Preparation method of lithium titanate material and lithium titanate battery containing lithium titanate material

Abstract

The invention discloses a preparation method of a lithium titanate material and a lithium titanate battery containing the lithium titanate material, and the preparation method comprises the following steps: (1) mixing lithium titanyl oxalate and ammonium titanyl oxalate in water, and carrying out spray drying granulation to obtain ammonium titanyl oxalate double salt; and (2) sintering the obtained lithium titanyl ammonium oxalate double salt to obtain the lithium titanate material. The lithium titanate material is prepared by sintering the compound containing both titanium and lithium in molecules, and titanium atoms and lithium atoms are uniformly mixed in the molecular-level size, so that the lithium titanate material obtained after high-temperature decomposition has more ideal distribution uniformity of lithium and titanium elements; moreover, after the decomposition reaction, except the lithium titanate, other byproducts are gas, and high-purity lithium titanate can be obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of battery materials, in particular to a preparation method of lithium titanate material and a lithium titanate battery comprising the same. BACKGROUND

[0002] Lithium ion batteries are rapidly developing in commercial applications, which is closely related to the progress of electrode materials. The preparation of lithium titanate material is still mainly based on solid phase method, which is completed by solid phase mixing and sintering. The solid phase method uses titanium dioxide, lithium carbonate or lithium hydroxide as raw materials, which has the advantages of easy availability and low cost. However, the disadvantages are also obvious: ① The titanium dioxide is very unstable due to different sources and production processes, and the impurities are difficult to control, which directly affects the stability and reliability of the lithium titanate material; ② The solid phase mixing of raw materials cannot achieve uniform mixing, and the sintered lithium titanate material is prone to "rich lithium" and "poor lithium" regions, resulting in unsatisfactory electrochemical performance; ③ Due to the large particle size of titanium dioxide, the sintered lithium titanate particles are only larger, and it is almost impossible to obtain smaller lithium titanate particles. Therefore, due to the uneven mixing of raw materials and the limitation of titanium source particle size, the electrochemical performance of the lithium titanate material prepared by the solid phase method cannot be fully utilized; combined with the instability of titanium dioxide raw materials, the electrical performance of the lithium titanate battery is not ideal. Under the trend of material refinement and nanometerization, the solid phase method cannot meet the development needs of lithium titanate material and lithium titanate battery.

[0003] Patent CN101704681B discloses a preparation method of spinel structure lithium titanate, in which titanium salt is prepared into a titanium-containing solution, and titanium oxalate powder is first prepared as a lithium titanate precursor; then the solid lithium source is ball milled with the precursor at room temperature, and then calcined to obtain spinel structure lithium titanate. This preparation method of lithium titanate only replaces titanium dioxide in the solid phase reaction with titanium oxalate, which enriches the titanium source, but the subsequent ball milling process with lithium source is the same as the traditional solid phase reaction for preparing lithium titanate, and the problems existing in the solid phase synthesis of lithium titanate are still not solved. SUMMARY

[0004] The present application is to overcome the above-mentioned problems in the prior art of preparing lithium titanate material by solid phase method, and to provide a preparation method of lithium titanate material and a lithium titanate battery comprising the same. The lithium titanate material is prepared by sintering a compound containing titanium and lithium in the molecule. Since the titanium atoms and lithium atoms are "mixed uniformly" in the molecular level, the lithium titanate material obtained by high temperature decomposition has more ideal uniformity of lithium and titanium elements; and after the decomposition reaction, the remaining by-products are gases (water is also discharged from the reaction system in the form of gas at high temperature), so high-purity lithium titanate can be obtained.

[0005] In order to achieve the above object, the present application adopts the following technical solutions: In a first aspect, the present application provides a preparation method of lithium titanate material, comprising the following steps: (1) mixing lithium oxotitanate and ammonium oxotitanate in water, and then spray drying and granulating to obtain lithium ammonium oxotitanate complex salt; (2) sintering the obtained lithium ammonium oxotitanate complex salt to obtain lithium titanate material.

