All-solid-state battery and preparation method thereof

Abstract

The invention provides an all-solid-state battery and a preparation method thereof, and relates to the field of batteries. A first lithium supplementing layer, a second lithium supplementing layer, a solid electrolyte layer and a silicon negative electrode are sequentially arranged between the positive electrode current collector and the negative electrode current collector of the all-solid-state battery; the first lithium supplementing layer comprises the following raw materials in percentage by mass: 40-50% of an LNO lithium supplementing agent, 40-50% of sulfide electrolyte, 3-10% of a conductive agent and 0.01-10% of a binder, wherein the total mass of the raw materials is 100%; the second lithium supplementing layer is prepared from the following raw materials in percentage by mass: 60%-80% of an NCM ternary positive electrode material, 1%-2% of graphene coated Li5FeO4, 15%-30% of sulfide electrolyte, 1%-5% of a conductive agent and 0.01%-10% of a binder, wherein the total mass of the raw materials is 100%. According to the all-solid-state battery provided by the invention, the gradient lithium supplementing layer is innovatively constructed between the positive electrode current collector and the solid electrolyte layer, and interface stability is realized from double dimensions of physical barrier and electrochemical regulation.

Description

Technical Field

[0001] This application relates to the field of batteries, and more particularly to an all-solid-state battery and its preparation method. Background Technology

[0002] All-solid-state batteries are hailed as the ultimate solution for next-generation power batteries due to their high safety and theoretical energy density. However, their industrialization process is severely constrained by solid-solid interface problems: there are serious interfacial instabilities and side reactions between the positive electrode active material (such as high-nickel NCM) and the sulfide solid electrolyte. This not only leads to a sharp increase in interfacial impedance, but also irreversibly consumes a large amount of lithium ions during the first charge and discharge of the battery, resulting in low initial coulombic efficiency and a significant reduction in effective cycle capacity.

[0003] To compensate for irreversible lithium loss during the initial charge-discharge cycle, introducing a positive electrode lithium replenisher has become a key technological approach. However, existing lithium replenisher materials themselves have significant bottlenecks: on the one hand, their particle size is generally large, which not only affects the effective release of lithium capacity but also disrupts the continuity of the electrode microstructure, leading to obstructed ion / electron transport pathways; on the other hand, the lithium replenisher is thermodynamically unstable with the sulfide electrolyte, easily causing side reactions upon contact, increasing interfacial impedance, and potentially triggering gas generation. Even more challenging is the need for precise control of the amount of lithium replenisher added—too little results in negligible lithium replenishment, failing to compensate for initial lithium loss; while too much exacerbates interfacial side reactions and introduces excessive inactive substances, ultimately harming the overall battery performance. Therefore, developing novel lithium replenishers with smaller particle size and higher stability, and achieving precise control over their application in the electrode, has become a crucial step in advancing the development of high-performance all-solid-state batteries.

[0004] In response to the problems of severe interfacial side reactions, excessively high interfacial impedance and poor cycle stability of high-nickel ternary cathode (NCM) solid-state batteries, this invention focuses on solving the following technical difficulties: (1) Traditional Li5FeO4 lithium supplementation material has an excessively large contact area with the solid electrolyte due to its large particle size (6-10μm), which triggers irreversible interfacial chemical reactions; (2) The surface of NCM material undergoes chemical / electrochemical corrosion with sulfide / oxide solid electrolyte under high voltage, generating a high-impedance interfacial layer; (3) The charge transport impedance continues to rise due to the propagation of interfacial cracks during cycling. Summary of the Invention

[0005] The purpose of this application is to provide an all-solid-state battery and a method for preparing the same, in order to solve the above-mentioned problems.

