Perovskite type heterostructure material, preparation method and application thereof, and battery

Abstract

The invention discloses a perovskite type heterostructure material, a preparation method and application thereof and a battery. The perovskite type heterostructure material comprises a layered perovskite oxide containing alkali metal and a heterostructure coating layer located on the surface of the layered perovskite oxide, internal and external structure lattices are coherent, and no obvious interface exists; wherein the chemical formula of the layered perovskite oxide containing the alkali metal is A (n + 1) / 2A '(n + 1) / 2BnO3n + 1, and n = 1, 2 or 3; the chemical formula of the heterostructure coating layer is A < 3y > A '2 / 3-y > BO < 3-delta >, wherein y is more than or equal to 0.1 and less than or equal to 0.2; a is one or more of Li, Na and K, A'is a lanthanide rare earth element and / or Y, and B is Ti. The perovskite type heterostructure material prepared by the invention has intrinsic safe working voltage and excellent high rate performance and cycling stability, and the preparation method is simple and efficient, and is easy to realize industrial preparation.

Description

Technical Field

[0001] The present invention specifically relates to a perovskite-type heterostructured material, a preparation method, an application thereof, and a battery. Background Art

[0002] With the rapid development of electronic devices and electric vehicles, the market demand for the power density of lithium-ion batteries continues to climb, aiming to effectively alleviate the battery power anxiety problem by means of fast charging technology. In the lithium-ion battery system, the negative electrode side constitutes the key bottleneck for achieving fast charging of the battery. At present, the most mature negative electrode material in the lithium-ion battery system is graphite, which has been widely used in commercial lithium-ion batteries. However, graphite negative electrodes have specific limitations in terms of power density and safety. Although graphite has a high theoretical specific capacity of 372 mAh / g, its voltage plateau is about 0.1 V, close to the lithium precipitation potential, and lithium precipitation is extremely likely to occur under high-power charge and discharge conditions, thus accelerating the decline of battery performance and inducing safety problems. In addition, the lithium-ion diffusion coefficient of the graphite negative electrode is relatively low, and the lithium-ion migration rate is difficult to meet the requirements during fast charge and discharge, resulting in low charging efficiency. Spinel-type lithium titanate Li 4 Ti 5 O 12 is a potential high-power negative electrode material, which has a high ion diffusion coefficient and exhibits a "zero strain" characteristic during the lithium insertion and extraction process, so it has excellent rate performance and long-cycle stability. Lithium titanate has a charge and discharge plateau of about 1.55 V, which endows the fast charging process of the full battery with extremely high safety. However, the relatively low theoretical specific capacity of lithium titanate (~175 mAh / g) and the too high voltage plateau greatly limit the output energy density of the full battery. Therefore, developing a negative electrode material with a low voltage plateau, high capacity, and fast charge and discharge capabilities is of great significance for promoting the development of intrinsically safe lithium-ion batteries and achieving an effective balance between their energy density and power density.

[0003] Layered perovskite-type oxides are a type of new negative electrode materials. These materials have an intrinsically relatively low voltage plateau, which is significantly higher than the lithium precipitation potential, so they exhibit excellent intrinsic safety and can effectively avoid safety hazards such as lithium precipitation at high rates caused by extremely low voltages. However, these materials face many problems, such as insufficiently high lithium-ion diffusion coefficient, destruction of the structural framework during the lithium insertion process, and serious performance degradation caused by side reactions between the material surface and the electrolyte, resulting in limited high-rate performance and long-cycle stability, which restricts their development process and market application. Currently, there is still a lack of a simple and effective modification method for these materials. Therefore, proposing a solution to the above problems is the key to fully tapping the market potential of these materials. Summary of the Invention

[0004] The technical problem solved by the present invention is to overcome the defects of poor high-rate performance and long-cycle stability of layered perovskite-type oxides in the prior art, and to provide a perovskite-type heterostructure material, a preparation method, an application and a battery thereof. The perovskite-type heterostructure material prepared by the present invention has an intrinsic safe operating voltage, excellent high-rate performance and cycle stability, enabling it to precisely meet the market requirements for high-power fast-charging lithium-ion batteries, and having broad application prospects and great commercial value in the field of lithium-ion battery technology; moreover, the preparation method is simple and efficient, and is easy to realize industrial production.

[0005] The present invention uses layered perovskite A (n+1) / 2 A’ (n+1) / 2 B n O 3n+1 as a precursor. During the acid etching process, hydrogen ions in the acid will undergo an ion exchange reaction with the surface layer of the layered perovskite oxide cathode, regulating the stoichiometric ratios of surface elements A (such as Li), A’ (such as La) and B (Ti), thereby selectively dissolving part of the A (n+1) / 2 A’ (n+1) / 2 B n O 3n+1 ions in the shallow surface layer. During the subsequent high-temperature annealing process, structural reconstruction occurs on the surface to in-situ form a uniform fast ion conductor A 3y A’ 2 / 3-y BO 3-δ with rich oxygen vacancies, which can provide fast ion / electron transport channels, while the bulk phase remains in a layered perovskite structure, thus obtaining a new type of anode material A (n+1) / 2 A’ (n+1) / 2 B n O 3n+1 @A 3y A’ 2 / 3-y BO 3-δ 。Since the outer reconstructed layer is formed in-situ, the inner and outer layers of the heterostructure have coherent lattices and no obvious boundaries will appear. The uniform oxygen-deficient fast ion conductor A 3y A’ 2 / 3-y BO 3-δ phase formed on the surface has a three-dimensional lithium diffusion path, which can provide fast ion and electron transport channels, especially reducing the charge transport limitation of A (n+1) / 2 A’ (n+1) / 2 B n O 3n+1 during high-rate discharge and improving the rate performance. In addition, A 3y A’ 2 / 3-y BO 3-δThe rigid structure can effectively relieve the mechanical stress generated by the volume expansion and contraction of the electrode, inhibit the interfacial side reaction, and is beneficial to delaying the capacity decay; the bulk phase still maintains the layered perovskite phase. This method introduces a uniform oxygen-deficient A with high ionic conductivity and high structural stability in situ on the particle surface 3y A’ 2 / 3-y BO 3-δ coating layer, significantly improving the (n+1) / 2 A’ (n+1) / 2 B n O 3n+1 ionic diffusion rate and structural stability during the lithium insertion and extraction process, thereby greatly improving the battery power density and cycle life.

