A method for synthesizing high-purity lithium-ion battery electrode material by molten salt method

Abstract

The application discloses a method for synthesizing high-purity lithium ion battery electrode material by a molten salt method and belongs to the technical field of lithium ion battery materials. The preparation method comprises the following steps: uniformly grinding and mixing a lithium source compound, a titanium source compound, a NaCl molten salt and a small amount of LiCl, heating to a certain temperature, keeping the temperature for a period of time, cooling to room temperature, and washing, filtering and drying the product to obtain the target material. The application is a modified method for synthesizing Li4Ti5O 12 by a NaCl molten salt method. The purpose of inhibiting side reactions and impurity generation can be achieved by adding a small amount of LiCl in the precursor mixture, so that the high-purity lithium ion battery Li4Ti5O 12 material is synthesized, and the electrochemical performance of the material is improved.

Description

Technical Field

[0001] This invention relates to a method for synthesizing high-purity lithium-ion battery electrode materials using the molten salt method, belonging to the field of lithium-ion battery material technology. Background Technology

[0002] Li4Ti5O 12 As an electrode material for lithium-ion batteries, it is known as a "zero-strain" material because its lattice constant and cell volume remain almost unchanged (<1%) during battery cycling, resulting in good cycle stability and a long service life; it also exhibits a very stable charge and discharge voltage of approximately 1.55V (vs. Li). + The voltage of Li₄Ti₅O₂ is higher than that of lithium dendrite formation, which can prevent dendrite formation during charge and discharge, thus providing good safety. 12 It has become one of the most promising anode materials for replacing graphite.

[0003] Preparation of Li4Ti5O 12 The main methods for preparing inorganic non-metallic materials include solid-state methods, sol-gel methods, molten salt methods, and hydrothermal methods. Among these, the molten salt method for preparing inorganic non-metallic materials typically allows reactants to diffuse and disperse rapidly in the liquid medium of molten salt, achieving mixing at the molecular or even atomic scale. After the reaction, the presence of the molten salt prevents particle aggregation or bonding at high temperatures, resulting in excellent dispersibility of the product. Considering these factors, the molten salt method can prepare uniformly dispersed micron-sized products in a relatively short time and at relatively low temperatures.

[0004] Currently, Li4Ti5O is being prepared. 12 The molten salt systems used in the materials mainly include LiCl, as well as LiCl-KCl, NaCl-KCl, and LiNO3-LiOH. For example, patent (application number 201410306558.2) discloses the synthesis of near-spherical Li4Ti5O using a NaCl-KCl (molar ratio 1:1) system. 12 Materials. Compared to other molten salt systems, NaCl molten salt is low in cost and less polluting, showing promising application prospects. However, current research indicates that in a pure NaCl molten salt system, high-temperature sintering can lead to the formation of Li₄Ti₅O. 12 During material processing, a small amount of NaCl reacts with titanium and lithium source compounds, resulting in the formation of impurity NaLiTi3O7, which severely affects the material's performance. Summary of the Invention

[0005] The purpose of this invention is to provide a method for synthesizing high-purity lithium-ion battery electrode materials using the molten salt method. Utilizing the characteristics of the NaCl molten salt method, this method synthesizes lithium-ion battery Li4Ti5O with uniformly dispersed particle size and an octahedral structure. 12Anode material; by controlling the addition of a small amount of additive LiCl to suppress the formation of NaLiTi3O7 impurities, high-purity lithium titanate material is synthesized; this synthesis method is simple to operate, low in cost, and has the prospect of large-scale application; the method of the present invention specifically includes the following steps:

[0006] (1) Weigh the titanium source compound, lithium source compound, and NaCl molten salt, grind them thoroughly to obtain a precursor mixture; wherein, the weighing of lithium source compound, titanium source compound and NaCl is calculated according to the molar ratio of Li, Ti and NaCl as 4:5:(1~2.5).

[0007] (2) Add an appropriate amount of LiCl to the precursor mixture, mix evenly and dry; wherein the molar ratio of LiCl to TiO2 is less than 0.05:1.

[0008] (3) The dried mixture is sintered at high temperature and kept at that temperature for a period of time to ensure the reaction occurs.

[0009] (4) The cooled product was washed with deionized water, filtered and dried to obtain a high-purity lithium-ion battery anode, Li4Ti5O. 12 Material.

