Boosting Zinc Storage Performance of Li3 VO4 Cathode Material for Aqueous Zinc Ion Batteries via Carbon-Incorporation: A Study Combining Theory and Experiment.

In the search for sustainable cathode materials for aqueous zinc ion batteries (AZIBs), vanadium (V)-based materials have garnered interest, primarily due to their abundance and multiple oxidation states. Among the contenders, Li3 VO4 (LiVO) stands out for its affordability, high specific capacity, and elevated ionic conductivity. However, its limited electrical conductivity results in significant resistance polarization, limiting its rate capability, especially under high currents. Through density functional theory (DFT) calculations, this study evaluates the electrochemical implications of carbon (C) incorporation within the LiVO matrix. The findings indicate that C integration significantly ameliorates the conductivity of LiVO. Moreover, C serves as a barrier, mitigating direct interactions between Zn2+ and LiVO, which in turn expedites Zn2+ diffusion. When considering various C materials for this role, glucose is emerged as the optimal candidate. The LiVO/C-glucose composite (LiVO/C-G) is observed to undergo dual phase transitions during charge-discharge cycles, resulting in an amorphous vanadium-oxygen (VO) derivative, paving the way for subsequent electrochemical reactions. Collectively, the insights pave a promising avenue for refining AZIB cathode design and performance.

Polypyrrole-Doped NH4 V3 O8 with Oxygen Vacancies as High-Performance Cathode Material for Aqueous Zinc-Ion Batteries.

The inherent slow diffusion dynamics of aqueous zinc-ion batteries (AZIBs) act as a significant hindrance to their universal utilization as energy storage systems, largely attributed to the scarcity of superior cathode materials. In this study, a novel method that amalgamates oxygen defect engineering and polymer intercalation, guided by theoretical computations, to confront this challenge, is introduced. This approach begins with density functional theory calculations, demonstrating that the shielding effect rendered by polypyrrole (PPy) between NH4 V3 O8 (NVO) layers, along with the cooperative influence of oxygen defects (Od ), optimizes the kinetic transport of Zn2+ . Leveraging these theoretical outcomes, a two-step hydrothermal synthesis procedure is devised to fabricate PPy-intercalated NVO embedded with Od (NVO-Od @PPy). The empirical findings corroborate the theoretical predictions, showcasing that the NVO-Od @PPy//Zn system manifests exceptional cycling stability. Specifically, the NVO-Od @PPy electrode delivers an optimal reversible capacity, yielding 421 mAh g-1 at a current density of 0.1 A g-1 . Remarkably, even at an elevated current density of 10 A g-1 , it sustains a capacity of 175.7 mAh g-1 , while maintaining a capacity retention of 99% over 1000 cycles. This research provides pivotal insights for the engineering of high-performing cathode materials for AZIBs, paving the way for their future advancements.

Coaxial spinning fabricated high nitrogen-doped porous carbon walnut anchored on carbon fibers as anodic material with boosted lithium storage performance.

Commercial graphite with low theoretical capacity cannot meet the ever-increasing requirement demands of lithium-ion batteries (LIBs) caused by the rapid development of electric devices. Rationally designed carbon-based nanomaterials can provide a wide range of possibilities to meet the growing requirements of energy storage. Hence, the porous walnut anchored on carbon fibers with reasonable pore structure, N-self doping (10.2 at%) and novel structure and morphology is designed via interaction of inner layer polyethylene oxide and outer layer polyacrylonitrile and polyvinylpyrrolidone during pyrolysis of the obtained precursor, which is fabricated by coaxial electrospinning. As an electrode material, the as-made sample shows a high discharge capacity of 965.3 mA h g-1 at 0.2 A g-1 in the first cycle, retains a capacity of 819.7 mA h g-1 after 500 cycles, and displays excellent cycling stability (475.2 mA h g-1 at 1 A g-1 after 1000 cycles). Moreover, the capacity of the electrode material still keeps 260.5 mA h g-1 at 5 A g-1 after 1000 cycles. Therefore, the obtained sample has a bright application prospect as a high performance anode material for LIBs. Besides, this design idea paves the way for situ N-enriched carbon material with novel structure and morphology by coaxial electrospinning.

A green approach to prepare hierarchical porous carbon nanofibers from coal for high-performance supercapacitors.

A green method is designed to obtain hierarchical porous carbon nanofibers from coal. In the work, deionized water, coal, polyvinyl alcohol and Pluronic F127 are used as the aqueous solution, carbon source, spinning assistant and soft template for spinning, respectively. As electrode materials for supercapacitors, the obtained hierarchical porous carbon nanofibers exhibit a high specific capacitance of 265.2 F g-1 at 1.0 A g-1 in 6 M KOH, a good rate performance with a capacitance of 220.3 F g-1 at 20.0 A g-1 with the retention of 83.1% and a superior cycle stability without capacitance loss after 20 000 charge/discharge cycles at 10.0 A g-1. Compared with the carbon nanofibers constructed without Pluronic F127, the enhanced electrochemical performance of the sample benefits from a larger contact surface area and the mesoporous structure formed by decomposition of Pluronic F127 and good structural stability. This work not only provides a green route for high-value utilization of coal in energy storage, but also paves a new way to make hierarchical porous carbon nanofibers from coal for supercapacitor electrodes with high specific capacitance and long cycle life.