Lowering sensitivity of anode materials for lithium ion batteries towards humidity

Sensitivity of anode materials towards humidity is an important factor for the performance of lithium ion batteries. Here it is demonstrated for the first time that the sensitivity of composite anode materials prepared of metals such as copper and silver with natural graphite can be strikingly lowered. The composites are prepared by adsorbing metal ions from solutions onto the surface of natural graphite followed by heat-treatment at high temperature. Results from X-ray photoelectron spectroscopy, high resolution electron microscopy, thermogravimmetry, differential thermal analysis, and capacity measurements indicate that the deposited metals exist in two forms, viz. metallic and carbidic M_xC (M=Cu and Ag), and remove/cover (i.e. deactivated) the active hydrophilic sites at the surface of graphite. As a result, in the presence of high humidity the composites absorb less water, and the obtained electrochemical performance including reversible capacity, coulombic efficiency in the first cycle and cycling behavior is markedly improved. This approach provides a potentially powerful method to manufacture lithium ion batteries under less critical conditions.