WO2016157087A1

WO2016157087A1 - Compound of genereal formula (kat+)(an -)·xl

Info

Publication number: WO2016157087A1
Application number: PCT/IB2016/051784
Authority: WO
Inventors: Maciej DRANKA; Grażyna ŻUKOWSKA; Janusz ZACHARA; Piotr Jankowski; Władysław WIECZOREK; Marcin POTERAŁA; Michał KALITA
Original assignee: Ipchem Sp. Z O. O.
Priority date: 2015-03-30
Filing date: 2016-03-30
Publication date: 2016-10-06
Also published as: PL411822A1

Abstract

A compound of general Formula (1) : (Cat⁺)(An^-) · xL, wherein: Cat+ is a lithium or sodium cation having a constant coordination number of the cation CN_Li5-6 or CN_NA=6-7, L is a ligand selected from the group consisting of molecules of the general formula CH₃(OCH₃CH₂)_NOCH₃, where N is a number from 1 to 8, acetonitrile, ethylene carbonate, propylene carbonate, H₂O, ROH wherein R is C₁-C₄ alkyl, or mixtures thereof. An^- is an anion of the formula 2, wherein R₁ is C-C≡N or a nitrogen atom, R₂ is a nitrogen atom or C-R₃, wherein R₃ represents a halogen atom, a CN group, a NO2 group, a C₁-C₃ alkyl optionally substituted by fluorine or chlorine, x is a positive number not higher than 3.

Description

A compound of general formula (Cat⁺)(An-)-xL

Present invention relates to a compound of the general formula (Cat⁺)(An^~)-xL for use as a crystalline solid electrolyte dedicated to the power sources.

Solid Polymer Electrolytes (SPEs) are materials known in the art. They are used, inter alia, as separators of the electrodes in batteries, in which lithium or sodium cations are responsible for the charge transport. Such materials are known from the publication "Ionic Conducting Materials and Structural Spectroscopies; Series: Electronic Materials: Science & Technology", Vol. 10, P. Knauth, J. Schoonman, (Eds.), Springer, 2008.

The ionic conductivity in the solid electrolytes is much lower than in the typical liquid ones. Despite of that, a variety of advantages of solid electrolyte batteries over liquid electrolyte ones make the battery interesting for many applications. SPEs have good mechanical properties; SPE-based battery is: safe due to the impossibility of electrolyte leakage, simple in construction as there is no need of additional separator between the electrodes and has low self-discharge current.

On the other hand, if the SPE-based battery would have been developed, the conductivity of the SPE used in it should be sufficiently high. It is understood that the sufficient value of the conductivity in such systems is not lower than 10^~5 S/cm. In conventional systems, such as poly(ethylene oxide) -LiCICuiPEO-LiCICu), PEO-U PF6, PEO-UBF4 or PEO-UCF3SO3, this conductivity value is achieved at temperatures above 40°C. In systems with imide-type anions, like PEO-Li[(CF3S02)2N](PEO-LiTfSI), the conductivity values are about one order of magnitude higher than in the conventional systems. Unfortunately, high total conductivity is eliminated by a significantly low cation transference number (about 0.2) of the imide-based electrolyte. It means that the cationic conductivity of the system is relatively low, despite the relatively high anionic conductivity.

An additional difficulty related to the use of polymer electrolytes comes from the fact that the melting point of the PEO crystalline phase is slightly lower than 70°C. Since this phase is dominating in the majority of PEO-based SPEs, it means that the electrolyte above this temperature melts and the high-viscosity liquid is formed. In combination with previous notes on the low conductivity at temperatures close to room temperature and lower, it means that the basic problem limiting the use of solid electrolytes in batteries is related to the fact that the range of the temperatures in which the SPE has significantly high cationic conductivity and it is solid, is too narrow. This problem is pointed out for a number of years in the literature.

