received by the International Bureau on 26 June 2018 (26.06.2018)

1. A battery separator for a lithium battery comprising:

at least one microporous separator membrane or sub-membrane comprising a plurality of porous or microporous polymer microiayers or nanolayers, wherein at least one of the individual microiayers or nanolayers comprises a different or distinct polymer, molecular weight polymer, homopolymer, copolymer, and/or polymer blend, comprises a different or distinct additive, agent, material, and/or filler, or comprises combinations of different or distinct polymers, molecular weight polymers,

homopolymers, copolymers, polymer blends, additives, agents, materials, and/or fillers as compared to an adjacent individual microlayer or nanolayer, wherein the

microporous separator membrane or sub-membrane has a puncture strength of 290 gf or more.

2. The battery separator of claim 1 wherein a plurality of said separator membranes or sub-membranes of polymer microiayers or nanolayers are laminated to each other or to a microporous polymer membrane.

3. The battery separator of claim 1 wherein at least one of said separator membranes or sub-membranes of polymer microiayers or nanolayers has at least three microiayers or nanolayers.

4. The battery separator of claim 1 wherein at least one of said separator membranes or sub-membranes of polymer microlayers or nanolayers is made of one or more polyolefins.

5. The battery separator of claim 1 wherein at least one of said separator membranes or sub-membranes of polymer microlayers or nanolayers is made up of coextruded dry process polyolefin microlayers or nanolayers.

6. The battery separator of claim 1 comprising at least two said separator membranes or sub-membranes of polymer microlayers or nanolayers.

7. The battery separator of claim 1 comprising at least three said separator membranes or sub-membranes of polymer microlayers or nanolayers.

8. A battery separator or separator membrane as shown or described herein.

9. A lithium battery comprising the battery separator of claim 1.

10. A lithium battery comprising the battery separator of claim 8.

11. An improved separator, membrane or base film wherein the separator is a multilayer separator, membrane, or base film that that comprises one or more microporous co-extruded multi-microlayer or multi-nanolayer polymer membranes or sub-membranes adapted to be laminated or adhered to another polymer membrane, wherein at least one of the individual microlayers or nanolayers comprises a different or distinct polymer, molecular weight polymer, homopolymer, copolymer, and/or polymer blend, comprises a different or distinct additive, agent, material, and/or filler, or comprises combinations of different or distinct polymers, molecular weight polymers, homopolymers, copolymers, polymer blends, additives, agents, materials, and/or fillers as compared to an adjacent individual microlayer or nanolayer.

12. A battery separator or separator membrane that comprises one or more co-extruded multi-microlayer membranes laminated or adhered to another polymer membrane, wherein the separator or separator membrane may provide improved strength, for example, improved puncture strength, particularly at a certain thickness, and may exhibit improved shutdown and/or a reduced propensity to split, and wherein at least one of the individual microlayers comprises a different or distinct polymer, molecular weight polymer, homopolymer, copolymer, and/or polymer blend, comprises a different or distinct additive, agent, material, and/or filler, or comprises combinations of different or distinct polymers, molecular weight polymers, homopolymers, copolymers, polymer blends, additives, agents, materials, and/or fillers as compared to an adjacent individual microlayer.

13. A battery separator or separator membrane comprising one or more co- extruded multi-microlayer or multi-nanolayer membranes optionally laminated or adhered to another polymer membrane, and that may exhibit improved strength, improved puncture strength, particularly at a certain thickness, and/or that may exhibit improved shutdown and/or a reduced propensity to split, and wherein at least one of the individual microlayers or nanolayers comprises a different or distinct polymer, molecular weight polymer, homopolymer, copolymer, and/or polymer blend, comprises a different or distinct additive, agent, material, and/or filler, or comprises combinations of different or distinct polymers, molecular weight polymers, homopolymers, copolymers, polymer blends, additives, agents, materials, and/or fillers as compared to an adjacent individual microlayer or nanolayer.

14. A lithium battery comprising the battery separator of claim 11.

15. A lithium battery comprising the battery separator of claim 12.

16. A lithium battery comprising the battery separator of claim 13.

17. A secondary lithium battery comprising the battery separator of claim 1.

18. A lithium ion battery comprising the battery separator of claim 1.

19. An improved battery separator comprising a multilayer microporous film that comprises 9 or more layers, wherein at least three consecutive layers of the microporous film have a thickness of from 0.1 to 3 microns.

