Multifunctional solid electrolyte and preparation method and application thereof

Abstract

The invention belongs to the technical field of batteries, and particularly relates to a multifunctional solid electrolyte as well as a preparation method and application thereof. Compared with the prior art, the preparation method provided by the invention is a low-temperature synthesis process, the high-dispersity nanoscale solid electrolyte powder can be simply and efficiently prepared, in-situ coating can be realized, the interface stability of the LATP solid electrolyte material is improved, and the high-pressure resistance and oxidative decomposition resistance are improved; the electrochemical stability window is obviously widened; the solid electrolyte with low volume density can be obtained, and the mass energy density of the battery cell is improved; in addition, the prepared solid electrolyte has continuous water absorption, when the solid electrolyte is applied to a battery cell, a B amorphous layer continuously and slowly separated out on the ceramic surface can form stable unitary extremely weak acid H3BO3 with trace H2O in the battery cell through direct contact with a positive electrode, an electrolyte and the like in the battery cell, and the effect of greatly reducing moisture in the battery cell is achieved; the side reaction is reduced; and the cycle performance is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries, and in particular relates to a multifunctional solid electrolyte and a preparation method and application thereof. Background Art

[0002] Solid-state batteries are a new type of lithium-ion battery that uses solid electrolytes. Compared with traditional liquid lithium-ion batteries, they have the advantages of high energy density, good safety, long cycle life and wide application range. They are considered to be the key condition for achieving the complete replacement of existing fuel vehicles by new energy vehicles. They have been widely researched and applied in the new energy industry and are expected to promote green and low-carbon development.

[0003] Lithium oxide NASICON type Li 1.3 Al 0.3 Ti 1.7 (PO4)3 (LATP) has the properties of high lithium ion conductivity and wide electrochemical window, becoming one of the most commercially promising solid electrolyte materials. The existing modification methods of LATP materials are mainly element doping and surface coating modification, and then the purpose of improving performance is achieved by improving ion / electronic conductivity, improving surface stability, and improving the surface state of the electrolyte. At present, conventional LATP materials can have 10 -4 mS / cm ionic conductivity and 10 -8 The electronic conductivity of S / cm can be as high as 10 after targeted modification. -3 The ionic conductivity of mS / cm is 10 - 1 Electronic conductivity in mS / cm.

[0004] Conventional existing solid electrolyte preparation processes include high-temperature solid-phase reaction and wet chemical preparation processes. In the actual battery cell application process, the crystal particle size and size distribution of the powder are usually also key factors in its performance. Whether it is in positive electrode coating or diaphragm coating, it is usually hoped that it has a nano-scale and uniform particle size to achieve the best use state. Existing solid-phase reaction technology usually prepares micron-scale powders, which are then combined with mechanical grinding to achieve nano-scale use requirements. The crushing effect is limited. Although liquid-phase synthesis technology can prepare nano-scale powders, the particle size is usually 200-500nm, and it is difficult to prepare powders less than 100nm. Even with additional mechanical sand milling process, it is still difficult to achieve the preparation of particle sizes below 200nm, and agglomeration is more serious during the preparation process, and it still needs to be mechanically ground before use. Therefore, there is an urgent need to develop an efficient nanopowder dispersion technology that meets the use requirements of existing technologies.

[0005] Chinese patent publication number CN115425214B discloses that by introducing an excess of fluxing agent B2O3 into a solid electrolyte precursor, it can reduce the synthesis temperature during the high-temperature phase formation process of the electrolyte, and at the same time coat the electrolyte surface. After sintering, it fills the ceramic pores to form a dense ceramic, which strengthens the grain boundaries and enhances the agglomeration of grains, and finally coats the surface of the positive electrode active material. However, this preparation method requires multiple wet ball milling and fine grinding processes, and requires a lot of time and special grinding equipment, which is costly. In addition, the powder agglomerates seriously after grinding. Even if it is crushed to a smaller size, the grain boundaries are difficult to open, making it difficult to achieve the effect of dispersed nanopowders.

[0006] In addition, the existing inorganic coating process for electrolyte surface requires first preparing a pure phase electrolyte at high temperature, and then undergoing multiple steps such as coating-calcination-crushing to achieve the coating modification effect. The operation is complicated and the coating uniformity is poor. In addition, after the electrolyte is calcined twice, Li volatilization is serious, and lithium-deficient phase impurities are very likely to appear, reducing ionic conductivity. Moreover, the existing solid electrolyte modification usually only focuses on improving the physical and chemical properties of the material itself. In battery cell applications, using the same amount of coated solid electrolyte, the increased coating layer mass compared to before coating will inevitably cause a loss in battery mass energy density. Summary of the Invention

[0007] In view of this, the technical problem to be solved by the present invention is to provide a multifunctional solid electrolyte with high dispersibility, high interface stability and low volume density, as well as a preparation method and application thereof.

[0008] The present invention provides a method for preparing a multifunctional solid electrolyte, comprising the following steps:

[0009] S1) mixing a titanium source, a complexing agent, a lithium source, an aluminum source, a phosphorus source, and a boron source in water to react to obtain a transparent sol;

[0010] S2) removing the solvent from the transparent sol to obtain a dry gel;

[0011] S3) grinding and crushing the dried gel to obtain LABTP precursor powder;

[0012] S4) calcining the LABTP precursor powder at a high temperature in an oxidizing atmosphere to obtain doped LABTP powder;

[0013] S5) annealing the doped LABTP powder to obtain a multifunctional solid electrolyte.

