one double or triple bonds (e.g., alkene or alkyne).

In some embodiments, the capping group is methyl, ethyl, propyl or n-butyl. In some embodiments, the capping group is methyl or n-butyl. In some embodiments, at least a portion of the capped glycol esters is provided as methylated glycol esters and at least another portion is provided as butylated glycol esters.

In some embodiments, the capped glycol esters consist methyl capping (or end groups, EG) or n-butyl capping (or end groups, EG).

In some embodiments, the capping group as described above is further substituted with a halogen or a nonmetal group selected, for example, from F, Cl, Br, I, B, N, O, S, P, Si, As, Se and Te, provided that the nonmetal group is not reactive towards crosslinking or under crosslinking conditions.

In some embodiments, in a copolymer of the invention, EG is selected from any aliphatic, cyclic, polycyclic and aromatic groups. In some embodiments, EG is methyl, ethyl, propyl, n-butyl and pentyl.

In some embodiments, EG is methyl or butyl.

In some embodiments, the polymer of the invention is a grafted PAA-based copolymer of the structure PAA-g-mPEGn, wherein g indicates presence of PEG as a grafted glycol functionality comprising n number of repeated PEG units and m indicates a methyl capping end group the number of glycol units, designated by integer n, may be for example 2, 7, 12 and 17, yielding PEG120, PEG350, PEG550 and PEG750, respectively.

In some embodiments, the copolymer is butylated PAA-g-bPEGn, wherein b indicates an n-butyl capping end group n is in integer indicating the number of glycol units, being, for example 2, yielding PEG 160.

In some embodiments, the copolymer of the invention is any one of PAA-g- mPEG2, PAA-g-bPEG2, PAA-g-mPEG7, PAA-g-mPEGi2, and PAA-g-mPEGn, each designating a grafted PAA with a methylated (m) or a butylated (b) glycol functionality, i.e., mPEG or bPEG, having the indicated number of glycol units.

Excluded from the scope of the invention, as defined for example by the general structures (I) and (II), are PAA-g-mPEG9 and PAA-g-mPEO (PEO= polyethylene oxide).

Grafted co-polymers as provided herein may have a grafting degree (GD) ranging between 5 and 30%. In some embodiments, the GD is between 5 and 25%, at times between 5 and 20%, or between 5 and 15%, or between 5 and 10%. In yet other embodiments, the GD is between 25 and 30%, between 20 and 30%, between 15 and 30% or between 10 and 30%. In some embodiments, the GD is between 9 and 22%.

In the context of the herein disclosure, the terms “ grafting degree ” or “ grafting yield means the proportion of the ester groups of the backbone directly or covalently linked to the branch units as defined herein. In most cases, GD is calculated as follows:

Grafting yield, % = (Wg - W0) / W0 x 100 wherein Wg is the weight of the grafted polymer after grafting and W0 is the weight of polymer before the modification. Such a degree or yield can be calculated via methods known to a person of skill in the art, and may include NMR and FTIR analysis, as described in G. S. Ahmed, M. Gilbert, S. Mainprize & M. Rogerson (2009) FTIR analysis of silane grafted high density polyethylene, Plastics, Rubber and Composites, 38:1, 13-20 and in Papke, N. and Karger-Kocsis, J. (1999), Determination methods of the grafting yield in glycidyl methacrylate-grafted ethylene/propylene/diene rubber (EPDM-g-GMA): Correlation between FTIR and 1H-NMR analysis. J. Appl. Polym. Sci., 74: 2616-2624, accordingly, and which are incorporated herein by reference.

Grafted co-polymers as provided herein are those having a glass transition temperature (Tg) lower than 30°C. In some cases, the Tg ranged between -50 and 30°C, between -45 and 30°C, between -40 and 30°C, between -35 and 30°C, between -30 and 30°C, between -25 and 30°C, between -20 and 30°C, between -15 and 30°C, between - 10 and 30°C, between -5 and 30°C, between 0 and 30°C, between 10 and 30°C, between 15 and 30°C, between 20 and 30°C, or between 25 and 30°C. In some other cases, the Tg ranges between 5 and 10°C, between 5 and 15°C, between 5 and 20°C, or between 5 and 25 °C.

The term “ glass transition ”, means the progressive and reversible transition in amorphous materials from a stiff, “glassy” state into a viscous or less of a stiff state as the temperature increases. The “ glass-transition temperature ( herein Tg )” characterizes the scope of temperatures over which glass transition occurs.

