Preparation method of lithium difluorobisoxalato phosphate concentrated solution

Abstract

The invention relates to a preparation method of a lithium difluoro-bis (oxalate) phosphate concentrated solution, the lithium difluoro-bis (oxalate) phosphate concentrated solution is composed of lithium difluoro-bis (oxalate) phosphate and an aprotic solvent, the aprotic solvent comprises any one or a combination of at least two of diethyl carbonate, ethyl methyl carbonate, ethylene carbonate or propylene carbonate, the concentration of the lithium difluoro-bis (oxalate) phosphate in the lithium difluoro-bis (oxalate) phosphate concentrated solution is 10-35 wt%. The lithium difluoro bis (oxalate) phosphate concentrate provided by the invention exists in a non-proton electrolyte state, so that an evaporative crystallization process is omitted, and the production cost is reduced; the product transportation cost can be reduced through pipeline transportation; and compared with a lithium phosphate solid difluoro bis (oxalate), the process of re-dissolution during use is omitted, the risk of impurity introduction is avoided, and the use cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of battery manufacturing technology, and in particular to a method for preparing a concentrated lithium difluorodioxanol phosphate solution. Background Technology

[0002] Lithium difluorodioxanol phosphate (LiDF) is an important electrolyte, mainly used in the non-aqueous electrolytes of lithium (sodium) ion batteries. Therefore, its purity and impurity control requirements are extremely high. The content of impurities in LiDF, such as moisture, alkali metals, heavy metals, chloride ions, sulfate ions, or free acids, must be strictly controlled. Otherwise, it will cause problems such as increased internal resistance, rapid capacity decay, and shortened cycle life, thus affecting the safety of the battery.

[0003] Therefore, obtaining lithium difluorodioxanol phosphate products with high purity and low content of harmful impurities is of great practical significance.

[0004] Furthermore, solid lithium difluorodioxanol phosphate needs to be dissolved again during use, which introduces some impurities and increases the cost. Therefore, a new solution is needed to directly obtain high-purity lithium difluorodioxanol phosphate solution with low impurity content, simplifying the preparation process and enabling direct application in lithium (sodium) ion batteries. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a lithium difluorodioxanol phosphate concentrate. This concentrate exists as a non-proton electrolyte, exhibiting low acidity, low chlorine content, and high purity, making it directly suitable for preparing electrolytes for lithium-ion or sodium-ion batteries. Compared to the process mentioned in the Nikon patent, we improve the feeding conditions and method of lithium hexafluorophosphate by performing intermittent dissolution. This avoids the generation of excessive heat of dissolution due to large-scale dissolution of lithium hexafluorophosphate, which would lead to its decomposition and increase the acidity of the system. Furthermore, operating at low temperatures saves significant time and effectively improves production efficiency. Simultaneously, by reducing the moisture content of oxalic acid, side reactions during the reaction process are reduced. The reduced dosage effectively decreases product decomposition and improves product purity. Furthermore, by optimizing the silicon tetrachloride feeding method through surface dripping, not only is the amount of silicon tetrachloride used reduced, but also the equipment cleaning costs associated with handling silicon tetrachloride efflorescence are decreased, significantly improving production efficiency and lowering production costs. Simultaneously, the prepared lithium difluorodioxanol phosphate concentrate eliminates the evaporation and crystallization process, greatly reducing energy consumption. During transportation, it can be conveyed via pipelines, further reducing product transportation costs and improving safety during transit. Compared to solid lithium difluorodioxanol phosphate, the process of redissolving during use is omitted, avoiding the risk of impurity introduction and significantly reducing usage costs.

[0006] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a lithium difluorodioxazophosphate concentrate, wherein the lithium difluorodioxazophosphate concentrate is composed of lithium difluorodioxazophosphate and an aprotic solvent, wherein the aprotic solvent includes any one or a combination of at least two of diethyl carbonate, methyl ethyl carbonate, ethylene carbonate or propylene carbonate. The lithium difluorodioxanol phosphate concentrate has a lithium difluorodioxanol phosphate concentration of 10~35wt%, such as 10wt%, 14wt%, 18wt%, 20wt%, 22wt%, 24wt%, 26wt%, 28wt%, 30wt%, 32wt%, 34wt%, or 35wt%.

[0007] The lithium difluorodioxanol phosphate concentrate provided by this invention exists in a non-proton electrolyte state. Compared with solid lithium difluorodioxanol phosphate, it eliminates the process of redissolving during use, avoids the risk of introducing impurities, and reduces the cost of use.

[0008] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0009] Preferably, the concentrated lithium difluorodioxazophosphate solution has an acidity of <100ppm, such as 90ppm, 80ppm, 70ppm, 60ppm, 50ppm, 40ppm, 30ppm, 20ppm, 10ppm or 1ppm, a water content of <50ppm, such as 40ppm, 35ppm, 30ppm, 25ppm, 20ppm, 15ppm, 10ppm, 5ppm or 1ppm, and a chloride ion concentration of <20ppm, such as 19ppm, 18ppm, 17ppm, 16ppm, 15ppm, 14ppm, 13ppm, 12ppm, 11ppm, 10ppm, 9ppm, 8ppm, 7ppm, 6ppm, 5ppm, 4ppm, 3ppm, 2ppm or 1ppm.

[0010] In this invention, the concentrated lithium difluorodioxarate phosphate has low acidity, low water content, and low chloride ion concentration, thus avoiding the influence of impurities on electrolyte performance during use and meeting the usage standards for battery-grade electrolytes.

[0011] In a second aspect, the present invention also provides a method for preparing the lithium difluorodioxanol phosphate concentrate according to the first aspect, the preparation method comprising the following steps: (1) In an inert and dry atmosphere, lithium hexafluorophosphate, aprotic solvent and oxalic acid are mixed evenly to obtain a reaction solution (the moisture content of oxalic acid after drying is required to be ≤200ppm). (2) Maintain an inert and dry atmosphere, add silicon tetrachloride dropwise into the reaction solution described in step (1) to carry out the reaction, and after degassing, obtain the concentrated liquid precursor; (3) Maintain an inert and dry atmosphere and treat the concentrate precursor in step (2) with an ion exchange resin to remove acid, thereby obtaining lithium difluorooxalate phosphate concentrate.

