Metal-organic framework based solid-state electrolytes and methods of making and using the same

Abstract

The application discloses a metal organic framework reference solid-state electrolyte and a preparation method and application thereof, the electrolyte takes a commercial diaphragm as a base, takes a metal organic framework as a carrier, and has metal nanoparticles deposited on the base; wherein the metal nanoparticles provide nucleation sites for the metal organic framework on the base; the thickness of the metal organic framework layer of the electrolyte is 0.2-30 microns, and the mass of the electrolyte is 0.2-30 mg / cm 2 The application has the following advantages: (1) the electrolyte can construct a high specific energy lithium metal battery; (2) the electrolyte has excellent mechanical stability, and can still maintain structural stability even after experiencing hundreds of electrochemical cycles; (3) the electrolyte has good compatibility with lithium metal, and can significantly improve the cycle life of the lithium metal battery; and (4) a soft package battery of LiNi 0.8 Co 0.15 Al 0.05 O2 / / Li (NCA / / Li, 3-35 mg cm ‑2 NCA loading) has an energy density of 200-450 Wh / kg and stable electrochemical performance (50-1000 cycle life, 60-95% capacity retention rate).

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of electrochemistry, and relates to a material capable of being used in a high-voltage lithium metal battery to realize a high-energy-density lithium metal battery, in particular to a metal-organic framework-based reference solid-state electrolyte and a preparation method and application thereof. BACKGROUND

[0002] The growing demand for electric portable devices and electric vehicles (EVs) makes it necessary to develop electrochemical energy conversion and storage devices capable of providing higher energy density. Pairing lithium metal with various high-voltage cathode materials and assembling them into high-voltage lithium metal batteries (LMBs) is considered to be a promising strategy for constructing high-energy-density electrochemical energy conversion and storage devices. However, the development of next-generation high-energy-density LMBs is severely limited by the inherent defects of the current electrolyte system. For example, high-voltage lithium metal batteries assembled with conventional liquid electrolytes usually suffer from severe electrolyte decomposition problems due to the high reactivity between the liquid electrolyte and the surface of the charged transition metal oxide, which ultimately reduces the performance of the battery. In addition, the severe interaction between the electrolyte solvent molecules and the lithium metal and the transition metal ions shuttling from the positive electrode exacerbate the failure of the lithium metal negative electrode, while accelerating the uncontrollable growth of dendritic lithium, greatly reducing the service life of the battery. Worse still, conventional high-voltage lithium metal batteries often use a large dose of liquid electrolyte during assembly, which greatly reduces the energy density of the high-voltage lithium metal battery. Therefore, in order to further promote the development of lithium metal batteries, the above problems need to be reasonably solved. SUMMARY

[0003] Technical problem solved: In order to improve the energy density of the lithium metal battery, the present application takes a crack-free ultrathin metal-organic framework flexible porous metal-organic skeleton (MOF) film as a carrier, which has a thickness of only 8.2-38 μm (of which the MOF layer is only 0.2-30 μm) and a mass of only 0.2-30 mg / cm 2 (absorbing trace amounts of organic electrolyte in the channel). At the same time, the crack-free ultrathin metal-organic framework reference solid-state electrolyte has excellent mechanical and thermal stability, and can still maintain structural stability even after experiencing hundreds of electrochemical cycles. The soft-packaged battery assembled with the crack-free ultrathin metal-organic framework reference solid-state electrolyte has an energy density of 200-450 Wh / kg and stable electrochemical performance (50-1000 cycles of cycle life). 0.8 Co 0.15 Al 0.05 O2 / / Li(NCA / / Li, 3-35 mg cm -2 NCA loading). In view of this, the present application provides a metal-organic framework-based reference solid-state electrolyte and a preparation method and application thereof.

[0004] Technical solution: metal organic framework reference solid electrolyte, the electrolyte takes commercial separator as a base, takes metal organic framework as a carrier, and deposits metal nanoparticles on the base; wherein, the metal nanoparticles provide nucleation sites for the metal organic framework on the base; the thickness of the metal organic framework layer of the electrolyte is 0.2-30 μm or less, and the mass of the electrolyte is 0.2-30 mg / cm 2 .

[0005] Preferably, the metal nanoparticles are at least one of Fe, Ag, Au, Ti, Ni, Co, Ru, Rh, Pd, Zn, Cr, Pt.

