A solid-state battery electrode, its preparation method, and its application.

Abstract

This invention belongs to the field of solid-state batteries, and relates to a solid-state battery electrode, its preparation method, and its application. The solid-state battery electrode includes a positive electrode sheet, a porous polymer membrane, a composite electrolyte incorporated in the pores of the positive electrode sheet and the porous polymer membrane, and a lithium-free coating composited on the surface of the porous polymer membrane. The positive electrode sheet is coated onto an aluminum foil surface and dried to obtain a positive electrode sheet; then, a porous polymer membrane is placed on its surface to obtain a porous polymer membrane / positive electrode sheet electrode; an electrolyte solution is prepared and coated onto its surface, followed by in-situ polymerization and curing to obtain an electrolyte composite porous polymer membrane / positive electrode sheet electrode; a lithium-free coating slurry is then coated onto its surface and dried to obtain a solid-state battery electrode. Using this electrode as the working electrode and a lithium sheet as the counter electrode, a solid-state battery is assembled. The solid-state battery electrode of this invention exhibits low interfacial impedance due to in-situ polymerization and curing; and has a lithium-ion concentration gradient that accelerates lithium-ion migration, exhibiting high ionic conductivity, ultimately achieving long-life cycle life in solid-state applications.

Description

Technical Field

[0001] This invention belongs to the field of solid-state battery technology, and relates to a solid-state battery electrode, its preparation method, and its application. Background Technology

[0002] Lithium metal is the preferred choice for realizing next-generation high-energy-density lithium batteries due to its high theoretical capacity (3860 mAh / g) and lowest electrode potential (-3.04 V). However, traditional organic electrolyte systems are prone to side reactions with lithium metal, leading to increased battery polarization and reduced battery life. Furthermore, electrolytes cannot effectively suppress lithium dendrite growth, easily causing short circuits and safety accidents. In contrast, solid-state electrolytes offer advantages such as high stability, low flammability, and no leakage. Therefore, replacing the electrolyte with a solid-state electrolyte can effectively improve the energy density and safety performance of lithium batteries.

[0003] Currently, mainstream solid-state electrolytes are mainly divided into two categories: inorganic solid-state electrolytes and organic polymer solid-state electrolytes. Inorganic solid-state electrolytes typically possess high ionic conductivity and good flame retardant properties, but they exhibit high interfacial contact impedance and poor stability with the electrode. Organic polymer solid-state electrolytes, on the other hand, possess high flexibility, promoting good interfacial contact between the polymer electrolyte and the electrode, and are easily processed into films. However, these electrolytes have low ionic conductivity at room temperature and a narrow voltage window, making it difficult to meet the requirements for battery operation at room temperature. Addressing the respective problems of inorganic and organic polymer solid-state electrolytes, in recent years, researchers have proposed combining inorganic and organic polymer solid-state electrolytes to achieve functional hybridization, forming composite electrolytes that leverage the advantages of both. For example, Xu et al. {Xu Z, Yang T, Chu X, Su H, Wang Z, Chen N, Gu B, Zhang H, Deng W, Zhang H and Yang W. Stronglewis acid-base and weak hydrogen bond synergistically enhancing ionic conductivity of poly(ethylene oxide)@SiO2 electrolytes for a high ratecapability Li-metal battery[J]. ACS Applied Materials & Interfaces, 2020, 12: 10341-10349} uniformly dispersed SiO2 nanoparticles in PEO electrolyte, forming a composite electrolyte with a high room temperature ionic conductivity (0.11 mS / cm). Moreover, the Li / / LiFePO4 battery based on this composite electrolyte achieved 100 stable cycles. Similarly, Fu et al. {Fu K, Gong Y, Dai J, Gong A, Han X, Yao Y, Wang C, Wang Y, Chen Y, Yan C, Li Y, Wachsman ED and Hu L. Flexible, solid-state, ion-conducting membrane with 3D garnet nanofiber networks for lithium batteries[J]. Proceedings of the National Academy of Sciences of the United States of America, 2016, 113: 7094-7099.} gradually added PEO solution dropwise to a three-dimensional Li-ion network fabricated by electrospinning.6.4 La3Zr2Al 0.2 O 12 A three-dimensional, continuous PEO-LLZAO composite electrolyte is formed on the framework. This composite electrolyte exhibits a room-temperature ionic conductivity of 0.25 mS / cm, and a lithium-lithium symmetric battery conductivity of 0.2 mA / cm. 2 It can cycle stably for over 500 hours. Organic-inorganic composite solid electrolytes combine the advantages of both. However, composite electrolytes cannot simultaneously meet the different requirements of the positive and negative electrodes of solid-state batteries, making it difficult for the electrolyte to possess both high ionic conductivity and low interfacial impedance. Summary of the Invention

[0004] To address the technical problem that existing composite electrolytes cannot simultaneously meet the different requirements of the positive and negative electrodes in solid-state batteries, making it difficult for the electrolyte to possess both high ionic conductivity and low interfacial impedance, this invention proposes a solid-state battery electrode, its preparation method, and its applications. The solid-state battery electrode of this invention exhibits low interfacial impedance due to in-situ polymerization and solidification; furthermore, this solid-state battery electrode possesses a lithium-ion concentration gradient (i.e., high lithium-ion concentration on the positive electrode side, low lithium-ion concentration in the porous polymer film, and no lithium-ion concentration on the lithium-free coating side), which accelerates lithium-ion migration, resulting in high ionic conductivity and ultimately achieving long-life solid-state cycling.

