Highly Concentrated Electrolyte towards Enhanced Energy Density and Cycling Life of Dual‐Ion Battery

Rational Design of Functional Electrolytes Towards Commercial Dual-Ion Batteries

Dual-ion batteries (DIBs) based on anion (de)intercalation into low-cost graphitic carbon cathodes hold great promise in grid-scale energy storage. Different from the electrolyte in rocking-chair batteries, which only serves as a charge transporter, both cations and anions in the electrolyte for DIBs participate in battery reactions. Hence, the impact of the electrolyte formulation on cycle life, energy density, as well as cost has become a subject of vital importance. This review discussed the challenges and recent progress of electrolytes for DIBs, with a particular focus on the exploration of electrolytes with high oxidation stability, high salt concentration, high ionic conductivity, and low cost. Moreover, the influence of varied ion concentrations at different state-of-charge levels on the electrolyte properties such as ionic conductivity and electrochemical stability is analyzed. Finally, perspectives on the current limitations and future research directions of electrolytes for DIBs are provided.

Opportunities and Limitations of Ionic Liquid- and Organic Carbonate Solvent-Based Electrolytes for Mg-Ion-Based Dual-Ion Batteries

Dual-ion batteries (DIBs) offer a great alternative to state-of-the-art lithium-ion batteries, based on their high promises due to the absence of transition metals and the use of low-cost materials, which could make them economically favorable targeting stationary energy storage applications. In addition, they are not limited by certain metal cations, and DIBs with a broad variety of utilized ions could be demonstrated over the last years. Herein, a systematic study of different electrolyte approaches for Mg-ion-based DIBs was conducted. A side-by-side comparison of Li- and Mg-ion-based electrolytes using activated carbon as negative electrode revealed the opportunities but also limitations of Mg-ion-based DIBs. Ethylene sulfite was successfully introduced as electrolyte additive and increased the specific discharge capacity significantly up to 93±2 mAh g-1 with coulombic efficiencies over 99 % and an excellent capacity retention of 88 % after 400 cycles. In addition, and for the first time, highly concentrated carbonate-based electrolytes were employed for Mg-ion-based DIBs, showing adequate discharge capacities and high coulombic efficiencies.