[0012] The method for preparing lithium difluorodioxanol phosphate concentrate provided by this invention avoids the use of hydrogen fluoride as a raw material, and also avoids the risks associated with the use of hydrogen fluoride, thereby further improving the yield; combined with degassing concentration and resin treatment to remove impurities, the obtained lithium difluorodioxanol phosphate concentrate has high purity.

[0013] In this invention, the entire reaction must be carried out in an inert and dry atmosphere; otherwise, the resulting lithium difluorooxalate phosphate concentrate system will have high acidity, chloride ion content, and water content.

[0014] Preferably, the inert dry atmosphere includes dry nitrogen or dry argon. Preferably, a method for secondary purification of the introduced inert dry atmosphere is provided as follows: First stage: Most of the moisture in the gas is initially removed by silica gel desiccant; Second stage: Using the HKUST-1 metal-organic framework adsorption column, moisture is selectively adsorbed by utilizing its porous structure and copper ion coordination, reducing the moisture content in the gas to ≤5ppm. The specific steps are as follows: First-stage silica gel drying: Use coarse-pore (pore size 60~100Å) or fine-pore (pore size 20~30Å) silica gel with a bulk density of 0.6~0.8 g / cm³; gas flow rate 4-10 L / min, which can pre-treat the initial moisture content ≤50ppm to ≤20ppm.

[0015] Second-stage HKUST-1 adsorption: HKUST-1 adsorption column, filled with gas at a flow rate of 5-10 L / min, 20%-40% of the column volume; adsorption conditions are flow rate ≤ 5 L / min, temperature 20~30℃, adsorption capacity ≥ 0.5 g / g MOF; The target purity for the secondary purification process is ≤5ppm for moisture and ≤10ppm for oxygen content. Preferably, the mass ratio of lithium hexafluorophosphate to the aprotic solvent in step (1) is 1:(2~20), for example 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, 1:19 or 1:20, and more preferably 1:(8~18).

[0016] When the mass ratio of lithium hexafluorophosphate to the aprotic solvent in this invention is 1:(8~18), the prepared lithium difluorooxalate phosphate concentrate not only has low acidity but also high purity.

[0017] Preferably, the molar ratio of lithium hexafluorophosphate to oxalic acid in step (1) is 1:(1.995~2.1000), for example 1:1.995, 1:1.997, 1:1.999, 1:2.004, 1:1, 1:2.009, 1:2.014, 1:2.019 or 1:2.1000, and more preferably 1:(1.995~2.015).

[0018] In this invention, when the molar ratio of lithium hexafluorophosphate to oxalic acid is 1:(0.995~2.015), the prepared lithium difluorodioxalate phosphate concentrate not only has low acidity but also high purity.

[0019] Preferably, the mixing in step (1) includes: first dissolving lithium hexafluorophosphate in a non-protic solvent, and then adding oxalic acid.

[0020] Preferably, the mixing and dissolving method includes maintaining the temperature during the stirring process.

[0021] Preferably, the stirring time is 5 to 15 minutes, such as 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, 10 minutes, 11 minutes, 12 minutes, 13 minutes, 14 minutes, or 15 minutes.

[0022] Preferably, the temperature for dissolving lithium hexafluorophosphate is -10 to 10°C, such as -10°C, -5°C, 0°C, 5°C, 10°C, etc.

[0023] Preferably, the temperature for dissolving oxalic acid is 0~40℃, such as 0℃, 5℃, 10℃, 15℃, 20℃, 25℃, 30℃, 35℃, 40℃, etc.

[0024] Preferably, the molar ratio of lithium hexafluorophosphate in step (1) to silicon tetrachloride in step (2) is 1:(0.995~1.100), for example 1:0.995, 1:0.997, 1:1.000, 1:1.005, 1:1.010, 1:1.020, 1:1.030, 1:1.040, 1:1.050, 1:1.080 or 1:1.100, etc., preferably 1:(0.998~1.015).

[0025] When the molar ratio of lithium hexafluorophosphate in step (1) to silicon tetrachloride in step (2) is 1:(0.998~1.015), the prepared lithium difluorooxalate phosphate concentrate has not only low acidity but also high purity.

[0026] Preferably, the temperature of the reaction solution in step (1) is -5~40℃, for example -5℃, 5℃, 10℃, 15℃, 20℃, 25℃, 30℃, 35℃, 40℃, etc.

[0027] Preferably, the reaction temperature in step (2) is 0~50℃, for example 0℃, 5℃, 10℃, 15℃, 20℃, 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, etc.

[0028] In this invention, silicon tetrachloride can only effectively participate in the reaction when the reaction temperature is between 0 and 50°C. If the temperature is too high, silicon tetrachloride will volatilize severely and fail to participate in the reaction; if the temperature is too low, the reaction rate will be slow and the reaction will be incomplete.

[0029] Preferably, the reaction time is 1 to 8 hours, such as 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, or 8 hours.

[0030] In this invention, silicon tetrachloride can only be effectively added to the reaction by using the surface-to-surface dropping method. If the liquid-to-top dropping method is used, silicon tetrachloride will volatilize severely and fail to participate in the reaction, resulting in excessive silicon tetrachloride consumption and difficulty in removing subsequent impurity ions. If the temperature is too low, the reaction rate will be slow and the reaction will be incomplete, resulting in energy waste and increased costs.

[0031] It should be noted that the temperature of the reaction in step (2) is the same as the temperature of the reaction solution in step (1).

[0032] Preferably, the degassing in step (2) includes degassing with positive pressure replenishment of inert gas or degassing with negative pressure.

[0033] It should be noted that both positive pressure inert gas degassing and negative pressure degassing can remove hydrogen chloride and silicon tetrafluoride from the system after the reaction, but positive pressure inert gas degassing takes a little longer.

[0034] In this invention, a degassing method is used to further reduce the amount of hydrogen chloride and silicon tetrafluoride in the system after the reaction, thereby reducing the acidity and chloride ion concentration of the system.

[0035] Preferably, the degassing pressure in step (2) is 0.5~10 kPa, for example, 0.5 kPa, 1 kPa, 1.5 kPa, 2 kPa, 2.5 kPa, 3 kPa, 3.5 kPa, 4 kPa, 4.5 kPa, 5 kPa, 5.5 kPa, 6 kPa, 6.5 kPa, 7 kPa, 7.5 kPa, 8 kPa, 8.5 kPa, 9 kPa, 9.5 kPa or 10 kPa.

