Aqueous positive pole piece composition containing water-soluble lithium-containing compound and secondary battery

Abstract

The invention relates to a water-based positive pole piece composition, which contains a positive active material, a conductive agent, a water-based adhesive, a water-soluble lithium-containing compound, and optionally water and a dispersant. The invention also relates to a positive pole piece prepared from the aqueous positive pole piece composition, a secondary battery comprising the positive pole piece, a battery pack comprising the secondary battery, and an electric device comprising the secondary battery or the battery pack.

Description

Aqueous positive electrode sheet composition containing water-soluble lithium-containing compound and secondary battery Technical Field

[0001] The present application relates to an aqueous positive electrode sheet composition comprising a positive electrode active material, a conductive agent, an aqueous binder, a water-soluble lithium-containing compound, and optionally water and a dispersant. The present application also relates to a positive electrode sheet prepared from the aqueous positive electrode sheet composition, a secondary battery comprising the positive electrode sheet, a battery pack comprising the secondary battery, and an electrical device. Background Art

[0002] Secondary batteries, due to their low cost, long lifespan, and excellent safety, have become the most popular energy storage system and are now widely used in pure electric vehicles, hybrid electric vehicles, and smart grids. The cathodes in secondary batteries are often made using an oil-based slurry, typically consisting of a binder called polyvinylidene fluoride (PVDF) and a solvent called N-methylpyrrolidone (NMP). However, both PVDF and NMP are petroleum-derived chemicals. During the slurry mixing and coating process, large amounts of toxic NMP fumes can evaporate into the air, polluting the environment and posing a threat to humans. Furthermore, the synthesis and post-processing of NMP and PVDF are complex, energy-intensive, and expensive. Consequently, researchers are exploring the development of aqueous cathode systems. These systems avoid the use of the organic solvent NMP, reducing environmental and human hazards. Furthermore, they avoid the large-scale use of the fluoropolymer PVDF and the complex recovery of the NMP solvent, potentially reducing battery cell production costs and enabling large-scale, cost-effective applications.

[0003] Another common problem with lithium-ion secondary batteries is that during the initial charge, a large amount of lithium ions released from the positive electrode are consumed to form the SEI film on the negative electrode surface. This irreversible consumption of the positive electrode lithium source during the initial charge exceeds 10%, and the initial coulombic efficiency is less than 90%. Furthermore, lithium-ion secondary batteries continue to consume active lithium during normal use. This can lead to a reduction in the battery's initial capacity and shortened battery life.

[0004] Therefore, there is still a need to provide an aqueous composition for preparing positive electrode sheets for secondary batteries, which can prepare positive electrode sheets with improved properties, so that the secondary battery constructed by the positive electrode sheets has improved environmental friendliness and initial capacity retention rate, and extends the battery life.

[0005] Summary of the Invention

[0006] The present application is made in view of the above-mentioned problems, and its purpose is to provide an aqueous positive electrode plate composition to solve the technical problems of excessive reduction in initial capacity and shortened life of secondary batteries prepared therefrom.

[0007] In order to achieve the above-mentioned objectives, the first aspect of the present application provides an aqueous positive electrode plate composition, wherein the composition contains a positive electrode active material, a conductive agent, an aqueous binder and a water-soluble lithium-containing compound, and optionally water and a dispersant.

[0008] The aqueous positive electrode plate composition of the present application can compensate for the loss of the initial charge and discharge capacity and the initial charge and discharge efficiency of the battery cell by including a water-soluble lithium-containing compound, and inhibit the precipitation of lithium ions from the positive electrode active material particles in the solvent water. In addition, the water-soluble lithium-containing compound can be directly added to the aqueous positive electrode plate composition in the prior art, and is non-selective for all types of materials in the formula, has strong formula adaptability, and has a large operational space. The anions of the water-soluble lithium-containing compound other than lithium ions will lose electrons during the charging process, and eventually decompose to form gases that are harmless to the battery, such as N2, CO2, and CO. These gases can be removed before packaging or from subsequent safety outlets, and have no effect on the proportion of the main material content in the electrode.

[0009] In any embodiment, the water-soluble lithium-containing compound is an organic acid salt of lithium. In any embodiment, the water-soluble lithium-containing compound is selected from one or more of lithium oxide, lithium hydroxide, lithium azide, lithium chloride, lithium sulfate, lithium nitrate, lithium salicylate, lithium citrate, lithium oxalate, lithium glycolate, lithium malate, lithium tartrate, lithium lactate, lithium malonate, lithium succinate, lithium formate, and lithium acetate. By selecting the specific type of the lithium-containing compound, the battery capacity retention rate can be further improved.

[0010] In any embodiment, the water-soluble lithium-containing compound has an oxidation peak value between 3.5 and 4.4 V. In any embodiment, the water-soluble lithium-containing compound has a solubility in water at 25° C. of ≥600 mg / ml, optionally ≥1000 mg / ml. Selecting a lithium-containing compound with a higher solubility allows for more rapid replenishment of lithium source loss.

[0011] In any embodiment, the content of the water-soluble lithium-containing compound in the composition is 1-20 wt %, optionally 3-10 wt %, based on the total weight of the aqueous positive electrode sheet composition.

[0012] In any embodiment, the solid content of the aqueous positive electrode plate composition is 30-65% by weight, optionally 45-55% by weight. In any embodiment, the weight ratio of the positive electrode active material, conductive agent, and aqueous binder contained in the aqueous positive electrode plate composition is 90-98:0.5-2:1-8, optionally 95-97:0.8-1.2:2-4.

[0013] In any embodiment, the positive electrode active material is selected from one or more of lithium iron phosphate, lithium manganese phosphate, lithium cobalt phosphate, lithium iron manganese phosphate, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide. In any embodiment, the conductive agent comprises one or more of conductive carbon black, superconducting carbon black, conductive graphite, acetylene black, Ketjen black, graphene, and carbon nanotubes.

