Patent Application
20250140905
Materials according to embodiments relate to ionic conductors for use as anolytes, catholytes or solid electrolytes in Li solid-state batteries.
The field of battery research is in the midst of a paradigm shift from conventional liquid electrolyte systems to all-solid-state batteries (SSBs) with solid state electrolytes (SEs), owing to their high safety and potentially large volumetric energy density by enabling both the use of lithium metal anodes and the bipolar stacking of electrodes.
This transition brings a significant change in the kinetics of interfacial electrochemistry governing the battery performance because of the rigid solid-solid interface between active materials and SE in SSBs. In a typical liquid electrolyte cell, the active material surface is completely covered by the fluidic electrolyte, whereas a solid electrolyte forms a point contact with the active material due to its intrinsically rigid nature, thereby inducing sluggish charge transfer and mass transport kinetics at the interface. Thus, to achieve SSBs, an important prerequisite is forming and maintaining a well-defined solid-solid interface with intimate contact between the SE and cathode/anode active materials during electrochemical cycling.
Recently, halide ionic conductors, particularly chlorides, were raised as a promising class of solid electrolytes. They are ionically conductive and easily deformable like sulfides, but they do not suffer from the same poor oxidative stability of sulfides. The oxidation potential of chlorides and fluorides is generally much higher (comparable to oxides), leading to an excellent compatibility with 4V-class cathodes.
However, there are problems with some embodiments, including the following:
Information disclosed in this Background section has already been known to the inventors before achieving the disclosure of the present application or is technical information acquired in the process of achieving the disclosure. Therefore, it may contain information that does not form the prior art that is already known to the public.
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.
Compounds with ML predicted hardness≤2.5 GPa (that is the calculated hardness of Li3PS4, here used as a reference) were computationally characterized using density-functional theory (DFT) calculations to identify thermodynamically stable compounds and to confirm their mechanical properties. Potential ionic conductor candidates were then sorted out using migration energy barriers estimated based on the empirical Bond Valence Sum method and in some cases also ab initio Molecular Dynamics (AIMD).
With the use of the computational screening described above, new deformable halide ionic conductors have been designed with good electrochemical stability against either Li metal or high voltage cathodes (or both), to be employed as anolytes or catholytes (or SEs), respectively.
Interface stability calculations show that some of the new compounds mentioned above are also chemically stable against commonly used oxide SEs, i.e., Li7La3Zr2O12 (LLZO), and cathodes, i.e., Li3MnNiCoO6 (NMC) and LiCoO2 (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.
The materials in the present disclosure are newly designed compounds predicted to have favorable mechanical and (electro) chemical properties as well as high ionic conductivity.
An embodiment of the present disclosure includes a deformable halide-based ionic conductor having one of the following formulas:
Another embodiment includes the aforementioned deformable halide-based ionic conductor, having one of the following formulas:
Another embodiment includes a catholyte comprising a deformable halide-based ionic conductor having one of the following formulas:
Another embodiment includes the aforementioned catholyte, wherein the deformable halide-based ionic conductor has the formula CsLi2Cl3, wherein the CsLi2Cl3 has an orthorhombic crystal structure.
Another embodiment includes the aforementioned catholyte, wherein the deformable halide-based ionic conductor has the formula KLi2F3.
Another embodiment includes the aforementioned catholyte, wherein the deformable halide-based ionic conductor has the formula Li2HfF6.
Another embodiment includes the aforementioned catholyte, wherein the deformable halide-based ionic conductor has the formula Li3SiB3(ClF3)4.
Another embodiment includes the aforementioned catholyte, wherein the deformable halide-based ionic conductor has the formula Li2ZnF4.
Another embodiment includes a solid electrolyte separator comprising a deformable halide-based ionic conductor having one of the following formulas:
Another embodiment includes the aforementioned solid electrolyte separator, comprising a solid electrolyte having the formula CsLi2Cl3, wherein the CsLi2Cl3 has an orthorhombic crystal structure.
Another embodiment includes a solid state battery comprising an anode, a cathode, and a solid electrolyte separator, wherein the solid state battery comprises any aforementioned catholyte or any aforementioned solid electrolyte separator.
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:
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.
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.
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.
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 (O2−, S2−, Se2−, Te2−), halides (Cl−, F−, Br−, I−) or pseudo-halides (BH4−, BF4−, AlH4−, AlF4−, OH−, SH−), 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,
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 Li3PS4, used as reference material for good deformability.
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).
That is, compounds with ML predicted hardness <=2.5 GPa (that is the hardness of Li3PS4, 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
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).
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.
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.
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., a solid electrolyte separator in a solid state lithium battery cell.
An embodiment of the aforementioned solid electrolyte separator can be assembled together with a cathode active material layer and an anode active material layer to be used in an embodiment which is a solid state lithium battery comprising a cathode active material layer, an anode active material layer, and a solid electrolyte layer formed between the cathode active material layer and the anode active material layer, wherein the solid electrolyte layer comprises any of the aforementioned materials.
Embodiments will now be illustrated by way of the following examples, which do not limit the embodiments in any way.
With the use of the computational screening described above, new deformable halide ionic conductors have been designed with good electrochemical stability against either Li metal or high voltage cathodes (or both), to be employed as anolytes or catholytes (or SEs), respectively.
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., Li7La3Zr2O12 (LLZO), and cathodes, i.e., Li3MnNiCoO6 (NMC) and LiCoO2 (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.
Table 1 set forth below shows new deformable ionic conductors designed with the computational workflow described in the present disclosure. The screening criteria were Ehull≤30 meV/atom (thermodynamic stability), hardness≤2.5 GPa, energy barrier for ionic migration≤0.5 eV, and absence from Materials Project database of compounds with either the same composition or the same structure (or both).
The following observations can be made from the aforementioned new deformable ionic conductors designed with the computational workflow described in the present disclosure.
All of the newly designed compounds are halides, particularly chlorides and fluorides.
CsLi2Cl3, NaLi3I4, NaLi3Br4 and NaLi3Cl4 are electrochemically stable vs. Li metal (red_volt≈0V) and therefore usable as anolytes.
CsLi2Cl3 is also stable at high voltage (oxi_volt=4.34V vs. Li/Li+), and can therefore be used also as a catholyte or solid electrolyte (SE) in a solid-state battery (SSB).
In regard to CsLi2Cl3,
KLi2F3, Li2HfF6, Li3SiB3(ClF3)4 and Li2ZnF4 are stable at high voltage (oxi_volt >4.5V) and therefore usable as catholytes.
KLi2F3 is also stable down to 0.45V vs. Li/Li+ and might therefore be kinetically stabilized as anolyte vs. Li metal anode.
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 below).
Thus, Tables 2-4 show the computed interface stability against oxides commonly used in SSBs, namely LLZO (SE), LCO and NMC (cathodes).
As shown above, predicted reaction energies (e_rxn) are generally low or null for compounds with low valence metals, namely, Cs+, Na+, K+, and Ag+.
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.
This application is based on and claims priority from U.S. Provisional Application No. 63/546,793 filed on Nov. 1, 2023 in the U.S. Patent and Trademark Office, the disclosure of which is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 63546793 | Nov 2023 | US |
