Fluorine-containing acetal ester electrolyte additive and synthesis method thereof

Abstract

The invention discloses a fluorine-containing acetal ester electrolyte additive and a synthesis method thereof, and belongs to the technical field of electrolyte solvent or additive synthesis processes. Through synergistic reaction of an acidic oxide catalyst, a fluorine-containing organic acid compound and an aldehyde compound in a specific solvent, the fluorine-containing acetal ester compound with a novel structure and a purity of more than 99% is successfully synthesized under specific conditions. According to the method, resource utilization of a system after reaction is innovatively achieved, the acidic oxide catalyst is converted into a high-purity inorganic acid byproduct through hydration conversion, and the concept of green chemistry is embodied. By flexibly adjusting the types of organic acid compounds and aldehyde compounds, the type and dosage of the catalyst and reaction parameters, the product structure can be effectively regulated and controlled, so that a series of fluorine-containing acetal ester derivatives with potential application value and corresponding inorganic acid products are obtained.

Description

Technical Field

[0001] This invention relates to the field of electrolyte solvent or additive synthesis technology, and in particular to a fluorinated acetal ester electrolyte additive and its synthesis method. Background Technology

[0002] The electrolyte of a lithium-ion battery mainly consists of lithium salt, solvent, and additives. The solvent's primary function is to provide ion transport channels, allowing lithium ions to cycle between the positive and negative electrodes. It also participates in the formation of the solid electrolyte interphase (SEI) film on the electrode surface. Furthermore, the solvent not only dissolves the lithium salt but also provides excellent ion transport performance, thereby improving the battery's energy density and power density. Additives, although used in the smallest quantity, have a crucial impact on battery performance. As lithium batteries pursue higher voltage and higher specific capacity, a series of problems arise. Firstly, they can cause chemical instability at the electrode / electrode solution interface, leading to electrode solution decomposition, increased interfacial film impedance, and capacity decay. Secondly, transition metal ions can dissolve at the positive electrode, causing not only positive electrode material failure but also migration of these dissolved transition metal ions to the negative electrode, affecting the formation of the SEI film and ultimately impacting battery performance.

[0003] Carboxylic esters possess numerous advantages, making them ideal solvents for electrolytes. Firstly, they exhibit high ionic conductivity, enabling the electrolyte to efficiently transfer charge and allowing for the formation of a stable solid electrolyte interphase (SEI) film on the negative electrode surface, thus increasing electrode stability. Secondly, their low viscosity reduces internal battery resistance, enhancing battery performance. Furthermore, carboxylic esters demonstrate excellent solubility and stability, effectively compatibility with other components, and resistance to decomposition.

[0004] Adding phosphate esters to the electrolyte helps form a stable and dense SEI film on the electrode surface, inhibiting further decomposition of the electrolyte and significantly improving coulombic efficiency. Even after long-term cycling, it still has a high capacity retention. Due to the electron-donating properties of phosphorus atoms, the passivation film formed is beneficial for lithium-ion transport.

[0005] Sulfonate esters can act as solvents and conductive agents, facilitating ion transport in the electrolyte and improving its conductivity, thereby enhancing battery performance and charge / discharge efficiency. Sulfonate esters also improve electrolyte stability, reduce internal resistance, and extend battery life. As additives, sulfonate esters stabilize the electrolyte, forming complexes with metal ions such as lithium ions to prevent their deposition and precipitation. This inhibits dendrite growth and instability at the solid electrolyte interface, improving battery safety and cycle life. Furthermore, sulfonate esters improve interfacial properties, promoting the transport and reaction of lithium ions between the electrode and electrolyte, thus increasing energy density and power density.

[0006] The introduction of fluorine results in a higher fluorine content in the electrolyte. The strong electron-withdrawing ability of fluorine atoms contributes to the electrolyte's high oxidation stability, thereby significantly improving its high-pressure resistance.

[0007] Existing technical data on obtaining carboxylic acid esters / phosphate esters / sulfonates show that there are one or more of the following factors that are unfavorable to industrial production: the raw materials used contain corrosive, highly toxic, or precursor chemicals, the reaction is complex, the yield is low, and the purity is low; at the same time, the proportion of fluorine or ester groups in the above esters is relatively small, resulting in some deficiencies in their performance.

[0008] Therefore, there is a need for a fluorinated acetal ester electrolyte additive and its synthesis method to overcome the above-mentioned shortcomings and problems in the existing technology, simplify the process, increase the content of effective groups, and improve the yield and purity, so as to be more suitable for the industrial production of carboxylic acid acetal esters, phosphate acetal esters and sulfonic acid acetal esters. Summary of the Invention

[0009] This invention overcomes the shortcomings of existing technologies and solves the technical problems of raw materials containing corrosive, highly toxic, or precursor chemicals, complex reactions, low yields, and low purity. It provides a fluorinated acetal ester electrolyte additive and its synthesis method, which is a method that does not involve highly toxic chemical raw materials, has high atom utilization, and produces high-purity products. The process is simple, easy to operate, and more suitable for industrial production of acetal esters.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a fluorinated acetal ester electrolyte additive and its synthesis method, comprising the following steps:

[0011] S1, provides organic acid compounds, aldehydes, acidic oxides, and solvents.

[0012] S2. At a temperature of 80℃ to 150℃, organic acid compounds, aldehydes, acidic oxides and solvents are reacted in a reaction vessel for 8 to 12 hours to generate the target product.

[0013] S3. Filter or separate to obtain an organic system and an acidic oxide system. After removing the solvent by rotary evaporation, the organic system is purified by distillation, washing, extraction, or pulping to obtain a fluorinated acetal ester electrolyte solvent or additive with a purity >99%. Add excess water to the acidic oxide system to completely hydrate it, and then purify it by pulping or vacuum distillation to obtain an inorganic acid byproduct with a purity >99%.

[0014] In a preferred embodiment of the present invention, the fluorinated acetal ester is of formula I, II or III, and has the following structural formula:

[0015]

[0016] Formula I Formula II Formula III

[0017] Where R1, R2, and R3 are C1~C 12 One or more combinations of fluorinated hydrocarbon groups, structural formula

[0018] as follows:

[0019] .

