Preparation method for improving rate capability of lithium titanate negative electrode material

Abstract

The invention discloses a preparation method for improving the rate capability of a lithium titanate negative electrode material, and relates to the technical field of lithium battery preparation. Ion doping is performed on the surface of the LTO material through a simple hydrothermal method, the conductivity of the traditional LTO material can be improved through introduction of Ru < 3 + >, and the rate capability is improved; meanwhile, a low-valence anion Cl <-> is introduced to the 32e position of O < 2->, part of Ti < 4 + > is converted into Ti < 3 + >, and the conductivity of the electrode is improved due to the mixed valence state, so that the charge impedance is reduced, and the phenomenon of electrode polarization is reduced; then, CeO2 is introduced to the 16d position of Ti < 4 + > through a high-temperature calcination method, doping of high-valence cations Ce < 4 + > can generate certain defects in crystal lattices, resistance to lithium ion transmission is changed, the conductivity and the ion diffusion coefficient of the crystal lattices are improved, impedance of a pole piece can be reduced in a multi-ion doping mode, and therefore the rate performance of the battery end is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery preparation, and in particular to a preparation method for improving the rate performance of lithium titanate negative electrode materials. Background Art

[0002] As a new type of chemical energy, lithium batteries have rapidly developed into the most important and advanced secondary batteries due to their high energy density and environmental friendliness.

[0003] Spinel structured lithium titanate Li4Ti5O 12 (LTO) has become a potential lithium battery negative electrode material due to its high safety, stable charge and discharge platform, and excellent cycle performance. 12 The conductivity is very poor, and the capacity decays seriously during the charge and discharge process of large current.

[0004] Therefore, we propose a preparation method to improve the rate performance of lithium titanate negative electrode materials, which can improve the rate performance of Li4Ti5O while ensuring the rate performance of the battery end. 12 conductivity. Summary of the Invention

[0005] The object of the present invention is to provide a preparation method for improving the rate performance of lithium titanate negative electrode materials, so as to solve the problems raised in the prior art.

[0006] To achieve the above object, the present invention provides the following technical solution: a preparation method for improving the rate performance of lithium titanate negative electrode material, comprising the following steps: Step 1: Mix the modified LTO (lithium titanate) material, the binder, and the conductive agent, and stir evenly to obtain a negative electrode slurry; Step 2: Coat the negative electrode slurry on copper foil and vacuum dry it to obtain a lithium titanate negative electrode material.

[0007] Furthermore, in step 1, the mass ratio of the modified LTO material, the binder and the conductive agent is (85~95): (1.2~2.7): (0.1~0.9).

[0008] Furthermore, in step 2, the vacuum drying process conditions are: temperature 100° C. to 120° C., time 8 h to 12 h.

[0009] Furthermore, in step 2, the coating thickness of the negative electrode slurry is 4 μm to 8 μm.

[0010] Furthermore, in step 1, the binder is a mixture of CMC (carboxymethyl cellulose) and SBR (styrene-butadiene rubber); The mass ratio of the CMC to the SBR is (0.8-1.8): (0.4-0.9).

[0011] Furthermore, in step 1, the conductive agent is SUPER P Li (super dense high conductive carbon black).

[0012] Furthermore, in step 1, the modified LTO material is prepared by the following process: S1: Mix LTO (lithium titanate), RuCl3 (ruthenium trichloride) and deionized water, stir evenly, bake, filter, wash and vacuum dry to obtain an intermediate material; S2: Mix the intermediate material with CeO2 (cerium oxide), and calcine under nitrogen atmosphere to obtain a modified LTO material.

[0013] Furthermore, in S1, the mass ratio of LTO, RuCl3 and deionized water is (90~115):1:(200~300).

[0014] Furthermore, in S1, the baking process conditions are: temperature 100°C~160°C, time 8h~12h.

[0015] Furthermore, in S1, the process conditions for vacuum drying are: temperature 80°C to 100°C, and time 1h to 3h.

[0016] Furthermore, the mass ratio of CeO2 to LTO is 1:(70~90).

[0017] Furthermore, in S2, the calcination process conditions are: temperature 500°C~600°C, time 6h~8h.

