My projects
Current personal projects
Lithium Inventory
2023 - present
Lithium Inventory is intended to be a knowledge hub for battery science and electrochemistry, focusing primarily on cell chemistry, experimental methods and fundamental concepts. Lithium Inventory is developed out of educational material formerly hosted on this site, particularly the introduction to electrochemical impedance spectroscopy (EIS).
Basic battery cell property modelling
I am collecting together the code I use (written in Julia) to estimate basic battery cell properties (capacity, energy, energy density, specific energy etc), and including some Jupyter notebooks with some example use cases. I have used this code often for reality checking the potential of new battery chemistries and for predicting the potential for products from some startup companies developing new battery technologies.
Current academic projects
Heterogeneous ageing of lithium-ion batteries
2020 - present
Characterising heterogeneous (non-uniform) ageing in large format Li-ion cells has developed as a research interest both in internal research projects and the externally-funded ALINE project.
As part of the fourth phase of the Swedish automotive industry – academia collaboration, I initiated the project “HALIBATT” together with my former colleague Matilda Klett. I am co-supervising an industrial PhD student, Aamer Siddiqui, with the aim to develop rapid methods for cell teardown and quantification of heterogeneity in a large format cell.
Within this project I have patented a rapid post mortem electrochemical method to map local state of health in a large format cell.
Ageing mechanisms in Ni-rich NMC & NCA electrodes
2019 - present
I am coordinating the third phase of a large research collaboration between industry and academia in Sweden (Scania, AB Volvo, Volvo Car Corporation, Uppsala University, KTH, Chalmers, Swedish Environmental Research Institute), named “ALINE”. I am also co-supervising the PhD student based at Uppsala for this project, Anastasiia Mikheenkova as well as planning and carrying out cell teardown and electrochemical characterisation.
In the project so far, we have conducted cycle ageing tests of two series of automotive battery cells and are investigating the major degradation mechanisms. We completed a large study of the degradation of 2170 format cylindrical cells obtained from teardown of a Tesla Model 3 vehicle, determining that significant degradation routes included loss of silicon when cycled at lower states of charge (SoC) resistance growth and loss of NCA when cycled at higher temperature. We have also observed lithium plating under mild cycling conditions in large format prismatic cells, quantifying the lithium plating with 7Li NMR (led by Alex Smith at KTH).
Previous personal projects
impedanceR
impedanceR is an R package containing a set of functions for simulating (not fitting) electrochemical impedance spectra. It was heavily used in my teaching and for creating the examples in my guide to EIS.
arbintools
arbintools was a collection of data importing and analysis scripts written in R for accomplishing everyday tasks with handling data from Arbin battery cycling instruments. The functionality is quite limited and I no longer update the package as I no longer work with Arbin instruments.
Previous academic projects
LiNi0.5Mn1.5O4 (LNMO)
2018 - 2023
Scania has co-funded two PhD projects at Uppsala University, together with Volkswagen, focused on the LNMO electrode. I participated in on study during the first project (carried out by Burak Aktekin) in which we investigated the effect of cross talk on the capacity degradation of LNMO-based batteries with a Li4Ti5O12 negative electrode.
After joining Scania, I became the project lead for the second project and co-supervisor to Alma Mathew. Alma’s project aimed to identify binders and electrolytes suited to the strongly oxidising LNMO electrode. Alma and I developed “synthetic charge-discharge profile voltammetry” (SCPV) as a method to quantify parasitic oxidation reactions and studied the degradation processes of polyacrylonitrile (PAN) used as a binder. Together with a postdoc, Girish Salian, we also studied the performance and degradation of various binder and electrolyte candidates.
Intermittent current interruption (ICI)
2015 - 2021
ICI, an electrochemical method I developed in 2015, characterizes internal resistance in batteries. Originally used in the lithium-sulfur (Li-S) project, the first version of the method determined resistance from a voltage drop after interrupting the current for a specific time.
Later, I improved the accuracy and relevance of the method by adding a regression analysis to quantify the resistance independently of time. Together with my student Yu-Chuan Chien we developed ICI further to measure the resistance resulting from mass transport (diffusion) using the same data. Eventually, we showed that this allows the determination of the solid-state diffusion coefficient in Li-ion electrode materials under specific conditions.
Beyond Li-S batteries, this method has been widely extended to most modern battery chemistries and has been validated by and applied to modelling. It finds wide application in the investigation of Li-ion and Na-ion materials and cells, including commercial formats. Moreover, it serves as a complementary method in in situ and operando characterization studies.
Nowadays, ICI is increasingly used as a routine electrochemical method in several universities and companies.
