Negative electrode plate, secondary battery comprising the negative electrode plate, and an electrical device

Abstract

A negative electrode plate comprising a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer comprises a negative electrode active material, characterized in that the negative electrode plate satisfies an equation which is as follows: 0.15 ≤ (F × ps) / (ρ × 100) ≤ 10; In the equation, F is a cohesive force of the negative electrode plate, the unit is N / m; ps is a D V 50-particle size change rate of the negative electrode active material before and after holding the pressure for 30 seconds at a pressure of 4T, the unit is %; and p is a compressed density of the negative electrode plate; the unit is g / cm³. 3 .

Description

BACKGROUNDTechnical field

[0001] The present invention relates to the technical field of batteries, particularly to a negative electrode plate or a negative pole piece, a secondary battery comprising the negative electrode plate, and an electrical device. Description of the state of the art

[0002] The depletion of traditional petrochemical fuels and environmental pollution are becoming increasingly serious. Electricity, as a clean energy source, is being used on an ever-increasing scale. Currently, the electric vehicle industry is booming. Lithium-ion batteries have the advantages of high energy density, good cycle performance, and environmental friendliness. Therefore, they are used in the electric vehicle industry and energy storage.

[0003] However, over time, the problems of declining mileage and service life severely limit automobile development. To solve these problems, one of the most effective methods is to improve the service life of the battery, which is the lifeblood of the electric vehicle. Battery service life depends on several factors, such as the expansion of the electrode plates, gas formation in the battery, etc.

[0004] In the production of lithium batteries, the positive electrode plate (or positive pole piece), the negative electrode plate, and the separator are usually assembled into a battery core using a winding or lamination device. A positive electrode circle is wound around a negative electrode circle within the battery in a winding structure, and the thickness expansion ratios of the positive electrode plate and the negative electrode plate are uneven. If the thickness expansion ratio of the negative electrode plate is much larger than that of the positive electrode plate and accumulates to a certain extent, the electrode plates will deform and wrinkle. These wrinkles easily lead to black spots and lithium precipitation in the battery, reducing the battery capacity and thus shortening the battery life.

[0005] As for gas generation, it is generally considered to be caused by the presence of side reactions in the electrochemical process, and its composition is complicated and includes oxygen (O2), carbon dioxide (CO2), carbon monoxide (CO), methane (CH4), ethane (C2H6), etc. With the increase of the number of cycles, the generated gas accumulates and, at a certain value, threatens the internal pressure of the individual battery, so that the battery life decreases.

[0006] How to improve the service life of a lithium-ion battery is therefore a technical problem that experts urgently need to solve. SUMMARY

[0007] An object of the present invention is to overcome the disadvantages of the prior art and to provide a negative electrode plate, a secondary battery comprising the negative electrode plate, and an electrical device. The negative electrode plate has a low thickness expansion rate during a cycle, which contributes to improving the gassing of the battery and extending the battery life. The invention is defined by the features of the independent claims. Advantageous embodiments are subject to the dependent claims.

[0008] To achieve the above-mentioned object, in a first aspect of the present invention, the present invention provides a negative electrode plate comprising a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer comprises a negative electrode active material. The negative electrode plate satisfies an equation as follows: 0.15≤(F×ps) / (ρ×100)≤10; in the equation, F is a cohesive force of the negative electrode plate, the unit is N / m; ps is a D V 50-Particle size change rate of the negative electrode active material before and after holding the pressure for 30 seconds at a pressure of 4T, the unit is %; and ρ is the compressed density or compression of the negative electrode plate, in the unit g / cm 3 .

[0009] In an alternative embodiment of the present invention, the negative electrode plate satisfies an equation as follows: 1.9≤(F×ps) / (ρ×100)≤6.

[0010] In an alternative embodiment of the present invention, the negative electrode plate satisfies an equation as follows: 0.3≤1 / ps+7 / α≤1.2; in the equation, α is a contact angle of the negative electrode active material layer with a solvent with the unit °, the solvent is a mixed solution of ethylene carbonate and methyl ethyl carbonate in a weight ratio of 1:1.

[0011] In an alternative embodiment of the present invention, the negative electrode plate satisfies an equation as follows: 0.33≤1 / ps+7 / α≤0.5.

[0012] In an alternative embodiment of the present invention, the range of ps is between 1% and 20%.

[0013] In an alternative embodiment of the present invention, the range of ps is between 4.5% and 14%.

[0014] In an alternative embodiment of the present invention, the range of F is between 10 N / m and 80 N / m.

[0015] In an alternative embodiment of the present invention, the range of F is between 25 N / m and 65 N / m.

[0016] In an alternative embodiment of the present invention, the range of ρ is between 1.3 g / cm 3 and 1.8 g / cm 3 .

[0017] In an alternative embodiment of the present invention, the range of ρ is between 1.45 g / cm 3 and 1.7 g / cm 3 .

[0018] In an alternative embodiment of the present invention, the range of α is between 20° and 50°.

[0019] In an alternative embodiment of the present invention, the range of α is between 22° and 31°.

[0020] In an alternative embodiment of the present invention, the negative electrode active material comprises a carbon material comprising at least one of the following materials: synthetic graphite, natural graphite, hard carbon, soft carbon, and mesocarbon microbeads.

[0021] In a second aspect of the present invention, the present invention provides a secondary battery comprising a positive electrode plate, a negative electrode plate which is the above-mentioned negative electrode plate, and an electrolytic solution.

[0022] In a third aspect of the present invention, the present invention provides an electrical device comprising the secondary battery.

[0023] The present invention has the following advantageous effects.

[0024] The present invention enables the negative electrode plate to have a lower thickness expansion rate during a high-temperature cycle by rationally controlling the cohesive force and the compacted density of the negative electrode plate, as well as the contact angle between the negative electrode active material layer in the negative electrode plate and the solvent and the particle size change rate of the negative electrode active material, so that the gassing of the battery and the cycle life of the battery are improved. DESCRIPTION OF THE DESIGNS

[0025] To clarify the objectives, technical solutions, and advantages of the embodiments of the invention, the technical solutions of the embodiments of the invention are described clearly and comprehensively below. Of course, the described embodiments are part of the invention and not all embodiments. Based on the embodiments of the invention, all other embodiments that a person skilled in the art can derive without inventive effort also fall within the scope of the invention.

[0026] The present invention includes, among the technical features described openly, both a closed technical solution consisting of the mentioned features and an open technical solution containing the mentioned features.

[0027] For the purposes of the present invention, reference is made to numerical ranges which, unless otherwise stated, are to be considered continuous and include both the minimum and maximum values ​​of the range, as well as any value between the minimum and maximum values. When a range refers to an integer, it also includes any integer between the minimum and maximum values ​​of the range. When multiple ranges are specified to describe a feature or characteristic, the ranges may also be combined. In other words, unless otherwise stated, all ranges disclosed herein also include all subranges contained therein.