[0018] In the above technical solution, the surface of LTO material is ion-doped by a simple hydrothermal method, Ru 3+ The introduction of O can improve the conductivity of traditional LTO materials and improve the rate performance; at the same time, 2- The 32e position of the low-valent anion Cl is introduced - , part of Ti 4+ Transformed into Ti 3+ The mixed valence increases the conductivity of the electrode, which is beneficial to reduce the charge impedance and thus reduce the electrode polarization phenomenon; then, the Ti 4+ The 16d position of CeO2 is introduced, and the high-valent cation Ce 4+ Doping will produce certain defects in the lattice, change the resistance to lithium ion transmission, increase the conductivity and ion diffusion coefficient of the lattice, and reduce the impedance of the electrode through multi-ion doping, thereby improving the rate performance of the battery end.

[0019] Furthermore, the obtained lithium titanate negative electrode material is used to prepare button batteries, and the specific process is as follows: Select a battery shell, place the lithium titanate negative electrode material, add the electrolyte, place the diaphragm, positive electrode material and gasket shrapnel in sequence, and finally assemble the battery shell to obtain a button battery.

[0020] Furthermore, the model of the battery shell is CR2032; The positive electrode material is a lithium sheet.

[0021] Furthermore, the diaphragm is one of a polyvinylidene fluoride diaphragm, a polypropylene diaphragm, and a polyethylene diaphragm; The thickness of the separator was 20 μm.

[0022] Furthermore, the surface of the modified LTO material is coated with polyaniline and subjected to ultraviolet irradiation. The specific preparation process is as follows: The modified LTO material is mixed with hydrochloric acid, ultrasonically dispersed, aniline is added, and the mixture is stirred in an ice bath. An ammonium persulfate solution is added and stirred for 5 to 7 hours. The mixture is centrifuged, washed, and dried. The resulting product is subjected to ultraviolet irradiation to obtain a polyaniline-coated modified LTO material.

[0023] Furthermore, the ratio of modified LTO material to hydrochloric acid was 1 g: (50–60) mL; The concentration of the hydrochloric acid is 1 mol / L.

[0024] Furthermore, the mass ratio of the modified LTO material, aniline and ammonium persulfate solution is 1: (0.5~1): (0.25~0.5).

[0025] Furthermore, the process conditions of the ultraviolet irradiation are: wavelength 280nm~380nm, irradiation time 1h~2h.

[0026] Furthermore, the ammonium persulfate solution is a mixed solution of ammonium persulfate and hydrochloric acid; The molar ratio of ammonium persulfate to hydrochloric acid is 1:1; The concentration of the hydrochloric acid is 1 mol / L.

[0027] Furthermore, the centrifugal process conditions are: rotation speed 2000 rpm~3000 rpm, time 5 min~15 min.

[0028] Furthermore, the drying process conditions are: temperature 50°C~60°C, time 8h~12h.

[0029] In the above technical solution, polyaniline is coated on the surface of the modified LTO material. Polyaniline has good electronic conductivity and can form a conductive network between the modified LTO materials, thereby improving the electron transmission capacity and thus improving the rate performance of the battery. On the other hand, after ultraviolet irradiation, the hydroxyl groups produced by polyaniline can form hydrogen bonds with the hydroxyl groups in the carboxymethyl cellulose molecules in the binder. The presence of a large number of hydrogen bonds can cause physical cross-linking between polyaniline and carboxymethyl cellulose, thereby improving the bonding performance and reducing the shedding of the modified LTO material during the charging and discharging process, thereby improving the stability and service life of the battery.

[0030] Compared with the prior art, the present invention has the following beneficial effects: 1. The LTO material surface is ion doped by a simple hydrothermal method, Ru 3+ The introduction of O can improve the conductivity of traditional LTO materials and improve the rate performance; at the same time, 2- The 32e position of the low-valent anion Cl is introduced - , part of Ti 4+ Transformed into Ti 3 + The mixed valence increases the conductivity of the electrode, which is beneficial to reduce the charge impedance and thus reduce the electrode polarization phenomenon; then, the Ti 4+ The 16d position of CeO2 is introduced, and the high-valent cation Ce 4+ Doping will produce certain defects in the lattice, change the resistance to lithium ion transmission, increase the conductivity and ion diffusion coefficient of the lattice, and reduce the impedance of the electrode through multi-ion doping, thereby improving the rate performance of the battery end.

[0031] 2. Polyaniline is coated on the surface of the modified LTO material. Polyaniline has good electronic conductivity and can form a conductive network between the modified LTO materials, thereby improving the electron transmission capacity and thus improving the rate performance of the battery.

