An electrolyte, a battery containing the electrolyte, and an electric device

Abstract

The application provides an electrolyte, a battery containing the electrolyte and a power device, and belongs to the technical field of battery electrolytes. The electrolyte comprises a lithium salt, a solvent and an additive, wherein the additive is a halogenated diphenyl derivative, a bis(halogenated phenyl) compound or a halogenated sulfur-containing heterocyclic compound. When the electrolyte is used in a battery, the electrolyte can effectively inhibit the decomposition of the electrolyte and the generation of reducing gas generated by side reactions. The SEI film can prevent solvent molecules from being embedded in graphite, improve the coulombic efficiency and cycle stability of the battery, and thus improve the reversibility of the electrolyte in the graphite negative electrode. In a lithium ion battery, the electrolyte effectively improves the compatibility of the graphite negative electrode with the solvent, has excellent cycle life and high coulombic efficiency, and further improves the comprehensive electrochemical performance of the battery.

Description

TECHNICAL FIELD

[0001] The application relates to an electrolyte and a battery and a power utilization device containing the electrolyte, and belongs to the technical field of electrolytes for batteries. BACKGROUND

[0002] Lithium-ion batteries (LIBs) have become the preferred energy storage system for electric vehicles and portable electronic devices due to their high specific energy, low self-discharge, good cycle characteristics, no memory effect, and environmental friendliness. The core structure of lithium-ion batteries includes positive electrode materials, negative electrode materials, electrolytes, separators, and metal housings. Among them, the positive electrode and the negative electrode play a key role in the battery operation, responsible for the storage and release of lithium ions. Graphite is the most widely used negative electrode material in the current lithium-ion battery market due to its high theoretical specific capacity (372 mAh / g), low operating potential (~0.1 V vs. Li / Li + ), and good structural stability (volume change <10%).

[0003] Currently, commercial lithium-ion battery electrolytes generally use electrolytes based on ethylene carbonate (EC) solvent systems. EC molecules can preferentially undergo reduction decomposition on the surface of the graphite negative electrode, forming a stable solid electrolyte interphase (SEI), thereby realizing the reversible insertion / extraction of lithium ions in the graphite negative electrode. However, EC-based electrolytes have high melting points (38 ℃), poor oxidation stability (<4.3 V vs. Li / Li + ), and electrode crosstalk, which limits the application range of LIBs. Propylene carbonate (PC) is a solvent with high dielectric constant and wide liquid phase range, with a low freezing point, wide temperature range, strong solvation ability, and high flash point (132 ℃). In addition, it also has high negative electrode stability and good compatibility with high-nickel positive electrodes, however, when paired with graphite negative electrodes, PC is difficult to form a stable SEI layer on the graphite surface due to its large molecular size and different reduction decomposition path, leading to severe decomposition at the negative electrode interface. This undesirable interfacial behavior can cause severe capacity decay, which limits the practical application of PC in lithium-ion batteries. In addition to PC, many ether and amine solvents also have poor compatibility with graphite anodes, such as dimethoxyethane (DME), N,N-dimethylformamide (DMF), and dioxolane (DOL). Developing electrolyte systems that can be compatible with graphite negative electrodes and have excellent electrochemical performance is of great significance for realizing wide temperature range and high-performance lithium-ion batteries.

[0004] Researchers have successfully overcome the poor compatibility of PC solvent with graphite negative electrode by increasing the concentration of lithium salt to form high-concentration electrolyte (HCEs) or introducing diluents to construct local high-concentration electrolyte (LHCEs). However, practical application still faces challenges such as high cost, environmental impact, and long-term stability. In contrast, using electrolyte additives is a more cost-effective and environmentally friendly solution. Additives can be preferentially reduced in the electrolyte and form a stable SEI layer on the negative electrode surface, thereby achieving reversible cycling of LIBs based on PC solvent electrolyte. This strategy not only reduces the overall cost of the electrolyte, but also has good practical application prospects. However, the currently disclosed additives do not have ideal application effects, especially in terms of cycle performance and compatibility with the negative electrode. SUMMARY

[0005] Therefore, the present application first provides an electrolyte, which is designed to achieve compatibility between the electrolyte and the graphite negative electrode by preferentially reducing the graphite negative electrode to form a stable SEI film, while also having good coulombic efficiency and cycle life.

[0006] Specifically, the present application is achieved by the following scheme:

[0007] An electrolyte, comprising a lithium salt, a solvent and an additive, the mass percentage of the additive in the electrolyte is not less than 0.1%, and the additive comprises a first type of additive and a second type of additive.

[0008] The first type of additive is a halogenated biphenyl compound or a bis(halogenated phenyl) compound,

[0009] The structural formula of the halogenated biphenyl compound satisfies: wherein X is selected from H atom, halogen atom or halogenated alkyl group (X cannot be all H atoms),

[0010] The structural formula of the bis(halogenated phenyl) compound satisfies: wherein X is selected from H atom, halogen atom or halogenated alkyl group (X cannot be all H atoms), and R is selected from any one of alkyl group, carbonate group, sulfate group, sulfonate group, sulfite group, and halogenated phenyl group.

[0011] The second type of additive is a halogenated sulfur-containing heterocyclic compound, and the structural formula of the halogenated sulfur-containing heterocyclic compound satisfies: wherein R is selected from CH, C-X or N, and X is selected from H, halogen atom or halogenated alkyl group (X cannot be all H).

[0012] Further, as a preferred:

[0013] In the first type of additive,

[0014] X is a halogen atom, the number of halogen atoms is 2-10; X is a haloalkyl group, the number of halogen atoms in the haloalkyl group is 1-3.

