A positive electrode of a lithium-ion solid-state battery, its preparation process, and a lithium-ion solid-state battery

Abstract

The present invention discloses a positive electrode of a lithium-ion solid-state battery, a preparation process thereof, and a lithium-ion solid-state battery. The preparation process of the positive electrode of the lithium-ion solid-state battery of the present invention comprises the following steps: S1. Coating a positive electrode active material layer on the surface of a positive electrode current collector and drying; S2. Coating a solid electrolyte coating slurry on the surface of the positive electrode active material layer, wherein the solid electrolyte coating slurry comprises a substance that is solid at normal temperature and forms a gas at 60-200 °C; S3. Heating and drying at 60-200 °C to obtain the solid electrolyte coating; while heating, applying pressure to the surface of the positive electrode current collector forming the solid electrolyte coating for compaction to obtain the positive electrode of the lithium-ion solid-state battery. The solid electrolyte coating of the positive electrode of the lithium-ion solid-state battery of the present invention has a moderate solid content, and the solid electrolyte coating has good stability and uniformity, so that the prepared lithium-ion solid-state battery has good capacity retention rate.

Description

Technical Field

[0001] The present invention belongs to the field of lithium ion solid-state batteries, and specifically relates to a lithium ion solid-state battery positive electrode and a preparation process thereof, and in particular to a lithium ion solid-state battery prepared by using the lithium ion solid-state battery positive electrode. Background Art

[0002] All-solid-state lithium-ion batteries generally include three parts: positive electrode, negative electrode, and solid electrolyte. Among them, the positive electrode includes positive electrode active material, binder, and conductive agent; the negative electrode includes negative electrode active material, binder, conductive agent or lithium metal is used as the negative electrode; the solid electrolyte includes binder and electrolyte material, and the electrolyte material is selected from oxide or sulfide solid electrolyte.

[0003] In the prior art, it is advantageous to coat a solid electrolyte layer on the surface of the electrode active material layer, and a thinner coating layer is more conducive to improving battery performance. The solid electrolyte coating includes a binder and an electrolyte material, and the electrolyte material is selected from oxide or sulfide solid electrolytes. The composition of the solid electrolyte coating can be the same as or different from the solid electrolyte, and there is no special limitation. However, due to the limitations of current coating technology, the stability of the coating layer is affected if the coating is too thin. At the same time, during the coating process, too high a solid content is not conducive to reducing the thickness of the coating layer, and too low a solid content is not conducive to the stability of the coating layer, and the uniformity of the coating layer is ensured.

[0004] CN110400905A discloses a pole piece containing a solid electrolyte, including a pole piece body and a solid electrolyte coating coated on one side surface or both sides of the pole piece body, wherein the thickness of the solid electrolyte coating is 5-20 μm; the solid electrolyte coating comprises the following raw materials, calculated by weight: 0.5-2 parts of dispersant, 10-40 parts of solid electrolyte, 1-5 parts of binder, 50-100 parts of solvent A, and 50-100 parts of solvent B; the preparation method of the pole piece and its application in lithium batteries are also disclosed, wherein the pole piece surface is very smooth, and the diaphragm required in traditional batteries is omitted, and the performance is better than that of traditional batteries. However, the solid electrolyte coating of the invention is also difficult to control the coating thickness during coating, thereby affecting the stability and uniformity of the coating.

[0005] Therefore, finding a suitable solid electrolyte coating and coating method is extremely beneficial for the preparation of lithium-ion solid-state batteries with good electrical properties. Summary of the invention

[0006] In view of the deficiencies of the prior art, the purpose of the present invention is to provide a positive electrode for a lithium-ion solid-state battery, its preparation process, and a lithium-ion solid-state battery. The solid electrolyte coating of the positive electrode for the lithium-ion solid-state battery has a moderate solid content, good stability and uniformity, so that the prepared lithium-ion solid-state battery has a good capacity retention rate.

[0007] One of the purposes of the present invention is to provide a preparation process for a positive electrode of a lithium-ion solid-state battery. To achieve this purpose, the present invention adopts the following technical solutions:

[0008] A preparation process for a positive electrode of a lithium-ion solid-state battery, the positive electrode includes a positive electrode active material layer, and the positive electrode active material layer includes positive electrode active materials.

