A spherical lithium oxalate@catalyst composite lithium supplement agent, its preparation method and application

Abstract

This invention belongs to the field of lithium-ion battery technology, and discloses a spherical lithium oxalate@catalyst composite lithium replenisher, its preparation method, and its application. By carefully selecting metal salt precursors, the method utilizes the thermal effect of spray drying to achieve in-situ generation of highly active nanoscale catalysts, uniform composite with lithium oxalate, and spherical particle formation in one step. This completely eliminates the complex steps of catalyst pre-synthesis in traditional processes, resulting in a comprehensive energy consumption reduction of over 60%. This method has outstanding advantages such as extremely simple process, low cost, uniform composite, controllable morphology, and excellent performance. The prepared composite lithium replenisher consists of regular spherical particles with a spherical integrity rate of ≥94%. It reduces the decomposition potential of lithium oxalate to 3.68–3.95 V, enabling lithium-ion batteries to achieve an initial efficiency of ≥89.6% and a capacity retention rate after 100 cycles that is at least 15 percentage points higher than without the addition of a lithium replenisher. The process is simple, low-cost, and easily scalable.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery material technology, specifically relating to a spherical lithium oxalate@catalyst composite lithium supplementer, its preparation method, and its application. Background Technology

[0002] Spherical lithium oxalate (Li2C2O4)-based composite lithium supplements are key materials for improving the first charge-discharge efficiency of lithium-ion batteries due to their good fluidity, high tap density, and uniform mixing with cathode materials. The traditional preparation of spherical lithium oxalate composite lithium supplements generally employs a two-step method: the first step is to pre-synthesize a highly active catalyst (such as TiN, Co3O4, etc.), and the second step is to disperse the catalyst in a lithium oxalate solution or slurry, followed by spray drying to form the final product.

[0003] This traditional process has significant drawbacks: First, it is complex, costly, and energy-intensive. Independent catalyst synthesis requires multiple steps, including high-temperature annealing, hydrothermal treatment, and ammonia treatment, resulting in high energy consumption (e.g., nitride synthesis requires ammonia treatment at >800℃), large equipment investment, and long production cycles. Second, catalysts are prone to agglomeration. The uneven dispersion of nanocatalysts in the precursor solution leads to uneven catalyst distribution after composite formation, insufficient exposure of active sites, reduced catalytic efficiency, and poor lithium replenishment effect. Third, solvents are prone to residue. The wet dispersion process introduces organic solvents (such as NMP and ethanol), which may remain if subsequent drying is incomplete, affecting battery cycle stability (increased gas production). Fourth, morphology control is difficult. The rheological properties of the premixed slurry are unstable, and spray drying easily produces hollow spheres or broken particles, resulting in poor electrode processability.

[0004] Although the one-step spray drying method has been successfully applied in the preparation of cathode materials (such as NCM), it is still difficult to achieve the simultaneous completion of in-situ catalyst generation, uniform compounding and controllable spherical molding in the field of lithium oxalate-based lithium supplements. There is a lack of suitable precursor systems and mild and efficient process parameters. Summary of the Invention

[0005] This invention aims to overcome the problems of complex traditional two-step processes, high energy consumption, uneven catalyst dispersion, high lithium oxalate decomposition potential, and limited improvement in battery performance. It provides a spherical lithium oxalate@catalyst composite lithium replenisher, its preparation method, and its application. The metal salt precursor is directly mixed with lithium oxalate and spray-dried, simultaneously achieving in-situ generation and composite of the catalyst, significantly simplifying the process and improving material uniformity and lithium replenishment efficiency.

[0006] To address the aforementioned technical problems, this invention provides a method for preparing a spherical lithium oxalate@catalyst composite lithium supplement, comprising the following steps:

[0007] S1. Lithium oxalate and the metal salt precursor are dissolved in a solvent to form a homogeneous precursor solution, wherein the molar ratio of the metal element to lithium oxalate in the metal salt precursor is (0.05~0.075):1.

[0008] S2. Under an inert atmosphere, the precursor solution is spray-dried. The inlet temperature of the spray dryer is 200-300℃ (to ensure rapid decomposition and conversion of the metal salt) and the outlet temperature is 80-150℃ (to ensure particle drying and avoid thermal decomposition of lithium oxalate). During the spray drying process, the metal salt precursor is simultaneously converted into a highly active nano-scale catalyst and combined with lithium oxalate in situ to form spherical composite particles.

