http://english.cas.cn/newsroom/research-news/202606/t20260609_1161418.shtml
https://academic.oup.com/nsr/advance-article/doi/10.1093/nsr/nwag306/8696162?login=false
A membrane that is thinner than a human hair could power next-generation energy storage. A research team led by Prof. LI Xianfeng from the CAS Dalian Institute of Chemical Physics (DICP) has separating the formation processes of different pore structures, including macrovoids and cellular pores.
Based on these findings, the team developed a free-standing ultrathin porous polymeric membrane with a thickness of only 2.7 μm that simultaneously offers high selectivity and high conductivity. When applied in a vanadium flow battery, the membrane demonstrated outstanding electrochemical performance.
NIPS is a classical method for preparing porous polymeric membranes and has been widely used in industrial membrane manufacturing for more than six decades. However, because multiple pore structures form simultaneously during the NIPS process, the underlying mechanism of microstructure formation remains incompletely understood. This knowledge gap has hindered the rational design of membrane structures and the precise control of membrane performance.
The researchers revealed that macrovoid formation originates from hydrodynamic instability and demonstrated that macrovoid growth can be precisely controlled by tuning the interface geometry between the nonsolvent and the polymer solution. They further clarified the thermodynamic origin of cellular pore formation and established a quantitative model linking cellular pore area density to key thermodynamic parameters.
By eliminating the mass-transfer interference and spatial heterogeneity introduced by macrovoids, the researchers revealed the intrinsic relationship between membrane formation kinetics and solvent–nonsolvent interdiffusion during the NIPS process.
The researchers then investigated the structure–property relationship of porous membranes fabricated via NIPS. Guided by this relationship, they developed a free-standing porous membrane just 2.7 μm thick. When tested in a vanadium flow battery, the membrane achieved an energy efficiency exceeding 80% at a current density of 220 mA/cm².
