WO2010051746A1 - Cathode active material, lithium ion secondary battery and rechargable battery having the same - Google Patents

Cathode active material, lithium ion secondary battery and rechargable battery having the same Download PDF

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Publication number
WO2010051746A1
WO2010051746A1 PCT/CN2009/074769 CN2009074769W WO2010051746A1 WO 2010051746 A1 WO2010051746 A1 WO 2010051746A1 CN 2009074769 W CN2009074769 W CN 2009074769W WO 2010051746 A1 WO2010051746 A1 WO 2010051746A1
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active material
cathode active
cathode
lifepo
material according
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PCT/CN2009/074769
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French (fr)
Inventor
Ye Tian
Tangli Cheng
Xiaobing Xi
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BYD Co Ltd
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BYD Co Ltd
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Priority claimed from US12/316,165 external-priority patent/US8062559B2/en
Priority claimed from US12/316,180 external-priority patent/US8057711B2/en
Priority claimed from CN2008101892388A external-priority patent/CN101478042B/en
Priority claimed from CN200810189233A external-priority patent/CN101740749A/en
Priority claimed from CN2008101892354A external-priority patent/CN101740750B/en
Application filed by BYD Co Ltd filed Critical BYD Co Ltd
Publication of WO2010051746A1 publication Critical patent/WO2010051746A1/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/364—Composites as mixtures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/581—Chalcogenides or intercalation compounds thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/581—Chalcogenides or intercalation compounds thereof
    • H01M4/5815—Sulfides
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to rechargeable batteries, more specifically, to a composite compound having a mixed crystalline structure that can be used as a cathode material for lithium secondary batteries.
  • Lithium secondary batteries are widely used in various devices such laptop computers, cameras, camcorders, PDAs, cell phones, iPods and other portable electronic devices. These batteries are also growing in popularity for defense, automotive and aerospace applications because of high energy density thereof.
  • a cathode material for lithium battery is disclosed in U.S. Pat. Application No. 2007/0207385A1 including a first compound and a second compound.
  • the first compound has a formula of A 3x Ml 2y (P ⁇ 4 ) 3 .
  • the second compound is at least one compound selected from the group consisting of SiC, BN and metal oxide having a formula of M2 a O b , coating on the first compound.
  • A is at least one element selected from the group consisting of Groups IA, HA and IIIA.
  • Each of the Ml and M2 is selected from at least one element from Groups HA, IIIA, IVA and VA and transition metal elements, respectively. More specifically, each of the Ml and M2 is at least one element selected from the group consisting of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Be, Mg, Ca, Sr, B, Al, Sn, Ga, In, Si and Ge. And the material of LiFePO 4 /ZnO/C, LiFeP0 4 /ZnA10 2 /C, LiFePO 4 /CuO/C and LiFePO 4 /ZnAlO/C are disclosed in the examples of the application.
  • the present invention needs to provide a cathode active material, which has a novel crystal structure that may enhance electrical properties of the battery significantly. Further, the present invention needs to provide a lithium ion secondary battery having a cathode made therefrom.
  • a cathode active material comprising a mixed crystal.
  • the mixed crystal may have: a first crystalline substance having at least one member with one of following general formulas Li x M' y (X0 4 ) z , LiM 5 XO 5 , LiM 5 XO 6 and LiM 5 X 2 O 7 in which 0 ⁇ x/z ⁇ l and 0 ⁇ y/z ⁇ l .l, the M 5 may be an element selected from a group consisting of Na, Mn, Fe, Co, Ni, Ti, V, Y, Mg, Ca, Nb and Zn, and the X may be an element selected from a group consisting of P, S, As, Mo and W; and a second crystalline substance having one or more members with a general formula of A a M b N c O d , in which A, M and N may be different metals selected from groups HA, IIIA, IVA, VA, IB, HB, IIIB, IVB,
  • a lithium ion secondary battery in which the battery may comprise a battery shell, electrodes and electrolyte with the electrodes and electrolyte being sealed within the battery shell, the electrodes having wounded or stacked cathode, anode and divider film.
  • the cathode may further comprise the cathode active material as described above.
  • the present invention for the first time, successfully provides a lithium metal intercalation compound with a mixed crystal.
  • the novel cathode material disclosed in the present invention significantly improves electrical properties of lithium batteries.
  • FIG. 1 shows a XRD pattern of a composite compound according to Example i
  • Fig. 2 shows a XRD pattern of a composite compound according to Example 2
  • Fig. 3 shows a XRD pattern of a composite compound according to Example 3.
  • Fig. 4 shows a XRD pattern of a composite compound according to Example 4.
  • Fig. 5 shows a XRD pattern of a composite compound according to Example 5; and Fig. 6 shows a XRD pattern of a composite compound according to Example
  • a mixed crystal can be referred to as a solid solution. It is a crystal containing a second constituent, which fits into and is distributed in the lattice of the host crystal.
  • IUPAC Compendium of Chemical Terminology 2nd is a crystal containing a second constituent, which fits into and is distributed in the lattice of the host crystal.
  • a cathode active material can be provided having a mixed crystal structure.
  • the mixed crystal structure may have: a first crystalline substance having one or more members with the general formulas Li x M' y (X0 4 ) z , LiM 5 XO 5 , LiM 5 XO 6 and LiM 5 X 2 O 7 , in which:
  • M 5 may be an element selected from the group of Na, Mn, Fe, Co, Ni, Ti, V, Y, Mg, Ca, Nb and Zn;
  • X may be an element selected from the group of P, S, As, Mo and W; and a second crystalline substance having one or more members with the general formula A a MbN c Od, in which:
  • A, M and N are different metals selected from groups HA, IIIA, IVA, VA, IB, HB, IIIB, IVB, VB, VIB, VIIB and VIII in the periodic table; and
  • the cathode active material may have electrical conductivity of about 0.01 to about 10 S/cm at about 25 0 C.
  • the mixed crystal structure can be formed by sintering two or more compounds, the intermediary mixture having oxygen vacancies or metallic crystalline structures. The two or more compounds do not exhibit any major chemical reactions when mixed together. However, upon sintering, a large number of crystalline defects can be formed, thereby altering the electronic states of the compounds creating a large number of oxygen vacancies. These oxygen vacancies provide the needed carriers, thus greatly enhancing the electrical conductivity of the mixed crystal.
  • the cathode active material can achieve electrical conductivity of about 0.1 to 2S/cm at about 25°C with a Simens per centimeter, which is larger than traditional lithium iron phosphate cathode active materials.
  • the first crystalline substance and the second crystalline substance may have a molar ratio of about 1 to 0.01-0.05.
  • the first crystalline substance can have a mixed crystalline structure with the general formula Li x M' y (X ⁇ 4 ) z including one or more members selected from the group consisting of LiFeO 4 , LiMnPO 4 and LiCoPO 4 etc.
  • single-crystalline structures including Li 3 Fe 2 (PO 4 ) S , LiTi 2 (PO 4 ) 3 , Li 3 V 2 (PO 4 ) 3 and Li 2 Na V 2 (PO 4 ) 3 may be incorporated.
  • the first crystalline substance can be LiTiPOs.
  • the first crystalline substance can include LiVMoO 6 and LiVWO 6 respectively.
  • the first crystalline substance can include LiVP 2 O 7 and LiFeAs 2 O 7 .
  • M' may include element Fe and one or more members selected form the group consisting of Mn, Co, Ni, Ti, Y, Mg, Ca and Zn, and the amount of Fe is from 90 % to 100 % by molar.
  • the first crystalline substance can include one or more members selected from LiFePO 4 , Li 0 99 Y 0 01 FePO 4 and LiR 1 Fe I-1 PO 4 , in which 0 ⁇ i ⁇ 0.1, R may be one or more members selected from elements Mn, Co, Ni, Ti, Mg, Ca and Zn.
