Perovskite type titanate material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of lithium ion battery materials, and discloses a perovskite type titanate material as well as a preparation method and application thereof, the structural formula of the perovskite type titanate material is AxByTiOz, an A-site element is an alkali metal element, a B-site element is a Y element and / or a lanthanide element, 0 < x < = 1, 0 < y < = 1, and x + 3y + 4 = 2z. The perovskite type titanate material meeting the chemical general formula of AxByTiOz is designed, the obtained perovskite type titanate material AxByTiOz can be used as a lithium ion battery negative electrode material, compared with a lithium titanate negative electrode, the perovskite type titanate material AxByTiOz has high energy density brought by more ideal working potential, meanwhile, compared with a graphite carbon material, the perovskite type titanate material AxByTiOz has high lithium intercalation state thermal stability, and the performance of the perovskite type titanate material AxByTiOz is improved. And high safety and high energy density of the lithium ion battery can be considered at the same time.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium ion battery materials, and more specifically, relates to a perovskite titanate material and a preparation method and application thereof. Background Art

[0002] Lithium-ion batteries have become the most popular energy storage devices due to their high energy density, long cycle life, no memory effect, low price, and environmental friendliness. In the past decade, they have been widely used in electric vehicles, portable smart devices, energy storage grids and other fields. The negative electrode is one of the key components of the battery. Currently, most commercial lithium-ion batteries use graphite-based carbon materials as the negative electrode, which has a low working potential (~0.1V vs.Li + / Li, close to the lithium precipitation potential, easy to produce lithium dendrites), and highly reactive lithium-intercalation compounds make it a potential safety risk and cannot meet the application requirements of high safety conditions. In addition, graphite-based carbon materials are carbon materials, and the thermal stability of the lithium-intercalation state is not ideal.

[0003] On the other hand, lithium titanate negative electrode is due to the lithium titanate material (Li4Ti5O 12 ) has a spinel crystal structure and is stable. Although lithium titanate is considered to be a highly safe negative electrode material for lithium-ion batteries due to its high working potential and small volume expansion during charge and discharge, its high working potential (~1.55V vs.Li + / Li) makes the battery system energy density extremely low and cannot meet the actual use requirements. Therefore, it is urgent to develop lithium-ion battery negative electrode materials with both high safety and high energy density. Summary of the invention

[0004] In view of the above defects or improvement needs of the prior art, the object of the present invention is to provide a perovskite-type titanate material and a preparation method and application thereof, wherein the perovskite-type titanate material is designed to satisfy the chemical formula A x B y TiO z Perovskite titanate material, the obtained perovskite titanate material A x B y TiO z It can be used as a negative electrode material for lithium-ion batteries. Compared with lithium titanate negative electrodes, it has a higher energy density brought by a more ideal working potential. At the same time, compared with graphite-like carbon materials, it has high thermal stability in the lithium-intercalated state, which can take into account both the high safety and high energy density of lithium-ion batteries.

[0005] To achieve the above object, according to one aspect of the present invention, a perovskite titanate material is provided, characterized in that the perovskite titanate material has a structural formula of A x B y TiOz , wherein the A-site element is an alkali metal element, the B-site element is a Y element and / or a lanthanide element, 0<x≤1, 0<y≤1, and x+3y+4=2z.

[0006] As a further preference of the present invention, the A-site element is one or more of Li, Na, and K; and the B-site element is one or more of Y, Nd, and Sm.

[0007] According to another aspect of the present invention, the present invention provides a method for preparing a perovskite titanate material, characterized in that it comprises the following steps:

[0008] S1. According to structural formula A x B y TiO z A source material, B source material and titanium source material are weighed in the nominal chemical dosage ratio of the A-site element, the B-site element and the Ti element, and the respective source materials are mixed and fully dispersed to obtain a uniformly mixed and fully dispersed precursor; the particle size of any particle in the precursor is reduced to the size of a primary particle;

[0009] Wherein, the A-site element is an alkali metal element, and the A source material contains the A-site element; the B-site element is a Y element and / or a lanthanide element, and the B source material contains the B-site element; 0<x≤1, 0<y≤1, and x+3y+4=2z;

[0010] S2. The precursor obtained in step S1 is heat treated in an oxygen-containing atmosphere to undergo a solid phase reaction, thereby obtaining A x B y TiO z Perovskite-type titanate material; wherein the heat treatment temperature is 600-1300° C. and the treatment time is 1-80 hours.

[0011] According to another aspect of the present invention, the present invention provides a method for preparing a perovskite titanate material, characterized in that it comprises the following steps:

[0012] (1) According to structural formula A x B y TiO z The nominal chemical dosage ratio of the A-site element, the B-site element and the Ti element is used to weigh the A source material, the B source material and the titanium source material, and each source material is fully dispersed to reduce the particle size of each source material to the size of primary particles;

[0013] Wherein, the A-site element is an alkali metal element, and the A source material contains the A-site element; the B-site element is a Y element and / or a lanthanide element, and the B source material contains the B-site element; 0<x≤1, 0<y≤1, and x+3y+4=2z;

[0014] (2) mixing and fully dispersing the source materials obtained in step (1) to obtain a uniformly mixed precursor;

[0015] (3) heat treating the precursor obtained in step (2) under an oxygen-containing atmosphere to perform a solid phase reaction, thereby obtaining A x B y TiO z Perovskite-type titanate material; wherein the heat treatment temperature is 600-1300° C. and the treatment time is 1-80 hours.

