Aqueous rechargeable Zn–MnOx batteries are very attractive due to their low‐cost and high energy density. However, Mn(III) disproportionation and Jahn–Teller distortion can induce Mn(II) dissolution and irreversible phase changes, greatly deteriorating the cycling life. Herein, a multi‐valence cobalt‐doped Mn3O4 (Co‐Mn3O4) with high capacity and reversibility, which lies in the multiple roles of the various states of doped cobalt, is reported. The Co2+ doping between the phase change product δ‐MnO2 layer acts as a “structural pillar,” and the Co4+ in the layer can increase the conductivity of Mn4+ and hold the high specific capacity. More importantly, Co ion (Co2+, Co3+) doping can effectively inhibit the Jahn–Teller effect in discharge products and promote ion diffusion. Using X‐ray absorption spectra results and density functional theory modelling, the multiple roles of doped cobalt are verified. Specifically, the Co‐Mn3O4 cathode shows high specific capacity of 362 mAh g–1 and energy density of 463.1 Wh kg–1 at 100 mA g–1. After 1100 cycles at 2.0 A g–1, the capacity retention rate reaches 80%. This work brings a new idea and approach to the design of highly reversible Mn‐based oxides cathode materials for Zn‐ion batteries.

In recent years, rechargeable aqueous zinc‐ion batteries (ZIBs) have received much attention. However, the disproportionation effect of Mn2+ seriously affects the capacity retention of ZIBs during cycling. Here, the capacity retention of the Mn3O4 cathode is improved by effective valence engineering. The valence engineering of Mn3O4 is caused by bulk oxygen defects, which are in situ derived from the Mn‐metal organic framework during carbonization. Bulk oxygen defects can change the (MnO6) octahedral structure, which improves structural stability and inhibits the dissolution of Mn2+. The ZIB assembled from bulk oxygen defects Mn3O4@C nanorod arrays (Od‐Mn3O4@C NA/CC) exhibits an ultra‐long cycle life, reaching 84.1 mAh g−1 after 12 000 cycles at 5 A g−1 (up to 95.7% of the initial capacity). Furthermore, the battery has a high specific capacity of 396.2 mAh g−1 at 0.2 A g−1. Ex situ characterization results show that initial Mn3O4 is converted to ramsdellite MnO2 for insertion and extraction of H+ and Zn2+. First‐principles calculations show that the charge density of Mn3+ increases greatly, which improves the conductivity. In addition, the flexible quasi‐solid‐state ZIB is successfully assembled using Od‐Mn3O4 @ C NA/CC. Valence engineering induced by bulk oxygen defects can help develop advanced cathodes for aqueous ZIB.

No abstract

No abstract

No abstract

Zinc metal batteries show tremendous applications in wide-scale storages still impeded by aqueous electrolytes corrosion and interfacial water splitting reaction. Herein, a zincophobic electrolyte containing succinonitrile (SN) additive is proposed, the SN electrolyte shows a lower affinity for zinc but a stronger affinity for solid-state interphase (SEI). In the SN electrolyte, zinc hydroxide sulfate (ZHS) is more inclined to accumulate horizontally, forming a dense SEI protective layer on the surface of the Zn anode, effectively slowing down the corrosion of Zn and dendrite growth. The zincophobic SN electrolyte enables excellent performance: zinc plating/stripping Coulombic efficiency of 99.71% for an average of 400 cycles; stable cycles in a symmetric cell for 4000 h (0.9% zinc utilization) and 325 h (86.1% zinc utilization). The soft pack battery using limited zinc delivers maximum energy density of 57.0 Wh kg −1 (based on mass loading of cathode materials and anode materials). Such a simple additive strategy provides a theoretical reference for zinc chemistry in a mild electrolyte environment in practical applications.

The theoretical specific capacity of tin oxide (SnO2) anode material is more than twice that of graphite material (782 vs 372 mAh g–1), whereas its potential usage is limited fatally by its huge volume expansion during lithiation. An effective solution is to encapsulate tin oxide into hollow structure such as yolk‐shell based on the principle of confinement. However, in light of the restricted space of active substance, this kind of hollow electrode always has the low capacity, severely limiting its commercial value. Herein, a peapod‐like Cu‐SnO2@copper foam (CF) as high area specific capacity anode based on the Kirkendall effect, in which the “pod and peas” in the peapod‐like structure are composed of SnO2 and Cu nanoparticles, respectively, is tactfully designed and constructed. Compared to other SnOx‐based electrodes with different hollow structure designs in published reports, the unique peapod‐like Cu‐SnO2@CF anode delivers a remarkably high first reversible capacity of 5.80 mAh cm‐2 as well as excellent cycle stability with 66.7% capacity retention and ≈100% coulombic efficiency after 200 cycles at a current density of 1 mA cm–2, indicative of its quite promising application toward high‐performance lithium‐ion batteries.

No abstract