[0036] Preferably, the degassing temperature in step (2) is 0~50℃, such as 0℃, 5℃, 10℃, 15℃, 20℃, 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, etc. The optimal temperature is 20~40℃. If the temperature is too high, the product will decompose finely, and the color and purity will decrease accordingly, affecting the product performance.

[0037] Preferably, the degassing time in step (2) is 2 to 6 hours, such as 2 hours, 3 hours, 4 hours, 5 hours or 6 hours.

[0038] Preferably, the resin used in the perion exchange resin deacidification treatment in step (3) includes a strong basic anion exchange resin and / or a weak basic anion exchange resin.

[0039] Preferably, before the resin treatment in step (3), an aprotic solvent is added.

[0040] It should be noted that before the resin treatment in step (3), the concentration of the concentrate precursor in step (2) needs to be 0.5 to 2 wt% higher than the concentration of the target lithium difluorodioxanol phosphate concentrate product. If the concentration of the concentrate precursor in step (2) is too high, that is, the difference between the concentration of the concentrate precursor and the target lithium difluorodioxanol phosphate concentrate product exceeds 0.5 to 2 wt%, it is necessary to add aprotic solvent.

[0041] In this invention, the use of resin-treated concentrate precursors can further and effectively reduce the acid, chloride ion and water content in the system, achieving the usage standards for battery-grade electrolytes.

[0042] As a preferred technical solution, the preparation method includes the following steps: (1) In an inert and dry atmosphere, lithium hexafluorophosphate is mixed with an aprotic solvent and stirred for 5 to 15 minutes to dissolve it. Then, oxalic acid is added and mixed evenly. The temperature of the resulting reaction solution is controlled to be -5 to 40°C. Wherein, the mass ratio of lithium hexafluorophosphate to the aprotic solvent is 1:(8~18); the molar ratio of lithium hexafluorophosphate to oxalic acid is 1:(1.995~2.015); the inert drying atmosphere includes dry nitrogen or dry argon. (2) Add silicon tetrachloride dropwise into the reaction solution described in step (1). After the addition is complete, react at 0~50℃ for 1~8h, and degas at 0.5~10kPa and 20~40℃ for 2~6h to obtain the precursor concentrate. Wherein, the molar ratio of lithium hexafluorophosphate in step (1) to silicon tetrachloride in step (2) is 1:(0.995~1.015); the degassing includes positive pressure replenishment of inert gas degassing or negative pressure degassing; (3) The concentrate precursor described in step (2) is treated with an ion exchange resin to obtain lithium difluorodioxanol phosphate concentrate; If the concentration of the concentrate precursor in step (2) is too high, i.e., the difference between the concentration of the concentrate and the target lithium difluorodioxanol phosphate concentrate product exceeds 0.5~2wt%, before the resin treatment, an aprotic solvent is added until the product concentration is 0.5~2wt% higher than the target lithium difluorodioxanol phosphate concentrate product concentration; the resin in the resin treatment includes a strong basic anion exchange resin and / or a weak basic anion exchange resin. Furthermore, a method for fluorination of a strongly basic anion exchange resin is provided to prepare a fluoropyridinyl strongly basic anion exchange resin, as detailed below: By weight, add 100-120 parts of strong basic anion exchange resin, 10-20 parts of o-fluorobenzoyl chloride, 0.05-0.4 parts of 2-fluoro-6-pyridinecarboxyl chloride (CAS: 64197-03-1), 1000-1500 parts of dichloroethane, and 2-4 parts of zinc chloride to the polymerization reactor. Control the reaction temperature at 40-50℃ and react in the dark for 10-20 hours. Filter, wash with dichloroethane until no chloride ions are present, and dry to obtain fluoropyridine-based strong basic anion exchange resin.

[0043] The strongly basic anion exchange resin includes: D201: macroporous strongly basic styrene-based anion exchange resin, D202: macroporous type II strongly basic anion exchange resin, and 201×7 anion exchange resin.

[0044] The weakly basic anion exchange resins include: D301 macroporous weakly basic anion exchange resin, D311 macroporous weakly basic acrylic anion exchange resin, and Amberlite IRA-45 macroporous weakly basic anion exchange resin.

[0045] The reaction mechanism of the above anion exchange resin is as follows: Coordination substitution reaction: In step (1), lithium hexafluorophosphate dissociates into ions in an aprotic solvent, and oxalic acid, acting as a bidentate ligand, reacts with PF6. - A coordination exchange reaction occurs, gradually replacing fluoride ions to form an intermediate complex; in step (2), silicon tetrachloride acts as a Lewis acid to promote the reaction, allowing oxalate to completely replace PF6. -The two fluorine atoms in the phosphate group generate difluorodioxarate phosphate, which then combines with lithium ions to form lithium difluorodioxarate phosphate.

[0046] Ion exchange purification: Step (3) uses strong and weak base anion exchange resins to adsorb residual PF6 through electrostatic interaction, hydrogen bonding or coordination. - Cl - Fluoropyridinyl strong basic anion exchange resin, after fluorination treatment, exhibits enhanced selective adsorption of fluorinated impurity ions, thereby further improving the purification effect, in addition to removing anionic and acidic impurities.

[0047] Thirdly, the present invention also provides an application of lithium difluorodioxarate phosphate concentrate, wherein the lithium difluorodioxarate phosphate concentrate described in the first aspect, or the lithium difluorodioxarate phosphate concentrate prepared by the preparation method described in the second aspect, is used to formulate a non-aqueous electrolyte for lithium-ion batteries or sodium-ion batteries.

