Battery cell structure

Abstract

The application provides an electric core structure and relates to the technical field of batteries. The electric core structure comprises positive pole pieces and negative pole pieces arranged alternately. The positive pole piece comprises a positive pole insulating layer, a first conductive layer and a second conductive layer on the surface of the positive pole insulating layer, a first positive pole active material layer on the surface of the first conductive layer, and a second positive pole active material layer on the surface of the second conductive layer; the negative pole piece comprises a negative pole insulating layer, a third conductive layer and a fourth conductive layer on the surface of the negative pole insulating layer, a first negative pole active material layer on the surface of the third conductive layer, and a second negative pole active material layer on the surface of the fourth conductive layer; the adjacent positive pole pieces and negative pole pieces are separated by a separation film, the current of the first conductive layer and the second conductive layer of the positive pole piece is respectively led out through a first pole lug and a second pole lug; and the current of the third conductive layer and the fourth conductive layer of the negative pole piece is respectively led out through a third pole lug and a fourth pole lug. The electric core structure can improve the performance defects of lithium batteries.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery, in particular to a battery cell structure. BACKGROUND

[0002] The common lithium battery structure generally uses aluminum foil and copper foil as positive and negative electrodes, and the performance of the lithium battery of this type is more likely to have defects. SUMMARY

[0003] The purpose of the embodiment of the present application is to provide a battery cell structure which can improve the performance defects of the prior art lithium battery.

[0004] The embodiment of the present application is implemented as follows:

[0005] The embodiment of the present application provides a battery cell structure, comprising: positive electrode sheets and negative electrode sheets arranged alternately;

[0006] The positive electrode sheet comprises a positive electrode insulating layer, a first conductive layer and a second conductive layer on two surfaces of the positive electrode insulating layer, a first positive electrode active material layer on the surface of the first conductive layer, and a second positive electrode active material layer on the surface of the second conductive layer;

[0007] The negative electrode sheet comprises a negative electrode insulating layer, a third conductive layer and a fourth conductive layer on two surfaces of the negative electrode insulating layer, a first negative electrode active material layer on the surface of the third conductive layer, and a second negative electrode active material layer on the surface of the fourth conductive layer;

[0008] The adjacent positive electrode sheet and negative electrode sheet are separated by a separation film;

[0009] The current of the first conductive layer and the second conductive layer of the positive electrode sheet is respectively led out through the first tab and the second tab;

[0010] The current of the third conductive layer and the fourth conductive layer of the negative electrode sheet is respectively led out through the third tab and the fourth tab.

[0011] The beneficial effects of the battery cell structure of the embodiment of the present application include:

[0012] The cell structure includes positive electrode sheets and negative electrode sheets arranged alternately, and the adjacent positive electrode sheets and negative electrode sheets are separated by a separator. In the process of charging and discharging of the battery, any one of the first positive active material layer and the second positive active material layer and any one of the first negative active material layer and the second negative active material layer and the separator can constitute a lithium ion battery. Due to the existence of the positive insulating layer and the negative insulating layer, the lithium ion battery can be isolated. The current of the first conductive layer and the second conductive layer is respectively led out through the first tab and the second tab, and the current of the third conductive layer and the fourth conductive layer is respectively led out through the third tab and the fourth tab, so that the whole cell structure can be regarded as a plurality of independent lithium ion batteries. The plurality of independent lithium ion batteries do not share a current collector, and the plurality of independent lithium ion batteries jointly determine the performance of the whole cell structure. By designing the performance of the plurality of independent lithium ion batteries, the performance defects of the lithium battery can be overcome. BRIEF DESCRIPTION OF DRAWINGS

[0013] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor.

[0014] Figure 1 A cross-sectional view of a cell structure according to an embodiment of the present application;

[0015] Figure 2 A first tab arrangement of a cell structure according to an embodiment of the present application;

[0016] Figure 3 A second tab arrangement of a cell structure according to an embodiment of the present application;

[0017] Figure 4 A third tab arrangement of a cell structure according to an embodiment of the present application;

[0018] Figure 5 A fourth tab arrangement of a cell structure according to an embodiment of the present application;

[0019] Figure 6 A fifth tab arrangement of a cell structure according to an embodiment of the present application;

[0020] Figure 7 A sixth tab arrangement of a cell structure according to an embodiment of the present application;

[0021] Figure 8 A seventh tab arrangement of a cell structure according to an embodiment of the present application;

[0022] Figure 9 A cross-sectional view of another battery cell structure according to an embodiment of the present application;

[0023] Figure 10 A tab arrangement of an eighth battery cell structure according to an embodiment of the present application;

[0024] Figure 11 A tab arrangement of a ninth battery cell structure according to an embodiment of the present application.

[0025] Figure: 10 - battery cell structure; 11 - positive electrode sheet; 111 - positive electrode insulating layer; 112 - first conductive layer; 113 - second conductive layer; 114 - first positive electrode active material layer; 115 - second positive electrode active material layer; 12 - negative electrode sheet; 121 - negative electrode insulating layer; 122 - third conductive layer; 123 - fourth conductive layer; 124 - first negative electrode active material layer; 125 - second negative electrode active material layer; 13 - first separator film; 14 - second separator film; 151 - first tab; 152 - second tab; 153 - third tab; 154 - fourth tab; 16 - winding symmetry plane. DETAILED DESCRIPTION

[0026] In order to make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. The components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0027] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work are within the scope of protection of the present application.

[0028] In addition, the specific conditions are not specified in the embodiments, and the conventional conditions or the conditions recommended by the manufacturer are used. The reagents or instruments used are not specified by the manufacturer, and are conventional products that can be obtained by market purchase.

[0029] Schemes A and / or B refer to Scheme A or Scheme B, or a combination of Scheme A and Scheme B.

[0030] The following specifically describes the battery cell structure 10 according to the embodiments of the present application:

[0031] The embodiment of the present application provides a kind of electric core structure 10, it includes the positive pole sheet 11 and negative pole sheet 12 (refer to Figure 1 And Figure 9 ) Wherein, electric core structure 10 can be winding structure, can also be laminated structure.

[0032] Positive pole sheet 11 includes positive pole insulating layer 111, the first conductive layer 112 and the second conductive layer 113 on the two surfaces of positive pole insulating layer 111, the first positive pole active material layer 114 on the surface of first conductive layer 112 and the second positive pole active material layer 115 on the surface of second conductive layer 113.

[0033] Negative pole sheet 12 includes negative pole insulating layer 121, the third conductive layer 122 and the fourth conductive layer 123 on the two surfaces of negative pole insulating layer 121, the first negative pole active material layer 124 on the surface of third conductive layer 122 and the second negative pole active material layer 125 on the surface of fourth conductive layer 123.

[0034] The positive pole sheet 11 and negative pole sheet 12 of adjacent arrangement are separated by isolation film.

[0035] The current of the first conductive layer 112 and the second conductive layer 113 of positive pole sheet 11 is respectively exported by the first lug 151 and the second lug 152.

[0036] The current of the third conductive layer 122 and the fourth conductive layer 123 of negative pole sheet 12 is respectively exported by the third lug 153 and the fourth lug 154.

