Vacancy Engineering in Anode Materials for High-Power K-Ion Batteries

Lead Research Organisation: University College London
Department Name: Chemistry


Energy storage is a tremendous research focus of our time and plays a vital role in tackling climate change and enabling a low carbon economy. It is the technology that will accelerate the transition to electric vehicles and facilitate the efficient utilisation of renewable energy in the grid scale applications. Today's massive production of Li-ion batteries (LIBs) has resulted in the supply risk of Li and Co, which would place future UK battery industry subject to external market and geopolitical forces. There is an immediate need to exempt from the over-reliance on LIBs through developing the next generation batteries that are based on earth-abundant elements. K-ion batteries (KIBs) offer cost-effectiveness and environmental sustainability, as they are based on K (2.09% abundance in the earth's crust, vs. 0.002% Li) and a Co-free system. KIBs possess the advantages of K having the closest reduction potential to Li (-2.92 V vs. -3.04 V) and being able to reversibly intercalate into graphite, which makes it possible to achieve high energy density and directly utilise the existing LIB manufacturing facilities. In practical applications such as grid-level storage where considerations of cell weight and size take a back seat to cost-per-kWh, KIBs represent a very attractive candidate.

Building on our previous work on KIBs, our ambition is to develop high-performance KIBs and unlock the potential of KIBs as the next generation batteries. The major challenge of developing KIBs is the large size of K-ion because it causes kinetic difficulties to store K-ion. This project presents the design of electrode materials' structural defects, in accordance with the time scales of K-ion kinetics, to achieve high performance of KIBs. We will study crystalline structures that have directional pathways for K-ion insertion and diffusion at a long-range time scale, which allows to achieve high energy density. More importantly, we will investigate the approach of creating oxygen vacancies that allows a fast K-ion knetics at a short-range time scale and therefore a high power density. Simultaneously, developing KIBs requires the understanding of the complex processes occurring within the electrodes. We will perform materials characterisation and chemical analysis to understand the benefits of oxygen vacancies, especially the spatial effect of the vacancies, and acquire much-needed clarity on the fundamental chemistry of reversible K-ion storage, which is important as the development of KIBs is still in its infancy. This will suggest promising avenues for the improvement of KIB electrode materials in a wide range and generate the knowledge that could be transferred to other energy applications. The novelty in the approach is fundamentally different from the previous considerations of enhancing charge transport in the field of KIBs. The project includes the following:

(i) Explore titanium niobium oxides (TNOs) as a new type of KIB anodes to reversibly store K-ion, which will identify promising materials put through as the model materials for the design of OVs.
(ii) Create and control oxygen vacancies located in the surface or towards the bulk of TNOs and investigate the spatial effect of the vacancies on the enhancement of electrode power density.
(iii) Perform in-situ and ex-situ characterisations of anodes with and without oxygen vacancies to best characterise, understand and explain the K-ion kinetics upon the designed structural engineering.
(iv) Demonstrate KIB full-cell prototypes in a lab scale based on the advantages of performance, low-cost and environmental sustainability of the anodes (TNOs) developed in the project and the state-of-the-art cathodes (Prussian blue analogues).
(v) Engage with all stakeholders in the UK's battery industry and be an advocate for KIBs.

Planned Impact

This project and its outcomes will have major impact on the following aspects:

To achieve the ambitious 2040 goal to out-sale petrol and diesel vehicles, it is imperative to develop low-cost and high-performing batteries that can be put into use in a foreseeable future. The successful delivery of this project will lead to prototypes of K-ion batteries (KIBs) based on earth abundant elements, attract academic and industrial interest, and preparation for future commercialisation. It is also envisaged that besides electric vehicles, KIBs are an affordable solution for stationary energy storage and integrate renewables energy (e.g., wind and solar) into grid for off-peak consumption. In a medium term of 4-10-year window, the outcome of this project will have impact through potential intellectual property generated in the field of KIB technology, focused academic and industrial collaborations on KIB materials exploitation and cell management, and employment opportunities in battery production. This will boost the UK's capability in various strategically relevant scientific and technological domains. In a long term of 10-50-year window, the outcome of this project will change the supply chain of KIBs in the UK and around the world and stimulate global knowledge transfer across various energy applications.

