D-Lactitol restructures thick inner Helmholtz plane and coordinates multi-Zn2+ solvation sheath via unique adsorption geometry and super-multi zincophilic/hydrophilic sites
Conventional electrolyte additives often suffer from insufficient zincophilic/hydrophilic sites and limited molecular dimensions, constraining their regulation capability. Herein, we investigate D-lactitol (LAC), a super polyol additive featuring nine uniformly distributed hydroxyl groups and extended molecular length of 7.605 Å. Abundant zincophilic/hydrophilic sites enable LAC to concurrently coordinate three Zn 2+ solvation sheaths while maintaining interactions with surrounding free water molecules through remaining hydroxyls. Moreover, vertically oriented adsorption of LAC molecules on Zn anode surface expands inner Helmholtz plane from 1.5 Å to 8 Å. The unique adsorption geometry and sterically distributed hydroxyl groups bring about physical blocking, chemical screening, Zn 2+ flux homogenization, and structural resilience. These effects collectively inhibit water and SO 4 2− access, guide dominant Zn (002) plane deposition, promote uniform transport of high-flux Zn 2+ . Consequently, LAC extends cycling lifetime of Zn||Zn symmetric cells from 27 h to 1582 h at 10 mA cm −2 /1 mAh cm −2 and from 24 h to 310 h at 20 mA cm −2 /20 mAh cm −2 , and achieves stable cycling for 326 h at a high depth of discharge (58.07 %). In Zn||Cu asymmetric cell, over 5420 cycles, LAC maintains an exceptional average Coulombic efficiency of 99.74 %. Furthermore, LAC enhances cycling stability and rate performance of Zn||MnVO full cells. This study advances molecular engineering of electrolyte additives for advanced Zn anodes.
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