[0037] Electric core structure 10 includes the positive pole sheet 11 and negative pole sheet 12 of alternate arrangement, the positive pole sheet 11 and negative pole sheet 12 of adjacent arrangement are separated by isolation film, so in the process that battery carries out charge and discharge, any one of the first positive pole active material layer 114 and the second positive pole active material layer 115 and any one of the first negative pole active material layer 124 and the second negative pole active material layer 125 and isolation film can constitute a lithium ion battery, due to the existence of positive pole insulating layer 111 and negative pole insulating layer 121, can isolate the lithium ion battery constituted, the current of the first conductive layer 112 and the second conductive layer 113 is respectively exported by the first lug 151 and the second lug 152, the current of the third conductive layer 122 and the fourth conductive layer 123 is respectively exported by the third lug 153 and the fourth lug 154, so that whole electric core structure 10 can be regarded as multiple independent lithium ion batteries, multiple independent lithium ion batteries do not share current collector, and multiple independent lithium ion batteries jointly determine the performance of whole electric core structure 10. Through the design of the performance of multiple independent lithium ion batteries, the performance defects of lithium battery can be overcome.

[0038] The first, second, third and fourth tabs 151, 152, 153 and 154 respectively correspond to one layer of conductive layer, the tabs at the same position correspond to the same conductive layer, and the first, second, third and fourth tabs 151, 152, 153 and 154 can be provided in multiple numbers, respectively, and the tabs at the same position are connected by welding or other connection methods, so that the electricity of the plurality of first conductive layers 112, the plurality of second conductive layers 113, the plurality of third conductive layers 122 and the plurality of fourth conductive layers 123 can be collected respectively, and the first, second, third and fourth conductive layers 112, 113, 122 and 123 do not interfere with each other during the tab convergence process, and two independent lithium ion batteries can be completely separated.

[0039] Exemplarily, the first positive active material layer 114 and the first negative active material layer 124 and the isolation film can constitute an independent lithium ion battery, the second positive active material layer 115 and the second negative active material layer 125 can constitute an independent lithium ion battery, the first positive active material layer 114 and the second negative active material layer 125 can constitute an independent lithium ion battery, and the second positive active material layer 115 and the first negative active material layer 124 can constitute an independent lithium ion battery. The whole battery structure 10 can form at least two of the above batteries according to the arrangement and combination of the positive and negative electrode plates.

[0040] Exemplarily, the first negative active material layer 124 and the first positive active material layer 114 arranged adjacently are separated by the first isolation film 13, and the second positive active material layer 115 and the second negative active material layer 125 arranged adjacently are separated by the second isolation film 14. In the battery structure 10, the first positive active material layer 114, the first conductive layer 112, the positive insulating layer 111, the second conductive layer 113, the second positive active material layer 115, the second isolation film 14, the second negative active material layer 125, the fourth conductive layer 123, the negative insulating layer 121, the third conductive layer 122, the first negative active material layer 124 and the first isolation film 13 are arranged in turn and overlapped cyclically.

[0041] In other embodiments, the first positive active material layer 114, the first conductive layer 112, the positive insulating layer 111, the second conductive layer 113, the second positive active material layer 115, the isolation film, the first negative active material layer 124, the third conductive layer 122, the negative insulating layer 121, the fourth conductive layer 123, the second negative active material layer 125 and the isolation film can be arranged in turn and overlapped cyclically.

[0042] Exemplarily, the capacity ratio of any one of the first negative active material layer 124 and the second negative active material layer 125 to any one of the first positive active material layer 114 and the second positive active material layer 115 is 1.07-1.2, so that lithium ions can move from the positive electrode to the negative electrode of the lithium ion battery without causing lithium precipitation. The capacity ratio can be referred to as CB value or NP ratio. Exemplarily, the capacity ratio is 1.07, 1.08, 1.09, 1.1, 1.12, 1.14, 1.15, 1.16, 1.18 or 1.2.

[0043] In a possible embodiment, the first conductive layer 112 and the second conductive layer 113 of the positive electrode tab 11 are arranged in a staggered manner at the tab, the first conductive layer 112 and the positive electrode insulating layer 111 extend outward relative to the second conductive layer to form a first tab 151, and the second conductive layer 113 and the positive electrode insulating layer 111 extend outward relative to the first conductive layer 112 to form a second tab 152.

[0044] The third conductive layer 122 and the fourth conductive layer 123 of the negative electrode tab 12 are arranged in a staggered manner at the tab, the third conductive layer 122 and the negative electrode insulating layer 121 extend outward relative to the fourth conductive layer 123 to form a third tab 153, and the fourth conductive layer 123 and the negative electrode insulating layer 121 extend outward relative to the fourth conductive layer 123 to form a fourth tab 154.

[0045] In other embodiments, the first tab 151 can be welded to the first conductive layer 112, the second tab 152 can be welded to the second conductive layer 113, the third tab 153 can be welded to the third conductive layer 122, and the fourth tab 154 can be welded to the fourth conductive layer 123, so as to respectively lead out the current of the first conductive layer 112, the second conductive layer 113, the third conductive layer 122 and the fourth conductive layer 123.

[0046] With the following cell structure as an example, referring to Figure 1 , the first negative active material layer 124 and the first positive active material layer 114 arranged adjacently are separated by the first separation film 13, and the second positive active material layer 115 and the second negative active material layer 125 arranged adjacently are separated by the second separation film 14.

[0047] When the cell structure 10 is a jelly-roll structure or a stack structure, the first tab 151, the second tab 152, the third tab 153 and the fourth tab 154 can be arranged on the same side in the height direction of the cell structure 10 (refer to Figures 1-8 ), or can be distributed on both sides in the height direction of the cell structure 10 (refer to Figures 9-11 ).

[0048] When the battery cell structure 10 is a jelly-roll structure, and the first tab 151, the second tab 152, the third tab 153 and the fourth tab 154 are arranged on the same side of the battery cell structure 10 in the height direction, the arrangement of the tabs is also various, and the arrangement of the tabs is further introduced as follows, which includes:

[0049] (1) Referring to FIG. 1, the first tab 151 and the fourth tab 154 are arranged on one side of the winding symmetry plane 16 of the jelly-roll structure, and the second tab 152 and the third tab 153 are arranged on the other side of the winding symmetry plane 16 of the jelly-roll structure; in the length direction of the jelly-roll structure, the first tab 151 is arranged between the second tab 152 and the third tab 153. Figure 2

[0050] (2) Referring to FIG. 2, the second tab 152 and the third tab 153 are arranged on one side of the winding symmetry plane 16 of the jelly-roll structure, and the first tab 151 and the fourth tab 154 are arranged on the other side of the winding symmetry plane 16 of the jelly-roll structure; in the length direction of the jelly-roll structure, the fourth tab 154 is arranged between the second tab 152 and the third tab 153. Figure 3

[0051] (3) Referring to FIG. 3, the first tab 151 and the second tab 152 are arranged on one side of the winding symmetry plane 16 of the jelly-roll structure, and the third tab 153 and the fourth tab 154 are arranged on the other side of the winding symmetry plane 16 of the jelly-roll structure; in the length direction of the jelly-roll structure, the third tab 153 is arranged between the first tab 151 and the second tab 152. Figure 4

[0052] (4) Referring to FIG. 4, the first tab 151 and the second tab 152 are arranged on one side of the winding symmetry plane 16 of the jelly-roll structure, and the third tab 153 and the fourth tab 154 are arranged on the other side of the winding symmetry plane 16 of the jelly-roll structure, and the first tab 151 and the third tab 153 are arranged on both sides of the winding symmetry plane 16 of the jelly-roll structure; in the length direction of the jelly-roll structure, the first tab 151 is arranged between the second tab 152 and the third tab 153. Figure 5

[0053] (5) Referring to FIG. 5, the first tab 151, the second tab 152, the third tab 153 and the fourth tab 154 are arranged on the same side of the winding symmetry plane 16 of the jelly-roll structure. Figure 6 (6) Referring to FIG. 6, the first tab 151, the second tab 152, the third tab 153 and the fourth tab 154 are all formed on both sides of the winding symmetry plane 16 of the jelly-roll structure.