[0016] As a further preference of the present invention, in step (2), the mixing is carried out by dry mixing or wet mixing with the participation of a solvent.

[0017] As a further preference of the present invention, the sufficient dispersion in step (1) and step (2) is selected from a dry process and a wet process;

[0018] Among them, the dry process is carried out in a mixer, an air mill, a sand mill, a ball mill, or an air flow pulverizer. The principle is to perform high-speed shearing on the material and the collision between the materials to achieve uniform dispersion and reduce the particle size. When a mixer, a sand mill, a ball mill or an air mill is used, the rotation speed is 500-20000rpm and the processing time is 30 seconds to 2 hours. When an air flow pulverizer is used, the pulverization flux is 0.5-100Kg / h and the air flow pressure is 0.2-50Mpa.

[0019] The wet process is to disperse the material to be treated into a solvent and then stir it to achieve uniform mixing; the solvent is one or more of water, methanol, ethanol, isopropanol, ethylene glycol, glycerol, n-propanol, isobutanol, n-butanol, acetic acid, hydrochloric acid, sulfuric acid, and nitric acid; preferably, the concentration of the A-site element in the solution system is 0.001-20 mol / L, and the concentration of the B-site element and the Ti ion in the solution system is 0.001-15 mol / L.

[0020] As a further preferred embodiment of the present invention, in step S1 or step (1), the titanium source material is one or more of isopropyl titanate, titanium sulfate, titanium tetrachloride, titanium trichloride, titanyl sulfate, titanium tetraisopropoxide, butyl titanate, titanium tetrafluoride, potassium titanium oxalate, and titanium dioxide;

[0021] The A-site element is one or more of Li, Na, and K;

[0022] When the A-site element contains Li, the corresponding A source material includes one or more of lithium oxalate, lithium carbonate, lithium bicarbonate, lithium oxide, lithium hydroxide, lithium ethoxide, lithium peroxide, lithium nitrate, lithium sulfate, and lithium acetate;

[0023] When the A-site element contains Na, the corresponding A source material includes one or more of sodium oxalate, sodium carbonate, sodium bicarbonate, sodium oxide, sodium hydroxide, sodium ethoxide, sodium peroxide, sodium nitrate, sodium sulfate, and sodium acetate;

[0024] When the A-site element contains K, the corresponding A source material includes one or more of potassium oxalate, potassium carbonate, potassium bicarbonate, potassium oxide, potassium hydroxide, potassium ethoxide, potassium peroxide, potassium nitrate, potassium sulfate, and potassium acetate;

[0025] The B-site element is one or more of Y, Nd, and Sm;

[0026] When the B-site element contains Y, the corresponding B source material includes one or more of yttrium oxide, yttrium oxalate, hydrated yttrium carbonate, yttrium nitrate hexahydrate, and yttrium sulfate octahydrate;

[0027] When the B-site element contains Nd, the corresponding B source material includes one or more of neodymium oxide, neodymium oxalate, hydrated neodymium carbonate, hydrated neodymium nitrate, and hydrated neodymium sulfate;

[0028] When the B-site element contains Sm, the corresponding B source material includes one or more of samarium oxide, samarium oxalate, hydrated samarium carbonate, hydrated samarium nitrate, and hydrated samarium sulfate.

[0029] As a further preferred embodiment of the present invention, in step S2 or step (3), the heating rate of the heat treatment is 0.5-20° C. per minute.

[0030] According to another aspect of the present invention, the present invention provides the use of the above-mentioned perovskite titanate material as a negative electrode material for a lithium ion battery.

[0031] According to another aspect of the present invention, the present invention provides a lithium-ion battery, the negative electrode plate of which adopts the above-mentioned perovskite titanate material as an active material.

[0032] Through the above technical scheme conceived by the present invention, compared with the prior art, the perovskite titanate material in the present invention has a general structural formula of A x B y TiO z (Wherein, the A-position element is +1 valence, and can be one or more of Li, Na, K, Rb, and Cs; the B-position element is +3 valence, and can be a Y element or a lanthanide element; the lanthanide elements include lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium; 0<x≤1, 0<y≤1, and the values ​​of x, y, and z satisfy A x B y TiO z The valence balance rule of the chemical formula, i.e. x+3y+4=2z), has a high theoretical specific capacity (>200mAh g -1), ideal working potential (<0.5V vs.Li + / Li), the lithium-ion battery prepared with it as the negative electrode will have both high safety and high energy density.

