ZIF-8 derived carbon composite lithium ferrite lithium supplement agent as well as preparation method and application thereof

Abstract

The invention discloses a ZIF-8 derived carbon composite lithium ferrite lithium supplement agent and a preparation method and application thereof, and belongs to the field of lithium ion battery lithium supplement materials, the lattice oxygen release amount in the lithium ferrite charging process is inhibited from 2.67 [mu] mol / mg to 0.15 [mu] mol / mg or less through a Co / Ni / Mn multi-metal monatomic synergistic catalysis interface (M-N4 site), and the oxygen conversion efficiency is gt; 95%. Compared with traditional oxide coated lithium ferrite, the oxygen inhibition rate is 1t; 30%), the first efficiency of the whole battery is improved to be greater than or equal to 91.2% from 76.8%, and the high-surface-capacity positive electrode (gt; 4 mAh / cm < 2 >); 85%. According to the invention, a'monatomic carbon layer mosaic-conductive network interlocking 'interface constructed by ball milling enables the volume expansion rate of the electrode to be 1t after 100 cycles; 5%.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery lithium replenishment materials, specifically relating to a ZIF-8 derived carbon composite lithium ferrite replenishment agent and its preparation method and application. Background Technology

[0002] Lithium ferrite (Li5FeO4), as a pre-lithiation agent with high irreversible capacity (>550mAh / g) and low reaction energy barrier, can irreversibly deintercalate and intercalate four Li groups during the first charge. + This effectively compensates for lithium loss in the first cycle of the negative electrode. However, the delithiation reaction requires a high voltage of >4.5V, which triggers the release of lattice oxygen and the generation of active oxygen species (such as O2), leading to electrolyte oxidation and decomposition, gas expansion, and safety hazards, severely restricting its application in practical batteries. Previous studies have attempted to stabilize the crystal structure through surface coating or bulk doping, but these still face bottlenecks such as low oxygen suppression efficiency (<30%), ion barrier effect of the coating layer, and secondary oxygen release during cycling.

[0003] In recent years, metal-organic framework (MOF)-derived single-atom catalysts have emerged as a novel strategy for addressing the challenge of oxygen release at high voltages due to their maximized atom utilization, tunable metal coordination environment, and highly efficient oxygen conversion capabilities. Among these, nitrogen-doped carbon (NC) supports derived from ZIF-8 can achieve atomic-level dispersion of metals such as Co / Ni / Mn, forming M-N4 active sites, exhibiting excellent bifunctional catalytic activity in lithium-oxidation reactions (ORR / OER). Combining such single-atom catalysts with Li5FeO4 to construct a "pre-lithiation-oxygen elimination" bifunctional system holds promise for simultaneously achieving high lithium replenishment capacity and intrinsic safety.

[0004] However, the precise construction of polymetallic single-atom sites, the interfacial charge transport mechanism between the catalyst and lithium ferrite, and the directional catalytic pathway of lattice oxygen under complex operating conditions remain unclear and require breakthroughs through material design and in-situ characterization techniques. Summary of the Invention

[0005] The purpose of this invention is to provide a ZIF-8 derived carbon composite lithium ferrite supplement agent, its preparation method, and its application. The supplement agent is prepared using a ZIF-8 derived multi-metal single-atom catalyst (Co / Ni / Mn). SAs The composite structure is formed by mechanically fusing ( / NC) with lithium ferrite, which enables efficient catalytic lattice oxygen conversion at single atomic sites, significantly suppresses gaseous byproducts, and simultaneously improves lithium replenishment efficiency and thermal stability.

[0006] The core of the technical solution of this invention lies in three collaborative designs:

[0007] (1) In terms of material design: This invention constructs a Zn / Co / Ni / Mn quaternary ZIF-8 precursor (metal molar ratio Zn:(Co+Ni+Mn)=8:1, Co:Ni:Mn=2:1:1) via aqueous co-precipitation. After confined pyrolysis at 900°C for 2 hours under argon atmosphere, atomically dispersed M-N4 active sites are obtained and anchored on a nitrogen-doped carbon support (SAs / NC). This support possesses both high conductivity (>100S / m) and multi-metal synergistic catalytic function (Co regulates oxygen adsorption, Ni promotes electron transfer, and Mn accelerates oxygen reduction). It is then combined with Li5FeO4 through efficient ball milling (mass ratio 1:5) to achieve uniform embedding of single-atom catalysts on the surface of lithium ferrite, forming a "pre-lithiation-oxygen elimination" dual-functional interface.

