Millisecond spray drying enables overcoming the immiscibility gap in solid-solution, forming a supersaturated metastable phase of Li 3 VO 4 –Li 2 MoO 4 for high-power Li-ion storage.

A previously inaccessible metastable solid-solution phase, Li3-xV1-xMoxO4 (LVMoO), has been successfully synthesized for the first time over a remarkably wide compositional range (0.25 <= x <= 0.75). This new phase forms a single, impurity-free solid solution adopting a phenakite-type lattice, extending compositional limits far beyond equilibrium thermodynamic boundaries. The breakthrough is enabled by a kinetically driven spray-drying process in which ultrafast solvent evaporation within less than one second forces the simultaneous co-precipitation of V and Mo species. This suppresses sequential crystallization and prevents phase segregation, thereby stabilizing supersaturated nonequilibrium states. Operating at only 160 degrees C, the process requires no post-calcination and yields homogeneous, waste-free powders suitable for large-scale production. XRD confirms continuous lattice incorporation of V and Mo across the solid-solution series, while SEM-EDX analyses reveal composition-dependent nanostructures with uniform elemental distributions. A representative composition, Li2.5V0.5Mo0.5O4 (x = 0.5), delivers a high reversible capacity of 650 mAh g(-1) together with exceptional rate performance: 411 mAh g(-1) during delithiation at 15 A g(-1), and, strikingly, 326 mAh g(-1) during lithiation at 5 A g(-1). These results establish nonequilibrium spray drying as a significant and scalable synthetic route for supersaturated LVMoO solid solutions that unite high energy, high power, and long-term durability.

To design nanostructured electrodes capable of sustaining both high energy and power in sodium-ion supercapacitors, we present a mechanistically defined synthesis strategy that couples interfacial nano-pitting of carbon frameworks with in situ sulfate-substituted crystallization of Na2.85V2(PO4)2.85(SO4)0.15 (NVPS) nanodots. By integrating phosphate-sulfate ultracentrifugation pretreatment with brief thermal annealing, NVPS nanodots (5 nm) are homogeneously dispersed and tightly anchored along multi-walled carbon nanotube (MWCNT) networks. Mechanistic analysis revealed that a bifunctional role of Na2SO4: it induces localized sodification-assisted etching that forms ≈5 nm nanopits serving as confined nucleation cavities, while sulfate species participate in NVPS crystallization within these domains. Concurrent redeposition of sodified carbon fragments during ultracentrifugation further reinforces interfacial stability, producing nanodots electronically bridged and mechanically stabilized by the carbon matrix. The resulting NVPS/MWCNT composites exhibit exceptional rate capability, delivering 97 mAh g-1 (83% of the theoretical capacity) at 1000C, corresponding to a full charge-discharge cycle of 3.6 s. This ultrafast behavior originates from the formation of robust, strongly coupled nanodot-carbon junctions that facilitate rapid electron transport and sodium-ion intercalation. This sulfate-directed nano-pitting approach provides a generalizable and scalable route to engineer high-density nanodot/carbon hybrid architectures that bridge the gap between battery-type and capacitor-type storage.

Cation-deficient Y 2 Ti 2 O 5 S 2 with alternating perovskite-like TiO 5 S slabs and rock-salt [Y 2 S 2 ] 2+ layers exhibits excellent rate capability up to 230C and retains 95% capacity after 1,000 cycles, showing great promise as a durable high-power anode.

Electric double-layer capacitors (EDLCs), or supercapacitors, are high-performance energy storage devices known for their superior power density, rapid charge-discharge capabilities, and long cycle life. The electrolyte composition, specifically the choice of solvent and salt, plays a critical role in determining the voltage range, energy efficiency, and cycle lifespan of EDLCs. This study explores the novel electrolyte spiro1,1'-bipyrolidinium tetrafluoroborate (SBPBF4), selected for its high solubility and outstanding electrochemical stability at elevated voltages. SBPBF4, with its unique cyclic structure among quaternary ammonium salts, offers advantages particularly suited for high-voltage applications. This study investigates SBPBF4 in low-viscosity solvents, namely acetonitrile (AN) and dimethyl carbonate (DMC), chosen for their complementary properties that could further enhance SBPBF4's performance. A central focus is on the electrolyte's impact on stability and gas generation in both symmetrical AC//AC and hybrid LTO//AC configurations. Findings indicate that SBPBF4 enhances float durability and minimizes gas generation, an effect attributed to the resistance of the SBP+ cation to Hofmann elimination. This resistance interrupts degradation cycles typically triggered by interactions between residual water and solvents, stabilizing the electrolyte and preventing reductive decomposition at the negative electrode surface. Understanding these mechanisms is essential for optimizing low-viscosity solvent-based electrolytes and ensuring reliable operation in EDLCs and hybrid supercapacitors.

