A method for synthesizing solid electrolyte material

Abstract

The present invention discloses a method for synthesizing a solid electrolyte material. The method comprises: low-temperature oxidation of a LATP precursor; short-term high-temperature sintering of the precursor in a protective atmosphere; low-temperature oxidation removal; and dynamic high-temperature sintering for carbon removal. The solid electrolyte nano-lithium aluminum titanium phosphate (LATP) material produced by the present method exhibits high ionic conductivity. Lithium-ion batteries prepared from this material exhibit low low-temperature DCR, high capacity utilization, and excellent cycling performance.

Description

Technical Field

[0001] The present invention relates to the technical field of solid electrolyte materials for lithium ion batteries, in particular to a method for synthesizing solid electrolyte materials, and more particularly to a method for synthesizing nano solid electrolyte lithium aluminum titanium phosphate materials. Background Art

[0002] Lithium-ion batteries have been widely used in electric vehicles, power tools, and energy storage due to their high energy density, lightweight, high voltage, safety, and low environmental pollution. Currently, commercial lithium-ion batteries mostly use organic liquid electrolytes or gel electrolytes, which are flammable and explosive, posing a significant safety hazard. Furthermore, lithium metal anodes are prone to the formation of lithium dendrites, which can pierce the separator, causing internal short circuits and thermal runaway. Therefore, conventional lithium-ion batteries cannot use lithium metal as the anode, which limits further improvements in battery energy density.

[0003] Solid-state electrolytes, due to their high thermal stability and effective suppression of lithium anode dendrite growth, can improve the safety of lithium-ion batteries. Solid-state electrolytes are primarily categorized into three main systems: polymer electrolytes, oxide electrolytes, and sulfide electrolytes. Oxide electrolytes, due to their high energy density, excellent stability, long cycle life, and low cost, have attracted considerable research attention. Lithium aluminum titanium phosphate (LATP), a typical oxide solid-state electrolyte, has also become a research focus. Particle size plays a crucial role in ionic conductivity. Furthermore, particle size affects the density of the solid-state electrolyte membrane, which in turn affects the overall lithium-ion conductivity of the solid-state battery, hindering its capacity and rate performance. Therefore, the synthesis of nanoscale LATP is crucial. The main methods for LATP synthesis include solid-phase and sol-gel methods. LATP synthesized by solid-phase methods generally results in large particles and is prone to agglomeration. Even post-processing methods such as airflow milling and / or ball milling cannot achieve particle sizes below 100 nm, effectively preventing true nanoscale performance. Summary of the Invention

[0004] In view of the deficiencies in the prior art, the present invention aims to provide a synthesis method and application of a solid electrolyte material.

[0005] The method for synthesizing the solid electrolyte material provided by the present invention comprises the following steps:

[0006] 1) The LATP precursor is crushed, then placed in an oxidizing atmosphere, heated to reaction temperature 1, kept warm, and then cooled to room temperature;

[0007] 2) heating the material obtained in 1) to reaction temperature 2 in an inert atmosphere, keeping the temperature, and then cooling to room temperature;

[0008] 3) crushing the material obtained in 2), then placing it in an oxidizing atmosphere, heating it to reaction temperature 3, keeping it warm, and then cooling it to room temperature;

[0009] 4) The material obtained in step 3) is placed in a dual-temperature zone reactor, first evacuated, then oxygen is introduced from the bottom, then evacuated again, then ventilated from the top, and then vibrated. The above process is repeated for a period of time, and then cooled to room temperature to obtain nano-LATP material.

[0010] The present invention prepares nano-LATP through a four-step sintering method. The first step is to oxidize the LATP precursor at low temperature to carbonize the organic matter in the precursor, while removing most of the free water and bound water in the organic matter, enriching lithium, aluminum, titanium and phosphorus. The second step is to sinter the precursor at high temperature for a short time in a protective atmosphere, so that the lithium, aluminum, titanium and phosphorus react to form amorphous LATP. The high-temperature sintering time is short and the protective atmosphere is present, so the surface of the generated amorphous LATP is coated with a large amount of carbon, which can effectively inhibit the growth of LATP and maintain the primary particle size ≤10nm. The third step is low-temperature oxidation and carbon removal. By adopting a stepped temperature insulation oxidation, it can effectively prevent the heat released by carbon decomposition from causing local excessive temperature, which leads to further growth of LATP particles. The low-temperature oxidation and carbon removal process does not completely remove the carbon on the LATP surface, but still retains a small amount of carbon. The fourth step is dynamic high-temperature sintering and carbon removal. The dynamic high-temperature sintering method is used to treat LATP. On the one hand, it can prevent the agglomeration of multiple nano-LATP particles and cause excessive particle growth. On the other hand, it can fully remove carbon and further improve the crystallinity of LATP.