[0009] The preparation process for the positive electrode of the lithium-ion solid-state battery includes the following steps:

[0010] S1. Coating a positive electrode active material layer on the surface of a positive electrode current collector and drying it.

[0011] S2. Coating a solid electrolyte coating slurry on the surface of the positive electrode active material layer, and the solid electrolyte coating slurry includes substances that are solid at normal temperature and form gases at 60-200 °C.

[0012] S3. Heating and drying at 60-200 °C, so that the substances that are solid at normal temperature and form gases at 60-200 °C in the solid electrolyte coating slurry decompose or volatilize to form gases, obtaining the solid electrolyte coating; while heating, applying pressure to the surface of the positive electrode current collector forming the solid electrolyte coating for compaction, obtaining the positive electrode for the lithium-ion solid-state battery.

[0013] Among them, the substance that is solid at normal temperature and forms a gas at 60-200 °C is any one or a mixture of at least two of ammonium bicarbonate, ammonium carbonate, and aluminum chloride.

[0014] The mass percentage of the substance that is solid at normal temperature and forms a gas at 60-200 °C accounts for 5-40% of the total mass of the formulation system.

[0015] The porosity of the solid electrolyte coating < 3%.

[0016] The solvent is a non-aqueous solvent.

[0017] By introducing solid substances that are easily decomposed and sublimated at low temperatures into the solid electrolyte coating, the present invention improves the solid content of the solid electrolyte coating during the coating process, reduces the requirements for coating equipment, saves costs, and at the same time, in the subsequent process, due to the decomposition of the solid substances that are easily decomposed and sublimated at low temperatures to generate gases or sublimation, the thickness of the coating is significantly reduced after drying and discharging the solvent.

[0018] Among them, the mass percentage of the substance that is solid at room temperature and forms a gas at 60 to 200 °C is 5 to 40% of the total mass of the formulation system.

[0019] Preferably, when the substance that is solid at room temperature and forms a gas at 60 to 200 °C is ammonium bicarbonate, the mass percentage of the ammonium bicarbonate is 15 to 40% of the total mass of the formulation system. For example, the mass percentage of the ammonium bicarbonate is 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, etc. of the total mass of the formulation system.

[0020] Preferably, when the substance that is solid at room temperature and forms a gas at 60 to 200 °C is ammonium carbonate, the mass percentage of the ammonium carbonate is 20 to 30% of the total mass of the formulation system. For example, the mass percentage of the ammonium carbonate is 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, etc. of the total mass of the formulation system.

[0021] Preferably, when the substance that is solid at room temperature and forms a gas at 60 to 200 °C is aluminum chloride, the mass percentage of the aluminum chloride is 5 to 30% of the total mass of the formulation system. For example, the mass percentage of the aluminum chloride is 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, etc. of the total mass of the formulation system.

[0022] The porosity of the solid electrolyte coating is < 3%, preferably the porosity is < 1.5%. For example, the porosity of the solid electrolyte coating is 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, etc.

[0023] The thickness of the solid electrolyte coating is 5 to 30 μm. For example, the thickness of the solid electrolyte coating is 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm, etc.

[0024] Preferably, the solid electrolyte coating further comprises a solid electrolyte material and a binder.

[0025] The binder includes but is not limited to polyvinylidene fluoride and / or polytetrafluoroethylene. The solid electrolyte coating may further include PEO. For the solid electrolyte material, it may be a fast ion conductor or other known solid electrolyte materials. Fast ion conductors, also known as lithium ion conductive substances, generally refer to substances with good ion conduction performance. The fast ion conductor can be an organic substance or an inorganic substance, including but not limited to LiNbO 3 、Li 4 Ti 5 O 4 、Li 3 PO 4 and LiTFSI, etc.

[0026] The known solid electrolyte materials include any one of oxide solid electrolytes, sulfide solid electrolytes, selenide solid electrolytes, and polymer solid electrolytes.

[0027] The oxide solid electrolyte is an oxide-based solid electrolyte. Specifically, examples include LiPON (lithium oxynitride phosphate), Li 1.3 Al 0.3 Ti 0.7 (PO 4 ) 3 、La 0.5 1Li 0.34 TiO 0.74 、Li 3 PO 4 、Li 2 SiO 2 and Li 2 SiO 4 、any one of lithium lanthanum zirconium oxide or lithium lanthanum titanium oxide.

