Next Generation Solid-State Batteries

Lead Research Organisation: University of Cambridge
Department Name: Chemistry

Abstract

Solid-state Li-ion batteries (SSLBs) represent the ultimate in battery safety, eliminating the flammable organic electrolyte. The SSLB would find potential uses in industries where battery safety is paramount, such as the automotive industry (in cars, e-bikes and buses) and also in smaller applications where the elimination of the liquid electrolyte results in more ready compatibility with other devices, e.g., a battery on a chip or sensor. These batteries can compete with traditional lithium ion batteries in terms of volumetric energy density but they suffer from low power density. Very recently several viable inorganic solid Li-ion conducting electrolytes been identified with conductivities approaching those of liquids, which motivates this research proposal. Strategies for lowering interfacial resistances, particularly between the electrolyte and electrodes, and for building inherently scaleable devices that can be cycled multiple times, without mechanical failure, are now urgently required to produce practical devices.

This multi-institutional project brings together experienced, world-leading researchers from the University of Cambridge, the University of Oxford, and Imperial College with distinct but complementary expertise to attack a number of challenging critical issues in this field. Two classes of these solid electrolytes, oxide garnets and sulphide glass ceramics, have been found to have very high room-temperature ionic conductivities. A number of characteristics have been identified that may provide either relative benefits or disadvantages: higher-modulus materials may cycle more stably in batteries; tougher materials may be more easily brought into industrial practice; polycrystalline character may limit apparent bulk-transport rates, lowering power efficiency; interfaces may be chemically unstable, affecting long-term state of health; etc. We propose to implement fundamental studies that shed light on the relative benefits and disadvantages of the oxide and sulphide ion-conductor paradigms, using the Li6.55Ga0.15*0.3La3Zr2O12 (* = vacancy) (LLZO) garnet and the P2S5-Li2S (PSLS) glass ceramic as model materials.

The project centres around three experimental work packages that focus on 1) quantifying bulk properties and making them reproducible; specifically, issues of moisture and carbon-dioxide sensitivity of the electrolytes will be addressed to produce films with reduced resistances at the interfaces between particles. LLZO and PSLS films will be contrasted, and transport through them will be investigated via a number of in operando (in situ) metrologies, e.g., 6Li tracer and NMR studies in close concert with theoretical studies of ionic transport. 2) illustrating chemistry of the solid-electrolyte/Li two-dimensional interface and probing its morphological stability over time; we seek to identify the critical parameters needed to mitigate Li-metal dendrite formation and growth, and which allow smooth Li-plating on the electrolyte surface. 3) producing tailored, cohesive three-dimensional interfaces with complex morphologies that do not crack on extensive cycling. The development of materials with much larger electrode/electrolyte contact areas will increase Li+ exchange between phases within the electrode, increasing rate performance. A multiscale modelling effort cuts across the 3 work packages, aiming to produce fundamental physical insight, synthesize experimental outputs, and guide experimental design. The goals for the theory portion are unique in the sense that the models will aim for true 'multiscale' character, integrating atomistic and continuum perspectives. Overall, the project aims to provide new new strategies to improve the performance of SSLBs but will also result in new electrolyte designs that are suitable for to protect Li metal in other so-called "beyond Li-ion" batteries such as Li-air and Li-S and smaller batteries for internet communications technologies.

Planned Impact

Economy: Solid-state Li-ion batteries (SSLBs) represent the ultimate in battery safety, eliminating the flammable electrolyte. Industries where battery safety is paramount have initiated major R&D activities in this area. The solid-state electrolyte films developed as part of this programme will also enable a protected Li anode, useful for transformative beyond-Li technologies such as Li/air or Li/sulphur batteries. Smaller SSLBs can replace primary batteries in smaller devices (e.g. batteries on chips, sensors) where the lack of liquid electrolyte allows increasing compatibility with the device (e.g., chip, antennae). Our SSLB programme will generate new technology and IP in these emerging new fields, from materials production to methods of producing scaleable electrodes and devices. Importantly, new UK specialism and knowledge will be developed, advancing national capabilities. We build on considerable UK historical expertise in ceramics and solid-state ionics that has already made significant contributions to UK industry. Implementing new technologically-relevant multi-scale modelling paradigms will reduce UK industries' R&D costs by making possible computational prototyping and design. The economic impact of our research will lie in maintaining the UK's international leadership in synthesis, analysis, and modelling of cutting-edge energy-storage systems, ensuring that any resulting IP is retained, licensed and exploited by UK research groups and industry.

Society: It is hard to overstate the impact of a disruptive automotive battery technology. By displacing the internal combustion engine in vehicles, automotive SSLBs (and eventually Li-air and Li-sulphur batteries) would help meet the DECC's target of sourcing 10% of energy for transport from renewables by 2020 and facilitate greenhouse-gas emissions reduction of 80% by 2050. Li-ion battery development is strong enough here that David Willetts identified energy storage as one of the UK's Eight Great Technologies for Policy Exchange in 2013, recognizing that energy-storage R&D will enable the UK to gain from the global transition to new energy sources.

