CN-117550576-B - NASICON solid electrolyte, low-temperature synthesis method thereof and solid battery

Abstract

The invention mainly discloses a method for synthesizing NASICON solid electrolyte at low temperature, which comprises the following steps of uniformly stirring Na x M 2 (PO 4 ) 3 in a lithium source solution, reacting at low temperature, and cooling to obtain the NASICON solid electrolyte Li x M 2 (PO 4 ) 3 . The Li + /Na + ion exchange is carried out in the lithium-rich aqueous solution at low temperature, so that the prepared solid electrolyte inherits the original stable structure and excellent ion conductivity of the precursor material, the phase structure and the ion conductivity in the Li x M 2 (PO 4 ) 3 material are regulated and controlled from the synthesis source, the coordination environment of Li + is optimally regulated through the low-temperature ion exchange environment, the migration energy barrier is reduced, the migration path is widened, and the Li x M 2 (PO 4 ) 3 solid electrolyte with excellent performance is prepared. The invention also discloses the solid electrolyte prepared by the method and a battery containing the solid electrolyte.

Inventors

• ZHENG JUNBO
• ZHANG JIARUI
• ZHENG SHAN

Assignees

• 湖南荷力士新能源科技有限公司

Dates

Publication Date

20260512

Application Date

20230926

Claims (4)

1. 1. A method for synthesizing NASICON solid electrolyte at low temperature, which is characterized by comprising the following steps: (1) The preparation of the Na x M 2 (PO 4 ) 3 precursor comprises the steps of uniformly mixing a sodium source, an M source and a phosphate-containing phosphorus source according to chemical proportion, and sintering, wherein the sintering is a two-stage sintering process, namely, firstly, heating to 450-600 ℃ at the speed of 5-7 ℃ per min, sintering for 7-15 h, then heating to 900-1400 ℃ at the speed of 6-9 ℃ per min, and sintering for 8-15 h; (2) Uniformly stirring the Na x M 2 (PO 4 ) 3 precursor prepared in the step (1) in a lithium source solution taking deionized water as a solvent, carrying out Li + /Na + ion exchange reaction at a low temperature of 60-100 ℃, cooling after the reaction is finished, washing, filtering and drying to obtain a NASICON solid electrolyte Li x M 2 (PO 4 ) 3 , wherein M is at least one of Zr, ti and Al, x is more than or equal to 1 and less than or equal to 1.5, and the molar ratio of Na in Na x M 2 (PO 4 ) 3 to lithium in the lithium source solution is 1:3-5.
2. 2. The method for synthesizing NASICON solid electrolyte according to claim 1, wherein the lithium source is one or more of lithium hydroxide, lithium chloride, and lithium acetate.
3. 3. The method for synthesizing NASICON solid state electrolyte according to claim 1, wherein the sodium source is at least one of sodium acetate and its hydrate, sodium carbonate and its hydrate, and sodium hydroxide, the M source is at least one of acetate and its hydrate, carbonate and its hydrate, and oxide of M, and the phosphorus source is at least one of phenylphosphoric acid, orthophosphoric acid, and monoammonium phosphate.
4. 4. The method for synthesizing a NASICON solid electrolyte at a low temperature according to claim 3, wherein the molar ratio of sodium in the sodium source, M in the M source and phosphorus in the phosphorus source is 1-1.5:2:3.

Description

NASICON solid electrolyte, low-temperature synthesis method thereof and solid battery Technical Field The invention belongs to the technical field of electrolyte, in particular to a solid electrolyte of a lithium ion battery, and particularly relates to a method for synthesizing a super-ion conductor NASICON solid electrolyte at low temperature. Background Lithium ion batteries are the main power source of new energy automobiles, however, the safety of the lithium ion batteries is always limited by the risks caused by inflammable, reactive and volatile liquid electrolytes and the combustion and explosion of the batteries themselves under extreme conditions. The use of highly stable solid electrolytes is an important approach to solving the above-mentioned safety problems. As a core component of a lithium ion solid-state battery, a solid-state electrolyte is required to have high ion conductivity, low ion diffusion resistance, a wide electrochemical window, good thermodynamic stability, sufficient mechanical flexibility, and excellent chemical suitability. Super ion conductor type (NASICON) solid state electrolytes are of great interest due to their high ionic conductivity, excellent chemical and thermodynamic stability, good positive electrode suitability, extremely low raw material cost and manufacturing cost, especially Na xM2(PO4)3 solid state electrolytes have great potential in solid state sodium ion battery applications due to their stable phase structure and higher ionic conductivity. However, in the lithium ion battery field, the size of the transmission channel of NASICON-type solid electrolyte is not suitable for lithium ion migration, mainly because Li + occupies a hexahedral position with low energy in the conventional high-temperature calcination synthesis process of Li xM2(PO4)3 material, and the ion channel in the migration process is very narrow and the migration energy barrier is large, so that the ion conductivity of the material is poor. In order to improve the application defect of NASCION type Li xM2(PO4)3 solid electrolyte in lithium ion all-solid batteries, hetero element doping is mostly adopted to optimize Li xM2(PO4)3, grain boundary phase engineering is carried out on a negative electrode material and an electrolyte interface, a composite positive electrode is applied to a positive electrode material and the electrolyte interface, and the like. However, the inherent drawbacks of the prior art methods to the high temperature synthesis process of Li xM2(PO4)3 solid state electrolytes are difficult to avoid and hardly demonstrate the advantages of NASICON solid state electrolytes. Patent document with publication number CN109742449a discloses a preparation method of NASICON type solid electrolyte, which comprises uniformly mixing raw materials, performing solid phase reaction at room temperature to obtain a precursor, and melting at high temperature by using metal salt generated In situ In the precursor as a flux, wherein a=al, in, b=zr, hf. The NASICON type solid electrolyte obtained by the preparation method does not regulate and control the diffusion behavior of Li + from the synthesis source, the synthesis process inevitably involves high-temperature long-time calcination, and the involved equipment is complex, the energy consumption is high, the process is complex, and the NASICON type solid electrolyte is not suitable for large-scale production. Patent document with publication number CN110165292A discloses a modified NASICON type solid electrolyte tablet and a preparation method thereof, wherein the chemical general formula of the NASICON type solid electrolyte tablet is Li 1+xAl(Ti/Ge)2-x(PO4)3, a lithium source, a titanium source or a germanium source, an aluminum source and a phosphorus source are weighed according to a molar ratio, mixed and ball-milled, dried and sintered to obtain solid electrolyte powder, and then mixed with lithium salt with low boiling point, pressed and sintered to obtain the modified NASICON type solid electrolyte tablet. The NASICON solid electrolyte sheet prepared by the method does not solve the problems of high lithium ion migration energy barrier and narrow migration path of the material, and the room temperature conductivity is not obviously improved. Disclosure of Invention Aiming at the defects and shortcomings in the prior art, the invention aims to provide a method for synthesizing NASICON solid electrolyte at low temperature. In order to achieve the above object, the present invention provides the following specific technical solutions. A method for synthesizing a NASICON solid electrolyte at low temperature comprises the following steps of uniformly stirring Na xM2(PO4)3 in a lithium source solution, reacting at a low temperature of 60-100 ℃, and cooling to obtain the NASICON solid electrolyte Li xM2(PO4)3, wherein M is at least one of Zr, ti and Al, and x is more than or equal to 1 and less than or equal to 1.5. In a further preferred e