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China team develops new high-performance cathode for Li-sulfur batteries

Researchers led by Prof. Jian Liu and Prof.Zhongshuai Wu from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences have developed Fe1-xS-decorated mesoporous carbon spheres as a cathode material for lithium-sulfur batteries.

Fe1−xS‐NC has a high specific surface area (627 m2 g−1), large pore volume (0.41 cm3 g−1), and enhanced adsorption and electrocatalytic transition toward lithium polysulfides (LiPs). The material shows excellent polysulfide catalytic activity and cyclic stability. An open-access paper on their work is published in the journal Advanced Energy Materials.

Lithium-sulfur batteries have a high theoretical energy density of 2600 Wh kg-1 and a theoretical capacity of 1675 mAh g-1. However, the slow conversion reaction dynamics of sulfur in the process of charging and discharging lead to low utilization rate of sulfur and a serious polysulfide shuttle effect. This further causes low capacity and stability of lithium-sulfur batteries.

An electrocatalytic system is needed such that the catalytic transformation of polysulfide can be realized efficiently and steadily under high sulfur loading, resulting in high cyclic stability of the lithium-sulfur battery.

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Schematic illustration for molecular-level design of pyrrhotite electrocatalyst decorated hierarchical porous carbon spheres as nanoreactors for lithium-sulfur batteries. (Image by DICP)


In the current study, the researchers designed a mesoporous carbon material decorated with highly dispersed Fe1-xS electrocatalyst nanoparticles (Fe1-xS-NC), and applied it as lithium-sulfur battery cathode for high catalytic activity and high sulfur loading.

The material features low mass density, high porosity, and highly dispersed electrocatalyst, which significantly improves the adsorption and catalytic conversion capacity of polysulfides.

The researchers found that there was virtually no decay in capacity of Fe1-xS-NC from an initial value of 1070 mAh g-1 after 200 cycles and under a current density of 0.5 C.

The high electrocatalytic activity of Fe1−xS nanoparticles coupled with their high electronic conductivity and accessibility allow for efficient adsorption and conversion of LiPs to Li2S. The electrocatalysts are well dispersed in the hierarchically porous carbon spheres with large mesoporous cavities, which can accommodate high sulfur loading, modulate volume variations during charge/discharge cycles and enhance mass transfer of electrolyte to active sites. As a result, high‐performance cathode with exceptional stability (no capacity fading at 0.5 C after 200 cycles), high rate capability and excellent cycling performance at high sulfur loading of 8.14 mg cm−2, are achieved for LSBs.

This work demonstrates the potential applicability of well-dispersed metal sulfides at low metal loading inside highly porous carbon spheres as high‐performance nanoreactors for LSBs. The results can also open opportunities for construction of more complex architectures such as hollow structures, yolk–shell or multishell particles doped with metal sulfides via molecular‐level design to improve the performance of LSBs in terms of long‐term cycling stability and high sulfur loading. Molecular level design could also be an attractive method for the synthesis of highly dispersed metal nitrides, oxides, phosphides, or halides inside a carbon support by the suitable choice of a precursor and synthesis methods.

—Boyjoo et al.

Resources

  • Boyjoo, Y., Shi, H. D., Olsson, E., Cai, Q., Wu, Z.‐S., Liu, J., Lu, G. Q. (2020) “Molecular‐Level Design of Pyrrhotite Electrocatalyst Decorated Hierarchical Porous Carbon Spheres as Nanoreactors for Lithium–Sulfur Batteries.” Adv. Energy Mater. 2000651 doi: 10.1002/aenm.202000651

Comments

gryf

Lately, I have been focusing on the Samsung All Solid State Battery (ASSB) which looks very promising and uses a ceramic electrolyte. However, there may be an alternative ASSB that uses Solid Polymer Electrolytes (SPE).

The research posted here looks into sulfur‐based cathodes using FeS nanoparticles embedded within the carbon spheres. The interesting part, if you read the open source article, is in addition to the high performance and long life is the way the cathode is made. using a resorcinol‐formaldehyde (RF) resin. In Part 2, Results and Discussion, “In this work, the metal precursor is directly added into the mixture during the polymer resin synthesis and resorcinol sulfide (RS) is used as a source of C and S.”

The reason to bring this up is that yesterday I read in InsideEVS that Nissan had licensed All-Polymer Battery Tech To a new company called APB (a subsidiary of Sanyo Chemical) to use in energy storage systems. Not sure what material is used in the battery except that it is polymer. You can read about it here (https://www.sanyo-chemical.co.jp/eng/products_info/development/battery) and here (https://powerpulse.net/all-polymer-battery-startup-apb-closes-¥8-billion-financing/). This is a Bipolar All-Polymer Battery and the was developed by Hideaki Horie (a legend at Nissan who worked on the Nissan Leaf).

Lithium Metal Polymer batteries have been around for some time (Bollore Blue Solutions builds a 250 kWh battery for Bus applications - https://blue-storage.com/en/our-product/). However, these batteries operate around 60°C (140°F) and have an energy density of only 121 Wh/kg. What is needed is a battery with a Solid Polymer electrolytes (SPE) that operates at a lower temperature and has good conductivity.

Recently, there was research into a “Natural halloysite nano-clay electrolyte for advanced all-solid-state lithium-sulfur batteries” (https://www.sciencedirect.com/science/article/abs/pii/S2211285516305407) that had a SPE, operated at 25 °C with exceptional ionic conductivity of 1.11×10− cm−1.

This work was headed by Jan Miller of the University of Utah. Could this be related to the "Nikola Battery" (note: Trevor Milton, CEO is from Utah).
Can all of this lead to the next generation ASSB?

SJC_1

The lithium anode coatings and new solvents seem to be the next step in higher energy density.

yoatmon

New advancements being proposed in battery technology are all based on different chemistries and materials but the cell architecture always remains the old common two-dimensional structure. The expected quantum leap will never occur until the cell architecture is changed to a three-dimensional structure. A three-dimensional structure will allow high contact surface and subsequently lower internal resistance and mass whilst increasing energy density considerably. Currently the "Lithium horse" is being flogged to death and a far better alternative - Magnesium - is being wholly ignored.
Optimized 3D structures can be achieved only with 3D printers. There simply is no other way to to ensure precise reproduction of the necessary micro structures. The presently employed procedures leave the development of such structures to the chaotic reign of chance.

gryf

The All-Polymer Battery is a 3-D Bipolar structure and the entire Battery Pack is "printed" in rolls like a newspaper. Everything is polymer:the cathode, anode, electrolyte, and current collectors. It uses thick anodes and cathodes that are binder free. This is better than the CTP (cell-to-pack) technology which BYD and CATL are using that impresses Elon Musk. Note: the BYD Blade Battery has a gravimetric cell-to-pack ratio of 84.5 % (the Tesla Model 3 has 71%). This battery could be over 90%.

This is the company website (https://apb.co.jp/en/).

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