Cathode materials for secondary (rechargeable) lithium batteries

Abstract

The invention relates to materials for use as electrodes in an alkali-ion secondary (rechargeable) battery, particularly a lithium-ion battery. The invention provides transition-metal compounds having the ordered-olivine, a modified olivine, or the rhombohedral NASICON structure and the polyanion (PO 4 ) 3− as at least one constituent for use as electrode material for alkali-ion rechargeable batteries.

What is claimed is:  
     
         1 . A cathode material for a rechargeable electrochemical cell, said cell also comprising an anode and an electrolyte, the cathode material comprising a compound having the formula LiMPO 4 , where M is at least one first-row transition-metal cation.  
     
     
         2 . The cathode material of  claim 1 , where M is further defmed as being selected from the group consisting of Mn, Fe, Co, and Ni.  
     
     
         3 . The cathode material of  claim 1 , where M is further defined as being a combination of cations, at least one of which is selected from the group consisting of Mn, Fe, Co and Ni.  
     
     
         4 . The cathode material of  claim 3 , where M is Fe 1-x Mn x  or Fe 1-x Ti x  and 0<x<1.  
     
     
         5 . The cathode material of  claim 2 , wherein the cathode material has the formula LiFePO 4 .  
     
     
         6 . A cathode material for a rechargeable electrochemical cell, said cell also comprising an anode and an electrolyte, the cathode material comprising a rhombohedral NASICON material having the formula Y x M 2 (PO 4 ) 3 , where M is at least one first-row transition-metal cation and 0≦x≦5 and Y is Li or Na.  
     
     
         7 . The cathode material of  claim 5 , where M is selected from the group consisting of Fe, V, Mn, and Ti.  
     
     
         8 . The cathode material of  claim 7 , wherein the cathode material has the formula Li 3+x Fe 2 (PO 4 ) 3 , where 0≦x≦2.  
     
     
         9 . The cathode material of  claim 7 , wherein the cathode material has the formula Li 3 Fe 2 (PO 4 ) 3 .  
     
     
         10 . The cathode material of  claim 7 , having the formula Li 1+x Ti 2 (PO 4 ) 3 .  
     
     
         11 . The cathode material of  claim 7 , having the formula Li 2 FeTi(PO 4 ) 3 .  
     
     
         12 . The cathode material of  claim 7 , having the formula Li x TiNb(PO 4 ) 3 , where 0≦x≦2.  
     
     
         13 . The cathode material of  claim 7 , having the formula Li 1+x FeNb(PO 4 ) 3 , where 0≦x≦2.  
     
     
         14 . The cathode material of  claim 7 , prepared by the process comprising the steps: 
 (a) preparing Na 2 Fe 2 (PO 4 ) 3 ; and    (b) contacting said Na 2 Fe 2 (PO 4 ) 3  with a molten lithium salt, such that an ionic exchange reaction occurs.    
     
     
         15 . The cathode material of  claim 7 , prepared by a direct solid state reaction.  
     
     
         16 . A cathode material for a rechargeable electrochemical cell, said cell also comprising an anode and an electrolyte, the cathode material comprising a rhombohedral NASICON material having the formula Y x M 2 (PO 4 ) y (XO 4 ) 3-y , where 0<y≦3, M is a transition-metal atom, 0≦x≦5, Y is Li or Na, and X=Si, As, or S.  
     
     
         17 . The cathode material of  claim 16 , wherein the cathode material has the formula Li 1-+x Fe 2 (SO 4 ) 2 (PO 4 ), where 0≦x≦2.  
     
     
         18 . The cathode material of  claim 17 , prepared by the process comprising the steps: 
 (a) preparing an aqueous solution comprising FeCl 3 , (NH 4 ) 2 SO 4 , and LiH 2 PO 4 ;    (b) evaporating the solution to obtain dry material; and    (c) heating the dry material to about 500° C.    
     
     
         19 . A cathode material for a rechargeable electrochemical cell also comprising an anode and an electrolyte, the cathode comprising a rhombohedral NASICON material having the formula A 3-x V 2 (PO 4 ) 3 , where A may be Li, Na or a combination thereof and 0≦x≦2.  
     
     
         20 . The cathode material of  claim 19 , wherein the cathode material has the formula 
       Li 2-x NaV 2 (PO 4 ) 3 , where 0≦x≦2.    
     
     
         21 . The cathode material of  claim 19 , prepared by the process comprising the steps: 
 (a) preparing Na 3 V 2 (PO 4 ) 3 ; and    (b) contacting said Na 3 V 2 (PO 4 ) 3  with a molten lithium salt, such that an ionic exchange reaction occurs.    
     