Cation-disordered materials offer attractive potential for high-power energy storage by unlocking diversified ionic transport pathways, yet their practical realization remains challenging due to difficulties in stabilizing disorder. Here, we demonstrate spray-drying as a direct and scalable route to synthesize cation-disordered Li3VO4 without requiring postannealing or additional lithiation steps. By leveraging ultrafast solvent removal, this method induces flash crystallization in less than 1 s, kinetically "freezing" the metastable disordered phase. Structural analysis using synchrotron X-ray diffraction, Pair-Distribution Function analysis, and high-resolution Transmission Electron Microscopy reveals that ultrafast drying disrupts long-range cation ordering while preserving short-range periodicity, forming local cation-ordered domains within an average disordered structure. This nanoscale disorder, stabilized by antiphase domain boundaries, enhances lithium-ion diffusivity, delivering a high-power performance of 138 mAh g-1 at a 60C rate. By enabling precise control of cation disorder through drying kinetics, this study establishes spray-drying as a powerful and scalable platform for next-generation energy storage materials.

This study develops a highly densified bronze‐type TiO₂ (TiO 2 (B)) anode to enhance the volumetric energy and power density of supercapacitors. By integrating ultracentrifugation with strategic carbon reduction via annealing, a TiO₂(B) anode with fluid‐like lubrication, high compressibility, and improved electrode density is synthesized. The annealing process facilitated a hierarchical nanoporous TiO₂(B) network while preventing agglomeration, achieving an electrode density of 2.24 g cm⁻ 3 , surpassing conventional values. The densified electrode exhibited an exceptional volumetric capacity of 400 mAh cm⁻ 3 , maintaining high‐rate performance at 120C. This approach effectively links mechanical and physicochemical properties to electrochemical performance, offering a scalable strategy for optimizing TiO₂(B) anodes. The findings highlight the potential of highly densified TiO₂(B) for hybrid supercapacitors, particularly in applications requiring maximum energy and power density within compact volumes. These advancements hold promise for electric mobility, portable electronics, and renewable energy storage, where efficiency and performance are critical. By demonstrating a method for achieving high‐density energy storage, this study provides a framework for next‐generation supercapacitor materials. Addressing the growing demands of modern technologies, this research advances high‐performance, space‐efficient energy storage solutions crucial for future energy applications

This study provides an in-depth investigation into the interplay between crystal polymorphs and phosphorus (P) substitution in wurtzite-type Li3V1-x P x O4 (LVPO), focusing on how crystal phase and P-substitution effects can be independently optimized to enhance electrochemical properties as anodes in lithium-ion based energy storage systems. Through precise control of the cooling rate after high-temperature synthesis, both beta- and gamma-phase LVPO can be reproducibly synthesized with identical P content. Powder X-ray diffraction (XRD) and in situ XRD analyses reveal that increasing P content results in a progressive stabilization of the gamma-phase, demonstrating the pivotal role of P-substitution in altering the crystal structure. Electrochemical characterizations confirm that both beta- and gamma-LVPO exhibits smooth, single-phase (solid-solution-type) Li+ de/intercalation without undergoing any phase transition, a key feature that differentiates it from nonsubstituted beta-Li3VO4. Galvanostatic intermittent titration technique (GITT) measurements show that the Li-ion diffusion coefficients follow opposing trends in beta- and gamma-LVPO as P content increases, providing a clear explanation for the superior rate capabilities observed in gamma-LVPO. In addition, the study highlights an intriguing finding: P-substitution lowers the electrochemical redox potential, counteracting the conventional inductive effect typically reported in phosphate-based materials, thus revealing a novel mechanism by which redox behavior is sensitively influenced by local crystal environments. This work significantly advances the fundamental understanding of structure-property relationships in wurtzite-type materials, particularly in relation to how P-substitution and crystal phase transitions can optimize electrode performance. Moreover, the findings emphasize the potential of compositional and crystallographic tuning as a powerful strategy to develop high-rate anode materials with enhanced stability, improved Li+ diffusion, and controlled redox behavior, ultimately paving the way for the design of more efficient, stable, and high-rate lithium-ion energy systems.

