Improving High-Nickel Cathode Active Material Performance in Lithium-Ion Batteries with Functionalized Binder Chemistry

As the lithium-ion battery (LIB) market expands, driven mostly by the mass adoption of electric vehicles, LIB development is continually being pushed in the direction of higher energy density and lower cost. Both of these trends are leading to widespread development of LIB formulations using high-nickel cathode active materials, such as NMC811. In these materials, the high nickel content increases the amount of electrochemically accessible lithium in the cathode, increasing the cell energy density, while decreasing the amount of cobalt used, which decreases the cost of the cathode material. However, these materials also have drawbacks. First, NMC811 suffers from lower cycle life than higher-Co NMC materials such as NMC111 or NMC622. Second, NMC811 has poorer safety characteristics than lower energy density materials. Finally, NMC811 cathodes are known to experience gassing issues during cycling, which creates challenges in commercialization, especially for pouch cell battery designs. Many approaches have been explored in the industry to address these shortcomings, including active material modification, electrolyte design, etc. In this presentation, binder functionalization will be presented as an alternative pathway to improve high-Ni cathode performance. LIB cathode binder is commonly high molecular weight PVDF, which provides good mechanical properties at low weight fractions as well as high electrochemical stability, but it is predominantly inert. Here, approaches of introducing novel binders tailored for high-Ni cathode systems will be discussed. Effectiveness of modifications, specifically their impact on LIB cycle life and safety, will be discussed.