A non-aqueous electrolyte for lithium ion battery and a lithium ion battery

Abstract

The application discloses a lithium ion battery non-aqueous electrolyte and a lithium ion battery. The battery electrolyte comprises an electrolyte lithium salt, an organic solvent and a composite functional additive, and the composite functional additive comprises fluoroethylene carbonate, propylene sulfite, compound I and compound II. On the basis of the first two additives, the interaction of the multiple functional groups of the latter two can improve the stability of the positive and negative electrode film interface, and compared with the electrolyte additive with a single functional group, the normal temperature cycle and high temperature cycle performance of the battery can be improved. Especially for the lithium ion battery with graphite as the negative electrode material, a single crystal silicon and graphite composite material, or a silicon monoxide and graphite composite material, the lithium ion battery has high safety, excellent normal temperature cycle stability and high temperature cycle stability.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, specifically relating to a non-aqueous electrolyte for lithium-ion batteries and a lithium-ion battery. Background Technology

[0002] Lithium-ion batteries have gained widespread attention and application in various fields due to their numerous advantages over other power technologies. The first generation of commercially available lithium-ion battery cathode materials was layered LiCoO2. However, during charging and discharging, LiCoO2 undergoes an irreversible phase transition from a hexagonal to a monoclinic phase, and the electrolyte also experiences severe oxidative decomposition. In general, structural degradation under high voltage and instability at the electrode / electrolyte interface are key factors limiting its wider application. Nevertheless, due to its stable electrochemical performance and relatively easy preparation, LiCoO2 cathode batteries have maintained a dominant position in the 3C (computer, communication, and consumer electronics) lithium-ion battery market. The electrolyte, as a crucial component of lithium-ion batteries, acts as a link between the positive and negative electrode materials by transporting lithium ions. Importantly, adding a certain amount of electrolyte additives to a standard electrolyte can specifically improve certain battery performance characteristics. Therefore, the use of additives is currently the most common method for improving the performance of lithium-ion batteries.

[0003] CN 109687022 A discloses an electrolyte containing a fluorinated solvent and pyridine additives, and a lithium-ion battery using the electrolyte. This electrolyte utilizes pyridine compounds containing nitrile groups, and synergistically employs a fluorinated organic solvent with good wettability, which effectively improves the properties of the electrode / electrolyte interface film, inhibits the dissolution of transition metals, and enhances the cycle life of the lithium-ion battery under high temperature and high pressure.

[0004] CN 113948770 A discloses an electrolyte containing a silane compound with an acetylene group. Compared to conventional lithium-ion batteries that do not use the electrolyte of this invention, this invention provides a non-aqueous electrolyte that can suppress the reaction between the electrolyte and the negative electrode at high temperatures, thereby improving the high-temperature storage performance of lithium-ion batteries. The compound containing at least one acetylene group, as an electrolyte additive, can form an effective network polymer structure while maintaining electron-deficient properties. This structure is more conducive to the formation of a dense SEI film structure on the negative electrode surface, resulting in more ideal battery performance.

[0005] By adding electrolyte additives that optimize the electrode interface, improve the properties of the electrode / electrolyte interface film, reduce interfacial impedance, and suppress the dissolution of transition metals, batteries can exhibit excellent room-temperature and high-temperature cycling stability. Therefore, the development of novel electrolyte systems is an important direction in electrolyte materials research. Summary of the Invention

[0006] The purpose of this invention is to provide a non-aqueous electrolyte for lithium-ion batteries and a lithium-ion battery.

[0007] A non-aqueous electrolyte for lithium-ion batteries, the electrolyte comprising an electrolyte lithium salt, an organic solvent, and a composite functional additive; the composite functional additive comprising fluoroethylene carbonate, propylene sulfite, and a compound comprising at least one of compound I and compound II, wherein the structural formula of compound I is shown in structural formula I, and the structural formula of compound II is shown in structural formula II.

[0008] Structural Formula I; Structural Formula II;

[0009] Where R1 represents substituted hydrogen or substituted alkyl; R2, R3, and R4 represent substituted hydrogen, halogen, substituted alkyl, or substituted cyano; R5 and R6 represent substituted hydrogen, halogen, or substituted alkyl; R7, R9, and R... 10 R 11 For substituted alkynyl, substituted alkoxy, substituted silyl; R7, R9, R 10 R 11 At least one of them is a substituted silyl group, and R8 is a substituted alkyl group.

[0010] The structural formula of compound I is shown below:

[0011] Compound 1; Compound 2; Compound 3; Compound 4; Compound 5; Compound 6; Compound 7; Compound 8;

[0012] The structural formula of compound II is as follows:

[0013] Compound 9; Compound 10; Compound 11;

[0014] The structural combination of compound I and compound II in the composite functional additive is as follows:

[0015] Combination 1: and; ;

[0016] Combination 2: and ;

[0017] Combination 3: and ;

[0018] Combination 4: and ;

[0019] Combination 5: and ;

[0020] Combination 6: and ;

[0021] Combination 7: and ;

[0022] Combination 8: and ;

[0023] Combination 9: and ;

[0024] Combination 10: and ;

[0025] Combination 11: and ;

[0026] Combination 12: and ;

[0027] Combination 13: and ;

[0028] Combination 14: and ;

[0029] Combination 15: and ;

[0030] Combination 16: and ;

[0031] Based on the total mass of the battery electrolyte as 100%, the composite functional additive contains 1 to 10% by mass of compound I and compound II.

