WO2023245484A1 - 含有水溶性含锂化合物的水系正极极片组合物及二次电池 - Google Patents

含有水溶性含锂化合物的水系正极极片组合物及二次电池 Download PDF

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WO2023245484A1
WO2023245484A1 PCT/CN2022/100374 CN2022100374W WO2023245484A1 WO 2023245484 A1 WO2023245484 A1 WO 2023245484A1 CN 2022100374 W CN2022100374 W CN 2022100374W WO 2023245484 A1 WO2023245484 A1 WO 2023245484A1
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lithium
water
positive electrode
aqueous
composition according
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PCT/CN2022/100374
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English (en)
French (fr)
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程丛
陈均桄
裴海乐
杨丙梓
张盛武
王星会
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宁德时代新能源科技股份有限公司
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Priority to PCT/CN2022/100374 priority Critical patent/WO2023245484A1/zh
Publication of WO2023245484A1 publication Critical patent/WO2023245484A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers

Definitions

  • the present application relates to an aqueous positive electrode plate composition, which contains a positive active material, a conductive agent, a water-based binder and 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 including the positive electrode sheet, a battery pack including the secondary battery, and an electrical device.
  • Secondary batteries have become the most popular energy storage system due to their low cost, long life, and good safety. They are now widely used in pure electric vehicles, hybrid electric vehicles, smart grids and other fields.
  • the positive electrodes of secondary batteries are mostly made of oil-based formulas, which are generally a system composed of the adhesive polyvinylidene fluoride (PVDF) and the solvent N-methylpyrrolidone (NMP).
  • PVDF adhesive polyvinylidene fluoride
  • NMP solvent N-methylpyrrolidone
  • both PVDF and NMP are petroleum-derived chemical products. During the slurry mixing and coating process, a large amount of NMP toxic gases will volatilize into the air, polluting the environment and causing harm to the human body.
  • the synthesis and post-processing processes of NMP and PVDF are complex, consume high energy, and have high application costs.
  • lithium-ion secondary batteries In addition, a common problem currently existing in lithium-ion secondary batteries is that during the first charging process, a large amount of lithium ions released from the positive electrode are consumed to form an SEI film on the surface of the negative electrode. The irreversible consumption of the positive electrode lithium source exceeds 10% during the first charge, and in the first week Coulombic efficiency is less than 90%. Secondly, lithium-ion secondary batteries will continue to consume active lithium during normal use. The above will lead to a reduction in the initial capacity of the battery and a reduction in battery life.
  • This application was made in view of the above-mentioned problems, and its purpose is to provide an aqueous positive electrode sheet composition to solve the technical problems of excessive initial capacity reduction and reduced life span of secondary batteries prepared therefrom.
  • the first aspect of the present application provides an aqueous positive electrode sheet composition, wherein the composition contains a positive electrode active material, a conductive agent, a water-based binder and a water-soluble lithium-containing compound, and optionally water and dispersants.
  • the aqueous positive electrode sheet composition of the present application can compensate for the loss of the battery cell's first charge and discharge capacity and first charge and discharge efficiency, and inhibit the precipitation of lithium ions from the positive electrode active material particles in the solvent water.
  • the water-soluble lithium-containing compound can be directly added to the water-based positive electrode sheet composition in the prior art. It is non-selective to various materials in the formula, has strong formula adaptability, and has a large operating space.
  • the anions other than lithium ions of the water-soluble lithium-containing compound will lose electrons during the charging process and eventually decompose to form gases that are harmless to the battery, such as N 2 , CO 2 and CO, etc. These gases can be eliminated before packaging or from the subsequent safety outlet, without any impact on the proportion of the main material content in the pole piece.
  • the water-soluble lithium-containing compound is an organic acid salt of lithium.
  • the water-soluble lithium-containing compound is selected from the group consisting of lithium oxide, lithium hydroxide, lithium azide, lithium chloride, lithium sulfate, lithium nitrate, lithium salicylate, lithium citrate, lithium oxalate, hydroxyl
  • lithium acetate, lithium malate, lithium tartrate, lithium lactate, lithium malonate, lithium succinate, lithium formate, and lithium acetate By selecting the specific type of lithium-containing compound, the battery capacity retention rate can be further improved.
  • the water-soluble lithium-containing compound has an oxidation peak between 3.5 and 4.4V. In any embodiment, the water-soluble lithium-containing compound has a solubility in water at 25°C ⁇ 600 mg/ml, optionally ⁇ 1000 mg/ml. Choosing lithium-containing compounds with greater solubility can replenish the loss of lithium sources more quickly.
  • the content of the water-soluble lithium-containing compound in the composition is 1-20% by weight, optionally 3-10% by weight, based on the total weight of the aqueous cathode plate composition count.
  • the solid content of the aqueous positive electrode sheet composition is 30-65% by weight, optionally 45-55% by weight.
  • the weight ratio of the cathode active material, conductive agent and aqueous binder contained in the aqueous cathode plate composition is 90-98:0.5-2:1-8, optionally 95-95: 97:0.8-1.2:2-4.
  • the positive active material is selected from the group consisting of lithium iron phosphate, lithium manganese phosphate, lithium cobalt phosphate, lithium iron manganese phosphate, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, and lithium nickel manganese oxide. , one or more of lithium nickel cobalt manganese oxide and lithium nickel cobalt aluminum oxide.
  • the conductive agent includes one or more of conductive carbon black, superconducting carbon black, conductive graphite, acetylene black, Ketjen black, graphene, and carbon nanotubes.
  • the aqueous adhesive is selected from one or more of soluble polysaccharides and their derivatives and water-soluble or water-dispersible polymers.
  • the water-based adhesive is selected from the group consisting of 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 water-based adhesive is a compound of xanthan gum and acrylic acid copolymer, and the compound weight ratio is 2:1-0.2:2.8; optionally, the weight average molecular weight of xanthan gum is 300000-2000000g/mol, And the weight average molecular weight of the acrylic acid copolymer is 100000-1000000g/mol.
  • the aqueous adhesive includes a water dispersion solution and its emulsion with a solid component content of ⁇ 5%, or a solid that can form a stable dispersion with water with a solid component content of ⁇ 1%.
  • the dispersant is selected from the group consisting of polyamide dispersants, poly(meth)acrylate dispersants, polycarboxylate dispersants, sulfonate dispersants, and silicate dispersants. , phosphate dispersants, polyethylene imine dispersants, amino-containing polymers and their amine salt dispersants.
  • the composition is in the form of an aqueous slurry, or the dried product of the slurry.
  • the present application also relates to a method for preparing an aqueous positive electrode sheet composition selected from the first aspect of the present application, including the following steps:
  • a second aspect of the present application provides a positive electrode sheet prepared by using an aqueous positive electrode sheet composition selected from the first aspect of the present application.
  • a third aspect of the present application provides a secondary battery including a positive electrode plate selected from the second aspect of the present application.
  • a fourth aspect of the present application provides a battery pack including the secondary battery selected from the third aspect of the present application.
  • a fifth aspect of the present application provides an electrical device, which includes a secondary battery selected from the third aspect of the present application or a battery pack of the fourth aspect of the present application.
  • Figure 1 is a schematic diagram of a lithium ion secondary battery in one embodiment of the present application.
  • FIG. 2 is an exploded view of the lithium ion secondary battery in one embodiment of the present application shown in FIG. 1 .
  • Figure 3 is a schematic diagram of a battery pack in an embodiment of the present application.
  • FIG. 4 is an exploded view of the battery pack in one embodiment of the present application shown in FIG. 3 .
  • Figure 5 is a schematic diagram of a device in which a battery pack is used as a power source in an embodiment of the present application.
  • any lower limit can be combined with any upper limit to form an unexpressed range; and any lower limit can be combined with other lower limits to form an unexpressed range, and likewise any upper limit can be combined with any other upper limit to form an unexpressed range.
  • each individually disclosed point or single value may itself serve as a lower or upper limit in combination with any other point or single value or with other lower or upper limits to form a range not expressly recited.
  • first discharge capacity and first discharge efficiency determine the basis for subsequent cycles, and whether the structure of most materials is stable is also determined by the first cycle discharge capacity and discharge efficiency, which in turn affects the design and material evaluation of full batteries.
  • deionized water is used as the solvent for the cathode slurry, the active material will undergo replacement of lithium ions and hydrogen ions when exposed to water, further causing capacity loss. This greatly limits the application and development of water-based cathodes.
  • the current solution is to use lithium replenishment technology to supplement the lithium loss during the cycle.
  • lithium replenishment technology There are currently two main methods of lithium replenishment technology, one is to replenish lithium in the negative electrode, and the other is to replenish lithium in the positive electrode.
  • the current methods of replenishing lithium in the negative electrode mainly fall into three categories: 1) Physical mixing, such as ultra-thin lithium foil embedding and stabilization Metal lithium powder; 2) Electrochemical prelithiation, such as using the potential difference to pressurize the silicon carbon negative electrode with electrolyte added into contact with metallic lithium to form lithiated silicon carbon; 3) Chemical prelithiation, such as SnLi synthesized by ball milling in an inert atmosphere x and LiF modification, etc.
  • Lithium replenishment of the negative electrode at the pole piece side involves the use of flammable and explosive metal lithium, which has high safety risks.
  • the chemical lithium replenishment process at the material end is complicated, and the material is highly alkaline, making material processing difficult.
  • replenishing lithium at the material end will damage the structure of the negative electrode. , affecting the cycle life.
