The Cr-birnessite was prepared by ion exchange from K-birnessite, which was synthesized by calcination of KMnO₄. Measurement methods of scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), atomic absorption spectrometry (AAS), slow-scanning cyclic voltammetric and galvanostatic discharge/charge characteristics of the Cr-birnessite were applied. Potentiostatic method was used for the determination of a chemical diffusion coefficient D. XRD patterns indicate that Cr-birnessite has layered structure. Slow-scanning voltammograms exhibit single peak occurring in the range of －0.2 to 0 V on discharge and two peaks at about －0.3 and 0 V on charge. The galvanostatic discharge/charge curves indicate that the Cr-birnessite has better rechargeability at a high discharge/charge rate. Li^＋can reversibly intercalate into and de-intercalate from the Cr-birnessite during discharge and charge. The average value of the chemical diffusion coefficient D of Li^＋ intercalated into the Cr-birnessite is 1.57×10^－10cm²·s^－1.

Key words: birnessite, Cr^3＋-doped, aqueous rechargeable battery, cycling ability, lithium intercalation