  • the second crystalline substance can include one or more members selected from the group consisting of Bi 4 Ti 3 Oi 2 , CuNb 2 Oo, MnTaO 4 , FeWO 4 , ZnZrNb 2 Og, NiNb 2 O 6 , NiZrNb 2 O 8 , FeTiNb 2 O 8 , MnTiNb 2 O 8 , MgSnNb 2 O 8 , ZnTa 2 O 6 , Cu 0 S 5 Zn 0 1 5Nb 2 O 6 , YBa 3 Ti 2 O 8 5, Zr 0 75 Ti 0 75 Sn 0 5O 4 , HfTiO 4 and MgNb 2 O 6 .
  • the mixed crystal structure can further include carbon, which is about 1-5 % of the mixed crystal structure by weight. The carbon can further enhance the electrical conductivity of the mixed crystal.
  • a method of preparing a cathode active material for lithium secondary batteries comprising the following steps:
  • A, M and N are different metals selected from groups HA, IIIA, IVA, VA, IB, HB, IIIB, IVB, VB, VIB, VIIB and VIII in the periodic table; 0 ⁇ a ⁇ 6, 0 ⁇ b ⁇ 6, 0 ⁇ c ⁇ 6 and 0 ⁇ d ⁇ 12; a and b cannot both be O at the same time; and
  • the first material and the second material may have a molar ratio of about 1 to 0.01-0.05.
  • the second material can be formed by heating oxide compounds of A, M and N with a molar ratio of a : b : c at about 400 to 1000 0 C for about 8 to 15 hours.
  • the sintered product can be measured with a Rigaku D/MAX-2200/PC x-ray diffraction (XRD) instrument to acquire an XRD pattern thereof, which can subsequently be compared with known chemical standards provided by the system.
  • the oxide compound or oxygen-containing compound of A can be oxides of A and/or sintered products of oxides of A and other compounds, the oxides of A and other compounds include hydroxides of A, carbonates of A, and bicarbonates of A.
  • the oxide compound or oxygen-containing compound of M can be oxides of M and/or sintered products of oxides of M and other compounds, the oxides of M and other compounds include hydroxides of M, carbonates of M, and bicarbonates of M.
  • the oxide compound or oxygen-containing compound of N can be oxides of N and/or sintered products of oxides of N and other compounds, the oxides of N and other compounds include hydroxides of N, carbonates of N, and bicarbonates of N.
  • the first material may include one or more members selected from the group consisting of LiFePO 4 , LiMnPO 4 , LiCoPO 4 , Li 3 Fe 2 (PO 4 ) S , LiTi 2 (PO 4 ),, Li 3 V 2 (PO 4 ),, Li 2 NaV 2 (PO 4 ),, Li 0 99 Yo O iFePO 4 , LiR 1 Fe 1-1 PO 4 , LiTiPO 5 , LiVMoO 6 , LiVWO 6 , LiVP 2 O 7 and LiFeAs 2 O 7 in which 0 ⁇ i ⁇ 0.1, R is one or more members selected from elements Mn, Co, Ni, Ti, Mg, Ca and Zn.
  • the first material may include one or more members selected from LiFePO 4 , Li 0 99 Y 0 0 1 FePO 4 and LiR 1 Fe I-1 PO 4 .
  • the second material can include one or more members selected from the group consisting of Bi 4 Ti 3 Oi 2 , CuNb 2 O 6 , MnTaO 4 , FeWO 4 , ZnZrNb 2 O 8 , NiNb 2 O 6 , NiZrNb 2 O 8 , FeTiNb 2 O 8 , MnTiNb 2 O 8 , MgSnNb 2 O 8 , ZnTa 2 O 6 , Cu 0 85 Zn 0 I5 Nb 2 O 6 , YBa 3 Ti 2 O 8 5 , Zr 0 75 Ti 0 75 Sn 0 5 O 4 , HfTiO 4 and MgNb 2 O 6 .
  • the method may further comprise sintering a carbon additive into the two crystalline substances, the carbon additive capable of providing the mixed crystal with about 1-5 % of carbon by weight.
  • the carbon additive includes one or more members selected from the group consisting of carbon black, acetylene black, graphite, glucose, sucrose, citric acid, starch, dextrin, polyethylene glycol, and other organic and inorganic sources.
  • the examples are for illustration purpose rather than for limitation. A person skilled in the art can use equivalents thereof to achieve the same as described herein.
  • a heating rate of the sintering step ranges from 5 to 20 0 C per minute, a sintering temperature thereof from 500 to 800 0 C, and a sintering time thereof from 5 to 32 hours.
  • the sintering atmosphere is chose according the selected materials. For example, when the first or second material is easily oxidized, the sintering atmosphere may be inert atmosphere or reduction atmosphere; and when the first or second material is not easily oxidized, the sintering atmosphere may be any atmosphere.
  • a lithium ion secondary battery having a battery shell, electrodes and electrolyte, the electrodes and electrolyte being sealed within the battery shell, the electrodes having wounded or stacked cathode, anode and divider film, the cathode further including the cathode active materials described above.
  • the cathode may include cathode components such as the cathode active materials described above with adhesives.
  • the adhesives can be hydrophobic or hydrophilic binding additives without any specific binder ratio restrictions.
  • the hydrophilic to hydrophobic adhesive binder can have weight ratios of about 0.3 : 1 to about 1 : 1.
  • the adhesive can be solid, aqueous or as an emulsion.
  • the concentration can be adjusted accordingly based on methods of preparing the cathode, anode and the slurry viscosity and coating.
  • the hydrophilic adhesive solution has a concentration of about 0.5 to 4 weight percent while the hydrophobic latex binder has a concentration of about 10 to 80 weight percent.
  • Hydrophobic adhesives can include PTFE, styrene butadiene rubber, or mixtures thereof.
  • Hydrophilic adhesives can include HPMC, CMC, hydroxyethyl cellulose, polyvinyl alcohol, or mixtures thereof.
  • the binder content can be about 0.01 to 8 % by weight of the total cathode active material.
  • conductive agents may be incorporated or added in the cathode active material, the conductive agents include, but without limitation, graphite, carbon fiber, carbon black, metal powders and fibers as well as any suitable material understood by one skilled in the art.
  • the conductive agent can be about
  • the method of preparing the cathode includes using solvents to dissolve the cathode active material and mixing with adhesives and conductive agents to form a cathode slurry.
  • the cathode slurry can be applied onto cathode collectors, dried, rolled or compressed, and sliced into pieces to produce the cathode. In one example, the slurry can be dried at about 100 to 150 0 C for about 2 to 10 hours.
  • the cathode collectors include aluminum foil, copper foil, nickel-plated steel or punched stainless steel.
  • the types of solvent to use include N-methyl pyrrolidone (NMP), dimethylformamide (DMF), diethyl formamide (DEF), dimethyl sulfoxide (DMSO), tetrahydrofuran (THF), water, alcohol and mixtures thereof.
  • NMP N-methyl pyrrolidone
  • DMF dimethylformamide
  • DEF diethyl formamide
  • DMSO dimethyl sulfoxide
  • THF tetrahydrofuran
  • water alcohol and mixtures thereof.
  • the amount of solvent to use can be adjusted accordingly to provide the proper slurry coating and viscosity. In one instance, the amount of solvent can be about 40 to 90 % by weight of the cathode active material.
  • the method of preparing the cathode and types of solvents, adhesives, conductive agents and cathode collectors can also incorporate other techniques understood by one skilled in the art.
  • the lithium secondary battery includes a battery shell, electrodes and electrolyte, the electrodes and electrolyte capable of being sealed within the battery shell.
  • the electrodes may include wounded or stacked cathode, anode and divider film with the cathode utilizing the cathode active material of the presently disclosed embodiments.
