Composite lithium supplement agent and preparation method and application thereof

Abstract

The invention discloses a composite lithium supplement agent and a preparation method and application thereof, and belongs to the technical field of lithium ion batteries, the composite lithium supplement agent comprises an organic lithium supplement agent and a catalyst, the catalyst is a metal oxide cluster dispersed on a carbon material, and the lithium supplement agent is dispersed on the surface of the catalyst. According to the invention, the catalyst and the lithium supplement agent are compounded through recrystallization and freeze drying to obtain the composite lithium supplement agent. The porous conductive network and highly dispersed active sites of the carrier in the catalyst significantly reduce the oxygenolysis potential of the lithium supplement agent, and release the theoretical capacity of the lithium supplement agent under low potential. According to the composite lithium supplement agent provided by the invention, the cycle stability of the battery is improved, the first-circle charging capacity of the battery is improved, and the lithium supplement purpose of the lithium ion battery can be effectively realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium ion batteries, and in particular relates to a composite lithium supplement and a preparation method and application thereof. Background Art

[0002] In the context of clean energy transformation, lithium-ion batteries with high energy density and environmentally friendly properties have become the core of modern energy storage systems and are widely used in portable electronic devices and electric vehicles. As the performance requirements of these applications continue to increase, the development of lithium-ion batteries with higher energy density has become a key research direction. During the first cycle of the battery, the formation of the solid electrolyte interface film and side reactions lead to irreversible loss of active lithium, which seriously restricts the actual available capacity of the battery. Pre-lithiation technology can effectively compensate for the initial lithium loss by introducing additional active lithium sources into the electrode material or electrolyte during the battery manufacturing stage, significantly improving the first efficiency and energy density of the battery, becoming a key strategy to solve this problem.

[0003] Lithium replenishers primarily include negative electrode replenishers such as metallic lithium powder, lithium foil, and lithium alloys; positive electrode replenishers such as lithium-rich compounds like Li₅FeO₄ and Li₂O; electrolyte replenisher additives; and organic replenishers. Currently, commercial application of lithium replenisher technology still faces numerous challenges. Metallic lithium replenishers pose high safety risks and complex processes; electrolyte additives have limited replenishment capacity; and lithium-rich positive electrode replenishers face limitations such as high decomposition potential and low replenishment efficiency.

[0004] While organic lithium supplements have addressed some of the aforementioned issues to a certain extent, they also have some inherent shortcomings. For example, some organic lithium supplements have poor conductivity and high oxidative decomposition potentials, making them difficult to match with low-voltage cathode materials. Furthermore, the solubility and dispersibility of some organic lithium supplements need to be improved, which can lead to uneven lithium supplementation and, in turn, affect the consistency of overall battery performance.

[0005] Therefore, developing a new lithium supplement system that is efficient, stable, safe, controllable, and compatible with existing battery production processes, and optimizing its application process have become key technical difficulties that urgently need to be overcome in the current lithium-ion battery field. This is of great significance for promoting the commercial application of high-energy-density lithium-ion batteries. Summary of the Invention

[0006] The purpose of the present invention is to provide a composite lithium supplement agent and its preparation method and application, so as to solve the problem that organic lithium supplement agents have poor lithium supplement effect.

[0007] The purpose of the present invention can be achieved through the following technical solutions: The first aspect of the present application provides a composite lithium supplement comprising an organic lithium supplement and a catalyst, wherein the catalyst comprises a carbon material and a metal oxide cluster supported on the carbon material, and the lithium supplement is dispersed on the surface of the catalyst; the general chemical formula of the lithium supplement is Li2C x O y , wherein 2≤x≤6, 4≤y≤6, including at least one of Li2C2O4, Li2C4O4, Li2C3O5, Li2C4O6, and Li2C6O6.

[0008] In some possible implementations, the catalyst is prepared by using one or more Anderson-type polyoxometalates as precursors, combining with carbon materials through electrostatic interaction, and then undergoing heat treatment.

[0009] In some possible implementations, the Anderson-type polyoxometalate has the general formula [XM6O 24 ] n- ; wherein X is one of Fe, Co, Ni, Cu, Zn, Pt, and Rh; and M is one of V, Mo, W, Nb, and Ta.

