Bimetallic selenides with nanostructures have attracted widespread interest to improve the electrochemical properties of supercapacitors due to their intrinsic properties such as high energy storage capacity, stability, and reliability. Herein, we report the novel synthesis of binder-free pinecone-like nanostructure arrays of Ni2MnSe4 on nickel foam via a facile electrodeposition technique. The electrode materials with various stoichiometric ratios of Ni:Mn as NixMn3-xSe4 (x = 1, 2, and 2.5) are synthesized to study the effect on their surface morphology and electrochemical properties. Ni2MnSe4 is optimized with pinecone-like structure arrays formed by intraconnected rough nanosheets (two-dimensional structure) with interconnected microstructures (pinecone structure), which further offers continuous channels for rapid electron/ion transfer and accelerates the diffusion kinetics of the counter ions, thus leading to improved capacitive property of the electrode material. The as-prepared Ni2MnSe4 electrode exhibits the areal capacitance value of 2160 mF cm−2 at 4 mA cm−2 with superior cycling stability (92 % of capacitance retention over 10,000 cycles). Additionally, the Ni2MnSe4 is utilized as a positive electrode for a semi-solid-state hybrid supercapacitor device (SHSC). The assembled SHSC delivers the energy and power density values of 0.15 mWh cm−2 and 15.51 mW cm−2, respectively with excellent prolonged cycling stability.

Engineering multicomponent nanomaterials as an electrode with rationalized ordered structures is a promising strategy for fulfilling the high-energy storage needs of supercapacitors (SCs). Even now, the fundamental barrier to utilizing hydroxides/hydroxyl carbonates is their poor electrochemical performance, resulting from the significantly poor electrical conductivity and sluggish charge storage kinetics. Hence, a multilayered structural approach is primarily and successfully used to construct electrodes as one of the efficient approaches. This method has made it possible to develop well-ordered nanostructured electrodes with good performance by taking advantage of tunable approach parameters. Herein, we report the design of multilayered heterostructure porous zinc-nickel nanosheets@nickel flakes hydroxyl carbonates and/or hydroxides integrated with conductive PEDOT fibrous network (i.e., ZnNi@Ni@PEDOT) via facile synthesis methods. The combined hybrid electrode acquires the features of high electrical conductivity from one part and various valance states from another one to develop a well-organized nanosheet/flake/fibrous-like heterostructure with decent mechanical strength, creating robust synergistic results. Thus, the designed binder-free ZnNi@Ni@PEDOT electrode delivers a high areal capacity value of 1050.1 µA h cm−2 at 3 mA cm−2 with good cycling durability, significantly outperforming other individual electrodes. Moreover, its feasibility is also tested by constructing a hybrid electrochemical cell (HEC). The assembled HEC exhibits a high areal capacity value of 783.8 µA h cm−2 at 5 mA cm−2, and even at a high current density of 100 mA cm−2 (484.6 µA h cm−2), the device still retains a rate capability of 61.82%. Also, the HEC shows maximum energy and power densities of 0.595 mW h cm−2 and 77.23 mW cm−2, respectively, along with good cycling stability. The obtained energy storage capabilities effectively power various electronic components. These results provide a viable and practical way to construct a positive electrode with innovative heterostructures for high-performance energy storage devices and profoundly influence the development of electrochemical SCs.

The ever-growing demand for safe and renewable energy storage systems has driven the renaissance of aqueous zinc (Zn)-metal batteries (ZMBs). Zn metal has the characteristics of high specific capacity, low cost, environmental friendliness, and intrinsic safety, but severe side reactions and Zn dendrite growth lead to low Coulombic efficiency and short cycle life of Zn metal anode, which restricts the commercial development of rechargeable aqueous ZMBs. Herein, a Ti3C2Tx MXene-derived ZnF2-rich multifunctional interfacial layer is prepared. In this architecture, the as-formed ZnF2-rich layer can redistribute Zn-ion flux on the electrode/electrolyte surface and suppress side reactions. Meanwhile, the results indicate that the ZnF2 can lower the desolvation energy barrier of Zn ions and enhance the Zn-ion transfer kinetics. Accordingly, the Zn@MXene anode delivers a long cycle life over 800 h at the current density of 5.0 mA cm−2 with a capacity of 5.0 mAh cm−2. Surprisingly, the Zn@MXene anode can still achieve dendrite-free Zn deposition for more than 320 h even at the current density of 10.0 mA cm−2 with a capacity of 10.0 mAh cm−2. Additionally, the assembled Zn@MXene//VO2 full-cell exhibits better cycling stability and more excellent rate performance compared to the pristine Zn//VO2 full-cell, implying the potential of this idea to develop high-power rechargeable aqueous Zn-ion batteries.

Recently, perovskites are attracting great attention in the field of energy harvesting through triboelectric nanogenerators as a promising technology owing to their easy synthesis process, ferroelectric/dielectric nature, and low toxicity. Herein, we proposed the vanadium-doped sodium niobate (NaNbO3) (V–NaNbO; VNNb)/polydimethylsiloxane (PDMS) composite film-based hybrid nanogenerators (HNGs) for mechanical/biomechanical energy harvesting. Initially, the perovskite NNb and VNNb microparticles (MPs) were synthesized and mixed inside PDMS to form a negative triboelectric film. The aluminum film was used as a positive triboelectric material and to support the waste-to-wealth concept, discarded plastic was used as a substrate material. Various HNGs were assembled and operated in a contact-separation mode and a comparative study of variation in electrical output depending on the type/amount of filler particles was thoroughly investigated. The VNNb/PDMS-based HNG produced an enhanced electrical output of ∼200 V, ∼5.7 μA, 4.8 W/m2 as compared to the bare PDMS- and NNb/PDMS-based HNGs. The fabricated HNG was robust and generated a highly stable electrical output that was further utilized to charge capacitors and power small electronics. Moreover, owing to the flexible nature and highly efficient electrical output of the HNG, it was successfully demonstrated as a biomechanical energy harvester.