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Nano-sized SiO electrodes to advance Li-ion cells

Posted: 16 Jul 2014     Print Version  Bookmark and Share

Keywords:National Institute for Materials Science  lithium ion batteries  silicon oxide  electrode 

An article recently published in the Science and Technology of Advanced Materials has revealed an approach with industrial potential to produce nano-sized composite silicon-based powders as negative electrodes for the next generation lithium ion batteries. For quite some time, the growing lithium ion battery market has been on the hunt for a technology to increase battery capacity while retaining capacity for long recharging process.

Structuring materials for electrode at the nanometre-length scale has been known to be an effective way to meet this demand. However, such nanomaterials would essentially need to be produced by high throughput processing in order to transfer these technologies to industry.

Lithium-ion battery testing

Lithium-ion battery testing (Copyright: Argonne National Laboratory/Flickr)

The authors have successfully produced nanocomposite SiO powders by plasma spray physical vapour deposition using low cost metallurgical grade powders at high throughputs. Using this method, they demonstrated an explicit improvement in the battery capacity cycle performance with these powders as electrode.

The uniqueness of this processing method is that nanosized SiO composites are produced instantaneously through the evaporation and subsequent co-condensation of the powder feedstock. The approach is called plasma spray physical vapour deposition (PS-PVD). In Fig. 1, raw SiO and PS-PVD SiO composites are shown.

FE-SEM images of the raw SiO

Field emission scanning electron microscope (FE-SEM) images of the raw SiO (a), plasma sprayed (PS-PVD) powder with CH4 addition (C/Si = 1) (b) and its higher magnification (Copyright : Sci. Technol. Adv. Mater. Vol. 15 (2014) p. 025006)

The composites are 20nm particles, which are composed of a crystalline Si core and SiOx shell. Furthermore, the addition of methane (CH4) promotes the reduction of SiO and results in the decreased SiO-shell thickness. The core-shell structure is formed in a single-step continuous processing.

PS-PVD Si core and SiOx shell composites

High resolution transmission electron microscopy images of the PS-PVD Si core and SiOx shell composites processed (a) without and (b) with 1.1 slm methane (CH4) gas addition. The CH4 promotes the reduction of SiO and decreases the irreversible capacity associated with Li-O formation. (Copyright: Sci. Technol. Adv. Mater. Vol. 15 (2014) p. 025006)

As a result, the irreversible capacity was effectively decreased, and half-cell batteries made of PS-PVD powders have exhibited improved initial efficiency and maintenance of capacity as high as 1000 mAhg?1 after 100 cycles at the same time.





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