An electroless nickel process was used for the preparation of a thin-film current collector for concentric three-dimensional lithium and lithium-ion microbatteries. Ni–P coatings were deposited autocatalytically with the use of nickel sulfamate or nickel sulfate as a source of Ni2+ and sodium hypophosphite as a reducing agent. The synergistic effect of sodium acetate and citric acid was found to provide marked improvement in the pH stability of the sulfamate electrolyte. This enabled deposition of a conformal, fine-grained film on the high-aspect-ratio glass capillary and perforated-silicon substrates.