[0014] In any embodiment, the aqueous adhesive is selected from one or more of soluble polysaccharides and their derivatives, and water-soluble or water-dispersible polymers. The aqueous adhesive is selected from methylcellulose and its salts, xanthan gum and its salts, chitosan and its salts, alginic acid and its salts; and polyethyleneimine and its salts, polyacrylamide, acrylic acid copolymers, and their derivatives. The aqueous adhesive is a mixture of xanthan gum and acrylic acid copolymer in a weight ratio of 2:1 to 0.2:2.8. Optionally, the xanthan gum has a weight-average molecular weight of 300,000 to 2,000,000 g / mol, and the acrylic acid copolymer has a weight-average molecular weight of 100,000 to 1,000,000 g / mol.

[0015] In any embodiment, the aqueous adhesive comprises an aqueous dispersion solution and an emulsion thereof with a solid content of ≥5%, or comprises a solid that can form a stable dispersion with a solid content of ≥1% with water.

[0016] In any embodiment, the dispersant is selected from polyamide dispersants, poly(meth)acrylate dispersants, polycarboxylate dispersants, sulfonate dispersants, silicate dispersants, phosphate dispersants, polyethyleneimine dispersants, amino-containing polymers and amine salt dispersants.

[0017] In any embodiment, the composition is in the form of an aqueous slurry, or in the form of a product obtained by drying the slurry.

[0018] The present application also relates to a method for preparing the aqueous positive electrode plate composition selected from the first aspect of the present application, comprising the following steps:

[0019] 1) mixing a water-soluble lithium-containing compound with deionized water to prepare a saturated aqueous solution of the water-soluble lithium-containing compound;

[0020] 2) mixing a positive electrode active material, a conductive agent, an aqueous binder, and optionally a dispersant to obtain a mixture;

[0021] 3) uniformly mixing the saturated aqueous solution obtained in step 1) and the mixture obtained in step 2) to form a slurry; and

[0022] 4) Optionally drying the slurry.

[0023] A second aspect of the present application provides a positive electrode sheet, which is prepared by using the aqueous positive electrode sheet composition selected from the first aspect of the present application.

[0024] A third aspect of the present application provides a secondary battery comprising a positive electrode sheet selected from the second aspect of the present application.

[0025] A fourth aspect of the present application provides a battery pack comprising a secondary battery selected from the third aspect of the present application.

[0026] A fifth aspect of the present application provides an electrical device comprising a secondary battery selected from the third aspect of the present application or a battery pack according to the fourth aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] To more clearly illustrate the technical solution of this application, the following briefly introduces the drawings required for use in the embodiments of this application. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without inventive effort.

[0028] FIG1 is a schematic diagram of a lithium-ion secondary battery in one embodiment of the present application.

[0029] FIG. 2 is an exploded view of the lithium-ion secondary battery in one embodiment of the present application shown in FIG. 1 .

[0030] FIG3 is a schematic diagram of a battery pack in one embodiment of the present application.

[0031] FIG. 4 is an exploded view of the battery pack shown in FIG. 3 according to one embodiment of the present application.

[0032] FIG5 is a schematic diagram of a device using a battery pack as a power source in one embodiment of the present application.

[0033] Description of Reference Numerals

[0034] 1 battery pack

[0035] 2 upper box

[0036] 3 lower cabinets

[0037] 4 battery modules

[0038] 5Lithium-ion secondary batteries

[0039] 51 shell

[0040] 52 electrode assembly

[0041] 53 cover DETAILED DESCRIPTION

[0042] For the sake of clarity, this application specifically discloses certain numerical ranges. However, any lower limit may be combined with any upper limit to form an unspecified range; and any lower limit may be combined with other lower limits to form an unspecified range, and similarly, any upper limit may be combined with any other upper limit to form an unspecified range. In addition, each individually disclosed point or single value may itself serve as a lower limit or upper limit and be combined with any other point or single value, or with other lower limits or upper limits, to form an unspecified range.

[0043] Among current secondary batteries, aqueous cathode slurries using water as a solvent for the preparation of positive electrode sheets are gaining increasing attention due to their low cost and environmental friendliness. When using aqueous cathode slurries, it has been found that lithium ions and transition metal ions readily precipitate from the surface of the positive electrode active material particles in the presence of the solvent water, leading to increased losses in the initial charge and discharge capacity and efficiency of the battery cell, and decreased energy density and cycle performance. Furthermore, lithium-ion batteries also continuously consume active lithium during normal use. This can lead to a reduction in the initial capacity of the battery cell and a shortened battery life.

[0044] Research has shown that the initial discharge capacity and efficiency determine the foundation for subsequent cycling, and the structural stability of most materials is also determined by the discharge capacity and efficiency of the initial cycle, which in turn influences the design and material evaluation of the entire battery. In particular, if deionized water is used as the solvent for the cathode slurry, the active material will exchange lithium ions for hydrogen ions when exposed to water, further resulting in capacity loss. This significantly limits the application and development of aqueous cathodes.

[0045] In response to the phenomenon that the SEI film of the negative electrode of lithium-ion batteries consumes active lithium, resulting in a decrease in the initial capacity of the battery and a shortened lifespan, the current solution is to use lithium replenishment technology to replenish the lithium loss during the cycle. There are currently two main ways of lithium replenishment technology, one is negative electrode lithium replenishment, and the other is positive electrode lithium replenishment. Among them, there are three main methods for negative electrode lithium replenishment: 1) physical mixing, such as ultra-thin lithium foil press-embedding and stabilized metal lithium powder; 2) electrochemical pre-lithiation, such as using the potential difference to pressurize the silicon-carbon negative electrode with added electrolyte into contact with metal lithium to form lithiated silicon-carbon; 3) chemical pre-lithiation, such as SnLi synthesized by ball milling in an inert atmosphere. x Lithium replenishment at the negative electrode end involves the use of flammable and explosive lithium metal, which poses a high safety risk. The chemical lithium replenishment process at the material end is complex, and the material is highly alkaline, making it difficult to process. In addition, lithium replenishment at the material end damages the negative electrode structure and affects the cycle life. Overall, lithium replenishment at the negative end poses significant safety risks and complex and difficult processing issues.