20. The battery separator of claim 19, wherein at least three consecutive layers of the microporous film have a thickness of from 0.1 to 2.5 microns.

21. The battery separator of claim 20, wherein at least three consecutive layers of the microporous film have a thickness of from 0.1 to 2.0 microns.

22. The battery separator of claim 19, wherein the multilayer microporous film has a thickness of 1 micron to 30 microns.

23. The battery separator of claim 22, wherein the multilayer microporous film has a thickness of 1 micron to 20 microns.

24. The battery separator of claim 23, wherein the multilayer microporous film has a thickness of 1 micron to 15 microns.

25. The battery separator of claim 24, wherein the multilayer microporous film has a thickness of 1 micron to 10 microns.

26. The battery separator of claim 19, wherein the at least three consecutive layers are coextruded layers.

27. The battery separator of claim 26, wherein the at least three consecutive coextruded layers were laminated with at least one other layer to form the microporous polymer film.

28. The battery separator of claim 27, wherein the at least one other layer is a coextruded layer.

29. The battery separator of claim 19, wherein the at least three consecutive layers comprise a polyolefin or a polyolefin blend.¹

30. The battery separator of claim 29, wherein the at least three consecutive layers each comprise polyethylene.

31. The battery separator of claim 29, wherein the at least three consecutive layers each comprise polypropylene.

32. The battery separator of claim 19, wherein the multilayer microporous film comprises 12 or more layers.

33. The battery separator of claim 32, wherein the multilayer microporous film comprises 15 or more layers.

34. The battery separator of claim 33, wherein the multilayer microporous film comprises 18 or more layers.

35. The battery separator of claim 34, wherein the multilayer microporous film comprises 21 or more layers.

36. The battery separator of claim 35, wherein the multilayer microporous film comprises 24 or more layers.

37. The battery separator of claim 36, wherein the multilayer microporous film comprises 27 or more layers.

38. The battery separator of claim 37, wherein the multilayer microporous film comprises 30 or more layers.

39. The battery separator of claim 19, wherein the multilayer microporous film has a puncture strength of 290 gf or more.

40. The battery separator of claim 39, wherein the multilayer microporous film has a puncture strength of 300 gf or more.

41. The battery separator of claim 40, wherein the multilayer microporous film has a puncture strength of 310 gf or more.

42. A battery comprising one or more of the battery separator of claim 19.

43. A method for forming an improved battery separator comprising a multilayer microporous membrane, the method comprising:

coextruding at least three layers; and

laminating the at least two coextruded layers to at least one other layer to form the multilayer microporous membrane.

44. The method of claim 43, wherein at least four layers are coextruded.

45. The method of claim 44, wherein at least five layers are coextruded.

46. The method of claim 45, wherein at least six layers are coextruded.

47. The method of claim 46, wherein at least seven layers are coextruded.

48. The method of claim 47, wherein at least eight layers are coextruded.

49. The method of claim 48, wherein at least nine layers are coextruded.

50. The method of claim 49, wherein at least ten layers are coextruded.

no

51. The method of claim 43, wherein the at least one other layer is a coextruded layer.

52. The method of claim 43, wherein the at least one other layer is a mono- extruded layer.

53. The method of claim 43, wherein the at least two coextruded layers are laminated to two other layers.

54. The method of claim 53, wherein one of the two other layers is laminated on a first side of the at least two coextruded layers and the second of the two other layers is laminated on a side of the at least two coextruded layers that is opposite to the first side.

55. The method of claim 53, wherein at least one of the two other layers is a coextruded layer.

56. The method of claim 55, wherein both of the two other layers are coextruded layers.

57. The method of claim 54, wherein at least one of the two other layers is a coextruded layer.

in

58. The method of claim 56, wherein both of the two other layers are coextruded layers.

59. The method of claim 43, wherein at least one of the at least two

coextruded layers and the other layer comprises a polyolefin or a polyolefin blend.

60. The method of claim 58, wherein at least one of the at least two

coextruded layers comprises a different polyolefin or polyolefin blend that the other layer does.

61. The method of claim 59, wherein at least one of the at least two

coextruded layers comprises polypropylene and the other layer comprises polyethylene.

62. The method of claim 60, wherein at least one of the at least two

coextruded layers comprises polyethylene and the other layer comprises polypropylene.