[0010] In some possible implementations, the carbon material is one or more of porous carbon (Ketjenblack), graphene oxide, and carbon nanotubes.

[0011] In some possible implementations, the catalyst accounts for 12.5 wt% to 50.0 wt% of the composite lithium supplement.

[0012] In some possible implementations, the particle size of the composite lithium supplement is 10 μm to 20 μm.

[0013] The second aspect of the present application provides a method for preparing a composite lithium supplement, comprising the following steps: The lithium supplement agent and the catalyst are mixed, and deionized water and ethanol are added for recrystallization. The crystallized product is vacuum freeze-dried to obtain a composite lithium supplement agent.

[0014] In some possible implementations, the volume ratio of the deionized water to the ethanol is 1:(1-5).

[0015] In some possible implementations, the recrystallization temperature is 60-80° C.; and the vacuum freeze-drying condition is 1.0-10 Pa.

[0016] The third aspect of the present application provides a use of a composite lithium supplement in a lithium-ion battery. The lithium-ion battery comprises a positive electrode material, a separator, and a negative electrode material.

[0017] In some possible implementations, the positive electrode material includes the above-mentioned composite lithium supplement.

[0018] In some possible implementations, the separator includes the above-mentioned composite lithium supplement agent.

[0019] Beneficial effects of the present invention: The present invention provides a composite lithium supplement comprising an organic lithium supplement and a catalyst, wherein the catalyst is a metal oxide cluster supported on a carbon material, and the lithium supplement is dispersed on the catalyst surface. The catalyst and the lithium supplement are combined by recrystallization and freeze-drying to form the composite lithium supplement. The porous conductive network and highly dispersed active sites of the support significantly reduce the oxidative decomposition potential of the lithium supplement, releasing the theoretical capacity of the lithium supplement at low potentials. The composite lithium supplement enhances the battery's cycling stability and increases the battery's first-cycle charge capacity, effectively achieving lithium replenishment for lithium-ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention will be further described below with reference to the accompanying drawings.

[0021] Figure 1 TEM images of the catalyst PtMo6@N-RGO and the clusters in the carbon nanopores in Example 1 of the present invention; Figure 2 This is a SEM image of the composite lithium supplement in Example 1 of the present invention; Figure 3 TEM images of the catalyst Pt / FeMo6@N-RGO and the clusters in the carbon nanopores in Example 2 of the present invention; Figure 4 Schematic diagram comparing the first charge curves of the composite lithium supplement provided in Example 1 of the present invention and Comparative Examples 1, 3, 4, and 5 in a positive electrode application system; Figure 5 Schematic diagram comparing the oxidative decomposition potentials of the composite lithium supplement provided by Example 1 of the present invention and Comparative Examples 1, 3, 4, and 5 in a positive electrode application system. DETAILED DESCRIPTION

[0022] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0023] Unless otherwise specified, the experimental methods in the following examples are conventional methods and were performed according to the techniques or conditions described in the literature in the field or according to the product instructions. The materials and reagents used in the following examples, unless otherwise specified, were all commercially available.

[0024] The following is a detailed description of a composite lithium supplement and its preparation method and application in the examples of the present application.

[0025] Example 1

[0026] This embodiment provides a composite lithium supplement, which is prepared by the following steps: The first step is to dissolve squaric acid and lithium carbonate in deionized water in a 1:1 molar ratio, stir and dissolve, add the squaric acid solution into the lithium carbonate solution, heat and stir to react, and evaporate Li2C4O4 crystals at 60°C. After grinding, the lithium supplement Li2C4O4 is obtained.

[0027] Step 2: 200 mg of graphene oxide and 200 mg of polyethyleneimine (PEI, Mw ~ 600) were added to 100 mL of deionized water and ultrasonically dispersed for 1 hour. Then, 200 μL of hydrazine hydrate was added and refluxed at 95 °C under NH3 atmosphere for 12 hours. After cooling to room temperature, the mixture was filtered, washed, and freeze-dried. 50 mg of the above sample and 30 mg of Na6[H5PtMo6O 24 ]·29H2O was dispersed in 30mL deionized water, stirred for 6 hours, filtered, washed and freeze-dried to obtain the catalyst PtMo6@N-RGO. TEM images of the catalyst PtMo6@N-RGO and the clusters in the carbon nanopores are shown in Figure 1. Figure 1 shown.

