Atomic force microscopy (AFM) has been used to characterize the structural evolution of the MoO3(010) surface during the initial stage of Li+ intercalation. Lithiation was observed in situ using model cells comprised of a single crystal MoO3 cathode, a dilute propylene carbonate (PC)-based electrolyte, and an Li metal anode. The insertion of Li+ into MoO3 results in the topotactic nucleation and growth of acicular LixMoO3 (x similar to 0.25) precipitates at the (010) surface. Because the interlayer spacing of LixMoO3 (d=7.88 Angstrom) is greater than that of MoO3 (d=b/2=6.93 Angstrom), the LixMoO3 precipitates expand out of the (010) surface as they grow into the MoO3 crystal along <010>. The local strain associated with this expansion causes the LixMoO3 precipitates to crack parallel to the MoO3 <001> and (010) axes once their height exceeds approximately 20 nm. With continued Li+ intercalation, cracking becomes more prominent, and the (010) surface begins to fragment and disintegrate. Anisotropies in Li+ ion uptake and the influence of surface morphology on Li,MoO3 precipitation and crack propagation are described. (C) 2003 Elsevier Science B.V. All rights reserved.