[0010] Preferably, in step (2) of the present invention, the drying temperature is 50-150°C and the drying time is 2-24 hours.

[0011] Preferably, in step (3) of the present invention, the sintering atmosphere is air, the heating rate is 2-20℃ / min, the holding temperature is 700-800℃, and the holding time is 2-24h.

[0012] Preferably, in step (4) of the present invention, deionized water is used for washing, the drying temperature is 50-150°C, and the drying time is 2-24 hours.

[0013] Advantages and effects of the present invention:

[0014] This invention can obtain a high-purity Li₄Ti₅O with a particulate dispersion and an octahedral structure. 12 Materials: This invention uses NaCl as the molten salt, which is abundant and has low environmental pollution. However, in a pure NaCl molten salt system, lithium and titanium source compounds will undergo side reactions with a small amount of NaCl to generate NaLiTi3O7 and LiCl. Therefore, by adding a small amount of LiCl to the precursor mixture, the side reactions and impurity formation can be suppressed, thus synthesizing high-purity lithium-ion battery Li4Ti5O7. 12 Materials, thereby improving the electrochemical performance of materials. Attached Figure Description

[0015] Figure 1 The synthesized product Li4Ti5O in Example 112 XRD pattern of the product of Comparative Example 1.

[0016] Figure 2 The synthesized product Li4Ti5O in Example 1 12 First charge-discharge curves at 0.2C rate compared to the product of Comparative Example 1.

[0017] Figure 3 The synthesized product Li4Ti5O in Example 1 12 SEM image. Detailed Implementation

[0018] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited to the content described.

[0019] Example 1

[0020] Synthesis of Li4Ti5O by Modified NaCl Molten Salt Method 12 The specific preparation process of the material is as follows:

[0021] (1) Weigh Li2CO3, TiO2, NaCl and LiCl according to a molar ratio of 2:5:2.25:0.25, grind them thoroughly to obtain a precursor mixture; add LiCl to the precursor mixture (wherein the molar ratio of LiCl to TiO2 is less than 0.05:1), mix evenly and place it in a vacuum drying oven at 80℃ for 12h, mix evenly and transfer it to a crucible.

[0022] (2) After drying, the crucible is placed in a muffle furnace and heated to 800℃ at a rate of 3℃ / min and held for sintering for 10h.

[0023] (3) After cooling to room temperature, the sintered material is washed in deionized water to separate the NaCl in the material, and the filtered material is dried in a vacuum drying oven at 80°C for 12 hours to obtain the target product.

[0024] Comparative Example 1

[0025] Synthesis of Li4Ti5O by Unmodified NaCl Molten Salt Method 12 The specific preparation process of the material is as follows:

[0026] (1) Weigh Li2CO3, TiO2 and NaCl according to the molar ratio of 2:5:2.25, put them into a mortar, mix them evenly, transfer them to a crucible, and put them into a vacuum drying oven at 80℃ for 12h.

[0027] (2) After drying, the crucible is placed in a muffle furnace and heated to 800℃ at a rate of 3℃ / min and held for sintering for 10h.

[0028] (3) After cooling to room temperature, the sintered material is washed in deionized water to separate the NaCl in the material, and the filtered material is dried in a vacuum drying oven at 80°C for 12 hours to obtain the target product.

[0029] Example 1: Synthesis of Li4Ti5O by Modified NaCl Molten Salt Method 12 The XRD pattern and the first charge-discharge curve at 0.2C rate of the product compared with that of Comparative Example 1 are shown in the appendix. Figure 1 and attached Figure 2 It is evident that the product of Comparative Example 1 contains some NaLiTi3O7 impurities, while the material synthesized using Example 1 is pure phase Li4Ti5O. 12 No impurity phases were observed; the material synthesized in Example 1 exhibited superior performance compared to the material in Comparative Example 1, and avoided the reduction in the charge / discharge plateau caused by the impurity NaLiTi3O7; the synthesized product Li4Ti5O 12 See attached SEM image. Figure 3 It can be seen that the particle size of the material is 1-4μm, and the material has an octahedral structure.

[0030] Example 2

[0031] The target chemical formula for synthesis is Li4Ti5O 12 The specific preparation process of the material is as follows:

[0032] (1) Weigh Li2CO3, TiO2, NaCl and LiCl according to a molar ratio of 4:5:2.5:0.25, grind them thoroughly to obtain a precursor mixture; add LiCl to the precursor mixture (wherein the molar ratio of LiCl to TiO2 is less than 0.05:1), mix evenly and place it in a vacuum drying oven at 80℃ for 12h, mix evenly and transfer it to a crucible.