[0006] Preferably, the metal organic framework is at least one of Cu3(BTC)2(HKUST-1) with copper as a metal center ion, 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 ; ZIF-7 with zinc as a metal center ion, Zn3(BTC)2, Zn(tbip), Zn2(bptc), Zn4O(H2O)3(adc)3(PCN-13), Zn2(cnc)2(dpt)Guest, 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-8, ZIF-22 with cobalt as the metal center ion, Co3(u3-OH)2(2,4-pdc)2(CUK-1Mn(ndc); CrIII3O(H2O)2F(ntc) with chromium as the metal center ion 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; Fe(py)2[Pt(CN)4], MIL-89, Fe-MIL-88B-NH2 with iron as the metal center ion. Wherein: btc is 1,3,5-benzoic acid, ndc is 2,6-naphthalene dimethyl dicarboxylate, pda is 1,4-benzenedicarboxylic 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-naphthalene tetraformic anhydride, tpic is 5-tert-butyl-1,3-benzenedicarboxylic acid, bdt is 1,4-benzene dithiol, bptc is 6,6'-dimethyl-2,2'-bipyridine, adc is 9,10-anthracene dicarboxylic acid, apt is 4-aminophenyl tetrazolylate, pyta is 2,4,6-pyridine tricarboxylic acid, bdc is terephthalic acid, ted is triethylene diamine, btb is 1,3,5-benzenetriamine, 2,4-pdc is pyridine-2,4-dicarboxylate, dtp is 2,3-pyrazine-tetrazolylate, F-pymo is 2-hydroxy-5-fluoropyrimidine, IM is imidazole acid salt, nIM is 2-nitroimidazole acid salt, cbIM is 5-chlorobenzimidazole acid salt, pyenH2 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-trithiol triazine, DMF is dimethyl formamide, dpni is bis(4-pyridyl) naphthalene diimide.

[0007] The preparation method of any one of the above metal organic framework reference solid state electrolytes, the method comprising the following steps:

[0008] Step 1, depositing metal nanoparticles on the surface of a commercial separator

[0009] Metal nanoparticles with high conductivity are deposited on the surface of a commercial separator by sputtering technology, providing nucleation sites for the subsequent in-situ electrochemical synthesis of metal organic framework materials.

[0010] For example, the Pt metal nanoparticles, the specific preparation method is as follows:

[0011] Preparation of the PP separator with Pt metal nanoparticles deposited on the surface: first, the commercialized separator with the size of 4*5 cm 2 was cleaned with alcohol, and then was placed in a vacuum Pt metal deposition instrument to be vacuumized. When the vacuum degree was enough, the Pt spraying current was adjusted to 25 μA, and the deposition time was set to 145 seconds, so that the PP separator with Pt metal nanoparticles deposited on the surface was obtained.

[0012] Step 2, preparation of the mother liquor for in-situ electrochemical synthesis of metal organic framework materials

[0013] The metal salt was dissolved in the organic solvent A with the concentration of 0.05-5 mol / L, the organic ligand was dissolved in the organic solvent B with the concentration of 0.05-5 mol / L, and then the two solutions were mixed and ultrasonicated, so that the mother liquor for in-situ electrochemical synthesis of metal organic framework materials was obtained.

[0014] For example, the ZIF-8 MOF was synthesized, and the specific preparation steps of the mother liquor for metal organic framework materials were as follows:

[0015] 0.55 g of zinc acetate was dissolved in 25 mL of methanol solvent, and 0.41 g of 2-methylimidazole was dissolved in 25 mL of methanol solvent. Then, the two were mixed and ultrasonicated, so that the mother liquor for in-situ electrochemical synthesis of ZIF-8 metal organic framework materials was obtained.

[0016] Step 3, in-situ electrochemical synthesis of metal organic framework

[0017] The separator treated in step 1 was used as the negative electrode of the electrochemical workstation, and the graphite electrode was used as the positive electrode, and then the two electrodes were inserted into the mother liquor prepared in step 2, and then a current of 0.1-1.5 mA / cm 2 was applied for 0-4 hours, so that the ultrathin metal organic framework material uniformly grown on the commercialized separator without cracks was obtained, and finally was placed in a blast drying oven to be dried at 40-80 °C for 2-36 hours to remove the organic solvent and moisture introduced in the synthesis process.

[0018] For example, the Pt metal nanoparticles and ZIF-8 MOF were deposited: the PP separator with Pt metal nanoparticles deposited on the surface prepared in step 1 was pasted on the conductive aluminum tape ring (the outer diameter was 18 mm, and the inner diameter was 14 mm), and then was connected to the negative electrode of the electrochemical workstation as the electrode, and the graphite electrode was connected to the positive electrode of the electrochemical workstation. The two electrodes obtained above were inserted into the mother liquor for in-situ electrochemical synthesis of ZIF-8 metal organic framework materials prepared in step 2, and then a current of 0.7 mA / cm 2The current is controlled to be 0.1 mA / cm2, and the uniform crack-free ultra-thin ZIF-8 metal organic framework material grown on the PP separator is obtained. Finally, the material is placed in a blast drying oven at 80°C for 12 hours to remove the methanol solvent and moisture introduced during the synthesis process.