[0033] The present invention is the first to use perovskite titanate material A x B y TiO z As negative electrode active material used in lithium-ion battery negative electrode, perovskite titanate material A x B y TiO z Compared with traditional graphite negative electrode materials, it has higher thermal stability, ideal working potential (higher than graphite), can reduce the hidden dangers of lithium dendrites, and has higher energy density than lithium titanate negative electrode materials (this is because perovskite titanate material A x B y TiO z The working potential of the positive electrode is lower than that of lithium titanate; when the positive electrode material is fixed, the higher the working potential of the negative electrode, the smaller the voltage difference between the positive and negative electrodes, and the lower the energy density), which can take into account both the safety and energy density of lithium-ion batteries.

[0034] The present invention can obtain the perovskite titanate negative electrode material A by simple mixing and heat treatment. x B y TiO z , by controlling the particles in the precursor of the solid phase reaction to a primary particle size, the path of ion transmission in the solid phase reaction can be effectively shortened, and the solid phase reaction can be more easily fully occurred to form a target material with better crystallinity. The preparation method of the present invention has a simple process and low cost. The preparation method of the present invention first fully disperses the various alkali metal sources, titanium sources, and rare earth element raw materials required, and reduces the material particle size to the primary particle size in order to further fully mix the raw materials; in the subsequent source material mixing process, taking solid-state mixing as an example, in the solid-state mixing process, the density, particle size, and specific surface area of ​​the primary particles of various raw materials bring about differences in particle mass, particle surface energy, and powder energy, so that small-sized particles spontaneously adsorb to the surface of large-sized particle materials to reduce the total energy, thereby achieving an energy stable state to form a uniform mixing of the raw materials, effectively avoiding the stratification of the materials and the occurrence of uneven agglomeration. Similarly, under liquid-containing conditions, fully dispersed primary particles of raw materials will also promote the uniform mixing of the precursor. Finally, a solid-phase reaction is caused by heat treatment to generate perovskite-type titanate material A x B y TiO z . BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1This is the XRD spectrum of NaYTiO4 prepared in Example 1 of the present invention.

[0036] Figure 2 This is a scanning electron microscope (SEM) image of NaYTiO4 prepared in Example 1 of the present invention.

[0037] Figure 3 This is the first charge and discharge performance curve of NaYTiO4 prepared in Example 1 of the present invention.

[0038] Figure 4 The cycle performance of NaYTiO4 prepared in Example 1 of the present invention.

[0039] Figure 5 This is the charge and discharge curve of graphite reported in the prior art.

[0040] Figure 6 This is the charge and discharge curve of lithium titanate reported in the prior art.

[0041] Figure 7 This is a differential scanning calorimetry (DSC) test curve of lithium-intercalated graphite reported in the prior art.

[0042] Figure 8 It is a comparison diagram of differential scanning calorimetry (DSC) test curves of lithium-intercalated graphite (Gr) and NaYTiO4 (NYTO) prepared in Example 1 of the present invention.

[0043] Fig. 9 This is the rate performance of NaYTiO4 prepared in Example 1 of the present invention.

[0044] Fig.10 The cycle performance of the full battery with NaYTiO4 as the negative electrode prepared in Example 1 of the present invention.

[0045] Fig.11 This is the XRD spectrum of LiYTiO4 prepared in Example 2 of the present invention.

[0046] Fig.12 The cycle performance of LiYTiO4 prepared in Example 2 of the present invention.

[0047] Fig.13 This is the XRD spectrum of NaNdTiO4 prepared in Example 4 of the present invention.

[0048] Fig.14 This is a scanning electron microscope (SEM) image of NaNdTiO4 prepared in Example 4 of the present invention.

[0049] Fig.15 The cycle performance of NaNdTiO4 prepared in Example 4 of the present invention.

[0050] Fig.16 This is the XRD spectrum of NaYTiO4 prepared in Example 6 of the present invention.

[0051] Fig.17 This is the XRD pattern of the product obtained in Comparative Example 1 of the present invention.

[0052] Fig.18 This is the XRD pattern of the product obtained in Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0053] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0054] Example 1

[0055] A perovskite titanate material is prepared by the following method:

[0056] (1) Weigh 383 g of Y(NO3)3·6H2O, 240 g of Ti(SO4)2, and 60 g of Na2CO3 and uniformly disperse them into primary particles using a ball mill at 300 rpm;

[0057] (2) Then, the obtained raw material in the primary particle state was dissolved in 4000 mL of ethanol, and the mixture was fully stirred for 1 h to obtain a mixed solution, and the mixed solution was placed in a blast oven and dried at 60° C. for 12 h to obtain a powder mixture precursor;

[0058] (3) placing the obtained powder mixture in a muffle furnace, heating it to 1000°C at a heating rate of 1°C / min under air conditions, keeping it at that temperature for 2 hours, and then cooling it naturally to room temperature to obtain a primary product of NaYTiO4;

[0059] In this embodiment, in order to obtain NaYTiO which is more suitable as a negative electrode material for lithium-ion batteries 4， The primary NaYTiO4 was washed three times with deionized water, placed in a forced air oven, and dried at 60°C for 6 hours to obtain the preferred NaYTiO4 material.