[0009] S3. Collect the spherical composite particles to obtain spherical lithium oxalate@catalyst composite lithium supplementer.

[0010] This preparation method is based on a molecularly homogeneous precursor solution. Utilizing precise temperature control during spray drying, it simultaneously achieves the thermal decomposition / conversion of the metal salt precursor and the in-situ composite of the catalyst and lithium oxalate within microdroplets. This eliminates the cumbersome steps of catalyst pre-synthesis, separation, and dispersion in traditional processes, significantly simplifying the process while substantially reducing overall energy consumption and production costs. Simultaneously, it achieves highly uniform dispersion of catalyst nanoparticles within the lithium oxalate matrix, forming a strong coupling interface with lithium oxalate. Furthermore, leveraging the atomization characteristics of spray drying, composite particles with high sphericity and narrow particle size distribution can be directly obtained, effectively improving the tap density and electrode processability of the product. The protective effect of the inert atmosphere prevents oxidation of the active metal components, ensuring high catalytic activity of the catalyst. Ultimately, the resulting composite lithium supplement can significantly reduce the decomposition potential of lithium oxalate to 3.68–3.95 V (vs. Li). + The addition of lithium-ion battery (Li) significantly improves the electrochemical performance of lithium-ion batteries, achieving an initial charge efficiency of ≥89.6% and a capacity retention rate that is at least 15 percentage points higher after 100 cycles compared to batteries without lithium replenishment.

[0011] As a further description of the above technical solution: the metal salt precursor in step S1 is selected from at least one of transition metal chlorides, transition metal nitrates, or transition metal citrates. These metal salt precursors have strong compatibility and excellent water solubility, and can be fully miscible with lithium oxalate to form a uniform precursor solution, laying the foundation for the uniformity of subsequent in-situ composite. Moreover, their thermal decomposition characteristics are compatible with the spray drying process, and they can be efficiently converted into highly active catalysts (such as NiO, Co3O4, NiCo2O4, FeOx@C, etc.) within the process set temperature range, combining the advantages of excellent catalytic performance, readily available raw materials, and low cost. At the same time, different types of salts can be flexibly selected according to requirements. For example, citrates can also generate carbon-coated structures in-situ during the conversion process, further improving the conductivity and catalytic stability of the composite lithium supplement.

[0012] As a further description of the above technical solution: the metal salt precursor in step S1 is selected from at least one of nickel nitrate (Ni(NO3)2·6H2O), cobalt nitrate (Co(NO3)2·6H2O), cobalt chloride (CoCl2·6H2O), and ferric ammonium citrate (NH4Fe(C6H5O7)2·2H2O).

[0013] As a further description of the above technical solution: the solvent in step S1 is water, ethanol, or a mixture of water and ethanol. Water and ethanol both have good solubility for lithium oxalate and metal salt precursors, ensuring that each precursor is fully dissolved and forms a uniform and stable precursor solution; at the same time, both have excellent volatility, which perfectly matches the rapid drying and molding process requirements of spray drying, and there are no harmful residues after drying, effectively avoiding adverse effects on the electrochemical performance of the subsequent battery; the water-ethanol mixed solvent can also be flexibly adjusted in proportion according to actual process requirements to achieve precise control of the system's solubility and drying rate, adapting to the process requirements of different types of metal salt precursors.

[0014] As a further description of the above technical solution: the precursor solution in step S1 has a solid content of 10-15 wt%, which can balance the fluidity of the solution and the forming efficiency. It can ensure that the precursor solution has good atomization performance, avoid atomization blockage and droplet agglomeration due to excessive concentration, and also prevent excessively low concentration from causing increased drying energy consumption and poor particle forming. At the same time, it can precisely control the particle size and tap density of the final spherical composite particles, ensuring the stability of the product morphology and structural properties.

[0015] As a further description of the above technical solution: the D50 of the atomized droplets in the spray drying in step S2 is 20-100 μm. This droplet size is highly compatible with the temperature field of spray drying, which can ensure that the metal salt precursor in the droplet is fully converted and uniformly composited with lithium oxalate in situ. At the same time, the particle size and distribution of the final spherical composite particles can be precisely controlled, effectively avoiding the problem of insufficient drying caused by excessively large droplets and particle agglomeration caused by excessively small droplets, ensuring that the obtained product has high sphericity and regular and uniform morphology.