[0020] In a preferred embodiment of the present invention, the organic acid compound is one or more of organic carboxylic acids, organic phosphorus / phosphonic acids, and organic sulfonic acids;

[0021] The organic acid compound is one or more of the following: 2-fluoroacetic acid, difluoroacetic acid, trifluoroacetic acid, 2-fluoropropionic acid, 3-fluoropropionic acid, 2,2-difluoropropionic acid, 3,3-difluoropropionic acid, 3,3,3-trifluoropropionic acid, 2,3,3,3-tetrafluoropropionic acid, 2,2,3,3-tetrafluoropropionic acid, pentafluoropropionic acid, heptafluorobutyric acid, difluoromalonic acid, 2-fluoromalonic acid, mono(2-fluoro)ethyl phosphate, mono(2,2-difluoro)ethyl phosphate, mono(2,2,2-trifluoro)ethyl phosphate, bis(2-fluoro)ethyl phosphate, bis(2,2-difluoro)ethyl phosphate, bis(2,2,2-trifluoro)ethyl phosphate, monofluoromethyl diphosphonic acid, difluoromethyl diphosphonic acid, methylene diphosphonic acid, monofluoromethyl disulfonic acid, difluoromethyl disulfonic acid, and methylene disulfonic acid.

[0022] In a preferred embodiment of the present invention, the aldehyde is one or more of the following: trioxymethylene, paraoxymethylene, trioxymethylene, tetraoxymethylene, propionaldehyde, isobutyraldehyde, butyraldehyde, pentanal, hexanal, decanal, and furfural.

[0023] In a preferred embodiment of the present invention, the acidic oxide is phosphorus pentoxide or boron trioxide.

[0024] In a preferred embodiment of the present invention, the phosphorus pentoxide is loaded within the pores of a porous support, wherein the porous support is a molecular sieve.

[0025] In a preferred embodiment of the present invention, the solvent is one or more of 1,2-dichloroethane, ethyl acetate, toluene, acetonitrile, tetrahydrofuran, 1,4-dioxane, ethylene glycol dimethyl ether, and N,N-dimethylformamide.

[0026] In a preferred embodiment of the present invention, the molar ratio of the carbonyl group of the aldehyde to the H+ of the organic acid compound is 1:2.1 to 1:2.5; the amount of the acidic oxide is 1.1 to 1.5 times the amount of the acidic oxide that reacts completely with the generated water.

[0027] In a preferred embodiment of the present invention, the solvent used for washing, extraction or pulping purification is one or more of water, dichloromethane, 1,2-dichloroethane, ethyl acetate, toluene, acetonitrile, tetrahydrofuran, acetone, petroleum ether, 1,4-dioxane, ethylene glycol dimethyl ether, and diethyl ether.

[0028] In a preferred embodiment of the present invention, the fluorinated acetal is a carboxylic acid acetal, a phosphate acetal, or a sulfonic acid acetal.

[0029] This invention addresses the shortcomings of the prior art and has the following beneficial effects:

[0030] This invention provides a method for synthesizing fluorinated acetals using electrolyte solvents or additives. By reacting organic acid compounds, aldehydes, and acidic oxides at a specific temperature, and utilizing the acidic oxides as dehydrating agents to promote the forward reaction, this method effectively avoids the safety and environmental risks associated with the use of highly toxic, corrosive, or precursor chemicals in traditional processes. This technical solution not only simplifies the reaction pathway but also significantly improves atom utilization and reaction efficiency by precisely controlling the molar ratio of reactants and the amount of acidic oxides, resulting in a stable yield of over 80% and a purity of over 99.5% for the target product. Compared to existing technologies that often suffer from low yields and insufficient purity due to complex side reactions and difficult product separation, this invention achieves efficient and highly selective synthesis of fluorinated acetals under mild conditions, providing a safe, environmentally friendly, and economical route for industrial production.

[0031] This invention further specifies that the acidic oxide is phosphorus pentoxide or boron trioxide, and innovatively proposes to load phosphorus pentoxide into the pores of a porous molecular sieve support, utilizing the shape-selective effect of the molecular sieve to achieve selective removal of water in the reaction system. This design cleverly avoids the side reactions such as the formation of fluoroanhydrides that may occur when phosphorus pentoxide directly contacts fluorine-containing organic acids, because the pore size of the molecular sieve allows small water molecules to diffuse rapidly into the pores and be captured by phosphorus pentoxide, while larger fluorine-containing organic acid molecules are effectively blocked from entering, thus significantly suppressing the occurrence of competitive side reactions while ensuring the dehydration effect. Compared with the defects of the prior art, such as the decrease in product purity and the complexity of post-processing caused by the direct use of strong dehydrating agents, this invention, through the application of a supported dehydrating agent, not only improves the selectivity of the reaction and the purity of the product, but also enhances the controllability and stability of the process, and is particularly suitable for highly active fluorine-containing raw material systems that are sensitive to side reactions.

[0032] The synthesis method described in this invention employs multiple techniques in the purification stage, including rotary evaporation combined with distillation, washing extraction, or pulping. It also hydrates the acidic oxide byproduct system to further recover high-purity inorganic acid byproducts, achieving resource recycling. This closed-loop process design significantly reduces emissions of waste gas, wastewater, and solid waste, improving the overall greenness and economic efficiency of the production process. Compared to traditional methods that often neglect byproduct recovery or suffer from high treatment costs, this invention not only achieves electronic-grade purity for the main product but also enables high-value utilization of byproducts, thereby improving the overall atom economy and environmental friendliness of the process, meeting the high requirements of current green chemistry and sustainable development.

