Carbon-based catalytic lithium oxalate composite lithium supplement and its application in lithium ion battery

Abstract

This invention discloses a method for preparing a carbon-based catalytic lithium squarate composite lithium supplement and its application in lithium-ion batteries, belonging to the field of lithium-ion battery material technology. The composite lithium supplement is composed of spherical lithium squarate and a carbon-based conductive agent in a mass ratio of 6-8:2-4. The carbon-based conductive agent is one or more of ordered mesoporous carbon (CMK-3), Ketjen black (KB), superconducting carbon black (SP), acetylene black (AB), single-arm carbon nanotubes (SWCNT), and multi-walled carbon nanotubes (MWCNT), and possesses abundant carbon vacancy defects and Zigzag / Armchair carbon boundaries. This lithium supplement is added to lithium-ion batteries as a positive electrode additive, and the addition ratio can be flexibly adjusted according to the positive electrode material system and lithium content. This invention enhances the conductivity and electrochemical activity of lithium squarate through carbon-based catalysis, resulting in a complete decomposition voltage of <4.2V and an initial decomposition capacity of ≥400mAh / g. The preparation process is simple, scalable, and has significant industrial application value.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery material technology, specifically relating to a carbon-based catalytic lithium squaric acid composite lithium replenisher, as well as the preparation method of the composite lithium replenisher and its application in high-energy, high-safety lithium-ion batteries. Background Technology

[0002] As a new generation of green energy storage devices, lithium-ion batteries have become the core energy supply device in aerospace, new energy vehicles, and large-scale electrochemical energy storage due to their advantages such as high energy density, long cycle life, and high charge and discharge efficiency. With the rapid development of various application fields, the market requirements for the energy density, cycle stability, and safety performance of lithium-ion batteries continue to rise, especially in aerospace power supplies and high-end new energy vehicles, which have put forward stringent industry standards for the specific energy and cycle life of batteries.

[0003] Pre-lithiation technology is a core method to compensate for the irreversible loss of active lithium during the first charge-discharge cycle of lithium-ion batteries. Among them, self-sacrificial lithium replenishing agents have become the mainstream research direction of pre-lithiation technology due to their characteristics such as no residual decomposition products, no negative impact on the battery system, and excellent environmental stability. Lithium squartz oxide, as a carbon oxide-based self-sacrificial lithium replenishing agent, has outstanding advantages such as high theoretical specific capacity, decomposition products of only CO2, and good water and oxygen stability, making it a lithium replenishing material with great prospects for industrial application. However, lithium squartz oxide itself is an insulator with poor intrinsic conductivity and low electrochemical activity. It also suffers from problems such as high decomposition activation voltage, slow decomposition kinetics, and limited lithium replenishment efficiency, which makes it difficult to fully utilize its lithium replenishment performance and meet the application requirements of high-energy-density lithium-ion batteries.

[0004] To improve the electrochemical performance of lithium squartz oxide, existing technologies often employ simple compounding of conductive agents to enhance its conductivity. However, traditional conductive agents exhibit poor interfacial bonding with lithium squartz oxide, achieving only physical mixing without forming effective electron transport channels. Furthermore, they fail to catalyze the decomposition reaction of lithium squartz oxide, resulting in persistently high decomposition voltages in the composite system. This voltage window is incompatible with mainstream cathode materials such as ternary and lithium iron phosphate, hindering the full release of lithium replenishment capacity. Meanwhile, carbon-based materials are currently the most widely used conductive agents in lithium squartz oxide replenishment systems. However, the microstructure, defect types, and contents of different carbon-based materials vary significantly. The catalytic mechanism of their defect sites and carbon boundary structures in the lithium squartz oxide decomposition reaction remains unclear. The industry struggles to accurately screen carbon matrices and optimize composite formulations. Additionally, traditional composite processes lack effective control over dispersibility, leading to particle agglomeration and phase separation, further reducing the electrochemical performance of the replenishment system.

