A method for preparing nano-lithium aluminum titanium phosphate solid electrolyte material by a room-temperature aqueous gel method

Abstract

The present invention discloses a method for preparing a nano lithium titanium aluminum phosphate solid electrolyte material by a room-temperature aqueous gel method, belonging to the technical field of the preparation of solid electrolytes for lithium-ion batteries. In this method, a lithium source, an aluminum source, a titanium source, and a phosphorus source are first mixed with water in a certain manner and aged at room temperature to form an aqueous gel precursor of the lithium titanium aluminum phosphate solid electrolyte. Subsequently, the precursor gel is heated and calcined to obtain the nano lithium titanium aluminum phosphate solid electrolyte material. The chemical formula of the nano solid electrolyte material is Li1+ x Al x Ti 2‑x (PO4)3. The material particles are closely arranged and have relatively uniform particle sizes, with the particle sizes ranging from 50 to 300 nm. The method for preparing the nano lithium titanium aluminum phosphate solid electrolyte material by the room-temperature aqueous gel method provided in this application has a simple preparation process, a relatively low synthesis temperature, low raw material costs, environmental friendliness, and is convenient for industrial production. The synthesized product has a high product yield, a high sphericity, a uniform particle size distribution, and a high purity.

Description

Technical Field

[0001] The present invention relates to the technical field of the preparation of solid electrolytes for lithium-ion batteries, and more particularly, to a method for preparing a nano-lithium aluminum titanium phosphate solid electrolyte material by a room-temperature aqueous gel method. Background Art

[0002] Lithium-ion batteries are currently the most mature lithium-based secondary batteries, with advantages such as high voltage, high specific energy, long cycle life, stable working voltage, and low self-discharge. The liquid electrolytes commonly used in commercial lithium-ion batteries are volatile, leaky, flammable, and have poor impact resistance, resulting in safety hazards such as fire and explosion in lithium-ion batteries. Replacing the flammable and explosive liquid electrolyte with an inert inorganic solid electrolyte is an important way to improve the safety of lithium-ion batteries. Solid electrolytes are light in weight, have a high energy density, and have good mechanical properties, which can effectively inhibit the growth of lithium dendrites and further improve the safety of the battery.

[0003] Solid electrolytes can be divided into two categories: polymers and inorganic solid electrolytes. Among them, the research on inorganic solid electrolytes with advantages such as easy preparation, high safety, high room-temperature conductivity, and high electrochemical stability has attracted much attention. Classified by their structure, inorganic solid electrolytes can be divided into three major systems: oxides, sulfides, and halides. Among them, oxide solid electrolyte materials have become the most commercially promising solid electrolyte materials due to their easily available raw materials, relatively simple preparation process, strong compatibility with existing battery cell processes, high ionic conductivity, good chemical stability, non-reaction with oxygen and moisture, and excellent processing performance. The oxide system mainly includes several categories such as the NASICON (sodium superionic conductor) structure system, the LISICON (lithium superionic conductor) structure system, the perovskite structure system, and the garnet structure system. Among them, the NASICON-type structured lithium aluminum titanium phosphate Li 1+x Al x Ti 2-x (PO4)3 (0 < x ≤ 1) solid electrolyte material has a high ionic conductivity (room-temperature ionic conductivity > 10 -4 S / cm), a wide electrochemical window, good thermal / chemical stability, and high mechanical strength, and is one of the most promising solid electrolyte materials for all-solid-state lithium-ion batteries, attracting extensive attention at home and abroad.

[0004] There are various methods for preparing lithium titanium aluminum phosphate solid electrolytes, and common ones include solid-phase sintering method, co-precipitation method, sol-gel method, melt quenching method, microwave synthesis method, and so on. Although the solid-phase method has a simple process, it generally uses multiple raw materials such as lithium source, titanium source, aluminum source, and phosphorus source. There are many types of raw materials, large differences in specific gravity, and large differences in particle size, which easily lead to poor mixing effect of the precursor. The required phase formation temperature is very high, and the energy consumption is serious, resulting in low purity of the prepared lithium titanium aluminum phosphate. At the same time, the solid electrolyte sintered has a high degree of hardening and serious wall sticking phenomenon, increasing the difficulty of subsequent processing. The co-precipitation method needs to introduce a precipitant for mixing and heating and go through steps such as filtration, washing, and drying. The steps are cumbersome, and the products after ball milling of inorganic powders are not easy to collect, time-consuming and laborious, and the discharge rate is low, causing great waste and increasing the cost of mass production of lithium titanium aluminum phosphate. The traditional sol-gel method generally uses titanium tetrachloride as the titanium source, which is extremely easy to react with the moisture in the air to produce HCl acid mist, which is harmful to the human body and the environment; or uses titanium alkoxides such as tetrabutyl titanate. This raw material has a high price and high cost. This raw material is extremely easy to react with the moisture in the air and is difficult to store. This raw material is flammable and has potential safety hazards. In addition, organic solvents harmful to the human body, such as ethylene glycol, need to be used, and the water solvent and organic solvent need to be removed by heating, with high energy consumption and a relatively cumbersome process.