[0005] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0006] A solid-state battery electrode comprises a positive electrode, a porous polymer film, a composite electrolyte incorporated in the pores of the positive electrode and the porous polymer film, and a lithium-free coating incorporated on the surface of the porous polymer film.

[0007] Furthermore, the positive electrode sheet is composed of aluminum foil and a positive electrode coating.

[0008] Furthermore, the thickness of the positive electrode coating is 20–200 μm, preferably 30–120 μm.

[0009] Furthermore, the positive electrode coating is composed of positive electrode material, conductive carbon, and adhesive.

[0010] Furthermore, the cathode material is any one of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, lithium nickel cobalt manganese oxide, or lithium nickel cobalt aluminum oxide.

[0011] Furthermore, the conductive carbon is any one of carbon black, Ketjen black, carbon nanofibers, or carbon nanotubes.

[0012] Furthermore, the adhesive is any one of polytetrafluoroethylene, polyvinylidene fluoride, polyurethane, or polyimide.

[0013] Furthermore, the porous polymer membrane is a commercially available porous polyethylene membrane or porous polypropylene membrane.

[0014] Furthermore, the thickness of the porous polymer membrane is 5–20 μm, preferably 7–15 μm.

[0015] Furthermore, the lithium-free coating consists of lithium-free particles and an adhesive.

[0016] Furthermore, the thickness of the lithium-free coating is 0.5–10 μm, preferably 2–5 μm.

[0017] Furthermore, the lithium-free particles are any one of nano-silicon, nano-silicon suboxide, nano-magnesium oxide, nano-zinc oxide, nano-germanium oxide, nano-tin oxide, nano-antimony oxide, or nano-bismuth oxide.

[0018] Furthermore, the lithium-free particle content is 30-90%, preferably 40-70%.

[0019] Furthermore, the adhesive is any one of polytetrafluoroethylene, polyvinylidene fluoride, polyurethane, or polyimide.

[0020] Furthermore, the composite electrolyte is composed of a sulfide electrolyte and a polymer electrolyte.

[0021] Furthermore, the sulfide electrolyte is Li 10 GeP2S 12 Li6PS5Cl, Li7P3S 1l Any one of them.

[0022] Furthermore, the sulfide electrolyte content is 23-71%, preferably 38-62%.

[0023] Furthermore, the polymer electrolyte is composed of a polymer and a lithium salt, and is formed by the polymerization of polymer monomers and lithium salt under the action of an azobisisobutyronitrile initiator.

[0024] Furthermore, the polymer monomer is any one of ethylene oxide, acrylic acid, or methyl methacrylate.

[0025] Furthermore, the lithium salt is lithium bisfluorosulfonylimide or lithium bistrifluoromethanesulfonylimide.

[0026] Furthermore, the method for preparing a solid-state battery electrode includes the following steps:

[0027] (1) The positive electrode material, conductive carbon, and adhesive are uniformly dispersed in N-methylpyrrolidone to form a slurry, which is then coated on the surface of aluminum foil and dried to form a positive electrode sheet;

[0028] (2) Subsequently, a porous polymer film is placed on the surface of the positive electrode to form a porous polymer film / positive electrode electrode;

[0029] (3) Next, the sulfide electrolyte, lithium salt, polymer monomer, and azobisisobutyronitrile initiator are dispersed in ethyl methyl carbonate to form an electrolyte solution, which is then coated on the surface of the porous polymer membrane / positive electrode. The electrolyte solution is diffused into the pores of the positive electrode and the porous polymer membrane by capillary action, and then heated at 80°C to polymerize and solidify in situ to form an electrolyte composite porous polymer membrane / positive electrode.

[0030] (4) Finally, lithium-free particles and adhesive are uniformly dispersed in N-methylpyrrolidone to form a slurry and coated on the surface of the porous polymer membrane / positive electrode of the electrolyte composite, and dried to form a solid battery electrode.

[0031] Furthermore, in step (3), the mass ratio of sulfide electrolyte, lithium salt, polymer monomer, and azobisisobutyronitrile is (23-71):(9-25):(18-50):2.

[0032] Furthermore, in step (4), the mass ratio of lithium-free particles to adhesive is (30-90):(10-70).

[0033] Furthermore, the application of the solid-state battery electrode in the solid-state battery is as follows: the solid-state battery electrode is used as the working electrode, and a lithium metal sheet is used as the counter electrode to assemble a solid-state battery.