[0014] Preferably, the titanium source is selected from tetrabutyl titanate and / or isopropyl titanate;

[0015] The complexing agent is selected from one or more of citric acid, oxalic acid, glucose, ethylene glycol, and urea;

[0016] The lithium source is selected from one or more of lithium hydroxide, lithium carbonate, lithium bicarbonate, lithium nitrate, lithium acetate, and lithium oxalate;

[0017] The aluminum source is selected from one or more of aluminum nitrate, aluminum sulfate, and aluminum trichloride;

[0018] The phosphorus source is selected from ammonium dihydrogen phosphate and / or dihydrogen phosphate;

[0019] The boron source is selected from boron oxide and / or boron phosphate.

[0020] Preferably, the molar ratio of titanium ions to the complexing agent in the titanium source is 1:(3 - 5).

[0021] Preferably, the molar ratio of lithium atoms, aluminum atoms, boron atoms, and titanium atoms in the lithium source, aluminum source, boron source, and titanium source is a(1 + x):x - y:y:2 - x, where x is 0.1 - 0.8, 0 < y < x, and a is 1.05 - 1.2.

[0022] Preferably, step S2) is specifically: heating and evaporating the solvent of the transparent sol, and then heating and drying to obtain a dried gel; the temperature for heating and evaporating the solvent is 50°C - 90°C; the time for heating and evaporating the solvent is 2 - 8 h; the temperature for heating and drying is 80°C - 150°C; the time for heating and drying is 12 - 24 h.

[0023] Preferably, the temperature for high-temperature calcination in step S4) is 550°C - 800°C; the time for high-temperature calcination is 2 - 6 h.

[0024] Preferably, the temperature for annealing treatment in step S5) is 100°C - 200°C; the time for annealing treatment is 10 - 14 days.

[0025] Preferably, after the annealing treatment in step S5), it is dispersed in water and / or an alcohol solvent, filtered, and dried to obtain a multifunctional solid electrolyte;

[0026] The dispersion is specifically stirring first and then ultrasonic treatment; the time for stirring is 10 - 30 min; the time for ultrasonic treatment is 10 - 30 min; the temperature for drying is 60°C - 80°C; the time for drying is 4 - 12 h.

[0027] The present invention also provides a multifunctional solid electrolyte prepared by the above preparation method.

[0028] The present invention also provides a lithium-ion battery, including the multifunctional solid electrolyte prepared by the above preparation method.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1) The preparation method provided by the present invention is a low-temperature synthesis process. In addition to serving as a raw material, B2O3 in the precursor also plays a fluxing role during the high-temperature calcination process. The synthesis temperature is reduced to below 600°C compared to 900°C in traditional high-temperature solid-phase reactions. The phase formation temperature decreases with increasing doping levels. The powder micromorphology exhibits a spherical shape with low crystallinity rather than a cubic crystal shape. The average primary particle size is less than 100nm, which is much lower than that of conventional preparation processes.

[0031] 2) The preparation method provided by the present invention can simply and efficiently prepare highly dispersible nano-scale solid electrolyte powders. In the solid electrolyte, B and Al elements are co-doped into the Ti element site in LiTi2(PO4)3. The B atoms at the Ti element site are in a relatively unstable state because they have an atomic radius much smaller than that of Al and Ti and a weaker bond energy in the BO cubic tetrahedron, resulting in a lower diffusion migration potential energy barrier for B. Therefore, under the action of kinetic driving, some B atoms can easily escape from the LABTP lattice, floating on the crystal surface and in the gaps to form an amorphous layer of B or B2O3, which reacts with H2O in the air to generate crystalline H3BO3. The prepared ceramic powder is then directly washed and stirred with water to remove the water-soluble H3BO3, which can easily open the grain boundaries and disaggregate the grain agglomerates, ultimately obtaining highly dispersible nano-scale LABTP powder.

[0032] 3) The preparation method provided by the present invention can achieve in-situ coating. The low-melting-point B2O3 has good wettability with other intermediate phases during the high-temperature synthesis process, can fully fill the pores between ceramics and promote the reaction. The trace amount of B2O3 that has not completely reacted on the surface reacts with Li2O at high temperature to generate an electron / ion mixed dual ion conductor reactant Li3BO3, which adheres to the surface of the grain. No secondary sintering is required, and the surface coating can be performed as the phase is generated. At the same time, part of the B2O3 reacts with Li2O vapor at high temperature to generate Li3BO3, which has a partial coating effect, improves the interfacial stability of the LATP solid electrolyte material, improves its high-voltage resistance to oxidative decomposition, and significantly broadens its electrochemical stability window. It can effectively inhibit the oxidative decomposition of LATP in high-voltage positive electrode systems above 4.5V, and is adaptable to high-voltage battery systems above 4.5V.

[0033] 3) The preparation method provided by the present invention can obtain a solid electrolyte with low volume density. By controlling the appropriate B element doping ratio and process conditions, it is possible to maximize the overflow of B atoms from the crystal lattice while maintaining the original crystal structure without collapse. That is, partial vacancy defects are generated at the Ti element site, reducing the average atomic distribution density per unit volume. Under the premise of producing the same beneficial effects, the mass energy density of the battery cell can be improved;

[0034] 5) The preparation method provided by the present invention can produce a solid electrolyte with continuous water absorption. When applied to a battery cell, the B amorphous layer that continuously and slowly precipitates on the ceramic surface can directly contact the interior of the battery cell, including the positive electrode and electrolyte, and form a stable monobasic extremely weak acid H3BO3 with the trace amount of H2O therein, thereby significantly reducing the moisture content in the battery cell, reducing side reactions, and improving cycle performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is the XRD pattern of the solid electrolyte obtained in Example 2 of the present invention;

[0036] Figure 2 is a SEM image of the solid electrolyte obtained in Example 2 of the present invention;

[0037] Figure 3 TEM image of the solid electrolyte obtained in Example 2 of the present invention;

[0038] Figure 4 This is a SEM image of the solid electrolyte obtained in Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0039] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0040] The present invention provides a preparation method of a multifunctional solid electrolyte, comprising the following steps: S1) mixing a titanium source, a complexing agent, a lithium source, an aluminum source, a phosphorus source and a boron source in water for reaction to obtain a transparent sol; S2) removing the solvent from the transparent sol to obtain a dried gel; S3) grinding and crushing the dried gel to obtain a LABTP precursor powder; S4) calcining the LABTP precursor powder at a high temperature in an oxidizing atmosphere to obtain a doped LABTP powder; and S5) annealing the doped LABTP powder to obtain a multifunctional solid electrolyte.

