Lithium-sulfur accumulator

The lithium-sulfur accumulator is a type of accumulator that is still being researched and developed. The theoretically maximum possible energy density of this battery, which is based on the elements lithium and sulfur , is 2600 Wh / kg (2800 Wh / l), whereby only the masses of sulfur and lithium are taken into account when calculating these values and complete conversions are assumed. These theoretical values ​​are among the highest of all accumulators, but in practice only an energy density of up to 350 Wh / kg was achieved, which corresponds to almost 15% of the purely theoretical value. Up to now, higher energy densities have only been possible at the expense of the battery life. Typical accumulators with an energy density of 350 Wh / kg can so far store and release the corresponding amount of energy over around one hundred charging and discharging cycles. Unlike z. B. Lithium-ion batteries , the cell voltage does not change linearly to the charge level, instead there are two plateaus, at 2.4 and 2.1 volts. The determination of the charge level is therefore a little more complex.

The first patent for a battery, for which the pair of lithium and sulfur was proposed among other material combinations, was filed in 1958 and granted in 1962.

Electrochemistry

During the discharge, lithium is dissolved at the anode . At the cathode, it combines with sulfur , there arise lithium sulfides, when fully discharged, the lithium sulfide Li ₂ S:

${\displaystyle \mathrm {S_{8}+16\ Li\longrightarrow \ 8\ Li_{2}S} }$

During the charging process, the resulting compound is dissolved again and sulfur is re-formed. Lithium metal is deposited again on the negative pole or a lithium alloy is formed:

${\displaystyle \mathrm {8\ Li_{2}S\longrightarrow \ S_{8}+16\ Li} }$

Mixtures of different lithium sulfides are formed as intermediate products during discharging and charging. When discharging, the proportion of sulfur in the mixture continues to decrease because the lithium content continues to increase. This can be done schematically with the series:

${\displaystyle \mathrm {S_{8}\longrightarrow \ Li_{2}S_{8}\longrightarrow \ Li_{2}S_{6}\longrightarrow \ Li_{2}S_{5}\longrightarrow \ Li_{2}S_{4}\longrightarrow \ Li_{2}S_{3}\longrightarrow \ Li_{2}S_{2}\longrightarrow \ Li_{2}S} }$

are shown, but the sulfides Li ₂ S ₈ , Li ₂ S ₆ , Li ₂ S ₅ , Li ₂ S ₄ and Li ₂ S ₂ can be present in a mixture next to one another in very different concentrations.

The reaction corresponds to that of sodium-sulfur accumulators , with lithium taking over the function of sodium .

In the lithium-sulfur accumulator, the charge is transported within the electrolyte by lithium ions. In the lithium-sulfur battery, a chemical reaction takes place in which substances are completely converted, whereby u. Under certain circumstances, crystals of sulfur or lithium sulfide can be newly formed or dissolved, while an intercalation reaction takes place in lithium-ion batteries .

Since sulfur as an insulator has extremely poor electrical conductivity, it must be present in a conductive mixture so that the discharge can start. To do this, carbon is added to the sulfur . If the amount of carbon is too small, the sulfur is only used incompletely due to the lack of electrical contact, and the specific capacity becomes too small. If the amount of carbon is too large, the associated additional mass of electrochemically inactive material also leads to low specific capacities. A significant part of the research activities therefore tries to optimize this property by using special types of carbon: Not only are graphite and various types of carbon black tested, but also graphene , carbon nanotubes and porous carbons.

But there are also variants due to different electrolytes and different mixtures at the anode: In addition to the use of metallic lithium, silicon and tin in particular, as in the tin-sulfur-lithium accumulator , have been proposed as anode materials that are intended to improve cyclability.

For the lithium-sulfur cell, the most important components besides lithium are sulfur and carbon, inexpensive, widely used and readily available. Sulfur and carbon are non-toxic, but the lithium sulfides that are produced during discharge are toxic, they react with acids to form toxic hydrogen sulfide gas . Therefore, the cells must be closed gas-tight.

state of research

For more than four decades, the cells produced in research suffered from poor rechargeability, as the charge and discharge cycles led to a rapid loss of capacity. Only since about 2013 have there been reports from research groups that have operated lithium-sulfur batteries for a thousand cycles and more.

A review article published in December 2014 lists e.g. B. List publications from eleven groups that have reached this number of cycles. This includes scientists at the Dresden Fraunhofer IWS , in 2013 a new battery structure with a silicon - carbon - anode imagined that the number of charge cycles and button cells sevenfold from 200 to 1400th At the beginning of 2014, the research group achieved 2000 cycles. Also in 2013, researchers at the Lawrence Berkeley National Laboratory reported that their optimized sulfur electrode had a higher capacity than the cathode in lithium-ion cells after 1500 charge-discharge cycles. They used a special electrolyte based on an ionic liquid . In the meantime 3000 or over 4000 cycles have been demonstrated.

In 2016, researchers at Cambridge University reported further advances in electrode durability. This shows that high cycle numbers are possible in principle, but further improvements are necessary until the Li-S cells are a real alternative to conventional lithium-ion batteries, which are also constantly being improved.

Australian researchers stated in January 2020 that they had developed the most powerful lithium-sulfur battery to date, in which they use a particularly robust sulfur electrode in which the sulfur is embedded in a special layer of a binder and carbon, which increases the power and reduce capacity loss.

After the British company OXIS Energy reported in October 2018 that it had developed a cell with 425 Wh / kg, a new article was published in August 2020 in which a ceramic layer around the cathode is reported, and 470 Wh / kg have now been achieved and it can be assumed that 500 Wh / kg can be achieved within one year.

