Lithium metal battery and preparation method and electric device using same

Abstract

The application provides a lithium metal battery and a preparation method and an electric device. The preparation method of the lithium metal battery comprises the following steps: dissolving a metal nitride in a first organic solvent to form a metal nitride solution; coating the metal nitride solution on the surface of a metal lithium sheet, air-drying, and forming a composite film on the surface of the metal lithium sheet; assembling the metal lithium sheet with the composite film on the surface into a battery with a lithium sheet and performing electrochemical deposition to prepare a negative electrode sheet; and assembling the negative electrode sheet with a positive electrode sheet, injecting a first electrolyte, and obtaining the lithium metal battery. By introducing a polar bond between metal and nitrogen elements on the surface of lithium, the reduction of nitrate and the formation of a SEI rich in Li3N can be promoted in the subsequent process of injecting an electrolyte containing lithium nitrate. By performing electrochemical deposition on the metal lithium sheet with the composite film on the surface, relatively stable lithium ions can be deposited on the surface, so that the surface capacity of the negative electrode sheet in the lithium metal battery is increased, and the conductivity of the lithium metal battery is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium ion batteries, and particularly relates to a lithium metal battery and a preparation method and an electric device. BACKGROUND

[0002] Lithium metal has attracted extensive attention due to its low redox potential (-3.040 V) and high energy density (3861 mAh·g -1 ). Due to serious interface problems, including lithium dendrites and strong volume change of the lithium anode in the charging and discharging process, which causes the rupture of the SEI film on the surface of the lithium anode, and further leads to the suboptimal electrochemical performance, and even internal short circuit and thermal runaway. It is considered that the construction of the SEI layer rich in Li3N is a method to solve the bottleneck of the lithium metal anode (LMA), and by forming an SEI film rich in Li3N on the surface of the lithium metal anode, uniform lithium deposition / stripping and inhibition of lithium dendrites and dead lithium can be effectively promoted.

[0003] LiNO3 can be used as an additive to introduce Li3N into the SEI layer, however, in the actual design of the lithium metal electrolyte, LiNO3 has no obvious effect on inhibiting the formation of dead lithium and improving the performance of the lithium metal, and no obvious improvement is found, therefore, how to improve the negative electrode of the lithium metal battery to form an SEI film rich in Li3N in cooperation with the LiNO3 electrolyte is a problem to be solved at present. SUMMARY

[0004] The application provides a lithium metal battery and a preparation method and an electric device, and aims to solve the problem that the existing lithium metal electrolyte has limited effect on inhibiting lithium dendrites of the lithium metal battery and improving the conductivity of the lithium metal battery.

[0005] In one aspect, the application provides a preparation method of a lithium metal battery, comprising the following steps:

[0006] dissolving the metal nitride in a first organic solvent to form a metal nitride solution;

[0007] spraying the metal nitride on the surface of the lithium metal sheet, air-drying, and forming a composite film on the surface of the lithium metal sheet;

[0008] assembling the lithium metal sheet with the composite film on the surface into a battery with a lithium sheet and performing electrochemical deposition to make a negative electrode sheet;

[0009] assembling the negative electrode sheet with a positive electrode sheet, injecting a first electrolyte, and obtaining the lithium metal battery.

[0010] In some embodiments, the metal nitride comprises one or more of vanadium nitride, aluminum nitride, chromium nitride, dysprosium nitride, titanium nitride, yttrium nitride, holmium nitride, molybdenum nitride, chromium nitride, europium nitride, ytterbium nitride, indium nitride, gallium nitride, samarium nitride, lutetium nitride, zirconium nitride, hafnium nitride, yttrium nitride, lanthanum nitride, niobium nitride, or tantalum nitride.

[0011] In some embodiments, the first organic solvent comprises one or more of N-methylpyrrolidone, dimethyl carbonate, dimethyl sulfoxide, N,N-dimethylformamide, or N-methyl-2-pyrrolidone.

[0012] In some embodiments, the mass percentage of the metal nitride in the first organic solvent is 0.5% to 10%.

[0013] In some embodiments, the coating thickness of the metal nitride solution is 5 to 10 4 nm.

[0014] In some embodiments, the temperature of the air drying is -80 to -40℃, room temperature 25±3℃.

[0015] In some embodiments, the time of the air drying is 6 to 20h.

[0016] In some embodiments, the step of assembling the metal lithium sheet with the composite film on the surface into a battery and electrochemically depositing further comprises:

[0017] Assembling by sequentially and intervally pasting n pieces of the metal lithium sheet with the composite film on the surface and n+1 pieces of lithium sheet.

