A Versatile Carbon Nanotube-Based Scalable Approachfor Improving Interfaces in Li-Ion Battery Electrodes

摘要

Resistive interfaces within the electrodes limit the energy and power densities of a battery, for example, a Li-ion battery (LIB). Typically, active materials are mixed with conductive additives in organic solvents to form a slurry, which is then coated on current collectors (e.g., bare or carbon-coated Al foils) to reduce the inherent resistance of the active material. Although many approaches using nanomaterials to either replace Al foils or improve conductivity within the active materials have been previously demonstrated, the resistance at the current collector active material interface (CCAMI), a key factor for enhancing the energy and power densities, remains unaddressed. We show that carbon nanotubes (CNTs), either directly grown or spray-coated on Al foils, are highly effective in reducing the CCAMI resistance of traditional LIB cathode materials (LiFePO4 or LFP and LiNi0.33Co0.33Mn0.33O2 or NMC). Moreover, the CNT coatings displace the need for currently used toxic organic solvents (e.g., N-methyl-2-pyrrolidone) by providing capillary channels, which improve the wetting of aqueousdispersions containing active materials. The vertically aligned CNT-coatedelectrodes exhibited energy densities as high as (1) ∼500 Wh kg^–1 at ∼170 W kg^–1 forLFP and (2) ∼760 W h kg^–1 at ∼570W kg^–1 for NMC. The LIBs with CCAMI-engineered electrodeswithstood discharge rates as high as 600 mA g^–1 for500 cycles in the case of LFP, where commercial electrodes failed.The CNT-based CCAMI engineering approach is versatile with wide applicabilityto improve the performance of even textured active materials for bothcathodes and anodes.