Nickel (Ni) Coated Copper Foil Roll as Solid-State Battery Anode Current Collector, CSSBACCNCFR

In All-Solid-State Batteries (ASSBs), particularly those utilizing sulfide-based solid electrolytes (such as Li2S}-P2S5, LGPS, or LPSCl), the choice of negative (anode) current collector is a critical bottleneck. While pure copper (Cu) foil is the standard for conventional liquid lithium-ion batteries, it fails catastrophically in sulfide solid-state environments. Nickel-coated copper foil (Ni-Cu) has emerged as one of the most effective, commercially viable solutions to bridge this gap.

Nickel (Ni) possesses excellent chemical and electrochemical stability against sulfur species at low potentials (the anode operating window). Applying a sub-micron or micron-level nickel layer onto copper foil introduces several structural advantages: (1) Chemical Barrier Layer: The nickel coating acts as a dense, inert physical shield. It prevents the highly reactive sulfur atoms in the electrolyte from diffusing into and reacting with the underlying copper substrate. (2) Suppression of Lithium-Nickel Alloying: Unlike elements like Al, Zn, or Sn, nickel does not easily alloy with lithium at room temperature under standard anode operating potentials. This ensures that the current collector remains structurally intact during lithium plating/stripping, making it highly suitable for anode-free (lithium-metal-free) solid-state battery architectures. (3) Mechanical and Stress Accomodation: Solid-state batteries require high stack pressures (ranging from 1-5 MPa to maintain contact during operation. Pure Cu can undergo severe plastic deformation or creep under high localized stress. Ni-coated Cu benefits from the higher mechanical hardness of nickel, minimizing micro-cracking and deformation at the interface where the solid electrolyte particles press into the foil.

References:

1. M. Li, et al., Understanding the Stability of Copper Current Collector with Sulfide Electrolyte in All-Solid-State Batteries, Advanced Energy Materials, 2024, 14, 2303156. 
2. Z. Geng, et al., Comparative stability of copper foil current collectors in sulfide-based all-solid-state batteries: effects of processing routes and carbon coating, Ionics, DOI:10.1007/s11581-026-07228-1.