Novel graphitic sheets with ripple-like folds as an NCA cathode coating layer for high-energy-density lithium-ion batteries

Carbon-Coatings Improve Performance of Li-Ion Battery

The development of lithium-ion batteries largely relies on the cathode and anode materials. In particular, the optimization of cathode materials plays an extremely important role in improving the performance of lithium-ion batteries, such as specific capacity or cycling stability. Carbon coating modifying the surface of cathode materials is regarded as an effective strategy that meets the demand of Lithium-ion battery cathodes. This work mainly reviews the modification mechanism and method of carbon coating, and summarizes the recent progress of carbon coating on some typical cathode materials (LiFePO₄, LiMn₂O₄, LiCoO₂, NCA (LiNiCoAlO₂) and NCM (LiNiMnCoO₂)). In addition, the limitations of the carbon coating on the cathode are also introduced. Suggestions on improving the effectiveness of carbon coating for future study are also presented.

Nanoscale-engineered LiCoO2as a high energy cathode for wide temperature lithium-ion battery applications-role of coating chemistry and thickness

Extending the charge cutoff voltage of LiCoO₂(LCO) beyond 4.2 V is considered as a key parameter to obtain higher energy densities. Following gaps have been identified based on a thorough literature survey especially for higher cutoff voltage of nanoscale engineered LCO cathodes, (i) different metal oxides and metal fluoride surface coatings have been mostly done independently by different groups, (ii) room temperature performance was the focus with limited investigations at high temperature, (iii) nonexistence of low temperature cycling studies and (iv) no reports on high rate capability of LCO beyond 4.5 V (especially at 4.8 V) needs to be investigated. Herein, we report the effect of nanoscale engineering of LCO along with the role of coating chemistry and thickness to study its electrochemical performance at higher voltages and at wide operating temperatures. Surface coating was implemented with different metal oxides and a metal fluoride with tunable thickness. At 4.5 V, 5 wt% Al₂O₃coated LiCoO₂(LCO@Al₂O₃-5) delivered a reversible capacity of 169 mAh g^-1at 100 mA g^-1and 151 mAh g^-1at high rate of 10 C (2 A g^-1) and 72% retention at the end of 500 cycles. At 55 °C, it exhibited better stability over 500 cycles at 5 C and even at -12.5 °C it maintained 72% of its initial capacity after 100 cycles at 200 mA g^-1. At 4.8 V cut-off, LCO@Al₂O₃-5 rendered reversible capacity of 213 mAh g^-1at 100 mA g^-1, a high value compared to literatures reported for LCO. Also noted that it delivered a capacity of 126 mAh g^-1at a current density of 1 A g^-1, whereas bare could only exhibit 66 mAh g^-1under same testing conditions. Enhanced performance of LCO@Al₂O₃-5 can be ascribed to the lower charge transfer resistance derived from the stable solid solution formation on the interface.Ex situXRD andex situRaman analysis at different stages of charge/discharge cycles correlates the enhanced performance of LCO@Al₂O₃-5 with its structural stability and minimal structural degradation.