Polycyclic compound and preparation method therefor, use thereof, electrolyte, and battery

Abstract

The present application discloses a polycyclic compound, a preparation method therefor, a use thereof, an electrolyte, and a battery. The polycyclic compound comprises: a compound represented by formula I. The content of the compound having a cis structure represented by formula II in the compound represented by formula I is ≥98 wt%, R1 and R2 each independently being any one of H, F, alkyl, and fluoroalkyl.

Description

Polycyclic compounds, their preparation methods, uses, electrolytes, and batteries

[0001] This application claims priority to Chinese Patent Application No. 202410906445X, filed on July 8, 2024, entitled "Polycyclic Compounds and Preparation Methods Thereof, Uses, Electrolytes and Batteries Thereof", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application belongs to the field of batteries, specifically relating to polycyclic compounds, their preparation methods, uses, electrolytes, and batteries. Background Technology

[0003] With the rapid development of markets such as electronic devices, electric vehicles, smart homes, power tools, and intelligent transportation, the demand for batteries is constantly increasing. Lithium-ion batteries, for example, are widely used in consumer electronics, energy storage and power batteries, and smart homes due to their advantages such as high specific energy, long cycle life, and low self-discharge. Typically, a battery includes a positive electrode, a negative electrode, a separator, and an electrolyte. The electrolyte usually includes a solvent, a lithium salt electrolyte, and electrolyte additives. Adding electrolyte additives can improve battery performance. Choosing appropriate additives has a significant impact on the battery's electrochemical performance. Summary of the Invention

[0004] This application aims to address one of the related technical problems to a certain extent.

[0005] The technical solution of this application was developed by the inventor based on the following discoveries:

[0006] Currently, with increasing demands for battery range and mounting pressure on cell costs, the selection of transition metals in cathode active materials has become a mainstream development direction. Materials such as NCM (lithium nickel manganese cobalt oxide), LNMO (lithium nickel manganese oxide), or LMFP (lithium manganese iron phosphate) are seeing continuous development in the power and energy storage fields. However, these materials share a common problem: with cycling, due to intrinsic stability issues or the influence of acidic components in the electrolyte, transition metals dissolve. This dissolved transition metal can lead to cathode material structural collapse and capacity decay, and can also catalyze electrolyte reactions, resulting in high-temperature gas generation and decreased interface stability. As a crucial component of lithium-ion batteries, the electrolyte significantly impacts the overall battery performance. Additives are an important part of the electrolyte, and suitable additives can significantly improve the battery's electrochemical performance. Therefore, selecting appropriate additives to reduce the negative impact of transition metals on battery electrochemistry is crucial. The inventors have discovered that applying the compound shown in Formula I as an additive to lithium-ion battery electrolytes has a good effect on improving the battery's electrochemical performance. Specifically, it not only facilitates the formation of a dense CEI film at the positive electrode and a dense SEI film at the negative electrode, but also forms a small amount of inorganic salts (in lithium batteries, these inorganic salts include Li₂SO₄ and / or Li₂O) in the CEI film formed by the decomposition of the positive electrode. This improves the rigidity and flexibility of the positive electrode interface layer, inhibits electrolyte decomposition, and enhances the stability of the positive electrode interface film. Furthermore, the CEI film formed by the compound shown in Formula I can also reduce the electrochemical impedance of the positive electrode and accelerate the formation of active ions (such as Li₂O). + The compound in Formula I increases the transmission rate and helps form a more stable electrode-electrolyte interface, reducing the battery's internal resistance and interfacial reactions, thus protecting the positive electrode. In addition, it can suppress the dissolution of transition metal ions in the positive electrode active material, reduce the battery's cycle capacity decay, and improve cycle stability. Furthermore, the compound in Formula I generates lithium carbonate in the SEI film formed on the negative electrode, which helps improve the uniformity and stability of the SEI film. Moreover, the compound in Formula I has low impedance, which also helps reduce battery impedance.

[0007] However, based on the conventional synthesis process and raw material selection of the compound shown in Formula I, the target product usually contains different conformations and other impurities. The different conformations include the cis structure shown in Formula II and the trans structure shown in Formula III. The inventors found that the compound with the cis structure shown in Formula II is easy to gain electrons and be reduced, leading to the breakage of the SO single bond. After the breakage, the O, S=O and the three O atoms in the S=O on the other cyclic sulfate ester group in the transition state can form a claw-shaped spatial structure, which can easily capture metal ions and form a cage-like complex. This can stabilize the dissolved transition metal, reduce the catalytic decomposition side reaction of the transition metal on the SEI film, and suppress the negative impact caused by the deposition of the transition metal in elemental form after reduction at the negative electrode. Even with bond rotation, the space between the substituted or unsubstituted DTD (i.e., substituted or unsubstituted vinyl sulfate) rings on both sides of the trans structure shown in Formula III is still greater than that of the cis structure. The overlap of the substituted or unsubstituted DTD rings on both sides is weakened, making it difficult to form a suitable intermediate cage structure to capture and stabilize the transition metal. In other words, the trans structure shown in Formula III cannot effectively eliminate the side reactions caused by the transition metal, which will reduce the improvement effect of Formula I compound on battery performance.

[0008] In view of this, the first objective of this application is to provide a polycyclic sulfate product, wherein the target product is predominantly cis-structured, thereby reducing the impact of transition metal dissolution on battery performance while improving battery performance.

[0009] In a first aspect of this application, a polycyclic compound is proposed, comprising: a compound of Formula I, wherein the content of the compound of Formula II having a cis structure in the compound of Formula I is ≥98 wt%.

[0010] R1 and R2 are each independently any one of H, F, alkyl, and fluoroalkyl.

[0011] The polycyclic compounds described in this application have the following beneficial effects: By controlling the content of the compound with the cis structure shown in Formula II in the compound shown in Formula I to be ≥98wt%, the problem of reduced performance improvement due to the presence of the trans structure in the compound shown in Formula I can be effectively reduced. Therefore, when the polycyclic compounds are used as electrolyte additives in batteries, the electrochemical performance of the batteries can be improved, and the high-temperature performance and cycle performance can be enhanced.

[0012] In some embodiments, the polycyclic compound satisfies at least one of the following conditions:

[0013] (i) The polycyclic compounds also include chlorinated organic compounds, and the total content of chlorinated organic compounds is ≤300 ppm based on the mass of the polycyclic compounds;

[0014] (ii) Polycyclic compounds also include other organic compounds selected from one or more of the following six compounds: Based on the mass of polycyclic compounds, the total content of other organic matter is ≤1000ppm.

[0015] (iii) Based on the mass of the polycyclic compound, the content of the compound represented by Formula I is ≥99wt%. The high purity of this polycyclic compound can further improve its effect on the electrochemical performance of the battery;

[0016] (iv) The content of the compound with the cis structure shown in Formula II in the compound shown in Formula I is ≥98.9 wt%. This can further improve the effect of this polycyclic compound on the electrochemical performance of the battery;

[0017] (v) The compounds shown in Formula I also include the compounds with the trans structure shown in Formula III, wherein the content of the compounds with the trans structure shown in Formula III in the compounds shown in Formula I is ≤1%.

[0018] (ⅵ) R1 and R2 are each independently any one of H, F, and fluoromethyl.

[0019] In some embodiments, the polycyclic compound satisfies at least one of the following conditions:

[0020] (a) Chlorinated organic compounds include chlorinated organic compounds that do not contain cyclic sulfate groups and cyclic carbonate groups, chlorinated organic compounds that contain only cyclic carbonate groups, chlorinated organic compounds that contain only cyclic sulfate groups, and chlorinated organic compounds that contain 1 to 2 cyclic carbonate groups and 1 cyclic sulfate group.

[0021] (b) Based on the mass of the polycyclic compound, the total content of chlorinated organic matter is ≤100ppm; this can further improve the problem that the compound shown in Formula I has a reduced effect on improving the electrochemical performance of the battery due to the presence of chlorinated organic impurities.

[0022] (c) Based on the mass of the polycyclic compound, the total content of other organic matter is ≤200ppm; this can further improve the problem that the compound shown in Formula I has a reduced effect on improving the electrochemical performance of the battery due to impurities.

[0023] (d) Based on the mass of the polycyclic compound, the content of the compound represented by Formula I is ≥99.9 wt%;

[0024] This can further improve the effect of the polycyclic compound on the electrochemical performance of the battery.

[0025] (e) The content of the compound with the trans structure shown in Formula I is ≤0.5%. This can further reduce the problem that the improvement effect of the compound shown in Formula I on the electrochemical performance of the battery is reduced due to the presence of the trans structure.

[0026] In some embodiments, the content of the compound with the cis structure shown in Formula II in the compound shown in Formula I is ≤99.99 wt%; and / or, the content of the compound with the trans structure shown in Formula III in the compound shown in Formula I is ≥0.01 wt%. Thus, costs can be reduced while ensuring that the improvement effect of the compound shown in Formula I on the battery electrochemical performance is reduced due to the presence of the trans structure.

[0027] In some embodiments, the polycyclic compound satisfies at least one of the following conditions:

[0028] (α) Chlorinated organic compounds include One or more of the following;

[0029] (β) Based on the mass of the polycyclic compound, the total content of chlorinated organic compounds is ≤50ppm. This can further improve the problem of the reduced improvement effect of the compound shown in Formula I on the electrochemical performance of the battery due to chlorinated organic impurities;

[0030] (γ) The content of the compound with the cis structure shown in Formula II in the compound represented by Formula I is ≥99.9 wt%;

[0031] This can further improve the effect of the polycyclic compound on the electrochemical performance of the battery.

[0032] (δ) The content of the compound with the trans structure shown in Formula III in the compound represented by Formula I is ≤0.1%; thereby, the effect of this polycyclic compound on improving the electrochemical performance of the battery can be further improved.

[0033] The compounds represented by formula (ε) include The compounds shown in Formula II include

[0034] (ζ) The content of the compound with the trans structure shown in Formula III in the compound represented by Formula I is ≥0.01wt%.

[0035] (η) The content of the compound with the cis structure shown in Formula II in the compound shown in Formula I is ≤99.99wt%.

[0036] Based on the same inventive concept as the first aspect of this application, it is desirable to obtain a polycyclic compound product with a purity ≥98wt% of the compound having a cis structure as shown in Formula I. Based on this objective, a method for preparing polycyclic compounds according to the second aspect of this application has been developed.

[0037] Existing synthetic processes for preparing compounds of Formula I generally suffer from problems such as high levels of byproducts, low synthesis efficiency, and low yields. For example, a method involves transesterification of hexaols and carbonates under catalysis, followed by recrystallization with sulfonyl chloride to obtain the target product. However, this method has poor selectivity, making it difficult to obtain a single target product, resulting in low yields and numerous impurities. Furthermore, the purity and conformation of the hexaol feedstock can affect the content of byproducts in the target product, thereby impacting the improvement of battery electrochemical performance. This application achieves the second objective by selecting specific hexaol feedstocks and controlling the content of other configurations within the hexaol feedstocks.

[0038] In a second aspect of this application, a method for preparing polycyclic compounds is provided, comprising:

[0039] (1) Mix hexahydrol, monohydric alcohol, carbonate and basic catalyst and carry out transesterification reaction to obtain compound 1;

[0040] (2) Compound 1 was dissolved in a solvent and then condensed with thionyl chloride to obtain compound 2;

[0041] (3) The compound 2 was reacted with an oxidizing agent to obtain the compound shown in Formula I.

[0042] The structural formulas of compounds 1 and 2 are as follows: Hexahydrols include In hexahydrols The mass percentage content is ≤2%, and R1 and R2 are independently any one of H, F, alkyl, and fluoroalkyl.

[0043] The method for preparing polycyclic compounds described in this application has the following advantages: hexahydrols possess great flexibility and strong intermolecular forces, and their four carbon atoms are chiral, allowing for a variety of possible molecular conformations. Taking the case where both R1 and R2 are H atoms as an example, i.e., the hexahydrol used in this application... Using mannitol as a raw material, the main methods for industrial production of this hexahydrol currently include kelp extraction and catalytic hydrogenation. Catalytic hydrogenation is the internationally dominant method for mannitol production. This is primarily because the kelp extraction process, which involves refining to remove polysaccharides and other impurities, is cumbersome, has low yields, and high production costs. Furthermore, the source of the raw material is limited by region and season. Considering the cost of raw materials, catalytic hydrogenation typically uses inexpensive sucrose as a raw material. Through hydrolysis and isomerization, sucrose, fructose, or fructose syrup are obtained and then used as a raw material for catalytic hydrogenation. However, regardless of the raw material used, sorbitol is inevitably present in mannitol production. Currently, the mannitol products prepared by mainstream methods contain approximately the same amount of sorbitol as mannitol. Furthermore, because mannitol can co-crystallize with sorbitol, separation is difficult. Although purification processes involving concentration, cooling crystallization, separation, and drying can increase the mannitol content, and the more purification cycles, the higher the purity of the mannitol, the higher the cost of the mannitol raw materials. Therefore, for cost considerations, except in special fields such as pharmaceuticals and food where mannitol has proven effective while sorbitol has not, where the sorbitol content in mannitol is controlled, other fields, especially the chemical industry, do not have special requirements for the sorbitol content in mannitol in order to reduce production costs. Those skilled in the art, unaware of the impact of the trans structure shown in Formula III on the performance of the compound represented by Formula I, do not control the content of sorbitol in the hexahydrol. The content of hexahydrol. In this application, hexahydrol is used. Using this hexaol as a raw material, by controlling the content of... The mass percentage of the compound is ≤2%, which ensures that the final compound of Formula I is predominantly of the cis structure shown in Formula II, significantly reducing the content of the trans structure shown in Formula III in the final product. This means that the formation of trans structure byproducts can be suppressed from the perspective of raw material conformation. Therefore, this effectively addresses the problem that the presence of the trans structure in the compound of Formula I leads to a decrease in the improvement effect of the compound on the electrochemical performance of the battery, and further improves the improvement effect of the prepared polycyclic compound on the electrochemical performance of the battery (such as high-temperature performance and cycle performance).

