Ether electrolyte and lithium metal battery

Abstract

The present application relates to an ether electrolyte and a lithium metal battery. The ether electrolyte provided by the present application includes a solvent, a solute and a diluent; the solvent includes an ether solvent, and the ether solvent includes at least one of diethylene glycol dimethyl ether, triethylene glycol dimethyl ether or tetraethylene glycol dimethyl ether; the diluent includes at least one of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, bis(2,2,2-trifluoroethyl) ether, and octafluoropentyl-1,1,2,2-tetrafluoroethyl ether. The ether electrolyte of the present application includes a solvent, a solute and a diluent, and by making special restrictions on the type of solvent, it is possible to enhance the binding force between the solute and the solvent, improve the oxidative stability of the ether electrolyte, thereby being able to improve the operating voltage and cycle life of the electrolyte, and thus greatly improving the coulombic efficiency of the lithium metal battery.

Description

Technical Field

[0001] The present application relates to the field of energy storage, and in particular to an ether electrolyte and a lithium metal battery. Background Art

[0002] Lithium metal batteries have the characteristics of high energy density and excellent power performance, and have broad application prospects in mobile phones, laptops, power tools and electric vehicles.

[0003] Currently, the electrolytes used in lithium metal batteries include organic carbonate electrolytes and ether-based electrolytes. Carbonate electrolytes are more active than lithium, and the SEI generated on the surface of lithium metal is unstable, resulting in low lithium metal coulombic efficiency (CE) and affecting its cyclability. Therefore, the long-cycle stability performance of lithium metal batteries using organic carbonate electrolytes as electrolytes is not satisfactory. Ether-based electrolytes have the ability to obtain better lithium metal coulombic efficiency and inhibit the growth of lithium dendrites, and are very suitable for lithium metal batteries. However, due to the low oxidative stability of ether-based electrolytes, their application in high-voltage lithium metal batteries is limited. Summary of the Invention

[0004] In response to the shortcomings of the existing technology, the present application provides an ether electrolyte and a lithium metal battery. The ether electrolyte of the present application can enhance the binding force between the solute and the solvent by specifically limiting the type of solvent, thereby improving the oxidative stability of the ether electrolyte, thereby increasing the operating voltage and cycle life of the electrolyte, and further greatly improving the coulombic efficiency of the lithium metal battery.

[0005] A first aspect of the present application provides an ether electrolyte, comprising a solvent, a solute and a diluent; the solvent comprises an ether solvent, and the ether solvent comprises at least one of diethylene glycol dimethyl ether, triethylene glycol dimethyl ether or tetraethylene glycol dimethyl ether; the diluent comprises at least one of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, bis(2,2,2-trifluoroethyl) ether, and octafluoropentyl-1,1,2,2-tetrafluoroethyl ether.

[0006] Furthermore, the ether solvent is selected from triethylene glycol dimethyl ether.

[0007] Furthermore, the molar ratio of the solvent, solute and diluent is 1:(0.5-2):(0-10).

[0008] Preferably, the molar ratio of the solvent, solute and diluent is 1:(0.64-1.2):(1-10).

[0009] Furthermore, the molar ratio of the solvent, solute and diluent is 1:(0.64-1.2):3.

[0010] Furthermore, the operating voltage of the ether electrolyte is greater than or equal to 4.6V.

[0011] Furthermore, the solute is a lithium salt.

[0012] Furthermore, the lithium salt is selected from any one of LiPF6, LiBF4, LiTFSi, LiFSi or LiBOB.

[0013] Furthermore, the weight percentage of the ether solvent in the total solvent is 0.01% to 100%.

[0014] A second aspect of the present application provides a lithium metal battery comprising a positive electrode, a negative electrode and the above-mentioned ether electrolyte.

[0015] Furthermore, the positive electrode includes a positive electrode active material; the positive electrode active material includes at least one positive electrode active material having a thermodynamic electrochemical potential greater than 4.5V.

