Lithium lanthanum oxyfluoride solid electrolyte material, and preparation method and application thereof

Abstract

This invention relates to a lithium lanthanum oxyfluoride solid electrolyte material, its preparation method, and its application. A first solution is obtained by mixing and stirring a lanthanum source and an organic ligand in a first solvent; a second solution is obtained by mixing and stirring a lithium source and an M source in a second solvent; a third mixture is obtained by mixing and stirring the first solution with the second solution; a fourth mixture is obtained by adding a fluorine source to the third mixture and stirring to adjust the solid content of the solution to 10–35 wt%, and then adjusting the pH of the solution to 4.8–6.0; the fourth mixture is spray-dried to obtain a precursor; the precursor is sintered, and the sintered product is pulverized to obtain the oxyfluoride solid electrolyte material. This invention achieves ionic-level uniform mixing of raw materials through a stepwise dissolution process, suppressing side reactions and impurity phase formation, and improving phase purity and ionic conductivity.

Description

Technical Field

[0001] This invention relates to the field of solid electrolyte materials technology, and in particular to a lithium lanthanum oxyfluoride solid electrolyte material, its preparation method, and its application. Background Technology

[0002] Existing solid electrolytes mainly include polymer solid electrolytes, sulfide solid electrolytes, and oxide solid electrolytes. Among them, sulfide solid electrolytes have attracted widespread attention due to their high ionic conductivity; however, these materials readily react with moisture in the air to generate toxic hydrogen sulfide gas, exhibiting poor stability and insufficient safety. Therefore, developing a novel solid electrolyte material that combines high stability and high ionic conductivity has become a research hotspot.

[0003] Among numerous candidate materials, oxyfluoride solid electrolytes are considered a promising new type of material due to their excellent ionic conductivity and electrochemical stability, which can meet the performance requirements of all-solid-state lithium metal batteries. However, the preparation process of this type of material has a significant impact on the final performance, and existing methods still have certain limitations.

[0004] Currently, the preparation of oxyfluoride solid electrolytes mainly includes high-temperature solid-state methods, mechanical ball milling, and solution gelation methods. In high-temperature solid-state methods and mechanical ball milling, the distribution of different raw materials is often uneven during mixing, resulting in insufficient particle contact. This leads to component segregation during sintering, forming impurity phases or defective structures, which in turn causes ion channel blockage, resulting in low ionic conductivity of the electrolyte material and unstable phase purity and performance of the final product. While solution gelation methods can achieve a certain degree of uniform mixing at the molecular scale, in practice, precipitation, hydrolysis, or partial insolubility of raw materials during the dissolution stage often leads to unstable solution systems, easily forming colloids or secondary phases, affecting subsequent sintering processes and the performance of the finished product. Therefore, existing preparation processes generally suffer from problems such as uneven mixing, impurity phase formation, insufficient conductivity, and poor stability. There is an urgent need to develop a novel preparation method that can achieve ion-level uniform mixing, suppress side reactions, and improve phase purity and ionic conductivity. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a lithium lanthanum oxyfluoride solid electrolyte material, its preparation method, and its applications. The proposed preparation method addresses common problems in existing oxyfluoride solid electrolyte preparation methods, such as uneven raw material mixing, easy component segregation during sintering, impurity phase formation, low electrolyte ionic conductivity, and unstable finished product performance. By employing stepwise dissolution to achieve ionic-level uniform mixing of raw materials, mutual interference and side reactions during dissolution are reduced. Simultaneously, precipitation and colloidal phase formation are effectively suppressed in the solution stage, and the uniform ionic distribution of components in the instantaneously solidified droplets during spray drying is utilized to avoid component segregation and impurity peak formation during subsequent sintering. This results in the preparation of an oxyfluoride solid electrolyte with high phase purity, high stability, and high ionic conductivity.

[0006] To achieve the above objectives, in a first aspect, the present invention provides a method for preparing a lithium lanthanum oxyfluoride solid electrolyte material, comprising:

[0007] Lanthanum source and organic ligand are added to a first solvent and mixed to obtain a first solution; the first solution includes organic ligand and La 3+ The soluble complex formed;

[0008] The lithium source and the M source are added to the second solvent and mixed to obtain the second solution; the second solvent serves as an auxiliary solvent, enabling lithium ions to insert into the M–O bond, pre-forming a Li–M–O ordered structure, and stabilizing the M ions through complexation; wherein M is one or more of Nb, Sb, Bi, V, and Ta;

[0009] The first solution is added to the second solution, and the mixture is stirred to obtain a third mixture; La is released from the soluble complex. 3+ It is contained within the pre-formed Li–M–O ordered structure framework, forming a La–Li–M complex;

[0010] A fluorine source was added to the third mixture, and the solid content of the solution was adjusted to 10-35 wt% after mixing. After the solid content stabilized, the pH of the solution was adjusted to 4.8-6.0 to obtain the fourth mixture.

[0011] The fourth mixed solution was spray-dried to obtain the precursor;

[0012] The precursor is sintered, and the sintered product is then pulverized to obtain the oxyfluoride solid electrolyte material.

[0013] Preferably, the lanthanum source includes one or more combinations of lanthanum nitrate, lanthanum chloride, and lanthanum acetate;

[0014] The organic ligands include one or more combinations of oxalic acid, citric acid, tartaric acid, and ethylenediaminetetraacetic acid.

[0015] The addition ratio of the lanthanum source to the organic ligand is based on the La content in the lanthanum source. 3+ The organic ligand is added at a molar ratio of 1:1 to 1:4.

