Sulfurized Polyacrylonitrile Cathodes with High Compatibility in Both Ether and Carbonate Electrolytes for Ultrastable Lithium–Sulfur Batteries

Abstract

Sulfurized polyacrylonitrile (SPAN) is a promising material capable of suppressing polysulfide dissolution in lithium-sulfur (Li-S) batteries with carbonate electrolyte. However, undesirable spontaneous formation of soluble polysulfides may arise in the ether electrolyte, and the conversion of sulfur in SPAN during the lithiation/delithiation processes is yet to be understood. Here, a highly reliable Li-S system using a freestanding fibrous SPAN cathode, as well as the sulfur conversion mechanism involved, is demonstrated. The SPAN shows high compatibility in both ether and carbonate electrolytes. The sulfur atoms existing in the form of short S 2  and S 3  chains are covalently bonded to the pyrolyzed PAN backbone. The electrochemical reduction of the SPAN by Li + is a single-phase solid-solid reaction with Li 2 S as the sole discharge product. Meanwhile, the parasitic reaction between Li + and CN bonds exists upon the first discharge, and the residual Li + enhances the conductivity of the backbone. The recharge ability and rate capability are kinetically dominated by the activation of Li 2 S nanoflakes generated during discharge. At 800 mA g −1 , a specific capacity of 1180 mAh g −1 is realized without capacity fading in the measured 1000 cycles, which makes SPAN promising for practical application.

Binder-Free Electrodes and Their Application for Li-Ion Batteries

“…This disadvantage can be addressed by additives. Liu et al showed the PAN fibers with an appropriate amount of CNTs can still be self-standing after sulfurization [115]. The sulfur only exists in the form of Li 2 S 2 and Li 2 S 3 rather than polysulfides in the sulfurized PAN.…”

“…d Inorganic particles encapsulated carbon fibers [114]. e The modification of carbon fibers [115]. f Carbon fiber membrane with nanoparticles [38].…”

Prospect of Sulfurized Pyrolyzed Poly(acrylonitrile) (S@pPAN) Cathode Materials for Rechargeable Lithium Batteries

“…[25] Sulfur undergoes as ingle-electron process, which yielded atheoretical capacity of 837 mAh g À1 .The extra capacity originated from the conjugative structure when combined with the reaction pathway.A lthough both of conclusions self-consistently illustrated the source of extra capacity,t he p-conjugated pyridinic carbon matrix cannot afford such high capacity. [19,21,26] Wang et al revealed that the lithiation process of S@pPAN is as ingle-phase solid-solid route with the sole discharge product being Li 2 S. [27] The irreversible capacity of Li with C = Nb onds during the initial discharge process would lead to exceeding capacity and enhance ionic conductivity.T hey further confirmed that the control step of the rate capacity is the activation process of Li 2 S. Recently,Xie et al introduced small amount of selenium (Se) to alter the structure of S@pPAN composite. [28] It delivered excellent performance,b oth in ester and ether electrolytes.Based on the above analysis,weassume that the molecular structure of the S@pPAN composite should be highly dependent on the precursor PA N, the synthesis temperature,t ime,a nd pressure.…”

The rechargeable aluminum-ion battery with different composite cathodes: A review

“…In comparison with liquid electrolyte Li batteries, solid-state batteries have lower power densities. This is the result of limited kinetics of the electrodes, the compatibility of the electrode/electrolyte interface, and the solid electrolyte low ionic conductivity [72]. Recently, the development of high ionic-conductive solid electrolytes has made the production of solid-state Li batteries possible with a power performance similar to liquid-electrolyte batteries.…”