A composite pole piece and its application

Abstract

The present invention provides a composite pole piece and its application. The composite pole piece of the present invention comprises a current collector, at least one surface of the current collector comprises an active layer region, the active layer region is provided with an active layer, wherein at least one of the active layers is a first active layer; the first active layer comprises an edge portion, part or all of the edge portion is a capacitor material layer, and the rest of the first active layer is a battery material layer. The composite pole piece can enable the battery to have relatively excellent energy density, rate performance, cycle expansion performance and cycle performance.

Description

Technical Field

[0001] The invention relates to a composite pole piece and application thereof, belonging to the field of batteries. Background Art

[0002] Nowadays, lithium-ion batteries have become energy storage devices for mainstream electronic products, and people's requirements for the comprehensive performance of lithium-ion batteries have also increased. However, the existing active materials for lithium-ion batteries can only meet the requirements of higher energy density, and there is still room for improvement in the rate performance of lithium-ion batteries. Studies have found that the capacitor materials used to prepare lithium-ion capacitors have greater ion adsorption performance, which can improve the rate performance of the battery.

[0003] Therefore, the prior art mixes capacitor materials with conductive agents and binders to prepare capacitor layers, so that the active layer in the electrode includes alternately stacked capacitor layers and conventional active material layers. Although this technical means can improve the rate performance of the battery without losing the energy density of the battery, the electrode still has the problem of local lithium deposition in the electrode during long-term charging and discharging, which in turn affects the cycle performance of the battery.

[0004] Therefore, there is an urgent need to provide a pole piece that can enable the battery to have both excellent rate performance and cycle performance without sacrificing the energy density of the battery. Summary of the invention

[0005] The present invention provides a composite pole piece, which can enable a battery to have both excellent rate performance and cycle performance without losing the energy density of the battery.

[0006] The present invention provides an electrode assembly, which includes the above-mentioned composite pole piece, so that the battery can have both excellent rate performance and cycle performance without losing the energy density of the battery.

[0007] The present invention provides a battery, which includes the above-mentioned electrode assembly, so that the battery can have excellent rate performance and cycle performance while having a higher energy density.

[0008] The present invention provides a composite pole piece, comprising a current collector, wherein at least one surface of the current collector comprises an active layer region, wherein the active layer region is provided with an active layer, wherein at least one of the active layers is a first active layer;

[0009] The first active layer includes an edge portion, part or all of the edge portion is a capacitor material layer, and the rest of the first active layer is a battery material layer.

[0010] The composite pole piece as described above, wherein the active layer region is provided with an active layer, and the active layer is a first active layer.

[0011] The composite pole piece as described above, wherein the active layer region includes N stacked active layers, at least one of the N active layers is a first active layer, and N≥2.

[0012] The composite pole piece as described above, wherein the N active layers further include a second active layer,

[0013] The second active layer is selected from a full capacitor material layer and / or a full battery material layer.

[0014] The composite pole piece as described above, wherein the first active layer is a full capacitor material layer; and / or the Nth active layer is a full capacitor material layer.

[0015] The composite pole piece as described above, wherein the current collector further comprises a pole ear region;

[0016] The tab region is located at an edge of the surface of the current collector extending along the first direction, and the size of the tab region in the second direction is equal to the size of the current collector in the second direction;

[0017] The tab region and the active layer region are distributed on the surface of the current collector in the second direction.

[0018] The composite pole piece as described above, wherein the active layer region is provided with an active layer, and the active layer is a first active layer;

[0019] At least the edge portion close to the tab region is a capacitor material layer.

[0020] The composite pole piece as described above, wherein the current collector further comprises a pole ear region;

[0021] The tab region is located at an edge of the surface of the current collector extending along the first direction, and a size of the tab region in the second direction is smaller than a size of the current collector in the second direction;

[0022] The active layer area is arranged around the outer periphery of the tab area.

[0023] The composite pole piece as described above, wherein the active layer region is provided with an active layer, and the active layer is a first active layer;

[0024] The active layer region includes a first area close to the periphery of the tab region, and the capacitor material layer is at least located in the first area.

[0025] The present invention also provides an electrode assembly, which includes the composite electrode sheet as described above.

[0026] The electrode assembly as described above, wherein the electrode assembly comprises a first peripheral electrode sheet group, an intermediate electrode sheet group, and a second peripheral electrode sheet group stacked in a thickness direction;

[0027] The number of pole pieces in the first peripheral pole piece group is equal to the number of pole pieces in the second peripheral pole piece group, the intermediate pole piece group is a capacitor pole piece, and at least one pole piece in the first peripheral pole piece group and / or the second peripheral pole piece group is the composite pole piece.

[0028] The present invention also provides a battery, comprising the electrode assembly as described above.

