Metal-metal carbide / lithium supplement agent composite lithium supplement layer derived from organic metal framework and preparation method and application thereof

Abstract

The invention discloses an organic metal framework derived metal-metal carbide / lithium supplement agent composite lithium supplement layer as well as a preparation method and application thereof, and belongs to the technical field of lithium supplement of a positive electrode of a lithium ion battery. The invention solves the problems of large catalyst consumption, incomplete decomposition of the lithium supplement agent and poor lithium supplement effect of the lithium supplement agent for decomposition and lithium supplement. An MOF material of a small-particle-size lithium supplement agent and metal A is prepared, MOF and a metal B source are subjected to heat treatment to obtain a catalyst, the catalyst and the small-particle-size lithium supplement agent serve as active materials, and the active materials are mixed with a conductive agent, a binder and a solvent and coated to obtain a composite lithium supplement layer. According to the method, the interface electron reconstruction effect caused by strong interaction between metal and metal carbide is utilized, so that metal sites efficiently adsorb oxygen atoms in the lithium supplementing agent, an energy barrier required by Li-O bond breakage is weakened, and the lithium supplementing agent is driven to efficiently decompose and supplement lithium. The composite lithium supplement layer has the advantages of low decomposition voltage, high lithium ion utilization rate and good lithium supplement effect.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery cathode lithium replenishment technology, and in particular relates to an organometallic framework-derived metal-metal carbide / lithium replenishment agent composite lithium replenishment layer, its preparation method and application. Background Technology

[0002] During the initial charge and discharge of a lithium-ion battery, irreversible electrochemical decomposition of the electrolyte on the electrode surface and the formation and stabilization of the solid electrolyte interphase (SEI) film on the negative electrode material surface irreversibly consume a large number of active lithium ions in the battery system, leading to a significant decrease in the battery's actual capacity and energy density. Using positive electrode pre-lithiation technology is an effective solution to compensate for this lithium loss. Among various positive electrode lithium replenishing agents, lithium oxalate and lithium squaric acid, for example, demonstrate great application potential due to their excellent air stability and moderate specific capacity.

[0003] However, lithium oxalate, lithium squarate and other lithium replenishing agents have strong Li-O bonds in their molecules, which makes the voltage required for their electrochemical decomposition too high. This voltage generally exceeds the electrochemical window of conventional carbonate-based electrolytes and the working voltage range of mainstream cathode materials. As a result, the lithium replenishing agents are difficult to fully decompose in the cathode and have low lithium ion utilization, which seriously restricts their actual lithium replenishment effect.

[0004] To overcome this obstacle, existing technologies typically employ a strategy of introducing catalysts to reduce the decomposition voltage of lithium replenishing agents. However, current catalyst-catalyzed lithium replenishing agent decomposition schemes still suffer from problems such as high catalyst dosage, limited reduction in lithium replenishing agent decomposition voltage, and incomplete lithium replenishing agent decomposition (e.g., Chinese patents CN120497342A and CN118763221A). Incompletely decomposed lithium replenishing agents remain in the positive electrode, forming electrochemically inert components, which not only reduce the overall energy density of the battery but may also hinder some lithium-ion migration and charge transport. Therefore, developing novel catalytic systems capable of achieving efficient lithium replenishing agent decomposition even with low addition amounts, enabling the full release of lithium ions within the normal operating voltage range of the battery, has become a pressing technological bottleneck in this field. Summary of the Invention

