Ren Feihong, Li Zhendong, Chen Jiahe, Huguet Patrice, Peng Zhe, Deabate Stefano
IEM (Institut Européen des Membranes), UMR 5635 (UM-ENSCM-CNRS), Université de Montpellier, Place E. Bataillon, F-34095 Montpellier, France.
Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, China.
ACS Appl Mater Interfaces. 2022 Jan 26;14(3):4211-4219. doi: 10.1021/acsami.1c21638. Epub 2022 Jan 11.
The latest developments of localized high-concentration electrolytes (LHCEs) shed light on stabilizing the high-energy-density lithium (Li) metal batteries. It is generally considered that the nonsolvating diluents introduced into the LHCEs improve the viscosity and wettability of high-concentration electrolytes (HCEs) without changing their inner solvation structures, thus maintaining the highly coordinated contact ion pairs (CIPs) and ionic aggregates (AGGs) of the precursor HCEs with limited free solvent numbers and high Coulombic efficiency (CE) of Li metal anodes. Herein, we show an unexpected effect of the diluent amount on the solvation structures of the LHCEs: as the diluent amount increases, the proportions of free solvent molecules and CIPs rise up simultaneously. The latter is probably due to the partial splits of the AGGs via the dipole-dipole interactions between the diluent and solvent molecules. Accordingly, a moderately diluted LHCE shows the best Coulombic efficiency of Li metal anodes (99.6%), compared with the precursor HCE (97.4%) or highly diluted LHCE (99.0%). This work reveals a new criterion of the LHCE chemical formulation for the designing of advanced electrolytes for high-energy-density batteries.
局部高浓度电解质（LHCEs）的最新进展为稳定高能量密度锂（Li）金属电池提供了思路。一般认为，引入到LHCEs中的非溶剂化稀释剂可改善高浓度电解质（HCEs）的粘度和润湿性，而不改变其内部溶剂化结构，从而保持前驱体HCEs具有高度配位的接触离子对（CIPs）和离子聚集体（AGGs），同时具有有限的自由溶剂量和锂金属负极的高库仑效率（CE）。在此，我们展示了稀释剂用量对LHCEs溶剂化结构的意外影响：随着稀释剂用量增加，自由溶剂分子和CIPs的比例同时上升。后者可能是由于AGGs通过稀释剂与溶剂分子之间的偶极-偶极相互作用而部分分裂。因此，与前驱体HCE（97.4%）或高度稀释的LHCE（99.0%）相比，适度稀释的LHCE显示出锂金属负极的最佳库仑效率（99.6%）。这项工作揭示了用于设计高能量密度电池先进电解质的LHCE化学配方的新准则。
