Lithium titanate negative electrode material, preparation method thereof and lithium titanate battery

Abstract

The invention relates to the technical field of batteries, in particular to a lithium titanate negative electrode material, a preparation method of the lithium titanate negative electrode material and a lithium titanate battery, and the preparation method comprises the following steps: mixing lithium titanate with water to prepare lithium titanate slurry, and carrying out ball milling; after ball milling, adding a carbon source into the lithium titanate slurry, and carrying out spray drying and sintering; and after sintering, vacuum drying is performed, and CO2-containing gas is introduced in the drying process for purging. According to the preparation method of the lithium titanate negative electrode material, the alkalinity of the prepared lithium titanate material can be reduced, and when the lithium titanate material prepared by the preparation method is used for preparing a battery, the adverse effect on the battery can be reduced.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically, to lithium titanate anode materials, their preparation methods, and lithium titanate batteries. Background Technology

[0002] Lithium-ion batteries have many advantages such as high specific energy, low cost, long cycle life, and high energy storage efficiency, and have been widely used in various fields; among them, lithium titanate batteries are a typical example.

[0003] A lithium titanate battery is a type of battery that uses lithium titanate material as the negative electrode. The preparation method of lithium titanate material usually involves mixing lithium source and titanium source and then calcining at high temperature.

[0004] However, during the preparation of lithium titanate materials using relevant technologies, the lithium source decomposes into lithium oxide (Li2O) during high-temperature calcination, which remains on the surface of the lithium titanate material. Lithium oxide (Li2O) has strong hygroscopic properties and can absorb moisture and CO2 from the air to form LiOH and Li2CO3. LiOH is a strong alkali that is soluble in water, which will increase the alkalinity of the lithium titanate material and have an adverse effect on the battery. Summary of the Invention

[0005] The purpose of this invention is to provide a lithium titanate anode material, a method for preparing the same, and a lithium titanate battery. The method for preparing the lithium titanate anode material can reduce the alkalinity of the prepared lithium titanate material, and when the lithium titanate material prepared by this method is used to prepare a battery, it can reduce the adverse effects on the battery.

[0006] This invention is implemented as follows: In a first aspect, the present invention provides a method for preparing a lithium titanate anode material, comprising: Lithium titanate was mixed with water to prepare a lithium titanate slurry, which was then ball-milled. After ball milling, a carbon source is added to the lithium titanate slurry, followed by spray drying and sintering. After sintering, the material is vacuum dried, and CO2-containing gas is introduced during the drying process for purging.

[0007] In an optional embodiment, the amount of carbon source added is 0.3 to 0.6% of the mass of lithium titanate solids in the lithium titanate slurry.

[0008] In an optional implementation, the carbon source is carbon black.

[0009] In an optional embodiment, the sintering temperature is 550~750℃, and the heating rate is 2-5℃ / h.

[0010] In an optional embodiment, the D50 of the ball-milled lithium titanate slurry is 0.1-0.2 μm.

[0011] In an optional embodiment, a gas containing 15-25 vol% CO2 is purged during the drying process.

[0012] In an optional embodiment, the vacuum drying temperature is 150-180°C.

[0013] In an optional embodiment, the lithium titanate is further washed with water before preparing the lithium titanate slurry.

[0014] Secondly, the present invention provides a lithium titanate anode material, which is prepared by the preparation method of lithium titanate anode material according to any of the foregoing embodiments.

[0015] Thirdly, the present invention provides a lithium titanate battery, wherein the raw materials for preparing the negative electrode of the lithium titanate battery include the lithium titanate negative electrode material prepared by the preparation method of the lithium titanate negative electrode material of any of the foregoing embodiments, or the lithium titanate negative electrode material of the foregoing embodiments.

