RELATED APPLICATION

The present application claims priority, under applicable law, to Canadian patent application No. 2,953,163 filed on Dec. 23, 2016, the content of which is incorporated herein by reference in its entirety and for all purposes.

TECHNICAL FIELD

The present application relates to compounds based on an element from the boron family, their preparation processes and their use as salts and/or additives in electrolyte compositions.

BACKGROUND

A lithium-ion battery includes a negative electrode, a positive electrode, a separator and an electrolyte. The negative electrode and the positive electrode consist of one or two active materials (lithium insertion and extraction), a mixture of electronic conductors, a polymer used to bind the particles together and to adhere to the current collector (usually aluminum or copper). The electrolyte consists of one or more lithium salts dissolved in a liquid solvent (usually a mixture of organic carbonates) or in a polymer solvent. Additives may be added to the electrolyte solution to improve the battery's resistance to temperature, high-voltage, aluminum corrosion, etc.

Lithium-ion batteries for electric cars and other electrical devices available today most often use liquid electrolytes based on lithium hexafluorophosphate (LiPF6) in a mixture of carbonates. The popularity of this salt is mainly due to the formation of a passivation layer on aluminum (most used current collector for cathodes). However, LiPF6is thermally unstable but also chemically unstable since it can react with a protic species (e.g. H2O, etc.) to form a toxic gas, very aggressive and undesirable, hydrogen fluoride (HF). Even if all precautions are taken to avoid contact of LiPF6with a protic species, a high risk exists, which involves degradation of the battery resulting in a reduced life and potential safety problems. In addition, the cost of this salt remains relatively high. These major disadvantages have encouraged research for salts replacing LiPF6with improved electrochemical, thermal, chemical properties and others.

Various salts have been proposed as candidates for replacing LiPF6. These salts nevertheless have disadvantages which limit or prevent their use. For example, lithium hexafluoroarsenate (LiAsF6), because of the toxicity of arsenic derivatives and degradation products, cannot be used. Another example, lithium perchlorate (LiClO4), is a highly reactive salt that can explode under abusive oxidative conditions. Lithium (trifluoromethylsulfonyl)imide (LiTFSI), on the other hand, corrodes the aluminum of the current collector. Boron-based salts have also been proposed, such as lithium tetrafluoroborate (LiBF4), which has been criticized for its low conductivity and its limited solubility in carbonates, still has the advantage of being inexpensive and not very sensitive to moisture and therefore safer. Lithium (oxalato)borate (LiBOB), which has many advantages such as high electrochemical and thermal stability (293° C.), generates gas when LiCoO2-based cathodes are used. In view of the chemical, electrochemical and thermal properties, as well as their moisture stability, boron-based lithium salts have been developed in recent years and more particularly borates and boroxines.

Generally, borates are prepared using an alcohol, a carboxylic acid, or a dicarboxylic acid, but also multifunctional carboxylic acid-alcohol molecules from B(OR)3or Ar—B(OR)2(J. Power Sources,2014, 247, 813;J. Phys. Chem.,2009, 113, 5918;J. Electrochem. Soc.,1998, 145, 2813). Preparation of lithiated borates was obtained by using a nucleophile (alcohol) or a carboxylic acid in the presence of a lithium base such as LiOH, Li2CO3, or Li (J. Electrochem. Soc.,1996, 143, 3572) and a boron-based compound: B(OMe)3, LiBF4and BF3.

The preparation of boroxines is, in turn, generally carried out by dehydration of ArB(OH)2or ArOB(OH)2, to obtain respectively (BOAr)3or B(O(OAr)3(J. Power Sources,2014, 247, 813;J. Phys. Chem.,2009, 113, 5918;J. Am. Chem. Soc.,2013, 135, 10990). For this type of reaction, the substituted boric acid (ArB(OH)2or ArOB(OH)2) must be prepared beforehand, the preparation of boroxines therefore being carried out in two steps. The addition of a boroxine like trimethylboroxine (TMB) in an electrolyte composition, at a concentration of 0.5 to 1 wt % has improved the electrolyte's electrochemical properties. TMB is preferentially oxidized and forms an SEI on the cathode. It has been shown that the addition of a boroxine can improve ionic conductivities, as well as the capacity retention (J. Electro. Soc.,2014, 161, 2255;Electrochem. Comm.,2013, 28, 20;Electrochemica Acta,2015, 173, 804).

In order to improve battery life and safety, it is crucial to improve the properties (such as thermal, electrochemical, moisture stability, etc.) of existing electrolytes, by developing new salts and/or additives for electrolyte compositions.

