Composite nano organic lithium supplementing agent, preparation method thereof and positive electrode sheet

Abstract

The application belongs to the technical field of energy storage batteries, and discloses a composite nano organic lithium supplementing agent, a preparation method thereof and a positive electrode sheet. The composite nano organic lithium supplementing agent is composed of an active lithium source, a catalyst, a conductive network material and various auxiliary additives, and through precise control of the proportion of each component and the preparation process, the supplementing performance of lithium is optimized. The preparation of the active lithium source at a specific pH value can control the nucleation and growth process kinetics of the active lithium source, and at the pH value, the spray drying process can ensure the precipitation of spherical nanoparticles, and can provide sufficient recyclable lithium. The catalyst uses the ligand-metal charge transfer principle to reduce the oxidation decomposition potential of the unsaturated C=O bond in the carboxylate of the active lithium source. The conductive network material constructs an efficient electron transport path, and the dispersibility, stability and mechanical properties of the lithium supplementing agent are optimized through auxiliary additives. The composite nano organic lithium supplementing agent has excellent mechanical properties, good decomposition kinetics and good conductive performance, and can fully supplement lithium. After being applied to a lithium ion battery, the composite nano organic lithium supplementing agent can significantly improve the initial coulomb efficiency, energy density and cycle stability of the battery, and is suitable for new system batteries such as high-voltage positive electrode materials and silicon-based negative electrodes.

Description

Technical Field

[0001] This invention belongs to the field of energy storage battery technology, specifically relating to a composite nano-organic lithium supplement agent and its preparation method, and a positive electrode sheet, which is particularly suitable for lithium-ion batteries with high energy density and long cycle life. Background Technology

[0002] Lithium-ion batteries have been widely used in new energy vehicles, energy storage power stations, portable electronic devices, and other fields. As the industry's requirements for battery performance continue to increase, new systems and technologies such as silicon-based anodes, lithium-rich / high-nickel cathodes, and dry-process thick electrodes have gradually become research hotspots. However, these new systems generally suffer from significant irreversible lithium loss.

[0003] In lithium-ion batteries, irreversible lithium loss mainly originates from the initial construction and repeated reconstruction of the SEI / CEI film on the negative electrode side, the consumption of active lithium on the positive electrode side, and multiphase interface side reactions. These processes directly lead to low initial coulombic efficiency, limited energy density, and decreased cycle stability. As energy storage and power batteries continue to evolve towards higher energy density, longer lifespan, and higher safety, new systems such as silicon-based negative electrodes, lithium-rich / high-nickel positive electrodes, thick electrodes, fast charging, dry electrodes, and (semi)solid-state batteries are becoming more sensitive to the availability of cyclic active lithium. Therefore, lithium replenishment technology is transforming from an "optional" approach into a key means of overcoming the limitations of material systems and cell design boundaries.

[0004] Existing lithium replenishment systems can be divided into inorganic and organic lithium replenishment agents. Inorganic lithium replenishment agents are represented by iron-based lithium-rich oxides (Li5FeO4) and nickel-based lithium-rich oxides (Li2NiO2). These agents can achieve high lithium replenishment capacity at potentials below 4V, but their production processes are complex and costly. They also exhibit sensitivity to air and water during practical operation and suffer from severe gas generation issues during cell operation, especially during high-voltage, high-temperature storage. Therefore, they are almost exclusively used in small quantities in low-voltage lithium iron phosphate battery systems. Organic lithium replenishment agents, on the other hand, have lower costs, simpler preparation processes, and can generate gas only once through formation degassing, without affecting subsequent cell operation. Therefore, they are a superior choice for high-voltage cathode materials, such as lithium cobalt oxide and ternary cathode materials.

[0005] Current organic lithium supplements are represented by lithium oxalate, but due to its high lithium release potential, poor conductivity, and slow decomposition process, it may not decompose completely, affecting its subsequent use. For example, the lithium oxalate supplement disclosed in invention patent CN119627111A includes lithium oxalate, a conductive agent, and a catalyst, wherein the catalyst is non-metallic doped manganese dioxide. The lithium oxalate, non-metallic doped manganese dioxide, and conductive agent are mixed in water and then spray-dried to obtain the lithium oxalate supplement. Lithium oxalate supplements disclosed in CN118231661A include a three-dimensional network structure and matrix particles filled within the three-dimensional network structure; wherein the three-dimensional network structure is assembled from carbon nanotubes, and the matrix particles include lithium oxalate particles, conductive carbon particles, and catalyst particles. The above-mentioned prior art uses lithium oxalate with added catalyst to reduce the lithium release potential. However, due to the lack of control over the size of the supplement, a lower lithium release potential cannot be obtained, limiting its application as a lithium supplement.

