High-Rate, Ultralong Cycle-Life Lithium/Sulfur Batteries
Enabled by Nitrogen-Doped Graphene
- Publication date
- Publisher
Abstract
Nitrogen-doped
graphene (NG) is a promising conductive matrix material for fabricating
high-performance Li/S batteries. Here we report a simple, low-cost,
and scalable method to prepare an additive-free nanocomposite cathode
in which sulfur nanoparticles are wrapped inside the NG sheets (S@NG).
We show that the Li/S@NG can deliver high specific discharge capacities
at high rates, that is, ∼1167 mAh g<sup>–1</sup> at
0.2 C, ∼1058 mAh g<sup>–1</sup> at 0.5 C, ∼971
mAh g<sup>–1</sup> at 1 C, ∼802 mAh g<sup>–1</sup> at 2 C, and ∼606 mAh g<sup>–1</sup> at 5 C. The cells
also demonstrate an ultralong cycle life exceeding 2000 cycles and
an extremely low capacity-decay rate (0.028% per cycle), which is
among the best performance demonstrated so far for Li/S cells. Furthermore,
the S@NG cathode can be cycled with an excellent Coulombic efficiency
of above 97% after 2000 cycles. With a high active S content (60%)
in the total electrode weight, the S@NG cathode could provide a specific
energy that is competitive to the state-of-the-art Li-ion cells even
after 2000 cycles. The X-ray spectroscopic analysis and ab initio
calculation results indicate that the excellent performance can be
attributed to the well-restored C–C lattice and the unique
lithium polysulfide binding capability of the N functional groups
in the NG sheets. The results indicate that the S@NG nanocomposite
based Li/S cells have a great potential to replace the current Li-ion
batteries