In-situ formed core-shell structure solid electrolyte material and preparation method and application thereof

Abstract

The invention belongs to the technical field of battery solid electrolyte materials, and discloses an in-situ formed core-shell structure solid electrolyte material and a preparation method and application thereof. A shell layer of the material is Li1 + xAlxTi2-x (PO4) 3 with + 4 valence Ti, a core layer of the material is Li3AlxTi2-x (PO4) 3 with + 3 valence Ti, the shell layer material is obtained through in-situ oxidation of the core layer material, the two materials have the same lattice system, the shell layer and the core layer are tightly combined, and the phenomenon that a shell layer prepared through traditional coating is prone to falling off is solved. The core layer of the material is a lithium-rich state material, 2-x Li < + > in the material structure is separated and contributes active lithium ions under high potential, the material has high ionic conductivity, electronic conductivity and lithium supplement characteristics, and the shell layer material ensures good air stability and application stability; when the material is applied to a lithium ion battery, the discharge capacity, the first-circle coulombic efficiency, the rate capability and the cycling stability of the battery can be remarkably improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of battery solid-state electrolyte materials, and particularly relates to an in-situ formed core-shell structure solid-state electrolyte material and a preparation method and application thereof. BACKGROUND

[0002] With large-scale commercial application of lithium ion batteries, traditional liquid lithium ion batteries cannot meet the demand for energy density in the fields of power, energy storage, electronic consumption and the like. Especially in the field of power batteries, with continuous popularization and update of electric vehicles, higher requirements are put forward for energy density, power density and safety of lithium ion batteries. Solid-state batteries are a new form of lithium ion secondary batteries, which utilize a solid-state electrolyte to partially or completely replace traditional electrolyte to form a semi / full solid-state battery. The solid-state electrolyte is a key component of the solid-state battery, which has excellent ionic conductivity, non-flammability, non-corrosion, non-volatility, non-leakage and the like, and helps the solid-state lithium battery to realize high safety, energy density, power density and long cycle life.

[0003] Research on solid-state electrolyte materials is still in the exploratory stage. At present, mainstream material systems are divided into oxides, sulfides and polymers, among which oxides have better chemical stability than sulfides and higher ionic conductivity than polymers. Lithium aluminum titanium phosphate (LATP) material is considered to be one of the materials with the most commercial prospects.

[0004] At present, LATP materials are mainly applied in electrode material coating, positive and negative electrode sheet blending, separator coating and composite film formation, and the application is mainly for semi-solid-state batteries. In the above applications, LATP mainly improves the cycle stability and safety performance of semi-solid-state batteries through its chemical stability, thermal chemical stability and good ionic conductivity; but it does not have active lithium ions, and the electronic conductivity is usually below 10 -10 S / cm, which limits the battery capacity and rate performance in some application scenarios (such as positive electrode coating and electrode sheet blending). Therefore, it is necessary to develop LATP materials with high ionic conductivity and multi-functionality to meet the needs of practical applications. SUMMARY

[0005] In order to overcome the shortcomings and deficiencies of the prior art, the primary purpose of the present application is to provide an in-situ formed core-shell structure solid-state electrolyte material. The material of the present application is composed of lithium aluminum titanium phosphate material containing titanium elements with different valence positions to form a core-shell structure, and the shell material is formed in-situ from the core material, which has good structural stability, high ionic conductivity, electronic conductivity and lithium supplement characteristics, and good air stability and application stability.

[0006] Another purpose of the present application is to provide a preparation method of the above-mentioned core-shell structure solid-state electrolyte material.

[0007] Another object of the present application is to provide an application of the core-shell structure solid-state electrolyte material.

[0008] The object of the present application is achieved by the following solutions: A core-shell structure solid-state electrolyte material formed in situ, comprising a Li3Al x Ti 2-x (PO4)3 material, and a Li x Ti 2-x (PO4)3 material on the surface of the Li 1+x Al x Ti 2-x (PO4)3 material, wherein 0≤x≤1.

[0009] The particle size D50 of the solid-state electrolyte material is 100-1000 nm.

[0010] In the solid-state electrolyte material, the Li3Al x Ti 2-x (PO4)3 is the core layer, the Li 1+x Al x Ti 2-x (PO4)3 is the shell layer; the Li 1+x Al x Ti 2-x (PO4)3 shell layer has a thickness of 30-400 nm.

