Advances and Prospects of High-Voltage Spinel Cathodes for Lithium-Based Batteries.

Insertion compounds have been dominating the cathodes in commercial lithium-ion batteries. In contrast to layered oxides and polyanion compounds, the development of spinel-structured cathodes is a little behind. Owing to a series of advantageous properties, such as high operating voltage (≈4.

High-Energy, Single-Ion-Mediated Nonaqueous Zinc-TEMPO Redox Flow Battery.

Two distinct advantages of nonaqueous redox flow batteries (RFBs) are the feasibility of building a high cell voltage (without a constraint of the water-splitting potential) and the operability at low temperatures (without a concern of freezing below 0 °C). However, electrochemically active organic redox couples are usually selectively soluble in specific nonaqueous solvents, and their solubility is relatively low (in contrast to that in aqueous solutions). The selective and low solubility of redox couples seriously constrict the practical energy density of nonaqueous RFBs.