[0060] Example 2

[0061] If the A-position element does not meet the target requirements (the target A-position element is A'), you can further use A x B y TiO z The material is used as raw material, combined with the A' source material, and the target A' is formed by ion exchange reaction. xB y TiO z Perovskite titanate material (of course, the ion exchange can be repeated multiple times to ensure that the product of the target metal element is obtained).

[0062] This embodiment provides a perovskite titanate material, which is prepared by the following method:

[0063] (1) Weigh 200 g of NaYTiO4 and 300 g of LiNO3 obtained in Example 1 and disperse them respectively using a sand mill at a speed of 800 rpm to make them in a primary particle state;

[0064] (2) then mixing the obtained raw materials in the primary particle state and using a shear mixer to shear and stir at a speed of 2000 rpm for 5 min to obtain a uniformly mixed precursor mixture;

[0065] (3) placing the powder mixture precursor in a muffle furnace, heating it to 300°C at a heating rate of 5°C / min under air conditions, keeping it at that temperature for 3 hours for ion exchange, and naturally cooling it to room temperature to obtain the initial product LiYTiO4;

[0066] (4) Repeat steps (1), (2) and (3) twice with the primary LiYTiO4 obtained in step (3) and the LiNO3 raw material, so as to perform ion exchange three times in total to obtain the target LiYTiO4 product.

[0067] In this embodiment, in order to further obtain LiYTiO4 material with high electrochemical performance, the obtained LiYTiO4 powder material is washed with ionized water, placed in a blast oven, and dried at 60°C for 6 hours to obtain a preferred LiYTiO4 material.

[0068] Example 3

[0069] A perovskite titanate material is prepared by the following method:

[0070] (1) Weigh 160 g TiO2, 349 g Sm2O3, and 150 g Na2C2O4 and place them in a planetary ball mill. Mill them at 300 rpm for 5 h to obtain uniformly dispersed primary particles. Then, mill and mix them for 2 h to obtain a mixed powder.

[0071] (2) The raw material in the primary particle state was then placed in a sand mill, sanded at a speed of 1000 rpm for 2 h, spray dried to obtain a uniformly mixed powder precursor, and heated to 1000 ° C at a heating rate of 5 ° C / min in a muffle furnace under air conditions for 3 hours, and naturally cooled to room temperature to obtain a primary product NaSmTiO4;

[0072] In this embodiment, in order to further obtain NaSmTiO4 material with high electrochemical performance, the primary NaSmTiO4 powder material is washed with ionized water, placed in a blast oven, and dried at 60°C for 6 hours to obtain the preferred NaSmTiO4 material.

[0073] Example 4

[0074] A perovskite titanate material is prepared by the following method:

[0075] (1) Weigh 420 g of Nd(NO3)3·6H2O, 240 g of Ti(SO4)2, and 60 g of Na2CO3 and stir them in a shear mixer at 5000 rpm for 10 min to disperse the above raw materials into primary particles;

[0076] (2) The primary particle-state raw material obtained above was dissolved in 10000 mL of water, and ammonia water was added dropwise to adjust the pH to 7. After sufficient stirring, the mixture was placed in a hydrothermal reactor and subjected to a hydrothermal reaction at 240° C. and 10 MPa for 1 hour to obtain a fully dispersed precursor;

[0077] (3) placing the obtained precursor in a muffle furnace, heating it to 600°C at a heating rate of 2°C / min under air conditions, keeping it at that temperature for 1 hour, and naturally cooling it to room temperature to obtain the initial product NaNdTiO4;

[0078] In this embodiment, in order to further obtain NaNdTiO4 material with high electrochemical performance, the primary NaNdTiO4 powder material is washed with ionized water, placed in a blast oven, and dried at 60°C for 6 hours to obtain the preferred NaNdTiO4 material.

[0079] Example 5

[0080] A perovskite titanate material is prepared by the following method:

[0081] (1) Weigh 5.31 g LiNO3, 48.22 g Nd(NO3)3·6H2O, and 68.06 g Ti(OC4H9)4 and dissolve them in 500 mL ethanol. Stir evenly for 1 h, then add 84.06 g C6H8O7·H2O, add ammonia water dropwise to adjust the pH to 7 to form a sol, and stir at 70°C for 5 h to form a purple gel.

[0082] (2) drying the purple gel in a forced air oven at 180° C. for 12 h to obtain a precursor; the particle size of any particle in the precursor has been reduced to the size of a primary particle;

[0083] (3) Place the precursor in a muffle furnace, heat it to 1100°C at 5°C / min under air conditions, keep it at that temperature for 8 hours, and then cool it down to room temperature naturally to obtain the target Li 0.35Nd 0.55 TiO3 material.

