Electrochemical storage cells have a variety of constructions. In constructions often used in rechargeable cells, sheet electrodes are wound into what is termed a "jellyroll"electrode assembly or core. Flexible positive and negative sheet electrodes are placed side-to-side, separated by a porous nonconductive material, and wound tightly in a spiral fashion to create the cylindrical jellyroll assembly. The assembly is then placed in a container and electrical connections completed between the electrodes and the associated terminals. An electrolyte is added to the container and allowed to permeate the assembly.

The manner of fabricating jellyroll electrode assemblies and integrating them into completed cells has been extensively developed in the industry.

Due in part to the design of sheet electrodes, completing an effective electrical connection between the electrodes and the cell terminals is particularly difficult in cells having a jellyroll construction. The electrodes consist generally of active material deposited onto the two sides of a thin conductive substrate. The substrate acts both as a structural frame on which the active material is supported and retained and as an electrical conduit to collect and deliver the electrical current produced. Due to processing requirements, and to maximize capacity, the substrate is preferably entirely covered with active material-leaving no convenient bare location for an electrical connection to the substrate. Various methods of connecting the electrodes to the cell terminals have been developed. In several cell designs, a small portion of active material is cleaned from one isolated location on the side of the substrate. At this point a metal tab is then welded or otherwise attached to the substrate. The tab is then connected to the cell terminal.

Examples of these methods are provided in U. S. Patent Nos. 4,049,882 to Beatty and 5,434,017 to Berkowitz, et al. However, such discrete substrate connections are often

inadequate due to the resulting high electrode internal resistance. The higher internal resistance is partly a consequence of the long path length from the extremes of an elongated electrode to the comparatively small tab. This is a problem particularly in more recent cell designs operating at high drain rates. In addition, the processing steps required to secure and connect the tabs are relatively complex and prone to problems.

To simplify construction and reduce internal resistance some cell designs attempt an electrical connection with an entire edge of the electrodes. This is accomplished by using a flat current collector that is pressed into contact with the spiral edge of the jellyroll.

As a consequence of the spiral structure, each end of a jellyroll presents in a small area one entire edge of one electrode. By slightly axially offsetting the sheet electrodes before winding, the electrodes are each separately exposed at opposite ends of the jellyroll. There they can be separately accessed for connection. Various collectors for connecting to the spiral edges of jellyroll assemblies are disclosed in U. S. Patents No. 3,960,603 to Morioka et al.; 4,554,227 to Takagaki et al.; and 4,529,675 to Sugalski. Several designs provide for welding of a current collector to the substrate edge to increase electrical continuity.

Although the cross-sectional edge of the substrate is often bare and exposed to allow an electrical connection, the edge contact area is small and does not allow for secure attachment of the current collector. In addition, due to the active material's proximity errant portions may hold off a collector and prevent proper connection. Because the active material is not generally weldable or highly conductive it does not provide a surface for effective connection.

It has been found that a collector may be more effectively secured and connected to the electrode spiral edge if the sides of the substrate are bare of active material a short distance back from the exposed spiral edge (see U. S. Patent 4,332,867 to Tsuda et al.).

This increases the available surface for effective electrical connection and reduces the probability of active material protruding above the spiral edge and preventing complete contact by the collector. There are essentially two methods of providing such a bared edge region: either no active material is deposited on that portion of the substrate during processing-or active material is deposited on the entire substrate and then removed from the desired regions. Processing difficulties arise with some substrates which use the first approach. For example, many substrates are calendered after deposition of a pasted active material. In calendering, an electrode passes between rollers that compress the active

material to increase density. Where active material is deposited on only part of the substrate, subsequent calendering distorts the substrate due to uneven tension and stretching. To avoid these processing problems, it is preferred to deposit active material over the entire substrate sides and then clean the active material from a narrow edge region -after calendering-to provide a connection surface. However, active materials are designed to adhere to the substrate and are not easily removed. In addition, to minimize the effect on capacity of the electrode and cell, only a very narrow band of active material should be removed. Existing methods of processing electrodes do not provide adequate means of cleaning narrow bands of active material from coated electrodes. What is needed is a method of cleaning active material from a narrow region of a substrate along its edge.

