Composite current collector, negative electrode-free solid-state battery and preparation method thereof

Abstract

The application discloses a kind of composite current collector, anode-free solid-state battery and preparation method thereof, belong to the technical field of anode-free solid-state battery.The preparation method of the composite current collector includes: the powder of metal continuous phase and 0.5-10wt% interface modification phase is mixed;Mixed powder is sprayed onto garnet electrolyte substrate by atmospheric plasma spraying, to form composite coating;The interface modification phase includes lithiumophilic substance, lithium ion conductor and solid-state electrolyte stabilizer.The preparation method can be integrated by one-step spraying, realize current collection, lithium guide, interface enhancement, guide lithium uniform deposition, obtain low interface resistance, long cycle life, high safety anode-free solid-state battery.

Description

Technical Field

[0001] This invention relates to a negative electrode-free solid-state battery, and particularly to a composite current collector, a negative electrode-free solid-state battery, and a method for preparing the same. Background Technology

[0002] Solid-state lithium batteries are considered the mainstream development direction for next-generation energy storage devices due to their high safety and high energy density. As an important technological branch of solid-state lithium batteries, electrodeless solid-state batteries employ an innovative structure. During the first charge, lithium ions migrate from the positive electrode material and are reduced and deposited in situ on the surface of the negative electrode current collector to form a functional metallic lithium negative electrode, thus eliminating the need for a traditional battery negative electrode. This structure does not require a pre-placed lithium source during assembly, which can greatly improve the battery's energy density and has therefore attracted widespread attention.

[0003] However, existing methods for fabricating electrodeless solid-state batteries still face many technical challenges, making large-scale commercialization difficult. Among them, the main technical barriers include: (1) Current collector preparation technology barrier: Anode-free batteries need to prepare an ultra-thin, dense, firmly attached metal current collector (usually copper) with excellent electronic conductivity on the surface of brittle solid electrolytes such as LLZO, LLZTO, LATP, LAGP, etc. While the current mainstream physical vapor deposition methods such as magnetron sputtering and electron beam evaporation can achieve high film quality, they have problems such as extremely low deposition rate (usually <1μm / h), high equipment investment cost, and difficulty in achieving large-area uniform deposition, which seriously restrict the cost and efficiency of large-scale production of current collectors; (2) Interface contact and stability barrier: In anode-free solid batteries, the solid-solid contact between the current collector and the solid electrolyte usually generates high interface impedance, which affects the ion / electron transport efficiency. In addition, during the lithium deposition / stripping process, the uneven electric field distribution and lithium ion flow on the surface of the current collector can easily induce the formation and growth of lithium dendrites, which then penetrate the electrolyte layer and cause the battery to short-circuit and fail.

[0004] On the other hand, plasma spraying technology, as a surface engineering technology that uses high-temperature plasma jets to melt powder raw materials and spray them onto the substrate at high speed to form a coating, has outstanding advantages such as fast deposition rate (up to several kg / h), controllable coating structure, good compatibility with complex-shaped substrates, and easy scalability. It has been widely used in thermal barrier coatings, wear-resistant coatings and other fields. Among them, atmospheric plasma spraying (APS), as a mature high-speed, large-area coating preparation technology, has been tried to be used in the preparation of solid electrolyte thin film LLZO, but it still has the following obvious limitations: (1) Single function, not involving the preparation of current collectors: This technology mainly focuses on the preparation of the electrolyte itself and does not involve the construction of a metal current collector layer with specific functions on the electrolyte surface, which cannot meet the core requirements of negative electrode batteries for current collectors; (2) Interface problems have not been specifically solved: Although the bulk density of the prepared LLZO film has been improved by annealing and other treatments, there are still problems such as poor interlayer bonding and grain boundaries. Problems such as the formation of heterogeneous phases (e.g., LiAlO2) are not addressed. At the same time, no functional design is made for the uniformity of lithium deposition and dendrite suppression at the current collector / electrolyte interface. (3) Process limitations lead to insufficient electrochemical performance: Problems such as lithium volatilization and amorphous phase formation in the APS process result in its ionic conductivity being lower than the ideal level, making it difficult to meet the requirements of high-performance batteries for electrolytes. (4) The current collector-electrolyte integration is not achieved: This technology only completes the preparation of the electrolyte membrane, without combining it with the current collector preparation and interface modification, and fails to form a complete and scalable integrated solution suitable for negative electrode batteries.