[0006] In addition, the invention patent with publication number CN118299578A discloses the use of lithium formate as an active lithium source in conjunction with a catalyst and conductive substrate. However, in the process of controlling the particle size of the lithium supplement material within 5-100nm by using the confinement method of ion exchange resin adsorption and pyrolysis, the sintering temperature reaches 300-450℃. At this temperature, the lithium supplement is very easy to decompose or agglomerate, and may even react chemically with the catalyst and conductive substrate. This results in high energy consumption and makes it difficult to accurately control the particle size within the above range, leading to uncontrollable product performance.

[0007] Therefore, developing a composite nano-organic lithium supplement with controllable particle size, excellent decomposition kinetics, good conductivity, sufficient lithium replenishment, and good stability is of great significance for promoting the development of high-energy-density lithium-ion batteries. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of existing organic lithium supplements and provide a composite nano-organic lithium supplement, its preparation method, and a positive electrode sheet. By regulating the preparation process of the core functional components of the lithium supplement, combined with catalysts, conductive network materials, and auxiliary additives, the lithium supplement performance is comprehensively optimized.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] This invention provides a method for preparing a composite nano-organic lithium supplement, specifically including the following steps:

[0011] (1) Dissolve lithium carbonate in deionized water and heat until it is fully dissolved. Then, use a peristaltic pump with pH feedback to slowly pump carboxylic acid into the lithium carbonate solution until the pH reaches 8-10 and maintains the pH value in this range to obtain an active lithium source solution. The amount of lithium carbonate and formic acid in the solution meets the molar ratio of lithium to carboxylic acid in the product.

[0012] (2) The catalyst was uniformly dispersed in deionized water and the catalyst size was reduced to 100 nm-1 μm by using zirconium bead milling to obtain a catalyst dispersion.

[0013] (3) The catalyst dispersion after sand milling is uniformly dispersed with conductive network material, nonionic dispersant, anionic dispersant, anti-caking agent and binder in proportion to the active lithium source solution prepared in step (1). The solid content of the mixture is controlled to be 10-25wt%. Then spray drying is carried out. The active lithium source precipitates during the spray drying process and forms spherical particles with a size of 10-100nm. Under the action of nonionic dispersant, anionic dispersant, anti-caking agent and binder, they are uniformly attached to the conductive network with the catalyst.

[0014] (4) Collect the spray-dried product, heat it and then vacuum dry it to obtain a composite nano organic lithium supplement.

[0015] Preferably, the composite nano-organic lithium supplement agent comprises, by mass percentage: 60-80% active lithium source, 5-15% catalyst, 5-20% conductive network material, 0.5%-2% nonionic dispersant, 0.5%-2% anionic dispersant, 0.5%-2% anti-caking agent, and 0.5%-2% binder. The molar ratio of the carboxylate group of the active lithium source to the coordinated unsaturated sites in the catalyst is (10-50):1, and can be selected as 20:1, 30:1, or 40:1.

[0016] Preferably, in step (1), the amount of lithium carbonate used is 5-20g, the amount of deionized water is 100-300mL, the heating temperature is 50-80℃, the concentration of the carboxylic acid is 0.5-2g / mL, the carboxylic acid includes one or more of oxalic acid, formic acid, acetic acid, propionic acid, and squaric acid, and the obtained active lithium source solution includes one or more of lithium oxalate, lithium formate, lithium acetate, lithium propionate, and lithium squaric acid.

[0017] Preferably, the catalyst in step (2) includes one or more of manganese oxide, cobalt oxide, lithium cobalt oxide, iron oxide, and titanium oxide, the amount of catalyst used is 2-10g, the amount of deionized water is 50-200mL, the mesh size of zirconium beads is 1000-2000 mesh, and the catalyst size range is reduced to 100nm-500nm; the inlet air temperature of spray drying in step (3) is 120-180℃, the outlet air temperature is 60-90℃, and the air flow rate is 0.5-2m³ / min; the heating temperature in step (4) is 80-120℃, and the drying time is 4-8h.

[0018] Preferably, the conductive network material includes one or more of Ketjenblack, Super P, and carbon nanotubes.

[0019] Preferably, the nonionic dispersant is one or more of polyethylene glycol, polypropylene glycol, Tween-80, and Span-60; the anionic dispersant is one or more of sodium dodecyl sulfate and sodium dodecylbenzene sulfonate; the anti-caking agent includes one or more of fumed silica, talc, and diatomaceous earth with a particle size of 10-50 nm; and the binding aid includes one or more of sodium carboxymethyl cellulose and hydroxypropyl methylcellulose.

