Ether-based electrolyte and its use in batteries

Abstract

The present disclosure provides an ether-based electrolyte and its application in batteries, wherein the ether-based electrolyte comprises: an ether-based solvent and an electrolyte salt; the ether-based solvent comprises ether-based solvent A or ether-based solvent B, the general structural formula of the ether-based solvent A is: the general structural formula of the ether-based solvent B is: wherein n is 3-4, m is 1-3, and R is independently selected from any one of methyl, ethyl, chlorine, fluorine, monochloromethyl, dichloromethyl, trichloromethyl, monofluoromethyl, difluoromethyl, trifluoromethyl, monofluoroethyl, difluoroethyl and trifluoroethyl.

Description

TECHNICAL FIELD

[0001] The present disclosure belongs to the field of batteries, and particularly relates to an ether-based electrolyte and application thereof in batteries. BACKGROUND

[0002] Lithium metal battery (LMB) has characteristics such as high energy density, and is a very promising next-generation energy storage battery system. Compared with the traditional graphite negative electrode, lithium metal has attracted the attention of many scholars and companies due to its high theoretical specific capacity (3860 mAh g -1 ) and low standard electrode potential (-3.04 V, relative to the standard hydrogen electrode). By matching lithium metal with some high-voltage and high-capacity positive electrode materials, a lithium metal battery with high energy density can be obtained.

[0003] Currently, there are two types of electrolyte solutions commonly used in lithium metal batteries: carbonate and ether-based electrolytes. Organic carbonate electrolytes are often used in high-voltage lithium metal batteries due to their excellent oxidation stability (>4.5 V, relative to Li / Li + ). However, due to the strong reactivity of carbonate electrolytes with lithium metal, continuous side reactions can easily lead to a decrease in lithium metal coulombic efficiency (CE) and affect the long cycle stability of the lithium metal electrode.

[0004] Ether-based electrolytes are currently known to have good compatibility with lithium metal, and have good lithium metal coulombic efficiency and the ability to inhibit lithium dendrite growth, making them very suitable for lithium metal batteries. However, ether-based electrolytes have low oxidation stability (<4 V, relative to Li / Li + ), and are easily oxidized and decomposed on the surface of high-voltage positive electrodes. When the salt concentration of ether-based electrolytes is 1 M, they cannot be applied to other high-voltage positive electrode materials (such as high-nickel LiNi 0.8 Mn 0.1 Co 0.1 O2(NMC811) positive electrodes), which in turn limits the application of ether-based electrolytes in the field of high-voltage batteries. SUMMARY

[0005] In view of the above technical problems, the present disclosure provides an ether-based electrolyte and application thereof in batteries, in order to at least partially solve the above technical problems.

[0006] In order to solve the above technical problems, as one aspect of the present disclosure, an ether-based electrolyte is provided, comprising:

[0007] an ether-based solvent and an electrolyte salt;

[0008] The ether-based solvent includes ether-based solvent A or ether-based solvent B, and the structure general formula of the ether-based solvent A is:

[0009]

[0010] The ether solvent B has the following general structure:

[0011]

[0012] wherein n is 3-4, m is 1-3, and R is independently selected from any one of methyl, ethyl, chloro, fluoro, monochloromethyl, dichloromethyl, trichloromethyl, monofluoromethyl, difluoromethyl, trifluoromethyl, monofluoroethyl, difluoroethyl, trifluoroethyl.

[0013] In one embodiment, the ether electrolyte further comprises a diluent.

[0014] In one embodiment, the ether solvent A or the ether solvent B comprises at least one of the following:

[0015] 1,4-dimethoxybutane, 1,3-dimethoxypropane, 1,3-diethoxypropane, 1,3-bis(chloromethoxy)propane, 1-methoxy-3-(3-methoxypropoxy)propane, 2,6,10,14-tetraoxypentadecane.

[0016] In one embodiment, the electrolyte salt comprises any one or more of lithium salt, sodium salt, potassium salt, magnesium salt, zinc salt.

