Delayed Phase Transition and Improved Cycling/Thermal Stability by Spinel LiNi_0.5Mn_1.5O₄ Modification for LiCoO₂ Cathode at High Voltages

Abstract

Increasing the upper cutoff voltage is capable of achieving higher charge capacity, whereas this strategy always causes a dramatic degradation of cycling and thermal stability. In this study, we first report spinel LiNi0.5Mn1.5O4-modified LiCoO2 (LiCoO2@LiNi0.5Mn1.5O4) as an outstanding cathode material. LiCoO2@LiNi0.5Mn1.5O4 retains capacity retention of 81.4% in a full cell between 4.45 and 3.00 V after 400 cycles at 0.5 C and is superior to 55.3% of pure LiCoO2. In situ X-ray diffraction at an upper cutoff voltage of 4.75 V in combination with differential capacity curve reveals that the promoted cycling performance is ascribed to a delay of O3 → H1–3 → O1 phase transitions and a suppression of cobalt dissolution-induced side reactions. Moreover, LiNi0.5Mn1.5O4 modification improves the thermal stability of LiCoO2 by depressing the release of oxygen and the formation of cobalt dendrites.

Multicomponent two-layered cathode for thick sintered lithium-ion batteries

“…This speculation was also consistent with the observation of a small amount of capacity below 1.2 V, where LCO may have underwent mild irreversible structural collapse at the higher potential the sintered cathode was subjected to relative to the composite cathodes. 49,50 The first experimental dQ/dV peak was at 2.52 V, which was lower than the OCV calculation (2.57 V) and the discrepancy was attributed to the electronically resistive Li 0.5 Mn 2 O 4 phase. The first experimental dQ/dV peak position was slightly higher than that of experimental dQ/dV of the CC:LMO:LCO case (2.50 V), which possibly originated from the reduced ionic overpotential from a reduced ionic path with LMO being next to separator.…”

“…Although both two-layer electrodes were charged to 2.8 V, for CC:LCO:LMO more Li + was extracted from the LCO layer due to relatively lower electronic overpotential, which may have resulted in some irreversible structural collapse in the LCO layer. [46][47][48][49][50] This structural collapse coupled with Li + extraction may have resulted in some of the Li + then inserting into the LMO during the lower voltage LMO process on discharge rather than the no longer available small amount of capacity in the LCO phase. At C/20 charge/discharge, a capacity of 101 mA h g À1 cathode was reached, much larger than that of the CC:LMO:LCO.…”

“…Such capacity fading was consistent with previous reports for structural collapse of the LCO due to overcharge, which could have resulted due to the relatively high potential experienced by the cathodes in the sintered electrode cell. 49,50 Analysis of lithium intercalation as a function of cell depth was also extracted from simulations of the CC:LCO:LMO case and can be found in Fig. 5c.…”

Advancing to 4.6 V Review and Prospect in Developing High‐Energy‐Density LiCoO2 Cathode for Lithium‐Ion Batteries

“…Accordingly, the coatings with Li + conductivity draw increasing research attention. [89,92,[143][144][145][146][147] As summarized in Table 2, lots of recent efforts have been directed to the construction of Li-ion conductive coating so as to improve the electrochemical performance of the HV-LCO. A large variety of coating species have been introduced to the LCO surface for its protection, which features different Li + conductors including cathode materials, inorganic fast Li-ion conductors and Li-ion conductive polymers.…”

A review – exploring the performance degradation mechanisms of LiCoO2 cathodes at high voltage conditions and some optimizing strategies

“…Additionally, O 2À is oxidized due to the delithiation and irreversible diffusion of cobalt ions at high voltage, resulting in oxygen loss, which leads to irreversible phase transitions. [131][132][133][134][135][136] The coating layer can effectively restrain the phase change in order to reduce the loss of oxygen. However, as shown in Fig.…”