[0020] On the other hand, the present invention also provides a composite nano-organic lithium supplement obtained by the above preparation method, wherein the composite nano-organic lithium supplement comprises at least one of the following (1)-(6):

[0021] (1) The particle size of the composite nano-organic lithium supplement is 0.5-4 μm, d 50 It is 2 μm;

[0022] (2) The specific surface area of ​​the composite nano-organic lithium supplement is 5-10 m². 2 / g;

[0023] (3) The tap density of the composite nano-organic lithium supplement is ≥0.6 g / cm³. 3 ;

[0024] (4) The conductivity of the composite nano-organic lithium supplement is ≥1000 S / m;

[0025] (5) The lithium replenishment capacity of the composite nano-organic lithium replenisher reaches 471 mAh / g;

[0026] (6) The lithium replenishment potential of the composite nano-organic lithium replenisher is 4.00-4.20 V;

[0027] (7) The shear strength of the composite nano-organic lithium supplement is expressed as the viscosity of the slurry after the positive electrode active material: lithium supplement: polyvinylidene fluoride binder: conductive carbon are dispersed in N-methylpyrrolidone with a solid content of 60% in a ratio of 92:2:3:3.

[0028] The present invention also provides a positive electrode sheet containing the composite nano-organic lithium supplement agent as described above.

[0029] Preferably, the content of the lithium supplement is 0.1-10 wt%. The positive electrode sheet also includes a positive electrode active material, a binder, and a conductive agent. The positive electrode active material includes one or more of lithium cobalt oxide, ternary positive electrode material, lithium manganese oxide, and lithium iron phosphate. The binder includes one or more of polyvinylidene fluoride and polytetrafluoroethylene. The conductive agent includes one or more of acetylene black and conductive graphite.

[0030] In this invention, the active lithium source is the core component providing recyclable lithium ions, accounting for 60-80% to ensure sufficient lithium replenishment capacity. One or more of lithium oxalate, lithium formate, lithium acetate, lithium propionate, and lithium squartz are selected, with their core active group being the carboxylate group (-COO⁻), which can decompose and release lithium ions during battery formation to replenish irreversible lithium losses. Among these, lithium formate and lithium acetate have simple carboxylate structures, are more easily activated by catalysts, decompose quickly, and have high lithium replenishment efficiency. Lithium oxalate, lithium propionate, and lithium squartz can be flexibly combined according to the actual battery system requirements to adjust the decomposition potential and kinetic performance of the lithium replenishing agent.

[0031] This invention precisely controls the pH value during the preparation of lithium carboxylate, an active lithium source. This is because in a neutral environment, both the cations and anions in lithium carboxylate are fully coordinated with water molecules, making it difficult to break their solvation structure during evaporation. The cations and anions cannot break free of the hydrated shell to participate in crystallization, making initial nucleation difficult and tending to form large-sized particles. Acidic pH may corrode oxide catalysts. Therefore, in a slightly alkaline environment of pH 8-10, hydroxide ions disrupt the lithium ion hydrated layer, promoting large-scale and uniform crystal nucleation in the initial stage of evaporation, ensuring uniform and controllable growth size. This allows for the precipitation of particles with a size of 10-10 during spray drying. The spherical particles are 0 nm in size, and can be selected from 20-90 nm. In the example, the size can be a typical but non-limiting particle size such as 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, or any range between two particle sizes. With the help of nonionic dispersants, anionic dispersants, anti-caking agents, and binders, the active lithium source and catalyst are uniformly attached to the conductive network. By reducing the size of the active lithium source, the catalytic effect of the catalyst on the active lithium source can be improved, while its lithium replenishment potential can be reduced. The resulting composite structure can fully improve the electrical conductivity between the active lithium source and the catalyst, and improve the lithium replenishment effect.

[0032] In addition, in this invention, the catalyst accounts for 5-15% of the total mass, and its size is controlled within 100nm-1μm, preferably 100nm-500nm. In exemplary cases, this size can be typical but not limiting particle sizes such as 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, and 450nm, or any range between two particle sizes. This size range can increase the contact area between the catalyst and the active lithium source, thus fully utilizing the catalytic effect. The catalyst is selected from one or more of manganese oxide, cobalt oxide, lithium cobalt oxide, iron oxide, and titanium oxide, and its metal ions (such as Mn²⁺) are used. + / Mn³ + Co² + / Co³ + Fe² + / Fe³ + Ti³ + / Ti + The oxide has incomplete 3d orbitals and coordinating unsaturated sites on its surface. These sites become "active centers" that interact with the carboxylate ions of the active lithium source. In this invention, the unsaturated C=O bond in the carboxylate ions of the active lithium source acts as a "ligand." The lone pair electrons on its oxygen atom undergo charge transfer to the empty d orbitals of the catalyst metal ion, forming a temporary "ligand-metal complex." This leads to a decrease in the electron cloud density and weakening of the C=O bond, thereby reducing the energy threshold required for oxidative decomposition, accelerating the decomposition process, and improving the lithium replenishment kinetics. The molar ratio of the carboxylate ions of the active lithium source to the coordinating unsaturated sites in the catalyst is (10-50):1, which ensures that the catalyst can sufficiently reduce the oxidative decomposition potential of the unsaturated C=O bonds in the carboxylate ions of the active lithium source through the ligand-metal charge transfer (LMCT) principle.

