Aqueous redox flow batteries (ARFBs) based on the electrolyte solutions of redox-active organic molecules are very attractive for the application of large-scale electrochemical energy storage. We propose a high-performance ARFB system utilizing 2hydroxy-3-carboxy-1,4-naphthoquinone (2,3-HCNQ) and K 4 Fe-(CN) 6 as the anolyte and catholyte active species, respectively. The 2,3-HCNQ molecule exhibits high solubility and can carry out a reversible two-electron redox process with rapid redox kinetics. The assembled 2,3-HCNQ/K 4 Fe(CN) 6 ARFB delivered a cell voltage of 1.02 V and realized a peak power density of 0.255 W cm −2 . The 2,3-HCNQ/K 4 Fe(CN) 6 ARFB can be stably operated at a current density of 100 mA cm −2 for long-term cycling (with a capacity retention of ∼94.7% after 100 cycles).

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Redox flow batteries are promising for large-scale energy storage, but some long-standing problems such as safety issues, system cost and cycling stability must be resolved. Here we demonstrate a type of redox flow battery that is based on all-polymer particulate slurry electrolytes. Micro-sized and uniformly dispersed all-polymer particulate suspensions are utilized as redox-active materials in redox flow batteries, breaking through the solubility limit and facilitating the application of insoluble redox-active materials. Expensive ion-exchange membranes are replaced by commercial dialysis membranes, which can simultaneously realize the rapid shuttling of H + ions and cut off the migration of redox-active particulates across the separator via size exclusion. In result, the all-polymer particulate slurry redox flow batteries exhibit a highly reversible multi-electron redox process, rapid electrochemical kinetics and ultra-stable long-term cycling capability.

Rechargeable magnesium batteries (RMBs) based on metal Mg anodes have shown great potential owing to the abundant natural resources, high volumetric capacity, and low safety hazard. Nevertheless, the development of RMBs is hampered by the sluggish kinetics of Mg2+ diffusion and the limited cyclability of cathode materials. Herein, nonstoichiometric copper selenide (Cu2–xSe) are synthesized via a solution‐based method and exploited as a durable cathode material based on ionic displacement mechanism for RMBs. The copper ions in the Se2− based sub‐lattices are reversibly exchanged by Mg2+ ions without causing lattice collapse. Owing to the same face‐centered cubic Se2− sub‐lattices and similar unit cell size of Cu2–xSe and MgSe, the energy barrier for lattice reconstruction during cycling processes is very low, significantly improving the rate performance, structural stability, and cycle life of the Cu2–xSe cathode. Moreover, metal Cu is in situ generated during discharging, thus greatly facilitating electron transport. Comprehensive characterizations confirm that the Cu2–xSe cathode undergoes reversible copper ion extrusion/reinjection during the discharge−charge steps. This work suggests the great potential for exploring high‐performance electrode materials based on ionic displacement mechanism for advanced multivalent‐ion secondary batteries.

Rechargeable lithium metal batteries are of tremendous interest due to the high theoretical capacity and low reduction potential of lithium metal anode. However, the formation of unstable solid electrolyte interphase (SEI) results in lithium dendrite growth and low Coulombic efficiency during Li plating/stripping processes. Herein, we report an effective strategy to stabilize Li metal anode by in situ constructing antimony-based lithiophilic interphase on Li anode (Sb–Li) using antimony triiodide-tetrahydrofuran (THF) solution. The antimony-based lithiophilic interphase is composed of amorphous antimony and lithium compounds, revealed by in-depth X-ray photoelectron spectroscopy. The Sb–Li anode enables dendrite-free Li deposition in both ether- and ester-based electrolytes. As a result, as-assembled lithium–sulfur (Li–S) batteries with Sb–Li anode exhibit an initial capacity of 915 mAh g–1 at 1.0 C and a capacity retention >83% after 400 cycles. Operando Raman analysis confirmed that the antimony-based lithiophilic interphase can prevent parasitic side reactions, and also relieve the shuttle effect of polysulfides. Furthermore, Sb–Li|LiFePO4 cells have also realized high rate performance and stable cyclability. We expect this effective strategy for stabilizing Li metal anode will provide a valuable route to develop high-energy Li metal batteries.

Comprised of a battery anode and a supercapacitor cathode, hybrid lithiumion capacitors (HLICs) are found to be an effective solution to realize both high power density and high energy density at the same time. Organic-inorganic hybrid materials with well-organized framework guided by the reticular chemistry are one of the promising anode materials for HLICs because of rich active sites and ordered porosity. Herein, metal−organic framework consisting of Zr 4+ metal ions and tetrathiafulvalene-based ligands (Zr-MOF) is proposed as the pseudocapacitive anode of HLICs. The Zr-MOF possesses high stability, high crystallinity, and multiple meso-microporous channels favorable for ion transport. The as-prepared Zr-MOF||activated carbon HLICs present high energy density (122.5 Wh kg −1 ), high power density (12.5 kW kg −1 ), and stable cycling performance (86% capacity retention after 1000 cycles at 2000 mA g −1 ) within the operating voltage range of 1.0-4.0 V. The results expand the direct application of MOF for bridging the performance gap between batteries and supercapacitors.

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