[0041] The present invention has no special restrictions on the sources of all raw materials.

[0042] Mix a titanium source, a complexing agent, a lithium source, an aluminum source, a phosphorus source and a boron source in water to obtain a transparent sol; the titanium source can be any titanium source well-known to those skilled in the art without any special limitation. In the present invention, it is preferably a titanate, more preferably tetrabutyl titanate and / or isopropyl titanate; the complexing agent can be any complexing agent well-known to those skilled in the art without any special limitation. In the present invention, it is preferably one or more of citric acid, oxalic acid, glucose, ethylene glycol and urea; the molar ratio of titanium ions in the titanium source to the complexing agent is preferably 1:(3 - 5); optionally, the molar ratio of titanium ions in the titanium source to the complexing agent is 1:3, 1:4, 1:5 or within the range between any two of the above ratios; the molar ratio of lithium atoms, aluminum atoms, boron atoms to titanium atoms in the lithium source, aluminum source, boron source and titanium source is a(1 + x):x - y:y:2 - x, x is preferably 0.1 - 0.8, more preferably 0.3 - 0.7, still more preferably 0.4 - 0.7. In some embodiments provided by the present invention, x is specifically 0.4, 0.5 or 0.7; 0 < y < x, preferably 0.01 - 0.4, more preferably 0.05 - 0.3. In some embodiments provided by the present invention, y is specifically 0.05, 0.1, 0.15, 0.2, 0.25 or 0.3; a is preferably 1.05 - 1.2, more preferably 1.05 - 1.15, still more preferably 1.1; the lithium source can be any lithium source well-known to those skilled in the art without any special limitation. In the present invention, it is preferably one or more of lithium hydroxide, lithium carbonate, lithium bicarbonate, lithium nitrate, lithium acetate and lithium oxalate; the aluminum source can be any aluminum source well-known to those skilled in the art without any special limitation. In the present invention, it is preferably one or more of aluminum nitrate, aluminum sulfate and aluminum trichloride; the phosphorus source can be any phosphorus source well-known to those skilled in the art without any special limitation. In the present invention, it is preferably ammonium dihydrogen phosphate and / or dihydrogen phosphate; the boron source can be any boron source well-known to those skilled in the art without any special limitation. In the present invention, it is preferably boron oxide and / or boron phosphate; the mixing reaction is preferably carried out under room temperature conditions; the time of the mixing reaction is preferably 1 - 3 h; optionally, the time of the mixing reaction is 1 h, 2 h, 3 h or within the range between any two of the above values.

[0043] In a specific embodiment provided by the present invention, first mix the titanium source and the complexing agent in water, and then add the lithium source, aluminum source, phosphorus source and boron source for mixing reaction to obtain a transparent sol.

[0044] In another specific embodiment provided by the present invention, first mix the titanium source, lithium source, aluminum source, phosphorus source and boron source in water, and then add the complexing agent for mixing reaction to obtain a transparent sol.

[0045] After removing the solvent from the transparent sol, a dry gel is obtained; in the present invention, this step is specifically as follows: heating the transparent sol to evaporate the solvent, and then heating and drying to obtain a dry gel; the temperature of the heating evaporation solvent is preferably 50°C to 90°C; optionally, the temperature of the heating evaporation solvent is 50°C, 60°C, 70°C, 80°C, 90°C or a range between any two of the above values; the time of the heating evaporation solvent is preferably 2 to 8 hours; optionally, the time of the heating evaporation solvent is 2 hours, 4 hours, 6 hours, 8 hours or a range between any two of the above values. range; by heating and evaporating the solvent, a wet transparent sol can be obtained; the heating and drying temperature is preferably 80°C to 150°C; optionally, the heating and drying temperature is 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C or a range between any two of the above values; the heating and drying time is preferably 12 to 24h; optionally, the heating and drying time is 12h, 14h, 16h, 18h, 20h, 22h, 24h or a range between any two of the above values.

[0046] The dried gel is ground and crushed to obtain LABTP precursor powder.

[0047] The LABTP precursor powder is calcined at a high temperature in an oxidizing atmosphere to obtain a doped LABTP powder; the oxidizing atmosphere is any oxidizing atmosphere well known to those skilled in the art and is not particularly limited. In the present invention, it is preferably air and / or oxygen; the temperature of the high-temperature calcination is preferably 550°C to 800°C; optionally, the temperature of the high-temperature calcination is 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, or a range between any two of the above values; the time of the high-temperature calcination is preferably 2 to 6 hours; optionally, the time of the high-temperature calcination is 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, or a range between any two of the above values; high-temperature calcination can achieve the removal of organic impurities and calcination into a phase.

[0048] The doped LABTP powder is annealed; the annealing temperature is preferably 100°C to 200°C; optionally, the annealing temperature is 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C or a range between any two of the above values; the annealing time is preferably 10 to 14 days; optionally, the annealing time is 10 days, 11 days, 12 days, 13 days, 14 days or a range between any two of the above values; the annealing is preferably carried out in a constant temperature box or a muffle furnace; the annealing treatment can cause B / B2O3 to precipitate on the powder surface / grain boundary and form a uniform and dense amorphous layer.

