Old solar panels can be recycled into lithium-ion batteries

Chinese researchers have found a way to make silicon from old solar panels into powerful anodes for lithium-ion batteries.

They say their research, published in Nature Sustainability, paves the way for “game-changing”, durable batteries.

“This work not only suggests a more sustainable supply source for silicon particles but also addresses the major challenges facing micro-sized silicon anode materials,” says co-first author Dr Tao Liu, a researcher at the Qingdao Institute of Bioenergy and Bioprocess Technology of the Chinese Academy of Sciences.

Silicon has long been examined as a possible component for the anodes of lithium-ion batteries.

At the moment, commercial batteries usually use graphite anodes, but silicon is more abundant and capable of making a more energy-dense battery. In their paper, the researchers say that batteries based on graphite are “rapidly approaching their energy density ceilings” of about 300 watt-hours per kilogram, meaning they “cannot meet the ever-increasing demands of electric vehicles”.

Unfortunately, for now silicon usually makes batteries with very short lifespans. Silicon tends to change in size when charged and discharged in a lithium-ion battery, meaning it quickly causes mechanical faults and degrades the battery’s performance over time.

This research solved the problem by using micrometre-sized particles of silicon, about the same size as red blood cells. These particles were made by milling old solar panels (or photovoltaic waste).

The particles were mixed into a specially designed electrolyte, made from lithium hexafluorophosphate and a couple of carbon-based solvents. This formula, say the researchers, could both keep the silicon particles stable and allow them to perform at high levels.

The researchers made a battery with this formula that retained 83% of its capacity after being charged and discharged 200 times. It had an energy density of 341 watt-hours per kilogram, making it higher performing than commercial lithium-ion batteries.

“The sustainable sourcing of silicon from discarded solar panels mitigates both the economic and environmental impacts of photovoltaic waste,” says co-first author Dr Tiantian Dong, also from the Qingdao Institute.

“Converting waste into valuable battery components significantly reduces the cost of lithium-ion batteries and increases their accessibility.”

The researchers hope that their work will help to improve next-generation batteries used in electric vehicles and grid storage.

“By using recycled materials and advanced chemical engineering, we have demonstrated that high-performance and environmentally sustainable lithium-ion batteries are not only possible, but also within reach,” says lead researcher Professor Guanglei Cui.