[0018] Injecting a second electrolyte and applying electricity to complete electrochemical deposition.

[0019] Wherein, n = 1 to 20.

[0020] The second electrolyte is a solution of lithium salt dissolved in a second organic solvent, the lithium salt comprises one or more of lithium perchlorate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium hexafluorophosphate, lithium bisoxalate borate, lithium difluoro oxalate borate, lithium bisdifluorosulfonylimide, lithium bis-trifluoromethylsulfonylimide, and the second organic solvent comprises one or more of N-methylpyrrolidone, dimethyl carbonate, dimethyl sulfoxide, N,N-dimethylformamide, or N-methyl-2-pyrrolidone.

[0021] In some embodiments, the current density of the electricity application is 0.1 to 10 mA / cm 2 , the face capacity of stripping / deposition is 0.1 to 50 mAh / cm 2 ; and the cycle number is 1 to 20 cycles.

[0022] In some embodiments, the first electrolyte comprises a solute selected from at least one of lithium nitrate, potassium nitrate, rubidium nitrate, cesium nitrate, nickel nitrate, zinc nitrate, manganese nitrate, indium nitrate, and magnesium nitrate.

[0023] In another aspect, the embodiments of the present application provide a lithium metal battery prepared by the preparation method of any of the above embodiments, the lithium metal battery comprising a positive electrode sheet and a negative electrode sheet, the surface capacity of the negative electrode sheet being 0.1-5000 mAh / cm 2 .

[0024] Finally, the embodiments of the present application also provide a power consumption device comprising the battery of the above embodiments.

[0025] The present application provides a preparation method of a lithium metal battery, comprising the following steps: dissolving a metal nitride in a first organic solvent to form a metal nitride solution; coating the metal nitride solution on the surface of a lithium metal sheet, air-drying, and forming a composite film on the surface of the lithium metal sheet; assembling the lithium metal sheet with the composite film on the surface and a lithium sheet into a battery and performing electrochemical deposition to make a negative electrode sheet; assembling the negative electrode sheet and a positive electrode sheet, injecting a first electrolyte, and obtaining a lithium metal battery. By introducing a polar bond between the metal and nitrogen elements on the surface of lithium, the ionic covalent property of the nitrogen-oxygen bond can be changed in the subsequent process of injecting the electrolyte containing lithium nitrate, promoting the electron transfer in the nitrogen-oxygen bond breaking process, and further promoting the reduction of nitrate and the formation of SEI rich in Li3N. At the same time, by electrochemically depositing the lithium metal sheet with the composite film on the surface, a relatively stable lithium ion can be deposited on the surface of the treated lithium metal sheet, thereby increasing the surface capacity of the negative electrode sheet in the lithium metal battery and improving the conductivity of the lithium metal battery. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by a person skilled in the art without creative labor fall within the scope of protection of the present application.

[0027] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, an electrical connection, or a connection that allows for mutual communication; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two elements or the interaction between two elements. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances. In the description of this application, "multiple" means two or more, unless otherwise expressly and specifically limited. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more features.

[0028] The following disclosure provides many different embodiments or examples for implementing different structures of this application. To simplify the disclosure of this application, the components and arrangements of specific examples are described below. Of course, these are merely examples and are not intended to limit this application.

[0029] The first embodiment of this application provides a method for preparing a lithium metal battery, comprising the following steps:

[0030] S1. Dissolve the metal nitride in a first organic solvent to form a metal nitride solution;

[0031] S2. Coat the surface of the lithium metal sheet with the metal nitride solution and air dry to form a composite film on the surface of the lithium metal sheet.

[0032] S3. Assemble the lithium metal sheet with the composite film on its surface and the lithium sheet into a battery and perform electrochemical deposition to make the negative electrode sheet;

[0033] S4. Assemble the negative electrode and the positive electrode, and inject the first electrolyte to obtain a lithium metal battery.

[0034] In some embodiments, the first electrolyte includes a solute selected from at least one of lithium nitrate, potassium nitrate, rubidium nitrate, cesium nitrate, nickel nitrate, zinc nitrate, manganese nitrate, indium nitrate, and magnesium nitrate.

[0035] Generally, the solute is one of the important substances for introducing Li3N into the SEI film. Taking lithium nitrate (LiNO3) as an example, especially in lithium-sulfur batteries, reduction and decomposition of LiNO3 are key to constructing an ideal Li3N-rich SEI film. The Li2N in the Li3N crystal structure creates cation vacancies on the SEI film surface, which can increase lithium-ion conductivity, reduce resistance, improve conductivity, and increase Young's modulus.

