Improving lithium–sulphur batteries through spatial control of sulphur species deposition on a hybrid electrode surface

Abstract

Lithium-sulphur batteries are attractive owing to their high theoretical energy density and reasonable kinetics. Despite the success of trapping soluble polysulphides in a matrix with high surface area, spatial control of solid-state sulphur and lithium sulphide species deposition as a critical aspect has not been demonstrated. Herein, we show a clear visual evidence that these solid species deposit preferentially onto tin-doped indium oxide instead of carbon during electrochemical charge/discharge of soluble polysuphides. To incorporate this concept of spatial control into more practical battery electrodes, we further prepare carbon nanofibers with tin-doped indium oxide nanoparticles decorating the surface as hybrid three-dimensional electrodes to maximize the number of deposition sites. With 12.5 ml of 5 M Li 2 S 8 as the catholyte and a rate of C/5, we can reach the theoretical limit of Li 2 S 8 capacity B1,470 mAh g À 1 (sulphur weight) under the loading of hybrid electrode only at 4.3 mg cm À 2 .

A highly efficient polysulfide mediator for lithium–sulfur batteries

“…Recent reports have visually demonstrated the binding of LiPSs with metallic metal oxide sulfur hosts such as Ti 4 O 7 (ref. 32) and spatially localized deposition of Li 2 S on conductive indium-tin oxide 33 . With d-MnO 2 -a poor semiconductor-the interaction is based on a very different principle, as detailed in the next section.…”

“…Similarly, binding polysulfides onto hydrophilic metal oxide hosts was shown to significantly aid in maintaining high-capacity retention [29][30][31] . More recently, high-surface-area polar metallic oxides have been used as a two-in-one approach to provide both a 'sulfiphilic' surface and supply electron transport to effect surface-enhanced redox chemistry 32 ; or to spatially locate Li 2 S deposition and enhance redox 33 . Organometallic redox mediators are shown to provide better utilization of Li 2 S (ref.…”

Leaf‐Like Graphene‐Oxide‐Wrapped Sulfur for High‐Performance Lithium–Sulfur Battery

“…Based on the result of self‐discharge investigation, leaf‐like GO/S composites can largely limit the self‐discharge of Li–S battery. However, to further reduce the self‐discharge of Li–S batteries, a synergy of methods are still needed such as optimizing the electrolyte,7, 8 designing new battery structure,52, 53 protecting Li anode,54, 55 and spatially controlling sulphur species deposition 56. For comparison, conventional GO/S composite was synthesized and investigated as electrode for Li–S battery (Figure S9, Supporting Information).…”

Chloride‐Reinforced Carbon Nanofiber Host as Effective Polysulfide Traps in Lithium–Sulfur Batteries

“…Among various alternatives, rechargeable batteries that use earth abundant elements and cost‐effective materials are considered to be promising candidates to meet these performance goals and potentially offer opportunities in large‐scale deployment. In particular, sulfur appeals to the battery community because of its high energy density on both volume (2.8 kWh L −1 ) and weight (2.5 kWh kg −1 ) basis 7, 8, 9, 10. Unlike the widespread LIBs that host lithium in its ionic state and generally yield fewer than one electron per metal atom, a lithium–sulfur battery achieves its high energy (theoretical capacity of 1675 mAh g −1 ) from the multi‐step electrochemical redox reactions by bonding to two Li ions non‐topotactically (S 8 + 16Li ↔ 8Li 2 S) and offer up to two electrons per sulfur atom.…”

“…Hollow structures can also be created in each nanofiber in order to increase the space for hosting polysulfides 8, 29, 30, 31. More interestingly, binder‐free solid carbon nanofibers with or without surface decoration have been reported as free‐standing sulfur cathode 10, 32, 33. The empty space among nanofibers is sufficient to host sulfur and accommodates the volume change during the redox reactions.…”