Maximizing calendering effects through the mechanical pulverization of Co-free nickel-rich cathodes in lithium-ion cells

Abstract Calendering is a technique used to maximize the volumetric energy density of battery electrodes. However, higher amounts of calendering result in increased tortuosity and particle cracking. We propose a novel packing structure of electrode particles to maximize calendering benefits while minimizing particle fracture. Cobalt-free layered oxide cathode LiNi 0.92 Mn 0.04 Al 0.04 O 2 (NMA) particles are pulverized through ball-milling and coated with lithium phosphate. Pulverized and pristine NMA are fabricated into “bimodal” electrodes, whereas “unimodal” electrodes consist of only pristine NMA. Each electrode type was made into 30% porosity, 40% porosity, and uncalendered coin cell samples. X-ray diffraction suggests that the unimodal samples suffer from more particle fracture than the bimodal samples when calendered to the same porosity of 30%. Electrochemical impedance spectroscopy suggests that the bimodal electrodes exhibit lower surface film resistance. This is supported by enhanced capacity retention for the bimodal samples after 100 cycles. Graphical abstract Impact statement Calendering is an essential manufacturing process for Li-ion batteries (LIBs). Despite calendering increasing the energy density of electrodes and improving ionic and electronic connections, it also enhances particle cracking and hinders Li-ion migration. In this article, we investigate a novel “bimodal” packing configuration of a Co-free cathode material and analyze the configuration’s impact on particle cracking at different levels of calendering. There is an increasing effort to eliminate Co in LIB cathode materials due to its expensive and controversial mining conditions. Through electrochemical and structural characterization techniques, we probe particle cracking at different levels of calendering in bimodal and control electrodes. We report the ability of our bimodal configuration to decrease particle cracking and enhance capacity retention. We believe this work is highly impactful because it suggests a direct application to manufacture design of next-generation, Co-free cathodes which have accelerated intragranular cracking compared to current LIB cathodes.