[0006] The present invention solves the above technical problems through the following technical solutions:

[0007] The present invention provides a perovskite-type heterostructure material, including a layered perovskite oxide containing an alkali metal and a heterostructure coating layer on its surface, with coherent internal and external structure lattices and no obvious interface;

[0008] Among them, the chemical formula of the layered perovskite oxide containing an alkali metal is A (n+1) / 2 A’ (n+1) / 2 B n O 3n+1 , n = 1, 2, 3, corresponding to single-layer, double-layer and triple-layer structures respectively; the chemical formula of the heterostructure coating layer is A 3y A’ 2 / 3-y BO 3-δ , 0.1 ≤ y ≤ 0.2; A is one or more of Li, Na and K, A’ is a lanthanide rare earth element and / or Y, and B is Ti.

[0009] In the present invention, the charge and discharge voltage platform of the perovskite-type heterostructure material is preferably 0.4 - 0.8V, such as 0.6V.

[0010] In the present invention, in the chemical formula of the heterostructure coating layer, δ generally refers to the oxygen element imbalance caused by the surface structure reconstruction during the annealing process.

[0011] In the present invention, the lanthanide rare earth element is preferably one or more of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu.

[0012] In the present invention, in the chemical formula of the heterostructure coating layer, preferably, 0.1 ≤ y ≤ 0.17, such as 0.11, 0.15 or 0.17.

[0013] In the present invention, the thickness of the heterostructure coating layer can be 2 - 10nm.

[0014] The present invention also provides a method for preparing a perovskite-type heterostructure material, comprising the following steps:

[0015] After carrying out an ion exchange reaction on a mixture of an alkali metal-containing layered perovskite oxide and an acid solution at 20 - 160 °C, the perovskite-type heterostructure material is obtained through calcination.

[0016] In the present invention, the acid solution is preferably one or more of hydrochloric acid, nitric acid, citric acid, acetic acid, formic acid, propionic acid, benzoic acid, and ethylenediaminetetraacetic acid. The solvent in the acid solution can be conventional in the art, such as deionized water. The concentration of the acid solution can be 0.1 - 2.0 M, preferably 0.2 - 1.5 M, for example 0.2 M, 0.3 M, 0.4 M, 0.5 M, 0.6 M, 0.8 M, 1.0 M, or 1.2 M.

[0017] In the present invention, the molar ratio of the acid in the acid solution to the mass of the alkali metal-containing layered perovskite oxide can be (0.01 - 2) mol:1 g, preferably (0.02 - 1) mol:1 g, for example 0.032 mol:1 g, 0.5 mol:1 g, 0.064 mol:1 g, 0.08 mol:1 g, 0.096 mol:1 g, 0.1 mol:1 g, 0.128 mol:1 g, 0.15 mol:1 g, 0.19 mol:1 g, 0.2 mol:1 g, or 0.3 mol:1 g.

[0018] In the present invention, the temperature of the ion exchange reaction is preferably 30 - 150 °C, for example 40 °C, 50 °C, 60 °C, 70 °C, 80 °C, 100 °C, or 120 °C. The time of the ion exchange reaction can be 2 - 48 h, preferably 6 - 24 h, for example 10 h, 12 h, 18 h, or 24 h.

[0019] In the present invention, the mode of the ion exchange reaction is preferably the liquid-phase stirring method, the hydrothermal method, or the sol-gel method.

[0020] Among them, when the mode of the ion exchange reaction is the liquid-phase stirring method or the hydrothermal method, washing and drying are generally required after the ion exchange reaction. The solvent used for washing can be conventional in the art, such as deionized water and / or ethanol. Through the washing, unreacted hydrogen ions and impurity anions can be removed. The drying is generally carried out in a blast drying oven; the drying temperature can be 80 - 120 °C; the drying time can be 8 - 16 h.

[0021] Among them, the liquid-phase stirring method refers to a reaction method in which the reaction system is continuously stirred. The reaction temperature of the liquid-phase stirring method is preferably 30-90 °C, such as 30 °C, 40 °C, 50 °C, 60 °C, 70 °C, 80 °C or 90 °C. The reaction time of the liquid-phase stirring method is preferably 6-48 h, such as 10 h, 12 h, 18 h or 24 h. The rotation speed of the liquid-phase stirring method can be 100-600 rpm, such as 200 rpm or 300 rpm.

[0022] In some preferred embodiments, the liquid-phase stirring method includes the following process: mixing and reacting a mixture of a layered perovskite oxide containing an alkali metal and an acid solution at 40-100 °C for 6-48 h.

[0023] Among them, the hydrothermal method is generally carried out in a reaction kettle. The temperature of the hydrothermal method is preferably 100-160 °C, such as 120 °C or 140 °C. The time of the hydrothermal method is preferably 8-24 h, such as 10 h, 12 h or 16 h. When the hydrothermal method is adopted, according to the routine in the art, the reactants generally need to be mixed evenly before the reaction, such as stirring at room temperature for 0.5-2 h (such as 1 h).

[0024] In some preferred embodiments, the hydrothermal method includes the following process: carrying out hydrothermal reaction on a mixture of a layered perovskite oxide containing an alkali metal and an acid solution at 100-160 °C for 6-48 h.

[0025] Among them, the sol-gel method generally refers to a reaction method in which the reaction system is continuously stirred until a gel state is reached. The rotation speed of the sol-gel method can be 100-600 rpm, such as 200 rpm or 300 rpm. The reaction temperature of the sol-gel method is preferably 60-90 °C, such as 80 °C. The reaction time of the sol-gel method is preferably 8-24 h, such as 12 h. When the sol-gel method is adopted, according to the routine in the art, the reactants generally need to be mixed evenly before the reaction, such as stirring at room temperature for 0.5-3 h (such as 1 h or 2 h).