[0019] Step 4, preparation of the crack-free ultra-thin metal organic framework reference solid-state electrolyte

[0020] The material obtained in Step 3 is attached to the surface of one lithium metal, and the other surface is added with liquid organic electrolyte and then attached to the surface of another lithium metal to form a lithium / / lithium symmetric battery. After 10 cycles of charging and discharging, the crack-free ultra-thin metal organic framework material uniformly grown on the commercial separator is taken out from between the two lithium metals to obtain a crack-free ultra-thin metal organic framework reference solid-state electrolyte containing a small amount of electrolyte.

[0021] Taking the deposition of Pt metal nanoparticles and ZIF-8 MOF as an example: one side of the crack-free ultra-thin ZIF-8 metal organic framework material uniformly grown on the PP separator obtained in Step 3 is attached to the surface of one lithium metal, and the other surface is added with 10 μL of liquid organic electrolyte (for example, LiPF6-EC / DMC electrolyte) and then attached to the surface of another lithium metal to form a lithium / / lithium symmetric battery. After 10 cycles of lithium deposition / stripping at a current density of 1 mA / cm2, each cycle lasting 1 hour, the crack-free ultra-thin ZIF-8 metal organic framework material uniformly grown on the PP separator is taken out from between the two lithium metals to obtain a crack-free ultra-thin ZIF-8 metal organic framework reference solid-state electrolyte containing only a small amount of electrolyte. Subsequently, the obtained crack-free ultra-thin metal organic framework reference solid-state electrolyte is combined with different electrodes to form various lithium metal batteries. 2 The current is controlled to be 0.1 mA / cm2, and the uniform crack-free ultra-thin ZIF-8 metal organic framework material grown on the PP separator is obtained. Finally, the material is placed in a blast drying oven at 80°C for 12 hours to remove the methanol solvent and moisture introduced during the synthesis process.

[0022] Preferably, in Step 2, the organic solvent A is at least one of methanol, ethanol, and acetone; and the organic solvent B is at least one of dimethylformamide, N-methylpyrrolidone, methanol, and acetone.

[0023] Preferably, in Step 4, the organic electrolyte is at least one of ester or ether, specifically: 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, LiTFSI-DOL:DME.

[0024] Use of any of the above described metal organic framework based solid state electrolytes in the preparation of high voltage lithium metal batteries.

[0025] Preferably, the metal organic framework based solid state electrolyte is placed between a high voltage cathode and a metal lithium anode.

[0026] Preferably, the high voltage cathode is LNMO (LiNi 0.5 Mn 1.5 O4), nickel cobalt manganese ternary material 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 (LiNi 0.3 Co 0.3 Mn 0.3 O2), nickel cobalt aluminum ternary material NCA (LiNi 0.8 Co 0.15 Al 0.05 O2), Li2MnO4, LiCoMnO4 (LCMO), LNMO, NCM811, NCM622, NCM532, NCM333, NCA, Li2MnO4, LiCoO2, LiNiO2, LiFePO4, S, Li2O2 / LiO2.

[0027] Preferably, the quasi-solid state electrolyte assembled high voltage LiNi 0.8 Co 0.15 Al 0.05 O2 / / Li (NCA / / Li, 3-35 mg cm - 2 The pouch cell has an energy density of 200-450 Wh / kg and stable electrochemical performance (50-1000 cycle life).

[0028] The working principle of the quasi-solid electrolyte of the present application is that: after in-situ electrochemical growth of crack-free ultrathin metal organic framework material on the surface of a commercialized separator, reassembling into a battery and after several cycles of electrochemical cycling, a crack-free ultrathin metal organic framework material-based quasi-solid electrolyte adsorbing trace functional electrolyte in the pores is obtained. The quasi-solid electrolyte takes a crack-free ultrathin metal organic framework flexible porous metal organic framework (MOF) film as a carrier, the thickness of which is only 8.2-38 μm (of which the MOF layer is only 0.2-30 μm), and the mass is only 0.2-30 mg / cm 2 (absorbing trace organic electrolyte in the pores). In addition, compared with the traditional electrolyte, the electrolyte adsorbed in the pores of the MOF has a more aggregated electrolyte configuration. Benefiting from the more aggregated electrolyte configuration, the solvent molecules, lithium ions and anions in the electrolyte in the pores of the MOF are combined more closely, so that it is more difficult for the oxidation and decomposition of the solvent molecules to occur during the electrochemical cycling, making the electrolyte in the pores more stable. At the same time, the crack-free ultrathin metal organic framework reference solid electrolyte has excellent mechanical stability and thermal stability, and can still maintain structural stability even after experiencing several hundred cycles of electrochemical cycling.

