Composite dispersing agent for supplementing lithium to positive electrode, lithium ion battery and preparation and formation methods of lithium ion battery

Abstract

The invention discloses a composite dispersing agent for positive electrode lithium supplementation, a lithium ion battery and preparation and formation methods of the lithium ion battery, the composite dispersing agent contains an auxiliary dispersing agent, and the auxiliary dispersing agent is prepared by carrying out amino-alkylene addition reaction on amino, allyl dimethyl phosphate and lithium acrylate. The functional polymer containing the phosphate ester and the lithium complex is obtained; the lithium ion battery provided by the invention comprises a composite dispersing agent for supplementing lithium to a positive electrode, the formation method disclosed by the invention comprises the following steps: performing liquid injection and standing on the lithium ion battery for 12-96 hours, and then performing formation treatment on the lithium ion battery at a preset magnetic field intensity. The preparation method has the beneficial effects that the dispersing aid promotes uniform dispersion of positive electrode material particles, the prepared lithium ion battery is treated by a formation method of external magnetic field intensity, the discharge capacity, cycle life, charge-discharge efficiency and other electrochemical performance indexes of the battery are remarkably improved, the current density can be improved, the formation time can be remarkably shortened, and the production cost is reduced. The production efficiency is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion batteries, and particularly relates to a composite dispersant for lithium supplementation of the positive electrode, a lithium-ion battery and its preparation and formation methods, especially a composite dispersant containing phosphate ester and lithium complex, (triethoxysilylpropyl)-O-polyoxyethylene polyurethane as a co-dispersant to improve the specific capacity of the battery, a lithium-ion battery and its preparation and formation methods. Background Art

[0002] Lithium-ion batteries currently have extremely broad applications in the fields of electric vehicles and energy storage. However, with the continuous development of society, the requirements for the energy density of batteries have become higher. In the first cycle, the lithium-ion battery itself will consume the active lithium in the battery due to the formation of the solid electrolyte interface membrane (SEI) on the negative electrode, resulting in a decrease in the overall energy density of the battery.

[0003] At present, the production of lithium-ion batteries is mainly divided into two stages: the first stage is to prepare and assemble lithium-ion batteries, and the second stage is to perform formation treatment on the assembled lithium-ion batteries. In the first stage, in order to improve the overall energy density of the battery, it is usually necessary to supplement lithium to the battery. The existing lithium supplementation technologies are mainly divided into positive electrode lithium supplementation and negative electrode lithium supplementation. Due to the great safety and convenience of the positive electrode lithium supplementation technology, it has become the research focus of lithium supplementation technology. Patent 202211376564.6 provides a cyanophosphite additive as a positive electrode lithium supplement agent. Although this lithium supplement agent makes up for the loss of active lithium to a certain extent during the first charge-discharge process of the lithium battery and forms a good positive and negative electrode interface layer inside the battery, due to the surface tension of the positive electrode material, its wettability and dispersibility in the electrolyte are poor, which further causes the positive electrode material particles to be unevenly dispersed, resulting in agglomeration and sedimentation phenomena between the particles. This directly leads to the situation that during the formation process of the battery, the lithium supplement agent may not be able to completely de-lithiate. This will cause some lithium to still be trapped in the lithium supplement agent and cannot be effectively supplemented into the battery system, thereby affecting the improvement effect of the battery capacity and making the actual available capacity of the battery after the formation treatment in the second stage lower than expected. Since the de-lithiation potential of the positive electrode lithium supplement agent is inconsistent with that of the positive electrode material and the addition amount of the lithium supplement agent is small and does not support high-current de-lithiation, in order to make the lithium supplement agent fully de-lithiate, the currently commonly used method is to use a small current. For example, Patent CN116190661B provides a method for activating active lithium in a pre-lithiated positive electrode cell. The positive electrode material layer of the positive electrode plate of the pre-lithiated positive electrode cell contains a positive electrode lithium supplement agent, and the positive electrode lithium supplement agent contains active lithium; the method includes: activating the active lithium by applying a high voltage during the process of preparing the capacity of the cell, and the high voltage is 4.2 - 4.5V. Patent CN116706285A discloses a formation method, a lithium-ion battery and an application of a full cell containing a positive electrode lithium supplement agent. This application charges to the first platform voltage and the second platform voltage in sequence with a smaller current density. Although the above patents optimize the formation process of the cell after lithium supplementation, when forming, a small current must be used to complete the formation treatment of the lithium-ion battery, which greatly prolongs the formation time of the battery, resulting in a decrease in formation efficiency and further leading to low battery production efficiency, which is very unfavorable for industrial production.

