.jpg)
Image Credits: silabob/shutterstock.com
Lithium batteries are used extensively across daily life, including powering smartphones, electric cars, and hoverboards, to name just a few. Over the past few decades, a lot of effort has been put into discovering new cathode coating materials and technologies for the purpose of improving the electrochemical performance of cathode materials and battery safety, among other reasons.
Benefits of Lithium Batteries
If lithium battery-powered electric vehicles replaced the majority of gasoline-powered vehicles, greenhouse gas emissions would likely be reduced by a substantial margin.
Lithium also has the lowest reduction potential of any element, enhancing their overall cell potential. It is also the third lightest element and along with having one of the smallest ionic radii of any single charged ion, it makes lithium batteries capable of possessing a high power density and gravimetric and volumetric capacity.
Issues with Lithium Batteries
But while lithium batteries are highly energy efficient, there are concerns over their long-term suitability for meeting the world’s energy needs, for instance, for use in powering electric grid applications, or for improving the quality of energy gathered from renewable options, such as wind and solar sources. At present, they prove costly when used for electric grids or transportation, and the reserves of lithium and other metals may not last for long enough to be a reliable long-term solution. However, a shortage of lithium stores is thought to be unlikely in the near future.
Regarding cathode coating for lithium batteries, a number of factors can affect the coating’s performance in different ways, for instance, the structure and properties of the coating material, the cathode, and the coating technology. It’s essential that structure is understood to enable Li+ migration and electron transfer to improve the performance of a cathode.
Reasons for a New Coating for Lithium Batteries
A lot of research has been put into finding methods of improving a battery’s electrochemical performance, as the cathode is an essential part in a secondary (rechargeable) lithium battery. One common method for improving battery performance is altering the cathode surface coating. This is said to improve the performance of the cathode by changing the surface chemistry or by making a physical layer of protection. As a whole, a cathode coating layer should have stable chemical properties that do not lead to negative reactions between the coating and the electrode, and a high redox potential so the cathode coating isn’t oxidized at high voltages.
Recent, commonly used materials to alter cathodes include:
- A number of oxides
- Active electrode materials
- Phosphate
- Carbon
Common coating methods include:
- Co-precipitation
- Sol-gel
- Vapor deposition
- Dry coating methods
These methods are thought to enhance electrochemical performance in cathode material under certain conditions.
Cathode Coating and Battery Safety
Safety is also another key reason why research is going into finding new cathode coatings for lithium batteries. Although the lithium batteries that power everyday devices such as smartphones are unlikely to catch fire, work is still being done to lessen fire risks even further. Thin films of protective materials that react to increases in temperate inside the battery are being explored for this purpose. The alterations in the material’s various properties and structure block the current, letting the battery cool safely. Modifications to electrolyte solutions inside the battery are also being developed, wherein the electrolyte solutions would have chemical additives that prevent combustion.
However, once these alterations to the battery coating or electrolyte solutions have been activated, the battery is no longer reusable, or, the effect of the materials is reduced due to slow response times or the ability to only operate in a small voltage range.
New Cathode Coatings in Development
A thermoresponsive material has been developed to combat this issue, which is made from polyethylene and spiky nickel microparticles coated with graphene. It is more than 1,000 times as sensitive to changes in temperature when compared with other materials, and it also allows the battery to be reused after it has cooled. Its functionality in large batteries, for instance, those used to power electric cars, is not yet fully understood.
Graphene-tin oxides are also an option being keenly explored by researchers for use on lithium battery anodes. The benefits of graphene-tin oxide are threefold. It possesses a high theoretical charging capacity, graphene has high conductivity, and graphene oxide and tin oxide nanocrystals are in close contact in this particular particulate coating method. However, this process has historically been expensive and only possible at high temperatures. With new technology, this process can be carried out at room temperature and in environmentally friendly ways.
Current Types of Coating for Lithium Batteries
Oxides
While the cycle life of cathode materials can be increased with oxides, they can have very different electrochemical properties.
Active Electrode Materials
- Li4Ti5O12
- LiFePO4
- LiNiPO4
- LiCoO2
Phosphate
Carbon
Carbon materials are used to modify cathode materials that have poor conductivity.
Alternative Coating Materials
- Fluoride
- Silicate
- Polymers
- Metals
Summary
There are numerous reasons for new coating materials to be developed for lithium batteries, from battery performance and safety, in particular reducing combustion risks in batteries used in everyday devices such as smartphones. While promising new developments have been made, they do pose certain drawbacks when considered for use in larger batteries to power bigger equipment, like electric vehicles. Generally, there is a paucity of in-depth studies exploring the individual factors that affect cathode performance, as most studies concentrate on the performance of cathode materials.
Sources and Further Reading
Disclaimer: The views expressed here are those of the author expressed in their private capacity and do not necessarily represent the views of AZoM.com Limited T/A AZoNetwork the owner and operator of this website. This disclaimer forms part of the Terms and conditions of use of this website.