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Magnesium (Mg) metal secondary batteries have attracted much attention for their high safety and high energy density characteristics. However, the significant issues of the cathode/electrolyte interphase (CEI) in Mg batteries are still being ignored. In this work, a significant CEI layer on the typical Mo6S8 cathode surface has been unprecedentedly constructed through the oxidation of the chloride‐free magnesium tetrakis(hexafluoroisopropyloxy)borate (Mg[B(hfip)4]2) salt under a proper charge cut‐off voltage condition. The CEI has been identified to contain BxOy effective species originating from the oxidation of [B(hfip)4]− anion. It is confirmed that the BxOy species is beneficial to the desolvation of solvated Mg2+, speeding up the interfacial Mg2+ transfer kinetics, thereby improving the Mg2+‐storage capability of Mo6S8 host. The firstly reported CEI in Mg batteries will give deeper insights into the interface issues in multivalent electrochemical systems. [ABSTRACT FROM AUTHOR]

Rechargeable aqueous Zn/MnO2 batteries are very potential for large-scale energy storage applications owing to their low cost, inherent safety, and high theoretical capacity. However, the MnO2 cathode delivers unsatisfactory cycling performance owing to its low intrinsic electronic conductivity and dissolution issue. Herein, we design and synthesize a Ag-doped sea-urchin-like MnO2 material for rechargeable zinc-ion batteries (ZIBs). Doping Ag was found to reduce charge transfer resistance, increase the redox activity, and improve the cycling stability of MnO2. The unique sea-urchin-like structure maintains rich active sites for charge storage. As a result, the Ag-doped MnO2-based ZIB presents a high reversible specific capacity to 315 mA h g−1 at 50 mA g−1, excellent rate performance, and a capacity retention of 94.4% when cycling over 500 cycles. An ex situ TEM test demonstrates the low-dissolution property of Ag-doped MnO2. A flexible quasi-solid-state ZIB is successfully assembled using Ag-doped MnO2 on graphite paper, which shows a stable specific capacity of 171 mA h g−1 at 1 A g−1 when cycled over 600 cycles. Our investigation demonstrates the significant role played by Ag doping in enhancing the ZIB performance of MnO2, and gives some insight into developing advanced active materials by heteroatom doping. [ABSTRACT FROM AUTHOR]

Chalcogenides have been viewed as important conversion‐type Mg2+‐storage cathodes to fulfill the high volumetric energy density promise of magnesium (Mg) batteries. However, the low initial Columbic efficiency and the rapid capacity degradation remain challenges for the chalcogenide cathodes, as the clear Mg2+‐storage mechanism has yet to be clarified. Herein, we illustrate that the charge storage mechanism of the Cu2−xSe cathode is a reversible displacement reaction along with a polyselenide (PSe) mediated solution process of anion‐compensation. The unique anion redox improves charge storage, while the dissolution of PSe also leads to performance degradation. To address this issue, we introduce Mo6S8 into the Cu2−xSe cathode to immobilize PSe, which significantly improves performance, especially the reversible capacity (from 140 mAh g−1 to 220 mAh g−1). This work provides inspiration for the modification of the Mg2+‐storage cathode, which is a milestone for high‐performance Mg batteries. [ABSTRACT FROM AUTHOR]

Aqueous cells with zinc‐metal anodes featuring safety and low cost, are beneficial for diversifying energy‐storage technologies, while their energy density and cyclability have been long limited by side‐reactions and dendrite issues, especially at the practical device level. Though sustained efforts are underway to renovate electrodes and electrolytes, the roles of other indispensable components, such as separators, in the cell operation have been not fully unexplored thus far. Here, it is demonstrated that both the reversibility and utilization of aqueous zinc anodes can be improved by using a single‐ion Zn2+‐conducting nanocellulose membrane as the separator. Even without any treatments to the electrodes and thereof interfaces, this functional membrane marked by synergetic optimization on key required properties regarding mechanical strength, preferred Zn2+ conduction and hydrophilicity, mitigates H2 evolution, corrosion, and dendrite growth on zinc anodes, thus enabling >80% depth‐of‐discharge stable cycling under practically feasible lean electrolyte (electrolyte‐to‐capacity ratio = 1.0 g Ah−1) and high areal capacity (8.0 mAh cm−2) conditions. These findings translate to an excellent capacity retention of exceeding 95% after 150 cycles for full cells with practically high‐loading cathodes (17 mg cm−2). This work provides a simple yet practical avenue to high‐energy, long‐cycling aqueous zinc‐metal batteries. [ABSTRACT FROM AUTHOR]

Cheap, high-rate and long-life batteries are urgently needed for grid-scale storage of renewable energy. Rechargeable zinc (Zn) batteries are potential candidates due to the high volumetric energy density and low cost of Zn anode. However, conventional Zn batteries employing metal oxide cathodes usually suffer from poor rate capabilities caused by the high migration barrier of Zn2+ in the metal oxide host structure. Here, we circumvent this dilemma by integrating Zn electrochemistry with bis(trifluoromethanesulfonyl) imide (TFSI−) anion (de)intercalation into graphite cathode based on a Zn(TFSI) 2 /acetonitrile electrolyte. Owing to the fast intercalation of TFSI− along with the efficient Zn/Zn2+ redox kinetics, our Zn/graphite batteries enable an ultrafast charging rate up to 200C (to be fully charged in 18 s) and deliver a high power density of 16.3 kW kg−1, which is comparable to those of supercapacitors. Besides, the rational utilization of the acetonitrile-based electrolyte further endows the resultant battery with dendrite-free Zn deposition, high voltage output (>2.2 V) as well as wide-temperature adaptability from −40 to 80 °C, which is quite promising for grid-scale energy storage. Our work opens a new avenue for building high-rate low-cost batteries through coupling anion intercalation chemistry with multivalent metal anodes. • A Zn/graphite battery involving TFSI− intercalation into graphite is constructed. • An ultrafast charging rate up to 200C can be realized. • The battery has wide-temperature adaptability from −40 to 80 °C. [ABSTRACT FROM AUTHOR]