[0005] In summary, although APS technology has shown potential in the fabrication of large-area ceramic electrolytes, there is currently no mature technical solution to apply it to solve the core challenges of anode-free all-solid-state batteries, particularly the integrated fabrication of current collectors and the modification of interfacial functions. Therefore, developing a new current collector technology that balances efficient fabrication with excellent interfacial performance is of great significance for advancing the practical application of anode-free solid-state batteries. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a composite current collector that integrates the current collector and electrolyte through atmospheric plasma spraying (APS) technology, along with its corresponding negative electrode-free battery and preparation method. The preparation method achieves integrated current collector-electrolyte construction while solving the problems of high solid-solid interface impedance and uneven lithium deposition in existing technologies, overcoming the limitations of existing APS processes on electrochemical performance, and simultaneously completing current collector preparation and interface modification.

[0007] The technical solution of the present invention is as follows: A method for preparing a composite current collector, comprising: The powder of the continuous metal phase and the powder of the interface-modified phase are mixed to obtain a mixed powder; The mixed powder is sprayed onto a solid electrolyte substrate or a pretreated solid electrolyte substrate by atmospheric plasma spraying to form a composite coating. Wherein, the solid electrolyte substrate is selected from garnet-type electrolyte substrates; the continuous metal phase is selected from metals and / or alloys; the interface modification phase includes a lithiophilic material, a lithium-ion conductor, and a solid electrolyte stabilizer in a mass ratio of (5-6):(1-2.5):(1-2.5), wherein the lithiophilic material includes one or more of zinc, tin, tin dioxide, and zinc oxide; the mass of the interface modification phase powder is 0.5-10% of the total mass of the mixed powder.

[0008] In the above technical solutions of the present invention, the lithium-ion conductor refers to one or more of solid materials with lithium-ion conductivity, such as lithium zirconate and lithium lanthanum zirconate; the solid electrolyte stabilizer refers to one or more of additives that can enhance the stability of solid electrolytes, such as lithium metaborate (LiBO2), lithium tetraborate (Li2B4O7), lithium triborate (Li3B3O6), lithium oxide (Li2O), and boron oxide (B2O3).

[0009] The composite current collector obtained by the above technical solution of the present invention is an integrated composite coating directly formed on a solid electrolyte substrate. The composite coating is composed of a continuous metal phase and an interface modification phase uniformly dispersed in the continuous metal phase, with a density ≥95%.

[0010] In the above technical solutions of the present invention, the solid electrolyte substrate is a garnet-type electrolyte material with a high melting point (usually >1500°C). The residence time in the plasma jet during atmospheric plasma spraying is extremely short (usually <1 millisecond). Multiple factors ensure that the solid electrolyte substrate will not suffer functional damage due to the high temperature of spraying, and enable it to interact appropriately with the mixed powder (this interaction does not depend on the long-term heating of the substrate by the plasma arc, but mainly on the instantaneous energy exchange of the molten particles of the mixed powder when they impact the substrate), forming a composite coating with a density ≥95% and a solid electrolyte-composite current collector solid-solid interface with a bonding strength ≥30MPa, low interfacial impedance, and uniform lithium deposition.

[0011] In the above technical solutions of this invention, the continuous metal phase provides an electronic conductivity pathway, and the interface modification phase, through synergistic effects with each other and with the continuous metal phase, functionalizes the solid-solid interface, comprehensively solving key issues such as interface ion transport, uniform lithium nucleation and deposition, and interface bonding stability. Specifically, the lithiophilic material can alloy with the deposited lithium, significantly reducing the lithium nucleation overpotential and guiding lithium to achieve lateral, uniform two-dimensional layered deposition, rather than three-dimensional dendritic growth; the lithium-ion conductor can improve the ion transport capability of the current collector / electrolyte interface, reduce interface impedance, and enhance rate performance; the solid electrolyte stabilizer, under the high temperature of the spraying process, forms a transition layer at the interface between the coating and the solid electrolyte substrate, enhancing coating adhesion and suppressing interface side reactions, thus alleviating internal stress caused by mismatched thermal expansion coefficients.

[0012] According to some preferred embodiments of the present invention, the continuous metal phase is selected from one or more of copper, nickel and their alloys.

[0013] According to some preferred embodiments of the present invention, the lithiophilic substance includes one or more of zinc, tin, tin dioxide, and zinc oxide.