[0016] The beneficial effects of this application are:

[0017] The ether electrolyte provided by the present application includes a solvent, a solute and a diluent; the solvent includes an ether solvent, and the ether solvent includes at least one of diethylene glycol dimethyl ether, triethylene glycol dimethyl ether or tetraethylene glycol dimethyl ether; the diluent includes at least one of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, bis(2,2,2-trifluoroethyl) ether, and octafluoropentyl-1,1,2,2-tetrafluoroethyl ether. The ether electrolyte of the present application includes a solvent, a solute and a diluent. By making special restrictions on the type of solvent, the binding force between the solute and the solvent can be enhanced, and the oxidative stability of the ether electrolyte can be improved, thereby improving the operating voltage and cycle life of the electrolyte, and thus greatly improving the coulomb efficiency of the lithium metal battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Graph showing the long cycle stability of Li|| single crystal NMC811 batteries at 4.6 V for the ether electrolytes in Example 1, Example 3, Comparative Example 1, and Example 2;

[0019] Figure 2 Graph showing the long cycle stability of Li|| single crystal NMC811 batteries at 4.7 V for the ether electrolytes in Example 1, Example 3, Comparative Example 1, and Example 2;

[0020] Figure 3This is a charge-discharge curve of the first cycle of the Li|| single crystal NMC811 battery at a voltage of 4.7V using the ether electrolyte in Comparative Example 1;

[0021] Figure 4 This is the first cycle charge and discharge curve of the Li|| single crystal NMC811 battery at a voltage of 4.7V using the ether electrolyte in Example 1;

[0022] Figure 5 This is the first cycle charge and discharge curve of the Li|| single crystal NMC811 battery at a voltage of 4.7V using the ether electrolyte in Example 2;

[0023] Figure 6 This is the first cycle charge and discharge curve of the Li|| single crystal NMC811 battery at a voltage of 4.7V using the ether electrolyte in Example 3;

[0024] Figure 7 Graphs showing the long cycle stability of Li|| single crystal NMC811 batteries under harsh conditions for the ether electrolytes in Example 1, Example 3, Comparative Example 1, and Example 2;

[0025] Figure 8 Graph showing the long cycle stability of Li||polycrystalline NMC811 batteries at 4.7 V for the ether electrolytes in Example 1, Example 3, Comparative Example 1, and Example 2;

[0026] Figure 9 1 is a graph showing the long cycle stability of Li||lithium cobalt oxide batteries at a voltage of 4.6 V for the ether electrolyte in Comparative Example 1 and the ether electrolyte in Example 2;

[0027] Figure 10 1 is a self-discharge curve of a Li|| single crystal NMC811 battery at a voltage of 4.6 V for the ether electrolytes in Example 1, Example 3, Comparative Example 1, and Example 2;

[0028] Figure 11 This is a long cycle stability diagram of the Li|| high nickel NMC battery of Example 4 at a voltage of 4.6V using the ether electrolyte. DETAILED DESCRIPTION

[0029] For the sake of clarity, only some numerical ranges are specifically disclosed herein. However, any lower limit may be combined with any upper limit to form an unspecified range; and any lower limit may be combined with other lower limits to form an unspecified range, and similarly, any upper limit may be combined with any other upper limit to form an unspecified range. In addition, each individually disclosed point or single value may itself serve as a lower limit or upper limit and be combined with any other point or single value, or with other lower limits or upper limits, to form an unspecified range.

[0030] In the description herein, unless otherwise specified, “above” and “below” include the number itself.

[0031] Unless otherwise specified, the terms used in this application have the commonly understood meanings commonly understood by those skilled in the art. Unless otherwise specified, the numerical values ​​of the various parameters mentioned in this application can be measured using various measurement methods commonly used in the art (for example, they can be tested according to the methods given in the examples of this application).

[0032] The term "about" is used to describe and illustrate small variations. When used in conjunction with an event or situation, the term may refer to an example in which the event or situation occurs precisely as well as an example in which the event or situation occurs very approximately. For example, when used in conjunction with a numerical value, the term may refer to a range of variation less than or equal to ±10% of the numerical value, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%. In addition, amounts, ratios, and other numerical values ​​are sometimes presented in this article in a range format. It should be understood that such range formats are for convenience and brevity and should be flexibly understood to include not only the numerical values ​​explicitly designated as range limits, but also all individual numerical values ​​or subranges encompassed within the range, as if each numerical value and subrange were explicitly designated.

[0033] A list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single component or multiple components. Item B may contain a single component or multiple components. Item C may contain a single component or multiple components.

[0034] The present application will be further described below in conjunction with specific embodiments. It should be understood that these specific embodiments are only used to illustrate the present application and are not used to limit the scope of the present application.

[0035] 1. Ether electrolyte

[0036] The ether electrolyte provided by the present application includes a solvent, a solute and a diluent; the solvent includes an ether solvent, and the ether solvent includes at least one of diethylene glycol dimethyl ether, triethylene glycol dimethyl ether or tetraethylene glycol dimethyl ether; the diluent includes at least one of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, bis(2,2,2-trifluoroethyl) ether, and octafluoropentyl-1,1,2,2-tetrafluoroethyl ether. The ether electrolyte of the present application includes a solvent, a solute and a diluent. By making special restrictions on the type of solvent, the binding force between the solute and the solvent can be enhanced, and the oxidative stability of the ether electrolyte can be improved, thereby improving the operating voltage and cycle life of the electrolyte, and thus greatly improving the coulomb efficiency of the lithium metal battery.

