An electrolyte additive and method of use thereof and battery containing the additive

Abstract

The application belongs to the field of lithium batteries, and provides an electrolyte additive and a use method thereof. The electrolyte additive is a negatively charged porous inorganic nanosheet. The electrolyte additive provided by the application, i.e. the negatively charged porous inorganic nanosheet, is added into an electrolyte for dispersion. Under the action of an electric field force, the negatively charged porous inorganic nanosheets can form a stable porous structure on the surface of a lithium negative electrode, so as to inhibit the growth of lithium dendrites.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of lithium batteries, and particularly relates to an electrolyte additive, a use method thereof and a battery containing the additive. BACKGROUND

[0002] Lithium metal anode is considered as an ideal anode material for the next generation of lithium battery storage systems. However, its practical application is hindered by two major problems, i.e. lithium dendrite growth and solid electrolyte interface (SEI) instability, which cause the problems of low coulombic efficiency, capacity fading and poor safety of lithium batteries. In order to solve these problems, various strategies have been proposed. Among these strategies, electrolyte design promotes robust SEI formation and improves uniform lithium ion flux by reasonably adjusting the combination of salt, solvent and additive; electrode design suppresses dendrite initiation by adjusting the lithium ion flux on the anode surface. Common electrode engineering methods include constructing a 3D conductive body, decorating a lithiumophilic surface and their synergistic regulation. However, both electrolyte design and electrode design have their own shortcomings. Electrolyte regulation, although simple in regulation method, cannot effectively regulate the lithium ion flux. Electrode design can more effectively regulate the lithium ion flux on the electrode surface, but the regulation process is complex.

[0003] The present application provides an electrolyte additive, a use method thereof and a battery containing the additive, to solve the problem that the existing lithium battery technology cannot balance the effectiveness of regulating the lithium ion flux on the lithium electrode surface and the simplicity of the regulation method. SUMMARY

[0004] In order to solve the problem that the existing lithium battery technology cannot balance the effectiveness of regulating the lithium ion flux on the lithium electrode surface and the simplicity of the regulation method, the present application provides an electrolyte additive, a use method thereof and a battery containing the additive.

[0005] The electrolyte additive is a negatively charged porous inorganic nanosheet.

[0006] Further, the substrate of the negatively charged porous inorganic nanosheet is a two-dimensional nanosheet, and the material is selected from one or more of single metal oxides, double metal / triple metal oxides, metal sulfides and double metal / triple metal sulfides.

[0007] Further, the single metal oxide is selected from one or more of titanium oxide, zinc oxide, tin oxide, manganese oxide, cobalt oxide, nickel oxide and iron oxide;

[0008] The double metal / triple metal oxide is selected from multiple ones of titanium iron oxide, cobalt manganese oxide, nickel iron oxide and iron cobalt nickel oxide;

[0009] The metal sulfide is selected from one or more of titanium sulfide, zinc sulfide, tin sulfide, manganese sulfide, cobalt sulfide, nickel sulfide and iron sulfide.

[0010] The double metal / triple metal sulfide is selected from a plurality of titanium iron sulfide, cobalt manganese sulfide, nickel iron sulfide and iron cobalt nickel sulfide.

[0011] Further, the mass percentage of the electrolyte additive in the electrolyte is 0.1-10%.

[0012] Further, the thickness of the negatively charged porous inorganic nanosheet is between 0.6-10 nm.

[0013] Further, under the condition that the ambient temperature is 0-120℃, the electrolyte additive is dispersed in the electrolyte, and the concentration of the electrolyte additive in the electrolyte is 0.01-10 mg / mL.

[0014] An object of the present application is to provide a method for using an electrolyte additive, which comprises the following steps:

[0015] The electrolyte additive according to any one of the above is added to the electrolyte, and the solvent of the electrolyte comprises one or more of ethylene carbonate / diethyl carbonate, 1,3-dioxolane and 1,2-dimethoxyethane.

[0016] Further, the electrolyte additive must be freeze-dried or naturally air-dried before use.

[0017] An object of the present application is to provide a battery, which contains the electrolyte additive according to any one of the above in the electrolyte solution of the battery.

[0018] Further, the anode of the battery is a lithium electrode, and the electrolyte comprises one or more of ethylene carbonate / diethyl carbonate, 1,3-dioxolane and 1,2-dimethoxyethane.

