Dry-method battery pole piece, preparation method thereof and lithium ion battery

Abstract

The invention provides a dry battery pole piece, a preparation method thereof and a lithium ion battery. The dry-method battery pole piece comprises a self-supporting electrode film, a lithium supplementing layer and a metal current collector layer are sequentially arranged on the surface of one side of the self-supporting electrode film, and the lithium supplementing layer is located between the self-supporting electrode film and the metal current collector layer. The lithium supplement function and the current collection function are integrated, the two problems of uneven lithium supplement and weak interface bonding force of a traditional dry-method pole piece are solved, the interlayer stripping strength is remarkably improved, the mechanical integrity of an electrode structure is guaranteed, the lithium supplement uniformity is achieved, the initial coulombic efficiency of a battery is finally improved, and the battery performance is improved. Meanwhile, the high-temperature cycle life and the fast charging performance of the battery are remarkably improved, and the diversified requirements of new energy automobiles and energy storage systems can be met.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, specifically relating to a dry-process battery electrode, its preparation method, and a lithium-ion battery. Background Technology

[0002] Dry electrode technology, by eliminating the solvent coating and drying processes, boasts advantages such as being environmentally friendly and having high production efficiency, making it a research hotspot in the lithium-ion battery field. Self-supporting electrode films, composed of active materials, conductive agents, and fibrous binders, maintain structural integrity without the need for substrate support, but still face many bottlenecks in their integration with current collectors and performance optimization.

[0003] Currently, the bonding of dry electrodes and current collectors mainly relies on two methods: one is to pre-coat conductive adhesive on the surface of the metal foil current collector and then bond it to the self-supporting film through high-temperature hot pressing. This method not only increases the cost of conductive adhesive materials and the hot pressing process, but the adhesive layer may also introduce additional interfacial impedance. The second method is to use a glue-free composite mode, but this requires a rolling process with extremely high pressure, which can easily lead to damage to the internal active material structure of the electrode and reduce the battery's cycle performance. At the same time, high-capacity electrodes (such as silicon-based and tin-based anodes) suffer from severe irreversible lithium loss during the first charge and discharge process, resulting in a decrease in the battery's initial coulombic efficiency and energy density. Existing lithium replenishment technologies (such as lithium foil adhesion and lithium-rich additives) are mostly independent of the current collector preparation process, requiring additional process steps, and it is difficult to achieve synergistic optimization of lithium replenishment uniformity and current collector bonding stability.

[0004] In summary, the shortcomings of existing technologies include: 1) Poor interfacial adhesion: In traditional composite methods, the bonding force between the dry electrode and the current collector depends on the adhesive layer or mechanical pressure, which easily leads to peeling problems and affects battery cycle life. 2) High process complexity: Steps such as hot pressing and additional lithium replenishment increase the production process, reduce production efficiency, and increase equipment investment costs. 3) Limited energy density: Traditional metal foil current collectors are relatively thick (usually 10-15μm), with a high proportion of inactive materials, which restricts the improvement of battery energy density. 4) Uneven lithium replenishment effect: Independent lithium replenishment processes are difficult to achieve a uniform distribution of lithium on the electrode surface, easily leading to localized lithium excess or deficiency.

[0005] Therefore, how to solve the problems of weak interfacial bonding, complex process, low energy density and uneven lithium replenishment in dry battery electrodes, and achieve the integrated lithium replenishment function and current collector function, is an urgent technical problem to be solved. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a dry-process battery electrode, its preparation method, and a lithium-ion battery. This invention integrates lithium replenishment and current collection functions by stacking a lithium replenishment layer and a metal current collector layer directly onto a self-supporting electrode film. This structural design effectively solves the two major problems of uneven lithium replenishment and weak interfacial bonding in traditional dry-process electrodes. It not only significantly improves interlayer peel strength and ensures the mechanical integrity of the electrode structure but also achieves uniform lithium replenishment, ultimately improving the battery's initial coulombic efficiency. Simultaneously, it significantly improves the battery's high-temperature cycle life and fast-charging performance, meeting the diverse needs of new energy vehicles and energy storage systems.

[0007] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a dry-process battery electrode sheet, the dry-process battery electrode sheet comprising a self-supporting electrode film, wherein a lithium replenishment layer and a metal current collector layer are sequentially disposed on one side surface of the self-supporting electrode film, and the lithium replenishment layer is located between the self-supporting electrode film and the metal current collector layer.

[0008] This invention integrates lithium replenishment and current collection functions by stacking the lithium replenishment layer and the metal current collector layer and directly constructing them on a self-supporting electrode film. This structural design effectively solves the two major problems of uneven lithium replenishment and weak interfacial bonding in traditional dry electrode sheets. It not only significantly improves the interlayer peel strength and ensures the mechanical integrity of the electrode structure, but also achieves uniform lithium replenishment, ultimately improving the battery's initial coulombic efficiency. At the same time, it significantly improves the battery's high-temperature cycle life and fast-charging performance, meeting the diverse needs of new energy vehicles and energy storage systems.

[0009] Preferably, the areal density of the self-supporting electrode film is 100-300 g / m³. 2 For example, it could be 100g / m 2 200g / m 2 Or 300g / m 2 wait.

[0010] Preferably, the thickness of the self-supporting electrode film is 50-200 μm, for example, it can be 50 μm, 100 μm, 150 μm or 200 μm.

[0011] Preferably, the self-supporting electrode film comprises the following components by mass percentage: The active material is 80-95%, for example, it can be 80%, 85%, 90% or 95%, etc.; the conductive agent is 3-15%, for example, it can be 3%, 5%, 10% or 15%, etc.; and the fibrous binder is 2-5%, for example, it can be 2%, 3%, 4% or 5%, etc.

[0012] Preferably, the active material includes any one of ternary active materials, silicon-based active materials, tin-based active materials, or graphite active materials.

[0013] Preferably, the conductive agent includes carbon black and / or acetylene black, etc.

[0014] Preferably, the fibrous binder comprises any one or a combination of at least two of polyvinyl alcohol, polypropylene, or polytetrafluoroethylene.

