Battery electrolyte and battery

Abstract

The invention provides a battery electrolyte and a battery, the battery electrolyte comprises a lithium salt, a first additive and an organic solvent, and the first additive is fluorinated polyoxyethylene ether. The fluorinated polyoxyethylene ether has relatively low surface tension, so that the wettability and permeability of the battery electrolyte are further improved, the electrolyte can be in full contact with positive and negative electrode materials, the transmission effect of ions in the battery is improved, the internal resistance of the battery is further reduced, and the rate capability of the battery is improved; and meanwhile, the fluorinated polyoxyethylene ether has a relatively high flash point, so that the battery electrolyte can be ignited at a relatively high temperature, thereby improving the flame-retardant capability of the battery and further improving the safety performance of the battery.

Description

Technical Field

[0001] The present application belongs to the field of battery technology, and specifically relates to a battery electrolyte and a battery. Background Art

[0002] With the rapid development of pure electric vehicles and hybrid electric vehicles, higher requirements are placed on the energy density, cycle life, rate performance and battery safety performance of lithium-ion batteries. Lithium batteries are mainly composed of electrolytes, separators, positive electrode materials and negative electrode materials. As one of the four key materials, electrolyte plays a vital role in the performance of lithium-ion batteries. However, the electrolyte of lithium batteries in related technologies has poor wettability with positive and negative electrode materials, and the flame retardant performance of the electrolyte is poor. Summary of the invention

[0003] The technical problem to be solved by the present application is to provide a battery electrolyte and a battery to solve the problem that the electrolyte in the related art is not effective in improving the rate performance and safety performance of the battery.

[0004] In order to solve the above technical problems, the present application is implemented through the following technical solutions:

[0005] In a first aspect, the present application proposes a battery electrolyte comprising: a lithium salt, a first additive and an organic solvent, wherein the first additive is a fluoropolyoxyethylene ether.

[0006] Furthermore, the molecular formula of the fluoropolyoxyethylene ether is: R f X(CH2CH2O) n R1 or R f X(CHCH3CH2O) n R1;

[0007] Among them, R f is a fluorinated alkyl group having 2-18 carbon atoms, X is selected from one of oxygen (-O-), sulfur (-S-), amine oxide (-NO-), amide (CO-NH) or sulfonamide (-SO2N-), R1 is an alkyl group having 1-4 carbon atoms, and the value of n is 1-25.

[0008] Furthermore, the content of the first additive in the electrolyte is 0.1 wt% to 2 wt%.

[0009] Furthermore, the electrolyte also includes a second additive, which is selected from at least one of propylene sulfite, vinyl sulfate, vinylene carbonate, fluoroethylene carbonate, lithium bis(oxalatoborate), lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethylsulfonate)imide.

[0010] Furthermore, the content of the second additive in the electrolyte is 3wt% to 10wt%.

[0011] Furthermore, the content of the lithium salt in the electrolyte is 8wt% to 20wt%.

[0012] Furthermore, the lithium salt includes at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, and lithium perchlorate.

[0013] Furthermore, the content of the organic solvent is 74wt% to 85wt%.

[0014] Further, the organic solvent includes two or more of diethyl carbonate, ethyl methyl carbonate, dimethyl carbonate, ethylene carbonate, vinylene carbonate and vinyl vinylene carbonate.

[0015] In a second aspect, the present application also proposes a battery, comprising the battery electrolyte described in any one of the above items.

[0016] Compared with the prior art, the embodiments of the present application have the following advantages:

[0017] In the embodiment of the present application, the provided battery electrolyte includes: lithium salt, a first additive and an organic solvent, wherein the first additive is fluoropolyoxyethylene ether. Fluoropolyoxyethylene ether has a lower surface tension, further improving the wettability and permeability of the battery electrolyte, enabling the electrolyte to fully contact with the positive and negative electrode materials, improving the transmission effect of ions inside the battery, thereby reducing the internal resistance of the battery, thereby improving the rate performance of the battery; at the same time, fluoropolyoxyethylene ether has a higher flash point, so that the battery electrolyte can be ignited at a higher temperature, thereby improving the flame retardant ability of the battery, thereby improving the safety performance of the battery.

[0018] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. DETAILED DESCRIPTION

[0019] The following will be combined with the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0020] The terms "first", "second", etc. in the specification and claims of this application are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchanged where appropriate, so that the embodiments of this application can be implemented in an order other than those described here. In this application, "and / or" describes the association relationship of associated objects, indicating that there can be three relationships:

[0021] The electrolyte and battery provided in the embodiments of the present application are described in detail below through specific embodiments and their application scenarios.

[0022] The embodiment of the present application provides a battery electrolyte, comprising: a lithium salt, a first additive and an organic solvent, wherein the first additive is a fluoropolyoxyethylene ether.

[0023] In the embodiments of the present application, by adding fluorinated polyoxyethylene ether additives to the electrolyte, the fluorinated polyoxyethylene ether, on the one hand, has a lower surface tension and can quickly wet the surfaces of the positive and negative electrodes in the battery, forming a liquid film on the surface of the positive and negative electrode materials, thereby improving the wettability and permeability between the electrolyte and the positive and negative electrodes, and then improving the diffusion of interface ions, thereby improving the rate performance of the battery; on the other hand, the fluorinated polyoxyethylene ether has a higher flash point, excellent thermal stability and chemical inertness, which allows the electrolyte to burn only at a higher temperature, thereby improving the flame retardant ability of the electrolyte and thus improving the safety performance of the battery.

