Tailored PVDF Graft Copolymers via ATRP as High-Performance NCM811 Cathode Binders
Tong Liu, Rohan Parekh, Piotr Mocny, Brian P. Bloom, Yuqi Zhao, So Young An, Bonian Pan, Rongguan Yin, David H. Waldeck, Jay Whitacre, Krzysztof Matyjaszewski
Abstract
High Resolution Image Download MS PowerPoint Slide High-nickel layered oxides, e.g., LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811), are promising candidates for cathode materials in high-energy-density lithium-ion batteries (LIBs). Complementing the notable developments of modification of active materials, this study focused on the polymer binder materials, and a new synthetic route was developed to engineer PVDF binders by covalently grafting copolymers from poly(vinylidene fluoride- co -chlorotrifluoroethylene) (PVDF-CTFE) with multiple functionalities using atom transfer radical polymerization (ATRP). The grafted random copolymer binder provided excellent flexibility (319% elongation), adhesion strength (50 times higher than PVDF), transition metal chelation capability, and efficient ionic conductivity pathways. The NCM811 half-cells using the designed binders exhibited a remarkable rate capability of 143.4 mA h g –1 at 4C and cycling stability with 70.1% capacity retention after 230 cycles at 0.5 C, which is much higher than the 52.3% capacity retention of nonmodified PVDF. The well-retained structure of NCM811 with the designed binder was systematically studied and confirmed by post-mortem analysis.