[0005] To overcome the shortcomings of existing catalytic lithium replenishment agents, such as large catalyst dosage, incomplete lithium replenishment, and poor lithium replenishment effect, this invention provides an organometallic framework-derived metal-metal carbide / lithium replenishment agent composite lithium replenishment layer, its preparation method, and its application.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: One objective of this invention is to provide a method for preparing a metal-metal carbide / lithium supplementation composite lithium supplementation layer derived from an organometallic framework, the method comprising the following steps: (1) Preparation of small-particle-size lithium supplement: The lithium supplement and ball milling beads are mixed and ball milled to obtain a small-particle-size lithium supplement with a particle size of 1~10μm; (2) Preparation of MOF materials: The inorganic salt and organic ligand of metal A are dissolved in a solvent, mixed and allowed to stand. After standing, the mixture is centrifuged, washed and vacuum dried to obtain the MOF material of metal A. (3) Preparation of metal-metal carbide catalysts derived from organometal frameworks: The MOF material of metal A is mixed with the metal source B to obtain a mixture, and the mixture is heat-treated in an inert gas to obtain metal-metal carbide catalysts derived from organometal frameworks. (4) Preparation of lithium replenishment layer: The metal-metal carbide catalyst derived from the organometal framework and the small-particle-size lithium replenishment agent are mixed as active materials, and mixed with conductive agent, binder and solvent to obtain lithium replenishment slurry. The lithium replenishment slurry is coated and vacuum dried to obtain the metal-metal carbide / lithium replenishment agent composite lithium replenishment layer derived from the organometal framework.

[0007] Further specified, (1) the lithium supplement is one or more of Li2C2O4, Li2C3O3, Li2C3O5, Li2C4O4, Li2C4O6, Li2C5O5, Li2C6O6, Li2CO3, LiCHO2, LiC2H3O2, Li2O, Li2O2, Li4SiO4, Li5FeO4, Li2NiO2, Li2N4O2C2, Li6MnO4, Li2MnO3, Li8ZrO6, Li4EDTA, and Li5DTPA mixed in any proportion.

[0008] Further specified, (1) the mass ratio of lithium supplement and ball milling beads is 1: (10~30).

[0009] Further specified, (1) the ball milling time is 10~20h and the rotation speed is 200~500rpm.

[0010] Further specifying, (2) the inorganic salt of metal A is one or more of the nitrates, acetates, and chlorides of Co, Ni, Mn, Fe, Mg, Zn, Cr, Cu, and Al mixed in any proportion.

[0011] Further specifying, (2) the organic ligand is one or more of 2-methylimidazole, terephthalic acid, pyromellitic acid, 2,5-dihydroxyterephthalic acid, biphenyl-4,4'-dicarboxylic acid, 4,4'-bipyridine, triazole, and tetraazole mixed in any proportion.

[0012] Further specifying, in (2), the molar ratio of the inorganic salt to the organic ligand of metal A is 1:(4~10).

[0013] Further specifying, (2) the solvent is one or more of methanol, ethanol, isopropanol, water, N,N-dimethylformamide, N,N-diethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, and acetonitrile mixed in any proportion.

[0014] Further, in (2), the standing temperature is 25~200℃ and the time is 1~24h.

[0015] Further specifying, in (3), the mass ratio of the MOF material of metal A to the source of metal B is 1:(1~4).

[0016] Further specifying, (3) the metal B source is one or more of the secondary metal salts, metal acetylacetonates, metal nitrates, metal acetates, and metal chlorides of Mo, Co, W, Ni, Cr, V, Nb, and Ti, mixed in any proportion.

[0017] Further specified, (3) the inert gas is nitrogen or argon; the heat treatment temperature is 300~1000℃, the time is 0.5~24h, and the heating rate is 1~5℃ / min.

[0018] Further specifying, (4) the mass ratio of small-particle-size lithium supplementer to organometal framework-derived metal-metal carbide catalyst is (4~15):1.

[0019] Further specifying, the mixing method in (4) is one or more of grinding, ball milling, co-recrystallization, freeze drying, and spray drying.

[0020] Further specifying, (4) the coating method is to coat the lithium replenishing slurry onto one or more of the following: the surface of aluminum foil, the surface of the positive electrode material, and the surface of the separator.

[0021] The second objective of this invention is to provide a metal-metal carbide / lithium replenishing agent composite lithium replenishing layer derived from the organometallic framework obtained by the above preparation method.