[0028] In the present invention, the specific methods for dispersing and stirring the treatment are not particularly limited.

[0029] If the reagents or instruments used in the invention are not specified by the manufacturer, they are commercially available products.

[0030] One embodiment of the present invention provides a negative electrode plate comprising a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer comprises a negative electrode active material. The negative electrode plate satisfies an equation as follows: 0.15≤(F×ps) / (ρ×100)≤10; in the equation, F is a cohesive force of the negative electrode plate in the unit N / m; ps is a particle size change rate D V 50 of the negative electrode active material before and after holding the pressure for 30 seconds at a pressure of 4T and with the unit %; and ρ is a compressed density of the negative electrode plate with the unit g / cm3.

[0031] The present invention enables the negative electrode plate to have a lower thickness expansion rate during cycling by rationally controlling the cohesive force and compacted density of the negative electrode plate, as well as the contact angle between the negative electrode active material layer in the negative electrode plate and the solvent and the particle size change rate of the negative electrode active material, and after the negative electrode plate is applied to the secondary battery, the gassing of the battery and the cycle life of the battery are improved.

[0032] In the present invention, the particle size change rate (ps) of the negative electrode active material is calculated from the change of D V50 of the negative electrode active material before and after holding the pressure for 30 seconds at a pressure of 4T. The negative electrode active material generally includes primary particles and / or secondary particles. After the negative electrode active material is held at a pressure of 4T for 30 seconds, the secondary particles may be broken into several smaller particles, or the primary particles and / or secondary particles may be broken to a certain extent. The particle size change rate of the negative electrode active material is related to the particle strength. Generally speaking, the smaller the particle size change rate, the higher the particle strength.The inventors found that the higher the particle size change rate of the negative electrode active material and the lower the rebound rate of the particles under external stress, the smaller the particle thickness. The negative electrode plate made of the negative electrode active material with the higher particle size change rate has a relatively lower thickness expansion rate during cycling, which contributes to improving the cycle life of the battery. However, if the particle size change rate is too high, the new interface created by the crushing of the negative electrode active material is relatively larger, so too much active lithium is consumed, leading to a reduction in the cycle life of the battery. Furthermore, if the particle size change rate of the negative electrode active material is too high, it may cause an excessive irreversible oxidation reaction of the lithium ions in the negative electrode.Negative electrode plate may be damaged due to an excessive number of crushed or pulverized particles, resulting in an increase in the amount of gas generated when the battery is stored at high temperatures.

[0033] Increasing the compacted density (p) of the negative electrode plate helps improve the electron-conductive properties of the electrode plate and reduce the internal resistance of the battery. However, increasing the compacted density can also lead to a higher particle size change rate of the negative electrode active material, resulting in the consumption of active lithium. At the same time, the compacted density is also related to the porosity of the electrode plate. If the compacted density is too high, the porosity of the negative electrode plate decreases, resulting in a reduction in the electrode plate's ability to absorb the electrolyte solution. If the compacted density is low, the interior of the negative electrode plate may have larger pores and channels, where gas is more likely to accumulate and form.

[0034] The cohesive force (F) reflects the bonding force between the particles of the negative electrode active material. With appropriate cohesive force, the negative electrode plate exhibits good structural stability, which helps reduce the degree of loosening between the particles, improves the battery's cycle life, reduces gas generation, and prevents the electrode plate from increasing in thickness during cycling. If the cohesive force is too high, the negative electrode active materials may be too close together, and the permeability of the electrolyte solution may be hindered, thus reducing the battery's cycle life.

[0035] The particle size change rate, compacted density, and cohesive force affect the thickness expansion rate of the negative electrode plate during cycling, as well as the gas evolution and cycle performance of the battery, to varying degrees, and specifically influence each other. It is difficult to control the battery to achieve lower gas evolution and thickness expansion rate of the electrode layer, as well as higher cycle performance, by controlling a single variable. By rationally controlling F, ps, and ρ to satisfy the above equation, the present invention enables a lower thickness expansion rate of the negative electrode plate of the battery during cycling, thus improving gas evolution and cycle life of the battery.

[0036] In the present invention, the value of (F×ps) / (ρ×100) may be, for example, 0.15, 0.2, 0.3, 0.5, 0.8, 1.0, 2.0, 5.0, 8.0 or 10.0 or an interval between two of the above values.

[0037] In one of the implementations, the negative electrode plate satisfies an equation as follows: 1.9≤(F×ps) / (ρ×100)≤6.

[0038] When the particle size change rate, compacted density, and cohesive force of the negative electrode plate also satisfy the above equation, the cohesive force, compacted density of the negative electrode plate, and the particle size change rate of the negative electrode active material are in a more suitable range, so that when the prepared negative electrode plate is used in a secondary battery, the expansion rate of the negative electrode plate is lower, the gas evolution of the battery is lower, and the cycle performance is better.

[0039] In one of the implementations, the negative electrode plate satisfies an equation as follows: 0.3≤1 / ps+7 / α≤1.2; in the equation, α is a contact angle of the negative electrode active material layer with a solvent and with the unit °, where the solvent is a mixed solution of ethylene carbonate and methyl ethyl carbonate in a weight ratio of 1:1.

[0040] In an alternative implementation, the negative electrode plate satisfies an equation as follows: 0.33≤1 / ps+7 / α≤0.5.

[0041] Ethylene carbonate and methyl ethyl carbonate are commonly used electrolyte solvents in lithium-ion batteries. The contact angle (α) between the mixed solvent and the negative electrode active material layer reflects the degree of wetting of the negative electrode plate with the electrolyte solvent. The size of the contact angle is related to the particle size distribution of the negative electrode active material, the compacted density of the negative electrode plate, and the tightness between the particles of the negative electrode active material. A relatively small contact angle indicates that the electrolyte solution can better penetrate into the electrode layer, thereby avoiding an increase in resistance and lithium precipitation due to insufficient liquid absorption, thus extending the battery life.

[0042] When the values ​​of α and ps of the negative electrode material are reasonably controlled so that the value of 1 / ps+7 / α is 0.3-1.2, the contact angle of the negative electrode active material layer and the particle size change rate of the negative electrode active material are both within a suitable range, the gas generation of the prepared negative electrode plate is lower, and the cycle life is relatively higher.

[0043] In the context of the present invention, the value of 1 / ps+7 / α may be, for example, 0.3, 0.35, 0.4, 0.5, 0.7, 1.0 or 1.2 or an interval between two of these values.

[0044] In one implementation, the range of ps is between 1% and 20%. For example, the value of ps can be 1%, 2%, 5%, 10%, 15%, 18%, or 20%.

[0045] In an alternative implementation, the range of ps is between 3% and 13%.

