Copper nitrate hydrate (Cu(NO3)2·2.5H2O) exhibits superior high lithium storage capacity (2285 mAh g−1) as anode material for lithium-ion batteries. The structural transformation and lithium storage mechanism of Cu(NO3)2·2.5H2O are thoroughly studied by various advanced analytical techniques. It is found that the lithium storage process of Cu(NO3)2·2.5H2O is associated with a quasi-reversible electrochemical conversion reaction. During the discharge process, the electrochemical reaction of Cu(NO3)2·2.5H2O with lithium results in the formation of Cu, LiNO3, Li3N, Li2O and H2O. In the reverse charge process, Cu(NO3)2 can be generated by a conversion reaction. As a result, Cu(NO3)2·2.5H2O shows the reversible charge capacities of 1632.1 mAh g−1 in 0.0–3.4 V and 689.1 mAh g−1 in 1.0–3.4 V, respectively.