Lithium-ion battery

Abstract

A lithium-ion battery, comprising a cathode plate and an anode plate, wherein the porosity of the anode plate is N, and the value range of N is N≥50％; and the reaction capacity of the anode plate is Ca, the reaction capacity of the cathode plate is Cc, and the reaction capacity Ca of the anode plate and the reaction capacity Cc of the cathode plate meet the condition: 0＜Ca / Cc≤0.95. In the present application, the reaction capacity of an anode plate is controlled to be less than the reaction capacity of a cathode plate, such that the mass proportion of an anode active material in the lithium-ion battery is reduced on the premise of ensuring the battery capacity, and the mass energy density is improved by means of reducing active substances; moreover, the anode plate with high porosity is used, such that after lithium is completely intercalated into the anode active material, excess lithium on a cathode side can be induced to be controllably precipitated from pores of the anode plate in the form of lithium metal, thereby preventing uncontrollable precipitation of lithium on the surface of the anode plate, and taking both relatively high safety and cycle performance into consideration.

Description

lithium-ion batteries Technical Field

[0001] The present application belongs to the technical field of lithium-ion batteries, and specifically relates to a lithium-ion battery. Background Art

[0002] The overall capacity of a lithium-ion battery is determined by the capacity per unit area of ​​the cathode material inside the battery. To increase the battery's mass energy density (i.e., mass-to-capacity ratio), the battery's weight needs to be minimized while maintaining a constant charge. Prior art methods for reducing battery weight primarily involve reducing the mass proportion of inactive components and structural parts within the battery. These methods include using thinner electrode current collectors, using porous current collectors, reducing the amount of liquid injected into the battery, using thinner and lighter separators, and using thinner and lighter battery packaging bags.

[0003] During charging, lithium ions are released from the cathode material and then embedded in the anode material. During discharge, lithium ions are released from the anode material and then embedded in the cathode material. This cycle repeats, enabling repeated charging and discharging of the secondary battery. In practical battery design, to prevent uncontrolled lithium deposition on the anode electrode surface, which can lead to safety issues such as reduced cycle life and even battery short circuits, it is necessary to ensure that the lithium capacity that can be embedded in the anode material is greater than the lithium capacity that can be extracted from the cathode material. This portion of anode material that exceeds the cathode material capacity is used to prevent lithium ions from precipitating outside the anode material. During actual battery operation, it does not participate in lithium insertion or extraction and is considered an inactive component. Existing technologies have considered reducing the amount of this inactive component to increase the gravimetric energy density of lithium-ion batteries. However, the mass compression capacity of inactive components within the battery is limited, and increasing the gravimetric energy density of batteries by reducing the amount of inactive anode material is approaching its limit, making it difficult to further increase the gravimetric energy density of lithium-ion batteries. Therefore, existing technologies cannot simultaneously control lithium deposition (cycling performance) and further improve energy density.

[0004] Summary of the Invention

[0005] In order to solve the above problems, while taking into account both further improving the energy density of lithium-ion batteries and controlling the problem of lithium deposition, this application proposes a lithium-ion battery that uses a high-porosity anode electrode. During the battery charging process, when the anode material is fully embedded with lithium, it can induce the excess lithium on the cathode side to be controllably deposited on the anode side in the form of lithium metal, thereby preventing uncontrollable lithium deposition on the surface of the anode electrode and ensuring the cycle life of the lithium-ion battery. On this basis, by controlling the reaction capacity of the anode electrode to be lower than the reaction capacity of the cathode electrode, the mass proportion of active material in the anode electrode of the lithium-ion battery is reduced while ensuring the battery capacity, effectively improving the mass energy density of the lithium-ion battery while also taking into account higher cycle performance.

[0006] The lithium-ion battery provided in this application adopts the following scheme:

[0007] A lithium-ion battery comprises a cathode plate and an anode plate, wherein the porosity of the anode plate is N, and the value range of N is N≥50%; the reaction capacity of the anode plate is C a , the reaction capacity of the cathode plate is C c , the reaction capacity of the anode plate C a and the reaction capacity C of the cathode plate c Satisfy the conditions: 0<C a / C c ≤0.95. The lithium-ion battery of the present application adopts an anode plate with a high porosity (N≥50%). During the battery charging process, when the anode material is fully embedded with lithium, it can induce the excess lithium on the cathode side to be controlled and precipitated in the pores of the anode plate in the form of lithium metal, thereby preventing uncontrollable lithium precipitation on the surface of the anode plate. By controlling the porosity ≥50% to ensure safety, the anode reaction capacity C a Less than the cathode reaction capacity C c , both satisfy 0<C a / C c ≤0.95, breaking through the inertial thinking in this field that the anode lithium insertion capacity must be no less than the cathode lithium removal capacity. Under the premise of ensuring the battery capacity, the mass proportion of active materials in the anode electrode of the lithium-ion battery is reduced, and the mass energy density is improved by reducing the active material, while also taking into account higher safety performance and cycle performance.

[0008] Unlike traditional anode plates, the capacity of the anode plates in this application includes two parts: 1. The capacity exerted by the redox reaction between the anode material and lithium ions, that is, the capacity exerted by the lithium insertion of the anode material, which is defined in this application as the reaction capacity of the anode plate (lithium insertion capacity); 2. The capacity exerted by the lithium precipitated in the pores of the anode plate, which is defined in this application as the controllable lithium precipitation capacity of the anode plate. In this application, the reaction capacity and controllable lithium precipitation capacity of the anode plate together constitute the anode plate capacity. Therefore, although this application reduces the active material of the anode plate and reduces its reaction capacity, the lithium metal precipitated in the pores of the anode plate can still participate in the cycle and manifest as lithium precipitation capacity, so that the capacity of the anode plate is not reduced, and the mass of the anode active material is reduced while ensuring the capacity, so that the mass energy density of the lithium-ion battery is improved.

[0009] In addition, the reaction capacity (delithiation capacity) of the cathode electrode in the present application is the capacity exerted by the redox reaction of the cathode material, that is, the capacity exerted by the delithiation of the cathode material.

[0010] Furthermore, in the above lithium-ion battery, the reaction capacity C of the anode electrode is aand the reaction capacity C of the cathode plate c Conditions met: 0.20≤C a / C c ≤0.80. By controlling the relationship between the anode reaction capacity and the cathode reaction capacity, the active material in the anode electrode can be further reduced, thereby improving the mass energy density of the lithium-ion battery.