[0016] The present invention has the following beneficial effects: In the preparation method of lithium titanate material provided in this invention, a carbon source is added to the lithium titanate slurry, and after spray drying, sintering is performed. This allows the carbon source mixed into the lithium titanate material to carbonize at high temperature to generate carbon dioxide. The residual LiOH on the lithium titanate surface reacts with the formed carbon dioxide at high temperature to convert into Li₂CO₃, thus reducing the residual LiOH content on the lithium titanate surface for the first time. Subsequently, during vacuum drying, a gas containing carbon dioxide is further introduced to further utilize the carbon dioxide gas to react with the remaining LiOH on the lithium titanate surface, converting it into Li₂CO₃, further reducing the LiOH content. This ensures that the alkalinity of the final lithium titanate anode material is significantly reduced. Furthermore, the preparation method of this invention has fewer process steps and is simple and easy to operate.

[0017] The lithium titanate anode material provided in this embodiment of the invention is prepared by the aforementioned preparation method. The residual LiOH content on the surface of the lithium titanate anode material is greatly reduced, which can reduce the alkalinity of the lithium titanate anode material.

[0018] The negative electrode preparation of the lithium titanate battery provided in this embodiment of the invention is far removed from the aforementioned lithium titanate negative electrode material. Since the alkalinity of the lithium titanate negative electrode material is reduced, the adverse effects on the prepared battery can be reduced. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0020] The inventors discovered that the method of preparing lithium titanate anode material by high-temperature calcination of mixed titanium and lithium sources provided by the related technology will cause the lithium source to decompose at high temperature to form (Li2O) residue on the surface of the lithium titanate material. Lithium oxide (Li2O) has strong hygroscopicity and can absorb moisture and CO2 from the air to form LiOH and Li2CO3. LiOH is a strong alkali that is soluble in water, which will increase the alkalinity of the lithium titanate material and have an adverse effect on the battery.

[0021] If the alkalinity of lithium titanate material is reduced by coating, for example by coating the surface of lithium titanate with fast ion conductor lithium aluminum titanium phosphate to reduce residual alkalinity, it will increase the number of process steps, increase the preparation cost, and reduce the production efficiency.

[0022] If the alkalinity of lithium titanate material is reduced by methods such as acid soaking, the safety of the production process will be reduced, and the electrochemical performance of the lithium titanate material itself will be adversely affected.

[0023] To address the aforementioned issues, namely, to reduce the gaps in lithium titanate materials, decrease processing steps, ensure process safety, and mitigate adverse effects on the electrochemical performance of lithium titanate materials, this disclosure provides a novel method for preparing lithium titanate anode materials. The lithium titanate anode materials prepared by this method can be used to prepare battery anodes.

[0024] The method for preparing lithium titanate anode material disclosed herein includes: Lithium titanate was mixed with water to prepare a lithium titanate slurry, which was then ball-milled. After ball milling, a carbon source is added to the lithium titanate slurry, followed by spray drying and sintering. After sintering, the material is vacuum dried, and CO2-containing gas is introduced during the drying process for purging.

[0025] Adding a carbon source to a lithium titanate slurry and then sintering it after spray drying allows the carbon source mixed into the lithium titanate material to carbonize at high temperature, generating carbon dioxide. This causes the residual LiOH on the lithium titanate surface to react with the formed carbon dioxide at high temperature, converting it into Li₂CO₃, thus reducing the residual LiOH content on the lithium titanate surface for the first time. Subsequently, during vacuum drying, a gas containing carbon dioxide is further introduced to further utilize the carbon dioxide gas to react with the remaining LiOH on the lithium titanate surface, converting it into Li₂CO₃, thereby further reducing the LiOH content and ensuring that the alkalinity of the final lithium titanate anode material is significantly reduced. Furthermore, the preparation method of this invention has fewer process steps and is simple and easy to operate.

[0026] Optionally, the solid content of the lithium titanate slurry can be selected as needed, for example, 10~30%.

[0027] Optionally, the diameter of the grinding balls used in the ball mill can be selected as needed, for example: 0.2~0.5mm.

[0028] Optionally, the amount of carbon source added is 0.3~0.6% of the mass of lithium titanate solids in the lithium titanate slurry. Adding an appropriate amount of carbon source allows for calcination of the lithium titanate slurry to generate a suitable amount of carbon dioxide, ensuring that the LiOH on the lithium titanate surface is reliably converted to Li2CO3, thereby reducing the alkalinity of the lithium titanate and avoiding waste of the carbon source.

