KR20250147507A - Method for preparing lithium bis(oxalato) borate anhydride - Google Patents

Abstract

In a method for producing lithium bis(oxalato)borate anhydride, a lithium compound, a boron compound, and an oxalic acid compound are added to water and heated to a temperature of 100°C to 120°C to obtain a mixture. The mixture is heated to a temperature of 120°C to 160°C under a nitrogen atmosphere and a pressure of 1.5 bar to 4.5 bar to obtain lithium bis(oxalato)borate hydrate. The lithium bis(oxalato)borate hydrate is heated to a temperature of 150°C to 170°C to obtain lithium bis(oxalato)borate anhydride. Accordingly, a method for producing lithium bis(oxalato)borate hydrate is provided, which improves the efficiency and economic feasibility of the process and has a high yield and purity.

Description

Method for preparing lithium bis(oxalato)borate anhydride

The present invention relates to a method for producing lithium bis(oxalato)borate anhydride.

Secondary batteries, which can be repeatedly charged and discharged, are widely used as power sources for portable electronic devices such as mobile phones and laptops. Among secondary batteries, lithium secondary batteries are actively being developed and applied due to their high operating voltage and energy density per unit weight, as well as their advantages in fast charging and lightweight design.

A lithium secondary battery may include, for example, an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, and an electrolyte solution impregnating the electrode assembly.

Meanwhile, as the range of applications for lithium secondary batteries expands, demand for superior cycle life, high capacity, and operational stability is increasing. Accordingly, the development of lithium secondary batteries that provide consistent output and capacity even during repeated charging and discharging is essential.

Additionally, as demand for high-voltage, high-energy-density secondary batteries grows, research is being conducted on additives to electrolytes. For example, lithium bis(oxalato)borate can be used as an electrolyte additive to improve the low-temperature performance of lithium secondary batteries.

For example, Korean Patent Publication No. 10-2008-0000595 discloses an electrolyte solution containing lithium bis(oxalato)borate as an electrolyte additive for a lithium secondary battery.

Korean Patent Publication No. 10-2008-0000595

One object of the present invention is to provide a method for producing lithium bis(oxalato)borate anhydride.

In a method for producing lithium bis(oxalato)borate according to exemplary embodiments of the present invention, a lithium compound, a boron compound, and an oxalic acid compound may be added to water and heated to a temperature of 100°C to 120°C to obtain a mixture. The mixture may be heated to a temperature of 120°C to 160°C under a nitrogen atmosphere and a pressure of 1.5 bar to 4.5 bar to obtain lithium bis(oxalato)borate hydrate. The lithium bis(oxalato)borate hydrate may be heated to a temperature of 150°C to 170°C to obtain lithium bis(oxalato)borate anhydride.

In some embodiments, the heating temperature in the step of obtaining the lithium bis(oxalato)borate hydrate may be 130°C to 150°C.

In some embodiments, the step of obtaining the lithium bis(oxalato)borate hydrate may be performed under a pressure of 2 bar to 4 bar.

In some embodiments, the heating temperature in the step of obtaining the lithium bis(oxalato)borate anhydride may be 155°C to 165°C.

In some embodiments, the lithium compound may include one or more of lithium hydroxide monohydrate and lithium hydroxide anhydrous, the boron compound may include boric acid, and the oxalic acid compound may include one or more of oxalic acid dihydrate and oxalic acid anhydride.

In some embodiments, the step of obtaining the mixture may include adding the lithium compound and the boron compound to water and heating to a temperature of 70° C. to 80° C.; and further adding the oxalic acid compound and heating to a temperature of 100° C. to 120° C.

In some embodiments, the lithium bis(oxalato)borate anhydride can be purified.

In some embodiments, the step of purifying the lithium bis(oxalato)borate anhydride may include adding a solvent to the lithium bis(oxalato)borate anhydride, concentrating under reduced pressure, and recrystallizing.