[0006] To achieve the above objectives, this application adopts the following technical solution: A solid-state battery, wherein a first lithium replenishment layer, a second lithium replenishment layer, a solid electrolyte layer and a silicon anode are sequentially disposed between the positive electrode current collector and the negative electrode current collector; The first lithium replenishment layer, calculated based on 100% of its total raw material mass, includes 40%-50% LNO lithium replenishing agent (which can be any value between 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, or 40%-50%), 40%-50% sulfide electrolyte (which can be any value between 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, or 40%-50%), 3%-10% conductive agent (which can be any value between 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or 3%-10%), and 0.01%-10% binder (which can be any value between 0.01%, 0.05%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or 0.01%-10%). The second lithium replenishment layer, calculated based on the total mass of its raw materials (100%), includes 60%-80% NCM ternary cathode material (which can be any value between 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, or 60%-80%), 1%-2% graphene-coated Li5FeO4 (which can be any value between 1%, 1.5%, 2%, or 1%-2%), and 15%-30% sulfide electrolyte (which can be any value between 1% and 30%). 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30% or any value between 15% and 30%), conductive agent 1%-5% (can be 1%, 2%, 3%, 4%, 5% or any value between 1% and 5%) and adhesive 0.01%-10% (can be 0.01%, 0.05%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or any value between 0.01% and 10%).

[0007] During the initial charge and discharge of lithium-ion batteries, side reactions such as the formation of the solid electrolyte interphase (SEI) film consume some active lithium ions, leading to a decrease in reversible capacity. To compensate for this lithium loss, lithium replenishment additives are often introduced into the positive electrode to improve the overall energy density of the battery. However, these lithium replenishment additives are prone to side reactions with the solid electrolyte, affecting battery performance. To address these issues, this paper proposes a carbon-coated lithium replenishment additive and designs a bilayer lithium replenishment structure integrated on the positive electrode side. The aim is to address lithium loss during the initial charge and discharge phases in a tiered manner through the synergistic effect of internal basic lithium replenishment and external buffer lithium replenishment, thereby achieving efficient and stable replenishment of active lithium.

[0008] Using LNO as the inner lithium replenishment layer (closer to the current collector side) allows for the preferential and concentrated release of a large number of lithium ions during the first charge of the battery. The primary function of these lithium ions is to rapidly and fully compensate for the unavoidable initial lithium loss that occurs throughout the battery (especially during the formation of the SEI film on the negative electrode side). This ensures that the positive electrode active material can achieve its theoretical capacity in the first cycle, laying the foundation for high energy density. Using a mixture of carbon-coated LFO and NCM as the outer lithium replenishment layer (closer to the separator / electrolyte side) not only provides replenishment during the first cycle but also continuously and slowly releases lithium ions in later stages of long-term battery cycling to compensate for the continuous decay of active lithium during cycling caused by interfacial side reactions and the continuous thickening / repair of the SEI film. Furthermore, carbon-coated LFO as the outer lithium replenishment agent can prevent side reactions between the electrolyte and the positive electrode material.

[0009] Preferably, the graphene-coated Li5FeO4 has a particle size of 1-5 μm, more preferably 1.2-2.8 μm, and the thickness of the graphene coating layer is 2-10 nm.

[0010] Optionally, the particle size of the graphene-coated Li5FeO4 can be any value between 1μm, 2μm, 3μm, 4μm, 5μm or 1-5μm, and the thickness of the graphene coating can be any value between 2nm, 3nm, 4nm, 5nm, 6nm, 7nm, 8nm, 9nm, 10nm, 11nm, 12nm, 13nm, 14nm, 15nm or 2-15nm.

[0011] Preferably, the method for preparing the graphene-coated Li5FeO4 includes: The Li5FeO4 was refined by ultrasonic resonance and sand milling and / or ball milling. Then, a mixture of acetylene and argon-hydrogen gas was introduced into a tube furnace with air venting to perform chemical vapor deposition to obtain the graphene-coated Li5FeO4.

[0012] Preferably, the LNO lithium supplement has a particle size of 1-10 μm, more preferably 1-3 μm.

[0013] Optionally, the particle size of the LNO lithium supplement can be any value between 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm or 1-10μm.

[0014] By using a multi-stage particle size control process, the average particle size (D50) of Li5FeO4 lithium supplement is reduced from the conventional 5-10μm to the target level, the specific surface area is increased by 3-5 times, the density of active sites for lithium supplementation reaction is increased by more than 200%, and the problem of easy particle agglomeration is avoided.

[0015] Preferably, the amount of graphene-coated Li5FeO4 is 1-2 wt% of the NCM ternary cathode material.

