solid electrolyte – Lightsources.org

Development of Solid Electrolyte to Enhance Lithium Battery Performance

2025/02/052025/02/10

How convenient would it be if we could use smartphone batteries longer and more safely? A research team led by Professor Moon Jeong Park at POSTECH (Pohang University of Science and Technology) has announced an innovative research outcome that could turn this vision into reality, gaining significant attention from both academia and the public. In particular, this study builds upon their previous research published in Science last year, where they introduced the “plumber’s nightmare” structure to maximize lithium-ion battery performance, making it even more meaningful.

Lithium-ion batteries are broadly used in modern technologies, including smartphones. While the electrolyte is one of the core components of a battery, conventional liquid electrolytes have risks of leakage or explosion. Solid-state electrolytes are emerging as an alternative, but there have been limitations in balancing the electrolyte’s ‘mechanical strength’ and ‘ionic conductivity’.

A research team led by Professor Park Moon Jeong, Dr. Kim Ji-hoon, and doctoral student Lee Ho-joon from the Department of Chemistry at POSTECH has presented an innovative method that dramatically improves both the ionic conductivity and mechanical properties of batteries by adding only a tiny amount of lithium salt – less than one-tenth the level used in conventional electrolyte production that used more than a few mole concentration of lithium salt to increase ionic conductivity.

The key to this approach is that adding a very small amount of lithium salt to the PS-b-PEO¹⁾ block copolymer²⁾ selectively locates it at the terminal hydroxy groups (-OH) of the PEO chain. Through this, the research team succeeded in forming a sophisticated “plumber’s nightmare” structure unobserved in conventional polymer electrolyte systems.

The “plumber’s nightmare” structure refers to an arrangement where all polymer chain ends are entangled inward, just like plumbing pipes gather internally. This structure has six channels formed by the polymer chains, all connected. The structure provides a stable ion pathway as the lithium ions are locally present in the hydroxy groups at the center of the polymer channels. As a result, it creates an environment where ions can move quickly and efficiently while maintaining the hard and robust structure of the electrolyte.

BESSY II shows how solid-state batteries degrade

2024/07/092024/07/09

Solid-state batteries have several advantages: they can store more energy and are safer than batteries with liquid electrolytes. However, they do not last as long and their capacity decreases with each charge cycle. But it doesn’t have to stay that way: Researchers are already on the trail of the causes. In the journal ACS Energy Letters, a team from HZB and Justus-Liebig-Universität, Giessen, presents a new method for precisely monitoring electrochemical reactions during the operation of a solid-state battery using photoelectron spectroscopy at BESSY II. The results help to improve battery materials and design.

Solid-state batteries use a solid ion conductor between the battery electrodes instead of a liquid electrolyte, which allows lithium to be transported during charging and discharging. This has advantages including increased safety during operation and generally higher capacity. However, the lifetime of solid-state batteries is still very limited. This is because decomposition products and interphases form at the interfaces between the electrolyte and the electrode, which hinders the transport of the lithium ions and leads to consumption of active lithium so that the capacity of the batteries decreases with each charge cycle.

What happens during operation?

Now a team led by HZB researchers Dr. Elmar Kataev and Prof. Marcus Bär has developed a new approach to analyse the electrochemical reactions at the interface between solid electrolyte and electrode with high temporal resolution. Kataev explains the research question: “Under what conditions and at what voltage do such reactions occur, and how does the chemical composition of these intermediate phases evolve during cell operation?”

Best candidate LiPSCl examined

For the study, they analysed samples of the solid electrolyte Li₆PS₅Cl, a material that is considered the best candidate for solid-state batteries as it possesses high ionic conductivity. They worked closely with the team of battery expert Professor Jürgen Janek from the Justus Liebig University Giessen (JLU Giessen). An extremely thin layer of nickel (30 atomic layers or 6 nanometres) served as the working electrode. A film of lithium was pressed onto the other side of the Li₆PS₅Cl pellet to act as a counter electrode.

Read more on HZB website

Image: SEM images of LPSCl pellets before (left) and after (right) the operando HAXPES experiment

A first step to designing better solid-state batteries

2023/05/232023/06/05

Electrifying transportation is an essential step towards mitigating climate change. To improve the power, efficiency and safety of electric vehicles, researchers must continue to develop better batteries. All-solid-state lithium batteries (SSBs), which have a solid electrolyte instead of a liquid, are safer than traditional lithium-ion batteries because they are less flammable and more stable at higher temperatures. They could also have higher energy densities than lithium-ion batteries, allowing for longer lasting batteries in smaller sizes for portable electronics and other applications.

A research team led by Joshua Gallaway of Northeastern University in Boston and scientists at the Department of Energy’s (DOE) Argonne National Laboratory recently tested how the composition of thick cathodes affected electrochemical reactions in SSBs. The team used the resources of the Advanced Photon Source (APS), a DOE Office of Science user facility at Argonne. Their discoveries were published in the journal ACS Energy Letters.

“How all-solid-state batteries are designed will determine what their applications will be and how they will be optimized moving forward,” — Josh Gallaway, Northeastern University

Gallaway relates batteries to sandwiches — they are comprised of an anode on one side, a cathode on the other, a separator in the middle, and electrolyte solution throughout. When batteries provide power, lithium ions flow from the anode to cathode through the electrolyte. While SSBs don’t require traditional separators because the electrolyte separates the anode and cathode, they do require thick cathodes.

In this study, Gallaway and his colleagues evaluated batteries with thick cathodes that were comprised of two materials: a sulfide solid electrolyte called LPSC and an NMC (nickel, manganese, cobalt) cathode active material (CAM). They altered the composition of these two materials, so some batteries were 80% CAM, 20% LPSC, while others were 70% CAM, 30% LPSC and 40% CAM, 60% LPSC. Then, they used X-ray imaging and scattering at APS beamline 6-BM-A to measure six slices within the cathode and solid-state electrolyte.