Summary of the Invention The present invention is devices and methods for forming narrow bands of exposed substrate on the sides of coated substrates.

An object of the invention is a method of removing a narrow band of coating from a thin substrate by moving an inclined circular blade over the surface of the substrate.

Another object of the invention is a pair of inclined blades drawn simultaneously over the sides of a thin substrate adjacent an edge to clean a coating from the substrate along a narrow band adjacent the edge.

A further object of the invention is a method for increasing the exposed contact area on the end of a spiral wound electrode while only minimally reducing the functional capacity of the electrode.

Yet another object of the invention is an improved process for fabricating electrochemical cells in which the sides of electrodes adjacent the electrode edges are cleaned of active material before the electrodes are wound into a jellyroll assembly to improve connectivity with other cell components.

The following devices and methods are directed to improving physical and electrical connectivity to conductive electrodes in electronic and electrical devices. Where electrode substrates are covered on their sides with a coating, a narrow band of the coating is removed to provide additional connection surface and reduce the potential for the coating interfering with connectivity. When the electrodes are to be wound into a spiral configuration, the narrow band of coating is removed adjacent an edge, such that when the

electrode is wound an exposed spiral edge is created. This more exposed spiral edge provides improved connectivity when other components such as electrochemical cell collectors are pressed or welded to the spiral end of the electrode.

In order to remove a coating from a very narrow band or strip of a thin substrate, a circular rotary blade is moved over the substrate surface with the tip of the blade penetrating the coating layer. By inclining the plane of the blade at a small angle with respect to the blade's path over the electrode, very narrow bands of coating may be removed-much smaller than the diameter of the blade. As the blade moves over the substrate, the blade rotates-either as a result of friction forces or driven-which assists in carrying away the removed coating. Because of how the blade is held and moved, forces are imparted to the electrode that push it both out-of-plane and in a direction parallel and transverse to the electrode. Alternatively, the relative motion of the blade and electrode may be produced by holding the blade stationary and moving the electrode. In such a configuration, the blade is held at an angle with respect to the electrode path. In various embodiments, the out-of-plane forces are balanced by a second blade positioned and moved in a like manner against the opposite side of the electrode. The blade forces are also used to push the electrode against a support surface that bears against the electrode cross-sectional edge to position the electrode with respect to the blades. The blade forces may also induce the electrode to buckle. Supports directed at the sides of the electrode are used to guide and maintain the electrode in position. Support is preferably accomplished by pairs of rollers located before and after the blades. The rollers each have a pliable surface that grips the electrode to prevent twisting and buckling. After the electrode passes between the blades it is drawn past rotating brushes that remove any loose or residual coating particles. The electrode may be drawn through the blades by a driven takeup wheel or other means. An adjustable carriage is provided to adjustably position the blades with respect to the electrode. The blades are mounted on two portions of the carriage that are operable to move the blades toward and away from the plane of the electrode. Further adjustment structures move the blades transversely across the plane of the electrode to determine the position of the cleaned band.

Various configurations and alternative embodiments are provided. In one configuration, the blade tips are pressed against the electrode by springs or similar structures. The blade axes may be inclined with respect to the electrode plane. Where it is

desired to clean multiple bands on each side of an electrode, the electrode may be passed multiple times between the blades. Alternatively, additional pairs of blades may be employed to remove coating from multiple bands on each side. In an alternative to stationary blades, the electrode may be held stationary while the blades are moved to effect the same results. By employing these inventive devices, improved methods of producing electrodes and fabricating electrode-containing devices with better connectivity are made possible. Other objects and embodiments of the invention will become clear from the illustrations and following detailed description of the invention.