[0022] Further defining the composite lithium replenishment layer, it obtains a metal-metal carbide catalyst based on an organometal framework precursor. It utilizes the interfacial electronic reconstruction effect caused by the strong interaction between the metal and the metal carbide, which enables the metal sites to efficiently adsorb oxygen atoms in the lithium replenishment agent, thereby lengthening and weakening the Li-O bond, and ultimately driving the efficient decomposition and lithium replenishment of the lithium replenishment agent.

[0023] The third objective of this invention is to provide an application of the above-mentioned composite lithium replenishment layer in the preparation of lithium-ion batteries.

[0024] Furthermore, the composite lithium replenishing layer is used as a positive electrode lithium replenishing agent in the process of preparing lithium-ion batteries.

[0025] The present invention has the following beneficial effects: (1) The catalyst used in the composite lithium replenishment layer of this invention is an organic framework material (MOF) of metal A as a precursor, which is constructed in situ through one-step calcination with metal B source. In this process, the metal ions of MOF are reduced to metal A, and its organic ligands participate as a carbon source to generate metal B carbides. The composite lithium replenishment layer obtains a metal-metal carbide catalyst based on the organometal framework precursor. It utilizes the interfacial electronic reconstruction effect caused by the strong interaction between metal and metal carbide to enable the metal sites to efficiently adsorb oxygen atoms in the lithium replenishment agent, thereby lengthening and weakening the energy barrier required for Li-O bond breaking, and finally driving the lithium replenishment agent to decompose and replenish lithium efficiently. Specifically, based on the electronegativity difference between metal A and metal B carbides in the catalyst, electronic reconstruction occurs at the interface between the two. Electrons migrate from metal A to metal B carbides. This electron migration effect enhances the adsorption capacity of metal A for oxygen atoms in the lithium replenishment agent, thereby effectively weakening the energy barrier required for Li-O bond breaking and significantly improving the decomposition activity of the lithium replenishment agent.

[0026] (2) To optimize the reaction interface, this invention involves uniformly mixing and coating an organometallic framework-derived metal-metal carbide catalyst with a lithium replenishing agent to ultimately form the integrated composite lithium replenishing layer. The organometallic framework-derived metal-metal carbide / lithium replenishing agent composite lithium replenishing layer provided by this invention has a low decomposition voltage, high lithium-ion utilization rate of the lithium replenishing agent, and good lithium replenishment effect.

[0027] (3) The present invention constructs a metal-metal carbide catalyst based on MOF material, which significantly enhances the adsorption and activation ability of Li–O bond in lithium replenishment agent, effectively reduces its decomposition energy barrier, and can achieve efficient decomposition of composite lithium replenishment layer within the positive electrode working voltage range with a small amount of catalyst, with a decomposition efficiency of over 99%.

[0028] (4) The composite lithium replenishment layer prepared by the present invention can efficiently release active lithium ions and significantly compensate for the irreversible lithium ion loss during the first cycle of the battery. Attached Figure Description

[0029] Figure 1 The image shows a SEM image of Co-Mo2C prepared in Example 1. Figure 2 The image shows the XRD pattern of Co-Mo2C prepared in Example 1. Figure 3 The first charge-discharge curves of the half-cells prepared using the composite lithium replenishment layers of Examples 1-3 are shown. Figure 4 The first charge-discharge curves of NCM83|| graphite full cells without using the composite lithium replenishment layer and the composite lithium replenishment layer of Example 1 are shown. Detailed Implementation