[0028] The polymer electrolyte of the present invention generally contains a metal salt and a polymer. When the metal battery according to the present invention is a lithium battery, a lithium salt can be used as the metal salt. As the lithium salt, at least any one of an inorganic lithium salt and an organic lithium salt can be used. As the polymer, there is no particular limitation as long as it forms a complex with the lithium salt, and examples thereof include polyethylene oxide and the like.

[0029] Examples of sulfide solid electrolytes include Li 2 SP 2 S 5 , Li 2 SP 2 S 5 -LiI, Li 2 SP 2 S 5 -Li 2 O. Li 2 SP 2 S 5 -Li 2 O-LiI、Li 2 S-SiS 2 , Li 2 S-SiS 2 -LiI, Li 2 S-SiS 2 -LiBr, Li 2 S-SiS 2 -LiCl, Li 2 S-SiS 2 -B 2 S 3 -LiI, Li 2 S-SiS 2 -P 2 S 5 -LiI, Li 2 SB 2 S 3 , Li 2 SP 2 S 5 -Z m S n , Li 2 S-GeS 2 , Li 2 S-SiS 2 -Li 3 PO 4 or Li 2 S-SiS 2 -Li x MO y, where m and n are positive numbers, Z is any one of Ge, Zn, and Ga, x and y are positive numbers, and M is any one of P, Si, Ge, B, Al, Ga, and In. It should be noted that the above Li 2 S-P 2 S 5 in the description refers to the sulfide solid electrolyte material formed using a raw material composition containing Li 2 S and P 2 S 5 . The same applies to other descriptions.

[0030] In addition to the above ion conductor, the sulfide solid electrolyte material may further contain lithium halide. Examples of the lithium halide include LiF, LiCl, LiBr, and LiI, among which LiCl, LiBr, and LiI are preferred. The proportion of LiX (X = F, I, Cl, Br) in the sulfide solid electrolyte material is, for example, in the range of 5 mol% - 30 mol%, and can be in the range of 15 mol% - 25 mol%.

[0031] As the solid electrolyte used in the present invention, in addition to the above, for example, Li 2 Ti(PO 4 ) 3 -AlPO 4 (Ohara glass), etc.

[0032] Preferably, an oxide solid electrolyte is used in this application.

[0033] The positive electrode of the lithium-ion solid-state battery of the present invention has no particular limitation on the composition of the active material layer.

[0034] For example, for the positive electrode active material layer, the positive electrode active material includes but is not limited to LiCoO 2 , LiMnO 2 , LiNiO 2 , LiVO 2 , ternary material NMC, LiMn 2 O 4 , Li(Ni 0.5 Mn 1.5 )O 4 , LiFePO 4 , LiMnPO 4 , LiNiPO 4 and LiCoPO 4 , etc. The binder includes but is not limited to polyvinylidene fluoride PVDF, polytetrafluoroethylene PTFE, styrene-butadiene rubber SBR, and styrene-butadiene rubber, etc. The conductive agent includes but is not limited to acetylene black, Ketjen black, super-P, and carbon fiber, etc.

[0035] Ammonium carbonate and ammonium bicarbonate will form water during the decomposition process. Therefore, during the heating process, the temperature must be higher than 60 °C to ensure that the water generated by the reaction completely volatilizes. When using these two substances, the coating thickness should not be too thick, otherwise the water inside the coating will be difficult to volatilize due to the resistance inside the coating, which will affect the battery performance. The sublimation temperature of aluminum chloride is slightly higher and it takes time to volatilize. Therefore, a longer residence time needs to be set in the heating area.

[0036] In step S3, for ammonium bicarbonate and ammonium carbonate, the residence time for heating is 2 - 10 min, such as 2 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, etc. It only needs to ensure that the water completely volatilizes. The temperature is preferably 100 - 115 °C, such as 100 °C, 101 °C, 102 °C, 103 °C, 104 °C, 105 °C, 106 °C, 107 °C, 108 °C, 109 °C, 110 °C, 111 °C, 112 °C, 113 °C, 114 °C, 115 °C, etc. If the temperature is too high or the residence time is too long, it is easy to cause the binder to age and affect the battery performance. For aluminum chloride, the temperature is preferably 185 - 200 °C, such as 185 °C, 186 °C, 187 °C, 188 °C, 189 °C, 190 °C, 191 °C, 192 °C, 193 °C, 194 °C, 195 °C, 196 °C, 197 °C, 198 °C, 199 °C, 200 °C, etc., and the residence time is 15 - 30 min, such as 15 min, 16 min, 17 min, 18 min, 19 min, 20 min, 21 min, 22 min, 23 min, 24 min, 25 min, 26 min, 27 min, 28 min, 29 min, 30 min, etc. It only needs to ensure that the aluminum chloride completely volatilizes.