[0011] In step 1) of the above method, the chemical formula of the LATP precursor is: Li 1+x Al x Ti 2-x (PO4)3, where x is 0.3 to 0.5;

[0012] Specifically, the LATP precursor is prepared by a method comprising the following steps:

[0013] Obtain a lithium source, an aluminum source, a titanium source, a phosphorus source, an acidic chelating agent and an alcohol solvent; prepare the acidic chelating agent into an acidic chelating agent aqueous solution, add the titanium source to the acidic chelating agent aqueous solution, and stir for 2 to 6 hours to obtain a first mixed solution; then add the lithium source and the phosphorus source to the first mixed solution, and stir for 1 to 5 hours to obtain a second mixed solution; then add the aluminum source to the second mixed solution, and stir for 1 to 5 hours to obtain a third mixed solution; add the alcohol solvent to the third mixed solution to obtain a liquid sol; adjust the pH of the liquid sol to 6 to 8 to obtain a neutral liquid sol, and dry the neutral liquid sol to obtain a LATP precursor.

[0014] Wherein, the lithium source is one or more of lithium carbonate, lithium nitrate, lithium hydroxide and lithium oxide;

[0015] The aluminum source is one or more of aluminum carbonate, aluminum nitrate, aluminum oxide, aluminum hydroxide and aluminum chloride;

[0016] The titanium source is one or more of titanic acid, tetraethyl titanate, tetrabutyl titanate and isopropyl titanate;

[0017] The phosphorus source is one or more of phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate and ammonium phosphate;

[0018] The acidic complexing agent is one or more of citric acid, malic acid, malonic acid, succinic acid, succinic acid, glycolic acid, glycine, lactic acid, tartaric acid and ethylenediaminetetraacetic acid;

[0019] The alcohol solvent is one or more of anhydrous ethanol, ethylene glycol and glycerol;

[0020] The molar ratio of lithium source, aluminum source, titanium source and phosphorus source conforms to the following chemical formula: Li 1+x Al x Ti 2-x (PO4)3, where x is 0.3 to 0.5;

[0021] The mass concentration of the acidic complexing agent aqueous solution is 40 to 60 wt.%;

[0022] The molar ratio of the sum of the moles of the acidic complexing agent and the alcohol solvent to the metal cation in the lyosol is (6-10):1;

[0023] The molar ratio of the acidic complexing agent to the alcohol solvent is 1:1;

[0024] The drying temperature of the neutral liquid sol is 100-150° C., and the drying time is 10-15 hours.

[0025] In step 1), the particle size of the LATP precursor after crushing is controlled to be Dmin ≥ 0.8 μm, D10 ≥ 1.2 μm, D50 2.0 to 10 μm, D90 ≤ 15 μm, and Dmax ≤ 20 μm;

[0026] The oxidizing atmosphere is a mixture of air and oxygen, wherein the oxygen concentration is controlled at 21-95%;

[0027] Reaction temperature 1 is 300-500°C, and the holding time is 5-20h;

[0028] In step 2), the inert atmosphere is a mixture of one or more gases selected from nitrogen, helium, neon, argon, krypton, xenon, and radon;

[0029] Reaction temperature 2 is 600-800°C, and the holding time is 0.5-2.0h;

[0030] In step 3), the particle size of the material after crushing is controlled to be Dmin ≥ 30 nm, D10 ≥ 50 nm, D50 is 100 to 300 nm, D90 ≤ 500 nm, and Dmax ≤ 1.0 μm;

[0031] The oxidizing atmosphere is a mixture of air and oxygen, wherein the oxygen concentration is controlled at 21-95%;

[0032] Reaction temperature 3 is a step temperature, with a controlled temperature range of 300-500°C, and a holding time of 3-10 hours for each step temperature; specifically, it can be heated to 400°C, 450°C, and 475°C in sequence, with each temperature being held for 5 hours;

[0033] In step 4), the temperature of the upper temperature zone of the dual-temperature zone reactor is controlled at 650-750°C, and the temperature of the lower temperature zone is controlled at 750-850°C;

[0034] The pressure in the reaction chamber is maintained at -0.04 to -0.08 MPa by pumping air, then blowing oxygen from the bottom for 1 to 10 seconds, with the oxygen pressure at 0.2 to 0.8 MPa, followed by a 2 to 10 minute standstill, and then pumping air again to maintain the pressure in the chamber at -0.04 to -0.08 MPa, then blowing oxygen from the top for 1 to 10 seconds, and then a 0.5 to 5 minute standstill, and vibrating the furnace body with an air hammer once, and repeating this process 100 to 500 times. The resulting nano-LATP material is a secondary particle formed by the agglomeration of primary particles, wherein the primary particle size is ≤10 nm and the secondary particle size is ≤40 nm; it is well dispersed and has an ion conductivity of ≥7×10 -4 S / cm.

[0035] The nano-lithium aluminum titanium phosphate LATP material prepared by the above method and its application in lithium-ion batteries also fall within the protection scope of the present invention.

[0036] The present invention also provides a lithium-ion battery, which uses the nano-lithium aluminum titanium phosphate LATP material as a solid electrolyte.

