WO2018054709A1

WO2018054709A1 - Solid lithium electrolytes and process of production

Info

Publication number: WO2018054709A1
Application number: PCT/EP2017/072758
Authority: WO
Inventors: Heino Sommer; Stefan Sedlmaier; Sylvio Indris; Juergen Janek
Original assignee: Basf Se; Karlsruher Institut für Technologie
Priority date: 2016-09-20
Filing date: 2017-09-11
Publication date: 2018-03-29

Abstract

The present invention relates to a process for preparing solid electrolytes, to compounds, which can be used as precursors for the preparation of said solid electrolytes, to particular solid electrolytes, and to separators, electrochemical cells, batteries and devices all comprising said particular solid electrolytes.

Description

SOLID LITHIUM ELECTROLYTES AND PROCESS OF PRODUCTION

The present invention relates to a process for preparing solid electrolytes, to compounds, which can be used as precursors for the preparation of said solid electrolytes, to particular solid electrolytes, and to separators, electrochemical cells, batteries and devices all comprising said particular solid electrolytes. Secondary batteries, accumulators or "rechargeable batteries" are just some embodiments by which electrical energy can be stored after generation and used when required. Owing to the significantly better power density, there has been in recent times a move away from the water- based secondary batteries toward development of those batteries in which the charge transport in the electrical cell is accomplished by lithium ions.

However, the energy density of conventional lithium ion accumulators, which have a carbon anode, a cathode based on metal oxides and a non-aqueous electrolyte comprising organic solvents, is limited. New horizons with regard to energy density have been opened up by systems employing a lithium anode such as all-solid-state lithium battery comprising a metallic lithium anode and a solid lithium-ion conducting inorganic electrolyte.

The solid electrolytes useful for all-solid-state lithium batteries have to fulfill many requirements such as high ionic conductivity, chemical compatibility with cathode and anode materials, electrochemical stability, mechanical stability and economic producibility.

J. Am. Chem. Soc. 2013, 135, 975-978 and US 2013/0295469 A1 , both disclose a method for forming U3PS4 from L12S and P2S5 in a solvent such as THF. In J. Am. Chem. Soc. 2013, 135, 975-978 the formation of U3PS4 · 3THF and its conversion to U3PS4 is described. US 2015/0318569 A1 discloses a method for manufacturing a sulfide solid electrolyte including loading a raw material for manufacturing a sulfide solid electrolyte which is mainly composed of a substance represented by the general formula of (100-x)(0.75Li2S.0.25P2Ss).xLil (here, 0<x<100), into a vessel; and amorphizing the raw material after said loading, wherein a reaction site temperature in the vessel is controlled so that x included in the general formula and the re- action site temperature y [degrees centigrade] in the vessel in said amorphizing satisfy y<-2.00x+1 .79x10². In the experimental part x is varied in the range from 15 to 30.

J. Am. Chem. Soc. 2015, 137, 1384-1387 and WO 2016/014149 A1 , both disclose a solid electrolyte of formula U7P2S8I for a battery and a method of making a battery including a U7P2S8I electrolyte. It is described, that U7P2S8I is preferably obtained by mixing and heating U3PS4 in form of the acetonitrile adduct with Lil in the ratio of 2 to 1. Proceeding from this prior art, a first object of the invention was to provide an economic and reproducible process for the preparation of new or known solid electrolytes, which can be used as components of rechargeable electrochemical cells, a second object of the invention was to provide suitable new starting materials for the new process, and a third object of the invention was to provide new solid electrolytes with improved properties, such as ionic conductivity, chemical compatibility with cathode and anode materials, electrochemical stability or mechanical stability.

The first object is achieved by a process for preparing a solid electrolyte of general formula (I) Li⁺4-2a₊c₊2d₊e M²⁺ _a P⁵⁺1-b-c-d As⁵⁺b D⁴⁺ _c E ⁺d S²-4-e-f N ^" _e T^2"f l^"l-g X^"g (I) in which the variables are each defined as follows:

M is Mg, Ca, Zn or a mixture thereof, preferably Mg or Zn, in particular Mg,

D is Si, Ti, Ge, Sn or a mixture thereof, preferably Ge,

E is B, Al, Ga, In or a mixture thereof, preferably Al,

T is O, Se, Te or a mixture thereof, preferably O or Se, in particular O,

X is F, CI, Br, CN, OCN, SCN, N₃ or a mixture thereof, preferably Br, a is in the range from 0 to 2, preferably from 0 to 1 , more preferably from 0 to 0.5, in particular from 0 to 0.25

b is in the range from 0 to 1 , preferably from 0 to 0.5,

c is in the range from 0 to 1 , preferably from 0 to 0.5,

d is in the range from 0 to 1 , preferably from 0 to 0.5,

e is in the range from 0 to 4, preferably from 0 to 2,

f is in the range from 0 to 4, preferably from 0 to 2,

g is in the range from 0 to 1 , preferably from 0 to 0.5, wherein the sum of b+c+d is in the range from 0 to 1 , preferably from 0 to 0.5, in particular from 0 to 0.25, and

wherein the sum of e+f is in the range from 0 to 4, preferably from 0 to 2, in particular from 0 to 1 , comprising the process steps of a) preparing a mixture comprising a compound A) of general formula (II) Li⁺ ₃-2a'₊c₊2d₊e M²V P⁵⁺i-b-c-d As⁵⁺ _b D⁴⁺ _c E³⁺ _d S -₄-e-f N^3" _e T^2" _f ^* h Solv (II), a compound B) of general formula (III) Li⁺1-2a" M²V ΐ -g X-g (III) in which the variables M, D, E, T, X, b, c, d, e, f and g are each defined as described above and the other variables are each defined as follows:

Solv is a polar solvent molecule selected from the group consisting of ethers, acetals, amides, alcohols and mixtures thereof, preferably an ether selected from THF and DME, in particular DME, a' is in the range from 0 to 1 .5, preferably from 0 to 0.75,

a" is in the range from 0 to 0.5, preferably from 0 to 0.25,

h is in the range from 1 to 6, preferably from 1 to 4, and at least one organic solvent, b) converting the mixture prepared in process step a) to the solid electrolyte of general formula (I) by removing the organic solvent and heating the formed solidified material at a temperature in the range from 50 °C up to 600 °C.