[0036] In the preparation process of lithium metal batteries, after the formation of the electrolyte-electrode interface, lithium nitrate anions are easily adsorbed on the surface of the lithium current collector to form an IHP plane. When the reduction potential is approximately 1.7 V vs. Li / Li + , the adsorbed LiNO3 decomposes into Li3N, a series of other nitrides and N2. Subsequently, the voltage drops above the Li nucleation potential, resulting in the formation of an SEI film layer containing the deposition products of solvents and Li salts. The decomposition of LiNO3 additives can result in the presence of a large amount of Li3N and LiN x O y , and the more reasonable decomposition process is LiNO3-LiNO2-LiNO-Li3N, with a decrease in valence from +5 to -3. LiNO is the key to the decomposition of lithium nitrate.

[0037] In addition, taking metal nitride as an example, by using a metal nitride solution to in-situ treat a lithium metal sheet, a polar nitrogen-vanadium bond can be introduced on the surface of the lithium metal. In the subsequent process of pouring electrolyte, the dipole-dipole interaction can increase the ionic characteristics of the N=O bond, while the decrease in covalence can reduce the separation between the bonding and antibonding orbitals, induce the N=O bond to crack, and promote its deep decomposition, thereby reducing the lithium dissociation energy barrier, enhancing the conversion of LiNO3, and solving the problem that lithium nitrate additives are not easy to decompose.

[0038] In some embodiments, the metal nitride includes one or more of vanadium nitride, aluminum nitride, chromium nitride, dysprosium nitride, titanium nitride, yttrium nitride, holmium nitride, molybdenum nitride, chromium nitride, europium nitride, ytterbium nitride, indium nitride, gallium nitride, samarium nitride, lutetium nitride, zirconium nitride, hafnium nitride, yttrium nitride, lanthanum nitride, niobium nitride, or tantalum nitride, and is further preferably vanadium nitride.

[0039] In some embodiments, the organic solvent includes one or more of N-methyl pyrrolidone (NMP), dimethyl carbonate (DMC), dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), or N-methyl-2-pyrrolidone (DNF). Since the above-mentioned organic solvents have strong solubility and low activity, they are not easy to react with lithium metal and will not generate by-products to affect the in-situ treatment of the lithium metal sheet.

[0040] In some embodiments, the mass percentage of the metal nitride in the organic solvent is 0.5% to 10%. It can be understood that the mass percentage of the metal nitride in the organic solvent can be any value or a range between any two values of 0.5%, 1%, 4%, 7%, and 10%. When the mass percentage of the metal nitride in the organic solvent meets the above-mentioned value range, the in-situ treatment of the lithium metal sheet has a relatively ideal effect.

[0041] In some embodiments, the coating thickness of the metal nitride solution is 5-10 4 nm. It can be understood that the coating thickness (unit: nm) can be any value or a range between any two values selected from 5, 50, 100, 200, 500, 1000, 2000, 5000, and 10000. It can be understood that when the coating thickness of the metal nitride solution meets the above range, the composite film formed on the surface of the lithium metal sheet has a good effect on protecting the electrode and promoting the N=O cleavage in the first electrolyte.

[0042] In some embodiments, the dew point of air drying is -80 to -40℃, and the normal temperature is 25±3℃.

[0043] In some embodiments, the air drying time is 6-20h. It can be understood that the air drying time (unit: h) can be any value or a range between any two values selected from 6, 10, 14, 18, and 20.

[0044] In some embodiments, the step of assembling the metal lithium sheet with the surface covered with the composite film into a battery and performing electrochemical deposition further comprises:

[0045] Assembling by sequentially and intervally pasting n pieces of the metal lithium sheet with the surface covered with the composite film and n+1 pieces of lithium sheet;

[0046] Injecting the second electrolyte, applying electricity, and completing the electrochemical deposition;

[0047] Wherein, n=1-20.

[0048] The second electrolyte does not contain any additive, and is only a solution formed by dissolving lithium salt in an organic solvent, wherein the lithium salt is selected from one or more of lithium perchlorate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium hexafluorophosphate, lithium bisoxalate borate, lithium difluoro oxalate borate, lithium bisdifluorosulfonylimide, and lithium bis-trifluoromethylsulfonylimide, and the organic solvent is selected from one or more of N-methyl pyrrolidone, dimethyl carbonate, dimethyl sulfoxide, N,N-dimethylformamide, or N-methyl-2-pyrrolidone.