[0046] Compared with negative electrode lithium replenishment, the positive electrode lithium replenishment process is simple. The lithium source is added during the positive electrode slurry stirring process, which can completely avoid the safety risks and cost increase risks of negative electrode lithium replenishment. The positive electrode lithium replenishment process is to add a small amount of high-capacity lithium replenishment additives to the positive electrode during the positive electrode homogenization process. During the charging process, the excess Li element is released from these high-capacity positive electrode materials and embedded in the negative electrode to replenish the irreversible capacity of the first charge and discharge. Among them, the positive electrode lithium replenishment mainly uses lithium-rich materials, such as lithium-rich xLiMO2·(1-x)Li2MnO3, which can be regarded as a solid solution of Li2MnO3 and LiMO2 (M represents a transition metal), specifically Li2Mn2O4, Li2NiO2, Li6CoO4 and Li2CuO2. These lithium replenishment materials have high environmental requirements and require a dry environment. They will react strongly with water and become unstable, which limits their application in aqueous positive electrodes.

[0047] Therefore, there is a need in the art to provide an aqueous positive electrode sheet composition that can be used to prepare a positive electrode sheet with improved performance, so that the secondary battery has improved first discharge capacity and first discharge efficiency, and can also inhibit the precipitation of lithium ions during subsequent use.

[0048] Specifically, the first aspect of the present application provides an aqueous positive electrode plate composition, wherein the composition contains a positive electrode active material, a conductive agent, an aqueous binder and a water-soluble lithium-containing compound, and optionally water and a dispersant.

[0049] The inventors have discovered that adding a water-soluble lithium-containing compound to the aqueous conductive composition used to prepare the positive electrode plate can effectively solve the above-mentioned problems in the prior art. The addition of the water-soluble lithium-containing compound, on the one hand, inhibits the precipitation of lithium ions from the positive electrode active material particles in the solvent water, and on the other hand, the lithium ions in the soluble lithium salt can directly compensate for the lithium loss during the first charge and discharge of the battery cell. In addition, for the added water-soluble lithium-containing compound, its anions other than lithium ions will lose electrons during the charging process, and eventually decompose to form gases that are harmless to the battery, such as N2, CO2 and CO. These gases can be discharged before packaging or from subsequent safety outlets, and have no effect on the proportion of the main material content in the electrode. In this application, the water-soluble lithium-containing compound refers to the lithium-containing compound that can be substantially dissolved in deionized water to form free Li +, for example, its solubility in deionized water is ≥20 mg / ml, optionally ≥30 mg / ml, and further optionally ≥50 mg / ml. In some embodiments, the solubility of the water-soluble lithium-containing compound in deionized water at 25°C is at least 20 mg / ml, optionally at least 30 mg / ml, and further optionally at least 50 mg / ml. The aqueous positive electrode sheet composition of the present application may contain water as a solvent, and may also contain a small amount of other solvents, such as commonly used organic solvents. In one embodiment, the content of the organic solvent is less than 5% by weight, optionally less than 1% by weight, based on the total weight of the aqueous positive electrode sheet composition. In one embodiment, only water is used as the solvent for the aqueous positive electrode sheet composition. The water-soluble lithium-containing compound can first be formulated into a saturated aqueous solution with deionized water, and then evenly mixed with other components to obtain the aqueous positive electrode sheet composition of the present application. In one embodiment, in the obtained aqueous positive electrode sheet composition, the water-soluble lithium-containing compound is in a saturated state in the solvent water. When the battery loses a lot of lithium after the initial charge and discharge cycle, or lithium is precipitated in subsequent use, the Li + It can be embedded in the positive electrode sheet to replenish the lost lithium source. In the present application, the aqueous positive electrode sheet composition can be present in the form of an aqueous slurry or a product obtained by drying the slurry. The drying can be performed, for example, by oven drying or spray drying.

[0050] In some embodiments, the water-soluble lithium-containing compound is an organic acid salt of lithium. The organic acid can be an organic acid commonly used in the art, such as formic acid, acetic acid, succinic acid, salicylic acid, citric acid, malonic acid, etc. The water-soluble lithium-containing compound can also be a lithium salt of a common inorganic acid, such as sulfuric acid, nitric acid, hydrochloric acid, and phosphoric acid. The water-soluble lithium-containing compound can also be an oxide, hydroxide, azide, and halide of lithium. In some embodiments, the water-soluble lithium-containing compound is selected from one or more of lithium oxide, lithium hydroxide, lithium azide, lithium chloride, lithium sulfate, lithium nitrate, lithium salicylate, lithium citrate, lithium oxalate, lithium glycolate, lithium malate, lithium tartrate, lithium lactate, lithium malonate, lithium succinate, lithium formate, and lithium acetate. By selecting the specific type of the lithium-containing compound, the battery capacity retention rate can be further improved.

[0051] In some embodiments, the oxidation peak of the water-soluble lithium-containing compound is between 3.5 and 4.4 V. The oxidation peak is measured by cyclic voltammetry, which is a method of reversing the scanning potential at a certain potential and observing the oxidation current and reduction current at the same time to obtain the oxidation current peak and the reduction current peak. The current and the corresponding point can be used to characterize various properties of the system. The oxidation peak is determined herein by dissolving the water-soluble lithium salt in water, adding an adhesive and conductive carbon, and coating it on an aluminum foil current collector to make a positive electrode sheet, which is then assembled with a lithium sheet and a diaphragm into a button cell, and then performing a cyclic voltammetry test using a chemical workstation.

