Characteristics and properties of nano-LiCoO(2) synthesized by pre-organized single source precursors: Li-ion diffusivity, electrochemistry and biological assessment

BACKGROUND: LiCoO(2) is one of the most used cathode materials in Li-ion batteries. Its conventional synthesis requires high temperature (>800 °C) and long heating time (>24 h) to obtain the micronscale rhombohedral layered high-temperature phase of LiCoO(2) (HT-LCO). Nanoscale HT-LCO is of interest to improve the battery performance as the lithium (Li(+)) ion pathway is expected to be shorter in nanoparticles as compared to micron sized ones. Since batteries typically get recycled, the exposure to nanoparticles during this process needs to be evaluated. RESULTS: Several new single source precursors containing lithium (Li(+)) and cobalt (Co(2+)) ions, based on alkoxides and aryloxides have been structurally characterized and were thermally transformed into nanoscale HT-LCO at 450 °C within few hours. The size of the nanoparticles depends on the precursor, determining the electrochemical performance. The Li-ion diffusion coefficients of our LiCoO(2) nanoparticles improved at least by a factor of 10 compared to commercial one, while showing good reversibility upon charging and discharging. The hazard of occupational exposure to nanoparticles during battery recycling was investigated with an in vitro multicellular lung model. CONCLUSIONS: Our heterobimetallic single source precursors allow to dramatically reduce the production temperature and time for HT-LCO. The obtained nanoparticles of LiCoO(2) have faster kinetics for Li(+) insertion/extraction compared to microparticles. Overall, nano-sized LiCoO(2) particles indicate a lower cytotoxic and (pro-)inflammogenic potential in vitro compared to their micron-sized counterparts. However, nanoparticles aggregate in air and behave partially like microparticles. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12951-017-0292-3) contains supplementary material, which is available to authorized users.