[0011] Furthermore, in the above lithium-ion battery, the reaction capacity C of the anode electrode is a and the reaction capacity C of the cathode plate c Satisfy the conditions: 0.40≤C a / C c ≤0.60.

[0012] Preferably, the porosity N of the anode electrode is in the range of 50% ≤ N ≤ 90%. This application controls the porosity to be between 50% and 90%, so that the excess lithium released can be controlled and precipitated at the anode. This improves safety and cycle performance, while avoiding excessive volume of the anode electrode due to excessively high porosity, thereby ensuring that the anode electrode has an appropriate volume that is beneficial for application. In some application scenarios where volume requirements are not high, the porosity of the anode electrode can meet N>90%, so that the pores of the anode electrode can accommodate more lithium ions for controllable precipitation.

[0013] Furthermore, in order to take into account excellent safety, cycle performance and appropriate volume, the porosity N of the anode plate is in the range of 65%≤N≤76%.

[0014] Preferably, the porosity N of the anode plate and the reaction capacity C of the anode plate are a and the reaction capacity C of the cathode plate c Satisfy the relationship I: N≥[-0.9375×(C a / C c )+1.0625]×100%. By controlling the relationship between the porosity of the anode plate, the reaction capacity of the anode plate, and the reaction capacity of the cathode plate, the excess lithium ions of the cathode material can be completely absorbed by the pores of the anode plate after reducing the amount of positive electrode material, which can improve the energy density and avoid the uncontrollable precipitation of lithium on the surface of the anode plate, which helps to achieve the best energy density and cycle performance. Furthermore, when the porosity N of the anode plate and the reaction capacity C of the anode plate are a and the reaction capacity C of the cathode plate c Satisfy the relationship I: N>[-0.9375×(C a / C c )+1.0625]×100%, it is beneficial to further improve the cycle performance of lithium-ion batteries.

[0015] Preferably, the anode plate has a two-dimensional structure and / or a three-dimensional structure. The anode material can be a material with a two-dimensional structure, a material with a three-dimensional structure, or a mixture of a material with a two-dimensional structure and a material with a three-dimensional structure, that is, the anode plate can have a composite structure including two-dimensional and three-dimensional structures.

[0016] Preferably, the anode plate comprises at least one of silicon oxide, silicon carbon, pure silicon, silver, tin, hard carbon, soft carbon, graphite, and lithium titanate. The use of lithium-intercalated materials such as graphite, hard carbon, soft carbon, and silicon as anode materials is technologically mature and widely available. In this application, pure silicon refers to silicon with a purity of 99% or greater; soft carbon refers to amorphous carbon that can graphitize at temperatures above 2000°C; and hard carbon refers to amorphous carbon that is difficult to graphitize even at temperatures above 2500°C.

[0017] Preferably, the cathode plate comprises at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium manganese oxide, lithium iron phosphate, lithium-rich manganese-based materials, and sulfur. In this application, the lithium-rich manganese-based material refers to a material composed of Li2MnO3 and LiMO2 (M=Ni 1 / 2 Mn 1 / 2 and / or Mn x Ni y Co (1-x-y) ) materials.

[0018] Based on the lithium-ion battery of the present application, by controlling the reaction capacity C of the anode plate a and the reaction capacity C of the cathode plate c Satisfy the conditions: 0<C a / C c≤0.95. During the charging process of a lithium-ion battery, the cathode electrode provides lithium ions and the anode electrode receives lithium ions. This application improves the energy density of the lithium-ion battery by reducing the amount of anode active material while keeping the amount of lithium ions provided unchanged by controlling the reaction capacity relationship between the cathode and the anode. The anode electrode cannot receive all the lithium ions that are present in the cathode electrode. Therefore, this application controls the porosity N of the anode electrode to be ≥50%, so that the excess lithium ions are precipitated inside the pores of the anode electrode, avoiding the problem of lithium precipitation on the surface of the anode electrode, and making the lithium-ion battery have better cycle performance and safety performance. The lithium ions that enter the pores of the anode electrode and the lithium ions embedded in the structure of the anode active material still participate in the cycle process, so the amount of active lithium in the battery has not decreased. However, due to the reduction in the reaction capacity of the anode electrode, the corresponding anode material load per unit area is also lower. Therefore, the mass of the active material in the anode electrode in the lithium-ion battery is reduced while ensuring the battery capacity, so the energy density can be effectively improved. Therefore, the present application controls the reaction capacity ratio between the anode and cathode plates and the porosity of the anode plates, so that the active lithium will not be reduced, the load of the anode plates can be reduced, and lithium plating can be avoided, thereby improving the energy density, safety performance and cycle performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] FIG1 is a surface photograph of the anode electrode piece obtained by disassembling the lithium-ion battery of Comparative Example 1 in a fully charged state;

[0020] FIG2 is a cross-sectional photograph of the anode electrode piece obtained by disassembling the lithium-ion battery of Comparative Example 1 in a fully charged state;

[0021] FIG3 is a surface photograph of the anode electrode piece obtained by disassembling the lithium-ion battery of Comparative Example 2 in a fully charged state;

[0022] FIG4 is a cross-sectional photograph of the anode electrode piece obtained by disassembling the lithium-ion battery of Comparative Example 2 in a fully charged state;

[0023] FIG5 is a surface photograph of the anode electrode piece obtained by disassembling the lithium-ion battery of Example 1 in a fully charged state;

[0024] FIG6 is a cross-sectional photograph of the anode electrode piece obtained by disassembling the lithium-ion battery of Example 1 in a fully charged state;

[0025] FIG7 shows the ratio of the porosity N to the capacity per unit area of ​​the anode and cathode electrodes (C a / C c )’s corresponding relationship curve. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of this application more clearly understood, the present application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0027] In the lithium-ion battery of the present application, the reaction capacity of the anode plate is reduced (ie, 0<C a / C c ≤0.95), on the basis of keeping the amount of lithium ions that can be extracted from the cathode unchanged, the mass of the anode active material in the lithium-ion battery can be reduced, thereby improving the energy density of the battery. On this basis, since the capacity of the anode electrode that can embed lithium is less than the capacity of the cathode electrode that can extract lithium, during the battery charging process, when the anode material is completely embedded with lithium, some lithium ions will not be able to enter the anode active material. However, at the same time, due to the use of a high-porosity (N≥50%) anode electrode, the lithium ions that cannot enter the anode active material will enter the pores in the form of metallic lithium, that is, part of the lithium ions on the cathode side are embedded in the active material on the anode side, and the rest will enter the pore structure on the anode side. Since the excess lithium ions have entered the pores, lithium deposition will not occur on the surface of the electrode, avoiding or reducing safety issues such as short circuits caused by uncontrollable lithium deposition.

