Silica-supported nanostructured copper phyllosilicate: Boosting stability, capacity, and conductivity of Li-ion battery Si-based anodes

Abstract

Explosive demand for large-scale rechargeable batteries has driven the search for alternative electrode materials with higher energy density, lower toxicity, lower cost, and more natural abundance. Si-based materials, e.g., Si, SiO, SiO2, and silicates have emerged as promising choices, with extremely high capacities from most cost-effective and abundant sources. However, these compounds still suffer from major issues, such as extreme volume change, poor cycling stability, high manufacturing costs, and low conductivity. Herein, we have prepared low-cost porous nanosized silica-supported copper phyllosilicate, x CuPS/SiO2, with different Cu loadings and investigated them as anode material in Li cells. Due to the highly dispersed Cu species strongly interacted with nanosphere SiO2 support matrix, 20CuPS/SiO2 has been found to deliver a capacity as high as ∼3550 mAh g‒1 at 500 mA g‒1 with an impressive capacity retention of 99% upon conversion reactions with Li+, and a reversible capacity of 2216 mAh g‒1 at 5000 mA g‒1. These values are among the highest ever reported for Si-, silicate-, silica-, and copper oxide-based anodes. Various phases, i.e., CuO, Li4SiO4, SiO, Si, Li2O, Cu, and LixSi, are formed in the SiO2 nanodomain, as confirmed by various ex situ characterization techniques, and the redox mechanism has been proposed. The components, particularly Li4SiO4, Li2O, and SiO2, are shown to help buffer volumetric or structural changes induced by the redox processes. The nanosized composite and the in situ -formed metallic Cu play a crucial role in rapid charge-transfer kinetics. These synergistic effects ultimately result in an unprecedented electrochemical performance of x CuPS/SiO2 observed in this work.