According to a manufacturing method according to exemplary embodiments, a lithium compound, a boron compound, and an oxalic acid compound are reacted to obtain lithium bis(oxalato)borate hydrate, and the hydrate is dried to obtain lithium bis(oxalato)borate anhydride.

According to the above manufacturing method, lithium bis(oxalato)borate hydrate can be obtained by heating at a low temperature in a pressure range higher than atmospheric pressure, and the hydrate can be dried at a low temperature. Accordingly, the efficiency and economic feasibility of the process can be improved, and the yield and purity in the production of lithium bis(oxalato)borate anhydride can be improved.

FIG. 1 is a schematic flowchart illustrating a method for preparing lithium bis(oxalato)borate anhydride according to exemplary embodiments.
Figures 2a to 2m are graphs showing the results of FT-IR analysis performed on lithium bis(oxalato)borate anhydride of examples and comparative examples.
Figure 3 is a graph showing the results of ¹¹ B-NMR analysis performed on lithium bis(oxalato)borate anhydride of Example 1.
Figure 4 is a graph showing the results of ¹³ C-NMR analysis performed on lithium bis(oxalato)borate anhydride of Example 1.

Embodiments of the present invention provide a method for preparing lithium bis(oxalato)borate anhydride.

Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. However, these are merely exemplary and the present invention is not limited to the specific embodiments described as examples.

FIG. 1 is a schematic flowchart illustrating a method for preparing lithium bis(oxalato)borate anhydride according to exemplary embodiments.

Referring to FIG. 1, lithium bis(oxalato)borate hydrate is prepared from reactants such as a lithium compound, a boron compound, and an oxalic acid compound, and then lithium bis(oxalato)borate anhydride can be prepared from the prepared lithium bis(oxalato)borate hydrate.

For example, at step S10, a lithium compound, a boron compound, and an oxalic acid compound can be reacted to obtain lithium bis(oxalato)borate hydrate.

In some embodiments, a lithium compound, a boron compound, and an oxalic acid compound may be added to water and heated to a temperature of 100° C. to 120° C. to obtain a mixture, and the mixture may be heated to a temperature of 120° C. to 160° C. under a nitrogen atmosphere and a pressure of 1.5 bar to 4.5 bar to obtain lithium bis(oxalato)borate hydrate.

In some embodiments, the lithium compound may include one or more of lithium hydroxide monohydrate and lithium hydroxide anhydrous, the boron compound may include boric acid, and the oxalic acid compound may include one or more of oxalic acid dihydrate and oxalic acid anhydride.

For example, the lithium compound may include lithium hydroxide monohydrate, the boron compound may include boric acid, and the oxalic acid compound may include oxalic acid dihydrate.

In some embodiments, the step of obtaining the mixture may include adding the lithium compound and the boron compound to water and heating to a temperature of 70° C. to 80° C.; and further adding the oxalic acid compound and heating to a temperature of 100° C. to 120° C.

In some embodiments, the step of obtaining the mixture may further include refluxing for 1 to 3 hours. For example, the refluxing may be further performed after the oxalic acid compound is additionally added and heated as described above.

In some embodiments, the step of obtaining the mixture may be performed for 1 to 3 hours. Accordingly, the reaction between the lithium compound, the boron compound, and the oxalic acid compound may sufficiently occur.

In some embodiments, the heating temperature in the step of obtaining the lithium bis(oxalato)borate hydrate may be 120°C to 160°C, for example, 130°C to 150°C, 130°C to 140°C, or 140°C to 150°C.

If the heating temperature in the step of obtaining the lithium bis(oxalato)borate hydrate is less than 120°C, the reaction may not occur sufficiently, thereby lowering the yield of lithium bis(oxalato)borate, and if the heating temperature exceeds 160°C, a side reaction may occur, thereby lowering the yield of lithium bis(oxalato)borate.

In some embodiments, the step of obtaining the lithium bis(oxalato)borate hydrate can be performed under a pressure of 1.5 bar to 4.5 bar, for example, 2 bar to 4 bar, 2.5 bar to 3.5 bar, 2 bar to 3 bar, or 3 bar to 4 bar.