[0044] In some embodiments, a hexahydrol, a monohydric alcohol, a carbonate, and a basic catalyst are mixed to carry out a transesterification reaction, satisfying at least one of the following conditions:

[0045] (A) After the transesterification reaction is completed, the following steps are also taken: depressurization treatment in order to remove low-boiling-point components.

[0046] (B) The conditions for the transesterification reaction are: temperature 65–100℃, pressure controlled at ≤2.5 MPa, and reaction time 0.5–6 h; further, the temperature for the transesterification reaction is 70–90℃, the pressure is 0.5–2.2 MPa, and the time is 0.5–6 h; even further, the temperature for the transesterification reaction is 75–85℃, and the pressure is 1–2 MPa. This allows for a balance between a high feed conversion rate and a suitable transesterification reaction rate, resulting in compound 1 with high selectivity and yield, and low impurity content.

[0047] (C) The molar ratio of carbonate to hexahydrol is (3:1) to (5:1). This is beneficial for obtaining a suitable transesterification reaction rate and high conversion rate, as well as for reducing the impurity content in the final product.

[0048] (D) The molar ratio of the monohydric alcohol to the hexahydric alcohol is (10:1) to (20:1); further, the molar ratio of the monohydric alcohol to the hexahydric alcohol is (12:1) to (18:1); and even further, the molar ratio of the monohydric alcohol to the hexahydric alcohol is (14:1) to (16:1). In this application, the monohydric alcohol is used as a solvent. The amount added is generally sufficient to completely dissolve the reaction raw materials, hexahydric alcohol and carbonate. Under normal circumstances, a molar ratio of monohydric alcohol to hexahydric alcohol greater than or equal to 10 is sufficient to meet the dissolution requirements. The prior art mentions that it is okay to add an excess of methanol solvent in order to dissolve the reaction raw materials. However, the inventors have found that the content of monohydric alcohol also affects the selectivity of the transesterification reaction. If the content of monohydric alcohol is too high (for example, when the molar ratio of monohydric alcohol to hexahydric alcohol is greater than 20:1), it will reduce the selectivity of the transesterification reaction to a certain extent. Based on this, controlling the molar ratio of monohydric alcohol to hexahydric alcohol to (10:1) to (20:1), or (12:1) to (18:1), or (14:1) to (16:1) is beneficial to obtaining a suitable transesterification reaction rate and high conversion rate, and also beneficial to reducing the impurity content in the final product.

[0049] (E) Based on the mass of the hexahydrol, the amount of basic catalyst is 0.01–5 wt%, optionally 0.02–0.5 wt%, and further optionally 0.02–0.1 wt%. This not only facilitates the smooth progress of the transesterification reaction but also reduces the risk of increased thionyl chloride usage and the generation of more sulfur dioxide in the subsequent condensation reaction due to excessive use of basic catalyst.

[0050] (F) Carbonates include one or more of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, and diphenyl carbonate.

[0051] (G) Monohydric alcohols include one or more of methanol, ethanol, propanol, isopropanol, butanol, and tert-butanol.

[0052] (H) Alkaline catalysts include one or more of sodium hydroxide, potassium hydroxide, potassium carbonate, sodium carbonate, lithium carbonate, sodium methoxide, sodium ethoxide, sodium tert-butoxide, potassium tert-butoxide, triethylamine, and pyridine.

[0053] (I) In hexahydrols, The mass percentage content is ≤1%; furthermore, in hexaol, The mass percentage content is ≤0.5%; furthermore, in hexaol, The mass percentage content is ≤0.1%.

[0054] In some embodiments, the hexahydrol, The mass percentage content is ≥0.01%.

[0055] In some implementations, at least one of the following conditions is met:

[0056] (I) In step (2), after the condensation reaction is completed, a reflux deacidification treatment is further included, which can reduce the residual HCl produced by the condensation reaction; optionally, the temperature of the reflux deacidification treatment is 40-80°C, and / or the time of the reflux deacidification treatment is 10-50 min. Meeting the reflux deacidification treatment conditions is beneficial to further reduce the residual HCl produced by the esterification reaction.

[0057] (II) In step (2), after dissolving compound 1 in a solvent, thionyl chloride is added dropwise to carry out the condensation reaction. This can effectively suppress impurities. The generation of .

[0058] (III) In step (2), the condensation reaction is carried out at a temperature of 20–100 °C for 1–4 h. This allows for a better balance between reaction efficiency and the purity of the final product.

[0059] (IV) In step (2), the molar ratio of compound 1 to thionyl chloride is 1:(2-3), and the addition time of thionyl chloride is 0.5-2 h. This balances the reaction rate and also helps to improve the purity of compound 2 and the final product, while reducing the impurity content.

[0060] (V) In step (2), the solvent includes one or more of the following: ether solvents, N,N-dimethylformamide, N,N-dimethylacetamide, tetrahydrofuran, and ester solvents.

[0061] (VI) In step (3), the oxidant is provided in the form of an aqueous solution. After reacting compound 2 with the oxidant, the reaction product is further subjected to a heating treatment to remove moisture.

[0062] (VII) After the transesterification reaction, a reduced pressure treatment is also performed to remove low-boiling-point components. This is beneficial for further improving the purity of the compound represented by Formula I and reducing the impurity content.

[0063] In a third aspect of this application, a polycyclic compound prepared by the above-described method is provided. The polycyclic compound prepared includes: the compound shown in Formula I, wherein the content of the compound with the cis structure shown in Formula II in the compound shown in Formula I is ≥98 wt%. The features and effects described in the above-described method for preparing polycyclic compounds also apply to this polycyclic compound, and will not be repeated here.

[0064] In a fourth aspect of this application, the use of the above-described polycyclic compound and the above-described method for preparing the polycyclic compound in the fields of electrolytes and batteries is proposed.

[0065] In a fifth aspect of this application, an electrolyte is provided, comprising: an electrolyte additive, wherein the electrolyte additive includes the aforementioned polycyclic compound, or a polycyclic compound prepared by the aforementioned method for preparing polycyclic compounds. Using this electrolyte in a battery can significantly improve the battery's high-temperature performance and cycle performance.

[0066] In some embodiments, the content of electrolyte additives is 0.1 to 5 wt%, based on the total mass of the electrolyte.

[0067] In a sixth aspect of this application, a battery is provided, comprising: the electrolyte described above.

[0068] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0069] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0070] Figure 1 is a flowchart of the preparation of a polycyclic compound according to an embodiment of this application.

[0071] Figure 2 is the 1H NMR spectrum of the final product obtained according to Example 1 of this application.

[0072] Figure 3 is the 1H NMR spectrum of the final product prepared according to Comparative Example 3 of this application.

[0073] Figure 4 is a high-performance liquid chromatogram of crude mannitol; where 1 indicates the peak position at 2.723 min, representing mannitol, and 2 indicates the peak position at 3.944 min, representing sorbitol.

[0074] Figure 5 shows the high performance liquid chromatograms; where the peak position at 9.883 min indicated by 3 represents the cis polycyclic compound and the peak position at 10.523 min indicated by 4 represents the trans polycyclic compound. Detailed Implementation

[0075] The embodiments of this application are described in detail below and are intended to explain this application, but should not be construed as limiting this application.

[0076] In a first aspect of this application, a polycyclic compound is proposed, comprising: a compound of Formula I, wherein the content of the compound of Formula II having a cis structure in the compound of Formula I is ≥98 wt%.

[0077] R1 and R2 are each independently any one of H, F, alkyl, and fluoroalkyl.

[0078] It should be noted that R1 and R2 can be the same or different; alkyl and fluoroalkyl can be alkyl and fluoroalkyl with 1 to 10 carbon atoms, respectively. In addition, fluoroalkyl can be alkyl that is partially or completely substituted with fluorine. Taking R1 and R2 as examples where both are H, in this polycyclic compound, the compound shown in Formula I is mainly composed of the cis polycyclic compound structure shown in Formula II (i.e., with the plane containing the carbon skeleton as the reference, the DTD ring is on the same side of the plane), and its content accounts for more than 98 wt%. For example, the content of the compound with the cis structure shown in Formula II in the compound shown in Formula I can be 98 wt%, 98.2 wt%, 98.4 wt%, 98.5 wt%, 98.7 wt%, 98.9 wt%, 99 wt%, 99.2 wt%, 99.4 wt%, 99.5 wt%, 99.7 wt%, 99.9 wt%, 99.92 wt%, 99.95 wt%, 99.97 wt%, or 99.99 wt%, etc.

[0079] The compound shown in Formula I can be used as an additive in the electrolyte to improve the electrochemical performance of the battery. Specifically, the compound shown in Formula I readily forms a dense CEI film at the positive electrode and a dense SEI film at the negative electrode during the battery formation stage. The CEI film formed by the decomposition of the positive electrode will generate a small amount of inorganic salts (in lithium batteries, these include Li₂SO₄ and / or Li₂O), improving the rigidity and flexibility of the positive electrode interface layer, inhibiting electrolyte decomposition, and enhancing the stability of the positive electrode interface film. Furthermore, the CEI film formed by the compound shown in Formula I can also reduce the electrochemical impedance of the positive electrode and accelerate the reaction of active ions (such as Li₂SO₄ and / or Li₂O). +The transfer rate of the compound helps to form a more stable electrode-electrolyte interface, reducing the internal resistance and interfacial reaction of the battery, thus protecting the positive electrode. In addition, it can suppress the dissolution of transition metal ions in the active material of the positive electrode, reduce the battery's cycle capacity decay, and improve cycle stability. In the SEI film formed on the negative electrode, it generates lithium carbonate, which helps to improve the uniformity and stability of the SEI film. Furthermore, the compound shown in Formula I is easy to gain electrons and be reduced, leading to the breakage of SO single bonds. After the breakage, the O, S=O and the three O atoms in the S=O of the other cyclic sulfate ester group in the transition state can form a claw-shaped spatial structure, which can easily capture metal ions and form a cage-like complex. This can stabilize the dissolved transition metal, reduce the catalytic decomposition side reaction of the transition metal on the SEI film, and suppress the negative impact caused by the deposition of the transition metal in elemental form after reduction on the negative electrode. Moreover, the compound shown in Formula I has low impedance, which is also beneficial to reduce battery impedance.

[0080] However, based on the conventional synthesis process and raw material selection of the compound shown in Formula I, the target product usually contains different conformations and other impurities. The different conformations include the cis structure shown in Formula II and the trans structure shown in Formula III. The inventors found that the compound with the cis structure shown in Formula II is easy to gain electrons and be reduced, leading to the breakage of the SO single bond. After the breakage, the O, S=O and the three O atoms in the S=O on the other cyclic sulfate ester group in the transition state can form a claw-shaped spatial structure, which can easily capture metal ions and form a cage-like complex. This can stabilize the dissolved transition metal, reduce the catalytic decomposition side reaction of the transition metal on the SEI film, and suppress the negative impact caused by the deposition of the transition metal in elemental form after reduction at the negative electrode. Even with bond rotation, the space between the substituted or unsubstituted DTD (i.e., substituted or unsubstituted vinyl sulfate) rings on both sides of the trans structure shown in Formula III is still greater than that of the cis structure. The overlap of the substituted or unsubstituted DTD rings on both sides is weakened, making it difficult to form a suitable intermediate cage structure to capture and stabilize the transition metal. In other words, the trans structure shown in Formula III cannot effectively eliminate the side reactions caused by the transition metal, which will reduce the improvement effect of the Formula 1 compound on battery performance.

[0081] In this application, by controlling the content of the compound with the cis structure shown in Formula II in the compound shown in Formula I to be ≥98wt%, the problem of reduced battery performance improvement caused by the presence of the trans structure in the compound shown in Formula I can be effectively reduced. Therefore, when polycyclic compounds are used as electrolyte additives in batteries, the electrochemical performance of the batteries can be improved, and the high-temperature performance and cycle performance can be enhanced.

[0082] In some specific embodiments of this application, when at least one of R1 and R2 is not H, when synthesizing the compound shown in Formula I, an alcoholic raw material containing the corresponding substitution position and substituent type can be obtained in advance, and then the compound shown in Formula I can be synthesized using the alcoholic raw material through processes such as transesterification reaction and condensation reaction.