[0032] 3. After the polyaniline-coated modified LTO material is subjected to ultraviolet irradiation, the hydroxyl groups produced by the polyaniline can form hydrogen bonds with the hydroxyl groups in the carboxymethyl cellulose molecules in the binder. The presence of a large number of hydrogen bonds can cause physical cross-linking between the polyaniline and the carboxymethyl cellulose, thereby improving the bonding performance and reducing the shedding of the modified LTO material during the charge and discharge process, thereby improving the stability and service life of the battery. DETAILED DESCRIPTION

[0033] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0034] In the following specific embodiments, SUPER P Li, CAS No. 1333-86-4, mesh size 325; LTO, CAS No. 12031-82-2, particle size 300 nm; Lithium sheet, diameter 15.8mm, thickness 0.5mm; CeO2, particle size 30 μm; Hydrochloric acid, concentration 1 mol / L; Button battery charge and discharge tester, model CT2001A, from Wuhan Blue Electric Electronics Co., Ltd. Preparation of electrolyte: Mix 1M LiPF6 (lithium hexafluorophosphate) solution with EC (ethylene carbonate) and EMC (ethyl methyl carbonate), stir evenly to obtain a mixed solution, and then add VC (vinylene carbonate) to obtain an electrolyte; the volume ratio of EC to EMC is 3:7, and VC accounts for 1.5% of the total volume of the mixed solution.

[0035] Example 1: A preparation method for improving the rate performance of lithium titanate negative electrode material, comprising the following steps: (1) Preparation of modified LTO materials: S1: LTO, RuCl3 and deionized water are mixed, stirred evenly, baked, filtered, washed and vacuum dried to obtain an intermediate material; S2: The intermediate material is mixed with CeO2, and calcined under nitrogen atmosphere to obtain a modified LTO material; in S1, the mass ratio of LTO, RuCl3 and deionized water is 100:1:200; in S1, the baking process conditions are: temperature 160°C, time 12h; in S1, the vacuum drying process conditions are: temperature 100°C, time 3h; in S2, the mass ratio of CeO2 to LTO is 1:85; in S2, the calcination process conditions are: temperature 600°C, time 8h; (2) Preparation of lithium titanate negative electrode materials: CMC and SBR were mixed in a mass ratio of 1.8:0.9 to obtain a binder; Step 1: Mix the modified LTO material, binder, and SUPER P Li and stir evenly to obtain a negative electrode slurry; Step 2: Coat the negative electrode slurry on copper foil and vacuum dry to obtain a lithium titanate negative electrode material; In step 1, the mass ratio of the modified LTO material, binder, and conductive agent is 95:2.7:0.9; In step 2, the vacuum drying process conditions are: temperature 120°C, time 12h; In step 2, the coating thickness of the negative electrode slurry is 8μm; The lithium titanate negative electrode material obtained by the above process can be used to prepare button batteries, which includes the following steps: Select a battery shell, place the lithium titanate negative electrode material, add the electrolyte, place a 20μm thick polyvinylidene fluoride separator, a lithium sheet and a gasket shrapnel in sequence, and finally assemble the battery shell to obtain a button battery.

[0036] Example 2: Compared with Example 1, the mass ratio of LTO, RuCl3 and deionized water in S1 was adjusted to 90:1:200, and the other conditions remained unchanged.

[0037] Example 3: Compared with Example 1, the mass ratio of LTO, RuCl3 and deionized water in S1 was adjusted to 95:1:200, and the other conditions remained unchanged.

[0038] Example 4: Compared with Example 1, the mass ratio of LTO, RuCl3 and deionized water in S1 was adjusted to 110:1:200, and the other conditions remained unchanged.

[0039] Example 5: Compared with Example 1, the mass ratio of LTO, RuCl3 and deionized water in S1 was adjusted to 115:1:200, and the other conditions remained unchanged.

[0040] Example 6: Compared with Example 1, the mass ratio of CeO2 to LTO is adjusted to 1:70, and the other conditions remain unchanged.

[0041] Example 7: Compared with Example 1, the mass ratio of CeO2 to LTO is adjusted to 1:80, and the other conditions remain unchanged.

[0042] Example 8: Compared with Example 1, the mass ratio of CeO2 to LTO is adjusted to 1:90, and the other conditions remain unchanged.