[0019] The negatively charged porous inorganic nanosheet provided by the present application is added to the electrolyte for dispersion. Under the action of the electric field force, these negatively charged porous inorganic nanosheets can form a stable porous structure on the surface of the lithium negative electrode, thereby inhibiting the growth of lithium dendrites. The method for using the electrolyte additive provided by the present application is simple, and the electrolyte additive can be uniformly deposited under the action of the electric field. Therefore, the growth of dendrites can be effectively inhibited on a large scale. On the other hand, the electrolyte additive used in this method has the characteristics of low cost, and is therefore suitable for large-scale practical applications. Compared with traditional electrode surface structure modification and organic electrolyte additives, this method combines the advantages of both methods. Not only is the operation simple, but the effect is also remarkable. This new type of inorganic electrolyte additive will also provide new ideas for the performance improvement of other types of batteries. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 a-c are Ti treated by hydrogen iodide in Example 1 0.8 Fe 0.2 S2 obtained Ti 0.8 S2 0.8- TEM image of porous inorganic nanosheets, Figure 1 d is Ti without treatment by hydrogen iodide 0.8 Fe 0.2 TEM image of S2;

[0021] Figure 2 are optical photographs before and after adding negatively charged porous inorganic nanosheets into electrolyte in Example 1;

[0022] Figure 3 are cycle data of symmetric cells obtained in Examples 1-12;

[0023] Figure 4 are effects on full cell performance with pure current collector as negative electrode and lithium iron phosphate as positive electrode after adding porous / inorganic nanosheets into electrolyte in Examples 13-20;

[0024] Figure 5 are effects on full cell performance with lithium sheet as negative electrode and lithium iron phosphate as positive electrode after adding porous inorganic nanosheets into electrolyte in Examples 21-24. DETAILED DESCRIPTION

[0025] In order to make the above objectives, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application will be described in detail below with reference to the accompanying drawings, but it should not be understood as limiting the scope of the present application.

[0026] Considering the simplicity of adding additives to electrolyte, we propose a new rational electrode design method through the concept of electrolyte additives. By adding materials for building 3D electrodes into electrolyte, they will self-assemble into a layered structure on the current collector under the electric field between the cathode and anode. In this case, electrode modification will be easier and the uniformity of modification on lithium metal anode can also be well controlled, even in large size anodes. In order to realize the proposed idea, several basic requirements should be met: (1) the additive should be stable in ordinary lithium battery electrolyte; (2) the additive should have electric charge to move under the electric field to achieve self-adaptive electrode surface modification; (3) the additive should organize into a suitable structure that can effectively inhibit the growth of lithium dendrites.

[0027] The present application provides a negatively charged porous inorganic nanosheet, the substrate is a two-dimensional nanosheet, and the material is selected from one or more of single metal oxides, double metal / triple metal oxides, metal sulfides and double metal / triple metal sulfides.

[0028] Optionally, the single metal oxide is selected from one or more of titanium oxide, zinc oxide, tin oxide, manganese oxide, cobalt oxide, nickel oxide and iron oxide.

[0029] Optionally, the double metal / triple metal oxide is selected from one or more of titanium iron oxide, cobalt manganese oxide, nickel iron oxide and iron cobalt nickel oxide.

[0030] Optionally, the metal sulfide is selected from one or more of titanium sulfide, zinc sulfide, tin sulfide, manganese sulfide, cobalt sulfide, nickel sulfide and iron sulfide.

[0031] Optionally, the double metal / triple metal sulfide is selected from one or more of titanium iron sulfide, cobalt manganese sulfide, nickel iron sulfide and iron cobalt nickel sulfide.

[0032] Optionally, the thickness of the negatively charged porous inorganic nanosheet is between 0.6 and 10 nm.