[0034] The present invention has the following beneficial effects:

[0035] (1) On the one hand, this invention utilizes an in-situ polymerization process to composite the electrolyte within the pores of the positive electrode and the porous polymer membrane, ensuring good interfacial contact between the composite electrolyte and the positive electrode, reducing the interfacial impedance between the electrolyte and the positive electrode, eliminating residual stress at the interface, and guaranteeing good mechanical properties of the electrolyte. In this composite electrolyte, the sulfide electrolyte is used to improve the ionic conductivity of the electrolyte, while the polymer electrolyte is used to improve the toughness of the electrolyte (especially to form a stable interfacial contact with the positive electrode). When the sulfide electrolyte content in the composite electrolyte is too low, the composite electrolyte will exhibit low ionic conductivity. Conversely, when the sulfide electrolyte content in the composite electrolyte is too high, the composite electrolyte will exhibit poor toughness. Therefore, only when the contents of the sulfide electrolyte and the polymer electrolyte are appropriate can the battery exhibit a long cycle life.

[0036] (2) On the other hand, the present invention utilizes the reaction between lithium-free particles in the lithium-free coating and metallic lithium to form an alloy layer, thereby wetting the metallic lithium anode, forming a stable interface and inhibiting dendrite growth. When the lithium-free particle content in the lithium-free coating is too low, there will not be enough lithium-free particles to react with metallic lithium to form a stable interface, which will lead to increased polarization and reduced cycle performance. When the lithium-free particle content in the lithium-free coating is too high, the lithium-free coating will lack sufficient toughness to withstand the volume effect brought about by the reaction between lithium-free particles and metallic lithium, which will lead to poor interfacial contact and reduced lifespan.

[0037] (3) In addition, the solid-state battery electrode prepared by the present invention consists of three layers with lithium ion concentration gradients, namely, the positive electrode side has a high lithium ion concentration, the porous polymer film has a low lithium ion concentration, and the lithium-free coating side has no lithium ion concentration. Therefore, the lithium ion concentration gradient structure in the solid-state battery electrode is beneficial to accelerating lithium ion migration and improving ionic conductivity, and ultimately improving the cycle life of the battery.

[0038] (4) When the solid-state battery electrode prepared by the present invention comprises a positive electrode sheet, a porous polymer film, a composite electrolyte incorporated in the pores of the positive electrode sheet and the porous polymer film, and a lithium-free coating incorporated on the surface of the porous polymer film, the performance of the solid-state battery is better demonstrated. Compared with the solid-state battery of Comparative Example 1, the interfacial impedance is 1358 Ω·cm. 2 The ionic conductivity is 0.68 mS / cm, and the number of revolutions required for the specific capacity to decay to 80% is 112. The interfacial impedance of the solid-state battery in Comparative Example 2 is 452 Ω·cm. 2 The ionic conductivity is 0.15 mS / cm, and the number of cycles required for the specific capacity to decay to 80% is 57; while the interface impedance of the solid-state battery in Comparative Example 3 is 4680 Ω·cm. 2 The ionic conductivity is 0.31 mS / cm, and the number of cycles required for the specific capacity to decay to 80% is 88. Taking Example 1 of this invention as an example, the interfacial impedance of the prepared solid-state battery is 364 Ω·cm. 2 (Compared to Comparative Example 1, this was reduced by 3.7 times; compared to Comparative Example 2, it was reduced by 1.2 times; and compared to Comparative Example 3, it was reduced by 12.8 times). The ionic conductivity was 1.36 mS / cm (compared to Comparative Example 1, this was increased by 2 times; compared to Comparative Example 2, this was increased by 9 times; and compared to Comparative Example 3, this was increased by 4.4 times). Moreover, this solid-state battery also exhibited a high initial discharge specific capacity of 154 mAh / g and could be stably cycled for more than 352 cycles (compared to Comparative Example 1, this was increased by 3.1 times; compared to Comparative Example 2, this was increased by 6.2 times; and compared to Comparative Example 3, this was increased by 4 times). Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 This is a schematic diagram of the solid-state battery electrode in Embodiment 1 of the present invention, wherein 1 is an aluminum foil, 2 is a positive electrode coating, 3 is a composite electrolyte in the pores of the positive electrode coating and the porous polymer membrane, 4 is a porous polymer membrane, and 5 is a lithium-free coating.

[0041] Figure 2 The diagram shows the interface impedance of the solid-state battery electrodes in Embodiment 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3 of the present invention.

[0042] Figure 3 The diagram shows the ionic conductivity of the solid-state battery electrodes in Examples 1, 1, 2 and 3 of this invention. Detailed Implementation

[0043] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] Example 1

[0045] A method for preparing and applying a solid-state battery electrode, comprising the following steps:

[0046] (1) Preparation of lithium iron phosphate positive electrode: Lithium iron phosphate, Ketjen black and polyvinylidene fluoride are dispersed in N-methylpyrrolidone at a mass ratio of 90:5:5 to form a slurry, which is then coated on the surface of aluminum foil and dried to form a lithium iron phosphate positive electrode with a coating thickness of 100μm.

[0047] (2) Preparation of porous polyethylene film / lithium iron phosphate positive electrode: A commercially available 10 μm porous polyethylene film is placed on the surface of the prepared lithium iron phosphate positive electrode to form a porous polyethylene film / lithium iron phosphate positive electrode.

