Purity of Lithium layer is critical for the performance, storage capacity and the lifetime of solid-state batteries. The shortcomings in the purity of material cannot be negated in the rolled Lithium foil available commercially in the market. In addition to the impurity related problems, the active materials are not homogenous and not binder-free.
Magnetron sputtering, the most popular Physical Vapour Deposition (PVD) technique offers pure, binder-free, and homogeneous layers of cathode material with high-homogeneity, binder-free and importantly high purity.
PVD processes enables to coat precisely thick different layer of materials such as Lithium and Lithium-based material such as
o Lithium Phosphorus Oxide
o Lithium Cobalt Oxide
o Lithium Manganese Cobalt Oxide
sandwiched as a single system on different kind of substrates such as metallic foils or metallized polymer films.
PVD techniques are highly useful for addressing various aspects of development within a broad spectrum of solid-state battery technology.
As PVD is a high vacuum coating technology, the material deposited for battery ends up in the purest form in the battery device and delivers high level performance. Also, such high purity by PVD technology offers high surface reactivity, which is not achievable for conventional rolling method engaged in the battery technology.
PVD processes increase profit margin with less production cost
PVD processes increase profit margin with less production cost as less raw materials are required for battery layers, as the thickness of PVD deposited Lithium anode is four to five-fold thinner than the Lithium anode material made by conventional rolling method.
Picture: PVD battery (left) with minimally used material compared to the conventional rolling battery (right) where high volume of Lithium has been wasted
Integrated PVD processes allow to deposit the Lithium layer with the thickness of 15-25µm on one side or both sides of a 7 – 12µm thick metal substrate. Important to be noted that the PVD coating processes facilitate to coat Lithium layer on the substrate thinner than that of the coating.
Such arrangement is possible only with PVD accurately. In case if the substrate is flexible (polymer) it needs to be metallized before coating functional layers. Such metallization of polymers can also be done by PVD processes.
PVD techniques can be utilized to tune the fundamental functionalities of material layers in the battery such as
· the influence of the crystalline structure
· crystal orientation and defects on the electronic and ionic conductivity
· electrochemical performance
· and underlying material transformations over aging.
Employing PVD technology for the development of novel materials helps to screen different material for high throughput and check their suitability and appropriateness for battery technology. The fabrication of thin film battery components, such as thin separator layers and various coatings for design and development of battery technology are very much possible by PVD with high accuracy and reproducibility.
In order to further advance the development and performance of solid-state batteries by PVD technology, the focus is on:
Attempting different combination of cathode materials in PVD system to test their battery functionalities combining with strong theoretical understanding and computational methodology such as data mining.
Employing ion-beam assisted tuning in PVD for the deposition processes of intercalation electrodes with required crystal structure while maintaining the process temperature well below the crystallization temperature.
the research on developing efficient diffusion barriers to withstand high sintering temperatures without being damaged, which is very crucial to hold the stack of cathode active material and the electrolyte in the battery.
The development goes on….