[0029] The composite pole piece provided by the present invention has at least one surface of the current collector of the composite pole piece including an active layer area, the active layer area is provided with an active layer, the active layer includes a first active layer, part or all of the edge of the first active layer is a capacitor material layer, and the rest is a battery material layer. The capacitor material layer has a large ion adsorption capacity, which can improve the rate performance of the battery. Furthermore, when the capacitor material layer is located at part or all of the edge of the first active layer, the capacitor material layer can improve the kinetic performance of the edge, so that the lithium ions enriched in the edge can be fully deintercalated, avoiding lithium precipitation at the edge, and improving the cycle performance of the battery; and the battery material layer can ensure the energy density of the battery. Therefore, the composite pole piece of the present invention can ensure that the battery has both excellent rate performance and cycle performance while ensuring the energy density of the battery.

[0030] The electrode assembly provided by the present invention includes the above-mentioned composite pole piece, so the electrode assembly can not only ensure the energy density of the battery, but also enable the battery to have excellent rate performance, and the edge of the electrode assembly is not easy to deposit lithium, and the cycle performance of the battery can also be improved.

[0031] The battery provided by the present invention includes the above-mentioned electrode assembly, so the battery can have excellent cycle performance and rate performance without losing energy density, and is suitable for wide application and promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the following briefly introduces the drawings required for use in the embodiments of the present invention or related technologies. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0033] Figure 1 A side view of a composite pole piece according to a first embodiment of the present invention;

[0034] Figure 2A top view of the first active layer in some embodiments of the present invention;

[0035] Figure 3 A side view of a composite pole piece according to a second embodiment of the present invention;

[0036] Figure 4 is a side view of a composite pole piece according to a third embodiment of the present invention;

[0037] Figure 5 is a side view of a composite pole piece according to a fourth embodiment of the present invention;

[0038] Figure 6 A top view of a composite pole piece according to a fourth embodiment of the present invention;

[0039] Figure 7 A top view of a composite pole piece according to a fifth embodiment of the present invention;

[0040] Figure 8 Schematic diagram of the structure of the electrode assembly in some embodiments of the present invention.

[0041] Description of reference numerals:

[0042] 1: first active layer;

[0043] 2: Current collector;

[0044] 3: second active layer;

[0045] 4: the first peripheral pole piece group;

[0046] 5: the second peripheral pole piece group;

[0047] 6: middle pole piece group;

[0048] 11: Battery material layer;

[0049] 12: Capacitor material layer;

[0050] 21: Pole ear area;

[0051] 22: active layer area;

[0052] 221: The first area. DETAILED DESCRIPTION

[0053] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0054] Figure 1 A side view of a composite pole piece according to a first embodiment of the present invention; Figure 2 FIG. 1 is a top view of the first active layer in some embodiments of the present invention. Figure 1 and Figure 2 As shown, the first aspect of the present invention provides a composite pole piece, comprising a current collector 2, at least one surface of the current collector 2 comprises an active layer region 22, the active layer region 22 is provided with an active layer, wherein at least one active layer is a first active layer 1;

[0055] The first active layer 1 includes an edge portion, part or all of which is a capacitor material layer 12 , and the rest of the first active layer 1 is a battery material layer 11 .

[0056] The present invention does not specifically limit the current collector 2, and a current collector 2 commonly used in the art can be selected. In some embodiments, the current collector 2 can be a metal foil, a composite foil of a metal and a polymer, or other composite foils with high conductivity. The current collector 2 can also be various foils including a conductive layer, the thickness of the current collector 2 can be 4-50 μm, the thickness of the conductive layer can be 0.5-5 μm, and further, the thickness of the conductive layer can be 5-20 μm. The current collector 2 can also be a foil with through holes in the thickness direction, or a foil with an etched surface.

[0057] In the present invention, the current collector 2 has two surfaces with the largest area and arranged opposite to each other. At least one surface of the current collector 2 includes an active layer region 22 for arranging an active layer, and the active layer is used for inserting and extracting lithium ions to ensure the normal operation of the composite electrode.

[0058] In the present invention, at least one active layer is the first active layer 1, and the first active layer 1 has two active layer surfaces with the largest area and arranged opposite to each other, and four side surfaces, and the positions of the four side surfaces are the edges of the first active layer. The first active layer 1 of the present invention has a first edge and a second edge in the first direction, and a third edge and a fourth edge in the second direction, and the first direction is perpendicular to the second direction. It can be understood that if the first direction is the length direction of the current collector 2, the second direction is the width direction of the current collector 2; if the first direction is the width direction of the current collector 2, the second direction is the length direction of the current collector 2. In the present invention, the portion of the first active layer 1 close to the first edge, the second edge, the third edge and the fourth edge is called an edge portion.

[0059] In the following, the technical solution of the present invention is exemplified with the first direction being the length direction of the current collector 2 and the second direction being the width direction of the current collector 2. In the first active layer 1 of the present invention, there are two edge portions arranged along the first direction, two edge portions arranged along the second direction, and a center portion surrounded by four edge portions. Among these four edge portions, at least one edge portion may be provided with a capacitor material layer 12, or at least part of at least one edge portion may be provided with a capacitor material layer 12. For example, when a capacitor material layer 12 is provided on an edge portion, the remaining three edge portions and the center portion are the rest, and the battery material layer 11 is provided on the rest; when a portion of an edge portion is provided with a capacitor material layer 12, the other portions of this edge portion, the other three edge portions and the center portion are the rest, and the battery material layer 11 is provided on the rest.