If the step of obtaining the above lithium bis(oxalato)borate hydrate is performed at a pressure of less than 1.5 bar, the reaction may not occur sufficiently and the yield of lithium bis(oxalato)borate may decrease, and if it is performed at a pressure of more than 4.5 bar, a side reaction may occur and the yield and purity of lithium bis(oxalato)borate may deteriorate.

When the above-described temperature and pressure ranges are satisfied, lithium bis(oxalato)borate hydrate can be obtained by heating at a low temperature in a pressure range higher than atmospheric pressure, thereby reducing energy consumption associated with high-temperature heating. In addition, the yield and purity of lithium bis(oxalato)borate hydrate can be increased.

In some embodiments, the step of obtaining the lithium bis(oxalato)borate hydrate may be performed for 3 to 5 hours. Accordingly, the reaction can occur smoothly and lithium bis(oxalato)borate hydrate can be sufficiently obtained.

For example, at step S20, the lithium bis(oxalato)borate hydrate can be dried to convert it into lithium bis(oxalato)borate anhydride.

In some embodiments, the lithium bis(oxalato)borate hydrate may be heated to a temperature of 150° C. to 170° C. to obtain lithium bis(oxalato)borate anhydride. For example, the heating temperature may be 155° C. to 165° C., 150° C. to 160° C., or 160° C. to 170° C.

Within the above heating temperature range, moisture of lithium bis(oxalato)borate hydrate can be removed without using a dryer, and lithium bis(oxalato)borate can be obtained in high yield, thereby improving the efficiency and economy of the process.

In some embodiments, the lithium bis(oxalato)borate anhydride may be purified. The purification step may be additionally included in the manufacturing method according to the above-described embodiments to further improve the purity of the lithium bis(oxalato)borate anhydride.

In some embodiments, the step of purifying the lithium bis(oxalato)borate anhydride may include adding a solvent to the lithium bis(oxalato)borate anhydride, concentrating under reduced pressure, and recrystallizing.

For example, a first solvent can be added to the lithium bis(oxalato)borate anhydride, dissolved and filtered to remove impurities, and then the solvent can be removed by performing a reduced pressure concentration, and then a second solvent can be added to remove the remaining impurities, followed by filtering and drying, thereby obtaining lithium bis(oxalato)borate with high purity and high yield.

For example, the first solvent added to lithium bis(oxalato)borate anhydride may be dimethoxyethane, acetonitrile, acetone, ethyl acetate, ethylene carbonate, etc., and the second solvent added before filtration and drying may be ethyl methyl carbonate, dimethyl carbonate, ethanol, etc.

For example, the first solvent added to lithium bis(oxalato)borate anhydride may be dimethoxyethane, and the second solvent added before filtration and drying may be ethyl methyl carbonate.

In some embodiments, the purification of the lithium bis(oxalato)borate anhydride may be performed for 4 to 6 hours. Accordingly, impurities may be sufficiently removed to obtain high-purity lithium bis(oxalato)borate.

In exemplary embodiments, lithium bis(oxalato)borate manufactured according to the above-described manufacturing method can be used as an electrolyte additive for a lithium secondary battery.

Hereinafter, exemplary embodiments and comparative examples of the present invention are described. However, the following examples are merely exemplary embodiments of the present invention, and the present invention is not limited to the following examples.

Examples and Comparative Examples

(1) Example 1

1) Preparation of lithium bis(oxalato)borate hydrate

In a 1000 mL autoclave equipped with a stirrer, condenser, and thermometer, 63.8 g (1.03 mol) of boric acid, 43.3 g (1.03 mol) of lithium hydroxide monohydrate, and 129.9 g (7.21 mol) of water were added under _a N 2 atmosphere and stirred at 80°C. Then, while maintaining the internal temperature at 80°C, 260.2 g (2.06 mol) of oxalic acid dihydrate was added. Afterwards, the mixture was reacted for 2 hours while stirring at 110°C.