[0052] In some embodiments, the solubility of the water-soluble lithium-containing compound in water at 25°C is ≥600 mg / ml, optionally ≥1000 mg / ml. The increase in solubility allows more lithium ions to be stored in a unit mass of solvent, which helps to improve the ability of the conductive composition to replenish lithium ions. At a certain temperature and pressure, the maximum amount of a substance that dissolves in a certain amount of a given solvent is called solubility. The solubility of a solid or liquid substance is generally expressed in grams of the substance that can be dissolved in 100 g of solvent. Test methods include common chromatography, spectrophotometry, chemical titration, etc. In this application, the solubility of the water-soluble lithium-containing compound in water at 25°C is determined by the standard GB-T 21845-2008 chemical water solubility test.

[0053] In some embodiments, the water-soluble lithium-containing compound is present in the composition in an amount of 1-20% by weight, optionally 3-10% by weight, based on the total weight of the aqueous positive electrode sheet composition. In some embodiments, the aqueous positive electrode sheet composition has a solid content of 30-65% by weight, optionally 45-55% by weight. In some embodiments, the weight ratio of the positive electrode active material, conductive agent, and aqueous binder contained in the aqueous positive electrode sheet composition is 90-98:0.5-2:1-8, optionally 95-97:0.8-1.2:2-4. A saturated aqueous solution of the water-soluble lithium-containing compound can be formed by adding an excess amount of the water-soluble lithium-containing compound to deionized water. The saturated aqueous solution is added to a mixture formed by mixing the positive electrode active material, conductive agent, aqueous binder, and optionally a dispersant, and the amount of the saturated aqueous solution added is adjusted to obtain a predetermined solid content of the aqueous positive electrode sheet composition.

[0054] In some embodiments, the positive electrode active material is selected from one or more of lithium iron phosphate, lithium manganese phosphate, lithium cobalt phosphate, lithium iron manganese phosphate, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide. In some embodiments, the conductive agent comprises one or more of conductive carbon black, superconducting carbon black, conductive graphite, acetylene black, Ketjen black, graphene, and carbon nanotubes. This application has no particular restrictions on the conventional components that form the positive electrode plate composition, and can be configured according to conventional requirements in the field, so it has strong adaptability.

[0055] In some embodiments, the aqueous adhesive is selected from one or more of soluble polysaccharides and their derivatives, and water-soluble or water-dispersible polymers. In further embodiments, the aqueous adhesive is selected from methylcellulose and its salts, xanthan gum and its salts, chitosan and its salts, alginic acid and its salts; and polyethyleneimine and its salts, polyacrylamide, acrylic acid copolymers, and their derivatives.

[0056] In particular, the aqueous adhesive is a compound of xanthan gum and acrylic copolymer, with a compound weight ratio of 2:1-0.2:2.8; optionally, the weight average molecular weight of the xanthan gum is 300,000-2,000,000 g / mol, and the weight average molecular weight of the acrylic copolymer is 100,000-1,000,000 g / mol.

[0057] In the composition of the positive electrode sheet, the choice of adhesive has a substantial impact on the mechanical properties of the sheet. Conventionally used thermoelastic adhesives such as butadiene-styrene copolymer (SBR) silicone rubber can effectively solve the problem of electrode brittleness, but the adhesion between the electrode current collector and the electrode film layer is insufficient, and the electrode is prone to powdering or even large-scale debonding, resulting in an increase in the polarization internal resistance of the battery, affecting the battery cell rate and cycle performance, and even affecting the safety performance of the battery cell in severe cases. In some embodiments of the present application, by optimizing the type and ratio of the adhesive in the composition of the positive electrode sheet composition, the electrode sheet has high flexibility, especially for maintaining the flexibility of thick coatings and high-pressure dense electrodes. Under the premise of ensuring the high stability of the composition, the cohesion and adhesion of the electrode sheet can be balanced. The present invention uses an aqueous adhesive as a binder and deionized water as a solvent to mix and stir into a slurry. The slurry is uniform and the conductive agent and the adhesive have good dispersion effects. The electrode sheet obtained by coating has a smooth surface appearance, no particle protrusions, and is firmly bonded to the current collector aluminum foil. The positive electrode material is not easy to lose powder or peel off during the winding process, which meets the high-speed winding requirements of the electrode and the assembled battery is stable.

[0058] Furthermore, on the one hand, the positive electrode film does not shed powder or peel off during the battery charging and discharging process, and the structure is stable, which can effectively inhibit the polarization of the electrode and reduce the internal resistance of the battery, thereby improving the capacity retention rate of the battery; on the other hand, the electrode is highly flexible and can withstand the increased stress caused by the expansion of the positive electrode during the battery charging and discharging process. The electrode will not break, ensuring the safety and reliability of the battery during application.

[0059] In some embodiments, the aqueous adhesive comprises an aqueous dispersion solution and an emulsion thereof with a solid content of ≥5%, or comprises a solid that can form a stable dispersion with a solid content of ≥1% with water.

[0060] In some embodiments, the dispersant is selected from polyamide dispersants, poly (meth) acrylate dispersants, polycarboxylate dispersants, sulfonate dispersants, silicate dispersants, phosphate dispersants, polyethyleneimine dispersants, amino-containing polymers and amine salt dispersants. For example, the dispersant may be polybutyl acrylate, methoxy polyethylene glycol methacrylate, sodium polyacrylate, sodium styrene sulfonate, etc. The dispersant can be adsorbed on the surface of the particles in the positive electrode conductive slurry through physical or chemical action to avoid collision and agglomeration between particles and reduce the viscosity of the slurry. In this way, the amount of solvent used can be reduced while improving the dispersion effect of the positive active material. The content of the dispersant in the aqueous positive electrode composition can be adjusted in a wide range, for example, it can be 0.5-10% by weight, optionally 1-3% by weight, based on the total weight of the aqueous positive electrode composition.

