Method for preparing battery-grade lithium fluoride and byproduct industrial-grade lithium fluoride from industrial-grade lithium carbonate

Abstract

The invention discloses a method for preparing battery-grade lithium fluoride from industrial-grade lithium carbonate. The method comprises the following steps: pretreating and crushing the industrial-grade lithium carbonate; pulping, introducing carbon dioxide, carrying out primary hydrogenation reaction, filtering, and carrying out primary hydrogenation to obtain a liquid; adding an organic phosphate type complexing agent, reacting for a certain time, and filtering to obtain a lithium bicarbonate crude solution; dropwise adding a small amount of HF, reacting for a certain time, and filtering to obtain filtrate A; heating the filtrate A for pyrolysis, filtering to obtain a filter cake B, washing the filter cake B, adding water for pulping, introducing carbon dioxide for secondary hydrogenation reaction to obtain a lithium bicarbonate refined solution, dropwise adding HF into the lithium bicarbonate refined solution, filtering to obtain a filter cake C, and washing and drying the filter cake C to obtain the battery-grade lithium fluoride. The invention provides a method for deeply removing impurity ions such as Ca < 2 + > and Mg < 2 + >, and waste liquids in different steps are fully recycled, so that the recycling rate of lithium resources reaches 98% or above, and the quality of obtained battery-grade lithium fluoride is superior to the requirements in the standard HG / T 4507-2013.

Description

Technical Field

[0001] The invention belongs to the technical field of new energy, and specifically relates to a method for preparing battery-grade lithium fluoride from industrial-grade lithium carbonate and producing by-product industrial-grade lithium fluoride. Background Art

[0002] With the continuous consumption of fossil fuels and the growing energy demand of mankind, people are increasing their research on green new energy as a substitute for fossil fuels. At present, the development of new energy vehicles has received more and more attention from various countries, which has also rapidly driven the development of the battery industry. As the leader among current batteries, lithium-ion batteries are the focus of current research due to their high energy density, long service life, and no memory effect. Lithium hexafluorophosphate is an important solute in the electrolyte of lithium-ion batteries, with good dissociation, solubility, and ion conductivity. As an important precursor of lithium hexafluorophosphate, the purity of lithium fluoride directly affects the quality of lithium hexafluorophosphate products, and thus affects the performance of lithium-ion batteries.

[0003] In industrial production, lithium fluoride is mostly produced from industrial-grade lithium carbonate (98.5-99.5%), which contains more Ca 2+ Mg 2+ 、Na + , K + Most of the impurities can be removed by simple hydrogenation operation, but it is still difficult to obtain battery-grade lithium fluoride that meets the requirements, so it is necessary to deeply remove the impurities.

[0004] Compared with ordinary complexing agents, organic phosphate complexing agents have high complexing capacity, large complexing stability constant, and metal ions are not easy to dissociate after being complexed. They also have good chemical stability and are easily biodegradable, and have great potential.

[0005] Secondly, in the process of preparing battery-grade lithium fluoride, a large amount of wastewater and other wastes are often generated. How to effectively utilize these wastes will greatly reduce environmental pollution and production costs.

[0006] In this regard, the problem solved by the present invention is to develop a method for preparing battery-grade lithium fluoride with simple process, low pollution and high product quality. Summary of the invention

[0007] In view of the above-mentioned problems that the current preparation of lithium fluoride has complicated processes, waste is not effectively utilized, and the product purity is insufficient, the present invention provides a method for preparing battery-grade lithium fluoride and by-product industrial-grade lithium fluoride from industrial-grade lithium carbonate, the main purpose of which is: (1) By adding an organic phosphate-type complexing agent with high complexing capacity, large complexing stability constant, good chemical stability and easy biodegradation and combining it with the HF droplet addition process to perform deep impurity removal, the problem of Ca in the final product when the raw material is industrial-grade lithium carbonate is solved. 2+ Mg 2+ At the same time, the industrial-grade lithium fluoride obtained as a by-product can be used in the glass and ceramic industry to increase production added value.

[0008] (2) By recycling the waste liquid in the process and recovering the waste residue, the solid waste and liquid waste generated in the lithium fluoride production process can be solved. This not only reduces waste emissions, but also increases the recovery rate of Li resources to more than 98%.