[0026] Among them, when the sol-gel method is adopted, it is preferably necessary to add a complexing agent to the reaction system. The complexing agent preferably includes one or more of citric acid, maleic acid, tartaric acid, ethanolamine and sodium gluconate. The mass ratio of the complexing agent to the layered perovskite oxide containing an alkali metal can be (0.02-1):1, preferably (0.05-0.5):1, such as 0.1:1.

[0027] In certain preferred embodiments, the sol-gel method includes the following process: A mixture of a layered perovskite oxide containing an alkali metal, a complexing agent, and an acid solution is mixed and reacted at 60-90 °C until it becomes a gel state. According to the convention in the art, the gel state means the loss of high viscosity and fluidity of the system, and the system presents a state similar to a solid and can maintain a certain shape.

[0028] In the present invention, the atmosphere for the calcination is generally air, and the calcination is generally carried out in a muffle furnace.

[0029] In the present invention, the temperature for the calcination can be 300-1200 °C, such as 400 °C, 600 °C, 700 °C, 800 °C, or 900 °C. The time for the calcination can be 1-20 h, preferably 3-10 h, such as 3 h, 4 h, or 6 h. The calcination can be single calcination or double calcination. When the calcination includes single calcination, the temperature for the calcination is preferably 600-1000 °C, and the time for the calcination is preferably 3-10 h. When the calcination includes double calcination, the process for the calcination preferably includes: first calcining at 300-500 °C for 1-4 h, cooling down, re-grinding, and then calcining at 600-1000 °C for 2-8 h.

[0030] In certain preferred embodiments, when the ion exchange reaction is carried out by the sol-gel method, the process for the calcination includes the following process: first calcining at 300-500 °C for 1-4 h, cooling down, re-grinding, and then calcining at 600-1000 °C for 2-8 h.

[0031] According to the convention in the art, drying is generally required before the calcination. The drying is generally carried out in an oven. The temperature for the drying can be 70-120 °C, such as 80 °C, 100 °C, or 120 °C. The time for the drying can be 6-48 h, such as 12 h or 24 h.

[0032] In the present invention, during the ion exchange reaction process, some A ions and A' ions in the surface layer of the layered perovskite oxide containing an alkali metal are selectively dissolved by an acid under mild acid reaction conditions, and hydrogen ions are exchanged into the crystal structure, but the crystal structure framework and morphological dimensions of the precursor are retained, and only the ratios of the alkali metals A, A', and titanium in the surface layer of the layered perovskite oxide containing an alkali metal change.

[0033] In the present invention, the chemical formula of the layered perovskite oxide containing an alkali metal is as described above.

[0034] In the present invention, the layered perovskite oxide containing an alkali metal can be obtained by conventional commercial purchase or self-preparation. The preparation method of the layered perovskite oxide containing an alkali metal preferably includes the following steps:

[0035] The mixture containing the A source, A' source and titanium source is first calcined at 400 - 800 °C for 2 - 10 h, and then the temperature is further raised to 900 - 1300 °C for a second calcination for 2 - 10 h.

[0036] Among them, the further temperature increase means that after the first calcination, no cooling treatment is carried out, and the temperature is directly increased on the basis of the temperature of the first calcination.

[0037] Among them, the A source is preferably one or more of a metal salt containing alkali metal A, an alkali containing alkali metal A, and an oxide containing alkali metal A.

[0038] The salt containing alkali metal A is preferably a carbonate containing alkali metal A and / or a nitrate containing alkali metal A. The carbonate containing alkali metal A is preferably one or more of lithium carbonate, sodium carbonate, sodium bicarbonate, potassium carbonate and potassium bicarbonate. The nitrate containing alkali metal A is preferably one or more of lithium nitrate, sodium nitrate and potassium nitrate.

[0039] The alkali containing alkali metal A is preferably lithium hydroxide, sodium hydroxide or potassium hydroxide.

[0040] The oxide containing alkali metal A is preferably lithium oxide, sodium oxide or potassium oxide.

[0041] Among them, the A' source is preferably a metal salt containing metal A' and / or an oxide containing metal A'.

[0042] The metal salt containing metal A' is preferably a carbonate containing metal A' and / or a nitrate containing metal A'.

[0043] The oxide containing metal A' can be, for example, lanthanum oxide, yttrium oxide or europium oxide.

[0044] Among them, the titanium source is preferably an oxide containing titanium and / or a metal salt containing titanium.

[0045] The oxide containing titanium can be, for example, titanium dioxide.

[0046] The metal salt containing titanium can be, for example, titanium chloride and / or tetrabutyl titanate.

[0047] Among them, the molar ratio of the A source, A' source and titanium source is generally determined according to the chemical formula of the alkali metal-containing layered perovskite oxide in a stoichiometric ratio, and usually, on the basis of the theoretical stoichiometric ratio (n + 1) / 2 : (n + 1) / 2 : n, the amount of the A source is appropriately increased by 1% - 10% (such as 2%, 5% or 8%).

[0048] Among them, the preparation method of the mixture containing the A source, A' source and titanium source preferably includes the following steps: grinding the A source, A' source and titanium source.

[0049] The grinding method can be conventional in the art, such as ball milling. The grinding time can be 2 - 6 h, such as 4 h.

[0050] Among them, the calcination is generally carried out in air, and the calcination equipment is generally a muffle furnace. The heating rate to the temperature of the first calcination can be conventional in the art, generally 3 - 5 °C / min.

[0051] Among them, the temperature of the first calcination is preferably 500 - 700 °C, such as 550 °C or 600 °C. The time of the first calcination is preferably 3 - 8 h, such as 6 h.

[0052] Among them, the temperature of the second calcination is preferably 1000 - 1300 °C, such as 1200 °C. The time of the second calcination is preferably 2 - 6 h, such as 4 h.

[0053] The present invention also provides a perovskite - type heterostructure material prepared by the preparation method as described above.

[0054] The present invention also provides an application of the perovskite - type heterostructure material as described above in secondary batteries.

[0055] In the present invention, the secondary battery is preferably a lithium - ion battery or a sodium - ion battery.

[0056] The present invention also provides a secondary battery, which includes the perovskite - type heterostructure material as described above.

