electrodes for energy storage devices

Abstract

The present invention provides an apparatus comprising electrodes for an energy storage device configured to exhibit excellent mechanical stability without requiring a bulk polymer binder. [Solution] An electrode active layer is disclosed comprising a network of high aspect ratio carbon elements (e.g., carbon nanotubes, graphene flakes, etc.) that entangle or intertwine with the active material, thereby providing a highly conductive scaffold that supports the layer. A surface treatment agent can be applied to the high aspect ratio carbon elements to promote adhesion to the active material and any underlying electrode layer, thereby improving the overall cohesiveness and mechanical stability of the active layer. This surface treatment agent forms only a thin (in some cases, even monomolecular) layer on the network and does not contain bulk binder material, thus leaving large voids that can instead be filled with the active material. The resulting active layer can be formed with excellent mechanical stability, even with large thickness and high active material mass loading.

Claims

1. It is a device, An electrode active layer, A network of high aspect ratio carbon elements, wherein voids are defined within the network, A plurality of electrode active material particles are disposed within the gaps in the network and are intertwined with the network, An apparatus comprising an electrode active layer comprising a surface treatment agent on the surface of the high aspect ratio carbon element that promotes adhesion between the high aspect ratio carbon element and the active material particles.

2. The apparatus according to the prior claim, wherein the high aspect ratio carbon element comprises an element having two main dimensions and one sub-dimension, and the ratio of the lengths of each of the main dimensions is at least 10 times that of the sub-dimension.

3. The apparatus according to any one of the prior claims, wherein the high aspect ratio carbon element comprises an element having two main dimensions and one sub-dimension, the ratio of the length of each of the main dimensions being at least 100 times that of the sub-dimension.

4. The apparatus according to any one of the prior claims, wherein the high aspect ratio carbon element comprises an element having two main dimensions and one sub-dimension, and the ratio of the length of each of the main dimensions is at least 1,000 times that of the sub-dimension.

5. The apparatus according to any one of the prior claims, wherein the high aspect ratio carbon elements each include an element having two main dimensions and one sub-dimension, and the ratio of the length of each of the main dimensions to that of the sub-dimension is at least 100,000 times.

6. The apparatus according to any one of the prior claims, wherein the high aspect ratio carbon elements each include an element having one main dimension and two sub-dimensions, and the ratio of the length of each main dimension to the length of each sub-dimension is at least 10 times that of each sub-dimension.

7. The apparatus according to any one of the prior claims, wherein the high aspect ratio carbon elements each include an element having one main dimension and two sub-dimensions, and the ratio of the length of each main dimension to the length of each sub-dimension is at least 100 times that of each sub-dimension.

8. The apparatus according to any one of the prior claims, wherein the high aspect ratio carbon elements each include an element having one main dimension and two sub-dimensions, and the ratio of the length of each main dimension to the length of each sub-dimension is at least 1,000 times that of each sub-dimension.

9. The apparatus according to any one of the prior claims, wherein the high aspect ratio carbon elements each include an element having one main dimension and two sub-dimensions, and the ratio of the length of each main dimension to the length of each sub-dimension is at least 10,000 times that of each sub-dimension.

10. The apparatus according to any one of the prior claims, wherein the high aspect ratio carbon element comprises a carbon nanotube or a bundle of carbon nanotubes.

11. The apparatus according to any one of the prior claims, wherein the high aspect ratio carbon element comprises graphene flakes.

12. The apparatus according to any one of the prior claims, wherein the electrode active layer contains less than 10% by weight of a polymer binder disposed in the void.

13. The apparatus according to any one of the prior claims, wherein the electrode active layer contains less than 1% by weight of a polymer binder disposed in the void.

14. The apparatus according to any one of the prior claims, wherein the electrode active layer contains less than 1% by weight of a polymer binder disposed in the void.

15. The apparatus according to any one of the prior claims, wherein the electrode active layer substantially contains polymer materials other than the surface treatment agent.

16. The apparatus according to any one of the prior claims, wherein the electrode active layer substantially does not contain a polymer material.

17. The apparatus according to any one of the prior claims, wherein the surface treatment agent comprises a material soluble in a solvent having a boiling point of less than 202°C.

