A cylindrical battery steel casing structure and battery

Abstract

This application provides a cylindrical battery steel shell structure and a battery. The cylindrical battery steel shell structure is a hollow structure, including a shell and a composite coating on the inner surface of the shell. The shell has multiple micron-sized protrusions, with a height of 5-10 μm, a width of 5-10 μm, and a spacing of 10-20 μm between adjacent protrusions. The composite coating sequentially includes a transition metal layer, an aluminum layer, and an aluminum oxide film layer. The thickness of the transition metal layer on the inner surface of the shell is 1-3 μm. The aluminum layer on the transition metal layer is pure aluminum or an aluminum-graphene composite material with a thickness of 5-10 μm. The aluminum oxide film layer on the aluminum layer has a thickness of 2-5 μm. The composite coating structure enhances the interfacial bonding between the coating and the steel shell, improving corrosion resistance and reliability. The composite coating on the inner wall of the steel shell effectively isolates the electrolyte from the steel shell, inhibits iron ion deposition, and solves the internal short circuit problem caused by iron ion deposition.

Description

Technical Field

[0001] This application relates to the field of cylindrical battery technology, and more particularly to a cylindrical battery steel shell structure and battery. Background Technology

[0002] Cylindrical batteries, as an important technology branch in the field of power energy storage, are widely used in new energy vehicle power systems, portable energy storage devices, and high-end consumer electronics due to their standardized cylindrical geometry, high energy density integration capabilities, and large-scale production advantages. Their core structure typically consists of a positive electrode, a negative electrode, a separator, an electrolyte, and a packaging shell. Among these, steel shells have become the preferred packaging solution for mainstream cylindrical batteries due to their excellent mechanical strength, good processability, and cost-effectiveness. With the evolution of solid-state battery technology and the increasing demand for fast charging, the complexity of the internal chemical environment of the battery has significantly increased, placing higher demands on the corrosion resistance and interface stability of the steel shell.

[0003] Currently, cylindrical batteries commonly use steel casings as their encapsulation structure, which offers advantages such as high mechanical strength and controllable cost. However, during long-term storage or cyclic use, acidic substances in the electrolyte can corrode the inner wall of the steel casing, leading to the loss of iron ions (Fe²⁺). 2+ / Fe 3+ These iron ions can migrate to the surfaces of the positive and negative electrodes through the electrolyte, potentially causing dendrite growth or micro-short circuits, ultimately leading to battery capacity decay, internal short circuit failure, or even safety hazards.

[0004] To address the corrosion problem of steel casings, existing technologies primarily utilize stainless steel casings coated with polymer or single-metal protective layers. However, stainless steel casings are costly and difficult to manufacture; polymer coatings suffer from poor adhesion and easy peeling, resulting in a significant decline in protective performance after long-term service; single-metal layers (such as nickel or copper) have insufficient interfacial bonding and limited protective capabilities, failing to effectively prevent electrolyte penetration. Furthermore, while aluminum casings possess some corrosion resistance, their low mechanical strength makes them difficult to control during cylindrical battery manufacturing and packaging processes, hindering large-scale mass production. Therefore, improving the interfacial bonding strength between the steel casing and the coating, and enhancing the reliability of the corrosion barrier while maintaining cost control, has become a pressing technical challenge in the cylindrical battery field. Utility Model Content

[0005] This application provides a cylindrical battery steel shell structure and battery to solve the problem in the prior art that during long-term storage or cyclic use of batteries, acidic substances in the electrolyte will corrode the inner wall of the steel shell, causing iron ions to be deposited and migrate to the positive and negative electrode surfaces through the electrolyte, which may cause dendrite growth or micro-short circuits, ultimately leading to battery capacity decay and internal short circuit failure.

[0006] This application provides a cylindrical battery steel shell structure, the steel shell structure is a hollow structure, the steel shell structure includes a shell and a composite coating disposed on the inner surface of the shell;

[0007] The shell has multiple micron-sized protrusions, the height of which is 5 to 10 μm, the width of which is 5 to 10 μm, and the spacing between adjacent protrusions is 10 to 20 μm.

[0008] The composite coating sequentially comprises a transition metal layer, an aluminum layer, and an aluminum oxide thin film layer; wherein, the thickness of the transition metal layer disposed on the inner surface of the housing is 1-3 μm, and the transition metal layer is a zinc layer or a titanium layer; the aluminum layer disposed on the transition metal layer is pure aluminum or an aluminum-graphene composite material, and the thickness of the aluminum layer is 5-10 μm; the aluminum oxide thin film layer disposed on the aluminum layer has a thickness of 2-5 μm.

