Cathode active material for overcharge protection in secondary lithium batteries

Abstract

A method of manufacturing a battery cathode includes forming a mixture having a lithium metal oxide and an overcharge protection additive, the overcharge protection additive having an operating voltage higher than an operating voltage of the lithium metal oxide. The lithium metal oxide is provided in an amount sufficient to provide a desired operating capacity for a lithium ion battery cell, and the overcharge protection additive has a higher operating voltage than the lithium metal oxide such that the overcharge protection additive can undergo reversible lithium removal during overcharging of the lithium ion battery cell. The method also includes contacting the mixture with a current collector.

1 . A method of employing an overcharge protection additive in a lithium ion battery cell, the lithium ion battery cell having a positive electrode comprising a mixture of a lithium metal oxide and the overcharge protection additive, the overcharge protection additive having an operating voltage higher than an operating voltage of the lithium metal oxide, the method comprising:
 operating the lithium ion battery cell at a voltage at which the overcharge protection additive is inactive, and at an operating capacity defined by the amount of the lithium metal oxide present in the positive electrode, wherein a state of charge (SOC) of the lithium ion battery cell is defined by the state of the lithium metal oxide; and   overcharging the lithium ion battery cell beyond the operating voltage of the lithium metal oxide such that the lithium ion battery cell is charged at least to 130% SOC and the overcharge protection additive of the positive electrode becomes active, the overcharging causing reversible lithium extraction from the overcharge protection additive.   
     
     
         2 . The method of  claim 1 , wherein during the overcharging the overcharge protection additive accepts surplus current and prevents sharp potential excursions in the potential of the positive electrode resulting in a plateau-like voltage curve as the lithium ion battery cell is charged beyond the capacity provided by the lithium metal oxide. 
     
     
         3 . The method of  claim 1 , comprising:
 releasing gas as a result of oxidation of the overcharge protection additive during the overcharging; and   activating a current interrupt device (CID) in the lithium ion battery cell using the released gas.   
     
     
         4 . The method of  claim 1 , wherein the lithium metal oxide is selected from the group consisting of lithium cobalt oxide, lithium manganese oxide, lithium nickel manganese cobalt oxide, lithium nickel cobalt aluminum oxide, lithium titanate, and mixtures thereof. 
     
     
         5 . The method of  claim 4 , wherein the overcharge protection additive is selected from the group consisting of a Li-rich layered oxide, a lithium oxide spinel, an olivine phosphate, and combinations thereof. 
     
     
         6 . The method of  claim 1 , wherein the overcharge protection additive comprises a material of formula xLi 2 M 1 O 3 ·(1-x)LiM 2 O 2 , wherein:
 M 1  is selected from the group consisting of Mn, Ti, and Zr; 
 M 2  is selected from the group consisting of Mn, Ni, Co, Cr, and combinations thereof; and 
 x is greater than 0 and smaller than 1. 
 
     
     
         7 . A method of manufacturing a lithium ion battery cell comprising:
 producing a cathode active material by a process comprising mixing a lithium metal oxide and an overcharge protection additive, wherein the lithium metal oxide is in an amount sufficient to provide a desired operating capacity for the lithium ion battery cell, and wherein the overcharge protection additive is in a form from which lithium ions can be reversibly extracted during overcharging of the lithium ion battery cell;   producing a positive electrode using the cathode active material;   producing an electrode assembly using a negative electrode having an anode active material, a separator, and the positive electrode;   introducing an electrolyte to the electrode assembly; and   enclosing the electrode assembly and the electrolyte with a housing.   
     
     
         8 . The method of  claim 7 , comprising forming the lithium ion battery cell up to a cutoff voltage, wherein the cutoff voltage is lower than a voltage at which the overcharge protection additive becomes active. 
     
     
         9 . The method of  claim 8 , wherein the lithium ion battery cell is formed up to the cutoff voltage such that lithium extraction during charge occurs first from the lithium metal oxide, and then from the overcharge protection additive in the event of an overcharge. 
     
