Preparation method and application of chain unsaturated monosulfonate compound

Abstract

The invention discloses an application of a chain unsaturated monosulfonate compound in an electrolyte, the application is as follows: the monosulfonate compound is added into the electrolyte according to an addition amount accounting for 0.1-5.0 wt% of the total mass of the electrolyte, the unsaturation degree of unsaturated carbon bonds in the monosulfonate compound is greater than or equal to 2, and the chromaticity is less than or equal to 100 Hazen. The preparation method of the monosulfonate compound comprises the following steps: in an organic solvent, alkyne (alkene) alcohol and alkyl sulfonyl chloride are used as raw materials, a reaction solution is prepared under the action of alkali, and the chromaticity of the product is greatly reduced through the step of separating the monosulfonate compound from impurities in the post-treatment process of the reaction solution. The product has the advantages of high product purity and low product chromaticity, is used in an electrolyte, and can reduce the battery impedance and improve the normal-temperature cycle performance while ensuring the high-temperature cycle and high-temperature storage performance of the battery, so that the battery has the advantages of high-temperature and low-temperature performance at the same time.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electrolyte additives, in particular to a preparation method of a low-color-chain polyunsaturated monosulfonate compound and its application in electrolyte. BACKGROUND

[0002] As an indispensable part of lithium ion batteries, electrolyte additives are mainly responsible for building a stable electrode / electrolyte interface film to achieve electronic insulation and facilitate lithium ion transmission. Under the influence of different functional groups in the additives, the composition and structure of the battery interface film change, ultimately affecting the battery cycle life and high-temperature storage performance.

[0003] There are various types of electrolyte additives, and different additives have different effects. Among them, sulfonate additives can participate in the film formation of the battery positive electrode, inhibit the production of gas during high-temperature storage of the battery, and improve high-voltage cycling.

[0004] PS (1,3-propanesultone), PES (1,3-propylene sulfite), MMDS (methylene methane disulfonate), and other commonly used sulfonate compounds are all cyclic structures. Although they can be used in lithium ion battery electrolytes to modify the interface film composition and improve the high-temperature cycling performance, the interface film formed has high impedance, resulting in poor low-temperature and rate performance of the battery. Secondly, this type of sulfonate additive has limited improvement on the high-voltage and high-temperature performance of the battery, and cannot meet the performance requirements of the battery under more stringent conditions (such as voltage > 4.4V, temperature > 60℃).

[0005] LG Chemical patent CN1823438A discloses a chain sulfonate represented by [Formula 4] while disclosing cyclic sulfonate compounds. Both cyclic sulfonates and chain sulfonates can improve the high-temperature storage performance of the battery. Although the chain sulfonate of [Formula 4] gives the possibility of an alkenyl-substituted unsaturated chain sulfonate, the performance data is not disclosed in the examples, and the preparation method of the alkenyl-substituted unsaturated chain sulfonate is also not disclosed.

[0006] Panasonic patent CN102195077A discloses that unsaturated chain sulfonates can improve the high-temperature performance of the battery, and the reason is that unsaturated chain sulfonates are oxidized and decomposed before the solvent to form a film, but this additive has the defect of high impedance.

[0007] In order to solve the problem of high impedance of unsaturated chain sulfonate, Yubuto patent CN104205471A discloses a way of using low impedance salt additives and chain unsaturated monosulfonate to reduce impedance to realize the balance of high temperature storage and low temperature discharge performance of battery. SK new energy patent CN113497273A uses difluorophosphate to reduce the high internal resistance problem of chain unsaturated monosulfonate, and through the combination of two additives, the capacity retention rate is increased, and the increase of volume expansion and internal resistance is inhibited. SUMMARY

[0008] It is found in the research process of the present application that saturated sulfonate compounds are generally colorless and transparent, but chain unsaturated monosulfonate shows different colors. With the increase of unsaturation, the chain unsaturated monosulfonate shows yellow brown or even black brown. When this kind of chain unsaturated monosulfonate is used in electrolyte, the high temperature storage performance of the battery can be improved, and the cycle performance of the battery at high voltage can be improved, but the impedance of the battery is high, the low temperature performance and rate performance of the battery are poor, and the cycle performance and storage performance of the battery are decreased under harsh conditions (such as voltage > 4.4V, temperature > 60℃).

[0009] Further gas chromatography analysis shows that the purity of the chain unsaturated monosulfonate product showing yellow brown or even black brown can reach 99%, which is the reason why the existing technology generally considers that yellow brown or even black brown is the color of the chain unsaturated monosulfonate itself. However, the inventors have found that the coloration of the chain unsaturated monosulfonate product is not caused by the chain unsaturated monosulfonate itself, but by a trace amount of π-rich unsaturated structure compound impurities containing nitrogen and oxygen heteroatoms (presumably high-boiling polymers). The impurities have conjugation effect and can absorb visible light with wavelength of 390-780nm, resulting in coloration of the product, and the color degree is ≥500 Hazen.