[0014] According to some preferred embodiments of the present invention, the lithium-ion conductor comprises lithium zirconate and / or lithium lanthanum zirconate.

[0015] According to some preferred embodiments of the present invention, the solid electrolyte stabilizer is selected from one or more of lithium metaborate (LiBO2), lithium tetraborate (Li2B4O7), lithium triborate (Li3B3O6), lithium oxide (Li2O), and boron oxide (B2O3).

[0016] According to some preferred embodiments of the present invention, the solid electrolyte substrate is selected from LLZTO ceramic sheets and / or LLZO ceramic sheets.

[0017] According to some preferred embodiments of the present invention, the thickness of the solid electrolyte substrate is 10-100 μm.

[0018] According to some preferred embodiments of the present invention, the thickness of the composite coating is 3-20 μm.

[0019] The inventors unexpectedly discovered that this preferred embodiment can further ensure the high energy density of the composite coating.

[0020] According to some preferred embodiments of the present invention, the powder of the continuous metal phase has a particle size of 15-45 μm and a purity of ≥99.9%.

[0021] According to some preferred embodiments of the present invention, the particle size of the powder of the interface-modified phase is 1 nm-10 μm.

[0022] According to some preferred embodiments of the present invention, the preparation method further includes: after forming the composite coating, performing heat treatment, the heat treatment including: holding at 200-400°C for 1-3 hours in an inert atmosphere.

[0023] According to some preferred embodiments of the present invention, the atmospheric plasma spraying power is 25-40kW, the spraying distance is 80-120mm, and the powder feeding rate is 20-40g / min.

[0024] The inventors unexpectedly discovered that this preferred embodiment can ensure that the powder particles are moderately melted (achieving coating densification) with lower power and a longer spraying distance, while the thermal and kinetic energy reaching the substrate surface is at an optimal window, so that it can form a coating interface with high adhesion without causing lattice decomposition or macroscopic cracking of the substrate material.

[0025] According to some preferred embodiments of the present invention, obtaining the pretreated solid electrolyte substrate includes: polishing the solid electrolyte substrate until its Ra value is < 0.1 μm, followed by cleaning and drying to obtain the pretreated solid electrolyte substrate.

[0026] The inventors unexpectedly discovered that the smooth surface of the pretreated solid electrolyte substrate obtained by the above preferred embodiments not only enhances the bonding force but also significantly reduces the microscopic protrusions on the surface (which are more likely to become crack sources under thermal shock). Its smooth and complete surface can more uniformly disperse and conduct instantaneous thermal stress, resulting in a composite current collector with excellent comprehensive performance.

[0027] According to some preferred embodiments of the present invention, the preparation method includes: The solid electrolyte substrate was polished until its Ra value was < 0.1 μm, then cleaned and dried to obtain the pretreated solid electrolyte substrate. A continuous metal phase powder with a particle size of 15-45 μm and an interface-modified phase powder with a particle size of 1 nm-10 μm are mixed to obtain a mixed powder; the mass percentage of the interface-modified phase powder in the mixed powder is 0.5-10%. The mixed powder is sprayed onto a pretreated solid electrolyte substrate by atmospheric plasma spraying at a power of 25-40kW, a spraying distance of 80-120mm, and a powder feeding rate of 20-40g / min to form a composite coating and obtain a composite sample. The composite sample was kept at 200-400℃ for 1-3 hours in an inert atmosphere to obtain a composite current collector.

[0028] The present invention further provides a composite current collector prepared according to the above preparation method.

[0029] The composite current collector has a density of ≥95%, which can effectively block the longitudinal penetration of lithium dendrites; its bonding strength with the solid electrolyte substrate is ≥30 MPa, ensuring the mechanical stability of the interface and low contact resistance.

[0030] The present invention further provides a negative electrode-free solid-state battery containing the above composite current collector.

[0031] According to some preferred embodiments of the present invention, the method for preparing the negative electrode-free solid-state battery includes: assembling the composite current collector and the positive electrode layer into a negative electrode-free battery, wherein the positive electrode layer contains a positive electrode active material, and the positive electrode active material is selected from one or more of NCM811, NCM922, NCA, lithium-rich manganese-based materials, and LCO materials.