[0054] Figure 7

[0055] ​​​​​​When the battery cell structure 10 is a winding structure, and the first tab 151, the second tab 152, the third tab 153 and the fourth tab 154 are distributed on opposite sides in the height direction of the battery cell structure 10, the arrangement of the tabs is similar to the above-mentioned (1)-(4) ways, except that in the (1)-(4) ways, the tabs on one side of the winding symmetry plane 16 of the winding structure and the tabs on the other side of the winding symmetry plane 16 of the winding structure are distributed on both sides in the height direction of the winding structure.

[0056] The arrangement of the tabs when the battery cell structure 10 is a stacking structure is described below:

[0057] When the battery cell structure 10 is a stacking structure, the first tab 151, the second tab 152, the third tab 153 and the fourth tab 154 can be arranged on the same side in the height direction of the battery cell structure 10 (see Figure 8 ), or can be distributed on both sides in the height direction of the battery cell structure 10 (see Figures 10-11 ).

[0058] Further, the first positive active material layer 114 and the second positive active material layer 115 are different, and / or the first negative active material layer 124 and the second negative active material layer 125 are different. That is, the first positive active material layer 114 and the second positive active material layer 115 can be different, and at the same time, the first negative active material layer 124 and the second negative active material layer 125 can be different, or the first positive active material layer 114 and the second positive active material layer 115 can be different, or the first negative active material layer 124 and the second negative active material layer 125 can be different. Such an arrangement makes the plurality of independent lithium ion batteries different, and by designing the performance of the plurality of independent lithium ion batteries, the performance defects of a single active material lithium battery can be improved.

[0059] It should be noted that the first positive active material layer 114 and the second positive active material layer 115 being different can mean that the types of active materials of the first positive active material layer 114 and the second positive active material layer 115 are different, or that the types of active materials of the first positive active material layer 114 and the second positive active material layer 115 are the same, but the particle size, specific surface area, gram capacity, etc. are different. It can be understood that, in addition to containing active materials, the first positive active material layer 114 and the second positive active material layer 115 can also contain adhesives, conductive agents, etc.

[0060] Regardless of whether the active material of the first positive electrode active material layer 114 and the second positive electrode active material layer 115 is the same or different, the active material of the first positive electrode active material layer 114 can be selected from lithium iron phosphate, single-crystal lithium nickel cobalt manganese oxide, polycrystal lithium nickel cobalt manganese oxide, lithium titanate, lithium manganate, or lithium cobaltate, and the active material of the second positive electrode active material layer 115 can also be selected from lithium iron phosphate, single-crystal lithium nickel cobalt manganese oxide, polycrystal lithium nickel cobalt manganese oxide, lithium titanate, lithium manganate, or lithium cobaltate.

[0061] Optionally, the D10 particle size of the lithium iron phosphate of the embodiment of the present application is greater than 0.4 μm, the D50 particle size is 0.8-4 μm, and the D90 particle size is 3-10 μm. The specific surface area of the lithium iron phosphate is 8-16 m 2 / g, and the specific capacity is 100-160 mAh / g. Optionally, the tap density of the lithium iron phosphate is 2.1-2.6 g / cm 3 , and the particle arrangement is good.

[0062] Optionally, the D10 particle size of the single-crystal lithium nickel cobalt manganese oxide of the embodiment of the present application is greater than 1.5 μm, the D50 particle size is 4-10 μm, and the D90 particle size is 9-20 μm. The specific surface area of the single-crystal lithium nickel cobalt manganese oxide is 0.3-0.6 m 2 / g, and the specific capacity is 160-210 mAh / g. Optionally, the coating amount of the single-crystal lithium nickel cobalt manganese oxide is 10-26 mg / cm 2 . Optionally, the tap density of the single-crystal lithium nickel cobalt manganese oxide is 3.2-3.75 g / cm 3 .

[0063] Optionally, the D10 particle size of the polycrystal lithium nickel cobalt manganese oxide of the embodiment of the present application is greater than 1.5 μm, the D50 particle size is 8-12 μm, and the D90 particle size is 18-34 μm. The specific surface area of the polycrystal lithium nickel cobalt manganese oxide is 0.2-0.6 m 2 / g, and the specific capacity of the polycrystal lithium nickel cobalt manganese oxide is 165-211 mAh / g. Optionally, the coating amount of the single-crystal lithium nickel cobalt manganese oxide is 10-26 mg / cm 2 . Optionally, the tap density of the polycrystal lithium nickel cobalt manganese oxide is 3.2-3.6 g / cm 3 .

[0064] Illustratively, when the active material of the first positive electrode active material layer 114 and the second positive electrode active material layer 115 is lithium iron phosphate, single-crystal lithium nickel cobalt manganese oxide, or polycrystal lithium nickel cobalt manganese oxide, the coating amount of the lithium iron phosphate is 5-22 mg / cm 2 , the coating amount of the single-crystal lithium nickel cobalt manganese oxide is 10-26 mg / cm 2 , and the coating amount of the polycrystal lithium nickel cobalt manganese oxide is 10-26 mg / cm 2 .

[0065] The heavier the coating amount of the active material of the first positive electrode active material layer 114 and the second positive electrode active material layer 115, the less likely to dry, low coating efficiency, and prone to cracking. Large coating amount, large DCR, large polarization, not conducive to capacity development, large cell heating. But the large coating amount can improve the energy density. If the coating amount is small, the thickness is thin, the path of ion migration into the internal active material is shorter, which is conducive to improving the rate. The coating amount of the active material of the first positive electrode active material layer 114 and the second positive electrode active material layer 115 in the embodiment of the application is appropriate, which is conducive to the cell structure 10 having good comprehensive performance. Exemplarily, the coating amount of lithium iron phosphate is 5 mg / cm 2 , 8 mg / cm 2 , 10 mg / cm 2 , 12 mg / cm 2 , 15 mg / cm 2 , 18 mg / cm 2 or 22 mg / cm 2 . Exemplarily, the coating amount of single-crystal lithium nickel cobalt manganese oxide and polycrystalline lithium nickel cobalt manganese oxide is 10 mg / cm 2 , 12 mg / cm 2 , 15 mg / cm 2 , 18 mg / cm 2 , 22 mg / cm 2 or 26 mg / cm 2 .