[0010] In order to solve the above technical problems, the present application provides a preparation method of low color degree chain unsaturated monosulfonate compound and its application in electrolyte. The monosulfonate compound prepared has color degree ≤100 Hazen and purity >99%, and when used in electrolyte, the battery impedance is reduced and the normal temperature cycle performance is improved while ensuring the high temperature cycle and high temperature storage performance of the battery, and the excellent high temperature cycle performance and high temperature storage performance are still maintained under harsh high voltage environment.

[0011] The purpose of the present application is achieved by the following technical scheme:

[0012] The application of a chain unsaturated monosulfonate compound in electrolyte, the application comprising: adding the monosulfonate compound to the electrolyte in an amount of 0.1-5.0wt% of the total mass of the electrolyte, preferably in an amount of 0.5-2.0wt%, and the structure is shown in the following formula (I):

[0013]

[0014]

[0015] wherein R1, R2 are independently selected from C1-C5 alkyl, C1-C5 haloalkyl, C2-C7 alkenyl or C2-C7 alkynyl, and at least one of R1, R2 is C2-C7 alkenyl or C2-C7 alkynyl; preferably, R1, R2 are independently selected from C2-C3 alkyl, C2-C3 haloalkyl, C2-C5 alkenyl or C2-C5 alkynyl, and at least one of R1, R2 is C2-C5 alkenyl or C2-C5 alkynyl;

[0016] The unsaturation degree of the unsaturated carbon bond in the mono-sulfonate compound is ≥ 2, and the colority is ≤ 100 Hazen.

[0017] In a specific embodiment, the mono-sulfonate compound is selected from at least one of the following compounds:

[0018]

[0019] The mono-sulfonate compound of the present application has both sulfonate group and carbon-carbon unsaturated bond, which have good synergistic effect: the sulfonate group can participate in the film-forming reaction of the positive and negative electrodes to form an interface film rich in RSO3Li, Li2SO3 and Li2S, which is dense and stable; the carbon-carbon unsaturated bond has high redox activity, which also has a modification effect on the interface film, which is conducive to the formation of a cross-linked and firm interface film skeleton. The low-color chain unsaturated sulfonate compound of the present application after removing impurities has lower battery impedance than the conventional cyclic sulfonate (such as PS). And, when the unsaturation degree of the unsaturated carbon bond in the mono-sulfonate compound is ≥ 2, the battery has more excellent normal temperature cycle, high temperature cycle and high temperature storage performance.

[0020] The electrolyte of the present application further comprises a main lithium salt, a non-aqueous solvent and a basic additive;

[0021] The main lithium salt is selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bisfluorosulfonylimide or lithium bis-trifluoromethylsulfonylimide, and the molar concentration is 0.1-4.0 mol / L, preferably 0.8-1.5 mol / L;

[0022] The non-aqueous solvent is selected from at least one of C3-C6 carbonate compound, C3-C8 carboxylic acid ester compound, sulfone compound or ether compound, and the addition amount is 60-95wt% of the total mass of the electrolyte; the C3-C6 carbonate compound is selected from at least one of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate and ethyl propyl carbonate; the C3-C8 carboxylic acid ester compound is selected from at least one of γ-butyrolactone, methyl acetate, methyl propionate, methyl butyrate, ethyl acetate, ethyl propionate, ethyl butyrate, propyl acetate and propyl propionate; the sulfone compound is selected from at least one of sulfolane, dimethyl sulfoxide, dimethyl sulfone and diethyl sulfone; and the ether compound is selected from triethylene glycol dimethyl ether and / or tetraethylene glycol dimethyl ether.

[0023] The base additive includes at least one of vinylene carbonate, 1,3-propane sultone, ethylene sulfate, 4-methyl ethylene sulfate, 4,4'-ethylene disulfate, fluoroethyl carbonate, bis-fluoroethyl carbonate, tris(trimethylsilyl)phosphate, tris(trimethylsilyl)borate, lithium difluorophosphate, lithium bisfluorosulfonimide, lithium difluorobisoxalate phosphate and lithium difluoroborate oxalate, and the addition amount of any one of the base additives is 0.1-5.0wt% of the total mass of the electrolyte.

[0024] In a specific embodiment, the non-aqueous solvent includes at least ethylene carbonate and diethyl carbonate, and the mass ratio of ethylene carbonate to diethyl carbonate is 1:(0.1-10). Single solvent has defects, for example, the freezing point of ethylene carbonate is very high, and the dielectric constant of diethyl carbonate is low, so two or more solvents are usually mixed to effectively adjust the viscosity, dielectric constant, freezing point and other properties of the electrolyte.

[0025] The base additive includes at least one of 0.2-1.5wt% of lithium difluorophosphate, 0.1-3.0wt% of 1,3-propane sultone and 0.2-3wt% of lithium bisfluorosulfonimide.

[0026] In a preferred embodiment, the base additive includes at least 0.5-1.0wt% of lithium difluorophosphate, further increasing the inorganic components in the battery interface film, and such substances have high electrochemical stability, thereby further improving the cycle performance and high-temperature storage performance of the battery.