The grafted co-polymers may have molecular weights (Mw) between 250,000 and 550,000 g/mol. In some embodiments, the Mw ranges between 250,000 and 300,000 g/mol, between 250,000 and 350,000 g/mol, between 250,000 and 400,000 g/mol, between 250,000 and 450,000 g/mol, or between 250,000 and 500,000 g/mol. In some further embodiments, the Mw ranges between 250,000 and 300,000 g/mol, between 250,000 and 350,000 g/mol, between 250,000 and 400,000 g/mol, between 250,000 and 450,000 g/mol, or between 250,000 and 500,000 g/mol.

In yet another aspect, the invention further provides a grafted co-polymer of PAA selected from [PAA] _m -g-[bPEG] _n -ω-end _a and [PAA] _m -g-[mPEG] _n -ω-end _b , wherein ω-end _a and ω-end _b are each, independently, an end group (EG) selected as described above, m designates the number of repeating units in PAA chain and n designates the number of branches comprising mPEG or bPEG (methylated or butylated).

In some embodiments, m ranges between 310 and 1400 and independently n may be between 4850 and 5940.

In some embodiments, the Mw of the PAA is between 350,000 and 450,000 g/mol. The Mw of a single branch comprising bPEG or mPEG may be between 100 and 800 g/mol, or between 120 and 750 g/mol.

In some non-limiting examples, the ω-end _a capping group is mono n-butyl, and the ω-end _b capping group is methyl.

Any of the polymers of the invention may be a RAFT-based polymer, wherein the polymer comprising a carbon backbone substituted with a plurality of glycol ester functionalities, as defined, wherein at least a portion of said glycol ester functionalities is capped with an end group being or comprising a non-reactive (or unreactive) functionality different from a glycol, and wherein each of the polymer termini is substituted with a RAFT terminus. The expression ” RAFT-based polymer ” refers to such embodiments wherein the polymer of the invention is formed by copolymerization using RAFT technology. As known in the art, Reversible Addition-Fragmentation chain Transfer (RAFT) polymerization is a versatile controlled radical polymerization method. To achieve proper RAFT copolymerization, RAFT agents such as dithioesters and trithiocarbonates may be used.

Non-limiting examples of RAFT agents include 2-[[(2-carboxyethyl) sulfanylthiocarbonyl]-sulfanyl]propanoic acid, 4-((((2-carboxyethyl)thio) carbono thioyl)thio)-4-cyanopentanoic acid, 2-cyanobutan-2-yl 4-chloro-3, 5-dimethyl- 1H- pyrazole- 1 -carbodithioate, 2-cy anobutanyl-2-yl 3 ,5 -dimethyl- 1 H-pyrazole- 1 - carbodithioate, 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoic acid, cyanomethyl (3,5-dimethyl-lH-pyrazole)-carbodithioate, cyanomethyl methyl (phenyl)carbamodithioate, S,S -dibenzyl trithiocarbonate, and 2-(dodecyl thiocarbonothioylthio)propionic acid.

In some embodiments, the RAFT agent is S,S-dibenzyl trithiocarbonate. Dissociation of the RAFT agent during the copolymerization reaction, results in fragments of the RAFT agent being covalently associated to the termini of the formed polymer. When S,S -dibenzyl trithiocarbonate is used as an exemplary

RAFT agent, a polymer formed may have at each of the polymer termini a different substituting fragment of the agent. In the case of S,S -dibenzyl trithiocarbonate, a polymer of structure (I) or (II) may be represented as structures (III) and (IV), respectively: (IV), wherein in structures (III) and (IV), each of variants EG, v, x, m and n are as defined herein, e.g., for structures (I) and (II), respectively. Ph designates a phenyl ring. A polymer of structure (IV) may be represented as structure (V): wherein all variables are as defined herein.

When other RAFT agents are used, the polymer formed may have different “ RAFT termini" . In other words, depending on the RAFT agent and the degradation of the agent during copolymerization, each of the polymer termini may have a RAFT terminus that is based on the RAFT agent used.

Without wishing to be bound by theory, the RAFT agent which may be used may be of the general structure , wherein Z is selected from

-SC ₁₂ H ₂₅ , -SC(CH )(CN)-CH ₂ CH ₂ C0 ₂ H, -SCH ₃ , - S CH(Ph) -C O ₂ CH ₃ , -SCH ₂ Ph, -SC(CH ₃ ) ₂ -COOC ₄ H ₉ , -OC ₂ H ₅ , -SCH(CH ₃ )-COOCH ₃ ), -NPh ₂ ,