[0060] The present invention does not impose any particular limitation on the specific size of the edge portion.

[0061] like Figure 1 As shown, taking an edge portion arranged along the second direction as an example, the size L1 of the edge portion in the first direction and the size La of the current collector 2 in the first direction satisfy L1 / La=5-50%. In a specific embodiment, L1=5-200mm. It can be understood that another edge portion arranged along the second direction has the same definition as above. Similarly, the size L2 of the two edge portions arranged along the first direction respectively satisfies L2 / Lb=5-50% with the size Lb of the current collector 2 in the second direction. In a specific embodiment, L2=5-200mm.

[0062] It should be emphasized that the four edge portions may satisfy the above-mentioned limitations at the same time, or may be different from each other.

[0063] In the present invention, the capacitor material layer 12 includes a capacitor material, which has a large ion adsorption capacity, can enable lithium ions to be quickly deintercalated and deintercalated, and improve the rate performance of the battery. The capacitor material of the present invention can be selected from capacitor materials commonly used in the art, for example, the capacitor material is at least one of activated carbon, graphene, porous carbon and other porous materials. It is understood that the capacitor material layer 12 may also include a binder, a conductive agent and other functional additives.

[0064] In the present invention, the battery material layer 11 includes battery active materials, which are positive electrode active materials or negative electrode active materials commonly used in lithium ion batteries in the field. The battery materials can make the battery have excellent energy density. Among them, the positive electrode active material can be at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium manganese oxide and lithium-rich manganese-based materials; the negative electrode active material can be at least one of artificial graphite, natural graphite, mesophase carbon microbeads, petroleum coke, hard carbon and silicon-based negative electrodes. It can be understood that the battery material layer 11 can also include a binder, a conductive agent and other functional additives.

[0065] In the present invention, the binder can be selected from any material having a bonding effect, for example, the binder is a polymer material such as resin or rubber; the conductive agent can be selected from at least one of conductive carbon black, carbon nanotubes and graphene; other functional additives can be various additives for improving battery performance, for example, dispersants.

[0066] It can be understood that the composite electrode sheet of the present invention can be a composite positive electrode sheet or a composite negative electrode sheet. When the composite electrode sheet is a composite positive electrode sheet, the composite positive electrode sheet includes a positive electrode current collector, at least one surface of the positive electrode current collector includes an active layer area 22, the active layer area 22 is provided with an active layer, at least one active layer is a first active layer 1, the first active layer 1 includes an edge portion, part or all of the edge portion is a capacitor material layer 12, and the rest of the first active layer 1 is a positive electrode active material layer. When the composite electrode sheet is a composite negative electrode sheet, the composite negative electrode sheet includes a negative electrode current collector, at least one surface of the negative electrode current collector includes an active layer area 22, the active layer area 22 is provided with an active layer, at least one active layer is a first active layer 1, the first active layer 1 includes an edge portion, part or all of the edge portion is a capacitor material layer 12, and the rest of the first active layer 1 is a negative electrode active material layer.

[0067] In the present invention, the capacitor material layer 12 has a large ion adsorption capacity and can improve the rate performance of the battery. When the capacitor material layer 12 is located in part or all of the edge of the first active layer 1, the capacitor material layer 12 can improve the kinetic performance of the edge, so that the lithium ions enriched in the edge can be fully deintercalated, avoiding lithium precipitation in the edge, and improving the cycle performance of the battery; at the same time, the rest of the first active layer 1 is the battery material layer 11, and the battery material layer 11 helps to improve the energy density of the battery. Therefore, the present invention can obtain a composite electrode that does not lose the energy density of the battery and can make the battery have both excellent cycle performance and rate performance by matching the capacitor material layer 12 and the battery material layer 11.

[0068] like Figure 1 As shown, in some embodiments of the present invention, the active layer region 22 is provided with an active layer, and the active layer is a first active layer 1 .

[0069] Figure 3 A side view of a composite pole piece according to a second embodiment of the present invention; Figure 4 FIG. 1 is a side view of a composite electrode according to a third embodiment of the present invention. Figure 3 or Figure 4 As shown, in some embodiments of the present invention, the active layer region 22 includes N stacked active layers, at least one of the N active layers is a first active layer 1, and N≥2.

[0070] The present invention does not limit the specific position and number of the first active layer 1 in the N active layers, as long as at least one of the N active layers is the first active layer 1 .

[0071] like Figure 3 or Figure 4 As shown, in some embodiments of the present invention, the N active layers further include a second active layer 3,

[0072] The second active layer 3 is selected from a full capacitor material layer and / or a full battery material layer.

[0073] In the present invention, a full capacitor material layer refers to an active layer whose entire layer is a capacitor material layer, and a full battery material layer refers to an active layer whose entire layer is a battery material layer. It can be understood that the second active layer 3 is an active layer without partitions, including capacitor material or battery material.