[0029] Optionally, the carbon source is carbon black.

[0030] Of course, in other embodiments, the carbon source can also be glucose, sucrose, ethylene glycol, etc., and no specific limitation is made here.

[0031] Optionally, after adding a carbon source to the lithium titanate slurry, the inlet temperature of the spray dryer is 280~335℃ (e.g., 280℃, 285℃, 290℃, 295℃, 300℃, 310℃, 320℃, 330℃, 335℃, etc., which are not specifically limited here), and the outlet temperature is 100~120℃ (e.g., 100℃, 105℃, 110℃, 115℃, 120℃).

[0032] Optionally, the sintering temperature is 550~750℃ (e.g., 550℃, 600℃, 650℃, 700℃, 750℃, etc., which are not specifically limited here), and the heating rate is 2-5℃ / h (e.g., 2℃ / h, 3℃ / h, 4℃ / h, 5℃ / h, etc., which are not specifically limited here).

[0033] Sintering within the above temperature range ensures reliable carbonization of the carbon source and generates sufficient carbon dioxide to react with the residual LiOH on the surface of lithium titanate, thereby significantly reducing the amount of residual LiOH on the lithium titanate surface and lowering the alkalinity of lithium titanate.

[0034] Optionally, the sintering temperature is 650~750℃. Sintering within this temperature range can more reliably reduce the alkalinity of lithium titanate.

[0035] Optimizing the heating rate of sintering can ensure the steady carbonization of the carbon source to produce carbon dioxide. At the same time, it can reliably react with the residual LiOH on the surface of lithium titanate while producing carbon dioxide, thereby reducing the amount of residual LiOH and lowering the alkalinity of lithium carbonate.

[0036] Optionally, the D50 of the ball-milled lithium titanate slurry is 0.1-0.2 μm.

[0037] Optionally, during the drying process, a gas containing 15-25 vol% (e.g., 15 vol%, 18 vol%, 20 vol%, 22 vol%, 25 vol%, etc., without specific limitation) of CO2 can be introduced for purging. Purging with a gas containing an appropriate amount of CO2 during drying allows the LiOH remaining on the surface of lithium titanate to further react and form Li2CO3, thereby significantly reducing the amount of LiOH remaining on the surface of lithium titanate and lowering the alkalinity of lithium titanate.

[0038] Optionally, the number of times the purging is performed can be selected as needed, such as 1 time, 2 times, 3 times, 4 times, 5 times, 6 times, 7 times, etc., without specific limitations.

[0039] Optionally, the vacuum drying temperature is 150-180℃, such as 150℃, 160℃, 170℃, 180℃, etc., without specific limitations. Optimizing the vacuum drying temperature ensures both the efficiency and thoroughness of the drying process, and also ensures that the carbon dioxide gas introduced during the drying process reliably reacts with the residual LiOH on the lithium titanate surface to generate Li2CO3, thus significantly reducing the amount of LiOH remaining on the lithium titanate surface and lowering the alkalinity of the lithium titanate.

[0040] Optionally, the lithium titanate may also be washed with water before the preparation of the lithium titanate slurry.

[0041] Washing lithium titanate with water can reduce the amount of water-soluble lithium compounds (Li2O) remaining on the surface of lithium titanate raw materials before preparing lithium titanate slurry. This fundamentally reduces the content of residual LiOH on the surface of lithium titanate. In other words, by removing the water-soluble lithium compounds (Li2O) remaining on the surface of lithium titanate raw materials through washing, the amount of LiOH formed after lithium compounds (Li2O) absorb water and CO2 can be reduced, thereby fundamentally reducing the generation of alkaline substances on the surface of lithium titanate and reducing the alkalinity of lithium titanate.

[0042] It should be noted that the lithium titanate raw material used to prepare the lithium titanate slurry in this disclosure can be prepared by high-temperature calcination. For example, the titanium source and lithium source are dispersed in water and spray-dried (inlet temperature 270~350℃, outlet temperature 100~120℃) to obtain a lithium-titanium mixture, and then the lithium-titanium mixture is calcined at a temperature of 850~880℃ and a heating rate of 1~3℃ / h.

