Metallic tin (Sn) has always been considered as an anode candidate for nonaqueous lithium-ion batteries (LIBs). Nevertheless, there were hardly any attempts to use Sn as an anode material in aqueous batteries. Although Sn possesses relatively high specific capacity (451.54 mAh/g, two-electron transfer reaction), mild electrode potential (−0.1375 V vs the standard hydrogen electrode, Sn2+ + 2e– = Sn), high hydrogen overpotential, and environmental friendliness, it also suffers from bad reversibility and low Coulombic efficiency (CE) in common aqueous electrolytes. In this work, a dendrite-free Sn anode with highly improved reversibility in an aqueous electrolyte was realized using a type of “water-in-salt” electrolyte (1 m Sn(OTf)2 + 20 m LiTFSI). The results of Fourier transform infrared (FTIR) spectra and density functional theory (DFT) calculations have verified the significant impact of highly concentrated LiTFSI salt on Sn2+ hydrolysis, which is the key factor in improving the reversibility of the Sn anode and suppressing the dendrite formation. A Sn/LiFePO4 cell applying this electrolyte was acquired with a discharge plateau at around 0.6 V. In the cyclability test, the Sn anode exhibited a stable discharge capacity of more than 107 mAh/g with a Coulombic efficiency (CE) of 95% for 35 cycles (0.2C rate).
Hao Liu,Jinhao Xie,Fang Yang,Peng Zhang,Chaolun Liang,Yanxia Yu,Peng Liu,Xihong Lu
The inactive “dead Sn” formation and the unfavorable hydrogen evolution reaction (HER) are the two issues limiting the lifespan and coulombic efficiency of Sn anodes in aqueous acidic batteries, particularly in high-areal-capacity cases. Herein, we propose the utilization of triethyl phosphate (TEP) as a bifunctional electrolyte additive to simultaneously modulate the interfacial properties and reshape the Sn 2+ solvation structure. Systematic characterizations evidence that the presence of such dual-functional TEP additive can substantially prohibit hydrogen evolution and promote the “dead-Sn-free” Sn deposition. Accordingly, both Sn||Sn and Sn||Cu cells assembled in TEP-modified electrolyte present exceptional cycling performance, maintaining continuous operation for over 760 h at 5mAh cm −2 and 5 mA cm −2 . When coupled with a MnO 2 cathode, the existence of TEP additive endows Sn||MnO 2 full batteries with a remarkable upgrade of rate capability and cycling stability. This study demonstrates that regulating interfacial adsorption and electrolyte solvation structure is a highly effective strategy to enhance the overall performance of Sn anodes.
An efficient interface and composition modification strategy is proposed to significantly increase the rate capacity and initial Coulombic efficiency (ICE) of SnO anodes via energy band structure modulation for Na-ion batteries (SIBs). The as-fabricated SnO@Bi@C material with Bi nanocrystals homogeneously dispersed on and around the SnO surface is prepared by an electrospinning method. The excellently dispersed Bi nanocrystals realize an effective interface contact with SnO and Na2O, which effectively lowers the electron conduction barriers and promotes sodium-ion release and transport upon the desodiation process, increasing the rate capacity and ICE of the SnO anode. The prepared SnO@Bi@C exhibits a much higher rate capacity up to 10 A g–1, except an improved ICE of 80.67%, compared to 57.38% of SnO@C. Importantly, the intercalation of Na+ between layer-structured Bi galleries provides a good basis for excellent cycle stability due to the highways constructed inside the prepared composites. This finding provides an effective tactic to establish ion transport high-speed channels, which essentially increase the rate performance and the ICE of the SnO-based anodes.
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