Method for dry preparation of all-solid-state battery and all-solid-state battery

Abstract

The application provides a method for preparing a full solid-state battery by a dry method and a full solid-state battery. The method comprises the following steps: preparing a negative electrode mixed powder and a sulfide solid-state electrolyte mixed powder; in a water-free and oxygen-free environment, the negative electrode mixed powder is sprayed onto a substrate by using an electrostatic spraying device, and a pre-lithiated negative electrode layer is obtained after solidification; the sulfide solid-state electrolyte mixed powder is sprayed onto the surface of the pre-lithiated negative electrode layer by using the electrostatic spraying device, and an electrolyte layer is obtained after solidification; a dry film-forming positive electrode material is compounded with the other side of the electrolyte layer, and a full solid-state battery is assembled. The application provides a preparation method for the full solid-state battery without solvent participation in the whole process, and effectively solves the technical problems of low first coulomb efficiency and poor interface contact performance between the electrode material and the electrolyte in the solid-state battery.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of all-solid-state battery materials, and particularly relates to a method for preparing an all-solid-state battery by a dry method and an all-solid-state battery. BACKGROUND

[0002] At present, lithium ion batteries have been widely used in human daily life and industrial production process due to their high energy density and long cycle life. However, the traditional liquid battery contains flammable and explosive organic electrolyte, and thus has serious safety hazards. In abnormal conditions such as overcharging and external mechanical damage leading to internal short circuit, the electrolyte may catch fire or even explode, which seriously limits the development and application of lithium ion batteries.

[0003] Compared with the traditional liquid lithium ion battery, the all-solid-state lithium ion battery uses a solid-state electrolyte with good thermal stability and safety to replace the traditional organic electrolyte, which effectively solves the problems of poor safety performance, narrow working temperature range and low electrochemical window in the liquid battery. In addition, the solid-state lithium battery system can adopt a stacked structure, and multiple electrodes can be stacked through structural design during battery assembly, which is expected to prepare a single cell battery with high output voltage.

[0004] Sulfide solid-state electrolyte is considered to be the most promising electrolyte in recent years due to its ion conductivity comparable to that of liquid electrolyte. The production technology of the solid-state electrolyte layer disclosed in the prior art can be divided into two categories: wet film forming technology and dry film forming technology. On the one hand, in the wet coating process, in order to ensure that the electrolyte film can become a continuous phase, a binder needs to be added to the solid-state electrolyte to prepare a slurry, which is coated on the substrate or electrode surface. The above method can prepare an electrolyte layer with uniform thickness and thin thickness. Although the thinner the electrolyte layer is, the more conducive to the rapid transmission of lithium ions, the stability of the sulfide electrolyte is poor, sensitive to solvents, and the side reaction with solvents can easily lead to a decrease in conductivity, and the presence of the binder can hinder ion transmission and increase the internal resistance of the electrolyte layer. On the other hand, the dry film preparation technology mainly mixes the electrolyte powder and the easily fibrillated polymer, and the easily fibrillated polymer is fibrillated under high shear force to prepare an ultra-thin electrolyte layer. The above method can effectively avoid the influence of solvents on the conductivity of sulfide electrolyte, but the uniformity of the mixture of electrolyte powder and polymer is difficult to control during the preparation process, and it is difficult to prepare a relatively thin electrolyte layer, and the preparation method has high requirements for equipment, which has great challenges in production application.

[0005] In addition to the above problems, the negative material will consume part of the lithium ion to form a solid-state electrolyte interface (SEI film) during the first cycle of the battery, thereby producing irreversible capacity loss, affecting the energy density and cycle life of the battery. In addition, there is also a problem of poor solid-solid interface contact performance in the solid-state battery system, which results in serious interface impedance between the electrolyte layer and the electrode, thus affecting the overall performance of the battery.

[0006] Therefore, in the art, there is an urgent need to develop a kind of all-solid-state battery, which not only has high ionic conductivity and low interface impedance, but also has good electrochemical performance. SUMMARY

[0007] In view of the deficiencies of the prior art, the purpose of the present application is to provide a method for preparing an all-solid-state battery by dry method and an all-solid-state battery. The present application provides a method for preparing an all-solid-state battery without solvent participation throughout the process, effectively solving the technical problems of low first coulomb efficiency and poor interface contact performance between electrode material and electrolyte in solid-state battery.