[0084] Example 6

[0085] A perovskite titanate material is prepared by the following method:

[0086] (1) Weigh 160 g TiO2, 259 g Y2O3, and 150 g Na2C2O4 and place them in a planetary ball mill. Mill them at 300 rpm for 5 h to obtain uniformly dispersed primary particles. Then, mill and mix them for 2 h to obtain a mixed powder.

[0087] (2) The raw material in the primary particle state was then placed in a sand mill, sanded at a speed of 1000 rpm for 2 h, spray dried to obtain a uniformly mixed powder precursor, and heated to 1300° C. at a heating rate of 5° C. / min in a muffle furnace under air conditions for 3 hours, and naturally cooled to room temperature to obtain a primary product of NaYTiO4;

[0088] In this embodiment, in order to further obtain NaYTiO4 material with high electrochemical performance, the primary NaYTiO4 powder material is washed with ionized water, placed in a blast oven, and dried at 60°C for 6 hours to obtain the final NaYTiO4 product.

[0089] Performance Test:

[0090] The crystal phase structure of the electrode materials prepared in all the examples was characterized by X-ray diffractometer and analyzed to determine the molecular formula of the material.

[0091] In the electrochemical test, the electrode materials prepared in all embodiments have an active material mass ratio of 70%, a conductive agent (i.e., Super P) mass ratio of 20%, a binder (i.e., a 5 wt % aqueous solution prepared by mixing CMC and SBR in a mass ratio of 1:1) mass ratio of 10%, and a conventional wet method for preparing the electrode, with a surface loading of 2 mg / cm 2 , compacted density is 0.6g / cm 3 , the test conditions are normal temperature test.

[0092] Figure 1 This is the X-ray diffraction pattern of NaYTiO4 prepared in Example 1. From the figure, it can be seen that the characteristic peak of NaYTiO4 appears in the sample.

[0093] Figure 2 This is a scanning electron microscope (SEM) image of NaYTiO4 prepared in Example 1. It can be seen from the image that the sample particle size distribution is uniform and the size is 1-3 microns.

[0094] Figure 3This is the first charge and discharge capacity performance diagram of NaYTiO4 prepared in Example 1 at 0.1C rate. The active material mass ratio in the pole piece is 70%, the conductive agent mass ratio is 20%, the binder mass ratio is 10%, and the pole piece surface loading is 2mg / cm 2 , compacted density is 0.6g / cm 3 It can be seen from the figure that the first discharge capacity of NaYTiO4 is as high as 231mAh / g at a current density of 0.1C in the voltage range of 0.01-1.5V, and the discharge platform is about 0.1V and 0.3V (the working potential is moderate, higher than graphite and lower than lithium titanate, which is an ideal working potential), indicating that the NaYTiO4 constructed according to the present invention can effectively release its capacity.

[0095] Figure 4 This is a cycle performance diagram of a button cell test using NaYTiO4 as the active material prepared in Example 1. The active material mass ratio in the pole piece is 70%, the conductive agent mass ratio is 20%, the binder mass ratio is 10%, and the pole piece surface loading is 2 mg / cm 2 , compacted density is 0.6g / cm 3 It can be seen from the figure that when NaYTiO4 is cycled at a charge and discharge current of 0.1C, it can provide good discharge capacity with little attenuation. After 100 cycles at a current density of 0.1C, the discharge capacity of the material is still as high as 173mAh / g, and the coulombic efficiency is close to 100%, indicating that NaYTiO4 has a good cycle life.

[0096] Figure 5 This is the charge and discharge curve of graphite reported in the prior art (see: Lu Hao, Liu Boyan, Chu Geng, et al. Industrialization Technology Progress of Negative Electrode Materials for Lithium-ion Batteries [J]. Energy Storage Science and Technology. 2016, 5(02): 109-119.). It can be seen that the discharge platform of graphite is around 0.1V.

[0097] Figure 6 The charge and discharge curve of lithium titanate reported in the prior art (see: Lu Hao, Liu Boyan, Chu Geng, et al. Industrialization Technology Progress of Negative Electrode Materials for Lithium-ion Batteries [J]. Energy Storage Science and Technology. 2016, 5(02): 109-119.) shows that the discharge platform of lithium titanate is around 1.55V. Figure 3 and Figure 6 By comparison, it is not difficult to see that the working potential of the NaYTiO4 material obtained based on the present invention will be lower than that of the lithium titanate negative electrode, and correspondingly, the energy density will be higher.

[0098] Figure 7This is a differential scanning calorimetry (DSC) test diagram of lithium-intercalated graphite reported in the prior art (see: Zheng Y, Shi Z, Ren D, et al. In-depth investigation of the exothermic reactions between lithiated graphite and electrolyte in lithium-ion battery [J]. Journal of energy chemistry. 2022, 69: 593-600.). The blue line is lithium-intercalated graphite, and the test environment is a nitrogen atmosphere.