[0066] Exemplarily, the first positive electrode active material layer 114 and the second positive electrode active material layer 115 are different, including: the types of active materials of the first positive electrode active material layer 114 and the second positive electrode active material layer 115 are the same, and any one of the following schemes or multiple schemes:

[0067] In one possible embodiment, the D10 particle size of the active material of the first positive electrode active material layer 114 and the second positive electrode active material layer 115 differs by 0.05-0.3 μm, the D50 particle size differs by 1-4 μm, and the D90 particle size differs by 3-5 μm.

[0068] It should be noted that the D10 particle size in the embodiment of the application refers to the particle size of the cumulative distribution of 10% of the particles, the D50 particle size refers to the particle size of the cumulative distribution of 50% of the particles, and the D90 particle size refers to the particle size of the cumulative distribution of 90% of the particles.

[0069] The active material with large particle size has long ion migration path but poor rate, the active material with small particle size has good rate and is not easy to form dead zone inside the particle, has long cycle life, the D10 particle size of the active material of the first positive electrode active material layer 114 and the second positive electrode active material layer 115 is different by 0.05-0.3 μm, the D50 particle size is different by 1-4 μm, the D90 particle size is different by 3-5 μm, the lithium ion battery composed of the positive electrode active material layer of the positive electrode active material with small particle size can improve the defect of poor rate of the lithium ion battery composed of the positive electrode active material layer of the positive electrode active material with large particle size. In addition, the first positive electrode active material layer 114 and the second positive electrode active material layer 115 both use active materials with different particle size ranges, which can improve the tap density.

[0070] It should be noted that in the embodiments of the present application, the particle size of the active material of the first positive electrode active material layer 114 can be larger than that of the active material of the second positive electrode active material layer 115, or the particle size of the active material of the second positive electrode active material layer 115 can be larger than that of the active material of the first positive electrode active material layer 114, as long as the D10 particle size of the active material of the first positive electrode active material layer 114 and the second positive electrode active material layer 115 is different by 0.05-0.3 μm, the D50 particle size is different by 1-4 μm, and the D90 particle size is different by 3-5 μm.

[0071] Optionally, the D10 particle size of the active material of the first positive electrode active material layer 114 and the second positive electrode active material layer 115 is different by 0.05 μm, 0.08 μm, 0.1 μm, 0.2 μm or 0.3 μm.

[0072] Optionally, the D50 particle size of the active material of the first positive electrode active material layer 114 and the second positive electrode active material layer 115 is different by 1 μm, 2 μm, 3 μm or 4 μm. Optionally, the D90 particle size of the active material of the first positive electrode active material layer 114 and the second positive electrode active material layer 115 is different by 3 μm, 4 μm or 5 μm.

[0073] In a possible embodiment, the active material of the first positive electrode active material layer 114 and the second positive electrode active material layer 115 is lithium iron phosphate, part or all of the surface of the lithium iron phosphate is coated with a carbon coating layer, and the carbon coating amount of the lithium iron phosphate of the first positive electrode active material layer 114 and the second positive electrode active material layer 115 is different by ≥0.1%, wherein the carbon coating amount is the ratio of the weight of the carbon coating layer to the weight of the carbon coating layer and the lithium iron phosphate.

[0074] The carbon-coated lithium iron phosphate can improve the conductivity of the active material of the first positive electrode active material layer 114 and the second positive electrode active material layer 115, improve the electronic conductivity, have a good rate, and have good overall electrical performance of the battery structure. The carbon-coated amount of the lithium iron phosphate of the first positive electrode active material layer 114 and the second positive electrode active material layer 115 is different by ≥0.1%, which can sufficiently ensure the difference between the lithium ion batteries. It should be noted that in the embodiments of the present application, the carbon-coated amount of the lithium iron phosphate of the first positive electrode active material layer 114 can be greater than the carbon-coated amount of the lithium iron phosphate of the second positive electrode active material layer 115, or the carbon-coated amount of the lithium iron phosphate of the second positive electrode active material layer 115 can be greater than the carbon-coated amount of the lithium iron phosphate of the first positive electrode active material layer 114.

[0075] Optionally, the weight of the carbon-coated layer is 0.8-1.6% of the total weight of the carbon-coated layer and the lithium iron phosphate, for example, 0.8%, 0.9%, 1.0%, 1.2%, 1.4%, 1.5%, or 1.6%.

[0076] In a possible embodiment, the specific surface area of the active material of the first positive electrode active material layer 114 and the second positive electrode active material layer 115 is different by 0.1-8 m 2 / g.

[0077] The specific surface area of the particles = total surface of the particles / total mass, so the specific surface area of the particles is large, the particle size of the corresponding particles is small, and the ions have more entry paths, so the rate is good. However, a large specific surface area consumes more lithium ions to form an SEI film, and the first efficiency is low. In the embodiments of the present application, the specific surface area of the active material of the first positive electrode active material layer 114 and the second positive electrode active material layer 115 is different by 0.1-8 m 2 / g, which not only ensures the difference between the two lithium ion batteries, but also complements the performance of the lithium ion battery composed of the positive electrode active material layer of the active material with a small specific surface area and the lithium ion battery composed of the positive electrode active material layer of the active material with a large specific surface area, so that the entire battery structure has a good rate and a good first efficiency. It should be noted that in the embodiments of the present application, the specific surface area of the first positive electrode active material layer 114 can be greater than the specific surface area of the active material of the second positive electrode active material layer 115, or the specific surface area of the active material of the second positive electrode active material layer 115 can be greater than the specific surface area of the active material of the first positive electrode active material layer 114.

[0078] For example, the specific surface area of the active material of the first positive electrode active material layer 114 and the second positive electrode active material layer 115 is different by 0.1 m 2 / g, 0.5 m 2 / g, 1 m 2 / g, 2 m 2 / g, 3 m 2 / g, 4m 2 / g, 5m 2 / g, 6m 2 / g, 7m 2 / g or 8m 2 / g.

[0079] In a possible implementation, the gram capacity of the active material of the first positive electrode active material layer 114 and the second positive electrode active material layer 115 is different by 10-60 mAh / g.

[0080] A high gram capacity of the active material can reduce the coating thickness, thereby reducing the process difficulty and improving the energy density. If the gram capacity of the active material of the same material is small, the coating thickness needs to be increased, and the energy density of the battery is low, but the cost is generally low. In the embodiment of the application, the gram capacity of the active material of the first positive electrode active material layer 114 and the second positive electrode active material layer 115 is different by 10-60 mAh / g, which not only ensures the difference between the two lithium ion batteries, but also the performance of the lithium ion battery composed of the positive electrode active material layer of the active material with small gram capacity and the lithium ion battery composed of the positive electrode active material layer of the active material with large gram capacity can be complementary. The entire battery structure has high discharge rate, high initial energy density and appropriate cost. It should be noted that in the embodiment of the application, the gram capacity of the first positive electrode active material layer 114 can be greater than the gram capacity of the active material of the second positive electrode active material layer 115, or the gram capacity of the second positive electrode active material layer 115 can be greater than the gram capacity of the active material of the first positive electrode active material layer 114.

