Composite electrode material, preparation method thereof and lithium ion battery

Abstract

The application discloses a kind of composite electrode material, its preparation method and lithium ion battery, belong to electrode material technical field.The composite electrode material is micron level dense nanocrystal, the micron level dense nanocrystal is micron level mixed inlay structure, inside is polycrystalline structure, internal grain is nanometer level electrode material, and fast ion conductor is distributed at the internal grain boundary.The application is applied to low temperature lithium ion battery aspect, solves the problem that present technical cannot solve micron level electrode material at low temperature stable lithium ion storage, can realize electrode material at low temperature service environment efficient lithium storage.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electrode materials, and particularly relates to a composite electrode material, a preparation method thereof and a lithium ion battery. BACKGROUND

[0002] Lithium ion batteries are widely used in portable electronic devices, electric vehicles and energy storage systems due to their high energy density, long cycle life and relatively light weight. However, the performance of standard lithium ion batteries will decrease significantly at low temperatures, which is mainly caused by factors such as increased viscosity, reduced conductivity of electrolyte and weakened activity of electrode materials. In order to improve the low-temperature energy storage performance of lithium ion batteries and enable them to be applied in low-temperature fields such as high altitudes, high latitudes and space, the current modification is mainly directed to electrolyte. Electrode materials are the key components that determine the overall energy and power density of the battery, but there are few reports on improving the intrinsic low-temperature energy storage performance of electrode materials, especially for micron-sized electrode materials which are more practical.

[0003] In order to improve the performance of electrode materials in low-temperature service environment, the morphology and crystal structure of electrode material particles are usually designed, such as using nanomaterials or special porous structures to enhance the reaction activity and conductivity of electrode materials. Chinese patent CN116632201A discloses a high-performance lithium ion battery low-temperature anode material-amorphous tin / carbon nanotube composite, which uses nanometerization strategy to composite nanoscale amorphous tin and carbon nanotubes, thereby realizing high low-temperature capacity and good cycle performance, but the volume energy density of nanometerized products is low, so the cost is high; Chinese patent CN116404236A discloses a niobium-based low-temperature lithium ion battery, which uses carbon coating strategy to coat niobium pentoxide with carbon, thereby improving its conductivity and fully exerting the low-temperature performance of niobium pentoxide, but the improvement effect of carbon coating strategy is limited, resulting in a small improvement in the low-temperature performance of the material.

[0004] Micron-sized electrode materials with large size are beneficial to obtain high quality and volume energy density, and can meet the demand of future device miniaturization and are more practical. However, the bulk ion transport process of large-size, high-density micron electrode materials is slow, especially at low temperatures. Therefore, it is of important practical significance for the development of lithium ion battery technology to develop micron-sized electrode materials with strong low-temperature adaptability, which can still store lithium ions efficiently and stably at low temperatures. SUMMARY

[0005] In view of the deficiencies of the prior art, the technical problem to be solved by the present application is to overcome the problem that the micro-scale electrode material cannot be stably stored with lithium ions at low temperature, and to provide a composite electrode material capable of efficiently storing lithium ions at low temperature, a preparation method thereof and a lithium ion battery.

[0006] To solve the technical problem, the technical scheme adopted by the present application is:

[0007] The present application provides a composite electrode material, which is a micro-scale dense nanocrystal.

[0008] Preferably, the size of at least one dimension of the micro-scale dense nanocrystal is selected from any value in the range of 1-10 mu m, and the size of the internal grain is selected from any value in the range of 100-200 nm; the mass fraction of the fast ion conductor in the composite electrode material is selected from any value in the range of 0.1-30%.

[0009] Preferably, the electrode material is selected from any one of lithium cobaltate, lithium manganate, lithium nickel cobalt manganate, lithium iron phosphate, lithium titanate, and graphite; the fast ion conductor includes Li, M, and A, M is at least one of transition metal, In, Al, Ge, and Sn, A is at least one of F, Cl, Br, I, and O, and the molar ratio of Li, M, and A is Li:M:A=(3.2-0.2):(1.2-0.8):(6.2-0.8).