[0015] The first additive is at least one of decafluorobiphenyl, nonafluorobiphenyl, octafluorobiphenyl, heptafluorobiphenyl, hexafluorobiphenyl, pentafluorobiphenyl, tetrafluorobiphenyl, trifluorobiphenyl, decachlorobiphenyl, nonachlorobiphenyl, octachlorobiphenyl, heptachlorobiphenyl, hexachlorobiphenyl, pentachlorobiphenyl, tetrachlorobiphenyl, trichlorobiphenyl, dichlorobiphenyl, 2-bromo-4'-chloro-1,1'-biphenyl, 4-bromo-2-fluorobiphenyl, 3'-fluoro-2,4,6-trichlorobiphenyl, 3'-fluoro-2,4,4'-trichlorobiphenyl, 2',4'-dichloro-3,5-difluorobiphenyl, 2',3'-dichloro-3,5-difluorobiphenyl, 4-bromo-2,3-dichloro-4'-fluoro-1,1'-biphenyl, 2',3'-dichloro-3,4-difluorobiphenyl, 3-fluoro-2,2',5-trichlorobiphenyl, 3'-fluoro-2,3,4'-trichlorobiphenyl, 2',4'-dichloro-2,5-difluorobiphenyl, 5-bromo-2'-chloro-2,4,6'-trifluoro-1'-biphenyl, 2',3'-dichloro-2,3,4,5-tetrafluorobiphenyl, 2',4'-dichloro-2,3,4,5-tetrafluorobiphenyl, dibromo-octafluorobiphenyl, 3-chloro-4'-(trifluoromethyl)-1,1'-biphenyl, 4-(trifluoromethyl)-biphenyl, tetradecafluorotriphenyl, bis(pentafluorophenyl)methane, bis(pentafluorophenyl) carbonate, pentafluorophenyl pentafluorophenyl sulfonate, dipentafluorophenyl sulfate, dipentafluorophenyl sulfite. More preferably, at least one of decafluorobiphenyl, 2-bromo-4'-chloro-1,1'-biphenyl, bis(pentafluorophenyl) carbonate.

[0016] In the second additive, X is a halogen atom, the number of halogen atoms is 2-4; X is a haloalkyl group, the number of halogen atoms in the haloalkyl group is 1-3.

[0017] The second additive is at least one of 2-fluorothiophene, 3-fluorothiophene, 2,3-difluorothiophene, 2,4-difluorothiophene, 2,5-difluorothiophene, 3,4-difluorothiophene, 2,3,4-trifluorothiophene, 2,3,5-trifluorothiophene, 2,4,5-trifluorothiophene, 2,3,4,5-tetrafluorothiophene, 2-chlorothiophene, 3-chlorothiophene, 2,3-dichlorothiophene, 2,4-dichlorothiophene, 2,5-dichlorothiophene, 3,4-dichlorothiophene, 2,3,4-trichlorothiophene, 2,3,5-trichlorothiophene, 2,4,5-trichlorothiophene, 2,3,4,5-tetrachlorothiophene, 2-bromothiophene, 3-bromothiophene, 2,3-dibromothiophene, 2,4-dibromothiophene, 2,5-dibromothiophene, 3,4-dibromothiophene, 2,3,4-tribromothiophene, 2,3,5-tribromothiophene, 2,4,5-tribromothiophene, 2,3,4,5-tetrabromothiophene, 2-chloro-4-fluoro-thiophene, 2-chloro-4-fluoro-thiophene, 4-chloro-2-fluoro-thiophene, 2-chloro-3-fluoro-thiophene, 2-chloro-5-fluoro-thiophene, 3-bromo-2-fluoro-thiophene, 2-bromo-3-fluoro-thiophene, 2-bromo-4-fluoro-thiophene, 4-bromo-2-fluoro-thiophene, 5-bromo-2-fluoro-thiophene, 3-bromo-4-fluoro-thiophene, 3-bromo-2-chlorothiophene, 2-bromo-3-chloro-thiophene, 2-bromo-4-chloro-thiophene, 4-bromo-2-chloro-thiophene, 2-bromo-5-chloro-thiophene, 3-bromo-4-chloro-thiophene, 3-bromo-2,5-dichlorothiophene, 4-bromo-3-chloro-2-fluoro-thiophene, 3,4-dibromo-2-chloro-thiophene, 3,5-dibromo-2-chloro-thiophene, 4-bromo-2,3-dichlorothiophene, 3,4-dibromo-2,5-dichlorothiophene, 4,5-dichloro-2-fluoro-1,3-thiazole, 2,4-dichlorothiazole, 2,4,5-trichlorothiazole, 2,4,5-tribromothiazole, 5-(difluoromethyl)-2,4-difluoro-thiophene, 2,5-difluoro-1,3,4-thiadiazole, 2,5-dichloro-1,3,4-thiadiazole, 2,5-dibromo-1,3,4-thiadiazole, 2-chloro-5-fluoro-1,3,4-thiadiazole, 2-bromo-5-fluoro-1,3,4-thiadiazole, 2-bromo-5-chloro-1,3,4-thiadiazole, 2,5-bis(trifluoromethyl)-1,3,4-thiadiazole, 2,5-bis(1,1,2,2,2-pentafluoroethyl)-1,3,4-thiadiazole, 2,5-bis(1,1,2,2,2-pentafluoroethyl)-1,3,4-thiadiazole. More preferably, at least one of 2,3,4,5-tetrachlorothiophene, 2,4-dichlorothiazole.

[0018] The halogen atom is F, Cl or Br.

[0019] The mass percentage of the additive in the electrolyte is 0.4-10%, preferably 0.7-5.0%.

[0020] The lithium salt is any one of lithium bisfluorosulfonylimide (LiFSI), lithium bistrifluoromethylsulfonylimide (LiTFSI), lithium oxoborate (LiBOB), lithium difluoro oxoborate (LiDFOB), lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), and the like inorganic anion lithium salt and organic anion lithium salt. More preferably, the lithium salt is selected from at least one of lithium hexafluorophosphate (LiPF6) and lithium bisfluorosulfonylimide (LiFSI).

[0021] The lithium salt concentration is 0.1-6.0 mol / L. More preferably, the lithium salt concentration in the electrolyte is 0.6-1.5 mol / L. Preferably, it is 1.0-1.5 mol / L.