[0049] After annealing, it is preferably dispersed in water and / or an alcohol solvent, filtered, and dried to obtain a multifunctional solid electrolyte; the alcohol solvent is an alcohol solvent well known to those skilled in the art, and there is no special limitation. In the present invention, it is preferably ethanol; the dispersion method is a method well known to those skilled in the art, and there is no special limitation. In the present invention, it is preferably stirred first and then ultrasonicated; the stirring time is preferably 10 to 30 minutes; optionally, the stirring time is 10 minutes, 15 minutes, 20 minutes, 25 minutes, 30 minutes or a range between any two of the above values; the stirring is preferably carried out under heating conditions; the stirring temperature is preferably 60°C to 80°C; the stirring temperature is 60°C, 65°C, 70°C, 75°C, 80°C or any two of the above values. values; the ultrasonic time is preferably 10 to 30 min; optionally, the ultrasonic time is 10 min, 15 min, 20 min, 25 min, 30 min or a range between any two of the above values; it is further preferred in the present invention to repeat the steps of dispersing and filtering, and then drying; the number of repetitions is preferably 1 to 3 times, more preferably 2 to 3 times; the drying temperature is preferably 60°C to 80°C; optionally, the drying temperature is 60°C, 65°C, 70°C, 75°C, 80°C or a range between any two of the above values; the drying time is preferably 4 to 12 h; optionally, the drying time is 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, 12 h or a range between any two of the above values.

[0050] The present invention also provides a multifunctional solid electrolyte prepared by the above preparation method.

[0051] The present invention also provides a lithium ion battery comprising the multifunctional solid electrolyte prepared by the above preparation method.

[0052] Specifically, the battery includes a positive electrode, a separator and a negative electrode; the positive electrode includes the above-mentioned modified composite solid electrolyte; the negative electrode includes the above-mentioned multifunctional solid electrolyte.

[0053] More specifically, the positive electrode includes a positive electrode active layer; the mass concentration of the modified composite solid electrolyte in the positive electrode active layer is 0.5wt% to 10wt%, more preferably 0.5wt% to 8wt%, more preferably 0.5wt% to 5wt%, more preferably 0.5wt% to 3wt%, and most preferably 1wt% to 2wt%; the positive electrode active layer also includes a positive electrode active material, a positive electrode conductive agent and a positive electrode binder; the mass ratio of the positive electrode active material, the positive electrode conductive agent and the positive electrode binder is preferably (80 to 95): (1 to 5): (1 to 5), more preferably (80 to 95): (3 to 5): (3 to 5), and more preferably 90:4.5:3.5; the positive electrode active material is a positive electrode active material well known to those skilled in the art. The positive electrode conductive agent can be any conductive agent well known to those skilled in the art, and there are no special restrictions. In the present invention, it is preferably one or more of: lithium nickel cobalt manganese oxide (NCM), lithium cobalt oxide (LCO) and lithium iron phosphate (LFP); the positive electrode conductive agent can be any conductive agent well known to those skilled in the art, and there are no special restrictions. In the present invention, it is preferably one or more of: carbon black SUPER-P, conductive graphite KS-6, carbon nanofibers, carbon nanotubes CNT, acetylene black, graphene and Ketjen carbon; the positive electrode binder can be any binder well known to those skilled in the art, and there are no special restrictions. In the present invention, it is preferably one or more of: polyvinylidene fluoride, polyacrylamide, polymethyl methacrylate-butyl acrylate, ethylene-vinyl acetate copolymer, polyvinyl acetate, polyurethane and polytetrafluoroethylene.

[0054] More specifically, the negative electrode is preferably a lithium metal sheet.

[0055] In a specific embodiment provided by the present invention, the battery further includes an electrolyte; the electrolyte is any electrolyte well known to those skilled in the art and is not particularly limited. In the present invention, it preferably includes a lithium salt and a solvent; the lithium salt is any lithium salt well known to those skilled in the art and is not particularly limited. In the embodiment provided by the present invention, LiFP6 is specifically used as an example for illustration; the concentration of the lithium salt in the electrolyte is preferably 1 to 1.2 mol / L; the solvent is any solvent well known to those skilled in the art and is not particularly limited, including but not limited to one or more of organic carbonate solvents, ether solvents, and sulfone solvents; the organic carbonate solvent includes but is not limited to one or more of dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC) and propylene carbonate (PC); the ether solvent includes but is not limited to ethylene glycol dimethyl ether (DME) and / or tetrahydrofuran (THF); in the embodiment provided by the present invention, EC, DMC and EMC with a volume ratio of 1:2:2 are specifically used as solvents for illustration.

[0056] The present invention also provides a method for preparing a battery, comprising the following steps: B1) mixing the above-mentioned multifunctional solid electrolyte, solvent, binder and surfactant to obtain an electrolyte slurry; mixing the multifunctional solid electrolyte, positive electrode active material, positive electrode conductive agent and positive electrode binder to obtain a positive electrode slurry; B2) coating the electrolyte slurry on a diaphragm to obtain a diaphragm of a composite electrolyte layer; coating the positive electrode slurry on a positive electrode current collector to obtain a positive electrode sheet; B3) assembling the positive electrode sheet, the diaphragm of the composite electrolyte layer and the negative electrode sheet to obtain a battery.

[0057] The present invention has no special restrictions on the sources of all raw materials, as long as they are commercially available. The multifunctional solid electrolyte, positive electrode active material, positive electrode conductive agent and positive electrode binder are all as described above and will not be repeated here.

[0058] According to the present invention, the solvent in the electrolyte slurry is any solvent well known to those skilled in the art and is not particularly limited. In the present invention, it is preferably one or more of water, ethanol, isopropanol and N-methylpyrrolidone (NMP); the mass ratio of the multifunctional solid electrolyte to the solvent is preferably (20-40): (80-60), more preferably (25-35): (75-65), and more preferably 30:70; the binder is any binder well known to those skilled in the art and is not particularly limited. In the present invention, it is preferably one or more of polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC) and polyacrylate or polyvinylidene fluoride (PVDF); the mass of the binder is preferably 0.5% to 2% of the mass of the electrolyte slurry, more preferably 1%; the surfactant is any surfactant well known to those skilled in the art and is not particularly limited. In the present invention, it is preferably sodium dodecyl sulfonate and / or lithium dodecyl sulfate; the mass of the surfactant is preferably 0.1% to 1% of the mass of the electrolyte slurry, more preferably 0.3% to 0.6%, and more preferably 0.5%.

