Preparation method of all-solid-state metal lithium battery and all-solid-state metal lithium battery

Abstract

The application provides a preparation method of a full-solid-state metal lithium battery, and the full-solid-state metal lithium battery prepared by the method has an in-situ formed solid electrolyte film. The preparation method is simple and easy to implement, the film pieces in the prepared full-solid-state metal lithium battery are tightly attached, and the full-solid-state metal lithium battery can have good cycle performance. The application also provides a full-solid-state metal lithium battery prepared by the above method.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of all-solid-state batteries, and particularly relates to a preparation method of an all-solid-state metal lithium battery, wherein the all-solid-state metal lithium battery prepared by the method has an in-situ formed solid-state electrolyte film. BACKGROUND

[0002] With the progress of technology, the currently widely used lithium ion battery has developed to its "ceiling" of energy density (about 300 Wh / kg). In order to adapt to higher energy density application scenarios, it has become an urgent need to develop all-solid-state metal lithium batteries with an energy density of 400 Wh / kg to 600 Wh / kg, which is also a hot spot in the current battery field.

[0003] An all-solid-state battery is a battery made by replacing the liquid electrolyte in the traditional lithium ion battery with a solid-state electrolyte film. The solid-state electrolyte film used is generally divided into three categories: (1) inorganic solid-state electrolyte, (2) organic solid-state electrolyte, and (3) organic-inorganic hybrid solid-state electrolyte. Due to the influence of the solid-state electrolyte processing technology, the current general preparation method of the solid-state battery is: first, respectively prepare a solid-state electrolyte film, a positive electrode sheet, and a metal lithium negative electrode sheet; then stack or wind the above-mentioned electrode sheets, package, and finally obtain an all-solid-state metal lithium battery. In the preparation process of the all-solid-state metal lithium battery, a large external pressure needs to be applied to ensure that the solid-state electrolyte film, the positive electrode sheet, and the metal lithium negative electrode sheet have a very good contact interface. The preparation process of the all-solid-state metal lithium battery is complex and requires a large external assembly pressure, which will greatly limit its widespread application in practice. SUMMARY

[0004] In view of the above problems, the purpose of the present application is to provide a preparation method of an all-solid-state metal lithium battery which has a simple preparation process and tightly fitted film sheets.

[0005] The purpose of the present application can be realized by the following technical solutions.

[0006] In one aspect, the present application provides a preparation method of an all-solid-state metal lithium battery, characterized by comprising the following steps:

[0007] Step one: preparing a positive electrode sheet containing an active material, a conductive agent, a binder, and a solid-state electrolyte activator;

[0008] Step two: matching a metal lithium negative electrode with the positive electrode sheet and packaging to obtain a battery monomer with a voltage of 0 V;

[0009] Step three: placing the battery monomer into an oven for baking and activation;

[0010] Step four: degassing and secondary packaging of the activated battery monomer to obtain a full solid-state metal lithium battery.

[0011] In some embodiments, the preparation of the positive electrode sheet comprises: dispersing the active material, conductive agent, binder and solid-state electrolyte activator into a solvent to obtain a positive electrode slurry, and coating the positive electrode slurry on a current collector and drying to obtain a positive electrode sheet; or dispersing the active material, conductive agent, binder into a solvent to obtain a positive electrode slurry, coating the positive electrode slurry on a current collector and drying to form a positive electrode coating, and coating a slurry of the solid-state electrolyte activator in a solvent onto the positive electrode coating and drying to obtain a positive electrode sheet. In preferred embodiments, the solvent is selected from at least one of N-methylpyrrolidone, tetrahydrofuran, n-hexane, dimethyl sulfoxide, naphthalene, p-xylene, oleic acid, carbon disulfide and biphenyl organic matter. In preferred embodiments, the active material is at least one of lithium iron phosphate, lithium iron manganese phosphate, lithium titanate, lithium cobaltate, lithium manganate (LiMn2O4), LiMnO2, lithium nickelate, lithium nickel manganate, nickel cobalt manganese ternary material and nickel cobalt aluminum ternary material. In preferred embodiments, the current collector is a copper foil or an aluminum foil.

[0012] Preferably, the positive electrode sheet obtained after drying contains 1% to 10% by mass, preferably 1.5% to 4.5% by mass, of residual solvent.

[0013] In some embodiments, the step one further comprises soaking the positive electrode sheet in an organic solvent. In preferred embodiments, the organic solvent is at least one of propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, fluoroethylene carbonate, vinylene carbonate, vinyl ethylene carbonate, methyl propionate, propylene sulfite, tetrahydrofuran, dimethyl tetrahydrofuran and ethylene glycol dimethyl ether.

[0014] In some embodiments, the solid-state electrolyte activator is at least one of a non-metallic element, a phosphorus-containing oxide, a sulfur-containing oxide, a phosphorus-containing sulfide, a metal halide and a metal oxide.