[0006] The present application uses ammonium oxotitanate and lithium oxotitanate as raw materials, prepares lithium ammonium oxotitanate complex salt, and then sintering the lithium ammonium oxotitanate complex salt to prepare lithium titanate, and the reaction principle is:

[0007] The present application uses lithium ammonium oxotitanate complex salt containing titanium and lithium in the molecule as raw material. Since the titanium atoms and lithium atoms are "mixed uniformly" in the size of the molecule, the lithium titanate material obtained by high temperature decomposition has more ideal uniformity of lithium and titanium element distribution. Moreover, after the decomposition reaction of the lithium ammonium oxotitanate complex salt, the remaining by-products are all gases (water is also discharged from the reaction system in the form of gas at high temperature), so that very high purity lithium titanate can be obtained. The lithium titanate material in the present application is used as electrode material, and the battery made of it has better and more stable performance, especially the cycle performance is obviously improved, which can reach more than 20,000 times (room temperature, 100% SOC).

[0008] As a preferred, in step (1), the lithium oxotitanate and ammonium oxotitanate are mixed in water according to the mass ratio of titanium atoms to lithium atoms of 1:0.78-1:0.82.

[0009] As a preferred, the particle size D50 of the lithium ammonium oxotitanate complex salt obtained in step (1) is 15-80 μm.

[0010] As a preferred, the sintering temperature in step (2) is 500-860 ℃.

[0011] As a preferred, the sintering time in step (2) is 3-18 hours.

[0012] As a preferred, the temperature rising rate in the 200-450 ℃ stage during the sintering process in step (2) is not more than 1 ℃ / min.

[0013] The process of sintering lithium ammonium oxotitanate complex salt into lithium titanate can be roughly divided into two stages: ① Between 200℃ and 450℃, the lithium ammonium titanium oxalate complex salt is decomposed into lithium titanate, carbon dioxide, carbon monoxide and water, wherein the carbon dioxide, carbon monoxide and water are in gaseous form and escape from the reaction system; because a large amount of gas is generated, the heating rate is controlled to prevent the generated gas from carrying the lithium titanate out of the reaction system or the rapid generation of gas from causing a safety problem due to the increase in the pressure of the reaction system.

[0014] ② Between 500℃ and 860℃, lithium titanate crystals are generated and the crystal grains grow; the heating rate and the final temperature of this stage determine the morphology and size of the lithium titanate crystals.

[0015] In a second aspect, the present application provides a lithium titanate battery, comprising a positive electrode, a negative electrode, a separator, an electrolyte and an outer package; the negative electrode material in the negative electrode comprises the lithium titanate material prepared by the above preparation method.

[0016] Preferably, the positive electrode material in the positive electrode is at least one of lithium nickel cobalt manganese oxide, lithium manganese iron phosphate, lithium manganate, a nickel-manganese binary material and a lithium-rich manganese-based material.

[0017] Preferably, the electrolyte comprises a solvent, an additive and a lithium salt, and the mass fraction of the additive is 0-5%.

[0018] Preferably, the additive is at least one of vinylene carbonate, 1,3-propane sulfone lactone, ethylene sulfate, fluoroethylene and vinyl ethylene carbonate.

[0019] Therefore, the present application has the following beneficial effects: (1) The lithium ammonium titanium oxalate complex salt containing titanium and lithium simultaneously in the molecule is used as the raw material, and the lithium titanate material obtained by high-temperature decomposition has good uniformity of the distribution of lithium and titanium elements; (2) After the decomposition of the lithium ammonium titanium oxalate complex salt, the remaining by-products are all gases, which can be discharged from the reaction system, so that high-purity lithium titanate can be obtained; (3) The lithium titanate material in the present application is used as the electrode material, and the battery made therefrom has better and stable performance, and the cycle performance is obviously improved. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is the SEM image of the lithium titanate material prepared in Example 1 of the present application.

[0021] Figure 2 is the SEM image of the lithium titanate material prepared in Comparative Example 1 of the present application.

[0022] Figure 3 is the XRD image of the lithium titanate material prepared in Example 1 of the present application.

[0023] Figure 4 is the cycle performance test curve of the lithium titanate battery in Example 1 of the present application.

[0024] Figure 5 is the cycle performance test curve of the lithium titanate battery in Example 2 of the present application.

[0025] Figure 6 is the cycle performance test curve of the lithium titanate battery in Example 3 of the present application.

[0026] Figure 7 is the cycle performance test curve of the lithium titanate battery in Example 4 of the present application.

[0027] Figure 8 is the cycle performance test curve of the lithium titanate battery in Comparative Example 1 of the present application.

[0028] Figure 9 is the cycle performance test curve of the lithium titanate battery in Comparative Example 2 of the present application.