[0024] Optionally, the molecular formula of the fluoropolyoxyethylene ether is: R f X(CH2CH2O) n R1 or R f X(CHCH3CH2O) n R1; where R f is a fluorinated alkyl group having 2 to 18 carbon atoms, X can be selected from one of oxygen (-O-), sulfur (-S-), amine oxide (-NO-), amide (CO-NH) or sulfonamide (-SO2N-), R1 is an alkyl group having 1 to 4 carbon atoms, and the value of n can be 1 to 25.

[0025] In the embodiment of the present application, the fluoropolyoxyethylene ether can be made to have a higher surface activity by the fluorinated alkyl functional group in the fluoropolyoxyethylene ether, and this higher surface activity enables the fluoropolyoxyethylene ether to significantly reduce the surface tension of the electrolyte at a lower concentration, and with the increase of the number of carbon atoms in the fluoroalkyl group, the surface activity of the fluoropolyoxyethylene ether will be correspondingly enhanced, so that the wettability is correspondingly improved, but the excessive number of carbon atoms will affect the solubility of the fluoropolyoxyethylene ether in the solvent, so the number of carbon atoms of the fluoroalkyl group is set in the present application at 2-18. At the same time, according to different performance and application requirements, X can be selected from one of oxygen (-O-), sulfur (-S-), amine oxide (-NO-), amide (CO-NH) or sulfonamide (-SO2N-). In addition, when the value of n is 1-25, the fluoropolyoxyethylene ether can have better reactivity and stability.

[0026] Optionally, based on the total mass of the battery electrolyte, the content of the fluoropolyoxyethylene ether is 0.1wt% to 2wt%. By setting the content of the fluoropolyoxyethylene ether in the battery electrolyte between 0.1wt% and 2wt%, the effect of the fluoropolyoxyethylene ether in improving the wettability and flame retardancy of the electrolyte can be further exerted. It is understandable that if the content of the fluoropolyoxyethylene is too much, it will affect the role of the second additive in the electrolyte, thereby affecting the performance of the battery, while if the content of the fluoropolyoxyethylene is too little, the improvement of the wettability and safety performance of the electrolyte is limited, and it cannot meet the actual application requirements.

[0027] For example, the content of fluoropolyoxyethylene ether in the battery electrolyte can be set to any value such as 0.1wt%, 0.5wt%, 1wt%, 1.5wt%, 2wt%, or a range between any two values.

[0028] Optionally, the battery electrolyte further includes a second additive, the second additive being selected from at least one of propylene sulfite (PS), vinyl sulfate (DTD), vinylene carbonate (VEC), fluoroethylene carbonate (FEC), lithium bis(oxalatoborate) (LiBOB), lithium bis(fluorosulfonyl)imide (LiFSI) and lithium bis(trifluoromethanesulfonate)imide (LiTFSI).

[0029] In the embodiment of the present application, by adding a second additive to the electrolyte, the second additive can, on the one hand, optimize the solid electrolyte interface (SEI) film and improve the cycle stability of the battery; on the other hand, it can improve the solubility and ionization ability of the lithium salt in the electrolyte, thereby improving the conductivity of the electrolyte; in addition, the second additive can cooperate with the first additive to improve the interface characteristics between the electrolyte and the positive and negative electrode materials, so that the electrolyte can better wet the electrode materials and improve the overall performance of the battery.

[0030] For example, the second additive may be PS, which can not only form a SEI film on the surface of the electrode material, but also effectively prevent problems such as internal short circuit and dendrite growth of the battery, thereby improving the overall performance of the battery, and PS can effectively improve the low-temperature characteristics of the electrolyte, so that the battery can still maintain good performance in a low-temperature environment;

[0031] Alternatively, the second additive may be FEC, which can effectively inhibit the decomposition of the electrolyte and the corrosion of the electrode under high temperature conditions, thereby significantly improving the high temperature cycle performance, capacity retention rate and safety performance of the battery.

[0032] It should be noted that the type of the second additive can be flexibly set according to actual needs and is not limited here.

[0033] Optionally, based on the total mass of the battery electrolyte, the content of the second additive is 3wt% to 10wt%. By setting the content of the second additive in the battery electrolyte to be between 3wt% and 10wt%, the effect of the second additive in improving the conductivity of the electrolyte and the cycle stability of the battery can be more effectively exerted. However, when the content of the second additive is too much, such as when the amount of FEC added is too much, the SEI film formed on the surface of the electrode material is too dense, which increases the transmission impedance of lithium ions, thereby reducing the discharge specific capacity of the battery; and when the content of the second additive is too little, an effective SEI film cannot be formed on the surface of the electrode material to protect the electrode material, thereby affecting the cycle stability of the battery.

[0034] For example, the content of the second additive in the battery electrolyte can be set to any value such as 3wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, or a range between any two values.

[0035] Optionally, based on the total mass of the battery electrolyte, the content of the lithium salt is between 8wt% and 20wt%. By setting the content of the lithium salt in the battery electrolyte between 8wt% and 20wt%, the lithium salt can provide a suitable lithium ion concentration for the electrolyte, improve the conductivity of the battery electrolyte, accelerate the migration speed of lithium ions, and thus improve the rate performance and service life of the battery.

[0036] It is understandable that if the content of lithium salt in the electrolyte is too much, the concentration of lithium ions in the electrolyte will increase, affecting the formation and stability of the SEI film. At the same time, excessive lithium salt will lead to enhanced interactions between ions in the electrolyte, thereby increasing the viscosity of the electrolyte and increasing the internal resistance of the battery, thereby limiting the discharge and charging rate of the battery and reducing the performance of the battery. When the content of lithium salt in the electrolyte is too little, the number of lithium ions available for reaction in the electrolyte will decrease, which will not only reduce the capacity of the battery, but also affect the use of the battery.