[0037] According to some embodiments of the present application, the ether solvent is selected from triethylene glycol dimethyl ether. It can be understood that, compared with other ether solvents, the use of ether solvents including triethylene glycol dimethyl ether in lithium metal batteries enables lithium metal batteries to have excellent coulombic efficiency, while having better high voltage resistance and high temperature storage performance.

[0038] According to some embodiments of the present application, the molar ratio of the solvent, solute and diluent can be 1: (0.5-2): (0-10), further, the molar ratio of the solvent, solute and diluent can be 1: (0.64-1.2): (1-10), further, the molar ratio of the solvent, solute and diluent can be 1: (0.64-1.2): 3, optionally, the molar ratio of the solvent, solute and diluent can be specifically 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: 1.05: 3, 1: 1.10: 3, 1: 1.15: 3, 1: 1.2: 3 or a range consisting of any two of these values.

[0039] According to some embodiments of the present application, the operating voltage of the ether electrolyte is greater than or equal to 4.6V.

[0040] According to some embodiments of the present application, the solute is a lithium salt.

[0041] According to some embodiments of the present application, the lithium salt is selected from any one of LiPF6, LiBF4, LiTFSi, LiFSi or LiBOB. In some embodiments, the lithium salt is selected from LiFSi.

[0042] According to some embodiments of the present application, the weight percentage of the ether solvent in the solvent is 0.01% to 100%. In some embodiments, the weight percentage of the ether solvent in the solvent can be 0.01%, 0.05%, 1%, 2%, 3%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, or a range consisting of any two of these values.

[0043] 2. Lithium Metal Batteries

[0044] The lithium metal battery provided in the present application includes a positive electrode, a negative electrode and the ether electrolyte described in the present application.

[0045] Optionally, the negative electrode includes a negative electrode active material, which is a material that can accept and release lithium ions, such as soft carbon, hard carbon, artificial graphite, natural graphite, silicon, silicon oxide, lithium metal, silicon-carbon composite, lithium titanate, metals that can form alloys with lithium, etc. In some specific embodiments, the negative electrode active material can be selected from lithium metal materials. The positive electrode includes a positive electrode active material, and the type of positive electrode active material is not particularly limited as long as it can electrochemically absorb and release metal ions (for example, lithium ions). In some embodiments, the positive electrode active material is a substance containing lithium and at least one transition metal.

[0046] According to some embodiments of the present application, the positive electrode active material is selected from at least one of positive electrode active materials having a thermodynamic electrochemical potential greater than 4.5 V. The positive electrode active material having a thermodynamic electrochemical potential greater than 4.5 V may specifically include LiNi 0.8 Co 0.1 Mn 0.1 O2(NMC811), lithium cobalt oxide, NMC532, NMC622, NCA, LiNiPO4, LiCoPO4, Li3V2(PO4)3, LiMnO2, LiMn2O4, Li2MnO4, LiNi 0.5 Mn 0.5 O2、LiNi 0.85 Co 0.10 Al 0.05 O2、LiNi 0.33 Co 0.33 Mn 0.33 O2、LiNi 0.45 Co 0.10 Al 0.45 O2、LiMn 1.8 Al 0.2 O4 and LiMn 1.5 Ni 0.5O4, etc. It can be understood that the ether electrolyte of the present application has excellent oxidation resistance to the above-mentioned specific positive electrode active materials. When a positive electrode made of the above-mentioned positive electrode active materials is assembled into a battery with the ether electrolyte of the present application, the battery can have good cycle performance and capacity retention rate under high voltage, thereby improving the high-voltage resistance and high-temperature storage performance of the battery.

[0047] To make the present invention easier to understand, specific embodiments of the present invention will be further described below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein.

[0048] Examples and Comparative Examples

[0049] Example 1:

[0050] This embodiment provides an ether electrolyte, which has the following composition: the electrolyte solvent is an ether solvent (diglyme, i.e., diethylene glycol dimethyl ether G2), the solute is lithium bis(fluorosulfonyl)imide, and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether is a diluent; lithium bis(fluorosulfonyl)imide, solvent, and diluent are weighed to prepare ether electrolyte 2, and the molar ratio of the solute, ether solvent, and diluent added is 1:1:3.

