Effects of SiO2 Particle Size in Soggy-Sand Electrolyte on Electrochemical Performance of Zinc-Ion Batteries

The presence of free water molecules in the aqueous electrolyte leads to serious side reactions at the interface, easy dissolution of the cathode material, and uncontrolled growth of zinc dendrites in Zn-ion batteries, which hinders their practical applications. Here, we propose a type of SiO 2 -based soggy-sand electrolyte (ZnSO 4 +MnSO 4 electrolyte with SiO 2 , SiO 2 -ZMSO 4 ) and focus on the effect of the SiO 2 nanoparticle size on the performance of soggy-sand electrolyte. It is found that SiO 2 with smaller nanoparticle size provides higher porosity, and the SiO 2 network-formed can effectively trap the free water in the electrolyte, which increases the ionic conductivity of electrolyte, widens working voltage window, and decreases the internal resistance of batteries. As a result, the Zn//MnO 2 batteries with 20 nm SiO 2 -based soggy-sand electrolyte show stable cycling performance and rate capacities. The specific capacity of the battery can be maintained at 198.5 mAh g −1 after 1200 cycles at 1 A g −1 without capacity degradation. The specific capacity can be increased by 100 mAh g −1 even at a high rate of 5 A g −1 . This study provides the rule of particle selection for the development of aqueous soggy-sand electrolytes used in aqueous rechargeable batteries. Graphical In this study, a novel and practical electrolyte is proposed by adding different particle sizes of SiO 2 to the conventional electrolyte and reveals the effectiveness in zinc-ion batteries. The SiO 2 with smaller particle size has larger surface porosity and a denser network structure can be formed in the electrolyte, effectively reducing the number of free water and achieving high-performance aqueous zinc-ion batteries with a specific capacity of 183 mAh g −1 after 500 cycles at 1 A g −1 .