Nonaqueous electrolyte compositions

Abstract

Electrolyte compositions containing a solvent, a co-solvent, certain cyclic carboxylic acid anhydride additives, certain phosphorus-containing additives, and an electrolyte salt are described. The electrolyte compositions are useful in electrochemical cells, such as lithium ion batteries where they provide significantly improved cycle life with no loss of discharge capacity.

What is claimed is: 
     
         1 . An electrolyte composition comprising:
 a) at least one solvent;   b) at least one co-solvent;   c) at least one cyclic carboxylic acid anhydride selected from the group consisting of   
       
         
           
           
               
               
           
         
         wherein R 7  to R 14  are independently H, F, C 1  to C 10  alkyl optionally substituted with fluorine, alkoxy, and/or thioalkyl, C 2  to C 10  alkene, or C 6  to C 10  aryl; 
         d) at least one phosphorus-containing additive selected from the group consisting of organic phosphates, organic phosphonates, and partial salts thereof; and 
         e) at least one electrolyte salt. 
       
     
     
         2 . The electrolyte composition of  claim 1 , wherein the solvent is a non-fluorinated solvent. 
     
     
         3 . The electrolyte composition of  claim 2 , wherein the non-fluorinated solvent is selected from the group consisting of ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, propylene carbonate, and mixtures thereof. 
     
     
         4 . The electrolyte composition of  claim 1 , wherein the solvent is a fluorinated solvent selected from the group consisting of:
 a) a fluorinated acyclic carboxylic acid ester represented by the formula:
   R 1 —COO—R 2  
 
   b) a fluorinated acyclic carbonate represented by the formula:
   R 3 —OCOO—R 4 , and
 
   c) a fluorinated acyclic ether represented by the formula:
   R 5 —O—R 6  
 
   wherein R 1 , R 2 , R 3 , R 4 , R 5 , and R 6 , independently represent an alkyl group; the sum of carbon atoms in any of R 1  and R 2 , R 3  and R 4 , and R 5  and R 6  is 2 to 7; at least two hydrogens in R 1  and/or R 2 , R 3  and/or R 4 , and R 5  and/or R 6  are replaced by fluorines; and neither R 1 , R 2 , R 3 , R 4 , R 5 , nor R 6  contains a —CH 2 F or —CHF— group.   
     
     
         5 . The electrolyte composition of  claim 4 , wherein the fluorinated acyclic carboxylic acid ester is selected from one or more members of the group consisting of CH 3 —COO—CH 2 CF 2 H, CH 3 CH 2 —COOCH 2 CF 2 H, F 2 CHCH 2 —COO—CH 3 , F 2 CHCH 2 —COO—CH 2 CH 3 , CH 3 —COO—CH 2 CH 2 CF 2 H, CH 3 CH 2 —COO—CH 2 CH 2 CF 2 H, F 2 CHCH 2 CH 2 —COO—CH 2 CH 3 , and CH 3 —COO—CH 2 CF 3 . 
     
     
         6 . The electrolyte composition of  claim 5 , wherein the fluorinated acyclic carboxylic acid ester is 2,2-difluoroethyl acetate or 2,2-difluoroethyl propionate, or a mixture thereof. 
     
     
         7 . The electrolyte composition of  claim 1 , wherein the co-solvent is selected from one or more members of the group consisting of ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, butylene carbonate, ethylene carbonate, and ethyl methyl sulfone. 
     
     
         8 . The electrolyte composition of  claim 7 , wherein the co-solvent is ethylene carbonate. 
     
     
         9 . The electrolyte composition of  claim 1 , wherein the cyclic carboxylic acid anhydride is selected from one or more members of the group consisting of maleic anhydride, succinic anhydride, glutaric anhydride, 2,3-dimethylmaleic anhydride, citraconic anhydride, 1-cyclopentene-1,2-dicarboxylic anhydride, 2,3-diphenylmaleic anhydride, 3,4,5,6-tetrahydrophthalic anhydride, 2,3-dihydro-1,4-dithiiono-[2,3-c] furan-5,7 dione, and phenylmaleic anhydride. 
     
     
         10 . The electrolyte composition of  claim 9 , wherein the cyclic carboxylic acid anhydride is maleic anhydride. 
     
     
         11 . The electrolyte composition of  claim 1 , wherein the organic phosphates are represented by the formula: 
       
         
           
           
               
               
           
         
       
       wherein R 15 , R 16 , and R 17  are each independently linear or branched C 1  to C 10  alkyl or fluoroalkyl, C 3  to C 10  cyclic alkyl, C 2  to C 10  ether, C 2  to C 10  ether wherein at least one of the hydrogens is replaced with a fluorine, R 15  and R 16 , R 16  and R 17 , or R 15  and R 17  may be joined to form a ring. 
     