The above mixture was reacted for 4 hours under conditions of a pressure of 3 bar and an internal temperature of 140°C in a N ₂ atmosphere to obtain a solution containing lithium bis(oxalato)borate hydrate and impurities.

2) Preparation of lithium bis(oxalato)borate anhydride

A solution containing the obtained lithium bis(oxalato)borate hydrate was dried by heating under atmospheric pressure and 160°C conditions, thereby obtaining a solid containing bis(oxalato)borate anhydride and impurities.

3) Purification of lithium bis(oxalato)borate anhydride

800 g of dimethoxyethane was added to the above solid and stirred for 3 hours. The stirred solution was filtered through a 1.0 μm filter to remove impurities, and the obtained solution was concentrated under reduced pressure at 40°C. After that, 300 g of ethyl methyl carbonate was added and stirred at 55°C for 2 hours to obtain a slurry. The obtained slurry was filtered and dried to obtain 187.68 g of lithium bis(oxalato)borate anhydride (yield 93.8%, purity 99.9% or higher).

(2) Example 2

Lithium bis(oxalato)borate hydrate and lithium bis(oxalato)borate anhydride were prepared in the same manner as in Example 1, except that the reaction pressure of the mixture was changed from 3 bar to 2 bar when preparing lithium bis(oxalato)borate hydrate, and the anhydride was purified, thereby obtaining 181.16 g of lithium bis(oxalato)borate anhydride (yield 90.6%, purity 99.9% or higher).

(3) Example 3

Lithium bis(oxalato)borate hydrate and lithium bis(oxalato)borate anhydride were prepared in the same manner as in Example 1, except that the reaction pressure of the mixture was changed from 3 bar to 4 bar when preparing lithium bis(oxalato)borate hydrate, and the anhydride was purified, thereby obtaining 180.22 g of lithium bis(oxalato)borate anhydride (yield 90.1%, purity 99.9% or higher).

(4) Example 4

Lithium bis(oxalato)borate hydrate and lithium bis(oxalato)borate anhydride were prepared in the same manner as in Example 1, except that the heating temperature was changed from 160°C to 150°C when preparing lithium bis(oxalato)borate anhydride, and the anhydride was purified, thereby obtaining 187.20 g of lithium bis(oxalato)borate anhydride (yield 93.6%, purity 99.9% or higher).

(5) Example 5

Lithium bis(oxalato)borate hydrate and lithium bis(oxalato)borate anhydride were prepared in the same manner as in Example 1, except that the heating temperature was changed from 160°C to 170°C when preparing lithium bis(oxalato)borate anhydride, and the anhydride was purified, thereby obtaining 184.10 g of lithium bis(oxalato)borate anhydride (yield 92.1%, purity 99.9% or higher).

(6) Comparative Example 1

1) Preparation of lithium bis(oxalato)borate hydrate

In a 1000 mL autoclave equipped with a stirrer, condenser, and thermometer, 63.8 g (1.03 mol) of boric acid, 43.3 g (1.03 mol) of lithium hydroxide monohydrate, and 129.9 g (7.21 mol) of water were added under an _N 2 atmosphere, stirred at 80°C, and then 260.2 g (2.06 mol) of oxalic acid dihydrate was added while maintaining the internal temperature at 80°C.

Afterwards, the reaction was conducted for 6 hours at an internal temperature of 80°C and atmospheric pressure to obtain a solution containing lithium bis(oxalato)borate hydrate and impurities. The solution was cooled to room temperature and filtered to obtain lithium bis(oxalato)borate hydrate.

2) Preparation of lithium bis(oxalato)borate anhydride

Using a dryer, the obtained lithium bis(oxalato)borate hydrate was dried at 200°C for 24 hours to obtain 139.96 g of lithium bis(oxalato)borate anhydrate (yield 70.0%, purity 95% or less).

