Initial Background Research

In the 21st century, climate change and energy crisis have become the main challenges to realize the sustainable development goals. Lithium-ion batteries (LIBs) are widely used in new energy vehicles, electronic products and energy storage due to their advantages of high energy density, good energy efficiency and low pollution. According to a report by the International Energy Agency (IEA), the global demand for batteries will rise sharply, and it is expected that by 2030, the global installed scale of energy storage will reach 1,500 GW, of which 90% will be battery storage, and the scale of battery energy storage will reach 1,200 GW.

However, the wide application of lithium batteries also brings the challenge of waste battery disposal. China, as the world's largest producer and consumer of lithium batteries, the problem of waste battery disposal is particularly serious. According to the report of relevant departments, 4,000 tons of waste lithium batteries contain 1,100 tons of heavy metals and 200 tons of toxic electrolytes, which may pollute soil and water bodies and affect human health through the food chain if not handled properly. At the same time, waste batteries contain a large number of recyclable metal resources, if not recycled, not only a waste of resources, but also exacerbate the exploitation of mineral resources, damage to the local ecological environment, triggering soil erosion and dust pollution, affecting the living environment of local residents, contrary to the concept of sustainable development.

Fig. 1 Environmental Pollution of Used Batteries

In order to cope with these challenges, recycling and reusing used lithium batteries have become the best solution. However, the current global lithium battery recycling rate is very low, and a large amount of lithium resources are wasted and pollute the environment. This is mainly due to the fact that the existing industrialized recycling technologies are still not mature enough, and there is a big difference between theory and practice in the application process. In order to solve these problems, BIT-China focuses on the recycling and reuse of used lithium-ion batteries this year, and plans to use synthetic biology technology to build an experimental system to realize battery recycling.

Background Deepening

In order to understand the current situation of the lithium battery market, we consulted Prof. Sun Kening, a professor and doctoral supervisor at the School of Chemistry and Chemical Engineering of Beijing Institute of Technology, who is an expert in the field of lithium batteries and an executive of Beijing Huitao New Energy Technology Co.

Fig. 2 Communication with Prof. Sun Kening

He gave us a detailed explanation of the current situation of the lithium battery market. After decades of development and innovation, China's lithium battery industry chain has been gradually perfected, covering the whole process from production to recycling, and the related industries have achieved great improvement in both quantity and quality, with the market expanding continuously. At the same time, he also talked about the world battery market, predicting that the future market will continue to maintain the trend of increasing.

When Prof. Sun Kening talked about the world market for lithium batteries, he mentioned the EU Batteries and Waste Batteries Regulation, which came into force on February 18th this year, and suggested that we should pay attention to the industry guidelines, which may have an impact on the future market development trend.

We then reviewed the relevant documents. This new regulation applies to all batteries, including used portable batteries, electric vehicle batteries, industrial batteries and others. The regulation sets out a framework for restricting hazardous substances in batteries, ensuring that batteries placed on the EU single market will only be allowed to contain a limited number of essential hazardous substances, and that substances of concern used in batteries will be regularly reviewed. It also stipulates that from 2025, recycling efficiency, material recovery and recycling targets will be phased in, and that all collected waste batteries must be recycled and a high level of recycling must be achieved, particularly for key raw materials such as cobalt, lithium and nickel.

For an in-depth look at this new legislation, we consulted with Mr. Gong Xiangqian, who is a member of the International Union for Conservation of Nature (IUCN). Mr. Gong Xiangqian is a member of the Legal Committee of the International Union for Conservation of Nature (IUCN) and the Executive Director of the China European Law Research Association, and is highly accomplished in the field of European regulations and international law. Mr. Gong told us that the introduction of this new regulation shows that the global battery industry is paying more and more attention to environmental protection and sustainability, and in the future will pay more and more attention to the recycling of lithium batteries. The demand for batteries will increase, the requirements will become more stringent, and there is an urgent need to invent a green and low-carbon recycling technology.

Fig. 3 Dialogue with Prof. Gong Xiangqian

In order to further explore the significance and feasibility of lithium battery recycling, we asked Prof. Chen Renjie from the School of Materials of Beijing Institute of Technology. He summarized the new “3R” principle of “redesign, reuse, and recycle” for developing new sustainable battery systems, as well as the more comprehensive “efficiency” principle of “recycling”. The new “3R” principle of “redesign, reuse, and recycle” and the more comprehensive “3E” evaluation standard of “efficiency, economy, and environment”.

