Electrolyte, electrochemical device, and electronic device

Abstract

The application provides an electrolyte, an electrochemical device and an electronic device. The electrolyte comprises a first component, a second component, a first lithium salt and a second lithium salt. The first component comprises at least one of compounds represented by formula (I) and formula (II), R1 and R2 are each independently selected from C1 to C 10 alkyl, C1 to C 10 haloalkyl, C1 to C 10 alkoxy or C1 to C 10 haloalkoxy, R3 is selected from C1 to C 10 alkylene, C1 to C 10 haloalkylene, C1 to C 10 alkylene, C1 to C 10 haloalkylene; the second component comprises a cyclic carbonate; the first lithium salt comprises at least one of lithium bisfluorosulfonimide or lithium bis-trifluoromethylsulfonimide; the second lithium salt comprises at least one of lithium difluoro(oxalato)borate or lithium tetrafluoroborate; wherein the mass percentage of the first component is a, the mass percentage of the second component is b, the mass percentage of the first lithium salt is x, and the mass percentage of the second lithium salt is y, based on the mass of the electrolyte, 0.005≤b / x≤0.2, and 0.003≤y / a≤0.08.

Description

Technical Field

[0001] The present application relates to the field of electrochemical energy storage, and in particular to an electrolyte, an electrochemical device using the electrolyte, and an electronic device using the electrochemical device. Background Art

[0002] Lithium metal batteries have higher energy density than lithium-ion batteries. However, lithium metal negative electrodes are also more reactive than the negative electrodes of lithium-ion batteries. During static storage, there are more significant galvanic corrosion and chemical corrosion processes, which affects the calendar life of the battery. Summary of the Invention

[0003] The present application provides an electrolyte, an electrochemical device, and an electronic device that can increase the calendar life of a lithium metal battery.

[0004] In a first aspect, the present application provides an electrolyte solution comprising a first component, a second component, a first lithium salt, and a second lithium salt, wherein the first component comprises at least one of the compounds represented by formula (I) and formula (II).

[0005] (I), (II), R1 and R2 are each independently selected from C1 to C 10 Alkyl, C1 to C 10 Halogenated alkyl, C1 to C 10 Alkoxy or C1 to C 10 Haloalkoxy, R3 is selected from C1 to C 10 Alkylene, C1 to C 10 Halogenated alkylene, C1 to C 10 Alkyleneoxy or C1 to C 10 A halogenated alkylene oxide; the second component includes a cyclic carbonate; the first lithium salt includes at least one of lithium bis(fluorosulfonyl)imide or lithium bis(trifluoromethylsulfonyl)imide; the second lithium salt includes at least one of lithium difluorooxalatoborate or lithium tetrafluoroborate; wherein, based on the mass of the electrolyte, the mass proportion of the first component is a, the mass proportion of the second component is b, the mass proportion of the first lithium salt is x, the mass proportion of the second lithium salt is y, 0.005≤b / x≤0.2, 0.003≤y / a≤0.08.

[0006] The electrolyte provided herein, when used in a lithium metal battery, comprises a first component and a first lithium salt, each serving as the primary solvent and primary salt, respectively, while a second component and the second lithium salt serve as additives. In this electrolyte, on the one hand, the boron atoms in the second lithium salt can coordinate with the oxygen atoms in the first component. This coordination structure dissolves and recrystallizes LiF in the SEI film, thereby improving the distribution of LiF in the SEI film. On the other hand, hydrolysis of the second lithium salt in the electrolyte can catalyze the ring-opening polymerization of the second component, increasing the organic content of a portion of the SEI film, helping to reduce corrosion of the lithium metal during storage, thereby extending the calendar life of the lithium metal battery.

[0007] Based on the first aspect, in some embodiments, 15%≤a≤60% is beneficial for obtaining an electrolyte with lower viscosity, higher ionic conductivity and greater stability at the positive and negative electrode interfaces, thereby improving the calendar life of the lithium metal battery.

[0008] Based on the first aspect, in some embodiments, 0.2%≤b≤5% is conducive to further forming a low-impedance and stable SEI film, thereby improving the calendar life of the lithium metal battery.

[0009] Based on the first aspect, in some embodiments, 15%≤x≤65% is conducive to further forming a low-impedance and stable SEI film, thereby improving the calendar life of the lithium metal battery.

[0010] Based on the first aspect, in some embodiments, 0.1%≤y≤2%, which is conducive to further forming a low-resistance and stable SEI film, thereby improving the calendar life of the lithium metal battery.

[0011] Based on the first aspect, in some embodiments, 0.02≤b / x≤0.1 and 0.01≤y / a≤0.05 are beneficial for further forming a low-resistance and stable SEI film, thereby improving the calendar life of the lithium metal battery.

