Synergistic Structure and Iron‐Vacancy Engineering Realizing High Initial Coulombic Efficiency and Kinetically Accelerated Lithium Storage in Lithium Iron Oxide

Abstract

Transition metal oxides with high capacity still confront the challenges of low initial coulombic efficiency (ICE, generally <70%) and inferior cyclic stability for practical lithium-storage. Herein, a hollow slender carambola-like Li 0.43 FeO 1.51 with Fe vacancies is proposed by a facile reaction of Fe 3+ -containing metal-organic frameworks with Li 2 CO 3 . Synthesis experiments combined with synchrotron-radiation X-ray measurements identify that the hollow structure is caused by Li 2 CO 3 erosion, while the formation of Fe vacancies is resulted from insufficient lithiation process with reduced Li 2 CO 3 dosage. The optimized lithium iron oxides exhibit remarkably improved ICE (from 68.24% to 86.78%), high-rate performance (357 mAh g −1 at 5 A g −1 ), and superior cycling stability (884 mAh g −1 after 500 cycles at 0.5 A g −1 ). Paring with LiFePO 4 cathodes, the full-cells achieve extraordinary cyclic stability with 99.3% retention after 100 cycles. The improved electrochemical performances can be attributed to the synergy of structural characteristics and Fe vacancy engineering. The unique hollow structure alleviates the volume expansion of Li 0.43 FeO 1.51 , while the in situ generated Fe vacancies are powerful for modulating electronic structure with boosted Li + transport rate and catalyze more Li 2 O decomposition to react with Fe in the first charge process, hence enhancing the ICE of lithium iron oxide anode materials.

Design of 3D Metal–Organic Material with Multiple Redox-Active Sites for High-Performance Lithium-Ion Batteries

“…In the initial cycle, the discharge and charge capacities were 2288 and 799 mA h g –1 , respectively, resulting in a limited initial Coulombic efficiency (ICE) of 35% lower than common oxide anodes. The low ICE could be associated with unstable anode surface, side reactions, interfacial lithium storage, and the formation of SEI during the decomposition of the organic electrolyte during the first cycle, , which aligned with the findings from the CV curves (Figure S2). After 20 cycles, the Coulombic efficiency (CE) significantly improved, approaching 100%, while maintaining a stabilized reversible capacity of 660 mA h g –1 .…”

Introduction of SnS2 to Regulate the Ferrous Disulfide Phase Evolution for the Construction of Triphasic Heterostructures Enabling Kinetically Accelerated and Durable Sodium Storage

“…[17,18,21,37,[44][45][46][47][48][49][50][51][52][53][54] Galvanostatic intermittent titration technique (GITT) methods are carried out to evaluate the sodium ions diffusion ability in the as-prepared electrodes during the discharge and charge processes. [55,56] As shown in Figure 4h, the voltage-time curves of as-prepared electrodes are similar to their corresponding discharge-charge curves. According to the Equation (1), the diffusion coefficient of Na + (D Na + ) at different states is calculated and depicted in Figure 4i (the meaning of the parameters can be referred to in our previous works).…”

“…According to the Equation (1), the diffusion coefficient of Na + (D Na + ) at different states is calculated and depicted in Figure 4i (the meaning of the parameters can be referred to in our previous works). [ 55 ] To summarize, the values of D Na + change dynamically with the different discharge/charge of depth. The lower D Na + of FFS‐TH in some potential ranges would be imputed to the adsorption of Na + by the strong BEF (induced by triphasic heterojunction) and electrical double layer.…”

Dual‐Ligand Strategy to Construct Metal Organic Gel Catalyst with the Optimized Electronic Structure for High‐Efficiency Overall Water Splitting and Flexible Metal–Air Battery

“…The stronger symmetrical EPR signal of P‐CoFe‐H 3 with g value of 2.004 was shown in Figure 2d, indicating the existence of unpaired electrons captured by oxygen vacancies. [ 30 ] The results also confirm the incorporation of Fe species can induce a greater extent of mismatch and re‐arrangement of electrons, thereby introducing more defects and effectively exposing Co nodes to afford abundant active sites for catalytic process. [ 31 ] The specific surface area (SSA) and pore properties of P‐CoFe‐H 3 were confirmed by N 2 adsorption‐desorption technique.…”