[0051] Example 2:

[0052] This embodiment provides an ether electrolyte, which has the following composition: the electrolyte solvent is an ether solvent (triglyme, i.e., triethylene glycol dimethyl ether G3), the solute is lithium bis(fluorosulfonyl)imide, and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether is a diluent; lithium bis(fluorosulfonyl)imide, solvent, and diluent are weighed to prepare a localized high-concentration ether electrolyte 3, and the molar ratio of the solute, ether solvent, and diluent added is 1:1:3.

[0053] Example 3:

[0054] This embodiment provides an ether electrolyte, which has the following composition: the electrolyte solvent is an ether solvent (tetraglyme, i.e., tetraethylene glycol dimethyl ether G4), the solute is lithium bis(fluorosulfonyl)imide, and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether is a diluent; lithium bis(fluorosulfonyl)imide, solvent, and diluent are weighed to prepare a localized high-concentration ether electrolyte 4, and the molar ratio of the solute, ether solvent, and diluent added is 1:0.64:3.

[0055] Example 4:

[0056] This embodiment provides an ether electrolyte having the following composition: the electrolyte solvent is an ether solvent (triglyme, i.e., triethylene glycol dimethyl ether G3), the solute is lithium bis(fluorosulfonyl)imide, and 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether is a diluent; lithium bis(fluorosulfonyl)imide, solvent, and diluent are weighed to prepare a localized high-concentration ether electrolyte 5, and the molar ratio of the solute, ether solvent, and diluent added is 1:1:3.

[0057] Comparative Example 1:

[0058] This embodiment provides an ether electrolyte having the following composition: the electrolyte solvent is an ether solvent (1,2-dimethoxyethane, ethylene glycol dimethyl ether DME), the solute is lithium bis(fluorosulfonyl)imide, and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether is a diluent; lithium bis(fluorosulfonyl)imide, the solvent, and the diluent are weighed to prepare a localized high-concentration ether electrolyte 1, wherein the molar ratio of the solute, the ether solvent, and the diluent added is 1:1.2:3.

[0059] Effect embodiment 1:

[0060] The ether electrolytes of Comparative Example 1, Example 1, Example 2, and Example 3 were selected as the research objects of this embodiment. 0.8 Co 0.1 Mn 0.1 O2)(2mAh cm -2 ) as the positive electrode, Li metal (450μm) as the negative electrode, and 75μl of electrolyte were used to carry out charge and discharge procedures at a voltage of 4.6V to test its cycle performance.

[0061] The test results show that compared with Comparative Example 1, Example 1 and Example 3, the ether electrolyte 3 of Example 2 has good cycle performance at a voltage of 4.6V.

[0062] The battery cycle stability of Example 2 has a capacity retention rate of up to 82% after 350 cycles, while the capacity retention rates of Comparative Example 1, Example 1 and Example 3 are respectively around 250 cycles, and are less than 80%.

[0063] Effect embodiment 2:

[0064] The ether electrolyte of Example 2 was selected as the research object of this effect embodiment, and the ether electrolytes in Example 1, Example 3, and Comparative Example 1 were used as the control group. 0.8 Co 0.1 Mn 0.1 O2)(2mAh cm -2) as the positive electrode, Li metal (450μm) as the negative electrode, and 75μl of electrolyte were used to test the cycle performance by charge and discharge program at 4.7V voltage.

[0065] Test results see Figure 2 Compared with the ether electrolytes in Example 1, Example 3, and Comparative Example 1, the ether electrolyte in Example 2 also has good cycle performance at a voltage of 4.7V. The ether electrolytes in Comparative Example 1 and Example 3 have a large overcharge phenomenon of electrolyte decomposition. See the test results for details. Figure 3-6 Although the capacities of the ether electrolyte of Example 1 and the ether electrolyte of Example 2 were similar in the first 80 cycles, the capacity of the ether electrolyte of Example 1 dropped sharply after 80 cycles.

[0066] Effect embodiment 3:

[0067] The ether electrolyte of Example 2 was selected as the research object of this effect embodiment, and the ether electrolytes in Example 1, Example 3, and Comparative Example 1 were used as the control group. 0.8 Co 0.1 Mn 0.1 O2)(4mAh cm -2 ) as the positive electrode, Li metal (50μm) as the negative electrode, and 20μl of electrolyte were used to carry out charge and discharge procedures at a voltage of 4.7V to test its cycle performance.

[0068] Test results see Figure 7 Compared with the ether electrolytes in Example 1, Example 3, and Comparative Example 1, the ether electrolyte in Example 2 has good cycle performance at a voltage of 4.7 V. After 100 cycles, the capacity retention rate is 94%, while the ether electrolytes in Example 1, Example 3, and Comparative Example 1 all die due to overcharge before 80 cycles.