  • supplementing lithium at the negative end involves greater safety risks and complex and difficult processing technology problems.
  • the positive electrode lithium supplement process is simple.
  • the lithium source is added through the positive electrode stirring process, which can completely avoid the safety risks and cost increases of negative electrode lithium supplement.
  • the positive electrode lithium replenishment process is to add a small amount of high-capacity lithium replenishment additives to the positive electrode during the homogenization process. During the charging process, the excess Li elements are extracted from these high-capacity positive electrode materials and embedded into the negative electrode to supplement the first charge and discharge. irreversible capacity.
  • lithium-rich materials such as lithium-rich xLiMO 2 ⁇ (1-x)Li 2 MnO 3 , which can be regarded as a solid solution of Li 2 MnO 3 and LiMO 2 (M represents transition metal).
  • M represents transition metal
  • Li 2 Mn 2 O 4 Li 2 NiO 2 , Li 6 CoO 4 and Li 2 CuO 2 , etc.
  • These lithium supplementation materials have high environmental requirements and require a dry environment. They will react strongly and become unstable when exposed to water. Their limitations Application in water system cathodes.
  • the first aspect of the application provides an aqueous positive electrode sheet composition, wherein the composition contains a positive electrode active material, a conductive agent, a water-based binder and a water-soluble lithium-containing compound, and optionally water and dispersed agent.
  • the addition of the water-soluble lithium-containing compound inhibits the precipitation of lithium ions from the positive active material particles in the solvent water.
  • 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.
  • 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 N 2 , CO 2 and CO, etc.
  • water-soluble lithium-containing compound means that the lithium-containing compound can be substantially dissolved in deionized water to form free Li + , for example, its solubility in deionized water is ⁇ 20 mg/ml, optionally ⁇ 30mg/ml, further optionally ⁇ 50mg/ml.
  • the water-soluble lithium-containing compound has a solubility in deionized water at 25°C of at least 20 mg/ml, optionally at least 30 mg/ml, further optionally at least 50 mg/ml.
  • the aqueous positive electrode plate composition of the present application may contain water as a solvent, or may 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 cathode plate composition. In one embodiment, only water is used as the solvent for the aqueous positive electrode plate composition.
  • the water-soluble lithium-containing compound can first be prepared with deionized water to form a saturated aqueous solution, and then mixed evenly with other components to obtain the water-based positive electrode sheet composition of the present application.
  • the water-soluble lithium-containing compound in the obtained aqueous positive electrode sheet composition, is in a saturated state in the solvent water.
  • the Li + in the water-soluble lithium-containing compound can be embedded in the positive electrode piece, thereby replenishing the lost lithium source.
  • the aqueous positive electrode sheet composition may exist in the form of an aqueous slurry, or in the form of a dried product of the slurry. The drying can be carried out, for example, by oven drying, or by spray drying.
  • the water-soluble lithium-containing compound is an organic acid salt of lithium.
  • the organic acid can be an organic acid commonly used in this field, 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.
  • the inorganic acid can be, for example, sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, etc.
  • the water-soluble lithium-containing compound may also be lithium oxides, hydroxides, azides, and halides.
  • the water-soluble lithium-containing compound is selected from the group consisting of lithium oxide, lithium hydroxide, lithium azide, lithium chloride, lithium sulfate, lithium nitrate, lithium salicylate, lithium citrate, lithium oxalate, hydroxyl
  • lithium oxide lithium oxide
  • lithium hydroxide lithium azide
  • lithium chloride lithium sulfate
  • lithium nitrate lithium salicylate
  • lithium citrate lithium oxalate
  • hydroxyl One or more of lithium acetate, lithium malate, lithium tartrate, lithium lactate, lithium malonate, lithium succinate, lithium formate, and lithium acetate.
  • the water-soluble lithium-containing compound has an oxidation peak between 3.5-4.4V.
  • the oxidation peak is measured by cyclic voltammetry. By reversing the scanning potential at a certain potential and observing the oxidation current and reduction current at the same time, the oxidation current peak and reduction current peak can be obtained, as well as the passing current and the corresponding point position.
  • Various properties of the system can be characterized.
  • the determination of the oxidation peak in this article is to dissolve the water-soluble lithium salt in water, add a binder and conductive carbon, and coat it on the aluminum foil current collector to make a positive electrode piece, and then assemble it with the lithium piece and separator to form a button battery. Subsequently, a cyclic voltammetry test was performed using a chemical workstation.
  • the water-soluble lithium-containing compound has a solubility in water at 25°C ⁇ 600 mg/ml, optionally ⁇ 1000 mg/ml.
  • the increase in solubility allows more lithium ions to be stored in unit mass of the solvent, which helps to improve the ability of the conductive composition to replenish lithium ions.
  • the maximum amount of a substance that can be dissolved in a given amount of solvent at a certain temperature and pressure is called solubility.
  • the solubility of a solid or liquid substance is generally expressed by the number of grams of the substance that can be dissolved in 100g of solvent. Testing methods include commonly used chromatography, spectrophotometry, chemical titration, etc. In this application, the solubility of the water-soluble lithium-containing compound in water at 25°C is determined through the standard GB-T 21845-2008 chemical water solubility test.
  • the content of the water-soluble lithium-containing compound in the composition is 1-20% by weight, optionally 3-10% by weight, based on the total weight of the aqueous cathode plate composition count.
  • the solid content of the aqueous positive electrode sheet composition is 30-65% by weight, optionally 45-55% by weight.
  • the weight ratio of the cathode active material, conductive agent and aqueous binder contained in the aqueous cathode plate composition is 90-98:0.5-2:1-8, optionally 95-95: 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 the mixture formed by mixing the positive electrode active material, the conductive agent, the aqueous binder and optionally the dispersant, and the added amount of the saturated aqueous solution is adjusted to obtain the predetermined water-based positive electrode. Solid content of tablet composition.
  • the positive active material is selected from 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 , one or more of lithium nickel cobalt manganese oxide and lithium nickel cobalt aluminum oxide.
  • the conductive agent includes one or more of conductive carbon black, superconducting carbon black, conductive graphite, acetylene black, Ketjen black, graphene, and carbon nanotubes. This application has no special restrictions on the conventional components that form the positive electrode plate composition, and can be configured according to the conventional requirements in the field, so it has strong adaptability.
  • the aqueous adhesive is selected from one or more of soluble polysaccharides and their derivatives, and water-soluble or water-dispersible polymers.
  • the water-based adhesive is selected from the group consisting of methylcellulose and its salts, xanthan gum and its salts, chitosan and its salts, alginic acid and its salts; and polyethylene Imines and their salts, polyacrylamide, acrylic acid copolymers and their derivatives.
  • the water-based adhesive is a compound of xanthan gum and acrylic acid copolymer, and the weight ratio of the compound is 2:1-0.2:2.8; optionally, the weight average molecular weight of xanthan gum is 300000-2000000g /mol, and the weight average molecular weight of the acrylic copolymer is 100000-1000000g/mol.
  • thermoelastic adhesives such as butadiene-styrene copolymer (SBR) silicone rubber can effectively solve the problem of pole piece brittleness, the bonding force between the pole piece current collector and the pole piece membrane layer is insufficient. , the pole pieces are prone to powder loss, or even large-area defilming, which leads to an increase in the polarization internal resistance of the battery, affecting the cell rate and cycle performance, and in severe cases, even affecting the safety performance of the cell.
  • SBR butadiene-styrene copolymer
  • the electrode piece has high flexibility performance, especially for thick-coated, high-pressure dense electrode pieces. Sexual maintenance.
  • the cohesion and adhesive force of the pole pieces can be balanced.
  • water-based binder is used as the binder and deionized water is used as the solvent, mixed and stirred to form a slurry.
  • the slurry is uniform and the conductive agent and the binder have good dispersion effects.
  • the pole piece produced 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 and peel off during the winding process, which meets the high-speed winding requirements of the pole piece, and the assembled battery is stable.
  • the positive electrode plate film layer does not fall off and has a stable structure, which can effectively suppress the polarization of the electrode plate and reduce the internal resistance of the battery, thus improving the capacity retention rate of the battery;
  • the pole piece is highly flexible and can withstand the increased stress caused by the expansion of the positive pole piece during battery charging and discharging. The pole piece will not break, ensuring the safety and reliability of the battery during application.
  • the aqueous adhesive includes a water dispersion solution and its emulsion with a solid component content of ⁇ 5%, or a solid that can form a stable dispersion with water with a solid component content of ⁇ 1%.
  • the dispersant is selected from the group consisting of polyamide dispersants, poly(meth)acrylate dispersants, polycarboxylate dispersants, sulfonate dispersants, and silicate dispersants. , phosphate dispersants, polyethylene imine dispersants, amino-containing polymers and their amine salt dispersants.
  • 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 particles in the positive electrode conductive slurry through physical or chemical effects to avoid collision and agglomeration between particles and reduce the viscosity of the slurry. As a result, the amount of solvent used can be reduced while improving the dispersion effect of the cathode active material.
  • the content of the dispersant in the water-based positive electrode sheet composition can be adjusted within a wide range, for example, it can be 0.5-10% by weight, optionally 1-3% by weight, based on the water-based positive electrode sheet composition. Total weight.
  • the present application also relates to a method for preparing an aqueous positive electrode sheet composition selected from the first aspect of the present application, including the following steps:
  • step 3 the addition amount of the saturated aqueous solution relative to the mixture can be adjusted so that the solid content of the formed slurry is in the range of 30-65% by weight, optionally 45-55% by weight.