[0029] Beneficial effects: (1) the crack-free ultrathin metal organic framework reference solid electrolyte has a thickness of only 8.2-30 μm, and a light mass of only 0.2-30 mg / cm 2 , which is crucial for building high specific energy lithium metal batteries; (2) the crack-free ultrathin metal organic framework reference solid electrolyte has excellent mechanical stability, and can still maintain structural stability even after experiencing several hundred cycles of electrochemical cycling, which is a key to realizing long-life lithium metal batteries; (3) the crack-free ultrathin metal organic framework reference solid electrolyte has good compatibility with lithium metal, so that the cycle life of the lithium metal battery can be significantly improved, and the assembled pouch battery of LiNi 0.8 Co 0.15 Al 0.05 O2 / / Li (NCA / / Li, 3-35 mg cm -2 NCA loading) has an energy density of 200-450 Wh / kg and stable electrochemical performance (50-1000 cycles of cycle life). BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 a is a flow chart for preparing a crack-free ultrathin metal organic framework on the surface of a 20 μm commercialized PP separator, Figure 1 b is an electron photo of a 20 μm commercialized PP separator and a scanning electron microscope image magnified by 100,000 times; Figure 1 c is an electron photo of a 20 μm commercialized PP separator with Pt particles deposited on the surface and a scanning electron microscope image magnified by 100,000 times; Figure 1d is the electron photo and the scanning electron microscope graph of 100,000 times magnification of the surface of the 20 μm commercial PP separator prepared with the crack-free ultrathin metal organic framework;

[0031] Figure 1 e is the electron photo and the optical electron microscope graph of the surface of the 20 μm commercial PP separator prepared with the crack-free ultrathin metal organic framework after bending, once folding and twice folding;

[0032] Figure 2 a is the X-ray diffraction graph of the surface of the 8 μm commercial PP separator prepared with the crack-free ultrathin metal organic framework; Figure 2 b is the cross-sectional scanning electron microscope graph of 100,000 times magnification of the surface of the 8 μm commercial PP separator prepared with the crack-free ultrathin metal organic framework; Figure 2 c is the thickness and mass comparison graph of the surface of the 8 μm commercial PP separator prepared with the crack-free ultrathin metal organic framework and the 8 μm commercial PP separator and the 8 μm commercial PP separator with the surface deposited Pt particles, Figure 2 d is the thermal stability graph of the surface of the 8 μm commercial PP separator prepared with the crack-free ultrathin metal organic framework and the 8 μm commercial PP separator at 120°C;

[0033] Figure 3 a is the lithium-lithium symmetric battery electrochemical curve graph of the lithium / / lithium symmetric battery assembled with the metal lithium negative electrode and the quasi-solid-state electrolyte based on the crack-free ultrathin metal organic framework material according to the application (with 1 mol / L lithium hexafluorophosphate ethylene carbonate / dimethyl carbonate electrolyte as the reference electrolyte); Figure 3 b is the lithium electrochemical cycle curve graph of the battery assembled with the 8 μm commercial PP separator, the metal lithium negative electrode and the quasi-solid-state electrolyte based on the crack-free ultrathin metal organic framework material according to the application and the NCA (LiNi 0.8 Co 0.15 Al 0.05 O2) positive electrode; Figure 3 c is the scanning electron microscope graph of the lithium metal electrode after cycling with the quasi-solid-state electrolyte based on the crack-free ultrathin metal organic framework material according to the application under 20,000 times magnification, Figure 3 d is the scanning electron microscope graph of the lithium metal electrode after cycling with the quasi-solid-state electrolyte based on the crack-free ultrathin metal organic framework material according to the application under 100,000 times magnification;

[0034] Figure 4 a is the X-ray diffraction graph of the quasi-solid-state electrolyte based on the crack-free ultrathin metal organic framework material according to the application before and after cycling; Figure 4b is the scanning electron microscope image of the post-cycling crack-free ultrathin metal-organic framework material based quasi-solid-state electrolyte under 200,000 times magnification; Figure 4 c is the lithium polysulfide penetration experiment image of the post-cycling crack-free ultrathin metal-organic framework material based quasi-solid-state electrolyte;