[0033] The negatively charged porous inorganic nanosheet provided by the present application can fully meet the new reasonable electrode design as an electrolyte additive. First, the porous inorganic nanosheet is negatively charged. The electrostatic repulsion between each nanosheet can ensure its stability in electrolyte with high polarity. Second, the porous nanosheet has weak van der Waals force due to the pores on it, which can avoid its re-stacking in the process of electrostatic deposition. Under the electric field between the two electrodes, the porous inorganic nanosheet is stacked into a hierarchical porous structure instead of a densely packed film. This morphology not only provides high-dimensional space for lithium deposition, but also promotes ion transport within the anode. Third, these porous inorganic nanosheet materials are lithiumophilic materials and do not show volume change during lithium metal plating / stripping, which helps to induce true nucleation of lithium metal and stabilize the SEI. In addition, the negative charge and nanopores help to regulate the lithium ion flux close to the current collector surface.

[0034] The present application adds the charged porous inorganic nanosheet powder into the electrolyte for dispersion, thereby obtaining an electrolyte containing the negatively charged porous inorganic nanosheet. Optionally, the mass percentage of the electrolyte additive in the electrolyte is 0.1-10%.

[0035] The electrolyte is used for performance research of symmetric batteries and full batteries.

[0036] The electrolyte additive provided by the present application is applied to a symmetric battery, which is assembled according to a CR2032 button cell, and the assembly method is as follows:

[0037] For symmetric cells, the foam copper (3D Cu foam) / copper foil (Cu foil) was cut into a 14 mm diameter disc by a puncher and used as the working electrode, lithium metal was used as the counter electrode, the electrolyte was 1.0 M lithium hexafluorophosphate (LiPF6) mixed with ethylene carbonate (EC) / diethyl carbonate (DEC) in a volume ratio of 1:1, the separator was polypropylene (PP) film, and the assembly environment was a single-station lithium battery glove box with water and oxygen values of less than 0.1 ppm. The electrolyte containing porous inorganic nanosheets was used for comparison with the electrolyte without porous inorganic nanosheets.

[0038] The electrolyte additive provided by the application is applied to a full cell, and the following method is used for assembly:

[0039] For a full cell, the negative electrode contains two types, one is direct foam copper or copper foil; the other is lithium sheet. The positive electrode material is lithium iron phosphate active material. The positive electrode is prepared as follows: lithium iron phosphate, conductive carbon black and polyvinylidene fluoride (PVDF) binder are mixed in a mass ratio of 8:1:1, an appropriate amount of NMP is added into the mixture, and magnetic stirring is performed for 12 hours to form a slurry. The slurry is coated on the copper foil using a doctor blade, and then placed in a vacuum oven at 60 degrees for vacuum drying for 12 hours. After the copper foil with uniform active material coating is completely dried, the copper foil is cut into a 14 mm diameter disc using a puncher to prepare an electrode, wherein the active material loading content is 0.5-1.5 mg / cm -2 The electrolyte containing porous inorganic nanosheets is used for comparison with the electrolyte without porous inorganic nanosheets.

[0040] As a result, by using the porous inorganic nanosheet dispersed electrolyte, the Li / Li symmetric cell and the Li / LiFePO4 full cell show better performance than the cell without the porous inorganic nanosheet in the electrolyte.

[0041] Example 1

[0042] (1) Ti 0.8 S2 0.8- Preparation of the electrolyte of the porous inorganic nanosheet

[0043] Ti 0.8 Fe 0.2 S2 0.8 S2 0.8- porous inorganic nanosheet. Under the condition of an ambient temperature of 25°C, 10 mg of Ti 0.8 S2 0.8- The porous two-dimensional nanosheet is dissolved in 5 ml of electrolyte, the solvent of the electrolyte is 1:1 by volume mixed ethylene carbonate (EC) / diethyl carbonate (DEC), the solute is lithium hexafluorophosphate (LiPF6), and the concentration of LiPF6 in the electrolyte is 1 mol / L.

[0044] (2) containing negative Ti 0.8 S2 0.8- Preparation of CR2032 button half-cell of electrolyte of porous inorganic nanosheet

[0045] The Ti 0.8 S2 0.8- The electrolyte of porous inorganic nanosheet was assembled into CR2032 button half-cell and tested by constant current charge and discharge, with current density of 1 mA cm -2 The working electrode was copper foam (3D Cu foam), and the counter electrode was lithium sheet. 3D Cu@HNS indicates Ti 0.8 S2 0.8- The current collector formed by depositing the porous inorganic nanosheet on the copper foam.

