DEFORMABLE HALIDE IONIC CONDUCTORS FOR USE AS ANOLYTES, SOLID ELECTROLYTES OR CATHOLYTES IN SOLID STATE BATTERIES

Abstract

An anolyte includes a deformable halide-based ionic conductor having one of the following formulas: CsLi.sub.2Cl.sub.3, wherein the CsLi.sub.2Cl.sub.3 has an orthorhombic crystal structure, NaLi.sub.3I.sub.4, NaLi.sub.3Br.sub.4, NaLi.sub.3Cl.sub.4, and KLi.sub.2F.sub.3. A solid state battery includes an anode, a cathode, and a solid electrolyte, wherein the solid state battery comprises the aforementioned anolyte.

Claims

1. An anolyte comprising a deformable halide-based ionic conductor having one of the following formulas: CsLi.sub.2Cl.sub.3, wherein the CsLi.sub.2Cl.sub.3 has an orthorhombic crystal structure, NaLi.sub.3I.sub.4, NaLi.sub.3Br.sub.4, NaLi.sub.3Cl.sub.4, and KLi.sub.2F.sub.3.

2. The anolyte according to claim 1, wherein the deformable halide-based ionic conductor has the formula CsLi.sub.2Cl.sub.3, wherein the CsLi.sub.2Cl.sub.3 has an orthorhombic crystal structure.

3. The anolyte according to claim 1, wherein the deformable halide-based ionic conductor has the formula NaLi.sub.3I.sub.4.

4. The anolyte according to claim 1, wherein the deformable halide-based ionic conductor has the formula NaLi.sub.3Br.sub.4.

5. The anolyte according to claim 1, wherein the deformable halide-based ionic conductor has the formula NaLi.sub.3Cl.sub.4.

6. The anolyte according to claim 1, wherein the deformable halide-based ionic conductor has the formula KLi.sub.2F.sub.3.

7. A solid state battery comprising an anode, a cathode, and a solid electrolyte, wherein the solid state battery comprises an anolyte according to claim 1.

8. A solid state battery comprising an anode, a cathode, and a solid electrolyte, wherein the solid state battery comprises an anolyte according to claim 2.

9. A solid state battery comprising an anode, a cathode, and a solid electrolyte, wherein the solid state battery comprises an anolyte according to claim 3.

10. A solid state battery comprising an anode, a cathode, and a solid electrolyte, wherein the solid state battery comprises an anolyte according to claim 4.

11. A solid state battery comprising an anode, a cathode, and a solid electrolyte, wherein the solid state battery comprises an anolyte according to claim 5.

12. A solid state battery comprising an anode, a cathode, and a solid electrolyte, wherein the solid state battery comprises an anolyte according to claim 6.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0029] Example embodiments of the present disclosure will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings in which:

[0030] FIG. 1 is a graph showing the distribution of ML-predicted hardness for 40,000 LiX+LiX+MX compositions.

[0031] FIG. 2 is a diagram showing the computational workflow for new deformable materials design.

[0032] FIG. 3 is a graph showing the ab initio Molecular Dynamics (AIMD) calculated ionic conductivity for CsLi.sub.2Cl.sub.3.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0033] The embodiments of the disclosure described herein are example embodiments, and thus, the disclosure is not limited thereto, and may be realized in various other forms. Each of the embodiments provided in the following description is not excluded from being associated with one or more features of another example or another embodiment also provided herein or not provided herein but consistent with the disclosure. For example, even if matters described in a specific example or embodiment are not described in a different example or embodiment thereto, the matters may be understood as being related to or combined with the different example or embodiment, unless otherwise mentioned in descriptions thereof. In addition, it should be understood that all descriptions of principles, aspects, examples, and embodiments of the disclosure are intended to encompass structural and functional equivalents thereof. In addition, these equivalents should be understood as including not only currently well-known equivalents but also equivalents to be developed in the future.

[0034] As used herein, expressions such as at least one of, when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list. For example, the expression, at least one of a, b and c, should be understood as including only a, only b, only c, both a and b, both a and c, both b and c, or all of a, b and c.

[0035] An efficient Machine Learning (ML)-driven computational workflow for the design of new deformable SE materials has been devised as shown in the present disclosure.