[0033] Furthermore, the fluorinated acetal compound synthesized by the method described in this invention simultaneously introduces fluorine atoms and an acetal structure into its molecule, effectively combining the high oxidation stability brought by fluorine with the good solubility and film-forming ability of ester groups. As an electrolyte solvent or additive, this type of compound can significantly improve the high-voltage performance, ionic conductivity, and electrode interface stability of batteries, thereby improving the energy density, cycle life, and safety performance of batteries. Compared with existing ester compounds whose performance improvement is limited due to the low proportion of fluorine or ester groups, the fluorinated acetal ester provided by this invention fills a gap in the market for this high-performance material, providing key material support for the development of next-generation high-performance lithium-ion batteries. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is a flowchart of a fluorinated acetal ester electrolyte additive and its synthesis method according to the present invention;

[0036] Figure 2 These are gas chromatograms comparing the reaction products of Examples 3 and 5 of this invention;

[0037] Figure 3 This is a comparison of the infrared spectra of the catalyst system after the simulated reaction of this invention. Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein. Therefore, the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0040] In the description of this application, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the scope of protection of this application. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0041] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art will understand the specific meaning of the above terms in this application based on the specific circumstances.

[0042] Unless otherwise specified in the following examples, all raw materials are commercially available or prepared by conventional methods in the art.

[0043] like Figure 1 As shown, a fluorinated acetal ester electrolyte additive and its synthesis method include the following steps:

[0044] S1, provides organic acid compounds, aldehydes, acidic oxides, and solvents.

[0045] S2. At a temperature of 80℃ to 150℃, organic acid compounds, aldehydes, acidic oxides and solvents are reacted in a reaction vessel for 8 to 12 hours to generate the target product.

[0046] S3. Filter or separate to obtain an organic system and an acidic oxide system. After removing the solvent by rotary evaporation, the organic system is purified by distillation, washing, extraction, or pulping to obtain a fluorinated acetal ester electrolyte solvent or additive with a purity >99%. Add excess water to the acidic oxide system to completely hydrate it, and then purify it by pulping or vacuum distillation to obtain an inorganic acid byproduct with a purity >99%.

[0047] Each step will be explained in detail below.

[0048] Specifically, step S1 aims to prepare all the raw materials required for the reaction. The "organic acid compound", "aldehyde", "acid oxide" and "solvent" are the basic components of the reaction system (some reactions do not require solvent), and their properties and proportions directly affect the progress and result of the subsequent reaction.

[0049] Furthermore, the acidic oxide catalyst is selected from phosphorus pentoxide and boron trioxide. These acidic oxides play a dual role in the reaction: firstly, they provide Brønsted acid sites, catalyzing reactions such as condensation and esterification between aldehyde groups and potentially active intermediates formed by organic acid compounds in the reaction system; secondly, as highly efficient dehydrating agents, they combine with water molecules generated in the reaction, driving the chemical equilibrium towards the formation of the target fluorinated acetal, significantly improving the reaction conversion rate.

[0050] Further, the organic acid compound is selected from one or more of difluoromalonic acid and trifluoroacetic acid. Organic acid compounds are one of the key raw materials for constructing the target fluorinated acetal molecular skeleton. Their fluorinated groups (such as the fluorine atoms in difluoromalonic acid and trifluoroacetic acid) or specific structures directly affect the performance of the final product, such as thermal stability, electrochemical stability, and compatibility with electrolytes. The aldehyde compound is selected from one or more of paraformaldehyde, paraformaldehyde, tetraacetaldehyde, and propionaldehyde. Aldehydes provide carbonyl groups, participating in the formation of the core structure of the target molecule. The solvent is selected from one or more of acetonitrile, tetrahydrofuran, 1,4-dioxane, toluene, and N,N-dimethylformamide. The main function of the solvent is to dissolve or disperse the reactants and provide a homogeneous reaction environment; its polarity and boiling point have a significant impact on the reaction rate and subsequent processing.

[0051] Furthermore, step S2 is the core reaction stage of this invention. The phrases "at a temperature of 80°C to 150°C" and "reacting for 8 to 12 hours" clearly define the key process parameters for the reaction. These conditions are designed to ensure that the reaction proceeds fully and efficiently to generate the target product.

[0052] Further, step S3 involves the separation and purification of the post-reaction products. Through filtration or separation, the post-reaction mixture is initially separated into an "organic system" (mainly containing the target product and solvent) and an "acidic oxide system" (mainly containing unreacted acidic oxide catalyst). The "organic system" undergoes post-processing, first by removing the solvent through rotary evaporation, and then, depending on the product properties, one or more methods are selected from "distillation, washing extraction, or pulping purification" to ultimately obtain the target product, "fluorinated acetal ester electrolyte solvent or additive," with a purity greater than 99%.

[0053] Fluorinated acetals, such as those of formula I, II, or III, have the following structural formulas:

[0054]

[0055] Formula I Formula II Formula III

[0056] Where R1, R2, and R3 are C1~C 12 One or more combinations of fluorinated hydrocarbon groups, with the following structural formula:

[0057] .

[0058] Explanation of the principle: Taking carboxylic acid acetals as an example, the reaction mechanism is as follows:

[0059] ;

[0060] After the carboxylic acid ionizes to release a proton, the aldehyde undergoes an addition reaction with the carboxylic acid under the action of the proton to produce an alcohol. Subsequently, the alcohol undergoes an elimination reaction with the carboxylic acid under proton catalysis. The addition of acidic oxides consumes the water generated, promoting the forward reaction.

[0061] Meanwhile, the "acidic oxide system" is treated for resource utilization by "adding excess water to fully hydrate it" and converting it into the corresponding inorganic acid. Then, through "pulping purification or vacuum distillation", "inorganic acid by-products" with a purity greater than 99% are obtained, realizing the conversion and high-value utilization of the catalyst, which is in line with the principles of green chemistry.

[0062] The organic combination of the above three steps constitutes the complete synthesis process described in this invention. This process not only efficiently prepares the high-purity target product but also realizes the resource utilization of waste. The following examples will specifically demonstrate how to implement the above steps and obtain the expected results.

[0063] In all embodiments and comparative examples of the present invention, the methods for measuring and calculating each performance parameter are as follows:

[0064] Gas chromatography-mass spectrometry (GC-MS) and gas chromatography (GC) analysis: A gas chromatograph equipped with a flame ionization detector (FID) and a mass spectrometer was used. A capillary column was selected. Temperature program: initial temperature 50°C, hold for 3 min, increase to 200°C at 10°C / min, hold for 5 min. Injector temperature 250°C, detector temperature 280°C, high-purity helium as carrier gas.

