Application of lithium triacetate as a coating additive for cathode materials and its application in cathode materials

Abstract

This invention discloses the application of lithium triacetate as a coating additive for cathode materials and its application in cathode materials. In this invention, lithium triacetate is used as a coating additive for cathode materials. On the one hand, triacetate ions can complex with metal ions on the surface of the cathode material, which is beneficial to the formation of the subsequent lithium-ion conductive layer. At the same time, it can also improve the stability of the coating layer and inhibit the peeling off of the coating layer. On the other hand, the use of lithium salt can prevent the direct use of triacetate from corroding the cathode material and damaging the material structure. It can also act as a lithium supplement agent to provide lithium ions to the cathode material, while avoiding the introduction of other metal ions and eliminating the adverse effects of other metal ions on the performance of the cathode material.

Description

Technical Field

[0001] This invention relates to the field of lithium battery cathode material technology, and more specifically, to the application of lithium triacetate as a coating additive for cathode materials and its application in cathode materials. Background Technology

[0002] Developing next-generation batteries with lower costs, longer cycle life, and better performance is crucial for deploying lithium-ion batteries in electric vehicles and power grid systems. Cathode materials, as a major component of lithium-ion batteries, play a key role in the overall performance of the battery. Recently, high-nickel ternary layered oxides and high-voltage ternary layered oxides have become research hotspots in the battery industry to further improve the energy density of current lithium-ion batteries. However, the increasing nickel content and application voltage in current layered cathodes bring a series of challenges. High nickel content and high application voltage make issues such as the chemical-mechanical stability, thermal stability, structural stability, and interfacial stability of the materials more prominent, thus posing a severe challenge to the commercial deployment of these materials.

[0003] Coating can alter the inherent surface and interfacial properties of materials, and is an effective means to improve the interfacial stability and electrochemical performance of ternary cathode materials. However, the type of coating agent and the coating method have a significant impact on the electrical performance of coated and modified ternary cathode materials. Therefore, selecting appropriate coating agents and coating methods is crucial. Summary of the Invention

[0004] The purpose of this invention is to provide the application of lithium triacetate as a coating additive for cathode materials and its application in cathode materials to improve the cycle performance of cathode materials.

[0005] This invention is implemented as follows:

[0006] In a first aspect, the present invention provides an application of lithium triacetate as a coating additive for a positive electrode material, wherein the molecular formula of lithium triacetate is C6H. 9-x NO6Li x , where x = 1, 2 or 3.

[0007] Secondly, the present invention provides a method for preparing the coating additive for the cathode material described in the foregoing embodiments, comprising:

[0008] Lithium hydroxide and aminotriacetic acid are reacted in a solution system to obtain the coating additive for the cathode material;

[0009] Preferably, the molar ratio of lithium hydroxide to aminotriacetic acid is 1-3;

[0010] Preferably, the reaction time is 10 min-120 min, and the solution pH is 6-8;

[0011] Preferably, after the reaction is completed, the product is dried for the first time at a temperature of 80℃-150℃ for 12h-48h.

[0012] Thirdly, the present invention provides a positive electrode material, comprising a matrix and a coating layer covering the matrix, wherein the matrix is ​​a ternary material, the coating layer comprises lithium ions and aminotriacetic acid ions, and the mass fraction of aminotriacetic acid ions in the positive electrode material is 0.1%-1.5%.

[0013] Fourthly, the present invention provides a method for preparing the cathode material described in the foregoing embodiments, comprising:

[0014] The matrix particles are mixed with a washing solution containing lithium triacetate and washed with water, followed by solid-liquid separation and a second drying to obtain the cathode material.

[0015] In some embodiments, the matrix has the chemical formula LiNi. a Co b Mn c O2, where a+b+c=1, where 0.8≤a<1, 0<b≤0.2, 0<c≤0.2.

[0016] In some embodiments, the concentration of lithium triacetate in the washing solution is 5 g / L-100 g / L;

[0017] And / or, the mass ratio of the matrix to the washing liquid is 0.4-2, preferably 0.5-1.

[0018] In some embodiments, the washing step takes 0.5 min to 3 min;

[0019] And / or, the water washing step is accompanied by stirring, with a stirring speed of 80 rpm to 300 rpm;

[0020] And / or, the pressure of the second drying step is 10. 2 Pa ~10 5 Pa;

[0021] And / or, the temperature of the second drying step is 90℃-150℃, and the time is 5h-24h.

[0022] Fifthly, the present invention provides a positive electrode sheet, comprising a positive electrode material as described in the foregoing embodiments or a positive electrode material prepared by the preparation method described in any of the foregoing embodiments.

[0023] In a sixth aspect, the present invention provides a lithium-ion battery, including a positive electrode as described in the foregoing embodiments.

[0024] In a seventh aspect, the present invention provides an electrical device comprising a lithium-ion battery as described in the foregoing embodiments.

