Aqueous Dual-Electrolyte Full-Cell System for Improving Energy Density of Sodium-Ion Batteries

Abstract

Sodium-ion batteries (SIBs) are regarded as one of the most promising candidates for next-generation energy storage devices and have been gradually grasping market share for their low cost and similar reaction mechanism and production process as compared to lithium-ion batteries. However, the low energy density of SIBs restricts their practical applications. For example, regular full cells of a Prussian blue cathode and NASICON anode have only a low discharge capacity (about 77 mA h/g at 1 C). Taking into account the compatibility of the electrolyte and electrode materials, a novel strategy for a viable aqueous dual-electrolyte sodium-ion battery (ADESIB) has been proposed using Na 2 SO 4 solution as the anolyte and redox-active sodium hexacyanoferrate Na 4 Fe(CN) 6 solution as the catholyte to accommodate a NASICON NaTi 2 (PO 4 ) 3 anode and Prussian blue Na 2 NiFe(CN) 6 cathode. The capacity of Na + ion deinsertion/ insertion electrodes combined with the redox chemistry of the Na 4 Fe(CN) 6 catholyte thus enhances overall charge storage and energy density. The ADESIB delivers a capacity of about 113 mA h/g at 1 C, showing a 43% improvement over batteries with a regular single Na 2 SO 4 electrolyte. Additionally, the dual-electrolyte full-cell system is proved to reach a 84.7% capacity retention after 1000 cycles, mainly due to the synergy of the electrolytes in both sides. This pioneering research proposes an aqueous dual-electrolyte sodium-ion full cell, showing potential applications in a new sodium-ion full battery system.

A Comprehensive Evaluation of Battery Technologies for High–Energy Aqueous Batteries

“…[386][387][388][389] However, few studies have taken a comprehensive approach considering the optimal combination of the most fundamental anode, electrolyte, and cathode components. While a constant metal anode/cathode material can operate stably across a range of aqueous electrolytes, the electrochemical performances, such as battery voltage and specific [397] Copyright 2022, American Chemical Society. c) Improved battery voltage by dual electrolyte design.…”

“…[395,396] The dual-electrolyte design demonstrates effectiveness in enhancing electrode/electrolyte compatibility to enable a higher specific capacity and a maximum redox potential (Figure 18b). [397] For example, alkaline/acid hybrid electrolytes offer a wide potential window from -1.6 to 1.4 V vs. the saturated calomel electrode (Figure 18c). [398] An aqueous Zn battery constructed with a dual-electrolyte design to improve electrode-electrolyte compatibility demonstrated an operating voltage of approximately 2.5 V. [399,400] Similar voltage enhancements were observed in a Zn-Br battery with a dualelectrolyte configuration.…”

“…Reproduced with permission. [ 397 ] Copyright 2022, American Chemical Society. c) Improved battery voltage by dual electrolyte design.…”

“…b) Improved specific capacity by dual electrolyte battery design. Reproduced with permission [397]. Copyright 2022, American Chemical Society.…”