Modified lithium aluminum titanium phosphate solid electrolyte, preparation method and application thereof

Abstract

The present invention provides a modified lithium titanium aluminum phosphate solid electrolyte, a preparation method and application thereof. The preparation method comprises: obtaining a lithium titanium aluminum phosphate precursor, adding a pore-forming agent SeS2 and / or polymethyl methacrylate equivalent to 36-45% of its mass, obtaining a mixed material, performing pore-forming sintering, and obtaining porous lithium titanium aluminum phosphate; refluxing and recrystallizing naphthaldehyde, hydrazine and acid to obtain an organic gel factor, and sequentially impregnating the organic gel factor in a Ca-containing 2+ Solution and Co 3+ The solution is prepared to obtain a second metal organic gel CaCoG; finally, the porous lithium titanium aluminum phosphate is immersed therein under heating, and the modified lithium titanium aluminum phosphate solid electrolyte is obtained after standing. The present invention combines the solid lithium titanium aluminum phosphate electrolyte with the semi-solid bimetallic-organic gel, so that the basic resistance between the solid electrolyte and the pole piece is smaller, the battery efficiency is higher, the ion conductivity is higher, and the battery cycle performance and rate performance are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion battery solid electrolyte materials, and in particular to a modified lithium titanium aluminum phosphate solid electrolyte, a preparation method and application thereof. Background Art

[0002] Lithium-ion batteries have the advantages of high energy density and long service life, and are increasingly widely used in portable electronic products, electric vehicles and other fields. The energy density of traditional liquid lithium-ion batteries has reached its limit, and there are safety issues such as easy leakage, easy corrosion, and easy combustion, making all-solid-state lithium-ion batteries with higher energy density, longer service life and better safety a research hotspot. The main components of all-solid-state lithium-ion batteries are positive electrodes, negative electrodes and solid electrolytes. While acting as ion conductors, solid electrolytes also block the free passage of electrons. Due to the solid-state nature of solid electrolytes themselves, there are many problems in the actual application process. There will be insufficient contact with the pole piece, and insufficient contact will increase the contact resistance of the entire lithium battery and reduce efficiency. Summary of the invention

[0003] The main purpose of the present invention is to provide a modified lithium aluminum titanium phosphate solid electrolyte, a preparation method and application thereof, so as to solve the problems of large contact resistance and low ion transmission efficiency of solid electrolytes in the prior art.

[0004] In order to achieve the above-mentioned object, according to one aspect of the present invention, a method for preparing a modified lithium titanium aluminum phosphate solid electrolyte is provided, comprising the following steps: step S1, obtaining a lithium titanium aluminum phosphate precursor; step S2, adding a pore-forming agent to the lithium titanium aluminum phosphate precursor to obtain a mixed material, and sintering the mixed material to obtain porous lithium titanium aluminum phosphate; step S3, dissolving naphthaldehyde, hydrazine and acid in a solvent, refluxing and filtering in sequence to obtain a filtrate, and recrystallizing the filtrate to obtain an organic gel factor; and immersing the organic gel factor in a Ca-containing 2+ solution, obtaining a first metal organic gel CaG; immersing the first metal organic gel CaG in a Co-containing 3+ In the solution, a second metal organic gel CaCoG is obtained; in step S4, porous lithium titanium aluminum phosphate is immersed in the second metal organic gel CaCoG under heating, and a modified lithium titanium aluminum phosphate solid electrolyte is obtained after standing; wherein the pore-forming agent is SeS2 and / or polymethyl methacrylate, and the mass of the added pore-forming agent is 36-45% of the mass of the lithium titanium aluminum phosphate precursor.

[0005] Further, step S1 comprises: weighing a lithium source, an aluminum source, a titanium source and a phosphorus source, performing a first ball milling dispersion in ethanol, and then sequentially drying and sintering to obtain a lithium aluminum titanium phosphate precursor; preferably, among the lithium source, the aluminum source, the titanium source and the phosphorus source, Li:Al:Ti:PO4 3- The molar ratio of elements is (1+x):x:(2-x):3, 0.4≤x≤0.5; more preferably, the lithium source is one or more of lithium carbonate, lithium dihydrogen phosphate and lithium hydroxide, the aluminum source is aluminum dihydrogen phosphate and / or aluminum oxide, the titanium source is titanium dioxide, and the phosphorus source is ammonium dihydrogen phosphate and / or aluminum dihydrogen phosphate.

[0006] Further, in step S1, the rotation speed of the first ball milling dispersion is 400-500 rpm, and the time is 4-6 hours; preferably, the drying temperature is 90-95°C, and the time is 3-5 hours; more preferably, the sintering process includes a first sintering and a second sintering, and preferably the heating rate of the first sintering is 1-3°C / min, the sintering temperature is 400-480°C, and the sintering time is 3-6 hours; preferably, the heating rate of the second sintering is 1-3°C / min, the sintering temperature is 800-900°C, and the sintering time is 2-6 hours.

[0007] Furthermore, in step S2, the pore size of the porous lithium aluminum titanium phosphate is 140nm~200um, and the porosity is 29~50%; preferably, the heating rate of the pore-forming sintering is 1~3℃ / min, the sintering temperature is 800~900℃, and the sintering time is 8~10h; more preferably, before the pore-forming sintering, the mixed material is also subjected to the steps of second ball milling dispersion and tableting in sequence, and the second ball milling dispersion speed is preferably 400~500rpm, and the time is 6~8h, and the tableting pressure is preferably 1~2MPa, and the time is 40~50s.