[0009] To this end, the present invention provides a specific technical solution, which specifically includes the following steps: (1) crushing a certain mass of industrial grade lithium carbonate; (2) mixing the crushed lithium carbonate and water in a certain proportion, stirring and slurrying, introducing a certain flow rate of carbon dioxide under a certain temperature condition to carry out a hydrogenation reaction, stopping the reaction after a certain time and filtering; (3) adding a certain amount of an organic phosphate-type complexing agent to the solution after the primary hydrogenation reaction, and filtering to obtain a crude lithium bicarbonate solution; (4) Add a small amount of HF to the lithium bicarbonate crude liquid, react for a certain period of time, filter to obtain filtrate A, wash and dry filter cake A to obtain industrial grade lithium fluoride; (5) Pyrolyzing and crystallizing the filtrate A at a certain temperature, and filtering after a certain period of time to obtain the filtrate B and the filter cake B; (6) After the filter cake B is washed, a washing liquid A is obtained. The washed filter cake B is slurried with deionized water in a certain ratio, and carbon dioxide is introduced at a certain gas flow rate to perform a secondary hydrogenation reaction. After a certain reaction time, a refined lithium bicarbonate liquid is obtained; (7) Add a certain amount of HF to the refined lithium bicarbonate solution, react for a certain period of time, and then filter to obtain filtrate C and filter cake C; (8) The filter cake C is washed to obtain washing liquid B, and the washed filter cake C is dried to obtain battery-grade lithium fluoride.

[0010] (9) The filtrate B and the washing liquid A are combined and recycled as the reaction liquid for the next batch of hydrogenation; (10) The filtrate C and the washing liquid B are combined and recycled as the reaction liquid for the next batch of secondary hydrogenation.

[0011] Furthermore, in step (1), the industrial-grade lithium carbonate is pulverized in a jet mill, the feed air pressure and the pulverizing air pressure are controlled to be 0.2-1.0 MPa, the pulverizing time is 1-4 h, and the pulverized particle size is 5-10 μm.

[0012] Furthermore, the beating operation in step (2) includes: the ratio of industrial-grade lithium carbonate to deionized water is 1:(20-50), and the stirring speed is 300-600 r / min.

[0013] Furthermore, in step (2), the reaction temperature of the primary hydrogenation is 5-30°C, the reaction time is 2 h-8 h, and the carbon dioxide gas flow rate is 3-15 L / min.

[0014] Furthermore, the organic phosphonate complexing agent used in step (3) is one or more of diethylenetriamine penta (methylene phosphonic acid) sodium, ethylenediamine tetra (methylene phosphonic acid) sodium, and aminotri (methylene phosphonic acid) sodium.

[0015] Furthermore, the amount of the organic phosphonate complexing agent used in step (3) is: the mass of the organic phosphonate complexing agent is 0.02%-0.05% of the mass of the solution after the first hydrogenation, and the reaction time is 30-120 min.

[0016] Furthermore, the amount of HF added in step (4) is 0.1%-0.8% of the mass of the lithium bicarbonate crude solution, and the reaction time is 0.5 h-2 h.

[0017] Furthermore, the drying temperature in step (4) is 80-120° C., and the drying time is 8-24 h.

[0018] Furthermore, in step (5), the temperature of the pyrolysis crystallization is 70-90° C., and the time of the pyrolysis crystallization is 0.5 h-4 h.

[0019] Furthermore, the preparation method according to claim 1 is characterized in that the mass of the washing liquid in step (6) is 10-25 times the mass of the filter cake B, and the slurrying method of the washed filter cake B and deionized water is the same as that in step (2).

[0020] Furthermore, in step (6), the reaction temperature of the secondary hydrogenation is 5-30°C, the reaction time is 1 h-5 h, and the gas flow rate of the carbon dioxide is 3-15 L / min.

[0021] Furthermore, the amount of HF added dropwise in step (7) is 0.5-0.7 times the mass of the industrial-grade lithium carbonate mentioned in step (1), and the reaction time is 0.5-2 h.

[0022] Furthermore, the mass of the washing liquid used in step (8) is 8-20 times the mass of the filter cake C.

