TY - JOUR
T1 - Suppressing dissolution of vanadium from cation-disordered Li2-xVO2F via a concentrated electrolyte approach
AU - Cambaz, Musa Ali
AU - Vinayan, Bhaghavathi P.
AU - Pervez, Syed Atif
AU - Johnsen, Rune E.
AU - Gesswein, Holger
AU - Guda, Alexander A.
AU - Rusalev, Yury V.
AU - Kinyanjui , Michael Kiarie
AU - Kaiser, Ute
AU - Fichtner, Maximilian
PY - 2019
Y1 - 2019
N2 - Li2VO2F with the cation-disordered rock-salt
structure is an attractive high-energy-density positive electrode
material but suffers from severe capacity fading upon cycling. The
underlying reasons are yet unclear. In this study, we unveil the
overlooked role of vanadium dissolution and electrode-electrolyte
interactions and provide insight into the failure mechanism. Interfacial
reactions, in general, can be tuned by either surface coatings or the
modification of the electrolyte chemistry. Here we modify the
interfacial reactions through, the use of a concentrated electrolyte 5.5
M LiFSI in dimethyl carbonate (1:2.16 molar ratio salt to solvent),
effectively reducing vanadium dissolution. Moreover, it results in a
lower interfacial resistance build-up as compared to conventional 1.0 M
LiPF6 electrolyte, thus increasing the cycling stability. The solubility
of vanadium enhances significantly with higher oxidation states.
Furthermore, a chemical pre-lithiation strategy has been presented,
which allows the full lithiation of VO2F to Li2VO2F,
with an outlook on the intermediate phases. We argue that the
optimization of cathode-electrolyte interactions is of significant
importance to improve the cycling performance of disordered rock-salts,
where a thorough understanding of the limiting factors is still missing.
AB - Li2VO2F with the cation-disordered rock-salt
structure is an attractive high-energy-density positive electrode
material but suffers from severe capacity fading upon cycling. The
underlying reasons are yet unclear. In this study, we unveil the
overlooked role of vanadium dissolution and electrode-electrolyte
interactions and provide insight into the failure mechanism. Interfacial
reactions, in general, can be tuned by either surface coatings or the
modification of the electrolyte chemistry. Here we modify the
interfacial reactions through, the use of a concentrated electrolyte 5.5
M LiFSI in dimethyl carbonate (1:2.16 molar ratio salt to solvent),
effectively reducing vanadium dissolution. Moreover, it results in a
lower interfacial resistance build-up as compared to conventional 1.0 M
LiPF6 electrolyte, thus increasing the cycling stability. The solubility
of vanadium enhances significantly with higher oxidation states.
Furthermore, a chemical pre-lithiation strategy has been presented,
which allows the full lithiation of VO2F to Li2VO2F,
with an outlook on the intermediate phases. We argue that the
optimization of cathode-electrolyte interactions is of significant
importance to improve the cycling performance of disordered rock-salts,
where a thorough understanding of the limiting factors is still missing.
U2 - 10.1021/acs.chemmater.9b02074
DO - 10.1021/acs.chemmater.9b02074
M3 - Journal article
SN - 0021-9606
VL - 31
SP - 7941
EP - 7950
JO - Journal of Chemical Physics
JF - Journal of Chemical Physics
IS - 19
ER -