Effect Of Dissolution Status Of Lignin-based Expander On Performance Of Lead-acid Battery And Its Mechanism

Lead-acid battery was invented by Plante in 1859,and it has been widely applied in automotive and industrial fields.With increasingly higher requirements of automobile battery,application area and cycle life of lead-acid batteries have become more and more significant.As an important additive to increase the initial capacity and improve the low temperature performance of lead-acid battery,the application of lignin-based expander still has many shortcomings such as source dependence,unclear mechanism and complex quality control processes.In order to solve the above problems,the relationship between solubility of ligninbased expander and battery performance was studied.The interaction between lignin-based expander and lead was studied,and the mechanism of lignin-based expander in lead-acid batteries was proposed.A new idea and theoretical guidance for industrial selection of ligninbased expander was provided.In this study,commercial lignin-based expanders LC-V,LS-H and LS-U were chosen to be modified by alkyl cross-linking to obtain samples with increased molecular weight and decreased solubility.The effects of lignin-based expander on the viscosity of water-mixed lead powder,the morphology of cured lead plate and the performance of experimental battery were studied.The results showed that water-soluble lignin-based expander could reduce the viscosity of water-mixed lead powder,and with the increase of lignin-based expanders' sulfonation degree,the viscosity of water-mixed lead paste was lower.The viscosity of water-mixed lead powder decreased as the amount of lignin-based expander increased in range of 0.04 wt.% to 0.30 wt.%(base on the quantity of lead powder).Comparing the effect of solubility on experimental battery performance,it showed that as the acid solubility of samples decreased,the content of 3BS in negative plate increased,the static charge accept and dynamic charge accept performance increased,the primary capacity and the low-temperature discharge performance at-18°C of battery decreased.The mechanism of lignin-based expander in lead-acid batteries was investigated via studying the complexing ability of water-soluble lignin with lead ions and lignin adsorption capacity with lead plates.The results showed that the hydrophilic groups of lignin-based expander such as carboxyl groups,hydroxyl groups and sulfonic acid groups could complex with lead ions,and complexation ability increased with the rise of temperature and pH.In sulfuric acid and water,lignin-based expander was adsorbed on the surface of lead plate,which led to an inhibitory effect on the redox process of negative plate.It was proved that lignin-based expander could combine with lead ions in sulfuric acid electrolyte,and discharge process was promoted by releasing product inhibition on negative plate surface.The dissolution-adsorption mechanism of lignin-based expander in lead-acid batteries was updated.The ionization of lignosulfonates' carboxyl groups,hydroxyl groups and sulfonic acid groups under different pH conditions was investigated by CTAB precipitation method.It indicated that sulfonic acid groups of lignosulfonates and sulfonated alkali lignin could ionize fully at pH 1.0 to 2.0.Depending on the effect of solvents on samples solubility,lignosulfonates and lignin carboxylates could be distinguished by the solubility differences in sulfuric acid and water.And lignin salts and alkali lignin could be distinguished by solubility differences in water and ethanol.It provided a methodological guide for rapid screening and selection of technical lignin.