Solid-state battery system and preparation method thereof

Abstract

The invention belongs to the field of lithium batteries, and particularly relates to a solid-state battery system and a preparation method thereof. The solid-state battery system comprises a composite electrolyte positive electrode and a porous negative electrode; according to the composite electrolyte positive electrode, a connecting framework is constructed on a high-nickel NCM-based positive electrode, and a solid electrolyte film is fixed through the connecting framework to realize a composite structure of the positive electrode and an electrolyte. According to the invention, a core-shell-framework integrated in-situ construction mode is matched with a negative-electrode-free setting mode, so that the active proportion of the positive electrode is greatly increased, the problem of low energy density of a traditional solid-state battery is solved, and meanwhile, the wide-temperature-range working performance of the solid-state battery is greatly expanded bidirectionally.

Description

Technical Field

[0001] This invention belongs to the field of lithium batteries, and particularly relates to a solid-state battery system and its preparation method. Background Technology

[0002] With the continued growth in demand for new energy sources, lithium-ion batteries have become the core power source for consumer electronics, electric vehicles, and energy storage systems. However, traditional liquid lithium batteries use organic electrolytes, which pose safety hazards such as easy leakage, flammability, and poor thermal stability. Especially under conditions of thermal runaway, overcharging, or mechanical damage, they are highly susceptible to combustion or even explosion. To address these issues, all-solid-state lithium batteries (ASSLBs) have emerged. They replace traditional liquid electrolytes with solid electrolytes, fundamentally improving battery safety, energy density, and thermal stability, and are considered a core direction for next-generation lithium battery technology.

[0003] However, current all-solid lithium batteries face numerous technical hurdles. For example, common PEO or polycarbonate polymer all-solid lithium batteries exhibit poor overall electrochemical performance, failing to meet the requirements of automotive batteries. Oxide systems, such as LLZO all-solid lithium batteries, offer advantages in terms of high safety and extensive research, but industrialization is challenging due to poor interfacial contact between the positive and negative electrodes and the electrolyte, resulting in high brittleness. Sulfide-based all-solid lithium batteries, including common systems like Li2S-P2S5 and Li6PS5Cl, represent a key research direction for automotive all-solid lithium batteries. These typically exhibit excellent electrochemical performance, but their electrochemical window and temperature adaptability are relatively limited.

[0004] Halide systems are a relatively unique type of all-solid lithium battery system, possessing advantages such as a wide electrochemical window, good cathode compatibility, and excellent environmental adaptability, but they typically exhibit lower energy density. Therefore, effectively improving the energy density of halide systems to enable their effective application in automotive batteries is a crucial research direction. Summary of the Invention

[0005] To address the problems of poor electrochemical performance or poor environmental adaptability in existing all-solid lithium battery systems, this invention provides a solid-state battery system, as well as the preparation and combination method of the core components of the solid-state battery system—the positive electrode, the electrolyte, and the negative electrode, i.e., the preparation method of the solid-state battery system.

[0006] The main objective of this invention is: I. A positive electrode system with an extremely high proportion of active materials was constructed by simulating the concept of a fully active electrode, and a composite electrolyte positive electrode was constructed by effectively combining a halide electrolyte system with good stability and strong adaptability based on this positive electrode system. II. Improve the problem of poor chemical stability and compatibility between halide solid electrolytes and conventional negative electrodes; Third, ensure that the solid-state battery system can achieve a high energy density that closely meets the requirements of automotive batteries.

[0007] To achieve the above objectives, the present invention adopts the following technical solution.

[0008] A method for preparing a solid-state battery system. The method includes: 1) Disperse high-nickel NCM raw material powder in water to prepare a suspension. Then prepare lithium source solution and zirconium source dilute sol separately. Slowly add lithium source solution to suspension and stir evenly. Then slowly add zirconium source dilute sol and stir continuously. The resulting slurry is dried and heat-treated to obtain positive electrode active material. 2) Mix the positive electrode active material, LY framework material and conductive agent evenly to form a mixed powder. Add liquid additives to the mixed powder and stir and / or grind it into a paste. Then, coat it on the current collector and perform segmented drying and pressing to obtain a composite framework positive electrode sheet. 3) Take the LY flexible film and attach it to the composite framework positive electrode sheet, and then perform segmented pressing to obtain the composite electrolyte positive electrode; 4) A solid-state battery system can be formed by assembling and pressing a composite electrolyte positive electrode and a porous negative electrode.

[0009] As a preferred option Step 1) The high-nickel NCM is a NiCoMn ternary cathode material with a Ni content ≥90%; In particular, the high-nickel NCM used in this invention are all commercially available NCM900505 cathode materials, and are single-crystal powders with a mesh size ≥300 mesh; In step 1), the ratio of high-nickel NCM to water in the preparation of the suspension is 100 g: (400-600) mL. Step 1) The lithium source solution is a suspension with a lithium ion concentration of 1.5–2.0 mol / L and a volume of 20–30 mL / L; Step 1) The zirconium source dilute sol is a zirconium oxide sol with a solid content of 5-10 wt%. The zirconium oxide sol is calculated based on the atomic ratio of Li and Zr contained in the lithium source solution and the zirconium source dilute sol, and the atomic ratio of Zr contained in the zirconium source dilute sol to Li in the lithium source solution is controlled to be 1:(2-2.2).

[0010] As a preferred option Step 1) The lithium source solution is slowly added to the suspension at a rate of 3-5% VOL of total lithium source solution per minute. After the addition is completed, the mixture is stirred at 60-120 rpm for 25-35 minutes. Step 1) The zirconium source dilute sol is added slowly at a rate of 4-6% VOL of total zirconium source dilute sol per minute, and then stirred continuously at 120-180 rpm for 90-150 min.

[0011] As a preferred option Step 1) The drying process includes sequential atomization drying and fluidization drying; Step 1) The heat treatment is carried out at 450-500 ℃ for 100-150 min.

[0012] As a preferred option Step 2) The LY skeleton material is Li3YCl6 powder with a mesh size ≥ 300 mesh; Step 2) The conductive agent is vapor-grown carbon fiber; Step 2) The positive electrode active material, LY skeleton material and conductive agent are mixed and dry-mixed at a mass ratio of 92:(5~7):(1.5~2.5).