[0008] To achieve this purpose of the application, the following technical solutions are adopted:

[0009] In a first aspect, the present application provides a method for preparing an all-solid-state battery by dry method, which comprises the following steps:

[0010] Preparation of negative electrode mixed powder and sulfide solid-state electrolyte mixed powder;

[0011] In a water-free and oxygen-free environment, the negative electrode mixed powder is sprayed onto the substrate using an electrostatic spraying device, and after solidification, a pre-lithiated negative electrode layer is obtained;

[0012] The sulfide solid-state electrolyte mixed powder is then sprayed onto the surface of the pre-lithiated negative electrode layer using an electrostatic spraying device, and after solidification, an electrolyte layer is obtained;

[0013] The dry film-forming positive electrode material is compounded with the other side of the electrolyte layer, and an all-solid-state battery is assembled.

[0014] It should be noted that the dry film-forming positive electrode material provided by the present application uses a dry film-forming preparation method that does not include electrostatic spraying. Due to the high tap density of the positive electrode material, the use of electrostatic spraying is not ideal, and it is easy to produce uneven thickness and difficult to produce electrostatic adsorption, so other commonly used dry film-forming methods in the art are used to prepare the positive electrode material.

[0015] In the present application, the substrate includes but is not limited to lithium foil.

[0016] The application adopts an electrostatic spraying method to prepare a pre-lithiated negative electrode layer and an electrolyte layer, and then integrates the composite with a positive electrode, thereby improving the first cycle coulomb efficiency of the full solid-state battery and improving the cycle performance of the full solid-state battery. Firstly, the pre-lithiation of the negative electrode can reduce the irreversible capacity loss of the battery in the first charge-discharge process. Since the reaction activity of lithium metal is high, it is easy to react with active materials, solvents and the like in the negative electrode layer, so the application directly sprays the negative electrode layer on the surface of the lithium metal by dry mixing and electrostatic spraying, thereby avoiding the side reaction between the conventional solvent used in the pre-lithiation process and the lithium metal, and further affecting the pre-lithiation effect.

[0017] Secondly, in the full solid-state battery, the solid-solid interface contact problem is one of the main reasons affecting the performance of the battery. At present, the preparation process of the commonly used solid-state battery mainly adopts independent preparation of the positive electrode, the electrolyte layer and the negative electrode to form an assembly, and then the assembly is combined by pressure. However, the effect of improving the electrolyte layer / electrode interface contact by relying on subsequent pressure is limited. Therefore, the application adopts an electrostatic spraying method to prepare an integrated electrolyte layer / pre-lithiated negative electrode layer on the surface of the negative electrode layer, thereby greatly improving the interface contact problem between the negative electrode layer and the electrolyte layer.

[0018] Finally, in the process of preparing a solid-state electrolyte film by the flow casting method disclosed in the prior art, the binder needs to be mixed and dissolved with an organic solvent, but the sulfide electrolyte is prone to react with the organic solvent to affect the conductivity. Therefore, the dry spraying method is used in the application to avoid the adverse effects of the solvent in the preparation process of the electrolyte layer.

[0019] Preferably, the thickness Y of the negative electrode mixed powder spraying and the thickness X of the substrate satisfy the following relationship:

[0020] Y=6X+10, wherein X≤15 μm.

[0021] Preferably, the thickness Y of the negative electrode mixed powder spraying and the thickness X of the substrate satisfy the following relationship:

[0022] Y=6X+10, wherein 5 μm≤X≤10 μm, and 40 μm≤Y≤70 μm.

[0023] In the application, by adjusting the relationship between the thickness Y of the negative electrode mixed powder spraying and the thickness X of the substrate, the negative electrode layer has a suitable pre-lithium amount, and the N / P ratio is 1.1.

[0024] Preferably, the thickness Z of the sulfide solid-state electrolyte mixed powder spraying and the thickness X of the substrate satisfy the following relationship:

[0025] Z=4.8X+8, wherein X≤15 μm.

[0026] Preferably, the thickness Z of the sulfide solid electrolyte mixed powder spray and the thickness X of the substrate satisfy the following relationship:

[0027] Z = 4.8X + 8, wherein 5pm≤X≤10pm, 32pm≤Z≤56pm.

[0028] In the present application, by regulating the relationship between the thickness Z of the sulfide solid electrolyte mixed powder spray and the thickness X of the substrate, the sulfide electrolyte layer is allowed to rapidly transport lithium ions while not being punctured by lithium dendrites to cause short circuit during battery cycling.

[0029] Preferably, the thickness Z of the sulfide solid electrolyte mixed powder spray and the thickness Y of the negative electrode mixed powder spray satisfy the following relationship:

[0030] Z = 0.8Y, wherein 40pm≤Y≤70pm.