[0046] Example 2

[0047] The difference from Example 1 is that no Ti 0.8 S2 0.8- Porous inorganic nanosheet, and the working electrode was copper foil (Cu foil).

[0048] Example 3

[0049] The difference from Example 2 is that no Ti 0.8 S2 0.8- Porous inorganic nanosheet, and the working electrode was copper foam (3D Cu foam).

[0050] Example 4

[0051] The difference from Example 1 is that in step (1), non-porous Ti 0.8 Fe 0.2 S2 instead of Ti 0.8 S2 0.8- Porous inorganic nanosheet. 3D Cu@NS indicates Ti 0.8 Fe 0.2 S2 porous inorganic nanosheet deposited on the copper foam to form a current collector.

[0052] Example 5

[0053] The difference from Example 1 is that in step (2), the current density used is 3 mA cm -2 .

[0054] Example 6

[0055] The difference from Example 2 is that in step (2), the current density used is 3 mA cm -2 .

[0056] Example 7

[0057] The difference from Example 3 is that the current density used in step (2) is 3 mA cm -2 .

[0058] Example 8

[0059] The difference from Example 4 is that the current density used in step (2) is 3 mA cm -2 .

[0060] Example 9

[0061] The difference from Example 1 is that the current density used in step (2) is 5 mA cm -2 .

[0062] Example 10

[0063] The difference from Example 2 is that the current density used in step (2) is 5 mA cm -2 .

[0064] Example 11

[0065] The difference from Example 3 is that the current density used in step (2) is 5 mA cm -2 .

[0066] Example 12

[0067] The difference from Example 4 is that the current density used in step (2) is 5 mA cm -2 .

[0068] Example 13

[0069] The difference from Example 1 is that Ti 0.6 Mo 0.2 O2 0.8- porous inorganic nanosheets are used instead of Ti 0.8 S2 0.8- porous two-dimensional nanosheets in step (1), and the positive electrode used in step (2) is lithium iron phosphate, and the charge and discharge current density is 1C.

[0070] Example 14

[0071] The difference from Example 13 is that the negative electrode used in step (2) is copper foil, and there is no Ti 0.6 Mo 0.2 O2 0.8 porous inorganic nanosheets in the electrolyte.

[0072] Example 15

[0073] The difference from Example 13 is that the negative electrode used in step (2) is lithium sheet, and there is no Ti in the electrolyte 0.6 Mo 0.2 O2 0.8 porous inorganic nanosheets.

[0074] Example 16

[0075] The difference from Example 13 is that the negative electrode used in step (2) is copper foam, and there is no porous inorganic nanosheet in the electrolyte.

[0076] Example 17

[0077] The difference from Example 13 is that the charge-discharge current density in step (2) is 0.2C, 0.5C, 1C, 2C, 5C.

[0078] Example 18

[0079] The difference from Example 14 is that the charge-discharge current density in step (2) is 0.2C, 0.5C, 1C, 2C, 5C.

[0080] Example 19

[0081] The difference from Example 15 is that the charge-discharge current density in step (2) is 0.2C, 0.5C, 1C, 2C, 5C.

[0082] Example 20

[0083] The difference from Example 16 is that the charge-discharge current density in step (2) is 0.2C, 0.5C, 1C, 2C, 5C.

[0084] Example 21

[0085] The difference from Example 13 is that the negative electrode used in step (2) is lithium sheet, and the porous inorganic nanosheet used in step (1) is Ti 0.8 O2 0.8- .

[0086] Example 22

[0087] The difference from Example 21 is that no porous inorganic nanosheet is added to the electrolyte in step (1).

[0088] Example 23

[0089] The difference from Example 21 is that the charge-discharge current density in step (2) is 0.2C, 0.5C, 1C, 2C, 5C.

[0090] Example 24

[0091] The difference from Example 22 is that the charge-discharge current density in step (2) is 0.2C, 0.5C, 1C, 2C, 5C.

[0092] Result analysis:

[0093] Figure 1 a-c are Ti 0.8 Fe 0.2 S2 obtained in Example 1 by hydrogen iodide treatment 0.8 S2 0.8- TEM image of the porous inorganic nanosheet, it can be seen that the nanosheet surface is rich in nanopores. Figure 1 d is Ti 0.8 Fe 0.2 TEM image of S2, which shows that the assembly morphology of the porous nanosheet will be beneficial to provide more nucleation sites to suppress lithium dendrite growth.