[0016] Optionally, the amount of graphene-coated Li5FeO4 can be any value between 1wt%, 1.5wt%, 2wt%, or 1-2wt% of the NCM ternary cathode material.

[0017] Preferably, the sulfide electrolyte includes one or more of LiPSX, LiGePS, and LiPS, wherein X = Cl, Br, or I.

[0018] Preferably, the conductive agent includes one or more of acetylene black, Ketjen black, carbon fiber, and fumed carbon fiber.

[0019] Preferably, the adhesive comprises one or more of polytetrafluoroethylene (PTFE), polyethylene, polypropylene, ethylene / propylene copolymer, polybutadiene, polyethylene oxide, chlorosulfonated polyethylene, and polyvinylpyrrolidone.

[0020] Preferably, the thickness of the first lithium replenishment layer is 15-20 μm; The thickness of the second lithium replenishment layer is 200-250 μm.

[0021] Optionally, the thickness of the first lithium replenishment layer can be any value between 15μm, 16μm, 17μm, 18μm, 19μm, 20μm or 15-20μm; the thickness of the second lithium replenishment layer can be any value between 200μm, 210μm, 220μm, 230μm, 240μm, 250μm or 200-250μm.

[0022] This application also provides a method for preparing the all-solid-state battery described above, comprising: The raw materials of the first lithium replenishment layer are mixed with a solvent to obtain a slurry, which is then coated onto the positive electrode current collector. The raw materials for the second lithium replenishment layer are mixed with a solvent to obtain a slurry, which is then coated onto the surface of the first lithium replenishment layer and dried to obtain a positive electrode sheet. Preparation of a solid electrolyte layer and a silicon anode; The positive electrode, the solid electrolyte layer, and the silicon negative electrode are assembled to obtain the all-solid-state battery.

[0023] Compared with the prior art, the beneficial effects of this application include: The all-solid-state battery provided in this application constructs a gradient lithium replenishment between the positive electrode current collector and the solid electrolyte layer by setting two lithium replenishment layers. This achieves interface stability from both physical barrier and electrochemical regulation dimensions, thereby simultaneously suppressing oxygen loss from the surface of the positive electrode material and electrolyte decomposition. After 200 cycles, the interfacial impedance stabilizes at 100 Ω·cm. ２ The second lithium replenishment layer is composed of graphene-coated Li5FeO4, which effectively reduces the interfacial side reactions between the LFO material and the sulfide solid electrolyte. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope of this application.

[0025] Figure 1 A schematic diagram of the lithium replenishment structure of a solid-state battery provided in an embodiment; Figure 2 The image shows a SEM image of graphene-coated Li5FeO4 obtained in the example.

[0026] Figure label: 1-Positive current collector; 2-First lithium replenishing agent layer; 3-Second lithium replenishing agent layer; 4-Solid electrolyte layer; 5-Silicon negative electrode; 6-Negative current collector. Detailed Implementation

[0027] The implementation schemes of this application will be described in detail below with reference to specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating this application and should not be regarded as limiting the scope of this application. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0028] Example 1 This embodiment provides a solid-state battery, the structural schematic diagram of which is shown below. Figure 1 As shown. From top to bottom, it includes: positive electrode current collector 1, first lithium replenishing agent layer 2, second lithium replenishing agent layer 3, solid electrolyte layer 4, silicon negative electrode 5, and negative electrode current collector 6.

[0029] The preparation method is as follows: The LNO particle size was refined using an ultrafine rotary disc mill and an acoustic resonance device, resulting in a particle size of 3-5 µm. The refined LNO, LPSC, VGCF, and PVDF were then mixed in a weight ratio of 50:40:8:2, and solvent was added to prepare a uniform slurry. This slurry was then coated onto an aluminum current collector, with the LNO lithium-added layer controlled to be 20 µm thick.