[0083] In some specific embodiments of this application, R1 and R2 can each be H independently, that is, the compound represented by Formula I can include: Accordingly, the compounds represented by Formula II may include The compounds represented by Formula III may include The compound shown in Formula I exhibits strong polarity, resulting in weak interactions with other nonpolar molecules and minimal intermolecular friction and collisions. Compared to other sulfate ester compounds, it demonstrates better stability, operating stably over a wide voltage range. It also exhibits good cycle life and capacity retention, along with superior high-temperature performance, maintaining stable electrochemical performance at high temperatures and thus extending battery life. Furthermore, the compound's oxidation and reduction potentials are both higher than those of conventional electrolyte solvents. During battery cycling, it preferentially undergoes reduction at the negative electrode and oxidation at the positive electrode, readily forming a dense CEI film at the positive electrode and a dense SEI film at the negative electrode. This further enhances the electrochemical performance improvement effect of this polycyclic compound.

[0084] In some specific embodiments of this application, the polycyclic compound may further include chlorinated organic compounds. Based on the mass of the polycyclic compound, the total content of the chlorinated organic compounds may be ≤300ppm, for example, ≤300ppm, ≤280ppm, ≤250ppm, ≤220ppm, ≤200ppm, ≤180ppm, ≤150ppm, ≤120ppm, ≤100ppm, ≤80ppm, ≤50ppm, ≤40ppm, ≤30ppm, ≤20ppm, ≤10ppm, ≤5ppm, etc. The content of free chloride ions in the electrolyte is strictly controlled, generally required to be less than 5 ppm. Free chloride ions not only easily induce corrosion of the positive electrode foil (such as aluminum foil), but also easily lead to the dissolution of transition metal ions in the positive electrode of the battery, which has a great impact on battery performance. At present, most people skilled in the art are committed to reducing the content of free chloride ions in the electrolyte, but in reality, the performance still cannot reach the optimal level. The inventors of this application have found that conventional methods for detecting chloride ions in electrolytes cannot detect certain chlorinated organic compounds with specific structures, because these chlorinated organic compounds with specific structures are difficult to remove chloride under existing test conditions, so that they exist in the form of chloride ions. Therefore, existing test methods cannot detect them, causing people skilled in the art to ignore the control of the content of chlorinated organic compounds. However, these chlorine-containing compounds with specific structures have a significant negative impact on electrolyte performance. The reason may be that battery cells usually contain trace amounts of water and some residual alkaline substances. If there are too many chlorine-containing organic impurities in the electrolyte additives, when applied to the electrolyte, under high temperature and high pressure conditions during battery operation, especially under the influence of residual alkaline substances, the chlorine-containing organic impurities are prone to hydrolysis, leading to an increase in the free chlorine content in the electrolyte. This not only easily induces corrosion of the positive electrode foil (such as aluminum foil), but also easily leads to the dissolution of transition metal ions from the positive electrode. This not only reduces the structural stability of the positive electrode active material, but the dissolved transition metal ions are also prone to deposit on the negative electrode surface, resulting in the continuous decomposition and regeneration of the SEI film, and the continuous consumption of active lithium. The dissolution of transition metal ions, the decomposition and regeneration of the SEI film all promote the decomposition of the electrolyte, which in turn easily leads to battery capacity decay, increased polarization due to SEI film thickening or electrolyte consumption and by-product blockage of lithium insertion / extraction channels, and increased short-circuit risk. This has a significant impact on low-temperature discharge, high-temperature storage and cycle performance. Even though the moisture content in the battery cell is controlled under the relevant standards, the requirements for free chloride ions are more stringent than those for moisture. In other words, even if the moisture content in the battery cell is not high, if the moisture content exceeds the free chloride ion standard, the hydrolysis of chlorinated organic matter can easily cause the free chloride ion content to exceed the standard, thereby deteriorating the performance.However, conventional synthesis processes based on the compounds shown in Formula I inevitably contain impurities, making it difficult to obtain products with high purity and low impurity content. In particular, existing synthesis methods using sulfonyl chloride as a reactant generally contain a large number of chlorinated organic impurities. These impurity components include, but are not limited to, chlorinated organic compounds that do not contain cyclic sulfate groups and cyclic carbonate groups, chlorinated organic compounds that contain only cyclic carbonate groups, chlorinated organic compounds that contain only cyclic sulfate groups, and chlorinated organic compounds that contain 1-2 cyclic carbonate groups and 1 cyclic sulfate group. These types of chlorinated organic impurities are prone to hydrolysis. Introducing polycyclic compounds as additives into the electrolyte can easily lead to an increase in the free chlorine content in the electrolyte, which can not only easily cause corrosion of the positive electrode foil but also easily cause the dissolution of transition metal ions in the positive electrode active material, thus reducing the effect of the compounds shown in Formula I on improving the electrochemical performance of the battery. In this application, by controlling the total content of chlorinated organic compounds in the polycyclic compound to ≤300ppm, the increase in free chlorine content in the electrolyte due to the introduction of additives can be effectively reduced. This reduces the risk of corrosion of the positive electrode foil and dissolution of transition metal ions in the positive electrode due to the increased free chlorine content. Thus, the problem of reduced improvement effect of the compound shown in Formula I on battery electrochemical performance caused by the presence of chlorinated organic impurities can be effectively improved, thereby improving the improvement effect of the polycyclic compound on battery electrochemical performance and achieving enhanced high-temperature performance and cycle performance.

[0085] In some specific embodiments of this application, the chlorinated organic compounds may include, but are not limited to, chlorinated organic compounds that do not contain cyclic sulfate groups and cyclic carbonate groups, chlorinated organic compounds that contain only cyclic carbonate groups, chlorinated organic compounds that contain only cyclic sulfate groups, and chlorinated organic compounds that contain 1 to 2 cyclic carbonate groups and 1 cyclic sulfate group. In the synthesis process of the compound shown in Formula I, chlorinated organic compounds may be generated due to excessive hexahydrol usage, insufficient transesterification reaction, and insufficient condensation reaction conditions. The chlorinated organic impurities given are common impurities in the target product when preparing the compound shown in Formula I using hexahydrol, carbonate, and thionyl chloride as raw materials. Reducing the content of chlorinated organic compounds is beneficial to further improve the effect of polycyclic compounds on the electrochemical performance of batteries.

[0086] In some specific embodiments of this application, based on the mass of the polycyclic compound, the total content of chlorinated organic matter can be ≤100 ppm, for example, ≤100 ppm, ≤80 ppm, ≤50 ppm, ≤30 ppm, or 1–99 ppm. Meeting the given range can further reduce the increase in free chlorine content in the electrolyte that may result from the introduction of the polycyclic compound, thereby further reducing the risk of corrosion of the positive electrode foil and dissolution of transition metal ions in the positive electrode due to the increased free chlorine content. This further improves the problem of reduced improvement effect of the compound shown in Formula I on the battery's electrochemical performance caused by the presence of impurities, and thus improves the improvement effect of the polycyclic compound on the battery's electrochemical performance. Furthermore, based on the mass of the polycyclic compound, the total content of chlorinated organic matter can be ≤50 ppm, thereby further improving the problem of reduced improvement effect of the compound shown in Formula I on the battery's electrochemical performance caused by the presence of impurities.

[0087] In some specific embodiments of this application, chlorinated organic compounds may include One or more of these, for example, if R1 and R2 are both H, chlorinated organic compounds can include One or more of the following. The three chlorinated organic compounds are common chlorinated organic impurities in the target product when preparing the compound of Formula I using hexahydrol, carbonate, and thionyl chloride as raw materials. These chlorinated organic compounds are prone to hydrolysis to form free chlorine, increasing the risk of corrosion of the positive electrode foil and dissolution of transition metal ions from the positive electrode. Reducing the content of these three chlorinated organic compounds helps to further reduce the increase in free chlorine content in the electrolyte that may be caused by the introduction of polycyclic compounds, reducing the risk of dissolution of transition metal ions from the positive electrode, and improving the effect of polycyclic compounds on the electrochemical performance of the battery. Furthermore, based on the mass of the polycyclic compound, The total content can be ≤100ppm, preferably ≤50ppm, for example ≤45ppm, ≤40ppm, ≤35ppm, ≤30ppm, ≤20ppm, ≤10ppm, or ≤5ppm, etc. This can further improve the problem of the reduced improvement effect of the compound shown in Formula I on the electrochemical performance of the battery due to chlorinated organic impurities.

[0088] In some specific embodiments of this application, the polycyclic compound further includes a compound with a trans structure as shown in Formula III. The content of the compound with a trans structure as shown in Formula I is ≤1%, for example, it can be 1%, 0.9%, 0.8%, 0.7%, 0.6%, 0.5%, 0.4%, 0.3%, 0.2%, or 0.1%, etc. This further avoids the problem that the presence of the compound with a trans structure as shown in Formula III reduces the improvement effect of the target product on the side reactions initiated by transition metal dissolution, and further improves the effect on the electrochemical performance of the battery when the polycyclic compound is introduced as an additive into the electrolyte, thereby obtaining improved high-temperature performance and cycle performance. Further, based on the mass of the polycyclic compound, the content of the compound with a trans structure as shown in Formula III can be ≤0.5%, and optionally ≤0.1%. The structural formula of the compound with a trans structure as shown in Formula III is as follows:

[0089] In some specific embodiments of this application, R1 and R2 can be independently any one of H, F, or fluoromethyl, which not only facilitates the synthesis of the compound shown in Formula I, but also further avoids the introduction of chlorine-containing compounds into the additive, reducing the free chlorine content that may be generated after introducing the electrolyte additive into the electrolyte. When at least one of R1 and R2 is F or fluoromethyl, fluorine substitution or fluoromethyl substitution can be performed on the hexaol terminal group first. The terminal group is more active and easier to substitute. Then, the hexaol with fluorine or fluoromethyl substitution at the terminal group is mixed with raw materials such as carbonate to carry out transesterification reaction, as well as subsequent condensation reaction and oxidation reaction.

[0090] In some specific embodiments of this application, the polycyclic compound may also include other organic compounds, which are selected from one or more of the following six compounds: For example, assuming that R1 and R2 are both H, the other organic compounds can be one or more of the following six compounds: The given compounds are common impurities in the target product when preparing the compound of Formula I using hexahydrols, carbonates, and thionyl chloride as raw materials. Reducing the total content of other compounds is beneficial to further improve the effect of polycyclic compounds on the electrochemical performance of the battery. Specifically, based on the mass of the polycyclic compound, the total content of these six compounds can be ≤1000 ppm, for example, ≤900 ppm, ≤800 ppm, ≤700 ppm, ≤600 ppm, ≤500 ppm, ≤300 ppm, ≤200 ppm, ≤100 ppm, ≤50 ppm, ≤30 ppm, etc. Reducing the total content of these six impurities helps to further reduce the risk of a decrease in the effect of the compound of Formula I on the electrochemical performance of the battery due to the presence of impurities. Controlling the total impurity content to meet the given range can further improve the effect of polycyclic compounds on the electrochemical performance of the battery. Furthermore, based on the mass of the polycyclic compound, the total content of the six compounds can be ≤200 ppm.

[0091] In some specific embodiments of this application, based on the mass of the polycyclic compound, the content of the compound represented by Formula I can be 99 to 99.99 wt%, for example, 99 wt%, 99.1 wt%, 99.5 wt%, 99.8 wt%, 99.9 wt%, 99.95 wt%, or 99.99 wt%, etc.; in particular, when the content of the compound represented by Formula I is greater than 99.9 wt%, the effect of the polycyclic compound on improving the electrochemical performance of the battery can be further improved.

[0092] In some specific embodiments of this application, the content of the compound with the cis structure shown in Formula II of the compound shown in Formula I can be ≥98.9 wt%, for example, it can be 98.1 wt%, 98.2 wt%, 98.3 wt%, 98.5 wt%, 98.7 wt%, 98.9 wt%, 98.95%, 99%, 99.1 wt%, 99.2 wt%, 99.3 wt%, 99.5 wt%, 99.7%, 99.9 wt%, 99.95 wt%, or 99.99 wt%. In particular, when the content of the compound with the cis structure shown in Formula II of the compound shown in Formula I is ≥98.9 wt%, the effect of the polycyclic compound on improving the electrochemical performance of the battery can be further improved. Further, the content of the compound with the cis structure shown in Formula II of the compound shown in Formula I can be ≥99.9 wt%.

[0093] In some specific embodiments of this application, the content of the compound with the cis structure shown in Formula II in the compound shown in Formula I is ≤99.99 wt%; and / or, the content of the compound with the trans structure shown in Formula III in the compound shown in Formula I is ≥0.01 wt%. Since the amount of the compound shown in Formula 1 added to the electrolyte does not exceed 5 wt%, when the content of the compound with the cis structure shown in Formula II in the compound shown in Formula I is ≥99.99 wt%, and the content of the compound with the trans structure shown in Formula III in the compound shown in Formula I is less than 0.01 wt%, that is, the content of the compound with the trans structure shown in Formula III in the electrolyte is less than 5 ppm, the influence of the compound with the trans structure shown in Formula III on the effect of the compound shown in Formula 1 is also very small due to its very low content in the entire electrolyte system. In this case, even if the content of the compound with the cis structure shown in Formula II in the compound shown in Formula 1 is further increased, the performance improvement of the battery will be very small. Therefore, based on a comprehensive consideration of performance and cost factors, the content of the compound with the cis structure shown in Formula II in the compound shown in Formula I is further selected to be ≤99.99 wt%.