[0061] The present application also relates to a method for preparing the aqueous positive electrode plate composition selected from the first aspect of the present application, comprising the following steps:

[0062] 1) mixing a water-soluble lithium-containing compound with deionized water to prepare a saturated aqueous solution of the water-soluble lithium-containing compound;

[0063] 2) mixing a positive electrode active material, a conductive agent, an aqueous binder, and optionally a dispersant to obtain a mixture;

[0064] 3) uniformly mixing the saturated aqueous solution obtained in step 1) and the mixture obtained in step 2) to form a slurry; and

[0065] 4) Optionally drying the slurry.

[0066] In step 3), the amount of the saturated aqueous solution added to the mixture can be adjusted so that the solid content of the formed slurry is in the range of 30-65 wt %, optionally 45-55 wt %.

[0067] The second aspect of the present application provides a positive electrode sheet, which is prepared by using an aqueous positive electrode sheet composition selected from the first aspect of the present application. The main feature of the positive electrode sheet of the present application is that the composition forming it uses water as a solvent, and a water-soluble lithium-containing compound is additionally added. On the basis of the specific aqueous positive electrode sheet composition, a positive electrode sheet can be made by conventional methods, for example, by uniformly coating the aqueous positive electrode sheet composition on a positive electrode collector, and then drying, cold pressing, and cutting to obtain a positive electrode sheet. The selection of the positive electrode collector can be found in the specific description of the positive electrode sheet below.

[0068] A third aspect of the present application provides a secondary battery comprising a positive electrode sheet selected from the second aspect of the present application.

[0069] A fourth aspect of the present application provides a battery pack comprising a secondary battery selected from the third aspect of the present application.

[0070] A fifth aspect of the present application provides an electrical device comprising a secondary battery selected from the third aspect of the present application or a battery pack according to the fourth aspect of the present application.

[0071] The materials of the components of the secondary battery of the present application can be selected from a wide range. In some embodiments, the secondary battery is particularly a lithium-ion secondary battery. The battery cells of the lithium-ion secondary battery are described in detail below.

[0072] Typically, a lithium-ion secondary battery consists of a positive electrode, a negative electrode, a separator, and an electrolyte. During the battery's charge and discharge processes, active ions are inserted and removed between the positive and negative electrodes. The separator is placed between the positive and negative electrodes to provide isolation. The electrolyte conducts ions between the positive and negative electrodes.

[0073] [Electrolyte]

[0074] The electrolyte conducts ions between the positive and negative electrodes and consists of electrolyte salts and solvents.

[0075] In the present application, the electrolyte salt may be a commonly used electrolyte salt in lithium-ion secondary batteries, such as a lithium salt, including the lithium salts described above as high thermal stability salts, lithium salts as low impedance additives, or lithium salts that inhibit corrosion of aluminum foil. As an example, the electrolyte salt may be selected from one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium difluorophosphate (LiPO2F2), lithium difluorobis(oxalatophosphate) (LiDFOP), lithium fluorosulfonate (LiSO3F), difluorobis(oxalato) (NDFOP), Li2F(SO2N)2SO2F, KFSI, CsFSI, Ba(FSI)2, and LiFSO2NSO2CH2CH2CF3.

[0076] The type of solvent is not particularly limited and can be selected according to actual needs. In some embodiments, the solvent is a non-aqueous solvent. Alternatively, the solvent may include one or more of linear carbonate, cyclic carbonate, and carboxylate. In some embodiments, the solvent may be selected from 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), tetrahydrofuran, sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS) and diethyl sulfone (ESE).

[0077] In some embodiments, the electrolyte may optionally include other additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high temperature performance, and additives that improve battery low temperature performance. As an example, the additive is selected from at least one of a cyclic carbonate compound containing an unsaturated bond, a halogen-substituted cyclic carbonate compound, a sulfate compound, a sulfite compound, a sultone compound, a disulfonic acid compound, a nitrile compound, an aromatic compound, an isocyanate compound, a phosphazene compound, a cyclic acid anhydride compound, a phosphite compound, a phosphate compound, a borate compound, and a carboxylate compound.

[0078] [Positive electrode]

[0079] The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector. The positive electrode active material layer includes a positive electrode active material and a conductive agent.

[0080] As an example, the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode active material layer is provided on either or both of the two facing surfaces of the positive electrode current collector.

[0081] In the lithium-ion secondary battery of the present application, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (e.g., aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (e.g., a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0082] The positive electrode active material layer disposed on the surface of the positive electrode current collector includes a positive electrode active material. The positive electrode active material used in this application may be any conventional positive electrode active material used in secondary batteries. In some embodiments, the positive electrode active material may include one or more selected from lithium transition metal oxides, olivine-structured lithium-containing phosphates, and their respective modified compounds. Examples of lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their modified compounds. Examples of olivine-structured lithium-containing phosphates may include, but are not limited to, one or more of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, a composite material of lithium manganese iron phosphate and carbon, and their modified compounds. All of these materials can be obtained commercially. The surface of the positive electrode active material may be coated with carbon.

[0083] The positive electrode active material layer may optionally include a conductive agent. However, the type of conductive agent is not particularly limited, and those skilled in the art may select one based on actual needs. For example, the conductive agent used in the positive electrode material may be selected from one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0084] The positive electrode active material layer also includes an aqueous binder. The aqueous binder can be selected from one or more of soluble polysaccharides and their derivatives, and water-soluble or water-dispersible polymers. For example, the aqueous binder can include methylcellulose and its salts, xanthan gum and its salts, chitosan and its salts, alginic acid and its salts; as well as polyethyleneimine and its salts, polyacrylamide, acrylic acid copolymers, and their derivatives. In particular, the aqueous binder is a mixture of xanthan gum and acrylic acid copolymer in a weight ratio of 2:1 to 0.2:2.8. Optionally, the weight-average molecular weight of the xanthan gum is 300,000 to 2,000,000 g / mol, and the weight-average molecular weight of the acrylic acid copolymer is 100,000 to 1,000,000 g / mol.