[0081] Exemplarily, the gram capacity of the active material of the first positive electrode active material layer 114 and the second positive electrode active material layer 115 is different by 10 mAh / g, 20 mAh / g, 30 mAh / g, 40 mAh / g, 50 mAh / g or 60 mAh / g.

[0082] Optionally, the compaction density of the first positive electrode active material layer 114 and the second positive electrode active material layer 115 is different by ≥0.02 g / cm 3 , for example, 0.02 g / cm 3 , 0.04 g / cm 3 , 0.06 g / cm 3 , 0.08 g / cm 3 , 0.10 g / cm 3 , 0.15 g / cm 3 , 0.20 g / cm 3 .

[0083] In a possible implementation, the thickness difference between the first conductive layer 112 and the second conductive layer 113 is 0.1-1 μm, for example, 0.1 μm, 0.3 μm, 0.5 μm, 0.8 μm, or 1 μm. The thickness of the first conductive layer 112 and the second conductive layer 113 is 0.1-3 μm, for example, 0.1 μm, 0.5 μm, 1 μm, 2 μm, or 3 μm.

[0084] In a possible implementation, the thickness difference between the first positive electrode active material layer 114 and the second positive electrode active material layer 115 is 5-50 μm, for example, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, or 50 μm.

[0085] The thicknesses of the first conductive layer 112, the second conductive layer 113, the first positive electrode active material layer 114, and the second positive electrode active material layer 115 affect the process difficulty. If the thickness is too thick, it is not easy to dry, the coating efficiency is low, and cracks are likely to occur. The thicknesses of the first conductive layer, the second conductive layer, the first positive electrode active material layer 114, and the second positive electrode active material layer 115 in the embodiments of the present application are appropriate, the path of ion migration into the internal active material is short, the polarization is small, which is conducive to the rate charge and discharge, and the DCR is small, and the cycle performance is good.

[0086] The following describes the case where the active materials of the first positive electrode active material layer 114 and the second positive electrode active material layer 115 are different. When the active materials of the first positive electrode active material layer 114 and the second positive electrode active material layer 115 are different, the first positive electrode active material layer 114 and the second positive electrode active material layer 115 can be ensured to be different by any one or more of the following schemes.

[0087] Exemplarily, the active material of the first positive electrode active material layer 114 is lithium iron phosphate, and the active material of the second positive electrode active material layer 115 is single-crystal lithium nickel cobalt manganese oxide. Exemplarily, the active material of the first positive electrode active material layer 114 is lithium iron phosphate, and the active material of the second positive electrode active material layer 115 is polycrystal lithium nickel cobalt manganese oxide. Exemplarily, the active material of the first positive electrode active material layer 114 is single-crystal lithium nickel cobalt manganese oxide, and the active material of the second positive electrode active material layer 115 is lithium iron phosphate. Exemplarily, the active material of the first positive electrode active material layer 114 is single-crystal lithium nickel cobalt manganese oxide, and the active material of the second positive electrode active material layer 115 is polycrystal lithium nickel cobalt manganese oxide. Exemplarily, the active material of the first positive electrode active material layer 114 is polycrystal lithium nickel cobalt manganese oxide, and the active material of the second positive electrode active material layer 115 is single-crystal lithium nickel cobalt manganese oxide. Exemplarily, the active material of the first positive electrode active material layer 114 is polycrystal lithium nickel cobalt manganese oxide, and the active material of the second positive electrode active material layer 115 is single-crystal lithium nickel cobalt manganese oxide.

[0088] In a possible embodiment, the D10 particle size of the active materials of the first positive electrode active material layer 114 and the second positive electrode active material layer 115 differs by 1-3 μm, the D50 particle size differs by 2-5 μm, and the D90 particle size differs by 3-25 μm.

[0089] The active material with large particle size has a long ion migration path but poor rate, and the active material with small particle size has good rate and is less likely to form a dead zone inside the particle, thus having long cycle life. In the case where the active materials of the first positive electrode active material layer 114 and the second positive electrode active material layer 115 are different, by setting the D10 particle size of the active materials of the first positive electrode active material layer 114 and the second positive electrode active material layer 115 to differ by 1-3 μm, the D50 particle size to differ by 2-5 μm, and the D90 particle size to differ by 3-25 μm, the lithium ion battery composed of the positive electrode active material layer of the active material with small particle size can improve the defect of poor rate of the lithium ion battery composed of the positive electrode active material layer of the active material with large particle size. It should be noted that in the embodiments of the present application, the particle size of the active material of the first positive electrode active material layer 114 can be larger than that of the active material of the second positive electrode active material layer 115, or the particle size of the active material of the second positive electrode active material layer 115 can be larger than that of the active material of the first positive electrode active material layer 114.

[0090] Exemplarily, the D10 particle size of the active materials of the first positive electrode active material layer 114 and the second positive electrode active material layer 115 differs by 1 μm, 1.5 μm, 2 μm, 2.5 μm, or 3 μm.

[0091] Exemplarily, the D50 particle size of the active materials of the first positive electrode active material layer 114 and the second positive electrode active material layer 115 differs by 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm or 5 μm.

[0092] Exemplarily, the D90 particle size of the active materials of the first positive electrode active material layer 114 and the second positive electrode active material layer 115 differs by 3 μm, 5 μm, 8 μm, 10 μm, 13 μm, 15 μm, 20 μm or 25 μm.

[0093] In a possible embodiment, the specific surface area of the active materials of the first positive electrode active material layer 114 and the second positive electrode active material layer 115 differs by 7-15 m 2 / g.

[0094] The specific surface area of the particles is large, the corresponding particle size is small, the ion has more entry paths, and thus the rate is good. However, the specific surface area is large, and the formation of the SEI film consumes more lithium ions, and the first efficiency is low. In the embodiments of the present application, in the case where the types of the active materials of the first positive electrode active material layer 114 and the second positive electrode active material layer 115 are different, the specific surface area of the active materials of the first positive electrode active material layer 114 and the second positive electrode active material layer 115 differs by 7-15 m 2 / g, not only can the two lithium ion batteries be different, but also the performance of the lithium ion battery composed of the positive electrode active material layer of the active material with small specific surface area and the lithium ion battery composed of the positive electrode active material layer of the active material with large specific surface area can be complementary, and the entire battery structure has good rate and good first efficiency.

[0095] Exemplarily, the specific surface area of the active materials of the first positive electrode active material layer 114 and the second positive electrode active material layer 115 differs by 7 m 2 / g, 8 m 2 / g, 9 m 2 / g, 10 m 2 / g, 11 m 2 / g, 12 m 2 / g, 13 m 2 / g, 14 m 2 / g or 15 m 2 / g.

[0096] In a possible embodiment, the specific surface area of the active materials of the first positive electrode active material layer 114 and the second positive electrode active material layer 115 differs by 7-15 m

[0097] In the embodiments of the present application, in the case that the active materials of the first positive electrode active material layer 114 and the second positive electrode active material layer 115 are different in kind, the gravimetric capacity of the active materials of the first positive electrode active material layer 114 and the second positive electrode active material layer 115 differs by 20-110 mAh / g, not only can the two lithium ion batteries be ensured to be different, but also the performance of the lithium ion battery composed of the positive electrode active material layer of the active material with small gravimetric capacity and the lithium ion battery composed of the positive electrode active material layer of the active material with large gravimetric capacity can be complementary, and the entire battery structure has both high discharge rate and high energy density.