[0094] Currently, common synthetic processes for the compounds shown in Formula I suffer from poor selectivity of the target product, low yield, and numerous impurities in the generated target product. Furthermore, they involve large solvent consumption, cumbersome processes, and are unsuitable for industrial production. Therefore, it is urgent to find a method with high conversion rate, high yield, and relatively simple reaction steps suitable for industrial production of polycyclic sulfates. Meanwhile, the selection and purity of raw materials can lead to different conformations and other impurities in the target product. As mentioned earlier, the trans structure shown in Formula III cannot effectively eliminate side reactions caused by transition metals, reducing the improvement effect of the cis structure on battery performance. Compounds with the cis structure shown in Formula II, however, significantly improve the side reactions caused by transition metal dissolution. Based on the same inventive concept as the first aspect of this application, it is desirable to obtain a polycyclic compound product with a purity ≥98 wt% of the cis structure shown in Formula II of the compound shown in Formula I. Based on this objective, a method for preparing polycyclic compounds according to the second aspect of this application has been developed. The synthetic route involves transesterifying a substituted or unsubstituted hexaol to form a substituted or unsubstituted EC (substituted or unsubstituted ethylene carbonate) ring, followed by condensation oxidation. For example, if both R1 and R2 are hydrogen atoms:

[0095] In a second aspect of this application, a method for preparing polycyclic compounds is provided, comprising:

[0096] (1) Mix hexahydrol, monohydric alcohol, carbonate and basic catalyst and carry out transesterification reaction to obtain compound 1;

[0097] (2) Compound 1 was dissolved in a solvent and then condensed with thionyl chloride to obtain compound 2;

[0098] (3) Compound 2 was reacted with an oxidizing agent to obtain the compound shown in Formula I.

[0099] The structural formulas of compounds 1 and 2 are as follows: Hexahydrols include In hexahydrols The mass percentage content is ≤2%, and R1 and R2 are independently any one of H, F, alkyl, and fluoroalkyl.

[0100] For example, Figure 1 shows a configuration using mannitol as the hexaol, with... It is a carbonate, with H3C-OH as a monohydric alcohol, and combined with thionyl chloride. Using raw materials to prepare the target product The flowchart also shows the intermediate products, target product, and potential impurities such as chlorinated organics and other organic compounds that may be generated during the preparation process. Specifically, the hexaol... The mass percentage content can be 2%, or it can be ≤1.8%, ≤1.5%, ≤1.2%, ≤1%, ≤0.9%, ≤0.8%, ≤0.7%, ≤0.6%, ≤0.5%, ≤0.4%, ≤0.3%, ≤0.2%, or ≤0.1%, etc.

[0101] Hexahydrols possess high flexibility and strong intermolecular forces, and their four carbon atoms are chiral, allowing for a wide range of possible molecular conformations. This application employs... Hexahydrols are used as raw materials, but inevitably some substances will be present in them. The structure of the hexahydrol is adopted by mannitol. Taking hexahydrol as an example, compared to sorbitol and galactitol Choosing mannitol as a raw material not only results in high selectivity for the target product, but also ensures that the target product predominates in the cis structure shown in Formula II. Taking mannitol as an example, the main methods currently used for the industrial production of this hexaol include kelp extraction and catalytic hydrogenation. Catalytic hydrogenation is the internationally dominant method for mannitol production, primarily because the kelp purification process for removing polysaccharides and other impurities is cumbersome, has low yield, high production costs, and the source of raw materials is limited by region and season. Considering the cost of raw materials, catalytic hydrogenation typically uses inexpensive sucrose as a raw material. Sucrose, fructose, or fructose syrup are obtained through hydrolysis and isomerization, and then catalytic hydrogenation is performed using these as raw materials. However, regardless of the raw material used, sorbitol is inevitably present in mannitol production. Currently, the mannitol products prepared by mainstream methods contain approximately the same amount of sorbitol as mannitol. Furthermore, because mannitol can co-crystallize with sorbitol, separation is difficult. Although purification processes involving concentration, cooling crystallization, separation, and drying can increase the mannitol content, and the more purification cycles, the higher the purity of the mannitol, the higher the cost of the mannitol raw materials. Therefore, for cost considerations, except in special fields such as pharmaceuticals and food where mannitol has proven effective while sorbitol has not, where the sorbitol content in mannitol is controlled, other fields, especially the chemical industry, do not impose special requirements on the sorbitol content in mannitol to reduce production costs. Previously, those skilled in the art were unaware of the impact of byproducts (such as the trans structure shown in Formula III) on the properties of compounds of Formula 1, and therefore often neglected to control the sorbitol content in mannitol. However, in practice, taking R1 and R2 as H as an example, in the trans structure formed by the reaction of sorbitol in this application, even through bond rotation, the spatial distance between the DTD (i.e., vinyl sulfate) rings on both sides is still greater than that of the cis structure. The overlap of the DTD rings on both sides is weakened, making it difficult to form a suitable intermediate cage structure to capture and stabilize the transition metal. Therefore, based on the special principle of the target product in this application, the content of the cis structure compound shown in formula II of the hexahydrol must be controlled in the preparation method of this application.

[0102] In this application, a hexaol having a cis-structure is used. Using this hexaol as a raw material, by controlling the content of... The mass percentage of the compound is ≤2%, which ensures that the final compound of Formula I is predominantly of the cis structure shown in Formula II, significantly reducing the content of the trans structure shown in Formula III in the final product. This means that the formation of trans structure byproducts can be suppressed from the perspective of raw material conformation. Therefore, this effectively addresses the problem that the presence of the trans structure in the compound of Formula I leads to a decrease in the improvement effect of the compound on the electrochemical performance of the battery, and further improves the improvement effect of the prepared polycyclic compound on the electrochemical performance of the battery (such as high-temperature performance and cycle performance).

[0103] In some specific embodiments of this application, the conditions for the transesterification reaction can be: temperature 65–100°C, pressure controlled at ≤2.5 MPa, and reaction time 0.5–6 h. For example, the temperature of the transesterification reaction can be 65°C, 70°C, 80°C, 90°C, or 100°C, the pressure can be 0.2 MPa, 0.4 MPa, 0.6 MPa, 0.8 MPa, 1 MPa, 1.2 MPa, 1.4 MPa, 1.6 MPa, 1.8 MPa, 2 MPa, 2.2 MPa, or 2.5 MPa, and the time can be 0.5 h, 1 h, 2 h, 3 h, 4 h, 5 h, or 6 h.

[0104] Referring to Figure 1, in step (1), the reactivity of the terminal (positions 1 and 6) hydroxyl groups of the hexahydrol is suppressed by using a monohydric alcohol and controlling the pressure to be less than 2.5 MPa. Then, the reaction temperature is increased to 65–100°C, which is higher than the boiling point of the monohydric alcohol (the lowest boiling point of the monohydric alcohol used in this application is methanol at 65°C), thereby increasing the reactivity of the intermediate (positions 2, 3, 4, and 5) hydroxyl groups of the hexahydrol. This makes the reactivity of the intermediate hydroxyl groups of the hexahydrol much higher than that of the terminal hydroxyl groups. Furthermore, under heating and pressurization conditions, compared to the hydroxyl groups at positions 2 and 3... The product generated by the reaction of the hydroxyl groups at positions 4 and 5, and the product generated by the reaction of the hydroxyl groups at positions 3 and 4 (i.e., compound 1) have good symmetry and better stability. Therefore, under these conditions, the selectivity for compound 1 and the conversion efficiency of compound 1 in the transesterification reaction can be improved, and the intermediate product containing compound 1 can be obtained with high conversion and high selectivity. Compared with the low selectivity and easy generation of by-products when synthesizing the target product shown in formula I using conventional processes, the process of step (1) of this application can effectively reduce the residual hexahydrol content and impurities in the transesterification reaction product. The content of [unclear] will help to further reduce the impurities that may be present in the condensation reaction product of step (2). The formation of [something], and impurities that may be generated in subsequent oxidation reactions. The content of.

[0105] In this application, because a monohydric alcohol is used as a reactant, its boiling point (the lowest boiling point among the monohydric alcohols used in this application is methanol at 65°C) limits its operation. Under normal or negative pressure conditions, the monohydric alcohol evaporates and refluxes when the temperature reaches its boiling point within the reaction system. During this reflux, the solution temperature and vapor temperature continuously adjust to each other, eventually reaching a dynamic equilibrium. The inventors discovered that under this dynamic equilibrium, the temperature of the reaction system stabilizes around the boiling point of the monohydric alcohol, making it difficult to increase the temperature and thus limiting the reaction rate. The pressurization method in this application not only enhances the selectivity of the reaction in conjunction with the monohydric alcohol but also raises its boiling point, allowing for a suitable increase in reaction temperature and ultimately improving the reaction rate. However, excessively low pressure during the transesterification reaction (e.g., negative pressure) leads to the removal of a large amount of monohydric alcohol from the reaction system, which is detrimental to improving the selectivity of the transesterification reaction and suppressing impurities. The formation of [the product]; however, excessive pressure during the transesterification reaction can hinder the transesterification process as the reaction proceeds, leading to a decrease in conversion rate and an increase in raw material residue. In this application, by controlling the temperature, pressure, and time of the transesterification reaction to meet the above-mentioned ranges, a high raw material conversion rate and a suitable transesterification reaction rate can be achieved, thereby obtaining compound 1 with high selectivity and yield and low impurity content.

[0106] In addition, in step (1), no additional organic solvent is used in the transesterification reaction. Carbonate and monohydric alcohol are both reactants and solvents, which is not only environmentally friendly but also easy to operate. It can effectively improve the problems of low reaction conversion rate, complicated reaction steps, more impurities and inconvenience for industrial production that exist in the synthesis of the compound shown in Formula I.

[0107] Therefore, in some embodiments of this application, polycyclic compounds can be prepared by combining the selection of hexahydrol raw materials and controlling the above-mentioned transesterification reaction conditions. This not only results in high selectivity and high conversion rate for the compound shown in Formula I, but also produces a compound with a predominantly cis structure and low levels of trans structures and impurities. This effectively improves the problems of low reaction conversion rate, cumbersome reaction steps, excessive trans structure byproducts and impurities, and inconvenience for industrial production that exist during the synthesis of the compound shown in Formula I. It also facilitates obtaining a compound with high purity, where the mass percentage of the target product with a cis structure shown in Formula II in the compound shown in Formula I is ≥98 wt%. The prepared polycyclic compounds, when used in electrolytes, can not only effectively reduce the content of the trans-structure compound shown in Formula III in the electrolyte, but also reduce the content of chlorinated organic compounds that may be introduced into the electrolyte and the content of free chlorine that may be generated by chlorinated organic compounds. This can reduce the risk of corrosion of the positive electrode foil and dissolution of transition metal ions in the positive electrode due to the increased free chlorine content in the electrolyte. Thus, it can effectively improve the problem that the presence of the trans-structure in the compound shown in Formula I and the presence of chlorinated organic impurities leads to a decrease in the improvement effect of the compound shown in Formula I on the electrochemical performance of the battery. In addition, it can improve the improvement effect of the prepared polycyclic compounds on the electrochemical performance of the battery (such as high-temperature performance and cycle performance).

[0108] Furthermore, in some specific embodiments of this application, the temperature of the transesterification reaction can be 70-90°C and the pressure can be 0.5-2.2 MPa. More preferably, the temperature of the transesterification reaction can be 75-85°C and the pressure can be 1-2 MPa. This is beneficial to further balance a high feed conversion rate and a suitable transesterification reaction rate, thereby obtaining compound 1 with high selectivity and yield and low impurity content.

[0109] It should be noted that in some specific embodiments of this application, Hexahydrols with a mass percentage ≤2% The source of the target hexaol is not particularly limited, and those skilled in the art can choose flexibly according to actual needs. For example, they can optimize the preparation process of the hexaol to improve the purity of the target hexaol, or they can purify existing target hexaols to reduce the content of the target hexaol. The structural content can also be obtained by purchasing from manufacturers with the capability to produce the target hexaol. For example, it can be based on... The difference in solubility at different temperatures enables the separation of the two substances, thereby reducing the target hexaol. In To determine the content of mannitol, taking mannitol as an example, it can be purified by recrystallization based on the difference in solubility of mannitol and sorbitol at different temperatures. For example, existing mannitol can be prepared into an aqueous solution with a mass concentration of 50%, concentrated at 80°C, cooled and crystallized, then the crystals can be separated and dried, and finally packaged at low temperature. The more times the purification is performed, the higher the purity of the mannitol and the lower the sorbitol content.