     
         12 . The electrolyte composition of  claim 11 , wherein the organic phosphate is selected from the group consisting of tris(1,1,1,3,3,3-hexafluoropropan-2yl) phosphate, tris(2,2,2-trifluoroethyl) phosphate, tri(2,2,3,3,3-pentafluoropropyl) phosphate, tris(2,2,3,3-tetrafluoropropyl) phosphate, triethyl phosphate, trimethyl phosphate, tripropyl phosphate, triisopropyl phosphate, tris(2,2,3,3,4,4,5,5,6,6-decafluorohexyl) phosphate, and tris(2,2-difluoroethyl) phosphate. 
     
     
         13 . The electrolyte composition of  claim 1 , wherein the partial salt of an organic phosphate is represented by the following formulae 
       
         
           
           
               
               
           
         
       
       wherein R 15  and R 16 , are each independently linear or branched C 1  to C 10  alkyl or fluoroalkyl, C 3  to C 10  cyclic alkyl, C 2  to C 10  ether, C 2  to C 10  ether wherein at least one of the hydrogens is replaced with a fluorine, R 15  and R 16  may be joined to form a ring, M +  is a cation selected from the group consisting of lithium, sodium, potassium, rubidium, and cesium, and M +2  is cation selected from the group consisting of beryllium, magnesium, calcium, strontium, and barium. 
     
     
         14 . The electrolyte composition of  claim 1 , wherein the organic phosphonates are represented by the formula: 
       
         
           
           
               
               
           
         
       
       wherein R 15 , R 16 , and R 17  are each independently linear or branched C 1  to C 10  alkyl or fluoroalkyl, C 3  to C 10  cyclic alkyl, C 2  to C 10  ether, C 2  to C 10  ether wherein at least one of the hydrogens is replaced with a fluorine, R 15 and R 16 , R 16  and R 17 , or R 15  and R 17  may be joined to form a ring. 
     
     
         15 . The electrolyte composition of  claim 14 , wherein the organic phosphonate is dimethylmethylphosphonate. 
     
     
         16 . The electrolyte composition of  claim 1 , wherein the partial salt of an organic phosphonate is represented by the following formula 
       
         
           
           
               
               
           
         
       
       wherein R 15  and R 17  are each independently linear or branched C 1  to C 10  alkyl or fluoroalkyl, C 3  to C 10  cyclic alkyl, C 2  to C 10  ether, C 2  to C 10  ether wherein at least one of the hydrogens is replaced with a fluorine, R 15  and R 17  may be joined to form a ring, M +  is a cation selected from the group consisting of lithium, sodium, potassium, rubidium, and cesium, and M +2  is cation selected from the group consisting of beryllium, magnesium, calcium, strontium, and barium. 
     
     
         17 . The electrolyte composition of  claim 1  further comprising an additive selected from the group consisting of lithium bis(oxalato)borate and fluoroethylene carbonate. 
     
     
         18 . The electrolyte composition of  claim 1  comprising a fluorinated acyclic carboxylic acid ester, ethylene carbonate, an organic phosphate or organic phosphonate additive, maleic anhydride, and fluoroethylene carbonate. 
     
     
         19 . An electrochemical cell comprising:
 (a) a housing;   (b) an anode and a cathode disposed in said housing and in ionically conductive contact with one another;   (c) the electrolyte composition of  claim 1  disposed in said housing and providing an ionically conductive pathway between said anode and said cathode; and   (d) a porous separator between said anode and said cathode.   
     
     
         20 . The electrochemical cell of  claim 19 , wherein said electrochemical cell is a lithium ion battery. 
     
     
         21 . The electrochemical cell of  claim 20 , wherein the anode is lithium titanate or graphite. 
     
     
         22 . The electrochemical cell of  claim 20 , wherein the cathode comprises a cathode active material exhibiting greater than 30 mAh/g capacity in the potential range greater than 4.6 V versus a Li/Li +  reference electrode. 
     
     
         23 . The electrochemical cell of  claim 20 , wherein the cathode comprises a cathode active material which is charged to a potential greater than or equal to 4.35 V versus a Li/Li +  reference electrode. 
     
     
         24 . The electrochemical cell of  claim 20 , wherein the cathode comprises a lithium-containing manganese composite oxide having a spinel structure as active material, the lithium-containing manganese composite oxide being represented by the formula:
   Li x Ni y M z Mn 2−y−z O 4−d      
       wherein x is 0.03 to 1.0; x changes in accordance with release and uptake of lithium ions and electrons during charge and discharge; y is 0.3 to 0.6; M comprises one or more of Cr, Fe, Co, Li, Al, Ga, Nb, Mo, Ti, Zr, Mg, Zn, V, and Cu; z is 0.01 to 0.18, and d is 0 to 0.3. 
     
     
         25 . The electrochemical cell of  claim 24 , wherein y is 0.38 to 0.48, z is 0.03 to 0.12, and d is 0 to 0.1. 
     
     
         26 . The electrochemical cell of  claim 24 , wherein M is one or more of Li, Cr, Fe, Co, and Ga. 
     
     
         27 . An electronic device comprising an electrochemical cell according to  claim 19 .