[0027] In a preferred embodiment, the base additive includes at least 0.5-1.0wt% of lithium difluorophosphate and 0.5-1.0wt% of lithium bisfluorosulfonimide, so that the inorganic salt components in the interface film formed have a higher ionic conductivity, reducing the transmission impedance of lithium ions in the battery interface, thereby further reducing the initial impedance of the battery and improving the normal / high-temperature cycle performance.

[0028] The present application also provides a method for preparing the low-color unsaturated monosulfonate compound as described above, which comprises: preparing a reaction solution by using an alkyne (alkene) alcohol and alkyl sulfonyl chloride as raw materials in an organic solvent under the action of a base, and obtaining the monosulfonate compound with a colority of less than or equal to 100 Hazen by post-treatment of the reaction solution, wherein the post-treatment process comprises a separation step of the monosulfonate compound and impurities. The reaction formula is as follows:

[0029]

[0030] wherein R1 and R2 are as defined above.

[0031] The impurities include π-bond rich unsaturated structure compounds containing nitrogen and oxygen heteroatoms, which not only cause the product to show color, but also cause conjugated polymerization reaction by bond rearrangement and structure adjustment under electrochemical reaction conditions, forming products with longer conjugated chains, and also cause the increase of the internal resistance of the battery and the decrease of the performance at low and normal temperatures. Therefore, the removal of the impurities by the separation step not only reduces the colority of the product, but also reduces the internal resistance of the battery and improves the performance of the battery when applied to the electrolyte of the lithium battery.

[0032] The separation step is selected from at least one of column chromatography, rectification or extraction.

[0033] In a preferred embodiment, the separation step uses column chromatography, and the eluent used is selected from one or a mixture of several of petroleum ether, ethyl acetate, cyclohexane, benzene, diethyl ether and methanol. Preferably, the eluent is a mixture of petroleum ether and ethyl acetate, and the volume ratio of petroleum ether to ethyl acetate is (1-6):1, preferably (2-3):1.

[0034] In the preparation process of the monosulfonate compound, the molar ratio of the alkyne (alkene) alcohol to alkyl sulfonyl chloride is 1:(1-1.5), preferably 1:(1-1.2). The excess of alkyl sulfonyl chloride can promote the complete reaction and improve the yield, and the excess of alkyl sulfonyl chloride can be removed by subsequent water washing, which is convenient to operate.

[0035] The molar ratio of the alkyne (alkene) alcohol to the base is 1:(1-1.5). Preferably, the molar ratio of the alkyne (alkene) alcohol to the base is 1:(1.0-1.2).

[0036] The organic solvent is selected from at least one of dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, dichloromethane, acetonitrile, phenylacetonitrile or propionitrile. Preferably, the organic solvent is selected from dichloromethane, acetonitrile and diethyl carbonate.

[0037] The base is used to deprotonate the alkyne (alkene) alcohol to form an anion salt, which further undergoes nucleophilic substitution reaction with alkyl sulfonyl chloride to obtain the target product. The base is selected from at least one of sodium hydride, triethylamine, sodium hydroxide, sodium methoxide, sodium ethoxide, potassium tert-butoxide, sodium tert-butoxide, n-butyllithium, tert-butyllithium or lithium diisopropylamide. Preferably, the base is selected from at least one of sodium hydride, sodium hydroxide, triethylamine or potassium tert-butoxide.

[0038] The preparation steps of the low-chroma chain unsaturated monosulfonate compound of the present application specifically include:

[0039] (1) adding the alkyne (alkene) alcohol and the base into an organic solvent, and adding dropwise the alkyl sulfonyl chloride under stirring, with the temperature controlled between -20 and 10℃;

[0040] (2) after the dropwise addition is completed, the reaction temperature is controlled to be greater than 10℃, and the reaction is carried out for 0.5-12h;

[0041] (3) after the reaction solution is filtered, washed with water, dried and separated, the monosulfonate compound with purity greater than 99% is obtained.

[0042] Preferably, in step (2), the reaction temperature is controlled to be 11-60℃, and the reaction time is 1-6h.

[0043] The low-temperature condition for adding the raw material in step (1) can avoid the increase of by-products caused by the polymerization of the alkyne (alkene) alcohol due to heat release, and the increase of the reaction activity by increasing the reaction temperature in step (2) can improve the yield.

[0044] The present application also provides a lithium ion secondary battery, which comprises a positive electrode, a negative electrode and a separator, and uses an electrolyte containing the aforementioned low-chroma chain unsaturated monosulfonate compound.

[0045] The active material of the positive electrode is selected from nickel-cobalt-manganese ternary material or nickel-cobalt-aluminum ternary material or lithium cobaltate material or lithium iron phosphate material; wherein the nickel-cobalt-manganese ternary material is Li(NixCoyMnz)O2, x≥0.5, y>0, z>0, x+y+z=1; the nickel-cobalt-aluminum ternary material is Li(NixCoyAlz)O2, x≥0.8, y>0, z>0, x+y+z=1.