Another important issue is the problem of stability of SPEs in time. It is believed that a majority of the charge carriers transport takes place in the amorphous phase of the polymer. As the degree of crystallization of the polymer matrix increases with time and the precipitation of the salt is observed, the ion transport properties of the electrolyte are getting worse in time. Therefore, the ion transport properties of the salt-in-polymer-type solid polymer electrolyte are not stable in time.

To overcome this problem, a number of solutions were elaborated. Plasticization of the electrolyte using the ionic liquids resulted in a significant increase in ionic conductivity, but the addition of such plasticizer lowered the melting point of the studied system. This has limited the applicability of such material as SPE. Moreover, the resulting material has generally worse mechanical properties. Also plasticization with ionic liquids leads to a significant increase in the ionic conductivity of the electrolyte, what is known from the patent application US US2005287441 (Al). Unfortunately, the use of such additive significantly lowers the transference number down to values below 0.2, and leads to losing of the mechanical properties of the material. Additives like ceramic powders and polymers also improves properties of polymer electrolytes, but the expected conductivity values ionic electrolyte composite do not achieve sufficiently high values.

Yet another method leading to obtaining the solid electrolyte is based on using adducts (solvates) of the salts as an electrolytes. This idea arose from studies on the crystalline, solid, PEO-based electrolytes. The first important observation leading to obtaining of such materials is the fact that in several systems of high crystallinity, ionic conductivity may be higher than in the analogical but amorphous systems. The ion transport properties of the adducts of formula LiX-n (CH3(OCH2CH2)MOCH3) were different from those exhibited by the polymer electrolytes. Character of the conductivity (cationic or anionic) in adduct-type electrolytes is strongly dependent on the stoichiometry of the system and polyether used (i.e. on the value of "M" in a compound of the formula (CH3(OCH2CH2)MOCH3) . In most systems, anionic conductivity was dominating. In the adduct of the formula LiAsF6-(CH3(OCH2CH2)30CH3), unexpectedly, almost single-ion cationic conductivity was observed (ty+ = 0.8). Unfortunately, the overall ionic conductivity of such a system was not sufficiently high (less than 10^~5 S/cm at 50°C). It should be noted, however, the majority of both the high crystalline electrolytes and the adducts has low temperature of melting, and, due to that, their use as electrolytes does not solve the problem of a narrow range of temperatures at which the material i. is solid and ii. has sufficiently high cationic conductivity.

The relatively high melting point is observed in case of adducts of cryptands or crown ethers and imides or amidates. Amidates or imides mentioned here are derivatives of triflic (trifluoromethanesulfonic) acid. Adducts of this type exhibit have high melting points and high values of the ionic conductivity. The properties of the studied salts and the type of solvating compounds strongly suggest, however, that also in these systems the observed conductivity is predominantly of anionic type. I n systems known in the art, ionic conductivity comes from the mobility of the charged species in the electric field. The increase of the number of these charged species results in the increase of the aggregation, which in turn results in the lower mobility of the species. Therefore, one can usually observe the initial increase in conductivity with increasing salt concentration in the system, resulting from the growing number of charge carriers. With further increasing salt concentration, ionic conductivity reaches a maximum value and then decreases because of ongoing aggregation of the ions.

The present invention relates to a compound of general Formula 1:

(Cat⁺)(An ) · xL

Formula 1 wherein:

Cat⁺ is a lithium or sodium cation,

L is a ligand selected from the group consisting of molecules of the general formula CH3(OCH3CH2)NOCH3, wherein N is a number from 1 to 8, acetonitrile, ethylene carbonate, propylene carbonate, H₂0, ROH wherein R is C1-C4 alkyl, or mixtures thereof

An^" is an anion of the formula 2

Formula 2 wherein

Ri is C-C≡N or a nitrogen atom,

R₂ represents a nitrogen atom or C-R3, wherein R3 represents a halogen atom, a CN group, a N0₂ group, a C1-C3 alkyl optionally substituted by fluorine or chlorine, x is a positive number not higher than 3, having a permanent coordination number of the cation CNy = 5-6 or CNNa= 6-7. The preferred substituents are Ri=N, R₂=N, R₃=CF₃, CN or CI. I n the other preferred embodiment of the invention, Ri=R₂=-C-CN .