[0004] Therefore, how to find a positive electrode lithium supplementation composite dispersant lithium-ion battery and its preparation and formation methods to solve the problems that the lithium supplement agent may not be able to completely de-lithiate, the lithium supplement agent needs to be completely de-lithiated under high-current conditions at its de-lithiation potential, the loss of active lithium in the first cycle is large, and the formation time is long has become one of the urgent problems to be solved by many front-line researchers and scientific research enterprises in this field. Summary of the Invention

[0005] In view of the above problems, the purpose of the present invention is to provide a composite dispersant for lithium supplementation of the positive electrode, a lithium-ion battery, and its preparation and formation methods, which can promote the uniform dispersion of positive electrode material particles in the electrolyte, compensate for the loss of active lithium in the first cycle, improve the overall performance of the battery, enable formation treatment with a large current, greatly shorten the formation time, and improve production efficiency.

[0006] To achieve the above object and other related objects, the technical solution adopted by the present invention is as follows: The present invention provides a preparation method of a composite dispersant for lithium supplementation of the positive electrode, comprising the following steps: Step 1, prepare a co-dispersant: Put 35-70 parts of N-(triethoxysilylpropyl)-O-polyoxyethylene polyurethane, 100-120 parts of dichloroethane, 15-30 parts of dimethyl allyl phosphate, 0.05-0.5 parts of lithium acrylate, and 3-6 parts of ethylenediamine weighed according to mass parts into a reaction vessel, react at 70-85 °C for 100-150 min, then cool to room temperature, and distill the obtained reaction product to obtain the co-dispersant; Step 2, weigh 90-95 parts of a high molecular polyurethane hyperdispersant and 5-10 parts of the co-dispersant according to mass parts, and mix them evenly to obtain the additive for lithium supplementation of the positive electrode.

[0007] Preferably, the model of the high molecular polyurethane hyperdispersant is one of NEO-1063, LS501A, HY-6350, and LD-1652.

[0008] The present invention provides a composite dispersant for lithium supplementation of the positive electrode prepared by the above preparation method.

[0009] The reaction mechanism of the co-dispersant prepared by the present invention is as follows: The amino groups of N-(triethoxysilylpropyl)-O-polyoxyethylene polyurethane respectively carry out amino-olefin addition reactions with dimethyl allyl phosphate and lithium acrylate to obtain a mixture containing phosphate ester and lithium complex as the co-dispersant mixture. This co-dispersant enables the material to have good hydrophilicity and lipophilicity, and can effectively form a stable interfacial layer between the aqueous phase and the oil phase, thereby promoting the uniform dispersion of positive electrode material particles.

[0010] The present invention provides a positive electrode slurry for lithium supplementation, comprising a composite dispersant for lithium supplementation of the positive electrode, or the composite dispersant for lithium supplementation of the positive electrode prepared by the above preparation method.

[0011] The present invention provides a method for preparing a lithium-supplemented cathode slurry, which is characterized by comprising the following steps: Weigh 80-98 parts by mass of a cathode active material, 0.1-10 parts of a lithium-supplement agent, 1-5 parts of a cathode binder, and 0.1-5 parts of a cathode conductive agent, add 50-60 parts of N-methylpyrrolidone and 1-5 parts of a composite dispersant at 20-60 °C, and stir and mix evenly to obtain a lithium-supplemented cathode slurry.

[0012] The present invention provides a lithium-supplemented cathode, comprising the composite dispersant for lithium-supplementing the cathode, or the composite dispersant for lithium-supplementing the cathode prepared by the preparation method.

[0013] The present invention provides a method for preparing a lithium-supplemented cathode slurry, comprising the following steps: Coating the lithium-supplemented cathode slurry on a current collector, drying, rolling, slitting, and die-cutting to prepare a lithium-supplemented cathode.

[0014] The present invention provides a lithium-ion battery, comprising the composite dispersant, or the composite dispersant for lithium-supplementing the cathode prepared by the preparation method.

