Patent Application
20230116369
The present invention relates to the field of batteries, and in particular to batteries with solid electrolyte, such as sulfides.
The solid sulfide electrolytes have reached sufficient maturity for the industrial use thereof to be envisaged. The high ionic conductivity values thereof combined with the ductility thereof and the limited density thereof make same serious candidates for the first generations of all-solid batteries which can compete with the energy densities of current Li-ion batteries with liquid electrolytes.
However, such advantages are counterbalanced by the low stability of sulfides. In the presence of moisture, sulfides are likely to react and spontaneously release a toxic gas, H2S. In addition, sulfides have limited windows of potential stability and can thus degrade when in contact with the active electrode materials with which same are associated in cells. Since such active materials are often oxides (mainly in the positive electrode), another phenomenon related to space charges can be a source of additional charging.
Hence the stability of electrolytes thus remains to be improved, while maintaining a satisfactory conductivity and energy densities, in order to accelerate the progress of all-solid technologies so that the industrialization thereof can be envisaged with limited safety risks.
Oxides, on the other hand, are generally more stable (electrochemically and chemically) but have lower ionic conductivities and require heat treatments at high temperature (>700° C.), which are not suitable for an industrial application. Moreover, the higher density thereof and the poor ductility thereof limit the energy densities which can be obtained during the use thereof.
Novel mixed inorganic compounds have now been discovered which have, in particular, improved stability compared to sulfide electrolytes, while maintaining the electrochemical performance thereof, in particular without degrading the ionic conductivity.
According to a first subject matter, the present invention relates to a composition with formula (I):
((A(t-v)Bv/2)[(PS4)(1-x)(OHzAUX1)x])(1-y)(LinX2)y (I)
Wherein:
A=Li,Na,K;
B=Mg,Ca;
X1=F,Cl,Br,I;
X2=N,O,S,F,Cl,Br,I,BH4,CiBjHj+1;
n is such that:
n=3 for X2=N, or
n=2 for X2=0,S, or
n=1 for X2=F,Cl,Br,I,BH4,CiBjHj+1;
0<y<0.40,
0<x<0.7,
0<z<1;
u is either positive, negative or zero, and such that u+z=0;
0≤v≤0.3;
2.8≤t≤3.5;
Where it is understood that X2≠X1
In the compounds with formula (I) according to the invention, the presence of oxide makes it possible to increase the stability of sulfide electrolytes, to reduce the risks associated with the use thereof while maintaining their electrochemical performance: The compounds with formula (I) are used for the conduction of alkaline ions (in particular lithium).
Due to the mixed oxide and sulfide composition thereof, same combine the advantages of the different families of inorganic electrolytes while limiting the disadvantages thereof, in particular with regard to the low stability of sulfides.
The compounds with formula (I) thus make it possible to simplify the use of inorganic sulfide-based electrolytes and to accelerate the progress of all-solid technologies due to industrialization with limited safety risks.
The following embodiments can be mentioned, each of the embodiments being taken individually or according to each of the possible combinations thereof:
A=Li and X1=Cl; and/or
t=3,u=0,y=0 and z=0.
In particular, according to one embodiment, the compound with formula (I) is represented by formula (I′):
Li3(PS4)1-x(OCl)x (I′)
x being defined as above.
According to one embodiment, x is preferentially between 0.02 and 0.20.
Indeed, and without wishing to be bound by theory, the inventors have demonstrated a synergistic effect for the mixed electrolytes according to the invention for values of x less than 0.2: for such values, the electrolyte causes a lower release of H2S than the release from mixed electrolyte with a higher amount of Li3OCl (x greater than 0.2), whereas a lower release could be expected due to a lower amount of sulfides in the mixture.
As compounds corresponding to formula (I) according to the invention, the following representative compounds can be mentioned:
Li3(PS4)0.884(OCl)0.116
Li3(PS4)0.793(OCl)0.207
Li3[(PS4)0.85(OCl)0.15])0.80(LiBr)0.20
Li3.2[(PS4)0.90(OCl)0.10])0.70(Lil)0.30
(Li2.8Mg0.1)[(PS4)0.90(OCl)0.10]
(Li3[(PS4)0.85(OCl)0.15])0.95(Li3N)0.05
Li3[(PS4)0.85(OBr)0.15])0.90(Lil)0.10
(Li2.98[(PS4)0.80(OH)0.02Br0.20])0.90(Lil)0.10
According to another subject matter, the present application further relates to the preparation method of compounds with formula (I) according to the invention, said method comprising the step of co-grinding the precursors of the compound with formula (I). In particular, said precursors may be chosen from compounds with formula:
A2O,BO,A2S,LiX1,LiX2,P2S5,AOH
Wherein A, B, X1 are defined as in formula (I).
Generally, the co-grinding step is carried out by mixing said precursors in the desired proportions, typically in proportions observing the molar ratios required by formula (I).
According to one embodiment, the co-grinding can be carried out at ambient temperature.
According to one embodiment, the co-grinding can be carried out using a ball mill.
Typically, the co-grinding can be carried out by a mill marketed by Fritsch (Fritsch 7), with balls with a diameter comprised between 0.1 and 15 mm, in 10 to 50 ml bowls, during cycles lasting between 1 minute and 2 hours for a total duration comprised between 5 and 100 h, at a rotational speed comprised between 100 and 1000 rpm. Typically, the particle size of the mixture after co-grinding is less than 10 μm, in particular less than 1 μm.