[0013] As a preferred option Step 2) The liquid additive is anhydrous xylene, and its dosage is 0.2-0.4 mL / g of mixed powder; Step 2) The current collector is an oil-based carbon-coated aluminum foil, and the coating amount of the paste slurry is 20-25 mg / cm². 2 .

[0014] As a preferred option Step 2) The segmented drying and pressing process includes: Vacuum dry at 60–80 °C for 50–70 min, then hot press at 130–160 °C and 320–380 MPa for 12–18 min, and then vacuum dry at 140–180 °C to constant weight.

[0015] As a preferred option Step 3) The LY flexible film is a Li3YCl6 flexible thin film with a thickness of 20-30 μm; Step 3) The segmented pressing process includes pressing at 5-10 MPa for 10-20 min, then hot pressing at 140-160 ℃ and 50-70 MPa for 5-10 min, cooling to room temperature, and then pressing at 5-10 MPa for 1-2 min.

[0016] As a preferred option Step 4) The porous negative electrode is a zinc oxide-loaded copper foam negative electrode; Step 4) The assembly and pressing include: The porous negative electrode is bonded to one side of the LY flexible membrane on the composite electrolyte positive electrode, and then pressed at 8-12 MPa for 25-35 min.

[0017] A solid-state battery system, The solid-state battery system includes a composite electrolyte positive electrode and a porous negative electrode; The composite electrolyte cathode is a composite structure in which a connecting framework is constructed on a high-nickel NCM-based cathode, and a solid electrolyte film is fixed by the connecting framework to achieve the composite structure of cathode and electrolyte.

[0018] The core of the technical solution of this invention lies in constructing a special "core-shell-framework integrated" in-situ composite electrolyte positive electrode, and providing a "negative electrode-free" system that can cooperate very effectively with it. The "negative electrode-free" system means that the negative electrode does not undergo pre-lithiation or add lithium-containing components, so as to form an effective combination.

[0019] Therefore, the first step in this invention is to select a suitable positive electrode active material. NCM ternary cathode material, as a typical high energy density cathode material, has the characteristics of high specific capacity and high operating voltage, and it also significantly helps to improve the reversible capacity of the battery. Compared with other common materials such as lithium iron phosphate (LFP) and lithium manganese oxide (LMO), it exhibits more obvious comprehensive advantages in terms of energy density, specific capacity, stability and rate performance.

[0020] However, compared to other NCM ternary cathode materials, the NCM ternary cathode material used in this invention requires a nickel content of over 90%, which is a relatively unique aspect. This is because in NCM ternary cathode materials, nickel content is generally directly proportional to performance but inversely proportional to stability; that is, the higher the nickel content, the stronger the theoretical performance, but the worse the stability exhibited in practice, especially in terms of structural and thermal stability. For example, compared to NCM811, NCM900505 is more prone to nickel content issues in actual use. 2+ and Li +While NCM ternary cathode materials exhibit irreversible phase transitions, such as from layered structures to spinel / rock salt phases, due to cation mixing, they also possess near-irreplaceable advantages in energy density potential and cost-effectiveness. Therefore, this invention employs a special shell coating treatment to mitigate this instability. A Li-Zr coating layer is constructed using a combination of lithium hydroxide aqueous solution and zirconium oxide sol. This significantly suppresses the inherent defects of NCM900505 ternary cathode materials, substantially improving their stability and inhibiting cation mixing. This is primarily because the coating layer stabilizes the interface, forming a physical coating of the NCM ternary cathode, reducing direct contact between the NCM ternary cathode and the solid electrolyte, suppressing side reactions, improving interface stability, reducing interface impedance, and minimizing cycle capacity decay. More importantly, the presence of zirconium ions may pre-dope into the NCM lattice, occupying transition metal sites and forming structural support, stabilizing the lattice structure, and inhibiting nickel ion migration. This multi-effect synergistic effect significantly optimizes and enhances the performance of NCM ternary cathode materials. This invention employs a mixture of lithium and zirconium sources to construct a lithium-zirconium composite coating layer, such as lithium zirconate, instead of a single zirconium oxide coating. The main purpose is to further enhance lithium-ion conductivity. Lithium zirconate is an excellent lithium-ion conductor, providing a channel for lithium-ion migration and reducing the interfacial impedance between the cathode and the solid electrolyte. At the same time, its chemical properties are similar to those of the electrolyte Li3YCl6 used in this invention. This chemical similarity helps to form a more stable and tighter interfacial bond during processing, reducing internal stress caused by the mismatch in thermal expansion coefficients between different materials, thereby maintaining the integrity of the interface during long-term cycling. Therefore, the shell formed by this invention has multiple benefits, including physical protection, high-efficiency lithium conduction, and potential reinforcement of the bulk structure.

[0021] In addition to its high nickel content, the positive electrode active material used in this invention requires special attention: the NCM900505 used must be in single-crystal form. This is because commercially available and laboratory-synthesized NCM900505 exists in both polycrystalline and single-crystal forms. While single-crystal particles are typically larger than polycrystalline primary particles, resulting in a longer lithium-ion diffusion path and potentially limiting rate performance to some extent, they offer superior structural stability and are well-suited to the technical solution of this invention, balancing performance and stability to ensure the long-term cycle performance of the battery system.

[0022] Based on the special cathode material and coating material used, this invention specifically selected Li3YCl6 as the filler framework material and electrolyte. Li3YCl6 is a relatively common halide electrolyte material, similar to Li3YBr6, which has similar electrochemical properties. However, compared to Li3YBr6, Li3YCl6 exhibits extremely high oxidation stability. Although Li3YBr6 can theoretically produce superior electrochemical performance, such as higher ionic conductivity, the NCM ternary cathode material used in this invention indicates that this invention aims to construct a high-voltage electrochemical system. Li3YBr6 is prone to oxidation and decomposition under high voltage, resulting in very poor cycle stability. Li3YBr6 is very likely to decompose and oxidize at the interface with the cathode material, leading to battery failure. Therefore, Li3YCl6 is currently the best performing material in experiments. Furthermore, compared to other sulfide electrolytes and oxide electrolytes, it exhibits higher room-temperature ionic conductivity, especially in oxide electrolyte systems where the difference is even greater. Furthermore, by employing Li3YCl6 material as a solid electrolyte, this invention effectively eliminates chemical and electrochemical interface problems caused by material mismatch, constructing a homogeneous interface with continuous chemical potential and unimpeded ion transport. This significantly reduces interface resistance, achieving complete fusion of the cathode and electrolyte into a cathode-electrolyte composite. The Li3YCl6 material tightly coats the NCM active material particles, forming a continuous ion conduction network. Since the framework and electrolyte membrane are made of the same material, lithium ions can be efficiently transported in a single phase after entering the composite cathode from the electrolyte membrane, avoiding transport obstacles at the interfaces of different electrolyte materials. At the same time, Li3YCl6 material has good compressibility, and using it as a framework material helps to form a tight and stable solid-solid contact with the NCM active material during the pressing process, ensuring the structural integrity of the electrode and long-term electrochemical performance. Ultimately, a highly homogeneous solid-solid interface is constructed, which is crucial for maximizing the performance of high-nickel NCM materials and ensuring long-term cycle stability.