[0022] The solvent is dimethoxyethane (DME), N,N-dimethylformamide (DMF), propylene carbonate (PC), and 1,3-dioxolane (DOL).

[0023] The second aspect of the application is to provide a battery containing the above-mentioned electrolyte, which comprises a positive active material, a negative active material and an electrolyte, the positive active material is a ternary positive material (LiNi 0.8 Co 0.1 Mn 0.1 O2), lithium cobaltate positive material (LiCoO2), lithium manganate positive material (LiMnO2) or lithium iron phosphate positive material (LiFePO4), and the negative active material is artificial graphite, natural graphite or composite graphite.

[0024] The third aspect of the application is to provide a power consuming device containing the above-mentioned battery.

[0025] When the electrolyte of the application is used in a lithium ion battery, the advantages and technical effects are as follows:

[0026] 1、The halogenated biphenyl compound, the double (halogenated phenyl) compound and the halogenated sulfur-containing heterocyclic compound are used in the embodiment of the application, the preferential reduction characteristics of the compounds on the graphite negative electrode are utilized, and a stable solid-state electrolyte interface film (SEI) is generated on the graphite surface in the charging and discharging process. The SEI film has high chemical and electrochemical stability, can effectively block the further insertion of solvent molecules, and allows lithium ions to pass through smoothly, thereby maintaining ionic conductivity. When the halogen atoms or halogenated alkyl groups in the additive are reduced on the electrode surface, fluorine, chlorine or bromine-containing compounds are formed, which are the main components of the SEI film, and the resistance to reduction and barrier property of the SEI film are enhanced. The biphenyl and phenyl compounds in the first type of additive can improve the mechanical strength of the SEI film due to the rigid structure, prevent the SEI film from being broken or dissolved in the cycle process, and further improve the cycle stability and coulombic efficiency of the battery. The second type of additive can form a SEI film containing sulfur and nitrogen on the negative electrode surface, the generated SEI film is dense and has high thermal stability, and the interface impedance is reduced, thereby improving the cycle performance of the battery.

[0027] 2、The electrolyte can effectively improve the matching performance of the electrolyte and the graphite negative electrode.

[0028] 3、The electrolyte has excellent compatibility with the positive electrode, and long cycle life and high coulombic efficiency of the lithium ion battery are achieved. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0030] Figure 1 (a) in the figure is a charge-discharge curve of a graphite||Li asymmetric battery of the electrolyte prepared in Example 1, Figure 1 (b) in the figure is a cycle life curve of a graphite||Li asymmetric battery of the electrolyte prepared in Example 1, Figure 1 (c) in the figure is a cycle life curve of a LiNi 0.8 Co 0.1 Mn 0.1 O2||graphite battery prepared in Example 1;

[0031] Figure 2 (a) in the figure is a charge-discharge curve of a graphite||Li asymmetric battery of the electrolyte prepared in Example 2, Figure 2 (b) in the figure is a cycle life curve of a graphite||Li asymmetric battery of the electrolyte prepared in Example 2, Figure 2(c) is the cycle life plot of LiNi 0.8 Co 0.1 Mn 0.1 O2||graphite cells;

[0032] Figure 3 (a) is the charge-discharge plot of a graphite||Li asymmetric cell of electrolyte prepared in Example 3, Figure 3 (b) is the cycle life plot of a graphite||Li asymmetric cell of electrolyte prepared in Example 3, Figure 3 (c) is the charge-discharge plot of LiNi 0.8 Co 0.1 Mn 0.1 O2||graphite cells;

[0033] Figure 4 (a) is the charge-discharge plot of a graphite||Li asymmetric cell of electrolyte prepared in Example 4, Figure 4 (b) is the cycle life plot of a graphite||Li asymmetric cell of electrolyte prepared in Example 4, Figure 4 (c) is the charge-discharge plot of LiNi 0.8 Co 0.1 Mn 0.1 O2||graphite cells;

[0034] Figure 5 (a) is the charge-discharge plot of a graphite||Li asymmetric cell of electrolyte prepared in Example 5, Figure 5 (b) is the cycle life plot of a graphite||Li asymmetric cell of electrolyte prepared in Example 5,

[0035] Figure 6 (a) is the charge-discharge plot of a graphite||Li asymmetric cell of electrolyte prepared in Example 6, Figure 6 (b) is the cycle life plot of a graphite||Li asymmetric cell of electrolyte prepared in Example 6, Figure 6 (c) is the charge-discharge plot of LiFeP04||graphite cells of electrolyte prepared in Example 6;

[0036] Figure 7 (a) is the charge-discharge plot of a graphite||Li asymmetric cell of electrolyte prepared in Example 7, Figure 7 (b) is the cycle life plot of a graphite||Li asymmetric cell of electrolyte prepared in Example 7, Figure 7 (c) is the charge-discharge plot of LiNi 0.8 Co0.1 Mn 0.1 O2|| Graphite battery cycle life plot;

[0037] Figure 8 (a) of FIG. 8 is a charge-discharge plot of a graphite || Li asymmetric battery of the electrolyte prepared in Example 8, Figure 8 (b) of FIG. 8 is a cycle life plot of a graphite || Li asymmetric battery of the electrolyte prepared in Example 8, Figure 8 (c) of FIG. 8 is a charge-discharge plot of the electrolyte prepared in Example 8 in a LiFeP04|| graphite battery;

[0038] Figure 9 (a) of FIG. 9 is a charge-discharge plot of a graphite || Li asymmetric battery of the electrolyte prepared in Comparative Example 1, Figure 9 (b) of FIG. 9 is a charge-discharge plot of the electrolyte prepared in Comparative Example 1 in a LiNi 0.8 Co 0.1 Mn 0.1 O2|| Graphite battery cycle life plot; Figure 9 (c) of FIG. 9 is a charge-discharge plot of the electrolyte prepared in Comparative Example 1 in a LiFeP04|| graphite battery;

