Revealing the Valence Evolution of Metal Element in Heterostructures for Ultra‐High Power Li‐Ion Capacitors

Abstract

The difficulty in matching cathode and anode kinetics due to slow ion transport in anodes constrains the development of lithium‐ion capacitors. Heterogeneous structures with built‐in electric field can promote lithium‐ion migration and improve the anode reaction kinetics. However, the valence evolution of metal elements in heterostructures during charging/discharging processes is often overlooked. Inspired by theoretical calculations, transition metal selenides heterostructures (FeSe2/CoSe2) with low migration energy barriers (E b = 0.35 eV) are successfully engineered and fabricated. As expected, the designed heterostructure material exhibits outstanding rate performance (512 mAh g−1 at 30 A g−1) and ultra‐high pseudocapacitance contribution (98.02% at 1.0 mV s−1), exceeding the state‐of‐the‐art values for anodes. Impressively, synchrotron X‐ray absorption spectroscopy (SXAS) and ex situ XPS find that the valence states of the Fe and Co elements in the heterogeneous structure gradually increase as charging and discharging proceeds, inducing a continuous climb in reversible specific capacity, while further reducing the migration energy barrier in the heterogeneous structure (E b = 0.20 eV). This work reveals that the valence states of iron and cobalt elements increase as charging and discharging proceeds, providing theoretical guidance for improving the anode kinetics and revealing the capacity rise mechanism of other transition metal compounds.

Eliminating the Mn 3d Orbital Degeneracy to Suppress the Jahn–Teller Distortion for Stable MnO2 Cathode

“…Afterward, all peaks restored to their initial state upon charge process, suggesting the good structural reversibility of com‐MnO 2 . [ 44–49 ] For the ex situ XRD analysis of cub‐MnO 2 (Figure S22, Supporting Information), we noticed minor shifts in the (100) and (110) peaks in contrast to those observed in com‐MnO 2 during the electrochemical process. This observation can be attributed to the decreased changes in the lattice parameters, which results from the weakened Mn 3+ /Mn 4+ couple, corresponding to the CV result.…”

Recent Advances in Hybrid Lithium-Ion Capacitors: Materials and Processes

“…To address the current challenges of LICs, such as the imbalance in electrode kinetics, and limited energy density, enormous efforts have been made to establish a solid foundation for the industrialization of high-performance LICs. − This comprehensive review focuses on the research work conducted by our group, particularly including cathode materials (section ), anode materials (section ), anode prelithiation (section ), conductive additives (section ), and electrolytes (section ). Finally, a brief conclusion and outlook are presented in section .…”

Structural, Electronic and Vibrational Properties of B24N24 Nanocapsules: Novel Anodes for Magnesium Batteries

“…Additionally, they should refrain from undergoing chemical reactions or dissolution in the electrolyte. Nanomaterials play a pivotal role in advancing ion battery technologies due to their proven efficacy as electrode candidates, offering superior ionic and electronic conductivity when compared with their bulk counterparts [35][36][37][38][39][40][41][42][43][44][45][46][47][48][49]. The synergy between materials science and high-performance computing (HPC) has opened exciting opportunities for accelerating the discovery of novel electrode nanomaterials.…”