Ternary positive electrode material modified with glassy metal-organic framework, and preparation method therefor and use thereof

Abstract

A ternary positive electrode material modified with a glassy metal-organic framework, and a preparation method therefor and the use thereof. The ternary positive electrode material modified with a glassy metal-organic framework is obtained by grinding and mixing a ternary positive electrode material and a metal-organic framework, and then subjecting same to a melt quenching treatment under a protective atmosphere. Forming a crack-free glassy metal-organic framework containing nano / sub-nano pores on a surface of the ternary positive electrode material can significantly improve the stability of the ternary positive material, alleviate the dissolution of transition metals, and ultimately improve the electrochemical performance of batteries and prolong the service life of the batteries.

Description

A glassy metal-organic framework material modified ternary cathode material and its preparation method and application Technical Field

[0001] The present invention relates to a metal-organic framework material modified ternary positive electrode material, specifically to a glassy metal-organic framework material coated modified ternary positive electrode material, and also to a preparation method and application of a glassy metal-organic framework material modified ternary positive electrode material, belonging to the technical field of lithium batteries. Background Art

[0002] Rechargeable batteries, especially lithium-ion batteries, have become popular in the past few decades and are widely used to power various electronic devices. The rapid development of various electronic devices not only places high demands on their capacity and cycle life, but also places higher demands on the safety performance of lithium-ion batteries. x Co y Mn z O2, LiNi x Co y Al z O2, referred to as NCM, NCA) to replace traditional positive electrodes such as lithium iron phosphate can effectively improve the energy density of the battery. However, the layered ternary positive electrode materials used in lithium batteries have high reactivity during the charge and discharge process of the battery, and are very easy to react with the liquid electrolyte, causing the battery to usually suffer from serious electrolyte decomposition problems. In addition, the continuous embedding and extraction of solvated lithium ions in the layered ternary positive electrode material will damage the original layered structure of the ternary material, causing the structure of the ternary material to transform into a rock salt phase and the dissolution of transition metal ions (nickel, cobalt, manganese) in the ternary material. The dissolved transition metal ions will shuttle to the negative electrode (graphite negative electrode or metal lithium negative electrode, etc.), exacerbating the failure of the negative electrode material and uncontrollable dendrite lithium growth, which will ultimately greatly reduce the electrochemical performance and service life of the battery.

[0003] Chinese patent CN110165204A discloses a metal-organic framework material coated ternary cathode material and its preparation method. This method can effectively reduce the corrosion and decomposition of the ternary cathode material in the electrolyte and improve the battery cycle stability by modifying the metal-organic framework material on the surface of the ternary cathode material. This method uses a hydrothermal precipitation method to grow the metal-organic framework material on the ternary cathode material. However, the hydrothermal method has an uneven coating layer during the process of coating the framework material on the surface of the ternary cathode material. The hydrothermal method also affects the structural stability of the ternary cathode material itself, and the performance improvement achieved by the coating is very limited. In addition, the hydrothermal coating method has complex steps, causes environmental pollution due to the introduction of organic reagents, and is expensive, which leads to increased costs.

[0004] Summary of the Invention

[0005] In response to the technical problems existing in the prior art, the first purpose of the present invention is to provide a glassy metal-organic framework material modified ternary positive electrode material. By forming a crack-free glassy metal-organic framework material containing nano and sub-nano pores on the surface of the ternary positive electrode material, the direct contact between the ternary positive electrode material body and the liquid electrolyte can be completely avoided, and the side reactions between the electrolyte and the positive electrode material can be significantly slowed down. At the same time, the nano and sub-nano pores can enable the solvated lithium ions to remove part of the solvent molecules in the solvation shell when passing through the pores, while further reducing the electrochemical / chemical decomposition of the solvent molecules in the bulk phase of the ternary positive electrode material, achieving a favorable positive electrode interface mode (CEI) dominated by anion decomposition, thereby significantly improving the stability of the ternary positive electrode material, alleviating the dissolution of transition metals, and ultimately improving the electrochemical performance and service life of the battery.

[0006] The second object of the present invention is to provide a method for preparing a ternary positive electrode material modified by a glassy metal-organic framework material. This method can achieve surface coating modification of the ternary positive electrode material by a glassy metal-organic framework material through a one-step melt quenching process. The method is simple to operate, low in cost, and is conducive to industrial production.

[0007] The third object of the present invention is to provide an application of a glassy metal-organic framework material modified ternary positive electrode material, which can be used as a lithium metal or lithium ion battery positive electrode material to improve the energy density and service life of lithium ion batteries / lithium metal batteries. For example, a soft-pack battery after the glassy metal-organic framework material modified ternary positive electrode material is matched with a lithium metal negative electrode has a high energy density of 350-400Wh / kg and stable cycle stability (60-90% capacity retention rate after 50-500 cycles).

[0008] In order to achieve the above technical objectives, the present invention provides a glassy metal-organic framework material modified ternary cathode material, which is composed of a ternary cathode material and a glassy metal-organic framework material coating layer on its surface.

[0009] The present invention uses a glassy metal-organic framework material to coat and modify the surface of the ternary positive electrode material. The glassy metal-organic framework material has good surface integrity and is free of cracks, and forms a short-range ordered and long-range disordered nano and sub-nano pore structure. Based on the presence of the crack-free glassy metal-organic framework material, the direct contact between the ternary positive electrode material body and the liquid electrolyte can be completely avoided, and the side reaction between the electrolyte and the positive electrode material can be significantly slowed down. At the same time, the nano and sub-nano pores on its surface can allow the solvated lithium ions to remove part of the solvent molecules in the solvation shell when passing through the pores, while further reducing the electrochemical / chemical decomposition of the solvent molecules in the bulk phase of the ternary positive electrode material, achieving a favorable positive electrode interface mode (CEI) dominated by anion decomposition, thereby significantly improving the stability of the ternary positive electrode material, alleviating the dissolution of transition metals, and ultimately improving the electrochemical performance and service life of the battery.