[0033] In this invention, the conductive network material accounts for 5-20%, and is selected from one or more of Ketjen Black, Super P, and carbon nanotubes. Ketjen Black has a large specific surface area and good dispersibility, which can fill voids; carbon nanotubes are one-dimensional nanostructures, which are easy to construct continuous conductive pathways with short electron transport paths, and can also serve as a framework to improve the mechanical strength of the composite structure; Super P is low in cost and readily available, and can assist in the construction of the conductive network. By rationally combining the three conductive materials, a three-dimensional continuous conductive network can be formed, which significantly improves the conductivity of the lithium replenishing agent, accelerates electron transport, provides an efficient electronic pathway for the oxidation reaction during the decomposition of the lithium replenishing agent, and avoids decomposition obstruction due to electron accumulation; at the same time, the three-dimensional network ensures that the lithium replenishing agent has sufficient shear resistance during the preparation of the electrode material slurry, and the active particles of the lithium replenishing agent do not fall off from the conductive network; in addition, after the lithium replenishing agent decomposes, the residual conductive network material can maintain the conductive structure of the electrode and does not affect the internal resistance of the electrode.

[0034] In this invention, nonionic dispersants are suitable for aqueous / polar solvent systems, which helps disperse the lithium supplementation agent components in aqueous solvent systems. Anionic dispersants have strong dispersing effects and are suitable for the dispersion of catalyst nanoparticles. The synergistic effect of the two dispersants can effectively solve the problem of agglomeration of active lithium source, catalyst, and conductive network material in solution, ensuring uniform dispersion of each component and improving the structural uniformity of the lithium supplementation agent. In addition, anti-caking agents are selected from one or more of fumed silica, talc, and diatomaceous earth with a particle size of 10-50nm. Through physical barrier effect, they reduce the interaction force between lithium supplementation agent particles, prevent agglomeration due to moisture absorption and agglomeration during spraying and storage, ensure the fluidity of the lithium supplementation agent, and facilitate subsequent mixing with the cathode material. The binder is selected from one or more of sodium carboxymethyl cellulose and hydroxypropyl methylcellulose, which can improve the mechanical strength of lithium supplementation agent particles, avoid breakage during slurry preparation and stirring and rolling preparation of electrode sheets, and enhance the adhesion between the lithium supplementation agent and the cathode active material and current collector, thereby improving the stability of the electrode structure.

[0035] The beneficial effects of this invention include:

[0036] (1) By precisely controlling the pH value during the preparation of the active lithium source, spherical particles with a size of 10-100 nm are precipitated during the spray drying process. By reducing the size of the active lithium source, the catalytic effect of the catalyst on the active lithium source can be improved, while reducing its lithium replenishment potential. The resulting composite structure can fully improve the electrical conductivity between the active lithium source and the catalyst, and improve the lithium replenishment effect.

[0037] (2) By adjusting the ratio and performance of active lithium source, catalyst and conductive network material, and combining the ligand-metal charge transfer catalysis principle with the construction of a three-dimensional conductive network, the decomposition kinetics and conductivity of lithium supplementation agent are significantly improved, solving the problems of slow decomposition and insufficient lithium supplementation of traditional organic lithium supplementation agents.

[0038] (3) The introduction of auxiliary additives optimizes the preparation process, storage stability and mechanical properties of lithium supplementation agent, ensuring that the lithium supplementation agent has a uniform structure, good fluidity and high mechanical strength. The shear strength of the obtained composite nano organic lithium supplementation agent is expressed as the viscosity of the slurry after dispersion is <4996mPa.S, which facilitates the size control of the active lithium source, making it less prone to agglomeration and clumping during spray drying, and also facilitates mixing with positive electrode materials to prepare electrode sheets.

[0039] (4) The preparation process of this invention is simple and the cost is controllable. It does not require high-energy-consuming methods such as high-temperature sintering. It can be mass-produced through conventional processes such as pH adjustment, sand milling, and spray drying.