[0028] In the lithium-ion battery of this application, the relevant materials and their preparation methods and the testing methods of relevant performance are as follows:

[0029] Anode plate

[0030] In the present application, the conventional coating and cold pressing method can be used to prepare the anode electrode sheet, which specifically includes uniformly dispersing the raw materials such as lithium-intercalated anode material, binder, conductive agent, solvent dispersant, etc. to form a slurry, coating the slurry on the anode current collector, drying, and cold pressing to obtain the anode electrode sheet.

[0031] In order to control the porosity of the anode electrode to be not less than 50%, a lithium-intercalated anode material with a three-dimensional porous structure can be used when preparing the slurry; a lithium-intercalated anode material with a large particle size can be used; the solid content of the anode slurry can be reduced; a pore-forming agent can be added to the anode slurry, and the pore-forming agent decomposes into gas and escapes during the drying process of the electrode to form holes inside the anode electrode; the cold pressing pressure of the electrode can be reduced; and the electrode cold pressing process can be omitted.

[0032] In the present application, the anode electrode can also be prepared by the electrospinning method, which specifically includes uniformly dispersing the lithium-intercalated anode material, the polymer main material, and the solvent dispersant into a spinning solution, and then using an electrospinning device to prepare an anode electrode with a three-dimensional porous structure constructed from a one-dimensional fiber structure.

[0033] cathode plate

[0034] In this application, the cathode electrode sheet can be prepared using a conventional coating and cold pressing method. Taking the ternary positive electrode as an example, the ternary positive electrode material (NCM811), conductive carbon black, and polyvinylidene fluoride (PVDF) are thoroughly stirred and mixed in an N-methylpyrrolidone solvent system at a weight ratio of approximately 97.7%:1.0%:1.3% to prepare a positive electrode slurry. The prepared positive electrode slurry is coated on the positive electrode current collector aluminum foil, dried, and cold pressed to obtain the positive electrode, i.e., the cathode electrode sheet of this application.

[0035] In the lithium-ion battery of the present application, the capacity per unit area of ​​the anode electrode can be reduced by reducing the anode material load in the anode electrode, and the capacity per unit area of ​​the cathode electrode can be increased by increasing the cathode material load in the cathode electrode. In the present application, the mass energy density of the lithium-ion battery is calculated by dividing the battery capacity by the battery mass. When the anode material load in the anode electrode is reduced, the amount of lithium ions that can be released by the cathode material remains unchanged, which corresponds to the battery capacity of the lithium-ion battery remaining unchanged. The mass of the anode active material is reduced, which corresponds to the total mass of the lithium-ion battery being reduced, and the mass energy density is improved. When the cathode material load in the cathode electrode is increased, the amount of lithium ions that can be released by the cathode material increases, which corresponds to the battery capacity of the lithium-ion battery being increased. The anode material in the anode electrode is reduced compared to conventional lithium-ion batteries, which is equivalent to a reduction in the total mass of the lithium-ion battery, and the mass energy density of the lithium-ion battery is improved.

[0036] The lithium-ion battery of the present application further includes: an electrolyte and a separator.

[0037] electrolyte

[0038] In this application, conventional ether or carbonate electrolytes can be used. Taking a conventional ether electrolyte as an example, in a dry argon atmosphere, dioxolane (DOL) and ethylene glycol dimethyl ether (DME) are first mixed in a 1:1 volume ratio, and then lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) is added, dissolved, and mixed evenly to obtain an ether electrolyte with a lithium salt concentration of 1M.

[0039] Lithium-ion battery full battery

[0040] In this application, a full lithium-ion battery cell can be prepared using conventional methods, with a separator separating the cathode and anode electrodes. The separator can be a conventional separator and may include a substrate layer and a surface treatment layer. For example, a porous polyethylene film with a thickness of 9 μm can be used as a separator between the cathode and anode electrodes, and assembled together with the anode electrode, cathode electrode, and electrolyte to form a full battery.

[0041] The lithium-ion battery of the present application can be a button battery, a soft-pack battery, a square battery, a special-shaped battery or the like.

[0042] The porosity of the anode electrode is tested using the gas replacement method. The test method is as follows: Cut an anode electrode sample of appropriate mass, vacuum dry the sample, and place it in the sample chamber of the true density tester. The test system is then sealed and completely evacuated. First, the sample chamber and expansion chamber are independently sealed, and then nitrogen is introduced into each chamber. The gas pressures in the sample chamber and expansion chamber are recorded as P1 and Pa respectively. The valve between the sample chamber and expansion chamber is then opened to connect the two. After the pressure stabilizes, the pressure in the sample chamber and expansion chamber is recorded as P2. The true volume V of the sample can then be calculated according to the following formula: Among them, V CELL is the volume of the sample chamber of the true density tester, V EXP is the volume of the expansion chamber of the true density tester; the apparent volume V0 of the sample can be obtained by measuring the area S of the sample, the total thickness H of the anode electrode and the thickness h of the anode current collector: V0 = S × (Hh); the porosity of the electrode can be calculated

[0043] Calculation method of battery theoretical mass energy density: In this application, in order to facilitate the comparison of the theoretical energy density of lithium-ion batteries of various embodiments and comparative examples, all embodiments and comparative examples use the same 10μm thick copper foil as the anode current collector; the same 12μm thick aluminum foil as the cathode current collector; the same 9μm thick porous polyethylene film as the separator; and the injection volume is designed to be one-tenth of the cathode loading. It should be noted that the use of this condition to assemble a full battery for measurement and comparison is only to unify the measurement scale of the theoretical energy density of lithium-ion batteries and facilitate the performance comparison of the embodiments and comparative examples, and does not limit the materials and sizes of the lithium-ion batteries of this application; the lithium-ion batteries of this application can select different types and sizes of anode current collectors, cathode current collectors and separator materials according to different application requirements.