[0005] Existing studies have shown that particle size plays a crucial role in ionic conductivity. Therefore, lithium titanium aluminum phosphate materials with nano-level particle sizes exhibit excellent ionic conductivity. However, the existing methods generally have problems such as poor product quality, high cost of raw materials used, or complex processes increasing processing costs, and the particle sizes of lithium titanium aluminum phosphate materials with nano-level particle sizes prepared by conventional methods are uncontrollable and the particle size uniformity is poor. Therefore, aiming at the problems existing in the existing preparation schemes, it is urgent to develop a lithium titanium aluminum phosphate solid electrolyte with good quality, uniform particle size, and excellent ionic conductivity and a preparation method for lithium titanium aluminum phosphate solid electrolyte with low cost and simple process. Summary of the Invention

[0006] One of the technical problems to be solved by the present invention is to overcome the problems of complex preparation process, high cost (expensive raw materials, sintering and caking, wall sticking, need to be broken, etc.), and poor quality (large particle size, uneven distribution) of the existing technology methods, and provide a method for preparing nano lithium titanium aluminum phosphate solid electrolyte materials by a room-temperature aqueous gel method.

[0007] The present invention provides a method for preparing nano lithium titanium aluminum phosphate solid electrolyte materials by a room-temperature aqueous gel method, including the following steps:

[0008] S1. According to Li 1+x Al x Ti 2-xWeigh the lithium source, aluminum source, phosphorus source, and titanium citrate according to the stoichiometric ratio of (PO4)3, and dissolve them in deionized water respectively to obtain a lithium source dispersion system, an aluminum source dispersion system, a phosphorus source dispersion system, and an aqueous titanium citrate solution, where 0 < x ≤ 1. Each substance is weighed according to the corresponding molar ratio of lithium, aluminum, titanium, and phosphorus, and the lithium source is in excess by 5% - 10%. Subsequently, stir and mix the lithium source dispersion system, aluminum source dispersion system, and phosphorus source dispersion system at room temperature until clear to obtain a lithium-aluminum-phosphorus composite aqueous solution;

[0009] S2. Pour the lithium-aluminum-phosphorus composite aqueous solution obtained in step S1 into the aqueous titanium citrate solution with stirring at room temperature to obtain a clear and transparent lithium aluminum phosphate lithium titanate precursor aqueous solution. Subsequently, age the aqueous solution at room temperature to obtain a lithium aluminum phosphate lithium titanate precursor aqueous gel, and finally heat the aqueous gel to obtain a lithium aluminum phosphate lithium titanate precursor dry gel;

[0010] S3. Calcinate the lithium aluminum phosphate lithium titanate precursor dry gel obtained in step S2 to obtain a nano lithium aluminum phosphate lithium titanate solid electrolyte material.

[0011] Compared with the prior art, especially compared with the preparation of lithium aluminum phosphate lithium titanate solid electrolyte by the traditional sol-gel method, the present invention provides a method for preparing nano lithium aluminum phosphate lithium titanate solid electrolyte material by room temperature aqueous gel method: First, prepare the dispersion systems of the raw materials of the lithium aluminum phosphate lithium titanate precursor. The dispersion systems before reaction and mixing exist in a solution state, and the precursor raw material molecules all exist in the form of ions, so that their subsequent mixing reaches the molecular or ionic level. A large number of titanium citrate molecules are in-situ hydrolyzed from the aqueous titanium citrate solution at room temperature. These released citrate molecules crosslink with each other to form a macromolecular network. When the molecules of the lithium source, aluminum source, and phosphorus source enter the crosslinked network formed by these citrate molecules, they quickly complex into a larger crosslinked network, and finally form a hydrogel together with the water molecules in the system. In the lithium aluminum phosphate lithium titanate hydrogel system, all the raw materials participating in the reaction are mixed at the molecular level, and the nucleating particles are all confined in the tiny hydrogel network. After drying, the hydrogel takes these tiny hydrogel networks as the growth units during calcination, restricting the growth space of the particles, and finally synthesizing a nano-scale lithium aluminum phosphate lithium titanate solid electrolyte material. Moreover, the particle size range can be regulated by controlling the calcination temperature and time.

[0012] And compared with the preparation methods of the prior art, the present invention has the following beneficial effects:

[0013] The preparation method of the present invention uses cheap and easily available raw materials and utilizes an aqueous system to synthesize lithium aluminum titanium phosphate. Its preparation process is simple, with low cost. The prepared material has small particle size, narrow particle size distribution, large specific surface area, and good electrochemical performance. The produced product has closely arranged particles, relatively uniform particle size, and the particle size can be adjusted between 50 and 300 nm. The present invention effectively solves the problems that the particle size of the product obtained by the traditional preparation method is uncontrollable, the process is complex, or the raw materials used are expensive and the process is uneconomical. In particular, the traditional dissolution-gel method for preparing lithium aluminum titanium phosphate uses organic or inorganic additives or complexing agents, and the process of evaporating the sol to dryness takes too long, resulting in high energy consumption. The present invention synthesizes a hydrogel precursor of lithium aluminum titanium phosphate with water as the solvent at room temperature through an in-situ complexation technology, and a nanoscale lithium aluminum titanium phosphate precursor can be obtained through subsequent low-temperature sintering. The synthesized product shows good uniformity, with closely arranged and uniform-sized particles. Moreover, the solvent of this preparation method is mainly water, which is environmentally friendly, and it can industrially produce a nanoscale lithium aluminum titanium phosphate solid electrolyte material with a particle size between 50 and 300 nm.

