Nonaqueous electrolyte solution and nonaqueous electrolyte solution secondary battery employing the same

Abstract

A subject for the invention is to provide an electrolyte solution and a secondary battery which are preventd from causing or suffering battery performance deterioration in high-temperature storage or high-temperature trickle charge. The invention relates to a nonaqueous electrolyte solution for a secondary battery which comprises solute, phosphinic ester compound, and nonaqueous organic solvent containing these, characterized in that the content of the phosphinic ester compound has been regulated to a specific amount based on the total weight of the nonaqueous electrolyte solution.

1 . A nonaqueous electrolyte solution for a secondary battery, comprising solute, phosphinic ester compound, and nonaqueous organic solvent containing them, wherein the content of the phosphinic ester compound is from 0.01% by weight to 4.5% by weight, based on the total weight of the nonaqueous electrolyte solution.  
     
     
         2 . The nonaqueous electrolyte solution for a secondary battery according to  claim 1 , wherein the phosphinic ester is one selected from the group consisting of compounds represented by the following formula (1) and compounds represented by the following formula (2):  
       
         
           
           
               
               
           
         
         wherein R 1  to R 3  each independently represents one member selected from the group consisting of (i) a chain or cyclic alkyl group which has 1 to 8 carbon atoms and may be substituted with one or more halogen atoms, (ii) a phenyl group which may be substituted with one or more halogen atoms, (iii) a phenyl group which may be substituted with one or more alkyl groups having 1 to 4 carbon atoms, and (iv) a phenyl group which may be substituted with one or more halogen atoms and one or more alkyl groups having 1 to 4 carbon atoms, provided that when the pair of R 1  and R 2  or the pair of R 2  and R 3  is alkyl groups, then the groups may be bonded to each other to form a ring structure:  
         
           
             
             
                 
                 
             
           
         
         wherein R 11  and R 12  each independently represents a chain or cyclic alkyl group, which has 1 to 8 carbon atoms and may be substituted with one or more halogen atoms or a phenyl group which may be substituted with one or more halogen atoms, provided that when R 11  and R 12  each is an alkyl group, they may be bonded to each other to form a ring structure, L represents a connecting group having a valence of z and constituted of one or more atoms selected from the group consisting of a carbon atom, a hydrogen atom, and an oxygen atom, and z represents an integer of 2 to 8.  
       
     
     
         3 . The nonaqueous electrolyte solution for a secondary battery according to  claim 2 , wherein the phosphinic ester comprises a compound having formula (1), wherein R 1  to R 3  each independently represents one selected from the group consisting of (i) a chain alkyl group which has 1 to 8 carbon atoms and may be substituted with one or more halogen atoms, (ii) a phenyl group which may be substituted with one or more halogen atoms, (iii) a phenyl group which may be substituted with one or more alkyl groups having 1 to 4 carbon atoms, and (iv) a phenyl group which may be substituted with one or more halogen atoms and one or more alkyl groups having 1 to 4 carbon atoms.  
     
     
         4 . The nonaqueous electrolyte solution for a secondary battery according to  claim 2 , wherein the phosphinic ester comprises a compound having formula (2), wherein R 11  and R 12  each independently represents a chain alkyl group which has 1 to 4 carbon atoms and may be substituted with one or more halogen atoms, L represents a chain hydrocarbon connecting group having a valence of z and having 2 to 8 carbon atoms, and z represents an integer of 2 to 4.  
     
     
         5 . The nonaqueous electrolyte solution for a secondary battery according to  claim 1 , wherein the nonaqueous electrolyte solution for a secondary battery further comprises an overcharge inhibitor or a film formation agent.  
     
     
         6 . The nonaqueous electrolyte solution for a secondary battery according to  claim 1 , wherein the nonaqueous organic solvent in the nonaqueous electrolyte solution is a mixed solvent comprising a cyclic carbonate and a member selected from the group consisting of chain carbonates and cyclic esters.  
     
     
         7 . A nonaqueous-electrolyte secondary battery comprising a negative electrode capable of absorbing/releasing lithium, a positive electrode, and the nonaqueous electrolyte solution for a secondary battery defined in  claim 1 .  
     
     
         8 . The nonaqueous-electrolyte secondary battery according to  claim 7 , wherein the positive electrode comprises a lithium-transition metal composite oxide.  
     
     
         9 . The nonaqueous-electrolyte secondary battery according to  claim 7 , wherein the negative electrode comprises a carbonaceous material wherein the value of d for a lattice plane (002 plane) in X-ray diffraction is from 0.335 to 0.340 nm.