[0043] Example 9: Compared with Example 1, the mass ratio of CeO2 to LTO is adjusted to 1:95, and the other conditions remain unchanged.

[0044] Example 10: Using Example 1 as a comparison, the process parameters were adjusted, and the other conditions remained unchanged. The specific process is as follows: (1) Preparation of modified LTO materials: S1: LTO, RuCl3 and deionized water are mixed, stirred evenly, baked, filtered, washed and vacuum dried to obtain an intermediate material; S2: The intermediate material is mixed with CeO2, and calcined under nitrogen atmosphere to obtain a modified LTO material; in S1, the mass ratio of LTO, RuCl3 and deionized water is 100:1:250; in S1, the baking process conditions are: temperature 130°C, time 10h; in S1, the vacuum drying process conditions are: temperature 90°C, time 2h; in S2, the mass ratio of CeO2 to LTO is 1:85; in S2, the calcination process conditions are: temperature 550°C, time 7h; (2) Preparation of lithium titanate negative electrode materials: CMC and SBR were mixed in a mass ratio of 1.3:0.4 to obtain a binder; Step 1: Mix the modified LTO material, binder, and SUPER P Li and stir evenly to obtain a negative electrode slurry; Step 2: Coat the negative electrode slurry on copper foil and vacuum dry to obtain a lithium titanate negative electrode material; In step 1, the mass ratio of the modified LTO material, binder, and conductive agent is 90:2.0:0.5; In step 2, the vacuum drying process conditions are: temperature 110°C, time 10 hours; In step 2, the coating thickness of the negative electrode slurry is 6 μm; The lithium titanate negative electrode material obtained by the above process can be used to prepare button batteries, which includes the following steps: Select a battery shell, place the lithium titanate negative electrode material, add the electrolyte, place a 20μm thick polyvinylidene fluoride separator, a lithium sheet and a gasket shrapnel in sequence, and finally assemble the battery shell to obtain a button battery.

[0045] Example 11: Using Example 1 as a comparison, the process parameters were adjusted, and the other conditions remained unchanged. The specific process is as follows: (1) Preparation of modified LTO materials: S1: LTO, RuCl3 and deionized water are mixed, stirred evenly, baked, filtered, washed and vacuum dried to obtain an intermediate material; S2: The intermediate material is mixed with CeO2, and calcined under nitrogen atmosphere to obtain a modified LTO material; in S1, the mass ratio of LTO, RuCl3 and deionized water is 100:1:300; in S1, the baking process conditions are: temperature 100°C, time 8h; in S1, the vacuum drying process conditions are: temperature 80°C, time 1h; in S2, the mass ratio of CeO2 to LTO is 1:85; in S2, the calcination process conditions are: temperature 500°C, time 6h; (2) Preparation of lithium titanate negative electrode materials: CMC and SBR were mixed in a mass ratio of 0.8:0.6 to obtain a binder; Step 1: Mix the modified LTO material, binder, and SUPER P Li and stir evenly to obtain a negative electrode slurry; Step 2: Coat the negative electrode slurry on copper foil and vacuum dry to obtain a lithium titanate negative electrode material; In step 1, the mass ratio of the modified LTO material, binder, and conductive agent is 85:1.2:0.1; In step 2, the vacuum drying process conditions are: temperature 100°C, time 8h; In step 2, the coating thickness of the negative electrode slurry is 4μm; The lithium titanate negative electrode material obtained by the above process can be used to prepare button batteries, which includes the following steps: Select a battery shell, place the lithium titanate negative electrode material, add the electrolyte, place a 20μm thick polyvinylidene fluoride separator, a lithium sheet and a gasket shrapnel in sequence, and finally assemble the battery shell to obtain a button battery.