In one embodiment of the present invention, the inventive process is characterized in that the solid electrolyte of general formula (I) is crystalline.

The inventive process is particularly useful for preparing new compounds of general formula (I), wherein the elements Li, P, S and I are at least partially substituted by other elements, without completely changing the original crystal structure type of U4PS4I.

In one embodiment of the present invention, the inventive process is characterized in that in above defined general formula (I) the sum of a+b+c+d+e is > 0, preferably in the range from 0.01 to 2, more preferably the range from 0.02 to 0.5.

In one embodiment of the present invention, the inventive process is characterized in that the variables are each defined as follows:

M is Mg,

D is Ge,

E is Al,

T is O,

X is Br, a is in the range from 0 to 0.5, in particular from 0 to 0.25,

b is in the range from 0 to 0.5, in particular from 0 to 0.25, is in the range from 0 to 0.5, in particular from 0 to 0.25,

is in the range from 0 to 0.5, in particular from 0 to 0.25,

is in the range from 0 to 2, preferably from 0 to 1 , in particular from 0 to 0.5,

is in the range from 0 to 0.5, in particular from 0 to 0.25

Solv is an ether selected from THF and DME,

a' is in the range from 0 to 0.375,

a" is in the range from 0 to 0.125,

h is in the range from 1 to 6, preferably from 1 to 4, wherein the sum of b+c+d is in the range from 0 to 0.5, in particular from 0 to 0.25, and wherein the sum of e+f is in the range from 0 to 2, in particular from 0 to 1.

In a further embodiment of the present invention, the inventive process is characterized the variables are each defined as follows:

M is Mg,

D is Ge,

E is Al,

T is O,

X is Br, is in the range from 0 to 0.5, in particular from 0 to 0.25,

is in the range from 0 to 0.5, in particular from 0 to 0.25,

is in the range from 0 to 0.5, in particular from 0 to 0.25

Solv is an ether selected from THF and DME,

a' is in the range from 0 to 0.375,

a" is in the range from 0 to 0.125,

h is in the range from 1 to 6, preferably from 1 to 4, wherein the sum of b+c+d is in the range from 0 to 0.5, in particular from 0 to 0.25, the sum of e+f is in the range from 0 to 2, in particular from 0 to 1 , and the sum of a+b+c+d+e is > 0, preferably in the range from 0.01 to 2, more preferably the range from 0.02 to 0.5. The first object is also achieved by a process for preparing a solid electrolyte of general formula (I)

Li⁺4-2a M²⁺ _a P⁵⁺ S ^" ₄ l^"l-g X^"g (I) in which the variables are each defined as follows:

M is Mg, Ca, Zn or a mixture thereof, preferably Mg or Ca, in particular Ca,

X is F, CI, Br, CN, OCN, SCN, N₃ or a mixture thereof, a is in the range from 0 to 2, preferably from 0 to 1 , more preferably from > 0 to 0.5, in particular from 0.01 to 0.5,

g is in the range from 0 to 1 , preferably from 0 to 0.5, comprising the process steps of a) preparing a mixture comprising a compound A) of general formula (II)

Li⁺3-2a' M²V P⁵⁺ S^2"4 ^* h Solv (II), a compound B) of general formula (III)

in which the variables M, X and g are each defined as described above and the other variables are each defined as follows: Solv is a polar solvent molecule selected from the group consisting of ethers, acetals, amides, alcohols and mixtures thereof a' is in the range from 0 to 1 .5, preferably from 0 to 0.75, more preferably from 0 to 0.1 , a" is in the range from 0 to 0.5, preferably from 0 to 0.25, more preferably from > 0 to 0.5, in particular from 0.01 to 0.5,

h is in the range from 1 to 6, preferably from 1 to 4, and at least one organic solvent, b) converting the mixture prepared in process step a) to the solid electrolyte of general formula (I) by removing the organic solvent and heating the formed solidified material at a temperature in the range from 50 °C up to 600 °C. In a further embodiment of the present invention, the above-mentioned inventive process characterized in that the variables are each defined as follows:

M is Mg,

X is Br, is in the range from 0 to 0.5, in particular from 0 to 0.25,

is in the range from 0 to 0.5, in particular from 0 to 0.25 Solv is an ether selected from THF and DME, in particular DME,

a' is in the range from 0 to 0.375,

a" is in the range from 0 to 0.125,

h is in the range from 1 to 6, preferably from 1 to 4.

In a further embodiment of the present invention, the above-mentioned inventive process characterized in that the variables are each defined as follows:

M is Ca,

X is Br, a is in the range from 0 to 0.5, preferably from 0 to 0.25, more preferably from > 0 to 0.25, in particular from 0.0.1 to 0.25,

g is in the range from 0 to 0.5, in particular from 0 to 0.25

Solv is an ether selected from THF and DME, in particular DME,

a' is in the range from 0 to 0.1.5, preferably from 0 to 0.5

a" is in the range from 0 to 0.5, preferably from > 0 to 0.5, more preferably from > 0.01 to 0.5, h is in the range from 1 to 6, preferably from 1 to 4.

Certain compounds A) of general formula (II) and compounds B) of general formula (III) are in principle known to the person skilled in the art. Known examples of compound A) are for example U3PS4 · 3THF, U3PS4 · 2ACN or of Li₃PS₄ · 2EtOAc.

Compounds B) are generally known, since all lithium halides and all halides of magnesium, calcium and zinc are commercially available. Each component B) of general formula (III) is availa- ble by mixing the appropriate metal halides in the desired stoichiometry.

In one embodiment of the present invention, the inventive process is characterized in that in process step a) the compound A) of general formula (II) is crystalline U3PS4 · DME or U3PS4 · 2DME, in particular U3PS4 · DME, and compound B) of general formula (III) is Lil.

