Navigating phase diagram complexity to guide robotic inorganic materials synthesis

Efficient synthesis recipes are needed both to streamline the manufacturing of complex materials and to accelerate the realization of theoretically predicted materials. Oftentimes the solid-state synthesis of multicomponent oxides is impeded by undesired byproduct phases, which can kinetically trap reactions in an incomplete non-equilibrium state. We present a thermodynamic strategy to navigate high-dimensional phase diagrams in search of precursors that circumvent low-energy competing byproducts, while maximizing the reaction energy to drive fast phase transformation kinetics. Using a robotic inorganic materials synthesis laboratory, we perform a large-scale experimental validation of our precursor selection principles. For a set of 35 target quaternary oxides with chemistries representative of intercalation battery cathodes and solid-state electrolytes, we perform 224 reactions spanning 27 elements with 28 unique precursors. Our predicted precursors frequently yield target materials with higher phase purity than when starting from traditional precursors. Robotic laboratories offer an exciting new platform for data-driven experimental science, from which we can develop new insights into materials synthesis for both robot and human chemists

Pliable Lithium Superionic Conductor for AllSolid-State Batteries

The key challenges in all-solid-state batteries (ASSBs) are establishing and maintaining perfect physical contact between rigid components for facile interfacial charge transfer, particularly between the solid electrolyte and cathode, during repeated electrochemical cycling. Here, we introduce inorganic-based pliable solid electrolytes that exhibit extraordinary clay-like mechanical properties (storage and loss moduli <1 MPa) at room temperature, high lithium-ion conductivity (3.6 mS cm(-1)), and a glass transition below -50 degrees C. The unique mechanical features enabled the solid electrolyte to penetrate into the high-loading cathode like liquid, thereby providing complete ionic conduction paths for all cathode particles as well as maintaining the pathway even during cell operation. We propose a design principle in which the complex anion formation including Ga, F, and a different halogen can induce the claylike features. Our findings provide new opportunities in the search for solid electrolytes and suggest a new approach for resolving the issues caused by the solid electrolyte-cathode interface in ASSBs

High-energy and durable lithium metal batteries using garnet-type solid electrolytes with tailored lithium-metal compatibility

Lithium metal batteries using solid electrolytes are considered to be the next-generation lithium batteries due to their enhanced energy density and safety. However, interfacial instabilities between Li-metal and solid electrolytes limit their implementation in practical batteries. Herein, Li-metal batteries using tailored garnet-type Li7-xLa3-aZr2-bO12 (LLZO) solid electrolytes is reported, which shows remarkable stability and energy density, meeting the lifespan requirements of commercial applications. We demonstrate that the compatibility between LLZO and lithium metal is crucial for long-term stability, which is accomplished by bulk dopant regulating and dopant-specific interfacial treatment using protonation/etching. An all-solid-state with 5 mAh cm(-2) cathode delivers a cumulative capacity of over 4000 mAh cm(-2) at 3 mA cm(-2), which to the best of our knowledge, is the highest cycling parameter reported for Li-metal batteries with LLZOs. These findings are expected to promote the development of solid-state Li-metal batteries by highlighting the efficacy of the coupled bulk and interface doping of solid electrolytes. Lithium-metal batteries (LMBs) have attracted intense interest but the instability issues limit its practical deployment. Here, the authors report a durable LMB with high energy density using a garnet-type solid electrolyte with a tailored Li-metal compatibility

Design of Li[subscript 1+2x]Zn[subscript 1−x]PS[subscript 4], a New Lithium Ion Conductor

Recent theoretical work has uncovered that a body-centered-cubic (bcc) anion arrangement leads to high ionic conductivity in a number of fast lithium-ion conducting materials. Using this structural feature as a screening criterion, we find that the I[4 with combining macron] material LiZnPS[subscript 4] contains such a framework and has the potential for very high ionic conductivity. In this work, we apply ab initio computational techniques to investigate in detail the ionic conductivity and defect properties of this material. We find that while the stoichiometric structure has poor ionic conductivity, engineering of its composition to introduce interstitial lithium defects is able to exploit the low migration barrier of the bcc anion framework. Our calculations predict a solid-solution regime extending to x = 0.5 in Li[subscript 1+2x]Zn[subscript 1−x]PS[subscript 4], and yield a new ionic conductor with exceptionally high lithium-ion conductivity, potentially exceeding 50 mS cm[supercript −1] at room temperature.National Science Foundation (U.S.) (ACI-1053575

Interface Stability in Solid-State Batteries

Development of high conductivity solid-state electrolytes for lithium ion batteries has proceeded rapidly in recent years, but incorporating these new materials into high-performing batteries has proven difficult. Interfacial resistance is now the limiting factor in many systems, but the exact mechanisms of this resistance have not been fully explained - in part because experimental evaluation of the interface can be very difficult. In this work, we develop a computational methodology to examine the thermodynamics of formation of resistive interfacial phases. The predicted interfacial phase formation is well correlated with experimental interfacial observations and battery performance. We calculate that thiophosphate electrolytes have especially high reactivity with high voltage cathodes and a narrow electrochemical stability window. We also find that a number of known electrolytes are not inherently stable but react in situ with the electrode to form passivating but ionically conducting barrier layers. As a reference for experimentalists, we tabulate the stability and expected decomposition products for a wide range of electrolyte, coating, and electrode materials including a number of high-performing combinations that have not yet been attempted experimentally.Samsung Advanced Institute of Technolog