[0044] In order to more intuitively illustrate the improvement in energy density of the lithium-ion battery configured with a lithium-poor anode material in this application, the theoretical mass energy density of the battery is calculated based on the total mass M (mg) of the four main materials of the battery, namely the cathode electrode, the anode electrode, the electrolyte and the separator. At 25°C, the battery is charged at a constant current of 0.2C to the charge cut-off voltage, and then charged at a constant voltage to a current of 0.025C. At this time, the battery is fully charged, and the charge capacity at this time is recorded, which is the charge capacity of the first cycle; after the battery is allowed to stand for 5 minutes, it is discharged at a constant current of 0.5C to the discharge cut-off voltage. This is a cyclic charge and discharge process; the battery is subjected to a 5-cycle charge and discharge process, and the discharge capacity A (mAh) of the 5th cycle is recorded; the discharge voltage U (V) of the 5th cycle is recorded. The theoretical mass energy density W (Wh / kg) of the battery can be calculated according to the following formula:

[0045] Cycling performance test method: At 25°C, charge the battery at a constant current of 0.2C to the charge cutoff voltage. Then, charge at a constant voltage to a current of 0.025C. At this point, the battery is fully charged. The charge capacity at this point is recorded as the first cycle charge capacity. After the battery rests for 5 minutes, discharge it at a constant current of 0.5C to the discharge cutoff voltage. This constitutes one cycle of charge and discharge. The discharge capacity at this point is recorded as the first cycle discharge capacity. The battery is cyclically charged and discharged according to the above method, recording the discharge capacity after each cycle until the battery's discharge capacity decays to 80% of the first cycle discharge capacity. The number of cycles at this point is used to characterize the battery's cycling performance. The higher the number of cycles, the better the battery's cycling performance.

[0046] In the theoretical mass energy density and cycle performance test of lithium-ion batteries, the specific values ​​of the charge cut-off voltage and the discharge cut-off voltage are not strictly limited in this application and can be determined according to the lithium-ion battery system composed of different positive electrode materials and negative electrode materials in the field. For example, when the anode material of the lithium-ion battery is a ternary material, the charge cut-off voltage is 4.3V and the discharge cut-off voltage is 2.8V.

[0047] In the lithium-ion battery system of the present application, the anode and cathode plates have the same area in the working state, so the capacity per unit area C of the anode plate can be used. a1 (Anode surface capacity) represents the reaction capacity of the anode plate, and the unit area capacity C of the cathode plate is used. c1 (Cathode surface capacity) represents the reaction capacity of the cathode plate, which is expressed as the unit area capacity of the anode plate / the unit area capacity of the cathode plate. a / C c .

[0048] The capacity per unit area of ​​the anode plate in this application is C a1 and the unit area capacity C of the cathode plate c1 The reaction capacity (lithium insertion capacity) of the anode electrode can be measured by a method comprising the following steps: a , divided by the area of ​​the anode plate to obtain the unit area capacity C of the anode plate a1 ; Test to obtain the reaction capacity (lithium removal capacity) C of the cathode electrode c , divided by the area of ​​the cathode plate to obtain the unit area capacity C of the cathode plate c1 .

[0049] In some embodiments, the lithium insertion capacity C of the anode electrode is a Or the lithium removal capacity C of the cathode electrode c Follow this method to test:

[0050] Assemble the test battery by using the anode or cathode electrode as the electrode to be tested, the electrode to be tested as the cathode and the pure lithium electrode as the anode. Then charge the test battery at a constant current of 0.1C to the charge termination voltage, and then discharge it at a constant current of 0.1C to the discharge termination voltage. The discharge capacity of the test battery is the lithium insertion capacity C of the tested anode electrode. a Or the lithium removal capacity C of the tested cathode electrode c .

[0051] In some embodiments, the charge termination voltage and the discharge termination voltage are determined as follows:

[0052] When the anode electrode is the cathode, the charge termination voltage is 3V and the discharge termination voltage is 0.005V; or, when the cathode electrode is the cathode, the delithiation capacity C of the cathode electrode is c The test methods include:

[0053] When the cathode material of the cathode electrode is lithium cobalt oxide, the charge termination voltage is 4.5V and the discharge termination voltage is 3.2V; when the cathode material of the cathode electrode is one of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and lithium manganese oxide, or any combination and any proportion of the mixture, the charge termination voltage is 4.3V and the discharge termination voltage is 2.8V; when the cathode material of the cathode electrode is lithium iron phosphate, the charge termination voltage is 4.0V and the discharge termination voltage is 2.5V; when the cathode material of the cathode electrode is lithium-rich manganese-based material, the charge termination voltage is 4.8V and the discharge termination voltage is 3.0V; when the cathode material of the cathode electrode is sulfur, the charge termination voltage is 3.0V and the discharge termination voltage is 1.7V.

[0054] In some embodiments, the capacity per unit area of ​​the cathode plate C c1 The value range is 2mAh≤C c1 ≤5mAh; and / or, the capacity per unit area of ​​the anode plate C a1 The value range is 1mAh≤C a1 ≤4mAh. In this application, increasing the cathode electrode sheet's areal capacity (corresponding to selecting a higher cathode material loading) is beneficial to increasing the total capacity of the lithium-ion battery; by controlling the anode electrode sheet's areal capacity to a lower level (corresponding to selecting a lower anode material loading), the lithium-ion battery's mass is reduced without affecting its total capacity. Therefore, by controlling the optional range of the cathode and anode electrode sheet's per unit area capacity and coordinating them, the lithium-ion battery can ensure a high mass energy density.

[0055] Example

[0056] The technical solution of the present application is described below with reference to specific embodiments and comparative examples. Unless otherwise specified, the raw materials used in the following embodiments are all from common commercially available products, and the devices or equipment used are all purchased from conventional market sales channels.

[0057] Example 1

[0058] In the lithium-ion battery of this embodiment, the cathode current collector is an aluminum foil with a thickness of 12 μm, the cathode material is lithium nickel cobalt manganese oxide NCM811, and the cathode loading is 18.37 mg / cm 2 The anode current collector is a copper foil with a thickness of 10 μm, and the anode material is a silicon oxide material. The obtained anode electrode has a three-dimensional structure and the anode load is 2.25 mg / cm 2 A porous polyethylene film with a thickness of 9 μm is used as a separator and placed between the cathode and anode plates. An ether electrolyte with a lithium salt concentration of 1M is used, and the injection volume is one-tenth of the cathode load. The separator, anode plate, cathode plate and electrolyte are assembled together to form a full battery.

[0059] The performance of the anode and cathode plates was tested: the porosity of the anode plate was determined to be N=50% by using a gas replacement method.

[0060] The anode electrode is used as the electrode to be tested, the electrode to be tested is used as the positive electrode, and the pure lithium sheet is used as the negative electrode to assemble a test battery. Then the test battery is first charged at a constant current of 0.1C to a charge termination voltage of 3V, and then discharged at a constant current of 0.1C to a discharge termination voltage of 0.005V. The discharge capacity of the test battery is obtained, which is the reaction capacity C of the tested anode electrode. a The capacity per unit area of ​​the anode plate is calculated by dividing the reaction capacity of the anode plate by the plate area. a1 =3.02mAh / cm 2 .

