The success of rechargeable lithium-ion batteries has brought indisputable convenience to human society for the past two decades. However, unlike commercialized intercalation cathodes, high-energy-density sulphur cathodes are still in the stage of research because of the unsatisfactory capacity retention and long-term cyclability. The capacity degradation over extended cycles originates from the soluble polysulphides gradually diffusing out of the cathode region. Here we report an applicable way to recharge lithium-sulphur cells by a simple charge operation control that offers tremendous improvement with various lithium-sulphur battery systems. Adjusting the charging condition leads to long cycle life (over 500 cycles) with excellent capacity retention (>99%) by inhibiting electrochemical reactions along with severe polysulphide dissolution. This charging strategy and understanding of the reactions in different discharge steps will advance progress in the development of lithium-sulphur batteries.
A sandwiched electrode containing pristine Li2S powder in between two layers of binder-free carbon nanotube electrodes is developed. The carbon matrix provides an ion and electron accessible environment, and a space for trapping the active material. Exceptionally high capacities with superior stability and rate capability are obtained.
A lithium/dissolved polysulfide cell is developed utilizing a self-weaving, free-standing multiwalled carbon nanotube (MWCNT) “paper” as a host for the dissolved polysulfide active material and the reaction products. Exceptionally high capacities of 1600 mAh g−1 initially and 1411 mAh g−1 after 50 cycles (based on the mass of sulfur) are obtained at a rate of C/10.
