Potassium metal is an appealing alternative to lithium as an alkali metal anode for future electrochemical energy storage systems. However, the use of potassium metal is hindered by the growth of unfavourable deposition (e.g., dendrites) and volume changes upon cycling. To circumvent these issues, we propose the synthesis and application of nitrogen and zinc codoped porous carbon nanofibres that act as potassium metal hosts. This carbonaceous porous material enables rapid potassium infusion (e.g., < 1 s cm−2) with a high potassium content (e.g., 97 wt. %) and low potassium nucleation overpotential (e.g., 15 mV at 0.5 mA cm−2). Experimental and theoretical measurements and analyses demonstrate that the carbon nanofibres induce uniform potassium deposition within its porous network and facilitate a dendrite-free morphology during asymmetric and symmetric cell cycling. Interestingly, when the potassium-infused carbon material is tested as an active negative electrode material in combination with a sulfur-based positive electrode and a nonaqueous electrolyte solution in the coin cell configuration, an average discharge voltage of approximately 1.6 V and a discharge capacity of approximately 470 mA h g−1 after 600 cycles at 500 mA g−1 and 25 °C are achieved.

As a promising cathode material for lithium−sulfur (Li-S) batteries, sulfurized polyacrylonitrile (SPAN) with uniform dispersion of short-chain sulfur moieties on its organic skeletons can effectively avoid lithium polysulfides dissolution and exhibit high specific capacity and long-term cycling stability. However, the practical battery performance of the SPAN cathode is dramatically limited by its relatively poor ionic and electronic accessibility. In this work, a three-dimensional (3D) network of Se 0.05 S 0.95 PAN nanofibers incorporated with commercial and low-cost Ketjen black (KB), denoted as ES-KBS@Se 0.05 S 0.95 PAN, is prepared through the electrospinning method. This unique 3D nanofiber structure is beneficial to transport lithium ions and electrons and accommodate volume expansion during lithiation/delithiation processes for Li-S batteries, leading to tremendous improvement of sulfur utilization, rate capability, and long-term cycling performance. ES-KBS@Se 0.05 S 0.95 PAN exhibits an ultrahigh reversible capacity of 1491 mAh g −1 at 0.1C and 1130 mAh g −1 at 5C and retains 1224 mAh g −1 after 500 cycles at 1C, corresponding to a capacity retention of 96.4%. This work proposes a facile strategy for the preparation of sulfur cathodes applicable in lithium−sulfur batteries.

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