[0048] Compared with the prior art, the present invention has at least the following beneficial effects: 1) The lithium difluorodioxarate phosphate concentrate provided by the present invention exists in the form of a non-proton electrolyte, with low acidity, low chlorine content and high purity, and can be directly used for the preparation of electrolytes for lithium-ion batteries or sodium-ion batteries. 2) This invention improves the feeding conditions and methods of lithium hexafluorophosphate by performing intermittent dissolution, which avoids the generation of a large amount of heat of dissolution due to the large amount of lithium hexafluorophosphate dissolution, which would lead to the decomposition of lithium hexafluorophosphate and increase the acidity of the system. Combined with low temperature conditions, it saves a lot of time and effectively improves production efficiency. 3) This invention optimizes the moisture conditions of oxalic acid, thereby reducing side reactions during the reaction process, effectively reducing product decomposition, and improving product purity; 4) By optimizing the feeding method of silicon tetrachloride and adding it by dripping from the surface, this invention not only reduces the amount of silicon tetrachloride used, but also reduces the equipment cleaning costs caused by handling silicon tetrachloride escaping, thus greatly improving production efficiency and reducing production costs. 5) The lithium difluorodioxanol phosphate concentrate provided by this invention can be transported through pipelines, reducing product transportation costs; compared with solid lithium difluorodioxanol phosphate, the process of redissolving during use is omitted, avoiding the risk of introducing impurities and greatly reducing usage costs. 6) The preparation of the lithium difluorodioxanol phosphate concentrate provided by the present invention eliminates the evaporation and crystallization process, thereby reducing production costs; 7) This invention prepares lithium difluorodioxanol phosphate solution through a simple and efficient one-step reaction, reducing production capacity loss. By controlling the ratio of reaction raw materials, the prepared lithium difluorodioxanol phosphate solution has a low initial acidity and chloride ion concentration. Then, through subsequent processing, the impurity content in the system is quickly and efficiently reduced to obtain a concentrated lithium difluorodioxanol phosphate solution that meets the standards for use as a battery electrolyte.

[0049] 8) This patent achieves comprehensive control of acidity, moisture and chloride ions through two-stage gas purification (silica gel + HKUST-1), precise raw material ratio and resin deacidification, and the product performance reaches the industry-leading level.

[0050] 9) When the lithium difluorodioxarate phosphate concentrate prepared by this invention is used to prepare electrolyte, it can form a stable SEI film on the electrode surface, thereby improving the battery cycle life; it is also suitable for lithium-ion batteries and sodium-ion batteries, expanding the application scenarios, and can also show good performance under special conditions such as low temperature environment. Attached Figure Description

[0051] Figure 1 This is the 19F-NMR spectrum of the lithium difluorodioxarate phosphate concentrate prepared in Example 1 of this invention. Detailed Implementation

[0052] The features of the present invention are further illustrated below through embodiments, but the scope of protection of this patent is not limited to the embodiments.

[0053] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0054] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0055] Example 1

[0056] This embodiment provides a method for preparing a lithium difluorodioxarate phosphate concentrate, wherein the lithium difluorodioxarate phosphate concentrate is composed of lithium difluorodioxarate phosphate and methyl ethyl carbonate; the concentration of lithium difluorodioxarate phosphate in the lithium difluorodioxarate phosphate concentrate is 20 wt%.

[0057] The preparation method of the lithium difluorodioxanol phosphate concentrate includes the following steps: (1) In a dry nitrogen atmosphere, add 100.8g of methyl ethyl carbonate, set the solvent temperature to 10℃, weigh 15.19g of lithium hexafluorophosphate and add it to the reaction flask, stir for 15min to completely dissolve the lithium hexafluorophosphate, add 18.05g of oxalic acid to the reaction flask, and keep the resulting reaction solution at 40℃. (2) After the temperature is constant, 16.99g of silicon tetrachloride is slowly added to the reaction solution dropwise (a large amount of acidic gas is generated during the dropwise process). After the dropwise addition is complete, the reaction is carried out at 40℃ for 4 hours, and then degassed under negative pressure at 5kPa and 30℃ for 3 hours to obtain the concentrated solution precursor. (3) Maintain an inert and dry atmosphere, add methyl ethyl carbonate to the concentrate precursor, and perform chromatography with a fluoropyridinyl strong base anion exchange resin to obtain lithium difluorodioxarate phosphate concentrate.

[0058] 100g of a strong base anion exchange resin (D201: macroporous strong base styrene anion exchange resin), 10g of o-fluorobenzoyl chloride, 0.2g of 2-fluoro-6-pyridinecarboxyl chloride (CAS: 64197-03-1), 1000g of dichloroethane, and 2g of zinc chloride were added to a polymerization reactor. The reaction temperature was controlled at 40℃, and the reaction was carried out in the dark for 20 hours. After filtration, the resin was washed with dichloroethane until no chloride ions were removed, and then dried to obtain a fluoropyridine-based strong base anion exchange resin.

[0059] The method for secondary purification using an inert, dry atmosphere is as follows: First-stage silica gel drying: Fine-pore (pore size 20 to 30 Å) silica gel with a bulk density of 0.6 g / cm³ and a gas flow rate of 10 L / min can pre-treat the initial moisture content from ≤50 ppm to ≤20 ppm.

[0060] Second-stage HKUST-1 adsorption: HKUST-1 adsorption column, filled to 20% of the column volume at a gas flow rate of 10 L / min; adsorption conditions are flow rate ≤ 5 L / min, temperature 20℃, and adsorption capacity ≥ 0.5 g / g MOF.

[0061] After secondary purification, the moisture content was measured to be 4.2 ppm and the oxygen content was 8.5 ppm.

[0062] A few drops of the filtrate were transferred to an NMR tube, and an internal standard was added. Deuterated acetonitrile was added to dissolve the filtrate, and NMR (F-spectrum) analysis was performed. The content of the filtrate was calculated from the proportionality integral of the NMR data. The integral proportions of lithium difluorooxalate phosphate were 93%, lithium tetrafluorooxalate phosphate 6%, and lithium difluorophosphate 1%. To determine the concentration of the acid, a titration method was used, yielding a result of 20 ppm. The chloride ion concentration was determined using silver nitrate titration under ice-water bath conditions, yielding a result of 5 ppm. The moisture content was determined using a moisture analyzer, yielding a result of 15 ppm.

[0063] Example 2

[0064] This embodiment provides a method for preparing a lithium difluorodioxarate phosphate concentrate, wherein the lithium difluorodioxarate phosphate concentrate is composed of lithium difluorodioxarate phosphate and methyl ethyl carbonate; the concentration of lithium difluorodioxarate phosphate in the lithium difluorodioxarate phosphate concentrate is 20 wt%.