[0011] The core-shell structure solid-state electrolyte material of the present application has a shell layer of Li 1+x Al x Ti 2-x (PO4)3 material, and a core layer of Li3Al x Ti 2-x (PO4)3 material, the shell layer material is obtained by in-situ oxidation of the core layer material, the two materials have the same crystal lattice system, and the shell layer and the core layer are tightly combined; in the commercial coating preparation of the core-shell material, a physical coating method is usually used, which has a higher requirement for the particle size of the shell coating material, and the physical coating method has obvious phenomena of uneven coating and coating layer falling off in the post-processing process. The in-situ coating method of the present application perfectly solves the phenomena of uneven coating and coating layer falling off in the traditional physical coating method.

[0012] In the material of the present application, the core layer is a Li3Al x Ti 2-xThe (PO4) 3 material is in a lithium-rich state, the proportion of lithium ions is increased, the crystal structure is changed, the lithium ion migration channel is widened, and the lithium ion conductivity is significantly improved; the Ti element in the material is in +3 valence, the outermost electrons are easy to jump, so that the material has electronic conductivity; 2-x Li + Can be removed at a high potential, Ti 3+ Is oxidized to Ti 4+ , and the removed 2-x Li + Can supplement the active Li consumed by the battery when forming SEI or CEI + , improve the discharge capacity and the first circle coulomb efficiency of the battery, and further improve the overall performance of the battery. However, Li3Al x Ti 2-x (PO4) 3 material has strong reactivity, and is easy to be oxidized in an air environment or a complex electrochemical environment to form uncontrollable complex products, so the shell layer Li 1+x Al x Ti 2-x (PO4) 3 material is prepared in situ on the outer layer, a stable, uniform and compact shell layer with controllable shell thickness is formed, the air stability of the material is improved, the contact between the electrolyte or other additives and the core layer material is effectively blocked, the side reaction is avoided during the preparation and working process of the battery, which is beneficial to improve the applicability of the overall material and is beneficial to the processing and storage of the material in the air environment. In addition, in the process of in-situ oxidation of the shell layer by secondary sintering, Ti 3+ Is oxidized to Ti 4+ , and the excess Li + forms Li2O, when the temperature is low or the holding time is short, the shell layer formed has a thin thickness, the content of Li2O produced is small, and the lithium evaporation phenomenon is removed; when the temperature is high or the holding time is long, the shell layer formed has a thick thickness, the content of Li2O produced is more, the lithium evaporation phenomenon is intensified, and the Li2O produced is completely volatilized, so the Li2O produced in the secondary sintering process does not affect the stability and performance of the material. Based on this, the core-shell structure solid electrolyte material has high ion conductivity, electronic conductivity and lithium supplement characteristics, and good air stability and application stability.

[0013] The application further provides a preparation method of the core-shell structure solid electrolyte material formed in-situ, comprising the following steps: mixing a lithium source, an aluminum source, a titanium source and a phosphorus source in a stoichiometric ratio to obtain a material precursor by a dry mixing method, and performing primary sintering in an inert or reducing atmosphere to obtain Li3Al x Ti 2-xThe obtained material is crushed, ground and dried to obtain a micro-nano powder, and the micro-nano powder is subjected to secondary sintering in an oxygen atmosphere to obtain a core-shell material with a uniform and compact shell.

[0014] As a preferred technical solution of the present application, the lithium source can be a lithium source commonly used in the art, i.e., can include but is not limited to at least one of Li2CO3, Li2O, LiOH, LiOH·H2O, Li2C2O4, LiH2PO4, Li3PO4, etc.

[0015] As a preferred technical solution of the present application, the aluminum source can be an aluminum source commonly used in the art, i.e., can include but is not limited to at least one of Al2O3, Al(OH) 3、 Al2(CO3)3, AlPO4, Al(PO3)3, etc.

[0016] As a preferred technical solution of the present application, the titanium source can be a titanium source commonly used in the art, i.e., can include but is not limited to at least one of Ti2O3, Ti2(SO4)3, Ti powder, TiO2, Ti(OH)3, etc.

[0017] As a preferred technical solution of the present application, the phosphorus source can be a phosphorus source commonly used in the art, i.e., can include but is not limited to at least one of NH4H2PO4, (NH4)2HPO4, LiH2PO4, P2O5, AlPO4, Al(PO3)3, Li3PO4, etc.