[0010] As a preferred solution, the glassy metal-organic framework material coating layer has a thickness of 5 to 300 nm and has no surface cracks. Glassy metal-organic framework materials can reach nanometer-level thickness and have no surface cracks, which is very beneficial for improving battery energy density.

[0011] As a preferred solution, the glassy metal-organic framework material coating layer contains nanopores, and the pore window size of the nanopores is 0.1nm to 3nm. The nano- or sub-nanoscale pores enable the solvated lithium ions to remove part of the solvent molecules in the solvation shell when passing through the pores, while further reducing the electrochemical / chemical decomposition of the solvent molecules in the bulk phase of the ternary positive electrode material, and realizing a favorable positive electrode interface film (CEI) dominated by anion decomposition, thereby significantly improving the stability of the ternary positive electrode material, alleviating the dissolution of transition metals, and ultimately improving the electrochemical performance and service life of the battery. The metal organic framework material crystal itself has a long-range ordered nanopore structure, and after melt quenching, the nanopores are converted into short-range ordered and long-range disordered structures after becoming glassy. These nanopore structures are beneficial for lithium ion transport.

[0012] As a preferred embodiment, the mass ratio of the glassy metal-organic framework material coating layer is 0.5 to 30 wt%. More preferably, the mass ratio of the glassy metal-organic framework material coating layer is 0.5 to 15 wt%. If the mass ratio of the glassy metal-organic framework material coating layer is too low, it is difficult to form a complete glassy metal-organic framework material coating layer. If the mass ratio of the glassy metal-organic framework material coating layer is too high, the coating layer is too thick, which is not conducive to obtaining a high energy density.

[0013] As a preferred embodiment, the glassy metal organic framework material coating layer is composed of at least one of the following metal organic framework materials: Zn-dmbIm, ZIF-8, ZIF-62, ZIF-8, ZIF-4, [Zn(HPO4)(H2PO4)2](H2Im)2, Zn(Im)2, Zn2(-DOBDC)(Zn-MOF-74), Zn4O(BDC)3(MOF-5), Zn4O(BTB) 2 / MOF-177, Zn(tbip), Zn2(bptc), Zn4O(H2O)3(adc)3(PCN-13), Zn2(cnc)2(dpt), Zn2(cnc)2(dpt), Zn3(OH)(p-cdc) 2.5 、Zn3(OH)(p-cdc) 2.5 (DMF)3, Zn(dtp), Zn(bIM)(nIM)(ZIF-68), Zn4O(btb)2(MOF-177), Zn2(ndc)2(dpni), [Zn(bdc)(4,40-bipy) 0.5 ](MOF-508), Zn(cbIM)(nIM)(ZIF-69), Zn(bdc)(ted) 0.5 ,Zn(BDC),Zn4O(BDC)3,Zn(TPTC),Zn 20 (cbIM) 39 (OH)(ZIF-100), Zn(cbIM)2(ZIF-95), Zn(NDI-X), ZIF-22, ZIF-67, ZIF-62, ZIF-4, Cu-P-dmbIm, Cu3(BTC)2(HKUST-1), Cu(BDC), Cu2(pzdc)2(pyz), Cu(hfipbb)(H2hfipbb) 0.5 ,Cu(bdt),[Cu(pzdc)2(pyz)],Cu2(bdc) 2x H2O, [Cu2(ndc)2(dabco)], Cu2(D-cam)2P), Cu(F-pymo)2Zn(IM) 1.13 (nIM) 0.87 (ZIF-70), Cu(gla)(4,40-bipy) 0.5 , Cd-PdmbIm, Cd(H2PO4)2(HTr)2, Mn-P-dmbIm, CrIII3O(H2O)2F(ntc) 1.5 (MIL-102), MIL-101(Cr), Al-MIL-53, Al(OH)(BDC), MIL-96(Al), Al12 O(OH) 18 (H2O)3[Al2(OH)4](btc)6, [Fe3(im)6(Him)2], Fe(py)2[Pt(CN)4], MIL-89, Fe-MIL-88B-NH2, where: btc is 1,3,5-benzoic acid, ndc is dimethyl 2,6-naphthalene dicarboxylate, pda is 1,4-phenylenedicarboxylic acid, pzdc is 2,3-pyrazine dicarboxylic acid, pyz is pyrazine, H2hfipbb is 2,2-bis(4-carboxyphenyl)hexafluoropropane, ntc is 1,4,5,8-naphthalenetetracarboxylic anhydride, tpic is 5-tert-butyl-1,3-benzenedicarboxylic acid, bdt is 1,4-phenyldithiol, bptc is 6,6'-dimethyl-2,2'-bipyridine, adc is 9,10-anthracene dicarboxylic acid, apt is 4-aminophenyl tetrazolate, pyta 2 ,4,6-pyridinetricarboxylate, bdc is terephthalic acid, ted is triethylenediamine, btb is 1,3,5-phenyltrimethylbenzene, 2,4-pdc is pyridine-2,4-dicarboxylate, dtp is 2,3-pyrazine-tetrazolate, F-pymo is 2-hydroxy-5-fluoropyrimidine, IM is imidazolate, nIM is 2-nitroimidazolate, cbIM is 5-chlorobenzeneimidazolate, pyenH 2 is 5-methyl-4-pyridone-3-carboxamide, 4,4'-bipy is 4'-methyl-2,2'-bipyridine-4-carboxylic acid, GLA is glutaric acid salt, CNC is 4-cinnamic acid, DPT is 3,6-di-4-pyridyl-1,2,4,5-tetrazine, TATB is 2,4,6-trimercapto-s-triazine, DMF is dimethylformamide, and DPNI is bis(4-pyridyl)naphthalene diimide. These metal-organic framework materials are all common metal-organic framework materials in the prior art and can be purchased directly or simply synthesized with reference to existing literature. Using one or more combinations of these metal-organic framework materials, a glassy metal-organic framework material can be formed by melt quenching treatment for coating a ternary cathode material.

