Combined Effects of Citric Acid and Ascorbic Acid Used As Low-Temperature Surface Modifiers to Enhance the Cyclability of Si Anode in an Li-Ion Battery

We successfully achieved surface modification of Si at a low temperature (150 °C) by using citric acid and ascorbic acid as surface modifiers and enhanced the electrochemical performance of a Si-based anode. A simple planetary ball-milling process followed by heat treatment over a range of temperatures (150–500 °C) was used to carry out the surface modification. This important investigation confirmed that the heat treatment temperature significantly affected the molecular structure in the modification layer, and its thickness led to a higher discharge capacity for low-temperature-modified Si compared to that in other series of high-temperature-annealed samples. Among all the surface-modified Si samples, the electrochemical performance using the M-Si 150 °C as the anode material achieved an excellent capacity of 1787 mAh g⁻¹ after 100 charge/discharge cycles with a 75.8% retention. The same device delivered excellent rate capability, with a capacity of ∼1012 mAh g⁻¹ (1 C) and 593 mAh g⁻¹ (2 C) at the high-current rate. The capacity regained to ∼2012 mAh g⁻¹ with the reversal of the current rate to 0.1 C, with a very high retention of 103%, indicating significantly enhanced strength of the modified Si anode in a lithium-ion battery.