(7) Comparative Example 2

Lithium bis(oxalato)borate hydrate and lithium bis(oxalato)borate anhydride were prepared in the same manner as in Example 1, except that the reaction pressure of the mixture was changed from 3 bar to atmospheric pressure when preparing lithium bis(oxalato)borate hydrate, and the anhydride was purified, thereby obtaining 160.4 g of lithium bis(oxalato)borate anhydride (yield 80.2%, purity 90.0% or less).

(8) Comparative Example 3

Lithium bis(oxalato)borate hydrate and lithium bis(oxalato)borate anhydride were prepared in the same manner as in Example 1, except that the reaction pressure of the mixture was changed from 3 bar to 5 bar when preparing lithium bis(oxalato)borate hydrate, and the anhydride was purified, thereby obtaining 159.08 g of lithium bis(oxalato)borate anhydride (yield 79.5%, purity 99.9% or higher).

(9) Comparative Example 4

Lithium bis(oxalato)borate hydrate and lithium bis(oxalato)borate anhydride were prepared in the same manner as in Example 1, except that the reaction pressure of the mixture was changed from 3 bar to 200 torr (0.266645 bar) when preparing lithium bis(oxalato)borate hydrate, and the anhydride was purified, thereby obtaining 145.02 g of lithium bis(oxalato)borate anhydride (yield 72.3%, purity 90.0% or higher).

(10) Comparative Example 5

Lithium bis(oxalato)borate hydrate and lithium bis(oxalato)borate anhydride were prepared in the same manner as in Example 1, except that the heating temperature was changed from 160°C to 140°C when preparing lithium bis(oxalato)borate anhydride, and the anhydride was purified, thereby obtaining 165.46 g of lithium bis(oxalato)borate anhydride (yield 82.7%, purity 99.5% or less).

(11) Comparative Example 6

Lithium bis(oxalato)borate hydrate and lithium bis(oxalato)borate anhydride were prepared in the same manner as in Example 1, except that the heating temperature was changed from 160°C to 180°C when preparing lithium bis(oxalato)borate anhydride, and the anhydride was purified, thereby obtaining 170.06 g of lithium bis(oxalato)borate anhydride (yield 85.0%, purity 99.9% or higher).

(12) Comparative Example 7

Lithium bis(oxalato)borate hydrate and lithium bis(oxalato)borate anhydride were prepared in the same manner as in Example 1, except that the reaction temperature of the mixture was changed from 140°C to 110°C when preparing lithium bis(oxalato)borate hydrate, and the anhydride was purified, thereby obtaining 161.88 g of lithium bis(oxalato)borate anhydride (yield 80.9%, purity 99.5% or less).

(13) Comparative Example 8

Lithium bis(oxalato)borate hydrate and lithium bis(oxalato)borate anhydride were prepared in the same manner as in Example 1, except that the reaction temperature of the mixture was changed from 140°C to 180°C when preparing lithium bis(oxalato)borate hydrate, and the anhydride was purified, thereby obtaining 166.04 g of lithium bis(oxalato)borate anhydride (yield 83.02%, purity 99.9% or higher).

In the examples and comparative examples, the reaction conditions (pressure and temperature) of the mixture in the production of lithium bis(oxalato)borate hydrate and the reaction conditions (temperature) in the production of lithium bis(oxalato)borate anhydride are described in Table 1 below.

Reaction conditions of the mixture in the preparation of lithium bis(oxalato)borate hydrate Reaction conditions for the preparation of lithium bis(oxalato)borate anhydride Reaction pressure
(bar) Reaction temperature
(℃) Reaction temperature
(℃) Example 1 3 140 160 Example 2 2 140 160 Example 3 4 140 160 Example 4 3 140 150 Example 5 3 140 170 Comparative Example 1 1 80 200 Comparative Example 2 1 140 160 Comparative Example 3 5 140 160 Comparative Example 4 0.266645 140 160 Comparative Example 5 3 140 140 Comparative Example 6 3 140 180 Comparative Example 7 3 110 160 Comparative Example 8 3 180 160

Experimental example

(1) Yield evaluation

The yield (%) was calculated by calculating the molar ratio of the obtained lithium bis(oxalato)borate anhydride to the starting material of each of the examples and comparative examples as a percentage.