[0018] As a preferred technical solution of the present application, the material precursor can be mixed in a crusher, a double-motion mixer, a three-dimensional mixer, a V-shaped mixer, a single-cone double-screw mixer, etc.

[0019] As a preferred technical solution of the present application, the sintering temperature of the primary sintering can be 600-1000°C, and the holding time can be 4-20h.

[0020] As a preferred technical solution of the present application, the inert or reducing atmosphere can be at least one of an argon atmosphere, a nitrogen atmosphere, a hydrogen atmosphere, a carbon monoxide atmosphere, etc.

[0021] As a preferred technical solution of the present application, the crushing can be performed by using a multi-stage crushing device, such as a jaw crusher, a cone crusher, a roller crusher, a flat airflow pulverizer, a fluidized bed airflow pulverizer, a planetary ball mill, etc.

[0022] As a preferred technical solution of the present application, the grinding device can be a sand mill.

[0023] As a preferred technical solution of the present application, the particle size D50 of the micro-nano powder is 100-900nm.

[0024] As a preferred technical scheme of the present application, the sintering temperature of the secondary sintering can be 400-800 DEG C, and the holding time can be 2-8h.

[0025] The core-shell material prepared by the method has a shell material of Li 1+x Al x Ti 2-x (PO4)3, and a core material of Li3Al x Ti 2-x (PO4)3, wherein 0<=x<=1. The core-shell material has a particle size D50 of 100-1000nm, and a shell thickness of 30-400nm.

[0026] When the core-shell material is applied to a battery, the shell thickness of 30nm or more can effectively inhibit the side reaction of the battery in the initial stage, and the smaller the ratio of the shell thickness / particle size, the better the technical effects of the lithium supplementing property of the 2-x Li + The lithium supplementing property of the 2-x Li

[0027] The core-shell structure solid electrolyte material has high ion conductivity, electron conductivity and lithium supplementing property, and has good air stability and application stability, and can be applied to the field of lithium ion batteries.

[0028] The present application has the following advantages: (1) The present application provides a composite solid electrolyte material coated in situ, the shell is Li 1+x Al x Ti 2-x (PO4)3 material, which has excellent ion conductivity and stability; the core is Li3Al x Ti 2-x (PO4)3 material, which has excellent ion and electron conductivity and lithium supplementing property. (2) The core-shell structure solid electrolyte material has a shell material obtained by in-situ oxidation of the core material, and the shell and the core have similar crystal systems, and the shell and the core are tightly connected and do not fall off. In addition, the shell is a tightly and uniformly coated layer, and the thickness can be controlled. (3) The core-shell structure solid electrolyte material can improve the air stability of the whole material, which is beneficial to the subsequent processing and storage of the electrolyte material in the air environment. In the application process, the shell material can effectively prevent other additives or electrolyte from contacting the core material, avoid the occurrence of side reactions, and improve the applicability of the whole material. (4) The core-shell structure solid electrolyte material of the present application has significantly improved ion conductivity and electronic conductivity of the core layer material relative to the shell layer material, and can release 2-x Li + Lithium is supplemented, the Coulomb efficiency of the applied battery is improved, and the material formed after release can still function as a solid electrolyte material in the battery; (5) The material synthesis method and coating method of the present application are simple, do not require harsh conditions such as complex process, high temperature and high pressure, or expensive raw materials, and can be completed based on existing industrial equipment, and are easy to scale up. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor.

[0030] Figure 1 The figure is a structural schematic diagram of the core-shell structure solid electrolyte material of the present application.

[0031] Figure 2 The figure is a phase diagram of the core-shell structure solid electrolyte material of the present application. DETAILED DESCRIPTION

[0032] The present application will be further described in detail below in conjunction with the embodiments, but the embodiments of the present application are not limited thereto. The materials involved in the following embodiments can be obtained from commercial channels if not otherwise specified. The methods are conventional methods if not otherwise specified. The amounts of the components are measured by mass parts and volume parts, g and mL.

