This study presents a high-performance lithium-ion battery with nano-porous Si anode etched from polycrystalline Si particles. Nano-pores formed in micro-sized particles help relieve volume expansion/shrinkage effectively. Meanwhile, the formation of nano-porous skeleton in micro-sized particles greatly reduces the agglomeration of Si particles in nano-sized units and helps improve the cyclic performance of batteries. Pyrolyzed polyacrylonitrile mixed in anode acts as conductive agent and binder, and the network structure enhances the conductivity. The battery with 1μm porous Si and PPAN composite electrode exhibits a remarkably improved electrochemical performance with a coulombic efficiency ≥99.5% even after 220 cycles. Excellent electrochemical performance is observed under galvanostatic mode with a current density of 0.3A/g. High initial discharge (lithiation) capacity of 3652mAh/g and charge (delithiation) capacity of 3067mAh/g are observed with an initial coulombic efficiency of 84%, which increases to 97.2% at the second cycle. The charge capacity remains as high as 2043mAh/g with a coulombic efficiency of ≥99.5% even after 100 cycles.