[0014] In a possible implementation manner, in the step S1, the lithium source is selected from at least one of lithium oxide, anhydrous lithium hydroxide, lithium hydroxide monohydrate, lithium chloride, lithium nitrate, lithium formate, anhydrous lithium acetate, lithium acetate dihydrate, lithium carbonate, lithium oxalate, lithium citrate, lithium phosphate, lithium tartrate, lithium hydrogen phosphate, lithium dihydrogen phosphate, lithium dihydrogen phosphate, lithium ammonium phosphate; the aluminum source is selected from at least one of aluminum chloride, anhydrous aluminum nitrate, aluminum nitrate nonahydrate, aluminum dihydrogen phosphate, aluminum acetate, aluminum phosphate, aluminum oxalate, aluminum carbonate, aluminum hydroxide; the phosphorus source is any one or a combination of multiple of white phosphorus, red phosphorus, black phosphorus, phosphorus trioxide, phosphorus pentoxide, phosphoric acid, metaphosphoric acid, ammonium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, lithium phosphate, lithium dihydrogen phosphate, lithium dihydrogen phosphate.

[0015] In a possible implementation manner, the lithium source is at least one of lithium hydroxide monohydrate, lithium nitrate, anhydrous lithium acetate, lithium acetate dihydrate, lithium carbonate; the aluminum source is at least one of aluminum chloride, aluminum nitrate nonahydrate, aluminum dihydrogen phosphate, aluminum hydroxide, aluminum carbonate; the phosphorus source is at least one of phosphoric acid, ammonium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, aluminum dihydrogen phosphate.

[0016] By the selection of the above lithium source, aluminum source, and phosphorus source, the preparation cost of the method for preparing the nanoscale lithium aluminum titanium phosphate solid electrolyte material by the room-temperature aqueous gel method in the present invention is further reduced, and the quality of the final product is improved through the selection of raw materials in the above possible implementation manners.

[0017] In a possible implementation, in step S2, the conditions for the aging treatment are as follows: aging the lithium titanium aluminum phosphate precursor aqueous solution at room temperature for 5 to 30 minutes to obtain a lithium titanium aluminum phosphate precursor aqueous wet gel.

[0018] Through aging at room temperature, the lithium titanium aluminum phosphate precursor aqueous solution is gradually transformed into a hydrocolloid of the precursor, and the hydrocolloid further swells into a wet gel. The selected aging time can not only ensure the sufficient swelling of the sol but also prevent the time from being too long to reduce production efficiency.

[0019] In a possible implementation, in step S2, the conditions for heating the aqueous wet gel are as follows: heating at a temperature of 60 to 120 °C for 30 to 360 minutes to obtain a lithium titanium aluminum phosphate precursor dry gel.

[0020] The selected drying temperature of the wet gel is relatively mild, not too high, and the time is not too long. It only needs to ensure that there is no obvious water attachment, which both ensures the maximum possible reduction of energy consumption and saves production costs.

[0021] In a possible implementation, in step S3, the calcination is carried out in multiple stages, including the first stage and the second stage. The calcination temperature in the first stage is 300 to 500 °C, the heating rate is 2 to 10 °C / min, and the holding time is 2 to 6 hours; the calcination temperature in the second stage is 650 to 900 °C, the heating rate is 2 to 10 °C / min, and the holding time is 0.5 to 10 hours.

[0022] Low-temperature calcination in the first stage can remove volatile components and organic impurities in the reactants, avoid the reaction between impurity molecules and reactants, and the calcination temperature in the low-temperature stage is relatively low, which can reduce unnecessary energy waste; the calcination in the second stage can ensure the full reaction and crystallization of the reactants, and the relatively low sintering temperature will not promote the growth of lithium titanium aluminum phosphate grains. Therefore, the prepared lithium titanium aluminum phosphate material has smaller particle size, narrower particle size distribution, and fewer aggregates. At the same time, the prepared ultra-fine lithium titanium aluminum phosphate nanoparticles also have ultra-high relative density, higher ion concentration, and larger interfacial contact area, high ion mobility, and can form a larger continuous conduction path for lithium ion transmission.

[0023] The second technical problem to be solved by the present invention is to provide a nano lithium titanium aluminum phosphate solid electrolyte to solve the problems of poor quality, uneven particle size, and general ion conductivity of the nano lithium titanium aluminum phosphate solid electrolyte in the prior art.

[0024] To solve the above problems, the present invention provides a nano lithium titanium aluminum phosphate solid electrolyte, which is prepared by the preparation method.

[0025] Compared with the prior art, the nano-lithium titanium aluminum phosphate solid electrolyte material in the present invention has small particle size, narrow particle size distribution, large specific surface area, good electrochemical performance, and the produced product has closely arranged particles and relatively uniform particle size, which can be adjusted between 50 and 300 nm and has a high ionic conductivity.

[0026] In a possible implementation manner, the molecular formula of the solid electrolyte powder material is Li 1+x Al x Ti 2-x (PO4)3, and the particle size of the solid electrolyte material is 50 - 300 nm.

[0027] In a possible implementation manner, 0.3 ≤ x ≤ 0.5.

[0028] x can take any value between 0 and 1, such as x = 0.3, 0.4, 0.5.