[0046] Example 12: Compared with Example 1, a method for preparing a lithium titanate negative electrode material by coating polyaniline on the surface of a modified LTO material to improve the rate performance includes the following steps: (1) Preparation of polyaniline-coated modified LTO materials: S1: LTO, RuCl3 and deionized water are mixed, stirred evenly, baked, filtered, washed and vacuum dried to obtain an intermediate material; S2: The intermediate material is mixed with CeO2, and calcined under nitrogen atmosphere to obtain a modified LTO material; in S1, the mass ratio of LTO, RuCl3 and deionized water is 100:1:200; in S1, the baking process conditions are: temperature 160°C, time 12h; in S1, the vacuum drying process conditions are: temperature 100°C, time 3h; in S2, the mass ratio of CeO2 to LTO is 1:85; in S2, the calcination process conditions are: temperature 600°C, time 8h; The modified LTO material was mixed with hydrochloric acid, ultrasonically dispersed, aniline was added, stirred in an ice bath, and ammonium persulfate solution was added. The mixture was stirred for 7 hours, centrifuged, washed, and dried. The resulting product was irradiated at a wavelength of 380 nm for 2 hours to obtain a polyaniline-coated modified LTO material. The ratio of the modified LTO material to hydrochloric acid was 1 g:60 mL. The mass ratio of the modified LTO material, aniline, and ammonium persulfate solution was 1:1:0.5. The centrifugal process conditions were: speed 3000 rpm, time 15 minutes; and the drying process conditions were: temperature 60°C, time 12 hours. (2) Preparation of lithium titanate negative electrode materials: CMC and SBR were mixed in a mass ratio of 1.8:0.9 to obtain a binder; Step 1: Mix the modified LTO material, binder, and SUPER P Li and stir evenly to obtain a negative electrode slurry; Step 2: Coat the negative electrode slurry on copper foil and vacuum dry to obtain a lithium titanate negative electrode material; In step 1, the mass ratio of the modified LTO material, binder, and conductive agent is 95:2.7:0.9; In step 2, the vacuum drying process conditions are: temperature 120°C, time 12h; In step 2, the coating thickness of the negative electrode slurry is 8μm; The lithium titanate negative electrode material obtained by the above process can be used to prepare button batteries, which includes the following steps: Select a battery shell, place the lithium titanate negative electrode material, add the electrolyte, place a 20μm thick polyvinylidene fluoride separator, a lithium sheet and a gasket shrapnel in sequence, and finally assemble the battery shell to obtain a button battery.

[0047] Example 13: Using Example 12 as a comparison, the process parameters were adjusted, and the other conditions remained unchanged. The specific process is as follows: (1) Preparation of polyaniline-coated modified LTO materials: S1: LTO, RuCl3 and deionized water are mixed, stirred evenly, baked, filtered, washed and vacuum dried to obtain an intermediate material; S2: The intermediate material is mixed with CeO2, and calcined under nitrogen atmosphere to obtain a modified LTO material; in S1, the mass ratio of LTO, RuCl3 and deionized water is 100:1:250; in S1, the baking process conditions are: temperature 130°C, time 10h; in S1, the vacuum drying process conditions are: temperature 90°C, time 2h; in S2, the mass ratio of CeO2 to LTO is 1:85; in S2, the calcination process conditions are: temperature 550°C, time 7h; The modified LTO material was mixed with hydrochloric acid, ultrasonically dispersed, aniline was added, stirred in an ice bath, and ammonium persulfate solution was added. The mixture was stirred for 6 hours, centrifuged, washed, and dried. The resulting product was irradiated at a wavelength of 330 nm for 1.5 hours to obtain a polyaniline-coated modified LTO material. The ratio of the modified LTO material to hydrochloric acid was 1 g:55 mL. The mass ratio of the modified LTO material, aniline, and ammonium persulfate solution was 1:0.7:0.35. The centrifugal process conditions were: speed 2500 rpm, time 10 minutes; and the drying process conditions were: temperature 55°C, time 10 hours. (2) Preparation of lithium titanate negative electrode materials: CMC and SBR were mixed in a mass ratio of 1.8:0.9 to obtain a binder; Step 1: Mix the modified LTO material coated with polyaniline, a binder, and SUPER P Li, stir evenly, and obtain a negative electrode slurry; Step 2: Coat the negative electrode slurry on copper foil and vacuum dry to obtain a lithium titanate negative electrode material; In step 1, the mass ratio of the modified LTO material coated with polyaniline, the binder, and the conductive agent is 90:2.0:0.5; In step 2, the vacuum drying process conditions are: temperature 110°C, time 10 hours; In step 2, the coating thickness of the negative electrode slurry is 6 μm; The lithium titanate negative electrode material obtained by the above process can be used to prepare button batteries, which includes the following steps: Select a battery shell, place the lithium titanate negative electrode material, add the electrolyte, place a 20μm thick polyvinylidene fluoride separator, a lithium sheet and a gasket shrapnel in sequence, and finally assemble the battery shell to obtain a button battery.

