Formation of Lithium‐Graphite Intercalation Compounds in Nonaqueous Electrolytes and Their Application as a Negative Electrode for a Lithium Ion (Shuttlecock) Cell

Abstract

Electrochemical reduction of natural graphite was carried out in 1M LiClO4 ethylene carbonate (EC)/1,2‐dimethoxyethane (DME) (1:1 by volume) solution at 30°C. Natural graphite was reduced stepwise to LiC6 (golden yellow in color). The staging phenomenon was observed by x‐ray diffraction (XRD). The first stage ( LiC6 ; cL=3.70true3_Å ) and the second stage ( LiC12 ; d2=7.06Å ) compounds were identified as a commensurate structure in which lithium atoms form a close‐packed two‐dimensional array. A second‐stage compound false(LiC18false) with a different in‐plane lithium ordering based on a LiC9 two‐dimensional packing in lithium intercalated sheets also was observed; also third ( LiC27 ; d3=10.4Å ), fourth‐( LiC36 ; d4=13.8Å ), and eighth‐( LiC72 ; d8=27.2Å ) stage compounds were identified. The electrochemical oxidation of the first‐stage compound false(LiC6false) was examined and shown to be reversible over the entire range, i.e., □C6+xnormalLi⇄LixC6 . The reaction mechanism for the reduction of graphite and the oxidation of the first‐stage compound are discussed in relation to the staging phenomenon from the detailed open‐circuit voltage and XRD data. The chemical potential of LiC6 was estimated to be −3.6 kcal · mol−1 from the observed reversible potential. The feasibility of using a lithium‐graphite intercalation compound in lithium ion (shuttlecock) cells is described, and the innovative secondary systems, □C6/LiCoO2 and □C6/LiNiO2 fabricated in discharged states, are demonstrated.

Approaching the limits of transparency and conductivity in graphitic materials through lithium intercalation

“…This is due to the decomposition of the electrolyte and a solid electrolyte interphase formation 11,27 . No obvious change in the transmittance of the ultrathin graphite samples is observed for voltages greater than 0.2 V. A sudden increase in the transmittance (18-layer graphite from 74.4 to 77.2%, 38-layer graphite from 55.9 to 59.2%) occurs after 0.2 V, which we identify with the formation of LiC 36 (stage IV) 28 from ultrathin graphite sheets. From 0.2 to 0.1 V, a gradual change in the transmittance is observed, presumably due to the formation of LiC 27 and LiC 18 (ref.…”

Li Intercalation into Graphite: Direct Optical Imaging and Cahn–Hilliard Reaction Dynamics

“…The GIC undergoes first order phase transitions through a sequence of dilute stage 1', stage 4, stage 3, stage 2 and finally stage 1 17,18 .…”

Cycling performance of low-cost lithium ion batteries with natural graphite and LiFePO4

“…In the fresh cell, there are three peaks for charge and discharge. Each peak is assigned to the lithium intercalation/deintercalation into/from graphite layer [10,11] because LiFePO 4 has only one plateau for charge and discharge [4]. However, after 100 cycles, the third high voltage peak disappeared in dQ/dV plot.…”

“…However, after 100 cycles, the third high voltage peak disappeared in dQ/dV plot. The third peak for lithium intercalation in graphite is assigned to region I at the lowest potential, which is related to the reaction of lithium with graphite between LiC 12 and LiC 6 [11]. This means that the anode in the pouch cell was not fully charged to final stage because of capacity fading.…”