[0023] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention removes Ca by adding an organic phosphate type complexing agent having high complexing capacity, large complexing stability constant, good chemical stability and easy biodegradation to the solution of industrial grade lithium carbonate after primary hydrogenation. 2+ Mg 2+ , Fe 3+ Then, a small amount of HF was added to further remove Ca 2+ Mg 2+ The combination of the two-step impurity removal can significantly reduce the impurity ion content in the final product. The industrial-grade lithium fluoride produced in this process can be used in the glass and ceramics industry.

[0024] 2. The lithium source solution after secondary hydrogenation is directly reacted with HF to obtain high-purity battery-grade lithium fluoride, which fully meets the requirements of standard HG / T 4507-2013. In addition, compared with the traditional process for preparing lithium fluoride, the present invention recycles the filtrate B, filtrate C, washing liquid A, and washing liquid B in the process, which is simple in process, not only greatly reduces wastewater discharge, but also improves the utilization rate of lithium sources. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a production process flow chart of the present invention. DETAILED DESCRIPTION

[0026] The endpoints and any values ​​of the ranges disclosed in the present invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed in the present invention.

[0027] In order to better understand the present invention, the content of the present invention is further described below in conjunction with embodiments and related drawings, but the content of the present invention is not limited to the following embodiments.

[0028] Example 1 The present invention provides a method for preparing battery-grade lithium fluoride from industrial-grade lithium carbonate and producing industrial-grade lithium fluoride as a by-product, the preparation method comprising the following steps: (1) 10 kg of industrial-grade lithium carbonate was crushed using a jet mill. The feed air pressure and crushing air pressure were controlled to be 0.2 MPa, the crushing time was 2 h, and the crushed particle size was 10 μm.

[0029] (2) The crushed lithium carbonate and water were mixed at a ratio of 1:20, stirred and slurried, the stirring speed was 400 r / min, the reaction temperature was controlled at 5°C, and carbon dioxide was introduced at a gas flow rate of 3 L / min to carry out a primary hydrogenation reaction. The reaction was stopped after 6 hours and filtered to obtain a primary hydrogenation solution.

[0030] (3) Adding a complexing agent, sodium diethylenetriamine penta(methylenephosphonate), to the primary hydrogenation solution in an amount of 0.02% of the mass of the solution after the primary hydrogenation, reacting for 30 minutes, and then filtering to obtain a crude lithium bicarbonate solution.

[0031] (4) Add 0.2% by weight of HF to the crude lithium bicarbonate solution of step (3), react for 0.5 h, and filter to obtain filtrate A and filter cake A. The filter cake A is washed with pure water and dried at 80° C. for 24 h to obtain industrial grade lithium fluoride.

[0032] (5) The filtrate A was subjected to thermal decomposition and crystallization at 70°C. After 4 h of thermal decomposition and crystallization, the filtrate B and filter cake B were obtained by filtration. The filter cake B was washed with pure water 10 times the mass of the filter cake B to obtain the washed filter cake B and washing liquid A.

[0033] (6) The washed filter cake B was mixed with pure water at a mass ratio of 1:20, stirred and slurried, the stirring speed was 400 r / min, the reaction temperature was controlled at 5 °C, and carbon dioxide was introduced at a gas flow rate of 3 L / min for secondary hydrogenation reaction. The reaction was stopped after 6 h to obtain a carbonated cleaned refined liquid.

[0034] (7) Add 0.5 times the mass of HF of the industrial-grade carbonic acid mentioned in step (1) to the refined lithium bicarbonate liquid, react for 0.5 h, and then filter to obtain filtrate C and filter cake C.

[0035] (8) The filter cake C is washed with pure water 10 times the mass of the filter cake C. The washed filter cake C is dried at 80° C. for 24 h and then weighed to obtain battery-grade lithium fluoride. In addition, the generated washing liquid B is retained.

[0036] Example 2 The present invention provides a method for preparing battery-grade lithium fluoride from industrial-grade lithium carbonate and producing industrial-grade lithium fluoride as a by-product, the preparation method comprising the following steps: (1) 10 kg of industrial grade lithium carbonate was crushed using a jet mill. The feed air pressure and crushing air pressure were controlled to be 0.5 MPa, the crushing time was 3 h, and the crushed particle size was 8 μm.