[0032] According to some preferred embodiments of the present invention, the method for preparing the negative electrode-free solid-state battery includes: forming a positive electrode layer containing the positive electrode active material and the positive electrode current collector on the other side of the solid electrolyte substrate where the composite current collector is not bonded, and then applying pressure to encapsulate the battery with a casing to obtain the negative electrode-free solid-state battery.

[0033] In the first charge of the electrodeless solid-state battery of the present invention, lithium ions are released from the positive electrode, pass through the solid electrolyte, and are reduced to metallic lithium on the composite current collector, thereby forming a lithium metal negative electrode in situ.

[0034] The present invention has the following beneficial effects: The beneficial effects of this invention are: (1) This invention innovatively applies plasma spraying technology to the preparation of current collectors for all-solid-state batteries, realizing the one-step completion of current collector preparation and interface modification. Its process is simple and breaks through the complexity and high cost bottleneck of traditional multi-step processing (such as sputtering the current collector first, and then vapor deposition or coating the modification layer). Through the synergistic effect between plasma spraying process and composite current collector formulation, the interface bonding is strengthened and the structure is controlled. (2) In the preparation method of the present invention, the high-speed molten particles of the raw material powder of the composite current collector can form a mechanical interlock and micro-area metallurgical bond with the substrate, and the obtained composite current collector has high density (≥95%), strong interfacial bonding force (≥30MPa) and low interfacial resistance. (3) In the composite current collector of the present invention, a lithiophilic material, a lithium-ion conductor and a solid electrolyte stabilizer are used as interface modification phases. The built-in lithiophilic nanoparticles can serve as nucleation sites, and the lithium-ion conductor and the solid electrolyte stabilizer can construct a more stable and efficient ion / electron mixed conductive interface. The three work together to effectively guide the uniform deposition of lithium, fundamentally suppress dendrites, improve cycle life and safety, and make the capacity retention rate of the battery reach more than 92% after 200 cycles. (4) The preparation method of the present invention can precisely control the thickness, density and distribution and content of the composite current collector and the interface modification phase by adjusting the spraying parameters and powder composition, so as to meet the design requirements of different battery systems and have extremely high flexibility. (5) The atmospheric plasma spraying technology used in this invention is mature and has a fast deposition rate (more than 100 times that of magnetron sputtering). It is easy to integrate into a continuous production line and can achieve large-area, high-efficiency, and low-cost manufacturing, with great potential for large-scale application. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the structure of a negative electrode-free solid-state battery containing a composite current collector in the embodiment, wherein 1-battery casing, 2-positive current collector, 3-positive active material, 4-solid electrolyte, and 5-composite current collector. Detailed Implementation

[0036] The present invention will be further described in detail below through specific embodiments, but it should not be construed as limiting the scope of the invention to the following examples. Various substitutions or modifications made based on ordinary technical knowledge and conventional methods in the art without departing from the above-described methodological spirit of the invention should be included within the scope of the invention.

[0037] The structure of the negative electrode-free solid-state battery assembled in the following embodiments is shown in the attached figure. Figure 1 As shown, it includes a battery casing 1, a positive current collector 2 and a composite current collector 5 located inside the battery casing 1, a positive active material 3 located on the positive current collector 2, and a solid electrolyte substrate 4 located between the positive active material 3 and the composite current collector 5.

[0038] Example 1 The Cu-ZnO composite current collector was prepared using the following steps: (1) Select a dense LLZTO ceramic sheet with a thickness of 30μm and a diameter of 15mm, polish its surface with diamond polishing liquid to Ra about 0.05μm, then ultrasonically clean it with anhydrous ethanol for 30min and dry it to obtain a smooth substrate; (2) Weigh 98 g of spherical copper powder with an average particle size of 30 μm, zinc oxide (ZnO) with an average particle size of 8 μm, and lithium zirconate and lithium metaborate (LiBO2) powders, wherein the mass ratio of zinc oxide, lithium zirconate and lithium metaborate (LiBO2) is 6:2:2, and the total amount of the three is 5 g. Mix them in a three-dimensional mixer for 3 h to obtain mixed powder. (3) The mixed powder was sprayed onto a smooth substrate using an atmospheric plasma spraying equipment (Praxair SG-100) to form a composite coating with a thickness of about 8 μm, and a composite sample was obtained; wherein the spraying power was 30kW (current 500A, voltage 60V), the main gas argon flow rate was 40SLPM, the auxiliary gas hydrogen flow rate was 10SLPM, the spraying distance was 100mm, and the powder feeding rate was 30g / min; (4) The composite sample was transferred to a tube furnace filled with high-purity argon gas, heated to 300°C at a heating rate of 5°C / min and held for 1 hour, and then cooled with the furnace to obtain Cu-ZnO composite current collector.