SUMMARY

According to a first aspect, the present application relates to compounds based on an element from the boron family. For example, the compounds are of Formula I or II, and/or their salts:



wherein:M is an atom selected from the elements of column 13 (Group IIIA) of the periodic table of the elements, for example, a boron, aluminum, gallium, indium or thallium atom, for example a boron, aluminum, gallium or indium atom, or a boron or aluminum atom;X is independently selected from O, S, NH, NR, or a C(O)O or S(O)2O group, wherein said group is attached to M by an oxygen atom;R is independently selected from substituted or unsubstituted linear or branched alkyl, cycloalkyl and aryl groups, or 2 or 3 R groups combined with X radicals attached thereto form a 5 to 7 membered ring comprising M, or a bicyclic group having from 7 to 10 members comprising M, and/or at most one XR is a hydroxyl group; andA+is a metallic cation or a cation of an organic base, and where the total molar ratio of A+relative to the rest of the molecule is adjusted to achieve electroneutrality.

According to one embodiment, A+is a metallic cation, for example, selected from cations of the elements Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr, Ba, Al, Zn, Cu, Sc, Y, Fe, Co, Ni, Ti, Sn, V, Cr, or Mn. According to one embodiment, A+is a cation of an alkali or alkaline earth metal (Li+, Na+, K+, Rb+, Cs+, Be2+, Mg2+, Ca2+, Sr2+, and Ba2+), for example, A+is Li+.

According to another embodiment, A+is an organic cation, for instance, selected from ammonium, alkylammonium, dialkylammonium, trialkylammonium, tetraalkylammonium, triarylammonium, tricycloalkylammonium, tetracycloalkylammonium, imidazolium, 1,3-dialkylimidazolium, 4,5-dicyanoimidazolium, N-alkylpyrrolidinium, N-alkylpiperidinium, oxoniums, trialkyloxonium, sulfoniums, trialkylsulfonium, triarylsulfonium, tricycloalkylsulfonium, phosphoniums, tetraalkylphosphonium, tetraarylphosphonium, tetracycloalkylphosphonium, trialkylphosphonium, triarylphosphonium, tricycloalkylphosphonium, trialkylselenium, tetraalkylarsonium, and other similar bases. According to another embodiment, A+is an organic cation of an organic base, for instance selected from trimethylamine, triethylamine, tripropylamine, tributylamine, N-alkylpyrrolidine, N-alkylmorpholine, N-methylimidazole, 4,5-dicyanoimidazole, pyridine, picoline, lutidine, quinoline, N,N-dimethylaniline, diisopropylethylamine, quinuclidine, trimethylphosphine, and other similar organic bases.

According to an embodiment, the compound of Formula I is selected from the compounds of Formulae I(a), I(b1), I(b2) and I(c), and/or their salts:

wherein X, M, are as previously defined,R3is a substituted or unsubstituted group selected from linear or branched alkyls, cycloalkyls and aryls;R4is, independently in each occurrence, selected from hydrogen, halogen, and substituted or unsubstituted linear or branched alkyl, cycloalkyl and aryl groups, or R4groups combined with their adjacent carbon atoms form a mono or bicyclic cycloalkyl or an aryl, and where n is different from 1 when X is O or NH in each occurrence;n is an integer selected from 1, 2, 3 and 4; andm is an integer selected from 0, 1, and 2.

According to one embodiment, the compound of Formula II is selected from compounds of Formulae II(a), II(b1), II(b2) and II(c) and/or their salts:



wherein X, M, R3, R4, A+, n and m are as previously defined.

According to one embodiment, the compound is of Formula III, and/or its salts:



wherein M and X are as previously defined; and

R1is independently selected from substituted or unsubstituted linear or branched alkyl, cycloalkyl and aryl groups.

According to one of the above embodiments, at least one of the compound's X group is a C(O)O or S(O)2O group. For example, at least one group X is a S(O)2O group. In some embodiments, all X moieties of the compound bound to the M atom are S(O)2O groups.

According to one of the above embodiments, the compound is as described, and M is a boron atom. According to another embodiment, M is an aluminum atom. According to a further embodiment, M is a gallium atom. According to yet another embodiment, M is an indium atom.

According to one example, the compound of Formula I as herein described, is selected from the following compounds:



where A+is as previously defined.

According to another example, the compound of Formula II as herein described, is selected from the following compounds:



where A+is as previously defined.

According to an additional example, the compound of Formula III as described herein, is selected from the following compounds:



where A+is as previously defined.

According to another aspect, the present application relates to a process for preparing a compound as described herein, comprising a step of contacting a compound of Formula IV:
M(X′)3(IV)wherein M is as previously defined and X′ is selected from hydrogen, OH, halogen (e.g. F, Cl, Br), C1-C4alkyl, O—C1-C4alkyl (e.g. OMe, OEt, Oi-Pr), C1-C4alkylcarboxylate, sulfate, phosphate, or a salt of the compound of Formula IV, for instance, a compound of Formula (IV) or one of its salt is selected from B(OH)3, BH3, NaBH4, LiBH4, BBr3, BCl3, BF3, BMe3, BEt3, B(i-Pr)3, B(OMe)3, LiBF4, Al(OH)3, AlBr3, AlCl3, Al(OMe)3, Al(OEt)3Al(Oi-Pr)3, Al(OC(O)C2H5)3, Al(OC(O)CH(CH3)2)3, Al(OC(O)CH3)3, AlPO4, Al2(SO4)3, AlMe3, AlEt3, Al(i-Pr)3, LiAlH4and LiAlCl4;

with at least one compound of Formula V:
RXH  (V)where R and X are as previously defined and where two or three R groups may be linked to form a single compound comprising two or three XH groups.

