Storage Lithium Properties Of Selenide And Sulfide As Electrodes For Lithium Ion Batteries

Ni Co2S4 and Sn S-Sn Se thin films, Fe2 Se S were synthesized by plused laser deposition and solid state reaction, respectively, as electrodes for lithium ion batteries. Their electrochemical properties were studied by galvanostatic charge-discharge measurements and cyclic voltammogram tests. The structure, composition, and morphology of electrode materials during cycle were characterized by XRD, SEM, HRTEM, SAED and XAS. Their electrochemical reaction mechanisms were studied. The content mainly includes the following the parts:(1) Ni Co2S4 thin films were synthesized by plused laser deposition. The results reveal that the first discharge capacity of Ni Co2S4 thin film was 698 m Ah·g-1,capacity maintained 365 m Ah·g-1 after 200 cycles. Ni Co2S4 thin film reacted with Li during first discharge to form Li2 S 、 Ni and Co, but the electrochemical reaction during the following cycles was the r eversible decomposition and generatation of Ni S and Co S composite film. Ni S and Co S composite films showed higher capacity and better cycle performance than Ni S or Co S films.(2) Sn S-Sn Se composite thin films were synthesized by plused laser deposition. Its first discharge capacity was 1225.8 m Ah g-1 and capacity after three cycles maintained about 650 m Ah·g-1. Sn S-Sn Se composite thin film firstly reacted with Li during discharge to form Li2S、Li2Se and Sn, then Sn reacted with Li to form LixSn alloy. During the charge, LixSn firstly decomposed to form elementary Sn, then Sn catalyzed Li2 S and Li2 Se to decompose to rebuild Sn S-Sn Se composite thin film. Li2 S and Li2 Se produced during discharge can suffer a certain amount of volume change which enhanced the cycle performance. Sn S-Sn Se composite thin film had more grain boundary than Sn S or Sn Se thin film which could effectively enhance electrochemical activity and increase capacity.(3) Fe2 Se S was synthesized by solid state reaction. The results suggested that its discharging products were Fe、Li2Se and Li2 S, and the first discharge and charge capacity of Fe2 Se S/Li were 471 m Ah g-1 and 436 m Ah g-1, respectively. The first coulomb efficiency was 92.56%. The capacity and cycle performance of Fe2 Se S was better than Fe Se or Fe S.