[0065] The preparation method of the lithium difluorodioxanol phosphate concentrate includes the following steps: (1) In a dry nitrogen atmosphere, add 100.8g of methyl ethyl carbonate, set the solvent temperature to 10℃, weigh 15.19g of lithium hexafluorophosphate and add it to the reaction flask, stir for 15min to completely dissolve the lithium hexafluorophosphate, add 18.05g of oxalic acid to the reaction flask, and keep the resulting reaction solution at 40℃. (2) After the temperature is constant, 16.99g of silicon tetrachloride is slowly added to the reaction solution by dripping it through the surface (a large amount of acidic gas is generated during the dripping process). After the dripping is completed, the reaction is carried out at 40℃ for 4 hours, and then degassed under negative pressure at 5kPa and 30℃ for 3 hours to obtain the concentrated liquid precursor. (3) Maintain an inert and dry atmosphere, add methyl ethyl carbonate to the concentrate precursor, and perform chromatography with a fluoropyridinyl strong base anion exchange resin to obtain lithium difluorodioxarate phosphate concentrate.

[0066] 110g of a strong base anion exchange resin (D202: a macroporous type II strong base anion exchange resin), 15g of o-fluorobenzoyl chloride, 0.3g of 2-fluoro-6-pyridinecarboxyl chloride (CAS: 64197-03-1), 1250g of dichloroethane, and 3g of zinc chloride were added to a polymerization reactor. The reaction temperature was controlled at 45℃, and the reaction was carried out in the dark for 15 hours. After filtration, the resin was washed with dichloroethane until no chloride ions were removed, and then dried to obtain a fluoropyridine-based strong base anion exchange resin.

[0067] The method for secondary purification using an inert, dry atmosphere is as follows: First-stage silica gel drying: Fine-pore (pore size 20 to 30 Å) silica gel with a bulk density of 0.7 g / cm³ and a gas flow rate of 8 L / min can pre-treat the initial moisture content from ≤50 ppm to ≤20 ppm.

[0068] Second-stage HKUST-1 adsorption: HKUST-1 adsorption column, filled to 30% of its volume at a gas flow rate of 8 L / min; adsorption conditions: flow rate ≤ 5 L / min, temperature 25℃, adsorption capacity ≥ 0.5 g / g MOF.

[0069] After secondary purification, the moisture content was measured to be 4.0 ppm and the oxygen content was 8.1 ppm.

[0070] A few drops of the filtrate were placed in an NMR tube, and an internal standard was added. Deuterated acetonitrile was added to dissolve the filtrate, and NMR (F-spectrum) analysis was performed. The proportions of lithium difluorooxalate phosphate in the filtrate were calculated from the proportionality integral of the NMR data. The proportions were: lithium difluorooxalate phosphate 85%, lithium tetrafluorooxalate phosphate 8%, lithium difluorophosphate 5%, and lithium hexafluorophosphate 2%. To determine the acid concentration, a titration method was used, yielding a result of 26 ppm. The chloride ion concentration was determined using silver nitrate titration under ice-water bath conditions, yielding a result of 7 ppm. The moisture content was determined using a moisture analyzer, yielding a result of 24 ppm.

[0071] Example 3

[0072] This embodiment provides a method for preparing a lithium difluorodioxarate phosphate concentrate, which is composed of lithium difluorodioxarate phosphate and methyl ethyl carbonate; the concentration of lithium difluorodioxarate phosphate in the lithium difluorodioxarate phosphate concentrate is 10 wt%.

[0073] The preparation method of the lithium difluorodioxanol phosphate concentrate includes the following steps: (1) In a dry nitrogen atmosphere, add 100.8g of methyl ethyl carbonate, set the solvent temperature to 10℃, weigh 6.03g of lithium hexafluorophosphate and add it to the reaction flask, stir for 15min to completely dissolve the lithium hexafluorophosphate, add 7.17g of oxalic acid to the reaction flask, and keep the resulting reaction solution at 40℃. (2) After the temperature is constant, 6.74 g of silicon tetrachloride is slowly added to the reaction solution dropwise (a large amount of acidic gas is generated during the dropwise process). After the dropwise addition is complete, the reaction is carried out at 40°C for 4 hours, and then degassed under negative pressure at 5 kPa and 30°C for 3 hours to obtain the concentrated solution precursor. (3) Maintain an inert and dry atmosphere, add methyl ethyl carbonate to the concentrate precursor, and perform chromatography with a fluoropyridinyl strong base anion exchange resin to obtain lithium difluorodioxarate phosphate concentrate.

[0074] 110g of a strong base anion exchange resin (201×7 anion exchange resin), 15g of o-fluorobenzoyl chloride, 0.3g of 2-fluoro-6-pyridinecarboxyl chloride (CAS: 64197-03-1), 1250g of dichloroethane, and 3g of zinc chloride were added to a polymerization reactor. The reaction temperature was controlled at 45℃, and the reaction was carried out in the dark for 15 hours. After filtration, the resin was washed with dichloroethane until no chloride ions were removed, and then dried to obtain a fluoropyridine-based strong base anion exchange resin.

[0075] The method for secondary purification using an inert, dry atmosphere is as follows: First-stage silica gel drying: Fine-pore (pore size 20 to 30 Å) silica gel with a bulk density of 0.7 g / cm³ and a gas flow rate of 6 L / min can pre-treat the initial moisture content from ≤50 ppm to ≤20 ppm.

[0076] Second-stage HKUST-1 adsorption: HKUST-1 adsorption column, filled to 30% of its volume at a gas flow rate of 6 L / min; adsorption conditions: flow rate ≤ 5 L / min, temperature 25℃, adsorption capacity ≥ 0.5 g / g MOF.

[0077] After secondary purification, the moisture content was measured to be 3.9 ppm and the oxygen content was 7.8 ppm.

[0078] A few drops of the filtrate were placed in an NMR tube, and an internal standard was added. Deuterated acetonitrile was added to dissolve the filtrate, and NMR (F-spectrum) analysis was performed. The content of the filtrate was calculated from the proportionality integral of the NMR data. The integral proportions were: lithium difluorooxalate phosphate 90%, lithium tetrafluorooxalate phosphate 8%, and lithium difluorophosphate 2%. To determine the concentration of the acid, a titration method was used, and the result was 28 ppm. The chloride ion concentration was determined using silver nitrate titration under ice-water bath conditions, and the result was 18 ppm. The moisture content was determined using a moisture analyzer, and the result was 22 ppm.

[0079] Example 4

[0080] This embodiment provides a method for preparing a lithium difluorodioxarate phosphate concentrate, which is composed of lithium difluorodioxarate phosphate and methyl ethyl carbonate; the concentration of lithium difluorodioxarate phosphate in the lithium difluorodioxarate phosphate concentrate is 35 wt%.

