Ultrahigh areal capacity silicon anodes realized via manipulating electrode structure

High areal capacity is critical towards the practical application of silicon anodes for high-energy lithium ion batteries. Herein, a free-standing silicon-graphene (3D-Si/G) anode with ultrahigh areal capacity is proposed by manipulating electrode structure using 3D-printing. For the 3D-Si/G electrodes with the circle-grid pattern, electrode thickness and printed filament spacing can be precisely constructed and adjusted by controlling a computer program. In this configuration, the tailored free space between and inside the filaments are enough to withstand volume fluctuation of silicon anodes, which significantly improves the structure stability and integrity of electrodes and endows the great accessibility to lithium ions transport in thick electrodes. Furthermore, the unique edge-coaxial and internal-disordered structure in printed filaments greatly enhances the electrode mechanical stability. Simultaneously, the graphene framework with excellent electron-ion transport characteristic ensures fast electrochemical reaction kinetics and low electrochemical polarization in thick electrodes. Therefore, the optimized 3D-Si/G electrode achieves a favorable cycle stability with 8.5 mAh cm−2 after 70 cycles (capacity retention of 75.4%). And the 3D-Si/G thick electrode with four layers achieves a reversible ultrahigh areal capacity of 16.2 mAh cm−2. More importantly, the easy ink preparation and controllable printing process provide broad prospects for the commercial application of silicon anodes.