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Two new approaches to high-performance SiOx anodes for Li-ion batteries

21 July 2017

Although silicon is a very attractive anode material because of its higher energy density, its huge volume change over repeated charge−discharge cycles rapidly degrades cycle life. As an alternative approach to mitigate the well-known drawbacks of silicon while retaining the energy density advantages, silicon monoxide (SiOx, x ≈ 1) has become attractive as well (e.g., earlier post).

SiOx offers high reversible specific capacity and improved cyclic performance; however, it still suffers from inevitable volumetric changes and poor electrical conductivity. A number of research efforts have tackled those challenges as well. Now, separate research teams in China and the US report two new approaches toward a commercially viable SiOx electrode.

A team at the University of Kentucky (Chen et al.) has synthesized a high performance binder-free SiOx/C composite electrode for Li-ion batteries by mixing SiOx particles and Kraft lignin. After a heat treatment, the lignin formed a conductive matrix hosting SiOx particles, ensuring electronic conductivity, connectivity, and accommodation of volume changes during lithiation/delithiation. No conventional binder or conductive agent was necessary.

The composite electrode showed excellent performance, maintaining ∼900 mAh g−1 after 250 cycles at a rate of 200 mA g−1, and good rate capability.

They attributed the excellent electrochemical performance to the comparatively small volume change of SiOx-based electrodes (160%) and the flexibility of the lignin-derived carbon matrix to accommodate the volume change. A paper on their work is published in the Journal of Power Sources.

The team in China (Zhang et al.) developed a mild and efficient method to prepare a micro-sized SiOx/C core–shell composite. By mixing citric acid and ball-milled SiOx and subjecting them to carbonization, they obtained a uniform SiOx/C core–shell composite with a micro-sized SiOx core and conformal carbon shell.

The carbon shell effectively enhanced the electrical conductivity of SiOx and mitigated the volume changes of SiOx during lithiation and delithiation. The SiOx/C composite electrode delivered a reversible specific capacity of 1296.3 mAh g–1; coulombic efficiency of as high as 99.8%; and capacity retention of 65.1% (843.5 mAh g–1) after 200 cycles.

The composite also exhibited excellent rate capability. The approach is mild, mass-productive, and cost-effective and, thus, can be employed in large-scale production of high-performance SiOx/C composite anode material, the team said. A paper on their work is published in the ACS journal Energy & Fuels.

Resources

  • Tao Chen, Jiazhi Hu, Long Zhang, Jie Pan, Yiyang Liu, Yang-Tse Cheng (2017) “High performance binder-free SiOx/C composite LIB electrode made of SiOx and lignin,” Journal of Power Sources, Volume 362, Pages 236-242 doi: 10.1016/j.jpowsour.2017.07.049

  • Junying Zhang, Xiaoming Zhang, Chunqian Zhang, Zhi Liu, Jun Zheng, Yuhua Zuo, Chunlai Xue, Chuanbo Li, and Buwen Cheng (2017) “Facile and Efficient Synthesis of a Microsized SiOx/C Core–Shell Composite as Anode Material for Lithium Ion Batteries” Energy & Fuels doi: 10.1021/acs.energyfuels.7b00775

July 21, 2017 in Batteries | Permalink | Comments (3)

Comments

Stop investing wasted money toward pure evs and start investing today in multi generators serial hybrid.

Note to green car congress : When i type ev it indicate with a red sign that there is a misspelling. Correct this error as ev is now a word.

Spell checking is a function of your browser, not the web site.  The other PEBCAK.

¿200 ciclos?. No lo entiendo ¿Todos se ponen de acuerdo en los 200 ciclos?. Que alguien me explique como pueden llamar viable a un Anodo que apenas alcanza los 200 ciclos. Las baterías milagrosas siguen sin "querer" llegar. Aunque sinceramente admiro su esfuerzo mientras en USA se invierte en I+D aquí en Españistan se invierten en aeropuertos vacios o lineas de AVE sin pasajeros.

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