[0037] (2) The crushed lithium carbonate and water were mixed at a ratio of 1:30, stirred and slurried, the stirring speed was 500 r / min, the reaction temperature was controlled to be 10°C, and carbon dioxide was introduced at a gas flow rate of 5 L / min to carry out a primary hydrogenation reaction. The reaction was stopped after 6 hours and filtered to obtain a primary hydrogenation solution.

[0038] (3) Adding a complexing agent, sodium ethylenediaminetetramethylenephosphonate, to the primary hydrogenation solution in an amount of 0.03% of the mass of the solution after the primary hydrogenation, reacting for 60 minutes, and then filtering to obtain a crude lithium bicarbonate solution.

[0039] (4) Add 0.5% by weight of HF to the crude lithium bicarbonate solution of step (3), react for 1 h, filter to obtain filtrate A and filter cake A, wash filter cake A with pure water, and dry at 90° C. for 16 h to obtain industrial grade lithium fluoride.

[0040] (5) The filtrate A was subjected to thermal decomposition and crystallization at 80°C. After 3 h of thermal decomposition and crystallization, the filtrate B and filter cake B were obtained by filtration. The filter cake B was washed with pure water 15 times the mass of the filter cake B to obtain washed filter cake B and washing liquid A.

[0041] (6) The washed filter cake B was mixed with pure water at a mass ratio of 1:30, stirred and slurried, the stirring speed was 500 r / min, the reaction temperature was controlled at 10°C, and carbon dioxide was introduced at a gas flow rate of 5 L / min for secondary hydrogenation reaction. The reaction was stopped after 6 h to obtain a carbonated cleaned refined liquid.

[0042] (7) Add 0.6 times the mass of HF of the industrial-grade carbonic acid mentioned in step (1) to the refined lithium bicarbonate solution, react for 1 h, and filter to obtain filtrate C and filter cake C.

[0043] (8) The filter cake C is washed with pure water 15 times the mass of the filter cake C. The washed filter cake C is dried at 90° C. for 16 h and then weighed to obtain battery-grade lithium fluoride. In addition, the generated washing liquid B is retained.

[0044] Example 3 The present invention provides a method for preparing battery-grade lithium fluoride from industrial-grade lithium carbonate and producing industrial-grade lithium fluoride as a by-product, the preparation method comprising the following steps: (1) 10 kg of industrial grade lithium carbonate was crushed using a jet mill. The feed air pressure and crushing air pressure were controlled to be 1.0 MPa, the crushing time was 4 h, and the crushed particle size was 5 μm.

[0045] (2) The crushed lithium carbonate and water were mixed at a ratio of 1:40, stirred and slurried, the stirring speed was 600 r / min, the reaction temperature was controlled at 15°C, and carbon dioxide was introduced at a gas flow rate of 10 L / min to carry out a primary hydrogenation reaction. After the reaction was stopped for 3 hours and filtered, a primary hydrogenation solution was obtained.

[0046] (3) Adding a complexing agent, sodium aminotri(methylenephosphonate), to the primary hydrogenation solution in an amount of 0.04% of the mass of the solution after the primary hydrogenation, reacting for 90 minutes, and then filtering to obtain a crude lithium bicarbonate solution.

[0047] (4) Add 0.8% by weight of HF to the crude lithium bicarbonate solution of step (3), react for 2 h, filter to obtain filtrate A and filter cake A, wash filter cake A with pure water, and dry at 120 °C for 8 h to obtain industrial grade lithium fluoride.

[0048] (5) The filtrate A was subjected to thermal decomposition and crystallization at 90°C. After 1 h of thermal decomposition and crystallization, the filtrate B and filter cake B were obtained by filtration. The filter cake B was washed with pure water 20 times the mass of the filter cake B to obtain the washed filter cake B and washing liquid A.

[0049] (6) The washed filter cake B was mixed with pure water at a mass ratio of 1:40, stirred and slurried, the stirring speed was 600 r / min, the reaction temperature was controlled at 15 °C, and carbon dioxide was introduced at a gas flow rate of 10 L / min for secondary hydrogenation reaction. The reaction was stopped after 3 h to obtain a carbonated cleaned refined liquid.