[0110] In some specific embodiments of this application, high-performance liquid chromatography (HPLC) columns can be used to detect hexaols. The content of mannitol and sorbitol was determined. Taking mannitol and sorbitol as examples, 1.0 g of sample was weighed and placed in a clean beaker, and 100 mL of ultrapure water:acetonitrile = 1:1 (v / v) mixed solution was added and stirred thoroughly. The solution was filtered through a 0.22 μm pore size aqueous filter membrane, and a 20 μL liquid chromatograph was used for sampling and detection by high-performance liquid chromatography (HPLC). The HPLC instrument was an Agilent 1290 Infinite II (equipped with an ELSD detector), the column was an Agilent Poroshell 120EC-C18, 4.6*150 mm*2.7 μm, the column temperature was 30℃, the injection volume was 10 μL, mobile phase A was 0.1% trifluoroacetic acid aqueous solution (0.1% v / v), mobile phase B was acetonitrile, the flow rate was 1 mL / min, and gradient elution was used. The mass percentage of mannitol and sorbitol in the raw material was quantified by the area normalization method in the obtained chromatogram.

[0111] In some specific embodiments of this application, referring to Figure 1, in step (1), the molar ratio of carbonate to hexahydrol can be (3:1) to (5:1), such as 3 / 1, 3.5 / 1, 4 / 1, 4.5 / 1, or 5 / 1. Based on the amount of hexahydrol, appropriately increasing the amount of carbonate is beneficial to accelerating the transesterification reaction, improving the conversion rate of raw materials, reducing the content of unreacted hexahydrol in the intermediate product, and thus helping to reduce impurities in the final product. The content of carbonate is controlled within a specified range in this application, which allows the transesterification reaction to have a suitable reaction rate, thereby improving the utilization rate of raw materials and the yield of compound 1, and reducing impurities in the final product. The content of [specific substances] can be reduced, and the excessively rapid transesterification reaction caused by high carbonate content can be mitigated, leading to the reaction of the terminal hydroxyl groups of the hexaol to generate impurities. This reduces the risk of impurities that may form subsequently. The content of.

[0112] In some specific embodiments of this application, referring to Figure 1, in step (1), the molar ratio of monohydric alcohol to hexahydric alcohol can be (10:1) to (20:1), for example, it can be 10 / 1, 12 / 1, 14 / 1, 16 / 1, 18 / 1, 20 / 1, etc. More preferably, the molar ratio of monohydric alcohol to mannitol can be (12:1) to (18:1), and even more preferably, the molar ratio of monohydric alcohol to mannitol can be (14:1) to (16:1). In this application, the monohydric alcohol serves as a solvent, and its addition is generally sufficient to completely dissolve the reactants mannitol and carbonate. Typically, a molar ratio of monohydric alcohol to mannitol greater than or equal to 10 satisfies the dissolution requirement. While existing technologies suggest that excessive methanol can be added to dissolve the reactants, the inventors have discovered that the content of the monohydric alcohol also affects the selectivity of the transesterification reaction. If the monohydric alcohol content is too high (e.g., a molar ratio of monohydric alcohol to mannitol greater than 20:1), it can reduce the selectivity of the transesterification reaction to some extent. Controlling the relative amounts of monohydric alcohol and mannitol within the aforementioned range satisfies the requirement for the monohydric alcohol as a solvent to dissolve the reactants, while also reducing the risk that a large amount of monohydric alcohol could significantly inhibit the transesterification reaction. This facilitates the smooth progress of the transesterification reaction and ensures a suitable reaction rate. Furthermore, it reduces the risk of insufficient monohydric alcohol leading to the reaction of the terminal hydroxyl groups of mannitol, which could generate impurities. This can further reduce the impurities that may form subsequently. The content of.

[0113] In some specific embodiments of this application, in step (1), based on the mass of the hexahydrol, the amount of alkaline catalyst can be 0.01–5 wt%, for example, 0.01 wt%, 0.1 wt%, 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, etc. Controlling the amount of alkaline catalyst within the above range is beneficial for the smooth progress of the transesterification reaction and can also reduce the risk of increased thionyl chloride usage and the generation of more sulfur dioxide in the subsequent condensation reaction due to excessive alkaline catalyst usage.

[0114] In some specific embodiments of this application, in step (1), the amount of alkaline catalyst can be 0.02 to 0.5 wt% based on the mass of mannitol, and more preferably, the amount of alkaline catalyst can be 0.02 to 0.1 wt% based on the mass of mannitol. In this application, in order to facilitate industrialization, it is desirable to simplify the post-processing of each reaction step. Since an alkaline catalyst is used in the transesterification reaction in step (1), the system after the reaction is likely to be alkaline. If a neutralization or purification process is not carried out, the alkaline catalyst will consume thionyl chloride in the second step during the condensation reaction, affecting the condensation reaction. However, if the alkaline catalyst is removed, the post-processing of step (1) will be relatively complicated. For example, it is necessary to add acidic substances such as oxalic acid to adjust the pH value, and then carry out post-processing steps such as filtration and recrystallization. In this application, by further reducing the amount of alkaline catalyst used, the post-processing steps such as pH adjustment, filtration, and recrystallization after step (1) can be simplified. However, if the catalyst content is reduced, it will easily affect the reaction rate. This application can compensate for the defects caused by the reduction of catalyst amount by heating and pressurizing, thereby achieving the purpose of simplifying the post-processing. On this basis, by further adjusting the relative amounts of mannitol, monohydric alcohol, and carbonate, as well as the reaction temperature and pressure conditions to meet the above range, the defects caused by the reduction of catalyst amount can be further compensated, thereby achieving the purpose of simplifying the post-processing.

[0115] In some specific embodiments of this application, in step (1), the carbonate may be one or more of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, and diphenyl carbonate, including but not limited to dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, and diphenyl carbonate.

[0116] In some specific embodiments of this application, in step (1), the monohydric alcohol may be one or more of methanol, ethanol, propanol, isopropanol, butanol, and tert-butanol.

[0117] In some specific embodiments of this application, in step (1), the alkaline catalyst may be one or more of sodium hydroxide, potassium hydroxide, potassium carbonate, sodium carbonate, lithium carbonate, sodium methoxide, sodium ethoxide, sodium tert-butoxide, potassium tert-butoxide, triethylamine, and pyridine.

[0118] In some specific embodiments of this application, in the hexaol, The mass percentage content can be ≤1%; furthermore, in this hexaol The mass percentage content can be ≤0.5%; furthermore, in this hexaol The mass percentage content can be ≤0.1%. This can further reduce the content of byproducts with the trans structure shown in Formula III in the final product.

[0119] In some specific embodiments of this application, in the hexaol, The mass percentage content is ≥0.01%. Taking mannitol as an example, the main methods used for the industrial production of this hexahydrol currently include kelp extraction and catalytic hydrogenation. Catalytic hydrogenation is the main method for mannitol production internationally. This is mainly because the kelp purification process to remove impurities such as polysaccharides is cumbersome, has a low yield, and high production costs. Moreover, the source of raw materials is limited by region and season. Considering the cost of raw materials, catalytic hydrogenation usually uses inexpensive sucrose as raw material. Sucrose, fructose, or fructose syrup are obtained through hydrolysis and isomerization, and then catalytic hydrogenation is carried out using these as raw materials. However, regardless of the raw material used, sorbitol is inevitably present in the production of mannitol. The products prepared by the current mainstream methods generally contain sorbitol in a manner that is approximately equal to that of mannitol. At the same time, because mannitol can co-crystallize with sorbitol, separation is difficult. Although the mannitol content can be increased through purification processes such as concentration, cooling crystallization, separation, and drying, and the purity of mannitol is higher with more purification cycles, the cost of mannitol raw materials is also higher. According to experimental results, when the sorbitol content in mannitol is below 0.01 wt%, the performance improvement of the battery when the product prepared from this mannitol is used in the battery is negligible, with only a small increase in sorbitol content. This may be because the content of compound 1 in the electrolyte is no more than 5 wt%. When the sorbitol content in mannitol is below 0.01 wt%, the content of the trans-structure compound (Formula III) in the electrolyte of compound 1 will be less than 5 ppm. Since the content is very small in the entire electrolyte system, the effect of the trans-structure compound (Formula III) on the effect of compound 1 is also small. Under these circumstances, even if the content of the trans-structure compound (Formula III) in the compound of formula 1 is further reduced (i.e., the sorbitol content in mannitol is reduced), the performance improvement of the battery will be minimal. Therefore, considering both performance and cost, and while meeting the requirement of improving battery performance, among hexaols... A mass percentage content ≥0.01% is more preferred. In some specific embodiments of this application, the hexahydrol can be mannitol, and the mass percentage content of sorbitol in the mannitol can be ≤2%, preferably ≤1%, more preferably ≤0.5%, and more preferably ≤0.1%. Therefore, it is possible to obtain... The main target product.

[0120] In some specific embodiments of this application, step (1), after the transesterification reaction, may further include: a reduced pressure treatment to remove low-boiling-point components, thereby improving the purity of the compound represented by Formula I in the final product and reducing the impurity content. As some specific examples, the reduced pressure treatment may be a reduced pressure distillation treatment. Optionally, the pressure of the reduced pressure treatment may be -90 to -80 kPa (i.e., 90 to 80 kPa lower than standard atmospheric pressure), for example, -90 kPa, -85 kPa, -80 kPa, etc., and the temperature of the reduced pressure treatment may be 30 to 60°C, for example, 35°C, 40°C, 45°C, 50°C, 55°C, etc., thereby further facilitating the removal of low-boiling-point components.

[0121] In some specific embodiments of this application, step (2) may further include a reflux deacidification treatment after the condensation reaction is completed. This can reduce the residual HCl produced by the condensation reaction, thereby reducing the free chlorine content that may be introduced into the electrolyte subsequently. In some specific embodiments, the reflux deacidification temperature can be 40–80°C, for example, 40°C, 50°C, 60°C, 70°C, or 80°C. In some specific embodiments, the reflux deacidification temperature can be 10–50 min, for example, 15 min, 20 min, 30 min, 40 min, or 50 min. Meeting the reflux deacidification treatment conditions is beneficial for further reducing the residual HCl produced by the condensation reaction.

[0122] In some specific embodiments of this application, referring to Figure 1, in step (2), compound 1 can be dissolved in a solvent and then thionyl chloride can be added dropwise to carry out a condensation reaction. By slowly adding thionyl chloride to the mixture in this manner to react with compound 1, side reactions that may be caused by a relative excess of thionyl chloride can be significantly reduced, thereby better suppressing impurities. The generation of .

[0123] In some specific embodiments of this application, in step (2), the temperature of the condensation reaction can be 20–100°C, for example, 20–60°C, 20°C, 25°C, 30°C, 50°C, 60°C, 80°C, or 100°C. Controlling the temperature of the condensation reaction to meet the given conditions is beneficial for reducing the potential increase in the reactivity of thionyl chloride due to excessively high reaction temperature, which could lead to the depletion of chlorine-containing impurities (such as...). This reduces the risk of increased reaction rate, longer reaction time, and decreased production efficiency due to excessively low reaction temperature, thus achieving a better balance between reaction efficiency and the purity of the final product. Furthermore, the condensation reaction time can be 1–4 hours, for example, 1 hour, 2 hours, 3 hours, or 4 hours. This time is from the addition of thionyl chloride to the end of the condensation reaction. This time can be adaptively adjusted according to the addition time of thionyl chloride, allowing the reaction to continue for a period after the thionyl chloride is added to ensure complete condensation.

[0124] In some specific embodiments of this application, in step (2), the molar ratio of compound 1 to thionyl chloride can be 1:(2-3), for example, 1 / 2, 1 / 2.2, 1 / 2.5, 1 / 2.8, 1 / 3, etc., and the addition time of thionyl chloride can be 0.5-2h, for example, 0.5h, 0.8h, 1h, 1.5h, or 2h, etc. By controlling the amount of thionyl chloride added to meet the given range, it is beneficial to reduce the risk of mannitol conversion rate decrease due to relative thionyl chloride deficiency, the risk of incomplete reaction of hydroxyl groups, and the resulting decrease in purity and yield of compound 2 and the target product shown in Formula I. It is also beneficial to reduce the risk of increased chlorine impurities caused by excessive thionyl chloride addition. Furthermore, by ensuring that the addition time of thionyl chloride meets the given range, a suitable thionyl chloride addition rate can be obtained, which can improve the reaction rate and reduce the risk of increased chlorine impurities caused by excessively rapid thionyl chloride addition. Therefore, it is possible to balance the reaction rate and improve the purity of compound 2 and the final product, while reducing the impurity content.

[0125] In some specific embodiments of this application, in step (2), the solvent may be one or more of the following: ether solvents, N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAC), tetrahydrofuran, and ester solvents.

[0126] In some specific embodiments of this application, in step (3), the oxidant can be provided in the form of an aqueous solution, and the reaction of compound 2 with the oxidant can further include: heating the reaction product to remove moisture. As a specific example, when the solvent added in step (2) can azeotropically react with water, the heating treatment can be used to azeotropically treat the reaction product. Azeotropic treatment is also beneficial to further reduce metal cation impurities and free chloride ions that may be introduced into the final product during the reaction process.

