Achieving three-dimensional lithium sulfide growth in lithium-sulfur batteries using high-donor-number anions

Abstract

Uncontrolled growth of insulating lithium sulfide leads to passivation of sulfur cathodes, which limits high sulfur utilization in lithium-sulfur batteries. Sulfur utilization can be augmented in electrolytes based on solvents with high Gutmann Donor Number; however, violent lithium metal corrosion is a drawback. Here we report that particulate lithium sulfide growth can be achieved using a salt anion with a high donor number, such as bromide or triflate. The use of bromide leads to ~95 % sulfur utilization by suppressing electrode passivation. More importantly, the electrolytes with high-donor-number salt anions are notably compatible with lithium metal electrodes. The approach enables a high sulfur-loaded cell with areal capacity higher than 4 mA h cm−2 and high sulfur utilization ( > 90 %). This work offers a simple but practical strategy to modulate lithium sulfide growth, while conserving stability for high-performance lithium-sulfur batteries.

Expediting redox kinetics of sulfur species by atomic‐scale electrocatalysts in lithium–sulfur batteries

“…The nucleation and growth of Li 2 S 1/2 are intimately affected by current density, deposit-substrate affinity, and intrinsic nucleation sites on substrates. [59][60][61][62][63][64] The atomic Co-N-C electrocatalysts favor Li 2 S 1/2 nucleation through lithium bonds and sulfiphilic sites. 55 The high electrocatalytic property toward LiPS conversion endows the current density peak of the Co-N-C based cell with 1650 s ahead in comparison with C based cell ( Figure 2B).…”

“…The nucleation and growth of Li 2 S 1/2 are intimately affected by current density, deposit‐substrate affinity, and intrinsic nucleation sites on substrates . The atomic Co‐N‐C electrocatalysts favor Li 2 S 1/2 nucleation through lithium bonds and sulfiphilic sites .…”

Mechanism of Li2S formation and dissolution in Lithium-Sulphur batteries

“…Many studies consider Li2S to form via direct electroreduction of Li2S2 (or higher-order PSs) at the carbon-electrolyte interface [8][9][10][11][12] . However, as electrodeposition of an insulator is in principle self-limited, the fact that Li2S deposits are beyond tens and hundreds of nm in size [13][14][15] suggest that they form via a solution-mediated process. This is supported by the finding that capacity is limited by mass transport in the tortuous Li2S-carbon pore network.…”

Hollow multishelled structural NiO as a “shelter” for high-performance Li–S batteries

“…Li-S batteries with unique multi-electron, multi-phase, multistage reaction characteristics possess an ultra-high theoretical energy density. 1 However, the practical application of Li-S batteries is limited by several challenges including the volume expansion of sulfur, the intrinsic insulating lithium sulfide, 2 and the shuttle effect of soluble lithium polysulfides (Li 2 S n , 4 p n p 8, LiPSs), 3 which result in a low utilization of active materials and Coulombic efficiency, rapid capacity decay and poor practically-achievable energy density. 4 To address these problems, tremendous efforts have been devoted to constructing sulfur hosts and battery configurations, for instance from the initial non-polar mesoporous carbon materials 5 to the heteroatom-doped carbon materials, 6,7 and metal compounds, [8][9][10] as well as the functionalization of separators 11,12 and interlayers.…”

“…Polysulfide is reduced to solid insoluble Li 2 S, which causes pore blockage and forms a passivation layer on the surface of carbon fiber, thus not only limiting the diffusion of Li + , but also delaying the reduction of PS in the pore structure which may cause polysulfides to shuttle to the negative electrode. 2 In the AB/CC-S electrode, the acetylene black interlayer could physically limit the shuttle effect of LiPSs, leading to improved sulfur utilization. In the NiO HoMSs/CC-S electrode, in addition to the physical-confinement of LiPSs by the acetylene black, the NiO HoMSs could not only chemically anchor polysulfides but also physically confine LiPS diffusion with favorable multishelled structures, thus significantly improving sulfur utilization and specific capacity.…”