[0014] As a preferred solution, the ternary cathode material is NCM955 (LiNi 0.9 Co 0.05 Mn 0.05 O2), NCM811(LiNi 0.8 Co 0.1 Mn 0.1 O2), NCM622(LiNi 0.6 Co 0.2 Mn 0.2 O2), NCM532(LiNi 0.5 Co 0.3 Mn 0.2 O2), NCM333(LiNi0.3 Co 0.3 Mn 0.3 O2), NCA(LiNi 0.8 Co 0.15 Al 0.05 O2) at least one.

[0015] The present invention also provides a method for preparing a glassy metal organic framework material modified ternary cathode material, which comprises grinding and mixing the ternary cathode material and the metal organic framework material, and then subjecting the mixture to a melt quenching treatment under a protective atmosphere.

[0016] The key to the present invention is to use a melt quenching method to in-situ coat the metal organic framework material on the surface of the ternary cathode material. The melt quenching method can make the metal organic framework material form a glassy metal organic framework material with nanometer-level thickness, no cracks, and complete structure. In particular, the crack-free glassy metal organic framework material coating layer has nanometer or sub-nanometer-level short-range ordered and long-range disordered nanopores (0.1nm to 3nm). The glassy metal organic framework material modified ternary cathode material (abbreviated as GM@NCM) has a crack-free glassy metal organic framework material coating layer. The existence of the glassy metal organic framework material can completely avoid the direct contact between the ternary cathode material and the liquid electrolyte, and can significantly slow down the side reaction between the electrolyte and the cathode material. The nano / sub-nano pores of the glassy metal organic framework material can make the solvated lithium ions remove part of the solvent molecules in the solvation shell when passing through the pores, while further reducing the electrochemical / chemical decomposition of the solvent molecules in the bulk phase of the ternary cathode material, and realizing a favorable positive electrode interface mode (CEI) dominated by anion decomposition, thereby significantly improving the stability of the ternary cathode material, alleviating the dissolution of transition metals, and ultimately improving the electrochemical performance and service life of the battery.

[0017] As a preferred solution, the grinding and mixing time is 15 to 30 minutes.

[0018] As a preferred solution, the melt quenching treatment conditions are: a temperature of 120-350°C for 20-60 minutes. If the temperature is too low, it is difficult to form the metal-organic framework material into a molten glass state to achieve coating of the ternary cathode material. If the temperature is too high, the metal-organic framework material is easily carbonized and cannot form a molten glass state.

[0019] As a preferred solution, the protective atmosphere is an inert gas such as nitrogen or argon. Melt quenching must be carried out in a protective atmosphere. If it is in an oxidizing atmosphere, the metal organic framework material is difficult to exist stably.

[0020] The present invention also provides an application of a glassy metal organic framework material modified ternary positive electrode material, which is used as a positive electrode material for lithium metal or lithium ion batteries.

[0021] The method for preparing the crack-free glassy metal-organic framework material modified lithium battery ternary positive electrode material of the present invention comprises the following steps:

[0022] Step 1: Prepare metal organic framework material powder by existing conventional methods:

[0023] The metal salt is dissolved in solvent A (concentration is 0.01 mol / L to 5 mol / L), and the organic ligand is dissolved in solvent B (concentration is 0.01 mol / L to 5 mol / L), and then the two solutions are mixed and ultrasonically stirred to obtain a metal organic framework material; preferably, solvent A is at least one of methanol, ethanol, acetone, water, phosphoric acid, dimethylformamide, and N-methylpyrrolidone; and organic solvent B is at least one of methanol, ethanol, acetone, water, phosphoric acid, dimethylformamide, and N-methylpyrrolidone.

[0024] Taking the synthesis of Zn-dmbIm MOF as an example, the specific synthesis steps are as follows:

[0025] 219.5 mg of Zn(OAc)2·2H2O was placed in a mortar with 292.4 mg of 5,6-dimethylbenzimidazole and 210 μL of phosphoric acid and manually ground for 15 minutes. The powder was washed three times with dichloromethane and dried at 70°C for 10 hours to obtain Zn-dmbIm MOF powder.

[0026] Step 2: Preparation of crack-free glassy metal-organic framework modified ternary materials:

[0027] Commercial lithium battery ternary cathode materials and the resulting metal-organic framework material powder were ground in a mortar / ball mill for 15 to 30 minutes. The mixture was then calcined in a tube furnace at 120 to 450°C under an inert atmosphere for 30 minutes. When the temperature dropped to room temperature, the sample was removed to obtain a crack-free glassy metal-organic framework material-modified ternary cathode material (GM@NCM or GM@NCA). Depending on the weight percentage of the added metal-organic framework material powder, crack-free glassy metal-organic framework material-modified ternary cathode materials (abbreviated as GM-1@NCM to GM-30@NCM or GM-1@NCA to GM-30@NC) with a coating amount ranging from 1% to 30wt% were obtained.

[0028] Step 3: Positive electrode preparation method:

[0029] The crack-free glassy metal-organic framework material modified ternary positive electrode material is uniformly mixed with a conductive carbon material (carbon nanotubes, Super P, Carbon black, etc.), a binder (at least one of polyvinylidene fluoride, poly(vinylidene fluoride-co-hexafluoropropylene), polyacrylic acid, carboxymethyl cellulose, and styrene-butadiene rubber, with the weight percentage of the binder being 3-10%), and a solvent (N-methylpyrrolidone, water, etc.), and then coated on the surface of an aluminum foil and dried to obtain a positive electrode sheet.

