Anode property of boron-doped graphite materials for rechargeable lithium-ion batteries

Anode properties of boron-doped graphites were investigated by means of ele ctrochemical measurements. A discharge capacity of about 315 mAh/g was obta ined for 3.8 mass% boron-doped pitch coke-derived graphite in galvanostatic measurements. Increased discharge capacity for boron-doped graphite compar ed with boron-free one was considered to be mainly due to the enhanced grap hitization by boron. Also, in this measurements, a shoulder was observed at 1.3 V (vs. Li/Li+) in boron-doped graphites. This peculiar reaction was co nfirmed to be the diffusion control and reversible process by the cyclic-vo ltammogram measurements, and it occurred before intercalation of lithium-io n into graphite-layers in charge process and after deintercalate of lithium -ion from graphite layers in discharge process. These phenomena are inferre d to be explained as that the lithium atom can be trapped easily to boron s olid-solution phase due to the valence band hole created by boron. This cap acity existed at high potential is probably worthwhile for the utilization as the signal of the ending of discharge process to prevent over-dischargin g in rechargeable lithium-ion batteries. (C) 2001 Elsevier Science Ltd. All rights reserved.