  • the divider film can be situated between the cathode and anode for preventing electrical shortcuts and for maintaining the electrolytic solution.
  • the divider film can include any membrane including, but without limitation, micro-porous membrane polyolefin, polyethylene fibers, ultra-fine glass fibers and fiber paper.
  • the anode can incorporate any anode active materials and known methods of forming such materials as known in the arts.
  • the anode active material can be provided in slurry form and coated onto anode collectors similar to the cathode collectors above.
  • the anode active material may include carbon additives such as non-carbon graphite, graphite, and polymers having undergone high-temperature carbon oxidation.
  • the carbon additive can also include pyrolytic coal, coke, organic polymer sintered materials and activated carbons.
  • the organic polymer sintered materials include phenolic resin, epoxy resin, and carbonized products obtained by sintering.
  • Adhesives can utilize traditional adhesives for lithium secondary batteries including polyvinyl alcohol, PTFE, carboxymethyl cellulose (CMC), hydroxymethyl cellulose (HMC), and styrene butadiene rubber (SBR).
  • the adhesive binder can be about 0.5 to 8 weight percent of the total anode active material.
  • the anode active material can further include conductive agents, the conductive agent capable of increasing electrical conductivity and reducing internal resistance of the battery.
  • the conductive agent may include, but without limitation to, carbon black, nickel powder and copper powder etc. Other conductive agents known by one skilled in the art may also be utilized and can be about 0.1 to 12 weight percent of the anode active material.
  • the method of preparing the anode may include: using solvents to dissolve the anode active material and mixing with adhesives and conductive agents to form anode slurry.
  • the anode slurry can be applied onto the anode collectors similar to that of the cathode slurry described above, dried, rolled or compressed, and sliced into pieces to produce the anode.
  • the slurry can be dried at about 100 to 150 0 C for about 2 to 10 hours.
  • the types of solvent for dissolving the anode active material include N-methyl pyrrolidone (NMP), dimethylformamide (DMF), diethyl formamide (DEF), dimethyl sulfoxide (DMSO), tetrahydrofuran (THF), water, alcohol and mixtures thereof.
  • NMP N-methyl pyrrolidone
  • DMF dimethylformamide
  • DEF diethyl formamide
  • DMSO dimethyl sulfoxide
  • THF tetrahydrofuran
  • water alcohol and mixtures thereof.
  • the amount and concentration of solvents to use can be adjusted accordingly to provide the proper slurry coating and viscosity.
  • the amount of anode slurry applied to the anode collector can be about 40 to 90 weight percent of the anode active material.
  • the electrolyte for the lithium secondary battery can be a non-aqueous electrolyte, which can be formed by dissolving lithium salt in a non-aqueous solvent.
  • the lithium salt electrolyte can include one or more members selected from lithium hexafluorophosphate (LiPF 6 ), lithium perchlorate (LiClO 4 ), lithium tetrafluoroborate (LiBF 4 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium hexafluorosilicate (LiSiF 6 ), lithium tetraphenylborate (LiB(C 6 H 5 ) 4 ), lithium chloride (LiCl), lithium bromide (LiBr), lithium aluminum tetrachloride (LiAlCl 4 ), LiC(S ⁇ 2 CF 3 ) 3 , LiCH 3 SO 3 , and LiN(SO 2 CFs) 2 .
  • the non-aqueous solvent can be chain ester and ester ring mixed solution, the chain ester being one or more members of dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC), methylpropyl carbonate (MPC), dimethylpropyl carbonate (DPC) and other fluoride or sulfur-containing unsaturated key chain organic esters, with the ester ring being one or more members of ethylene carbonate (EC), propylene carbonate (PC), vinylene carbonate (VC), gamma-butyrolactone ( ⁇ -BL), sodium fluoride and other lactone-containing or unsaturated organic ester rings.
  • the lithium salt electrolyte has a concentration of about 0.1 to 2 mole per liter.
  • the presently disclosed lithium secondary batteries can be provided by processes known by one skilled in the art.
  • the preparation method may include winding or stacking cathode, anode and divider films into the battery core, and placing the battery core into the battery shell, adding the electrolyte, and sealing the battery accordingly.
  • the winding, stacking and sealing of the batteries can utilize traditional techniques as understood by one skilled in the art.
  • other known steps of manufacturing the lithium secondary battery can be incorporated.
  • EXAMPLE 1 Firstly, Mix MnCO 3 , TiO 2 and Nb 2 Os with a molar ratio of 1 : 1 : 1, grind the mixture in a ball mill for 5 hours, heat in a nitrogen atmosphere at 10 0 C per minute to 500 0 C and continue sintering the product for 10 hours. With a Rigaku D/MAX-2200/PC, an XRD pattern is obtained on the resulting product. In comparison with the standard XRD pattern for MnTiNb 2 Og, it is determined that the sintered product is MnTiNb 2 Os.
  • the LiFePO 4 can be prepared by mixing lithium carbonate, ferrous oxalate, and ammonium dihydrogen phosphate in a Li : Fe : P molar ratio of 1 : 1 : 1.
  • the LiFePO 4 can be prepared by other lithium, iron and phosphate sources or by a third party.
  • the LiFePO 4 can be prepared by mixing lithium oxalate, iron oxide and diammonium hydrogen phosphate in a Li : Fe : P molar ratio of 0.95 : 1 : 1, which can be added to the ZnTa 2 Oo at a diammonium hydrogen phosphate to ZnTa 2 Oo molar ratio of 1 : 0.03 (taking into account the phosphorous components in the mixture).
  • the LiFePO 4 can be prepared by other lithium, iron and phosphate sources or by a third party.
  • the LiFePO 4 can be prepared by mixing lithium hydroxide, ferrous carbonate and phosphoric acid in a Li : Fe : P molar ratio of 1.05 : 1 :1.05, which can be added to the YBa 3 Ti 2 Og 5 at a phosphoric acid to YBa 3 Ti 2 Og S molar ratio of 1 : 0.02 (taking into account the phosphorous components in the mixture).
  • the LiFePO 4 can be prepared by other lithium, iron and phosphate sources or by a third party.
  • EXAMPLE 4 Mix CuO, ZnO and Nb 2 O 5 with a molar ratio of 0.85 : 0.15 : 1, grind the mixture in a ball mill for 5 hours, heat in a nitrogen atmosphere at a heating rate of 7 0 C per minute to 1000 0 C and continue sintering the product for 15 hours. With the Rigaku D/MAX-2200/PC, an XRD pattern can be carried out on the resulting product. And it is determined that the sintered product is Cuo 85 Zn 0 15 Nb 2 Oo in comparison with the standard XRD pattern of Cuo 85 Zn 0 15 Nb 2 Oo.
  • Example 1 The remaining steps incorporate those used in Example 1 , with the difference being that the Cuo 85Zn 0 15Nb 2 Oo substitutes the MnTiNb 2 Os to provide a LiFePO 4 / Cuo 85Zn 0 15Nb 2 Oo / C mixed crystal cathode active material.
  • the remaining steps are the same as those used in Example 1, with the difference being that the Zr 0 7S Ti 0 7S Sn 0 S O 4 substitutes the MnTiNb 2 Og to provide a LiFePO 4 / Zr 0 75 Ti 0 75 Sn 0 5 O 4 / C mixed crystal cathode active material.
  • the remaining steps are the same as those used in Example 1, with the difference being that the ZnAlO 2 substitutes the MnTiNb 2 Og to provide a LiFePO 4 / ZnAlO 2 / C mixed crystal cathode active material.
  • LiMn 0 02 Fe 0 98 PO 4 a mixture Li 2 CO 3 , FeC 2 O 4 -2H 2 O, NH 4 H 2 PO 4 and MnCO 3 in a molar ratio to the stoichiometry of LiMn 0 02 Fe 0 9 sPO 4 . Grind the mixture in a ball mill with ethanol for 5 hours, remove and dry at room temperature.
