Compound and application thereof, electrolyte and semi-solid battery

Abstract

The invention provides a compound and application thereof, an electrolyte and a semi-solid battery. The compound is used as an electrolyte additive, and can have a synergistic effect with a positive electrode coated with a solid electrolyte: in a battery charging process, the compound is subjected to electrochemical polymerization on a positive electrode interface to form a layer of functional polymer interface with a stable structure. And the interface can be combined with a solid electrolyte coating layer on the surface of the positive electrode to form a stable composite interface, so that the charge distribution of the interface is effectively regulated and controlled, the lithium ion transmission is promoted, the rate capability and the high-temperature cycle life of the battery are remarkably improved, the decomposition and heat release of a CEI membrane can be inhibited, and the thermal stability and the safety of the battery are enhanced. Researches prove that the semi-solid battery prepared by adopting the scheme is excellent in long circulation, rate and safety performance.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, specifically relating to a compound and its application, an electrolyte, and a semi-solid-state battery. Background Technology

[0002] In recent years, consumers have increasingly higher demands for the energy density and safety performance of lithium-ion batteries. Traditional lithium-ion batteries use liquid organic electrolytes, which pose safety hazards such as leakage, electrode corrosion, or combustion and explosion. Some studies have reported that using flame-retardant additives or high-safety additives can effectively improve the safety of batteries using liquid electrolytes, but the improvement is limited. Therefore, all-solid-state batteries, due to their high energy density and high safety, have become an ideal alternative to traditional lithium-ion batteries.

[0003] However, despite the numerous advantages of all-solid-state batteries, they still face many challenges in practical applications. First, the solid-solid interface between the solid electrolyte and the electrode suffers from insufficient contact and high interfacial impedance, severely limiting ion transport across the interface and resulting in poor rate performance and capacity utilization. Second, many solid electrolytes (especially oxides) still exhibit low intrinsic ionic conductivity at room temperature, limiting battery performance under ambient conditions. Therefore, reducing interfacial impedance and improving the bulk ionic conductivity of materials has become a key focus and challenge in current research.

[0004] To address these issues, researchers have attempted various methods to improve the interfacial contact impedance between solid electrolytes and electrodes. However, current methods have not yet fully resolved the problems of high interfacial impedance and low ion transport efficiency. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a compound and its application, an electrolyte, and a semi-solid-state battery. The compound can be used as an electrolyte additive, paired with a positive electrode coated with a solid electrolyte. The additive constructs a flexible and highly thermally stable CEI film, while the solid electrolyte provides a rigid framework and fast ion channels. The two work synergistically to form a multi-level interfacial synergistic mechanism, improving battery cycle life and safety.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a compound having the structure of formula I, formula II or formula III:

[0008] Formula I; Formula II; Formula III;

[0009] Wherein, L is selected from substituted or unsubstituted C1~C6 alkylene groups, substituted or unsubstituted C1~C6 fluoroalkylene groups or aryl groups;

[0010] n is an integer between 0 and 3;

[0011] R is selected from cyano, substituted or unsubstituted C1~C6 alkyl, -SO3H or -PO3H2;

[0012] R1, R2, R3, R4, R5, and R6 are independently selected from hydrogen, cyano, substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C1-C6 alkoxy, or halogen.

[0013] At least one of R, R1, and R2 is a cyano group; at least one of R3 and R4 is a cyano group; and at least one of R5 and R6 is a cyano group.

[0014] Preferably, R1, R2, R3, R4, R5, and R6 are independently selected from hydrogen, methyl, ethyl, propyl, cyano, trifluoromethyl, perfluoroalkyl, methoxy, ethoxy, or halogen.

[0015] Preferably, the compound is selected from any one of the following formulas 1 to 9:

[0016] .

[0017] Secondly, the present invention provides an application of the above-mentioned compound as an electrolyte additive.

[0018] Thirdly, the present invention provides an electrolyte comprising a lithium salt, an organic solvent, a basic additive, lithium trifluoromethanesulfonate, and the above-mentioned compounds;

[0019] The amount of lithium trifluoromethanesulfonate added accounts for 0-1% of the total mass of the electrolyte;

[0020] The amount of the compound added is 0.1-2% of the total mass of the electrolyte.

[0021] Preferably, the lithium salt is selected from any one or more of lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium perchlorate, lithium tetrafluoroborate, or lithium bis(oxalato)borate; the amount of lithium salt added accounts for 12-18% of the total mass of the electrolyte.