[0023] As another important component of the solid-state battery system, this invention also adjusts the negative electrode. As mentioned earlier, the solid-state battery system of this invention is highly sensitive to lithium metal, especially the Li3YCl6 material used in the framework and electrolyte, which is easily reduced by lithium metal, forming an unstable mixed conductive interface. Therefore, this invention adaptively adjusts and improves the negative electrode, constructing a special porous negative electrode that is traditionally considered "negative electrode-free," without pre-lithiation and with zero excess lithium. Porous copper foam is used as a three-dimensional current collector, providing a large specific surface area and effectively buffering volume changes during charge and discharge, ensuring cycle stability, and effectively utilizing its good conductivity. Based on this, zinc oxide is used for loading and activation. Zinc oxide, as the negative electrode material, has a lithium storage mechanism of conversion reaction ZnO + 2Li. + +2e - Zn + Li₂O possesses an extremely high theoretical specific capacity, while the three-dimensional porous current collector, copper foam, mitigates its volume expansion effect, thus exhibiting excellent compatibility with the battery system of this invention. Furthermore, to further optimize overall battery performance, the negative electrode of this invention can also be prepared using the following methods: Zinc acetate dihydrate was dissolved in ethanol to prepare a seed crystal solution of 0.005–0.010 mol / L. Copper foam was cut to the required size (corresponding to the carbon-coated aluminum foil of the positive electrode current collector) and ultrasonically cleaned sequentially in acetone, ethanol, and deionized water for 15 min. Then, it was pretreated by standing in a 0.1–0.2 mol / L hydrochloric acid aqueous solution for 30–60 s. After drying, it was immersed in the seed crystal solution for 15 min for thorough wetting. After removal, it was annealed in air at 320–350 °C for 15–20 min. This immersion and annealing process was repeated 2–3 times. Finally, it was transferred to a 0.025–0.100 mol / L zinc nitrate hexahydrate aqueous solution, and hexamethylenetetramine was added at a concentration of 0.025–0.050 mol / L. The mixture was then subjected to hydrothermal treatment at 90–95 °C for 6–12 h. After cooling, it was removed, cleaned, and dried to obtain the target negative electrode product.

[0024] The constructed anode product has a multi-level, multi-scale three-dimensional micro-nano structure, which further has a larger specific surface area and stronger electrochemical activity. Moreover, the growth of the secondary nanostructure can effectively buffer the volume expansion of ZnO by up to 300% during the lithium insertion / extraction process, prevent the pulverization and damage of the electrode structure, and thus significantly improve cycle stability.

[0025] The beneficial effects of this invention are: This invention significantly increases the positive electrode activity ratio by matching the "core-shell-framework integration" in-situ construction method with the "no negative electrode" setting method, solving the problem of low energy density in traditional solid-state batteries, and at the same time greatly expanding the wide temperature range performance of solid-state batteries. Attached Figure Description

[0026] Figure 1 This is an SEM characterization image of the copper foam used in the preceding embodiments of the present invention; Figure 2 SEM characterization of the porous negative electrode prepared in the preceding embodiment of the present invention. Figure 1 ; Figure 3 SEM characterization of the porous negative electrode prepared in the preceding embodiment of the present invention. Figure 2 ; Figure 4 This is an interface characterization diagram of the composite electrolyte positive electrode prepared in Example 1 of the present invention. Detailed Implementation

[0027] The present invention will be further described clearly and in detail below with reference to specific embodiments and the accompanying drawings. Those skilled in the art will be able to implement the present invention based on these descriptions. Furthermore, the embodiments of the present invention described below are generally only some, not all, of the embodiments of the present invention. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0028] Unless otherwise specified, all raw materials used in the embodiments of the present invention are commercially available or obtainable by those skilled in the art; unless otherwise specified, all methods used in the embodiments of the present invention are methods mastered by those skilled in the art.

[0029] Preliminary Examples: Unless otherwise specified, the porous negative electrodes used in the embodiments of the present invention are all prepared by the following methods: Zinc acetate dihydrate was dissolved in ethanol to prepare a seed crystal solution of 0.010 mol / L. Copper foam was cut to the required size and ultrasonically cleaned in acetone, ethanol and deionized water for 15 min in sequence. Then it was placed in 0.1 mol / L hydrochloric acid aqueous solution for static etching for 45 s to complete the pretreatment. After drying, the copper foam was immersed in the seed crystal solution for 15 min to fully wet it. After removal, it was annealed at 350 ℃ for 15 min in air atmosphere. The immersion and annealing were repeated 3 times. Then it was transferred to a mixed aqueous solution containing 0.050 mol / L zinc nitrate hexahydrate and 0.030 mol / L hexamethylenetetramine and hydrothermally heated at 95 ℃ for 9 h. After cooling to room temperature, it was removed, washed with deionized water and dried at 60 ℃ to obtain a porous negative electrode.

[0030] The SEM characterization of the copper foam before and after the reaction is as follows: Figure 1 , Figure 2 and Figure 3 As shown, from Figure 1 and Figure 2 The characterization results clearly show that this example achieved the loading of zinc oxide structures on the surface of copper foam through treatment, and from... Figure 3 The results clearly show that the present invention effectively prepared and constructed a zinc oxide load with a nanowire structure, which significantly increased the specific surface area of ​​the porous anode. Furthermore, this nanostructure feature further weakens the destructive effect of volume expansion on zinc oxide during charge-discharge cycles, which is beneficial to improving the cycle stability of the battery system.