[0017] In one embodiment, the lithium salt comprises any one or more of the following:

[0018] LiPF6, LiBF4, Li2SO4, LiClO4, LiNO3, LiCF3SO3, Li(CF3SO2)2N, Li(FSO2)2N, Li(CF3CF2SO2)2N;

[0019] The sodium salt comprises any one or more of the following:

[0020] NaClO4, NaNO3, NaF, Na(FSO2)2N, Na(CF3CF2SO2)2N, NaPF6, Na2SO4, NaCF3SO3;

[0021] The potassium salt comprises any one or more of the following:

[0022] KNO3, KClO4, KPF6, K(FSO2)2N, K(CF3SO2)2N, K2SO4;

[0023] The magnesium salt comprises any one or more of the following:

[0024] Mg(CF3SO3)2, MgCl2, MgSO4;

[0025] The above-mentioned zinc salt includes any one or more of the following:

[0026] Zn(CF3SO3)2, ZnSO4, Zn(CH3OO)2.

[0027] In one embodiment, the molar ratio of the above-mentioned ether solvent A or the above-mentioned ether solvent B to the above-mentioned electrolyte salt is 1:0.2-5.

[0028] In one embodiment, the above-mentioned diluent includes at least one of the following:

[0029] 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1-(2,2,2-trifluoroethoxy)-1,1,2,2-tetrafluoroethane, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, bis(2,2,2-trifluoroethyl) ether, tris(2,2,2-trifluoroethyl) orthoformate, 1H,1H,5H-octafluoropentyl acrylate-1,1,2,2-tetrafluoroethyl ether, fluorobenzene, 1,3,5-trifluorobenzene.

[0030] In one embodiment, the mass percentage of the above-mentioned ether solvent A or the above-mentioned ether solvent B in the above-mentioned ether electrolyte is 1%-100%wt.

[0031] In one embodiment, the molar ratio of the above-mentioned ether solvent A or the above-mentioned ether solvent B, the electrolyte salt, and the diluent includes 1:(0.2-5):(1-10).

[0032] As another aspect of the present disclosure, there is also provided an application of the ether electrolyte in a battery, including using the above-mentioned ether electrolyte, wherein the battery includes a lithium metal battery, a lithium ion battery, a sodium metal battery, a sodium ion battery, a potassium metal battery, a potassium ion battery, a magnesium metal battery, a zinc metal battery.

[0033] Based on the above technical solutions, the ether electrolyte and its application in a battery provided by the present disclosure at least have one of the following beneficial effects:

[0034] (1) In the embodiments of the present disclosure, an ether electrolyte containing ether solvent A or ether solvent B and an electrolyte salt is provided, and by adjusting the number of intermediate carbon atoms in the ether chain of the ether solvent A or the ether solvent B and adjusting the ratio of the ether solvent A or the ether solvent B to the electrolyte salt, the stability of the ether electrolyte against oxidation can be optimized.

[0035] (2) In the embodiments of the present disclosure, an ether-based electrolyte containing ether solvent A or ether solvent B, electrolyte salt and diluent is also provided. By adjusting the number of intermediate carbon atoms in the ether chain of ether solvent A or ether solvent B, and adjusting the ratio of ether solvent A or ether solvent B, electrolyte salt and diluent, the oxidation resistance and high voltage resistance (up to 4.7V) of the ether-based electrolyte can be further improved, thereby improving the coulombic efficiency of the lithium metal battery. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 is a long cycle stability graph of the ether-based electrolyte in Examples 1-2 and Comparative Example 1 of the present disclosure at 4.7V voltage Li||single crystal NMC811 battery;

[0037] Figure 2 is a coulombic efficiency graph of the ether-based electrolyte in Examples 1-2 and Comparative Example 1 of the present disclosure at 4.7V voltage Li||single crystal NMC811 battery;

[0038] Figure 3A is the first cycle charge-discharge curve graph of the ether-based electrolyte in Comparative Example 1 of the present disclosure at 4.7V voltage Li||single crystal NMC811 battery;

[0039] Figure 3B is the first cycle charge-discharge curve graph of the ether-based electrolyte in Example 2 of the present disclosure at 4.7V voltage Li||single crystal NMC811 battery;

[0040] Figure 3C is the first cycle charge-discharge curve graph of the ether-based electrolyte in Example 1 of the present disclosure at 4.7V voltage Li||single crystal NMC811 battery;

[0041] Figure 4 is a slow charge and fast discharge performance graph of the ether-based electrolyte in Examples 1-2 and Comparative Example 1 of the present disclosure at 4.7V voltage Li||polycrystal NMC811 battery;