[0039] Further, refer to the appendix. Figure 1 Using NCM811 active material as positive electrode active material 3 and aluminum foil as positive electrode current collector 2, the NCM811 active material is pressed onto the aluminum foil by dry method to form a positive electrode sheet, which is then closely attached to the ceramic surface of the solid electrolyte substrate 4 (i.e. the smooth substrate described in step (1)) that is not covered by Cu-ZnO composite current collector. Under a pressure of 20MPa, it is packaged with Cu-ZnO composite current collector 5 and battery shell 1 through stainless steel clamps to obtain a negative electrode-free solid battery.

[0040] Example 2 The Cu-Zn composite current collector was prepared using the following steps: (1) Select a dense LLZTO ceramic sheet with a thickness of 80μm and a diameter of 15mm, polish its surface with diamond polishing liquid to Ra about 0.05μm, then ultrasonically clean it with anhydrous ethanol for 30min and dry it to obtain a smooth substrate; (2) Weigh 99 g of spherical copper powder with an average particle size of 25 μm, zinc powder with an average particle size of 7 μm, lithium lanthanum zirconate powder, and lithium triborate (Li3B3O6) powder, wherein the mass ratio of zinc powder, lithium lanthanum zirconate powder, and lithium triborate is 5:2.5:2.5, and the total weight of the three is 7 g. Mix them in a three-dimensional mixer for 2 h to obtain mixed powder. (3) The mixed powder was sprayed onto a smooth substrate using an atmospheric plasma spraying equipment (Praxair SG-100) to form a composite coating with a thickness of about 5 μm, and a composite sample was obtained; wherein the spraying power was 35 kW, the main gas argon flow rate was 40 SLPM, the auxiliary gas hydrogen flow rate was 10 SLPM, the spraying distance was 100 mm, and the powder feeding rate was 30 g / min; (4) The composite sample was transferred to a tube furnace filled with high-purity argon gas, heated to 250°C at a heating rate of 5°C / min and held for 1.5h. Then it was cooled with the furnace to obtain the Cu-Zn composite current collector.

[0041] Furthermore, the Cu-Zn composite current collector was assembled into a negative electrode-free solid-state battery using the same method as in Example 1.

[0042] Comparative Example 1 The Cu-ZnO composite current collector was prepared using the following steps: (1) Select a dense LLZTO ceramic sheet with a thickness of 30μm and a diameter of 15mm, polish its surface with diamond polishing liquid to Ra about 0.05μm, then ultrasonically clean it with anhydrous ethanol for 30min and dry it to obtain a smooth substrate; (2) Weigh 98 g of spherical copper powder with an average particle size of 30 μm, zinc oxide (ZnO) with an average particle size of 8 μm, and lithium zirconate and lithium metaborate (LiBO2) powders, wherein the mass ratio of zinc oxide, lithium zirconate and lithium metaborate (LiBO2) is 6:2:2, and the total amount of the three is 5 g. Mix them in a three-dimensional mixer for 3 h to obtain mixed powder. (3) The mixed powder is loaded into the mold and cold-pressed under a pressure of 30MPa to obtain a green blank; then the green blank is placed in a vacuum sintering furnace and held at 1000℃ for 3h to carry out densification sintering, and then cooled to obtain a high-density, high-strength composite sintered target. (4) In a magnetron sputtering apparatus, the aforementioned composite sintered target is installed at the cathode target position. After evacuating to a high vacuum, argon gas is introduced as the working gas and the process pressure is maintained at 1.3 Pa. The target material is sputtered by bombarding the target surface with argon ions, and a composite coating with a thickness of approximately 8 μm is deposited on the smooth substrate. The deposition process is carried out in an argon atmosphere with a background vacuum of 5.0 × 10⁻⁶ Pa. -4 The working pressure was 0.5 Pa, the sputtering power was 200 W, and the deposition time was about 10 h to obtain a composite sample; (5) The composite sample was transferred to a tube furnace filled with high-purity argon gas, heated to 300°C at a heating rate of 5°C / min and held for 1 hour, and then cooled with the furnace to obtain Cu-ZnO composite current collector.

