Reticular V₂O₅·0.6H₂O Xerogel as Cathode for Rechargeable Potassium Ion Batteries

Potassium ion batteries (KIBs), because of their low price, may exhibit advantages over lithium ion batteries as potential candidates for large-scale energy storage systems. However, owing to the large ionic radii of K-ions, it is challenging to find a suitable intercalation host for KIBs and thus the rechargeable KIB electrode materials are still largely unexplored. In this work, a reticular V₂O₅·0.6H₂O xerogel was synthesized via a hydrothermal process as a cathode material for rechargeable KIBs. Compared with the orthorhombic crystalline V₂O₅, the hydrated vanadium pentoxide (V₂O₅·0.6H₂O) exhibits the ability of accommodating larger alkali metal ions of K⁺ because of the enlarged layer space by hosting structural H₂O molecules in the interlayer. By intercalation of H₂O into the V₂O₅ layers, its potassium electrochemical activity is significantly improved. It exhibits an initial discharge capacity of ∼224.4 mA h g^–1 and a discharge capacity of ∼103.5 mA h g^–1 even after 500 discharge/charge cycles at a current density of 50 mA g^–1, which is much higher than that of the V₂O₅ electrode without structural water. Meanwhile, X-ray diffraction and X-ray photoelectron spectroscopy combined with energy dispersive spectroscopy techniques are carried out to investigate the potassiation/depotassiation process of the V₂O₅·0.6H₂O electrodes, which confirmed the potassium intercalation storage mechanisms of this hydrated material. The results demonstrate that the interlayer-spacing-enlarged V₂O₅·0.6H₂O is a promising cathode candidate for KIBs

Li₅AlO₄‑Assisted Low-Temperature Sintering of Dense Li₇La₃Zr₂O₁₂ Solid Electrolyte with High Critical Current Density

In recent years, solid electrolytes (SEs) have been developed a lot due to the superior safety of solid-state batteries (SSBs) upon liquid electrolyte-based commercial batteries. Among them, garnet-type Li7La3Zr2O12 (LLZO) is one of the few SEs that is stable to lithium anode with high Li+ conductivity and the feasibility of preparation under ambient air, which makes it a promising candidate for fabricating SSBs. However, high sintering temperature (>1200 °C) prevents its large-scale production, further hindering its application. In this work, the Li5AlO4 sintering aid is proposed to decrease the sintering temperature and modify the grain boundaries of LLZO ceramics. Li5AlO4 generates in situ Li2O atmosphere and molten Li–Al–O compounds at relatively low temperatures to facilitate the gas–liquid–solid material transportation among raw LLZO grains, which decreases the densification temperature over 150 °C and strengthens the grain boundaries against lithium dendrites. As an example, Ta-doped LLZO ceramics without excessive Li sintered with 2 wt % Li5AlO4 at 1050 °C delivered high relative density > 94%, an ionic conductivity of 6.7 × 10–4 S cm–1, and an excellent critical current density (CCD) of 1.5 mA cm–2 at room temperature. In comparison, Ta-doped LLZO with 15% excessive Li sintered at 1200 °C delivered low relative density < 89%, a low ionic conductivity of ∼2 × 10–4 S cm–1, and a poor CCD of 0.5 mA cm–2. Li symmetric cells and Li-LFP full cells fabricated with Li5AlO4-assised ceramics were stably cycled at 0.2 mA cm–2 over 2000 h and at 0.8C over 100 cycles, respectively

Optimizing Li_1.3Al_0.3Ti_1.7(PO₄)₃ Particle Sizes toward High Ionic Conductivity

NASICON-type Li1.3Al0.3Ti1.7(PO4)3 (LATP) has attracted a lot of attention because of its high ionic conductivity and stability to air and moisture. However, the size effect of LATP primary particles on ionic conductivity is ignored. In this study, different sizes of LATP particles are prepared to investigate the morphology, relative density, and ionic conductivity of the LATP solid electrolyte. The influences of particle size and sintering temperature on the microstructure, phase composition, and electrical properties of LATP ceramics were systematically studied. The medium-sized LATP particle (2 μm) presents a great microstructure with a high relative density of over 97%, the highest ionic conductivity of 6.7 × 10–4 S cm–1, and an activation energy of 0.418 eV. The Li–Li symmetric cells and Li–LFP batteries delivering good electrochemical performance were fabricated with highly conductive LATP ceramics. These results make significant strides in elucidating the relationship between the particle sizes of LATP and its electrochemical performance