[0050] (7) Add 0.7 times the mass of HF of the industrial-grade carbonic acid mentioned in step (1) to the refined lithium bicarbonate solution, react for 2 h, and filter to obtain filtrate C and filter cake C.

[0051] (8) The filter cake C is washed with pure water 20 times the mass of the filter cake C. The washed filter cake C is dried at 120° C. for 8 h and then weighed to obtain battery-grade lithium fluoride. In addition, the generated washing liquid B is retained.

[0052] Example 4 The present invention provides a method for preparing battery-grade lithium fluoride from industrial-grade lithium carbonate and producing industrial-grade lithium fluoride as a by-product, the preparation method comprising the following steps: (1) 10 kg of industrial-grade lithium carbonate was crushed using a jet mill. The feed air pressure and crushing air pressure were controlled to be 0.2 MPa, the crushing time was 2 h, and the crushed particle size was 10 μm.

[0053] (2) The crushed lithium carbonate and water were mixed at a ratio of 1:20, stirred and slurried, the stirring speed was 400 r / min, the reaction temperature was controlled at 5°C, and carbon dioxide was introduced at a gas flow rate of 3 L / min to carry out a primary hydrogenation reaction. The reaction was stopped after 6 hours and filtered to obtain a primary hydrogenation solution.

[0054] (3) Adding ethylenediaminetetraacetic acid (EDTA) as a complexing agent to the primary hydrogenation solution in an amount of 0.02% of the mass of the solution after the primary hydrogenation, reacting for 30 minutes, and then filtering to obtain a crude lithium bicarbonate solution.

[0055] (4) Add 0.2% by weight of HF to the crude lithium bicarbonate solution of step (3), react for 0.5 h, and filter to obtain filtrate A and filter cake A. The filter cake A is washed with pure water and dried at 80° C. for 24 h to obtain industrial grade lithium fluoride.

[0056] (5) The filtrate A was subjected to thermal decomposition and crystallization at 70°C. After 4 h of thermal decomposition and crystallization, the filtrate B and filter cake B were obtained by filtration. The filter cake B was washed with pure water 10 times the mass of the filter cake B to obtain the washed filter cake B and washing liquid A.

[0057] (6) The washed filter cake B was mixed with pure water at a mass ratio of 1:20, stirred and slurried, the stirring speed was 400 r / min, the reaction temperature was controlled at 5 °C, and carbon dioxide was introduced at a gas flow rate of 3 L / min for secondary hydrogenation reaction. The reaction was stopped after 6 h to obtain a carbonated cleaned refined liquid.

[0058] (7) Add 0.5 times the mass of HF of the industrial-grade carbonic acid mentioned in step (1) to the refined lithium bicarbonate liquid, react for 0.5 h, and then filter to obtain filtrate C and filter cake C.

[0059] (8) The filter cake C is washed with pure water 10 times the mass of the filter cake C. The washed filter cake C is dried at 80° C. for 24 h and then weighed to obtain battery-grade lithium fluoride. In addition, the generated washing liquid B is retained.

[0060] Example 5 The present invention provides a method for preparing battery-grade lithium fluoride and by-product industrial-grade lithium fluoride from industrial-grade lithium carbonate. In the preparation method, the filtrate B and the washing liquid A in Example 1 are used as water for mixing and pulping with the crushed lithium carbonate in step (2) of Example 1, and the filtrate C and the washing liquid B are used as water for mixing and pulping with the crushed lithium carbonate in step (6) of Example 1. The rest are the same as in Example 1, and the cycle is repeated 4 times.

[0061] Example 6 The present invention provides a method for preparing battery-grade lithium fluoride and by-product industrial-grade lithium fluoride from industrial-grade lithium carbonate. In the preparation method, the filtrate B and the washing liquid A in Example 2 are used as water for mixing and pulping with the crushed lithium carbonate in step (2) in Example 2, and the filtrate C and the washing liquid B are used as water for mixing and pulping with the crushed lithium carbonate in step (6) in Example 2. The rest is the same as in Example 2, and the cycle is repeated 4 times.