Specifically, the yield was calculated as a percentage of the molar ratio of the obtained lithium bis(oxalato)borate anhydride to the introduced lithium hydroxide monohydrate, boric acid, and oxalic acid dihydrate.

(2) Purity assessment

In the examples and comparative examples described above, the contents of each residual component relative to the Li ion component of the obtained lithium bis(oxalato)borate anhydride were measured using ICS-2100 (manufactured by Thermofisher Scientific) equipment, and the purity was calculated.

(3) Turbidity evaluation

In the examples and comparative examples described above, the turbidity of the obtained lithium bis(oxalato)borate anhydride was measured using TL2300 (manufactured by HACH).

(4) Color evaluation

In the examples and comparative examples described above, APHA was measured for the obtained lithium bis(oxalato)borate anhydride using OME7700 (manufactured by Nippon Denshoku).

The evaluation results are shown in Table 2 below.

transference number
(%) water
(%) Turbidity
(NTU) Color
(APHA) Example 1 93.8 ≥99.9 0.3 8 Example 2 90.6 ≥99.9 0.3 12 Example 3 90.1 ≥99.9 0.7 11 Example 4 93.6 ≥99.9 0.4 9 Example 5 92.1 ≥99.9 0.5 14 Comparative Example 1 70.0 ≤95.0 5.3 25 Comparative Example 2 80.2 ≤90.0 5.2 39 Comparative Example 3 79.5 ≥99.9 1.1 23 Comparative Example 4 72.3 ≤90.0 6.9 23 Comparative Example 5 82.7 ≤99.5 5.6 25 Comparative Example 6 85.0 ≥99.9 1.0 14 Comparative Example 7 80.9 ≤99.5 7.1 26 Comparative Example 8 83.0 ≥99.9 2.4 19

Referring to Table 2, lithium bis(oxalato)borate anhydride obtained according to the manufacturing methods of the examples had improved yield and purity, and lower turbidity and color. On the other hand, lithium bis(oxalato)borate anhydride obtained according to the manufacturing methods of the comparative examples had lower yield and purity, and higher turbidity and color.

(5) Evaluation of metal foreign matter

In the examples and comparative examples described above, the concentrations of metals contained in the obtained lithium bis(oxalato)borate anhydride were measured using Avio 550 Max (manufactured by Perkin Elmer).

The measurement results are shown in Table 3 below (units are ppm, and if not detected, N/D is shown).

Na
(ppm) Al
(ppm) K
(ppm) Ca
(ppm) Cr
(ppm) Fe
(ppm) Cu
(ppm) Zn
(ppm) Total
(ppm) Example 1 1.3 N/D N/D 0.6 N/D N/D N/D N/D 1.9 Example 2 2.4 N/D 0.3 4.0 N/D N/D N/D N/D 6.7 Example 3 2.2 N/D 0.2 2.6 0.0 N/D N/D N/D 5.0 Example 4 2.3 N/D 0.4 0.8 N/D 0.0 N/D N/D 3.5 Example 5 2.0 N/D 0.5 2.9 N/D 0.7 N/D N/D 6.1 Comparative Example 1 7.1 0.2 3.5 7.6 0.1 0.3 0.1 0.3 19.2 Comparative Example 2 12.5 N/D 1.7 13.1 N/D 0.2 N/D 0.5 28.0 Comparative Example 3 4.6 N/D 2.6 3.6 N/D 0.5 N/D N/D 11.3 Comparative Example 4 5.0 N/D 7.2 18.2 N/D 0.6 N/D 0.7 31.7 Comparative Example 5 2.4 N/D 1.5 7.5 N/D 0.8 N/D 0.6 12.8 Comparative Example 6 3.7 N/D 3.2 3.0 N/D 0.6 N/D N/D 10.5 Comparative Example 7 8.4 0.5 6.8 3.5 0.6 0.3 N/D N/D 20.1 Comparative Example 8 3.8 N/D 1.9 4.9 0.0 N/D N/D 0.1 10.7

Referring to Table 3, the lithium bis(oxalato)borate anhydride obtained according to the manufacturing method of the examples had a low concentration of metal foreign substances, but the lithium bis(oxalato)borate anhydride obtained according to the manufacturing method of the comparative examples had a high concentration of metal foreign substances.

