Bonding modified MOF (Metal Organic Framework) derived ternary precursor, positive electrode material, preparation of positive electrode material and battery

Abstract

The invention provides a bonding modified MOF (Metal Organic Framework) derived ternary precursor, a positive electrode material, preparation of the positive electrode material and a battery. The MOF derived ternary precursor comprises an inner core and a modification layer coating the outer part of the inner core, the inner core comprises a NiCoMn-MOF material, and the modification layer comprises an organic silicon compound and / or an organic boron compound; the modification layer and the inner core are in bonding connection through a Si-O bond and / or a B-O bond. In the MOF-derived ternary precursor, the modification layer and the core are bonded and connected through a Si-O bond and / or a B-O bond, so that the structural stability of the MOF-derived ternary precursor and the ternary positive electrode material is improved, and a coating layer finally formed by the modification layer also improves the interface performance of the ternary positive electrode material; the existence of the modification layer also reduces the residual alkali on the surface of the ternary positive electrode material prepared from the MOF-derived ternary precursor.

Description

Technical Field

[0001] This invention belongs to the field of battery technology and relates to a bond-modified MOF-derived ternary precursor, particularly to the bond-modified MOF-derived ternary precursor, cathode material, its preparation and battery. Background Technology

[0002] In lithium-ion batteries, ternary cathode materials, as commonly used cathode materials, face three major challenges: 1) Severe surface side reactions: Under high voltage (>4.5V vs. Li⁺ / Li), their surface easily reacts with the electrolyte, generating inert products such as Li₂CO₃ and LiF, forming a poor interfacial film. This not only leads to a significant increase in the impedance of the ternary cathode material, but also consumes electrolyte and active lithium, deteriorating electrochemical performance; 2) Uneven elemental distribution: During the solid-state synthesis of ternary cathode materials, uneven mixing of raw materials and differences in reaction kinetics easily lead to uneven Ni distribution. 2+ and / or Mn 4+ Segregation disrupts lattice order, causes lattice distortion, and reduces ion diffusion rate; 3) Insufficient structural stability (polycrystalline): During cycling, polycrystalline ternary cathode materials are prone to stress accumulation at grain boundaries, which can lead to electrolyte intrusion, active material pulverization, and ultimately rapid capacity decay of the battery.

[0003] Existing technologies disclose methods to optimize the performance of ternary cathode materials through surface coating or MOF derivation, but both have significant shortcomings: On the one hand, traditional surface coating (such as Al2O3 coating) only adheres to the material surface through physical action, resulting in weak bonding force. It is prone to detachment and failure during cycling and cannot continuously suppress surface side reactions. On the other hand, although MOF derivation can prepare single-crystal ternary cathode materials and significantly improve the uniformity of element distribution, it lacks precise control over the material surface and is difficult to construct an effective protective interface. It is not only prone to interfacial side reactions with the electrolyte, but also leaves serious residual alkali on the product surface, further aggravating the instability of the interface.

[0004] CN112993229A discloses a multi-metal MOF gradient-coated modified ternary precursor and its preparation method. The coating method is a one-step surface growth method. The following process steps are adopted: (1) The prepared ternary precursor is dispersed in a non-aqueous solvent, cobalt / manganese / nickel salt is added, then imidazole ligand is added, after reaction, pyromellitic acid / terephthalic acid is added, and then antimony / bismuth / tin salt is added; (2) The resulting mixture is washed with water, washed with alcohol, and dried to obtain the MOF-coated modified ternary precursor.

[0005] CN118221955A discloses a ternary MOF precursor and a high-nickel ternary single crystal material and their preparation method. The preparation method of the ternary MOF precursor includes: dissolving terephthalic acid in a first solvent, then adding a precipitant to the first solvent and stirring to obtain a first solution; dissolving three salts with cations of nickel, cobalt and manganese respectively in a second solvent to obtain a second solution; mixing the first solution and the second solution to obtain a third solution and adjusting the pH, then stirring the third solution at a first temperature for a first time to obtain a fourth solution; placing the fourth solution in a reaction vessel and reacting at a second temperature for a second time; obtaining a precipitate by centrifuging the fourth solution; washing the precipitate to neutrality with a detergent; and then drying the precipitate to obtain the ternary MOF precursor.

[0006] Existing ternary precursor materials all have certain drawbacks. These include weak bonding due to the coating or modification layer only physically adhering to the material surface; difficulty in constructing a protective layer on the surface of the ternary precursor; and significant residual alkali on the surface of the ternary cathode material prepared from the ternary precursor, resulting in insufficient electrochemical performance. Therefore, developing a novel bonded-modified MOF-derived ternary precursor, cathode material, and its preparation and battery application is crucial. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a bonded modified MOF-derived ternary precursor, a cathode material, its preparation, and a battery. In summary, in the bonded modified MOF-derived ternary precursor provided by the present invention, the modification layer and the core are bonded together via Si-O bonds and / or BO bonds, improving the structural stability of the MOF-derived ternary precursor and the ternary cathode material. The final coating layer formed by the modification layer also improves the interfacial performance of the ternary cathode material. Furthermore, the presence of the modification layer reduces the residual alkali on the surface of the ternary cathode material prepared from the MOF-derived ternary precursor. Therefore, the battery containing the ternary cathode material prepared from the MOF-derived ternary precursor exhibits good cycle stability, high initial charge-discharge efficiency, and excellent rate performance.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a bond-modified MOF-derived ternary precursor, the MOF-derived ternary precursor comprising a core and a modification layer covering the core.

[0010] The core includes NiCoMn-MOF material, and the modification layer includes organosilicon compounds and / or organoboron compounds;

[0011] The modified layer is bonded to the core via Si-O bonds and / or BO bonds.

[0012] In the MOF-derived ternary precursor provided by this invention, the modification layer and the core are bonded together by Si-O bonds and / or BO bonds, resulting in a strong bond between the modification layer and the core. The modification layer is not easily detached. After the ternary cathode material is prepared using the MOF-derived ternary precursor, the coating layer formed by the modification layer and the cathode material core formed by the core are still bonded together by Si-O bonds and / or BO bonds. The coating layer of the ternary cathode material is not easily detached during cycling. Therefore, the ternary cathode material prepared using the ternary precursor has excellent cycling performance (high cycling stability under high voltage).

[0013] In the MOF-derived ternary precursor provided by this invention, a modification layer can be constructed on the core surface by simply bonding an organosilicon compound and / or an organoboron compound to the NiCoMn-MOF material. This results in a protective coating layer forming in the ternary cathode material layer prepared from the MOF-derived ternary precursor, improving the interfacial properties of the cathode material. Therefore, the cycle performance of the ternary cathode material is further enhanced.

[0014] The MOF-derived ternary precursor provided by the present invention has a modification layer, and the ternary cathode material prepared with the MOF-derived ternary precursor has a low surface residual alkali content (the residual alkali content is reduced to less than 1 wt% of the total mass of the ternary cathode material); therefore, the battery containing the ternary cathode material exhibits high first charge-discharge efficiency and rate performance.

