Chitosan Undercoating for Battery Tab Adhesion

The patent removes harmful metal crosslinking agents (Zr, Ti, Hf) from the surface treatment agent formulation. Instead, it uses organic crosslinking agents derived from chitosan and carboxylic acid compounds that do not elute in HF and electrolyte environments, thereby eliminating the source of the problem while maintaining crosslinking functionality.

The patent employs readily available chitosan and common carboxylic acid compounds (succinic acid, glutaric acid, adipic acid) as crosslinking agents. These organic compounds form stable crosslinks that do not elute like metal agents, providing durable adhesion without requiring expensive or rare metal materials.

The patent completely removes trivalent chromium compounds from the formulation. Instead, it uses environmentally benign organic crosslinking agents (carboxylic acid compounds) that achieve comparable or superior HF-resistance without the toxicological and environmental problems associated with chromium.

The patent changes the chemical nature of the crosslinking agent from inorganic metal-based (chromium) to organic molecule-based (carboxylic acid compounds). This fundamental parameter change maintains the crosslinking function and HF-resistance while eliminating environmental harm.

The patent creates a composite crosslinked structure by combining chitosan (providing adhesion and film formation) with carboxylic acid compounds (providing crosslinking). This composite organic system forms a stable network that resists thermal degradation and chemical elution better than metal-based crosslinking alone.

The patent uses stable organic crosslinking agents that do not elute like metal agents. The carboxylic acid-chitosan crosslinks form durable bonds that maintain adhesion strength at high temperatures where metal agents would degrade and elute.