[0016] The first solvent includes one or more of the following: hydrogen peroxide, deionized water, ethanol, N-methylpyrrolidone (NMP), pyridine, and hydrofluoric acid;

[0017] The lithium source includes one or more combinations of lithium nitrate, lithium carbonate, lithium hydroxide, lithium oxalate, and lithium acetate.

[0018] The M source includes: an inorganic or organic salt of M, wherein the inorganic salt includes one or more of nitrates, chlorides, oxalates, carbonates, and metaacids; and the organic salt includes one or more of oxalates, citrates, tartrates, or acetates.

[0019] The second solvent includes one or more of the following: hydrogen peroxide, deionized water, ethanol, ethylene glycol, NMP, and hydrofluoric acid;

[0020] The fluorine source includes one or more combinations of hydrogen fluoride, ammonium fluoride, and ammonium bifluoride.

[0021] Preferably, the mixing and stirring specifically involves mixing and stirring in a mixing device;

[0022] The mixing equipment includes one or more of the following: a magnetic stirrer, a vertical mixing tank, a static mixer, a high-speed disperser, and a mechanically stirred reactor;

[0023] The stirring and mixing time for preparing the first solution is 0.5-6 hours;

[0024] The stirring and mixing time for preparing the second solution is 0.5-6 hours;

[0025] The stirring and mixing time for preparing the third mixture is 0.5-6 hours;

[0026] After adding the fluorine source to the third mixture, the stirring time is 0.5-3 hours.

[0027] Preferably, the method for adjusting the solid content of the solution specifically includes evaporation concentration or dilution; the evaporation concentration includes heating evaporation or vacuum evaporation; the dilution includes adding deionized water or ethylene glycol for dilution;

[0028] The pH of the solution is adjusted by adding ammonia; the pH of the solution is preferably adjusted to 5.0-5.5.

[0029] Preferably, the spray drying process is carried out in a spray drying device, wherein the inlet temperature of the spray drying device is 150℃-260℃ and the outlet temperature is 60℃-150℃.

[0030] Preferably, the sintering is carried out in a sintering device, which includes any one of a box furnace, a tube furnace, a pusher furnace, a roller kiln, and a rotary furnace.

[0031] The sintering includes single sintering or segmented sintering.

[0032] More preferably, the conditions for the first sintering are: heating to 700℃-1100℃ at a heating rate of 1℃ / min-10℃ / min under an inert atmosphere, and holding at that temperature for 1 hour-12 hours; the inert atmosphere includes one or a combination of nitrogen atmosphere and argon atmosphere.

[0033] The conditions for segmented sintering are as follows: under an inert atmosphere, the temperature is increased to 400℃-600℃ at a heating rate of 1℃ / min-10℃ / min, held for 3-5 hours, and then increased to 900℃-1100℃ at a heating rate of 2℃ / min-8℃ / min, held for 5-7 hours.

[0034] Preferably, the pulverization process is carried out in a pulverization device; the pulverization device includes a fluidized bed jet mill or a flat jet mill.

[0035] Secondly, embodiments of the present invention provide a lithium lanthanum oxyfluoride solid electrolyte material prepared by the preparation method described in the first aspect above, wherein the general chemical formula of the lithium lanthanum oxyfluoride solid electrolyte is Li. 2-x La (1+x) / 3 M2O6F, 0 < x ≤ 0.5; M is one or more of Nb, Sb, Bi, V, and Ta.

[0036] Thirdly, embodiments of the present invention provide a lithium battery comprising a lithium lanthanum oxyfluoride solid electrolyte material prepared by the preparation method described in the first aspect above.

[0037] The preparation method of lithium lanthanum oxyfluoride solid electrolyte material provided in this invention overcomes the problems of uneven raw material mixing, insufficient component contact, frequent side reactions, and unstable phases that are common in existing solid-phase methods, mechanical ball milling methods, and sol-gel methods by adopting a stepwise dissolution combined with spray drying and sintering process.

[0038] 1. The preparation method of this invention can achieve ion-level uniform mixing: This invention uses a stepwise dissolution process to first stabilize lanthanum ions under the action of organic ligands to form a soluble complex, and then combine it with the pre-formed Li–M–O structure, so that the La ions released from the soluble complex are... 3+ The elements are contained within a pre-formed Li–M–O ordered framework, forming a La–Li–M complex. Finally, a fluorine source is introduced, ensuring that all elements achieve ionic-level uniform distribution in solution. Compared to traditional processes, this effectively avoids ion channel blockage and performance degradation caused by insufficient mixing of raw materials.

[0039] 2. The preparation method of the present invention can suppress side reactions and precipitation: under the condition of pre-formation of Li–M–O structure, La 3+ It can be stably contained by the framework, thus avoiding the generation of H during the hydrolysis of M ions. + Inducing La 3+ The reaction produces a precipitate. Simultaneously, when the fluorine source is introduced, La... 3+ It is already in a state of organic ligand coordination saturation, which significantly reduces the probability of LaF3 colloidal secondary phase formation and improves the stability of the solution system.

[0040] 3. The preparation method of this invention ensures solution stability and process controllability: by precisely controlling the pH of the system at 4.8–6.0, fluorine is mainly produced as F. - The presence of this form reduces the risk of HF volatilization, ensuring the safety and controllability of the reaction. Simultaneously, by evaporation, concentration, or dilution, the solid content of the solution is adjusted to 10–35 wt%, ensuring uniform droplet distribution during spray drying and providing a stable precursor for subsequent sintering.