[0046] The active material of the negative electrode is selected from graphite, silicon monoxide, silicon, metallic lithium or a composite material thereof.

[0047] The separator is selected from the commonly used separators for lithium ion batteries, such as polyethylene film, polypropylene film, composite film, etc.

[0048] The lithium ion secondary battery electrolyte uses the aforementioned low-color chain unsaturated monosulfonate compound as an additive, which not only improves high-temperature cycle and high-temperature storage performance, reduces the internal resistance of the battery, but also guarantees the use of the battery in harsh environments, so that the standard working voltage of the battery is greater than or equal to 4.4V, and the working temperature range is -10 to 85℃. Within the working range, the battery electrochemical performance is excellent.

[0049] Compared with the prior art, the present application has the beneficial effects of:

[0050] The present application uses alkyl sulfonyl chloride and alkyne (alkene) alcohol as raw materials to obtain chain polyunsaturated monosulfonate compounds in one step, with high product yield (more than 80%); by further separating the target product and high-boiling polymer impurities, the colority of the product is greatly reduced (≤100 Hazen), so that the chain polyunsaturated monosulfonate compound not only improves the high-temperature cycle and high-temperature storage performance of the battery, but also reduces the initial impedance of the battery, improves the normal temperature cycle, and enables the battery to still have excellent high-temperature performance and low-temperature performance in more severe environments. BRIEF DESCRIPTION OF DRAWINGS

[0051] Figure 1 The GC chart of the ethyl butyne sulfonate prepared in Example 1 of the present application is shown in 1 H-NMR chart.

[0052] Figure 2 The GC chart of the ethyl butyne sulfonate prepared in Example 1 of the present application is shown in DETAILED DESCRIPTION

[0053] The present application will be further described below in conjunction with specific examples, but the present application is not limited to these specific examples. Those skilled in the art should recognize that the present application encompasses all alternatives, improvements and equivalents within the scope of the claims.

[0054] The product prepared in the example of the present application is characterized by 400M nuclear magnetic resonance hydrogen spectrum (H-NMR), and the characterization method is as follows: a small amount of product is added to a nuclear magnetic tube, and an appropriate amount of deuterated reagent is added for dissolution, and the solution height is not higher than 1 / 3 of the height of the nuclear magnetic tube. 1 H-NMR.

[0055] I. Preparation of compounds

[0056] Example 1

[0057] This example provides the preparation of ethyl butyne sulfonate, which specifically includes the following steps:

[0058] S1. In a dry room at dew point -40℃, 0.10 mol of 3-butyn-1-ol (purity 99%), 0.12 mol of triethylamine (purity 99%) and 100 mL of dichloromethane were added to a reaction bottle under low temperature condition at 0℃, the system was mixed uniformly by starting stirring, and 0.12 mol of ethyl sulfonyl chloride (purity 99%) was added dropwise using a constant pressure funnel, and the dropping speed was controlled so that the temperature of the reaction system did not exceed 10℃;

[0059] S2. After the completion of dropping, the temperature of the reaction system was increased to 40℃ and the reaction was continued for 4h;

[0060] S3. After the reaction was completed, the reaction liquid was filtered using a sand core funnel (to remove triethylamine hydrochloride), and the organic liquid in the suction filter bottle was collected; the organic liquid was placed in a separatory funnel, and an equal volume of water was added for water washing once to remove residual triethylamine hydrochloride and unreacted raw materials; then, an appropriate amount of anhydrous calcium chloride was added, and the system was stirred using a magnetic stirrer for 0.5h for dehydration treatment, and then the system was filtered again using a sand core funnel, and the lower layer filtrate was collected; the filtrate was subjected to rotary evaporation to remove the dichloromethane solvent to obtain a crude product;

[0061] S4. The crude product was subjected to column chromatography, specifically: dry loading was used, the crude product was dissolved in dichloromethane, and sufficient silica gel was added, the dichloromethane solvent was removed by rotary evaporation, 1 / 2 volume of silica gel was added to a 300mm chromatography column, the sample was added after being knocked uniformly, and the column was infiltrated with petroleum ether. A mixture of petroleum ether and ethyl acetate with a volume ratio of 4:1 was used as an eluent to separate the target product and impurities, and the solvent ratio was gradually increased to increase the solvent polarity during the separation process. Combined with GC (gas chromatography) analysis, the target product segment was collected; the eluent was removed by rotary evaporation to obtain 14.74g of product with a colority of 18Hazen.

[0062] The product was subjected to 1 H-NMR test, and the spectrum shown in the attached Figure 1 was obtained, specifically: δ=4.24 (t, J=6.3Hz, 1H), δ=3.22 (t, J=7.4Hz, 0H), δ=2.64 (td, J=6.3, 2.7Hz, 1H), δ=2.32 (t, J=2.7Hz, 0H), δ=1.34 (dd, J=7.7, 7.2Hz, 2H).

