Engendering High Energy Density LiFePO4 Electrodes with Morphological and Compositional Tuning

Improving the energy density of Li-ion batteries is critical to meet the requirements of electric vehicles and energy storage systems. In this work, LiFePO₄ active material was combined with single-walled carbon nanotubes as the conductive additive to develop high-energy-density cathodes for rechargeable Li-ion batteries. The effect of the morphology of the active material particles on the cathodes' electrochemical characteristics was investigated. Although providing higher packing density of electrodes, spherical LiFePO₄ microparticles had poorer contact with an aluminum current collector and showed lower rate capability than plate-shaped LiFePO₄ nanoparticles. A carbon-coated current collector helped enhance the interfacial contact with spherical LiFePO₄ particles and was instrumental in combining high electrode packing density (1.8 g cm^-3) with excellent rate capability (100 mAh g^-1 at 10C). The weight percentages of carbon nanotubes and polyvinylidene fluoride binder in the electrodes were optimized for electrical conductivity, rate capability, adhesion strength, and cyclic stability. The electrodes that were formulated with 0.25 wt.% of carbon nanotubes and 1.75 wt.% of the binder demonstrated the best overall performance. The optimized electrode composition was used to formulate thick free-standing electrodes with high energy and power densities, achieving the areal capacity of 5.9 mAh cm^-2 at 1C rate.

Peel and Penetration Resistance of Porous Polyethylene Terephthalate Material Produced by CO₂-Assisted Polymer Compression

CO₂-assisted polymer compression (CAPC) involves adhering fiber sheets without impurities at room temperature and producing porous materials suitable for use in medical and skin-contactable products. The mechanical strength of the resultant porous material has not yet been reported. The penetration resistance of the CAPC material, which is a laminated material comprising fibrous polymer sheets, was measured, and this increased gradually with the density. Additionally, a T-type peel test was performed on the CAPC material, and the peel resistance increased rapidly with the density. The peel resistance enhancement is effectively explained by the cross-sectional analysis model.