[0042] Figure 5 is a fast charge and slow discharge performance graph of the ether-based electrolyte in Examples 1-2 and Comparative Example 1 of the present disclosure at 4.7V voltage Li||polycrystal NMC811 battery;

[0043] Figure 6 is a leakage current test graph of the ether-based electrolyte in Examples 1-2 and Comparative Example 1 of the present disclosure at 4.7V voltage Li||single crystal NMC811 battery;

[0044] Figure 7 is a long cycle stability graph of the ether-based electrolyte in Example 3 of the present disclosure at 4.7V voltage Li||single crystal NMC811 battery;

[0045] Figure 8is the first cycle charge-discharge curve of the Li||single crystal NMC811 battery of the ether-based electrolyte in Example 4 of the present disclosure at a voltage of 4.7V.

[0046] Figure 9 is the long cycle stability graph of the Li||single crystal NMC811 battery of the ether-based electrolyte in Example 5 of the present disclosure at a voltage of 4.7V. DETAILED DESCRIPTION

[0047] In order to make the purpose, technical solutions and advantages of the present disclosure clearer, the present disclosure will be further described in detail below in combination with specific embodiments.

[0048] Based on the low oxidation stability of the ether-based electrolyte in the prior art, when the concentration of the ether-based electrolyte is 1M, the ether-based electrolyte is not suitable for use with other higher voltage cathode materials, which limits the application of the ether-based electrolyte in batteries. Therefore, the present disclosure provides an ether-based electrolyte and its application in batteries, in order to realize that the ether-based electrolyte can have high oxidation resistance, high voltage resistance during the application of the cathode material, and improve the coulomb efficiency and long cycle stability of the battery during actual application.

[0049] According to an embodiment of the present disclosure, an ether-based electrolyte is provided, comprising: an ether-based solvent and an electrolyte salt; the ether-based solvent comprises ether-based solvent A or ether-based solvent B, and the structural general formula of the ether-based solvent A is:

[0050]

[0051] The structural general formula of the ether-based solvent B is:

[0052]

[0053] wherein n is 3-4, m is 1-3, and R is independently selected from any one of methyl, ethyl, chlorine, fluorine, monochloromethyl, dichloromethyl, trichloromethyl, monofluoromethyl, difluoromethyl, trifluoromethyl, monofluoroethyl, difluoroethyl and trifluoroethyl.

[0054] In the embodiment of the present disclosure, the ether-based electrolyte composed of the ether-based solvent A or the ether-based solvent B and the electrolyte salt can optimize the oxidation resistance stability of the ether-based electrolyte by adjusting the number of intermediate carbon atoms in the ether chain of the ether-based solvent A or the ether-based solvent B.

[0055] According to an embodiment of the present disclosure, the ether-based electrolyte further comprises a diluent, i.e., the ether-based electrolyte can also be composed of the ether-based solvent A or the ether-based solvent B, the electrolyte salt and the diluent.

[0056] According to embodiments of the present disclosure, the ether solvent A or the ether solvent B includes at least one of 1,4-dimethoxybutane, 1,3-dimethoxypropane, 1,3-diethoxypropane, 1,3-bis(chloromethoxy)propane, 1-methoxy-3-(3-methoxypropoxy)propane, 2,6,10,14-tetraoxypentadecane. For the ether solvent A consisting of other R groups, no more specific limitations are made here.

[0057] According to embodiments of the present disclosure, the electrolyte salt includes any one or more of lithium salt, sodium salt, potassium salt, magnesium salt, zinc salt.

[0058] According to embodiments of the present disclosure, the lithium salt includes any one or more of LiPF6, LiBF4, Li2SO4, LiClO4, LiNO3, LiCF3SO3, Li(CF3SO2)2N, Li(FSO2)2N, Li(CF3CF2SO2)2N.

[0059] According to embodiments of the present disclosure, the sodium salt includes any one or more of NaClO4, NaNO3, NaF, Na(FSO2)2N, Na(CF3CF2SO2)2N, NaPF6, Na2SO4, NaCF3SO3.

[0060] According to embodiments of the present disclosure, the potassium salt includes any one or more of KNO3, KClO4, KPF6, K(FSO2)2N, K(CF3SO2)2N, K2SO4.

[0061] According to embodiments of the present disclosure, the magnesium salt includes any one or more of Mg(CF3SO3)2, MgCl2, MgSO4.