[0015] The MOF-derived ternary precursor provided by this invention includes NiCoMn-MOF material in its core. When preparing ternary cathode material using the MOF-derived ternary precursor, the NiCoMn-MOF material forms a carbon material framework and a ternary material loaded on the carbon material framework. The presence of the carbon material framework not only improves the uniformity of the ternary material distribution but also improves the conductivity of the ternary cathode material. Therefore, the first charge-discharge efficiency and rate performance of the ternary cathode material are further improved.

[0016] In summary, the MOF-derived ternary precursor with bonding modification provided by this invention has a modified layer that is bonded to the core via Si-O bonds and / or BO bonds, thereby improving the structural stability of both the MOF-derived ternary precursor and the ternary cathode material. The final coating layer formed by the modified layer also improves the interfacial properties of the ternary cathode material. Furthermore, the presence of the modified layer reduces the residual alkali on the surface of the ternary cathode material prepared from the MOF-derived ternary precursor. Therefore, batteries containing ternary cathode materials prepared from the MOF-derived ternary precursor exhibit good cycle stability, high initial charge-discharge efficiency, and excellent rate performance.

[0017] Preferably, the NiCoMn-MOF material comprises [Ni x Co y Mn z (DOBDC)·nH2O materials, [Ni x Co y Mn z (BTC)·nH2O materials, [Ni x Co y Mn z (BPDC)·nH2O material or [Ni x Co y Mn z Any one or at least two of the materials (NDC)·nH2O, typical but non-limiting combinations include [Ni x Co y Mn z (DOBDC)·nH2O materials and [Ni x Co y Mn z The combination of (BTC)·nH2O materials, [Ni x Co y Mn z (BTC)·nH2O materials and [Ni x Co y Mn z The combination of (BPDC)·nH2O materials, [Ni x Co y Mn z (BPDC)·nH2O materials and [Ni x Co y Mn z Combinations of (NDC)·nH2O materials, or [Ni x Co y Mn z (DOBDC)·nH2O materials, [Ni x Co y Mnz (BTC)]·nH2O material and [Ni x Co y Mn z (BPDC)]·nH2O material combination.

[0018] Preferably, in the [Ni x Co y Mn z (DOBDC)]·nH2O material, 0.35 < x < 0.95, 0.025 < y < 0.32, 0.025 < z < 0.33, and n is 2 - 8.

[0019] Preferably, the [Ni x Co y Mn z (DOBDC)]·nH2O material is a single - crystal material.

[0020] Preferably, in the [Ni x Co y Mn z (BTC)]·nH2O material, 0.35 < x < 0.95, 0.025 < y < 0.32, 0.025 < z < 0.33, and n is 2 - 8.

[0021] Preferably, the [Ni x Co y Mn z (BTC)]·nH2O is a single - crystal material.

[0022] Preferably, in the [Ni x Co y Mn z (BPDC)]·nH2O material, 0.35 < x < 0.95, 0.025 < y < 0.32, 0.025 < z < 0.33, and n is 2 - 8.

[0023] Preferably, the [Ni x Co y Mn z (BPDC)]·nH2O is a single - crystal material.

[0024] Preferably, in the [Ni x Co y Mn z (NDC)]·nH2O material, 0.35 < x < 0.95, 0.025 < y < 0.32, 0.025 < z < 0.33, and n is 2 - 8.

[0025] Preferably, the [Ni x Co y Mnz (NDC)]·nH2O material is a single crystal material.

[0026] In the present invention, the [Ni x Co y Mn z (DOBDC)]·nH2O material, [Ni x Co y Mn z (BTC)]·nH2O material, [Ni x Co y Mn z (BPDC)]·nH2O material and [Ni x Co y Mn z (NDC)]·nH2O material, independently of each other, is 0.35 < x < 0.95. The value of x can be, for example, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90 or 0.95, but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0027] In the present invention, the [Ni x Co y Mn z (DOBDC)]·nH2O material, [Ni x Co y Mn z (BTC)]·nH2O material, [Ni x Co y Mn z (BPDC)]·nH2O material and [Ni x Co y Mn z (NDC)]·nH2O material, independently of each other, is 0.025 < y < 0.32. The value of y can be, for example, 0.025, 0.05, 0.075, 0.10, 0.125, 0.15, 0.175, 0.20, 0.225, 0.25, 0.275, 0.30 or 0.32, but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0028] In the present invention, the [Ni x Co y Mn z (DOBDC)]·nH2O material, [Ni x Co y Mn z (BTC)]·nH2O material, [Nix Co y Mn z (BPDC)]·nH2O material and [Ni x Co y Mn z (NDC)]·nH2O material, independently for each, 0.025 < z < 0.33. The value of z can be, for example, 0.025, 0.05, 0.075, 0.10, 0.125, 0.15, 0.175, 0.20, 0.225, 0.25, 0.275, 0.30 or 0.33, but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0029] In the present invention, the [Ni x Co y Mn z (DOBDC)]·nH2O material, [Ni x Co y Mn z (BTC)]·nH2O material, [Ni x Co y Mn z (BPDC)]·nH2O material and [Ni x Co y Mn z (NDC)]·nH2O material, independently for each, n is 2 - 8. The value of n can be, for example, 2, 3, 4, 5, 6, 7 or 8.

[0030] Preferably, the organosilicon compound includes any one or a combination of at least two of a silane coupling agent, a polysiloxane or a silane polymer. Typical but non - restrictive combinations include a combination of a silane coupling agent and a polysiloxane, a combination of a polysiloxane and a silane polymer, a combination of a silane coupling agent and a silane polymer, or a combination of a silane coupling agent, a polysiloxane and a silane polymer.

[0031] Preferably, the organoboron compound includes any one or a combination of at least two of a borate ester, phenylboronic acid, aminoboric acid or a borane - amine complex. Typical but non - restrictive combinations include a combination of a borate ester and phenylboronic acid, a combination of aminoboric acid and a borane - amine complex, a combination of phenylboronic acid and aminoboric acid, or a combination of a borate ester, phenylboronic acid and a borane - amine complex.

[0032] In a second aspect, the present invention provides a method for preparing the MOF - derived ternary precursor described in the first aspect. The preparation method includes:

[0033] After mixing the NiCoMn - MOF material with the modification solution, a solvothermal reaction is carried out to obtain the MOF - derived ternary precursor;

[0034] The NiCoMn-MOF material contains active groups;

[0035] The modified solution contains organosilicon compounds and / or organoboron compounds, wherein the organosilicon compounds and / or organoboron compounds contain groups that can undergo bonding reactions with the active groups.

[0036] In the preparation method of the present invention, the NiCoMn-MOF material contains active groups, and the organosilicon compound and / or organoboron compound contains groups that can undergo bonding reactions with the active groups. Therefore, when the NiCoMn-MOF material and the modification solution are mixed and subjected to a solvothermal reaction, the NiCoMn-MOF material with active groups will undergo a bonding reaction with the organosilicon compound and / or organoboron compound to form Si-O bonds and / or BO bonds. The organosilicon compound and / or organoboron compound will coat the surface of the NiCoMn-MOF material to form a modification layer, thereby obtaining the MOF-derived ternary precursor.