18. The apparatus according to any one of the prior claims, wherein the surface treatment agent comprises a material soluble in a solvent having a boiling point of less than 185°C.

19. The apparatus according to any one of the prior claims, wherein during the formation of the active layer, the material forming the surface treatment agent is dissolved in a solvent having a boiling point of less than 202°C.

20. The apparatus according to any one of the prior claims, wherein, during the formation of the active layer, the material forming the surface treatment agent is dissolved in a solvent having a boiling point of less than 185°C.

21. The apparatus according to any one of the prior claims, wherein during the formation of the active layer, the material for forming the surface treatment agent is dissolved in a solvent containing isopropyl alcohol.

22. The apparatus according to any one of the prior claims, wherein during the formation of the active layer, the material forming the surface treatment agent is dissolved in a solvent that is substantially free of n-methyl-2-pyrrolidone.

23. The apparatus according to any one of the prior claims, wherein, during the formation of the active layer, the material forming the surface treatment agent is dissolved in a solvent substantially free of pyrrolidone compounds.

24. The apparatus according to any one of the prior claims, wherein the network is at least 90% by weight of carbon.

25. The apparatus according to any one of the prior claims, wherein the network is at least 95% by weight of carbon.

26. The apparatus according to any one of the prior claims, wherein the network is at least 99% by weight of carbon.

27. The apparatus according to any one of the prior claims, wherein the network is at least 99.9% by weight of carbon.

28. The apparatus according to any one of the prior claims, wherein the network includes an electrically interconnected network of carbon elements exhibiting connectivity exceeding a penetration threshold.

29. The apparatus according to any one of the prior claims, wherein the network defines one or more highly conductive paths.

30. The apparatus according to claim 29, wherein the aforementioned path has a length exceeding 100 μm.

31. The apparatus according to claim 29, wherein the aforementioned path has a length exceeding 1,000 μm.

32. The apparatus according to claim 29, wherein the aforementioned path has a length exceeding 10,000 μm.

33. The apparatus according to any one of the prior claims, wherein the network includes one or more structures formed from the carbon elements, and the structures have a total length of at least 10 times the length of the maximum dimension of the carbon elements.

34. The apparatus according to any one of the prior claims, wherein the network comprises one or more structures formed from the carbon elements, and the structures have a total length at least 100 times the length of the maximum dimension of the carbon elements.

35. The apparatus according to any one of the prior claims, wherein the network includes one or more structures formed from the carbon elements, and the structures have a total length of at least 1,000 times the length of the maximum dimension of the carbon elements.

36. The apparatus according to any one of the prior claims, wherein the surface treatment agent includes a surfactant layer disposed on the carbon element.

37. The apparatus according to claim 36, wherein the surfactant layer is bonded to the carbon element.

38. The apparatus according to claim 36 or 37, wherein the surfactant layer comprises a plurality of surfactant elements, each having a hydrophobic end and a hydrophilic end, the hydrophobic end being disposed proximally to one surface of the carbon element, and the hydrophilic end being disposed distally to one surface of the carbon element.

39. The apparatus according to claim 38, wherein the hydrophilic end of at least a portion of the surfactant element forms a bond with the active material particles.

40. The apparatus according to claim 39, wherein the bond includes an ionic bond.

41. The apparatus according to claim 39, wherein the bond includes a covalent bond.

42. The apparatus according to claim 39, wherein the bond includes at least one from the list consisting of π-π bonds, hydrogen bonds, and electrostatic bonds.

43. The hydrophilic end of the surfactant element has a polar charge of the first polarity, The apparatus according to claim 38, wherein the active material particles have a polar charge of a second polarity opposite to that of the first polarity.

44. The apparatus according to any one of claims 36 to 43, wherein the surfactant layer comprises a water-soluble surfactant.

45. The apparatus according to any one of claims 36 to 44, wherein the surfactant layer contains ions from hexadecyltrimethylammonium hexafluorophosphate.

