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Chinese scientists have proposed using recycled silicon from discarded solar cells to build battery anodes.
Scientists led by the Kunming University of Science and Technology in China have proposed reusing silicon from discarded solar cells to develop composite silicon-carbon anode materials that could be used in battery anodes.
“The objective of our work is to propose a simple and efficient recycling method that allows the silicon of photovoltaic modules to be reused at the end of their useful life”, explains the main author of the research, Shaoyuan Li, to pv magazine . “Based on current conventional technical methods such as acid and alkali leaching, one ton of end-of-life PV modules can recover 40kg of silicon material, which can generate a net income of $104.9. If the recycled silicon material is combined with graphite through a simple ball milling process to produce a carbon-silicon composite anode, it can generate revenue of $1,883.”
In the study “ High-performance silicon carbon anodes based on value-added recycling strategy of end-of-life photovoltaic modules ” its useful life), published in Energy , the researchers explained that the waste silicon (W-Si) powder needed for battery anodes was obtained by pulverizing fragments of solar cells with a vibratory mill.
The cells had previously been mechanically disassembled from the modules and then cut into 6 mm x 6 mm fragments. These fragments were then immersed in a toluene solution for 24 hours to dissolve the ethyl vinyl acetate (EVA) encapsulant. "To further remove the EVA, the EVA-wrapped cell fragments were placed in a tubular oven for pyrolysis at 550 C for 2 h under an argon atmosphere," they explained. “Deionized water and ethanol were used for ultrasonic cleaning several times to obtain fragments of solar cells.”
Using these fragments, the research group developed residual silicon powder by combining the recycled silicon with graphite using a simple ball milling process. The resulting composite material, named W-Si-rM@G , showed remarkable electrochemical performance.
“It had an initial discharge capacity of up to 1,770 mA h g-1, maintained a good specific capacity of 913 mA h g-1 after 200 cycles at a current density of 500 mA g-1, and mean coulomb efficiency reached 98.99%, which was only a 0.24% capacity loss,” Li explained, noting that the use of graphite created a buffer space for the volumetric expansion of the silicon, thus improving the cyclic stability of the material. "The graphite had good contact with the silicon particles, and the introduction of the graphite greatly improved the electrical conductivity of the silicon material."
Looking ahead, the scientists stated that further work is needed to create a comprehensive and efficient end-of-life PV module recycling industry, and underlined the current difficulties in creating profitable companies in this sector without public support. “The recycling of photovoltaic modules at the end of their useful life has some economic viability, but it is not profitable enough to keep a company running well,” they said. |