[0037] In the preparation method provided by the present invention, the modification of NiCoMn-MOF material can be achieved through solvothermal reaction, which not only preserves the integrity of the single crystal structure of NiCoMn-MOF material, but also achieves atomic-level uniform distribution of Si and / or B elements in the modified layer.

[0038] Preferably, the active groups in the NiCoMn-MOF material include any one or a combination of at least two of hydroxyl, carboxyl, or amino groups. Typical but non-limiting combinations include combinations of hydroxyl and carboxyl groups, combinations of carboxyl and amino groups, combinations of hydroxyl and amino groups, or combinations of hydroxyl, carboxyl, and amino groups.

[0039] Preferably, the method for preparing the NiCoMn-MOF material includes: mixing Ni salt, Co salt, Mn salt, ligand and solvent to obtain a mixed solution, and heat-treating the obtained mixed solution to obtain the NiCoMn-MOF material.

[0040] Preferably, the Ni salt includes any one or a combination of at least two of Ni(NO3)2, NiSO4, NiCl2, Ni(CH3COO)2, NiC2O4, or Ni3(C6H5O7)2. Typical but non-limiting combinations include combinations of Ni(NO3)2 and NiSO4, combinations of NiCl2 and Ni(CH3COO)2, combinations of NiC2O4 and Ni3(C6H5O7)2, or combinations of Ni(NO3)2, NiSO4, and NiCl2.

[0041] Preferably, the Co salt includes any one or a combination of at least two of Co(NO3)2, CoSO4, CoCl2, Co(CH3COO)2, CoC2O4, Co3(C6H5O7)2, CoBr2, or Co(NH2SO3)2. Typical but non-limiting combinations include the combination of Co(NO3)2 and CoSO4, the combination of CoCl2 and Co(CH3COO)2, the combination of CoC2O4 and Co3(C6H5O7)2, or the combination of Co(NO3)2, CoSO4, and CoCl2.

[0042] Preferably, the Mn salt includes any one or a combination of at least two of Mn(NO3)2, MnSO4, MnCl2, Mn(CH3COO)2 or Mn3(C6H5O7)2. Typical but non-limiting combinations include the combination of Mn(NO3)2 and MnSO4, the combination of MnCl2 and Mn(CH3COO)2, the combination of MnSO4 and Mn3(C6H5O7)2, or the combination of Mn(NO3)2, MnCl2 and Mn(CH3COO)2.

[0043] Preferably, the ligand comprises any one or a combination of at least two of 2,5-dihydroxyterephthalic acid (DOBDC), trimesolic acid (BTC), biphenyl-4,4-dicarboxylic acid (BPDC), or 2,6-naphthalenedicarboxylic acid (NDC). Typical but non-limiting combinations include combinations of 2,5-dihydroxyterephthalic acid and trimesolic acid, combinations of biphenyl-4,4-dicarboxylic acid and 2,6-naphthalenedicarboxylic acid, combinations of trimesolic acid and biphenyl-4,4-dicarboxylic acid, or combinations of 2,5-dihydroxyterephthalic acid, trimesolic acid, and 2,6-naphthalenedicarboxylic acid.

[0044] Preferably, the solvent comprises any one or a combination of at least two of N,N-dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide, ethanol, methanol, ethylene glycol, acetonitrile, tert-butanol, or water. Typical but non-limiting combinations include combinations of N,N-dimethylformamide and N-methylpyrrolidone, dimethyl sulfoxide and ethanol, methanol and ethylene glycol, acetonitrile and tert-butanol, water and N-methylpyrrolidone, or N,N-dimethylformamide, dimethyl sulfoxide, and water.

[0045] Preferably, in the mixture, the molar ratio of Ni salt, Co salt and Mn salt is (0.35~0.95):(0.025~0.32):(0.025~0.33).

[0046] In this invention, the molar ratio of Ni salt to Co salt in the mixture is (0.35~0.95):(0.025~0.32), for example, it can be 0.35:0.025, 0.40:0.05, 0.50:0.10, 0.60:0.15, 0.70:0.20, 0.80:0.25, 0.90:0.30 or 0.95:0.32, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0047] In this invention, the molar ratio of Ni salt to Mn salt in the mixture is (0.35~0.95):(0.025~0.33), for example, it can be 0.35:0.025, 0.40:0.05, 0.50:0.10, 0.60:0.15, 0.70:0.20, 0.80:0.25, 0.90:0.30 or 0.95:0.33, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0048] Preferably, in the mixture, the ratio of the total molar amount of Ni salt, Co salt and Mn salt to the molar amount of ligand is 1:(0.5~1.5), for example, it can be 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1.0, 1:1.1, 1:1.2, 1:1.3, 1:1.4 or 1:1.5, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0049] Preferably, the concentration of Ni salt in the mixed solution is 0.01 mol / L to 2.0 mol / L, for example, it can be 0.01 mol / L, 0.05 mol / L, 0.1 mol / L, 0.3 mol / L, 0.5 mol / L, 0.8 mol / L, 1.0 mol / L, 1.2 mol / L, 1.5 mol / L, 1.8 mol / L or 2.0 mol / L, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0050] Preferably, the heat treatment temperature is 100℃~140℃ and the time is 20~30h.

[0051] In this invention, the temperature of the heat treatment is 100℃~140℃, for example, it can be 100℃, 105℃, 110℃, 115℃, 120℃, 125℃, 130℃, 135℃ or 140℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0052] In this invention, the heat treatment time is 20 to 30 hours, for example, it can be 20 hours, 21 hours, 22 hours, 23 hours, 24 hours, 25 hours, 26 hours, 27 hours, 28 hours, 29 hours or 30 hours, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0053] Preferably, in the modified solution, the organosilicon compound includes any one or a combination of at least two of silane coupling agents, polysiloxanes, or silane polymers. Typical but non-limiting combinations include combinations of silane coupling agents and polysiloxanes, combinations of polysiloxanes and silane polymers, combinations of silane coupling agents and silane polymers, or combinations of silane coupling agents, polysiloxanes, and silane polymers.

[0054] Preferably, the silane coupling agent includes KH550 type silane coupling agent.

[0055] Preferably, in the modified solution, the organoboron compound includes any one or a combination of at least two of borate esters, phenylboronic acid, aminoboronic acid, or boraneamine complexes. Typical but non-limiting combinations include combinations of borate esters and phenylboronic acid, combinations of aminoboronic acid and boraneamine complexes, combinations of phenylboronic acid and aminoboronic acid, or combinations of borate esters, phenylboronic acid, and boraneamine complexes.

[0056] Preferably, the solvent in the modified solution includes any one or a combination of at least two of ethanol, N,N-dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide, ethanol, methanol, ethylene glycol, acetonitrile, tert-butanol, or water. Typical but non-limiting combinations include combinations of ethanol and N,N-dimethylformamide, N-methylpyrrolidone and dimethyl sulfoxide, methanol and ethylene glycol, acetonitrile and tert-butanol, water and N-methylpyrrolidone, or ethanol, dimethyl sulfoxide, and water.