[0081] The preparation method of the lithium difluorodioxanol phosphate concentrate includes the following steps: (1) In a dry nitrogen atmosphere, add 100.8g of methyl ethyl carbonate, set the solvent temperature to 10℃, weigh 32.72g of lithium hexafluorophosphate and add it to the reaction flask, stir for 15min to completely dissolve the lithium hexafluorophosphate, add 38.88g of oxalic acid to the reaction flask, and keep the resulting reaction solution at 40℃. (2) After the temperature is constant, 36.59g of silicon tetrachloride is slowly added to the reaction solution dropwise (a large amount of acidic gas is generated during the dropwise process). After the dropwise addition is complete, the reaction is carried out at 40℃ for 4 hours, and then degassed under negative pressure at 5kPa and 30℃ for 3 hours to obtain the concentrated solution precursor. (3) Maintain an inert and dry atmosphere, add methyl ethyl carbonate to the concentrate precursor, and perform chromatography with a fluoropyridinyl strong base anion exchange resin to obtain lithium difluorodioxarate phosphate concentrate.

[0082] 120g of a strong base anion exchange resin (201×7 anion exchange resin), 20g of o-fluorobenzoyl chloride, 0.4g of 2-fluoro-6-pyridinecarboxyl chloride (CAS: 64197-03-1), 1500g of dichloroethane, and 4g of zinc chloride were added to a polymerization reactor. The reaction temperature was controlled at 50℃, and the reaction was carried out in the dark for 10 hours. After filtration, the resin was washed with dichloroethane until no chloride ions were removed, and then dried to obtain a fluoropyridine-based strong base anion exchange resin.

[0083] The method for secondary purification using an inert, dry atmosphere is as follows: First-stage silica gel drying: Fine-pore (pore size 20 to 30 Å) silica gel with a bulk density of 0.8 g / cm³ and a gas flow rate of 5 L / min can pre-treat the initial moisture content from ≤50 ppm to ≤20 ppm.

[0084] Second-stage HKUST-1 adsorption: HKUST-1 adsorption column, filled to 40% of its volume at a gas flow rate of 5 L / min; adsorption conditions: flow rate ≤ 5 L / min, temperature 30℃, adsorption capacity ≥ 0.5 g / g MOF.

[0085] After secondary purification, the moisture content was measured to be 3.7 ppm and the oxygen content was 7.8 ppm.

[0086] A few drops of the filtrate were transferred to an NMR tube, and an internal standard was added. Deuterated acetonitrile was added to dissolve the filtrate, and NMR (F-spectrum) analysis was performed. The proportions of the filtrate were calculated from the proportionality integral of the NMR data. The proportions of lithium difluorooxalate phosphate were 88%, lithium tetrafluorooxalate phosphate were 9%, and lithium difluorophosphate was 2%. To determine the concentration of the acid, a titration method was used, yielding a result of 35 ppm. The chloride ion concentration was determined using silver nitrate titration under ice-water bath conditions, yielding a result of 14 ppm. The moisture content was determined using a moisture analyzer, yielding a result of 19 ppm.

[0087] Example 5

[0088] This embodiment provides a method for preparing lithium difluorodioxanol phosphate concentrate. The concentration and composition of lithium difluorodioxanol phosphate concentrate are consistent with those in Example 1. The difference from Example 1 is that in the preparation method of lithium difluorodioxanol phosphate concentrate, the reaction solution in step (2) is heated to 50°C, and the remaining preparation methods and parameters are consistent with those in Example 1.

[0089] A few drops of the filtrate were transferred to an NMR tube, and an internal standard was added. Deuterated acetonitrile was added to dissolve the dissolved filtrate, and NMR (F-spectrum) analysis was performed. The content of the filtrate was calculated from the proportionality integral of the NMR data. The integral proportions of lithium difluorooxalate phosphate were 80%, lithium tetrafluorooxalate phosphate phosphate 11%, and lithium difluorophosphate 9%. To determine the concentration of the acid, a titration method was used, yielding a result of 90 ppm. The chloride ion concentration was determined using silver nitrate titration under ice-water bath conditions, yielding a result of 18 ppm. The moisture content was determined using a moisture analyzer, yielding a result of 21 ppm.

[0090] Example 6

[0091] This embodiment provides a method for preparing lithium difluorodioxanol phosphate concentrate. The concentration and composition of lithium difluorodioxanol phosphate concentrate are consistent with those in Example 1. The difference between Example 1 and Example 2 is that in the preparation method of lithium difluorodioxanol phosphate concentrate, the reaction solution in step (2) is heated to 20°C. The remaining preparation methods and parameters are consistent with those in Example 1.

[0092] A few drops of the filtrate were transferred to an NMR tube, and an internal standard was added. Deuterated acetonitrile was added to dissolve the filtrate, and NMR (F-spectrum) analysis was performed. The content of the filtrate was calculated from the proportionality integral of the NMR data. The integral proportions of lithium difluorooxalate phosphate were 70%, lithium tetrafluorooxalate phosphate phosphate 21%, and lithium difluorophosphate 9%. To determine the concentration of the acid, a titration method was used, yielding a result of 30 ppm. The chloride ion concentration was determined using silver nitrate titration under ice-water bath conditions, yielding a result of 20 ppm. The moisture content was determined using a moisture analyzer, yielding a result of 18 ppm.

[0093] Example 7

[0094] This embodiment provides a method for preparing lithium difluorodioxanol phosphate concentrate. The concentration of lithium difluorodioxanol phosphate in the concentrate is the same as in Example 1. The difference from Example 1 is that in the preparation method of lithium difluorodioxanol phosphate concentrate, the amount of silicon tetrachloride added in step (2) is 16.90g, and the rest of the preparation method and parameters are the same as in Example 1.

[0095] A few drops of the filtrate were placed in an NMR tube, and an internal standard was added. Deuterated acetonitrile was added to dissolve the filtrate, and NMR (F-spectrum) analysis was performed. The content of the filtrate was calculated from the proportionality integral of the NMR data. The integral proportions of lithium difluorooxalate phosphate were 89%, lithium tetrafluorooxalate phosphate were 8%, and lithium difluorophosphate was 3%. To determine the concentration of the acid, a titration method was used, and the result was 100 ppm. The chloride ion concentration was determined using silver nitrate titration under ice-water bath conditions, and the result was 6 ppm. The moisture content was determined using a moisture analyzer, and the result was 14 ppm.

