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 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 defined 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 x (PO 4 ) 3 . 
     
     
         11 . The cathode material of  claim 7 , having it formula Li 3 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 y 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 ) 3 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 x (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 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 3+ , 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 wherein 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; and 
 3+s·p=x−y+t+2q+3r; 
 
 
       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 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 sulfur (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 , where 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 lithium-titanium spinel having the formula Li 1+x Ti 2−x O 4  where 0≦x≦1/3 and 0≦z≦1−2x. 
     
     
         30 . The battery of  claim 29 , wherein said cathode further comprises a conducive 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 dichalcogenide, 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 diallylether of an ethylene glycol having a molecular weight ≦2000. 
     
     
         43 . The battery of  claim 42 , wherein said aprotic solvent is a diallylether of an ethylene glycol having a molecular weight ≦2000. 
     
     
         44 . The battery of  claim 43 , wherein said diallylether comprises a mono-ethylene glycol. 
     
     
         45 . The battery of  claim 43 , wherein said diallylether comprises a di-ethylene glycol. 
     
     
         46 . The battery of  claim 43 , wherein said diallylether comprise a tri-ethylene glycol. 
     
     
         47 . The battery of  claim 43 , wherein said diallylether comprises a tetra-ethylene glycol. 
     
     
         48 . The battery of  claim 43 , wherein said diallylether comprises an oligo-ethylene glycol higher than a tetra-ethylene glycol. 
     
     
         49 . The battery of  claim 42 , wherein said diallylether 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 comprising of Fe, V, Mn, and Ti. 
     
     
         52 . The battery of  claim 28 , wherein the cathode material has the formula Li 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 y 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+x  Fe 2 (PO 4 )(SO 4 ) 2 , wherein 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 ) x , 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 3−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 .