Enhanced electrochemical performance of the LiNi0.8Co0.1Mn0.1O2 cathode via in-situ nanoscale surface modification with poly(imide-siloxane) binder

Abstract

The Ni-rich layered oxide cathode (LiNi0.8Co0.1Mn0.1O2, NCM811) suffers from serious interfacial side reactions and phase transition during high-voltage cycling (4.7 V), causing the poor rate capability and sharp capacity fading. Herein, a beneficial strategy is proposed, combining rigid/flexible chains, to exploit an endurable poly(imide-siloxane) (PIS) binder with transitable ion channel by structural tailoring and copolymerization. The in-situ formed nanoscale PIS layer on the NCM811 particle surface provides stern resistance to extreme conditions and strong attractive interactions, which enable a firm cathode-electrolyte interface and facile ion transfer path during charge-discharge process. The fabricated PIS-based cathodes under 4.3 V cutoff voltage exhibit higher capacity retention (83% vs. 69%, 1.0C, 500 cycles) and higher rate capacity (137.6 mAh g−1 vs. 123.6 mAh g−1, 5.0C), in contrast to the cathodes with polyvinylidene fluoride (PVDF) binder. Further test under 4.7 V cutoff voltage indicates the rate capacity of PIS-based cathodes is superior than that of PVDF-based cathodes (163.2 mAh g−1 vs. 119.7 mAh g−1, 5.0C), as well as superior capacity retention (74 % vs. 34%, 0.2C, 100 cycles). This work provides a valuable guideline for designing a polymer binder by focusing on stabilizing high-voltage cathode structure and facilitating ion diffusion.