[0085] In this application, the positive electrode sheet can be prepared according to methods known in the art. For example, a carbon-coated positive electrode active material, a conductive agent, and an aqueous binder can be dispersed in a solvent (e.g., water) to form a uniform positive electrode slurry; the positive electrode slurry is coated on a positive electrode current collector, and after drying, cold pressing, and other processes, a positive electrode sheet is obtained.

[0086] [Negative electrode]

[0087] The negative electrode sheet includes a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode material layer includes a negative electrode active material.

[0088] As an example, the negative electrode current collector has two surfaces facing each other in its thickness direction, and the negative electrode material layer is disposed on either or both of the two facing surfaces of the negative electrode current collector.

[0089] In the lithium-ion secondary battery of the present application, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base material. The composite current collector may be formed by forming a metal material (e.g., copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material base material (e.g., a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0090] In the lithium-ion secondary battery of the present application, the negative electrode material layer generally comprises a negative electrode active material and an optional binder, an optional conductive agent, and other optional additives, and is generally formed by coating and drying a negative electrode slurry. The negative electrode slurry coating is generally formed by dispersing the negative electrode active material and the optional conductive agent and binder in a solvent and stirring the mixture uniformly. The solvent may be N-methylpyrrolidone (NMP) or deionized water.

[0091] The specific type of negative electrode active material is not limited. Active materials known in the art for use in negative electrodes of lithium-ion secondary batteries can be used, and those skilled in the art can select according to actual needs. As an example, the negative electrode active material can be selected from one or more of graphite, soft carbon, hard carbon, mesocarbon microbeads, carbon fibers, carbon nanotubes, elemental silicon, silicon oxides, silicon-carbon composites, and lithium titanate.

[0092] As an example, the conductive agent may be selected from one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0093] As an example, the binder can be selected from one or more of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).

[0094] Other optional auxiliary agents include, for example, thickeners (such as sodium carboxymethyl cellulose (CMC-Na)).

[0095] [Isolation film]

[0096] The lithium-ion secondary battery using an electrolyte also includes an isolation membrane. The isolation membrane is arranged between the positive electrode plate and the negative electrode plate to play an isolation role. The present application has no particular restrictions on the type of isolation membrane, and any well-known porous structure isolation membrane with good chemical stability and mechanical stability can be selected. In some embodiments, the material of the isolation membrane can be selected from one or more of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The isolation membrane can be a single-layer film or a multi-layer composite film, without special restrictions. When the isolation membrane is a multi-layer composite film, the materials of each layer can be the same or different, without special restrictions.

[0097] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0098] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0099] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the secondary battery can also be a soft package, such as a pouch-type soft package. The soft package can be made of plastic, such as polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0100] The present application has no particular limitation on the shape of the secondary battery, which may be cylindrical, square, or any other shape. For example, FIG1 shows a lithium-ion secondary battery 5 having a square structure as an example.

[0101] In some embodiments, referring to FIG2 , the outer packaging may include a shell 51 and a cover plate 53. Specifically, the shell 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to seal the receiving cavity. The positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the lithium-ion secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0102] In some embodiments, lithium-ion secondary batteries can be assembled into a battery module 4. The number of lithium-ion secondary batteries contained in the battery module 4 can be one or more. The specific number can be selected by those skilled in the art according to the application and capacity of the battery module 4. In the battery module 4, multiple lithium-ion secondary batteries 5 can be arranged in sequence along the length direction of the battery module. Of course, they can also be arranged in any other manner. The multiple lithium-ion secondary batteries 5 can further be fixed by fasteners. Optionally, the battery module 4 can also include a shell having a storage space, and the multiple lithium-ion secondary batteries 5 are accommodated in the storage space.

[0103] In some embodiments, the lithium-ion secondary batteries 5 or battery modules 4 can be assembled into a battery pack 1 , and the number of lithium-ion secondary batteries 5 or battery modules 4 contained in the battery pack 1 can be selected by those skilled in the art based on the application and capacity of the battery pack 1 .

[0104] Figures 3 and 4 illustrate an example battery pack 1. Referring to Figures 3 and 4 , the battery pack 1 may include a battery box and a plurality of battery cells disposed within the box. The battery box comprises an upper case 2 and a lower case 3. The upper case 2 can be placed over the lower case 3 to form an enclosed space for accommodating the battery cells.

[0105] In addition, the present application also provides a device, which includes a battery pack provided in the present application. The battery pack can be used as a power source for the device, and can also be used as an energy storage unit for the device. The device can be, but is not limited to, a mobile device (such as a mobile phone, a laptop computer, etc.), an electric vehicle (such as 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, etc.), an electric train, a ship and a satellite, an energy storage system, etc. As the device, a battery pack can be selected according to its usage requirements.

[0106] Figure 5 shows an example device. This device is a pure electric vehicle, hybrid electric vehicle, or plug-in hybrid electric vehicle. To meet the device's requirements for high power and high energy density of lithium-ion secondary batteries, a battery pack or battery module can be used.

[0107] Example

[0108] Below, the examples of the present application are described. The examples described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If no specific techniques or conditions are specified in the examples, the techniques or conditions described in the literature in this field or the product instructions are used. The reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially. Unless otherwise specified, all content ratios are weight ratios, and all experiments are carried out at room temperature (25°C) and normal pressure.

[0109] Example 1

[0110] (1) Preparation of positive electrode sheet

[0111] Lithium acetate and deionized water were mixed and stirred to prepare a saturated aqueous solution of lithium acetate. The solubility of lithium acetate in deionized water at 25°C is 29 g / 100 ml.