46. The apparatus according to any one of claims 36 to 45, wherein the surfactant layer comprises an ion from at least one of the following: hexadecyltrimethylammonium tetrafluoroborate, N-(cocoalkyl)-N,N,N-trimethylammonium methyl sulfate, cocamidopropyl betaine hexadecyltrimethylammonium acetate, and hexadecyltrimethylammonium nitrate.

47. The apparatus according to any one of claims 36 to 46, wherein the surfactant layer includes a layer of surfactant ions formed by dissolving an ionic compound in a solvent.

48. The apparatus according to claim 47, wherein the active layer includes residual counterions for the surfactant ions formed by dissolving the ionic surfactant compound in a solvent.

49. The apparatus according to claim 48, wherein the counterions are selected to be suitable for use in an electrochemical cell.

50. The apparatus according to claim 49, wherein the counterion substantially does not contain a halide group.

51. The apparatus according to any one of claims 48 to 50, wherein the residual counterions substantially do not contain bromine.

52. The apparatus according to any one of claims 51, wherein the ionic surfactant compound comprises at least one selected from the list consisting of hexadecyltrimethylammonium tetrafluoroborate, hexadecyltrimethylammonium tetrafluoroborate, N-(cocoalkyl)-N,N,N-trimethylammonium methyl sulfate, cocamidopropyl betaine hexadecyltrimethylammonium acetate, and hexadecyltrimethylammonium nitrate.

53. The apparatus according to any one of the prior claims, wherein the carbon element is functionalized.

54. The apparatus according to claim 53, wherein the carbon element is functionalized with a surfactant material.

55. The apparatus according to claim 53 or 54, wherein the carbon element is functionalized with a functional group that promotes adhesion of active material particles to a network.

56. The apparatus according to claim 55, wherein the functional group comprises at least one from the list consisting of a carboxyl group, a hydroxyl group, an amine group, and a silane group.

57. The apparatus according to any one of claims 48 to 56, wherein the functionalized carbon element is formed from a dry aqueous dispersion containing nanoform carbon and a surfactant.

58. The apparatus according to claim 57, wherein the functionalized carbon element is formed from a freeze-dried aqueous dispersion containing nanoform carbon and a surfactant.

59. The apparatus according to claim 57 or 58, wherein the aqueous dispersion is substantially free of acid.

60. The apparatus according to any one of the prior claims, wherein the surface treatment agent includes a thin polymer layer disposed on the carbon element that promotes adhesion of the active material to the network.

61. The apparatus according to claim 60, wherein the thin polymer layer comprises a self-assembled polymer.

62. The apparatus according to claim 60 or 61, wherein the thin polymer layer is bonded to the active material via hydrogen bonds.

63. The apparatus according to any one of claims 60 to 62, wherein the thin polymer layer has a maximum thickness of 1 nm or less in the direction perpendicular to the outer surface of the network.

64. The apparatus according to any one of claims 60 to 63, wherein the thin polymer layer has a maximum thickness of 10 nm or less in the direction perpendicular to the outer surface of the network.

65. The apparatus according to any one of claims 60 to 64, wherein the thin polymer layer has a maximum thickness of 50 nm or less in a direction perpendicular to the outer surface of the network.

66. The apparatus according to any one of claims 60 to 65, wherein less than 1 volume percent of the voids defined by the network is filled with the thin polymer layer.

67. The apparatus according to any one of claims 60 to 66, wherein less than 0.1 volume percent of the voids defined by the network is filled with the thin polymer layer.

68. The apparatus according to any one of claims 60 to 67, wherein less than 0.1 volume percent of the voids defined by the network is filled with the thin polymer layer.

69. The apparatus according to any one of claims 1 to 35, wherein the surface treatment agent includes a layer of carbonaceous material formed from a pyrolysis polymer material.

70. The apparatus according to claim 69, wherein the layer of carbonaceous material formed from a pyrolysis polymer material promotes adhesion of active material particles to a network.

71. The apparatus according to any one of the prior claims, wherein the active material particles include a metal oxide.

72. The apparatus according to any one of the prior claims, wherein the active material particles include a lithium metal oxide.

73. The apparatus according to any one of the prior claims, wherein the active material is entangled in the network.

74. The apparatus according to any one of the prior claims, wherein the surface treatment agent promotes adhesion between the active material layer and the current collector layer.