[0031] Example 1: A solid-state battery system, which is prepared by the following method: 1) Disperse 300-mesh single-crystal NCM900505 powder in deionized water at a ratio of 100 g: 500 mL to prepare a suspension; Prepare a 1.75 mol / L hydrated lithium hydroxide aqueous solution as the lithium source solution, and then dilute a commercially available zirconia sol (HN-RJ80-20%) with a solid content of 20 wt% with deionized water to a solid content of 5 wt% as the dilute zirconia source sol. The lithium source solution was slowly and uniformly added to the suspension at a ratio of 25 mL / L over 25 min. After stirring at 90 rpm for 30 min, the amount of zirconium source dilute sol was calculated according to the atomic ratio of Li to Zr in the lithium source solution and zirconium source dilute sol of 2:1. The zirconium source dilute sol was slowly and uniformly added to the zirconium source dilute sol over 20 min, while stirring at 90 rpm during the addition process. After the addition was completed, the mixture was continuously stirred at 150 rpm for 120 min to obtain a slurry. The slurry was then subjected to atomization drying and fluidized bed drying to obtain a powder. The powder was then heat-treated at 450 ℃ for 120 min to obtain the positive electrode active material. 2) Mix the positive electrode active material, 300-mesh Li3YCl6 powder, and vapor-grown carbon fiber (VGCF) at a mass ratio of 92:6:2 to form a uniform mixed powder. Add anhydrous xylene to the mixed powder at a ratio of 0.3 mL / g, stirring to form a paste. Add 20 mg / cm³ of the mixture. 2 The coating amount is determined by coating the paste onto the oil-based carbon-coated aluminum foil, first vacuum drying at 60 ℃ for 60 min, then hot pressing at 150 ℃ and 350 MPa for 15 min, and then vacuum drying at 160 ℃ to constant weight to obtain the composite framework positive electrode sheet. 3) Take 300 mesh Li3YCl6 powder and press it into a Li3YCl6 flexible film with a thickness of 20±1 μm at 150 ℃ and 400 MPa. Attach the Li3YCl6 flexible film to the composite framework positive electrode sheet and press it at 10 MPa for 12 min, then hot press it at 150 ℃ and 60 MPa for 8 min. After cooling to room temperature, press it at 5 MPa for 2 min to obtain the composite electrolyte positive electrode. 4) The porous negative electrode is attached to one side of the Li3YCl6 flexible film on the composite electrolyte positive electrode and then pressed at 10MPa for 30 min to form the target solid-state battery system.

[0032] The interface characterization diagram of the composite electrolyte cathode is as follows: Figure 4 As shown. From Figure 4 It is evident that the composite electrolyte cathode achieves an effective transition through the formation of Li3YCl6 material, and its hybrid growth as a framework material combined with the cathode active material results in an extremely tight composite between the cathode and electrolyte components, making it almost impossible to discern a clear boundary. The degree of bonding between the two is highly consistent with expectations. The overall composite electrolyte cathode is a composite structure where a connecting framework is constructed on a high-nickel NCM-based cathode, and the solid electrolyte film is fixed through the connecting framework to achieve the composite structure of the cathode and electrolyte.

[0033] In addition, the electrochemical performance of the solid-state battery system prepared in this example was characterized, and the characterization results are shown in the table below.

[0034]

[0035] Except for the wide temperature range performance characterization, all other performance characterizations were conducted under standard conditions of 20 °C.

[0036] In the table: wide temperature range performance characterization refers to performing 0.5C / 20 cycles under specified temperature conditions, recording the remaining capacity after the cycle, and comparing the characterization results with those under the standard condition of 20 ℃. "↓" indicates the decrease and "↑" indicates the increase. Rate performance refers to performing 150 cycles under specified rate conditions, recording the remaining capacity after the cycle, and comparing the characterization results with those under the 0.5C rate conditions. "↓" indicates the decrease and "↑" indicates the increase.

[0037] The characterization results clearly demonstrate that the battery produced in this example exhibits excellent electrochemical performance, particularly in energy density and wide-temperature operating performance. The energy density reaches the critical threshold of 400 Wh / kg for automotive batteries. The wide-temperature operating performance is attributed to its ability to maintain high conductivity stability even at low temperatures, while the unique core-shell-skeleton structure and the effective buffering effect of the porous negative electrode ensure the overall stability of the battery system at high temperatures, significantly enhancing its environmental adaptability.

[0038] Meanwhile, thanks to the robust interface and structure, the solid-state battery system of this invention has extremely high cycle stability. In the first 150 cycles, the capacity retention rate is even stable at an extremely high level of ≥99.5%, and even after 800 cycles, the capacity retention rate can still reach more than 80%. This greatly breaks through the limits of conventional high-nickel ternary cathode materials, indicating that the core-shell-skeleton technology of this invention has extremely strong effectiveness.

[0039] Example 2: A solid-state battery system, which is prepared by the following method: 1) Disperse 300-mesh single-crystal NCM900505 powder in deionized water at a ratio of 100 g: 500 mL to prepare a suspension; Prepare a 2.0 mol / L hydrated lithium hydroxide aqueous solution as the lithium source solution, and then dilute a commercially available zirconia sol (HN-RJ80-20%) with a solid content of 20 wt% with deionized water to a solid content of 10 wt% as the dilute zirconia source sol. The lithium source solution was slowly and uniformly added to the suspension at a ratio of 25 mL / L over 25 min. After stirring at 90 rpm for 30 min, the amount of zirconium source dilute sol was calculated according to the atomic ratio of Li to Zr in the lithium source solution and zirconium source dilute sol of 2.2:1. The zirconium source dilute sol was slowly and uniformly added to the zirconium source dilute sol over 20 min, while stirring at 90 rpm during the addition process. After the addition was completed, the mixture was continuously stirred at 150 rpm for 120 min to obtain a slurry. The slurry was then subjected to atomization drying and fluidized bed drying to obtain a powder. The powder was then heat-treated at 450 ℃ for 120 min to obtain the positive electrode active material. 2) Mix the positive electrode active material, 300-mesh Li3YCl6 powder, and vapor-grown carbon fiber at a mass ratio of 92:6:2 to form a uniform mixed powder. Add anhydrous xylene to the mixed powder at a ratio of 0.3 mL / g, stirring to form a paste. Add 20 mg / cm³ of the mixture to the mixture. 2The coating amount is determined by coating the paste onto the oil-based carbon-coated aluminum foil, first vacuum drying at 60 ℃ for 60 min, then hot pressing at 150 ℃ and 350 MPa for 15 min, and then vacuum drying at 160 ℃ to constant weight to obtain the composite framework positive electrode sheet. 3) Take 300 mesh Li3YCl6 powder and press it into a Li3YCl6 flexible film with a thickness of 20±1 μm at 150 ℃ and 400 MPa. Attach the Li3YCl6 flexible film to the composite framework positive electrode sheet and press it at 10 MPa for 12 min, then hot press it at 150 ℃ and 60 MPa for 8 min. After cooling to room temperature, press it at 5 MPa for 2 min to obtain the composite electrolyte positive electrode. 4) The porous negative electrode is attached to one side of the Li3YCl6 flexible film on the composite electrolyte positive electrode and then pressed at 10MPa for 30 min to form the target solid-state battery system.

