Rechargeable aqueous Zn-ion batteries are attractive cheap, safe and green energy storage technologies but are bottlenecked by limitation in high-capacity cathode and compatible electrolyte to achieve satisfactory cyclability. Here we report the application of nonstoichiometric ZnMnO/carbon composite as a new Zn-insertion cathode material in aqueous Zn(CFSO) electrolyte. In 3 M Zn(CFSO) solution that enables ∼100% Zn plating/stripping efficiency with long-term stability and suppresses Mn dissolution, the spinel/carbon hybrid exhibits a reversible capacity of 150 mAh g and a capacity retention of 94% over 500 cycles at a high rate of 500 mA g. The remarkable electrode performance results from the facile charge transfer and Zn insertion in the structurally robust spinel featuring small particle size and abundant cation vacancies, as evidenced by combined electrochemical measurements, XRD, Raman, synchrotron X-ray absorption spectroscopy, FTIR, and NMR analysis. The results would enlighten and promote the use of cation-defective spinel compounds and trifluoromethanesulfonic electrolyte to develop high-performance rechargeable zinc batteries.

A key challenge faced by organic electrodes is how to promote the redox reactions of functional groups to achieve high specific capacity and rate performance. Here, we report a two-dimensional (2D) microporous covalent-organic framework (COF), poly(imide-benzoquinone), via in situ polymerization on graphene (PIBN-G) to function as a cathode material for lithium-ion batteries (LIBs). Such a structure favors charge transfer from graphene to PIBN and full access of both electrons and Li ions to the abundant redox-active carbonyl groups, which are essential for battery reactions. This enables large reversible specific capacities of 271.0 and 193.1 mAh g at 0.1 and 10 C, respectively, and retention of more than 86 % after 300 cycles. The discharging/charging process successively involves 8 Li and 2 Li in the carbonyl groups of the respective imide and quinone groups. The structural merits of PIBN-G will trigger more investigations into the designable and versatile COFs for electrochemistry.

Potassium-ion batteries (KIBs) are plagued by a lack of materials for reversible accommodation of the large-sized K ion. Herein we present, the Bi anode in combination with the dimethoxyethane-(DME) based electrolyte to deliver a remarkable capacity of ca. 400 mAh g and long cycle stability with three distinct two-phase reactions of Bi↔ KBi ↔K Bi ↔K Bi. These are ascribed to the gradually developed three-dimensional (3D) porous networks of Bi, which realizes fast kinetics and tolerance of its volume change during potassiation and depotassiation. The porosity is linked to the unprecedented movement of the surface Bi atoms interacting with DME molecules, as suggested by DFT calculations. A full KIB of Bi//DME-based electrolyte//Prussian blue of K Fe[Fe(CN) ] is demonstrated to present large energy density of 108.1 Wh kg with average discharge voltage of 2.8 V and capacity retention of 86.5 % after 350 cycles.

Dipotassium terephthalate coupled with an ether-based electrolyte is used as a novel anode for potassium-ion batteries and exhibits superior electrochemical performance.