[0061] The cathode electrode is used as the electrode to be tested, the electrode to be tested is used as the positive electrode, and the pure lithium sheet is used as the negative electrode to assemble a test battery. Then the test battery is first charged at a constant current of 0.1C to a charge termination voltage of 4.5V, and then discharged at a constant current of 0.1C to a discharge termination voltage of 3.2V. The discharge capacity of the test battery is obtained, which is the reaction capacity C of the cathode electrode tested. c The cathode electrode capacity per unit area is calculated by dividing the cathode electrode reaction capacity by the electrode area. c1 =3.75mAh / cm 2 , the unit area capacity of the anode plate / the unit area capacity of the cathode plate = C a / C c =0.81≤0.95.

[0062] Example a

[0063] The lithium-ion battery of this embodiment differs from that of embodiment 1 only in that the porosity N of the anode plate obtained by gas displacement method is 30%. The anode loading is 2.65 mg / cm2 The unit area capacity of the anode plate is 3.56 mAh / cm 2 The unit area capacity of the cathode plate is 3.75 mAh / cm 2 Calculate the capacity per unit area of ​​the anode plate / the capacity per unit area of ​​the cathode plate = the reaction capacity of the anode plate / the reaction capacity of the cathode plate = C a / C c =0.95.

[0064] Example b

[0065] The lithium-ion battery of this embodiment differs from that of embodiment 1 only in that the porosity N of the anode plate obtained by gas displacement method is 85%. The anode loading is 0.56 mg / cm 2 The unit area capacity of the anode plate is 0.75 mAh / cm 2 The unit area capacity of the cathode plate is 3.75 mAh / cm 2 Calculate the capacity per unit area of ​​the anode plate / the capacity per unit area of ​​the cathode plate = the reaction capacity of the anode plate / the reaction capacity of the cathode plate = C a / C c =0.20.

[0066] Example 2

[0067] The lithium ion battery of this embodiment differs from that of embodiment 1 only in that the anode loading is 1.67 mg / cm 2 The unit area capacity of the anode plate is 2.25 mAh / cm 2 The unit area capacity of the cathode plate is 3.75 mAh / cm 2 Calculate the capacity per unit area of ​​the anode plate / the capacity per unit area of ​​the cathode plate = the reaction capacity of the anode plate / the reaction capacity of the cathode plate = C a / C c =0.60.

[0068] Example 3

[0069] The lithium-ion battery of this embodiment differs from that of embodiment 1 only in that the porosity N of the anode plate obtained by gas displacement method is 65%. The anode loading is 1.40 mg / cm 2 The unit area capacity of the anode plate is 1.88 mAh / cm 2 The unit area capacity of the cathode plate is 3.75 mAh / cm 2 Calculate the capacity per unit area of ​​the anode plate / the capacity per unit area of ​​the cathode plate = the reaction capacity of the anode plate / the reaction capacity of the cathode plate = C a / Cc =0.50.

[0070] Example 4

[0071] The lithium ion battery of this embodiment differs from that of embodiment 3 only in that the anode loading is 1.67 mg / cm 2 The unit area capacity of the anode plate is 2.25 mAh / cm 2 The unit area capacity of the cathode plate is 3.75 mAh / cm 2 Calculate the capacity per unit area of ​​the anode plate / the capacity per unit area of ​​the cathode plate = the reaction capacity of the anode plate / the reaction capacity of the cathode plate = C a / C c =0.60.

[0072] Example 5

[0073] The lithium ion battery of this embodiment differs from that of embodiment 3 only in that the anode loading is 1.22 mg / cm 2 The unit area capacity of the anode plate is 1.64 mAh / cm 2 The unit area capacity of the cathode plate is 3.75 mAh / cm 2 Calculate the capacity per unit area of ​​the anode plate / the capacity per unit area of ​​the cathode plate = the reaction capacity of the anode plate / the reaction capacity of the cathode plate = C a / C c =0.60.

[0074] Example 6

[0075] The lithium-ion battery of this embodiment is different from that of embodiment 5 only in that the porosity N of the anode electrode plate obtained by gas replacement method is 76%.

[0076] Example 7

[0077] The lithium ion battery of this embodiment is different from that of embodiment 3 only in that the cathode loading is 10.58 mg / cm 2 , the anode loading is 0.8 mg / cm 2 The test results show that the unit area capacity of the anode plate is 1.08 mAh / cm 2 The unit area capacity of the cathode plate is 2.16 mAh / cm 2 , the unit area capacity of the anode plate / the unit area capacity of the cathode plate = the reaction capacity of the anode plate / the reaction capacity of the cathode plate = C a / C c =0.50.

[0078] Example 8

[0079] The lithium ion battery of this embodiment is different from that of embodiment 3 only in that the cathode loading is 13.18 mg / cm 2 , the anode loading is 1 mg / cm 2 The test results show that the unit area capacity of the anode plate is 1.35 mAh / cm 2 The unit area capacity of the cathode plate is 2.69 mAh / cm 2 , the unit area capacity of the anode plate / the unit area capacity of the cathode plate = the reaction capacity of the anode plate / the reaction capacity of the cathode plate = C a / C c =0.50.

[0080] Example 9

[0081] The lithium ion battery of this embodiment is different from that of embodiment 3 only in that the cathode loading is 15.78 mg / cm 2 , the anode loading is 1.21 mg / cm 2 The test results show that the unit area capacity of the anode electrode is 1.62 mAh / cm 2 The unit area capacity of the cathode plate is 3.22 mAh / cm 2 , the unit area capacity of the anode plate / the unit area capacity of the cathode plate = the reaction capacity of the anode plate / the reaction capacity of the cathode plate = C a / C c =0.50.

[0082] Example 10

[0083] The lithium ion battery of this embodiment differs from that of embodiment 3 only in that the anode material is silicon carbon material and the anode loading is 1.32 mg / cm 2 The anode plate has a three-dimensional structure. The porosity N of the anode plate is 65% as determined by the gas replacement method. The unit area capacity of the anode plate is 1.88 mAh / cm 2 The unit area capacity of the cathode plate is 3.75 mAh / cm 2 , the unit area capacity of the anode plate / the unit area capacity of the cathode plate = the reaction capacity of the anode plate / the reaction capacity of the cathode plate = C a / C c =0.50.