[0008] Further, in step S3, the naphthaldehyde is one or more of 1-naphthaldehyde, 1-hydroxy-2-naphthaldehyde and o-hydroxynaphthaldehyde; the hydrazine is 3,4,5-tribenzoylhydrazide; the acid is acetic acid; the solvent is ethanol; preferably, the molar ratio of naphthaldehyde to hydrazine is (1-2):1; more preferably, the Ca-containing 2+ The solution is one or more of calcium perchlorate, calcium chlorate and calcium hypochlorite, containing Co 2+ The solution is one or more of cobalt sulfate, cobalt carbonate and cobalt chloride.

[0009] Further, in step S3, reflux is performed under stirring, the stirring speed is 200 to 300 r / min, and the reflux time is 20 to 24 h; preferably, the first metal-organic gel CaG is immersed in Co 3+ After being dissolved in the solution, it is dried at 55-65° C. for 4-5 h to obtain the second metal-organic gel CaCoG.

[0010] Furthermore, in step S4, the second metal organic gel CaCoG is heated to 80-85°C for impregnation, the impregnation pressure is 0.25-0.35 MPa, and the impregnation time is 2-3 hours; preferably, in step S4, after standing for 3-5 hours, it is dried at 55-65°C for 4-5 hours to obtain a modified lithium aluminum titanium phosphate solid electrolyte.

[0011] According to another aspect of the present invention, a modified lithium aluminum titanium phosphate solid electrolyte is provided, which is obtained by the preparation method of the present invention.

[0012] According to another aspect of the present invention, there is provided a use of the modified lithium aluminum titanium phosphate solid electrolyte in a lithium ion battery.

[0013] According to another aspect of the present invention, a battery is provided, comprising a positive electrode, a negative electrode and an electrolyte, wherein the electrolyte comprises the above-mentioned modified lithium aluminum titanium phosphate solid electrolyte.

[0014] The technical scheme of the present invention is applied, and the lithium titanium aluminum phosphate substrate is pore-formed by doping a certain proportion of pore-forming agent, and then the synthesized metal-organic gel is heated to change its thixotropy so that it enters the pore structure of the lithium titanium aluminum phosphate, and is left to solidify in the lithium titanium aluminum phosphate material. The present invention combines the solid lithium titanium aluminum phosphate electrolyte with the semi-solid bimetallic-organic gel. Under the action of the bimetallic-organic gel, the obtained modified lithium titanium aluminum phosphate solid electrolyte can achieve a tighter combination when in contact with the battery pole piece, so that the basic resistance between the solid electrolyte and the pole piece is smaller, thereby improving the battery efficiency. Moreover, due to the embedding of the bimetallic organic gel in the modified lithium titanium aluminum phosphate solid electrolyte of the present invention, compared with the all-solid electrolyte, the transfer of electrons in the solid electrolyte can be accelerated, and the ion transmission efficiency is higher, the ion conductivity is higher, and the overall cycle performance and rate performance of the battery are significantly improved. DETAILED DESCRIPTION

[0015] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below in conjunction with the embodiments.

[0016] As described in the background of the present invention, the prior art has the problems of large contact resistance of solid electrolytes and low ion transfer efficiency. In order to solve the above problems, in a typical embodiment of the present invention, a method for preparing a modified lithium titanium aluminum phosphate solid electrolyte is provided, comprising the following steps: step S1, obtaining a lithium titanium aluminum phosphate precursor; step S2, adding a pore-forming agent to the lithium titanium aluminum phosphate precursor to obtain a mixed material, pore-forming sintering the mixed material to obtain a porous lithium titanium aluminum phosphate; step S3, dissolving naphthaldehyde, hydrazine and acid in a solvent, refluxing and filtering in turn to obtain a filtrate, recrystallizing the filtrate to obtain an organic gel factor; immersing the organic gel factor in a Ca-containing 2+ solution, obtaining a first metal organic gel CaG; immersing the first metal organic gel CaG in a Co-containing 3+ In the solution, a second metal organic gel CaCoG is obtained; in step S4, porous lithium titanium aluminum phosphate is immersed in the second metal organic gel CaCoG under heating, and a modified lithium titanium aluminum phosphate solid electrolyte is obtained after standing; wherein the pore former is SeS2 and / or polymethyl methacrylate, and the mass of the added pore former is 36-45% of the mass of the lithium titanium aluminum phosphate precursor, wherein G is an organic gel.

[0017] The present invention firstly dopes a certain proportion of pore-forming agent into a lithium titanium aluminum phosphate precursor, obtains a mixed material for pore-forming sintering, obtains a pore structure on the surface of the lithium titanium aluminum phosphate precursor, obtains a porous lithium titanium aluminum phosphate, and after sintering, it is a regular block ceramic material. The inventor unexpectedly found in the research process that when the mass of the added pore-forming agent is less than 36%, the surface pore structure of the lithium titanium aluminum phosphate precursor is less, and the metal-organic gel that can enter it later is less, and the effect of reducing contact resistance and improving ion transmission efficiency cannot be achieved. When the mass of the added pore-forming agent is higher than 45%, the surface pore structure of the lithium titanium aluminum phosphate precursor is too much, and the lithium titanium aluminum phosphate matrix material is too little, so that the ion conductivity of the modified lithium titanium aluminum phosphate solid electrolyte is insufficient. Therefore, the present invention limits the mass of the added pore-forming agent to 36-45% of the mass of the lithium titanium aluminum phosphate precursor. If the volatilization temperature of the pore-forming agent is too low, the solid electrolyte will volatilize before forming, causing the collapse of part of the pore structure. Therefore, the pore-forming agent is limited to SeS2 or polymethyl methacrylate, preferably SeS2, which has a higher volatilization temperature and is conducive to the formation of porous solid electrolytes.