[0036] First, thousands of charge-balanced compositions by combinations of LiX and MX binaries were generated. LiX+LiX+MX (40 k) and LiX+LiX+LiX+MX (>265 k) combinations were considered, where the anion species X and X are chalcogenides (O.sup.2, S.sup.2, Se.sup.2, Te.sup.2), halides (Cl.sup., F.sup., Br.sup., I.sup.) or pseudo-halides (BH.sub.4.sup., BF.sub.4.sup., AlH.sub.4.sup., AlF.sub.4.sup., OH.sup., SH.sup.), and M is Na, Mg, Al, K, Ca, Sc, Ti, Cu, Zn, Ga, Rb, Sr, Y, Zr, Nb, Mo, Pd, Ag, Cd, In, Sn, Cs, Ba, La, Ce, Nd, Hf, Ta, W, Pt, Au, Hg, Tl, Pb, Bi. In this regard, FIG. 1 is a graph showing the distribution of ML-predicted hardness for 40 k LiX+LiX+MX compositions.

[0037] Then, the hardness of all generated compositions was predicted using a ML model trained exclusively on compositional features and selected compositions with predicted hardness<=2.5 GPa, that is the hardness of Li.sub.3PS.sub.4, used as reference material for good deformability.

[0038] Structures for the selected compositions were generated by mapping onto 1100 prototype crystal structures from the public database AFLOW [Comp. Mat. Sci. 136, S1-S828 (2017), Comp. Mat. Sci. 161, S1-S1011 (2019), Comp. Mat. Sci. 199, 110450 (2021)]. The obtained compounds were then optimized by DFT relaxation and computationally characterized regarding thermodynamic and electrochemical stability, mechanical deformability (DFT computed hardness) and ionic conductivity (energy barriers for ionic migration estimated on the basis of the empirical Bond Valence Sum method). For some promising candidates, the conductivity was also calculated by ab initio Molecular Dynamics (AIMD).

[0039] That is, compounds with ML predicted hardness<=2.5 GPa (that is the hardness of Li.sub.3PS.sub.4, here used as a reference) were computationally characterized using DFT calculations to identify thermodynamically stable compounds and to confirm their mechanical properties. Potential ionic conductor candidates were then sorted out using the estimated migration energy barriers and in some cases also ab initio Molecular Dynamics (AIMD). The computational workflow for new deformable materials design is shown in FIG. 2.

[0040] With the use of the computational screening described above, 5 new deformable halide ionic conductors have been designed with good electrochemical stability against Li metal, to be employed as anolytes in SSBs.

[0041] Among these 5 newly designed halide ionic conductors, some are also predicted to have wide voltage stability windows (>4V) and are therefore potentially usable also as SE separators and/or catholytes.

[0042] Interface stability calculations show that some of the 5 new compounds of the present disclosure are also chemically stable against commonly used oxide SEs, i.e., Li.sub.7La.sub.3Zr.sub.2O.sub.12 (LLZO), and cathodes, i.e. Li.sub.3MnNiCoO.sub.6 (NMC) and LiCoO.sub.2 (LCO). The predicted chemical stability rules out side chemical reactions at the interface with such oxide phases, thus ensuring long cycle life of the SSB.

[0043] Embodiments of the deformable halide ionic conductors of the present disclosure can be made using a standard solid-state method for making halides (e.g., in an air free environment). In this method, precursor powders are combined in a certain ratio depending on the composition of the target material. In a typical preparation, precursors may consist of a lithium halide (e.g., lithium chloride) and at least one other metal halide precursor, such as a metal fluoride, metal bromide, metal iodide, or metal chloride (e.g., silver chloride).

[0044] The precursor mixture may be mixed by a method such as ball milling or planetary milling to produce a homogeneous mixture. Mixing may be done with a suitable solvent such as ethanol, isopropanol, ethylene glycol, or acetone to assist with the uniform dispersion of the precursors.

[0045] The precursor mixture may then be heat treated to an appropriate temperature for an appropriate period of time to produce a halide powder with the desired composition and crystal structure.

[0046] Subsequently the halide powder may be compressed using a hydraulic uniaxial press to form a densely packed pellet. Heat treatment may then be applied at an appropriate temperature for an appropriate period of time to produce a dense pellet which may be used as, e.g., an anolyte in a solid state lithium battery cell.

EXAMPLES

[0047] Embodiments will now be illustrated by way of the following examples, which do not limit the embodiments in any way.

[0048] With the use of the computational screening described above, new deformable halide ionic conductors have been designed with good electrochemical stability against Li metal and, in some cases, also against high voltage cathodes, to be employed as anolytes or catholytes (or SEs), respectively.