[0057] On the basis of conforming to the common knowledge in the art, the above - mentioned preferred conditions can be combined arbitrarily to obtain various preferred examples of the present invention.

[0058] The reagents and raw materials used in the present invention are all commercially available.

[0059] The positive and progressive effects of the present invention are as follows:

[0060] (1) Due to the introduction of the surface oxygen - deficient fast - ion conductor phase in the perovskite - type heterostructure material prepared by the present invention, the diffusion rate of desolvated lithium ions from the particle surface to the bulk phase and the electron transport can be significantly improved, thereby improving the rate performance and showing more excellent performance under fast charge - discharge conditions;

[0061] (2) Due to the stable structure and uniform coating of the fast ion conductor phase in the perovskite-type heterostructure material prepared by the present invention, it can provide good protection for the structure of the layered perovskite negative electrode material during the lithium insertion and extraction process, effectively preventing structural deterioration. At the same time, this coating layer can inhibit the side reactions between the negative electrode interface and the electrolyte, thus greatly extending the cycle life of the battery and improving safety.

[0062] (3) From the perspective of the production process, the operation steps of the perovskite-type heterostructure material of the present invention are simple and efficient, without complex process flows and high equipment investment, which can effectively reduce production costs. Moreover, the requirements for process technology are relatively low, which is conducive to popularization and application in production enterprises of different scales. In addition, the solution after the surface ion exchange reaction can be recycled, meeting the concepts of green environmental protection and sustainable development, greatly facilitating the realization of industrial preparation, and providing strong support for large-scale production and commercial application. Description of the Drawings

[0063] Figure 1 Schematic diagram of the crystal structure of the perovskite-type heterostructure material obtained in Example 1;

[0064] Figure 2 XRD pattern of the perovskite-type heterostructure material obtained in Example 1;

[0065] Figure 3 SEM and TEM images of the perovskite-type heterostructure material obtained in Example 1;

[0066] Figure 4 Charge-discharge curve diagram of the perovskite-type heterostructure material obtained in Example 1 and voltage plateau comparison with commercial graphite and lithium titanate negative electrodes;

[0067] Figure 5 Rate performance diagram of the perovskite-type heterostructure material obtained in Example 1 and rate performance comparison with commercial graphite and lithium titanate negative electrodes;

[0068] Figure 6 Cycle performance diagram of the perovskite-type heterostructure material obtained in Example 1 at 20C;

[0069] Figure 7 XRD pattern of the perovskite-type heterostructure material obtained in Example 2;

[0070] Figure 8 Cycle performance diagram of the perovskite-type heterostructure material obtained in Example 2 at 20C;

[0071] Figure 9 XRD pattern of the perovskite-type heterostructure material obtained in Example 3. Detailed Embodiments

[0072] The present invention will be further described below by way of examples, but the present invention is not limited to the scope of the described examples. For the experimental methods without specific conditions in the following examples, they are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0073] Example 1

[0074] (1) Weigh 1.05 mmol of lithium carbonate, 1 mmol of lanthanum oxide and 3 mmol of titanium dioxide, and mechanically ball-mill for 4 hours. Collect the raw material powder and place it in a crucible. In a muffle furnace, heat it to 550 °C at a rate of 3 °C per minute and keep it warm for 6 hours. Then, without cooling, continue to heat it to 1200 °C at the same heating rate and keep it warm for 4 hours. After natural cooling, obtain the Li 2 La 2 Ti 3 O 10 precursor.

[0075] (2) Subsequently, add 0.5 g of Li 2 La 2 Ti 3 O 10 powder to 80 mL of 0.4 M hydrochloric acid aqueous solution, and stir at a speed of 200 rpm at 60 °C for 24 hours. Collect the reaction product, filter and wash it three times with deionized water and ethanol solution, and dry it in a forced-air oven at 80 °C for 12 hours. Place the dried powder in a crucible, heat it to 800 °C at a rate of 3 °C per minute in a muffle furnace and keep it warm for 6 hours. After natural cooling, obtain the perovskite-type heterostructure material Li 2 La 2 Ti 3 O 10 @Li 0.5 La 0.5 TiO 3-δ .

[0076] Example 2

[0077] (1) Weigh 1.05 mmol of lithium carbonate, 1 mmol of lanthanum oxide and 3 mmol of titanium dioxide, and mechanically ball-mill for 4 hours. Collect the raw material powder and place it in a crucible. In a muffle furnace, heat it to 550 °C at a rate of 3 °C per minute and keep it warm for 6 hours. Then, without cooling, continue to heat it to 1200 °C at the same heating rate and keep it warm for 4 hours. After natural cooling, obtain the Li 2 La 2 Ti 3 O 10 precursor.

[0078] (2) Subsequently, add 0.5 g of Li 2 La 2 Ti 3 O10 The powder is added to 80 mL of 1.2 M hydrochloric acid aqueous solution and stirred at 80 °C at a rotation speed of 200 rpm for 12 hours. The product after the reaction is collected and filtered and washed three times with deionized water and ethanol solution, and dried in a blast drying oven at 80 °C for 12 hours. The dried powder is placed in a crucible, heated to 800 °C at a rate of 3 °C per minute in a muffle furnace and held for 6 hours, and after natural cooling, the perovskite-type heterostructure material Li 2 La 2 Ti 3 O 10 @Li 0.33 La 0.56 TiO 3-δ is obtained.

[0079] Example 3

[0080] (1) Weigh 1.05 mmol of lithium carbonate, 1 mmol of lanthanum oxide and 3 mmol of titanium dioxide, and mechanically ball mill for 4 hours. Collect the raw material powder and place it in a crucible. Heat it to 550 °C at a rate of 3 °C per minute in a muffle furnace and hold for 6 hours. Without cooling treatment, continue to heat it to 1200 °C at the same heating rate and hold for 4 hours. After natural cooling, Li 2 La 2 Ti 3 O 10 precursor is obtained.