[0018] Secondly, the metal-organic gel is prepared by dissolving naphthaldehyde, hydrazine and acid in a solvent, reacting, refluxing and filtering in sequence, removing the generated precipitate, obtaining a filtrate, and recrystallizing the filtrate in a solvent to obtain an organic gel factor; the organic gel factor is immersed in a Ca-containing 2+ solution, using the organic gel factor as a template to obtain a first metal organic gel CaG; immersing the first metal organic gel CaG in a Co-containing3+ In the solution, the first metal organic gel CaG is used as a template to obtain the second metal organic gel CaCoG. The above two metal ions can be smoothly loaded in the organic gel during the impregnation loading process, with a high loading rate, and the bimetallic loading can better promote lithium ion transmission in the electrolyte; finally, the porous lithium aluminum titanium phosphate is immersed in the second metal organic gel CaCoG under heating, and the thixotropy of the metal-organic gel is changed by heating to make it enter the pore structure of the lithium aluminum titanium phosphate. The heating is stopped and the material is allowed to stand to solidify in the lithium aluminum titanium phosphate material, thereby obtaining a modified lithium aluminum titanium phosphate solid electrolyte.

[0019] Unlike traditional solid electrolytes, the present invention combines solid lithium titanium aluminum phosphate electrolyte with semi-solid bimetallic-organic gel, and fully considers the contact problem between the solid electrolyte and the pole piece and the transmission efficiency of internal ions on the basis of ensuring the overall mechanical properties. The contact between the simple solid electrolyte and the pole piece is point-to-point contact, and the impedance is relatively large. Under the action of the bimetallic-organic gel, when the modified lithium titanium aluminum phosphate solid electrolyte is in contact with the battery pole piece, the part filled with gel replaces some points with surfaces, and the overall contact area becomes larger, which can achieve a tighter combination, so that the basic resistance between the solid electrolyte and the pole piece is smaller, thereby improving the battery efficiency. Moreover, the binding of gel electrolytes to ions is less than that of solid electrolytes, and the ion channels are also larger. The transmission rate of ions in gel electrolytes is much higher than that of solid electrolytes. Due to the embedding of the bimetallic organic gel in the modified lithium titanium aluminum phosphate solid electrolyte of the present invention, compared with the all-solid electrolyte, the ion transmission efficiency is higher and the ion conductivity is higher, which significantly improves the overall cycle performance and rate performance of the battery. The method for preparing a solid-semisolid electrolyte in a lithium-ion battery of the present invention solves the problems of low ion transmission efficiency and large contact resistance in the solid electrolyte, and is a method for preparing a modified LATP solid electrolyte in a lithium-ion battery that is more stable and has better performance.

[0020] The use of a solid phase method to synthesize a lithium aluminum titanium phosphate precursor can further improve its stability and facilitate preparation. In a preferred embodiment, step S1 comprises: weighing a lithium source, an aluminum source, a titanium source and a phosphorus source, performing a first ball milling dispersion in ethanol, and then drying and sintering in sequence to obtain a lithium aluminum titanium phosphate precursor; preferably, among the lithium source, the aluminum source, the titanium source and the phosphorus source, Li:Al:Ti:PO4 3-The molar ratio of elements is (1+x):x:(2-x):3, 0.4≤x≤0.5; the raw materials of the lithium aluminum titanium phosphate precursor can be conventional materials in the art. In order to further improve the stability of the lithium aluminum titanium phosphate precursor and facilitate SeS2 pore formation, more preferably, the lithium source is one or more of lithium carbonate, lithium dihydrogen phosphate and lithium hydroxide, the aluminum source is aluminum dihydrogen phosphate and / or aluminum oxide, the titanium source is titanium dioxide, and the phosphorus source is ammonium dihydrogen phosphate and / or aluminum dihydrogen phosphate.

[0021] In the preparation process of the lithium aluminum titanium phosphate precursor of the present invention, a ball milling dispersion process is adopted, and the particle size distribution is more uniform. In a preferred embodiment, in step S1, the rotation speed of the first ball milling dispersion is 400-500 rpm, and the time is 4-6 hours; preferably, the drying temperature is 90-95°C, and the time is 3-5 hours, so as to further remove the anhydrous ethanol in the material and prepare for subsequent sintering; more preferably, the sintering process includes a first sintering and a second sintering, and preferably the heating rate of the first sintering is 1-3°C / min, and the sintering temperature is 1-20°C / min. The sintering temperature is 400-480°C and the sintering time is 4-6h; the heating rate of the second sintering is preferably 1-3°C / min, the sintering temperature is 800-900°C and the sintering time is 2-6h. The first sintering under the above conditions can more smoothly form the transition state LATP precursor and prevent the subsequent remaining substances from affecting the formation process; the second sintering, on the one hand, makes the solid electrolyte more smoothly formed, and on the other hand, makes the pore-forming agent volatilize to form a porous structure, which is more convenient for the subsequent filling of the metal organic gel and further improves the ionic conductivity of the material.

[0022] As described above, the present invention dopes a certain proportion of pore-forming agent into the lithium titanium aluminum phosphate precursor for pore-forming sintering, obtains a pore structure on the surface of the lithium titanium aluminum phosphate precursor, and obtains porous lithium titanium aluminum phosphate. In a preferred embodiment, in step S2, the pore size of the porous lithium titanium aluminum phosphate obtained is 140nm~200um, and the porosity is 29~50%; preferably, the heating rate of the pore-forming sintering is 1~3℃ / min, the sintering temperature is 800~900℃, and the sintering time is 8~10h. In the above sintering Under the pore-forming process, the pore-forming agent can better play a pore-forming role and obtain a pore structure with a target pore size and porosity on the surface of the lithium aluminum titanium phosphate precursor; more preferably, before the pore-forming sintering, the mixed material is also subjected to the steps of second ball milling dispersion and tableting in sequence, and the second ball milling dispersion speed is preferably 400-500rpm, and the time is 6-8h, so that the mixed material can be mixed more fully, and the tableting pressure is preferably 1-2MPa, and the time is 40-50s, which is convenient for material shaping and performance testing.

