Composite materials of silver and natural graphite as anode with low sensibility to humidity

Sensitivity of anode materials to 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 of silver and natural graphite can be strikingly lowered. The composites are prepared by depositing silver ions onto the surface of natural graphite. After the following beat-treatment, silver ions turn into metallic silver and carbide AgxC by covering and/or removing active sites that absorb water very easily. Under high humidity condition (about 1000 ppm H2O), the composite materials absorb strikingly less water resulting in still good electrochemical performance. In comparison, natural graphite without this treatment shows fast fade in capacity under high humidity even though it is good in cycling under low humidity (<100 ppm H2O). Silver is a good matrix for lithium storage, and is assumed to contribute to reversible capacity since it enhances with the amount of deposited silver. This method can effectively lower the sensitivity of anode materials to humidity, and is promising in manufacturing lithium ion batteries under less critical conditions. (C) 2002 Elsevier Science B.V. All rights reserved.