Y2Ti2O5S2 (YTOS) is a unique cation-deficient Ruddlesden-Popper structured material composed of alternating perovskite-like slabs (TiO5S octahedra) and rock-salt [Y2S2]2+ layers. Despite its potential for lithium-ion storage, research on YTOS as an energy storage material remains limited, underscoring its novelty and unexplored capabilities. The addition of 1 wt% single-walled carbon nanotubes (SWCNTs) significantly improved the electrochemical performance of YTOS, resulting in enhanced capacity, superior output characteristics, and improved cycle stability compared to the pristine material. The resulting composite demonstrates superior rate capability (up to 230C) and outstanding cycleability, retaining 95% of its capacity even after 1000 cycles. Operando XRD and Ti K-edge XAFS analyses reveal fully reversible orthorhombic-tetragonal phase transitions and stable Ti3+/Ti4+ redox activity during 500 cycles, while unchanged Y K-edge spectra confirm the structural stability conferred by the yttrium sublattice. Hybrid supercapacitor full cell assemblies with activated carbon (YTOS & Vert;AC) display minimal polarization and remarkable durability over 10 000 cycles at 10C, highlighting the material's suitability for high-power capability. This work presents a promising approach for developing high-performance energy storage materials, as the YTOS anode offers both high energy density and excellent cycle life, making it an excellent candidate for advanced lithium-ion batteries and hybrid supercapacitors.

Polyanion-substituted sodium vanadium phosphate (Na3V2(PO4)3, NVP) derivatives, including SO4, BO3, WO4, and SiO4 substitutions, were systematically synthesized and impregnated with a nanocarbon network via ultracentrifugation. Among them, nanosized (5-30 nm), highly crystalline, and well-dispersed sulfate-substituted NVP (NVPS) nanodots were directly nucleated onto multiwalled carbon nanotubes, enabling ultrafast electrochemical kinetics. This nanoscale architecture delivered exceptional rate capability, achieving 97 mAh g-1 at 1000C (3.6 s discharge), corresponding to 83% of the theoretical capacity, outperforming conventional NVP. The electrochemical kinetics analysis using a cavity microelectrode revealed reduced polarization, enhanced capacitive charge storage, and rapid sodium ion diffusion during intercalation/deintercalation, facilitated by the conformal interface between NVPS and MWCNT, possibly by sulfate-induced surface modifications. These findings establish polyanion substitution and ultracentrifugation-assisted materials processing as a transformative strategy for overcoming intrinsic transport limitations in NASICON-type phosphates, positioning NVPS as a benchmark material for next-generation high-power sodium-ion batteries and hybrid capacitors.

This study investigates mechanochemical synthesis and cation-disordering mechanism of wurtzite-type Li3VO4 (LVO), highlighting its promise as a high-performance anode material for lithium-ion batteries and hybrid supercapacitors. Mechanochemical treatment of pristine LVO using a high-energy ball mill results in a "pure cation-disordered" LVO phase, allowing for meticulous analysis of cation arrangement. The X-ray and neutron diffraction study demonstrates progressive loss of order in LVO crystal with increasing milling duration. High-resolution transmission electron microscopy reveals disrupted lattice fringes, indicating cationic misalignment. Pair-distribution function analysis confirms loss of cation arrangements and the presence of short-range order. Combination of these multiple analytical techniques achieves a comprehensive understanding of cation regularity and clearly demonstrates order/disorder dichotomy in cation-disordered materials, ranging from short (<8 & Aring;) to middle-long range (8-30 & Aring;), using an integrated superstructure model of the cation-disordered LVO crystals. Electrochemical testing reveals that mechanochemically treated LVO exhibits superior rate capability, with a 70% capacity retention at a high current density of 50C-rate. Lithium diffusion coefficient measurements demonstrate enhanced lithium-ion mobility in the mechanochemically treated LVO, attributed to cation-disordering effect. These findings provide valuable insights into mechanochemical cation-disordering in LVO, presenting its potential as an efficient anode material for lithium-ion-based electrochemical energy storage.

The substitution of Ti 4+ into LVP increased the electron density of the V–O bonds and modified the LVP surface morphology, resulting in suppressed vanadium dissolution and longer cyclability over 10 000 cycles for LVP cathode-based full cells.