[0010] Preferably, the specific surface area of the micro-scale dense nanocrystal is not more than 50 m 2 / g, and the tap density is not less than 0.8 g / cm 3 .

[0011] The present application further provides a preparation method of the composite electrode material, which comprises a precursor preparation step and a precursor calcination step.

[0012] Preferably, the precursor preparation step comprises grinding or ball-milling the electrode material and the fast ion conductor to obtain a precursor; and the precursor calcination step comprises calcining the ball-milled precursor at less than 650 DEG C to obtain the composite electrode material.

[0013] Preferably, the precursor preparation step comprises: dissolving a Li source, an M source and an A source in a solvent to form a mixed solution, adding electrode material powder to the mixed solution, mixing to obtain a solid-liquid mixture, and performing hydrothermal reaction or solvothermal reaction on the solid-liquid mixture, and then washing and drying to obtain the precursor; and the precursor calcination step comprises: calcining the precursor obtained by hydrothermal reaction or solvothermal reaction at 350-1000℃ to obtain the composite electrode material.

[0014] Preferably, in the precursor preparation step, the Li source is at least one selected from lithium hydroxide, lithium nitrate, lithium sulfate, lithium carbonate, lithium phosphate, lithium hydrogen phosphate, lithium chlorate, lithium fluoride, lithium chloride, lithium bromide, lithium iodide, lithium formate, lithium citrate and lithium tert-butoxide; the molar ratio of Li to M in the Li source and the M source is Li:M=10:1-0.2:1; the molar ratio of Li to A in the Li source and the A source is Li:A=8:1-0.2:1; the concentration of Li ions in the mixed solution is 0.1-10 mol / L; the solvent is deionized water, methanol, ethanol, ethylene glycol, isopropanol or acetonitrile alone or a mixture of two or more thereof; the hydrothermal temperature of the hydrothermal reaction ranges from 60 to 240℃, the hydrothermal temperature rising rate is 1-10℃ / min, the hydrothermal time is 12-36h, and the reaction pressure is 0.15-60MPa.

[0015] Preferably, in the precursor calcination step, the calcination temperature rising rate is 1-10℃ / min, the calcination time is 5-12h, the calcination atmosphere is air, nitrogen, argon, argon-hydrogen mixed gas or vacuum, the background gas flow rate is 10-50mL / min or the vacuum degree is 10 -7 -10 -5 Pa.

[0016] The application also provides a lithium ion battery, wherein the electrode material of the lithium ion battery is the composite electrode material according to any one of the technical solutions.

[0017] Compared with the prior art, the application has the following beneficial effects:

[0018] The application provides a composite electrode material, wherein ion channels are constructed in a micron-level electrode particle body phase, the internal grains are nanometer-level electrode materials used as lithium storage phases, and fast ion conductors are distributed at internal grain boundaries and used as fast continuous bulk phase ion transmission channels, so that the micron-level electrode material realizes stable lithium ion storage at low temperatures.

[0019] The application provides a preparation method of the composite electrode material, and has the characteristics of simple synthesis operation, short time, low energy consumption and low-cost batch production.

[0020] The application also provides a lithium ion battery with excellent lithium storage performance at low temperature, especially in a low-temperature environment (below -20 DEG C), which can be applied in extremely low-temperature environments such as severe cold and high altitude. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 A structural schematic diagram of the composite electrode material provided by the embodiment of the application;

[0022] Figure 2 A rate performance graph of the lithium titanate-lithium lanthanum titanate composite electrode material and the nanoscale lithium titanate at room temperature provided by the embodiment 1 of the application;

[0023] Figure 3 A cycle performance graph of the lithium titanate-lithium lanthanum titanate composite electrode material and the nanoscale lithium titanate at -20 DEG C, 200 m A·g -1 provided by the embodiment 1 of the application;

[0024] Figure 4 A rate performance graph of the lithium titanate-lithium indium chloride composite electrode material and the nanoscale lithium titanate at -20 DEG C provided by the embodiment 3 of the application. DETAILED DESCRIPTION

[0025] The technical solutions in the specific embodiments of the application will be described in detail and completely below with reference to the drawings. Obviously, the described embodiments are only part of the specific embodiments of the general technical solution of the application, rather than all the embodiments. All other embodiments obtained by those skilled in the art based on the general concept of the application fall within the scope of protection of the application.