[0127] In some specific embodiments of this application, in step (3), after the oxidation reaction is completed, the reaction product can be washed with water to remove inorganic salts. Specifically, the organic phase in the reaction product can be separated, and deionized water can be added for extraction and layering. After repeating this process multiple times, the solvent is removed to obtain the compound shown in Formula I. In some specific embodiments, solvent removal can be achieved by vacuum treatment, wherein the pressure of the vacuum treatment can be -90 to -80 kPa (i.e., 90 to 80 kPa lower than standard atmospheric pressure), for example, -90 kPa, -85 kPa, -80 kPa, etc., and the temperature of the vacuum treatment can be 30 to 60°C, for example, 35°C, 40°C, 45°C, 50°C, 55°C, etc., which is beneficial for further removal of solvent components.

[0128] In some specific embodiments of this application, the specific type of oxidant in step (3) is not particularly limited. Those skilled in the art can flexibly select it according to actual needs. For example, the oxidant may include, but is not limited to, one or more of hydrogen peroxide, sodium hypochlorite, and sodium periodate. For example, the oxidant may be sodium hypochlorite. As another example, the oxidant may be hydrogen peroxide. Choosing hydrogen peroxide can not only further reduce the chlorine-containing impurities that may be introduced into the final product, but also remove the generated moisture through heating treatment.

[0129] In some specific embodiments of this application, in step (3), the oxidant may include sodium hypochlorite and / or sodium periodate, and the molar ratio of compound 2 to the oxidant may be 1:(2-2.5), for example, 1 / 2, 1 / 2.1, 1 / 2.2, 1 / 2.3, 1 / 2.4, or 1 / 2.5. Controlling the content of the oxidant to meet the given range is beneficial for fully oxidizing compound 2, improving the yield and purity of the target product shown in Formula I, and also reducing the chlorine-containing impurities and / or inorganic salt impurities that may be introduced when the amount of oxidant is too large.

[0130] In some specific embodiments of this application, in step (3), the oxidant may include sodium hypochlorite and / or sodium periodate. The oxidant may be provided in the form of an aqueous solution. Before the reaction of compound 2 with the oxidant, the condensation reaction product is dissolved in a non-aqueous solvent, and then the oxidant is added to carry out the oxidation reaction. After the oxidation reaction, the process further includes: (4-1) heating the reaction product to remove moisture; (4-2) after the moisture is removed, inorganic salts precipitate out and are removed by filtration. This can remove moisture and inorganic salts from the final product, such as reducing the content of sodium hypochlorite or sodium periodate to tens or even a few ppm, while avoiding the loss of the target product caused by the water washing process.

[0131] It should be noted that the method for preparing polycyclic compounds in the second aspect of this application is based on the same inventive concept as the polycyclic compound in the first aspect of this application. The features and effects described for the polycyclic compound in the first aspect of this application are also applicable to the method for preparing polycyclic compounds in the second aspect of this application, and will not be repeated here.

[0132] In a third aspect of this application, a polycyclic compound prepared by the above-described method is provided. The polycyclic compound prepared includes: the compound shown in Formula I, wherein the content of the compound with the cis structure shown in Formula II in the compound shown in Formula I is ≥98 wt%. The features and effects described in the above-described method for preparing polycyclic compounds also apply to this polycyclic compound, and will not be repeated here.

[0133] In a fourth aspect of this application, the use of the aforementioned polycyclic compound and the method for preparing the polycyclic compound is proposed in the fields of electrolytes and batteries. The features and effects described for the aforementioned polycyclic compound and the method for preparing the polycyclic compound also apply to this use, and will not be repeated here.

[0134] In a fifth aspect of this application, an electrolyte is provided, comprising: an electrolyte additive, wherein the electrolyte additive includes the aforementioned polycyclic compound, or a polycyclic compound prepared by the aforementioned method for preparing polycyclic compounds. It should be noted that the features and effects described for the aforementioned polycyclic compound and the aforementioned method for preparing polycyclic compounds also apply to this electrolyte, and will not be elaborated upon here. In general, using this electrolyte in a battery can significantly improve the battery's high-temperature performance and cycle performance.

[0135] Typically, electrolytes also include electrolyte salts and organic solvents. Optionally, the electrolyte can be used in lithium batteries. Taking lithium batteries as an example, the electrolyte salt can be a lithium salt. The organic solvent is the main component of the electrolyte and an important carrier for ion transport. It allows the organic solvent to have high lithium salt solubility, thus giving the electrolyte high ionic conductivity. When the lithium salt dissolves in the organic solvent, it releases lithium ions. The lithium ions form a solvation structure with the organic solvent, which facilitates the rapid migration of lithium ions.

[0136] In some specific embodiments of this application, based on the total mass of the electrolyte, the content of electrolyte additives can be 0.1–5 wt%, for example, 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, etc. Controlling this range helps to control the content of compounds (byproducts) with the trans structure shown in Formula III in the electrolyte to below 500 ppm. Therefore, using the electrolyte in a battery can effectively improve the battery's high-temperature performance and cycle performance.

[0137] In some specific embodiments of this application, the organic solvent may include cyclic compounds and linear compounds. The cyclic compounds may include, but are not limited to, at least one of propylene carbonate, ethylene carbonate, γ-butyrolactone, sulfolane, and fluoroethylene carbonate. The linear compounds may include, but are not limited to, at least one of dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl propyl carbonate, ethyl acetate, propyl propionate, ethyl propionate, propyl acetate, methyl propionate, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, and 2,2-difluoroethyl acetate. Organic solvents within the given range, after dissolving lithium salts, can give the electrolyte a higher ionic conductivity, thereby further improving the electrochemical performance of the battery.

[0138] In some specific embodiments of this application, the specific composition of the organic solvent can be flexibly adjusted according to the actual situation of the battery system, etc. For example, as some specific examples, the organic solvent may include ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a mass ratio of 1:(0.5-2):(0.5-2). This organic solvent can be suitable for using layered transition metal oxidants, etc., as positive electrode active materials (e.g., those with the chemical formula Li). a Ni b Co c M1 d M2 e O f R g A positive electrode active material, wherein 1≤a≤1.2, 0.6≤b≤1, 0≤c≤1, 0≤d≤1, 0≤e≤0.2, b+c+d+e=1, 1≤f≤2, 0≤g≤1, f+g=2; M1 includes Mn and / or Al, M2 includes at least one of Zr, Zn, Cu, Cr, Mg, Fe, V, Ti, Sr, Sb, Y, W, Nb, and R includes at least one of N, F, S, Cl) in a battery system.

[0139] In some specific embodiments of this application, the lithium salt may include a main salt, which may include lithium hexafluorophosphate (LiPF6) and / or lithium bisfluorosulfonylimide (LiFSI). Optionally, the mass percentage of lithium hexafluorophosphate in the electrolyte may be 4% to 18%; and / or, the mass percentage of lithium bisfluorosulfonylimide in the electrolyte may be 0% to 10%. Since lithium salt accounts for a relatively high proportion of the cost in the electrolyte, controlling the lithium salt content within the given range is beneficial for ensuring sufficient dissolution of the lithium salt in the organic solvent and for achieving both high ionic conductivity and low manufacturing cost in the electrolyte. Further optionally, the mass percentage of the organic solvent in the electrolyte may be 10% to 90%.

[0140] In some specific embodiments of this application, in addition to the above-mentioned components, the electrolyte may optionally include a small amount of other conventional additives or auxiliaries that can improve certain battery performance. Those skilled in the art can select them according to actual needs, and will not elaborate further here.

[0141] In a sixth aspect of this application, a battery is proposed, comprising the aforementioned electrolyte. It should be noted that the features and effects described for the electrolyte in this application also apply to this battery, and will not be repeated here. In general, this battery exhibits good high-temperature performance and cycle performance. Furthermore, it should be noted that the type of battery is not particularly limited, and those skilled in the art can flexibly choose according to actual needs; for example, it can be a rechargeable battery.

[0142] Typically, a battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0143] In some embodiments of this application, the positive electrode sheet may include a positive current collector and a positive active material layer disposed on the surface of the positive current collector. The positive active material layer includes a positive active material, a conductive agent, and a binder. The positive current collector may include a metal foil or a composite positive current collector. For example, the metal foil may be aluminum foil. The composite positive current collector may include a polymer base layer and a metal layer formed on at least one side surface of the polymer base layer. For example, the composite negative current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, etc.) on a polymer base material (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), etc.). The positive active material includes lithium iron phosphate, nickel-cobalt-manganese ternary materials, lithium manganese iron phosphate, lithium manganese oxide, lithium nickel manganese oxide, lithium cobalt oxide, nickel-cobalt-aluminum, lithium-rich manganese oxide, or sodium electrode materials, and may also be a commonly used positive active material in the art. The conductive agent and binder may be conventional materials in the art.

[0144] In some embodiments of this application, the negative electrode sheet may include a negative electrode current collector and a negative electrode active material layer disposed on the surface of the negative electrode current collector. The negative electrode active material layer may include a negative electrode active material, a conductive agent, and a binder. The negative electrode current collector may be a metal foil or a composite current collector. For example, the metal foil may be copper foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. For example, the composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), etc.). The negative electrode active material may include commonly used negative electrode active materials in the art (such as, but not limited to, at least one of graphite, silicon-carbon composite materials, silicon materials, lithium metal, lithium titanate, etc.). The conductive agent and binder may be conventional materials in the art.

[0145] In some embodiments of this application, the separator can be a separator known in the art that can be used in batteries and is stable to the electrolyte used. Its material can include, but is not limited to, at least one of polyolefin, aromatic polyamide, polytetrafluoroethylene, and polyethersulfone, such as polyethylene separator, polypropylene separator, PE ceramic coated separator, etc., and can be flexibly selected as needed.

[0146] The embodiments of this application are described in detail below. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. In addition, unless otherwise specified, all reagents used in the following embodiments are commercially available or can be synthesized according to the methods described herein or known methods. For reaction conditions not listed, they are also readily available to those skilled in the art.

[0147] Example 1

[0148] 1. Preparation of polycyclic compounds:

[0149] (i) Mannitol, dimethyl carbonate, methanol, and sodium hydroxide were added to a reactor and reacted at 1 MPa and 75 °C for 1 h. The low-boiling material was then removed under reduced pressure at (-85±5) kPa and 50 °C to obtain a dried product mainly composed of compound 1. The structural formula of compound 1 is as follows: In this embodiment, Sorbitol accounts for 2 wt% of the total mass of mannitol.

[0150] (ii) Dissolve the dried product in dichloromethane (mass ratio of dichloromethane to dried product is 5:2), and add thionyl chloride dropwise to the dried product solution at room temperature over a period of 1.5 h, stirring for 3 h. The molar ratio of thionyl chloride to thionyl chloride was 1:2.1; the mixture was refluxed at 40°C for 30 min to remove acid, yielding the reaction product, which included compound 2. The structural formula of compound 2 is as follows: In this embodiment,

[0151] (iii) Add a 12% sodium hypochlorite aqueous solution to the reaction product of step (2) to carry out an oxidation reaction, separate the layers, take the organic phase, wash and extract the layers with deionized water, repeat 3 times, remove the solvent under reduced pressure at (-85±5) kPa and 30℃ to obtain the final product shown in Formula I. In this embodiment, The molar ratio of sodium hypochlorite to compound 2 is 2:1.

[0152] 2. Preparation of the positive electrode sheet

[0153] LiNi, the positive electrode active material 0.5 Co 0.2 Mn 0.3 O2 cathode material (NCM523), acetylene black, carbon nanotubes, and polyvinylidene fluoride (PVDF) were dispersed in NMP solvent at a mass ratio of 96.3:2:0.5:1.2 to obtain a cathode active material slurry. This slurry was then uniformly coated onto both sides of a cathode current collector aluminum foil. After drying, rolling, baking, slitting, and spot welding of tabs, a cathode sheet was obtained. The total thickness of the cathode sheet was 116 μm, and the compaction was 3.3 g / cm³. 3 Double-sided surface density 33 mg / cm³ 2 (Excluding foil)

[0154] 3. Preparation of negative electrode sheet

[0155] Artificial graphite, conductive agent Super P (conductive carbon black), binder styrene-butadiene rubber, and dispersant CMC (sodium carboxymethyl cellulose) were dispersed in deionized water at a mass ratio of 95:1.5:2:1.5 and stirred evenly to obtain a negative electrode active material layer slurry. The negative electrode active material layer slurry was uniformly coated on both sides of the negative electrode current collector copper foil. After drying, rolling, baking, slitting, and spot welding of electrode tabs, the negative electrode sheet was obtained. The total thickness of the negative electrode sheet was 134 μm, and the compaction was 1.6 g / cm³. 3 Double-sided surface density 20 mg / cm³ 2 (Excluding foil)

[0156] 4. Preparation of electrolyte

[0157] The electrolyte comprises, by mass percentage: lithium salt, organic solvent, and additives. The lithium salt comprises lithium hexafluorophosphate (LiPF6) at a mass percentage of 12.5%. The organic solvent is composed of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a mass ratio of EC:EMC:DEC = 3:5:2. The final product obtained in step 1 is used as the electrolyte additive. The electrolyte additive obtained in step 1 has a mass percentage of 0.5% in the electrolyte and is replenished to 100% with solvent.

