Sodium-ion batteries are a potentially low-cost and safe alternative to the prevailing lithium-ion battery technology. However, it is a great challenge to achieve fast charging and high power density for most sodium-ion electrodes because of the sluggish sodiation kinetics. Here we demonstrate a high-capacity and high-rate sodium-ion anode based on ultrathin layered tin(II) sulfide nanostructures, in which a maximized extrinsic pseudocapacitance contribution is identified and verified by kinetics analysis. The graphene foam supported tin(II) sulfide nanoarray anode delivers a high reversible capacity of ∼1,100 mAh g−1 at 30 mA g−1 and ∼420 mAh g−1 at 30 A g−1, which even outperforms its lithium-ion storage performance. The surface-dominated redox reaction rendered by our tailored ultrathin tin(II) sulfide nanostructures may also work in other layered materials for high-performance sodium-ion storage.

Tremendous efforts have been dedicated into the development of high‐performance energy storage devices with nanoscale design and hybrid approaches. The boundary between the electrochemical capacitors and batteries becomes less distinctive. The same material may display capacitive or battery‐like behavior depending on the electrode design and the charge storage guest ions. Therefore, the underlying mechanisms and the electrochemical processes occurring upon charge storage may be confusing for researchers who are new to the field as well as some of the chemists and material scientists already in the field. This review provides fundamentals of the similarities and differences between electrochemical capacitors and batteries from kinetic and material point of view. Basic techniques and analysis methods to distinguish the capacitive and battery‐like behavior are discussed. Furthermore, guidelines for material selection, the state‐of‐the‐art materials, and the electrode design rules to advanced electrode are proposed.

Nanoscale surface engineering is playing important role in enhancing the performance of battery electrode. VO2 is one of high-capacity but less-stable materials and has been used mostly in the form of powders for Li-ion battery cathode with mediocre performance. In this work, we design a new type of binder-free cathode by bottom-up growth of biface VO2 arrays directly on a graphene network for both high-performance Li-ion and Na-ion battery cathodes. More importantly, graphene quantum dots (GQDs) are coated onto the VO2 surfaces as a highly efficient surface "sensitizer" and protection to further boost the electrochemical properties. The integrated electrodes deliver a Na storage capacity of 306 mAh/g at 100 mA/g, and a capacity of more than 110 mAh/g after 1500 cycles at 18 A/g. Our result on Na-ion battery may pave the way to next generation postlithium batteries.

Honeycomb-like MoS2 nanoarchitectures anchored into 3D graphene foam are successfully fabricated as a high-performance positive electrode for enhanced Li-ion storage. The unique 3D interpenetrating honeycomb-like structure is the key to the high performance. High reversible capacity, superior high-rate capability, and excellent cycling stability are demonstrated.

Novel, porous NiCo2O4 nanotubes (NCO-NTs) are prepared by a single-spinneret electrospinning technique followed by calcination in air. The obtained NCO-NTs display a one-dimensional architecture with a porous structure and hollow interiors. The effect of precursor concentration on the morphologies of the products is investigated. Due to their unique structure, the prepared NCO-NT electrode exhibits a high specific capacitance (1647 F g(-1) at 1 A g(-1)), excellent rate capability (77.3 % capacity retention at 25 A g(-1)), and outstanding cycling stability (6.4 % loss after 3000 cycles), which indicates it has great potential for high-performance electrochemical capacitors. The desirable enhanced capacitive performance of NCO-NTs can be attributed to the relatively large specific surface area of these porous and hollow one-dimensional nanostructures.

Although being considered as one of the most promising cathode materials for Lithium-ion batteries (LIBs), LiNi1/3Co1/3Mn1/3O2 (NCM) is currently limited by its poor rate performance and cycle stability resulting from the thermodynamically favorable Li+/Ni2+ cation mixing which depresses the Li+ mobility. In this study, we developed a two-step method using fluffy MnO2 as template to prepare hierarchical porous nano-/microsphere NCM (PNM-NCM). Specifically, PNM-NCM microspheres achieves a high reversible specific capacity of 207.7 mAh g−1 at 0.1 C with excellent rate capability (163.6 and 148.9 mAh g−1 at 1 C and 2 C), and the reversible capacity retention can be well-maintained as high as 90.3% after 50 cycles. This excellent electrochemical performance is attributed to unique hierarchical porous nano-/microsphere structure which can increase the contact area with electrolyte, shorten Li+ diffusion path and thus improve the Li+ mobility. Moreover, as revealed by XRD Rietveld refinement analysis, a negligible cation mixing (1.9%) and high crystallinity with a well-formed layered structure also contribute to the enhanced C-rates performance and cycle stability. On the basis of our study, an effective strategy can be established to reveal the fundamental relationship between the structure/chemistry of these materials and their properties.

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