AMorphous Silicon Alloy Anodes for Multiple Battery Systems - "AMorpheuS"

Lead Research Organisation: University of Cambridge
Department Name: Chemistry

Abstract

Carbon anodes for Li-ion batteries (LIBs) are regarded as one limiting factor preventing Li-ion batteries from being a viable option for transport applications (which require higher capacity for extended driving ranges) or grid storage applications (which require long cycle life). Compared to carbon, silicon has a much higher energy density and has been the focus of considerable research effort in recent years, stimulating the formation of high-profile, high-investment university spin-out companies such as Amprius and Nexeon. Silicon is the second most abundant element in the earth's crust and is thus a sustainable battery material candidate from a cost and availability perspective. However, despite its desirable properties for Li-ion batteries, it is also renowned for its drawbacks, namely large volume expansion, pulverisation and continued lithium loss through chemical reactions with the electrolyte (which the lithium ions diffuse in). Such phenomena have hindered the successful widespread uptake of this material in commercial Li-ion batteries, despite the myriad of global research groups working on finding ways to make it viable, e.g. by nano-structuring.

Project AMorpheuS presents an alternative way to fabricate Si anodes that does not rely on complex, costly nanostructuring or attempting to control electrode architectures. The approach is simply to deposit from solution using electrodeposition methods and to passivate the amorphous thin films with polymer chemistries that have already been shown to be effective as binders for Si electrodes. A fundamental understanding of the structural and surface properties of these electrodes will be obtained during realistic battery operation so as to identify the optimum Si alloy and polymer chemistry and optimise performance rationally. This project will develop Si electrodes that are not exclusively destined for use in Li-ion systems but can also be reversibly cycled in Na-ion and Li-S batteries. A variety of Si-alloy chemistries will be explored, including Si-Sn alloys, since these show considerable promise as anodes for Na-ion batteries. A goal is to develop the first Si-based Na anode.

This flexibility opens up numerous technology transfer opportunities in a variety of emerging battery systems focused on higher energy, sustainable, and safer technologies (e.g. Li-ion, Na-ion and LiS, respectively). The new batteries will be tested in the UK's first full battery prototyping line in a non-commercial environment.

Fully understanding what occurs in a battery as it is charged / discharged is complex. The battery is a closed system with constantly changing domains. Central to the success of this project is the application of in-situ characterisation techniques for analysing real-time, dynamic structural and surface changes that occur as Li ions pass back and forth between the anode and cathode (or why they do not). This knowledge will subsequently guide continued improvements in electrode designs. The major techniques proposed to gain a comprehensive understanding of the chemistry occurring in the battery as it is charged/discharged are multinuclear NMR and X-ray computed tomography. These techniques have provided battery researchers with a wealth of vital, real-time insight - especially regarding failure mechanisms in silicon materials.

Project AMorpheuS's approach will reduce the need for additional processing of materials in the electrodes, e.g., (i) high surface area carbons (which need energy-intense mixing processes) and (ii) industry-standard binders (which require toxic solvents to enable them to be processed into coatings). This strategy will reduce production time and eliminate toxic chemicals. These improvements will significantly reduce manufacturing cost and increase the UK's energy security.

Planned Impact

AMorpheuS will prepare a novel amorphous Si-alloy anode with inherent degradation resistance that can be deployed in a number of Li-ion & beyond- Li-ion battery types and will positively impact the UK's "Energy Trilemma" around cost, environmental concerns and energy security.

The demand for rechargeable lithium-ion batteries (LIBs) has grown significantly since 1991, increases in Li consumption having grown at a rate of ca. 22% per annum since 2000. Despite its maturity in portable electronics, analysts foresee a continued boom in sales revenues across all industry sectors, from consumer electronics and EVs to grid storage. More recently, Na-ion batteries (NIBs) have gained recognition as promising candidates for next-generation, large-scale energy storage systems. Unlike Li, sodium is an abundant and inexpensive element that shares many properties with Li as an energy storage material. This means that Na-ion batteries can be successfully developed using approaches previously used with LIBs and represent a more sustainable technology than Li. LiS systems are also gaining more attention, having demonstrated higher energy density than LiCoO2-graphite LIBs, and show great potential for transport applications. The ability to inexpensively develop, at scale, an anode that could be used in all of these types of battery will simplify manufacturing routes and stimulate growth within the UK.

Society: Energy production and storage are now central paradigms to our quality of life. The traditional grid system (macrogrid) is costly, inefficient and carries risks of localized incidents being able to disturb the "whole". Microgrids, on the other hand, are obviously smaller and combine power generation, load management and energy storage assets - all controlled in a coordinated network. Having the ability to locally store renewable solar energy, for example, will significantly impact domestic energy costs and reduce issues relating to intermittency.