The precursors A20, BO, A2S, LiX1, LiX2, P2S5, AOH are commercially available, e.g., such materials are available from Aldrich or Alfa Aesar.
Typically, the precursors are in crystalline form.
According to one embodiment, the compounds with formula (I) obtained by the process according to the invention, have an amorphous structure.
According to one embodiment, in the case of compound (I′), the preparation method for compound (I′) comprises the step of co-grinding the precursors Li2O, LiCl, Li2S and P2S5.
Advantageously, some of the precursors can be in the form of a mixture beforehand. Thus, e.g. the co-grinding can be carried out by mixing a composition (II) comprising Li2O and LiCl and a composition (III) comprising Li2S and P2S5, in the ratio Li2S/P2S5=3.
The compositions (II) and (III) are mixed for co-grinding in the proportions:
Li2O+LiCl (II)
3 Ll2S+P2S5 (III)
Advantageously, the synthesis process according to the invention does not comprise high temperature annealing, unlike for most oxides. It is therefore favorable for large-scale production of such materials.
According to another subject matter, the present invention further relates to an electrolyte for a battery comprising a compound with formula (I) according to the invention.
According to one embodiment, said electrolyte is a solid.
According to one embodiment, said electrolyte is suitable for “all solid” batteries.
Thus, according to another subject matter, the present invention further relates to an electrochemical element comprising an electrolyte according to the invention.
The electrochemical cell according to the invention is particularly suitable for lithium batteries, such as Li-ion, Li primary (non-rechargeable) and Li-S batteries and the equivalents thereof with other alkaline elements (Na-ion, K-ion, etc.) for the corresponding formulations.
According to another subject matter, the present invention further relates to an electrochemical module comprising a stack of at least two elements according to the invention, each element being electrically connected with one or a plurality of other elements.
The term “module” refers herein to the assembly of a plurality electrochemical elements.
According to another subject matter, the present invention further relates to a battery comprising one or a plurality of modules according to the invention.
The term “battery” or “accumulator” refers herein to the assembly of a plurality of modules, where said assemblies can be in series and/or parallel. The invention preferentially relates to batteries of which capacity is greater than 100 mAh, typically 1 to 100Ah.
The following examples illustrate in a representative and non-limiting manner, an embodiment according to the invention.
Selected compositions:
The Li3(PS4)1-x(OCl)x compounds were prepared from the precursors Li2O, LiCl, Li2S and P2S5. Precursor masses are calculated for obtaining the desired stoichiometry.
Table 1 shows the masses of the different precursors for producing
Li3(PS4)1-x(OCl)x compounds for the different values of x
The mixtures are carried out by ball milling (Fritsch 7) in 25 ml ZrO2 bowls with 4 balls with a diameter of 10 mm. The bowls are rotated at 500 rpm for several 30-minute cycles. The powder inside the bowls is detached from the walls every 5 hours so as to homogenize the sample.
The evolution of the X-ray diffraction graph (DRX) of the compound Li3(PS4)0.884(OCl)0.116 as a function of the grinding time is shown in
The DRXs of the other mixtures after 29 h of mechano-synthesis are shown in
The release of hydrogen sulfide was measured for a mixed electrolyte according to the invention Li3PS4:Li3OCl according to two compositions with x=0.116 and 0.207. The release was compared with the release from a sample of sulfide-alone electrolyte (amorphous LPS) with similar mass.
In order to measure the release of H2S, 25 mg of powder were introduced at the initial time into a 2.5 l container which could be hermetically sealed and wherein an H2S detector (accuracy of 1 ppm) was placed. In the present example, the container contained ambient air at atmospheric pressure and ambient temperature, so as to assess the risk associated with the release of H2S under standard conditions in which the materials could be found. The H2S concentration in the chamber was recorded at regular intervals as soon as the sample was introduced.
The results are shown in
Since the main function of the electrolyte is the conduction of ions, measurements of ionic conductivity were performed so as to verify the evolution thereof according to the compositions studied. For a given composition, powder coming from the synthesis was introduced into a cell similar to a pelletizing mold, the pistons of which were made of stainless steel and the body was made of insulating material. A pressure of 2t/cm2 was maintained on the cell during the conductivity measurement. Such measurement was made by impedance (1 MHz to 200 mHz), at a plurality of temperature values from 20° C. to 60° C. The resistance value R from the measurement allowed us to calculate the conductivity value σ via the relation
The thickness e of the compressed pellet was measured with a micrometer (accuracy: 1 μm) and the surface area S was the surface area of the cell used.
The conductivity values obtained at 20 and 60° C. are given in Table 2.
Such measurements show that the conductivity does not vary greatly from one sample to another, despite the decrease in the amount of sulfides.
The reduction in the quantity of H2S released is thus not to the detriment of the capacity of the material to conduct lithium ions.
| Number | Date | Country | Kind |
|---|---|---|---|
| FR20 02987 | Mar 2020 | FR | national |
The present application is a U.S. National Phase Application under 35 U.S.C. § 371 of International Patent Application No. PCT/EP2021/057459 filed Mar. 23, 2021, which claims priority of French Patent Application No. 20 02987 filed Mar. 26, 2020. The entire contents of which are hereby incorporated by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2021/057459 | 3/23/2021 | WO |