[0037] For example, the content of lithium salt in the battery electrolyte can be set to any value such as 8wt%, 10wt%, 12wt%, 15wt%, 17wt%, 19wt%, 20wt%, or a range between any two values.

[0038] Optionally, the lithium salt includes at least one of lithium hexafluorophosphate (LiFP6), lithium tetrafluoroborate (LiBF4), and lithium perchlorate (LiClO4). Among them, LiFP6 has a moderate ion migration number, a moderate dissociation constant, good antioxidant properties and good aluminum foil passivation ability in an organic solvent, and can match various positive and negative electrode materials.

[0039] Optionally, based on the total mass of the battery electrolyte, the content of the organic solvent is 74wt% to 85wt%. By setting the content of the organic solvent in the battery electrolyte to be between 74wt% and 85wt%, the organic solvent with a suitable content not only has a higher dielectric constant and can better dissolve the lithium salt, but also has a lower viscosity, which can make the lithium ions in the electrolyte migrate more easily.

[0040] Among them, when the content of organic solvent is too much, it will not only dilute the lithium salt in the electrolyte, reduce the ion concentration in the electrolyte, and make the movement of electrons and ions between the positive and negative electrodes more difficult, thus causing the battery reaction to be unbalanced, exacerbating the problems of overcharging, overdischarging and short circuit of the battery, but also increase the pressure inside the battery due to the volatility and expandability of the organic solvent itself, thereby increasing the risk of battery explosion or fire. When the content of organic solvent is too little, on the one hand, it will cause the ion transmission of the electrolyte to be blocked, thereby reducing the load capacity of the battery, and on the other hand, it will reduce the number of ions available for reaction in the electrolyte, reducing the capacity of the battery, thus affecting the battery's service time and endurance.

[0041] For example, the content of the organic solvent in the battery electrolyte can be set to any value such as 74wt%, 76wt%, 78wt%, 80wt%, 82wt%, 85wt%, or a range between any two values.

[0042] Optionally, the organic solvent includes two or more of diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), ethylene carbonate (EC), vinylene carbonate (VC) and vinyl vinylene carbonate (VEC).

[0043] Exemplarily, the organic solvent can be a combination of EMC, EC and DMC. EMC has low viscosity, high flash point, good solubility and chemical stability. EC has a higher dielectric constant and higher viscosity, which helps the dissolution of lithium salts in the electrolyte and the formation of SEI film. DMC has a lower viscosity and helps the migration of lithium ions. The combination of EMC, EC and DMC helps to improve the conductivity and low-temperature performance of the electrolyte.

[0044] The present application also provides a battery, which includes the battery electrolyte, positive electrode plate, and negative electrode plate in the above embodiment; wherein the electrolyte in the electrolyte plays a role of conducting ions between the positive electrode plate and the negative electrode plate.

[0045] Specifically, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector, wherein the positive electrode active material layer includes a positive electrode active material, and the positive electrode active material includes at least one of lithium ion transition metal oxides, lithium ion transition metal phosphates and variants, lithium ion transition metal sulfates, and Prussian blue compounds;

[0046] Specifically, the negative electrode plate includes a negative electrode current collector and a negative electrode active material layer arranged on the negative electrode current collector. The above-mentioned negative electrode active material layer can adopt negative electrode active materials used for batteries, for example, selected from metal negative electrode materials or non-metallic negative electrode materials; the metal negative electrode material is preferably metal foil or alloy compound such as metallic lithium, lithium alloy, tin, antimony, etc.; the non-metallic negative electrode material is preferably any one of hard carbon, soft carbon, graphite, and silicon oxide, or a combination of at least two of them.

[0047] In some embodiments, the battery also includes a separator, which is arranged between adjacent positive electrode sheets and negative electrode sheets to separate the positive electrode sheets and the negative electrode sheets to prevent the positive electrode sheets and the negative electrode sheets from short-circuiting due to contact. The separator can be a conventional separator in the art, and the battery can be a lithium-ion battery.

[0048] In practical applications, the negative electrode sheet, the separator and the positive electrode sheet are stacked in order and wound to obtain a core, the core is packaged to obtain a bare cell, and the bare cell is baked and then injected with electrolyte, formed, sealed and sorted to obtain the above-mentioned battery.

[0049] The present application is described in detail below through examples.

[0050] Example 1

[0051] (1) Preparation of electrolyte:

[0052] Weigh the preset weights of EMC, DMC, EC, and VC respectively and mix them evenly to obtain a mixed solvent, add LiFP6 to the obtained mixed solvent one by one, stir to obtain a mixed solution, and add the first additive and the second additive to the mixed solution. Among them, the addition amount of EMC is 33wt% of the total mass of the electrolyte, the addition amount of DMC is 24.99wt% of the total mass of the electrolyte, the addition amount of EC is 17.97wt% of the total mass of the electrolyte, the addition amount of VC is 3.98wt% of the total mass of the electrolyte, the addition amount of LiFP6 is 15.98wt% of the total mass of the electrolyte, the first additive includes fluoropolyoxyethylene ether, and the addition amount of fluoropolyoxyethylene ether is 0.1wt% of the total mass of the electrolyte, and the second additive includes: PS and FEC, the addition amount of PS is 2.99wt% of the total mass of the electrolyte, and the addition amount of FEC is 0.99wt% of the total mass of the electrolyte.

[0053] (2) Preparation of lithium-ion batteries

[0054] The positive electrode sheet, separator and negative electrode sheet are prepared respectively, and the positive electrode sheet, separator and negative electrode sheet are stacked in order so that the separator is in the middle of the positive and negative electrode sheets. The bare cell is obtained by winding, hot pressing and shaping, and the tabs are welded. The bare cell is placed in an outer packaging aluminum-plastic film and baked in an oven at 85±10℃ for 24h. The above-prepared electrolyte is injected into the dried battery, and the battery is allowed to stand, formed and divided to complete the preparation.