[0062] According to embodiments of the present disclosure, the zinc salt includes any one or more of Zn(CF3SO3)2, ZnSO4, Zn(CH3OO)2.

[0063] According to embodiments of the present disclosure, the molar ratio of the ether solvent A or the ether solvent B and the electrolyte salt is 1:0.2-5, which can be optionally 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:1, 1:1.5, 1:2, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, etc.

[0064] In the embodiments of the present disclosure, according to the different solubilities of the electrolyte salt in the ether solvent A or the ether solvent B, there are different ratios between the ether solvent A or the ether solvent B and the electrolyte salt, and when the molar ratio of the ether solvent A or the ether solvent B to the electrolyte salt is low, that is, the content of the ether solvent A or the ether solvent B in the ether electrolyte is low, it is helpful to improve the oxidation resistance of the ether electrolyte.

[0065] According to the embodiments of the present disclosure, the diluent includes at least one of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1-(2,2,2-trifluoroethoxy)-1,1,2,2-tetrafluoroethane, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, bis(2,2,2-trifluoroethyl) ether, tris(2,2,2-trifluoroethyl) orthoformate, 1H,1H,5H-octafluoropentyl acrylate-1,1,2,2-tetrafluoroethyl ether, fluorobenzene, 1,3,5-trifluorobenzene.

[0066] In the embodiments of the present disclosure, the ether electrolyte composed of the ether solvent A or the ether solvent B, the electrolyte salt and the diluent, the viscosity of the ether electrolyte can be reduced by using the diluent, and the ion conductivity and the wettability of the metal electrode and the electrolyte are improved.

[0067] According to the embodiments of the present disclosure, in the ether electrolyte composed of the ether solvent A or the ether solvent B, the electrolyte salt and the diluent, the mass percentage of the ether solvent A or the ether solvent B in the ether electrolyte is 1%-100%wt, which can be 1%, 2%, 3%, 4%, 5%, 10%, 15%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%wt, etc.

[0068] According to the embodiments of the present disclosure, the molar ratio of the ether solvent A or the ether solvent B, the electrolyte salt and the diluent includes 1:(0.2-5):(1-10), and the molar ratio can be 1:0.64:3, 1:0.70:3, 1:0.75:3, 1:0.80:3, 1:0.85:3, 1:0.90:3, 1:0.95:3, 1:1.0:3, 1:1:3, 1:2:3, 1:2:4, 1:2:5, 1:2:6, 1:2:7, 1:2:8, 1:2:9, 1:2:10, 1:3:2, 1:3:5, 1:5:4, 1:5:6, 1:4:8, etc.

[0069] In the embodiments of the present disclosure, according to the different solubilities of the electrolyte salt in the ether solvent A or the ether solvent B and the diluent, there are different mass percentages and molar ratios of the ether solvent A or the ether solvent B in the ether electrolyte, and when the content of the ether solvent A or the ether solvent B in the ether electrolyte is reduced, it is helpful to improve the oxidation resistance of the ether electrolyte.

[0070] According to an embodiment of the present disclosure, the ether-based electrolyte has a use voltage greater than or equal to 4.2 V, and can be up to 4.7 V.

[0071] According to an embodiment of the present disclosure, the ether-based electrolyte is also provided for use in a battery, wherein the battery is any one of a lithium metal battery, a lithium ion battery, a sodium metal battery, a sodium ion battery, a potassium metal battery, a potassium ion battery, a magnesium metal battery, and a zinc metal battery.

[0072] According to an embodiment of the present disclosure, the battery comprises a positive electrode material, a negative electrode material, and the ether-based electrolyte.

[0073] According to an embodiment of the present disclosure, the negative electrode material comprises Li metal.

[0074] According to an embodiment of the present disclosure, the positive electrode material comprises a positive electrode active material, wherein the positive electrode active material comprises a positive electrode active material with a thermodynamic electrochemical potential greater than 4.2 V.

[0075] According to an embodiment of the present disclosure, the positive electrode active material is at least one of LiNi 0.8 Co 0.1 Mn 0.1 O2, LiMn2O4, LiMnO4, LiMnO, and LiMnO3.

[0076] In an embodiment of the present disclosure, the ether-based electrolyte is used in the field of lithium metal batteries, which can improve the oxidation resistance and high voltage resistance (up to 4.7 V) of lithium metal batteries, and further improve the coulomb efficiency and long-term cycle stability in the actual application process of lithium metal batteries.