[0059] According to the present invention, the thickness of the electrolyte slurry coated on the diaphragm in step B2) is preferably 10 to 500 μm; optionally, the thickness of the electrolyte slurry coated on the diaphragm is 10 μm, 20 μm, 50 μm, 80 μm, 100 μm, 120 μm, 150 μm, 180 μm, 200 μm, 250 μm, 300 μm, 350 μm, 400 μm, 450 μm, 500 μm or a range between any two of the above values.

[0060] In a specific embodiment provided by the present invention, an electrolyte is added in the step B3); the electrolyte is the same as described above and will not be described again here.

[0061] To further illustrate the present invention, a multifunctional solid electrolyte provided by the present invention, its preparation method and application are described in detail below with reference to examples.

[0062] The reagents used in the following examples were all of commercially available high purity grade (purity greater than 99%).

[0063] Example 1

[0064] Using the sol-gel method, lithium nitrate, aluminum nitrate, tetrabutyl titanate, ammonium dihydrogen phosphate, boron oxide were mixed according to Li 1.4 Al 0.35 B 0.05 Ti 1.6 The stoichiometric ratio of (PO4)3 is weighed, with a 10% excess of Li. The weighed titanium source, lithium source, aluminum source, boron source, and phosphorus source are sequentially added to a beaker containing an appropriate amount of deionized water and thoroughly stirred to dissolve. A citric acid complexing agent, four times the amount of the titanium source, is added and stirred for 2 hours to form a clear, transparent sol. The solvent is then removed by heating and stirring at 80°C for 2 hours to form a solid gel. The gel is then placed in a 150°C forced air drying oven for 12 hours before being removed and ground to obtain a completely dry precursor powder.

[0065] The above-mentioned precursor powder is placed in a corundum crucible, and an atmosphere furnace is used to remove organic impurities and calcine it into a phase under oxygen atmosphere conditions. The holding temperature is set to 700°C and the holding time is 3 hours. Then, after cooling to room temperature, LABTP electrolyte powder is obtained.

[0066] The electrolyte powder is placed in a constant temperature box or muffle furnace and kept at 100°C for 14 days for annealing treatment to precipitate and enrich B / B2O3 on the powder surface / grain boundary to form a uniform and dense amorphous layer. It is then taken out and cooled to room temperature.

[0067] The above-mentioned appropriate amount of powder was added to ethanol and stirred for washing. The stirring temperature was set to 60°C to accelerate the dissolution of H3BO3. After stirring for 30 minutes, ultrasonic dispersion was performed for 30 minutes to obtain a suspension. The suspension was centrifuged and filtered to obtain a washed powder. The above-mentioned washing and filtering processes were repeated 2 to 3 times. The finally obtained powder was collected and placed in a blast drying oven and dried at 60°C for 12 hours to finally obtain a dry, highly dispersed nano-LABTP electrolyte powder.

[0068] Example 2

[0069] Using the sol-gel method, lithium nitrate, aluminum nitrate, tetrabutyl titanate, ammonium dihydrogen phosphate, boron oxide were mixed according to Li 1.4 Al 0.3 B 0.1 Ti 1.6The stoichiometric ratio of (PO4)3 is weighed, with a 10% excess of Li. The weighed titanium source, lithium source, aluminum source, boron source, and phosphorus source are sequentially added to a beaker containing an appropriate amount of deionized water and thoroughly stirred to dissolve. An oxalic acid complexing agent, three times the amount of the titanium source, is added and stirred for 1 hour to form a clear, transparent sol. The solvent is then removed by heating and stirring at 50°C for 4 hours to form a solid gel. The gel is then placed in an 80°C forced air drying oven for 24 hours before being removed and ground to obtain a completely dry precursor powder.

[0070] The above-mentioned precursor powder was placed in a corundum crucible, and organic impurities were removed and calcined into a phase using a muffle furnace under air atmosphere conditions. The holding temperature was set to 550°C and the holding time was 6 hours. After cooling to room temperature, LABTP electrolyte powder was obtained.

[0071] The electrolyte powder is placed in a constant temperature box or muffle furnace and kept at 200°C for 10 days for annealing treatment to precipitate and enrich B / B2O3 on the powder surface / grain boundary to form a uniform and dense amorphous layer. It is then taken out and cooled to room temperature.

[0072] The above-mentioned appropriate amount of powder was added to deionized water and stirred for washing. The stirring temperature was set to 80°C to accelerate the dissolution of H3BO3. After stirring for 10 minutes, ultrasonic dispersion was performed for 10 minutes to obtain a suspension. The suspension was centrifuged and filtered to obtain the washed powder. The above-mentioned washing and filtering processes were repeated 2 to 3 times. The finally obtained powder was collected and placed in a blast drying oven and dried at 80°C for 4 hours to finally obtain dry highly dispersed nano-LABTP electrolyte powder.

[0073] The solid electrolyte obtained in Example 2 was analyzed by X-ray diffraction, and its XRD pattern was as follows: Figure 1 shown.

[0074] The solid electrolyte obtained in Example 2 was analyzed using a scanning electron microscope, and its SEM image was obtained as shown in FIG. Figure 2 shown.

[0075] The solid electrolyte obtained in Example 2 was analyzed using a transmission electron microscope, and its TEM image was obtained as shown in FIG. Figure 3 shown.

