CN-122000440-A - Surface modification method of LLZO solid electrolyte powder

CN122000440ACN 122000440 ACN122000440 ACN 122000440ACN-122000440-A

Abstract

The invention relates to the technical field of solid electrolytes, in particular to a surface modification method of LLZO solid electrolyte powder, which comprises the steps of carrying out surface chemical analysis on original LLZO powder to obtain a lithium carbonate index for representing the content of impurities on the surface of the original LLZO powder, judging the qualification of the original powder based on the lithium carbonate index, mixing the qualified original powder with a modified precursor solution, reacting under preset conditions to form a uniform gel coating layer on the surface of the powder to obtain gel coating intermediate powder, carrying out characterization on the gel coating intermediate powder to obtain a coating quality index, judging the qualification of coating based on the coating quality index, carrying out heat treatment on the gel coating intermediate powder qualified in coating to obtain surface modified LLZO powder, carrying out electrochemical performance test on the surface modified LLZO powder to obtain a performance evaluation index, and judging the qualification of surface modification. The invention improves the electrochemical stability of LLZO powder.

Inventors

MENG XIAOXU
WANG RUIDONG
LU JIAFEI
LI YING
CHEN MIAOMIAO

Assignees

内蒙古镧铈稀材科技有限公司

Dates

Publication Date: 20260508
Application Date: 20260115

Claims (10)

1. A method for surface modification of LLZO solid state electrolyte powder, comprising: step S1, carrying out surface chemical analysis on original LLZO powder to obtain a lithium carbonate index used for representing the content of surface impurities; Step S2, based on a comparison result of the lithium carbonate index and a preset threshold, judging the qualification of the original powder, and under the condition of disqualification, determining a pretreatment strategy of the original powder based on a difference value of the lithium carbonate index and the preset threshold; Step S3, mixing qualified original powder with a modified precursor solution, and reacting under preset conditions to form a uniform gel coating layer on the surface of the powder to obtain gel coated intermediate powder, wherein the preset conditions comprise stirring for a preset duration at a preset stirring speed and a preset heating program under the protection of inert atmosphere; S4, obtaining a coating quality index by characterizing the gel coating intermediate powder, judging the qualification of coating based on the comparison result of the coating quality index and a preset quality index, and adjusting the stirring speed and the heating rate in the step S3 based on the variation coefficient of the thickness of the coating layer under the condition of disqualification; s5, performing heat treatment on gel-coated intermediate powder qualified in coating, crystallizing a coating layer and performing limited interface interdiffusion with the surface of the LLZO matrix to form a chemically combined composite interface layer, so as to obtain surface modified LLZO powder; and S6, performing electrochemical performance test on the surface modified LLZO powder obtained in the step S5 to obtain a performance evaluation index, judging the qualification of the surface modification according to the comparison result of the performance evaluation index and a preset evaluation index, and reducing the heat treatment temperature of the step S5 or increasing the coating reaction time of the step S3 based on the ion conductivity and the critical current density under the condition of disqualification.
2. The surface modification method of LLZO solid state electrolyte powder according to claim 1, wherein the lithium carbonate index R is a ratio of a sum of two characteristic peak intensities of lithium carbonate asymmetric stretching vibration and lithium carbonate out-of-plane bending vibration to an internal standard peak intensity.
3. The surface modification method of LLZO solid electrolyte powder according to claim 2, characterized in that in the step S2, failure of the original powder is determined based on the comparison result that the lithium carbonate index is greater than or equal to a preset threshold value, and a pretreatment strategy of the original powder is determined based on the difference between the lithium carbonate index and the preset threshold value.
4. The method for surface modification of LLZO solid electrolyte powder according to claim 3, wherein in the step S2, a pretreatment strategy of the raw powder is determined based on a difference between the lithium carbonate index and a preset threshold value, comprising, If the lithium carbonate index difference is smaller than the preset difference, determining that the pretreatment strategy of the original powder is to automatically execute a heat cleaning procedure; if the lithium carbonate index difference is greater than or equal to the preset difference, determining that the pretreatment strategy of the original powder is to automatically execute a heat cleaning and mechanical activation combined program; The lithium carbonate index difference value is the difference value between the lithium carbonate index and a preset threshold value.
5. The surface modification method of LLZO solid state electrolyte powder according to claim 4, wherein the process of step S3 comprises: step S31, preparing a modified precursor solution; Step S32, under the protection of inert atmosphere and stirring, adding qualified original powder into a precursor solution to form uniform suspension, and carrying out mixing treatment to enable the precursor to be uniformly adsorbed on the surfaces of powder particles; Step S33, introducing a hydrolysis medium into the suspension system, and adjusting the reaction temperature to promote the precursor adsorbed on the surface to generate hydrolysis-polycondensation reaction, so as to form a uniform amorphous gel coating layer on the surface of the powder in situ; and step S34, carrying out solid-liquid separation on the reacted system, and washing and primarily drying the obtained solid product to obtain intermediate powder with the gel layer coated on the surface.
6. The method for modifying the surface of the LLZO solid electrolyte powder according to claim 5, wherein in the step S4, the coating failure is determined based on the comparison result that the coating quality index is smaller than the preset quality index, and the preset condition parameter of the step S3 is adjusted based on the coating thickness variation coefficient.
7. The surface modification method of LLZO solid state electrolyte powder according to claim 6, wherein the coating quality index is determined according to coating coverage and coating layer thickness uniformity index.
8. The surface modification method of LLZO solid state electrolyte powder according to claim 7, characterized in that in the step S4, it is determined to increase the preset stirring speed in the step S3 based on a condition that the coating layer thickness variation coefficient is greater than or equal to a first preset variation coefficient and less than a second preset variation coefficient; And determining to synchronously reduce the temperature rising rate of the hydrolysis-polycondensation reaction in the step S3 on the basis of increasing the preset stirring speed based on the condition that the coating layer thickness variation coefficient is larger than or equal to a second preset variation coefficient.
9. The surface modification method of LLZO solid electrolyte powder according to claim 8, wherein the adjustment range of the preset stirring speed in the step S3 is positively correlated with a difference between the coefficient of variation and the first preset coefficient of variation.
10. The surface modification method of LLZO solid state electrolyte powder according to claim 9, characterized in that the process of step S6 comprises: obtaining ion conductivity and critical current density by performing electrochemical performance test on the surface modified LLZO powder; calculating and obtaining a performance evaluation index according to the ion conductivity and the critical current density; comparing the performance evaluation index with a preset evaluation index; And judging that the surface modification is unqualified based on the comparison result that the performance evaluation index is smaller than a preset evaluation index, and reducing the heat treatment temperature of the step S5 based on the condition that the ion conductivity is smaller than the preset conductivity, or increasing the coating reaction duration of the step S3 based on the condition that the critical current density is smaller than the preset current density.

