New Lithium Salt Forms Interphases Suppressing Both Li Dendrite and Polysulfide Shuttling

Abstract

1675 mA h g −1 ), low-toxicity, high natural abundance of sulfur, as well as environmental friendliness. [1][2][3][4][5] However, two major challenges closely associated with the electrolytes prevented any immediate commercialization of LSB: 1) the incessant reaction between Li-metal and electrolytes, leading to the constant growth of Li dendrite and inactive Li [6][7][8] and 2) the dissolution of the intermediate polysulfides and their subsequent shuttling. [9][10] These irreversible and parasitic processes result in fast capacity degradation, persistent loss of active materials (both Li and S), severe self-discharge and even catastrophic safety hazard. [11][12] Aiming to resolve these parasitic reactions, significant efforts have been made to develop new electrolyte formulations, including electrolyte additives [13][14][15] solvents, [16][17] and Li salts, with structures of either unsaturation or fluorination that can contribute unique interphasial chemistries to protect Li-metal or suppress polysulfide dissolution and shuttling. [18][19] Among these components, new anionic compounds (counterions of Li + in the salts) are rather rare as compared with new molecular compounds (solvents and additives), mainly due to the much higher difficulty associated with their designing and synthesis. Hence, how anions contribute to interphases remains little understood, although a few successful examples of anionderived interphases, as represented by LiBOB and LiDFOB in nonaqueous and LiTFSI in aqueous electrolytes, suggests that the protections provided by such interphases often outperform their molecular counterparts. In particular, for the interphase protecting Li-metal anode, the anion-derived interphase seems to be more effective than those formed by solvents or additives. [20][21][22][23] One challenge presented for anion-derived interphases is their negatively charged nature, which discourages their presence in the inner-Helmholtz layer at anode surface. [24] In the case of water-in-salt electrolytes (WiSE), such "anode challenge" was partially offset by superconcentration, which compresses the anions into the inner-Helmholtz layer and forces an interphasial chemistry that is otherwise impossible in diluted aqueous electrolyte. The astonishing benefit brought by such anion-derived interphase is an electrochemical stability window of 3-4 V. [25][26] Superconcentration concept has also been applied on both Li-metal anode [27] and sulfur-cathode, [28] in the hope that the interphasial chemistries formed by the existing Lithium-sulfur batteries (LSBs) are considered promising candidates for the next-generation energy-storage systems due to their high theoretical capacity and prevalent abundance of sulfur. Their reversible operation, however, encounters challenges from both the anode, where dendritic and dead Li-metal form, and the cathode, where polysulfides dissolve and become parasitic shuttles. Both issues arise from the imperfection of interphases between electrolyte and electrode. Herein, a new lithium salt based on ...

Low‐Density Fluorinated Silane Solvent Enhancing Deep Cycle Lithium–Sulfur Batteries’ Lifetime

“…Herein, we proposed a novel LFE (0.4 m LiTFSI + 0.4 m LiNO 3 + DME/DOL/TFMTMS [48/17/35]), in which 0.1 m LiHDFD was added to form cathode–electrolyte interface on the sulfur cathode, as proven in Xu's previous work. [ 19 ] This LFE's density was only 1.02 g mL −1 , much lower than that of previous electrolytes. It presented with a much larger volume relative to that of conventional electrolytes (≈1.17 g mL −1 ) and HCEs (1.52 g mL −1 ) under the same mass (Figure S8a, Supporting Information).…”

Recent Advances in Silicon‐Based Electrodes: From Fundamental Research toward Practical Applications

“…[116][117][118] Suppressing dendrite formation is, therefore, of paramount importance, and a variety of techniques have been investigated, including material tailoring, electrolyte optimization, functionalizing the separator, and building artificial anode/electrolyte interfaces. [119][120][121][122] Electrolyte gas generation is another safety concern and a common cause for battery performance degradation, which originates from the chemical and redox decomposition of the electrolyte throughout the working lifetime of LIBs. [123,124] The decomposition of electrolyte solvents contributes to the production of multiple gases, such as CO 2 , CO, H 2 , and ether, and is affected by the temperature and state-of-charge (SOC) of the battery.…”

“…[ 116–118 ] Suppressing dendrite formation is, therefore, of paramount importance, and a variety of techniques have been investigated, including material tailoring, electrolyte optimization, functionalizing the separator, and building artificial anode/electrolyte interfaces. [ 119–122 ]…”

Electrospinning‐Based Strategies for Battery Materials

“…[ 59 ] However, several challenges hinder their applications including the poor electrical conductivity of sulfur and Li 2 S, high solubility of polysulfide and large volume change of 80%, [ 4c ] which lead to low rate capacity, poor Coulomb efficiency, and fast capacity degradation. [ 60 ] Due to the high electrical conductivity, porous structure, and excellent mechanical stability, porous carbon nanomaterials are widely chosen as sulfur hosts, which can enable fast electron transport, effective ion diffusion, good accommodation of volume change, and absorption of polysulfide. The electrospinning‐based technique has become research hotspot on the preparation of CNFs with different porous structures from 0D hollow spheres to 1D hollow channels.…”