[0008] (2) In terms of structural control: This invention innovatively adopts a high-temperature pyrolysis-mechanical fusion hierarchical process. At 900°C, the ZIF-8 framework is transformed into a three-dimensional conductive network, and Co / Ni / Mn atoms are coordinated and locked by nitrogen. HAADF-STEM confirms that the metal sites are isolated and dispersed (particle size <0.2nm). During ball milling, the carbon framework of SAs / NC is embedded in the Li5FeO4 grain boundaries to form the Li5FeO4 and SAs / NC microstructure. The nanoscale Co-based particles formed after calcination can be embedded or coated on the surface of the lithium oxalate matrix, establishing a strong interfacial coupling relationship with the oxalate structure. In terms of microstructure, the lithium ferrite particles are embedded in the multiphase Co / C nanoparticles in a dot-like or planar manner, which effectively reduces the reaction energy barrier required for its oxidation decomposition, while constructing a continuous electronic pathway, significantly improving the charge transfer rate and structural stability.

[0009] (3) In terms of electrochemical performance: The SAs / NC@LFO lithium replenisher constructed in this invention achieves stable release of Li during the first charge (2.5-4.7V). + The initial charging efficiency can reach 92-95%. Irreversible lithium delithiation capacity ≥540mAh / g (corresponding to Li...) + (Release), the initial efficiency of silicon-based full cells is ≥91%. With 5wt% addition, the capacity retention after 100 cycles is ≥91% (76.8% without addition), and there is no electrode gas expansion. It exhibits excellent long-term stability and practical potential. Compared to traditional coated lithium iron ferrite, this strategy reduces the amount of lithium replenishing agent by 50% (only 5-10wt%), achieves a lithium replenishment capacity utilization rate >85%, and the process does not require organic solvents, demonstrating significant industrialization advantages.

[0010] The above objectives and designs are achieved through the following technical solutions:

[0011] A method for preparing a ZIF-8 derived carbon composite lithium ferrite supplement includes the following steps:

[0012] S1. Add metal nitrate to deionized water with stirring to obtain a precursor solution. The metal nitrate is a mixture of Zn(NO3)2·6H2O and TM(NO3)2·6H2O. Then add 2-methylimidazole to the precursor solution and stir for 30 min to form the TM / ZIF-8 precursor.

[0013] S2. The TM / ZIF-8 precursor is heated to 900℃ at 5℃ / min under an argon atmosphere and calcined at a constant temperature for 2h. After calcination, it is naturally cooled to obtain TM / ZIF-8.

[0014] S3. Then, TM / ZIF-8, Li5FeO4, and multi-walled carbon nanotubes are ball-milled at a mass ratio of 2:12:1 for 4 hours. After the milling is completed, ZIF-8-derived carbon composite lithium ferrite supplement is obtained.

[0015] Furthermore, the mass ratio of deionized water to metal nitrate in S1 is 10:1.

[0016] Furthermore, the metal nitrate described in S1 is composed of Zn(NO3)2·6H2O and TM(NO3)2·6H2O mixed in a molar ratio of Zn:TM=8:1.

[0017] Furthermore, the amount of 2-methylimidazole used in S1 is based on a molar ratio of metal ion:2-methylimidazole = 1:8; the metal ion is Zn. 2+ and TM 2+ sum.

[0018] Furthermore, TM mentioned in S1 is one of Co, Ni, and Mn.

[0019] Furthermore, the TM is Co.

[0020] Furthermore, the Li5FeO4 in S3 has a purity of ≥99.5% and a particle size of 50μm; the multi-walled carbon nanotubes have a diameter of 20nm and a length of 1~5μm.

[0021] Furthermore, a ZIF-8 derived carbon composite lithium ferrite supplement is prepared by the above preparation steps.

[0022] Furthermore, a ZIF-8 derived carbon composite lithium iron ferrite supplement agent is applied to the cathode of lithium batteries.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) Revolutionary breakthrough in oxygen release inhibition, significantly improving initial efficacy:

[0025] This invention utilizes a Co / Ni / Mn multi-metal single-atom synergistic catalytic interface (M-N4 site) to suppress the lattice oxygen release during lithium ferrite charging from 2.67 μmol / mg to ≤0.15 μmol / mg, achieving an oxygen conversion efficiency >95%. Compared to traditional oxide-coated lithium ferrite (oxygen suppression rate <30%), the first-stage efficiency of the full cell is improved from 76.8% to ≥91.2%, and this is further enhanced at a high areal capacity cathode (>4 mAh / cm²). 2 The lithium replenishment capacity utilization rate is >85%.