[0029] Through the further optimization of the above x data, the present invention further improves the electrochemical performance of the solid electrolyte powder material product. Description of the Drawings

[0030] Figure 1 It is the process flow chart of a method for preparing nano-lithium titanium aluminum phosphate solid electrolyte material by a room-temperature aqueous gel method in the present invention;

[0031] Figure 2 It is the scanning electron microscope (SEM) image of nano-lithium titanium aluminum phosphate Li 1.3 Al 0.3 Ti 1.7 (PO4)3 prepared in Example 1;

[0032] Figure 3 It is the X-ray diffraction (XRD) pattern of nano-lithium titanium aluminum phosphate Li 1.3 Al 0.3 Ti 1.7 (PO4)3 prepared in Example 1;

[0033] Figure 4 It is the scanning electron microscope (SEM) image of nano-lithium titanium aluminum phosphate Li 1.3 Al 0.3 Ti 1.7 (PO4)3 prepared in Example 2;

[0034] Figure 5 It is the scanning electron microscope (SEM) image of nano-lithium titanium aluminum phosphate Li 1.3 Al 0.3 Ti 1.7(SEM) image of (PO4)3;

[0035] Figure 6 The nano-lithium titanium aluminum phosphate Li 1.4 Al 0.4 Ti 1.6 (XRD) pattern of (PO4)3;

[0036] Figure 7 The nano-lithium titanium aluminum phosphate Li 1.5 Al 0.5 Ti 1.5 (XRD) pattern of (PO4)3. Detailed implementation manners

[0037] The present invention will be further described in detail below with reference to the accompanying drawings in specific implementation manners. In the following implementation manners, many detailed descriptions are provided to enable a better understanding of the present application. However, those skilled in the art can easily recognize that some of the features can be omitted in different situations, or can be replaced by other materials or methods. In some cases, some operations related to the present application are not shown or described in the specification, in order to avoid overshadowing the core part of the present application by excessive descriptions. For those skilled in the art, it is not necessary to describe these related operations in detail, and they can fully understand the related operations based on the descriptions in the specification and the general technical knowledge in the art.

[0038] In addition, the features, operations or characteristics described in the specification can be combined in any appropriate manner to form various implementation manners. At the same time, the steps or actions in the method description can also be reordered or adjusted in an obvious manner by those skilled in the art. Therefore, the various sequences in the specification and drawings are only for clearly describing a certain embodiment, and do not mean a necessary sequence, unless it is stated that a certain sequence must be followed.

[0039] It should be noted that the values given in the following embodiments are as accurate as possible. However, those skilled in the art understand that due to inevitable measurement errors and experimental operation problems, each number should be understood as an approximate number rather than an absolutely accurate value. For example, due to the error of the weighing instrument, the weight values of the raw materials for preparing the solid electrolyte material in each embodiment should be understood to have an error of ±2% or ±1%.

[0040] The present invention provides a nano-lithium titanium aluminum phosphate solid electrolyte powder and a preparation method thereof. Figure 1 is the process flow chart of a method for preparing a nano-lithium titanium aluminum phosphate solid electrolyte material by a room-temperature aqueous gel method in the present invention. The following combinesFigure 1 A further description is given of a method for preparing a nano-lithium aluminum titanium phosphate solid electrolyte material by a room-temperature aqueous gel method and its preparation method provided by the present invention.

[0041] The present invention provides a method for preparing a nano-lithium aluminum titanium phosphate solid electrolyte material by a room-temperature aqueous gel method, comprising the following steps:

[0042] S1. Weigh lithium source, aluminum source, phosphorus source and titanium citrate according to the stoichiometric ratio of Li 1+x Al x Ti 2-x (PO4)3, and dissolve them in deionized water respectively to obtain a lithium source dispersion system, an aluminum source dispersion system, a phosphorus source dispersion system and an aqueous titanium citrate solution, where 0 < x ≤ 1, and each substance is weighed according to its corresponding molar ratio of lithium, aluminum, titanium and phosphorus, with the lithium source being in excess by 5% - 10%. Subsequently, the lithium source dispersion system, the aluminum source dispersion system and the phosphorus source dispersion system are stirred and mixed at room temperature until clear to obtain a lithium-aluminum-phosphorus composite aqueous solution;

[0043] S2. The lithium-aluminum-phosphorus composite aqueous solution obtained in step S1 is poured into the aqueous titanium citrate solution with stirring at room temperature to obtain a clear and transparent lithium aluminum titanium phosphate precursor aqueous solution. Subsequently, the aqueous solution is aged at room temperature to obtain a lithium aluminum titanium phosphate precursor aqueous wet gel. Finally, after heating the aqueous wet gel, a lithium aluminum titanium phosphate precursor dry gel is obtained;

[0044] S3. The lithium aluminum titanium phosphate precursor dry gel obtained in step S2 is calcined to obtain a nano-lithium aluminum titanium phosphate solid electrolyte material.

[0045] As a preferred solution, in step S1, the lithium source is selected from at least one of lithium oxide, anhydrous lithium hydroxide, lithium hydroxide monohydrate, lithium chloride, lithium nitrate, lithium formate, anhydrous lithium acetate, lithium acetate dihydrate, lithium carbonate, lithium oxalate, lithium citrate, lithium phosphate, lithium tartrate, lithium hydrogen phosphate, lithium dihydrogen phosphate, lithium hydrogen diphosphate, lithium ammonium phosphate; the aluminum source is selected from at least one of aluminum chloride, anhydrous aluminum nitrate, aluminum nitrate nonahydrate, aluminum dihydrogen phosphate, aluminum acetate, aluminum phosphate, aluminum oxalate, aluminum carbonate, aluminum hydroxide; the phosphorus source is selected from any one or a combination of white phosphorus, red phosphorus, black phosphorus, phosphorus trioxide, phosphorus pentoxide, phosphoric acid, metaphosphoric acid, ammonium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, lithium phosphate, lithium dihydrogen phosphate, lithium hydrogen diphosphate.

[0046] As a preferred solution, the lithium source is at least one of lithium hydroxide monohydrate, lithium nitrate, anhydrous lithium acetate, lithium acetate dihydrate, and lithium carbonate; the aluminum source is at least one of aluminum chloride, aluminum nitrate nonahydrate, aluminum dihydrogen phosphate, aluminum hydroxide, and aluminum carbonate; the phosphorus source is at least one of phosphoric acid, ammonium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and aluminum dihydrogen phosphate.