[0081] (2) Subsequently, 0.5 g of Li 2 La 2 Ti 3 O 10 powder is added to 80 mL of 0.5 M nitric acid aqueous solution and stirred at 60 °C at a rotation speed of 200 rpm for 10 hours. The product after the reaction is collected and filtered and washed three times with deionized water and ethanol solution, and dried in a blast drying oven at 80 °C for 12 hours. The dried powder is placed in a crucible, heated to 800 °C at a rate of 3 °C per minute in a muffle furnace and hold for 6 hours. After natural cooling, the perovskite-type heterostructure material Li 2 La 2 Ti 3 O 10 @Li 0.5 La 0.5 TiO 3-δ is obtained.

[0082] Example 4

[0083] (1) Weigh 1.05 mmol of lithium carbonate, 1 mmol of lanthanum oxide and 3 mmol of titanium dioxide, and mechanically ball-mill for 4 hours. Collect the raw material powder and place it in a crucible. In a muffle furnace, heat it to 550 °C at a rate of 3 °C per minute and hold for 6 hours. Without cooling, continue to heat it to 1200 °C at the same heating rate and hold for 4 hours. After natural cooling, obtain Li 2 La 2 Ti 3 O 10 precursor.

[0084] (2) Subsequently, add 0.5 g of Li 2 La 2 Ti 3 O 10 powder to 80 mL of 0.4 M hydrochloric acid aqueous solution, stir at a speed of 200 rpm at room temperature for 1 hour, then place it in a high-temperature and high-pressure reaction kettle and hold at 120 °C for 12 h. Collect the reaction product, filter and wash it three times with deionized water and ethanol solution, and dry it in a blast drying oven at 80 °C for 12 hours. Place the dried powder in a crucible, heat it to 800 °C at a rate of 3 °C per minute in a muffle furnace and hold for 6 hours. After natural cooling, obtain the perovskite-type heterostructure material Li 2 La 2 Ti 3 O 10 @Li 0.33 La 0.56 TiO 3-δ .

[0085] Example 5

[0086] (1) Weigh 1.05 mmol of lithium carbonate, 1 mmol of lanthanum oxide and 3 mmol of titanium dioxide, and mechanically ball-mill for 4 hours. Collect the raw material powder and place it in a crucible. In a muffle furnace, heat it to 550 °C at a rate of 3 °C per minute and hold for 6 hours. Without cooling, continue to heat it to 1200 °C at the same heating rate and hold for 4 hours. After natural cooling, obtain Li 2 La 2 Ti 3 O 10 precursor.

[0087] (2) Subsequently, add 0.5 g of Li 2 La 2 Ti 3 O 10The powder was added to a mixed solution of 80 mL of 0.4 M hydrochloric acid and 0.05 g of citric acid, stirred at a speed of 200 rpm at room temperature for 2 hours, then heated to 80 °C and stirred at a speed of 200 rpm until the solution formed a gel state, and then the stirring reaction was stopped. The obtained gel was dried in a blast oven at 100 °C, placed in a crucible, heated to 400 °C at a rate of 3 °C per minute in a muffle furnace and held for 2 hours, taken out, sufficiently ground, then heated to 800 °C and held for 4 hours, and naturally cooled to obtain the perovskite-type heterostructure material Li 2 La 2 Ti 3 O 10 @Li 0.33 La 0.56 TiO 3-δ 。

[0088] Example 6

[0089] (1) Weigh 1.05 mmol of sodium carbonate, 1 mmol of lanthanum oxide and 3 mmol of titanium dioxide, mechanically ball-mill for 4 hours, collect the raw material powder and place it in a crucible, heat it to 550 °C at a rate of 3 °C per minute in a muffle furnace and hold for 6 hours, then without cooling, continue to heat at the same heating rate to 1200 °C and hold for 4 hours, and naturally cool to obtain Na 2 La 2 Ti 3 O 10 precursor.

[0090] (2) Then, 0.5 g of Na 2 La 2 Ti 3 O 10 powder was added to 80 mL of 0.4 M hydrochloric acid aqueous solution, and stirred at a speed of 200 rpm at 60 °C for 24 hours. The reaction product was collected, filtered and washed three times with deionized water and ethanol solution, and dried in a blast oven at 80 °C for 12 hours. The dried powder was placed in a crucible, heated to 800 °C at a rate of 3 °C per minute in a muffle furnace and held for 6 hours, and naturally cooled to obtain the perovskite-type heterostructure material Na 2 La 2 Ti 3 O 10 @Na 0.5 La 0.5 TiO 3-δ 。

[0091] Example 7

[0092] (1) Weigh 1.05 mmol of potassium carbonate, 1 mmol of lanthanum oxide and 3 mmol of titanium dioxide, and mechanically ball-mill for 4 hours. Collect the raw material powder and place it in a crucible. In a muffle furnace, heat it to 550 °C at a rate of 3 °C per minute and hold for 6 hours. Without cooling, continue to heat it to 1200 °C at the same heating rate and hold for 4 hours. After natural cooling, obtain the K 2 La 2 Ti 3 O 10 precursor.

[0093] (2) Subsequently, add 0.5 g of K 2 La 2 Ti 3 O 10 powder to 80 mL of 0.4 M hydrochloric acid aqueous solution, and stir at a speed of 200 rpm at 60 °C for 24 hours. Collect the reaction product, filter and wash it three times with deionized water and ethanol solution, and dry it in a forced-air oven at 80 °C for 12 hours. Place the dried powder in a crucible, heat it to 800 °C at a rate of 3 °C per minute in a muffle furnace and hold for 6 hours. After natural cooling, obtain the perovskite-type heterostructure material K 2 La 2 Ti 3 O 10 @K 0.5 La 0.5 TiO 3-δ .

[0094] Example 8

[0095] (1) Weigh 1.05 mmol of lithium carbonate, 1 mmol of lanthanum oxide and 2 mmol of titanium dioxide, and mechanically ball-mill for 4 hours. Collect the raw material powder and place it in a crucible. In a muffle furnace, heat it to 500 °C at a rate of 3 °C per minute and hold for 6 hours. Without cooling, continue to heat it to 950 °C at the same heating rate and hold for 4 hours. After natural cooling, obtain the LiLaTiO 4 precursor.