[0043] Furthermore, the obtained Cu-ZnO composite current collector was assembled into a negative electrode-free solid-state battery using the same method as in Example 1.

[0044] Comparative Example 2 Pure copper current collectors are prepared using the following steps: (1) Select a dense LLZTO ceramic sheet with a thickness of 30μm and a diameter of 15mm, polish its surface with diamond polishing liquid to Ra about 0.05μm, then ultrasonically clean it with anhydrous ethanol for 30min and dry it to obtain a smooth substrate; (2) Weigh 98 g of spherical copper powder with an average particle size of 30 μm, place it in a three-dimensional mixer and mix for 3 h to obtain mixed copper powder; (3) The mixed copper powder was sprayed onto a smooth substrate using an atmospheric plasma spraying equipment (Praxair SG-100) to form a copper coating with a thickness of about 8 μm, thus obtaining a composite sample; wherein the spraying power was 30kW (current 500A, voltage 60V), the main gas argon flow rate was 40SLPM, the auxiliary gas hydrogen flow rate was 10SLPM, the spraying distance was 100mm, and the powder feeding rate was 30g / min; (4) The composite sample was transferred to a tube furnace filled with high-purity argon gas, heated to 300°C at a heating rate of 5°C / min and held for 1 hour, and then cooled with the furnace to obtain a pure copper current collector.

[0045] Furthermore, the obtained pure copper current collector was assembled into a negative electrode-free solid-state battery using the same method as in Example 1.

[0046] Comparative Example 3 The Cu-ZnO composite current collector was prepared using the following steps: (1) Select a dense LLZTO ceramic sheet with a thickness of 30μm and a diameter of 15mm, polish its surface with diamond polishing liquid to Ra about 0.05μm, then ultrasonically clean it with anhydrous ethanol for 30min and dry it to obtain a smooth substrate; (2) Weigh 97 g of spherical copper powder with an average particle size of 30 μm and 3 g of zinc oxide powder with an average particle size of 8 μm, and mix them in a three-dimensional mixer for 3 h to obtain mixed powder; (3) The mixed powder was sprayed onto a smooth substrate using an atmospheric plasma spraying equipment (Praxair SG-100) to form a composite coating with a thickness of about 8 μm, and a composite sample was obtained; wherein the spraying power was 30kW (current 500A, voltage 60V), the main gas argon flow rate was 40SLPM, the auxiliary gas hydrogen flow rate was 10SLPM, the spraying distance was 100mm, and the powder feeding rate was 30g / min; (4) The composite sample was transferred to a tube furnace filled with high-purity argon gas, heated to 300°C at a heating rate of 5°C / min and held for 1 hour, and then cooled with the furnace to obtain Cu-ZnO composite current collector.

[0047] Furthermore, the obtained Cu-ZnO composite current collector was assembled into a negative electrode-free solid-state battery using the same method as in Example 1.

[0048] Comparative Example 4 The Cu-lithium zirconate composite current collector was prepared by the following steps: (1) Select a dense LLZTO ceramic sheet with a thickness of 30μm and a diameter of 15mm, polish its surface with diamond polishing liquid to Ra about 0.05μm, then ultrasonically clean it with anhydrous ethanol for 30min and dry it to obtain a smooth substrate; (2) Weigh 97.5 g of spherical copper powder with an average particle size of 30 μm and 2.5 g of lithium zirconate powder, and mix them in a three-dimensional mixer for 3 h to obtain mixed powder; (3) The mixed powder was sprayed onto a smooth substrate using an atmospheric plasma spraying equipment (Praxair SG-100) to form a composite coating with a thickness of about 8 μm, and a composite sample was obtained; wherein the spraying power was 30kW (current 500A, voltage 60V), the main gas argon flow rate was 40SLPM, the auxiliary gas hydrogen flow rate was 10SLPM, the spraying distance was 100mm, and the powder feeding rate was 30g / min; (4) The composite sample was transferred to a tube furnace filled with high-purity argon gas, heated to 300°C at a heating rate of 5°C / min and held for 1 hour, and then cooled with the furnace to obtain Cu-lithium zirconate composite current collector.

[0049] Furthermore, the obtained Cu-lithium zirconate composite current collector was assembled into a negative electrode-free solid-state battery using the same method as in Example 1.