75. The apparatus according to claim 74, wherein the surface treatment agent includes a functional group bonded to the current collector layer.

76. The apparatus according to claim 75, wherein the functional group is bonded to the current collector layer having non-covalent bonds.

77. The apparatus according to claim 75, wherein the functional group is bonded to the current collector layer having at least one selected from the list consisting of π-π bonds, hydrogen bonds, and ionic bonds.

78. The apparatus according to any one of claims 74 to 77, wherein the current collector includes a metal foil.

79. The apparatus according to any one of claims 74 to 77, wherein the active material layer has a thickness of at least 200 μm in the direction perpendicular to the current collector.

80. The apparatus according to any one of claims 74 to 77, wherein the active material layer has a thickness of at least 300 μm in the direction perpendicular to the current collector.

81. The apparatus according to any one of claims 74 to 77, wherein the active material layer has a thickness of at least 400 μm in the direction perpendicular to the current collector.

82. The system further comprises an energy storage cell, and the energy storage cell is A first electrode comprising the active material layer, The second electrode and A permeable separator disposed between the first electrode and the second electrode, The apparatus according to any one of the prior claims, comprising an electrolyte for wetting the first and second electrodes.

83. It is a method, The process involves dispersing high-aspect-ratio carbon elements and surface treatment agent materials in a solvent to form an initial slurry, wherein the dispersion step results in the formation of the surface treatment agent on the high-aspect-ratio carbon elements. The active material is mixed into the first slurry to form the final slurry, The final slurry is coated onto the substrate, A method comprising drying the final slurry to form an electrode active layer.

84. The method according to claim 83, wherein the high aspect ratio carbon element comprises an element having two main dimensions and one minor dimension, and the ratio of the lengths of each of the main dimensions is at least 10 times that of the minor dimension.

85. The method according to claim 83 or 84, wherein the high aspect ratio carbon element comprises an element having two main dimensions and one sub-dimension, the ratio of the length of each of the main dimensions to that of the sub-dimension being at least 100 times.

86. The method according to any one of claims 83 to 85, wherein the high aspect ratio carbon element comprises an element having two main dimensions and one sub-dimension, the ratio of the length of each of the main dimensions to that of the sub-dimension being at least 1,000 times.

87. The method according to any one of claims 83 to 86, wherein the high aspect ratio carbon element comprises an element having two main dimensions and one sub-dimension, the ratio of the length of each of the main dimensions to that of the sub-dimension is at least 100,000 times.

88. The method according to any one of claims 83 to 87, wherein the high aspect ratio carbon element comprises an element having one main dimension and two sub-dimensions, the ratio of the length of each main dimension to the length of each sub-dimension being at least 10 times that of each sub-dimension.

89. The method according to any one of claims 83 to 88, wherein the high aspect ratio carbon element comprises an element having one main dimension and two sub-dimensions, the ratio of the length of each main dimension to the length of each sub-dimension being at least 100 times.

90. The method according to any one of claims 83 to 89, wherein the high aspect ratio carbon element comprises an element having one main dimension and two sub-dimensions, the ratio of the length of each main dimension to the length of each sub-dimension being at least 1,000 times.

91. The method according to any one of claims 83 to 90, wherein the high aspect ratio carbon element comprises an element having one main dimension and two sub-dimensions, the ratio of the length of each main dimension to the length of each sub-dimension being at least 10,000 times that of each sub-dimension.

92. The method according to any one of claims 83 to 91, wherein the high aspect ratio carbon element comprises a carbon nanotube or a bundle of carbon nanotubes.

93. The method according to any one of claims 83 to 92, wherein the high aspect ratio carbon element comprises graphene flakes.

94. The method according to any one of claims 83 to 93, wherein the initial slurry has a solid content in the range of 0.1% by weight to 20.0% by weight.

95. The method according to any one of claims 83 to 94, wherein the final slurry has a solid content in the range of 10.0% to 80% by weight.

