| Lithium-sulfur batteries are considered to be a promising energy storage device owing to its high theoretical specific capacity,high theoretical specific energy and low cost.However,the lifespan of lithium-sulfur（Li-S）batteries cannot meet the requirements of practical applications due to the volume effect of sulfur,the uneven deposition of lithium and the shuttle effect of polysulfides during the charging and discharging process.In this paper,Li-S batteries with self-healing electrode/electrolyte interface are designed,which effectively solve the problem of uneven lithium deposition,sulfur volume effect and polysulfide shuttling.In order to improve the stability of the lithium anode/electrolyte interface,a polyethyleneimine-based interface-layer containing imine bonds and trifluorophenyl groups was constructed on the surface of Li anode.The PEI-based interfacial-layer containing reversible imine bonds exhibits self-healing ability and the formed SEI layer is in-situ embedded into the self-healing PEI-based interface-layer.The interface-layer promotes the repair of the damaged SEI layer during the charging and discharging process,so that the SEI layer maintain morphological integrity during long-term cycling.The stable SEI layer effectively prevents the reaction of polysulfides with Li anode,and contributes to the stability of the Li anode/electrolyte interface.In addition,the grafted trifluorophenyl groups in the PEI based interface-layer can dynamically coordinate with Li+,which enable the interface-layer to adjust the distribution of Li+at the electrode/electrolyte interface.The uniform Li+distribution avoids the uneven deposition of lithium and improves the stability of the Li anode/electrolyte interface.Symmetric Li||Li cell using the anodes could be plated and stripped for 600 h with a stable overpotential(1.0 m A cm-2,1.0 m Ah cm-2).The assembled Li||Cu asymmetric cell can maintain～95%coulombic efficiency for 250 times of deposition/delithiation(1.0 m Ah cm-2,0.5m A cm-2).The same stability was also observed when the cells were tested at a higher current density range of 2.0 m A cm-2.At the rate of 0.2 C,the Li-S battery using the anodes exhibits a specific capacity of～700 m Ah g-1after testing for 100cycles at a sulfur loading of～5 mg cm-2,showing a retention rate of 91.0%.In order to improve the stability of the sulfur cathode/electrolyte interface,a self-healing PDMS-based elastic interface layer was constructed on the surface of the sulfur particles.The excellent elasticity of the interface-layer enables the fragmented sulfur particles gather together,which ensures the microstructural integrity of the sulfur during the charging and discharging process.Even if the interface-layer was broken by the volume change of sulfur,it timely restored through self-healing.At the same time,the interface-layer can also inhibit the dissolution and diffusion of polysulfides,and avoid the damage of polysulfides to the electrode/electrolyte interface.The Li-S battery using the cathodes exhibits a specific capacity of 696.1 m Ah g-1after testing for 107 cycles,showing a retention rate of 88.5%.To improve the electrode/electrolyte interface stability,a polyurethane/polyolefin composite solid state electrolyte with urethane/urea groups was prepared.The strong interaction between the urethane/urea groups and Li+/TFSI-can promote the dissociation of the lithium salt,and the dissociated lithium salt reduces the crystallinity of the polymer and provides an additional transport pathway for lithium ions,so that the electrolyte exhibits good ionic conductivity.The dissociated lithium salt also enhances the mobility of the PU segment,and the strong polarity of the urethane/urea groups and the good mobility of the PU segment enable the assembled solid-state lithium-sulfur battery to exhibit a self-healing electrode/electrolyte interface.The solid-state Li-S battery using the PO-PU-Li TFSI exhibits a self-healing electrode/electrolyte interface due to the strong polarity of the urethane/urea groups and the good mobility of the PU segments.The self-healing property allows the electrode and electrolyte to maintain tight contact and even enables the broken electrode/electrolyte interface to self-heal during cycling,which reduces the interface resistance and promotes uniform lithium deposition.At the rate of 0.1 C,the solid-state Li-S battery using the electrolytes exhibits a specific capacity of 670.4 m Ah g-1after testing for 100 cycles at a sulfur loading of～4 mg cm-2,showing a retention rate of 81.0%.The solid-state lithium-sulfur battery using the above-mentioned S cathode,Li anode and solid-state electrolyte exhibits excellent electrochemical performance.At room temperature,the lithium-sulfur battery exhibits a specific capacity of 538.0m Ah g-1after testing for 40 cycles,showing a retention rate of 88%.The stable electrode/electrolyte interfaces of the lithium-sulfur battery during cycling was in-situ observed by a laser confocal microscope. |
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