[0037] The beneficial effects of the present invention are:

[0038] 1. The present invention uses a four-step sintering method to prepare nano-LATP. First, a LATP precursor is oxidized at low temperature. The organic matter in the precursor is carbonized, removing most of the free and bound water in the organic matter, and enriching lithium, aluminum, titanium, and phosphorus. Second, the precursor is sintered at high temperature for a short time in a protective atmosphere, causing the lithium, aluminum, titanium, and phosphorus to react and form amorphous LATP. Due to the short high-temperature sintering time and the presence of a protective atmosphere, the surface of the resulting amorphous LATP is coated with a large amount of carbon, which effectively inhibits LATP growth and maintains a primary particle size of ≤10nm. Third, low-temperature oxidation and carbon removal are performed. This step uses a stepped temperature insulation oxidation method to effectively prevent the release of heat from carbon decomposition, which can effectively prevent local overheating and further growth of LATP particles. To ensure good dispersibility of nano-LATP and reduce agglomeration, the third step of low-temperature oxidation and carbon removal does not completely remove the carbon on the LATP surface; a small amount of carbon will remain. Fourth, dynamic high-temperature sintering and carbon removal are performed. The dynamic high-temperature sintering method is used to treat LATP. On the one hand, it can avoid the agglomeration of multiple nano-LATP particles causing excessive particle growth. On the other hand, it can fully remove carbon and further improve the crystallinity of LATP.

[0039] 2. The nano-LATP synthesized in this invention has a primary particle size of ≤10nm, a secondary particle size of ≤40nm, and is well dispersed, with an ion conductivity of ≥7×10 -4 S / cm.

[0040] 3. The equipment investment of the present invention is small, the process is controllable, and the batch stability of the product is good. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 The XRD patterns of the intermediates and finished products in the process of preparing the nano-LATP material in Example 1 of the present invention are shown.

[0042] Figure 2 This is a TEM image of the nano-LATP material prepared in Example 1 of the present invention.

[0043] Figure 3 This is a TEM image of LATP prepared in Comparative Example 1 of the present invention.

[0044] Figure 4 Comparison of XRD spectra of LATP materials prepared in Example 1 of the present invention and Comparative Example 1.

[0045] Figure 5 The LATP-coated LiNi prepared in Example 5 of the present invention 0.88 Co 0.07 Mn 0.05 SEM image of O2 single crystal ternary material.

[0046] Figure 6 The LATP-coated LiNi prepared in Example 5 of the present invention0.88 Co 0.07 Mn 0.05 TEM image of O2 single crystal ternary material.

[0047] Figure 7 The LATP-coated LiNi prepared in Comparative Example 8 of the present invention 0.88 Co 0.07 Mn 0.05 SEM image of O2 single crystal ternary material.

[0048] Figure 8 The LATP-coated LiNi prepared in Comparative Example 8 of the present invention 0.88 Co 0.07 Mn 0.05 TEM image of O2 single crystal ternary material.

[0049] Figure 9 The LATP-coated LiNi prepared in Comparative Example 9 of the present invention 0.88 Co 0.07 Mn 0.05 TEM image of O2 single crystal ternary material. DETAILED DESCRIPTION

[0050] The present invention will be further described in detail below in conjunction with specific embodiments. The examples provided are only for illustrating the present invention and are not intended to limit the scope of the present invention. The examples provided below can serve as a guide for further improvements by those skilled in the art and are not intended to limit the present invention in any way.

[0051] Unless otherwise specified, the experimental methods in the following examples are conventional methods and were performed according to the techniques or conditions described in the literature in the field or according to the product instructions. The materials and reagents used in the following examples, unless otherwise specified, were all commercially available.

[0052] The first aspect of the present invention discloses a method for synthesizing nano-lithium aluminum titanium phosphate material, which specifically comprises the following steps:

[0053] S1, crushing the LATP precursor, then placing it in an oxidizing atmosphere, heating it to reaction temperature 1, keeping it warm, and then cooling it to room temperature;

[0054] S2, heating the material obtained in step S1 to reaction temperature 2 in an inert atmosphere, keeping the temperature, and then cooling to room temperature;

[0055] S3, crushing the material obtained in S2, then placing it in an oxidizing atmosphere, heating it to reaction temperature 3, keeping it warm, and then cooling it to room temperature;

[0056] S4, taking the material obtained in step S3 and placing it in a dual-temperature zone reactor, first evacuating the air, then introducing oxygen from the bottom, evacuating the air again, then ventilating the top, and then vibrating. The above process is repeated for a period of time, and the nano-LATP material is obtained after cooling to room temperature.