[0022] Preferably, the basic additive is selected from any one or more of sulfonate compounds, sulfate compounds, unsaturated cyclic carbonate compounds, borate compounds, trimethylsilyl ester compounds, or nitrile compounds, and the amount of the basic additive is 0.1-8% of the total mass of the electrolyte.

[0023] Preferably, the organic solvent is selected from any one or more of propylene carbonate, ethylene carbonate, methyl ethyl carbonate, dimethyl carbonate, diethyl carbonate, ethyl acetate, propyl acetate, propyl propionate, methyl butyrate, methyl acetate, ethyl propionate, or γ-butyrolactone.

[0024] Fourthly, the present invention provides a semi-solid battery comprising a positive electrode, a negative electrode, a separator, and the electrolyte described above, wherein the surface of the active material of the positive electrode is coated with a solid electrolyte.

[0025] The solid electrolyte layer is selected from lithium lanthanum zirconium oxide and / or lithium titanium aluminum phosphate.

[0026] Preferably, the active material of the positive electrode is selected from any one or more of lithium nickel cobalt manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt aluminum oxide, lithium cobalt oxide, or lithium manganese oxide.

[0027] Preferably, the positive electrode further includes a conductive agent and a binder.

[0028] Preferably, the conductive agent is selected from any one or more of conductive carbon black, carbon nanotubes, graphene, carbon fiber, or Ketjen black.

[0029] Preferably, the adhesive is selected from any one or more of polypropylene, polyethylene, polyvinylidene fluoride, vinylidene fluoride, hexafluoropropylene, polytetrafluoroethylene, or polyhexafluoropropylene.

[0030] Preferably, the active material of the negative electrode is selected from any one or more of graphite, hard carbon, soft carbon, silicon, or silicon-oxygen materials.

[0031] Preferably, the diaphragm is selected from PE diaphragm or PP diaphragm.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] (1) This invention provides a cyano-containing compound with a structure of Formula I, Formula II, or Formula III, which can be used as an additive for electrolytes and paired with a positive electrode coated with a solid electrolyte. The additive can undergo electrochemical oxidation on the surface of the active material of the positive electrode to form a cationic free radical intermediate, which then polymerizes into a film via a free radical chain reaction. This polymer film can uniformly shape the interfacial electric field, reduce the localization and accumulation of charge on the electrode surface, thereby inhibiting the oxidative decomposition of the electrolyte, and exhibits high thermal stability, improving the interfacial stability of the CEI film. Furthermore, the cyano group in the compound may complex with dissolved transition metal ions or anchor on the positive electrode surface, thereby helping to stabilize the positive electrode interfacial structure and reducing structural failure caused by the dissolution of metal ions.

[0034] (2) Under extreme high temperature conditions, the composite cathode of solid electrolyte inhibits the release of active oxygen from the cathode material, inhibits the failure of the cathode material, and inhibits electron leakage. At the same time, the polymer film formed by the cyano compound additive at the cathode interface has high thermal stability, can maintain the integrity of the interface, reduce the reaction of active oxygen released by the cathode material with the electrolyte at high temperature, thereby delaying thermal runaway. The solid electrolyte layer and the polymer film work together to greatly improve the thermal stability of the cathode.

[0035] (3) The cyano compound additive provided by the present invention is used in combination with lithium trifluoromethanesulfonate to form an organic-inorganic composite CEI membrane, which improves the ionic conductivity and enhances the flexibility and mechanical strength of the CEI membrane. Detailed Implementation

[0036] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0037] This invention provides a compound having the structure of formula I, formula II, or formula III:

[0038] Formula I; Formula II; Formula III;

[0039] Wherein, L is selected from substituted or unsubstituted C1~C6 alkylene groups, substituted or unsubstituted C1~C6 fluoroalkylene groups or aryl groups;

[0040] n is an integer from 0 to 3, specifically 0, 1, 2, or 3, etc.

[0041] R is selected from cyano, substituted or unsubstituted C1~C6 alkyl, -SO3H or -PO3H2;

[0042] R1, R2, R3, R4, R5, and R6 are independently selected from hydrogen, cyano, substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C1-C6 alkoxy, or halogen.

[0043] At least one of R, R1, and R2 is a cyano group; at least one of R3 and R4 is a cyano group; and at least one of R5 and R6 is a cyano group.

[0044] The substituted group in the above "substituted or unsubstituted" can be selected from halogens.

[0045] In this invention, the halogen can be F, Cl, Br or I, etc.