Supercapacitors have emerged as pivotal energy conversion-storage systems in contemporary renewable and sustainable nanotechnology, offering a cost-effective and eco-friendly alternative. With material properties being paramount to their performance, supercapacitors stand out from conventional batteries due to their exceptional high-power capabilities and longevity, making them versatile for various applications. Their remarkable features, such as high-power capabilities and extended cycle-life, make them highly attractive for advanced hybrid configurations, serving both mobile and stationary purposes across diverse applications. The drive to shape the next generation of energy technologies fuels the development of composite materials, integrating elements like nanocarbon/graphene and metal oxides to enhance electrochemical performance. Material selection plays a critical role in supercapacitors, as different materials used as electrodes and electrolytes significantly influence functionality and characteristics, particularly in determining thermal and electrical properties. Leveraging innovative techniques such as "Ultracentrifugation" and “Spray-Dry Synthesis,” nanoarchitecture electrode materials are engineered for improved performance and safety. Collaborations with Li-predoping technology experts aim to develop groundbreaking Li-ion-based energy facilitators like the "iE7" SuperRedox Capacitor, capable of seamlessly balancing high power and energy demands. By integrating advancements in material science, pre-doping techniques, and cell design, the vision extends beyond innovation to lead the transition towards solar regeneration, driving electrification, and decarbonization across extensive mobility and heavy-duty sectors. References: K. Naoi et al., Adv. Mater., 28, 6751 (2016); E. Iwama, K. Naoi et al., ACS Nano, 10, 5398 (2016); P. Simon, K. Naoi et al., Nat. Ener., 1, 16070 (2016); K. Naoi et al., Acc. Chem. Res., 46,1075 (2013); K. Naoi et al., Ener. Environ. Sci., 5, 9363 (2012). K. Naoi et al., Chem. of Mater., 36, 2495 (2024); K. Naoi et al., J. Mater. Chem. A, 12, 2081 (2024); K. Naoi et al., J. Mater. Chem. A, 12, 1703 (2024); K. Fujii, K. Naoi et al., Phys. Chem. Chem. Phys., 26, 3920 (2024); K. Naoi et al., J. Electrochem. Soc., 170, 010524 (2023); K. Naoi et al., ACS Appl. Ener. Mater., 6, 9, 4657 (2023); K. Naoi et al., J. Mater. Chem. A, 11, 1841 (2023). Figure 1

Electrochemical capacitors are known for their high power density and cyclability, and various redox reactions can be utilized to improve their energy density. A great variety of redox materials have been investigated recently for use in electrochemical capacitors, not only transition metal oxides, which have been studied for many years. In this review, we provide a comprehensive explanation of redox materials for electrochemical capacitors. Manganese oxides and ruthenium oxides, which are typical metal oxides exhibiting pseudocapacitance, are first discussed. Nickel oxides used in hybrid capacitors are also covered. Various 0D and 2D nanomaterials are highlighted. Pseudo-capacitance using nanosized complex materials and metal-organic frameworks is also presented. Furthermore, electrolyte systems that exhibit redox characteristics for electrochemical capacitors are also reviewed.

This study explores the complex relationship between soil electricity generating capacity, bacterial community dynamics, and soil chemical and physical properties across diverse regions of Japan. First, soil samples were systematically collected and analyzed. Subsequent investigations evaluated soil microbial biomass carbon, dissolved organic carbon (DOC), and total dissolvable iron (DFeT) concentrations. In the experiments, soil samples underwent a rigorous 60-day microbial fuel cell trial, wherein power density and total energy output were measured. Significant variations in power density were observed among different soil samples; specifically, a sugarcane field designated as Okinawa-3 and a peach orchard soil as Nagano-2 demonstrated relatively high total energy output. Analysis of soil bacterial community structures identified some families which showed positive correlations with increased electricity generation capabilities. Correlation analyses revealed associations between these bacterial communities and key soil parameters, particularly with DOC and DFeT concentrations. Redundancy analysis revealed intricate connections between soil properties and electricity generation capacities. Particularly noteworthy was the positive correlation between Acidobacteriaceae and DOC, as well that between Sphingomonadaceae and electricity generation, highlighting the crucial roles of soil microbial communities and chemical compositions in driving electricity generation processes.

Nano-V2(PO4)3/KB cathodes demonstrated an ultrafast cathode reaction with Mg2+ insertion/extraction at ambient temperature through a solid-solution reaction.