[0057] Preferably, in the mixture, the molar ratio of the NiCoMn-MOF material to the total molar ratio of the organosilicon compound and organoboron compound in the modification solution is 1:(0.5~5), for example, it can be 1:0.5, 1:0.8, 1:1, 1:1.2, 1:1.5, 1:1.8, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5 or 1:5, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0058] Preferably, the total molar concentration of the organosilicon compound and the organoboron compound in the modified solution is 0.1 mol / L to 0.5 mol / L, for example, it can be 0.1 mol / L, 0.15 mol / L, 0.2 mol / L, 0.25 mol / L, 0.3 mol / L, 0.35 mol / L, 0.4 mol / L, 0.45 mol / L or 0.5 mol / L, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0059] Preferably, the temperature of the solvothermal reaction is 40℃~80℃, and the time is 6h~12h.

[0060] In this invention, the temperature of the solvothermal reaction is 40℃~80℃, for example, it can be 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃ or 80℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0061] In this invention, the solvothermal reaction time is 6h to 12h, for example, it can be 6h, 7h, 8h, 9h, 10h, 11h or 12h, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0062] Preferably, in the solvothermal reaction, the active groups on the ligands of the NiCoMn-MOF material undergo a bonding reaction with organosilicon compounds and / or organoboron compounds to introduce Si-O and / or BO bonds and form a modification layer to obtain the MOF precursor.

[0063] Thirdly, the present invention provides a ternary cathode material, wherein the ternary cathode material is prepared from the MOF-derived ternary precursor described in the first aspect.

[0064] Preferably, the ternary cathode material includes a cathode material core and a coating layer covering the outside of the cathode material core.

[0065] Preferably, the cathode material core includes LiNi. x Co y Mn z O2 and carbon materials.

[0066] Preferably, the coating layer comprises silicon oxide and / or boron oxide.

[0067] Preferably, the silicon oxide comprises SiO2.

[0068] Preferably, the boron oxide includes B2O3.

[0069] Fourthly, the present invention provides a preparation process for a ternary cathode material, the preparation process comprising:

[0070] The MOF-derived ternary precursor described in the first aspect is mixed with a lithium source and then subjected to gradient sintering to obtain a ternary cathode material.

[0071] Preferably, in the mixture, the molar ratio of the MOF-derived ternary precursor to the lithium source is 1:(1.05~1.2), for example, it can be 1:1.05, 1:1.06, 1:1.07, 1:1.08, 1:1.09, 1:1.10, 1:1.11, 1:1.12, 1:1.13, 1:1.14, 1:1.15, 1:1.16, 1:1.17, 1:1.18, 1:1.19 or 1:1.2, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0072] Preferably, the gradient sintering includes a first sintering, a second sintering, and a third sintering performed sequentially.

[0073] Preferably, the first sintering temperature is 250℃~350℃ and the time is 1.5h~2.5h.

[0074] In this invention, the temperature of the first sintering is 250℃~350℃, for example, it can be 250℃, 260℃, 270℃, 280℃, 290℃, 300℃, 310℃, 320℃, 330℃, 340℃ or 350℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0075] In this invention, the first sintering time is 1.5h to 2.5h, for example, it can be 1.5h, 1.6h, 1.7h, 1.8h, 1.9h, 2.0h, 2.1h, 2.2h, 2.3h, 2.4h or 2.5h, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0076] Preferably, the second sintering temperature is 450℃~650℃ and the time is 1.5h~2.5h.

[0077] In this invention, the second sintering temperature is 450℃~650℃, for example, it can be 450℃, 475℃, 500℃, 525℃, 550℃, 575℃, 600℃, 625℃ or 650℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0078] In this invention, the second sintering time is 1.5h to 2.5h, for example, it can be 1.5h, 1.6h, 1.7h, 1.8h, 1.9h, 2.0h, 2.1h, 2.2h, 2.3h, 2.4h or 2.5h, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0079] Preferably, the third sintering temperature is 600℃~800℃ and the time is 2.5h~3.5h.

[0080] In this invention, the temperature of the third sintering is 600℃~800℃, for example, it can be 600℃, 625℃, 650℃, 675℃, 700℃, 725℃, 750℃, 775℃ or 800℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0081] In this invention, the third sintering time is 2.5h to 3.5h, for example, it can be 2.5h, 2.6h, 2.7h, 2.8h, 2.9h, 3.0h, 3.1h, 3.2h, 3.3h, 3.4h or 3.5h, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0082] Preferably, the mixing and gradient sintering process further includes a first heating rate of 1°C / min to 5°C / min, for example, 1°C / min, 1.5°C / min, 2°C / min, 2.5°C / min, 3°C / min, 3.5°C / min, 4°C / min, 4.5°C / min or 5°C / min, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable, and the endpoint temperature is the temperature of the first sintering.

[0083] Preferably, a second heating is further included between the first sintering and the second sintering, and the rate of the second heating is 1℃ / min to 5℃ / min, for example, it can be 1℃ / min, 1.5℃ / min, 2℃ / min, 2.5℃ / min, 3℃ / min, 3.5℃ / min, 4℃ / min, 4.5℃ / min or 5℃ / min, and the endpoint temperature is the temperature of the third sintering;

[0084] Preferably, the sintering process further includes cooling, the cooling method including natural cooling, and the final temperature of the cooling is 5°C to 35°C, for example, 5°C, 10°C, 15°C, 20°C, 25°C, 30°C or 35°C, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0085] Fifthly, the present invention provides a battery comprising the ternary cathode material described in the third aspect.

[0086] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0087] Compared with the prior art, the present invention has the following beneficial effects:

[0088] (1) In the MOF-derived ternary precursor provided by the present invention, the modification layer and the core are connected by Si-O bonds and / or BO bonds, and the modification layer and the core have a strong bonding force. The modification layer is not easy to fall off. After the ternary cathode material is prepared by the MOF-derived ternary precursor, the modification layer forms a coating layer and the core of the cathode material formed by the core is still connected by Si-O bonds and / or BO bonds. The coating layer of the ternary cathode material is not easy to fall off during cycling. Therefore, the ternary cathode material prepared by the ternary precursor has excellent cycling performance (high cycling stability under high voltage).

[0089] (2) In the MOF-derived ternary precursor provided by the present invention, a modification layer can be constructed on the core surface by simply bonding organosilicon compounds and / or organoboron compounds to the NiCoMn-MOF material, thereby forming a protective coating layer in the ternary cathode material layer prepared by the MOF-derived ternary precursor, which improves the interfacial performance of the cathode material; therefore, the cycle performance of the ternary cathode material is further improved.

[0090] (3) The MOF-derived ternary precursor provided by the present invention has a modification layer, and the ternary cathode material prepared with the MOF-derived ternary precursor has a low surface residual alkali content (the residual alkali content is reduced to less than 1 wt% of the total mass of the ternary cathode material); therefore, the battery containing the ternary cathode material exhibits high first charge-discharge efficiency and rate performance.

[0091] (4) In the MOF-derived ternary precursor provided by the present invention, the core includes NiCoMn-MOF material; when preparing ternary cathode material with MOF-derived ternary precursor, NiCoMn-MOF material will form carbon material skeleton and ternary material loaded on the carbon material skeleton. The presence of carbon material skeleton not only improves the uniformity of ternary material distribution, but also improves the conductivity of ternary cathode material; therefore, the first charge-discharge efficiency and rate performance of the ternary cathode material are further improved. Detailed Implementation

[0092] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0093] Example 1

[0094] This embodiment provides a bond-modified MOF-derived ternary precursor, which includes a core and a modification layer covering the core.