[0084] Example 11

[0085] The lithium ion battery of this embodiment is different from that of embodiment 3 only in that the anode material is pure silicon material and the anode loading is 0.80 mg / cm 2The anode plate has a three-dimensional structure. The porosity N of the anode plate is 65% as determined by the gas replacement method. The unit area capacity of the anode plate is 1.88 mAh / cm 2 The unit area capacity of the cathode plate is 3.75 mAh / cm 2 , the unit area capacity of the anode plate / the unit area capacity of the cathode plate = the reaction capacity of the anode plate / the reaction capacity of the cathode plate = C a / C c =0.50.

[0086] Example 12

[0087] The lithium-ion battery of this embodiment differs from that of embodiment 3 only in that the cathode material is lithium cobalt oxide (LCO) and the cathode loading is 16.56 mg / cm 2 The anode material is silicon oxide, and the anode load is 1.09 mg / cm 2 The test results show that the unit area capacity of the anode plate is 1.47 mAh / cm 2 The unit area capacity of the cathode plate is 2.93 mAh / cm 2 , the unit area capacity of the anode plate / the unit area capacity of the cathode plate = the reaction capacity of the anode plate / the reaction capacity of the cathode plate = C a / C c =0.50.

[0088] Example 13

[0089] The lithium ion battery of this embodiment is different from that of embodiment 3 only in that the cathode material is lithium manganate LMO and the cathode loading is 19.02 mg / cm 2 The anode material is silicon oxide, and the anode load is 1.09 mg / cm 2 The test results show that the unit area capacity of the anode plate is 1.05 mAh / cm 2 The unit area capacity of the cathode plate is 2.08 mAh / cm 2 , the unit area capacity of the anode plate / the unit area capacity of the cathode plate = the reaction capacity of the anode plate / the reaction capacity of the cathode plate = C a / C c =0.50.

[0090] Comparative Example 1

[0091] The lithium-ion battery of this comparative example differs from that of Example 1 only in that the porosity N of the anode plate obtained by gas displacement method is 25%. The anode loading is 2.93 mg / cm 2 The unit area capacity of the anode plate is 3.94 mAh / cm 2The unit area capacity of the cathode plate is 3.75 mAh / cm 2 Calculate the capacity per unit area of ​​the anode plate / the capacity per unit area of ​​the cathode plate = the reaction capacity of the anode plate / the reaction capacity of the cathode plate = C a / C c =1.05.

[0092] Comparative Example 2

[0093] The lithium-ion battery of this comparative example differs from that of Example 1 only in that the porosity N of the anode plate obtained by gas displacement method is 25%. The anode loading is 2.25 mg / cm 2 The unit area capacity of the anode plate is 3.01 mAh / cm 2 The unit area capacity of the cathode plate is 3.75 mAh / cm 2 Calculate the capacity per unit area of ​​the anode plate / the capacity per unit area of ​​the cathode plate = the reaction capacity of the anode plate / the reaction capacity of the cathode plate = C a / C c =0.80.

[0094] Comparative Example 3

[0095] The lithium-ion battery of this comparative example differs from that of Example 1 only in that the porosity N of the anode plate obtained by gas displacement method is 37%. The anode loading is 2.25 mg / cm 2 The unit area capacity of the anode plate is 3.02 mAh / cm 2 The unit area capacity of the cathode plate is 3.75 mAh / cm 2 Calculate the capacity per unit area of ​​the anode plate / the capacity per unit area of ​​the cathode plate = the reaction capacity of the anode plate / the reaction capacity of the cathode plate = C a / C c =0.81.

[0096] Comparative Example 4

[0097] The lithium-ion battery of this comparative example differs from that of Example 7 only in that the porosity N of the anode plate obtained by gas displacement method is 25%. The anode loading is 1.69 mg / cm 2 The unit area capacity of the anode plate is 2.27 mAh / cm 2 The unit area capacity of the cathode plate is 2.16 mAh / cm 2 Calculate the capacity per unit area of ​​the anode plate / the capacity per unit area of ​​the cathode plate = the reaction capacity of the anode plate / the reaction capacity of the cathode plate = C a / C c =1.05.

[0098] Comparative Example 5

[0099] The lithium-ion battery of this comparative example differs from that of Example 8 only in that the porosity N of the anode plate obtained by gas displacement method is 25%. The anode loading is 2.10 mg / cm 2 The unit area capacity of the anode plate is 2.83 mAh / cm 2 The unit area capacity of the cathode plate is 2.69 mAh / cm 2 Calculate the capacity per unit area of ​​the anode plate / the capacity per unit area of ​​the cathode plate = the reaction capacity of the anode plate / the reaction capacity of the cathode plate = C a / C c =1.05.

[0100] Comparative Example 6

[0101] The lithium-ion battery of this comparative example differs from that of Example 9 only in that the porosity N of the anode plate obtained by gas displacement method is 25%. The anode loading is 2.52 mg / cm 2 The unit area capacity of the anode plate is 3.38 mAh / cm 2 The unit area capacity of the cathode plate is 3.22 mAh / cm 2 Calculate the capacity per unit area of ​​the anode plate / the capacity per unit area of ​​the cathode plate = the reaction capacity of the anode plate / the reaction capacity of the cathode plate = C a / C c =1.05.

[0102] Comparative Example 7

[0103] The lithium-ion battery of this comparative example differs from that of Example 10 only in that the porosity N of the anode plate obtained by gas displacement method is 25%. The anode loading is 2.76 mg / cm 2 The unit area capacity of the anode plate is 3.94 mAh / cm 2 The unit area capacity of the cathode plate is 3.75 mAh / cm 2 Calculate the capacity per unit area of ​​the anode plate / the capacity per unit area of ​​the cathode plate = the reaction capacity of the anode plate / the reaction capacity of the cathode plate = C a / C c =1.05.

[0104] Comparative Example 8

[0105] The lithium-ion battery of this comparative example differs from that of Example 11 only in that the porosity N of the anode plate obtained by gas displacement method is 25%. The anode loading is 1.68 mg / cm 2The unit area capacity of the anode plate is 3.94 mAh / cm 2 The unit area capacity of the cathode plate is 3.75 mAh / cm 2 Calculate the capacity per unit area of ​​the anode plate / the capacity per unit area of ​​the cathode plate = the reaction capacity of the anode plate / the reaction capacity of the cathode plate = C a / C c =1.05.