[0057] The present invention uses a four-step sintering method to prepare nano-LATP. First, a LATP precursor is oxidized at low temperature. The organic matter in the precursor is carbonized, removing most of the free water and bound water in the organic matter, and enriching lithium, aluminum, titanium, and phosphorus. Second, the precursor is sintered at high temperature for a short time in a protective atmosphere, causing the lithium, aluminum, titanium, and phosphorus elements to react and form amorphous LATP. Due to the short high-temperature sintering time and the presence of a protective atmosphere, the surface of the generated amorphous LATP is coated with a large amount of carbon, which can effectively inhibit LATP growth and maintain a primary particle size of ≤10nm. Third, low-temperature oxidation and carbon removal are carried out. This step uses stepped temperature insulation oxidation to effectively prevent the heat released by carbon decomposition from causing local excessive temperatures and leading to further growth of LATP particles. To ensure that the nano-LATP has good dispersibility and reduce agglomeration, the third step of low-temperature oxidation and carbon removal does not completely remove the carbon on the LATP surface, and a small amount of carbon will still remain. Fourth, dynamic high-temperature sintering and carbon removal are carried out. The dynamic high-temperature sintering method is used to treat LATP. On the one hand, it can prevent the agglomeration of multiple nano-LATP particles and cause excessive particle growth. On the other hand, it can fully remove carbon and further improve the crystallinity of LATP. The nano-LATP synthesized by this invention has a primary particle size of ≤10nm and a secondary particle size of ≤40nm, and is well dispersed, with an ionic conductivity of ≥7×10 -4 S / cm.

[0058] Furthermore, the chemical formula of the LATP precursor in step S1 is: Li 1+x Al x Ti 2-x (PO4)3, where x is 0.3-0.5, is prepared according to the method described in patent CN202211268119.8.

[0059] Furthermore, in step S1, the particle size of the LATP precursor after crushing is controlled to be Dmin≥0.8μm, D10≥1.2μm, D50 is 2.0-10μm, D90≤15μm, and Dmax≤20μm;

[0060] Furthermore, in steps S1 and S3, the oxidizing atmosphere is a mixture of air and oxygen, wherein the oxygen concentration is controlled at 21 to 95%;

[0061] Furthermore, in step S1, the reaction temperature 1 is 300-500° C., and the holding time is 5-20 h;

[0062] Furthermore, the inert atmosphere in step S2 is a mixture of one or more gases selected from nitrogen, helium, neon, argon, krypton, xenon and radon;

[0063] Furthermore, in step S2, the reaction temperature 2 is 600-800° C., and the holding time is 0.5-2.0 h;

[0064] Furthermore, in step S3, the particle size of the material after crushing is controlled to be Dmin≥30nm, D10≥50nm, D50 is 100-300nm, D90≤500nm, and Dmax≤1.0μm;

[0065] Furthermore, in step S3, the reaction temperature 3 is a step temperature, the temperature range is controlled at 300-500° C., and the holding time of each step temperature is 3-10 hours;

[0066] Furthermore, in step S4, the reaction furnace is divided into two temperature zones, the temperature of the upper temperature zone is controlled at 650-750°C, and the temperature of the lower temperature zone is controlled at 750-850°C;

[0067] Furthermore, in step S4, the air is pumped out to maintain the air pressure in the reaction furnace chamber at -0.04 to -0.08 MPa, and then oxygen is blown into the reaction furnace chamber from the bottom for 1 to 10 seconds, the oxygen pressure is 0.2 to 0.8 MPa, and then the reaction furnace chamber is allowed to stand for 2 to 10 minutes. The air is then pumped out to maintain the air pressure in the reaction furnace chamber at -0.04 to -0.08 MPa, and then oxygen is blown into the reaction furnace chamber from the top for 1 to 10 seconds, and the reaction furnace chamber is allowed to stand for 0.5 to 5 minutes. The furnace body is vibrated once with an air hammer, and this is repeated 100 to 500 times.

[0068] Another aspect of the present invention provides the use of the nano-lithium aluminum titanate phosphate (LATP) material in a lithium-ion battery, where the nano-lithium aluminum titanate phosphate (LATP) material serves as a solid electrolyte for the lithium-ion battery. The nano-lithium aluminum titanate phosphate (LATP) material has high ionic conductivity, and the lithium-ion battery prepared from the nano-lithium aluminum titanate phosphate (LATP) material exhibits low low-temperature DCR, high capacity utilization, and excellent cycling performance.

[0069] Example 1

[0070] The LATP precursor was prepared according to the method described in Example 1 of patent CN202211268119.8. The specific operation was as follows: lithium carbonate, aluminum carbonate, tetraethyl titanate, and phosphoric acid were prepared according to the mass ratio of elements Li:Al:Ti:P=1.3:0.3:1.7:3. At the same time, citric acid and anhydrous ethanol were prepared according to the mass ratio (citric acid + anhydrous ethanol): (Li + +Al 3+ +Ti 4+)=7:1, with a mass ratio of citric acid to anhydrous ethanol of 1:1. Once prepared, citric acid is first prepared into a 40% wt citric acid solution. Subsequently, tetraethyl titanate, lithium carbonate, phosphoric acid, aluminum carbonate, and anhydrous ethanol are added in four steps, stirring continuously for 3 hours, 2 hours, 2 hours, and 1 hour, respectively, to obtain a lyosol. Ammonia is added to the lyosol to adjust the pH to 7.0. The lyosol is then dried in a 110°C oven for 2 hours to obtain the LATP precursor.