A compound of general Formula 1 is used as a solid electrolyte for crystalline power sources.

It has unexpectedly been found that the increasing ion aggregation is also associated with disproportionation of the cations to the centers of different neighborhood. This observation was used to design a new class of solid electrolytes. Structure of this type forms when the salt:solvate mola r ratio is high, namely, when Li (or Na) : O_SOiv < 1 : 3 relation is fulfilled; in this relation, Li (or Na) is number of the cations and O a number of the oxygens which are able to solvate the cation. Such systems are characterized with high ionic conductivity and high temperatures of melting. A common feature of these systems is presence of two types of metal centers of different coordination sphere. In the first type of metal centers, the coordination sphere is predominantly fulfilled with donor centers from anions leading to the formation of the polyanions, while the coordination sphere of the cations of the second type is enriched in the donor centers of the solvent, what facilitates dissociation of the cation. Therefore, the construction of a new class of compounds are based on aggregated structures with polyanionic skeleton in the form of a coordination polymer having structure of the chain, ribbon, layer or three-dimensional structure, wherein part of the metal centers is bound and used to immobilize anions. Other metal cations are either in part or entirely solvated by the solvent, which means that their mobility is much higher than anions. Therefore, in such system cationic transference number is significantly increased. Moreover, it can be noticed by the one skilled in the art that disproportionation leads to the structures in which cations has "nitrogen-only" and "oxygen-only" neighborhood. This process might be driven by tendency of the cation, which acts as a hard acid, to to preferably be surrounded by the hard bases, like e.g. oxygen atoms. Appropriate selection of the amount and type of the solvent lead to the obtaining of the material in which "free" solvates of cations and polyanions are present. Thanks to a very high salt concentration in such systems (2.0-6.0 mol/kg of the electrolyte), despite the fact that the part of cations is bonded in the polyanion subnet, the number of cations which are mobile is large enough to ensure a sufficiently high cationic conductivity of the system. Therefore, the presence of isolated ions in the system is not necessary. The situation in such system is contrary to that which is observed for known-in-the-art solid polymeric electrolytes of "salt- in-polymer" type, in which the primary objective is to provide a system of possibly high degree of salt dissociation (in other words, of the weakest association).

The compound of the invention has optimum conductivity parameters which occurs at high salt concentrations, in systems containing small amounts of the solvent. This distinguishes the present compound from the classic systems, where the total number of charge carriers is significantly lower. In some embodiments of the invention, it is possible to obtain systems in which cation-cation pairs can be observed, i.e. systems in which two cations do not interact directly with anionic subnet, but only with solvent molecules. Also in such systems, ion transport is realized by cations.

In some embodiments of the invention, it is possible to obtain mixed systems, ie. systems in which more than one solvating compound was used to coordinate cation. For example, it is possible to obtain adducts in which cation have coordination sphere made of glymes of various length or in which cation have coordination sphere made of acetonitrile and glyme molecules.

Preferably, the selection of the anion leads to obtain system in which coordination number of the cation is constant (for example, 5 or 6 in the case of lithium, 6 or 7 in the case of sodium) and independent from the ratio between the donor centers of the ligand to donor centers of the solvent in the cation coordination sphere. This makes the exchange of ligands easier and facilitates the disproportionation.