[0112] The positive electrode active material, lithium iron phosphate, the conductive agent, conductive carbon black, and an aqueous binder were mixed in a weight ratio of 96:1:3, wherein the aqueous binder was a mixture of xanthan gum and acrylic acid copolymer, with a weight ratio of 1:1. The saturated aqueous solution of lithium acetate obtained above was added to the mixture of positive electrode active materials and stirred thoroughly to form a slurry. The amount of the saturated aqueous solution of lithium acetate added was adjusted to achieve a solid content of 50% by weight.

[0113] Finally, the aqueous positive electrode sheet composition (slurry) is evenly coated on the positive electrode current collector aluminum foil, and then dried, cold pressed, and cut to obtain a single-sided positive electrode sheet with a film weight of 350mg / 1540.25mm 2 The positive electrode.

[0114] (2) Preparation of negative electrode sheet

[0115] The active material artificial graphite, the conductive agent carbon black, the binder styrene-butadiene rubber (SBR), and the thickener sodium carboxymethyl cellulose (CMC) are dissolved in the solvent deionized water in a weight ratio of 96.2:0.8:0.8:1.2, and mixed evenly to prepare a negative electrode slurry; the negative electrode slurry is evenly coated on the negative electrode current collector copper foil once or multiple times, and the negative electrode sheet is obtained after drying, cold pressing, and slitting.

[0116] (3) Preparation of electrolyte

[0117] In an argon atmosphere glove box (H2O<0.1ppm, O2<0.1ppm), organic solvents ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed uniformly in a volume ratio of 3 / 7, 12.5% ​​LiPF6 lithium salt was added and dissolved in the organic solvent, and stirred uniformly to obtain an electrolyte.

[0118] (4) Isolation film

[0119] An 8μm PE porous film is used as the substrate, and a 2μm ceramic coating is coated on both sides to serve as the isolation membrane.

[0120] (5) Preparation of lithium-ion batteries

[0121] The positive electrode sheet, separator, and negative electrode sheet prepared as described above were stacked in order, with the separator positioned between the positive and negative electrode sheets to provide isolation. The cells were then wound to obtain a bare cell. The tabs were welded to the bare cell and placed in an aluminum casing. The cells were then baked at 80°C to remove moisture. The electrolyte was then injected and sealed to obtain an uncharged battery. The uncharged battery then underwent a series of steps, including resting, hot and cold pressing, formation, shaping, and capacity testing, to obtain the lithium-ion secondary battery product of Example 1.

[0122] Examples 2-6

[0123] Except for the difference in the type of materials used to form the saturated water-soluble lithium-containing compound in the formula, other steps are the same as those in Example 1.

[0124] Comparative Example 1

[0125] Except for selecting lithium phosphate instead of lithium acetate, other steps are the same as those in Example 1.

[0126] Comparative Example 2

[0127] Except for selecting lithium carbonate instead of lithium acetate, other steps are the same as those in Example 1.

[0128] Comparative Example 3

[0129] Except that deionized water (ie, not containing the water-soluble lithium-containing compound) is directly used as the solvent, other steps are the same as those in Example 1.

[0130] Pole-level performance test

[0131] 1. Porosity test of positive electrode sheet

[0132] Taking Example 1 as an example, the positive electrode film was peeled off with tape. The porosity (P1) within a region H / 3 from the surface and the porosity (P2) within a region H / 3 from the positive electrode current collector were measured according to GB / T 24586-2009. The parameter α = P1 / P2. The parameter α indicates the porosity distribution along the thickness of the electrode sheet. α is generally required to be ≤ 1.2, preferably 0.7-1.0.

[0133] Battery performance test

[0134] 1. Initial gram capacity test of battery positive electrode active material

[0135] Taking Example 1 as an example, the battery capacity test process is as follows: at 25°C, the battery corresponding to Example 1 is charged to 3.65V at a constant current of 1 / 3C, and then charged at a constant voltage of 3.65V to a current of 0.05C; after standing for 5 minutes, it is discharged to 2.5V at a constant current of 1 / 3C to obtain the initial capacity of the secondary battery.

[0136] Initial gram capacity of the positive electrode active material (mAh / g) = initial capacity of the secondary battery / mass of the positive electrode active material.

[0137] 2. Battery capacity retention test

[0138] Taking Example 1 as an example, the battery capacity retention rate test process is as follows: at 25°C, the battery corresponding to Example 1 is charged to 3.65V at a constant current of 1 / 3C, then charged to a current of 0.05C at a constant voltage of 3.65V, left for 5 minutes, and then discharged to 2.7V at 1 / 3C. The obtained capacity is recorded as the initial capacity C0. Repeat the above steps for the same battery mentioned above, and at the same time record the discharge capacity Cn of the battery after the nth cycle. The battery capacity retention rate after each cycle is Pn = Cn / C0*100%. In this test process, the first cycle corresponds to n = 1, the second cycle corresponds to n = 2, ... and the 100th cycle corresponds to n = 100. The battery capacity retention rate data corresponding to Example 1 in Table 1 is the data measured after 800 cycles under the above test conditions, that is, the value of P800.

[0139] The lithium-ion battery products of Comparative Examples 1-3 and Examples 2-6 were also tested according to the above steps. The test results are summarized in Table 1 below.

[0140] Table 1: Performance test results of secondary batteries of Comparative Examples 1-3 and Examples 1-6

[0141]

[0142] As can be seen from Examples 1-6, all secondary batteries fabricated using aqueous positive electrode compositions incorporating water-soluble lithium-containing compounds exhibited high battery capacity retention (≥98.0%). These batteries also exhibited good uniformity (α value) and high initial gram capacity. In particular, Examples 3 and 4, which used lithium citrate and lithium dihydrogen phosphate with solubilities greater than 100g / 100ml, achieved the highest battery capacity retention.