[0040] (5) When the composite nano-organic lithium replenishing agent of the present invention is applied to a lithium-ion battery, the lithium replenishing capacity is 408-491mAh / g and the lithium replenishing potential is 4.00-4.20V. It can quickly and fully decompose and release lithium ions during the formation process, effectively replenishing the irreversible lithium loss of the battery. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 This is a SEM image of the composite nano-organic lithium supplement prepared in Example 1 of the present invention.

[0043] Figure 2 This is a magnified SEM image of the composite nano-organic lithium supplement prepared in Example 1 of the present invention.

[0044] Figure 3 This is a SEM image of the composite nano-organic lithium supplement prepared in Comparative Example 1 of this invention.

[0045] Figure 4 The charging curve of the composite nano-organic lithium supplement prepared in Example 1 of this invention is shown.

[0046] Figure 5 The charging curve of the composite nano-organic lithium supplement prepared in Comparative Example 1 of this invention is shown.

[0047] Figure 6 The images show the charge-discharge curves of the composite nano-lithium supplement agent and the lithium cobalt oxide / graphite conductive network material system (LCO + lithium supplement agent) prepared in Example 1 of this invention, as well as the charge-discharge curves without the composite nano-lithium supplement agent (LCO). Detailed Implementation

[0048] The present invention will be described in detail below with reference to specific embodiments and examples, thereby making the advantages and various effects of the present invention more clearly apparent. Those skilled in the art should understand that these specific embodiments and examples are for illustrative purposes only and are not intended to limit the present invention.

[0049] Throughout this specification, unless otherwise specified, the terminology used herein should be understood as having the meaning commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In the event of any conflict, this specification shall prevail.

[0050] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0051] Example 1

[0052] The preparation process of the composite nano-organic lithium supplement: The composite nano-organic lithium supplement is prepared according to the following mass percentages: 60% lithium formate, 15% lithium cobalt oxide (size 100-200nm), 20% conductive network material (where Ketjen Black: Super P: carbon nanotube = 50:25:25), 2% polyethylene glycol, 1% sodium dodecyl sulfate, 1% fumed silica with a particle size of 10-50nm, and 1% sodium carboxymethyl cellulose. Specific operations include:

[0053] (1) Dissolve lithium carbonate in 100-300 mL of deionized water and heat it to 50-80 °C until it is fully dissolved. Then, use a peristaltic pump with pH feedback to slowly pump formic acid into the lithium carbonate solution until the pH reaches 8-10 and the pH value is controlled within this range to obtain lithium formate active lithium source solution. The ratio of lithium carbonate to formic acid meets the molar ratio of lithium to carboxylate in the product. By controlling the addition rate of formic acid through pH feedback, the reaction process can be precisely controlled to ensure the generation of high-purity active lithium source and avoid local over-reaction or insufficiency.

[0054] (2) The lithium cobalt oxide catalyst was uniformly dispersed in deionized water and milled with 1000-2000 mesh zirconium beads to reduce the catalyst size to 100nm-1μm to obtain a catalyst dispersion.

[0055] (3) The catalyst dispersion after sand milling is uniformly dispersed with conductive network material, nonionic dispersant, anionic dispersant, anti-caking agent and binder in proportion to the active lithium source solution prepared in step (1), and the solid content of the mixture is controlled to be 10-25wt%. Then spray drying is carried out. The inlet air temperature of spray drying is 120-180℃ and the outlet air temperature is 60-90℃.

[0056] (4) Collect the spray-dried product, heat it to 80-120℃ and vacuum dry it for 4-8 hours to obtain the composite nano organic lithium supplement.

[0057] SEM images of the obtained composite nano-organic lithium supplement are attached. Figure 1 , Figure 2 As shown, the nano-scale lithium supplement is uniformly distributed within the secondary spherical particles. The nano-scale lithium supplement achieves high decomposition kinetics, while the three-dimensional conductive network further enhances the conductivity of the composite structure. The spherical structure is beneficial for improving the compaction density and shear strength of the composite material, ensuring that the particles do not disintegrate during slurry preparation and still provide sufficient conductive structure after the lithium supplement decomposes.

[0058] Example 2

[0059] Unlike Example 1, the composite nano-organic lithium supplement in Example 2 consists of 70% lithium formate + 15% manganese oxide (size 100-200nm) + 10% conductive network material (where Ketjen Black: Super P: carbon nanotube = 50:25:25), 2% Tween-80, 2% sodium dodecyl sulfate, 0.5% talc, and 0.5% sodium carboxymethyl cellulose. Manganese oxide is used as a catalyst in the preparation process, and the rest of the preparation process is the same as in Example 1.