[0030] Step 4: Lithium Metal Battery Assembly:

[0031] The positive electrode prepared in step 3 is used, lithium metal is used as the negative electrode, and an organic electrolyte is used to assemble a high-performance lithium metal button cell and a soft pack cell. The preferred organic electrolyte is an ester or ether, specifically at least one of: LiPF6-EC:DMC, LiPF6-EC:DMC:DEC, LiPF6-EC:DEC:EMC, LiPF6-EC:DEC-FEC, LiTFSI-EC:DMC, LiTFSI-EC:DMC:DEC, LiTFSI-EC:DEC:EMC, LiTFSI-EC:DEC-FEC, LiFSI-EC:DMC, LiFSI-EC:DMC:DEC, LiFSI-EC:DEC:EMC, LiFSI-EC:DEC-FEC, LiClO4-PC, LiTFSI-PC, and LiTFSI-DOL:DME.

[0032] The lithium metal ternary button battery prepared by the present invention can still maintain a high specific capacity (about 170mAh / g, 80% capacity retention rate) after 1000 cycles; the soft-pack battery has an energy density of 350-400Wh / kg and stable electrochemical performance (50-500 cycle life, 60-95% capacity retention rate).

[0033] The working principle of the glassy metal-organic framework material modified ternary positive electrode material of the present invention to improve the energy density / specific capacity and life of lithium metal batteries is that: the presence of a crack-free glassy metal-organic framework material coating layer on the surface of the ternary positive electrode material can completely avoid direct contact between the ternary positive electrode material body and the liquid electrolyte, and can significantly slow down the side reactions between the electrolyte and the positive electrode material. In addition, the special nano and sub-nano pores of the glassy metal-organic framework material can enable the solvated lithium ions to remove some solvent molecules in the solvation shell when passing through the pores, while further reducing the electrochemical / chemical decomposition of solvent molecules in the bulk phase of the ternary positive electrode material, achieving a favorable positive electrode interface mode (CEI) dominated by anion decomposition, thereby significantly improving the stability of the ternary positive electrode material, alleviating the dissolution of transition metals, and ultimately improving the electrochemical performance and service life of the battery.

[0034] Compared with the existing technology, the technical solution of the present invention brings the following beneficial technical effects:

[0035] The coating modification of ternary positive electrode materials in the present invention is different from the conventional coating strategy. For the first time, it is proposed to use a metal-organic framework material with nano and sub-nano pores and a glassy state to coat the ternary positive electrode material. The existing technology uses the traditional hydrothermal method to generate a coating strategy of metal-organic framework materials on the surface of the ternary positive electrode material, which makes it difficult for the metal-organic framework material to completely cover the surface of the ternary positive electrode material, and the coating layer is usually thick, which is not conducive to the improvement of the battery energy density. Compared with the conventional hydrothermal coating strategy, the key to the technical solution of the present invention is to adopt a melt quenching coating strategy, which uses the metal-organic framework material to turn into a liquid under heating conditions, thereby penetrating into the interior of the ternary positive electrode material. After cooling, the surface of the metal-organic framework material originally in powder form is transformed into a glassy state in situ, achieving a complete and crack-free coating of the ternary positive electrode material, and the coating layer is relatively thin (5 to 300 nm, 0.5 to 30 wt% by mass). More importantly, the pore size of the glassy metal-organic framework coating is 0.1nm to 3nm. During the battery charge and discharge process, the solvated lithium ions can remove some of the solvent molecules in the solvation shell when passing through the pores. While further reducing the electrochemical / chemical decomposition of solvent molecules in the bulk phase of the ternary cathode material, a favorable cathode interface mode (CEI) dominated by anion decomposition is achieved, thereby significantly improving the stability of the ternary cathode material, alleviating the dissolution of transition metals, and ultimately improving the electrochemical performance and service life of the battery. More specifically:

[0036] 1) The present invention utilizes the special property of metal-organic framework materials that they transform from a crack-free glassy state after melt quenching, and in situ coats the surface of commercial lithium battery ternary positive electrode materials with a crack-free glassy metal-organic framework material with a nano / sub-nano pore structure, thereby achieving complete and crack-free coating of the ternary positive electrode material, and the coating layer is relatively thin (5 to 300 nm, mass percentage of 0.5 to 30 wt%), which is conducive to the construction of high-energy-density lithium metal batteries.

[0037] 2) The crack-free glassy metal-organic framework material coating layer of the present invention has a pore window size of 0.1 nm to 3 nm. During the battery charge and discharge process, the solvated lithium ions can remove some of the solvent molecules in the solvation shell when passing through the pores, while further reducing the electrochemical / chemical decomposition of the solvent molecules in the bulk phase of the ternary cathode material. At the same time, a favorable cathode interface mode (CEI) dominated by anion decomposition is achieved, which alleviates the dissolution of transition metals and significantly improves the stability of the ternary cathode material.

[0038] 3) The ternary cathode material (taking NCM811 as an example) uniformly coated with the crack-free glassy metal-organic framework material of the present invention can significantly improve the cycle life of the lithium metal battery. When assembled into a soft-pack battery with a lithium metal negative electrode, it exhibits a high energy density of 350 to 400 Wh / kg and stable cycle stability (60 to 90% capacity retention after 50 to 500 cycles).

