In this paper, we present the direct application of AgNO3 as a novel host material for lithium storage. Fabricated as cathode material, commercial AgNO3 particles show an initial charge capacity at 157.1 mAh g−1, and retain a capacity of only 11.5 mAh g−1 after 100 cycles. By preparing AgNO3 nanosheets supported on conductive carbon three-dimensional substrate, enhanced lithium storage performance can be achieved. As-prepared AgNO3 nanosheets exhibit the charge capacity at 141.7 mAh g−1 in the first cycle, and maintain at 82.0 mAh g−1 after 100 cycles. The three-dimensional carbon substrate with considerable strength and tenacity supporting AgNO3 nanosheets presents fast electron/ion transport, large electroactive surface area, and excellent structural stability. The reaction mechanism of AgNO3 with Li is also studied by ex situ and in situ techniques during the initial cycle. It can be concluded that lithium storage process of AgNO3 is associated with a quasi-reversible electrochemical conversion reaction. During the discharge process, the electrochemical reaction of AgNO3 with Li results in the formation of Ag and LiNO3. In the reverse charge process, AgNO3 can be re-generated by its conversion reaction. Therefore, it is anticipated that AgNO3 nanosheets can be a probable cathode candidate for lithium-ion batteries.