[0046] In some preferred embodiments of the present invention, the compound has the structure of Formula I, Formula II or Formula III above, wherein R1, R2, R3, R4, R5, R6 are independently selected from hydrogen, methyl, ethyl, propyl, cyano, trifluoromethyl, perfluoroalkyl, methoxy, ethoxy or halogen.

[0047] In some specific embodiments of the present invention, the compound is selected from any one of the following formulas 1 to 9:

[0048] .

[0049] The present invention also provides a method for preparing the cyano-containing compound represented by Formula I above, as follows:

[0050] The compound shown in Formula B and the compound shown in Formula C are mixed and reacted to obtain the cyano-containing compound shown in Formula A (i.e., Formula I);

[0051] Formula A; Formula B; Formula C.

[0052] In some embodiments of the present invention, the molar ratio of the compound represented by Formula B to the compound represented by Formula C is 1:(1.03~1.2), such as 1:1.03, 1:1.1, 1:1.15, or 1:1.2; the reaction temperature is 110~130℃, such as 110℃, 120℃, or 130℃; and the reaction time is 3~6 h, such as 3 h, 4 h, or 6 h.

[0053] The present invention also provides a method for preparing the cyano-containing compound represented by Formula II above, as detailed below:

[0054] Under conditions of 25–30 °C, 3-thiophenecarboxaldehyde and N-[(benzenesulfonyl)oxy]ethyliminolate are dissolved in dichloromethane in a round-bottom flask. The molar ratio of 3-thiophenecarboxaldehyde to N-[(benzenesulfonyl)oxy]ethyliminolate is 1:(1–1.1), such as 1:1, 1:1.02, 1:1.05, or 1:1.1, preferably 1:1.05. Trifluoromethanesulfonic acid (TfOH) is slowly added under ice-water bath cooling. The reaction is continued with stirring at room temperature for 20–30 h, such as 20 h, 24 h, or 30 h, preferably 24 h. The mixture is then diluted with dichloromethane and filtered through a silica gel / Celite® liner. Collect the filtrate, remove the solvent under reduced pressure, and purify the crude product by silica gel column chromatography (eluent: hexane / ethyl acetate = 90 / 10, volume ratio; or pentane / ethane = 80 / 20, volume ratio).

[0055] This invention also provides a method for preparing the cyano-containing compound represented by Formula III above, the synthetic route of which is as follows:

[0056] .

[0057] Specifically, the following steps are included:

[0058] Cyanonitrobenzene was dissolved in a mixed solvent of ethanol / water (3:1, v / v). While maintaining ice bath conditions with stirring, concentrated hydrochloric acid (1.2 mol) was slowly added dropwise to the system, and stannous chloride dihydrate (SnCl₂·2H₂O, cyanonitrobenzene to SnCl₂·2H₂O molar ratio 1:2.2-3) was added slowly in portions. The reaction was maintained at low temperature for 1 hour, then gradually raised to room temperature with stirring, and monitored by TLC until the starting material disappeared. After the reaction was complete, the reaction solution was cooled to 0°C, and a saturated sodium bicarbonate (NaHCO₃) aqueous solution was slowly added with stirring to adjust the pH to 8-9. The mixture was extracted three times with ethyl acetate, the organic phases were combined, washed with saturated brine, dried over anhydrous sodium sulfate, filtered, and the filtrate was concentrated under reduced pressure to obtain the crude product, cyanoaniline, which was purified by column chromatography or recrystallization.

[0059] The compound provided by this invention is a cyano-containing compound, which can be used as an additive in electrolytes.

[0060] Specifically, the present invention also provides an electrolyte comprising a lithium salt, an organic solvent, a basic additive, lithium trifluoromethanesulfonate, and the above-mentioned compounds.

[0061] The lithium salt is selected from any one or more of lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium perchlorate, lithium tetrafluoroborate, or lithium bis(oxalato)borate. The amount of lithium salt added accounts for 12-18% of the total mass of the electrolyte, such as 12%, 13%, 14%, 15%, 16%, 17%, or 18%.

[0062] The organic solvents mentioned above are selected from any one or more of propylene carbonate, ethylene carbonate, methyl ethyl carbonate, dimethyl carbonate, diethyl carbonate, ethyl acetate, propyl acetate, propyl propionate, methyl butyrate, methyl acetate, ethyl propionate, or γ-butyrolactone.