[0025] The present invention has the following beneficial effects:

[0026] In this invention, lithium triacetate is used as a coating additive for the cathode material. On the one hand, triacetate ions can complex with metal ions on the surface of the cathode material, which is beneficial to the formation of the subsequent lithium-ion conductive layer. At the same time, it can also improve the stability of the coating layer and inhibit the peeling off of the coating layer. On the other hand, the use of lithium salt can prevent the direct use of triacetate from corroding the cathode material and damaging the material structure. It can also act as a lithium supplement agent to provide lithium ions to the cathode material, while avoiding the introduction of other metal ions and eliminating the adverse effects of other metal ions on the performance of the cathode material. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 SEM image of the cathode material prepared in Example 1;

[0029] Figure 2 The graph shows a comparison of the cycle performance of cathode materials prepared in some embodiments and comparative examples. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0031] This invention provides an application of lithium aminotriacetate as a coating additive for positive electrode materials, wherein the molecular formula of lithium aminotriacetate is C6H. 9-x NO6Li x , where x = 1, 2 or 3.

[0032] In this invention, lithium triacetate is used as a coating additive for the cathode material. On the one hand, triacetate ions can complex with metal ions on the surface of the cathode material, which is beneficial to the formation of the subsequent lithium-ion conductive layer. At the same time, it can also improve the stability of the coating layer and inhibit the peeling off of the coating layer. On the other hand, the use of lithium salt can prevent the direct use of triacetate from corroding the cathode material and damaging the material structure. It can also act as a lithium supplement agent to provide lithium ions to the cathode material, while avoiding the introduction of other metal ions and eliminating the adverse effects of other metal ions on the performance of the cathode material.

[0033] This invention provides a method for preparing the coating additive for the cathode material described in the foregoing embodiments, comprising:

[0034] Lithium hydroxide and aminotriacetic acid are reacted in a solution system to obtain the coating additive for the cathode material.

[0035] The specific chemical reaction equation is as follows:

[0036] N(CH2COOH)3+ x LiOH → N(CH2COO)3H 3-x Li x + x H2O, where x = 1, 2, 3

[0037] The present invention provides a method for preparing lithium triacetate, which is simple, easy to operate, has mild reaction conditions, and is relatively environmentally friendly.

[0038] In some embodiments, the molar ratio of lithium hydroxide to nitric acid triacetic acid is 1-3. By adjusting the amount of raw materials, one or more of lithium monotriacetic acid, lithium ditriacetic acid, and lithium tritriacetic acid can be obtained. Among them, as the lithium molar ratio increases, the first-cycle capacity, first-cycle efficiency, and cycle performance of the material first increase and then decrease. Therefore, the lithium molar ratio should not be too high.

[0039] In some embodiments, the reaction time is 10 min-120 min, specifically any value between 10 min, 20 min, 40 min, 60 min, 80 min, 100 min, 120 min, or 10 min-120 min, and the solution pH is 6-8, specifically any value between 6, 7, 8, or 6-8; this reaction is an acid-base neutralization reaction, with a relatively fast reaction rate and few side reactions.

[0040] In some embodiments, after the reaction is completed, the product is subjected to a first drying process at a temperature of 80°C-150°C, specifically any value between 80°C, 100°C, 120°C, 140°C, 150°C, or 80°C-150°C, for a time of 12h-48h, specifically any value between 12h, 24h, 36h, 48h, or 12h-48h. The solvent is removed by drying to obtain solid lithium nitrilotriacetate for easy storage.

[0041] This invention provides a cathode material, comprising a substrate and a coating layer covering the substrate. The substrate is a ternary material, and the coating layer comprises lithium ions and nitric acid triacetate ions. The mass fraction of nitric acid triacetate ions in the cathode material is 0.1%-1.5%, specifically, it can be any value between 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 1%, 1.5%, or 0.1%-1.5%.

[0042] If the content of lithium triacetate in the cathode material is too low, it will not be able to form an effective physical barrier on the substrate surface, and the effect on improving cycle stability will be limited; however, if the content of lithium triacetate is too high, it will reduce the capacity of the material. Therefore, the content of lithium triacetate needs to be within a reasonable range.

[0043] It should be noted that in the cathode material, some of the nitric acid ions in the coating layer will complex with the metal on the surface of the cathode material to form nitric acid metal complex salts. Therefore, the content of the coating additive is calculated based on the nitric acid ions here.

[0044] This invention provides a method for preparing the cathode material described in the foregoing embodiments, comprising:

[0045] The matrix particles are mixed with a washing solution containing lithium triacetate and washed with water, followed by solid-liquid separation and a second drying to obtain the cathode material.

[0046] In this invention, lithium triacetate is coated onto the surface of substrate particles using a water-washing coating method. The water wash solution contains triacetate ions, which form a lithium-ion conductive layer during subsequent drying, achieving the desired coating effect. This results in a stable, non-detachable coating layer that acts as a physical barrier, suppressing side reactions of the cathode material in the electrolyte and thus improving the material's cycle performance. Additionally, the water wash solution contains Li... + And H + The low concentration inhibits the formation of Li during the matrix washing process. + / H + The exchange process inhibits the dissolution of lithium ions, which helps maintain the stability of the matrix material.