[0041] 4. The preparation method of the present invention can improve the purity of the sintered phase: spray drying is used to achieve instantaneous fixation of the ionic mixing state in the droplets, preventing component segregation and impurity peak generation caused by uneven diffusion during drying or sintering.

[0042] 5. The preparation method of the present invention can improve the overall performance of the electrolyte: the solid electrolyte Li obtained by the present invention 2- x La (1+x) / 3 M2O6F, with its stable La–Li–M–O–F framework in its crystal structure, can effectively improve lithium-ion conductivity. Compared with materials obtained by traditional processes, the solid electrolyte obtained by this invention not only has higher ionic conductivity, but also exhibits excellent electrochemical stability and process repeatability.

[0043] In summary, this invention achieves ionic-level uniform mixing, suppresses side reactions, and improves phase purity through the combined effects of stepwise dissolution and spray drying. Ultimately, it significantly enhances the ionic conductivity and electrochemical stability of the lithium lanthanum oxyfluoride solid electrolyte, meeting the requirements of all-solid-state lithium batteries for high-performance electrolytes. Attached Figure Description

[0044] Figure 1 The images show a comparison of X-ray diffraction (XRD) patterns of the solid electrolyte materials prepared in Example 1 and Comparative Examples 1 and 2 of this invention. Detailed Implementation

[0045] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0046] This invention provides a method for preparing a lithium lanthanum oxyfluoride solid electrolyte material. The technical solution of this invention's method for preparing the lithium lanthanum oxyfluoride solid electrolyte material will be described below.

[0047] The main steps of the preparation method of the lithium lanthanum oxyfluoride solid electrolyte material of the present invention include:

[0048] Step 110: Add the lanthanum source and organic ligand to the first solvent and stir for 0.5 to 6 hours until the solution becomes clear to obtain the first solution.

[0049] The lanthanum source includes one or more combinations of lanthanum nitrate, lanthanum chloride, and lanthanum acetate.

[0050] Organic ligands include one or more combinations of oxalic acid, citric acid, tartaric acid, and ethylenediaminetetraacetic acid;

[0051] The first solvent includes one or more of the following: hydrogen peroxide, deionized water, ethanol, N-methylpyrrolidone (NMP), pyridine, and hydrofluoric acid.

[0052] La from lanthanum sources 3+ The molar ratio with the organic ligand is 1:1 to 1:4.

[0053] This step involves adding organic ligands (such as oxalic acid or citric acid) to the solution to stabilize La. 3+ The ions form soluble complexes, thus preventing precipitation in subsequent steps. That is, the first solution includes organic ligands and La... 3+ The soluble complex formed.

[0054] Step 120: Add the lithium source and the M source to the second solvent and stir for 0.5 to 6 hours until fully dissolved to obtain the second solution.

[0055] The lithium source includes one or more combinations of lithium nitrate, lithium carbonate, lithium hydroxide, lithium oxalate, and lithium acetate.

[0056] M is one or more of Nb, Sb, Bi, V, and Ta; the source of M includes: inorganic or organic salts of M, where inorganic salts include one or more of nitrates, chlorides, oxalates, carbonates, and metaacids; and organic salts include one or more of oxalates, citrates, tartrates, or acetates.

[0057] The second solvent includes one or more of hydrogen peroxide, deionized water, ethanol, ethylene glycol, NMP, and hydrofluoric acid. The second solvent acts as an auxiliary solvent, enabling lithium ions to insert into M–O bonds, pre-forming an ordered Li–M–O structure, and stabilizing M ions through complexation.

[0058] Step 130: Add the first solution to the second solution and continue stirring and mixing for 0.5 to 6 hours to obtain the third mixture.

[0059] During the mixing process, La is released from the soluble complex. 3+ It is contained within the pre-formed Li–M–O ordered structure framework, forming a La–Li–M complex.

[0060] The Li–M–O structure pre-formed in the second solution can stably accommodate La. 3+ Therefore, it effectively avoids the formation of metal ions with high valence states (such as Nb). 5+ V 5+ H produced by hydrolysis (etc.) + Effects on the system. Due to the hydrolysis of high-valence metal ions in water, H+ is released. + If lanthanum in the system lacks a stable structure, it may induce La 3+ The precipitate forms La(OH)3.

[0061] Step 140: Add a fluoride source to the third mixture and stir for 0.5 to 3 hours. Then, adjust the solid content of the solution to 10 to 35 wt% by evaporation concentration or dilution. After the solid content is stable, add ammonia water to adjust the pH of the solution to 4.8 to 6.0 to obtain the fourth mixture.

[0062] The fluorine source includes one or more combinations of hydrogen fluoride, ammonium fluoride, and ammonium bifluoride.

[0063] Evaporation concentration may specifically include heating evaporation or vacuum evaporation; dilution may specifically involve adding deionized water or ethylene glycol; preferably, after the solid content is stable, ammonia is added to adjust the pH of the solution to 5.0-5.5.

[0064] In this step, the solid content of the solution is first adjusted to 10–35 wt% by evaporation and concentration or dilution. This is to ensure that the solution concentration and viscosity are within the range suitable for spray drying, thereby guaranteeing the uniformity and controllability of droplet formation. Subsequently, under stable solid content conditions, ammonia is added to adjust the pH to 4.8–6.0, so that fluorine mainly forms as F. - The presence of this form avoids pH fluctuations caused by changes in solution volume or component concentration processes, thus ensuring the stability and controllability of the solution system. Under conditions of stable solid content, adding ammonia to adjust the pH will not significantly affect the overall concentration and viscosity of the solution, thereby ensuring that the system viscosity remains within the range suitable for spray drying, while also guaranteeing the accuracy of pH control and the stability of the system.