     
         10 . The method of  claim 7 , wherein the lithium metal oxide is selected from the group consisting of lithium cobalt oxide, lithium manganese oxide, lithium nickel manganese cobalt oxide, lithium nickel cobalt aluminum oxide, and mixtures thereof, and the overcharge protection additive comprises a lithium-rich layered oxide or a high-voltage spinel. 
     
     
         11 . The method of  claim 7 , wherein mixing the lithium metal oxide and the overcharge protection additive comprises mixing the lithium metal oxide and the overcharge protection additive with an agitator. 
     
     
         12 . The method of  claim 7 , comprising integrating a current interrupt device (CID) in the lithium ion battery cell, wherein the CID is configured to conduct current from terminals of the lithium ion battery cell to the positive and negative electrodes of the lithium ion battery cell until a pressure in the lithium ion battery cell exceeds a threshold, the threshold being a pressure at which the CID is configured to deform and break the electrical connection between the terminals and the electrodes. 
     
     
         13 . The method of  claim 12 , wherein the overcharge protection additive is selected such that oxidation of the overcharge protection additive results in gaseous products that facilitate tripping of the CID before the lithium metal oxide or the electrolyte undergo oxidative side-reactions. 
     
     
         14 . The method of  claim 13 , wherein the lithium ion battery cell is manufactured to exclude gassing additives in the electrolyte. 
     
     
         15 . The method of  claim 7 , wherein the lithium ion battery cell is manufactured to be substantially free of overcharge protection electrolyte additives including polymeric film precursors, redox shuttles, and gassing additives. 
     
     
         16 . The method of  claim 7 , wherein introducing the electrolyte to the electrode assembly and enclosing the electrode assembly and the electrolyte with the housing comprise enclosing the electrode assembly in a battery case and injecting the electrolyte into the battery case. 
     
     
         17 . The method of  claim 7 , wherein introducing the electrolyte to the electrode assembly and enclosing the electrode assembly and the electrolyte with the housing comprise enclosing the electrode assembly in a pouch, injecting electrolyte into the pouch, and sealing the pouch. 
     
     
         18 . A method of manufacturing a battery cathode, comprising:
 forming a mixture comprising a lithium metal oxide and an overcharge protection additive, the lithium metal oxide of the mixture being in an amount sufficient to provide a desired operating capacity for a lithium ion battery cell, and the overcharge protection additive of the mixture having a higher operating voltage than the lithium metal oxide such that the overcharge protection additive can undergo reversible lithium removal during overcharging of the lithium ion battery cell; and   contacting the mixture with a current collector.   
     
     
         19 . The method of  claim 18 , wherein the lithium metal oxide is selected from the group consisting of lithium cobalt oxide, lithium manganese oxide, lithium nickel manganese cobalt oxide, lithium nickel cobalt aluminum oxide, lithium titanate, and mixtures thereof. 
     
     
         20 . The method of  claim 18 , wherein the overcharge protection additive is selected from the group consisting of a Li-rich layered oxide, a lithium oxide spinel, an olivine phosphate, and combinations thereof. 
     
     
         21 . The method of  claim 18 , wherein the overcharge protection additive comprises a material of formula xLi 2 M 1 O 3 ·(1-x)LiM 2 O 2 , wherein:
 M 1  is selected from the group consisting of Mn, Ti, and Zr; 
 M 2  is selected from the group consisting of Mn, Ni, Co, Cr, and combinations thereof; and 
 x is greater than 0 and smaller than 1. 
 
     
     
         22 . The method of  claim 18 , wherein the overcharge protection additive comprises a material of formula Li 1+y Mn 2−y O 4 , wherein y is greater than 0 and at most equal to ⅓. 
     
     
         23 . The method of  claim 18 , wherein the overcharge protection additive comprises a material of formula LiMPO 4 , wherein M is selected from the group consisting of Mn, Co, Ni, Fe, Zn, Cu, Ti, Sn, Zr, V, Al, and mixtures thereof.