[0029] Figure 10 is the cycle performance test curve of the lithium titanate battery in Comparative Example 3 of the present application. DETAILED DESCRIPTION

[0030] The present application will be further described in conjunction with the accompanying drawings and specific embodiments.

[0031] In the present application, unless specified, all the equipment and raw materials can be purchased from the market or commonly used in the industry, and the methods in the following examples are the conventional methods in the field, unless specified.

[0032] General Examples: A preparation method of a lithium titanate material, comprising the following steps: (1) mixing lithium oxatitanate and ammonium oxatitanate in water, and then spray drying and granulating to obtain an ammonium lithium oxatitanate complex salt; (2) sintering the obtained ammonium lithium oxatitanate complex salt to obtain a lithium titanate material.

[0033] As a specific embodiment, in step (1), the lithium oxatitanate and the ammonium oxatitanate are mixed in water according to a mass ratio of titanium atoms to lithium atoms of 1:0.78-1:0.82.

[0034] As a specific embodiment, the particle size D50 of the ammonium lithium oxatitanate complex salt obtained in step (1) is 15-80 μm.

[0035] As a specific embodiment, the sintering temperature in step (2) is 500-860 °C.

[0036] As a specific embodiment, the sintering time in step (2) is 3-18 hours.

[0037] As a specific implementation method, the heating rate in step (2) during the sintering process in the 200-450℃ range does not exceed 1℃ / min.

[0038] Example 1: A method for preparing lithium titanate material, comprising the following steps: (1) Dissolve 3 mol of titanium oxalate monohydrate in 8 L of water, add 2 mol of lithium titanium oxalate hydrate in batches while stirring, and after stirring until the solid is completely dissolved, use a spray dryer to spray dry, control the receiving temperature between 80 and 115℃, and obtain lithium titanium oxalate double salt with a particle size D50 in the range of 15 to 80 μm. (2) The obtained lithium titanate ammonium double salt was placed in a crucible and sintered in a high-temperature furnace. The sintering method was as follows: the temperature was increased from room temperature to 200℃ at a heating rate of 1℃ / min, then increased to 500℃ at a heating rate of 0.5℃ / min, and then increased to 650℃ at a heating rate of 1℃ / min and held for 8 hours to obtain lithium titanate material. Its SEM and XRD patterns are shown below. Figure 1 and Figure 3 As shown; from Figure 1 As can be seen, the particle size of the lithium titanate material prepared by this invention is between 0.2 and 1 μm.

[0039] The above-mentioned lithium titanate material, conductive carbon black, and binder PVDF were mixed in a mass ratio of 95:3:2 to prepare a slurry, which was then coated on a 13μm aluminum foil to prepare the battery negative electrode. The lithium nickel manganese oxide material, conductive carbon black, and binder PVDF were mixed in a mass ratio of 95:2:3 to prepare a slurry, which was then coated on a 13μm aluminum foil to prepare the battery positive electrode. After stacking a 16μm wet-process PE separator, an electrolyte (electrolyte composition: solvent: EMC+DEC+PC, mass ratio 2:6:2; solute: 1mol / L LiPF6) was injected, charged, and then encapsulated to obtain a lithium titanate battery. The cycle performance was as follows: Figure 4 As shown in the image.

[0040] The above-mentioned lithium titanate material, conductive agent carbon black, and binder PVDF were mixed in a mass ratio of 92:4:4 to prepare a slurry, which was then coated on a 15μm aluminum foil as the positive electrode of the coin cell. A lithium metal sheet was used as the negative electrode of the coin cell. A 20μm wet-process PE separator was used, and an electrolyte (electrolyte composition: solvent: EMC+DEC+PC, mass ratio 2:6:2; solute: 1mol / L LiPF6) was added. The coin cell was then encapsulated, and the specific capacity of the lithium titanate material was measured as shown in Table 1.

[0041] Example 2: A method for preparing lithium titanate material, comprising the following steps: (1) Dissolve 3 mol of ammonium titanyl oxalate monohydrate in 8 L of water, and add 1.92 mol of lithium titanyl oxalate hydrate in batches under stirring, and spray dry using a spray dryer after the solids are completely dissolved, with the control of the temperature of the collected material being between 80-115°C, to obtain lithium ammonium titanyl oxalate double salt with a particle size D50 in the range of 15-80 μm; (2) Put the obtained lithium ammonium titanyl oxalate double salt into a sagger, and sinter in a high-temperature furnace; the sintering method is as follows: increase the temperature from room temperature to 200°C at a rate of 2°C / min, then increase the temperature to 500°C at a rate of 0.3°C / min, and then increase the temperature to 780°C at a rate of 2°C / min and keep for 6 h, to obtain lithium titanate material.

