Si-based Composite Anode for Li-ion Batteries with Enhanced Cycle Stability via Doping Cu3Si Phase Achieved by Modified Coating of PDA

Abstract

Silicon (Si) is a promising anode material for Li-ion batteries but its application is limited due to its severe volume change during the lithiation/delithiation process leading to a fast degradation of cycle performance. Applying transition metals to dope into the bulk of Si forming active/inactive silicide phase is proved an effective and practical method to solve this issue. However, the classic high-energy ball milling method is faced with the challenges of strict requirements to the machine, long-time working and difficulty to control the morphology of the product. Aiming to this point, the present study proposes a facile and “softer” method via coating the polydopamine (PDA) with the assistance of CuCl2·2H2O followed by a high-temperature annealing process to successfully fabricate the Si-based anode material with a unique structure of Si-Cu3Si@C. We firstly achieved the doping of Cu3Si and at the same time coating the carbon layer on the surface of Si. Owing to the synergistic effect of carbonized PDA layer and doped Cu3Si phase, both structural stability and electronic conductivity of electrode have been significantly enhanced. The Si-Cu3Si@C composite anode not only exhibited a high initial reversible capacity of 2356.7 mAh·g-1 with an initial coulombic efficiency of 83.6%, but also demonstrated a good capacity retention of 89.7% after 100 cycles at the current density of 400 mA·g-1. We believe this work can pave a new way to improve the Si-based anode material.