[0106] Comparative Example 9

[0107] The lithium-ion battery of this comparative example differs from that of Example 12 only in that the porosity N of the anode plate obtained by gas displacement method is 25%. The anode loading is 2.29 mg / cm 2 The unit area capacity of the anode plate is 3.08 mAh / cm 2 The unit area capacity of the cathode plate is 2.93 mAh / cm 2 Calculate the capacity per unit area of ​​the anode plate / the capacity per unit area of ​​the cathode plate = the reaction capacity of the anode plate / the reaction capacity of the cathode plate = C a / C c =1.05.

[0108] Comparative Example 10

[0109] The lithium-ion battery of this comparative example differs from that of Example 13 only in that the porosity N of the anode plate obtained by gas displacement method is 25%. The anode loading is 1.62 mg / cm 2 The unit area capacity of the anode plate is 2.18 mAh / cm 2 The unit area capacity of the cathode plate is 2.08 mAh / cm 2 Calculate the capacity per unit area of ​​the anode plate / the capacity per unit area of ​​the cathode plate = the reaction capacity of the anode plate / the reaction capacity of the cathode plate = C a / C c =1.05.

[0110] Test Example 1

[0111] The lithium-ion batteries of Examples 1 to 13 (including Example a and Example b) and Comparative Examples 1 to 10 were respectively subjected to battery theoretical mass energy density tests and cycle performance tests. The test results of each Example and Comparative Example are shown in Table 1 below.

[0112] Table 1

[0113] In Comparative Examples 1 to 3 and Examples 1 to 6 (including Example a and Example b), the cathode plate adopts the same design: the cathode active material is NCM811 ternary material, the theoretical mass energy density is 209.1 mAh / g, and the cathode plate surface capacity (capacity per unit area) is 3.75 mAh / cm 2 The lithium-intercalated anode material uses silicon oxide, with a theoretical mass energy density of 1600 mAh / g. Comparative Example 1 uses a conventional battery design, with an anode area capacity (i.e., capacity per unit area) of 3.94 mAh / cm 2 , which is 1.05 times the surface capacity of the cathode. The porosity of the anode electrode is 25%. The theoretical mass energy density of the full battery is calculated to be 361.49Wh / Kg. After the full battery is cycled for 154 times in the voltage range of 2.8 to 4.3V, the battery capacity decays to 80%.

[0114] Comparative Example 2 reduces the amount of lithium-intercalated anode material used, and the surface capacity of the anode plate is reduced to 80% of the surface capacity of the cathode plate, which is 3.01 mAh / cm 2 , the porosity of the anode plate is still maintained at 25%. Due to the reduction of the anode load, the theoretical mass energy density of the full battery is increased to 379.04Wh / kg. However, after the lithium-intercalated anode material on the anode side is completed, since there is not enough space inside the anode plate to accommodate the remaining lithium on the cathode side, lithium metal is easily precipitated on the surface of the anode plate and forms lithium dendrites. Therefore, the full battery short-circuit occurs after 47 cycles in the voltage range of 2.8 to 4.3V. Comparative Example 3 increases the porosity of the anode plate to 37% on the basis of Comparative Example 2. Since the battery mass remains unchanged, only the discharge voltage of the full battery fluctuates slightly, so the theoretical mass energy density of the full battery remains basically unchanged. Although the battery life is slightly extended after the anode plate porosity is increased, a short circuit still occurs at the 73rd cycle, indicating that the 37% anode plate porosity is still not enough to prevent lithium precipitation on the anode plate surface.

[0115] In Example 1, the porosity of the anode plate is further increased to 50%. At this time, the capacity of the full battery decays to 80% after 182 cycles in the voltage range of 2.8 to 4.3 V. In Examples a to b and Examples 2 to 6, different designs are made for the surface capacity and porosity of the anode plate based on Example 1. By comparing Comparative Example 1 with Examples a to b and Examples 1 to 6, it can be found that when the porosity of the anode plate is not less than 50%, the battery design with the lithium-poor anode material (i.e., controlling C a / C cThe ratio of the anode surface capacity to the cathode surface capacity is below 0.95) and can significantly improve the mass energy density of the battery while preventing short circuits. According to the mass energy density and cycle performance test results, the theoretical mass energy density of the lithium-ion batteries of Examples 1 to 6 and Example b can reach 383.54 to 415.51Wh / kg, which is further improved compared to Example a. It can be seen that the control of the ratio of the anode surface capacity to the cathode surface capacity in this application makes C a / C c Satisfy 0.20≤C a / C c ≤0.80, reducing the loading of anode active materials while ensuring the total capacity of the lithium-ion battery can further improve the mass energy density of the lithium-ion battery while meeting better cycle performance.

[0116] Examples 7 to 9 and Comparative Examples 4 to 6 were tested for different cathode electrode sheet surface capacity designs. The cathode materials used in these six groups of experiments were all NCM811 ternary materials with a mass energy density of 209.1 mAh / g. The anode material used was silicon oxide material with a theoretical mass energy density of 1600 mAh / g. The results show that in batteries with different cathode designs, controlling the ratio of anode surface capacity to cathode surface capacity below 0.95 and constructing a porosity of ≥50% inside the anode electrode can effectively improve the theoretical mass energy density of the battery and ensure high cycle performance.

[0117] Examples 10 to 13 and Comparative Examples 7 to 10 were verified for different battery systems. The cathode plates in Examples 10 and 11 and Comparative Examples 7 and 8 adopted the same design: the cathode active material was NCM811 ternary material, with a theoretical mass energy density of 209.1 mAh / g and an areal capacity of 3.75 mAh / cm 2 . The lithium-intercalated anode material used in Example 10 and Comparative Example 7 is silicon-carbon material with a theoretical mass energy density of 1700mAh / g; the lithium-intercalated anode material used in Example 11 and Comparative Example 8 is pure silicon nanoparticles with an average particle size of 60nm, and a theoretical mass energy density of 3500mAh / g. The lithium-intercalated anode materials used in Examples 12, 13 and Comparative Examples 9 and 10 are all silicon oxide with a theoretical mass energy density of 1600mAh / g; the cathode active material used in Example 12 and Comparative Example 9 is lithium cobalt oxide material with a theoretical mass energy density of 185mAh / g and a surface capacity of 2.93mAh / cm 2 The cathode material used in Example 13 and Comparative Example 10 is lithium manganate material, with a theoretical mass energy density of 113.1 mAh / g and a surface capacity of 2.08 mAh / cm 2The results show that the strategy of improving the battery mass energy density by controlling the ratio of the anode surface capacity to the cathode surface capacity to ≤0.95 and ensuring the anode electrode porosity to ≥50% in this application is applicable to different battery systems and battery designs.