[0055] Among them, the preparation methods of the positive electrode plate, the separator, and the negative electrode plate can refer to the preparation methods in the relevant technology, and this application will not repeat them here.

[0056] Example 2

[0057] The difference between Example 2 and Example 1 is that: in the preparation process of the electrolyte, the addition amount of EMC is 32.84wt% of the total mass of the electrolyte, the addition amount of DMC is 24.88wt% of the total mass of the electrolyte, the addition amount of EC is 17.9wt% of the total mass of the electrolyte, the addition amount of VC is 3.98wt% of the total mass of the electrolyte, and the addition amount of LiFP6 is 15.92wt% of the total mass of the electrolyte. The first additive includes fluoropolyoxyethylene ether, and the addition amount of fluoropolyoxyethylene ether is 0.5wt% of the total mass of the electrolyte. The second additive includes: PS and FEC, the addition amount of PS is 2.99wt% of the total mass of the electrolyte, and the addition amount of FEC is 0.99wt% of the total mass of the electrolyte.

[0058] Example 3

[0059] The difference between Example 3 and Example 1 is that: in the preparation process of the electrolyte, the addition amount of EMC is 32.67wt% of the total mass of the electrolyte, the addition amount of DMC is 24.75wt% of the total mass of the electrolyte, the addition amount of EC is 17.82wt% of the total mass of the electrolyte, the addition amount of VC is 3.96wt% of the total mass of the electrolyte, and the addition amount of LiFP6 is 15.84wt% of the total mass of the electrolyte. The first additive includes fluoropolyoxyethylene ether, and the addition amount of fluoropolyoxyethylene ether is 1wt% of the total mass of the electrolyte. The second additive includes: PS and FEC, the addition amount of PS is 2.97wt% of the total mass of the electrolyte, and the addition amount of FEC is 0.99wt% of the total mass of the electrolyte.

[0060] Example 4

[0061] The difference between Example 4 and Example 1 is that: in the preparation process of the electrolyte, the addition amount of EMC is 32.51wt% of the total mass of the electrolyte, the addition amount of DMC is 24.63wt% of the total mass of the electrolyte, the addition amount of EC is 17.73wt% of the total mass of the electrolyte, the addition amount of VC is 3.94wt% of the total mass of the electrolyte, and the addition amount of LiFP6 is 15.75wt% of the total mass of the electrolyte. The first additive includes fluoropolyoxyethylene ether, and the addition amount of fluoropolyoxyethylene ether is 1.5wt% of the total mass of the electrolyte. The second additive includes: PS and FEC, the addition amount of PS is 2.95wt% of the total mass of the electrolyte, and the addition amount of FEC is 0.99wt% of the total mass of the electrolyte.

[0062] Example 5

[0063] The difference between Example 5 and Example 1 is that: in the preparation process of the electrolyte, the addition amount of EMC is 32.4wt% of the total mass of the electrolyte, the addition amount of DMC is 24.52wt% of the total mass of the electrolyte, the addition amount of EC is 17.62wt% of the total mass of the electrolyte, the addition amount of VC is 3.92wt% of the total mass of the electrolyte, and the addition amount of LiFP6 is 15.63wt% of the total mass of the electrolyte. The first additive includes fluoropolyoxyethylene ether, and the addition amount of fluoropolyoxyethylene ether is 2wt% of the total mass of the electrolyte. The second additive includes: PS and FEC, the addition amount of PS is 2.93wt% of the total mass of the electrolyte, and the addition amount of FEC is 0.98wt% of the total mass of the electrolyte.

[0064] Example 6

[0065] The difference between Example 6 and Example 1 is that: in the preparation process of the electrolyte, the addition amount of EMC is 31.99wt% of the total mass of the electrolyte, the addition amount of DMC is 23.99wt% of the total mass of the electrolyte, the addition amount of EC is 14.98wt% of the total mass of the electrolyte, the addition amount of VC is 3.98wt% of the total mass of the electrolyte, and the addition amount of LiFP6 is 18.98wt% of the total mass of the electrolyte. The first additive includes fluoropolyoxyethylene ether, and the addition amount of fluoropolyoxyethylene ether is 0.1wt% of the total mass of the electrolyte. The second additive includes: PS and FEC, the addition amount of PS is 4.99wt% of the total mass of the electrolyte, and the addition amount of FEC is 1.99wt% of the total mass of the electrolyte.

[0066] Example 7

[0067] The difference between Example 7 and Example 1 is that: in the preparation process of the electrolyte, the addition amount of EMC is 31.84wt% of the total mass of the electrolyte, the addition amount of DMC is 23.98wt% of the total mass of the electrolyte, the addition amount of EC is 14.9wt% of the total mass of the electrolyte, the addition amount of VC is 3.98wt% of the total mass of the electrolyte, and the addition amount of LiFP6 is 18.83wt% of the total mass of the electrolyte. The first additive includes fluoropolyoxyethylene ether, and the addition amount of fluoropolyoxyethylene ether is 0.5wt% of the total mass of the electrolyte. The second additive includes: PS and FEC, the addition amount of PS is 4.98wt% of the total mass of the electrolyte, and the addition amount of FEC is 1.99wt% of the total mass of the electrolyte.

