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Preparation and Performance Studies of Si-SiO_x-Sn/C Anode Material for Li-ion Batteries

Author: MaChengHai
Tutor: GaoLiJun
School: Nanchang University
Course: Physical and chemical
Keywords: Silicon - silicon oxide - tin / carbon composites Lithium ion battery Anode material Electrochemical properties
CLC: TM912
Type: Master's thesis
Year: 2011
Downloads: 110
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Abstract

Carbon material as an anode material for lithium-ion batteries, has a very good cycle life and safety. Although carbon materials showed good reversibility and cycle, but the theoretical specific capacity of 372 mAh g-1, can not meet the needs of the high energy density of electronic products and electric vehicles using lithium ion battery. As a lithium-ion battery anode material silicon has the highest theoretical capacity (4200 mAhg-1) tin also has a high theoretical capacity (994 mAhg-1). However, the battery charging and discharging process, with the lithium ion embedded and prolapse, volume expansion and contraction easily fragmentation electrode capacity fading quickly after a few cycles, or even disappear. Therefore, at present, a lot of research workers are devoted to research and to solve the problem of poor cycle performance. This thesis is based on a large number of domestic and foreign literature research, followed by the cutting edge of research in the field, carbothermal reduction and high-temperature solid-phase synthesis of the modified silicon - silicon oxide - tin / the carbon lithium ion battery anode composite and the effects of different temperature and carbon modified material properties. Then, the material characterization methods and means of electrochemical tests combined, were tested on the material properties, experimental study concluded as follows .1. Carbothermal reduction method, silicon - silicon oxide - tin / carbon composites prepared material as an anode material for lithium-ion batteries, electrochemical performance. Under a nitrogen atmosphere were calcined at different temperatures, and naturally cooled to room temperature to obtain a calcined at various temperatures for different samples, the current density is 150 mAg-1 under test than the discharge capacity and cycle characteristics, to obtain the samples prepared in 950 ℃ first times discharge capacity of up to $ 1475 mAhg-1, 60 cycles remains the highest specific capacity on silicon - silicon oxide - tin / carbon composite materials as anode material obtained at 950 ℃, the electrochemical the best performance. 2 by the polymerization of furfuryl alcohol and hydrochloric acid reaction, the use of high-temperature solid phase prepared by a the carbon modified silicon - silicon oxide - tin / carbon composites, and carbon and the unused carbon modified silicon - silicon oxide - tin / composite materials for comparison, were characterized by XRD and SEM to study its electrochemical properties. Silicon - silicon oxide - tin / carbon composite material (a) and carbon-modified silicon - silicon oxide - tin / carbon composite material (b) current density of 150 mAg-1 charge and discharge, (a) first The discharge capacity was 1475mAhg-1, the first charge than the capacity for 575mAhg-1; (b) The initial discharge capacity of up to 1595 mAhg-1, the first charge than the capacity of 712 mAhg-1. The carbon modified silicon - silicon oxide - tin / carbon composites in current density for 90mAg 150mAg-1 225mAg-1 initial discharge capacity of 1628mAh g-1, 1595mAh g-1, 1184mAh g-1, as the current density increases, the first discharge capacity decreased. 225 mA g-1 under the charging and discharging cycle, as compared with 20 times the capacity after 120 cycles can be kept at 60% for the high magnification. Thus, it can be seen that the carbon-modified silicon - silicon oxide - tin / carbon composite negative electrode material have greatly improved discharge capacity, cycle characteristics are significantly improved, and greatly improved electrochemical performance.

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