Rechargeable zinc batteries (RZBs) have received much attention due to high theoretical specific capacity and high hydrogen overpotential of zinc, low cost, and safety. However, the electrolyte leakage, dendritic zinc deposition, some side reactions, and zinc hydroxide sulfate (ZHS) byproduct formation on the zinc negative electrode cause the deterioration of RZBs. Hydrogel electrolytes retaining large quantities of electrolytes can suppress leakage and regulate the transport of zinc ions via a three-dimensional host polymer network, overcoming these drawbacks. In this study, flexible alginate hydrogel electrolyte membranes (AHEMs) were successfully prepared by combining the formation of hydrogel membranes using 1,3-propanediol as a plasticizer with subsequent immersion in a Zn²⁺-containing aqueous solution. The AHEM exhibited ionic conductivity comparable to that of corresponding Zn²⁺-containing solution. Zinc deposition proceeded uniformly in AHEM, and the formation of ZHS was effectively suppressed. The symmetric Zn/AHEM/Zn cell showed a stable voltage profile without short-circuits for more than 2000 h in a charge-discharge test at 4 mA cm⁻² for 30 min. The pouch-type quasi-solid-state Zn/AHEM/MnO₂ cell maintained approximately 70 % of its maximum discharge capacity even after 300 cycles in the charge-discharge cycle test at a 3 C-rate (= 924 mA g⁻¹).

The charge-discharge behaviors of pillared carbon thin-films as an anode of all-solid-state lithium-ion batteries were investigated, using LiBH₄ as the solid electrolyte. The reduced contact area between the pillared carbon thin films and the solid electrolyte resulted in the suppression of side reactions originating from the solid electrolyte. The capacity of the pillared carbon thin-film electrodes increased with the increase in the Si content and reached a very high value of 1278 mAh g⁻¹. Lithium ions were intercalated into the interlayer space of the pillared carbon and the interlayer distance increased from 1.33 to 1.42 nm upon lithium storage. A slight change in the XANES spectrum of the pillared carbon in the Si K-edge region after the introduction of lithium ion indicated that lithium ions were introduced in the vicinity of silicon atom surrounded by 3 oxygen atoms and one methyl group. The present results indicate that pillared carbon is a promising anode material for all-solid-state lithium-ion batteries.

A comparative study was conducted on the electrochemical interaction between CO₂ and various bipyridines, including 2,2′-, 3,3′-, and 4,4′-bipyridine (4,4′-BPy), as well as perfluoro-4,4′-bipyridine (PF-4,4′-BPy). Among these, 4,4′-BPy exhibited the most robust performance, particularly when paired with weakly coordinating quaternary ammonium cations, such as tetrabutylammonium (Bu₄N⁺). The use of these bulky cations proved highly effective in facilitating the electrochemical interaction with CO₂, likely due to their attenuated electrostatic interaction with the bipyridine anionic species, which facilitates reversible CO₂ binding. In contrast, PF-4,4′-BPy exhibited no electrochemical interaction with CO₂; its radical anion showed insufficient nucleophilicity to overcome the activation barrier for CO₂ binding, while the corresponding dianion was highly unstable, leading to rapid decomposition potentially initiated by a reductive defluorination process.

Li metal has a high theoretical capacity (3860 mAh g⁻¹) and the lowest electrochemical potential (−3.04 V vs. the standard hydrogen electrode). Li deposition/dissolution at the interface between the current collector (CC)/sulfide solid electrolyte (SSE), with Li⁺ ion supply from the positive electrode, is important for fabricating all-solid-state cells with high energy density. However, repeated inhomogeneous Li deposition/dissolution at the CC/SSE interface leads to short-circuiting of the cells.

In this study, to promote homogeneous Li deposition, all-solid-state cells with a composite of SnF₂ and acetylene black (SnF₂–AB) at the interface between the CC and SSE were fabricated, and the Li deposition behavior was investigated. Li₃PS₄ (LPS) and 54Li₃PS₄·46LiI (LPSI) glasses were used as SSE. During Li deposition, the cell without the SnF₂–AB layer short-circuited immediately because of inhomogeneous Li deposition. In contrast, in the cell with the SnF₂–AB layer, SnF₂ reacted with Li to form Li₁₇Sn₄ and LiF, which mainly remained within the SnF₂–AB layer, promoting homogeneous Li deposition at the CC/SnF₂–AB interface and suppressing short-circuiting of the cell. The use of LPSI instead of LPS in a cell with a SnF₂–AB layer suppressed the formation of Li₂S during reductive decomposition of the solid electrolyte, resulting in improved Li deposition capacity. The insertion of the SnF₂–AB layer effectively promotes homogeneous Li deposition and is useful for applications in anode-free all-solid-state batteries.

Amorphous powder in the Li₂O-CaO-ZrO₂-P₂O₅ system were prepared by using mechanochemical synthesis process at room temperature. Amorphous materials with the nominal composition of Li_1+2xCa_xZr_2−x(PO₄)₃ (LCZP) (x = 0.05, 0.08, 0.1) were calcinated at 900 °C in air. The calcinated LCZP materials were sintered at 1100 °C. The NASICON-structured LCZP(x = 0.08) solid electrolytes after sintering exhibited relatively high lithium-ion conductivities of 1.2 × 10⁻⁵ S cm⁻¹ at 25 °C. The activation energy (E_a) was 35 kJ mol⁻¹. The LCZP solid electrolytes obtained via the crystallization of amorphous materials would be a potential candidate as lithium-ion conductors for all-solid-state battery applications.

In power-type lithium-ion batteries (LIBs), the reaction distribution formed during high-rate operation significantly influences their performance. The reaction distribution in the electrode cross-sectional direction has been studied; however, in-plane reaction distribution, which can be an issue for large cells, remains poorly understood. In this study, we applied an electrode-freezing technique that can preserve reaction inhomogeneity at high rates to investigate the relationship between the in-plane reaction distribution and electrode design. The reaction distributions of LiNi_1/3Co_1/3Mn_1/3O₂ positive and hard carbon negative electrodes were analyzed using synchrotron-based Ni K-edge X-ray absorption fine structure and ion chromatography, respectively. The results showed that reducing electrode thickness significantly increased the in-plane inhomogeneity, with preferential reaction progress near the current-collector tabs. On the other hand, such pronounced in-plane reaction distributions did not necessarily degrade the power performance of the cell, suggesting the importance of cross-sectional inhomogeneity. This study shows that the dominant direction of reaction distribution in power-type LIBs varies depending on electrode thickness and C-rate, providing useful insights for electrode design optimized for high-rate operation.

It was found that when an Al substrate was anodized in 0.3 M oxalic acid containing 50 mM sulfuric acid, the growth rate of the anodic porous alumina film (APAF) formed was significantly higher than that formed in an electrolyte without sulfuric acid. In contrast, adding small amounts of sulfuric acid did not promote the dissolution of the APAF. In other words, adding a small amount of sulfuric acid to the oxalic acid electrolyte enables the formation of a thick APAF before the sample surface is dissolved. As a result, it was possible to produce an ordered APAF with a sub-millimeter-scale thickness using an oxalic acid electrolyte with a small amount of sulfuric acid. The thick APAF obtained using this process is expected to be a promising template for fabricating various one-dimensional nanomaterials, such as nanotubes and nanofibers.