Fig. 4 Communication with Prof. Chen Renjie

During our conversation with Prof. Chen, we studied the importance of lithium battery recycling and the shortcomings of the existing technology. Prof. Chen told us that according to some reports, lithium resources are expected to be depleted by 2050, so all countries are researching advanced lithium battery recycling technologies. Standing in the academic world, Prof. Chen told us the importance of this technology, which has already had a large impact in the academic world.

Mineral resources of key metals needed for lithium batteries are available in the Xinjiang Uygur Autonomous Region (XUAR), so we also talked to the XUAR Department of Natural Resources and asked them about the significance of recycling lithium-ion batteries from the government department's perspective. The relevant departments told us that this can not only solve the environmental pollution problem and alleviate the mining of metal resources, but also drive the development of the local economy. The landing of the new technology will revolutionize the industrial chain, bring economic gains, and increase jobs to alleviate the employment problem.

In addition, in August this year we participated in the World Battery and Energy Storage Industry Expo held in Guangzhou, which brought together many well-known companies in the battery field, including BYD, Weilan New Energy and other well-known companies. We had a great time communicating with the technical and marketing staff of these battery companies, and listened to the suggestions and opinions of professionals in different fields on our project, which deepened our members' understanding of the existing world battery development industry.

Fig. 5 World Battery and Energy Storage Expo

At the expo, we also heard the views of several companies on lithium-ion recycling technology, and they agreed that this technology is of great significance. And the recycling of lithium-ion batteries was also a hot topic of their attention, and this technology will have great potential in the future, which may further promote the current global energy structure change. At the same time, we talked about our technology for some of the companies at the conference, and they expressed their affirmation of our project and looked forward to the future application of our project.

Fig. 6 Communicating with technical personnel of enterprises

Preliminary project design

While browsing the official website of the United Nations to learn about sustainable development, we noticed that among the 17 UN Sustainable Development Goals, Goal 12 - Ensure sustainable consumption and production patterns is very suitable for our project, and we put the concept of “Recycling & Recovery” into it. We incorporated the concept of “Recycle & Recovery” into the design of the project. After this research, we designed the Ouroboros project to recycle lithium-ion batteries.

In the first step, we produced the required leachate - citric acid, gluconic acid and hydrogen peroxide - by culturing Aspergillus niger and Picrospermum berghei, which exhibits the enzyme glucose oxidase (GOx) on its surface. Subsequently, the black powder was treated by media leaching to obtain a solution containing metal ions.

In the second step we developed an expression vector for Pichia pastoris to construct a yeast surface display system and to display a variety of metal ion binding peptides that selectively adsorb specific metal ions. After adsorption, we can recover these adsorbed metal ions through a decoupling process, which can be applied to the mineralization process.

In addition, through simulation experiments, we found that some of the peptides exhibited the potential for self-assembly, a property that predicts their great potential application in improving adsorption efficiency.

In the last step, we chose to recombinantly express the efficient urease gene of S. pasteurii in E. coli and constructed a dual plasmid system to enhance the expression efficiency. The urease catalyzed the hydrolysis of urea to produce ammonia and carbonate ions, which raised the environmental pH, and the carbonate combined with metal ions to form carbonate precipitates, which were used as feedstock for the fabrication of the new batteries, completing our design.

Once the initial design of the project was completed, advice was immediately sought from industry. Professor Li Li, a professor at the School of Materials of Beijing Institute of Technology and a researcher at the Beijing Electric Vehicle Collaborative Innovation Center, affirmed our design and, based on his many years of experience working with lithium recycling, felt that our idea of bio-lithium recycling was basically feasible, and encouraged us to use the new technology to improve the existing recycling system.

For the consideration of genetic lines and experimental design, we consulted Prof. Li Chun from Tsinghua University. He is also the Chinese executive member of the Biocatalysis Branch of the Asian Federation of Biotechnology and the executive member of the Asian Synthetic Biology Consortium, and is highly established in the field of synthetic biology. Prof. Li praised our experimental design and was surprised that as undergraduates we could conceive such a large and complete experimental design. For our wet experiment, he suggested us to use multi-copy lithium binding peptide, which we also simulated and verified, and the result was indeed that multi-copy binding was more effective. After thinking about it, we added all the useful suggestions into our experimental design.

Fig. 7 Prof. Li Chun

Project improvement

After a comprehensive literature research, we initiated an experiment for the efficient recovery of metal ions from used batteries. In the field of bioleaching, we mainly considered two leaching methods: two-step leaching and media method. In two-step leaching, the material to be leached is added after the logarithmic growth period of Aspergillus niger in the expectation of achieving a high leaching rate of metal ions at this stage. The media method, on the other hand, involves using only pure media for leaching by first separating the bacteria from the medium, which in turn allows for increased leaching efficiency through heating when needed.