  • a second aspect of the present application provides a positive electrode sheet 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 additionally adds a water-soluble lithium-containing compound.
  • the cathode plate can be made by conventional methods, for example, by evenly coating the aqueous cathode plate composition on the cathode current collector, and then drying and cooling Press and cut to obtain the positive electrode piece.
  • the positive electrode current collector please refer to the detailed description of the positive electrode plate below.
  • a third aspect of the present application provides a secondary battery including a positive electrode plate selected from the second aspect of the present application.
  • a fourth aspect of the present application provides a battery pack including the secondary battery selected from the third aspect of the present application.
  • a fifth aspect of the present application provides an electrical device, which includes a secondary battery selected from the third aspect of the present application or a battery pack of the fourth aspect of the present application.
  • each component of the secondary battery of the present application can be selected from a wide range.
  • the secondary battery is specifically a lithium ion secondary battery.
  • the battery cells of the lithium ion secondary battery will be described in detail below.
  • a lithium-ion secondary battery typically includes a positive electrode plate, a negative electrode plate, a separator and an electrolyte.
  • active ions are embedded and detached back and forth between the positive electrode piece and the negative electrode piece.
  • the isolation film is arranged between the positive electrode piece and the negative electrode piece to play the role of isolation.
  • the electrolyte plays a role in conducting ions between the positive and negative electrodes.
  • the electrolyte plays a role in conducting ions between the positive and negative electrodes.
  • the electrolyte includes electrolyte salts and solvents.
  • the electrolyte salt can be a commonly used electrolyte salt in lithium ion secondary batteries, such as lithium salt, including the above-mentioned lithium salt as a high thermal stability salt, a lithium salt as a low resistance additive, or lithium that inhibits aluminum foil corrosion. Salt.
  • the electrolyte salt may be selected from lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium bisfluorosulfonyl imide (LiFSI), bistrifluoromethanesulfonyl Lithium imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluoromethanesulfonate borate (LiDFOB), lithium difluorophosphate (LiPO 2 F 2 ), lithium difluorodioxalate phosphate (LiDFOP), fluorosulfonic acid Lithium (LiSO 3 F), difluorodioxalate (NDFOP), Li 2 F(SO 2 N) 2 SO 2 F, KFSI, CsFSI, Ba(FSI) 2 and LiFSO 2 NSO 2 CH 2 CH 2 CH 2 CH 2
  • the solvent is a non-aqueous solvent.
  • the solvent may include one or more of chain carbonate, cyclic carbonate, and carboxylic acid ester.
  • 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), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate Ester (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB) , one of ethyl
  • additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain properties of the battery, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, and battery low-temperature performance. additives, etc.
  • the additive is selected from the group consisting of unsaturated bond-containing cyclic carbonate compounds, halogen-substituted cyclic carbonate compounds, sulfate compounds, sulfite compounds, sultone compounds, disulfonic acid compounds, nitrile compounds, aromatic compounds At least one of a 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.
  • 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.
  • the positive electrode current collector has two surfaces facing each other in its own thickness direction, and the positive electrode active material layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the positive electrode current collector can be a metal foil or a composite current collector.
  • the metal foil aluminum foil can be used.
  • 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 layer.
  • the composite current collector can be formed by forming metal materials (such as aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on polymer material substrates (such as polypropylene (PP), polyterephthalene). Formed on substrates such as ethylene formate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • the positive active material layer disposed on the surface of the positive current collector includes a positive active material.
  • the positive active material used in the present application may have any conventional positive active material used in secondary batteries.
  • the cathode active material may include one or more selected from the group consisting of lithium transition metal oxides, lithium-containing phosphates with an olivine structure, and their respective modified compounds.
  • lithium transition metal oxides may include, but are not limited to, 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 One or more of lithium nickel cobalt aluminum oxide and its modified compounds.
  • lithium-containing phosphates with an olivine structure may include, but are not limited to, lithium iron phosphate, composites of lithium iron phosphate and carbon, lithium manganese phosphate, composites of lithium manganese phosphate and carbon, lithium iron manganese phosphate, lithium iron manganese phosphate
  • the positive active material may be coated with carbon on its surface.
  • the positive active material layer optionally includes a conductive agent.
  • a conductive agent used for the cathode material may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the positive active material layer also includes a water-based binder.
  • the water-based adhesive may be selected from one or more types of soluble polysaccharides and their derivatives and water-soluble or water-dispersible polymers.
  • the water-based binder may be 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 water-based adhesive is a compound of xanthan gum and acrylic acid copolymer, and the weight ratio of the compound is 2:1-0.2:2.8; optionally, the weight average molecular weight of xanthan gum is 300000-2000000g /mol, and the weight average molecular weight of the acrylic copolymer is 100000-1000000g/mol.
  • the positive electrode piece can be prepared according to methods known in the art.
  • the carbon-coated cathode active material, conductive agent and aqueous binder can be dispersed in a solvent (such as water) to form a uniform cathode slurry; the cathode slurry is coated on the cathode current collector and dried After drying, cold pressing and other processes, the positive electrode piece is obtained.
  • 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, where the negative electrode material layer includes a negative electrode active material.
  • the negative electrode current collector has two surfaces opposite in its own thickness direction, and the negative electrode material layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.
  • the negative electrode current collector can be a metal foil or a composite current collector.
  • the metal foil copper foil can be used.
  • 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 can be formed by forming metal materials (such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyterephthalene). Formed on substrates such as ethylene formate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • the negative electrode material layer usually contains a negative electrode active material and an optional binder, an optional conductive agent and other optional auxiliaries, and is usually formed by coating and drying the negative electrode slurry.
  • Negative electrode slurry coating is usually formed by dispersing the negative electrode active material and optional conductive agent and binder in a solvent and stirring evenly.
  • the solvent can be N-methylpyrrolidone (NMP) or deionized water.
  • the specific type of negative electrode active material is not limited. Active materials known in the art that can be used in the negative electrode of lithium ion secondary batteries can be used, and those skilled in the art can select according to actual needs.
  • the negative active material may be selected from one or more of graphite, soft carbon, hard carbon, mesocarbon microspheres, carbon fibers, carbon nanotubes, elemental silicon, silicon oxide compounds, silicon carbon composites, and lithium titanate. kind.
  • the conductive agent may be selected from one or more types of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the binder may be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), One or more of polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • SBR styrene-butadiene rubber
  • PAA polyacrylic acid
  • PAAS sodium polyacrylate
  • PAM polyacrylamide
  • PVA polyvinyl alcohol
  • SA sodium alginate
  • PMAA polymethacrylic acid
  • CMCS carboxymethyl chitosan
  • auxiliaries are, for example, thickeners (such as sodium carboxymethyl cellulose (CMC-Na)).
  • Lithium-ion secondary batteries using an electrolyte also include a separator.
  • the isolation film is arranged between the positive electrode piece and the negative electrode piece to play the role of isolation.
  • the type of isolation membrane in this application. Any well-known porous structure isolation membrane with good chemical stability and mechanical stability can be used.
  • the material of the isolation membrane can be selected from at least one type selected from the group consisting of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation film can be a single-layer film or a multi-layer composite film, with no special restrictions. When the isolation film is a multi-layer composite film, the materials of each layer can be the same or different, and there is no particular limitation.
  • the positive electrode piece, the negative electrode piece and the separator film can be made into an electrode assembly through a winding process or a lamination process.
  • the secondary battery may include an outer packaging.
  • the outer packaging can be used to package the above-mentioned electrode assembly and electrolyte.
  • the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.
  • the outer packaging of the secondary battery may also be a soft bag, such as a bag-type soft bag.
  • the material of the soft bag may be plastic. Examples of plastics include polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).
  • FIG. 1 shows a square-structured lithium ion secondary battery 5 as an example.
  • the outer package may include a housing 51 and a cover 53 .
  • the housing 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 housing 51 has an opening communicating with the accommodation cavity, and the cover plate 53 can cover the opening to close the accommodation cavity.
  • the positive electrode piece, the negative electrode piece and the isolation film can be formed into the electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is packaged in the containing cavity.
  • the electrolyte soaks into 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.
  • lithium-ion secondary batteries can be assembled into the battery module 4.
  • the number of lithium-ion secondary batteries contained in the battery module 4 can be one or more. Those skilled in the art can determine the specific number according to the application of the battery module 4. and capacity to choose.
  • a plurality of lithium ion secondary batteries 5 may be arranged in sequence along the length direction of the battery module. Of course, it can also be arranged in any other way. Furthermore, the plurality of lithium ion secondary batteries 5 can be fixed by fasteners.
  • the battery module 4 may further include a housing having an accommodation space in which a plurality of lithium ion secondary batteries 5 are accommodated.
  • the above-mentioned lithium ion secondary batteries 5 or battery modules 4 can be assembled into a battery pack 1 .
  • the number of lithium ion secondary batteries 5 or battery modules 4 contained in the battery pack 1 can be determined by those skilled in the art according to the battery pack 1 Choose your application and capacity.
  • the battery pack 1 may include a battery box and a plurality of battery cells arranged in the battery box.
  • the battery box includes an upper box 2 and a lower box 3.
  • the upper box 2 can be covered with the lower box 3 and form a closed space for accommodating battery cells.
  • this application also provides a device, which includes the battery pack provided by this application.
  • the battery pack can be used as a power source for the device or as an energy storage unit for the device.