[0035] Figure 5 a is a structural schematic diagram of a soft pack battery assembled by using the crack-free ultrathin metal-organic framework material based quasi-solid-state electrolyte, a metal lithium negative electrode and an NCA positive electrode; Figure 5 b is an electrochemical charge-discharge curve diagram of a soft pack battery assembled by using the crack-free ultrathin metal-organic framework material based quasi-solid-state electrolyte, a metal lithium negative electrode and an NCA positive electrode under a loading condition of 25 mg / cm 2 ; Figure 5 c is an electrochemical cycle curve diagram and an electronic photograph diagram of a soft pack battery assembled by using the crack-free ultrathin metal-organic framework material based quasi-solid-state electrolyte, a metal lithium negative electrode and an NCA positive electrode under a loading condition of 25 mg / cm 2 ; DETAILED DESCRIPTION

[0036] The following examples further illustrate the present application, but should not be construed as limiting the application. Modifications and substitutions can be made to the methods, steps or conditions of the present application without departing from the spirit and scope of the application. If not specifically mentioned, the technical means used in the examples are conventional means known to those skilled in the art.

[0037] Example 1

[0038] The sputtering technology is used to deposit metal nanoparticles with high conductivity on the surface of commercial PP separator, which provides nucleation sites for subsequent in-situ electrochemical synthesis of metal-organic framework materials. Secondly, the size of the PP separator is 4x 5 cm 2commercialized separator was cleaned with alcohol and then put into a vacuum Pt metal deposition instrument to be vacuumized. When the vacuum degree was enough, the Pt spraying current was adjusted to 25 μA, and the deposition time was set to 145 seconds to obtain a PP separator with Pt metal nanoparticles deposited on the surface (since the deposition of metal particles on the surface of the non-conductive separator is only to provide nucleation sites for the subsequent in-situ electrochemical growth of metal organic framework materials (MOF) on the PP separator, therefore, other conductive metal particles such as Fe, Ag, Au, Ti, Ni, Co, Ru, Rh, Pd, Zn, Cr, etc. can be used to deposit on the PP separator to grow a crack-free ultrathin metal organic framework material uniformly); 0.55 g of zinc acetate was dissolved in 25 mL of methanol solvent, and 0.41 g of 2-methyl imidazole was dissolved in 25 mL of methanol solvent. Then the two were mixed and ultrasonicated to obtain a mother liquor for in-situ electro-synthesized ZIF-8 metal organic framework material; the prepared PP separator with Pt metal nanoparticles deposited on the surface was pasted on a conductive aluminum tape ring (outer diameter 18 mm, inner diameter 14 mm), and then it was connected as an electrode to the negative electrode of an electrochemical workstation, while a graphite electrode was connected as a positive electrode to the electrochemical workstation. The above two electrodes were inserted into the mother liquor for in-situ electro-synthesized ZIF-8 metal organic framework material prepared in the second step, and then a current of 0.7 mA / cm 2 2 was applied for 1 hour, to obtain a crack-free ultrathin ZIF-8 metal organic framework material grown uniformly on the PP separator (usually, metal organic framework materials can be obtained only in the corresponding metal salt solution and organic ligand solution, and the additional current only induces the directional movement of metal salt ions to the conductive PP separator with deposited metal particles, and does not affect the in-situ growth of MOF material on the separator. Therefore, this method can in principle be used to grow different MOF (such as each metal organic framework material in the technical solution) materials in-situ electrochemically on the PP surface.); finally, it was placed in a blast drying oven at 80°C for 12 hours to remove the methanol solvent and moisture introduced during the synthesis process; one side of the obtained crack-free ultrathin ZIF-8 metal organic framework material grown uniformly on the PP separator was pasted on the surface of a lithium metal, and after 10 μL of liquid organic electrolyte (for example, LiPF6-EC / DMC electrolyte) was added to the other side of the surface, it was pasted on the surface of another lithium metal to assemble a lithium / / lithium symmetric battery. In 1 mA / cm 2Current density, after 10 times of lithium deposition / delamination under the condition of 1 hour per deposition / delamination, the crack-free ultrathin ZIF-8 metal organic framework material is uniformly grown on the PP separator and taken out from the middle of the two lithium metals, obtaining the crack-free ultrathin ZIF-8 metal organic framework-based benchmark solid-state electrolyte containing only a small amount of electrolyte (the remaining organic electrolyte (such as various organic ester and ether electrolytes as claimed in the technical solution) has similar electrolyte composition and similar solvated lithium ion size to LiPF6-EC / DMC electrolyte, so in principle, under the dual action of external voltage and the narrow pores of the metal organic framework material, it is used to prepare the crack-free ultrathin ZIF-8 metal organic framework-based benchmark solid-state electrolyte containing a small amount of electrolyte). Then, the obtained crack-free ultrathin metal organic framework-based benchmark solid-state electrolyte and different electrodes are combined to assemble various lithium metal batteries.

