High-voltage operation by mechanical interlocking adhesion of nickel-rich cathode and functional separator in lithium-ion batteries

High-voltage operating is an effective route to provide upgrading the energy density of advanced lithium-ion batteries (LIBs). However, detrimental capacity decay caused by the high-voltage cycling makes it difficult to obtain stable long-term operation. Use of electrolyte additive can suppress fast capacity decay, but the prolonged effectiveness is hindered by the increased gaseous product at the electrode. In this work, we apply a functional separator having an adhesive layer on the ceramic-coated separator in high-voltage operating LIB. Mechanical interlocking adhesion between the electrode and separator prevents delamination resulting in high-capacity retention during the 500 charge-discharge cycles with the cut-off voltage of 4.5 V even with the reactive vinylene carbonate additive. This was evidenced by the X-ray inspection designed for the detection of gas pockets in pouch cells, caused by the continuous gas pressure build-up during the early cycles. Results indicate that the suppression of the gas pocket led to the prevention of capacity decay and provided a powerful strategy to extend the effect of increasing operating voltage. The approaches in this study not only highlight the importance of mechanical interlocking between the electrode and separator but also present insights into the electrode interfaces, which are still not fully understood.