Key Takeaways & Executive Findings
- •• • Ru@NC catalyst reduces charge-discharge polarization to 0.89 V, a significant improvement over conventional catalysts that often exceed 1.0 V, directly enhancing energy efficiency and reducing heat generation in Li-O2 batteries. • • The battery achieves a prolonged lifespan exceeding 200 cycles, indicating stable cycling performance critical for practical deployment in grid-scale energy storage. • • The Mott-Schottky heterointerface induces a built-in electric field that accelerates oxygen intermediate conversion, as evidenced by the formation of nanosheet-like Li2O2 with low interfacial impedance, which is key to reducing charge transfer resistance. • • The catalyst's moderate LiO2 affinity promotes a solution-mediated growth mechanism, yielding Li2O2 nanosheets that improve cathode kinetics and rate capability, as demonstrated by superior rate performance.
Abstract
Aprotic lithium-oxygen (Li-O2) batteries are severely limited by slow cathode reaction kinetics and large polarization. Herein, we design and prepare a Mott-Schottky catalyst by uniformly embedding ultrafine Ru nanoparticles on nitrogen-doped carbon (Ru@NC) nanoflakes to accelerate oxygen redox kinetics of Li-O2 batteries. The Mott-Schottky effect of Ru@NC drives spontaneous electron rearrangement in the NC matrix and induces a strong built-in electric field at heterointerfaces, which accelerates the activation and conversion of oxygen intermediates. The obtained Ru@NC possesses rich Mott-Schottky heterointerfaces and defective carbon structures, which provide extensive adsorption and nucleation sites. More importantly, Ru@NC manifests moderate affinity for the intermediate LiO2, inducing formation of unique nanosheet-like Li2O2 with low Li2O2/cathode interfacial impedance, which further enhances oxidation kinetics. These enable the Li-O2 battery with Ru@NC to deliver a remarkably reduced polarization of 0.89 V, superior rate performance, and prolonged lifespan of over 200 cycles. This work will provide valuable guidelines for engineering advanced electrocatalysts for high-performance Li-O2 batteries and beyond.
1. Introduction
Aprotic lithium-oxygen batteries offer an ultrahigh theoretical energy density of 3600 Wh kg−1, positioning them as a leading candidate for next-generation energy storage. However, their commercial viability is undermined by sluggish oxygen reduction and evolution kinetics, leading to large voltage hysteresis and poor cycle life. Conventional Pt-based catalysts, while active, suffer from scarcity and low selectivity, and the random deposition of insulating Li2O2 toroids blocks cathode pores, increasing interfacial impedance and polarization. These bottlenecks have stalled practical adoption despite decades of research.
This work addresses these limitations by engineering a Mott-Schottky catalyst comprising ultrafine Ru nanoparticles on nitrogen-doped carbon (Ru@NC). The heterojunction between Ru and NC creates a built-in electric field that drives interfacial charge redistribution, enhancing electron donation and catalytic activity. Crucially, the moderate adsorption strength of Ru@NC towards LiO2 intermediates redirects Li2O2 growth from large toroids to thin nanosheets, reducing interfacial impedance and improving oxidation kinetics. This targeted design yields a low polarization of 0.89 V and a cycle life exceeding 200 cycles, directly tackling the key barriers of overpotential and stability in Li-O2 batteries.
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LI Yajing, SUN Yinjing, YANG Xueyun, WANG Yingli, LI Caixia, LIANG Haojie, SHI Xianxian, WANG Lei, LV Qingliang (2026). Interfacial charge redistribution in ultrafine ruthenium nanoparticle-decorated N-modified carbon catalysts accelerates oxygen redox for lithium-oxygen batteries. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-025-3706-3
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Frequently Asked Questions
What is the specific role of the Mott-Schottky effect in enhancing the oxygen reduction and evolution kinetics?
The Mott-Schottky effect at the Ru/NC interface induces a built-in electric field that drives spontaneous electron redistribution from Ru to the N-doped carbon matrix. This enriches the surface electron density, facilitating the activation of oxygen and the conversion of intermediates, as evidenced by the reduced polarization of 0.89 V and improved rate performance.
How does the Ru@NC catalyst influence the morphology of Li2O2 and what is the impact on battery performance?
Ru@NC exhibits moderate affinity for LiO2, promoting a surface-mediated growth that yields nanosheet-like Li2O2 instead of large toroids. This morphology reduces the Li2O2/cathode interfacial impedance, enhancing charge transfer and oxidation kinetics, which contributes to the low polarization and extended cycle life of over 200 cycles.
What are the key performance metrics of the Ru@NC-based Li-O2 battery compared to state-of-the-art catalysts?
The Ru@NC-based battery achieves a polarization of 0.89 V, which is significantly lower than the >1.0 V typically reported for many catalysts. It also demonstrates superior rate performance and a cycle life exceeding 200 cycles, indicating improved stability and efficiency.
What is the scalability potential of the Ru@NC synthesis method for industrial production?
The synthesis involves uniform embedding of ultrafine Ru nanoparticles on N-doped carbon nanoflakes, which is a scalable wet-chemical approach. However, the use of ruthenium, a precious metal, may pose cost constraints. Future work should explore reducing Ru loading or substituting with earth-abundant alternatives while maintaining the Mott-Schottky effect.
What are the main degradation mechanisms that limit the cycle life of Li-O2 batteries, and how does Ru@NC address them?
Degradation primarily arises from the accumulation of insulating Li2O2 and parasitic reactions with the electrolyte. Ru@NC mitigates this by promoting uniform nanosheet-like Li2O2 deposition, which reduces cathode passivation and interfacial impedance. The catalyst's stability over 200 cycles suggests effective suppression of side reactions, though long-term durability beyond 200 cycles remains to be tested.
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