Lithium oxalate lithium supplement and preparation method and application thereof
By preparing a nickel nitride-carbon heterojunction catalyst and combining it with lithium oxalate, the problem of high decomposition voltage of lithium oxalate in lithium-ion batteries was solved, thereby improving the energy density and stability of lithium-ion batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HU NAN SHENG RONG KE JI YOU XIAN GONG SI
- Filing Date
- 2026-02-27
- Publication Date
- 2026-06-02
AI Technical Summary
Lithium oxalate in lithium-ion batteries suffers from high electrochemical decomposition voltage, which leads to battery stability risks and limited charging cutoff voltage, making it difficult to fully release its lithium replenishment capacity. Existing improvement methods have failed to effectively reduce the decomposition voltage or increase energy density.
A nickel nitride-carbon heterojunction catalyst was prepared by liquid-phase dispersion combined with solid-phase calcination. It was then compounded with lithium oxalate. By optimizing the electronic structure through a built-in electric field, the energy barrier for lithium oxalate decomposition was reduced, and an efficient electron transport network was constructed.
It significantly reduces the decomposition voltage of lithium oxalate, improves the energy density and stability of lithium-ion batteries, and achieves efficient lithium replenishment performance of lithium oxalate.
Smart Images
Figure CN122136369A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of lithium supplementation technology, specifically relating to a lithium oxalate supplementation agent, its preparation method, and its application. Background Technology
[0002] Lithium oxalate (Li₂C₂O₄), as a potential lithium replenishing agent with a theoretical specific capacity of up to 540 mAh / g, has significant application value in improving the first charge-discharge efficiency and energy density of lithium-ion batteries. However, the core technical obstacle facing lithium oxalate in practical applications lies in its excessively high electrochemical decomposition voltage (typically greater than 4.7V vs. Li₂C₂O₄). + / Li). This high decomposition voltage not only leads to stability risks such as electrolyte oxidation and decomposition and cathode material structure damage during cycling, but also makes it difficult to fully release its lithium replenishment capacity due to the limited charging cut-off voltage, which seriously restricts the actual improvement of energy density.
[0003] To overcome the above-mentioned shortcomings, there are currently three main methods for improving the lithium supplementation performance of lithium oxalate: First, the composite material structure method: This method involves physically mixing lithium oxalate with conductive agents (such as superconducting carbon black SP), carbon nanotubes, or graphene to construct a core-shell coated structure or a three-dimensional interconnected conductive network. The aim is to improve the interfacial contact between lithium oxalate particles and the conductive network, thereby promoting electron transport. However, this method only improves conductivity at the physical level and cannot reduce the energy barrier of the lithium oxalate decomposition reaction itself from a chemical reaction kinetics perspective. Therefore, its effect on reducing the decomposition voltage is extremely limited.
[0004] Second, the intrinsic modification method: This method involves synthesizing nanoscale lithium oxalate (such as nanosheets or nanoparticles) or designing special morphologies to shorten the transport path of lithium ions and electrons, increase the specific surface area of the reaction, and reduce polarization. However, this method is essentially limited to optimizing the intrinsic properties of the material and fails to effectively reduce the activation energy of the lithium oxalate delithiation reaction, still resulting in the problem of excessively high decomposition voltage.
[0005] Third, the single-phase catalyst method: This method introduces single-phase catalysts such as metal nanoparticles, transition metal oxides (e.g., Co3O4), or carbides (e.g., Mo2C) into lithium oxalate, aiming to provide active sites to enhance the catalytic effect of specific reaction steps. However, single-phase catalysts typically possess only a single active site, limiting their catalytic ability for the complex multi-step reactions involved in lithium oxalate delithiation. Furthermore, the contact between the catalyst, lithium oxalate, and the conductive agent is mostly physical, resulting in high interfacial impedance, high charge transport resistance, and unstable performance in practical applications, making it difficult to fully realize the catalyst's efficiency. Summary of the Invention
[0006] Therefore, the purpose of this invention is to provide a lithium oxalate supplement, its preparation method, and its application.