In one embodiment of the present invention, the inventive process is characterized in that in process step a) the compound A) of general formula (II) is crystalline L13 PS₄ · DME or L13 PS₄ · 2DME, in particular U3PS4 · DME, compound B) of general formula (III) is Lil and the organic solvent is DME.

In one embodiment of the present invention, the inventive process is characterized in that in process step a) the compound A) of general formula (II) is crystalline L13 PS₄ · DME, compound B) of general formula (III) is Li 2(0.25 - 0.3) Mg²⁺ ₀.25 - o.3 1^" or L _ ₂(o.oi - 0.1) Ca²⁺o.oi - o.i I^" and the organic solvent is DME.

In one embodiment of the present invention, the inventive process is characterized in that in process step a) the compound A) of general formula (II) is defined as compound A1 ) of general formula (11-1 ) as described below.

In process step a) a mixture comprising as a first component a compound A) of general formula Li⁺3-2a'₊c₊2d+e M²V P⁵⁺i-b-c-d As⁵⁺ _b D⁴⁺ _c E³⁺ _d S^2" ₄-e-f N^3" _e T^2" _f ^* h Solv (II), as a second component a compound B) of general formula Li⁺i-2a- M²V -_g X^" _g (III) and as a third component at least one organic solvent, wherein the variables are defined as described above.

In one embodiment of the present invention, the inventive process is characterized in that the variable Solv is a polar aprotic solvent molecule selected from the group consisting of ethers, acetals, amides and mixtures thereof. Preferred polar aprotic solvent molecules are dimethoxy- ethane (DME), dichloromethane (DCM), tetrahydrofuran (THF), ethyl acetate (EtOAc), dimethyl- formamide (DMF), N-methylformamide (NMF), dimethylsulfoxide (DMSO), acetone, hexa- methylphosphoric triamide (HMPT), N-methylpyrrolidone (NMP) or 1 ,3-dioxolane, particularly preferred DME, DMF, NMF, DMSO, 1 ,3-Dioxolane, DCM, HMPT or NMP.

The third component, the organic solvent, can be varied in a wide range. Preferably the organic solvent is a polar solvent, in particular an aprotic polar solvent. A preferred aprotic polar solvent is dimethoxyethane (DME), dichloromethane (DCM), tetrahydrofuran (THF), ethyl acetate (EtOAc), acetonitrile (MeCN), dimethylformamide (DMF), N-methylformamide (NMF), dimethyl- sulfoxide (DMSO), acetone, hexamethylphosphoric triamide (HMPT), N-methylpyrrolidone (NMP) or 1 ,3-dioxolane.

The molar ratio of compound A) to compound B) in the mixture prepared in process step a) can be varied in a wide range. Preferably the molar ratio of compound A) to compound B) in the mixture prepared in process step a) is in the range from 0.66 to 1 .5, more preferably from 0.75 to 1 .25, in particular from 0.9 to 1.1.

In one embodiment of the present invention, the inventive process is characterized in that in process step a) the molar ratio of compound A) to compound B) is in the range from 0.66 to 1 .5. The sum of the mass fractions of components A), B) and the organic solvent, which are mixed together in process step a), can be varied in a broad range depending on the presence of further additional components in said mixture. Preferably the sum of the mass fractions of components A), B) and the organic solvent in the mixture is in the range from 0.6 to 1 , more preferably in the range from 0.8 to 1 , in particular in the range from 0.9 to 1.

Components A) and B) are in most cases solid materials at room temperature (20 °C). Further compound A) and compound B) can be completely or partly soluble in the used organic solvent. The order of mixing components A) and B) and the organic solvents can be varied. For exam- pie, a mixture of compound B) and the organic solvent is formed in form of a solution or a suspension followed by addition of compound A). Alternatively, a first mixture of compound A) and the organic solvent is combined with a second mixture of compound B) and the organic solvent. It is also possible to mix first compound A) with compound B), preferably both in powder form, and then combining said mixture with the organic solvent.

In one embodiment of the present invention, the inventive process is characterized in that in process step a) the compound A) and compound B) are both mixed in powder form, before the at least one organic solvent is added in order to form the mixture, preferably a liquid mixture, e.g. a solution or a suspension.

In process step b) the mixture, which was prepared in process step a), is converted to the solid electrolyte of general formula (I) by removing the organic solvent or solvents and heating the formed solidified material at a temperature in the range from 50 °C up to 600 °C. According to the present invention the term "solidified material" means that the material is structural rigid at room temperature (20 °C) and shows resistance to changes of shape or volume. The solidified material usually still comprises certain amounts of organic solvents, in particular as long as the applied temperature is not higher than the boiling point of the respective solvent. The organic solvent or solvents are usually removed from the mixture prepared in process step a) by evaporating the organic solvent molecules. The conditions for evaporating one or more organic solvents from a solution and/or suspension are known to the person skilled in the art. The decreasing content of organic solvent molecules in the mixture and in the formed solidified material can be easily monitored by FT-IR analysis.

Since the boiling point of an organic solvent depends on the pressure, process step b) can be performed under reduced pressure in order to accelerate the removal of organic solvent molecules. The appropriate pressure in process step b) is preferably adjusted by considering the optimal temperature for the formation of the solid electrolyte of general formula (I) and the need for removal of organic solvent molecules. The time needed for evaporating a solvent at a given temperature varies depending on the conditions applied. Dynamic conditions, e.g. atmosphere circulation or constant exchange of the atmosphere in order to remove solvent vapors continuously, decrease the time needed for evaporating a solvent when compared to static methods, wherein the atmosphere e.g. does not moved or is not exchanged (stagnant atmosphere).

In process step b) the organic solvents molecules, which can be still present in the solidified material, are finally completely removed during the formation of the solid electrolyte of general formula (I), preferably at a temperature in the range from 50 °C up to 600 °C, preferably in the range from 90 °C up to 300 °C.

The time for converting the solidified material to the solid electrolyte of general formula (I) can be varied in a wide range depending on the final, usually highest temperature reached and on the heating rate used in order to reach the final temperature.