After determining the basic information of these two methods, we had an in-depth communication with Prof. Zhang Guimin from Beijing University of Chemical Technology. Prof. Zhang is a professor at the Beijing University of Chemical Technology and a board member of the China Biofermentation Industry Association, and has a wealth of research experience. Prof. Zhang pointed out that a large number of negatively charged biomolecules existed on the surface of Aspergillus niger, which might have an adsorption effect on metal ions and thus promote the leaching effect of the two-step method. Therefore, she suggested us to add a set of comparison experiments for verification.

Fig. 8 Prof. Zhang Guimin

We designed and implemented the comparison experiments of the two leaching methods and observed the adsorption of Aspergillus niger on four target metal ions by scanning electron microscope technique. The experimental results showed that Prof. Zhang's hypothesis was not valid and the adsorption of Aspergillus niger significantly limited the final leaching rate. In addition, the leaching rate of the two-step method was significantly lower than that of the media method due to the temperature limitation. Based on these results, we finally chose the media method as the optimal leaching method.

When we carried out the adsorption experiments, we envisioned to use the self-assembly technique to improve the binding ability of metal-binding peptides, we carried out the self-assembly structure prediction of peptides by alphafold and got the results after assembly, but we didn't know the mechanism and wanted to get the results when we got more peptides, for this reason, we approached Dr. Yu Yang from the Institute of Biochemistry, Beijing Institute of Technology, to show him the We showed him the molecular docking results obtained by using the software, and asked for advice on how to use molecular dynamics simulation to study the assembly between peptides.

Fig. 9 Communication with Prof. Yu Yang

Dr. Yu explained to us the basic principles of molecular dynamics based on Newtonian mechanics calculations, including energy calculations, molecular force field, etc. The force on a part of the molecule is obtained by taking the gradient, and the kinetic trajectory is obtained by using Newtonian mechanics and numerical calculations. Boundary setting issues were discussed, and it was determined that our molecules of about 10 peptides could simulate the assembly process of about 30 or so. Dr. Yu also introduced the cluster used for his own calculations and was willing to assist us with more accurate kinetic simulation calculations, which has significant implications for our modeling work.

We encountered some problems in performing quantum chemistry simulation calculations with machine learning, so we asked Prof. Chen shilv of the Institute of Computational Chemistry at Beijing Institute of Technology for advice. He is an expert in peptide and metal ion calculations in the field of computational chemistry.

Fig. 10 Communication with Prof. Chen Shilv

When optimizing the structure of metal ion-bound peptides, Prof. Chen suggested that we should first make sure that the amino acid chains are connected correctly, and adjust the structure of the input peptide chains as long as they are chemically reasonable, without overlapping, too close to the atoms, etc. Otherwise, we may judge the chain building error in the machine learning method and get the wrong result when the peptide chain is incorrectly decomposed, but the result may not be optimal, so it is better to try more structures. structure.

Add metal ions to the optimized structure. For the setting of spin state, it is better to try several ways of setting because the coordination may lead to multiple changes. As the peptide itself may be charged, it needs to pay attention to the pH and H⁺ transfer of the environment, which can be disregarded for the ligand ion. Reduce small molecules such as H₂O, Cl^-, etc., during calculations; too many small molecules increase the complexity of the state, which may have unintended negative effects.

Since we would like to use structure optimization to show the assembly process, and molecular dynamics simulation is more commonly used in such studies, we asked our teacher about molecular dynamics simulation. According to Prof. Chen, both are processes on the potential energy surface, and the algorithms for calculation are similar. But the basic principles are different: molecular dynamics simulation is based on Newtonian mechanics, and structure optimization is based on quantum chemical calculations. The goal of molecular dynamics simulation is not to find the structure with the smallest energy, so it will vibrate repeatedly, transform around the low-energy barrier structure and vibrate repeatedly, while the structure optimization gives priority to finding the most stable structure.

In addition, Prof. Chen suggested that we add binding energy calculations to calculate the energies of peptides, metal ion reactants, and products, respectively, to derive the binding energy and determine the selectivity of the peptides.

For the background of the project, Prof. Chen suggested to add evidence of the difficulty of separating these ions by simple inorganic chemistry methods, such as Ksp data, which will better reflect the practical significance of our project.