[0068] Example 8

[0069] The difference between Example 8 and Example 1 is that: in the preparation process of the electrolyte, the addition amount of EMC is 31.67wt% of the total mass of the electrolyte, the addition amount of DMC is 23.75wt% of the total mass of the electrolyte, the addition amount of EC is 14.82wt% of the total mass of the electrolyte, the addition amount of VC is 3.96wt% of the total mass of the electrolyte, and the addition amount of LiFP6 is 18.83wt% of the total mass of the electrolyte. The first additive includes fluoropolyoxyethylene ether, and the addition amount of fluoropolyoxyethylene ether is 1wt% of the total mass of the electrolyte. The second additive includes: PS and FEC, the addition amount of PS is 4.98wt% of the total mass of the electrolyte, and the addition amount of FEC is 1.99wt% of the total mass of the electrolyte.

[0070] Example 9

[0071] The difference between Example 9 and Example 1 is that: in the preparation process of the electrolyte, the addition amount of EMC is 31.51wt% of the total mass of the electrolyte, the addition amount of DMC is 23.83wt% of the total mass of the electrolyte, the addition amount of EC is 14.73wt% of the total mass of the electrolyte, the addition amount of VC is 3.94wt% of the total mass of the electrolyte, and the addition amount of LiFP6 is 18.77wt% of the total mass of the electrolyte. The first additive includes fluoropolyoxyethylene ether, and the addition amount of fluoropolyoxyethylene ether is 1.5wt% of the total mass of the electrolyte. The second additive includes: PS and FEC, the addition amount of PS is 4.93wt% of the total mass of the electrolyte, and the addition amount of FEC is 1.99wt% of the total mass of the electrolyte.

[0072] Example 10

[0073] The difference between Example 10 and Example 1 is that: in the preparation process of the electrolyte, the addition amount of EMC is 31.6wt% of the total mass of the electrolyte, the addition amount of DMC is 23.82wt% of the total mass of the electrolyte, the addition amount of EC is 14.82wt% of the total mass of the electrolyte, the addition amount of VC is 3.92wt% of the total mass of the electrolyte, and the addition amount of LiFP6 is 18.63wt% of the total mass of the electrolyte. The first additive includes fluoropolyoxyethylene ether, and the addition amount of fluoropolyoxyethylene ether is 2wt% of the total mass of the electrolyte. The second additive includes: PS and FEC, the addition amount of PS is 4.92wt% of the total mass of the electrolyte, and the addition amount of FEC is 1.99wt% of the total mass of the electrolyte.

[0074] Embodiment 11

[0075] The difference between Example 11 and Example 1 is that: in the preparation process of the electrolyte, the addition amount of EMC is 33.99wt% of the total mass of the electrolyte, the addition amount of DMC is 25.99wt% of the total mass of the electrolyte, the addition amount of EC is 16.98wt% of the total mass of the electrolyte, the addition amount of VC is 4.98wt% of the total mass of the electrolyte, and the addition amount of LiFP6 is 8.99wt% of the total mass of the electrolyte. The first additive includes fluoropolyoxyethylene ether, and the addition amount of fluoropolyoxyethylene ether is 0.1wt% of the total mass of the electrolyte. The second additive includes: PS and FEC, the addition amount of PS is 6.98wt% of the total mass of the electrolyte, and the addition amount of FEC is 1.99wt% of the total mass of the electrolyte.

[0076] Example 12

[0077] The difference between Example 12 and Example 1 is that: in the preparation process of the electrolyte, the addition amount of EMC is 33.84wt% of the total mass of the electrolyte, the addition amount of DMC is 25.98wt% of the total mass of the electrolyte, the addition amount of EC is 16.88wt% of the total mass of the electrolyte, the addition amount of VC is 4.9wt% of the total mass of the electrolyte, and the addition amount of LiFP6 is 8.96wt% of the total mass of the electrolyte. The first additive includes fluoropolyoxyethylene ether, and the addition amount of fluoropolyoxyethylene ether is 0.5wt% of the total mass of the electrolyte. The second additive includes: PS and FEC, the addition amount of PS is 6.96wt% of the total mass of the electrolyte, and the addition amount of FEC is 1.98wt% of the total mass of the electrolyte.

[0078] Example 13

[0079] The difference between Example 13 and Example 1 is that: in the preparation process of the electrolyte, the addition amount of EMC is 33.67wt% of the total mass of the electrolyte, the addition amount of DMC is 25.75wt% of the total mass of the electrolyte, the addition amount of EC is 16.73wt% of the total mass of the electrolyte, the addition amount of VC is 4.98wt% of the total mass of the electrolyte, and the addition amount of LiFP6 is 8.96wt% of the total mass of the electrolyte. The first additive includes fluoropolyoxyethylene ether, and the addition amount of fluoropolyoxyethylene ether is 1wt% of the total mass of the electrolyte. The second additive includes: PS and FEC, the addition amount of PS is 6.94wt% of the total mass of the electrolyte, and the addition amount of FEC is 1.97wt% of the total mass of the electrolyte.

[0080] Embodiment 14

[0081] The difference between Example 14 and Example 1 is that: in the preparation process of the electrolyte, the addition amount of EMC is 33.51wt% of the total mass of the electrolyte, the addition amount of DMC is 25.63wt% of the total mass of the electrolyte, the addition amount of EC is 16.66wt% of the total mass of the electrolyte, the addition amount of VC is 4.95wt% of the total mass of the electrolyte, and the addition amount of LiFP6 is 8.83wt% of the total mass of the electrolyte. The first additive includes fluoropolyoxyethylene ether, and the addition amount of fluoropolyoxyethylene ether is 1.5wt% of the total mass of the electrolyte. The second additive includes: PS and FEC, the addition amount of PS is 6.93wt% of the total mass of the electrolyte, and the addition amount of FEC is 1.99wt% of the total mass of the electrolyte.