-SCH(COOC ₂ H)(COOC ₂ H ₅ ), -SCH ₂ CN, -SC(CH ₃ )(CH ₂ CH ₃ )-CN, -N(CH ₃ )-4-pyridine, -S-CH ₂ CN, -SCH(CH ₃ )C0 ₂ CH ₃ , -SC(CH ₃ ) ₂ CN, -SCH ₂ CH ₃ , -SCH(CH ₃ )- 0CH ₂ CH(CH ₃ ) ₂ , and others; G is selected from -C ₁₂ H ₂₅ , -C(CH ₃ )(CN)-CH ₂ CH ₂ C0 ₂ H,

-CH ₃ , -CH(Ph)-C0 ₂ CH ₃ , -CH ₂ Ph, -C(CH ₃ ) ₂ -COOC ₄ H ₉ , -CH(CH ₃ )-COOCH ₃ ),

-CH(COOC ₂ H)(COOC ₂ H ₅ ), -CH2CN, -C(CH ₃ )(CH ₂ CH ₃ )-CN, -CH ₂ CN, -CH(CH ₃ )C0 ₂ CH ₃ , -C(CH ₃ ) ₂ CN, -CH ₂ CH ₃ , -CH(CH ₃ )-0CH ₂ CH(CH ₃ ) ₂ , and others. Thus, polymers of the invention may be represented by structures (VI) or (VII): (VI),

(VII), wherein

Z may be selected from -SC ₁₂ H ₂₅ , -SC(CH ₃ )(CN)-CH ₂ CH ₂ C0 ₂ H, -SCH ₃ , -SCH(Ph)-C0 ₂ CH ₃ , -SCH2PI1, -SC(CH ₃ )2-COOC ₄ H ₉ , -OC2H5, -SCH(CH ₃ )-COOCH ₃ ), -NPh ₂ , -SCH(COOC ₂ H)(COOC ₂ H ₅ ), -SCH ₂ CN, -SC(CH ₃ )(CH ₂ CH ₃ )-CN, -N(CH ₃ )-4- pyridine, -S-CH ₂ CN, -SCH(CH ₃ )C0 ₂ CH ₃ , -SC(CH ₃ ) ₂ CN, -SCH ₂ CH ₃ , and -SCH(CH ₃ )- OCH ₂ CH(CH ₃ )2,

G may be selected from -C12H25, -C(CH ₃ )(CN)-CH ₂ CH ₂ C0 ₂ H, -CH ₃ , -CH(Ph)- CO2CH3, -CH ₂ Ph, -C(CH ₃ )2-COOC ₄ H9, -CH(CH ₃ )-COOCH ₃ ),

-CH(COOC ₂ H)(COOC ₂ H ₅ ), -CH2CN, -C(CH ₃ )(CH ₂ CH ₃ )-CN, -CH ₂ CN, -CH(CH ₃ )C0 ₂ CH3, -C(CH ₃ ) ₂ CN, -CH2CH3, and -CH(CH3)-OCH ₂ CH(CH ₃ )2, and each of EG, v, x, m and n are as defined herein. Ph designates a phenyl ring. Polymers of structure (VII) may alternatively be represented by structure (VIII): wherein all variables are as defined above.

Polymers of the invention may be manufactured by a variety of methodologies known in the art. For example, the polymers may be manufactured by substituting a backbone polymer with a plurality of functionalities that can be transformed into the final polymers of the invention; by utilizing a polymeric backbone with inherent substituents that may be manipulated into desired structures; by copolymerization; by grafting techniques; by melt polymerization of mixtures of different monomers; or by any other method.

In some embodiments, polymers of the invention are formed by grafting.

In some embodiments, polymers of the invention are formed by copolymerization.

In some embodiments, polymers of the invention are formed by RAFT copolymerization .

In a further aspect, the invention contemplates a process for manufacturing a polymer of the invention, the process comprising reacting a mixture of acrylic acid monomers under conditions permitting polymerization thereof, wherein the mixture comprises a first population of acrylic acid monomers comprising bear (or unsubstituted or non-esterified) acrylic acid monomers, and a second population of acrylic acid monomers comprising acrylate esters.

In some embodiments, the acrylate esters are glycol ester functionalities, each capped with an end group, e.g., having the general structure

In some embodiments, the acrylate esters are active ester groups susceptible towards nucleophilic attack and replacement with a glycol-based functionality.

The “ conditions permitting polymerization ” of the acrylic acid monomer populations into polymers of the invention may include one or more of increased pressure or reduced pressure conditions; high thermal conditions; presence of a radical initiator; presence or absence of a solvent; presence of a polymerization or a crosslinking agent or initiator, e.g., a RAFT agent; and others, as known in the art.

In some embodiments, the conditions permitting polymerization include presence of a radical initiator, such as azobisizobutironitrile (AIBN), and/or presence of a RAFT agent, as disclosed herein.