[0012] Based on the first aspect, in some embodiments, 0.005≤b / a≤0.2. This allows the electrolyte to have good viscosity, ionic conductivity, and stability at the positive and negative electrode interfaces, thereby facilitating uniform deposition of lithium metal and further forming a low-impedance and stable SEI film, thereby extending the calendar life of the lithium metal battery.

[0013] Based on the first aspect, in some embodiments, 0.003≤y / x≤0.1 is conducive to forming a small-particle-sized LiF SEI film, reducing the impedance of the SEI film, and further facilitating the formation of a low-impedance and highly stable SEI film, thereby improving the calendar life of the lithium metal battery.

[0014] Based on the first aspect, in some embodiments, the first component includes at least one of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dipropyl ether, ethylene glycol dibutyl ether, ethylene glycol methyl ethyl ether, 1,2-propylene glycol dimethyl ether, 1,3-propylene glycol dimethyl ether, dimethoxymethane, ethyl ether, propyl ether, isopropyl ether, ethyl propyl ether, butyl ether, tetrahydropyran, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxane, or 1,4-dioxane. The electrolyte containing the first component has low viscosity, high ionic conductivity, and good stability at the positive and negative electrode interfaces, thereby facilitating the improvement of the calendar life of the lithium metal battery.

[0015] Based on the first aspect, in some embodiments, the second component includes at least one of ethylene carbonate, fluoroethylene carbonate, bisfluoroethylene carbonate, vinylene carbonate, or vinyl ethylene carbonate. The second component is conducive to further forming a low-resistance and stable SEI film, thereby improving the calendar life of the lithium metal battery.

[0016] Based on the first aspect, in some embodiments, the electrolyte further includes a third component, and the third component includes at least one of formulas (III-1) to (III-14):

[0017] (III-1), (III-2), (III-3), (III-4), (III-5), (III-6), (III-7), (III-8), (III-9), (III-10), (III-11), (III-12), (III-13), (III-14). This is beneficial for further optimizing the viscosity and ionic conductivity of the electrolyte, improving the stability of the positive and negative electrode interfaces, and thus increasing the calendar life of lithium metal batteries.

[0018] Based on the first aspect, in some embodiments, the mass proportion of the third component, c, based on the mass of the electrolyte, satisfies 10% ≤ c ≤ 60%. This is beneficial for further optimizing the viscosity and ionic conductivity of the electrolyte, improving the stability of the electrolyte at the positive / negative electrode interface, and thereby extending the calendar life of the lithium metal battery.

[0019] Based on the first aspect, in some embodiments, 0.2≤c / a≤4. This is beneficial for the third component and the first component to cooperate with the second lithium salt to further form a low-resistance and stable SEI film, thereby improving the calendar life of the lithium metal battery.

[0020] A second aspect of the present application provides an electrochemical device, comprising a negative electrode plate, the electrochemical device also comprising an electrolyte, the negative electrode plate comprising a negative electrode current collector and a negative electrode active material disposed on the surface of the negative electrode current collector, the negative electrode active material being selected from at least one of lithium metal or a lithium alloy; the lithium alloy comprising at least one of lithium tin, lithium zinc, lithium aluminum, lithium magnesium, lithium silver, lithium gold, lithium gallium, lithium indium, lithium platinum, lithium boron, lithium carbon or lithium silicon alloy.

[0021] Based on the second aspect, in some embodiments, the electrochemical device has a liquid retention capacity of P g / Ah, 1.5 ≤ P ≤ 4, and 0.35 ≤ P × (x + y) ≤ 2.2. This facilitates the formation of a low-impedance and stable SEI film, thereby extending the calendar life of the lithium metal battery.

[0022] The third aspect of the present application provides an electronic device, including an electrochemical device. The electrochemical device includes the electrolyte, which can increase the calendar life of the electrochemical device, thereby facilitating an increase in the service life of the electronic device. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present application are described clearly and in detail below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present application. The terms used in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application.

[0024] An embodiment of the present application provides an electrochemical device, which includes a housing, an electrode assembly, and an electrolyte. The electrode assembly and the electrolyte are both located in the housing.

[0025] The outer shell may be a packaging bag encapsulated by a packaging film (such as an aluminum-plastic film), for example, the electrochemical device is a soft-pack battery.

[0026] The electrode assembly includes a positive electrode sheet, a negative electrode sheet, and a separator, with the separator being disposed between the positive and negative electrode sheets. The electrode assembly can be a laminated structure, formed by stacking the positive electrode sheet, separator, and negative electrode sheet. In other embodiments, the electrode assembly can also be a wound structure, formed by stacking the positive electrode sheet, separator, and negative electrode sheet and then winding them.

[0027] electrolyte

[0028] The present application provides an electrolyte, which includes a first component, a second component, a first lithium salt, and a second lithium salt. The first component includes at least one of the compounds represented by formula (I) and formula (II).