Aging-Induced Chemical and Morphological Modifications of Thin Film Iron Oxide Electrodes for Lithium-Ion Batteries

Spectroscopic (XPS, ToF-SIMS) and microscopic (SEM, AFM) analytical methods have been applied to iron oxide (∼Fe₂O₃) using a thin film approach to bring new insight into the aging mechanisms of conversion-type anode materials for lithium-ion batteries. The results show that repeated lithiation/delithiation causes both chemical and morphological modifications affecting the electrochemical performance. The SEI layer formed by reductive decomposition of the electrolyte remains stable in composition (mostly Li₂CO₃) but irreversibly thickens upon multicycling. Irreversible swelling of the material accompanied by penetration of the SEI layer and accumulation of non-deconverted material in the bulk of the oxide thin film occurs upon repeated conversion/deconversion. After initial pulverization of the thin film microstructure, grain growth and aggregation are promoted by multicycling. This leads to capacity increase in the first few cycles, but upon further cycling volume expansion and accumulation of non-deconverted material lead to deterioration of the electrode performances

Networked Spin Cages: Tunable Magnetism and Lithium Ion Storage via Modulation of Spin-Electron Interactions

A networked spin cage comprising infinite Co^II₆L₄ cages arrays (where Co = Co­(NCS)₂ and L = 1,3,5-tri-(4-pyridyl)-verdazal radical) is synthesized and found to exhibit tunable magnetic and electrochemical properties via inclusion of guests. SQUID investigation reveals the coexistence of ferromagnetic and anti-ferromagnetic interactions between the Co­(II) ion center and radical ligands. Inclusion of electron-deficient guests (e.g., tetracyanoethylene) dramatically enhances spin concentration and increases anti-ferromagnetic interactions due to the formation of charge-transfer complex between the host and the guest. In addition, introduction of electron-rich guests (e.g., tetrathiafulvalene) into the networked spin cages doubles the capacity for binding the lithium ions

Phase Restructuring in Transition Metal Dichalcogenides for Highly Stable Energy Storage

Achieving homogeneous phase transition and uniform charge distribution is essential for good cycle stability and high capacity when phase conversion materials are used as electrodes. Herein, we show that chemical lithiation of bulk 2H-MoS₂ distorts its crystalline domains in three primary directions to produce mosaic-like 1T′ nanocrystalline domains, which improve phase and charge uniformity during subsequent electrochemical phase conversion. 1T′-Li_<i>x</i>MoS₂, a macroscopic dense material with interconnected nanoscale grains, shows excellent cycle stability and rate capability in a lithium rechargeable battery compared to bulk or exfoliated-restacked MoS₂. Transmission electron microscopy studies reveal that the interconnected MoS₂ nanocrystals created during the phase change process are reformable even after multiple cycles of galvanostatic charging/discharging, which allows them to play important roles in the long term cycling performance of the chemically intercalated TMD materials. These studies shed light on how bulk TMDs can be processed into quasi-2D nanophase material for stable energy storage

Synthesis and Study of Steering of Azido-tetrazole Behavior in Tetrazolo[1,5‑<i>c</i>]pyrimidin-5-amine-Based Energetic Materials

Tetrazoles and their derivatives are essential for compound synthesis due to their versatility, effectiveness, stability in air, and cost-efficiency. This has stimulated interest in developing techniques for their production. In this work, four compounds, tetrazolo[1,5-c]pyrimidin-5-amine (1), N-(4-azidopyrimidin-2-yl)nitramide (2), tetrazolo[1,5-c]pyrimidin-5(6H)-one (3), and tetrazolo[1,5-a]pyrimidin-5-amine (4), were obtained from commercially available reagents and straightforward synthetic methodologies. These new compounds were characterized by infrared (IR), 13C, and 1H NMR spectroscopy, differential scanning calorimetry (DSC), and single-crystal X-ray diffraction. The solvent, temperature, and electron-donating group (EDG) factors that were responsible for the steering of azido-tetrazole equilibrium in all compounds were also studied. In addition, the detonation performance of the target compounds was calculated by using heats of formation (HOFs) and crystal densities. Hirshfeld surface analysis was used to examine the intermolecular interactions of the four synthesized compounds. The results show that the excellent properties of 1–4 are triggered by ionic bonds, hydrogen bonds, and π–π stacking interactions, indicating that these compounds have the potential to be used in the development of high-performance energetic materials. Additionally, DFT analysis is in support of experimental results, which proved the effect of different factors that can influence the azido-tetrazole equilibrium in the synthesized pyrimidine derivatives in the solution

