New battery breakthrough: It sequesters carbon while discharging, and its energy density is 7 times that of lithium batteries.

September 28, 2023
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The application of batteries is of very important significance. Power batteries are the core of electrification in the transportation field and can indirectly promote the significant reduction of carbon dioxide emissions; the application of batteries in the energy storage field can ensure the stability and reliability of renewable energy power supply.


But how do we make batteries cheap, have high energy density, and have a longer lifespan? Scientists are constantly exploring, and various technical routes are also showing their magic. Lithium-ion batteries are currently the mainstream.


Now there is a new technology that not only has a battery energy density that is more than 7 times that of traditional lithium-ion batteries, but can also fix carbon dioxide into carbonate and carbon while outputting electrical energy. It is lithium-carbon dioxide batteries (Li-CO2 Batteries). ).

Lithium-carbon dioxide batteries have the dual advantages of energy storage and carbon sequestration, which can be described as "killing two birds with one stone."


This new electrochemical energy storage system with broad application prospects has attracted the research interest of scientific researchers since its inception.


However, the development and application of any new technology needs to be implemented step by step. The researchers said that the development of lithium-carbon dioxide batteries is still in its early stages. For example, the production method of the most important catalyst is still relatively slow and inefficient. It is necessary to find efficient electrocatalysts and deeply understand their reaction mechanisms.


Therefore, the University of Surrey, Imperial College London and Peking University have recently developed a new electrochemical test platform that can help accelerate the evaluation and development of lithium-carbon dioxide battery catalysts. Compared with traditional methods, this new method is extremely cost-effective, efficient and controllable, and is expected to overcome the problems faced by the development and application of lithium-carbon dioxide batteries.


The past and present of lithium-carbon dioxide batteries


Secondary (rechargeable) lithium-ion batteries in the modern sense were born in 1983, which also allowed Dr. Akira Yoshino, a key figure in promoting the development of lithium-ion batteries at that time, to win the Nobel Prize in Chemistry.

Later, in order to meet the use requirements of more equipment and constraints, researchers continued to invest in research on lithium-oxygen (Li-O2) batteries (ie, lithium-air batteries). Today's lithium-carbon dioxide batteries are also developed on this basis.


Lithium carbon dioxide batteries work on the principle that when the battery is charged, lithium ions move from the positive electrode of the battery through the electrolyte to the negative electrode. The carbon used as the negative electrode has a layered structure with many micropores. The lithium ions that reach the negative electrode are embedded in the micropores of the carbon layer. Therefore, the more lithium ions embedded, the higher the charging capacity.

In the same way, during the use (discharge) of the battery, the lithium ions embedded in the carbon layer of the negative electrode escape and move back to the positive electrode. The more lithium ions that return to the positive electrode, the higher the discharge capacity.


As a rechargeable battery with great development potential, lithium-carbon dioxide batteries have extremely high energy density, and batteries with higher energy density can store more electricity per unit volume.


It is understood that the current energy density of mainstream lithium iron phosphate batteries is below 200Wh/kg, and the energy density of ternary lithium batteries is between 200-300Wh/kg. Sun Shigang, an academician of the Chinese Academy of Sciences, said that the current energy density of lithium-ion batteries is close to the ceiling. The theoretical energy density of lithium-carbon dioxide batteries is as high as 1876Wh/kg, which is more than 7 times that of ordinary lithium-ion batteries.

Not only that, the reversible electrochemical reaction in Li-CO2 batteries: 4Li + 3CO2 =2Li2CO3 + C (E0 = 2.80 V vs Li/Li+) is also a new way to fix CO2. Traditional CO2 fixation methods require continuous energy supply. If this energy supply is based on fossil fuel production capacity, more CO2 will be emitted. In comparison, lithium-carbon dioxide batteries sequester carbon in a much cleaner way.


It can be said that lithium-carbon dioxide batteries are both a key battery technology and an important carbon sequestration technology that can make dual contributions to combating climate change.


But it is still in the early stages of development. There are many factors that affect the performance of lithium-carbon dioxide batteries.


During the battery reaction process, lithium carbonate (Li2CO3), as the main discharge product, is a wide-bandgap insulator, which will cause its decomposition kinetics to slow down during charging; during the cycle, Li2CO3 undergoes incomplete decomposition and irreversible transformation. The formation of and the accumulation of solid carbonate materials on the cathode surface will also lead to a significant decrease in electrochemical performance until the "sudden death" of the Li-CO2 battery.


To address this problem, developing bidirectional catalysts to accelerate the conversion reaction kinetics during discharge and charging is the key to improving the energy efficiency and cycle life of Li-CO2 batteries.


What is the use of a multifunctional electrochemical test platform?


To address the corresponding challenges, researchers from the University of Surrey, Imperial College London and Peking University designed a multifunctional on-chip electrochemical testing platform that can perform multiple tasks simultaneously. This platform facilitates electrocatalyst screening, optimization of operating conditions, and study of CO2 conversion in high-performance lithium-CO2 batteries.


The researchers said that traditional Li-CO2 battery catalyst exploration methods mainly rely on trial-and-error methods and single-mode characterization/testing techniques, which are time-consuming and inefficient.


Therefore, it is necessary to establish a simplified multi-functional testing platform to quickly screen catalysts and conduct multi-mode characterization tests in a short time and nanoscale spatial resolution, so as to more comprehensively understand the emerging technology of Li-CO2 batteries and accelerate its development. develop.


The "lab-on-a-chip LCB platform" developed and designed by the researchers has the functions of three-electrode electrochemical testing, catalyst screening, and in-situ detection of chemical composition and morphological evolution.


Using this platform, the researchers systematically evaluated the potential of a series of candidate catalysts to promote transformation reactions and studied their reversibility and reaction pathways.


Candidate catalysts include platinum, gold, silver, copper, iron and nickel in a high-density nanoparticle state. Finally, it was found that when platinum nanoparticles are used as catalysts, the battery has obvious minimum polarization performance (0.55 V), the highest reversibility, and a new reaction path, demonstrating superior performance. This experimental result also reveals the development potential of lithium-carbon dioxide batteries.


The researchers say the lithium-carbon dioxide battery (LCB) platform could also play an important role in further exploration, including:


(1) Screen electrolytes with stable solvents for lithium-carbon dioxide battery reactions by integrating microfluidic systems or patterning different quasi-solid electrolytes on the platform;


(2) Explore different lithium anode protection strategies or screen other prelithiated anodes for lithium-carbon dioxide batteries.


"Developing new technologies for negative emissions is crucial. Our lab-on-a-chip platform will play a key role in achieving this. It can also be applied to other systems such as metal-air batteries, fuel cells and photoelectrochemical cells." Imperial London said Yulong Zhao, senior lecturer at the college.

Overall, the design of the LCB platform is expected to overcome the problems faced by the development of lithium-carbon dioxide batteries, including rapid screening of catalysts, research on reaction mechanisms, and practical applications from nanoscience to cutting-edge carbon removal technology.