A dry solid-state battery and a preparation process thereof

Abstract

The application relates to the technical field of lithium ion batteries, and particularly discloses a dry solid-state battery and a preparation process. The composite positive electrode adopts a convex point array carbon-coated aluminum film, effectively improves the interface contact area, forms mechanical occlusion through the convex point structure, greatly improves the interface adhesion and the bonding strength, reduces the initial impedance, simultaneously inhibits the impedance increment in the cycle process, and prolongs the cycle life of the battery; solves the problem that the low-temperature ion transmission efficiency is lower than the active material utilization rate, the micron-nanopore channel structure of the multistage pore positive electrode active material can shorten the ion transmission path, the Li6PS5Cl electrolyte component and the lithium layer on the surface of the composite negative electrode cooperatively optimize the ion conduction environment, the capacity retention rate is significantly improved at low temperature, and the active material utilization rate and the high-rate discharge performance are simultaneously enhanced; and the cracking and delamination problems in the production and cycle processes are avoided, so that the stability of the battery in the use process is ensured.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and in particular to a dry solid-state battery and its preparation process. Background Technology

[0002] Currently, solid-state batteries, with their advantages of high energy density, high safety, and long cycle life, have become the core development direction for next-generation power batteries and energy storage batteries. Dry manufacturing processes, due to their characteristics of not requiring organic solvents, good environmental friendliness, and controllable electrode structure, are one of the key technological paths for the large-scale production of solid-state batteries.

[0003] Existing dry solid-state battery technology has many shortcomings: weak bonding between the electrode and electrolyte interface, high initial impedance with a large increase after cycling; low ion transport efficiency at low temperatures, with capacity retention of less than 50%; poor electrode mechanical strength, making it prone to cracking and delamination during production and cycling; and solid active material structure, resulting in long ion transport paths, low utilization, and poor high-rate performance.

[0004] To address these issues, this application presents an improved dry solid-state battery design and fabrication process. Summary of the Invention

[0005] The purpose of this invention is to provide a dry solid-state battery and its fabrication process, aiming to solve the technical problems of existing technologies such as weak electrode-electrolyte interface bonding, high initial impedance with large increase after cycling; low ion transport efficiency at low temperatures and capacity retention of less than 50%; poor electrode mechanical strength, easy cracking and delamination during production and cycling; and solid active material structure with long ion transport path, low utilization and poor high-rate performance.

[0006] To achieve the above objectives, the present invention employs a dry-process solid-state battery fabrication process, comprising the following steps: A mixture of 82-95 wt% hierarchical porous positive electrode active material, 3-8 wt% Li6PS5Cl, and 2-5 wt% carbon nanotubes and graphene aerogel was added to a vacuum shear mixer and sheared at 8000-15000 r / min for 60-300 min at a dew point < -55℃ to obtain the first powder. Cool the vacuum shear mixer to -5~5℃, add 1~4wt% polyN-isopropylacrylamide modified PVDF to the first powder, LCST=45℃, and stir at a low speed of 400~800r / min for 30~90min to obtain the second powder. The second powder was frozen at -20~-10℃ for 1~3h, and then sublimated at a vacuum degree <1Pa and a temperature of 60~100℃ to form 10~30μm three-dimensional network fibers of polyN-isopropylacrylamide modified PVDF, thus obtaining the third powder. The third powder is hot-rolled into a 50-600μm film at 180-280℃ and 8-18MPa. The film and the carbon-coated aluminum film with bump array are then rolled together at 200-250℃ and 5-10MPa to obtain a composite positive electrode. Using 5-12μm copper foil as the current collector, natural graphite with a particle size of 1-5μm is dry-sprayed to form a substrate with a density of 1.2-1.4 g / cm³. 3 - Surface density 1.6~1.8 g / cm³ 3 A gradient carbon substrate with a thickness of 10~30μm; 30-100nm nano-silicon and hard carbon are mixed in a ratio of 3:7, and 2-5wt% elastic binder is added. The mixture is then extruded and pressed into a 40-100μm composite layer at -5-10℃ using a twin-screw extruder. The composite layer is then transferred to the surface of the gradient carbon substrate, and the bonding strength is enhanced by low-temperature rolling to obtain a pre-formed negative electrode. Under argon protection, the pre-formed negative electrode is immersed in a 0.5~2.0mol / L lithium naphthalene tetrahydrofuran solution at -10~0℃ for 30~60s, and a 50~200nm lithium layer is formed on the surface to obtain a composite negative electrode; Li7La3Zr2O with a particle size of 800~1200nm 12 The base powder is obtained by calcining at 800~1000℃ for 2~5h, cooling and mixing with 1~3wt% LiPO3 glass powder; The base powder is pressed into a blank with a thickness of ≥2cm. Al2O3-ZrO2 bilayer transition layer of 5~20nm is deposited alternately using ALD technology, with the ratio of Al2O3 to ZrO2 being 1:2. The deposited blank is cut to a thickness of 3~60μm and polished on both sides to Ra≤0.05μm to obtain a solid electrolyte layer. The composite positive electrode, the solid electrolyte layer and the composite negative electrode prepared above are stacked in sequence, and pre-pressed at -10~0℃ and 1~3MPa for 600~900s, and then hot-pressed at 50~90℃ and 3~8MPa for 1200~1800s to obtain a dry solid-state battery.