[0074] It can be understood that the N active layers include a first active layer 1 and a second active layer 3 which are stacked. The present invention does not limit the stacking order of the first active layer 1 and the second active layer 3. The first active layer 1 and the second active layer 3 may be stacked alternately, or the first active layer 1 and the second active layer 3 may be stacked without any interval. For example, when N=4, the active layer may be obtained by stacking the first active layer 1, the second active layer 3, the first active layer 1, and the second active layer 3 in sequence; the active layer may also be obtained by stacking the first active layer 1, the first active layer 1, the second active layer 3, and the second active layer 3.

[0075] like Figure 4 As shown, in some embodiments of the present invention, the first active layer is a full capacitor material layer; and / or, the Nth active layer is a full capacitor material layer.

[0076] It can be understood that when N≥2, the first active layer is an active layer disposed on the surface of the current collector 2, and the Nth active layer is an active layer disposed on the outermost side of the composite pole piece. When the N active layers include a first active layer 1 and a second active layer 3 stacked in layers, the active layer disposed on the surface of the current collector 2 is a full capacitor material layer; and / or, the outermost active layer of the composite pole piece is a full capacitor material layer.

[0077] On the one hand, when the battery is charged and discharged, the temperature of the area near the surface of the current collector 2 in the composite pole piece is relatively high, so the speed of lithium ion deintercalation is relatively fast. When the active layer disposed on the surface of the current collector 2 is a full capacitor material layer, the full capacitor material layer can improve the dynamic performance of the area near the surface of the current collector 2, so as to match the deintercalation speed of lithium ions in the area near the surface of the current collector 2 in the composite pole piece, avoid polarization of the area near the surface of the current collector 2, and improve the cycle performance of the battery. On the other hand, the outermost active layer of the composite pole piece is enriched with lithium ions. When the outermost active layer of the composite pole piece is a full capacitor material layer, the full capacitor material layer can improve the dynamic performance of the outermost active layer of the composite pole piece, enable the lithium ions enriched in the outermost active layer to be fully deintercalated, avoid lithium ion enrichment on the outermost side of the composite pole piece, and improve the cycle performance of the battery.

[0078] Therefore, in a preferred embodiment, the first active layer is a full capacitor material layer; and the Nth active layer is a full capacitor material layer.

[0079] The present invention does not limit the thickness of the full capacitor material layer arranged on the surface of the current collector 2 and the thickness of the full capacitor material layer arranged on the outermost side of the composite pole piece. In some embodiments, the thickness H1 of the full capacitor material layer arranged on the surface of the current collector 2 and the total thickness H of the active layer can satisfy: H1 / H=5-50%. In a specific embodiment, H1=1-150μm; in some embodiments, the thickness H2 of the capacitor material layer arranged on the outermost side of the composite pole piece and the total thickness H of the active layer can satisfy: H2 / H=5-50%. In a specific embodiment, H2=1-150μm.

[0080] In the present invention, the total thickness of the active layer can be understood as the thickness of the active layer arranged on one surface of the current collector 2. The present invention does not specifically limit the total thickness of the active layer. In some embodiments, the total thickness of the active layer arranged on one surface of the current collector 2 can be 20-250 μm.

[0081] In one embodiment, as long as the first active layer in the composite pole piece is a full capacitor material layer; and / or the Nth active layer in the composite pole piece is a full capacitor material layer, the composite pole piece can also enable the battery to have excellent cycle performance, rate performance and energy density. When the thickness of the first active layer and / or the thickness of the Nth active layer satisfies the above relationship, it helps to further improve the performance of the composite pole piece.

[0082] In the present invention, the active layer can be disposed on the surface of the current collector by using a coating method such as gravure coating, extrusion coating or transfer coating. The active layers on both surfaces of the current collector 2 can be symmetrical or asymmetrical.

[0083] Figure 5 is a side view of a composite pole piece according to a fourth embodiment of the present invention; Figure 6 FIG. 4 is a top view of a composite electrode according to a fourth embodiment of the present invention. Figure 5 or Figure 6 As shown, in some embodiments of the present invention, the current collector 2 further includes a tab region 21;

[0084] The tab region 21 is located at an edge of the surface of the current collector 2 extending along the first direction, and the size of the tab region 21 in the second direction is equal to the size of the current collector 2 in the second direction;

[0085] The tab region 21 and the active layer region 22 are distributed on the surface of the current collector 2 in the second direction.

[0086] It can be understood that in the present invention, the surface of the current collector 2 has two edges extending along the first direction, and the tab region 21 is located at any one of the edges. That is, the current collector 2 of the present invention includes the tab region 21 and the active layer region 22 connected to each other in the second direction, and the tab is arranged in the tab region 21 and extends in the first direction.

[0087] like Figure 5 or Figure 6 As shown, in some embodiments of the present invention, the active layer region 22 is provided with an active layer, and the active layer is a first active layer 1;

[0088] At least the edge portion close to the tab region 21 is the capacitor material layer 12 .