Environment: Legislation-driven goals such as the EU's 20-20-20 strategy are striving for a 20% reduction in CO2 emissions, a 20% increase energy efficiency, and a 20% increase in renewable energy systems by 2020. This project can deliver in all three of these areas. According to the IEA's Energy Technology Perspectives scenario, PV-harnessed energy is forecast to save 30 Gt of potential CO2 emissions by 2050, and the capability to incorporate longer-lasting, efficient energy storage into renewable energy technologies is essential for this to be achieved. By eliminating the need to use conventional anode components such as conductive additives and polymer binder systems, there will be a reduction in the use of toxic battery solvents such as N-methyl pyrrolidone (NMP), a known teratogen.

Economy: The market for energy storage on the grid (ESG) alone is forecast to surpass $30bn by 2022. Long duration energy storage by advanced batteries will multiply the technology options available to make this viable. Considerable market opportunities also exist in the transport and portable electronics sectors. Technology transfer and commercial exploitation of this research to produce a new range of longer-lasting, higher energy density batteries, (with better design-through-innovation manufacturing) would create market share and generate significant economic benefits for the UK in these three areas.

Knowledge: New understanding of the structural dynamics and surface evolution established in novel a-Si anodes for several competing battery technologies. New approaches in electrode fabrication will generate degradation-resistant anodes and develop and disseminate expertise. Advancing knowledge within electrodeposition will allow exploitation possibilities not only in energy storage but within surface science innovations for other research areas, e.g. corrosion inhibition. Technology transfer opportunities exist with UK battery companies such as Sharp, Faradion, QinetiQ, JLR and Oxis Energy.

Publications

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Ferrari, S (2015) Journal of Power Sources in Latest advances in the manufacturing of 3D rechargeable lithium microbatteries

 
Description Through the AMorpheus Grant, we have developed ways to generate battery electrodes using alternative manufacturing approaches. This has involved transfer from other technologies of innovative approaches to Li-ion energy storage devices and has been achieved in these key areas:

(1) Courtesy of a HVM Catapult Fellowship, secured to support the Amorpheus project, a visiting academic Dr Shashi Paul from De Montfort's Emerging Technologies Research Centre was able to participate in the project. This used a technique developed for solar cells and directly applied it to fabricating battery electrode synthesis, without the time-consuming processes currently used in battery manufacturing. The work was very effective in producing high quality structures in collaboration with the other project consortium partners. Electrodes made in this manner show good charge-discharge behavior for many cycles and this is a good measure of battery performance.
(2) Another key finding of AMorpheous is an understanding of the molecular composition of the Solid-Electrolyte Interface (SEI) layer formed on Silicon anodes (both additive-free nanowires as well as nanoparticles mixed with CMC binder and carbon) in the presence of FEC (a well-known additive). FEC leads to less soluble decomposition. The ability of FEC to inhibit the soluble decomposition products is likely one of the reasons behind the enhanced cycle life in the presence of FEC. Additionally, the organic non-crystalline polymeric species in the SEI were identified by 1H and 13C solution NMR and ssNMR (solid-state NMR) as well as DNP (Dynamic Nuclear Polarization) experiments. These confirmed the presence of oligomeric species at early stages of cycling, that further reacted forming a more highly cross linked polymeric SEI than that formed in the absence of FEC. The degree of crosslinking is therefore thought to be crucial in the improved cycle life of the Si electrodes.
(3) AMorpheus research centred on generating silicon-containing structures. One of the issues with using silicon is that it has a reactive surface that consumes lithium (detrimental to a battery's performance). One of the work packages used a number of approaches to protecting the surface of silicon, including super-acid passivation. Again, this work began to show interesting results in solar research and so has been incorporated into the AMorpheus work and extended to form the baseline for an EPSRC Fellowship to demonstrate that this chemistry can be applied to advance both energy harvesting & energy storage. From the knowledge generated from the SEI studies, we are attempting now the rational design of inorganic-organic polymers (polyphosphazenes) with enhanced elasticity. These polymers are deposited on silicon thin films. The findings so far show no Li dendrite formation, however there is a decrease in the coulombic efficiency due to degradation of the electrolyte. More crosslinking and copolymerization with FEC are being introduced based on the results mentioned above.
(4) Key progress has been made in the visualization of the morphological processes on Silicon electrodes during operation by CT X-ray microscopy, including Si particle evolution at early stages of lithiation, formation of micro-cracks and propagation leading to particle fracture. Moreover, X-ray nano-CT have enabled us to 3D reconstruct Si electrodes with 150 nm spatial resolution allowing us to visualize particle cracking with increased cycling and the appearance of a low X-ray attenuating phase associated with Si degradation.
Exploitation Route Key publications will enable the findings to be used / reproduced by others and also represent a data foundation for further applications to develop this approach in energy storage technologies. Findings are being taken forward by the design of the SEI layer and others will also be possible if a current Fellowship application is successful.
Sectors Chemicals,Creative Economy,Education,Energy,Environment,Government, Democracy and Justice,Manufacturing, including Industrial Biotechology,Transport,Other