[0007] The multi-level porous positive electrode active material is any one or a combination of high-nickel ternary materials, lithium-rich manganese-based materials, and lithium iron phosphate materials. The mass ratio of carbon nanotubes to graphene aerogel is 2:1 to 4:1, and the filling rate in the pores is ≥90%.

[0008] The molecular weight of the poly(N-isopropylacrylamide) modified PVDF is 50,000 to 150,000. The elastic adhesive is styrene-butadiene rubber modified PTFE; The purity of the nano-silicon is ≥99.9%, and the surface is modified by 1~5nm carbon coating.

[0009] During the freezing of the second powder, the cooling rate is 10~20℃ / min, the heating rate for sublimation is 1~3℃ / min, and the sublimated powder is treated with an airflow of 300~400m / s for 10~20s to remove loose particles from the surface.

[0010] The protrusions of the carbon-coated aluminum film with the protrusion array are semi-circular or semi-elliptical protrusions. The radius of the arc at the top of the semi-circular protrusion is 2.5~10μm; the major axis of the semi-elliptical protrusion is 8~25μm, the minor axis is 5~15μm, and the radius of the arc at the top is 1.5~5μm; the porosity of the carbon-coated aluminum film with the protrusion array is 25%~40%, and the resistivity is ≤5×10⁻⁶. -4 Ω·cm.

[0011] The pressure for dry spraying natural graphite is 0.3~0.8MPa, and the spraying rate is 5~10g / min; The lithium content of the lithium naphthalene and tetrahydrofuran mixed solution is 0.05~0.1 mol / L, and the total thickness of the composite negative electrode is 60~150 μm.

[0012] Among them, in the case of Li7La3Zr2O 12 The heating rate during calcination is 2~5℃ / min, and the holding time after calcination is completed is 3~4h; The ALD deposition temperature is 120~180℃, the Al2O3 precursor is trimethylaluminum, the ZrO2 precursor is tetrabutylzirconium, and the deposition rate is 0.1~0.3nm / cycle.

[0013] In this process, the composite positive electrode, the solid electrolyte layer, and the composite negative electrode are stacked in sequence, and the temperature of the upper roller during hot pressing is 60~80℃ and the temperature of the lower roller is 70~90℃.

[0014] The multi-level porous positive electrode active material includes the following preparation process: LiNi 0.8 Co 0.1 Mn 0.1 O2 and 5-10 wt% water-soluble pore-forming agent are mixed at a ratio of 1:3 to form a slurry. The water-soluble pore-forming agent is polyvinyl alcohol. Spray drying is carried out under the conditions of inlet air temperature of 200-250℃, outlet air temperature of 80-100℃, and atomization pressure of 0.3-0.6MPa to form spherical particles of 5-10μm. Micron-sized pores of 1-5μm are dispersed inside the spherical particles, and the porosity is 15-25%. Spherical particles are placed in a tubular furnace filled with argon gas. The argon gas purity is ≥99.99%, the flow rate is 100~200 sccm, and the oxygen content in the furnace is ≤100ppm. The furnace is heated, and the heating rate is 5~10℃ / min when the temperature rises from room temperature to 300℃, and 3~5℃ / min when the temperature rises from 300℃ to the target temperature. The target temperature is 400~600℃. After reaching the target temperature, the temperature is maintained for 2~4 hours to remove the water-soluble pore-forming agent, which causes slight sintering of the pore walls of the spherical particles, forming nanopores of 50~500nm with a porosity of 8~12%. After the holding period, argon gas is continuously introduced until the furnace temperature naturally cools down to below 100℃. The sintered particles are removed by screening with a 200-mesh sieve, and then the multi-level porous positive electrode active material with a particle size of 4.5~10.5μm is screened out by an air classifier.

[0015] The present invention also provides a dry solid-state battery, which is prepared by the dry solid-state battery preparation process described above, including a composite negative electrode, a solid electrolyte layer at the upper end of the composite negative electrode, and a composite positive electrode at the upper end of the solid electrolyte layer. The composite anode includes a gradient carbon substrate, a composite layer at the upper end of the gradient carbon substrate, and a lithium layer deposited on the outer wall of the gradient carbon substrate and the composite layer. The solid electrolyte layer includes a thick blank, and the outer wall of the thick blank is alternately deposited with an Al2O3-ZrO2 bilayer transition layer. The composite positive electrode includes a membrane, and the lower end of the membrane is provided with a carbon-coated aluminum film with a bump array.