[0095] The core includes NiCoMn-MOF material ([Ni 0.8 Co 0.1 Mn 0.1 (DOBDC)·nH2O single crystal material, where n is 2~8);

[0096] The modified layer includes phenylboronic acid;

[0097] The modification layer and the kernel are connected by a BO bond;

[0098] The preparation method of the MOF-derived ternary precursor includes:

[0099] (1) Ni(NO3)2, Co(NO3)2, Mn(NO3)2, 2,5-dihydroxyterephthalic acid ligand and N,N-dimethylformamide solvent were mixed to obtain a mixed solution. The mixed solution was heat-treated at 120℃ for 25h to obtain NiCoMn-MOF material.

[0100] In the mixture, the molar ratio of Ni(NO3)2, Co(NO3)2, and Mn(NO3)2 is 0.8:0.1:0.1; the total molar amount of Ni(NO3)2, Co(NO3)2, and Mn(NO3)2 is in the same ratio as the molar amount of 2,5-dihydroxyterephthalic acid ligand, which is 1:1; and the concentration of Ni(NO3)2 in the mixed solution is 0.5 mol / L.

[0101] (2) After mixing the NiCoMn-MOF material obtained in step (1) with the modification solution (solvent is ethanol), a solvothermal reaction was carried out at 60℃ for 9 h to obtain the MOF-derived ternary precursor;

[0102] The NiCoMn-MOF material contains active groups (hydroxyl groups);

[0103] The modified solution contains phenylboronic acid; the phenylboronic acid contains borate groups (-B(OH)2) that can bond with the active group (hydroxyl group);

[0104] In the mixture, the molar ratio of NiCoMn-MOF material to phenylboronic acid in the modification solution is 1:2.5; the molar concentration of phenylboronic acid in the modification solution is 0.3 mol / L.

[0105] This embodiment also provides a ternary cathode material, which includes a cathode material core and a coating layer covering the cathode material core.

[0106] The cathode material core includes LiNi. 0.8 Co 0.1 Mn 0.1 O2 and carbon materials;

[0107] The coating layer includes B2O3;

[0108] The preparation process of the ternary cathode material includes:

[0109] The MOF-derived ternary precursor described in this embodiment, with a molar ratio of 1:1.05, was mixed with lithium hydroxide. The mixture was then heated to 300°C at a rate of 3°C / min and held for 2 hours. The temperature was then increased to 550°C at a rate of 3°C / min and held for 2 hours. The temperature was then increased to 700°C at a rate of 3°C / min and held for 3 hours. Finally, the mixture was cooled to 25°C to obtain the ternary cathode material.

[0110] Example 2

[0111] This embodiment provides a bond-modified MOF-derived ternary precursor, which includes a core and a modification layer covering the core.

[0112] The core includes NiCoMn-MOF material ([Ni 0.75 Co 0.12 Mn 0.13 (BTC)·nH2O single crystal material, where n is 2~8);

[0113] The modified layer includes a silane coupling agent;

[0114] The modified layer is connected to the core via Si-O bonds;

[0115] The preparation method of the MOF-derived ternary precursor includes:

[0116] (1) NiSO4, CoSO4, MnSO4, pyromellitic acid ligand and N-methylpyrrolidone solvent were mixed to obtain a mixed solution. The mixed solution was heat-treated at 100℃ for 30h to obtain NiCoMn-MOF material.

[0117] In the mixture, the molar ratio of NiSO4, CoSO4, and MnSO4 is 0.75:0.12:0.13; the total molar amount of NiSO4, CoSO4, and MnSO4 is in the ratio of the molar amount of pyromellitic acid ligand to the total molar amount of pyromellitic acid ligand, which is 1:0.5; and the concentration of NiSO4 in the mixed solution is 2.0 mol / L.

[0118] (2) After mixing the NiCoMn-MOF material obtained in step (1) with the modification solution (solvent is N-methylpyrrolidone), a solvothermal reaction was carried out at 40℃ for 12h to obtain the MOF-derived ternary precursor;

[0119] The NiCoMn-MOF material contains active groups (hydroxyl groups);

[0120] The modified solution contains a silane coupling agent; the silane coupling agent contains a siloxane group (-Si(OR)3) that can bond with the active group (hydroxyl group);

[0121] In the mixture, the molar ratio of NiCoMn-MOF material to the total molar ratio of silane coupling agent in the modification solution is 1:0.5; the total molar concentration of silane coupling agent in the modification solution is 0.5 mol / L.

[0122] This embodiment also provides a ternary cathode material, which includes a cathode material core and a coating layer covering the cathode material core.

[0123] The cathode material core includes LiNi. 0.75 Co 0.12 Mn 0.13 O2 and carbon materials;

[0124] The coating layer includes SiO2;

[0125] The preparation process of the ternary cathode material includes:

[0126] The MOF-derived ternary precursor described in this embodiment, with a molar ratio of 1:1.1, was mixed with lithium hydroxide. The mixture was then heated to 350°C at a rate of 5°C / min and held for 1.5 h. The temperature was then increased to 650°C at a rate of 5°C / min and held for 1.5 h. The temperature was then increased to 800°C at a rate of 5°C / min and held for 2.5 h. Finally, the mixture was cooled to 35°C to obtain the ternary cathode material.

[0127] Example 3

[0128] This embodiment provides a bond-modified MOF-derived ternary precursor, which includes a core and a modification layer covering the core.

[0129] The core includes NiCoMn-MOF material ([Ni 0.85 Co 0.08 Mn 0.07 (BPDC)·nH2O single crystal material, where n is 2~8);

[0130] The modified layer includes a silane coupling agent and a borate ester;

[0131] The modified layer is connected to the core by Si-O and BO bonds;

[0132] The preparation method of the MOF-derived ternary precursor includes:

[0133] (1) Ni(NO3)2, Co(NO3)2, Mn(NO3)2, biphenyl-4,4-dicarboxylic acid ligand and N,N-dimethylformamide solvent were mixed to obtain a mixed solution. The mixed solution was heat-treated at 140℃ for 20h to obtain NiCoMn-MOF material.

[0134] In the mixture, the molar ratio of Ni(NO3)2, Co(NO3)2, and Mn(NO3)2 is 0.85:0.08:0.07; the total molar amount of Ni(NO3)2, Co(NO3)2, and Mn(NO3)2 is in the ratio of the molar amount of biphenyl-4,4-dicarboxylic acid ligand to 1:1.5; and the concentration of Ni(NO3)2 in the mixed solution is 0.01 mol / L.

[0135] (2) After mixing the NiCoMn-MOF material obtained in step (1) with the modification solution (solvent is ethanol), a solvothermal reaction is carried out at ~80℃ for 6h to obtain the MOF-derived ternary precursor;

[0136] The NiCoMn-MOF material contains active groups (hydroxyl groups);

[0137] The modified solution contains a silane coupling agent and a borate ester (the molar ratio of the silane coupling agent to the borate ester is 1:1); the silane coupling agent and the borate ester contain siloxane groups (-Si(OR)3) and borate ester groups (-B(OR)2) that can bond with the active group (hydroxyl group);

[0138] In the mixture, the molar ratio of the NiCoMn-MOF material to the total molar ratio of the silane coupling agent and borate ester in the modification solution is 1:5; the total molar concentration of the organosilicon compound and the organoboron compound in the modification solution is 0.1 mol / L.

