Electrocapillary boosting electrode wetting for high-energy lithium-ion batteries

Large, thick, and highly pressed electrodes are desirable for high-energy lithium-ion batteries (LIBs), as they help to reduce the mass ratio and cost of the inert materials. However, this energy-density-oriented electrode technology sets new challenges for electrolyte filling and electrode wetting, which profoundly limits the production efficiency and battery performance. In this perspective, we pioneer and document well the proposal of accelerating electrode wetting via electrocapillary. First, the fundamental principles of electrode wetting, as well as characterization approaches including conventional surface analysis, electrochemical methodologies, and in situ spectroscopic imaging techniques, are outlined. Then, the fundamentals of electrocapillarity and the key elements (electrodes, electrolytes, and voltages) involved in electrocapillarity are carefully reviewed. In addition, the feasibility of employing electrocapillarity to boost electrode wetting is discussed according to the Lippmann equation. Moreover, the effect of electrocapillarity on promoting battery filling is successfully verified using commercial 3.1 Ah LiFePO₄ (LFP)/graphite (Gr) pouch cells. Ultrasonic imaging indicates that the sample subjected to the electrocapillary effect is completely wetted within 2 h, whereas the control sample remains incompletely wetted even after 5 h. This work is meaningful for efficient battery manufacturing by providing a novel strategy to accelerate battery filling.