[0063] The amount of lithium trifluoromethanesulfonate added accounts for 0 to 1% of the total mass of the electrolyte, such as 0%, 0.1%, 0.2%, 0.3%, 0.5%, 0.8%, 1%, etc.

[0064] The aforementioned basic additives are selected from any one or more of sulfonate compounds, sulfate compounds, unsaturated cyclic carbonate compounds, borate compounds, trimethylsilyl ester compounds, or nitrile compounds. The amount of the basic additives added accounts for 0.1% to 8% of the total mass of the electrolyte, such as 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, or 8%.

[0065] In this invention, the amount of the compound added accounts for 0.1 to 2% of the total mass of the electrolyte, such as 0.1%, 0.3%, 0.5%, 0.8%, 1%, 1.3%, 1.5%, 1.8% or 2%.

[0066] Furthermore, this invention also provides a semi-solid-state battery, comprising a positive electrode, a negative electrode, a separator, and the aforementioned electrolyte. Preferably, the surface of the active material of the positive electrode is coated with a solid electrolyte, which is selected from lithium lanthanum zirconium oxide (LLZO) and / or lithium titanium aluminum phosphate (LATP). The key point of this invention is the use of an electrolyte containing the aforementioned compounds in conjunction with a positive electrode coated with a solid electrolyte. In the battery's operating state, when the electrolyte comes into contact with the active material coated with the solid electrolyte, the compounds undergo electrochemical oxidation on the surface of the positive electrode active material, forming a polymer film. This inhibits the oxidative decomposition of the electrolyte and improves the thermal stability of the CEI film. In addition, the cyano groups in the compounds may complex and anchor to the positive electrode surface by combining with dissolved transition metal ions, thereby helping to stabilize the positive electrode interface structure and reduce structural failure caused by metal ion dissolution. Combined with a solid electrolyte-coated positive electrode, the additives construct a flexible and highly thermally stable CEI film, while the solid electrolyte provides a rigid framework and fast ion channels. The synergistic effect of both forms a multi-level interfacial synergistic mechanism, improving battery cycle life and safety.

[0067] In this invention, the active material of the positive electrode is selected from any one or more of lithium nickel cobalt manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt aluminum oxide, lithium cobalt oxide, or lithium manganese oxide. The positive electrode also includes a conductive agent and a binder. The conductive agent is selected from any one or more of conductive carbon black, carbon nanotubes, graphene, carbon fiber, or Ketjen black; the binder is selected from any one or more of polypropylene, polyethylene, polyvinylidene fluoride, vinylidene fluoride, hexafluoropropylene, polytetrafluoroethylene, or polyhexafluoropropylene.

[0068] In this invention, the active material of the negative electrode is selected from any one or more of graphite, hard carbon, soft carbon, silicon, or silicon-oxygen materials.

[0069] In this invention, the diaphragm is selected from PE diaphragm or PP diaphragm.

[0070] In some embodiments of the present invention, the present invention assembles a battery using the following method:

[0071] The positive electrode, separator, and negative electrode are wound together into a core, sealed with aluminum-plastic film, and then baked to ensure the electrode moisture content meets requirements. After baking, the cell is injected with electrolyte (the electrolyte mentioned above contains a cyano compound) at an injection rate of 1.5 Ah / g. It then undergoes formation, aging, and capacity testing to obtain the finished soft-pack battery cell. The formation conditions are: charging at 0.1 C for 3 hours, followed by a 5-minute rest; charging at 0.2 C for 2 hours, followed by a 5-minute rest. The aging conditions are: aging at 45°C for 48 hours. Capacity testing is performed at a 0.2 C rate.

[0072] The preparation of the above-mentioned positive and negative electrode sheets can be carried out in accordance with the technical means known to those skilled in the art, without any special restrictions.

[0073] The obtained battery underwent cycle testing, high-temperature storage testing, rate testing, and thermal chamber testing. Characterization results confirmed that the battery exhibits excellent long cycle life, high-temperature storage stability, high-rate discharge performance, and successfully passed the thermal chamber test. Its superior overall performance is attributed to the synergistic effect of the cyano-containing compound additive and the positive electrode solid electrolyte coating layer, which constructs a highly efficient ion transport channel at the positive electrode interface and optimizes the interfacial charge distribution. This composite interfacial structure effectively reduces the battery's internal resistance and significantly improves interfacial thermal stability, thereby comprehensively enhancing the battery's electrochemical and safety performance.

[0074] To further illustrate the present invention, the following embodiments provide a detailed description. The experimental materials used in the following embodiments of the present invention are all commercially available products.