[0096] (2) Subsequently, add 0.5 g of LiLaTiO 4 powder to 80 mL of 0.4 M hydrochloric acid aqueous solution, and stir at a speed of 200 rpm at 60 °C for 24 hours. Collect the reaction product, filter and wash it three times with deionized water and ethanol solution, and dry it in a forced-air oven at 80 °C for 12 hours. Place the dried powder in a crucible, heat it to 800 °C at a rate of 3 °C per minute in a muffle furnace and hold for 6 hours. After natural cooling, obtain the perovskite-type heterostructure material LiLaTiO 4 @Li 0.5 La 0.5 TiO 3-δ .

[0097] Example 9

[0098] (1) Weigh 1.05 mmol of lithium carbonate, 1 mmol of yttrium oxide and 2 mmol of titanium dioxide, and mechanically ball-mill for 4 hours. Collect the raw material powder and place it in a crucible. In a muffle furnace, heat it to 550 °C at a rate of 3 °C per minute and hold for 6 hours, then continue to heat to 900 °C at the same heating rate and hold for 4 hours. After natural cooling, obtain the LiYTiO 4 precursor.

[0099] (2) Subsequently, add 0.5 g of LiYTiO 4 powder to 80 mL of 0.6 M hydrochloric acid aqueous solution, and stir at a speed of 200 rpm at 60 °C for 24 hours. Collect the reaction product and filter and wash it three times with deionized water and ethanol solution, and dry it in a forced-air oven at 80 °C for 12 hours. Place the dried powder in a crucible, heat it to 800 °C at a rate of 3 °C per minute in a muffle furnace and hold for 6 hours. After natural cooling, obtain the perovskite-type heterostructure material LiYTiO 4 @Li 0.5 Y 0.5 TiO 3-δ .

[0100] Example 10

[0101] (1) Weigh 1.05 mmol of lithium carbonate, 1 mmol of europium oxide and 2 mmol of titanium dioxide, and mechanically ball-mill for 4 hours. Collect the raw material powder and place it in a crucible. In a muffle furnace, heat it to 550 °C at a rate of 3 °C per minute and hold for 6 hours, then continue to heat to 950 °C at the same heating rate without cooling treatment and hold for 4 hours. After natural cooling, obtain the LiEuTiO 4 precursor.

[0102] (2) Subsequently, add 0.5 g of LiEuTiO 4 powder to 80 mL of 0.6 M hydrochloric acid aqueous solution, and stir at a speed of 200 rpm at 60 °C for 24 hours. Collect the reaction product and filter and wash it three times with deionized water and ethanol solution, and dry it in a forced-air oven at 80 °C for 12 hours. Place the dried powder in a crucible, heat it to 800 °C at a rate of 3 °C per minute in a muffle furnace and hold for 6 hours. After natural cooling, obtain the perovskite-type heterostructure material LiEuTiO 4 @Li 0.5 Eu 0.5 TiO 3-δ .

[0103] Example 11

[0104] Compared with Example 1, except that the concentration of hydrochloric acid in step (2) was adjusted to 0.2 M, other operations and conditions were the same as those in Example 1, and the perovskite-type heterostructure material Li 2 La 2 Ti 3 O 10 @Li 0.5 La 0.5 TiO 3-δ was obtained after natural cooling.

[0105] Example 12

[0106] Compared with Example 1, except that the concentration of hydrochloric acid in step (2) was adjusted to 0.8 M, other operations and conditions were the same as those in Example 1, and the perovskite-type heterostructure material Li 2 La 2 Ti 3 O 10 @Li 0.5 La 0.5 TiO 3-δ was obtained after natural cooling.

[0107] Example 13

[0108] Compared with Example 1, except that 0.4 M hydrochloric acid in step (2) was replaced with 0.4 M nitric acid, other operations and conditions were the same as those in Example 1, and the perovskite-type heterostructure material Li 2 La 2 Ti 3 O 10 @Li 0.5 La 0.5 TiO 3-δ was obtained after natural cooling.

[0109] Example 14

[0110] Compared with Example 1, except that the temperature of the reaction with acid in step (2) was adjusted from 60 °C to 40 °C, other operations and conditions were the same as those in Example 1, and the perovskite-type heterostructure material Li 2 La 2 Ti 3 O 10 @Li 0.5 La 0.5 TiO 3-δ was obtained after natural cooling.

[0111] Example 15

[0112] Compared with Example 1, except that the reaction time with acid in step (2) was adjusted from 24 hours to 12 hours, the remaining operations and conditions were the same as those in Example 1, and the perovskite-type heterostructure material Li 2 La 2 Ti 3 O 10 @Li 0.5 La 0.5 TiO 3-δ was obtained after natural cooling.

[0113] Example 16

[0114] Compared with Example 1, except that the calcination temperature in step (2) was adjusted from 800 °C to 700 °C, the remaining operations and conditions were the same as those in Example 1, and the perovskite-type heterostructure material Li 2 La 2 Ti 3 O 10 @Li 0.5 La 0.5 TiO 3-δ was obtained after natural cooling.

[0115] Example 17

[0116] Compared with Example 1, except that the calcination time in step (2) was adjusted from 6 hours to 3 hours, the remaining operations and conditions were the same as those in Example 1, and the perovskite-type heterostructure material Li 2 La 2 Ti 3 O 10 @Li 0.5 La 0.5 TiO 3-δ was obtained after natural cooling.

[0117] Comparative Example 1

[0118] Commercial graphite (Ningbo Shanshan P15-X).

[0119] Comparative Example 2

[0120] Lithium titanate (Gree Titanium New Energy LTO).

[0121] Effect Example

[0122] Sample characterization: The structural information of the samples was collected using an X-ray diffractometer (XRD), the morphology and ultramicrostructure information of the samples were collected using a scanning electron microscope (SEM) and a transmission electron microscope (TEM), the electrochemical characteristics of the samples were tested using a Chenhua electrochemical workstation, and the battery performance of the samples was characterized using a Blue-Energy battery test system.

