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Calcium metal batteries, as one of the promising alternatives beyond Li‐metal technology, is held back by the lack of suitable cathodes of considerable energy storage capability, and Ca anodes of long‐term stability and lower polarization potentials for Ca‐plating/stripping. Here, by recycling cellulose waste paper, feasible cathodes for Ca‐metal batteries of good high‐voltage and wide‐window‐voltage adaptability (0.005–4.9 V versus Ca/Ca2+), and impressive energy density (≈517.5 Wh kg−1 at 0.1 A g−1) are developed. Meanwhile, through tailorable Ca‐plating/stripping potentials (∆V≈ 0.65 V) realized by a modified electrolyte of Li+, Ca2+, BF4−, and PF6− multi‐ions system, the proof‐of‐concept Ca‐metal batteries not only delivered enhanced storage capability (101 mAh g−1 versus 51 mAh g−1 at 0.1 A g−1 in the window voltage of 2.0–4.7 V) and cycling stability (≈77% capacity retention for 100 cycles), but also simultaneously show a high output average working voltage of ≈3.2 V. The work provides a hint that mixed metal deposition under multi‐ions electrolyte system may address the challenging issues faced by single alkali or alkaline‐earth metal batteries. [ABSTRACT FROM AUTHOR]

Porous NiCo 2 S 4 nanosheets derived from bimetallic MOFs directly grow on a conductive substrate as a binder-free electrode. The unique open-structure NiCo 2 S 4 with porosity facilitates the diffusion of electrolyte and possess abundant electroactive sites, which presents a high specific capacity and long-term cycling stability. An assembled hybrid capacitor exhibits the practical performance of high energy density and excellent cycling property. • The porous NiCo 2 S 4 nanosheet arrays derived from bimetallic Metal-organic frameworks derivatives are prepared. • The effect of NiCo 2 S 4 morphology on electrochemical performance and reaction mechanism are discussed. • A hybrid supercapacitor device exhibits high energy density and superior cycling stability. Recently, metal-organic frameworks (MOFs) derived materials in the form of bulk powders with attractive chemical and structural properties show broad application in electrochemical energy storage. Bimetallic materials-based MOFs usually show better electrochemical properties than that of monometallic derivatives, while achieving the bimetallic MOFs-derived materials on current collector as a binder-free electrode is still a challenge. Here we report a new approach to directly obtain a binder-free electrode of bimetallic MOFs-derived NiCo 2 S 4 nanosheet arrays on nickel foam (NF) substrate. The porous NiCo 2 S 4 nanosheet arrays providing fast electrolyte permeation and rich electrochemical active sites, show an excellent specific capacity of 1354.4 C g−1, high rate performance, and outstanding cycling stability of 82.6% retention after 10,000 cycles. A hybrid supercapacitor assembled with the as-obtained binder-free electrode as a cathode and active carbon as an anode, exhibits high energy density of 49.1 Wh kg−1 at a power density of 375 W kg−1 and superior cycling stability of 94.5% retention after 10,000 cycles. These results offer a novel and general approach to construct binder-free electrode materials with advanced performance for the portable and practical energy storage device. [ABSTRACT FROM AUTHOR]