[0031] In the present application, by regulating the relationship between the thickness Z of the sulfide solid electrolyte mixed powder spray and the thickness Y of the negative electrode mixed powder spray, the ion transport path between the positive and negative electrodes is short and the appropriate N / P ratio is satisfied.

[0032] Preferably, the negative electrode mixed powder comprises, by mass percentage, 75-85% negative electrode active material, 1-5% conductive agent, 1-15% first sulfide solid electrolyte, and 1-5% binder, preferably 78-83% negative electrode active material, 2-4% conductive agent, 6-10% first sulfide solid electrolyte, and 1.5-3% binder.

[0033] In the present application, the mass percentage of the negative electrode active material is 75-85%, preferably 78-83%, for example, it can be 75%, 78%, 80%, 82%, 83%, 85%, etc.

[0034] In the present application, the mass percentage of the conductive agent is 1-5%, preferably 2-4%, for example, it can be 1%, 2%, 3%, 4%, 5%, etc.

[0035] In the present application, the mass percentage of the first sulfide solid electrolyte is 1-15%, preferably 6-10%, for example, it can be 1%, 5%, 6%, 8%, 10%, 12%, 15%, etc.

[0036] In the present application, the mass percentage of the binder is 1-5%, preferably 1.5-3%, for example, it can be 1%, 1.5%, 2%, 3%, 4%, 5%, etc.

[0037] Preferably, the negative electrode active material comprises any one of carbon nanomaterial, alloy-based negative electrode material, tin-based negative electrode material, lithium-containing transition metal nitride material, or nano-oxide material, or a combination of at least two of them.

[0038] Preferably, the particle size of the negative active material is in the range of 50-500 nm, preferably 100-300 nm, for example, it can be 50 nm, 80 nm, 100 nm, 150 nm, 200 nm, 250 m, 300 nm, 500 nm, etc.

[0039] Preferably, the powder compaction density of the negative active material is 0.6-2 g / cm 3 , preferably 1-1.8 g / cm 3 , for example, it can be 0.6 g / cm 3 , 0.8 g / cm 3 , 1 g / cm 3 , 1.2 g / cm 3 , 1.4 g / cm 3 , 1.6 g / cm 3 , 1.8 g / cm 3 , 2 g / cm 3 , etc.

[0040] Preferably, the first sulfide solid-state electrolyte includes Li2S-P2P5, Li 3.4 Si 0.4 P 0.6 S4, Li 10 SiP2S 12 , Li 0.35 Si 1.35 P 1.65 S 12 , Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 , Li 10 GeP2S 12 , Li 10.35 Ge 1.35 P 0.75 S4, Li 3.25 Ge 0.25 P 0.75 S4, Li 10 GeP2S 11.7 O 0.3 , Li 9.6 P3S 12 , Li7P3S 11 , Li9P3S9O3, Li 9.81 Sn 0.81 P 2.19 S 12 , Li 10 (Si 0.5 Ge 0.5 )P2S12 Li(Ge 0.5 Sn 0.5) P2S 12 Li(Si 0.5 Sn 0.5 )P2S 12 Li6PS5X, Li7P2S8I or Li 10 SnP2S 12 X is selected from any one of Cl, Br or I.

[0041] Preferably, the binder comprises any one of or a combination of polyvinylidene fluoride, styrene butadiene rubber, sodium carboxymethylcellulose, polyacrylic acid or sodium alginate.

[0042] Preferably, the sulfide solid electrolyte mixture powder comprises, by mass percentage, 90-99% of the second sulfide solid electrolyte and 1-10% of the polymer, preferably 95-98% of the second sulfide solid electrolyte and 2-5% of the polymer.

[0043] In the present application, the mass percentage of the second sulfide solid electrolyte is 90-99%, preferably 95-98%, for example, it can be 90%, 92%, 95%, 96%, 97%, 98%, 99%, etc.

[0044] In the present application, the mass percentage of the polymer is 1-10%, preferably 2-5%, for example, it can be 1%, 2%, 3%, 4%, 5%, 8%, 10%, etc.