[0029] (I)

[0030] (II)

[0031] R1 and R2 are each independently selected from C1 to C 10 Alkyl, C1 to C 10 Halogenated alkyl, C1 to C 10 Alkoxy or C1 to C 10 Haloalkoxy, R3 is selected from C1 to C 10 Alkylene, C1 to C 10 Halogenated alkylene, C1 to C 10 Alkyleneoxy or C1 to C 10 A haloalkyleneoxy group; the second component includes a cyclic carbonate; the first lithium salt includes at least one of lithium bis(fluorosulfonyl)imide (LiFSI) or lithium bis(trifluoromethylsulfonyl)imide (LiTFSI); the second lithium salt includes at least one of lithium difluorooxalatoborate (LiDFOB) or lithium tetrafluoroborate (LiBF4);

[0032] Among them, based on the mass of the electrolyte, the mass proportion of the first component is a, the mass proportion of the second component is b, the mass proportion of the first lithium salt is x, and the mass proportion of the second lithium salt is y, 0.005≤b / x≤0.2, 0.003≤y / a≤0.08.

[0033] The electrolyte provided herein, when used in a lithium metal battery, comprises a first component and a first lithium salt, each serving as the primary solvent and primary salt, respectively, while a second component and a second lithium salt serve as additives. In this electrolyte, on the one hand, the boron atoms in the second lithium salt can coordinate with the oxygen atoms in the first component. This coordination structure has the ability to dissolve and recrystallize LiF in the SEI film, thereby improving the distribution of LiF in the SEI film and making it more uniform. On the other hand, hydrolysis of the second lithium salt in the electrolyte can catalyze the ring-opening polymerization of the second component, increasing the organic content of a portion of the SEI film, helping to reduce corrosion of the lithium metal during storage, thereby extending the calendar life of the lithium metal battery.

[0034] Controlling the values ​​of b / x and y / a within the above ranges facilitates the formation of a low-impedance and stable SEI film, reducing chemical and galvanic corrosion of lithium metal in lithium metal batteries, thereby improving the calendar life of lithium metal batteries. If b / x < 0.005, the organic content of the SEI film formed in the lithium metal battery is relatively low, which is not conducive to improving the chemical and galvanic corrosion of lithium metal, thereby hindering the calendar life of the lithium metal battery. If b / x > 0.2, the organic content of the SEI film formed in the lithium metal battery is relatively high, resulting in high impedance, which is not conducive to uniform deposition of lithium metal and thus detrimental to improving the calendar life of the lithium metal battery. If y / a < 0.003, the content of the second lithium salt is relatively low, and its participation in improving film formation is low, which is not conducive to improving the calendar life of the lithium metal battery. If y / a > 0.08, the electrolyte viscosity begins to increase and the ionic conductivity decreases, which is not conducive to uniform deposition of lithium metal, thereby detrimental to improving the calendar life of the lithium metal battery. In some embodiments, the ratio of b / x can be 0.005, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.18, 0.19, 0.2, or any value within a range formed by any two of the foregoing values. The ratio of y / a can be 0.003, 0.005, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, or any value within a range formed by any two of the foregoing values.

[0035] In some embodiments, 0.02≤b / x≤0.1 and 0.01≤y / a≤0.05 are beneficial to increasing the organic component of a portion of the SEI film, further forming a low-resistance and stable SEI film, thereby increasing the calendar life of the lithium metal battery.

[0036] In some embodiments, in the electrolyte, 15%≤a≤60%. The mass proportion of the first component is within the above range, which is conducive to obtaining an electrolyte with lower viscosity, higher ionic conductivity and more stability at the positive and negative electrode interfaces, thereby helping to improve the calendar life of the lithium metal battery. If a<15%, the electrolyte viscosity is high and the ionic conductivity is poor, which has no obvious effect on improving the uniform deposition of lithium metal and has no obvious effect on improving the calendar life of the lithium metal battery. If a>60%, the electrolyte has poor stability at the positive and negative electrode interfaces and has no obvious effect on improving the calendar life of the lithium metal battery. In some embodiments, a can be 15%, 18%, 20%, 22%, 25%, 28%, 30%, 33%, 35%, 40%, 45%, 50%, 55%, 58%, 60% or any value within the range formed by any two of the above values.

[0037] In some embodiments, in the electrolyte, 0.2%≤b≤5%. The mass proportion of the second component is within the above range, which is conducive to further forming a low-impedance and stable SEI film, thereby improving the calendar life of the lithium metal battery. If b<0.2%, the second component does not significantly improve the degree of film formation, and the effect on improving the calendar life of the lithium metal battery is not obvious. If b>5%, it has no obvious effect on improving the formation of a low-impedance SEI film and the uniform deposition of lithium metal, and the effect on improving the calendar life of the lithium metal battery is not obvious. In some embodiments, b can be 0.2%, 0.5%, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5% or any value within the range formed by any two of the above values.

