Of Al And Al Intermetallic Compound As Cathode Materials For Lithium Ion Secondary Battery

In search of new non-carbonaceous anode material for lithium ion secondary batteries, Aluminum and Al-based intermetallic compound (Al-Y, Al-Cu) prepared by hot vacuum casting were tested as negative materials. Their crystal structures , mechanism of Lithium intercalation and electrochemical performances were studied by XRD, SEM, micro-electrode cyclic voltammetry, galvanostatic charge/discharge test and measurement, AC impedance measurement and so on. The conclusions were showed as following:1. Aluminum electrode showed relatively good property in the cycles as negative material of lithium-ion secondary batteries . Its capacity reached 400mAh/g ,which is higher than the theoretical capacity of carbon. During charge-discharge progress, Al reacted with Li to form AlLi where somewhat Al₄Li₉ was formed afterwards. Small current charge could activate aluminum and following larger current could show its relatively large capacity.2. The oxidation peak of Al-Y samples was observed at about 0.5V and reductive peak at 0.3V. Their potential difference was about 0.2V, which meant their polarization was small. The capacity of Al-Y reached 500mAh/g, but capacity faded significantly after the first cycle due to the great volume change of alloy in cycles resulting the break-down of the grains of negative materials ,which led to the decrease of amount of effective and active materials. The cyclic performance should be improved.3. The oxidation peak of Al-Cu samples was observed at about 0.5V and reductive peak at 0.1V. cyclic voltammetry curves overlapped well ,which indicated certain electrochemical property. Al-Cu sample reached 500mAh/g whose cyclic efficiency was relatively high ,which suggested its potential to replace carbon..4. The order of magnitude of lithium diffusion coefficient in aluminum was estimated at 10^-1010^-13cm/s by AC impedance measurement.