Fe-based hybrid electrocatalysts for nonaqueous lithium-oxygen batteries

Synergistic effect of oxygen vacancies and in-situ formed bismuth metal centers on BiVO4 as an enhanced bifunctional Li-O2 batteries electrocatalyst

Bismuth Vanadate (BiVO4) is a promising oxide-based photoanode for electrochemical applications, yet its practical use is constrained by poor charge transport properties, particularly under dark conditions. This study introduces a novel BiVO4 variant (Bi-BiVO4-10) that incorporates abundant oxygen vacancies and in-situ formed Bi metal, significantly enhancing its electrical conductivity and catalytic performance. Bi-BiVO4-10 demonstrates superior electrochemical performances compared to conventional BiVO4 (C-BiVO4), demonstrated by its most positive half-wave potential with the highest diffusion-limiting current in the oxygen reduction reaction (ORR) and earliest onset potential in the oxygen evolution reaction (OER). Notably, Bi-BiVO4-10 is explored for the first time as an electrocatalyst for lithium-oxygen (Li-O2) cells, showing reduced overcharge (610 mV) in the first cycle and extended cycle life (1050 h), outperforming carbon (320 h) and C-BiVO4 (450 h) references. The enhancement is attributed to the synergy of oxygen vacancies, Bi metal formation, increased surface area, and improved electrical conductivity, which collectively facilitate Li2O2 growth, enhance charge transport kinetics, and ensure stable cycling. Theoretical calculations reveal enhanced chemical interactions between intermediate molecules and the defect-rich surfaces of Bi-BiVO4-10, promoting efficient discharge and charge processes in Li-O2 batteries. This research highlights the potential of unconventional BiVO4-based materials as durable electrocatalysts and for broader electrochemical applications.

Kinetically Stable Oxide Overlayers on Mo3 P Nanoparticles Enabling Lithium-Air Batteries with Low Overpotentials and Long Cycle Life

The main drawbacks of today's state-of-the-art lithium-air (Li-air) batteries are their low energy efficiency and limited cycle life due to the lack of earth-abundant cathode catalysts that can drive both oxygen reduction and evolution reactions (ORR and OER) at high rates at thermodynamic potentials. Here, inexpensive trimolybdenum phosphide (Mo₃ P) nanoparticles with an exceptional activity-ORR and OER current densities of 7.21 and 6.85 mA cm^-2 at 2.0 and 4.2 V versus Li/Li⁺ , respectively-in an oxygen-saturated non-aqueous electrolyte are reported. The Tafel plots indicate remarkably low charge transfer resistance-Tafel slopes of 35 and 38 mV dec^-1 for ORR and OER, respectively-resulting in the lowest ORR overpotential of 4.0 mV and OER overpotential of 5.1 mV reported to date. Using this catalyst, a Li-air battery cell with low discharge and charge overpotentials of 80 and 270 mV, respectively, and high energy efficiency of 90.2% in the first cycle is demonstrated. A long cycle life of 1200 is also achieved for this cell. Density functional theory calculations of ORR and OER on Mo₃ P (110) reveal that an oxide overlayer formed on the surface gives rise to the observed high ORR and OER electrocatalytic activity and small discharge/charge overpotentials.

ORR in Non-Aqueous Solvent for Li-Air Batteries: The Influence of Doped MnO2-Nanoelectrocatalyst

One of the major drawbacks in Lithium-air batteries is the sluggish kinetics of the oxygen reduction reaction (ORR). In this context, better performances can be achieved by adopting a suitable electrocatalyst, such as MnO2. Herein, we tried to design nano-MnO2 tuning the final ORR electroactivity by tailoring the doping agent (Co or Fe) and its content (2% or 5% molar ratios). Staircase-linear sweep voltammetries (S-LSV) were performed to investigate the nanopowders electrocatalytic behavior in organic solvent (propylene carbonate, PC and 0.15 M LiNO3 as electrolyte). Two percent Co-doped MnO2 revealed to be the best-performing sample in terms of ORR onset shift (of ~130 mV with respect to bare glassy carbon electrode), due to its great lattice defectivity and presence of the highly electroactive γ polymorph (by X-ray diffraction analyses, XRPD and infrared spectroscopy, FTIR). 5% Co together with 2% Fe could also be promising, since they exhibited fewer diffusive limitations, mainly due to their peculiar pore distribution (by Brunauer-Emmett-Teller, BET) that disfavored the cathode clogging. Particularly, a too-high Fe content led to iron segregation (by energy dispersive X-ray spectroscopy, EDX, X-ray photoelectron spectroscopy, XPS and FTIR) provoking a decrease of the electroactive sites, with negative consequences for the ORR.