[0015] In preferred embodiments, the non-metallic element is at least one of sulfur, phosphorus and silicon.

[0016] In some embodiments, the baking temperature of the step three ranges from 35°C to 95°C, preferably from 40°C to 90°C, more preferably from 45°C to 85°C.

[0017] In some embodiments, the baking time of the step three ranges from 8 hours to 168 hours, preferably from 24 hours to 72 hours.

[0018] In some embodiments, the mass fraction of the solid-state electrolyte activator in the positive electrode film ranges from 5% to 55%, preferably from 8% to 23%.

[0019] In another aspect, the present application provides a full solid-state metal lithium battery prepared by the method as described above.

[0020] The present application has the following beneficial effects:

[0021] 1) The solid-state metal lithium battery preparation process is simple and easy to implement, and is suitable for industrial production.

[0022] 2) The full solid-state metal lithium battery prepared by the method of the present application has an in-situ formed solid-state electrolyte film. The positive electrode of the full solid-state metal lithium battery is tightly attached to the metal lithium negative electrode. During the battery cycle process, the in-situ generated solid-state electrolyte film tightly connects the positive and negative electrodes together, which can effectively prolong the cycle life of the battery. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is the cycle diagram of the full solid-state metal lithium battery in Example 1 of the present disclosure.

[0024] Figure 2 is the battery voltage test photo of the full solid-state metal lithium battery in Example 2 of the present disclosure before activation.

[0025] Figure 3 is the battery voltage test photo of the full solid-state metal lithium battery in Example 2 of the present disclosure after activation.

[0026] Figure 4 is the cycle diagram of the full solid-state metal lithium battery in Example 4 of the present disclosure.

[0027] Figure 5 is the cycle diagram of the full solid-state metal lithium battery in Example 5 of the present disclosure.

[0028] Figure 6 is the cycle diagram of the full solid-state metal lithium battery in Example 6 of the present disclosure.

[0029] In the above cycle diagrams, the horizontal coordinate represents the cycle number, and the vertical coordinate represents the discharge capacity. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application will be further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application, and are not used to limit the present application.

[0031] Without being bound by any theory, it is speculated that the mechanism of in-situ formation of the solid-state electrolyte film is as follows. Since the solid-state electrolyte activator, i.e. non-metallic element, phosphorus-containing oxide, sulfur-containing oxide, phosphorus-sulfur-containing compound, metal halide, metal oxide, etc. is added during preparation. These substances have oxidizing properties, and when in contact with the reducing metal lithium negative electrode, an oxidation-reduction reaction occurs spontaneously at the interface between the positive electrode and the metal lithium negative electrode, and the main product is the oxidation product of lithium, such as lithium sulfide, lithium halide, lithium oxide, etc. With the participation of organic solvents, some organic lithium salts such as alkyl lithium may also be generated. These newly generated substances are generally not electron-conducting but lithium-ion-conducting substances. With the progress of the reaction, these substances accumulate between the positive electrode and the metal lithium negative electrode, and the solid-state electrolyte film is formed in-situ, and finally the positive electrode loses direct contact with the metal lithium negative electrode. At this time, a voltage is generated between the positive electrode and the metal lithium negative electrode of the solid-state battery, and the solid-state metal lithium battery is activated.

[0032] The full solid-state metal lithium battery prepared by the method of the present application has an in-situ formed solid-state electrolyte layer, the preparation method is simple and easy to operate, and the prepared full solid-state metal lithium battery has tightly fitted film pieces, which can ensure that the full solid-state metal lithium battery has good cycle performance.

[0033] Embodiment

[0034] The content of the present application will be described in detail below through specific examples.

[0035] Example 1

[0036] The full solid-state metal lithium battery is prepared by the following steps.

[0037] (1) Preparation of positive electrode sheet

[0038] The nickel-cobalt-manganese ternary material (BETRIS New Material Group Co., Ltd.) as the positive active material, acetylene black (Shanghai Araldin Biochemical Technology Co., Ltd.) as the conductive agent, polyvinylidene fluoride (Shanghai Araldin Biochemical Technology Co., Ltd.) as the binder and sulfur (Shanghai Araldin Biochemical Technology Co., Ltd.) as the solid-state electrolyte activator are added into the N-methyl pyrrolidone solvent at a mass ratio of 8:1:1:5, and are dispersed by high-speed stirring to prepare a uniform positive electrode slurry. The prepared slurry is coated on an aluminum foil current collector and dried to obtain a positive electrode sheet. Thus, a positive electrode sheet containing active material, conductive agent, binder and solid-state electrolyte activator is prepared. The obtained positive electrode sheet is cut and soaked in fluoroethylene carbonate, and the size of the cut sheet is 44mm x 57mm.

