A method for preparing a lithium titanate material and a lithium titanate battery comprising the same

Abstract

The application discloses a preparation method of a lithium titanate material and a lithium titanate battery containing the same, and the preparation method comprises the following steps: (1) mixing lithium oxotitanate and ammonium oxotitanate in water, and then performing spray drying and granulation to obtain an oxalate lithium-ammonium complex salt; and (2) sintering the obtained oxalate lithium-ammonium complex salt to obtain the lithium titanate material. The lithium titanate material is prepared by sintering a compound containing titanium and lithium simultaneously in a molecule, and since the titanium atoms and the lithium atoms are "mixed uniformly" in the size of a molecule, the lithium titanate material obtained through high-temperature decomposition is more ideal in uniformity of distribution of lithium and titanium elements; and after the decomposition reaction, all the by-products except the lithium titanate are gases, so that the lithium titanate with high purity can be obtained.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, and in particular to a method for preparing lithium titanate material and a lithium titanate battery containing the same. Background Technology

[0002] The rapid development of lithium-ion batteries in commercial applications is closely related to advancements in electrode materials. The preparation of lithium titanate materials still primarily relies on the solid-state method, involving solid-state mixing and calcination. The solid-state method uses titanium dioxide, lithium carbonate, and / or lithium hydroxide as raw materials, offering advantages such as readily available raw materials and low cost. However, it also has significant disadvantages: ① Titanium dioxide is highly unstable due to variations in source and production process, and impurities are difficult to control, directly affecting the stability and reliability of lithium titanate materials; ② Furthermore, the solid-state mixing process cannot achieve uniform mixing, leading to "lithium-rich" and "lithium-poor" regions in the calcined lithium titanate material, resulting in suboptimal electrochemical performance; ③ Due to the large particle size of titanium dioxide, the primary calcination of lithium titanate particles only results in larger particles, making it almost impossible to obtain smaller lithium titanate particles. Therefore, the solid-state method's lithium titanate materials suffer from material limitations due to uneven raw material mixing and the particle size limitation of the titanium source raw materials, resulting in suboptimal electrochemical performance. Combined with the instability of titanium dioxide, this ultimately leads to unsatisfactory electrical performance in lithium titanate batteries. With the trend towards materials becoming more refined and nanoscale, solid-state methods are no longer sufficient to meet the development needs of lithium titanate materials and lithium titanate batteries.

[0003] Patent CN101704681B discloses a method for preparing spinel-structured lithium titanate. The method involves preparing a titanium salt solution, first preparing an oxalate-oxytitanic acid powder as a precursor for lithium titanate, then ball-milling a solid lithium source with the precursor at room temperature, followed by calcination to obtain spinel-structured lithium titanate. This method simply replaces titanium dioxide with oxalate-oxytitanic acid in the solid-state reaction, thus enriching the titanium source. However, the subsequent ball-milling and mixing process with the lithium source is the same as the traditional solid-state reaction method for preparing lithium titanate, and the problems inherent in solid-state synthesis in lithium titanate reactions remain unresolved. Summary of the Invention

[0004] This invention aims to overcome the aforementioned problems in the solid-state preparation of lithium titanate materials in the prior art, and provides a method for preparing lithium titanate materials and a lithium titanate battery containing the same. The lithium titanate material is prepared by sintering a compound containing both titanium and lithium within the molecule. Since the titanium and lithium atoms are "uniformly mixed" at the molecular level, the lithium titanate material obtained after high-temperature decomposition has a more ideal uniformity of lithium and titanium element distribution. Furthermore, after the decomposition reaction, all byproducts except lithium titanate are gases (water is also discharged from the reaction system in gaseous form at high temperature), so high-purity lithium titanate can be obtained.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides a method for preparing lithium titanate material, comprising the following steps:

[0007] (1) Lithium oxalate and ammonium oxalate were mixed in water and then spray-dried and granulated to obtain lithium oxalate ammonium double salt.

[0008] (2) The obtained lithium oxalate titanium ammonium double salt was sintered to obtain lithium titanate material.