Description of the Drawings Figure 1 depicts an isometric view of a wound electrochemical cell electrode assembly and a current collector. The electrode assembly includes an electrode with an edge cleaned according to the present invention.

Figure 2 depicts the manner in which rotary blades are directed to a continuous electrode to clean the electrode substrate sides adjacent one edge.

Figure 3 depicts a side view of a device for cleaning an electrode according to the present invention.

Figure 4 is a top view of the same device shown in Figure 3.

Figure 5 is an embodiment of the invention in which the rotary blades are biased against the electrode.

Figure 6 depicts an alternative configuration in which the axes of the rotary blades are inclined with respect to the plane of the electrode.

Description of the Preferred Embodiments Figure 1 depicts a typical jellyroll configuration electrode assembly 100. Two electrodes are wound together and offset slightly axially so that in the figure the spiral edge 10 of only one electrode 12 can be seen. Active material 14 has been cleaned from a narrow portion of the substrate sides 18 adjacent the substrate cross-sectional edge 20 to create a narrow bared strip 22 on the substrate 16. A typical collector 30 is shown separated from the spiral edge 10. In application, the collector 30 is pressed onto the spiral edge 10 (and possibly welded) generally in the orientation shown. The active material has been cleaned away sufficiently to ensure complete contact of the collector 30

with the cross-sectional edge 20. Various existing designs of collectors provide conductive elements protruding from the contacting face of the collector. These protruding elements penetrate the edge and cleaned bare strip 22 of the electrode 12 during welding to create a continuous connection. An electrical strap, or other means of connectivity, is provided between the collector 30 and a cell terminal. A similar collector may be used on the opposite end of the electrode assembly.

Figure 2 is an isometric view showing the interaction of a single blade 24 with an electrode 12 to clean the substrate's adjacent edge according to one embodiment of the present invention. Herein"edge"is intended to mean generally a combination of the cross- sectional edge 20 of the substrate (which is generally at right angles to the substrate sides 18) and the immediately adjacent portions of the electrode. Where a specific operation is intended to be directed solely to the"cross-sectional edge"that specific reference is used.

During operation, the electrode 12 is oriented in a vertical plane and is moved along an electrode path 26. The blade 24 is a generally planar beveled rotary blade that is free- spinning about a blade axis 28. The blade axis 28 is orthogonal to the plane of the blade which is defined as the plane passing through all points of the blade tip. The blade axis 28 is also preferably parallel to the electrode plane 97 (see Figure 5), and has an acute included blade angle 40 with respect to a vertical axis 42. The vertical axis is perpendicular to the electrode path 26. In embodiments where the blade axis 28 is not parallel to the electrode plane (see Figure 6) the blade angle 40 is the angle between the projections of the vertical axis and blade axis on the electrode plane. The blade is positioned near the electrode cross-sectional edge 20 such that the blade tip 44 meets the plane of the substrate side 18. As the electrode 12 is moved relative to the blade 24 and along the electrode path (from right to left in the figure), the blade 24 separates the active material from the substrate 16 along a strip adjacent the cross-sectional edge 20. The angle of the blade 24 to the active material 14 and substrate 16 results in a plowing or scraping action. A ribbon 46 of removed active material is shown in the figure. The dimension of the width 48 of the cleaned bare strip 22 is a function, in part, of the blade angle 40 and the blade diameter and position of the blade with respect to the cross-sectional edge 20.

Cleaning a narrow strip may be difficult if a blade with too great a diameter (little curvature) is used as the blade angle 40 required will be unmanageably small. Examples of functional blade parameters are given below.