[0047] It should be noted that in this invention, the washing solution containing lithium triacetate can be obtained by dissolving lithium triacetate, or by reacting lithium hydroxide with lithium triacetate in water to obtain a reaction solution. As long as the lithium concentration and the concentration of triacetate are equal, the two methods have little impact on the cathode material.

[0048] In some embodiments, the matrix has the chemical formula LiNi. a Co b Mn c O2, where a+b+c=1, where 0.8≤a<1, 0<b≤0.2, 0<c≤0.2.

[0049] In this embodiment, the matrix particles are high-nickel ternary materials. The residual alkali on the surface of the high-nickel ternary materials can be removed during the water washing process, exposing more lithium active sites, which is more conducive to improving the discharge capacity of the material.

[0050] In some embodiments, the concentration of lithium triacetate in the washing solution is 5 g / L-100 g / L, specifically any value between 5 g / L, 10 g / L, 15 g / L, 20 g / L, 30 g / L, 40 g / L, 50 g / L, 60 g / L, 70 g / L, 80 g / L, 90 g / L, 100 g / L, or 5 g / L-100 g / L. Increasing the concentration of lithium triacetate leads to an increase in the content of triacetate ions in the cathode material. A reasonable lithium triacetate concentration is beneficial for balancing the capacity and cycle performance of the cathode material.

[0051] In some embodiments, the mass ratio of the substrate to the washing liquid is 0.4-2, specifically any value between 0.4, 0.6, 0.8, 1.0, 1.5, 2 or 0.4-2, preferably 0.5-1. Increasing the amount of washing liquid is beneficial to the dissolution of lithium in the substrate, which in turn leads to a decrease in electrical performance. Therefore, the amount of washing liquid should not be too high.

[0052] In some embodiments, the washing step takes 0.5 min to 3 min, specifically any value between 0.5 min, 1 min, 1.5 min, 2 min, 2.5 min, 3 min, or 0.5 min to 3 min. Increasing the washing time facilitates the dissolution of lithium in the matrix, which in turn leads to a decrease in electrical performance. Therefore, the washing time should not be too long.

[0053] In some embodiments, the washing step is accompanied by stirring at a speed of 80 rpm to 300 rpm, specifically 80 rpm, 100 rpm, 150 rpm, 200 rpm, 250 rpm, 300 rpm, or any value between 80 rpm and 300 rpm. Stirring facilitates full contact between the matrix particles and the washing solution, and promotes uniform coating of the matrix particles. However, the stirring speed needs to be appropriate. If the speed is too low, it will not be conducive to the uniform dispersion of the matrix particles in the washing solution. If the speed is too high, the matrix particles will collide with each other, which will not only hinder the uniform coating of the matrix particles, but may also cause cracks in the matrix particles, affecting the strength of the cathode material and thus the cycle performance of the cathode material.

[0054] In some embodiments, the pressure of the second drying step is 10. 2 Pa ~10 4 Pa, specifically, can be 10 2 Pa, 10 3 Pa, 10 4 Pa or 10 2 Pa ~10 4 Any value between Pa; experimental results show that the pressure during the drying of the positive electrode material will affect the initial efficiency and cycle performance.

[0055] In some embodiments, the temperature of the second drying step is 90℃-150℃, specifically any value between 90℃, 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, or 110℃-150℃, and the time is 5h-24h, specifically any value between 5h, 8h, 12h, 16h, 20h, 24h, or 8h-24h. The purpose of the second drying is to remove moisture from the cathode material, therefore the temperature does not need to be too high.

[0056] The present invention provides a positive electrode sheet, comprising the positive electrode material as described in the foregoing embodiments or the positive electrode material prepared by the preparation method described in any one of the foregoing embodiments.

[0057] In the positive electrode sheet of this application, the positive electrode film layer typically comprises the aforementioned positive electrode material, as well as optionally a binder and optionally a conductive agent, and is usually formed by coating a positive electrode slurry and then drying and cold pressing it. The positive electrode slurry is typically formed by dispersing the aforementioned positive electrode material, optionally a conductive agent, and optionally a binder in a solvent and stirring them evenly. The solvent may be N-methylpyrrolidone (NMP).

[0058] In some alternative embodiments, the positive electrode film may contain 70% to 97% by weight of positive electrode material, based on the total weight of the positive electrode film. Optionally, the weight percentage of the positive electrode material in the positive electrode film is 85% to 97%, 90% to 97%, or 95% to 97%. By adjusting the proportion of positive electrode material in the positive electrode film, the energy density and cycle life of the lithium-ion battery can be further improved.

[0059] In some embodiments, the binder for the positive electrode film may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and modified polymers thereof.

[0060] Conductive agents can improve the electronic conductivity of the positive electrode film. In some optional embodiments, the positive electrode film may contain 2% to 20% by weight of conductive agent, based on the total weight of the positive electrode film. Optionally, the conductive agent may account for 2% to 10% or 2% to 5% by weight of the positive electrode film.