[0040] The solid-state battery system prepared in this example was subjected to the same electrochemical performance characterization as in Example 1, and the characterization results are shown in the table below.

[0041]

[0042] Example 3: A solid-state battery system, which is prepared by the following method: 1) Disperse 300-mesh single-crystal NCM900505 powder in deionized water at a ratio of 100 g: 500 mL to prepare a suspension; Prepare a 1.5 mol / L hydrated lithium hydroxide aqueous solution as the lithium source solution, and then dilute a commercially available zirconia sol (HN-RJ80-20%) with a solid content of 20 wt% with deionized water to a solid content of 7.5 wt% as the dilute zirconia source sol. The lithium source solution was slowly and uniformly added to the suspension at a ratio of 25 mL / L over 25 min. After stirring at 90 rpm for 30 min, the amount of zirconium source dilute sol was calculated according to the atomic ratio of Li to Zr in the lithium source solution and zirconium source dilute sol of 2:1. The zirconium source dilute sol was slowly and uniformly added to the zirconium source dilute sol over 20 min, while stirring at 90 rpm during the addition process. After the addition was completed, the mixture was continuously stirred at 150 rpm for 120 min to obtain a slurry. The slurry was then subjected to atomization drying and fluidized bed drying to obtain a powder. The powder was then heat-treated at 450 ℃ for 120 min to obtain the positive electrode active material. 2) Mix the positive electrode active material, 300-mesh Li3YCl6 powder, and vapor-grown carbon fiber at a mass ratio of 92:6:2 to form a uniform mixed powder. Add anhydrous xylene to the mixed powder at a ratio of 0.3 mL / g, stirring to form a paste. Add 20 mg / cm³ of the mixture to the mixture. 2 The coating amount is determined by coating the paste onto the oil-based carbon-coated aluminum foil, first vacuum drying at 60 ℃ for 60 min, then hot pressing at 150 ℃ and 350 MPa for 15 min, and then vacuum drying at 160 ℃ to constant weight to obtain the composite framework positive electrode sheet. 3) Take 300 mesh Li3YCl6 powder and press it into a Li3YCl6 flexible film with a thickness of 20±1 μm at 150 ℃ and 400 MPa. Attach the Li3YCl6 flexible film to the composite framework positive electrode sheet and press it at 10 MPa for 12 min, then hot press it at 150 ℃ and 60 MPa for 8 min. After cooling to room temperature, press it at 5 MPa for 2 min to obtain the composite electrolyte positive electrode. 4) The porous negative electrode is attached to one side of the Li3YCl6 flexible film on the composite electrolyte positive electrode and then pressed at 10MPa for 30 min to form the target solid-state battery system.

[0043] The solid-state battery system prepared in this example was subjected to the same electrochemical performance characterization as in Example 1, and the characterization results are shown in the table below.

[0044]

[0045] Based on the characterization results of Examples 1-3 above, the solid-state battery system of the present invention exhibits high performance stability, with specific capacity generally reaching above 210 mAh / g. Although some samples showed energy densities below 400 Wh / kg, the overall energy density remained around 400 Wh / kg. Furthermore, its wide-temperature-range operating performance was generally excellent.

[0046] Comparative Example 1: A solid-state battery system, which is prepared by the following method: 1) Disperse 300-mesh polycrystalline NCM900505 powder in deionized water at a ratio of 100 g: 500 mL to prepare a suspension; Prepare a 1.75 mol / L hydrated lithium hydroxide aqueous solution as the lithium source solution, and then dilute a commercially available zirconia sol (HN-RJ80-20%) with a solid content of 20 wt% with deionized water to a solid content of 5 wt% as the dilute zirconia source sol. The lithium source solution was slowly and uniformly added to the suspension at a ratio of 25 mL / L over 25 min. After stirring at 90 rpm for 30 min, the amount of zirconium source dilute sol was calculated according to the atomic ratio of Li to Zr in the lithium source solution and zirconium source dilute sol of 2:1. The zirconium source dilute sol was slowly and uniformly added to the zirconium source dilute sol over 20 min, while stirring at 90 rpm during the addition process. After the addition was completed, the mixture was continuously stirred at 150 rpm for 120 min to obtain a slurry. The slurry was then subjected to atomization drying and fluidized bed drying to obtain a powder. The powder was then heat-treated at 450 ℃ for 120 min to obtain the positive electrode active material. 2) Mix the positive electrode active material, 300-mesh Li3YCl6 powder, and vapor-grown carbon fiber at a mass ratio of 92:6:2 to form a uniform mixed powder. Add anhydrous xylene to the mixed powder at a ratio of 0.3 mL / g, stirring to form a paste. Add 20 mg / cm³ of the mixture to the mixture. 2 The coating amount is determined by coating the paste onto the oil-based carbon-coated aluminum foil, first vacuum drying at 60 ℃ for 60 min, then hot pressing at 150 ℃ and 350 MPa for 15 min, and then vacuum drying at 160 ℃ to constant weight to obtain the composite framework positive electrode sheet. 3) Take 300 mesh Li3YCl6 powder and press it into a Li3YCl6 flexible film with a thickness of 20±1 μm at 150 ℃ and 400 MPa. Attach the Li3YCl6 flexible film to the composite framework positive electrode sheet and press it at 10 MPa for 12 min, then hot press it at 150 ℃ and 60 MPa for 8 min. After cooling to room temperature, press it at 5 MPa for 2 min to obtain the composite electrolyte positive electrode. 4) The porous negative electrode is attached to one side of the Li3YCl6 flexible film on the composite electrolyte positive electrode and then pressed at 10MPa for 30 min to form the target solid-state battery system.