In solid electrolytes, systems of the low interaction energy between positively and negatively charged ions are preferred. Hence, anions used in the compound of the invention should have a high softness (in the Pearson scale) and should be flexible in adjusting its properties to the acidic properties of the cation. It means that the anion has ability to stabilize itself in the structure of the material using any number of its donor centers (1-6), without affecting by the geometry of its centers on construction of the coordination sphere of the cation. This makes possible the maintaining of the coordination number of the cation and its stable surrounding, what is determined first of all by cation properties allowing e.g. disproportionation processes. Such properties have anions with five-membered aromatic ring with 0 to 3 nitrogen atoms within the ring and at least two carbon atoms substituted with nitrile groups.

The obtained compounds of the invention may also find application in preparation of water-free adducts (compounds). This drying method has been used previously, for example, in the case of LiPF6 salt, and allowed to receive LiPF6 free of hydrogen fluoride (precisely saying, HF content in LiPF6 was less than 10 ppm). Preparation of a compound according to the procedures presented as embodiments of this invention in Examples, followed by use them as a solid electrolyte, makes possible to introduce water-free salt into the electrolyte (H₂0 content below 100 ppm, including water in the structure of crystals); the purity of the salt can be higher than 99.9%.

The invention makes possible the production of the new type of solid, crystalline electrolytes, with a well-defined structure, having high melting point. Electrolytes can be used in chemical power sources, which are used to power the devices and in the conversion and accumulation of energy, especially with sources unstable over time, such as wind or photovoltaic power plants. The use thereof in the batteries, in which transport of lithium and sodium cations between the electrodes is required is preferred. Such electrolytes exhibit simultaneously: high melting point, high (more than 0.8) cation transference number and high conductivity (from over 1.3 · 10^~5 S/cm at room temperature to 4.5 · 10^~4 S / cm at 116°C). This means that the obtained electrolyte can be used over a wide range of temperatures (from 20 up to 120°C).

Thanks to the acid-base disprortionation which occurs in the coordination sphere of the metal centers of the obtained compounds, the receiving of the material, in which isolated or easy-dissociating cations or dications of potentially high mobility are present and anions are immobilized in the anionic subnet of chain, ribbon, plane, or 3-D network topology, is possible. The obtained material has very high conductivity (10^~5-10^~3 S/cm) when one takes into consideration that it is solid, and (what is important) remains solid material at a wide temperature range (from 20 to 120°C).

The proper selection of the salt, the solvating compound and the proportions between them leads to the suitable ionic aggregation with subsequent disproportionation and releasing the free, solvated cations. This results in obtaining of the system which in the same time exhibits high ionic conductivity, high cation transference number and high melting point, in contrast to the systems known in the art.

The invention is illustrated in the drawings. Fig. 1 shows the structure of the compound of Example la, Fig. 2 presents the structure of the compound of Example lb, Fig. 3 shows the structure of the compound of Example lc, Fig. 5 presents thermal dependence of the conductivity of the crystalline [Li2(G4)2²⁺] [Li4TDl6^2~] as a function of temperature, Fig. 6 shows the structure of the compound of Example 2, in Figures 7, 8, 9, 10, 11 the structure of the compound of Example 3, 4, 5, 6 and 7, respectively, are presented.

Examples

Example 1

The results of the structural studies for the LiTDI- glycol-type polyether complexes, with various lithium cation to donor centers ratio, are presented in Table below. Various crystalline phases of significantly different structural type were obtained. Gl is an abbreviation for ethylene glycol dimethyl ether (glyme), G2 is diethylene glycol dimethyl ether (diglyme), G3 - triethylene glycol dimethyl ether (triglyme), G4 - tetraethylene glycol dimethyl ether (tetraglyme), respectively. Table 1. Characteristics of a series of synthesized compounds with variable ratio between solvent donor centers and the salt obtained from X-ray measurements.

This presented example shows that at Li : O ratio not higher than 1 : 3, novel phases are formed, in which the phenomenon of the disproportionation of the metal centers can be observed, and novel structural motifs: chains, layers and 3-D structures can be seen.

