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Energy materials for a low carbon future

Discussion meeting

Starts:

September
172018

09:00

Ends:

September
182018

17:00

Location

The Royal Society, London, 6-9 Carlton House Terrace, London, SW1Y 5AG

Overview

Scientific discussion meeting organised by Professor Saiful Islam, Professor Peter Bruce FRS, Professor Richard Catlow FRS, Professor Jenny Nelson FRS

Computer simulation of lithium battery material showing curved ion conduction pathways

The provision of clean sustainable energy is one of the greatest challenges of our time. New low carbon technologies for energy conversion and storage require fundamental advances in the science of energy materials. This meeting brought together world-renowned experts in the field including batteries, solar power and fuel cells, and aimed at setting the agenda for future energy materials research.

Download a one page summary of the discussion meeting talk schedule (PDF).

The schedule of talks and speaker biographies are below. Recorded audio of the presentations will be available on this page after the meeting has taken place. 

Enquiries: contact the Scientific Programmes team

Event organisers

Select an organiser for more information

Schedule of talks

17 September

Session 1 09:00-12:30

New energy materials and energy policy

9 talks Show detail Hide detail

Chairs

Professor Saiful Islam, University of Bath, UK

09:05-09:30 New perovskite materials for solar cells and optoelectronics

Professor Henry Snaith FRS, University of Oxford, UK

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09:35-09:45 Discussion

09:45-10:15 New materials for rechargeable lithium batteries

Professor Jean-Marie Tarascon ForMemRS, College de Paris, France

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10:15-10:30 Discussion

10:30-11:00 Coffee break

11:00-11:30 Reversible electrochemical cells for fuel to and from electricity

Professor Sossina M Haile, Northwestern University, USA

Abstract

Over the past decade, the availability of electricity from sustainable energy sources has risen dramatically while the cost has fallen steeply. These factors have driven a surge in activity in the development of energy storage technologies. While much of this effort has been directed towards grid scale batteries, reversible hydrogen electrochemical cells offer untapped opportunities. In particular, electrochemical cells based on proton conducting ceramic oxides are attractive candidates for interconversion between hydrogen and electricity. When operated to produce electricity these function as fuel cells, and when operated to create hydrogen, they function as electrolysis cells. The proton conducting nature of the electrolyte provides inherent advantages in the gas flow configuration over traditional oxide cells in which the electrolyte is an oxygen ion conductor. However, despite high conductivity in protonic ceramic oxides, electrochemical performance as reported in the open literature has remained low. Moreover, the most commonly pursued electrolyte compositions suffer from poor chemical stability. Professor Haile describes here recent progress achieved using a combination of three advances: a new electrolyte composition, a new air electrode, and processing methods to decrease the contact resistance between these two components. The resulting cells display exceptional power densities in fuel cell mode, and extremely high electricity-to-hydrogen conversion efficiency in electrolysis mode. In addition, the cells are extremely stable over hundreds of hours of operation. As such, protonic ceramic electrochemical cells are likely to play a major role in a sustainable energy future.

Major funding sources
ARPA-e DEAR0000498
NSF DMR-1505103

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11:30-11:45 Discussion

11:45-12:15 Energy policy and innovation

Professor Jim Skea CBE OBE, Imperial College London and Co-chair IPCC Working Group III, UK

Abstract

The energy sector is going through a period of unprecedented change, one driver being new levels of ambition for climate policy. The 2015 Paris Agreement sets a limit of ”well below two degrees” global warming and includes a “net zero” ambition for the second half of the twenty first century. This means that greenhouse gases must be extracted from the atmosphere at least at the same rate as they are emitted. At the same time, the only area in which real world developments have kept pace with policy ambition has been in the field of renewable energy with falling prices and rapid rates of new deployment. This talk will highlight ways in which advances in materials could contribute to an energy transition, including renewable energy and the integration of high levels of renewables into grids through energy storage but also identifying potential contributions in terms of negative emission technologies. The talk will conclude with some thoughts about the UK’s role in the wider global transition.

