| Popis: |
Today’s anode for lithium ion batteries is dominated by graphite, with a low operate voltage at 0.1 V vs. Li+/Li, easy to format lithium dendrite and cause to safety risk. As an alternative anode material, the “zero-strain” spinel structure Li4Ti5O12 could avoid Li plating with a relative high intercalation potential (1.55 V vs. Li+/Li) and exhibits an excellent cycling stability. However, the slightly low capacity and high voltage of Li4Ti5O12 result in low energy density. Therefore, it is very important, but nevertheless a challenge, to develop a negative electrode material with a large capacity and an intercalation potential below 1 V, but not close to the Li plating potential, to ensure the safety of batteries. Herein, we report a new anode material of Li2TiSiO5 as anode material for LIBs. The electrochemical profile, structure and Li storage mechanism were extensively studied. The crystal structure of Li2TiSiO5 is illustrated as a layered structure with infinite sheets of distorted TiO6 octahedra and SiO4 tetrahedra, linked by Li atoms. The distorted TiO6 octahedral and SiO4 tetrahedral networks are thought to be the origin of the structural stability of this material. The crystal structure is depicted in Fig. 1b (left) and the details are summarized in Table 1. Along with the refined structure of Li2TiSiO5, the nuclear-density difference (Fourier) map in Fig. 1b (middle) reveals negative nuclear density only at the 4d, 4e, and Ti (2c) sites, implying that lithium can only reside at these sites. The 4e sites are indicated by the yellow balls in Fig. 1b (right). Figure 2 give the typical charge/discharge curve of Li 2TiSiO5 at between 0 and 3 V (vs. Li+/Li), delivers a reversible charge capacity (Li-ion extraction) of 308 mAh/g, with a voltage plateau below 1.0 V. Fig. 1 (a) Crystal structure characterization of Li2TiSiO5 and (b) typical charge/discharge curve of Li2TiSiO5 Figure 1 |
