Ultra‐Small Ferromagnetic Fe₃O₄ Nanoparticles Modified Separator for High‐Rate and Long Cycling Lithium‐Sulfur Batteries

Abstract

As a promising energy storage system with high specific capacity, lithium‐sulfur (Li−S) battery is striving for a high‐rate and longer lifetime. Whereas the slow redox kinetics and the shuttle effect of polysulfides (PSs) still severely restrict the performance of Li−S batteries. Here, a rational designed ferromagnetic Fe3O4 nanoparticles (FM‐Fe3O4 NPs) modified separator is engineered for Li−S batteries. Moreover, the particle size of FM‐Fe3O4 NPs was tuned to enhance the energy storage performance. Consequently, the cells with FM‐Fe3O4 NPs modified separator achieved a high‐rate and long cycling performance, the specific capacity could reach 672.8 mAh g−1 and a low fading rate (0.028 % per cycle over 700 cycles) at a high rate of 5 C. Experimental results reveals that FM‐Fe3O4 NPs could mitigate shuttle effect, enable efficient redox reactions, and protect the Li anode from severe corrosion. The performance‐enhanced mechanism is further discovered by DFT calculations, the results show that FM‐Fe3O4 NPs act as mediators of redox reaction to block PSs shuttle and dynamically facilitate conversion via changing the molecular structure of PSs and reducing reaction barrier. This work provides a new pathway to improving Li−S batteries based on ferromagnetic materials, which may be generalized to other advanced batteries.

Spin Effect to Promote Reaction Kinetics and Overall Performance of Lithium‐Sulfur Batteries under External Magnetic Field

“…Yue et al. also reported an improved LiPS blocking when adding ferromagnetic Fe 3 O 4 nanoparticles into the separator, but no clear relationship between the particles’ ferromagnetism and the enhanced performance was established [36] . Li et al.…”

Spin Effect to Promote Reaction Kinetics and Overall Performance of Lithium‐Sulfur Batteries under External Magnetic Field

“…[35] Yue et al also reported an improved LiPS blocking when adding ferromagnetic Fe 3 O 4 nanoparticles into the separator, but no clear relationship between the particles' ferromagnetism and the en-hanced performance was established. [36] Li et al proposed a semiliquid Li-LiPS battery using a ferrofluid containing Li 2 S 8 and ferromagnetic γ-Fe 2 O 3 nanoparticles as a flowable catholyte. [37] An applied magnetic field could be used to keep the ferrofluid in close contact with the current collector and potentially to flow the catholyte in a flow battery configuration without the need for pumps.…”