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Uniform second Li ion intercalation in solid state ϵ-LiVOPO4

DOI: 10.1063/1.4960452 DOI Help

Authors: Linda W. Wangoh (Binghamton University) , Shawn Sallis (Binghamton University) , Kamila M. Wiaderek (Advanced Photon Source, Argonne National Laboratory) , Yuh-chieh Lin (Department of NanoEngineering, University of California) , Bohua Wen (NECCES, Binghamton University) , Nicholas Quackenbush (Binghamton University) , Natasha A. Chernova (NECCES, Binghamton University) , Jinghua Guo (Advanced Light Source, Lawrence Berkeley National Laboratory) , Lu Ma (Advanced Photon Source, Argonne National Laboratory) , Tianpin Wu (Advanced Photon Source, Argonne National Laboratory) , Tien-lin Lee (Diamond Light Source) , Christoph Schlueter (Diamond Light Source) , Shyue Ping Ong (Department of NanoEngineering, University of California) , Karena W. Chapman (Advanced Photon Source, Argonne National Laboratory) , M. Stanley Whittingham (NECCES, Binghamton University) , Louis F.j. Piper (Binghamton University)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Applied Physics Letters , VOL 109

State: Published (Approved)
Published: August 2016
Diamond Proposal Number(s): 11246 , 12546

Abstract: Full, reversible intercalation of two Li+ has not yet been achieved in promising VOPO4 electrodes. A pronounced Li+ gradient has been reported in the low voltage window (i.e., second lithium reaction) that is thought to originate from disrupted kinetics in the high voltage regime (i.e., first lithium reaction). Here, we employ a combination of hard and soft x–ray photoelectron and absorption spectroscopy techniques to depth profile solid state synthesized LiVOPO4 cycled within the low voltage window only. Analysis of the vanadium environment revealed no evidence of a Li+ gradient, which combined with almost full theoretical capacity confirms that disrupted kinetics in the high voltage window are responsible for hindering full two lithium insertion. Furthermore, we argue that the uniform Li+ intercalation is a prerequisite for the formation of intermediate phases Li1.50VOPO4 and Li1.75VOPO4. The evolution from LiVOPO4 to Li2VOPO4 via the intermediate phases is confirmed by direct comparison between O K–edge absorption spectroscopy and density functional theory.

Journal Keywords: Li ion battery, HAXPES, XAS

Subject Areas: Energy, Chemistry, Materials

Instruments: I09-Surface and Interface Structural Analysis

Other Facilities: APS - V K-edge XAS, ALS - complementary O K-edge XAS to evaluate air exposure effects.