This means that in the structure of the compounds, two different types of cations a re present. One type of the cations has dicyanoimidazolate anions in its coordination sphere, what leads to the immobilization of the anions. The other type of cations has coordination sphere formed from the solvent molecules only. This allows easier dissociation of this type of cations. In all cases, the average coordination number of Li is in the range between 5 and 6. In the same time, the coordination number of the anion changes, what proves the easiness of ligand exchange and the correct choice of the anion in order to obtain the disporoportionated system.

Example la

Preparation of the solvate crystalline form of the Li(Gl) i-TDI. A solution containing about 30 mg of LiTDI and about 50 mm³ of Gl was placed in an hermetic vial and heated up to about 40°C with continuous stirring. After slow cooling down to room temperature within a few hours, the sample was stored at about 4°C for several days. After that, the crystals were filtered off to give the crystalline product with a molar ratio of Li : O = 1 : 2. Raman (Selected bands, cm ¹) 2261, 2240, 1504, 1467, 1324, 1239, 1193, 1009, 872. mp = 15°C. Crystallographic data for C20H20F6U2N8O4 ( = 564.32 g/mol) : monoclinic, group P2i/c, a = 8.47493(18) A, b = 27.8768(6) A, c = 11.9413(2) A, β = 100.526(2), V=2773.70(10) A³.

The structure of the compound is presented in Fig. 1.

X-ray studies performed on single crystals showed that in the obtained product, after disproportionation there are two types of the lithium centers- Li2 and Lil. The first type Li2 cations possess in its coordination sphere 4 nitrogen atoms (Nl, N3, N6 and N7) and is part of the chain-like polyanions of general formula [Li(TDI)2]n^n~. Characteristic dimeric subunits containing ten membered Li ring (NCCN Li are linked by bridging the TDI anions, forming the coordination polymer. The cations of the second type (Lil) have a completely different coordination sphere and are linked to the chain as a terminal group by weak lithium- imidazolium nitrogen -Lil-N2 bond with a length of 2.124(11) A. Geometry of the coordination sphere of the solvated lithium Lil is slightly deformed octahedron, with imidazole nitrogen N2, fluorine and four oxygen atoms (01-04) from two solvent molecules in the corners. The construction of the coordination sphere of the terminal lithium Lil which is almost com pletely solvent-separated, shows that Lil will participate in the ion conduction through its dissociation and rearrangement structure to the polyanionic, immobilized chain.

Example lb

This example illustrates the procedure for the preparation of the electroactive material with the structure similar to the one presented in Example la, but of higher melting point. A solution containing about 50 mg of the LiTDI and about 50 mm³ of G3 was heated to about 120°C and then slowly cooled down to room temperature to give a mixture of crystals of the two solvates: one, undesired, has stoichiometry Li(G3)-TDI and it is in the form of ionic pairs (Li : O = 1 : 4, mp = 41°C). Raman (cm ¹): 2259, 2233, 1500, 1464, 1454, 1322, 1316, 1277, 1244, 1178, 1124, 1005, 989, 976, 864. The other is the complex of the disproportionated Li(G3)o.5-TDI (Li : O = 1 : 2, (mp = 110°C), which is desired product. Raman (cm ¹) : 2233 1492, 1454, 1320, 1280, 1234, 1169, 1124, 991, 867. Heating the mixtu re to about 45°C results in the melting of the undesired phase and allows easy filtration of the pure crystals of the Li(G3)₀.5-TDI . Crystallographic data for C₄oH36Fi2Li₄Ni608 (M = 1124.61 g/mol): monoclinic, P2i group, a = 8.4348(3) A, b = 27.1900(11) A, c = 12.0553(4) A, β = 103.843(4)°, V = 2684.50 (18) A³.

The structure of the compound is presented in Fig. 2.