The heating rate itself, which is applied in process step b) in order to reach the final temperature can be varied in a wide range. Preferably, the final temperature of process step b) is reached by a heating rate in the range from 0.1 K/min to 200 K/min, more preferably in the range from 0.2 K/min to 50 K min, much more preferably in the range from 0.5 K/min to 20 K/min, in particular in the range from 0.5 K/min to 1 K/min.

In one embodiment of the present invention, the inventive process is characterized in that in process step b) the formed solidified material is heated for a period in the range from 0.003 h to 12 h, preferably in the range from 0.05 to 3 h.

In one embodiment of the present invention, the inventive process is characterized in that in process step b) the formed solidified material is heated at a temperature in the range from 50 °C up to 600 °C for a for a period in the range from 0.003 h to 12 h, preferably at a temperature in the range from 90 °C up to 300 °C for a for a period in the range from 0.04 h to 3 h.

By selecting the appropriate equipment, it is also possible to perform both process steps of the above-described process steps back-to-back without isolating the respective intermediates. For instance, a spray drying process can be used for process step a) via mixing the compound A) with compound B) in a twin nozzle, followed by process step b) in the drying chamber of the spray dryer and in a belt dryer or a rotary kiln, which are connected directly to the spray dryer.

The inventive process represents an economic and reproducible process, which gives access to the solid electrolytes of general formula (I). The present invention further provides a compound A1 ) of general formula (11-1 )

Li⁺3-2a'₊c₊2d_+e M²V P⁵⁺i-b-c-d As⁵⁺ _b D⁴⁺ _c E³⁺ _d S²-₄-_e-_f N^3" _e T^2" _f ^* h Solv (11-1 ), in which the variables are each defined as follows:

M is Mg, Ca, Zn or a mixture thereof, preferably Mg or Zn, in particular Mg,

D is Si, Ti, Ge, Sn or a mixture thereof, preferably Ge,

E is B, Al, Ga, In or a mixture thereof, preferably Al,

T is O, Se, Te or a mixture thereof, preferably O or Se, in particular O,

Solv is DME, DMF, NMF, DMSO, 1 ,3-Dioxolane, DCM, HMPT or NMP, preferably DME a' is in the range from 0 to 1 .5, preferably from 0 to 0.75,

b is in the range from 0 to 1 , preferably from 0 to 0.5,

c is in the range from 0 to 1 , preferably from 0 to 0.5,

d is in the range from 0 to 1 , preferably from 0 to 0.5,

e is in the range from 0 to 4, preferably from 0 to 2,

f is in the range from 0 to 4, preferably from 0 to 2,

h is 1 , 2, 3 or 4, wherein the sum of b+c+d is in the range from 0 to 1 , preferably from 0 to 0.5, in particular from 0 to 0.25, and wherein the sum of e+f is in the range from 0 to 4, preferably from 0 to 2, in particular from 0 to 1 .

In one embodiment of the present invention, the inventive compound A1 ) is characterized the variables are each defined as follows:

M is Mg,

D is Ge,

E is Al,

T is O,

Solv is DME, a' is in the range from 0 to 0.375,

b is in the range from 0 to 0.5, in particular from 0 to 0.25,

c is in the range from 0 to 0.5, in particular from 0 to 0.25,

d is in the range from 0 to 0.5, in particular from 0 to 0.25,

e is in the range from 0 to 2, in particular from 0 to 1 ,

f is in the range from 0 to 2, in particular from 0 to 1 ,

h is 1 , 2, 3 or 4, wherein the sum of b+c+d is in the range from 0 to 0.5, in particular from 0 to 0.25, and wherein the sum of e+f is in the range from 0 to 2, in particular from 0 to 1.

In one embodiment, the present invention further provides a compound A1 ) of general formula (11-1 )

Li⁺ ₃-2a' M²V P⁵⁺ S^2"4 ^* h Solv (11-1 ), in which the variables are each defined as follows: M is Mg, Ca, Zn or a mixture thereof, preferably Mg or Ca, in particular Ca,

Solv is DME, DMF, NMF, DMSO, 1 ,3-Dioxolane, DCM, HMPT or NMP, preferably DME a' is in the range from 0 to 1 .5, preferably from 0 to 0.75, more preferably from 0 to 0.1 , in particular 0,

h is 1 , 2, 3 or 4.

In one embodiment of the present invention, the inventive compound A1 ) is characterized in that

Compounds A1 ) of general formula (11-1 )

Li⁺3-2a'₊c₊2d_+e M²V P⁵⁺i-b-c-d As⁵⁺ _b D⁴⁺ _c E³⁺ _d

N^3" _e T^2" _f ^* h Solv (11-1 ), wherein the variables and indices are defined as described above, can be prepared by a pro- cess comprising the process steps of aa) preparing a mixture of appropriate starting materials comprising the required elements selected from the group consisting of Li, Mg, Ca, Zn, P, As, Si, Ti, Ge, Sn, B, Al, Ga, In, S, N, O, Se and Te, preferably consisting of Li, Mg, P, As, Ge, Al, S, N and O, wherein in said mixture the elements are available in the following molar ratio:

0 to 5 molar equivalents of Li,

0 to 1 .5 molar equivalents of M,

0 to 1 molar equivalents of P,

0 to 1 molar equivalents of D,

0 to 1 molar equivalents of E,

0 to 4 molar equivalents of S, and

0 to 4 molar equivalents of T, in a solvent selected from the group consisting of DME, DMF, DMSO, 1 ,3-Dioxolane,

DCM, HMPT and NMP, and bb) isolation of the solid compound A1 ) formed in process step aa).