[0039] 4) Compared with the existing hydrothermal method to achieve metal-organic framework material coating of ternary positive electrode materials, the present invention adopts a melt quenching method to achieve metal-organic framework material coating of ternary positive electrode materials, which has the following obvious advantages: without using additional solvents, the originally uneven metal-organic framework material coating layer is converted into a liquid state after heating, and then infiltrated into the ternary positive electrode material. After quenching, a more stable glassy metal-organic framework material can be formed, further improving the structural stability of the ternary positive electrode material. The method is simpler, more environmentally friendly, and has lower cost. At the same time, the ternary positive electrode material coated with the glassy metal-organic framework material has excellent electrochemical performance, which is far better than conventional hydrothermal coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In Figure 1, a and b are scanning electron microscope images of Zn-dmbIm powder at a magnification of 50,000 times and transmission electron microscope images at a magnification of 100,000 times, as well as the corresponding local magnification images, respectively; c and d are scanning electron microscope images of Zn-dmbIm glass at a magnification of 10,000 times and transmission electron microscope images at a magnification of 50,000 times, as well as the corresponding local magnification images, respectively; e and f are X-ray diffraction patterns of Zn-dmbIm powder and Zn-dmbIm glass, respectively; g and h are experimental images of Zn-dmbIm glass inhibiting lithium polysulfide penetration.

[0041] In Figure 2, a and b are scanning electron microscope images of the bare NCM811 positive electrode material at a magnification of 25,000 times and 100,000 times, respectively; e and f are transmission electron microscope images of the bare NCM811 positive electrode material and the corresponding local magnification images, respectively; c and d are scanning electron microscope images of the NCM811 ternary positive electrode material (GM@NCM811) uniformly coated with crack-free glassy metal-organic framework material at a magnification of 25,000 times and 100,000 times, respectively; g and h are transmission electron microscope images of the bare NCM811 positive electrode material and the corresponding local magnification images, respectively.

[0042] In Figure 3, a and b are scanning electron microscope images of the NCM811 ternary material uniformly coated with a crack-free glassy metal-organic framework material (GM@NCM811; the mass ratio of the two is: 5wt%:95wt%) at a magnification of 25,000 times and 100,000 times, respectively; c and d are scanning electron microscope images of the NCM811 ternary material uniformly coated with a crack-free glassy metal-organic framework material (GM@NCM811; the mass ratio of the two is: 10wt%:90wt%) at a magnification of 25,000 times and 100,000 times, respectively.

[0043] In Figure 4, a is a scanning electron microscope image of the NCM811 ternary material (Cu-GM@NCM811; the mass ratio of the two is: 5wt%:95wt%) uniformly coated with a crack-free glassy metal-organic framework material at a magnification of 100,000 times; b is a scanning electron microscope image of the NCM811 ternary material (Cu-GM@NCM811; the mass ratio of the two is: 10wt%:90wt%) uniformly coated with a crack-free glassy metal-organic framework material at a magnification of 25,000 times; c is a scanning electron microscope image of the NCM811 ternary material (Cu-GM@NCM811; the mass ratio of the two is: 20wt%:80wt%) uniformly coated with a crack-free glassy metal-organic framework material at a magnification of 25,000 times.

[0044] In Figure 5, a and b are the scanning electron microscope and FIB images of the bare NCM811 positive electrode material after 400 cycles, respectively; c and d are the scanning electron microscope and FIB images of the crack-free glassy metal-organic framework material modified NCM811 ternary positive electrode material (GM@NCM811) after 400 cycles, respectively; e and f are the transmission electron microscope images of the bare NCM811 positive electrode material at different magnifications after 400 cycles, respectively; g and h are the transmission electron microscope images of the crack-free glassy metal-organic framework material modified NCM811 ternary positive electrode material (GM@NCM811) after 400 cycles, respectively; i is the ICP test results of the electrolyte and metallic lithium in the two batteries after 400 cycles.

[0045] Figure 6 shows the electrochemical cycling performance of a cathode prepared from a crack-free glassy metal organic framework modified NCM811 ternary cathode material (Cu-GM@NCM811) for a lithium metal button cell at a current density of 1C, where the cathode loading is 7.1 mg / cm 2 .

[0046] Figure 7 (a) shows the electrochemical cycling performance comparison of the cathode prepared by bare NCM811 and crack-free glassy metal organic framework material modified NCM811 ternary cathode material (GM@NCM811) for metal lithium button batteries at a current density of 1C; (b) shows the electrochemical cycling performance comparison of the cathode prepared by crack-free glassy metal organic framework material modified NCM811 ternary cathode material (GM@NCM811) for metal lithium soft pack batteries under limited lithium (N / P ratio of 4) and high cathode loading (cathode loading of 27.1 mg / cm 2 ) under the conditions of electrochemical cycling performance. DETAILED DESCRIPTION

[0047] The following specific examples are intended to further illustrate the present invention in detail, rather than to limit the scope of protection of the claims.

[0048] Unless otherwise specified, the chemical reagents involved in the following specific examples are conventional commercially available reagents.

[0049] Example 1

[0050] 219.5 mg of Zn(OAc)2·2H2O, 292.4 mg of 5,6-dimethylbenzimidazole, and 210 μL of phosphoric acid were placed in a mortar and manually ground for 15 minutes. The powder was washed three times with dichloromethane and dried at 70°C for 10 hours to obtain Zn-dmbIm powder. Finally, the pre-dried Zn-dmbIm powder was placed in a vacuum drying oven at 120°C for 12 hours to remove the phosphoric acid solvent, dichloromethane, and moisture introduced during the synthesis process. The vacuum-dried Zn-dmbIm powder was then heated in a tube furnace at 170°C under an inert atmosphere for 30 minutes and then cooled to room temperature to obtain Zn-dmbIm glass.

