An electrochemical reactor that enables continuous and uniform flow of high-viscosity slurry for semi-solid flow batteries

Official URL: https://dx.doi.org/10.1016/j.cej.2025.170707

Conventional flow batteries are promising candidates for grid-scale energy storage. However, its reactor features narrow transport channels and relies on an externally driven mode, which restricts its use to low-viscosity electrolytes and makes it unsuitable for high-viscosity semi-solid slurries. In this work, inspired by the working principle of screw pumps, we demonstrate a proof-of-concept electrochemical reactor for the transport of high-viscosity slurries in semi-solid flow batteries (SSFBs). The screw pump transports slurry through rotational motion with controllable speed, ensuring smooth and continuous material delivery with precise velocity regulation. In a typical system composed of a LiFePO4 slurry (10 wt% LFP with 2.4 wt% Ketjenblack functioned as the positive electrode) and metallic lithium (represented the negative electrode), stable charging and discharging was achieved for over 400 h at 0.5 mA cm−2 (based on the geometrical area of the current collector, 8 cm2) in both static and flow mode, accompanied by an energy efficiency of ≈80 %. Moreover, finite element simulations revealed that a smooth flow of 0.46 mL h−1 throughout the reactor could be achieved at a low power consumption of 0.504 × 10−3 mW when the rotation speed was 0.5 rev h−1 and the inlet pressure was 40 Pa. Both theoretical and experimental results indicated that this low-flow, low-energy consumption operational mode was particularly advantageous for high-viscosity, high-energy density active slurries. Therefore, the design strategy presented herein offers valuable insights into developing stable, energy-dense, and cost-effective SSFB devices for future energy storage applications.