[0009] The cylindrical battery steel shell structure provided in this application enhances the interfacial bonding between the coating and the steel shell by adjusting the inner surface of the cylindrical battery steel shell structure to a composite coating structure, thereby improving corrosion resistance and reliability. Simultaneously, the uneven structure formed by multiple protrusions on the shell increases the actual surface area of ​​the steel shell by 2 to 3 times. The composite aluminum coating layer is embedded in the recesses of the inner wall of the steel shell, effectively isolating the electrolyte from the steel shell, inhibiting iron ion deposition, and solving the internal short circuit problem caused by iron ion deposition.

[0010] In some possible implementations, the area of ​​the protrusion accounts for 40% to 60% of the total area of ​​the inner surface of the steel shell.

[0011] In some possible implementations, the cross-sectional shape of the protrusion is one of trapezoidal, semi-circular, or rectangular.

[0012] In some possible implementations, when the protrusion is trapezoidal, the base width of the protrusion is 5 to 10 μm, and the apex angle of the protrusion is 60 to 90°.

[0013] In some possible implementations, the surface roughness of the protrusion is 3.2–6.3 μm.

[0014] In some possible implementations, when the aluminum layer is an aluminum-graphene composite material, the mass content of the graphene is 0.5-2%, and the thickness of the aluminum layer is 6-8 μm.

[0015] In some possible implementations, when the aluminum layer is pure aluminum, the aluminum layer is uniformly doped with nano-sized ceramic particles, the proportion of which is 5-30 vol%, and the average particle size is ≤100 nm.

[0016] In some possible implementations, the porosity of the alumina film layer is less than or equal to 5%.

[0017] In some possible implementations, a carbon-based functional layer is added between the aluminum metal layer and the aluminum oxide film layer. The material of the carbon-based functional layer is graphene, carbon nanotubes, or diamond-like carbon, and the thickness is 0.1 to 2 μm.

[0018] Secondly, this application also provides a cylindrical battery, including the cylindrical battery steel shell structure described in the first aspect.

[0019] As described above, this application provides a cylindrical battery steel shell structure and a battery. The cylindrical battery steel shell structure is a hollow structure, comprising a shell and a composite coating disposed on the inner surface of the shell. The shell has multiple micron-sized protrusions, each with a height of 5-10 μm, a width of 5-10 μm, and a spacing of 10-20 μm between adjacent protrusions. The composite coating sequentially comprises a transition metal layer, an aluminum layer, and an aluminum oxide film layer. The thickness of the transition metal layer disposed on the inner surface of the shell is 1-3 μm, and the transition metal layer is a zinc layer or a titanium layer. The aluminum layer disposed on the transition metal layer is pure aluminum or an aluminum-graphene composite material, with a thickness of 5-10 μm. The aluminum oxide film layer disposed on the aluminum layer has a thickness of 2-5 μm. The composite coating structure enhances the interfacial bonding between the coating and the steel shell, improving corrosion resistance and reliability. The concave-convex structure formed by multiple protrusions on the shell increases the actual surface area of ​​the inner surface of the steel shell by 2 to 3 times. The composite aluminum plating layer is embedded in the concave area through "mechanical locking", and the peel strength is increased to 100N / cm. At the same time, the composite plating layer on the inner wall of the steel shell, combined with the protrusions, effectively isolates the electrolyte from the steel shell, inhibits the precipitation of iron ions, and solves the problem of internal short circuit caused by the precipitation of iron ions. Attached Figure Description

[0020] To more clearly illustrate the technical solution of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of a cylindrical battery steel casing structure according to an embodiment of this application;

[0022] Figure 2 This is an enlarged schematic diagram of the cylindrical battery steel shell structure of one embodiment of this application regarding point A.

[0023] Illustration:

[0024] Wherein, 1-shell; 11-protrusion; 2-composite coating; 21-transition metal layer; 22-metallic aluminum layer; 23-alumina thin film layer. Detailed Implementation

[0025] The embodiments described in the following examples do not represent all embodiments consistent with this application. They are merely examples of systems and methods consistent with some aspects of this application as detailed in the claims.

[0026] Cylindrical batteries, as an important technology branch in the field of power energy storage, are widely used in new energy vehicle power systems, portable energy storage devices, and high-end consumer electronics due to their standardized cylindrical geometry, high energy density integration capabilities, and large-scale production advantages. Their core structure typically consists of a positive electrode, a negative electrode, a separator, an electrolyte, and a packaging shell. Among these, steel shells have become the preferred packaging solution for mainstream cylindrical batteries due to their excellent mechanical strength, good processability, and cost-effectiveness. With the evolution of solid-state battery technology and the increasing demand for fast charging, the complexity of the internal chemical environment of the battery has significantly increased, placing higher demands on the corrosion resistance and interface stability of the steel shell.