The obtained compound has similar structure and characteristics as presented in Example la, but has higher melting point thanks to the use of the long-chain solvating ether (triglyme). Here, the terminal lithium cation Lil is solvated by a single molecule of triglyme instead of two glyme molecules. Example lc

A crystalline solvate Li(Gl)o.sTDI having two various lithium centers with different coordination spheres after disproportionation was obtain by mixing about 40 mg of LiTDI and about 40 mm³ of Gl followed by heating the mixture in a closed vessel for one hour at about 50°C.

After cooling the mixture down to room temperature, and leaving the reaction mixture for several days at this temperature, the crystalline product was filtered off yielding crystalline solvate Li(Gl)o.sTDI. mp = 120°C. Raman (cm ¹): 2259, 2235 1501 1498 1458 1321 1317 1283 1247, 1188, 1122, 1024, 1005, 996, 876. Crystallographic data for

(M = 474.20 g/mol): monoclinic, group P2i/c, a = 10.2026(5) A, b = 15.9759(4) A, c = 19.3596(10) A, β = 131.122(8)°, V=2377.1(3) A³.

The structure of the compound is illustrated in Fig. 3.

It was found on the basis of X-ray crystal structure determination that in the formed solvate, two types of the lithium cations exist. The first type of the cations (Lil) has in its coordination sphere only two imidazole anions coordinated by nitrogen atoms Nl and N5 and two oxygen atoms 01 and 02 coming from the solvent (glyme). The second type of cation- Li2- has the pure-nitrogen environment and is bound to four imidazolate anions by N2 N4, N6 and N7 atoms.

Example Id

Preparation of the crystalline form of a solvate of [Li2(G4)2²⁺] [Li₄TDl6^2~] stoichiometry. A mixture containing about 50 mg of LiTDI and about 30 mm³ of G4 was placed in a hermetic vial and heated to about 130°C with continuous stirring. After slow cooling to room temperature, the sample was left at this temperature. After a few days the product was dried to yield a crystalline solvate of a molar ratio of Li: O = 1:1.67. Raman (cm ¹): 2255, 2229, 1496, 1466, 1454, 1320, 1310, 1271, 1236, 1189, 1129, 1006, 987, 877. mp=123°C. Crystallographic data for C56H₄4Fi8Li6N240io (M = 1596.79 g / mol): triclinic, P I group, a=12.5479 (3) A, b=15.4547 (4) A, c=19.8730 (5) A, a = 93.364 (2) °, β = 90.7184 (19)°, γ=107.775 (2)°, V = 3661.68 (16) A³. In tetraglyme complex of the above composition (Li: O = 1: 1.67), lithium cations(Lil and Li2) after disproportionation are completely surrounded by polyether (oxygen atoms Ol-OlO) and isolated from the layered, anionic, polymeric subnet built from the second type lithium cations and TDI anions. In case of this compound, the major advantage is generating dimeric dications Li2(G4)₂ ²⁺ which will raise the cation transference number t+. X-ray studies show that the construction of the coordination sphere of the solvent-enriched lithium cations Lil and Li2 (G4) allows their easy dissociation from aggregated polianionic layer with immobilized anions of the TDI. Consequently, the crystalline material of defined structure, which has very good parameters as a solid electrolyte, is formed. The constitution of the obtained compound is presented in Fig. 4. Example le

The measurements of the ionic conductivity for [Li2(G4)2²⁺] [L14TDI6^2"] solvate.

The thermal dependence of the conductivity of the crystalline [Li2(G4)2²⁺] [L14TDI6^2"] is shown in Fig. 5.

Ionic conductivity in the test system, below the melting point of the compound (about 120°C), has Arrhenius-type character, typical for the crystalline systems, with activation energy equal to 15.4 kJ/mol. Melting of the material results in the increase of the ionic conductivity of the system (E_a = 18.4 kJ/mol^-1). When the temperature of the system decreases again, a solid and amorphous (glassy) material is formed; its conductivity is significantly lower in comparison to the starting material (at 30°C it is approx. 50% conductivity of the crystalline material). Interestingly, conductivity measurements made during the seasoning of the material after melting reveals that the conductivity increases over time, finally reaching the value observed for the starting crystalline material.

