Particle emission of Nano-enhanced Li-ion batteries during combustion and pyrolysis treatments

The prevalent use of Li-ion batteries (LIBs) has risen concern about the health hazard they might induce with regard to some of their toxic constituents. Beside chemical safety aspects, the occurrence of performance-enhanced electrodes made of composite materials containing microparticles and nanoparticles is another point to be considered with regard to occupational and user exposure to airborne (nano)particles (NPs) potentially emitted during the life cycle of LIBs. In this study, we investigated the emission of airborne particles during combustion in air at 850 °C (mimicking an accidental scenario of defective devices) and during pyrolysis in nitrogen gas at 1000 °C (mimicking end-of-life treatment) of fresh and aged composite anodes containing Si and Si@C NPs. Cycling of the cells resulted in the loss of surface integrity of the anode active layer and in the partial fusion of the Si-based NPs with a sixfold to eightfold increase in size. Such alteration induced fivefold to tenfold higher levels of particles released by aged anodes compared to fresh ones, with a shift towards larger population sizes, both in combustion and pyrolysis assays. Combustion was 10 to 30 times less emissive than pyrolysis, due to the better completion of the carbon matrix degradation with oxygen. The only significant difference in emission between the Si-based composite anodes and the reference anodes (without Si NPs) was observed with aged anodes during pyrolysis assays (10- to 20-fold increase). From a nanosafety aspect, this point should be mitigated given the size of the emitted particles.