The crystal structure and phase purity of electrodes were analysed using X-ray powder diffraction (XRD, Stoe STADI P XRD diffractometer) in Debye-Scherrer geometry using a Mo Kα X-ray source (λ = 0.0709 nm) at 50 kV, 40 mA. Diffraction patterns were recorded in a 2θ angle range between 5 and 40°.