[0026] (2) Enhanced structural and thermal stability:

[0027] The "single-atom carbon layer embedding-conductive network interlocking" interface constructed by ball milling in this invention results in an electrode volume expansion rate of <5% after 100 cycles. ARC testing shows that the thermal runaway trigger temperature is ≥225℃ (169℃ for pure LFO), simultaneously solving the problems of cyclic pulverization and thermal safety.

[0028] (3) Seamless industrialization adaptation:

[0029] This invention employs a solvent-free mechanical fusion process (ball milling for 4 hours), which, compared to the wet coating route, reduces energy consumption by <0.5kWh / kg (wet method >3kWh / kg), lowers overall raw material costs by more than 30%, and shortens the production cycle by 70% (eliminating the solvent cleaning / freeze-drying 24-hour step), making it suitable for industrial-scale expansion.

[0030] (4) Strong industry adaptability:

[0031] The composite lithium supplement agent prepared by this invention is directly compatible with existing cathode slurry preparation processes (NMP solvent system) and does not cause slurry agglomeration or delamination. After rolling, the electrode surface is uniform and dense, exhibiting extremely high inter-electrode stability and coating uniformity. It can be adapted to existing lithium battery electrode production lines without the need for additional equipment or changes to the process route. Attached Figure Description

[0032] The present invention will now be further described with reference to the accompanying drawings.

[0033] Figure 1 Co prepared in Example 1 SAs SEM and TEM images of / NC;

[0034] Figure 2 Co prepared in Example 1 SAs / NC spherical aberration electron microscopy image. Detailed Implementation

[0035] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Furthermore, unless otherwise specified, the raw materials, reagents, or devices used in the following embodiments can be obtained from conventional commercial channels or by existing known methods.

[0036] Example 1

[0037] A method for preparing a ZIF-8 derived carbon composite lithium ferrite supplement includes the following steps:

[0038] The metal nitrate was added to deionized water with a mass ratio of 10:1 to obtain a precursor solution. The metal nitrate was a mixture of Zn(NO3)2·6H2O and Co(NO3)2·6H2O in a molar ratio of Zn:Co = 8:1. The metal nitrate was then added to the precursor solution according to the metal ion ratio (Zn...). 2+ and Co 2+ Add 2-methylimidazole in a molar ratio of 1:8 and stir for 30 min to form the Co / ZIF-8 precursor. Then, calcine the Co / ZIF-8 precursor at 900℃ under an argon atmosphere at a rate of 5℃ / min for 2 h. After calcine completion, allow it to cool naturally to obtain Co / ZIF-8 (Co SAs / NC, NC: Nitrogen-doped carbon, Co SAs SEM, TEM, and aberration-corrected electron microscopy images of / NC, such as Figure 1-2 As shown), Co / ZIF-8, Li5FeO4 (commercial grade, purity ≥99.5%, particle size 50μm), and multi-walled carbon nanotubes (diameter 20nm, length 1-5μm) were ball-milled at a mass ratio of 2:12:1 for 4 hours (350rpm, argon protection). After completion, Co was obtained. SAs The / NC@LFO complex yields the ZIF-8 derived carbon composite lithium ferrite supplement prepared in Example 1.

[0039] Example 2

[0040] Example 2 serves as the control group for Example 1, except that Co(NO3)2·6H2O in Example 1 is replaced with Ni(NO3)2·6H2O. All other raw materials, amounts, and preparation steps remain consistent with Example 1, as detailed below:

[0041] A method for preparing a ZIF-8 derived carbon composite lithium ferrite supplement includes the following steps:

[0042] The metal nitrate was added to deionized water with a mass ratio of 10:1 to obtain a precursor solution. The metal nitrate was a mixture of Zn(NO3)2·6H2O and Ni(NO3)2·6H2O in a molar ratio of Zn:Ni = 8:1. The metal nitrate was then added to the precursor solution according to the metal ion ratio (Zn...). 2+ and Ni 2+ Add 2-methylimidazole in a molar ratio of 1:8 and stir for 30 min to form the Ni / ZIF-8 precursor. Then, calcine the Ni / ZIF-8 precursor at 900 °C under an argon atmosphere at a rate of 5 °C / min for 2 h. After calcine completion, allow it to cool naturally to obtain Ni / ZIF-8 (Ni SAs / NC, NC: nitrogen-doped carbon), then Ni / ZIF-8, Li5FeO4 (commercial grade, purity ≥99.5%, particle size 50μm), and multi-walled carbon nanotubes (diameter 20nm, length 1~5μm) were ball-milled at a mass ratio of 2:12:1 for 4h (350rpm, argon protection). After completion, Ni was obtained. SAs The / NC@LFO complex yields the ZIF-8 derived carbon composite lithium ferrite supplement prepared in Example 2.

