Elastic properties of lithium cobalt oxide (LiCoO2)

All solid-state Li-ion batteries offer unprecedented improvements in energy density and safety compared to contemporary Li-ion batteries. As one of the most common oxide cathode materials for traditional Li-ion batteries, LiCoO2 (LCO) is also under consideration for use in all solid-state batteries. However, differences in the coefficients of thermal expansion (CTE) between LCO and the solid electrolyte during composite electrode fabrication, and the differential expansion and contraction during electrochemical cycling resulting from Li insertion and de-insertion, will cause stresses resulting in battery capacity fade. To characterize the thermo-mechanical properties, this study utilized hot pressing to prepare high relative density (95%) LCO polycrystalline pellets. The elastic modulus (E), shear modulus (G), hardness (H), and Poisson’s ratio (υ) of LCO were determined to be ∼191 GPa, ∼80 GPa, ∼8.2 GPa (at peak indentation loads ≤5 mN), and 0.24, respectively. The CTE was determined to be ∼1.3 × 10−5/°C over the temperature range 50–400 °C. We believe these data are important to predict or increase the cycle life of commercially available LCO as a cathode material for state-of-the-art Li-ion and advanced solid-state batteries.