[0030] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification. Many specific details are set forth in the following description to provide a thorough understanding of the present invention; however, the present invention may also be implemented in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0031] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0032] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0033] Example 1 (1) Preparation of small-particle-size lithium supplement: Anhydrous lithium oxalate and zirconium oxide ball milling beads were placed in a ball mill at a mass ratio of 1:20 and ball milled at a speed of 400 rpm. After 10 hours, the ball milling beads and lithium oxalate were separated to obtain small-particle-size lithium oxalate with a particle size of 2-5 μm. (2) Preparation of MOF material: 5 mmol of cobalt nitrate hexahydrate and 20 mmol of 2-methylimidazole were dissolved in 100 mL of methanol. After stirring for 10 min, the mixture was allowed to stand at 25 °C (room temperature) for 24 h. The mixture was centrifuged with methanol and the supernatant was discarded. Fresh methanol was added to the solid precipitate and the mixture was redispersed by stirring or sonication. The mixture was centrifuged again and the supernatant was discarded. This washing process was repeated 3 times. The obtained solid was vacuum dried at 80 °C for 10 h to obtain Co-MOF. (3) Preparation of organometallic framework-derived metal-metal carbide catalyst: 0.2 g Co-MOF and 0.2 g ammonium molybdate were thoroughly ground and mixed. The resulting mixture was placed in a tube furnace and heated to 750 °C at a rate of 2 °C / min under a nitrogen atmosphere. The temperature was held for 3 h and then naturally cooled to room temperature to obtain the Co-Mo2C catalyst, i.e., the organometallic framework-derived metal-metal carbide catalyst. Its microstructure is as follows: Figure 1 As shown; (4) The small-particle-size lithium oxalate and Co-Mo2C catalyst are thoroughly mixed at a mass ratio of 6:1. The resulting mixture is used as the active material and is mixed with the conductive agent Super P and the binder PVDF at a mass ratio of 6:3:1 to form a lithium replenishing slurry. After thorough mixing, it is coated onto aluminum foil and placed in an oven at 120°C for vacuum drying for 12 hours to obtain a lithium replenishing layer.

[0034] Example 2 The difference between this embodiment and embodiment 1 is that in step (4), the mass ratio of small-particle-size lithium oxalate to Co-Mo2C catalyst is 8:1, and the remaining process operations and parameter settings are the same as in embodiment 1.

[0035] Example 3 The difference between this embodiment and embodiment 1 is that in step (4), the mass ratio of small-particle-size lithium oxalate to Co-Mo2C catalyst is 10:1, and the remaining process operations and parameter settings are the same as in embodiment 1.

[0036] Example 4 The difference between this embodiment and embodiment 1 is that: in step (3), ammonium molybdate is replaced with sodium tungstate to obtain Co-W2C catalyst; in step (4), the mass ratio of small-particle-size lithium oxalate to Co-W2C catalyst is 4:1; and the remaining process operations and parameter settings are the same as in embodiment 1.

[0037] Example 5 The difference between this embodiment and embodiment 1 is that: in step (2), cobalt nitrate hexahydrate is replaced with zinc acetate dihydrate to obtain Zn-MOF; in step (4), the mass ratio of small-particle-size lithium oxalate to Zn-Mo2C catalyst is 4:1; and the remaining process operations and parameter settings are the same as in embodiment 1.

[0038] Comparative Example 1 The difference between this comparative example and Example 1 is that this comparative example provides a lithium replenishing layer with a commercial lithium replenishing agent. It does not prepare small-particle-size lithium replenishing agents, MOF materials, and metal-metal carbide catalysts. Commercial lithium oxalate is directly mixed with conductive agent SuperP and binder PVDF at a mass ratio of 6:3:1 to form a lithium replenishing slurry. After thorough mixing, it is coated onto aluminum foil and placed in an oven at 120°C for vacuum drying for 12 hours. The remaining process operations and parameter settings are the same as in Example 1 to obtain the lithium replenishing layer.

[0039] Comparative Example 2 This comparative example provides a lithium replenishment layer with a small particle size lithium replenishing agent.

[0040] (1) Preparation of small-particle-size lithium supplement: Lithium oxalate and zirconium oxide ball milling beads are put into a ball mill at a mass ratio of 1:20 and ball milled at a speed of 400 rpm. After 10 hours, the ball milling beads and lithium oxalate are separated to obtain small-particle-size lithium oxalate. (2) Small-particle-size lithium oxalate, conductive agent Super P, and binder PVDF are mixed in a mass ratio of 6:3:1 to form a lithium replenishing slurry. After thorough mixing, the slurry is coated onto aluminum foil and placed in an oven at 120°C for vacuum drying for 12 hours to obtain a lithium replenishing layer.