[0043] When preparing lithium titanate raw materials, the molar ratio of Li to Ti in the titanium source and lithium source is (4~4.5):5.

[0044] The present invention will be further described in detail below with reference to the embodiments.

[0045] Example 1 (1) Add 4000ml of deionized water to the dispersion tank, and add 1600g of titanium dioxide and 594.3g of lithium hydroxide (molar ratio Li:Ti=4.04:5) in sequence. After uniform dispersion for 2h, a lithium-titanium mixed slurry is obtained. The lithium-titanium mixed slurry is subjected to a first spray drying with an inlet temperature of 335℃ and an outlet temperature of 100℃ to obtain a uniformly mixed lithium-titanium mixture. The lithium-titanium mixture is calcined in a muffle furnace at 875℃ for 12h with a heating rate of 2℃ / h to obtain lithium titanate material. (2) Add 1000g of lithium titanate material to 4000ml of deionized water and mix evenly to obtain lithium titanate slurry. Use a Buchner funnel to filter and wash the lithium titanate slurry to obtain washed lithium titanate material. (3) 1000g of washed lithium titanate was mixed with deionized water to prepare a slurry with a solid content of 20%. After dispersing for 2 hours, it was transferred to a sand mill and ground with 0.3mm zirconium balls for 10 hours to obtain a slurry with D50=0.115μm. 3g of carbon black (0.3wt%) was added to the slurry, and then the nano slurry was spray-dried for the second time. The spray drying inlet temperature was 335℃ and the outlet temperature was 100℃ to obtain spray powder with a particle size of D50=10.32μm. Then the spray powder was sintered at a high temperature of 750℃ in air atmosphere for 6 hours with a heating rate of 3℃ / h. The sintered lithium titanate material was passed through a 250-mesh sieve, and then the sieved material was dried in a vacuum drying oven at 160℃ for 9 hours. During the drying period, it was purged 5 times with dry air containing 20vol%CO2 to finally obtain the surface-modified lithium titanate anode material.

[0046] Example 2 (1) Add 4000ml of deionized water to a dispersion tank, then add 1600g of titanium dioxide and 603.1g of lithium hydroxide (molar ratio Li:Ti=4.1:5) in sequence, and disperse evenly for 2h to obtain a lithium-titanium mixed slurry; subject the lithium-titanium mixed slurry to a first spray drying, with an inlet temperature of 285℃ and an outlet temperature of 120℃ to obtain a uniformly mixed lithium-titanium mixture; calcine the lithium-titanium mixture in a muffle furnace at 875℃ for 12h, with a heating rate of 2℃ / h to obtain lithium titanate material; (2) Add 1000g of lithium titanate material to 4000ml of deionized water and mix evenly to obtain lithium titanate slurry. Use a Buchner funnel to filter and wash the lithium titanate slurry to obtain washed lithium titanate material. (3) 1000g of washed lithium titanate was mixed with deionized water to prepare a slurry with a solid content of 20%. After dispersing for 2 hours, the slurry was transferred to a sand mill and ground for 10 hours with 0.3mm zirconium balls to obtain a slurry with D50=0.134μm. 3g of carbon black (0.3wt%) was added to the slurry, and then the nano slurry was spray-dried for the second time. The spray drying inlet temperature was 285℃ and the outlet temperature was 120℃ to obtain spray powder with a particle size of D50=9.39μm. Then the spray powder was sintered at a high temperature of 750℃ in air atmosphere for 6 hours with a heating rate of 3℃ / h. The sintered lithium titanate material was passed through a 250-mesh sieve, and then the sieved material was dried in a vacuum drying oven at 160℃ for 9 hours. During the drying period, it was purged 5 times with dry air containing 20vol%CO2 to finally obtain the surface-modified lithium titanate anode material.