The angle of the blade and the consequent direction of the cutting forces creates a downward force (relatively in the figure) on the electrode 12. These downward forces retain the electrode in position and tight against a supporting and positioning surface. In Figure 2 a support 50 having a flat sliding surface 52 parallel to the electrode cross- sectional edge 20 is provided for this purpose. This support surface 52 establishes the position of the electrode 12 by locating the electrode edge. Because the electrode 12 is typically thin and therefore not very stiff, it is susceptible to buckling under the induced blade forces. Tensioning of the electrode and other additional support may be necessary to prevent buckling. Frictional forces between the active material 14 and the blade 24 also cause the blade 24 to rotate continuously bringing new portions of the blade tip to bear on the active material. The rotating blade helps to drag away the active material as it is separated from the substrate. Too large a blade angle 40 will result in a buildup of active material and potentially much higher drag on the electrode, increasing the potential for buckling. Larger blade angles also reduce blade rotation such that at a maximum angle (less than 90 degrees) rotation will stop, resulting in quick erosion and flattening of the blade tip. The maximum angle is dependent upon such factors as the thickness and nature of the coating. In the other extreme, a blade angle of effectively zero degrees results in the blade tip cutting without removing the active material. With these requirements, the blade is considered"at an angle"to the path to produce the desired results of the invention, when the blade angle 40 is between the limits of 0 to 90 degrees. Forces are also created which would push the electrode 12 away from the blade 24. For this reason, a single blade as shown in Figure 2 is not preferable in practice. As shown in the preferred embodiment of Figures 3 and 4, two blades on opposite sides of the electrode 12 are used to balance the forces on the electrode 12 and prevent the electrodes moving away from the blades 24.

Figures 3 and 4 present two views of an electrode cleaning device 60 in operation with an electrode 12 positioned between a pair of rotary blades 24. In Figure 3 only one of the blades 24 can be seen. Each blade 24 is supported on one half a split translating carriage 62. Both halves of the carriage 62 are supported in turn on a vertically adjustable base 64 that pivots about a pivot point 66. The vertical position of the base 64 with the carriage 62 is adjusted by a spring loaded threaded adjuster 68. In this configuration, the included angle of each blade 24 is relatively fixed by these elements, although varying slightly with height adjustment. A wear plate 70 is provided before and after the blades

24. The wear plate 70 includes a guide surface 72 that supports the electrode 12 vertically and guides it past the blades 24. The wear plate 70 is not continuous because of the presence of the blade 24. Alternative structures may be used to substitute for the wear plate 70 and guide surface 72. A series of horizontal axis rollers is one example. Another alternative structure is one or more belts moving with the electrode to eliminate friction. A guide roller pair 74 is also placed both before and after the blades 24 to guide and support the electrode and provide tension to assist in maintaining the electrode in a vertical plane between the blades 24. The blade supporting structures, and the wear plate 70 and guide roller pairs 74, are fixed to a rigid frame 76 to maintain the relative positions of the blades and electrode. In the mode of operation shown, a continuous electrode is drawn from a payoff reel 78, is passed through the cleaning device 60 from right to left, and is collected on a takeup reel 80. The takeup reel 80 is motor driven to draw the electrode through the cleaning device 60. Alternatively, other structures such as mated drive wheels on opposite sides of the electrode may be used to draw the electrode. Tension in the electrode is produced by the inherent resistance of friction and mass of the payoff reel 78 and may also be induced such as by a brake on the payoff reel 78. Additional tension is created between the blades and the takeup reel 80 due to the blade forces on the electrode. As the electrode passes the rotary blades 24, the active material 14 is cleaned from a narrow band forming the bared strip 22 at the bottom of the sides of the electrode. Rotary brushes 82 are provided on both sides of the electrode to remove loose or residual active material that may remain on the electrode. In the figures, the brushes 82 are shown with a fixed vertical axis.

More preferably, the brushes are inclined such that the brush ends wipe across the cleaned strip 22. Also, by biasing the brushes toward the electrode, effective contact can be maintained despite any wear and shortening of the brush bristles that may occur. In a preferred embodiment, the brushes are motor driven to increase the scrubbing effect. One alternative device to perform the same secondary cleaning function as each brush is a mill wheel rotating at a high speed preferably across or at an angle to the bared strip. Mill wheels are particularly effective where hard or brittle coatings must be removed. In another embodiment, mill wheels are used in conjunction with brushes.