[0015] The present invention further provides a method for preparing a lithium-ion battery, which is characterized by comprising the following steps: Step (1), preparing a lithium-supplemented cathode: Weigh 80-98 parts by mass of a cathode active material, 0.1-10 parts of a lithium-supplement agent, 1-5 parts of a cathode binder, and 0.1-5 parts of a conductive agent, add 50-60 parts of N-methylpyrrolidone and 1-5 parts of the composite dispersant at 20-60 °C, stir and mix evenly to obtain a lithium-supplemented cathode slurry, and then coat the lithium-supplemented cathode slurry on a current collector and prepare a lithium-supplemented cathode by rolling; Step (2), making a negative electrode sheet: Dissolve 1-10 parts of a negative electrode binder in 50-130 parts of deionized water by mass, then add 0.5-10 parts of a conductive agent and 80-97 parts of a negative electrode active material, stir at 20-45 °C to obtain a negative electrode slurry, and then screen, coat, dry, roll, slit, and die-cut the negative electrode slurry to make a negative electrode sheet; Step (3), assembling the lithium-supplemented cathode, the negative electrode sheet, a separator, an electrode liquid, and a housing to obtain a lithium-ion battery comprising the lithium-supplemented cathode.

[0016] Preferably, the cathode active material is at least one of lithium cobaltate, lithium iron phosphate, lithium manganese iron phosphate, spinel lithium manganate, ternary cathode material, and lithium-rich manganese cathode material.

[0017] Preferably, the lithium-supplement agent is at least one of lithium-rich iron ferrate, squaric acid lithium, lithium-rich nickelate, lithium carbonate, and hexalithium cobalt tetraoxide.

[0018] Preferably, the positive electrode binder is at least one of polyvinylidene fluoride, polyimide, and polytetrafluoroethylene.

[0019] Preferably, the conductive agent is at least one of conductive carbon black, conductive graphite, carbon fiber, carbon nanotube, and graphene.

[0020] Preferably, the negative electrode binder in step 2 is at least one of sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, styrene-butadiene rubber, and polyacrylic acid.

[0021] Preferably, the conductive agent is at least one of conductive carbon black, conductive graphite, carbon fiber, carbon nanotube, and graphene.

[0022] Preferably, the negative electrode active material is at least one of artificial graphite, natural graphite, hard carbon, and silicon-carbon.

[0023] The present invention also provides a formation method for a lithium-ion battery, which is characterized by including the following steps: injecting electrolyte into the lithium-ion battery and standing for 12 - 96 hours, and then performing formation treatment on the lithium-ion battery at a predetermined magnetic field strength.

[0024] Preferably, the formation method for the lithium-ion battery further includes standing, air extraction, capacity grading, and K value testing for the formed battery.

[0025] Preferably, the magnetic field strength is 10 mT - 1500 mT.

[0026] Preferably, the temperature of the formation treatment is 20°C - 60°C.

[0027] Preferably, the formation treatment includes the following four stages: The first stage: constant current charging at a current of 0.01C - 0.2C until 10% - 30% SOC; The second stage: constant current and constant voltage charging at a current of 0.5C - 2.0C until the upper limit voltage or 100% - 120% SOC; The third stage: constant current discharging at a current of 0.33C - 1.0C until the lower limit voltage or 0% - 10% SOC; The fourth stage: constant current and constant voltage charging at a current of 1.0C - 2.0C until 5% - 90% SOC.

[0028] Compared with the prior art, the beneficial effects of the present invention are mainly reflected in: 1. The present invention prepares a new composite dispersant, which includes a polymer polyurethane hyperdispersant and a co-dispersant. The co-dispersant is obtained by carrying out an amino-olefin addition reaction between an amino group and dimethyl allyl phosphate and lithium acrylate to obtain a functionalized polymer containing phosphate esters and lithium complexes. This molecular structure enables the material to have good hydrophilicity and lipophilicity, and can effectively form a stable interfacial layer between the aqueous phase and the oil phase, thereby promoting the uniform dispersion of the cathode material particles.

[0029] 2. Since the co-dispersant molecule contains polar groups such as phosphate esters and lithium salts, these groups can interact with the charges on the surface of the cathode material, reduce the surface tension of the material, and improve its wettability and dispersibility in the electrolyte. At the same time, these polar groups can also form coordination bonds or electrostatic forces with the ions in the electrolyte, further enhancing the dispersion stability of the material.

[0030] 3. The (triethoxysilylpropyl)-O-polyoxyethylene polyurethane segment in the co-dispersant has a certain flexibility and length, and can form a steric hindrance effect between the cathode material particles to prevent agglomeration and sedimentation between the particles. This steric hindrance effect helps to maintain the uniform distribution state of the cathode material in the electrolyte.