[0139] This embodiment also provides a ternary cathode material, which includes a cathode material core and a coating layer covering the cathode material core.

[0140] The cathode material core includes LiNi. 0.85 Co 0.08 Mn 0.07 O2 and carbon materials;

[0141] The coating layer includes SiO2 and B2O3;

[0142] The preparation process of the ternary cathode material includes:

[0143] The MOF-derived ternary precursor described in this embodiment, with a molar ratio of 1:1.2, was mixed with lithium hydroxide. The mixture was then heated to 250°C at a rate of 1°C / min and held for 2.5 h. The temperature was then increased to 450°C at a rate of 1°C / min and held for 2.5 h. The temperature was then increased to 600°C at a rate of 1°C / min and held for 3.5 h. Finally, the mixture was cooled to 5°C to obtain the ternary cathode material.

[0144] Example 4

[0145] This embodiment provides a bond-modified MOF-derived ternary precursor, wherein the core includes NiCoMn-MOF material ([Ni 0.8 Co 0.1 Mn 0.1 (NDC)·nH2O single crystal material, where n is 2~8);

[0146] The 2,5-dihydroxyterephthalic acid ligand in step (1) of the preparation method of the MOF-derived ternary precursor is replaced with an equal molar amount of 2,6-naphthalenedicarboxylic acid ligand, and the rest is the same as in Example 1.

[0147] This embodiment also provides a ternary cathode material, except that the MOF-derived ternary precursor used in the preparation process of the ternary cathode material is replaced with the MOF-derived ternary precursor provided in this embodiment, and the rest is the same as in Embodiment 1.

[0148] Example 5

[0149] This embodiment provides a bond-modified MOF-derived ternary precursor. Except for step (1) of the preparation method of the MOF-derived ternary precursor, in which the total molar amount of Ni(NO3)2, Co(NO3)2, and Mn(NO3)2 is in a ratio of 1:0.2 to the molar amount of 2,5-dihydroxyterephthalic acid ligand, all other steps are the same as in Example 1.

[0150] This embodiment also provides a ternary cathode material, except that the MOF-derived ternary precursor used in the preparation process of the ternary cathode material is replaced with the MOF-derived ternary precursor provided in this embodiment, and the rest is the same as in Embodiment 1.

[0151] Example 6

[0152] This embodiment provides a bond-modified MOF-derived ternary precursor. Except for step (1) of the preparation method of the MOF-derived ternary precursor, in which the total molar amount of Ni(NO3)2, Co(NO3)2, and Mn(NO3)2 is in a molar ratio of 1:2 to the molar amount of 2,5-dihydroxyterephthalic acid ligand, all other steps are the same as in Example 1.

[0153] This embodiment also provides a ternary cathode material, except that the MOF-derived ternary precursor used in the preparation process of the ternary cathode material is replaced with the MOF-derived ternary precursor provided in this embodiment, and the rest is the same as in Embodiment 1.

[0154] Example 7

[0155] This embodiment provides a bond-modified MOF-derived ternary precursor. Except for step (2) of the preparation method of the MOF-derived ternary precursor, in which the molar ratio of NiCoMn-MOF material to phenylboronic acid in the modification solution is 1:0.2, all other steps are the same as in Example 1.

[0156] This embodiment also provides a ternary cathode material, except that the MOF-derived ternary precursor used in the preparation process of the ternary cathode material is replaced with the MOF-derived ternary precursor provided in this embodiment, and the rest is the same as in Embodiment 1.

[0157] Example 8

[0158] This embodiment provides a bond-modified MOF-derived ternary precursor. Except for step (2) of the preparation method of the MOF-derived ternary precursor, in which the molar ratio of NiCoMn-MOF material to phenylboronic acid in the modification solution is 1:6, all other steps are the same as in Example 1.

[0159] This embodiment also provides a ternary cathode material, except that the MOF-derived ternary precursor used in the preparation process of the ternary cathode material is replaced with the MOF-derived ternary precursor provided in this embodiment, and the rest is the same as in Embodiment 1.

[0160] Example 9

[0161] This embodiment provides a bond-modified MOF-derived ternary precursor. Except for step (2) of the preparation method of the MOF-derived ternary precursor, in which a solvothermal reaction is carried out at 30°C, the rest is the same as in Example 1.

[0162] This embodiment also provides a ternary cathode material, except that the MOF-derived ternary precursor used in the preparation process of the ternary cathode material is replaced with the MOF-derived ternary precursor provided in this embodiment, and the rest is the same as in Embodiment 1.

[0163] Example 10

[0164] This embodiment provides a bond-modified MOF-derived ternary precursor. Except for step (2) of the preparation method of the MOF-derived ternary precursor, in which a solvothermal reaction is carried out at 95°C, the rest is the same as in Example 1.

[0165] This embodiment also provides a ternary cathode material, except that the MOF-derived ternary precursor used in the preparation process of the ternary cathode material is replaced with the MOF-derived ternary precursor provided in this embodiment, and the rest is the same as in Embodiment 1.

[0166] Example 11

[0167] This embodiment provides a bond-modified MOF-derived ternary precursor, which is the same as that in Embodiment 1.

[0168] This embodiment provides a ternary cathode material. Except for replacing the preparation process of the ternary cathode material with "mixing the MOF-derived ternary precursor of this embodiment with lithium hydroxide in a molar ratio of 1:1.05, heating it to 700°C at a rate of 3°C / min, holding it at that temperature for 6 hours, and then cooling it to 25°C to obtain the ternary cathode material", everything else is the same as in Example 1.

[0169] Comparative Example 1

[0170] This comparative example provides a bond-modified MOF-derived ternary precursor, except that the complex in the NiCoMn-MOF material in the core is perfluoroterephthalic acid, and the modified layer and the core are connected only by physical contact (the modified layer and the core are not bonded together by Si-O bonds and / or BO bonds).

[0171] Except for replacing the 2,5-dihydroxyterephthalic acid ligand in step (1) of the preparation method of the MOF-derived ternary precursor with a perfluoroterephthalic acid ligand, the rest are the same as in Example 1.

[0172] This comparative example also provides a ternary cathode material, except that the MOF-derived ternary precursor used in the preparation process of the ternary cathode material is replaced with the MOF-derived ternary precursor provided in this comparative example, and all other aspects are the same as in Example 1.

[0173] Comparative Example 2

[0174] This comparative example provides a bond-modified MOF-derived ternary precursor, except that the modification layer covering the core is omitted;

[0175] Except for step (2) of the preparation method of the MOF-derived ternary precursor, the rest is the same as in Example 1.

[0176] This comparative example also provides a ternary cathode material, except that the MOF-derived ternary precursor used in the preparation process of the ternary cathode material is replaced with the MOF-derived ternary precursor provided in this comparative example, and all other aspects are the same as in Example 1.