[0033] Example 1

[0034] Lithium source Li2CO3, aluminum phosphorus source Al(PO3)3, titanium source Ti2O3, and phosphorus source NH4H2PO4 were mixed in a crusher at a stoichiometric ratio of 1.5:0.15:0.85:2.55, the mixing time was 5 min, and the rotation speed was 2000 rpm. The mixed material was sintered in an argon atmosphere furnace for the first time, the sintering temperature was 600℃, and the holding time was 20 h. The sintered material was crushed by a jaw crusher and a sand mill, vacuum dried at 80℃ to obtain a powder with a D50 of 300 nm; the powder was sintered in an oxygen atmosphere furnace for the second time, the sintering temperature was 400℃, the holding time was 3 h, and the sintered material had a shell layer of Li 1.3 Al 0.3 Ti 1.7 (PO4)3, and a core layer of Li3Al0.3 Ti 1.7 Coated solid-state electrolyte of (PO4)3, wherein the shell thickness is 50 nm, and the overall particle size is 300 nm. The schematic structure of the core-shell solid-state electrolyte material of the present application is shown in Figure 1 .

[0035] Example 2

[0036] The lithium source Li2O, the aluminum source Al(OH)3, the titanium source Ti2O3, and the phosphorus source NH4H2PO4 were mixed in a ratio of 1.5:0.4:0.8:3 by stoichiometric ratio in a double-motion mixer, the mixing time was 10 min, and the rotation speed was 1000 rpm. The mixed material was sintered once in an atmosphere furnace with argon gas atmosphere, the sintering temperature was 1000℃, and the holding time was 4 h. The sintered material was crushed by a conical crusher and a sand mill, and vacuum dried at 80℃ to obtain a powder with a D50 of 900 nm; the powder was sintered twice in an atmosphere furnace with oxygen gas atmosphere, the sintering temperature was 800℃, the holding time was 8 h, and the sintering was completed to obtain a coated solid-state electrolyte of (PO4)3 with a shell layer of Li3Al(PO4)3 and a core layer of Li3Al(PO4)3, wherein the shell thickness was 50 nm, and the overall particle size was 300 nm. 1.4 Al 0.4 Ti 1.6 (PO4)3, the core layer was Li3Al 0.4 Ti 1.6 Coated solid-state electrolyte of (PO4)3, wherein the shell thickness was 400 nm, and the overall particle size was 1000 nm.

[0037] Example 3

[0038] The lithium source Li2C2O4, the aluminum source Al2O3, the titanium source Ti powder, the titanium source TiO2, and the phosphorus source (NH4)2HPO4 were mixed in a ratio of 1.5:0.25:0.375:1.125:3 by stoichiometric ratio in a three-dimensional mixer, the mixing time was 10 min, and the rotation speed was 1000 rpm. The mixed material was sintered once in an atmosphere furnace with hydrogen gas atmosphere, the sintering temperature was 750℃, and the holding time was 10 h. The sintered material was crushed by a pair-roller crusher and a sand mill, and vacuum dried at 80℃ to obtain a powder with a D50 of 500 nm; the powder was sintered twice in an atmosphere furnace with oxygen gas atmosphere, the sintering temperature was 650℃, the holding time was 5 h, and the sintering was completed to obtain a coated solid-state electrolyte of (PO4)3 with a shell layer of Li3Al(PO4)3 and a core layer of Li3Al(PO4)3, wherein the shell thickness was 200 nm, and the overall particle size was 550 nm. 1.5 Al 0.5 Ti 1.5 (PO4)3, the core layer was Li3Al 0.5 Ti 1.5 Coated solid-state electrolyte of (PO4)3, wherein the shell thickness was 400 nm, and the overall particle size was 1000 nm.

[0039] Example 4

[0040] LiH2PO4, Al2(CO3)3, Ti(OH)3 were mixed in a V-type mixer at a stoichiometric ratio of 3:0.35:1.3, the mixing time was 20 min, and the rotation speed was 800 rpm. The mixed material was sintered in a CO2 atmosphere furnace for the first time, the sintering temperature was 900°C, and the holding time was 8 h. The sintered material was crushed by a flat airflow crusher and a sand mill, and vacuum dried at 80°C to obtain a powder with a D50 of 600 nm; the powder was sintered in an O2 atmosphere furnace for the second time, the sintering temperature was 400°C, the holding time was 4 h, and the sintered material was obtained, which was a coated solid-state electrolyte with a shell of LiTi2(PO4)3 and a core of Li3Al(PO4)3, wherein the shell thickness was 80 nm, and the overall particle size was 600 nm. 1.7 Al 0.7 Ti 1.3 (PO4)3, and a core of Li3Al 0.7 Ti 1.3 (PO4)3, wherein the shell thickness was 80 nm, and the overall particle size was 600 nm.