Public: The PI has a strong track record in engagement, appearing, for example, on the BBC Radio 4 programme "Putting Science to Work" in 2015, and working with the World Economic Forum to help write "Energy Harnessing: New Solutions for Sustainability and Growing Demand". All the CIs have considerable experience with public engagement, have presented research to such diverse groups as schoolchildren, science journalists, and members of parliament. Specifically, we will produce a hands-on annual presentation for the Cambridge Science Festival on "beyond Li-ion technologies", designed for children ages 4-12 and building on past successful hands-on projects in the Chemistry Department, where the children grew Zn dendrites in simplified Zn primary cells. We will work with Cambridge's Public Engagement office and Women in Science group to engage growing public interest in energy and nanotechnology and explain how fundamental science enables technology development in the energy area.

People: The project will train 3 PDRAs trained in best practices of materials synthesis and analysis, and 2 PDRAs in modelling of technologically relevant materials, including multi-scale modelling. By working in research teams, both theorists and experimentalists will be gain familiarity with their counterparts' techniques. These skills will be disseminated into academia/industry as the researchers continue in their careers. Direct knowledge of commercial relevance through interfacing with industry and end-use will provide relevant transferable-skills training for the researchers in this project. We will train a new generation of PDRAs and students, growing the battery expertise relating to battery characterisation, and materials in the UK, supporting future EV/ICT industries.

Publications

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Griffith K (2019) Ionic and Electronic Conduction in TiNb 2 O 7 in Journal of the American Chemical Society

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Kasemchainan J (2018) All-Solid-State Batteries and their Remaining Challenges in Johnson Matthey Technology Review

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Li G (2019) Dendrite nucleation in lithium-conductive ceramics. in Physical chemistry chemical physics : PCCP

 
Description Garnet-type solid electrolytes have attracted great interest in energy storage research thanks to their high ionic conductivity at room temperature (10-3 S cm-1) and their electrochemical stability in the presence of lithium metal, which make them suitable candidates for the development of all solid state lithium-ion batteries. Despite these advantages, the formation of lithium dendrites following charge/discharge limits their applicability and commercialisation. In this grant we have studied the mechanism of formation and the chemical nature of dendrites using a combination of surface sensitive chemical analysis, nuclear magnetic resonance (NMR) techniques, and electrochemical measurements.
In the first year of the grant, we set up a working kit based on magnetic resonance imaging (MRI; analogous to medical device) for Li dendrite detection. Subsequently, we were able to image the lithium dendrites formed prior to and after short-circuiting in electrochemical cells based on the above mentioned garnet electrolytes. This MRI set-up also allowed us to probe the local ionic conductivity in differently doped garnet electrolytes.
In addition, we investigated the distribution of these dopants that are used to stabilize the fast Li-conductor garnet structure. We have observed that different dopants have different distributions along grains and grain boundaries as well as along the depth. A lower current density for dendrite formation (i.e. easier formation) is systematically observed in materials with a more inhomogeneous distribution within grains and grain boundaries. Furthermore, we found a strong dependency of their local environment on the synthesis conditions, which could be one of the reasons for the varying lithium ion conductivity in the literature. Finally, aluminium (one of the most employed dopants) seems to be involved in the chemical composition of dendrites although further studies need to be performed to elucidate if it is forming an Al-Li alloy or if it comes from the original Al oxide segregation in the grain boundaries.
Years 2 and three focused on DFT calculations of LLZO structure and the role of doping. DFT calculations focused on energy of configurations and calculation of NMR observables. The result of the study is a JACS paper resolving a debate in the literature concerning where Al and Ga dope in LLZO.
A second focus involved the synthesis of new sulphide ionic conductors. A new ionic conductor was identified that is inherently stable against Li metal and a paper is being written up.
Finally, DFT and MD simulations were used to study how ions move in the new sulphide materials and LLZO.
Exploitation Route The experimental results we have obtained will be used to simulate possible dendritic growth mechanism to suppress these degradation phenomena in solid state batteries. In addition, knowledge of the dependency of dopant distribution on reaction conditions can be exploited to improve lithium ionic conductivity by engineering the local distribution of the dopants in the garnet structure.

Furthermore, the experimental work performed using surface analysis has pioneered the development of a new equipment "High Five: Resolution, Sensitivity, in operando Control, Ultra High Vacuum and Ion Sectioning in a Single Instrument" awarded with a strategic equipment grant EP/P029914/1that will be unique for the analysis of the chemical compositions of a wide range of materials and systems under in situ and in operando conditions.

Our findings on conductivity and lithium metal dendrite formation are of high interest for the further development of all-solid-state batteries especially in the field of electro mobility, where the inherent improved safety and perspective higher capacity of these batteries are crucial for consumer acceptance and extended range.