In some embodiments, the process for manufacturing a polymer of the invention comprises reacting a mixture of acrylic acid monomers in the presence of at least one RAFT agent and at least one radical initiator to cause polymerization of the acrylic acid monomers. In some embodiments, the ratio amount RAFT agenhmonomer is between 1:200 to 1:3000, or is 1:250, or 1:300, 1:400, 1:500, 1:600, 1:700, 1:800, 1:900, 1:1000, 1:1500, or 1:200.

The invention further provides a process for manufacturing a polymer of the invention, the process comprising reacting a mixture of acrylic acid monomers in presence of a RAFT agent under conditions permitting polymerization thereof, wherein the mixture comprises a first population of acrylic acid monomers comprising bear (or unsubstituted or non-esterified) acrylic acid monomers, and a second population of acrylic acid monomers comprising acrylate esters, as defined. In some embodiments, the process is carried out in an organic solvent. In some embodiments, the organic solvent is an aprotic solvent. In some embodiments, the solvent is selected from DMF, hexane, toluene, benzene, THF, DMSO, Dioxane, NMP, DMAc, water.

In some embodiments, the process is carried out at a temperature between room temperature (23-30°C) and the boiling temperature of the solvent. In some embodiments, the temperature is between room temperature and 100°C.

The invention further provides a process comprising reacting a carboxylic acid functionality of a polyacrylic acid (PAA) backbone with a glycol- functionality having an unreactive capping group different from the glycol-type functionality. In some embodiments, the process comprises obtaining PAA of a desired molecular weight and reacting said PAA with an amount of a glycol material under conditions permitting esterification of at least a portion of carboxylic acid functionalities present on the PAA.

Thus, the process of the invention, according to yet another aspect, is a one-pot or one-step process comprising reacting PAA with an amount of a glycol material under conditions permitting esterification of at least a portion of carboxylic acid functionalities present on the PAA.

The glycol material is typically a glycol of a structure suitable of forming the glycol ester functionalities depicted in structures (I) through (IV). The glycol material is typically of the structure , wherein each of m, n and EG is as disclosed herein. In some embodiments, the PAA is dissolved in a solvent. In some embodiments, the solvent is an organic solvent or an aprotic solvent. In some embodiments the solvent is selected from dimethyl formamide (DMF), dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), N-methylpyrrolidone (NMP), ethanol and water.

In some embodiments, the process may be carried out in absence of a solvent. Such a one pot solvent-free process may comprise reacting a carboxylic acid moiety of a PAA backbone with a glycol material having a nonreactive capping group which is different from the glycol functionality, as disclosed herein.

In some embodiments, the process is carried out in presence of an acid.

In some embodiments, the acid is p-toluenesulfonic acid (pTSA).

Also provided are polymers, co-polymers or grafted polymers manufactured according to any one of the processes of the invention disclosed herein.

Generally speaking, electrodes used in electric storage devices usually include: (a) an electrode active material which is an electrochemically active component into which lithium or sodium ions are intercalated; (b) a conductive material that promotes electron transfer; (c) an electrode binder which binds the active material and conductive material with the current collector; and (d) a current collector which purpose is to collect the electrons. The electrode binder (c) plays an important role in electrode formulations as it helps maintaining the physical structure of the electrode while preserving the electron and ion conductivity thereof.

Currently available binders suffer from at least one of the following: (a) the binders fail to form strong interactions with active materials and maintain adhesion; (b) the binders do not enable a continuous conductive network within the electrode; (c) the binders do not exhibit adequately high failure strain to adapt to volume changes during cycling (i.e., charging and discharging) without breaking; (d) the binders are not electrochemically stable in the rough battery environment; and (e) the binders are not safe and in some cases may be toxic.

As the inventors of the technology disclosed herein have shown, polymers of the invention may be used as superior electrode binders which efficiently bind the active material and the conductive material with the current collector, without suffering from any of the deficiencies noted above. As a binder, the polymer maintains adhesion of the active material while enabling a continuous conductive network; it is adaptable to the massive volume changes during cycling while maintaining the form of the electrode; and it does not exhibit any safety or toxicity concerns.

Thus, in a further of its aspects, the invention provides a binder (i.e., adhesive) material comprising or consisting a polymer of the invention or a polymer manufactured according to the invention.

Also provided herein is a device/element comprising a polymer as defined herein. The device/element may be, without limitation, an electrode, an energy storage device (e.g., battery), a photovoltaic device, a solid polymer electrolyte, an optical device, or an opto-electronic device.

In yet another aspect, the present invention provides an electrode comprising an electrode active material and a binder of the present invention.

In some embodiments, the electrode is a battery electrode.

