文章信息/Info

Title:

In situ Transmission Electron Microscopy Observation of the Electrochemical Behavior and Mechanism of CuO nanowires

作者:

蘇慶梅; 杜秀梅; 杜高輝; 許并社

太原理工大學(xué) 新材料界面科學(xué)與工程教育部重點實驗室

Author(s):

SU Qingmei;  DU Gaohui;  XU Bingshe

Key Laboratory of Materials Interface Science and Engineering, Ministry of Education, Taiyuan University of Technology

關(guān)鍵詞:

鋰離子電池; 電化學(xué)行為; CuO納米線; 原位透射電鏡

DOI:

10.7502/j.issn.1674-3962.2015.05.03

文獻標志碼:

A

摘要:

過渡金屬氧化物是具有前景的鋰離子電池負極材料，但是其在電化學(xué)反應(yīng)循環(huán)中的反應(yīng)行為和轉(zhuǎn)變反應(yīng)機制尚不明確。針對此問題，我們利用原位透射電鏡研究了CuO納米線的電化學(xué)反應(yīng)過程。結(jié)果表明：放電過程中電化學(xué)反應(yīng)界面沿著CuO納米線軸向方向移動，且反應(yīng)的界面始終保持錐形，表明Li+離子的傳輸是從外向內(nèi)進行的；且鋰化的進行引起了納米線的徑向膨脹和軸向延長及彎曲，徑向膨脹為~40%，軸向膨脹為~43.1%，體積膨脹為~185.8%。待首次放電完成后，CuO納米線轉(zhuǎn)化為Cu納米晶（2~3 nm）分散在Li2O基體中，而在去鋰化后并沒有氧化為CuO，而是生成了Cu2O，此不可逆的相轉(zhuǎn)變是造成電池充放電循環(huán)中首次不可逆比容量損失的主要原因。

Abstract:

Transition metal oxides have been used as one of the most promising candidates as anode materials for lithium ion batteries (LIBs). However, their electrochemical process remains unclear. Here we directly observe the dynamic behaviors and conversion mechanism of CuO nanowire in LIBs by in situ transmission electron microscopy. The results show that a reaction front propagates progressively along the nanowire and always keeps a conical shape during the whole process. The conical reaction interface also verifies that lithiation proceeds from the nanowire surface towards its center. After lithiation, the originally straight CuO nanowire became heavily distorted and prolonged. The lithiation process causes an axial elongation of 43.1%, a radial expansion of 40%, and the total volume expansion of 185%. Also, single crystalline CuO nanowires are found to transform to multicrystalline nanowires consisting of many Cu nanograins (2~3 nm) embedded in Li2O matrix. The delithiated product is not CuO but Cu2O, accounting for the irreversible electrochemical process and the large capacity fading of the anode material in the first cycle.