In Figure 4, both blades 24 can be seen. Preferably, the two blades 24 are located so that the blade tips 44 will contact an electrode 12 at the same point (although on opposite sides) on the electrode. This balances the cutting forces such that an electrode

will not be thrust away from either blade 24. Although perfect relative alignment of the two blades is the objective, some variation is acceptable. However, severe misalignment may result in twisting or bending of the cleaned strip 22. The two halves of the carriage are adjusted transversely toward and away from the electrode path 26 by means of a common drive mechanism 84 that maintains a symmetric positioning of the carriage halves and the two blades 24. The drive mechanism 84 is a common screw drive with right and left-handed threaded portions driving the respective carriage halves in opposite directions.

Other known mechanisms for this function are applicable as well. Similarly, the height adjustment described above may be accomplished by a variety of structures that will be well known to those skilled in designing such devices. Although the adjustment features described provide benefits in practice, in alternative embodiments the blades are fixed in a predetermined position to affect the desired action on a particular electrode.

In Figure 4 the matching sets of guide rollers can be seen. Each pair 74 consists of a fixed roller 86 and a tensioned roller 88. The fixed rollers 86 do not translate but freely rotate. Each tensioned roller 88 is pivotally attached to a fixed roller 86 through an idler arm 89 that pivots about the center of the opposite fixed roller 86. The two idler arms 89 are interconnected by a spring 90 that biases both tensioned rollers 88 against their respective fixed roller 86. The rollers each have a soft rubber rolling surface 92.

Preferably, the rubber has a durometer of about A60. The combination of the rubber rolling surface 92 and the roller tensioning gives each roller pair 74 a grip on an electrode 12 passing between. This helps in maintaining the electrode 12 in place during operation.

Despite the presence of a wear plate 70 to prevent vertical movement, the electrode may buckle and bend due to the blade forces. These motions are resisted by the sets of rollers that allow motion along the electrode path 26 but resist downward and twisting motions between the rollers. Although paired rollers are preferred, other configurations of rollers, including configurations using unpaired single rollers or rolling surfaces in combination with sliding guide surfaces are contemplated to perform the same function. The electrode path between the payoff and takeup reels may be complex. However, with respect to the interaction of the blades and the electrode elements, the relevant electrode path and electrode plane are those in the immediate vicinity of the blades. The electrode plane 97 of interest is defined by the electrode supports, such as the roller pairs, which control and limit the course of the electrode past the blades. Alternative support structures are

contemplated in other configurations.

To initiate operation of the cleaning device shown, the blades 24 are preset to a height approximately matching the bottom edge of the electrode 12. The blade carriage 62 is then backed off by operation of the drive mechanism 84 to withdraw the blades from the electrode path. A length of an electrode is placed between the rollers and tensioned. The carriage drive mechanism 84 is then operated to bring both blades 24 to within close proximity to the electrode without touching. The height of the blades may be adjusted to the desired cleaning height at this point. The blades are then drawn together until both blades penetrate the active material and just touch the electrode substrate sides 18. The electrode is then drawn through the rollers (right to left in the figure) and past the blades 24 to clean the electrode edge. After an initial length has passed the blades, the electrode may be stopped, the cleaned strip width measured, and the blades adjusted up or down to obtain the proper width. Alternatively, the electrode may be drawn through the rollers with the blades initially withdrawn from contact. The blades are then moved into position gradually while the electrode is moving. This alternative may reduce initial blade forces for some active materials. In another alternative method, the blades are positioned, in a first pass, to penetrate only partially the thickness of the active material. Multiple passes of the blade or blades over the same location remove consecutively deeper portions of the active material to gradually clean the targeted strip. Using the devices shown in the figures, similar results can be obtained by moving the electrode in the opposite direction with respect to the blade and support surfaces (from left to right in the figure). However, this mode is not preferred due to less effective separation and removal of the active material and additional difficulties in supporting the electrode. Other alternative methods of using the described devices in various sequence of operations are contemplated.

