Battery Cathode with Vertically Aligned Microstructure Fabricated by Directional Ice Templating.

Area of Science:

• Materials Science
• Electrochemistry
• Chemical Engineering

Background:

• Conventional slurry coating (SC) for battery electrodes results in random microstructures with tortuous pores, hindering lithium-ion diffusion and limiting capacity at high discharge rates.
• The use of toxic and combustible organic solvents like N-methyl-2-pyrrolidone in SC processing poses environmental and safety concerns.

Purpose of the Study:

• To develop a novel directional ice templating (DIT) method for fabricating LiNi$_{0.8}$Mn$_{0.1}$Co$_{0.1}$O$_{2}$ (NMC811) cathodes.
• To create electrodes with vertically aligned lamellae and pore channels for improved ion and electron transport.
• To enable more sustainable aqueous processing of battery electrodes.

Main Methods:

• Directional ice templating (DIT) utilizing in situ evolved ice structures to form anisotropic microstructures.
• Surface-sensitive techniques including time-of-flight secondary ion mass spectrometry, transmission electron microscopy, and X-ray photoelectron spectroscopy were employed.
• Characterization of electrode performance, including areal capacity and discharge rate capabilities.

Main Results:

• DIT successfully created NMC811 cathodes with vertically aligned structures, doubling electrode mass loading.
• The DIT cathode exhibited significantly higher areal capacities (12 mAh cm⁻²) compared to SC electrodes (7.0 mAh cm⁻²) at 1.4 mA cm⁻².
• At a higher current density of 5.7 mA cm⁻², DIT cathodes maintained superior capacities (9.8 mAh cm⁻² and 186 mAh g⁻¹) over SC electrodes (2.1 mAh cm⁻² and 64 mAh g⁻¹).

Conclusions:

• Directional ice templating (DIT) effectively overcomes the trade-off between high energy density and fast discharging in NMC811 cathodes.
• DIT facilitates faster dual electron and ion transport through vertically aligned structures.
• This method offers a pathway towards more sustainable and efficient battery electrode manufacturing, potentially eliminating hazardous organic solvents.