A New Look at Lithium Cobalt Oxide in a Broad Voltage Range for Lithium-Ion Batteries

Abstract

The electrochemical behaviors and lithium-storage mechanism of LiCoO2 in a broad voltage window (1.0−4.3 V) are studied by charge−discharge cycling, XRD, XPS, Raman, and HRTEM. It is found that the reduction mechanism of LiCoO2 with lithium is associated with the irreversible formation of metastable phase Li1+x CoII IIIO2−y and then the final products of Li2O and Co metal. During the charging process, the Li2O/Co mixture can be oxidized into CoO, and then the Li2O/CoO mixture can result in the formation of Co3O4 in the higher-voltage region. Li x CoO y is the final product when the active material is charged to 4.3 V. During the subsequent cycles, the lithium uptake/release reactions are related to the reversible conversion of Co ↔ CoO ↔ Co3O4 ↔ Li x CoO y .

Enhanced Overdischarge Stability of LiCoO2by a Solution Deposited AlPO4Coating

“…4 II-III O 2-y (0 < x, 0 ≤ y). 35 As shown for cycles 13, 16 and 19 in Figure 3c, the features of the voltage profile change significantly compared to cycle 10 as the LiCoO 2 is repeatedly overinserted. The plateau at around 1.3-1.4 V vs. Li/Li + becomes much less pronounced and by cycle 19, the plateau is no longer present.…”

“…As shown, after over-insertion of lithium, the discharge voltage plateau of the as-received LiCoO 2 becomes less pronounced, with the over-insertion steps leading to rounding of the profile towards the end of discharge, consistent with a prior study. 35 Such a change in the discharge profile of the cathode is unfavorable for lithium ion cell function as it leads to a decreased average discharge voltage and therefore discharge energy. In the present case, during cycle 19, the discharge energy is about 96% of its original value in cycle 10.…”

“…The initial decrease in electrode potential has been attributed to the formation of a metastable, high valence cobalt phase, Li 1+x Co II-III O 2-y (0 < x, 0 ≤ y). 35 After the potential of the electrode decreases to about 1. 4 II-III O 2-y (0 < x, 0 ≤ y).…”

Tartaric acid-assisted sol–gel synthesis of LiNi0.5Co0.5−Ti O2 (0 ⩽x⩽ 0.5) as cathode materials for lithium-ion batteries

“…The preparation of electrode and battery for electrochemical characterization can be found elsewhere [34]. The active electrode is comprised of active material (80 wt.%), acetylene black (AB, 12 wt.%) and polyvinylidene fluoride (PVDF, 8 wt.%).…”

Synthesis of LiNi0.65Co0.25Mn0.1O2 as cathode material for lithium-ion batteries by rheological phase method

“…The earliest and dominant commercial cathode material applied in lithium-ion batteries is LiCoO 2 [1,2]. However, the following drawbacks impede its development: (i) Co is expensive and toxic.…”