Appropriate starting materials are known by the person skilled in the art. Examples of some starting materials for the different elements are listed below:

Li: Li, Li₂S, Li₂0, Li₂Se or Li₃PS₄, n-BuLi, sec-BuLi, tert-BuLi

Mg: Mgl₂, MgBr₂, MgCI₂, MgS, Mg(Me)₂,

Ca: CaCI₂, CaBr₂, Cab

Zn: Znl₂, ZnBr₂, ZnCI₂

P: P₂S₅, P₂0₅, Li₃PS₄,

As: LisAsSs, AsP

Si: SiS₂, Li₄Si0₄

Ti: TiS₂, Li₄Ti0₄

Ge: GeS₂, Li₄GeS₄,

Sn: SnS₂, Li₄SnS₄,

B: B₂S₃, B(OH)₃,

Al: AI(0-i-Prop)₃, AIBu₃, AIPh₃

Ga: Ga₂S₃, LiGaS₂,

In: ln₂S₃, LilnS₂

S: S, H₂S, Li₂S, P₂S₅, Li₃PS₄

N: NH₃, Li₇PN₄, OP(NH₂)₃, SP(NH₂)₃

O: 0₂, H₂0, Li₂0, Li₃P0₄, Li₄Si0₄,

Se: Li₂Se

Te: Li₂Te

X: LiF, LiCI, LiBr, LiCN, LiOCN, LiSCN, LiN₃

I: Lil

The present invention further provides a solid electrolyte of general formula (1-1 ) Li⁺ _4-2a+c₊₂d₊e M²⁺ _a P⁵⁺1-b-c-d AS⁵⁺b D⁴⁺c E³⁺ _d S²-_4-e-f N^3" _e T^2"f ΐ -g X^"g (1-1 ) in which the variables are each defined as follows:

M is Mg, Ca, Zn or a mixture thereof, preferably Mg or Zn, in particular Mg,

D is Si, Ti, Ge, Sn or a mixture thereof, preferably Ge,

E is B, Al, Ga, In or a mixture thereof, preferably Al,

T is O, Se, Te or a mixture thereof, preferably O or Se, in particular O,

X is F, CI, Br, CN, OCN, SCN, N₃ or a mixture thereof, preferably Br, a is in the range from 0 to 1 , preferably 0 to 0.5, more preferably 0 to 0.25,

b is in the range from 0 to 0.5, preferably 0 to 0.25,

c is in the range from 0 to 0.5, preferably 0 to 0.25, d is in the range from 0 to 0.5, preferably 0 to 0.25,

e is in the range from 0 to 2, preferably 0 to 0.5,

f is in the range from 0 to 2, preferably 0 to 0.5,

9 is in the range from 0 to 0.5, preferably 0 to 0.25, wherein the sum of b+c+d is in the range from 0 to 0.5, preferably from 0 to 0.25, the sum of e+f is in the range from 0 to 2, preferably from 0 to 0.5, and the sum of a+b+c+d+e is > 0, preferably in the range from 0.01 to 2, more preferably the range from 0.02 to 0.5. In one embodiment, the present invention further provides a solid electrolyte of general formula

(1-1 )

Li⁺4-2a M²⁺ _a P⁵⁺ S^2" ₄ l^"l-g X^"g (1-1 ) in which the variables are each defined as follows:

M is Mg, Ca, Zn or a mixture thereof, preferably Mg or Ca, in particular Ca,

X is F, CI, Br, CN, OCN, SCN, N₃ or a mixture thereof, preferably Br, a is in the range from > 0 to 0.5, preferably from 0.01 to 0.5, more preferably from 0.01 to 0.25,

g is in the range from 0 to 0.5, preferably 0 to 0.25, more preferably 0.

In one embodiment of the present invention, the inventive solid electrolyte of general formula (I- 1 ) is characterized in that it

M is Ca,

X is F, CI, Br, CN, OCN, SCN, N₃ or a mixture thereof, preferably Br, a is in the range from 0.01 to 0.25, in particular 0.01 to 0.1

g is in the range from 0 to 0.25, preferably 0 to 0.1 , more preferably 0.

M is Mg,

X is F, CI, Br, CN, OCN, SCN, N₃ or a mixture thereof, preferably Br, a is in the range from 0.01 to 0.5, in particular 0.25 to 0.3

g is in the range from 0 to 0.25, preferably 0 to 0.1 , more preferably 0. In one embodiment of the present invention, the inventive solid electrolyte is characterized in that it is Li₄- 2(0.25 -o.3)Mgo.25-o.3PS4l or Li₄ - 2(o.oi - o.i)Cao.oi - o.i PS₄l, preferably Li₃.45Mgo.28PS₄l or Li3.95Cao.o2PS₄l, in particular Li₃.95Cao.o2PS₄l. Solid electrolytes of general formula (1-1 ) show advantages compared to Li₄PS₄l with respect to at least one of the following properties: ionic conductivity, chemical compatibility with cathode and anode materials, electrochemical stability or mechanical stability.

The solid electrolytes of general formula (1-1 ) can be used alone or in combination with addi- tional components for producing a solid structure for an electrochemical cell, such as a cathode, an anode or a separator. A separator separates a cathode and an anode from each other in an electrochemical cell, in particular in all-solid-state lithium batteries. The cathode of an all-solid- state lithium battery usually comprises beside an active cathode material as a further component a solid electrolyte. Also the anode of an all-solid-state lithium battery usually comprises be- side an active anode material as a further component a solid electrolyte. The form of the solid structure for an electrochemical cell, in particular for an all-solid-state lithium battery, depend in particular on the form of the produced electrochemical cell itself.

In the context with the present invention, the electrode where during discharging a net negative charge occurs is called the anode and the electrode where during discharging a net positive charge occurs is called the cathode.

The present invention further provides the use of the solid electrolyte of general formula (1-1 ) as described above as component of a solid structure for an electrochemical cell selected from the group consisting of cathode, anode and separator.

The present invention further provides a solid structure for an electrochemical cell selected from the group consisting of cathode, anode and separator, wherein the solid structure for an electrochemical cell comprises the solid electrolyte of general formula (1-1 ) as described above.

The present invention further provides an electrochemical cell comprising at least one solid structure for an electrochemical cell as described above, which comprises at least the solid electrolyte of general formula (1-1 ). The inventive electrochemical cell is preferably a rechargeable electrochemical cell comprising as components a) at least one anode a), β) at least one cathode β),

Y) at least one separator, wherein at least one of the three components is a solid structure selected from the group consisting of cathode, anode and separator comprising the solid electrolyte of general formula (1-1 ) as described above. As regards suitable electrochemically active cathode materials and suitable electrochemically active anode materials reference is made to the relevant prior art, e.g. appropriate monographs and reference works: e.g. Wakihara et al. (editor): Lithium ion Batteries, 1 ^st edition, Wiley VCH, Weinheim, 1998; David Linden: Handbook of Batteries (McGraw-Hill Handbooks), 3^rd edition, Mcgraw-Hill Professional, New York 2008; J. O. Besenhard: Handbook of Battery Materials. Wiley-VCH, 1998.

