High electrochemical performance bendable Li secondary batteries based on a three-dimensional metal foam-type current collector

Highlights: • 3D structured metal foam increases the surface area for redox reaction. • 3D structured metal foam enhances the electrical conductivity. • The Ni-Cr alloy foam exhibit a high areal capacity of 3.5 mAh cm⁻² at a 0.2C. • The Ni-Cr alloy foam exhibit a low charge transfer resistance of 6 Ω. - Abstract: Bendable lithium secondary batteries have many limitations, including low electrochemical performances and poor mechanical flexibility. Here, we bendable pouch batteries are fabricated using LiFePO₄/C as the active material and three-dimensional Nickel-Chromium alloy metal foam as the current collector of positive electrodes. The advantages of using the three-dimensional structured metal foam include a high surface area for the redox reaction, high electronic conductivity, and short diffusion length for the lithium ion. We demonstrate the use of bendable lithium secondary batteries with a high areal capacity of about 3.5 mAh cm⁻² at C-rate of 0.2, a high capacity retention rate in cycle life behavior, and a greatly low charge transfer resistance of around 6–8 Ω. Moreover, our bendable pouch batteries can be repeatedly bent to radii of 12.5 and 2.5 mm for several hundred times without fractures in the electrode and capacity fading.