[0049] Interface stability calculations show that some of the new compounds of the present disclosure are also chemically stable against commonly used oxide SEs, i.e., Li.sub.7La.sub.3Zr.sub.2O.sub.12 (LLZO). The predicted chemical stability rules out side chemical reactions at the interface with such oxide phases, thus ensuring long cycle life of the SSB.

[0050] Table 1 set forth below shows new deformable ionic conductors designed with the computational workflow described in the present disclosure. The screening criteria were E.sub.hull30 meV/atom (thermodynamic stability), hardness2.5 GPa, energy barrier for ionic migration0.5 eV, and absence from Materials Project database of compounds with either the same composition or the same structure (or both).

TABLE-US-00001 TABLE 1 New deformable ionic conductors Ion- migration Space Energy Crystal group E.sub.hull Reduction Oxidation Hardness barrier Formula system symbol (meV/atom) Voltage Voltage (GPa) (eV) 0 CsLi2Cl3 orthorhombic Cmcm 9 0.00 4.34 1.352 0.413 1 NaLi3I4 orthorhombic Pmn2_1 13 0.05 2.55 0.537 0.314 2 NaLi3Br4 orthorhombic Pmn2_1 16 0.05 3.25 0.876 0.273 3 NaLi3Cl4 orthorhombic Pmn2_1 18 0.05 3.85 0.989 0.270 4 KLi2F3 orthorhombic Pnma 20 0.45 5.85 1.497 0.411

[0051] The following observations can be made from the aforementioned new deformable ionic conductors designed with the computational workflow described in the present disclosure.

[0052] All of the newly designed compounds are halides, including chlorides and fluorides.

[0053] CsLi.sub.2Cl.sub.3, NaLi.sub.3I.sub.4, NaLi.sub.3Br.sub.4 and NaLi.sub.3Cl.sub.4 are electrochemically stable vs. Li metal (red_volt0V) and therefore usable as anolytes.

[0054] KLi.sub.2F.sub.3 is also stable down to 0.45V vs. Li/Li+ and might therefore be kinetically stabilized as anolyte vs. Li metal anode.

[0055] CsLi.sub.2Cl.sub.3 and KLi.sub.2F.sub.3 are also stable at high voltage (oxi_volt=4.34V and 5.85V vs. Li/Li+), and can therefore be used also as SE separators and/or catholytes in the SSB.

[0056] In regard to CsLi.sub.2Cl.sub.3, FIG. 3 is a graph showing the ab initio Molecular Dynamics (AIMD) calculated ionic conductivity for CsLi.sub.2Cl.sub.3.

[0057] All compounds with low valence M cations are thermodynamically stable or have very low reaction energies (indicating low driving force for reaction) against oxides like LLZO, LCO and NMC (see Tables 2-4).

TABLE-US-00002 TABLE 2 Predicted interface reactions against Li7La3Zr2O12 (LLZO) Reaction energy Formula Reaction vs. LLZO (eV/atom) 0 CsLi2Cl3 1 NaLi3I4 0.5 Li7La3Zr2O12 + 0.5 NaLi3I4 > 0.5 0.015 Li6Zr2O7 + 0.5 NaI + Li2O + 1.5 LaIO 2 NaLi3Br4 3 NaLi3Cl4 4 KLi2F3

TABLE-US-00003 TABLE 3 Predicted interface reaction against Li3MnCoNiO6 (NMC) Reaction energy Formula Reaction vs. NMC (eV/atom) 0 CsLi2Cl3 1 NaLi3I4 2 NaLi3Br4 3 NaLi3Cl4 4 KLi2F3

TABLE-US-00004 TABLE 4 Predicted interface reactions against LiCoO2 (LCO) Reaction energy Formula Reaction vs. LCO (eV/atom) 0 CsLi2Cl3 1 NaLi3I4 2 NaLi3Br4 3 NaLi3Cl4 4 KLi2F3

[0058] Thus, Tables 2-4 show the computed interface stability against oxides commonly used in SSBs, namely LLZO (SE), LCO and NMC (cathodes).

[0059] As shown above, predicted reaction energies (e_rxn) are generally low or null for compounds with low valence metals, namely, Cs.sup.+, Na.sup.+, and K.sup.+. In this regard, the dash in the tables means null, which is no reaction.

[0060] The foregoing is illustrative of exemplary embodiments and is not to be construed as limiting the disclosure. Although a few exemplary embodiments have been described, those skilled in the art will readily appreciate that many modifications are possible in the above embodiments without materially departing from the disclosure.