Web links

• Kevin Bullis: Sultry hope. In: Technology Review. Heise Zeitschriften Verlag, May 22, 2009, accessed on August 19, 2009 . 
• Electrochemical Characteristics of Lithium / Sulfur Battery (PDF file; 10 kB)
• Fundamental Chemistry of Sion Power Li / S Battery. IBA-HBC 2006 (PDF file; 1.86 MB)
• What you need to know about lithium-sulfur batteries. In: www.elektroniknet.de. WEKA Fachmedien, February 6, 2014, accessed on February 12, 2014 . 
• Lithium-sulfur high-energy accumulators with reversible matrix-intercalated sulfur cathodes (PDF English)

Individual evidence

1. ↑ Khalil Amine, Ryoji Kanno, Yonhua Tzeng: Rechargeable lithium batteries and beyond: Progress, challenges, and future directions . In: Cambridge University Press (Ed.): MRS Bulletin . tape 39 , no. 05 , 2014, p. 395–401 , doi : 10.1557 / mrs.2014.62 (English).
2. ^ Bill Moore: Sion Introduces a Lithium Sulfur Rechargeable Battery. EVWorld.com, Inc., accessed June 8, 2014 . 
3. ↑ ^{a b c} Mathias Bloch: What you need to know about lithium-sulfur batteries. WEKA FACHMEDIEN GmbH, February 6, 2014, accessed on June 8, 2014 . 
4. ↑ ^{a b} Hong-Jie Peng, Jia-Qi Huang, Xin-Bing Cheng, Qiang Zhang: Review on High-Loading and High-Energy Lithium – Sulfur Batteries . In: Advanced Energy Materials . Wiley, 2017, ISSN  1614-6840 , 1700260, doi : 10.1002 / aenm.201700260 ( wiley.com ).
5. ↑ ^{a b} With Ultralight Lithium-Sulfur Batteries, Electric Airplanes Could Finally Take Off. In: spectrum.ieee.org. August 19, 2020, accessed on August 19, 2020 . 
6. ↑ Patent US3043896 : Electric Dry Cells and Storage Batteries. Applied on November 24, 1958 , published on July 10, 1962 , applicant: Electric Techniques Corporation NV, Willemstad, Curaçao, inventor: Danuta Herbert, Juliusz Ulam (application in France: Nov. 26, 1957). ‌
7. ↑ Tudron, FB, Akridge, JR, and Puglisi, VJ (2004): Lithium-Sulfur Rechargeable Batteries: Characteristics, State of Development, and Applicability to Powering Portable Electronics ( Memento of the original of July 14, 2011 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF; 330 kB)  (Tucson, AZ: Sion Power).
8. ↑ Xin Fang, Huisheng Peng: A Revolution in Electrodes: Recent Progress in Rechargeable Lithium – Sulfur Batteries . The game of Li-S Batteries. In: small . tape 11 , no. 13 . WILEY-VCH, April 1, 2015, ISSN  1613-6829 , p. 1488–1511 , doi : 10.1002 / smll.201402354 ( edu.cn [PDF; accessed on May 8, 2016]). A Revolution in Electrodes: Recent Progress in Rechargeable Lithium – Sulfur Batteries ( Memento of the original from May 8, 2016 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice.  
9. ↑ Longer life for lithium-sulfur batteries , press release No. V of Fraunhofer IWS Dresden from April 1, 2013, accessed on April 11, 2013.
10. ↑ ^{a b} Min-Kyu Song, Yuegang Zhang, Elton J. Cairns: A Long-Life, High-Rate Lithium / Sulfur Cell: A Multifaceted Approach to Enhancing Cell Performance . In: Nano Letters . 2013, doi : 10.1021 / nl402793z .
11. ↑ Feng Wu, Yusheng Ye, Renjie Chen, Ji Qian, Teng Zhao, Li Li, Wenhui Li: Systematic Effect for an Ultralong Cycle Lithium – Sulfur Battery . In: Nano Letters . tape 15 , no. 11 . American Chemical Society ACS, October 26, 2015, ISSN  1530-6992 , p. 7431-7439 , doi : 10.1021 / acs.nanolett.5b02864 .
12. ↑ Yunhua Xu, Yang Wen, Yujie Zhu, Karen Gaskell, Katie A. Cychosz, Bryan Eichhorn, Kang Xu, Chunsheng Wang: Confined Sulfur in Microporous Carbon Renders Superior Cycling Stability in Li / S Batteries . In: Advanced Functional Materials . tape 25 , no. 27 . Wiley-VCH, June 1, 2015, p. 4312–4320 , doi : 10.1002 / adfm.201500983 .
13. ↑ http://www.cam.ac.uk/research/news/next-generation-smartphone-battery-inspired-by-the-gut
14. ↑ Ariel Rosenman, Elena Markevich, Gregory Salitra, Doron Aurbach, Arnd Garsuch, Frederick Francois Chesneau: Review on Li-Sulfur Battery Systems: an Integral Perspective . In: Advanced Energy Materials . Special Issue: Understanding the Lithium – Sulfur Battery System at Relevant Scales. tape 5 , no. 16 . Wiley-VCH, August 19, 2015, ISSN  1614-6840 , doi : 10.1002 / aenm.201500212 .
15. ↑ New super battery recycles waste product. In: n-tv.de. January 8, 2020, accessed January 11, 2020 . 
16. ↑ Mahdokht Shaibani et al .: Expansion-tolerant architectures for stable cycling of ultrahigh-loading sulfur cathodes in lithium-sulfur batteries . In: Science Advances . tape 6 , no. 1 , 2020, doi : 10.1126 / sciadv.aay2757 .
17. ↑ OXIS ENERGY Progresses its Lithium Sulfur (Li-S) cell technology to 450WH / kg. - Oxis Energy. In: oxisenergy.com. October 3, 2018, accessed October 4, 2018 .