[0098] Exemplarily, the gravimetric capacity of the active materials of the first positive electrode active material layer 114 and the second positive electrode active material layer 115 differs by 20 mAh / g, 30 mAh / g, 40 mAh / g, 50 mAh / g, 60 mAh / g, 70 mAh / g, 80 mAh / g, 90 mAh / g, 100 mAh / g or 110 mAh / g.

[0099] The compaction densities of the first positive electrode active material layer 114 and the second positive electrode active material layer 115 differ by ≥0.8 g / cm 3 , for example, 0.8 g / cm 3 , 1 g / cm 3 , 1.5 g / cm 3 or 2 g / cm 3 .

[0100] In a possible embodiment, the thickness difference of the first conductive layer 112 and the second conductive layer 113 is 0.1-1.8 μm, for example, 0.1 μm, 0.3 μm, 0.5 μm, 0.8 μm, 1 μm, 1.5 μm or 1.8 μm. In a possible embodiment, the thickness difference of the first positive electrode active material layer 114 and the second positive electrode active material layer 115 is 5-50 μm, for example, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm or 50 μm.

[0101] The thickness of the first conductive layer 112 and the second conductive layer 113 is 0.1-3 μm, for example, 0.1 μm, 0.5 μm, 1 μm, 2 μm or 3 μm.

[0102] The thickness of the first conductive layer 112, the second conductive layer 113, the first positive electrode active material layer 114 and the second positive electrode active material layer 115 affects the process difficulty. If the thickness is too thick, it is not easy to dry, the coating efficiency is low, and cracks are prone to occur. The thickness of the first conductive layer, the second conductive layer, the first positive electrode active material layer 114 and the second positive electrode active material layer 115 in the embodiments of the present application is appropriate, the path of ion migration into the internal active material is short, the polarization is small, which is conducive to the rate charge and discharge, and the DCR is small, and the cycle performance is good.

[0103] The first negative active material layer 124 and the second negative active material layer 125 of the embodiment of the present application are not described simultaneously below.

[0104] When the first active positive material layer 115 and the second active positive material layer 115 are different, the first negative active material layer 124 and the second negative active material layer 125 can be the same or different. When the first negative active material layer 124 is different, the active material of the first negative active material layer 124 can be different in type, or the active material of the first negative active material layer 124 can be the same in type but different in particle size, specific surface area, gram capacity, etc.

[0105] Regardless of whether the active material of the first negative active material layer 124 and the second negative active material layer 125 is the same or different in type, the active material of the first negative active material layer 124 is selected from graphite, silicon-carbon, or mesocarbon microbeads, and the active material of the second negative active material layer 125 is also selected from graphite, silicon-carbon, or mesocarbon microbeads.

[0106] Optionally, the D10 particle size of the graphite of the embodiment of the present application is >4 μm, the D50 particle size is 7-15 μm, and the D90 particle size is ≤30 μm. Optionally, the specific surface area of the graphite is 0.5-8 m 2 / g, the gram capacity is 250-360 mAh / g, the coating amount is 5-15 mg / cm 2 , and the compacted density is 1.1-1.8 g / cm 3 .

[0107] Optionally, the D10 particle size of the silicon-carbon of the embodiment of the present application is 1-4 μm, the D50 particle size is 4-8 μm, and the D90 particle size is 9-12 μm. Optionally, the specific surface area of the silicon-carbon is 0.5-8 m 2 / g, the gram capacity is 360-1000 mAh / g, the coating amount is 5-10 mg / cm 2 , and the compacted density is 1.1-2 g / cm 3 .

[0108] Optionally, the D10 particle size of the mesocarbon microbeads of the embodiment of the present application is >4 μm, the D50 particle size is 7-15 μm, and the D90 particle size is ≤30 μm. Optionally, the specific surface area of the mesocarbon microbeads is 0.5-4 m 2 / g, the gram capacity is 200-400 mAh / g, the coating amount is 5-10 mg / cm 2 , and the compacted density is 1-2 g / cm 3 .

[0109] Exemplarily, when the active materials of the first negative active material layer 124 and the second negative active material layer 125 are of the same kind, the D10 particle diameter of the active materials of the first negative active material layer 124 and the second negative active material layer 125 differs by 0.1-4 μm, the D50 particle diameter differs by 0.1-8 μm, and the D90 particle diameter differs by 0.1-10 μm.

[0110] Optionally, when the active materials of the first negative active material layer 124 and the second negative active material layer 125 are of the same kind, the specific surface area of the active materials of the first negative active material layer 124 and the second negative active material layer 125 differs by 0.2-8 m 2 / g, for example, 0.2 m 2 / g, 0.5 m 2 / g, 1 m 2 / g, 2 m 2 / g, 3 m 2 / g, 4 m 2 / g, 5 m 2 / g, 6 m 2 / g, 7 m 2 / g, or 8 m 2 / g.

[0111] Optionally, when the active materials of the first negative active material layer 124 and the second negative active material layer 125 are of the same kind, the gravimetric capacity of the active materials of the first negative active material layer 124 and the second negative active material layer 125 differs by 10-100 mAh / g, for example, 10 mAh / g, 20 mAh / g, 30 mAh / g, 40 mAh / g, 50 mAh / g, 60 mAh / g, 70 mAh / g, 80 mAh / g, 90 mAh / g, or 100 mAh / g.

[0112] Optionally, when the active materials of the first negative active material layer 124 and the second negative active material layer 125 are of the same kind, the compaction density of the active materials of the first negative active material layer 124 and the second negative active material layer 125 differs by 0.1-1.8 g / cm 3 , for example, 0.1 g / cm 3 , 0.3 g / cm 3 , 0.5 g / cm 3 , 0.8 g / cm 3 , 1.0 g / cm 3 , 1.1 g / cm 3 , 1.3 g / cm 3 , 1.5 g / cm 3 , or 1.8 g / cm 3 .

[0113] Optionally, the thickness of the third conductive layer 122 and the fourth conductive layer 123 is 0.1-2 μm. When the active material of the first negative electrode active material layer 124 and the second negative electrode active material layer 125 is the same, the thickness difference of the third conductive layer 122 and the fourth conductive layer 123 is 0.1-1 μm. Optionally, the thickness difference of the first negative electrode active material layer 124 and the second negative electrode active material layer 125 is 5-100 μm.

[0114] When the active material of the first negative electrode active material layer 124 and the second negative electrode active material layer 125 is different, the first negative electrode active material layer 124 can be graphite, and the second negative electrode active material layer 125 can be silicon-carbon; or the first negative electrode active material layer 124 can be silicon-carbon, and the second negative electrode active material layer 125 can be graphite; or the first negative electrode active material layer 124 can be silicon-carbon, and the second negative electrode active material layer 125 can be mesocarbon microbeads.

[0115] Illustratively, when the active material of the first negative electrode active material layer 124 and the second negative electrode active material layer 125 is different, the D10 particle size of the active material of the first negative electrode active material layer 124 and the second negative electrode active material layer 125 differs by 0.1-4 μm, the D50 particle size differs by 0.1-10 μm, and the D90 particle size differs by 0.1-20 μm.