Covalent Organic Framework with Frustrated Bonding Network for Enhanced Carbon Dioxide Storage

Two-dimensional covalent organic framework (COF) materials can serve as excellent candidates for gas storage due to their high density of periodically arranged pores and channels, which can be tethered with functional groups. However, post-functionalization tends to disturb the structure of the COF; thus, it is attractive to develop synthetic approaches that generate built-in functionalities. Herein, we develop a new strategy for the construction of 2D-COFs with built-in, unreacted periodic bonding networks by solvent-directed divergent synthesis. Tetraphenylethane (TPE), which combines both π-rigidity for stacking and rotational flexibility, is selected as the central core for COF construction. By solvent control, two distinct COF structures could be constructed, arising from a [4 + 4] condensation pathway (TPE-COF-I) or an unusual [2 + 4] pathway (TPE-COF-II). TPE-COF-II contains unreacted linker units arranged around its pores and shows greatly enhanced carbon dioxide adsorption performance (23.2 wt %, 118.8 cm³ g^–1 at 1 atm, 273 K), which is among the best COF materials for CO₂ adsorption reported to date

Crystal Engineering of Naphthalenediimide-Based Metal–Organic Frameworks: Structure-Dependent Lithium Storage

Metal–organic frameworks (MOFs) possess great structural diversity because of the flexible design of linker groups and metal nodes. The structure–property correlation has been extensively investigated in areas like chiral catalysis, gas storage and absorption, water purification, energy storage, etc. However, the use of MOFs in lithium storage is hampered by stability issues, and how its porosity helps with battery performance is not well understood. Herein, through anion and thermodynamic control, we design a series of naphthalenediimide-based MOFs <b>1–4</b> that can be used for cathode materials in lithium-ion batteries (LIBs). Complexation of the <i>N</i>,<i>N</i>′-di­(4-pyridyl)-1,4,5,8-naphthalenediimide (DPNDI) ligand and CdX₂ (X = NO₃^– or ClO₄^–) produces complexes MOFs <b>1</b> and <b>2</b> with a one-dimensional (1D) nonporous network and a porous, noninterpenetrated two-dimensional (2D) square-grid structure, respectively. With the DPNDI ligand and Co­(NCS)₂, a porous 1D MOF <b>3</b> as a kinetic product is obtained, while a nonporous, noninterpenetrated 2D square-grid structure MOF <b>4</b> as a thermodynamic product is formed. The performance of LIBs is largely affected by the stability and porosity of these MOFs. For instance, the initial charge–discharge curves of MOFs <b>1</b> and <b>2</b> show a specific capacity of ∼47 mA h g^–1 with a capacity retention ratio of >70% during 50 cycles at 100 mA g^–1, which is much better than that of MOFs <b>3</b> and <b>4</b>. The better performances are assigned to the higher stability of Cd­(II) MOFs compared to that of Co­(II) MOFs during the electrochemical process, according to X-ray diffraction analysis. In addition, despite having the same Cd­(II) node in the framework, MOF <b>2</b> exhibits a lithium-ion diffusion coefficient (<i>D</i>_Li) larger than that of MOF <b>1</b> because of its higher porosity. X-ray photoelectron spectroscopy and Fourier transform infrared analysis indicate that metal nodes in these MOFs remain intact and only the DPNDI ligand undergoes the revisible redox reaction during the lithiation–delithiation process

Additional file 1 of In silico analysis of the wheat BBX gene family and identification of candidate genes for seed dormancy and germination

Supplementary Material