[0028] In the third step, PtMo6@N-RGO and Li2C4O4 were mixed in a mass ratio of 2:6, 40 mL of deionized water and 80 mL of ethanol were added thereto and rotary evaporated at 80 °C. The rotary evaporated product was freeze-dried under vacuum to obtain a composite lithium supplement. The pressure range of vacuum freeze drying was 1.0~10Pa. The SEM image of the composite lithium supplement is shown in the figure below. Figure 2 As shown, the particle size of the composite lithium supplement is 10-20 μm.

[0029] Example 2

[0030] This embodiment provides a composite lithium supplement. Compared with embodiment 1, the difference is that in the second step, Na6[H5PtMo6O 24 ]·29H2O and (NH4)3[FeMo6O 18 (OH)6]·7H2O was used to synthesize the catalyst Pt / FeMo6@N-RGO. TEM images of the catalyst Pt / FeMo6@N-RGO and the clusters in the carbon nanopores are shown in Figure 2. Figure 3 As shown, the particle size of the composite lithium supplement is 10-20 μm.

[0031] The remaining raw materials and preparation process remain the same as in Example 1.

[0032] Example 3

[0033] This embodiment provides a composite lithium supplement. Compared with embodiment 1, the difference lies in the following steps: The 200 mg of graphene oxide in the second step was replaced with 200 mg of Ketjenblack to synthesize the catalyst PtMo6@N-KJ.

[0034] The remaining raw materials and preparation process remain the same as those in Example 1, and the particle size of the composite lithium supplement is 10-20 μm.

[0035] Example 4

[0036] This embodiment provides a composite lithium supplement. Compared with Example 3, the difference lies in that in the second step, 200 mg of graphene oxide in the second step is replaced with carbon nanotubes to synthesize the catalyst PtMo6@N-CNT.

[0037] The remaining raw materials and preparation process remain the same as those in Example 1, and the particle size of the composite lithium supplement is 10-20 μm.

[0038] Example 5

[0039] This embodiment provides a composite lithium supplement. Compared with Example 1, the difference is that the Li2C4O4 synthesized in the first and third steps is replaced by Li2C2O4, the mass ratio of PtMo6@N-RGO to Li2C2O4 is 3:5, and the remaining raw materials and preparation process remain the same as Example 1. The particle size of the composite lithium supplement is 10-20 μm.

[0040] Example 6

[0041] This embodiment provides a composite lithium supplement. Compared with Example 2, the difference is that the Li2C4O4 synthesized in the first and third steps is replaced by Li2C2O4, and the mass ratio of the catalyst Pt / FeMo6@N-RGO and Li2C2O4 is 3:5.

[0042] The remaining raw materials and preparation process remain the same as those in Example 2, and the particle size of the composite lithium supplement is 10-20 μm.

[0043] Example 7

[0044] This embodiment provides a composite lithium supplement. Compared with Example 3, the difference is that the Li2C4O4 synthesized in the first and third steps is replaced by Li2C2O4, and the mass ratio of the catalyst PtMo6@N-KJ and Li2C2O4 is 3:5.

[0045] The remaining raw materials and preparation process remain the same as those in Example 3, and the particle size of the composite lithium supplement is 10-20 μm.

[0046] Example 8

[0047] This embodiment provides a composite lithium supplement. Compared with Example 4, the difference is that the Li2C4O4 synthesized in the first and third steps is replaced by Li2C2O4, the mass ratio of PtMo6@N-CNT catalyst to Li2C2O4 is 3:5, and the remaining raw materials and preparation process remain the same as Example 4. The particle size of the composite lithium supplement is 10-20 μm.

[0048] Comparative Example 1

[0049] Compared with Example 1, this comparative example differs in that no catalyst is added, and the remaining raw materials and preparation process remain the same as those in Example 1.

[0050] Comparative Example 2

[0051] The difference between this comparative example and Example 5 is that no catalyst is added, and the other raw materials and preparation process remain the same as those in Example 5.