96. The method according to any one of claims 83 to 95, wherein the solvent has a boiling point of less than 202°C.

97. The method according to any one of claims 83 to 96, wherein the solvent has a boiling point of less than 185°C.

98. The method according to any one of claims 83 to 97, wherein the solvent has a boiling point of less than 125°C.

99. The method according to any one of claims 83 to 98, wherein the solvent has a boiling point of 100°C or lower.

100. The method according to any one of claims 83 to 99, wherein the solvent comprises at least one from the list consisting of methanol, ethanol, 2-propanol, and water.

101. The apparatus according to any one of claims 83 to 100, wherein, during the formation of the active layer, the material forming the surface treatment agent is dissolved in a solvent substantially free of pyrrolidone compounds.

102. The method according to any one of claims 83 to 101, wherein the solvent is substantially free of n-methyl-2-pyrrolidone.

103. The method according to any one of claims 83 to 102, wherein the surface treatment agent material includes a surfactant.

104. The method according to claim 103, wherein the surfactant is substantially free of halogen groups.

105. The method according to claim 104, wherein the surfactant is substantially free of bromine.

106. The method according to any one of claims 83 to 105, wherein forming the surface treatment agent includes forming a surfactant layer disposed on the carbon element.

107. The method according to any one of claims 83 to 106, wherein the surface treatment agent is a self-organized layer.

108. The method according to claim 106 or 107, wherein forming the surfactant layer includes arranging a plurality of surfactant elements on the surface of the carbon element, each of the surfactant elements having a hydrophobic end and a hydrophilic end, the hydrophobic end being located proximal to one surface of the carbon element, and the hydrophilic end being located distal to one surface of the carbon element.

109. The method according to claim 108, further comprising forming a bond with the active material particles at the hydrophobic end of at least a portion of the surfactant element.

110. The method according to claim 109, wherein the bond includes an ionic bond.

111. The method according to claim 109, wherein the bond includes a covalent bond.

112. The method according to claim 109, wherein the bond comprises at least one from the list consisting of π-π bonds, hydrogen bonds, and electrostatic bonds.

113. The hydrophilic end of the surfactant element has a polar charge of the first polarity, The method according to claim 108, wherein the active material particles have a polar charge of a second polarity opposite to that of the first polarity.

114. The method according to any one of claims 103 to 113, wherein the surfactant material comprises at least one selected from the list consisting of hexadecyltrimethylammonium tetrafluoroborate, hexadecyltrimethylammonium tetrafluoroborate, N-(cocoalkyl)-N,N,N-trimethylammonium methyl sulfate, cocamidopropyl betaine hexadecyltrimethylammonium acetate, and hexadecyltrimethylammonium nitrate.

115. The method according to any one of claims 83 to 114, wherein the initial slurry is formed by dispersing high aspect ratio carbon elements and a surface treatment agent material in a solvent, and the force applied to the aggregated carbon elements is used to slide the elements away from each other along a direction perpendicular to the short axis of the elements.

116. The method according to any one of claims 83 to 114, comprising drying the final slurry at a temperature below 202°C.

117. The method according to any one of claims 83 to 114, comprising drying the final slurry at a temperature of less than 185°C.

118. The method according to any one of claims 83 to 114, comprising drying the final slurry at a temperature of less than 125°C.

119. The method according to any one of claims 83 to 114, comprising drying the final slurry at a temperature of 100°C or less.

120. The method according to any one of claims 83 to 119, further comprising calendering the active layer to promote adhesion between the active material and the network.

121. It is a method, The process involves dispersing high-aspect-ratio carbon elements and surface treatment agent materials in an aqueous solvent to form an initial slurry, wherein the dispersion step results in the formation of the surface treatment agent on the high-aspect-ratio carbon elements. A method comprising drying the initial slurry to remove substantially all moisture, thereby producing a dry powder of the high aspect ratio carbon having the surface treatment agent on its surface.

122. The method according to claim 121, wherein drying the initial slurry includes freeze-drying the initial slurry.

123. The method according to claim 121 or claim 122, wherein the aqueous solvent and initial slurry substantially do not contain any substance that damages the high aspect ratio carbon elements.