[0045] Preferably, the second sulfide solid electrolyte comprises Li2S-P2P5, Li 3.4 Si 0.4 P 0.6 S4, Li 10 SiP2S 12 , Li 0.35 Si 1.35 P 1.65 S 12 , Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 , Li 10 GeP2S 12 , Li 10.35 Ge 1.35 P 0.75 S4, Li 3.25 Ge 0.25 P 0.75 S4, Li 10 GeP2S 11.7 O 0.3Li 9.6 P3S 12 Li7P3S 11 Li9P3S9O3 9.81 Sn 0.81 P 2.19 S 12 Li 10 (Si 0.5 Ge 0.5 )P2S 12 Li(Ge 0.5 Sn 0.5) P2S 12 Li(Si 0.5 Sn 0.5 )P2S 12 Li6PS5X, Li7P2S8I or Li 10 SnP2S 12 X is selected from any one of Cl, Br or I.

[0046] Preferably, the polymer comprises any one of polyvinylidene fluoride, styrene butadiene rubber, sodium carboxymethylcellulose, polyacrylic acid or sodium alginate or a combination of at least two thereof.

[0047] Preferably, the mass ratio of the negative electrode mixed powder to the sulfide solid electrolyte mixed powder is (2-3):(4-5), for example, it can be 2:4, 2:5, 3:5, 3:4, etc.

[0048] In the present application, by regulating the mass ratio of the negative electrode mixed powder to the sulfide solid electrolyte mixed powder, the ion transport path between the positive and negative electrodes is short and meets the appropriate N / P ratio, and too low mass ratio will lead to the existence of lithium dendrites, thereby causing short circuit by piercing the electrolyte layer, and vice versa, which will increase the ion transport path and affect the battery cycle performance.

[0049] Preferably, the preparation method of the negative electrode mixed powder comprises the following steps:

[0050] The negative electrode active material, the conductive agent, the first sulfide solid electrolyte and the binder are once mixed and once ball milled in a water-free and oxygen-free environment with a dew point temperature less than -50°C to obtain the negative electrode mixed powder.

[0051] Preferably, the preparation method of the sulfide solid electrolyte mixed powder comprises the following steps:

[0052] The second sulfide solid electrolyte and the polymer are twice mixed and twice ball milled in a water-free and oxygen-free environment with a dew point temperature less than -50°C to obtain the sulfide solid electrolyte mixed powder.

[0053] Preferably, the spraying of the negative electrode mixed powder onto the substrate is performed by using an electrostatic spray gun.

[0054] Preferably, the voltage of the electrostatic spray gun is set to 10-20KV, for example, it can be 10KV, 12KV, 15KV, 18KV, 20KV, etc.; the distance between the nozzle of the electrostatic spray gun and the substrate is 1-10cm, for example, it can be 1cm, 2cm, 5cm, 8cm, 10cm, etc.

[0055] Preferably, the spraying of the sulfide solid electrolyte mixed powder on the surface of the pre-lithiated negative electrode layer is performed by using an electrostatic spray gun.

[0056] Preferably, the voltage of the electrostatic spray gun is set to 10-20KV, for example, it can be 10KV, 12KV, 15KV, 18KV, 20KV, etc.; the distance between the nozzle of the electrostatic spray gun and the surface of the pre-lithiated negative electrode layer is 1-8cm, for example, it can be 1cm, 3cm, 5cm, 8cm, etc.

[0057] In a second aspect, the present application provides a full solid-state battery, which is prepared by the method for preparing a full solid-state battery by dry method according to the first aspect.

[0058] Compared with the prior art, the present application has the following beneficial effects:

[0059] The present application provides a method for preparing a full solid-state battery by dry method. Firstly, the present application sprays a negative electrode layer on the surface of lithium metal by dry mixing and electrostatic spraying method, avoiding the side reaction between the solvent used in the pre-lithiation process and lithium metal, thereby affecting the pre-lithiation effect. Secondly, the present application prepares an integrated electrolyte layer / pre-lithiated negative electrode layer by using the electrostatic spraying method on the surface of the negative electrode layer, which greatly improves the interface contact problem between the negative electrode layer and the electrolyte layer. Finally, the present application uses the dry spraying method to avoid the adverse effects of the solvent in the preparation process of the electrolyte layer. BRIEF DESCRIPTION OF DRAWINGS

[0060] Figure 1 The electrostatic spraying schematic diagram provided for Example 1. DETAILED DESCRIPTION

[0061] The technical solutions of the present application will be further described below by combining the drawings and specific embodiments. Those skilled in the art should understand that the embodiments are only to help understand the present application and should not be regarded as specific limitations on the present application.