[0048] (3) Preparation of electrolyte-composite porous polyethylene film / lithium iron phosphate positive electrode: Li 10 GeP2S 12Lithium difluorosulfonamide, ethylene oxide, and azobisisobutyronitrile initiator are dispersed in methyl ethyl carbonate at a mass ratio of 50:16:32:2 to form an electrolyte solution, which is then coated onto the surface of a porous polyethylene film / lithium iron phosphate positive electrode. After the electrolyte solution diffuses into the pores of the positive electrode and the porous polyethylene film, it is heated at 80°C to polymerize and solidify in situ to form an electrolyte composite porous polyethylene film / lithium iron phosphate positive electrode.

[0049] (4) Solid-state battery electrode preparation and solid-state battery assembly and testing: Nano-silicon particles and polyvinylidene fluoride were uniformly dispersed in N-methylpyrrolidone at a mass ratio of 50:50 to form a slurry, which was then coated on the surface of the electrolyte composite porous polyethylene membrane / lithium iron phosphate positive electrode. After drying, a lithium-free coating with a thickness of 4 μm was formed to form a solid-state battery electrode. Figure 1 The electrodes were pressed between two stainless steel sheets, and AC impedance testing was performed at 25°C within the range of 0.1Hz to 1MHz to obtain the interfacial impedance and ionic conductivity data of the solid-state battery electrodes. The corresponding test results are shown in [Figure / Table / Insert Table ... Figure 2 and Figure 3 Finally, the solid-state battery electrodes were paired with lithium sheets to assemble a solid-state battery, and its cycle performance was tested at a 0.1C rate. The corresponding test results are shown in Table 1.

[0050] Figure 1 This is a schematic diagram of the solid-state battery electrode in this embodiment, where 1 is an aluminum foil, 2 is a positive electrode coating, 3 is a composite electrolyte in the pores of the positive electrode coating and the porous polymer membrane, 4 is a porous polymer membrane, and 5 is a lithium-free coating.

[0051] Figure 2 The diagram shows the interfacial impedance of the solid-state battery electrodes in this embodiment, Comparative Example 1, Comparative Example 2, and Comparative Example 3.

[0052] Figure 3 The diagram shows the ionic conductivity of the solid-state battery electrodes in this embodiment, Comparative Example 1, Comparative Example 2, and Comparative Example 3.

[0053] The results show that the interfacial impedance of the battery is 364 Ω·cm. 2 The ionic conductivity is 1.36 mS / cm. Such low interfacial impedance and high lithium-ion conductivity are attributed to the excellent interfacial contact between the composite electrolyte and the positive electrode, and the lithium-ion concentration gradient structure facilitates rapid ion migration. Furthermore, the battery exhibits a high initial discharge specific capacity of 154 mAh / g at 0.1C rate and can cycle stably for over 352 cycles.

[0054] Comparative Example 1

[0055] A method for preparing and applying a solid-state battery electrode, differing from Example 1 in that the solid-state battery electrode does not have a lithium-free coating, and the steps are as follows:

[0056] The porous polyethylene membrane / lithium iron phosphate positive electrode prepared in Example 1 was pressed between two stainless steel sheets. AC impedance spectroscopy was performed at 25°C within the range of 0.1 Hz to 1 MHz to obtain interfacial impedance and ionic conductivity data. The corresponding test results are shown below. Figure 2 and Figure 3 Finally, the electrode was paired with a lithium sheet to assemble a solid-state battery, and its cycle performance was tested at a 0.1C rate. The corresponding test results are shown in Table 1. The results show that the interfacial impedance of the battery is 1358 Ω·cm. 2 The ionic conductivity is 0.68 mS / cm.

[0057] The increased interfacial impedance and decreased lithium-ion conductivity are attributed to the lack of a lithium-free coating, which prevents the formation of a stable lithium-ion gradient flow. This hinders ion migration, indirectly leading to decreased ion conductivity and increased interfacial impedance. Consequently, the battery exhibits an initial discharge specific capacity of 146 mAh / g and can cycle stably for over 112 cycles.

[0058] Comparative Example 2

[0059] A method for preparing and applying a solid-state battery electrode, differing from Example 1 in that the composite electrolyte of this solid-state battery electrode does not contain a sulfide electrolyte, and the steps are as follows:

[0060] (1) Preparation of electrolyte composite porous polyethylene film / lithium iron phosphate positive electrode: Lithium difluorosulfonyl imide, ethylene oxide and azobisisobutyronitrile initiator are dispersed in methyl ethyl carbonate at a mass ratio of 32:64:4 to form an electrolyte solution, which is then coated on the surface of porous polyethylene film / lithium iron phosphate positive electrode. After the electrolyte solution diffuses into the pores of the positive electrode and the porous polyethylene film, it is heated at 80°C to polymerize and solidify in situ to form electrolyte composite porous polyethylene film / lithium iron phosphate positive electrode.