[0047] The solid-state battery system prepared in this example was subjected to the same electrochemical performance characterization as in Example 1, and the characterization results are shown in the table below.

[0048]

[0049] Based on the characterization results above, this example sample, which simply replaced the single-crystal NCM900505 ternary cathode material with polycrystalline NCM900505 ternary cathode material of the same mesh size, already experienced a significant performance degradation, particularly in energy density and high-temperature performance. This is mainly because the polycrystalline high-nickel ternary cathode material significantly increases the interface density, leading to a higher probability of harmful interface reactions. Simultaneously, the polycrystalline high-nickel ternary cathode material has a poorer ability to cope with the lattice stress caused by lithium-ion insertion / extraction, potentially making the cathode active material more prone to microcrack formation and propagation, further impairing high-temperature stability and cycle stability. Furthermore, the polycrystalline high-nickel ternary cathode material also presents challenges in compaction due to its morphological characteristics and low tap density, contributing to the significant decrease in energy density.

[0050] Comparative Example 2: A solid-state battery system, which is prepared by the following method: 1) Disperse 300-mesh single-crystal NCM900505 powder in deionized water at a ratio of 100 g: 500 mL to prepare a suspension; Prepare a 1.75 mol / L hydrated lithium hydroxide aqueous solution as the lithium source solution, and then dilute a commercially available zirconia sol (HN-RJ80-20%) with a solid content of 20 wt% with deionized water to a solid content of 5 wt% as the dilute zirconia source sol. The lithium source solution was slowly and uniformly added to the suspension at a ratio of 25 mL / L over 25 min. After stirring at 90 rpm for 30 min, the amount of zirconium source dilute sol was calculated according to the atomic ratio of Li to Zr in the lithium source solution and zirconium source dilute sol of 2:1. The zirconium source dilute sol was slowly and uniformly added to the zirconium source dilute sol over 20 min, while stirring at 90 rpm during the addition process. After the addition was completed, the mixture was continuously stirred at 150 rpm for 120 min to obtain a slurry. The slurry was then subjected to atomization drying and fluidized bed drying to obtain a powder. The powder was then heat-treated at 450 ℃ for 120 min to obtain the positive electrode active material. 2) Mix the positive electrode active material, 300-mesh Li3YBr6 powder, and vapor-grown carbon fiber at a mass ratio of 92:6:2 to form a uniform mixed powder. Add anhydrous xylene to the mixed powder at a ratio of 0.3 mL / g, stirring to form a paste. Add 20 mg / cm³ of the mixture to the mixture. 2 The coating amount is determined by coating the paste onto the oil-based carbon-coated aluminum foil, first vacuum drying at 60 ℃ for 60 min, then hot pressing at 150 ℃ and 350 MPa for 15 min, and then vacuum drying at 160 ℃ to constant weight to obtain the composite framework positive electrode sheet. 3) Take 300 mesh Li3YBr6 powder and press it into a Li3YBr6 flexible film with a thickness of 20±1 μm at 150 ℃ and 400 MPa. Attach the Li3YBr6 flexible film to the composite framework positive electrode sheet and press it at 10 MPa for 12 min, then hot press it at 150 ℃ and 60 MPa for 8 min. After cooling to room temperature, press it at 5 MPa for 2 min to obtain the composite electrolyte positive electrode. 4) The porous negative electrode is attached to one side of the Li3YBr6 flexible film on the composite electrolyte positive electrode and then pressed at 10MPa for 30 min to form the target solid-state battery system.

[0051] The solid-state battery system prepared in this example was subjected to the same electrochemical performance characterization as in Example 1, and the characterization results are shown in the table below.

[0052]

[0053] Based on the characterization results above, this example demonstrates that simply replacing the crucial framework material and solid electrolyte material from Li3YCl6 to Li3YBr6 resulted in a significant decrease in some core performance characteristics, particularly cycle stability and high-temperature stability. This is primarily because Li3YBr6 exhibits poor oxidation stability compared to Li3YCl6. Furthermore, Li3YBr6 itself has poor compatibility with the specific system of this invention. Although it performs slightly better than Li3YCl6 in rate capability, its contribution to relative capacity and energy density is not significant, remaining almost identical to Li3YCl6. Instead, it leads to a significant deterioration in wide-temperature-range performance and a severe decline in long-term cycle stability, failing to meet the stability requirements of the battery.

