A High-Performance Zn2+-Selective Scanning Electrochemical Microscopy Probe: In Situ Deciphering of Interfacial Zn2+ Heterogeneity for Aqueous Zinc-Ion Battery Engineering

Dendrite growth and parasitic reactions in aqueous zinc-ion batteries (AZIBs) are intrinsically driven by heterogeneous interfacial Zn2+ distribution, but conventional characterization techniques cannot achieve real-time, micron-scale quantitative tracking of dynamic Zn2+ evolution. Herein, we report a high-performance Zn2+-selective scanning electrochemical microscopy (SECM) probe based on a multiwalled carbon nanotube (MWCNT)-modified all-solid-state ion-selective membrane. The MWCNT-modified interface effectively suppresses the water-layer effect, reducing the fitted interfacial resistance component from 17,442 to 389 Ω. The optimized probe exhibits a wide linear response range of 10-5-1 × 10-1 M (R2 = 0.999, slope = -19.8 mV·dec-1), an ultrafast response time of <10 s, low potential drift (<10 mV/2000 s), excellent anti-interference against common interfering ions (Na+, K+, Mg2+, Al3+), and a long service life of 45 days. Notably, in situ SECM mapping reveals severe Zn2+ concentration fluctuations (0.178-0.303 M) at the Zn anode in blank electrolyte, which are effectively homogenized to a narrow range of 0.235-0.255 M by 0.01 M mesylacetone additive. This work provides a powerful in situ platform for deciphering AZIB interfacial dynamics and guiding advanced electrolyte design.