Synergistic mediation of polysulfide immobilization and conversion by a catalytic and dual-adsorptive system for high performance lithium-sulfur batteries
© 2020 Elsevier B.V. Although various inorganic particles have been confirmed as effective trappers to restrict the shuttle effect of lithium polysulfides (LiPSs) in lithium-sulfur batteries (LSB), the further reduction of LiPSs is impeded due to their low conductivity. This process results in sluggish redox kinetics at the interface of cathode/electrolyte and escaped LiPSs to electrolytes during long-term cycling. Herein, by advantageous functional integration of immobilization and conversion capability for LiPSs, a 3D aerogel with the composition of Co@CoO@N-doped carbon@graphene (Co@CoO@N-C/rGO) is designed and prepared. The dual-shells of N-C and polar CoO enable the strong chemical adsorption towards LiPSs through pyridinic – N-Li-bond and Co···S coordination, respectively. And the conductive Co core acts as a “scissor”, which catalyzes the transformation of adsorbed LiPSs into low-order ones, thus accelerating the kinetics of the liquid–solid nucleation and growth of Li2S. Moreover, the matrix of rGO serves as electrical networks, significantly promoting the transfer of electrons to the redox-active sites. Based on these synergetic effects, the LSB using Co@CoO@N-C/rGO modified separators exhibits outstanding electrochemical performance. For example, even at a rate of 1C, the cell still delivers a stable capacity of 555.4 mAh g−1 after 500 cycles for a pure sulfur electrode. Moreover, the relevant kinetic mechanisms including in situ Raman test are expounded in detail.