Understanding Reaction Pathways in High Dielectric Electrolytes Using β-Mo2C as a Catalyst for Li-CO2 Batteries.,ACS Applied Materials & Interfaces

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Understanding Reaction Pathways in High Dielectric Electrolytes Using β-Mo2C as a Catalyst for Li-CO2 Batteries.
ACS Applied Materials & Interfaces ( IF 8.3 ) Pub Date : 2020-06-25 , DOI: 10.1021/acsami.0c06835
Mihye Wu _{1,

2,

3} , Ju Ye Kim _{1,

2} , Hyunsoo Park ₁ , Do Youb Kim ₃ , Kyeong Min Cho _{1,

2} , Eunsoo Lim ₄ , Oh B Chae ₅ , Sungho Choi ₃ , Yongku Kang _{3,

6,

7} , Jihan Kim ₁ , Hee-Tae Jung _{1,

2}

Affiliation

The rechargeable Li–CO₂ battery has attracted considerable attention in recent years because of its carbon dioxide (CO₂) utilization and because it represents a practical Li–air battery. As with other battery systems such as the Li-ion, Li–O₂, and Li–S battery systems, understanding the reaction pathway is the first step to achieving high battery performance because the performance is strongly affected by reaction intermediates. Despite intensive efforts in this area, the effect of material parameters (e.g., the electrolyte, the cathode, and the catalyst) on the reaction pathway in Li–CO₂ batteries is not yet fully understood. Here, we show for the first time that the discharge reaction pathway of a Li–CO₂ battery composed of graphene nanoplatelets/beta phase of molybdenum carbide (GNPs/β-Mo₂C) is strongly influenced by the dielectric constant of its electrolyte. Calculations using the continuum solvents model show that the energy of adsorption of oxalate (C₂O₄^2–) onto Mo₂C under the low-dielectric electrolyte tetraethylene glycol dimethyl ether is lower than that under the high-dielectric electrolyte N,N-dimethylacetamide (DMA), indicating that the electrolyte plays a critical role in determining the reaction pathway. The experimental results show that under the high-dielectric DMA electrolyte, the formation of lithium carbonate (Li₂CO₃) as a discharge product is favorable because of the instability of the oxalate species, confirming that the dielectric properties of the electrolyte play an important role in the formation of the discharge product. The resulting Li–CO₂ battery exhibits improved battery performance, including a reduced overpotential and a remarkable discharge capacity as high as 14,000 mA h g^–1 because of its lower internal resistance. We believe that this work provides insights for the design of Li–CO₂ batteries with enhanced performance for practical Li–air battery applications.

中文翻译：

使用β-Mo2C作为Li-CO2电池的催化剂，了解高介电电解质中的反应途径。

近年来，可充电式Li-CO ₂电池由于其二氧化碳（CO ₂）的利用率以及代表了实用的Li-air电池而备受关注。与其他电池系统（例如锂离子，LiO ₂和Li-S电池系统）一样，了解反应路径是实现高电池性能的第一步，因为性能会受到反应中间体的强烈影响。尽管在该领域进行了大量努力，但尚未完全了解材料参数（例如，电解质，阴极和催化剂）对Li-CO ₂电池反应路径的影响。在这里，我们首次展示了Li–CO ₂的放电反应途径石墨烯纳米片/钼碳化物（的GNP /β-沫的β相构成的电池₂ C）强烈地受到它的电解质的介电常数的影响。使用连续溶剂模型进行的计算表明，在低介电电解质四甘醇二甲醚下，草酸盐（C ₂ O ₄^2–）吸附在Mo ₂ C上的能量比在高介电电解质N，N-下的低。二甲基乙酰胺（DMA），表明电解质在确定反应途径中起关键作用。实验结果表明，在高介电常数的DMA电解液下，碳酸锂（Li ₂ CO₃）由于草酸盐种类的不稳定性，因此作为放电产物是有利的，证实了电解质的介电性质在放电产物的形成中起重要作用。所得的Li–CO ₂电池具有更高的电池性能，包括更低的过电位和显着的放电容量，因为其较低的内阻，其放电容量高达14,000 mA hg ^–1。我们相信，这项工作可为设计具有更高性能的Li-CO ₂电池提供实际见解，以用于实际的Li-air电池应用。

更新日期：2020-07-22

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