[0023] In a preferred embodiment, in step S3, the naphthaldehyde is one or more of 1-naphthaldehyde, 1-hydroxy-2-naphthaldehyde and o-hydroxynaphthaldehyde; the hydrazine is 3,4,5-tribenzoylhydrazide; the acid is acetic acid; the solvent is ethanol; preferably, the molar ratio of naphthaldehyde to hydrazine is (1-2):1; more preferably, the Ca-containing 2+ The solution is one or more of calcium perchlorate, calcium chlorate and calcium hypochlorite, containing Co 2+ The solution is one or more of cobalt sulfate, cobalt carbonate and cobalt chloride. The above raw materials are more suitable for the preparation of the metal organic gel of the present invention, and are easy to obtain, which can further reduce the cost.

[0024] In order to make the reaction between the naphthalene material and hydrazine proceed more fully, in a preferred embodiment, in step S3, reflux is performed under stirring, the stirring speed is 200 to 300 r / min, and the reflux time is 20 to 24 h; preferably, the first metal-organic gel CaG is immersed in Co 3+ After being dissolved in the solution, it is dried at 55-65° C. for 4-5 h to obtain the second metal-organic gel CaCoG.

[0025] In order to further improve the impregnation effect of porous LATP in metal-organic gel, better reduce contact resistance and improve ion transfer efficiency, in a preferred embodiment, in step S4, the second metal-organic gel CaCoG is heated to 80-85°C for impregnation, the impregnation pressure is 0.25-0.35MPa, and the impregnation time is 2-3h; preferably, in step S4, after standing for 3-5h, it is dried at 55-65°C for 4-5h to obtain a modified lithium aluminum titanium phosphate solid electrolyte.

[0026] The inventor unexpectedly found during the research process that when the porous lithium aluminum titanium phosphate is immersed in the heated second metal organic gel CaCoG, if the immersion temperature is lower than 80°C and the time is less than 2h, too little metal-organic gel will enter the pore structure of the porous lithium aluminum titanium phosphate, and the effect of reducing contact resistance and improving ion transmission efficiency will not be achieved; if the immersion temperature is higher than 85°C and the time is greater than 3h, some compounds in the metal-organic gel will volatilize and decompose, which is also not conducive to obtaining a modified lithium aluminum titanium phosphate solid electrolyte with low contact resistance and high ion transmission efficiency. Therefore, the present invention limits the heating temperature of the metal-organic gel CaCoG to 80-85°C and the immersion time to 2-3h.

[0027] In another typical embodiment of the present invention, a modified lithium aluminum titanium phosphate solid electrolyte is provided, which is obtained by the preparation method of the present invention. Due to the use of the preparation method of the present invention, the obtained modified LATP material has low contact resistance and high ion transfer efficiency.

[0028] In another typical embodiment of the present invention, the application of the modified lithium aluminum titanium phosphate solid electrolyte in a lithium ion battery is provided, which can further reduce the contact resistance and improve the ion transfer efficiency.

[0029] In another typical embodiment of the present invention, a battery is provided, comprising a positive electrode, a negative electrode and an electrolyte, wherein the electrolyte comprises the above-mentioned modified lithium aluminum titanium phosphate solid electrolyte, and can have good cycle performance and rate performance.

[0030] The present application is further described in detail below in conjunction with specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in the present application.

[0031] Example 1

[0032] S1, by element Li:Al:Ti:PO4 3- Lithium dihydrogen phosphate, aluminum oxide, titanium dioxide, and ammonium dihydrogen phosphate were weighed at a molar ratio of 1.4:0.4:1.6:3, dispersed by ball milling at 400 rpm in anhydrous ethanol for 6 h, and dried at 90 °C for 5 h. After grinding, the temperature was increased to 400 °C at a rate of 2 °C / min and sintered for 6 h, and then the temperature was increased to 900 °C at the same heating rate and kept at this condition for 3 h. After sintering, the mixture was naturally cooled, crushed, and ground to obtain a LATP precursor.

[0033] S2. Add SeS2 powder equivalent to 36% of the mass of LATP precursor to the prepared LATP precursor powder, and disperse it by ball milling at 400 rpm for 8 h. Press the mixed powder at 1 MPa pressure for 45 s to obtain flaky LATP. Heat the prepared flakes to 900 °C at a rate of 2 °C / min and sinter for 8 h. After natural cooling, obtain a porous LATP sheet.

[0034] S3, preparing a metal-organic gel, dissolving 1-naphthaldehyde (10m mol), 3,4,5-tribenzoylhydrazide (10m mol), and acetic acid (10mL) in ethanol (200mL), stirring and refluxing at 200r / min for 24h, removing the generated precipitate, and recrystallizing in anhydrous ethanol to obtain an organic gel factor, and using the organic gel factor as a template, impregnating a calcium perchlorate solution to form a metal-organic gel CaG, and further using CaG as a template, impregnating a cobalt sulfate solution, and drying at 55°C for 5h to obtain a metal-organic gel CaCoG;

[0035] S4. Heat the metal-organic gel CuCoG to 80°C, place the porous LATP sheet in the gel, immerse it under a pressure of 0.3 MPa for 3 hours, stop heating and let it stand for 5 hours after immersion, and dry it at 55°C for 5 hours to obtain a modified LATP solid electrolyte material composited with a semi-solid metal-organic gel and LATP.