[0039] Figure 10 (a) of FIG. 10 is a charge-discharge plot of a graphite || Li asymmetric battery of the electrolyte prepared in Comparative Example 2, Figure 10 (b) of FIG. 10 is a charge-discharge plot of the electrolyte prepared in Comparative Example 2 in a LiNi 0.8 Co 0.1 Mn 0.1 O2|| Graphite battery cycle life plot;

[0040] Figure 11 (a) of FIG. 11 is a charge-discharge plot of a graphite || Li asymmetric battery of the electrolyte prepared in Comparative Example 3, Figure 11 (b) of FIG. 11 is a charge-discharge plot of the electrolyte prepared in Comparative Example 3 in a LiNi 0.8 Co 0.1 Mn 0.1 O2|| Graphite battery cycle life plot;

[0041] Figure 12 (a) of FIG. 12 is a charge-discharge plot of a graphite || Li asymmetric battery of the electrolyte prepared in Comparative Example 4, Figure 12 (b) of FIG. 12 is a cycle life plot of a graphite || Li asymmetric battery of the electrolyte prepared in Comparative Example 4, Figure 12 (c) of FIG. 12 is a charge-discharge plot of the electrolyte prepared in Comparative Example 4 in a LiFeP04|| graphite battery, Figure 12 (d) of FIG. 12 is a charge-discharge plot of the electrolyte prepared in Comparative Example 4 in a LiNi0.8 Co 0.1 Mn 0.1 O2|| Graphite battery cycle life curve.

[0042] In the above cycle life curve, the upper line corresponds to the trend of the change of coulombic efficiency in the right vertical coordinate, and the lower line corresponds to the trend of the change of specific capacity in the left vertical coordinate. DETAILED DESCRIPTION

[0043] In order to make the technical problems, technical solutions and beneficial effects of the present application clearer, the technical solutions in the embodiments of the present application will be further described in detail below with reference to the accompanying drawings in the embodiments of the present application. It should be understood that the specific embodiments described herein are only used to explain the present application and not used to limit the technical solutions of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0044] Embodiment 1

[0045] The electrolyte of the present embodiment is prepared by the following method:

[0046] Propylene carbonate and LiPF6 are mixed and stirred at room temperature until the lithium salt is completely dissolved. Then 1 wt% of decafluorobiphenyl is added, and the stirring is continued until the electrolyte is clear. The prepared electrolyte has a lithium salt concentration of 1.0 mol / L.

[0047] The electrolyte of the above formulation is used for battery performance test, and the results are shown in Figure 1 .

[0048] Figure 1 (a) in FIG. 1 is the charge-discharge curve of the electrolyte in a graphite||Li battery, the test rate is 0.1 C charge-discharge for 3 cycles, and 0.2 C charge-discharge for long cycle. It can be seen that the above electrolyte can realize efficient and reversible charge-discharge cycle.

[0049] Figure 1 (b) in FIG. 1 is the cycle life curve of the electrolyte used in a graphite||Li battery, wherein the surface capacity of the graphite electrode sheet is 1.50 mAh·cm -2 , the test voltage range is 0.001 V~1.0 V, and the test procedure is 0.1 C charge-discharge for three cycles and 0.2 C long cycle. It can be seen that the capacity retention rate of the above electrolyte is 93.66% after 150 cycles, and the average coulombic efficiency is close to 100%.

[0050] Figure 1 (c) in FIG. 1 is the cycle life curve of the electrolyte used in a LiNi 0.8 Co 0.1 Mn0.1 O2|| graphite battery test, where LiNi 0.8 Co 0.1 Mn 0.1 The areal capacity of the O2 electrode is 1.7 mAh·cm -2 The test voltage range is 2.8 V~4.55 V, the test rate is 0.1 C charge-discharge for 3 cycles, and 0.5 C long cycle. It can be seen that the above electrolyte can still have a capacity retention rate of 99% after 200 cycles, and the average coulombic efficiency is close to 100%. It shows that the additive can effectively prevent the decomposition of the electrolyte.

[0051] Example 2

[0052] The electrolyte of this example is prepared as follows:

[0053] Propylene carbonate is mixed with LiFSI and stirred at room temperature until the lithium salt is completely dissolved. Then 1 wt% of trichlorobenzene is added, and the electrolyte is continuously stirred until it is clear. The prepared electrolyte has a lithium salt concentration of 1.0 mol / L.

[0054] The electrolyte of the above formulation is used for battery performance test, and the results are shown in Figure 2 .

[0055] Figure 2 (a) in the above table is the charge-discharge curve of the electrolyte in a graphite||Li battery, the test rate is 0.1 C charge-discharge for 3 cycles, and 0.2 C long cycle. It can be seen that the above electrolyte can realize efficient and reversible charge-discharge cycle.

[0056] Figure 2 (b) in the above table is the cycle life curve of the electrolyte used in a graphite||Li battery, where the areal capacity of the graphite electrode is 1.80 mAh·cm -2 The test voltage range is 0.001 V~1.5 V, the test procedure is 0.1 C charge-discharge for 3 cycles, and 0.2 C long cycle. It can be seen that the capacity retention rate of the above electrolyte is 94.27% after 150 cycles, and the average coulombic efficiency is close to 100%.

[0057] Figure 2 (c) in the above table is the charge-discharge curve of the electrolyte used in a LiNi 0.8 Co 0.1 Mn 0.1 O2|| graphite battery test, where LiNi 0.8 Co 0.1 Mn 0.1 The areal capacity of the O2 electrode is 2.1 mAh·cm -2, the test voltage range is 0.001 V~1.0 V, the test procedure is 0.1 C charge-discharge three times, and 0.5 C long cycle. It can be seen that the capacity retention rate of the above electrolyte is 98.25% after 150 cycles, and the average coulombic efficiency is close to 100%.