     
         22 . The cathode material of  claim 19 , prepared by a direct solid-state reaction.  
     
     
         23 . A cathode material for a rechargeable electrochemical cell, said cell also comprising an anode and an electrolyte, the cathode material comprising a compound having the formula: 
       Li x+y M 1-(y+d+t+q+r) D d T t Q q R r [PO 4 ] 1-(p+s+v) [SO 4 ] p [SiO 4 ] s [VO 4 ] v   where 
 M may be Fe 2+  or Mn 2+  or mixtures thereof;  
 D is a metal in the +2 oxidation state selected from the group consisting of: 
 Mg 2+ , Ni 2+ , Co 2+ , Zn 2+ , Cu 2+ , and Ti 2+ ;  
 
 T is a metal in the +3 oxidation state selected from the group consisting of: 
 Al 3+ , Ti 3+ , Cr 3+ , Fe 3+ ; Mn 3+ , Ga 3+ , Zn 2+ , and V 3+ ;  
 
 Q is a metal in the +4 oxidation state selected from the group consisting of: 
 Ti 4+ ,Ge 4+ , Sn 4+ , and V 4+ ;  
 R is a metal in the +5 oxidation state selected from the group consisting of:  
 V 5+ , Nb 5+ , and Ta 5+ ;  
 
 0≦x≦1; 
 0 ≦y, d, t, q, r, p, s, v≦1 where at least one of y, d, t, q, r, p, s, and v differ from 0 and 
   y+d+t+q+r ≦1; p+s+v ≦1;and3 +s−p=x−y−t+ 2 q+ 3 r;   
 
   where x is the degree of intercalation during operation of the electrode material, y represents the fraction of lithium ions on the initial Fe 2+  sites; d represents the fraction of divalent ions (noted as D) on the initial Fe 2+  sites; t represents the fraction of trivalent ions (noted as T) on the initial Fe 2+  sites; q represents the fraction of lo tetravalent ions (noted as Q) on the initial Fe 2+  sites; r represents the fraction of pentavalent ions (noted as R) on the initial Fe 2+  sites; p represents the fraction of hexavalent suflur (as discrete SO 4   2−  tetrahedra) on the initial P 5+  sites; s represents the fraction of tetravalent silicon (as discrete SiO 4   2−  tetrahedra) on the initial P 5+  sites; and v represents the fraction of pentavalent vanadium ions on the initial P 5+  sites, and M, D, T, Q and R reside in octahedral sites.    
     
     
         24 . A secondary battery comprising an anode, a cathode and an electrolyte, said cathode comprising an ordered olivine compound having the formula LiMPO 4 , where M is at least one first-row transition-metal cation.  
     
     
         25 . The battery of  claim 23 , where M is further defined as being selected from the group consisting of Mn, Fe, Co, and Ni.  
     
     
         26 . The battery of  claim 23 , where M is further defined as being a combination of cations, at least one of said cations being selected from the group consisting of Mn, Fe, Co, and Ni.  
     
     
         27 . The battery of  claim 25 , wherein M is Fe 1-x Mn x  or Fe 1-x Ti x , where 0≦x≦1.  
     
     
         28 . A secondary battery comprising an anode, a cathode and an electrolyte, said cathode comprising a modified olivine compound as set forth in  claim 23 .  
     
     
         29 . The battery of  claim 28 , wherein the anode comprises a compound selected from the group consisting of a metallic lithium, a lithium alloy, a lithium-carbon intercalation compound, a lithium-transition metal mixed nitride of antifluorite and a lithium-titanium spinel having the formula Li 1+x+z Ti 2-x O 4  where 0≦x≦⅓ and 0≦z≦1−2x.  
     
     
         30 . The battery of  claim 29 , wherein said cathode further comprises a conductive additive.  
     
     
         31 . The battery of  claim 30 , wherein said conductive additive is carbon.  
     
     
         32 . The battery of  claim 29 , wherein said cathode further comprises an intercalation material with fast diffusion kinetics.  
     
     
         33 . The battery of  claim 32 , wherein said intercalation material is selected from the group consisting of a lamellar dichalcognenide, a vanadium oxide having the formula VO x  where 2.1≦x≦2.5, and a NASICON-related material.  
     
     
         34 . The battery of  claim 33 , wherein said NASICON-related material is selected from the group consisting of Li 3 Fe 2 (PO 4 ) 3  and Li 3-x Fe 2-x Ti x (PO 4 ) 3 .  
     
     
         35 . The battery of  claim 29 , wherein said cathode further comprises a polymeric binder.  
     