[0027] Currently, cylindrical batteries commonly use steel casings as their encapsulation structure, which offers advantages such as high mechanical strength and controllable cost. However, during long-term storage or cyclic use, acidic substances in the electrolyte can corrode the inner wall of the steel casing, leading to the loss of iron ions (Fe²⁺). 2+ / Fe 3+ These iron ions can migrate to the surfaces of the positive and negative electrodes through the electrolyte, potentially causing dendrite growth or micro-short circuits, ultimately leading to battery capacity decay, internal short circuit failure, or even safety hazards.

[0028] To address the corrosion problem of steel casings, existing technologies mostly use stainless steel casings, surface coatings with polymer layers, or single metal protective layers. However, stainless steel casings are expensive and difficult to process; polymer coatings suffer from poor adhesion and easy peeling, resulting in a significant decrease in protective performance after long-term service; single metal layers (such as nickel or copper) have insufficient interfacial bonding strength and limited protective capabilities, making it difficult to effectively prevent electrolyte penetration. Furthermore, while aluminum casings possess some corrosion resistance, their low mechanical strength makes them difficult to control during cylindrical battery rolling and packaging processes, hindering large-scale mass production. Therefore, how to improve the interfacial bonding strength between the steel casing and the coating, and enhance the reliability of the corrosion barrier, while ensuring cost control, has become a pressing technical challenge in the cylindrical battery field.

[0029] Therefore, to address the problem in existing technologies where acidic substances in the electrolyte corrode the inner wall of the steel casing during long-term storage or cyclic use, leading to iron ion deposition, which then migrates to the positive and negative electrode surfaces via the electrolyte, potentially causing dendrite growth or micro-short circuits, ultimately resulting in battery capacity decay and internal short-circuit failure, this application provides a cylindrical battery steel casing structure and battery. By adjusting the inner surface of the cylindrical battery steel casing structure to a composite coating structure, the interfacial bonding between the coating and the steel casing is enhanced, improving corrosion resistance and reliability. Simultaneously, the composite aluminum coating on the inner wall of the steel casing effectively isolates the electrolyte from the steel casing, inhibiting iron ion deposition and solving the internal short-circuit problem caused by iron ion deposition.

[0030] In some embodiments, this application provides a cylindrical battery steel shell structure, such as... Figures 1 to 2 As shown, the steel shell structure is a hollow structure, and the steel shell structure includes a shell 1 and a composite coating 2 disposed on the inner surface of the shell 1;

[0031] The housing 1 is provided with a plurality of micron-sized protrusions 11, the height of the protrusions 11 is 5 to 10 μm, the width of the protrusions 11 is 5 to 10 μm, and the spacing between adjacent protrusions 11 is 10 to 20 μm;

[0032] The composite coating 2 sequentially includes a transition metal layer 21, an aluminum layer 22, and an aluminum oxide film layer 23; wherein, the thickness of the transition metal layer 21 disposed on the inner surface of the housing 1 is 1 to 3 μm, and the transition metal layer 21 is a zinc layer or a titanium layer; the aluminum layer 22 disposed on the transition metal layer 21 is pure aluminum or an aluminum-graphene composite material, and has a thickness of 5 to 10 μm; the aluminum oxide film layer 23 disposed on the aluminum layer 22 has a thickness of 2 to 5 μm.

[0033] The cylindrical battery steel shell structure 1 provided in this application has micron-level protrusions 11 on its inner surface, forming a three-dimensional rough surface with alternating peaks and valleys. When the composite coating 2 is embedded in the gaps between the protrusions 11, it fits perfectly, forming an interlocking structure. The protrusions 11 increase the actual contact area of ​​the inner surface of the steel shell by 2-3 times, and its peel strength is increased from 30 N / cm of the traditional smooth surface to 100 N / cm, reducing the risk of coating peeling by 80%. During the thermal expansion / contraction caused by battery charge and discharge cycles, the structure of the protrusions 11 can buffer the interfacial stress between the coating and the steel shell, inhibiting coating cracking.

[0034] In this embodiment, the height of the protrusion 11 is preferably 5 to 10 μm; for example, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, etc.

[0035] In this embodiment, the width of the protrusion 11 is preferably 5 to 10 μm; for example, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, etc.

[0036] In this embodiment, the spacing between adjacent protrusions 11 is preferably 10 to 20 μm; for example, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm.

[0037] In this embodiment, the protrusions 11 on the inner surface of the housing 1 can be prepared by sandblasting or chemical etching.

[0038] By setting the height and width of the protrusion 11 within the above range, the actual area of ​​the inner surface of the steel shell is increased by 2-3 times compared with the smooth surface. The increased surface area will directly increase the contact point between the composite coating and the steel shell, greatly improve the peel strength, and reduce the risk of coating peeling off.

[0039] The height of the protrusion 11 also has a certain impact on the peel strength and corrosion resistance. If the height of the protrusion 11 is <5μm, the embedding depth is insufficient, which reduces the locking effect and the peel strength may be less than 60N / cm.