[0007] In a first aspect, the present invention provides a lithium oxalate supplement, comprising: a nickel nitride-carbon heterojunction catalyst and lithium oxalate adsorbed on the surface and / or in the pores of the nickel nitride-carbon heterojunction catalyst; The preparation method of the nickel nitride-carbon heterojunction catalyst includes the following steps: Nitrogen and nickel sources are dissolved in a solvent, and a carbon source is added and stirred to form a dispersion. The dispersion is evaporated to dryness and then pulverized to obtain a precursor. The precursor is calcined in a nitrogen-containing atmosphere to obtain a nickel nitride-carbon heterojunction catalyst.
[0008] Preferably, the mass ratio of the nickel nitride-carbon heterojunction catalyst to lithium oxalate is (5~30):(70~95), and more preferably (5~20):(80~95).
[0009] Preferably, the nitrogen source is one or two of carbodiamine, melamine, polydopamine, acrylonitrile, ethylenediamine and hydrazine hydrate; the nickel source is one or two of nickel nitrate and nickel chloride; and the carbon source is one or more of carbon nanotubes, conductive carbon black (SP) and graphene.
[0010] Preferably, the solvent is one or both of deionized water and ethanol.
[0011] Preferably, the molar ratio of the nitrogen source to the nickel source is (2~5):1; and the mass ratio of the carbon source to the total mass of the nitrogen and nickel sources is (1~10):1.
[0012] Preferably, the nitrogen-containing atmosphere is one of a mixture of hydrogen and nitrogen, ammonia, or nitrogen; more preferably, the volume ratio of hydrogen to nitrogen in the mixture of hydrogen and nitrogen is (0.02~0.12):1.
[0013] Preferably, the calcination temperature is 400~800℃ and the calcination time is 2~5h.
[0014] Secondly, the present invention provides a method for preparing a lithium oxalate lithium supplement, comprising the following steps: A nickel nitride-carbon heterojunction catalyst was dispersed in a solvent to obtain a dispersion; an aqueous solution of lithium oxalate was added dropwise to the dispersion, and after the addition was complete, the mixture was spray-dried to obtain a mixed powder; the mixed powder was heat-treated under an inert atmosphere to obtain a lithium oxalate supplement.
[0015] Preferably, the solvent is anhydrous ethanol.
[0016] Preferably, the mass ratio of the nickel nitride-carbon heterojunction catalyst to lithium oxalate is (5~30):(70~95), and more preferably (5~20):(80~95).
[0017] Preferably, the inlet air temperature of the spray dryer is 170~230℃.
[0018] Preferably, the heat treatment temperature is 200~400℃ and the heat treatment time is 1~3h.
[0019] Preferably, the inert atmosphere is an argon atmosphere or a nitrogen atmosphere.
[0020] Thirdly, the present invention provides a positive electrode material, including the aforementioned lithium oxalate lithium supplement.
[0021] Compared with the prior art, one or more of the above technical solutions can achieve at least one of the following beneficial effects: This invention prepares a nickel nitride-carbon heterojunction catalyst by liquid-phase dispersion combined with solid-phase calcination. The catalyst has both high catalytic activity and excellent electronic conductivity. Furthermore, the built-in electric field formed at the heterojunction interface can optimize the electronic structure. When combined with lithium oxalate, it can effectively reduce the electrochemical decomposition energy barrier of lithium oxalate during lithium replenishment. Attached Figure Description
[0022] Figure 1 The image shows the XRD pattern of the nickel nitride-carbon heterojunction catalyst prepared in Example 1.
[0023] Figure 2 This is a SEM image of the nickel nitride-carbon heterojunction catalyst prepared in Example 1.
[0024] Figure 3 The image shows a SEM image of the nickel nitride-carbon catalyst prepared in Comparative Example 1. Detailed Implementation
[0025] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.
[0026] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.
[0027] As mentioned above, in a first aspect, the present invention provides a lithium oxalate supplement, comprising: a nickel nitride-carbon heterojunction catalyst and lithium oxalate adsorbed on the surface or in the pores of the nickel nitride-carbon heterojunction catalyst; The preparation method of the nickel nitride-carbon heterojunction catalyst includes the following steps: After dissolving nitrogen and nickel sources in a solvent, a carbon source is added and stirred to form a dispersion. The dispersion is then evaporated to dryness and pulverized to obtain a precursor. The precursor is calcined under a mixed atmosphere to obtain a nickel nitride-carbon heterojunction catalyst.