[0041] Example 5

[0042] LiOH·H2O, Ti2O3, and P2O5 were mixed in a single-cone double-helix mixer at a stoichiometric ratio of 3:1:1.5, the mixing time was 10 min, and the rotation speed was 500 rpm. The mixed material was sintered in a N2 atmosphere furnace for the first time, the sintering temperature was 900°C, and the holding time was 14 h. The sintered material was crushed by a fluidized bed airflow mill and a sand mill, and vacuum dried at 80°C to obtain a powder with a D50 of 800 nm; the powder was sintered in an O2 atmosphere furnace for the second time, the sintering temperature was 500°C, the holding time was 8 h, and the sintered material was obtained, which was a coated solid-state electrolyte with a shell of LiTi2(PO4)3 and a core of Li3Ti2(PO4)3, wherein the shell thickness was 200 nm, and the overall particle size was 800 nm.

[0043] Example 6

[0044] Li3PO4, AlPO4, Ti2(SO4)3, NH4H2PO4 in a ratio of 1:1:0.5:1 by stoichiometric ratio in a V-type mixer, the mixing time is 20 min, and the rotating speed is 1500 rpm. The mixed material is sintered in a hydrogen-argon mixed atmosphere furnace for the first time, the sintering temperature is 600°C, and the holding time is 8h. The sintered material is crushed by a planetary ball mill and a sand mill, and vacuum dried at 80°C to obtain a powder with a D50 of 100 nm; the powder is sintered in an oxygen atmosphere furnace for the second time, the sintering temperature is 400°C, the holding time is 2h, and the sintered material is obtained, which is a coated solid-state electrolyte with a shell layer of Li2AlTi(PO4)3 and a core layer of Li3AlTi(PO4)3, wherein the shell layer thickness is 30 nm, and the overall particle size is 100 nm.

[0045] Example 7

[0046] LiH2PO4, Al2O3, Ti2O3 in a ratio of 3:0.15:0.85 by stoichiometric ratio in a crusher, the mixing time is 5 min, and the rotating speed is 2000 rpm. The mixed material is sintered in a hydrogen-nitrogen mixed atmosphere furnace for the first time, the sintering temperature is 800°C, and the holding time is 6h. The sintered material is crushed by a planetary ball mill and a sand mill, and vacuum dried at 80°C to obtain a powder with a D50 of 500 nm; the powder is sintered in an oxygen atmosphere furnace for the second time, the sintering temperature is 400°C, the holding time is 3h, and the sintered material is obtained, which is a coated solid-state electrolyte with a shell layer of Li 1.3 Al 0.3 Ti 1.7 (PO4)3, and a core layer of Li3Al 0.3 Ti 1.7 (PO4)3, wherein the shell layer thickness is 50 nm, and the overall particle size is 500 nm.

[0047] Comparative Example 1 The conventional Li 1.3 Al 0.3 Ti 1.7 (PO4)3 powder with a particle size of 300 nm is selected as a comparison for ion conductivity, electron conductivity, and lithium supplement capacity tests.

[0048] Comparative Example 2 The specific operation is the same as that in Example 7, and a lithium-rich Li3Al 0.3 Ti 1.7 (PO4)3 material is directly synthesized, and the powder with a D50 of 500 nm is obtained without surface in-situ oxidation to prepare a coating layer.

[0049] Comparative Example 3 The specific operation is the same as that in Example 7, and Li3Al 0.3 Ti 1.7 (PO4)3material, and a powder with a D50 of 500 nm was obtained. Subsequently, the powder was subjected to secondary sintering in an atmosphere furnace with oxygen gas, the sintering temperature was 300°C, and the holding time was 1 h, to obtain a coated powder material with a shell layer of 20 nm.

[0050] Comparative Example 4 The specific operation is the same as that in Example 7, and Li3Al 0.3 Ti 1.7 (PO4)3material, and a powder with a D50 of 500 nm was obtained. Subsequently, the powder was subjected to secondary sintering in an atmosphere furnace with oxygen gas, the sintering temperature was 300°C, and the holding time was 1 h, to obtain a coated powder material with a shell layer of 20 nm. 1.3 Al 0.3 Ti 1.7 (PO4)3material, and a powder with a D50 of 500 nm was obtained. Subsequently, the powder was subjected to secondary sintering in an atmosphere furnace with oxygen gas, the sintering temperature was 300°C, and the holding time was 1 h, to obtain a coated powder material with a shell layer of 20 nm. 0.3 Ti 1.7 (PO4)3material, and a powder with a D50 of 500 nm was obtained. Subsequently, the powder was subjected to secondary sintering in an atmosphere furnace with oxygen gas, the sintering temperature was 300°C, and the holding time was 1 h, to obtain a coated powder material with a shell layer of 20 nm.