URL https://www.cambridge.org/core/journals/mrs-advances/article/electrodeposition-of-si-and-snbased-amorphous-films-for-high-energy-novel-electrode-materials/E2E795D70350D36E4A33353B37EE96EA
 
Description The work on silicon SEI has had significant impact globally. This work and earlier NMR studies on silicon have resulted in the PI being recognised as a world leader in silicon technology. She has been asked to consult for a number of companies in this area. A recent example is a new collaboration with TDK in Japan. This has involved a visit by TDK researchers to the UK and a return visit to Japan to consult on SEI formation on Si-polymer composites. A second example, is the one-year visit by Dr Keitaro Kitaro from Sony corporation to learn NMR methods and apply them to the battery material SiO. Prof. Grey visited Murata in 2020 (Sony having sold its battery business to Murata)
Sector Chemicals,Communities and Social Services/Policy,Creative Economy,Education,Energy,Environment,Manufacturing, including Industrial Biotechology,Pharmaceuticals and Medical Biotechnology
Impact Types Economic,Policy & public services

 
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 HVM Catapult
Amount £29,788 (GBP)
Organisation University of Warwick 
Sector Academic/University
Country United Kingdom
Start 11/2015 
End 11/2018
 
Title purpose-built coin cell for operando neutron imaging 
Description A modified, purpose-built coin cell was used for operando neutron imaging. This initial cell design contained glass fibre separator. Initial low energy resolved white beam imaging showed that glass fibre is a high neutron absorber, owing to the presence of boron. Subsequent cells contained standard polyolefin separator. Initial neutron imaging results showed a possible small signal due to delithiation of graphite but this was swamped by the strong Bragg edge associated with stainless steel and the high absorption of hydrogen in the electrolyte. The cell will be re-designed to include the use of, e.g., an aluminium casing and deuterated electrolyte, as well as employing more active material. 
Type Of Material Improvements to research infrastructure 
Provided To Others? No  
Impact Still under developement, will enable imaging of low density components through metal casing. 
 
Description AMorpheus collaboration with the Department of Engineering at the University of Warwick 
Organisation University of Warwick
Country United Kingdom 
Sector Academic/University 
PI Contribution Provision of samples to be surface engineered with follow up physical and electrochemical characterisation as outlined in the work package requirements of Project AMorpheus.
Collaborator Contribution Novel surface passivation technique used in solar applications to be applied to energy storage components for Li-ion batteries
Impact A Fellowship to EPSRC is under application incorporating information directly generated by this collaboration. It proposes to further grow this collaboration to extend some of the work package elements from Project AMorpheus beyond the scope of the current funding
Start Year 2018
 
Description Catapult High Value Manufacturing Fellowship awarded to De Montfort University to support AMorpheus 
Organisation De Montfort University
Country United Kingdom 
Sector Academic/University 
PI Contribution Warwick University award HVM Catapult Fellowships which aim to strengthen relations between academics and manufacturers, and accelerate the transition of research from the laboratory to industry. This award contributes £20k p.a. for any collaborative research activity and DMU-Warwick's collaboration is to develop an alternative material strategy to the main activities outlined in Project AMorpheus. This work has also lead to an STFC Proof-of-Concept grant application for £40k to conduct a 10 month feasibility study
Collaborator Contribution Contribution of academic expertise and equipment use for the development of the PVD Process to deposit Si/Sn-based alloy films for Li-ion batteries. This directly compares with and supports the core activities of AMorpheus. These materials will be used in each characterisation and development work packages of the consortium activities (Cambridge & UCL) and will significantly contribute to high quality publication and conference papers
Impact Publications underway, additional EPSRC funding applications to extend the work beyond the Fellowship. Multi-disciplinary activities: Physics (PVD development), Electrochemistry (battery testing, electrodeposition), Material Science (generation of alloy films & particles), Chemistry (electrolyte additives, metal-organic frameworks, composite microstructures)
Start Year 2016
 
