Dynamic Structure Discovery and Ion Transport in Liquid Battery Electrolytes
Doktorsavhandling, 2020

The lithium-ion battery (LIB), the realisation of which earned the Nobel Prize in Chemistry 2019, has since its 1991 commercialisation become the dominant energy storage technology first for cell phones and other mobile electronics, then for power tools and other domestic appliances, and currently for electric cars and other vehicles. However, many applications would still benefit from higher power and energy densities, longer life-lengths and safer batteries. Such improvements would for example accelerate the electrification of transport, lower the pollution and the greenhouse gas emissions. Electrolytes are extremely crucial for the operation of the LIBs, yet they have so far changed surprisingly little the last 25 years. Further improvement can be made by novel electrolyte concepts. Highly concentrated electrolytes (HCEs) may enable higher energy and power densities, as well as improved thermal, chemical and electrochemical stabilities as compared to the current state-of-the-art, while also being more flexible in their composition. They also have more complex structures and ion transport mechanisms. I here present a novel method for studying both more standard electrolytes and HCEs by analysing molecular dynamics simulation trajectories. This method automatically detects the time-dependent structures present and characterises them by statistical physics, giving an extraordinarily detailed view of the structure and dynamics. I describe the theory and implementation of this method as well as its application to several HCEs and the ubiquitous LP30 electrolyte. These studies enhance the picture of ion transport conveyed previously and future application should add substantially to the design of battery electrolytes and beyond.

dynamic structure discovery

ion transport mechanisms

lithium-ion batteries

electrolytes

statistical physics

PJ-salen, Fysik Origo byggnad
Opponent: Prof. Arnulf Latz, Institute of Engineering Thermodynamics, German Aerospace Center (DLR), Tyskland

Författare

Rasmus Andersson

Chalmers, Fysik, Materialfysik

Ion Transport Mechanisms via Time-Dependent Local Structure and Dynamics in Highly Concentrated Electrolytes

Journal of the Electrochemical Society,; Vol. 167(2020)

Artikel i vetenskaplig tidskrift

R. Andersson, F. Årén, A.A. Franco, P. Johansson. CHAMPION: Chalmers Hierarchical Atomic, Molecular, Polymeric & Ionic Analysis Toolkit

R. Andersson, F. Årén, A.A. Franco, P. Johansson. Structure, Dynamics and Ion Transport Mechanisms in Lithium-Ion Battery Electrolytes: Origin and Onset of Highly Concentrated Electrolyte Behavior

R. Andersson, O. Borodin, P. Johansson. Structure and Dynamics of Ion Transport in the Ubiquitous Lithium-ion Battery Electrolyte LP30

Batterielektrolyternas hemliga liv

Litiumjonbatterier har erövrat världen via mobiltelefoner och laptops, och är nu i färd med att slå igenom även i fordon och storskalig ellagring och därmed accelerera en grön omställning.

Dagens litiumjonbatterier är dock inte perfekta. Elektrolyterna som transporterar joner mellan elektroderna innehåller brandfarliga, instabila och giftiga ingredienser. Dessvärre är de svåra att modifiera utan prestandaförluster. För nya säkrare, grönare och starkare batterier behövs nya elektrolytkoncept.

Ett sådant är högkoncentrerade elektrolyter, som består av samma sorts beståndsdelar som dagens elektrolyter: ett salt av litiumjoner och negativa joner som lösts upp i ett lösningsmedel. Skillnaden mot dagens elektrolyter är att salthalten är mycket högre, vilket gör elektrolyten stabilare och öppnar upp för nya sammansättningar och egenskaper.

Högkoncentrerade elektrolyter är, liksom andra lovande framtidskoncept, svårare att förstå på den molekylära skalan vilket dock är nödvändigt för att sätta riktningen för framtida forskning och utveckling. För att bidra till förståelsen av elektrolyter i allmänhet har jag utvecklat metoder och mjukvaran CHAMPION för att hitta vilka atomer som hänger ihop och beskriva deras beteende i detalj. I avhandlingen tillämpas metoderna på ett antal ganska olika batterielektrolyter, men troligen kan metoderna användas även för helt andra material. Arbetet har också lett till en patentansökan och till grundandet av företaget Compular AB där jag är medgrundare.

The secret life of battery electrolytes

Lithium-ion batteries have conquered the world via cell phones and laptops and are now en route to disrupt transport and large-scale energy storage, thereby accelerating a green transition.

Lithium-ion batteries are not perfect, though. The electrolytes transporting ions between the electrodes contain flammable, unstable, and toxic ingredients. They are unfortunately hard to modify without performance losses. Safer, greener and stronger batteries are therefore in need of new electrolyte concepts.

 One such candidate is highly concentrated electrolytes, which consist of the same kind of ingredients as today's electrolytes: a salt of lithium ions and negative ions dissolved in a solvent. Compared to today's electrolytes the salt content is much higher, making the electrolyte more stable and opening up a larger design space.

 Highly concentrated electrolytes and other promising concepts are harder to understand on the molecular scale, which however is necessary for guiding further research and development. To advance the understanding of electrolytes in general I have developed methods and the software CHAMPION to find out which atoms move together and study their behaviour in great detail. The methods are here applied to a number of quite different battery electrolytes, and the methods can likely also be used for completely different materials. The work has also resulted in a pending patent and in the founding of the start-up Compular AB of which I am a co-founder.

Drivkrafter

Hållbar utveckling

Innovation och entreprenörskap

Styrkeområden

Transport

Energi

Materialvetenskap

Ämneskategorier

Fysikalisk kemi

Fysik

Den kondenserade materiens fysik

Fundament

Grundläggande vetenskaper

Infrastruktur

C3SE (Chalmers Centre for Computational Science and Engineering)

ISBN

978-91-7905-413-7

Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 4880

Utgivare

Chalmers tekniska högskola

PJ-salen, Fysik Origo byggnad

Opponent: Prof. Arnulf Latz, Institute of Engineering Thermodynamics, German Aerospace Center (DLR), Tyskland

Mer information

Senast uppdaterat

2020-11-27