An organic lithium supplementing agent tetrahydroxyanthraquinone lithium salt, a preparation method and application thereof

Abstract

The application discloses a preparation method and application of an organic lithium supplementing agent tetrahydroxyanthraquinone lithium salt, which comprises the following steps: dissolving tetrahydroxyanthraquinone in methanol, adding dropwise a lithium hydroxide solution, and reacting at 25-50 DEG C for 2-6 hours; removing the methanol and by-product water by external steam distillation, and drying the solid to obtain the tetrahydroxyanthraquinone lithium salt; coating the tetrahydroxyanthraquinone lithium salt with a conductive polymer polybenzo difuran diketone to obtain the organic lithium supplementing agent tetrahydroxyanthraquinone lithium salt, which has an electrical conductivity of 5.2*10 ‑3 (S*cm ‑1 ); and the organic lithium supplementing agent is applied to a lithium iron phosphate-graphite battery, the first coulomb efficiency is increased from 88% to 93%, the capacity retention rate can still reach more than 98.94% after 150 cycles of charging and discharging, the capacity retention rate is increased by 5.63% compared with a lithium iron phosphate battery without adding the lithium supplementing agent, and the service life of the battery is effectively prolonged.

Description

Technical Field

[0001] This invention belongs to the field of battery electrode material synthesis, specifically relating to an organic lithium supplementer, tetrahydroxyanthraquinone lithium salt, its preparation method, and its application. Background Technology

[0002] With the increasing demand for energy density in lithium-ion batteries, high-capacity material systems are gradually becoming mainstream. However, these advanced electrode materials often suffer from significant irreversible lithium loss during the first charge-discharge cycle, resulting in low initial coulombic efficiency and limiting the release of full-cell energy density. To address this issue, "lithium replenishment technology" has emerged, among which sacrificial lithium replenishers have attracted considerable attention due to their ability to directly compensate for active lithium loss. Existing lithium replenishers are mainly divided into two categories: inorganic and organic. Compared to inorganic lithium replenishers, which typically suffer from problems such as excessively high decomposition potential, numerous residual impurities, and poor compatibility with electrolytes, organic lithium replenishers are considered a highly promising lithium replenishment solution due to their advantages such as high theoretical specific capacity, decomposition products that are mainly gaseous with no solid residue, and strong designability of molecular structures.

[0003] However, the currently published and widely studied organic lithium supplements still face serious challenges: poor air stability, most carboxylic acid organic lithium supplements are extremely sensitive to moisture and carbon dioxide, and are very prone to hygroscopic hydrolysis, leading to premature failure during electrode slurry preparation; uncontrolled gas generation, excessive gas generation or decomposition rate can cause cell expansion and increased internal pressure, seriously affecting battery safety and cycle life; some organic lithium supplements have high solubility in commonly used organic electrolytes, leading to continuous loss of active materials during cycling, resulting in rapid capacity decay and low coulombic efficiency.

[0004] Studies have revealed that anthraquinone compounds exhibit excellent electrochemical performance due to their stable conjugated structure and reversible multi-electron redox properties. Tetrahydroxyanthraquinone (THAQ), a typical polyhydroxy substituted anthraquinone derivative, can coordinate with lithium ions to form lithium salts, significantly improving its stability and electronic conductivity in electrolytes. It also enables reversible lithium ion insertion and extraction, resulting in a high specific capacity (its theoretical specific capacity is approximately 360 mAh / g). Its tetrahydroxy structure allows for stepwise lithium removal / oxidation, enabling a smoother and more controllable gas release process, avoiding cell expansion problems caused by sudden and violent gas generation. Summary of the Invention

[0005] To address the above problems, this invention provides an organic lithium supplement, tetrahydroxyanthraquinone lithium salt, its preparation method, and its application. Tetrahydroxyanthraquinone is used as a raw material, and tetrahydroxyanthraquinone lithium salt is obtained through neutralization, external evaporation, and drying. The organic lithium supplement, tetrahydroxyanthraquinone lithium salt, is then coated onto the tetrahydroxyanthraquinone lithium salt.

