Lithium mixed inorganic electrolyte

Abstract

The present invention relates to novel mixed compounds based on oxides and sulfides with improved sulfide stability and their use as solid electrolytes. The invention also relates to electrochemical elements and lithium batteries containing said electrolytes.

Description

Technical Field

[0001] This invention relates to the field of batteries, and more particularly to batteries having a solid electrolyte such as a sulfide. Background Technology

[0002] Solid sulfide electrolytes have reached a level of maturity sufficient for envisioning industrial applications. Their high ionic conductivity, combined with their ductility and limited density, makes first-generation all-solid-state batteries equally important candidates, with energy densities comparable to current lithium-ion batteries using liquid electrolytes.

[0003] However, the low stability of sulfides negates these advantages. In the presence of moisture, sulfides can react and spontaneously release the toxic gas H₂S. Furthermore, sulfides have a limited potential stability window, thus degrading upon contact with the active electrode materials associated with them in the battery. Since these active materials are typically oxides (primarily in the positive electrode), another phenomenon related to space charge can be a source of additional charge.

[0004] Therefore, the stability of electrolytes still needs to be improved while maintaining satisfactory conductivity and energy density to accelerate the advancement of all-solid-state technology, thereby enabling its industrialization with limited safety risks.

[0005] On the other hand, oxides are generally more stable (electrochemically and chemically), but have lower ionic conductivity and require heat treatment at high temperatures (>700°C), which is unsuitable for industrial applications. Furthermore, their higher density and poorer ductility limit the energy density achievable during their use. Summary of the Invention

[0006] Novel mixed inorganic compounds have now been discovered that exhibit improved stability, particularly compared to sulfide electrolytes, while maintaining their electrochemical properties, especially without reducing ionic conductivity.

[0007] According to the first subject matter, the present invention relates to compounds having formula (I):

[0008] ((A (t-v) B v / 2 (PS4) (1-x) (OH z A u X1) x ]) (1-y) (Li n X2) y (I)

[0009] in:

[0010] A = Li, Na, K;

[0011] B = Mg, Ca;

[0012] X1 = F, Cl, Br, I;

[0013] X2=N, O, S, F, Cl, Br, I, BH4, C i B j H j+1 ;

[0014] n can take the following values:

[0015] When X2 = N, n = 3, or

[0016] When X2 = O and S, n = 2, or

[0017] X2=F, Cl, Br, I, BH4, C i B j H j+1 When n = 1;

[0018] Where i and j are integers, and i = 1 or 2 and 8 ≤ j ≤ 11;

[0019] 0 <y<0.40,

[0020] 0 <x<0.7,

[0021] 0 <z<1;

[0022] u is positive, negative, or zero, and makes u+z=0;

[0023] 0 ≤ v ≤ 0.3;

[0024] 2.8 ≤ t ≤ 3.5;

[0025] X1 and X2 are understood as X2≠X1. Detailed Implementation

[0026] In the compounds of formula (I) according to the invention, the presence of oxides makes it possible to increase the stability of sulfide electrolytes to reduce the risks associated with their use while maintaining their electrochemical performance: compounds of formula (I) are used for the conduction of alkaline ions (especially lithium).

[0027] Due to its mixed oxide and sulfide composition, it combines the advantages of different types of inorganic electrolytes while limiting their disadvantages, particularly the low stability of the sulfides.

[0028] Therefore, compounds of formula (I) can simplify the use of inorganic sulfide-based electrolytes and accelerate the advancement of all-solid-state technologies with limited safety risks due to industrialization.

[0029] The following implementations may be mentioned, each of which is carried out individually or according to each of its possible combinations:

[0030] -A = Li and X1 = Cl; and / or

[0031] -t=3, u=0, y=0, z=0.

[0032] In particular, according to one embodiment, a compound having formula (I) is represented by formula (I'):

[0033] Li3 (PS4) 1-x (OCl) x (I')

[0034] X is as defined above.