[0065] Furthermore, due to the use of a distributed preparation method, when the fluorine source is introduced, La 3+ It is already in a state of organic ligand coordination saturation, which significantly reduces the probability of LaF3 colloidal secondary phase formation and improves the stability of the solution system.

[0066] The mixing and stirring involved in steps 110-140 above can specifically be carried out in a mixing device; the mixing device that can be selected includes one or more of the following: magnetic stirrer, vertical mixing tank, static mixer, high-speed disperser, and mechanically stirred reactor. The mixing device and specific stirring process parameters used in different steps can be the same or different. The setting and selection of the mixing equipment and parameters are all routine operations for those skilled in the art and can be adjusted according to the actual specific process requirements.

[0067] In the preparation steps, the amount of each raw material (lithium source, lanthanum source, M source, fluorine source) added can be determined according to the general chemical formula Li 2- x La (1+x) / 3 The required stoichiometry of M2O6F (0 < x ≤ 0.5) is determined by the specific method of measurement, which is a routine operation known to those skilled in the art.

[0068] Step 150: Spray dry the fourth mixed solution to obtain the precursor.

[0069] Specifically, the spray drying process is carried out in a spray drying equipment, preferably with the inlet temperature of the spray drying equipment set at 150℃-260℃ and the outlet temperature at 60℃-150℃.

[0070] Step 160: The precursor is sintered, and the sintered product is pulverized to obtain an oxyfluoride solid electrolyte material.

[0071] Specifically, sintering equipment includes any one of the following: box furnace, tube furnace, pusher furnace, roller kiln, and rotary furnace.

[0072] Sintering can be carried out in one-time integral sintering or segmented sintering. The appropriate sintering method can be selected according to the specific material properties and product requirements.

[0073] For example, the conditions for a single sintering can be: heating to 700℃-1100℃ at a heating rate of 1℃ / min-10℃ / min under an inert atmosphere, and holding at that temperature for 1 hour-12 hours.

[0074] For example, the conditions for segmented sintering can be as follows: under an inert atmosphere, the temperature is increased to 400℃-600℃ at a heating rate of 1℃ / min-10℃ / min, held for 3-5 hours, and then increased to 900℃-1100℃ at a heating rate of 2℃ / min-8℃ / min, held for 5-7 hours.

[0075] The aforementioned inert atmosphere may specifically include one or a combination of nitrogen atmosphere and argon atmosphere.

[0076] The pulverization process is carried out in pulverization equipment; the pulverization equipment may specifically include a fluidized bed air jet mill or a flat air jet mill. In a specific example, the pressure of the compressed air in the fluidized bed air jet mill is set between 2 MPa and 5 MPa, and the dew point of the compressed air is less than -20°C.

[0077] This invention achieves ionic-level uniform mixing of raw materials through a stepwise dissolution method in steps 110 to 140, while simultaneously reducing the mutual influence of elements during the dissolution process. Specifically, when the lithium source and niobium source are mixed, Li... + It can insert MO bonds to form an ordered Li–M–O structure; subsequently, when co-dissolved with a lanthanum source, this structure can stably accommodate lanthanum ions, avoiding the H+ generated by the hydrolysis of high-valence metal M ions. + Lanthanum precipitation is induced; when the fluorine source is added last, the lanthanum ions are already saturated with ligands, thereby reducing the formation of LaF3 colloids and significantly increasing the precipitation barrier, achieving homogeneity and stability of the solution system. In step 150, the mixture is instantaneously dried by spray drying, locking the ionic mixing state within the spray droplets and maintaining this state during sintering, thus effectively avoiding component segregation and impurity peak formation during sintering.

[0078] Thus, this invention achieves ionic-level uniform mixing, suppresses side reactions, and improves phase purity through the combined effect of stepwise dissolution and spray drying, ultimately significantly enhancing the ionic conductivity and electrochemical stability of the lithium lanthanum oxyfluoride solid electrolyte, meeting the requirements of all-solid-state lithium batteries for high-performance electrolytes.

[0079] The solid electrolyte Li prepared by this invention 2-x La (1+x) / 3M₂O₆F, 0 < x ≤ 0.5; M is one or more of Nb, Sb, Bi, V, and Ta. Its crystal structure features a stable La–Li–M–O–F framework, which effectively improves lithium-ion conductivity. Compared to materials obtained through traditional processes, the solid-state electrolyte obtained in this invention not only exhibits higher ionic conductivity but also demonstrates superior electrochemical stability and process repeatability.

[0080] The oxyfluoride solid electrolyte material Li prepared by this invention 2-x La (1+x) / 3 M2O6F possesses high ionic conductivity and good chemical and electrochemical stability, making it suitable for use in solid-state lithium batteries, such as as an electrolyte in all-solid-state lithium metal batteries. In battery applications, the solid-state electrolyte of this invention provides continuous and uniform ion channels, effectively improving lithium-ion migration efficiency, reducing internal resistance, and significantly suppressing side reactions and interfacial instability due to its stable La–Li–M–O–F framework structure, thereby enhancing battery cycle life and rate performance. This material is applicable to various lithium metal anode and high-voltage cathode systems, meeting the performance requirements of high-safety, high-energy-density all-solid-state lithium batteries.

[0081] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0082] Example 1

[0083] This embodiment provides a Li 1.25 La 0.58 The preparation method of Nb₂O₆F oxyfluoride solid electrolyte specifically includes the following steps:

[0084] Step 1, according to the oxyfluoride solid electrolyte Li 1.25 La 0.58 The elemental molar ratio of Nb2O6F is lithium nitrate, lanthanum nitrate, ammonium niobate oxalate and ammonium fluoride.

