The world of modern technology is one of out with the old, in with the new. For battery technology, that means the expected demise of lead-acid batteries and replacement by a more efficient, cheaper, and environmentally-friendly alternative. This is good news, but leaves the problem of what to do with all the lead in the batteries currently in use when the time comes to dispose of them? Researchers at MIT have an answer – use it to make solar cells.
Perovskite solar cells are one of those new technologies that seems too good to be true. Using cheaper, more common elements than conventional silicon cells, perovskite cells are made using a much simpler process involving lower temperatures. Despite being a relatively new technology, remarkable progress has been made in only a couple of years, with the cells reaching efficiencies of 19 percent – rapidly approaching that of many commercial cells.
The only snag is that one of the common elements used in the perovskite cells is lead, a fairly toxic heavy metal, the mining and production of which has significant environmental impacts. Lead is also a key component in larger batteries, such as those used in cars, and are also environmentally hazardous to make.
But the good news is that as alternatives to lead become cheaper, more efficient, and readily available, the lead variety is expected to be phased out of service in coming decades. However, this presents its own problems. Namely, what to do with the old lead-acid batteries – of which there around 200 million currently in use in the US alone.
According to MIT professor Angela M. Belcher, at the moment, around 90 percent of the lead recovered from old batteries goes into making new ones. But if the lead-acid battery market dries up, there will be a huge surplus of the material, which could poses a real headache for those tasked with getting rid of it.
But turning two negatives into a positive, an MIT research team has proposed a new use for the material – taking the lead from old lead-acid batteries and recycling it for use in the manufacture of perovskite cells. Importantly, the recycled material works as well as virgin metal straight from the mine and a little bit also goes a long way. Since the perovskite photovoltaic material goes on as a thin film, the team says that one car battery can make enough cells to power 30 households.
In addition, the simpler, low-temperature process used to manufacture perovskite solar cells is not only more environmentally friendly than those used for conventional silicon solar panels, but easily scalable. The finished panels are also encapsulated, which means the lead is contained until the panel is itself recycled at the end of its service life.
"It is important that we consider the life cycles of the materials in large-scale energy systems," says MIT professor Paula T. Hammond. "And here we believe the sheer simplicity of the approach bodes well for its commercial implementation."
The recycling process is described in the journal Energy and Environmental Science.
The video below shows the recycling process in action.