The electrode active material, as used in devices of the invention, is an inorganic or organic material configured to intercalate lithium and/or sodium ions or any other monovalent ions and discharge them under the operating conditions of the electrode. The electrode active material may be any suitable active material which is known in the art. Without being limited to the following examples, active materials used according to the invention may be selected from lithium/sodium containing compounds/substances, transition metal-based oxides, carbon-based substances, lithium/sodium metal and a combination thereof.

The active material comprised in the electrode may be that which is capable of obtaining a reversible intercalation and deintercalation of lithium and/or sodium ions, where such materials can be selected from carbon-based materials. For example, and without being limited thereto, the material may be amorphous carbon, crystalline carbon, or a combination or mixture thereof. Crystalline carbon may include amorphous, circular, flake, plate, or fiber natural graphite, or artificial graphite. Amorphous carbon may include soft carbon, hard carbon, mesophase pitch carbide, mesa carbon microbeads, sintered cokes, and alloy-based materials such as silicon and tin.

In some embodiments, the active material is graphite or a graphite-silicon.

Transition metal-based oxides as described above may include (without limitation), sodium titanate, molybdenum oxide, titanium oxide, lithium titanium oxide, vanadium oxide, lithium vanadium oxide, tungsten oxide, lithium vanadium phosphate, sodium vanadium phosphate and lithium rich Mn/Ni layered oxides.

In some embodiments, the active material may be selected from LiCIO ₄ , LiBOB, LiDFOB, LiTFSI, and other lithium salts.

In yet further embodiments, the electrode may further comprise a conductive additive, which further improves electrical conductivity of the electrode. A non-limiting list of conductive additives may include carbon-based materials such as artificial graphite, natural graphite, super P carbon black, ketjen black, acetylene black, carbon black, hard carbon, carbon fiber or carbon nanotubes; a metal -based materials of a metal powder or a metal fiber including one or more of copper, nickel, aluminum and silver; and a conductive polymer material (e.g., polyphenylene derivative). In some embodiments, the conductive additive is a combination of at least one of the materials as described above.

In another aspect, the invention provides an electrode as described herein, wherein the binder is a grafted co-polymer selected from [PAA] _m -g-[PEG] _n -ω-end _a , wherein ω-end _a is selected as described above. In some embodiments, the MW of said co-polymer is optionally between 250,000 and 550,000 g/mol, the Tg is optionally between -50 °C and 30°C and the grafting degree (GD) is optionally between 5 and 30%.

In terms of electrodes (or battery electrodes) and specifically a silicon-based anode, the present invention aims to resolve silicon-based active material related issues such as volume expansion by generating a strong and uniform yet flexible interactions with the silicon particles. Commonly used in the art PAA binders exhibit strong binding forces to the active material, however the high Tg and brittleness of PAA as -is results in unsatisfactory anode performance. Following the expansion of silicon due to silicon lithiation processes, the binder of the invention preserves the connectivity and conductivity of the electrode (due to the excellent conductivity properties of glycol-type structures), thereby providing a superior mechanical (by virtue of the unique strength and robustness of PAA) and electrochemical performance of the electrode. The specific composition of the grafted co-polymer which includes a poly(acrylic acid) segment (PAA) as a backbone, and a plurality of esterified glycol-type functionalities further having co-end groups together with the relatively high Mw (of between 250,000 and 550,000 g/mol), relatively low Tg (of between -50 and 30) and a GD ranging between 5 and 30%, provides the electrode with an increased strength, flexibility (in terms of the ability to expend without breaking) and conductivity.

In a general sense, an electrolyte serves as a conduction enhancer which promotes the movement of ions from the cathode (positive) to the anode (negative) when charging and in a reverse fashion on discharge. Such electrolytes may appear in their solid, liquid or semisolid (gel-like) forms. The use of a liquid electrolyte may impose problems associated with the reliability of the battery, such as leakage of the electrolyte out of the battery, solvent vaporization, and dissolution of electrode active material in the electrolytic solution. Since the electrolyte, in most cases comprises an organic solvent, a spontaneous ignition may also occur. In contrast, solid polymer electrolytes do not exhibit any leakage issues.

In some embodiments, the electrolyte is a solid polymer electrolyte. In some embodiments, the solid polymer electrolyte consists or comprises inorganic solid electrolytes. In some embodiments, the inorganic solid electrolyte is selected from oxides, sulfides or phosphates-based materials. Non-limiting examples include lithium superionic conductor (LISICON), such as Li mGcPiS 12 (LGPS), Li mSiPiS 12 (LiSiPS), LiePSsCl (LiPS); argyrodite-like (such as LLPSsX, X = Cl, Br, I); garnets (such as lithium lanthanum zirconium oxide, LasLLOnZn, LLZO), sodium superionic conductor (NASICON), such as LTP, LATP, LAGP; lithium nitrides, such as L1 ₃ N; lithium hydrides (LiBFL); lithium halides; and others.