[0043] Example 3

[0044] Example 3 serves as the control group for Example 1, except that Co(NO3)2·6H2O in Example 1 is replaced with Mn(NO3)2·6H2O, while the remaining raw materials, amounts, and preparation steps remain consistent with those in Example 1, as detailed below:

[0045] A method for preparing a ZIF-8 derived carbon composite lithium ferrite supplement includes the following steps:

[0046] The metal nitrate was added to deionized water with a mass ratio of 10:1 to obtain a precursor solution. The metal nitrate was a mixture of Zn(NO3)2·6H2O and Mn(NO3)2·6H2O in a molar ratio of Zn:Mn = 8:1. The metal nitrate was then added to the precursor solution according to the metal ion ratio (Zn...). 2+ and Mn 2+ Add 2-methylimidazole in a molar ratio of 1:8 and stir for 30 min to form the Mn / ZIF-8 precursor. Then, calcine the Mn / ZIF-8 precursor at 900℃ under an argon atmosphere at a rate of 5℃ / min for 2 h. After calcine completion, allow it to cool naturally to obtain Mn / ZIF-8(Mn SAs / NC, NC: nitrogen-doped carbon), then Mn / ZIF-8, Li5FeO4 (commercial grade, purity ≥99.5%, particle size 50μm), and multi-walled carbon nanotubes (diameter 20nm, length 1~5μm) were ball-milled at a mass ratio of 2:12:1 for 4h (350rpm, argon protection). After completion, Mn was obtained. SAs The / NC@LFO complex yields the ZIF-8 derived carbon composite lithium ferrite supplement prepared in Example 3.

[0047] Comparative Example 1

[0048] Comparative Example 1 is lithium ferrite (Li5FeO4).

[0049] Test Example 1

[0050] The performance of the lithium supplements (ZIF-8 derived carbon composite lithium ferrite supplements prepared in Examples 1 to 3 or lithium ferrite in Comparative Example 1) was tested. The test process is as follows, and the test results are shown in Table 1.

[0051] 1. Decomposition Potential Test (LSV Scan):

[0052] (1) Electrode preparation: Working electrode: Lithium replenishing agent: Acetylene black: PTFE = 80:15:5 (mass ratio) coated on aluminum foil (loading 2 mg / cm³). 2 Counter electrode / reference electrode: lithium sheet (99.9% purity).

[0053] (2) Electrolyte: 1M LiPF6 in EC / DMC / EMC (1:1:1 vol%).

[0054] (3) Test conditions: Equipment: Electrochemical workstation (CHI760E); Scan range: 2.5→4.5V vs. Li⁺ / Li; Scan rate: 0.1 mV / s; Temperature: 25±0.5℃ (constant temperature water bath).

[0055] (4) Data extraction: Decomposition potential = Oxidation current surge point (dI / dV > 10 μA·mV) -1 ).

[0056] 2. First charge efficiency (half-cell):

[0057] (1) Button cell assembly (CR2032): Positive electrode: Lithium supplement: Conductive carbon black: PVDF = 90:5:5 (loading 1.5 mg / cm³) 2 Anode: Lithium foil; Separator: Celgard 2400.

[0058] (2) Charge and discharge protocol: Equipment: Blue Electric test system; Voltage range: 2.5-4.7V; Current density: 0.1C (20mA / g, based on the mass of lithium ferrite); Standing time: 5min (charge and discharge room).

[0059] (3) Calculation: First efficiency = (first discharge capacity / first charge capacity) × 100%.

[0060] 3. Irreversible delithiation amount:

[0061] (1) The steps are the same as the “first charging efficiency” test.

[0062] (2) Calculation: Irreversible delithiation capacity = initial charge capacity - initial discharge capacity (unit: mAh / g).

[0063] 4. Oxygen release (DEMS verification):

[0064] (1) In-situ battery design: Positive electrode: lithium replenishment (load 10mg) is placed in a sealed DEMS chamber; Electrolyte: 50μL (same as above).

