Lanthanum niobate perovskite thin films for Li-ion microbatteries

The development of high-performance microbatteries for the Internet of Things (IoT) and smart devices applications requires anode materials that combine a high energy density with fast charge/discharge capabilities. In this study, we report on the synthesis of La–Nb–O thin film anode for Li-ion high-power microbatteries. The thin films were obtained by reactive co-sputtering, which is compatible with miniaturization and microelectronic processes. By adjusting the power applied to La and Nb targets, we controlled the La/Nb atomic ratio and selectively promoted the formation of La 1/3 NbO 3 , a vacancy-rich perovskite phase. X-Ray Diffraction (XRD), Raman spectroscopy, and Transmission Electron Microscopy (TEM) observations reveal the formation of a mixed-phase composed of an orthorhombic La 1/3 NbO 3 matrix and LaNbO 4 grains for La/Nb ratios slightly above 1/3, while pure LaNbO 4 are formed for higher La/Nb ratios. Electrochemical tests demonstrated that LaNbO 4 is electrochemically inactive while La 1/3 NbO 3 -containing thin films exhibit high areal and gravimetric capacities (up to 73 μAh cm −2 and 203 mAh g −1 , respectively) and good rate capability and reversibility (10 μAh.cm −2 in 200 s charge or discharge). A description of Li + insertion site and occupancy is given based on theoretical and experimental considerations, which suggests that 1.44 Li + could be inserted per La 1/3 NbO 3 unit. • La 1 / 3 NbO 3 perovskite thin films deposited by reactive magnetron co-sputtering. • Ordered A-site vacancy superstructure creates Li diffusion channels in the a–b planes. • High reversible capacities up to 203 mAh g −1 achieved in perovskite thin films. • Up to 1.44 Li + per La 1 / 3 NbO 3 formula unit described from electrochemical data. • Li + preferentially occupies 4-coordinate square planar windows of the perovskite cavity.