[0006] This invention is achieved through the following technical solution: An organic lithium supplement, tetrahydroxyanthraquinone lithium salt, is composed of tetrahydroxyanthraquinone lithium salt, a conductive polymer, and a dispersant. The molecular formula of the tetrahydroxyanthraquinone lithium salt is C2. 14 H4O6Li4, the conductive polymer contains polybenzodifurandione, the dispersant is a polycarboxylate dispersant, and the mass ratio of the tetrahydroxyanthraquinone lithium salt: conductive polymer: dispersant is 100:(5-20):(0.5-2).

[0007] Furthermore, the preparation method of the organic lithium supplement, tetrahydroxyanthraquinone lithium salt, specifically includes the following steps: 1) Under a nitrogen atmosphere, tetrahydroxyanthraquinone and methanol are added to a reactor and stirred. After complete dissolution, lithium hydroxide solution is added dropwise. After the addition is completed, the reaction is carried out at 25°C for 1-2 hours, and then the temperature is raised to 50°C for 1-4 hours. 2) The solvent methanol and by-product water are removed by external evaporation. The precipitated solid is washed with methanol and then dried in an oven to obtain tetrahydroxyanthraquinone lithium salt.

[0008] 3) The obtained tetrahydroxyanthraquinone lithium salt was coated. Under a nitrogen atmosphere, the tetrahydroxyanthraquinone lithium salt, conductive polymer and dispersant were mixed, and the mixture was ball-milled and spray-dried to obtain the organic lithium supplement tetrahydroxyanthraquinone lithium salt.

[0009] According to the preparation method described above, in step 1), the molar ratio of tetrahydroxyanthraquinone to lithium hydroxide is 1:4.0 to 4.2, and the mass ratio of tetrahydroxyanthraquinone to methanol is 1:5.5 to 12.5.

[0010] According to the preparation method described above, in step 1), the lithium hydroxide solution is a methanol solution of lithium hydroxide, and the dropping rate is 1.0 to 4.0 g / min, wherein the mass fraction of lithium hydroxide is 7.8 to 11.7%.

[0011] According to the preparation method described above, in step 2), the amount of methanol used to wash the solid is 0.1 to 0.6 times the mass of tetrahydroxyanthraquinone, the drying temperature is 75 to 85°C, and the negative pressure is -0.095 to -0.01 MPa.

[0012] According to the preparation method described above, the conductive polymer is a polybenzodifurandione solution, the amount of polybenzodifurandione solution is 5-20% of the mass of tetrahydroxyanthraquinone lithium salt, wherein the content of polybenzodifurandione solution is 1-3%, and the amount of dispersant is 0.5-2% of the mass of tetrahydroxyanthraquinone lithium salt.

[0013] Application of an organic lithium supplement, tetrahydroxyanthraquinone lithium salt, in lithium battery cathode materials.

[0014] According to the application described, the organic lithium supplement, tetrahydroxyanthraquinone lithium salt, is added to lithium-ion batteries using lithium iron phosphate as the positive electrode material and graphite as the negative electrode material.

[0015] According to the application described, the amount of the organic lithium supplement, tetrahydroxyanthraquinone lithium salt, added is 0.5 to 3% of the mass of the cathode material.

[0016] Beneficial effects of this invention: This invention prepares lithium salts using tetrahydroxyanthraquinone as a raw material, with a theoretical specific capacity of up to 360 mAh / g. This is because the raw material's core contains multiple reversibly redox-active carbonyl and phenolic hydroxyl groups, which, through multi-electron transfer (Li₂THAQ), enable the production of lithium salts. Li3THAQ Li4THAQ) achieves high capacity; converting tetrahydroxyanthraquinone to lithium salt reduces its solubility in organic electrolytes, suppresses the "shuttle effect," improves cycle stability and coulombic efficiency, and enhances ion conductivity. An organic lithium supplement was prepared by coating tetrahydroxyanthraquinone lithium salt with polybenzodifurandione, achieving a conductivity of 5.2 × 10⁻⁶. -3 (S·cm) -1 By applying organic lithium replenishing agents to lithium iron phosphate-graphite batteries, the initial coulombic efficiency increased from 88% to 93%. After 150 charge-discharge cycles, the capacity retention rate still reached over 98.94%. Compared to lithium iron phosphate batteries without added lithium replenishing agents, the capacity retention rate was improved by 5.63%, effectively extending the battery life. Attached Figure Description