[0015] Preferably, the lithium replenishment layer is a metallic lithium layer.

[0016] Preferably, the thickness of the lithium replenishment layer is 30-100nm, for example, it can be 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm or 100nm.

[0017] In this invention, an appropriate lithium replenishment layer thickness can effectively improve the overall performance of the battery. If the lithium replenishment layer is too thin, it will lead to a decrease in the battery's initial efficiency and cycle performance, while if the thickness is too thick, it will easily cause lithium plating, dendrite formation, and safety risks.

[0018] Preferably, the metal current collector layer has a gradient structure.

[0019] Along the direction away from the lithium replenishment layer, the metal current collector layer includes a transition layer and a main layer, and the metal in the transition layer forms alloy bonds with the lithium in the lithium replenishment layer.

[0020] In this invention, a gradient structure of "transition layer-main layer" is used to construct the metal current collector layer, which can not only strengthen the interface bonding, but also ensure the stability of current collection.

[0021] Preferably, the metal in the transition layer includes nickel and / or titanium. This invention utilizes the high reactivity of nickel and / or titanium with lithium to form stable alloy bonds, thereby strengthening interfacial bonding.

[0022] Preferably, the thickness of the transition layer is 5-10 nm, for example, it can be 5 nm, 6 nm, 7 nm, 8 nm, 9 nm or 10 nm.

[0023] In this invention, the appropriate thickness of the transition layer can precisely control the degree of interfacial alloying reaction, which avoids insufficient interfacial bonding and increased interfacial impedance due to insufficient thickness, and also prevents stress concentration, microcracks or interlayer delamination caused by excessive thickness in the alloy layer, thereby improving the stability of the interfacial structure and improving the cycle life and charge-discharge reliability of the battery.

[0024] Preferably, the metal in the main body layer includes copper or aluminum.

[0025] It should be noted that copper is used in the main body layer for the negative electrode, while aluminum is used in the main body layer for the positive electrode.

[0026] Preferably, the thickness of the main body layer is 5-8 μm, for example, it can be 5 μm, 6 μm, 7 μm or 8 μm.

[0027] In this invention, a suitable thickness of the main body layer can ensure the stability of current collection.

[0028] Preferably, the main body layer has a porous structure, and the porosity of the main body layer is 15-20%, for example, it can be 15%, 16%, 17% or 18%, etc.

[0029] In this invention, the main body layer has a porous structure with a porosity of 15-20%, which helps to increase the wetting area of ​​the electrolyte.

[0030] Preferably, a protective layer is provided on the outer surface of the main body layer, the protective layer comprising an aluminum oxide layer and / or a lithium fluoride layer.

[0031] In this invention, the use of an alumina layer and / or a lithium fluoride layer as a protective layer can effectively suppress the reaction between the current collector and the electrolyte at high temperatures.

[0032] Preferably, the thickness of the protective layer is 10-20 nm, for example, it can be 10 nm, 12 nm, 14 nm, 16 nm, 18 nm or 20 nm.

[0033] Preferably, a release film is laminated on the outer surface of the metal current collector layer, and the release film is peeled off before the winding or stacking process of battery assembly.

[0034] In this invention, the release film can effectively prevent physical damage, oxidation and contamination of the metal current collector layer surface caused by friction, scratching or environmental contact during the subsequent cutting, die-cutting, transportation and storage of the electrode, thereby ensuring the cleanliness and integrity of the electrode interface and playing a role in temporarily protecting the metal current collector layer. On the other hand, it can be recycled through negative pressure adsorption, realizing recycling and greatly reducing the cost of consumables.

[0035] Preferably, the release film includes a silicone-free fluoroplastic release film or a nano-ceramic coated release film.

[0036] It should be noted that when the main layer is an aluminum layer, a nano-ceramic coated release film is used; when the main layer is a copper layer, a silicone-free fluoroplastic release film is used.

[0037] Preferably, the release film has a peel force of 8-12 g / in, for example, 8 g / in, 9 g / in, 10 g / in, 11 g / in, or 12 g / in. It should be noted that "in" refers to inches.

[0038] In this invention, the release film has a peeling force of 8-12 g / in, which ensures the ease of subsequent release film peeling.

[0039] In a second aspect, the present invention provides a method for preparing a dry-process battery electrode as described in the first aspect, the method comprising the following steps: A self-supporting electrode film is provided as the target substrate.

[0040] A lithium replenishment layer and a metal current collector layer are sequentially prepared on one side surface of the target substrate to obtain the dry-process battery electrode.

[0041] The preparation process provided by this invention is simple and efficient, eliminating the cost of conductive adhesive materials and the steps of hot pressing and independent lithium replenishment. The investment cost is low, and the production cost of a single GWh battery is reduced by about 10%-15%. The elimination of conductive adhesive alone can reduce the cost by 800,000 yuan / GWh. This process is compatible with existing dry electrode production lines, without the need for large-scale modification of the original production lines, which facilitates industrial promotion.

[0042] Preferably, the method for preparing the lithium replenishment layer includes magnetron sputtering.

[0043] Preferably, the parameters in the magnetron sputtering method include: sputtering temperature of 20-80℃, such as 20℃, 30℃, 40℃, 50℃, 60℃, 70℃ or 80℃, etc.; sputtering power of 80-200W, such as 80W, 90W, 100W, 150W or 200W, etc.; and deposition time of 15-60s, such as 15s, 20s, 30s, 40s, 50s or 60s, etc.

[0044] Preferably, ion beam-assisted deposition is also introduced during the preparation of the lithium replenishment layer.

[0045] In this invention, the use of ion beam-assisted deposition technology helps to improve the interfacial bonding between the lithium replenishment layer and the self-supporting electrode film.

[0046] Preferably, the metal current collector layer has a gradient structure, which is prepared by magnetron sputtering or vacuum evaporation.

[0047] Preferably, a release film is laminated on the outer surface of the metal current collector layer, and the release film is peeled off before the winding or stacking process of battery assembly.