This project aims to make significant development in KIB technology by tuning materials' structural defects and enabling high battery performance. As the UK government has now a legally binding target to bring all greenhouse gas emission to net zero by 2050, KIB is an immediate cost-effective and environmentally sustainable energy storage solution and its development will reinforce the transition to electric vehicles and reduce CO2 emission within the UK energy landscape. Damaging effects of transport emissions on the health of the public will be minimised in an affordable low carbon society. The development of KIBs will contribute to large employment of renewable energies in the UK and be used in large-scale stationary energy storage. The ability to store energy at a large scale will have significant influence on providing energy to remote areas and helping aid organisations in the regions where power grid may be damaged by natural disasters. In addition, the increase of the UK's capacity in energy storage will generate large saving on power bills for the public.

In a short term of 3 years, this project will provide highly skilled researchers, i.e., the PRDA and PhD student involved in the project, who will have gained experimental and technical skills as well as knowledge in electrochemical energy storage. They will be exposed to different disciplines to better understand how to bridge fundamental science and practical applications as well as the associated societal and economic issues. The knowledge, skills and experience will be important for these researchers to work in academia and hi-tech sectors with the goal of market innovation for battery technologies and beyond. This project will be a platform for MSci, MSc and BSc students to work on mini-projects. It will help them to engage with nanomaterials, analytical equipment tools, electrochemical technologies, and will therefore enhance their employability.

This project will deliver understanding of the limiting issues of enhancing battery performance and the solutions to these issues. It will also generate insights into the (physio)chemical processes that may occur in battery reactions and even be initially unknown. The understanding and insights will be applicable across many topics, from electrochemical applications to nanotechnology and further to materials sciences. The project will also produce titanium niobium oxides and Prussian blue analogues with structural/compositional features and low production cost. These materials can be used in a wide range of applications, such as medicine, pathology, machinery, etc.


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Title The critical role of hybrid nanostructures for potassium-ion, potassium sulphur, and potassium selenium batteries 
Description The image was created to highlight the critical role of hybrid nanostructures for electrochemical potassium storage. The image was selected by the RSC journal Nanoscale Advances as the front cover of Issue 19, 2021. 
Type Of Art Image 
Year Produced 2021 
Impact This is the first review article that discusses in detail the role of hybrid nanostructures in improving the performance of a range of potassium battery chemistries. Due to the rapidly growing attention on potassium based batteries in the research community in recent years, this image and its being selected as a front cover of an international scientific journal will undoutedly accelerate the impact of potassium battery chemistries and the associated materials development. 
Description 1. We have demonstrated Ti-Nb-O family can be a new type of K-ion battery anode materials and capable of reversibly store K-ion. Two Ti-Nb-O materials, Wadsley-Roth (WR) structure TiNb24O62 (TNO) and layered structure KTiNbO5 (KTNO), have been demonstrated in this regards for the first time.
2. The mechanism of storing K-ion in TNO and KTNO was investigated by using ex-situ characterizations and proven to be an intercalation process.
3. The reversible capacities of TNO and KTNO are among the highest of intercalation-type oxide anodes of K-ion batteries. The rate capability fo the anodes are demonstrated up to 1 A/g, being one of the best results.
4. The effect of oxygen vacancy (OV) in TNO anodes was investigated for the TiNb24O62 anode. We created OVs in the anode structure simultaneously when fabricating TNO/reduced graphene oxide (rGO) composite. The presence of OVs improved K-ion kinetics, and therefore TNO with OVs outperformed TNO without OVs. The improvement was further enhanced by the presence of rGO in the composite.
5. K-ion battery full cells were demonstrated in a lab scale by using KTNO as an example.
6. Several objectives have been met including exploring Ti-Nb-O materials as new K-ion battery anodes, ustilizing OVs to improve K-ion kinetics, investigating the electrochemical mechanism of K-ion storage, and demonstrating K-ion full cells using the newly explored Ti-Nb-O anodes. One objective that has not been met is to control the distribution of OVs at the surface or in the bulk of the oxides. This is due to the difficulty to control the formation of OVs in one-step synthesis.
Exploitation Route The findings obtained so far can be taken forward via two pathways. First, the new K-ion battery anodes could be applied to Na-ion batteries, as both battery systems face the same challenge, i.e., sluggish kinetics of ion diffusion. This pathway has been explored in the work of TNO/rGO anode, where the anode was capable of storing Na-ion reversibly. Second, the new K-ion battery anode with a layered structure could be engineered in the way that interlayer space can be expanded to further facilitate K-ion intercalation and diffusion.
Moreover, the findings obtained proved Nb based oxides are great candidates as K-ion and Na-ion battery anodes, as the structural features of the oxides meet the requirement to store large-sized ions. It is worth furher attention of the research community of post-lithium batteries to continue exploring new Nb based oxide anodes.
Sectors Energy,Environment,Manufacturing, including Industrial Biotechology