[0032] The lithium salt is any one or a combination of at least two of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium bis(oxalato)borate, lithium difluorooxalato)borate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium difluorophosphate, or lithium difluorobis(oxalato)phosphate.

[0033] Based on the total mass of the battery electrolyte as 100%, the mass percentage of the electrolyte lithium salt is 10% to 45%.

[0034] The organic solvent is at least one of carbonate, halocarbonate, carboxylic acid ester, propionate, fluoroether, aromatic hydrocarbon or haloaromatic hydrocarbon;

[0035] The halogen in the halocarbonate or haloaromatic hydrocarbon is at least one of F, Cl, Br or I.

[0036] The carbonate includes one or a combination of at least two of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, or ethyl methyl carbonate.

[0037] The halogenated carbonates include at least one or a combination of at least two of the following: fluoroethylene carbonate, difluoroethylene carbonate, difluoropropylene carbonate, ethyl trifluorocarbonate, trifluoroethyl methyl carbonate, trifluoromethyl ethylene carbonate, 4-trifluoromethyl ethylene carbonate, chloroethylene carbonate, di(2,2,2-trifluoroethyl) carbonate, methyl trifluoropropionate, ethyl 3,3,3-trifluoroethylene carbonate, methyl 2-(trifluoromethyl)benzoate, ethyl 4,4,4-trifluorobutyrate, or 1,1,1,3,3,3-hexafluoroisopropyl acrylate.

[0038] The carboxylic acid esters include one or a combination of at least two of the following: propyl butyrate, propyl acetate, isopropyl acetate, butyl propionate, isopropyl propionate, ethyl butyrate, methyl propionate, ethyl propionate, or propyl propionate.

[0039] The propionate is at least one of methyl propionate (EM), ethyl propionate (EP), and propyl propionate (PP);

[0040] The fluoroether is a fluoroether containing 7 or fewer carbon atoms in its molecule;

[0041] The halogenated aromatic hydrocarbon is one or a combination of at least two of the following: monofluorobenzene, difluorobenzene, 1,3,5-trifluorobenzene, trifluorotoluene, 2-fluorotoluene, or 2,4-dichlorotrifluorotoluene.

[0042] Based on the total mass of the battery electrolyte being 100%, the mass percentage of the organic solvent is 40-85%.

[0043] A battery, wherein the battery pack contains a non-aqueous electrolyte for lithium-ion batteries;

[0044] The battery is a lithium-ion battery, sodium-ion battery, potassium-ion battery, magnesium-ion battery, aluminum-ion battery, or supercapacitor.

[0045] The negative electrode material of the lithium-ion battery is graphite, or a composite material of monocrystalline silicon and graphite, or a composite material of silicon suboxide and graphite, or lithium titanate, or Nb2O5.

[0046] The beneficial effects of this invention are as follows: This invention employs pyridine compounds containing alkynyl groups and silanes. Firstly, the unsaturated effect of the alkynyl group, combined with the silane, yields a polyacetylene-derived polymer chain structure, forming an effective network polymer structure. This facilitates the formation of a dense and stable CEI / SEI film on the material surface, effectively inhibiting the oxidative decomposition of the electrolyte and resulting in superior performance. Simultaneously, the Lewis base nature of pyridine, coupled with the presence of cyano substituents, effectively controls the acid content in the electrolyte and allows it to complex with metal ions, inhibiting their dissolution. This is particularly beneficial for lithium-ion batteries with graphite, composite materials of monocrystalline silicon and graphite, or composite materials of silicon suboxide and graphite as the negative electrode material, resulting in excellent performance. Detailed Implementation

[0047] To facilitate understanding of the present invention, a more comprehensive description will be given below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0048] The general testing platform used in Examples 1-16 and Comparative Example 1 is as follows: the positive electrode uses PVDF-900 binder, Super-P composite conductive agent, lithium cobalt oxide (LCO) positive electrode material, and NMP (N-methyl-2-pyrrolidone) solvent. N- The negative electrode uses graphite material (model QCG-H2), conductive agent Super-P, solvent CMC, H2O, and binder SBR as raw materials. The process involves coating, slicing, rolling, cutting, drying, applying tape, winding the cells, drying at 80℃ for 48 hours, and then filling and sealing the lithium-ion battery according to different electrolyte formulations, followed by 24 hours of resting, formation, first final sealing, aging, and second final sealing to prepare lithium-ion soft-pack batteries. The batteries are then tested for high-temperature cycle performance and high-temperature storage performance.