[0089] In the present invention, when the active layer region 22 is provided with an active layer, the active layer is the first active layer 1 , and the capacitor material layer 12 in the first active layer 1 is close to the edge of the tab region 21 .

[0090] It can be understood that the pole ear set in the pole ear area 21 is used to extract electrons in the battery, so the current density near the edge of the pole ear area 21 is relatively concentrated, so that at least the edge near the pole ear area 21 is a capacitor material layer 12. The capacitor material layer 12 can improve the dynamic performance of the edge near the pole ear area 21, so that more lithium ions near the edge of the pole ear area 21 can be deintercalated, thereby dispersing the current density near the edge of the pole ear area 21 and improving the cycle performance of the battery.

[0091] Figure 7 FIG. 1 is a top view of a composite electrode according to a fifth embodiment of the present invention. Figure 7 As shown, in some embodiments of the present invention, the current collector 2 further includes a tab region 21;

[0092] The tab region 21 is located at an edge of the surface of the current collector 2 extending along the first direction, and the size of the tab region 21 in the second direction is smaller than the size of the current collector 2 in the second direction;

[0093] The active layer region 22 is disposed around the outer periphery of the tab region 21 .

[0094] It is understood that the tab region 21 can be disposed at any position of an edge extending along the first direction. In some embodiments, the tab region 21 has two ends in the first direction, and the two ends are spaced from two edges of the surface of the current collector 2 extending along the second direction.

[0095] like Figure 7 As shown, in some embodiments of the present invention, the active layer region 22 is provided with an active layer, and the active layer is a first active layer 1;

[0096] The active layer region 22 includes a first region 221 close to the outer periphery of the tab region 21 , and the capacitor layer is at least located in the first region 221 .

[0097] In the present invention, when the active layer region 22 is provided with an active layer, the active layer is the first active layer 1 , and the capacitor material layer 12 in the first active layer 1 is at least provided on the periphery of the tab region 21 .

[0098] It can be understood that the lugs provided in the lug area 21 are used to extract electrons from the battery, so the current density at the periphery of the lug area 21 is relatively concentrated, making the periphery of the lug area 21 a capacitor material layer 12. The capacitor material layer 12 can improve the dynamic performance of the periphery of the lug area 21, so that more lithium ions at the periphery of the lug area 21 can be deintercalated, thereby dispersing the current density at the periphery of the lug area 21 and improving the cycle performance of the battery.

[0099] In the present invention, in the first direction, the tab region 21 has one periphery, and in the second direction, the tab region 21 has two peripheries. The present invention does not limit the size of the periphery of the tab region 21.

[0100] Taking an outer periphery extending in the first direction as an example, the dimension L3 of the outer periphery in the second direction satisfies L3 / La=5-50% with the dimension La of the current collector 2 in the second direction. In a specific embodiment, L3=5-200mm. It can be understood that the dimensions L4 of the two outer peripheries extending in the second direction respectively satisfy L4 / Lb=5-50% with the dimension Lb of the current collector 2 in the first direction. In a specific embodiment, L4=5-200mm. It should be emphasized that the three outer peripheries can meet the above-mentioned limitations at the same time or they can be different from each other.

[0101] A second aspect of the present invention provides an electrode assembly, comprising the above-mentioned composite electrode sheet.

[0102] It is understood that the electrode assembly of the present invention can be a wound electrode assembly or a laminated electrode assembly. The electrode assembly includes a stacked positive electrode sheet, a separator and a negative electrode sheet, wherein the positive electrode sheet and / or the negative electrode sheet includes at least one composite electrode sheet of the present invention.

[0103] The present invention does not specifically limit the diaphragm, and a diaphragm commonly used in the art can be selected. In some embodiments, the diaphragm can be a porous membrane such as polyethylene or aramid; the diaphragm can also be a porous membrane with a glue layer or a ceramic layer on at least one surface. In the present invention, the thickness of the diaphragm can be 5-30 μm, and the thickness of the glue layer or the ceramic layer can be 0.5-5 μm. Furthermore, the diaphragm is a porous membrane provided with a glue layer or a ceramic layer, and the thickness of the diaphragm is 5-15 μm.

[0104] When the electrode assembly is a winding structure, the active layer of at least one electrode piece in the electrode assembly near the winding center is a capacitor material layer 12; and / or, the active layer of at least one electrode piece in the electrode assembly near the pole ear area 21 is a capacitor material layer; and / or, the active layer on the surface of the electrode assembly is a capacitor material layer, and the electrode assembly has excellent rate performance, energy density and cycle performance.

[0105] When the electrode assembly is a laminated structure, Figure 8 Schematic diagram of the structure of the electrode assembly in some embodiments of the present invention. Figure 8 As shown, in some embodiments of the present invention, the electrode assembly includes a first peripheral pole piece group 4, an intermediate pole piece group 6 and a second peripheral pole piece group 5 which are stacked in the thickness direction;

[0106] The number of pole pieces in the first peripheral pole piece group 4 is equal to the number of pole pieces in the second peripheral pole piece group 5, the intermediate pole piece group 6 is a capacitor pole piece, and at least one pole piece in the first peripheral pole piece group 4 and / or the second peripheral pole piece group 5 is a composite pole piece.

