Energy Storage |Hot Paper|
Hierarchically Porous Multilayered Carbon Barriers for
High-Performance Li–S Batteries
Zhi Chang, Bing Ding, Hui Dou,* Jie Wang, Guiyin Xu, and XiaogangZhang
Abstract: As one of the most promising energystoragede-
vices, the practical application of lithium–sulfur batteries is
limited by the low electrical conductivity of sulfur and the
notable “shuttle effects” of sulfur-based electrodes. In this
work, we describe ahierarchically porousN-doped zeolitic
imidazolateframework-8 (ZIF-8)-derived carbon nanosphere
(N-ZDC) with an outer shell and an inner honeycomb-like in-
terconnectednanosheet network as sulfur host material for
high-performance and long-term lithium–sulfur batteries.
The N-ZDC serves as multilayered barrier against the dissolu-
tion of lithium polysulfides. The porously inner interconnect-
ed carbon network of the N-ZDC facilitates the electron and
ion transportation,ensures ahigh sulfur loading, and accom-
modates avolume expansionofthe sulfur species. As a
result, the optimized N-ZDC
/S electrodes displayed high ini-
tial specific capacities of 1343, 1182, and 698 mAh g
1, and 2C,respectively,and an ultraslow capacity decay of
only 0.048 %per cycleat2Cover800 cycles. Even with a
high sulfur loading of 3.1 mgcm
reversible capacity of 956 mAh g
and stabilizes at
544 mAh g
after 500 cycles at 0.5 C, revealing the great po-
tential of the novel carbon nanospheresfor energy storage
Lithium–sulfur (Li–S) batteries have emerged as one of the
most promising candidates for next-generation electrical-
energy storage due to their high theoretical energy density,
low costs, andenvironmental friendliness.
challenges plaguing the development of Li–S batteries need to
For example, Li–S batteries are known to suffer
from low sulfur utilization,alarge volumeexpansion, and a
fast capacity decay during the cycling process. The low sulfur
utilization is generally caused by the insulating nature of
sulfur,whereas the poor cyclestabilityismainly due to the no-
table “shuttle effects” caused by the high dissolubility of lithi-
um polysulfides (Li
,4 n 8).
In order to address the undesirable effects aforementioned,
variouscarbon–sulfur composites have been designed for trap-
ping active materials in electrically conductive carbon.
to the excellent conductivity and sorption property of carbon
hosts, the electronic conductivity of the sulfur composite elec-
trodes was greatlyenhanced. In addition, the diffusion of the
lithium polysulfides in the electrolyte during cycling is also
suppressed, which leads to an improved sulfur utilization and
Since the report of Nazar et al. on the ordered
various carbonaceous materials
have been employed as conducting and confining host materi-
als, including mesoporous carbon,
and carbon nanotubes (CNTs).
spheres are expected to promote the electron transfer,supply
sufficient room for sulfur loading, trap the soluble polysulfides,
and accommodate the volumetric expansion during the
charge/discharge process due to their high surface area, tuna-
ble porosity,and large inner space.
However,the cycle per-
formance is still unsatisfactory duetothe easy infusion of or-
ganic electrolyte solvents into the nanopores of the carbon
host. In addition, owing to the non-polar surface of the carbon
host, the dissolution of polysulfides cannot be suppressed ef-
fectively,especially during long cycles.
when used as the sulfur host materials, the large inner cavity
of the hollow carbon spheres lead to low volumetric energy
Due to large specific surface areas, carbon
nanosheets can afford ahigh sulfur loading andprovide suffi-
cient reactive and absorption sites for the sulfur species.
However,neither hollow carbon sphere nor carbon nanosheet
hosts can perfectly meet the requirementsfor the ideal host
materials, which can provide high sulfur loading and good
electrochemical performance. Therefore, carbon hosts forhigh-
performance Li–S batteries are still highly needed.
It hasbeen reported that the conductivity of carbonmateri-
als can be enhanced by doping with heteroatom elements,
such as Nand B.
More importantly,strong interactions be-
and Natoms in the carbon matrixexist according
to density functional theoryand diffusion experiments.
[a] Z. Chang, Dr.B.Ding,Prof. H. Dou, Dr.J.Wang, G. Xu, Prof. X. G. Zhang
Jiangsu Key LaboratoryofMaterial and Technology
for Energy Conversion
College of Material Science and Technology
Nanjing University of Aeronautics and Astronautics
Nanjing,210016 (P.R. China)
Supporting information and the ORCID identification number(s) for the au-
thor(s) of this article can be found under :
Chem. Eur.J.2018, 24,3768 –3775 2018 Wiley-VCH Verlag GmbH &Co. KGaA, Weinheim3768