[0061] In some embodiments, the conductive agent of the positive electrode film may include one or more of superconducting carbon, carbon black (such as SuperP, acetylene black, Ketjen black), carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0062] It should be noted that the composition or parameters of each positive electrode film layer given in this application refer to the composition or parameter range of the single-sided film layer of the positive electrode current collector. When the positive electrode film layer is disposed on two opposite surfaces of the positive electrode current collector, if the composition or parameters of the positive electrode film layer on either surface meet the requirements of this application, it is considered to fall within the protection scope of this application.

[0063] The present invention provides a lithium-ion battery, including a positive electrode as described in the foregoing embodiments, and further including a negative electrode, an electrolyte and a separator.

[0064] [Negative electrode plate]

[0065] The negative electrode sheet of this application includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector.

[0066] As an example, the negative electrode current collector has two surfaces opposite each other in its thickness direction, and the negative electrode film layer is laminated on either or both of the two opposite surfaces of the negative electrode current collector.

[0067] The negative electrode current collector can be made of a material with good conductivity and mechanical strength, serving both as a conductor and a current collector. In some embodiments, the negative electrode current collector can be made of copper foil.

[0068] In the negative electrode sheet of this application, the negative electrode film layer typically includes negative and positive electrode materials, as well as optional binders, optional conductive agents, and other optional additives. It is usually formed by coating a negative electrode slurry onto a negative electrode current collector, followed by drying and cold pressing. The negative electrode slurry coating is typically formed by dispersing the negative and positive electrode materials, as well as optional conductive agents, optional binders, and optional additives, in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP) or deionized water.

[0069] In some embodiments, the negative and positive electrode materials may include one or more of artificial graphite, natural graphite, silicon-based materials, and tin-based materials. Optionally, the negative and positive electrode materials may include one or more of artificial graphite and natural graphite. Optionally, the negative and positive electrode materials may include artificial graphite.

[0070] In some embodiments, the conductive agent may include one or more of superconducting carbon, carbon black (e.g., SuperP, acetylene black, Ketjen black, etc.), carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0071] In some embodiments, the adhesive may include one or more of styrene-butadiene rubber (SBR), waterborne acrylic resin, polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0072] In some embodiments, other optional additives include thickeners (e.g., sodium carboxymethyl cellulose CMC-Na), PTC thermistor materials, etc.

[0073] [Electrolytes]

[0074] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific limitations on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be selected from electrolyte solutions. The electrolyte solution includes an electrolyte salt and a solvent.

[0075] In some embodiments, the electrolyte salt may be selected from one or more of LiPF6 (lithium hexafluorophosphate), LiBF4 (lithium tetrafluoroborate), LiClO4 (lithium perchlorate), LiAsF6 (lithium hexafluoroarsenate), LiFSI (lithium bis(fluorosulfonyl)imide), LiTFSI (lithium bis(trifluoromethanesulfonyl)imide), LiTFS (lithium trifluoromethanesulfonate), LiDFOB (lithium difluorooxalate borate), LiBOB (lithium dioxalate borate), LiPO2F2 (lithium difluorophosphate), LiDFOP (lithium difluorodioxalate phosphate), and LiTFOP (lithium tetrafluorooxalate phosphate).

[0076] In some embodiments, the solvent may be selected from one or more of ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0077] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, additives that improve battery low-temperature performance, etc.

[0078] [Isolation membrane]

[0079] The separator is disposed between the positive and negative electrode plates, serving as a barrier. The lithium-ion battery of this application does not have particular limitations on the type of separator; any known porous separator used in lithium-ion batteries can be selected. For example, the separator can be selected from glass fiber film, non-woven fabric film, polyethylene film, polypropylene film, polyvinylidene fluoride film, and one or more multilayer composite films comprising one or more of these materials.

[0080] Positive electrode, negative electrode, and separator can be stacked or wound to form an electrode assembly, with the separator positioned between the positive and negative electrode to provide isolation. The electrode assembly is then placed in an outer package, filled with electrolyte, and sealed to obtain a lithium-ion battery.

[0081] The outer packaging of a lithium-ion battery is used to encapsulate the electrode assembly and electrolyte. In some embodiments, the outer packaging of a lithium-ion battery can be a rigid shell, such as a hard plastic shell, aluminum shell, steel shell, etc. The outer packaging of a lithium-ion battery can also be a pouch, such as a pouch. The material of the pouch can be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), etc.

[0082] This application does not impose any particular restrictions on the shape of the lithium-ion battery; it can be cylindrical, square, or any other arbitrary shape.

[0083] In some embodiments, lithium-ion batteries can be assembled into battery modules, and the number of lithium-ion batteries contained in a battery module can be multiple, the specific number of which can be adjusted according to the application and capacity of the battery module.

[0084] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0085] The present invention provides an electrical device including a lithium-ion battery as described in the foregoing embodiments.

[0086] This application also provides an apparatus comprising at least one of the lithium-ion battery, battery module, or battery pack described in this application. The lithium-ion battery, battery module, or battery pack can be used as a power source for the apparatus or as an energy storage unit. The apparatus can be, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc. The apparatus can select the lithium-ion battery, battery module, or battery pack according to its usage requirements.