[0099] Figure 8 It is the differential scanning calorimetry (DSC) test diagram of the lithium-intercalated graphite and the lithium-intercalated NaYTiO4 prepared in Example 1, and the test environment is a nitrogen atmosphere. It can be seen that the heat released by the lithium-intercalated NYTO is less than that of graphite. The lithium-intercalation process is electrochemical lithiation, with graphite or NaYTiO4 as the active material, respectively. The mass ratio of graphite / NaYTiO4 active material is 94%, the mass ratio of conductive agent (i.e., Super P) is 3%, and the mass ratio of binder (i.e., CMC and SBR are mixed in a mass ratio of 1:1 to prepare a 5wt% aqueous solution) is 3%. The traditional wet method is used to prepare the pole piece, and the pole piece surface loading is 5mg / cm 2 , compacted density is 1g / cm 3 , assemble half-cells, discharge them to 0.01V to make the graphite / NaYTiO4 completely lithium-intercalated, then disassemble the half-cells, soak the pole pieces in dimethyl carbonate (DMC) for 12 hours, dry and scrape off the powder on the pole pieces as DSC test samples. The graphite used in the experiment is Kruder graphite (ordinary type), model MA-EN-AN-0019. The DSC test graph of the lithium-intercalated graphite measured in the experiment (i.e., Figure 8 The Gr curve shown) and Figure 7 The trend and value are roughly consistent, which ensures the accuracy of the DSC test. It can be seen that compared with graphite-based carbon materials, the NaYTiO4 material obtained based on the present invention has high thermal stability in the lithium-intercalated state.

[0100] Fig. 9 This is the rate performance diagram of the button cell test using NaYTiO4 as the active material prepared in Example 1. The active material mass ratio in the pole piece is 70%, the conductive agent mass ratio is 20%, the binder mass ratio is 10%, and the pole piece surface loading is 2 mg / cm 2 , compacted density is 0.6g / cm 3It can be seen from the figure that when NaYTiO4 is charged and discharged at 0.1C, it can provide a discharge capacity of 201mAh / g. Even when the material is charged and discharged at a current density of 2C, its discharge capacity is still as high as 77mAh / g, and the coulombic efficiency is close to 100%, indicating that NaYTiO4 has good rate performance.

[0101] Fig.10 This is a cycle performance diagram of a button-type full-cell test using NaYTiO4 as the active material prepared in Example 1. The negative electrode material is NaYTiO4, the positive electrode material is commercial nickel cobalt manganese oxide (NCM), and the electrolyte is LB-015 (i.e., 1.0M LiPF6 in EC:DEC=1:1Vol%with5.0%FEC). The mass ratio of active material in the NaYTiO4 negative electrode sheet is 70%, the mass ratio of conductive agent is 20%, the mass ratio of binder is 10%, and the surface loading of the sheet is 2mg / cm 2 , compacted density is 0.6g / cm 3 The mass ratio of active material in the NCM positive electrode is 80%, the mass ratio of conductive agent is 10%, the mass ratio of binder is 10%, and the surface loading of the electrode is 2mg / cm 2 , compacted density is 1.2g / cm 3 The electrochemical performance of the NaYTiO4 / NCM full battery was tested in the voltage range of 2.8-4.2V. After 3 cycles of activation at a current density of 0.1C and cycling at a current density of 0.5C, the discharge capacity of the full battery at 0.5C was 137mAh / g, and the discharge capacity decay was very small. This shows that the NaYTiO4 constructed according to the present invention can effectively release its capacity in the full battery.

[0102] Fig.11 This is the X-ray diffraction pattern of LiYTiO4 prepared in Example 2. From the figure, it can be seen that the characteristic peak of LiYTiO4 appears in the sample.

[0103] Fig.12 This is a cycle performance diagram of a button cell test using LiYTiO4 as the active material prepared in Example 2. The active material mass ratio in the pole piece is 70%, the conductive agent mass ratio is 20%, the binder mass ratio is 10%, and the pole piece surface loading is 2 mg / cm 2 , compacted density is 0.6g / cm 3 It can be seen from the figure that when LiYTiO4 is cycled at a charge and discharge current of 0.1C, it can provide good discharge capacity with little attenuation. After 100 cycles at a current density of 0.1C, the discharge capacity of the material is still as high as 211mAh / g, and the coulombic efficiency is close to 100%, indicating that LiYTiO4 has a good cycle life.

[0104] Fig.13This is the X-ray diffraction pattern of NaNdTiO4 prepared in Example 4. From the figure, it can be seen that the characteristic peak of NaNdTiO4 appears in the sample.

[0105] Fig.14 This is a scanning electron microscope (SEM) image of NaNdTiO4 prepared in Example 4. It can be seen from the image that the sample particle size distribution is uniform and the size is 1-3 microns.

[0106] Fig.15 This is a cycle performance diagram of a button cell test using NaNdTiO4 as the active material prepared in Example 4. The active material mass ratio in the pole piece is 70%, the conductive agent mass ratio is 20%, the binder mass ratio is 10%, and the pole piece surface loading is 2 mg / cm 2 , compacted density is 0.6g / cm 3 It can be seen from the figure that when NaNdTiO4 is cycled at a charge and discharge current of 0.1C, it can provide good discharge capacity with little attenuation. After 100 cycles at a current density of 0.1C, the discharge capacity of the material is as high as 145mAh / g, and the coulombic efficiency is close to 100%, indicating that NaNdTiO4 has a good cycle life.