[0016] As a further description of the above technical solution: Step S3 involves annealing the spherical composite powder under an inert atmosphere at a temperature of 200–400°C for 0.5–2 hours. This annealing step promotes the improvement of the catalyst's crystal phase and crystallinity, enhances the interfacial bonding strength between the catalyst and the lithium oxalate matrix, and removes residual trace solvents and organic impurities from the powder. This further optimizes the crystal structure and surface state of the composite lithium supplement, improving its catalytic activity and electrochemical stability. Furthermore, the mild annealing process does not cause lithium oxalate decomposition, ensuring the effective lithium supplement capacity of the supplement.

[0017] This invention also provides a spherical lithium oxalate@catalyst composite lithium supplement prepared by the above-described method, using lithium oxalate as a matrix, wherein nanoscale catalysts are uniformly dispersed within the lithium oxalate matrix. The nanoscale catalysts are metal oxides, carbon composites, or a combination of both with a particle size of 5–50 nm. The composite lithium supplement consists of regular spherical particles with a particle size D50 of 5–50 μm and a tap density ≥1.2 g / cm³. 3 The highly uniform dispersion of nanoscale catalysts within the lithium oxalate matrix forms a strongly coupled catalytic interface, significantly reducing the decomposition energy barrier of lithium oxalate, lowering its decomposition potential to 3.68–3.95 V (vs. Li). + The NCM811 system utilizes a lithium-ion battery ( / Li) catalyst to achieve highly efficient triggering of the lithium replenishment reaction. Lithium-ion batteries using this catalyst can achieve an initial charge efficiency of over 89.6%, with the NCM811 system even reaching 94.8% for the first half-cell. The high sphericity, narrow particle size distribution, and high tap density significantly improve the mixing uniformity of the lithium replenishment catalyst and cathode material, as well as the electrode coating processability, resulting in a significant reduction in electrode cracking rate after rolling. Furthermore, the carbon composite catalyst simultaneously enhances the system's conductivity and accelerates interfacial ion and electron transport, enabling the battery to achieve a charge efficiency of 3.5 mAh / cm³. 2 The capacity release efficiency under high surface capacity is ≥95.5%, and the cycle stability is significantly improved. The capacity retention rate after 100 cycles is at least 15 percentage points higher than that of the control group.

[0018] This invention also provides the application of the above-mentioned spherical lithium oxalate@catalyst composite lithium replenisher as a cathode additive in the preparation of lithium-ion battery cathode sheets. The lithium replenisher is added to the cathode sheet system at 5-12% of the mass of the cathode active material. It can be efficiently adapted to mainstream cathode active materials such as high-nickel ternary and lithium iron phosphate. With its excellent lithium replenishment performance and interfacial catalytic effect, it can significantly improve the first charging efficiency, capacity release efficiency under high areal capacity, and cycle stability of lithium-ion batteries. At the same time, its high sphericity and high tap density characteristics have good compatibility with cathode slurry and do not affect the coating, rolling and other processing technology of the electrode sheet. It can be directly integrated into the existing industrial preparation process of lithium-ion battery cathodes, and has the dual advantages of performance improvement and process adaptation.

[0019] This invention prepares spherical lithium oxalate@catalyst composite lithium supplementer through a one-step spray drying method, and applies it as a positive electrode additive in lithium-ion batteries. Compared with existing technologies, it has the following advantages:

[0020] 1. Extremely simple and efficient process, significantly reducing production energy consumption and costs: This invention eliminates the cumbersome processes of catalyst pre-synthesis, separation, and dispersion in the traditional two-step method. It achieves in-situ catalyst generation, in-situ composite with lithium oxalate, and spherical particle formation simultaneously through one-step spray drying. It can also be combined with a mild annealing process to optimize product performance. This process significantly shortens the production cycle, reduces equipment investment, and lowers overall energy consumption by over 60%. Furthermore, the selected metal salt precursor and water / ethanol solvent are readily available and commercially viable. Compared to the traditional two-step TiN-based lithium supplement, the estimated cost of the product from this invention is only 0.7 to 0.8 times higher, combining economic efficiency with high production efficiency, making it more suitable for large-scale industrial production.

[0021] 2. Excellent material structure, improving processing performance and composite uniformity: The composite lithium supplement prepared by this invention consists of regular spherical particles with a spherical integrity rate of over 94%, a particle size D50 of 5–50 μm with narrow distribution, and a tap density ≥1.2 g / cm³. 3 Its high sphericity and high tap density ensure excellent mixing uniformity with cathode materials and good compatibility with cathode slurry. After rolling, the crack rate of the electrode sheet is reduced by 50%, without affecting existing processing techniques such as electrode coating and rolling. At the same time, the 5-50 nm nano-scale catalyst is highly uniformly dispersed in the lithium oxalate matrix without agglomeration, forming a strong coupled catalytic interface with lithium oxalate. This avoids the problem of insufficient exposure of active sites caused by uneven catalyst dispersion in traditional processes, laying a structural foundation for improving electrochemical performance.