[0026] In one aspect, the application provides a composite electrode material, as shown in the formula: Figure 1 The composite electrode material is a micron-level dense nanocrystal, and the micron-level dense nanocrystal is a micron-level mixed mosaic structure, the inside of which is a polycrystal structure, the internal grains of which are nanoscale electrode materials, and fast ion conductors are distributed at the grain boundaries of the internal grains. The composite electrode material constructs ion channels in the micron-level electrode particle body phase, wherein the internal grains are nanoscale electrode materials used as lithium storage phases, and the fast ion conductors are distributed at the grain boundaries of the internal grains and used as fast continuous bulk phase ion transmission channels, realizing stable lithium ion storage of the micron-level electrode material at low temperature. Further, the fast ion conductors are oxide systems (lithium lanthanum titanate LLTO, lithium lanthanum zirconium oxide LLZO, etc.), halide systems (LiInZrCl, LiInYCl, LiInYF, etc.); and the electrode materials are oxide systems and polyanion systems.

[0027] It should be noted that the micron-sized electrode material of large size is beneficial to obtain high quality and volumetric energy density, can meet the demand of miniaturization of future devices and is more practical. However, the bulk ion transport process of the micron electrode material of large size and high density is slow, especially at low temperature. In order to realize high-efficiency lithium storage of the electrode material in a low-temperature service environment, the prior art method usually nanocrystallizes the electrode material. However, the nanoelectrode material has low particle packing density, high specific surface area and serious surface side reaction, and often needs a large amount of conductive agent, binder and electrolyte, resulting in low overall energy density and poor stability of the battery. In view of this problem, the present application provides an oxide electrode material filled with a fast ion conductor at a grain boundary and a preparation method thereof. Taking a large-size micron lithium titanate-lithium lanthanum titanate / lithium indium chloride composite electrode material as an example, the composite electrode material not only has high tap density, but also can realize dual fast transmission of ions and electrons in the material bulk phase, especially still has high rate performance and long cycle stability at extremely low temperature (below -20 DEG C). Specifically, unlike the agglomeration or assembly of nanoelectrode particles, the micron-sized dense nanocrystal is a primary particle, and the size range is obviously different. The composite electrode material has the structural characteristics of large size (ensuring high volumetric energy density) and network mixed inlay, has ion-electron dual fast transmission channels, can integrate the advantages of high tap density, low specific surface area and fast ion transmission, improve the rate performance at room temperature and low temperature, and realize excellent lithium storage performance at low temperature, especially at low temperature environment (below -20 DEG C), and can be applied to extremely low temperature environments such as severe cold and high altitude.

[0028] In a preferred embodiment, the micron-sized dense nanocrystal has a size of at least one dimension selected from any value in 1-10 microns, and the internal grain has a size selected from any value in 100-200 nm; the mass ratio of the fast ion conductor in the composite electrode material is selected from any value in 0.1-30%. The technical solution specifically limits the size of the micron-sized dense nanocrystal, ensures that the composite electrode material is micron-sized, is beneficial to obtain high quality and volumetric energy density, can meet the demand of miniaturization of future devices and is more practical. It can be understood that the size of the micron-sized dense nanocrystal can also be 2 microns, 3 microns, 4 microns, 5 microns, 6 microns, 7 microns, 8 microns, 9 microns and any point value in the range thereof, the size of the internal grain can also be 120 nm, 140 nm, 160 nm, 180 nm and any point value in the range thereof, and the mass ratio of the fast ion conductor in the composite electrode material can also be 5%, 10%, 15%, 20%, 25% and any point value in the range thereof.

[0029] In a preferred embodiment, the electrode material is selected from any one of lithium cobaltate, lithium manganate, lithium nickel cobalt manganate, lithium iron phosphate, lithium titanate, graphite; the fast ion conductor comprises Li, M, A, M is at least one of transition metal, In, Al, Ge, Sn element, A is at least one of F, Cl, Br, I, O, and the molar ratio of Li, M, A is Li:M:A=(3.2-0.2):(1.2-0.8):(6.2-0.8).