[0005] Furthermore, existing lithium squartz oxide (LSO) supplementary lithium agents suffer from poor adaptability. Their fixed addition ratios for different cathode material systems prevent flexible adjustments based on the lithium content, structural characteristics, and actual battery application requirements of the cathode material. This easily leads to insufficient or excessive lithium supplementation. Insufficient supplementation results in low initial efficiency and energy density failing to meet design requirements, while excessive supplementation wastes materials and may even trigger side reactions, affecting the battery's cycle stability and safety. Therefore, developing a carbon-based catalytic lithium squartz oxide composite supplementary lithium agent, through precise screening of highly efficient carbon-based conductive agents with specific defect structures, and optimizing the composite process to achieve a tight bond and synergistic effect between the two, reducing the decomposition voltage of LSO and improving supplementary lithium efficiency, while simultaneously designing flexible addition adaptation schemes, has become a key technological bottleneck for promoting the large-scale application of high-energy-density lithium-ion batteries in high-end fields. Summary of the Invention

[0006] The technical problem to be solved by this invention is to overcome the defects of existing lithium squartz oxide lithium replenishment agents, such as poor conductivity, high decomposition voltage, low lithium replenishment efficiency, poor synergistic effect with conductive agents, fixed addition ratio, and poor compatibility. This invention provides a carbon-based catalytic lithium squartz oxide composite lithium replenishment agent, its preparation method, and its application. Through carbon-based catalysis, the electrochemical performance of lithium squartz oxide is synergistically improved, achieving high-efficiency lithium replenishment at low voltage. At the same time, a flexible addition scheme is designed to improve the compatibility of the lithium replenishment agent with different cathode material systems, further improving the energy density, cycle stability, and safety of lithium-ion batteries.

[0007] This invention is achieved through the following technical solution:

[0008] This invention provides a carbon-based catalytic lithium squarate composite lithium supplement, which is composed of lithium squarate and a carbon-based conductive agent in a mass ratio of 6-8:2-4. The carbon-based conductive agent is one or more of ordered mesoporous carbon (CMK-3), Ketjen black (KB), superconducting carbon black (SP), acetylene black (AB), single-arm carbon nanotubes (SWCNT), and multi-walled carbon nanotubes (MWCNT). The carbon-based conductive agent has abundant carbon vacancy defects and Zigzag / Armchair carbon boundaries, which are obtained through DFT calculations. The carbon vacancy defects can effectively adsorb lithium squarate molecules and reduce the energy barrier of the decomposition reaction, while the Zigzag / Armchair carbon boundaries can construct efficient electron transport channels and promote rapid electron transfer. The synergistic effect of the two enables low-voltage and high-efficiency decomposition of lithium squarate, solving the problem of slow decomposition kinetics of pure lithium squarate.

[0009] Preferably, the lithium squarate is in the form of nanospheres with a particle size of 2-10 μm and a first-week decomposition capacity of ≥400 mAh / g. This nanosphere morphology can significantly increase the contact area between lithium squarate and carbon-based conductive agent, enhance the interfacial bonding between the two, and further improve the catalytic efficiency and electrochemical performance of the composite system.

[0010] Preferably, the composite lithium replenishing agent is a spherical powder with a complete decomposition voltage of <4.2 V, a first-week decomposition capacity of ≥400 mAh / g, and a lithium replenishment efficiency that is more than 30% higher than that of pure lithium squartz. It is fully compatible with the voltage windows of mainstream lithium-ion battery cathode material systems such as ternary lithium and lithium iron phosphate, and has no compatibility issues.

[0011] This invention also provides a method for preparing the above-mentioned carbon-based catalytic lithium squaric acid composite lithium supplement, comprising the following steps:

[0012] Pretreatment of carbon-based conductive agent: The carbon-based conductive agent is calcined at 500-700℃ for 2-4 hours in an inert gas atmosphere (nitrogen or argon) to remove adsorbed impurities and amorphous carbon on the surface of the carbon-based conductive agent, enhance the activity of defect sites on the surface of the carbon-based conductive agent, and improve its catalytic performance for the decomposition reaction of lithium squaric acid. After natural cooling, it is ready for use.

[0013] Preparation of composite slurry: Add 20% by mass of carbon-based conductive agent and CMC dispersant to deionized water. Mix the nano-spherical lithium squarate and the pretreated carbon-based conductive agent in deionized water at a mass ratio of 6-8:2-4. Mechanically stir at 300-500 r / min for 4-6 h to obtain a uniformly dispersed composite slurry. The dispersant CMC can effectively prevent the agglomeration of lithium squarate and carbon-based conductive agent during the mixing process, ensuring full contact and uniform dispersion of the two.