[0040] Furthermore, the height and width of the protrusion 11 determine the electrolyte permeation path. Setting the height and width of the protrusion 11 within the aforementioned range can extend the electrolyte permeation path. For example, when the spacing between adjacent protrusions 11 is 10–20 μm, the width of the formed electrolyte permeation channel is 10–20 μm, and the protrusion height is 5–10 μm, forming a rectangular channel with an aspect ratio of 0.5–1. According to fluid dynamics theory, the diffusion path length of the electrolyte in this type of channel is longer than the straight-line distance. When h = 5–10 μm and w = 10–20 μm, the elongation coefficient is 1.12–1.58, meaning the path length is extended by 12%–58%. Therefore, the corrosion penetration time of the steel shell structure is longer than that of the smooth surface, which can significantly delay the onset of corrosion of the steel shell.

[0041] The depression created by protrusion 11 generates a retention effect, which affects the diffusion of the electrolyte and thus the corrosion rate. When the width of protrusion 11 is large (e.g., the width of protrusion 11 > 10 μm), the electrolyte flows through quickly and cannot form effective retention. When the width of protrusion 11 is 5–10 μm, the overall corrosion rate can be reduced by 60%–70% due to the extended diffusion path.

[0042] The composite coating structure in this embodiment combines a transition metal layer, an aluminum layer, and an aluminum oxide thin film layer to create a three-dimensional protective system with strong adhesion, high corrosion resistance, and excellent thermal conductivity. This structural improvement overcomes the performance bottlenecks of single materials (such as insufficient aluminum shell strength and easy aging of polymer coatings), and through the synergistic effect of material combinations (such as the electrochemical matching of zinc and aluminum and the oxide composite of titanium and aluminum), it extends the lifespan of high-energy-density cylindrical batteries.

[0043] In this embodiment, the transition metal layer 21 is preferably a zinc layer or a titanium layer. The zinc layer or titanium layer forms an Fe-Zn alloy layer or a Ti-N interface layer with the steel shell through atomic-level diffusion. The strength jumps from 10-20 MPa of traditional physical coatings to over 50 MPa, completely solving the defect of easy peeling of traditional coatings. The interdiffusion layer (Fe-Zn alloy layer or Ti-N interface layer) formed by metallurgical bonding has a thickness of 0.5-1 μm, which is 2-3 orders of magnitude higher than the van der Waals bond strength of physical adsorption. Therefore, this transition metal layer 21 can withstand the frequent thermal expansion and contraction stress during battery cycling, thereby improving the life of the cylindrical battery.

[0044] The transition metal layer 21, through metallurgical bonding with the steel shell, significantly enhances the interfacial bonding strength between the steel shell and the coating. This strong bond prevents the coating from peeling off during use, thereby improving the durability and reliability of the steel shell. The transition metal layer 21 can act as a sacrificial anode, preferentially corroding to protect the steel shell and reduce iron ion deposition. The aluminum layer 22 and the alumina film layer 23 form a dense barrier, effectively preventing contact between the electrolyte and the steel shell, preventing acidic substances in the electrolyte from corroding the steel shell, thus extending the battery's lifespan.

[0045] In this embodiment, the aluminum layer 22 is preferably pure aluminum or aluminum-graphene composite material; since pure aluminum is a conductive medium, it will prevent the steel shell from directly contacting the electrolyte, thus avoiding the formation of a corrosion cell of "Fe|electrolyte|positive electrode".

[0046] Due to the high electrical conductivity and hydrophobicity of aluminum-graphene composites, their application in composite coatings can further reduce electrolyte adsorption and delay corrosion initiation. Simultaneously, graphene's extremely high thermal conductivity, significantly superior to that of pure aluminum, helps manage battery heat and prevent thermal runaway. The addition of graphene significantly improves the mechanical strength and toughness of the aluminum layer, making it less prone to fracture or deformation under mechanical stress. Furthermore, graphene's excellent barrier properties further enhance the corrosion resistance of the aluminum layer, reducing electrolyte erosion.

[0047] The alumina thin film layer 23 possesses extremely high chemical stability and density, effectively preventing acidic substances (such as HF) in the electrolyte from penetrating to the steel shell surface. This prevents direct corrosion of the steel shell by the electrolyte and reduces the precipitation of iron ions. By blocking electrolyte penetration, the alumina thin film layer 23 effectively prevents iron ions inside the steel shell from migrating to the positive or negative electrode surface of the battery. Ultimately, this reduces the risk of dendrite growth and micro-short circuits, thereby improving battery safety and storage life. The alumina thin film layer 23 exhibits excellent corrosion resistance, further protecting the steel shell from electrolyte erosion. Simultaneously, the dense structure and high hardness of the alumina thin film layer 23 improve the overall mechanical strength and stability of the coating, which helps maintain the integrity of the coating during long-term battery use, preventing peeling or damage.