[0047] As a preferred solution, in the step S2, the conditions for the aging treatment are: aging the aqueous solution of the lithium aluminum titanium phosphate precursor at room temperature for 5 to 30 min to obtain a wet gel of the lithium aluminum titanium phosphate precursor in an aqueous system.

[0048] As a preferred solution, in the step S2, the conditions for heating the wet gel in the aqueous system are: heating at a temperature of 60 to 120 °C for 30 to 360 min to obtain a dry gel of the lithium aluminum titanium phosphate precursor.

[0049] As a preferred solution, in the step S3, the calcination is carried out in multiple stages, including a first stage and a second stage. The calcination temperature in the first stage is 300 to 500 °C, the heating rate is 2 to 10 °C / min, and the holding time is 2 to 6 h; the calcination temperature in the second stage is 650 to 900 °C, the heating rate is 2 to 10 °C / min, and the holding time is 0.5 to 10 h.

[0050] The present invention also provides a nano lithium aluminum titanium phosphate solid electrolyte, which is prepared by the preparation method.

[0051] As a preferred solution, the molecular formula of the solid electrolyte powder material is Li 1+x Al x Ti 2-x (PO4)3, and the particle size of the solid electrolyte material is 50 to 300 nm.

[0052] As a preferred solution, 0.3 ≤ x ≤ 0.5.

[0053] To better understand the technical solutions provided by the present invention, the following uses multiple specific examples to separately illustrate the specific process and characteristics of preparing the nano lithium aluminum titanium phosphate solid electrolyte by using the method provided by the present invention. However, it should be understood that these examples are only for more detailed description and should not be construed as limiting the present invention in any form, that is, it is not intended to limit the protection scope of the present invention.

[0054] For those not specified in the examples in terms of specific technologies or conditions, they can all be carried out according to the technologies or conditions described in the literature in the field or according to the product instructions. In the following examples, the unit g is used for mass calculation, and the cases of converting it into mass ratios should also be within the protection scope of the present invention.

[0055] Example 1

[0056] This example provides a method for preparing nano - lithium aluminum titanium phosphate solid electrolyte material by room - temperature aqueous gel method. The preparation method includes the following steps:

[0057] S1. Weigh 91.27 g of lithium hydroxide monohydrate (10 wt% excess) according to the stoichiometric ratio of Li 1.3 Al 0.3 Ti 1.7 (PO4)3 (x = 0.3) and dissolve it in 150 g of deionized water. Weigh 169.68 g of aluminum nitrate nonahydrate and dissolve it in 150 g of deionized water. Weigh 517.55 g of 85% phosphoric acid solution, dilute it with 125 g of deionized water, and then mix these three solutions and stir at room temperature until clear to obtain a lithium - aluminum - phosphorus composite aqueous solution;

[0058] Weigh 927.82 g of titanium citrate and dissolve it in 1200 g of deionized water to obtain an aqueous solution of titanium citrate;

[0059] S2. Pour the lithium - aluminum - phosphorus composite aqueous solution obtained in step S1 into the aqueous solution of titanium citrate with stirring at room temperature to obtain a clear and transparent lithium aluminum titanium phosphate precursor aqueous solution. Then age this aqueous solution at room temperature for 20 min to obtain a lithium aluminum titanium phosphate precursor aqueous wet gel. Finally, heat this aqueous wet gel at 80 °C for 120 min to obtain a lithium aluminum titanium phosphate Li 1.3 Al 0.3 Ti 1.7 (PO4)3 precursor dry gel;

[0060] S3. Calcinate the lithium aluminum titanium phosphate Li 1.3 Al 0.3 Ti 1.7 (PO4)3 precursor dry gel obtained in step S2 to obtain a lithium aluminum titanium phosphate Li 1.3 Al 0.3 Ti 1.7 (PO4)3 solid electrolyte material. Among them, the first - stage calcination temperature is 300 °C, the heating rate is 5 °C / min, and the holding time is 2 h; the second - stage calcination temperature is 750 °C, the heating rate is 5 °C / min, and the holding time is 2 h.

[0061] Figure 2 SEM image of the nano - solid electrolyte lithium aluminum titanium phosphate Li 1.3 Al 0.3 Ti 1.7 (PO4)3 prepared in Example 1. It can be seen from the figure that the nano - lithium aluminum titanium phosphate Li 1.3Al 0.3 Ti 1.7 (PO4)3 material exhibits good uniformity, with the particles arranged closely and evenly in size, and the average particle size is about 70 nm.

[0062] Figure 3 The nano solid electrolyte lithium aluminum titanium phosphate Li 1.3 Al 0.3 Ti 1.7 (PO4)3 XRD pattern is shown, where the main characteristic diffraction peaks of the sample are consistent with the standard card (JCPDS#35-0754). The diffraction peaks are sharp and have high intensity, without impurity peaks, indicating that the sample has good crystallinity and high purity.