[0158] 5. Lithium-ion battery manufacturing

[0159] The prepared positive electrode, negative electrode, and 12μm thick ceramic separator were stacked in sequence. The separator was placed between the positive and negative electrode. After winding, the wound body was flattened and placed in an aluminum-plastic film packaging bag. It was vacuum baked at 75℃ for 48h to obtain the cell to be injected with electrolyte. Then, the electrolyte was injected into the cell in a glove box. After encapsulation, formation, aging, and capacity testing, the lithium-ion battery was completed with a designed capacity of 1700mAh.

[0160] Examples 2-26 and Comparative Examples 1-8

[0161] The differences between Examples 2-26 and Comparative Examples 1-8 and Example 1 are detailed in Tables 1-2.

[0162] The structure, purity, cis-trans structure composition, content of chlorinated organic impurities, and cycle performance of the polycyclic compounds obtained in Examples 1-26 and Comparative Examples 1-8 were tested. The test methods are shown below, and the test results are shown in Table 2.

[0163] (1) The content of sorbitol in mannitol raw material was determined by high performance liquid chromatography; the compound structure of the obtained polycyclic compound final product was determined by nuclear magnetic resonance (NMR) spectroscopy; the components of the obtained polycyclic compound final product were quantitatively analyzed by liquid chromatography; the content of chlorine-containing organic matter was analyzed by high performance liquid chromatography; the content of target product with cis structure in the final product was determined by high performance liquid chromatography.

[0164] ①The specific method for determining mannitol and sorbitol using high performance liquid chromatography is as follows:

[0165] 1) Reagents and instruments used in the experiment:

[0166] a) Acetonitrile (HPLC grade).

[0167] b) Trifluoroacetic acid (AR or GR grade).

[0168] c) Deionized water (prepared using a pure water system).

[0169] d) Column: AQ C-184.6*250mm.5μm.

[0170] e) Electronic balance: accuracy 0.00001g.

[0171] f) High performance liquid chromatograph (with ELSD detector): Agilent 1260 Infinity II.

[0172] 2) Test conditions:

[0173] a) Mobile phase:

[0174] Mobile phase A: 0.1% trifluoroacetic acid + 95% water + 5% acetonitrile solution (0.1% v / v). Accurately transfer 1 ml of trifluoroacetic acid into 1 L of acetonitrile-water mixed solution, mix well and sonicate.

[0175] Mobile phase B: 95% acetonitrile + 5% aqueous solution (v / v).

[0176] Diluent: Acetonitrile.

[0177] The gradient elution procedure is shown in Table 1.

[0178] Table 1

[0179] b) Flow rate: 1.0 mL / min.

[0180] c) Injection volume: 5 μL.

[0181] d) Column temperature: 30℃.

[0182] e) Data collection time: 16 min.

[0183] 3) Experimental steps:

[0184] Sample preparation: In a glove box, add acetonitrile to the sample vial to dissolve the sample, and wash the sample vial three times with acetonitrile. Pour the solution into a 50 mL volumetric flask, add acetonitrile to make up to volume, shake well, filter through a 0.45 μm filter into an ampoule, and test on the instrument. For the peak results of the test sample, except for the blank spectrum peak, integrate all other peaks, calculate the purity using the area normalization method, and take the arithmetic mean as the determination result.

[0185] In addition, repeatability tests were performed on 6 samples, and the sample purity was calculated using area normalization, and the repeatability RSD% was calculated. Samples from 0h and 24h were examined, with one parallel sample required for the 24h sample. A total of 8 test samples were prepared for each sample: 6 repeatability tests + 2 24h samples = 8 test samples.

[0186] In order to clearly show the peak position of sorbitol in the spectrum, high performance liquid chromatography was used to detect crude mannitol as an example. The detection results are shown in Figure 4.

[0187] ②The specific method for testing the target product and isomers using high performance liquid chromatography is as follows:

[0188] 1) Reagents and instruments used in the experiment:

[0189] a) Acetonitrile (HPLC grade).

[0190] b) Trifluoroacetic acid (AR or GR grade).

[0191] c) Deionized water (prepared using a pure water system).

[0192] d) Column: AQ C-184.6*250mm.5μm.

[0193] e) Electronic balance: accuracy 0.00001g.

[0194] f) High performance liquid chromatograph (with CAD detector): Thermo Fisher U3000.

[0195] 2) Test conditions:

[0196] a) Mobile phase:

[0197] Mobile phase A: 0.1% trifluoroacetic acid + 95% water + 5% acetonitrile solution (0.1% v / v). Accurately transfer 1 ml of trifluoroacetic acid into 1 L of acetonitrile-water mixed solution, mix well and sonicate.

[0198] Mobile phase B: 95% acetonitrile + 5% aqueous solution (v / v).

[0199] Diluent: Acetonitrile.

[0200] The gradient elution procedure is shown in Table 2.

[0201] Table 2

[0202] b) Flow rate: 1.0 mL / min.

[0203] c) Injection volume: 5 μL.

[0204] d) Column temperature: 30℃.

[0205] e) Data collection time: 16 min.

[0206] 3) Experimental steps:

[0207] Sample preparation: In a glove box, add acetonitrile to the sample vial to dissolve the sample, and wash the sample vial three times with acetonitrile. Pour the solution into a 50 mL volumetric flask, add acetonitrile to make up to volume, shake well, filter through a 0.45 μm filter into an ampoule, and test on the instrument. For the peak results of the test sample, except for the blank spectrum peak, integrate all other peaks, calculate the purity using the area normalization method, and take the arithmetic mean as the determination result.

[0208] In addition, repeatability tests were performed on 6 samples, and the sample purity was calculated using area normalization, and the repeatability RSD% was calculated. Samples from 0h and 24h were examined, with one parallel sample required for the 24h sample. A total of 8 test samples were prepared for each sample: 6 repeatability tests + 2 24h samples = 8 test samples.

[0209] The polycyclic compound obtained in Example 1 was used as an example for detection by high performance liquid chromatography, and the detection results are shown in Figure 5.

[0210] (2) Room temperature cycle performance test: The formed battery was charged at 25°C with a constant current of 3C to 4.35V, and then charged at a constant voltage of 4.35V to the cutoff current of 0.05C. Then the battery was discharged at 1C to the voltage of 2.75V. The charge and discharge cycle was repeated for 800 cycles. The discharge capacity of the 800th cycle was recorded and divided by the discharge capacity of the 1st cycle to obtain the capacity retention rate.

[0211] (3) High temperature cycle performance test: The formed battery was charged at 45°C with a constant current of 1C to 4.35V, and then charged at a constant voltage of 4.35V to the cutoff current of 0.05C. Then the battery was discharged at 1C to the voltage of 2.75V. The charge and discharge cycle was repeated for 500 cycles. The discharge capacity of the 500th cycle was recorded and divided by the discharge capacity of the 1st cycle to obtain the capacity retention rate.

[0212] (4) High-temperature storage performance test: At 25℃, the battery was charged at a constant current of 1C to 4.35V, then charged at a constant voltage of 4.35V to a cutoff current of 0.05C. The battery was then discharged at a constant current of 1C to 2.75V, and the discharge capacity was recorded as C1. The battery was then transferred to a high temperature of 60℃ and left to stand for 14 days before being discharged at a constant current of 1C. The discharge capacity was recorded as C2. The capacity retention rate at 60℃ = C2 / C1 × 100%.

[0213] Example 27

[0214] The preparation of the polycyclic compound is exactly the same as in Example 9. The main differences lie in the preparation of the negative electrode, positive electrode, electrolyte, and lithium battery. The test conditions for related experiments also differ, as detailed below:

[0215] 1. Preparation of positive electrode sheet

[0216] LiFePO4 cathode material (LFP), acetylene black, carbon nanotubes, polyvinylidene fluoride (PVDF), and lithium supplementer LFO were dispersed in NMP solvent at a mass ratio of 93.5:2:0.5:2:2 to obtain a cathode active material slurry. This slurry was then uniformly coated onto both sides of an aluminum foil current collector. After drying, rolling, baking, slitting, and spot welding of tabs, a cathode sheet was obtained. The total thickness of the cathode sheet was 198 μm, and the compaction was 2.2 g / cm³. 3 Double-sided surface density 40 mg / cm³ 2 (Excluding foil)

[0217] 2. Preparation of negative electrode sheet

[0218] Artificial graphite, conductive agent Super P (conductive carbon black), binder styrene-butadiene rubber, and dispersant CMC (sodium carboxymethyl cellulose) were dispersed in deionized water at a mass ratio of 95:1.5:2:1.5 and stirred evenly to obtain a negative electrode active material layer slurry. The negative electrode active material layer slurry was uniformly coated on both sides of the negative electrode current collector copper foil. After drying, rolling, baking, slitting, and spot welding of electrode tabs, the negative electrode sheet was obtained. The total thickness of the negative electrode sheet was 129 μm, and the compaction was 1.5 g / cm³. 3 Double-sided surface density 18 mg / cm³ 2 (Excluding foil)

[0219] 3. Preparation of electrolyte

[0220] The electrolyte comprises, by mass percentage, lithium salt, organic solvent, and additives. The lithium salt comprises lithium hexafluorophosphate (LiPF6) at a mass percentage of 12.5%. The organic solvent is composed of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a mass ratio of EC:PC:EMC:DMC = 2:1:6:1. The conventional additive is 2.5% VC. The final product obtained in step 1 is used as the electrolyte additive. The electrolyte additive obtained in step 1 has a mass percentage of 0.5% in the electrolyte, which is replenished to 100% with solvent.

[0221] 4. Lithium-ion battery manufacturing

[0222] The prepared positive electrode, negative electrode, and 12μm thick ceramic separator were stacked in sequence. The separator was placed between the positive and negative electrode. After winding, the wound body was flattened and placed in an aluminum-plastic film packaging bag. It was vacuum baked at 75℃ for 48h to obtain the cell to be injected with electrolyte. Then, the electrolyte was injected into the cell in a glove box. After encapsulation, formation, aging, and capacity testing, the lithium-ion battery was completed with a designed capacity of 1500mAh.

[0223] 5. Test conditions

[0224] (1) Room temperature cycle performance test: The formed battery was charged at 25°C with a constant current of 1C to 3.65V, and then charged at a constant voltage of 3.65V to the cutoff current of 0.05C. Then the battery was discharged at 1C to 2.0V. The charge and discharge cycle was repeated for 5000 cycles. The discharge capacity of the 5000th cycle was recorded and divided by the discharge capacity of the 1st cycle to obtain the capacity retention rate.

[0225] (3) High temperature cycle performance test: The formed battery was charged at 45°C with a constant current of 1C to 3.65V, and then charged at a constant voltage of 3.65V to the cutoff current of 0.05C. Then the battery was discharged at 1C to 2.0V. The charge and discharge cycle was repeated for 2000 cycles. The discharge capacity of the 2000th cycle was recorded and divided by the discharge capacity of the 1st cycle to obtain the capacity retention rate.

[0226] (4) High-temperature storage performance test: At 25℃, the battery was charged at a constant current of 1C to 3.65V, then charged at a constant voltage of 3.65V to a cutoff current of 0.05C. The battery was then discharged at a constant current of 1C to 2.0V, and the discharge capacity was recorded as C1. The battery was then transferred to a high temperature of 60℃ and left to stand for 90 days, after which it was discharged at a constant current of 1C, and the discharge capacity was recorded as C2. The capacity retention rate at 60℃ = C2 / C1 × 100%.

[0227] Example 28

[0228] The preparation of the polycyclic compound is exactly the same as in Example 9. The main differences lie in the preparation of the negative electrode, positive electrode, electrolyte, and lithium battery. The test conditions for related experiments also differ, as detailed below:

[0229] 1. Preparation of positive electrode sheet

[0230] LiMnFePO4 (LMFP), acetylene black, carbon nanotubes, and polyvinylidene fluoride (PVDF) were dispersed in NMP solvent at a mass ratio of 94.1:2:0.5:3.4 to obtain a positive electrode active material slurry. This slurry was then uniformly coated onto both sides of a positive electrode current collector aluminum foil. After drying, rolling, baking, slitting, and spot welding of tabs, a positive electrode sheet was obtained. The total thickness of the positive electrode sheet was 168 μm, and the compaction was 2.3 g / cm³. 3 Double-sided surface density 35 mg / cm³ 2 (Excluding foil)

[0231] 2. Preparation of negative electrode sheet

[0232] Artificial graphite, conductive agent Super P (conductive carbon black), binder styrene-butadiene rubber, and dispersant CMC (sodium carboxymethyl cellulose) were dispersed in deionized water at a mass ratio of 95:1.5:2:1.5 and stirred evenly to obtain a negative electrode active material layer slurry. The negative electrode active material layer slurry was uniformly coated on both sides of the negative electrode current collector copper foil. After drying, rolling, baking, slitting, and spot welding of electrode tabs, the negative electrode sheet was obtained. The total thickness of the negative electrode sheet was 112 μm, and the compaction was 1.6 g / cm³. 3 The areal density of both sides is 16.4 mg / cm³. 2 (Excluding foil)

[0233] 3. Preparation of electrolyte

[0234] The electrolyte comprises, by mass percentage: lithium salt, organic solvent, and additives. The lithium salt comprises lithium hexafluorophosphate (LiPF6) at a mass percentage of 12.5%. The organic solvent is composed of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a mass ratio of EC:PC:EMC:DEC = 2:1:5:2. The conventional additive is 1.7% VC. The final product obtained in step 1 is used as the electrolyte additive. The electrolyte additive obtained in step 1 has a mass percentage of 0.5% in the electrolyte and is replenished to 100% with solvent.