[0016] The present invention provides a dry-process solid-state battery and its fabrication process, which has the following beneficial effects: 1. The composite cathode adopts a carbon-coated aluminum film with a bump array, which effectively increases the interface contact area and forms a mechanical interlock through the bump structure, overcoming the limitation of weak bonding between the electrode and electrolyte interface. Combined with the "pre-pressing + gradient hot pressing" process, it greatly improves the interface adhesion and bonding strength, reduces the initial impedance, and suppresses the impedance increase during cycling, thus extending the battery cycle life. 2. To solve the problem of low-temperature ion transport efficiency being lower than the utilization rate of active materials, the micron-nano pore structure of the multi-level porous positive electrode active material can shorten the ion transport path. The Li6PS5Cl electrolyte component and the lithium layer on the surface of the composite negative electrode synergistically optimize the ion conduction environment, significantly improving the capacity retention rate at low temperatures, and simultaneously enhancing the utilization rate of active materials and high-rate discharge performance. 3. The three-dimensional network fiber formed by poly(N-isopropylacrylamide) modified PVDF in the composite positive electrode and the styrene-butadiene rubber modified PTFE and gradient carbon substrate structure used in the composite negative electrode together improve the toughness and structural stability of the electrode, avoid cracking and delamination problems during production and cycling, and ensure the stability of the battery during use. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a cross-sectional view of the structure of a semi-circular bump array carbon-coated aluminum film used in a dry solid-state battery according to the present invention.

[0019] Figure 2 This is a cross-sectional view of the structure of a semi-elliptical bump array carbon-coated aluminum film used in a dry solid-state battery according to the present invention.

[0020] 1-film, 2-carburized aluminum film with bump array, 3-gradient carbon substrate, 4-composite layer, 5-lithium layer, 6-thick preform, 7-double transition layer. Detailed Implementation

[0021] This invention provides a dry-process fabrication process for solid-state batteries, comprising the following steps: S1: Add 82~95wt% of hierarchical porous positive electrode active material, 3~8wt% of Li6PS5Cl, 2~5wt% of carbon nanotubes and graphene aerogel to a vacuum shear mixer, and shear at 8000~15000r / min for 60~300min at a dew point < -55℃ to obtain the first powder. S2: Cool the vacuum shear mixer to -5~5℃, add 1~4wt% polyN-isopropylacrylamide modified PVDF to the first powder, LCST=45℃, and stir at a low speed of 400~800r / min for 30~90min to obtain the second powder; S3: Freeze the second powder at -20~-10℃ for 1~3h, then sublimate it at a vacuum degree <1Pa and a temperature of 60~100℃ to form 10~30μm three-dimensional network fibers of polyN-isopropylacrylamide modified PVDF, and obtain the third powder. S4: The third powder is hot-rolled at 180~280℃ and 8~18MPa to form a 50~600μm film 1. The film 1 and the convex array carbon-coated aluminum film 2 are rolled together at 200~250℃ and 5~10MPa to obtain a composite positive electrode. S5: Using 5~12μm copper foil as the current collector, natural graphite with a particle size of 1~5μm is dry-sprayed to form a substrate with a density of 1.2~1.4g / cm³. 3 - Surface density 1.6~1.8 g / cm³3 3. Gradient carbon substrates with a thickness of 10~30μm; S6: Mix 30~100nm nano-silicon and hard carbon in a ratio of 3:7, add 2~5wt% elastic binder, and extrude the mixture at -5~10℃ using a twin-screw extruder to form a 40~100μm composite layer 4. Transfer the composite layer 4 to the surface of the gradient carbon substrate 3 and enhance the bonding strength by low-temperature rolling to obtain a pre-formed negative electrode. S7: Under argon protection, the pre-formed negative electrode is immersed in a 0.5~2.0mol / L lithium naphthalene tetrahydrofuran solution at -10~0℃ for 30~60s, and a 50~200nm lithium layer 5 is formed on the surface to obtain a composite negative electrode; S8: Li7La3Zr2O with a particle size of 800~1200nm 12 The base powder is obtained by calcining at 800~1000℃ for 2~5h, cooling and mixing with 1~3wt% LiPO3 glass powder; S9: Press the base powder into a blank 6 with a thickness of ≥2cm, and use ALD technology to alternately deposit a 5~20nm Al2O3-ZrO2 double-layer transition layer 7 with a ratio of Al2O3 to ZrO2 of 1:2. Cut the deposited blank 6 to a thickness of 3~60μm and polish both sides to Ra≤0.05μm to obtain a solid electrolyte layer. S10: The composite positive electrode, the solid electrolyte layer and the composite negative electrode prepared above are stacked in sequence, and pre-pressed at -10~0℃ and 1~3MPa for 600~900s, and then hot-pressed at 50~90℃ and 3~8MPa for 1200~1800s to obtain a dry solid-state battery.

[0022] Furthermore, the multi-level porous positive electrode active material adopts any one or more combinations of high-nickel ternary materials, lithium-rich manganese-based materials, and lithium iron phosphate materials; The mass ratio of carbon nanotubes to graphene aerogel is 2:1 to 4:1, and the filling rate in the pores is ≥90%.

[0023] Furthermore, the molecular weight of the poly(N-isopropylacrylamide) modified PVDF is 50,000 to 150,000; The elastic adhesive is styrene-butadiene rubber modified PTFE; The purity of the nano-silicon is ≥99.9%, and the surface is modified by 1~5nm carbon coating.

[0024] Furthermore, during the freezing of the second powder, the cooling rate is 10~20℃ / min, the heating rate for sublimation is 1~3℃ / min, and the sublimated powder is treated with an airflow of 300~400m / s for 10~20s to remove loose particles from the surface.