  • the device may be, but is not limited to, a mobile device (such as a mobile phone, a laptop, 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, or an electric golf ball). vehicles, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.
  • a battery pack can be selected according to its usage requirements.
  • Figure 5 is an example device.
  • the device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc.
  • battery packs or battery modules can be used.
  • the water-based binder is a compound mixture of xanthan gum and acrylic acid copolymer, and the compound weight ratio is 96:1:3. is 1:1.
  • the water-based 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 positive electrode with a single-sided positive electrode sheet film layer weight of 350 mg/1540.25 mm 2 Extreme piece.
  • SBR binder styrene-butadiene rubber
  • CMC thickener sodium carboxymethylcellulose
  • An 8 ⁇ m PE porous film is used as the base, and a 2 ⁇ m ceramic coating is coated on both sides as an isolation membrane.
  • Example 1 peel off the positive electrode film layer through tape, and test the porosity P1 in the area H/3 of the positive electrode film layer from the surface and the area H/3 of the positive electrode film layer from the positive electrode current collector according to GB/T 24586-2009.
  • the porosity P2 inside, parameter ⁇ P1/P2.
  • Parameter ⁇ indicates the porosity distribution in the thickness direction of the pole piece. It is usually required that ⁇ 1.2, preferably 0.7-1.0.
  • Example 1 the battery capacity test process is as follows: at 25°C, charge the battery corresponding to Example 1 with a constant current of 1/3C to 3.65V, and then charge with a constant voltage of 3.65V until the current is 0.05C; After standing for 5 minutes, discharge to 2.5V at a constant current of 1/3C to obtain the initial capacity of the secondary battery.
  • 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.
  • Examples 1-6 all secondary batteries produced using aqueous positive electrode sheet compositions containing water-soluble lithium-containing compounds exhibit high battery capacity retention rates ( ⁇ 98.0%). These cells also have better uniformity ( ⁇ value) and higher initial gram capacity.
  • Examples 3 and 4 using lithium citrate and lithium dihydrogen phosphate with a solubility greater than 100g/100ml obtained the highest battery capacity retention rate.
  • Comparative Examples 1 and 2 used water-insoluble or poorly water-soluble lithium-containing compounds under the same conditions, and the capacity retention rate of their batteries was significantly lower than that of Examples 1-6 of the present invention.
  • Comparative Example 3 without adding water-soluble lithium-containing compounds, the battery capacity retention rate was significantly reduced, indicating that the lithium ions were greatly lost after multiple cycles and were not effectively replenished, thus affecting the performance and performance of the battery. life.
  • its ⁇ value is also significantly low, showing poor uniformity of the positive electrode piece.

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Abstract

本申请涉及一种水系正极极片组合物，其中所述组合物中含有正极活性材料、导电剂、水性粘接剂和水溶性含锂化合物，以及任选地水和分散剂。本申请还涉及由所述水系正极极片组合物制备的正极极片、包含所述正极极片的二次电池、包含所述二次电池的电池包以及包含所述二次电池或所述电池包的用电装置。

Description

含有水溶性含锂化合物的水系正极极片组合物及二次电池 技术领域
本申请涉及一种水系正极极片组合物，其含有正极活性材料、导电剂、水性粘接剂和水溶性含锂化合物，以及任选地水和分散剂。本申请还涉及由所述水系正极极片组合物所制备的正极极片、包含所述正极极片的二次电池以及包含该二次电池的电池包以及用电装置。
背景技术
二次电池因其成本低、寿命长、安全性好等特点成为最受欢迎的能量存储系统，现已被广泛应用于纯电动汽车、混合电动汽车以及智能电网等领域。二次电池的正极大多采用油系配方进行浆料制作，其普遍为粘接剂聚偏二氟乙烯(PVDF)和溶剂N-甲基吡咯烷酮(NMP)组成的体系。但PVDF和NMP均为石油衍生化学产品,在浆料搅拌和涂布过程中，大量NMP毒性气体会挥发到空气中，污染环境并对人体产生危害。并且，NMP和PVDF合成及后处理过程复杂，能耗高，应用成本较高。基于此，研究人员正在尝试开发水系正极体系，一方面可避免有机溶剂NMP的使用，减少对环境及人类的危害，另一方面不涉及氟聚合物PVDF的大量使用及NMP溶剂的复杂回收，可降低电芯制作成本，实现规模化降本应用。
另外，锂离子二次电池目前存在的普遍问题是在首次充电过程中会消耗大量从正极脱出的锂离子来形成负极表面的SEI膜，首次充电中正极锂源的不可逆消耗超过10％，首周库伦效率低于90％。其次，锂离子二次电池在正常使用过程中也会持续消耗活性锂。以上会导致电池初始容量降 低及电池寿命减少。
因此，目前仍然需要提供一种制备二次电池正极极片所用的水系组合物，其可制备具有改善特性的正极极片，使得由所述正极极片构建的二次电池具有改善的环境友好性以及初始容量保持率，并且延长电池使用寿命。
发明内容
本申请是鉴于上述课题而进行的，其目的在于提供一种水系正极极片组合物，以解决由其制备的二次电池初始容量降低过大以及寿命减少的技术问题。
为了达到上述目的，本申请第一方面提供一种水系正极极片组合物，其中所述组合物中含有正极活性材料、导电剂、水性粘接剂和水溶性含锂化合物，以及任选地水和分散剂。