[0046] Within the range of ps, the particle size change rate of the negative electrode active material is reasonable, which contributes to a relatively low thickness expansion rate of the negative electrode plate during cycling, low consumption of active lithium, high cycle life of the battery, and low gas evolution.

[0047] Regarding the method for determining the particle size change rate ps, it is not limited within the scope of the present invention, and a person skilled in the art would be able to determine the particle size change rate of the negative electrode active material using conventional technical means. For example, ps can be determined using the following method.

[0048] The lithium-ion battery was disassembled to obtain a negative electrode plate. The negative electrode plate was soaked in dimethyl carbonate (DMC) at room temperature for 60 minutes. The negative electrode plate was removed and dried at room temperature with a humidity of ≤15%. The negative electrode active material layer on the current collector surface was scraped off and dissolved in an inorganic acid (e.g., hydrochloric acid), washed, stirred, filtered, and dried. The resulting material was then dissolved in distilled water, stirred to wash off the hydrochloric acid from the surface, and dried to obtain a negative electrode active material.

[0049] The negative electrode active material was dispersed in deionized water containing a dispersant (a nonylphenol polyoxyethylene ether with a content of 0.03 wt%) to form a mixture. The mixture was sonicated for 2 minutes and then placed in a particle size tester to obtain a D V 50-test to perform so that D V 50 before the holding pressure, which is known as D V 50 vor dem Druck is recorded.

[0050] Then, solid-liquid separation and drying were performed on the mixture containing the negative electrode active material to recover the negative electrode active material. The negative electrode active material was pressurized with a powder compactor at a pressure of 4T for 30 seconds. After the pressurization, the negative electrode active material was removed to undergo another D V50 test in a particle size tester according to the method mentioned above to obtain a D V 50 after holding pressure, which is known as D V 50 nach dem Druck was recorded. The particle size change rate ps of the negative electrode active material is obtained by calculation: ps=(DV50before printing−DV50after printing) / DV50before printing×100%; where D V 50 is the particle size corresponding to the time when the cumulative volume distribution percentage of the negative electrode active material reaches 50%, with the unit µm.

[0051] The particle size change rate of the negative electrode active material depends on various factors and can be controlled by adjusting the raw material for preparing the negative electrode active material, the pulverization conditions, and the heat treatment conditions in the preparation process. It is also possible to obtain a negative electrode active material with a specific particle size change rate through bulk sieving.

[0052] In one implementation, the range of F is between 10 N / m and 80 N / m. For example, F can be 10 N / m, 12 N / m, 15 N / m, 20 N / m, 30 N / m, 50 N / m, 60 N / m, 65 N / m, 70 N / m, 75 N / m, or 80 N / m.

[0053] In an alternative implementation, the range of F is between 20 N / m and 65 N / m.

[0054] The value of cohesive force is generally related to the type and amount of binder in the negative electrode active material layer, and the value of cohesive force can be controlled by selecting different types of binders and adjusting the amount of binder added.

[0055] In the present invention, it is preferable that the cohesive force of the negative electrode plate is 10 N / m to 80 N / m, more preferably 20 N / m to 65 N / m. When the cohesive force is high, the stress acting on the negative electrode plate due to the expansion of the negative electrode active material can be suppressed to a certain extent, so that the thickness expansion rate of the negative electrode plate is significantly suppressed. Furthermore, when the cohesive force is high, it contributes to improving the surface fracture and pulverization of the negative electrode active material layer in the negative electrode plate, thereby reducing the loss of the negative electrode active material and thus avoiding the consumption of a large amount of electrolyte solution for a new film formation reaction caused by the loss of the negative electrode active material, thereby improving the gassing of the battery.However, if the cohesive force value is further increased, a larger amount of binder may be required. Due to the poor conductivity and ion-conducting properties of the binder, the presence of a large amount of binder can lead to higher electrode foil resistance, lithium precipitation, and other phenomena that affect battery life.

[0056] In the present invention, the method for determining the cohesive force is not limited. Those skilled in the art are able to determine the cohesive force of the negative electrode plate using conventional technical means. For example, it can be determined using the following method.

[0057] The electrode plate of the negative electrode sample was cut into a long electrode plate with a width of approximately 25 mm and a length of approximately 100 mm. The electrode plate was attached to the stainless steel plate wiped with alcohol. A green adhesive tape with a width of 20 mm was adhered to the surface of the electrode plate. One side of the adhesive tape was pulled upward and clamped to an upper end of a universal testing machine. The stainless steel plate with the electrode plate was clamped to the lower end of the multi-force tensile tester. Then, the test was carried out with the multi-force tensile tester controlling the stretching speed to 5 mm / min and the stretching distance to 20 mm. The tensile test data was recorded in the unit of N / m during the stretching process, and the electrode plate was tested no less than 3 times.The cohesive force value was calculated by taking the average value of the test data.

[0058] In one of the implementations, the range of p is between 1.3 g / cm3 and 1.8 g / cm3. For example, ρ can be 1.3 g / cm3, 1.35 g / cm3, 1.4 g / cm3, 1.5 g / cm3, 1.6 g / cm3, 1.65 g / cm3, 1.7 g / cm3, 1.75 g / cm3 or 1.8 g / cm3.

[0059] In an alternative implementation, the range of ρ is between 1.45 g / cm3 and 1.7 g / cm3.

[0060] The higher the compacted density of the negative electrode plate, the higher the electron and ion conductivity between the negative electrode active materials. The lower the compacted density, the more pronounced the pore structure in the negative electrode active material layer of the negative electrode plate, which facilitates the liquid-phase diffusion of ions in the pores of the negative electrode plate and can also cause gas generated during battery cycling to accumulate in the pores. When ρ is within the above-mentioned preferred range, the battery has both low gas evolution and high cycle performance.

[0061] As for the method for determining the compacted density, the present invention is not limited, and one skilled in the art can determine the compacted density of the negative electrode plate by conventional technical means.

[0062] For example, the compressed density of the negative electrode plate can be determined as follows.

[0063] A negative electrode plate was disassembled, washed, and dried from a fully discharged lithium-ion battery. The negative electrode plate was weighed with a range S using an electronic balance, recording the weight as W1 and measuring the thickness T1 of the negative electrode plate to the nearest ten-thousandth of a micrometer. The negative electrode active material layer was washed with DMC solvent. The resulting negative electrode current collector was then dried to measure its weight, recorded as W2, and its thickness T2 to the nearest ten-thousandth of a micrometer. The weight W0, thickness T0, and compacted density ρ of the negative electrode active material layer located on one side of the negative electrode current collector were calculated using the following equations. When W0=W1-W2 and T0=T1-T2, the compacted density ρ=1.15×W0 / (T0×S).It should be noted that the negative electrode plate in the fully discharged lithium-ion battery has a specific degree of thickness rebound, and the degree of thickness rebound in the negative electrode plate using the graphite material as the negative electrode active material is approximately 15%. Therefore, in the present invention, the compacted density is calculated by multiplying by a factor of 1.15.

