As a key structure protecting the internal components of a battery, the surface treatment technology of the battery steel casing directly affects the reaction risk between the battery and the electrolyte, as well as the overall safety. While traditional nickel plating improves the corrosion resistance of the battery steel casing, uneven plating or porosity in acidic electrolyte environments can still exacerbate reactions. In recent years, the industry has significantly reduced the interaction risk between the steel casing and the electrolyte through material innovation, process optimization, and structural improvements, providing a more reliable guarantee for battery safety.
The pre-plating nickel process, by depositing a nickel layer before stamping the steel strip and then forming a nickel-iron alloy layer through high-temperature annealing, fundamentally solves the problem of plating uniformity. Compared to post-plating nickel, the pre-plated nickel steel casing has a tighter bond between the plating and the substrate, reducing the electrolyte penetration path. The nickel-iron interdiffusion structure in the alloy layer enhances corrosion resistance, especially in acidic electrolytes, where the alloy layer effectively blocks direct contact between the electrolyte and the steel substrate, reducing the probability of side reactions. Furthermore, the pre-plating nickel process allows for precise control of the plating thickness, ensuring the structural stability of the battery steel casing under complex operating conditions while meeting lightweight requirements.
Alloy catalyst technology provides an environmentally friendly alternative for steel casing surface treatment. This technology forms a nanoscale alloy layer on the steel surface through a "penetration + deposition" reaction, and its dense structure effectively isolates the electrolyte. Compared to traditional nickel plating, steel casings treated with alloy catalyst significantly extend their salt spray resistance test time and are free of harmful substances such as cyanide and hexavalent chromium, meeting international environmental standards. In electrolyte corrosion tests, steel casings treated with this technology exhibit lower reactivity, making them particularly suitable for the power battery field, where safety requirements are stringent.
Surface sealing technology is another key means of reducing the risk of electrolyte reaction. Traditional chromic acid passivation is gradually being phased out due to environmental concerns, while phosphoric acid and phytic acid passivation technologies effectively block contact between the electrolyte and the steel casing by forming a dense passivation film. Combined with the sealing process, the porosity of the passivation film is further reduced, maintaining stable chemical inertness even in high-temperature or high-humidity environments. Some companies employ a double-layer sealing design, with an inner layer of chemical passivation and an outer layer of physical adsorption. This composite structure significantly improves the corrosion resistance of the steel casing in electrolytes.
Laser texturing technology enhances the adhesion between the coating and the substrate by creating a micro-nano-level rough structure on the steel casing surface. The uniformly distributed micro-pits can store a small amount of electrolyte, forming a lubricating layer and reducing frictional damage between the steel casing and the electrode. Simultaneously, the microstructure increases the contact path length between the electrolyte and the steel casing, reducing the local reaction rate. In the UV coating process, the surface roughness of the laser-textured steel casing is controllable, ensuring uniform coating coverage and further preventing electrolyte penetration.
The synergistic optimization of the core-shell structure cathode material and the steel casing surface treatment provides a systematic solution to reduce the risk of electrolyte reaction. By constructing a manganese-rich shell layer on the cathode material surface, direct reaction between the electrolyte and the high-nickel core can be suppressed, while the battery steel casing side uses a pre-plated nickel + sealing process to form a double protective barrier. This design not only reduces the gases produced by electrolyte decomposition but also lowers the risk of metal ions being released after the steel casing corrodes, thus improving the overall safety of the battery.
From an industrial application perspective, leading battery companies have widely adopted pre-nickel-plated steel casings and alloy catalyst technologies, significantly reducing the cost per GWh production line, and their products have obtained international certifications such as UL and CE. A traditional electroplating plant in Northeast China, after its transformation, saw a significant increase in orders for new energy components, resulting in record-breaking annual profits. These cases demonstrate that optimized steel casing surface treatment technology not only improves battery safety but also brings significant economic benefits to enterprises.
In the future, with the development of next-generation energy storage technologies such as solid-state batteries, steel casing surface treatment technology will face even higher requirements. By continuously optimizing the pre-nickel plating process, developing new environmentally friendly passivation technologies, and exploring laser and chemical composite treatment methods, the reaction risk between the steel casing and the electrolyte is expected to be further reduced. This will provide solid support for the development of power batteries towards higher energy density, longer lifespan, and greater safety.