本申请的水系正极极片组合物通过包含水溶性含锂化合物，可补偿电芯首次充放电容量和首次充放电效率的损失，抑制正极活性材料颗粒在溶剂水中的锂离子析出。另外，所述水溶性含锂化合物可在现有技术中的水系正极极片组合物中直接加入，对配方中的各类材料均无选择性，配方适配性强，可操作空间大。所述水溶性含锂化合物的除锂离子外的阴离子在充电过程中会失去电子，并最终分解形成对电池无害的气体，如N 2、CO 2和CO等。这些气体可在封装前或从后续的安全出气口排除，对极片中的主材含量占比无任何影响。
在任意实施方式中，所述水溶性含锂化合物为锂的有机酸盐。在任意实施方案中，所述水溶性含锂化合物选自氧化锂、氢氧化锂、叠氮化锂、氯化锂、硫酸锂、硝酸锂、水杨酸锂、柠檬酸锂、草酸锂、羟基乙酸锂、苹果酸锂、酒石酸锂、乳酸锂、丙二酸锂、琥珀酸锂、甲酸锂、乙酸锂中 的一种或多种。通过对所述含锂化合物的具体种类进行选择，可进一步改善电池容量保持率。
在任意实施方式中，所述水溶性含锂化合物的氧化峰值介于3.5-4.4V。在任意实施方式中，所述水溶性含锂化合物在25℃下在水中的溶解度≥600mg/ml，可选地≥1000mg/ml。选择溶解度较大的含锂化合物，可以更加快速地补充锂源的损失。
在任意实施方式中，所述水溶性含锂化合物在所述组合物中的含量为1-20重量％，可选地为3-10重量％，基于所述水系正极极片组合物的总重量计。
在任意实施方式中，所述水系正极极片组合物的固含量为30-65重量％，可选地为45-55重量％。在任意实施方式中，所述水系正极极片组合物中包含的正极活性材料、导电剂和水性粘接剂的重量比为90-98：0.5-2：1-8，可选地为95-97：0.8-1.2：2-4。
在任意实施方式中，所述正极活性材料选自磷酸铁锂、磷酸锰锂、磷酸钴锂、磷酸铁锰锂、锂钴氧化物、锂镍氧化物、锂锰氧化物、锂镍锰氧化物、锂镍钴锰氧化物、锂镍钴铝氧化物中的一种或多种。在任意实施方式中，所述导电剂包含导电炭黑、超导炭黑、导电石墨、乙炔黑、科琴黑、石墨烯、碳纳米管中的一种或多种。
在任意实施方式中，所述水性粘接剂选自可溶性多糖类及其衍生物以及水溶性或水分散性聚合物中的一种或多种。所述水性粘接剂选自甲基纤维素及其盐类、黄原胶及其盐类、壳聚糖及其盐类、海藻酸及其盐类；以及聚乙烯亚胺及其盐类、聚丙烯酰胺、丙烯酸共聚物及其衍生物。所述水性粘接剂为黄原胶和丙烯酸共聚物的复配物，复配重量比例为2:1-0.2:2.8；可选地，黄原胶的重均分子量为300000-2000000g/mol，并且丙烯酸共聚物的重均分子量为100000-1000000g/mol。
在任意实施方式中，所述水性粘接剂包含固体组分含量为≥5％的水分散溶液及其乳液，或者包含可与水形成固体组分含量为≥1％的稳定分散液的固体。
在任意实施方式中，所述分散剂选自聚酰胺类分散剂、聚(甲基)丙烯酸酯类分散剂、聚羧酸盐类分散剂、磺酸盐类分散剂、硅酸盐类分散剂、磷酸盐类分散剂、聚乙烯亚胺分散剂、含氨基聚合物及其胺盐类分散剂。
在任意实施方式中，所述组合物以水性浆料的形式存在，或者以所述浆料经过干燥的产物而存在。
本申请还涉及一种制备选自本申请的第一方面的水系正极极片组合物的方法，包括以下步骤：
1)将水溶性含锂化合物与去离子水混合，配置成所述水溶性含锂化合物的饱和水溶液；
2)将正极活性材料、导电剂、水性粘接剂和任选地分散剂混合得到混合物；
3)将步骤1)中得到的所述饱和水溶液与步骤2)中得到的所述混合物均匀混合形成浆料；以及
4)任选地对所述浆料进行干燥。
本申请的第二方面提供一种正极极片，其通过使用选自本申请的第一方面的水系正极极片组合物而制备。
本申请的第三方面提供一种二次电池，其包括选自本申请的第二方面的正极极片。
本申请的第四方面提供一种电池包，其包括选自本申请的第三方面的二次电池。
本申请的第五方面提供一种用电装置，其包括选自本申请的第三方面的二次电池或者本申请的第四方面的电池包。
附图说明
为了更清楚地说明本申请的技术方案，下面将对本申请实施例中所需要使用的附图作简单的介绍。显而易见地，下面所描述的附图仅仅是本申请的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据附图获得其他的附图。
图1是本申请一个实施方式中的锂离子二次电池的示意图。
图2是图1所示的本申请一个实施方式中的锂离子二次电池的分解图。
图3是本申请一个实施方式中的电池包的示意图。
图4是图3所示的本申请一个实施方式中的电池包的分解图。
图5是本申请一个实施方式中的电池包用作电源的装置的示意图。
附图标记说明
1电池包
2上箱体
3下箱体
4电池模块
5锂离子二次电池
51壳体
52电极组件
53盖板
具体实施方式
为了简明，本申请具体地公开了一些数值范围。然而，任意下限可以与任意上限组合形成未明确记载的范围；以及任意下限可以与其它下限组 合形成未明确记载的范围，同样任意上限可以与任意其它上限组合形成未明确记载的范围。此外，每个单独公开的点或单个数值自身可以作为下限或上限与任意其它点或单个数值组合或与其它下限或上限组合形成未明确记载的范围。
目前的二次电池中，由于具有成本低廉且环境友好的特点，采用水作为溶剂的水系正极极片浆料来制备正极极片越来越受到关注。在使用水系正极极片浆料的情况下，发现正极活性材料颗粒表面在溶剂水存在下容易析出锂离子和过渡金属离子，导致电芯首次充放电容量和首次充放电效率损失加剧，能量密度和循环性能下降。其次，锂离子电池在正常使用过程中也会持续消耗活性锂。以上会导致电芯初始容量降低及电池寿命减少。
研究表明，首次放电容量和首次放电效率决定了后续循环的基础，并且多数材料的结构是否稳定也是由首次循环的放电容量和放电效率决定，进而影响全电池的设计和材料评价。尤其是，若正极浆料的溶剂采用去离子水，由于活性物质遇水会产生锂离子与氢离子的置换，会进一步产生容量损失。这大大限制了水系正极的应用发展。
针对锂离子电池负极SEI膜消耗活性锂导致电池初始容量降低及寿命减少的现象，目前的解决方案是通过补锂技术，补充循环过程中锂损耗。当下补锂技术主要有两种方式，一种是负极补锂，一种是正极补锂，其中负极补锂目前的方法主要有三类：1)物理混合，比如超薄锂箔压嵌与稳定化金属锂粉；2)电化学预锂化，比如利用电势差将添加电解液的硅碳负极与金属锂施压接触并形成锂化硅碳；3)化学预锂化，如惰性气氛球磨合成的SnLi x与LiF修饰等。极片端负极补锂，涉及到可燃可爆的金属锂使用，安全风险较高，材料端化学补锂工艺复杂，且材料碱性较强，材料加工困难，另外材料端补锂，对负极结构破坏，影响循环寿命，总体而言， 负极端补锂，存在较大的安全风险和复杂困难的加工工艺问题。
相比负极补锂，正极补锂工艺简单，通过正极搅浆过程加入锂源，完全可避免负极端补锂存在的安全风险和成本增加风险。正极补锂工艺是在正极匀浆的过程中，向其中添加少量的高容量补锂添加剂，在充电的过程中，多余的Li元素从这些高容量正极材料脱出，嵌入到负极中补充首次充放电的不可逆容量。其中正极补锂最主要是采用富锂材料，如富锂xLiMO 2·(1-x)Li 2MnO 3，其可以看作是Li 2MnO 3和LiMO 2(M代表过渡金属)的固溶体，具体如Li 2Mn 2O 4、Li 2NiO 2、Li 6CoO 4与Li 2CuO 2等，这些补锂材料对环境要求较高，需要干燥环境，遇水会发生强烈反应而不稳定，其限制了在水系正极中的应用。
因此，本领域需要提供一种水系正极极片组合物，其可用于制备具有改善的性能的正极极片，使得二次电池具有改善的首次放电容量和首次放电效率，并且还可以抑制锂离子在后续使用过程中的析出。
具体的，本申请第一方面提供一种水系正极极片组合物，其中所述组合物中含有正极活性材料、导电剂、水性粘接剂和水溶性含锂化合物，以及任选地水和分散剂。
本发明人发现，在用于制备正极极片的水系导电组合物中加入水溶性含锂化合物，可以有效解决现有技术出现的上述问题。所述水溶性含锂化合物的加入，一方面抑制正极活性材料颗粒在溶剂水中的锂离子析出，另一方面，可溶性锂盐中的锂离子可直接补偿电芯首次充放电过程中的锂损失。另外，对于所加入的水溶性含锂化合物，其除锂离子外的阴离子在充电过程中会失去电子，并最终分解形成对电池无害的气体，如N 2、CO 2和CO等。这些气体可在封装前或从后续的安全出气口排出，对极片中的主材含量占比无任何影响。在本申请中，水溶性含锂化合物指的是所述含锂化合物可实质性地溶解于去离子水中形成游离Li +，例如，其在去离子水 中的溶解度≥20mg/ml，可选地≥30mg/ml，进一步可选地≥50mg/ml。在一些实施方式中，所述水溶性含锂化合物在25℃在去离子水中的溶解度为至少20mg/ml，可选地为至少30mg/ml，进一步可选地为至少50mg/ml。本申请的水系正极极片组合物可包含水作为溶剂，也可含有少量的其他溶剂，例如常用的有机溶剂。在一个实施方案中，所述有机溶剂的含量低于5重量％，可选地低于1重量％，基于水系正极极片组合物的总重量计。在一个实施方案中，仅使用水作为水系正极极片组合物的溶剂。所述水溶性含锂化合物可首先与去离子水配制成饱和水溶液，再与其他组分混合均匀，从而得到本申请的水系正极极片组合物。在一个实施方案中，在得到的水系正极极片组合物中，所述水溶性含锂化合物在溶剂水中处于饱和状态。当电池在初次充放电循环后大量损耗锂，或者在后续使用中析出锂时，所述水溶性含锂化合物中的Li +可嵌入正极极片中，从而补充损耗的锂源。在本申请中，所述水系正极极片组合物可以以水性浆料的形式存在，或者以所述浆料经过干燥的产物而存在。所述干燥可通过，例如烘箱进行烘干，或者通过喷雾干燥而进行。
在一些实施方式中，所述水溶性含锂化合物为锂的有机酸盐。所述有机酸可以为本领域中常用的有机酸，例如甲酸、乙酸、琥珀酸、水杨酸、柠檬酸、丙二酸等。所述水溶性含锂化合物也可以是常见的无机酸的锂盐，所述无机酸可为例如硫酸、硝酸、盐酸以及磷酸等。所述水溶性含锂化合物还可为锂的氧化物、氢氧化物、叠氮化物以及卤化物。在一些实施方案中，所述水溶性含锂化合物选自氧化锂、氢氧化锂、叠氮化锂、氯化锂、硫酸锂、硝酸锂、水杨酸锂、柠檬酸锂、草酸锂、羟基乙酸锂、苹果酸锂、酒石酸锂、乳酸锂、丙二酸锂、琥珀酸锂、甲酸锂、乙酸锂中的一种或多种。通过对所述含锂化合物的具体种类进行选择，可进一步改善电池容量保持率。