63. The method of claim 53, wherein the two other layers each comprise polypropylene or each comprise polyethylene.

64. The method of claim 54, wherein the two other layers each comprise polypropylene or each comprise polyethylene.

65. The method of claim 55, wherein the two other layers each comprise polypropylene or each comprise polyethylene.

66. The method of claim 56, wherein the two other layers each comprise polypropylene or each comprise polyethylene.

67. The method of claim 57, wherein the two other layers each comprise polypropylene or each comprise polyethylene.

68. The method of claim 58, wherein the two other layers each comprise polypropylene or each comprise polyethylene.

69. The method of claim 57, wherein the at least one of the two other layers is a coextruded layer that is coextruded with two or more other layers.

70. The method of claim 69, wherein the at least one of the two other layers is a coextruded layer that is coextruded with three or more other layers.

71. The method of claim 70, wherein the at least one of the two other layers is a coextruded layer that is coextruded with four or more other layers.

72. The method of claim 71 , wherein the at least one of the two other layers is a coextruded layer that is coextruded with five or more other layers.

73. The method of claim 72, wherein the at least one of the two other layers is a coextruded layer that is coextruded with six or more other layers.

74. The method of claim 73, wherein the at least one of the two other layers is a coextruded layer that is coextruded with seven or more other layers.

75. The method of claim 74, wherein the at least one of the two other layers is a coextruded layer that is coextruded with eight or more other layers.

76. The method of claim 75, wherein the at least one of the two other layers is a coextruded layer that is coextruded with nine or more other layers.

77. The method of claim 56, wherein the at least one of the two other layers is a coextruded layer that is coextruded with two or more other layers.

78. The method of claim 77, wherein the at least one of the two other layers is a coextruded layer that is coextruded with three or more other layers.

79. The method of claim 78, wherein the at least one of the two other layers is a coextruded layer that is coextruded with four or more other layers.

80. The method of claim 79, wherein the at least one of the two other layers is a coextruded layer that is coextruded with five or more other layers.

81. The method of claim 80, wherein the at least one of the two other layers is a coextruded layer that is coextruded with six or more other layers.

82. The method of claim 81 , wherein the at least one of the two other layers is a coextruded layer that is coextruded with seven or more other layers.

83. The method of claim 82, wherein the at least one of the two other layers is a coextruded layer that is coextruded with eight or more other layers.

84. The method of claim 83, wherein the at least one of the two other layers is a coextruded layer that is coextruded with nine or more other layers.

85. The method of claim 57, wherein the at least one of the two other layers is a coextruded layer that is coextruded with two or more other layers.

86. The method of claim 85, wherein the at least one of the two other layers is a coextruded layer that is coextruded with three or more other layers.

87. The method of claim 86, wherein the at least one of the two other layers is a coextruded layer that is coextruded with four or more other layers.

88. The method of claim 87, wherein the at least one of the two other layers is a coextruded layer that is coextruded with five or more other layers.

89. The method of claim 89, wherein the at least one of the two other layers is a coextruded layer that is coextruded with six or more other layers.

90. The method of claim 89, wherein the at least one of the two other layers is a coextruded layer that is coextruded with seven or more other layers.

91. The method of claim 90, wherein the at least one of the two other layers is a coextruded layer that is coextruded with eight or more other layers.

92. The method of claim 91 , wherein the at least one of the two other layers is a coextruded layer that is coextruded with nine or more other layers.

93. The method of claim 58, wherein the at least one of the two other layers is a coextruded layer that is coextruded with two or more other layers.

94. The method of claim 93, wherein the at least one of the two other layers is a coextruded layer that is coextruded with three or more other layers.

95. The method of claim 94, wherein the at least one of the two other layers is a coextruded layer that is coextruded with four or more other layers.

96. The method of claim 95, wherein the at least one of the two other layers is a coextruded layer that is coextruded with five or more other layers.

97. The method of claim 96, wherein the at least one of the two other layers is a coextruded layer that is coextruded with six or more other layers.

98. The method of claim 97, wherein the at least one of the two other layers is a coextruded layer that is coextruded with seven or more other layers.

99. The method of claim 98, wherein the at least one of the two other layers is a coextruded layer that is coextruded with eight or more other layers.

100. The method of claim 99, wherein the at least one of the two other layers is a coextruded layer that is coextruded with nine or more other layers.