[0048] Example 14: Using Example 12 as a comparison, the process parameters were adjusted, and the other conditions remained unchanged. The specific process is as follows: (1) Preparation of polyaniline-coated modified LTO materials: S1: LTO, RuCl3 and deionized water are mixed, stirred evenly, baked, filtered, washed and vacuum dried to obtain an intermediate material; S2: The intermediate material is mixed with CeO2, and calcined under nitrogen atmosphere to obtain a modified LTO material; in S1, the mass ratio of LTO, RuCl3 and deionized water is 100:1:300; in S1, the baking process conditions are: temperature 100°C, time 8h; in S1, the vacuum drying process conditions are: temperature 80°C, time 1h; in S2, the mass ratio of CeO2 to LTO is 1:85; in S2, the calcination process conditions are: temperature 500°C, time 6h; The modified LTO material was mixed with hydrochloric acid, ultrasonically dispersed, aniline was added, stirred in an ice bath, and ammonium persulfate solution was added. The mixture was stirred for 5 hours, centrifuged, washed, and dried. The resulting product was irradiated at a wavelength of 280 nm for 1 hour to obtain a polyaniline-coated modified LTO material. The ratio of the modified LTO material to hydrochloric acid was 1 g:50 mL. The mass ratio of the modified LTO material, aniline, and ammonium persulfate solution was 1:0.5:0.25. The centrifugal process conditions were: speed 2000 rpm, time 5 minutes; and the drying process conditions were: temperature 50°C, time 8 hours. (2) Preparation of lithium titanate negative electrode materials: CMC and SBR were mixed in a mass ratio of 1.8:0.9 to obtain a binder; Step 1: Mix the modified LTO material coated with polyaniline, a binder, and SUPER P Li, stir evenly, and obtain a negative electrode slurry; Step 2: Coat the negative electrode slurry on copper foil and vacuum dry to obtain a lithium titanate negative electrode material; In step 1, the mass ratio of the modified LTO material coated with polyaniline, the binder, and the conductive agent is 85:1.2:0.1; In step 2, the vacuum drying process conditions are: temperature 100°C, time 8h; In step 2, the coating thickness of the negative electrode slurry is 4μm; The lithium titanate negative electrode material obtained by the above process can be used to prepare button batteries, which includes the following steps: Select a battery shell, place the lithium titanate negative electrode material, add the electrolyte, place a 20μm thick polyvinylidene fluoride separator, a lithium sheet and a gasket shrapnel in sequence, and finally assemble the battery shell to obtain a button battery.

[0049] Comparative Example 1: Compared with Example 1, RuCl3 was not added when preparing the modified LTO material, and other conditions remained unchanged.

[0050] Comparative Example 2: Compared with Example 1, CeO2 was not added when preparing the modified LTO material, and other conditions remained unchanged.

[0051] Comparative Example 3: Using Example 1 as a comparison, the LTO material was not modified and other conditions remained unchanged.

[0052] Comparative Example 4: Using Example 12 as a comparison, the modified LTO material was not coated with polyaniline, but was directly irradiated with UV light, with other conditions remaining unchanged.

[0053] Comparative Example 5: Using Example 12 as a comparison, the modified LTO material was coated with polyaniline, but was not subjected to UV irradiation, and the other conditions remained unchanged.

[0054] Experiment: A button battery charge and discharge tester was used to perform charge and discharge tests on the button batteries in the embodiment and comparative example at 1C (charge and discharge at a current of 1 times the rated capacity of the battery), 3C (charge and discharge at a current of 3 times the rated capacity of the battery), and 5C (charge and discharge at a current of 5 times the rated capacity of the battery). The charge cut-off voltage was 2.0V and the discharge cut-off voltage was 0.01V. The test results are as follows:

