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 (LiNi0.8Co0.1Mn0.1O2, 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 inter phases, 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.

Automated summary

This study presents a cathode tailoring strategy that enhances the energy density and lifespan of lithium-ion batteries. By using gas phase polymerization technique, an oCVD PEDOT coating is applied to reduce inactive materials and increase the active material content in the cathode, resulting in significantly higher capacity retention. The formation of cathode electrolyte inter phases is eliminated, ensuring high-performance and safe batteries.