Increasing the oxygen-containing functional groups of oxidized multi-walled carbon nanotubes to improve high-rate-partial-state-of-charge performance

Multi-walled carbon nanotubes (MWCNTs) with different oxygen functional groups were prepared from hot nitric acid reflux treatment. The acid-treated MWCNTs (a-MWCNTs) were introduced to negative active materials (NAMs) of lead-acid batteries (LABs) and the high-rate-partial-state-of-charge (HRPSoC) performance of the LABs was evaluated. A-MWCNTs with high quantities of carboxylic (COO-) and carbonyl (C=O) functional groups significantly improve the lead sulfate (PbSO4) reduction to lead (Pb) and thereby improve HRPSoC cycle life. The addition of a-MWCNTs to NAMs is helpful for the formation of larger crystals of ternary lead sulfate (3BS). The improved LABs performance is due to the formation of a sponge crisscrossed rod-like structure at the negative plate in the presence of a-MWCNTs. This unique channels structure is conducive to the diffusion of the electrolyte into the negative plate and delays the PbSO4 accumulation during HRPSoC cycles. The HRPSoC cycle life with a-MWCNTs is significantly prolonged up to the longest cycles of 39 580 from 19 712. In conclusion, oxygen-containing groups on the a-MWCNTs showed significant influence on the curing process and forming process and then improved HRPSoC performance.