[0071] The LATP precursor was air flow milled to control the particle size D50 to 5.0 μm (Dmin = 0.85 μm, D10 = 1.52 μm, D50 = 5.0 μm, D90 = 10.54 μm, Dmax = 17.59 μm), and then placed in dry compressed air (oxygen concentration of 25%), heated to 400 ° C at a heating rate of 2 ° C / min, and kept warm for 8 hours. After the end of the heat preservation, it was naturally cooled to room temperature to obtain a pretreated LATP precursor;

[0072] The pretreated LATP precursor was heated to 700°C at a rate of 10°C / min in a nitrogen atmosphere, kept at this temperature for 1.0 h, and then cooled to room temperature by nitrogen air cooling to obtain carbon-coated amorphous LATP;

[0073] The carbon-coated amorphous LATP was crushed using a jet mill and the D50 particle size was controlled to 188 nm (Dmin = 41 nm, D10 = 65 nm, D50 = 188 nm, D90 = 471 nm, Dmax = 723 nm). The product was then placed in dry compressed air (oxygen concentration was 25%) and heated to 400 ° C, 450 ° C, and 475 ° C at a heating rate of 2 ° C / min. Each temperature was kept for 5 h and then naturally cooled to room temperature.

[0074] Finally, the LATP was placed in a dual-temperature reactor with an upper temperature zone of 700°C and a lower temperature zone of 800°C. The reactor was first evacuated to reduce the pressure in the chamber to -0.06 MPa. Oxygen was then introduced from the bottom for 4 seconds at a pressure of 0.4 MPa. The reactor was allowed to stand for 5 minutes. The reactor was then evacuated again to reduce the pressure to -0.06 MPa. Oxygen was introduced from the top for 4 seconds. The reactor was allowed to stand for 2 minutes, and the reactor was vibrated once with an air hammer. These steps were repeated 200 times. The reactor was then naturally cooled to room temperature to obtain highly dispersible nano-LATP powder.

[0075] The pretreated LATP precursor was subjected to protective atmosphere high temperature sintering, low temperature gradient oxidation and dynamic high temperature sintering to obtain intermediates and finished products for XRD characterization, such as Figure 1It can be found that the pretreated LATP precursor is amorphous LATP after sintering in a protective atmosphere, and then the crystallinity of LATP is improved after low-temperature gradient oxidation. Finally, after dynamic high-temperature sintering, LATP has good crystallinity.

[0076] Figure 2 This is the TEM image of the prepared nano-LATP material.

[0077] Comparative Example 1

[0078] Lithium carbonate, aluminum carbonate, tetraethyl titanate, and phosphoric acid were mixed in a mass ratio of Li:Al:Ti:P = 1.3:0.3:1.7:3. The mixture was then heated to 700°C in dry compressed air (with an oxygen concentration of 25%) at a rate of 2°C / min, held for 10 hours, and allowed to cool naturally to room temperature. The mixture was then crushed using a jet mill to a particle size D50 of 200 nm. This yielded LATP powder prepared by the solid-phase method.

[0079] Figure 3 TEM image of the prepared LATP.

[0080] Compare Figure 2 and Figure 3 It was found that the LATP in Example 1 was secondary particles agglomerated from primary particles, with a primary particle size of 6 nm and a secondary particle size of 25 nm. However, the LATP particles synthesized in Comparative Example 1 had different sizes, and the general particle size was larger. The average particle size was measured to be 180 nm.

[0081] Figure 4 The XRD spectra of the LATP materials prepared in Example and Comparative Example 1 are shown in FIG. Figure 4 It can be seen that the substances synthesized by both are LATP phase.

[0082] Example 2

[0083] After the LATP precursor is crushed by air flow powder, low-temperature oxidation is performed, and the sintering temperature is increased to 500° C. The other steps are the same as those in Example 1.

[0084] Comparative Example 2

[0085] After the LATP precursor is crushed by air flow powder, low-temperature oxidation is performed, and the sintering temperature is increased to 600° C. The other steps are the same as those in Example 1.

[0086] Example 3

[0087] The high-temperature sintering holding time of the pretreated LATP precursor at 700° C. in a nitrogen atmosphere was extended to 2.0 h. The other steps were the same as those in Example 1.

[0088] Comparative Example 3

[0089] The pretreated LATP precursor was sintered at 700° C. for 1 h in dry compressed air (oxygen concentration of 25%). Other steps were the same as those in Example 1.

[0090] Comparative Example 4

[0091] The high-temperature sintering holding time of the pretreated LATP precursor at 700° C. in a nitrogen atmosphere was extended to 5 h. The other steps were the same as those in Example 1.

[0092] Example 4

[0093] The carbon-coated amorphous LATP was placed in dry compressed air and heated to 400°C, 450°C, and 475°C at a heating rate of 2°C / min, each temperature was maintained for 9 hours, and then naturally cooled to room temperature. The other steps were the same as in Example 1.

[0094] Comparative Example 5

[0095] The carbon-coated amorphous LATP was placed in dry compressed air and heated to 400°C, 450°C, and 475°C at a heating rate of 2°C / min, each temperature was maintained for 20 hours, and then naturally cooled to room temperature. The other steps were the same as in Example 1.

[0096] Comparative Example 6

[0097] After the carbon-coated amorphous LATP was oxidized at a gradient temperature and low temperature, it was placed in an oxygen atmosphere and heated to 700° C. at a heating rate of 2° C. / min and kept at that temperature for 5 h. The other steps were the same as in Example 1.