[0077] The technical solutions of the present disclosure are further described and illustrated below by specific embodiments in conjunction with the accompanying drawings. It should be noted that the specific embodiments described below are only illustrative, and the protection scope of the present disclosure is not limited thereto. The chemical reagents and raw materials used in the following embodiments are commercially available or self-made by known preparation methods.

[0078] Comparative Example

[0079] Comparative Example 1

[0080] Comparative Example 1 provides an ether-based electrolyte, which is composed of an ether-based solvent A, an electrolyte salt, and a diluent, wherein the ether-based solvent A is 1,2-dimethoxyethane, the electrolyte salt is lithium bisfluorosulfonylimide, and the diluent is 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether.

[0081] The local high-concentration ether-based electrolyte is prepared by taking lithium bisfluorosulfonylimide, adding 1,2-dimethoxyethane with a mass percentage of about 10% wt, and diluent.

[0082] Embodiment

[0083] Embodiment 1

[0084] The ether-based electrolyte provided by Embodiment 1 is composed of ether-based solvent A, electrolyte salt and diluent, wherein the ether-based solvent A is 1,3-dimethoxypropane, the electrolyte salt is lithium bisfluorosulfonylimide, and the diluent is 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether.

[0085] The local high-concentration ether-based electrolyte is prepared by taking lithium bisfluorosulfonylimide, adding 1,3-dimethoxypropane with a mass percentage of about 10% wt, and diluent.

[0086] Embodiment 2

[0087] The ether-based electrolyte provided by Embodiment 2 is composed of ether-based solvent A, electrolyte salt and diluent, wherein the ether-based solvent A is 1,4-dimethoxybutane, the electrolyte salt is lithium bisfluorosulfonylimide, and the diluent is 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether.

[0088] The local high-concentration ether-based electrolyte is prepared by taking lithium bisfluorosulfonylimide, adding 1,4-dimethoxybutane with a mass percentage of about 12% wt, and diluent.

[0089] The ether-based electrolytes in Embodiments 1-2 are selected as research objects, and Comparative Example 1 is used as a control group. 0.8 Co 0.1 Mn 0.1 O2)(2mAh cm -2 ) as the positive electrode, and Li metal (450 μm) as the negative electrode to prepare a battery. The lithium metal batteries prepared by using the ether-based electrolytes in Embodiments 1-2 and Comparative Example 1 are subjected to a charge-discharge program at a voltage of 4.7 V, so as to test the cycle stability of the lithium metal batteries in the ether-based electrolytes. The specific test results are shown in Table 1. Figure 1

[0090] Figure 1 ​is a long cycle stability graph of the ether-based electrolyte in Examples 1-2 and Comparative Example 1 of the present disclosure for Li||single crystal NMC811 battery at 4.7V voltage.

[0091] As shown in Figure 1 , the capacity of the battery in Comparative Example 1 is only 4% after 150 cycles. It is worth noting that the capacity of the battery in Example 2 decays faster in the first 50 cycles, indicating that the ether-based electrolyte in Example 2 has poorer oxidation resistance. In order to explore whether it is the cathode material (single crystal NMC811) in Example 2 that causes the sharp decline in battery capacity, the battery after 50 cycles was replaced with a new Li electrode and subjected to long-term cycle test again, and it was found that the cycle stability of the battery in Example 2 did not recover after replacing the new Li electrode, but instead continued to decline, indicating that the cathode in Example 2 had a more serious side reaction, causing the sharp decline in lithium metal battery capacity. Compared with Examples 2 and Comparative Example 1, the capacity retention rate of Li||single crystal NMC811 battery in Example 1 is as high as 87% after 150 cycles at 4.7V voltage, indicating that the ether-based electrolyte in Example 1 has higher oxidation resistance, which may form an excellent protective layer, thereby making the single crystal NMC811 have good stability.

[0092] Figure 2 is a coulombic efficiency graph of the ether-based electrolyte in Examples 1-2 and Comparative Example 1 of the present disclosure for Li||single crystal NMC811 battery at 4.7V voltage.

[0093] As shown in Figure 2 , compared with the coulombic efficiency of the ether-based electrolyte in Comparative Example 1 and Example 2, the ether-based electrolyte battery in Example 1 has a higher coulombic efficiency of 99.5% at 4.7V voltage, while the coulombic efficiency of the ether-based electrolyte batteries in Comparative Example 1 and Example 2 is only 95.6% and 94.1%, respectively. The higher coulombic efficiency of the electrolyte in Example 1 also corresponds to its better long cycle stability.