[0069] Effect embodiment 4:

[0070] The ether electrolyte of Example 2 was selected as the research object of this effect embodiment, and the ether electrolytes in Example 1, Example 3, and Comparative Example 1 were used as the control group. 0.8 Co 0.1 Mn 0.1 O2)(2mAh cm -2 ) as the positive electrode, Li metal (450μm) as the negative electrode, and 75μl of electrolyte were used to test the cycle performance by charge and discharge program at 4.7V voltage.

[0071] Test results see Figure 8 Compared with the ether electrolytes in Example 1, Example 3 and Comparative Example 1, the ether electrolyte in Example 2 has good cycle performance at a voltage of 4.7V.

[0072] The number of battery cycles at which the capacity retention rate reaches 80% is arranged from high to low as follows: the ether electrolyte of Example 2 (200 cycles) >> the ether electrolyte of Example 3 (150 cycles) > the ether electrolyte of Example 1 (75 cycles) > the ether electrolyte of Comparative Example 1 (36 cycles).

[0073] Effect embodiment 5:

[0074] The ether electrolyte of Example 2 was selected as the research object of this embodiment, and the ether electrolyte of Comparative Example 1 was used as the control group. -2 ) as the positive electrode, Li metal (450μm) as the negative electrode, and 75μl of electrolyte were used to carry out charge and discharge procedures at a voltage of 4.6V to test its cycle performance.

[0075] Test results see Figure 9 Compared with the ether electrolyte in Comparative Example 1, the ether electrolyte in Example 2 has a capacity retention rate of 90% after 100 cycles at a voltage of 4.6 V.

[0076] Effect Example 6:

[0077] The ether electrolyte of Example 2 was selected as the research object of this effect embodiment, and the ether electrolytes in Example 1, Example 3, and Comparative Example 1 were used as the control group. -2 ) as the positive electrode, Li metal (450μm) as the negative electrode, and 75μl of electrolyte were stored at 50℃ for three days at a voltage of 4.6V, and the self-discharge performance was tested.

[0078] Test results see Figure 10 Compared with the ether electrolytes in Example 1, Example 3, and Comparative Example 1, the ether electrolyte in Example 2 can achieve a higher capacity retention rate of 96% after being stored at a voltage of 4.6 V for three days.

[0079] Effect Example 7:

[0080] The ether electrolyte of Example 4 was selected as the research object of this effect embodiment, high nickel NMC positive electrode (Ni ratio: 90%), and Li metal (450μm) was used as the negative electrode. Figure 11 The ether electrolyte of Example 4 was used at a high rate (1C, 5 mA / cm 2 ) After thirty cycles, the capacity retention rate is 100%, and the specific capacity is as high as 195mAh / g at 1C.

[0081] Although some exemplary embodiments of the present application have been illustrated and described, the present application is not limited to the disclosed embodiments. On the contrary, those skilled in the art will recognize that some modifications and changes may be made to the described embodiments without departing from the spirit and scope of the present application as described in the appended claims.

Claims

1. An ether electrolyte, characterized in that It includes a solvent, a solute and a diluent; the solvent includes an ether solvent, the ether solvent is triethylene glycol dimethyl ether, or the ether solvent is a mixed liquid formed by at least one of diethylene glycol dimethyl ether and tetraethylene glycol dimethyl ether and triethylene glycol dimethyl ether; the diluent includes at least one of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, bis(2,2,2-trifluoroethyl) ether, and octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, and the molar ratio of the solvent, the solute and the diluent is 1:(0.64-1.2):(1-10); the solute is a lithium salt, and the lithium salt is selected from any one of LiPF6, LiTFSi or LiFSi.

2. The ether electrolyte according to claim 1, characterized in that The ether solvent is selected from triethylene glycol dimethyl ether.

3. The ether electrolyte according to claim 1, characterized in that The molar ratio of the solvent, the solute and the diluent is 1:(0.64-1.2):

3.

4. The ether electrolyte according to claim 1, characterized in that The operating voltage of the ether electrolyte is greater than or equal to 4.6V.

5. The ether electrolyte according to claim 1, characterized in that The weight percentage of the ether solvent in the solvent is 0.01% to 100%.

6. A lithium metal battery, characterized in that The invention comprises a positive electrode, a negative electrode and the ether electrolyte according to any one of claims 1 to 5.

7. The lithium metal battery according to claim 6, characterized in that The positive electrode includes a positive electrode active material; the positive electrode active material includes at least one positive electrode active material having a thermodynamic electrochemical potential greater than 4.5V.

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