[0037] In step S3, while heating, pressure is applied to the surface of the positive current collector forming the solid electrolyte coating for compaction; specifically, when heating in the heating area, a double-sided roller structure is used to apply pressure to the surface of the positive current collector, such as the aluminum foil surface, for compaction. Applying pressure can, on the one hand, ensure that the gases generated during the reaction and sublimation processes are exhausted, and on the other hand, can prevent the gases generated from damaging the microstructure of the solid electrolyte coating, further improving the density of the solid electrolyte coating.

[0038] As a preferred embodiment of the present invention, the preparation process of the positive electrode of the lithium-ion solid-state battery includes the following steps:

[0039] S1. Coating a positive electrode active material layer on the surface of the positive current collector and drying.

[0040] S2. Coat a solid electrolyte coating slurry on the surface of the positive electrode active material layer, where the solid electrolyte coating slurry includes a substance that is solid at room temperature and forms a gas at 60-200 °C;

[0041] S3. Heat and dry at 60-200 °C so that the substance that is solid at room temperature and forms a gas at 60-200 °C in the solid electrolyte coating slurry decomposes or volatilizes to form a gas, obtaining the solid electrolyte coating; while heating, apply pressure to the surface of the positive electrode current collector on which the solid electrolyte coating is formed for compaction, obtaining the positive electrode of the lithium-ion solid-state battery;

[0042] Among them, the substance that is solid at room temperature and forms a gas at 60-200 °C is any one or a mixture of at least two of ammonium bicarbonate, ammonium carbonate, and aluminum chloride;

[0043] The porosity of the solid electrolyte coating ≤ 0.5%, for example, the porosity of the solid electrolyte coating is 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, etc.

[0044] Among them, a lithium-ion solid-state battery further includes a negative electrode, and a solid electrolyte is further provided outside the solid electrolyte coating.

[0045] The composition of the solid electrolyte is different from that of the solid electrolyte coating.

[0046] The thickness of the solid electrolyte is 10-300 μm, for example, the thickness of the solid electrolyte is 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, 190 μm, 200 μm, 210 μm, 220 μm, 230 μm, 240 μm, 250 μm, 260 μm, 270 μm, 280 μm, 290 μm, 300 μm, etc.

[0047] The second object of the present invention is to provide a preparation process for a lithium-ion solid-state battery, and the preparation process includes the following steps:

[0048] A) Preparation of the positive electrode plate

[0049] Use the positive electrode of the lithium-ion solid-state battery prepared by the preparation process described in Object One as the positive electrode plate;

[0050] B) Stack the prepared positive electrode plate, lithium metal negative electrode plate, and lithium lanthanum zirconium oxide solid electrolyte, and assemble to obtain the lithium-ion solid-state battery.

[0051] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0052] For the positive electrode of the lithium-ion solid-state battery of the present invention, the solid electrolyte coating has a moderate solid content, and the solid electrolyte coating has good stability and uniformity, enabling the prepared lithium-ion solid-state battery to have good capacity retention. The initial efficiency is 91 - 94%, the capacity retention after 50 cycles is 91.6 - 94.6%, and the capacity retention after 100 cycles is 82.2 - 86.8%.

[0053] The preparation process of the positive electrode of the lithium-ion solid-state battery of the present invention reduces the requirements for coating equipment and saves costs. Brief Description of the Drawings

[0054] Figure 1 It is the SEM image of the solid electrolyte layer coated in Example 1 of the present invention;

[0055] Figure 2 It is the SEM image of the solid electrolyte layer coated in Example 2 of the present invention;

[0056] Figure 3 It is the SEM image of the solid electrolyte layer coated in Example 3 of the present invention;

[0057] Figure 4 It is the SEM image of the solid electrolyte layer coated in Comparative Example 1 of the present invention. Detailed Description of the Invention

[0058] The following combines the attached Figures 1-4 drawings and further illustrates the technical solutions of the present invention through specific embodiments.