[0107] It can be understood that the pole pieces other than the first peripheral pole piece group 4 and the second peripheral pole piece group 5 are the intermediate pole piece group 6 .

[0108] In the present invention, the capacitor electrode sheet includes a current collector 2 and a capacitor layer disposed on at least one surface of the current collector 2. When the current collector 2 is a positive electrode current collector, the capacitor electrode sheet can be used as a positive electrode sheet, and when the current collector 2 is a negative electrode current collector, the capacitor electrode sheet can be used as a negative electrode sheet.

[0109] The present invention does not specifically limit the first peripheral electrode sheet group 4 and the second peripheral electrode sheet group 5 , and they may be any positive electrode sheet and negative electrode sheet.

[0110] When the lithium-ion battery is charged and discharged, the temperature of the area where the intermediate electrode group 6 is located is higher, so the speed of lithium ion deintercalation is faster. When the intermediate electrode group 6 is a capacitor electrode, the capacitor electrode can improve the dynamic performance of the area where the intermediate electrode group 6 is located. The capacitor electrode can match the deintercalation speed of lithium ions in the area where the intermediate electrode group 6 is located, avoid polarization in the area where the intermediate electrode group 6 is located, and improve the cycle performance of the battery.

[0111] The present invention does not limit the number of pole pieces in the intermediate pole piece group 6. In some embodiments, the number M1 of pole pieces in the intermediate pole piece group 6 is 1-20; and / or the number M1 of pole pieces in the intermediate pole piece group 6 and the total number M of pole pieces in the electrode assembly satisfy: M1 / M=1-50%.

[0112] In some embodiments, the outermost electrode piece in the first peripheral electrode piece group 4 close to the electrode assembly is a capacitor electrode piece, and the outermost electrode piece in the second peripheral electrode piece group 5 close to the electrode assembly is a capacitor electrode piece, which can further improve the cycle performance of the battery.

[0113] The number M2 of the capacitor pole pieces in the first peripheral pole piece group 4 is 1-20; and / or, the number M2 of the capacitor pole pieces in the first peripheral pole piece group 4 and the total number M of pole pieces in the electrode assembly satisfy: M2 / M=1-50%; and / or,

[0114] The number M3 of the capacitor pole pieces in the second peripheral pole piece group 5 is 1-20; and / or, the number M3 of the capacitor pole pieces in the second peripheral pole piece group 5 and the total number M of pole pieces in the electrode assembly satisfy: M3 / M=1-50%.

[0115] A third aspect of the present invention provides a battery comprising the above-mentioned electrode assembly.

[0116] The battery of the present invention comprises the above-mentioned electrode assembly, so the battery can have both relatively excellent cycle performance and rate performance without losing energy density.

[0117] The technical scheme of the present invention is further illustrated below in conjunction with specific examples. All parts, percentages, and ratios described in the following examples are based on weight, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further treatment, and the instruments used in the examples are commercially available.

[0118] Example 1

[0119] The lithium ion battery of this embodiment is prepared by the following steps:

[0120] 1) Positive electrode

[0121] The positive electrode sheet includes a positive electrode current collector, which is an aluminum foil provided with a conductive layer, and includes a pole ear area and an active layer area connected to each other in the length direction of the aluminum foil, the pole ear area is used to set the pole ear, and the active layer area is used to set the first active layer, the first active layer includes an edge portion, all of which are capacitor material layers, and the rest of the first active layer is a positive electrode active material layer;

[0122] Among them, the thickness of the positive electrode current collector is 10 μm, and the thickness of the conductive layer is 1 μm;

[0123] The first active layer has two edge portions arranged along the length direction and two edge portions arranged along the width direction. The size L2 of the two edge portions arranged along the length direction satisfies L2 / Lb=5% with the size Lb of the current collector in the width direction, and the size L1 of the two edge portions arranged along the width direction satisfies L1 / La=10% with the size La of the current collector in the length direction.

[0124] The positive electrode active material layer includes lithium nickel cobalt manganese oxide, polyvinylidene fluoride and a conductive agent (including carbon black and carbon nanotubes), and the mass ratio of lithium nickel cobalt manganese oxide, polyvinylidene fluoride and a conductive agent (including carbon black and carbon nanotubes) is 95%:2.5%:2.5%;

[0125] The capacitor material layer includes activated carbon, polyvinylidene fluoride and a conductive agent (including carbon black and carbon nanotubes), and the mass ratio of the activated carbon, polyvinylidene fluoride and the conductive agent (including carbon black and carbon nanotubes) is 90%:7%:3%.

[0126] 2) Negative electrode

[0127] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on both surfaces of the negative electrode current collector;

[0128] The negative electrode current collector is a copper foil provided with a conductive layer, the thickness of the negative electrode current collector is 6 μm, and the thickness of the conductive layer is 1 μm;

[0129] The negative electrode active material layer includes graphite, a binder (including sodium carboxymethyl cellulose and styrene butadiene rubber) and carbon black, and the mass ratio of graphite, the binder (including sodium carboxymethyl cellulose and styrene butadiene rubber) and carbon black is 94%:4%:2%.