More about ICI here, and a tutorial on data analysis using ICI to calculate diffusion coefficients.
Lithium-sulfur (Li-S) batteries
2012 - 2021
My interests in Li-S batteries broadly concerned understanding fundamental limitations to performance and the effects of inactive materials (binder & conductive additive) in this regard.
Together with my student Fabian Jeschull we studied the role of polyethylene glycol (PEG) and polyethylene oxide (PEO) in sulfur electrodes and found the polymers to have the effect of locally (and beneficially) modifying the electrolyte system in the electrode, contrary to other reports at the time. Following this, we demonstrated an optimised binder system of PEO mixed with poly(vinylpyrrolidone) (PVP) where both binders helped to improve energy density and capacity retention relative to the conventional choice, PVdF. We later showed that PVdF in fact is a poor choice for the Li-S system as it blocks porosity in the electrodes which is needed to host the discharge products of the reaction. Based on this research, another student, Viking Ă–sterlund, optimised a sulfur electrode preparation procedure for high loading, high sulfur content and good electrochemical performance. We demonstrated that the performance improvement from the binders was strongly dependent on the chemical functionality rather than only mechanical properties of the electrode, and together with two postdocs (Andreas Bergfelt and Hohyoun Jang) we began to develop binders based on single polymers incorporating multiple functionalities. However, we did not identify any other materials which improved on the performance of the original PEO:PVP blend.
A number of side projects took place simultaneously, most notably a project with Scania and student Anurag Yalamanchili on lithium plating/stripping behaviour and self-discharge, and the development of intermittent current interruption (ICI).
In 2017 I took on a PhD student, Yu-Chuan Chien, with the initial goal to study the effect of compressing (calendering) the electrodes to improve energy density. This led to a deep investigation of the mechanism of Li2S precipitation and influence of the electrode structure and electrolyte chemistry. Yu-Chuan extended the ICI concept and applied it to an operando X-ray diffraction study of the cell reaction, later using this approach to study the effect of loading and electrolyte composition. Yu-Chuan later took a similar approach to study the evolution of amorphous discharge products by small angle scattering techniques. In collaboration with Nuria Garcia-Araez’s group at the University of Southampton, we also studied the changes in electrode surface area and effect of compression using electrochemical impedance spectroscopy.
Lithium-oxygen batteries
2012
Following my PhD I briefly worked on the lithium-oxygen battery as part of the EU project “LABOHR”, which sought to develop a Li-O2 battery based on separating the oxygen harvesting (air -> solution) and oxygen reduction processes. I identified ethyl viologen as a compound capable of redox mediating or shuttling the oxygen reduction reaction (ORR), with significant implications for practical energy density. We subsequently demonstrated the redox shuttle reaction in an ionic liquid electrolyte, the first such report of a redox shuttle for the discharge reaction.
3D microbatteries
2008 - 2012
For my PhD, supervised by John R. Owen I worked on methods to fabricate polymer electrolytes (solids and gels) for3D microbatteries, as part of an EU project called “SUPERLION”. My approach was based on electropolymerisation, by direct reduction of a monomer to initiate a polymerisation reaction at an electrode surface of arbitrary structure and subsequently cause the precipitation of the polymer on that surface. Initially, I worked with polyacrylonitrile (PAN), the electropolymerisation of which had been demonstrated in the 1980s and which could be swelled with liquid electrolytes to form a gel. We demonstrated that PAN could be formed by electropolymerisation as a sufficiently thin, pinhole-free film which could in principle be used as a separator. I later investigated the electropolymerisation of acrylonitrile using oxygen reduction to initiate the reaction, which afforded higher purity PAN and a more efficient electrochemical reaction.
The ultimate goal of my doctoral thesis was to develop polyether-based electrolytes (based on acrylate derivatives of polyethylene glycol). I demonstrated this was in principle possible to achieve on carbon foam-based electrode structures and with alloying anodes (e.g. Ni-Sn and Cu2Sb), and studied the electropolymerisation process with electrochemical quartz crystal microbalance (EQCM). However, stable battery operation was not demonstrated before the completion of the project.
Read more about the oxygen-initated electropolymerisation of acrylonitrile here.
LiFePO4 derivatives
2006 - 2007
For my undergraduate degree project supervised by John R. Owen, I synthesised carbon-coated LiFePO4 from a previously-developed solution-based method and investigated its electrochemical performance as a positive electrode material for Li-ion batteries. I studied the use of different carbon sources in the synthesis and synthesised the Co-doped analogue LiFe1-xCoxPO4.