[0107] Fig.16 This is the X-ray diffraction pattern of NaYTiO4 prepared in Example 6. From the figure, it can be seen that obvious characteristic peaks of NaYTiO4 appear in the sample.

[0108] Comparative Example 1

[0109] A perovskite titanate material is prepared by the following method:

[0110] (1) Weigh 160 g TiO2, 259 g Y2O3, and 150 g Na2C2O4 and place them in a planetary ball mill. Mill them at 300 rpm for 5 h to obtain uniformly dispersed primary particles. Then, mill and mix them for 2 h to obtain a mixed powder.

[0111] (2) The raw material in the primary particle state was then placed in a sand mill, sand-milled at a speed of 1000 rpm for 2 h, spray-dried to obtain a uniformly mixed powder precursor, and heated to 500° C. at a heating rate of 5° C. / min in a muffle furnace under air conditions for 3 hours, and naturally cooled to room temperature to obtain a primary product;

[0112] Similarly, in order to further obtain NaYTiO4 material with high electrochemical performance, the primary powder material was washed with ionized water, placed in a forced air oven, and dried at 60°C for 6 h to obtain the final product.

[0113] Fig.17This is the X-ray diffraction diagram of the product obtained in Comparative Example 1. The characteristic peak of NaYTiO4 cannot be clearly seen in the figure. It can be seen that the solid phase reaction temperature used in Comparative Example 1 is too low and the target NaYTiO4 product cannot be obtained.

[0114] Comparative Example 2

[0115] A perovskite titanate material is prepared by the following method:

[0116] (1) Weigh 160 g TiO2, 259 g Y2O3, and 150 g Na2C2O4 and place them in a planetary ball mill. Mill them at 300 rpm for 5 h to obtain uniformly dispersed primary particles. Then, mill and mix them for 2 h to obtain a mixed powder.

[0117] (2) The raw material in the primary particle state is then placed in a sand mill, sand-milled at a speed of 1000 rpm for 2 h, spray-dried to obtain a uniformly mixed powder precursor, and heated to 1400° C. at a heating rate of 5° C. / min in a muffle furnace under air conditions for 3 hours, and naturally cooled to room temperature to obtain a primary product;

[0118] Similarly, in order to further obtain NaYTiO4 material with high electrochemical performance, the primary powder material was washed with ionized water, placed in a forced air oven, and dried at 60°C for 6 h to obtain the final product.

[0119] Fig.18 This is the X-ray diffraction diagram of the product prepared in Comparative Example 2. From the figure, it can be seen that the characteristic peak of NaYTiO4 in the sample is not obvious, and there are many miscellaneous peaks. It can be seen that the solid phase reaction temperature used in Comparative Example 2 is too high, and the target NaYTiO4 product cannot be obtained.

[0120] The above embodiments are only examples. For example, the atmosphere of the solid phase reaction can be either air or pure oxygen atmosphere (especially when prepared in large quantities, pure oxygen can be preferably used); for another example, the primary particles can be fully dispersed using either a dry process or a wet process, wherein the specific operation process of the dry process can also refer to the prior art (such as Chinese patents 2022109822400, 2022109819840, etc.) and use other equipment, such as a mixer, a gas mill, a sand mill, a ball mill, an air flow mill and other equipment, which can shear the powder material at high speed and make the materials collide with each other and disperse in a short time to make the materials dispersed evenly, and the processing time can be, for example, 30 seconds to 2 hours. The processing temperature and processing time during the heat treatment process can also be adjusted according to the actual situation to obtain perovskite titanate materials of different particle sizes and crystallinity. In addition, other conductive agents and binders can also be used for the negative electrode sheet of a lithium-ion battery constructed based on the perovskite titanate material of the present invention.

[0121] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A perovskite titanate material, characterized in that: The structural formula of the perovskite titanate material is A x B y TiO z , wherein the A-site element is an alkali metal element, the B-site element is a Y element and / or a lanthanide element, 0<x≤1, 0<y≤1, and x+3y+4=2z.

2. The perovskite titanate material according to claim 1, characterized in that: The A-site element is one or more of Li, Na, and K; the B-site element is one or more of Y, Nd, and Sm.

3. A method for preparing a perovskite titanate material, characterized in that: The following steps are involved: S1. According to structural formula A x B y TiO z A source material, B source material and titanium source material are weighed in the nominal chemical dosage ratio of the A-site element, the B-site element and the Ti element, and the respective source materials are mixed and fully dispersed to obtain a uniformly mixed and fully dispersed precursor; the particle size of any particle in the precursor is reduced to the size of a primary particle; Wherein, the A-site element is an alkali metal element, and the A source material contains the A-site element; the B-site element is a Y element and / or a lanthanide element, and the B source material contains the B-site element; 0<x≤1, 0<y≤1, and x+3y+4=2z; S2. The precursor obtained in step S1 is heat treated in an oxygen-containing atmosphere to undergo a solid phase reaction, thereby obtaining A x B y TiO z Perovskite-type titanate material; wherein the heat treatment temperature is 600-1300° C. and the treatment time is 1-80 hours.