[0060] Example 3

[0061] Unlike Example 1, the composite nano-organic lithium supplement in Example 3 consists of 80% lithium acetate + 10% cobalt oxide (size 100-200nm) + 5% conductive network material (where Ketjen Black: Super P: carbon nanotube = 50:25:25), 0.5% Span-60, 0.5% sodium dodecylbenzenesulfonate, 2% diatomaceous earth, and 2% sodium hydroxypropyl methylcellulose. In the preparation process, acetic acid is slowly pumped into the lithium carbonate solution as a carboxylic acid, and cobalt oxide is used as a catalyst. The rest of the preparation process is the same as in Example 1.

[0062] Example 4

[0063] Unlike Example 1, the composite nano-organic lithium supplement in Example 4 consists of 60% lithium acetate + 15% iron oxide (size 100-200nm) + 20% conductive network material (where Ketjen Black: Super P: carbon nanotube = 50:25:25), 2% polyethylene glycol, 1% sodium dodecyl sulfate, 1% fumed silica with a particle size of 10-50nm, and 1% sodium carboxymethyl cellulose. In the preparation process, acetic acid is slowly pumped into the lithium carbonate solution as a carboxylic acid, and iron oxide is used as a catalyst. The rest of the preparation process is the same as in Example 1.

[0064] Example 5

[0065] Unlike Example 1, the composite nano-organic lithium supplement in Example 3 consists of 60% lithium propionate + 15% titanium dioxide (size 100-200nm) + 20% conductive network material (where Ketjen Black: Super P: carbon nanotube = 50:25:25), 2% polyethylene glycol, 1% sodium dodecyl sulfate, 1% fumed silica with a particle size of 10-50nm, and 1% sodium carboxymethyl cellulose. In the preparation process, propionic acid is slowly pumped into the lithium carbonate solution as a carboxylic acid, and titanium dioxide is used as a catalyst. The rest of the preparation process is the same as in Example 1.

[0066] Example 6

[0067] Unlike Example 1, the composite nano-organic lithium supplement in Example 6 consists of 60% lithium squartz oxide + 15% lithium cobalt oxide (size 100-200nm) + 20% conductive network material (where Ketjen Black: Super P: carbon nanotube = 50:25:25), 2% polyethylene glycol, 1% sodium dodecyl sulfate, 1% fumed silica with a particle size of 10-50nm, and 1% sodium carboxymethyl cellulose. In the preparation process, squartz acid is slowly pumped into the lithium carbonate solution as a carboxylic acid. The rest of the preparation process is the same as in Example 1.

[0068] Example 7

[0069] Unlike Example 1, the composite nano-organic lithium supplement in Example 7 consists of 60% lithium oxalate + 15% lithium cobalt oxide (size 100-200nm) + 20% conductive network material (where Ketjen Black: Super P: carbon nanotube = 50:25:25), 2% polyethylene glycol, 1% sodium dodecyl sulfate, 1% fumed silica with a particle size of 10-50nm, and 1% sodium carboxymethyl cellulose. In the preparation process, oxalic acid is slowly pumped into the lithium carbonate solution as a carboxylic acid. The rest of the preparation process is the same as in Example 1.

[0070] Comparative Example 1

[0071] Unlike Example 1, in Comparative Example 1, after the lithium carbonate to formic acid molar ratio of 1:2 was naturally added, the pH value was not adjusted. The reaction was carried out naturally under weakly acidic conditions, and the organic lithium supplement was obtained by spray drying in the same proportion as in Example 1.

[0072] Comparative Example 2

[0073] Unlike Example 1, in Comparative Example 2, after the lithium carbonate and acetic acid were added naturally in step (1) at a molar ratio of 1:2, no pH adjustment was performed. The reaction was carried out naturally under weakly acidic conditions, and the organic lithium supplement was obtained by spray drying in the same proportion as in Example 1.

[0074] Comparative Example 3

[0075] Unlike Example 1, in Comparative Example 3, after the lithium carbonate and oxalic acid were added naturally in step (1) at a molar ratio of 1:2, no pH adjustment was performed. The reaction was carried out naturally under weakly acidic conditions, and the organic lithium supplement was obtained by spray drying in the same proportion as in Example 1.

[0076] Comparative Examples 4-7

[0077] Unlike Example 1, the organic lithium supplements in Comparative Examples 4-7 do not contain a catalyst. They are prepared according to step (1) in Examples 1-7, consisting of 75% lithium formate, 75% lithium acetate, 75% lithium propionate, 75% lithium squartzate, 75% lithium oxalate, 20% conductive network material (where Ketjenblack:super P:carbon nanotubes = 50:25:25), 2% polyethylene glycol, 1% sodium dodecyl sulfate, 1% fumed silica with a particle size of 10-50 nm, and 1% sodium carboxymethyl cellulose. In the preparation process, the synthesized lithium formate, lithium acetate, lithium propionate, lithium squartzate, lithium oxalate, conductive network material (where Ketjenblack:super P:carbon nanotubes = 50:25:25), polyethylene glycol, sodium dodecyl sulfate, fumed silica, and sodium carboxymethyl cellulose are directly prepared in proportion to obtain the organic lithium supplement.