[0085] Step 2: Add the weighed lanthanum nitrate and oxalic acid in a molar ratio of 1:3 to a magnetic stirrer and mix with deionized water for 1 hour to obtain the first solution;

[0086] Step 3: Place the weighed lithium nitrate and ammonium niobate oxalate into a magnetic stirrer and mix them in a 1:1 volume ratio of deionized water and ethylene glycol for 2 hours to obtain the second solution.

[0087] Step 4: Add the first solution to the second solution and continue stirring for 30 minutes to obtain the third mixed solution;

[0088] Step 5: Add ammonium fluoride to the third mixed solution and continue stirring for 30 minutes. Adjust the solid content to 20 wt% by evaporation and concentration. After the solid content is stable, add ammonia water to adjust the pH of the solution to 5.0 to form the fourth mixed solution.

[0089] Step 6: The fourth mixed solution is spray-dried in a spray dryer to obtain the precursor; wherein the inlet temperature is 240℃ and the outlet temperature is 120℃.

[0090] Step 7: Transfer the precursor to a tube furnace, maintain a nitrogen atmosphere, and heat it to 900℃ at a rate of 2℃ / min, hold for 5 hours, and then pulverize it using a fluidized bed jet mill to obtain the oxyfluoride solid electrolyte material Li. 1.25 La 0.58 Nb₂O₆F; wherein, the pressure of the compressed air used for pulverization is 3.5 MPa, and the dew point of the compressed air is -30℃.

[0091] Example 2

[0092] This embodiment provides a Li 1.38 La 0.54 The preparation method of Nb₂O₆F oxyfluoride solid electrolyte specifically includes the following steps:

[0093] Step 1, according to the oxyfluoride solid electrolyte Li 1.38 La 0.54 The elemental molar ratio of Nb₂O₆F is lithium oxalate, lanthanum nitrate, ammonium niobate oxalate, and ammonium fluoride.

[0094] Step 2: The weighed lanthanum nitrate and oxalic acid were added to a mechanically stirred reactor at a molar ratio of 1:2.5 and mixed with deionized water for 1 hour to obtain the first solution;

[0095] Step 3: Place the weighed lithium oxalate and ammonium niobate oxalate into a magnetic stirrer and mix them in a 1:1 volume ratio of deionized water and ethylene glycol for 2 hours to obtain the second solution.

[0096] Step 4: Add the first solution to the second solution and continue stirring for 60 minutes to obtain the third mixed solution;

[0097] Step 5: Add ammonium fluoride to the third mixed solution and continue stirring for 30 minutes. Adjust the solid content to 25 wt% by evaporation and concentration. After the solid content is stable, add ammonia water to adjust the pH of the solution to 5.3 to form the fourth mixed solution.

[0098] Step 6: The fourth mixed solution is spray-dried in a spray dryer to obtain the precursor; wherein the inlet temperature is 240℃ and the outlet temperature is 120℃.

[0099] Step 7: Transfer the precursor to a tube furnace, maintain a nitrogen atmosphere, and heat it to 950°C at a rate of 2°C / min, hold for 5 hours, and then pulverize it using a fluidized bed jet mill to obtain the oxyfluoride solid electrolyte material Li. 1.38 La 0.54 Nb₂O₆F; wherein, the pressure of the compressed air used for pulverization is 3.0 MPa, and the dew point of the compressed air is -30℃.

[0100] Example 3

[0101] This embodiment provides a Li 1.25 La 0.58 The preparation method of Bi2O6F oxyfluoride solid electrolyte specifically includes the following steps:

[0102] Step 1, according to the oxyfluoride solid electrolyte Li 1.25 La 0.58 The elemental molar ratio of Bi2O6F is lithium nitrate, lanthanum nitrate, bismuth ammonium citrate, and ammonium fluoride.

[0103] Step 2: The weighed lanthanum nitrate and oxalic acid were added to a mechanically stirred reactor at a molar ratio of 1:3 and mixed with deionized water for 1 hour to obtain the first solution;

[0104] Step 3: Place the weighed lithium nitrate and bismuth ammonium citrate into a magnetic stirrer and mix them in a 1:1 volume ratio of deionized water and ethylene glycol for 2 hours to obtain the second solution.

[0105] Step 4: Add the first solution to the second solution and continue stirring for 60 minutes to obtain the third mixed solution;

[0106] Step 5: Add ammonium fluoride to the third mixed solution and continue stirring for 30 minutes. Adjust the solid content to 15 wt% by adding deionized water. After the solid content stabilizes, add ammonia water to adjust the pH of the solution to 5.0 to form the fourth mixed solution.

[0107] Step 6: The fourth mixed solution is spray-dried in a spray dryer to obtain the precursor; wherein the inlet temperature is 240℃ and the outlet temperature is 120℃.

[0108] Step 7: Transfer the precursor to a tube furnace, maintain a nitrogen atmosphere, and heat it to 950°C at a rate of 2°C / min, hold for 5 hours, and then pulverize it using a fluidized bed jet mill to obtain the oxyfluoride solid electrolyte material Li.1.25 La 0.58 Bi2O6F; wherein, the pressure of the compressed air used for pulverization is 3.0 MPa, and the dew point of the compressed air is -30℃.

[0109] Example 4

[0110] This embodiment provides a Li 1.25 La 0.58 The preparation method of V2O6F oxyfluoride solid electrolyte specifically includes the following steps:

[0111] Step 1, according to the oxyfluoride solid electrolyte Li 1.25 La 0.58 The elemental molar ratio of V2O6F is lithium oxalate, lanthanum nitrate, ammonium metavanadate and ammonium fluoride.