4. A method for preparing a perovskite titanate material, characterized in that: The following steps are involved: (1) According to structural formula A x B y TiO z The nominal chemical dosage ratio of the A-site element, the B-site element and the Ti element is used to weigh the A source material, the B source material and the titanium source material, and each source material is fully dispersed to reduce the particle size of each source material to the size of primary particles; Wherein, the A-site element is an alkali metal element, and the A source material contains the A-site element; the B-site element is a Y element and / or a lanthanide element, and the B source material contains the B-site element; 0<x≤1, 0<y≤1, and x+3y+4=2z; (2) mixing and fully dispersing the source materials obtained in step (1) to obtain a uniformly mixed precursor; (3) heat treating the precursor obtained in step (2) under an oxygen-containing atmosphere to perform a solid phase reaction, thereby obtaining A x B y TiO z Perovskite-type titanate material; wherein the heat treatment temperature is 600-1300° C. and the treatment time is 1-80 hours.

5. The preparation method according to claim 4, characterized in that: In step (2), the mixing is carried out by dry mixing or wet mixing with the participation of a solvent.

6. The preparation method according to claim 4, characterized in that: The sufficient dispersion in step (1) and step (2) is selected from a dry process and a wet process; Among them, the dry process is carried out in a mixer, an air mill, a sand mill, a ball mill, or an air flow pulverizer. The principle is to perform high-speed shearing on the material and the collision between the materials to achieve uniform dispersion and reduce the particle size. When a mixer, a sand mill, a ball mill or an air mill is used, the rotation speed is 500-20000rpm and the processing time is 30 seconds to 2 hours. When an air flow pulverizer is used, the pulverization flux is 0.5-100Kg / h and the air flow pressure is 0.2-50Mpa. The wet process is to disperse the material to be treated into a solvent and then stir it to achieve uniform mixing; the solvent is one or more of water, methanol, ethanol, isopropanol, ethylene glycol, glycerol, n-propanol, isobutanol, n-butanol, acetic acid, hydrochloric acid, sulfuric acid, and nitric acid; preferably, the concentration of the A-site element in the solution system is 0.001-20 mol / L, and the concentration of the B-site element and the Ti ion in the solution system is 0.001-15 mol / L.

7. The preparation method according to claim 3 or 4, characterized in that: In step S1 or step (1), the titanium source material is one or more of isopropyl titanate, titanium sulfate, titanium tetrachloride, titanium trichloride, titanyl sulfate, titanium tetraisopropoxide, butyl titanate, titanium tetrafluoride, potassium titanium oxalate, and titanium dioxide; The A-site element is one or more of Li, Na, and K; When the A-site element contains Li, the corresponding A source material includes one or more of lithium oxalate, lithium carbonate, lithium bicarbonate, lithium oxide, lithium hydroxide, lithium ethoxide, lithium peroxide, lithium nitrate, lithium sulfate, and lithium acetate; When the A-site element contains Na, the corresponding A source material includes one or more of sodium oxalate, sodium carbonate, sodium bicarbonate, sodium oxide, sodium hydroxide, sodium ethoxide, sodium peroxide, sodium nitrate, sodium sulfate, and sodium acetate; When the A-site element contains K, the corresponding A source material includes one or more of potassium oxalate, potassium carbonate, potassium bicarbonate, potassium oxide, potassium hydroxide, potassium ethoxide, potassium peroxide, potassium nitrate, potassium sulfate, and potassium acetate; The B-site element is one or more of Y, Nd, and Sm; When the B-site element contains Y, the corresponding B source material includes one or more of yttrium oxide, yttrium oxalate, hydrated yttrium carbonate, yttrium nitrate hexahydrate, and yttrium sulfate octahydrate; When the B-site element contains Nd, the corresponding B source material includes one or more of neodymium oxide, neodymium oxalate, hydrated neodymium carbonate, hydrated neodymium nitrate, and hydrated neodymium sulfate; When the B-site element contains Sm, the corresponding B source material includes one or more of samarium oxide, samarium oxalate, hydrated samarium carbonate, hydrated samarium nitrate, and hydrated samarium sulfate.

8. The preparation method according to claim 3 or 4, characterized in that: In step S2 or step (3), the heating rate of the heat treatment is 0.5-20°C per minute.

9. Use of the perovskite titanate material as claimed in claim 1 or 2 as a negative electrode material for lithium-ion batteries.

10. A lithium ion battery, characterized in that: The negative electrode plate adopts the perovskite titanate material as claimed in claim 1 or 2 as the active material.

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