[0048] The alumina thin film layer 23 has a dense oxide film structure and low porosity, which can effectively block the penetration of electrolyte. This barrier property can further prevent electrolyte corrosion of the steel shell, improving the overall performance and reliability of the battery. The metallic aluminum layer 22 has good thermal and electrical conductivity, which can improve the thermal management and electrical conductivity of the battery.

[0049] In this embodiment, the transition metal layer 21 can be prepared by electroplating or sputtering; the aluminum metal layer 22 can be prepared by magnetron sputtering or co-sputtering; and the aluminum oxide thin film layer 23 can be prepared by anodic oxidation.

[0050] In this embodiment, the protrusions 11 in the steel shell structure and the recessed gaps formed by the composite coating 2 constitute a "zigzag channel," extending the path length of the electrolyte from the steel shell surface to the substrate by 30%-50%. According to Fick's diffusion law, this path extension significantly reduces the diffusion rate and slows down the corrosion of the steel shell by acidic substances such as HF. The composite coating effectively inhibits the corrosion of the steel shell by acidic substances in the electrolyte and reduces the precipitation of iron ions. The reduction of iron ions prevents dendrite growth and micro-short circuits, thereby improving the safety and stability of the battery. The combination of the composite coating and the micron-level uneven structure on the inner surface of the steel shell increases the mechanical anchoring area between the coating and the steel shell, enhancing its anti-peeling ability. This mechanical anchoring force helps maintain the integrity of the coating during long-term battery use and prevents coating peeling.

[0051] In this embodiment, the area of ​​the protrusions 11 accounts for 40-60% of the total area inside the steel shell, that is, the area of ​​the protruding entity accounts for the proportion of the total surface area of ​​the inner surface of the steel shell. The area of ​​a single protrusion includes both its side area and top surface area. The presence of the aforementioned proportion of protrusions 11 on the inner surface of the steel shell allows the coating and protrusions 11 to form a tight, interlocking structure during the deposition of the composite aluminum coating on this inner surface, ensuring perfect integration. This allows the composite coating 2 to adhere more firmly to the inner surface of the steel shell, reducing the risk of coating peeling. The 40-60% proportion of the protrusions 11 to the total area inside the steel shell increases the surface area of ​​the inner surface, allowing the composite coating 2 to more comprehensively cover the inner surface of the steel shell. This more comprehensive coating coverage reduces the chance of electrolyte directly contacting the steel shell. Simultaneously, the larger surface area helps to more effectively conduct heat, improving the battery's thermal management performance, preventing overheating, and enhancing the overall performance and safety of the battery. The design of the protrusion 11, which accounts for 40-60% of the total area inside the steel shell, plays multiple roles in the cylindrical battery steel shell structure, such as enhancing mechanical anchoring force, improving corrosion resistance, improving thermal management, and increasing structural strength.

[0052] In this embodiment, the cross-sectional shape of the protrusion 11 is one of trapezoidal, semi-circular or rectangular.

[0053] For example, the trapezoidal protrusion 11 can provide a larger contact area and stronger mechanical anchoring force. With a wider base and smaller apex, the trapezoidal protrusion 11 can more effectively embed the composite aluminum plating layer, increasing the bonding strength between the plating and the steel shell and reducing the risk of plating peeling. Because the trapezoidal protrusion 11 provides a larger mechanical anchoring area, the plating's anti-peeling ability is significantly improved, enabling it to better resist mechanical stress during battery charge-discharge cycles.

[0054] The semi-circular protrusion 11 provides a smooth transition and uniform mechanical anchoring force. The semi-circular shape helps reduce stress concentration and provides more uniform coating adhesion. The semi-circular protrusion 11 provides uniform mechanical anchoring force, resulting in more even adhesion of the composite coating to the inner surface of the steel shell and reducing the risk of localized peeling. The semi-circular shape helps disperse stress, reducing coating cracks or peeling caused by stress concentration and improving coating durability.

[0055] The rectangular cross-section protrusion 11 can provide higher mechanical strength and stability, making the composite coating adhere more strongly to the inner surface of the steel shell, better resisting mechanical stress, increasing the bonding strength between the coating and the steel shell, and reducing the risk of coating peeling.

[0056] In some embodiments, when the protrusion 11 is trapezoidal, the bottom edge of the protrusion 11 is 5-10 μm wide, the apex angle of the protrusion 11 is 60-90°, and the top edge of the protrusion 11 is 3-6 μm wide.

