Core-shell structured LiFePO4/C nanocomposite battery material for lithium production from brines
Min Zhang, Nuria Garcı́a-Aráez
Abstract
The development of affordable and environmentally friendly methods to produce lithium is urgently required to cope with the accelerating growth of the lithium battery market. Battery materials such as LiFePO4 can be used to selectively sequestrate lithium from brine natural resources, thus producing a high-purity lithium salt for battery manufacture, but the long-term stability of the material is currently not sufficient for practical applications. Here, we report, for the first time, the development of a nanosized core-shell structured LiFePO4/C material for applications in lithium production from brines. This LiFePO4/C with a LiFePO4-core (∼123 nm size) covered by a pinhole-free carbon shell (∼5 nm thickness) was prepared via solvothermal synthesis, and the carbon content was optimised to 5 wt%. The optimal core-shell structured LiFePO4/C material exhibits a lithium extraction capacity of ca. 160 mA h g-1 at C/10 and ca. 130 mA h g-1 at 1C, and >87 % capacity retention after 50 cycles of lithium sequestration and release at C/10 in synthetic brines. This excellent electrochemical performance is attributed to the homogenous nanosizing of the LiFePO4 particles as well as the full coverage of the carbon coating, which provides effective protection by preventing the direct contact of LiFePO4 with the brines, thus stopping the surface degradation reactions that compromise the long-term stability. A direct comparison with three commercial LiFePO4 materials demonstrates that, while similar performance is obtained in non-aqueous lithium-ion batteries, for lithium production applications, core-shell nanostructuring is crucial to achieve high capacity and preserve the material's longevity.