[0118] Test Example 2

[0119] At 25°C, the lithium-ion batteries of Comparative Example 1, Comparative Example 2, and Example 1 were respectively charged at a constant current of 0.2C to the charge cut-off voltage, and then charged at a constant voltage to a current of 0.025C, at which time the battery was fully charged. The anode electrode of the lithium-ion battery was removed from the fully charged state, and the surface and cross-section of the anode electrode were observed using an optical microscope. Figure 1 is a surface photograph of the anode electrode obtained by disassembling the lithium-ion battery of Comparative Example 1 in the fully charged state, and Figure 2 is a cross-sectional photograph of the anode electrode obtained by disassembling the lithium-ion battery of Comparative Example 1 in the fully charged state. Since the anode electrode of Comparative Example 1 is equipped with a sufficient amount of lithium-intercalated anode material, the lithium inside the cathode material is completely embedded in the lithium-intercalated anode material, so no obvious lithium precipitation phenomenon is observed on the surface of the anode electrode. However, since Comparative Example 1 uses more anode material, its theoretical mass energy density is low, only 361.49Wh / kg.

[0120] Figures 3 and 4 are surface and cross-sectional photographs of the anode electrode piece removed from the full battery in Comparative Example 2 when fully charged, respectively. It can be seen that very obvious lithium deposition occurred at the edge of the electrode piece. This shows that lithium deposition on the surface of the anode electrode piece is the main reason for the premature short circuit of the battery in Comparative Example 2 and the number of cycles being only 47.

[0121] Figures 5 and 6 are respectively the surface and cross-sectional photos of the anode electrode piece removed from the full battery in Example 1 under the fully charged state. It can be seen that the lithium metal is uniformly deposited inside the anode electrode piece, so no obvious local lithium deposition is observed on the electrode piece surface; and from the lithium ion battery performance test results of Example 1, it can be seen that the lithium ion battery of Example 1 has a theoretical mass energy density of 383.54Wh / kg based on the number of cycles reaching 182, taking into account both excellent mass energy density and cycle performance. The results of Figures 1 to 6 prove that the unit area capacity of the anode electrode piece and the unit area capacity of the cathode electrode piece set in this application make C a / C c Satisfy the conditions: 0<C a / C c ≤0.95, combined with the porosity N≥50% of the anode electrode, the excess lithium ions in the cathode are precipitated inside the pores of the anode electrode, avoiding the precipitation of lithium ions on the surface of the anode electrode and the occurrence of lithium dendrites, reducing the risk of premature short circuit, and being able to improve the energy density of lithium-ion batteries while improving the cycle performance and safety performance.

[0122] Test Example 3

[0123] The reaction capacity ratio (C a / C c ) and the anode plate porosity (N) are presented in the form of a scatter plot. Based on Examples 2 and 5, in which the cycle performance is relatively low, the relationship between N and C in Examples 2 and 5 is established. a / C c The corresponding relationship is y = -0.9375x + 1.0625, and the result is shown in Figure 7. Since the reaction capacity ratio of the anode electrode and the cathode electrode (C a / C c ) is reduced, the difference between the amount of lithium ions that can be released from the cathode electrode and the amount of lithium ions that can be embedded in the anode electrode increases, so a higher porosity of the anode electrode is required to accommodate the lithium ions released from the cathode electrode to avoid the problem of lithium ion precipitation on the surface of the anode electrode. a / C c The corresponding relationship is determined by N≥[-0.9375×(C a / C c )+1.0625]×100%, and N≥50%. When the value of N is within this range, the lithium-ion battery can be guaranteed to have excellent cycle performance. For example, the cycle performance test results of the ternary lithium-ion batteries of Examples 1 to 6 (the positive electrode material is NCM811 and the negative electrode material is silicon oxide) are more than 170 cycles. When N<[-0.9375×(C a / C c )+1.0625]×100%, its cycle performance is poor. In addition, when N>[-0.9375×(C a / C c )+1.0625]×100% (corresponding to the point above y=-0.9375x+1.0625 in FIG7 ), and when N≥50%, the cycle performance test results of Example 1 [corresponding to the point (0.8, 0.5) in FIG7 ], Example 3 [corresponding to the point (0.5, 0.65) in FIG7 ], Example 4 [corresponding to the point (0.6, 0.65) in FIG7 ], and Example 6 [corresponding to the point (0.44, 0.76) in FIG7 ] can reach more than 180 cycles, which is better than N=[-0.9375×(C a / C c )+1.0625]×100% (corresponding to the point on the y=-0.9375x+1.0625 curve in FIG7 ) further improves the cycle performance of the lithium-ion battery.

[0124] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A lithium ion battery, characterized in that: The lithium-ion battery comprises a cathode electrode sheet and an anode electrode sheet; The porosity of the anode electrode sheet is N, and the value range of N is N≥50%; The reaction capacity of the anode electrode plate is Ca, and the reaction capacity of the cathode electrode plate is Cc. The reaction capacity Ca of the anode electrode plate and the reaction capacity Cc of the cathode electrode plate satisfy the condition: 0<Ca / Cc≤0.

95.

2. The lithium-ion battery according to claim 1, characterized in that The reaction capacity Ca of the anode electrode and the reaction capacity Cc of the cathode electrode satisfy the condition: 0.20≤Ca / Cc≤0.

80.

3. The lithium-ion battery according to claim 2, characterized in that: The reaction capacity Ca of the anode electrode and the reaction capacity Cc of the cathode electrode satisfy the condition: 0.40≤Ca / Cc≤0.

60.

4. The lithium-ion battery according to claim 1, characterized in that: The porosity N of the anode plate has a value range of 50%≤N≤90%.

5. The lithium-ion battery according to claim 4, characterized in that: The porosity N of the anode plate has a value range of 65%≤N≤76%.

6. The lithium-ion battery according to claim 1, characterized in that The anode electrode sheet has a two-dimensional structure and / or a three-dimensional structure.

7. The lithium-ion battery according to claim 1, characterized in that: The anode electrode plate includes at least one of silicon oxide, silicon carbon, pure silicon, silver, tin, hard carbon, soft carbon, graphite, and lithium titanate.

8. The lithium-ion battery according to claim 1, characterized in that The cathode electrode plate includes at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium manganese oxide, lithium iron phosphate, lithium-rich manganese-based material, and sulfur.

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