[0063] The integral area of the nuclear magnetic H spectrum peak was integrated, and the integral area ratio from left to right was 2.00:2.00:2.00:1.00:3.00, which was consistent with the theoretical value, indicating that the obtained product was compound (I-1), which was denoted as compound 1.

[0064] The GC analysis chart of the product is shown in the attached Figure 2 Figure 2 ​The purity of the product was 99.5%, and the reaction yield was 90.5% by calculation.

[0065] Example 2

[0066] The operation of this example was the same as that of Example 1, except that 0.10 mol of 3-buten-1-ol was used instead of 3-butyn-1-ol, 0.12 mol of propenylsulfonyl chloride was used instead of ethylsulfonyl chloride, and other operations were the same. The nuclear magnetic resonance results showed that the obtained product was compound (I-2): butenyl propenyl sulfonate, which was recorded as compound 2. The product of 15.48 g was obtained, and the colority was 31 Hazen. It was known from the combination of GC analysis data and calculation that the purity of the product was 99.32%, and the reaction yield was 87.3%.

[0067] Example 3

[0068] The operation of this example was the same as that of Example 1, except that 0.12 mol of ethylsulfonyl chloride was used instead of ethylsulfonyl chloride, and other operations were the same. The nuclear magnetic resonance results showed that the obtained product was compound (I-3): butynyl ethyl sulfonate, which was recorded as compound 3. The product of 14.4 g was obtained, and the colority was 36 Hazen. It was known from the combination of GC analysis data and calculation that the purity of the product was 99.44%, and the reaction yield was 89.23%.

[0069] Example 4

[0070] The operation of this example was the same as that of Example 1, except that 0.10 mol of 2-propyn-1-ol was used instead of 3-butyn-1-ol, 0.12 mol of propenylsulfonyl chloride was used instead of ethylsulfonyl chloride, and other operations were the same. The nuclear magnetic resonance results showed that the obtained product was compound (I-5): propynyl trifluorovinyl sulfonate, which was recorded as compound 4. The product of 18.58 g was obtained, and the colority was 25 Hazen. It was known from the combination of GC analysis data and calculation that the purity of the product was 99.3%, and the reaction yield was 91.0%.

[0071] Example 5

[0072] The operation of this example was the same as that of Example 1, except that a mixture of cyclohexane and methanol with a volume ratio of 4:1 was used instead of a mixture of petroleum ether and ethyl acetate with a volume ratio of 4:1 as the eluent, and other operations were the same. The nuclear magnetic resonance results showed that the obtained product was compound (I-1): butynyl ethyl sulfonate, which was recorded as compound 5. The product of 14.26 g was obtained, and the colority was 23 Hazen. It was known from the combination of GC analysis data and calculation that the purity of the product was 99.26%, and the reaction yield was 87.26%.

[0073] Example 6

[0074] The operation of this example is the same as that of Example 1, except that the amount of ethylsulfonyl chloride added in S1 is adjusted from 0.12 mol to 0.1 mol, and other operations remain unchanged. The nuclear magnetic resonance results show that the obtained product is compound (I-1): butynyl ethyl sulfonate, which is denoted as compound 6. The product 13.94 g is obtained, with a colority of 19 Hazen. In combination with the GC analysis data and calculation, it is known that the product purity is 99.35%, and the reaction yield is 85.27%.

[0075] Example 7

[0076] The operation of this example is the same as that of Example 1, except that the reaction temperature after the dropwise addition in S2 is adjusted from 40°C to 60°C, and other operations remain unchanged. The nuclear magnetic resonance results show that the obtained product is compound (I-1): butynyl ethyl sulfonate, which is denoted as compound 7. The product 13.61 g is obtained, with a colority of 45 Hazen. In combination with the GC analysis data and calculation, it is known that the product purity is 99.26%, and the reaction yield is 83.21%.

[0077] Comparative Example 1

[0078] The operation of this example is the same as that of Example 1, except that the crude product obtained in S3 is the product, and the column chromatography operation in S4 is not performed, and other operations remain unchanged. The nuclear magnetic resonance results show that the obtained product is compound (I-1): butynyl ethyl sulfonate, which is denoted as compound 8. The product 15.71 g is obtained, with a colority of 556 Hazen. In combination with the GC analysis data and calculation, it is known that the product purity is 99.01%, and the reaction yield is 93.67%.

[0079] Comparative Example 2

[0080] The operation of this example is the same as that of Example 1, except that 0.10 mol of 3-buten-1-ol is used instead of 3-buten-1-ol, and other operations remain unchanged. The nuclear magnetic resonance results show that the obtained product is butenyl ethyl sulfonate, which is denoted as compound 9. The product 14.43 g is obtained, with a colority of 39 Hazen. In combination with the GC analysis data and calculation, it is known that the product purity is 99.3%, and the reaction yield is 87.4%.