Description Prof. Richard Walton-MOFs-Silicon 
Organisation University of Warwick
Department Warwick Mathematics Institute
Country United Kingdom 
Sector Academic/University 
PI Contribution In order to compare c-Si particles with electrodeposited films and PVD generated Si-based anodes, the other form of Si worthy of exploration are amorphous particles. A proposal was submitted to an STFC Proof-of-concept call to explore mesoporous amorphous Si particle synthesis.
Collaborator Contribution The proposal for mesoporous amorphous Si particles incorporates the research of Prof. Richard Walton (Dept of Chemistry, Warwick) and his work on flexible metal-organic frameworks (MOFs) to create "breathable" amorphous Si anodes. Glyme is the solvent medium for generating a-Si particles using silicon tetrachloride and Mg powder at 100oC for 10h followed by annealing under N2 @ 800oC for 1 hour.
Impact Proposal submission
Start Year 2017
 
Description British Science Festival lecture "It's Electrifying", University of Warwick, September 2019 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Other audiences
Results and Impact Dissemination of research.
Year(s) Of Engagement Activity 2019
URL https://britishsciencefestival.org/event/its-electrifying/
 
Description CAM-IES symposium on Photovoltaics and Thermoelectrics 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact The purpose of the workshop was to bring together the photovoltaic and energy harvesting communities, featuring talks relevant to both themes. Discussion sessions enabled both groups to interact. An audience vote was held on the the next workshop topic to be held (industry workshop on the Internet of Things).
Year(s) Of Engagement Activity 2017
 
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 panel at AIP/CAM-IES Conference 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Chairing talks and participation in discussion panel at AIP/CAM-IES Conference on Interfaces in Energy Materials, Trinity College Cambridge, 10-12 April 2018
Year(s) Of Engagement Activity 2018
URL https://horizons.aip.org/energymaterials/
 
Description Early career research talks, CAM-IES Autumn Symposium, QMUL, 21 September 2017 
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 Technical workshop for young researchers featuring talks, posters and networking sessions. Delegates joined the CAM-IES UK community of energy materials researchers. Travel bursaries were provided to all students and postdocs outside of the London area.
Year(s) Of Engagement Activity 2017
 
Description Interview for a UK Education Select Committe to understand advances in new battery materials; Symposium presentation for a ThinkScience event at University of Warwick Chemistry Dpe 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact For the education select committee the panel of around 20 teaching executives from across the UK were visiting to find out about the research and teaching occurring around materials and energy storage innovations. A discussion and Q&A discussion followed that received excellent feedback around our activities in both research and post graduate teaching. The Think Science event was a multi-disciplinary event hosted by Warwick Chemistry that brought together many departments to present and discuss themes around the new advances in materials chemistry.
Year(s) Of Engagement Activity 2017,2018
 
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 Joint Anglo-German Discussion Meeting, Darmstadt, September 2015 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Presentation at conference.
Year(s) Of Engagement Activity 2015
 
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
 
Description Radio 4 Programme on Mitigating Air Pollution in Cities 
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 Media (as a channel to the public)
Results and Impact "Putting Science to Work" Radio 4 Programme on Mitigating Air Pollution in Cities, with Jim Al-Khalili. As described in the BBC website: As the recent VW scandal reminds us, the exhaust from petrol and, in particular, diesel cars are damaging our health. So what can science do to help? Jim Al-Khalili invites three scientists into the studio to explain how their research or technology could help reduce pollution from dirty car exhausts. Professor of Chemistry, Tony Ryan makes the case for smart materials that absorb noxious gases. If only everyone could treat their jeans with nanoparticles that that clean up the air as they walk around town. Professor Clare Grey and her team are working on the next generation of batteries for electric cars. And engineer, Bernard Porter is a champion of hydrogen fuel cells. So, which technology is best designed to help us reduce air pollution in our cities? Who deserves the lion's share of Jim's imaginary pot of research funding to help us tackle this problem?. Outcome - lion share of funding allocated to CPG
Year(s) Of Engagement Activity 2015
URL http://www.bbc.co.uk/programmes/b06rxyct
 
Description Royal Academy Masterclass for schools in the Midlands 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Schools
Results and Impact Local schools were invited to nominate two year 9 pupils (of different gender) to attend the Saturday morning Royal Institution Engineering Masterclasses in WMG, at the University of Warwick. This Series aims to open the eyes of young people to the excitement, beauty and value of engineering, and in turn, inspire the next generation of scientists, mathematicians and engineers. The Series is delivered by staff and students from WMG. Each masterclass focuses on an aspect of modern engineering and is presented by an engineer actively involved in research or working in industry. The classes take the form of interactive workshop sessions.
Year(s) Of Engagement Activity 2013,2014,2015,2016,2017
URL https://warwick.ac.uk/fac/sci/wmg/about/outreach/rimasterclass2020/