[0116] Optionally, the specific surface area of the active material of the first negative electrode active material layer 124 and the second negative electrode active material layer 125 differs by 0.5-8 m 2 / g, for example, 0.5 m 2 / g, 1 m 2 / g, 2 m 2 / g, 3 m 2 / g, 4 m 2 / g, 5 m 2 / g, 6 m 2 / g, 7 m 2 / g, or 8 m 2 / g.

[0117] Optionally, the gravimetric capacity of the active material of the first negative electrode active material layer 124 and the second negative electrode active material layer 125 differs by 10-200 mAh / g, for example, 10 mAh / g, 20 mAh / g, 30 mAh / g, 40 mAh / g, 50 mAh / g, 60 mAh / g, 70 mAh / g, 80 mAh / g, 90 mAh / g, 100 mAh / g, 120 mAh / g, 150 mAh / g, 180 mAh / g, or 100 mAh / g.

[0118] Optionally, the compaction density of the active material of the first negative electrode active material layer and the second negative electrode active material layer differs by 0.1-1.8 g / cm3 for example 0.1 g / cm 3 , 0.3 g / cm 3 , 0.5 g / cm 3 , 0.8 g / cm 3 , 1.0 g / cm 3 , 1.1 g / cm 3 , 1.3 g / cm 3 , 1.5 g / cm 3 or 1.8 g / cm 3 .

[0119] Optionally, when the active materials of the first negative active material layer 124 and the second negative active material layer 125 are different in kind, the thickness difference between the third conductive layer and the fourth conductive layer is 0.1-1.8 μm. Optionally, the thickness difference between the first negative active material layer 124 and the second negative active material layer 125 is 5-100 μm.

[0120] The arrangement of the tabs of the battery cell structure 10 of the embodiment of the present application is described as follows:

[0121] With the battery cell structure as an example, it is referred to Figure 1 that the first negative active material layer 124 and the first positive active material layer 114 arranged adjacently are separated by the first separation film 13, and the second positive active material layer 115 and the second negative active material layer 125 arranged adjacently are separated by the second separation film 14. The battery cell structure 10 has four tabs, which are the first tab 151, the second tab 152, the third tab 153 and the fourth tab 154, respectively, as referred to Figure 9 .

[0122] The battery cell structure 10 of the present application is further described in detail in combination with the embodiments.

[0123] Embodiment 1

[0124] The embodiment provides a wound battery cell structure, which comprises positive electrode sheets and negative electrode sheets arranged alternately.

[0125] The positive electrode sheet comprises a positive electrode insulating layer, a first conductive layer and a second conductive layer on two surfaces of the positive electrode insulating layer, a first positive active material layer on the surface of the first conductive layer, and a second positive active material layer on the surface of the second conductive layer. The first conductive layer and the second conductive layer are arranged in a staggered manner at the tabs, the first conductive layer and the positive electrode insulating layer extend outward relative to the second conductive layer to form a first tab, and the second conductive layer and the positive electrode insulating layer extend outward relative to the first conductive layer to form a second tab.

[0126] The negative electrode sheet comprises a negative electrode insulating layer, a third conductive layer and a fourth conductive layer on two surfaces of the negative electrode insulating layer, a first negative electrode active material layer on a surface of the third conductive layer, and a second negative electrode active material layer on a surface of the fourth conductive layer. The third conductive layer and the fourth conductive layer are arranged in a staggered manner at the tab, and the third conductive layer and the negative electrode insulating layer extend outward relative to the fourth conductive layer to form a third tab, and the fourth conductive layer and the negative electrode insulating layer extend outward relative to the fourth conductive layer to form a fourth tab.

[0127] The first tab and the fourth tab are arranged on one side of the winding symmetry plane of the winding structure, and the second tab and the third tab are arranged on the other side of the winding symmetry plane of the winding structure; in the length direction of the winding structure, the first tab is arranged between the second tab and the third tab.

[0128] The first negative electrode active material layer and the first positive electrode active material layer in the adjacent positive electrode sheet and negative electrode sheet are arranged close to each other, and the second negative electrode active material layer and the second positive electrode active material layer are arranged close to each other, the first negative electrode active material layer and the first positive electrode active material layer arranged adjacent to each other are separated by a first separation film, and the second negative electrode active material layer and the second positive electrode active material layer arranged adjacent to each other are separated by a second separation film.

[0129] The capacity ratio (CB1 value) of the first negative electrode active material layer to the first positive electrode active material layer is 1.1, and the capacity ratio (CB2 value) of the second negative electrode active material layer to the second positive electrode active material layer is 1.1.

[0130] Specific parameters of the active materials of the first positive electrode active material layer, the second positive electrode active material layer, the first negative electrode active material layer and the second negative electrode active material layer are shown in Table 1 and Table 2.

[0131] It should be noted that the first positive electrode active material layer and the second positive electrode active material layer are the same in this aspect, and the first negative electrode active material layer and the second negative electrode active material layer are the same in this aspect.

[0132] Example 2

[0133] Example 2 provides a winding cell structure, which has the same structure as the winding cell structure of Example 1, and the only difference is that the active materials of the first positive electrode active material layer and the second positive electrode active material layer of Example 2 are different from those of Example 1, and the active materials of the first negative electrode active material layer and the second negative electrode active material layer are different from those of Example 1. The setting conditions of the first positive electrode active material layer and the second positive electrode active material layer are recorded in Table 1, and the setting conditions of the active materials of the first negative electrode active material layer and the second negative electrode active material layer are recorded in Table 2.

[0134] Comparative Example 1

[0135] Comparative Example 1 provides a wound battery cell structure which has the same structure as the wound battery cell structure of Example 1, except that the D10 particle size of lithium iron phosphate in the second positive electrode active material layer of Comparative Example 1 is 0.6 μm, the D50 particle size is 2.8 μm, the D90 particle size is 9.6 μm, the specific surface area is 12 m 2 / g, the gravimetric capacity is 146 mAh / g, the coating amount is 20 mg / cm 2 , the compaction density is 2.35 g / cm 3 , and the weight of the carbon coating layer is 0.8% of the total weight of the carbon coating layer and lithium iron phosphate.

[0136] Table 1. Partial parameters of the first positive electrode active material layer and the second positive electrode active material layer of Examples 1-2 and Comparative Example 1

[0137]

[0138]

[0139] Table 2. Partial parameters of the first negative electrode active material layer and the second negative electrode active material layer of Examples 1, 2 and Comparative Example 1

[0140]

[0141]

[0142] Test Example

[0143] (1) The discharge capacity ratio (the ratio of the discharge capacity to the rated capacity), the weight energy density, the 75% capacity cycle number, the operating temperature range and the discharge DC resistance under 50% SOC conditions of the battery cell structure of Examples 1-2 and Comparative Example 1 at a 3C discharge rate at 25°C were tested, and the results are shown in Table 3. Among them, the DC resistance test method under 50% SOC conditions is to discharge for 30S at a 3C discharge rate at 25°C and 50% SOC, and the discharge DC resistance DCR is calculated, wherein DCR = ohmic resistance + electrochemical impedance + concentration difference impedance.