[0065] (2) Test conditions: Equipment: Mass spectrometry coupled with electrochemical system (GAMRY+Hiden HPR-20); Charging: 0.05C to 4.7V (constant current + constant voltage to I<0.01C); Gas monitoring: O2 (m / z=32), CO2 (m / z=44).

[0066] (3) Quantitative: Oxygen release amount = ∫(O2 signal intensity × calibration coefficient) / mass of positive electrode active material.

[0067] 5. First-efficiency and cycle life of the entire battery:

[0068] (1) Full cell assembly: Cathode: NCM811: Lithium supplement: PVDF: Carbon nanotubes = 88:10:1:1 (loading 40mg / cm³) 2 ); Anode: Silicon-carbon anode (Si:C=10:90, initial efficiency 86%); N / P ratio: 1.15.

[0069] (2) Test protocol: First effect: 0.1C charge and discharge (2.8-4.3V); Cyclic: 0.5C constant current charge and discharge (100 cycles, 25℃).

[0070] (3) Calculation: First efficiency = (first discharge capacity / first charge capacity) × 100%; Capacity retention rate = (discharge capacity in week 100 / discharge capacity in week 5) × 100%.

[0071] 6. Thermal runaway temperature (ARC test):

[0072] (1) Sample preparation: Fully charged battery (disassemble and remove the positive electrode after charging to 4.7V); sealed in an ARC-specific high-pressure crucible (sample amount 200mg).

[0073] (2) Test conditions: Equipment: THT ARC (Accelerated Calorimeter); Starting temperature: 50℃, heating step size: 5℃; Self-heating threshold: 0.02℃ / min.

[0074] (3) Data extraction: Thermal runaway initiation temperature = inflection point where the self-heating rate is > 0.2℃ / min.

[0075] 7. Volumetric expansion rate (in-situ XRD):

[0076] (1) In-situ battery assembly: Positive electrode: lithium supplement (loading 15mg) coated on Be window (transparent to X-ray); Counter electrode: lithium sheet.

[0077] (2) Test conditions: Equipment: XRD diffractometer (Brook D8, Cu Kα) coupled with electrochemical module; Scan range: 2θ=10°-80°, step size 0.02°; Cycle: 0.5C charge and discharge (full charge state in the first and 100th cycles).

[0078] (3) Calculation: Volume expansion rate = [V 100 - V1] / V1 ×100% (V = cell volume, obtained through Rietveld refinement).

[0079] Table 1 Test Results

[0080] Test Project Example 1 (Co-based) Example 2 (Ni-based) Example 3 (Mn-based) Comparative Example 1 (Pure LFO) Decomposition potential (V) 4.68 4.62 4.59 4.58 First charge efficiency (%) 95.2 93.8 92.5 78.3 Irreversible delithiation amount (mAh / g) 556 548 542 520 Oxygen release (μmol / mg) 0.08 0.12 0.15 2.67 Full battery first efficiency (%) 93.7 92.1 91.2 76.8 100-week capacity retention rate (%) 91.8 89.3 87.6 71.2 Thermal runaway temperature (°C) 243 231 225 169 Volume expansion rate (%) 4.2 5.7 6.8 18.8

[0081] Mechanism analysis of this invention:

[0082] In ZIF-8 derived Co / Ni / Mn single-atom catalysts, atomically dispersed M-N4 sites (M=Co, Ni, Mn) achieve revolutionary oxygen suppression through precise d-band electron modulation: Co sites (high-spin d-band electrons) 7 ): In an octahedral field, an unfilled eg↑ orbit (dz) is formed. 2 dx 2 -y 2 The high density of states peak near the Fermi level significantly enhances the lattice oxygen adsorption energy (DFT calculated binding energy ΔEads = -1.8 eV). During the delithiation of lithium ferrite, the M-N4 site eradicates oxygen release through a three-stage combined catalysis of "adsorption-transfer-conversion". This mechanism, through three progressive steps of d-band density of states regulation → chemical bond recombination → dynamic path optimization, elevates material design from "empirical modification" to "precise electronic-scale control", laying a theoretical foundation for high-safety pre-lithiation agents.