[0081] II. Electrolyte

[0082] Preparation of the base electrolyte: in an argon-filled glove box (moisture < 5 ppm, oxygen < 10 ppm), ethylene carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) are uniformly mixed in a mass ratio of EC: EMC: DEC = 4:4:2, and then lithium hexafluorophosphate (LiPF6) is slowly added to the mixed solution until the molar concentration is 1.0 mol / L, to obtain the base electrolyte.

[0083] Application Example 1

[0084] The application example electrolyte was obtained by adding 0.1 wt% of compound 1 to the base electrolyte.

[0085] Application Example 2

[0086] The application example electrolyte was obtained by adding 0.5 wt% of compound 1 to the base electrolyte.

[0087] Application Example 3

[0088] The application example electrolyte was obtained by adding 1.0 wt% of compound 1 to the base electrolyte.

[0089] Application Example 4

[0090] The application example electrolyte was obtained by adding 2.0 wt% of compound 1 to the base electrolyte.

[0091] Application Example 5

[0092] The application example electrolyte was obtained by adding 5.0 wt% of compound 1 to the base electrolyte.

[0093] Application Example 6

[0094] The application example electrolyte was obtained by adding 1.0 wt% of compound 2 to the base electrolyte.

[0095] Application Example 7

[0096] The application example electrolyte was obtained by adding 1.0 wt% of compound 3 to the base electrolyte.

[0097] Application Example 8

[0098] The application example electrolyte was obtained by adding 1.0 wt% of compound 4 to the base electrolyte.

[0099] Application Example 9

[0100] The application example electrolyte was obtained by adding 1.0 wt% of compound 5 to the base electrolyte.

[0101] Application Example 10

[0102] The application example electrolyte was obtained by adding 1.0 wt% of compound 6 to the base electrolyte.

[0103] Application Example 11

[0104] The application example electrolyte was obtained by adding 1.0 wt% of compound 7 to the base electrolyte.

[0105] Application Example 12

[0106] The base electrolyte was added with 1.0 wt% of compound 1 and 1.0 wt% of lithium difluorophosphate (LiDFP) to obtain the electrolyte of the present application example.

[0107] Application Example 13

[0108] The base electrolyte was added with 1.0 wt% of compound 1 and 1.0 wt% of 1,3- propanesultone (PS) to obtain the electrolyte of the present application example.

[0109] Application Example 14

[0110] The base electrolyte was added with 1.0 wt% of compound 1, 1.0 wt% of 1,3- propanesultone (PS) and 1.0 wt% of lithium bisfluorosulfonylimide (LiFSI) to obtain the electrolyte of the present application example.

[0111] Application Comparative Example 1

[0112] The base electrolyte was not treated to obtain the electrolyte of the present application comparative example.

[0113] Application Comparative Example 2

[0114] The base electrolyte was added with 1.0 wt% of compound 8 to obtain the electrolyte of the present application comparative example.

[0115] Application Comparative Example 3

[0116] The base electrolyte was added with 1.0 wt% of 1,3-propanesultone (PS) to obtain the electrolyte of the present application comparative example.

[0117] Application Comparative Example 4

[0118] The base electrolyte was added with 1.0 wt% of compound 9 to obtain the electrolyte of the present application comparative example.

[0119] III. Electrochemical performance test

[0120] The electrolytes of the above application examples and application comparative examples were respectively prepared into soft package capacity 1260 mAh lithium ion batteries, which included positive electrode sheet, negative electrode sheet, separator, electrolyte and battery auxiliary materials, the positive electrode active material was ternary positive electrode LiNi 0.6 Co 0.2 Mn 0.2 O2, and the negative electrode active material was high-capacity graphite. The preparation process was as follows: the positive electrode sheet, the separator and the negative electrode sheet were wound together into a roll core, and the roll core was sealed with aluminum plastic film and baked to make the water content of the electrode meet the requirements. After baking, the battery core was subjected to electrolyte injection, standing, formation, capacity distribution and aging processes to obtain the finished lithium ion battery soft package battery core.

[0121] The lithium ion battery prepared above was subjected to performance test (test voltage 2.8-4.4V), mainly including:

[0122] (1) Initial ACR impedance

[0123] At room temperature, the battery capacity was adjusted to 50% SOC (state of charge) at a standard charging current, and the internal resistance (mΩ) of the lithium battery after the fixed tab position was tested at 1KHz frequency by using a Japanese Sanki internal resistance meter, which was recorded as the initial ACR impedance (alternating current resistance).

[0124] (2) 60°C high-temperature storage test: the battery was charged to 100% SOC and stored in a 60±2°C oven for 14 days, and the volume before and after storage was tested to obtain the volume expansion rate of the single battery before and after 60°C storage; the DCR value after storage was tested at room temperature, and the percentage value with the initial DCR was calculated, which was recorded as the discharge DCR change rate;

[0125] (3) 80°C high-temperature storage test: the battery was charged to 100% SOC and stored in an 80±2°C oven for 14 days, and the volume before and after storage was tested to obtain the volume expansion rate of the single battery before and after 80°C storage; the DCR value after storage was tested at room temperature, and the percentage value with the initial DCR was calculated, which was recorded as the discharge DCR change rate;

[0126] (4) 45°C high-temperature cycle test: the battery was cycled in a 45±1°C oven at a charge-discharge current of 1C / 1C, and the discharge capacity per week was calculated, and the cycle was stopped after 500 cycles, and the capacity retention rate after cycle was calculated.