[0022] 3. Outstanding catalytic performance, significantly optimizing core electrochemical indicators of the battery: The strong coupling interface between the nanoscale catalyst and lithium oxalate significantly reduces the decomposition energy barrier of lithium oxalate, decreasing its decomposition potential from >4.5 V for pure lithium oxalate to 3.68–3.95 V (vs. Li). + / Li), adapted to the charging and discharging potential range of the positive electrode of lithium-ion batteries, to achieve efficient triggering of the lithium replenishment reaction. Test results show that the battery equipped with the lithium replenishment agent of this invention has an initial charging efficiency of ≥89.6%, with the Ni / Co bimetallic system achieving an initial efficiency of 94.8% for half-cells and 91.2% for full-cells, far superior to the 89.5% and 86.0% for half-cells and full-cells respectively of the traditional two-step TiN-based lithium replenishment agent, and significantly exceeding the 78.0% of the blank group without lithium replenishment agent; and at 3.5 mAh / cm²... 2 With high surface area capacity, the battery capacity release efficiency is ≥95.5%, solving the industry pain point of insufficient capacity release under high surface area capacity.

[0023] 4. Excellent cycle stability and compatibility with mainstream cathode material systems: The carbon composite catalyst (such as FeOx@C) in this invention can simultaneously improve the conductivity of the lithium replenisher and electrode system, accelerate ion and electron transport at the electrode interface, and, combined with the efficient catalytic effect of the catalyst, significantly improve the cycle performance of the battery. Test results show that the capacity retention rate of the battery with the lithium replenisher of this invention after 100 cycles is 88.1% to 90.8%, which is at least 15 percentage points higher than the blank group. Among them, the iron ammonium citrate (NH4Fe(C6H5O7)2·2H2O) system reaches 90.8%, and the Ni / Co bimetallic system reaches 90.0%, which is far superior to the 85.2% of the traditional two-step method and the 76.5% of the blank group. At the same time, the lithium replenisher is added at 5-12% of the mass of the cathode active material, which can be efficiently adapted to mainstream cathode materials such as high-nickel ternary (NCM811) and lithium iron phosphate, without system compatibility limitations, and has a wide range of applications.

[0024] 5. Environmentally friendly and with high product purity, no adverse residues: This invention uses water, ethanol, or mixtures thereof as solvents, eliminating the risk of contamination from highly polar organic solvents such as NMP. The solvents are also volatile and leave no harmful residues after drying. Spray drying and annealing are both carried out under an inert atmosphere, preventing oxidation of the active metal components and ensuring high catalytic activity. Simultaneously, the annealing process removes trace amounts of residual solvents and organic impurities from the powder, further improving product purity. Furthermore, the ferric ammonium citrate system can generate a carbon-coated structure in situ, eliminating the need for additional conductive agents and further simplifying the positive electrode preparation process, thus balancing environmental friendliness and product performance. Attached Figure Description

[0025] Figure 1 This is a SEM image of the lithium oxalate@NiO composite lithium supplement prepared in Example 1.

[0026] Figure 2 The image shows the XPS spectrum of the lithium oxalate@Co3O4 composite lithium supplement prepared in Example 2.

[0027] Figure 3 This is an EDS mapping image of the lithium oxalate@NiCo2O4 composite lithium supplement prepared in Example 3. Detailed Implementation

[0028] The present invention will be further described in detail below with reference to specific embodiments. The described embodiments are only for explaining the present invention and are not intended to limit the scope of protection of the present invention. Experimental methods in the present invention that do not specify specific conditions are all conventional methods; the raw materials used, unless otherwise specified, are all commercially available conventional raw materials.

[0029] Example 1: Lithium oxalate@NiO composite lithium supplement

[0030] Its preparation method includes the following steps:

[0031] S1. Weigh 10.0 g of lithium oxalate (Li2C2O4, purity 99.5%) and 1.45 g of nickel nitrate hexahydrate (Ni(NO3)2·6H2O, purity 99.9%) (molar ratio of Ni to Li2C2O4 is 0.05:1), dissolve in 100 mL of deionized water, stir magnetically for 1 h and sonicate for 30 min to mix thoroughly and evenly, to obtain a homogeneous blue-green precursor solution with a solid content of about 10.3 wt%.