[0014] Drying and molding: The composite slurry is spray-dried with the following process parameters: feed rate 10-20 mL / min, inlet temperature 180-200 ℃, and outlet temperature 80-100 ℃, to obtain a pre-dried composite powder. The powder is then dried in a vacuum oven at 120 ℃ for 12 h to completely remove moisture and residual solvent from the powder, resulting in carbon-based catalytic lithium squaric acid composite lithium supplementer spherical powder.

[0015] This invention also provides the application of the above-mentioned carbon-based catalytic lithium squaric acid composite lithium replenisher in lithium-ion batteries. The composite lithium replenisher powder is added as a positive electrode additive to the positive electrode slurry of a lithium-ion battery and coated into an electrode sheet. It is then assembled with a silicon-based or graphite-based negative electrode, electrolyte, and separator to form a lithium-ion battery. The addition ratio of the composite lithium replenisher can be flexibly adjusted according to the positive electrode material system of the lithium-ion battery, the lithium content of the positive electrode material, and the actual application requirements of the battery to achieve precise lithium replenishment and avoid the problems of insufficient or excessive lithium replenishment.

[0016] Beneficial effects

[0017] The positive and progressive effects of this invention are as follows:

[0018] (1) This invention uses DFT calculations to accurately screen carbon-based conductive agents with abundant carbon vacancy defects and Zigzag / Armchair carbon boundaries, and combines them with nano-spherical lithium squartz at the optimal mass ratio. The carbon vacancy defects and carbon boundary structures synergistically catalyze the decomposition of lithium squartz, reducing the complete decomposition voltage of the composite lithium replenishment agent to <4.2 V, increasing the lithium replenishment efficiency by more than 30%, and achieving a first-week decomposition capacity of ≥400 mAh / g. This solves the core problems of poor conductivity, high decomposition voltage, and low lithium replenishment efficiency of existing lithium squartz replenishment agents, and is fully compatible with mainstream cathode material systems.

[0019] (2) This invention optimizes the preparation process of carbon-based catalytic lithium squaric acid composite lithium supplement. The catalytic activity is enhanced by calcination pretreatment of carbon-based conductive agent, and the addition of dispersant CMC ensures uniform dispersion and tight bonding of lithium squaric acid and carbon-based conductive agent. Spherical composite powder is obtained by spray drying, which effectively avoids particle agglomeration, phase separation and other phenomena, improves the electrochemical performance and structural stability of composite lithium supplement, and the product batch consistency is good.

[0020] (3) When the composite lithium replenishing agent of the present invention is used as a positive electrode additive in lithium-ion batteries, it abandons the design of fixed addition ratio. The addition ratio can be flexibly adjusted according to the positive electrode material system, lithium content and actual application requirements of the battery to achieve precise lithium replenishment, avoid the problem of insufficient or excessive lithium replenishment, improve the application adaptability of the lithium replenishing agent, and is suitable for different types of lithium-ion battery systems.

[0021] (4) The decomposition product of the composite lithium replenishment agent of the present invention is only CO2. Some of the CO2 can be dissolved in the electrolyte to inhibit the thermal decomposition and oxidation of the electrolyte, improve the stability and flame retardancy of the battery system, and the decomposition leaves no residue and will not have a negative impact on the electrochemical reaction of the lithium-ion battery. After addition, it can effectively make up for the irreversible loss of active lithium in the first cycle of the battery, and significantly improve the energy density, cycle stability and safety performance of the lithium-ion battery.

[0022] (5) The composite lithium supplement preparation process of the present invention is simple, convenient to operate, and the raw material cost is controllable. It can achieve continuous large-scale production at the kilogram level and is fully compatible with the existing lithium-ion battery preparation process. It does not require modification of existing production equipment and can be directly integrated into the positive electrode preparation process of lithium-ion batteries. It is suitable for high-energy and high-safety lithium-ion batteries in aerospace, new energy vehicles, large-scale energy storage and other fields, and has significant industrial application value and broad market prospects.

[0023] Industrial application

[0024] The carbon-based catalytic lithium squaric acid composite lithium supplement of the present invention has a simple preparation process, convenient operation, and controllable raw material costs. It can achieve continuous large-scale production at the kilogram level, and the product batches have good stability and high consistency. The composite lithium supplement is fully compatible with the existing lithium-ion battery preparation process, without the need to modify existing production equipment, and can be directly integrated into the positive electrode preparation process of lithium-ion batteries, reducing the modification cost for industrial applications.

