Intercalation Hosts for Multivalent‐Ion Batteries

Abstract

The widespread application of rechargeable batteries in portable electronics, electric vehicles, grid energy, and renewable energy storage necessitates high performance and cost-effective solutions. [1] To date, the vast majority of rechargeable battery products are based on the lithium-ion intercalation chemistry. [2] State-of-the-art commercial lithium-ion cells offer energy densities of %260 Wh Kg À1 (%680 Wh L À1 ), and long cycle life (several thousand cycles). [2] However, the Achilles heel for lithium-ion technology is cost. Lithium is a limited resource on the planet, and its price has reported to have increased by %738% since January 2021. [3] Consequently, lithium-ion battery cost is projected to rise to %$115 per kWh by 2023. [4] As an alternative to lithium, earthabundant, and cheaper metals such as aluminum (Al), calcium (Ca), magnesium (Mg), and zinc (Zn) have been actively researched in battery systems. [5][6][7][8][9][10][11] These metals are multivalent (carry two or more ionic charge) and hence one ion insertion will deliver two or more electrons per ion during battery operation. The main advantage of multivalent ions is that to achieve a certain specific capacity, the number of ions that are required to participate in the redox process is lower for multivalent as compared to monovalent ions. Therefore, multivalent ions offer the promise of improved performance and lower cost. However, the higher ionic charge of multivalent ions presents its own set of unique challenges. One obvious distinction between monovalent and multivalent ions is the difference in charge density (i.e., for similar ionic size, multivalent ions bear double, or triple the amount of monovalent ionic charge). The higher charge density of multivalent ions generates a stronger electric field which causes a bigger solvation sheath in the electrolyte (Figure 1a), which results in a higher "desolvation penalty" before insertion inside the electrode. Moreover, higher charge density multivalent ions strongly interact with ions in the intercalation host resulting in a relatively high migration barrier and slower diffusion kinetics (Figure 1b). It is also a considerable challenge to find durable intercalation materials for multivalent ions. As shown schematically in Figure 1c, often, multivalent ion insertion is responsible for mechanical degradation (stress-induced cracking) of the host, and the material loses its integrity. Owing to the aforementioned reasons, intercalation hosts for multivalent-ion batteries suffer from poor specific capacity (low energy density), sluggish diffusion kinetics (low power density), higher polarization, reduced coulombic and roundtrip efficiency, as well as insufficient cycle life when compared to their monovalent counterparts.Given the problems accompanying multivalent ions, it becomes critical to find high-performing and stable intercalation host materials for multivalent-ion batteries. In this perspective,

Selenium doping induced phase transformation and interlayer expansion boost the zinc storage performance of molybdenum disulfide

“…15,16 Nevertheless, the electrostatic interaction between multivalent Zn 2+ and strongly electronegative sulfur groups restricts the diffusion of Zn 2+ in host materials, which greatly limits the reversible capacity and rate performance of MoS 2 as a cathode in AZIBs. 17,18 To address the above issues, enlarging the layer distance, 19 introducing S vacancies, 20 and phase engineering 21 have been commonly used to improve the capacity and Zn 2+ transfer dynamics of MoS 2 . Among them, phase engineering has attracted widespread attention due to the higher intrinsic electrical conductivity and lower diffusion energy barrier of metallic 1T-MoS 2 than those of semiconductive 2H-MoS 2 .…”

Unlocking the potential of open-tunnel oxides: DFT-guided design and machine learning-enhanced discovery for next-generation industry-scale battery technologies

“…[43][44][45] Hence, selecting the most appropriate candidate from the myriad options becomes a challenge akin to finding a 'needle in a haystack'. 9 Given the limited availability of known open-tunnel oxides with suitable pore sizes for accommodating multiply charged ions, a comprehensive exploration of new compounds becomes imperative.…”

“…49 To forecast the structural stability of TMOs, a DFT-based energy hull diagram can be constructed by evaluating the formation energy across all conceivable stoichiometric ratios. 9 However, the computationally intensive nature of this procedure is exacerbated by the intricate crystal structures and substantial unit cells of TMOs. Furthermore, addressing the ''Needle in a Haystack'' conundrum using DFT poses challenges due to the multitude of potential multivalent ion insertion sites and the potential for cation disorder.…”

“…Before selecting stable configurations with acceptable pore architectures for intercalating multiply charged ions, it is critical to analyze the structural stability of potential TMOs to assure their synthesizability. 49…”

“…B represents the transition metal. The s, r, m, and n, denote the stoichiometry ratio 9. In our ML model, we allocated 80% of our randomly selected data to the training dataset, while the remaining 20% constitutes the testing dataset.…”