[0087] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0088] Example 1:

[0089] This embodiment provides a method for preparing a positive electrode material, including the following steps:

[0090] 1) Dissolve 12.6g of lithium hydroxide monohydrate in 100mL of deionized water, add 19.2g of nitric acid triacetic acid while stirring, continue stirring and react for 1h, heat in an oil bath at 120℃ to evaporate the water, grind and pass through a 200-mesh sieve to obtain trilithium nitric acid triacetic acid.

[0091] 2) Dissolve 20g of the above-mentioned trilithium triamine triacetate in 1L of deionized water, and add 2kg of high-nickel ternary cathode material LiNi. 0.96 Co 0.03 Mn 0.01 Stirring at 100 rpm for 0.5 min under O2, centrifugation to collect the solid, and vacuum drying at 100℃ and 0.01 MPa for 6 h yielded trilithium triamine triacetate-coated modified ternary cathode material. SEM images are shown below. Figure 1 As shown in the figure, some particles have come off the material surface. This is because the primary particles of the high-nickel ternary material are too small, resulting in poor adhesion to the secondary particles.

[0092] Example 2:

[0093] This embodiment provides a method for preparing a positive electrode material, which differs from Example 1 only in that the molar ratio of lithium hydroxide to nitric acid is 2:1. The method specifically includes the following steps:

[0094] 1) Dissolve 8.4g of lithium hydroxide monohydrate in 100mL of deionized water, add 19.2g of nitric acid while stirring, continue stirring and react for 1h, heat in an oil bath at 120℃ to evaporate the water, grind and pass through a 200-mesh sieve to obtain dilithium nitric acid.

[0095] 2) Dissolve 20g of the above-mentioned lithium triacetate in 1L of deionized water, and add 2kg of high-nickel ternary cathode material LiNi. 0.96 Co 0.03 Mn 0.01 Stirring at 100 rpm for 0.5 min under O2, collecting the solid by centrifugation, and drying under vacuum at 100℃ and 0.01 MPa for 6 h, yielding dilithium triacetate-coated modified ternary cathode material.

[0096] Example 3:

[0097] This embodiment provides a method for preparing a positive electrode material, which differs from Example 1 only in that the molar ratio of lithium hydroxide to nitric acid is 1:1. The method specifically includes the following steps:

[0098] 1) Dissolve 4.2g of lithium hydroxide monohydrate in 100mL of deionized water, add 19.2g of nitric acid while stirring, continue stirring and react for 1h, heat in an oil bath at 120℃ to evaporate the water, grind and pass through a 200-mesh sieve to obtain lithium nitric acid monohydrate.

[0099] 2) Dissolve 20g of the above-mentioned lithium triacetate in 1L of deionized water, and add 2kg of high-nickel ternary cathode material LiNi. 0.96 Co 0.03 Mn 0.01 Stirring at 100 rpm for 0.5 min with O2, collecting the solid by centrifugation, and drying under vacuum at 100℃ and 0.01 MPa for 6 h, yielding a lithium triacetic acid-coated modified ternary cathode material.

[0100] Example 4:

[0101] This embodiment provides a method for preparing a cathode material, which differs from Example 1 only in that the mass ratio of the washing solution to the high-nickel ternary cathode material is approximately 1:1. The method specifically includes the following steps:

[0102] 1) Dissolve 12.6g of lithium hydroxide monohydrate in 100mL of deionized water, add 19.2g of nitric acid triacetic acid while stirring, continue stirring and react for 1h, heat in an oil bath at 120℃ to evaporate the water, grind and pass through a 200-mesh sieve to obtain trilithium nitric acid triacetic acid.

[0103] 2) Dissolve 20g of the above-mentioned trilithium triamine triacetate in 1L of deionized water, and add 1kg of high-nickel ternary cathode material LiNi. 0.96 Co 0.03 Mn 0.01 Stirring at 100 rpm for 0.5 min with O2, collecting the solid by centrifugation, and drying under vacuum at 100℃ and 0.01 MPa for 6 h, yielding trilithium triamine triacetate-coated modified ternary cathode material.

[0104] Example 5:

[0105] This embodiment provides a method for preparing a positive electrode material, which differs from Embodiment 1 only in that the water washing time is extended. Specifically, it includes the following steps:

[0106] 1) Dissolve 12.6g of lithium hydroxide monohydrate in 100mL of deionized water, add 19.2g of nitric acid triacetic acid while stirring, continue stirring and react for 1h, heat in an oil bath at 120℃ to evaporate the water, grind and pass through a 200-mesh sieve to obtain trilithium nitric acid triacetic acid.

[0107] 2) Dissolve 20g of the above-mentioned trilithium triamine triacetate in 1L of deionized water, and add 2kg of high-nickel ternary cathode material LiNi. 0.96 Co 0.03 Mn 0.01 Stirring at 100 rpm for 3 min with O2, collecting the solid by centrifugation, and drying under vacuum at 100℃ and 0.01 MPa for 6 h, yielding trilithium triamine triacetate-coated modified ternary cathode material.