101. A battery separator made by the method of claim 43.

102. A battery separator comprising a multilayer microporous film, which comprises: a first region comprising two or more layers, wherein the first region comprises mostly discontinuous amorphous regions when viewed in the z-direction of the film using SEM; and a

second region comprising at least one layer, wherein the second region comprises two or more layers and amorphous regions with a maximum width of 0.8 microns when viewed in the z-direction of the film using SEM.

103. The battery separator of claim 102, wherein the maximum width of the amorphous regions is 0.7 microns.

104. The battery separator of claim 103, wherein the maximum width of the amorphous regions is 0.6 microns.

105. The battery separator of claim 101 , wherein 50% or more, 60% or more, 70% or more, 80% or more, or 90% or more of the amorphous regions in the first region are discontinuous.

106. The battery separator of claim 101 , wherein at least one of the first and second regions comprises one or more layers that comprise a polyolefin.

107. The battery separator of claim 101 , wherein the first region comprises at least one layer that comprises polyethylene and the second region comprises at least one layer that comprises polypropylene.

108. The battery separator of claim 101 , wherein at least one of the first region and the second region comprises a co-extruded bi-layer, tri-layer, or multi-layer film.

109. The battery separator of claim 108, wherein the first region comprises a co-extruded bi-layer, tri-layer or multi-layer film.

110. The battery separator of claim 108 wherein the first region and the second region comprise a co-extruded bi-layer, tri-layer or multi-layer film.

111. The battery separator of claim 108 wherein the first region, the second, region, and a third region of the microporous multilayer battery separator each comprise a co-extruded bi-layer, tri-layer or multi-layer film. 2. The battery separator of claim 108 wherein at least one of the second and a third region of the microporous multilayer battery separator a co-extruded bi-layer, tri- layer or multi-layer film.

113. The battery separator of claim 112 wherein the second region comprises a co-extruded bi-layer, tri-layer or multi-layer film.

114. The battery separator of claim 112 wherein the third region comprises a co-extruded bi-layer, tri-layer or multi-layer film.

115. A battery separator comprising a multilayer microporous film that has an average dielectric breakdown value (V) that is higher than that of a tri-layer microporous film having the same thickness, Gurley and/or porosity as the multilayer microporous film.

116. The battery separator of claim 115, comprising a multilayer microporous film that has an average dielectric breakdown value (V) that is 1 to 35% higher than that of a tri-layer microporous film having the same thickness, Gurley and/or porosity as the multilayer microporous film. 7. The battery separator of claim 6, comprising a multilayer microporous film that has an average dielectric breakdown value (V) that is 5 to 35% higher than that of a tri-layer microporous film having the same thickness, Gurley and/or porosity as the multilayer microporous film.

118. The battery separator of claim 17, comprising a multilayer microporous film that has an average dielectric breakdown value (V) that is 10 to 35% higher than that of a tri-layer microporous film having the same thickness, Gurley and/or porosity as the multilayer microporous film.

119. The battery separator of claim 118, comprising a multilayer microporous film that has an average dielectric breakdown value (V) that is 15 to 35% higher than that of a tri-layer microporous film having the same thickness, Gurley and/or porosity as the multilayer microporous film.

120. The battery separator of claim 119, comprising a multilayer microporous film that has an average dielectric breakdown value (V) that is 20 to 35% higher than that of a tri-layer microporous film having the same thickness, Gurley, and/or porosity as the multilayer microporous film.

121. The battery separator of claim 115, wherein the minimum dielectric breakdown value of the multilayer microporous film is higher, for example, 3 to 20% higher, 5 to 15% higher, or 10 to 15% higher, than that of a tri-layer microporous film having the same thickness, Gurley, and/or porosity as the multilayer microporous film.

122. The battery separator of claim 116, wherein the minimum dielectric breakdown value of the multilayer microporous film is higher, for example, 3 to 20% higher, 5 to 15% higher, or 10 to 15% higher, than that of a tri-layer microporous film having the same thickness, Gurley, and/or porosity as the multilayer microporous film.

123. The battery separator of claim 117, wherein the minimum dielectric breakdown value of the multilayer microporous film is higher, for example, 3 to 20% higher, 5 to 15% higher, or 10 to 15% higher, than that of a tri-layer microporous film having the same thickness, Gurley, and/or porosity as the multilayer microporous film.