[0042] Mix the above lithium titanate material, conductive agent carbon black, and binder PVDF in a mass ratio of 95:3:2 to prepare a slurry, coat on a 13 μm aluminum foil, and prepare a battery negative electrode; mix the lithium nickel-manganese oxide material, conductive agent carbon black, and binder PVDF in a mass ratio of 95:2:3 to prepare a slurry, coat on a 13 μm aluminum foil, and prepare a battery positive electrode; use a 16 μm wet PE separator to laminate, inject electrolyte (composition of electrolyte: solvent: EMC+DEC+PC, mass ratio 2:6:2; solute: 1 mol / L LiPF6), and package after charging to obtain a lithium titanate battery, and the cycle performance is as shown in Table 1. Figure 5

[0043] Mix the above lithium titanate material, conductive agent carbon black, and binder PVDF in a mass ratio of 95:3:2 to prepare a slurry, coat on a 13 μm aluminum foil, and prepare a battery negative electrode; mix the lithium nickel-manganese oxide material, conductive agent carbon black, and binder PVDF in a mass ratio of 95:2:3 to prepare a slurry, coat on a 13 μm aluminum foil, and prepare a battery positive electrode; use a 16 μm wet PE separator to laminate, inject electrolyte (composition of electrolyte: solvent: EMC+DEC+PC, mass ratio 2:6:2; solute: 1 mol / L LiPF6), and package after charging to obtain a lithium titanate battery, and the cycle performance is as shown in Table 1.

[0044] Example 3: A preparation method of a lithium titanate material, the steps being: (1) Dissolve 5 mol of ammonium titanyl oxalate monohydrate in 8 L of water, and add 4 mol of lithium titanyl oxalate hydrate in batches under stirring, and spray dry using a spray dryer after the solids are completely dissolved, with the control of the temperature of the collected material being between 80-115°C, to obtain lithium ammonium titanyl oxalate double salt with a particle size D50 in the range of 15-80 μm; (2) Put the obtained lithium ammonium titanyl oxalate double salt into a sagger, and sinter in a high-temperature furnace; the sintering method is as follows: increase the temperature from room temperature to 200°C at a rate of 2°C / min, then increase the temperature to 500°C at a rate of 0.6°C / min, and then increase the temperature to 860°C at a rate of 2°C / min and keep for 4 h, to obtain lithium titanate material.​

[0045] The above-mentioned lithium titanate material, conductive carbon black, and binder PVDF were mixed in a mass ratio of 95:3:2 to prepare a slurry, which was then coated on a 13μm aluminum foil to prepare the battery negative electrode. The lithium nickel manganese oxide material, conductive carbon black, and binder PVDF were mixed in a mass ratio of 95:2:3 to prepare a slurry, which was then coated on a 13μm aluminum foil to prepare the battery positive electrode. After stacking a 16μm wet-process PE separator, an electrolyte (electrolyte composition: solvent: EMC+DEC+PC, mass ratio 2:6:2; solute: 1mol / L LiPF6) was injected, charged, and then encapsulated to obtain a lithium titanate battery. The cycle performance was as follows: Figure 6 As shown in the image.

[0046] The above-mentioned lithium titanate material, conductive agent carbon black, and binder PVDF were mixed in a mass ratio of 92:4:4 to prepare a slurry, which was then coated on a 15μm aluminum foil as the positive electrode of the coin cell. A lithium metal sheet was used as the negative electrode of the coin cell. A 20μm wet-process PE separator was used, and an electrolyte (electrolyte composition: solvent: EMC+DEC+PC, mass ratio 2:6:2; solute: 1mol / L LiPF6) was added. The coin cell was then encapsulated, and the specific capacity of the lithium titanate material was measured as shown in Table 1.