[0075] I. Preparation of Electrolyte

[0076] Preparation of the basic electrolyte: In an argon-filled glove box (moisture < 0.1 ppm, oxygen < 0.1 ppm), ethylene carbonate (EC), propylene carbonate (PC), propyl propionate (PP), and fluoroethylene carbonate (FEC) were mixed evenly in a mass ratio of EC:PC:PP:FEC = 10:15:40:8. Lithium hexafluorophosphate (LiPF6) with a LiPF6 content of 1.2 mol / L was slowly added to the solution. 1% by mass of 1,3-propanesulfonate lactone (PS) and 3% by mass of hexanetrionitrile (HTCN) were also added to obtain the basic electrolyte formulation.

[0077] II. Battery fabrication:

[0078] Preparation of the positive electrode: Lithium aluminum titanium phosphate (LATP) solid electrolyte coated with lithium cobalt oxide (LiCoO2) (or uncoated lithium cobalt oxide (LiCoO2)), conductive carbon black, carbon nanotubes, and polytetrafluoroethylene were uniformly coated onto a 12 μm aluminum foil in a mass ratio of 97:1.2:0.8:1, with a double-sided coating areal density of 380 g / m². 2 The compacted density is 4.2 g / cm³. 3 .

[0079] Preparation of the negative electrode sheet: The negative electrode active material is graphite. Artificial graphite, conductive carbon black, sodium carboxymethyl cellulose, styrene-butadiene rubber, polyacrylic acid, and carbon nanotubes are uniformly coated onto a 6 μm copper foil in a mass ratio of 95.5:0.6:0.8:1.5:1.5:0.1. The double-sided coating surface density is 240 g / m². 2 The compacted density is 1.6 g / cm³. 3 .

[0080] Battery assembly: The positive electrode, PP separator, and negative electrode are wound together into a core, sealed with aluminum-plastic film, and then baked to ensure the electrode moisture content meets the requirements. After baking, the cell is injected with electrolyte at an injection coefficient of 1.5 Ah / g. Then, it undergoes formation, aging, and capacity testing to obtain the finished soft-pack cell. The formation conditions are: charging at 0.1 C for 3 hours and resting for 5 minutes; charging at 0.2 C for 2 hours and resting for 5 minutes. The aging conditions are: aging at 45℃ for 48 hours. Capacity testing is performed at a rate of 0.2 C.

[0081] Preparation Examples 1-6

[0082] Specifically, the synthetic routes for preparing the cyanopyrrole compounds of Examples 1-6 are shown below:

[0083] .

[0084] Specifically, the following steps are included:

[0085] A 100 mL three-necked flask was selected, and nitrogen gas was continuously purged into the sealed environment for 30 min. 0.1 mol of the corresponding pyrrole compound from the above synthetic route and 0.105 mol of allyl cyanide were weighed and added to 30 mL of 15 wt% toluene (PhMe) containing 1,8-diazabicycloundec-7-ene (DBU). The mixture was reacted at 120 °C with stirring for 4 h. Anhydrous magnesium sulfate was then added to the mixed solution to remove water. The solution was filtered, concentrated by rotary evaporation, and compound A was obtained by rapid chromatography.

[0086] Preparation Example 7

[0087] This preparation example provides a compound 7 with structural formula 7, and its synthetic route is shown below:

[0088] ;

[0089] The specific preparation method is as follows:

[0090] Under conditions of 25°C, 3-thiophenecarboxaldehyde and ethyl N-[(benzenesulfonyl)oxy]ethyleneimine were dissolved in dichloromethane in a round-bottom flask at a molar ratio of 1:1.05. Trifluoromethanesulfonic acid (TfOH) was slowly added under ice-water bath cooling. The reaction was continued with stirring at room temperature for 24 hours. The mixture was diluted with dichloromethane and filtered through a silica gel / Celite® liner. The filtrate was collected, the solvent was removed by vacuum distillation, and the crude product was purified by silica gel column chromatography (eluent: hexane / ethyl acetate = 90 / 10, v / v).