[0082] Embodiment 15

[0083] The difference between Example 15 and Example 1 is that: in the preparation process of the electrolyte, the addition amount of EMC is 33.4wt% of the total mass of the electrolyte, the addition amount of DMC is 25.52wt% of the total mass of the electrolyte, the addition amount of EC is 16.62wt% of the total mass of the electrolyte, the addition amount of VC is 4.91wt% of the total mass of the electrolyte, and the addition amount of LiFP6 is 8.65wt% of the total mass of the electrolyte. The first additive includes fluoropolyoxyethylene ether, and the addition amount of fluoropolyoxyethylene ether is 2wt% of the total mass of the electrolyte. The second additive includes: PS and FEC, the addition amount of PS is 6.92wt% of the total mass of the electrolyte, and the addition amount of FEC is 1.98wt% of the total mass of the electrolyte.

[0084] Example 16

[0085] The difference between Example 16 and Example 1 is that: in the preparation process of the electrolyte, the addition amount of EMC is 31.96wt% of the total mass of the electrolyte, the addition amount of DMC is 21.99wt% of the total mass of the electrolyte, the addition amount of EC is 16.99wt% of the total mass of the electrolyte, the addition amount of VC is 3.99wt% of the total mass of the electrolyte, and the addition amount of LiFP6 is 19.99wt% of the total mass of the electrolyte. The first additive includes fluoropolyoxyethylene ether, and the addition amount of fluoropolyoxyethylene ether is 0.1wt% of the total mass of the electrolyte. The second additive includes: PS and FEC, the addition amount of PS is 3.99wt% of the total mass of the electrolyte, and the addition amount of FEC is 0.99wt% of the total mass of the electrolyte.

[0086] Embodiment 17

[0087] The difference between Example 17 and Example 1 is that: in the preparation process of the electrolyte, the addition amount of EMC is 31.84wt% of the total mass of the electrolyte, the addition amount of DMC is 21.88wt% of the total mass of the electrolyte, the addition amount of EC is 16.9wt% of the total mass of the electrolyte, the addition amount of VC is 3.98wt% of the total mass of the electrolyte, and the addition amount of LiFP6 is 19.92wt% of the total mass of the electrolyte. The first additive includes fluoropolyoxyethylene ether, and the addition amount of fluoropolyoxyethylene ether is 0.5wt% of the total mass of the electrolyte. The second additive includes: PS and FEC, the addition amount of PS is 3.99wt% of the total mass of the electrolyte, and the addition amount of FEC is 0.99wt% of the total mass of the electrolyte.

[0088] Embodiment 18

[0089] The difference between Example 18 and Example 1 is that: in the preparation process of the electrolyte, the addition amount of EMC is 31.67wt% of the total mass of the electrolyte, the addition amount of DMC is 21.75wt% of the total mass of the electrolyte, the addition amount of EC is 16.82wt% of the total mass of the electrolyte, the addition amount of VC is 3.96wt% of the total mass of the electrolyte, and the addition amount of LiFP6 is 19.84wt% of the total mass of the electrolyte. The first additive includes fluoropolyoxyethylene ether, and the addition amount of fluoropolyoxyethylene ether is 1wt% of the total mass of the electrolyte. The second additive includes: PS and FEC, the addition amount of PS is 3.97wt% of the total mass of the electrolyte, and the addition amount of FEC is 0.99wt% of the total mass of the electrolyte.

[0090] Embodiment 19

[0091] The difference between Example 19 and Example 1 is that: in the preparation process of the electrolyte, the addition amount of EMC is 31.68wt% of the total mass of the electrolyte, the addition amount of DMC is 21.63wt% of the total mass of the electrolyte, the addition amount of EC is 16.83wt% of the total mass of the electrolyte, the addition amount of VC is 3.94wt% of the total mass of the electrolyte, and the addition amount of LiFP6 is 19.75wt% of the total mass of the electrolyte. The first additive includes fluoropolyoxyethylene ether, and the addition amount of fluoropolyoxyethylene ether is 1.5wt% of the total mass of the electrolyte. The second additive includes: PS and FEC, the addition amount of PS is 3.75wt% of the total mass of the electrolyte, and the addition amount of FEC is 0.92wt% of the total mass of the electrolyte.

[0092] Embodiment 20

[0093] The difference between Example 20 and Example 1 is that: in the preparation process of the electrolyte, the addition amount of EMC is 31.76wt% of the total mass of the electrolyte, the addition amount of DMC is 21.72wt% of the total mass of the electrolyte, the addition amount of EC is 16.62wt% of the total mass of the electrolyte, the addition amount of VC is 3.92wt% of the total mass of the electrolyte, and the addition amount of LiFP6 is 19.63wt% of the total mass of the electrolyte. The first additive includes fluoropolyoxyethylene ether, and the addition amount of fluoropolyoxyethylene ether is 2wt% of the total mass of the electrolyte. The second additive includes: PS and FEC, the addition amount of PS is 3.42wt% of the total mass of the electrolyte, and the addition amount of FEC is 0.93wt% of the total mass of the electrolyte.

[0094] Embodiment 21

[0095] The difference between Example 21 and Example 1 is that: during the preparation process of the electrolyte, the amount of EMC added is 34.96wt% of the total mass of the electrolyte, the amount of DMC added is 24.99wt% of the total mass of the electrolyte, the amount of EC added is 20.95wt% of the total mass of the electrolyte, the amount of VC added is 3.99wt% of the total mass of the electrolyte, and the amount of LiFP6 added is 10.98wt% of the total mass of the electrolyte. The first additive includes fluoropolyoxyethylene ether, and the amount of fluoropolyoxyethylene ether added is 0.1wt% of the total mass of the electrolyte. The second additive includes: PS and FEC, the amount of PS added is 2.99wt% of the total mass of the electrolyte, and the amount of FEC added is 1.04wt% of the total mass of the electrolyte.