[0047] Example 3 Steps (1) and (2) are the same as in Example 1; (3) 1000g of washed lithium titanate was mixed with deionized water to prepare a slurry with a solid content of 20%. After dispersing for 2 hours, the slurry was transferred to a sand mill and ground for 10 hours with 0.3mm zirconium balls to obtain a slurry with D50=0.115μm. 6g of carbon black (0.6wt%) was added to the slurry, and then the nano slurry was spray-dried for the second time. The spray drying inlet temperature was 285℃ and the outlet temperature was 120℃ to obtain spray powder with a particle size of D50=9.16μm. Then the spray powder was sintered at a high temperature of 750℃ in air atmosphere for 6 hours with a heating rate of 3℃ / h. The sintered lithium titanate material was passed through a 250-mesh sieve, and then the sieved material was dried in a vacuum drying oven at 160℃ for 9 hours. During the drying period, it was purged 5 times with dry air containing 20vol%CO2 to finally obtain the surface-modified lithium titanate anode material.

[0048] Example 4 Steps (1) and (2) are the same as in Example 2; (3) 1000g of washed lithium titanate was mixed with deionized water to prepare a slurry with a solid content of 20%. After dispersing for 2 hours, the slurry was transferred to a sand mill and ground for 10 hours with 0.3mm zirconium balls to obtain a slurry with a D50 of 0.134μm. 6g of carbon black (0.6wt%) was added to the slurry, and then the nano slurry was spray-dried for the second time. The spray drying inlet temperature was 285℃ and the outlet temperature was 120℃ to obtain spray powder with a particle size of D50 of 10.12μm. Then the spray powder was sintered at a high temperature of 750℃ in air atmosphere for 6 hours with a heating rate of 3℃ / h. The sintered lithium titanate material was passed through a 250-mesh sieve, and then the sieved material was dried in a vacuum drying oven at 160℃ for 9 hours. During the drying period, it was purged 5 times with dry air containing 20vol%CO2 to finally obtain the surface-modified lithium titanate anode material.

[0049] Example 5: The steps are the same as in Example 1, except that the high-temperature sintering temperature in step (3) is 550℃.

[0050] Example 6: The steps are the same as in Example 2, except that the high-temperature sintering temperature in step (3) is 550℃.

[0051] Example 7: The steps are the same as in Example 3, except that the high-temperature sintering temperature in step (3) is 550℃.

[0052] Example 8: The steps are the same as in Example 4, except that the high-temperature sintering temperature in step (3) is 550℃.

[0053] Example 9 The difference from Example 1 is that in step (3), 4g of carbon black (0.4wt%) is added to the slurry, the temperature of the sintering spray powder is 650℃, and the heating rate is 2℃ / h; in step (4), the drying temperature is 180℃, and the gas used for purging contains 15vol%CO2; other processes are the same as in Example 1.

[0054] Example 10 The difference between Example 10 and Example 1 is that: in step (3), 5g of carbon black (0.5wt%) is added to the slurry, the temperature of the sintering spray powder is 720℃, and the heating rate is 5℃ / h; in step (4), the drying temperature is 150℃, and the gas used for purging contains 25vol%CO2; other processes are the same as in Example 1.

[0055] Comparative Example 1 The difference from Example 1 is that step (2) is omitted, and the other processes are the same as in Example 1.

[0056] Comparative Example 2 The difference from Example 3 is that step (2) is omitted, and the other processes are the same as in Example 3.

[0057] Comparative Example 3 The difference from Example 5 is that step (2) is omitted; other processes are the same as in Example 5.

[0058] Comparative Example 4: The difference from Example 7 is that step (2) is omitted; other processes are the same as in Example 7.

[0059] Comparative Example 5: The difference from Example 1 is that step (2) is omitted and carbon black is not added to the slurry in step (3). Other processes are the same as in Example 1.

[0060] Comparative Example 6: The difference from Example 5 is that step (2) is omitted and step (3) does not involve adding carbon black to the slurry; the other processes are the same as in Example 5.

[0061] Water-soluble lithium (WS-Li) was tested in Examples 1-8 and Comparative Examples 1-6.