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12:15-12:30 Discussion

12:30-13:30

LUNCH

Session 2 13:30-17:00

Transport processes in energy materials

11 talks Show detail Hide detail

Chairs

Professor Jenny Nelson FRS, Imperial College London, UK

13:30-14:00 Transport in perovskite solar cells

Professor Laura Herz, University of Oxford, UK

Abstract

Organic-inorganic metal halide perovskites have emerged as attractive materials for solar cells with power-conversion efficiencies now exceeding 22%. The researchers discuss the processes that have enabled these materials to be such efficient light-harvesters and charge collectors. The group particularly focuses on the fundamental scientific mechanism that will underpin photovoltaic operation when the Shockley-Queisser limit of maximum efficiency of a single-junction cell is approached. The researchers demonstrate that at the intrinsic limit, the mobility of charge-carriers is predominantly governed by interaction of carriers with optical vibrations of the lead halide lattice (Fröhlich interaction). In the absence of trap-mediated charge recombination, bimolecular (band-to-band) recombination will dominate the charge-carrier losses near the Shockley-Queisser limit. The researchers show that in methylammonium lead triiodide perovskite, such processes can be fully explained as the inverse of absorption, and exhibit a dynamic that is heavily influenced by photon reabsorption inside the material. Therefore, predictions of intrinsic charge-carrier mobilities and recombination rates can be readily made from easily accessible parameters, such as photon absorption spectra, phonon frequencies and the dielectric function, which allows for a targeted design of new materials for solar energy harvesting.

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14:00-14:15 Discussion

14:15-14:45 Transport in lithium batteries and solid oxide fuel cells

Professor Clare Grey FRS, University of Cambridge, UK and Stony Brook University, USA

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14:45-15:00 Discussion

15:00-15:30 Tea break

15:30-16:00 Advances in the understanding of high performance thermoelectrics

Professor Mercouri G Kanatzidis, Northwestern University, USA

Abstract

Thermoelectric solid-state energy conversion technology can provide a reliable and clean way to generate operative electricity from waste heat, which is a promising strategy for addressing energy conservation and management. Thus, there is a broad based push from the science and technology community to develop highly efficient thermoelectric materials as a possible route to address the worldwide power generation from heat.  Today there is a variety of effective strategies to improve the properties of these narrow gap semiconductors such as achieving extremely low thermal conductivity and raising the power factors. The so-called nanostructuring and mesoscale approach has led to a new era of investigation for bulk thermoelectrics. Currently lead chalcogenides incorporating second phases hold the record in figure of merit for high temperature power generation applications. Nanostructures enable effective phonon scattering of a significant portion of the phonon spectrum while mesostructures tend to scatter phonons with long mean free paths remain. By combining all relevant length-scales in a hierarchical fashion, from atomic-scale disorder and nanoscale endotaxial precipitates to mesoscale phonon scattering, a large enhancement in the thermoelectric performance of bulk materials can be achieved. Progress on device and module assembly is excellent and modules with conversion efficiency of over 12% for a delta T of 590 K have been demonstrated using nanostructured PbTe-based materials. Interestingly, nanostructuring is not necessary to obtain record high thermoelectric performance. Several systems based on PbTe and PbSe will be described that lack nanostructuring but feature mesoscale structuring and point defects, which can also achieve very low thermal conductivity. Comparisons with nanostructured materials will be made. Finally, SnSe is a new striking example of a single-phase two-dimensional material which has shed new light in thermal transport and chare transport properties both in p-type and n-type doping. The state of the art in our understanding of this system will be presented.

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16:00-16:15 Discussion

16:15-16:45 Experimental realization and theoretical understanding of high open-circuit voltages in lead-halide perovskites?

Dr Thomas Kirchartz, Forschungszentrum Jülich, Germany

Abstract

Efficiencies of lead-halide perovskite based solar cells have increased over the last several years at a speed that is unprecedented in the history of photovoltaic technologies. What is striking is in particular how relatively little engineering was needed to achieve high open-circuit voltages (Voc) that even now come similarly close to the Shockley-Queisser limit than those of Si solar cells after 60 years of technological development. This development inspires two questions, namely how far can we go technologically, and how do we characterise and understand these results? Here, Dr Kirchartz will present experimental results on very high open-circuit voltages and discuss the transient and steady state characterisation of these high Voc materials and devices. In the second part of the talk Dr Kirchartz will discuss what we know about non-radiative recombination in these semiconductors and discuss why the material properties of lead-halide perovskites are beneficial for achieving low recombination rates at a given charge carrier concentration.