[0039] As shown in Figure 1 a, the 20 μm commercialized PP separator is interwoven by a large number of micron-sized fibers, and the staggered fibers form a loose and porous micro-nano structure. As shown in Figure 1 b, the surface of the 20 μm commercialized PP separator deposited with Pt metal nanoparticles is covered with Pt metal nanoparticles. As shown in Figure 1 c, after in-situ electro-synthesis of ZIF-8 metal organic framework material, the surface of the 20 μm commercialized PP separator is covered with a layer of crack-free, closely packed ZIF-8 metal organic framework, and the ZIF-8 particles are all about 0.5-1 μm in size.

[0040] Example 2

[0041] The difference from Example 1 is that a commercialized PP separator with a thickness of 8 μm is used.

[0042] The obtained 8 μm commercialized PP separator surface is prepared with crack-free ultrathin metal organic framework for X-ray diffraction test. As shown in Figure 2 a, the diffraction peak corresponding to the crack-free ultrathin metal organic framework grown on the surface of the 8 μm commercialized PP separator shows its excellent crystallinity. As shown in Figure 2 b, the thickness of the crack-free ultrathin metal organic framework grown on the surface of the 8 μm commercialized PP separator is only about 1 μm. As shown in Figure 2 c, the thickness of the crack-free ultrathin metal organic framework prepared on the surface of the 8 μm commercialized PP separator is only 9 μm, and the mass is only 0.816 mg / cm 2The obtained 8 pm commercialized PP separator surface-prepared crack-free ultrathin metal-organic framework was placed on a hot plate at 120 °C for thermal stability test. The results showed that the 8 pm commercialized PP separator surface-prepared crack-free ultrathin metal-organic framework could withstand high temperature of 120 °C, while the 8 pm commercialized PP separator could not withstand high temperature of 120 °C and was quickly pyrolyzed to cause serious structure shrinkage.

[0043] Example 3

[0044] The 8 pm commercialized PP separator surface-prepared crack-free ultrathin metal-organic framework based quasi-solid-state electrolyte prepared in Example 2 was assembled into lithium / / lithium symmetric cells and NCA / / Li cells with metal lithium, specifically as follows:

[0045] The metal lithium was mechanically pressed on a stainless steel sheet to obtain a lithium metal electrode. The obtained 8 pm commercialized PP separator surface-prepared crack-free ultrathin metal-organic framework based quasi-solid-state electrolyte was placed between two lithium metal electrodes. In an argon atmosphere glove box, R2032 button cells were used to package the cells in the order of negative electrode shell, spring sheet, gasket, positive electrode sheet, and positive electrode shell. The ethylene carbonate / dimethyl carbonate electrolyte with 1 mole per liter of lithium hexafluorophosphate (1 M LiPF6-EC / DMC electrolyte) was used as the reference electrolyte. The packaged cells were left to stand for 24 hours, and the above assembled cells were subjected to electrochemical test using Beidou battery test system. During the test, the cells were first charged at a current density of 2 mA / cm2for 1 hour. 2

[0046] ​NCA high-voltage cathode material and conductive agent, binder were mechanically ground and mixed uniformly according to the mass ratio of 8:1:1, and then a proper amount of N-methyl pyrrolidone was added. After stirring uniformly, the mixture was coated on an aluminum foil current collector. The electrode was dried in a vacuum condition to obtain a lithium ion high-voltage cathode NCA. The obtained electrode was sheeted using a tablet press to obtain the desired electrode sheet. Metallic lithium was mechanically pressed on a stainless steel sheet to obtain a lithium metal anode. In an argon atmosphere glove box, the above-mentioned 8 μm commercial PP separator surface prepared crack-free ultra-thin metal organic framework quasi-solid electrolyte obtained in Example 2 was placed between the NCA high-voltage cathode and the lithium metal anode, and was packaged into an R2032 button cell according to the order of anode shell, spring sheet, gasket, metallic lithium / / porous material self-supporting film based quasi-solid electrolyte / / NCM811, anode shell. For the ordinary comparative sample battery, an R2032 button cell was used, and the battery was packaged according to the order of anode shell, spring sheet, gasket, Celgard separator, anode sheet, and anode shell. The electrolyte used for the comparative group battery test was 1 mol per liter lithium hexafluorophosphate ethylene carbonate / dimethyl carbonate electrolyte (1M LiPF6-EC / DMC electrolyte). The packaged battery was allowed to stand for 24 hours, and the above-mentioned assembled battery was subjected to electrochemical testing using a Beidou battery test system. The lithium metal anode after electrochemical testing was subjected to scanning electron microscopy to observe the dendrite formation on the lithium metal surface.