[0038] In some embodiments, 15%≤x≤65%. The mass proportion of the first lithium salt is within the above range, which is conducive to further forming a low-impedance and stable SEI film, thereby improving the calendar life of the lithium metal battery. If x<15%, the inorganic component in the formed SEI film is relatively low and the impedance is relatively large, which has an insignificant effect on improving the stability of the electrolyte at the positive and negative electrode interfaces, and has an insignificant effect on improving the calendar life of the lithium metal battery. If b>65%, the viscosity of the electrolyte is relatively high and the ionic conductivity is relatively low, which has an insignificant effect on improving the uniform deposition of lithium metal, and thus has an insignificant effect on improving the calendar life of the lithium metal battery. In some embodiments, x can be 15%, 18%, 20%, 22%, 25%, 28%, 30%, 33%, 35%, 40%, 45%, 50%, 55%, 58%, 60%, 65%, or any value within the range formed by any two of the above values.

[0039] In some embodiments, 0.1%≤y≤2%, and the mass proportion of the second lithium salt is within the above range, which is conducive to further forming a low-impedance and stable SEI film, thereby improving the calendar life of the lithium metal battery. If y<0.1%, it has no significant effect on improving the degree of SEI film formation, and the effect on improving the calendar life of the lithium metal battery is not obvious; if y>2%, it may reduce the electrolyte ion conductivity, and has no significant effect on improving the SEI film and the uniform deposition of lithium metal, and has no significant effect on improving the calendar life of the lithium metal battery. In some embodiments, y can be 0.1%, 0.2%, 0.5%, 0.8%, 1%, 1.5%, 2%, or any value within the range formed by any two of the above values.

[0040] In some embodiments, 0.005 ≤ b / a ≤ 0.2, and the mass ratio of the second component to the first component is within the above range, so that the electrolyte has good viscosity, ionic conductivity, and stability at the positive and negative electrode interfaces, which is conducive to the uniform deposition of lithium metal and the further formation of a low-impedance and stable SEI film, thereby improving the calendar life of the lithium metal battery. If b / a < 0.005, the second component participates in the formation of the SEI film to a small extent, has no significant effect on the formation of a stable SEI film, and has little effect on improving the calendar life of the lithium metal battery. If b / a > 0.2, the effect on improving the calendar life of the lithium metal battery is not significant. In some embodiments, the ratio of b / a can be 0.005, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.18, 0.19, 0.2, or any value within the range formed by any two of the above values.

[0041] In some embodiments, 0.003≤y / x≤0.1. The mass ratio of the second lithium salt to the first lithium salt is within the above range, which is conducive to the formation of a SEI film of small-particle LiF, reduces the impedance of the SEI film, and is conducive to the further formation of a low-impedance and stable SEI film, thereby improving the calendar life of the lithium metal battery. If y / x<0.003, it has no obvious effect on the formation of a SEI film rich in small-particle LiF, has no obvious effect on the formation of a low-impedance and stable SEI film, and has no obvious effect on improving the calendar life of the lithium metal battery. If y / x>0.1, it has no obvious effect on the formation of a low-impedance and stable SEI film, and has no obvious effect on improving the calendar life of the lithium metal battery. In some embodiments, the ratio of y / x can be 0.003, 0.005, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, or any value within the range formed by any two of the above values.

[0042] In some embodiments, the first component includes at least one of ethylene glycol dimethyl ether (DME), ethylene glycol diethyl ether (DEE), ethylene glycol dipropyl ether (DPE), ethylene glycol dibutyl ether (DBE), ethylene glycol methyl ethyl ether (MEE), 1,2-propylene glycol dimethyl ether (1,2-DMP), 1,3-propylene glycol dimethyl ether (1,3-DMP), dimethoxymethane (DMM), diethyl ether (EE), propyl ether (PE), isopropyl ether (IPE), ethylpropyl ether (EPE), butyl ether (BE), tetrahydropyran (THP), tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-MeTHF), 1,3-dioxane (1,3-DX), or 1,4-dioxane (1,4-DX). The electrolyte containing the first component has low viscosity, high ionic conductivity, and good stability at the positive and negative electrode interfaces, thereby improving the calendar life of the lithium metal battery.

[0043] In some embodiments, the second component includes at least one of ethylene carbonate (EC), fluoroethylene carbonate (FEC), bisfluoroethylene carbonate (DFEC), vinylene carbonate (VC), or vinylethylene carbonate (VEC). These second components facilitate the formation of a low-resistance and stable SEI film, thereby extending the calendar life of the lithium metal battery.