[0036] Example 2

[0037] S1, by element Li:Al:Ti:PO4 3- The molar ratio of the elements is 1.4:0.4:1.6:3. Lithium dihydrogen phosphate, aluminum oxide, titanium dioxide and ammonium dihydrogen phosphate are weighed, dispersed by ball milling at 400 rpm in anhydrous ethanol for 5 h, and dried at 90 °C for 4 h. After grinding, the temperature is increased to 420 °C at a rate of 2 °C / min and sintered for 4 h, and then the temperature is increased to 900 °C at the same heating rate and kept at this condition for 4 h. After sintering, the mixture is naturally cooled, crushed and ground to obtain a LATP precursor.

[0038] S2. Add SeS2 powder equivalent to 38% of the mass of LATP precursor to the prepared LATP precursor powder, and disperse it by ball milling at 450rpm for 7h. Press the mixed powder at 1MPa pressure for 45s to obtain flaky LATP. Heat the prepared flakes to 900℃ at a rate of 2℃ / min and sinter for 9h. After natural cooling, obtain porous LATP flakes.

[0039] S3, preparing a metal-organic gel, dissolving 1-naphthaldehyde (10m mol), 3,4,5-tribenzoylhydrazide (10m mol), and acetic acid (10mL) in ethanol (200mL), stirring and refluxing at 200r / min for 22h, removing the generated precipitate, and recrystallizing in anhydrous ethanol to obtain an organic gel factor, and using the organic gel factor as a template, impregnating a calcium perchlorate solution to form a metal-organic gel CaG, and further using CaG as a template, impregnating a cobalt sulfate solution, and drying at 60°C for 5h to obtain a metal-organic gel CaCoG;

[0040] S4. Heat the metal-organic gel CuCoG to 82°C, place the porous LATP sheet in the gel, immerse it under a pressure of 0.3 MPa for 2.5 hours, stop heating and let it stand for 4 hours after immersion, and dry it at 60°C for 5 hours to obtain a modified LATP solid electrolyte material composited with a semi-solid metal-organic gel and LATP.

[0041] Example 3

[0042] S1, by element Li:Al:Ti:PO4 3- The molar ratio of the elements is 1.4:0.4:1.6:3. Lithium dihydrogen phosphate, aluminum oxide, titanium dioxide and ammonium dihydrogen phosphate are weighed, dispersed by ball milling at 500 rpm in anhydrous ethanol for 6 hours, and dried at 90°C for 3 hours. After grinding, the temperature is increased to 450°C at a rate of 2°C / min and sintered for 4 hours, and then the temperature is increased to 850°C at the same heating rate and kept at this condition for 6 hours. After sintering, the mixture is naturally cooled, crushed and ground to obtain a LATP precursor.

[0043] S2. Add SeS2 powder equivalent to 40% of the mass of LATP precursor to the prepared LATP precursor powder, and disperse it by ball milling at 500 rpm for 6 hours. Press the mixed powder at 1 MPa pressure for 45 seconds to obtain a sheet of LATP. Heat the prepared sheet to 850°C at a rate of 2°C / min and sinter for 10 hours. After natural cooling, a porous LATP sheet is obtained.

[0044] S3, preparing a metal-organic gel, dissolving 1-naphthaldehyde (10m mol), 3,4,5-tribenzoylhydrazide (10m mol), and acetic acid (10mL) in ethanol (200mL), stirring and refluxing at 200r / min for 20h, removing the generated precipitate, and recrystallizing in anhydrous ethanol to obtain an organic gel factor, and using the organic gel factor as a template, impregnating a calcium perchlorate solution to form a metal-organic gel CaG, and further using CaG as a template, impregnating a cobalt sulfate solution, and drying at 65°C for 5h to obtain a metal-organic gel CaCoG;

[0045] S4. Heat the metal-organic gel CuCoG to 85°C, place the porous LATP sheet in the gel, immerse it under a pressure of 0.3 MPa for 2 hours, stop heating and let it stand for 3 hours after immersion, and dry it at 65°C for 5 hours to obtain a modified LATP solid electrolyte material composited with a semi-solid metal-organic gel and LATP.

[0046] Example 4

[0047] S1, by element Li:Al:Ti:PO4 3- The molar ratio of the elements is 1.4:0.4:1.6:3. Lithium dihydrogen phosphate, aluminum oxide, titanium dioxide and ammonium dihydrogen phosphate are weighed, dispersed by ball milling at 500 rpm in anhydrous ethanol for 4 h, and dried at 95 °C for 5 h. After grinding, the temperature is increased to 480 °C at a rate of 2 °C / min and sintered for 3 h, and then the temperature is increased to 800 °C at the same heating rate and kept at this condition for 6 h. After sintering, it is naturally cooled, crushed and ground to obtain the LATP precursor;

[0048] S2. Add SeS2 powder equivalent to 42% of the mass of LATP precursor to the prepared LATP precursor powder, and disperse it by ball milling at 450rpm for 6h. Press the mixed powder at 1MPa pressure for 45s to obtain flaky LATP. Heat the prepared flakes to 800℃ at a rate of 2℃ / min and sinter for 10h. After natural cooling, obtain porous LATP flakes.

[0049] S3, preparing a metal-organic gel, dissolving 1-naphthaldehyde (10m mol), 3,4,5-tribenzoylhydrazide (10m mol), and acetic acid (10mL) in ethanol (200mL), stirring and refluxing at 300r / min for 20h, removing the generated precipitate, and recrystallizing in anhydrous ethanol to obtain an organic gel factor, and using the organic gel factor as a template, impregnating a calcium perchlorate solution to form a metal-organic gel CaG, and further using CaG as a template, impregnating a cobalt sulfate solution, and drying at 65°C for 4h to obtain a metal-organic gel CaCoG;

[0050] S4. Heat the metal-organic gel CuCoG to 85°C, place the porous LATP sheet in the gel, immerse it under a pressure of 0.3 MPa for 3 hours, stop heating and let it stand for 5 hours after immersion, and dry it at 65°C for 4 hours to obtain a modified LATP solid electrolyte material composited with a semi-solid metal-organic gel and LATP.