  • LiMg 0 03 Fe 0 97 PO 4 a mixture Li 2 CO 3 , FeC 2 O 4 -2H 2 O, NH 4 H 2 PO 4 and MgO in a molar ratio to the stoichiometry of LiMg 0 03 Fe 0 97 PO 4 . Grind the mixture in a ball mill with ethanol for 5 hours, remove and dry at room temperature.
  • LiZn 0 07 Fe 0 93 PO 4 a mixture Li 2 CO 3 , FeC 2 O 4 -2H 2 O, NH 4 H 2 PO 4 and ZnCO 3 in a molar ratio to the stoichiometry Of LiZn 0 07 Fe 0 93 PO 4 . Grind the mixture in a ball mill with ethanol for 5 hours, remove and dry at room temperature.
  • Example B of U.S. Patent Application No. 2007/0207385 provides a cathode material with LiFePO 4 to ZnAlO 2 with a molar ratio of 1 : 0.04 and carbon additive to provide a total carbon content of 5 % by weight in the final product.
  • the ZnAlO 2 and carbon additive are coated on the exterior surfaces of the LiFePO 4 to provide a cathode active material having LiFePO 4 / ZnAlO 2 / C.
  • the cathode active materials of the present embodiments can achieve electrical conductivity up to 1.8 S / cm measured by a Siemens per Centimeter.
  • the cathode active material of Comparative example Rl obtained by known publication having ZnAlO 2 and carbon additives coated on the surfaces of LiFePO 4 , achieves electrical conductivity of 2.6 x 10 "6 S / cm while the cathode active material of Example A7, having similar composition to that of Comparative example Rl but provides by the presently disclosed method, achieves electrical conductivity of 0.5 S / cm, the latter being 19,000 times more electrically conductive.
  • NMP N-methylpyrrolidone
  • PVDF polyvinylidene fluoride
  • NMP N-methylpyrrolidone
  • each of batteries Al -Al 5 and ACl Separately place each of batteries Al -Al 5 and ACl on the testing cabinet.
  • Using a current of 0.5 C discharge the battery from 3.8 V to 2.5 V and record the discharge capacity as the battery's initial discharge capacity.
  • the following equation is used to calculate the battery's specific discharge capacity.
  • the test results for batteries Al -Al 5 and ACl are shown in Table 2.
  • Capacity maintenance rate (Discharge capacity after n th cycle / initial discharge capacity ) x 100 %
  • the cathode active materials according to Examples 1-15 of the presently disclosed invention are able to achieve better electrical performance than Comparative example Rl .
  • the cathode active materials of batteries Al -Al 5 are able to achieve specific discharge capacity of at least 123 mAh/g at 0.5 C and maintain greater than 95 % discharge capacity after 500 cycles.
  • the cathode active material of Comparative example Rl achieved specific discharge capacity of 112 mAh/g and maintained 90.12 % discharge capacity after 500 cycles while cathode active material of Example 7, having similar composition to that of Comparative example Rl but provided by the presently disclosed method, achieved specific discharge capacity of 126 mAh/g and maintained 96.44 % discharge capacity after 500 cycles. Accordingly, the cathode active materials for lithium secondary batteries and methods of manufacturing the same according to the presently disclosed embodiments are able to provide superior electrical performance, e.g., higher electrical conductivity, discharge capacity and discharge capacity maintenance or retention rate.

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Abstract

A composite lithium compound having a mixed crystalline structure, the mixed crystal has a first crystalline substance having one or more members with following general formulas LixM’y(XO4)z, LiM’ XO5, LiM’XO6, and LiM’X2O7, in which M’ is an element selected from a group consisting of Na, Mn, Fe, Co, Ni, Ti, V, Y, Mg, Ca, Nb and Zn; the X is an element selected from a group consisting of P, S, As, Mo and W; and a second crystalline substance having one or more members with a general formula of AaMbNcOd. Further, a lithium ion secondary battery and a rechargeable battery with a cathode comprising the same are provided.

Description

CATHODE ACTIVE MATERIAL, LITHIUM ION SECONDARY BATTERY AND RECHARGABLE BATTERY HAVING THE SAME
CROSS-REFERENCE TO RELATED APPLICATION This application claims priority to Chinese Patent Application No.
200810173652.X, filed on November 5, 2008, which is hereby incorporated by reference in its entirety.
This application claims priority to Chinese Patent Application No.
200810175243.3, filed on November 6, 2008, which is hereby incorporated by reference in its entirety.
This application claims priority to Chinese Patent Application No. 200810189238.8, filed on December 26, 2008, which is hereby incorporated by reference in its entirety.
This application claims priority to Chinese Patent Application No. 200810189233.5, filed on December 26, 2008, which is hereby incorporated by reference in its entirety.
This application claims priority to Chinese Patent Application No.
200810189235.4, filed on December 26, 2008, which is hereby incorporated by reference in its entirety. This application claims priority to U.S. Patent Application No. 12/316,180, filed on December 9, 2008, which is hereby incorporated by reference in its entirety.
This application claims priority to U.S. Patent Application No. 12/316,165, filed on December 9, 2008, which is hereby incorporated by reference in its entirety. FIELD OF THE INVENTION
The present invention relates to rechargeable batteries, more specifically, to a composite compound having a mixed crystalline structure that can be used as a cathode material for lithium secondary batteries.
BACKGROUND OF THE RELATED ART
Lithium secondary batteries are widely used in various devices such laptop computers, cameras, camcorders, PDAs, cell phones, iPods and other portable electronic devices. These batteries are also growing in popularity for defense, automotive and aerospace applications because of high energy density thereof.
Presently, to enhance the electrical properties of lithium secondary batteries, the high valence metal is used for coating and doping. A cathode material for lithium battery is disclosed in U.S. Pat. Application No. 2007/0207385A1 including a first compound and a second compound. The first compound has a formula of A3xMl2y(Pθ4)3 . The second compound is at least one compound selected from the group consisting of SiC, BN and metal oxide having a formula of M2aOb, coating on the first compound. And A is at least one element selected from the group consisting of Groups IA, HA and IIIA. Each of the Ml and M2 is selected from at least one element from Groups HA, IIIA, IVA and VA and transition metal elements, respectively. More specifically, each of the Ml and M2 is at least one element selected from the group consisting of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Be, Mg, Ca, Sr, B, Al, Sn, Ga, In, Si and Ge. And the material of LiFePO4/ZnO/C, LiFeP04/ZnA102/C, LiFePO4/CuO/C and LiFePO4/ZnAlO/C are disclosed in the examples of the application. The electrical properties of the coated cathode material have been enhanced, but the electrical conductivity is still too low, approximately at about 10~5 S/cm, and the battery prepared by using such cathode material has poor specific capacity and cycle performance. SUMMARY OF THE INVENTION
In viewing thereof, the present invention needs to provide a cathode active material, which has a novel crystal structure that may enhance electrical properties of the battery significantly. Further, the present invention needs to provide a lithium ion secondary battery having a cathode made therefrom.
According to an embodiment of the invention, a cathode active material comprising a mixed crystal is provided. The mixed crystal may have: a first crystalline substance having at least one member with one of following general formulas LixM'y(X04)z, LiM5XO5, LiM5XO6 and LiM5X2O7 in which 0<x/z<l and 0<y/z<l .l, the M5 may be an element selected from a group consisting of Na, Mn, Fe, Co, Ni, Ti, V, Y, Mg, Ca, Nb and Zn, and the X may be an element selected from a group consisting of P, S, As, Mo and W; and a second crystalline substance having one or more members with a general formula of AaMbNcOd, in which A, M and N may be different metals selected from groups HA, IIIA, IVA, VA, IB, HB, IIIB, IVB, VB, VIB, VIIB and VIII of the periodic table, 0<a<6, 0<b<6, 0<c<6 and 0<d<12, and a and b cannot both be zero at the same time.
