Metal Ti quantum chain-inlaid 2D NaSn₂(PO₄)₃/H-doped hard carbon hybrid electrodes with ultrahigh energy storage density

We report the development of a new hybrid electrode that allows for a reinforcing combination of different energy storage mechanisms, providing enhanced energy and power densities. This hybrid electrode is composed of chain-like metal titanium (zero valency state) quantum dots (<10 nm), two-dimension NaSn2(PO4)3 layer and H-doped hard carbon layer, and possesses unique sandwich and hierarchically meso-macroporous structures. These chain-like quantum dots are inlaid on the edge of ultra-thin NaSn2(PO4)3 nanosheets by using a convenient and economic method, enhancing its conductivity. This design takes advantage of the unique properties of each component and nanostructure, resulting in synergistic effects to improve the charge transfer and energy storage. The hybrid electrode not only shows high capacity, outstanding rate performance and long cycling stability, but also matches well with porous Na3V2(PO4)3 cathode. Remarkably, the Na/Li mixed-ion full battery exhibits significant improvements on the energy and power densities (555 Wh Kg-1/804 W Kg-1 at 1C). Detailed charge storage mechanism investigation reveals that the prelithiation reduces the pseudocapacitive of hybrid electrode and increases its battery behavior, resulting in an ultrahigh energy storage density. Our findings demonstrate that this hybrid electrode is a new potential candidate for high-performance mixed-ion batteries.