Recent Progress on Catalysts for the Positive Electrode of Aprotic Lithium-Oxygen Batteries †

Rechargeable aprotic lithium-oxygen (Li-O2) batteries have attracted significant interest in recent years owing to their ultrahigh theoretical capacity, low cost, and environmental friendliness. However, the further development of Li-O2 batteries is hindered by some ineluctable issues, such as severe parasitic reactions, low energy efficiency, poor rate capability, short cycling life and potential safety hazards, which mainly stem from the high charging overpotential in the positive electrode side. Thus, it is of great significance to develop high-performance catalysts for the positive electrode in order to address these issues and to boost the commercialization of Li-O2 batteries. In this review, three main categories of catalyst for the positive electrode of Li-O2 batteries, including carbon materials, noble metals and their oxides, and transition metals and their oxides, are systematically summarized and discussed. We not only focus on the electrochemical performance of batteries, but also pay more attention to understanding the catalytic mechanism of these catalysts for the positive electrode. In closing, opportunities for the design of better catalysts for the positive electrode of high-performance Li-O2 batteries are discussed.

Single and polycrystalline CeO2 nanorods as oxygen-electrode materials for lithium-oxygen batteries

Single and polycrystalline CeO₂ nanorods (NRs) were prepared for application as oxygen-electrode electrocatalysts for lithium-oxygen batteries. The CeO₂ NRs were prepared via a time-controlled hydrothermal process. At a high current rate of 1000 mA g^-1, the single crystalline CeO₂ NRs exhibited a higher reversibility and a lower voltage gap than polycrystalline CeO₂ NRs. We compared the oxygen reduction and evolution kinetics of single and polycrystalline CeO₂ NRs using electrochemical impedance spectroscopy.

Strategies toward High-Performance Cathode Materials for Lithium-Oxygen Batteries

Rechargeable aprotic lithium (Li)-O₂ batteries with high theoretical energy densities are regarded as promising next-generation energy storage devices and have attracted considerable interest recently. However, these batteries still suffer from many critical issues, such as low capacity, poor cycle life, and low round-trip efficiency, rendering the practical application of these batteries rather sluggish. Cathode catalysts with high oxygen reduction reaction (ORR) and evolution reaction activities are of particular importance for addressing these issues and consequently promoting the application of Li-O₂ batteries. Thus, the rational design and preparation of the catalysts with high ORR activity, good electronic conductivity, and decent chemical/electrochemical stability are still challenging. In this Review, the strategies are outlined including the rational selection of catalytic species, the introduction of a 3D porous structure, the formation of functional composites, and the heteroatom doping which succeeded in the design of high-performance cathode catalysts for stable Li-O₂ batteries. Perspectives on enhancing the overall electrochemical performance of Li-O₂ batteries based on the optimization of the properties and reliability of each part of the battery are also made. This Review sheds some new light on the design of highly active cathode catalysts and the development of high-performance lithium-O₂ batteries.

Co-VN encapsulated in bamboo-like N-doped carbon nanotubes for ultrahigh-stability of oxygen reduction reaction

The electrocatalytic activity of carbon-based non-precious metal composites towards oxygen reduction reaction (ORR) is far from that of the recognized Pt/C catalyst. Thus, it is necessary to exploit novel catalysts based on multicomponent carbon-based composites with both high activity and high stability. Herein, a bottom-up strategy was used for constructing bamboo-like N-doped graphitic CNTs with a few encapsulated Co and VN nanoparticles (namely, NGT-CoV) by adopting melamine as both a nitrogen source and a carbon source. During the synthesis, melamine initially coordinated with cobalt and vanadium ions and then decomposed into carbon nitride nanosheet structures. Simultaneously, cobalt ions/clusters were converted into metal nanocatalysts by the reduced gases that were generated, which further rearranged the carbon nitride nanostructures to form N-doped CNTs. The presence of vanadium species strengthened the electronic structure and increased the contents of Co and N species by enhancing the interactions among Co and N species. The optimized NGT-Co₃₅V₆₅-45-900 exhibited an E_onset of 0.92 V (vs. RHE), an E_1/2 of 0.81 V (vs. RHE), and a Tafel slope of 66.1 mV dec^-1 in the ORR. It also displayed much higher durability (a negative shift in E_1/2 of only 11 mV after 10 000 cycles) and methanol tolerance than a commercial Pt/C catalyst. The excellent performance should be attributed to the high exposure level of active sites that originated from Co-N, VN and N-doped bamboo-like graphitic CNTs. Moreover, the skeleton composed of hollow graphitic ultra-long CNTs could not only provide smooth mass transport pathways but also facilitate fast electron transfer.

Functional and stability orientation synthesis of materials and structures in aprotic Li–O2batteries

This review presents the recent advances made in the functional and stability orientation synthesis of materials/structures for Li–O₂batteries.