[0025] Furthermore, the bumps of the carbon-coated aluminum film 2 with bump array are semi-circular bumps or semi-elliptical bumps. The radius of the arc at the top of the semi-circular bump is 2.5~10μm; the major axis of the semi-elliptical bump is 8~25μm, the minor axis is 5~15μm, and the radius of the arc at the top is 1.5~5μm; the porosity of the carbon-coated aluminum film 2 with bump array is 25%~40%, and the resistivity is ≤5×10⁻⁶. -4 Ω·cm.

[0026] Furthermore, the pressure for dry spraying natural graphite is 0.3~0.8MPa, and the spraying rate is 5~10g / min; The lithium content of the lithium naphthalene and tetrahydrofuran mixed solution is 0.05~0.1 mol / L, and the total thickness of the composite negative electrode is 60~150 μm.

[0027] Furthermore, in the study of Li7La3Zr2O 12 The heating rate during calcination is 2~5℃ / min, and the holding time after calcination is completed is 3~4h; The ALD deposition temperature is 120~180℃, the Al2O3 precursor is trimethylaluminum, the ZrO2 precursor is tetrabutylzirconium, and the deposition rate is 0.1~0.3nm / cycle.

[0028] Furthermore, during the hot pressing of the composite positive electrode, the solid electrolyte layer, and the composite negative electrode stacked sequentially, the upper roller temperature is 60~80℃ and the lower roller temperature is 70~90℃.

[0029] Furthermore, the multi-level porous positive electrode active material includes the following preparation process: LiNi 0.8 Co 0.1 Mn 0.1 O2 and 5-10 wt% water-soluble pore-forming agent are mixed at a ratio of 1:3 to form a slurry. The water-soluble pore-forming agent is polyvinyl alcohol. Spray drying is carried out under the conditions of inlet air temperature of 200-250℃, outlet air temperature of 80-100℃, and atomization pressure of 0.3-0.6MPa to form spherical particles of 5-10μm. Micron-sized pores of 1-5μm are dispersed inside the spherical particles, and the porosity is 15-25%. Spherical particles are placed in a tubular furnace filled with argon gas. The argon gas purity is ≥99.99%, the flow rate is 100~200 sccm, and the oxygen content in the furnace is ≤100ppm. The furnace is heated, and the heating rate is 5~10℃ / min when the temperature rises from room temperature to 300℃, and 3~5℃ / min when the temperature rises from 300℃ to the target temperature. The target temperature is 400~600℃. After reaching the target temperature, the temperature is maintained for 2~4 hours to remove the water-soluble pore-forming agent, which causes slight sintering of the pore walls of the spherical particles, forming nanopores of 50~500nm with a porosity of 8~12%. After the holding period, argon gas is continuously introduced until the furnace temperature naturally cools down to below 100℃. The sintered particles are removed by screening with a 200-mesh sieve, and then the multi-level porous positive electrode active material with a particle size of 4.5~10.5μm is screened out by an air classifier.

[0030] Please see Figure 1 and Figure 2 The present invention also provides a dry solid-state battery, which is prepared by the dry solid-state battery preparation process described above, including a composite negative electrode, a solid electrolyte layer at the upper end of the composite negative electrode, and a composite positive electrode at the upper end of the solid electrolyte layer. The composite anode includes a gradient carbon substrate 3, a composite layer 4 is provided at the upper end of the gradient carbon substrate 3, and a lithium layer 5 is deposited on the outer wall of the gradient carbon substrate 3 and the composite layer 4. The solid electrolyte layer includes a thick blank 6, and the outer wall of the thick blank 6 is alternately deposited with an Al2O3-ZrO2 double transition layer 7. The composite positive electrode includes a membrane 1, and the lower end of the membrane 1 is provided with a carbon-coated aluminum film 2 with a bump array.

[0031] Example 1, A mixture of 82wt% hierarchical porous positive electrode active material, 8wt% Li6PS5Cl, and 5wt% carbon nanotubes and graphene aerogel (mass ratio 2:1) was added to a vacuum shear mixer and sheared at 8000 r / min for 300 min at a dew point < -55℃ to obtain the first powder. The temperature of the vacuum shear mixer was lowered to -5℃, and 4wt% poly(N-isopropylacrylamide) modified PVDF (molecular weight 50000) was added to the first powder. The mixture was stirred at a low speed of 400r / min for 90min to obtain the second powder. The second powder was frozen at -20℃ for 3 hours (cooling rate 10℃ / min), and then sublimated at 60℃ under vacuum <1Pa (heating rate 1℃ / min). After sublimation, it was treated with a 300m / s airflow for 20 seconds to obtain the third powder. The third powder was hot-rolled at 180℃ and 8MPa to form a 50μm film 1, which was then rolled together with a semi-circular convex carbon-coated aluminum film (top arc radius 2.5μm, porosity 25%) at 200℃ and 5MPa to obtain a composite positive electrode. Using 5μm copper foil as the current collector, natural graphite with a particle size of 1~5μm was dry-sprayed (spraying pressure 0.3MPa, spraying rate 5g / min) to form an underlayer with a density of 1.2g / cm³. 3 Surface density 1.6 g / cm³ 3 3. Gradient carbon substrate with a thickness of 10 μm; 30nm nano-silicon (1nm carbon-coated) was mixed with hard carbon at a ratio of 3:7, and 2wt% styrene-butadiene rubber modified PTFE was added. The mixture was then extruded by a twin-screw extruder at -5℃ and pressed into a 40μm composite layer 4. The composite layer 4 was then transferred to the surface of a gradient carbon substrate 3 and rolled at low temperature to obtain a pre-formed negative electrode. The pre-formed negative electrode was immersed in a 0.5 mol / L lithium naphthalene tetrahydrofuran solution (lithium content 0.05 mol / L) at -10℃ for 60 s, and a 50 nm lithium layer was formed on the surface, resulting in a composite negative electrode (total thickness 60 μm). Li7La3Zr2O with a particle size of 800 nm 12 The mixture was calcined at 800℃ for 5 hours (heating rate 2℃ / min, holding for 3 hours), and after cooling, it was mixed with 1wt% LiPO3 glass powder to obtain the basic powder. The base powder was pressed into a 2cm thick blank 6. A 5nm Al2O3-ZrO2 bilayer transition layer 7 was alternately deposited using ALD technology (120℃, Al2O3 precursor trimethylaluminum, ZrO2 precursor tetrabutylzirconium, deposition rate 0.1nm / cycle). The deposited thick blank 6 was cut to a thickness of 3μm and polished on both sides to Ra≤0.05μm to obtain a solid electrolyte layer. The composite positive electrode, solid electrolyte layer, and composite negative electrode are stacked in sequence, pre-pressed at -10℃ and 1MPa for 900s, and then hot-pressed at 50℃ and 3MPa for 1800s (upper roller 60℃, lower roller 70℃) to obtain a dry solid-state battery.