[0058] Example 3

[0059] The electrolyte of this example is prepared as follows:

[0060] Dimethoxyethane is mixed with appropriate amount of LiPF6, and stirred at room temperature until the lithium salt is completely dissolved. Then 1.5 wt% of 2-bromo-4'-chloro-1,1'-biphenyl is added, and continue to stir until the electrolyte is clear. The prepared electrolyte has a lithium salt concentration of 1.2 mol / L.

[0061] The electrolyte of the above formula is used for battery performance test, and the results are shown in Figure 3 .

[0062] Figure 3 (a) in FIG. 1 is the charge-discharge curve of the electrolyte in a graphite||Li battery, the test rate is 0.1 C charge-discharge three times, and 0.5 C long cycle. It can be seen that the above electrolyte can realize efficient and reversible charge-discharge cycle.

[0063] Figure 3 (b) in FIG. 1 is the cycle life curve of the electrolyte used in a graphite||Li battery, wherein the surface capacity of the graphite electrode is 1.80 mAh·cm -2 , the test voltage range is 0.001 V~1.0 V, the test procedure is 0.1 C charge-discharge three times, and 0.5 C long cycle. It can be seen that the capacity retention rate of the above electrolyte is 98.25% after 150 cycles, and the average coulombic efficiency is close to 100%.

[0064] Figure 3 (c) in FIG. 1 is the test of the electrolyte used in a LiNi 0.8 Co 0.1 Mn 0.1 O2||graphite battery, wherein the surface capacity of the LiNi 0.8 Co 0.1 Mn 0.1 O2 electrode is 1.7 mAh·cm -2 , the test voltage range is 2.8 V~4.55 V, the test rate is 0.1 C charge-discharge three times, and 0.5 C long cycle. It can be seen that the capacity retention rate of the above electrolyte is 94.5% after 200 cycles, and the average coulombic efficiency is close to 100%. It shows that the additive can effectively avoid the decomposition of the electrolyte.

[0065] Example 4

[0066] This example is an electrolyte, which is prepared as follows:

[0067] Dimethoxyethane is mixed with appropriate amount of LiTFSI, and stirred at room temperature until the lithium salt is completely dissolved. Then 3 wt% of 4-bromo-2-fluorobiphenyl is added, and continue to stir until the electrolyte is clear. The prepared electrolyte has a lithium salt concentration of 1.5 mol / L.

[0068] The electrolyte of the above formulation is used for battery to test the electrical performance, and the results are shown in Figure 4 .

[0069] Figure 4 (a) in FIG. 1 is a charge-discharge curve of the electrolyte in a graphite||Li battery, and the test rate is 0.1 C charge-discharge for 3 cycles, and 0.5 C charge-discharge for long cycle. It can be seen that the above electrolyte can realize efficient and reversible charge-discharge cycle.

[0070] Figure 4 (b) in FIG. 1 is a cycle life curve of the electrolyte used in a graphite||Li battery, wherein the surface capacity of the graphite electrode sheet is 2.2 mAh·cm -2 , the test voltage range is 0.001 V~1.5 V, and the test procedure is 0.1 C charge-discharge for three cycles and 0.5 C long cycle. It can be seen that the above electrolyte has an average coulombic efficiency close to 100% after 150 cycles at a rate of 0.5 C.

[0071] Figure 4 (c) in FIG. 1 is a test of the electrolyte used in a LiNi 0.8 Co 0.1 Mn 0.1 O2||graphite battery, wherein the surface capacity of the LiNi 0.8 Co 0.1 Mn 0.1 O2 electrode sheet is 1.9 mAh·cm -2 , the test voltage range is 2.8 V~4.55 V, and the test rate is 0.1 C charge-discharge for 3 cycles and 0.5 C charge-discharge for long cycle. It can be seen that the above electrolyte still has a capacity retention rate of 93.6% and an average coulombic efficiency close to 100% after 200 cycles, which shows that the additive can effectively prevent the decomposition of the electrolyte.

[0072] Example 5

[0073] This example is an electrolyte, which is prepared as follows:

[0074] Propylene carbonate was mixed with appropriate amount of LiBOB and stirred at room temperature until the lithium salt was completely dissolved. Then 4 wt% of 4-(trifluoromethyl)-diphenyl was added and the electrolyte was stirred until it was clear. The concentration of lithium salt in the prepared electrolyte was 1 mol / L.

[0075] The electrolyte of the above formulation was used in battery for electrical performance test, and the results are shown in Figure 5 .

[0076] Figure 5 (a) in FIG. 1 is a charge-discharge curve of the electrolyte in a graphite||Li battery, and the test rate was 0.1 C charge-discharge for 3 cycles and 0.2 C long cycle. It can be seen that the above electrolyte can realize efficient and reversible charge-discharge cycle.

[0077] Figure 5 (b) in FIG. 1 is a cycle life curve of the electrolyte used in a graphite||Li battery, wherein the surface capacity of the graphite electrode sheet is 2.4 mAh·cm -2 , the test voltage range is 0.001 V~1.0 V, and the test procedure is 0.1 C charge-discharge for 3 cycles and 0.2 C long cycle. It can be seen that the average coulombic efficiency of the above electrolyte is close to 100% after 150 cycles at a rate of 0.2 C.

[0078] Example 6

[0079] The electrolyte of the present example was prepared according to the following method:

[0080] N,N-dimethylformamide was mixed with appropriate amount of LiPF6 and stirred at room temperature until the lithium salt was completely dissolved. Then 5 wt% of bis(pentafluorophenyl) carbonate was added and the electrolyte was stirred until it was clear. The concentration of lithium salt in the prepared electrolyte was 1.3 mol / L.

[0081] The electrolyte of the above formulation was used in battery for electrical performance test, and the results are shown in Figure 6 .

[0082] Figure 6 (a) in FIG. 1 is a charge-discharge curve of the electrolyte in a graphite||Li battery, and the test rate was 0.1 C charge-discharge for 3 cycles and 0.5 C long cycle. It can be seen that the above electrolyte can realize efficient and reversible charge-discharge cycle.