[0030] In a preferred embodiment, the specific surface area of the micron-sized dense nanocrystal is not more than 50 m 2 / g, and the tap density is not less than 0.8 g / cm 3 .

[0031] It should be noted that the difficulty in preparing the above composite electrode material lies in: 1) the fast ion conductor accounts for a very small proportion, but needs to be uniformly distributed in the electrode material bulk phase; 2) the two are stably bonded through bonding to form micron-sized dense particles.

[0032] Another aspect of the present application provides a preparation method of the composite electrode material according to any one of the above technical solutions, comprising a precursor preparation step and a precursor calcination step.

[0033] In a preferred embodiment, the precursor preparation step comprises: grinding or ball-milling the electrode material and the fast ion conductor to obtain a precursor; and the precursor calcination step comprises: calcining the ball-milled precursor at less than 650℃ to obtain the composite electrode material. This method takes advantage of the high flowability of the fast ion conductor in a glass state to quickly fill the intergranular boundaries of the electrode material nanocrystals, overcoming the above difficulties in the preparation of the composite electrode material. Specifically, the lithium source and the indium source are mixed and thoroughly ground, then lithium titanate is added and thoroughly ground, and finally the mixed powder is ball-milled at a speed of 400-600 rpm for 24-48 h; the ball-milled precursor is calcined in an Ar or N2 atmosphere at a temperature of 250-600℃, with a heating rate of 2-5℃ / min for 8-12 h.

[0034] In a preferred embodiment, the precursor preparation step comprises: dissolving the Li source, the M source and the A source in a solvent to form a mixed solution, adding the electrode material powder to the mixed solution and thoroughly mixing to obtain a solid-liquid mixture, and performing hydrothermal or solvothermal reaction on the solid-liquid mixture, then washing and drying to obtain the precursor; and the precursor calcination step comprises: calcining the precursor obtained by hydrothermal or solvothermal reaction at 350-1000℃ to obtain the composite electrode material. This method forms the fast ion conductor in situ at the intergranular boundaries of the electrode material nanocrystals, also overcoming the above difficulties in the preparation of the composite electrode material.

[0035] In a preferred embodiment, the Li source is selected from at least one of lithium hydroxide, lithium nitrate, lithium sulfate, lithium carbonate, lithium phosphate, lithium hydrogen phosphate, lithium chlorate, lithium fluoride, lithium chloride, lithium bromide, lithium iodide, lithium formate, lithium citrate, lithium tert-butoxide, lithium benzoate; the molar ratio of Li and M in the Li source and the M source is Li:M = 10:1-0.2:1; the molar ratio of Li and A in the Li source and the A source is Li:A = 8:1-0.2:1; the concentration of Li ions in the mixed solution is 0.1-10 mol / L; the solvent is one or a mixture of several of deionized water, methanol, ethanol, ethylene glycol, isopropanol, acetonitrile; the hydrothermal temperature of the hydrothermal reaction ranges from 60-240℃, the hydrothermal heating rate is 1-10℃ / min, the hydrothermal time is 12-36h, and the reaction pressure is 0.15-60MPa.

[0036] In a preferred embodiment, in the precursor calcination step, the calcination heating rate is 1-10℃ / min, the calcination time is 5-12h, the calcination atmosphere is air, nitrogen, argon, argon-hydrogen mixed gas or vacuum, the background gas flow rate is 10-50mL / min or the vacuum degree is 10 -7 -10 -5 Pa.

[0037] The above two preparation methods compound titanium lanthanum lithium titanate and indium lithium chloride in lithium titanate, and the high ion conductivity of titanium lanthanum lithium titanate and indium lithium chloride improves the ion conductivity of the composite material, and the lithium storage performance of the composite material is higher than the capacity of lithium titanate alone and titanium lanthanum lithium titanate / indium lithium chloride alone. Due to the support of titanium lanthanum lithium titanate and indium lithium chloride, the generation of large-size lithium titanate-lithium lanthanum titanate composite electrode material is induced, which has high tap density and high energy density. The intercrystalline ion transport channels generated by the crystallization of lithium lanthanum titanate and indium lithium chloride between the grain boundaries of lithium titanate crystals realize fast ion transport at low temperature.