[0096] Embodiment 22

[0097] The difference between Example 22 and Example 1 is that: during the preparation process of the electrolyte, the addition amount of EMC is 34.98wt% of the total mass of the electrolyte, the addition amount of DMC is 24.96wt% of the total mass of the electrolyte, the addition amount of EC is 20.54wt% of the total mass of the electrolyte, the addition amount of VC is 3.99wt% of the total mass of the electrolyte, and the addition amount of LiFP6 is 10.98wt% of the total mass of the electrolyte. The first additive includes fluoropolyoxyethylene ether, and the addition amount of fluoropolyoxyethylene ether is 0.5wt% of the total mass of the electrolyte. The second additive includes: PS and FEC, the addition amount of PS is 2.99wt% of the total mass of the electrolyte, and the addition amount of FEC is 1.06wt% of the total mass of the electrolyte.

[0098] Embodiment 23

[0099] The difference between Example 23 and Example 1 is that: in the preparation process of the electrolyte, the addition amount of EMC is 34.82wt% of the total mass of the electrolyte, the addition amount of DMC is 24.63wt% of the total mass of the electrolyte, the addition amount of EC is 20.59wt% of the total mass of the electrolyte, the addition amount of VC is 3.99wt% of the total mass of the electrolyte, and the addition amount of LiFP6 is 10.89wt% of the total mass of the electrolyte. The first additive includes fluoropolyoxyethylene ether, and the addition amount of fluoropolyoxyethylene ether is 1wt% of the total mass of the electrolyte. The second additive includes: PS and FEC, the addition amount of PS is 2.98wt% of the total mass of the electrolyte, and the addition amount of FEC is 1.1wt% of the total mass of the electrolyte.

[0100] Embodiment 24

[0101] The difference between Example 24 and Example 1 is that: during the preparation process of the electrolyte, the amount of EMC added is 34.24wt% of the total mass of the electrolyte, the amount of DMC added is 24.36wt% of the total mass of the electrolyte, the amount of EC added is 20.77wt% of the total mass of the electrolyte, the amount of VC added is 3.99wt% of the total mass of the electrolyte, the amount of LiFP6 added is 10.94wt% of the total mass of the electrolyte, the first additive includes fluoropolyoxyethylene ether, and the amount of fluoropolyoxyethylene ether added is 1.5wt% of the total mass of the electrolyte; the second additive includes: PS and FEC, the amount of PS added is 3.05wt% of the total mass of the electrolyte, and the amount of FEC added is 1.15wt% of the total mass of the electrolyte.

[0102] Embodiment 25

[0103] The difference between Example 25 and Example 1 is that: during the preparation process of the electrolyte, the amount of EMC added is 34.67wt% of the total mass of the electrolyte, the amount of DMC added is 24.05wt% of the total mass of the electrolyte, the amount of EC added is 20.63wt% of the total mass of the electrolyte, the amount of VC added is 3.69wt% of the total mass of the electrolyte, and the amount of LiFP6 added is 10.93wt% of the total mass of the electrolyte. The first additive includes fluoropolyoxyethylene ether, and the amount of fluoropolyoxyethylene ether added is 2wt% of the total mass of the electrolyte. The second additive includes: PS and FEC, the amount of PS added is 2.87wt% of the total mass of the electrolyte, and the amount of FEC added is 1.16wt% of the total mass of the electrolyte.

[0104] Comparative Example 1

[0105] The difference between Comparative Example 1 and Example 1 is that: during the preparation process of the electrolyte, the addition amount of EMC is 33wt% of the total mass of the electrolyte, the addition amount of DMC is 25wt% of the total mass of the electrolyte, the addition amount of EC is 18wt% of the total mass of the electrolyte, the addition amount of VC is 4wt% of the total mass of the electrolyte, the addition amount of LiFP6 is 16wt% of the total mass of the electrolyte, and the first additive is not added. The second additive includes: PS and FEC, the addition amount of PS is 3wt% of the total mass of the electrolyte, and the addition amount of FEC is 1wt% of the total mass of the electrolyte.

[0106] The process parameters of each embodiment and comparative example are shown in Table 1 (unit: wt %).

[0107] Table 1

[0108]

[0109]

[0110] The batteries prepared in each embodiment and comparative example were subjected to electrolyte wetting performance test, direct current resistance (DCR) test and safety performance test respectively, and the test methods are as follows:

[0111] (1) Electrolyte wetting performance test: During the injection phase of the battery preparation process, measure the same weight of electrolyte and inject the electrolyte into the battery cell, and record the time required for the electrolyte to be completely injected into the battery.

[0112] (2) DCR test: The batteries in each embodiment and comparative example were subjected to DCR test, and the number of test batteries was 8 respectively, and the average value of DCR of the 8 batteries was finally taken. The specific test process is: the temperature of the thermostat is set to 25±5℃, the battery is placed in the thermostat, and when the SOC of the battery is adjusted to 50%, the battery is discharged at a current of 30AH for 10 seconds, and the DCR value is calculated. Among them, DCR refers to the DC internal resistance of the battery, which represents the ratio of the voltage change of the battery under working conditions to the corresponding current change, usually in ohms (Ω); SOC represents the state of charge of the battery; 30AH represents the amount of electricity that can be achieved by continuous charging for 1 hour with a current of 30A.