[0143] In contrast, the capacity retention rates of the batteries in Comparative Examples 1 and 2, which used water-insoluble or poorly water-soluble lithium-containing compounds under otherwise identical conditions, were significantly lower than those of Examples 1-6 of the present invention. Furthermore, the capacity retention rate of the battery in Comparative Example 3, without the addition of a water-soluble lithium-containing compound, was significantly lower, indicating significant lithium ion loss after multiple cycles and ineffective replenishment, thus impacting battery performance and lifespan. Furthermore, the α value was significantly lower, indicating poor uniformity of the positive electrode sheet.

[0144] Although the present application has been described with reference to the embodiments, various modifications may be made thereto and components may be substituted with equivalents without departing from the scope of the present application. In particular, the various technical features described in the various embodiments may be combined in any manner as long as there are no structural conflicts. The present application is not limited to the specific embodiments disclosed herein, but encompasses all technical solutions within the scope of the claims.

Claims

1. A water-based positive electrode sheet composition, wherein the composition contains a positive electrode active material, a conductive agent, an aqueous binder and a water-soluble lithium-containing compound, and optionally water and a dispersant. 2 . The aqueous positive electrode sheet composition according to claim 1 , wherein the water-soluble lithium-containing compound is an organic acid salt of lithium.

3. The aqueous positive electrode plate composition according to claim 1, wherein the water-soluble lithium-containing compound is selected from one or more of lithium oxide, lithium hydroxide, lithium azide, lithium chloride, lithium sulfate, lithium nitrate, lithium salicylate, lithium citrate, lithium oxalate, lithium glycolate, lithium malate, lithium tartrate, lithium lactate, lithium malonate, lithium succinate, lithium formate, and lithium acetate. 4 . The aqueous positive electrode composition according to claim 1 , wherein the oxidation peak of the water-soluble lithium-containing compound is between 3.5 and 4.4 V. 5 . The aqueous positive electrode composition according to claim 1 , wherein the solubility of the water-soluble lithium-containing compound in water at 25° C. is ≥600 mg / ml, optionally ≥1000 mg / ml.

6. The aqueous positive electrode sheet composition according to any one of claims 1 to 5, wherein the content of the water-soluble lithium-containing compound in the composition is 1-20 weight%, optionally 3-10 weight%, based on the total weight of the aqueous positive electrode sheet composition. 7 . The aqueous positive electrode plate composition according to claim 1 , wherein the solid content of the composition is 30-65% by weight, optionally 45-55% by weight.

8. The aqueous positive electrode sheet composition according to any one of claims 1 to 7, wherein the weight ratio of the positive electrode active material, the conductive agent and the aqueous binder contained in the composition is 90-98:0.5-2:1-8, optionally 95-97:0.8-1.2:2-4.

9. The aqueous positive electrode sheet composition according to any one of claims 1 to 8, wherein the positive electrode active material is selected from one or more of lithium iron phosphate, lithium manganese phosphate, lithium cobalt phosphate, lithium iron manganese phosphate, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide.

10. The aqueous positive electrode plate composition according to any one of claims 1 to 9, wherein the conductive agent comprises one or more of conductive carbon black, superconducting carbon black, conductive graphite, acetylene black, Ketjen black, graphene, and carbon nanotubes. 11 . The aqueous positive electrode sheet composition according to claim 1 , wherein the aqueous binder is selected from one or more of soluble polysaccharides and their derivatives and water-soluble or water-dispersible polymers.

12. The aqueous positive electrode plate composition according to claim 11, wherein the aqueous binder is selected from methyl cellulose and its salts, xanthan gum and its salts, chitosan and its salts, alginic acid and its salts; and polyethyleneimine and its salts, polyacrylamide, acrylic acid copolymers and their derivatives.

13. The aqueous positive electrode plate composition according to claim 12, wherein the aqueous adhesive is a compound of xanthan gum and an acrylic copolymer, and the compound weight ratio is 2:1-0.2:2.8; optionally, the weight average molecular weight of the xanthan gum is 300,000-2,000,000 g / mol, and the weight average molecular weight of the acrylic copolymer is 100,000-1,000,000 g / mol.

14. The aqueous positive electrode plate composition according to claim 11, wherein the aqueous binder comprises an aqueous dispersion solution and an emulsion thereof with a solid content of ≥5%, or comprises a solid that can form a stable dispersion with a solid content of ≥1% with water.

15. The aqueous positive electrode plate composition according to any one of claims 1 to 14, wherein the dispersant is selected from polyamide dispersants, poly(meth)acrylate dispersants, polycarboxylate dispersants, sulfonate dispersants, silicate dispersants, phosphate dispersants, polyethyleneimine dispersants, amino-containing polymers and amine salt dispersants. 16 . The aqueous positive electrode sheet composition according to claim 1 , wherein the composition is in the form of an aqueous slurry, or in the form of a product obtained by drying the slurry.

17. A method for preparing the aqueous positive electrode composition according to any one of claims 1 to 16, comprising the following steps: 1) mixing a water-soluble lithium-containing compound with deionized water to prepare a saturated aqueous solution of the water-soluble lithium-containing compound; 2) mixing a positive electrode active material, a conductive agent, an aqueous binder, and optionally a dispersant to obtain a mixture; 3) uniformly mixing the saturated aqueous solution obtained in step 1) and the mixture obtained in step 2) to form a slurry; and 4) Optionally drying the slurry. 18 . A positive electrode sheet prepared by using the aqueous positive electrode sheet composition according to claim 1 . A secondary battery comprising the positive electrode sheet according to claim 18 . 20 . A battery pack comprising the secondary battery according to claim 19 . 21 . An electric device comprising the secondary battery according to claim 19 or the battery pack according to claim 20.

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