[0031] 4. Significantly improve the mixing effect of the cathode material in the electrolyte. The improvement of the mixing effect means that the cathode material particles can be more evenly distributed in the electrolyte, thereby improving the overall performance of the battery. Specifically, this can improve the electrochemical performance indicators such as the discharge capacity, cycle life, and charge-discharge efficiency of the battery.

[0032] 5. The present application performs formation treatment on the lithium-ion battery under a predetermined magnetic field strength. This formation method can better enable the capacity of the cathode lithium supplement additive to play a role by controlling the charging current density. Compared with the existing formation process, the new formation process can not only increase the current density, but also significantly shorten the formation time, effectively improve the capacity of the battery, improve the cycle performance of the battery, reduce energy consumption, and is conducive to industrial production. Detailed implementation mode

[0033] The following specific examples illustrate the implementation mode of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation modes, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0034] It should be noted that the process equipment or devices not specifically noted in the following examples all adopt conventional equipment or devices in the art.

[0035] In addition, it should be understood that one or more method steps mentioned in the present invention do not exclude the existence of other method steps before and after the combined steps or the insertion of other method steps between these explicitly mentioned steps, unless otherwise stated; it should also be understood that the combined connection relationship between one or more devices / apparatuses mentioned in the present invention does not exclude the existence of other devices / apparatuses before and after the combined devices / apparatuses or the insertion of other devices / apparatuses between these two explicitly mentioned devices / apparatuses, unless otherwise stated. Moreover, unless otherwise stated, the numbering of each method step is only a convenient tool for identifying each method step, rather than restricting the arrangement order of each method step or limiting the scope of implementation of the present invention. The change or adjustment of their relative relationship, without substantial change in the technical content, should also be regarded as the scope of implementation of the present invention.

[0036] Example 1 A preparation method of a composite dispersant for lithium supplementation of the positive electrode, comprising the following steps: Step 1, prepare a co-dispersant: Weigh 35 g of N-(triethoxysilylpropyl)-O-polyoxyethylene polyurethane, 100 g of dichloroethane, 15 g of dimethyl allyl phosphate, 0.05 g of lithium acrylate, and 3 g of ethylenediamine according to mass parts, put them into a reaction vessel, react at 70 °C for 100 min, and then cool to room temperature. Distill the obtained reaction product to obtain the co-dispersant; Step 2, weigh 95 g of a high molecular polyurethane super-dispersant and 5 g of the co-dispersant according to mass parts, and mix them evenly to obtain the lithium supplementation additive for the positive electrode.

[0037] The model of the high molecular polyurethane super-dispersant is NEO-1063.

[0038] A preparation method of a lithium ion battery, characterized by comprising the following steps: Step (1), prepare a lithium-supplemented positive electrode: Weigh 80 g of positive electrode active material, 0.1 g of lithium supplement agent, 1 g of positive electrode binder, and 0.1 g of conductive agent according to mass parts, add 50 g of N-methylpyrrolidone and 1 g of the composite dispersant at 20 °C, stir and mix evenly to obtain a lithium-supplemented positive electrode slurry, and then coat the lithium-supplemented positive electrode slurry on a current collector and prepare a lithium-supplemented positive electrode through roll pressing; Step (2), make a negative electrode sheet: Dissolve 1 g of negative electrode binder in 50 g of deionized water according to mass parts, then add 0.5 g of conductive agent and 80 g of negative electrode active material, stir at 20 °C to obtain a negative electrode slurry, and then screen, coat, dry, roll press, slit, and die cut the negative electrode slurry to make a negative electrode sheet; Step (3), assemble the lithium-supplemented positive electrode, negative electrode sheet, separator, electrode liquid, and housing to obtain a lithium ion battery containing the lithium-supplemented positive electrode.

[0039] The positive electrode active material is lithium cobaltate.

[0040] The lithium supplement agent is lithium-rich lithium ferrite.

[0041] The positive electrode binder is polyvinylidene fluoride.

[0042] The conductive agent is conductive carbon black.

[0043] The negative electrode binder in step 2 is sodium carboxymethyl cellulose.

[0044] The conductive agent is conductive carbon black.

[0045] The negative electrode active material is artificial graphite.

[0046] A formation method of a lithium-ion battery includes the following steps: After injecting electrolyte into the lithium-ion battery and standing for 12 hours, the lithium-ion battery is subjected to formation treatment at a predetermined magnetic field strength.

[0047] The formation method of the lithium-ion battery further includes standing, air extraction, capacity grading, and K value testing for the formed battery.