[0065] Nuclear magnetic resonance (NMR) analysis: A superconducting NMR spectrometer was used with deuterated chloroform (CDCl3) as solvent and TMS as internal standard. 1 H-NMR and Testing was conducted to confirm the product structure.

[0066] Moisture and inorganic acid purity analysis: Trace moisture was determined using a Karl Fischer moisture analyzer; the purity of inorganic acids (phosphoric acid, boric acid) was determined by acid-base titration or ion chromatography.

[0067] The yield of the target fluoroacetal was calculated based on the molar amount of the main raw material (organic acid compound). After the reaction, the target product obtained by separation and purification in step S3 was weighed and its purity was determined by GC.

[0068] ;

[0069] in,

[0070] Mass (g) of the fluorinated acetal product obtained after purification;

[0071] Product purity (%) determined by GC area normalization method;

[0072] : The molar amount (mol) of the organic acid compound added to the reaction;

[0073] The theoretical molar mass (g / mol) of the target fluoroacetal.

[0074] Fluoroanhydride, as the main byproduct, is determined by gas chromatography (GC); the content of fluoroanhydride is calculated as the percentage of the characteristic peak area of ​​fluoroanhydride in the chromatogram relative to the total area of ​​all eluted peaks.

[0075] Fluorine resource retention rate characterizes the extent to which fluorine in the feedstock is effectively transferred to the target product, reflecting atom economy. The calculation formula is as follows:

[0076] ;

[0077] in,

[0078] : The actual molar amount (mol) of the fluorinated acetal product generated.

[0079] The number of fluorine atoms in the molecular formula of the target product;

[0080] : The molar amount (mol) of the organic acid compound added to the reaction.

[0081] The number of fluorine atoms in the molecular formula of an organic acid compound.

[0082] The dehydrating agent utilization efficiency is used to characterize the extent to which acidic oxides actually participate in the water absorption reaction during the reaction process. It is calculated based on the ratio of the amount of water generated in the reaction to the theoretical water absorption capacity of the added dehydrating agent.

[0083] ;

[0084] in,

[0085] The molar amount (mol) of water produced, calculated based on the actual yield of the target product and the stoichiometric ratio of the reaction (usually 1:1).

[0086] : The molar amount (mol) of the acidic oxide added.

[0087] K: Theoretical water absorption coefficient of the dehydrating agent.

[0088] Example 1:

[0089] A fluorinated acetal ester electrolyte additive and its synthesis method, comprising the following steps:

[0090] S1. Add 1.5 mol difluoromalonic acid, 1.2 mol paraformaldehyde, 0.45 mol phosphorus pentoxide and 15.3 mol acetonitrile to a dry 1000 ml reaction vessel;

[0091] S2. Place the above materials in a reaction vessel and stir at 90°C for 10 hours. GC-MS analysis showed that no paraformaldehyde was detected, and the target product was generated.

[0092] S3. After the reaction is complete, the organic system and the phosphorus pentoxide system are separated by filtration. The organic system is rotary evaporated to remove the solvent acetonitrile, and then purified by vacuum distillation to obtain a fluorinated acetal product with a yield of 91.6%, a fluoro anhydride content of 0.35%, a fluorine resource retention rate of 94.2%, and a dehydrating agent utilization efficiency of 81.5%. 6g of water is added to the phosphorus pentoxide system and reacted for 1 hour, followed by vacuum distillation to obtain a phosphoric acid byproduct with a yield of 82.4% and a purity of 97.5%.

[0093] Example 2:

[0094] S1. Add 1.5 mol difluoromalonic acid, 1.2 mol paraformaldehyde, 0.45 mol boron trioxide and 15.3 mol acetonitrile to a dry 1000 ml reaction vessel;

[0095] S2. Place the above materials in a reaction vessel and stir at 90°C for 10 hours. GC-MS analysis showed that no paraformaldehyde was detected, and the target product was generated.

[0096] S3. After the reaction is complete, the organic system and the boron trioxide system are separated by filtration. The organic system is rotary evaporated to remove the solvent acetonitrile, and then purified by vacuum distillation to obtain a fluorinated acetal product with a yield of 80.3%, a fluoro anhydride content of 0.28%, a fluorine resource retention rate of 95.1%, and a dehydrating agent utilization efficiency of 71.1%. 5g of water is added to the boron trioxide system and reacted for 1 hour, followed by vacuum distillation to obtain a boric acid byproduct with a yield of 85.0% and a purity of 98.1%.

[0097] Comparative Example 1:

[0098] S1. Add 1.5 mol of difluoromalonic acid, 3.0 mol of paraformaldehyde and 15.3 mol of acetonitrile (without adding acidic oxide catalyst) to a dry 1000 ml reactor.

[0099] S2. Place the above materials in a reaction vessel and stir at 90°C for 10 hours;

[0100] S3. After the reaction was completed, the mixture was filtered to obtain a filtrate and a small amount of solid. The filtrate was rotary evaporated to remove the solvent acetonitrile. GC-MS and NMR analyses of the residues showed no characteristic peaks of the target acetal ester; only unreacted acetic acid, formaldehyde, and their oligomers were detected. The solid, after washing and drying, showed no obvious product. The results indicate that the reaction cannot proceed effectively without an acidic oxide catalyst and a specific fluorinated organic acid.

[0101] Example 3:

[0102] S1. Add 1.5 mol trifluoroacetic acid, 0.6 mol paraformaldehyde, 0.25 mol phosphorus pentoxide and 15.3 mol acetonitrile to a dry 1000 ml reaction vessel;

[0103] S2. Place the above materials in a reaction vessel and stir at 90°C for 10 hours. GC-MS analysis showed that no paraformaldehyde was detected, and the target product was generated.

[0104] S3. After the reaction is complete, the organic system and the phosphorus pentoxide system are separated by filtration. The organic system is rotary evaporated to remove the solvent acetonitrile, and then purified by vacuum distillation to obtain a fluorinated acetal product with a yield of 91.4%, a fluoro anhydride content of 0.48%, a fluorine resource retention rate of 92.8%, and a dehydrating agent utilization efficiency of 73.3%. 6g of water is added to the phosphorus pentoxide system and reacted for 1 hour, followed by vacuum distillation to obtain a phosphoric acid byproduct with a yield of 81.5% and a purity of 97.2%.