[0083] Figure 6 (b) in FIG. 1 is a cycle life curve of the electrolyte used in a graphite||Li battery, wherein the surface capacity of the graphite electrode sheet is 1.80 mAh·cm -2The test voltage range was 0.001 V to 1.0 V, and the test procedure was three cycles of charge and discharge at 0.1 C, followed by a long cycle at 0.5 C. It can be seen that after 150 cycles at 0.5 C, the average coulombic efficiency of the electrolyte is 99.94%, close to 100%.

[0084] Figure 6 In the diagram (c), the electrolyte used in the LiFePO4||graphite battery test is shown, where the areal capacity of the LiFePO4 electrode is 2.1 mAh·cm⁻¹. -2 The test voltage range was 2.8 V to 3.8 V, and the test rate was 3 cycles at 0.1 C and a long cycle at 0.5 C. It can be seen that the voltage plateau of LiFePO4 and graphite remained stable, demonstrating good electrochemical kinetic performance.

[0085] Example 7

[0086] This embodiment describes an electrolyte, the preparation method of which is as follows:

[0087] Propylene carbonate was mixed with an appropriate amount of LiPF6 and stirred at room temperature until the lithium salt was completely dissolved. Then, 0.7 wt% of 2,3,4,5-tetrachlorothiophene was added, and stirring continued until the electrolyte became clear. The resulting electrolyte had a lithium salt concentration of 1.0 mol / L.

[0088] The electrolyte with the above formula was used in the battery for electrical performance testing, and the results are as follows: Figure 7 As shown.

[0089] Figure 7 Figure (a) shows the charge-discharge curves of the electrolyte in a graphite-Li battery. The test rate was 0.1 C for 3 charge-discharge cycles and 0.2 C for long charge-discharge cycles. It can be seen that the above electrolyte can achieve efficient and reversible charge-discharge cycles.

[0090] Figure 7 (b) shows the cycle life curve of the electrolyte used in a graphite-Li battery, where the areal capacity of the graphite electrode is 1.80 mAh·cm⁻¹. -2 The test voltage range was 0.001 V to 1.0 V, and the test procedure was three cycles of charge and discharge at 0.1 C, followed by a long cycle at 0.2 C. It can be seen that after 150 cycles at 0.2 C, the average coulombic efficiency of the electrolyte is close to 100%.

[0091] Figure 7 (c) in the text refers to the electrolyte used in LiNi. 0.8 Co 0.1 Mn 0.1 O2 || Graphite battery testing, including LiNi 0.8 Co 0.1 Mn0.1 The surface capacity of the O2 electrode tab is 1.8 mAh cm -2 The test voltage range is 2.8 V~4.55 V, the test rate is 0.1 C charge and discharge for 3 cycles, and 0.5 C charge and discharge for long cycle. It can be seen that the above electrolyte can still have a capacity retention rate of 90.38% after 200 cycles, and the average coulombic efficiency is close to 100%. It shows that the additive can effectively prevent the decomposition of the electrolyte.

[0092] Example 8

[0093] The electrolyte of the present example is prepared as follows:

[0094] N,N-dimethylformamide is mixed with appropriate amount of LiPF6, and stirred at room temperature until the lithium salt is completely dissolved. Then 0.8 wt% of 2,4-dichlorothiazole is added, and continue to stir until the electrolyte is clear. The prepared electrolyte has a lithium salt concentration of 1.0 mol / L.

[0095] The electrolyte of the above formula is used for battery performance test, and the results are shown in Figure 8 .

[0096] Figure 8 (a) in the above table is the charge and discharge curve of the electrolyte in a graphite||Li battery, the test rate is 0.1 C charge and discharge for 3 cycles, and 0.2 C long cycle. It can be seen that the above electrolyte can realize efficient and reversible charge and discharge cycle.

[0097] Figure 8 (b) in the above table is the cycle life curve of the electrolyte used in a graphite||Li battery, wherein the surface capacity of the graphite electrode tab is 1.80 mAh cm -2 , the test voltage range is 0.001 V~1.0 V, the test procedure is 0.1 C charge and discharge for three cycles, and 0.2 C long cycle. It can be seen that the average coulombic efficiency of the above electrolyte is close to 100% after 150 cycles at a rate of 0.2 C.

[0098] Figure 8 (c) in the above table is the test of the electrolyte used in a LiFePO4||graphite battery, wherein the surface capacity of the LiFePO4 electrode tab is 2.3 mAh cm -2 , the test voltage range is 2.8 V~3.8 V, the test rate is 0.1 C charge and discharge for 3 cycles, and 0.5 C charge and discharge for long cycle. It can be seen that the voltage platform of LiFePO4 and graphite remains stable, showing good electrochemical kinetics.

[0099] Comparative Example 1

[0100] The preparation method of the electrolyte of the present comparative example is as follows:

[0101] An appropriate amount of LiPF6 was added to propylene carbonate, and the mixture was stirred until the lithium salt was completely dissolved and a clear electrolyte was obtained. The concentration of LiPF6 in the prepared electrolyte was 1.0 mol / L.

[0102] The electrolyte of the above formula was used for battery to test the electrical performance, and the results are shown in Figure 9 .

[0103] Figure 9 (a) in FIG. 1 is the charge-discharge image of the electrolyte in the graphite||Li asymmetric battery. It can be seen that the graphite negative electrode cannot realize reversible charge-discharge in the propylene carbonate-based electrolyte, which indicates that propylene carbonate as a single solvent for the electrolyte is not compatible with the graphite negative electrode material.

[0104] Figure 9 (b) in FIG. 1 is the electrolyte used for LiNi 0.8 Co 0.1 Mn 0.1 O2||graphite battery test, wherein the surface capacity of the LiNi 0.8 Co 0.1 Mn 0.1 O2 electrode sheet is 2.0 mAh·cm -2 , the test voltage range is 2.8 V~4.5 V, the test rate is 0.1 C charge-discharge for 3 cycles, and 0.5 C charge-discharge for long cycle. It can be seen that the curve shows abnormal capacity performance and no obvious charge-discharge voltage platform, indicating that the electrolyte with propylene carbonate as a single solvent cannot support the reversible charge-discharge of lithium ion battery.