[0083] This invention achieves the following through process optimization:

[0084] 1. Precise Material Design: This invention utilizes atomic-level coordination regulation of the M-N4 sites in a Co / Ni / Mn trimetallic system to construct a material with both high oxygen catalytic activity (TOF > 50 s⁻¹). -1 High ion conductivity (σ > 10) ⁻4 A triple functional interface with high lithium replenishment capacity (≥540 mAh / g) and high S / cm achieves a kinetic balance of "pre-lithiation-oxygen elimination-structural stability". A stable catalytic interface with "nanoscale embedding depth > 10 nm + Co 2p binding energy redshift > 0.8 eV" is obtained under a controllable process window at a ball milling energy of 1.2 kWh / kg, achieving enhanced dual coupling of physical contact and chemical bonding.

[0085] 2. Atomic-scale process window locking: This invention achieves enhanced lattice bonding at a ball milling energy density of 1.0 kWh / kg: Fe-O bond length stretching by 0.05 Å (XRD refinement); electronic coupling effect: Co 2p binding energy redshifted by 1.2 eV (XPS verification of strong electronic interaction); and the formation of a dual stable interface of physical embedding (carbon layer depth > 5 nm) and chemical bonding (MO-Fe).

[0086] 3. Closed-loop risk management across the entire chain: This invention addresses three major risks: electrode distortion, oxygen runaway, and single-atom inactivation, achieving a key parameter deviation of <3% (XRD half-width / first-efficiency) from gram-level laboratory to hundred-kilogram-level production line.

[0087] It should be noted that, in this document, terms such as “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.

[0088] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing ZIF-8 derived carbon composite lithium iron phosphate lithium supplementing agent, characterized in that, The method comprises the following steps: S1, stirring a metal nitrate into deionized water to obtain a precursor solution, wherein the metal nitrate is mixed by Zn(NO3)2·6H2O and TM(NO3)2·6H2O, and then 2-methylimidazole is added into the precursor solution and stirred for 30 min to form a TM / ZIF-8 precursor; S2, the TM / ZIF-8 precursor is heated to 900℃ at a rate of 5℃ / min under an argon atmosphere and calcined for 2h, and then naturally cooled to obtain TM / ZIF-8; S3, the TM / ZIF-8, Li5FeO4 and multi-walled carbon nanotubes are ball milled at a mass ratio of 2:12:1 for 4h to obtain a ZIF-8 derived carbon composite lithium ferrite lithium supplement agent.

2. The preparation method of ZIF-8 derived carbon composite lithium iron phosphate lithium supplement agent according to claim 1, characterized in that, The mass ratio of the deionized water to the metal nitrate in S1 is 10:

1.

3. The method according to claim 1, wherein the ZIF-8 derived carbon composite lithium iron phosphate lithium supplementing agent is characterized in that, The metal nitrate in S1 is mixed by Zn(NO3)2·6H2O and TM(NO3)2·6H2O at a molar ratio of Zn:TM=8:

1.

4. The method according to claim 1, wherein the ZIF-8 derived carbon composite lithium iron phosphate lithium supplementing agent is characterized in that, The amount of 2-methylimidazole used in S1 is according to the molar ratio of metal ion: 2-methylimidazole = 1 : 8; the metal ion is Zn 2+ and TM 2+ in sum.

5. The method according to claim 1, wherein the ZIF-8 derived carbon composite lithium iron phosphate lithium supplementing agent is characterized in that, The TM in S1 is one of Co, Ni and Mn.

6. The method according to claim 5, wherein the ZIF-8 derived carbon composite lithium iron phosphate lithium supplementing agent is prepared by the following steps: 1) preparing a ZIF-8 precursor; 2) preparing a ZIF-8 derived carbon composite lithium iron phosphate lithium supplementing agent by carbonizing the ZIF-8 precursor. The TM is Co.

7. The method according to claim 1, wherein the ZIF-8 derived carbon composite lithium iron phosphate lithium supplementing agent is characterized in that, The purity of the Li5FeO4 in S3 is ≥99.5%, and the particle size is 50μm; the diameter of the multi-walled carbon nanotubes is 20nm, and the length is 1-5μm.

8. A ZIF-8 derived carbon composite lithium iron phosphate lithium supplementing agent, characterized in that, The ZIF-8 derived carbon composite lithium ferrite lithium supplement agent is prepared by the preparation method in any one of claims 1-7.

9. A ZIF-8 derived carbon composite lithium iron phosphate lithium supplementing agent application, characterized in that, The ZIF-8 derived carbon composite lithium ferrite lithium supplement agent prepared by the preparation method in any one of claims 1-7 is applied to a lithium battery positive electrode.

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