[0028] This scheme achieves in-situ synthesis of nanoscale nickel nitride and controllable construction of the homogeneous heterojunction interface between the nanoscale nickel nitride and the carbon source material through a liquid-phase dispersion coupled with solid-phase calcination process. Compared with traditional physical blending methods, this significantly improves the catalytic decomposition efficiency of the conductive network. The system uses a conductive carbon source as a three-dimensional interconnected framework to construct a highly efficient electron transport network, providing a rapid electron channel for the decomposition reaction of lithium oxalate. Nickel nitride nanoparticles grow directly in situ on the surface and within the pore structure of the carbon source, forming a robust anchoring structure that ensures close electrical contact between the catalytic active sites and the conductive framework. This fundamentally eliminates the interfacial contact resistance between the catalyst and the conductive agent, enabling lossless and rapid electron transport from the current collector to the catalytic sites. These structural features not only enhance the potential stability of the catalyst but also fully release catalytic activity through the synergistic effect of both. During the nitriding process, nickel nitride forms a chemically bonded heterojunction interface with the carbon source matrix. The built-in electric field at this interface can effectively modulate the electronic state density on the nickel nitride surface and optimize its d-band center position, thereby moderately weakening the adsorption strength of reaction intermediates and significantly reducing the activation energy barrier of the stepwise lithium oxalate delithiation reaction. This in-situ constructed heterojunction structure endows the catalyst with intrinsic catalytic activity far exceeding that of physically mixed systems.
[0029] In this invention, the nickel nitride-carbon catalyst is formed by in-situ composite of a nickel source and a conductive carbon source (such as carbon nanotubes or conductive carbon black) through liquid-phase dispersion and solid-phase sintering, thus forming a nickel nitride-carbon heterojunction catalyst. The built-in electric field generated at the heterojunction interface can regulate the electronic state density on the surface of nickel nitride, effectively reducing the energy barrier of lithium oxalate decomposition reaction. At the same time, the catalyst itself constitutes part of the conductive network, realizing the integration of the functions of the catalytic active center and the electron transport channel, fundamentally eliminating the interfacial charge transport resistance.
[0030] This invention employs a continuous in-situ process of "nitriding followed by recrystallization": first, a nickel / carbon precursor is prepared and nitrided; then, it is mixed with lithium oxalate in liquid phase and recrystallized; finally, the interface is strengthened by spray drying and controlled heat treatment. This process not only ensures the high-quality formation of heterojunction catalysts but also achieves chemical anchoring and physical strengthening of the three-phase interface in the final product, avoiding interface contamination and performance degradation caused by multi-step separation. The process has high integration, strong controllability, and is easy to scale up.
[0031] In some embodiments, the mass ratio of the nickel nitride-carbon heterojunction catalyst to lithium oxalate is (5~30):(70~95), preferably (5~20):(80~95), including but not limited to: 5:95, 10:90, 15:85, 20:80, 25:75, 30:70, etc.
[0032] In this invention, by adjusting the ratio of nickel nitride-carbon heterojunction catalyst to lithium oxalate, the lithium replenishment voltage can be significantly reduced while ensuring the lithium replenishment capacity.
[0033] In some embodiments, the nitrogen source is one or two of carbodiamine, melamine, polydopamine (viscosity-average molecular weight of 4000-10000), acrylonitrile, ethylenediamine and hydrazine hydrate; the nickel source is one or two of nickel nitrate and nickel chloride; and the carbon source is one or more of carbon nanotubes, conductive carbon black (SP) and graphene.
[0034] In some embodiments, the solvent is one or both of deionized water and ethanol.
[0035] In some embodiments, the molar ratio of the nitrogen source to the nickel source is (2~5):1, including but not limited to: 2:1, 3:1, 4:1, 5:1, etc.; the mass of the carbon source is the ratio of the total mass of the nitrogen source and the nickel source to (1~10):1.