[0076] Example 3

[0077] Using the sol-gel method, lithium nitrate, aluminum nitrate, tetrabutyl titanate, ammonium dihydrogen phosphate, boron oxide were mixed according to Li 1.4 Al 0.25 B 0.15 Ti 1.6The stoichiometric ratio of (PO4)3 is weighed, with a 10% excess of Li. The weighed titanium source, lithium source, aluminum source, boron source, and phosphorus source are sequentially added to a beaker containing an appropriate amount of deionized water and thoroughly stirred to dissolve. An ethylene glycol complexing agent, five times the amount of the titanium source, is added and stirred for 3 hours to form a clear, transparent sol. The solvent is then removed by heating and stirring at 90°C for 8 hours to form a solid gel. The gel is then placed in a 120°C forced air drying oven for 18 hours before being removed and ground to obtain a completely dry precursor powder.

[0078] The above-mentioned precursor powder is placed in a corundum crucible, and an atmosphere furnace is used to remove organic impurities and calcine it into a phase under air atmosphere conditions. The holding temperature is set to 800°C and the holding time is 2h. Then, after cooling to room temperature, LABTP electrolyte powder is obtained.

[0079] The electrolyte powder is placed in a constant temperature box or muffle furnace and kept at 150°C for 14 days for annealing treatment to precipitate and enrich B / B2O3 on the powder surface / grain boundary to form a uniform and dense amorphous layer. It is then taken out and cooled to room temperature.

[0080] The above-mentioned appropriate amount of powder was added to ethanol and stirred for washing. The stirring temperature was set to 60°C to accelerate the dissolution of H3BO3. After stirring for 30 minutes, ultrasonic dispersion was performed for 10 minutes to obtain a suspension. The suspension was centrifuged and filtered to obtain a washed powder. The above-mentioned washing and filtering processes were repeated 2 to 3 times. The finally obtained powder was collected and placed in a blast drying oven and dried at 70°C for 8 hours to finally obtain dry highly dispersed nano-LABTP electrolyte powder.

[0081] Example 4

[0082] Using the sol-gel method, lithium nitrate, aluminum nitrate, tetrabutyl titanate, ammonium dihydrogen phosphate, boron oxide were mixed according to Li 1.4 Al 0.2 B 0.2 Ti 1.6 The stoichiometric ratio of (PO4)3 is weighed, with a 10% excess of Li. The weighed titanium source, lithium source, aluminum source, boron source, and phosphorus source are sequentially added to a beaker containing an appropriate amount of deionized water and thoroughly stirred to dissolve. A citric acid complexing agent, four times the amount of the titanium source, is added and stirred for 2 hours to form a clear, transparent sol. The solvent is then removed by heating and stirring at 80°C for 2 hours to form a solid gel. The gel is then placed in a 140°C forced air drying oven for 12 hours before being removed and ground to obtain a completely dry precursor powder.

[0083] The remaining steps are the same as those in Example 1.

[0084] Example 5

[0085] Using the sol-gel method, lithium nitrate, aluminum nitrate, tetrabutyl titanate, ammonium dihydrogen phosphate, boron oxide were mixed according to Li 1.4 Al 0.15 B 0.25 Ti 1.6 The stoichiometric ratio of (PO4)3 is weighed, with a 10% excess of Li. The weighed titanium source, lithium source, aluminum source, boron source, and phosphorus source are sequentially added to a beaker containing an appropriate amount of deionized water and thoroughly stirred to dissolve. A citric acid complexing agent, four times the amount of the titanium source, is added and stirred for 2 hours to form a clear, transparent sol. The solvent is then removed by heating and stirring at 80°C for 2 hours to form a solid gel. The gel is then placed in a 140°C forced air drying oven for 12 hours before being removed and ground to obtain a completely dry precursor powder.

[0086] The remaining steps are the same as those in Example 1.

[0087] Example 6

[0088] Using the sol-gel method, lithium nitrate, aluminum nitrate, tetrabutyl titanate, ammonium dihydrogen phosphate, boron oxide were mixed according to Li 1.4 Al 0.1 B 0.3 Ti 1.6 The stoichiometric ratio of (PO4)3 was weighed, with a 10% excess of Li.

[0089] The remaining steps are the same as those in Example 1.

[0090] Example 7

[0091] Using the sol-gel method, lithium nitrate, aluminum nitrate, tetrabutyl titanate, ammonium dihydrogen phosphate, boron oxide were mixed according to Li 1.5 Al 0.3 B 0.2 Ti 1.5 The stoichiometric ratio of (PO4)3 was weighed, with a 10% excess of Li.

[0092] The remaining steps are the same as those in Example 1.

[0093] Example 8

[0094] Using the sol-gel method, lithium nitrate, aluminum nitrate, tetrabutyl titanate, ammonium dihydrogen phosphate, boron oxide were mixed according to Li 1.5 Al 0.2 B 0.3 Ti 1.5 The stoichiometric ratio of (PO4)3 was weighed, with a 10% excess of Li.

[0095] The remaining steps are the same as those in Example 1.

[0096] Example 9

[0097] Using the sol-gel method, lithium nitrate, aluminum nitrate, tetrabutyl titanate, ammonium dihydrogen phosphate, boron oxide were mixed according to Li 1.3 Al 0.2 B 0.1 Ti 1.7 The stoichiometric ratio of (PO4)3 was weighed, with a 10% excess of Li.

[0098] The remaining steps are the same as those in Example 1.

[0099] Example 10

[0100] Using the sol-gel method, lithium nitrate, aluminum nitrate, tetrabutyl titanate, ammonium dihydrogen phosphate, boron oxide were mixed according to Li 1.3 Al 0.1 B 0.2 Ti 1.7 The stoichiometric ratio of (PO4)3 was weighed, with a 10% excess of Li.

[0101] The remaining steps are the same as those in Example 1.

