Positive active material for rechargeable lithium-sulfur batteries and method of preparing same

Abstract

A positive active material for a rechargeable lithium-sulfur battery includes a core of a sulfur compound and a surface-passivation layer formed on the core. The surface-passivation layer is made of a coating-element-included compound selected from the group consisting of a coating-element-included hydroxide, a coating-element-included oxyhydroxide, a coating-element-included oxycarbonate, a coating-element-included hydroxycarbonate, a mixture thereof.

1 . A method of preparing a positive active material comprising: 
 coating a sulfur compound with a coating liquid comprising a coating material source; and    drying the coated sulfur compound to form a surface-passivation layer on the sulfur compound.    
     
     
         2 . The method according to  claim 1 , further comprising adding the coating material source to an organic solvent to prepare the coating liquid, the coating material source comprising a coating element, an alkoxide of the coating element, a salt of the coating element, or an oxide of the coating element.  
     
     
         3 . The method according to  claim 1 , further comprising refluxing a mixture of the coating material source and an organic solvent to prepare the coating liquid, the coating material source comprising a coating element, an alkoxide of the coating element, a salt of the coating element, or an oxide of the coating element.  
     
     
         4 . The method according to  claim 1 , further comprising adding a salt of a coating element and an oxide of the coating element to water to prepare the coating liquid.  
     
     
         5 . The method according to  claim 1 , further comprising refluxing a mixture of water and a coating material source comprising a salt of a coating element or an oxide of the coating element to prepare the coating liquid.  
     
     
         6 . The method according to  claim 1 , wherein the coating liquid comprises a coating element that is soluble in an organic solvent or water.  
     
     
         7 . The method according to  claim 6 , wherein the coating element is selected from the group consisting of Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, and a mixture thereof.  
     
     
         8 . The method according to  claim 7 , wherein the coating element is selected from the group consisting of Al, Si, B, and a mixture thereof.  
     
     
         9 . The method according to  claim 8 , wherein the coating element is B.  
     
     
         10 . The method according to  claim 1 , wherein the coating material source is present at or between 0.1 and 50 wt % based on the weight of the coating liquid.  
     
     
         11 . The method according to  claim 10 , wherein the coating material source is present at or between 5 and 30 wt % based on the weight of the coating liquid.  
     
     
         12 . The method according to  claim 1 , wherein said coating the sulfur compound and said drying the coated sulfur compound are is performed by a one-shot process comprising introducing the sulfur compound and the coating liquid into a mixer, and heating the mixer as the sulfur compound and the coating liquid are agitated.  
     
     
         13 . The method according to  claim 12 , wherein the one-shot process further comprises injecting a blowing gas into the mixer or maintaining the mixer under a vacuum during the agitation and/or heating.  
     
     
         14 . A method of preparing a positive active material for a rechargeable lithium-sulfur battery, comprising: 
 coating a sulfur compound with a coating liquid including a coating material source comprising B; and    drying the coated sulfur compound to form a surface-passivation layer including B on the sulfur compound.    
     
     
         15 . The method according to  claim 14 , wherein the coating material source comprises HB(OH) 2 , B 2 O 3 , or H 3 BO 3 , the method further comprising adding HB(OH) 2 , B 2 O 3 , or H 3 BO 3  to an organic solvent to prepare the coating liquid.  
     
     
         16 . The method according to  claim 14 , further comprising refluxing a mixture of the coating material source and an organic solvent to prepare the coating liquid, the coating material source comprising HB(OH) 2 , B 2 O 3 , or H 3 BO 3 .  
     
     
         17 . The method according to  claim 14 , further comprising adding B 2 O 3  to water to prepare the coating liquid.  
     
     
         18 . The method according to  claim 14 , further comprising refluxing a mixture of B 2 O 3  and water to prepare the coating liquid.  
     
     
         19 . The method according to  claim 14 , wherein the coating material source is present at or between 0.1 and 50 wt % based on the weight of the coating liquid.  
     
     
         20 . The method according to  claim 19 , wherein the coating material source is present at or between 5 and 30 wt % based on the weight of the coating liquid.  
     
     
         21 . The method according to  claim 14 , wherein said coating the sulfur compound and said drying the coated sulfur compound are performed by a one-shot process comprising introducing the sulfur compound and the coating liquid into a mixer and heating the mixer while agitating the sulfur compound and the coating liquid.  
     
     
         22 . The method according to  claim 21 , wherein the the one shot process further comprises injecting a blowing gas into the mixer or maintaining the mixer under a vacuum while agitating and/or heating the sulfur compound and the coating liquid.  
     
     
         23 . The method according to  claim 12 , further comprising premixing the sulfur compound and the coating liquid prior to performing the one-shot process.  
     
     
         24 . The method according to  claim 12 , wherein the heating the mixer comprises heating the sulfur compound and the coating liquid at a temperature at or between roughly 50° C. and 100° C.