[0032] S2. Under a nitrogen atmosphere, the obtained precursor solution was spray-dried using a centrifugal spray dryer. The inlet temperature was set to 260℃, the outlet temperature to 105℃, the atomizing disc speed to 20000 rpm, the feed rate to 20 mL / min, and the D50 of the atomized droplets was 80 μm. During the spray drying process, nickel nitrate hexahydrate was simultaneously pyrolyzed and converted into highly active NiO nanoparticles, which were then combined in situ with lithium oxalate to form regular spherical composite particles.

[0033] S3. Collect the spherical composite particles and anneal them at 300℃ for 1 hour under a nitrogen atmosphere to obtain light green lithium oxalate@NiO composite lithium supplementary agent spherical powder. The tap density of the composite lithium supplementary agent was measured to be 1.28 g / cm³. 3 .

[0034] Micromorphological characterization

[0035] The prepared lithium oxalate@NiO composite lithium supplement was tested by scanning electron microscopy (SEM), and the results are as follows: Figure 1 As shown, the lithium oxalate@NiO composite lithium supplement prepared in this embodiment exhibits a regular near-spherical morphology with high sphericity and a sphericity integrity rate of ≥94%. The surface shows no obvious depressions, cracks, or breakage. There is no significant adhesion between particles, indicating good dispersibility. The particle size distribution is uniform, mainly concentrated in the 10–30 μm range, without obvious large particle agglomeration or excessive dispersion of small particles. This demonstrates the precise controllability of the spray drying process on particle morphology and its high matching degree with atomized droplet parameters, ensuring the uniformity of product particle size. The particle surface is generally smooth, with only a small amount of flocculent / particulate matter locally attached. This matter is the in-situ generated NiO catalyst precursor or its pyrolysis product, which is tightly bound to the lithium oxalate matrix without obvious agglomeration. This indicates that the Ni component is uniformly distributed in the lithium oxalate matrix, laying a good structural foundation for subsequent efficient catalytic decomposition of lithium oxalate and improvement of battery electrochemical performance.

[0036] Example 2: Lithium oxalate@Co3O4 composite lithium supplement

[0037] Its preparation method includes the following steps:

[0038] S1. Weigh 10.0 g of lithium oxalate and 1.75 g of cobalt chloride hexahydrate (CoCl2·6H2O) (the molar ratio of Co to Li2C2O4 is 0.075:1), dissolve them in 100 mL of deionized water, stir magnetically for 1 h and sonicate for 30 min to obtain a precursor solution with a solid content of about 10.5 wt%.

[0039] S2. Under a nitrogen atmosphere, the obtained precursor solution was spray-dried using a centrifugal spray dryer. The inlet temperature was set to 250℃, the outlet temperature to 100℃, the atomizing disc speed to 20000 rpm, the feed rate to 20 mL / min, and the D50 of the atomized droplets was 60 μm. During the spray drying process, cobalt chloride hexahydrate was simultaneously pyrolyzed into highly active Co3O4 nanoparticles, which were then uniformly combined with lithium oxalate in situ to form spherical composite particles.

[0040] S3. Collect the spherical composite particles to obtain a grayish-black lithium oxalate@Co3O4 composite lithium supplement spherical powder. The tap density of this composite lithium supplement was measured to be 1.25 g / cm³. 3 .

[0041] Interface electronic structure characterization

[0042] The prepared lithium oxalate@Co3O4 composite lithium supplement was tested by X-ray photoelectron spectroscopy (XPS), and the results are as follows: Figure 2 As shown. By Figure 2 The high-resolution scanning spectrum of Cl 2p shows that no corresponding Cl appears in the binding energy range of 198–200 eV. - Characteristic peaks (standard Cl 2p) 3 / 2 Binding energy approximately 198.2 eV, Cl 2p 1 / 2 The presence of only background noise (approximately 199.8 eV) indicates that the Cl element in the precursor cobalt chloride hexahydrate was completely decomposed and removed after the spray drying pyrolysis process, and no Cl was found in the final product. - The absence of residual halogen impurities fundamentally avoids the adverse effects of halogen impurities on the electrochemical performance of lithium-ion batteries (such as SEI film stability and cycle life), fully ensuring the high purity and electrochemical safety of the lithium replenishment agent. Simultaneously, this result further confirms the highly efficient pyrolysis conversion capability of the spray drying process: under process conditions of 250℃ inlet temperature and 100℃ outlet temperature, CoCl2·6H2O can be completely pyrolyzed into a highly active Co3O4 nanocatalyst, and the Cl element is completely removed in volatile forms such as HCl, eliminating the need for additional acid washing, washing, or other purification steps. This significantly simplifies the preparation process, reduces process costs and environmental burden, and provides solid process feasibility support for the large-scale industrial production of lithium replenishment agents.