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16:45-17:00 Discussion

17:00-17:20 Poster flash talks

17:20-18:30 Poster session

18 September

Session 3 09:00-09:30

Nanostructures and interfaces of energy materials

9 talks Show detail Hide detail

Chairs

Professor Peter Bruce FRS, University of Oxford, UK

09:00-09:30 Interfaces in solid-state batteries and solid oxide fuel cells

Professor Jürgen Janek, University of Giessen, Germany

Abstract

The thermodynamics and kinetics of solid/solid interfaces are critical for the function of solid-state devices. In this presentation, the current status of research on interfaces in solid-state batteries will be briefly reviewed and compared to the current understanding of interfaces in solid oxide fuel cells. Recently, solid-state batteries are considered as a potential next generation energy storage [1-3], competing with conventional lithium ion batteries. Interestingly, major hurdles on the way to commercialisation have still to be overcome, and the kinetics of interfaces needs to be improved. In particular, the lithium metal anode is a key issue, as it is also the cathode interface where oxidation of solid electrolytes may take place. It is interesting to compare the development of solid-state batteries, which has only started a few years ago, with the development of solid oxide fuel cells. On the route to commercial products, the electrode interfaces and the design of stable electrodes, that offer low impedance kinetics was also a key step towards success, in addition to the development of superior solid electrolytes. Professor Janek’s results will be presented, highlighting the current status of lithium solid electrolytes with high conductivity, the role of interface coatings and natural interphases, as well as the influence of chemo-mechanics on the properties of full battery cells.

References

1. J Janek and WG Zeier, Nat Energy 1 (2016) 16141

2. Y Kato, S Hori, T Saito, K Suzuki, M Hirayama, A Mitsui, M Yonemura, H Iba, and R Kanno,
      Nat Energy 1 (2016) 16030

3. Y J Nam, D Y Oh, S H Jung, and Y S Jung, J Power Sources 375 (2018) 93

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09:30-09:45 Discussion

09:45-10:15 Nanoscale effects and interfaces in lithium batteries

Professor Linda Nazar, University of Waterloo, Canada

Abstract

While it is widely acknowledged that traditional Li-ion batteries, which work on the principle of reversible storage of electrons and Li-ions in bulk materials, are approaching their limits, the question is: what real opportunities lie beyond? This presentation will focus on the challenge to find better electrochemical energy storage systems that go “beyond Li-ion” batteries. Topics will encompass multivalent intercalation batteries, solid-state batteries, and cells that operate on the basis of “conversion” chemistry rather than conventional intercalation chemistry. These represent new technologies that could meet the needs for high energy density and/or high power storage, yet many barriers remain to realising their full promise. They require cleverly designed nanomaterials for the electrodes, different electrolyte strategies than those used for Li-ion batteries and advanced electrode architectures based on nanostructured design. Guiding materials development also requires developing a fundamental understanding of the underlying chemistry of redox processes, which will be a focus of this lecture.

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10:15-10:30 Discussion

10:30-11:00 Coffee break

11:00-11:30 Nanostructures and interfaces of solid oxide fuel cell materials

Professor John Irvine, University of St Andrews, UK

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11:30-11:45 Discussion

11:45-12:15 Lithionics: store energy, compute data and chemically sense environment based on lithium

Professor Jennifer Rupp, Massachusetts Institute of Technology, USA

Abstract

Next generation of energy storage and sensors may largely benefit from fast Li+ ceramic electrolyte conductors to allow for safe and efficient batteries and real-time monitoring anthropogenic CO2. Recently, Li-solid state conductors based on Li-garnet structures received attention due to their fast transfer properties and safe operation over a wide temperature range. Through this presentation basic theory and history of Li-garnets will first be introduced and critically reflected towards new device opportunities demonstrating that these electrolytes may be the start of an era to not only store energy or sense the environment, but also to emulate data and information based on simple electrochemistry device architecture twists. The first part of the presentation focuses on the fundamental investigation of the electro-chemo-mechanic characteristics and design of disordered to crystallizing Li-garnet structure types and their description. Understanding the fundamental transport in solid state is discussed, asking the provocative question: how do Li-amorphous to crystalline structures conduct? How we can alter their charge and mass transport properties for solid electrolytes and towards electrodes is discussed. Here, the researcher firstly presents new Li-garnet battery architectures for which we discuss lithium titanate and antimony electrodes in their making, electrochemistry and assembly to full battery architectures. Secondly, new insights on degree of glassy to crystalline Li-garnet thin films are presented based on model experiments of the structure types. Here, the thermodynamic stability range of maximum Li-conduction, phase, nucleation and growth of nanostructure is discussed using high resolution TEM studies, near order Raman investigations on the Li-bands and electrochemical transport measurements. The insights provide novel aspects of material structure designs for both the Li-garnet structures (bulk to films) and their interfaces to electrodes, which we either functionalise to store energy for next generation solid state batteries or make new applications such as Li-operated CO2 sensor tracker chips. In the final part the presentation reviews in a more holistic picture how one can use such materials and change the electrochemistry from energy storage, chemical sensing to data emulation for which we see prospect for electric vehicles, the Internet of Things or hardware in artificial intelligence.

