多層奈米碳管混摻錫作為複合材料應用在高容量鋰離子二次電池負極之研究與應用

Abstract

鋰離子二次電池主要研發目標為使用時數長、電池性能佳、製造成本低等；近年來在高容量負極材料開發上， 許多研究均著重於石墨或碳材料表面之金屬修飾，進而提高負極材料之電容量及循環壽命。 本研究主要目的是探討，藉由奈米尺度的錫球和多壁奈米碳管混摻，並且經由高溫退火的製程後，作為鋰離子電池的負極材料，經由掃瞄式電子顯微鏡(SEM)與穿透式電子顯微鏡(TEM)分析，奈米尺度的錫球在奈米碳管的網狀結構之間，以及管內壁形成高度且隨機的分布。 為了檢驗充放電特性、循環壽命、以及鋰離子二次電池的相關電化學行為，我們使用連續循環充放電儀，以及循環伏安儀來對電極材料做相關的檢測。經過實驗證實，混參後負極材料的電化學行為相對單純的錫球或是奈米碳管，都有顯著的提升。另外在經過高溫退火製程的改善後，錫/奈米碳管複合材料的電容可以明顯增高到948.4 mAh/g，這個結果遠高於單純的錫球或是奈米碳管的電極材料，也大於未經過退火製程的錫/奈米碳管複合材料。此外在2C-rate 的高放電速率操作下，錫/奈米碳管複合材料仍然維持91.44％的高電容維持率。

Major goals of development of lithium-ion secondary batteries are elongated battery lifetime, excellent battery performance, and low cost manufacturing. In recent years, in respect of the development of high capacity anode materials, emphasis has been put in metal modification of graphite or carbonaceous surface in order to improve capacity and cycle life of the anode materials. This study aims to enhance the capacity of Sn/MWCNTs composite as an anode material. SEM and TEM examinations show that the nano-sized tin particles with spherical shape are randomly distributed outside and inside the net-like MWCNTs. The charge/discharge characteristics, cycle life performance, and electrochemical behaviors, are performed by continuous cycle cell charge/discharge tests, cycle life tests, and cyclic voltammetry tests, respectively. The electrochemical behavior of the nano-composite substantially elevates their performance as compared with Sn or MWCNTs. Particularly, the charge/discharge capacity of the Sn/MWCNTs composite anode, after RTA processing, is 948.4 mAh/g, which is far greater than the pristine one without RTA and is also markedly higher than unmodified MWCNTs or Tin. Besides, the rate capacity can be maintained 91.44% under 2C high discharge rate tests