Due to the serious imbalance between demand and supply of lithium, lithium extraction from brine has become a research hotspot. With the demand for power lithium-ion batteries (LIBs) increased rapidly, a large number of spent LiFePO4 power batteries have been scrapped and entered the recycling stage. Herein, a novel and efficient strategy is proposed to extract lithium from brine by directly reusing spent LiFePO4 powder without any treatment. Various electrochemical test results show that spent LiFePO4 electrode has appropriate lithium capacity (14.62 mgLi/gLiFePO4), excellent separation performance (αLi-Na = 210.5) and low energy consumption (0.768 Wh/gLi) in electrochemical lithium extraction from simulated brine. This work not only provides a novel idea for lithium extraction from brine, but also develops an effective strategy for recycling spent LIBs. The concept of from waste to wealth is of great significance to the development of recycling the spent batteries.