[0047] As shown in Figure 3 a, the lithium / / lithium symmetric battery using the 8 μm commercial PP separator surface prepared crack-free ultra-thin metal organic framework quasi-solid electrolyte showed excellent electrochemical performance, not only had a cycle life close to 1000 hours, but also had a stable voltage curve and voltage polarization. As shown in Figure 3 b, using NCA electrode as the anode, under the condition of 1C current density and 600 cycles, the battery using the 8 μm commercial PP separator surface prepared crack-free ultra-thin metal organic framework quasi-solid electrolyte according to the present application had higher capacity and coulombic efficiency and better cycle stability than the battery using 8 μm commercial PP separator and 1 mol per liter lithium hexafluorophosphate ethylene carbonate / dimethyl carbonate electrolyte (1M LiPF6-EC / DMC electrolyte). Figure 3 c and 3d, the lithium anode surface after cycling using the 8 μm commercial PP separator surface prepared crack-free ultra-thin metal organic framework quasi-solid electrolyte had no lithium dendrite formation.

[0048] The 8 μm commercial PP separator surface prepared crack-free ultra-thin metal organic framework quasi-solid electrolyte after cycling in Example 3 was subjected to X-ray diffraction, scanning electron microscopy, and lithium polysulfide penetration experiment of the 8 μm commercial PP separator surface prepared crack-free ultra-thin metal organic framework quasi-solid electrolyte after cycling. As shown inFigure 4 As shown in Figure a, the crack-free ultrathin metal-organic framework quasi-solid-state electrolyte prepared on the surface of an 8μm commercial PP membrane after 600 cycles still maintains almost the same excellent crystallinity as before cycling; Figure 4 As shown in b, the crack-free ultrathin metal-organic framework quasi-solid-state electrolyte prepared on the surface of an 8μm commercial PP membrane after 600 cycles still maintains an intact crack-free structure; Figure 4 As shown in c, the crack-free ultrathin metal-organic framework quasi-solid electrolyte prepared on the surface of an 8μm commercial PP membrane after 600 cycles can effectively block the shuttle of lithium polysulfides with a size of 1.1 nanometers, further verifying the structural integrity of the quasi-solid electrolyte after cycling.

[0049] Example 4

[0050] The crack-free ultrathin metal-organic framework quasi-solid-state electrolyte prepared on the surface of an 8μm commercial PP membrane obtained in Example 2 was assembled with a high-load, high-voltage cathode material NCA and a limited lithium metal anode into a high-voltage lithium metal pouch battery, specifically:

[0051] The NCA high-voltage cathode material, conductive agent, and binder were mechanically ground and mixed evenly at a mass ratio of 8:1:1. An appropriate amount of N-methylpyrrolidone was added, and after thorough mixing, the mixture was coated onto an aluminum foil current collector. The electrode was dried under vacuum to obtain the lithium-ion high-voltage cathode NCA (25.2 mg / cm³). 2 Based on the amount of high-voltage positive electrode active material, 3.96 times the excess lithium metal was mechanically pressed onto copper foil to obtain a lithium metal negative electrode. In an argon-atmosphere glove box, the crack-free ultrathin metal-organic framework quasi-solid-state electrolyte prepared on the surface of an 8μm commercial PP membrane, obtained in Example 2, was placed between the NCA high-voltage positive electrode and the lithium metal negative electrode. Through appropriate mechanical extrusion, a sandwich structure of NCA / / crack-free ultrathin metal-organic framework quasi-solid-state electrolyte prepared on the surface of an 8μm commercial PP membrane / / lithium metal was obtained. Tabs were then attached to the positive and negative electrodes to assemble a pouch battery. The packaged battery was left to stand for 24 hours, and electrochemical tests were performed on the assembled pouch battery using a Beidou battery testing system.

[0052] like Figure 5 As shown in Figure a, the pouch cell has five layers, consisting of an NCA high-voltage positive electrode, a crack-free ultrathin metal-organic framework quasi-solid-state electrolyte prepared on the surface of an 8μm commercial PP separator, and a lithium metal negative electrode. Figure 5 As shown in b and 5c, a loading of 25.2 mg / cm³ was used. 2The NCA is a positive electrode, and under the working conditions of a charging current density of 75 mAh / g and a discharging current density of 100 mAh / g, the NCA / / Li soft package battery assembled based on the ultra-thin metal organic framework quasi-solid electrolyte prepared on the surface of the 8 μm commercial PP separator has higher capacity and coulomb efficiency and better cycle stability, and when converted into energy density, an energy density of about 354 Wh / kg can be output.