[0063] Example 2

[0064] This example provides a method for preparing nano lithium aluminum titanium phosphate solid electrolyte material by room temperature aqueous gel method. The preparation method includes the following steps:

[0065] S1. Weigh 91.27 g of lithium hydroxide monohydrate (10 wt% excess) according to the stoichiometric ratio of Li 1.3 Al 0.3 Ti 1.7 (PO4)3 (x = 0.3) and dissolve it in 150 g of deionized water. Weigh 35.1 g of aluminum hydroxide and disperse it in 100 g of deionized water. Weigh 517.55 g of 85% phosphoric acid solution and dilute it with 125 g of deionized water. Then mix these three solutions and stir at room temperature until clear to obtain a lithium-aluminum-phosphorus composite aqueous solution;

[0066] Weigh 927.82 g of titanium citrate and dissolve it in 1200 g of deionized water to obtain an aqueous solution of titanium citrate;

[0067] S2. Slowly pour the lithium-aluminum-phosphorus composite aqueous solution obtained in step S1 into the aqueous solution of titanium citrate while stirring at room temperature to obtain a clear and transparent lithium aluminum titanium phosphate precursor aqueous solution. Then age this aqueous solution at room temperature for 30 min to obtain a lithium aluminum titanium phosphate precursor aqueous wet gel. Finally, heat this aqueous wet gel at 60 °C for 240 min to obtain the lithium aluminum titanium phosphate Li 1.3 Al 0.3 Ti 1.7 (PO4)3 precursor dry gel;

[0068] S3. Calcinate the lithium aluminum titanium phosphate Li 1.3 Al 0.3 Ti 1.7 (PO4)3 precursor dry gel obtained in step S2 to obtain lithium aluminum titanium phosphate Li 1.3Al 0.3 Ti 1.7 (PO4)3 solid electrolyte material. The calcination temperature in the first stage is 350 °C, the heating rate is 5 °C / min, and the heat preservation time is 2 h; the calcination temperature in the second stage is 800 °C, the heating rate is 5 °C / min, and the heat preservation time is 2 h.

[0069] Figure 4 For the nano-solid electrolyte lithium aluminum titanium phosphate Li 1.3 Al 0.3 Ti 1.7 (PO4)3 prepared in Example 2, as can be seen from the figure, the nano-lithium aluminum titanium phosphate Li 1.3 Al 0.3 Ti 1.7 (PO4)3 material shows good uniformity, the particles are closely arranged, the sizes are uniform, and the average particle size is about 110 nm.

[0070] Example 3

[0071] This example provides a method for preparing nano-lithium aluminum titanium phosphate solid electrolyte material by room-temperature aqueous gel method. The preparation method includes the following steps:

[0072] S1. Weigh 91.27 g of lithium hydroxide monohydrate (10 wt% excess) according to the stoichiometric ratio of Li 1.3 Al 0.3 Ti 1.7 (PO4)3 (x = 0.3), dissolve it in 150 g of deionized water, weigh 35.1 g of aluminum hydroxide and disperse it in 100 g of deionized water, weigh 517.55 g of 85% phosphoric acid solution, dilute it with 125 g of deionized water, and then mix these three solutions and stir at room temperature until clear to obtain a lithium-aluminum-phosphorus composite aqueous solution;

[0073] Weigh 927.82 g of titanium citrate and dissolve it in 1200 g of deionized water to obtain an aqueous solution of titanium citrate;

[0074] S2. Pour the lithium-aluminum-phosphorus composite aqueous solution obtained in step S1 into the aqueous solution of titanium citrate with stirring at room temperature to obtain a clear and transparent precursor aqueous solution of lithium aluminum titanium phosphate. Then age this aqueous solution at room temperature for 10 min to obtain a precursor aqueous wet gel of lithium aluminum titanium phosphate. Finally, heat this aqueous wet gel at 90 °C for 180 min to obtain the precursor dry gel of lithium aluminum titanium phosphate Li 1.3 Al 0.3 Ti 1.7 (PO4)3;

[0075] S3. For the lithium aluminum titanium phosphate Li obtained in step S21.3 Al 0.3 Ti 1.7 The lithium aluminum titanium phosphate Li 1.3 Al 0.3 Ti 1.7 (PO4)3 solid electrolyte material is obtained by calcining the (PO4)3 precursor dry gel. The calcination temperature in the first stage is 300 °C, the heating rate is 5 °C / min, and the holding time is 2 h; the calcination temperature in the second stage is 800 °C, the heating rate is 5 °C / min, and the holding time is 4 h.

[0076] Figure 5 For the nano solid electrolyte lithium aluminum titanium phosphate Li 1.3 Al 0.3 Ti 1.7 (PO4)3 prepared in Example 3, as can be seen from the figure, the nano lithium aluminum titanium phosphate Li 1.3 Al 0.3 Ti 1.7 (PO4)3 material shows good uniformity, the particles are closely arranged, the size is uniform, and the average particle size is about 200 nm.

[0077] Example 4

[0078] This example provides a method for preparing a nano lithium aluminum titanium phosphate solid electrolyte material by a room temperature aqueous gel method. The preparation method includes the following steps:

[0079] S1. Weigh 98.29 g of lithium hydroxide monohydrate (10 wt% excess) according to the stoichiometric ratio of Li 1.4 Al 0.4 Ti 1.6 (PO4)3 (x = 0.4) and dissolve it in 150 g of deionized water. Weigh 226.24 g of aluminum nitrate nonahydrate and dissolve it in 180 g of deionized water. Weigh 517.55 g of 85% phosphoric acid solution and dilute it with 125 g of deionized water. Then mix these three solutions and stir at room temperature until clear to obtain a lithium-aluminum-phosphorus composite aqueous solution;

[0080] Weigh 873.24 g of titanium citrate and dissolve it in 1200 g of deionized water to obtain an aqueous solution of titanium citrate;