[0030] LFO particles were refined using an ultrafine rotary disc mill and acoustic resonance equipment, resulting in a particle size of 1-3 µm. The LFO was then placed in a tube furnace, and inert gas was introduced into the tube to purge air, ensuring an oxygen content of less than 1 ppm and humidity of less than 5%. An acetylene and argon-hydrogen mixture was then introduced at a flow rate of 20 ml / min and 60 ml / min (99% argon and 1% hydrogen by volume). CVD treatment was performed for 5 minutes, forming a dense 5 nm carbon coating layer on the Li5FeO4 surface, resulting in carbon-coated small-particle Li5FeO4 (SEM images of the obtained material are shown below). Figure 2 As shown in the figure, the average particle size is 1.2 μm. C@LFO, NCM, LPSC, VGCF and PVDF were mixed in powder form at a weight ratio of 1:80:16:2:1, and solvent was added to prepare a uniform slurry, which was then coated on an LNO lithium supplementation layer with a thickness of 230 μm.

[0031] Silicon-based materials, elemental silicon, Super P, and PVDF are weighed in a mass ratio of 90:5:5. The resulting mixture is mixed with water as a solvent in a mass ratio of 2:8 and stirred using a stirrer to remove bubbles. The resulting slurry is coated onto a copper current collector and dried to form a negative electrode sheet.

[0032] Assembly was carried out in a glove box. The protective gas inside the glove box was argon, and the partial pressures of water and oxygen were both below 1 ppm. 90 mg of LPSC was prepared at a concentration of 2 tons / cm³. 2 Pressing the material under pressure creates a 300μm thick solid electrolyte layer. Next, positive and negative electrode plates are assembled at a pressure of 6 tons / cm². 2 Press the pressure and assemble it into a mold battery.

[0033] Example 2 Unlike Example 1, the refined LNO particles have a diameter of 5-6 μm, and the refined LFO particles have a diameter of 3-5 μm.

[0034] Example 3 Unlike Example 1, the refined LNO, sulfide solid electrolyte, conductive material and binder were mixed in powder form at a weight ratio of 40:50:8:2.

[0035] Example 4 Unlike Example 1, C@LFO, NCM, sulfide solid electrolyte, conductive material and binder were mixed in powder form at a weight ratio of 2:80:15:2:1.

[0036] Example 5 Unlike Example 1, CVD treatment for 10 min resulted in a dense 10-15 nm carbon coating layer on the Li5FeO4 surface.

[0037] Comparative Example 1 The only difference from Example 1 is that the particle size of LNO was not refined.

[0038] Comparative Example 2 The only difference from Example 1 is that the particle size of LFO was not refined.

[0039] Comparative Example 3 The only difference from Example 1 is that LFO was not carbon coated.

[0040] Comparative Example 4 The only difference from Example 1 is that NCM was not mixed with C@LFO, and the weight ratio of NCM, sulfide solid electrolyte, conductive material and binder was 80:17:2:1.

[0041] Comparative Example 5 The only difference from Example 1 is that the LNO lithium replenishment layer is replaced with an LFO lithium replenishment layer, and the refined LFO, sulfide solid electrolyte, conductive material and binder are in a weight ratio of 50:40:8:2.

[0042] Battery testing methods With a cutoff voltage of 2.5~4.0 V, the system was first charged and discharged at a rate of 0.1 C for 3 cycles, and then charged and discharged at a rate of 1 C for 100 cycles. The capacity retention rate was recorded, and the data are shown in Table 1.

[0043] Table 1. Capacity retention rate of button cell after 30 cycles and cycle count of symmetrical cell under short circuit.

[0044] As shown in Table 1, the LNO+C@LFO bilayer lithium compensation prepared in this application can significantly improve the first-cycle capacity of solid-state batteries, compensate for the lithium-ion loss caused by the formation of SEI in the first cycle, and improve their cycle performance. This is attributed to the fact that the rock salt phase structure (Fm-3m space group) of the inner LiNiO2 (LNO) forms a three-dimensional lithium-ion diffusion channel, which, together with the spinel framework (FeO4 tetrahedra and LiO6 octahedra are connected by common vertices) of the outer carbon-coated Li5FeO4 (C@LFO), forms a lithium compensation synergistic network. The carbon coating layer suppresses electron tunneling at high potentials through electron localization, while the low-barrier (<0.3eV) lithium migration path provided by the open framework of LFO promotes the directional transport of compensated lithium.