[0235] 4. Cell Testing

[0236] (1) Room temperature cycle performance test: The formed battery was charged at 25°C with a constant current of 3C to 4.25V, and then charged at a constant voltage of 4.25V to the cutoff current of 0.05C. Then the battery was discharged at 1C to the voltage of 2.5V. The charge and discharge cycle was repeated for 800 cycles. The discharge capacity of the 800th cycle was recorded and divided by the discharge capacity of the 1st cycle to obtain the capacity retention rate.

[0237] (2) High temperature cycle performance test: The formed battery was charged at 45°C with a constant current of 1C to 4.25V, and then charged at a constant voltage of 4.25V to the cutoff current of 0.05C. Then the battery was discharged at 1C to the voltage of 2.5V. The charge and discharge cycle was repeated for 500 cycles. The discharge capacity of the 500th cycle was recorded and divided by the discharge capacity of the 1st cycle to obtain the capacity retention rate.

[0238] (3) High-temperature storage performance test: At 25℃, the battery was charged at a constant current of 1C to 4.25V, then charged at a constant voltage of 4.25V to a cutoff current of 0.05C. The battery was then discharged at a constant current of 1C to 2.5V, and the discharge capacity was recorded as C1. The battery was then transferred to a high temperature of 60℃ and left to stand for 60 days, after which it was discharged at a constant current of 1C, and the discharge capacity was recorded as C2. The capacity retention rate at 60℃ = C2 / C1 × 100%.

[0239] Comparative Example 9

[0240] The difference from Example 27 is that the content of sorbitol in the hexahydrol used to prepare the polycyclic compound is 99 wt%, while the other preparation and testing methods are exactly the same.

[0241] Comparative Example 10

[0242] The difference from Example 28 is that the content of sorbitol in the hexahydrol used to prepare the polycyclic compound is 99 wt%, while the other preparation and testing methods are exactly the same.

[0243] Note: In Tables 3-1, 3-2, and 3-3, the hexahydric alcohols in the examples are... The main focus is on structure.

[0244] Note: In Table 4-1, ND indicates that the detection limit was exceeded and the substance was not detected.

[0245] Results and conclusions:

[0246] Based on the data in Tables 3-1, 3-2, 3-3, 4-1, 4-2, 4-3, and 4-4, it can be seen that the target product obtained by the method of the above embodiments of this application is mainly cis-structured, with a low mass percentage of trans-structure, generally below 2%. Taking Example 1 as an example, Figure 2 shows the 1H NMR spectrum of the final product obtained in Example 1. Compared with the reaction of Comparative Example 3, which uses hexaols mainly containing trans-structure as raw materials (Figure 3 shows the 1H NMR spectrum of the final product obtained in Comparative Example 3), the mass percentage of cis-structure in its product is higher, at 98.2%. Furthermore, as can be seen from Examples 1-8 and Comparative Examples 1-3, controlling the purity of mannitol can increase the content of the target product with a cis structure. In addition, as can be seen from Examples 9-11 and Examples 18-22, controlling the process conditions can further improve the selectivity of the target product and reduce the content of impurities, especially the content of chlorinated organic compounds. Under the same conditions, transesterification under specific heating and pressurization conditions can improve the selectivity and yield of the target product. Appropriately increasing the pressure is also beneficial to further improve the selectivity and yield of the target product.

[0247] As shown in Examples 1-5 and Comparative Examples 1-3, the higher the content of the cis-structure compound shown in Formula II and the lower the content of the trans-structure compound shown in Formula III in the final product, the better the performance of the final product in battery applications. As shown in Examples 6-8, when the content of the trans-structure compound shown in Formula III in Formula 1 is less than 0.01%, the performance improvement of the final product in battery applications is not significant as the content of the trans-structure compound shown in Formula III decreases. As shown in Examples 9-11 and Examples 18-22, the purity of the final product also affects its performance in batteries; if the purity is too low, it will have a significant negative impact on battery performance. As shown in Examples 18-22 and Comparative Examples 4-8, under the same preparation conditions, the higher the trans-structure content in the raw material hexaol, the worse the performance of the final product in batteries. Meanwhile, Examples 1, 27, 28, and Comparative Examples 1-3, 9, and 10 demonstrate that the product of this application has good effects in different battery systems. The inventors also discovered that the degree of transition metal dissolution varies under different battery systems, and the impact on battery performance is also different. In systems with more severe battery dissolution (e.g., battery systems under high voltage (4.35V) and 3C / 1C fast charging conditions), controlling the content of the compound with the cis structure shown in Formula II in the compound shown in Formula I has a more prominent effect on improving battery performance.

[0248] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0249] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. Polycyclic compounds, among which, include: The compound represented by Formula I, wherein the content of the compound with the cis structure represented by Formula II in the compound represented by Formula I is ≥98 wt%. R1 and R2 are each independently any one of H, F, alkyl, and fluoroalkyl.

2. The polycyclic compound according to claim 1, wherein, At least one of the following conditions must be met: (i) The polycyclic compound further includes chlorinated organic compounds, and the total content of the chlorinated organic compounds is ≤300 ppm based on the mass of the polycyclic compound; (ii) The polycyclic compound further includes other organic compounds selected from one or more of the following six compounds: Based on the mass of the polycyclic compound, the total content of the other organic compounds is ≤1000ppm; (iii) Based on the mass of the polycyclic compound, the content of the compound represented by Formula I is ≥99 wt%; (iv) The content of the compound with the cis structure shown in Formula I is ≥98.9 wt%; (v) The compound represented by Formula I also includes the compound with the trans structure represented by Formula III, wherein the content of the compound with the trans structure represented by Formula III in the compound represented by Formula I is ≤1%. (ⅵ) R1 and R2 are each independently any one of H, F, and fluoromethyl.

3. The polycyclic compound according to claim 2, wherein, At least one of the following conditions must be met: (a) The chlorinated organic compounds include chlorinated organic compounds that do not contain cyclic sulfate groups and cyclic carbonate groups, chlorinated organic compounds that contain only cyclic carbonate groups, chlorinated organic compounds that contain only cyclic sulfate groups, and chlorinated organic compounds that contain 1 to 2 cyclic carbonate groups and 1 cyclic sulfate group. (b) Based on the mass of the polycyclic compound, the total content of the chlorinated organic matter is ≤100 ppm; (c) Based on the mass of the polycyclic compound, the total content of the other organic compounds is ≤200 ppm; (d) Based on the mass of the polycyclic compound, the content of the compound represented by Formula I is ≥99.9 wt%; (e) The content of the compound with the trans structure shown in Formula I is ≤0.5wt%.

4. The polycyclic compound according to claim 2 or 3, wherein, At least one of the following conditions must be met: (α) The chlorine-containing organic compounds include: One or more of the following; (β) Based on the mass of the polycyclic compound, the total content of the chlorinated organic matter is ≤50ppm; (γ) The content of the compound with the cis structure shown in Formula II in the compound represented by Formula I is ≥99.9 wt%; (δ) The content of the compound with the trans structure shown in Formula I is ≤0.1%; (ε) The compounds represented by Formula I include The compounds represented by Formula II include (ζ) The content of the compound with the trans structure shown in Formula I is ≥0.01wt%; (η) The content of the compound with the cis structure shown in Formula II of the compound shown in Formula I is ≤99.99 wt%.

5. A method for preparing polycyclic compounds, wherein, include: (1) Mix hexahydrol, monohydric alcohol, carbonate and basic catalyst and carry out transesterification reaction to obtain compound 1; (2) Compound 1 was dissolved in a solvent and then condensed with thionyl chloride to obtain compound 2; (3) The compound 2 was reacted with an oxidizing agent to obtain the compound shown in Formula I. The structural formulas of compound 1 and compound 2 are as follows: The hexaol includes The hexahydrol The mass percentage content is ≤2%, wherein R1 and R2 are independently any one of H, F, alkyl, and fluoroalkyl; The compound represented by Formula I is:

6. The method according to claim 5, wherein, The process of mixing hexahydrol, monohydric alcohol, carbonate, and basic catalyst to carry out transesterification reaction satisfies at least one of the following conditions: (A) The transesterification reaction is further complicated by: depressurization treatment in order to remove low-boiling-point components; (B) The conditions for the transesterification reaction are: temperature 65-100℃, pressure ≤2.5 MPa, and reaction time 0.5-6 h; (C) The molar ratio of the carbonate to the hexahydrol is (3:1) to (5:1); (D) The molar ratio of the monohydric alcohol to the hexahydric alcohol is (10:1) to (20:1); (E) The amount of the basic catalyst is 0.01 to 5 wt%, based on the mass of the hexahydrol; (F) The carbonate includes one or more of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, and diphenyl carbonate; (G) The monohydric alcohol includes one or more of methanol, ethanol, propanol, isopropanol, butanol, and tert-butanol; (H) The alkaline catalyst includes one or more of sodium hydroxide, potassium hydroxide, potassium carbonate, sodium carbonate, lithium carbonate, sodium methoxide, sodium ethoxide, sodium tert-butoxide, potassium tert-butoxide, triethylamine, and pyridine; (I) Of the hexahydrol, The mass percentage content is ≤1%; (J) Of the hexahydrol, The mass percentage content is ≥0.01%.

7. The method according to claim 5 or 6, wherein, At least one of the following conditions must be met: (I) In step (2), after the condensation reaction is completed, the following further steps are taken: reflux deacidification treatment; optionally, the temperature of the reflux deacidification treatment is 40-80°C, and / or the time of the reflux deacidification treatment is 10-50 min; (II) In step (2), after dissolving the compound 1 in a solvent, thionyl chloride is added dropwise to carry out the condensation reaction; (III) In step (2), the temperature of the condensation reaction is 20 to 100°C and the time is 1 to 4 hours; (IV) In step (2), the molar ratio of compound 1 to thionyl chloride is 1:(2-3), and the addition time of thionyl chloride is 0.5-2h; (V) In step (2), the solvent includes one or more of the following: ether solvents, N,N-dimethylformamide, N,N-dimethylacetamide, tetrahydrofuran, and ester solvents; (VI) In step (3), the oxidant is provided in the form of an aqueous solution. After reacting the compound 2 with the oxidant, the reaction product is further subjected to a heating treatment to remove moisture.

8. The method according to any one of claims 5 to 7, wherein, The process of mixing hexahydrol, monohydric alcohol, carbonate, and basic catalyst to carry out transesterification reaction satisfies at least one of the following conditions: (①) The temperature of the transesterification reaction is 70-90℃ and the pressure is 0.5-2.2 MPa; (②) The molar ratio of the monohydric alcohol to the hexahydric alcohol is (12:1) to (18:1); (③) Based on the mass of the hexahydrol, the amount of the alkaline catalyst is 0.02 to 0.5 wt%. (④) Of the hexahydrol, The mass percentage content is ≤0.5%.

9. The method according to any one of claims 5 to 8, wherein, The process of mixing hexahydrol, monohydric alcohol, carbonate, and basic catalyst to carry out transesterification reaction satisfies at least one of the following conditions: (i) The temperature of the transesterification reaction is 75-85℃ and the pressure is 1-2 MPa; (ii) The molar ratio of the monohydric alcohol to the hexahydric alcohol is (14:1) to (16:1); (iii) Based on the mass of the hexahydrol, the amount of the alkaline catalyst is 0.02 to 0.1 wt%. (iv) Of the hexahydrols, The mass percentage content is ≤0.1%.

10. A polycyclic compound prepared by the method according to any one of claims 5 to 9, wherein, include: The content of the compound shown in Formula I, and the compound with the cis structure shown in Formula II in the compound shown in Formula 1, is ≥98wt%. The compound with the cis structure shown in Formula II is:

11. Use of the polycyclic compound of any one of claims 1 to 4 or the polycyclic compound prepared by any one of claims 5 to 9 in the field of electrolytes and batteries.

12. Electrolyte, wherein, include: Electrolyte additives, wherein the electrolyte additives comprise any one of the polycyclic compounds of claims 1 to 4, or polycyclic compounds prepared by any one of claims 5 to 9.

13. The electrolyte according to claim 12, wherein, Based on the total mass of the electrolyte, the content of the electrolyte additive is 0.1 to 5 wt%.

14. Batteries, of which, include: The electrolyte according to claim 12 or 13.

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