In some embodiments, the electrode is a cathode comprising an active material selected from lithium iron phosphate (LiFeP0 ₄ /C, LFP), LiMno _. 8Feo _. 2PO4 (LMFP) and lithium nickel cobalt manganese oxide (LiNiCoMn0 ₂ , NMC), e.g., NMC811, NMC532, NMC111, NMC622, etc, and others.

The polymer electrolyte of the invention including the novel polymers, as described herein, offers the combined advantages of PAA and PEG (optionally further substituted). PAA provides robustness (hardiness) without being too brittle. PEG provides excellent ion conductivity and elasticity without collapsing at high potentials. As such, polymer electrolytes of the invention are superior to those known in the art and provide lithium-ion conductivity of up to 10 ^"5 S/cm at ambient conditions.

Also provided herein is a method for increasing the capacity of an energy storage device, the method comprising mixing a polymer, as described herein, in electrode active material, to thereby obtain an electric storage device. Also provided is use of a polymer of the invention or a composition comprising same as a binder.

Further provided is a kit comprising an amount of a polymer of the invention and instructions of use. The invention further provides a polymer selected from:

PAA-g-bPEG160 _and PAA-g-mPEG350 , wherein each of v, x, n, and *, independently, is as defined herein.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to better understand the subject matter that is disclosed herein and to exemplify how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which: Figs. 1A-B illustrate manufacturing processes according to some embodiments of the invention, as well as exemplary polymers of the invention. Fig. 1A illustrates grafting methodologies and Fig. IB illustrates copolymerization with RAFT agents.

Fig. 2 illustrates a typical DSC curve of PAA-g-bPEG160 graft copolymer with marked glass-transition temperature.

Fig. 3 provides an overlay of DSC curves of several grafted polymers reported in this invention.

Fig. 4 provides an overlay of TGA curves of several grafted polymers reported in this invention.

Fig. 5 provides Niquist plot of the AC impedance data of the PAA-g-bPEG160- L1CIO4 SPE at room temperature.

Fig. 6 is SEM cross-section image of solid polymer electrolyte-coated composite anode as described herein.

Fig. 7 provides a comparison graph of first cycle charge and discharge (voltage vs capacity density) of the half-cells of commercial (full line) vs polymer-based anodes (dotted line) according to the invention .

Fig. 8 provides an electrochemical performance of anodes containing a commercial (circles) versus anode containing a grafted polymer (squares) as binders according to the invention.

Fig. 9 illustrates general synthesis process of PAA-g-PEG via RAFT copolymerization .

Fig. 10 provides NMR spectra of the PAA-g-PEG copolymers synthesized using different amount of RAFT agent. The ratio of (RAFT: Monomer) ramged from 1:250 to 1:2000. Integrating the protons of CEb groups of the ethylene glycol moieties relatively to the protons of the benzyl groups of the RAFT agent gives a molecular weight estimation of the resulting polymer.

Fig. 11 provides AC-impedance measurement and fit of the solid polymer electrolyte containing a copolymer and 10% of LiTFSi. Measuring the impedance of the resulting polymer at room temperature show an internal resistance of -50W which translates as ion conductivity after taking in account the surface area and the thickness.

Fig. 12 provides cyclic voltammetry curves of the solid polymer electrolyte containing 10% of LiTFSi and copolymer with MonomenRAFT ratio 750:1. Fig. 13 illustrates a correlation of ion conductivity at RT of the copolymer of PAA-g-PEG with the number of PEG-480 units.

Fig. 14 provides cyclic voltammetry of the SPE containing PAA-g-PEG480 copolymer with 1:1 molar ratio of AA:PEG-480 and 2.5% LiTFSI.

Figs. 15A-D provide a cyclic voltammetry curve (at lmV/s rate) of the SPE containing: Fig. 15A - 30% LiTFSI and copolymer with AA:PEG 80:20 molar ratio; Fig. 15B - 10% LiTFSI and copolymer with AA:PEG 90:10 molar ratio; Fig. 15C - 2.5% LiTFSI and copolymer with AA:PEG 40:60 molar ratio; Fig. 15D - 2.5% LiTFSI and a homopolymer. The SPEs did not show oxidative degradation until 4.5 V.

Fig. 16 provides cyclic voltammetry of the SPE containing PAA-g-PEG350 and 2.5% LiTFSI scanned at 0.2mV/s rate.