[0036] In some embodiments, the mixed atmosphere is a mixture of ammonia or hydrogen and nitrogen, wherein the volume ratio of hydrogen to nitrogen in the mixed atmosphere is (0.02~0.12):1, including but not limited to: 0.02:1, 0.03:1, 0.04:1, 0.05:1, 0.06:1, 0.07:1, 0.08:1, 0.09:1, 0.1:1, 0.11:1, 0.12:1, etc.
[0037] In some embodiments, the calcination temperature is 400~800℃, including but not limited to: 400℃, 500℃, 600℃, 700℃, 800℃, etc.; the calcination time is 2~5h, including but not limited to: 2h, 3h, 4h, 5h, etc.
[0038] Secondly, the present invention provides a method for preparing a lithium oxalate lithium supplement, comprising the following steps: A nickel nitride-carbon heterojunction catalyst was dispersed in a solvent to obtain a dispersion; an aqueous solution of lithium oxalate was added dropwise to the dispersion, and after the addition was complete, the mixture was spray-dried to obtain a mixed powder; the mixed powder was heat-treated under an inert atmosphere to obtain a lithium oxalate supplement.
[0039] This invention employs a progressive interface enhancement strategy—liquid-phase recrystallization, spray drying, and heat treatment—to achieve highly efficient microscale composite formation of lithium oxalate and nickel nitride / carbon heterojunction catalysts. Compared to conventional physical mixing methods, this significantly enhances the interfacial stability and effectiveness between the heterojunction catalytic sites and lithium oxalate. Specifically: First, liquid-phase recrystallization achieves molecular-level dispersion of the precursor. Lithium oxalate is dissolved in an ethanol dispersion of the nickel nitride / carbon heterojunction catalyst, and the recrystallization process is driven by solvent evaporation, resulting in the uniform coating of the lithium oxalate nanocrystals with heterojunction catalyst particles, forming a submicron-scale primary composite structure. Next, spray drying rapidly removes residual solvent, instantly solidifying the highly dispersed suspension into precursor powder, effectively "locking in" the homogeneous distribution of the multi-components and avoiding the risks of static sedimentation or secondary agglomeration. Finally, heat treatment strengthens the interfacial bonding, promoting stable physicochemical bonding between the nickel nitride / carbon heterojunction and the lithium oxalate particle surface through thermal activation, constructing a highly efficient catalytic-reaction heterojunction interface. The aforementioned synergistic effect can significantly reduce the decomposition voltage of lithium oxalate, expanding its application potential in lithium-ion battery systems.
[0040] This invention employs a multi-stage interface strengthening process—liquid-phase recrystallization, spray drying, and heat treatment—to achieve a uniformly dispersed and closely contacted three-phase co-continuous structure of nickel nitride / carbon heterojunction catalyst, lithium oxalate active material, and auxiliary conductive agent at the submicron scale. This structure overcomes the bottlenecks of uneven dispersion and interfacial contact inherent in traditional mechanical mixing, ensuring that lithium oxalate particles are simultaneously and fully coupled with the catalytic sites and conductive network, maximizing the synergistic catalytic effect and achieving a significant and stable reduction in decomposition voltage.
[0041] In some embodiments, the solvent is anhydrous ethanol.
[0042] In some embodiments, the mass ratio of the nickel nitride-carbon heterojunction catalyst to lithium oxalate is (5~30):(70~95), preferably (5~20):(80~95), including but not limited to: 5:95, 10:90, 15:85, 20:80, 25:75, 30:70, etc.
[0043] In some embodiments, the inlet air temperature of the spray dryer is 170~230℃, including but not limited to: 170℃, 180℃, 190℃, 200℃, 210℃, 220℃, 230℃, etc.
[0044] In some embodiments, the heat treatment temperature is 200~400℃, including but not limited to: 200℃, 250℃, 300℃, 350℃, 400℃, etc.; the heat treatment time is 1~3h, including but not limited to: 1h, 1.5h, 2h, 2.5h, 3h, etc.
[0045] In some embodiments, the inert atmosphere is an argon atmosphere or a nitrogen atmosphere.