[0041] Comparative Example 3 This comparative example provides a metal-carbon / lithium supplement composite lithium supplement layer derived from an organometallic framework.

[0042] (1) Preparation of small-particle-size lithium supplement: Lithium oxalate and zirconium oxide ball milling beads are put into a ball mill at a mass ratio of 1:20 and ball milled at a speed of 400 rpm. After 10 hours, the ball milling beads and lithium oxalate are separated to obtain small-particle-size lithium oxalate. (2) Preparation of MOF material: 5 mmol of cobalt nitrate and 20 mmol of 2-methylimidazole were dissolved in 100 mL of methanol. After stirring for 10 min, the mixture was allowed to stand at 25 °C (room temperature) for 24 h. The mixture was centrifuged with methanol and the supernatant was discarded. Fresh methanol was added to the solid precipitate and the mixture was redispersed by stirring or sonication. The mixture was centrifuged again and the supernatant was discarded. This washing process was repeated 3 times. The obtained solid was dried under vacuum at 80 °C for 10 h to obtain Co-MOF. (3) Preparation of metal-carbon catalyst: 0.2 g Co-MOF was placed in a tube furnace and heated to 750°C at a heating rate of 2°C / min under a nitrogen atmosphere. The temperature was kept constant for 3 h and then naturally cooled to room temperature to obtain the Co-C catalyst. (4) The small-particle-size lithium oxalate and Co-C catalyst are thoroughly mixed at a mass ratio of 4:1. The resulting mixture is used as the active material and is mixed with the conductive agent Super P and the binder PVDF at a mass ratio of 6:3:1 to form a lithium replenishing slurry. After thorough mixing, it is coated onto aluminum foil and placed in an oven at 120°C for vacuum drying for 12 hours to obtain the lithium replenishing layer.

[0043] Comparative Example 4 This comparative example provides a metal carbide-lithium replenishing agent composite lithium replenishing layer.

[0044] Small-particle-size lithium oxalate and molybdenum carbide were thoroughly mixed at a mass ratio of 4:1. The resulting mixture was used as the active material and mixed with conductive agent Super P and binder PVDF at a mass ratio of 6:3:1 to form a lithium replenishing slurry. After thorough mixing, the slurry was coated onto aluminum foil and dried in a vacuum oven at 120°C for 12 hours to obtain the lithium replenishing layer.

[0045] Comparative Example 5 This comparative example provides a metal / molybdenum carbide / lithium replenishing agent composite lithium replenishing layer derived from an organometallic framework.

[0046] (1) Preparation of small-particle-size lithium supplement: Lithium oxalate and zirconium oxide ball milling beads are put into a ball mill at a mass ratio of 1:20 and ball milled at a speed of 400 rpm. After 10 hours, the ball milling beads and lithium oxalate are separated to obtain small-particle-size lithium oxalate. (2) Preparation of MOF material: 5 mmol of cobalt nitrate and 20 mmol of 2-methylimidazole were dissolved in 100 mL of methanol. After stirring for 10 min, the mixture was allowed to stand at 25 °C (room temperature) for 24 h. The mixture was centrifuged with methanol and the supernatant was discarded. Fresh methanol was added to the solid precipitate and the mixture was redispersed by stirring or sonication. The mixture was centrifuged again and the supernatant was discarded. This washing process was repeated 3 times. The obtained solid was dried under vacuum at 80 °C for 10 h to obtain Co-MOF. (3) Preparation of metal-carbon catalyst: 0.2 g Co-MOF was placed in a tube furnace and heated to 750°C at a heating rate of 2°C / min under a nitrogen atmosphere. The temperature was kept constant for 3 h and then naturally cooled to room temperature to obtain the Co-C catalyst. (4) The Co-C catalyst and molybdenum carbide are mixed at a mass ratio of 1:1 to form a catalyst. Small-particle-size lithium oxalate and the catalyst are fully mixed at a mass ratio of 6:1. The resulting mixture is used as the active material. It is mixed with conductive agent Super P and binder PVDF at a mass ratio of 6:3:1 to form a lithium replenishing slurry. After being fully mixed, it is coated onto aluminum foil and placed in an oven at 120°C for vacuum drying for 12 hours to obtain a lithium replenishing layer.