[0177] The surface residual alkali content of the ternary cathode materials provided in the above embodiments and comparative examples was tested. The method for testing the surface residual alkali content of the ternary cathode materials included: accurately weighing 0.8g of sample into a 250mL Erlenmeyer flask, adding 50mL of boiled and cooled deionized water, and magnetically stirring for 30min; adding 3 drops of bromocresol green-methyl red mixed indicator, and titrating with 0.1mol / L standardized hydrochloric acid solution until a purple-red color was obtained and maintained for 30s; simultaneously performing a blank experiment, and calculating the residual alkali content according to the formula (the formula is: residual alkali content = residual alkali content + methyl red ... Alkali content (as Li2CO3, %) = [(V-V0)×C×53.00] / (m×1000)×100; where V is the volume of 0.1mol / L hydrochloric acid consumed by the sample (mL), V0 is the volume of hydrochloric acid consumed in the blank experiment (mL), C is the actual concentration of hydrochloric acid (mol / L), 53.00 is 1 / 2 of the molar mass of Li2CO3 (g / mol), and m is the sample mass (0.8g). The surface residual alkali content of the ternary cathode material obtained by the test is shown in Table 1.

[0178] Table 1

[0179]

[0180] The ternary cathode material provided in the above embodiments and comparative examples was used to prepare a cathode sheet. The method for preparing the cathode sheet includes: drying at 200°C for 8 hours in a nitrogen atmosphere to obtain a dried ternary cathode material; mixing the obtained dried ternary cathode material with polyvinylidene fluoride and conductive carbon black by grinding, then adding N-methylpyrrolidone, and continuing to grind until a thick and suitable uniform slurry is obtained; then uniformly coating the slurry onto a flat aluminum foil, and then placing it in a vacuum oven to dry at 90°C for 8-12 hours, and then cutting it to obtain a cathode sheet.

[0181] CR2032 type button half-cells were prepared using the obtained positive electrode sheet. The preparation method was as follows: the obtained positive electrode sheet was used as the positive electrode, polypropylene membrane as the separator, lithium metal as the negative electrode, and a mixed solution containing 1 mol / L LiPF6 (the solvent was composed of EC, DMC and EMC in a volume ratio of 1:1:1) was used as the electrolyte. The battery was assembled in a glove box filled and discharged with argon gas. The water and oxygen content in the glove box was strictly controlled and was less than 0.01 ppm. After assembly, CR2032 type button half-cells were obtained.

[0182] The obtained CR2032 button half-cell was then subjected to electrochemical performance testing, which included cycle stability testing, first charge-discharge efficiency testing, and rate performance testing.

[0183] The method for cycle stability testing includes: testing at 25℃ within a voltage range of 1.9V to 4.6V at a rate of 0.1C. The capacity retention rate of the CR2032 button half-cell after 500 cycles at 0.1C is shown in Table 1.

[0184] The method for testing the initial charge and discharge efficiency includes: testing at 25℃ within a voltage range of 1.9V to 4.3V at a rate of 0.1C; first, constant current charging to 4.3V followed by resting for 5 minutes, recording the total initial charge capacity; then, constant current discharging to 1.9V followed by resting for 5 minutes, recording the total initial discharge capacity, and then calculating the initial charge and discharge efficiency as shown in Table 1; where, initial charge and discharge efficiency = initial discharge capacity ÷ initial charge capacity × 100%.

[0185] The rate performance test method includes: at 25℃ and within a voltage range of 1.9V to 4.3V, first activate the battery by cycling at 0.1C for 3 cycles; then cycle at 0.5C and 1C for 5 cycles each, and record the average discharge capacity at 0.5C and 1C. Then, calculate the ratio of the average discharge capacity at 0.5C to the average discharge capacity at 1C to obtain the ratio of 0.5C to 1C for the CR2032 button cell (ratio of 0.5C / 1C = 0.5C ÷ 1C × 100%), as shown in Table 2.

[0186] Table 2

[0187]

[0188] From Table 1 and Table 2, we can obtain:

[0189] (1) The batteries prepared using the ternary cathode materials provided in Examples 1-4 exhibit excellent cycle stability, as well as high first charge-discharge efficiency and excellent rate performance.

[0190] (2) By comparing Example 1 with Examples 5 and 6, it can be seen that in this invention, the ratio of the total molar amount of Ni salt, Co salt and Mn salt to the molar amount of ligand will affect the performance of MOF-derived ternary precursor and ternary cathode material, thereby affecting the performance of battery. When the ratio of the total molar amount of Ni salt, Co salt and Mn salt to the molar amount of ligand is 1:(0.5~1.5), the battery exhibits better performance. This is because this ratio range is most favorable for forming NiCoMn-MOF material with complete crystallinity, regular morphology and uniform molecular dispersion. On the one hand, it is beneficial to prepare MOF-derived ternary precursor with complete crystallinity, regular morphology and uniform molecular dispersion. On the other hand, it is also beneficial to undergo bonding reaction with organosilicon compounds and / or organoboron compounds, thereby obtaining a modification layer uniformly coated on the outside of the core.

[0191] (3) By comparing Example 1 with Examples 7 and 8, it can be seen that in this invention, the molar amount of NiCoMn-MOF material and the ratio of the total molar amount of organosilicon compound and organoboron compound in the modification solution will affect the performance of MOF-derived ternary precursor and ternary cathode material, thereby affecting the performance of the battery. When the molar amount of NiCoMn-MOF material and the ratio of the total molar amount of organosilicon compound and organoboron compound in the modification solution is 1:(0.5~5), the battery exhibits better performance. This is because this ratio provides sufficient and non-excessive modifiers (organosilicon compound and / or organoboron compound), which is sufficient to ensure that a continuous, dense, uniform coating layer containing SiO2 and / or B2O3 with a thickness of nanometer level (preferably 1nm~5nm) is formed on the surface of the MOF core through Si-OM and BOM bonds. This coating layer can completely encapsulate the core without significantly hindering the transport kinetics, thereby improving the electrochemical performance of the battery.

[0192] (4) By comparing Example 1 with Examples 9 and 10, it can be seen that in step (2) of the preparation method of MOF-derived ternary precursor in this invention, the temperature of the solvothermal reaction will affect the performance of MOF-derived ternary precursor and ternary cathode material, thereby affecting the performance of battery. When the temperature of the solvothermal reaction is 40℃~80℃, the battery exhibits better performance. This is because within this temperature range, the solvent polarity and molecular diffusion rate are moderate, which can ensure that the active groups in NiCoMn-MOF material are in full contact with organosilicon compounds and / or organoboron compounds and undergo stable bonding, avoiding the problem of incomplete reaction and weak binding force of the modified layer at low temperature; and can also suppress the collapse of the skeleton of NiCoMn-MOF material caused by high temperature, ensuring that the modified layer is uniformly and densely coated on the surface of NiCoMn-MOF material.