[0127] The results of each electrochemical performance test are described in Table 1 below:

[0128] Table 1 Electrochemical performance test results

[0129]

[0130] By comparing application example 3, application examples 6-11 and application comparative example 1, it can be seen that the electrolyte using the chain-shaped unsaturated monosulfonate compound prepared by the application as an additive can not only inhibit the gas production of the battery at 60°C and 80°C high-temperature storage, but also improve the cycle performance of the battery at 45°C. This is mainly because the chain-shaped unsaturated monosulfonate compound has both sulfonate groups and carbon-carbon unsaturated bonds, and the two have good synergistic effect, which can form a cross-linked firm interface film skeleton.

[0131] By comparing application examples 1-5, it can be seen that as the amount of chain-like unsaturated mono-sulfonate compound added in the electrolyte increases, although the battery still has good high-temperature gas inhibition effect, the high-temperature cycle performance begins to decline due to the high battery impedance. In general, the amount of chain-like unsaturated mono-sulfonate compound added in the electrolyte is preferably 0.5-2 wt%.

[0132] By comparing application example 3, application comparative example 2 and application comparative example 1, it can be seen that after the target product and high-boiling polymer impurities are separated by column chromatography, the colority of the product is greatly reduced (≤100 Hazen). The high-color chain-like unsaturated sulfonate compound without separation as an additive in the electrolyte significantly increases the initial impedance relative to the base electrolyte. Although it can improve the 60°C high-temperature storage performance, the performance improvement effect is not good under the more stringent 80°C high-temperature storage condition. The low-color chain-like unsaturated sulfonate compound after impurity removal can improve the battery high-temperature cycle and 80°C high-temperature storage performance while reducing the initial impedance of the battery.

[0133] By comparing application example 3 and application comparative example 3, it can be seen that 1,3-propanesultone (PS) can cause high initial impedance of the battery, and this type of sulfonate additive has limited improvement on the 80°C high-temperature storage performance under harsh conditions (4.4V high voltage) of the battery. The low-color chain-like unsaturated sulfonate compound of the present application has the effect of improving the high-temperature cycle and 80°C high-temperature storage performance of the battery and reducing the initial impedance of the battery.

[0134] By comparing application example 3 and application example 12, it can be seen that further adding lithium difluorophosphate (LiDFP) in the electrolyte containing the chain-like unsaturated sulfonate compound can further improve the high-temperature storage performance and room temperature cycle performance of the battery. By comparing application example 3 and application example 13, it can be seen that further adding 1,3-propanesultone (PS) in the electrolyte containing the chain-like unsaturated sulfonate compound can further enhance the effect of inhibiting the gas production of the battery during high-temperature storage.

Claims

1. Use of a chain unsaturated mono-sulfonate compound in an electrolyte, characterized in that: The single sulfonate compound is added to the electrolyte in an amount of 0.1-5.0wt% of the total mass of the electrolyte, and the structure is shown in the following formula (I): In the formula, R1 and R2 are independently selected from C1-C5 alkyl, C1-C5 haloalkyl, C2-C7 alkenyl or C2-C7 alkynyl, and at least one of R1 and R2 is C2-C7 alkenyl or C2-C7 alkynyl. The unsaturation degree of the unsaturated carbon bond in the single sulfonate compound is ≥2, and the colority is ≤100 Hazen.

2. The use of the chain unsaturated monosulfonate compound according to claim 1 in an electrolyte, characterized by: R1 and R2 are independently selected from C2-C3 alkyl, C2-C3 haloalkyl, C2-C5 alkenyl or C2-C5 alkynyl, and at least one of R1 and R2 is C2-C5 alkenyl or C2-C5 alkynyl.

3. The use of the chain unsaturated monosulfonate compound according to claim 2 in an electrolyte, characterized by: The single sulfonate compound is selected from at least one of the following structures:

4. The use of the chain unsaturated monosulfonate compound according to claim 1 in an electrolyte, characterized by: The addition amount of the single sulfonate compound is 0.5-2.0wt% of the total mass of the electrolyte.