[0108] Example 6:

[0109] This embodiment provides a method for preparing a positive electrode material, which differs from Embodiment 1 only in that the second drying is carried out under normal pressure, and specifically includes the following steps:

[0110] 1) Dissolve 12.6g of lithium hydroxide monohydrate in 100mL of deionized water, add 19.2g of nitric acid triacetic acid while stirring, continue stirring and react for 1h, heat in an oil bath at 120℃ to evaporate the water, grind and pass through a 200-mesh sieve to obtain trilithium nitric acid triacetic acid.

[0111] 2) Dissolve 20g of the above-mentioned trilithium triamine triacetate in 1L of deionized water, and add 2kg of high-nickel ternary cathode material LiNi. 0.96 Co 0.03 Mn 0.01 Stirring at 100 rpm for 0.5 min with O2, collecting the solid by centrifugation, and drying in an oven at 120℃ and normal pressure for 12 h, yielding trilithium triamine triacetate-coated modified ternary cathode material.

[0112] Example 7:

[0113] This embodiment provides a method for preparing a cathode material, which differs from Example 1 only in that the concentration of trilithium triamine triacetate is reduced. Specifically, it includes the following steps:

[0114] 1) Dissolve 12.6g of lithium hydroxide monohydrate in 100mL of deionized water, add 19.2g of nitric acid triacetic acid while stirring, continue stirring and react for 1h, heat in an oil bath at 120℃ to evaporate the water, grind and pass through a 200-mesh sieve to obtain trilithium nitric acid triacetic acid.

[0115] 2) Dissolve 2g of the above-mentioned trilithium triamine triacetate in 1L of deionized water, and add 2kg of high-nickel ternary cathode material LiNi. 0.96 Co 0.03 Mn 0.01 Stirring at 100 rpm for 0.5 min with O2, collecting the solid by centrifugation, and drying under vacuum at 100℃ and 0.01 MPa for 6 h, yielding trilithium triamine triacetate-coated modified ternary cathode material.

[0116] Example 8:

[0117] This embodiment provides a method for preparing a cathode material, which differs from Example 1 only in that the concentration of trilithium triamine triacetate is increased. Specifically, it includes the following steps:

[0118] 1) Dissolve 12.6g of lithium hydroxide monohydrate in 100mL of deionized water, add 19.2g of nitric acid triacetic acid while stirring, continue stirring and react for 1h, heat in an oil bath at 120℃ to evaporate the water, grind and pass through a 200-mesh sieve to obtain trilithium nitric acid triacetic acid.

[0119] 2) Dissolve 50g of the above-mentioned trilithium triamine triacetate in 1L of deionized water, and add 2kg of high-nickel ternary cathode material LiNi. 0.96 Co 0.03 Mn 0.01 Stirring at 100 rpm for 0.5 min with O2, collecting the solid by centrifugation, and drying under vacuum at 100℃ and 0.01 MPa for 6 h, yielding trilithium triamine triacetate-coated modified ternary cathode material.

[0120] Example 9:

[0121] This embodiment provides a method for preparing a cathode material, which differs from Embodiment 1 only in that the vacuum drying pressure is reduced. Specifically, it includes the following steps:

[0122] 1) Dissolve 12.6g of lithium hydroxide monohydrate in 100mL of deionized water, add 19.2g of nitric acid triacetic acid while stirring, continue stirring and react for 1h, heat in an oil bath at 120℃ to evaporate the water, grind and pass through a 200-mesh sieve to obtain trilithium nitric acid triacetic acid.

[0123] 2) Dissolve 20g of the above-mentioned trilithium triamine triacetate in 1L of deionized water, and add 2kg of high-nickel ternary cathode material LiNi. 0.96 Co 0.03 Mn 0.01 Stirring at 100 rpm for 0.5 min with O2, collecting the solid by centrifugation, and drying under vacuum at 100℃ and 0.001 MPa for 6 h, yielding trilithium triamine coated modified ternary cathode material.

[0124] Example 10:

[0125] This embodiment provides a method for preparing a cathode material, which differs from Embodiment 1 only in that the vacuum drying pressure is increased. Specifically, it includes the following steps:

[0126] 1) Dissolve 12.6g of lithium hydroxide monohydrate in 100mL of deionized water, add 19.2g of nitric acid triacetic acid while stirring, continue stirring and react for 1h, heat in an oil bath at 120℃ to evaporate the water, grind and pass through a 200-mesh sieve to obtain trilithium nitric acid triacetic acid.

[0127] 2) Dissolve 20g of the above-mentioned trilithium triamine triacetate in 1L of deionized water, and add 2kg of high-nickel ternary cathode material LiNi. 0.96 Co 0.03 Mn 0.01 Stirring at 100 rpm for 0.5 min under O2, collecting the solid by centrifugation, and drying under vacuum at 100℃ and 0.1 MPa for 6 h, yielding trilithium triamine coated modified ternary cathode material.

