(Li, Al)-co-doped spinel, Li(Li0.1Al0.1Mn1.8)O4 as high performance cathode for lithium ion batteries

Abstract

(Li, Al)-co-doped manganese oxide spinel compounds, Li(Li0.1Al0.1Mn1.8)O4 are prepared at temperatures (T), 600, 650 and 750°C by polymer precursor method using polyvinyl pyrrolidone (PVP). The structure and morphology of the porous and sub-micron size particles of the compounds are characterized by the Rietveld refined X-ray diffraction (XRD), infrared and Raman spectroscopy, scanning electron microscopy (SEM), high resolution transmission electron microscopy (HR-TEM) and Brunauer, Emmett and Teller (BET) surface area techniques. Galvanostatic charge–discharge cycling in the voltage range of 3.5–4.3V vs. Li at various current (C) rates, 0.5–3C at 24°C up to 60 cycles and at 0.5C and at 55°C up to 50 cycles is carried out. The influence of the Li-excess, the type of Al3+ dopant cation and the amount of fuel (polyvinyl pyrrolidone) used in the synthesis on the electrochemical behavior of the spinel in a Li-cell at room (24°C) and at elevated temperature (55°C) has been studied. Results show that at 24°C and at 0.5C, the phases prepared at 600°C (I) and 650°C (II) showed reversible capacities of 79 and 105mAhg−1 and retained 99 (±1)% of the capacity after 50 cycles. At 1C, 2C and 3C rates, II showed stable capacities of 97, 83 and 57mAhg−1, respectively. At 55°C and at 0.5C, II showed a reversible capacity of 114mAhg−1 and retains 92% of it at the end of 50 cycles, signifying the best cathodic performance for a doped-LiMn2O4. Complementary cyclic voltammetry, impedance spectra and ex situ XRD data are described and discussed.