[0064] In one implementation, the range of α is between 20° and 50°. For example, α can be 20°, 22°, 25°, 30°, 35°, 40°, 43°, 45°, 48°, or 50°.

[0065] In an alternative implementation, the range of α is between 22° and 31°.

[0066] Within the above-mentioned range of α, the particle size distribution and the degree of interparticle compactness of the negative electrode active material in the negative electrode plate are suitable, which contributes to the electrolyte solution being able to wet the negative electrode plate quickly and efficiently. As a result, the battery's gas evolution is relatively low and the cycle performance is relatively better.

[0067] The invention is not limited to the method for determining the contact angle α. Those skilled in the art can use vinyl carbonate and methyl ethyl carbonate (1:1 weight ratio) as solvents to determine the contact angle between the negative electrode active material layer and the solvent, using conventional technical means. For example, the following methods can be used for detection.

[0068] Using ethylene carbonate and methyl ethyl carbonate (1:1 weight ratio) as solvents, a contact angle test for the negative electrode plate was conducted using a JC2000D2M contact angle tester manufactured by Zhongchen Digital Technology Equipment Co. Ltd., Shanghai. The specific test conditions were as follows: The negative electrode plate was kept at 25°C for 30 minutes. Then, the solvent was sequentially dropped onto the surface of the negative electrode plate at different locations (one drop at each location). The time at which the drop fully contacted the electrode plate was observed with the contact angle tester, and the contact angle at that time was calculated. The test results at different positions were averaged to obtain the contact angle of the negative electrode plate.

[0069] In one embodiment, the negative electrode active material comprises a carbon material comprising at least one of the following materials: synthetic graphite, natural graphite, hard carbon, soft carbon, and mesocarbon microbeads or microspheres.

[0070] Different carbon materials differ in their conductivity, capacity, and cycling stability. Natural graphite and synthetic graphite have higher electrical conductivity, offer better electronic conductivity, have good cycling stability, and a higher specific capacity, and can provide higher energy storage density. For the purposes of the present invention, synthetic graphite and / or natural graphite are preferable as negative electrode active materials.

[0071] The method for preparing the negative electrode active material is not particularly limited in the present invention, and a person skilled in the art can prepare the negative electrode active material by conventional means.

[0072] For example, the negative electrode active material can be prepared by the following method.

[0073] A graphite raw material was taken for crushing and the crushed product was ball milled at a ball to material ratio of (5-8) : 1 at 300-700 rpm for 1-4 hours to obtain a particle product.

[0074] After the particle product was formed, the result was placed in a reaction vessel of a granulator, to which amorphous carbon was added to perform granulation treatment to obtain a granulated product.

[0075] The granulated product was subjected to heat treatment, heated from room temperature to 800-1300°C at a heating rate of 1-5°C / min, kept at this temperature for 2-5 hours, then cooled to room temperature and heated again to 2200-3000°C at a heating rate of 5-10°C / min and kept at this temperature for 2-10 hours to obtain graphite particles.

[0076] The resulting graphite particles were crushed and then sieved and classified through a classification sieve to obtain a negative electrode active material.

[0077] In addition, a negative electrode active material with a suitable particle size change rate can be sieved by a variety of sieving methods.

[0078] Regarding the negative electrode plate, the present invention does not particularly limit the negative electrode current collector, as long as it has high conductivity without causing adverse chemical changes in the battery. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with one of the elements carbon, nickel, titanium, silver, or the like, or an aluminum-cadmium alloy can be used.

[0079] The negative electrode active material layer of the negative electrode plate may comprise, in addition to the negative electrode active material, a conductive agent and a binder.

[0080] The conductive agent serves to improve the conductivity of the negative electrode active material layer. The present invention has no particular limitations on the conductive agent, for example, carbon powder such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal black; graphite powder such as natural graphite or synthetic graphite; conductive fibers such as carbon fibers or metal fibers; or conductive whiskers such as zinc oxide whiskers or potassium titanate whiskers.

[0081] The binder serves to improve the adhesion between the conductive agent, the negative electrode active material, and the negative electrode current collector. The binder is not particularly limited in the present invention. For example, at least one of the following materials can be used: styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, aqueous acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0082] Furthermore, the negative electrode active material layer may comprise a thickener, which may be carboxymethyl cellulose.

[0083] The weight ratio of the negative electrode active material, the conductive agent, the binder and the thickener in the negative electrode active material layer may be (80-99):(1-10):(1-10):(0-5).

[0084] It should be noted that the preparation of the negative electrode plate is not particularly limited in the present invention, and a person skilled in the art can prepare the negative electrode plate by conventional methods.

[0085] The preparation of the negative electrode plate is carried out as follows.

[0086] A negative electrode active material and optionally a binder, a conductive agent, and a thickener were dissolved or dispersed in a solvent to prepare a negative electrode slurry.

[0087] A negative electrode current collector was coated with the negative electrode slurry and then rolled or dried to obtain a negative electrode plate; or,

[0088] The negative electrode slurry was cast onto a separate support, and then the film layer separated from the support was laminated onto the negative electrode current collector to obtain a negative electrode plate.

[0089] An embodiment of the present invention provides a secondary battery comprising a positive electrode plate, a negative electrode plate which is the negative electrode plate described above, and an electrolyte solution.

[0090] The positive electrode plate according to the invention comprises a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector. The positive electrode active material layer comprises a positive electrode active material and may also comprise a conductive agent and / or a binder.

[0091] The positive electrode current collector is not particularly limited in the present invention, as long as it has high conductivity without causing adverse chemical changes in the battery. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, or the like, or an aluminum-cadmium alloy may be used. The positive electrode current collector may be the same as or different from the negative electrode current collector of the present invention.

[0092] The positive electrode active material is a compound that can reversibly intercalate and intercalate lithium. The positive electrode active material may, for example, comprise a lithium composite metal oxide containing lithium and at least one metal from the group consisting of Mg, Al, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Y, Zr, Sn, Sb, W, Pb, and Bi, and preferably at least one from the group consisting of Co, Ni, and Mn. Specifically, the positive electrode active material may comprise at least one of the following compounds or materials: Li(Ni) 0,6 Mn 0,2 Co 0,2 )O2, Li(Ni 0,7 Mn 0,2 Co 0,10 )O2, Li(Ni 0,8 Mn 0,1 Co 0,1 )O2, Li(Ni 0,8 Co 0,15 Al 0,05 )O2, Li(Ni 0,86 Mn 0,07 Co 0,05 Al 0,02 )O2, and Li(Ni 0,9 Mn 0,05 Co 0,05 )O2.

