Accelerating the Discovery of Multivalent Cathode Materials Via High-Throughput First-Principles Calculations

Abstract

Batteries that shuttle multi-valent ions such as Mg2+ and Ca2+ ions are promising candidates for achieving higher energy density than available with current Li-ion technology. Finding electrode materials that reversibly store and release these multi-valent cations is considered a major challenge for enabling such multi-valent battery technology. In this work, we employ the recent advances in high-throughput first-principles calculations1 to design and evaluate multivalent intercalation cathode materials so that we are able to quickly seek and assess the feasibility of multi-valent insertion cathodes from an in silico big data approach prior to experimental synthesis and characterization. It is our hope that our research provides general guidelines for multi-valent cathode material engineering and moreover, can greatly expedite the material discovery process. We use density functional theory calculations (VASP code) combined with the robust high-throughput infrastructure1 (pymatgen, pymatpro and FireWorks codes) to automatically calculate and analyze the properties and viabilities of possible multivalent cathode compounds. Based on the calculated results, we estimate the insertion voltage, capacity, thermodynamic stability and thermal stability of charged and discharged states. Therefore, the compounds with both good energy storage capability and superior structural stability can be identified as promising candidate materials for future experimental investigation and validation. To date, we have calculated and evaluated over 1800+ newly designed structures with five possible working ions (Mg, Ca, Zn, Y, Al). In general, we find that multivalent cathodes exhibit lower voltages compared to Li cathodes; the voltages of Ca coumpounds are ~0.2-0.5V higher than those of Mg compounds; Zn compounds usually have much lower voltage (Fig. 1). As a showcase, we systemically evaluate the theoretical performance of the spinel structure host with the general formula AB2O4 across a matrix of chemical compositions spanning A={Al, Y, Mg, Ca, Zn} and B={Ti, V, Cr, Mn, Fe, Co, Ni} for multivalent cathode applications.2 As shown in Fig 2, considering all computed properties, Mn2O4 spinels are particularly interesting due to their stability. Among the divalent cations, both Mg2+ and Ca2+ may potentially be mobile in the spinel structure2,3, warranting further experimental and computational investigation (particularly at small particle sizes). Mixed spinel structures provide a promising avenue, as the Ni4+/3+ and Co4+/3+ show higher voltage than the Mn4+/3+ redox couple. Acknowledgement: This work was supported by Joint Center for Energy Storage Research (JCESR) and the infrastructure and algorithmic was supported by the Materials Project (BES DOE Grant No. EDCBEE). We also thank NERSC for providing computation resources.