[0098] Comparative Example 7

[0099] LATP was prepared using the method of Example 3 in patent CN202211268119.8.

[0100] test

[0101] 1. The LATP samples prepared in Examples 1-4 and Comparative Examples 1-6 were characterized by TEM. With the help of NanoMeasurer1.2 software, the above TEM images were imported into the software, the scale was set, and then the length of each particle was measured, measured in the longest direction, and finally the average length of all the measured particles was calculated; the secondary particles were large particles composed of multiple primary particles, and the TEM images showed that there were a large number of "black" primary particles inside the secondary particles; the primary average particle size and the secondary average particle size were obtained by measuring the lengths of the primary particles and the secondary particles and calculating the average value.

[0102] 2. The LATP materials prepared in Examples 1-4 and Comparative Examples 1-6 were placed in a mold and pressed at 18 MPa for 5 minutes to form a disc with a diameter of 10 mm and a thickness of 3 mm. The disc was then placed in a muffle furnace and heated to 950°C at a rate of 5°C / min for 5 hours. After the heating period, the disc was naturally cooled to room temperature. After sintering, the disc was polished with sandpaper until smooth and the surface residue was removed to obtain the corresponding solid electrolyte sheet. The solid electrolyte sheets of Examples 1-4 and Comparative Examples 1-6 obtained above were respectively subjected to gold spraying treatment to a thickness of ∼30 nm. After gold spraying, the disc was polished with sandpaper and then placed in a battery mold to obtain a test sample. The ionic conductivity of the above samples at 25°C was tested by AC impedance spectroscopy. The specific test results are shown in Table 1.

[0103] Table 1 shows the primary average particle size, secondary average particle size and ionic conductivity data of the LATP materials obtained in the above examples and comparative examples:

[0104] Table 1

[0105]

[0106] It can be seen from Table 1 that although the materials prepared in Example 1 and Comparative Example 2 are both LATP phases, the ionic conductivity of the two is quite different, with the former being 4.89×10 -4 S / cm.

[0107] In Comparative Example 2, compared with Examples 1-2, the low-temperature oxidation temperature is increased, resulting in the growth of primary particles and the decrease of ionic conductivity.

[0108] In Comparative Example 3, compared with Example 1, the high-temperature sintering atmosphere is changed and air is introduced, which will lead to more carbon loss and weaken the ability of carbon to inhibit the growth of LATP particles. As a result, the LATP particles grow and the ionic conductivity decreases.

[0109] Compared with Examples 1 and 3, the high-temperature sintering time in the protective atmosphere of Comparative Example 4 was prolonged, resulting in further growth of the particles and reduced ionic conductivity.

[0110] In Comparative Example 5, compared with Examples 1 and 4, the low-temperature decarbonization time is prolonged, resulting in further growth of the particles and reduced ionic conductivity.

[0111] In Comparative Example 6, compared with Example 1, the dynamic high-temperature sintering is changed to static sintering, which increases the contact between particles, causes the LATP particles to grow further, and reduces the ionic conductivity.

[0112] In Comparative Example 7, the sintering system of the LATP precursor is different from that in Example 1, resulting in larger LATP particle size, lower ionic conductivity, and reduced surface carbon content.

[0113] Example 5

[0114] The nano-LATP synthesized in Example 1 was used to coat LiNi 0.88 Co 0.07 Mn 0.05 O2 single crystal ternary material, the coating amount of LATP is 0.5% of the mass of the single crystal ternary material. The specific coating process is: take 1000gLiNi 0.88 Co 0.07 Mn 0.05 The O2 single crystal ternary material and 5g of LATP synthesized in Example 1 were added to a 3L polyethylene barrel, and then 500g of alumina balls with a diameter of 12mm were added according to a material-ball ratio of 2:1. After sealing, the materials were mixed using a 3D mixer for 3h. The mixed materials were placed in an oxygen atmosphere, heated from room temperature to 550℃, and kept warm for 5h. After the end of the heat preservation, they were naturally cooled to room temperature to obtain nano-LATP-coated LiNi 0.88 Co 0.07 Mn 0.05 O2 single crystal ternary material, and conduct battery charging and full battery performance evaluation.

[0115] Comparative Example 8

[0116] Nano-LATP synthesized in Comparative Example 1 was used to coat LiNi 0.88 Co 0.07 Mn 0.05 For O2 single crystal ternary material, the LATP coating amount is 0.5% of the mass of the single crystal ternary material, and the battery performance evaluation is carried out.

[0117] Comparative Example 9

[0118] Nano-LATP coated LiNi synthesized in Comparative Example 7 0.88 Co 0.07 Mn 0.05 For O2 single crystal ternary material, the LATP coating amount is 0.5% of the mass of the single crystal ternary material, and the battery performance evaluation is carried out.