[0093] It should be noted that the method for preparing the positive electrode plate is not particularly limited in the present invention, and a person skilled in the art can prepare the positive electrode plate by conventional methods.

[0094] The electrolyte solution of the present invention can be any electrolyte solution suitable for use in electrochemical energy storage devices in the prior art. The electrolyte solution comprises an electrolyte and a solvent. The electrolyte can generally comprise a lithium salt.

[0095] Specifically, the lithium salt comprises at least one of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonimide (LiFSI), lithium bistrifluoromethosulfonimide (LiTFSI), lithium triflate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorooxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP). The concentration of the electrolyte in the electrolyte solution can be 0.5 to 5 mol / L.

[0096] Specifically, the solvent includes at least one of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE). The solvent may be present in an amount of 70 to 98 wt% based on the weight of the electrolyte solution.

[0097] Furthermore, the electrolyte solution may comprise additives. In particular, the additive may include a membrane-forming additive for the negative electrode or negative electrode plate, and the additive may include a membrane-forming additive for the positive electrode or positive electrode plate. The additive may include an additive capable of improving specific properties of the battery, e.g., an additive for improving the overcharge properties of the battery, an additive for improving the high-temperature properties of the battery, or an additive for improving the low-temperature properties of the battery, etc.

[0098] The secondary battery may further include a separator disposed between the positive electrode plate and the negative electrode plate to separate the positive electrode plate and the negative electrode plate from each other and prevent the positive electrode plate and the negative electrode plate from contacting and causing a short circuit. The separator may be any material known in the art that can be used as a separator for electrochemical energy storage devices. Specifically, the separator comprises at least one of polyethylene, polypropylene, polyvinylidene fluoride, aramid, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester, and natural fiber.

[0099] One embodiment of the present invention provides an electrical device comprising the secondary battery described above. The secondary battery serves as a power supply for the electrical device.

[0100] An electric device refers to any device that can use electrical energy and convert it into mechanical energy, heat energy, light energy, etc., such as an electric motor, an electric heat engine, an electric light source, etc. The electric device may include, but is not limited to, a mobile device, an electric vehicle, an electric train, a ship and a satellite, an energy storage system, etc. The mobile device may be a mobile phone, a notebook or laptop, an unmanned aerial vehicle or drone, a sweeping robot, an electric cigarette, etc. The electric vehicle may be a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, or the like.

[0101] The invention is further illustrated by the following specific embodiments.

[0102] In particular embodiments of the present invention, the cohesive force F is determined as follows.

[0103] The lithium-ion battery was disassembled to obtain a negative electrode plate. The negative electrode plate was soaked in dimethyl carbonate (DMC) at room temperature for 60 minutes. The negative electrode plate was then removed and dried at room temperature with a humidity of ≤ 15% to obtain a sample electrode plate for testing.

[0104] A cohesive force test was conducted on the electrode plate to be tested. The electrode plate to be tested was cut into a long electrode plate with a width of approximately 25 mm and a length of approximately 150 mm. The electrode plate was attached to a stainless steel plate wiped with alcohol (industrial grade) with a double-sided adhesive tape 25 mm wide and 80 mm long on the surface of the electrode plate. At room temperature, a 2 kg cylindrical roller was used to press the tape back and forth three times. After pressing, the tape was freely bent 180°, and the free end of the tape and the test plate were clamped between the upper and lower clamps of a tensile machine. At this time, the peel area coincides with the line of the tensile machine.In the same environment, a tensile test machine was used to control the tensile speed at 100 mm / min and the effective tensile distance at 20-80 mm. Tensile test data was recorded during the tensile process in units of N / m. The electrode plate was tested no less than three times. The cohesive force value was calculated from the average of the test data.

[0105] In particular embodiments of the present invention, the particle size change rate ps is determined as follows.

[0106] The lithium-ion battery was disassembled to obtain a negative electrode plate. The negative electrode plate was soaked in dimethyl carbonate (DMC) at room temperature for 60 minutes. The negative electrode plate was then removed and dried at room temperature with a humidity of ≤ 15%. The negative electrode active material layer on the current collector surface was scraped off and dissolved in an inorganic acid (e.g., hydrochloric acid), washed, stirred, filtered, and dried. The resulting material was then dissolved in distilled water, stirred to wash off the hydrochloric acid from the surface, and dried to obtain a negative electrode active material.

[0107] The negative electrode active material was dispersed in deionized water containing a dispersant (a nonylphenol polyoxyethylene ether with a content of 0.03 wt%) to form a mixture. The mixture was sonicated for 2 minutes and then placed in a particle size tester to obtain a D V 50-test to perform so that D V 50 before the holding pressure, which is called D V 50 vor dem Druck is recorded.

[0108] Then, solid-liquid separation and drying were performed on the mixture containing the negative electrode active material to recover the negative electrode active material. The negative electrode active material was compressed with a powder compactor at a pressure of 4T for 30 seconds. After the pressure was maintained, the negative electrode active material was removed to undergo another D V50 test in a particle size tester according to the method mentioned above to obtain a D V 50 after holding the pressure known as D V 50 nach dem Druck was recorded. The particle size change rate ps of the negative electrode active material is obtained by calculation: ps=(DV50before printing−DV50after printing) / DV50before printing×100%

[0109] In particular embodiments of the present invention, the compacted density p is determined as follows.

[0110] From a fully discharged lithium-ion battery, a negative electrode plate was disassembled, washed, and dried. The negative electrode plate was weighed with a range S using an electronic balance, recording the weight as W1 and measuring the thickness T1 of the negative electrode plate to the nearest ten-thousandth of a micrometer. The negative electrode active material layer was washed with a DMC solvent. The resulting negative electrode current collector was then dried to measure its weight, recorded as W2, and its thickness T2 to the nearest ten-thousandth of a micrometer. The weight W0, thickness T0, and compacted density ρ of the negative electrode active material layer located on one side of the negative electrode current collector were calculated using the following equations. When W0=W1-W2 and T0=T1-T2, the compacted density ρ=1.15×W0 / (T0×S).

[0111] In particular embodiments of the present invention, the contact angle α is determined as follows.

[0112] Using ethylene carbonate and methyl ethyl carbonate (1:1 weight ratio) as solvents, a contact angle test for the negative electrode plate was conducted using a JC2000D2M contact angle tester manufactured by Zhongchen Digital Technology Equipment Co. Ltd., Shanghai. The specific test conditions were as follows: The negative electrode plate was kept at 25°C for 30 minutes. Then, the solvent was sequentially dropped onto the surface of the negative electrode plate at different locations (one drop at each location). The time at which the drop fully contacted the electrode plate was observed with the contact angle tester, and the contact angle at that time was calculated. The test results at the different locations were averaged to obtain the contact angle of the negative electrode plate. Examples and comparative examples

[0113] Each of Examples 1-16 and Comparative Examples 1-3 provides a lithium-ion battery, and the specific preparation method is as follows. (1) Preparation of the negative electrode plate

[0114] (1.1) The raw material (petroleum coke raw material) was taken for crushing. The crushed product was ball milled, with the ball milling rate controlled at 1 rpm, the ball milling time at 1 hours, and the ball-to-material ratio at 5:1 to obtain a particulate product.

