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Gel polymer electrolyte for stabilizing sulfur composite electrodes for long-life, high-energy Li-S batteries

24 July 2017

Researchers in Sweden and Italy have devised a simple strategy to address the issues currently hampering commercialization of high-energy density Li-sulfure batteries, including limited practical energy density, life time and the scaling-up of materials and production processes.

In a paper in the Journal ChemSusChem they report that using a novel gel polymer electrolyte (GPE) enables stable performance close to the theoretical capacity (1675 mAh g-1) of a low cost sulfur-carbon composite with high active material loading, i.e. 70% S. The GPE prevents sulfur dissolution and reduces migration of polysulfide species to the anode.

The challenges with an increased energy density and reduced cost of secondary batteries can only be tackled by new battery chemistries. Among the most promising chemistries is the one based on the electrochemical reaction of lithium and sulfur, the Li-sulfur battery. The interest in this technology is spurred by the high theoretical capacity (1675 mAh/g) and energy density (2600 Wh/kg). Furthermore, the natural abundance and the low cost of the active material, i.e. sulfur, are expected to reduce the costs of Li-sulfur based energy storage systems compared to current Li-ion batteries. However, in practice there are several problems which prevent the technology from being implemented. These arise from the fact that the intermediate products, polysulfides, formed during the electrochemical reaction, going from S to Li2S, are soluble in common electrolytes used, leading to a low cycle life.

To mitigate those problems large efforts have been spent in the last decade to find new electrolytes as well as to design advanced composite cathode materials that limit the dissolution of polysulfides. … In this paper, we report on a powerful strategy to stabilize a high-loading (i.e. 70% S) sulfur composite cathode using a polyvinylidene fluoride-based (PVdF) gel polymer electrolyte (GPE). The S-C composite is synthesized by a straightforward route using high energy mechanical milling (HEMM) technique, i.e. a process very suitable for scaling-up. With a standard liquid electrolyte this kind of electrode would be quickly dissolved leading to formation of polysulfides and capacity fading. We demonstrated that the GPE, prepared by solvent casting and swollen with a liquid electrolyte solution, mitigates sulfur dissolution thus stabilizing the delivered capacity to a value close to the theoretical limit for the Li-S process (1675 mAh g-1).

—Agostini et al.

The GPE was prepared by solvent casting providing a porous inner-structure in order to be able to trap a liquid electrolyte phase. The membrane has a low surface area of 3.5 m2/g and micro-pores with the size of about 10 nm in average—a low value compared to that of a commercial Whatman separator (i.e. 0.1 μm). Both surface area and pores size of the GPE membrane were tailored to reduce the electrolyte up-take during the swelling process in the liquid electrolyte solution.

The researchers compared the liquid electrolyte uptake of the GPE membrane and of a commercial Whatman separator. They found a huge difference in the amount of electrolyte taken up, 640% for the Whatman separator and about 40% for the GPE membrane, confirming that the difference in porosity and pore size reduces the volume available in the GPE membrane. Even though the uptake of the liquid electrolyte is lower the conductivity of the swollen GPE membranes is good.

They then tested the GPE in a Li-S cell utilizing a sulfur-carbon composite with high sulfur loading (70%) and compared the performance to cells using a standard Whatman separator.

Discharge capacity upon cycle number comparison between the cells using the GPE (green) and the Whatman membrane (red). Agostini et al. Click to enlarge.


  • Agostini, M., Lim, D. H., Sadd, M., Chiara, F., Navarra, M. A., Panero, S., Brutti, S., Matic, A. and Scrosati, B. (2017) “Stabilizing the performance of high-capacity sulfur composite electrodes by a novel gel polymer electrolyte configuration.” ChemSusChem doi: 10.1002/cssc.201700977

July 24, 2017 in Batteries, Li-Sulfur | Permalink | Comments (5)


Better electrolytes are key to good LiS performance.

The Next Gen Lithium battery will very likely be either Li-S of Li-Air. A clear picture of the components of the Li-S battery are starting to be developed.
The anode looks like it will be Lithium metal now that the problems with dendrites are being solved.
The electrolyte is the next critical component and most work is being done with solid electrolytes - either polymeric or glass ceramic - which are safer than liquid electrolytes.
There was an interesting NOVA TV show called "Search for the Super Battery" which reviewed Mike Zimmerman and Ionic Materials Solid Polymer Electrolyte.
John Goodenough at U of Texas is doing work on Glass Ceramic Electrolytes.
Bruno Scrosati who wrote this paper has an earlier work where his team discusses Solid Electrolytes, "Challenges and prospects of the role of solid electrolytes in the revitalization of lithium metal batteries" (
This paper focuses on the Sulfur Cathode and uses a Gel Polymer Electrolyte (basically a polymeric electrolyte with liquid electrolyte added).
Possibly all of the parts of the Li-S battery are ready for the Battery Manufacturers to work on the final development phase.

Estudios muy prometedores desde luego..........Pero el pionero sera Sion Power con su velda de 400wh/kg y 350 ciclos a 1C para 2018 y Oxis energy con su celda de 500wh/kg y 1.500 ciclos a 0,2C PARAQ 2019-2020.

No ones here dare to talk about where the ones parking in the streets will recharge and at what cost.

Street lights and associated wiring could be upgraded (to LED + better wiring + slow chargers) to accept/feed 3 to 6 PHEVs, BEVs and/or FCEVs per street light.

The cost of e-energy consumed could be coupled/added to parking fees. Payment could be with credit/debit cards. Extra revenues could be used to better maintain streets, sidewalks and pay for street lights.

No more free curbside parking.

Cities could resell e-energy at twice (+) their total cost.

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