Improved electrochemical behavior of W-coated SiO-graphite composite anode in lithium-ion secondary battery

Abstract

The electrochemical performance of a W-coated SiO-graphite composite anode was evaluated in Li-ion secondary coin cells. Tungsten was coated onto the SiO-graphite composite electrode by physical vapor deposition. The layered structure of the W-coated electrode was imaged using transmission electron microscopy and the uniformity of the coating was confirmed by electron probe microanalysis. In coin cells, the W-coated electrode showed a higher retention capacity and discharge capacity than the uncoated electrode at a C rate of 0.5 C after 100 cycles. The discharge capacity of the coated cell was 566 mAh g(-1) after the 1st cycle and 358 mAh g(-1) after the 100th cycle at a C rate of 0.5 C, whereas that of the uncoated cell was 517 mAh g(-1) after the 1st cycle and 269 mAh g(-1) after the 100th cycle. The retention capacity of the coated cell was 63.2 % after 100 cycles, whereas that of the uncoated cell was 52.0 %. A comparison of the W-coated and uncoated electrodes after 100 cycles revealed that the W layer, which has superior conductivity and mechanical properties, improved the electrochemical performance of the electrode. Impedance analysis also confirmed that the W coating enhanced the cell performance.