In Situ Formation of Liquid Crystal Interphase for Aqueous Dual-Electrode-Free Batteries
Authors: Li Yuqi 
Published: December 2024

Aqueous Zn/MnO₂ batteries have emerged as a promising solution in energy storage due to their inherent safety and environmental benefits. Over the past few decades, significant research efforts have been dedicated to enhancing their energy density and cycle life. However, challenges still remain in pushing these limits further, particularly with respect to simplifying battery design while maintaining performance and cost-efficiency. Traditional designs rely on separate anode and cathode materials, but a more streamlined approach could lead to breakthroughs in energy density and production costs.

In this work, we present a transformative strategy aimed at creating an ultra-simplified Zn/MnO₂ battery, consisting only of current collectors and electrolyte, with no anode or cathode at the initial stage—what we call a dual-electrode-free battery (DEFB)1. This design achieves impressive energy densities of up to ~213 Wh/kg, setting new benchmarks for cost-effectiveness and energy storage potential. However, the irreversible deposition of Zn and MnO₂ has previously resulted in short battery lifespans, preventing practical applications of such batteries.

Here we show that by leveraging soft template strategies, commonly used in material synthesis, we can overcome this limitation. We introduce trace amounts of surfactants into the electrolyte, triggering the in-situ formation of a liquid crystal interphase1. This novel interphase directs the deposition of Zn and MnO₂ along the c-axis, significantly enhancing the reversibility of deposition and stripping. As a result, we observe a substantial improvement in cycle life, with 80% capacity retention after 950 cycles—an unprecedented achievement for dual-electrode-free Zn/MnO₂ batteries. Our research highlights the innovative use of liquid crystals as an interphase, a concept rarely applied in the field of batteries. Traditionally, liquid crystals have been used as bulk electrolyte materials to enhance ionic transport, but their potential as a dynamic interphase layer has been untapped. By controlling the in-situ self-assembly processes of surfactant molecules into liquid crystal structures, we create a soft templating effect that enables highly reversible, patterned deposition. This process, confirmed through advanced soft matter characterizations such as cryo-TEM, marks a significant departure from traditional battery approaches, allowing for textured Zn and MnO₂ growth with minimal degradation. Moreover, this liquid crystal interphase chemistry holds promise for other electrode systems, such as cubic Cu, through the customization of liquid crystal phase structures. This opens up new possibilities for improving energy storage solutions2,3 beyond Zn/MnO₂ systems. Our method not only enhances the cycling stability of batteries but also provides a cost-effective and environmentally friendly pathway for advancing high-energy-density, long-cycle-life aqueous batteries.

References:

1. Yuqi Li, et al. Nature Energy, 2024, DOI: 10.1038/s41560-024-01638-z

2. Yuqi Li, et al. Nature Energy, 2024, DOI: 10.1038/s41560-023-01414-5

3. Yuqi Li, et al. Nature Energy, 2022, DOI: 10.1038/s41560-022-01033-6

Figure 1