[0032] Performance testing: Peel strength 45 N / m, volumetric conductivity 85 S / cm, initial impedance 80 mΩ·cm, discharge capacity retention 75% at -20℃, 1C discharge capacity 160 mAh / g, capacity retention 90% after 500 cycles, electrode mechanical strength 15 MPa.

[0033] Example 2, A mixture of 90wt% hierarchical porous positive electrode active material, 5wt% Li6PS5Cl, and 3wt% carbon nanotubes and graphene aerogel (mass ratio 3:1) was added to a vacuum shear mixer and sheared at 12000r / min for 180min at a dew point < -55℃ to obtain the first powder. The temperature of the vacuum shear mixer was lowered to 0℃, and 2wt% poly(N-isopropylacrylamide) modified PVDF (molecular weight 100,000) was added to the first powder. The mixture was stirred at a low speed of 600r / min for 60min to obtain the second powder. The second powder was frozen at -15℃ for 2 hours (cooling rate 15℃ / min), and then sublimated at 80℃ under vacuum <1Pa (heating rate 2℃ / min). After sublimation, it was treated with a 350m / s airflow for 15s to obtain the third powder. The third powder was hot-rolled at 180℃ and 8MPa to form a 50μm film 1, which was then rolled together with a semi-elliptical convex carbon-coated aluminum film (major axis 15μm, minor axis 10μm, top arc radius 3μm, porosity 32%) at 220℃ and 8MPa to obtain a composite cathode. Using 8μm copper foil as the current collector, natural graphite with a particle size of 1~5μm was dry-sprayed (spraying pressure 0.5MPa, spraying rate 8g / min) to form an underlayer with a density of 1.3g / cm³. 3 Surface density 1.7 g / cm³ 3 3. Gradient carbon substrate with a thickness of 20 μm; 60nm nano-silicon (3nm carbon-coated) was mixed with hard carbon at a ratio of 3:7, and 3wt% styrene-butadiene rubber modified PTFE was added. The mixture was then extruded by a twin-screw extruder at 2°C and pressed into a 70μm composite layer 4. The composite layer 4 was then transferred to the surface of a gradient carbon substrate 3 and rolled at low temperature to obtain a pre-formed negative electrode. The pre-formed negative electrode was immersed in a 1.2 mol / L lithium naphthalene tetrahydrofuran solution (lithium content 0.08 mol / L) at -5℃ for 45 s, and a 120 nm lithium layer was formed on the surface to obtain a composite negative electrode (total thickness 100 μm). Li7La3Zr2O with a particle size of 1000nm 12 The mixture was calcined at 900℃ for 3.5 h (heating rate 3℃ / min, holding for 3.5 h), and after cooling, it was mixed with 2wt% LiPO3 glass powder to obtain the basic powder. The base powder was pressed into a 3cm thick blank 6. A 12nm Al2O3-ZrO2 bilayer transition layer 7 was alternately deposited using ALD technology (150℃, Al2O3 precursor trimethylaluminum, ZrO2 precursor tetrabutylzirconium, deposition rate 0.2nm / cycle). The deposited thick blank 6 was cut to a thickness of 30μm and polished on both sides to Ra≤0.05μm to obtain a solid electrolyte layer. The composite positive electrode, solid electrolyte layer, and composite negative electrode are stacked sequentially, pre-pressed at -5℃ and 2MPa for 750s, and then hot-pressed at 70℃ and 5MPa for 1500s (upper roller 70℃, lower roller 80℃) to obtain a dry solid-state battery.

[0034] Performance testing: Peel strength 48 N / m, volumetric conductivity 89 S / cm, initial impedance 72 mΩ·cm, discharge capacity retention 78% at -20℃, 1C discharge capacity 165 mAh / g, capacity retention 92% after 500 cycles, electrode mechanical strength 17 MPa.