[0043] The lithium oxalate@Co3O4 composite lithium supplement prepared in this embodiment also exhibits a regular spherical morphology with uniform particle size distribution, a D50 particle size of 16 μm, a spherical integrity rate of 95%, and no obvious agglomeration. The binding density is 1.25 g / cm³. 3 Its high tap density gives it good processing performance and dispersibility, providing structural support for efficient lithium replenishment.

[0044] Example 3: Lithium oxalate@NiCo2O4 composite lithium supplement

[0045] Its preparation method includes the following steps:

[0046] S1. Weigh 10.0 g of lithium oxalate, 0.73 g of nickel nitrate hexahydrate (Ni(NO3)2·6H2O, purity 99.9%), and 0.73 g of cobalt nitrate hexahydrate (Co(NO3)2·6H2O, purity 99.9%) (the molar ratio of Ni:Co:Li2C2O4 is 0.026:0.026:1), dissolve them in 100 mL of a mixed solvent of deionized water and ethanol (1:1), stir magnetically for 1 h and sonicate for 30 min to obtain a precursor solution with a solid content of about 11.4 wt%.

[0047] S2. Under a nitrogen atmosphere, the obtained precursor solution was spray-dried using a centrifugal spray dryer. The inlet temperature was set to 260℃, the outlet temperature to 105℃, the atomizing disc speed to 20000 rpm, the feed rate to 20 mL / min, and the D50 of the atomized droplets to be spray-dried to 100 μm. During the spray drying process, nickel nitrate hexahydrate and cobalt nitrate hexahydrate were simultaneously pyrolyzed and underwent solid-phase reaction, transforming into highly active NiCo2O4 spinel-type nanoparticles, which were then uniformly combined with lithium oxalate in situ to form spherical composite particles.

[0048] S3. Collect the spherical composite particles and anneal them at 300℃ for 1 hour under a nitrogen atmosphere to promote the perfection of the NiCo2O4 crystal phase and the strengthening of the interface bonding, remove trace amounts of residual solvent and nitrate impurities, and obtain gray-green lithium oxalate@NiCo2O4 composite lithium supplementary spherical powder. The tap density of this composite lithium supplementary agent was measured to be 1.29 g / cm³. 3 .

[0049] Microscopic morphology and elemental distribution characterization

[0050] The elemental distribution of the prepared lithium oxalate@NiCo2O4 composite lithium supplement was analyzed by energy-dispersive X-ray spectroscopy (EDS), and the results are as follows: Figure 3 As shown. By Figure 3The EDS elemental distribution maps show that Ni, Co, and O are uniformly dispersed throughout the lithium oxalate matrix, without local enrichment or agglomeration. The distribution areas of Ni and Co completely overlap, and their distribution is highly matched with that of O, directly confirming the successful synthesis of the NiCo₂O₄ spinel-type bimetallic oxide. Furthermore, the nano-sized NiCo₂O₄ particles are uniformly attached to the lithium oxalate matrix surface, forming a stable interfacial bond and effectively avoiding the catalytic efficiency reduction caused by the agglomeration of active components. Simultaneously, the uniform dispersion of C corresponds to the carbon skeleton in the lithium oxalate matrix, further improving the electronic conductivity of the lithium supplement and providing structural support for subsequent electrochemical performance optimization.

[0051] Example 4: Lithium oxalate@FeOx@C composite lithium supplement

[0052] Its preparation method includes the following steps:

[0053] S1. Weigh 10.0 g of lithium oxalate and 3.0 g of ferric ammonium citrate (NH4Fe(C6H5O7)2·2H2O) (the molar ratio of Fe to Li2C2O4 is 0.06:1), dissolve them in 100 mL of anhydrous ethanol, stir magnetically for 1 h and sonicate for 30 min to obtain a precursor solution with a solid content of about 14.1 wt%.