[0050] Comparative Example 5 The Cu-lithium metaborate composite current collector was prepared by the following steps: (1) Select a dense LLZTO ceramic sheet with a thickness of 30μm and a diameter of 15mm, polish its surface with diamond polishing liquid to Ra about 0.05μm, then ultrasonically clean it with anhydrous ethanol for 30min and dry it to obtain a smooth substrate; (2) Weigh 97.5 g of spherical copper powder with an average particle size of 30 μm and 2.5 g of lithium metaborate (LiBO2) powder, and mix them in a three-dimensional mixer for 3 h to obtain mixed powder; (3) The mixed powder was sprayed onto a smooth substrate using an atmospheric plasma spraying equipment (Praxair SG-100) to form a composite coating with a thickness of about 8 μm, and a composite sample was obtained; wherein the spraying power was 30kW (current 500A, voltage 60V), the main gas argon flow rate was 40SLPM, the auxiliary gas hydrogen flow rate was 10SLPM, the spraying distance was 100mm, and the powder feeding rate was 30g / min; (4) The composite sample was transferred to a tube furnace filled with high-purity argon gas, heated to 300°C at a heating rate of 5°C / min and held for 1 hour, and then cooled with the furnace to obtain Cu-lithium metaborate composite current collector.

[0051] Furthermore, the obtained Cu-lithium metaborate composite current collector was assembled into a negative electrode-free solid-state battery using the same method as in Example 1.

[0052] Furthermore, the electrodeless solid-state batteries obtained in Examples 1-2 and Comparative Examples 1-5 were subjected to constant current charge-discharge cycle tests at 25°C (cutoff voltage 2.5-4.3V). The test methods were as follows: Initial battery capacity (mAh / g): The initial battery capacity is calculated based on the discharge capacity after the first charge-discharge test at a 0.1C rate. Capacity retention after 200 cycles at 0.5C: Under constant current charge-discharge cycling at 0.5C, if no failure occurs after 200 cycles, the capacity retention rate = (Discharge capacity at the 200th cycle / Initial discharge capacity) × 100%; Initial interfacial impedance of the battery (Ω·cm²): Measured by electrochemical impedance spectroscopy (EIS) at open circuit potential, with a frequency range of 0.1 Hz–1 MHz, and calculated by taking the high-frequency region and the real axis intercept; Interface impedance after cycling (Ω·cm²): After completing the specified number of cycles (200 cycles in the example, and the last cycle before failure in comparative examples 1 and 2), an EIS test is immediately performed under the same conditions as the initial interface impedance test of the battery.

[0053] Lithium deposition uniformity: After cycle testing, the battery was disassembled and the lithium deposition morphology on the surface of the composite current collector was observed using scanning electron microscopy (SEM). Adhesion to the substrate: After cycle testing, the battery was disassembled and the interface between the composite coating and the solid electrolyte substrate was observed using an optical microscope and SEM to check for peeling or detachment. Short circuit behavior: During cyclic testing, monitor abnormal voltage drops or sudden deformations of the charge-discharge curve as criteria for judging internal short circuits. Failure cause analysis: The main cause is determined by combining the capacity decay curve, impedance change, post-cycle morphology observation and voltage curve characteristics.

[0054] The test results are shown in Table 1:

[0055] As can be seen from Table 1, the batteries of Examples 1 and 2 exhibit excellent overall electrochemical performance and interfacial stability. Their initial capacity is comparable to that of the comparative examples, indicating that the preparation method of the present invention does not sacrifice the initial energy density of the battery.

[0056] In terms of cycling performance, Examples 1 and 2 achieved capacity retention of 92% and 90% respectively after 200 cycles, with slow increase in interfacial impedance, smooth and dense lithium deposition, and no dendrite penetration. This indicates that the simultaneous introduction of lithiophilic materials, lithium-ion conductors, and solid electrolyte stabilizers into the composite current collector can synergistically achieve uniform lithium deposition, enhanced interfacial ion transport, and improved interfacial bonding.

[0057] In the comparative example, Comparative Example 1, prepared by magnetron sputtering, had a slightly higher initial capacity, but suffered from high interfacial impedance, poor bonding, and uneven lithium deposition during cycling, leading to early short-circuit failure. This demonstrates that traditional physical vapor deposition methods struggle to achieve good interfacial bonding and structural control.

[0058] Comparative Example 2, with no interface modification phase, showed a sharp deterioration in battery cycle performance and severe lithium dendrite formation, indicating that solid-solid interface problems cannot be solved by relying solely on continuous metal phases.