[0035] Example 3, A mixture of 95wt% hierarchical porous positive electrode active material, 3wt% Li6PS5Cl, 2wt% carbon nanotubes and graphene aerogel (mass ratio 4:1) was added to a vacuum shear mixer and sheared at 15000r / min for 60min at a dew point < -55℃ to obtain the first powder. Reduce the temperature of the vacuum shear mixer to 5°C, add 1 wt% poly(N-isopropylacrylamide) modified PVDF (molecular weight 150,000) to the first powder, and stir at a low speed of 800 r / min for 30 min to obtain the second powder; The second powder was frozen at -10℃ for 1 hour (cooling rate 20℃ / min), and then sublimated at 100℃ under vacuum <1Pa (heating rate 3℃ / min). After sublimation, it was treated with a 400m / s airflow for 10 seconds to obtain the third powder. The third powder was hot-rolled at 280℃ and 18MPa to form a 600μm film 1, which was then rolled together with a semi-circular convex carbon-coated aluminum film (top arc radius 10μm, porosity 40%) at 250℃ and 10MPa to obtain a composite positive electrode. Using 12μm copper foil as the current collector, natural graphite with a particle size of 1~5μm was dry-sprayed (spraying pressure 0.8MPa, spraying rate 10g / min) to form an underlayer with a density of 1.4g / cm³. 3 Surface density 1.8 g / cm³ 3 3. Gradient carbon substrate with a thickness of 30 μm; 100nm nano-silicon (5nm carbon-coated) was mixed with hard carbon at a ratio of 3:7, and 5wt% styrene-butadiene rubber modified PTFE was added. The mixture was then extruded by twin screw extrusion at 10℃ and pressed into a 100μm composite layer 4. The composite layer 4 was then transferred to the surface of a gradient carbon substrate 3 and rolled at low temperature to obtain a pre-formed negative electrode. The pre-formed negative electrode was immersed in a 2 mol / L lithium naphthalene tetrahydrofuran solution (lithium content 0.1 mol / L) at 0℃ for 30s, and a 200 nm lithium layer was formed on the surface to obtain a composite negative electrode (total thickness 150 μm). Li7La3Zr2O with a particle size of 1200 nm 12 The mixture was calcined at 1000℃ for 5 hours (heating rate 5℃ / min, holding for 4 hours), and after cooling, it was mixed with 3wt% LiPO3 glass powder to obtain the basic powder. The base powder was pressed into a 4cm thick blank 6. A 20nm Al2O3-ZrO2 bilayer transition layer 7 was alternately deposited using ALD technology (180℃, Al2O3 precursor trimethylaluminum, ZrO2 precursor tetrabutylzirconium, deposition rate 0.3nm / cycle). The deposited thick blank 6 was cut to a thickness of 60μm and polished on both sides to Ra≤0.05μm to obtain a solid electrolyte layer. The composite positive electrode, solid electrolyte layer, and composite negative electrode are stacked sequentially, pre-pressed at 0℃ and 3MPa for 600s, and then hot-pressed at 90℃ and 8MPa for 1200s (upper roller 80℃, lower roller 90℃) to obtain a dry solid-state battery.

[0036] Performance testing: Peel strength 46 N / m, volumetric conductivity 87 S / cm, initial impedance 75 mΩ·cm, discharge capacity retention at -20℃ 76%, 1C discharge capacity 163 mAh / g, capacity retention after 500 cycles 91%, electrode mechanical strength 16 MPa.

[0037] Comparative Example 1: Key difference: Composite positive electrode without bump array carbon-coated aluminum film 2, other parameters are the same as in Example 2.

[0038] Performance testing: Peel strength 28 N / m, volumetric conductivity 88 S / cm, initial impedance 105 mΩ·cm, discharge capacity retention 77% at -20℃, 1C discharge capacity 164 mAh / g, capacity retention 91% after 500 cycles, electrode mechanical strength 16 MPa.

[0039] Comparative Example 2: Key difference: The positive electrode active material has a solid structure without hierarchical pores, while the other parameters are the same as in Example 2.

[0040] Performance testing: Peel strength 47 N / m, volumetric conductivity 89 S / cm, initial impedance 73 mΩ·cm, discharge capacity retention at -20℃ 52%, 1C discharge capacity 163 mAh / g, capacity retention after 500 cycles 86%, electrode mechanical strength 16 MPa.

[0041] Comparative Example 3: Key difference: The solid electrolyte layer does not have the Al2O3-ZrO2 bilayer transition layer 7, while the other parameters are the same as in Example 2.

[0042] Performance testing: Peel strength 30 N / m, volumetric conductivity 88 S / cm, initial impedance 110 mΩ·cm, discharge capacity retention 76% at -20℃, 1C discharge capacity 163 mAh / g, capacity retention 86% after 500 cycles, electrode mechanical strength 16 MPa.

[0043] Comparative Example 4: Key differences: The second powder does not undergo freeze-sublimation treatment, the binder is ordinary PVDF, and the remaining parameters are the same as in Example 2.