Description Diversifying battery chemistries and reducing over reliance on lithium are extremely important for future landscape of energy applications, particularly the applications for which cost-effective and environmental sustainablity outweight performance. The findings of this project diversifies battery chemistries and prove a feasible alternative of enegy storage technology. Moreover, it is crucial to enhance the public awareness of new energy storage technologies before they are accepted by the public. This project provides a platform to increase the visibility of K-ion battery to non-academic audience and reinforce the significance of achieving net zero via developping new energy storage technologies. The PI has coordinated an article "2023 roadmap of K-ion batteries" by the invitation of the IOP. The article received a great deal of attention from many areas outside of academia, including the world's first company focusing on commercializing K-ion batteries. Such link undoubtedly facilitates the conceptual delivery of new ion batteries to the society.
Impact Types Societal

Description Professional development of the PDRA supported by the award
Geographic Reach Local/Municipal/Regional 
Policy Influence Type Influenced training of practitioners or researchers
Description X-ray Absorption Spectroscopy (XAS) Data analysis Workshop received by the PDRA on the grant
Geographic Reach Local/Municipal/Regional 
Policy Influence Type Influenced training of practitioners or researchers
Description Intercalation-type anode materials for potassium-ion batteries
Amount £90,000 (GBP)
Organisation University College London 
Sector Academic/University
Country United Kingdom
Start 09/2021 
End 08/2024
Description Collaboration with computational simulations 
Organisation University of Science and Technology of China USTC
Country China 
Sector Academic/University 
PI Contribution Experimental work and results analysis
Collaborator Contribution Computaional work and results analysis
Impact Collaborative paper has been uploaded to ChemRvix (10.26434/chemrxiv-2022-kdz2g-v2 ) and is being under review by a journal.
Start Year 2022
Description Experimental collaboration 
Organisation University College London
Department Chemical Engineering
Country United Kingdom 
Sector Academic/University 
PI Contribution Experimental work and data analysis
Collaborator Contribution Specific equipment usage.
Impact A collaborative paper has been published.
Start Year 2022
Description Royal Society Short Industry Fellowship 
Organisation Deregallera Ltd
Country United Kingdom 
Sector Private 
PI Contribution Materials synthsis and characterisation, battery cell testing
Collaborator Contribution Materials supply, use of facilities, and staff time
Impact The fellowship is still ongoing.
Start Year 2022
Description Invited seminar (online) to University of Science and Technology of China 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Undergraduate students
Results and Impact 30-40 UG students attended the seminar online. The researh activities, UCL and UK higher education were introduced to them. The seminar sparked many of them to be interested in applying fundings/schorlarships/students to study a PhD at the UK.
Year(s) Of Engagement Activity 2022
Description Invited talk at the 33rd Annual Conference of the Chinese-German Chemical Association (CGCA) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Other audiences
Results and Impact More than 50 attendees including academia, institutions, business, and politics attended the 33rd Annual Conference of the CGCA. The attendees were from Germany, China, US, UK, Saudi Arabia, and France. Some of the research work I presented was carried out by the PDRA whose position is supported by the NIA. The presentation brought attention to potassium ion battereis from a wide range of audience, which is important as potassium battery chemistry is still a new research topic to Europe. It also sparked questions and discussions on potential international collaborations when proper funding calls are open.
Year(s) Of Engagement Activity 2021