[0130] 3) Electrode assembly

[0131] The positive electrode sheet and the separator of step 1) and the negative electrode sheet of step 2) are stacked and then wound to obtain an electrode assembly with a wound structure;

[0132] The diaphragm is a diaphragm with a coating layer, the material of the coating layer is a ceramic + polyvinylidene fluoride mixed coating, and the material of the diaphragm is polyethylene.

[0133] 4) Battery

[0134] Placing the electrode assembly obtained in step 3) in an outer packaging foil aluminum-plastic film, injecting electrolyte into the aluminum-plastic film, and performing vacuum packaging, standing, forming, shaping, and volume separation to obtain a lithium-ion battery;

[0135] The electrolyte is a lithium nickel cobalt manganese oxide electrolyte with a concentration of 1 mol / L, and the solvent is EC:DEC:DMC=3:2:5.

[0136] Example 2

[0137] The preparation method of the lithium ion battery of this embodiment is basically the same as that of embodiment 1, except that:

[0138] In step 1), the dimensions L2 of the two edge portions arranged along the length direction and the dimension Lb of the current collector in the width direction respectively satisfy L2 / Lb=10%.

[0139] Example 3

[0140] The preparation method of the lithium-ion battery of this embodiment is basically the same as that of embodiment 1, except that: in step 1), the active layer region includes a first active layer and a second active layer stacked in layers, the second active layer is arranged on the surface of the current collector, and the second active layer is a full positive electrode active material layer;

[0141] The full positive electrode active material layer includes lithium nickel cobalt manganese oxide, polyvinylidene fluoride and a conductive agent (including carbon black and carbon nanotubes), and the mass ratio of lithium nickel cobalt manganese oxide, polyvinylidene fluoride and a conductive agent (including carbon black and carbon nanotubes) is 95%:2.5%:2.5%;

[0142] The thickness H1 of the first active layer and the total thickness H of the active layer satisfy: H1 / H=30%;

[0143] The size L2 of the two edge portions arranged along the length direction respectively satisfies L2 / Lb=20% with the size Lb of the current collector in the width direction, and the size L1 of the two edge portions arranged along the width direction respectively satisfies L1 / La=20% with the size La of the current collector in the length direction.

[0144] Example 4

[0145] The preparation method of the lithium ion battery of this embodiment is basically the same as that of embodiment 1, except that: in step 2), the negative electrode sheet includes a negative electrode current collector, the negative electrode current collector is a copper foil provided with a conductive layer, and includes a tab region and an active layer region connected to each other in the length direction of the negative electrode current collector, the tab region is used to provide the tab, the active layer region includes a first active layer and a second active layer stacked, and the first active layer is provided on the surface of the current collector; the first active layer includes an edge portion, the entire edge portion is a capacitor material layer, the rest of the first active layer is a negative electrode active material layer, and the second active layer is a full negative electrode active material layer;

[0146] Among them, the thickness of the negative electrode current collector is 6μm, and the thickness of the conductive layer is 1μm;

[0147] The full negative electrode active material layer includes graphite, a binder (including sodium carboxymethyl cellulose and styrene-butadiene rubber) and carbon black, and the mass ratio of graphite, the binder (including sodium carboxymethyl cellulose and styrene-butadiene rubber) and carbon black is 94%:4%:2%;

[0148] The capacitor material layer includes activated carbon, polyvinylidene fluoride and a conductive agent (including carbon black and carbon nanotubes), and the mass ratio of activated carbon, polyvinylidene fluoride and a conductive agent (including carbon black and carbon nanotubes) is 90%:7%:3%;

[0149] The thickness H3 of the first active layer and the total thickness H of the active layer satisfy: H3 / H=30%;

[0150] In the first active layer, the size L2 of the two edge portions arranged along the length direction respectively satisfies L2 / Lb=20% with the size Lb of the current collector in the width direction, and the size L1 of the two edge portions arranged along the width direction respectively satisfies L1 / La=20% with the size La of the current collector in the length direction.

[0151] Comparative Example 1

[0152] The preparation method of the lithium ion battery of this comparative example is basically the same as that of Example 1, except that:

[0153] In step 1), the positive electrode sheet includes a positive electrode current collector and positive electrode active material layers disposed on two surfaces of the positive electrode current collector.