[0051] Figures 1a and 1b show scanning electron micrographs of the resulting Zn-dmbIm powder at 50,000x magnification and transmission electron micrographs at 100,000x magnification, respectively. As shown, the Zn-dmbIm particles are of varying sizes (0.3 to 3 μm) and possess a rich porous structure. Figures 1c and 1d show scanning electron micrographs of the resulting Zn-dmbIm glass at 10,000x magnification and 50,000x magnification, respectively. As shown, the Zn-dmbIm glass has become a crack-free monolith with a rich nanoporous structure. Figures 1e and f show X-ray diffraction patterns of the resulting Zn-dmbIm powder and glass, respectively. As can be seen, the diffraction peaks corresponding to the Zn-dmbIm powder indicate excellent crystallinity, while the melt-quenched Zn-dmbIm glass ultimately exhibits distinct amorphous diffraction peaks, verifying the feasibility of preparing Zn-dmbIm glass. Figure 1 g and h are the lithium polysulfide penetration experiments of Zn-dmbIm glass. It can be seen from the figure that for lithium polysulfide with a size of 1.3nm, due to the barrier of Zn-dmbIm glass, it still cannot pass through after 100 hours, verifying that the prepared Zn-dmbIm glass is crack-free.

[0052] Example 2

[0053] The Zn-dmbIm powder prepared in Example 1 was evenly ground with a commercial ternary cathode material (mass ratio: 5wt%:95wt%), and then calcined in an inert atmosphere at 170°C in a tube furnace for 30 minutes and cooled to room temperature to obtain a ternary material (GM@NCM) uniformly coated with a crack-free glassy metal-organic framework material.

[0054] Figures 2a and 2b show scanning electron micrographs (SEM) of the bare NCM811 cathode material at 25,000x and 100,000x magnifications, respectively; Figures 2e and f show transmission electron micrographs (TEM) of the bare NCM811 cathode material. As shown, the surface of the bare NCM811 material is relatively smooth, without any coating layer. Figures 2c and 2d show SEM images of the crack-free NCM811 ternary material uniformly coated with a glassy metal-organic framework (GM@NCM811) at 25,000x and 100,000x magnifications, respectively; Figures 2g and 2h show transmission electron micrographs of the bare NCM811 cathode material. As shown, the surface of the crack-free NCM811 ternary material uniformly coated with a glassy metal-organic framework (GM@NCM811) is slightly rougher than that of the bare NCM811 material, with a uniform coating layer of approximately 15 nm thickness observed, demonstrating the feasibility of the glassy metal-organic framework coating strategy.

[0055] Example 3

[0056] The Zn-dmbIm powder prepared in Example 1 was evenly ground with a commercial ternary cathode material (the mass ratios of the two were: 5wt%:95wt%; 10wt%:90wt%, respectively, to investigate the effects of different mass ratios on the coating). The mixture was then calcined in a tubular furnace at 170°C in an inert atmosphere for 30 minutes and cooled to room temperature to obtain a ternary material (GM@NCM) uniformly coated with a crack-free glassy metal-organic framework material.

[0057] Figures 3a and b show scanning electron micrographs of a crack-free NCM811 ternary material (GM@NCM811; the mass ratio of the two is 5wt%:95wt%) uniformly coated with a glassy metal-organic framework (GM@NCM811) at 25,000x and 100,000x magnifications, respectively. Figures 3c and 3d show scanning electron micrographs of a crack-free NCM811 ternary material (GM@NCM811; the mass ratio of the two is 10wt%:90wt%) uniformly coated with a glassy metal-organic framework (GM@NCM811) at 25,000x and 100,000x magnifications, respectively. As shown in the figures, the surface of the NCM811 ternary material (GM@NCM811) successfully coated with the glassy metal-organic framework (GM@NCM811) shows some accumulation of the glassy metal-organic framework compared to Figure 2, likely due to a slightly higher amount of glassy metal-organic framework coating.

[0058] Example 4

[0059] 199.7 mg of Cu(OAc)2·2H2O, 292.4 mg of 5,6-dimethylbenzimidazole, and 210 μL of phosphoric acid were placed in a mortar and manually ground for 15 minutes. The powder was washed three times with dichloromethane and dried at 70°C for 10 hours to obtain Cu-dmbIm powder. Finally, the pre-dried Cu-dmbIm powder was placed in a vacuum drying oven at 120°C for 12 hours to remove the phosphoric acid solvent, dichloromethane, and moisture introduced during the synthesis process. The vacuum-dried Cu-dmbIm powder was then heated in a tube furnace at 170°C under an inert atmosphere for 30 minutes and then cooled to room temperature to obtain Cu-dmbIm glass.

[0060] The obtained Zn-dmbIm powder was evenly ground with commercial ternary positive electrode materials (the mass ratio of the two was: 5wt%:95wt%; 10wt%:90wt%; 20wt%:80wt%), and then calcined in an inert atmosphere at 170°C in a tube furnace for 30 minutes and cooled to room temperature to obtain a ternary material (Cu-GM@NCM) uniformly coated with a crack-free glassy metal-organic framework material.

[0061] Figure 4a shows a scanning electron micrograph (SEM) of a crack-free NCM811 ternary material (Cu-GM@NCM811; the mass ratio of Cu-GM@NCM811 and Cu-GM@NCM811 is 5wt%:95wt%) uniformly coated with a glassy metal-organic framework (MOF) at a magnification of 100,000x. Figure 4b shows a SEM of a crack-free NCM811 ternary material (Cu-GM@NCM811; the mass ratio of Cu-GM@NCM811 and Cu-GM@NCM811 is 10wt%:90wt%) uniformly coated with a glassy metal-organic framework (MOF) at a magnification of 25,000x. Figure 4c shows a SEM of a crack-free NCM811 ternary material (Cu-GM@NCM811; the mass ratio of Cu-GM@NCM811 and Cu-GM@NCM811 is 20wt%:80wt%) uniformly coated with a glassy metal-organic framework (MOF) at a magnification of 25,000x. As shown in the figure, the surface of the NCM811 ternary material (Cu-GM@NCM811) was successfully coated with the glassy metal-organic framework (MOF).