[0128] Example 11:

[0129] This embodiment provides a method for preparing a positive electrode material, including the following steps:

[0130] 1) Dissolve 12.6g of lithium hydroxide monohydrate in 100mL of deionized water, add 19.2g of nitric acid triacetic acid while stirring, continue stirring and react for 1h, heat in an oil bath at 120℃ to evaporate the water, grind and pass through a 200-mesh sieve to obtain trilithium nitric acid triacetic acid.

[0131] 2) Dissolve 5g of the above-mentioned trilithium triamine triacetate in 1L of deionized water, and add 2kg of high-nickel ternary cathode material LiNi. 0.96 Co 0.03 Mn 0.01 Stirring at 300 rpm for 1.5 min under O2, collecting the solid by centrifugation, and drying under vacuum at 90℃ and 0.01 MPa for 24 h, yielding trilithium triamine coated modified ternary cathode material.

[0132] Example 12:

[0133] This embodiment provides a method for preparing a positive electrode material, including the following steps:

[0134] 1) Dissolve 12.6g of lithium hydroxide monohydrate in 100mL of deionized water, add 19.2g of nitric acid triacetic acid while stirring, continue stirring and react for 1h, heat in an oil bath at 120℃ to evaporate the water, grind and pass through a 200-mesh sieve to obtain trilithium nitric acid triacetic acid.

[0135] 2) Dissolve 20g of the above-mentioned trilithium triamine triacetate in 1L of deionized water, and add 2kg of high-nickel ternary cathode material LiNi. 0.96 Co 0.03 Mn 0.01 Stirring at 80 rpm for 3 min under O2, collecting the solid by centrifugation, and drying under vacuum at 150℃ and 0.01 MPa for 5 h, yielding trilithium triamine triacetate-coated modified ternary cathode material.

[0136] Comparative Example 1:

[0137] This comparative example provides a method for preparing a cathode material, including the following steps:

[0138] 2kg of high-nickel ternary cathode material LiNi 0.96 Co 0.03 Mn 0.01 O2 was added to 1L of stirred deionized water, and stirring was continued for 1 minute. Then, the water was removed by centrifugation, and the product was vacuum dried at 100℃ and 0.01Mpa for 12 hours to obtain a high-nickel ternary cathode material finished product washed with pure water.

[0139] Comparative Example 2:

[0140] This comparative example provides a method for preparing a cathode material, which differs from Example 1 only in that it includes the following steps:

[0141] Dissolve 12.6g of lithium hydroxide monohydrate in 1L of deionized water, and add 2kg of high-nickel ternary cathode material LiNi. 0.96 Co 0.03 Mn 0.01 Stirring at 100 rpm for 0.5 min with O2, collecting the solid by centrifugation, and drying under vacuum at 100℃ and 0.01 MPa for 6 h, yielding lithium hydroxide-coated modified ternary cathode material.

[0142] Comparative Example 3:

[0143] This comparative example provides a method for preparing a cathode material, which differs from Example 1 only in that it includes the following steps:

[0144] Dissolve 25.7g of trisodium triacetate in 1L of deionized water, and add 2kg of high-nickel ternary cathode material LiNi. 0.96 Co 0.03 Mn 0.01Stirring at 100 rpm for 0.5 min under O2, collecting the solid by centrifugation, and drying under vacuum at 100℃ and 0.01 MPa for 6 h, yielding trisodium triacetate-coated modified ternary cathode material.

[0145] Test case

[0146] Battery Assembly and Testing: Lithium-ion coin cells were assembled in an argon atmosphere glove box (H2O < 0.1 ppm, O2 < 0.1 ppm). The positive electrode material, conductive agent, and binder prepared in the examples and comparative examples were mixed uniformly at a ratio of 96:2:2. A nitrogen-methylpyrrolidone solvent was added and stirred to form a slurry, which was then coated. After drying at 110°C for 2 hours, the slurry was punched and dried again in a vacuum oven at 105°C for 4 hours. Coin cells were then assembled. The electrolyte was a mixture of LiPF6 dissolved in a 1:1 volume ratio of ethylene carbonate and diethyl carbonate. The separator was glass fiber, and the negative electrode was lithium metal sheet. After assembly, the cells were allowed to stand for 3 hours before the first cycle test. The test conditions were: charge / discharge capacity and first-cycle efficiency at 25°C, a test voltage range of 2.8~4.3V, and 0.1C, with 1C = 220 mAh / g. The test results are shown in Table 1.

[0147] Cyclic performance testing was conducted using an all-electric coin cell battery. The lithium metal anode was replaced with carbon material. After one cycle at 0.1C within the voltage range of 2.8~4.25V, the battery cycle stability was further tested at 1C. The test results (80 cycles) are shown in Table 1 and... Figure 2 As shown.

[0148] Electrochemical performance:

[0149] Table 1 shows the residual lithium compounds and first-cycle electrical performance of the comparative examples and embodiments. The residual lithium compounds were determined by acid-base titration, and the nitric acid triacetate was calculated based on the lithium nitric acid triacetate content in the washing solution before and after water washing. The first-cycle electrical performance data were obtained by testing using the Blue Battery Testing System.