124. The battery separator of claim 118, wherein the minimum dielectric breakdown value of the multilayer microporous film is higher, for example, 3 to 20% higher, 5 to 15% higher, or 10 to 15% higher, than that of a tri-layer microporous film having the same thickness, Gurley, and/or porosity as the multilayer microporous film.

125. The battery separator of claim 119, wherein the minimum dielectric breakdown value of the multilayer microporous film is higher, for example, 3 to 20% higher, 5 to 5% higher, or 10 to 5% higher, than that of a tri-layer microporous film having the same thickness, Gurley, and/or porosity as the multilayer microporous film.

126. The battery separator of claim 120, wherein the minimum dielectric breakdown value of the multilayer microporous film is higher, for example, 3 to 20% higher, 5 to 15% higher, or 10 to 5% higher, than that of a tri-layer microporous film having the same thickness, Gurley, and/or porosity as the multilayer microporous film.

127. The battery separator of claim 115, wherein nine or more layers are present in the multilayer microporous film.

128. The battery separator of claim 121 , wherein nine or more layers are present in the multilayer microporous film.

129. The battery separator of claim 115, wherein twelve or more layers are present in the multilayer microporous film.

130. The battery separator of claim 21 , wherein twelve or more layers are present in the multilayer microporous film.

131. The battery separator of claim 115, wherein fifteen or more layers are present in the multilayer microporous film. 32. The battery separator of claim 121 , wherein fifteen or more layers are present in the multilayer microporous film.

133. The battery separator of claim 115, wherein eighteen or more layers are present in the multilayer microporous film.

134. The battery separator of claim 121 , wherein eighteen or more layers are present in the multilayer microporous film.

135. The battery separator of claim 115, wherein twenty-one or more layers are present in the multilayer microporous film.

136. The battery separator of claim 12 , wherein twenty-one or more layers are present in the multilayer microporous film.

137. The battery separator of claim 115, wherein twenty-four or more layers are present in the multilayer microporous film.

138. The battery separator of claim 121 , wherein twenty-four or more layers are present in the multilayer microporous film.

139. The battery separator of claim 115, wherein twenty-seven or more layers are present in the multilayer microporous film.

140. The battery separator of claim 121 , wherein twenty-seven or more layers are present in the multilayer microporous film.

141. The battery separator of claim 115, wherein thirty or more layers are present in the multilayer microporous film.

142. The battery separator of claim 121 , wherein thirty or more layers are present in the multilayer microporous film.

143. The battery separator of claim 115, wherein at least one of the layers of the multilayer microporous film comprise a polyolefin.

144. The battery separator of claim 121 , wherein at least one of the layers of the multilayer microporous film comprises a polyolefin or polyolefin blend.

145. The battery separator of claim 143, wherein at least one of the layers of the multilayer microporous film comprise polyethylene or a polyethylene blend. 46. The battery separator of claim 144, wherein at least one of the layers of the multilayer microporous film comprises polyethylene or a polyethylene blend.

147. The battery separator of claim 143, wherein at least one of the layers of the multilayer microporous film comprises polypropylene or a polypropylene blend.

148. The battery separator of claim 144, wherein at least one of the layers of the multilayer microporous film comprises polypropylene or a polypropylene blend.

149. The battery separator of claim 143, wherein at least one of the layers of the multilayer microporous film comprises polypropylene or a polypropylene blend and at least one of the layers comprises polyethylene or a polyethylene blend.

150. The battery separator of claim 115, wherein the multilayer microporous film comprises: a first region comprising two or more layers, wherein the first region comprises polypropylene and mostly discontinuous amorphous regions when viewed in the z- direction of the film using SEM; and

a second region comprising at least one layer.

151. The battery separator of claim 121 , wherein the multilayer microporous film comprises:

a first region comprising two or more layers, wherein the first region comprises polypropylene and mostly discontinuous amorphous regions when viewed in the z- direction of the film using SEM and

a second region comprising at least one layer.

152. The battery separator of claim 115, wherein the multilayer microporous film comprises:

a first region comprising two or more layers, wherein the first region comprises polypropylene and mostly discontinuous amorphous regions when viewed in the z- direction of the film using SEM;

a second region comprising at least one layer; and

a third region comprising at least one layer.

153. The battery separator of claim 121 , wherein the multilayer microporous film comprises: a first region comprising two or more layers, wherein the first region comprises polypropylene and mostly discontinuous amorphous regions when viewed in the z- direction of the film of the film using SEM;

a second region comprising at least one layer; and

a third region comprising at least one layer.