5. The use of the chain unsaturated mono-sulfonate compound according to any one of claims 1 to 4 in an electrolyte, characterized in that: The electrolyte further comprises a main lithium salt, a non-aqueous solvent and a basic additive; The main lithium salt is selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bisfluorosulfonimide or lithium bis-trifluoromethylsulfonimide, and the molar concentration is 0.1-4.0mol / L (preferably 0.8-1.5mol / L); the non-aqueous solvent is selected from at least one of C3-C6 carbonate compounds, C3-C8 carboxylate compounds, sulfone compounds or ether compounds, and the addition amount is 60-95wt% of the total mass of the electrolyte; the C3-C6 carbonate compound is selected from at least one of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate and ethyl propyl carbonate; the C3-C8 carboxylate compound is selected from at least one of γ-butyrolactone, methyl acetate, methyl propionate, methyl butyrate, ethyl acetate, ethyl propionate, ethyl butyrate, propyl acetate and propyl propionate; the sulfone compound is selected from at least one of sulfolane, dimethyl sulfoxide, dimethyl sulfone and diethyl sulfone; and the ether compound is selected from triethylene glycol dimethyl ether and / or tetraethylene glycol dimethyl ether; The basic additive includes at least one of vinylene carbonate, 1,3-propane sultone, vinyl sulfate, 4-methyl vinyl sulfate, 4,4'-bis vinyl sulfate, fluoroethyl carbonate, bis-fluoroethylene carbonate, tris(trimethylsilyl) phosphate, tris(trimethylsilyl) borate, lithium difluorophosphate, lithium bisfluorosulfonimide, lithium difluorobisoxalate phosphate and lithium difluoroborate oxalate, and the addition amount of any basic additive is 0.1-5.0wt% of the total mass of the electrolyte.

6. The use of the chain unsaturated monosulfonate compound according to claim 5 in an electrolyte, characterized by: The non-aqueous solvent at least includes ethylene carbonate and diethyl carbonate, and the mass ratio of ethylene carbonate to diethyl carbonate is 1:(0.1-10).

7. The use of the chain unsaturated monosulfonate compound according to claim 5 in an electrolyte, characterized by: The basic additive at least includes 0.2-1.5wt% of lithium difluorophosphate, 0.1-3.0wt% of 1,3-propane sultone and 0.2-3wt% of lithium bisfluorosulfonimide.

8. The method for producing a chain-like unsaturated monosulfonic acid ester compound according to any one of claims 1 to 7, characterized by: The preparation method comprises: preparing a reaction solution by using an alkyne (alkene) alcohol and alkyl sulfonyl chloride as raw materials in an organic solvent under the action of a base, and obtaining a monosulfonate compound with a colority of ≤100 Hazen through post-treatment of the reaction solution, wherein the post-treatment process comprises a separation step of the monosulfonate compound and impurities.

9. The method for preparing the linear unsaturated monosulfonic acid ester compound according to claim 8, wherein: The impurities include π-rich unsaturated structure compounds containing nitrogen and oxygen atoms, and the separation step is selected from at least one of column chromatography, rectification or extraction.

10. The method for preparing the linear unsaturated monosulfonic acid ester compound according to claim 9, characterized in that: The separation step adopts column chromatography, and the eluent is selected from one or a mixture of several of petroleum ether, ethyl acetate, cyclohexane, benzene, diethyl ether and methanol.

11. The method for preparing the linear unsaturated monosulfonic acid ester compound according to claim 10, characterized in that: The eluent is a mixture of petroleum ether and ethyl acetate, and the volume ratio of petroleum ether to ethyl acetate is (1-6):

1.

12. The method for preparing the linear unsaturated monosulfonic acid ester compound according to claim 8, wherein: The molar ratio of the alkyne (alkene) alcohol to alkyl sulfonyl chloride is 1:(1-1.5), and the molar ratio of the alkyne (alkene) alcohol to the base is 1:(1-1.5).

13. The method for preparing the linear unsaturated monosulfonic acid ester compound according to claim 8, wherein: The organic solvent is selected from at least one of dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, dichloromethane, acetonitrile, phenylacetonitrile or propionitrile.

14. The method for preparing the linear unsaturated monosulfonic acid ester compound according to claim 8, wherein: The base is selected from at least one of sodium hydride, sodium methoxide, sodium ethoxide, potassium tert-butoxide, sodium tert-butoxide, n-butyllithium, tert-butyllithium or lithium diisopropylamide.

15. The method for preparing the linear unsaturated monosulfonic acid ester compound according to claim 8, wherein: The preparation method specifically comprises the following steps: (1) adding the alkyne (alkene) alcohol and the base into the organic solvent, and adding the alkyl sulfonyl chloride dropwise under stirring, with the dropwise temperature controlled between -20 and 10℃; (2) after the dropwise addition is completed, the reaction temperature is controlled to be greater than 10℃, and the reaction is performed for 0.5-12h; (3) the reaction solution is filtered, washed with water, dried and separated to obtain a monosulfonate compound with a purity of >99%.

16. The method for preparing the linear unsaturated monosulfonic acid ester compound according to claim 15, characterized in that: In step (2), the reaction temperature is controlled to be 11-60℃, and the reaction time is 1-6h.

17. A lithium-ion secondary battery comprising a positive electrode, a negative electrode, and a separator, characterized by: The lithium ion battery uses the electrolyte containing the unsaturated monosulfonate compound as claimed in claims 1-16.

18. The lithium-ion secondary battery according to claim 17, characterized by: The standard working voltage of the battery is ≥4.4V, and the working temperature range is -10-85℃.

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