[0062] Test method: 10g of lithium titanate material prepared in each example and comparative example was placed in a 250ml volumetric flask, and ultrapure water was added to make up to 250ml to prepare a suspension with a solid content of 4%. After stirring with a magnetic stirrer for 20min, the suspension was immediately filtered, and the lithium content in the filtrate was tested by ICP. The results are shown in Table 1.

[0063] Table 1

[0064] Comparing Examples 1-4 and Examples 5-8, it can be seen that when carbon black is added to the lithium titanate slurry, a higher sintering temperature can better remove water-soluble lithium (WS-Li) from the surface of lithium titanate and reduce the alkalinity of the lithium titanate material.

[0065] Comparative Examples 1 and 3 with Comparative Examples 1 and 2, and Comparative Examples 5 and 7 with Comparative Examples 3 and 4, it can be seen that washing the lithium titanate raw material with water can effectively reduce water-soluble lithium (WS-Li) and reduce the alkalinity of the final lithium titanate material.

[0066] Comparative Examples 1 and 5, and 5 and 6, show that washing the lithium titanate raw material with water and then mixing it with a carbon source and calcining it in subsequent processes can significantly reduce the water-soluble lithium (WS-Li) content of the lithium titanate material and reduce the alkalinity of the final lithium titanate material.

[0067] Comparing Examples 1, 5 and 9, 10, it can be seen that when the sintering temperature in step (3) is ≥650℃, the water-soluble lithium (WS-Li) can be reduced more effectively, and the alkalinity of the final lithium titanate material can be reduced.

[0068] In summary, the method for preparing lithium titanate anode material of the present invention can reduce the alkalinity of the obtained lithium titanate material, and can reduce the adverse effects on the battery when the lithium titanate material prepared by this method is used to prepare the battery.

[0069] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a lithium titanate negative electrode material, characterized by, The application relates to a lithium titanate battery negative electrode material preparation method. The lithium titanate is mixed with water to prepare a lithium titanate slurry and is ball milled; After the ball milling, a carbon source is added to the lithium titanate slurry and is spray dried and sintered; After the sintering, vacuum drying is carried out and a gas containing CO2 is introduced to perform purging during the drying process.

2. The method of claim 1, wherein the lithium titanate negative electrode material is prepared by the steps of: The added amount of the carbon source is 0.3-0.6% of the solid mass of the lithium titanate in the lithium titanate slurry. ​ 3. The method for preparing the lithium titanate anode material according to claim 1, characterized in that, The carbon source is carbon black. 4.The method of claim 1, wherein the lithium titanate negative electrode material is prepared by the steps of: mixing a lithium source and a titanium source to form a mixture; and heating the mixture at a temperature of 600-900 ℃ for 1-10 hours in an inert gas atmosphere. The sintering temperature is 550-750 DEG C and the temperature rising rate is 2-5 DEG C / h. 5.The method of claim 1, wherein the lithium titanate negative electrode material is prepared by the steps of: mixing a lithium source and a titanium source to form a mixture; and heating the mixture at a temperature of 600-900 ℃ for 1-10 hours in an inert gas atmosphere. The D50 of the lithium titanate slurry after the ball milling is 0.1-0.2 mu m.

6. The method for preparing the lithium titanate anode material according to claim 1, characterized in that, During the drying process, a gas containing 15-25 vol% of CO2 is introduced to perform purging.

7. The method for preparing the lithium titanate anode material according to claim 1, characterized in that, The vacuum drying temperature is 150-180 DEG C.

8. The method of producing a lithium titanate negative electrode material according to any one of claims 1 to 7, characterized by, The lithium titanate is washed with water before the preparation of the lithium titanate slurry.

9. A lithium titanate negative electrode material, characterized by, The lithium titanate battery negative electrode material is prepared by the lithium titanate battery negative electrode material preparation method.

10. A lithium titanate battery, characterized by, The raw material for preparing the negative electrode of the lithium titanate battery comprises the lithium titanate negative electrode material prepared by the lithium titanate battery negative electrode material preparation method or the lithium titanate negative electrode material of claim 9.

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