[0048] The magnetic field strength is 10 mT.

[0049] The temperature of the formation treatment is 20 °C.

[0050] The formation treatment includes the following four stages: The first stage: Constant current charging is carried out at a current of 0.01C until 10% SOC. The second stage: Constant current and constant voltage charging is carried out at a current of 0.5C until the upper limit voltage. The third stage: Constant current discharging is carried out at a current of 0.33C until the lower limit voltage. The fourth stage: Constant current and constant voltage charging is carried out at 1.0C until 5% SOC.

[0051] Example 2 A preparation method of a composite dispersant for positive electrode lithium supplement includes the following steps: Step 1, prepare an auxiliary dispersant: Weigh 45 g of N-(triethoxysilylpropyl)-O-polyoxyethylene polyurethane, 110 g of dichloroethane, 20 g of dimethyl allyl phosphate, 0.25 g of lithium acrylate, and 4 g of ethylenediamine according to mass parts, put them into a reaction vessel, react at 75 °C for 120 min and then cool to room temperature, and distill the obtained reaction product to obtain the auxiliary dispersant. Step 2, weigh 93.5 g of high molecular polyurethane hyperdispersant and 6.5 g of auxiliary dispersant according to mass parts, and mix them evenly to obtain the positive electrode lithium supplement additive.

[0052] The model of the polymer polyurethane hyperdispersant is LS501A.

[0053] A method for preparing a lithium-ion battery includes the following steps: Step (1), preparing a lithium-supplemented positive electrode: Weigh 86 g of positive electrode active material, 3 g of lithium-supplement agent, 2.5 g of positive electrode binder, and 1.5 g of conductive agent according to mass parts. Add 53.5 g of N-methylpyrrolidone and 2.5 g of the composite dispersant at 35°C, stir and mix evenly to obtain a lithium-supplemented positive electrode slurry. Then coat the lithium-supplemented positive electrode slurry on the current collector and prepare the lithium-supplemented positive electrode by rolling. Step (2), making a negative electrode sheet: Dissolve 4 g of negative electrode binder in 80 g of deionized water, then add 3.5 g of conductive agent and 86 g of negative electrode active material, stir at 28°C to obtain a negative electrode slurry. Then screen, coat, dry, roll, slit, and die-cut the negative electrode slurry to make a negative electrode sheet. Step (3), assembling the lithium-supplemented positive electrode, negative electrode sheet, separator, electrode liquid, and housing to obtain a lithium-ion battery containing the lithium-supplemented positive electrode.

[0054] The positive electrode active material is lithium iron phosphate.

[0055] The lithium-supplement agent is lithium squarate.

[0056] The positive electrode binder is polyimide.

[0057] The conductive agent is conductive graphite.

[0058] The negative electrode binder in Step 2 is lithium carboxymethyl cellulose.

[0059] The conductive agent is conductive graphite.

[0060] The negative electrode active material is natural graphite.

[0061] A method for forming a lithium-ion battery includes the following steps: After injecting liquid into the lithium-ion battery and standing for 40 hours, perform a forming treatment on the lithium-ion battery at a predetermined magnetic field strength.

[0062] The method for forming the lithium-ion battery further includes standing, degassing, grading, and K-value testing on the formed battery.

[0063] The magnetic field strength is 500 mT.

[0064] The temperature of the forming treatment is 35°C.

[0065] The forming treatment includes the following four stages: The first stage: Constant current charging is carried out at a current of 0.1C until 17% SOC. Second stage: Constant current and constant voltage charging at 1C current until 100% SOC; Third stage: Constant current discharging at 0.5C current until 0%; Fourth stage: Constant current and constant voltage charging at 1.3C until 35% SOC.

[0066] Example 3 A preparation method of a composite dispersant for lithium supplementation of the positive electrode, comprising the following steps: Step 1, preparing an auxiliary dispersant: Put 55g of N-(triethoxysilylpropyl)-O-polyoxyethylene polyurethane, 115g of dichloroethane, 20g of dimethyl allyl phosphate, 0.4g of lithium acrylate, and 5g of ethylenediamine weighed according to mass parts into a reaction vessel, react at 80°C for 140 minutes and then cool to room temperature, and distill the obtained reaction product to obtain the auxiliary dispersant; Step 2, weigh 92g of high molecular polyurethane hyperdispersant and 8g of auxiliary dispersant according to mass parts, and mix them evenly to obtain the lithium supplementation additive for the positive electrode.