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12:15-12:30 Discussion

12:30-13:30

LUNCH

Session 4 13:30-17:00

Materials modelling and design

8 talks Show detail Hide detail

Chairs

Professor Richard Catlow FRS, University College London, UK

13:30-14:00 Connecting electrochemical properties of battery materials to their electronic structure

Professor Anton Van der Ven, University of California, Santa Barbara, USA

Abstract

The ability to predict thermodynamic and kinetic properties of electrode and electrolyte materials from first principles is providing opportunities to explore and design new battery concepts. Challenges remain, however. Batteries are dynamical systems at the materials level, requiring long-range ion transport at room temperature that often induces a succession of phase transformations within the electrodes. Modelling batteries must address phenomena that occur at multiple length scales. In this talk, Professor Van der Ven will describe recent efforts at bridging the gap between the electronic structure of materials and well-established phenomenological theories that describe the behaviour of electrodes and electrolytes at meso and macroscopic length scales.

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14:00-14:15 Discussion

14:15-14:45 Beyond perovskites: chemical principles for next-generation solar energy materials

Professor Aron Walsh, Imperial College London, UK

Abstract

There are a large variety of materials being studied for application in solar energy conversion. The majority of compounds are based upon naturally occurring minerals. The general procedure has been to take a multi-component system and tune the chemical composition to optimise the optical absorption for the terrestrial solar spectrum. Other factors also determine whether a material can be practically employed in a photovoltaic or photoelectrochemical system, for example, the electronic band energies (work functions), defect chemistry, and thermodynamic stability. Firstly, Professor Walsh will discuss the latest advances in computer simulations for crystalline materials, including the benefits of statistically driven design (machine learning) [1]. Professor Walsh will then present his group’s recent progress into the optimisation and discovery of new materials for solar energy conversion with an emphasis on computing photovoltaic performance descriptors from computational chemistry [1-5], including advances in structure-property relationships in the kesterite (eg Cu2ZnSnS4) and perovskite (eg CsSnI3 and CH3NH3PbI3) families, in addition to the matlockite (PbFCl type) and herzenbergite (SnS type) systems. New directions in the field, including the development of photoferroic semiconductors, will also be addressed.

References

1. “Machine learning for molecular and materials science” Nature 559, 547 (2018)

2. “Point defect engineering in thin-film solar cells” Nature Reviews Materials 3, 194 (2018)

3. “Opposing effects of stacking faults and antisite domain boundaries on the conduction band edge in kesterite quaternary semiconductors” Physical Review Materials 2, 014602 (2018)

2. “Critical role of water in defect aggregation and chemical degradation of perovskite solar cells” J Physical Chemistry Letters 8, 2196 (2018)

5. “Computer-aided design of metal chalcohalide semiconductors: from chemical composition to crystal structure” Chemical Science 9, 1022 (2018)

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14:45-15:00 Discussion

15:00-15:30 Tea break

15:30-16:00 Design of porous materials for gas storage

Professor Andrew Cooper FRS, University of Liverpool, UK

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16:00-16:15 Discussion

16:15-17:00 Panel discussion

Professor Dame Julia Higgins DBE FREng FRS, Imperial College London, UK
Professor Hywel Thomas CBE FREng FRS, University of Cardiff, UK
Professor Sir David King FRS, Affiliate Partner, SYSTEMIQ Ltd, and Senior Policy Adviser to the President of Rwanda

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