[0055] Based on the data in the above table, we can draw the following conclusions: Compared with Example 1, the specific capacity of the button batteries prepared with the lithium titanate negative electrode materials obtained in Examples 2 to 5, Examples 6 to 9, Examples 10 and Example 11 decreased. It can be seen that when the mass ratio of LTO, RuCl3 and deionized water is 100:1:200, and the mass ratio of CeO2 to LTO is 1:85, the performance of the button batteries prepared according to the process parameters in Example 1 reaches the best state; Compared with Example 1, the specific capacity of the button batteries prepared from the lithium titanate negative electrode materials obtained in Comparative Examples 1 to 3 decreased significantly. 3+ and Ce 4+ Co-doping can reduce the impedance of the electrode, thereby improving the rate performance of the battery end; at the same time 2- The 32e position of the low-valent anion Cl is introduced - , part of Ti 4+ Transformed into Ti 3+ , the mixed valence state improves the conductivity of the electrode, which is beneficial to reduce the charge impedance and thus reduce the electrode polarization; Compared with Example 12, the specific capacity of the button batteries prepared with the lithium titanate negative electrode materials obtained in Comparative Examples 4 and 5 decreased. This is because polyaniline has good electronic conductivity and can form a conductive network between the modified LTO materials, thereby improving the electron transmission capacity and thus improving the rate performance of the battery. After the polyaniline is irradiated with ultraviolet light, the hydroxyl groups generated can form hydrogen bonds with the hydroxyl groups in the carboxymethyl cellulose molecules in the binder. The presence of a large number of hydrogen bonds can cause physical cross-linking between the polyaniline and the carboxymethyl cellulose, thereby improving the bonding performance and reducing the shedding of the modified LTO material during the charge and discharge process, thereby improving the stability and service life of the battery. In summary, the setting of the materials and process parameters used in this application can promote the performance improvement of button batteries prepared with the obtained lithium titanate negative electrode material.

[0056] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations that come within the meaning and range of equivalents of the claims be embraced therein.

Claims

1. A preparation method for improving the rate performance of lithium titanate negative electrode materials, characterized by: The following steps are involved: Step 1: Mix the modified LTO material, binder, and conductive agent, and stir evenly to obtain a negative electrode slurry; Step 2: coating the negative electrode slurry on copper foil and vacuum drying to obtain a lithium titanate negative electrode material; In step 1, the modified LTO material is prepared by the following process: S1: LTO, RuCl3 and deionized water are mixed, stirred evenly, baked, filtered, washed and vacuum dried to obtain an intermediate material; S2: Mix the intermediate material with CeO2 and calcine under nitrogen atmosphere to obtain a modified LTO material.

2. The method for improving the rate performance of lithium titanate negative electrode materials according to claim 1, characterized in that: In S1, the mass ratio of LTO, RuCl3 and deionized water is (90~115):1:(200~300).

3. The method for preparing a lithium titanate negative electrode material for improving rate performance according to claim 1, characterized in that: The mass ratio of CeO2 to LTO is 1:(70~90).

4. The method for preparing a lithium titanate negative electrode material for improving rate performance according to claim 1, characterized in that: In S1, the baking process conditions are: temperature 100℃~160℃, time 8h~12h; In S1, the process conditions of vacuum drying are: temperature 80°C~100°C, time 1h~3h.

5. The method for preparing a lithium titanate negative electrode material for improving rate performance according to claim 1, characterized in that: In S2, the calcination process conditions are: temperature 500°C~600°C, time 6h~8h.

6. The method for improving the rate performance of lithium titanate negative electrode materials according to claim 1, characterized in that: In step 1, the mass ratio of the modified LTO material, the binder and the conductive agent is (85-95): (1.2-2.7): (0.1-0.9).

7. The method for improving the rate performance of lithium titanate negative electrode materials according to claim 1, characterized in that: In step 2, the process conditions of vacuum drying are: temperature 100° C. to 120° C., and time 8 h to 12 h.

8. The method for improving the rate performance of lithium titanate negative electrode materials according to claim 1, characterized in that: In step 1, the binder is a mixture of CMC and SBR; The mass ratio of the CMC to the SBR is (0.8-1.8): (0.4-0.9).

9. The method for preparing a lithium titanate negative electrode material for improving rate performance according to claim 1, characterized in that: In step 1, the surface of the modified LTO material is coated with polyaniline and subjected to ultraviolet irradiation. The specific preparation process is as follows: The modified LTO material is mixed with hydrochloric acid, ultrasonically dispersed, aniline is added, and the mixture is stirred in an ice bath. An ammonium persulfate solution is added and stirred for 5 to 7 hours. The mixture is centrifuged, washed, and dried. The resulting product is subjected to ultraviolet irradiation to obtain a polyaniline-coated modified LTO material.

10. The lithium titanate negative electrode material obtained by the preparation method for improving the rate performance of a lithium titanate negative electrode material according to any one of claims 1 to 9, characterized in that: Application in the negative electrode of button batteries.

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