[0081] S2. Slowly pour the lithium-aluminum-phosphorus composite aqueous solution obtained in step S1 into the aqueous solution of titanium citrate while stirring at room temperature to obtain a clear and transparent lithium aluminum titanium phosphate precursor aqueous solution. Then age this aqueous solution at room temperature for 10 min to obtain a lithium aluminum titanium phosphate precursor aqueous wet gel. Finally, heat this aqueous wet gel at 60 °C for 240 min to obtain lithium aluminum titanium phosphate Li 1.4 Al0.4 Ti 1.6 (PO4)3 precursor dry gel

[0082] S3. Calcinate the lithium aluminum titanium phosphate Li 1.4 Al 0.4 Ti 1.6 (PO4)3 precursor dry gel to obtain lithium aluminum titanium phosphate Li 1.4 Al 0.4 Ti 1.6 (PO4)3 solid electrolyte material. The calcination temperature in the first stage is 350 °C, the heating rate is 5 °C / min, and the holding time is 2 h; the calcination temperature in the second stage is 750 °C, the heating rate is 5 °C / min, and the holding time is 3 h.

[0083] Figure 6 For the nano solid electrolyte lithium aluminum titanium phosphate Li 1.4 Al 0.4 Ti 1.6 (PO4)3 prepared in Example 4, the XRD pattern of which shows that the main characteristic diffraction peaks of the sample are consistent with the standard card (JCPDS#35-0754), the diffraction peak shape is sharp, the intensity is high, and there are no impurity peaks, indicating that the sample has good crystallinity and high purity.

[0084] Example 5

[0085] This example provides a method for preparing a nano lithium aluminum titanium phosphate solid electrolyte material by a room temperature aqueous gel method. The preparation method includes the following steps:

[0086] S1. Weigh 105.31 g of lithium hydroxide monohydrate (10 wt% excess) and dissolve it in 200 g of deionized water according to the stoichiometric ratio of Li 1.5 Al 0.5 Ti 1.5 (PO4)3 (x = 0.5), weigh 58.5 g of aluminum hydroxide and disperse it in 150 g of deionized water, weigh 517.55 g of 85% phosphoric acid solution, dilute it with 125 g of deionized water, and then mix these three solutions and stir at room temperature until clear to obtain a lithium-aluminum-phosphorus composite aqueous solution;

[0087] Weigh 818.66 g of titanium citrate and dissolve it in 1000 g of deionized water to obtain an aqueous solution of titanium citrate;

[0088] S2. Stir the lithium-aluminum-phosphorus composite aqueous solution obtained in step S1 and pour it into the titanium citrate aqueous solution at room temperature to obtain a clear and transparent lithium aluminum titanium phosphate precursor aqueous solution. Then, age this aqueous solution at room temperature for 20 min to obtain a lithium aluminum titanium phosphate precursor aqueous wet gel. Finally, heat this aqueous wet gel at 80 °C for 180 min to obtain a lithium aluminum titanium phosphate Li 1.5 Al 0.5 Ti 1.5 (PO4)3 precursor dry gel;

[0089] S3. Calcinate the lithium aluminum titanium phosphate Li 1.5 Al 0.5 Ti 1.5 (PO4)3 precursor dry gel to obtain a lithium aluminum titanium phosphate Li 1.5 Al 0.5 Ti 1.5 (PO4)3 solid electrolyte material. The calcination temperature in the first stage is 400 °C, the heating rate is 5 °C / min, and the holding time is 2.5 h; the calcination temperature in the second stage is 850 °C, the heating rate is 5 °C / min, and the holding time is 2 h.

[0090] Figure 7 The XRD pattern of the nano solid electrolyte lithium aluminum titanium phosphate Li 1.5 Al 0.5 Ti 1.5 (PO4)3 prepared in Example 5 is shown. It can be observed that the main characteristic diffraction peaks of the sample are consistent with the standard card (JCPDS#35-0754). The diffraction peak shapes are sharp, the intensities are high, and there are no impurity peaks, indicating that the sample has good crystallinity and high purity.

[0091] Through the above examples and the tests on the examples, it is further illustrated that the method for preparing a nano lithium aluminum titanium phosphate solid electrolyte material by a room-temperature aqueous gel method in the present invention uses cheap and easily available raw materials, synthesizes lithium aluminum titanium phosphate using an aqueous system, has a simple preparation process and low cost. The prepared nano lithium aluminum titanium phosphate solid electrolyte material has small particle size, narrow particle size distribution, large specific surface area, and good electrochemical performance. The produced product has closely arranged particles, relatively uniform particle size, and the particle size can be adjusted between 50 and 300 nm.

[0092] The method for preparing nano lithium titanium aluminum phosphate solid electrolyte material by room-temperature aqueous gel method of the present invention effectively solves the problems that the particle size of the products obtained by traditional preparation methods is uncontrollable, the process is complex, or the raw materials used are expensive and the process is uneconomical. In particular, the process of preparing lithium titanium aluminum phosphate by the traditional sol-gel method uses organic or inorganic additives or complexing agents, and the time-consuming evaporation of the sol is too long, resulting in high energy consumption. The method for preparing nano lithium titanium aluminum phosphate solid electrolyte material by room-temperature aqueous gel method of the present invention synthesizes a hydrogel precursor of lithium titanium aluminum phosphate with water as the solvent at room temperature through an in-situ complexation technology of self-generation. Through subsequent low-temperature sintering, a nano-scale lithium titanium aluminum phosphate precursor can be obtained. The synthesized product shows good uniformity, with close arrangement and uniform size between particles. Moreover, the solvent of this preparation method is mainly water, which is environmentally friendly, and can industrially produce nano lithium titanium aluminum phosphate solid electrolyte materials with particle sizes between 50 and 300 nm, solving the problems existing in the background technology.