[0054] Comparative Example 3: A solid-state battery system, which is prepared by the following method: 1) Disperse 300-mesh single-crystal NCM900505 powder in deionized water at a ratio of 100 g: 500 mL to prepare a suspension; Prepare a 1.75 mol / L hydrated lithium hydroxide aqueous solution as the lithium source solution, and then dilute a commercially available zirconia sol (HN-RJ80-20%) with a solid content of 20 wt% with deionized water to a solid content of 5 wt% as the dilute zirconia source sol. The lithium source solution was slowly and uniformly added to the suspension at a ratio of 25 mL / L over 25 min. After stirring at 90 rpm for 30 min, the amount of zirconium source dilute sol was calculated according to the atomic ratio of Li to Zr in the lithium source solution and zirconium source dilute sol of 2:1. The zirconium source dilute sol was slowly and uniformly added to the zirconium source dilute sol over 20 min, while stirring at 90 rpm during the addition process. After the addition was completed, the mixture was continuously stirred at 150 rpm for 120 min to obtain a slurry. The slurry was then subjected to atomization drying and fluidized bed drying to obtain a powder. The powder was then heat-treated at 450 ℃ for 120 min to obtain the positive electrode active material. 2) Mix the positive electrode active material, 300-mesh Li3YCl6 powder, and vapor-grown carbon fiber at a mass ratio of 92:6:2 to form a uniform mixed powder. Add anhydrous xylene to the mixed powder at a ratio of 0.3 mL / g, stirring to form a paste. Add 20 mg / cm³ of the mixture to the mixture. 2 The coating amount is determined by coating the paste onto the oil-based carbon-coated aluminum foil, first vacuum drying at 60 ℃ for 60 min, then hot pressing at 150 ℃ and 350 MPa for 15 min, and then vacuum drying at 160 ℃ to constant weight to obtain the composite framework positive electrode sheet. 3) Take 300 mesh Li3YCl6 powder and press it into a Li3YCl6 flexible film with a thickness of 20±1 μm at 150 ℃ and 400 MPa. Attach the Li3YCl6 flexible film to the composite framework positive electrode sheet and press it at 10 MPa for 12 min, then hot press it at 150 ℃ and 60 MPa for 8 min. After cooling to room temperature, press it at 5 MPa for 2 min to obtain the composite electrolyte positive electrode. 4) The ZnO-Cu negative electrode is bonded to the positive electrode of the composite electrolyte and one side of the Li3YCl6 flexible film is pressed together. Then, it is pressed at 10 MPa for 30 min to form the target solid-state battery system. The ZnO-Cu anode used in this example was prepared by the following method: Zinc acetate dihydrate was dissolved in ethanol to prepare a seed crystal solution of 0.010 mol / L. A copper current collector (copper sheet) was cut to the required size and ultrasonically cleaned in acetone, ethanol and deionized water for 15 min in sequence. Then it was placed in a 0.1 mol / L hydrochloric acid aqueous solution for static etching for 45 s to complete the pretreatment. After drying, the dried copper current collector was immersed in the seed crystal solution for 15 min to fully wet it. After removal, it was annealed at 350 ℃ for 15 min in air atmosphere. The immersion and annealing were repeated 3 times. Then it was transferred to a mixed aqueous solution containing 0.050 mol / L zinc nitrate hexahydrate and 0.030 mol / L hexamethylenetetramine and hydrothermally heated at 95 ℃ for 9 h. After cooling to room temperature, it was removed, cleaned with deionized water and dried at 60 ℃ to obtain the ZnO-Cu anode.

[0055] The solid-state battery system prepared in this example was subjected to the same electrochemical performance characterization as in Example 1, and the characterization results are shown in the table below.

[0056]

[0057] Based on the above characterization results, the negative electrode of this invention also has certain specific requirements. If the porous negative electrode of this invention is replaced with a similar dense electrode, it will lead to a severe deterioration in all performance aspects. Especially in terms of specific capacity and energy density, this is mainly due to the small surface area of ​​the dense current collector, resulting in reduced active material loading and utilization. Simultaneously, the cycle stability and rate performance also decrease significantly. This is because the dense current collector significantly exacerbates the volume expansion effect of zinc oxide, and long-term accumulated stress leads to active material shedding and interface degradation, resulting in poor overall structural stability. Furthermore, the dense current collector cannot effectively provide a fast transport channel, leading to severe obstruction of the overall reaction.

[0058] Comparative Example 4: A solid-state battery system, which is prepared by the following method: 1) Disperse 300-mesh single-crystal NCM900505 powder in deionized water at a ratio of 100 g: 500 mL to prepare a suspension; Prepare a 1.75 mol / L hydrated lithium hydroxide aqueous solution as the lithium source solution, and then dilute a commercially available zirconia sol (HN-RJ80-20%) with a solid content of 20 wt% with deionized water to a solid content of 5 wt% as the dilute zirconia source sol. The lithium source solution was slowly and uniformly added to the suspension at a ratio of 25 mL / L over 25 min. After stirring at 90 rpm for 30 min, the amount of zirconium source dilute sol was calculated according to the atomic ratio of Li to Zr in the lithium source solution and zirconium source dilute sol of 2:1. The zirconium source dilute sol was slowly and uniformly added to the zirconium source dilute sol over 20 min, while stirring at 90 rpm during the addition process. After the addition was completed, the mixture was continuously stirred at 150 rpm for 120 min to obtain a slurry. The slurry was then subjected to atomization drying and fluidized bed drying to obtain a powder. The powder was then heat-treated at 450 ℃ for 120 min to obtain the positive electrode active material. 2) Mix the positive electrode active material, 300-mesh Li3YCl6 powder, and vapor-grown carbon fiber at a mass ratio of 92:6:2 to form a uniform mixed powder. Add anhydrous xylene to the mixed powder at a ratio of 0.3 mL / g, stirring to form a paste. Add 20 mg / cm³ of the mixture to the mixture. 2 The coating amount is determined by coating the paste onto the oil-based carbon-coated aluminum foil, first vacuum drying at 60 ℃ for 60 min, then hot pressing at 150 ℃ and 350 MPa for 15 min, and then vacuum drying at 160 ℃ to constant weight to obtain the composite framework positive electrode sheet. 3) Take 300 mesh Li3YCl6 powder and press it into a Li3YCl6 flexible film with a thickness of 20±1 μm at 150 ℃ and 400 MPa. Attach the Li3YCl6 flexible film to the composite framework positive electrode sheet and press it at 10 MPa for 12 min, then hot press it at 150 ℃ and 60 MPa for 8 min. After cooling to room temperature, press it at 5 MPa for 2 min to obtain the composite electrolyte positive electrode. 4) Pre-lithiation of the porous negative electrode: SLMP powder was dispersed in anhydrous xylene to prepare a solvent with a concentration of 10 mg / mL, and 1 wt% PVDF was added as a binder. Then, the mixture was prepared at a concentration of 3 mL / cm². 2 The coating amount was determined by uniformly spraying SLMP xylene dispersion onto the porous negative electrode surface using atomized spraying. After coating, 1 MPa roller pressure was applied and the electrode was left to stand for 10 h for pre-lithiation. 5) The pre-lithiated porous negative electrode is attached to the composite electrolyte positive electrode and pressed onto one side of a Li3YCl6 flexible film. Then, it is pressed at 10 MPa for 30 min to form the target solid-state battery system.

[0059] The solid-state battery system prepared in this example was subjected to the same electrochemical performance characterization as in Example 1, and the characterization results are shown in the table below.