[0035] According to one implementation, x is preferably between 0.02 and 0.20.

[0036] Indeed, without being bound by theory, the inventors have demonstrated the synergistic effect of the mixed electrolytes according to the invention for values ​​of x less than 0.2: for these values, the electrolytes result in a lower release of H2S than from mixed electrolytes with a higher amount of Li3OCl (x greater than 0.2), and a lower release can be expected due to the lower amount of sulfides in the mixture.

[0037] As compounds corresponding to formula (I) of the present invention, the following representative compounds may be mentioned:

[0038] Li3 (PS4) 0.884 (OCl) 0.116

[0039] Li3 (PS4) 0.793 (OCl) 0.207

[0040] Li3[(PS4) 0.85 (OCl) 0.15 ]) 0.80 (LiBr) 0.20

[0041] Li 3.2 (PS4) 0.90 (OCl) 0.10 ]) 0.70 (LiI) 0.30

[0042] (Li 2.8 Mg 0.1 (PS4) 0.90 (OCl) 0.10 ]

[0043] (Li3[(PS4) 0.85 (OCl) 0.15 ]) 0.95 (Li3N) 0.05

[0044] Li3[(PS4) 0.85 (OBr) 0.15 ]) 0.90 (LiI) 0.10

[0045] (Li 2.98 (PS4) 0.80 (OH) 0.02 Br 0.20 ]) 0.90 (LiI) 0.10 .

[0046] According to another subject matter, this application also relates to a method for preparing a compound of formula (I) according to the invention, the method comprising the step of co-milling a precursor of a compound having formula (I). In particular, the precursor may be selected from compounds having the following formula:

[0047] A2O, BO, A2S, LiX1, LiX2, P2S5, AOH

[0048] Where A, B, and X1 are defined as in equation (I).

[0049] Typically, the co-grinding step is carried out by mixing the precursors in a desired ratio, usually in the molar ratio required by observation formula (I).

[0050] According to one embodiment, the co-grinding can be performed at ambient temperature.

[0051] According to one embodiment, the co-grinding can be performed using a ball mill. Typically, the co-grinding can be carried out using a Fritsch (Fritsch 7) mill, in a 10-50 ml bowl, during a cycle of 1 minute to 2 hours for a total duration of 5 to 100 hours, at a rotation speed of 100 to 1000 rpm, using balls with a diameter of 0.1 to 15 mm. Typically, the particle size of the co-grinded mixture is less than 10 μm, particularly less than 1 μm.

[0052] The precursors A2O, BO, A2S, LiX1, LiX2, P2S5, and AOH are commercially available, for example, from Aldrich or Alfa Aesar.

[0053] Typically, the precursor is in crystalline form.

[0054] According to one embodiment, the compound having formula (I) obtained by the method of the present invention has an amorphous structure.

[0055] According to one embodiment, in the case of compound (I'), the preparation method of compound (I') includes the step of co-milling the precursors Li2O, LiCl, Li2S, and P2S5. Advantageously, some precursors may be in the form of a mixture beforehand. Thus, for example, the co-milling can be carried out by mixing a composition (II) containing Li2O and LiCl with a composition (III) containing Li2S and P2S5 in a Li2S / P2S5 ratio of 3.

[0056] Compositions (II) and (III) are mixed in the following proportions for co-milling:

[0057] -x parts by weight of composition (II):

[0058] Li₂O + LiCl (II)

[0059] and

[0060] -(1-x) parts by weight of composition (III):

[0061] 3LI2S+P2S5 (III)

[0062] Advantageously, unlike most oxides, the synthesis method according to the invention does not involve high-temperature annealing. Therefore, it is advantageous for the large-scale production of this material.

[0063] According to another subject, the present invention also relates to an electrolyte for a battery comprising a compound of formula (I) according to the invention.

[0064] According to one embodiment, the electrolyte is a solid.

[0065] According to one embodiment, the electrolyte is suitable for "all-solid-state" batteries.

