The mechanism of side reaction induced capacity fading of Ni-rich cathode materials for lithium ion batteries

Ni-rich cathode materials show great potential of applying in high-energy lithium ion batteries,but their inferior cycling stability hinders this process.Study on the electrode/electrolyte interfacial reaction is indispensable to understand the capacity failure mechanism of Ni-rich cathode materials and further address this issue.This work demonstrates the domain size effects on interfacial side reactions firstly,and further analyzes the inherent mechanism of side reaction induced capacity decay through comparing the interfacial behaviors before and after MgO coating.It has been determined that LiF deposition caused thicker SEI films may not increase the surface film resistance,while HF erosion induced surface phase transition will increase the charge transfer resistance,and the later plays the dominant factor to declined capacity of Ni-rich cathode materials.This work suggests strategies to suppress the capacity decay of layered cathode materials and provides a guidance for the domain size control to match the various applications under different current rates.

Unrevealing the effects of low temperature on cycling life of 21700-type cylindrical Li-ion batteries

The low-temperature performance of Li-ion batteries(LIBs) has important impacts on their commercial applications. Besides the metallic lithium deposition, which is regarded as one of the main failure mechanisms of the LIBs at low temperatures, the synergistic effects originating from the cathode, anode, electrolyte, and separators to the batteries are still not clear. Here, the 21700-type cylindrical batteries were evaluated at a wide range of temperatures to investigate the failure mechanism of batteries. Voltage relaxation, and the post-mortem analysis combined with the electrochemical tests, unravel that the capacity degradation of batteries at low temperature is related to the lithium plating at graphite anodes,the formation of unsatisfied solid deposited/decomposed electrolyte mixture phase on the anode, the precipitation of solvent in the electrolytes and the block of separator pores, and the uneven dissolved transition metal-ions from the cathode. We hope this finding may open up a new avenue to alleviate the capacity degradation of advanced LIBs at low temperatures and shed light on the development of outstanding low-temperature LIBs via simultaneous optimization of all the components including electrodes, electrolytes and separators.

Research Progress of Lithium Plating on Graphite Anode in Lithium-Ion Batteries

Lithium plating on graphite anode is triggered by harsh conditions of fast charge and low temperature,which sig-nificantly accelerates SOH(state of health)degradation and may cause safety issues of lithium ion batteries(LIBs).This paper has reviewed recent research progress of lithium plating on graphite anode.Firstly,we summarize the forming mechanisms of Li plating with(corresponding influence factors,the detect-ing methods and hazard of Li plating.Then,approaches to suppress Li plating are discussed,including anode surface modification,electrolyte composition optimization and development of optimal charge.strategies.Finally,we con-clude and propose the remaining challenges and prospects in terms of mechanism research,detecting approaches,and suppressing methods of Li plating.This review highlights the development of Li plating research and plays a guiding rule of further study on Li plating in LIBs.