[0025] The lithium-ion battery with the addition of the composite lithium replenisher of this invention shows significant improvements in initial efficiency, energy density, cycle life, and safety performance. Furthermore, the addition ratio of the lithium replenisher can be flexibly adjusted according to the cathode material system, lithium content, and actual application requirements of the battery, making it highly adaptable. It can meet the differentiated needs of high-energy and high-safety lithium-ion batteries in various high-end fields such as aerospace, new energy vehicles, and large-scale electrochemical energy storage. It solves the technical bottleneck of existing lithium squaric acid lithium replenishers in high-end lithium-ion battery applications and has broad prospects for industrial application and significant market value.

[0026] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of the present invention is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, but all such changes and modifications fall within the scope of protection of the present invention. Detailed Implementation

[0027] Example 1

[0028] Pretreatment of carbon-based conductive agent: Ordered mesoporous carbon (CMK-3) was selected as the carbon-based conductive agent and placed in a calcination furnace under nitrogen atmosphere. It was calcined at 600 ℃ for 3 h to remove surface adsorbed impurities and amorphous carbon, enhance the activity of surface defect sites, and then allowed to cool naturally before use.

[0029] Preparation of composite slurry: 20% CMC dispersant of CMK-3 was added to deionized water. Nano-spherical lithium squartz (particle size 2-10 μm) and pretreated CMK-3 were added to deionized water at a mass ratio of 7:3. The mixture was mechanically stirred at 400 r / min for 4 h to obtain a uniformly dispersed composite slurry.

[0030] Drying and Shaping: The composite slurry was fed into a spray dryer with the following process parameters set: feed rate 12 mL / min, inlet temperature 190 ℃, and outlet temperature 90 ℃. Spray drying yielded a composite powder, which was then dried in a vacuum oven at 120 ℃ for 12 h to obtain spherical powder of a carbon-based catalytic lithium squaric acid composite lithium supplement. Morphology and structural characterization of the composite lithium supplement are shown in the appendix. Figure 1 , attached Figure 2 .

[0031] Battery preparation and testing: The above-mentioned composite lithium supplement powder was used as a positive electrode additive. The addition ratio was adjusted according to the lithium content of the ternary positive electrode material NCM811 and the battery design requirements. It was then added to the NCM811 positive electrode slurry and ground evenly. The mixture was then coated onto carbon-coated aluminum foil, vacuum dried at 120 ℃ for 24 h, rolled, and cut into electrode sheets with a diameter of 1.2 cm (loading 2 mg / cm). 2 The positive electrode, along with the silicon-carbon negative electrode, electrolyte (EC / EMC=1:1, 1 mol / L LiPF6, 2% VC+5wt% FEC), and separator, is assembled into a CR2032 coin cell.

[0032] Performance Testing: The battery's first-cycle charge / discharge voltage window is 2.5-4.2 V, and subsequent cycles are 2.5-4.0 V. Tested using the LAND battery testing system, the composite lithium replenisher exhibits a first-cycle decomposition capacity of 435 mAh / g and a complete decomposition voltage of 4.18 V, representing a 32% improvement in lithium replenishment efficiency compared to pure lithium squartz. The battery achieves 96.2% initial efficiency, and the discharge voltage after cycling is 3.58 V, showing no significant capacity decay and excellent cycle stability. The battery's first-cycle charge / discharge curves are attached. Figure 3 .

[0033] Example 2

[0034] Pretreatment of carbon-based conductive agent: Ketjen black (KB) was selected as the carbon-based conductive agent and placed in an argon atmosphere calcination furnace at 550℃ for 3.5h to remove surface adsorbed impurities and amorphous carbon. After natural cooling, it was ready for use.

[0035] Preparation of composite slurry: Add 20% by mass of KB dispersant CMC to deionized water, add nano-spherical lithium squartz (particle size 2-10 μm) and pretreated KB to deionized water at a mass ratio of 8:2, and mechanically stir at 350 r / min for 5 h to obtain a uniformly dispersed composite slurry.