[0009] This invention uses ammonium titanium oxalate and lithium titanium oxalate as raw materials to prepare lithium titanium oxalate ammonium complex salt, and then sintersulates the lithium titanium oxalate ammonium complex salt to produce lithium titanate. The reaction principle is as follows:

[0010]

[0011] This invention uses lithium oxalate-titanium ammonium complex salt, which contains both titanium and lithium intramolecularly, as a raw material. Because the titanium and lithium atoms are "uniformly mixed" at the molecular level, the lithium titanate material obtained after high-temperature decomposition exhibits a more ideal distribution of lithium and titanium elements. Furthermore, after the decomposition reaction of lithium oxalate-titanium ammonium complex salt, all byproducts except lithium titanate are gases (water is also discharged from the reaction system as a gas at high temperatures), thus yielding lithium titanate with very high purity. Using the lithium titanate material of this invention as an electrode material results in batteries with better and more stable performance, especially with significantly improved cycle performance, reaching over 20,000 cycles (room temperature, 100% SOC).

[0012] Preferably, 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 to 1:0.82.

[0013] Preferably, the particle size D50 of the lithium oxalate titanium ammonium complex salt obtained in step (1) is 15-80 μm.

[0014] Preferably, the sintering temperature in step (2) is 500–860°C.

[0015] Preferably, the sintering time in step (2) is 3 to 18 hours.

[0016] Preferably, the heating rate in step (2) during the sintering process in the 200-450℃ range does not exceed 1℃ / min.

[0017] The process of sintering lithium oxalate ammonium titanium double salt into lithium titanate can be roughly divided into two stages:

[0018] ① Between 200℃ and 450℃, lithium oxalate titanium ammonium double salt decomposes into lithium titanate, carbon dioxide, carbon monoxide and water. Carbon dioxide, carbon monoxide and water escape from the reaction system in gaseous form. Because a large amount of gas is produced, the heating rate must be controlled to prevent the reaction from being too fast, which could cause the produced gas to carry lithium titanate out of the reaction system or cause the reaction system pressure to rise too quickly, leading to safety issues.

[0019] ② Lithium titanate crystals are formed and grains grow between 500℃ and 860℃; the heating rate and final temperature at this stage determine the morphology and size of the lithium titanate crystals.

[0020] Secondly, the present invention provides a lithium titanate battery, comprising a positive electrode, a negative electrode, a separator, an electrolyte, and an outer packaging; the negative electrode material in the negative electrode comprises lithium titanate material prepared using the above-described preparation method.

[0021] Preferably, 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.

[0022] Preferably, the electrolyte includes a solvent, an additive, and a lithium salt, wherein the mass fraction of the additive is 0-5%.

[0023] Preferably, the additive is at least one selected from vinylene carbonate, 1,3-propane sulpholactone, vinyl sulfate, fluoroethylene ester, and vinyl ethylene carbonate.

[0024] Therefore, the present invention has the following beneficial effects:

[0025] (1) The lithium titanate material obtained by using lithium oxalate titanium ammonium double salt containing both titanium and lithium in the molecule as raw material and decomposing it at high temperature has good uniformity of lithium and titanium element distribution.

[0026] (2) After the decomposition of lithium oxalate titanium ammonium double salt, except for lithium titanate, the other by-products are all gases, which can be discharged from the reaction system, so high-purity lithium titanate can be obtained.

[0027] (3) Using the lithium titanate material of the present invention as the electrode material, the battery made has better and more stable performance, especially with a significant improvement in cycle performance. Attached Figure Description

[0028] Figure 1 This is a SEM image of the lithium titanate material prepared in Example 1 of the present invention.

[0029] Figure 2 This is a SEM image of the lithium titanate material prepared in Comparative Example 1 of this invention.

[0030] Figure 3This is the XRD pattern of the lithium titanate material prepared in Example 1 of the present invention.

[0031] Figure 4 This is the cycle performance test curve of the lithium titanate battery in Example 1 of the present invention.

[0032] Figure 5 This is the cycle performance test curve of the lithium titanate battery in Example 2 of the present invention.