[0047] Example 4: A method for preparing lithium titanate material, comprising the following steps: (1) Dissolve 5 mol of titanium oxalate monohydrate in 8L of water, add 4.1 mol of lithium titanium oxalate hydrate in batches while stirring, and after stirring until the solid is completely dissolved, spray dry using a spray dryer, and control the receiving temperature between 80 and 115℃ to obtain lithium titanium oxalate double salt with a particle size D50 in the range of 15 to 80 μm. (2) The obtained lithium oxalate titanium ammonium double salt was placed in a sagger and sintered in a high-temperature furnace. The sintering method was as follows: the temperature was raised from room temperature to 200℃ at a heating rate of 1℃ / min, then raised to 500℃ at a heating rate of 0.5℃ / min, and then raised to 650℃ at a heating rate of 1℃ / min and held for 8 hours to obtain lithium titanate material.

[0048] The above-mentioned lithium titanate material, conductive carbon black, and binder PVDF were mixed in a mass ratio of 95:3:2 to prepare a slurry, which was then coated on a 13μm aluminum foil to prepare the battery negative electrode. The lithium nickel manganese oxide material, conductive carbon black, and binder PVDF were mixed in a mass ratio of 95:2:3 to prepare a slurry, which was then coated on a 13μm aluminum foil to prepare the battery positive electrode. After stacking a 16μm wet-process PE separator, an electrolyte (electrolyte composition: solvent: EMC+DEC+PC, mass ratio 2:6:2; solute: 1mol / L LiPF6) was injected, charged, and then encapsulated to obtain a lithium titanate battery. The cycle performance was as follows: Figure 7 As shown in the image.

[0049] The lithium titanate material, conductive agent carbon black, and binder PVDF described above are mixed in a mass ratio of 92:4:4 to prepare a slurry, which is coated on a 15 pm aluminum foil to serve as a positive electrode of a button cell; a metal lithium sheet is used as a negative electrode of the button cell; a 20 pm wet PE separator is used, and an electrolyte (composition of the electrolyte: solvent: EMC+DEC+PC, mass ratio 2:6:2; solute: 1 mol / L LiPF6) is added to package a button cell, and the lithium titanate material gram capacity is measured as shown in Table 1.

[0050] Comparative Example 1 A method for preparing a lithium titanate material includes the following steps: Titanium dioxide is used as a titanium source, and lithium carbonate is used as a lithium source. The lithium carbonate and the titanium dioxide are mixed in a molar ratio of lithium atoms to titanium atoms of 4:5, ball milled in a planetary ball mill at room temperature for 8 hours, and then placed in a sagger and calcined in an air atmosphere at 800°C in a high-temperature furnace for 10 hours to obtain a lithium titanate material. The SEM image of the lithium titanate material is shown in Figure 2 It can be seen that the particle size of the lithium titanate material prepared in Comparative Example 1 is obviously larger than that of the lithium titanate material in Example 1.

[0051] The lithium titanate material, conductive agent carbon black, and binder PVDF described above are mixed in a mass ratio of 95:3:2 to prepare a slurry, which is coated on a 13 pm aluminum foil to prepare a battery negative electrode; the lithium nickel manganese oxide material, conductive agent carbon black, and binder PVDF are mixed in a mass ratio of 95:2:3 to prepare a slurry, which is coated on a 13 pm aluminum foil to prepare a battery positive electrode; a 16 pm wet PE separator is used, and an electrolyte (composition of the electrolyte: solvent: EMC+DEC+PC, mass ratio 2:6:2; solute: 1 mol / L LiPF6) is injected after lamination to package a lithium titanate battery after charging, and the cycle performance is shown in Figure 8 .

[0052] The lithium titanate material, conductive agent carbon black, and binder PVDF described above are mixed in a mass ratio of 92:4:4 to prepare a slurry, which is coated on a 15 pm aluminum foil to serve as a positive electrode of a button cell; a metal lithium sheet is used as a negative electrode of the button cell; a 20 pm wet PE separator is used, and an electrolyte (composition of the electrolyte: solvent: EMC+DEC+PC, mass ratio 2:6:2; solute: 1 mol / L LiPF6) is added to package a button cell, and the lithium titanate material gram capacity is measured as shown in Table 1.

