Real-time　observation　of　the　electrochemical　mechanistic　behavior　at　various　scales　offers　new　insightful　information　to　improve　the　performance　of　lithium-ion　batteries　(LIBs).　As　complementary　to　the　X-ray-based　techniques　and　electron　microscopy-based　methodologies,　neutron　scattering　provides　additional　and　unique　advantages　in　materials　research,　owing　to　the　different　interactions　with　atomic　nuclei.　The　non-Z-dependent　elemental　contrast,　in　addition　to　the　high　penetration　ability　and　weak　interaction　with　matters,　makes　neutron　scattering　an　advanced　probing　tool　for　the　in　operando　mechanistic　studies　of　LIBs.　The　neutron-based　techniques,　such　as　neutron　powder　diffraction,　small-angle　neutron　scattering,　neutron　reflectometry,　and　neutron　imaging,　have　their　distinct　functionalities　and　characteristics　regimes.　These　result　in　their　scopes　of　application　distributed　in　different　battery　components　and　covering　the　full　spectrum　of　all　aspects　of　LIBs.　The　review　surveys　the　state-of-the-art　developments　of　real-time　investigation　of　the　dynamic　evolutions　of　electrochemically　active　compounds　at　various　scales　using　neutron　techniques.　The　atomic-scale,　the　mesoscopic-scale,　and　at　the　macroscopic-scale　within　LIBs　during　electrochemical　functioning　provide　insightful　information　to　battery　researchers.　The　authors　envision　that　this　review　will　popularize　the　applications　of　neutron-based　techniques　in　LIB　studies　and　furnish　important　inspirations　to　battery　researchers　for　the　rational　design　of　the　new　generation　of　LIBs.　©　2022　Wiley-VCH　GmbH.