(6) FT-IR analysis

In the above-described examples and comparative examples, FT-IR analysis was performed on the obtained lithium bis(oxalato)borate anhydride using an IROS 05 FTIR spectrometer (manufactured by OSTEC) (ATR module, solid-state measurement conditions).

The FT-IR analysis results for Examples 1 to 5 are described in FIGS. 2a to 2e, respectively, and the FT-IR analysis results for Comparative Examples 1 to 8 are described in FIGS. 2f to 2m.

Referring to FIGS. 2 and 3, it can be seen that, compared to lithium bis(oxalato)borate anhydride obtained according to the manufacturing method of the examples, lithium bis(oxalato)borate anhydride obtained according to the manufacturing method of the comparative examples has a lower purity due to the generation of side products (e.g., lithium bis(oxalato)borate hydrate).

(7) NMR analysis

¹¹ B-NMR (160.47 MHz conditions) and ¹³ C-NMR (125.77 MHz conditions) analyses were performed on the lithium bis(oxalato)borate anhydride obtained in Example 1 described above using JNM-ECZ500R/S1 (manufactured by JEOL). The analysis results are shown in Figs. 3 and 4, respectively.

Referring to FIGS. 4 and 5, it can be seen that the lithium bis(oxalato)borate anhydride obtained according to the manufacturing method of Example 1 is of high purity with no side products.

Claims (8)

A step of adding a lithium compound, a boron compound, and an oxalic acid compound to water and heating to a temperature of 100°C to 120°C to obtain a mixture;
A step of heating the above mixture to a temperature of 120° C. to 160° C. under a nitrogen atmosphere and a pressure of 1.5 bar to 4.5 bar to obtain lithium bis(oxalato)borate hydrate; and
A method for producing lithium bis(oxalato)borate anhydride, comprising the step of heating the lithium bis(oxalato)borate hydrate at a temperature of 150°C to 170°C to obtain lithium bis(oxalato)borate anhydride.
A method for producing lithium bis(oxalato)borate anhydride according to claim 1, wherein the heating temperature in the step of obtaining the lithium bis(oxalato)borate hydrate is 130°C to 150°C.
A method for producing lithium bis(oxalato)borate anhydride according to claim 1, wherein the step of obtaining the lithium bis(oxalato)borate hydrate is performed under a pressure of 2 bar to 4 bar.
A method for producing lithium bis(oxalato)borate anhydride according to claim 1, wherein the heating temperature in the step of obtaining the lithium bis(oxalato)borate anhydride is 155°C to 165°C.
A method for producing lithium bis(oxalato)borate anhydride according to claim 1, wherein the lithium compound comprises at least one of lithium hydroxide monohydrate and lithium hydroxide anhydride, the boron compound comprises boric acid, and the oxalic acid compound comprises at least one of oxalic acid dihydrate and oxalic acid anhydride.
In claim 1, the step of obtaining the mixture comprises:
Adding the lithium compound and the boron compound to water and heating to a temperature of 70°C to 80°C; and;
A method for producing lithium bis(oxalato)borate anhydride, comprising additionally adding the above oxalic acid compound and heating at a temperature of 100°C to 120°C.
A method for producing lithium bis(oxalato)borate anhydride, further comprising a step of purifying the lithium bis(oxalato)borate anhydride according to claim 1.
A method for producing lithium bis(oxalato)borate anhydride according to claim 7, wherein the step of purifying the lithium bis(oxalato)borate anhydride comprises adding a solvent to the lithium bis(oxalato)borate anhydride, concentrating under reduced pressure, and recrystallizing.