Flexible anodic SnO2 nanoporous structures uniformly coated with polyaniline as a binder-free anode for lithium ion batteries

Recent Progress of Self-Supported Metal Oxide Nano-Porous Arrays in Energy Storage Applications

The demand for high-performance and cost-effective energy storage solutions for mobile electronic devices and electric vehicles has been a driving force for technological advancements. Among the various options available, transitional metal oxides (TMOs) have emerged as a promising candidates due to their exceptional energy storage capabilities and affordability. In particular, TMO nanoporous arrays fabricated by electrochemical anodization technique demonstrate unrivaled advantages including large specific surface area, short ion transport paths, hollow structures that reduce bulk expansion of materials, and so on, which have garnered significant research attention in recent decades. However, there is a lack of comprehensive reviews that discuss the progress of anodized TMO nanoporous arrays and their applications in energy storage. Therefore, this review aims to provide a systematic detailed overview of recent advancements in understanding the ion storage mechanisms and behavior of self-organized anodic TMO nanoporous arrays in various energy storage devices, including alkali metal ion batteries, Mg/Al-ion batteries, Li/Na metal batteries, and supercapacitors. This review also explores modification strategies, redox mechanisms, and outlines future prospects for TMO nanoporous arrays in energy storage.

A Hierarchical SnO2@Ni6MnO8 Composite for High-Capacity Lithium-Ion Batteries

Semiconductor-based composites are potential anodes for Li-ion batteries, owing to their high theoretical capacity and low cost. However, low stability induced by large volumetric change in cycling restricts the applications of such composites. Here, a hierarchical SnO₂@Ni₆MnO₈ composite comprising Ni₆MnO₈ nanoflakes growing on the surface of a three-dimensional (3D) SnO₂ is developed by a hydrothermal synthesis method, achieving good electrochemical performance as a Li-ion battery anode. The composite provides spaces to buffer volume expansion, its hierarchical profile benefits the fast transport of Li⁺ ions and electrons, and the Ni₆MnO₈ coating on SnO₂ improves conductivity. Compared to SnO₂, the Ni₆MnO₈ coating significantly enhances the discharge capacity and stability. The SnO₂@Ni₆MnO₈ anode displays 1030 mAh g^-1 at 0.1 A g^-1 and exhibits 800 mAh g^-1 under 0.5 A g^-1, along with high Coulombic efficiency of 95%. Furthermore, stable rate performance can be achieved, indicating promising applications.

P-doped porous carbon derived from walnut shell for zinc ion hybrid capacitors

Zinc ion hybrid capacitors (ZHCs) are expected to be candidates for large-scale energy storage products due to their high power density and large energy density. Due to their low cost and stability, carbon materials are generally the first choice for the cathode of ZHCs, but they face a challenge in the serious self-discharge behavior. Herein, zinc ion hybrid capacitors with high-performance are successfully assembled using a porous carbon cathode derived from low-cost p-doped waste biomass and a commercial zinc foil anode. The p-doped walnut shell ZHCs delivered a specific capacity of 158.9 mA h g⁻¹ with an energy density of 127.1 W h kg⁻¹ at a low current density. More importantly, the device had outstanding anti-self-discharge characteristics (retaining 77.98% of its specific capacity after a 72 h natural self-discharge test) and long-term cycle stability (retaining 88.2% of its initial specific capacity after 15 000 cycles at 7.5 A g⁻¹). This work presents guidance and support for the design and optimization of electrode materials for zinc ion supercapacitors and next-generation aqueous zinc ion energy storage performance.

A P-doped porous carbon cathode material from walnut shell is assembled with zinc foil to form typical ZHCs, which showed excellent energy storage characteristics and long-life cycle stability.