[0060]

[0061] Based on the above characterization results, pre-lithiation is absolutely necessary to avoid for the technical solution of this invention. The data shows that, apart from the initial coulombic efficiency increase due to compensation for irreversible lithium loss and the energy density increase resulting from improved initial efficiency, all other performance characteristics show a significant decline. This is mainly because pre-lithiation leads to interfacial side reactions between the negative electrode and the solid electrolyte of this invention, resulting in a continuous increase in interfacial impedance, decreased interfacial stability, and a degraded cross-section causing a significant reduction in cycle life due to active material loss. The severely increased interfacial impedance also leads to a precipitous drop in rate performance. On the other hand, the impact of pre-lithiation on wide-temperature-range performance is relatively complex. Pre-lithiation can improve coulombic efficiency and short-term performance, pre-form a stable SEI, reduce continuous side reactions at high temperatures, thus maintaining better initial capacity and resulting in superior performance at 40 °C. Simultaneously, by providing a lithium source in advance for SEI formation, it reduces irreversible lithium consumption in the first cycle, making the negative electrode interface more stable and optimizing lithium-ion transport kinetics, thereby mitigating increased polarization and capacity loss caused by low temperatures. Performance at low temperatures is relatively superior. However, at 80℃, the high temperature accelerates the activity and side reactions of lithium metal, leading to SEI instability, lithium dendrite growth or thermal runaway, resulting in a significant decrease in the stability of the battery system. This also causes a more significant decrease in the high-temperature cycle capacity retention rate compared to other temperature ranges.

[0062] However, overall, pre-lithiation is relatively disadvantageous for the technical solution of this invention.

Claims

1. A method for preparing a solid-state battery system, characterized in that, The method includes: 1) Disperse high-nickel NCM raw material powder in water to prepare a suspension. Then prepare lithium source solution and zirconium source dilute sol separately. Slowly add lithium source solution to suspension and stir evenly. Then slowly add zirconium source dilute sol and stir continuously. The resulting slurry is dried and heat-treated to obtain positive electrode active material. 2) Mix the positive electrode active material, LY framework material and conductive agent evenly to form a mixed powder. Add liquid additives to the mixed powder and stir and / or grind it into a paste. Then, coat it on the current collector and perform segmented drying and pressing to obtain a composite framework positive electrode sheet. 3) Take the LY flexible film and attach it to the composite framework positive electrode sheet, and then perform segmented pressing to obtain the composite electrolyte positive electrode; 4) A solid-state battery system can be formed by assembling and pressing a composite electrolyte positive electrode and a porous negative electrode.

2. The method for preparing a solid-state battery system according to claim 1, characterized in that, Step 1) The high-nickel NCM is a NiCoMn ternary cathode material with a Ni content ≥90%; In step 1), the ratio of high-nickel NCM to water in the preparation of the suspension is 100 g: (400-600) mL. Step 1) The lithium source solution is a suspension with a lithium ion concentration of 1.5–2.0 mol / L and a volume of 20–30 mL / L; Step 1) The zirconium source dilute sol is a zirconium oxide sol with a solid content of 5-10 wt%. The zirconium oxide sol is calculated based on the atomic ratio of Li and Zr contained in the lithium source solution and the zirconium source dilute sol, and the atomic ratio of Zr contained in the zirconium source dilute sol to Li in the lithium source solution is controlled to be 1:(2-2.2).

3. A method for preparing a solid-state battery system according to claim 1 or 2, characterized in that, Step 1) The lithium source solution is slowly added to the suspension at a rate of 3-5% VOL of total lithium source solution per minute. After the addition is completed, the mixture is stirred at 60-120 rpm for 25-35 minutes. Step 1) The zirconium source dilute sol is added slowly at a rate of 4-6% VOL of total zirconium source dilute sol per minute, and then stirred continuously at 120-180 rpm for 90-150 min.

4. The method for preparing a solid-state battery system according to claim 1, characterized in that, Step 1) The drying process includes sequential atomization drying and fluidization drying; Step 1) The heat treatment is carried out at 450-500 ℃ for 100-150 min.

5. The method for preparing a solid-state battery system according to claim 1, characterized in that, Step 2) The LY skeleton material is Li3YCl6 powder with a mesh size ≥ 300 mesh; Step 2) The conductive agent is vapor-grown carbon fiber; Step 2) The positive electrode active material, LY skeleton material and conductive agent are mixed and dry-mixed at a mass ratio of 92:(5~7):(1.5~2.5).

6. A method for preparing a solid-state battery system according to claim 1 or 5, characterized in that, Step 2) The liquid additive is anhydrous xylene, and its dosage is 0.2-0.4 mL / g of mixed powder; Step 2) The current collector is an oil-based carbon-coated aluminum foil, and the coating amount of the paste slurry is 20-25 mg / cm². 2 .

7. The method for preparing a solid-state battery system according to claim 1, characterized in that, Step 2) The segmented drying and pressing process includes: Vacuum dry at 60–80 °C for 50–70 min, then hot press at 130–160 °C and 320–380 MPa for 12–18 min, and then vacuum dry at 140–180 °C to constant weight.

8. The method for preparing a solid-state battery system according to claim 1, characterized in that, Step 3) The LY flexible film is a Li3YCl6 flexible thin film with a thickness of 20-30 μm; Step 3) The segmented pressing process includes pressing at 5-10 MPa for 10-20 min, then hot pressing at 140-160 ℃ and 50-70 MPa for 5-10 min, cooling to room temperature, and then pressing at 5-10 MPa for 1-2 min.

9. The method for preparing a solid-state battery system according to claim 1, characterized in that, Step 4) The porous negative electrode is a zinc oxide-loaded copper foam negative electrode; Step 4) The assembly and pressing include: The porous negative electrode is bonded to one side of the LY flexible membrane on the composite electrolyte positive electrode, and then pressed at 8-12 MPa for 25-35 min.

10. A solid-state battery system prepared by any one of claims 1 to 9, characterized in that, The solid-state battery system includes a composite electrolyte positive electrode and a porous negative electrode; The composite electrolyte cathode is a composite structure in which a connecting framework is constructed on a high-nickel NCM-based cathode, and a solid electrolyte film is fixed by the connecting framework to achieve the composite structure of cathode and electrolyte.

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