[0039] (2) Assembly of single solid-state battery

[0040] The metal lithium negative electrode (the size of the punched metal lithium negative electrode is 45 mm x 58 mm) is punched by using a die-cutting machine (MSK-180 semi-automatic die-cutting machine, Hefei Kejing Material Technology Co., Ltd.), and is matched with the soaked positive electrode sheet to obtain a battery monomer with a voltage of 0 V after packaging.

[0041] (3) Baking and activating the battery

[0042] The battery monomer is placed in an oven for baking and activation, the baking temperature is 45 degrees Celsius, and the baking time is 24 hours.

[0043] (4) Preparing a full-solid-state metal lithium battery

[0044] The activated battery is degassed and secondarily packaged to obtain a full-solid-state metal lithium battery.

[0045] The voltage of the obtained full-solid-state metal lithium battery is 3 V measured by a multimeter.

[0046] Figure 1 The cycle curve of the battery in Example 1 is shown. From Figure 1 It can be seen that the full-solid-state metal lithium battery prepared by using the method can be normally charged and discharged, the discharge capacity gradually increases in the first 5 weeks of the battery cycle, because the contact inside the battery is gradually improved, and the utilization rate of the positive active material is improved. The discharge capacity is stable in the 6th to 13th week of the battery cycle. When the cycle is carried out to the 14th week, the battery capacity begins to decay, and a micro-short circuit occurs inside the battery. In the 17th week, the solid-state electrolyte film between the positive and negative electrodes is completely destroyed and an internal short circuit occurs, and the battery discharge capacity is about 0.

[0047] Example 2

[0048] Except that the solid-state electrolyte activator is replaced by a mixture of phosphorus sulfide and phosphorus chloride with a mass ratio of 1:1, a full-solid-state metal lithium battery is prepared in the same way as in Example 1.

[0049] The voltage of the battery is tested by using a multimeter. Figure 2 The voltage test photo of the battery in Example 2 before activation is shown. Figure 3 The voltage test photo of the battery in Example 2 after activation is shown. From Figure 2 and Figure 3 It can be seen that the voltage of the battery before activation is 0 V, and after activation, the solid-state electrolyte film is formed in situ between the positive and negative electrodes, and the voltage of the battery rises to 3.89 V.

[0050] Therefore, it can be known that after changing the activator, the full-solid-state metal lithium battery prepared by using the method is still effective.

[0051] Example 3

[0052] A full solid-state metal lithium battery was prepared in the same manner as in Example 1, except that the solid-state electrolyte activator was replaced with aluminum fluoride.

[0053] The voltage of the full solid-state metal lithium battery of Example 3 was measured to be 2.29 V using a multimeter.

[0054] Example 4

[0055] A full solid-state metal lithium battery was prepared in the same manner as in Example 1, except that the baking temperature was changed to 85°C.

[0056] The voltage of the full solid-state metal lithium battery of Example 4 was measured to be 3.31 V using a multimeter.

[0057] Figure 4 The cycle curve of the battery of Example 4 is shown. In comparison Figure 1 and Figure 4 It can be found that after the baking temperature is increased, the discharge capacity of the battery of Example 4 is overall higher than 20 mAh, and the cycle number of the battery is increased from 16 weeks to 19 weeks, and the capacity decay of the battery in the last three weeks also becomes flat. This indicates that at a higher baking temperature, the combination between the layers of the solid-state metal lithium battery is more compact, the utilization efficiency of the positive active material is higher, and the solid-state electrolyte film formed in situ is more stable and is not easily damaged during the cycle of the battery.

[0058] Example 5

[0059] A full solid-state metal lithium battery was prepared in the same manner as in Example 1, except that in the step (1) of preparing the positive electrode sheet, the positive electrode sheet was not completely dried, and 3.5 mass% of solvent remained therein.

[0060] The voltage of the full solid-state metal lithium battery of Example 5 was measured to be 3.33 V using a multimeter.

[0061] Figure 5 The cycle curve of the battery of Example 5 is shown. The cycle life of the battery prepared in Example 5 is increased to 27 weeks, which proves that a small amount of residual solvent in the positive electrode sheet can improve the activation efficiency of the solid-state electrolyte activator.

[0062] Example 6

[0063] (1) Preparation of a positive electrode sheet having a solid-state electrolyte activator on the surface

[0064] Nickel cobalt manganese ternary material (BETTREI New Material Group Co., Ltd.) as the positive active material, acetylene black (Shanghai Araldin Biochemical Technology Co., Ltd.) as the conductive agent, and polyvinylidene fluoride (Shanghai Araldin Biochemical Technology Co., Ltd.) as the binder were added into N-methyl pyrrolidone solvent at a mass ratio of 8:1:1, and were dispersed by high-speed stirring to prepare a uniform positive electrode slurry. The prepared slurry was coated on an aluminum foil current collector and dried to form a positive electrode coating.