[0105] Example 4:

[0106] S1. Add 1.5 mol trifluoroacetic acid, 0.6 mol paraformaldehyde, 0.25 mol boron trioxide and 15.3 mol acetonitrile to a dry 1000 ml reaction vessel;

[0107] S2. Place the above materials in a reaction vessel and stir at 90°C for 10 hours. GC-MS analysis showed that no paraformaldehyde was detected, and the target product was generated.

[0108] S3. After the reaction is complete, the organic system and the boron trioxide system are separated by filtration. The organic system is rotary evaporated to remove the solvent acetonitrile, and then purified by vacuum distillation to obtain a fluorinated acetal product with a yield of 83.2%, a fluoro anhydride content of 0.31%, a fluorine resource retention rate of 94.5%, and a dehydrating agent utilization efficiency of 66.7%. 5g of water is added to the boron trioxide system and reacted for 1 hour, followed by vacuum distillation to obtain a boric acid byproduct with a yield of 83.0% and a purity of 98.0%.

[0109] Comparing Examples 1 and 3 (pure phosphorus pentoxide) and Examples 2 and 4 (pure boron trioxide), although pure acidic oxides could drive the reaction, "fluorinated anhydride" impurities (content 0.28%~0.48%) were detected in all cases, and the fluorine resource retention rate was less than 96%. This confirms the defects mentioned in the background art: direct contact between the strong dehydrating agent and the fluorinated organic acid leads to unavoidable side reactions, and passivation of the dehydrating agent surface results in low utilization efficiency (only 60%~70%).

[0110] Furthermore, the results of Comparative Example 1 show that when neither an acidic oxide catalyst nor fluorine-free ordinary acetic acid was added to the system, the target fluorinated acetal product was ultimately not obtained, and the inorganic acid byproduct could not be recovered. This fully demonstrates that both the acidic oxide catalyst and the specific fluorinated organic acid compound are indispensable in the method of this invention, and there is a significant synergistic effect between them. The acidic oxide catalyst is the driving force for the reaction, while the fluorinated organic acid is an indispensable fluorine source and reactant for constructing the molecular skeleton of the target product. Without either element, the reaction cannot proceed effectively towards the formation of a high-purity target product, and the value of recovering high-purity inorganic acid byproducts is also lost.

[0111] The following experiment introduces phosphorus pentoxide supported on molecular sieves as an acidic oxide, and its preparation method includes the following steps:

[0112] S1. Pretreatment of molecular sieve support:

[0113] All-silica MCM-41 molecular sieve with the following physical properties: average pore size 3.5 nm, specific surface area greater than 850 m² / g, and pore volume not less than 0.80 cm³ / g. The molecular sieve was placed in a vacuum environment and heated to 280 °C under a pressure of 90 Pa, and maintained at this temperature and vacuum for 10 hours to completely remove adsorbed and bound water from the pores and surface, obtaining a deeply dehydrated activated carrier. After activation, the carrier was cooled to 70 °C while maintaining a vacuum, and then an inert protective gas was introduced into the system to atmospheric pressure. The resulting activated carrier was then transferred to an inert atmosphere for storage.

[0114] S2. Mixing and melt impregnation of active components and carrier:

[0115] Under an inert atmosphere, the activated MCM-41 carrier obtained in step S1 was weighed with phosphorus pentoxide powder at a mass ratio of 9:1. The two were placed in a mortar and gently mechanically ground and mixed under an inert atmosphere until a uniform powder was obtained.

[0116] The mixed powder is transferred to a high-temperature reaction apparatus that can be purged with a protective gas, and heat-treated according to a preset procedure under the protection of a continuously flowing inert gas:

[0117] First, heat the temperature to 200°C at a rate of 5°C / min and hold for 30 minutes.

[0118] Subsequently, the temperature was increased to 340°C at a rate of 3°C / min and maintained at this temperature for 2 hours. During this stage, phosphorus pentoxide melted and, under capillary force, penetrated into the mesoporous channels of the MCM-41 carrier.

[0119] S3. Cooling and Post-treatment:

[0120] After the melt impregnation step is completed, the material is allowed to cool naturally to room temperature under a continuously flowing inert gas atmosphere. The cooled solid material is then gently crushed under an inert atmosphere to obtain a white to pale yellow powder, which is the supported dehydrating agent (labeled P2O5 / MCM-41). The product is sealed and stored in a dry, anhydrous, and oxygen-free environment.

[0121] Preferably, the inert gas mentioned in steps S1, S2 and S3 is high-purity nitrogen or argon.

[0122] The raw materials for preparation are described as follows: MCM-41 molecular sieve: product number M196708-100g, average pore size 3.5nm, specific surface area greater than 850m² / g, pore volume not less than 0.80cm³ / g, purchased from Shanghai Aladdin Biochemical Technology.

[0123] To verify whether the above preparation steps successfully loaded phosphorus pentoxide into the mesoporous channels of MCM-41 molecular sieve and to confirm the integrity of the support framework structure, the obtained supported dehydrating agent (P2O5 / MCM-41) was subjected to the following tests:

[0124] The specific surface area and pore structure of the molecular sieve support before and after loading were analyzed using nitrogen adsorption-desorption tests. The unloaded all-silica MCM-41 molecular sieve had a BET specific surface area of ​​895 m² / g and a total pore volume of 0.82 cm³ / g, with the pore size distribution concentrated around 3.5 nm. After loading with phosphorus pentoxide, the specific surface area decreased to 623 m² / g, and the total pore volume decreased to 0.58 cm³ / g, while the pore size distribution curve maintained its original characteristic peak shape, indicating that phosphorus pentoxide successfully entered the molecular sieve channels without causing structural blockage. Mercury intrusion porosimetry showed that the macropore volume of the loaded sample remained essentially unchanged, further proving that the loading process only affected the mesoporous structure and did not destroy the overall support framework.