[0044] In some embodiments, the electrolyte further includes a third component, and the third component includes at least one of formulas (III-1) to (III-14):

[0045] (III-1), (III-2), (III-3), (III-4), (III-5), (III-6), (III-7), (III-8), (III-9), (III-10), (III-11), (III-12), (III-13), (III-14) The inclusion of a third component in the electrolyte is beneficial for further optimizing the viscosity and ionic conductivity of the electrolyte, improving the stability of the positive and negative electrode interfaces, and thus extending the calendar life of the lithium metal battery.

[0046] In some embodiments, based on the mass of the electrolyte, the mass proportion of the third component is c, satisfying 10%≤c≤60%. The mass proportion of the third component within the above range is conducive to further optimizing the viscosity and ionic conductivity of the electrolyte, facilitating the uniform deposition of lithium metal, and further improving the stability of the electrolyte at the positive / negative electrode interface, thereby improving the calendar life of the lithium metal battery. In some embodiments, c can be 10%, 13%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, 33%, 35%, 40%, 45%, 50%, 55%, 58%, 60%, or any value within the range formed by any two of the above values.

[0047] In some embodiments, 0.2 ≤ c / a ≤ 4. The mass ratio of the third component to the first component within the above range improves the ionic conductivity of the electrolyte, facilitates the uniform transport and deposition of lithium ions, and also facilitates the third component and the first component to cooperate with the second lithium salt to regulate the composition of the SEI film, further forming a low-impedance and stable SEI film, thereby improving the calendar life of the lithium metal battery. In some embodiments, the c / a ratio can be 0.2, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 3.8, 4, or any value within the range formed by any two of the above values.

[0048] In some embodiments, the electrochemical device has a liquid retention capacity of P g / Ah, 1.5 ≤ P ≤ 4, and 0.35 ≤ P × (x + y) ≤ 2.2. Controlling the liquid retention capacity and its relationship with the first and second lithium salts within the above ranges can control the rate of change of lithium salt concentration during SEI film formation, thereby reducing the consumption of the first and second components and increasing the participation of the second component in film formation, which is conducive to further forming a low-impedance and stable SEI film, thereby improving the calendar life of the lithium metal battery. In some embodiments, P can be 1.5, 1.8, 2, 2.5, 3, 3.5, 3.8, 4, or any value within the range of any two of the above values. In some embodiments, [P × (x + y)] can be 0.35, 0.5, 0.7, 1, 1.2, 1.5, 1.8, 2, 2.2, or any value within the range of any two of the above values.

[0049] Positive electrode

[0050] There are no special restrictions on the positive electrode sheets in this application, as long as the purpose of this application can be achieved. The positive electrode sheets generally include a positive electrode current collector and a positive electrode active material. The above-mentioned positive electrode current collector is not particularly limited and can be any positive electrode current collector known in the art, such as copper foil, aluminum foil, aluminum alloy foil, and composite current collector. The above-mentioned positive electrode active material is not particularly limited and can be any positive electrode active material in the prior art, for example, it can include at least one of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, or lithium iron manganese phosphate.

[0051] In this application, the thickness of the positive electrode current collector and the positive electrode active material is not particularly limited as long as the purpose of this application can be achieved. For example, the thickness of the positive electrode current collector is 8 μm to 12 μm, and the thickness of the positive electrode active material is 30 μm to 120 μm.

[0052] In the present application, the positive electrode material layer may further include a conductive agent, and the present application has no particular restrictions on the conductive agent, as long as the purpose of the present application can be achieved. For example, it may include but is not limited to at least one of conductive carbon black (SuperP), carbon nanotubes (CNTs), carbon fibers, flake graphite, Ketjen black, graphene, metal materials or conductive polymers. The above-mentioned carbon nanotubes may include but are not limited to single-walled carbon nanotubes and / or multi-walled carbon nanotubes. The above-mentioned carbon fibers may include but are not limited to vapor-grown carbon fibers (VGCF) and / or nano-carbon fibers. The above-mentioned metal materials may include but are not limited to metal powder and / or metal fibers, and specifically, the metal may include but is not limited to at least one of copper, nickel, aluminum or silver. The above-mentioned conductive polymers may include but are not limited to at least one of polyphenylene derivatives, polyaniline, polythiophene, polyacetylene or polypyrrole.

[0053] In the present application, the positive electrode active material layer may also include a binder. There is no particular limitation on the binder in the present application, as long as the purpose of the present application can be achieved. For example, it may include but is not limited to polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylic (ester) styrene-butadiene rubber, epoxy resin, nylon, etc.

[0054] Optionally, the positive electrode may further include a conductive layer, which is located between the positive electrode current collector and the positive electrode material layer. The present application does not particularly limit the composition of the conductive layer, and it may be a conductive layer commonly used in the art, for example, including but not limited to the above-mentioned conductive agent and the above-mentioned binder.