[0061] (2) Electrode preparation and solid-state battery assembly and testing: Nano-silicon particles and polyvinylidene fluoride were uniformly dispersed in N-methylpyrrolidone at a mass ratio of 50:50 to form a slurry, which was then coated onto the surface of a porous polyethylene membrane / lithium iron phosphate positive electrode. After drying, a lithium-free coating with a thickness of 4 μm was formed on the composite electrode. The electrode was then pressed between two stainless steel sheets and subjected to AC impedance testing at 25°C between 0.1 Hz and 1 MHz to obtain the interfacial impedance and ionic conductivity data. The corresponding test results are shown in [Figure / Table / Insert Figure ... Figure 2 and Figure 3 Finally, the electrodes were paired with lithium sheets to assemble a solid-state battery, and its cycle performance was tested at 0.1C. The corresponding test results are shown in Table 1. The results show that the interfacial impedance of the battery is 452 Ω·cm. 2 The ionic conductivity is 0.15 mS / cm.

[0062] In-situ polymerization and the presence of a lithium-free coating reduced the interfacial impedance between the electrolyte and the positive and negative electrodes, but the electrolyte, lacking a high-ionic-conductivity sulfide electrolyte, exhibited low ionic conductivity. Consequently, the battery only showed an initial discharge specific capacity of 121 mAh / g and a cycle life of 57 cycles.

[0063] Comparative Example 3

[0064] A method for preparing and applying a solid-state battery electrode differs from Example 1 in that: although the composite electrolyte in this solid-state battery electrode contains a sulfide electrolyte, polyethylene oxide, lithium salt, and azobisisobutyronitrile, it has not undergone in-situ curing polymerization. The steps are as follows:

[0065] (1) Preparation of electrolyte composite porous polyethylene film / lithium iron phosphate positive electrode: Li 10 GeP2S 12 Lithium difluorosulfonamide, polyethylene oxide, and azobisisobutyronitrile initiator are dispersed in methyl ethyl carbonate at a mass ratio of 50:16:32:2 to form an electrolyte solution, which is then coated onto the surface of a porous polyethylene film / lithium iron phosphate positive electrode. After the electrolyte solution diffuses into the pores of the positive electrode and the porous polyethylene film, it is dried to form an electrolyte composite porous polyethylene film / lithium iron phosphate positive electrode.

[0066] (2) Electrode preparation and solid-state battery assembly and testing: Nano-silicon particles and polyvinylidene fluoride were uniformly dispersed in N-methylpyrrolidone at a mass ratio of 50:50 to form a slurry, which was then coated onto the surface of a porous polyethylene membrane / lithium iron phosphate positive electrode. After drying, a lithium-free coating with a thickness of 4 μm was formed on the composite electrode. The electrode was then pressed between two stainless steel sheets and subjected to AC impedance testing at 25°C between 0.1 Hz and 1 MHz to obtain the interfacial impedance and ionic conductivity data. The corresponding test results are shown in [Figure / Table / Insert Figure ... Figure 2 and Figure 3 Finally, the electrodes were paired with lithium sheets to assemble a solid-state battery, and its cycle performance was tested at 0.1C. The corresponding test results are shown in Table 1. The results show that the interfacial impedance of the battery is 4680 Ω·cm. 2 The ionic conductivity is 0.31 mS / cm.

[0067] The high interfacial impedance and low lithium-ion conductivity are attributed to the inability of the composite electrolyte to polymerize in situ, resulting in a large interfacial impedance with the positive electrode. However, the lithium-free particles in the lithium-free coating react with metallic lithium to form an alloy layer, which can adequately wet the metallic lithium negative electrode. Therefore, the battery exhibits only a first-cycle discharge specific capacity of 137 mAh / g and a cycle life of 88 cycles.

[0068] Table 1 Cyclic performance of solid-state electrodes with different structures

[0069]

[0070] Example 2

[0071] A method for preparing and applying a solid-state battery electrode, comprising the following steps:

[0072] (1) Preparation of lithium cobalt oxide positive electrode: Lithium cobalt oxide, carbon black and polytetrafluoroethylene are dispersed in N-methylpyrrolidone in a mass ratio of 90:5:5 to form a slurry, which is then coated on the surface of aluminum foil. After drying, lithium cobalt oxide positive electrode sheets with coating thicknesses of 10, 20, 30, 80, 120, 200 and 280 μm are formed respectively.

[0073] (2) Preparation of porous polypropylene film / lithium cobalt oxide positive electrode: A commercially available 10μm porous polypropylene film is placed on the surface of the prepared lithium cobalt oxide positive electrode to form a porous polypropylene film / lithium cobalt oxide positive electrode.

[0074] (3) Preparation of porous polypropylene membrane / lithium cobalt oxide positive electrode with electrolyte composite: Li 10 GeP2S 12 Lithium difluorosulfonamide, acrylic acid, and azobisisobutyronitrile initiator are dispersed in methyl ethyl carbonate at a mass ratio of 50:16:32:2 to form an electrolyte solution, which is then coated onto the surface of a porous polypropylene membrane / lithium cobalt oxide positive electrode. After the electrolyte solution diffuses into the pores of the positive electrode and the porous polypropylene membrane, it is heated at 80°C to polymerize and solidify in situ to form an electrolyte composite porous polypropylene membrane / lithium cobalt oxide positive electrode.