[0062] Example 7 The present invention provides a method for preparing battery-grade lithium fluoride and by-product industrial-grade lithium fluoride from industrial-grade lithium carbonate. In the preparation method, the filtrate B and the washing liquid A in Example 3 are used as water for mixing and pulping with the crushed lithium carbonate in step (2) in Example 3, and the filtrate C and the washing liquid B are used as water for mixing and pulping with the crushed lithium carbonate in step (6) in Example 3. The rest is the same as in Example 3, and the cycle is repeated 4 times.

[0063] Example 8 The present invention provides a method for preparing battery-grade lithium fluoride and by-product industrial-grade lithium fluoride from industrial-grade lithium carbonate. In the preparation method, the filtrate B and the washing liquid A in Example 4 are used as the water for mixing and pulping with the crushed lithium carbonate in step (2) in Example 1, and the filtrate C and the washing liquid B are used as the water for mixing and pulping with the crushed lithium carbonate in step (6) in Example 1. The rest is the same as in Example 1, and the cycle is repeated twice.

[0064] Comparative Example 1 The present invention provides a method for preparing battery-grade lithium fluoride and by-product industrial-grade lithium fluoride from industrial-grade lithium carbonate. The preparation method is substantially the same as that in Example 1, except that the primary hydrogenation solution obtained in step (2) does not undergo the steps of adding a complexing agent and dripping HF in steps (3) and (4), but directly proceeds to step (5) to start pyrolysis and crystallization.

[0065] Comparative Example 2 The present invention provides a method for preparing battery-grade lithium fluoride from industrial-grade lithium carbonate and producing industrial-grade lithium fluoride as a by-product. The preparation method is substantially the same as that in Example 2, except that the filter cake B in step (5) and the filter cake C in step (8) are not washed.

[0066] The impurity content of the battery-grade lithium fluoride obtained in Examples 1-6 was tested respectively, as shown in Table 1.

[0067] Table 1 Content (wt%) and impurity components of battery-grade lithium fluoride obtained in the present invention

[0068]

[0069] Result analysis: 1. It can be seen from Examples 1 to 4 and Comparative Example 1 that the addition of an organic phosphate complexing agent and the addition of HF are very critical. Adding an organic phosphate complexing agent to the primary hydrogenation liquid and then further adding HF can effectively reduce the Ca content in the product. 2+ Mg 2+ , Fe 3+ Compared with common complexing agents, organic phosphate complexing agents have a larger stability constant. Metal ions are not easily dissociated after being complexed, and can effectively complex Ca 2+ Mg 2+ After removing some metal ions, a small amount of HF, F - Will be with Ca 2+ Mg 2+ The plasma combines to form an insoluble precipitate, which is then removed. Combining the two methods can reduce the impurity ion content to below the standard, and the industrial-grade lithium fluoride generated during the process can be used in the glass industry, allowing solid waste to be further utilized.

[0070] 2. It can be seen from Examples 1 to 4 and Comparative Example 2 that the washing of filter cakes B and C is effective in removing soluble Na + , K + Plasma is crucial. The reason is that if filter cakes B and C are not washed, Na + , K + Plasma will remain on the surface of the solid or be mixed in the middle of the particles and is difficult to remove, which will cause the impurity ion detection to exceed the standard. By washing, this simple method can make the soluble Na + , K + The plasma dissolves in solution and is subsequently removed by solid-liquid separation.

[0071] 3. It can be seen from Examples 1 to 4 and Examples 5 to 8 that the reasonable recycling of the filtrate and washing liquid in different steps can effectively improve the utilization rate of lithium resources, thereby improving the yield of the final product without affecting its quality. The reason is that lithium carbonate has a certain solubility in water, and the filtrate B and washing liquid A contain Li + Using it as the mother liquor of the primary hydrogenation can reduce the loss of Li and improve the utilization rate of Li. - Using it as the mother liquor for secondary hydrogenation can not only reduce water consumption, but also reduce wastewater discharge and reduce treatment costs.

[0072] The above embodiments are only examples for clear explanation, and are not intended to limit the implementation methods. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here, so the obvious changes or modifications derived are still within the protection scope of the invention.