According to another embodiment of the invention, a lithium ion secondary battery is provided, in which the battery may comprise a battery shell, electrodes and electrolyte with the electrodes and electrolyte being sealed within the battery shell, the electrodes having wounded or stacked cathode, anode and divider film. And the cathode may further comprise the cathode active material as described above.
The present invention, for the first time, successfully provides a lithium metal intercalation compound with a mixed crystal. With the mixed crystalline structure, the novel cathode material disclosed in the present invention significantly improves electrical properties of lithium batteries.
Other variations, embodiments and features of the present invention will become evident from the following detailed description, drawings and claims. BRIEF DESCRIPTION OF THE DRAWINGS
These and other aspects and advantages of the invention will become apparent and more readily appreciated from the following descriptions taken in conjunction with the drawings in which: Fig. 1 shows a XRD pattern of a composite compound according to Example i;
Fig. 2 shows a XRD pattern of a composite compound according to Example 2;
Fig. 3 shows a XRD pattern of a composite compound according to Example 3;
Fig. 4 shows a XRD pattern of a composite compound according to Example 4;
Fig. 5 shows a XRD pattern of a composite compound according to Example 5; and Fig. 6 shows a XRD pattern of a composite compound according to Example
6.
DETAILED DESCRIPTION OF THE INVENTION
It will be appreciated by those of ordinary skill in the art that the invention can be embodied in other specific forms without departing from the spirit or essential character thereof. The presently disclosed embodiments are therefore considered in all respects to be illustrative but not restrictive.
Generally, a mixed crystal can be referred to as a solid solution. It is a crystal containing a second constituent, which fits into and is distributed in the lattice of the host crystal. One exemplary illustration of the existing solution may be found in, for example, IUPAC Compendium of Chemical Terminology 2nd
Edition (1997). Mixed crystals have been used in semiconductors for enhancing light output in light emitting diodes (LEDs). They have also been used to produce sodium-based electrolyte for galvanic elements. The current invention is the first time that a mixed crystal has been successfully prepared for lithium metal intercalation compounds. It is also the first time that a mixed crystalline structure has been used as a cathode material for lithium secondary batteries. The new cathode material disclosed in the present invention has significantly better electrical properties than traditional cathode materials.
The description thereof will be described in detail with reference to accompanying figures.
A cathode active material can be provided having a mixed crystal structure. The mixed crystal structure may have: a first crystalline substance having one or more members with the general formulas LixM'y(X04)z, LiM5XO5, LiM5XO6 and LiM5X2O7, in which:
0<x/z<l and O≤y/z≤l . l ;
M5 may be an element selected from the group of Na, Mn, Fe, Co, Ni, Ti, V, Y, Mg, Ca, Nb and Zn;
X may be an element selected from the group of P, S, As, Mo and W; and a second crystalline substance having one or more members with the general formula AaMbNcOd, in which:
A, M and N are different metals selected from groups HA, IIIA, IVA, VA, IB, HB, IIIB, IVB, VB, VIB, VIIB and VIII in the periodic table; and
0<a<6, 0<b<6, 0<c<6 and 0<d<12 except for a = b = zero, i.e., a and b cannot both be zero at the same time.
And the cathode active material may have electrical conductivity of about 0.01 to about 10 S/cm at about 25 0C. The mixed crystal structure can be formed by sintering two or more compounds, the intermediary mixture having oxygen vacancies or metallic crystalline structures. The two or more compounds do not exhibit any major chemical reactions when mixed together. However, upon sintering, a large number of crystalline defects can be formed, thereby altering the electronic states of the compounds creating a large number of oxygen vacancies. These oxygen vacancies provide the needed carriers, thus greatly enhancing the electrical conductivity of the mixed crystal. Accordingly, the cathode active material can achieve electrical conductivity of about 0.1 to 2S/cm at about 25°C with a Simens per centimeter, which is larger than traditional lithium iron phosphate cathode active materials. According to an embodiment of the invention, the first crystalline substance and the second crystalline substance may have a molar ratio of about 1 to 0.01-0.05.
The first crystalline substance can have a mixed crystalline structure with the general formula LixM'y(Xθ4)z including one or more members selected from the group consisting of LiFeO4, LiMnPO4 and LiCoPO4 etc. In other embodiments, single-crystalline structures including Li3Fe2(PO4)S, LiTi2(PO4)3, Li3V2(PO4)3 and Li2Na V2(PO4)3 may be incorporated. For the general formula LiM'XOs, the first crystalline substance can be LiTiPOs. For the general formula LiM' XOO, the first crystalline substance can include LiVMoO6 and LiVWO6 respectively. For the general formula LiM5X2O7, the first crystalline substance can include LiVP2O7 and LiFeAs2O7.
In the mixed crystalline structure with the general formula LixM'y(X04)z, M' may include element Fe and one or more members selected form the group consisting of Mn, Co, Ni, Ti, Y, Mg, Ca and Zn, and the amount of Fe is from 90 % to 100 % by molar. Then the first crystalline substance can include one or more members selected from LiFePO4, Li0 99Y0 01FePO4 and LiR1FeI-1PO4, in which 0<i<0.1, R may be one or more members selected from elements Mn, Co, Ni, Ti, Mg, Ca and Zn. The second crystalline substance can include one or more members selected from the group consisting of Bi4Ti3Oi2, CuNb2Oo, MnTaO4, FeWO4, ZnZrNb2Og, NiNb2O6, NiZrNb2O8, FeTiNb2O8, MnTiNb2O8, MgSnNb2O8, ZnTa2O6, Cu0 S5Zn0 15Nb2O6, YBa3Ti2O85, Zr0 75Ti0 75Sn05O4, HfTiO4 and MgNb2O6. The mixed crystal structure can further include carbon, which is about 1-5 % of the mixed crystal structure by weight. The carbon can further enhance the electrical conductivity of the mixed crystal.
According to an embodiment of the invention, a method of preparing a cathode active material for lithium secondary batteries is provided, comprising the following steps:
Providing a first material having one or more members with the general formulas LixM'y(X04)z, LiM5XO5, LiM5XO6 and LiM5X2O7, in which: 0<x/z<l and 0<y/z<l .l; M5 is selected from elements Na, Mn, Fe, Co, Ni, Ti, V, Y, Mg, Ca, Nb and Zn; X is selected from elements P, S, As, Mo and W;
Providing a second material having one or more members with the general formulas AaMbNcOd, in which: A, M and N are different metals selected from groups HA, IIIA, IVA, VA, IB, HB, IIIB, IVB, VB, VIB, VIIB and VIII in the periodic table; 0<a<6, 0<b<6, 0<c<6 and 0<d<12; a and b cannot both be O at the same time; and
Sintering the two materials to provide a mixed crystal.
The first material and the second material may have a molar ratio of about 1 to 0.01-0.05.
