Solar batteries: a new material makes it possible to simultaneously absorb light and store energy
IMAGE: ALBERTO JIMÉNEZ, ONE OF THE RESEARCHERS WHO CARRIED OUT THE STUDY view more
CREDIT: UNIVERSITY OF CORDOBA
The collaborative effort between the University of Cordoba and the Max Planck Institute for Solid State Research (Germany) is making progress on the design of a solar battery made from an abundant, non-toxic and easily synthesized material composed of 2D carbon nitride
Solar energy is booming. The improvement of solar technology's capacity to capture as much light as possible, convert it into energy and make it available to meet energy needs is key in the ecological transition towards a more sustainable use of energy sources.
In the process between the collection of light by the solar cell and the on-demand use of energy of, for instance, household appliances, storage plays a crucial role since the availability of solar energy has an inherent intermittency. To facilitate this storage process and deal with problems such as the environmental impact of the extraction, recycling or scarcity of some of the materials necessary for conventional batteries (such as lithium), the concept of the 'solar battery' was born. Solar batteries combine the solar cells that capture light with the storage of its energy in one single device, which then allows the energy to be used when needed.
Alberto Jiménez-Solano, a researcher at the Department of Physics of the University of Cordoba, together with a team from the Max Planck Institute for Solid State Research (Stuttgart, Germany), has carried out a study in which he has explored the design characteristics of a solar battery made from a material based on 2D carbon nitride.
"In Professor Bettina V. Lotsch's group, at the Max Planck Institute, they had managed to synthesize a material capable of absorbing light and storing that energy for later use on demand," explains Alberto Jiménez-Solano, "and it occurred to us to use it to create a solar battery".
To do this, the team first had to find a way to deposit a thin layer of that material (2D potassium carbon nitride, poly(heptazine imide), K-PHI) creating a stable structure to start manufacturing a photovoltaic device due to the fact that that material is normally in powder form or in aqueous suspensions of nanoparticles.
That previous work has now allowed them to present this solar battery design whereby, combining optical simulations and photoelectrochemical experiments, they are able to explain the characteristics of this device's high performance when capturing sunlight and storing energy.
The physical structure of the device consists of "a high-transparency glass, which has a transparent conductive coating (to allow the transport of load), and a series of layers of semi-transparent materials (with different functionalities), and another conductive glass that closes the circuit," describes the researcher. It is essentially a kind of sandwich made from various layers whose thicknesses have been studied to maximize both the level of light absorption and storage. In this case, the system they propose can absorb light on both sides since it is semi-transparent. They found that rear lighting had certain advantages; something that they managed to elucidate "by creating an initial theoretical design in accordance with the experimental restrictions" since this basic science project will not remain only on paper, but will also explore the experimental limits, coming up with feasible designs for these solar batteries.
This device would feature great versatility, since it makes it possible to both to obtain a large, one-off current (such as that needed by photography flash), and a smaller current, which could be sustained over time (such as that needed by a mobile phone).
This project demonstrates the performance of this device, made from a harmless, abundant, environmentally sustainable material (extracted from urea) which is easy to synthesize. The next steps include continuing to study its operation in various situations outside the laboratory, and adapting it to different manufacturing possibilities and needs.
Reference:
Gouder, Andreas & Yao, Liang & Wang, Yang & Podjaski, Filip & Rabinovich, Ksenia & Jiménez-Solano, Alberto & Lotsch, Bettina. (2023). Bridging the Gap between Solar Cells and Batteries: Optical Design of Bifunctional Solar Batteries Based on 2D Carbon Nitrides. Advanced Energy Materials. 13. 10.1002/aenm.202300245
JOURNAL
Advanced Energy Materials
METHOD OF RESEARCH
Experimental study
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
Bridging the Gap between Solar Cells and Batteries: Optical Design of Bifunctional Solar Batteries Based on 2D Carbon Nitrides
Developing a nonflammable electrolyte to prevent thermal runaway in lithium-ion batteries. Nonfluorinated, nonflammable electrolytes present a viable route to achieving thermally stable high-performance batteries.
- Tailoring the molecular structure of organic carbonates in commercial electrolytes reduces the fire hazard of batteries.