[0046] Thirdly, the present invention provides a positive electrode material, including the aforementioned lithium oxalate lithium supplement.
[0047] Example 1 S1. Carbonyl diamine and nickel nitrate are dissolved in deionized water at a molar ratio of 1:3. SP (the mass ratio of SP to the total mass of carbonyl diamine and nickel nitrate is 5:1) is added and stirred to form a dispersion. The dispersion is evaporated to dryness and then ground into powder to obtain a precursor. The precursor is calcined at 600℃ for 3 hours in a mixed atmosphere of hydrogen and nitrogen with a volume ratio of 0.05:1 (vacuum first and then gas is introduced) to obtain a nickel nitride-carbon heterojunction catalyst.
[0048] S2. The nickel nitride-carbon heterojunction catalyst is dispersed in anhydrous ethanol solution to obtain a dispersion. An aqueous solution of lithium oxalate is added dropwise to the dispersion at a mass ratio of lithium oxalate to nickel nitride-carbon heterojunction catalyst of 85:15 under stirring. After the addition is complete, the mixture is spray-dried (inlet air temperature is 200℃) to obtain a mixed powder. The mixed powder is ground into a fine powder and then heat-treated at 300℃ for 2 hours under a nitrogen atmosphere to obtain a lithium oxalate supplement.
[0049] The XRD pattern of the nickel nitride-carbon heterojunction catalyst prepared in this embodiment is shown below. Figure 1 As shown, it can be seen that there is a relatively obvious Ni3N absorption peak, which basically corresponds to the Ni3N peak of the standard card.
[0050] Comparative Example 1 S1. SP and nickel nitride are mixed evenly at a mass ratio of 12:1 to obtain a mixture. The mixture is then calcined at 600°C for 3 hours in a mixed atmosphere of hydrogen and nitrogen with a volume ratio of 0.05:1 (vacuum first, then gas is introduced) to obtain a nickel nitride-carbon catalyst.
[0051] S2, same as step S2 in Example 1.
[0052] SEM image of the nickel nitride-carbon heterojunction catalyst prepared in Example 1 is shown below. Figure 2 As shown, the SEM image of the nickel nitride-carbon catalyst prepared in Comparative Example 1 is as follows. Figure 3 As shown, it can be seen that the morphology of the nickel nitride-carbon heterojunction catalyst in Example 1 is completely different from that of the nickel nitride-carbon catalyst in Comparative Example 1.
[0053] Example 2 This is basically the same as Example 1, except that step S2 is different. The specific preparation method is as follows: S1, Same as Example 1.
[0054] S2. Lithium oxalate and nickel nitride-carbon heterojunction catalyst are mixed evenly at a mass ratio of 85:15 to obtain a mixed powder. The mixed powder is ground into fine powder and then heat-treated at 300°C for 2 hours under a nitrogen atmosphere to obtain lithium oxalate supplement.
[0055] Example 3 The method is basically the same as in Example 1, except that the calcination atmosphere in step S1 is different. The specific preparation method is as follows: S1 is basically the same as in Example 1, except that the calcination atmosphere is a nitrogen atmosphere.
[0056] S2, same as Example 1.
[0057] Example 4 The method is basically the same as in Example 1, except that the calcination atmosphere in step S1 is different. The specific preparation method is as follows: S1 is basically the same as in Example 1, except that the calcination atmosphere is an ammonia atmosphere.
[0058] S2, Same as Example 1 Example 5 The method is basically the same as in Example 1, except that the calcination atmosphere in step S1 is different. The specific preparation method is as follows: S1 is basically the same as in Example 1, except that the calcination atmosphere is hydrogen and nitrogen in a volume ratio of 0.12:1.
[0059] S2, same as Example 1.
[0060] Example 6 The method is basically the same as in Example 1, except that the calcination atmosphere in step S1 is different. The specific preparation method is as follows: S1 is basically the same as in Example 1, except that the calcination atmosphere is hydrogen and nitrogen in a volume ratio of 0.03:1.
[0061] S2, same as Example 1.