The new ionic conductor will have potential use in a solid state battery.
Sectors Chemicals,Electronics,Energy,Transport

 
Description Presentations of our results at conferences and scientific meetings have resonated well, and might have sparked new research ideas both in the academic context as well as within industry. Talks have been given in industries (e.g., Murata) to help inform the future of solid state batteries
First Year Of Impact 2018
Sector Electronics,Energy,Transport
Impact Types Societal,Economic,Policy & public services

 
Description Chair of Scientific Advisory Board of the Max Planc Institutie for Solid State research 2018-
Geographic Reach National 
Policy Influence Type Participation in a advisory committee
 
Description Presentation to an All-Party Parliamentary Climate Change Group event
Geographic Reach Multiple continents/international 
Policy Influence Type Gave evidence to a government review
Impact Helped shape grid storage policy.
 
Description Strategic equipment grant
Amount £1,725,000 (GBP)
Funding ID EP/P029914/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 09/2017 
End 09/2020
 
Title Magnetic resonance imaging (MRI) of lithium ion dendrites 
Description We have shown that 7Li MRI can be used as an approach to quantify dendrite formation in solid state batteries. 
Type Of Material Improvements to research infrastructure 
Year Produced 2018 
Provided To Others? No  
Impact The results have allowed us to correlate impedance measurements with Li moss and dendrite formation in a non-destructive way (without for example cross-sectioning the sample with focussed ion beams). A paper describing the work is under review. 
 
Description Faraday Institution Solid State Battery Fast Start Project 
Organisation University of Cambridge
Country United Kingdom 
Sector Academic/University 
PI Contribution The PI collaborates with Prof. Norman Fleck and jointly supervise a PhD student to examine chemical and mechanical origins for SSBs
Collaborator Contribution Prof. Fleck is a world-renowned expert on mechanical properties of ceramics. We are developing models for cracking and dendrite formation.
Impact Involves collaboration between chemists and mechanical engineers
Start Year 2018
 
Description Chair of student and early career scientist event 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Postgraduate students
Results and Impact Chaired a day of non-technical presentations of research work and impact by early career scientists at "CAM-IES Science Day"
Year(s) Of Engagement Activity 2018
 
Description Discussion Meeting (Royal Society) on energy materials 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Invited talk and discussion session on "Energy materials for a low carbon future", held at the Royal Society
Year(s) Of Engagement Activity 2018
URL https://royalsociety.org/science-events-and-lectures/2018/09/low-carbon-future/
 
Description Discussion at UK Redox Flow Network Meeting 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Industry/Business
Results and Impact Discussion panel at second annual UK Redox Flow Battery Network Meeting, where the research community explored challenges in the field and methods for collaboration to overcome such challenges, increase visibility of the research field, attract further funding, generate commercial ventures etc.
Year(s) Of Engagement Activity 2018
URL https://sites.google.com/view/ukrfbnetwork/home
 
Description Interview - Peter Bruce interviewed by Benchmark Mineral Intelligence on solid-state batteries 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Interview - Peter Bruce interviewed by Benchmark Mineral Intelligence on solid-state batteries, 11 Sept 2018
Year(s) Of Engagement Activity 2018
 
Description Interview on BBC World Service programme "Click" (August, 2018) 
Form Of Engagement Activity A broadcast e.g. TV/radio/film/podcast (other than news/press)
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Was interviewed on BBC World Service programme "Click" (August, 2018) about fast charging of batteries.
Year(s) Of Engagement Activity 2018
URL https://www.bbc.co.uk/programmes/w3cswhdm
 
Description Interview on Radio 4 Programme "The Life Scientific", March 2018 
Form Of Engagement Activity A broadcast e.g. TV/radio/film/podcast (other than news/press)
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Was interviewed in "The Life Scientific" Radio 4 Programme on "The Big Battery Challenge", March 2018
Year(s) Of Engagement Activity 2018
URL http://www.bbc.co.uk/programmes/b09tdr0r
 
Description Opened the New Chemistry Building at Lancaster University, October 2016 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Other audiences
Results and Impact Opened the New Chemistry Building at Lancaster University, October 2016
Year(s) Of Engagement Activity 2016
 
Description Plenary talk at International Battery Association Meeting, San Diego, March 2019 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact Gave plenary talk at the International Battery Association Meeting, San Diego, March 2019
Year(s) Of Engagement Activity 2019
URL http://iba-2019.org/
 
Description Presentation to an All-Party Parliamentary Climate Change Group event 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Presentation to an All-Party Parliamentary Climate Change Group event, 'Energy storage and the transition to a low carbon economy', Houses of Parliament, London, July 2016
Year(s) Of Engagement Activity 2016
URL http://www.policyconnect.org.uk/appccg/news/energy-storage-and-transition-low-carbon-economy-summary