[0193] (5) By comparing Example 1 and Example 11, it can be seen that in the preparation process of the ternary cathode material in this invention, gradient sintering is beneficial to improving the performance of the ternary cathode material, thereby affecting the performance of the battery. This is because gradient sintering is divided into multiple stages. The low temperature stage can slowly remove the moisture and residual organic matter in the precursor, avoiding rapid heating that could cause particle cracking. The medium temperature stage promotes uniform diffusion of the lithium source and reduces element segregation. The high temperature stage can densify the grains, reduce grain boundary defects, and suppress the dissolution of transition metal ions. Therefore, gradient sintering takes into account both reaction sufficiency and structural stability, thereby improving the cycle stability, first charge and discharge efficiency and rate performance of the ternary cathode material.

[0194] (6) As can be seen from the comparison between Example 1 and Comparative Examples 1 and 2, in the MOF-derived ternary precursor provided by the present invention, the modification layer and the core are connected by Si-O bonds and / or BO bonds, and the modification layer and the core have a strong bonding force. The modification layer is not easy to fall off. After the ternary cathode material is prepared by the MOF-derived ternary precursor, the coating layer formed by the modification layer and the cathode material core formed by the core are still connected by Si-O bonds and / or BO bonds. The coating layer of the ternary cathode material is not easy to fall off during cycling. Therefore, the ternary cathode material prepared by the ternary precursor has excellent cycling performance (high cycling stability under high voltage).

[0195] In the MOF-derived ternary precursor provided by this invention, a modification layer can be constructed on the core surface by simply bonding organosilicon compounds and / or organoboron compounds to the NiCoMn-MOF material. This results in a protective coating layer forming in the ternary cathode material layer prepared from the MOF-derived ternary precursor, improving the interfacial properties of the cathode material. Therefore, the cycle performance of the ternary cathode material is further enhanced.

[0196] The MOF-derived ternary precursor provided by the present invention has a modification layer, and the ternary cathode material prepared with the MOF-derived ternary precursor has a low surface residual alkali content (the residual alkali content is reduced to less than 1 wt% of the total mass of the ternary cathode material); therefore, the battery containing the ternary cathode material exhibits high first charge-discharge efficiency and rate performance.

[0197] The MOF-derived ternary precursor provided by this invention includes NiCoMn-MOF material in its core. When preparing ternary cathode material using the MOF-derived ternary precursor, the NiCoMn-MOF material forms a carbon material framework, and the ternary material is loaded on the carbon material framework. The presence of the carbon material framework not only improves the uniformity of the ternary material distribution but also improves the conductivity of the ternary cathode material. Therefore, the first charge-discharge efficiency and rate performance of the ternary cathode material are further improved.

[0198] In summary, the MOF-derived ternary precursor with bonding modification provided by this invention has a modified layer that is bonded to the core via Si-O bonds and / or BO bonds, thereby improving the structural stability of both the MOF-derived ternary precursor and the ternary cathode material. The final coating layer formed by the modified layer also improves the interfacial properties of the ternary cathode material. Furthermore, the presence of the modified layer reduces the residual alkali on the surface of the ternary cathode material prepared from the MOF-derived ternary precursor. Therefore, batteries containing ternary cathode materials prepared from the MOF-derived ternary precursor exhibit good cycle stability, high initial charge-discharge efficiency, and excellent rate performance.

[0199] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A bond-modified MOF-derived ternary precursor, characterized in that, The MOF-derived ternary precursor includes a core and a modification layer covering the core. The core includes NiCoMn-MOF material, and the modification layer includes organosilicon compounds and / or organoboron compounds; The modified layer is bonded to the core via Si-O bonds and / or BO bonds.

2. The MOF-derived ternary precursor according to claim 1, characterized in that, The NiCoMn-MOF material includes [Ni x Co y Mn z (DOBDC)·nH2O materials, [Ni x Co y Mn z (BTC)·nH2O materials, [Ni x Co y Mn z (BPDC)·nH2O material or [Ni x Co y Mn z Any one or at least a combination of two of the materials (NDC)·nH2O; Preferably, the organosilicon compound includes any one or a combination of at least two of silane coupling agents, polysiloxanes, or silane polymers; Preferably, the organoboron compound includes any one or a combination of at least two of borate esters, phenylboronic acid, aminoboronic acid, or boraneamine complexes.

3. A method for preparing the MOF-derived ternary precursor as described in claim 1 or 2, characterized in that, The preparation method includes: After mixing NiCoMn-MOF materials with a modification solution, a solvothermal reaction was carried out to obtain MOF-derived ternary precursors; The NiCoMn-MOF material contains active groups; The modified solution contains organosilicon compounds and / or organoboron compounds, wherein the organosilicon compounds and / or organoboron compounds contain groups that can undergo bonding reactions with the active groups.

4. The preparation method according to claim 3, characterized in that, The active groups in the NiCoMn-MOF material include any one or a combination of at least two of hydroxyl, carboxyl, or amino groups. Preferably, the method for preparing the NiCoMn-MOF material includes: mixing Ni salt, Co salt, Mn salt, ligand and solvent to obtain a mixed solution, and heat-treating the obtained mixed solution to obtain the NiCoMn-MOF material; Preferably, the ligand comprises any one or a combination of at least two of 2,5-dihydroxyterephthalic acid, pyromellitic acid, biphenyl-4,4-dicarboxylic acid, or 2,6-naphthalenedicarboxylic acid; Preferably, in the mixture, the ratio of the total molar amount of Ni salt, Co salt and Mn salt to the molar amount of ligand is 1:(0.5~1.5); Preferably, the heat treatment temperature is 100℃~140℃ and the time is 20~30h.

5. The preparation method according to claim 3, characterized in that, In the mixture, the molar amount of NiCoMn-MOF material is in the ratio of the total molar amount of organosilicon compounds and organoboron compounds in the modification solution to 1:(0.5~5); Preferably, the total molar concentration of the organosilicon compound and the organoboron compound in the modified solution is 0.1 mol / L to 0.5 mol / L; Preferably, the temperature of the solvothermal reaction is 40℃~80℃, and the time is 6h~12h.

6. A ternary cathode material, characterized in that, The ternary cathode material is prepared from the MOF-derived ternary precursor as described in claim 1 or 2.

7. The ternary cathode material according to claim 6, characterized in that, The ternary cathode material includes a cathode material core and a coating layer covering the outside of the cathode material core; Preferably, the cathode material core includes LiNi. x Co y Mn z O2 and carbon materials; Preferably, the coating layer comprises silicon oxide and / or boron oxide; Preferably, the silicon oxide comprises SiO2; Preferably, the boron oxide includes B2O3.

8. A preparation process for a ternary cathode material, characterized in that, The preparation process includes: The MOF-derived ternary precursor described in claim 1 or 2 is mixed with a lithium source and then subjected to gradient sintering to obtain a ternary cathode material.

9. The preparation process according to claim 8, characterized in that, The gradient sintering includes a first sintering, a second sintering, and a third sintering performed sequentially; Preferably, the first sintering temperature is 250℃~350℃, and the time is 1.5h~2.5h; Preferably, the second sintering temperature is 450℃~650℃, and the time is 1.5h~2.5h; Preferably, the third sintering temperature is 600℃~800℃ and the time is 2.5h~3.5h.

10. A battery, characterized in that, The battery comprises the ternary cathode material as described in claim 6 or 7.

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