Effect of Binders on the Performance of SPAN Cathode for Potassium-sulfur Batteries.

Owing to the large radius of potassium ions, the SPAN cathode suffers large volume change during the cycling process, which causes structure collapse and serious capacity fade. Herein, the effects of sodium carboxymethyl cellulose (CMC) and polyvinylidene fluoride (PVDF) on the electrochemical performance of SPAN cathode in K-S battery were investigated, and the reason of CMC binder improving the electrochemical performance of SPAN cathode was further explored by kinetic test and SEM test. The rate performance test results showed that the SPAN electrode prepared by CMC binder displayed capacity of 1 256, 1 161, 1 058, 946, 716, 538 mAh/g at 0. 1C, 0. 2C, 0. 5C, 1C, 2C, 3C. And the capacity remained 1 253 mAh/g when the current density returns to 0. 1C, which was far better than the rate performance of SPAN electrode prepared by PVDF binder. Besides, the cycle performance test results showed that the SPAN electrode prepared by CMC binder could deliver a high reversible capacity of 822 mAh/g after 100 cycles at 0. 5C, corresponding to a high capacity retention of 75. 6%. The mechanism test results showed that benefit from the abundant oxygen-containing active functional groups in the CMC structure which could not only strengthen chemical interactions with active materials, alleviate the volume change of SPAN cathode during the charge/discharge process, but also accelerate the transport of potassium ion. The SPAN electrode prepared by CMC binder demonstrated a high rate performance and cycle performance compared to the case of PVDF binder. The finding of this study provided an effective strategy to restrain the volume expansion of potassium-sulfur batteries, to maintain the stability of the conductive network inside the electrode, thereby to improve the rate performance and cycle stability. [ABSTRACT FROM AUTHOR]