[0094] Figure 3A is a first cycle charge-discharge curve graph of the ether-based electrolyte in Comparative Example 1 of the present disclosure for Li||single crystal NMC811 battery at 4.7V voltage; Figure 3B is a first cycle charge-discharge curve graph of the ether-based electrolyte in Example 2 of the present disclosure for Li||single crystal NMC811 battery at 4.7V voltage; Figure 3C is a first cycle charge-discharge curve graph of the ether-based electrolyte in Example 1 of the present disclosure for Li||single crystal NMC811 battery at 4.7V voltage.

[0095] As shown in Figures 3A-3CAs shown, when the voltage reaches 4.7 V, the ether electrolyte batteries of Comparative Example 1 and Example 2 show obvious overcharging due to electrolyte decomposition. This serious electrolyte decomposition not only leads to a large reduction in the amount of electrolyte in the battery, but also causes the acidic substances produced by electrolyte decomposition to cause obvious rupture of the positive monocrystal NMC811 particles, further inducing the dissolution of transition metals from the interior of the positive electrode particles, thereby causing a more serious attenuation of the first cycle discharge capacity. This serious side reaction exacerbates the accumulation of side reactions during the later cycles of the battery. The ether electrolyte in Example 1 does not show overcharging, indicating that the ether electrolyte in Example 1 does not show obvious side reactions with the positive electrode at high voltage, indicating that the ether electrolyte in Example 1 has stronger oxidation resistance than the ether electrolytes in Comparative Example 1 and Example 2.

[0096] To study the charge-discharge performance of ether electrolyte batteries at different rates, the ether electrolytes in Examples 1-2 were selected as the research object, and Comparative Example 1 was used as the control group. Polycrystalline NMC811 (LiNi 0.8 Co 0.1 Mn 0.1 O2)(2mAh cm -2 ) was used as the positive electrode, and Li metal (450μm) was used as the negative electrode to make batteries. At a voltage of 4.7 V, the batteries made of ether electrolytes in Examples 1-2 and Comparative Example 1 were subjected to charge-discharge procedures to test the rate performance of the batteries under different rates of ether electrolytes. The specific test results are shown in Figure 4 and Figure 5 , wherein the ether electrolyte in the lithium metal battery is 75μL.

[0097] First, Examples 1-2 and Comparative Example 1 were subjected to the same rate of charging (1 / 3C) and different rates of discharging. The specific results are shown in Figure 4 .

[0098] Figure 4 is the slow charging and fast discharging performance of the Li||polycrystalline NMC811 battery of the ether electrolytes in Examples 1-2 and Comparative Example 1 at a voltage of 4.7 V.

[0099] In Figure 4 , it can be found that the specific capacity of the ether electrolyte battery of Comparative Example 1 is less than 50mAh g -1 under the condition of 4C fast discharge, while the specific capacity of the ether electrolyte battery of Example 2 is 5mAh g -1 ; this phenomenon is due to the serious decomposition of the electrolytes in Comparative Example 1 and Example 2 at 4.7 V, which causes the positive electrode interfacial impedance to increase sharply, resulting in a cliff-like decrease in rate performance. The specific capacity of the ether electrolyte battery of Example 1 is as high as 180mAh g -1The main reason is that the ether electrolyte in Example 1 has strong antioxidant capacity and high ionic conductivity.

[0100] Secondly, Examples 1-2 and Comparative Example 1 were charged at different rates and discharged at the same rate (1 / 3C). Specific test results are as follows: Figure 5 As shown.

[0101] Figure 5 The graphs show the fast charge and slow discharge performance of Li|| polycrystalline NMC811 batteries with ether electrolytes in Examples 1-2 and Comparative Example 1 at 4.7V.

[0102] like Figure 5 As shown, under 4C fast charging conditions, the specific capacity of the ether electrolyte batteries in Comparative Example 1 and Example 2 is less than 10 mAh g. -1 In Example 1, the ether electrolyte achieved a specific capacity of 147 mAh g under rapid discharge conditions at 4C. -1 .

