Batteries & Supercaps最新文献

Two oxalatoborate ionic liquids (ILs), which are commonly utilized as electrolyte additives that form a protective layer on the cathode surface, are investigated for the first time as electrode additives. Cathodes based on LiNi_0.5Mn_1.5O₄ (LNMO) containing 3 wt % ILs, i. e., “IL-enriched cathodes”, exhibit capacity values above 120 mAh/g with high Coulombic efficiencies throughout cycling over 200 times. A cathode without ILs also exhibits a capacity of 119 mAh/g but its Coulombic efficiency becomes low and unstable after 109 cycles. In addition, when 0.3 M ILs are added to conventional carbonate-based electrolytes, the battery cycle life improves but there is a reduction in the capacity probably due to low ionic conductivity of the electrolyte mixtures. Post-mortem analyses of electrodes retrieved from cycled cells highlight less electrolyte decomposition and less cathode corrosion, enabled by using the IL as the additive in LNMO, which are confirmed by a particle shape with smooth surface identical to the fresh cathode. The study demonstrates that oxalatoborate ILs can be used as the electrode additive, and this provides a new concept for cathode formulations for high performance batteries with a small amount of ILs.

Lithium-ion battery (LIB) electrodes are typically produced with n-methyl-2-pyrrolidone, a toxic solvent that is a known carcinogen and reproductive hazard. Accordingly, aqueous processing has been an expanding area of research interest in the field of LIB manufacturing. Although aqueous processing has been widely successful in anode processing, serious challenges remain in processing the cathode. In this work, the drying mechanics of cathode processed with both solvents is investigated though implementation of a chemical-engineering-based model to better understand the utilization of heat provided by experimentally determining the heat and mass transfer coefficients. Electrochemical performance is also evaluated to determine the impact of drying temperature on cycling performance. Binder distribution is determined via various methods to confirm differences in binder homogeneity as a function of both solvent and drying temperature. Identified is the large difference in the efficiency in which the heat is used as well as an ideal drying temperature for both aqueous and non-aqueous processed cathodes. Also identified is the increased sensitivity to processing temperature for aqueous processed electrodes compared to non-aqueous processed counterparts, pointing to the possibility of tuned drying regimes which would capitalize on the potential cost savings of aqueous processing for cathodes.

Porous carbon materials are often difficult to achieve high density while possessing high porosity, which limits their application in compact energy storage. Here, a design of freestanding porous-yet-dense carbon films with a tunable density (1.08–1.33 g cm⁻³) and porosity (specific surface area of 0–423.8 m² g⁻¹) is presented through an assembly of porous carbon nanosheet with graphene oxide under vacuum filtration. The typical freestanding carbon films simultaneously deliver a high density of 1.08 g cm⁻³ and a high specific surface area of 423.8 m² g⁻¹ when the porous carbon nanosheet content is 75 wt.%. As anode materials for sodium-ion batteries, the optimized freestanding carbon films deliver high volumetric capacity (270 mAh cm⁻³ at 20 mA g⁻¹), high initial capacity efficiency (81 %) and superior long-term cycling stability (1300 cycles with a capacity decay rate of 0.012 % per cycle). This study provides a promising direction for creating freestanding electrodes that meet both high-porosity and high-density requirements for compact sodium-ion batteries.

Rechargeable magnesium batteries have attracted much attention due to the high theoretical volumetric capacity, abundance, and safety. However, solid-state Mg batteries have been rarely studied because of limited choices of solid-state electrolyte materials. In this research, poly(vinylidene fluoride)/poly(propylene carbonate) (PVDF/PPC) as matrix were prepared using a simple solution casting method. Ethylene carbonate (EC), diethyl carbonate (DEC), and magnesium(II) bis(trifluoromethanesulfonyl) imide [Mg(TFSI)₂] were selected to prepare liquid electrolyte. A classification of novel gel polymer electrolytes (GPEs), PVDF/PPC/Mg(TFSI)₂, was synthesized and investigated. The electrochemical measurements show that PVDF/PPC/Mg(TFSI)₂ polymer electrolytes exhibit a high ionic conductivity, close to 10⁻² S cm⁻¹, at room temperature. The electrochemical stability window of PVDF/PPC-based GPE was up to 3 V (versus Mg²⁺/Mg). Materials characterization shows that these GPEs have a porous structure, providing a pathway for magnesium ion transport. Thermal analysis and crystal structure results indicate that PVDF crystallinity was affected by the addition of PPC. Additionally, the ion transport mechanism in the gel polymer electrolyte has been discussed.