[0067] The model of the high molecular polyurethane hyperdispersant is HY-6350.

[0068] A preparation method of a lithium ion battery, comprising the following steps: Step (1), preparing a lithium-supplemented positive electrode: Weigh 92g of positive electrode active material, 7g of lithium supplement agent, 3.5g of positive electrode binder, and 3g of conductive agent according to mass parts, add 57 parts of N-methylpyrrolidone and 3.5g of the composite dispersant at 50°C, stir and mix evenly to obtain the lithium-supplemented positive electrode slurry, and then coat the lithium-supplemented positive electrode slurry on the current collector and prepare the lithium-supplemented positive electrode by rolling; Step (2), making a negative electrode sheet: Dissolve 7g of negative electrode binder in 110g of deionized water according to mass parts, then add 7g of conductive agent and 92g of negative electrode active material, stir at 35°C to obtain the negative electrode slurry, and then screen, coat, dry, roll, slit, and die-cut the negative electrode slurry to make the negative electrode sheet; Step (3), assembling the lithium-supplemented positive electrode, negative electrode sheet, separator, electrode liquid, and shell to obtain a lithium ion battery containing the lithium-supplemented positive electrode.

[0069] The positive electrode active material is lithium iron manganese phosphate.

[0070] The lithium supplement agent is lithium-rich lithium nickelate.

[0071] The positive electrode binder is polytetrafluoroethylene.

[0072] The conductive agent is carbon fiber.

[0073] The negative electrode binder in Step 2 is styrene-butadiene rubber.

[0074] The conductive agent is carbon nanotubes.

[0075] The negative electrode active material is hard carbon.

[0076] A formation method for a lithium-ion battery, comprising the following steps: injecting electrolyte into the lithium-ion battery and standing for 68 hours, and then performing formation treatment on the lithium-ion battery at a predetermined magnetic field intensity.

[0077] Preferably, the formation method for the lithium-ion battery further includes standing, degassing, grading, and K value testing of the battery after formation.

[0078] Preferably, the magnetic field intensity is 1000 mT.

[0079] Preferably, the temperature of the formation treatment is 45 °C.

[0080] Preferably, the formation treatment includes the following four stages: The first stage: constant current charging at 0.15C to 23% SOC; The second stage: constant current and constant voltage charging at 0.5C - 2.0C to 110% SOC; The third stage: constant current discharging at 0.7C to 5% SOC; The fourth stage: constant current and constant voltage charging at 1.6C to 65% SOC.

[0081] Example 4 A preparation method for a composite dispersant for positive electrode lithium supplementation, comprising the following steps: Step 1, preparing an auxiliary dispersant: putting 70 g of N-(triethoxysilylpropyl)-O-polyoxyethylene polyurethane, 120 g of dichloroethane, 30 g of dimethyl allyl phosphate, 0.5 g of lithium acrylate, and 6 g of ethylenediamine weighed according to mass parts into a reaction vessel, reacting at 85 °C for 150 min, then cooling to room temperature, and distilling the obtained reaction product to obtain the auxiliary dispersant; Step 2, weighing 90 g of a polymer polyurethane hyperdispersant and 10 g of the auxiliary dispersant according to mass parts, and mixing evenly to obtain the positive electrode lithium supplementation additive.

[0082] The model of the polymer polyurethane hyperdispersant is LD-1652.

[0083] A preparation method for a lithium-ion battery, comprising the following steps: Step (1), prepare the lithium - supplemented cathode: Weigh 98 g of cathode active material, 10 g of lithium - supplement agent, 5 g of cathode binder, and 5 g of conductive agent according to mass parts. Add 60 g of N - methylpyrrolidone and 5 g of the composite dispersant at 60 °C, stir and mix evenly to obtain the lithium - supplemented cathode slurry. Then coat the lithium - supplemented cathode slurry on the current collector and prepare the lithium - supplemented cathode through rolling. Step (2), fabricate the anode sheet: Dissolve 10 g of anode binder in 130 g of deionized water, then add 10 g of conductive agent and 97 g of anode active material, stir at 45 °C to obtain the anode slurry. Then sieve, coat, dry, roll, slit, and die - cut the anode slurry to fabricate the anode sheet. Step (3), assemble the lithium - supplemented cathode, anode sheet, separator, electrolyte, and shell to obtain a lithium - ion battery containing the lithium - supplemented cathode.

[0084] The cathode active material is a ternary cathode material.

[0085] The lithium - supplement agent is lithium carbonate.