Fig. 17A-B depicts formation and rate test performance of LFP cathode containing: (Fig. 17A) PAA-g-mPEG350 copolymer as binder, and (Fig. 17B) PAA-g- PEG480 copolymer as binder.

DETAILED DESCRIPTION OF EMBODIMENTS

Description of embodiments of the invention in the present application are provided by way of example and are not intended to limit the scope of the invention. The described embodiments comprise different features, not all of which are required in all embodiments of the invention. Some embodiments utilize only some of the features or possible combinations of the features. Variations of embodiments of the invention that are described, and embodiments of the invention comprising different combinations of features noted in the described embodiments, will occur to persons of the art. The scope of the invention is limited only by the claims.

Various synthetic methodologies are provided for manufacturing polymers of the invention. One of the synthetic pathways involves using oligo (ethyleneglycol) acrylate monomers as building materials. These monomers have a range of MWs which make them an interesting group of functional materials which allows a tunable property that results in a densely grafted polymers with a structure known as bottle brush polymers. Polymers based on these oligomers are amorphous, thus allowing for a high ion conductivity as opposed to a semi-crystalline such as PEO. However, as such, these densely grafted polymers exhibit poor mechanical properties and low processability. Therefore, they are less favorable candidates as solid polymer electrolytes. One of the methodologies for enhancing mechanical properties was to co-polymerize these monomers with another monomer which improves the mechanical strength of the resulting polymer. For this purpose, acrylic acid was used as an acrylate co-monomer. The presence of hydrogen bonds of the acrylic acid repeating units contributes to the enhanced mechanical property of the resulting copolymer.

Controlled radical polymerization (CRP) may be used as a polymerization method. Among CRPs, a reversible addition-fragmentation chain transfer (RAFT) [7,8] is a technique used to polymerize functional monomers according to the invention.

EXAMPLE 1: A process of the preparation of the new copolymer Solvent based grafting approach

In the solvent-based grafting approach, 2 g of PAA (0.0277 mol) were dissolved in 40 g of DMF solvent at room temperature (RT). 2.220 g of diethylene glycol mono-n- butyl ether (PEG160) (0.0139 mol) was added followed by addition of 277 μL of 1M solution of pTSA in DMF (0. 277 mmol). The reaction mixture was heated to 90 °C and reacted for 3h under stirring. Resulting grafting yield in such approach was 18%.

Bulk grafting approach

In a bulk approach, 2 g of PAA (0.0277 mol) was dissolved in 40 g of bPEG160 (excess) and with 560 pL of 1M pTSA in DMF (0. 554 mmol). The reaction mixture was heated to 100 °C and reacted for 15h to obtain 30% grafting yield. At the end of reaction, the mixture was cooled down to room temperature, precipitated and washed in diethyl ether and dried at 70 °C under vacuum until constant mass.

EXAMPLE 2: A process for preparing composite anode using PAA-g-mPEG120 polymer

PAA-g-mPEG based solid polymer electrolyte was prepared from a 7 wt. % polymer solution (depending on the grafted polymer type, the polymer weight ratio was between 5 and 10 wt. %) in DMAc with a lithium salt (L1CIO4, LiBOB, LiDFOB and/or other lithium salts) having [EO]:[Li] molar ratio varying from 2:1 to 20:1. Fig. 5 shows a typical Niquist lot of the AC impedance data at room temperature of PAA-g-bPEG grafted polymer containing 10% L1CIO4 salt. Therefrom, the calculated ionic conductivity of the SPE was in average s=1.63 10 ⁵ S/cm. Composite anodes containing PAA-g-mPEG and PAA-g-bPEG polymers give -20% more capacity density compared to a commercial one made of PAA polymer (see Fig. 7). Comparing the commercially available composite anode and the composite anode provided herein, the first cycle charge of the herein composite anode is 760mAh/g, while the commercially available composite anode comprising the same active material and PAA polymer is having a capacity of ~650mAh/g. Without being bound to theory, such phenomenon occurs due to the enhanced ion conductivity and improved lithium ions mobilization of the novel PAA-g-mPEG polymer, compared to the commercial one.

SEM image (Fig. 6) shows the cross-section of the SPE-coated composite anode with SPE thickness of about 12 microns and electrode thickness of about 50 microns.

EXAMPLE 3: PAA-g-PEG copolymer

Materials: acrylic acid, polymethyl ether PEG acrylate with Mw 480 g/mol, azobisizobutironitrile (AIBN), cyanomethyl dodecyl carbonotrithiolate, dibenzyl trithiocarbonate, 4-cyano-4-(dodecylsulfanylthiocarbonyl)sulfanulpentanoic acid, 2-(2- cyanoprop-2-yl)-S-dodecyltrithiocarbonate, DMF, hexane, toluene.