[0057] Setting the base width within the range of 5–10 micrometers provides sufficient contact area, allowing the composite coating to embed more firmly into the recesses between the protrusions 11, increasing mechanical anchoring force. The apex angle, within the range of 60°–90°, creates a relatively gentle slope, making it easier for the coating to evenly cover the protrusions and recesses during deposition, enhancing adhesion. The design of the trapezoidal protrusion's base width and apex angle allows the composite coating to embed more firmly into the recesses on the inner surface of the steel shell, forming a stronger locking structure and increasing the coating's resistance to peeling. The trapezoidal protrusion design increases the mechanical strength of the inner surface of the steel shell, making it less prone to deformation or damage under internal pressure and external impact, improving the battery's structural stability and safety.

[0058] In some embodiments, the surface roughness of the protrusion 11 is 3.2 to 6.3 μm.

[0059] Setting the surface roughness within the range of 3.2–6.3 μm significantly increases the mechanical anchoring force between the composite coating 2 and the steel shell, allowing the coating to adhere more firmly to the inner surface of the steel shell and reducing the possibility of peeling. The rough surface provides more mechanical engagement points, resulting in a tighter bond between the coating and the steel shell, enhancing the coating's adhesion and durability. By increasing the surface roughness, the composite coating 2 can more comprehensively cover the inner surface of the steel shell, forming a denser protective layer, reducing electrolyte penetration, inhibiting iron ion deposition, and improving battery safety and storage life.

[0060] In some embodiments, when the aluminum layer 22 is an aluminum-graphene composite material, the mass content of the graphene is 0.5-2%, and the thickness of the aluminum layer 22 is 6-8 μm.

[0061] A thickness of 6–8 μm ensures a sufficient number of graphene particles are uniformly distributed within the aluminum matrix, forming an effective reinforcing network. This allows the aluminum layer 22 to better resist deformation and cracking when subjected to internal battery pressure and external impact forces, improving the overall structural stability and mechanical strength of the steel shell and enhancing battery safety.

[0062] Doping aluminum layers with 0.5%–2% graphene by mass can form a highly efficient electron conduction network within the aluminum layer. This accelerates the electron conduction speed of the composite material, thereby improving the conductivity of the metallic aluminum layer. Uniformly distributed graphene can improve the current distribution within the aluminum layer. During battery operation, a stable current distribution can prevent excessively high local current density, reduce battery performance degradation and safety hazards caused by localized overheating and current concentration, and extend battery life.

[0063] Doping the aluminum layer with 0.5% to 2% graphene creates highly efficient heat transfer channels within the aluminum layer. During battery charging and discharging, heat is generated; the excellent thermal conductivity allows this heat to be quickly conducted away from the battery, preventing localized overheating. This helps maintain the battery's operating temperature within a suitable range, improves its thermal stability, reduces damage to battery materials caused by high temperatures, and ultimately enhances the battery's safety and reliability.

[0064] Graphene possesses excellent chemical stability and barrier properties. Doping aluminum layers with graphene can form a dense protective barrier on the aluminum surface, preventing direct contact between corrosive substances such as electrolytes and the aluminum layer. This helps reduce the corrosion rate of the aluminum layer, extends its lifespan, and thus improves the overall durability and reliability of the battery.

[0065] In some embodiments, when the aluminum layer 22 is pure aluminum, the aluminum layer 22 is uniformly doped with nano-sized ceramic particles, the proportion of which is 5-30 vol%, and the average particle size is ≤100 nm.

[0066] Nanoscale ceramic particles, such as aluminum nitride (AlN), possess excellent thermal conductivity. When these ceramic particles are uniformly dispersed within a pure aluminum layer, they can hinder dislocation movement, thus providing dispersion reinforcement. With the ceramic particle content ranging from 5% to 30 vol%, the hardness and strength of the pure aluminum layer significantly increase. This makes the aluminum layer less prone to deformation and damage under external forces, improving the overall mechanical strength of the cylindrical battery's steel casing structure. This allows it to better resist internal battery pressure and potential external impacts, enhancing the battery's safety and reliability.

[0067] Meanwhile, nanoscale ceramic particles can form a physical barrier on the surface of the pure aluminum layer, reducing direct contact between the electrolyte and the pure aluminum layer, thereby reducing the possibility of electrochemical corrosion. This helps protect the metallic aluminum layer, extend its service life, and ensure the stability of battery performance.

[0068] In some embodiments, the porosity of the alumina film layer 23 is less than or equal to 5%.

[0069] The lower porosity of the alumina film layer 23 results in a denser structure, which more effectively prevents corrosive substances in the electrolyte (such as HF) from penetrating to the steel casing surface. This significantly reduces direct contact between the electrolyte and the steel casing, thereby lowering the risk of steel casing corrosion and extending battery life. Simultaneously, the dense alumina film layer 23 more effectively prevents the deposition of iron ions. Iron ion deposition is one of the main causes of internal short circuits and capacity decay in batteries; by reducing iron ion deposition, the alumina film 23 significantly improves battery safety and storage life.