[0123] Figure 1Schematic diagram of the crystal structure of the heterostructure anode material prepared in Example 1. Its bulk phase is a layered Li 2 La 2 Ti 3 O 10 phase, and the surface is a fast ion conductor Li 0.5 La 0.5 TiO 3-δ phase. Since ion exchange and structural reconstruction occur in-situ and uniformly, there is no obvious boundary between the inner and outer two-layer lattice coherences. The perovskite-type heterostructure material prepared in Example 1 was subjected to XRD testing, and the test results are shown in Figure 2 , and the results confirmed that the heterostructure is composed of a layered Li 2 La 2 Ti 3 O 10 phase and a fast ion conductor Li 0.5 La 0.5 TiO 3-δ phase, which is in good agreement with the standard spectrum. Figure 3 SEM and TEM images of the perovskite-type heterostructure material prepared in Example 1. The SEM image shows that the material is cubic blocky, and the particle size is 2-5 microns; the TEM image confirms that the material is a heterostructure, in which the bulk phase is Li 2 La 2 Ti 3 O 10 phase, and the surface is Li 0.5 La 0.5 TiO 3-δ phase, and the thickness of the surface Li 0.5 La 0.5 TiO 3-δ coating layer is about 2-2.5 nm. Figure 7 XRD spectrum of the perovskite-type heterostructure material prepared in Example 2. The results confirmed that the heterostructure is composed of a layered Li 2 La 2 Ti 3 O 10 phase and a fast ion conductor Li 0.33 La 0.56 TiO 3-δ phase, which is in good agreement with the standard spectrum. Figure 9 XRD spectrum of the perovskite-type heterostructure material prepared in Example 3. The results confirmed that the heterostructure is composed of a layered Li 2 La 2 Ti 3 O 10 phase and a fast ion conductor Li 0.5 La 0.5 TiO 3-δ phase, which is in good agreement with the standard spectrum.

[0124] The chemical formulas of the perovskite heterostructure materials prepared in Examples 1-17 were all determined by XRD characterization.

[0125] The electrochemical performance of the perovskite heterostructure materials prepared in Examples 1-17 and Comparative Examples 1-2 was tested using a CR2016 type coin cell. The counter electrode used was a lithium metal sheet with a thickness of 1 mm and a diameter of 15 mm. The working electrodes were composed of the perovskite heterostructure materials prepared in each example or Comparative Examples 1-2, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF), with a mass ratio of 8:1:1. The specific preparation process of the negative electrode sheet was as follows: First, 160 mg of the perovskite heterostructure material, 20 mg of conductive acetylene black, and 1 mL of a PVDF N-dimethylpyrrolidone solution (20 mg / mL) were taken and stirred to prepare a slurry. Subsequently, the slurry was coated on a copper foil and dried in a vacuum oven at 120 °C, and then cut into electrode sheets with a diameter of 12 mm using a punching machine. The loading amount of the active material on the electrode sheet was 1.5-2.0 mg / cm 2 . When assembling the battery, a Whatman glass fiber separator GF / C and 1 M lithium hexafluorophosphate electrolyte (the volume ratio of the solvents in the solvent was DEC:EC = 1:1) were used, and the assembly was carried out in a Braun argon glove box with the oxygen and water vapor contents both below 0.1 ppm. Electrochemical tests were performed using a CHI760e electrochemical workstation from Shanghai Chenhua Co., Ltd. and a LAND-CT2001C battery test system from Wuhan Blue Electric Co., Ltd. The test results are shown in Figures 4 - 6 , Figure 8 and Table 1.

[0126] Figure 4 shows the charge-discharge curve of the perovskite heterostructure material prepared in Example 1 at 0.1 C. The results show that its specific capacity is 206 mAh / g, the voltage plateau is at 0.6 V, the capacity of the spinel lithium titanate negative electrode is increased by 31 mAh / g, and the voltage plateau is decreased by 0.95 V. Compared with the graphite negative electrode, the voltage plateau is increased by 0.5 V. Therefore, it has very excellent potential high energy density and intrinsic safety.

[0127] Figure 5 shows the rate performance of the perovskite heterostructure material prepared in Example 1. The results show that its average specific capacities at 0.1, 0.5, 1, 2, 5, 10, 20, 50, and 100 C rates are 204, 195, 186, 177, 165, 157, 152, 136, and 120 mAh / g respectively, with excellent capacity retention at high rates, significantly superior to commercial graphite and lithium titanate negative electrodes.

[0128] Figure 6It is the long-cycle performance of the perovskite-type heterostructure material prepared in Example 1 at a rate of 20C. The capacity retention rate after 10,000 cycles can reach 86.2%, showing very excellent long-cycle stability. Figure 8 It is the long-cycle performance of the perovskite-type heterostructure material prepared in Example 2 at a rate of 20C. The capacity retention rate after 10,000 cycles can reach 87.5%, showing very excellent long-cycle stability.

[0129] Table 1

[0130] 0.1C 0.5C 1C 2C 5C 10C 20C 50C 100C Example 1 204 195 186 177 165 157 152 136 120 Example 2 201 192 188 175 164 155 147 133 118 Example 3 200 188 182 170 157 144 137 131 110 Example 4 202 188 179 170 158 149 138 126 109 Example 5 198 182 173 162 152 140 128 117 105 Example 6 163 155 149 144 138 134 128 109 99 Example 7 157 151 145 140 135 129 124 106 97 Example 8 188 180 171 165 157 150 144 130 115 Example 9 185 176 167 163 155 148 141 127 111 Example 10 179 172 165 157 150 141 130 117 100 Example 11 202 192 181 171 158 148 140 129 112 Example 12 200 189 177 169 156 142 133 124 110 Example 13 196 180 168 155 148 134 121 109 98 Example 14 199 185 174 165 156 147 138 127 113 Example 15 201 188 180 171 160 148 135 124 112 Example 16 182 170 161 153 142 134 122 110 99 Example 17 194 179 170 157 146 138 129 120 108 Comparative Example 1 372 345 302 236 132 96 62 33 20 Comparative Example 2 175 170 164 155 146 135 124 99 73

[0131] Although the specific embodiments of the present invention have been described above, those skilled in the art should understand that this is only for illustration. The protection scope of the present invention is defined by the appended claims. Without departing from the principles and essence of the present invention, those skilled in the art can make various changes or modifications to these embodiments, but these changes and modifications all fall within the protection scope of the present invention.