[0125] Selective dehydration performance was verified by steam adsorption experiments. At 25℃, the adsorption capacity of water molecules on the supported catalyst reached 0.32 g / g, while the adsorption capacity of trifluoroacetic acid was only 0.05 g / g. Kinetic studies showed that water molecules reached adsorption equilibrium within 30 minutes, while trifluoroacetic acid only reached 15% of its equilibrium adsorption capacity within the same time, demonstrating that the molecular sieve channels have a significant selective permeability for water molecules.

[0126] In a simulated reaction experiment, after reacting the supported catalyst with trifluoroacetic acid at 90°C for 6 hours, no 1770 cm⁻¹ was detected by infrared spectroscopy. -1The characteristic absorption peak of the acid anhydride at the wavenumber was observed, while the control group, which directly used unloaded phosphorus pentoxide, showed a significant absorption peak at the same wavenumber, with a peak intensity of 0.25 Abs.

[0127] The characterization data above fully demonstrate that by loading phosphorus pentoxide onto an acid-resistant porous support, not only is high dispersion and stable anchoring of the active component achieved, but more importantly, selective dehydration channels are established using the shape-selective effect of the support. This design allows water molecules to rapidly enter the pores and be captured, while larger fluorinated organic acid molecules are effectively blocked, thus significantly suppressing side reactions while promoting the forward equilibrium of the reaction. This supported catalyst exhibits excellent catalytic performance and stability in the synthesis of fluorinated acetals, providing a reliable technical solution for the green synthesis of high-performance electrolyte materials.

[0128] Example 5:

[0129] S1. Add 1.5 mol trifluoroacetic acid, 0.6 mol paraformaldehyde, 0.075 mol phosphorus pentoxide supported on 44.8 g 3A molecular sieve, and 15.3 mol acetonitrile to a dry 1000 ml reaction vessel;

[0130] S2. Place the above materials in a reaction vessel and stir at 90°C for 10 hours. GC-MS analysis showed that no paraformaldehyde was detected, and the target product was generated.

[0131] S3. After the reaction is complete, the organic system and the supported catalyst system are separated by filtration. The organic system is rotary evaporated to remove the solvent acetonitrile, and then purified by vacuum distillation to obtain a fluorinated acetal product with a yield of 90.7%. The content of fluoro anhydride was not detected, the fluorine resource retention rate was 99.4%, and the dehydrating agent utilization efficiency was 90.0%. 2g of water was added to the supported catalyst system and reacted for 1 hour, followed by vacuum distillation to obtain a phosphoric acid byproduct with a yield of 98.2% and a purity of 99.9%.

[0132] Comparing Example 3 (pure phosphorus pentoxide) and Example 5 (supported phosphorus pentoxide), under the same raw material (trifluoroacetic acid), Example 5 used a supported dehydrating agent. Compared to the pure phosphorus pentoxide in Example 3, the content of fluoroanhydride decreased from 0.48% to undetectable, the fluorine resource retention rate increased from 92.8% to 99.4%, and the dehydrating agent utilization efficiency jumped from 65.2% to 96.5%. This significant difference strongly demonstrates that the "physical isolation" mechanism constructed by the molecular sieve support successfully blocked the side reaction pathways and solved the dehydrating agent passivation problem. Supported catalysts also facilitate catalyst recovery and reuse, offering potential process advantages.

[0133] In addition to the examples that focused on the effects of catalyst and organic acid types, the following series of experiments were systematically conducted to fully verify the universality of the method of the present invention, optimize process parameters, and examine the effects of different reactant combinations. These experiments further enriched the technical content of the present invention.

[0134] Example 6:

[0135] S1. Add 6.3 mol trifluoroacetic acid, 1 mol paraldehyde, and 1.2 mol boron trioxide supported on MCM-41 to a dry 1000 ml reactor;

[0136] S2. Under stirring, the above materials were reacted in a reactor at 95°C for 8 hours. GC-MS showed that no more metaldehyde was detected, and the target product was generated.

[0137] S3. After the reaction was completed, the organic system and the supported catalyst system were separated by filtration. The organic system was rotary evaporated to remove the solvent and then subjected to vacuum distillation to finally obtain the fluorinated acetal product with a yield of 87.2%. The content of fluoro anhydride was not detected, the fluorine resource retention rate was 99.1%, and the dehydrating agent utilization efficiency was 95.8%. 50g of water was added to the supported catalyst system and reacted for 1 hour. After filtration, the product was purified by slurrying with 50ml of tetrahydrofuran three times to obtain the boric acid byproduct with a yield of 96.5% and a purity of 99.85%.

[0138] Example 7:

[0139] S1. Add 3.15 mol difluoromalonic acid, 1 mol triacetaldehyde, 1.1 mol phosphorus pentoxide supported on MCM-41, and 500 ml N,N-dimethylformamide to a dry 1000 ml reaction vessel.

[0140] S2. Under stirring, the above materials were reacted in a reactor at 150°C for 10 hours. GC-MS analysis showed that no more metaldehyde was detected, and the target product was generated.

[0141] S3. After the reaction was completed, the organic system and the supported catalyst system were separated by liquid-liquid separation. The organic system was rotary evaporated to remove the solvent and then subjected to vacuum distillation to finally obtain the fluorinated acetal product with a yield of 82.7%. The content of fluoro anhydride was not detected, the fluorine resource retention rate was 99.0%, and the dehydrating agent utilization efficiency was 96.2%. 9g of water was added to the supported catalyst system and reacted for 1 hour before vacuum distillation to obtain the phosphoric acid byproduct with a yield of 97.8% and a purity of 99.88%.

[0142] Example 8:

[0143] S1. Add 4.2 mol of pentafluoropropionic acid, 2 mol of butyraldehyde, and 0.8 mol of boron trioxide supported on MCM-41 to a dry 1000 ml reactor;

[0144] S2. Under stirring, the above materials were reacted in a reactor at 95°C for 8 hours. GC-MS showed that no butyraldehyde was detected, and the target product was generated.

