Effects of Methoxyl Groups in Lignophenols on Charge and Discharge Performance of Lead-Acid Batteries

Abstract

Lignophenols as the additive for the negative active materials of lead-acid batteries were synthesized, by use of the phase-separation system, as the controlled molecular structures from native lignins based on the softwood (chamaecyparis obtuse) and the hardwood (fagus crenata). The relationship between molecular structures of the prepared lignophenols and the performance of batteries with the addition of the lignophenols to negative active materials has been investigated. The role of aromatic methoxyl groups of the lignophenols on the battery performance has been mainly investigated. Employed batteries were 2 V-3.3 Ah flooded cells consisting of one negative plate and two positive plates. When the methoxyl group contents in the lignophenols increased, the discharge capacity increased but the charge capacity decreased. It was considered that the methoxyl groups of the lignophenols were demethylated in the batteries. The discharge performance was improved because the particle growth and the reaction area of negative active materials were respectively suppressed and increased. Despite the increase in the reaction area, the charge reaction was suppressed. The difference of the effects of the demethylated lignophenols on the discharge and the charge performance was thought to be due to the behavior of the adsorption of the demethylated lignophenols on mainly lead ion.