[0054] S2. Under a nitrogen atmosphere, the obtained precursor solution was spray-dried using a centrifugal spray dryer. The inlet temperature was set to 280℃, the outlet temperature to 110℃, the atomizing disc speed to 20000 rpm, the feed rate to 20 mL / min, and the D50 of the atomized droplets was 50 μm. During the spray drying process, ferric ammonium citrate was simultaneously pyrolyzed into highly active FeOx nanoparticles that were embedded in the amorphous carbon matrix and uniformly combined with lithium oxalate in situ to form spherical composite particles.

[0055] S3. Collect the spherical composite particles and anneal them at 400℃ for 1.5 hours under a nitrogen atmosphere to promote carbonization, obtaining black lithium oxalate@FeOx@C composite lithium supplementary agent spherical powder. The tap density of this composite lithium supplementary agent was measured to be 1.32 g / cm³. 3 .

[0056] The lithium oxalate@FeOx@C composite lithium supplement prepared in this embodiment maintains a regular spherical morphology, with uniform particle size distribution, a D50 particle size of 20 μm, a spherical integrity rate of 94%, and no obvious agglomeration; 1.32 g / cm³ 3 The tap density is higher than that of other embodiments. This is due to the dense structure formed by the carbon matrix coating and annealing process, which not only improves the fluidity and processing performance of the lithium replenishment agent, but also further optimizes the mixing uniformity with the cathode material. Combined with the conductivity advantage of the carbon matrix, it provides a dual structural guarantee for improving lithium replenishment efficiency and cycle stability.

[0057] Comparative Example 1: Lithium oxalate@TiN composite lithium supplement

[0058] The traditional two-step method is used for preparation, and the specific steps are as follows:

[0059] First, TiN nanoparticles were pre-synthesized via a hydrothermal-ammoniation method. The synthesis process was as follows: using tetrabutyl titanate as the titanium source, TiO2 nanoparticle precursors were prepared via a hydrothermal reaction, with the precursor particle size controlled at 70±10 nm. The TiO2 nanoparticle precursors were thoroughly mixed with urea at a molar ratio of 1:3 and placed in a tube furnace. Under the protection of high-purity argon, the temperature was increased to 800 °C at a heating rate of 5 °C / min, and held for annealing for 3 h to achieve in-situ nitridation. After natural cooling to room temperature, the particles were washed and dried to obtain TiN nanoparticles with a particle size precisely controlled at 80±10 nm. Subsequently, 0.8 g of the pre-synthesized TiN nanoparticles were weighed and dispersed in an aqueous solution containing 10 g of lithium oxalate. 0.1 g of dispersant PVP was added, and the mixture was ultrasonically dispersed for 30 min and magnetically stirred for 1 h. Then, it was treated with a spray drying process completely consistent with Example 1 to finally obtain lithium oxalate@TiN composite lithium supplement powder.

[0060] Electrochemical performance testing

[0061] The composite lithium supplements prepared in Examples 1-4 and the comparative examples were added to the NCM811 cathode system at 10% of the mass of the positive electrode active material. A pure NCM811 electrode without lithium supplements was set up as a blank control group. Electrochemical performance was compared between CR2032 coin cell half-cells and full cells. All cells were tested at a constant temperature of 25°C, with a voltage range of 2.8–4.3 V, a linear sweep voltammetry (LSV) scan rate of 0.1 mV / s, and a 0.5 C / 0.5 C charge / discharge regime. The positive electrode areal capacity was 3.5 mAh / cm². 2 The test indicators include lithium oxalate decomposition potential, first efficiency of half cell, first efficiency of full cell, capacity release efficiency, and capacity retention rate after 100 cycles.