[0091] Preparation Examples 8-9

[0092] Specifically, the synthetic routes for preparing the cyanoaniline compounds of Examples 8-9 are shown below:

[0093] ;

[0094] The corresponding cyanonitrobenzene was dissolved in a mixed solvent of ethanol / water (3:1, v / v). Concentrated hydrochloric acid (1.2 mol) was slowly added dropwise to the system under ice bath cooling and stirring. While maintaining ice bath conditions, stannous chloride dihydrate (SnCl2·2H2O, molar ratio of cyanonitrobenzene to SnCl2·2H2O = 1:2.2) was slowly added in portions. The reaction was maintained at low temperature for 1 h, then gradually raised to room temperature with stirring, and monitored by TLC until the starting material spot disappeared. After the reaction was complete, the reaction solution was cooled to 0°C, and a saturated sodium bicarbonate (NaHCO3) aqueous solution was slowly added under stirring to adjust the pH to 8-9. The mixture was extracted three times with ethyl acetate, the organic phases were combined, washed with saturated brine, dried over anhydrous sodium sulfate, filtered, and the filtrate was concentrated under reduced pressure to obtain the crude product, cyanoaniline, which was purified by column chromatography or recrystallization.

[0095] The mass spectrometry data of the preparation examples 1-9 above are as follows:

[0096] 1. Preparation Example 1, corresponding to structural formula 1: GC-MS (m / z): calcd . for C8H 10 N2[M+1]+, 134.18, found 135.11;

[0097] 2. Preparation Example 2, corresponding to structural formula 2: GC-MS (m / z): calcd . for C7H8N2[M+1]+, 120.15, found 121.14;

[0098] 3. Preparation Example 3, corresponding to structural formula 3: GC-MS (m / z): calcd . for C9H 12 N2[M+1]+, 148.21, found 149.24;

[0099] 4. Preparation Example 4, corresponding to structural formula 4: GC-MS (m / z): calcd . for C7H6F2N2[M+1]+, 156.14, found 157.15;

[0100] 5. Preparation Example 5, corresponding to structural formula 5: GC-MS (m / z): calcd . for C8H7F3N2[M+1]+, 188.15, found 189.16;

[0101] 6. Preparation Example 6, corresponding to structural formula 6: GC-MS (m / z): calcd . for C9H6F3N3[M+1]+, 213.16, found 214.09;

[0102] 7. Preparation Example 7, corresponding to structural formula 7: GC-MS (m / z): calcd . for C5H3NS[M+1]+, 109.15, found 110.12;

[0103] 8. Preparation Example 8, corresponding to structural formula 8: GC-MS (m / z): calcd . for C7H6N2[M+1]+, 118.14, found 119.25;

[0104] 9. Preparation Example 9, corresponding to structural formula 9: GC-MS (m / z): calcd . for C8H5N3[M+1]+, 143.15, found 144.20.

[0105] Example 1

[0106] Take the base electrolyte and add 0.5% by mass of the compound of formula 1 to obtain the electrolyte of Example 1. The positive electrode is lithium aluminum titanium phosphate (LATP) solid electrolyte coated with lithium cobalt oxide (LiCoO2). The battery is assembled according to the above method for subsequent testing.

[0107] Example 2

[0108] Take the base electrolyte and add 0.5% by mass of the compound of formula 2 to obtain the electrolyte of Example 2. The positive electrode is lithium titanium aluminum phosphate (LATP) solid electrolyte coated with lithium cobalt oxide (LiCoO2). The battery is assembled according to the above method for subsequent testing.

[0109] Example 3

[0110] Take the base electrolyte and add 0.5% of the compound of formula 2 and 0.3% of lithium trifluoromethanesulfonate to obtain the electrolyte of Example 3, which is lithium cobalt oxide (LiCoO2) coated with lithium aluminum titanium phosphate (LATP) solid electrolyte. The battery was assembled according to the above method for subsequent testing.

[0111] Example 4

[0112] Take the base electrolyte and add 0.5% of the compound of structural formula 3 to obtain the electrolyte of Example 4. The positive electrode is lithium aluminum titanium phosphate (LATP) solid electrolyte coated with lithium cobalt oxide (LiCoO2). The battery is assembled according to the above method for subsequent testing.

[0113] Example 5

[0114] Take the basic electrolyte and add 1% of the compound of structural formula 5 to obtain the electrolyte of Example 5. The positive electrode is lithium titanium aluminum phosphate (LATP) solid electrolyte coated with lithium cobalt oxide (LiCoO2). The battery is assembled according to the above method for subsequent testing.

[0115] Example 6

[0116] Take the basic electrolyte and add 0.5% of the compound of structural formula 7 to obtain the electrolyte of Example 6. The positive electrode is lithium aluminum titanium phosphate (LATP) solid electrolyte coated with lithium cobalt oxide (LiCoO2). The battery is assembled according to the above method for subsequent testing.