[0066] Therefore, according to another subject, the present invention also relates to an electrochemical element comprising an electrolyte according to the invention.

[0067] The electrochemical cells according to the present invention are particularly suitable for lithium batteries, such as lithium-ion batteries, lithium primary batteries (non-rechargeable) and lithium-sulfur batteries, as well as equivalents of other alkaline elements (Na ions, K ions, etc.) in the corresponding formulations.

[0068] According to another subject matter, the present invention also relates to an electrochemical module comprising a stack of at least two electrochemical elements according to the invention, each element being electrically connected to one or more other electrochemical elements.

[0069] The term "module" here refers to the assembly of multiple electrochemical elements.

[0070] According to another subject, the present invention also relates to a battery comprising one or more modules according to the invention.

[0071] The term "battery" or "rechargeable battery" herein refers to a component of multiple modules, wherein said components may be connected in series and / or in parallel. The invention preferably relates to batteries with a capacity greater than 100 mAh, typically from 1 to 100 Ah. Attached Figure Description

[0072] [ Figure 1 ] Figure 1 The results show the Li3(PS4) grinding process over 29 hours in a ball mill. 1-x (OCl) x The X-ray diffraction spectrum of the compound as a function of x; the wavelength used is the K0 of copper. α Line (1.5406 angstroms).

[0073] [ Figure 2 ] Figure 2 The compound Li3(PS4) is shown. 0.884 (OCl) 0.116 The relationship between X-ray diffraction spectra and the time function of ball milling samples; the wavelength used is the K wavelength of copper. α Line (1.5406 angstroms).

[0074] [ Figure 3 ] Figure 3 Individual sulfide electrolyte samples (amorphous LPS) and Li3 (PS4) are shown. 1-x (OCl) x Comparison of H2S release amounts between compounds.

[0075] Example

[0076] The following examples illustrate embodiments of the invention in a representative and non-limiting manner.

[0077] Example 1: Preparation of Li-PSO-Cl composite material from Li2S-P2S5-Li2O-LiCl

[0078] Selected compound:

[0079] -X = 0.714, corresponding to 50% by mass of Li3OCl

[0080] -X = 0.384, corresponding to 20% by mass of Li3OCl

[0081] -X = 0.207, corresponding to 9.5% by mass of Li3OCl

[0082] -X = 0.116, corresponding to 5% by mass of Li3OCl

[0083] Li3(PS4) was prepared from precursors Li2O, LiCl, Li2S, and P2S5. 1-x (OCl) x Compounds. Calculate the precursor mass to obtain the required stoichiometry.

[0084] [Table 1]

[0085]

[0086] Table 1 shows the Li3(PS4) produced with different x values. 1-x (OCl) x Mass of different precursors of the compound

[0087] The mixture was milled in a 25 ml ZrO2 bowl (Fritsch 7) with four 10 mm diameter balls. The bowl was rotated at 500 rpm for several 30-minute cycles. Every 5 hours, the powder inside the bowl was separated from the walls to homogenize the sample.

[0088] Compound Li3(PS4) 0.884 (OCl) 0.116 The X-ray diffraction pattern (DRX) changes with grinding time as follows: Figure 2 As shown. The three precursors, Li₂S, LiCl, and Li₂O, disappeared after 29 hours of grinding. The precursors may have been nanostructured until they formed amorphous compounds, such as amorphous Li₃PS₄. Amorphous structures are characterized by a lack of medium- to long-range order, resulting in very broad diffraction lines. Therefore, the grinding time will be used as a reference for other mixtures. Figure 1 ).

[0089] DRX of other mixtures after 29 hours of mechanical synthesis, such as Figure 1 As shown. Similar to the compound with x = 0.116, the compound with x = 0.207 does not have any very significant peaks. For compound Li3(PS4) 0.616 (OCl) 0.384 And Li3 (PS4) 0.286 (OCl) 0.714 The precursor was still clearly visible 29 hours after mechanical synthesis. Figure 3 ).

