Solid state accumulator

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A solid-state accumulator , also known as a solid- state battery or solid-state battery , is a special type of accumulator in which both electrodes and the electrolyte are made of solid material.

Layout and function

Solid-state accumulators differ from conventional accumulators in particular in terms of the solid electrolyte . The job of the electrolyte is to conduct ions between the anode and cathode. The ion to be conducted is different depending on the cell chemistry, for example the lithium cation in lithium-ion batteries or the sodium cation in sodium-ion batteries. The charge transport in solid electrolytes is often based on various jump processes in the solid lattice . The characteristics of these processes differ depending on the electrolyte used and also depend on the formation of various defects such as Schottky defects , Frenkel defects or occupied interstitial spaces.

To use solid electrolytes in solid-state batteries, they should have the highest possible ionic conductivity and very low electronic conductivity . In order for solid-state batteries to exceed the energy density of conventional accumulators, metallic anodes must be used . In the case of a lithium-ion battery , metallic lithium would have to be used instead of the graphite previously used . Metallic lithium tends to form dendrites when the battery is cycled . Dendrites can grow from the lithium anode to the cathode and thereby cause an electrical short circuit . That is also the reason why the use of metallic lithium in conventional batteries has not been possible until now. Further requirements for solid electrolytes are therefore good stability towards lithium and against the formation of dendrites . The reasons for the formation of dendrites in lithium-ion solid-state batteries have not yet been fully clarified and are being intensively researched.

The material classes used for lithium-ion solid-state batteries can be classified differently. Often there is a division into three material classes: polymeric, sulfidic or oxidic electrolytes.

Construction of a lithium-air accumulator with a solid electrolyte

Current lithium- air solid-state accumulators use an anode made of lithium, an electrolyte that consists either of a ceramic or of glass or of a glass-ceramic composite material, and a cathode of porous carbon. The anode and cathode are i. d. Usually separated from the electrolyte by polymer-ceramic composites, which improve the charge transfer at the anode and connect the cathode electrochemically to the electrolyte. The polymer-ceramic composites serve to reduce drag.

Examples of such ion conductors are Ag 4 Rb I 5 for the charge transport of Ag + ions and LiI / Al 2 O 3 mixtures for the charge transport of Li + ions.

properties

Solid-state accumulators basically have the following two properties: low power density and high energy density . The first limitation arises because of the difficulty in transmitting high currents across solid-solid interfaces . On the other hand, these accumulators have certain advantages that outweigh this disadvantage: They are easy to miniaturize (e.g. they can be manufactured in the form of a thin layer ), and there is no risk that the electrolyte could damage the accumulator through leaks. They usually have a very long service life and shelf life and usually do not show any abrupt changes in their performance even with temperature fluctuations (which in the case of liquid electrolytes can lead to freezing or boiling of the electrolyte). Another advantage of solid-state batteries (in contrast to lithium-ion batteries) is that they are not flammable.

The main disadvantage of solid-state accumulators is the low ion conductivity of most glass-ceramic electrolytes. The ion conductivity of current solid state electrolytes is still lower than the ion conductivity of liquid electrolytes.

The volume-power density determines the size, the mass-power density the weight of the cells. This plays an essential role in electromobility. The Ragone diagram illustrates the relationship between power density and energy density. According to IBM researchers, the theoretically achievable specific energy of lithium-air batteries (without the weight of the oxygen in the air) is more than 11 kWh per kilogram (kWh / kg). The researchers believe that a practical lithium-air battery could reach about a tenth of this theoretical maximum value.

Previous lithium-ion batteries

The disadvantages of current lithium-ion batteries include e.g. B. necessary cooling and other devices that can make up more than half of a lithium-ion battery. In addition, most liquid electrolytes are flammable, which requires additional safety devices. In order to extend the service life of the electrodes, the accumulator must also be cooled and it must be prevented that the accumulator is completely charged or discharged. The solid-state accumulators from Sakti3 are still based on lithium-ion technology, but the liquid electrolyte is replaced by a thin layer of solid-state electrolyte that is non-flammable. Some prototypes were quite robust and withstood thousands of charge-discharge cycles.

Web links

Individual evidence

  1. ↑ a b Zhonghui Gao, Huabin Sun, Lin Fu, Fangliang Ye, Yi Zhang: Promises, Challenges, and Recent Progress of Inorganic Solid-State Electrolytes for All-Solid-State Lithium Batteries . In: Advanced Materials . tape 30 , no. 17 , April 2018, p. 1705702 , doi : 10.1002 / adma.201705702 ( wiley.com [accessed December 18, 2019]).
  2. ↑ Kian Kerman, Alan Luntz, Venkatasubramanian Viswanathan, Yet-Ming Chiang, Zhebo Chen: Review — Practical Challenges Hindering the Development of Solid State Li Ion Batteries . In: Journal of The Electrochemical Society . tape 164 , no. 7 , 2017, ISSN  0013-4651 , p. A1731 – A1744 , doi : 10.1149 / 2.1571707jes ( ecsdl.org [accessed December 18, 2019]).
  3. ↑ Fudong Han, Andrew S. Westover, Jie Yue, Xiulin Fan, Fei Wang: High electronic conductivity as the origin of lithium dendrite formation within solid electrolytes . In: Nature Energy . tape 4 , no. 3 , March 2019, ISSN  2058-7546 , p. 187–196 , doi : 10.1038 / s41560-018-0312-z ( nature.com [accessed December 18, 2019]).
  4. ↑ Joscha Schnell, Till Günther, Thomas Knoche, Christoph Vieider, Larissa Köhler: All-solid-state lithium-ion and lithium metal batteries - paving the way to large-scale production . In: Journal of Power Sources . tape 382 , April 2018, p. 160–175 , doi : 10.1016 / j.jpowsour.2018.02.062 ( elsevier.com [accessed December 18, 2019]).
  5. ↑ a b Binod Kumar, Jitendra Kumar: Cathodes for Solid-State Lithium-Oxygen Cells: Roles of Nasicon Glass-Ceramics . In: Journal of The Electrochemical Society . tape 157 , no. 5 , January 5, 2010, p. A611-A616 , doi : 10.1149 / 1.3356988 .
  6. ↑ Infinite Power Solutions introduces paper-thin battery. In: elektroniknet.de. June 6, 2012, accessed November 2, 2013 .
  7. ↑ The Battery 500 project: 800 km range for electric cars. IBM, accessed December 12, 2013 .
  8. ↑ a b Kevin Bullis: Solid-State Batteries. In: MIT Technology Review. May 2011, accessed November 2, 2013 .