The Electrochemistry of Germanium Nitride Versus Lithium
- PDF / 237,334 Bytes
- 7 Pages / 612 x 792 pts (letter) Page_size
- 50 Downloads / 172 Views
EE8.2.1
THE ELECTROCHEMISTRY OF GERMANIUM NITRIDE VERSUS LITHIUM N. Pereira a, b, M. Balasubramanian c, L. Dupont d, J. McBreen c, L.C. Klein b and G.G. Amatucci a a
Telcordia Technologies, Red Bank, NJ 07701, USA Rutgers University, Piscataway, NJ 08854, USA c Brookhaven National Laboratory, Upton, NY 11973, USA d Laboratoire de Réactivité et Chimie des Solides, Université de Picardie Jules Verne, 80039 Amiens, France b
E-mail: [email protected], [email protected]
ABSTRACT Germanium nitride (Ge3N4) was examined as a potential negative electrode material for Li-ion batteries. The electrochemistry of Ge3N4 versus Li showed high reversible capacity (500mAh/g) and good capacity retention during cycling. A combination of ex-situ and in-situ xray diffraction (XRD), ex-situ transmission electron microscopy (TEM) and ex-situ selective area electron diffraction (SAED) analyses revealed evidence supporting the conversion of a layer of Ge3N4 crystal into an amorphous Li3N+LixGe nanocomposite during the first lithiation. The nanocomposite was electrochemically active via a reversible Li-Ge alloying reaction while a core of unreacted Ge3N4 crystal remained inactive. The lithium/metal nitride conversion reaction process was kinetically hindered resulting in limited capacity. Mechanical milling was found to improve the material capacity.
INTRODUCTION Intensive effort has aimed at the development of alternative negative electrode materials which improve on the performance of graphite currently utilized in commercial Li-ion batteries. Although most work has concentrated on alloys and oxides, nitrides have been shown to exhibit interesting electrochemical properties. The ternary lithium transition metal nitrides of general formula Li3-xMxN (M= Cu, Ni, Co) [1-6], isostructural to the layered hexagonal Li3N, were investigated for their electrochemical properties. Li2.6Co0.4N was found to exhibit the best performance with high reversible capacity, 700mAh/g, and good cycling stability. However, this type of materials are moisture sensitive and need to be pre-delithiated before use as negative electrode in Li-ion batteries containing lithiated transition metal oxide such as LiCoO2. Binary nitrides such as Sn3N4 [7-8], InN [8] and Zn3N4 [7] were proposed to undergo an irreversible conversion reaction resulting in the generation of a Li3N matrix and an electrochemically active metal M (Eq.1) which subsequently react with Li via an alloying reaction (Eq.2).
(1) MxNy + 3y Li+ + 3y e- x M + y Li3N LizM (2) M + z Li+ + z e-
EE8.2.2
Our investigation of the reaction mechanism of Zn3N4 with Li revealed a first irreversible conversion reaction into LiZn+βLi3N was followed by a reversible conversion reaction of LiZn+βLi3N into LiZnN [9]. We believe the electromechanical grinding of the alloy to be the main cause responsible for the Zn3N4 poor cycle life. Finally, we identified Cu3N, where Cu does not alloy with Li, as an interesting negative electrode material candidate which exhibited improved cycling stability and excell
Data Loading...