[0150] Table 1

[0151]

[0152] Table 1 shows that the residual lithium level after water washing in the examples is significantly higher than that in the comparative examples, indicating that the addition of lithium triacetate additive during water washing can inhibit the Li-reaction reaction between high-nickel ternary materials and water. + / H + The exchange reaction, i.e., direct water washing, causes damage to the surface structure of high-nickel ternary materials, and the Li within the material lattice... + The stripping was severe. Lithium triacetate was used as a washing additive, resulting in a relatively high pH in the washing solution, which also contained a certain concentration of Li. + This reduces side reactions during the material washing process, thereby improving the material's first-cycle capacity, first-cycle efficiency, and cycle performance.

[0153] Examples 1, 2, and 3 compared the effects of prepared trilithium triamine, dilithium triamine, and monolithium triamine as washing additives on the materials. Trilithium triamine and dilithium triamine had higher residual lithium and lithium carbonate content, resulting in relatively better first-cycle electrical performance. This may be due to the relatively higher pH of their washing solution. + The higher concentration also results in a more significant inhibition of side reactions during material washing. However, lithium triacetate neutralizes the residual alkali on the material surface, leading to a lower residual alkali level and poorer electrical properties.

[0154] Examples 4, 5, and 6 compared the effects of water washing solid content, water washing time, and drying method on the material. Among them, the decrease in solid content and the extension of water washing time slightly reduced the lithium carbonate content and slightly degraded the electrical properties of the material, while the use of atmospheric pressure drying slightly increased the lithium carbonate content and relatively higher discharge capacity.

[0155] Examples 7 and 8 compared the effect of lithium triacetate coating on the material. If the coating is too low or too high, the first-cycle capacity and cycle retention will decrease.

[0156] Examples 9 and 10 compared the effects of vacuum drying pressure on the materials. Vacuum drying promotes the rapid evaporation of water solvents, which has a certain impact on the electrical properties of the materials. However, excessively high or low pressure will reduce the first-cycle capacity and cycle retention rate.

[0157] Comparative Examples 1, 2, and 3 compared the effects of water washing additives. When no additives were added during water washing, the capacity, initial efficiency, and cycle retention were all low. Adding lithium hydroxide to the water washing process suppressed the Li₂O₃ emissions from the material during washing. + / H + The exchange of side reactions protects the material structure, resulting in relatively high cycle life but a slight decrease in capacity; however, the addition of sodium nitrilotriacetate during water washing significantly reduces the material's initial capacity and electrical performance.

[0158] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a positive electrode material, characterized in that, include: The matrix particles were mixed with a washing solution containing lithium triacetate and washed with water, followed by solid-liquid separation and a second drying to obtain the cathode material; the molecular formula of the lithium triacetate is C6H. 9-x NO6Li x , where x = 1, 2 or 3; The method for preparing lithium triacetate includes: reacting lithium hydroxide and triacetate in a solution system; after the reaction is completed, the product is dried for the first time to obtain lithium triacetate. The cathode material includes a matrix and a coating layer covering the matrix. The matrix is ​​a ternary material, and the coating layer includes lithium ions and aminotriacetic acid ions. The mass fraction of aminotriacetic acid ions in the cathode material is 0.1%-1.5%.

2. The method for preparing the cathode material according to claim 1, characterized in that, The molar ratio of lithium hydroxide to triacetic acid is 1-3.

3. The method for preparing the cathode material according to claim 1, characterized in that, The reaction time is 10-120 minutes, and the solution pH is 6-8.

4. The method for preparing the cathode material according to claim 1, characterized in that, The first drying temperature is 80℃-150℃, and the time is 12h-48h.

5. The method for preparing the cathode material according to claim 1, characterized in that, The matrix has the chemical formula LiNi. a Co b Mn c O2, where a+b+c=1, where 0.8≤a<1, 0<b≤0.2, 0<c≤0.

2.

6. The method for preparing the cathode material according to claim 2, characterized in that, The concentration of lithium triacetate in the washing solution is 5 g / L-100 g / L; And / or, the mass ratio of the matrix to the washing solution is 0.4-2.

7. The method for preparing the cathode material according to claim 6, characterized in that, The mass ratio of the matrix to the washing solution is 0.5-1.

8. The method for preparing the cathode material according to claim 1, characterized in that, The washing step takes 0.5 min to 3 min; And / or, the water washing step is accompanied by stirring, with a stirring speed of 80 rpm to 300 rpm; And / or, the pressure of the second drying step is 10. 2 Pa~10 5 Pa; And / or, the temperature of the second drying step is 90℃-150℃, and the time is 5h-24h.

9. A positive electrode sheet, characterized in that, This includes cathode materials prepared by the preparation method according to any one of claims 1-8.

10. A lithium-ion battery, characterized in that, Including the positive electrode sheet as described in claim 9.

11. An electrical appliance, characterized in that, Including the lithium-ion battery as described in claim 10.

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