[0103] To better illustrate the high antioxidant capacity of the ether electrolyte in Example 1, the leakage current performance of the batteries containing the ether electrolytes of Examples 1-2 and Comparative Example 1 was investigated. Leakage current accurately reflects the reaction between the electrolyte and the positive electrode; a lower leakage current indicates fewer side reactions between the positive electrode and the electrolyte. The ether electrolytes of Examples 1-2 were selected as the research object, and the ether electrolyte of Comparative Example 1 was used as the control group. Single-crystal NCM811 (LiNi) was used as the control. 0.8 Co 0.1 Mn 0.1 O2)(2mAh cm -2 A battery was fabricated using a positive electrode (P) and a negative electrode (Li metal, 450 μm). Constant potential testing was then conducted, and the specific results are as follows: Figure 6 As shown.

[0104] Figure 6 These are leakage current test diagrams of Li|| monocrystalline NMC811 batteries with ether electrolytes in Examples 1-2 and Comparative Example 1 of this disclosure at a voltage of 4.7V.

[0105] like Figure 6 As shown, leakage current tests on the ether electrolyte batteries in Examples 1-2 and Comparative Example 1 revealed that Example 1 exhibited a lower leakage current, with a leakage current density of approximately 28 μA / cm². 2 Comparative Example 1 shows the largest leakage current, with a leakage current density of approximately 92 μA / cm². 2 Secondly, the leakage current density in Example 2 was 51 μA / cm. 2This fully demonstrates that the ether electrolyte in Example 1 has the least side reaction with the positive electrode, so that the ether electrolyte has strong oxidation resistance, and the experimental results are consistent with the above experimental results.

[0106] Example 3

[0107] Example 3 provides an ether electrolyte, which is composed of ether solvent A and electrolyte salt, wherein the ether solvent A is 1,3-dimethoxypropane, and the electrolyte salt is lithium bisfluorosulfonylimide.

[0108] Lithium bisfluorosulfonylimide is weighed, 1,3-dimethoxypropane with a mass percentage of 36%wt is added, and a diluent is prepared into an ether electrolyte with an ultra-concentrated concentration, wherein the molar ratio of the ether solvent A and the electrolyte salt in Example 3 is 1:1.

[0109] The ether electrolyte in Example 3 is selected as the research object, and a single crystal NCM811 (LiNi 0.8 Co 0.1 Mn 0.1 O2)(2mAh cm -2 ) is used as the positive electrode, and Li metal (450μm) is used as the negative electrode to make an ether electrolyte battery. The ether electrolyte battery in Example 3 is subjected to a charge-discharge program at a voltage of 4.7V, and the long cycle performance of the battery is tested, and the specific test results are shown in Figure 7 , wherein the ether electrolyte is 75μL.

[0110] Figure 7 is a long cycle stability diagram of the ether electrolyte in Example 3 of the present disclosure at a voltage of 4.7V Li||single crystal NMC811 battery.

[0111] As shown in Figure 7 , it is found that even under the ether electrolyte system at a higher concentration, the ether electrolyte battery in Example 3 still has a high capacity retention rate of about 97.5% after 50 cycles, which indicates that the lithium metal battery in Example 3 exhibits high high-voltage (4.7V) resistance even without using a diluent.

[0112] In order to explore the influence of other diluents on the oxidation resistance of the ether electrolyte, Example 4 is explored.

[0113] Example 4

[0114] Example 4 provides an ether electrolyte, which is composed of ether solvent A, electrolyte salt and diluent, wherein the ether solvent A is 1,3-dimethoxypropane, the electrolyte salt is lithium bisfluorosulfonylimide, and the diluent is 1-(2,2,2-trifluoroethoxy)-1,1,2,2-tetrafluoroethane.

[0115] Lithium bisfluorosulfonylimide was weighed, 1,3-dimethoxypropane was added at 11wt%, and a diluent was added to prepare a local high-concentration ether-based electrolyte, wherein the molar ratio of the ether-based solvent A, the electrolyte salt, and the diluent was 1:1:3 (the concentration of the ether-based electrolyte was about 1.2M).

[0116] The ether-based electrolyte in Example 4 was selected as the research object, and single-crystal NCM811 (LiNi 0.8 Co 0.1 Mn 0.1 O2) (2mAh cm -2 ) was used as the positive electrode, and Li metal (450μm) was used as the negative electrode to prepare an ether-based electrolyte battery. The ether-based electrolyte battery in Example 4 was subjected to a charge-discharge program at a voltage of 4.7V, and the long cycle performance of the battery was tested, and the specific test results are shown in Figure 8 , wherein the amount of the ether-based electrolyte was 75μL.

