Abstract:

Taking advantage of simultaneous thermochemical lithiation and densification of spark plasma sintering, the Li₂₁Si₅/graphene nanocomposites with uniform distribution and high density were prepared. Due to the two-dimensional structure and excellent electrical conductivity of graphene, and the presence of a high proportion of tightly bonded interfaces of Li₂₁Si₅/graphene, the volume shrinkage of the active particles during the delithiation process was limited effectively, and the charge transport inside the active particles was enhanced dramatically. Therefore, the composite exhibits excellent electrochemical performance. The specific capacities of pre-delithiation and the first lithiation were 968 mAh∙g^-1 and 1007 mAh∙g^-1, respectively, which are 3 times as high as those of the commercial lithium-carbon compound. Its first Coulomb efficiency was 94.5% at the same time. Moreover, the specific capacity remained 590 mAh∙g^-1 after 100 cycles, and the cyclic stability doubled compared to the composites prepared by carbon particles. Even at a high current density of 1 A∙g^-1, the specific capacity can be maintained at 540 mAh∙g^-1. This work provides a new approach for the development of lithium-rich alloy anode materials, which are promising in high energy density batteries, such as lithium ion-sulfur and lithium ion-oxygen systems.

Key words: lithiation, anode, graphene, nanocomposite, lithium-ion batteries