[0096] Example 8

[0097] This embodiment provides a method for preparing lithium difluorodioxanol phosphate concentrate. The concentration of lithium difluorodioxanol phosphate in the concentrate is the same as in Example 1. The difference from Example 1 is that in the preparation method of lithium difluorodioxanol phosphate concentrate, the amount of silicon tetrachloride added in step (2) is 17.24g, and the rest of the preparation method and parameters are the same as in Example 1.

[0098] A few drops of the filtrate were transferred to an NMR tube, and an internal standard was added. Deuterated acetonitrile was added to dissolve the filtrate, and NMR (F-spectrum) analysis was performed. The content of the filtrate was calculated from the proportionality integral of the NMR data. The integral proportions were: lithium difluorooxalate phosphate 90%, lithium tetrafluorooxalate phosphate 8%, and lithium difluorophosphate 2%. To determine the concentration of the acid, a titration method was used, yielding a result of 40 ppm. The chloride ion concentration was determined using silver nitrate titration under ice-water bath conditions, yielding a result of 20 ppm. The moisture content was determined using a moisture analyzer, yielding a result of 21 ppm.

[0099] Example 9

[0100] This embodiment provides a method for preparing lithium difluorodioxanol phosphate concentrate. The concentration of lithium difluorodioxanol phosphate in the concentrate is the same as in Example 1. The difference between Example 1 and Example 2 is that the amount of oxalic acid added in step (2) of the preparation method of the lithium difluorodioxanol phosphate concentrate is 17.96g. The rest of the preparation method and parameters are the same as in Example 1.

[0101] A few drops of the filtrate were transferred to an NMR tube, and an internal standard was added. Deuterated acetonitrile was added to dissolve the filtrate, and NMR (F-spectrum) analysis was performed. The content of the filtrate was calculated from the proportionality integral of the NMR data. The integral proportions of lithium difluorooxalate phosphate were 91%, lithium tetrafluorooxalate phosphate 7%, and lithium difluorophosphate 2%. To determine the concentration of the acid, a titration method was used, and the result was 20 ppm. The chloride ion concentration was determined using silver nitrate titration under ice-water bath conditions, and the result was 20 ppm. The moisture content was determined using a moisture analyzer, and the result was 22 ppm.

[0102] Example 10

[0103] This embodiment provides a method for preparing lithium difluorodioxanol phosphate concentrate. The concentration of lithium difluorodioxanol phosphate in the concentrate is the same as in Example 1. The difference between Example 1 and Example 2 is that the amount of oxalic acid added in step (2) of the preparation method of the lithium difluorodioxanol phosphate concentrate is 18.91g. The rest of the preparation method and parameters are the same as in Example 1.

[0104] A few drops of the filtrate were placed in an NMR tube, and an internal standard was added. Deuterated acetonitrile was added to dissolve the filtrate, and NMR (F-spectrum) analysis was performed. The content of the filtrate was calculated from the proportionality integral of the NMR data. The integral proportions were: lithium difluorooxalate phosphate 92%, lithium tetrafluorooxalate phosphate 7%, and lithium difluorophosphate 1%. To determine the concentration of the acid, a titration method was used. The calculated result was 100 ppm, which translates to 5 ppm per 1% mass. The chloride ion concentration was determined using silver nitrate titration under ice-water bath conditions, and the result was 6 ppm. The moisture content was determined using a moisture analyzer, and the result was 17 ppm.

[0105] Example 11

[0106] This embodiment provides a method for preparing lithium difluorodioxanol phosphate concentrate. The concentration and composition of lithium difluorodioxanol phosphate concentrate are consistent with those in Example 1. The difference from Example 1 is that in the preparation method of lithium difluorodioxanol phosphate concentrate, in step (1), when adding lithium hexafluorophosphate, the solvent temperature is 25°C.

[0107] A few drops of the filtrate were placed in an NMR tube, and an internal standard was added. Deuterated acetonitrile was added to dissolve the filtrate, and NMR (F-spectrum) analysis was performed. The content of the filtrate was calculated from the proportionality integral of the NMR data. The integral proportions of lithium difluorooxalate phosphate were 89%, lithium tetrafluorooxalate phosphate 9%, and lithium difluorophosphate 2%. To determine the concentration of the acid, a titration method was used, and the calculated result was 97 ppm. The chloride ion concentration was determined using silver nitrate titration under ice-water bath conditions, and the result was 11 ppm. The moisture content was determined using a moisture analyzer, and the result was 50 ppm.

[0108] Example 12

[0109] This embodiment provides a method for preparing lithium difluorodioxarate phosphate concentrate. The concentration and composition of lithium difluorodioxarate phosphate concentrate are consistent with those in Example 1. The difference from Example 1 is that the temperature in step (2) of the preparation method of lithium difluorodioxarate phosphate concentrate is 50°C.

[0110] A few drops of the filtrate were placed in an NMR tube, and an internal standard was added. Deuterated acetonitrile was added to dissolve the filtrate, and NMR (F-spectrum) analysis was performed. The content of the filtrate was calculated from the proportionality integral of the NMR data. The integral proportions of lithium difluorooxalate phosphate were 87%, lithium tetrafluorooxalate phosphate 9%, and lithium difluorophosphate 4%. To determine the concentration of the acid, a titration method was used, and the calculated result was 60 ppm. The chloride ion concentration was determined using silver nitrate titration under ice-water bath conditions, and the result was 11 ppm. The moisture content was determined using a moisture analyzer, and the result was 50 ppm; the color was also greater than 50.

[0111] The test results show that: (1) As can be seen from Examples 1 to 9, the acidity of the lithium difluorodioxanol phosphate concentrate is ≤100 ppm, the chloride ion content is ≤20 ppm, and the water content is ≤50 ppm. More preferably, as can be seen from Examples 1 to 4, by controlling the amount of reaction raw materials added and the reaction temperature, the acidity of the lithium difluorodioxanol phosphate concentrate is ≤20 ppm, the chloride ion content is ≤5 ppm, and the water content is ≤15 ppm.

[0112] (2) As can be seen from Examples 7 and 8, if the amount of silicon tetrafluoride added is large, there are side reactions in the reaction system, resulting in a high acidity of the prepared lithium difluorooxalate phosphate concentrate, and the silicon tetrachloride in the concentrate cannot be completely removed, resulting in a high chloride ion content.