[0115] After the particle product was formed, the resultant was put into a reaction vessel of a granulator, adding 1-5 wt% of binder (amorphous carbon) according to the total weight of the particle product to conduct granulation treatment to obtain a granulated product.

[0116] The granulated product was placed in a graphitization furnace for heat treatment, heated from room temperature to B2°C at a heating rate of B1°C / min, which was maintained for B3 hours, then cooled to room temperature, heated again to B5°C at a heating rate of B4°C / min, which was maintained for B6 hours to obtain graphite particles

[0117] The resulting graphite particles were crushed and then sieved and classified through a classification sieve to obtain a negative electrode active material.

[0118] (1.2) 95 parts by weight of negative electrode active material, 1.5 parts by weight of conductive agent (carbon black), 1.5 parts by weight of thickener (carboxymethyl cellulose, CMC), and 1~5 parts by weight of binder (styrene-butadiene rubber, SBR) were mixed. A negative electrode slurry was prepared using a vacuum mixer in a wet process. The negative electrode slurry was evenly coated on the negative electrode current collector (copper foil). The negative electrode slurry coated with the negative electrode current collector was placed in a furnace for drying and then rolled and cut. The negative electrode plate with a p value of 1.68 g / cm 3 was obtained by controlling the rolling conditions.

[0119] The conditions from A1 to A2, B1 to B6 for each example and comparative example are listed in Table 1.

[0120] In each of the examples and comparative examples, the value of the contact angle α of the negative electrode active material layer provided on the surface of the negative electrode plate satisfied the value shown in Table 2 by controlling the particle size distribution of the negative electrode active material; the value of the compacted density p of the negative electrode plate satisfied the value shown in Table 2 by controlling the coating and rolling conditions; and by controlling the addition amount of the amorphous carbon and the addition amount of the binder SBR, the value of the cohesive force F of the negative electrode plate satisfied the value shown in Table 2. Table 1 A1 (rpm) A2 (h or hours) B1 (°C / min) B2 (°C) B3 (h) B4 (°C / min) B5 (°C) B6 (h or hours) Example 1 500 1 3 1100 2 5 2700 3 Example 2 600 2 2 1200 3 5 2800 5 Example 3 650 2 3 1300 2,5 5 2700 8 Example 4 700 2 5 1050 4 8 2400 6 Example 5 780 2,5 1 900 5 7 2200 4 Example 6 500 1,5 1 1200 4,5 5 2800 8 Example 7 680 3 3,5 1050 2 8 2700 3 Example 8 400 1 3 1100 3 5 2700 5 Example 9 720 1,5 4 850 2,5 7 2800 5 Example 10 650 2 2 1200 5 5 2700 6 Example 11 800 1,5 3 1250 5 9 2700 9 Example 12 700 3 2 1200 3 5 2900 6 Example 13 450 1 1 900 4 5 2500 3 Example 14 780 3 1 1300 4 5 2900 8 Example 15 780 3,5 3,5 1000 2 7 2750 2 Example 16 800 4 1 1200 4 5 2800 6 Comparative Example 1 450 1 2 800 2,5 9 2400 5 Comparative Example 2 800 3,5 4 1250 5 5 2750 5 Comparative Example 3 500 1,5 1 800 3 6 2400 4 (2) Preparation of the positive electrode plate

[0121] The positive electrode active material Li(Ni 0,8 Mn 0,1 Co 0,1)O2, the binder (polyvinylidene fluoride), and the conductive agent (acetylene black) were mixed in a weight ratio of 98:1:1. N-methylpyrrolidone (NMP) was added to the mixture and stirred under the action of a vacuum mixer until the mixture formed a uniform, fluid positive electrode slurry. The positive electrode slurry, or positive electrode plate, was evenly coated onto the positive electrode current collector (aluminum foil) with a thickness of 9-12 µm. After drying (temperature 120°C, duration 8 hours), rolling, and cutting, the positive electrode plate was obtained. (3) Preparation of the electrolyte solution

[0122] The electrolyte solution was a 1.5 mol / L LiPF6 solution and the solvent was a mixed solution of ethylene carbonate and methyl ethyl carbonate (weight ratio 1:1). (4) Preparation of the separator

[0123] A polyethylene film with a thickness of 9 µm was used as a separator. (5) Preparation of the battery

[0124] The prepared positive electrode plate, separator, and negative electrode plate were wound to obtain a bare electrical core without liquid injection. The bare electrical core was placed in an outer packaging film. The above-mentioned prepared electrolyte solution was injected into the dried bare electrical core. The core was vacuum-packed, erected, formed, sorted, and subjected to other processes to obtain a lithium-ion battery. Table 2 hp (%) ρ (g / cm 3 ) F (N / m) α (°) (F*ps) / p*100 1 / (ps) +7 / α Example 1 11,5 1,48 25,1 22,0 1,95 0,41 Example 2 14,0 1,50 63,5 25,9 5,93 0,34 Example 3 9,2 1,7 58,3 27,2 3,16 0,37 Example 4 9,2 1,45 45,9 31,0 2,91 0,33 Example 5 4,5 1,47 64,8 28,0 1,98 0,47 Example 6 17,0 1,76 50,8 20,0 4,91 0,41 Example 7 5,6 1,33 72,0 43,6 3,03 0,34 Example 8 19,5 1,53 19,0 25,1 2,42 0,33 Example 9 3,8 1,31 66,0 48,9 1,91 0,41 Example 10 13,5 1,66 28,0 30,1 2,28 0,31 Example 11 4,8 1,46 63,7 22,3 2,09 0,52 Example 12 5,0 1,60 50,0 25,0 1,56 0,48 Example 13 18,2 1,35 72,0 37,0 9,71 0,24 Example 14 2,2 1,80 79,5 33,9 0,97 0,66 Example 15 1,1 1,30 39,0 27,0 0,33 1,17 Example 16 1,0 1,62 45,0 21,2 0,28 1,33 Comparative Example 1 18,6 1,33 79,2 21,4 11,08 0,38 Comparative 1,5 1,57 11,7 28,1 0,11 0,92 Example 2 Comparative Example 3 17,4 1,31 85 42 11,29 0,22

[0125] The lithium-ion batteries prepared in the examples and comparative examples were subjected to performance tests according to the following projects and methods. The results are shown in Table 3.