This study explores the potential of titanium ion (Ti4+) substitution in gamma-Li3VO4 (gamma-LVO) as an anode material for high-energy supercapacitors. A series of Li3+xV1-xTixO4 (x = 0, 0.05, 0.10, 0.15, and 0.20) are systematically synthesized to vary the Ti-substitution ratio within LVO, and their crystal phases were analyzed using X-ray diffraction (XRD). Additionally, the reactivity of Ti during charge-discharge cycles is assessed by monitoring in situ X-ray absorption fine structure (XAFS) spectral changes. Quenching methods and XRD measurements quantitatively reveal that substituting 20 atom % of V5+ with Ti4+ achieves a single-phase gamma-LVO, distinct from the nonsubstituted LVO (beta-phase LVO). The Ti-substituted gamma-phase LVO electrode displays a supercapacitor-like voltage curve and exceptional high-power performance during charge-discharge tests, benefiting from its high ionic conductivity stemming from the LISICON (Lithium Super Ionic CONductor) crystal structure. Furthermore, the Ti-substituted gamma-phase LVO electrode exhibits an impressive rate capability, retaining 50% of its capacity at a very high current density of 2 A g(-1) (10C-rate), while the nonsubstituted LVO retained only 13% under the same conditions. GITT analysis confirms a 100-fold higher Li+ diffusion coefficient for the Ti-substituted gamma-phase LVO electrode. A novel approach is employed to examine the kinetic effects of Ti substitution on gamma-phase stabilization: halting or quenching the gamma -> beta phase transition during cooling using liquid nitrogen, coupled with XRD measurements, facilitates a quantitative evaluation of the phase transition rate. The primary goal of this study is to conduct a comprehensive assessment of the crystal structure and its stability by taking advantage of the excellent traceability of the Ti element through X-ray measurements to achieve this aim.

Li-ion ordered complexes formed in DMC-based dual-cation electrolytes.

Potassium-ion batteries (PIBs) have garnered considerable attention as next-generation energy-storage devices because of their superior resource abundance and high energy density compared to those of lithium-ion batteries. However, the electrolytes of conventional PIBs contain organic solvents that cause ignition and leakage issues, preventing their practical application. This study focuses on organic ionic plastic crystals (OIPCs) of N-ethyl-N-methylpyrrolidinium bis(fluorosulfonyl)amide (P12FSA) as a solid electrolyte material with excellent flexibility and ionic conductivity. For use in quasi-solid-state PIBs, we developed P12FSA-based composite electrolytes containing K-salt (potassium bis(fluorosulfonyl)amide; KFSA) and polymer (poly(ethylene carbonate); PEC). The developed composites (P12FSA-KFSA (50-50 mol%) with 10 wt% PEC) displayed high ionic conductivity of 1.0 × 10–3 S cm–1 and enabled charge-discharge reactions involving K+ insertion/extraction in the graphite anode with high discharge capacity (207 mAh g–1). The observed capacity was higher than those of systems with low K-salt concentrations (P12FSA-KFSA (90-10 mol%) with/without PEC: ~0 mAh g–1) and high K-salt concentrations without PEC (P12FSA-KFSA (50-50 mol%): 24 mAh g–1). The combined results of Raman, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) revealed that the FSA–- and PEC-derived decomposition products (KF, K2CO3, RO–COOK) suppressed irreversible pyrrolidinium cation (P12+) insertion and excessive reductive decomposition at the graphite anodes. Moreover, the assembled PIB full cells (graphite anode//K2Mn[Fe(CN)6] cathode) with composite electrolytes (P12FSA-KFSA (50-50 mol%) with 10 wt% PEC) exhibited reversible charge-discharge cyclability (after 5 cycles: 102 mAh g–1 with capacity retention of 97 %). These results indicate that the following two factors are important in P12FSA-based OIPC electrolytes for use in graphite anode-based PIBs: (1) formation of FSA–-derived SEI suppressing P12+ insertion via an increase in the K-salt concentration, imparting preferential FSA– reduction, and (2) formation of PEC-derived SEI via the introduction of carbonate-based additives, suppressing excessive electrolyte decomposition. Particularly for the latter, introducing PEC realized not only the transformation to a quasi-solid-state electrolyte (enhancing the mechanical strength) but also the improving K+ insertion/extraction reversibility in the graphite anode. Our findings provide novel insights into OIPCs and ionic liquids with structures similar to that of P12+ for use in graphite anode-based PIBs.