[0145] S3. After the reaction is complete, the organic system and the supported catalyst system are separated by filtration. The organic system is rotary evaporated to remove the solvent and then subjected to vacuum distillation to finally obtain the fluorinated acetal product with a yield of 86.6%. The content of fluoro anhydride was not detected, the fluorine resource retention rate was 99.3%, and the dehydrating agent utilization efficiency was 95.5%. 50g of water was added to the supported catalyst system and reacted for 1 hour. After filtration, the mixture was purified by slurrying with 50ml of acetonitrile three times to obtain the boric acid byproduct with a yield of 96.2% and a purity of 99.80%.

[0146] Example 9:

[0147] S1. Add 1.6 mol monofluoromethyl diphosphonic acid, 1 mol trioxymethylene, 1.3 mol phosphorus pentoxide supported on MCM-41, and 500 ml of 1,2-dichloroethane to a dry 1000 ml reactor.

[0148] S2. Under stirring, the above materials were reacted in a reactor at 105°C for 10 hours. GC-MS showed that no trioxymethylene was detected, and the target product was generated.

[0149] S3. After the reaction was completed, the organic system and the supported catalyst system were separated by liquid-liquid separation. The organic system was rotary evaporated to remove the solvent and then subjected to vacuum distillation to finally obtain the fluorinated acetal product with a yield of 82.2%. The content of fluoro anhydride was not detected, the fluorine resource retention rate was 99.2%, and the dehydrating agent utilization efficiency was 95.1%. 20g of water was added to the supported catalyst system and reacted for 1 hour before vacuum distillation to obtain the phosphoric acid byproduct with a yield of 97.5% and a purity of 99.82%.

[0150] Example 10:

[0151] S1. Add 3.2 mol of bis(2,2,2-trifluoro)ethyl phosphate, 1.5 mol of isobutyraldehyde, and 0.6 mol of phosphorus pentoxide supported on MCM-41 to a dry 1000 ml reactor.

[0152] S2. Under stirring, the above materials were reacted in a reactor at 85°C for 10 hours. GC-MS showed that isobutyraldehyde was no longer present, and the target product was generated.

[0153] S3. After the reaction was completed, the organic system and the supported catalyst system were separated by liquid-liquid separation. The organic system was rotary evaporated to remove the solvent and then subjected to vacuum distillation to finally obtain the fluorinated acetal product with a yield of 86.3%. The content of fluoro anhydride was not detected, the fluorine resource retention rate was 99.5%, and the dehydrating agent utilization efficiency was 94.8%. 10g of water was added to the supported catalyst system and reacted for 1 hour before vacuum distillation to obtain the phosphoric acid byproduct with a yield of 96.0% and a purity of 99.85%.

[0154] Example 11:

[0155] S1. Add 3.3 mol methylene disulfonic acid, 1 mol paraformaldehyde, 1.3 mol boron trioxide supported on MCM-41, and 500 ml toluene to a dry 1000 ml reaction vessel;

[0156] S2. Under stirring, the above materials were reacted in a reactor at 130°C for 12 hours. GC-MS analysis showed that the trioxymethylene was produced, thus generating the target product.

[0157] S3. After the reaction is complete, the mixture is filtered while hot to separate the organic system and the supported catalyst system. The organic system is rotary evaporated to remove the solvent, and the resulting solid is purified by slurrying three times with a mixed solvent (80 ml methanol + 20 ml dichloromethane) to finally obtain a fluorinated acetal product with a yield of 80.5%. The content of fluoro anhydride was not detected, the fluorine resource retention rate was 99.1%, and the dehydrating agent utilization efficiency was 95.3%. 50 g of water is added to the supported catalyst system and reacted for 1 h. After filtration, the mixture is purified by slurrying three times with 50 ml acetonitrile to obtain a boric acid byproduct with a yield of 96.8% and a purity of 99.78%.

[0158] Example 12:

[0159] S1. Add 3.15 mol difluoromethyl disulfonic acid, 1 mol trioxymethylene, 1.3 mol boron trioxide supported on MCM-41, and 500 ml of 1,2-dichloroethane to a dry 1000 ml reaction vessel.

[0160] S2. Under stirring, the above materials were reacted in a reactor at 105°C for 12 hours. GC-MS analysis showed that the trioxymethylene was produced, thus generating the target product.

[0161] S3. After the reaction is complete, the mixture is filtered while hot to separate the organic system and the supported catalyst system. The organic system is rotary evaporated to remove the solvent, and the resulting solid is purified by pulping three times with a mixed solvent (80 ml acetonitrile + 20 ml tetrahydrofuran) to finally obtain a fluorinated acetal product with a yield of 84.2%. The content of fluoroanhydride was not detected, the fluorine resource retention rate was 99.3%, and the dehydrating agent utilization efficiency was 96.0%. 50 g of water is added to the supported catalyst system and reacted for 1 h. After filtration, the mixture is purified by pulping three times with 50 ml acetonitrile to obtain a boric acid byproduct with a yield of 97.2% and a purity of 99.86%.

[0162] Table 1 Test Results of Examples 1-12

[0163] Test Project Fluoroanhydride content (%) Fluorine resource retention rate (%) Dehydrating agent utilization efficiency (%) Example 1 0.35 94.2 81.5 Example 2 0.28 95.1 71.1 Example 3 0.48 92.8 73.3 Example 4 0.31 94.5 66.7 Example 5 Not detected 99.4 90.0 Example 6 Not detected 99.1 95.8 Example 7 Not detected 99.0 96.2 Example 8 Not detected 99.3 95.5 Example 9 Not detected 99.2 95.1 Example 10 Not detected 99.5 94.8 Example 11 Not detected 99.1 95.3 Example 12 Not detected 99.3 96.0

[0164] This invention innovatively employs acidic oxides supported within the pores of a porous molecular sieve as a dehydration system. Its core advantage lies in utilizing the "shape-selective confinement effect" of the support to precisely suppress competing side reactions. In conventional synthetic routes, strong dehydrating agents (such as pure phosphorus pentoxide) readily come into direct contact with fluorine-containing organic acid molecules, inducing vigorous dehydration to anhydride or decarboxylation side reactions, resulting in complex product compositions.

[0165] In this system, the size-screening effect of the molecular sieve channels creates a "micro-nano reaction window": directional diffusion: the extremely small water molecules generated in the reaction can diffuse into the channels without hindrance, where they are captured and solidified by the internally anchored phosphorus pentoxide. Spatial shielding: larger fluorinated organic acid molecules in the system are limited by the pore size and cannot enter the channels to undergo side reactions with the highly reactive phosphorus pentoxide.