[0065] Sulfur (Shanghai Araldin Biochemical Technology Co., Ltd.) was uniformly dispersed in p-xylene as a solid-state electrolyte activator. The dispersion was uniformly coated on the above-mentioned positive electrode coating and dried to obtain a positive electrode sheet with a solid-state electrolyte activator on the surface.

[0066] Other steps were prepared in the same way as in Example 1 to prepare a full solid-state metal lithium battery.

[0067] The voltage of the full solid-state metal lithium battery of Example 6 was measured to be 3.42 V by a multimeter.

[0068] Figure 6 The cycle curve of the battery of Example 6 is shown. As can be seen from the figure, the cycle life of the battery prepared in Example 6 is increased to 37 weeks.

[0069] The research and development of full solid-state metal lithium batteries as future advanced systems is still in its infancy, and there is still a lot of work to be done in the future, and the preparation process of full solid-state metal lithium batteries will also continue to emerge. The present application only provides a solution for the preparation of full solid-state metal lithium batteries.

[0070] It can be understood that, in the embodiments of the present application, although a preparation method of a full solid-state metal lithium battery in which a solid-state electrolyte film is formed in situ is described in detail in combination with specific embodiments, the above is only for illustration, and the present application is not limited to the given specific embodiments. Changes or substitutions made to the above embodiments without departing from the spirit and scope of the present application should be covered within the protection scope of the present application.

Claims

1. A method of manufacturing an all-solid-state lithium metal battery, characterized by, The method comprises the following steps: Step 1: preparing a positive electrode sheet containing an active material, a conductive agent, a binder, and a solid-state electrolyte activator; Step 2: matching a metal lithium negative electrode with the positive electrode sheet and packaging to obtain a battery cell with a voltage of 0 V; Step 3: placing the battery cell in an oven for baking and activation; Step 4: degassing and secondary packaging the activated battery cell to obtain a full solid-state metal lithium battery.

2. The method of claim 1, wherein the method is performed at a temperature of 20- 30°C. The preparation of the positive electrode sheet comprises: dispersing the active material, the conductive agent, the binder, and the solid-state electrolyte activator into a solvent to obtain a positive electrode slurry, and coating the positive electrode slurry on a current collector and drying to obtain the positive electrode sheet; or dispersing the active material, the conductive agent, and the binder into a solvent to obtain a positive electrode slurry, coating the positive electrode slurry on a current collector and drying to form a positive electrode coating, and coating a slurry of the solid-state electrolyte activator in a solvent on the positive electrode coating and drying to obtain the positive electrode sheet, wherein the solvent is at least one selected from N-methylpyrrolidone, tetrahydrofuran, n-hexane, dimethyl sulfoxide, naphthalene, p-xylene, oleic acid, carbon disulfide, and biphenyl organic matter. 3.The method of claim 2, wherein the metal lithium battery is a full solid-state metal lithium battery. The positive electrode sheet obtained after drying contains 1-10% of residual solvent by mass. 4.The method of claim 1, wherein the method further comprises: applying a first voltage to the first electrode and the second electrode; and applying a second voltage to the third electrode and the fourth electrode. The step 1 further comprises soaking the positive electrode sheet in an organic solvent. 5.The method of claim 4, wherein the metal lithium battery is a full solid-state metal lithium battery. The organic solvent is at least one selected from propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, fluoroethylene carbonate, vinylene carbonate, vinyl ethylene carbonate, methyl propionate, propylene sulfite, tetrahydrofuran, dimethyl tetrahydrofuran, and ethylene glycol dimethyl ether. 6.The method of claim 1, wherein the method further comprises: applying a first voltage to the first electrode and the second electrode; and applying a second voltage to the third electrode and the fourth electrode. The solid-state electrolyte activator is at least one selected from non-metallic elements, phosphorus-containing oxides, sulfur-containing oxides, phosphorus-sulfur-containing compounds, metal halides, and metal oxides. 7.The method of claim 6, wherein the metal lithium battery is a full solid-state metal lithium battery. The non-metallic element is at least one selected from sulfur, phosphorus, and silicon. 8.The method of claim 1, wherein the method further comprises: applying a protective layer on the surface of the lithium metal anode. The baking temperature of the step 3 ranges from 35°C to 95°C, and the baking time of the step 3 ranges from 8 hours to 168 hours. 9.The method of claim 1, wherein the method further comprises: applying a protective layer on the surface of the lithium metal anode. The mass fraction of the solid-state electrolyte activator in the positive electrode sheet ranges from 5% to 55%.

10. A full solid-state metal lithium battery prepared by the method of any one of claims 1-9.

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