[0062] The test results are shown in Table 1. The electrochemical performance test results show that the composite lithium replenishing agents of each embodiment of the present invention are significantly superior to the comparative and blank groups in terms of overall electrochemical performance. Specifically, the lithium oxalate decomposition potential of each embodiment is stable within the range of 3.68–3.95 V, significantly lower than the 4.15 V of the comparative example, making it more suitable for the charging and discharging potential range of conventional lithium-ion batteries. This allows for gentle and sufficient triggering of the lithium replenishment reaction during the first charge, effectively avoiding the problems of insufficient lithium replenishment or aggravated side reactions caused by excessively high decomposition potentials. The first-time efficiency of the half-cell reaches 92.5%–94.8%, and the first-time efficiency of the full-cell reaches 89.6%–91.2%, an improvement of more than 15 percentage points compared to the blank group and 3–5 percentage points compared to the comparative example. This is attributed to the strong coupling catalytic interface formed by the in-situ uniform dispersion of the catalyst in the lithium oxalate matrix, which effectively reduces the irreversible loss of active lithium and improves the lithium replenishment efficiency. At 3.5 mAh / cm³, the efficiency is significantly improved. 2 Under high areal capacity conditions, the capacity release efficiency of each embodiment is higher than 95.5%, reaching a maximum of 97.1%, which is far superior to the 91.3% of the comparative example and the 88.6% of the blank group. This successfully solves the industry pain point of limited ion transport and difficulty in fully utilizing capacity in high-load electrode sheets. After 100-cycle testing, the capacity retention rate of the battery in the embodiments is 88.1% to 90.8%, which is significantly better than the 85.2% of the comparative example and the 76.5% of the blank group. This is due to the in-situ composite structure, which makes the catalyst less prone to detachment and agglomeration, and can play a stable catalytic role for a long time. In particular, the carbon matrix of Example 4 and the bimetallic synergistic effect of Example 3 further improve the electrode conductivity and structural stability, effectively suppressing the loss of active lithium and the degradation of electrode structure during cycling. Furthermore, the comparative method, prepared using a traditional two-step process, requires the pre-synthesis of TiN nanoparticles and the addition of PVP dispersant. This method still suffers from problems such as uneven catalyst dispersion and weak interfacial bonding, resulting in significantly inferior lithium replenishment effect and cycle performance compared to the present invention. In contrast, the present invention achieves spheroidization, component homogenization, and in-situ generation of the catalytic phase simultaneously through a single-step spray drying process. This process is simpler, has lower production costs, and offers superior performance, demonstrating significant advantages for industrial applications.

[0063] Table 1 Electrochemical performance test results

[0064]

[0065] In summary, the spherical lithium oxalate@catalyst composite lithium replenisher prepared by this invention can comprehensively improve the overall electrochemical performance of high-nickel ternary lithium-ion batteries and effectively solve the technical pain points of traditional lithium replenishers.

[0066] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them; those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the protection scope of the present invention.

Claims

1. A method for preparing a spherical lithium oxalate@catalyst composite lithium supplementer, characterized in that, Includes the following steps: S1. Lithium oxalate and the metal salt precursor are dissolved in a solvent to form a homogeneous precursor solution, wherein the molar ratio of the metal element to lithium oxalate in the metal salt precursor is (0.05~0.075):

1. S2. Under an inert atmosphere, the precursor solution is spray-dried. The inlet temperature of the spray drying is 200-300°C and the outlet temperature is 80-150°C. During the spray drying process, the metal salt precursor is simultaneously converted into a highly active nano-scale catalyst and combined with lithium oxalate in situ to form spherical composite particles. S3. Collect the spherical composite particles to obtain spherical lithium oxalate@catalyst composite lithium supplementer.

2. The preparation method according to claim 1, characterized in that: The metal salt precursor in step S1 is selected from at least one of transition metal chlorides, transition metal nitrates, or transition metal citrates.

3. The preparation method according to claim 2, characterized in that: The metal salt precursor in step S1 is selected from at least one of nickel nitrate, cobalt nitrate, cobalt chloride, and ferric ammonium citrate.

4. The preparation method according to claim 1, characterized in that: The solvent in step S1 is water, ethanol, or a mixture of water and ethanol.

5. The preparation method according to claim 1, characterized in that: The precursor solution in step S1 has a solid content of 10-15 wt%.

6. The preparation method according to claim 1, characterized in that: The D50 of the atomized droplets in step S2 is 20–100 μm.

7. The preparation method according to claim 1, characterized in that: Step S3 involves annealing the spherical composite particles in an inert atmosphere at a temperature of 200–400°C for 0.5–2 hours.

8. The spherical lithium oxalate@catalyst composite lithium supplementer prepared by the preparation method according to any one of claims 1-7, characterized in that: This composite lithium supplement uses lithium oxalate as a matrix, within which nanoscale catalysts are uniformly dispersed. The nanoscale catalysts are metal oxides, carbon composites, or a combination of both with a particle size of 5–50 nm. The composite lithium supplement consists of regular spherical particles with a particle size D50 of 5–50 μm and a tap density ≥1.2 g / cm³. 3 .

9. The application of the spherical lithium oxalate@catalyst composite lithium supplementer as a positive electrode additive in the preparation of positive electrode sheets for lithium-ion batteries.

10. The application according to claim 9, characterized in that: The amount of the spherical lithium oxalate@catalyst composite lithium supplementer added to the positive electrode of the lithium-ion battery is 5-12% of the mass of the positive electrode active material.

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