The measured values of the ionic conductivity of the material exceeds 10^~5 S/cm at 20-120°C temperature range. At lower temperatures, conductivity of the studied system is higher than for PEO-LiPF₆, LiCIGvPEO or PEOL1CF3SO3 systems.

At temperatures close to room temperature, the conductivity of the studied system is similar to the conductivity of PEO-LiTfSI, however, at higher temperatures conductivity of the PEO-LiTfSI system is higher. It must be stressed, that in case of PEO-LiTfSI the conductivity is realized almost exclusively by anions.

Example If

The lithium cation transference number measurements for [Li2(G4)2²⁺][Li₄TDl6^2~] were performed at 30°C. The obtained value of the transference number (t+ = 0.82) indicates the cationic conductivity gives the dominant contribution to the overall conductivity.

Example 2.

Preparation of the crystalline form of sodium 2,3,4,5-tetracyanopyrrolate (NaTCP) having the structure Na(Gl)₃-Na₃(Gl)2TCP₄. A solution containing about 30 mg of NaTCP and about 50 mm³ of Gl was placed in an hermetic vial and heated to about 50°C with continuous stirring. After slow cooling down to the room temperature, the sample was placed for several days at 4°C to give the crystalline product.

In the obtained solvate of NaTCP and monoglyme (molar ratio Na : O = 1 : 2.5), four types of cationic centers after disproportionation can be distinguished. Three of them (Nal, Na2 and Na3) are involved in the formation of polymer layer of Na₃(Gl)2TCP₄ stoichiometry, spanned by TCP anions. Second type of cation- Na4- is almost completely solvated with three glyme molecules and is weakly bounded from the top and the bottom of layers by the imidazole nitrogen atom N14 to isolate them.

The constitution of the obtained compound is presented in Figure 6.

Crystallographic data for C52H47N2oNa₄Oio (M = 1204.05 g/mol): monoclinic, group P2i, a = 15.6393(8) A, b = 13.2754(5) A, c = 17.1779(7) A, β = 113.605(5), V = 3268.1(3) A³.

Example 3.

Using a procedure similar to that presented in Example 2, solvate of sodium 2,3,4,5-tetracyanopyrrolate (NaTCP) and propylene carbonate as a solvent was prepared. The obtained compound of formula Na(PC)₂ CP was obtained; Na : 0(_Coord) molar ratio is equal to 1 : 2. In the structure of the compound, one can distinguish two-dimensional layer of sodium cations and TCP anions surrounded by solvent molecules, which isolate both sides of the layer. Oxygen atoms 01 and 04 from propylene carbonate molecules are coordinated to sodium, whereas 02, 03, 05 and 06 oxygens of remain uncoordinated and do not affect the structure of the compound.

The structure of the obtained compound is presented in Figure 7.

The crystallographic data for Ci6Hi2NsNa06 (M = 269.23 g / mol): triclinic, P I group, a = 8.6621(5) A, b = 9.1262(4) A, c = 12.0925(8) A, a = 92.140(5)°, β = 98.746(5)°,

y = 94.495(4)°, V = 940.74(9) A³.

Example 4.

Using a procedure similar to that presented in Example 2, solvate of sodium 2,3,4,5- tetracyanopyrrolate (NaTCP) and 18-crown-6 (18C6) of formula Na₂(18C6)₂TCP₂ was obtained. This example illustrates the possibility of receiving systems with dications of the general formula Na₂(solv)_x ²⁺. The figure shows fragment of the crystal structure of the compound containing sodium dications surrounded by ether solvent. In this case, two sodium cations are associated by two crown ether molecules.

The structure of the obtained compound is presented in Figure 8.

