Researchers at King Abdullah University of Science and Technology have made great strides in renewable energy storage by using laser pulses to improve the electrode material MXene. Traditional MXene degrades over time, primarily due to the formation of molybdenum oxide. However, with the introduction of laser-processed nanodots, MXene has shown stronger lithium storage capabilities and faster charging speeds. Remarkably, in tests, the material achieved a fourfold increase in storage capacity, comparable to graphite, without any capacity loss being observed.
Researchers have used laser pulses to enhance the electrode properties of MXene, creating a potential breakthrough in rechargeable battery technology that could surpass traditional lithium-ion batteries.
As global society turns to renewable energy sources such as solar and wind power, demand for high-performance rechargeable batteries is increasing. These batteries are critical for storing energy from intermittent renewable energy sources. While today's lithium-ion batteries are efficient, there is still room for improvement. Developing new electrode materials is one way to improve their performance.
ZahraBayhan is developing batteries containing MXenes, which can replace graphite in some batteries due to their excellent conductivity. Image source: ©2023KAUST;AnastasiaSerin
MXene: a promising electrode material
Researchers at King Abdullah University of Science and Technology (KAUST) have shown how laser pulses can be used to change the structure of a promising alternative electrode material called MXene, thereby improving its energy capacity and other key properties. The researchers hope this strategy will help design better anode materials in next-generation batteries.
Graphite contains flat layers of carbon atoms, and during battery charging, lithium atoms are stored between these layers, a process called intercalation. MXenes also contain layers that can accommodate lithium, but these layers are made of transition metals such as titanium or molybdenum combined with carbon or nitrogen atoms, which makes the material highly conductive. The surfaces of these layers also contain other atoms such as oxygen or fluorine. Molybdenum carbide-based MXenes have particularly good lithium storage capabilities, but their performance degrades quickly after repeated charge-discharge cycles.
Solving performance degradation issues
The research team, led by Husam N. Alshareef and PhD student Zahra Bayhan, discovered that this degradation is caused by chemical changes in the MXene structure that form molybdenum oxide.
To solve this problem, the researchers used infrared laser pulses to form small "nanodots" of molybdenum carbide within MXene, a process known as laser scribing. These nanodots are about 10 nanometers wide and are connected to the layer of MXene through a carbon material.
There are several benefits to doing this. First, the nanodots provide additional storage capacity for lithium and speed up the charge and discharge process. Laser treatment also reduces the oxygen content in the material, helping to prevent the formation of problematic molybdenum oxide. Finally, the strong connection between the nanodots and the layers improves the conductivity of MXene and stabilizes its structure during charge and discharge. This provides an economical and fast way to tune battery performance.
Professors Zahra Bayhan and Husam Alshareef believe that laser scribing can be used as a general strategy to improve the performance of other MXenes. Image source: ©2023KAUST;AnastasiaSerin
Promising results and future applications
Anodes made from this laser-scribed material were tested for 1,000 charge-discharge cycles in lithium-ion batteries. Notably, the material with added nanodots increased its electricity storage capacity by four times compared to unmodified MXene, almost reaching the theoretical peak capacity of graphite. Furthermore, the laser-modified material maintained its full capacity throughout the testing phase.
The research team believes that laser scribing can be used as a general strategy to improve the performance of other MXenes. This could help develop a new generation of rechargeable batteries, for example using cheaper and more abundant metals than lithium. "Unlike graphite, MXenes can also incorporate sodium and potassium ions," Alshareef explains.