Neutron Depth Profiling: The Core Link Connecting the Microscopic Mechanisms of Lithium-Ion Batteries With Intelligent Design

Neutron Depth Profiling (NDP) is a non-destructive, in situ quantitative depth-analysis technique underpinned by neutron-induced nuclear reactions. Offering high ⁶Li-isotope sensitivity and nanometer-to-micrometer depth resolution, NDP delivers isotope-resolved lithium spatial information hardly accessible via conventional probes including secondary-ion mass spectrometry (SIMS), X-ray photoelectron spectroscopy (XPS), and operando neutron imaging, yet it suffers from depth-dependent resolution degradation, limited lateral performance, and requires large-scale neutron-beam facilities. This paper systematically reviews NDP fundamentals, global neutron-source progress, and cutting-edge battery applications, covering lithium-ion migration in electrodes, lithium dendrite nucleation and growth, and the "reversible short-circuit" effect at solid-electrolyte interfaces. The unique merit of NDP for quantitative ⁶Li depth-profiling is highlighted, while noting that NDP cannot independently resolve full-element maps or nanoscale interfaces and demands complementary characterizations. A roadmap integrating NDP with multimodal measurements and physics-informed machine learning for intelligent battery design is outlined, alongside open challenges: inversion non-uniqueness under low-signal conditions and translation from model cells to practical batteries. This work provides actionable guidelines to leverage NDP for bridging microscopic lithium mechanisms and rational design of next‑generation batteries with high safety and high energy density.