[0094] Figure 2 Ti 0.8 S2 0.8- Optical photograph before and after the porous inorganic nanosheet, the electrolyte changes from white to bright yellow, indicating that Ti 0.8 S2 0.8- Nanosheet stably exists in the electrolyte.

[0095] Figure 3 The cycle data of the symmetric battery obtained in Examples 1-12 shows that the porous titanium sulfide inorganic nanosheet as an electrolyte additive is beneficial to reduce lithium deposition and stripping overpotential, and increase the cycle stability of the symmetric battery, wherein, Figure a refers to the symmetric battery prepared in Examples 1-4, Figure b refers to the symmetric battery prepared in Examples 5-8, and Figure c refers to the symmetric battery prepared in Examples 9-12.

[0096] Figure 4 In Examples 13-20, the porous inorganic nanosheet Ti 0.6 Mo 0.2 O2 0.8- After adding to the electrolyte, the effect on the performance of the full battery with pure current collector as the negative electrode and lithium iron phosphate as the positive electrode, wherein, Figure a represents the test results of Examples 13-16, and Figure b represents the test results of Examples 17-20. It can be seen that the porous inorganic nanosheet has the effect of improving the interface reaction kinetics, thereby improving the cycle performance at the same rate.

[0097] Figure 5 In Examples 21-24, the negatively charged porous inorganic Ti 0.8 O2 0.8-The effect of the addition of the porous inorganic nanosheets to the electrolyte on the performance of a full cell with lithium foil as the negative electrode and lithium iron phosphate as the positive electrode was studied. The porous inorganic nanosheets were found to improve the kinetics of the interfacial reactions and thus the cycle performance at the same rate.

Claims

1. Use of a compound as an additive for lithium batteries electrolyte, characterized in that, The anode of the lithium battery is a lithium electrode; the electrolyte additive is a negatively charged porous inorganic nanosheet; The substrate of the negatively charged porous inorganic nanosheet is a two-dimensional nanosheet, and the material is selected from one or more of a single metal oxide, a double metal / triple metal oxide, a metal sulfide, and a double metal / triple metal sulfide; The single metal oxide is selected from one or more of titanium oxide, zinc oxide, tin oxide, manganese oxide, cobalt oxide, nickel oxide, and iron oxide; The double metal / triple metal oxide is selected from a plurality of titanium iron oxide, cobalt manganese oxide, nickel iron oxide, and iron cobalt nickel oxide; The metal sulfide is selected from one or more of titanium sulfide, zinc sulfide, tin sulfide, manganese sulfide, cobalt sulfide, nickel sulfide, and iron sulfide; The double metal / triple metal sulfide is selected from a plurality of titanium iron sulfide, cobalt manganese sulfide, nickel iron sulfide, and iron cobalt nickel sulfide.

2. Use according to claim 1, wherein The mass percentage of the electrolyte additive in the electrolyte is 0.1-10%.

3. The use according to claim 1, wherein The thickness of the negatively charged porous inorganic nanosheet is between 0.6-10 nm.

4. The use according to claim 1, wherein The electrolyte additive is dispersed in the electrolyte under the condition that the ambient temperature is 0-120°C, and the concentration of the electrolyte additive in the electrolyte is 0.01-10 mg / mL.

5. A method of using a lithium battery electrolyte additive, characterized by, Comprising the following steps: The electrolyte additive of any one of claims 1-4 is added to the electrolyte, which comprises one or more of ethylene carbonate / diethyl carbonate, 1,3-dioxolane, and 1,2-dimethoxyethane; The anode of the lithium battery is a lithium electrode.

6. The method of using a lithium battery electrolyte additive according to claim 5, wherein, The electrolyte additive must be freeze-dried or naturally air-dried before use.

7. A lithium battery, characterized by The electrolyte solution of the lithium battery comprises the electrolyte additive of any one of claims 1-4; The anode of the lithium battery is a lithium electrode.

8. The lithium battery of claim 7, wherein the lithium metal anode is a lithium foil anode. The electrolyte comprises one or more of ethylene carbonate / diethyl carbonate, 1,3-dioxolane, and 1,2-dimethoxyethane.

Images