[0075] (4) Solid-state battery electrode preparation and solid-state battery assembly and testing: Nano zinc oxide particles and polytetrafluoroethylene were uniformly dispersed in N-methylpyrrolidone at a mass ratio of 50:50 to form a slurry, which was then coated on the surface of the porous polypropylene membrane / lithium cobalt oxide positive electrode of the electrolyte composite. After drying, a lithium-free coating with a thickness of 5 μm was formed into a solid-state battery electrode, which was then paired with a lithium sheet to assemble a solid-state battery. Cyclic performance tests were conducted at a rate of 0.1C, and the corresponding test results are shown in Table 2.

[0076] Table 2 Cyclic performance of solid electrodes prepared with different cathode coating thicknesses

[0077]

[0078] The results show that within the optimal positive electrode coating thickness range, the solid-state battery exhibits the highest initial discharge specific capacity and the longest cycle life. When the positive electrode coating is too thin, the positive electrode side cannot maintain a consistently high lithium-ion concentration, reducing the lithium-ion migration rate and resulting in poor cycle performance. Conversely, when the positive electrode coating is too thick, the thick electrode is prone to powder shedding and cracking during electrode preparation and battery charging / discharging, which also reduces the battery's cycle performance.

[0079] Example 3

[0080] A method for preparing and applying a solid-state battery electrode, comprising the following steps:

[0081] (1) Preparation of lithium nickel cobalt manganese oxide positive electrode: Lithium nickel cobalt manganese oxide, carbon black and polytetrafluoroethylene are dispersed in N-methylpyrrolidone in a mass ratio of 90:5:5 to form a slurry, which is then coated on the surface of aluminum foil and dried to form a lithium nickel cobalt manganese oxide positive electrode with a coating thickness of 80μm.

[0082] (2) Preparation of porous polyethylene film / lithium nickel cobalt manganese oxide positive electrode: Commercially available porous polyethylene films with thicknesses of 3, 5, 7, 10, 15, 20 and 35 μm were placed on the surface of the prepared lithium nickel cobalt manganese oxide positive electrode to form a porous polyethylene film / lithium nickel cobalt manganese oxide positive electrode.

[0083] (3) Preparation of electrolyte composite porous polyethylene film / lithium nickel cobalt manganese oxide positive electrode: Li6PS5Cl, lithium bis(trifluoromethanesulfonylimide), acrylic acid, and azobisisobutyronitrile initiator were dispersed in ethyl methyl carbonate at a mass ratio of 50:16:32:2 to form an electrolyte solution, which was then coated on the surface of the porous polyethylene film / lithium nickel cobalt manganese oxide positive electrode. After the electrolyte solution diffused into the pores of the positive electrode and the porous polyethylene film, it was heated at 80°C to polymerize and solidify in situ to form the electrolyte composite porous polyethylene film / lithium nickel cobalt manganese oxide positive electrode.

[0084] (4) Solid-state battery electrode preparation and solid-state battery assembly and testing: Nano-magnesium oxide particles and polytetrafluoroethylene were uniformly dispersed in N-methylpyrrolidone at a mass ratio of 40:60 to form a slurry, which was then coated on the surface of the electrolyte composite porous polyethylene membrane / lithium nickel cobalt manganese oxide positive electrode. After drying, a lithium-free coating with a thickness of 3 μm was formed into a solid-state battery electrode, which was then paired with a lithium sheet to assemble a solid-state battery. Cyclic performance tests were conducted at a rate of 0.1C, and the corresponding test results are shown in Table 3.

[0085] Table 3 Cyclic performance of solid electrodes prepared with different porous polyethylene film thicknesses

[0086]

[0087] The results show that within the preferred porous polyethylene film thickness range, the solid-state battery exhibits the highest initial discharge specific capacity and the longest cycle life. When the porous polyethylene film is too thin, the structural advantage of the lithium-ion concentration gradient in the solid-state battery electrodes cannot be fully utilized. This is because the positive electrode side of the solid-state battery electrode has a high lithium-ion concentration, the porous polymer film has a low lithium-ion concentration, and the lithium-free coating side has no lithium-ion concentration. An excessively thin porous polymer film cannot form a stable and continuous lithium-ion concentration gradient with the lithium-free coating, leading to a reduced cycle life. Conversely, when the porous polyethylene film is too thick, the distance for lithium ions to travel from the positive electrode side to the lithium metal negative electrode side in the solid-state battery is too long, resulting in increased electrode polarization and a decrease in battery cycle performance.

[0088] Example 4

[0089] A method for preparing and applying a solid-state battery electrode, comprising the following steps:

[0090] The electrolyte composite porous polyethylene membrane / lithium nickel cobalt manganese oxide positive electrode sheet prepared using a 10 μm porous polyethylene membrane in Example 3 was used as the electrode. Then, nano-tin oxide particles and polytetrafluoroethylene were uniformly dispersed in N-methylpyrrolidone at a mass ratio of 50:50 to form a slurry, which was then coated on the surface of the electrolyte composite porous polyethylene membrane / lithium nickel cobalt manganese oxide positive electrode sheet. After drying, solid-state battery electrodes with lithium-free coating thicknesses of 0.3, 0.5, 2, 2.5, 5, 10, and 16 μm were formed, respectively. These electrodes were then paired with lithium sheets and assembled into solid-state batteries. Cyclic performance tests were conducted at a 0.1C rate, and the corresponding test results are shown in Table 4.