After determining the basic plan, we contacted Ms. Ma Yurong from Beijing Institute of Technology, who focuses on biomineralization and the crystallization process of biologically inspired inorganic crystals, and has made breakthroughs in the study of the formation mechanism of biominerals and the relationship between micro- and nanostructures and mechanical properties. She generously shared her experience in biomineralization and provided valuable advice on our project design.

Prof. Ma suggested us to use polarized light microscope to observe the biomineralization products. Given that ours are biological samples, she suggested that we could try to crush the samples to increase the number and size of crystals observed, and we could also try to lyophilize the samples with bacteria and analyze them in-situ to observe the interactions between the bacteria and the mineralization products.

Fig. 11 Communication with Prof. Ma Yurong

When asked about issues related to future industrialization, the professor suggested that if the yield of our final mineralization cannot meet the requirements, we can move towards biomimetic mineralization in the future. Biomimetic mineralization technology mimics the process of biomineralization in nature, using synthetic biomineralization-related molecules or materials to convert metal ions into minerals, which is environmentally friendly, selective, and has the advantages of high resource utilization. Combined with the design of our biomineralization project, the biomimetic mineralization technology can be applied to urease immobilization, metal ion adsorption and treatment of mineralization products, etc. It can improve the recovery rate and utilization efficiency of metal resources, reduce the cost of production, and realize the recycling of resources, which can provide a new way of thinking for solving the problems of metal resource shortage and environmental pollution.

This exchange provides valuable guidance for our team's research in the direction of biomineralization and points out the direction of future industrialization research. We will continue to optimize the experimental conditions, improve the mineralization efficiency, and explore the application prospects of biomimetic mineralization.

For the hardware design, we consulted Prof. Xiyan Xu, a member of the Specialized Committee on Environmental Protection of the Chinese Society of Chemical Industry, a senior member of the Chinese Nuclear Society and the Chinese Society of Environmental Science, and a professor at the Institute of Chemical Engineering, Beijing Institute of Technology. As an expert in the field of wastewater treatment and reactor design, he gave his opinion on our settling device. He pointed out that the existing design is not enough to achieve the ideal effect and suggested us to refer to the design of settling tank for wastewater treatment. We have thought about this and improved it, details of which can be found on our Hardware page.

Fig. 12 Communication with Prof. Xu Xiyan

In order to avoid the risks in the experiments, we talked with Prof. Li Chun from Tsinghua University and Dr. Huan Sun from Institute of Medicinal Plants, Chinese Academy of Medical Sciences. We discussed the safety precautions and operation rules in microbiology laboratory in depth. Both professors emphasized the strict biosafety operation standards in microbiology laboratories, including personal protective measures, disposal of biological experimental waste, disinfection and ventilation of laboratory space. At the same time, the teachers also mentioned some important rules that must be observed when conducting microbiology experiments, such as strictly controlling the biosafety level in the laboratory, rationally using the biosafety cabinet, and observing the prohibition of food and water in the laboratory. Such exchanges gave us a deeper understanding of microbiology laboratory safety, and we also paid more attention to the teacher's comments and suggestions, which will be a great guidance for our future experimental work.

Project Evaluation

Since we used a variety of engineered bacteria and testing techniques, accounting for costs and analyzing economic feasibility was a difficult task for us science students. So we sought help from Prof. Yiming Wei, a foreign member of the Russian Academy of Engineering and a member of the German National Academy of Engineering, and Prof. Xiaochen Yuan, a professor at the School of Management and Economics of the Beijing Institute of Technology, both of whom have made certain achievements in energy economics. In addition, Prof. Wei Yiming is also the core author of the Synthesis Report of the Sixth Assessment Report of the United Nations Intergovernmental Panel on Climate Change (IPCC) and the Coordinate Lead Author (CLA) of the Working Group III Report (there are 34 CLAs in the world), and he has done in-depth research on the climate crisis.

Fig. 13 Exchange with Prof. Wei Yiming and Prof. Yuan Xiaochen

The professors gave us a comprehensive overview of the current state of the carbon market and the energy economy market, emphasizing the potential for significant growth in the coming decades. As lithium resources dwindle, prices in the carbon market are expected to rise, as are battery products and related technologies, which bodes well for the bright future of our project.

In addition, the two professors helped us sort out how to calculate project costs, carbon reduction accounting, and market demand. According to rough calculations, our technology can make the company economically profitable and has great potential for development. They also pointed out the highlights of our project and the competition. When our recycling technology is mature, it will have certain competitiveness and influence in the future market. They suggested that we should carry out Green recycling assessment, resource criticality assessment, energy flow analysis environmental impact assessment, etc. to analyze the technology and find the direction of improvement. To analyze the technology in all aspects and find the direction of improvement. A rough costing based on the current data can be seen in the following PDF.