[0090] Example 2: H2S Release

[0091] For the mixed electrolyte Li3PS4:Li3OCl according to the present invention, the release of hydrogen sulfide was measured according to the two compounds at x = 0.116 and 0.207. This release was compared with the release of a single sulfide electrolyte (amorphous LPS) sample with a similar mass.

[0092] To measure H2S release, 25 mg of powder was introduced into a 2.5 L, sealable container at the initial time, containing an H2S detector (accuracy 1 ppm). In this embodiment, the container contained ambient air at atmospheric pressure and ambient temperature to assess the risk associated with H2S release under standard conditions where the material could be detected. Once the sample was introduced, the H2S concentration in the chamber was recorded at regular intervals.

[0093] The results are as follows Figure 3 As shown in the figure. The obtained curves indicate that the release amount of the compound with x = 0.116 is lower than that of the compound with x = 0.207, further suggesting that values ​​of x less than 0.2 have a synergistic effect.

[0094] Example 3: Conductivity Measurement

[0095] Since the primary function of an electrolyte is ion conduction, ionic conductivity was measured to verify its evolution according to the compounds studied. For a given compound, powder from synthesis was introduced into a unit similar to a granulation mold, with a piston made of stainless steel and a body made of insulating material. During conductivity measurements, a concentration of 2 t / cm was maintained on the cell. 2 The pressure was measured at multiple temperature values ​​from 20 to 60 F using impedance (1 MHz to 200 MHz). The measured resistance value R allowed the conductivity value σ to be calculated using the following formula [Mathematics 1].

[0096]

[0097] The thickness e of the compressed particles is measured using a micrometer (accuracy: 1μm), and the surface area S is the surface area of ​​the battery used.

[0098] Table 2 shows the conductivity values ​​obtained at 20°C and 60°C.

[0099] [Table 2]

[0100]

[0101] These measurements show that despite the reduced amount of sulfides, the electrical conductivity did not vary significantly between different samples.

[0102] Therefore, the reduction in H2S release does not impair the material's ability to conduct lithium ions.

Claims

1. A compound having formula (I): ((A (t-v) B v / 2 )[(PS4) (1-x) (OH z A u X1) x ]) (1-y) (Li n X2) y (I) in: A = Li, Na, K; B = Mg, Ca; X1 = F, Cl, Br, I; X2 = N、O、S、F、Cl、Br、I、BH4、C i B j H j+1 ; n can take the following values: When X2=N, n=3, or When X2=O and S, n=2, or X2 = F, Cl, Br, I, BH4, C i B j H j+1 When n = 1; Where i and j are integers, and i = 1 or 2 and 8 ≤ j ≤ 11; 0≤y<0.40， 0<x<0.7； u and z are zero; 0≤v≤0.3； 2.8≤t≤3.5； X1 and X2 are understood as X2≠X1.

2. The compound according to claim 1, wherein, The compound is the compound shown in formula (I): A = Li and X1 = Cl.

3. The compound according to claim 1 or 2, wherein, The compound is the compound shown in formula (I): y=0.

4. The compound according to claim 1 or 2, wherein, The compound is the compound shown in formula (I): t=3 and y=0.

5. The compound according to claim 1, wherein, Compounds having formula (I) are represented by formula (I'): Li3(PS4) 1-x (OCl) x (I') x is as defined in claim 1.

6. The compound according to claim 5, wherein, x is between 0.02 and 0.

20.

7. A method for preparing a compound having formula (I) according to any one of claims 1 to 6, wherein, The method includes the step of co-grinding the crystallization precursor until an amorphous mixture is obtained.

8. An electrolyte for a battery, comprising a compound having formula (I) according to any one of claims 1 to 6.

9. An electrochemical element comprising the electrolyte according to claim 8.

10. An electrochemical module comprising a stack of at least two electrochemical elements according to claim 9, each electrochemical element being electrically connected to one or more other electrochemical elements.

11. A battery comprising one or more electrochemical modules according to claim 10.

Images