[0051] Example 5

[0052] S1, by element Li:Al:Ti:PO4 3- The molar ratio of the elements is 1.4:0.4:1.6:3. Lithium dihydrogen phosphate, aluminum oxide, titanium dioxide and ammonium dihydrogen phosphate are weighed, dispersed by ball milling in anhydrous ethanol at 500 rpm for 5 h, and dried at 95 °C for 4 h. After grinding, the temperature is increased to 480 °C at a rate of 2 °C / min and sintered for 3 h, and then the temperature is increased to 900 °C at the same heating rate and kept at this condition for 4 h. After sintering, the mixture is naturally cooled, crushed and ground to obtain a LATP precursor.

[0053] S2. Add SeS2 powder equivalent to 45% of the mass of LATP precursor to the prepared LATP precursor powder, and disperse it by ball milling at 400 rpm for 6 hours. Press the mixed powder at 1 MPa pressure for 45 seconds to obtain a sheet of LATP. Heat the prepared sheet to 900°C at a rate of 2°C / min and sinter for 10 hours. After natural cooling, a porous LATP sheet is obtained.

[0054] S3, preparing a metal-organic gel, dissolving 1-naphthaldehyde (10m mol), 3,4,5-tribenzoylhydrazide (10m mol), and acetic acid (10mL) in ethanol (200mL), stirring and refluxing at 300r / min for 22h, removing the generated precipitate, and recrystallizing in anhydrous ethanol to obtain an organic gel factor, and using the organic gel factor as a template, impregnating a calcium perchlorate solution to form a metal-organic gel CaG, and further using CaG as a template, impregnating a cobalt sulfate solution, and drying at 60°C for 4h to obtain a metal-organic gel CaCoG;

[0055] S4. Heat the metal-organic gel CuCoG to 82°C, place the porous LATP sheet in the gel, immerse it under a pressure of 0.3 MPa for 2.5 hours, stop heating and let it stand for 5 hours after immersion, and dry it at 60°C for 4 hours to obtain a modified LATP solid electrolyte material composited with a semi-solid metal-organic gel and LATP.

[0056] Example 6

[0057] S1, by element Li:Al:Ti:PO4 3- The molar ratio of the elements is 1.5:0.5:1.5:3. Lithium dihydrogen phosphate, aluminum oxide, titanium dioxide and ammonium dihydrogen phosphate are weighed, dispersed by ball milling at 400 rpm in anhydrous ethanol for 6 h, and dried at 95 °C for 3 h. After grinding, the temperature is increased to 400 °C at a rate of 2 °C / min and sintered for 4 h, and then the temperature is increased to 900 °C at the same heating rate and kept at this condition for 5 h. After sintering, the mixture is naturally cooled, crushed and ground to obtain a LATP precursor.

[0058] S2. Add polymethyl methacrylate powder equivalent to 40% of the mass of LATP precursor to the prepared LATP precursor powder, and disperse by ball milling at 450 rpm for 7 h. Press the mixed powder at 1 MPa pressure for 45 s to obtain a sheet of LATP. Heat the prepared sheet to 900 °C at a rate of 2 °C / min and sinter for 8 h. After natural cooling, a porous LATP sheet is obtained.

[0059] S3, preparing a metal-organic gel, dissolving 1-naphthaldehyde (10m mol), 3,4,5-tribenzoylhydrazide (20m mol), and acetic acid (10mL) in ethanol (200mL), stirring and refluxing at 300r / min for 24h, removing the generated precipitate, and recrystallizing in anhydrous ethanol to obtain an organic gel factor, and using the organic gel factor as a template, impregnating a calcium perchlorate solution to form a metal-organic gel CaG, and further using CaG as a template, impregnating a cobalt sulfate solution, and drying at 55°C for 4.5h to obtain a metal-organic gel CaCoG;

[0060] S4. Heat the metal-organic gel CuCoG to 80°C, place the porous LATP sheet in the gel, immerse it under a pressure of 0.3 MPa for 2 hours, stop heating and let it stand for 3 hours after immersion, and dry it at 55°C for 4.5 hours to obtain a modified LATP solid electrolyte material composited with a semi-solid metal-organic gel and LATP.

[0061] Example 7

[0062] The difference between Example 7 and Example 1 is that in step S2, SeS2 powder equivalent to 30% of the mass of the LATP precursor is added to the prepared LATP precursor powder.

[0063] Example 8

[0064] The difference between Example 8 and Example 1 is that in step S2, SeS2 powder equivalent to 50% of the mass of the LATP precursor is added to the prepared LATP precursor powder.

[0065] Example 9

[0066] The difference between Example 9 and Example 1 is that in step S4, the metal-organic gel CuCoG is heated to 70° C., and the porous LATP sheet is placed in the gel and immersed at a pressure of 0.3 MPa for 1 hour.

[0067] Example 10

[0068] The difference between Example 10 and Example 1 is that in step S4, the metal-organic gel CuCoG is heated to 90° C., and the porous LATP sheet is placed in the gel and immersed for 4 hours at a pressure of 0.3 MPa.