According to one embodiment, the process comprises contacting about one equivalent of the compound of formula IV and the amount of compound of Formula V corresponding to 2, 3 or 4 molar equivalents of XH group, the presence of a base for forming a salt with XH groups neutralizing the function being excluded from the calculation. Examples of bases are described below, which may be inorganic or organic.

According to one embodiment, the compound of Formula V (RXH) is a compound selected from Formulae V(a) to V(c):

wherein X, n, m, R3, and R4are as previously defined.

According to one embodiment, at least one X group is a C(O)O or S(O)2O group, or at least one X group is a S(O)2O group.

According to one example, in the compound of Formula IV, M is a boron atom. According to another example, M is an aluminum atom.

In the above process and compounds, R3may be an alkyl, cycloalkyl or aryl substituted with at least one group selected from OH, NH2, N(R2)H, N(R2)2, CO2H and SO3H, or a salt thereof when applicable, where R2is selected from optionally substituted alkyl, cycloalkyl or aryl groups. For instance, R3is an alkyl, cycloalkyl or aryl substituted with at least one group selected from CO2H and SO3H or a salt formed of a CO2−or SO3−anion and an A+cation, where A+is as previously defined. According to another example, R3is selected from substituted or unsubstituted alkyl and phenyl groups, for instance, methyl, trifluoromethyl, carboxyphenyl, carboxyalkyl, and dicarboxyalkyl groups.

In the above process and compounds, R4may be a hydrogen atom in each occurrence.

According to an embodiment, the compound of Formula V is a compound of Formula V(b), n is equal to 2 and R4groups combined with carbon atoms attached thereto form an aryl group.

According to another embodiment, the compound of Formula V is selected from pinacol, orthanilic acid, sulfoacetic acid, sulfobenzoic acid, ethanolamine, methanesulfonic acid, triflic acid and sulfosuccinimic acid.

According to one embodiment, the above-described process comprises:preparing a compound of Formula I(a) comprising contacting the compound of Formula IV with about 3 molar equivalents of a compound of Formula V(a), optionally in the presence of a base; orpreparing a compound of Formula I(b1) comprising contacting the compound of Formula IV with about 1 molar equivalent of a compound of Formula V(a) and about 1 molar equivalent of a compound of Formula V(b), optionally in the presence of a base; orpreparing a compound of Formula I(b2) comprising contacting the compound of Formula IV with about 1 molar equivalent of a compound of Formula V(b), optionally in the presence of a base; orpreparing a compound of Formula I(c) comprising contacting the compound of Formula IV with about 1 molar equivalent of a compound of Formula V(c), optionally in the presence of a base; orpreparing a compound of Formula II(a) comprising contacting the compound of Formula IV with about 4 molar equivalents of a compound of Formula V(a) in the presence of a base; orpreparing a compound of Formula II(b1) comprising contacting the compound of Formula IV with about 1 molar equivalent of a compound of Formula V(b) and about 2 molar equivalents of a compound of Formula V(a) in the presence of a base; orpreparing a compound of Formula II(b2) comprising contacting the compound of Formula IV with about 2 molar equivalents of a compound of Formula V(b) in the presence of a base; orpreparing a compound of Formula II(c) comprising contacting the compound of Formula IV with about 1 molar equivalent of a compound of Formula V(c) and about 1 molar equivalent of a compound of Formula V(a) in the presence of a base.

According to another embodiment, the present application relates to a process from preparing a compound of Formula III, comprising a step of contacting a compound of Formula IV:
M(X′)3(IV)wherein M and X′ are as previously defined;with at least one compound of Formula VI:
R1XH  (VI)where R1and X are as defined herein.

For example, the process comprises preparing a compound of Formula III comprising contacting a compound of Formula IV with about 1 molar equivalent of a compound of Formula VI.

Preferentially, the processes as herein described comprise a step of removing water. According to one example, the process comprises a step of heating to reflux in the presence of a solvent forming an azeotrope with water. In another example, the process comprises the use of a desiccant.

In another aspect, the present application relates to the use of a compound as described herein, or a compound prepared by a process as described herein, in an electrolyte composition. The present application also relates to an electrolyte composition comprising at least one compound as described herein, or a compound prepared according to a process as described herein. According to one embodiment, the electrolyte composition further comprises a liquid solvent or a solvating polymer. For example, the electrolyte composition is a liquid electrolyte, or a gel polymer electrolyte, or a solid polymer electrolyte.

According to a last aspect, the present application relates to an electrochemical cell comprising an electrolyte composition, as described herein, between an anode and a cathode. For example, the electrochemical cell based on metal ion, such as Li+, Na+, K+, Rb+, Cs+, Be2+, Mg2+, Ca2+is of the lithium or lithium-ion battery type.

