Researchers treated MXene electrodes with lasers to improve lithium-ion battery performance

Researchers at King Abdullah University of Science and Technology (KAUST) in Saudi Arabia have found that laser scribing or creating nanodots on battery electrodes can improve their storage capacity and stability. The method can be applied to an alternative electrode material called MXene.

Lithium-ion batteries have multiple drawbacks in a wide range of applications, and researchers around the world are looking to improve the technology or find better alternatives.

MXene is a class of two-dimensional materials made of carbon and nitrogen atoms bonded to metals such as titanium or molybdenum. Despite being ceramic, these materials have good electrical conductivity and high capacitance, making them ideal for energy storage applications such as batteries.

Problems with using MXene

Lithium-ion batteries use graphite electrodes that contain layers of carbon atoms. When the battery is charged, lithium ions are stored between these layers, a process scientists call embedding.

MXene is more suitable as an electrode material than graphite because they provide additional storage space for lithium-ion embedding. The problem, however, is that the higher storage capacity is reduced after repeated charging and discharging cycles.

The KAUST researchers found that the reason for the decrease in capacity was a chemical change that led to the formation of molybdenum oxide within the MXene structure.

Improve performance with laser

The research team led by Husam N. Alshareef used a process called laser scribing, in which infrared laser pulses are used to create "nanodots" on molybdenum carbide on MXene electrodes. The nanodots are about 10 nanometers wide and are connected to the MXene layer by a carbon material, the press release said.

The laser-scribing material is used to make the anode and has been tested in more than 1,000 charge-discharge cycles in lithium-ion batteries. The researchers found that anodes with nanodots had four times the electrical storage capacity of anodes without them, and were also able to reach the theoretical maximum capacity of graphite. In addition, even after 1,000 cycles, there was no degradation in performance.

The researchers attribute the improved performance of the laser-scribing material to a variety of factors. The generation of nanodots provides additional storage space for the embedding of lithium ions, thus speeding up the charging process. It also reduces the oxygen content in the material, further preventing the formation of molybdenum oxide and reducing MXene electrode performance.

The connection between the nanodots and the layers further improves the material's electrical conductivity and stabilizes its structure. The researchers believe that the method could be used as a strategy to improve the performance of MXene, which also uses other metals.

While lithium prices have soared due to high demand, MXene can also be used with more abundant metal ions, such as sodium and potassium. It could also lead to the development of a new generation of rechargeable batteries.

"This provides a cost-effective and fast way to tune battery performance," added Dr. Zahra Bayhan. Student at King Abdullah University of Science and Technology.

MXene is a rapidly growing family of two-dimensional (2D) transition metal carbides/nitrides with promising applications in electronics and energy storage. In particular, Mo2CTx MXene, as an anode for lithium-ion batteries, has a higher capacity than other MXenes.

However, this enhanced capacity is accompanied by slow kinetics and poor cyclic stability. Studies have shown that the unstable cycling properties of Mo2CTx are attributable to partial oxidation to MoOx and resulting in structural degradation. A laser-induced Mo2CTx/Mo2C (LS-Mo2CTx) hybrid anode has been developed in which the Mo2C nanodots enhance REDOX kinetics and the laser-reduced oxygen content prevents oxidation-induced structural degradation.

At the same time, the strong connection between the laser-induced Mo2C nanodots and the Mo2CTx nanosheets enhances the conductivity and stabilizes the structure during the charge-discharge cycle. The prepared LS-Mo2CTx negative electrode exhibited enhanced capacity of 340 mAh g−1 versus 83 mAh g−1 (original) and improved cyclic stability (capacity retention of 106.2% versus 80.6% of the original) over 1000 cycles. Laser-induced synthesis methods highlight the potential of MXene-based hybrid materials for high-performance energy storage applications.

Source: Laser Network