Fabrication of Low-Tortuosity Ultrahigh-Area-Capacity Battery Electrodes through Magnetic Alignment of Emulsion-Based Slurries

High energy-density, low-cost batteries are critically important to a variety of applications ranging from portable electronics to electric vehicles (EVs) and grid-scale storage. While tremendous research effort has been focused on new materials or chemistries with high energy-density potential, design innovations such as low-tortuosity thick electrodes are another promising path toward higher energy density and lower cost. Growing demand for fast-charging batteries has also highlighted the need for negative electrodes that can accept high rate charging without metal deposition; low tortuosity can be a benefit in this regard. However, a general and scalable fabrication method for low-tortuosity electrodes is currently lacking. Here an emulsion-based, magnetic-alignment approach to producing thick electrodes (>400 µm thickness) with ultrahigh areal capacity (up to ≈14 mAh cm⁻² vs 2–4 mAh cm⁻² for conventional lithium ion) is reported. The process is demonstrated for LiCoO₂ and meso-carbon microbead graphite. The LiCoO₂ cathodes are confirmed to have low tortuosity via DC-depolarization experiments and deliver high areal capacity (>10 mAh cm⁻²) in galvanostatic discharge tests at practical C-rates and model EV drive-cycle tests. This simple fabrication method can potentially be applied to many other active materials to enable thick, low-tortuosity electrodes.