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Aqueous rechargeable multiple metal-ion storage battery (ARSB) has a large potential in energy storage devices due to their safe usage, low cost and high rate capability. Nevertheless, the performance of practical ARSB is largely restricted by low capacity and limited cathode materials. Herein, we demonstrate an efficient cathode material based on CoNi-layered double hydroxide (LDH) nanosheets arrays with abundant hydrogen vacancy induced by electrochemical activation process for high performance of cations storage. Consequently, the electrochemical activated CoNi-LDH (ECA-CoNi-LDH) nanosheets arrays exhibit high metal ion (Li+, Na+, Zn2+, Mg2+ and Ca2+) storage capacities, which is 9 times and 3 times higher that of unactivated CoNi-LDH arrays and ECA-CoNi-LDH without hierarchical structure, respectively. Moreover, the ECA-CoFe-LDH also shows the possibility for practical applications in actual batteries. By coupling with a Fe2O3/C anode, the assembled aqueous battery delivered a large energy density of 184.4 Wh kg−1 at power density of 4 Wh kg−1 in high voltage range of 0 ∼ 2 V. To our best knowledge, such high energy density and large working window of our assembled aqueous battery is exceeded other LDH-based aqueous battery or supercapacitor, and the energy density almost comparable than that of commercial Li-ion batteries. Moreover, almost no measurable capacitance losses can be detected even after 10000 cycles. In addition, this work also provides a strategy to develop a high energy density cathode for multiple metal-ion storage batteries.

SnO2 films as a promising electron transport layer (ETL) have been widely used in planar-type perovskite solar cells to achieve an impressive improvement in the conversion efficiency. However, compared with a mesoporous ETL, the interfacial charge carrier transfer of the SnO2 ETL is severely limited due to the issues of oxygen vacancy defects and crystal lattice mismatch between SnO2 and the perovskite, which generally leads to the growth of randomly stacked and porous perovskite layers and subsequently impacts the charge transport and transfer properties. In this work, we developed a facile approach by inducing a bifunctional molecule, β-alanine, into the SnO2 ETL, which can serve as a bridge to modulate the interfacial charge transfer and the perovskite crystallization kinetics. Benefited by the interfacial β-alanine, we grew a highly orientational perovskite layer that exhibited superior charge transport properties. Meanwhile, the β-alanine caused an intimate connection between the perovskite and SnO2 to enhance the interfacial charge transfer. As a result, the power conversion efficiency (PCE) of the β-alanine-modified device achieved a much-improved value of 19.67% and showed high reproducibility. This work provides a way for developing a high-performance ETL toward the scalable fabrication of highly efficient PSCs.

Aluminum ion aqueous batteries (AIBs) are among the most promising candidates for high energy density devices due to the multivalent redox processes associated with Al3+ ion intercalation. However, only a few stable AIB electrode materials have been reported so far. MoO3 is a very promising electrode material due to its octahedral layered crystal structure which can accommodate multivalent cation by intercalation. However, the poor electrochemical stability of MoO3 and the sluggish intercalation kinetics of Al3+ ion in Mo oxides electrodes limit its practical application. In this work, we propose a strategy to overcome such shortcomings of MoO3 by fabricating electrodes composed of self-ordered one-dimensional (1D) MoTaOx nanotubes synthesized via electrochemical anodization of Mo-Ta alloy substrates. We show that this approach allows for direct incorporation of Ta in the Mo oxide nanotubes. The resulting MoTaOx nanotubes, composed of octahedral MoO3 and rhombohedral Mo2Ta2O11 phases, exhibit remarkable electrochemical stability and Al-ion storage properties in aqueous electrolytes that are superior to that of pristine Mo oxide or other most efficient electrode materials reported to date. Such MoTaOx nanotube-based electrodes can achieve a specific capacity of 1180 mA h cm-3 (337 mA h g-1, 141 μA h cm-2) at 1.25 A cm-3 (∼0.35 A g-1, 0.15 mA cm-2). More importantly, the capacity retention of such nanotube array electrodes remains above 83% of the initial capacity after 3000 cycles.

Battery-type electrode materials show inferior power density due to sluggish ion-diffusion kinetics within the solid phase. Herein, we outline a strategy to improve the cation migration for ultrafast energy storage by utilizing a built-in electric field (BEF) at the heterostructure interface. Both theoretical calculations and Kelvin probe measurements reveal that two kinds of BEF – in opposite directions – are produced at fully charged and discharged states on co-axial MoOx/MoON nanotubes (NTs). The transport kinetics are greatly increased by the BEF effect, leading to a dramatic increase of capacitance, especially at a high charging rate. Subsequently, MoOx/MoON NTs exhibit a specific capacitance of 1976 F cm−3 at a current density of 2.5 A cm−3. And 1267 F cm−3 is retained at a high current density of 100 A cm−3, which can be ascribed to the improvement of fast ionic transport in the electrode bulk caused by the BEF effect. This work also inspires a new pathway toward rational engineering of heterostructures for high-capacitance and high-rate energy storage.