[0051] The products of Examples 1-7 and Comparative Examples 1-4 were subjected to performance testing, and the test results are shown in Figure 2 , Table 1 and Table 2: (1) The phase structure of the powder of the examples and comparative examples was determined by X-ray diffraction method, and the results are shown in Figure 2 ; (2) 1 g of the prepared powder was soaked in 9 g of deionized water to test the pH, denoted as p1; 1 g of the same group of powder was placed at 25°C and 50% humidity for 72 h, and then soaked in 9 g of deionized water to test the pH, denoted as p2; the difference (p2-p1) caused by the influence of the air oxidation of the material to generate lithium salt on the pH was used to characterize the air stability of the material; (3) 0.8 g of the powder to be tested was pressed into a ceramic sheet green body with a diameter of 15 mm under a pressure of 200 MPa using a unidirectional tablet press, and then buried in alumina crucible using mother powder, and sintered in a tube furnace with argon gas, the sintering temperature was 900°C, the holding time was 12 h, and the heating rate was 2°C / min. After sintering, the ceramic sheet was obtained, the ceramic sheet was polished flat on both sides, gold spraying was performed, and the ionic conductivity and electronic conductivity of the material ceramic sheet were tested by an electrochemical workstation; (4) NMP slurry was prepared according to the mass ratio of core-shell structure solid electrolyte: PVDF: SP = 8:1:1, and then homogenized. The homogenized slurry was coated on an aluminum foil current collector and baked to obtain a positive electrode. A conventional polypropylene separator was selected, and a lithium sheet was used as a negative electrode. The electrolyte was 1 mol·L -1LiPF6-ethylene carbonate (EC) / diethyl carbonate (EMC) / dimethyl carbonate (DMC) (volume ratio 1:1:1) was used as the electrolyte, and a 2032 button cell was assembled, and charge-discharge was carried out at 0.2C rate in the voltage range of 3.0-4.2V to test the lithium supplement capacity of the material; (5) LCO was selected as the positive active material, and during the positive electrode homogenate process, NMP slurry was prepared according to the mass ratio of LCO:core-shell structure solid electrolyte:PVDF:SP=94.8:1:2.2:2 and coated on an aluminum foil current collector, a conventional polypropylene separator was selected, lithium sheet was used as the negative electrode, and 1 mol·L -1 LiPF6-ethylene carbonate (EC) / diethyl carbonate (EMC) / dimethyl carbonate (DMC) (volume ratio 1:1:1) was used as the electrolyte, and a 2032 button cell was assembled, and charge-discharge was carried out at 0.2C rate in the voltage range of 3.0-4.2V to test the lithium supplement capacity of the material;

[0052] Table 1

[0053] As can be seen from Table 1, the core-shell structure solid electrolyte material of the application has significantly improved ionic conductivity and electronic conductivity, and shows different lithium supplement capacities according to different aluminum doping amounts and different shell thicknesses. The less the aluminum doping amount is, the smaller the shell thickness is, and the higher the lithium supplement capacity is. Compared with the conventional Li 1.3 Al 0.3 Ti 1.7 (PO4)3 material, the ionic conductivity and electronic conductivity of the material of the application are significantly improved. This is because 2-x unstable lithium ions exist in the crystal of the material of the application, and above 2.5V voltage, the 2-x lithium ions become active lithium ions in the battery, contributing to the lithium supplement capacity. The difference in pH test can determine that the in-situ oxidation coating of the application effectively improves the air stability of the overall material. In addition, the large difference in Example 4 is mainly due to the uneven physical coating layer and the falling off of the coating layer in the later crushing process, resulting in the exposure of part of the core layer material to the air and oxidation. In addition, it can be seen from the phase diagram of Figure 2 The phase of the material after one-time sintering in Example 1 is consistent with the standard card PDF #40-0095 of Li3Ti2(PO4)3, and after two-time sintering, a relatively thin shell layer is formed on the surface of the lithium-rich material. When the shell layer is relatively thin, the content is relatively small, and the phase test is difficult to detect, and the phase diagram is also consistent with the standard card PDF #40-0095 of Li3Ti2(PO4)3; when a relatively thick shell layer is formed on the surface of the lithium-rich material (such as Example 3), the phase of the synthesized material is a composite phase of LiTi2(PO4)3 (PDF #35-0754) and Li3Ti2(PO4)3 (PDF #40-0095).

