Polyimide encapsulated lithium-rich cathode material for high voltage lithium-ion battery

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Lithium-rich materials (xLi2MnO3·(1 - x)LiMO2) offer high specific energy and low cost for lithium-ion batteries.
• Challenges include poor cycle and rate capability, hindering practical application.
• Surface modification is crucial for improving cathode material performance.

Purpose of the Study:

• To enhance the electrochemical performance of lithium-rich Li1.2Ni0.13Mn0.54Co0.13O2 (LNMCO) cathode material.
• To investigate the effect of a polyimide (PI) nanolayer coating on LNMCO.
• To improve the cyclic stability and rate capability of LNMCO for lithium-ion batteries.

Main Methods:

• Coating LNMCO with a polyimide (PI) layer using a polyamic acid (PAA) precursor followed by thermal imidization.
• Characterization using X-ray diffraction (XRD), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HR-TEM).
• Surface analysis using X-ray photoelectron spectroscopy (XPS) to determine valence states and charge transfer.

Main Results:

• A uniform PI layer (approximately 3 nm) was successfully coated on LNMCO without structural damage.
• Evidence of charge transfer between the PI layer and LNMCO surface, indicated by a shift in Mn valence state.
• Significant improvements in cyclic stability and rate capability of the PI-coated LNMCO.

Conclusions:

• The PI nanolayer coating effectively passivates the LNMCO surface, preventing undesirable side reactions with the electrolyte.
• The improved interfacial stability at high voltage contributes to enhanced electrochemical performance.
• Polyimide coating presents a viable strategy for developing high-performance lithium-rich cathode materials.