[0038] The application also provides a lithium ion battery, wherein the electrode material of the lithium ion battery is the composite electrode material according to any one of the technical solutions described above. The lithium ion battery has excellent lithium storage performance at low temperature, especially in a low-temperature environment (below-20℃), and can be applied in extremely low-temperature environments such as severe cold and high altitude.

[0039] In order to more clearly and specifically introduce the composite electrode material, the preparation method thereof and the lithium ion battery provided by the embodiments of the application, the following will be described in combination with specific embodiments.

[0040] Embodiment 1

[0041] Precursor preparation: 10 mg of LiNO3, 70 mg of LaNO3were dissolved in 10 mL of ethanol and stirred at room temperature for 30 min; then 0.50 mL of tetrabutyl titanate was dissolved in 35 mL of isopropanol and stirred at room temperature for 1 h; then the two solutions were mixed and stirred for 30 min; then 15 mL of distilled water was added and stirred vigorously for 5 min; finally, the solution was transferred to a 100 mL hydrothermal reactor liner and 322 mg of lithium titanate powder was added.

[0042] Hydrothermal step: the precursor was heated to 180°C at a rate of 5°C / min and hydrothermal treatment was performed for 12 h.

[0043] Washing and drying step: the hydrothermally treated sample was filtered with ethanol for 3 times and then placed in a blast oven for drying at a temperature of 80°C for 12 h.

[0044] Calcination step: the precursor was ground thoroughly and placed in a muffle furnace, heated to 400°C at a rate of 5°C / min and calcined for 6 h, finally the lithium titanate-lithium lanthanum titanate composite electrode material of the example was prepared.

[0045] Example 2

[0046] Precursor preparation: 15 mg of lithium hydroxide monohydrate and 50 mg of LaNO3were dissolved in 10 mL of ethanol and stirred at room temperature for 30 min; then 0.30 mL of isopropyl titanate was dissolved in 35 mL of ethylene glycol and stirred at room temperature for 1 h; then the two solutions were mixed and stirred for 30 min; then 15 mL of distilled water was added and stirred vigorously for 5 min; finally, the solution was transferred to a 100 mL hydrothermal reactor liner and 459 mg of lithium titanate powder was added.

[0047] Hydrothermal step: the precursor was heated to 180°C at a rate of 5°C / min and hydrothermal treatment was performed for 12 h.

[0048] Washing and drying step: the hydrothermally treated sample was filtered with ethanol for 3 times and then placed in a blast oven for drying at a temperature of 80°C for 12 h.

[0049] Calcination step: the precursor was ground thoroughly and placed in a muffle furnace, heated to 600°C at a rate of 5°C / min and calcined for 6 h, finally the lithium titanate-lithium lanthanum titanate composite electrode material of the example was prepared.

[0050] Example 3

[0051] The precursor preparation: 2.600 g of lithium titanate, 0.154 g of lithium chloride, and 0.254 g of indium chloride were weighed and added to a ball mill jar, and 5 mm zirconia balls corresponding to the mass were added at a mass ratio of 1:20, and sealed, then the ball mill jar was placed in a ball mill to rotate at 600 rpm for 20 min, reverse rotation at 600 rpm for 20 min, and static for 10 min, repeating the procedure for 20 times, the above steps need to be carried out in an argon / nitrogen environment.

[0052] The calcination step: the above precursor was ground and placed in a tube furnace, heated to 500°C at a heating rate of 5°C / min under an argon / nitrogen atmosphere and calcined for 12 h, finally the lithium titanate-indium lithium chloride composite electrode material of the present embodiment was prepared.

[0053] Performance test

[0054] The materials prepared in the above embodiments 1, 2, and 3 were tested for performance.

[0055] The test results show that the lithium titanate-lanthanum titanate composite electrode material of embodiment 1 has excellent low-temperature lithium storage performance: at room temperature, it has a mass specific capacity of 180 mAh / g; at -20°C, it has a mass specific capacity of 90 mAh / g (200 mA / g current density), and the capacity retention rate is close to 99.5% after 200 cycles Figure 2 and Figure 3 ).