Novel Co-Ni bimetallic phosphides with a 2D/3D structure were developed by in-situ phosphorization and rapid surface reconstruction strategies for use as an efficient electrocatalyst toward overall water splitting. In-situ phosphorus diffusion from the substrate was confirmed by high-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS) depth profiles. The generation of cobalt oxyhydroxide was also verified during electrochemical treatment, achieving surface self-reconstruction. The obtained materials revealed efficient and stable electrocatalytic performance, with HER and OER overpotentials of 117 mV and 272 mV, respectively. A low cell voltage of 1.59 V was achieved for overall water splitting with long-term stability. These properties were ascribed to the 2D/3D nanostructure with abundant interface defects. In-situ Raman spectroscopy and density functional theory (DFT) calculations were carried out to further understand the electrocatalytic activity and the promoted mechanism of reconstruction-derived CoOOH on OER performance.

Flexible zinc (Zn) metal batteries (ZMBs) have attracted particular attention because of much high volumetric capacity of Zn anodes (5845 mAh/cm3) and abundant Zn resources in the earth. However, the unfavorable mechanical flexibility and poor cycling stability caused by the rigid and uncontrolled dendrites of Zn anodes hinder their development. Herein, a dendrite-free Zn metal anode is achieved by an ultrathin NH4V4O10 film–modified carbon cloth, which can be served as Zn nucleation sites to effectively reduce the overpotential for Zn uniform deposition. As a result, the half-cell with the carbon cloth@NH4V4O10-16 (CC@NVO-16) electrode exhibited a stable cycling performance of over 280 cycles at 1 mA/cm2 with high Coulombic efficiency of 99.21% and much lower overpotential. Excitingly, the flexible solid-state ZMB with the CC@NVO-16@Zn exhibits superior stability and a high energy density of 374.6 Wh/kg/980.0 W/kg, which is superior to the most recent report so far. This work also provides an efficient strategy in constructing long-life and safe flexible ZMB systems.

With a large-scale usage of portable electric appliances, a high demand for increasingly high density energy storage devices has emerged. MoO3 has, in principle, a large potential as negative electrode material in supercapacitive devices, due to high charge densities that can be obtained from its reversible redox reactions. Nevertheless, the extremely poor electrochemical stability of MoO3 in aqueous electrolytes prevents a practical use in high capacitance devices. In this work, we describe how to overcome this severe stability issue by forming amorphous molybdenum oxide/tantalum oxide nanotubes by anodic oxidation of a Mo-Ta alloy. The presence of a critical amount of Ta-oxide (> 20 at-%) prevents the electrochemical decay of the MoO3 phase and thus yields an extremely high stability. Due to the protection provided by tantalum oxide, no capacitance losses are measureable after 10000 charg-ing/discharging cycles.

In the present work, self-ordered MoO3-TiO2 nanotube layers have been fabricated from Ti-Mo (7 wt.% Mo) alloy through anodization, and characterized by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and photoelectrochemical measurements. In comparison with pure TiO2 nanotubes, the synthesized MoO3-TiO2 nanotubes showed an enhanced donor concentration, lower electron transfer resistance, and longer electron lifetime. Moreover, photoinduced-carrier-separation efficiency also improved remarkably on addition of MoO3 to the TiO2 nanotube matrix. It was also shown that these beneficial properties led to higher photocatalytic water splitting activity and photocurrent response in the MoO3-TiO2 nanotubes.

The oxygen evolution reaction (OER) is an essential process for water electrolysis and to realize the scalability of renewable energy sources. In this work, a strategy is developed to fabricate anisotropic metallic Cobalt-Molybdenum Nitride materials combining hollow 3D structures and 2D nanosheets which result highly active OER electrocatalysts. The sample structure and morphology is investigated to derive its formation process following the synthesis strategy relying on the ligand-metal interactions of metal-organic framework (ZIF-67 and Mo-aMOF). Three different sample morphologies with large specific surface areas are obtained by changing the water and 2-methylimidazole contents. After ammonification in NH3, the morphologies and the specific surface areas of the samples are preserved. The electronic structure can also be adjusted to regulate electron density of Co and Mo by N-doping. These Co-Mo binary metals offer a viable way for realizing the electronic transfer between the different components, as demonstrated by XPS. Taking advantage from the above features, the as-obtained electrocatalyst exhibits a high catalytic activity and long-term cyclic stability for OER with low overpotential (η10 is 294 mV).

In the present work we demonstrate the self-organized formation of anodic Mo-oxide nanotube arrays grown on a Mo sheet under suitable electrochemical conditions in glycerol/NH4F electrolytes. The resulting amorphous tubes can be crystallized by annealing to MoO2 or MoO3. The tube walls then can be further sulfurized fully or partially to Mo-sulfide to form well-ordered arrays of vertically aligned MoOx/MoS2 nanotubes. Under optimized conditions, defined MoS2 sheets form on the oxide walls in a layer by layer low angle zig-zag arrangement that provide a high density of reactive stacking faults. These core-shell nanotube arrays, consisting of tubes with a conductive suboxide core and a functional high defect density MoS2 coating, are highly promising for applications such as electrocatalysis (hydrogen evolution) or ion insertion devices.