Self‐Assembled Macrocyclic Copper Complex Enables Homogeneous Catalysis for High‐Loading Lithium–Sulfur Batteries

Abstract

The practical viability of high‐energy‐density lithium–sulfur (Li–S) batteries stipulates the use of a high‐loading cathode and lean electrolyte. However, under such harsh conditions, the liquid–solid sulfur redox reaction is much retarded due to the poor sulfur and polysulfides utilization, leading to low capacity and fast fading. Herein, a self‐assembled macrocyclic Cu(II) complex (CuL) is designed as an effective catalyst to homogenize and maximize the liquid‐involving reaction. The Cu(II) ion coordinated with four N atoms features a planar normaldsp2${\mathrm{d}}_{{\mathrm{sp}}^{2}}$ hybridization, showing a strong bonding affinity toward lithium polysulfides (LiPSs) along the normaldz2${\mathrm{d}}_{{z}^{2}}$ orbital via steric effects. Such a structure not only lowers the energy barrier of the liquid–solid conversion (Li2S4 to Li2S2) but also guides a 3D deposition of Li2S2/Li2S. As such, with a 1 wt% electrolyte additive of CuL, a high initial capacity of 925 mAh g−1 and areal capacity of 9.62 mAh cm−2 with a low decay of 0.3%/cycle can be achieved under a high sulfur loading of 10.4 mg cm−2 and low electrolyte/sulfur ratio of 6 µL mgs−1. This work is expected to inspire the design of homogenous catalysts and accelerate the uptake of high‐energy‐density Li–S batteries.

Kinetically Favorable Li–S Battery Electrolytes

“…It is well accepted that a homogeneous catalyst helps to enhance reaction kinetics and elevate sulfur utilization . Nevertheless, the underlying interaction nexus between homogeneous catalysts and sulfur species is still elusive.…”

“…It is well accepted that a homogeneous catalyst helps to enhance reaction kinetics and elevate sulfur utilization. 125 Nevertheless, the underlying interaction nexus between homogeneous catalysts and sulfur species is still elusive. In what follows, three representative studies focusing on deciphering the working mechanism of homogeneous catalysts will be presented and discussed, to further deepen the understanding of homogeneous catalysis in Li−S systems.…”

Surface-Phosphided Metal Oxide Microspheres as Catalytic Host of Sulfur to Enhance the Performance of Lithium–Sulfur Batteries

“…Significantly, two long discharge plateaus can be observed for the S/P-NCMO cathode at high rates compared to the S/NCMO cathode, demonstrating better reversibility and fast redox kinetics of the S/P-NCMO cathode. High sulfur loading and lean electrolyte usage are crucial for achieving high energy density toward commercialization of Li–S batteries. − As shown in Figure d, the higher sulfur loading leads inevitably to higher polarization in discharge/charge profiles, while the S/P-NCMO cathode still displays typically two discharge plateaus and large specific capacity under high sulfur loadings of 3.1 and 5.3 mg cm –2 and lean E/S ratio of 10 and 5.8 μL mg –1 at 0.1C rate, respectively. Specifically, the cathodes show high maximum specific capacities up to 925 and 756 mAh g s –1 , corresponding to the area capacities of 2.9 and 4.0 mAh cm –2 , as well as good cyclic stability after 100 cycles at 0.1C rate (Figure e).…”

Chlorine bridge bond-enabled binuclear copper complex for electrocatalyzing lithium–sulfur reactions

“…For instance, the oxygen-bridged indium-nickel atomic pairs recently have been reported as dual-atom active sites to promote CO 2 reduction 44 . However, heterogeneous molecule catalysts with atomic metal sites have been scarcely reported in LSB field to date 45 . Moreover, the function of binuclear metal centers in molecule catalysts can be conceived toward the optimal selection for breaking through the activity limitation of mononuclear metal center.…”