[0053] Comparative Example 2 A method for preparing a lithium titanate material includes the following steps: (1) titanium sulfate as titanium source, prepared into a solution containing 1 mol / L titanium 10 L, added oxalic acid 30 mol, stirred at 50 ℃ for 10 min, then frozen at 3 ℃ crystallization, standing for 5 h; the precipitated solid was filtered and washed with deionized water three times, then dried at 80 ℃ to obtain oxalate titanic acid precursor; (2) lithium hydroxide and the above precursor were mixed according to the molar ratio of lithium atom to titanium atom of 4:5, and ball milled in a planetary ball mill at room temperature for 8 h, then put into a crucible and calcined at 800 ℃ in an air atmosphere for 12 h in a high temperature furnace to obtain a lithium titanate material.

[0054] The lithium titanate material, conductive agent carbon black and binder PVDF were mixed in a mass ratio of 95:3:2 to prepare a slurry, coated on a 13 μm aluminum foil to prepare a battery negative electrode; the lithium nickel manganese oxide material, conductive agent carbon black and binder PVDF were mixed in a mass ratio of 95:2:3 to prepare a slurry, coated on a 13 μm aluminum foil to prepare a battery positive electrode; after laminating using a 16 μm wet PE separator, an electrolyte (electrolyte composition: solvent: EMC+DEC+PC, mass ratio 2:6:2; solute: 1 mol / L LiPF6) was injected, and after charging, a lithium titanate battery was packaged, and the cycle performance was as shown in Figure 9

[0055] The lithium titanate material, conductive agent carbon black and binder PVDF were mixed in a mass ratio of 95:3:2 to prepare a slurry, coated on a 13 μm aluminum foil to prepare a battery negative electrode; the lithium nickel manganese oxide material, conductive agent carbon black and binder PVDF were mixed in a mass ratio of 95:2:3 to prepare a slurry, coated on a 13 μm aluminum foil to prepare a battery positive electrode; after laminating using a 16 μm wet PE separator, an electrolyte (electrolyte composition: solvent: EMC+DEC+PC, mass ratio 2:6:2; solute: 1 mol / L LiPF6) was injected, and after charging, a lithium titanate battery was packaged, and the cycle performance was as shown in

[0056] Comparative Example 3: A preparation method of a lithium titanate material, comprising the following steps: (1) titanium sulfate as titanium source, prepared into a solution containing 1 mol / L titanium 10 L, added oxalic acid 30 mol, stirred at 50 ℃ for 10 min, then frozen at 3 ℃ crystallization, standing for 5 h; the precipitated solid was filtered and washed with deionized water three times, then dried at 80 ℃ to obtain oxalate titanic acid precursor; (2) lithium carbonate and the above precursor were mixed according to the molar ratio of lithium atom to titanium atom of 4.2:5, and ball milled in a planetary ball mill at room temperature for 8 h, then put into a crucible and calcined at 600 ℃ in an air atmosphere for 24 h in a high temperature furnace to obtain a lithium titanate material.

[0057] ​The lithium titanate material, conductive agent carbon black, and binder PVDF were mixed in a mass ratio of 95:3:2 to prepare a slurry, which was coated on a 13 μm aluminum foil to prepare a battery negative electrode; a lithium nickel manganese oxide material, conductive agent carbon black, and binder PVDF were mixed in a mass ratio of 95:2:3 to prepare a slurry, which was coated on a 13 μm aluminum foil to prepare a battery positive electrode; after lamination using a 16 μm wet PE separator, an electrolyte (electrolyte composition: solvent: EMC+DEC+PC, mass ratio 2:6:2; solute: 1 mol / L LiPF6) was injected, and after charging, the lithium titanate battery was packaged, and the cycle performance was as shown in Table 1. Figure 10

[0058] The lithium titanate material, conductive agent carbon black, and binder PVDF were mixed in a mass ratio of 95:3:2 to prepare a slurry, which was coated on a 13 μm aluminum foil to prepare a battery negative electrode; a lithium nickel manganese oxide material, conductive agent carbon black, and binder PVDF were mixed in a mass ratio of 95:2:3 to prepare a slurry, which was coated on a 13 μm aluminum foil to prepare a battery positive electrode; after lamination using a 16 μm wet PE separator, an electrolyte (electrolyte composition: solvent: EMC+DEC+PC, mass ratio 2:6:2; solute: 1 mol / L LiPF6) was injected, and after charging, the lithium titanate battery was packaged, and the cycle performance was as shown in Table 1.

[0059] Table 1: Test results of lithium titanate battery gram capacity.

