Aqueous zinc-ion batteries attract increasing attention due to their low cost, high safety, and potential application in stationary energy storage. However, the simultaneous realization of high cycling stability and high energy density remains a major challenge. To tackle the above-mentioned challenge, we develop a novel Zn/VO rechargeable aqueous hybrid-ion battery system by using porous VO as the cathode and metallic zinc as the anode. The VO cathode delivers a high discharge capacity of 238 mAh g at 50 mA g. 80% of the initial discharge capacity can be retained after 2000 cycles at a high current density of 2000 mA g. Meanwhile, the application of a "water-in-salt" electrolyte results in the increase of discharge platform from 0.6 to 1.0 V. This work provides an effective strategy to simultaneously enhance the energy density and cycling stability of aqueous zinc ion-based batteries.

Lithium–sulfur (Li–S) batteries have attracted remarkable attention due to their high theoretical capacity of 1675 mAh g−1, rich resources, inexpensiveness, and environmental friendliness. However, the practical application of the Li–S battery is hindered by the shuttling of soluble lithium polysulfides (LiPSs) and slow redox reactions. Herein, a 3D nitrogen‐doped graphene/titanium nitride nanowires (3DNG/TiN) composite is reported as a freestanding electrode for Li–S batteries. The highly porous conductive graphene network provides efficient pathways for both electrons and ions. TiN nanowires attached on the graphene sheets have a strong chemical anchor effect on the polysulfides, which is proved by the superior performance and by density functional theory calculations. As a result, the 3DNG/TiN cathode exhibits an initial capacity of 1510 mAh g−1 and the capacity remains at 1267 mAh g−1 after 100 cycles at 0.5 C. Even at 5 C, a capacity of 676 mAh g−1 is reached. With a high sulfur loading of 9.6 mg cm−2, the 3DNG cathode achieves an ultrahigh areal capacity of 12.0 mAh cm−2 at a high current density of 8.03 mA cm−2. This proposed unique structure gives a bright prospect in that high energy density and high power density can be achieved simultaneously for Li–S batteries.

Batteries are the most widely used energy storage devices, and the lithium‐ion battery is the most heavily commercialized and most widely used battery type in the industry. However, the current rapid development of society requires a major advancement in battery materials to achieve high capacity, long life cycle, low cost, and reliable safety. Therefore, many new efficient energy storage materials and battery systems are being developed and explored, and their working mechanisms must be clearly understood before industrial application. In recent years, density functional theory (DFT) has been employed in the energy storage field and has made significant contributions to the understanding of electrochemical reaction mechanisms and to virtual screening of promising energy storage materials. In this review, the applications of DFT to battery materials are summarized and exemplified by some representative and up‐to‐date studies in the literature. The main focuses in this review include the following: 1) structural stability estimation by cohesive energy, formation energy, Gibbs free energy, and phonon dispersion spectra calculations; 2) the Gibbs free energy calculations for electrochemical reactions, corresponding open‐circuit voltage, and theoretical capacity predictions of batteries; 3) the analyses of molecule orbitals, band structures, density of states (DOS), and charge distribution of battery materials; 4) ion transport kinetics in battery materials; 5) simulations of adsorption processes. We conclude the review with the discussion of the assessments and validation of the popular functionals against several benchmarks, and a few suggestions have been given for the selection of density functionals for battery material systems.

The practical application of the lithium–sulfur (Li–S) battery is seriously restricted by its shuttle effect, low conductivity, and low sulfur loading. Herein, first‐principles calculations are conducted to verify that the introduction of oxygen vacancies in TiO2 not only enhances polysulfide adsorption but also greatly improves the catalytic ability and both the ion and electron conductivities. A commercial polypropylene (PP) separator decorated with TiO2 nanosheets with oxygen vacancies (OVs‐TiO2@PP) is fabricated as a strong polysulfide barrier for the Li–S battery. The thickness of the OVs‐TiO2 modification layer is only 500 nm with a low areal mass of around 0.12 mg cm−2, which enhances the fast lithium‐ion penetration and the high energy density of the whole cell. As a result, the cell with the OVs‐TiO2@PP separator exhibits a stable electrochemical behavior at 2.0 C over 500 cycles, even under a high sulfur loading of 7.1 mg cm−2, and an areal capacity of 5.83 mAh cm−2 remains after 100 cycles. The proposed strategy of engineering oxygen vacancies is expected to have wide applications in Li–S batteries.

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