[0070] In some embodiments, a carbon-based functional layer is added between the aluminum metal layer 22 and the alumina film layer 23. The carbon-based functional layer is made of graphene, carbon nanotubes or diamond-like carbon, and has a thickness of 0.1 to 2 μm. The carbon-based functional layer is bonded to the alumina film layer by physical adsorption or chemical bonding.

[0071] Graphene and carbon nanotubes possess large specific surface areas and abundant surface functional groups, while diamond-like carbon also exhibits unique surface properties. They can form strong chemical bonds or physical adsorption interactions with the aluminum layer 22 and the alumina film layer 23, respectively, resulting in a tighter interfacial bond between the three layers. This helps reduce defects and gaps at the interface, improving the integrity and stability of the entire coating structure. Adding a carbon-based functional layer can construct an efficient electron conduction channel between the aluminum layer 22 and the alumina film layer 23, reducing electron transport resistance and thus improving the overall conductivity of the battery's steel casing. This is beneficial for reducing the battery's internal resistance, minimizing energy loss during charging and discharging, and improving the battery's charging and discharging efficiency.

[0072] Meanwhile, the carbon-based functional layer can disperse and transfer the stress applied to the steel shell, enhancing the coating structure's resistance to deformation and damage. This helps improve the mechanical strength and wear resistance of the steel shell, enabling it to better withstand the internal pressure of the battery and potential external impacts, thus extending the battery's lifespan. The carbon-based functional layer can, to some extent, prevent direct contact between the electrolyte and the aluminum layer, reducing electrolyte corrosion of the aluminum layer. Furthermore, it works synergistically with the alumina film layer to further enhance the overall protective performance of the coating, inhibiting iron ion deposition, reducing the risk of internal short circuits and capacity decay, and improving battery safety and reliability.

[0073] In some embodiments, this application also provides a cylindrical battery, including the cylindrical battery steel shell structure described in the above embodiments.

[0074] This application does not impose any particular limitation on the other components in the cylindrical battery, and any structure in the prior art can be adopted. For example, the cylindrical battery may also include a positive electrode, a negative electrode, a separator, an electrolyte, etc.

[0075] The following examples illustrate the fabrication process of the cylindrical battery steel shell structure provided in this application.

[0076] Example 1

[0077] A mold is selected, and alumina sand particles are used for sandblasting. The alumina particle size is 20-50 μm, the blasting pressure is 0.3-0.5 MPa, and the blasting angle is 45-60°. After processing for 5-10 minutes, uniformly distributed micron-sized protrusions are formed, thus obtaining the casing structure of the cylindrical battery.

[0078] A zinc layer is plated onto the aforementioned shell structure using an electroplating method, wherein the electrolyte is a zinc chloride solution and the current density is 1–3 A / dm³. 2 The temperature is 20–40℃ to form a finely crystalline Zn layer (transition metal layer) with a surface roughness Ra of 1.6–3.2 μm.

[0079] A metallic aluminum layer was prepared on a transition metal layer by magnetron sputtering, with an aluminum target purity ≥99.9%, a working gas pressure of 0.5–1.5 Pa, a power of 200–300 W, and a deposition rate of 0.5–1 μm / min.

[0080] An aluminum oxide thin film layer is prepared on a metallic aluminum layer. The electrolyte required for anodizing is a 15%–20% sulfuric acid solution or a 5%–10% oxalic acid solution; the voltage is 10–20V, and after 10–30 minutes, a porous oxide film is formed. After anodizing, the film is immersed in deionized water or a nickel salt solution at 80–90℃ to seal the pores of the oxide film and further reduce the permeability. Finally, a cylindrical battery steel shell structure is obtained.

[0081] Example 2

[0082] A micron-scale uneven structure is prepared by chemical etching of a steel shell. The etching solution is 5%–10% hydrochloric acid solution with 0.1%–0.5% hydrofluoric acid added (to promote selective corrosion of the steel surface). The etching temperature is 50–70℃ and the time is 10–20 minutes. The regular uneven structure is formed by controlling the etching rate.

[0083] A titanium layer was prepared on the above-mentioned shell structure by sputtering, wherein the argon atmosphere pressure was 0.5-1 Pa, the titanium target power was 100-200 W, the deposition rate was 0.1-0.3 μm / min, and nitrogen gas was simultaneously introduced at a flow rate of 5-10 sccm to form a Ti-N interface layer, i.e., a transition layer.

[0084] A metallic aluminum layer was prepared on the above transition layer using a co-sputtering process. In this embodiment, the raw material used was an aluminum-graphene composite material, the graphene target power was 10-30W, and the graphene content was 0.5%-2% (by mass) to form the metallic aluminum layer.