The crystallographic data for C₂oH₂₄N5Na06 (M = 226.72 g / mol): triclinic, P I group, a = 8.1064(18) A, b = 11.0135(17) A, c = 12.4274(16) A, a = 82.674(12)°, β = 89.783(14)°, Y = 81.594(15)°, V = 1088.5 (3) A³.

Example 5.

Using a procedure similar to that presented in Example 2, solvate of sodium 2,3,4,5- tetracyanopyrrolate (NaTCP) and ethylene carbonate (EC) was prepared. Compound of formula Na₂(EC) CP₂, with the Na : 0(_COord) molar ratio equal to 1 : 2, was obtained. In the synthesized system, the sodium Na2(EC)₄ ²⁺ dications are solvated by four molecules of the ethylene carbonate, which in turn are built-in into a three-dimensional structure by tetracyanopyrrolate anions. Oxygen atoms 01 and 04 are coordinated to sodium (Nal) while the oxygens 02 and 03 remain uncoordinated and do not affect the structure of the obtained compound.

The structure of the obtained compound is presented in Figure 9.

Example 6.

A solution containing about 30 mg of lithium 2,4,5-tricyanoimidazolate (LiTIM) and about 100 mm³ of acetonitrile was placed in an hermetic vial and warmed up to about 30°C with continuous stirring. After slow cooling to the room temperature, sample was stored at 4°C to give, after several days, a crystalline product, which was filtered off. The obtained system of the formula LiTIM-CHsCN is in the form of the three-dimensional coordination polymer containing in its construction channels, in which the ion transport can occur. Lithium cations are built in the three-dimensional structure by tricyanoimidazolate anions. This type of structure, with acetonitrile molecules located within the channels, allows for easy removal of the solvent and can be used to purification of the salt.

The constitution of the obtained compound is presented in Figure 10.

Crystallographic data for C6₄H2₄LisN₄8 (M = 1520.83 g/mol): orthorhombic, Pbcm group, a = 11.1500(4) A, b = 13.2983(3) A, c = 13.2279(3) A, V = 1961.39(9) A³.

Example 7.

A mixture containing about 50 mg of lithium dicyanotriazolate (LiDCTA) and about 30 mm³ of tetraglyme (G4)was placed in an hermetic vial and heated up to about 120°C with continuous stirring. After slowly cooling to room temperature, sample was left at this temperature. After a few days, the product was separated to give a crystalline solvate of the formula Li2(G4)²⁺-DCTA, having Li : O ratio equal to 1 : 2.5. The figure shows a structural fragment showing double cations of lithium solvated by tetraglyme molecules, which are formed in the obtained system.

The structure of the obtained compound is presented in Figure 11.

Crystallographic data for C9H11UN5O2.5 (M = 236.17 g / mol): monoclinic, /2/a group, a = 19.2050(7) A, b = 7.0800(3) A, c = 17.7789(6) A, β = 106.348(4)°, V = 2319.70(15) A³.

Claims

Claims:

1. The compound of general Formula 1:

(Cat⁺)(An ) · xL

Formula 1 wherein:

Cat⁺ is a lithium or sodium cation having a constant coordination number of the cation CNy = 5-6 or CN_Na = 6-7,

An^" is an anion of the formula 2

Formula 2 wherein

Ri is C-C≡N or a nitrogen atom, R₂ is a nitrogen atom or C-R3, wherein R3 represents a halogen atom, a CN group, a N0₂ group, a C1-C3 alkyl optionally substituted by fluorine or chlorine, x is a positive number not higher than 3.

2. The compound according to Claim 1, wherein Ri=N .

3. The compound according to Claim 1, wherein R₂=N .

4. The compound according to Claim 1, wherein R3=CF3.

5. The compound according to Claim 1, wherein R3=CN.

6. The compound according to Claim 1, wherein R3=CI.

7. The compound according to Claim 1, wherein Ri=R₂=-C-CN.

8. The use of a compound according to Claim 1 as crystalline solid electrolyte for power sources.