Making solar cells using waste from lead batteries

In a fine demonstration of innovative recycling, the waste lead from traditional lead-acid batteries can recovered and used to make perovskite – the promising material for building efficient solar cells.

A research team in China report this innovative conversion of the debris from old technology into cutting-edge new technology in the journal Nano Energy.

Vast numbers of lead-acid batteries are produced to supply electricity for vehicles, emergency lighting systems, aviation, military applications and much more, but most have a life cycle of only a few years. Lead-rich muddy waste accumulates inside the batteries, creating a serious pollution problem worldwide. Existing methods to recover lead from this waste are complex, energy intensive and expensive. These recycling processes also themselves cause further pollution.

“We have found a way to recycle the battery lead to make perovskite for renewable energy generation without causing secondary pollution,” says researcher Rusen Yang of Xidian University.

The materials called perovskites show great promise as the light-gathering semiconductors needed for a new generation of more efficient solar cells. They share the same arrangement of ions as the natural perovskite mineral, calcium titanate (CaTiO3), but incorporating ions such as lead and chloride into the perovskite arrangement generates a wide range of unnatural perovskites. These new perovskites display many useful properties, especially in their interaction with light.

Yang and his colleagues have come up with two simple routes to recycling the lead in battery waste. One route captures the lead from the cathode region of the battery, while the other grabs the lead produced at the anode. The crucial step in each route involves mixing lead-containing materials with acetic acid. We know a weak solution of acetic acid in everyday life as vinegar. The simple chemical steps make high-purity lead acetate, which the researchers then incorporate into the fabrication of perovskite crystals.

Many researchers have previously explored the potential of lead acetate as a starting material to avoid problems found using other sources of lead to make perovskites. Now Yang and his colleagues have not only confirmed the effectiveness of lead acetate in making good crystals, they have also opened up an excellent and environmentally friendly source of the lead.

A further advantage is that the perovskites produced in the new procedure turn out to be more suitable for solar cells than those made using earlier methods. The crystallization of the perovskite proceeds more smoothly, yielding dense films with high light-harvesting efficiency.

“Our research is still limited to the laboratory,” cautions Zhan'ao Tan of Beijing University of Chemical Technology, another member of the research team. This is the case for much of the research working towards commercial perovskite solar cells. Despite the great potential, most research teams are still trying to improve the stability and efficiency of perovskite solar cells.

The key next step for the researchers is to demonstrate that they can scale up their laboratory methods into a procedure suitable for industry.

Article details:

Yang, R. et al.: “Lead acetate produced from lead-acid battery for efficient perovskite solar cells,” Nano Energy (2020)