[0086] The cathode binder is polytetrafluoroethylene.

[0087] The conductive agent is carbon nanotubes.

[0088] The anode binder in Step 2 is polyacrylic acid.

[0089] The conductive agent is graphene.

[0090] The anode active material is silicon - carbon.

[0091] A formation method for a lithium - ion battery includes the following steps: After injecting electrolyte into the lithium - ion battery and standing for 96 hours, perform formation treatment on the lithium - ion battery at a predetermined magnetic field intensity.

[0092] The formation method for the lithium - ion battery further includes standing, degassing, grading, and K - value testing on the formed battery.

[0093] The magnetic field intensity is 1500 mT.

[0094] The temperature of the formation treatment is 60 °C.

[0095] The formation treatment includes the following four stages: The first stage: Constant - current charge at 0.2C until 30% SOC. The second stage: Constant - current and constant - voltage charge at 2.0C until 120% SOC. The third stage: Constant - current discharge at 1.0C until 10% SOC. Fourth stage: Constant current and constant voltage charging is carried out at 2.0C until 90% SOC.

[0096] Comparative Example 1 The difference between this example and Example 1 is that no co-dispersant is added to the composite dispersant, and the rest of the processes are exactly the same.

[0097] Comparative Example 2 The difference between this example and Example 1 is that dimethyl allyl phosphate is not added to the co-dispersant in the composite dispersant, and the rest of the processes are exactly the same.

[0098] Comparative Example 3 The difference between this example and Example 1 is that dimethyl allyl phosphate is not added to the co-dispersant in the composite dispersant, and the rest of the processes are exactly the same.

[0099] Table 1: Cathode lithium supplement composite dispersants with different ratios and reaction conditions in the examples Performance test: Performance tests were carried out on the lithium-ion batteries formed according to the formation methods provided in the examples and comparative examples. (1) In the voltage range of 2.5 - 4.2V, under the constant temperature condition of 25°C, the specific capacities of the sample batteries were tested at different rates of 1C, 5C, 10C, and 20C respectively; (2) In the voltage range of 2.5 - 4.2V, at a rate of 1C, under the constant temperature condition of 25°C, charge-discharge cycle tests were carried out on the sample batteries, and the number of cycle tests was 200 weeks. The test results are shown in Table 2.

[0100] Table 2 Test results of the cathode lithium supplement full battery As can be seen from the above results, the performance of the cathode lithium-supplemented full battery prepared by the preparation method of the present application is good. The co-dispersant in the cathode lithium-supplemented additive undergoes an amino-olefin addition reaction with dimethyl allyl phosphate and lithium acrylate through an amino group to obtain a functional polymer containing phosphate ester and lithium complex. This molecular structure enables the material to have good hydrophilicity and lipophilicity, and can effectively form a stable interfacial layer between the aqueous phase and the oil phase, thereby promoting the uniform dispersion of the cathode material particles. Moreover, the molecules of the co-dispersant contain polar groups such as phosphate ester and lithium salt, and these groups can interact with the charges on the surface of the cathode material, reduce the surface tension of the material, and improve its wettability and dispersibility in the electrolyte. At the same time, these polar groups can also form coordination bonds or electrostatic forces with the ions in the electrolyte, further enhancing the dispersion stability of the material. The (triethoxysilylpropyl)-O-polyoxyethylene polyurethane segment has a certain flexibility and length, and can form a steric hindrance effect between the cathode material particles to prevent agglomeration and sedimentation of the particles. This steric hindrance effect helps to maintain the uniform distribution state of the cathode material in the electrolyte. By using this material as a dispersant, the mixing effect of the cathode material in the electrolyte can be significantly improved. The improvement of the mixing effect means that the cathode material particles can be more evenly distributed in the electrolyte, thereby improving the overall performance of the battery. Specifically, this can improve the electrochemical performance indicators such as the discharge capacity, cycle life, and charge-discharge efficiency of the battery. In addition, the formation method protected by the present application can better improve the battery capacity by controlling the charging current density. The two stages of preparing the cathode lithium-supplemented full battery complement each other and work synergistically to improve the cycle performance of the battery, and further enhance the overall performance of the battery.

[0101] The above embodiments are intended to illustrate the implementation schemes disclosed in the present invention and should not be construed as limitations on the present invention. In addition, various modifications listed herein and changes in the methods and compositions of the invention are obvious to those skilled in the art without departing from the scope and spirit of the present invention. Although the present invention has been specifically described in conjunction with various specific preferred embodiments of the present invention, it should be understood that the present invention should not be limited to these specific embodiments. In fact, all obvious modifications to those skilled in the art as described above to obtain the invention should be included within the scope of the present invention.

