Lithium–sulfur (Li–S) batteries exhibit
unparalleled
theoretical capacity and energy density than conventional lithium
ion batteries, but they are hindered by the dissatisfactory “shuttle
effect” and the sluggish conversion kinetics owing to the low
lithium ion transport kinetics, resulting in rapid capacity fading.
Herein, a catalytic two-dimensional heterostructure composite is prepared
by evenly grafting mesoporous carbon on the MXene nanosheet (denoted
as OMC-g-MXene), serving as interfacial kinetic accelerators
in Li–S batteries. In this design, the grafted mesoporous carbon
in the heterostructure can not only prevent the stack of MXene nanosheets
with the enhanced mechanical property but also offer a facilitated
pump for accelerating ion diffusion. Meanwhile, the exposed defect-rich
OMC-g-MXene heterostructure inhibits the polysulfide
shuttling with chemical interactions between OMC-g-MXene and polysulfides and thus simultaneously enhances the electrochemical
conversion kinetics and efficiency, as fully investigated by in situ/ex
situ characterizations. Consequently, the cells with OMC-g-MXene ion pumps achieve a high cycling capacity (966 mAh g–1 at 0.2 C after 200 cycles), a superior rate performance (537 mAh
g–1 at 5 C), and an ultralow decaying rate of 0.047%
per cycle after 800 cycles at 1 C. Even employed with a high sulfur
loading of 7.08 mg cm–2 under lean electrolyte,
an ultrahigh areal capacity of 4.5 mAh cm–2 is acquired,
demonstrating a future practical application.
Lithium–sulfur (Li–S) batteries are famous for their high energy density and low cost, but prevented by sluggish redox kinetics of sulfur species due to depressive Li ion diffusion kinetics, especially under low‐temperature environment. Herein, a combined strategy of electrocatalysis and pore sieving effect is put forward to dissociate the Li+ solvation structure to stimulate the free Li+ diffusion, further improving sulfur redox reaction kinetics. As a protocol, an electrocatalytic porous diffusion‐boosted nitrogen‐doped carbon‐grafted‐CoP nanosheet is designed via forming the NCoP active structure to release more free Li+ to react with sulfur species, as fully investigated by electrochemical tests, theoretical simulations and in situ/ex situ characterizations. As a result, the cells with diffusion booster achieve desirable lifespan of 800 cycles at 2 C and excellent rate capability (775 mAh g−1 at 3 C). Impressively, in a condition of high mass loading or low‐temperature environment, the cell with 5.7 mg cm−2 stabilizes an areal capacity of 3.2 mAh cm−2 and the charming capacity of 647 mAh g−1 is obtained under 0 °C after 80 cycles, demonstrating a promising route of providing more free Li ions toward practical high‐energy Li–S batteries.
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