[0078] Testing procedure for composite nano-organic lithium replenisher: The capacity and voltage of the lithium replenisher were tested using coin cells. The lithium replenisher, conductive network material, and PVDF binder were mixed in a ratio of 8:1:1 to form a slurry, which was then coated onto aluminum foil, dried, and cut into pieces. Sodium metal was used as the counter electrode, and 1M NaPF6 EC:PC (5% FEC) was used as the electrolyte. The test was conducted at 0.1C (1C=450 mA / g).

[0079] In addition, the shear strength of the lithium supplement was determined by viscosity testing after slurry dispersion.

[0080] Examples 1-7 and Comparative Examples 1-7 were tested according to the above test procedure for the size of the active lithium source, the capacity for lithium replenishment, the lithium replenishment potential, as well as the viscosity and conductivity of the slurry, and the results are shown in Table 1.

[0081] Table 1. Performance test results of lithium replenishing agents obtained in Examples 1-7 and Comparative Examples 1-7

[0082]

[0083] From the appendix Figure 3 As can be seen from the data, the lithium supplement particle size prepared using Comparative Example 1 is 400-600 nm (see attached figure). Figure 3 (indicated by the middle arrow), significantly higher than in Example 1. From the table above and the appendix... Figure 4 It can be seen that the coin cell prepared using the lithium replenishing agent of Example 1 has a decomposition potential of 4.05V and a decomposition capacity of 452 mAh / g. (From the appendix...) Figure 5It can be seen that the coin cell prepared using the lithium supplement agent of Comparative Example 1 has a decomposition potential of 4.37V, exhibiting a high overpotential of approximately 0.15V, and a decomposition capacity of 419 mAh / g, indicating poor decomposition kinetics. The table above shows that the coin cells prepared using lithium supplement agents of Comparative Examples 1-3 without pH control all have decomposition potentials higher than 4.3V, and the active lithium source size is greater than 400 nm. The decomposition potentials of Comparative Examples 4-7 without catalyst are all higher than 4.35V, significantly inferior to the samples containing catalyst.

[0084] In addition, from the appendix Figure 6 As can be seen, when this lithium replenishing agent is mixed with lithium cobalt oxide (lithium replenishing agent: lithium cobalt oxide: conductive network material: PVDF = 2:93:3:2) and assembled with a graphite anode into a 1Ah pouch cell (LCO + lithium replenishing agent), the specific capacity is increased from 150 mAh / g to 156 mAh / g compared to a 1Ah pouch cell without lithium replenishing agent (lithium replenishing agent: conductive network material: PVDF = 95:3:2) (LCO).

[0085] In summary, a detailed comparison of all embodiments and comparative examples reveals that the organic composite nano-lithium supplement agent comprises 60-80% active lithium source, 5-15% catalyst, 5-20% conductive network material, 0.5%-2% nonionic dispersant, 0.5%-2% anionic dispersant, 0.5%-2% anti-caking agent, and 0.5%-2% binder. By precisely controlling the pH value during the preparation of the active lithium source, combined with the effects of the nonionic dispersant, anionic dispersant, anti-caking agent, and binder, it achieves high mechanical strength during spray drying, precipitating spherical particles with a size of 10-100 nm. These particles are uniformly attached to the conductive network along with the catalyst. This method reduces the size of the active lithium source, improves the catalytic effect of the catalyst on the active lithium source, and simultaneously lowers its lithium supplementation potential. The resulting composite structure significantly enhances the electrical conductivity between the active lithium source and the catalyst, thereby improving the lithium supplementation effect.

[0086] Finally, it should be noted that the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0087] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0088] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for preparing a composite nano-organic lithium supplement, characterized in that, Includes the following steps: (1) Dissolve lithium carbonate in deionized water and heat until it is fully dissolved. Then, use a peristaltic pump with pH feedback to slowly pump carboxylic acid into the lithium carbonate solution until the pH reaches 8-10 and maintains the pH value in this range to obtain an active lithium source solution. The amount of lithium carbonate and formic acid in the solution meets the molar ratio of lithium to carboxylic acid in the product. (2) The catalyst was uniformly dispersed in deionized water and the catalyst size was reduced to 100 nm-1 μm by using zirconium bead milling to obtain a catalyst dispersion. (3) The catalyst dispersion after sand milling is uniformly dispersed with conductive network material, nonionic dispersant, anionic dispersant, anti-caking agent and binder in proportion to the active lithium source solution prepared in step (1). The solid content of the mixture is controlled to be 10-25wt%. Then spray drying is carried out. The active lithium source precipitates during the spray drying process and forms spherical particles with a size of 10-100nm. Under the action of nonionic dispersant, anionic dispersant, anti-caking agent and binder, they are uniformly attached to the conductive network with the catalyst. (4) Collect the spray-dried product, heat it and then vacuum dry it to obtain a composite nano organic lithium supplement.