[0091] Table 4 Cyclic performance of solid electrodes prepared with different lithium-free coating thicknesses

[0092]

[0093] The results show that within the optimal range of lithium-free coating thickness, the solid-state battery exhibits the highest initial discharge specific capacity and the longest cycle life. When the lithium-free coating is too thin, it cannot adequately wet the lithium metal anode, easily leading to increased interfacial polarization and reduced battery performance. Therefore, adequate wetting of the lithium-free coating with the lithium metal anode relies on the reaction between the lithium-free particles in the coating and the lithium metal to form a stable interface. Conversely, when the lithium-free coating is too thick, the transport distance of lithium ions from the positive electrode side to the lithium metal anode side in the solid-state battery is too long, resulting in increased electrode polarization and reduced battery cycle performance.

[0094] Example 5

[0095] A method for preparing and applying a solid-state battery electrode, comprising the following steps:

[0096] The electrolyte composite porous polyethylene membrane / lithium nickel cobalt manganese oxide positive electrode sheet prepared using a 10 μm porous polyethylene membrane in Example 3 was used as the electrode. Then, nano-germanium oxide particles and polytetrafluoroethylene were uniformly dispersed in N-methylpyrrolidone at mass ratios of 15:85, 30:70, 40:60, 50:50, 70:30, 90:10, and 95:5 (corresponding to lithium-free particle contents of 15%, 30%, 40%, 50%, 70%, 90%, and 95%, respectively) to form a slurry, which was then coated on the surface of the electrolyte composite porous polyethylene membrane / lithium nickel cobalt manganese oxide positive electrode sheet. After drying, solid-state battery electrodes with a lithium-free coating thickness of 3 μm were formed and paired with lithium sheets to assemble solid-state batteries. Cyclic performance tests were conducted at a 0.1C rate, and the corresponding test results are shown in Table 5.

[0097] Table 5 Cycle performance of solid-state electrodes prepared with different lithium-free particle contents

[0098]

[0099] The results show that within the optimal range of lithium-free particle content, the solid-state battery exhibits the highest first-cycle discharge specific capacity and the longest cycle life. When the lithium-free particle content in the lithium-free coating is too low, there will not be enough lithium-free particles to react with metallic lithium to form a stable interface, leading to increased polarization and reduced cycle performance. Conversely, when the lithium-free particle content in the lithium-free coating is too high, the coating will lack sufficient toughness to withstand the volume effect during the reaction between the lithium-free particles and metallic lithium, resulting in poor interfacial contact and reduced lifespan.

[0100] Example 6

[0101] A method for preparing and applying a solid-state battery electrode, comprising the following steps:

[0102] (1) Preparation of lithium manganese oxide positive electrode: Lithium manganese oxide, carbon nanofibers and polyimide are dispersed in N-methylpyrrolidone in a mass ratio of 90:5:5 to form a slurry, which is then coated on the surface of aluminum foil and dried to form lithium cobalt oxide positive electrode with a coating thickness of 60 μm.

[0103] (2) Preparation of porous polypropylene film / lithium manganese oxide positive electrode: A commercially available 12μm porous polypropylene film is placed on the surface of the prepared lithium manganese oxide positive electrode to form a porous polypropylene film / lithium manganese oxide positive electrode.

[0104] (3) Preparation of porous polypropylene membrane / lithium manganese oxide positive electrode with electrolyte composite: Li7P3S 1lLithium difluorosulfonamide, methyl methacrylate, and azobisisobutyronitrile initiator are used in mass ratios of 14:28:56:2, 23:25:50:2, 38:20:40:2, 47:17:34:2, 62:12:24:2, 71:9:18:2, and 83:5:10:2 (corresponding to Li7P3S). 1l An electrolyte solution containing 14%, 23%, 38%, 47%, 62%, 71%, and 83% of the electrolyte is dispersed in ethyl methyl carbonate and coated onto the surface of a porous polypropylene membrane / lithium manganese oxide positive electrode. After the electrolyte solution diffuses into the pores of the positive electrode and the porous polypropylene membrane, it is heated at 80°C to polymerize and solidify in situ to form an electrolyte composite porous polypropylene membrane / lithium manganese oxide positive electrode.

[0105] (4) Solid-state battery electrode preparation and solid-state battery assembly and testing: Antimony oxide nanoparticles and polyimide were uniformly dispersed in N-methylpyrrolidone at a mass ratio of 50:50 to form a slurry, which was then coated on the surface of the electrolyte composite porous polypropylene membrane / lithium manganese oxide positive electrode. After drying, a lithium-free coating with a thickness of 5 μm was formed into a solid-state battery electrode, which was then paired with a lithium sheet to assemble a solid-state battery. Cyclic performance tests were conducted at a rate of 0.1C, and the corresponding test results are shown in Table 6.