Inventive electrochemical cells are preferably selected from alkali metal containing cells. More preferably, inventive electrochemical cells are selected from lithium-ion containing cells. In lithium-ion containing cells, the charge transport is effected by Li⁺ ions.

Suitable anodes and cathodes are described in detail in WO 2015/086759 A1 on page 10, line 26 to page 14, line 1 1 wherein said reference is incorporated by reference in its entirety for all useful purposes. In one embodiment of the present invention the electrochemical cell is characterized in that anode a) comprises metallic lithium.

In one embodiment of the present invention the electrochemical cell is characterized in that cathode β) comprises an active material selected from the group consisting of:

phosphates with olivine structure such as lithium iron phosphates (LiFeP0₄) and lithium manganese phosphate (LiMnP0₄) which can have a stoichiometric or non-stoichiometric composition and which can be doped or not doped, and

lithium containing transition metal spinels and lithium transition metal oxides with a layered crystal structure such as UC0O2, LiNio,5Mni,₅0_4-d, LiMn20₄ or NCMs such as Lii₊t(Nio,33Coo,33Mn₀,33)02, Lii₊t(Nio,5Coo,2Mn₀,3)02, Lii_+t(Nio,₄Coo,3Mno,₄)02,

Lii+t(Nio,₄Coo,2Mno,₄)02, Lii_+t(Nio,₄5Coo,ioMno,₄5)02 and Lii₊t(NixCOyMn_z)i-t02, wherein x is in the range from 0.5 to 0.95, y is in the range from 0 to 0.5, z is in the range from 0 to 0.5 and t is in the range from 0 to 0.1 , such as Lii_+t(Nio.6Coo.2Mno.2)i-t02, Lii+t(Nio.8Coo.i Mno.i)i- t02, Lii₊t(Nio.85Coo.o5Mn₀.i )i-t02,or Lii_+t(Nio.85Coo.i Mno.o5)i-t02.

In one embodiment of the present invention, inventive electrochemical cells can have a disc-like shape. In another embodiment, inventive electrochemical cells can have a prismatic shape.

In one embodiment of the present invention, inventive electrochemical cells can include a hous- ing that can be from steel or aluminium. In one embodiment of the present invention, inventive electrochemical cells are combined to all solid-state batteries, which have both solid electrodes and solid electrolytes.

Inventive electrochemical cells have overall advantageous properties. They have a long dura- tion with very low loss of capacity, good cycling stability, and a reduced tendency towards short circuits after longer operation and/or repeated cycling.

A further aspect of the present invention refers to batteries, more preferably to an alkali metal ion battery, in particular to a lithium ion battery comprising at least one inventive electrochemical cell, for example two or more. Inventive electrochemical cells can be combined with one another in inventive alkali metal ion batteries, for example in series connection or in parallel connection. Series connection is preferred.

Inventive batteries have advantageous properties. They have a long duration with very low loss of capacity, good cycling stability, and high temperature stability.

The inventive electrochemical cells or inventive batteries can be used for making or operating cars, computers, personal digital assistants, mobile telephones, watches, camcorders, digital cameras, thermometers, calculators, laptop BIOS, communication equipment or remote car locks, and stationary applications such as energy storage devices for power plants. A further aspect of the present invention is a method of making or operating cars, computers, personal digital assistants, mobile telephones, watches, camcorders, digital cameras, thermometers, calculators, laptop BIOS, communication equipment, remote car locks, and stationary applications such as energy storage devices for power plants by employing at least one inventive battery or at least one inventive electrochemical cell.

A further aspect of the present invention is the use of the electrochemical cell as described above in motor vehicles, bicycles operated by electric motor, aircraft, ships or stationary energy stores.

The use of inventive electrochemical cells in devices gives the advantage of prolonged run time before recharging and a smaller loss of capacity in the course of prolonged run time. If the intention were to achieve an equal run time with electrochemical cells with lower energy density, a higher weight for electrochemical cells would have to be accepted.

The present invention further provides a device comprising at least one inventive electrochemical cell as described above. Preferred are mobile devices such as are vehicles, for example automobiles, bicycles, aircraft, or water vehicles such as boats or ships. Other examples of mobile devices are those which are portable, for example computers, especially laptops, telephones or electrical power tools, for example from the construction sector, especially drills, battery-driven screwdrivers or battery-driven tackers. The invention is illustrated by the examples which follow, but these do not restrict the invention.

Figures in percent are each based on % by weight, unless explicitly stated otherwise. I. Synthesis of solid electrolytes

1.1 Synthesis of Li₄PS₄l (E1 ) and derivatives thereof (E2, E3)

1.1.1 Synthesis of Li₃ PS₄ · DME (PE1 )

Li3PS₄ · DME was synthesized by reacting L12S and P₄Sio in DME. All manipulations were carried out in an argon-filled glovebox (MBraun) with an O2 and H2O content below 0.1 ppm or on a Schlenk line. In a typical approach Li₂S (488.0 mg, 10.62 mmol; Alfa Aesar 99.9 %) and P2S5 (1 .012 g, 4.553 mmol; Sigma Aldrich 99 %) were mixed together and ground in an agate mortar and filled into a dried 100 ml Schlenk flask. After adding approx. 40 ml of anhydrous 1 ,2 di- methoxyethane (DME, Sigma Aldrich 99.5 %) the reaction mixture was stirred at room temperature. After 10 days the formed colorless precipitate was filtered off, washed two times with approx. 10 ml of DME and dried in vacuo until the pressure was below 1 · 10^~3 mbar. Li3PS₄ · DME (PE1 ) was obtained as a phase-pure, colorless powder that is sensitive to moist air. 1.1.2 Synthesis of Li₄PS₄l (E1 )