[0033] (2) After drying, the crucible is placed in a muffle furnace and heated to 800℃ at a rate of 3℃ / min and held for sintering for 24 hours.

[0034] (3) After cooling to room temperature, the sintered material is washed in deionized water to separate the NaCl in the material, and the filtered material is dried in a vacuum drying oven at 80°C for 12 hours to obtain the target product.

[0035] The Li4Ti5O prepared in this embodiment 12 The material structure and properties are similar to those in Example 1.

[0036] Example 3

[0037] The target chemical formula for synthesis is Li4Ti5O 12 The specific preparation process of the material is as follows:

[0038] (1) Weigh LiOH·H2O, TiO2, NaCl and LiCl according to a molar ratio of 4:5:2.25:0.10, grind them thoroughly to obtain a precursor mixture; add LiCl to the precursor mixture (wherein the molar ratio of LiCl to TiO2 is less than 0.05:1), mix evenly and place it in a vacuum drying oven at 80℃ for 12h, mix evenly and transfer it to a crucible.

[0039] (2) After drying, the crucible is placed in a muffle furnace and heated to 780°C at a rate of 3°C / min and held for sintering for 8 hours.

[0040] (3) After cooling to room temperature, the sintered material is washed in deionized water to separate the NaCl in the material, and the filtered material is dried in a vacuum drying oven at 80°C for 12 hours to obtain the target product.

[0041] The Li4Ti5O prepared in this embodiment 12 The material structure and properties are similar to those in Example 1.

[0042] Example 4

[0043] The target chemical formula for synthesis is Li4Ti5O 12 The specific preparation process of the material is as follows:

[0044] (1) Weigh Li2CO3, TiO2, NaCl and LiCl according to a molar ratio of 2:5:2.0:0.20, grind them thoroughly to obtain a precursor mixture; add LiCl to the precursor mixture (where the molar ratio of LiCl to TiO2 is less than 0.05:1), mix evenly and place it in a vacuum drying oven at 80℃ for 12h, mix evenly and transfer it to a crucible.

[0045] (2) After drying, the crucible is placed in a muffle furnace and heated to 800℃ at a rate of 3℃ / min and held for sintering for 10h.

[0046] (3) After cooling to room temperature, the sintered material is washed in deionized water to separate the NaCl in the material, and the filtered material is dried in a vacuum drying oven at 80°C for 12 hours to obtain the target product.

[0047] The Li4Ti5O prepared in this embodiment 12 The material structure and properties are similar to those in Example 1.

[0048] The above embodiments (in conjunction with the accompanying drawings) have provided a detailed description of the specific implementation of the present invention. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made to the present invention without departing from the principle of the present invention are included within the protection scope of the present invention.

Claims

1. A method for synthesizing high-purity lithium-ion battery electrode materials using a molten salt method, characterized in that, Includes the following steps: (1) Weigh titanium dioxide, lithium source compound, and NaCl molten salt, grind them thoroughly to obtain a precursor mixture; wherein, the weighing of lithium source compound, titanium dioxide and NaCl is calculated according to the molar ratio of Li, Ti and NaCl as 4:5:(1~2.5); (2) Add an appropriate amount of LiCl to the precursor mixture, mix evenly and dry; wherein the molar ratio of LiCl to TiO2 is less than 0.05:1; (3) The dried mixture is sintered at high temperature and kept at that temperature for a period of time to ensure the reaction occurs; (4) The cooled product is washed with deionized water, suction filtered and dried to obtain high-purity lithium-ion battery negative electrode Li4Ti5O12 12 material; In step (3), the sintering atmosphere is air, the heating rate is 2 ~ 20℃ / min, the holding temperature is 700 ~ 800℃, and the holding time is 2 ~ 24h.

2. The method for synthesizing high-purity lithium-ion battery electrode materials by molten salt method according to claim 1, characterized in that: In step (2), the drying temperature is 50 ~ 150℃ and the drying time is 2 ~ 24h.

3. The method for synthesizing high-purity lithium-ion battery electrode materials by molten salt method according to claim 1, characterized in that: In step (4), deionized water is used for washing, the drying temperature is 50~150℃, and the drying time is 2~24h.

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