In one embodiment, the second material can be formed by heating oxide compounds of A, M and N with a molar ratio of a : b : c at about 400 to 1000 0C for about 8 to 15 hours. The sintered product can be measured with a Rigaku D/MAX-2200/PC x-ray diffraction (XRD) instrument to acquire an XRD pattern thereof, which can subsequently be compared with known chemical standards provided by the system. The oxide compound or oxygen-containing compound of A can be oxides of A and/or sintered products of oxides of A and other compounds, the oxides of A and other compounds include hydroxides of A, carbonates of A, and bicarbonates of A. Likewise, the oxide compound or oxygen-containing compound of M can be oxides of M and/or sintered products of oxides of M and other compounds, the oxides of M and other compounds include hydroxides of M, carbonates of M, and bicarbonates of M. Similarly, the oxide compound or oxygen-containing compound of N can be oxides of N and/or sintered products of oxides of N and other compounds, the oxides of N and other compounds include hydroxides of N, carbonates of N, and bicarbonates of N. In some embodiments, the first material may include one or more members selected from the group consisting of LiFePO4, LiMnPO4, LiCoPO4, Li3Fe2(PO4)S, LiTi2(PO4),, Li3V2(PO4),, Li2NaV2(PO4),, Li0 99Yo OiFePO4, LiR1Fe1-1PO4, LiTiPO5, LiVMoO6, LiVWO6, LiVP2O7 and LiFeAs2O7 in which 0<i<0.1, R is one or more members selected from elements Mn, Co, Ni, Ti, Mg, Ca and Zn. In other embodiments, the first material may include one or more members selected from LiFePO4, Li0 99Y001FePO4 and LiR1FeI-1PO4.
The second material can include one or more members selected from the group consisting of Bi4Ti3Oi2, CuNb2O6, MnTaO4, FeWO4, ZnZrNb2O8, NiNb2O6, NiZrNb2O8, FeTiNb2O8, MnTiNb2O8, MgSnNb2O8, ZnTa2O6, Cu0 85Zn0 I5Nb2O6, YBa3Ti2O8 5, Zr0 75Ti0 75Sn0 5O4, HfTiO4 and MgNb2O6.
In some embodiments, the method may further comprise sintering a carbon additive into the two crystalline substances, the carbon additive capable of providing the mixed crystal with about 1-5 % of carbon by weight. The carbon additive includes one or more members selected from the group consisting of carbon black, acetylene black, graphite, glucose, sucrose, citric acid, starch, dextrin, polyethylene glycol, and other organic and inorganic sources. However, it should be noted that the examples are for illustration purpose rather than for limitation. A person skilled in the art can use equivalents thereof to achieve the same as described herein. And a heating rate of the sintering step ranges from 5 to 20 0C per minute, a sintering temperature thereof from 500 to 800 0C, and a sintering time thereof from 5 to 32 hours. The sintering atmosphere is chose according the selected materials. For example, when the first or second material is easily oxidized, the sintering atmosphere may be inert atmosphere or reduction atmosphere; and when the first or second material is not easily oxidized, the sintering atmosphere may be any atmosphere.
According to another embodiment of the invention, a lithium ion secondary battery may be provided, the lithium ion secondary battery having a battery shell, electrodes and electrolyte, the electrodes and electrolyte being sealed within the battery shell, the electrodes having wounded or stacked cathode, anode and divider film, the cathode further including the cathode active materials described above.
The cathode may include cathode components such as the cathode active materials described above with adhesives. The adhesives can be hydrophobic or hydrophilic binding additives without any specific binder ratio restrictions. In one instance, the hydrophilic to hydrophobic adhesive binder can have weight ratios of about 0.3 : 1 to about 1 : 1. The adhesive can be solid, aqueous or as an emulsion.
The concentration can be adjusted accordingly based on methods of preparing the cathode, anode and the slurry viscosity and coating. In one example, the hydrophilic adhesive solution has a concentration of about 0.5 to 4 weight percent while the hydrophobic latex binder has a concentration of about 10 to 80 weight percent.
Hydrophobic adhesives can include PTFE, styrene butadiene rubber, or mixtures thereof. Hydrophilic adhesives can include HPMC, CMC, hydroxyethyl cellulose, polyvinyl alcohol, or mixtures thereof. The binder content can be about 0.01 to 8 % by weight of the total cathode active material.
In addition, conductive agents may be incorporated or added in the cathode active material, the conductive agents include, but without limitation, graphite, carbon fiber, carbon black, metal powders and fibers as well as any suitable material understood by one skilled in the art. The conductive agent can be about
0.1 to 20 % by weight of the total cathode active material.
The method of preparing the cathode includes using solvents to dissolve the cathode active material and mixing with adhesives and conductive agents to form a cathode slurry. The cathode slurry can be applied onto cathode collectors, dried, rolled or compressed, and sliced into pieces to produce the cathode. In one example, the slurry can be dried at about 100 to 150 0C for about 2 to 10 hours. The cathode collectors include aluminum foil, copper foil, nickel-plated steel or punched stainless steel. The types of solvent to use include N-methyl pyrrolidone (NMP), dimethylformamide (DMF), diethyl formamide (DEF), dimethyl sulfoxide (DMSO), tetrahydrofuran (THF), water, alcohol and mixtures thereof. The amount of solvent to use can be adjusted accordingly to provide the proper slurry coating and viscosity. In one instance, the amount of solvent can be about 40 to 90 % by weight of the cathode active material. The method of preparing the cathode and types of solvents, adhesives, conductive agents and cathode collectors can also incorporate other techniques understood by one skilled in the art.
As discussed above, the lithium secondary battery includes a battery shell, electrodes and electrolyte, the electrodes and electrolyte capable of being sealed within the battery shell. The electrodes may include wounded or stacked cathode, anode and divider film with the cathode utilizing the cathode active material of the presently disclosed embodiments.
The divider film can be situated between the cathode and anode for preventing electrical shortcuts and for maintaining the electrolytic solution. In one instance, the divider film can include any membrane including, but without limitation, micro-porous membrane polyolefin, polyethylene fibers, ultra-fine glass fibers and fiber paper.
The anode can incorporate any anode active materials and known methods of forming such materials as known in the arts. The anode active material can be provided in slurry form and coated onto anode collectors similar to the cathode collectors above. Additionally, the anode active material may include carbon additives such as non-carbon graphite, graphite, and polymers having undergone high-temperature carbon oxidation. The carbon additive can also include pyrolytic coal, coke, organic polymer sintered materials and activated carbons. The organic polymer sintered materials include phenolic resin, epoxy resin, and carbonized products obtained by sintering.
Adhesives can utilize traditional adhesives for lithium secondary batteries including polyvinyl alcohol, PTFE, carboxymethyl cellulose (CMC), hydroxymethyl cellulose (HMC), and styrene butadiene rubber (SBR). The adhesive binder can be about 0.5 to 8 weight percent of the total anode active material.
The anode active material can further include conductive agents, the conductive agent capable of increasing electrical conductivity and reducing internal resistance of the battery. The conductive agent may include, but without limitation to, carbon black, nickel powder and copper powder etc. Other conductive agents known by one skilled in the art may also be utilized and can be about 0.1 to 12 weight percent of the anode active material.
The method of preparing the anode may include: using solvents to dissolve the anode active material and mixing with adhesives and conductive agents to form anode slurry. The anode slurry can be applied onto the anode collectors similar to that of the cathode slurry described above, dried, rolled or compressed, and sliced into pieces to produce the anode. In one example, the slurry can be dried at about 100 to 150 0C for about 2 to 10 hours. The types of solvent for dissolving the anode active material include N-methyl pyrrolidone (NMP), dimethylformamide (DMF), diethyl formamide (DEF), dimethyl sulfoxide (DMSO), tetrahydrofuran (THF), water, alcohol and mixtures thereof. The amount and concentration of solvents to use can be adjusted accordingly to provide the proper slurry coating and viscosity. Like the cathode slurry, the amount of anode slurry applied to the anode collector can be about 40 to 90 weight percent of the anode active material.