[0062] Example 5

[0063] The bare NCM811 ternary material and the NCM811 ternary material (GM@NCM811) uniformly coated with the crack-free glassy metal organic framework material obtained in Example 2 were assembled into button batteries together with metallic lithium. Specifically, R2032 button batteries were used, and 1 mol / L LiPF6-EC:DMC electrolyte was added in the order of negative electrode shell, spring sheet, gasket, lithium metal, PP separator, bare NCM811 / GM@NCM811 positive electrode material, and positive electrode shell for battery packaging. The packaged battery was left to stand for 16 hours, and the assembled battery was electrochemically tested using a blue battery test system. The bare NCM811 / GM@NCM811 positive electrode after 400 cycles of electrochemical testing was subjected to scanning electron microscopy, focused ion beam (FIB), and transmission electron microscopy tests; the electrolyte and metallic lithium in the two batteries after cycling were subjected to inductively coupled plasma (ICP) testing; to study the structural stability of the positive electrode material after cycling.

[0064] As shown in a and b in Figure 5, after 400 cycles of the battery using bare NCM811, the surface of the positive electrode material is covered with by-products, and obvious cracks appear inside the material; as shown in c and d in Figure 5, after 400 cycles of the battery assembled with NCM811 ternary material (GM@NCM811) uniformly coated with crack-free glassy metal-organic framework material, the surface of the GM@NCM811 positive electrode material is relatively smooth, with almost no by-products, and no cracks appear inside the material; as shown in e and f in Figure 5, a thicker positive electrode electrolyte interface film (CEI film) is generated on the surface of the bare NCM811 material after cycling, and the material changes from the original layered structure to a structure where layered and rock salt phases coexist. The original layered structure of the surface material is transformed into a structure where solvated lithium ions are embedded and deintercalated. As shown in Figure 5g and h, the surface of the NCM811 ternary material (GM@NCM811) uniformly coated with crack-free glassy metal-organic framework material after cycling still retains the original glass layer, and the original layered structure of the material is still well maintained during the lithium ion insertion and extraction process, verifying that the metal-organic framework glass material can effectively inhibit the phase change of the material and improve the structural stability of the material; as shown in Figure 5i, the ICP test results of the electrolyte and metallic lithium in the two batteries after cycling show that after coating with crack-free glassy metal-organic framework material, the transition metal dissolution of the battery is significantly inhibited, further verifying the important role of metal-organic framework glass material in improving the structural stability of the material.

[0065] Example 6

[0066] The bare NCM811 ternary material prepared in Example 2 and the NCM811 ternary material uniformly coated with a crack-free glassy metal organic framework material (GM@NCM811) were assembled with lithium metal into a button cell. Specifically, R2032 button cells were used, and the negative electrode shell, spring sheet, gasket, lithium metal, PP separator, bare NCM811 / GM@NCM811 positive electrode material (positive electrode loading of 7.3 mg / cm 2 ), positive electrode shell, add 1 mol per liter LiPF6-EC:DMC electrolyte for battery packaging. The packaged battery was left to stand for 16 hours, and the above assembled battery was electrochemically tested using a blue battery test system; the bare NCM811 ternary material and the crack-free glassy metal organic framework material obtained in Example 2 were uniformly coated with the NCM811 ternary material (GM@NCM811) and limited metallic lithium to form a soft pack battery, specifically: using aluminum-plastic film as the outer packaging, in accordance with lithium metal (N / P ratio of 4), PP diaphragm, GM@NCM811 positive electrode sheet (positive electrode loading of 27.1 mg / cm 2) in the order of 1 mol / L LiPF6-EC:DMC, with a total of five layers stacked. The battery was then packaged by adding an appropriate amount of 1 mol / L LiPF6-EC:DMC electrolyte. The packaged batteries were left to rest for 16 hours. Electrochemical testing of the assembled batteries was then performed using a BlueDian battery testing system to evaluate the battery's electrochemical cycling stability and energy density.

[0067] As shown in Figure 7a, the capacity of the lithium metal button cell based on the bare NCM811 cathode material decays rapidly at a current density of 1C, and after only 400 cycles, the capacity drops to less than 40mAh / g; while the battery based on the NCM811 ternary material uniformly coated with a crack-free glassy metal organic framework material (GM@NCM811) has excellent cycling performance at a current density of 1C, and even after 1000 cycles, it still has a capacity of more than 160mAh / g, with a capacity retention rate of more than 80%. As shown in Figure 7b, the soft-pack battery exhibits high capacity and coulombic efficiency and excellent cycling stability under the conditions of limited lithium and high-load cathode: it can output an energy density of about 380Wh / kg, and the battery can still maintain a capacity retention rate of more than 80% after 300 cycles.

[0068] Example 7

[0069] The NCM811 ternary material (Cu-GM@NCM811) uniformly coated with the crack-free glassy metal organic framework material prepared in Example 4 was assembled into a button cell with lithium metal. Specifically, R2032 button cells were used, and the cathode material (positive electrode loading of 7.1 mg / cm2) was prepared according to the following steps: 2 ), and the positive electrode shell, 1 mol / L LiPF6-EC:DMC electrolyte was added to package the battery. The packaged battery was left to stand for 16 hours, and the assembled battery was electrochemically tested using a BlueDian battery testing system.

[0070] As shown in Figure 6, the lithium metal battery based on the NCM811 ternary material (Cu-GM@NCM811) uniformly coated with crack-free glassy metal-organic framework material exhibits excellent cycling performance at a current density of 1C, maintaining a capacity of more than 160 mAh / g even after 400 cycles, with a capacity retention rate exceeding 80%. This result is significantly better than the electrochemical results of the button cell based on the bare NCM811 cathode material shown in Figure 7a of Example 6, further verifying the important role of metal-organic framework glass materials in improving the structural stability of the material.

Claims

1. A glassy metal-organic framework modified ternary cathode material, characterized by: It consists of a ternary positive electrode material and a glassy metal organic framework material coating layer on its surface.