[0062] Example 1

[0063] The present embodiment provides a method for preparing a full solid-state battery by dry method, which comprises the following steps:

[0064] Preparation of the negative electrode layer: In a dry room environment, the negative electrode mixed powder was weighed and mixed in proportion, including 84% nano-silicon powder (particle size range 100-200 nm, powder compaction density 1.2 g / cm 3 ), 1% conductive agent CNT powder, 10% Li6PS5Cl sulfide electrolyte powder, and 5% binder polyacrylic acid, and ball-milled for 2 h at a speed of 300 rpm / min. The mixed powder was placed in an electrostatic spray gun, the voltage of the electrostatic gun was set to 20 KV, the distance between the nozzle of the electrostatic spray gun and the lithium copper composite tape was 10 cm, the thickness of the lithium foil was 5 μm, and the spraying thickness was 40 μm. The above-prepared negative electrode was heated and cured at 135°C for 6 min, and the thickness of the cured negative electrode layer was 32 μm. Figure 1

[0065] Preparation of the electrolyte layer: The electrolyte mixed powder was weighed and mixed in proportion in a ball mill jar, including 95% Li6PS5Cl sulfide electrolyte powder and 5% binder polytetrafluoroethylene, and ball-milled for 2 h at a speed of 350 rpm / min. The mixed powder was placed in an electrostatic spray gun, the voltage of the electrostatic gun was set to 20 KV, the distance between the nozzle of the electrostatic spray gun and the above-mentioned negative electrode layer was 2 cm, and the spraying thickness was 32 μm. The above electrolyte layer-negative electrode layer was placed in a heating and curing oven at 120°C for 8 min, and the thickness of the cured electrolyte layer was 28 μm.

[0066] The mass ratio of the negative electrode mixed powder to the sulfide solid electrolyte mixed powder was 3:5.

[0067] Preparation of the all-solid-state battery: The prepared positive electrode sheet (NCM811 active material: electrolyte Li3InCl6: AB: PTFE = 80:10:5:5) was integrated with the above electrolyte layer-negative electrode layer by flat plate hot pressing, the pressure was 200 Mpa, the temperature was 70°C, and the pressure was maintained for 5 min. Then the tab was welded and the battery was packaged, and an all-solid-state battery was obtained.

[0068] Example 2

[0069] The difference between this example and Example 1 is that the specific preparation process of the negative electrode layer is as follows:

[0070] Preparation of the negative electrode layer:

[0071] In a dry room environment, the negative electrode mixed powder was weighed and mixed in proportion, including 85% nano-silicon powder (particle size range 400-500 nm, powder compaction density 0.6 g / cm 3 ​The negative electrode layer was prepared as follows: in a dry room environment, the negative electrode mixed powder included, by mass percentage: 84% micron silicon powder (particle size range 50-150 nm, powder compacted density 2 g / cm3), 1% conductive agent CNT powder, 10% Li6PS5Cl sulfide electrolyte powder, and 5% binder polyacrylic acid were weighed and mixed in a ball mill tank at a speed of 300 rpm / min for 2 h. The mixed powder was placed in an electrostatic spray gun, the voltage of the electrostatic gun was set to 20 KV, the distance between the nozzle of the electrostatic spray gun and the substrate lithium copper composite tape was 10 cm, the thickness of the lithium foil was 10 pm, and the spraying thickness was 70 pm. The prepared negative electrode was heated and cured at 135 °C for 8 min, and the thickness of the negative electrode layer after curing was 58 pm.

[0072] Example 3

[0073] The difference between this example and Example 1 is that the specific preparation process of the negative electrode layer and the electrolyte layer is as follows:

[0074] The negative electrode layer was prepared as follows: in a dry room environment, the negative electrode mixed powder included, by mass percentage: 84% micron silicon powder (particle size range 50-150 nm, powder compacted density 2 g / cm 3 ), 1% conductive agent CNT powder, 10% Li6PS5Cl sulfide electrolyte powder, and 5% binder polyacrylic acid were weighed and mixed in a ball mill tank at a speed of 300 rpm / min for 2 h. The mixed powder was placed in an electrostatic spray gun, the voltage of the electrostatic gun was set to 20 KV, the distance between the nozzle of the electrostatic spray gun and the substrate lithium copper composite tape was 10 cm, the thickness of the lithium foil was 10 pm, and the spraying thickness was 70 pm. The prepared negative electrode was heated and cured at 135 °C for 8 min, and the thickness of the negative electrode layer after curing was 58 pm.

