Effect of High Strength Clad Foil on Cycle Life of SiO Anode

摘要

Introduction Electric vehicles with longer driving range requires higher energy density materials such as Silicon and Silicon monoxide (SiO) as anode material. They are known of volume expansion and shrinkage during cycles which leads deformation of Cu foil and deteriorates cycle life of lithium ion batteries. Increasing foil thickness is not desirable from energy density point of view. In such a case, anode foil needs strength to suppress deformation, as well as low resistance. Experimental In order to increase cycle life of SiO anode, a clad foil with high strength and low resistance was applied. Three foils are rolled together to make a clad foil. The foil consists of three layers with Cu/Ni alloy/Cu. Ni alloy is for high strength, and Cu is for low resistance. SiO is mixed with polyimide binder, then coated on the clad foil (12 micro m) and rolled Cu foil (16 micro m). Cycle life at 1000mA/(g-SiO) was evaluated using coin cell. Conclusion 1. Tensile strength of Cu/Ni alloy/Cu clad foil is 880 MPa which is about double of rolled Cu foil. 2. Resistivity of the clad foil is 0.045 micro Ohm m, which is about double of electrolytic Cu foil, but less than 1/10 of high strength stainless steel foil. 3. After 50 cycles, rolled Cu foil was severely wrinkled, but the clad foil was not wrinkled. 4. Cycle life with the clad foil (12 micro m) is improved to about 800 cycles, comparing with 600 cycles of thicker rolled Cu foil (16 micro m).