Hunan team develops new strategy to prolong cycle life of Li-S batteries
13 June 2016
Researchers at Hunan University, China, have developed a new strategy to suppress the diffusion of polysulfides into the electrolyte in Li-Sulfur batteries, resulting in improved performance.
As described in a paper in the Journal of Power Sources, the research tea used hydrophilic carbon paper anchored by hierarchically porous cobalt disulfides as an interlayer for capturing polysulfides through physical absorption and chemical bonding. The sulfur-graphene composite with a sulfur content of 70.5% delivers a high initial capacity of 1239.5 mAh g−1 at 0.2 C and retains a reversible capacity of 818 mAh g−1 after 200 cycles.
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| The schematic diagram of CoS2/CP capturing Li2S. Ma et al. Click to enlarge. |
… in the progress of realizing the commercialization of Li-S battery, two main critical technical issues lead to low discharge capacity and short cycle life: the shuttling behavior of the dissolved polysulfides as well as the serious volume expansion of sulfur electrode. So far, various effective strategies are utilized to promote the discharge capacity and cycling lifetime. As one of the strategies, inserting a porous interlayer between the separator and sulfur electrode is widely applied to address the above-mentioned issues.
… We, herein, prepared an interlayer of the carbon paper anchored by hierarchical porous CoS2 (CoS2/CP). It was used to encapsulate the polysulfides and alleviate the volume expansion in the sulfur-reduced graphene oxide (S/rGO) cathode.
—Ma et al.
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| (a) Cycling performances of S/rGO electrode with CoS2/CP interlayer, S/rGO electrode with CP interlayer and S/rGO electrode without interlayer (bare S/rGO electrode) at 0.2 C. (b) Charge/discharge voltage profiles of S/rGO electrode with CoS2/CP interlayer. (c) Charge/discharge voltage profiles of S/rGO electrode with CP as interlayer. (d) Charge/ discharge voltage profiles of bare S/rGO electrode. (e) Discharge capacity comparison of S/rGO electrodes with CoS2/CP interlayer and CP interlayer at various rates. (f) Nyquist plots of impedance measurements of S/rGO electrodes with CoS2/CP interlayer and CP interlayer. Ma et al. Click to enlarge. |
The hierarchical porous CoS2/CP interlayer offers three main benefits, the team said:
It can act as the upper current collector, promote electron transport and provide a parallel buffering space between the CoS2/CP interlayer and Al foil for mitigating severe volume expansion. Furthermore, the existence of the upper current collector facilitates the dissolved polysulfides to capture the electrons quickly and enhance the utilization of the inner sulfur particles of the S/rGO cathode.
The hierarchical pore structure prolongs the path length of polysulfides arriving at the lithium anode, reducing impairment.
The polar Co-S bond can interact strongly with Li-S bond of Li2Sn/Li2S—i.e., tt is a highly effective approach for chemically bonding with Li2Sn/Li2S.
After two cycles’ at 0.1 C, a cell with an S/rGO electrode with CoS2/CP interlayer delivered the higher initial capacity of 1239.5 mAh g-1 in contrast to 950.0 mAh g-1 for S/rGO electrode with just a CP interlayer and 914.4 mAh g-1 for the bare S/rGO electrode.
Resources
Zhaoling Ma, Zhen Li, Kui Hu, Dongdong Liu, Jia Huo, Shuangyin Wang (2016) “The enhancement of polysulfide absorption in LiS batteries by hierarchically porous CoS2/carbon paper interlayer”, Journal of Power Sources, Volume 325, Pages 71-78 doi: 10.1016/j.jpowsour.2016.04.139
Resultados MUY pobres no es por desanimar pero veo un futuro muy incierto a las baterías de Li-S después de ver como el lider de esta tecnología Oxis Energy da pasos hacia atras y ver como han publicitado hace unos días una batería de 1,2kwh en un scooter Chino de 10ah y una energia gravimetrica de ¡¡¡¡¡152wh/kg!!!!! Como algo novedoso deja la moral por los suelos.......The future of battery tecnology is very black.
Posted by: Centurion | 13 June 2016 at 11:03 AM