[0075] The electrolyte layer was prepared as follows: the electrolyte mixed powder included, by mass percentage: 95% Li6PS5Cl sulfide electrolyte powder and 5% binder polytetrafluoroethylene were weighed and mixed in a ball mill tank at a speed of 350 rpm / min for 2 h. The mixed powder was placed in an electrostatic spray gun, the voltage of the electrostatic gun was set to 20 KV, the distance between the nozzle of the electrostatic spray gun and the above-mentioned negative electrode layer was 2 cm, and the spraying thickness was 56 pm. The electrolyte layer-negative electrode layer was placed in a heating device and heated and cured at 120 °C for 8 min, and the thickness of the electrolyte layer after curing was 48 pm. The other conditions were the same as in Example 1.

[0076] Example 4

[0077] The difference between this example and Example 1 is that the thickness of the lithium foil is 15 pm, the spraying thickness of the negative electrode mixed powder is adaptively 100 pm, and the thickness of the negative electrode layer after curing is 82 pm. The spraying thickness of the sulfide solid electrolyte mixed powder is adaptively 80 pm, and the thickness of the electrolyte layer after curing is 66 pm. The mass ratio of the negative electrode mixed powder to the sulfide solid electrolyte mixed powder is 1:2. The other conditions are the same as in Example 1.

[0078] Example 5

[0079] The difference between this example and Example 1 is that the mass ratio of the negative electrode mixed powder to the sulfide solid electrolyte mixed powder is 1:3, and the others are the same as Example 1.

[0080] Example 6

[0081] The difference between this example and Example 1 is that the mass ratio of the negative electrode mixed powder to the sulfide solid electrolyte mixed powder is 1:1, and the others are the same as Example 1.

[0082] Example 7

[0083] The difference between this example and Example 1 is that the thickness of the lithium foil is 20 μm, the spraying thickness of the negative electrode layer is adaptively 130 μm, and the thickness of the negative electrode layer after curing is 106 μm; the spraying thickness of the sulfide electrolyte layer is adaptively 104 μm, and the thickness of the electrolyte layer after curing is 89 μm, the mass ratio of the negative electrode mixed powder to the sulfide solid electrolyte mixed powder is 3:4, and the others are the same as Example 1.

[0084] Comparative Example 1

[0085] The difference between this comparative example and Example 1 is that the negative electrode powder is directly sprayed on the surface of the copper foil (without pre-lithiation), and the others are the same as Example 1.

[0086] Comparative Example 2

[0087] The difference between this comparative example and Example 1 is that:

[0088] Preparation of the negative electrode layer: In a dry room environment, 1.5% of the conductive agent CNT aqueous dispersion, 1.5% of the binder polyacrylic acid were weighed and mixed according to the solid content of 45% in deionized water, and magnetically stirred for 2 h. After the above glue dispersion was uniformly dispersed, 95% of the micron silicon powder was added and stirred for 2 h under vacuum at a speed of 500 r / min. The uniform slurry was prepared and coated to prepare the negative electrode.

[0089] Preparation of the electrolyte layer: 97% of the sulfide electrolyte Li6PS5Cl and 3% of the polytetrafluoroethylene were added to a ball mill tank and mixed uniformly at 240 r / min for 10 min. The mixed powder was placed in a high-speed mixer with paddles and mixed at high speed for 20 min. The mixed material was placed in a roller press machine and hot-rolled into a self-supporting solid electrolyte film (100°C). The thickness of the electrolyte layer was 30 μm, and the others were the same as Example 1.

[0090] Comparative Example 3

[0091] The comparative example provides a preparation method of a full solid-state battery, which comprises the following steps: in a dry room environment, a positive electrode mixed powder is weighed and mixed by mass percentage to include 80% active substance NCM811, 1% conductive agent CNT powder, 14% Li6PS5Cl sulfide electrolyte powder and 5% binder polyacrylic acid, the mixed powder is mixed by ball milling at a speed of 350 rpm / min for 4h, the mixed powder is placed in an electrostatic spray gun, the voltage of the electrostatic gun is set to 20KV, the distance between the nozzle of the electrostatic spray gun and the aluminum foil substrate is 7cm, and the spraying thickness is 25μm; the prepared positive electrode is heated and solidified at 135℃ for 6min, and the thickness of the solidified negative electrode layer is 18μm; then the electrolyte layer and the negative electrode layer are prepared in sequence according to the above method to obtain a full solid-state battery.

