Explosivity of nanomaterials for lithium-ion battery electrodes

As the European Union tries to develop important LIB production capacity by supporting the development of many gigafactories, new materials are under investigation to enhance the Lithiumion batteries (LIBs) performances. A promising way onwards seems to be the optimization of the chemical composition of LIBs using nanomaterials (NMs). NMs most frequently used as active materials for the anode are silicon, lithium titanate oxide (LTO) and graphite. In addition, carbon black (CB) is used as an additive to increase the conductivity and the electrical performance of LIBs. Even if NMs are beneficial for LIB performances, the reduction of the particle size might induce an explosive behaviour of the powder used during manufacturing. For this reason, a study on crucial NMs safety was conducted to evaluate both physicochemical characteristics and relating explosivity risks of those NMs to ensure their safe production, handling and use, including in the gigafactories under construction all over Europe. Firstly, the characterization of the pristine NMs was performed (i.e., median particle size (d50), and specific surface area (SSA)). Then, explosion parameters were assessed (i.e., minimum explosible concentration (MEC), maximum explosion pressure (Pmax) and deflagration index (Kst)) according to the standards. For LTO materials, no explosivity is observed due to the lack of combustibility and absence of any explosion-prone chemical group. A rise in the explosion's parameters was noted with the material's reduction in size from micro to nanoscale. In general, for the NMs, a smaller concentration of combustible dust mixed with air is needed for a deflagration to occur. This deflagration leads to higher maximum pressure values that in addition are set faster. For example, the micro-C exhibited no explosive behaviour, while the nano-C showed weak explosive severity (Kmax = 63 bar m/s). Consequently, the utilisation of nanomaterials in the production of LIBs necessitates that the risk assessment be conducted with due consideration of the heightened explosion risk that is due to their use.