[0069] Comparative Example 1

[0070] S1, by element Li:Al:Ti:PO4 3- Lithium dihydrogen phosphate, aluminum oxide, titanium dioxide, and ammonium dihydrogen phosphate were weighed at a molar ratio of 1.4:0.4:1.6:3, dispersed by ball milling at 400 rpm in anhydrous ethanol for 6 h, and dried at 90 °C for 5 h. After grinding, the temperature was increased to 400 °C at a rate of 2 °C / min and sintered for 6 h, and then the temperature was increased to 900 °C at the same heating rate and kept at this condition for 3 h. After sintering, the mixture was naturally cooled, crushed, and ground to obtain a LATP precursor.

[0071] S2. Add 36% of the mass of LATP precursor powder to the prepared LATP precursor powder, and disperse by ball milling at 400 rpm for 8 h. Press the mixed powder at 1 MPa for 45 s to obtain a sheet of LATP. Heat the prepared sheet to 900°C at a rate of 2°C / min and sinter for 8 h. After natural cooling, obtain a LATP sheet.

[0072] Comparative Example 2

[0073] S1, by element Li:Al:Ti:PO4 3- The molar ratio of the elements is 1.4:0.4:1.6:3. Lithium dihydrogen phosphate, aluminum oxide, titanium dioxide and ammonium dihydrogen phosphate are weighed, dispersed by ball milling at 400 rpm in anhydrous ethanol for 5 h, and dried at 90 °C for 4 h. After grinding, the temperature is increased to 420 °C at a rate of 2 °C / min and sintered for 4 h, and then the temperature is increased to 900 °C at the same heating rate and kept at this condition for 4 h. After sintering, the mixture is naturally cooled, crushed and ground to obtain a LATP precursor.

[0074] S2. Add SeS2 powder equivalent to 38% of the mass of LATP precursor to the prepared LATP precursor powder, and disperse it by ball milling at 450rpm for 7h. Press the mixed powder at 1MPa pressure for 45s to obtain flaky LATP. Heat the prepared flakes to 900℃ at a rate of 2℃ / min and sinter for 9h. After natural cooling, obtain porous LATP flakes.

[0075] S3, preparing metal-organic gel, dissolving 1-naphthaldehyde (10m mol), 3,4,5-tribenzoylhydrazide (10m mol), and acetic acid (10mL) in ethanol (200mL), stirring and refluxing at 200r / min for 22h, removing the generated precipitate, recrystallizing in anhydrous ethanol to obtain an organogel factor, and drying at 60°C for 5h to obtain an organogel G;

[0076] S4. Heat the organic gel G to 82°C, place the porous LATP sheet in the gel, immerse it under a pressure of 0.3 MPa for 2.5 hours, stop heating and let it stand for 4 hours after immersion, and dry it at 60°C for 5 hours to obtain a solid electrolyte material composed of a semi-solid metal-organic gel and LATP.

[0077] Performance test: NCM622 was used as the positive electrode material, battery-grade lithium sheet was used as the negative electrode material, and the prepared composite material was used as the solid electrolyte to assemble a simulated battery. The charge and discharge electrochemical window was 3.0-4.3V, and the high temperature performance test method was 55°C / 1C rate cycle. The materials prepared in the above Examples 1 to 10 and Comparative Examples 1 to 2 were made into batteries, and the battery performance test was carried out. The discharge specific capacity and cycle capacity retention rate are shown in Table 1.

[0078] Table 1

[0079]

[0080] As can be seen from the above, the battery made of the unmodified LATP solid electrolyte prepared in Comparative Example 1 has a discharge capacity of only 205.61 mAh / g at a rate of 0.2C, a discharge capacity of only 196.74 mAh / g at a rate of 1C, and a capacity retention rate of only 94.25% after 55°C / 50 cycles. Compared with Comparative Example 1, the battery made of the modified LATP solid electrolyte material prepared in Example 1 of the present invention has a discharge capacity of 225.42 mAh / g at a rate of 0.2C, a discharge capacity of 207.63 mAh / g at a rate of 1C, and a capacity retention rate of 99.87% after 55°C / 50 cycles, and the cycle performance is significantly improved.

[0081] The battery made of the modified LATP composite solid electrolyte of the organic gel without bimetallic modification prepared in Comparative Example 2 has a discharge capacity of only 198.94 mAh / g at 0.2C rate, a discharge capacity of only 176.85 mAh / g at 1C rate, and a capacity retention rate of only 93.46% after 55°C / 50 cycles. Compared with Comparative Example 2, the battery made of the modified LATP solid electrolyte material prepared in Example 2 of the present invention has a discharge capacity of 221.55 mAh / g at 0.2C rate, a discharge capacity of 206.47 mAh / g at 1C rate, and a capacity retention rate of 99.67% after 55°C / 50 cycles, and the cycle performance is significantly improved.

[0082] Compared with the test results of the comparative example, the materials prepared by the embodiments of the present invention are pore-forming the lithium titanium aluminum phosphate substrate by doping a certain proportion of pore-forming agent, and then the synthesized metal-organic gel is heated to change its thixotropy so that it enters the pore structure of the lithium titanium aluminum phosphate, and is statically cured in the lithium titanium aluminum phosphate material, and the solid lithium titanium aluminum phosphate electrolyte is combined with the semi-solid bimetallic-organic gel. Under the action of the bimetallic-organic gel, the modified lithium titanium aluminum phosphate solid electrolyte obtained can achieve a tighter combination when in contact with the battery pole piece, so that the basic resistance between the solid electrolyte and the pole piece is smaller, thereby improving the battery efficiency. Moreover, due to the embedding of the bimetallic organic gel in the modified lithium titanium aluminum phosphate solid electrolyte of each embodiment of the present invention, compared with the all-solid electrolyte in the comparative example, the transfer of electrons in the electrolyte can be accelerated, the ion transmission efficiency is higher, the ion conductivity is higher, and the overall cycle performance and rate performance of the battery are significantly improved. In summary, the material structure performance prepared by each embodiment of the present invention is better, the ion conductivity is better, it has excellent electrochemical properties, and can improve the safety performance of NCM622.

