Facile and Efficient Fabrication of Branched Si@C Anode with Superior Electrochemical Performance in LIBs.

One-dimensional Si nanostructures with carbon coating (1D Si@C) show great potential in lithium ion batteries (LIBs) due to small volume expansion and efficient electron transport. However, 1D Si@C anode with large area capacity still suffers from limited cycling stability. Herein, a novel branched Si architecture is fabricated through laser processing and dealloying. The branched Si, composed of both primary and interspaced secondary dendrites with diameters under 100 nm, leads to improved area capacity and cycling stability. By coating a carbon layer, the branched Si@C anode shows gravimetric capacity of 3059 mAh g-1 (1.14 mAh cm-2 ). At a higher rate of 3 C, the capacity is 813 mAh g-1 , which retained 759 mAh g-1 after 1000 cycles at 1 C. The area capacity is further improved to 1.93 mAh cm-2 and remained over 92% after 100 cycles with a mass loading of 0.78 mg cm-2 . Furthermore, the full-cell configuration exhibits energy density of 405 Wh kg-1 and capacity retention of 91% after 200 cycles. The present study demonstrates that laser-produced dendritic microstructure plays a critical role in the fabrication of the branched Si and the proposed method provides new insights into the fabrication of Si nanostructures with facility and efficiency.

Porous Si/Cu Anode with High Initial Coulombic Efficiency and Volumetric Capacity by Comprehensive Utilization of Laser Additive Manufacturing-Chemical Dealloying.

Si has been extensively investigated as an anode material for lithium-ion batteries because of its superior theoretical capacity. However, a scalable fabrication method for a Si-based anode with high initial coulombic efficiency (ICE) and large volumetric capacity remains a critical challenge. Herein, we proposed a novel porous Si/Cu anode in which planar Si islands were embedded in the porous Cu matrix through combined laser additive manufacturing and chemical dealloying. The compositions and dimensions of the structure were controlled by metallurgical and chemical reactions during comprehensive interaction. Such a structure has the advantages of micro-sized Si and porous architecture. The planar Si islands decreased the surface area and thus increased ICE. The porous Cu matrix, which acted as both an adhesive-free binder and a conductive network, provided enough access for electrolyte and accommodated volume expansion. The anode structure was well maintained without observable mechanical damage after cycling, demonstrating the high structure stability and integrity. The porous Si/Cu anode showed a high ICE of 93.4% and an initial volumetric capacity of 2131 mAh cm-3, which retained 1697 mAh cm-3 after 100 cycles at 0.20 mA cm-2. Furthermore, the full-cell configuration (porous Si/Cu //LiFePO4) exhibited a high energy density of 464.9 Wh kg-1 and a capacity retention of 84.2% after 100 cycles.