[0049] In some embodiments, the current density of the applied electricity is 0.1-10 mA / cm 2 , the surface capacity of the stripping / deposition is 0.1-50 mAh / cm 2 , and the cycle number is 1-20.

[0050] The second embodiment of the present application provides a lithium metal battery prepared by the preparation method in any of the above embodiments. The lithium metal battery comprises a positive electrode sheet and a negative electrode sheet, and the surface capacity of the negative electrode sheet is 0.1-5000 mAh / cm 2 .

[0051] The third embodiment of the present application also provides a power consumption device comprising the battery of the above embodiments.

[0052] The lithium metal battery and the preparation method thereof provided by the present application are described below in combination with specific embodiments.

[0053] Embodiment 1

[0054] The present embodiment provides a lithium metal battery, which is prepared by the following steps:

[0055] S1, uniformly dissolving 1wt% of vanadium nitride powder in DMF to form a vanadium nitride solution;

[0056] S2, uniformly spraying the vanadium nitride solution on the surface of the lithium metal sheet by using a syringe pump, and then air-drying in a fume hood at -55°C for 12 hours to obtain a lithium metal sheet with a composite film on the surface;

[0057] S3, stacking 7 pieces of the treated lithium metal sheet with a composite film on the surface and 6 pieces of untreated lithium sheet in turn, welding, and injecting liquid to assemble a soft-pack battery, and then packaging the soft-pack battery; using blue electricity, setting a current density of 0.5mA / cm 2 , stripping / depositing 2mAh / cm 2 of lithium, and cycling 5 times, finally depositing more stable lithium on the surface of the treated lithium, disassembling the battery to obtain a negative electrode sheet; the second electrolyte used in this process is 1.0M LiFSI dissolved in DME;

[0058] S4, preparing a positive electrode sheet: mixing lithium nickel cobalt manganese oxide ternary material LiNi9Co1Mn1O2, conductive agent SuperP, adhesive PVDF, and carbon nanotube (CNT) in a mass ratio of 96.5:2.5:1.0:0.5 to uniformly prepare a lithium ion battery positive electrode slurry with a certain viscosity, coating on an aluminum foil current collector, and drying at 85°C, then cold pressing; then cutting edges, cutting sheets, and slitting, and drying at 85°C for 8 hours under vacuum conditions to prepare a lithium metal battery positive electrode sheet meeting the requirements;

[0059] S5, washing 6 pieces of the negative electrode sheet with DMC, drying for 12h, and stacking, welding, injecting liquid, and packaging with 5 pieces of the positive electrode sheet; the first electrolyte in this process comprises solutes, solvents, diluents, etc., to obtain a lithium metal battery.

[0060] Embodiments 2-4

[0061] Embodiments 2-4 are consistent with the preparation steps of embodiment 1, except that the metal nitride in step S1 is different, and the specific material selection is shown in Table 1.

[0062] Embodiments 5-7

[0063] Examples 5-7 are consistent with the preparation steps of Example 1, except that the coating thickness of the metal nitride solution in step S2 is different, see Table 1 for details.

[0064] Examples 8-10

[0065] Examples 8-10 are consistent with the preparation steps of Example 1, except that the air-drying dew point in step S2 is different, see Table 1 for details.

[0066] Examples 11-16

[0067] Examples 11-16 are consistent with the preparation steps of Example 1, except that the current density, stripping / deposition area capacity and cycle number in step S3 are different, see Table 1 for details.

[0068] Examples 17-18

[0069] Examples 17-18 are consistent with the preparation steps of Example 1, except that the lithium salt in the electrolyte in step S3 is different, see Table 1 for details.

[0070] Examples 19-20

[0071] Examples 19-20 are consistent with the preparation steps of Example 1, except that the solute in the electrolyte in step S5 is different, see Table 1 for details.

[0072] Further provided are Comparative Examples 1-5

[0073] Comparative Example 1

[0074] Lithium is not treated, and is directly laminated, welded and injected with electrolyte to make a soft-pack battery of the same capacity as in Example 1.

[0075] Comparative Examples 2-3

[0076] The preparation steps of Comparative Examples 2-3 are consistent with those of Example 1, except that the coating thickness of the metal nitride solution is not in the range of 5-10 4 nm, see Table 1 for details.

[0077] Comparative Examples 4-5

[0078] The preparation steps of Comparative Examples 4-5 are consistent with those of Example 1, except that the deposition current density of Comparative Example 4 is different from that of Example 1, and the cycle number of Comparative Example 5 is different from that of Example 1, see Table 1 for details.