After consulting with the two professors, we took our costing records to an industrial investor, Mr. Han Xiuliang, who has many years of investment experience in the energy market. When he listened to our project introduction and costing, he affirmed that the costing was accurate in the general direction. At the same time, he also added that our direction is the hot field of investment now, the industrialization prospect is brighter, and this technology will be promising in the future. Our products can bring substantial benefits to enterprises, and encourage enterprises to actively participate in environmental protection work, to contribute to environmental protection. On the one hand, it brings economic benefits to enterprises, and on the other hand, it promotes sustainable development.

In order to get a clear picture of the real situation of the battery recycling enterprises in the market and listen to their real needs, we sought help from two lithium-ion battery recycling enterprises. We asked Mr. Xiao Fangping, CEO from Guangdong Shengxiang New Material Technology Co., Ltd. and Mr. Ding Anxing, CEO from Jiexing Lithium Co. They are both leaders in their companies and have a comprehensive understanding and unique personal insights into their companies and even the industry as a whole.

Fig. 14 Dialogue with Mr. Xiao Fangping

Fig. 15 Conversation with Mr. Ding Anxing

We asked them to review our project and asked them about the feasibility of industrializing the overall project. We received a positive response that our technology could be implemented in a facility that is not too different from the current chemical wet process, and that it might be possible to simply upgrade an existing chemical treatment plant to our project. In addition, both of them also encouraged our project to continue to explore the potential applications, such as the application of metal ion recovery in water, etc., and effectively contribute to the green circular economy in other aspects. In addition, after the project is industrialized, we can gain benefits from the maintenance of the supporting facilities and improve the competitiveness of the project.

SDG Work

At the beginning of our understanding of SDG, in order to understand how iGEM interacts with SDG, we interviewed Yaxin, the team leader of Heidelberg 2023, who is also the leader of the team's SDG work and led the team to the Best Sustainable Development Goals award. She explained to us the integration of synthetic biology and SDG, and how to make considerations and choices about SDG work. At the same time, after listening to our work plan, she suggested that we supplement our interviews with people in the battery-contaminated areas, which would give us a better understanding of the actual situation.

Fig. 16 Communication with Yaxin

This was our first contact with SDG in iGEM, and we learned a lot from her explanation to improve our work plan. After this exchange, we decided to make a distinctive SDG work, hoping to combine Human Practice and SDG to complement each other.

Stakeholders are the people we have to focus on when we do social practice work, and the program has to be adapted to their needs. So we thought about whether there are also Stakeholders that we need to pay attention to when we work on SDGs, and we drew on the idea of Human Practice to summarize the Stakeholders that SDGs may encounter.

Fig. 17 General SDGs Stakeholders

Therefore, when carrying out the activities, we fully considered the needs of different stakeholders, and carried out different activities and interviews for different segments of the population.

While conducting exchanges and human practice, we discovered the potential of the project and the direction of future applications, which have a positive effect on the realization of the SDG. The leaching part of the project can replace the existing inorganic acid leaching of the ore and reduce the pollution, which is in line with the concept of SDG 12. After talking with Fudan and Prof. Xu Xiyan, we also clarified that the adsorption and mineralization part can be applied to the enrichment and utilization of heavy metal ions in water, which not only realizes the recycling of high-value metals, but also purifies the water resources, which is in line with the SDG 6. Moreover, our hardware can also replace part of the manual labor, which prevents the workers from being exposed to the erosion of the chemical substances that may affect their health, and provides a safe and healthy jobs, advancing the realization of SDG 8.

In order to further promote sustainable development, we carried out some project iterations for SDG. For example, Prof. Wang Bo and Prof. Feng Xiao both mentioned that the industrialized cultivation of strains may produce too much carbon dioxide, exacerbating the greenhouse effect, which is against SDG 13. In response to this, we chose to use metal-organic framework materials to absorb carbon dioxide and achieve carbon cycling within the project.

Prof. Xu Xiyan found that we did not consider the industrial wastewater generated from mineralization when designing the hardware, and that direct discharge would lead to water pollution, which is not in line with the concept of SDG 6. So we decided to reflux the remaining solution of mineralization into the metal solution to improve the recovery rate of ions on one hand, and reduce the pollution of water environment on the other hand.

Detailed SDG content can be viewed on the Sustainable Development Goals page.