[0055] Negative electrode

[0056] In some embodiments, the negative electrode plate includes a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector, the negative electrode material layer includes at least one of lithium metal or lithium alloy; the lithium alloy includes at least one of lithium tin, lithium zinc, lithium aluminum, lithium magnesium, lithium silver, lithium gold, lithium gallium, lithium indium, lithium platinum, lithium boron, lithium carbon or lithium silicon alloy.

[0057] The negative electrode current collector is used to support the negative electrode material layer and conduct current, and can be in the shape of a foil or a mesh. The material of the negative electrode current collector includes at least one of copper foil, titanium foil, stainless steel, carbon paper or graphene paper.

[0058] In the present application, the negative electrode material layer may further include a conductive agent. The present application has no particular limitation on the conductive agent, as long as it can achieve the purpose of the present application. For example, it may include but is not limited to at least one of the above-mentioned conductive agents.

[0059] In the present application, the negative electrode material layer may further include a binder. The present application has no particular limitation on the binder, as long as it can achieve the purpose of the present application. For example, it may include but is not limited to at least one of the above-mentioned binders.

[0060] Optionally, the negative electrode may further include a conductive layer, which is located between the negative electrode current collector and the negative electrode material layer. The present application has no particular limitation on the composition of the conductive layer, which may be a conductive layer commonly used in the art, and may include but is not limited to the above-mentioned conductive agent and the above-mentioned binder.

[0061] Isolation film

[0062] The material and shape of the separator used in the secondary battery of the present application are not particularly limited and can be any technology disclosed in the prior art. In some embodiments, the separator includes a polymer or inorganic substance formed of a material that is stable to the electrolyte of the present application.

[0063] For example, the separator may include a substrate layer and a surface treatment layer. The substrate layer is a non-woven fabric, film, or composite film having a porous structure, and the material of the substrate layer is selected from at least one of polyethylene, polypropylene, polyethylene terephthalate, and polyimide. Specifically, polypropylene porous film, polyethylene porous film, polypropylene non-woven fabric, polyethylene non-woven fabric, or polypropylene-polyethylene-polypropylene porous composite film may be used.

[0064] A surface treatment layer is provided on at least one surface of the substrate layer. The surface treatment layer may be a polymer layer, an inorganic layer, or a layer formed by a mixture of a polymer and an inorganic material. The inorganic layer includes inorganic particles and a binder. The inorganic particles are selected from at least one of aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate.

[0065] The binder is selected from at least one of polyvinylidene fluoride, a copolymer of polyvinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinylalkoxide, polymethyl methacrylate, polytetrafluoroethylene, and polyhexafluoropropylene. The polymer contained in the polymer layer is selected from at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinylalkoxide, polyvinylidene fluoride, and poly(vinylidene fluoride-hexafluoropropylene).

[0066] According to some embodiments of the present application, the secondary battery of the present application includes, but is not limited to, a lithium ion battery or a sodium ion battery. In some embodiments, the secondary battery includes a lithium ion battery.

[0067] The present application also applies the electrochemical device to an electronic device to supply power to a load in the electronic device. The electrochemical device containing the electrolyte described above can improve the calendar life of the electrochemistry, thereby facilitating the improvement of the service life of the electronic device.

[0068] The electronic device or apparatus of the present application is not particularly limited. In some embodiments, the electronic device of the present application includes, but is not limited to, a notebook computer, a pen input type computer, a mobile computer, an electronic book player, a portable telephone, a portable facsimile machine, a portable copying machine, a portable printer, a head-mounted stereo headphone, a video recorder, a liquid crystal television, a portable cleaner, a portable CD player, a mini disc, a transceiver, an electronic organizer, a calculator, a memory card, a portable audio recorder, a radio, a backup power supply, an electric motor, an automobile, a motorcycle, a power-assisted bicycle, a bicycle, an illuminating appliance, a toy, a game machine, a clock, an electric tool, a flash, a camera, a household large storage battery, and a lithium ion capacitor, etc.

[0069] The present application is described below by specific examples and comparative examples. Those skilled in the art should understand that the preparation methods described in the present application are only examples, and any other suitable preparation method is within the scope of the present application.

[0070] Example 1

[0071] <Preparation of a soft-packaged battery>

[0072] (1) Preparation of a positive electrode sheet

[0073] The positive active material NCM811 (LiNi 0.8 Mn 0.1 Co 0.1O2), conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) are mixed in a weight ratio of 96:2:2, N-methylpyrrolidone (NMP) is added as a solvent, and a slurry with a solid content of 75% is prepared. The slurry is stirred under the action of a vacuum mixer until the system becomes a uniform positive electrode slurry. The positive electrode slurry is evenly coated on one surface of a positive electrode current collector aluminum foil with a thickness of 10 μm and dried at 90°C. After the above steps are completed, the single-sided coating of the positive electrode plate is completed. Thereafter, the above steps are repeated on the other surface of the positive electrode plate to obtain a positive electrode plate coated with positive electrode active material on both sides. After coating is completed, the positive electrode plate is cold pressed and cut into the required specifications for standby use. After testing, the single-sided thickness of the active material layer of the positive electrode plate is 60 μm, and the single-sided capacity is 4 mAh / cm 2 .