[0106] Table 6 Different Li7P3S 1l Cyclic performance of solid-state electrodes prepared with high concentration

[0107]

[0108] The results show that in the preferred Li7P3S 1l Within the specified content range, solid-state batteries exhibit the highest initial discharge specific capacity and the longest cycle life. When the composite electrolyte contains Li7P3S... 1l When the content is too low, the composite electrolyte will exhibit low ionic conductivity. However, when the Li7P3S content in the composite electrolyte is too low... 1l When the content is too high, the composite electrolyte will exhibit poor toughness. This is because the Li7P3S content in the composite electrolyte... 1l Sulfide electrolytes are used to improve the ionic conductivity of the electrolyte, while polymer electrolytes in composite electrolytes are used to improve the electrolyte's toughness, especially to form a stable interfacial contact with the positive electrode. An inappropriate ratio between the two will lead to reduced performance. Therefore, Li7P3S in composite electrolytes... 1l A suitable amount of polymer electrolyte is necessary for a battery to have a long cycle life.

[0109] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A solid-state battery electrode, characterized in that: The solid-state battery electrode includes a positive electrode sheet, a porous polymer film, a composite electrolyte incorporated in the pores of the positive electrode sheet and the porous polymer film, and a lithium-free coating incorporated on the surface of the porous polymer film. The method for preparing the solid-state battery electrode is as follows: (1) The positive electrode material, conductive carbon and adhesive are uniformly dispersed in N-methylpyrrolidone to form a slurry, which is then coated on the surface of aluminum foil and dried to form a positive electrode sheet; (2) Place the porous polymer film on the surface of the positive electrode obtained in step (1) to form a porous polymer film / positive electrode electrode; (3) Disperse the sulfide electrolyte, lithium salt, polymer monomer and azobisisobutyronitrile initiator in ethyl methyl carbonate to form an electrolyte solution, and coat it on the surface of the porous polymer membrane / positive electrode obtained in step (2), and polymerize and solidify in situ to form an electrolyte composite porous polymer membrane / positive electrode. (4) The lithium-free particles and adhesive are uniformly dispersed in N-methylpyrrolidone to form a slurry, and coated on the surface of the porous polymer membrane / positive electrode obtained in step (3), and dried to form a solid battery electrode. In step (3), the mass ratio of sulfide electrolyte, lithium salt, polymer monomer and azobisisobutyronitrile is (23~71):(9~25):(18~50):2, and the in-situ polymerization and curing temperature is 80℃; in step (4), the mass ratio of lithium-free particles to adhesive is (30~90):(10~70).

2. The solid-state battery electrode according to claim 1, characterized in that: The positive electrode sheet includes aluminum foil and a positive electrode coating, the thickness of which is 20~200 μm.

3. The solid-state battery electrode according to claim 2, characterized in that: The positive electrode coating includes a positive electrode material, conductive carbon, and an adhesive, wherein the positive electrode material is any one of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, lithium nickel cobalt manganese oxide, or lithium nickel cobalt aluminum oxide; the conductive carbon is any one of carbon black, carbon nanofibers, or carbon nanotubes; and the adhesive is any one of polytetrafluoroethylene, polyvinylidene fluoride, polyurethane, or polyimide.

4. The solid-state battery electrode according to claim 1, characterized in that: The porous polymer membrane is a porous polyethylene membrane or a porous polypropylene membrane, and the thickness of the porous polymer membrane is 5~20 μm.

5. The solid-state battery electrode according to claim 1, characterized in that: The composite electrolyte comprises a sulfide electrolyte and a polymer electrolyte, wherein the sulfide electrolyte is Li. 10 GeP2S 12 Li6PS5Cl or Li7P3S 1l Any one of them, the sulfide electrolyte content is 23-71% of the mass of the composite electrolyte.

6. The solid-state battery electrode according to claim 5, characterized in that: The polymer electrolyte is formed by polymerizing polymer monomers and lithium salts under the action of an azobisisobutyronitrile initiator, wherein the polymer monomers are any one of ethylene oxide, acrylic acid or methyl methacrylate, and the lithium salts are lithium bis(fluorosulfonyl)imide or lithium bis(trifluoromethanesulfonyl)imide.

7. The solid-state battery electrode according to claim 1, characterized in that: The lithium-free coating comprises lithium-free particles and an adhesive. The thickness of the lithium-free coating is 0.5~10 μm. The lithium-free particles are any one of nano-silicon, nano-silicon suboxide, nano-magnesium oxide, nano-zinc oxide, nano-germanium oxide, nano-tin oxide, nano-antimony oxide, or nano-bismuth oxide. The content of lithium-free particles is 30~90% of the mass of the lithium-free coating. The adhesive is any one of polytetrafluoroethylene, polyvinylidene fluoride, polyurethane, or polyimide.

8. A solid-state battery prepared using the solid-state battery electrode according to any one of claims 1-7, characterized in that: A solid-state battery is assembled using a solid-state battery electrode as the working electrode and a lithium metal sheet as the counter electrode.

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