Cathode degradation is a key factor that limits the lifetime of Li-ion batteries. To identify functional coatings that can suppress this degradation, we present a high-throughput density functional theory based framework which consists of reaction models that describe thermodynamic and electrochemical stabilities, and acid-scavenging capabilities of materials. Screening more than 130,000 oxygen-bearing materials, we suggest 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, we further present optimal hydrofluoric-acid scavengers such as Li2SrSiO4, Li2CaSiO4 and CaIn2O4 for the layered LiCoO2, and Li2GeO3, Li4NiTeO6 and Li2MnO3 for the spinel LiMn2O4 cathodes. These coating materials have the potential to prolong the cycle-life of Li-ion batteries and surpass the performance of common coatings based on conventional materials such as Al2O3, ZnO, MgO or ZrO2.

Anodes made of Li, Na, or Mg metal present a rare opportunity to double the energy density of rechargeable batteries. However, these metals are highly reactive with many electrolytes and yield electronically conductive phases that allow continued electrochemical reduction of the electrolyte. This reactivity degrades cell performance over time and poses a safety risk. Surface coatings on metal anodes can limit reactivity with electrolytes and improve durability. In this paper, we screen the Open Quantum Materials Database (OQMD) to identify coatings that exhibit chemical equilibrium with the anode metals and are electronic insulators. We rank the coatings according to their electronic bandgap. We identify 92 coatings for Li anodes, 118 for Na anodes, and 97 for Mg anodes. Only two compounds that are commonly studied as Li solid electrolytes pass our screens: Li 3 N and Li 3 Furthermore, layered-layered materials with high Mn contents suffer from limit cycle life due to voltage and capacity fade.4,5 Substituting a new silicon-carbon composite anode for a conventional graphite anode offers only 20% improvement in cell energy density. 6 Metal anodes, which are comprised entirely or almost entirely of the mobile element in a battery, present a rare opportunity for major improvement in energy density. For example, in a lithium battery with a LiNi 0.8 Co 0.15 Al 0.05 O 2 cathode, energy density can be doubled by substituting a lithium metal anode in place of a conventional graphite anode. 7 This doubling in energy density is attainable because metal anodes can eliminate host materials, polymeric binders, electrolytefilled pores, and even copper current collectors from the anode.8 Metal anodes comprised of pure elements also offer the lowest possible anode redox potential and therefore the highest possible cell voltage. In batteries where Na or Mg is the mobile element, anode host materials that operate by intercalation or conversion reactions exhibit particularly poor capacity, kinetics, and reversibility, and so Na or Mg metal anodes that eliminate these host materials are particularly attractive. 9,10A major challenge for the implementation of metal anodes is reactivity between the metals and electrolytes. Metal anodes must be electropositive to provide a sufficient cell voltage, but this electropositivity causes the metals to drive electrochemical reduction of electrolytes. Both liquid and solid electrolytes are often reactive at the anode surface.11,12 For graphite anodes in conventional lithium-ion batteries, reactivity can be mitigated by a passivation layer that forms in situ from the reaction products. 11,13 This passivation layer must be mechanically durable, electronically insulating to block electron transfer from the anode to the electrolyte, and chemically stable or metastable. For metal anodes, there is sparse evidence for passivation by in situ reactivity. Reactivity at the surface of metal anodes causes impedence growth that destroys cell performance, according to Luntz * Electrochemical Society Member....

The performance of olivine cathode materials can be improved using core/shell structures such as LiMnPO4/LiFePO4 and LiMnPO4/LiNiPO4. We use density functional theory to calculate the energetics, phase stability, and voltages of transition-metal mixing for a series of olivine phosphate materials. For LiMn1–y Fe y PO4, LiFe1–y Ni y PO4, and LiMn1–y Ni y PO4, we find phase-separating tendencies with (mean-field) maximum miscibility gap temperatures of 120, 320, and 760 K respectively. At room temperature, we find that Mn is completely miscible in LiFePO4, whereas Mn solubility in LiNiPO4 is just 0.3%. Therefore, we suggest that core/shell LiMnPO4/LiNiPO4 particles could be more effective at containing Mn in the particle core and limiting Mn dissolution into the electrolyte relative to LiMnPO4/LiFePO4 particles. We calculate shifts in redox potentials for dilute transition metals, M, substituted into Li x M′PO4 host materials. Unmixed Li x MnPO4 exhibits a redox potential of 4.0 V, but we find that dilute Mn in a LiNiPO4 shell exhibits a redox potential of 4.3 V and therefore remains redox inactive at lower cathode potentials. We find that strain plays a large role in the redox potentials of some mixed systems (Li x Mn1–y Fe y PO4) but not others (Li x Mn1–y Ni y PO4).