2. The glassy metal-organic framework modified ternary cathode material according to claim 1, characterized in that: The glassy metal organic framework material coating layer has a thickness of 5 to 300 nm and has no cracks on the surface.

3. A glassy metal organic framework modified ternary cathode material according to claim 1 or 2, characterized in that: The glassy metal organic framework material coating layer comprises nanopores; the pore window size of the nanopores is 0.1 nm to 3 nm.

4. A glassy metal organic framework modified ternary cathode material according to claim 1 or 2, characterized in that: The mass proportion of the glassy metal organic framework material coating layer is 0.5 to 30 wt %.

5. A glassy metal organic framework modified ternary cathode material according to claim 1 or 2, characterized in that: The glassy metal organic framework material coating layer is composed of at least one of the following metal organic framework materials: Zn-dmbIm, ZIF-8, ZIF-62, ZIF-8, ZIF-4, [Zn(HPO4)(H2PO4)2](H2Im)2, Zn(Im)2, Zn2(-DOBDC)(Zn-MOF-74), Zn4O(BDC)3(MOF-5), Zn4O(BTB)2 / MOF-177, Zn(tbip), Zn2(bptc), Zn4O(H2O)3(adc)3(PCN-13), Zn2(cnc)2(dpt), Zn2(cnc)2(dpt), Zn3(OH)(p-cdc) 2.5 、Zn3(OH)(p-cdc) 2.5 (DMF)3, Zn(dtp), Zn(bIM)(nIM)(ZIF-68), Zn4O(btb)2(MOF-177), Zn2(ndc)2(dpni), [Zn(bdc)(4,40-bipy) 0.5 ](MOF-508), Zn(cbIM)(nIM)(ZIF-69), Zn(bdc)(ted) 0.5 ,Zn(BDC),Zn4O(BDC)3,Zn(TPTC),Zn 20 (cbIM) 39 (OH)(ZIF-100), Zn(cbIM)2(ZIF-95), Zn(NDI-X), ZIF-22, ZIF-67, ZIF-62, ZIF-4, Cu-P-dmbIm, Cu3(BTC)2(HKUST-1), Cu(BDC), Cu2(pzdc)2(pyz), Cu(hfipbb)(H2hfipbb) 0.5 ,Cu(bdt),[Cu(pzdc)2(pyz)],Cu2(bdc) 2x H2O, [Cu2(ndc)2(dabco)], Cu2(D-cam)2P), Cu(F-pymo)2Zn(IM) 1.13 (nIM) 0.87 (ZIF-70), Cu(gla)(4,40-bipy) 0.5 , Cd-PdmbIm, Cd(H2PO4)2(HTr)2, Mn-P-dmbIm, CrIII3O(H2O)2F(ntc) 1.5 (MIL-102), MIL-101(Cr), Al-MIL-53, Al(OH)(BDC), MIL-96(Al), Al 12 O(OH) 18 (H2O)3[Al2(OH)4](btc)6, [Fe3(im)6(Him)2], Fe(py)2[Pt(CN)4], MIL-89, Fe-MIL-88B-NH2, where: btc is 1,3,5-benzoic acid, ndc is dimethyl 2,6-naphthalene dicarboxylate, pda is 1,4-phenylenedicarboxylic acid, pzdc is 2,3-pyrazine dicarboxylic acid, pyz is pyrazine, H2hfipbb is 2,2-bis(4-carboxyphenyl)hexafluoropropane, ntc is 1,4,5,8-naphthalenetetracarboxylic anhydride, tpic is 5-tert-butyl-1,3-benzenedicarboxylic acid, bdt is 1,4-phenyldithiol, bptc is 6,6'-dimethyl-2,2'-bipyridine, adc is 9,10-anthracene dicarboxylic acid, apt is 4-aminophenyl tetrazolate, pyta 2 ,4,6-pyridinetricarboxylate, bdc is terephthalic acid, ted is triethylenediamine, btb is 1,3,5-phenyltrimethylbenzene, 2,4-pdc is pyridine-2,4-dicarboxylate, dtp is 2,3-pyrazine-tetrazolate, F-pymo is 2-hydroxy-5-fluoropyrimidine, IM is imidazolate, nIM is 2-nitroimidazolate, cbIM is 5-chlorobenzeneimidazolate, pyenH 2 is 5-methyl-4-pyridone-3-carboxamide, 4,4'-bipy is 4'-methyl-2,2'-bipyridine-4-carboxylic acid, GLA is glutarate, CNC is 4-cinnamic acid, DPT is 3,6-di-4-pyridyl-1,2,4,5-tetrazine, TATB is 2,4,6-trimercapto-s-triazine, DMF is dimethylformamide, and DPNI is bis(4-pyridyl)naphthalene diimide.

6. A glassy metal organic framework modified ternary cathode material according to claim 1 or 2, characterized in that: The ternary positive electrode material is at least one of NCM955, NCM811, NCM622, NCM532, NCM333, and NCA.

7. The method for preparing a glassy metal organic framework modified ternary cathode material according to any one of claims 1 to 6, characterized in that: The ternary cathode material and the metal organic framework material are ground and mixed, and then placed in a protective atmosphere for melt quenching treatment to obtain the product.

8. The method for preparing a glassy metal organic framework modified ternary cathode material according to claim 7, characterized in that: The grinding and mixing time is 15 to 30 minutes.

9. The method for preparing a glassy metal organic framework modified ternary cathode material according to claim 7, characterized in that: The melt quenching treatment conditions are: temperature of 120-350° C. and time of 20-60 min.

10. Use of a glassy metal organic framework material modified ternary cathode material according to any one of claims 1 to 6, characterized in that: Used as positive electrode material for lithium metal or lithium ion batteries.

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