TY - JOUR
T1 - Hidden Two-Step Phase Transition and Competing Reaction Pathways in LiFePO4
AU - Koyama, Yukinori
AU - Uyama, Takeshi
AU - Orikasa, Yuki
AU - Naka, Takahiro
AU - Komatsu, Hideyuki
AU - Shimoda, Keiji
AU - Murayama, Haruno
AU - Fukuda, Katsutoshi
AU - Arai, Hajime
AU - Matsubara, Eiichiro
AU - Uchimoto, Yoshiharu
AU - Ogumi, Zempachi
N1 - Funding Information:
This work was supported by the Research and Development Initiative for Scientific Innovation of New Generation Battery (RISING) project under the auspices of New Energy and Industrial Technology Development Organization (NEDO), Japan. Operando XRD measurements were performed at BL28XU of SPring-8 (Proposal No. 2012B7601, 2013A7601 and 2013B7601).
Publisher Copyright:
© 2017 American Chemical Society.
PY - 2017/4/11
Y1 - 2017/4/11
N2 - LiFePO4 is a well-known electrode material that is capable of high-rate charging and discharging despite a strong phase-separation tendency of the lithium-rich and poor end-member phases. X-ray diffraction measurements (XRD) with high time-resolution are conducted under battery operation conditions to reveal the phase-transition mechanism of LiFePO4 that leads to the high rate capability. We here propose a hidden two-step phase transition of LiFePO4 via a metastable phase. The existence of the metastable phase, not just a member of a transient solid solution, is evidenced by the operando XRD measurements. Our two-step phase-transition model explains the behavior of LiFePO4 under the battery operation conditions. It also explains asymmetric behavior during the charging and discharging at high rates and low temperatures, as well as apparent single-step two-phase reaction between the end members at low rates at room temperature. This model also suggests underlying, rate-dependent electrochemical processes that result from a competing disproportion reaction of the metastable phase.
AB - LiFePO4 is a well-known electrode material that is capable of high-rate charging and discharging despite a strong phase-separation tendency of the lithium-rich and poor end-member phases. X-ray diffraction measurements (XRD) with high time-resolution are conducted under battery operation conditions to reveal the phase-transition mechanism of LiFePO4 that leads to the high rate capability. We here propose a hidden two-step phase transition of LiFePO4 via a metastable phase. The existence of the metastable phase, not just a member of a transient solid solution, is evidenced by the operando XRD measurements. Our two-step phase-transition model explains the behavior of LiFePO4 under the battery operation conditions. It also explains asymmetric behavior during the charging and discharging at high rates and low temperatures, as well as apparent single-step two-phase reaction between the end members at low rates at room temperature. This model also suggests underlying, rate-dependent electrochemical processes that result from a competing disproportion reaction of the metastable phase.
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U2 - 10.1021/acs.chemmater.6b05000
DO - 10.1021/acs.chemmater.6b05000
M3 - Article
AN - SCOPUS:85017536461
SN - 0897-4756
VL - 29
SP - 2855
EP - 2863
JO - Chemistry of Materials
JF - Chemistry of Materials
IS - 7
ER -