[0017] Figure 1 The infrared spectrum of the raw material tetrahydroxyanthraquinone; Figure 2 The infrared spectrum of lithium tetrahydroxyanthraquinone salt in Example 1; Figure 3 This is the EDS diagram of lithium supplement A in Example 1. Detailed Implementation

[0018] The specific details of this invention will be further explained below: This invention relates to an organic lithium supplement, tetrahydroxyanthraquinone lithium salt, comprising tetrahydroxyanthraquinone lithium salt, a conductive polymer, and a dispersant. The tetrahydroxyanthraquinone lithium salt has the molecular formula C2. 14 H4O6Li4, the conductive polymer contains polybenzodifurandione, the dispersant is a polycarboxylate dispersant, and the mass ratio of the tetrahydroxyanthraquinone lithium salt: conductive polymer: dispersant is 100:(5-20):(0.5-2).

[0019] The preparation of the organic lithium supplement, tetrahydroxyanthraquinone lithium salt, of this invention includes the following steps: Under a nitrogen atmosphere, tetrahydroxyanthraquinone and methanol were introduced into a reactor at a mass ratio of 1:5.5–12.5. Stirring was started, and after complete dissolution, a lithium hydroxide solution (a methanol solution of lithium hydroxide with a mass fraction of 7.8–11.7%) was added dropwise. The molar ratio of tetrahydroxyanthraquinone to lithium hydroxide was 1:4.0–4.2. After the addition was complete, the reaction was carried out at 25°C for 1–2 hours, followed by increasing the temperature to 50°C and reacting for another 1–4 hours. The solvent methanol and by-product water are removed by external evaporation. The precipitated solid is then washed with methanol. The amount of methanol used to wash the solid is 0.1 to 0.6 times the mass of tetrahydroxyanthraquinone. The solid is then transferred to an oven for drying to obtain tetrahydroxyanthraquinone lithium salt. The required drying temperature is 75 to 85°C and the negative pressure is -0.095 to -0.01 MPa.

[0020] Under a nitrogen atmosphere, tetrahydroxyanthraquinone lithium salt, a conductive polymer, and a dispersant are mixed. The conductive polymer is a polybenzodifurandione solution, and the amount of polybenzodifurandione solution used is 5-20% of the mass of tetrahydroxyanthraquinone lithium salt, wherein the polybenzodifurandione content in the polybenzodifurandione solution is 1-3%. The amount of dispersant used is 0.5-2% of the mass of tetrahydroxyanthraquinone lithium salt. After ball milling and spray drying, the organic lithium supplement tetrahydroxyanthraquinone lithium salt is obtained.

[0021] This invention relates to the application of the organic lithium supplement, tetrahydroxyanthraquinone lithium salt, in the positive electrode material of lithium batteries. The organic lithium supplement, tetrahydroxyanthraquinone lithium salt, is added to a lithium-ion battery using lithium iron phosphate as the positive electrode material and graphite as the negative electrode material. The amount of the organic lithium supplement, tetrahydroxyanthraquinone lithium salt, added is 0.5 to 3% of the mass of the positive electrode material.

[0022] The content of this invention will be described below with specific parameters: Example 1: Preparation of lithium salt of tetrahydroxyanthraquinone, a lithium supplement: Under a nitrogen atmosphere, 108.9 g of tetrahydroxyanthraquinone and 1190.0 g of methanol were added to a reactor, and stirring was started to aid dissolution. 39.3 g of lithium hydroxide was dissolved in 363.4 g of methanol and added dropwise to the reactor at a rate of 4.0 g / min. After the addition was complete, the reaction was carried out at 25 °C for 1 h, then the temperature was raised to 50 °C and the reaction was continued for 2 h. The solvent methanol and byproduct water were externally evaporated, and the precipitated solid was washed with 23.6 g of methanol and then dried in an oven at 80 °C and -0.098 MPa for 4 h to obtain 116.6 g of tetrahydroxyanthraquinone lithium salt. The purity was 99.68%, and the yield was 98.18%. The methanol washing process resulted in a 1.27% loss of tetrahydroxyanthraquinone lithium salt due to solubility (based on the total yield of tetrahydroxyanthraquinone lithium salt).