[0102] Comparative Example 1

[0103] Using high temperature solid phase method, lithium carbonate, aluminum oxide, titanium dioxide, ammonium dihydrogen phosphate were mixed according to Li 1.4 Al 0.4 Ti 1.6 Weigh the stoichiometric ratio of (PO4)3, with a 15% excess of Li. The weighed titanium, lithium, aluminum, boron, and phosphorus sources are placed sequentially into a ball mill with an appropriate ball-to-material ratio, followed by ethanol. Mill the mixture in a planetary ball mill at 500 rpm for 6 hours. The slurry is then poured into a glass tray and dried in a forced-air drying oven at 80°C for 12 hours to obtain a dry LATP precursor powder.

[0104] The above-mentioned precursor powder was placed in a corundum crucible and calcined at high temperature using a muffle furnace under air atmosphere conditions. The holding temperature was set to 900°C and the holding time was 6 hours. It was then cooled to room temperature and ground to obtain LATP electrolyte powder.

[0105] Comparative Example 2

[0106] (Sol-gel method for preparing Li 1.4 Al 0.4 Ti 1.6 (PO4)3 material)

[0107] Using the sol-gel method, lithium nitrate, aluminum nitrate, tetrabutyl titanate, and ammonium dihydrogen phosphate were mixed in the order of Li 1.4 Al 0.4 Ti 1.6The stoichiometric ratio of (PO4)3 is weighed, with a 10% excess of Li. The weighed titanium source, lithium source, aluminum source, boron source, and phosphorus source are sequentially added to a beaker containing an appropriate amount of deionized water and thoroughly stirred to dissolve. A citric acid complexing agent, four times the amount of the titanium source, is added and stirred for 2 hours to form a clear, transparent sol. The solvent is then removed by heating and stirring at 80°C for 2 hours to form a solid gel. The gel is then placed in a 150°C forced air drying oven for 12 hours before being removed and ground to obtain a completely dry precursor powder.

[0108] The above-mentioned precursor powder is placed in a corundum crucible, and an atmosphere furnace is used to remove organic impurities and calcine it into a phase under oxygen atmosphere conditions. The holding temperature is set to 700°C and the holding time is 3 hours. Then, after cooling to room temperature, LATP electrolyte powder is obtained.

[0109] The solid electrolyte obtained in Comparative Example 2 was analyzed using a scanning electron microscope, and its SEM image was obtained as shown in FIG. Figure 4 shown.

[0110] Comparative Example 3

[0111] Using the sol-gel method, lithium nitrate, aluminum nitrate, tetrabutyl titanate, and ammonium dihydrogen phosphate were mixed in the order of Li 1.5 Al 0.5 Ti 1.5 The stoichiometric ratio of (PO4)3 was weighed, with a 10% excess of Li.

[0112] The remaining steps are the same as those in Comparative Example 2.

[0113] Material characterization

[0114] Microscopic morphology characterization: Use field emission scanning electron microscope (SEM) or high-resolution transmission electron microscope (TEM) to perform microscopic morphology characterization on the prepared powder to observe information such as the particle size distribution, surface morphology and crystal structure of the crystals.

[0115] Phase structure characterization: X-ray diffractometer was used to test the phase purity and crystal structure of the powder and the theoretical density was calculated. The results are shown in Table 1.

[0116] Table 1 Theoretical density of electrolyte materials calculated after XRD refinement

[0117]

[0118]

[0119] Battery cell performance test

[0120] Diaphragm coating: LABTP powder was dissolved in deionized water, the solid mass fraction was controlled to 30%, and the mixture was homogenized for 2 hours using a high-speed stirring disperser. Then, 1% mass fraction of the binder polyvinyl alcohol (PVA) and 0.5% of the surfactant sodium dodecyl sulfate were added and the mixture was fully stirred and homogenized for 2 hours to obtain a coating slurry. A commercial 21 μm thick PE diaphragm was used as the base film. The slurry was scraped on a diaphragm coating machine with a scraping gap of 100 μm. The single-sided coated PE diaphragm was cut and dried at 80°C for 12 hours to obtain a LABTP-coated diaphragm.

[0121] Positive electrode blending: Using a 4.65V high-voltage LiCoO2 positive electrode active material system, the positive electrode active material LiCoO2, the conductive agent carbon nanotubes CNT, the binder polyvinylidene fluoride (PVDF) and the modified LABTP material were mixed uniformly in a mass ratio of 90:4.5:3.5:2, and the oily solvent NMP was added to control the solid content to 50%. After sufficient stirring, the positive electrode oily slurry was obtained; the slurry was coated on the aluminum foil current collector using an automatic doctor coater with a gap of 200μm, placed in a 120℃ oven for drying, and rolled on a roller press to a compaction density of 4.0g / cm 3 Finally, use a manual cutting machine to cut it into circular pole pieces with a diameter of 12 mm for later use.

[0122] Assembly: Using a CR2032 button cell, in an argon glove box, assemble the positive electrode sheet, LABTP-coated separator (the coated surface is opposite to the positive electrode sheet), negative lithium metal sheet, stainless steel gasket, and spring. After adding an appropriate amount of electrolyte (1.05M LiFP6 / EC:DMC:EMC, 1:2:2 Vol%), use a button cell assembly machine to assemble and seal the positive and negative electrodes to obtain the required battery to be tested.

[0123] Performance test: The button cells modified by separator coating and cathode blending were subjected to cycle testing. A blue battery test system was used to perform long cycle and other performance tests at a constant temperature of 25°C. The cycle rate was 1C and the cut-off voltage range was 3 to 4.65V. The battery cycle performance results are shown in Table 2.