[0033] Figure 6 This is the cycle performance test curve of the lithium titanate battery in Example 3 of the present invention.

[0034] Figure 7 This is the cycle performance test curve of the lithium titanate battery in Example 4 of the present invention.

[0035] Figure 8 This is the cycle performance test curve of the lithium titanate battery in Comparative Example 1 of this invention.

[0036] Figure 9 This is the cycle performance test curve of the lithium titanate battery in Comparative Example 2 of this invention.

[0037] Figure 10 This is the cycle performance test curve of the lithium titanate battery in Comparative Example 3 of this invention. Detailed Implementation

[0038] The present invention will now be further described with reference to the accompanying drawings and specific embodiments.

[0039] In this invention, unless otherwise specified, all equipment and raw materials are available from the market or commonly used in the industry. Unless otherwise specified, the methods in the following embodiments are conventional methods in the art.

[0040] General Implementation Examples:

[0041] A method for preparing lithium titanate material includes the following steps:

[0042] (1) Lithium oxalate and ammonium oxalate were mixed in water and then spray-dried and granulated to obtain lithium oxalate ammonium double salt.

[0043] (2) The obtained lithium oxalate titanium ammonium double salt was sintered to obtain lithium titanate material.

[0044] In one specific implementation, 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 to 1:0.82.

[0045] As one specific implementation, the particle size D50 of the lithium oxalate titanium ammonium complex salt obtained in step (1) is 15-80 μm.

[0046] In one specific implementation, the sintering temperature in step (2) is 500–860°C.

[0047] In one specific implementation, the sintering time in step (2) is 3 to 18 hours.

[0048] 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.

[0049] Example 1:

[0050] A method for preparing lithium titanate material, comprising the following steps:

[0051] (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.

[0052] (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.

[0053] 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.

[0054] 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.

[0055] Example 2:

[0056] A method for preparing lithium titanate material, comprising the following steps:

[0057] (1) Dissolve 3 mol of titanium oxalate monohydrate in 8 L of water, add 1.92 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 °C to obtain lithium titanium oxalate double salt with a particle size D50 in the range of 15 to 80 μm.

[0058] (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 2℃ / min, then raised to 500℃ at a heating rate of 0.3℃ / min, and then raised to 780℃ at a heating rate of 2℃ / min and held for 6 hours to obtain lithium titanate material.

[0059] 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 5 As shown in the image.

[0060] 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.

[0061] Example 3:

[0062] A method for preparing lithium titanate material, comprising the following steps:

[0063] (1) Dissolve 5 mol of titanium oxalate monohydrate in 8 L of water, add 4 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.

[0064] (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 2℃ / min, then raised to 500℃ at a heating rate of 0.6℃ / min, and then raised to 860℃ at a heating rate of 2℃ / min and held for 4 hours to obtain lithium titanate material.

[0065] 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.

[0066] 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.

[0067] Example 4:

[0068] A method for preparing lithium titanate material, comprising the following steps:

[0069] (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.

[0070] (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.

[0071] 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.

[0072] 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.

[0073] Comparative Example 1:

[0074] A method for preparing lithium titanate material, comprising the following steps:

[0075] Using titanium dioxide as the titanium source and lithium carbonate as the lithium source, lithium carbonate and titanium dioxide were mixed at a molar ratio of lithium atoms to titanium atoms of 4:5. The mixture was ball-milled in a planetary ball mill for 8 hours at room temperature, and then calcined in a crucible at 800°C in air for 10 hours to obtain lithium titanate material. Its SEM image is shown below. Figure 2 As shown in the figure, it can be seen that the particle size of the lithium titanate material prepared in Comparative Example 1 is significantly larger than that of the lithium titanate material in Example 1.

[0076] 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 8 As shown in the image.

[0077] 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.

[0078] Comparative Example 2:

[0079] A method for preparing lithium titanate material, comprising the following steps:

[0080] (1) Using titanium sulfate as the titanium source, prepare 10 L of a solution containing 1 mol / L titanium, add 30 mol of oxalic acid, stir the reaction at 50 °C for 10 minutes, then freeze crystallize at 3 °C and let stand for 5 hours; filter the precipitated solid and wash it three times with deionized water, then dry it at 80 °C to obtain the oxalate titanate precursor.