[0023] Under a nitrogen atmosphere, 60 g of the obtained tetrahydroxyanthraquinone lithium salt, 12 g of 3% polybenzodifuran dione solution, and 0.6 g of polycarboxylate dispersant were mixed and ball-milled. The mixture was then spray-granulated to obtain the organic lithium supplement, tetrahydroxyanthraquinone lithium salt A, abbreviated as lithium supplement A. The conductivity was measured to be 5.2 × 10⁻⁶. -3 (S·cm) -1 EDS analysis of lithium supplement A showed a carbon-to-oxygen ratio of 3.1:1, which meets the target carbon-to-oxygen ratio, indicating that the organic lithium supplement tetrahydroxyanthraquinone lithium salt has been successfully prepared. The EDS chromatogram is shown below. Figure 3 .

[0024] Example 2: Preparation of lithium salt of tetrahydroxyanthraquinone, a lithium supplement: Under a nitrogen atmosphere, 108.9 g of tetrahydroxyanthraquinone and 1190.0 g of methanol were added to a reactor, and stirring was started to aid dissolution. 39.3 g of lithium hydroxide was dissolved in 363.4 g of methanol and added dropwise to the reactor at a rate of 4.0 g / min. After the addition was complete, the reaction was carried out at 25 °C for 1 h, and then the temperature was raised to 50 °C for another 1 h. The solvent methanol and byproduct water were externally evaporated, and the precipitated solid was washed with 23.6 g of methanol and then dried in an oven at 80 °C and -0.098 MPa for 4 h to obtain 110.8 g of tetrahydroxyanthraquinone lithium salt. The purity was 98.74%, and the yield was 92.38%. The methanol washing process resulted in a 1.32% loss of tetrahydroxyanthraquinone lithium salt (based on the total yield of tetrahydroxyanthraquinone lithium salt), and 6.9 g of tetrahydroxyanthraquinone was detected in the methanol wash recovery liquid, accounting for approximately 6.3% of the total tetrahydroxyanthraquinone feed.

[0025] Under a nitrogen atmosphere, 60 g of the obtained tetrahydroxyanthraquinone lithium salt, 3 g of 1% polybenzodifuran dione solution, and 0.3 g of polycarboxylate dispersant were mixed and ball-milled. The mixture was then spray-granulated to obtain the organic lithium supplement, tetrahydroxyanthraquinone lithium salt B, abbreviated as lithium supplement B. The conductivity was measured to be 3.7 × 10⁻⁶. -3 (S·cm) -1 ).

[0026] The organic lithium supplement of this invention, tetrahydroxyanthraquinone lithium salt, was applied to the manufacture of lithium batteries, and then the performance of the batteries was evaluated. Preparation of positive electrode: Lithium iron phosphate, lithium supplement A / lithium supplement B, Super P conductive agent and PVDF binder are added to NMP in a mass ratio of 95.0%:1.5%:1.5%:2.0% and mixed to prepare positive electrode slurry; the slurry is coated on aluminum foil current collector, vacuum dried at 120℃ for 4h to remove solvent, and then cut into circular electrode sheets with a diameter of 14mm for later use.

[0027] Preparation of negative electrode: Artificial graphite, Super P conductive agent and CMC / SBR composite binder are added to deionized water in a mass ratio of 96%:1.5%:2.5% and mixed to prepare negative electrode slurry; the slurry is coated on copper foil, vacuum dried at 80℃ for 3h to remove solvent, and then cut into circular electrode sheets with a diameter of 16mm for later use.