[0047] Performance testing The lithium-replenishing layers coated on Al foil prepared in Examples 1-3 and Comparative Examples 1-4 were used as positive electrodes, lithium metal sheets as negative electrodes, polypropylene microporous membranes as separators, and EC / DMC solutions containing 1 mol / L LiPF6 (volume ratio 3:7) as electrolytes. The batteries were assembled into coin cells in a glove box filled with argon atmosphere. Constant current charge-discharge tests were then performed on the batteries, and the test results are shown in Table 1 and [Table data would be inserted here]. Figure 3 .

[0048] Table 1

[0049] From Table 1 and Figure 3The first-cycle charge-discharge curves of Examples 1-3 show that the catalyst of this invention plays a crucial role in improving the decomposition efficiency of the lithium replenishing agent. Commercially available lithium replenishing agents exhibit poor lithium replenishment performance, with a first-cycle charge specific capacity of only 6.010 mAh / g and a decomposition efficiency below 2%. Comparative Example 2 involved ball milling the lithium replenishing agent; although ball milling reduced the particle size, it was still insufficient to effectively promote lithium release, resulting in an extremely low first-cycle charge specific capacity of only 11.7 mAh / g, a decomposition efficiency below 2.5%, and poor electrochemical activity. In contrast, the composite lithium replenishing layers of Examples 1-5 all demonstrated significant performance improvements.

[0050] Further analysis revealed that the composition and structure of the catalyst significantly affect its performance. A comparison of Example 1 with Comparative Examples 3 and 4 showed that even when the catalyst dosage reached 25% of the mass of small-particle lithium oxalate, the catalytic effect of Co-C (Comparative Example 3) and molybdenum carbide (Comparative Example 4), containing only a single metal element, on the decomposition of lithium oxalate was significantly inferior to that of Co-Mo2C (Example 1), which had a catalyst dosage of only 16.67% of the lithium oxalate mass. Similar conclusions can be drawn from the comparative analysis of Example 4 with Comparative Example 3 and Example 5 with Comparative Example 4. Under the same catalyst dosage conditions, when a second metal element W was introduced into the Co-C catalytic system (Example 4), its catalytic effect on the decomposition of lithium oxalate was superior to that of the single-metal Co-C catalyst (Comparative Example 3). Similarly, under the same catalyst dosage, when a second metal element Zn was introduced into the Mo2C catalyst (Example 5), its catalytic performance was further improved compared to Comparative Example 4. The above results indicate that while both MOF-based carbon-supported metal A catalysts and metal B carbide catalysts possess certain catalytic activity, their effect on enhancing the decomposition activity of lithium supplementers is limited. However, when a second metal element with a different electronegativity is introduced into the MOF framework, an electronic coupling interface can be formed between metal A and metal B carbides, inducing interfacial electron transfer. This interfacial electron reconstruction effect successfully constructs a highly active catalytic center in the catalyst. As shown in Table 1, the Co-Mo2C catalyst in Example 1 successfully reduced the decomposition voltage of the lithium supplementer to 4.19 V and achieved a high decomposition rate of 99.49% at a cutoff voltage of 4.5 V, significantly reducing the kinetic barrier of the lithium supplementer decomposition reaction. By comparing Example 1 and Comparative Example 5, it can be found that, with the same catalyst dosage, simply physically mixing Co-C and Mo2C catalysts (Comparative Example 5) cannot achieve the same catalytic effect as Example 1. This indicates that the aforementioned interfacial electron reconstruction effect cannot be achieved through the mechanical coexistence of metal A and metal B carbides after simple physical mixing; its catalytic performance improvement depends on the tight chemical interface formed between the two.