[0074] (2) Preparation of negative electrode sheet

[0075] The metal lithium foil is placed on one surface of the negative electrode current collector copper foil with a thickness of 8 μm, and the roller is pressed with appropriate force to make the metal lithium and the current collector adhere to each other, thereby obtaining a negative electrode sheet with a single-sided load of 20 μm thick lithium foil.

[0076] (3) Preparation of electrolyte

[0077] In an argon atmosphere glove box with a water content of <10 ppm, the components were mixed in the proportions shown in Table 1 to form an electrolyte.

[0078] (4) Isolation film

[0079] A polyethylene (PE) porous polymer with a thickness of 12 μm was used as the separator.

[0080] (5) Assembly of lithium metal batteries

[0081] The positive and negative electrodes are connected to their respective tabs. The cells are then stacked in the following order: single-sided negative electrode, separator, double-sided positive electrode, separator, and finally single-sided negative electrode, to form a bare cell. The separator is positioned between the positive and negative electrodes to provide isolation. The bare cell is then placed in outer packaging, injected with electrolyte, and encapsulated. After formation, degassing, and trimming, the lithium metal battery is obtained.

[0082] Examples 2 to 33

[0083] The preparation methods of Examples 2 to 33 are substantially the same as those of Example 1, except that the composition and content of the remaining components in the electrolyte and the preparation parameters are recorded in Tables 1 to 4.

[0084] Example 34 to Example 37

[0085] The preparation methods of Examples 34 to 37 are roughly the same as those of Example 1, except that the composition and content of the remaining components in the electrolyte, or the content of the liquid retention amount is adjusted. The preparation parameters are recorded in Tables 1 to 5.

[0086] Comparative Examples 1 to 4

[0087] The preparation methods of Comparative Examples 1 to 4 are substantially the same as those of Example 1, except that the composition and content of the remaining components in the electrolyte and the preparation parameters are recorded in Table 1.

[0088] Calendar life test and liquid retention test were performed on lithium metal batteries assembled with the electrolytes prepared in each embodiment and comparative example. The test results are recorded in Tables 1 to 4.

[0089] Performance testing of lithium metal batteries:

[0090] (1) Calendar life test method:

[0091] At 25±5℃ and normal pressure, the prepared lithium metal battery was charged to 4.3V at a constant current rate of 0.5C, then charged to a current of 0.05C at a constant voltage, left to stand for 5min, discharged to 2.8V at a constant current rate of 1C, left to stand for 5min, and the discharge capacity was recorded as C0. The lithium metal battery was continued to be charged to 4.3V at a constant current rate of 0.5C, then charged to a current of 0.05C at a constant voltage, left to stand for 24h, and discharged to 2.8V at a constant current rate of 1C, left to stand for 5min, and the discharge capacity was recorded as C1. This is one charge and discharge cycle. Repeat the above cycle and record the discharge capacity C x (x is the number of cycles). At the same time, calculate the capacity retention rate = (C x / C0)×100%. When the capacity retention rate is lower than 80% for the first time, the number of cycles is the calendar life of the lithium metal battery.

[0092] (2) Test method for liquid retention:

[0093] The retention volume is the electrolyte retained in the lithium metal battery. By weighing, the mass of the dry cell is weighed before liquid injection to obtain the mass m1, and the total mass of the cell and the removed air bag is weighed after degassing and trimming to obtain the mass m2; the retention volume = (m2-m1) / C0, where the discharge capacity C0 is C0 in "(1) Calendar life test method".

[0094] Among them, through the liquid retention test, the liquid retention capacity of the lithium metal battery assembled in Example 1 is 3g / Ah.

[0095] Table 1 shows the test results of the examples and comparative examples.

[0096]

[0097] “ / ” in the table means it has not been added or does not exist.

[0098] In Table 1, compared to Comparative Examples 1 to 4, in Examples 1 to 16, when the first component, the second component, the first lithium salt, and the second lithium salt satisfy the relationship of 0.005 ≤ b / x ≤ 0.2 and 0.003 ≤ y / a ≤ 0.08, the calendar life of the lithium metal battery is significantly improved. This electrolyte is conducive to the formation of a low-impedance and stable SEI film, reducing chemical corrosion and galvanic corrosion of the lithium metal in the lithium metal battery, thereby improving the calendar life of the lithium metal battery.

[0099] When the components in the electrolyte satisfy 0.02≤b / x≤0.1 and 0.01≤y / a≤0.05, the calendar life of the lithium metal battery can be further improved.

