tailieunhanh - Lithium-ion Batteries Part 9

Tham khảo tài liệu 'lithium-ion batteries part 9', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | NASICON Open Framework Structured Transition Metal Oxides for Lithium Batteries 105 Voltage V vs. Li Li Fig. 8. Slow scan cyclic voltammetry of LixM2 MoC 4 3 vs. Li Li . Scan rate mV s Vmax V oxidation Vmin reduction . Prabaharan et al. 2004 2006 . During the continuation of the reduction process down to V two peaks were noticed at and V in the case of Li2Ni2 MoC4 3 and at and 2 V for Li2Co2 MoC4 3 indicating the reduction of Mo6 to Mo5 and Mo4 . During successive cycling these two peaks were found to merge into a single broad peak in both cases implying the slow and steady dynamics of Li into the active material. Upon further cycling we were able to observe a broad anodic peak at V representing the Mo oxidation followed by a high voltage peak at V indicating the oxidation of M2 cations back to 3 state. The slow scan cyclic voltammograms of LixM2 MoC4 3 composite electrodes vs. Li Li cycled between V and V for LixNi2 MoC4 3 and between V and V for LixCo2 MoC4 3 are shown in Fig. 8. The cells were first discharged to insert lithium in M2 MoC4 3 framework structure and then charged to extract lithium. The CV profiles demonstrate the electrochemical reversibility of the material and exhibits the reduction and oxidation peaks corresponding to the two transition metal ions M3 and Mo6 . During the first discharge from CCV the reduction of M3 M2 was observed at V and as the reduction process continues down to V two other broad peaks were observed at V and V in the case of LixNi2 MoC4 3 due to the reduction of Mo6 to its lower oxidation states . Cn the other hand a single reduction peak was observed at V for LixCo2 MoC4 3 indicating two-electron transfer during Mo6 reduction. Upon the first charge after discharge in lithium-free nickel molybdate oxidation of Mo back to its higher oxidation state 6 state and Ni2 Ni3 transitions were noticed at V V and V respectively. Whereas in .