A prototype device essentially as shown in Figures 3 and 4 was built and tested.

The electrode to be cleaned consisted of a continuous length of 1.34 inch (34.0 mm) wide nickel-plated steel substrate (with a perforation pattern) with a pasted and calendered active material matrix having a rubber-based binder system. The substrate had a nominal thickness of about 0.0021 inches (0.053 mm) and had an active material coating with a thickness of about 0.0095 inch (0.241 mm) on each side. The rotary blades were standard 2 inch (50.8 mm) diameter hardened steel blades with a double bevel as are commonly used for commercial cutting of fabric and paper materials. To limit the impact on the cell

capacity, the cleaned strip width should be as small as possible. It has been found that, in this particular configuration, at least about 0.015 inch (0.38 mm) of the substrate sides adjacent the cross-sectional edge must be cleaned to assure an effective connection to the edge after winding. If the cleaned strip width is less than about 0.010 inch (0.25 mm) an effective connection is less likely. To accommodate tolerances in the tests performed, the designed width of the cleaned strip was approximately 0.025 inch (0.63 mm). This designed width was obtained by angling the blades at approximately 5 degrees from the vertical and positioning them so that the blade tip was at the approximate middle of the cleaned strip width. The electrode was drawn through the blades at various linear speeds in the range of 20 to 40 ft/min (10.2 to 20.4 cm/sec). The tension in the electrode at the takeup reel was approximately 6 to 10 pounds. Electrodes were edge-cleaned by this device and successfully integrated into functional cells. The cleaned edges resulted in a higher success rate when collectors were welded to the spiral electrode assembly ends. In a subsequent configuration of the above prototype, both blades were motor driven in the direction of the moving substrate. This allowed higher linear speeds of 100 to 150 ft/min (51 to 102 cm/sec) without generating distorting tension in the electrode. Also, one blade was positioned 0.005 to 0.009 inches (0.013 to 0.022 cm) forward of the other and the blades brought closer to the centerline of the substrate. This induced slight local bending of the substrate which improved removal of active material without significant distortion of the substrate edge.

The above concepts of the invention are also employed in alternative structures and embodiments. The particular blade in the example above was selected for convenience. A double beveled blade is preferred, although other blade designs may be used. Larger diameter blades may be necessary if a much wider region is to be cleaned-although a 2- inch blade will suffice for most applications. If a much narrower strip is to be cleaned, a smaller diameter blade may be desired to enable maintaining a practical blade angle.

However, if it is necessary to only"chamfer"the active material or clear it away from the sides of the cross-sectional edge, a larger blade and higher blade angle may be more effective. The particular required combination of blade diameter and blade angle in any case is determined by trial and error for variations of strip width and thickness of active material. Toothed or serrated blades are also contemplated in alternative blade designs as potentially more effective in cleaning more hardened coatings. Such blades having

nonsmooth tips must be overdriven to be most effective in removing coatings.