[0059] Unless otherwise specified, various raw materials of the present invention can be purchased commercially or prepared according to conventional methods in the art.

[0060] Example 1

[0061] For the positive electrode of the lithium-ion solid-state battery in this example, the preparation method is as follows:

[0062] 1) Coat a positive electrode active material layer composed of 10wt% PTFE, 10wt% carbon fiber, and 80wt% lithium nickel cobalt manganese oxide on the surface of the aluminum foil and dry it;

[0063] 2) Dissolve 30wt% ammonium bicarbonate, 60wt% lithium lanthanum zirconium oxide, and 10wt% PTFE in NMP (the solid content of the slurry is 60wt%) to prepare a solid electrolyte coating solution. Set the coating thickness of the coater to 15μm and the conveying rate of the aluminum foil to 2m / s, and coat the solid electrolyte coating solution on the surface of the positive electrode active material layer;

[0064] 3) After coating, it enters the heating area. The drying temperature is 110 °C, the residence time is 5 min. After winding, it is further dried in an oven at 105 °C for 24 h. The dried electrode sheet is rolled and slit to obtain the positive electrode of the lithium-ion solid-state battery. The porosity of the solid electrolyte coating is 1.8%.

[0065] The positive electrode of the lithium-ion solid-state battery prepared above is used as the positive electrode sheet for the preparation of the lithium-ion solid-state battery. The specific process is as follows:

[0066] A) Preparation of the positive electrode sheet

[0067] The positive electrode of the lithium-ion solid-state battery prepared according to the above preparation method is used as the positive electrode sheet;

[0068] B) The prepared positive electrode sheet, lithium metal negative electrode sheet, and lithium lanthanum zirconium oxide-based solid electrolyte are laminated to assemble a solid-state lithium-ion battery.

[0069] Example 2

[0070] The positive electrode of the lithium-ion solid-state battery in this example is prepared as follows:

[0071] 1) A positive electrode active material layer composed of 10 wt% PTFE, 10 wt% carbon fiber, and 80 wt% lithium nickel cobalt manganese oxide is coated on the surface of the aluminum foil and dried;

[0072] 2) Dissolve 30 wt% ammonium carbonate, 60 wt% lithium lanthanum zirconium oxide, and 10 wt% PTFE in NMP (the solid content of the slurry is 60 wt%) to prepare a solid electrolyte coating solution. Set the coating thickness of the coater to 15 μm and the conveying rate of the aluminum foil to 2 m / s. Coat the solid electrolyte coating solution on the surface of the positive electrode active material layer;

[0073] 3) After coating, it enters the heating area. The drying temperature is 105 °C, the residence time is 5 min. After winding, it is further dried in an oven at 105 °C for 24 h. The dried electrode sheet is rolled and slit to obtain the positive electrode of the lithium-ion solid-state battery. The porosity of the solid electrolyte coating is 1.6%.

[0074] The positive electrode of the lithium-ion solid-state battery prepared above is used as the positive electrode sheet for the preparation of the lithium-ion solid-state battery. The specific process is as follows:

[0075] A) Preparation of the positive electrode sheet

[0076] The positive electrode of the lithium-ion solid-state battery prepared according to the above preparation method is used as the positive electrode sheet;

[0077] B) The prepared positive electrode sheet, lithium metal negative electrode sheet, and lithium lanthanum zirconium oxide-based solid electrolyte are laminated to assemble a solid-state lithium-ion battery.

[0078] Example 3

[0079] The positive electrode of the lithium-ion solid-state battery in this example is prepared as follows:

[0080] 1) Coat the surface of the aluminum foil with a positive electrode active material layer composed of 10 wt% PTFE, 10 wt% carbon fiber, and 80 wt% lithium nickel cobalt manganese oxide, and dry it;

[0081] 2) Dissolve aluminum chloride, lithium lanthanum zirconium oxide, and PTFE in NMP (the solid content of the slurry is 60 wt%) according to the mass ratio of 30 wt%, 60 wt%, and 10 wt% respectively to prepare a solid electrolyte coating solution. Set the coating thickness of the coater to 15 μm and the aluminum foil transfer rate to 2 m / s, and coat the solid electrolyte coating solution on the surface of the positive electrode active material layer;

[0082] 3) After coating, enter the heating area. The drying temperature is 195 °C, and the residence time is 20 min. After winding, dry it in an oven at 105 °C for 24 h. Roll and slit the dried electrode sheet to obtain the positive electrode of the lithium-ion solid-state battery. The porosity of the solid electrolyte coating is 1.5%.