[0079] Table 1

[0080]

[0081]

[0082] The electrical performance tests were performed on Examples 1-20 and Comparative Examples 1-5, and the results are shown in Table 2.

[0083] Table 2

[0084]

[0085]

[0086] As can be seen from Table 1 and Table 2, the lithium metal battery prepared by the scheme provided in the present application not only has an ideal initial efficiency, but also has good performance in cycle performance and high capacity retention rate. As can be seen from the comparison between the examples and Comparative Example 1, the soft pack battery prepared by directly stacking the untreated lithium sheet has an unsatisfactory initial efficiency and cycle performance. As can be seen from the comparison between the examples and Comparative Examples 2-5, when the coating thickness of the metal nitride solution or the process parameters of depositing lithium metal exceed the value range provided in the scheme of the present application, the initial efficiency of the battery is significantly reduced, and the capacity retention rate is also unsatisfactory.

[0087] The lithium metal battery and the preparation method and the electric device provided in the embodiments of the present application are described in detail above, and the principles and implementation manners of the present application are described by applying specific examples. The above description of the embodiments is only used to help understand the technical solutions of the present application and the core ideas thereof. It should be understood by those skilled in the art that the technical solutions recorded in the above embodiments can be modified, or some technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method of preparing a lithium metal battery, characterized by, The method comprises the following steps: dissolving metal nitride in a first organic solvent to form a metal nitride solution, the metal nitride including one or more of vanadium nitride, aluminum nitride, chromium nitride, dysprosium nitride, titanium nitride, yttrium nitride, holmium nitride, molybdenum nitride, chromium nitride, europium nitride, ytterbium nitride, indium nitride, gallium nitride, samarium nitride, lutetium nitride, zirconium nitride, hafnium nitride, yttrium nitride, lanthanum nitride, niobium nitride, or tantalum nitride; coating the metal lithium sheet with the metal nitride solution, air-drying to form a composite film on the surface of the metal lithium sheet; assembling the metal lithium sheet with the composite film on the surface into a battery with lithium sheets and performing electrochemical deposition to obtain a negative electrode sheet; assembling the negative electrode sheet with a positive electrode sheet, injecting a first electrolyte including a solute including lithium nitrate to obtain the lithium metal battery.

2. The method for preparing a lithium metal battery according to claim 1, wherein the first organic solvent includes one or more of N-methylpyrrolidone, dimethyl carbonate, dimethyl sulfoxide, N,N-dimethylformamide, or N-methyl-2-pyrrolidone. The mass percentage of the metal nitride in the first organic solvent is 0.5% to 10%.

3. The method for preparing a lithium metal battery according to claim 1, characterized in that, The dew point of the air-drying is -80 to -40℃, and the normal temperature is 25±3℃.

4. The method for preparing a lithium metal battery according to claim 1, characterized in that, The coating thickness of the metal nitride solution is 5 to 10 4 nm.

5. The method for preparing a lithium metal battery according to claim 1, characterized in that, The air-drying time is 6 to 20 hours.

6. The method for preparing a lithium metal battery according to claim 1, characterized in that, The step of assembling the metal lithium sheet with the composite film on the surface into a battery with lithium sheets and performing electrochemical deposition further comprises:

7. The method for preparing a lithium metal battery according to claim 1, characterized in that, n pieces of the metal lithium sheet with the composite film on the surface are sequentially and evenly attached to n+1 pieces of lithium sheets; injecting a second electrolyte and applying electricity to complete the electrochemical deposition; wherein n = 1 to 20; The second electrolyte is a solution of lithium salt dissolved in a second organic solvent, the lithium salt including one or more of lithium perchlorate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium hexafluorophosphate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium bis(difluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide; and the second organic solvent including one or more of N-methylpyrrolidone, dimethyl carbonate, dimethyl sulfoxide, N,N-dimethylformamide, or N-methyl-2-pyrrolidone. The battery as claimed in claim 9 is provided.

8. The method for preparing a lithium metal battery according to claim 7, characterized in that, The current density of the power supply is 0.1-10 mA / cm 2 The surface capacity of the stripping / deposition is 0.1-50 mAh / cm 2 ; and the cycle number is 1-20.

9. A lithium metal battery, characterized in that, The lithium metal battery is prepared by the preparation method in any one of claims 1-7, and includes a positive electrode sheet and a negative electrode sheet, a surface capacity of the negative electrode sheet is 0.1-5000 mAh / cm 2 .

10. An electrical device, characterized by ​

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