[0119] Example 6

[0120] 1. The nano-LATP in Example 5 and Comparative Example 7 were coated with LiNi 0.88 Co 0.07 Mn 0.05 The O2 single crystal ternary material, conductive agent SP and binder PVDF are prepared in a mass ratio of 97.5:1:1.5 using NMP as solvent to make the electrode, which is then coated on carbon-coated aluminum foil, dried at 100°C for 5 hours, and compacted on a roller press to obtain the positive electrode.

[0121] Lithium metal sheets were used as negative electrodes, 1M LiPF6 solution was used as electrolyte, and Cellgard 2300 was used as separator. These were assembled into button cells with the above-mentioned positive electrodes. Charge and discharge were performed at a rate of 0.2C within a cut-off voltage range of 2.8 to 4.35 V. The results are shown in Table 2.

[0122] 2. The nano-LATP in Example 5 and Comparative Example 7 were coated with LiNi 0.88 Co 0.07 Mn 0.05 O2 single crystal ternary material, conductive agent CNTs, and binder PVDF are mixed in a mass ratio of 98:1:1 with NMP as solvent, and the solid content is controlled to 70%. Then it is coated on the current collector aluminum foil, and the single surface density is controlled to 215g / m 2 The compaction density of the pole piece after roller pressing is 3.60g / cm 3 A 3Ah soft-pack battery was assembled with a NP ratio of 1.13, matched to a silicon-carbon anode, using a 1M LiPF6 solution as the electrolyte and Cellgard 2300 as the separator. The electrochemical performance of the product is shown in Table 2.

[0123] Example 5 and Comparative Example 8 respectively use LATP coated LiNi prepared in Example 1 and Comparative Example 1 0.88 Co 0.07 Mn 0.05 O2 single crystal ternary material, the obtained sample is scanned and characterized as follows Figure 5 and Figure 7 , the transmission characterization is performed as Figure 6 and Figure 8 It was found that the LATP synthesized in Example 1 could be evenly coated on the surface of the material, while the LATP synthesized in Comparative Example 1 coated the material unevenly and showed an island-like distribution.

[0124] Since LATP belongs to the lithium-poor phase, it will react with the residual alkali on the surface of the ternary material at high temperature, thereby reducing the residual alkali content of the material. As can be seen from Table 2, the residual alkali content of Comparative Example 8 is higher than that of Example 5, mainly because the latter is evenly coated and reacts with more residual alkali, while the former is unevenly coated, and the probability of reaction with residual alkali is reduced. In addition, the ternary material capacity of the LATP prepared in Example 1 coated in Example 5 is higher, the cycle performance and low-temperature power performance are better, and the DSC peak decomposition temperature is higher, which is all related to the uniform coating and high ionic conductivity. LATP is a fast ion conductor, and its coating on the surface of the ternary material will increase the ionic conductivity of the material, and uniform coating is more conducive to the material capacity and power performance. And uniform coating can reduce the contact area between the ternary material and the electrolyte, reduce the occurrence of side reactions, and also increase the thermal failure temperature of the ternary material.

[0125] Comparative Example 9: LiNi coated with LATP prepared in Comparative Example 70.88 Co 0.07 Mn 0.05 O2 single crystal ternary material, the obtained sample is characterized by transmission as follows Figure 9 Compared with Example 5, it was found that the LATP synthesized in Comparative Example 7 was not evenly coated on the material surface, and some areas of the material surface were exposed.

[0126] As shown in Table 2, the residual alkali content in Comparative Example 9 is higher than that in Example 5, mainly because the former cannot be coated evenly, and the probability of reacting with the residual alkali on the surface of the material is reduced. 0.88 Co 0.07 Mn 0.05 Compared to Example 5, the O2 single-crystal ternary material exhibits lower capacity, poorer cycling performance and low-temperature power performance, and a lower DSC peak decomposition temperature, all of which are related to uneven coating and low ionic conductivity. The uniformity of LATP coating is related to its surface carbon content, which helps nano-LATP disperse more easily during the coating process of the positive electrode material.

[0127] Table 2

[0128]

[0129] The present invention has been described in detail above. For those skilled in the art, without departing from the purpose and scope of the present invention, and without the need to carry out unnecessary experimental conditions, the present invention can be implemented in a wide range under equivalent parameters, concentrations and conditions. Although the present invention provides specific embodiments, it should be understood that further improvements can be made to the present invention. In short, according to the principles of the present invention, this application is intended to include any changes, uses or improvements to the present invention, including changes that depart from the disclosed scope in this application and are made using conventional techniques known in the art.