[0092] Test conditions

[0093] The full solid-state batteries provided by examples 1 to 7 and comparative examples 1 to 3 are tested, and the test method is as follows:

[0094] At 30℃, the charge-discharge rate is 0.3C, and the voltage range is 2.4-4.25V (Li + / Li)

[0095] The test results are shown in Table 1:

[0096] Table 1

[0097]

[0098] As can be seen from Table 1, the negative electrode layer and the electrolyte layer are prepared by the electrostatic spraying method, the mass ratio of the negative electrode mixed powder and the sulfide solid-state electrolyte mixed powder is adjusted, the ion transmission path between the positive and negative electrodes is short and meets the appropriate N / P ratio, which effectively improves the first cycle coulombic efficiency of the full solid-state battery and improves the cycle performance of the full solid-state battery.

[0099] Examples 5-6 are the cases where the mass ratio of the negative electrode mixed powder and the sulfide solid-state electrolyte mixed powder exceeds the limited range, and the comprehensive performance of the prepared battery is poor; example 7 is the case where the thickness of the lithium foil substrate is too large, and the obtained battery is prone to short circuit.

[0100] Compared with example 1, comparative example 1 does not perform pre-lithiation treatment, and the prepared battery has low first efficiency and poor cycle performance; comparative example 2 has poor effect by using wet process; in comparative example 3, due to the high tap density of the positive electrode material, the electrostatic spraying effect is not ideal, and it is easy to produce uneven thickness and not easy to produce electrostatic adsorption, so the performance of the prepared battery is poor.

[0101] Applicants declare that the process of the present application is illustrated by the above examples, but the present application is not limited to the above process steps, i.e. it does not mean that the present application must rely on the above process steps to be implemented. It should be understood by those skilled in the art that any improvement of the present application, equivalent replacement of the raw materials selected by the present application, addition of auxiliary ingredients, selection of specific modes, etc. fall within the protection scope and disclosure scope of the present application.

Claims

1. A method of dry preparation of an all-solid-state battery, characterized by, The method comprises the following steps: Preparation of negative electrode mixed powder and sulfide solid electrolyte mixed powder; In anhydrous and anaerobic environment, the negative electrode mixed powder is sprayed onto the substrate by using electrostatic spraying equipment, and the pre-lithiated negative electrode layer is obtained after solidification, wherein the substrate comprises lithium foil and / or lithium-copper composite tape; The sulfide solid electrolyte mixed powder is sprayed on the surface of the pre-lithiated negative electrode layer by using electrostatic spraying equipment, and the electrolyte layer is obtained after solidification; The dry film forming positive electrode material is compounded with the other side of the electrolyte layer, and a full solid-state battery is assembled; The dry film forming preparation method of the positive electrode material is a non-electrostatic spraying method.

2. The method of claim 1, wherein, The thickness Y of the negative electrode mixed powder sprayed and the thickness X of the substrate satisfy the following relationship: Y=6X+10, wherein X≤15μm.

3. The method of claim 2, wherein, The thickness Y of the negative electrode mixed powder sprayed and the thickness X of the substrate satisfy the following relationship: Y=6X+10, wherein 5μm≤X≤10μm, 40μm≤Y≤70μm.

4. The method of claim 1, wherein, The thickness Z of the sulfide solid electrolyte mixed powder sprayed and the thickness X of the substrate satisfy the following relationship: Z=4.8X+8, wherein X≤15μm.

5. The method of claim 4, wherein, The thickness Z of the sulfide solid electrolyte mixed powder sprayed and the thickness X of the substrate satisfy the following relationship: Z=4.8X+8, wherein 5μm≤X≤10μm, 32μm≤Z≤56μm.

6. The method of claim 1, wherein, The thickness Z of the sulfide solid electrolyte mixed powder sprayed and the thickness Y of the negative electrode mixed powder sprayed satisfy the following relationship: Z=0.8Y, wherein 40μm≤Y≤70μm.

7. The method of claim 1, wherein, The negative electrode mixed powder comprises, by mass percentage: 75-85% negative electrode active material, 1-5% conductive agent, 1-15% first sulfide solid electrolyte, and 1-5% binder.

8. The method of claim 7, wherein, The negative electrode mixed powder comprises, by mass percentage: 78-83% negative electrode active material, 2-4% conductive agent, 6-10% first sulfide solid electrolyte, and 1.5-3% binder.

9. The method of claim 8, wherein, The negative electrode active material comprises any one or a combination of at least two of carbon nanomaterial, alloy-based negative electrode material, tin-based negative electrode material, lithium-containing transition metal nitride material, or nano-oxide material.

10. The method of claim 8, wherein, The particle size range of the negative electrode active material is 50-500nm.

11. The method of claim 10, wherein, The particle size range of the negative electrode active material is 100-300nm.

12. The method of claim 8, wherein, The powder compaction density of the negative active material is 0.6-2 g / cm 3 .

13. The method of claim 12, wherein, The powder compacting density of the negative active material is 1 to 1.8 g / cm 3 .

