Negative electrodes for lithium- and sodium-ion batteries obtained by heat-treatment of petroleum cokes below 1000°C

Two petroleum cokes heat-treated at different temperatures are used to prepare suitable electrode materials for both lithium- and sodium-ion batteries. A combined mass spectrometry-Fourier transform infrared study allows us to detect a significant content in linear-chain hydrocarbons, which gives an extra contribution to the irreversible reaction with the alkali metals. Thus, low-temperature treated samples have low efficiencies, although their working voltages are sufficiently high that lithium metal deposition is not a problem under normal operating conditions. For sodium cells, low-temperature cokes decrease their capacity in increasing temperature, resulting from the lack of true intercalation in the graphitic materials. Capacities higher than 100 mAh/g reported in sodium cells using these soft carbon electrodes. (C) 2002 The Electrochemical Society.