Communication—XAFS Analysis of Discharge/Charge Reactions on the Li/CuCl₂Battery Cathode with LiPF₆/Methyl Difluoroacetate Electrolyte

Abstract

X-ray absorption fine structure (XAFS) analysis was performed on the CuCl2 cathode in Li/CuCl2 battery with LiPF6/methyl difluoroacetate (MFA) electrolyte to investigate the valence states of Cu during discharge/charge. X-ray absorption near edge structure (XANES) spectrum indicated that the Li/CuCl2 battery can discharge and charge reversibly. The disproportionation side reaction is confirmed to occur during charging. The side reaction, known to induce battery self-discharge, can be suppressed if reaction Cu + LiCl → CuCl + Li+ + e− proceeds completely, which may be accomplished by using a more homogeneous composition in the cathode.

High-Energy-Density Rechargeable Mg Battery Enabled by a Displacement Reaction

“…The rapid loss of capacity for the first 10 cycles can be attributed to some Mg 2+ trapped in CuS, indicated by a low Coulombic efficiency (less than 99.4%). In addition, the dissolution of copper ions into electrolyte also leads to a capacity loss (Cu concentration in cycled MACC electrolyte: 1.29 ppm according to ICP), which is common in copper-based cathodes. − The CuS/Mg full cells hold a capacity of ∼335 mA h/g after 80 cycles, which is much higher than that previously reported for CuS , and for the typical cathodes reported for RMBs (Table S1). It corresponds to a gravimetric energy density of ∼608 W h/kg, more than 4 times that of the Chevrel phase (140 W h/kg).…”

Charge-Discharge Characteristics of Li/CuCl_2 Batteries with LiPF_6/Methyl Difluoroacetate Electrolyte

“…Consequently, CuCl 2 was not formed or deposited on the electrode in the first cycle, according to the X-ray absorption fine structure (XAFS) analysis results. Only CuCl and Cu were detected in the cathode electrode under the fully charged condition 64) . Based on these results, the charged upper limit voltage was raised from 3.6 to 4.0 V in the current study to promote the formation and deposition of CuCl 2 .…”

Metal chloride cathodes for next-generation rechargeable lithium batteries

“…Ogumi’s group reported the application of CuCl 2 as a conversion-type cathode by utilizing fluorinated electrolytes. 21 , 68 , 69 Their particular electrolyte formulation of methyl difluoroacetate (MFA) as the solvent and LiPF 6 as the lithium salt successfully mitigated the dissolution of the CuCl 2 cathode. This improvement could be attributed to two factors.…”