The electrolyte for the lithium secondary battery can be a non-aqueous electrolyte, which can be formed by dissolving lithium salt in a non-aqueous solvent. The lithium salt electrolyte can include one or more members selected from lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), lithium hexafluorosilicate (LiSiF6), lithium tetraphenylborate (LiB(C6H5)4), lithium chloride (LiCl), lithium bromide (LiBr), lithium aluminum tetrachloride (LiAlCl4), LiC(Sθ2CF3)3, LiCH3SO3, and LiN(SO2CFs)2. The non-aqueous solvent can be chain ester and ester ring mixed solution, the chain ester being one or more members of dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC), methylpropyl carbonate (MPC), dimethylpropyl carbonate (DPC) and other fluoride or sulfur-containing unsaturated key chain organic esters, with the ester ring being one or more members of ethylene carbonate (EC), propylene carbonate (PC), vinylene carbonate (VC), gamma-butyrolactone (γ-BL), sodium fluoride and other lactone-containing or unsaturated organic ester rings. In one instance, the lithium salt electrolyte has a concentration of about 0.1 to 2 mole per liter.
The presently disclosed lithium secondary batteries can be provided by processes known by one skilled in the art. The preparation method may include winding or stacking cathode, anode and divider films into the battery core, and placing the battery core into the battery shell, adding the electrolyte, and sealing the battery accordingly. The winding, stacking and sealing of the batteries can utilize traditional techniques as understood by one skilled in the art. Furthermore, other known steps of manufacturing the lithium secondary battery can be incorporated.
The following will describe various embodiments of mixed-crystal cathode active materials according to the presently disclosed invention. EXAMPLE 1 Firstly, Mix MnCO3, TiO2 and Nb2Os with a molar ratio of 1 : 1 : 1, grind the mixture in a ball mill for 5 hours, heat in a nitrogen atmosphere at 10 0C per minute to 500 0C and continue sintering the product for 10 hours. With a Rigaku D/MAX-2200/PC, an XRD pattern is obtained on the resulting product. In comparison with the standard XRD pattern for MnTiNb2Og, it is determined that the sintered product is MnTiNb2Os. Mix LiFePO4 with the resulting MnTiNb2Og from above in a molar ratio of 1 : 0.04, add starch as a source of carbon (amount of carbon capable of providing 5 wt% of carbon content in the final product). In one example, the LiFePO4 can be prepared by mixing lithium carbonate, ferrous oxalate, and ammonium dihydrogen phosphate in a Li : Fe : P molar ratio of 1 : 1 : 1. Alternatively, the LiFePO4 can be prepared by other lithium, iron and phosphate sources or by a third party.
Grind the mixture in a ball mill for 10 hours, remove and dry at 80 0C. Heat the resulting powder in a nitrogen or argon atmosphere at 10 0C per minute to 600 0C, and continue sintering the product for 20 hours to provide a LiFePO4 / MnTiNb2Og / C mixed crystal cathode active material.
With the Rigaku D/MAX-2200/PC, an XRD pattern is carried out on the cathode active material as shown in Fig. 1. Looking at diffraction peaks of the sintered product, except for peaks corresponding to LiFePO4 and MnTiNb2Og, there is no new peak or feature which indicates that the LiFePO4 and MnTiNb2Og exist in two phases and that no new compound is created. Accordingly, this pattern demonstrates that the process described above provides a cathode active material having LiFePO4 / MnTiNb2Os / C in a mixed crystalline form. EXAMPLE 2
Mix ZnO and Ta2Os in a molar ratio of 1 : 1 , grind the mixture in a ball mill for 5 hours, heat in an oxygen atmosphere at 15 0C per minute to 800 0C and continue sintering the product for 8 hours. With the Rigaku D/MAX-2200/PC, an XRD pattern can be carried out on the resulting product. And it is determined that the sintered product is ZnTa2Oo by comparing it with a standard XRD pattern for ZnTa2Oo Mix LiFePO4 with the resulting ZnTa2Oo from above in a molar ratio of 1 :
0.03 with acetylene black as a source of carbon (amount of carbon capable of providing 0 % by weight of carbon content in the final product). The LiFePO4 can be prepared by mixing lithium oxalate, iron oxide and diammonium hydrogen phosphate in a Li : Fe : P molar ratio of 0.95 : 1 : 1, which can be added to the ZnTa2Oo at a diammonium hydrogen phosphate to ZnTa2Oo molar ratio of 1 : 0.03 (taking into account the phosphorous components in the mixture). Alternatively, the LiFePO4 can be prepared by other lithium, iron and phosphate sources or by a third party. Grind the mixture in a ball mill for 10 hours, remove and dry at 80 0C. Heat the resulting powder in a nitrogen or argon atmosphere at a heating rate of 5 0C per minute to 500 0C, and continue sintering the product for 30 hours to provide a LiFePO4 / ZnTa2Oo mixed crystal cathode active material.
With the Rigaku D/MAX-2200/PC, an XRD pattern is carried out on the cathode active material as shown in Fig. 2. Looking at the diffraction peaks of the sintered product, except for peaks corresponding to LiFePO4 and ZnTa2Oo, there is no new peak or feature which indicates that the LiFePO4 and ZnTa2Oo exist in two phases and that no new compound is created. Accordingly, it is determined that the process described above provides a cathode active material having LiFePO4 / ZnTa2Oo in a mixed crystal form. EXAMPLE 3
Mix Y2O3, BaCO3 and TiO2 in a molar ratio of 0.5 : 3 : 2, grind the mixture in a ball mill for 5 hours, heat it in a nitrogen atmosphere at a heating rate of 7 0C per minute to 1000 0C and continue sintering the product for 15 hours. With the Rigaku D/MAX-2200/PC, an XRD pattern can be carried out on the resulting product. And it is determined that the sintered product is YBa3Ti2Og S by comparing it with a standard XRD pattern Of YBa3Ti2Og 5.
Mix LiFePO4 with the resulting YBa3Ti2Og 5 from above in a molar ratio of 1 : 0.02 with carbon black as a source of carbon (amount of carbon capable of providing 2 wt% of carbon content in the final product). The LiFePO4 can be prepared by mixing lithium hydroxide, ferrous carbonate and phosphoric acid in a Li : Fe : P molar ratio of 1.05 : 1 :1.05, which can be added to the YBa3Ti2Og 5 at a phosphoric acid to YBa3Ti2Og S molar ratio of 1 : 0.02 (taking into account the phosphorous components in the mixture). Alternatively, the LiFePO4 can be prepared by other lithium, iron and phosphate sources or by a third party.
Grind the mixture in a ball mill for 10 hours, remove and dry at 80 0C. Heat the resulting powder in a nitrogen or argon atmosphere at a heating rate of 20 0C per minute to 800 0C, continue sintering the product for 8 hours to provide a LiFePO4 / YBa3Ti2Os 5 / C mixed crystal cathode active material.
With the Rigaku D/MAX-2200/PC, an XRD pattern is carried out on the cathode active material as shown in Fig. 3. Looking at the diffraction peaks of the sintered product, except for peaks corresponding to LiFePO4 and YBa3Ti2Og 5, there is no new peak or feature which indicates that the LiFePO4 and YBa3Ti2Og 5 exist in two phases and that no new compound is created. Accordingly, it is determined that the process described above provides a cathode active material having LiFePO4 / YBa3Ti2Og 5 / C in a mixed crystal form.
EXAMPLE 4 Mix CuO, ZnO and Nb2O5 with a molar ratio of 0.85 : 0.15 : 1, grind the mixture in a ball mill for 5 hours, heat in a nitrogen atmosphere at a heating rate of 7 0C per minute to 1000 0C and continue sintering the product for 15 hours. With the Rigaku D/MAX-2200/PC, an XRD pattern can be carried out on the resulting product. And it is determined that the sintered product is Cuo 85Zn0 15Nb2Oo in comparison with the standard XRD pattern of Cuo 85Zn0 15Nb2Oo.
The remaining steps incorporate those used in Example 1 , with the difference being that the Cuo 85Zn0 15Nb2Oo substitutes the MnTiNb2Os to provide a LiFePO4 / Cuo 85Zn0 15Nb2Oo / C mixed crystal cathode active material.