14. The method of claim 8, wherein, The first sulfide solid-state electrolyte includes Li 3.4 Si 0.4 P 0.6 S4, Li 10 SiP2S 12 , Li 0.35 Si 1.35 P 1.65 S 12 , Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 , Li 10 GeP2S 12 , Li 10.35 Ge 1.35 P 0.75 S4, Li 3.25 Ge 0.25 P 0.75 S4, Li 10 GeP2S 11.7 O 0.3 , Li 9.6 P3S 12 , Li7P3S 11 , Li9P3S9O3, Li 9.81 Sn 0.81 P 2.19 S 12 , Li 10 (Si 0.5 Ge 0.5 )P2S 12 , Li(Ge 0.5 Sn 0.5 )P2S 12 , Li(Si 0.5 Sn 0.5 )P2S 12 , Li6PS5X, Li7P2S8I or Li 10 SnP2S 12 , X is selected from any one of Cl, Br or I.

15. The method of claim 8, wherein, The binder comprises any one or a combination of at least two of polyvinylidene fluoride, styrene-butadiene rubber, sodium carboxymethyl cellulose, polyacrylic acid, or sodium alginate.

16. The method of claim 1, wherein, The sulfide solid electrolyte mixed powder comprises, by mass percentage: 90-99% second sulfide solid electrolyte and 1-10% polymer.

17. The method of claim 16, wherein, The sulfide solid electrolyte mixed powder comprises, by mass percentage: 95-98% second sulfide solid electrolyte and 2-5% polymer.

18. The method of claim 17, wherein, The second sulfide solid-state electrolyte includes Li 3.4 Si 0.4 P 0.6 S4, Li 10 SiP2S 12 , Li 0.35 Si 1.35 P 1.65 S 12 , Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 , Li 10 GeP2S 12 , Li 10.35 Ge 1.35 P 0.75 S4, Li 3.25 Ge 0.25 P 0.75 S4, Li 10 GeP2S 11.7 O 0.3 , Li 9.6 P3S 12 , Li7P3S 11 , Li9P3S9O3, Li 9.81 Sn 0.81 P 2.19 S 12 , Li 10 (Si 0.5 Ge 0.5 )P2S 12 , Li(Ge 0.5 Sn 0.5 )P2S 12 , Li(Si 0.5 Sn 0.5 )P2S 12 , Li6PS5X, Li7P2S8I or Li 10 SnP2S 12 , X is selected from any one of Cl, Br or I.

19. The method of claim 17, wherein, The polymer comprises any one or a combination of at least two of polyvinylidene fluoride, styrene-butadiene rubber, sodium carboxymethyl cellulose, polyacrylic acid, or sodium alginate.

20. The method of claim 1, wherein, The mass ratio of the negative electrode mixed powder to the sulfide solid electrolyte mixed powder is (2-3):(4-5).

21. The method of claim 1, wherein, The preparation method of the negative electrode mixed powder comprises the following steps: The negative electrode active material, the conductive agent, the first sulfide solid-state electrolyte, and the binder are once mixed and once ball-milled in a water-free and oxygen-free environment with a dew point temperature less than-50℃ to obtain the negative electrode mixed powder.

22. The method of claim 1, wherein, The preparation method of the sulfide solid-state electrolyte mixed powder comprises the following steps: The second sulfide solid-state electrolyte and the polymer are twice mixed and twice ball-milled in a water-free and oxygen-free environment with a dew point temperature less than-50℃ to obtain the sulfide solid-state electrolyte mixed powder.

23. The method of claim 1, wherein, The negative electrode mixed powder is sprayed onto the substrate by using an electrostatic spray gun.

24. The method of claim 23, wherein, The voltage of the electrostatic spray gun is set to 10-20KV, and the distance between the nozzle of the electrostatic spray gun and the substrate is 1-10cm.

25. The method of claim 1, wherein, The sulfide solid-state electrolyte mixed powder is sprayed onto the surface of the pre-lithiated negative electrode layer by using an electrostatic spray gun.

26. The method of claim 25, wherein, The voltage of the electrostatic spray gun is set to 10-20KV, and the distance between the nozzle of the electrostatic spray gun and the surface of the pre-lithiated negative electrode layer is 1-8cm.

27. An all-solid-state battery, characterized by comprising: The all-solid-state battery is prepared by the method for preparing an all-solid-state battery by a dry method according to any one of claims 1-26.

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