[0117] Example 7

[0118] Take the base electrolyte and add 0.5% of the compound of structure 9 to obtain the electrolyte of Example 7. The positive electrode is lithium aluminum titanium phosphate (LATP) solid electrolyte coated with lithium cobalt oxide (LiCoO2). The battery is assembled according to the above method for subsequent testing.

[0119] Comparative Example 1

[0120] Comparative Example 1 uses the base electrolyte; the positive electrode is an uncoated solid electrolyte positive electrode, namely lithium cobalt oxide (LiCoO2). The battery was assembled according to the above method for subsequent testing.

[0121] Comparative Example 2

[0122] Comparative Example 2 used the base electrolyte; the positive electrode was lithium titanium aluminum phosphate (LATP) solid electrolyte coated with lithium cobalt oxide (LiCoO2). The battery was assembled according to the above method for subsequent testing.

[0123] Comparative Example 3

[0124] Take the base electrolyte and add 0.3% lithium trifluoromethanesulfonate to obtain the electrolyte for Comparative Example 3. The positive electrode is lithium titanium aluminum phosphate (LATP) solid electrolyte coated with lithium cobalt oxide (LiCoO2). The battery is assembled according to the above method for subsequent testing.

[0125] Battery test

[0126] 1. Loop testing

[0127] Xinwei's test procedure settings: At a specific temperature, charge at a constant current of 1 C to the charging cutoff voltage of 4.55V, then charge at a constant voltage until the current drops to 0.05 C, and then discharge at a constant current of 1 C to 3.0 V to obtain the cycle capacity retention rate of different formulations.

[0128] Cycle capacity retention rate = discharge capacity in the last week / initial discharge capacity × 100%. When the capacity retention rate is 85%, the cycle is stopped.

[0129] ACR growth rate = (End-of-cycle ACR - Initial ACR) / Initial ACR × 100%.

[0130] 2. High-temperature storage performance test

[0131] The battery was charged and discharged at 25℃ for one cycle at a 1C rate, and the discharge capacity was recorded. Then, it was charged at a constant current of 1C until it reached 50% SOC. At 50% SOC, the battery DCIR was tested. Then, it was charged at a constant current of 1C until the cutoff voltage of 4.55V was reached. Then, it was charged at a constant voltage until the current dropped to 0.05C. The battery was placed in a high-temperature explosion-proof box and stored at 60℃ for one week. It was discharged at 25℃ at 1C to 3V. Then, it was charged and discharged at 1C for one cycle. The capacity retention rate and capacity recovery rate were calculated.

[0132] 60℃ storage capacity recovery rate = discharge capacity in the second cycle after high temperature storage / discharge capacity in the last week before high temperature storage × 100%.

[0133] 3. Ratio Performance Test

[0134] The battery is charged and discharged at different rates, and the capacity retention rate at different rates is calculated based on the 0.2 C base capacity.

[0135] 4. Security Testing:

[0136] Hot chamber test: The temperature chamber is heated from the ambient temperature to 130℃±2℃ at a rate of 5℃ / min, and then the temperature is maintained for 30 minutes before heating is stopped; the battery is considered to have passed if it does not catch fire or explode.

[0137] The test results are shown in Tables 1 and 2 below:

[0138] Table 1

[0139]

[0140] Table 2

[0141]

[0142] As can be seen from the structures of the embodiments and comparative examples, the cyano-containing compound provided by the present invention can effectively improve the high-temperature stability of the battery, inhibit the growth of cycle ACR, improve the high-temperature cycle performance of the battery, and improve battery safety. Data from Examples 2, 3, and Comparative Example 3 show that when the cyano-containing compound additive of the present invention is further used in combination with lithium trifluoromethanesulfonate, inorganic lithium can be formed on the electrode surface, thereby further improving the stability of the CEI film under high voltage. Results from Example 3 and Comparative Example 1 show that the cyano-containing compound provided by the present invention, as an electrolyte additive, works synergistically with the positive electrode solid electrolyte coating layer to construct a highly efficient ion transport channel at the positive electrode interface and optimize the interfacial charge distribution. This composite interfacial structure can effectively reduce the battery internal resistance and significantly improve the interfacial thermal stability, thereby comprehensively improving the electrochemical performance and safety performance of the battery.

