Yuxun Ren

A Lithium/Polysulfide Battery with Dual-Working Mode Enabled by Liquid Fuel and Acrylate-Based Gel Polymer Electrolyte

The low density associated with low sulfur areal loading in the solid-state sulfur cathode of current Li-S batteries is an issue hindering the development of this type of battery. Polysulfide catholyte as a recyclable liquid fuel was proven to enhance both the energy density and power density of the battery. However, a critical barrier with this lithium (Li)/polysulfide battery is that the shuttle effect, which is the crossover of polysulfides and side deposition on the Li anode, becomes much more severe than that in conventional Li-S batteries with a solid-state sulfur cathode. In this work, we successfully applied an acrylate-based gel polymer electrolyte (GPE) to the Li/polysulfide system. The GPE layer can effectively block the detrimental diffusion of polysulfides and protect the Li metal from the side passivation reaction. Cathode-static batteries utilizing 2 M catholyte (areal sulfur loading of 6.4 mg cm-2) present superior cycling stability (727.4 mAh g-1 after 500 cycles at 0.2 C) and high rate capability (814 mAh g-1 at 2 C) and power density (∼10 mW cm-2), which also possess replaceable and encapsulated merits for mobile devices. In the cathode-flow mode, the Li/polysulfide system with catholyte supplied from an external tank demonstrates further improved power density (∼69 mW cm-2) and stable cycling performance. This novel and simple Li/polysulfide system represents a significant advancement of high energy density sulfur-based batteries for future power sources.

Borophene and defective borophene as potential anchoring materials for lithium–sulfur batteries: a first-principles study

Lacking effective anchoring materials to suppress the severe shuttle effect is a longstanding issue hindering the development of lithium–sulfur (Li–S) batteries. In this work, a first-principles study is carried out to investigate the potential of borophene and defective borophene, which have high ionic conductivity and adsorbent ability, as anchoring materials for Li–S batteries. Borophene is found to exhibit ultra-high adsorption energies towards lithium polysulfides, but the material facilitates the decomposition of Li–S clusters, leading to an undesirable sulfur loss during battery cycling. For this reason, borophene is not an ideal anchoring material for Li–S batteries. On the contrary, defective borophene is found to show moderate adsorption energies ranging from 1 to 3 eV, which not only effectively anchors lithium polysulfides to suppress the shuttle effect, but also keeps their cyclic structures undecomposed. In addition, defective borophene exhibits a metallic characteristic during the whole reaction process, ensuring the lithium polysulfides be easily charged back and not accumulate on the anchoring materials. Given these advantages, it is expected that defective borophene is a promising anchoring material, leading to a suppressed shuttle effect and enhanced capacity retention for Li–S batteries.