Peer-Reviewed PublicationIMAGE: MOLECULAR DESIGN STRATEGY FOR HIGH-FLASHPOINT ELECTROLYTE AND COMPARISON OF ROOM TEMPERATURE IGNITION PROPERTY view more
CREDIT: KOREA INSTITUTE OF SCIENCE AND TECHNOLOGY
The Korea Institute of Science and Technology(KIST, President Seok-Jin Yoon) announced that a collaborative research team led by Dr. Minah Lee of the Energy Storage Research Center, Professor Dong-Hwa Seo of the Korea Advanced Institute of Science and Technology(KAIST), and Drs. Yong-Jin Kim and Jayeon Baek of the Korea Institute of Industrial Technology(KITECH) has developed a nonflammable electrolyte that does not catch fire at room temperature by tailoring the molecular structure of linear organic carbonate to prevent fire and thermal runaway in lithium-ion batteries.
As the use of medium and large-scale lithium-ion batteries in electric vehicles and energy storage systems(ESS) expands, concerns about fires and explosions are growing. Fires in batteries occur when batteries are short-circuited due to external impacts, abuse or aging, and the thermal runaway phenomenon accompanied by a serial exothermic reactions makes it difficult to extinguish the fire and poses a high risk of personal injury. In particular, the linear organic carbonate used in commercial electrolytes for lithium-ion batteries has a low flash point and easily catches fire even at room temperature, which is a direct cause of ignition.
Until now, in order to reduce the flammability of the electrolyte, Intensive fluorination in the solvent molecules or highly concentrated salts has been widely adopted. As a result, the lithium-ion transport in the electrolyte was reduced or those were incompatible with commercial electrodes, limiting their commercialization.
By simultaneously applying alkyl chain extension and alkoxy substitution to the diethyl carbonate(DEC) molecule, a typical linear organic carbonate used in commercial lithium-ion battery electrolytes, the researchers developed a new electrolyte, bis(2-methoxyethyl) carbonate(BMEC), with enhanced flash point and ionic conductivity by increasing intermolecular interactions and the solvation ability. The BMEC solution has a flash point of 121°C, which is 90°C higher than that of the conventional DEC solution, and thus is not ignitable in the temperature range for conventional battery operation. BMEC can dissociate lithium salt stronger than its simple alkylated counterpart, dibutyl carbonate(DBC), solving the problem of slower lithium ion transport when reducing flammability by increasing intermolecular interaction. As a result, it retains more than 92% of the original rate capability of the conventional electrolyte while significantly reducing the fire hazards.
In addition, the new electrolyte alleviated 37% of combustible gas evolution and 62% of heat generation than those of the conventional electrolyte. The research team demonstrated the stable operation of 1Ah lithium-ion batteries over 500 cycles by combining the new electrolyte with a high nickel cathode and a graphite anode. They also conducted a nail-penetration test on a 70% charged 4Ah-level Li-ion battery and confirmed the suppressed thermal runaway.
Dr. Minah Lee of the KIST stated, "The results of this research provide a new direction for designing nonflammable electrolytes, which has been inevitably sacrificed the electrochemical property or economic feasibility." "The developed nonflammable electrolyte has cost competitiveness and excellent compatibility with high-energy density electrode materials, so it is expected to be applied to the conventional battery manufacturing infrastructure. Ultimately, it will accelerate the emergence of high-performance batteries with excellent thermal stability."
Dr. Jayeon Baek of KITECH stated, "The BMEC solution developed in this research can be synthesized by transesterification using low-cost catalysts and easily scaled up. In the future, we will develop the synthesis method using C1 gas (CO or CO2) to enhance its eco-friendliness further."
Nail-penetration test results of 4Ah pouch cells using conventional and new electrolyte
(Left) Electrolyte of a commercial lithium-ion battery (DEC) and a new electrolyte (BMEC) developed by a joint research team from KIST, KITECH, and KAIST (right).
(Left) Electrolyte of a commercial lithium-ion battery (DEC) and a new electrolyte (BMEC) developed by a joint research team from KIST, KITECH, and KAIST (right).
CREDIT
Korea Institute of Science and Technology
Korea Institute of Science and Technology
KIST was established in 1966 as the first government-funded research institute in Korea. KIST now strives to solve national and social challenges and secure growth engines through leading and innovative research. For more information, please visit KIST’s website at https://eng.kist.re.kr/
This research was supported by the the National Research Council of Science & Technology and the Mid-Career Research Progam of the National Research Foundation of Korea grant by the Korea government Ministry of Science and ICT(Minister Jong-Ho Lee). The research result was published in the latest issue of Energy & Environmental Science (IF 32.5, JCR top 0.4%), an international journal in the field of energy and environmental science.
JOURNAL
Energy & Environmental Science
ARTICLE TITLE
Molecularly engineered linear organic carbonates as practically viable nonflammable electrolytes for safe Li-ion batteries
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