Shuaishuai Li,Xudun Shen,Bowang Zhao,Longnian Tang,Yechen Qian,Wenyao Li,Shijie Li
Aqueous sodium-ion batteries (ASIBs) are promising for large-scale electrical energy storage (LSEES) applications due to their cost and safety advantages. However, the low voltage stabilization window of water (∼1.23 V) and the lack of cathode with high specific capacity and long cycle life have limited their development. Cobalt-based Prussian blue analogues (NaCoPBAs) have the advantage of high theoretical specific capacity but short cycle life. Recently, the molecular crowding electrolyte (MCE) strategy has been proposed to improve the electrolyte voltage stability window (ESW) of electrolytes, in this work, we report an improved xMC (x: ratio, MC: molecular crowding agent) electrolyte that uses N–N dimethylacetamide (DMAC) as the molecular crowding agent and NaOTf as the advanced salt with an ESW of 2.65 V and excellent nonflammability. The side reactions of the NaCoPBA//Hard Carbon (HC) full-cell active material are improved with the aid of the electrolyte. Capacity retention of 75 % after 600 cycles with excellent cycling stability. These results demonstrate that this advanced MCE strategy can be utilized for practical applications designed for safety, high specific capacity and long cycle (ASIB).
Electrolytes serve as critical components in batteries and electrolytic cells. This study proposes a framework to assess the contributions of clusters to electric conductivity. Within this framework, clusters are first identified, and their molarities are calculated by integrating excess infrared spectroscopy with density functional theory (DFT). Subsequently, the self-diffusion coefficients of these clusters are estimated through the Stokes–Einstein relation. Finally, the conductivities of charged clusters are evaluated using the Nernst–Einstein equation. By combining these steps, the percentage contribution of charged clusters to overall electric conductivity is quantitatively determined. Taking the binary system of sodium trifluoromethanesulfonate (NaOTf) and 1,2-dimethoxyethane (DME) as a model electrolyte, liquid clusters, namely, Na+(DME)3, Na+(DME)2, OTf–(DME)4, Na(OTf)2–(DME)4, (Na)2OTf+(DME)4, NaOTf(DME)2, NaOTf(DME)3, as well as DME monomer, dimer, trimer, and tetramer, were identified in the binary mixtures. Contributions from charged clusters to the overall conductivity at each experimental concentration were derived. It was found that, at low salt concentrations, Na+(DME)3 plays the dominant role, while at high concentrations, the biggest contributor is OTf–(DME)4. Together with other techniques including nuclear magnetic resonance and molecular dynamics, DME was found to interact strongly with Na+, in a mode of bidentate to make a coordination number of six. On the contrary, the interaction between DME and OTf– is weak, with negligible hydrogen bonds. The present work addresses the conductivity properties of electrolytes at the cluster level, providing physical insights into the concerned topic. It may also shed light on the design of new electrolytes to meet the needs of vigorously developing battery industries.
危险品化学品经营许可证（带存储）