[0093] Those skilled in the art can understand that although some embodiments herein include certain features included in other embodiments rather than other features, the combination of the features of different embodiments means that it is within the scope of the present invention and forms different embodiments. For example, in the above claims, any one of the claimed embodiments can be used in any combination. The information disclosed in this background art section is only intended to deepen the understanding of the overall background art of the present invention, and should not be regarded as an admission or any form of suggestion that this information constitutes the prior art known to those skilled in the art.

[0094] In the description of the present application, the description with reference to the terms "one embodiment", "some embodiments", "in this embodiment", "specific example", or "some examples", etc. means that the specific features, mechanisms, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, mechanisms, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0095] As described above, only the specific embodiments of the present application are provided, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed in the present application should be covered by the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for preparing nano-lithium aluminum titanium phosphate solid electrolyte material by a room temperature aqueous gel method, characterized in that: The following steps are involved: S1. Press Li 1+x Al x Ti 2-x A lithium source, an aluminum source, a phosphorus source and titanium citrate are weighed in a stoichiometric ratio of (PO4)3, and are dissolved in deionized water to obtain a lithium source dispersion system, an aluminum source dispersion system, a phosphorus source dispersion system and a titanium citrate aqueous solution, respectively, wherein 0<x≤1, each substance is weighed according to its corresponding molar ratio of lithium, aluminum, titanium and phosphorus, and the lithium source is in excess of 5% to 10%, and then the lithium source dispersion system, the aluminum source dispersion system and the phosphorus source dispersion system are stirred and mixed at room temperature until clarified to obtain a lithium-aluminum-phosphorus composite aqueous solution; S2, pouring the lithium-aluminum-phosphorus composite aqueous solution obtained in the step S1 into the titanium citrate aqueous solution while stirring at room temperature to obtain a clear and transparent lithium aluminum titanium phosphate precursor aqueous solution; then aging the lithium aluminum titanium phosphate precursor aqueous solution at room temperature to obtain a lithium aluminum titanium phosphate precursor aqueous wet gel, and finally heating the aqueous wet gel to obtain a lithium aluminum titanium phosphate precursor dry gel; S3, calcining the lithium aluminum titanium phosphate precursor dry gel obtained in step S2 to obtain a nano lithium aluminum titanium phosphate solid electrolyte material; In the step S2, the aging treatment conditions are: aging the lithium aluminum titanium phosphate precursor aqueous solution at room temperature for 5 to 30 minutes to obtain a lithium aluminum titanium phosphate precursor aqueous wet gel; In the step S2, the conditions for heating the aqueous wet gel of the lithium titanium aluminum phosphate precursor are: heating at a temperature of 60 to 120° C. for 30 to 360 min to obtain a dry gel of the lithium titanium aluminum phosphate precursor; In step S3, the calcination is carried out in multiple stages, including a first stage and a second stage. The calcination temperature in the first stage is 300-500°C, the heating rate is 2-10°C / min, and the insulation time is 2-6 h; the calcination temperature in the second stage is 650-900°C, the heating rate is 2-10°C / min, and the insulation time is 0.5-10 h.

2. The method for preparing nano-lithium aluminum titanium phosphate solid electrolyte material by the room temperature aqueous gel method according to claim 1, characterized in that: In the step S1, the lithium source is selected from at least one of lithium oxide, anhydrous lithium hydroxide, lithium hydroxide monohydrate, lithium chloride, lithium nitrate, lithium formate, anhydrous lithium acetate, lithium acetate dihydrate, lithium carbonate, lithium oxalate, lithium citrate, lithium phosphate, lithium tartrate, lithium hydrogen phosphate, lithium dihydrogen phosphate, dilithium hydrogen phosphate, and lithium ammonium phosphate; the aluminum source is selected from at least one of aluminum chloride, anhydrous aluminum nitrate, nonahydrate aluminum nitrate, aluminum dihydrogen phosphate, aluminum acetate, aluminum phosphate, aluminum oxalate, aluminum carbonate, and aluminum hydroxide; the phosphorus source is selected from any one or more combinations of white phosphorus, red phosphorus, black phosphorus, phosphorus trioxide, phosphorus pentoxide, phosphoric acid, metaphosphoric acid, ammonium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, lithium phosphate, lithium dihydrogen phosphate, and dilithium hydrogen phosphate.

3. The method for preparing nano-lithium aluminum titanium phosphate solid electrolyte material by room temperature aqueous gel method according to claim 2, characterized in that: The lithium source is at least one of lithium hydroxide monohydrate, lithium nitrate, anhydrous lithium acetate, lithium acetate dihydrate, and lithium carbonate; the aluminum source is at least one of aluminum chloride, aluminum nitrate nonahydrate, aluminum dihydrogen phosphate, aluminum hydroxide, and aluminum carbonate; the phosphorus source is at least one of phosphoric acid, ammonium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and aluminum dihydrogen phosphate.

4. A nano-lithium aluminum titanium phosphate solid electrolyte material, characterized in that: The nano-lithium aluminum titanium phosphate solid electrolyte material is prepared by the preparation method described in any one of claims 1-3.

5. The nano-lithium aluminum titanium phosphate solid electrolyte material according to claim 4, characterized in that: The molecular formula of the nano-lithium aluminum titanium phosphate solid electrolyte powder material is Li 1+x Al x Ti 2-x (PO4)3, 0.3≤x≤0.5, and the particle size of the nano-lithium aluminum titanium phosphate solid electrolyte material is 50-300 nm.

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