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Conversion‐type tellurium‐based cathodes have attracted great attention in aqueous zinc‐ion batteries (AZIBs) due to potentially high capacity with impressive Te4+/Te0/Te2− conversion. However, impeded by the low‐conductivity Te4+ species and unpreferred kinetics, realizing deep zinc‐tellurium redox remains a major challenge. Herein, energetic NiTe2 nanosheets are first proposed and implemented as preprepared tellurium‐based deep redox cathodes in AZIBs with accelerated electron transport and favorable kinetics. Operando synchrotron X‐ray diffraction and comprehensive ex situ characterizations demonstrate that Te4+ species from direct oxidation of NiTe2 in dilute mild‐aqueous electrolyte undergo a thermodynamic two‐step TeO2→Te→ZnTe discharge process, while the intertwined tellurium oxides and high‐conductivity nickel monomers derived in situ from NiTe2 nanosheets promote a kinetics‐preferred one‐step ZnTe→TeO2 charging conversion with significantly boosted reversibility. Therefore, a high capacity of 510 mAh g−1 at 50 mA g−1 and 93% capacity retention over 400 cycles at 2000 mA g−1 are established. Operando pH tracking and electrode‐electrolyte engineering analyses define that the mild electrolyte environment rich in moisture and electrode conductivity optimization are both critical for achieving reversible tellurium deep redox conversion. [ABSTRACT FROM AUTHOR]

The further application of promising transition‐metal chalcogenides (TMCs) cathodes in dilute neutral aqueous Zn batteries (AZBs) is mainly plagued by unsatisfactory working voltages (usually <1 V vs Zn2+/Zn) and their conventional cationic redox centers reaching theoretical capacity limit. Hence, to break the confinement, a novel Zn‐Cu2‐xSe battery is developed in dilute neutral‐aqueous electrolyte by introducing a tailored charge‐carrier, which not only alters the intercalation potential of ions embedded into Cu2‐xSe (vs Zn2+/Zn, working voltage from ≈0.4 to ≈1.2 V) but also activates the anionic redox centers of Cu2‐xSe (capacity release from 143.4 to 323.2 mAh g−1 at 0.4 A g−1). In situ synchrotron X‐ray diffraction (SXRD) and substantial ex situ characterizations reveal the multi‐step phase conversion undergone by cathode and triggered additional Se‐based anionic (Sen2−/Se2−) reversible redox reaction. A multi‐electron synergistic transfer process established on the cationic‐anionic redox centers circumvents the slow relaxation of single‐ion charge compensation achieving high‐capacity and enhanced ion diffusion kinetics. As a result, an extraordinary energy density of up to 406.2 Wh kg−1 at 240 W kg−1 is implemented (calculated based on the mass of Cu2‐xSe cathode), which is ≈8.4 times higher than that of conventional Zn‐Cu2‐xSe batteries, representing an advanced development toward energetic AZBs. [ABSTRACT FROM AUTHOR]

Sodium‐ion capacitors (SICs) are emerging energy storage devices with high energy, high power, and durable life. Sn is a promising anode material for lithium storage, but the poor conductivity of the a‐NaSn phase upon sodaition hinders its implementation in SICs. Herein, a superior Sn‐based anode material consisting of plum pudding‐like Co2P/Sn yolk encapsulated with nitrogen‐doped carbon nanobox (Co2P/Sn@NC) for high‐performance SICs is reported. The 8–10 nm metallic nanoparticles produced in situ are uniformly dispersed in the amorphous Sn matrix serving as conductive fillers to facilitate electron transfer in spite of the formation of electrically resistive a‐NaSn phase during cycling. Meanwhile, the carbon shell buffers the large expansion of active Sn and provides a stable electrode–electrolyte interface. Owing to these merits, the yolk–shell Co2P/Sn@NC demonstrates a large capacity of 394 mA h g−1 at 100 mA g−1, high rate capability of 168 mA h g−1 at 5000 mA g−1, and excellent cyclability with 87% capacity retention after 10 000 cycles. By integrating the Co2P/Sn@NC anode with a peanut shell‐derived carbon cathode in the SIC, high energy densities of 112.3 and 43.7 Wh kg−1 at power densities of 100 and 10 000 W kg−1 are achieved. [ABSTRACT FROM AUTHOR]