All manipulations were carried out in an argon-filled glovebox (MBraun) with an O2 and H2O content below 0.1 ppm or on a Schlenk line. In a typical approach Li3PS₄ · DME (500.0 mg, 1 .851 mmol) (PE1 ) and Lil (185.7 mg, 1 .388 mmol; Sigma Aldrich 99.999 %) were mixed together, ground in an agate mortar, and dispersed in approx. 10 ml of DME in the space of a dried Schlenk tube. While stirring the initial yellow color of the mixture vanished within one minute. After further stirring for 1 day, the DME was removed in vacuo and the remaining colorless solid was dried at 50°C until the pressure was below 1 · 10^~3 mbar. In a final step further under vacuum, the solid was heated to temperatures between 200 and 300°C. Li₄PS₄l (E1 )v was obtained as a colorless, slightly gray powder that is sensitive to moist air.

1.1.3 Synthesis of Li₃.₄₅Mgo.28PS4l (E2)

All manipulations were carried out in an argon-filled glovebox (MBraun) with an O2 and H2O content below 0.1 ppm or on a Schlenk line. Li3PS₄ · DME (500.0 mg, 1.851 mmol) (PE1 ) was mixed together with Lil (1 1 1.5 mg, 0.833 mmol; Sigma Aldrich 99.999 %) and Mgl₂ (144.1 mg, 0.518 mmol; Sigma Aldrich 99.999 %), ground in an agate mortar, and dispersed in approx. 12 ml of DME in the space of a dried Schlenk tube. While stirring the initial yellow color of the mixture vanished within one minute. After further stirring for 1 day, the DME was removed in vacuo and the remaining colorless solid was dried at 50 °C until the pressure was below 1 · 10^~3 mbar. In a final step further under vacuum, the solid was heated to temperatures between 200 and 300 °C. Mg-doped Li₄PS₄l (E2) was obtained as a colorless, slightly gray powder that is sensitive to moist air. 1.1 .4 Synthesis of Li₃.95Cao.o2PS4l (E3)

All manipulations were carried out in an argon-filled glovebox (MBraun) with an O2 and H2O content below 0.1 ppm or on a Schlenk line. U3PS4 · DME (397.4 mg, 1 .471 mmol) (PE1 ) was mixed together with Lil (187.0 mg, 1.397 mmol; Sigma Aldrich 99.999 %) and (8.6 mg, 0.029 mmol; Sigma Aldrich 99.999 %), ground in an agate mortar, and dispersed in approx. 18 ml of DME in the space of a dried Schlenk tube. While stirring the initial yellow color of the mixture vanished within one minute. After further stirring for 1 day, the DME was removed in vacuo and the remaining colorless solid was dried at 50°C until the pressure was below 1 · 10^~3 mbar. In a final step further under vacuum, the solid was heated to temperatures between 200 and 300°C. Ca-doped U4PS4I (E3) was obtained as a colorless, slightly gray powder that is sensitive to moist air.

Characterization of precursors and solid electrolytes

11.1 Characterization of Li₃ PS₄ · DME (PE1 )

The resulting data of the crystallographic characterization of PE1 including details of the data collection are summarized in Table 1 and Table 2.

Table 1 : Crystallographic data of U3PS4^■ DME (PE1 ) and details of the data collection and relative structure solution and refinement (esd's in parentheses).

Crystal Structure Data

formula Li₃PS4-C4Hio0₂

formula mass / gmol-1 270.156

crystal system tetragonal

space group 141/amd (no. 141 )

cell parameters / A a = 8.55007(12)

b = 35.4241 (7)

cell volume / A³ V = 2589.63(9)

formula units Z / cell 8

X-ray density p / g-cnr³ 1 .426(2)

Data collection

diffractometer Stoe Stadi P

radiation Cu-Καΐ , λ = 1.540596 A

temperature / K 298(2)

Structure Solution and Refinement

structure solution method charge-flipping structure refinement method least-squares method

program used TOPAS-Academic V5

R indices R_P = 0.0377

wR_p = 0.0500

GoF = 1.772

Table 2. Atom coordinates, Wyckoff symbols and isotropic displacement parameters Biso / A² for the atoms in Li3PS₄-DME (esd's in parentheses).

Figure 1 .: Rietveld refinement of U3PS4^■ DME (PE1 ) (observed, calculated diffraction patterns as well as difference profile) against powder X-ray (Cu-K_Qi radiation, λ = 1 .5406 A) diffraction data; allowed peak positions are marked by vertical lines; the pattern proves phase-purity as no other reflections than the ones of L13PS4^■ DME are observed.

11.2 Characterization of Li₄PS₄l (E1 ), Li₃.₄5Mg₀.28PS l (E2) and Li₃.95Cao.o2PS l (E3)

The resulting data of the crystallographic characterization of E1 including details of the data collection are summarized in Table 3 and Table 4.

Table 3: Crystallographic data of Li₄PS₄l (E1 ) and details of the data collections and relative structure solution and refinement (esd's in parentheses).

Crystal Structure Data

formula L14PS4I

formula mass / gmoh¹ 314.707

crystal system tetragonal

space group P4/nmm (no. 129, origin choice 2)

cell parameter / A a = 8.48284(12)

c = 5.93013(1 1 )

cell volume / A³ V = 426.725(15)

formula units Z / cell 2 X-ray density p / g-cnr³ 2.449(6)

Data collection

type of diffractometer Stoe Stadi P and GEM (ISIS facility)

geometry Debye-Scherrer

radiation MoKd (λ = 0.7093 A), TOF neutrons

temperature / K 298(2)

data points 1 1506

number of observed reflections 4048

Structure solution and refinement

structure solution method charge flipping [i]

structure refinement method least-squares method, [ii] combined (X-ray and neutron) re- finement

program used TOPAS-Academic V5 [iii]

number of parameters 158

background function shifted Chebyshev

R indices R_P = 0.02181

wRp = 0.02973

Rbragg = 0.01589

GoF = 1.21499

G. Oszlanyi, A. Suto, Acta Crystallogr., Sect. A: Found. Crystallogr. 2004, 60, 134.

Bergmann, J.; Kleeberg, R.; Haase, A.; Breidenstein, B. Mat. Sci. Forum 2000, 347-349, 303.