[0062] Example 7 Compared with Example 1, the difference is that in step S2, the mass ratio of lithium oxalate to nickel nitride-carbon heterojunction catalyst is 95:5.
[0063] Example 8 Compared with Example 1, the difference is that in step S2, the mass ratio of lithium oxalate to nickel nitride-carbon heterojunction catalyst is 80:20.
[0064] Example 9 S1: Hydrazine hydrate and nickel chloride were dissolved in deionized water at a molar ratio of 5:1. Carbon nanotubes (the mass ratio of carbon nanotubes to the total mass of hydrazine hydrate and nickel chloride was 2:1) were added and stirred to form a dispersion. The dispersion was evaporated to dryness and then ground into powder to obtain a precursor. The precursor was calcined at 400℃ for 5 hours in a mixed atmosphere of hydrogen and nitrogen with a volume ratio of 0.05:1 (vacuum was first drawn and then the gas was introduced) to obtain a nickel nitride-carbon heterojunction catalyst.
[0065] S2: The nickel nitride-carbon heterojunction catalyst was dispersed in anhydrous ethanol solution to obtain a dispersion; an aqueous solution of lithium oxalate was added dropwise to the dispersion under stirring at a mass ratio of lithium oxalate to nickel nitride-carbon heterojunction catalyst of 80:20. After the addition was completed, the mixture was spray-dried (inlet air temperature of 170℃) to obtain a mixed powder; the mixed powder was ground into a fine powder and then heat-treated at 200℃ for 3 hours under a nitrogen atmosphere to obtain a lithium oxalate supplement.
[0066] Example 10 S1: Melamine and nickel chloride were dissolved in deionized water at a molar ratio of 2:1. Graphene (the mass ratio of graphene to the total mass of melamine and nickel chloride was 8:1) was added and stirred to form a dispersion. The dispersion was evaporated to dryness and then ground into powder to obtain a precursor. The precursor was calcined at 800°C for 2 hours in a mixed atmosphere of hydrogen and nitrogen with a volume ratio of 0.07:1 (vacuum was first drawn and then the gas was introduced) to obtain a nickel nitride-carbon heterojunction catalyst.
[0067] S2: The nickel nitride-carbon heterojunction catalyst was dispersed in anhydrous ethanol solution to obtain a dispersion; an aqueous solution of lithium oxalate was added dropwise to the dispersion under stirring at a mass ratio of lithium oxalate to nickel nitride-carbon heterojunction catalyst of 90:10. After the addition was completed, the mixture was spray-dried (inlet air temperature of 230℃) to obtain a mixed powder; the mixed powder was ground into a fine powder and then heat-treated at 400℃ for 1 hour under a nitrogen atmosphere to obtain a lithium oxalate supplement.
[0068] The lithium oxalate supplements prepared in Examples 1-10 and Comparative Example 1 were assembled into lithium-ion batteries. The specific assembly method is as follows: A positive electrode slurry was prepared by mixing the lithium oxalate supplement, conductive agent, binder, and solvent. The positive electrode slurry was coated onto a current collector to obtain a positive electrode sheet, and the negative electrode was a standard lithium electrode. The positive and negative electrodes were rolled, injected with electrolyte, assembled, and packaged to form a button-type lithium-ion battery. Constant current and constant voltage charging tests were performed at room temperature using a test current of 0.1C. The test voltage range was 2.0–4.8V, and the constant voltage cutoff current was 0.05C. The test results are shown in Table 1.