[0044] Performance testing: Peel strength 32 N / m, volumetric conductivity 70 S / cm, initial impedance 85 mΩ·cm, discharge capacity retention 75% at -20℃, 1C discharge capacity 150 mAh / g, capacity retention 80% after 500 cycles, electrode mechanical strength 8 MPa.

[0045] The performance test results are summarized in the table below: Examples 1, 2, and 3 all exhibit peel strength ≥45 N / m, volume conductivity ≥85 S / cm, discharge capacity retention rate ≥75% at -20℃, capacity retention rate ≥90% after 500 cycles, and electrode mechanical strength ≥15 MPa, effectively verifying the comprehensive optimization effect of the "multi-level porous cathode structure + interface modification + synergistic process" of the present invention.

[0046] Comparison of Comparative Example 1 (carbon-coated aluminum film without bump array 2) and Example 2: the peel strength decreased from 48 N / m to 28 N / m, and the initial impedance increased from 72 mΩ·cm to 105 mΩ·cm, which verifies the effect of bump array carbon-coated aluminum film 2 on improving interfacial bonding and ion transport efficiency.

[0047] Comparison of Comparative Example 2 (active material without hierarchical pores) and Example 2: The discharge capacity retention rate at -20℃ decreased from 78% to 52%, and the 1C discharge capacity decreased from 165mAh / g to 142mAh / g, verifying the value of hierarchical pore structure of hierarchical pore positive electrode active material in shortening ion transport path and improving low temperature and high rate performance.

[0048] Comparison of Comparative Example 3 (without Al2O3-ZrO2 bilayer transition layer 7) with Example 2: the peel strength decreased from 48 N / m to 30 N / m, and the initial impedance increased from 72 mΩ·cm to 110 mΩ·cm, verifying that Al2O3-ZrO2 bilayer transition layer 7 can optimize the interfacial compatibility between the electrolyte and the electrode.

[0049] Comparison of Comparative Example 3 (second powder without freeze-sublimation treatment, binder using ordinary PVDF) with Example 2: the mechanical strength of the electrode decreased from 17 MPa to 8 MPa, and the volume conductivity decreased from 89 S / cm to 70 S / cm, verifying the supporting role of the three-dimensional network bonding structure formed by freeze-sublimation treatment on mechanical strength and conductive network.

[0050] The above description discloses only one preferred embodiment of the present invention, and should not be construed as limiting the scope of the present invention. Those skilled in the art will understand that all or part of the processes of the above embodiments can be implemented, and equivalent changes made in accordance with the claims of the present invention are still within the scope of the invention.

Claims

1. A dry-process solid-state battery fabrication process, characterized in that, Includes the following steps: A mixture of 82-95 wt% hierarchical porous positive electrode active material, 3-8 wt% Li6PS5Cl, and 2-5 wt% carbon nanotubes and graphene aerogel was added to a vacuum shear mixer and sheared at 8000-15000 r / min for 60-300 min at a dew point < -55℃ to obtain the first powder. Cool the vacuum shear mixer to -5~5℃, add 1~4wt% polyN-isopropylacrylamide modified PVDF to the first powder, LCST=45℃, and stir at a low speed of 400~800r / min for 30~90min to obtain the second powder. The second powder was frozen at -20~-10℃ for 1~3h, and then sublimated at a vacuum degree <1Pa and a temperature of 60~100℃ to form 10~30μm three-dimensional network fibers of polyN-isopropylacrylamide modified PVDF, thus obtaining the third powder. The third powder is hot-rolled into a 50-600μm film at 180-280℃ and 8-18MPa. The film and the carbon-coated aluminum film with bump array are then rolled together at 200-250℃ and 5-10MPa to obtain a composite positive electrode. Using 5-12μm copper foil as the current collector, natural graphite with a particle size of 1-5μm is dry-sprayed to form a substrate with a density of 1.2-1.4 g / cm³. 3 - Surface density 1.6~1.8 g / cm³ 3 A gradient carbon substrate with a thickness of 10~30μm; 30-100nm nano-silicon and hard carbon are mixed in a ratio of 3:7, and 2-5wt% elastic binder is added. The mixture is then extruded and pressed into a 40-100μm composite layer at -5-10℃ using a twin-screw extruder. The composite layer is then transferred to the surface of the gradient carbon substrate, and the bonding strength is enhanced by low-temperature rolling to obtain a pre-formed negative electrode. Under argon protection, the pre-formed negative electrode is immersed in a 0.5~2.0mol / L lithium naphthalene tetrahydrofuran solution at -10~0℃ for 30~60s, and a 50~200nm lithium layer is formed on the surface to obtain a composite negative electrode; Li7La3Zr2O with a particle size of 800~1200nm 12 The base powder is obtained by calcining at 800~1000℃ for 2~5h, cooling and mixing with 1~3wt% LiPO3 glass powder; The base powder is pressed into a blank with a thickness of ≥2cm. Al2O3-ZrO2 bilayer transition layer of 5~20nm is deposited alternately using ALD technology, with the ratio of Al2O3 to ZrO2 being 1:

2. The deposited blank is cut to a thickness of 3~60μm and polished on both sides to Ra≤0.05μm to obtain a solid electrolyte layer. The composite positive electrode, the solid electrolyte layer and the composite negative electrode prepared above are stacked in sequence, and pre-pressed at -10~0℃ and 1~3MPa for 600~900s, and then hot-pressed at 50~90℃ and 3~8MPa for 1200~1800s to obtain a dry solid-state battery.