[0036] Drying and Shaping: The composite slurry was fed into a spray dryer with the following process parameters set: feed rate 15 mL / min, inlet temperature 185℃, and outlet temperature 85℃. Spray drying yielded a composite powder, which was then dried in a vacuum oven at 120℃ for 12 h to obtain spherical powder of a carbon-based catalytic lithium squaric acid composite lithium supplement. The morphology and structural characterization of the composite lithium supplement are shown in the appendix. Figure 4 , attached Figure 5 .

[0037] Battery preparation and testing: The above-mentioned composite lithium supplement powder was used as a positive electrode additive. The addition ratio was adjusted according to the lithium content of the lithium iron phosphate positive electrode material and the battery design requirements. It was added to the lithium iron phosphate positive electrode slurry and ground evenly. It was then coated on carbon-coated aluminum foil, vacuum dried at 120 ℃ for 24 h, and rolled to obtain a positive electrode sheet. The positive electrode sheet was then assembled with a graphite negative electrode, electrolyte (EC / EMC=1:1, 1mol / L LiPF6, 2% VC+5wt% FEC), and separator to form a soft-pack full cell.

[0038] Performance Testing: Tested using professional equipment, this pouch battery achieved a first-time efficiency of 95.8% and a specific energy of 292 Wh / kg. During simulated high and low temperature cycling, overcharge and over-discharge tests, the battery showed no significant bulging or leakage, demonstrating excellent thermal stability and flame retardancy. Safety performance was significantly improved, meeting the application requirements of high-end new energy vehicles. The formation curve of the pouch battery using KB+Li2C4O4 composite lithium supplement is attached. Figure 6 . Attached Figure Description

[0039] Appendix Figure 1 This is an SEM image of the composite lithium supplement agent from Example 1.

[0040] Appendix Figure 2 This is an SEM image of the composite lithium supplement agent from Example 1.

[0041] Appendix Figure 3 This is the XRD pattern of the composite lithium supplement in Example 1.

[0042] Appendix Figure 4 This is the first charge-discharge curve of the battery in Example 1.

[0043] Appendix Figure 5 This is an SEM image of the composite lithium supplement agent from Example 2.

[0044] Appendix Figure 6 This is an SEM image of the composite lithium supplement agent from Example 2.

[0045] Appendix Figure 7 This is the XRD pattern of the composite lithium supplement in Example 2.

[0046] Appendix Figure 8 This is the formation curve of the composite lithium supplement battery in Example 2.

Claims

1. A carbon-based catalytic lithium squaric acid composite lithium supplement agent, characterized in that, It is composed of lithium squaric acid and carbon-based conductive agent in a mass ratio of 6-8:2-4. The carbon-based conductive agent is one or more of ordered mesoporous carbon (CMK-3), Ketjen black (KB), superconducting carbon black (SP), acetylene black (AB), single-arm carbon nanotube (SWCNT), and multi-walled carbon nanotube (MWCNT). The carbon-based conductive agent has carbon vacancy defects and Zigzag / Armchair carbon boundaries.

2. The carbon-based catalytic lithium squaric acid composite lithium supplement agent as described in claim 1, characterized in that, The lithium squarate is in the form of nanospheres with a particle size of 2-10 μm.

3. The carbon-based catalytic lithium squaric acid composite lithium supplement agent as described in claim 1, characterized in that, The composite lithium replenishing agent has a complete decomposition voltage of <4.2V, a decomposition capacity of ≥400mAh / g in the first week, and a lithium replenishment efficiency that is more than 30% higher than that of pure lithium squartz.

4. A method for preparing a carbon-based catalytic lithium squaric acid composite lithium supplement agent according to any one of claims 1-3, characterized in that, Includes the following steps: (1) Pretreatment of carbon-based conductive agent: The carbon-based conductive agent is calcined at 500-700℃ for 2-4h in an inert gas atmosphere and cooled for later use; (2) Preparation of composite slurry: 20% of the mass fraction of carbon-based conductive agent CMC is added to deionized water, and lithium squartz acid and the pretreated carbon-based conductive agent are mixed at a mass ratio of 6-8:2-4. The mixture is mechanically stirred at 300-500r / min for 4-6h to obtain a uniform composite slurry; (3) Drying and molding: The composite slurry is spray-dried, and the resulting powder is dried in a vacuum oven at 120℃ for 12h to obtain carbon-based catalytic lithium squartz acid composite lithium supplement spherical powder.

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