Facet-Controlled LiMn2O4/C as Deionization Electrode with Enhanced Stability and High Desalination Performance
Yuxin Jiang, Liyuan Chai, Dehe Zhang, Fangping Ouyang, Xiangyuan Zhou, Sikpaam Issaka Alhassan, Sailin Liu, Yingjie He, Lvji Yan, Haiying Wang, Wenchao Zhang
Abstract
The scarcity of freshwater is a global challenge, and desalination is a rational path toward alleviating the crisis because saltwater covers most of the surface of planet Earth [ 1 , 2 , 3 ]. Most of the current desalination techniques (such as reverse osmosis and distillation) work under high-pressure or high-temperature conditions, which are cost-intensive and not energy-efficient [ 4 , 5 , 6 ]. A green, affordable method with low energy consumption under mild operation conditions is in high demand. As a newly developed technology, capacitive deionization (CDI) could be a rational choice due to its cost-effectiveness and energy efficiency [ 7 , 8 ]. A CDI cell provides an electric field that drives the salt ions to be adsorbed onto the electrode materials and simultaneously stores the energy. Traditional carbonaceous electrodes have low desalination capacities (< 15 mg g −1 ) because of the electrical double-layer (EDL) behavior of charge storage limited to the surface area [ 9 , 10 ]. In the quest for higher deionization performance, battery electrodes have been employed in recent research owing to their larger electrochemical capacities, such as sodium-ion battery materials (sodium transition metal oxides, transition metal oxides, sodium super ion conductor materials, and Prussian blue analogues) and chloride battery materials (Ag-based or Bi-based materials, etc.) [ 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 ]. Although quite a few studies have initiated the use of battery materials applied in deionization systems, these materials are still difficult to scale up for real applications due to the low energy density and instability of the battery materials in aqueous-based electrolytes [ 20 , 21 ].