[0048] Preferably, the composite process of the release film includes a low-temperature rolling process.

[0049] Preferably, in the low-temperature rolling method, the parameters include: rolling temperature of 60-80℃, for example, 60℃, 70℃ or 80℃, pressure of 0.5-1MPa, for example, 0.5MPa, 0.6MPa, 0.7MPa, 0.8MPa, 0.9MPa or 1MPa, and rolling speed of 5-10m / min, for example, 5m / min, 6m / min, 7m / min, 8m / min, 9m / min or 10m / min.

[0050] By combining the above-mentioned multiple parameters, the present invention can ensure that the release film is tightly bonded to the outer surface of the metal current collector layer without damaging the metal current collector layer.

[0051] Preferably, the preparation method includes the following steps: (1) Provide a self-supporting electrode film as the target substrate; the self-supporting electrode film comprises the following components by mass percentage: 80-95% active material, 3-15% conductive agent, and 2-5% fibrous binder; wherein the active material includes any one of ternary active material, silicon-based active material, tin-based active material or graphite active material.

[0052] (2) A lithium metal layer is deposited by sputtering on one side surface of the target substrate using magnetron sputtering.

[0053] Wherein, when the active material in the self-supporting electrode film is a silicon-based anode material or a tin-based anode material, the parameters of the magnetron sputtering method include: inert atmosphere, sputtering temperature 50-80℃, sputtering power 100-200W, deposition time 30-60s, and lithium metal layer thickness 50-100nm; when the active material in the self-supporting electrode film is a graphite anode material, the parameters of the magnetron sputtering method include: inert atmosphere, sputtering temperature 25-40℃, sputtering power 80-150W, deposition time 15-30s, and lithium metal layer thickness 30-50nm; during the sputtering deposition process, an argon ion beam with an energy of 50-100eV (e.g., 50eV, 60eV, 70eV, 80eV, 90eV, or 100eV, etc.) is introduced to assist deposition.

[0054] (3) Using magnetron sputtering or vacuum evaporation, a transition layer and a main layer are sequentially deposited on the surface of the lithium metal layer to form a gradient structure metal current collector layer.

[0055] The metal in the transition layer includes nickel and / or titanium, with a thickness of 5-10 nm; the metal in the main layer includes copper or aluminum, with a thickness of 5-8 μm; the main layer has a porous structure with a porosity of 15-20%.

[0056] (4) A release film is laminated on the outer surface of the metal current collector layer using a low-temperature rolling process, and the release film is peeled off before the winding or stacking process of battery assembly.

[0057] The parameters for the low-temperature rolling process include: rolling temperature 60-80℃, pressure 0.5-1MPa, and rolling speed 5-10m / min; the release film includes a silicone-free fluoroplastic release film or a nano-ceramic coated release film; and the peel force of the release film is 8-12g / in.

[0058] Thirdly, the present invention provides a lithium-ion battery, the lithium-ion battery comprising the dry-process battery electrode as described in the first aspect.

[0059] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0060] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention integrates the lithium replenishment layer and the metal current collector layer in a stacked manner and directly constructs them on the self-supporting electrode film, thereby realizing the integration of lithium replenishment and current collection functions. This structural design effectively solves the two major problems of uneven lithium replenishment and weak interfacial bonding force of traditional dry electrode sheets. It not only significantly improves the interlayer peel strength and ensures the mechanical integrity of the electrode structure, but also achieves lithium replenishment uniformity, which ultimately improves the first coulombic efficiency of the battery. At the same time, it significantly improves the high-temperature cycle life and fast charging performance of the battery, and can meet the diverse needs of new energy vehicles and energy storage systems.

[0061] (2) The preparation process provided by the present invention is simple and efficient. It eliminates the cost of conductive adhesive materials and the process steps of hot pressing and independent lithium replenishment, resulting in low investment costs. The production cost of a single GWh battery is reduced by about 10%-15%, of which the cost can be reduced by RMB 800,000 / GWh by eliminating the conductive adhesive alone. The process is compatible with the existing dry electrode production line and does not require large-scale modification of the original production line, making it easy to promote industrialization. Detailed Implementation

[0062] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0063] It should be noted that this invention does not limit the specific source of raw materials used in the following embodiments. Those skilled in the art should understand that, provided the technical specifications and purity requirements described in this invention are met, any commercially available product or equivalent substitute with the same or similar function can be used without affecting the implementation effect and scope of protection of this invention. The raw materials mentioned can be obtained from common domestic and international chemical reagent suppliers or through known synthesis methods.

[0064] Example 1 This embodiment provides a dry-process battery electrode sheet, which includes a self-supporting electrode film, and a lithium metal layer and a metal current collector layer are sequentially disposed on one side surface of the self-supporting electrode film.

[0065] The self-supporting electrode film is a silicon-based dry-process negative electrode self-supporting film (model TN-DS-Si-200) produced by Changzhou Tiannai Technology Co., Ltd., with an areal density of 200 g / m³. 2 The thickness is 100μm; the silicon-based dry anode self-supporting film comprises the following components by mass percentage: silicon-carbon composite material (model SCM-45, accounting for 85%) from Ningbo Shanshan New Material Technology Co., Ltd., superconducting carbon black (model SCB-3, accounting for 10%) from Shanghai Superconducting Technology Co., Ltd., and polyvinyl alcohol fiberized binder (model PVA-217, accounting for 5%) from Kuraray Corporation of Japan.

[0066] The lithium metal layer has a thickness of 75 nm; the metal current collector layer has a gradient structure; along the direction away from the lithium metal layer, the metal current collector layer includes a transition layer and a main layer, and the metal in the transition layer forms an alloy bond with the lithium in the lithium replenishment layer; the transition layer is an 8 nm thick nickel layer; the main layer is a 6 μm thick copper layer.

[0067] The outer surface of the metal current collector layer is coated with a release film for temporary protection of the metal current collector layer, and the release film is peeled off before the winding or stacking process of battery assembly; the release film is a silicone-free fluoroplastic release film (model SD-8030, thickness 25μm, peel force 10g / in) from Suzhou Sidike New Material Technology Co., Ltd.

