Boosting high-rate-partial-state-of-charge performance of lead-acid batteries by incorporating trace amount of sodium dodecyl sulfate modified multi-walled carbon nanotubes into negative active materials

In this work, trace amount of sodium dodecyl sulfate modified multi-walled carbon nanotubes acid-treated multi-walled carbon nanotubes (SDS-MWCNTs) is incorporated into the negative active materials (NAMs) of lead acid battery by simply blending the SDS-MWCNTs aqueous dispersion with the dry mixture of lead oxide powder, expanders and carbon black for lead paste preparation. As the sulfate groups on SDS can combine with Pb2+ ions to make PbSO4 to generate 3PbO center dot PbSO4 center dot H2O (3BS), the cured NAMs incorporated with SDS-MWCNTs exhibit an improved 3BS percentage as well as an increased 3BS crystal size. The 3BS percentage reaches 22.47% in the cured NAMs with 100 ppm SDS-MWCNTs, more than 5.4% higher than that in the NAMs without SDS-MWCNTs. After formation, the NAMs containing SDS-MWCNTs presents a morphology of the interconnected Pb rods, which accelerates the kinetics for the electrochemical reactions between Pb and PbSO4 and thus retards PbSO4 accumulation. Simulated cells are assembled, and the cell constructed by the negative plate containing 100 ppm SDS-MWCNTs can achieve a high-rate partial-state-of-charge (HRPSoC) cycle-life of 45,692 cycles, more than 2.1 times as long as that of the cell assembled with the negative plate without SDS-MWCNTs. Our method is of great convenience and low-cost, it is supposed to have a great feasibility in lead-acid battery industry.