[0052] Comparative Example 3

[0053] Compared with Example 1, this comparative example differs in that the recrystallization temperature of PtMo6@N-RGO and Li2C4O4 is 100°C, the remaining raw materials and preparation process remain the same as Example 1, and the particle size of the obtained composite lithium supplement agent is >20 μm.

[0054] Comparative Example 4

[0055] The difference between this comparative example and Example 1 is that the proportion of the catalyst in the composite lithium supplement agent is 10%, and the remaining raw materials and preparation process remain the same as those in Example 1.

[0056] Comparative Example 5

[0057] The difference between this comparative example and Example 1 is that the proportion of the catalyst in the composite lithium supplement agent is 50%, and the remaining raw materials and preparation process remain the same as those in Example 1.

[0058] Comparative Example 6

[0059] This comparative example differs from Example 1 in that, in the second step of catalyst preparation, 50 mg of graphene oxide, 9 mg of H2PtCl6·6H2O, and 24 mg of Na2MoO4·2H2O were dispersed in 30 mL of deionized water, stirred for 6 hours, filtered, washed, and freeze-dried to obtain the Pt-Mo@RGO catalyst. The remaining raw materials and preparation process remained the same as in Example 1.

[0060] Application Example 1-Application Example 8 and Comparative Application Example 1-Comparative Application Example 6

[0061] Preparation of a composite lithium supplement electrode: The lithium supplement, lithium iron phosphate, conductive agent carbon black (Super P), and binder polyvinylidene fluoride (PVDF) in Examples 1 to 8 and Comparative Examples 1 to 6 were mixed uniformly in 1.5 g of solvent N-methylpyrrolidone (NMP) at a mass ratio of 1:79:10:10 to obtain a positive electrode slurry; the positive electrode slurry was evenly coated on the surface of a carbon-coated aluminum foil, vacuum-dried at 60°C overnight, and roller-pressed to obtain a composite lithium supplement electrode.

[0062] The composite lithium supplement provided in the above examples and comparative examples were assembled into lithium-ion batteries according to the following methods: Negative electrode: commercial lithium sheet; electrolyte: commercial LB-008; CR 2032 model battery shell is used, and the button battery is assembled in the order of negative electrode shell, spring, gasket, lithium sheet, electrolyte, diaphragm, electrolyte, positive electrode sheet, and positive electrode shell.

[0063] Electrochemical performance test: The prepared button battery was charged to 4.5V at a constant current of 0.02C in the first cycle and discharged to 2.5V at a constant current. The relevant performance test results are shown in Table 1 below: Table 1

[0064] The comparison diagram of the first charge curve of the composite lithium supplement provided by Example 1 and Comparative Example 1, Comparative Example 3, Comparative Example 4, and Comparative Example 5 in the positive electrode application system is shown in FIG. Figure 4 As shown; Example 1 and Comparative Example 1, Comparative Example 3, Comparative Example 4, Comparative Example 5 provide a schematic diagram of the comparative oxidation decomposition potential of the composite lithium supplement in the positive electrode application system. Figure 5 shown.

[0065] Application Examples 9-16 and Comparative Application Examples 7-12

[0066] The positive electrode application was replaced by the separator application. The operation method was to mix 80% of the lithium supplement agents in Examples 1 to 8 and Comparative Examples 1 to 6, 10% of conductive carbon black (SP) and 10% of polyvinylidene fluoride (PVDF) in N-methylpyrrolidone (NMP) to prepare a slurry. The obtained slurry was coated on a commercial Gelgard 2400 with a coating machine. The coating thickness was 200 μm and the surface loading of the lithium supplement agent was 0.43 mg / cm 2 , and dried in a vacuum oven at 60 °C overnight.