[0105] Figure 9 (c) in FIG. 1 is the electrolyte used for LiFePO4||graphite battery test, wherein the surface capacity of the LiFePO4 electrode sheet is 1.7 mAh·cm -2 , the test voltage range is 2.8 V~3.8 V, the test rate is 0.1 C charge-discharge for 3 cycles, and 0.5 C charge-discharge for long cycle. It can be seen that the electrolyte cannot support the reversible charge-discharge of LiFePO4||graphite battery.

[0106] Comparative Example 2

[0107] The electrolyte preparation method of the present comparative example is as follows:

[0108] An appropriate amount of LiFSI was added to dimethoxyethane, and the mixture was stirred until the lithium salt was completely dissolved and a clear electrolyte was obtained. The concentration of LiFSI in the prepared electrolyte was 1.0 mol / L.

[0109] The electrolyte of the above formula was used for battery to test the electrical performance, and the results are shown in Figure 10 .

[0110] Figure 10 (a) is the charge-discharge image of the electrolyte in a graphite || Li asymmetric battery. It can be seen that the graphite negative electrode cannot realize reversible charge-discharge in the dimethoxyethane-based electrolyte, which indicates that dimethoxyethane as a single solvent of the electrolyte is incompatible with the graphite negative electrode material.

[0111] Figure 10 (b) is the electrolyte for LiNi 0.8 Co 0.1 Mn 0.1 O2|| graphite battery test, wherein the surface capacity of the LiNi 0.8 Co 0.1 Mn 0.1 O2 pole piece is 2.2 mAh·cm -2 -2. The test voltage range is 2.8 V~4.5 V, the test rate is 0.1 C charge-discharge for 3 cycles, and the long cycle is 0.5 C charge-discharge. It can be seen that the curve shows abnormal capacity performance and no obvious charge-discharge voltage platform, indicating that the electrolyte with dimethoxyethane as a single solvent cannot support the reversible charge-discharge of the lithium ion battery.

[0112] Comparative Example 3

[0113] The electrolyte preparation method of the present comparative example is as follows:

[0114] An appropriate amount of LiTFSI was added to N,N-dimethylformamide, and the mixture was stirred until the lithium salt was completely dissolved and a clear electrolyte was obtained. In the prepared electrolyte, the concentration of LiTFSI was 1.0 mol / L.

[0115] The electrolyte of the above formula was used for battery to test the electrical performance, and the results are shown in Figure 11 .

[0116] Figure 11 (a) is the charge-discharge image of the electrolyte in a graphite || Li asymmetric battery. It can be seen that the graphite negative electrode cannot realize reversible charge-discharge in the dimethoxyethane-based electrolyte, which indicates that dimethoxyethane as a single solvent of the electrolyte is incompatible with the graphite negative electrode material.

[0117] Figure 11 (b) is the electrolyte for LiNi 0.8 Co 0.1 Mn 0.1 O2|| graphite battery test, wherein the surface capacity of the LiNi 0.8 Co 0.1 Mn 0.1 O2 pole piece is 2.1 mAh·cm -2, the test voltage range is 2.8 V~4.5 V, the test rate is 0.1 C charge and discharge for 3 cycles, and 0.5 C charge and discharge for long cycle. It can be seen that the curve shows abnormal capacity performance, and there is no obvious charge and discharge voltage platform, which indicates that the electrolyte of N,N-dimethylformamide as a single solvent cannot support the reversible charge and discharge of lithium ion battery.

[0118] Comparative Example 4

[0119] This comparative example is a commercial ester-based electrolyte, and the electrolyte preparation method is as follows:

[0120] A certain amount of LiPF6 is slowly dissolved in ethylene carbonate and dimethyl carbonate in a volume ratio of 1:1, so that the concentration of lithium salt LiPF6 is 1 mol / L, that is, a conventional commercial ester-based electrolyte is prepared.

[0121] The electrolyte of the above formula is used for battery for electrical performance test, and the results are shown in Figure 12 .

[0122] Figure 12 (a) in FIG. 1 is a charge and discharge curve of a commercial ester-based electrolyte for a graphite||Li asymmetric battery, and the test procedure is: 0.1 C charge and discharge for three cycles, and 0.2 C long cycle. It can be seen that the reversibility of the electrolyte during charge and discharge is not as good as that of the electrolyte of the present application.

[0123] Figure 12 (b) in FIG. 1 is a cycle life curve of a commercial ester-based electrolyte for a graphite||Li asymmetric battery, wherein the surface capacity of the graphite electrode is 1.5 mAh·cm -2 , the test voltage range is 0.001 V~1.0 V, the test rate is 0.1 C charge and discharge for three cycles, and 0.2 C long cycle. It can be seen that the capacity retention rate of the electrolyte decreases significantly after 150 cycles.

[0124] Figure 12 (c) in FIG. 1 is a charge and discharge test curve of a commercial ester-based electrolyte for a LiFePO4||graphite battery, wherein the surface capacity of the LiFePO4 electrode is 2.1 mAh·cm -2 , the test voltage range is 2.8 V~3.8 V, the test rate is 0.1 C charge and discharge for three cycles, and 0.5 C charge and discharge for long cycle. It can be seen that the reversibility of the electrolyte during charge and discharge is poor.

[0125] Figure 12 (d) in FIG. 1 is a cycle life curve of a commercial ester-based electrolyte in a LiNi 0.8 Co 0.1 Mn 0.1 O2||graphite battery, wherein the surface capacity of the LiNi 0.8 Co0.1 Mn 0.1 The surface capacity of the O2 electrode plate is 1.4 mAh·cm -2 The test voltage range is 2.8 V~4.55V, the test rate is 0.1 C charging and discharging for 3 cycles, and 0.5 C charging and discharging for long cycle. It can be seen that the capacity retention rate of the above-mentioned electrolyte is only 74.72% after 200 cycles, and the cycle stability is not as good as that of the electrolyte of the present application.