[0069] Table 1 As can be seen from the data in Table 1, the lithium oxalate supplement prepared in Example 1 performed best, with high charging capacity and constant current charging ratio, and low Li release voltage. Comparative Example 1 showed significantly worse performance than Example 1, with a marked decrease in charging capacity and constant current charging ratio, and an increase in Li release voltage. This is because Comparative Example 1 did not form a heterojunction; the nickel nitride and SP were only simply mixed, failing to form a synergistic effect, leading to a decline in the performance of the supplement. Example 2 used a solid-phase mixture of lithium oxalate and nickel nitride-carbon heterojunction catalyst. Its charging capacity and constant current charging ratio were lower than those of Example 1, while its Li release voltage was higher. This may be because the wet mixing in Example 1 allowed lithium oxalate to penetrate into the catalyst and achieve uniform composite, while solid-phase mixing could not achieve deep fusion, affecting the lithium supplementation effect. Examples 3 and 4 showed lower charging capacity and constant current charging ratios than Example 1, and higher Li release voltage. This may be because the preparation of the nickel nitride-carbon heterojunction catalyst used a nitrogen atmosphere or reduced ammonia usage, resulting in a decrease in the number of heterojunctions and structural damage, affecting the performance of the supplement. The performance of Examples 5 and 6 decreased compared to Example 1. This may be because the hydrogen content was not properly controlled during the preparation of the nickel nitride-carbon heterojunction catalyst, affecting the formation of the heterojunction structure and weakening its synergistic effect with lithium oxalate. Examples 7 and 8 adjusted the mixing ratio of lithium oxalate and catalyst, while Examples 9 and 10 adjusted the preparation process parameters. Their charging capacity, Li release voltage, and constant current charge ratio fluctuated slightly, but the overall performance was better, indicating that the preparation system had good process stability.
[0070] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.
Claims
1. A lithium oxalate lithium supplement, characterized in that, include: Nickel nitride-carbon heterojunction catalyst and lithium oxalate adsorbed on the surface and / or in the pores of nickel nitride-carbon heterojunction catalyst; The preparation method of the nickel nitride-carbon heterojunction catalyst includes the following steps: Nitrogen and nickel sources are dissolved in a solvent, and a carbon source is added and stirred to form a dispersion. The dispersion is evaporated to dryness and then pulverized to obtain a precursor. The precursor is calcined in a nitrogen-containing atmosphere to obtain a nickel nitride-carbon heterojunction catalyst.
2. The lithium oxalate supplement agent according to claim 1, characterized in that, The mass ratio of the nickel nitride-carbon heterojunction catalyst to lithium oxalate is (5~30):(70~95).
3. The lithium oxalate supplement agent according to claim 1, characterized in that, The nitrogen source is one or two of carbodiamine, melamine, polydopamine, acrylonitrile, ethylenediamine, and hydrazine hydrate; And / or: the nickel source is one or both of nickel nitrate and nickel chloride; the carbon source is one or more of carbon nanotubes, conductive carbon black and graphene; And / or: The solvent is one or both of deionized water and ethanol.
4. The lithium oxalate supplement agent according to claim 1, characterized in that, The molar ratio of the nitrogen source to the nickel source is (2~5):1; the mass ratio of the carbon source to the total mass of the nitrogen and nickel sources is (1~10):
1.
5. The lithium oxalate supplement agent according to claim 1, characterized in that, The nitrogen-containing atmosphere is one of the following: a mixture of hydrogen and nitrogen, ammonia, or nitrogen.
6. The lithium oxalate supplement agent according to claim 5, characterized in that, The volume ratio of hydrogen to nitrogen in the mixed gas is (0.02~0.12):
1.
7. The lithium oxalate supplement agent according to claim 1, characterized in that, The calcination temperature is 400~800℃, and the calcination time is 2~5h.
8. The method for preparing lithium oxalate supplement according to any one of claims 1 to 7, characterized in that, Includes the following steps: A nickel nitride-carbon heterojunction catalyst was dispersed in a solvent to obtain a dispersion; an aqueous solution of lithium oxalate was added dropwise to the dispersion, and after the addition was complete, the mixture was spray-dried to obtain a mixed powder; the mixed powder was heat-treated under an inert atmosphere to obtain a lithium oxalate supplement.
9. The method for preparing lithium oxalate supplement according to claim 8, characterized in that, The solvent is anhydrous ethanol; And / or: the inlet air temperature of the spray dryer is 170~230℃; And / or: the heat treatment temperature is 200~400℃, and the heat treatment time is 1~3h; And / or: The inert atmosphere is an argon atmosphere or a nitrogen atmosphere.
10. A cathode material comprising the lithium oxalate lithium supplement agent according to any one of claims 1 to 7, or the lithium supplement agent prepared by any one of claims 8 to 9.