[0100] Table 2

[0101]

[0102] In combination with Table 2, in Examples 17 to 28, when the first component, the second component, the first lithium salt and the second lithium salt, the ratio of b / a, and the ratio of y / x in the electrolyte meet specific ranges, the corresponding lithium metal batteries have good calendar life.

[0103] Table 3

[0104]

[0105] With reference to Table 3, in Examples 29 to 33, when the electrolyte contains a third component and c satisfies a specific range, and the ratio of c / a satisfies a specific range, the corresponding lithium metal batteries all have good calendar life.

[0106] Table 4

[0107]

[0108] In Table 4, in Examples 34 to 37, the liquid retention amount in the lithium metal battery is adjusted, and when the liquid retention amount is within a specific range and P×(x+y) is within a specific range, the corresponding lithium metal batteries all have good calendar life.

[0109] The above disclosure is only a preferred embodiment of the present application and certainly cannot be used to limit the present application. Therefore, equivalent changes made based on the present application are still within the scope covered by the present application.

Claims

1. An electrolyte, characterized in that: The invention comprises a first component, a second component, a first lithium salt and a second lithium salt, wherein the first component comprises at least one of the compounds represented by formula (I) and formula (II), （I） (II) R1 and R2 are each independently selected from C1 to C 10 Alkyl, C1 to C 10 Halogenated alkyl, C1 to C 10 Alkoxy or C1 to C 10 Haloalkoxy, R3 is selected from C1 to C 10 Alkylene, C1 to C 10 Halogenated alkylene, C1 to C 10 Alkyleneoxy or C1 to C 10 Halogenated alkyleneoxy; The second component includes a cyclic carbonate; The first lithium salt includes at least one of lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethylsulfonyl)imide; The second lithium salt includes at least one of lithium difluorooxalatoborate or lithium tetrafluoroborate; Among them, based on the mass of the electrolyte, the mass proportion of the first component is a, the mass proportion of the second component is b, the mass proportion of the first lithium salt is x, and the mass proportion of the second lithium salt is y, 0.005≤b / x≤0.2, 0.003≤y / a≤0.08, 15%≤a≤60%, 15%≤x≤65%.

2. The electrolyte according to claim 1, wherein The electrolyte satisfies at least one of the following conditions: （1）0.2%≤b≤5%； （2）0.1%≤y≤2%； (3) 0.02≤b / x≤0.1 and 0.01≤y / a≤0.

05.

3. The electrolyte according to claim 1, wherein 0.005≤b / a≤0.

2.

4. The electrolyte according to claim 1, wherein 0.003≤y / x≤0.

1.

5. The electrolyte according to claim 1, wherein The first component includes at least one of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dipropyl ether, ethylene glycol dibutyl ether, ethylene glycol methyl ethyl ether, 1,2-propylene glycol dimethyl ether, 1,3-propylene glycol dimethyl ether, dimethoxymethane, ethyl ether, propyl ether, isopropyl ether, ethyl propyl ether, butyl ether, tetrahydropyran, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxane or 1,4-dioxane.

6. The electrolyte according to claim 1, wherein The second component includes at least one of ethylene carbonate, fluoroethylene carbonate, bisfluoroethylene carbonate, vinylene carbonate or vinylethylene carbonate.

7. The electrolyte according to any one of claims 1 to 6, wherein The electrolyte further includes a third component, and the electrolyte satisfies at least one of the following conditions: (1) The third component comprises at least one of formulas (III-1) to (III-14): (III-1)、 (III-2)、 (III-3)、 (III-4)、 (III-5)、 (III-6)、 (III-7)、 (III-8)、 (III-9)、 (III-10)、 (III-11)、 (III-12)、 (III-13)、 (III-14); (2) Based on the mass of the electrolyte, the mass proportion of the third component is c, which satisfies 10%≤c≤60%; (3) Based on the mass of the electrolyte, the mass proportion of the third component is c, 0.2≤c / a≤4.

8. An electrochemical device comprising a negative electrode plate, characterized in that: The electrochemical device further includes an electrolyte as described in any one of claims 1 to 7, the negative electrode plate includes a negative electrode current collector and a negative electrode material layer provided on at least one surface of the negative electrode current collector, the negative electrode material layer is selected from at least one of lithium metal or lithium alloy; the lithium alloy includes at least one of lithium tin, lithium zinc, lithium aluminum, lithium magnesium, lithium silver, lithium gold, lithium gallium, lithium indium, lithium platinum, lithium boron, lithium carbon or lithium silicon alloy.

9. The electrochemical device according to claim 8, wherein The liquid retention capacity of the electrochemical device is P g / Ah, 1.5≤P≤4, 0.35≤P×(x+y)≤2.

2.

10. An electronic device, characterized in that: Comprising the electrochemical device according to claim 8 or 9.

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