Claims

1. A method for preparing battery-grade lithium fluoride from industrial-grade lithium carbonate and producing industrial-grade lithium fluoride as a by-product, characterized in that: include: (1) crushing a certain mass of industrial grade lithium carbonate; (2) The crushed lithium carbonate is mixed with water in a certain proportion, stirred and slurried, and a certain flow rate of carbon dioxide is introduced under the condition of controlling a certain temperature to carry out a hydrogenation reaction. After a certain reaction time, the reaction is stopped and filtered; (3) adding a certain amount of an organic phosphate type complexing agent to the solution after the primary hydrogenation reaction and reacting for a certain period of time, and filtering to obtain a crude lithium bicarbonate solution; (4) Add a small amount of HF to the lithium bicarbonate crude liquid, react for a certain period of time, filter to obtain filtrate A and filter cake A, and wash and dry the filter cake A to obtain industrial grade lithium fluoride; (5) Pyrolyzing and crystallizing the filtrate A at a certain temperature, and filtering after a certain period of time to obtain the filtrate B and the filter cake B; (6) After the filter cake B is washed, a washing liquid A is obtained. The washed filter cake B is slurried with deionized water in a certain ratio, and carbon dioxide is introduced at a certain gas flow rate to perform a secondary hydrogenation reaction. After a certain reaction time, a refined lithium bicarbonate liquid is obtained; (7) Add a certain amount of HF to the refined lithium bicarbonate solution, react for a certain period of time, and then filter to obtain filtrate C and filter cake C; (8) The filter cake C is washed to obtain washing liquid B, and the washed filter cake C is dried to obtain battery-grade lithium fluoride; (9) The filtrate B and the washing liquid A are combined and recycled as the reaction liquid for the next batch of hydrogenation; (10) The filtrate C and the washing liquid B are combined and recycled as the reaction liquid for the next batch of secondary hydrogenation.

2. The preparation method according to claim 1, characterized in that In step (1), the industrial-grade lithium carbonate is pulverized in a jet mill, the feed air pressure and the pulverizing air pressure are controlled to be 0.2-1.0 MPa, the pulverizing time is 1-4 h, and the pulverized particle size is 5-10 μm.

3. The preparation method according to claim 1, characterized in that: The beating operation in step (2) includes: the mass ratio of industrial-grade lithium carbonate to deionized water is 1: (20-50), the stirring speed is 300-600 r / min; the reaction temperature of the primary hydrogenation is 5-30°C, the carbon dioxide gas flow rate is 3-15 L / min, and the reaction time is 2 h-8 h.

4. The preparation method according to claim 1, characterized in that: The organic phosphonate complexing agent used in step (3) is one or more of diethylenetriamine penta (methylene phosphonic acid) sodium, ethylenediamine tetra (methylene phosphonic acid) sodium, and aminotri (methylene phosphonic acid) sodium; the amount of the organic phosphonate complexing agent used is 0.02%-0.05% of the mass of the solution after the first hydrogenation, and the reaction time is 30-120 min.

5. The preparation method according to claim 1, characterized in that: The amount of HF added in step (4) is 0.1%-0.8% of the mass of the lithium bicarbonate crude liquid, the reaction time is 0.5 h-2 h, the drying temperature is 80-120 ° C, and the drying time is 8-24 h.

6. The preparation method according to claim 1, characterized in that The temperature of the pyrolysis crystallization in step (5) is 70-90° C., and the time of the pyrolysis crystallization is 0.5 h-4 h.

7. The preparation method according to claim 1, characterized in that: In step (6), the mass of the washing liquid is 10-25 times the mass of the filter cake B, and the pulping method of the washed filter cake B and deionized water is the same as that of step (2).

8. The preparation method according to claim 1, characterized in that The reaction temperature of the secondary hydrogenation in step (6) is 5-30°C, the gas flow rate of the carbon dioxide is 3-15 L / min, and the reaction time is 1 h-5 h.

9. The preparation method according to claim 1, characterized in that The amount of HF added dropwise in step (7) is 0.5-0.7 times the mass of the industrial-grade lithium carbonate referred to in step (1), and the reaction time is 0.5-2 h.

10. The preparation method according to claim 1, characterized in that: The mass ratio of the washing liquid used in step (8) is 1:(8-20).

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