Configuring Optimal FeS2@Carbon Nanoreactor Anodes: Toward Insights into Pyrite Phase Change/Failure Mechanism in Rechargeable Ni–Fe Cells

• DOI: 10.1021/acsami.9b12153
• Publication Date: 2019-10-21T20:14:22Z
• Authors: Jiajia Yao; Yani Liu; Han Zhang; Lai Ma; Ting Meng; Ning Li; Jian Jiang; Jianhui Zhu; Chang Ming Li
• Keywords: Nanoreactor; Carbon fibers

Pyrite FeS2 has long been a research focus as the alternative anode of rechargeable Ni–Fe cells owing to its eye-catching merits great earth-abundance, attractive electrical conductivity, and output capacity. However, further progress is impeded by unsatisfactory cyclic behaviors due still "ill-defined" phase changes. To gain insights into pyrite working principles/failure factors, we herein design core–shell hybrid FeS2@carbon nanoreactor, an optimal configuration approaching practical usage state. The resultant electrodes exhibit Max. specific capacity ∼272.89 mAh g–1 (at ∼0.81 A g–1), remarkably improved longevity/stability (beyond ∼80% retention after 103 cycles) superior rate capability (∼146.18 remained at ∼20.01 g–1) in contrast bare counterparts. as-built full can also impressive energy/power densities ∼87.38 Wh kg–1/ ∼ 11.54 kW kg–1. Moreover, refreshed redox reaction mechanism "FeS2OH ↔FeS2↔Fe0(in domains)" redefined based on real-time electrode characterizations distinct operation stages. In total period, configured pyrite-based anodes would stepwise undergo three critical stages nominally named "retention", "phase transition/coexistence", "degradation", each which closely related variations anodic compositions/structures. Combined with configurations in-depth clarifications inherent conversions, this study may guide us maximize utilization efficiency for all other aqueous electrochemical devices.