Description

Surface modification method of LLZO solid electrolyte powder Technical Field The invention relates to the technical field of solid electrolyte, in particular to a surface modification method of LLZO solid electrolyte powder. Background Solid state lithium batteries are considered as the core development of next generation energy storage technologies due to their potentially high energy density and intrinsic safety. Among the many solid electrolyte materials, LLZO has been attracting attention due to its high room temperature ionic conductivity, good thermodynamic stability for lithium metal, and a wide electrochemical window. However, LLZO still faces severe interfacial challenges in practical applications, which are largely due to its powder surface characteristics. First, the lithium element in LLZO is extremely active in chemical nature, and when the powder is exposed to air, it reacts rapidly with H 2 O and CO 2, forming insulating Li 2CO3 and LiOH layers on its surface. The insulating layer can severely impede the transport of lithium ions between the electrolyte particles, resulting in a significant decrease in overall ionic conductivity and a substantial increase in interface impedance between the electrolyte and the electrode. Second, even if treated in an inert atmosphere, the solid-solid contact between LLZO and the lithium metal anode is still not ideal, the interface wettability is poor, the contact resistance is high, and uneven growth and penetration of lithium dendrites are easily induced during the cycle. Furthermore, when LLZO is in direct contact with high voltage cathode materials (e.g., liCoO 2, NCM, etc.), unwanted interdiffusion and side reactions occur at the interface, forming a high-resistance mesophase, deteriorating the long cycle performance of the battery. The Chinese patent application publication No. CN118336097A discloses a preparation method of LLZO solid electrolyte material, which comprises the steps of preparing lithium lanthanum zirconium oxide powder material, mixing raw materials such as lithium hydroxide monohydrate, lanthanum oxide, zirconium dioxide and the like to form a wet mixture, drying, presintering, grinding and high-temperature sintering to prepare sample powder, preparing LLZO solid electrolyte sheet, weighing a proper amount of sample powder, and tabletting, sintering and the like to obtain the LLZO solid electrolyte material. However, the prior art does not contemplate passivation or protection of its highly active surface by surface modification, resulting in continuous and uncontrolled formation of Li 2CO3 in the resultant LLZO powder during subsequent storage, transportation and any air exposure prior to battery assembly. This not only significantly attenuates the material properties over time, but also results in poor consistency of the final battery product in terms of performance batch, low reproducibility, and severely affects the reliability of its industrial application. Disclosure of Invention Therefore, the invention provides a surface modification method of LLZO solid electrolyte powder, which is used for solving the problem that the material performance is remarkably attenuated with time caused by surface modification of the LLZO solid electrolyte powder in the prior art. To achieve the above object, the present invention provides a surface modification method of LLZO solid electrolyte powder, comprising: step S1, carrying out surface chemical analysis on original LLZO powder to obtain a lithium carbonate index used for representing the content of surface impurities; Step S2, based on a comparison result of the lithium carbonate index and a preset threshold, judging the qualification of the original powder, and under the condition of disqualification, determining a pretreatment strategy of the original powder based on a difference value of the lithium carbonate index and the preset threshold; Step S3, mixing qualified original powder with a modified precursor solution, and reacting under preset conditions to form a uniform gel coating layer on the surface of the powder to obtain gel coated intermediate powder, wherein the preset conditions comprise stirring for a preset duration at a preset stirring speed and a preset heating program under the protection of inert atmosphere; S4, obtaining a coating quality index by characterizing the gel coating intermediate powder, judging the qualification of coating based on the comparison result of the coating quality index and a preset quality index, and adjusting the stirring speed and the heating rate in the step S3 based on the variation coefficient of the thickness of the coating layer under the condition of disqualification; s5, performing heat treatment on gel-coated intermediate powder qualified in coating, crystallizing a coating layer and performing limited interface interdiffusion with the surface of the LLZO matrix to form a chemically combined composite interface layer, so as to obtain surfac