[0083] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a modified lithium aluminum titanium phosphate solid electrolyte, characterized in that: The following steps are involved: Step S1, obtaining a lithium aluminum titanium phosphate precursor; Step S2, adding a pore-forming agent to the lithium aluminum titanium phosphate precursor to obtain a mixed material, and subjecting the mixed material to pore-forming sintering to obtain porous lithium aluminum titanium phosphate; Step S3, dissolving naphthaldehyde, hydrazine and acid in a solvent, refluxing and filtering in sequence to obtain a filtrate, and recrystallizing the filtrate to obtain an organic gel factor; and immersing the organic gel factor in a Ca-containing 2+ In the solution, a first metal organic gel CaG is obtained; The first metal organic gel CaG is immersed in a Co-containing 3+ In the solution, a second metal organic gel CaCoG is obtained; Step S4, immersing the porous lithium aluminum titanium phosphate in the second metal organic gel CaCoG under heating, and obtaining the modified lithium aluminum titanium phosphate solid electrolyte after standing; Wherein, the pore-forming agent is SeS2 and / or polymethyl methacrylate, and the mass of the added pore-forming agent is 36-45% of the mass of the lithium titanium aluminum phosphate precursor.

2. The preparation method according to claim 1, characterized in that: The step S1 comprises: weighing a lithium source, an aluminum source, a titanium source and a phosphorus source, performing a first ball milling dispersion in ethanol, and then sequentially drying and sintering to obtain the lithium aluminum titanium phosphate precursor.

3. The preparation method according to claim 2, characterized in that: Among the lithium source, the aluminum source, the titanium source and the phosphorus source, Li:Al:Ti:PO4 3- The molar ratio of the elements is (1+x):x:(2-x):3, 0.4≤x≤0.

5.

4. The preparation method according to claim 3, characterized in that: The lithium source is one or more of lithium carbonate, lithium dihydrogen phosphate and lithium hydroxide, the aluminum source is aluminum dihydrogen phosphate and / or aluminum oxide, the titanium source is titanium dioxide, and the phosphorus source is ammonium dihydrogen phosphate and / or aluminum dihydrogen phosphate.

5. The preparation method according to claim 2, characterized in that: In the step S1, the first ball milling dispersion has a rotation speed of 400 to 500 rpm and a time of 4 to 6 hours.

6. The preparation method according to claim 5, characterized in that: The drying temperature is 90-95° C. and the drying time is 3-5 hours.

7. The preparation method according to claim 6, characterized in that: The sintering process includes a first sintering and a second sintering. The heating rate of the first sintering is 1-3°C / min, the sintering temperature is 400-480°C, and the sintering time is 3-6h; the heating rate of the second sintering is 1-3°C / min, the sintering temperature is 800-900°C, and the sintering time is 2-6h.

8. The preparation method according to claim 1 or 2, characterized in that: In the step S2, the pore size of the porous lithium aluminum titanium phosphate is 140nm-200um, and the porosity is 29-50%.

9. The preparation method according to claim 8, characterized in that: The heating rate of the pore-forming sintering is 1-3°C / min, the sintering temperature is 800-900°C, and the sintering time is 8-10h.

10. The preparation method according to claim 9, characterized in that: Before the pore-forming sintering, the mixed material is also subjected to the steps of second ball milling dispersion and tableting in sequence. The second ball milling dispersion has a rotation speed of 400-500 rpm and a time of 6-8 hours. The tableting pressure is 1-2 MPa and the time is 40-50 seconds.

11. The preparation method according to claim 1 or 2, characterized in that: In step S3, the naphthaldehyde is one or more of 1-naphthaldehyde, 1-hydroxy-2-naphthaldehyde and o-hydroxynaphthaldehyde; the hydrazine is 3,4,5-tribenzoylhydrazide; the acid is acetic acid; and the solvent is ethanol.

12. The preparation method according to claim 11, characterized in that: The molar ratio of the naphthaldehyde to the hydrazine is (1-2):

1.

13. The preparation method according to claim 12, characterized in that: The Ca-containing 2+ The solution is one or more of calcium perchlorate, calcium chlorate and calcium hypochlorite, wherein the Co 2+ The solution is one or more of cobalt sulfate, cobalt carbonate and cobalt chloride.

14. The preparation method according to claim 1 or 2, characterized in that: In the step S3, the reflux is performed under stirring, the stirring speed is 200 to 300 r / min, and the reflux time is 20 to 24 h.

15. The preparation method according to claim 14, characterized in that: The first metal-organic gel CaG is impregnated into the Co 3+ After being dissolved in the solution, the mixture is dried at 55-65° C. for 4-5 h to obtain the second metal-organic gel CaCoG.

16. The preparation method according to claim 1 or 2, characterized in that: In the step S4, the second metal organic gel CaCoG is heated to 80-85°C for the impregnation, the impregnation pressure is 0.25-0.35 MPa, and the impregnation time is 2-3 hours.

17. The preparation method according to claim 16, characterized in that: In the step S4, after standing for 3 to 5 hours, the mixture is dried at 55 to 65° C. for 4 to 5 hours to obtain the modified lithium aluminum titanium phosphate solid electrolyte.

18. A modified lithium aluminum titanium phosphate solid electrolyte, characterized in that: Obtained by the preparation method according to any one of claims 1 to 17.

19. Use of the modified lithium aluminum titanium phosphate solid electrolyte according to claim 18 in lithium ion batteries.

20. A battery comprising a positive electrode, a negative electrode and an electrolyte, characterized in that: The electrolyte comprises the modified lithium aluminum titanium phosphate solid electrolyte as claimed in claim 18.

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