[0113] (3) Battery safety test: The batteries in each embodiment and comparative example were subjected to an overcharge combustion test and a needle puncture combustion test, respectively, with 5 batteries tested.

[0114] The specific steps of the overcharged battery combustion test are: first, correctly install the battery on the battery charge and discharge tester, start the battery charge and discharge tester, charge the battery to 4.35V at a constant current of 5A, then charge the battery to 0.25A at a constant voltage of 4.35V, and finally let it stand for 2 hours to observe whether the battery has thermal runaway, explosion, combustion, etc.

[0115] The specific steps of the needle-puncture battery combustion test are as follows: place the battery on a stable test bench, use a high-temperature resistant steel needle with a diameter of 5mm to 8mm to penetrate the battery at a speed of 20 to 30mm / s from a direction perpendicular to the battery plate, leave the steel needle in the battery, let it stand for 1 hour, and observe whether the battery burns. The angle of the high-temperature resistant steel needle tip is 60°, and the surface of the steel needle is smooth and free of rust, oxide layer, oil and other pollutants.

[0116] The specific electrolyte wetting performance test data is shown in Table 2 below:

[0117] Table 2

[0118]

[0119]

[0120] It can be seen from the test results in Table 2 that when 42g of battery electrolyte is injected into the battery cell, the injection time used by the electrolyte in Examples 1 to 25 is less than that of the electrolyte in Comparative Example 1, which shows that the electrolyte in Examples 1 to 25 has better wettability with the surface of the electrode material. Specifically, in Examples 1 to 25, by selecting fluoropolyoxyethylene ether as the first additive, the surface tension of the electrolyte can be reduced, making it easier for the electrolyte to spread and penetrate on the surface of the electrode material, thereby improving the wettability of the electrolyte. Moreover, as the content of the first additive added to the battery electrolyte increases from 0.1wt% to 2wt%, the time required for the electrolyte to be completely injected into the battery cell shows a decreasing trend, which shows that the increase in the content of the first additive can effectively reduce the surface tension of the electrolyte, thereby further increasing the wettability of the electrolyte.

[0121] Table 3

[0122]

[0123]

[0124]

[0125] As shown in Table 3, it can be seen from the test results that the average DCR of the battery in Example 1-Example 25 is lower than the average DCR of the battery in Comparative Example 1, and as the content of the first additive added increases (0.1wt%≤first additive content≤2wt%), the average DCR of the battery decreases accordingly. Combined with Table 1, it can be seen that the electrolyte in Example 1-Example 25 has good wettability, which enables the electrolyte to fully contact with the electrode material, improves the transmission effect of ions inside the battery, and then reduces the internal resistance of the battery, thereby improving the rate performance of the battery, and as the content of the first additive increases, the internal resistance of the battery can be further reduced.

[0126] Table 4

[0127]

[0128]

[0129] It can be seen from the test results in Table 4 that the number of batteries that burned in the needle puncture battery combustion test and the number of batteries that burned in the overcharge battery test in Examples 1 to 25 is significantly less than that in Comparative Example 1, which shows that the safety performance of the battery is significantly improved, and with the increase in the content of the first additive (0.1wt%≤first additive content≤2wt%), the number of batteries that burned in the needle puncture battery test and overcharge battery test is significantly reduced. This is because the first additive has a higher flash point, so that the battery electrolyte can be ignited at a higher temperature, thereby improving the flame retardant performance of the battery, thereby reducing the probability of battery combustion, and as the content of the first additive increases, the safety performance of the battery also increases.

[0130] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they are aware of the basic creative concept. Therefore, the claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the embodiments of the present invention.

[0131] The above is a detailed introduction to a battery electrolyte provided by the present application. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A battery electrolyte, characterized in that: include: A lithium salt, a first additive and an organic solvent, wherein the first additive is fluoropolyoxyethylene ether.

2. The battery electrolyte according to claim 1, characterized in that The molecular formula of the fluoropolyoxyethylene ether is: f X(CH2CH2O) n R1 or R f X(CHCH3CH2O) n R1; Among them, R f is a fluorinated alkyl group having 2-18 carbon atoms, X is selected from one of oxygen (-O-), sulfur (-S-), amine oxide (-NO-), amide (CO-NH) or sulfonamide (-SO2N-), R1 is an alkyl group having 1-4 carbon atoms, and the value of n is 1-25.

3. The battery electrolyte according to claim 1, characterized in that The content of the first additive in the electrolyte is 0.1 wt % to 2 wt %.

4. The battery electrolyte according to claims 1-3, characterized in that: The invention also includes a second additive, which includes at least one of propylene sulfite, vinyl sulfate, vinylene carbonate, fluoroethylene carbonate, lithium bis(oxalatoborate), lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethylsulfonate)imide.

5. The battery electrolyte according to claim 4, characterized in that: The content of the second additive in the electrolyte is 3wt% to 10wt%.

6. The battery electrolyte according to any one of claims 1 to 3, characterized in that: The content of the lithium salt in the electrolyte is 8 wt % to 20 wt %.

7. The battery electrolyte according to claim 6, characterized in that: The lithium salt includes at least one of lithium hexafluorophosphate, lithium tetrafluoroborate and lithium perchlorate.

8. The battery electrolyte according to any one of claims 1 to 3, characterized in that: The content of the organic solvent is 74 wt% to 85 wt%.

9. The battery electrolyte according to claim 8, characterized in that: The organic solvent includes two or more of diethyl carbonate, ethyl methyl carbonate, dimethyl carbonate, ethylene carbonate, vinylene carbonate and vinyl vinylene carbonate.

10. A battery, characterized in that: Comprising the battery electrolyte as claimed in any one of claims 1 to 9.

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