在一些实施方式中，所述水溶性含锂化合物的氧化峰值介于3.5-4.4V。氧化峰通过循环伏安法测得，其通过在一定的电位下反转扫描电位，同时观察氧化电流和还原电流的方法，可以得到氧化电流峰和还原电流峰，通过电流及所对应的点位可以对体系的多种性质进行表征。本文中氧化峰的测定是将水溶性锂盐溶于水中后加入粘接剂和导电碳涂布于铝箔集流体上制成正极极片，然后将其与锂片和隔膜组装成扣式电池，随后利用化学工作站进行循环伏安测试得到。
在一些实施方式中，所述水溶性含锂化合物在25℃下在水中的溶解度≥600mg/ml，可选地≥1000mg/ml。溶解度的增大，使得单位质量的溶剂中可存储更多的锂离子，有助于提高所述导电组合物补充锂离子的能力。在一定的温度和压力下，物质在一定量的给定溶剂中溶解的最大量称为溶解度。固体或液体物质的溶解度，一般用100g溶剂中能够溶解物质的克数表示。测试方法有常用色谱法、分光光度法、化学滴定法等。在本申请中，通过标准GB-T 21845-2008化学品水溶解度试验来测定所述水溶性含锂化合物在25℃下在水中的溶解度。
在一些实施方式中，所述水溶性含锂化合物在所述组合物中的含量为1-20重量％，可选地为3-10重量％，基于所述水系正极极片组合物的总重量计。在一些实施方式中，所述水系正极极片组合物的固含量为30-65重量％，可选地为45-55重量％。在一些实施方式中，所述水系正极极片组合物中包含的正极活性材料、导电剂和水性粘接剂的重量比为90-98：0.5-2：1-8，可选地为95-97：0.8-1.2：2-4。可通过将所述水溶性含锂化合物过量加入去离子水中，形成所述水溶性含锂化合物的饱和水溶液。将所述饱和水溶液添加到由正极活性材料、导电剂和水性粘接剂以及任选地分散剂混合形成的混合物中，并调节所述饱和水溶液的添加量，从而得到预定的所述水系正极极片组合物的固含量。
在一些实施方式中，所述正极活性材料选自磷酸铁锂、磷酸锰锂、磷酸钴锂、磷酸铁锰锂、锂钴氧化物、锂镍氧化物、锂锰氧化物、锂镍锰氧化物、锂镍钴锰氧化物、锂镍钴铝氧化物中的一种或多种。在一些实施方式中，所述导电剂包含导电炭黑、超导炭黑、导电石墨、乙炔黑、科琴黑、石墨烯、碳纳米管中的一种或多种。本申请对于形成正极极片组合物的常规组分没有特殊限制，可以根据本领域的常规要求进行配置，因此具有很强的适配性。
在一些实施方式中，所述水性粘接剂选自可溶性多糖类及其衍生物以及水溶性或水分散性聚合物中的一种或多种。在进一步的实施方式中，所述水性粘接剂选自甲基纤维素及其盐类、黄原胶及其盐类、壳聚糖及其盐类、海藻酸及其盐类；以及聚乙烯亚胺及其盐类、聚丙烯酰胺、丙烯酸共聚物及其衍生物。
特别地，所述水性粘接剂为黄原胶和丙烯酸共聚物的复配物，复配重量比例为2:1-0.2:2.8；可选地，黄原胶的重均分子量为300000-2000000g/mol，并且丙烯酸共聚物的重均分子量为100000-1000000g/mol。
在正极极片组成中，粘接剂的选择对于极片的力学性能具有实质性的影响。常规采用的丁二烯-苯乙烯共聚物(SBR)有机硅橡胶等热弹性粘接剂，虽能有效解决极片脆性问题，但极片集流体与极片膜层之间的粘接力不足，极片易产生掉粉，甚至大面积脱膜，导致电池极化内阻增加，影响电芯倍率和循环性能，严重时甚至会影响电芯安全性能。在本申请的一些实施方案中，通过对正极极片组合物的组成中粘接剂类型和配比进行优化，使得极片具有高柔韧性性能，尤其是对于厚涂布、高压密极片柔韧性的保持。在保证组合物高稳定性的前提下，可使极片内聚力和粘接力达到平衡。本发明以水性粘结剂作为粘结剂、去离子水作为溶剂混合搅拌成浆 料，浆料均匀，导电剂、粘结剂分散效果良好。涂布制得的极片，表面外观光滑，无颗粒突起，与集流体铝箔的粘合牢靠。正极材料在卷绕过程中不易掉粉、脱膜，满足极片的高速卷绕需求，组装的电池稳定。
进一步的，一方面，电池充放电应用过程中正极极片膜层不掉粉脱膜，结构稳定，可有效抑制极片极化，减低电池内阻，从而改善电池的容量保持率；另一方面，极片柔韧性强，可承受电池充放电过程因正极极片膨胀而带来的应力增加，极片不会产生断裂，保障电池应用时的安全可靠性。
在一些实施方式中，所述水性粘接剂包含固体组分含量为≥5％的水分散溶液及其乳液，或者包含可与水形成固体组分含量为≥1％的稳定分散液的固体。
在一些实施方式中，所述分散剂选自聚酰胺类分散剂、聚(甲基)丙烯酸酯类分散剂、聚羧酸盐类分散剂、磺酸盐类分散剂、硅酸盐类分散剂、磷酸盐类分散剂、聚乙烯亚胺分散剂、含氨基聚合物及其胺盐类分散剂。例如，所述分散剂可为聚丙烯酸丁酯、甲氧基聚乙二醇甲基丙烯酸酯、聚丙烯酸钠、苯乙烯磺酸钠等。所述分散剂可通过物理或者化学作用吸附于正极极片导电浆料中的颗粒表面，避免颗粒间的碰撞团聚，降低浆料的黏度。由此，可以减少溶剂的使用量，同时改善正极活性材料的分散效果。所述分散剂在水系正极极片组合物中的含量可在宽范围内调节，例如可为0.5-10重量％，可选地为1-3重量％，基于所述水系正极极片组合物的总重量计。
本申请还涉及一种制备选自本申请的第一方面的水系正极极片组合物的方法，包括以下步骤：
1)将水溶性含锂化合物与去离子水混合，配置成所述水溶性含锂化合物的饱和水溶液；
2)将正极活性材料、导电剂、水性粘接剂和任选地分散剂混合得到混合物；
3)将步骤1)中得到的所述饱和水溶液与步骤2)中得到的所述混合物均匀混合形成浆料；以及
4)任选地对所述浆料进行干燥。
在步骤3)中，可调节所述饱和水溶液相对于所述混合物的加入量，使得形成的浆料的固含量在30-65重量％范围内，可选地为45-55重量％。
本申请的第二方面提供一种正极极片，其通过使用选自本申请的第一方面的水系正极极片组合物而制备。本申请的正极极片的主要特征在于形成其的组合物采用水作为溶剂，并且额外加入了水溶性含锂化合物。在所述特定的水系正极极片组合物的基础上，可通过常规方法制作正极极片，例如通过将所述水系正极极片组合物均匀涂覆于正极集流体上，之后经过烘干、冷压、分切，得到正极极片。正极集流体的选择可参见下文对于正极极片的具体描述。
本申请的第三方面提供一种二次电池，其包括选自本申请的第二方面的正极极片。
本申请的第四方面提供一种电池包，其包括选自本申请的第三方面的二次电池。
本申请的第五方面提供一种用电装置，其包括选自本申请的第三方面的二次电池或者本申请的第四方面的电池包。
本申请的二次电池的各组件的材料可在宽范围内进行选择。在一些实施方案中，所述二次电池特别地为锂离子二次电池。下文对所述锂离子二次电池的电池单体进行详细阐述。
通常情况下，锂离子二次电池包括正极极片、负极极片、隔离膜及电解质。在电池充放电过程中，活性离子在正极极片和负极极片之间往返嵌 入和脱出。隔离膜设置在正极极片和负极极片之间，起到隔离的作用。电解质在正极极片和负极极片之间起到传导离子的作用。
[电解液]
电解液在正极极片和负极极片之间起到传导离子的作用。电解液包括电解质盐和溶剂。
在本申请中，电解质盐可为锂离子二次电池中的常用电解质盐，例如锂盐，包括可为上述作为高热稳定性盐的锂盐、作为低阻抗添加剂的锂盐或抑制铝箔腐蚀的锂盐。作为实例，电解质盐可选自六氟磷酸锂(LiPF 6)、四氟硼酸锂(LiBF 4)、六氟砷酸锂(LiAsF 6)、双氟磺酰亚胺锂(LiFSI)、双三氟甲磺酰亚胺锂(LiTFSI)、三氟甲磺酸锂(LiTFS)、二氟草酸硼酸锂(LiDFOB)、二氟磷酸锂(LiPO 2F 2)、二氟二草酸磷酸锂(LiDFOP)、氟磺酸锂(LiSO 3F)、二氟二草酸盐(NDFOP)、Li 2F(SO 2N) 2SO 2F、KFSI、CsFSI、Ba(FSI) 2及LiFSO 2NSO 2CH 2CH 2CF 3中的一种以上。
溶剂的种类没有特别的限制，可根据实际需求进行选择。在一些实施方式中，溶剂为非水性溶剂。可选地，溶剂可包括链状碳酸酯、环状碳酸酯、羧酸酯中的一种或几种。在一些实施方式中，溶剂可选自碳酸亚乙酯(EC)、碳酸亚丙酯(PC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)、碳酸二甲酯(DMC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、碳酸亚丁酯(BC)、氟代碳酸亚乙酯(FEC)、甲酸甲酯(MF)、乙酸甲酯(MA)、乙酸乙酯(EA)、乙酸丙酯(PA)、丙酸甲酯(MP)、丙酸乙酯(EP)、丙酸丙酯(PP)、丁酸甲酯(MB)、丁酸乙酯(EB)、1,4-丁内酯(GBL)、四氢呋喃、环丁砜(SF)、二甲砜(MSM)、甲乙砜(EMS)及二乙砜(ESE)中的一种以上。
在一些实施方式中，电解液中还可选地包括其他添加剂。例如添加剂可以包括负极成膜添加剂，也可以包括正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温性能的添加剂、以及改善电池低温性能的添加剂等。作为示例，添加剂选自含有不饱和键的环状碳酸酯化合物、卤素取代的环状碳酸酯化合物、硫酸酯化合物、亚硫酸酯化合物、磺酸内酯化合物、二磺酸化合物、腈化合物、芳香化合物、异氰酸酯化合物、磷腈化合物、环状酸酐化合物、亚磷酸酯化合物、磷酸酯化合物、硼酸酯化合物、羧酸酯化合物中的至少一种。
[正极极片]
正极极片包括正极集流体以及设置在正极集流体至少一个表面的正极活性物质层，正极活性物质层包括正极活性材料和导电剂。
作为示例，正极集流体具有在其自身厚度方向相对的两个表面，正极活性物质层设置在正极集流体相对的两个表面的其中任意一者或两者上。
本申请的锂离子二次电池中，正极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可采用铝箔。复合集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层。复合集流体可通过将金属材料(例如铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