[0049] The electrolytes described in Examples 1-16 and Comparative Example 1 were tested as follows:

[0050] Cycling performance: The charging and discharging voltage range is 2.75V to 4.48V, the charging current is 1C (2.0A) to 4.48V, the constant voltage charging at 4.48V is carried out until the cutoff current is ≤0.05C (0.1A), and after resting for 5 minutes, the voltage is discharged at 1C (2.0A) to 2.75V and then rested for 5 minutes. The capacity retention rate is calculated for different numbers of cycles of electric discharge.

[0051] The electrolyte compositions of Examples 1-16 and Comparative Example 1 are shown in Table 1.

[0052] Table 1

[0053]

[0054] Lithium-ion batteries prepared using lithium cobalt oxide as the positive electrode material and the electrolyte formulations of Examples 1 to 15 and Comparative Example 1 were tested for room temperature cycling performance and high temperature cycling performance. The test results are shown in Tables 2 and 3 below:

[0055] Table 2 Battery Capacity Retention Rate During Cycling at 25℃

[0056]

[0057] Table 3 Battery Capacity Retention Rate at 45℃ High-Temperature Cycling

[0058]

[0059] As shown in Tables 2 and 3, the analysis of Comparative Example 1 and Examples 1-15 reveals that the performance of the Examples 1 is improved to a certain extent compared to Comparative Example 1. By adding ethylene fluorocarbonate, propylene sulfite, and at least one compound from Compound I and Compound II as composite functional additives, the synergistic effect of multiple functional groups effectively improves the battery's room temperature and high temperature cycle performance. This is particularly true for lithium-ion batteries with graphite, composite materials of monocrystalline silicon and graphite, or composite materials of silicon suboxide and graphite as the negative electrode material, resulting in excellent performance.

[0060] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A non-aqueous electrolyte for lithium-ion batteries, characterized in that, The electrolyte comprises a lithium electrolyte salt, an organic solvent, and a composite functional additive; the composite functional additive comprises fluoroethylene carbonate, propylene sulfite, compound I, and compound II. The structural formulas of compounds I and II are combined as follows: Combination 1: and ; Combination 2: and ; Combination 3: and ; Combination 4: and ; Combination 5: and ; Combination 6: and ; Combination 7: and ; Combination 8: and ; Combination 9: and ; Combination 10: and ; Combination 11: and ; Combination 12: and ; Combination 13: and ; Combination 14: and ; Combination 15: and ; Combination 16: and ; Based on the total mass of the battery electrolyte as 100%, the composite functional additive contains 1 to 10% by mass of compound I and compound II.

2. The non-aqueous electrolyte for lithium-ion batteries according to claim 1, characterized in that, The lithium salt is any one or a combination of at least two of lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium bis(oxalato)borate, lithium difluorooxalato)borate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium difluorophosphate, or lithium difluorobis(oxalato)phosphate.

3. The non-aqueous electrolyte for lithium-ion batteries according to claim 1, characterized in that, Based on the total mass of the battery electrolyte as 100%, the mass percentage of the electrolyte lithium salt is 10% to 45%.

4. The non-aqueous electrolyte for lithium-ion batteries according to claim 1, characterized in that, The organic solvent is at least one of carbonate, halocarbonate, carboxylic acid ester, fluoroether, aromatic hydrocarbon or haloaromatic hydrocarbon; The halogen in the halocarbonate or haloaromatic hydrocarbon is at least one of F, Cl, Br or I. The carbonate includes one or a combination of at least two of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, or ethyl methyl carbonate. The halogenated carbonates include at least one or a combination of at least two of the following: fluoroethylene carbonate, difluoroethylene carbonate, difluoropropylene carbonate, ethyl trifluorocarbonate, trifluoroethyl methyl carbonate, trifluoromethyl ethylene carbonate, 4-trifluoromethyl ethylene carbonate, chloroethylene carbonate, di(2,2,2-trifluoroethyl) carbonate, methyl trifluoropropionate, ethyl 3,3,3-trifluoroethylene carbonate, methyl 2-(trifluoromethyl)benzoate, ethyl 4,4,4-trifluorobutyrate, or 1,1,1,3,3,3-hexafluoroisopropyl acrylate. The carboxylic acid esters include one or a combination of at least two of the following: propyl butyrate, propyl acetate, isopropyl acetate, butyl propionate, isopropyl propionate, ethyl butyrate, methyl propionate, ethyl propionate, or propyl propionate. The fluoroether is a fluoroether containing 7 or fewer carbon atoms in its molecule; The halogenated aromatic hydrocarbon is one or a combination of at least two of the following: monofluorobenzene, difluorobenzene, 1,3,5-trifluorobenzene, trifluorotoluene, 2-fluorotoluene, or 2,4-dichlorotrifluorotoluene.

5. The non-aqueous electrolyte for lithium-ion batteries according to claim 1, characterized in that, Based on the total mass of the battery electrolyte being 100%, the mass percentage of the organic solvent is 40-85%.

6. A battery, characterized in that, The battery includes the non-aqueous electrolyte for lithium-ion batteries as described in claim 1; The negative electrode material of the lithium-ion battery is graphite, or a composite material of monocrystalline silicon and graphite, or a composite material of silicon suboxide and graphite, or lithium titanate, or Nb2O5.

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