In this study, a model AgNbO3 perovskite is prepared via polyacrylamide synthesis technique, and the underlying unique Li+ storage mechanism is studied. This structure is projected to provide low Li+ storage capacity due to all occupied crystallographic sites. It delivered a specific capacity of 17 mAh.g(-1) at 0.1A.g(-1) within the potential range of 1.2-3.0 V vs. Li+/Li. However, at lower potentials, the material undergoes activation for Li+ storage by a multistep structural transition that included in-situ Ag-exsolution from the A-site of the lattice and an electrochemically induced crystalline-to-amorphous transition. At low potential the materials delivers high specific capacity (226 mAh.g(-1) at 0.1 A.g(-1) in 0.01-3 V vs. Li+/Li potential range) due to the contribution of improved Nb-redox activity and nanoscale Ag-Li (de)alloying mechanisms that were comprehensively examined utilizing advanced characterization tools. In addition, good capacity retention of 72 mAh.g(-1) at high current density of 2A.g(-1) and an excellent cyclic stability with coulombic efficiencies above 99.9 % are obtained for 2500 cycles at 1 A.g(-1) underlining the performance and the stability of AgNbO3. This study introduces an alternative approach for tailoring electrode material using an electrochemically driven in-situ activation process. It also serves as a paradigm for the use of exsolved materials as negative electrodes in fast-charging batteries, paving the way for a better understanding of charge storage mechanisms in perovskites.