Ultrafast-Laser Micro-Structuring of LiNi$_{0.8}$Mn$_{0.1}$Co$_{0.1}$O$_2$ Cathode for High-Rate Capability of Three-Dimensional Li-ion Batteries

Femtosecond ultrafast-laser micro-patterning was employed to prepare a three-dimensional (3D) structure for the tape-casting Ni-rich LiNi$_{0.8}$Mn$_{0.1}$Co$_{0.1}$O$_2$ (NMC811) cathode. The influences of laser structuring on the electrochemical performance of NMC811 were investigated. The 3D-NMC811 cathode retained capacities of 77.8% at 2 C of initial capacity at 0.1 C, which was thrice that of 2D-NMC811 with an initial capacity of 27.8%. Cyclic voltammetry (CV) and impedance spectroscopy demonstrated that the 3D electrode improved the Li$^+$ ion transportation at the electrode–electrolyte interface, resulting in a higher rate capability. The diffusivity coefficient D$_{Li+}$, calculated by both CV and electrochemical impedance spectroscopy, revealed that 3D-NMC811 delivered faster Li$^+$ ion transportation with higher D$_{Li+}$ than that of 2D-NMC811. The laser ablation of the active material also led to a lower charge–transfer resistance, which represented lower polarization and improved Li$^+$ ion diffusivity.