Figures 5 and 6 depict additional alternative structures and features. In Figure 5 each blade 24 is supported on a shaft 93 that pivots about a shaft pivot pin 94 to allow the blades 24 to be directed toward an electrode 12 between the blades. The blades rotate freely on the shaft end. Both blades 24 are biased toward the electrode plane 97 to bear on an electrode 12. The biasing means may be a simple wound metal spring 95 secured to the blade shaft 93 or any of many equivalent devices such as: other metal springs, air cylinders, polymer springs. In the figure, each wound spring 95 is shown schematically connected to a fixed reference point. Alternatively, the biasing means may be placed between the blade 24 and the shaft 93 while the shaft is fixed. Other structures for biasing the blades are available and will be obvious to those skilled in the art. Biasing the blades provides automatic adjustment to variations in electrode dimension and position. The biasing force must be sufficient to ensure the blades continue to penetrate the active material to the desired depth. At the same time, blade biasing forces must be limited to prevent undue friction forces. The proper biasing forces are easily determined by experimentation. Each blade and shaft is locationally fixed or may be integrated into a movable carriage such as discussed above. Figure 6 depicts another alternative feature where the axis 28 of each blade 24 is tipped at the top away from the electrode 12. The resulting inclination angle 96 between the blade axis 28 and the electrode plane 97 is the same for each blade. Similarly, the blade axis 28 may be tipped at the top toward the electrode 12. This alternative results in the blade tip 44 being angled toward the active material being removed as the electrode 12 is drawn past the blade. Note that the plane of the inclination angle 96 is perpendicular to the plane of the blade angle 40 shown in Figure 2. In a separate configuration, inclined blades are also provided with a biasing means.

In an alternative method of operation, instead of moving the electrode, the electrode is held stationary and the blades are moved relatively to effect substantially the same process as described above. This may be more desirable if discrete electrode lengths, rather than continuous lengths, are to be edge-cleaned. Any of a number of jigs or holder designs may be used to retain the electrode so long as the blade path is clear. In yet a further embodiment, the rotary blades are driven rather than free-spinning.

The present methods and devices are easily adaptable to existing process lines for fabricating electrochemical cells. Often in fabrication of cell electrodes, continuous stock

substrate having a width of several electrodes is coated with an active material. Following any drying or calendering processes, the coated substrate is then slit lengthwise into several pieces having the proper electrode width. The present methods and devices may be introduced to such a process line following the slitting step and before combining the electrodes into an assembly. To maximize speed, multiple cleaning stations are used, each to address one of the several electrode pieces resulting from the slitting step.

Although the figures depict a horizontal mode, the same structures may be used in any angular orientation. Likewise, references herein to"vertical"directions are particularly with respect to the figures discussed and are not meant to be limiting on the implementation of the devices and methods described. Although the example and figures herein are directed to cleaning of a single electrode edge, the same device and methods may be employed to clean narrow strips at any edge, or a multiple of edges, of an electrode. In like manner, a narrow strip distant from a cross-sectional edge, such as in the middle of an electrode, may be cleaned using these methods. In other alternative devices for these purposes, additional pairs of blades and brushes are provided addressing the same electrode to clean multiple strips.

In the above, the term"clean"or to"bare"or"expose"the substrate means that a significant portion of a conductive surface is exposed along the strip addressed by the blades. It may not be necessary that the active material be entirely removed to significantly increase the effective electrical contact area. How cleanly the active material separates from the electrode substrate is partly dependent upon the nature of the active material and substrate. The present devices and methods are applicable to any electrodes having a flat sheet substrate and a softer or separable coating. Where the active material has a high level of toughness or the substrate is relatively thin, it may be necessary to provide greater restraint on the electrode to prevent buckling. Particularly abrasive active materials or coatings may require frequent replacement of blades and brushes due to wear.

Hole patterns in sheet substrates do not pose a difficulty as the blades simply slide past the holes during the cleaning operation. However, if the electrode edge is a result of slitting through a hole pattern, the cross-sectional edge may consist of relatively bendable teeth- like extensions (the inter-hole ligaments). In these cases, vertical support such as the rollers described above may be particularly required to prevent collapse of the edge against the surface of the wear plate.

The preceding discussion is provided for example only. Other variations of the claimed inventive concepts will be obvious to those skilled in the art. In particular, while the above discussion is in the context of electrochemical electrodes, the same methods are applicable to other technologies where coatings must be removed from the surface of thin substrates. Adaptation or incorporation of known alternative devices and materials, present and future is also contemplated. The intended scope of the invention is defined by the following claims.