[0068] This embodiment also provides a method for preparing the above-mentioned dry-process battery electrode, the method comprising the following steps: (1) Provide the above-mentioned self-supporting electrode film as the target substrate; place the target substrate in a plasma cleaner (Shenzhen KR-1000 type), introduce argon gas with a purity of 99.99%, and purge for 30s at a flow rate of 10L / min to remove surface dust and residual organic matter. After pretreatment, the surface contact angle of the target substrate is ≤30°.

[0069] (2) The JGP-560 multi-target magnetron sputtering instrument of Beijing Zhongke Keyi Co., Ltd. was used. The vacuum sputtering chamber was first evacuated to a background vacuum of 5×10⁻⁶. -4 Pa, then 99.999% pure argon gas is introduced as a protective gas to maintain a working vacuum of 1×10⁻⁶. -3 Pa.

[0070] A 99.9% high-purity lithium metal target (100mm diameter, 5mm thickness) produced by Qinghai Salt Lake Institute was selected. The sputtering temperature was set to 60℃, the RF sputtering power to 150W, the target-substrate distance to 8cm, and the deposition time to 45s, resulting in a 75nm thick lithium metal layer. During the sputtering deposition process, an ion beam-assisted system (ion source model: IBAD-80) was simultaneously activated at an energy of 80eV and a beam current density of 0.5mA / cm². 2 Argon ion beams are used to bombard the deposited surface vertically.

[0071] (3) Keep the vacuum environment of the multi-target magnetron sputtering instrument unchanged, and replace the target material with a 99.95% pure nickel target (model TA1, diameter 100mm) from Baoji Titanium Industry, and deposit a nickel layer with a thickness of 8nm. The parameters include: argon atmosphere, temperature 60℃, DC sputtering power 80W, and deposition time 10s. Then, replace the target material with a 99.99% oxygen-free copper target (model T2, diameter 100mm) from Jiangxi Copper Industry, and deposit a copper layer with a thickness of 6μm to obtain a metal current collector layer. The parameters include: argon atmosphere, temperature 80℃, DC sputtering power 300W, deposition time 120s, and argon flow rate stabilized at 20sccm.

[0072] (4) Using a low-temperature roll pressing method, a silicone-free fluoroplastic release film is laminated on the outer surface of the metal current collector layer using the XDL-120 low-temperature roll press of Wuxi Lead Intelligent Equipment Co., Ltd., for temporary protection of the metal current collector layer, and the release film is peeled off before the winding or stacking process of battery assembly.

[0073] The parameters in the low-temperature rolling method include: rolling temperature 70℃, linear pressure 0.8MPa, and rolling speed 8m / min.

[0074] test: The dry cell electrode sheet provided in the above embodiment is cut using a laser cutting machine (model G3015) from Shenzhen Dazheng to a size of 100mm×500mm with a cutting accuracy of ±0.1mm and no burrs on the edges. The cut electrode sheet is then placed in a glove box (Super 1220 from Chengdu Microna, with a water and oxygen content of <0.1ppm) and left to stand for 2 hours to eliminate surface stress, thus obtaining the electrode sheet to be assembled.

[0075] I. The interface peel strength of the electrode sheets to be assembled provided in the above embodiments and comparative examples was tested using a Shanghai Instron 5969 universal testing machine. The measured interface peel strength was 18 N / m.

[0076] II. Using the electrode to be assembled as the negative electrode, and paired with the NCM811 positive electrode (area density of 220g / m³) from Hunan Bangpu Circulation Technology Co., Ltd. 2 The electrolyte (containing 1 mol / L lithium hexafluorophosphate) of EC / DEC / EMC (volume ratio 1:1:1) from Shenzhen Xinzhoubang and the Celgard 2325 separator were assembled into a 3Ah soft-pack battery.

[0077] The initial coulombic efficiency of the 3Ah pouch battery was tested (the test method was as follows: at room temperature of 25℃, it was initially charged at 0.5C until fully charged, with a cutoff current of 0.05C, a discharge current of 0.05C, a discharge cutoff voltage of 2.7V, and the discharge capacity / charge capacity = initial coulombic efficiency), and the test result was 98.2%. The energy density at 1C rate and 25℃ was 380Wh / kg, the capacity retention rate after 500 cycles at 60℃ and 1C rate was 85%, and the capacity retention rate after 1C fast charging (4.3V cutoff voltage) was 91%.

[0078] Example 2 This embodiment provides a dry-process battery electrode sheet, which includes a self-supporting electrode film, and a lithium metal layer and a metal current collector layer are sequentially disposed on one side surface of the self-supporting electrode film.

[0079] The self-supporting electrode film is selected from the graphite dry-process negative electrode self-supporting film (model BT-TS-G-150) of Shenzhen BTR New Material Group Co., Ltd., with an areal density of 150 g / m³. 2 The thickness is 80μm; the graphite dry negative electrode self-supporting film comprises the following components by mass percentage: natural graphite (model TG-99, 90%) from Qingdao Taiyue Carbon Materials Co., Ltd., acetylene black (model HP-AB-1, 7%) from Shanghai Huipu Industrial Chemicals Co., Ltd., and polypropylene fiber binder (model PP-301, 3%) from Hyosung Group of South Korea.

[0080] The lithium metal layer has a thickness of 40 nm; the metal current collector layer has a gradient structure; along the direction away from the lithium metal layer, the metal current collector layer includes a transition layer and a main layer, and the metal in the transition layer forms an alloy bond with the lithium in the lithium replenishment layer; the transition layer is a 6 nm thick titanium layer; the main layer is a 5 μm thick copper layer.

[0081] The outer surface of the metal current collector layer is coated with a release film for temporary protection of the metal current collector layer, and the release film is peeled off before the winding or stacking process of battery assembly; the release film is a silicone-free fluoroplastic release film (model SD-8020, thickness 20μm, peel force 8g / in) from Suzhou Sidike New Material Technology Co., Ltd.