[0056] The test results show that the specific capacity, rate performance, and cycle stability of the lithium titanate-lanthanum lithium titanate composite electrode material obtained in embodiment 2 are close to those of embodiment 1.

[0057] The test results show that the lithium titanate-indium lithium chloride composite electrode material of embodiment 3 has excellent low-temperature lithium storage performance: at -20°C, it has a mass specific capacity of 180 mAh / g, and the rate performance is better than that of nano lithium titanate Figure 4 ).

Claims

1. A method for preparing a composite electrode material, characterized in that, The composite electrode material is a micron-scale dense nanocrystal, which is a primary particle. The micron-scale dense nanocrystal has a micron-scale hybrid mosaic structure with a polycrystalline structure inside. The internal grains are nanoscale electrode materials, and fast ion conductors are distributed at the boundaries between the internal grains. The size of at least one dimension of the micron-scale dense nanocrystals is selected from any value between 1 and 10 μm, and the size of the internal grains is selected from any value between 100 and 200 nm; the mass percentage of the fast ion conductor in the composite electrode material is selected from any value between 0.1 and 30%. The electrode material is lithium titanate; the fast ion conductor is lithium lanthanum titanate or lithium indium chloride. When the fast ion conductor is lithium lanthanum titanate, the composite electrode material is obtained by the following method: Precursor preparation: Li source and LaNO3 were weighed and dissolved in a solvent and stirred; then tetrabutyl titanate was measured and dissolved in a solvent and stirred; the two solutions were then mixed and stirred to obtain a mixed solution; distilled water was added and stirred vigorously; finally, the solution was transferred to the lining of a hydrothermal reactor and lithium titanate powder was added for hydrothermal reaction at a temperature of 180℃; the sample after hydrothermal treatment was filtered with ethanol and dried to obtain the precursor; Calcination step: The above precursor is thoroughly ground and then calcined at 400℃ to prepare lithium titanate-lithium titanate lanthanum composite electrode material. When the fast ion conductor is lithium indium chloride, the composite electrode material is obtained by the following method: Precursor preparation: Weigh lithium titanate, lithium chloride, and indium chloride, add them to a ball mill jar, and ball mill them. The ball milling process is carried out in an argon / nitrogen atmosphere. Calcination step: The above precursor is thoroughly ground and then calcined at 500°C to prepare lithium titanate-lithium indium chloride composite electrode material.

2. The method for preparing the composite electrode material according to claim 1, characterized in that, The specific surface area of ​​the micron-sized dense nanocrystals does not exceed 50 m². 2 / g, tap density not less than 0.8 g / cm³ 3 .

3. The method for preparing the composite electrode material according to claim 1, characterized in that, In the precursor preparation step, the Li source is selected from at least one of lithium hydroxide, lithium nitrate, lithium sulfate, lithium carbonate, lithium phosphate, dilithium hydrogen phosphate, lithium chlorate, lithium fluoride, lithium chloride, lithium bromide, lithium iodide, lithium formate, lithium citrate, lithium tert-butoxide, and lithium benzoate; the concentration of Li ions in the mixed solution is 0.1-10 mol / L; the solvent is one or a mixture of several of deionized water, methanol, ethanol, ethylene glycol, isopropanol, and acetonitrile; the hydrothermal heating rate is 1-10℃ / min, the hydrothermal time is 12-36 h, and the reaction pressure is 0.15-60 MPa.

4. The method for preparing the composite electrode material according to claim 1, characterized in that, In the calcination step, the calcination heating rate is 1-10℃ / min, the calcination time is 5-12 h, and the calcination atmosphere is air, nitrogen, argon, an argon-hydrogen mixture, or vacuum. The background gas flow rate is 10-50 mL / min or the vacuum degree is 10. -7 -10 -5 Pa.

5. A lithium-ion battery, characterized in that, The electrode material of the lithium-ion battery is a composite electrode material prepared by the method described in any one of claims 1-4.

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