[0112] Step 2: The weighed lanthanum nitrate and oxalic acid were added to a mechanically stirred reactor at a molar ratio of 1:2.5 and mixed with deionized water for 30 minutes to obtain the first solution;

[0113] Step 3: Place the weighed lithium oxalate and ammonium metavanadate into a magnetic stirrer and mix them in a 1:1 volume ratio of deionized water and ethylene glycol for 2 hours to obtain the second solution.

[0114] Step 4: Add the first solution to the second solution and continue stirring for 60 minutes to obtain the third mixed solution;

[0115] Step 5: Add ammonium fluoride to the third mixed solution and continue stirring for 30 minutes. Adjust the solid content to 20 wt% by evaporation and concentration. After the solid content is stable, add ammonia water to adjust the pH of the solution to 5.3 to form the fourth mixed solution.

[0116] Step 6: The fourth mixed solution is spray-dried in a spray dryer to obtain the precursor; wherein the inlet temperature is 240℃ and the outlet temperature is 120℃.

[0117] Step 7: Transfer the precursor to a tube furnace, maintain a nitrogen atmosphere, and heat it to 950°C at a rate of 2°C / min, hold for 5 hours, and then pulverize it using a fluidized bed jet mill to obtain the oxyfluoride solid electrolyte material Li. 1.25 La 0.58 V2O6F; wherein, the pressure of the compressed air used for pulverization is 3.0 MPa, and the dew point of the compressed air is -30℃.

[0118] Example 5

[0119] This embodiment provides a Li 1.38 La 0.54The preparation method of V2O6F oxyfluoride solid electrolyte specifically includes the following steps:

[0120] Step 1, according to the oxyfluoride solid electrolyte Li 1.38 La 0.54 The elemental molar ratio of V2O6F is lithium oxalate, lanthanum nitrate, ammonium metavanadate and ammonium fluoride.

[0121] Step 2: The weighed lanthanum nitrate and oxalic acid were added to a mechanically stirred reactor at a molar ratio of 1:2.5 and mixed with deionized water for 30 minutes to obtain the first solution;

[0122] Step 3: Place the weighed lithium oxalate and ammonium metavanadate into a magnetic stirrer and mix them in a 1:1 volume ratio of deionized water and ethylene glycol for 2 hours to obtain the second solution.

[0123] Step 4: Add the first solution to the second solution and continue stirring for 60 minutes to obtain the third mixed solution;

[0124] Step 5: Add ammonium fluoride to the third mixed solution and continue stirring for 30 minutes. Adjust the solid content to 20 wt% by evaporation and concentration. After the solid content is stable, add ammonia water to adjust the pH of the solution to 5.3 to form the fourth mixed solution.

[0125] Step 6: The fourth mixed solution is spray-dried in a spray dryer to obtain the precursor; wherein the inlet temperature is 240℃ and the outlet temperature is 120℃.

[0126] Step 7: Transfer the precursor to a tube furnace, maintain a nitrogen atmosphere, and heat it to 950°C at a rate of 2°C / min, hold for 5 hours, and then pulverize it using a fluidized bed jet mill to obtain the oxyfluoride solid electrolyte material Li. 1.38 La 0.54 V2O6F; wherein, the pressure of the compressed air used for pulverization is 3.0 MPa, and the dew point of the compressed air is -30℃.

[0127] Comparative Example 1

[0128] This comparative example provides a Li 1.25 La 0.58 The conventional preparation method of Nb₂O₆F oxyfluoride solid electrolyte includes the following steps:

[0129] According to the oxyfluoride solid electrolyte Li 1.25 La 0.58 The molar ratio of Nb2O6F is lithium carbonate, lanthanum trioxide, niobium pentoxide, and lithium fluoride. These are mixed in a planetary mixer for 6 hours to obtain a mixture.

[0130] The mixture was sintered in an atmosphere furnace. First, the temperature was increased to 500℃ at a rate of 5℃ / min and held for 6 hours. Then, the temperature was increased to 900℃ at a rate of 5℃ / min and held for 6 hours. The sintered material was then pulverized using a fluidized bed jet mill to obtain the oxyfluoride solid electrolyte material Li. 1.25 La 0.58 Nb₂O₆F, wherein the pressure of the compressed air used for pulverization is 3.5 MPa and the dew point of the compressed air is -30℃.

[0131] Comparative Example 2

[0132] This comparative example provides a Li 1.25 La 0.58 The conventional preparation method of Nb₂O₆F oxyfluoride solid electrolyte includes the following steps:

[0133] According to the oxyfluoride solid electrolyte Li 1.25 La 0.58 The elemental molar ratio of Nb2O6F is obtained by grinding lithium carbonate, lanthanum trioxide, niobium pentoxide, lithium fluoride and deionized water in a ball mill to obtain a mixed slurry with a solid content of 20%.

[0134] The mixed slurry was spray-dried in a spray dryer to obtain precursor powder. The inlet temperature was 240℃, and the outlet temperature was 120℃.

[0135] The precursor powder was sintered in an atmosphere furnace. The temperature was first increased to 500℃ at a rate of 5℃ / min and held for 6 hours, then increased to 900℃ at a rate of 5℃ / min and held for 6 hours. The sintered material was then pulverized using a fluidized bed jet mill to obtain the oxyfluoride solid electrolyte material Li. 1.25 La 0.58 Nb₂O₆F, wherein the pressure of the compressed air used for pulverization is 3.5 MPa and the dew point of the compressed air is -30℃.