[0059] Comparative Examples 3-5, which only added a single type of interface modification phase (lithophile, lithium-ion conductor, or solid electrolyte stabilizer), showed some improvement, but were still significantly inferior to the examples. In particular, Comparative Example 3 (which only added a lithiophile substance) still exhibited interface delamination, indicating that single-functional modification is insufficient to achieve synergistic optimization of interface stability and ion transport.

[0060] In summary, the composite current collector prepared by atmospheric plasma spraying in this invention is significantly superior to traditional methods and single-function modification schemes in terms of multifunctional synergistic modification of the interface, high bonding strength, high density and high process efficiency, and has obvious technical advantages and industrialization potential.

[0061] The above embodiments are merely preferred embodiments of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a composite current collector, characterized in that, It includes: The powder of the continuous metal phase and the powder of the interface-modified phase are mixed to obtain a mixed powder; The mixed powder is sprayed onto a solid electrolyte substrate or a pretreated solid electrolyte substrate by atmospheric plasma spraying to form a composite coating. Wherein, the solid electrolyte substrate is selected from garnet-type electrolyte substrates; the continuous metal phase is selected from metals and / or alloys; the interface modification phase includes a lithiophilic material, a lithium-ion conductor, and a solid electrolyte stabilizer in a mass ratio of (5-6):(1-2.5):(1-2.5); wherein, the lithiophilic material includes one or more of zinc, tin, tin dioxide, and zinc oxide; the mass of the interface modification phase powder is 0.5-10% of the total mass of the mixed powder.

2. The preparation method according to claim 1, characterized in that, in, The continuous metal phase is selected from one or more of copper, nickel and their alloys; and / or the lithium-ion conductor is selected from lithium zirconate and / or lithium lanthanum zirconate; and / or the solid electrolyte stabilizer is selected from one or more of lithium metaborate, lithium tetraborate, lithium triborate, lithium oxide, and boron oxide; and / or the solid electrolyte substrate is selected from LLZTO ceramic sheets and / or LLZO ceramic sheets.

3. The preparation method according to claim 1, characterized in that, in, The thickness of the solid electrolyte substrate is 10-100 μm; and / or the thickness of the composite coating is 3-20 μm; and / or the particle size of the metal continuous phase powder is 15-45 μm and the purity is ≥99.9%; and / or the particle size of the interface modification phase powder is 1 nm-10 μm.

4. The preparation method according to claim 1, characterized in that, It also includes: after forming the composite coating, performing heat treatment, the heat treatment including: holding at 200-400℃ for 1-3 hours in an inert atmosphere.

5. The preparation method according to claim 1, characterized in that, The atmospheric plasma spraying has a power of 25-40kW, a spraying distance of 80-120mm, and a powder feeding rate of 20-40g / min.

6. The preparation method according to claim 1, wherein obtaining the pretreated solid electrolyte substrate comprises: The solid electrolyte substrate was polished until its Ra value was < 0.1 μm, then cleaned and dried to obtain the pretreated solid electrolyte substrate.

7. The preparation method according to claim 1, comprising: The solid electrolyte substrate was polished until its Ra value was < 0.1 μm, then cleaned and dried to obtain the pretreated solid electrolyte substrate. A continuous metal phase powder with a particle size of 15-45 μm and an interface-modified phase powder with a particle size of 1 nm-10 μm are mixed to obtain a mixed powder; the mass percentage of the interface-modified phase powder in the mixed powder is 0.5-10%. The mixed powder is sprayed onto a pretreated solid electrolyte substrate by atmospheric plasma spraying at a power of 25-40kW, a spraying distance of 80-120mm, and a powder feeding rate of 20-40g / min to form a composite coating and obtain a composite sample. The composite sample was kept at 200-400℃ for 1-3 hours in an inert atmosphere to obtain a composite current collector.

8. The composite current collector prepared by the preparation method according to any one of claims 1-7.

9. A negative electrode-free solid-state battery containing the composite current collector as described in claim 8.

10. The method for preparing the negative electrode-free solid-state battery according to claim 9, comprising: The composite current collector and the positive electrode layer are assembled into a negative electrode-free battery. The positive electrode layer contains a positive electrode active material, which is selected from one or more of NCM811, NCM922, NCA, lithium-rich manganese-based materials, and LCO materials.

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