设置于正极集流体的表面上的正极活性物质层包括正极活性材料。本申请中所用的正极活性材料可具有二次电池中使用的任意常规正极活性材料。在一些实施方式中，正极活性材料可包含选自锂过渡金属氧化物、橄榄石结构的含锂磷酸盐及其各自的改性化合物中的一种或几种。锂过渡金 属氧化物的示例可包括但不限于锂钴氧化物、锂镍氧化物、锂锰氧化物、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、锂镍钴锰氧化物、锂镍钴铝氧化物及其改性化合物中的一种或几种。橄榄石结构的含锂磷酸盐的示例可包括但不限于磷酸铁锂、磷酸铁锂与碳的复合材料、磷酸锰锂、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料及其改性化合物中的一种或几种。这些材料均可以通过商业途径获得。正极活性材料表面上可包覆有碳。
正极活性物质层可选地包括导电剂。但对导电剂的种类不做具体限制，本领域技术人员可以根据实际需求进行选择。作为示例，用于正极材料的导电剂可以选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的一种以上。
正极活性物质层还包括水性粘结剂。水性粘接剂可选自可溶性多糖类及其衍生物以及水溶性或水分散性聚合物中的一种或多种。作为示例，水性粘结剂可以为甲基纤维素及其盐类、黄原胶及其盐类、壳聚糖及其盐类、海藻酸及其盐类；以及聚乙烯亚胺及其盐类、聚丙烯酰胺、丙烯酸共聚物及其衍生物。特别地，所述水性粘接剂为黄原胶和丙烯酸共聚物的复配物，复配重量比例为2:1-0.2:2.8；可选地，黄原胶的重均分子量为300000-2000000g/mol，并且丙烯酸共聚物的重均分子量为100000-1000000g/mol。
本申请中可按照本领域已知的方法制备正极极片。作为示例，可以将包覆碳的正极活性材料、导电剂和水性粘结剂分散于溶剂(例如水)中，形成均匀的正极浆料；将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，得到正极极片。
[负极极片]
负极极片包括负极集流体以及设置在负极集流体至少一个表面上的负极材料层，所述负极材料层包括负极活性物质。
作为示例，负极集流体具有在其自身厚度方向相对的两个表面，负极材料层设置在负极集流体相对的两个表面中的任意一者或两者上。
本申请的锂离子二次电池中，负极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铜箔。复合集流体可包括高分子材料基层和形成于高分子材料基材至少一个表面上的金属层。复合集流体可通过将金属材料(例如铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
本申请的锂离子二次电池中，负极材料层通常包含负极活性物质以及可选的粘结剂、可选的导电剂和其他可选助剂，通常是由负极浆料涂布干燥而成的。负极浆料涂通常是将负极活性物质以及可选的导电剂和粘结剂等分散于溶剂中并搅拌均匀而形成的。溶剂可以是N-甲基吡咯烷酮(NMP)或去离子水。
负极活性物质的具体种类不做限制，可以采用本领域已知的能够用于锂离子二次电池负极的活性物质，本领域技术人员可以根据实际需求进行选择。作为示例，负极活性物质可选自石墨、软碳、硬碳、中间相碳微球、碳纤维、碳纳米管、单质硅、硅氧化合物、硅碳复合物、钛酸锂中的一种或几种。
作为示例，导电剂可选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的一种以上。
作为示例，粘结剂可选自丁苯橡胶(SBR)、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸 钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的一种以上。
其他可选助剂例如是增稠剂(如羧甲基纤维素钠(CMC-Na))等。
[隔离膜]
采用电解液的锂离子二次电池中还包括隔离膜。隔离膜设置在正极极片和负极极片之间，起到隔离的作用。本申请对隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。在一些实施方式中，隔离膜的材质可选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的一种以上。隔离膜可以是单层薄膜，也可以是多层复合薄膜，没有特别限制。在隔离膜为多层复合薄膜时，各层的材料可以相同或不同，没有特别限制。
在一些实施方式中，正极极片、负极极片和隔离膜可通过卷绕工艺或叠片工艺制成电极组件。
在一些实施方式中，所述二次电池可包括外包装。该外包装可用于封装上述电极组件及电解质。
在一些实施方式中，所述二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。所述二次电池的外包装也可以是软包，例如袋式软包。软包的材质可以是塑料，作为塑料，可列举出聚丙烯(PP)、聚对苯二甲酸丁二醇酯(PBT)以及聚丁二酸丁二醇酯(PBS)等。
本申请对所述二次电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。例如，图1是作为一个示例的方形结构的锂离子二次电池5。
在一些实施方式中，参照图2，外包装可包括壳体51和盖板53。其中，壳体51可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体51具有与容纳腔连通的开口，盖板53能够盖设于所述开口， 以封闭所述容纳腔。正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件52。电极组件52封装于所述容纳腔内。电解液浸润于电极组件52中。锂离子二次电池5所含电极组件52的数量可以为一个或多个，本领域技术人员可根据具体实际需求进行选择。
在一些实施方式中，锂离子二次电池可以组装成电池模块4，电池模块4所含锂离子二次电池的数量可以为一个或多个，具体数量本领域技术人员可根据电池模块4的应用和容量进行选择。在电池模块4中，多个锂离子二次电池5可以是沿电池模块的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个锂离子二次电池5进行固定。可选地，电池模块4还可以包括具有容纳空间的外壳，多个锂离子二次电池5容纳于该容纳空间。
在一些实施方式中，上述锂离子二次电池5或者电池模块4可以组装成电池包1，电池包1所含锂离子二次电池5或者电池模块4的数量可由本领域技术人员根据电池包1的应用和容量进行选择。
图3和图4是作为一个示例的电池包1。参照图3和图4，在电池包1中可以包括电池箱和设置于电池箱中的多个电池单体。电池箱包括上箱体2和下箱体3，上箱体2能够盖设于下箱体3，并形成用于容纳电池单体的封闭空间。
另外，本申请还提供一种装置，所述装置包括本申请提供的电池包。所述电池包可以用作所述装置的电源，也可以用作所述装置的能量存储单元。所述装置可以但不限于是移动设备(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能系统等。作为所述装置，可以根据其使用需求来选择电池包。
图5是作为一个示例的装置。该装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该装置对锂离子二次电池的高功率和高能量密度的需求，可以采用电池包或电池模块。
实施例
以下，说明本申请的实施例。下面描述的实施例是示例性的，仅用于解释本申请，而不能理解为对本申请的限制。实施例中未注明具体技术或条件的，按照本领域内的文献所描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商者，均为可以通过市购获得的常规产品。如果无特殊标明，所有含量比例均为重量比，并且所有实验均在常温(25℃)和常压下进行。
实施例1
(1)正极极片的制备
将乙酸锂和去离子水混合并搅拌，配置成乙酸锂的饱和水溶液。乙酸锂在25℃下在去离子水中的溶解度为29g/100ml。
将正极活性材料磷酸铁锂、导电剂导电碳黑以及水性粘结剂按重量比为96:1:3混合，其中水性粘接剂采用黄原胶和丙烯酸共聚物复配混合物，复配重量比例为1:1。将上文所得乙酸锂的饱和水溶液加入正极活性材料的混合物中，充分搅拌混合均匀形成浆料。通过调节乙酸锂的饱和水溶液的加入量，使得所得浆料的固含量为50重量％。
最后将水系正极极片组合物(浆料)均匀涂覆于正极集流体铝箔上，之后经过烘干、冷压、分切，得到单侧正极极片膜层重量为350mg/1540.25mm 2的正极极片。
(2)负极极片的制备
将活性物质人造石墨、导电剂碳黑、粘结剂丁苯橡胶(SBR)、增稠剂羟甲基纤维素钠(CMC)按照重量比为96.2：0.8：0.8：1.2溶于溶剂去离子水中，混合均匀后制备成负极浆料；将负极浆料一次或多次均匀涂覆在负极集流体铜箔上，经过烘干、冷压、分切得到负极极片。
(3)电解液的制备
在氩气气氛手套箱中(H 2O<0.1ppm，O 2<0.1ppm)，将有机溶剂碳酸乙烯酯(EC)/碳酸甲乙酯(EMC)按照体积比3/7混合均匀，加入12.5％LiPF 6锂盐溶解于有机溶剂中，搅拌均匀，得到电解液。
(4)隔离膜
以8μm PE多孔薄膜为基底，双面涂布2μm后的陶瓷涂层后作为隔离膜。
(5)锂离子电池的制备
将如上所述制备的正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正、负极片之间起到隔离的作用，然后卷绕得到裸电芯，给裸电芯焊接极耳，并将裸电芯装入铝壳中，并在80℃下烘烤除水，随即注入电解液并封口，得到不带电的电池。不带电的电池再依次经过静置、热冷压、化成、整形、容量测试等工序，获得实施例1的锂离子二次电池产品。