[0136] Comparative Example 3

[0137] This invention provides a comparative example of Li 1.38 La 0.54 The conventional preparation method of Nb₂O₆F oxyfluorine solid electrolyte includes the following steps:

[0138] According to the oxyfluoride solid electrolyte Li 1.38 La 0.54 The molar ratio of Nb2O6F is lithium carbonate, lanthanum trioxide, niobium pentoxide, and lithium fluoride. These are mixed in a planetary mixer for 4 hours to obtain a mixture.

[0139] The mixture was sintered in an atmosphere furnace. The temperature was first increased to 500℃ at a rate of 5℃ / min and held for 6 hours, then increased to 1000℃ at a rate of 2℃ / min and held for 6 hours. The sintered material was then pulverized using a fluidized bed jet mill to obtain the oxyfluoride solid electrolyte material Li. 1.38 La 0.54 Nb₂O₆F, wherein the pressure of the compressed air used for pulverization is 3.0 MPa and the dew point of the compressed air is -30℃.

[0140] Comparative Example 4

[0141] This invention provides a comparative example of Li 1.38 La 0.54 The conventional preparation method of V2O6F oxyfluorine solid electrolyte includes the following steps:

[0142] According to the oxyfluoride solid electrolyte Li 1.38 La 0.54 The elemental molar ratio of V2O6F is lithium carbonate, lanthanum trioxide, vanadium pentoxide, and lithium fluoride. These are mixed in a planetary mixer for 6 hours to obtain a mixture.

[0143] The mixture was sintered in an atmosphere furnace. The temperature was first increased to 500℃ at a rate of 5℃ / min and held for 6 hours, then increased to 1000℃ at a rate of 2℃ / min and held for 6 hours. The sintered material was then pulverized using a fluidized bed jet mill to obtain the oxyfluoride solid electrolyte material Li. 1.38 La 0.54 V2O6F, wherein the pressure of the compressed air used for pulverization is 4.0 MPa and the dew point of the compressed air is -30℃.

[0144] The performance of the oxyfluoride solid electrolyte materials obtained in the above embodiments and comparative examples was tested and compared, as detailed below:

[0145] The density test was conducted using the following method:

[0146] 1. Sample preparation: The oxyfluoride solid electrolyte was pressed into ceramic sheets using a tablet press, and then sintered at 1000℃ for 5 hours to densify it, resulting in a densified ceramic sheet sample. The obtained ceramic sheet sample was then placed in a drying oven at 110℃ for 2 hours.

[0147] 2. Use an analytical balance to measure the mass W of the oxyfluoride solid electrolyte in air. (空气) ;

[0148] 3. Place the ceramic sample on the sample holder, connect the sample holder to an analytical balance to test the sample mass, and place the sample holder in deionized water to obtain the mass W of the oxyfluoride solid electrolyte in deionized water under the action of buoyancy. (水) ;

[0149] According to the formula:

[0150] ρ=ρ (水) ×W (空气) / (W (空气) -W (水) );

[0151] α = (ρ / ρ0) * 100%;

[0152] ρ is the bulk density of the oxyfluorine compound solid electrolyte ceramic sheet, expressed in grams per cubic centimeter (g / cm³). 3 );W (空气) W represents the mass of the oxyfluorine compound solid electrolyte ceramic sheet in air, expressed in grams (g). (水) ρ represents the mass of the oxyfluoride compound solid electrolyte ceramic sheet in deionized water, expressed in grams (g); (水) This refers to the density of water, expressed in grams per cubic centimeter (g / cm³). 3 ); ρ0 is the theoretical density of the oxyfluorine compound solid electrolyte ceramic sheet, in grams per cubic centimeter (g / cm³). 3 ).

[0153] Purity testing was conducted using the following method:

[0154] The purity data was obtained by calculating the content ratio of each phase using the "peak area fitting" method commonly used in existing technologies through XRD pattern analysis, and is recorded in Table 1. Here, purity refers to crystal phase purity. The XRD patterns of Example 1 and Comparative Examples 1 and 2 are shown below. Figure 1 XRD pattern analysis showed that the fluoride solid electrolyte prepared in Example 1 only showed the diffraction peaks of the target phase and no obvious impurity phase was detected, indicating that it has high phase purity; impurity phases were present in Comparative Examples 1 and 2; proving that the preparation method proposed in this invention can prepare high-purity fluoride solid electrolytes.

[0155] The ionic conductivity was tested using the following method:

[0156] 1. Grind the oxyfluoride solid electrolyte powder evenly, press it into a ceramic sheet, and sinter it at 1000℃ for 5 hours to densify it, thus obtaining a densified ceramic sheet sample.

[0157] 2. Polish the two circular surfaces of the sintered ceramic sheet with 400 grit, 1000 grit, and 3000 grit sandpaper in sequence until the entire surface is flat, clean, and free of defects;

[0158] 3. Use a digital thickness gauge to measure the thickness L of the ceramic sheet, and a vernier caliper to measure the diameter of the ceramic sheet. Further calculate the cross-sectional area of ​​the ceramic sheet's circular surface, denoted as S.

[0159] 4. Coat the surface of the polished solid electrolyte sheet sample with conductive silver paste, and then grind off the conductive silver paste on the side of the solid electrolyte sheet;

[0160] 5. Test under the conditions of temperature (25±2)℃ and humidity less than 50%. Turn on the Zahner electrochemical workstation and set the parameters: perturbation voltage 10mV, frequency 0.1~106Hz. Test the impedance curve. Use Zahner Analysis software to fit and calculate the resistance R. Calculate the room temperature ionic conductivity of the solid electrolyte according to the ionic conductivity formula σ=L / (R×S).

