Origin of extra capacity in the solid electrolyte interphase near high-capacity iron carbide anodes for Li ion batteries,Energy & Environmental Science

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Origin of extra capacity in the solid electrolyte interphase near high-capacity iron carbide anodes for Li ion batteries
Energy & Environmental Science ( IF 32.4 ) Pub Date : 2020-05-14 , DOI: 10.1039/c9ee04062e
Dongjiang Chen _{1,

2,

3,

4} , Chao Feng _{1,

2,

3,

4} , Yupei Han _{1,

2,

3,

4} , Bo Yu _{1,

2,

3,

4} , Wei Chen _{1,

2,

3,

4} , Ziqi Zhou _{1,

2,

3,

4} , Ning Chen _{1,

2,

3,

4} , John B. Goodenough _{5,

6,

7,

8} , Weidong He _{1,

2,

3,

4,

9}

Affiliation

Transition metal carbides (TMCs), known to deliver extra capacity beyond the theoretical limit, are proposed as emerging high-capacity anodes for next-generation lithium ion batteries (LIBs). Nevertheless, the underlying mechanism for the extra lithium storage in TMCs has not been revealed clearly due to the electrochemical inertness of TMCs to Li in cycling. Here, for the first time, by employing in situ Raman and X-ray photoelectron spectroscopies, we corroborate that the capacity enhancement of Fe₃C anodes originates from the physiochemical evolution of solid electrolyte interphase (SEI) and surface carbonaceous materials through three mechanisms: (i) Fe₃C catalyzes the reversible conversion between esters and ethers to store extra lithium ions in the SEI; (ii) Fe and inorganic components embedded in the SEI form a reversible surface-conversion reaction of Fe + 3LiF ⇌ FeF₃ + 3Li⁺ + 3e⁻ to contribute additional capacity; and (iii) surficial carbon delivers capacity through surface capacitive effects and Li⁺ inter/deintercalation processes. With the extra lithium ion storage in the SEI and carbon, the C@Fe₃C/Fe anode delivers a high reversible capacity of 808 mA h g⁻¹ after 700 cycles at 1 A g⁻¹. This study provides a fundamental basis for emerging high-capacity TMC anodes to be efficiently explored for next-generation LIBs.

中文翻译：

锂离子电池大容量碳化铁阳极附近固体电解质相间多余容量的起因

过渡金属碳化物（TMC）已知可以提供超出理论极限的额外容量，被提议作为下一代锂离子电池（LIB）的新兴高容量阳极。然而，由于TMC在循环中对Li的电化学惰性，尚未清楚揭示TMC中额外的锂存储的潜在机理。在这里，我们首次采用原位拉曼光谱和X射线光电子能谱，证实了Fe ₃ C阳极容量的提高源自固体电解质中间相（SEI）和表面碳质材料的物理化学演化，其机理包括以下三种机理：（i）铁₃C催化酯和醚之间的可逆转化，从而在SEI中存储额外的锂离子；（ⅱ）Fe和嵌入在SEI无机成分形成的Fe的可逆表面转化反应+ 3LiF⇌FEF ₃ + 3Li ⁺ + 3E ^-贡献额外的容量; （iii）表面碳通过表面电容效应和Li ⁺互穿/脱嵌过程传递容量。借助SEI和碳中额外的锂离子存储，C @ Fe ₃ C / Fe阳极在1 A g ^-1下循环700次后可提供808 mA hg ^-1的高可逆容量。这项研究为新兴的高容量TMC阳极为下一代LIB有效开发提供了基础。

更新日期：2020-05-14

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