2. The dry-process solid-state battery fabrication process as described in claim 1, characterized in that, The multi-level porous positive electrode active material is any one or a combination of high-nickel ternary materials, lithium-rich manganese-based materials, and lithium iron phosphate materials. The mass ratio of carbon nanotubes to graphene aerogel is 2:1 to 4:1, and the filling rate in the pores is ≥90%.

3. The dry-process solid-state battery fabrication process as described in claim 1, characterized in that, The molecular weight of the poly(N-isopropylacrylamide) modified PVDF is 50,000 to 150,000. The elastic adhesive is styrene-butadiene rubber modified PTFE; The purity of the nano-silicon is ≥99.9%, and the surface is modified by 1~5nm carbon coating.

4. The dry solid-state battery fabrication process as described in claim 1, characterized in that, When the second powder is frozen, the freezing cooling rate is 10~20℃ / min, the sublimation heating rate is 1~3℃ / min, and the sublimated powder is treated by an airflow of 300~400m / s for 10~20s to remove loose particles on the surface.

5. The dry-process solid-state battery fabrication process as described in claim 1, characterized in that, The protrusions of the carbon-coated aluminum film with the protrusion array are semi-circular protrusions or semi-elliptical protrusions. The radius of the arc at the top of the semi-circular protrusion is 2.5~10μm; the major axis of the semi-elliptical protrusion is 8~25μm, the minor axis is 5~15μm, and the radius of the arc at the top is 1.5~5μm. The porosity of the carbon-coated aluminum film with the bump array is 25%~40%, and the resistivity is ≤5×10⁻⁶. -4 Ω·cm.

6. The dry-process solid-state battery fabrication process as described in claim 1, characterized in that, The pressure for dry spraying natural graphite is 0.3~0.8MPa, and the spraying rate is 5~10g / min; The lithium content of the lithium naphthalene and tetrahydrofuran mixed solution is 0.05~0.1 mol / L, and the total thickness of the composite negative electrode is 60~150 μm.

7. The dry-process solid-state battery fabrication process as described in claim 1, characterized in that, In the study of Li7La3Zr2O 12 The heating rate during calcination is 2~5℃ / min, and the holding time after calcination is completed is 3~4h; The ALD deposition temperature is 120~180℃, the Al2O3 precursor is trimethylaluminum, the ZrO2 precursor is tetrabutylzirconium, and the deposition rate is 0.1~0.3nm / cycle.

8. The dry-process solid-state battery fabrication process as described in claim 1, characterized in that, The composite positive electrode, the solid electrolyte layer, and the composite negative electrode are stacked sequentially. During hot pressing, the upper roller temperature is 60~80℃ and the lower roller temperature is 70~90℃.

9. The dry-process solid-state battery fabrication process as described in claim 1, characterized in that, The multi-level porous positive electrode active material includes the following preparation process: LiNi 0.8 Co 0.1 Mn 0.1 O2 and 5-10 wt% water-soluble pore-forming agent are mixed at a ratio of 1:3 to form a slurry. The water-soluble pore-forming agent is polyvinyl alcohol. Spray drying is carried out under the conditions of inlet air temperature of 200-250℃, outlet air temperature of 80-100℃, and atomization pressure of 0.3-0.6MPa to form spherical particles of 5-10μm. Micron-sized pores of 1-5μm are dispersed inside the spherical particles, and the porosity is 15-25%. Spherical particles are placed in a tubular furnace filled with argon gas. The argon gas purity is ≥99.99%, the flow rate is 100~200 sccm, and the oxygen content in the furnace is ≤100ppm. The furnace is heated, and the heating rate is 5~10℃ / min when the temperature rises from room temperature to 300℃, and 3~5℃ / min when the temperature rises from 300℃ to the target temperature. The target temperature is 400~600℃. After reaching the target temperature, the temperature is maintained for 2~4 hours to remove the water-soluble pore-forming agent, which causes slight sintering of the pore walls of the spherical particles, forming nanopores of 50~500nm with a porosity of 8~12%. After the holding period, argon gas is continuously introduced until the furnace temperature naturally cools down to below 100℃. The sintered particles are removed by screening with a 200-mesh sieve, and then the multi-level porous positive electrode active material with a particle size of 4.5~10.5μm is screened out by an air classifier.

10. A dry-process solid-state battery, manufactured using the dry-process solid-state battery manufacturing process according to any one of claims 1-9, characterized in that, It includes a composite negative electrode, with a solid electrolyte layer at the upper end of the composite negative electrode, and a composite positive electrode at the upper end of the solid electrolyte layer; The composite anode includes a gradient carbon substrate, a composite layer at the upper end of the gradient carbon substrate, and a lithium layer deposited on the outer wall of the gradient carbon substrate and the composite layer. The solid electrolyte layer includes a thick blank, and the outer wall of the thick blank is alternately deposited with an Al2O3-ZrO2 bilayer transition layer. The composite positive electrode includes a membrane, and the lower end of the membrane is provided with a carbon-coated aluminum film with a bump array.

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