[0113] (3) As can be seen from Examples 9 and 10, if the amount of oxalic acid added is small, some silicon tetrafluoride does not participate in the reaction, resulting in a high chloride ion content in the prepared lithium difluorooxalate phosphate concentrate; if the amount of oxalic acid added is large, some oxalic acid does not participate in the reaction, and the remaining oxalic acid cannot be completely removed, resulting in a high acidity in the prepared lithium difluorooxalate phosphate concentrate.

[0114] (4) As can be seen from Examples 1 and 11, when the temperature of adding lithium hexafluorophosphate is too high, it will lead to the hydrolysis of lithium hexafluorophosphate, resulting in an increase in its acidity. The prepared lithium difluorooxalate phosphate concentrate has a high acidity and a decrease in purity.

[0115] (5) As can be seen from Examples 1 and 12, when the degassing temperature is too high, the prepared lithium difluorodioxanol phosphate concentrate has a higher color. At the same time, high temperature will cause the decomposition of lithium difluorodioxanol phosphate, resulting in increased acidity and decreased purity.

[0116] In summary, the lithium difluorodioxanol phosphate concentrate provided by this invention exists in a non-proton electrolyte state, with low acidity, low chlorine content, and high purity, and can be directly used in the preparation of electrolytes for lithium-ion or sodium-ion batteries. The preparation of the lithium difluorodioxanol phosphate concentrate eliminates the evaporation and crystallization process, reducing production costs. In addition, it can be transported through pipelines, further reducing product transportation costs. Compared with solid lithium difluorodioxanol phosphate, the process of redissolving during use is omitted, avoiding the risk of introducing impurities and greatly reducing usage costs.

[0117] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a concentrated lithium difluorodioxanol phosphate solution, characterized in that, Includes the following steps: (1) In an inert and dry atmosphere, lithium hexafluorophosphate, aprotic solvent and oxalic acid are mixed evenly to obtain a reaction solution. After drying, the moisture content of the oxalic acid is required to be ≤200ppm. (2) Maintain an inert and dry atmosphere, add silicon tetrachloride dropwise into the reaction solution described in step (1) to carry out the reaction, and after degassing, obtain the concentrated liquid precursor; (3) Maintain an inert and dry atmosphere and treat the concentrate precursor in step (2) with an ion exchange resin to remove acid, thereby obtaining lithium difluorooxalate phosphate concentrate.

2. The method for preparing a lithium difluorodioxanol phosphate concentrate according to claim 1, characterized in that: In step (1), the mass ratio of lithium hexafluorophosphate to the aprotic solvent is 1:(2~20).

3. The method for preparing a lithium difluorodioxanol phosphate concentrate according to claim 1, characterized in that: In step (1), the molar ratio of lithium hexafluorophosphate to oxalic acid is 1:(1.995~2.100).

4. The method for preparing a lithium difluorodioxanol phosphate concentrate according to claim 1, characterized in that: The mixing in step (1) includes: first dissolving lithium hexafluorophosphate in a non-protic solvent, and then adding oxalic acid; The temperature of the reaction solution in step (1) is -20~50℃, and the temperature of the reaction system during the feeding of lithium hexafluorophosphate is -20~25℃.

5. The method for preparing a lithium difluorodioxanol phosphate concentrate according to claim 1, characterized in that: The molar ratio of lithium hexafluorophosphate in step (1) to silicon tetrachloride in step (2) is 1:(0.995~1.100), and it is added by surface dropping.

6. The method for preparing a lithium difluorodioxanol phosphate concentrate according to claim 1, characterized in that: The reaction temperature in step (2) is -5~60℃, and the reaction time is 1~8h.

7. The method for preparing a lithium difluorodioxanol phosphate concentrate according to claim 1, characterized in that: The resin used in the acid removal treatment of the perion exchange resin in step (3) includes a strong basic anion exchange resin and / or a weak basic anion exchange resin. The strongly basic anion exchange resin is subjected to fluorination treatment to prepare a fluoropyridinyl strongly basic anion exchange resin, as detailed below: By weight, add 100-120 parts of strong basic anion exchange resin, 10-20 parts of o-fluorobenzoyl chloride, 0.05-0.4 parts of 2-fluoro-6-pyridinecarboxyl chloride, 1000-1500 parts of dichloroethane, and 2-4 parts of zinc chloride to the polymerization reactor. Control the reaction temperature at 40-50℃ and react in the dark for 10-20 hours. Filter, wash with dichloroethane until no chloride ions are present, and dry to obtain fluoropyridine-based strong basic anion exchange resin. The strongly basic anion exchange resin includes: D201: macroporous strongly basic styrene-based anion exchange resin, D202: macroporous type II strongly basic anion exchange resin, and 201×7 anion exchange resin. The weakly basic anion exchange resins include: D301 macroporous weakly basic anion exchange resin, D311 macroporous weakly basic acrylic anion exchange resin, and Amberlite IRA-45 macroporous weakly basic anion exchange resin.

8. The method for preparing a lithium difluorodioxanol phosphate concentrate according to claim 1, characterized in that: Step (3) Before the reaction begins, the introduced inert, dry atmosphere is subjected to secondary purification: First stage: Removing most of the moisture from the gas using silica gel desiccant; Second stage: Using the HKUST-1 metal-organic framework adsorption column, moisture is selectively adsorbed by utilizing its porous structure and copper ion coordination, reducing the moisture content in the gas to ≤5ppm. The metal-organic framework material HKUST-1 has a specific surface area ≥1500m² / g and an adsorption capacity ≥0.5g / g MOF.

9. The method for preparing a lithium difluorodioxanol phosphate concentrate according to claim 1, characterized in that: The lithium difluorodioxanol phosphate concentrate is composed of lithium difluorodioxanol phosphate and an aprotic solvent, wherein the aprotic solvent includes any one or a combination of at least two of diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, or propylene carbonate; the concentration of lithium difluorodioxanol phosphate in the lithium difluorodioxanol phosphate concentrate is 10~35wt%; the acidity of the lithium difluorodioxanol phosphate concentrate is <100ppm, the water content is <50ppm, and the chloride ion concentration is <20ppm.

10. An application of a lithium difluorodioxazone phosphate concentrate, characterized in that, The lithium difluorodioxazophosphate concentrate prepared by the preparation method according to any one of claims 1-9 is used to formulate a non-aqueous electrolyte for lithium-ion batteries or sodium-ion batteries.

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