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

Abstract 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 LiCoO 2 and meso‐carbon microbead graphite. The LiCoO 2 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.