[0083] Use the positive electrode of the lithium-ion solid-state battery prepared above as the positive electrode plate for the preparation of the lithium-ion solid-state battery. The specific process is as follows:

[0084] A) Preparation of the positive electrode plate

[0085] Use the positive electrode of the lithium-ion solid-state battery prepared according to the above preparation method as the positive electrode plate;

[0086] B) Stack the prepared positive electrode plate, lithium metal negative electrode plate, and lithium lanthanum zirconium oxide-based solid electrolyte to assemble a solid-state lithium-ion battery.

[0087] Example 4

[0088] Compared with Example 1, the difference is that rolling is carried out simultaneously during the heating process, and the rolling thickness is set to 90% of the thickness of the composite electrode plate when leaving the heating area obtained in Example 1. The porosity of the solid electrolyte coating is 0.3%.

[0089] Comparative Example 1

[0090] The difference between this comparative example and Example 1 is that in step 2), dissolve lithium lanthanum zirconium oxide and PTFE in NMP according to the mass ratio of 80 wt% and 20 wt% respectively to prepare a solid electrolyte coating solution. Set the coating thickness of the coater to 15 μm and the aluminum foil transfer rate to 2 m / s, and coat the solid electrolyte coating solution on the surface of the positive electrode active material layer.

[0091] The thicknesses of the solid electrolyte coatings prepared in Examples 1-4 and Comparative Example 1 were measured. The experimental results are shown in Table 1. The capacity retention rates of the lithium-ion solid-state batteries prepared with the obtained lithium-ion solid-state battery cathodes as the positive electrodes were measured. The experimental results are shown in Table 2. Among them, the test method was to perform charge and discharge tests on the batteries obtained in each example and comparative example at 25 ± 2 °C, with a charge and discharge voltage of 2.75~4.25 V and a current density of 0.1 C. The first efficiency, 50-cycle capacity retention rate, and 100-cycle capacity retention rate were tested respectively.

[0092] Figure 1 SEM image of the solid electrolyte layer coated for Example 1 Figure 2 SEM image of the solid electrolyte layer coated for Example 2 Figure 3 SEM image of the solid electrolyte layer coated for Example 3 Figure 4 SEM image of the solid electrolyte layer coated for Comparative Example 1. From Figures 1-4 it can be seen that after adding ammonium bicarbonate, ammonium carbonate, and aluminum chloride, the surface of the positive electrode becomes more uniform.

[0093] Table 1

[0094] Coating thickness (μm) Thickness after leaving the heating area (μm) Example 1 15.0 13.1 Example 2 15.0 12.6 Example 3 15.0 11.8 Example 4 15.0 10.4 Comparative Example 1 15.0 14.8

[0095] As can be seen from Table 1, when ammonium bicarbonate, ammonium carbonate, and aluminum chloride are heated, they will completely turn into gases. Therefore, they have a good effect on reducing the thickness. In Example 4, rolling was performed simultaneously during the heating process to obtain a thinner solid electrolyte layer. Ammonium carbonate and ammonium bicarbonate will form water during the decomposition process. Therefore, during the heating process, the temperature must be higher than 60 °C to completely volatilize the water generated by the reaction. And when using these two substances, the coating thickness cannot be too thick, otherwise the water inside the coating will be difficult to volatilize due to the resistance inside the coating, which will affect the battery performance. The sublimation temperature of aluminum chloride is slightly higher and it takes time to volatilize. Therefore, a longer residence time needs to be set in the heating area.

