Black TiO2-x-coated Si/SiOx Nanocomposites as Anode for Lithium Storage Materials

Abstract

Li-ion batteries are widely used in portable devices, electrical vehicles (EVs) and energy storage systems (ESSs) because of their high energy density and stable cycle performance. However, further advancement in the Li-ion battery technology is mandatory in terms of energy density and power density in order to meet the requirement of aforementioned applications. Si-based materials have attracted much attention as promising anode materials for Li-ion batteries due to their high theoretical capacity. However, Si-based anode materials are still not adopted in the commercially available Li-ion batteries due to poor cycle performance caused by huge volume change of Si during cycling. Among various Si-based anode materials, SiOx materials show that they can overcome these disadvantages. These materials show high capacity with improved cycle performance over prolonged cycle. Herein TiO2-x coated Si/SiOx nanocomposites are introduced as anode materials for Li-ion batteries. TiO2-x coated Si/SiOx nanocomposites show not only higher reversible capacity of approximately 1200 mAh g-1 but also stable cycle performance during 100 cycles. TiO2-x coating layer containing Ti3+ played a major role in the reduction of Si species of the Si/SiOx nanocomposite and the improvement of the electrical conductivity of the electrodes. Furthermore, they showed improved thermal stability by coating TiO2-x on the surface of the Si/SiOx nanocomposites. The structural properties and electrochemical properties will be discussed in detail in this work.|리튬 이온 전지는 높은 에너지 밀도와 안정적인 수명특성이 좋기 때문에 휴대용 기기, 전기차 (EVs)와 에너지 저장 시스템 (ESSs)에 널리 사용되고 있다. 하지만, 다양한 분야에 적용하기 위해 더 나은 전지 성능이 필요하다. 음극물질의 경우, Si 기반의 물질이 높은 이론 용량 때문에 음극 물질로써 많은 주목을 받고 있다. 그러나, Si 기반의 음극 물질은 충•방전 동안 Si의 심한 부피 팽창 때문에 수명 특성이 좋지 않아 상업적으로 사용할 수 없다. Si 기반의 음극 물질의 다양한 연구가 진행되는 가운데, SiOx 물질은 이러한 단점을 극복할 수 있는 물질 중의 하나이다. SiOx 물질은 높은 가역 용량과 개선된 수명 특성을 보여준다. 본 연구에서는 간단한 졸-겔 (sol-gel) 방법을 이용하여 TiO2-x를 코팅한 Si/SiOx 나노복합체를 소개하고자 한다. TiO2-x를 코팅한 Si/SiOx 나노복합체는 약 1200 mAh g-1의 높은 가역 용량을 구현하였고 100 사이클 동안 수명 특성이 안정적이었다. Ti3+가 있는 TiO2-x 코팅 층은 Si/SiOx 나노복합체에서 Si를 환원시키고 전극의 전기 전도도를 향상하는 데 중요한 역할을 했다. 그뿐만 아니라 Si/SiOx 나노복합체 표면에 TiO2-x를 코팅함으로써 열 안정성을 개선했다. 본 연구에서 구조 특성과 다양한 전기화학 특성을 분석하였다.; Li-ion batteries are widely used in portable devices, electrical vehicles (EVs) and energy storage systems (ESSs) because of their high energy density and stable cycle performance. However, further advancement in the Li-ion battery technology is mandatory in terms of energy density and power density in order to meet the requirement of aforementioned applications. Si-based materials have attracted much attention as promising anode materials for Li-ion batteries due to their high theoretical capacity. However, Si-based anode materials are still not adopted in the commercially available Li-ion batteries due to poor cycle performance caused by huge volume change of Si during cycling. Among various Si-based anode materials, SiOx materials show that they can overcome these disadvantages. These materials show high capacity with improved cycle performance over prolonged cycle. Herein TiO2-x coated Si/SiOx nanocomposites are introduced as anode materials for Li-ion batteries. TiO2-x coated Si/SiOx nanocomposites show not only higher reversible capacity of approximately 1200 mAh g-1 but also stable cycle performance during 100 cycles. TiO2-x coating layer containing Ti3+ played a major role in the reduction of Si species of the Si/SiOx nanocomposite and the improvement of the electrical conductivity of the electrodes. Furthermore, they showed improved thermal stability by coating TiO2-x on the surface of the Si/SiOx nanocomposites. The structural properties and electrochemical properties will be discussed in detail in this work.