[0126] (1) High-temperature storage gas generation: The obtained lithium-ion battery was charged to 4.25V at a constant current at a rate of 1C at 25 ± 2°C, and then charged at a constant voltage of 4.25V to a current of less than 0.05C, so that it was in a fully charged state of 4.25V. The volume of the fully charged battery was tested using the drainage method before storage and recorded as V0. The fully charged battery was placed in an oven at 60 ± 2°C. After 30 days, the battery was removed to test its volume immediately after storage and recorded as V1; Expansion rate of the battery volume=(V1−V0) / V0×100%. (2) Thickness expansion rate:

[0127] The resulting lithium-ion battery was charged to 4.45V at 60°C at a constant current of 0.5C and then discharged to 0.05C at a constant voltage. The battery was allowed to stand for 5 minutes at a fully charged thickness, recorded as W0, and then discharged to 3.0V at a constant current of 0.5C for 100 cycles. The thickness of the fully charged battery after the 100th cycle was recorded as W1. The thickness expansion rate of the negative electrode active material layer of the lithium-ion battery was calculated using the following equation: Thickness expansion rate(%)=(W1−W0) / W0×100%. (3) Service life at high temperatures:

[0128] High-temperature cycle life: The charge / discharge cycle test was conducted on the lithium-ion battery at 60°C using a battery charge / discharge cycle tester. The charge / discharge system: The battery was charged at a constant current of 1C to 4.25V, then charged at a constant voltage until the current dropped to 0.02C. After 5 minutes of standing, the battery was discharged at a constant current of 1C to 2.5V. This was a single cycle. Over the course of the cycles, the battery capacity decreased. The number of cycles at which the capacity dropped to 80% of the original discharge capacity was recorded as the battery's high-temperature cycle life. Table 3 Volume expansion rate (%) Thickness expansion rate (%) Service life at high temperatures Example 1 1,72 27,2 2455 Example 2 1,75 26,5 2485 Example 3 1,66 26,2 2475 Example 4 1,53 26,9 2480 Example 5 1,73 27,5 2460 Example 6 1,87 28,6 2445 Example 7 1,85 29,5 2440 Example 8 1,91 28,4 2415 Example 9 1,96 29,2 2430 Example 10 2,35 31,5 2335 Example 11 2,27 31,8 2310 Example 12 2,42 31,9 2300 Example 13 2,85 34,5 2235 Example 14 2,78 33,8 2250 Example 15 2,66 34,1 2245 Example 16 2,89 34,7 2225 Comparative Example 1 4,52 38,1 1710 Comparative Example 2 3,95 37,8 1650 Comparative Example 3 3,78 38,3 1665

[0129] The test results in Table 3 show that the negative electrode plate prepared or manufactured in each example of the present invention was used in a lithium-ion battery. The thickness expansion rate of each of the negative electrode plates after 100 cycles at 60°C was ≤ 35%. The volume expansion rate of each of the batteries after 30 days of storage at 60°C in a fully charged state was ≤ 3%. The high-temperature cycle life of each of the batteries was ≥ 2200 cycles.

[0130] From the comparison of Examples 10 to 11 with Examples 1 to 5, it is found that the negative electrode plate satisfies the following equation: 1.9≤(F×ps) / (ρ×100)≤6, it further satisfies an equation as follows: 0.33≤1 / ps+7 / α≤0.5, the cycle life of the lithium-ion battery was relatively higher, the volume expansion rate was relatively lower, and the thickness expansion rate of the negative electrode plate was also lower.

[0131] The comparison between Examples 6 to 9 and Examples 1 to 5 shows that when the negative electrode plate satisfies the equations: 1.9≤(F×ps) / (ρ×100)≤6 and 0.33≤1 / ps+7 / α≤0.5, and when ps is 4.5%-14%, ρ is 1.45-1.7 g / cm3, α is 22°-31°, and F is 25 N / m-65 N / m, the cycle performance, gas formation, and thickness change of the negative electrode plate of the prepared battery are relatively better.

[0132] The ratio of ps, p, and F of the negative electrode plate prepared in each comparative example does not conform to the equation described in the present invention: 0.15≤(F×ps) / (ρ×100)≤10. The cycle life of the lithium-ion battery using the negative electrode plate is only 1710. Gas generation is excessive after high-temperature storage. The thickness expansion rate of the negative electrode plate is too high after a high-temperature cycle.

Claims

[1] A negative electrode plate comprising a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer comprises a negative electrode active material, characterized by that the negative electrode plate satisfies an equation which is as follows: 0.15≤(F×ps) / (ρ×100)≤10; in the equation, F is a cohesive force of the negative electrode plate, the unit is N / m; ps is a D V 50-Particle size change rate of the negative electrode active material before and after holding the pressure for 30 seconds at a pressure of 4T, the unit is %; and p is a compressed density of the negative electrode plate, the unit is g / cm 3 . [2] Negative electrode plate according to claim 1, characterized bythat the negative electrode plate satisfies an equation as follows: 1.9≤(F×ps) / (ρ×100)≤6. [3] Negative electrode plate according to one of the preceding claims, characterized by that the negative electrode plate also satisfies an equation as follows: 0.3≤1 / ps+7 / α≤1.2; in the equation, α is a contact angle of the negative electrode active material layer with a solvent with the unit °, the solvent is a mixed solution of ethylene carbonate and methyl ethyl carbonate in a weight ratio of 1:

1. [4] Negative electrode plate according to one of the preceding claims, characterized by that the negative electrode plate satisfies an equation as follows: 0.33≤1 / ps+7 / α≤0.