[0081] (2) Lithium hydroxide was mixed with the above precursor at a mass ratio of lithium atoms to titanium atoms of 4:5 and ball-milled in a planetary ball mill for 8 hours at room temperature. Then it was placed in a sagger and calcined in an air atmosphere at 800°C for 12 hours to obtain lithium titanate material.

[0082] 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 9 As shown in the image.

[0083] 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.

[0084] Comparative Example 3:

[0085] A method for preparing lithium titanate material, comprising the following steps:

[0086] (1) Using titanium oxychloride as the titanium source, prepare 20L of solution containing 0.5mol / L titanium, add 30mol of potassium oxalate, stir and react at 60℃ for 2 hours, then freeze and crystallize at 1℃, let stand for 2 hours, filter the precipitated solid, wash it three times with deionized water, and then dry it at 50℃ to obtain the oxalate titanium acid precursor.

[0087] (2) Lithium carbonate was mixed with the above precursor at a mass ratio of lithium atoms to titanium atoms of 4.2:5. The mixture was ball-milled in a planetary ball mill at room temperature for 8 hours. Then it was placed in a sagger and calcined in an air atmosphere at 600°C for 24 hours to obtain lithium titanate material.

[0088] 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 10 As shown in the image.

[0089] 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.

[0090] Table 1: Specific capacity test results of lithium titanate batteries.

[0091]

[0092] As can be seen from Table 1, the lithium titanate material prepared by the method of the present invention in the examples has a significant advantage in specific capacity compared with the comparative example. Figures 3-9 As can be seen from the examples, the lithium titanate material prepared by the method of the present invention is used as the negative electrode material of the lithium titanate battery. The cycle performance of the battery is significantly improved compared with that of the comparative example, and can reach more than 20,000 cycles.

[0093] In Comparative Example 1, lithium titanate was prepared using a traditional solid-state sintering method with titanium dioxide as the titanium source and lithium carbonate as the lithium source. However, the titanium and lithium sources were difficult to mix uniformly, resulting in "lithium-rich" and "lithium-poor" regions in the sintered lithium titanate material. Consequently, its electrochemical performance was significantly lower than that of the examples. Furthermore, the particle size of the lithium titanate obtained in Comparative Example 1 was significantly larger than that in Example 1, which is detrimental to its electrochemical performance.

[0094] In Comparative Examples 2 and 3, oxalate-titanium oxalate precursors were first prepared and then mixed with a lithium source for sintering. The titanium and lithium sources were also difficult to mix uniformly, resulting in a decrease in electrochemical performance and battery cycle performance compared to the examples. Furthermore, the reactants in Comparative Examples 1 and 2 contained impurities such as sulfate, chloride, and potassium ions, which reduced the specific capacity of the lithium titanate material.

[0095] Therefore, this invention uses lithium oxalate-titanium ammonium complex salt, which contains both titanium and lithium intramolecularly, as a raw material. Because titanium and lithium atoms are "uniformly mixed" at the molecular level, the lithium titanate material obtained after high-temperature decomposition exhibits a more ideal distribution of lithium and titanium elements. Furthermore, after the decomposition reaction of lithium oxalate-titanium ammonium complex salt, all byproducts except lithium titanate are gases (water is also discharged from the reaction system as a gas at high temperatures), resulting in lithium titanate with very high purity. Using the lithium titanate material of this invention as an electrode material results in batteries with better and more stable performance, especially with significantly improved cycle performance, reaching over 20,000 cycles (room temperature, 100% SOC).

[0096] The above description of the embodiments is intended to help understand the technical methods and core ideas of the present invention. It should be noted that those skilled in the art can make appropriate modifications and substitutions to the present invention without departing from its principles. These modifications and substitutions do not constitute a change in the essential nature of the technical solutions of the embodiments of the present invention and are still within the protection scope of the present invention.

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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