[0143] In summary, this invention provides a cyano-containing compound having a structure of Formula I, Formula II, or Formula I-II, which can be used as an additive in an electrolyte and paired with a solid electrolyte-coated positive electrode. The solid electrolyte layer on the positive electrode surface provides rigid ion channels, suppressing structural failure and electron leakage of the positive electrode material. Simultaneously, the aforementioned cyano-containing compound undergoes electrochemical polymerization at the positive electrode interface during battery operation, forming a functional polymer film with high thermal stability. This polymer film, together with the pre-placed solid electrolyte coating layer, constitutes a robust composite interface, promoting lithium-ion transport and optimizing interfacial charge distribution, thereby significantly improving the battery's rate performance and high-temperature cycle life. The composite interface of the polymer film and the solid electrolyte coating effectively suppresses the thermal decomposition of the positive electrode material, enhancing the battery's thermal stability and safety. Studies have shown that semi-solid-state batteries using the aforementioned electrolyte and positive electrode exhibit excellent long-cycle performance, rate performance, and safety performance.

[0144] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A compound, characterized in that, It has a structure of formula I, formula II or formula III: ； Wherein, L is selected from substituted or unsubstituted C1~C6 alkylene groups, substituted or unsubstituted C1~C6 fluoroalkylene groups or aryl groups; n is an integer between 0 and 3; R is selected from cyano, substituted or unsubstituted C1-C6 alkyl, -SO3H or -PO3H2; R1, R2, R3, R4, R5, R6 are independently selected from hydrogen, cyano, substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C1-C6 alkoxy or halogen. At least one of R, R1, and R2 is a cyano group; at least one of R3 and R4 is a cyano group; and at least one of R5 and R6 is a cyano group.

2. The compound according to claim 1, characterized in that, R1, R2, R3, R4, R5, and R6 are independently selected from hydrogen, methyl, ethyl, propyl, cyano, trifluoromethyl, perfluoroalkyl, methoxy, ethoxy, or halogen.

3. The compound according to claim 1 or 2, characterized in that, The compound is selected from any one of the following formulas 1 to 9: 。 4. The use of any one of the compounds according to claims 1 to 3 as an electrolyte additive.

5. An electrolyte, characterized in that, Includes lithium salts, organic solvents, basic additives, lithium trifluoromethanesulfonate, and the compounds according to any one of claims 1 to 3; The amount of lithium trifluoromethanesulfonate added accounts for 0-1% of the total mass of the electrolyte; The amount of the compound added is 0.1-2% of the total mass of the electrolyte.

6. The electrolyte according to claim 5, characterized in that, The lithium salt is selected from any one or more of lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium perchlorate, lithium tetrafluoroborate, or lithium bis(oxalato)borate; the amount of lithium salt added accounts for 12-18% of the total mass of the electrolyte; The basic additive is selected from any one or more of sulfonate compounds, sulfate compounds, unsaturated cyclic carbonate compounds, borate compounds, trimethylsilyl ester compounds, or nitrile compounds, and the amount of the basic additive added accounts for 0.1% to 8% of the total mass of the electrolyte; The organic solvent is selected from any one or more of propylene carbonate, ethylene carbonate, methyl ethyl carbonate, dimethyl carbonate, diethyl carbonate, ethyl acetate, propyl acetate, propyl propionate, methyl butyrate, methyl acetate, ethyl propionate, or γ-butyrolactone.

7. A semi-solid-state battery, characterized in that, It includes a positive electrode, a negative electrode, a separator, and the electrolyte as described in claim 5 or 6, wherein the surface of the active material of the positive electrode is coated with a solid electrolyte; The solid electrolyte layer is selected from lithium lanthanum zirconium oxide and / or lithium titanium aluminum phosphate.

8. The semi-solid-state battery according to claim 7, characterized in that, The active material of the positive electrode is selected from any one or more of lithium nickel cobalt manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt aluminum oxide, lithium cobalt oxide, or lithium manganese oxide. The positive electrode also includes a conductive agent and a binder; The conductive agent is selected from any one or more of conductive carbon black, carbon nanotubes, graphene, carbon fiber, or Ketjen black. The adhesive is selected from any one or more of polypropylene, polyethylene, polyvinylidene fluoride, vinylidene fluoride, hexafluoropropylene, polytetrafluoroethylene, or polyhexafluoropropylene.

9. The semi-solid-state battery according to claim 7 or 8, characterized in that, The active material of the negative electrode is selected from any one or more of graphite, hard carbon, soft carbon, silicon, or silicon-oxygen materials.

10. The semi-solid-state battery according to any one of claims 7 to 9, characterized in that, The diaphragm is selected from PE diaphragm or PP diaphragm.

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