[0161] Where σ is the ionic conductivity of the oxyfluoride solid electrolyte ceramic sheet, in Siemens units per centimeter (S / cm); L is the thickness of the oxyfluoride solid electrolyte ceramic sheet, in centimeters (cm); R is the fitted impedance value of the oxyfluoride solid electrolyte ceramic sheet, in ohms (Ω); and S is the cross-sectional area of ​​the circular surface of the oxyfluoride solid electrolyte ceramic sheet, in square centimeters (cm²). 2 ).

[0162] Table 1

[0163]

[0164] According to Table 1, the comparison of density and purity between Comparative Examples 1-5 and Examples 1-4 shows that the application of ion-level mixing of raw materials can significantly improve the density of the material and the purity of the prepared powder, and the ionic conductivity is also significantly improved.

[0165] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a lithium lanthanum oxyfluoride solid electrolyte material, characterized in that, The preparation method includes: adding a lanthanum source and an organic ligand into a first solvent to obtain a first solution; the organic ligand and La in the first solution form a soluble complex 3+ a soluble complex The lithium source and the M source are added to the second solvent and mixed to obtain the second solution. The second solvent serves as an auxiliary solvent, enabling lithium ions to insert into the M–O bond, pre-forming a Li–M–O ordered structure, and stabilizing the M ions through complexation. M is one or more of Nb, Sb, Bi, V, and Ta. adding the first solution to the second solution to obtain a third mixture; La 3+ is accommodated by the preformed Li-M-O ordered structure framework to form a La-Li-M complex; A fluorine source was added to the third mixture, and the solid content of the solution was adjusted to 10–35 wt% after mixing. After the solid content stabilized, the pH of the solution was adjusted to 4.8–6.0 to obtain the fourth mixture. The fourth mixed solution was spray-dried to obtain the precursor; The precursor is sintered, and the sintered product is pulverized to obtain the oxyfluoride solid electrolyte material. The lanthanum source includes one or more combinations of lanthanum nitrate, lanthanum chloride, and lanthanum acetate. The organic ligands include one or more combinations of oxalic acid, citric acid, tartaric acid, and ethylenediaminetetraacetic acid. The addition ratio of the lanthanum source to the organic ligand is based on the La content in the lanthanum source. 3+ The organic ligand is added at a molar ratio of 1:1 to 1:

4. The first solvent includes one or more of the following: hydrogen peroxide, deionized water, ethanol, N-methylpyrrolidone (NMP), pyridine, and hydrofluoric acid; The lithium source includes one or more combinations of lithium nitrate, lithium carbonate, lithium hydroxide, lithium oxalate, and lithium acetate. The M source includes: an inorganic or organic salt of M, wherein the inorganic salt includes one or more of nitrates, chlorides, oxalates, carbonates, and metaacids; and the organic salt includes one or more of oxalates, citrates, tartrates, or acetates. The second solvent includes one or more of the following: hydrogen peroxide, deionized water, ethanol, ethylene glycol, NMP, and hydrofluoric acid; The fluorine source includes one or more combinations of hydrogen fluoride, ammonium fluoride, and ammonium bifluoride.

2. The preparation method according to claim 1, characterized in that, The mixing specifically involves stirring and mixing in a mixing device; The mixing equipment includes one or more of the following: a magnetic stirrer, a vertical mixing tank, a static mixer, a high-speed disperser, and a mechanically stirred reactor; The stirring and mixing time for preparing the first solution is 0.5-6 hours; The stirring and mixing time for preparing the second solution is 0.5-6 hours; The stirring and mixing time for preparing the third mixture is 0.5-6 hours; After adding the fluorine source to the third mixture, the stirring time is 0.5-3 hours.

3. The preparation method according to claim 1, characterized in that, The method for adjusting the solid content of the solution specifically includes evaporation concentration or dilution; the evaporation concentration includes heating evaporation or vacuum evaporation; the dilution includes adding deionized water or ethylene glycol for dilution. The pH of the solution is adjusted by adding ammonia; the pH of the solution is adjusted to 5.0-5.

5.

4. The preparation method according to claim 1, characterized in that, The spray drying process is carried out in a spray drying equipment, the inlet temperature of which is 150℃-260℃ and the outlet temperature is 60℃-150℃.

5. The preparation method according to claim 1, characterized in that, The sintering is carried out in a sintering device, which includes any one of the following: box furnace, tube furnace, pusher furnace, roller kiln, and rotary furnace; The sintering includes single sintering or segmented sintering.

6. The preparation method according to claim 5, characterized in that, The conditions for the first sintering are as follows: under an inert atmosphere, the temperature is increased to 700℃-1100℃ at a heating rate of 1℃ / min-10℃ / min, and held for 1 hour-12 hours. The inert atmosphere includes one or a combination of nitrogen atmosphere and argon atmosphere; The conditions for segmented sintering are as follows: under an inert atmosphere, the temperature is increased to 400℃-600℃ at a heating rate of 1℃ / min-10℃ / min, held for 3-5 hours, and then increased to 900℃-1100℃ at a heating rate of 2℃ / min-8℃ / min, held for 5-7 hours.

7. The preparation method according to claim 1, characterized in that, The pulverization process is carried out in pulverization equipment; the pulverization equipment includes a fluidized bed jet mill or a flat jet mill.

8. A lithium battery, characterized in that, The lithium battery includes a lithium lanthanum oxyfluoride solid electrolyte material prepared by any of the preparation methods described in 1-7.

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