A sinter-free future for solid-state battery designs

The newly developed sequential decomposition synthesis (SDS) method permits the fabrication of ceramic solid electrolytes with thickness close to today's polymer separators and offers opportunities to obtain the desired phase at reduced temperatures.</jats:p

First-Principles Studies on Cation Dopants and Electrolyte|Cathode Interphases for Lithium Garnets

Lithium garnet with the formula Li₇La₃Zr₂O₁₂ (LLZO) has many properties of an ideal electrolyte in all-solid state lithium batteries. However, internal resistance in batteries utilizing these electrolytes remains high. For widespread adoption, the LLZO’s internal resistance must be lowered by increasing its bulk conductivity, reducing grain boundary resistance, and/or pairing it with an appropriate cathode to minimize interfacial resistance. Cation doping has been shown to be crucial in LLZO to stabilize the higher conductivity cubic structure, yet there is still little understanding about which cations have high solubility in LLZO. In this work, we apply density functional theory (DFT) to calculate the defect energies and site preference of all possible dopants in these materials. Our findings suggest several novel dopants such as Zn²⁺ and Mg²⁺ predicted to be stable on the Li- and Zr-sites, respectively. To understand the source of interfacial resistance between the electrolyte and the cathode, we investigate the thermodynamic stability of the electrolyte|cathode interphase, calculating the reaction energy for LLMO (M = Zr, Ta) against LiCoO₂, LiMnO₂, and LiFePO₄ (LCO, LMO, and LFP, respectively) cathodes over the voltage range seen in lithium-ion battery operation. Our results suggest that, for LLZO, the LLZO|LCO is the most stable, showing only a low driving force for decomposition in the charged state into La₂O₃, La₂Zr₂O₇, and Li₂CoO₃, while the LLZO|LFP appears to be the most reactive, forming Li₃PO₄, La₂Zr₂O₇, LaFeO₃, and Fe₂O₃. These results provide a reference for use by researchers interested in bonding these electrolytes to cathodes

About the Compatibility between High Voltage Spinel Cathode Materials and Solid Oxide Electrolytes as a Function of Temperature.

The reactivity of mixtures of high voltage spinel cathode materials Li2NiMn3O8, Li2FeMn3O8, and LiCoMnO4 cosintered with Li1.5Al0.5Ti1.5(PO4)3 and Li6.6La3Zr1.6Ta0.4O12 electrolytes is studied by thermal analysis using X-ray-diffraction and differential thermoanalysis and thermogravimetry coupled with mass spectrometry. The results are compared with predicted decomposition reactions from first-principles calculations. Decomposition of the mixtures begins at 600 °C, significantly lower than the decomposition temperature of any component, especially the electrolytes. For the cathode + Li6.6La3Zr1.6Ta0.4O12 mixtures, lithium and oxygen from the electrolyte react with the cathodes to form highly stable Li2MnO3 and then decompose to form stable and often insulating phases such as La2Zr2O7, La2O3, La3TaO7, TiO2, and LaMnO3 which are likely to increase the interfacial impedance of a cathode composite. The decomposition reactions are identified with high fidelity by first-principles calculations. For the cathode + Li1.5Al0.5Ti1.5(PO4)3 mixtures, the Mn tends to oxidize to MnO2 or Mn2O3, supplying lithium to the electrolyte for the formation of Li3PO4 and metal phosphates such as AlPO4 and LiMPO4 (M = Mn, Ni). The results indicate that high temperature cosintering to form dense cathode composites between spinel cathodes and oxide electrolytes will produce high impedance interfacial products, complicating solid state battery manufacturing

About the Compatibility between High Voltage Spinel Cathode Materials and Solid Oxide Electrolytes as a Function of Temperature

The reactivity of mixtures of high voltage spinel cathode materials Li₂NiMn₃O₈, Li₂FeMn₃O₈, and LiCoMnO₄ cosintered with Li_1.5Al_0.5Ti_1.5(PO₄)₃ and Li_6.6La₃Zr_1.6Ta_0.4O₁₂ electrolytes is studied by thermal analysis using X-ray-diffraction and differential thermoanalysis and thermogravimetry coupled with mass spectrometry. The results are compared with predicted decomposition reactions from first-principles calculations. Decomposition of the mixtures begins at 600 °C, significantly lower than the decomposition temperature of any component, especially the electrolytes. For the cathode + Li_6.6La₃Zr_1.6Ta_0.4O₁₂ mixtures, lithium and oxygen from the electrolyte react with the cathodes to form highly stable Li₂MnO₃ and then decompose to form stable and often insulating phases such as La₂Zr₂O₇, La₂O₃, La₃TaO₇, TiO₂, and LaMnO₃ which are likely to increase the interfacial impedance of a cathode composite. The decomposition reactions are identified with high fidelity by first-principles calculations. For the cathode + Li_1.5Al_0.5Ti_1.5(PO₄)₃ mixtures, the Mn tends to oxidize to MnO₂ or Mn₂O₃, supplying lithium to the electrolyte for the formation of Li₃PO₄ and metal phosphates such as AlPO₄ and LiMPO₄ (M = Mn, Ni). The results indicate that high temperature cosintering to form dense cathode composites between spinel cathodes and oxide electrolytes will produce high impedance interfacial products, complicating solid state battery manufacturing