Rational construction of nanosized anode nanomaterials is crucial to enhance the electrochemical performance of lithium-/sodium-ion batteries (LIBs/SIBs). Various anode nanoparticles are created mainly via templating surface confinement, or encapsulation within precursors (such as metal-organic frameworks). Herein, low-content SnO2 nanodots on N-doped reduced graphene oxide (SnO2@N-rGO) were prepared as anode nanomaterials for LIBs and SIBs, via a distinctive lattice confinement of a CoAlSn-layered double hydroxide (CoAlSn-LDH) precursor. The SnO2@N-rGO composite exhibits the advantagous features of low-content (17.9 wt%) and uniform SnO2 nanodots (3.0 ± 0.5 nm) resulting from the lattice confinement of the Co and Al species to the surrounded Sn within the same crystalline layer, and high-content conductive rGO. The SnO2@N-rGO composite delivers a highly reversible capacity of 1146.2 mA h g-1 after 100 cycles at 0.1 A g-1 for LIBs, and 387 mA h g-1 after 100 cycles at 0.1 A g-1 for SIBs, outperforming N-rGO. Furthermore, the dominant capacitive contribution and the rapid electronic and ionic transfer, as well as small volume variation, all give rise to the enhancement. Precursor-based lattice confinement could thus be an effective strategy for designing and preparing uniform nanodots as anode nanomaterials for electrochemical energy storage.