[0117] Figure 8 is the first cycle charge-discharge curve of the Li||single-crystal NMC811 battery of the ether-based electrolyte in Example 4 at a voltage of 4.7V.

[0118] As shown in Figure 8 , another diluent was used to prepare an ether-based electrolyte, and compared with Example 1 and Comparative Example 1, Example 4 did not have obvious overcharging in the first cycle, indicating that the ether-based electrolyte prepared by replacing a kind of diluent also had good oxidation resistance at a high voltage of 4.7V.

[0119] Example 5

[0120] Example 5 provides an ether-based electrolyte, which is composed of an ether-based solvent B, an electrolyte salt, and a diluent, wherein the ether-based solvent B is 1-methoxy-3-(3-methoxypropoxy)propane, the electrolyte salt is lithium bisfluorosulfonylimide, and the diluent is 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether.

[0121] Lithium bisfluorosulfonylimide was weighed, 1-methoxy-3-(3-methoxypropoxy)propane was added at about 10wt%, and a diluent was added to prepare a local high-concentration ether-based electrolyte, wherein the molar ratio of the ether-based solvent B, the electrolyte salt, and the diluent was 1:1:3 (the concentration of the ether-based electrolyte was about 1M).

[0122] The ether-based electrolyte in Example 5 was selected as the research object, and single-crystal NCM811 (LiNi 0.8 Co 0.1 Mn 0.1 O2) (2mAh cm -2) is positive electrode, Li metal (450 μm) is negative electrode to make ether-based electrolyte battery. The ether-based electrolyte battery in example 5 is subjected to charge-discharge program at 4.7 V voltage, and the long cycle performance of the battery is tested, and the specific test results are as shown in Figure 9 Figure 5, wherein the ether-based electrolyte is 75 μL.

[0123] Figure 9 is the long cycle stability diagram of the ether-based electrolyte in example 5 of the present disclosure at 4.7 V voltage Li||single crystal NMC811 battery.

[0124] As shown in Figure 9 Figure 5, the capacity retention rate of the ether-based electrolyte in example 5 is 80% after 150 cycles at high voltage of 4.7 V, which shows good oxidation resistance. And this ether-based electrolyte with good oxidation resistance is mainly due to the extension of the ether chain of ether solvent B, which further reduces the highest occupied molecular orbital energy level of the ether solvent itself and promotes the formation of a more protective film, reducing the occurrence of side reactions between the ether-based electrolyte and the positive electrode.

[0125] The above specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present disclosure. It should be understood that the above description is only a specific embodiment of the present disclosure and is not intended to limit the present disclosure. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present disclosure shall be included in the protection scope of the present disclosure.

Claims

1. An ether-based electrolyte for use in lithium metal batteries, comprising an ether solvent, a diluent, and an electrolyte salt; in, The ether solvent is 1-methoxy-3-(3-methoxypropoxy)propane or 1,3-dimethoxypropane, and the ether solvent accounts for 10%-70% wt% of the ether electrolyte. The molar ratio of the ether solvent, electrolyte salt and diluent includes 1:(0.2~5):(1~10). The diluent comprises any one of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1-(2,2,2-trifluoroethoxy)-1,1,2,2-tetrafluoroethane, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, bis(2,2,2-trifluoroethyl) ether, tris(2,2,2-trifluoroethyl) orthoformate, 1H,1H,5H-octafluoropentyl acrylate-1,1,2,2-tetrafluoroethyl ether, fluorobenzene, and 1,3,5-trifluorobenzene; The ether-based electrolyte is suitable for high-voltage battery systems, including operating conditions up to 4.7V.

2. The ether electrolyte according to claim 1, wherein, The electrolyte salt is a lithium salt.

3. The ether electrolyte according to claim 2, wherein, The lithium salt includes any one or more of the following: LiPF6, LiBF4, Li2SO4, LiClO4, LiNO3, LiCF3SO3, Li(CF3SO2)2N, Li(FSO2)2N, Li(CF3CF2SO2)2N.

4. The application of an ether-based electrolyte in a battery, comprising using the ether-based electrolyte according to any one of claims 1-3, wherein, The battery is a lithium metal battery.

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