[0045] As shown in Table 1, the LNO+C@LFO bilayer lithium compensation system of this invention significantly improves the performance of solid-state batteries through multi-level structural synergy: the rock salt phase structure of the inner LiNiO2 (LNO) constructs a three-dimensional lithium-ion diffusion network, which forms a lithium compensation synergy system with the spinel framework of the outer carbon-coated Li5FeO4 (C@LFO), wherein the carbon coating layer, through sp... 2 The electronic localization effect of the hybrid orbitals suppresses electron interfacial tunneling at high voltages (>4.3V), while the low-barrier (<0.3eV) lithium migration channel provided by the LFO open framework promotes the directional transport of compensated lithium. During the first charge cycle, this composite structure undergoes lithium extraction via Li5FeO4 (Li5FeO4→LiFeO2+4Li). + +4e - +O2) releases active lithium, whose high lithium chemical potential drives lithium compensation flow, effectively compensating for irreversible lithium loss caused by SEI film formation. At the same time, gradient modulus design maintains the integrity of the interface structure through stress dissipation mechanism, ultimately achieving synergistic optimization of first-cycle coulombic efficiency improvement and long-cycle stability.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. An all-solid-state battery, characterized in that, A first lithium replenishment layer, a second lithium replenishment layer, a solid electrolyte layer, and a silicon anode are sequentially disposed between the positive electrode current collector and the negative electrode current collector. The first lithium replenishment layer, calculated based on 100% of its total raw material mass, includes 40%-50% LNO lithium replenishing agent, 40%-50% sulfide electrolyte, 3%-10% conductive agent, and 0.01%-10% binder; The second lithium replenishment layer, calculated based on the total mass of its raw materials as 100%, includes 60%-80% NCM ternary cathode material, 1%-2% graphene-coated Li5FeO4, 15%-30% sulfide electrolyte, 1%-5% conductive agent, and 0.01%-10% binder.

2. The all-solid-state battery according to claim 1, characterized in that, The graphene-coated Li5FeO4 has a particle size of 1-5 μm, preferably 1.2-2.8 μm, and the thickness of the graphene coating layer is 2-15 nm, preferably 2-10 nm.

3. The all-solid-state battery according to claim 1, characterized in that, The preparation method of the graphene-coated Li5FeO4 includes: The Li5FeO4 was refined by ultrasonic resonance and sand milling and / or ball milling. Then, a mixture of acetylene and argon-hydrogen gas was introduced into a tube furnace with air venting to perform chemical vapor deposition to obtain the graphene-coated Li5FeO4.

4. The all-solid-state battery according to claim 1, characterized in that, The LNO lithium supplement has a particle size of 1-10 μm, preferably 1-3 μm.

5. The all-solid-state battery according to claim 1, characterized in that, The amount of graphene-coated Li5FeO4 used is 1-2 wt% of the NCM ternary cathode material.

6. The all-solid-state battery according to claim 1, characterized in that, The sulfide electrolyte includes one or more of LiPSX, LiGePS, and LiPS, wherein X = Cl, Br, or I.

7. The all-solid-state battery according to claim 1, characterized in that, The conductive agent includes one or more of acetylene black, Ketjen black, carbon fiber, and fumed carbon fiber.

8. The all-solid-state battery according to claim 1, characterized in that, The adhesive includes one or more of polytetrafluoroethylene (PTFE), polyethylene, polypropylene, ethylene / propylene copolymer, polybutadiene, polyethylene oxide, chlorosulfonated polyethylene, and polyvinylpyrrolidone.

9. The all-solid-state battery according to any one of claims 1-8, characterized in that, The thickness of the first lithium replenishment layer is 15-20 μm; The thickness of the second lithium replenishment layer is 200-250 μm.

10. A method for preparing an all-solid-state battery according to any one of claims 1-9, characterized in that, include: The raw materials of the first lithium replenishment layer are mixed with a solvent to obtain a slurry, which is then coated onto the positive electrode current collector. The raw materials for the second lithium replenishment layer are mixed with a solvent to obtain a slurry, which is then coated onto the surface of the first lithium replenishment layer and dried to obtain a positive electrode sheet. Preparation of a solid electrolyte layer and a silicon anode; The positive electrode, the solid electrolyte layer, and the silicon negative electrode are assembled to obtain the all-solid-state battery.

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