[0082] This embodiment also provides a method for preparing the above-mentioned dry-process battery electrode, the method comprising the following steps: (1) Provide the above-mentioned self-supporting electrode film as the target substrate; use 99.99% pure helium as the purging gas, and process it for 20s with a flow rate of 8L / min through Kunshan Jingyuan's JY-800 gas purging machine. The surface resistivity of the target substrate after pretreatment is ≤50mΩ·cm.

[0083] (2) The Kurt J. Lesker sputtering system of Shenyang Scientific Instruments was used. The vacuum sputtering chamber was first evacuated to a background vacuum of 8×10⁻⁶. -4 Pa, then 99.999% pure argon gas is introduced as a protective gas to maintain a working vacuum of 1×10⁻⁶. -3 Pa.

[0084] A 99.9% pure lithium metal target (100mm diameter, 5mm thickness) from Xinjiang Zhonghe was selected. The sputtering temperature was set to 30℃, the RF sputtering power to 120W, the target-substrate distance to 8cm, and the deposition time to 20s, resulting in a 40nm thick lithium metal layer. During the sputtering deposition process, an ion beam-assisted system (ion source model: IBAD-80) was simultaneously activated at an energy of 60eV and a beam current density of 0.3mA / cm². 2 Argon ion beams are used to bombard the deposited surface vertically.

[0085] (3) Keep the vacuum environment of the sputtering system unchanged, and replace the target material with a 99.95% pure titanium target (model TA2, diameter 100mm) from Baoji Baotai, and deposit a titanium layer with a thickness of 6nm. The parameters include: argon atmosphere, DC sputtering power of 60W, and deposition time of 8s. Then, replace the target material with a 99.99% oxygen-free copper target (model T2, diameter 100mm) from Jiangxi Copper, and deposit a copper layer with a thickness of 5μm to obtain a metal current collector layer. The parameters include: argon atmosphere, DC sputtering power of 250W, deposition time of 100s, and argon flow rate stabilized at 18sccm.

[0086] (4) Using a low-temperature roll pressing method, a silicone-free fluoroplastic release film is laminated on the outer surface of the metal current collector layer using the XDL-120 low-temperature roll press of Wuxi Lead Intelligent Equipment Co., Ltd., for temporary protection of the metal current collector layer, and the release film is peeled off before the winding or stacking process of battery assembly.

[0087] The parameters in the low-temperature rolling method include: rolling temperature 65℃, linear pressure 0.6MPa, and rolling speed 10m / min.

[0088] test: The dry cell electrode sheet provided in the above embodiment is cut using a UV laser cutting machine (model JAT-100) from Guangzhou Jiete to a size of 100mm×500mm with an edge roughness Ra≤0.5μm, thus obtaining the electrode sheet to be assembled.

[0089] I. The interface peel strength of the electrode sheets to be assembled provided in the above embodiments and comparative examples was tested using a Shanghai Instron 5969 universal testing machine. The measured interface peel strength was 16 N / m.

[0090] 2. Using the electrode to be assembled as the negative electrode, and combining it with the NCM622 positive electrode from Hunan Bangpu Recycling Technology Co., Ltd., the EC / DEC / EMC (volume ratio 1:1:1) electrolyte from Shenzhen Xinzhoubang (containing 1 mol / L lithium hexafluorophosphate) and the Celgard 2325 separator, a 2Ah soft-pack battery is assembled.

[0091] The initial coulombic efficiency of the 3Ah pouch battery was tested (the test method was as follows: at room temperature of 25℃, it was initially charged at 0.5C until fully charged, with a cutoff current of 0.05C, a discharge current of 0.05C, a discharge cutoff voltage of 2.7V, and the discharge capacity / charge capacity = initial coulombic efficiency), and the test result was 99.1%. The energy density at 1C rate and 25℃ was 350Wh / kg, the capacity retention rate after 500 cycles at 60℃ and 1C rate was 88%, and the capacity retention rate after 1000 cycles at 1C charge and discharge rate at 25℃ was 92%.

[0092] Example 3 This embodiment provides a dry-process battery electrode sheet, which includes a self-supporting electrode film, and a lithium metal layer and a metal current collector layer are sequentially disposed on one side surface of the self-supporting electrode film.

[0093] The self-supporting electrode film is selected from Hunan Bangpu Recycling Technology Co., Ltd.'s NCM811 dry-process positive electrode self-supporting film (model BP-DS-N811-250), with an areal density of 250 g / m³. 2 The thickness is 120μm; the NCM811 dry-process positive electrode self-supporting film comprises the following components by mass percentage: NCM811 powder (model BP-N811, accounting for 92%) from Hunan Bangpu Recycling Technology Co., Ltd., conductive carbon black (model ECP-600JD, accounting for 5%) from Shanghai Superconducting Technology Co., Ltd., and polytetrafluoroethylene fiberized binder (model PTFE-6C, accounting for 3%) from 3M Company of the United States.

[0094] The lithium metal layer has a thickness of 60 nm; the metal current collector layer has a gradient structure; along the direction away from the lithium metal layer, the metal current collector layer includes a transition layer and a main layer, and the metal in the transition layer forms an alloy bond with the lithium in the lithium replenishment layer; the transition layer is a 7 nm thick titanium layer; the main layer is a 7 μm thick aluminum layer.

[0095] The outer surface of the metal current collector layer is coated with a release film for temporary protection of the metal current collector layer, and the release film is peeled off before the winding or stacking process of battery assembly; the release film is a nano-ceramic coated release film (model SW-C100, thickness 30μm, peel force 12g / in) from Suzhou Saiwu Applied Technology Co., Ltd.

[0096] This embodiment also provides a method for preparing the above-mentioned dry-process battery electrode, the method comprising the following steps: (1) Provide the above-mentioned self-supporting electrode film as the target substrate; place the target substrate in a plasma cleaner (Shenzhen KR-1200 type), introduce argon gas with a purity of 99.99%, purge for 40s at a flow rate of 12L / min to remove small molecules of residual adhesive on the surface, and the surface tension of the substrate after pretreatment is ≥40mN / m.