[0051] Figure 4The composite lithium replenishment layer of Example 1 is applied to the electrochemical performance of an NCM83||graphite full cell. As can be seen from the figure, the composite lithium replenishment layer (NCM-pre) of Example 1 increases the first-cycle discharge capacity of the full cell by 28.04 mAh / g compared to the cell without a lithium replenishment layer, further verifying its effectiveness and feasibility in practical battery systems.

[0052] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a metal-metal carbide / lithium supplementation composite lithium-supplementing layer derived from an organometallic framework, characterized in that, The method includes the following steps: (1) Preparation of small-particle-size lithium supplement: The lithium supplement and ball milling beads are mixed and ball milled to obtain a small-particle-size lithium supplement with a particle size of 1~10μm; (2) Preparation of MOF materials: The inorganic salt and organic ligand of metal A are dissolved in a solvent, mixed and allowed to stand. After standing, the mixture is centrifuged, washed and vacuum dried to obtain the MOF material of metal A. (3) Preparation of metal-metal carbide catalysts derived from organometal frameworks: The MOF material of metal A is mixed with the metal source B to obtain a mixture, and the mixture is heat-treated in an inert gas to obtain metal-metal carbide catalysts derived from organometal frameworks. (4) Preparation of lithium replenishment layer: The metal-metal carbide catalyst derived from the organometal framework and the small-particle-size lithium replenishment agent are mixed as active materials, and mixed with conductive agent, binder and solvent to obtain lithium replenishment slurry. The lithium replenishment slurry is coated and vacuum dried to obtain the metal-metal carbide / lithium replenishment agent composite lithium replenishment layer derived from the organometal framework.

2. The preparation method according to claim 1, characterized in that, (1) The lithium supplement is one or more of Li2C2O4, Li2C3O3, Li2C3O5, Li2C4O4, Li2C4O6, Li2C5O5, Li2C6O6, Li2CO3, LiCHO2, LiC2H3O2, Li2O, Li2O2, Li4SiO4, Li5FeO4, Li2NiO2, Li2N4O2C2, Li6MnO4, Li2MnO3, Li8ZrO6, Li4EDTA, and Li5DTPA mixed in any proportion.

3. The preparation method according to claim 1, characterized in that, (2) The inorganic salt of metal A is one or more of the nitrates, acetates, and chlorides of Co, Ni, Mn, Fe, Mg, Zn, Cr, Cu, and Al, mixed in any proportion; the organic ligand is one or more of 2-methylimidazolium, terephthalic acid, pyromellitic acid, 2,5-dihydroxyterephthalic acid, biphenyl-4,4'-dicarboxylic acid, 4,4'-bipyridine, triazole, and tetraazole, mixed in any proportion.

4. The preparation method according to claim 1, characterized in that, (2) The molar ratio of inorganic salt to organic ligand of metal A is 1:(4~10); the standing temperature is 25~200℃ and the time is 1~24h.

5. The preparation method according to claim 1, characterized in that, (3) The mass ratio of the MOF material of metal A to the source of metal B is 1: (1~4).

6. The preparation method according to claim 1, characterized in that, (3) The metal B source is one or more of the secondary metal salts, metal acetylacetone salts, metal nitrates, metal acetates, and metal chlorides of Mo, Co, W, Ni, Cr, V, Nb, and Ti, mixed in any proportion.

7. The preparation method according to claim 1, characterized in that, (4) The heat treatment temperature is 300~1000℃, the time is 0.5~24h, and the heating rate is 1~5℃ / min; the mass ratio of small particle size lithium supplement to metal-metal carbide catalyst is (4~15):

1.

8. A metal-metal carbide / lithium replenishing agent composite lithium replenishing layer derived from an organometallic framework obtained by the preparation method according to any one of claims 1 to 7.

9. The application of the composite lithium replenishment layer according to claim 8 in the preparation of lithium-ion batteries.

10. The application according to claim 9, characterized in that, Composite lithium replenishing layers are used as positive electrode lithium replenishing agents in the preparation of lithium-ion batteries.

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