A comprehensive cognition for the capacity fading mechanism of FeS₂ in argyrodite‐based all‐solid‐state lithium battery

Abstract

Sulfide solid state electrolyte (SSE) possesses high ionic conductivity and great processability but suffers from narrow electrochemical window. Conversion sulfide cathode FeS 2 has higher specific capacity and moderate redox potential, making it appropriate toward sulfide SSE. However, the complex reaction pathway and capacity fading mechanism in FeS 2 are rarely studied, especially in all-solid-state lithium battery (ASSLB). Herein, argyrodite sulfide SSE is paired with FeS 2 to investigate the electrochemical reaction pathways and the capacity fade mechanism. Instead of single conversion reaction, an anionic redox driven reaction of FeS 2 is revealed. The oxidization of Li 2 S vanishes and large quantity of inactive Li 2 S accumulates to cause the interfacial deterioration, along with the stress concentration during cycling, which leads to the rapid capacity fade of FeS 2 . Finally, a simple strategy of slurry-coated composite electrode with highly conductive network is proposed to direct the uniform deposition of Li 2 S and alleviate the stress concentration.

Lithium‐based batteries, history, current status, challenges, and future perspectives

“…361 A recent study shows that argyrodite and halide solid-state electrolytes are more promising materials for industrialisation compared with LGPS. 362,363 Another inorganic material type studied for use as a solid electrolyte are lithium cations like LiX, where X is an element such as nitrogen. For instance, the ionic conductivity of Li 3 N is 1 × 10 −3 S.cm −1 and Li 3 N-based electrolytes can be used in lithium-metal batteries.…”

“…However, a major problem associated with sulfide‐based solid electrolytes is their chemical instability with air, moisture, and cathode materials 361 . A recent study shows that argyrodite and halide solid‐state electrolytes are more promising materials for industrialisation compared with LGPS 362,363 …”

Synergistic Coupling of Sulfide Electrolyte and Integrated 3D FeS2 Electrode Toward Long‐Cycling All‐Solid‐State Lithium Batteries

“…[ 9–11 ] However, the huge volume change of FeS 2 based on the conversion reaction during cycling causes a continuous loss of active contacts, thereby deteriorating battery performances. [ 10,12,13 ] Furthermore, the detrimental polysulfide shuttle in FeS 2 could not be completely blocked even in polymer electrolyte‐based ASSLBs, [ 14–16 ] which also leads to rapid capacity fading.…”

“…Fortunately, when FeS 2 couples with sulfide electrolytes (SEs) for ASSLBs, the polysulfide shuttle effect can be essentially circumvented due to the direct solid–solid reaction of Li 2 S/S. [ 13,17–19 ] In addition, the electrochemical stability window of SEs matches well with the operating voltage of FeS 2 (1–3 V, vs Li + /Li), [ 12,20 ] which along with their good interface compatibility [ 21–23 ] enables the relatively stable operation of batteries. Nevertheless, intrinsic challenges remain, including severe volume expansion [ 24 ] and sluggish kinetics resulting from insulating discharge products ( Figure a); [ 10 ] the electrochemical performance of ASSLBs based on FeS 2 cathode and SEs is still far from satisfactory.…”

Vertical Graphene Sheet-Encapsulated Silicon Nanoparticles for Anodes of Polymer-Based All-Solid-State Batteries

“…Currently, dominant solid electrolytes encompass sulfide-based, oxide-based, and polymer-based solid electrolytes. The ionic conductivity of oxide-based solid electrolytes is relatively lower compared to sulfide-based solid electrolytes, and there are problems of chemical stability, serious interface issues, and synthesis difficulty. − For the sulfide-based ASSBs, Si as the anode has been reported several times in the literature. − However, cycling silicon-based sulfide solid-state batteries requires maintaining the applied pressure for an effective contact between silicon and electrolyte. ,, Moreover, Si displays intrinsically low electronic conductivity, and carbon induces significant solid sulfide electrolyte decomposition, adversely impacting the cycling performance. , The solid polymer electrolyte has good flexibility, and the battery does not need to be cycled under the applied pressure. , Poly­(ethylene oxide) (PEO) has emerged as the predominant polymer matrix choice, primarily attributable to its excellent compatibility with lithium salt, minimal interfacial resistances, facile synthesis, and low cost. − While PEO-based solid polymer electrolytes exhibit a relatively low ionic conductivity, the incorporation of inorganic fillers can substantially enhance both ionic conductivity and the stability of electrolytes toward lithium metal. , However, PEO polymer solid-state electrolytes are susceptible to be punctured by lithium dendrites, which restricts the use of lithium metal anodes. Conversely, the Si/C composite anodes significantly reduce the formation of lithium dendrites, making them more suitable for PEO polymer ASSBs.…”