[0028] Battery Assembly and Testing: Lithium iron phosphate, lithium iron phosphate + lithium supplement A, and lithium iron phosphate + lithium supplement B were assembled with artificial graphite to form CR2032 coin cells with an N / P ratio of 1.15. Charge-discharge tests were conducted in the 2.5–3.65V voltage range on a LANB TS test cabinet. Test data are shown in Tables 1 and 2. , , As shown in Table 2, after adding the lithium replenisher, the initial discharge specific capacity increased from 141 mAh / g to 149 mAh / g, an increase of 5%–6%, and the initial coulombic efficiency increased from 88% to 93%. Table 3 shows that after adding the lithium replenisher, the battery capacity decay rate decreased, and after 150 charge-discharge cycles, the capacity retention rate remained above 99%, representing a 5.63% improvement in capacity retention compared to lithium iron phosphate batteries without the lithium replenisher.

[0029] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. An organic lithium supplement, tetrahydroxyanthraquinone lithium salt, characterized in that, It includes a tetrahydroxyanthraquinone lithium salt, a conductive polymer, and a dispersant, wherein the tetrahydroxyanthraquinone lithium salt has the molecular formula C2. 14 H4O6Li4, the conductive polymer contains polybenzodifurandione, the dispersant is a polycarboxylate dispersant, and the mass ratio of the tetrahydroxyanthraquinone lithium salt: conductive polymer: dispersant is 100:(5-20):(0.5-2).

2. A method for preparing the organic lithium supplement tetrahydroxyanthraquinone lithium salt according to claim 1, characterized in that, Includes the following steps: (1) Under a nitrogen atmosphere, tetrahydroxyanthraquinone and methanol are added to the reactor, stirring is started, and after complete dissolution, lithium hydroxide solution is added dropwise. After the addition is finished, the reaction is carried out at 25°C for 1 to 2 hours, and then the temperature is raised to 50°C for 1 to 4 hours. (2) The solvent methanol and by-product water are removed by external evaporation. The precipitated solid is washed with methanol and then dried in an oven to obtain tetrahydroxyanthraquinone lithium salt. (3) Under a nitrogen atmosphere, tetrahydroxyanthraquinone lithium salt, conductive polymer and dispersant are mixed, ball milled and spray dried to obtain organic lithium supplement tetrahydroxyanthraquinone lithium salt.

3. The preparation method according to claim 2, characterized in that, In step (1), the molar ratio of tetrahydroxyanthraquinone to lithium hydroxide is 1:4.0 to 4.2, and the mass ratio of tetrahydroxyanthraquinone to methanol is 1:5.5 to 12.

5.

4. The preparation method according to claim 2, characterized in that, In step (1), the lithium hydroxide solution is a methanol solution of lithium hydroxide, wherein the mass fraction of lithium hydroxide is 7.8 to 11.7%.

5. The preparation method according to claim 2, characterized in that, In step (2), the amount of methanol used to wash the solid is 0.1 to 0.6 times the mass of tetrahydroxyanthraquinone, the drying temperature is 75 to 85°C, and the negative pressure is -0.095 to -0.01 MPa.

6. The preparation method according to claim 2, characterized in that, Step (3) The conductive polymer is a polybenzodifurandione solution. The amount of polybenzodifurandione solution is 5-20% of the mass of tetrahydroxyanthraquinone lithium salt. The content of polybenzodifurandione in the polybenzodifurandione solution is 1-3%, and the amount of dispersant is 0.5-2% of the mass of tetrahydroxyanthraquinone lithium salt.

7. The application of the organic lithium supplement, tetrahydroxyanthraquinone lithium salt, according to claim 1, in lithium battery cathode materials.

8. The application according to claim 7, characterized in that, The organic lithium supplement, tetrahydroxyanthraquinone lithium salt, is added to lithium-ion batteries using lithium iron phosphate as the positive electrode material and graphite as the negative electrode material.

9. The application according to claim 7 or 8, characterized in that, The amount of the organic lithium supplement, tetrahydroxyanthraquinone lithium salt, added is 0.5 to 3% of the mass of the cathode material.

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