     
         36 . The battery of  claim 35 , wherein said polymeric binder is selected from the group consisting of a homopolymer of tetrafluoroethylene, a copolymer of tetrafluoroethylene, an ethylene-propylene-diene terpolymer, a polyether, a polyester, a methylmethacrylate-based polymer, an acrylonitrile-based polymer, and a vinylidene fluoride-based polymer.  
     
     
         37 . The battery of  claim 36 , wherein said polymeric binder is a polyether.  
     
     
         38 . The battery of  claim 37 , wherein said polyether further comprises a salt comprising Li +  cations.  
     
     
         39 . The battery of  claim 38 , wherein said polyether is crosslinked.  
     
     
         40 . The battery of  claim 35 , wherein said polymeric binder has an ionic conductivity of between about 10 −7  and about 10 −2  (Scm −1 ).  
     
     
         41 . The battery of  claim 38 , wherein said polymeric binder is swollen by an aprotic solvent.  
     
     
         42 . The battery of  claim 41 , wherein said aprotic solvent is selected from the group consisting of: ethylene carbonate, propylene carbonate, dimethylcarbonate, diethylcarbonate, methyl-ethylcarbonate, γ-butyrolactone, a tetraalkylsulfamide, a dialkylether of an ethylene glycol having a molecular weight ≦2000.  
     
     
         43 . The battery of  claim 42 , wherein said aprotic solvent is a dialkylether of an ethylene glycol having a molecular weight ≦2000.  
     
     
         44 . The battery of  claim 43 , wherein said dialkylether comprises a mono-ethylene glycol.  
     
     
         45 . The battery of  claim 43 , wherein said dialkylether comprises a di-ethylene glycol.  
     
     
         46 . The battery of  claim 43 , wherein said dialkylether comprises a tri-ethylene glycol.  
     
     
         47 . The battery of  claim 43 , wherein said dialkylether comprises a tetra-ethylene glycol.  
     
     
         48 . The battery of  claim 43 , wherein said dialkylether comprises an oligo-ethylene glycol higher than a tetra-ethylene glycol.  
     
     
         49 . The battery of  claim 42 , wherein said dialkylether comprises a mixture of mono-, di-, tri-, tetra-, and higher oligo-ethylene glycols.  
     
     
         50 . A secondary battery comprising an anode, a cathode and an electrolyte, said cathode comprising a rhombohedral NASICON material having the formula Y x M 2 (PO 4 ) 3 , where M is at least one first-row transition-metal cation and 0≦x≦5 and Y is Li or Na, other than Li 2+x FeTi(PO 4 ) 3 .  
     
     
         51 . The battery of  claim 27 , where M is 'selected from the group consisting of Fe, V, Mn, and Ti.  
     
     
         52 . The battery of  claim 28 , wherein the cathode material has the formula Li 3+x Fe 2 (PO 4 ) 3 , where 0≦x≦2.  
     
     
         53 . The battery of  claim 29 , wherein the cathode material has the formula Li 3 Fe 2 (PO 4 ) 3 .  
     
     
         54 . The battery of  claim 28 , wherein the cathode material has the formula Li 2 FeTi(PO 4 ) 3 .  
     
     
         55 . The battery of  claim 28 , wherein the cathode material has the formula Li x TiNb(PO 4 ) 3 , where 0≦x≦2.  
     
     
         56 . The battery of  claim 28 , wherein the cathode material has the formula Li 1+x FeNb(PO 4 ) 3 , 0≦x≦2.  
     
     
         57 . A secondary battery comprising an anode, a cathode and an electrolyte, said cathode, comprising a rhombohedral NASICON material having the formula Y x M 2 (PO 4 ) y (XO 4 ) 3-y , where 0≦y≦3, M is a transition-metal atom, 0≦x≦5, Y is Li or Na, and X=Si, As, or S.  
     
     
         58 . The battery of  claim 34 , wherein said cathode material has the formula 
       Li 1+ Fe 2 (PO 4 )(SO 4 ) 2 , where 0≦x≦2.    
     
     
         59 . A secondary battery comprising an anode, a cathode and an electrolyte, said cathode comprising a rhombohedral NASICON material having the formula A 3-x V 2 (PO 4 ) 3 , where A may be Li, Na or a combination thereof and 0≦x≦2.  
     
     
         60 . The battery of  claim 36 , wherein the cathode material has the formula 
       Li 2+x NaV 2 (PO 4 ) 3 , where 0≦x≦2.    
     
     
         61 . A variable optical transmission device comprising transparent semi-conductor coated glass or plastic, and including at least one positive electrode and at least one negative electrode separated by a solid or gel electrolyte, wherein at least one electrode comprises a modified olivine compound as set forth in  claim 23.