[0096] Table 2

[0097] Initial efficiency (%) Capacity retention rate after 50 cycles (%) Capacity retention rate after 100 cycles (%) Example 1 92 91.6 82.2 Example 2 91 92.8 83.1 Example 3 93 93.3 85.6 Example 4 94 94.6 86.8 Comparative Example 1 90 89.2 78.6

[0098] As can be seen from the data in Table 2, compared with Comparative Example 1 where no substance that is solid at room temperature and forms a gas at 60~200 °C was added to the solid electrolyte layer, when the lithium-ion solid-state battery cathodes prepared in Examples 1-3 of the present invention were used as the positive electrode plates for lithium-ion solid-state batteries, the first efficiency and capacity retention rate of the batteries could be significantly improved; in Example 4, rolling was performed simultaneously during the heating process, which could further improve the first efficiency and capacity retention rate of the batteries.

[0099] The present invention illustrates the detailed process equipment and process flow of the present invention through the above embodiments. However, the present invention is not limited to the above detailed process equipment and process flow, that is, it does not mean that the present invention must rely on the above detailed process equipment and process flow to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent substitution of each raw material of the product of the present invention, the addition of auxiliary components, the selection of specific methods, etc., all fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A preparation process for the positive electrode of a lithium-ion solid-state battery, the positive electrode of the lithium-ion solid-state battery including a positive electrode active material layer, Characterized in that, The preparation process for the positive electrode of the lithium-ion solid-state battery includes the following steps: S1. Coating the positive electrode current collector surface with a positive electrode active material layer and drying; S2. Coating a solid electrolyte coating slurry on the surface of the positive electrode active material layer, the solid electrolyte coating slurry including a substance that is solid at normal temperature and forms a gas at 60 - 200 °C; S3. Heating and drying at 60 - 200 °C, such that the substance that is solid at normal temperature and forms a gas at 60 - 200 °C in the solid electrolyte coating slurry decomposes or volatilizes to form a gas, obtaining the solid electrolyte coating; while heating, applying pressure to the surface of the positive electrode current collector forming the solid electrolyte coating for compaction, obtaining the positive electrode of the lithium-ion solid-state battery; Wherein, the substance that is solid at normal temperature and forms a gas at 60 - 200 °C is any one or a mixture of at least two of ammonium bicarbonate, ammonium carbonate, and aluminum chloride; The mass percentage of the substance that is solid at normal temperature and forms a gas at 60 - 200 °C is 5 - 40% of the total mass of the formulation system; The porosity of the solid electrolyte coating ≤ 0.5%; The solvent is a non-aqueous solvent; The solid content of the solid electrolyte coating slurry is 60 wt%.

2. The preparation process according to claim 1, Characterized in that, When the substance that is solid at normal temperature and forms a gas at 60 - 200 °C is ammonium bicarbonate, the mass percentage of the ammonium bicarbonate is 15 - 40% of the total mass of the formulation system.

3. The preparation process according to claim 1, Characterized in that, When the substance that is solid at normal temperature and forms a gas at 60 - 200 °C is ammonium carbonate, the mass percentage of the ammonium carbonate is 20 - 30% of the total mass of the formulation system.

4. The preparation process according to claim 1, Characterized in that, When the substance that is solid at normal temperature and forms a gas at 60 - 200 °C is aluminum chloride, the mass percentage of the aluminum chloride is 5 - 30% of the total mass of the formulation system.

5. The preparation process according to claim 1 or 2, Characterized in that, The thickness of the solid electrolyte coating is .

6. The preparation process according to claim 1, Characterized in that, In step S3, for ammonium bicarbonate and ammonium carbonate, the heating temperature is 100 - 115 °C, and the heating residence time is 2 - 10 min.

7. The preparation process according to claim 1, Characterized in that, In step S3, for aluminum chloride, the heating temperature is 185 - 200 °C, and the heating residence time is 15 - 30 min.

8. The preparation process according to claim 1, Characterized in that, A solid electrolyte is further provided outside the solid electrolyte coating, and the composition of the solid electrolyte is different from that of the solid electrolyte coating.

9. The preparation process according to claim 8, Characterized in that, The thickness of the solid electrolyte is .

10. A preparation process for a lithium-ion solid-state battery, Characterized in that, The preparation process includes the following steps: A) Preparation of the positive electrode sheet The positive electrode of the lithium-ion solid-state battery prepared by the preparation process described in any one of claims 1-9 is used as the positive electrode plate; B) The obtained positive electrode plate, lithium metal negative electrode plate, and lithium lanthanum zirconium oxide solid electrolyte are laminated and assembled to obtain the lithium-ion solid-state battery.

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