154. A battery separator comprising a multilayer microporous film that, when measured using mercury intrusion porosimetry, exhibits a peak mercury intrusion value of log differential intrusion 5ml_/g or less.

155. The battery separator of claim 154, wherein the peak mercury intrusion value is log differential intrusion 4.5mL/g or less.

156. The battery separator of claim 155, wherein the peak mercury intrusion value is log differential intrusion 4 mL/g or less.

157. The battery separator of claim 156, wherein the peak mercury intrusion value is log differential intrusion 3.5 mL/g or less.

158. A battery separator comprising a multilayer microporous film having a MacMillan number above 5.

159. The battery separator of claim 158, wherein the MacMillan number is above 5.5.

160. The battery separator of claim 159, wherein the MacMillan number is above 6.

161. The battery separator of claim 160, wherein the MacMillan number is above 7.

162. The battery separator of claim 161 , wherein the MacMillan number is above 7.5.

163. The battery separator of claim 162, wherein the MacMillan number is above 8.

164. The battery separator of claim 163, wherein the MacMillan number is above 9.

165. The battery separator of claim 164, wherein the MacMillan number is above 10.

166. A battery separator comprising a multilayer microporous film having a tortuosity value of 1.6 or higher

167. The battery separator of claim 166, wherein the tortuosity value is 1.7 or higher.

168. The battery separator of claim 167, wherein the tortuosity value is 2.0 or higher.

169. A battery separator comprising a multilayer microporous film having a pin removal force of less than 50 N.

170. The battery separator of claim 169, wherein the pin removal force is less than 40 N.

171. The battery separator of claim 170, wherein the pin removal force is less than 30 N.

172. The battery separator of claim 171 , wherein the pin removal force is less than 20 N.

173. The battery separator of claim 172, wherein the pin removal force is less than 15 N.

174. The battery separator of claim 172, wherein the pin removal force is less than 10 N.

175. A battery separator comprising a multilayer microporous film that comprises:

a first region comprising two or more layers;

a second region comprising two or more layers that is on a first side of the first region; and

a third region comprising two or more layers that is on a side of the first region opposite the first side,

wherein at least one of the first, second or third regions comprises PE and has a crystallinity that is lower, when measured by DSC, than a PE-containing layer of a trilayer microporous film, where the trilayer microporous film has the same thickness as the multilayer microporous film.

176. The battery separator according to claim 175, wherein the crystallinity is 1 to 20% lower.

177. The battery separator according to claim 175, wherein the crystallinity is 1 to 17% lower.

178. The battery separator according to claim 175, wherein the crystallinity is 1 to 10% lower.

179. The battery separator according to claim 175, wherein the crystallinity is 1 to 5% lower.

180. A battery separator comprising a multilayer microporous film comprising at least two regions or sublayers each including at least two microlayers and having a mixed penetration (N) value of greater than 380 N.

181. The battery separator of claim 180, wherein the mixed penetration (N) value is greater than 400 N.

182. The battery separator of claim 180, wherein the mixed penetration (N) value is greater than 450 N.

183. The battery separator of claim 180, wherein the mixed penetration (N) value is greater than 500 N.

184. The battery separator of claim 180, wherein the mixed penetration (N) value is greater than 550 N.

185. The battery separator of claim 180, wherein the mixed penetration (N) value is greater than 600 N.

186. The battery separator of claim 180, wherein the mixed penetration (N) value is greater than 650 N.

187. The battery separator of claim 180, wherein the mixed penetration (N) value is greater than 700 N.

188. A battery separator comprising a multilayer microporous film having an electrical resistance less than or equal to 2.0.

189. The battery separator of claim 188, wherein the electrical resistance is less than or equal to 1.7.

190. The battery separator of claim 189, wherein the electrical resistance is less than or equal to 1.6.

191. The battery separator of claim 190, wherein the electrical resistance is less than or equal to 1.5.

192. The battery separator of claim 191 , wherein the electrical resistance is less than or equal to 1.4.

193. The battery separator of claim 192, wherein the electrical resistance is less than or equal to 1.3.

194. The battery separator of claim 189, wherein the electrical resistance is less than or equal to 1.2.

195. The battery separator of claim 189, wherein the electrical resistance is less than or equal to 1.1.

196. The battery separator of claim 189, wherein the electrical resistance is less than or equal to 1.0.

197. A battery separator comprising a multilayer microporous film, the multilayer microporous film comprising a region, which comprises two or more layers and polyethylene in one or more of the layers, wherein when this region is tested according Machine Learning Test described herein, the following is satisfied:

Wx≥: -4 or W^Tx> -2.654 .

