Ultrahigh active material content and highly stable Ni-rich cathode leveraged by oxidative chemical vapor deposition

Despite the huge achievements that have been made in developing lithium-ion batteries, there remain gaps between the existing demands and the current battery performance. As one of the key components, cathode needs to adopt a further enhanced design to realize a high energy density and long useful life battery. Here we report a cathode tailoring strategy, exploiting multi-functional conformal coatings that are mechanically flexible, thickness controllable at the nanometer scale, electronically conductive, and selectively permeable. We demonstrate a gas phase polymerization technique that successfully enhances the energy density and the lifespan of the battery, particularly for a Ni-rich cathode (LiNi 0.8 Co 0.1 Mn 0.1 O 2 , NCM811). Oxidative chemical vapor deposition (oCVD) yielded an extremely conformal polymer layer of poly (3,4-ethylene dioxythiophene) (PEDOT) that is chemisorbed on both primary and secondary particles in NCM811 with identified S-O bonds. The chemo-physical adhesion between the cathode particles and the highly conductive nature of oCVD PEDOT permit a significant reduction of inactive materials inclusion in the cathode and enable a noticeable high active materials content (up to 99% in weight percentage). ToF-SIMS results identified that the formation of cathode electrolyte interphases, especially between primary particles, has been eliminated in the PEDOT coated sample. As a result, the cathode enabled by multi-functional oCVD PEDOT exhibited much higher capacity retention (about 80% after 300 cycles) compared with the pristine sample (about 6% only after 200 cycles). These results offer a single-step rational cathode design strategy that ensures high-energy density, long-life, and safe lithium-ion batteries.