Electrochemical and Structural Investigation of Calcium Substituted Monoclinic Li3V2(PO4)3 Anode Materials for Li‐Ion Batteries. Issue 33 (31st July 2019)

• Record Type: Journal Article
• Authors: Fu, Qiang; Liu, Shuoqi; Sarapulova, Angelina; Zhu, Lihua; Etter, Martin; Welter, Edmund; Weidler, Peter G.; Knapp, Michael; Ehrenberg, Helmut; Dsoke, Sonia
• Is Part Of: Advanced energy materials. Volume 9:Issue 33(2019)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2019-07-31
• Subjects: Ca‐substitution -- in operando synchrotron diffraction -- in operando X‐ray absorption spectroscopy -- Li3V2(PO4)3 -- Li‐ion batteries; Energy harvesting -- Materials -- Periodicals; Energy conversion -- Materials -- Periodicals; Energy storage -- Materials -- Periodicals; Photovoltaics -- Periodicals; Fuel cells -- Periodicals; Thermoelectric materials -- Periodicals; 621.31
• DOI: 10.1002/aenm.201901864
• Languages: English
• ISSNs: 1614-6832

Abstract

Abstract: In this work, the effect of Li + substitution in Li3 V2 (PO4 )3 with a large divalent ion (Ca 2+ ) toward lithium insertion is studied. A series of materials, with formula Li3−2 x Ca x V2 (PO4 )3 /C ( x = 0, 0.5, 1, and 1.5) is synthesized and studied in the potential region 3–0.01 V versus Li + /Li. Synchrotron diffraction demonstrates that Li3 V2 (PO4 )3 /C has a monoclinic structure (space group P 21 / n ), while Ca1.5 V2 (PO4 )3 /C possesses a rhombohedral structure (space group R ‐3 c ). The intermediate compounds, Li2 Ca0.5 V2 (PO4 )3 /C and LiCaV2 (PO4 )3 /C, are composed of two main phases, including monoclinic Li3 V2 (PO4 )3 /C and rhombohedral Ca1.5 V2 (PO4 )3 /C. Cyclic voltammetry reveals five reduction and oxidation peaks on Li3 V2 (PO4 )3 /C and Li2 Ca0.5 V2 (PO4 )3 /C electrodes. In contrast, LiCaV2 (PO4 )3 /C and Ca1.5 V2 (PO4 )3 /C have no obvious oxidation and reduction peaks but a box‐type voltammogram. This feature is the signature for capacitive‐like mechanism, which involves fast electron transfer on the surface of the electrode. Li3 V2 (PO4 )3 /C undergoes two solid‐solution and a short two‐phase reaction during lithiation and delithiation processes, whereas Ca1.5 V2 (PO4 )3 /C only goes through capacitive‐like mechanism. In operando X‐ray absorption spectroscopy confirms that, in both Li3 V2 (PO4 )3 /C and Ca1.5 V2 (PO4 )3 /C, V ions are reduced during the insertion of the first three Li ions. This study demonstrates that the electrochemical characteristic of polyanionic phosphates can be easily tuned by replacing Li + with larger divalent cations. Abstract : This work demonstrates that Li3 V2 (PO4 )3 and Ca‐substituted samples are promising as high performance anode materials for Li‐ion batteries. In operando synchrotron diffraction and in operando X‐ray absorption spectroscopy reveal that the substitution of Li with Ca makes a significant change to the reaction mechanism, in agreement with the completely different voltammetric signature.