5. [5] Negative electrode plate according to one of the preceding claims, characterized by that a range of ps is between 1% and 20%. [6] Negative electrode plate according to one of the preceding claims, characterized bythat the range of ps is between 4.5% and 14%. [7] Negative electrode plate according to one of the preceding claims, characterized by that a range of F lies between 10 N / m and 80 N / m. [8] Negative electrode plate according to one of the preceding claims, characterized by that the range of F is between 25 N / m and 65 N / m. [9] Negative electrode plate according to one of the preceding claims, characterized by that a range of ρ between 1.3 g / cm 3 and 1.8 g / cm 3 lies. [10] Negative electrode plate according to one of the preceding claims, characterized by that the range of ρ between 1.45 g / cm 3 and 1.7g / cm 3 lies. [11] Negative electrode plate according to one of the preceding claims, characterized by that the range of α is from 20° to 50°. [12] Negative electrode plate according to one of the preceding claims, characterized bythat the range of α is between 22° and 31°. [13] Negative electrode plate according to one of the preceding claims, characterized by that the negative electrode active material comprises a carbon material comprising at least one of synthetic graphite and natural graphite. [14] Negative electrode plate according to one of the preceding claims, characterized by that the negative electrode active material comprises a / the carbon material comprising at least one of hard carbon, soft carbon and mesocarbon microspheres. [15] Negative electrode plate according to one of the preceding two claims, characterized by that the carbon material is natural graphite. [16] Negative electrode plate according to one of the preceding claims, wherein copper, stainless steel, aluminum, nickel, titanium, burnt carbon or an aluminum-cadmium alloy is provided or used for the negative electrode current collector. [17] The negative electrode plate according to any one of the preceding claims, wherein the negative electrode active material layer comprises, in addition to the negative electrode active material, a conductive agent and a binder. [18] The negative electrode plate according to claim 17, wherein the conductive agent comprises carbon powder, graphite powder, conductive fibers or conductive whiskers. [19] The negative electrode plate according to claim 17 or 18, wherein the binder comprises styrene-butadiene rubber, water-soluble unsaturated resin SR-1B, aqueous acrylic resin, polyacrylamide, polyvinyl alcohol, sodium alginate and / or carboxymethyl chitosan. [20] A negative electrode plate according to any one of the preceding claims, wherein the negative electrode active material layer comprises a thickener, e.g. carboxymethylcellulose. [21] The negative electrode plate according to claim 17 and 20, wherein a weight ratio of the negative electrode active material, the conductive agent, the binder and the thickener in the negative electrode active material layer is (80-99):(1-10):(1-10):(0-5). [22] Secondary battery, in particular lithium-ion battery, comprising a positive electrode plate, a negative electrode plate and an electrolyte solution or an electrolyte, characterized by that the negative electrode plate is the negative electrode plate according to one of claims 1 to 21. [23] The secondary battery according to claim 22, wherein the positive electrode plate comprises a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector, the positive electrode active material layer comprising a positive electrode active material. [24] A secondary battery according to claim 23, wherein copper, stainless steel, aluminum, nickel, titanium, burnt carbon or an aluminum-cadmium alloy is provided or used for the positive electrode current collector. [25] A secondary battery according to claim 23 or 24, wherein the positive electrode current collector is identical to or different from the negative electrode current collector. [26] The secondary battery according to any one of claims 23 to 25, wherein the positive electrode active material comprises a lithium composite metal oxide containing lithium and at least one metal selected from the group consisting of Mg, Al, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Y, Zr, Sn, Sb, W, Pb and Bi, and preferably at least one selected from the group consisting of Co, Ni, and Mn. [27] A secondary battery according to any one of claims 23 to 26, wherein the positive electrode active material comprises at least one of the following compounds or materials: Li(Ni 0,8 Mn 0,1 Co 0,1 )O2, Li(Ni 0,8 Co 0,15 Al 0,05 )O2, and Li(Ni 0,86 Mn 0,07 Co 0,05 Al 0,02 )O2. [28] A secondary battery according to any one of claims 23 to 27, wherein the positive electrode active material comprises at least one of the following compounds or materials: Li(Ni 0,6 Mn 0,2 Co 0,2 )O2 and Li(Ni 0,7 Mn0,2 Co 0,10 )O2. [29] A secondary battery according to any one of claims 23 to 28, wherein the positive electrode active material comprises at least the following compound or material Li(Ni 0,9 Mn 0,05 Co 0,05 )O2. [30] A secondary battery according to any one of claims 23 to 29, wherein the positive electrode active material layer comprises a conductive agent. [31] A secondary battery according to any one of claims 23 to 30, wherein the positive electrode active material layer comprises a binder. [32] A secondary battery according to any one of claims 22 to 31, wherein the electrolytic solution comprises an electrolyte and a solvent. [33] A secondary battery according to any one of claims 22 to 32, wherein the electrolyte comprises a lithium salt. [34] The secondary battery according to claim 33, wherein the lithium salt comprises at least one of lithium hexafluorophosphate or LiPF6, lithium tetrafluoroborate or LiBF4, lithium perchlorate or LiClO4, lithium hexafluoroarsenate or LiAsF6, lithium bisfluorosulfonimide or LiFSI, lithium bis-trifluoromethosulfonimide or LiTFSI, lithium triflate or LiTFS, lithium difluorooxalate borate or LiDFOB, lithium dioxalate borate or LiBOB, lithium difluorophosphate or LiPO2F2, lithium difluorooxalate phosphate or LiDFOP and lithium tetrafluorooxalate phosphate or LiTFOP. [35] A secondary battery according to any one of claims 32 to 34, wherein the concentration of the electrolyte in the electrolytic solution is 0.5 to 5 mol / L. [36] The secondary battery according to any one of claims 32 to 35, wherein the solvent comprises at least one of ethylene carbonate or EC, propylene carbonate or PC, ethyl methyl carbonate or EMC, diethyl carbonate or DEC, dimethyl carbonate or DMC, dipropyl carbonate or DPC, methyl propyl carbonate or MPC, ethyl propyl carbonate or EPC, butylene carbonate or BC, fluoroethylene carbonate or FEC, methyl formate or MF, methyl acetate or MA, ethyl acetate or EA, propyl acetate or PA, methyl propionate or MP, ethyl propionate or EP, propyl propionate or PP, methyl butyrate or MB, ethyl butyrate or EB, 1,4-butyrolactone or GBL, sulfolane or SF, dimethyl sulfone or MSM, methyl ethyl sulfone or EMS, and diethyl sulfone or ESE. [37] A secondary battery according to any one of claims 32 to 36, wherein the solvent is contained in an amount of 70 to 98 wt% based on the weight of the electrolytic solution. [38] A secondary battery according to any one of claims 22 to 37, wherein the electrolytic solution comprises a membrane-forming additive for the negative electrode plate and a membrane-forming additive for the positive electrode plate. [39] A secondary battery according to any one of claims 23 to 38, comprising a separator between the positive electrode plate and the negative electrode plate. [40] The secondary battery according to claim 39, wherein the separator comprises at least one of the following materials: polyethylene, polypropylene, polyvinylidene fluoride, aramid, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester and natural fiber. [41] A secondary battery according to any one of claims 22 to 40 for use in supplying power to an electrical device, the electrical device comprising: Electric motor, heat engine, light source, vehicle, train, ship, satellite, energy storage system, mobile phone, notebook, unmanned aerial vehicle, sweeping robot, or electronic cigarette. [42] The secondary battery of claim 41, wherein the vehicle is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, or an electric truck. [43] Electrical device, characterized by that it comprises the secondary battery according to one of claims 22 to 42. [44] An electrical device according to claim 43, wherein the secondary battery serves as a power supply for the electrical device. [45] An electrical device according to claim 44, which is configured as an electric motor, heat engine, light source, vehicle, train, ship, satellite, energy storage system, mobile phone, notebook, unmanned aerial vehicle, sweeping robot, or electronic cigarette. [46] The electric device of claim 45, wherein the vehicle is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, or an electric truck.