[0097] (2) A JGP-600 magnetron sputtering instrument from Beijing Zhongke Scientific Instruments Co., Ltd. was used. The vacuum sputtering chamber was first evacuated to a background vacuum of 6×10⁻⁶. -4 Pa, then 99.999% pure argon gas is introduced as a protective gas to maintain a working vacuum of 1×10⁻⁶. -3 Pa.

[0098] A 99.9% high-purity lithium metal target (100mm diameter, 5mm thickness) produced by Qinghai Salt Lake Institute was selected. The sputtering temperature was set to 70℃, the RF sputtering power to 180W, the target-substrate distance to 9cm, and the deposition time to 35s, resulting in a 60nm thick lithium metal layer. During the sputtering deposition process, an ion beam-assisted system (ion source model: IBAD-80) was simultaneously activated with an energy of 90eV and a beam current density of 0.4mA / cm². 2 Argon ion beams are used to bombard the deposited surface vertically.

[0099] (3) Keep the vacuum environment of the magnetron sputtering instrument unchanged, and replace the target material with a 99.95% pure titanium target (model TA2, diameter 100mm) from Baoji Baotai. Deposit a titanium layer with a thickness of 7nm. The parameters include: argon atmosphere, DC sputtering power 70W, and deposition time 9s. Then replace the target material with a 99.99% high-purity aluminum target (model 1060, diameter 100mm) from Henan Mingtai. Deposit a copper layer with a thickness of 7μm to obtain a metal current collector layer. The parameters include: argon atmosphere, DC sputtering power 350W, deposition time 140s, and argon flow rate stabilized at 22sccm.

[0100] (4) Using a low-temperature rolling press, a nano-ceramic coating release film is composited on the outer surface of the metal current collector layer using the XDL-120 low-temperature rolling press of Wuxi Lead Intelligent Equipment Co., Ltd., to temporarily protect the metal current collector layer, and the release film is peeled off before the winding or stacking process of battery assembly.

[0101] The parameters in the low-temperature rolling method include: rolling temperature 75℃, linear pressure 0.9MPa, and rolling speed 6m / min.

[0102] test: The dry-process battery electrode sheet provided in the above embodiment was cut using a laser cutting machine (model G3020) from Shenzhen Han's Laser Technology Co., Ltd. to a size of 100mm × 500mm. After cutting, the surface density fluctuation of the active material of the electrode sheet was ≤ ±2g / m³. 2 The electrode to be assembled is obtained.

[0103] I. The interface peel strength of the electrode sheets to be assembled provided in the above embodiments and comparative examples was tested using a Shanghai Instron 5969 universal testing machine. The measured interface peel strength was 17 N / m.

[0104] 2. Using the electrode to be assembled as the positive electrode, and combining it with a graphite negative electrode, Xinzhoubang electrolyte and Xingyuan material separator, a 4Ah soft pack battery is assembled.

[0105] The initial coulombic efficiency of the 4Ah pouch battery was tested (the test method was as follows: at room temperature of 25℃, it was initially charged at 0.5C until fully charged, with a cutoff current of 0.05C, a discharge current of 0.05C, a discharge cutoff voltage of 2.7V, and the discharge capacity / charge capacity = initial coulombic efficiency). The test result was 97.8%. The energy density at 1C and 25℃ was 400Wh / kg, the capacity retention rate after 500 cycles at 60℃ and 1C was 82%, and the capacity decay rate after high-temperature storage (85℃, 48h) was ≤5%.

[0106] Example 4 The difference between this embodiment and Embodiment 1 is that the rolling pressure is adjusted to make the main body layer have a porous structure, and the porosity of the main body layer is 18%.

[0107] The remaining preparation methods and parameters are consistent with those in Example 1.

[0108] Example 5 The difference between this embodiment and Embodiment 1 is that the ALD method is used to deposit an aluminum oxide layer with a thickness of 15 nm on the outer surface of the main body layer.

[0109] The remaining preparation methods and parameters are consistent with those in Example 1.

[0110] Example 6 The difference between this embodiment and Embodiment 1 is that the deposition time is adjusted so that the thickness of the lithium metal layer is 20 nm.

[0111] The remaining preparation methods and parameters are consistent with those in Example 1.

[0112] Example 7 The difference between this embodiment and Embodiment 1 is that the deposition time is adjusted so that the thickness of the lithium metal layer is 120 nm.

[0113] The remaining preparation methods and parameters are consistent with those in Example 1.

[0114] Example 8 The difference between this embodiment and Embodiment 2 is that the metal current collector layer does not contain a transition layer.

[0115] The remaining preparation methods and parameters are consistent with those in Example 2.

[0116] Example 9 The difference between this embodiment and Embodiment 1 is that the deposition time is adjusted so that the thickness of the transition layer is 15 nm.

[0117] The remaining preparation methods and parameters are consistent with those in Example 1.

[0118] Example 10 The difference between this embodiment and Embodiment 1 is that the transition layer is a copper layer.

[0119] The remaining preparation methods and parameters are consistent with those in Example 1.

[0120] Example 11 The difference between this embodiment and Embodiment 1 is that the parameters in the magnetron sputtering method for preparing the lithium metal layer include: setting the sputtering temperature to 30°C, the RF sputtering power to 150W, the target-substrate distance to 8cm, and the deposition time to 30s.

[0121] The remaining preparation methods and parameters are consistent with those in Example 1.

[0122] Example 12 The difference between this embodiment and Embodiment 1 is that no release film is provided.

[0123] The remaining preparation methods and parameters are consistent with those in Example 1.

[0124] Comparative Example 1 This comparative example provides a method for preparing a dry electrode sheet, including the following steps: (1) The same self-supporting electrode film as in Example 1 was used as the target substrate.

[0125] Jiangxi Copper T2 oxygen-free copper foil (model C1100) with a thickness of 10μm was selected, and its surface was pre-coated with Shanghai Kangda conductive adhesive (model KD-600, coating amount 5g / m). 2 (50% solids content).

