Early-Stage Sustainability Evaluation of Nanoscale Cathode Materials for Lithium Ion Batteries.

Results of an early-stage sustainability evaluation of two development strategies for new nanoscale cathode materials for Li-ion batteries are reported: (i) a new production pathway for an existing material (LiCoO2 ) and (ii) a new nanomaterial (LiMnPO4 ). Nano-LiCoO2 was synthesized by a single-source precursor route at a low temperature with a short reaction time, which results in a smaller grain size and, thereby, a better diffusivity for Li ions. Nano-LiMnPO4 was synthesized by a wet chemical method. The sustainability potential of these materials was then investigated (at the laboratory and pilot production scales). The results show that the environmental impact of nano-LiMnPO4 is lower than that of the other examined nanomaterial by several factors regardless of the indicator used for comparison. In contrast to commercial cathode materials, this new material shows, particularly on an energy and capacity basis, results of the same order of magnitude as those of lithium manganese oxide (LiMn2 O4 ) and only slightly higher values than those for lithium iron phosphate (LiFePO4 ); values that are clearly lower than those for high-temperature LiCoO2 .

Characteristics and properties of nano-LiCoO2 synthesized by pre-organized single source precursors: Li-ion diffusivity, electrochemistry and biological assessment.

BACKGROUND: LiCoO2 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 LiCoO2 (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 (Co2+) 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 LiCoO2 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 LiCoO2 have faster kinetics for Li+ insertion/extraction compared to microparticles. Overall, nano-sized LiCoO2 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.

Nanomaterials Meet Li-ion Batteries.

Li-ion batteries are used in many applications in everyday life: cell phones, laser pointers, laptops, cordless drillers or saws, bikes and even cars. Yet, there is room for improvement in order to make the batteries smaller and last longer. The Fromm group contributes to this research focusing mainly on nanoscale lithium ion cathode materials. This contribution gives an overview over our current activities in the field of batteries. After an introduction on the nano-materials of LiCoO(2) and LiMnPO(4), the studies of our cathode composition and preparation will be presented.