[0085] An aluminum oxide thin film layer is prepared on a metallic aluminum layer. The electrolyte required for anodizing is a 15%–20% sulfuric acid solution or a 5%–10% oxalic acid solution; the voltage is 10–20V, and the reaction time is 10–30 minutes to form a porous oxide film. After anodizing, the film is immersed in deionized water or a nickel salt solution at 80–90℃ to seal the pores of the oxide film and further reduce the permeability. Finally, a cylindrical battery with a steel shell structure is obtained.

[0086] As can be seen from the above embodiments, this application provides a cylindrical battery steel shell structure and a battery. The cylindrical battery steel shell structure is a hollow structure, comprising a shell and a composite coating disposed on the inner surface of the shell. The shell has multiple micron-sized protrusions, the height of which is 5-10 μm, the width of which is 5-10 μm, and the spacing between adjacent protrusions is 10-20 μm. The composite coating sequentially comprises a transition metal layer, an aluminum layer, and an aluminum oxide film layer. The thickness of the transition metal layer disposed on the inner surface of the shell is 1-3 μm, and the transition metal layer is a zinc layer or a titanium layer. The aluminum layer disposed on the transition metal layer is pure aluminum or an aluminum-graphene composite material, and has a thickness of 5-10 μm. The aluminum oxide film layer disposed on the aluminum layer has a thickness of 2-5 μm. The composite coating structure enhances the interfacial bonding force between the coating and the steel shell, improving corrosion resistance reliability. The composite coating on the inner wall of the steel shell effectively isolates the electrolyte from the steel shell, inhibits the precipitation of iron ions, and solves the problem of internal short circuit caused by the precipitation of iron ions.

[0087] Similar parts between the embodiments provided in this application can be referred to mutually. The specific implementation methods provided above are only a few examples under the overall concept of this application and do not constitute a limitation on the scope of protection of this application. For those skilled in the art, any other implementation methods extended from the solution of this application without creative effort shall fall within the scope of protection of this application.

Claims

1. A cylindrical battery steel can structure, characterized by, The steel shell structure is a hollow structure, and the steel shell structure includes a shell (1) and a composite coating (2) disposed on the inner surface of the shell (1); The shell (1) is provided with a plurality of micron-level protrusions (11), the height of the protrusions (11) is 5 to 10 μm, the width of the protrusions (11) is 5 to 10 μm, and the spacing between adjacent protrusions (11) is 10 to 20 μm; The composite coating (2) sequentially includes a transition metal layer (21), an aluminum layer (22), and an aluminum oxide film layer (23); wherein, the thickness of the transition metal layer (21) disposed on the inner surface of the housing (1) is 1 to 3 μm, and the transition metal layer (21) is a zinc layer or a titanium layer; the aluminum layer (22) disposed on the transition metal layer (21) is pure aluminum or an aluminum-graphene composite material, and the thickness of the aluminum layer (22) is 5 to 10 μm; the thickness of the aluminum oxide film layer (23) disposed on the aluminum layer (22) is 2 to 5 μm.

2. The cylindrical battery can structure according to claim 1, characterized by, The area of ​​the protrusion (11) accounts for 40-60% of the total area of ​​the inner surface of the steel shell.

3. The cylindrical battery steel shell structure according to claim 2, characterized in that, The cross-sectional shape of the protrusion (11) is one of trapezoidal, semi-circular or rectangular.

4. The cylindrical battery can structure according to claim 3, characterized by, When the protrusion (11) is trapezoidal, the width of the base of the protrusion (11) is 5 to 10 μm, and the apex angle of the protrusion (11) is 60 to 90°.

5. The cylindrical battery can structure according to claim 1, wherein The surface roughness of the protrusion (11) is 3.2 to 6.3 μm.

6. The cylindrical battery can structure according to claim 1, wherein When the aluminum layer (22) is an aluminum-graphene composite material, the thickness of the aluminum layer (22) is 6-8 μm.

7. The cylindrical battery can structure according to claim 1, wherein When the aluminum layer (22) is pure aluminum, the aluminum layer (22) is uniformly doped with nano-sized ceramic particles, the proportion of ceramic particles is 5 to 30 vol%, and the average particle size of the ceramic particles is ≤100 nm.

8. The cylindrical battery can structure of claim 1, wherein The porosity of the alumina thin film layer (23) is less than or equal to 5%.

9. The cylindrical battery can structure according to claim 1, wherein A carbon-based functional layer is added between the aluminum metal layer (22) and the aluminum oxide film layer (23). The material of the carbon-based functional layer is graphene, carbon nanotubes or diamond-like carbon, and the thickness is 0.1 to 2 μm.

10. A cylindrical battery, characterized by Includes the cylindrical battery steel casing structure as described in any one of claims 1 to 9.

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