[0124] Table 2 Battery cycle performance test results

[0125] Sample Group Initial capacity (mAh / g) Remaining capacity after 100 cycles (%) Example 1 195.6 85.4 Example 2 196.3 83.6 Example 3 193.5 84.4 Example 4 192.8 81.2 Example 5 194.4 84.8 Example 6 195.3 83.2 Example 7 193.2 84.1 Example 8 193.8 83.4 Example 9 194.3 83.6 Example 10 192.9 85.4 Comparative Example 1 192.6 79.3 Comparative Example 2 195.8 81.1 Comparative Example 3 193.5 78.4

[0126] Moisture test: Use a moisture meter to test the moisture content of the electrode or bare cell before and after cycling to observe the changes in trace moisture content. The moisture test results before and after battery cycling are shown in Table 3.

[0127] Table 3 Moisture test data before and after battery cycling

[0128]

[0129]

[0130] In summary, the present invention provides a low-temperature synthesis process for fine LATP powder. The added B2O3 spacer also has a fluxing effect, significantly reducing the synthesis temperature from 900°C to a minimum of 550°C, significantly inhibiting grain growth and achieving a grain size effect of 50nm. The present invention provides an in-situ Li3BO3-coated solid electrolyte, which does not require secondary sintering and can be surface-coated as the phase is generated. Part of the B2O3 reacts with Li2O vapor at high temperature to generate Li3BO3, which has a partial coating effect, improves the interface stability of the LATP solid electrolyte material, and can effectively inhibit the oxidative decomposition of LATP in high-voltage positive electrode systems above 4.5V. The present invention provides an efficient and low-cost solid electrolyte nanopowder dispersion process. B2O3 is dispersed at the grain boundaries and has a spacer effect. B2O3 is water-soluble, and the prepared powder does not require subsequent mechanical grinding or other crushing. Only a simple water washing process is required to effectively open the grain boundaries within the agglomerate, thereby realizing the preparation of single crystal powder. The present invention provides a preparation process for low-density LATP ceramics. The use of B element to achieve doping of Ti element sites. In the crystal structure, B is located at the center of the BO tetrahedral cubic structure, and its electron binding ability is far less than that of O atoms, resulting in strong vibrational transitions and high diffusion free energy, making it unstable in the LATP lattice. Moreover, B is a low-mass, small-radius atom, so under the action of the dynamic process, it is easy to escape slowly as B ions along the Li ion transmission channel, resulting in a large number of vacancies at the Ti element site. When the number of vacancies is controlled within a certain range, the original stable LATP crystal structure can be maintained. Therefore, a low theoretical density LATP powder material containing some lattice defects is ultimately achieved. The present invention provides a preparation process for self-water-absorbing LATP ceramics. LATP crystals can slowly release B2O3 over a long period of time, and then react with H2O in the environment to form a stable phase H3BO3. When used, they can continuously absorb water inside the battery cell, reducing the internal moisture of the battery cell, reducing side reactions, and improving cycle performance.

[0131] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a multifunctional solid electrolyte, characterized in that: It includes the following steps: S1) Mix a titanium source, a complexing agent, a lithium source, an aluminum source, a phosphorus source and a boron source in water and react to obtain a transparent sol; S2) Remove the solvent from the transparent sol to obtain a dry gel; S3) Grind and crush the dry gel to obtain a LABTP precursor powder; S4) Calcinate the LABTP precursor powder at a high temperature in an oxidizing atmosphere to obtain a doped LABTP powder; S5) Anneal the doped LABTP powder to obtain a multifunctional solid electrolyte.

2. The preparation method according to claim 1, characterized in that The titanium source is selected from tetrabutyl titanate and / or isopropyl titanate; The complexing agent is selected from one or more of citric acid, oxalic acid, glucose, ethylene glycol and urea; The lithium source is selected from one or more of lithium hydroxide, lithium carbonate, lithium bicarbonate, lithium nitrate, lithium acetate and lithium oxalate; The aluminum source is selected from one or more of aluminum nitrate, aluminum sulfate and aluminum trichloride; The phosphorus source is selected from ammonium dihydrogen phosphate and / or dihydrogen phosphate; The boron source is selected from boron oxide and / or boron phosphate.

3. The preparation method according to claim 1, characterized in that The molar ratio of titanium ions in the titanium source to the complexing agent is 1:(3-5).

4. The preparation method according to claim 1, characterized in that The molar ratio of lithium atoms, aluminum atoms, boron atoms and titanium atoms in the lithium source, aluminum source, boron source and titanium source is a(1 + x):x - y:y:2 - x, where x is 0.1 - 0.8, 0 < y < x, and a is 1.05 - 1.

2.

5. The preparation method according to claim 1, characterized in that Step S2) is specifically as follows: Heat the transparent sol to evaporate the solvent, and then heat and dry it to obtain a dry gel; the temperature for heating and evaporating the solvent is 50°C - 90°C; the time for heating and evaporating the solvent is 2 - 8 h; the temperature for heating and drying is 80°C - 150°C; the time for heating and drying is 12 - 24 h.

6. The preparation method according to claim 1, characterized in that In step S4), the temperature for high-temperature calcination is 550°C - 800°C; the time for high-temperature calcination is 2 - 6 h.

7. The preparation method according to claim 1, characterized in that In step S5), the temperature for annealing treatment is 100°C - 200°C; the time for annealing treatment is 10 - 14 days.

8. The preparation method according to claim 1, characterized in that After the annealing treatment in step S5), it is dispersed in water and / or an alcohol solvent, filtered, and dried to obtain a multifunctional solid electrolyte; The dispersion is specifically to stir first and then perform ultrasonic treatment; the stirring time is 10 - 30 min; the ultrasonic treatment time is 10 - 30 min; the drying temperature is 60°C - 80°C; the drying time is 4 - 12 h.

9. A multifunctional solid electrolyte prepared by the preparation method according to any one of claims 1 - 8.

10. A lithium ion battery, characterized in that: It includes a multifunctional solid electrolyte prepared by the preparation method according to any one of claims 1 - 8.

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