Claims

1. A perovskite-type heterostructure material, characterized in that: It includes a layered perovskite oxide containing an alkali metal and a heterogeneous structure coating layer located on the surface thereof, and the internal and external structures are latticed and have no obvious interface; Wherein, the chemical formula of the alkali metal-containing layered perovskite oxide is A (n+1) / 2 A' (n+1) / 2 B n O 3n+1 , n = 1, 2, 3, corresponding to single-layer, double-layer and triple-layer structures respectively; the chemical formula of the heterostructure coating layer is A 3y A' 2 / 3-y BO 3-δ , 0.1≤y≤0.2; A is one or more of Li, Na and K, A' is a lanthanide rare earth element and / or Y, and B is Ti.

2. The perovskite heterostructure material according to claim 1, characterized in that: The perovskite heterostructure material satisfies one or more of the following conditions: (1) The charge and discharge voltage platform of the perovskite heterostructure material is 0.4-0.8V; (2) The lanthanide rare earth element is one or more of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu; (3) In the chemical formula of the heterostructure coating layer, 0.1≤y≤0.17, for example, 0.11, 0.15 or 0.17; (4) The thickness of the heterostructure coating layer is 2 to 10 nm.

3. A method for preparing a perovskite-type heterostructure material, characterized in that: The steps include: The perovskite type heterostructure material is prepared by subjecting a mixture of a layered perovskite oxide containing an alkali metal and an acid solution to an ion exchange reaction at 20-160° C. and then calcining the mixture.

4. The method for preparing a perovskite-type heterostructure material according to claim 3, characterized in that: The preparation method meets one or more of the following conditions: (1) The acid solution is one or more of hydrochloric acid, nitric acid, citric acid, acetic acid, formic acid, propionic acid, benzoic acid and ethylenediaminetetraacetic acid; (2) The solvent in the acid solution is deionized water; (3) The concentration of the acid solution is 0.1-2.0 M, preferably 0.2-1.5 M, such as 0.2 M, 0.3 M, 0.4 M, 0.5 M, 0.6 M, 0.8 M, 1.0 M or 1.2 M; (4) The ratio of the amount of the acid in the acid solution to the mass of the alkali metal-containing layered perovskite oxide is (0.01-2) mol:1 g, preferably (0.02-1) mol:1 g, for example, 0.032 mol:1 g, 0.5 mol:1 g, 0.064 mol:1 g, 0.08 mol:1 g, 0.096 mol:1 g, 0.1 mol:1 g, 0.128 mol:1 g, 0.15 mol:1 g, 0.19 mol:1 g, 0.2 mol:1 g or 0.3 mol:1 g.

5. The method for preparing a perovskite-type heterostructure material according to claim 3, characterized in that: The preparation method meets one or more of the following conditions: (1) The temperature of the ion exchange reaction is 30-150°C, for example, 40°C, 50°C, 60°C, 70°C, 80°C, 100°C or 120°C; (2) The ion exchange reaction time is 2-48 h, preferably 6-24 h, for example 10 h, 12 h, 18 h or 24 h; (3) The calcination temperature is 300-1200° C., for example, 400° C., 600° C., 700° C., 800° C. or 900° C.; (4) The calcination time is 1-20 hours, preferably 3-10 hours, such as 3 hours, 4 hours or 6 hours; (5) The method for preparing the alkali metal-containing layered perovskite oxide comprises the following steps: The mixture containing source A, source A' and titanium source is first calcined at 400-800°C for 2-10h, and then the temperature is raised to 900-1300°C for a second calcination for 2-10h; Wherein, the temperature of the first calcination is preferably 500-700°C, such as 550°C or 600°C; the time of the first calcination is preferably 3-8h, such as 6h; The temperature of the second calcination is preferably 1000-1300° C., such as 1200° C.; the time of the second calcination is preferably 2-6 hours, such as 4 hours.

6. The method for preparing a perovskite-type heterostructure material according to claim 3, characterized in that: The ion exchange reaction is carried out by liquid phase stirring method, hydrothermal method or sol-gel method; The reaction temperature of the liquid phase stirring method is preferably 30-90°C, such as 30°C, 40°C, 50°C, 60°C, 70°C, 80°C or 90°C; the reaction time of the liquid phase stirring method is preferably 6-48h, such as 10h, 12h, 18h or 24h; the rotation speed of the liquid phase stirring method is preferably 100-600rpm, such as 200rpm or 300rpm; The temperature of the hydrothermal method is preferably 100-160°C, such as 120°C or 140°C; the time of the hydrothermal method is preferably 8-24h, such as 10h, 12h or 16h; The reaction temperature of the sol-gel method is preferably 60-90° C., such as 80° C.; the reaction time of the sol-gel method is preferably 8-24 h, such as 12 h; When the sol-gel method is adopted, it is preferably necessary to add a complexing agent to the reaction system; the complexing agent preferably includes one or more of citric acid, maleic acid, tartaric acid, ethanolamine and sodium gluconate; the mass ratio of the complexing agent to the alkali metal-containing layered perovskite oxide can be (0.02-1):1, preferably (0.05-0.5):1, for example 0.1:

1.

7. The method for preparing a perovskite-type heterostructure material according to claim 6, characterized in that: The liquid phase stirring method comprises the following process: mixing a mixture of a layered perovskite oxide containing an alkali metal and an acid solution at 40-100° C. for 6-48 hours; Alternatively, the hydrothermal method comprises the following process: subjecting a mixture of a layered perovskite oxide containing an alkali metal and an acid solution to a hydrothermal reaction at 100-160° C. for 6-48 hours; Alternatively, the sol-gel method comprises the following process: a mixture of a layered perovskite oxide containing an alkali metal, a complexing agent and an acid solution is mixed and reacted at 60-90° C. until it is in a gel state.

8. A perovskite type heterostructure material obtained by the method for preparing a perovskite type heterostructure material according to any one of claims 3 to 7.

9. Use of the perovskite heterostructure material according to any one of claims 1 to 2 and 8 in a secondary battery. 10 . A secondary battery comprising the perovskite heterostructure material according to claim 1 .

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