[0126] The above-mentioned examples use halogenated diphenyl compounds, bis (halogenated phenyl) compounds, and halogenated sulfur-containing heterocyclic compounds as additives. The additive generates a stable SEI film on the surface of graphite when applied to the charging and discharging process of the battery as an electrolyte component, which can effectively block the further insertion of solvent molecules, while allowing lithium ions to pass smoothly, maintaining ionic conductivity. The first type of additive (such as Examples 1-6 above) can improve the mechanical strength of the SEI film due to its rigid structure, preventing it from breaking or dissolving during the cycle process, further improving the cycle stability and coulombic efficiency of the battery. The second type of additive (such as Examples 7 and 8 above) can form a SEI film containing sulfur and nitrogen on the surface of the negative electrode. The generated SEI film is dense and has high thermal stability, and reduces the interfacial impedance, improving the cycle performance of the battery. Compared with the commercial ester-based electrolyte, the above-mentioned electrolyte significantly improves the cycle stability and coulombic efficiency of the battery.

[0127] The above-mentioned examples only express several feasible implementation manners of the present application, which are described in detail and specifically, but should not be understood as limiting the scope of the present application. The examples are not intended to limit the protection scope in the claims of the present application. For ordinary skilled persons in the art, several modifications and improvements can be made without departing from the concept of the present application, and any equivalent implementation or change made without departing from the present application should be included in the present application.

Claims

1. A battery, characterized by: The positive electrode active material, the negative electrode active material and the electrolyte, The positive electrode active material is a ternary positive electrode material, a lithium cobaltate positive electrode material, a lithium manganate positive electrode material or a lithium iron phosphate positive electrode material, The negative electrode active material is artificial graphite, natural graphite or composite graphite, The electrolyte comprises a lithium salt, a solvent and an additive, and the mass percentage of the additive in the electrolyte is 0.7-5%, The lithium salt is any one of lithium bisfluorosulfonylimide, lithium bistrifluoromethylsulfonylimide, lithium oxalate borate, lithium difluoro oxalate borate, lithium hexafluorophosphate, lithium tetrafluoroborate and an organic anion lithium salt; The solvent is propylene carbonate, dimethoxyethane, N,N-dimethylformamide or 1,3-dioxolane; The additive comprises a first type of additive and a second type of additive: The first type of additive is a halogenated biphenyl compound or a bis(halogenated phenyl) compound, and is at least one of bis(pentafluorophenyl)methane, bis(pentafluorophenyl) carbonate, pentafluorophenyl pentafluorophenyl sulfonate, dipentafluorophenyl sulfate, dipentafluorophenyl sulfite; The second type of additive is a halogenated sulfur-containing heterocyclic compound, at least one of 3-fluorothiophene, 2,3-difluorothiophene, 2,4-difluorothiophene, 2,5-difluorothiophene, 2,3,4-trifluorothiophene, 2,3,5-trifluorothiophene, 2,4,5-trifluorothiophene, 2,3,4,5-tetrafluorothiophene, 2-chlorothiophene, 3-chlorothiophene, 2,3-dichlorothiophene, 2,4-dichlorothiophene, 3,4-dichlorothiophene, 2,3,4-trichlorothiophene, 2,3,5-trichlorothiophene, 2,4,5-trichlorothiophene, 2,3,4,5-tetrachlorothiophene, 3-bromothiophene, 2,3-dibromothiophene, 2,4-dibromothiophene, 2,5-dibromothiophene, 2,3,4-tribromothiophene, 2,3,5-tribromothiophene, 2,4,5-tribromothiophene, 2,3,4,5-tetrabromothiophene, 2-chloro-4-fluoro-thiophene, 2-chloro-4-fluoro-thiophene, 4-chloro-2-fluoro-thiophene, 2-chloro-3-fluoro-thiophene, 2-chloro-5-fluoro-thiophene, 3-bromo-2-fluoro-thiophene, 2-bromo-3-fluoro-thiophene, 2-bromo-4-fluoro-thiophene, 4-bromo-2-fluoro-thiophene, 5-bromo-2-fluoro-thiophene, 3-bromo-4-fluoro-thiophene, 3-bromo-2-chlorothiophene, 2-bromo-3-chloro-thiophene, 2-bromo-4-chloro-thiophene, 4-bromo-2-chloro-thiophene, 2-bromo-5-chloro-thiophene, 3-bromo-4-chloro-thiophene, 3-bromo-2,5-dichlorothiophene, 4-bromo-3-chloro-2-fluoro-thiophene, 3,4-dibromo-2-chloro-thiophene, 3,5-dibromo-2-chloro-thiophene, 4-bromo-2,3-dichlorothiophene, 3,4-dibromo-2,5-dichlorothiophene, 4,5-dichloro-2-fluoro-1,3-thiazole, 2,4-dichlorothiazole, 2,4,5-trichlorothiazole, 2,4,5-tribromothiazole, 5-(difluoromethyl)-2,4-difluoro-thiophene, 2,5-difluoro-1,3,4-thiadiazole, 2,5-dichloro-1,3,4-thiadiazole, 2,5-dibromo-1,3,4-thiadiazole, 2-chloro-5-fluoro-1,3,4-thiadiazole, 2-bromo-5-fluoro-1,3,4-thiadiazole, 2-bromo-5-chloro-1,3,4-thiadiazole, 2,5-bis(trifluoromethyl)-1,3,4-thiadiazole, 2,5-bis(1,1,2,2,2-pentafluoroethyl)-1,3,4-thiadiazole, 2,5-bis(1,1,2,2,2-pentafluoroethyl)-1,3,4-thiadiazole.

2. An electrical device comprising the battery of claim 1.

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