[0126] (2) Using Wuxi Pioneer's XDL-300 hot press, copper foil is laminated on one side of the self-supporting electrode film. The parameters include: temperature 120℃, pressure 5MPa, and hot pressing time 60s.

[0127] (3) Using Shenzhen Jiyang's JYG-100 roller pressing and laminating machine, a 5μm thick metal lithium foil (purity 99.9%) produced by Qinghai Salt Lake was laminated to the other side of the self-supporting electrode film. The roller pressing pressure was 3MPa to obtain a dry electrode sheet.

[0128] The interface peel strength of the dry electrode sheet provided in the above comparative example was tested using a Shanghai Instron 5969 universal testing machine, and the interface peel strength was measured to be 5.2 N / m.

[0129] The dry electrode sheet provided in the comparative example was cut and used as the negative electrode, and paired with the NCM811 positive electrode (area density of 220 g / m³) from Hunan Bangpu Recycling Technology Co., Ltd. 2 The electrolyte (containing 1 mol / L lithium hexafluorophosphate) of EC / DEC / EMC (volume ratio 1:1:1) from Shenzhen Xinzhoubang and the Celgard 2325 separator were assembled into a 3Ah soft-pack battery.

[0130] The initial coulombic efficiency of the 3Ah pouch battery was tested (the test method was as follows: at room temperature of 25℃, it was initially charged at 0.5C until fully charged, with a cutoff current of 0.05C, a discharge current of 0.05C, a discharge cutoff voltage of 2.7V, and the discharge capacity / charge capacity = initial coulombic efficiency), and the test result was 82.5%; the energy density at 1C rate and 25℃ was 320Wh / kg, the capacity retention rate after 500 cycles at 60℃ and 1C rate was 68%, and the capacity retention rate after 1C fast charging (4.3V cutoff voltage) was 72%.

[0131] Comparative Example 2 The difference between this comparative example and Example 3 is that no lithium metal layer is provided.

[0132] The remaining preparation methods and parameters are consistent with those in Example 3.

[0133] Performance testing The electrode interface peel strength obtained from the above embodiments and comparative tests, as well as the initial coulombic efficiency, energy density, capacity retention rate after 500 cycles, capacity retention rate after 1C fast charging, and capacity decay rate at high temperature storage of the battery were statistically analyzed, as shown in Table 1.

[0134] Table 1 analyze: As shown in Table 1, this invention integrates lithium replenishment and current collection functions by combining the lithium replenishment layer and the metal current collector layer in a stacked manner and directly constructing them on the self-supporting electrode film. This structural design effectively solves the two major problems of uneven lithium replenishment and weak interfacial bonding in traditional dry electrode sheets. It not only significantly improves the interlayer peel strength and ensures the mechanical integrity of the electrode structure, but also achieves uniform lithium replenishment. Ultimately, this improves the battery's initial coulombic efficiency, which can reach up to 99.1%. At the same time, it significantly improves the battery's high-temperature cycle life (capacity retention rate of up to 88% after 500 cycles at 60℃) and fast-charging performance (capacity retention rate of up to 92% after 1C fast charging), which can meet the diverse needs of new energy vehicles and energy storage systems.

[0135] As can be seen from the comparison between Example 1 and Examples 6-7, if the thickness of the lithium metal layer is too small, the amount of lithium replenishment will be insufficient, which will not be able to fully compensate for the irreversible capacity loss in the first cycle of the battery, resulting in a significant decrease in the initial coulombic efficiency of the battery; if the thickness of the lithium metal layer is too large, the excess lithium metal will easily form lithium dendrites, which will pierce the separator and cause an internal short circuit in the battery. At the same time, it will increase the overall thickness of the electrode, reduce the energy density of the battery, and the lithium layer itself will easily fall off, affecting the stability of the electrode structure.

[0136] A comparison of Examples 1 and 8-9 shows that if the metal current collector layer does not contain a transition layer, the electrode interface peel strength decreases significantly. The copper layer cracks after 10 bends, and the initial coulombic efficiency, energy density, and high-temperature cycle life of the resulting battery all decrease significantly. If the transition layer is too thick, it increases the electrode interface contact resistance, leading to deterioration of the battery's fast-charging performance, increased raw material costs, and the excessive thickness of the transition layer can easily cause delamination, thus weakening the interface bonding effect.

[0137] As can be seen from the comparison between Example 1 and Example 10, if the transition layer is a copper layer, the interface affinity between the transition layer and the lithium replenishment layer and the metal current collector layer is poor, and it cannot play an effective connecting role. The peel strength between the electrode layers decreases, and although the copper layer itself has excellent conductivity, it is not flexible enough. The electrode is easy to break when it is bent, which leads to fluctuations in the electrochemical performance of the battery, and the initial coulombic efficiency and high temperature cycle life are both poor.

[0138] A comparison of Examples 1 and 11 shows that if the active material in the self-supporting electrode film is a silicon-carbon composite material, and the lithium metal layer is prepared using the magnetron sputtering method with the parameters described above, the interface between the lithium metal layer and the silicon-carbon active material is not tightly bonded, and gaps are easily formed. This leads to obstructed lithium ion transport during lithium replenishment, poor lithium replenishment uniformity, poor initial coulombic efficiency of the battery, and the lithium layer is easily detached during the volume expansion of the silicon-carbon material, affecting the cycle stability of the battery.

[0139] A comparison of Examples 1 and 12 shows that if a release film is not provided, the lithium replenishment layer is prone to sticking to the mold during the preparation process, resulting in damage to the surface of the lithium replenishment layer and uneven thickness. This not only affects the integrity of the electrode appearance but also causes deviations in the amount of lithium replenishment, resulting in large fluctuations in the initial coulombic efficiency of the battery. At the same time, the surface roughness of the electrode increases, making it easy to scratch the separator during subsequent assembly, which poses a safety hazard.

