When compared to expensive lithium metal, the metal sodium resources on Earth are abundant and evenly distributed. Therefore, low-cost sodium-ion batteries are expected to replace lithium-ion batteries and become the most likely energy storage system for large-scale applications. Among the many anode materials for sodium-ion batteries, hard carbon has obvious advantages and great commercial potential. In this review, the adsorption behavior of sodium ions at the active sites on the surface of hard carbon, the process of entering the graphite lamellar, and their sequence in the discharge process are analyzed. The controversial storage mechanism of sodium ions is discussed, and four storage mechanisms for sodium ions are summarized. Not only is the storage mechanism of sodium ions (in hard carbon) analyzed in depth, but also the relationships between their morphology and structure regulation and between heteroatom doping and electrolyte optimization are further discussed, as well as the electrochemical performance of hard carbon anodes in sodium-ion batteries. It is expected that the sodium-ion batteries with hard carbon anodes will have excellent electrochemical performance, and lower costs will be required for large-scale energy storage systems.

Porous carbon materials have demonstrated exceptional performance in various energy and environment-related applications. Recently, research on supercapacitors has been steadily increasing, and porous carbon materials have emerged as the most significant electrode material for supercapacitors. Nonetheless, the high cost and potential for environmental pollution associated with the preparation process of porous carbon materials remain significant issues. This paper presents an overview of common methods for preparing porous carbon materials, including the carbon-activation method, hard-templating method, soft-templating method, sacrificial-templating method, and self-templating method. Additionally, we also review several emerging methods for the preparation of porous carbon materials, such as copolymer pyrolysis, carbohydrate self-activation, and laser scribing. We then categorise porous carbons based on their pore sizes and the presence or absence of heteroatom doping. Finally, we provide an overview of recent applications of porous carbon materials as electrodes for supercapacitors.

Having a high theoretical capacity density of 4200 mAh g⁻¹, silicon has been highlighted as one of the most promising anode materials for lithium-ion batteries. Countless silicon-based materials have been proposed and reported in research articles, mostly synthesized using bottom-up methods. While the infamous volume expansion issue can be settled with the bottom-up processes, the complicated protocols and high cost leave a non-neglectable gap between laboratory-scale and mass production. The top-down ball-milling method is still favored by industrial suppliers because of its simplicity and cost-effectiveness, even with compromised electrochemical performances. This paper reviews the latest development of ball-milling-based silicon anode materials. Although the ball-milling process seems straightforward, the procedures and parameters influencing the product have hardly been discussed in research papers compared to the bottom-up ones. This paper reviews recent advances in ball-milling-based silicon anode materials, provides a material comparison, and discusses how ball milling can provide lithium-ion batteries with greater possibilities at a larger scale.

Sodium-ion batteries (SIBs) have garnered significant interest due to their potential as viable alternatives to conventional lithium-ion batteries (LIBs), particularly in environments where low-temperature (LT) performance is crucial. This paper provides a comprehensive review of current research on LT SIBs, focusing on electrode materials, electrolytes, and operational challenges specific to sub-zero conditions. Recent advancements in electrode materials, such as carbon-based materials and titanium-based materials, are discussed for their ability to enhance ion diffusion kinetics and overall battery performance at colder temperatures. The critical role of electrolyte formulation in maintaining battery efficiency and stability under extreme cold is highlighted, alongside strategies to mitigate capacity loss and cycle degradation. Future research directions underscore the need for further improvements in energy density and durability and scalable manufacturing processes to facilitate commercial adoption. Overall, LT SIBs represent a promising frontier in energy storage technology, with ongoing efforts aimed at overcoming technical barriers to enable widespread deployment in cold-climate applications and beyond.

Two organic small molecule hole transport materials, 5-((3,6-bis(4-(bis(4-methoxyphenyl)amino)phenyl)thieno[3,2-b]thiophen-2-yl)methylene)-3-ethyl-2-thioxothiazolidin-4-one (shortly named C3-D) and 5,5′-((3,6-bis(4-(bis(4-methoxyphenyl)amino)phenyl)thieno[3,2-b]thiophene-2,5-diyl)bis(methaneylylidene))bis(3-ethyl-2-thioxothiazolidin-4-one) (shortly named C3-S), are designed with rhodanine as the functional group and utilized in inverted planar perovskite solar cells (PSCs). With the functional group, both HTMs exhibit good mobility, matching HOMO/LUMO energy levels and excellent interactions with ITO and the perovskite layer, enhancing hole extraction, transport, and defect passivation in inverted PSCs. As a result, the device based-on C3-D presents a champion power conversion efficiency (PCE) of 21.50% with J_SC = 24.49 mA cm⁻², V_OC = 1.072 V, and FF = 81.9%, while the device based-on C3-S shows a PCE of 19.24% with J_SC = 23.11 mA cm⁻², V_OC = 1.065 V, and FF = 78.2%. Additionally, the C3-D-based device also demonstrates superior stability compared to C3-S, retaining over 85% of the initial value after being kept for 500 h at room temperature in ambient air at 35% relative humidity, and over 60% of the initial value after being kept for 500 h at 85 °C in a N₂ glovebox, respectively. These results far surpass the performance of devices based-on a non-functional HTM, TT-3,6-TPA, as reported in the literature (a PCE of 0.7% with J_SC = 2.90 mA cm⁻², V_OC = 0.95 V, and FF = 27.0%). Therefore, these findings indicate that combining hetero-atomic functionalized groups with typical hole transport fragments could be a promising research avenue for enhancing the performance of inverted planar PSCs and facilitating the commercialization of perovskite solar cells.

Among the various metal oxide nanomaterials, manganese oxides, which can exist in different structures and valence states, are considered highly promising anode materials for lithium-ion batteries (LIBs). However, conventional manganese oxides, such as MnO and MnO₂, face significant challenges during the cycling process. Specifically, poor electronic conductivity and large volume changes result in low specific capacity during high current charging and discharging, as well as poor fast-charging performance. This work presents an approach to synthesizing porous hexagonal Mn₅O₈ nanosheets using hydrothermal and annealing methods and applies them as anode materials for LIBs. The Mn₅O₈ nanomaterials exhibit a thin plate morphology, which effectively reduces the distance for ion/electron transmission and mitigates the phenomenon of volume expansion. Additionally, the large pore size of Mn₅O₈ results in abundant interlayer and intralayer defects, which further enhance the rate of ion transmission. These unique characteristics enable Mn₅O₈ to demonstrate excellent electrochemical performance (938.7 mAh×g^-1 after 100 cycles at 100 mA×g^-1) and fast charging performance (675.7 mAh×g^-1 after 1000 cycles at 3000 mA×g^-1), suggesting that Mn₅O₈ nanosheets have the potential to be an ideal fast-charging anode material for LIBs.