[0054] Table 2

[0055] As can be seen from Table 2, by blending the material of the application into the positive electrode sheet, 2-x active lithium ions in the lithium-rich core layer material are partially released at a voltage of 3-4.53V, and the first charge-discharge capacity, coulombic efficiency and cycle stability of the battery are improved; and the core layer material can still function as a solid-state electrolyte after releasing 2-x active ions, and the higher ionic conductivity and electronic conductivity directly lead to the improvement of the rate performance of the battery; and as can be seen from Comparative Example 2, due to the protection of the shell material with good stability of the core material of the application, no side reaction occurs in the initial stage of the battery, ensuring the normal charging and discharging of the battery. In addition, as can be seen from Comparative Example 3, the shell thickness of the material of the application of 30nm or more can inhibit the side reaction of the battery in the initial stage, achieving good technical effects. And as can be seen from the examples, the smaller the ratio of the shell thickness / particle size of the material of the application, the better the technical effects achieved.

[0056] As can be seen, the core-shell structure composite lithium-rich solid-state electrolyte Li3Al x Ti 1-x The (PO4)3 material has lithium supplementing properties, and the ionic conductivity / electronic conductivity is significantly improved, and the discharge capacity, first cycle coulombic efficiency, rate performance and cycle stability of the lithium ion secondary battery prepared using the same are significantly improved.

[0057] The above examples are preferred embodiments of the application, but the embodiments of the application are not limited by the above examples, and any changes, modifications, substitutions, combinations and simplifications made without departing from the spirit and principles of the application shall be equivalent replacement methods, and all shall be included in the protection scope of the application.

Claims

1. An in-situ formed core-shell structured solid-state electrolyte material, characterized in that Li3Al x Ti 2-x (PO4)3material, and Li x Ti 2-x (PO4)3material, and Li 1+x Al x Ti 2-x (PO4)3material, wherein 0 < x < 1.

2. The core-shell structure solid-state electrolyte material of claim 1, wherein: The particle size D50 of the core-shell structure solid electrolyte material is 100-1000nm.

3. The core-shell structure solid-state electrolyte material of claim 1, wherein: Li3Al x Ti 2-x (PO4)3is a core layer, Li 1+x Al x Ti 2-x (PO4)3is a shell layer; the Li 1+x Al x Ti 2-x (PO4)3shell layer has a thickness of 30-400 nm.

4. A method of producing the core-shell structured solid electrolyte material according to any one of claims 1 to 3, characterized by The method comprises the following steps: A lithium source, an aluminum source, a titanium source and a phosphorus source are mixed by a dry method to obtain a material precursor in a stoichiometric ratio, and the material precursor is sintered once in an inert or reducing atmosphere to obtain a Li3Al x Ti 2-x (PO4)3 material; the obtained material is crushed, ground and dried to obtain a micro-nano powder, and the micro-nano powder is sintered twice in an oxygen atmosphere to obtain a core-shell material.

5. The method of claim 4, wherein: The stoichiometric ratio refers to the amount ratio calculated according to the target structural formula Li3Al x Ti 2-x (PO4)3, wherein 0≤x≤1.

6. The method of claim 4, wherein: The lithium source comprises at least one of Li2CO3, Li2O, LiOH, LiOH.H2O, Li2C2O4, LiH2PO4 and Li3PO4; the aluminum source comprises at least one of Al2O3, Al(OH)3, Al2(CO3)3, AlPO4 and Al(PO3)3; the titanium source comprises at least one of Ti2O3, Ti2(SO4)3, Ti powder, TiO2 and Ti(OH)3; and the phosphorus source comprises at least one of NH4H2PO4, (NH4)2HPO4, LiH2PO4, P2O5, AlPO4, Al(PO3)3 and Li3PO4.

7. The method of claim 4, wherein: The sintering temperature of the primary sintering is 600-1000 DEG C, and the holding time is 4-20h.

8. The method of claim 4, wherein: The particle size D50 of the micro-nano powder is 100-900nm.

9. The method of claim 4, wherein: The sintering temperature of the secondary sintering is 400-800 DEG C, and the holding time is 2-8h. 10.The application of the core-shell structure solid electrolyte material in the field of lithium ion batteries according to any one of claims 1-3.

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