2. The preparation method of the composite nano-organic lithium supplement according to claim 1, characterized in that, The composite nano-organic lithium supplement agent, by mass percentage, comprises: 60-80% active lithium source, 5-15% catalyst, 5-20% conductive network material, 0.5%-2% nonionic dispersant, 0.5%-2% anionic dispersant, 0.5%-2% anti-caking agent, and 0.5%-2% binder, wherein the molar ratio of the carboxylate group of the active lithium source to the coordinated unsaturated site in the catalyst is (10~50):

1.

3. The preparation method of the composite nano-organic lithium supplement according to claim 2, characterized in that, In step (1), the amount of lithium carbonate used is 5-20g, the amount of deionized water is 100-300mL, the heating temperature is 50-80℃, the concentration of the carboxylic acid is 0.5-2g / mL, and the carboxylic acid includes one or more of formic acid, acetic acid, propionic acid, squaric acid, and oxalic acid. The resulting active lithium source solution includes one or more of lithium formate, lithium acetate, lithium propionate, lithium squaric acid, and lithium oxalate.

4. The preparation method of the composite nano-organic lithium supplement according to claim 3, characterized in that, The catalyst in step (2) includes one or more of manganese oxide, cobalt oxide, lithium cobalt oxide, iron oxide, and titanium oxide. The amount of catalyst used is 2-10g, the amount of deionized water is 50-200mL, the mesh size of zirconium beads is 1000-2000 mesh, and the catalyst size range is reduced to 100nm-500nm. In step (3), the inlet air temperature of spray drying is 120-180℃, the outlet air temperature is 60-90℃, and the air flow rate is 0.5-2m³ / min. In step (4), the heating temperature is 80-120℃, and the drying time is 4-8h.

5. The preparation method of the composite nano-organic lithium supplement according to claim 4, characterized in that, The conductive network material includes one or more of Ketjen Black, Super P, and carbon nanotubes.

6. The preparation method of the composite nano-organic lithium supplement according to claim 5, characterized in that, The nonionic dispersant is one or more of polyethylene glycol, polypropylene glycol, Tween-80, and Span-60; the anionic dispersant is one or more of sodium dodecyl sulfate and sodium dodecylbenzene sulfonate; the anti-caking agent includes one or more of fumed silica, talc, and diatomaceous earth with a particle size of 10-50 nm; and the binder includes one or more of sodium carboxymethyl cellulose and hydroxypropyl methylcellulose.

7. The composite nano-organic lithium supplement obtained by the preparation method according to any one of claims 1-6, characterized in that, The composite nano-organic lithium supplement includes at least one of the following (1)-(7): (1) The particle size of the composite nano-organic lithium supplement is 0.5-4 μm, d 50 It is 2 μm; (2) The specific surface area of ​​the composite nano-organic lithium supplement is 5-10 m². 2 / g; (3) The tap density of the composite nano-organic lithium supplement is ≥0.6 g / cm³. 3 ; (4) The conductivity of the composite nano-organic lithium supplement is ≥1000 S / m; (5) The lithium replenishment capacity of the composite nano-organic lithium replenisher is 471 mAh / g; (6) The lithium replenishment potential of the composite nano-organic lithium replenisher is 4.00-4.20 V; (7) The shear strength of the composite nano-organic lithium supplement is expressed as the viscosity of the slurry after the positive electrode active material: lithium supplement: polyvinylidene fluoride binder: conductive carbon are dispersed in N-methylpyrrolidone with a solid content of 60% in a ratio of 92:2:3:

3.

8. A positive electrode sheet, characterized in that, The positive electrode sheet contains the composite nano-organic lithium supplement agent as described in claim 7.

9. The positive electrode sheet according to claim 8, characterized in that, The lithium supplement content is 0.1-10 wt%.

10. The positive electrode sheet according to claim 9, characterized in that, The positive electrode sheet further includes a positive electrode active material, a binder, and a conductive agent. The positive electrode active material includes one or more of lithium cobalt oxide, ternary cathode, lithium manganese oxide, and lithium iron phosphate. The binder includes one or more of polyvinylidene fluoride and polytetrafluoroethylene. The conductive agent includes one or more of acetylene black and conductive graphite.

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