[0154] Performance Testing

[0155] The following tests were performed on the batteries of the embodiment and the comparative example. The test results are shown in Table 1:

[0156] 1) Low temperature DC internal resistance (DCIR) test

[0157] Place the battery at 25℃±2℃ for 1H, discharge at 0.1C to the lower limit voltage, and place it at rest for 10min; charge at 0.1C to the upper limit voltage, with a cut-off current of 0.05C, and place it at rest for 10min; discharge at 0.1C to the lower limit voltage (for initial capacity), and place it at rest for 10min; charge at 0.1C to the upper limit voltage, with a cut-off current of 0.05C, and place it at rest in a constant temperature box for 24H; discharge at 1C for 30min, and place it at rest for 30min; discharge at 0.1C for 10s (sampled at the 200ms), and discharge at the standard discharge current for 30s (sampled at the 200ms);

[0158] DCIR=(V1-V2) / (1C-0.1C);

[0159] Among them, V1 is the terminal voltage corresponding to 0.1C discharge for 10s, and V2 is the voltage corresponding to 1C discharge for 5S.

[0160] 2) Anatomy of extreme charging at room temperature

[0161] a. Place the battery in a constant temperature box for 4 hours, discharge it at 0.2C to the lower limit voltage, and place it for 10 minutes; b. Charge it at the limit charging current to the upper limit voltage, cut off at 0.05C, and place it for 10 minutes; c. Charge it at the standard discharge current to the lower limit voltage, and place it for 10 minutes; d. Repeat steps b and c 20 times, disassemble the battery, and observe the lithium deposition of the battery.

[0162] 3) Anatomy of low temperature extreme charging

[0163] a. Place the battery in a constant temperature box for 24 hours, discharge it at 0.2C to the lower limit voltage, and place it for 10 minutes; b. Charge it at the limit charging current to the upper limit voltage, cut off at 0.05C, and place it for 10 minutes; c. Discharge it at the standard discharge current to the lower limit voltage, and place it for 10 minutes; d. Repeat steps b and c 20 times, disassemble the battery, and observe the lithium deposition of the battery.

[0164] 4) Cycle test

[0165] Place the battery at 45℃±2℃ for 10 minutes; discharge to the lower limit voltage with standard discharge current (for initial capacity test), place it for 10 minutes, charge to the upper limit voltage with standard charge current, cut off at 0.05C, and place it for 10 minutes; cycle the battery for 1000 times and test the final capacity of the battery; calculate the cycle capacity retention rate of the battery based on the initial capacity and final capacity.

[0166] Table 1

[0167]

[0168] It can be seen from Table 1 that the lithium ion battery prepared in the embodiment of the present invention has relatively excellent cycle performance, rate performance and energy density.

[0169] Each embodiment in this specification is described in a related manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. The above are only preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are included in the scope of protection of the present invention.

Claims

1. A composite pole piece, characterized in that: A current collector is included, wherein at least one surface of the current collector includes an active layer region, and the active layer region is provided with an active layer, wherein at least one of the active layers is a first active layer; The first active layer includes an edge portion, and the entire edge portion is a capacitor material layer, the capacitor material layer includes a capacitor material, and the capacitor material is selected from at least one of activated carbon, graphene and porous carbon; the rest of the first active layer is a battery material layer; the battery material layer includes a battery active material, and the battery active material includes a positive electrode active material or a negative electrode active material, and the positive electrode active material is selected from at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium manganese oxide and lithium-rich manganese-based materials; the negative electrode active material is selected from at least one of artificial graphite, natural graphite, mesophase carbon microbeads, petroleum coke, hard carbon and silicon-based negative electrodes; The active layer region includes N active layers stacked in layers, at least one of the N active layers is a first active layer, and N>2; The N active layers further include a second active layer, The second active layer is selected from a full capacitor material layer or a full battery material layer; The N active layers include the first active layer and the second active layer which are stacked, the active layer arranged on the surface of the current collector is a full capacitor material layer; the outermost active layer of the composite pole piece is a full capacitor material layer.

2. The composite pole piece according to claim 1, characterized in that: The current collector also includes a tab region; The tab region is located at an edge of the surface of the current collector extending along the first direction, and the size of the tab region in the second direction is equal to the size of the current collector in the second direction; The tab region and the active layer region are distributed on the surface of the current collector in the second direction.

3. The composite pole piece according to claim 2, characterized in that: At least the edge portion close to the tab region is a capacitor material layer.

4. The composite pole piece according to claim 1, characterized in that: The current collector also includes a tab region; The tab region is located at an edge of the surface of the current collector extending along the first direction, and a size of the tab region in the second direction is smaller than a size of the current collector in the second direction; The active layer area is arranged around the outer periphery of the tab area.

5. The composite pole piece according to claim 4, characterized in that: The active layer region includes a first area close to the periphery of the tab region, and the capacitor material layer is at least located in the first area.

6. An electrode assembly, characterized in that: A composite pole piece comprising any one of claims 1 to 5.

7. The electrode assembly according to claim 6, characterized in that: The electrode assembly comprises a first peripheral electrode sheet group, an intermediate electrode sheet group and a second peripheral electrode sheet group which are stacked in a thickness direction; The number of pole pieces in the first peripheral pole piece group is equal to the number of pole pieces in the second peripheral pole piece group, the intermediate pole piece group is a capacitor pole piece, and at least one pole piece in the first peripheral pole piece group and / or the second peripheral pole piece group is the composite pole piece.

8. A battery, characterized in that: Comprising the electrode assembly according to claim 6 or 7.

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