[0166] This "divide and conquer" strategy allows the system to break the thermodynamic equilibrium of the acetalization reaction without requiring extreme reaction temperatures. Experimental data show that the amount of anhydride impurities generated in the supported system is reduced by more than 80% compared to pure acid oxides. This is not a simple increase in purity, but a qualitative change in reaction selectivity.

[0167] In summary, this invention provides a fluorinated acetal ester electrolyte additive and its synthesis method. Through the synergistic reaction of an acidic oxide catalyst with fluorinated organic acid compounds and aldehydes in a specific solvent, under optimized conditions of 80-150℃ and 8-12 hours, novel fluorinated acetal ester compounds with low fluoroanhydride content were successfully synthesized. This method innovatively realizes the resource utilization of the post-reaction system, converting the acidic oxide catalyst into high-purity inorganic acid byproducts through hydration conversion, embodying the concept of green chemistry. This method has outstanding advantages such as controllable operation, high yield, and excellent and stable purity of both the main product and byproducts. By flexibly adjusting the types and amounts of organic acid compounds and aldehydes, catalysts, and reaction parameters, the product structure can be effectively controlled, thereby obtaining a series of fluorinated acetal ester derivatives with potential application value and corresponding inorganic acid products. The data from the examples fully demonstrate the necessity of the synergistic effect of acidic oxide catalysts and fluorinated organic acids for the successful synthesis of high-purity target products, as well as the influence of different reaction conditions on product yield and quality, providing a solid experimental basis for the application of this method.

[0168] Based on the preferred embodiments of the present invention described above, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A fluorinated acetal ester electrolyte additive and its synthesis method, characterized in that, Includes the following steps: S1. Provides organic acid compounds, aldehydes, acidic oxides, and solvents; S2. At a temperature of 80℃ to 150℃, organic acid compounds, aldehydes, acidic oxides and solvents are reacted in a reaction vessel for 8 to 12 hours to generate the target product. S3. Filter or separate to obtain an organic system and an acidic oxide system. After removing the solvent by rotary evaporation, the organic system is purified by distillation, washing, extraction, or pulping to obtain a high-purity fluorinated acetal ester electrolyte solvent or additive. Add excess water to the acidic oxide system to completely hydrate it, and then purify it by pulping or vacuum distillation to obtain a high-purity inorganic acid byproduct.

2. The fluorinated acetal ester electrolyte additive and its synthesis method according to claim 1, characterized in that: The fluorinated acetal ester, such as Formula I, Formula II or Formula III, has the following structural formula: Formula I Formula II Formula III Where R1, R2, and R3 are C1~C 12 One or more combinations of fluorinated hydrocarbon groups, structural formula as follows: 。 3. The fluorinated acetal ester electrolyte additive and its synthesis method according to claim 1, characterized in that: The organic acid compound is one or more of organic carboxylic acids, organic phosphorus / phosphonic acids, and organic sulfonic acids; The organic acid compound is one or more of the following: 2-fluoroacetic acid, difluoroacetic acid, trifluoroacetic acid, 2-fluoropropionic acid, 3-fluoropropionic acid, 2,2-difluoropropionic acid, 3,3-difluoropropionic acid, 3,3,3-trifluoropropionic acid, 2,3,3,3-tetrafluoropropionic acid, 2,2,3,3-tetrafluoropropionic acid, pentafluoropropionic acid, heptafluorobutyric acid, difluoromalonic acid, 2-fluoromalonic acid, mono(2-fluoro)ethyl phosphate, mono(2,2-difluoro)ethyl phosphate, mono(2,2,2-trifluoro)ethyl phosphate, bis(2-fluoro)ethyl phosphate, bis(2,2-difluoro)ethyl phosphate, bis(2,2,2-trifluoro)ethyl phosphate, monofluoromethyl diphosphonic acid, difluoromethyl diphosphonic acid, methylene diphosphonic acid, monofluoromethyl disulfonic acid, difluoromethyl disulfonic acid, and methylene disulfonic acid.

4. The fluorinated acetal ester electrolyte additive and its synthesis method according to claim 1, characterized in that: The aldehyde is one or more of the following: trioxymethylene, paraoxymethylene, trioxymethylene, tetraoxymethylene, propionaldehyde, isobutyraldehyde, butyraldehyde, pentanaldehyde, hexanal, decanal, and furfural.

5. The fluorinated acetal ester electrolyte additive and its synthesis method according to claim 1, characterized in that: The acidic oxide is phosphorus pentoxide or boron trioxide.

6. The fluorinated acetal ester electrolyte additive and its synthesis method according to claim 5, characterized in that: The phosphorus pentoxide is loaded within the pores of a porous support, which is a molecular sieve.

7. The fluorinated acetal ester electrolyte additive and its synthesis method according to claim 1, characterized in that: The solvent is one or more of 1,2-dichloroethane, ethyl acetate, toluene, acetonitrile, tetrahydrofuran, 1,4-dioxane, ethylene glycol dimethyl ether, and N,N-dimethylformamide.

8. The fluorinated acetal ester electrolyte additive and its synthesis method according to claim 1, characterized in that: The molar ratio of the carbonyl group of the aldehyde to the H+ of the organic acid compound is 1:2.1 to 1:2.5; the amount of the acidic oxide used is 1.1 to 1.5 times the amount of the acidic oxide that reacts completely with the generated water.

9. The fluorinated acetal ester electrolyte additive and its synthesis method according to claim 1, characterized in that: The solvent used for washing, extraction, or pulping purification is one or more of the following: water, dichloromethane, 1,2-dichloroethane, ethyl acetate, toluene, acetonitrile, tetrahydrofuran, acetone, petroleum ether, 1,4-dioxane, ethylene glycol dimethyl ether, and diethyl ether.

10. The fluorinated acetal ester electrolyte additive and its synthesis method according to claim 1, characterized in that: The fluorinated acetal is a carboxylic acid acetal, a phosphate acetal, or a sulfonic acid acetal.

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