Claims

1. A method for synthesizing a solid electrolyte material, characterized in that: The method comprises the following steps: 1) The LATP precursor is crushed, then placed in an oxidizing atmosphere, heated to reaction temperature 1, kept warm, and then cooled to room temperature; 2) heating the material obtained in 1) to reaction temperature 2 in an inert atmosphere, keeping the temperature, and then cooling to room temperature; 3) crushing the material obtained in 2), then placing it in an oxidizing atmosphere, heating it to reaction temperature 3, keeping it warm, and then cooling it to room temperature; 4) The material obtained in step 3) is placed in a dual-temperature zone reactor, and the air is first pumped out, and then oxygen is introduced from the bottom, and then the air is pumped out again, and then the air is ventilated from the top, and then the reactor is vibrated. The above process is repeated for a period of time, and the reactor is cooled to room temperature to obtain the nano-LATP material; In step 1), the chemical formula of the LATP precursor is: Li 1+x Al x Ti 2-x (PO4)3, where x is 0.3 to 0.5; In step 1), the reaction temperature 1 is 300-500°C and the holding time is 5-20h; In step 2), the reaction temperature 2 is 600-800°C, and the holding time is 0.5-2.0h; In step 3), the reaction temperature 3 is a step temperature, the temperature range is controlled at 300-500°C, and the holding time of each step temperature is 3-10 hours; In step 4), the temperature of the upper temperature zone of the dual-temperature zone reactor is controlled at 650-750°C, and the temperature of the lower temperature zone is controlled at 750-850°C; Vacuum the chamber to maintain the pressure at -0.04~-0.08MPa, then blow oxygen in from the bottom for 1~10s, the oxygen pressure is 0.2~0.8MPa, then let it stand for 2~10min, then evacuate the chamber to maintain the pressure at -0.04~-0.08MPa, then blow oxygen in from the top for 1~10s, let it stand for 0.5~5min, vibrate the furnace body with an air hammer once, and repeat 100~500 times.

2. The method according to claim 1, characterized in that In step 1), the LATP precursor is prepared by a method comprising the following steps: Obtaining a lithium source, an aluminum source, a titanium source, a phosphorus source, an acidic complexing agent, and an alcohol solvent; preparing the acidic complexing agent into an acidic complexing agent aqueous solution, adding the titanium source to the acidic complexing agent aqueous solution, and stirring for 2 to 6 hours to obtain a first mixed solution; Then, the lithium source and the phosphorus source are added to the first mixed solution, and stirred for 1 to 5 hours to obtain a second mixed solution; Then, the aluminum source is added to the second mixed solution and stirred for 1 to 5 hours to obtain a third mixed solution; An alcohol solvent is added to the third mixed solution to obtain a lyosol; the pH of the lyosol is adjusted to 6-8 to obtain a neutral lyosol; the neutral lyosol is dried to obtain a LATP precursor.

3. The method according to claim 2, characterized in that The lithium source is one or more of lithium carbonate, lithium nitrate, lithium hydroxide and lithium oxide; The aluminum source is one or more of aluminum carbonate, aluminum nitrate, aluminum oxide, aluminum hydroxide and aluminum chloride; The titanium source is one or more of titanic acid, tetraethyl titanate, tetrabutyl titanate and isopropyl titanate; The phosphorus source is one or more of phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate and ammonium phosphate; The acidic complexing agent is one or more of citric acid, malic acid, malonic acid, succinic acid, succinic acid, glycolic acid, glycine, lactic acid, tartaric acid and ethylenediaminetetraacetic acid; The alcohol solvent is one or more of anhydrous ethanol, ethylene glycol and glycerol; The molar ratio of lithium source, aluminum source, titanium source and phosphorus source conforms to the following chemical formula: Li 1+x Al x Ti 2-x (PO4)3, where x is 0.3 to 0.5; The mass concentration of the acidic complexing agent aqueous solution is 40-60wt.%; The molar ratio of the sum of the moles of the acidic complexing agent and the alcohol solvent to the metal cation in the lyosol is (6-10):1; The molar ratio of the acidic complexing agent to the alcohol solvent is 1:1; The drying temperature of the neutral liquid sol is 100-150° C., and the drying time is 10-15 hours.

4. The method according to claim 1, wherein: In step 1), the particle size of the LATP precursor after crushing is controlled to be Dmin ≥ 0.8 μm, D10 ≥ 1.2 μm, D50 is 2.0-10 μm, D90 ≤ 15 μm, and Dmax ≤ 20 μm; The oxidizing atmosphere is a mixture of air and oxygen, wherein the oxygen concentration is controlled at 21-95%.

5. The method according to claim 1, wherein: In step 2), the inert atmosphere is a mixture of one or more gases selected from nitrogen, helium, neon, argon, krypton, xenon and radon.

6. The method according to claim 1, wherein: In step 3), the particle size of the material after crushing is controlled to be Dmin ≥ 30 nm, D10 ≥ 50 nm, D50 is 100-300 nm, D90 ≤ 500 nm, and Dmax ≤ 1.0 μm; The oxidizing atmosphere is a mixture of air and oxygen, wherein the oxygen concentration is controlled at 21-95%.

7. A solid electrolyte nano-lithium aluminum titanium phosphate (LATP) material prepared by the method according to any one of claims 1 to 6, wherein the nano-LATP material is a secondary particle agglomerated from primary particles, wherein the primary particle size is ≤10 nm and the secondary particle size is ≤40 nm; and the ionic conductivity is ≥7×10-4 S / cm.

8. Use of the solid electrolyte nano-lithium aluminum titanium phosphate (LATP) material according to claim 7 in lithium-ion batteries.

9. A lithium-ion battery, comprising the solid electrolyte nano-lithium aluminum titanium phosphate (LATP) material according to claim 7 as a solid electrolyte.

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