Battery Cathode with Vertically Aligned Microstructure Fabricated by Directional Ice Templating

Conventional slurry coating (SC) makes battery electrodes with random microstructure containing tortuous pores that restrict lithium ion diffusion and reduce battery capacities at faster discharge rates. Herein, a novel directional ice templating (DIT) is developed to make LiNi_0.8Mn_0.1Co_0.1O₂ (NMC811) cathodes that double the electrode mass loading and contain vertically aligned lamellae of electrode materials and pore channels to provide fast dual electron and ion transport. DIT uses in situ evolved ice structures to form the anisotropic microstructure. The effects on the chemical composition, bonding, and morphology of the NMC811 particles are studied using a range of surface-sensitive techniques including time-of-flight secondary ion mass spectrometry, transmission electron microscopy, and X-ray photoelectron spectroscopy to guide the development of potentially more sustainable aqueous processing and eliminate the toxic, combustible organic solvent N-methyl-2-pyrrolidone in conventional electrode processing. The DIT cathode breaks the trade-off between high energy densities and fast discharging, exhibiting higher areal capacities (12 mAh cm^-2) than the SC electrode (7.0 mAh cm^-2) at a discharge current density of 1.4 mA cm^-2, and maintains higher capacities at 9.8 mAh cm^-2 and 186 mAh g^-1 than 2.1 mAh cm^-2 and 64 mAh g^-1 for SC when the current is increased to 5.7 mA cm^-2.