General polymerization protocol: lg of PEG-480 was mixed in lg of DMF. Thereafter we added the appropriate amount of reversible addition-fragmentation chain transfer (RAFT) agent and AIBN. Molar ratios of monomer : RAFT agent were ranging from 250: 1 to 2000: 1 and all the ranges in between. The reaction was left to last under vigorous stirring from 3 to 7 days, depending on the temperature of the reaction mixture.

Exemplary synthesis utilizing dibenzyl trithiocarbonate as RAFT agent is illustrated in Fig. 9. Other and different RAFT agents were also used in a similar manner to the procedure above.

Purification procedure: The polymer was dissolved further with more 5gr of toluene. After that it was precipitated out in excess hexane and dried in a vacuum oven of 70°C for 48-72 hours. Results

Comparative NMR analysis is provided in Fig. 10. The NMR shows the elements of the polymer compared to the RAFT agent. The polymer was synthesized in a range of MonomenRAFT ratio (250:1-750:1). The molecular weight of the resulting polymer was estimated by integrating the CH ₂ protons of PEG-480 in relative with the aromatic moieties of the RAFT agent.

EIC li-ion conductivity analysis is shown on Fig. 11. The ion conductivity of the SPE was measured ast different temperature by adding different amounts of the LiTFSi. The best ion conductivity was achieved with 2.5% of LiTFSi. Increasing the amount of lithium salt decreased the ion conductivity due to some crystalline moieties they create in the polymeric media.

Cyclic voltammetry of solid electrolyte of PAA-g-PEG polymer with 750:1 monomenRAFT molar ratio and 2.5% LiTFSi salt is shown in Fig. 12. We tested the stability of the resulting polymer in the voltage range of 0-5V. We observed that this polymer is stable and have negligible current <10-5 mA till the -4.5V. We observed some oxidation only at higher voltage (>4.5V). Moreover, the main oxidation reaction is at the first cycle only. On the coming cycles this become minor due to plating of lithium.

Ion conductivity of the copolymers with different AA:PEG480 molar ratios (monomenRAFT = 2000:1) is show in Fig. 13. Fig. 13 shows correlation of ion conductivity at RT of the copolymer of PAA-g-PEG with the amount of PEG-480 units. By slightly changing the ratio between the AA and PEG-480 monomers we can finetune the ion conductivity of the resulting polymer.

Cyclic voltammetry results with different AA:PEG480 monomer molar ratios and different LiTFSi salt content is shown on Fig. 14 and Fig. 15. Fig. 14 shows cyclic voltammetry of the SPE containing PAA-g-PEG480 copolymer with 1:1 molar ratio of AA:PEG-480 and 2.5% LiTFSI. Fig. 15A-D show cyclic voltammetry analyses (at lmV/s rate) of the SPE containing: Fig. 15A - 30% LiTFSI and copolymer with AA:PEG 80:20 molar ratio; Fig. 15B - 10% LiTFSI and copolymer with AA:PEG 90:10 molar ratio; Fig. 15C - 2.5% LiTFSI and copolymer with AA:PEG 40:60 molar ratio; Fig. 15D - 2.5% LiTFSI and a homopolymer. The SPEs did not show oxidative degradation until 4.5 V.

Fig. 16 shows cyclic voltammetry of an SPE containing 2.5% LiTFSI and a copolymer PAA-g-PEG350 prepared by grafting method. For all the copolymers, prepared by both RAFT and grafting method, cyclic voltammetry results show repeatable cycles. The deposition of lithium on stainless steel appears at -0.5V and the reverse scan, stripping of lithium from the SS electrode is observed at ~0.2 V. Secondary Li deposition peak is appearing at IV at cathodic peaks and at 1.5V of the anodic (lithium stripping). These secondary peaks are appearing due to the presence of the ester (carboxylic acid) groups and the different lithium transport mechanism in ester groups comparing to ether groups. Although the process remains reversible on cycling, the amount of cycled lithium decreases progressively. This phenomenon may be attributed to the formation of a passive layer on the SS electrode, that is phenomenologically similar to those commonly experienced in liquid organic electrolytes.

Fig. 17 shows a typical example of half-cell cathode performance (formation and rate test) at RT when using a grafted copolymer (Fig. 17A) and when using a RAFT copolymer (Fig. 17B). From what is known about the performance of LFP-based cathodes, the cathodes presented herein show superior performance in terms of stability and capacity density when prepared with PAA-g-PEG binders.