Improvement of electrochemical capability of sputtered silicon film anode for rechargeable lithium batteries

To improve the electrochemical properties of the silicon film anode in lithium cells, we prepared three types of silicon based-films, i.e., intrinsic silicon, n-type silicon, and Ag10Si90 binary films using r.f. magnetron sputtering. Based on galvanostatic charge-discharge tests and a.c. impedance measurements, the n-type silicon film and Ag10Si90 binary film cells exhibited a superior cycle life and lower electrochemical resistance compared with the intrinsic silicon film cell. The potential variation in the electrochemical alloying/de-alloying reactions of the Ag10Si90 binary film with lithium was different from that of the intrinsic silicon film, meaning that the Ag ingredient in the binary film affected the charge-discharge reaction. Furthermore, when a Ni plate roughened by chemical etching was used as a substrate, the Ag10Si90 film anode demonstrated an excellent capacity retention during 400 cycles with a high discharge capacity of >200 mu A h cm(-2) (corresponding to 1500 mA h g(-1)) at 0.5 mA cm(-2) (2.5 C).