[0060] As can be seen from Table 1, the lithium titanate material prepared in the examples using the method in the present application has a significant advantage in gram capacity compared to the comparative examples. As can be seen from Table 1, Figures 3-9 As can be seen from Table 1, the lithium titanate material prepared in the examples using the method in the present application has a significant advantage in gram capacity compared to the comparative examples. As can be seen from Table 1,

[0061] In Comparative Example 1, the lithium titanate was prepared by a traditional solid-phase sintering method using titanium dioxide as the titanium source and lithium carbonate as the lithium source. The titanium source and the lithium source were difficult to mix uniformly, and the sintered lithium titanate material was prone to have "rich lithium" regions and "poor lithium" regions, thus the electrochemical performance was significantly lower than that in the examples. Moreover, the particle size of the lithium titanate prepared in Comparative Example 1 was significantly larger than that in Example 1, which was not conducive to the electrochemical performance.

[0062] In Comparative Examples 2 and 3, the oxalate titanate precursor was first prepared, and then mixed with the lithium source for sintering. The titanium source and the lithium source were also difficult to mix uniformly, and the electrochemical performance was also lower than that in the examples, and the battery cycle performance decreased. Moreover, the reactants in Comparative Examples 1 and 2 contained impurities such as sulfate, chloride, and potassium ions, and the presence of impurities would reduce the gram capacity of the lithium titanate material.

[0063] ​Therefore, the application adopts the lithium ammonium oxalate titanate complex salt containing titanium and lithium simultaneously as raw material, since the titanium atom and lithium atom have been "mixed uniformly" in the size of molecular level, the lithium titanate material obtained by high temperature decomposition has more ideal uniformity of lithium and titanium element distribution; and after the decomposition reaction of the lithium ammonium oxalate titanate complex salt, the rest of the by-products are gas (water is also in the form of gas at high temperature and discharged from the reaction system), so the lithium titanate with very high purity can be obtained. The lithium titanate material in the application is used as electrode material, the battery made of the lithium titanate material has better and stable performance, especially the cycle performance is obviously improved, which can reach more than 20,000 times (room temperature, 100% SOC).

[0064] The above examples are intended to help understand the technical method and core idea of the application. It should be pointed out that for those skilled in the art, the application can be appropriately modified and replaced without departing from the principle of the application. These modifications and replacements do not constitute substantial changes to the technical solutions of the embodiments of the application and are still within the protection scope of the application.

Claims

1. A method for preparing lithium titanate material, characterized in that, Includes the following steps: (1) Lithium oxalate and ammonium oxalate were mixed in water and then spray-dried and granulated to obtain lithium oxalate ammonium double salt. (2) The obtained lithium oxalate titanium ammonium double salt was sintered to obtain lithium titanate material.

2. The method for preparing lithium titanate material according to claim 1, characterized in that, In step (1), lithium titanium oxalate and ammonium titanium oxalate are mixed in water at a molar ratio of titanium atoms to lithium atoms of 1:0.78~1:0.

82.

3. The method for preparing lithium titanate material according to claim 1 or 2, characterized in that, The particle size D50 of the lithium ammonium oxalate titanium complex salt obtained in step (1) is 15~80μm.

4. The method for preparing lithium titanate material according to claim 1, characterized in that, The sintering temperature in step (2) is 500~860℃.

5. The method for preparing lithium titanate material according to claim 1 or 4, characterized in that, The sintering time in step (2) is 3 to 18 hours.

6. The method for preparing lithium titanate material according to claim 1 or 4, characterized in that, In step (2), the heating rate during the sintering process in the 200~450℃ range shall not exceed 1℃ / min.

7. A lithium titanate battery, characterized in that, It includes a positive electrode, a negative electrode, a separator, an electrolyte, and outer packaging; the negative electrode material in the negative electrode includes lithium titanate material prepared using any one of the preparation methods described in claims 1 to 6.

8. The lithium titanate battery according to claim 7, characterized in that, The cathode material is at least one of lithium nickel cobalt manganese oxide, lithium manganese iron phosphate, lithium manganese oxide, nickel-manganese binary materials, and lithium-rich manganese-based materials.

9. The lithium titanate battery according to claim 7, characterized in that, The electrolyte comprises a solvent, an additive, and a lithium salt, wherein the mass fraction of the additive is 0-5%.

10. The lithium titanate battery according to claim 9, characterized in that, The additive is at least one of vinylene carbonate, 1,3-propane sulpholactone, vinyl sulfate, fluoroethylene ester, and vinyl ethylene carbonate.

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