[0144] Table 3. Performance test results of the battery cell structure of Examples 1-2 and Comparative Example 1

[0145]

[0146] Compared with Comparative Example 1, the active material particle size of the second positive electrode active material layer of Example 1 is small, the specific surface area is large, the electron migration path is short, the carbon coating amount is large, and the active material of the second negative electrode active material layer adopts mesocarbon microbeads, the mesocarbon microbeads have high specific capacity and good isotropy, thereby the rate of Example 1 is improved compared with Comparative Example 1, the cycle life is greatly improved, and the low-temperature working interval is widened to-30℃. In addition, compared with Comparative Example 1, the active material particle size of the second positive electrode active material layer of Example 1 is small, the kinetic performance is good, the electrochemical impedance and concentration difference impedance are relatively small, the thickness of the first conductive layer is unchanged, the ohmic impedance is unchanged, and therefore the overall DCR is reduced. In addition, the mesocarbon microbead particle size distribution of the second negative electrode active material layer is relatively narrow and small, the thickness of the second conductive layer is increased, and the DCR is relatively small.

[0147] Compared with Comparative Example 1, the active material of the second positive electrode active material layer of Example 2 is polycrystalline nickel-cobalt-manganese (811 system), the specific capacity of the polycrystalline nickel-cobalt-manganese material is much higher than that of lithium iron phosphate, and the weight per unit is also much heavier than that of lithium iron phosphate, so the coating weight and the compaction density are both larger, and finally the weight energy density is also greatly improved. In addition, the active material of the second positive electrode active material layer has a large particle size and a small specific surface area, so the cycle number is greatly reduced. The polycrystalline nickel-cobalt-manganese material has good conductivity, so it does not need carbon coating, and the overall rate performance is improved. The performance of the polycrystalline nickel-cobalt-manganese material at low temperature is relatively good, so the working temperature interval of the battery cell can be extended to-25℃ at low temperature. Compared with Comparative Example 1, the active material of the second negative electrode active material layer adopts silicon-carbon material, has high specific capacity, and the coating weight and the thickness of the electrode sheet are both reduced, so the energy density is also improved compared with Comparative Example 1. Because the volume expansion of Example 2 is large during the cycle process, the particles are easily broken, which causes the cycle performance to be slightly attenuated. In addition, compared with Comparative Example 1, the active material of the second positive electrode active material layer is polycrystalline nickel-cobalt-manganese, has good conductivity, is beneficial to reducing the ohmic impedance, and increases the thickness of the second conductive layer to improve the current-carrying capacity, thereby greatly reducing the ohmic impedance. The electrochemical impedance and the concentration difference impedance of the polycrystalline nickel-cobalt-manganese are not larger than those of lithium iron phosphate, so the overall DCR is greatly reduced. Compared with Comparative Example 1, the silicon-carbon material of Example 2 has slightly reduced conductivity (which will cause the DCR to increase), but the thickness of the conductive layer is increased, and the overall effect is that the negative electrode slightly increases the DCR, but the positive electrode greatly affects the DCR, so the overall DCR is reduced.

[0148] The above is only a preferred embodiment of the present application and is not intended to limit the present application. Those skilled in the art can make various modifications and changes to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A battery cell structure, characterized in that, The application relates to a battery cell structure. The battery cell structure comprises positive electrode sheets and negative electrode sheets arranged alternately. The positive electrode sheet comprises a positive electrode insulating layer, a first conductive layer and a second conductive layer arranged on two surfaces of the positive electrode insulating layer, a first positive electrode active material layer arranged on a surface of the first conductive layer, and a second positive electrode active material layer arranged on a surface of the second conductive layer. The negative electrode sheet comprises a negative electrode insulating layer, a third conductive layer and a fourth conductive layer arranged on two surfaces of the negative electrode insulating layer, a first negative electrode active material layer arranged on a surface of the third conductive layer, and a second negative electrode active material layer arranged on a surface of the fourth conductive layer. The positive electrode sheet and the negative electrode sheet arranged adjacently are separated by a separation film. The current of the first conductive layer and the second conductive layer of the positive electrode sheet is respectively led out through a first tab and a second tab, and the first conductive layer and the second conductive layer of the positive electrode sheet are arranged staggeredly at the tabs. The current of the third conductive layer and the fourth conductive layer of the negative electrode sheet is respectively led out through a third tab and a fourth tab, and the third conductive layer and the fourth conductive layer of the negative electrode sheet are arranged staggeredly at the tabs. The first positive electrode active material layer and the second positive electrode active material layer are different, the D10 particle size of the active materials of the first positive electrode active material layer and the second positive electrode active material layer is different by 0.05-0.3 microns, the D50 particle size is different by 1-4 microns, and the D90 particle size is different by 3-5 microns. And / or, the first negative electrode active material layer and the second negative electrode active material layer are different, the D10 particle size of the active materials of the first negative electrode active material layer and the second negative electrode active material layer is different by 0.1-4 microns, the D50 particle size is different by 0.1-8 microns, and the D90 particle size is different by 0.1-10 microns.

2. The cell structure of claim 1, wherein, The first conductive layer and the positive electrode insulating layer extend outward relative to the second conductive layer to form a first tab, and the second conductive layer and the positive electrode insulating layer extend outward relative to the first conductive layer to form a second tab. The third conductive layer and the negative electrode insulating layer extend outward relative to the fourth conductive layer to form a third tab, and the fourth conductive layer and the negative electrode insulating layer extend outward relative to the fourth conductive layer to form a fourth tab.

3. The cell structure of claim 1, wherein, The first tab, the second tab, the third tab and the fourth tab are arranged on the same side of the height direction of the battery cell structure.

4. The cell structure of claim 1, wherein, Two of the first tab, the second tab, the third tab and the fourth tab are arranged on one side of the battery cell structure, and the other two are arranged on the other side of the height direction of the battery cell structure.

5. The cell structure of claim 3 or 4, wherein, The battery cell structure is a winding structure, the first tab and the fourth tab are arranged on one side of the winding symmetry plane of the winding structure, the second tab and the third tab are arranged on the other side of the winding symmetry plane, and the first tab is arranged between the second tab and the third tab in the length direction of the winding structure.

6. The cell structure of claim 3 or 4, wherein, The electric core structure is a winding structure, the second and third tabs are distributed on one side of a winding symmetry plane of the winding structure, the first and fourth tabs are distributed on the other side of the winding symmetry plane; in the length direction of the winding structure, the fourth tab is arranged between the second and third tabs.

7. The cell structure of claim 3 or 4, wherein, The electric core structure is a winding structure, the first and second tabs are distributed on one side of a winding symmetry plane of the winding structure, the third and fourth tabs are distributed on the other side of the winding symmetry plane; in the length direction of the winding structure, the third tab is arranged between the first and second tabs.

8. The cell structure of claim 3 or 4, wherein, The electric core structure is a winding structure, the first and second tabs are distributed on one side of a winding symmetry plane of the winding structure, the third and fourth tabs are distributed on the other side of the winding symmetry plane; in the length direction of the winding structure, the first tab is arranged between the third and second tabs.

9. The cell structure of claim 3 or 4, wherein, The electric core structure is a winding structure, the first, second, third and fourth tabs are arranged on the same side of a winding symmetry plane of the winding structure.

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