实施例2-6
除配方中形成饱和水溶性含锂化合物的材料种类差异外，其他步骤与实施例1相同。
对比例1
除选择磷酸锂替代乙酸锂外，其他步骤与实施例1相同。
对比例2
除选择碳酸锂替代乙酸锂外，其他步骤与实施例1相同。
对比例3
除溶剂直接采用去离子水(即，不包含所述水溶性含锂化合物)外，其他步骤与实施例1相同。
极片层级性能测试
1、正极极片的孔隙率测试
以实施例1为例，通过胶带剥离正极膜层，参照GB/T 24586-2009测试正极膜层中距离表面H/3区域内的孔隙率P1和正极膜层中距离正极集流体H/3区域内的孔隙率P2，参数α＝P1/P2。参数α表明极片厚度方向上的孔隙率分布。通常要求α≤1.2，优选0.7-1.0。
电池性能测试
1、电池正极活性材料的初始克容量测试
以实施例1为例，电池容量测试过程如下：在25℃下，将实施例1对应的电池，以1/3C恒流充电至3.65V，再以3.65V恒定电压充电至电流为0.05C；静置5min后以1/3C恒流放电至2.5V，得到二次电池的初始容量。
正极活性材料的初始克容量(mAh/g)＝二次电池的初始容量/正极活性材料的质量。
2、电池容量保持率测试
以实施例1为例，电池容量保持率测试过程如下：在25℃下，将实施 例1对应的电池，以1/3C恒流充电至3.65V，再以3.65V恒定电压充电至电流为0.05C，搁置5min，再以1/3C放电至2.7V，所得容量记为初始容量C0。对上述同一个电池重复以上步骤，并同时记录循环第n次后电池的放电容量Cn，则每次循环后电池容量保持率Pn＝Cn/C0*100％。该测试过程中，第一次循环对应n＝1、第二次循环对应n＝2、……第100次循环对应n＝100。表1中实施例1对应的电池容量保持率数据是在上述测试条件下循环800次之后测得的数据，即P800的值。
对比例1-3和实施例2-6的锂离子电池产品同样按照上述步骤测试，测试结果总结于下表1中。
表1：对比例1-3和实施例1-6的二次电池的性能测试结果
Figure PCTCN2022100374-appb-000001
由实施例1-6可以看出，采用加入了水溶性含锂化合物的水系正极极片组合物所制作的二次电池全部展示出很高的电池容量保持率(≥98.0％)。这些电池同时也具有较好的均匀性(ɑ值)以及较高的初始克容量。特别地，使用溶解度大于100g/100ml的柠檬酸锂和磷酸二氢锂的实施例3和4得到了最高的电池容量保持率。
相比之下，对比例1和2在其他条件相同而使用不溶于水或难溶于水的含锂化合物，其电池的容量保持率明显低于本发明实施例1-6的容量保持率。另外，对比例3在未添加水溶性含锂化合物的情况下，其电池容量保持率明显降低，表明其锂离子在多次循环后损耗较大，未得到有效补充，因此影响了电池的性能和寿命。另外，其ɑ值也明显偏低，显示出正极极片均匀性不佳。
虽然已经参考实施例对本申请进行了描述，但在不脱离本申请的范围的情况下，可以对其进行各种改进并且可以用等效物替换其中的部件。尤其是，只要不存在结构冲突，各个实施例中所提到的各项技术特征均可以任意方式组合起来。本申请并不局限于文中公开的特定实施例，而是包括落入权利要求的范围内的所有技术方案。

Claims (21)

  1. 一种水系正极极片组合物，其中所述组合物中含有正极活性材料、导电剂、水性粘接剂和水溶性含锂化合物，以及任选地水和分散剂。
  2. 根据权利要求1所述的水系正极极片组合物，其中所述水溶性含锂化合物为锂的有机酸盐。
  3. 根据权利要求1所述的水系正极极片组合物，其中所述水溶性含锂化合物选自氧化锂、氢氧化锂、叠氮化锂、氯化锂、硫酸锂、硝酸锂、水杨酸锂、柠檬酸锂、草酸锂、羟基乙酸锂、苹果酸锂、酒石酸锂、乳酸锂、丙二酸锂、琥珀酸锂、甲酸锂、乙酸锂中的一种或多种。
  4. 根据权利要求1至3中任一项所述的水系正极极片组合物，其中所述水溶性含锂化合物的氧化峰值介于3.5-4.4V。
  5. 根据权利要求1至4中任一项所述的水系正极极片组合物，其中所述水溶性含锂化合物在25℃下在水中的溶解度≥600mg/ml，可选地≥1000mg/ml。
  6. 根据权利要求1至5中任一项所述的水系正极极片组合物，其中所述水溶性含锂化合物在所述组合物中的含量为1-20重量％，可选地为3-10重量％，基于所述水系正极极片组合物的总重量计。
  7. 根据权利要求1至6中任一项所述的水系正极极片组合物，其中所述组合物的固含量为30-65重量％，可选地为45-55重量％。
  8. 根据权利要求1至7中任一项所述的水系正极极片组合物，其中所述组合物中包含的正极活性材料、导电剂和水性粘接剂的重量比为90-98：0.5-2：1-8，可选地为95-97：0.8-1.2：2-4。
  9. 根据权利要求1至8中任一项所述的水系正极极片组合物，其中所述正极活性材料选自磷酸铁锂、磷酸锰锂、磷酸钴锂、磷酸铁锰锂、锂钴 氧化物、锂镍氧化物、锂锰氧化物、锂镍锰氧化物、锂镍钴锰氧化物、锂镍钴铝氧化物中的一种或多种。
  10. 根据权利要求1至9中任一项所述的水系正极极片组合物，其中所述导电剂包含导电炭黑、超导炭黑、导电石墨、乙炔黑、科琴黑、石墨烯、碳纳米管中的一种或多种。
  11. 根据权利要求1至10中任一项所述的水系正极极片组合物，其中所述水性粘接剂选自可溶性多糖类及其衍生物以及水溶性或水分散性聚合物中的一种或多种。
  12. 根据权利要求11所述的水系正极极片组合物，其中所述水性粘接剂选自甲基纤维素及其盐类、黄原胶及其盐类、壳聚糖及其盐类、海藻酸及其盐类；以及聚乙烯亚胺及其盐类、聚丙烯酰胺、丙烯酸共聚物及其衍生物。
  13. 根据权利要求12所述的水系正极极片组合物，其中所述水性粘接剂为黄原胶和丙烯酸共聚物的复配物，复配重量比例为2:1-0.2:2.8；可选地，黄原胶的重均分子量为300000-2000000g/mol，并且丙烯酸共聚物的重均分子量为100000-1000000g/mol。
  14. 根据权利要求11所述的水系正极极片组合物，其中所述水性粘接剂包含固体组分含量为≥5％的水分散溶液及其乳液，或者包含可与水形成固体组分含量为≥1％的稳定分散液的固体。
  15. 根据权利要求1至14中任一项所述的水系正极极片组合物，其中所述分散剂选自聚酰胺类分散剂、聚(甲基)丙烯酸酯类分散剂、聚羧酸盐类分散剂、磺酸盐类分散剂、硅酸盐类分散剂、磷酸盐类分散剂、聚乙烯亚胺分散剂、含氨基聚合物及其胺盐类分散剂。
  16. 根据权利要求1至15中任一项所述的水系正极极片组合物，其中所述组合物以水性浆料的形式存在，或者以所述浆料经过干燥的产物而存 在。
  17. 一种制备根据权利要求1至16中任一项所述的水系正极极片组合物的方法，包括以下步骤：
    1)将水溶性含锂化合物与去离子水混合，配置成所述水溶性含锂化合物的饱和水溶液；
    2)将正极活性材料、导电剂、水性粘接剂和任选地分散剂混合得到混合物；
    3)将步骤1)中得到的所述饱和水溶液与步骤2)中得到的所述混合物均匀混合形成浆料；以及
    4)任选地对所述浆料进行干燥。
  18. 一种正极极片，其通过使用根据权利要求1至16中任一项所述的水系正极极片组合物而制备。
  19. 一种二次电池，其包含根据权利要求18所述的正极极片。
  20. 一种电池包，其包含根据权利要求19所述的二次电池。
  21. 一种用电装置，其包含根据权利要求19所述的二次电池或者根据权利要求20所述的电池包。
PCT/CN2022/100374 2022-06-22 2022-06-22 含有水溶性含锂化合物的水系正极极片组合物及二次电池 WO2023245484A1 (zh)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2020119855A (ja) * 2019-01-28 2020-08-06 三菱ケミカル株式会社 非水系電解液電池
CN112673493A (zh) * 2020-03-20 2021-04-16 广东省皓智科技有限公司 二次电池的阴极的制备方法
CN112703621A (zh) * 2020-03-20 2021-04-23 广东省皓智科技有限公司 二次电池的阴极及阴极浆料
CN114243023A (zh) * 2022-02-25 2022-03-25 宁德时代新能源科技股份有限公司 正极浆料、制备正极极片的方法及正极极片、二次电池、电池模块、电池包和用电装置
CN114424365A (zh) * 2020-03-20 2022-04-29 广东省皓智科技有限公司 用于二次电池的阴极及阴极浆料

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2020119855A (ja) * 2019-01-28 2020-08-06 三菱ケミカル株式会社 非水系電解液電池
CN112673493A (zh) * 2020-03-20 2021-04-16 广东省皓智科技有限公司 二次电池的阴极的制备方法
CN112703621A (zh) * 2020-03-20 2021-04-23 广东省皓智科技有限公司 二次电池的阴极及阴极浆料
WO2021184790A1 (en) * 2020-03-20 2021-09-23 Guangdong Haozhi Technology Co. Limited Cathode and cathode slurry for secondary battery
CN114424365A (zh) * 2020-03-20 2022-04-29 广东省皓智科技有限公司 用于二次电池的阴极及阴极浆料
CN114243023A (zh) * 2022-02-25 2022-03-25 宁德时代新能源科技股份有限公司 正极浆料、制备正极极片的方法及正极极片、二次电池、电池模块、电池包和用电装置

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