For many lithium-ion cathode materials, transition metal (TM) dissolution into the electrolyte contributes to cell degradation. Cathode coatings can limit TM dissolution by containing TMs in cathode materials. We perform density functional theory calculations to evaluate cathode/coating pairs for TM containment, specifically focusing on reactive stability of coating/cathode pairs as well as TM solubility in the coating materials. We consider stability and containment of materials at both synthesis and operating conditions. We find that many cathode/coating pairs are reactive when lithiated, while other cathode-coating pairs are stable when lithiated but become reactive following delithiation. Of all the coatings that we considered, Li 3 PO 4 occupies a unique chemical position, in that its coatings on oxide cathode materials maintained equilibrium under both lithiated and delithiated conditions. Furthermore, for oxide cathode materials, the Li 3 PO 4 coatings exhibit low TM solubilities across all cathode states of charge. Our results demonstrate that Li 3 PO 4 is a promising candidate for stable coatings on oxide cathode materials to limit TM dissolution into the electrolyte. Li-ion batteries are the dominant power sources in consumer electronics, and they are emerging as cost-competitive players in lowcarbon electricity systems and vehicles. However, many technologies are encumbered by the limited durability of today's Li-ion cells. For these applications, battery manufacturers have an incentive to improve cell durability. Transition metal (TM) dissolution from the cathode is a major contributor to cell degradation during cycling and aging.1 TM dissolution from the cathode contributes directly to capacity loss by decreasing the amount of cathode material. Furthermore, TMs that dissolve from the cathode material can migrate through the electrolyte to the anode, where they can cause changes to the anode Solid Electrolyte Interphase (SEI).2,3 These changes to the SEI increase impedance, decrease cell capacity, and decrease lifespan.A variety of strategies have been used to limit degradation by TMs. Electrolyte additives have been used to control SEI formation and limit the impact of TMs in the electrolyte. 4,5 Molecules have been attached to the polymer separator to sequester TMs from the electrolyte before they reach the anode. 6 In this work, we consider upstream strategies that limit TM dissolution from the cathode into the electrolyte. These upstream strategies are complementary to other strategies, including SEI formation and TM sequestration. There are several distinct categories of strategies for limiting TM dissolution from the cathode. Electrolytes can be tailored to reduce reactivity with the cathode. 7-9Cathode materials can be doped to control the oxidation states of transition metals. 10,11 This doping can be applied to the entire cathode particle or just near the surface.12 Cathode materials can also be covered with surface coatings to limit TM dissolution. [13][14][15][16][17][18][19] Surface coati...

Lithium is an essential element for today’s high-performance batteries. Brine resources contain most of the world’s lithium reserves, but conventional processes for extracting lithium from brines are limited by low lithium recovery and large evaporation ponds. Lithium ion exchange is an alternative extraction method with potential to access lower-quality resources and decrease costs. Ion exchange materials absorb lithium from brine resources and then release the lithium in acid while absorbing hydrogen. New ion exchange materials are sought to facilitate this transformative approach. We use high-throughput density functional theory and specific ion interaction theory to predict promising new lithium metal oxide compounds suitable for lithium extraction. Starting from the Open Quantum Materials Database (OQMD) of ∼400,000 compounds, we consider 77 candidate lithium metal oxide compounds that are stable or nearly stable in their lithiated states. We interrogate this list for compounds that thermodynamically release lithium while binding hydrogen in acid and that also release hydrogen while binding lithium in brine. We further screen for selective binding of lithium relative to sodium in brine. We find that most candidate compounds either bind lithium in both acid and brine solutions or bind hydrogen in both acid and brine solutions. Such compounds are not suitable for lithium ion exchange. However, we identify nine compounds that are most promising for lithium extraction from brines: LiAlO2, LiCuO2, Li2MnO3, Li4Mn5O12, Li2SnO3, Li4TiO4, Li4Ti5O12, Li7Ti11O24, and Li3VO4. Four additional compounds are promising when the pH of the brine is adjusted to 10 to help drive hydrogen release: Li2TiO3, LiTiO2, Li2FeO3, and Li2Si3O7. Four of the previously mentioned compounds are also promising for Li extraction from seawater: Li2MnO3, Li4Mn5O12, Li7Ti11O24, and Li3VO4.