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Northwestern team devises new computational design framework for optimized coatings for Li-ion cathodes to prolong cycle life
23 January 2017
Researchers at Northwestern University, with a colleague from the University of Wisconsin, Madison, have developed a new computational design framework that can pinpoint optimal materials with which to coat the cathode in lithium-ion batteries. The optimized coatings have the potential to prolong the cycle-life of Li-ion batteries and surpass the performance of common coatings based on conventional materials.
The high-throughput density-functional-theory-based framework, presented in an open access paper in the journal Nature Communications, consists of reaction models that describe thermodynamic and electrochemical stabilities, and acid-scavenging capabilities of materials.
Major intrinsic causes of cathode degradation in Li-ion batteries include instability against irreversible phase transformations, for example, layered to spinel transformation in LixMO2 type cathodes, and dissolution of the redox-active transition metal ions into the electrolyte. Corrosive species are known to attack the cathode particles and accelerate transition metal dissolution, which often leads to a significant capacity loss upon cycling.
… While alternative strategies such as doping, tailoring the particle morphology or core–shell structures have been suggested, a common approach to suppressing cathode degradation has been applying protective coatings on cathode particles. … the complex nature of reactions between the cathode, coating and electrolyte prohibited the design of generic guidelines to find effective coatings beyond such simple binary oxides.
Northwestern Engineering professor Christopher Wolverton and his team previously developed the ever-growing Open Quantum Materials Database (OQMD). The OQMD is one of the world’s largest materials databases, is open to the public, and can be downloaded online.
… Here we introduce a comprehensive HT [high-throughput] materials design framework to discover cathode coatings by combining the Open Quantum Materials Database (OQMD), a large collection of HT DFT calculations of ∼300,000 inorganic materials, with reaction models to describe thermodynamic stability, electrochemical stability and HF-reactivity for any oxygen-bearing coating with non-intuitive, fully automated prediction of reaction products. With this framework, we design coatings with various functionalities geared towards specific battery chemistries; namely, (1) physical barriers for acid-free electrolytes, (2) HF-barriers for cathode particles fully covered with coatings and (3) HF-scavengers for particles with patchy coatings requiring active protection from HF-attack.—Aykol et al.
The team screened more than 130,000 oxygen-bearing materials, and suggested physical and hydrofluoric-acid barrier coatings such as WO3, LiAl5O8 and ZrP2O7 and hydrofluoric-acid scavengers such as Sc2O3, Li2CaGeO4, LiBO2, Li3NbO4, Mg3(BO3)2 and Li2MgSiO4.
Using a design strategy to find the thermodynamically optimal coatings for a cathode, they further presented optimal hydrofluoric-acid scavengers such as Li2SrSiO4, Li2CaSiO4 and CaIn2O4 for the layered LiCoO2, and Li2GeO3, Li4NiTeO6 and Li2MnO3 for the spinel LiMn2O4 cathodes.
A coating could serve multiple functions: it could provide a barrier around the cathode, preventing attack from hydrofluoric acid. Or a coating could preferentially react with the hydrofluoric acid, so there’s none left to react with the cathode.—Christopher Wolverton
The group ultimately identified and ranked 30 top candidates, one of which the Dow Chemical Company has experimentally tested to discover that the coating did successfully prevent battery degradation.
Having a massive database at hand allowed us to find the products of very complex, previously unexplored chemical reactions that determine the coating’s effectiveness. Not only can we unveil a list of promising functional coatings, but we are helping our experimental colleagues target their resources to the best candidates.—Leas author Muratahan Aykol, who is now a postdoctoral fellow at Lawrence Berkeley National Laboratory
Wolverton said this design strategy extends beyond developing better batteries. It also aims to fulfill the vision of the Materials Genome Initiative, established by President Barack Obama in 2011 to help accelerate the discovery, development, and deployment of new materials.
Muratahan Aykol, Soo Kim, Vinay I. Hegde, David Snydacker, Zhi Lu, Shiqiang Hao, Scott Kirklin, Dane Morgan & C. Wolverton (2016) “High-throughput computational design of cathode coatings for Li-ion batteries” Nature Communications 7, Article number: 13779 doi: 10.1038/ncomms13779