A. A. Coelho, TOPAS Academic: General Profile and Structure Analysis Software for Powder Diffraction Data, 5th ed.; Bruker AXS: Karlsruhe, Germany, 2012.

Table 4. Atom coordinates, Wyckoff symbols and isotropic displacement parameters Bi_S0 / A² for the atoms in U4PS4I (P1 ) in PAInmm (no. 129, origin choice 2) (esd's in parentheses). atom Wyckoff X y z occuBiso

symbol pancy

1(1 ) 2c 0.75 0.75 0.15298(1 1 ) 1 2.00(2)

S(1 ) 8i 0.25 0.94412(9) 0.2967(2) 1 1 .61 (3)

P(1 ) 2b 0.75 0.25 0.5 1 1 .63(5)

Li(1 ) 2c 0.75 0.75 0.594(4) 0.68(3) 2.5(5)

Li(2) 2a 0.25 0.75 0 0.58(4) 2.5(5)

Li(3) 8j 0.454(2) 0.454(2) 0.585(3) 0.38(2) 2.5(5)

Li(4) 4d 0 0 0 0.53(3) 2.5(5)

Li(5) 8i 0.75 0.12(2) 0.1 1 (2) 0.08(2) 2.5(5) Figure 2.: Rietveld refinement of U4PS4I (E1 ) (observed, calculated diffraction patterns as well as difference profiles) against powder X-ray (Μο-Κ_αι radiation, λ = 0.7093 A); allowed peak positions are marked by vertical lines: top, U4PS4I; bottom, minor impurity phase L12S.

Figure 3.: Arrhenius plot of a sample of Li₄PS₄l (E1 ); o(25°C) = 9.19-10^"5 S/cm.

Figure 4.: Impedance spectra in the Nyquist presentation of the U4PS4I (E1 , squares,

5.5^■ I O-⁵ S/cm), a Mg-doped (E2, triangles, 3.4 ^■ 10^"5 S/cm) and a Ca-doped U4PS4I sample (E3, circles, 3.9^■ 10^"4 S/cm) at room temperature.

11.3 Comparison of different solvent adducts of L13 PS4

Figure 5.: XRD patterns of a) DME-, b) ACN- (reflections of L12S are asterisked), and c) THF- adduct of L13PS4.

The adducts of U3PS4 have been synthesized using the solvents DME, acetonitrile and THF. The product from acetonitrile resulted in the ACN-adduct whose crystal structure appeared to be disordered (see both, sharp and broad reflections in XRD pattern in Figure 2b) and also con- sisting of additional L12S impurities (from incomplete reaction). The structure of the THF-adduct could also not be solved due to a very low symmetry (see pattern with many overlapping reflections).

Claims

A process for preparing a solid electrolyte of general formula (I)

M is Mg, Ca, Zn or a mixture thereof,

X is F, CI, Br, CN, OCN, SCN, N₃ or a mixture thereof, a is in the range from 0 to 2,

g is in the range from 0 to 1 , comprising the process steps of a) preparing a mixture comprising a compound A) of general formula (II)

in which the variables M, X and g are each defined as described above and the other variables are each defined as follows:

Solv is a polar solvent molecule selected from the group consisting of ethers, ace- tals, amides, alcohols and mixtures thereof a' is in the range from 0 to 1 .5,

a" is in the range from 0 to 0.5,

h is in the range from 1 to 6, and at least one organic solvent, b) converting the mixture prepared in process step a) to the solid electrolyte of general formula (I) by removing the organic solvent and heating the formed solidified material at a temperature in the range from 50 °C up to 600 °C. The process according to claim 1 , wherein the variables are each defined as follows:

M is Mg,

X is Br, a is in the range from 0 to 0.5,

g is in the range from 0 to 0.5,

Solv is an ether selected from THF and DME,

a' is in the range from 0 to 0.375,

a" is in the range from 0 to 0.125,

h is in the range from 1 to 6.

The process according to claim 1 or 2, wherein in process step a) the molar ratio of compound A) to compound B) is in the range from 0.66 to 1.5.

The process according to any of claims 1 to 3 claim wherein in process step a) compound A) and compound B) are both mixed in powder form, before the at least one organic solvent is added in order to form the mixture.

The process according to any of claims 1 to 4 claim wherein in process step b) the formed solidified material is heated for a period in the range from 0.003 h to 12 h.

Compound A1 ) of general formula (11-1 )

Li⁺ ₃-2a' M²V P⁵⁺ S^2"4 ^* h Solv (11-1 ), in which the variables are each defined as follows:

M is Mg, Ca, Zn or a mixture thereof,

Solv is DME, DMF, NMF, DMSO, 1 ,3-Dioxolane, DCM, HMPT or NMP, a' is in the range from 0 to 1 .5,

h is 1 , 2, 3 or 4.

A solid electrolyte of general formula (1-1 )

Li⁺4-2a M²⁺ _a P⁵⁺ S ^" ₄ l^"l-g X^"g (1-1 ) in which the variables are each defined as follows:

M is Mg, Ca, Zn or a mixture thereof, X is F, CI, Br, CN, OCN, SCN, N₃ or a mixture thereof, a is in the range from > 0 to 0.5,

g is in the range from 0 to 0.5.

8. Use of the solid electrolyte of general formula (1-1 ) according to claim 7 as component of a solid structure for an electrochemical cell selected from the group consisting of cathode, anode and separator. 9. A solid structure for an electrochemical cell selected from the group consisting of cathode, anode and separator, wherein the solid structure for an electrochemical cell comprises the solid electrolyte of general formula (1-1 ) according to claim 7.

10. An electrochemical cell comprising at least one solid structure for an electrochemical cell according to claim 9.

1 1 . A battery comprising at least one electrochemical cell according to claim 10.

12. A device comprising at least one electrochemical cell according to claim 10