[0140] As can be seen from the comparison between Example 1 and Comparative Example 1, if the dry electrode sheet prepared by the preparation method provided in the Comparative Example is used, not only will the interfacial peel strength of the electrode sheet decrease and the electrochemical performance of the battery be reduced, but the production cost per GWh will also be significantly increased compared with Example 1.

[0141] As can be seen from the comparison between Example 1 and Comparative Example 2, without the lithium metal layer, it is difficult to achieve the lithium replenishment function, the irreversible capacity loss of the battery during the first cycle increases significantly, the initial coulombic efficiency is low, and the capacity decay rate of the battery during the cycle is accelerated, which cannot meet the performance requirements of new energy vehicles and energy storage systems.

[0142] It should be noted that the present invention is illustrated through the above embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, additions of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A dry-process battery electrode, characterized in that, The dry-process battery electrode includes a self-supporting electrode film. A lithium replenishment layer and a metal current collector layer are sequentially disposed on one side surface of the self-supporting electrode film, and the lithium replenishment layer is located between the self-supporting electrode film and the metal current collector layer.

2. The dry-process battery electrode according to claim 1, characterized in that, The areal density of the self-supporting electrode film is 100-300 g / m³. 2 ; And / or, the thickness of the self-supporting electrode film is 50-200 μm; And / or, the self-supporting electrode film comprises the following components by mass percentage: Active material 80-95%, conductive agent 3-15%, fibrous binder 2-5%; The active material includes any one of ternary active materials, silicon-based active materials, tin-based active materials, or graphite active materials; And / or, the lithium replenishment layer is a metallic lithium layer; And / or, the thickness of the lithium replenishment layer is 30-100 nm.

3. The dry-process battery electrode according to claim 1, characterized in that, The metal current collector layer has a gradient structure; Along the direction away from the lithium replenishment layer, the metal current collector layer includes a transition layer and a main layer, and the metal in the transition layer forms alloy bonds with the lithium in the lithium replenishment layer.

4. The dry-process battery electrode according to claim 3, characterized in that, The metal in the transition layer includes nickel and / or titanium; And / or, the thickness of the transition layer is 5-10 nm; And / or, the metal in the main body layer includes copper or aluminum; And / or, the thickness of the main body layer is 5-8 μm; And / or, the main body layer has a porous structure, and the porosity of the main body layer is 15-20%; And / or, a protective layer is provided on the outer surface of the main body layer, the protective layer comprising an aluminum oxide layer and / or a lithium fluoride layer; The thickness of the protective layer is 10-20 nm.

5. The dry-process battery electrode according to claim 1, characterized in that, A release film is laminated on the outer surface of the metal current collector layer, and the release film is peeled off before the winding or stacking process of battery assembly. The release film includes a silicone-free fluoroplastic release film or a nano-ceramic coated release film; The release film has a peel force of 8-12 g / in.

6. A method for preparing a dry-process battery electrode as described in any one of claims 1-5, characterized in that, The preparation method includes the following steps: A self-supporting electrode film is provided as the target substrate; A lithium replenishment layer and a metal current collector layer are sequentially prepared on one side surface of the target substrate to obtain the dry-process battery electrode.

7. The preparation method according to claim 6, characterized in that, The method for preparing the lithium replenishment layer includes magnetron sputtering. In the magnetron sputtering method, the parameters include: sputtering temperature 20-80℃, sputtering power 80-200W, and deposition time 15-60s.

8. The preparation method according to claim 6, characterized in that, Ion beam-assisted deposition is also introduced during the preparation of the lithium replenishment layer; And / or, the metal current collector layer has a gradient structure, which is prepared by magnetron sputtering or vacuum evaporation. And / or, a release film is laminated on the outer surface of the metal current collector layer, and the release film is peeled off before the winding or stacking process of battery assembly. The composite process of the release film includes a low-temperature roll pressing method; In the low-temperature rolling method, the parameters include: rolling temperature 60-80℃, pressure 0.5-1MPa, and rolling speed 5-10m / min.

9. The preparation method according to claim 6, characterized in that, The preparation method includes the following steps: (1) A self-supporting electrode film is provided as the target substrate; the self-supporting electrode film comprises the following components by mass percentage: 80-95% active material, 3-15% conductive agent, and 2-5% fibrous binder; wherein the active material includes any one of ternary active material, silicon-based active material, tin-based active material or graphite active material; (2) A lithium metal layer is deposited by sputtering on one side surface of the target substrate using magnetron sputtering. Wherein, when the active material in the self-supporting electrode film is a silicon-based anode material or a tin-based anode material, the parameters of the magnetron sputtering method include: inert atmosphere, sputtering temperature 50-80℃, sputtering power 100-200W, deposition time 30-60s, and lithium metal layer thickness 50-100nm; when the active material in the self-supporting electrode film is a graphite anode material, the parameters of the magnetron sputtering method include: inert atmosphere, sputtering temperature 20-45℃, sputtering power 80-150W, deposition time 15-30s, and lithium metal layer thickness 30-50nm; an argon ion beam with energy of 50-100eV is introduced to assist in the sputtering deposition process; (3) Using magnetron sputtering or vacuum evaporation, a transition layer and a main layer are sequentially deposited on the surface of the lithium metal layer to form a gradient structure metal current collector layer; The transition layer comprises nickel and / or titanium, with a thickness of 5-10 nm; the main layer comprises copper or aluminum, with a thickness of 5-8 μm; the main layer has a porous structure with a porosity of 15-20%. (4) A release film is laminated on the outer surface of the metal current collector layer using a low-temperature rolling process, and the release film is peeled off before the winding or stacking process of battery assembly. The parameters for the low-temperature rolling process include: rolling temperature 60-80℃, pressure 0.5-1MPa, and rolling speed 5-10m / min; the release film includes a silicone-free fluoroplastic release film or a nano-ceramic coated release film; and the peel force of the release film is 8-12g / in.

10. A lithium-ion battery, characterized in that, The lithium-ion battery includes the dry-process battery electrode as described in any one of claims 1-5.

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