Lithium Titanate Cell

Abstract

The embodiment relates to the field of electrolyte selection in lithium ion cells which may employ Li4Ti5O12 compounds as negative electrode material and LiPF6 as the ionic salt component in the cell electrolyte solution. The embodiment further relates to improvements in lithium ion cell performance as a result of selection of specific formulation of electrolyte for lithium ion cells.

What is claimed is: 
     
         1 . An electrolyte for a lithium ion battery comprising at least one cyclic ester and at least one linear ester and a lithium salt wherein the lithium salt concentration exceeds the lithium salt concentration corresponding to maximum electrolyte ionic conductivity. 
     
     
         2 . The electrolyte of  claim 1  wherein the cyclic ester is ethylene carbonate and the linear ester is ethylmethyl carbonate. 
     
     
         3 . The electrolyte of  claim 2  wherein the lithium salt is LiPF 6 . 
     
     
         4 . The electrolyte of  claim 3  wherein the concentration of LiPF 6  is from about 1.2M to about 2.0M. 
     
     
         5 . The electrolyte of  claim 3  wherein the concentration of LiPF 6  is from about 1.3M to about 1.9M. 
     
     
         6 . The electrolyte of  claim 3  wherein the concentration of LiPF 6  is from about 1.3M to about 1.8M. 
     
     
         7 . The electrolyte of  claim 4  further comprising an additive. 
     
     
         8 . The electrolyte of  claim 7  wherein the additive is selected from the group consisting of organic sultones and organic anhydrides. 
     
     
         9 . The electrolyte of  claim 8  wherein the additive is 1,3 propanesultone. 
     
     
         10 . The electrolyte of  claim 8  wherein the additive is succinic anhydride. 
     
     
         11 . A lithium ion cell comprising at least one Li 4 Ti 5 O 12  compound as a negative electrode and at least one lithiated transition metal oxide or lithiated transition metal phosphate as positive electrode, a separator and a non-aqueous electrolyte comprising a LiPF 6  salt dissolved in a mixture of ethylene carbonate and ethyl methyl carbonate solvents wherein the concentration of the said LiPF 6  salt is equal or higher than 1.4 M. 
     
     
         12 . A lithium ion cell according to  claim 11  wherein the concentration of the said LiPF 6  salt is equal or higher than 1.6 M. 
     
     
         13 . A lithium ion cell comprising at least Li 4 Ti 5 O 12  compound as a negative electrode and at least one lithiated transition metal oxide or lithiated transition metal phosphate as positive electrode, a separator and a non-aqueous electrolyte including LiPF 6  salt dissolved in a mixture of organic carbonate cyclic esters and organic carbonate linear esters wherein the ethylene carbonate is at least 50% of the total amount of cyclic esters and ethyl methyl carbonate is at least 50% of the total amount of organic carbonate linear esters and the concentration of the said LiPF 6  salt is equal or higher than 1.4 M. 
     
     
         14 . A lithium ion cell according to  claim 13  wherein the concentration of the said LiPF 6  salt is equal or higher than 1.6 M. 
     
     
         15 . A lithium ion cell comprising at least Li 4 Ti 5 O 12  compound as a negative electrode and at least one lithiated transition metal oxide or lithiated transition metal phosphate as positive electrode, a separator and a non-aqueous electrolyte including LiPF 6  salt dissolved in a mixture of ethylene carbonate and ethyl methyl carbonate solvents and electrolyte additives wherein the concentration of the said LiPF 6  salt is equal or higher than 1.4 M and at least one of the said additives is from the family of the organic sultones. 
     
     
         16 . A lithium ion cell according to  claim 15  wherein the concentration of the said LiPF 6  salt is equal or higher than 1.6 M 
     
     
         17 . A lithium ion cell according to  claim 15  wherein the said organic sultone is propylene sultone. 
     
     
         18 . A lithium ion cell comprising at least Li 4 Ti 5 O 12  compound as a negative electrode and at least one lithiated transition metal oxide or lithiated transition metal phosphate as positive electrode, a separator and a non-aqueous electrolyte including LiPF 6  salt dissolved in a mixture of organic carbonate cyclic esters and organic carbonate linear esters and electrolyte additives wherein the ethylene carbonate is at least 50% of the total amount of cyclic esters and ethyl methyl carbonate is at least 50% of the total amount of organic carbonate linear esters and the concentration of the said LiPF 6  salt is equal or higher than 1.4 M and at least one of the said electrolyte additives is from the family of the organic sultones. 
     
     
         19 . A lithium ion cell according to  claim 18  wherein the concentration of the said LiPF 6  salt is equal or higher than 1.6 M. 
     
     
         20 . A lithium ion cell according to  claim 18  wherein the said organic sultone is 1,3-Propanesultone. 
     
     
         21 . A lithium ion cell comprising at least Li 4 Ti 5 O 12  compound as a negative electrode and lithiated transition metal oxide or lithiated transition metal phosphate as positive electrode, a separator and a non-aqueous electrolyte including LiPF 6  salt dissolved in a mixture of ethylene carbonate and ethyl methyl carbonate solvents and electrolyte additives wherein the concentration of the said LiPF 6  salt is equal or higher than 1.4 M and at least one of the said additives is from the family of the organic anhydrides. 
     
     
         22 . A lithium ion cell according to  claim 21  wherein the concentration of the said LiPF 6  salt is equal or higher than 1.6 M. 
     
     
         23 . A lithium ion cell comprising at least Li 4 Ti 5 O 12  compound as a negative electrode and at least one lithiated transition metal oxide or lithiated transition metal phosphate as positive electrode, a separator and a non-aqueous electrolyte including LiPF 6  salt dissolved in a mixture of organic carbonate cyclic esters and organic carbonate linear esters and electrolyte additives wherein the ethylene carbonate is at least 50% of the total amount of cyclic esters and ethyl methyl carbonate is at least 50% of the total amount of organic carbonate linear esters and the concentration of the said LiPF6 salt is equal or higher than 1.4 M and at least one of the said electrolyte additives is from the family of the organic anhydrides. 
     
     
         24 . A lithium ion cell according to  claim 23  wherein the concentration of the said LiPF 6  salt is equal or higher than 1.6 M. 
     
     
         25 . A lithium ion cell according to  claim 23  wherein the said organic anhydride is succinic anhydride. 
     
     
         26 . A lithium ion cell according to  claim 1  wherein the said Li 4 Ti 5 O 12  electrode is composed by Li 4 Ti 5 O 12  material having BET in the range of 4 m 2 /g to 12 m 2 /g. 
     
     
         27 . A lithium ion cell according to  claim 1  wherein the said Li 4 Ti 5 O 12  electrode is composed by Li 4 Ti 5 O 12  material having mean particle size between 4 and 20 microns. 
     
     
         28 . A lithium ion cell according to  claim 1  wherein the said Li 4 Ti 5 O 12  electrode is composed by Li 4 Ti 5 O 12  material having tap density in the range between 0.9 and 1.7 g/cc.