Claims

1. A preparation method of a composite dispersant for cathode lithium supplementation, characterized in that, It includes the following steps: Step 1: Prepare a co-dispersant: Put 35 - 70 parts by mass of N-(triethoxysilylpropyl)-O-polyoxyethylene polyurethane, 100 - 120 parts of dichloroethane, 15 - 30 parts of dimethyl allyl phosphate, 0.05 - 0.5 part of lithium acrylate, and 3 - 6 parts of hexamethylenediamine into a reaction vessel. React at 70 - 85 °C for 100 - 150 min and then cool to room temperature. Distill the obtained reaction product to get the co-dispersant; Step 2: Weigh 90 - 95 parts by mass of a high molecular polyurethane hyperdispersant and 5 - 10 parts of the co-dispersant prepared in Step 1, and mix them evenly to obtain a composite dispersant for lithium compensation of the positive electrode.

2. The preparation method of a composite dispersant for cathode lithium supplementation according to claim 1, characterized in that: The model of the high molecular polyurethane hyperdispersant is any one of NEO-1063, LS501A, HY-6350, and LD-1652.

3. A composite dispersant for lithium compensation of the positive electrode prepared by the preparation method described in Claim 1.

4. A lithium-ion battery, characterized in that: It includes the composite dispersant prepared by the preparation method described in any one of Claims 1 - 2, or the composite dispersant described in Claim 3.

5. The preparation method of the lithium-ion battery according to claim 4, characterized in that, It includes the following steps: Step 1: Prepare a lithium-compensated positive electrode: Weigh 80 - 98 parts by mass of a positive electrode active material, 0.1 - 10 parts of a lithium compensator, 1 - 5 parts of a positive electrode binder, and 0.1 - 5 parts of a conductive agent and place them in a reaction vessel. Add 50 - 60 parts of N-methylpyrrolidone and 1 - 5 parts of the composite dispersant at 20 - 60 °C, stir and mix evenly to obtain a lithium-compensated positive electrode slurry. Then coat, dry, roll, slit, and die-cut the lithium-compensated positive electrode slurry to prepare a lithium-compensated positive electrode; Step 2: Make a negative electrode sheet: First, dissolve 1 - 10 parts of a negative electrode binder in 50 - 130 parts of deionized water, add 0.5 - 10 parts of a conductive agent and 80 - 97 parts of a negative electrode active material, and stir at 20 - 45 °C to obtain a negative electrode slurry. Then screen, coat, dry, roll, slit, and die-cut the negative electrode slurry to make a negative electrode sheet; Step 3: Assemble the lithium-compensated positive electrode, the negative electrode sheet, a separator, an electrode liquid, and a housing to obtain a lithium-ion battery containing a lithium-compensated positive electrode.

6. The method for preparing a lithium-ion battery according to claim 5, characterized in that: The positive electrode active material is at least one of lithium cobaltate, lithium iron phosphate, lithium manganese iron phosphate, spinel lithium manganate, ternary positive electrode material, and lithium-rich manganese positive electrode material.

7. The manufacturing method of the lithium ion battery according to claim 5, characterized in that: The lithium compensator is at least one of lithium-rich iron ferrate, squaric acid lithium, lithium-rich nickelate, lithium carbonate, and hexalithium cobalt tetraoxide.

8. The formation method of the lithium ion battery according to claim 4, characterized in that, It includes the following steps: Let the lithium-ion battery stand for 12 - 96 hours and then perform formation treatment on the lithium-ion battery under a predetermined magnetic field intensity.

9. The formation method of the lithium-ion battery according to claim 8, wherein: The magnetic field intensity is 10 mT to 1500 mT.

10. The formation method of the lithium-ion battery according to claim 8, wherein, The ambient temperature of the formation treatment is 20 °C to 60 °C, and it includes the following four stages: The first stage: Constant current charge at a current of 0.01C to 0.2C until 10% to 30% SOC; The second stage: Constant current constant voltage charge at a current of 0.5C to 2.0C until the upper limit voltage or 100% to 120% SOC; The third stage: Constant current discharge at a current of 0.33C to 1.0C until the lower limit voltage or 0% to 10% SOC; Fourth stage: Constant current and constant voltage charging is carried out at 1.0C to 2.0C until 5% to 90% SOC.

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