Anisotropic battery electrodes that allow enhanced diffusion through the thickness of the electrode can be engineered to improve rate performance but direct measurement of 3D diffusion in these non-transparent nanoscale pores is extremely challenging. To address this, we used 1H and 7Li pulsed field gradient (PFG) NMR to measure anisotropic diffusion in a model porous silicon substrate. We show that NMR provides resolution for solvent (here, H2O, DMSO, and the battery electrolyte LIPF6:DC:EMC) in- and outside of the pores in the Si substrate. Exchange between ions/molecules in- and outside the pores is measured with 1H 2D exchange spectroscopy (EXSY). When the diffusivity of in-pore NMR peak is analyzed, the results are in reasonable agreement with the pore dimensions measured with electron microscopy. Better agreement is obtained for pore diameters; for pore length measurements, exchange between the pore and ex-pore solvent should be accounted for. These results suggest that PFG-NMR can serve as a non-destructive characterisation method for both in- and ex-situ analysis of materials ranging from complex battery and supercapacitor electrodes to catalyst supports and tissue scaffolds.