198. The battery separator of claim 197, wherein the following is satisfied:

W^Tx>1.3 or \Tx^'≥2.

199. A battery separator comprising a multilayer microporous film, the multilayer microporous film comprising a region, which comprises two or more layers and polypropylene in one or more of the layers, wherein when this region is tested according to the Machine Learning Test described herein, the following is satisfied:

Wx≥-5 or W^Tx^'≥ -3.

200. The battery separator of claim 199, wherein the following is satisfied:

W^Tx>0 orW^Tx> 3.

201. A battery separator comprising a microporous multilayer film having lower standard deviation value for the dielectric break down than a tri-layer microporous film having the same thickness, Gurley, and/or porosity as the multilayer microporous film.

202. The battery separator of claim 201 , wherein the standard deviation value is 10 to 60% lower.

203. The battery separator of claim 202, wherein the standard deviation value is 10 to 40% lower.

204. The battery separator of claim 201 , wherein the standard deviation value is 10 to 20% lower.

205. A battery separator having at least one multilayer microporous membrane or film having at least two regions or sublayers each including at least two microlayers, the multilayer membrane having or exhibiting at least one of following:

(a) mixed penetration (N) value greater than 380 N;

(b) mixed penetration (N) value greater than 600 N;

(c) a tortuosity of 1.8 or higher;

(d) an average dielectric breakdown value (V) that is 1 to 35% higher than that of a tri-layer microporous film having the same thickness, Gurley, and/or porosity as the multilayer microporous film;

(e) a minimum dielectric breakdown value (V) that is 3 to 20% higher than that of a tri-layer microporous membrane or film having the same thickness, Gurley, and/or porosity as the multilayer microporous membrane;

(f) having a standard deviation value for the dielectric break down that is 10 to 60% lower than that of a tri-layer microporous membrane or film having the same thickness, Gurley, and/or porosity as the multilayer microporous membrane

(g) that passes the nail penetration test;

(h) having at least one microlayer including, PO, PP and/or PE and an elastomer;

(i) having at least one microlayer including siloxane;

(j) having at least one microlayer that includes PP and an elastomer;

(k) having at least one microlayer including a co-polymer

(I) having at least one microlayer that includes PP and a co-polymer;

(m) having at least two microlayers that include different resins or resin blends; (n) when one of the regions comprises polypropylene in one or more of the microlayers, wherein when this region is tested according to the Machine Learning Test described herein, the following is satisfied:

(o) when one of the regions comprises polypropylene in one or more of the microlayers, wherein when this region is tested according to the Machine Learning Test described herein, the following is satisfied:

W^Tx^'> 0 or W^Tx^'≥ 3;

(p) when one of the regions comprises polyethylene in one or more of the microlayers, wherein when this region is tested according to the Machine Learning Test described herein, the following is satisfied:

W^Tx^'>-4 or W^Tx^'≥-2.654 ;

(q) when one of the regions comprises polyethylene in one or more of the microlayers, wherein when this region is tested according to the Machine Learning Test described herein, the following is satisfied:

\Ν^τχ≥1 .3 οτ Μ^χ≥2;

(r) wherein one of the regions comprises PE and has a crystallinity that is 1 to 20% lower, when measured by DSC, than that of a PE-containing layer of a tri-layer microporous membrane or film having the same thickness, Gurley, and/or porosity as the multilayer microporous film;

(s) the microporous multilayer membrane or film has 30 to 100 microlayers or more;

(t) wherein at least one of the microlayers comprises lithium stearate; (u) wherein the multilayer microporous film exhibits reduced MD or TD splittiness; (v) wherein at least one of the microlayers comprises PE beads;

(w) having a pin removal of less than 50 N;

(x) that exhibits reduced contact with pin;

(y) that has reduced MD or TD splittiness; and

(z) may be a precursor for at least one of transverse direction (TD) stretching, calendaring, and pore filling.

206. The battery separator of claim 205, wherein at least one side of the battery separator is coated.

207. The battery separator of claim 201 , wherein both sides of the battery separator are coated.

208. The battery separator of claim 201 , wherein at least one side is coated with a ceramic coating.