124. The method according to claim 123, wherein the aqueous solvent and initial slurry are substantially acid-free.

125. The method according to claim 124, wherein the initial slurry essentially consists of the high aspect ratio carbon element, the surface treatment agent material, and water.

126. Dispersing the dried powder of the high aspect ratio carbon together with the surface treatment agent in a solvent, and adding it, and an active material for forming a secondary slurry, The secondary slurry is coated onto the substrate, The method according to any one of claims 121 to 125, further comprising drying the secondary slurry to form an electrode active layer.

127. The method according to any one of claims 121 to 126, wherein the high aspect ratio carbon element comprises an element having two main dimensions and one minor dimension, and the ratio of the lengths of each of the main dimensions is at least 10 times that of the minor dimension.

128. The method according to any one of claims 121 to 127, wherein the high aspect ratio carbon element comprises an element having two main dimensions and one sub-dimension, and the ratio of the length of each of the main dimensions is at least 100 times that of the sub-dimension.

129. The method according to any one of claims 121 to 128, wherein the high aspect ratio carbon element comprises an element having two main dimensions and one sub-dimension, and the ratio of the length of each of the main dimensions is at least 1,000 times that of the sub-dimension.

130. The method according to any one of claims 121 to 129, wherein the high aspect ratio carbon element comprises an element having two main dimensions and one sub-dimension, and the ratio of the length of each of the main dimensions is at least 10,000 times that of the sub-dimension.

131. The method according to any one of claims 121 to 130, wherein the high aspect ratio carbon element comprises an element having one main dimension and two sub-dimensions, the ratio of the length of each main dimension to the length of each sub-dimension being at least 10 times that of each sub-dimension.

132. The method according to any one of claims 121 to 131, wherein the high aspect ratio carbon element comprises an element each having one main dimension and two sub-dimensions, and the ratio of the length of each main dimension to the length of each sub-dimension is at least 100 times that of each sub-dimension.

133. The method according to any one of claims 121 to 132, wherein the high aspect ratio carbon element comprises an element having one main dimension and two sub-dimensions, and the ratio of the length of each main dimension to the length of each sub-dimension is at least 1,000 times that of each sub-dimension.

134. The method according to any one of claims 121 to 133, wherein the high aspect ratio carbon element comprises a carbon nanotube or a bundle of carbon nanotubes.

135. The method according to any one of claims 121 to 134, wherein the high aspect ratio carbon element comprises graphene flakes.

136. The method according to any one of claims 121 to 135, wherein the solvent has a boiling point of less than 202°C.

137. The method according to any one of claims 121 to 135, wherein the solvent has a boiling point of less than 185°C.

138. The method according to any one of claims 121 to 135, wherein the solvent has a boiling point of less than 125°C.

139. The method according to any one of claims 121 to 135, wherein the solvent has a boiling point of 100°C or lower.

140. The method according to claims 121 to 139, wherein the secondary solvent comprises at least one from the list consisting of methanol, ethanol, 2-propanol, and water.

141. The method according to any one of claims 121 to 140, wherein the secondary solvent is substantially free of pyrrolidone compounds.

142. The method according to any one of claims 121 to 141, wherein the secondary solvent is substantially free of n-methyl-2-pyrrolidone.

143. The method according to any one of claims 121 to 142, wherein the surface treatment agent material includes a surfactant.

144. The method according to claim 143, wherein the surfactant is substantially free of halogen groups.

145. The method according to claim 144, wherein the surfactant is substantially free of bromine.

146. The method according to any one of claims 121 to 145, wherein forming the surface treatment agent includes forming a surfactant layer disposed on the carbon element.

147. The method according to claim 146, wherein the surfactant layer is a self-assembled layer.

148. The method according to any one of claims 126 to 147, comprising drying the secondary slurry at a temperature of less than 202°C.

149. The method according to any one of claims 126 to 147, comprising drying the secondary slurry at a temperature of less than 185°C.

150. The method according to any one of claims 126 to 147, comprising drying the secondary slurry at a temperature of less than 125°C.

151. The method according to any one of claims 126 to 147, comprising drying the secondary slurry at a temperature of 100°C or lower.

152. The method according to any one of claims 121 to 151, further comprising calendering the active layer to promote adhesion.

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