Claims

1. A metal-organic framework reference solid-state electrolyte, characterized in that, The electrolyte takes a commercial separator as a substrate, takes a metal organic framework as a carrier, and has metal nanoparticles deposited on the substrate; wherein the metal nanoparticles provide nucleation sites for the metal organic framework on the substrate; the thickness of the metal organic framework layer of the electrolyte is 0.2-30 µm, and the mass of the electrolyte is 0.2-30 mg / cm 2 ; The metal nanoparticles are at least one of Fe, Ag, Au, Ti, Ni, Co, Ru, Rh, Pd, Zn, Cr, Pt; The metal-organic framework reference solid-state electrolyte is prepared by the following method: Step 1: Depositing metal nanoparticles on the surface of a commercial separator Metal nanoparticles with high conductivity are deposited on the surface of a commercial separator by sputtering technology, providing nucleation sites for the subsequent in-situ electrochemical synthesis of metal-organic framework materials. Step 2: Preparing a mother liquor for in-situ electrochemical synthesis of metal-organic framework materials Dissolve metal salts in organic solvent A with a concentration of 0.05-5 mol / L, dissolve organic ligands in organic solvent B with a concentration of 0.05-5 mol / L, then mix the two solutions and ultrasonic them to obtain a mother liquor for in-situ electrochemical synthesis of metal-organic framework materials. Step 3: In-situ electrochemical synthesis of metal-organic framework The membrane treated in the first step is used as the negative electrode of an electrochemical workstation, a graphite electrode is used as the positive electrode, then the two electrodes are inserted into the mother liquor prepared in the second step, and then a current of 0.1-1.5 mA / cm 2 , and an application time of 0-4 hours are applied to obtain an ultrathin metal organic framework material which is uniformly grown on a commercial membrane and has no cracks, and finally the material is dried in a blast drying oven at 40-80°C for 2-36 hours to remove the organic solvent and moisture introduced in the synthesis process. Step 4: Preparing a crack-free ultra-thin metal-organic framework reference solid-state electrolyte The material prepared in Step 3 is attached to one side of a lithium metal surface, and the other side is dropped with a liquid organic electrolyte and attached to the other lithium metal surface to form a lithium / / lithium symmetric battery. After 10 charge and discharge cycles, the crack-free ultra-thin metal-organic framework material uniformly grown on the commercial separator is removed from between the two lithium metals to obtain a crack-free ultra-thin metal-organic framework reference solid-state electrolyte containing a small amount of electrolyte.

2. The MOF-based reference solid-state electrolyte of claim 1, wherein, The metal organic framework is at least one of: Cu3(BTC)2(HKUST-1) with copper as the metal center ion, 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 ; ZIF-7 with zinc as the metal center ion, Zn3(BTC)2, Zn(tbip), Zn2(bptc), Zn4O(H2O)3(adc)3(PCN-13), Zn2(cnc)2(dpt)•Guest, 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-8, ZIF-22 with cobalt as the metal center ion, Co3(u3-OH)2(2,4-pdc)2(CUK-1Mn(ndc); 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; Fe(py)2[Pt(CN)4], MIL-89, Fe-MIL-88B-NH2 with iron as the metal center ion.

3. The MOF-based reference solid-state electrolyte of claim 1, wherein, In Step 2, the organic solvent A is at least one of methanol, ethanol, and acetone; the organic solvent B is at least one of dimethylformamide, N-methylpyrrolidone, methanol, and acetone.

4. The MOF-based reference solid-state electrolyte of claim 1, wherein, In Step 4, the organic electrolyte is at least one of ester or ether, specifically: 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, LiTFSI-DOL:DME.

5. Use of the metal-organic framework reference solid-state electrolyte of any one of claims 1-4 in the preparation of a high-voltage lithium metal battery.

6. Use according to claim 5, characterized in that, The metal-organic framework reference solid-state electrolyte is placed between a high-voltage positive electrode and a lithium metal negative electrode.

7. Use according to claim 5, characterized in that, The high-voltage positive electrode is at least one of LNMO, NCM811, NCM622, NCM532, NCM333, NCA, Li2MnO4, LiCoO2, LiNiO2, LiFePO4, S, Li2O2 / LiO2.

8. Use according to claim 5, characterized in that, The energy density of the high-voltage lithium metal battery reaches 200-450 Wh / kg.

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