[0067] Table 2

[0068] Table 1, Table 2, Figure 4 and Figure 5 Analyzing the data in Application Examples 1-4 and Application Examples 9-12, and Comparative Application Example 1 and Comparative Application Example 7, it can be seen that under the action of the catalyst, lithium quartz reaches its theoretical specific capacity of 440 mAh / g at a low voltage of 4.0 V. This is due to the synergistic catalytic effect of the clustered catalyst metal sites in the composite lithium supplement, which promotes the decomposition of the lithium supplement. At the same time, the three-dimensional conductive network of the carbon support significantly improves the conductivity of the lithium supplement, thereby reducing its decomposition potential and increasing its decomposition capacity. From Application Example 1 and Comparative Application Example 3, and Application Example 9 and Comparative Application Example 9, the particle size of the composite lithium supplement in Application Examples 1 and Application Example 9 is 10-20 μm, while the particle size of the composite lithium supplement in Comparative Application Example 3 and Comparative Application Example 9 is greater than 20 μm. This shows that when the recrystallization temperature of the composite lithium supplement is higher than 80°C, the particle size of the composite lithium supplement increases, thereby increasing the oxidative decomposition potential of the lithium supplement and reducing its decomposition capacity. Application Example 1, Comparative Application Examples 4 and 5, and Application Examples 9, 10, and 11 show that a catalyst ratio in the composite lithium supplement exceeding 50% or less than 10% will correspondingly increase the oxidative decomposition potential of the supplement and reduce its decomposition capacity. This is because when the catalyst dosage is too low, contact with the supplement is limited, limiting the decomposition of the supplement. When the catalyst dosage is too high, the risk of catalytic electrolyte decomposition increases, ultimately leading to increased battery polarization, which in turn increases the oxidation potential of the supplement and reduces its decomposition capacity. A comparison of Application Example 1 with Comparative Application Example 6, and Application Example 9 with Comparative Application Example 12 shows that when the clusters in the catalyst are replaced with metal compounds, the catalyst does not effectively catalyze the supplement, but merely improves its conductivity. Application Examples 13-16 achieve the theoretical specific capacity of lithium oxalate, 525 mAh / g, at voltages <4.5 V, consistent with the analytical principle described above for lithium oxalate. According to the data of Application Examples 1 to 4, Application Examples 5 to 8, Comparative Application Example 1, and Comparative Application Example 2, it can be seen that the four catalysts listed can all reduce the oxidative decomposition potential of lithium squarate and lithium oxalate.

[0069] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0070] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A composite lithium supplement, characterized in that: It includes an organic lithium supplement and a catalyst, wherein the catalyst includes a carbon material and a metal oxide cluster supported on the carbon material, and the lithium supplement is dispersed on the catalyst surface. The general chemical formula of the lithium supplement is Li2C x O y , where 2≤x≤6, 4≤y≤6.

2. A composite lithium supplement according to claim 1, characterized in that: Including at least one of Li2C2O4, Li2C4O4, Li2C3O5, Li2C4O6, and Li2C6O6.

3. A composite lithium supplement according to claim 1, characterized in that: The catalyst uses one or more Anderson-type polyoxometalates as precursors, combines with carbon materials through electrostatic interaction, and is subsequently prepared by heat treatment.

4. A composite lithium supplement according to claim 3, characterized in that: The general formula of the Anderson type polyoxometalate is [XM6O 24 ] n- ; wherein X is one of Fe, Co, Ni, Cu, Zn, Pt, and Rh; and M is one of V, Mo, W, Nb, and Ta.

5. A composite lithium supplement according to claim 1, characterized in that: The carbon material is at least one of porous carbon, graphene oxide and carbon nanotubes.

6. A composite lithium supplement according to claim 1, characterized in that: The catalyst accounts for 12.5 wt% to 50.0 wt% of the composite lithium supplement agent.

7. A composite lithium supplement according to claim 1, characterized in that: The particle size of the composite lithium supplement agent is 10 μm to 20 μm.

8. A method for preparing a composite lithium supplement, for preparing the composite lithium supplement according to any one of claims 1 to 7, characterized in that: The steps include: The lithium supplement agent and the catalyst are mixed, and deionized water and ethanol are added for recrystallization. The crystallized product is vacuum freeze-dried to obtain a composite lithium supplement agent.

9. The method for preparing a composite lithium supplement according to claim 8, characterized in that: The volume ratio of deionized water to ethanol is 1:(1-5); and / or the recrystallization temperature is 60-80° C.; and the vacuum freeze-drying condition is 1.0-10 Pa.

10. Use of the composite lithium supplement according to any one of claims 1 to 7 in a lithium-ion battery.

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