Search

A much higher cell voltage of ca. 2.5 V than that of the typical Li-S battery was successfully achieved by combining the 5 V-class, spinel-type LiNi0.5Mn1.5O4 (LNMO) as a cathode and the rubber-derived sulfur composite as an anode. The cycling performance of the cell was improved by the PVDF coating only the cathode and coating both the cathode and anode, in which the discharge capacity retention increased from ca. 45 % to ca. 60 %. On the other hand, there was no difference in the cycling performance between the cell with the PVDF coating only the anode and the cell without the PVDF coating both the cathode and anode. There was no difference between the cycling performance of the half-cell of the LNMO cathode with the PVDF coating and without the PVDF coating, indicating that the PVDF coating on the cathode side does not prevent degradation of the electrolyte solution on the cathode surface. These results suggest that the PVDF coatings of the cathode surface play an important role as a protective layer in preventing the direct contact and side reaction between the polysulfides and cathode surface, thus leading to improvement of the cycling performance.

A rubber-derived sulfur composite cathode material for the Li-S battery/Li-ion battery was synthesized by the vulcanization process of butadiene rubber as a polymer source and a large amount of sulfur. In this study, the higher vulcanization temperature of 450 °C and a larger amount of sulfur (rubber : sulfur = 1 : 10, mass/mass) than the mass production process of the rubber were applied. The rubber-derived sulfur composite has a large amount of sulfur, ca. 58 wt% and a stable cycling ability with a capacity of 400 mAh g−1 at 30 °C. The cells consisting of the rubber-derived sulfur composite as the cathode and SiO as the anode displayed a great potential as for the next-generation LIBs because of its both electrodes containing no transition metals, outstanding electrochemical properties and safety performance. The cell showed a superior high and low temperature performance from −20–80 °C for over 100 cycles and a good rate performance in which the capacity of ca. 600 mAh g−1 was obtained at the 5 C-rate at 60 °C. In addition, there were no thermal runaway and no evolution of hydrogen sulfide in the nail penetration test.