With the Rigaku D/MAX-2200/PC, an XRD pattern is carried out on the cathode active material as shown in Fig. 4. Looking at the diffraction peaks of the sintered product, except for peaks corresponding to LiFePO4 and Cuo 85Zn0 15Nb2Oo, there is no new peak or feature, which indicates that the LiFePO4 and
Cuo 85Zn0 15Nb2Oo exist in two phases and that no new compound is created. Accordingly, this demonstrates that the process described above provides a cathode active material having LiFePO4 / Cuo 85Zn0 15Nb2Oo / C in a mixed crystal form. EXAMPLE 5
Mix ZrO2, TiO2 and SnO2 in a molar ratio of 0.75 : 0.75 : 0.5, grind the mixture in a ball mill for 5 hours, heat in a nitrogen atmosphere at a heating rate of 7 0C per minute to 1000 0C and continue sintering the product for 15 hours. With the Rigaku D/MAX-2200/PC, an XRD pattern can be carried out on the resulting product. In comparison with the standard XRD pattern of Zr0 75Tio 75Sn0 5O4, it is determined that the sintered product is Zr0 75Ti0 75Sn0 5O4. The remaining steps are the same as those used in Example 1, with the difference being that the Zr0 7STi0 7SSn0 SO4 substitutes the MnTiNb2Og to provide a LiFePO4 / Zr0 75Ti0 75Sn0 5O4 / C mixed crystal cathode active material.
With the Rigaku D/MAX-2200/PC, an XRD pattern is carried out on the cathode active material as shown in Fig. 5. Looking at the diffraction peaks of the sintered product, except for peaks corresponding to LiFePO4 and Zr0 75Ti0 75Sn0 5O4, there is no new peak or feature which indicates that the LiFePO4 and Zr0 75Ti0 75Sn0 5O4 exist in two phases and that no new compound is created. Accordingly, this demonstrates that the process described above provides a cathode active material having LiFePO4 / Zr0 75Ti0 75Sn0 5O4 / C in a mixed crystal form. EXAMPLE 6
Mix FeO and WO3 in a molar ratio of 1 : 1 , grind the mixture in a ball mill for 5 hours, heat in an oxygen atmosphere at a heating rate of 15 0C per minute to 800 0C and continue sintering the product for 8 hours. With the Rigaku D/MAX-2200/PC, an XRD pattern can be carried out on the resulting product. In comparison with the standard XRD pattern for FeWO4, it is determined that the sintered product is FeWO4.
The remaining steps are the same as those used in Example 1, with the difference being that the FeWO4 substitutes the MnTiNb2Og to provide a LiFePO4 / FeWO4 / C mixed crystal cathode active material. With the Rigaku D/MAX-2200/PC, an XRD pattern is carried out on the cathode active material as shown in Fig. 6. Looking at the diffraction peaks of the sintered product, except for peaks corresponding to LiFePO4 and FeWO4, there is no new peak or feature which indicates that the LiFePO4 and FeWO4 exist in two phases and that no new compound is created. Accordingly, this demonstrates that the process described above provides a cathode active material having LiFePO4 / FeWO4 / C in a mixed crystal form.
EXAMPLE 7
Mix ZnO and Al2O3 in a molar ratio of 2 : 1 , grind the mixture in a ball mill for 5 hours, heat in an oxygen atmosphere at 15 0C per minute to 800 0C and continue sintering the product for 8 hours. With the Rigaku D/MAX-2200/PC, an XRD pattern can be carried out on the resulting product. And, it is determined that the sintered product is ZnAlO2 in comparison with the standard XRD pattern for ZnAlO2. The remaining steps are the same as those used in Example 1, with the difference being that the ZnAlO2 substitutes the MnTiNb2Og to provide a LiFePO4 / ZnAlO2 / C mixed crystal cathode active material.
With the Rigaku D/MAX-2200/PC, an XRD pattern is carried out on the cathode active material. Upon examination of the diffraction peaks of the sintered product, except for peaks corresponding to LiFePO4 and ZnAlO2, there is no new peak or feature which indicates that the LiFePO4 and ZnAlO2 exist in two phases and that no new compound is created. Accordingly, this demonstrates that the process described above provides a cathode active material having LiFePO4 / ZnAlO2 / C in a mixed crystal form. EXAMPLE 8
According to the disclosed method of "A Method of Preparing Lithium Battery Cathode Active Material Li0 99 Yo 01FePO4" (JOURNAL OF FUNCTIONAL MATERIALS, VOLUME 36, ISSUE 5 (2005)) to prepare Li099 Yo 01FePO4. The steps are similar to those used in Example 1, with the difference being that the Li0 99 Yo 01FePO4 substitutes the LiFePO4 to provide a Li0 99 Yo 01FePO4 / MnTiNb2Og / C mixed crystal cathode active material.
With the Rigaku D/MAX-2200/PC, an XRD pattern is carried out on the cathode active material. Looking at the diffraction peaks of the sintered product, except for peaks corresponding to Li0 99 Yo 01FePO4 and MnTiNb2Og, there is no new peak or feature which indicates that the Li099 Yo 01FePO4 and MnTiNb2Og exist in two phases and that no new compound is created. Accordingly, this demonstrates that the process described above provides a cathode active material having Li099 Yo 01FePO4 / MnTiNb2Og / C in a mixed crystal form. EXAMPLE 9
According to the disclosed method of "The Preparation and Performance of Lithium Battery Cathode Active Material LiNi0 IFe0 9PO4" (THE CHINESE JOURNAL OF NONFERROUS METALS, VOLUME 16, ISSUE 4 (Apr. 2006)) to prepare LiTi0 05Fe0 95PO4. Mix Li2CO3, FeC2O4-2H2O, NH4H2PO4 and TiO2 in a molar ratio to the stoichiometry of LiTi0 05Fe0 95PO4. Grind the mixture in a ball mill with ethanol for 5 hours, remove and dry at room temperature. And then heat in an argon atmosphere at 320 0C for 7 hours; and continue sintering the product for 24 hours at 700 0C to provide LiTi0 05Fe0 95PO4. The steps are similar to those used in Example 1, with the difference being that the LiTi0 05Fe0 95PO4 substitutes the LiFePO4 to provide a LiTi0 05Fe0 95PO4 / MnTiNb2Og / C mixed crystal cathode active material.
With the Rigaku D/MAX-2200/PC, an XRD pattern is carried out on the cathode active material. Looking at the diffraction peaks of the sintered product, except for peaks corresponding to LiTi0 05Fe0 95PO4 and MnTiNb2Og, there is no new peak or feature which indicates that the LiTi0 05Fe0 95PO4 and MnTiNb2Og exist in two phases and that no new compound is created. Accordingly, this demonstrates that the process described above provides a cathode active material having LiTi0 05Fe0 95PO4 / MnTiNb2Og / C in a mixed crystal form. EXAMPLE 10
According to the disclosed method of "The Preparation and Performance of Lithium Battery Cathode Active Material LiNi0 IFe0 9PO4" (THE CHINESE JOURNAL OF NONFERROUS METALS, VOLUME 16, ISSUE 4 (Apr. 2006)) to prepare LiNi0 1 Fe0 9PO4. Mix Li2CO3, FeC2O4-2H2O, NH4H2PO4 and Ni(CH3COO)2-4H2O in a molar ratio to the stoichiometry of LiNi0 1Fe0 9PO4. Grind the mixture in a ball mill with ethanol for 5 hours, remove and dry at room temperature. And then heat in an argon atmosphere at 320 0C for 7 hours; continue sintering the product for 24 hours at 700 0C to provide LiNi0 1Fe0 9PO4. The steps are similar to those used in Example 1, with the difference being that the LiNi0 1Fe0 9PO4 substitutes the LiFePO4 to provide a LiNi0 1Fe0 9PO4 / MnTiNb2Os / C mixed crystal cathode active material.
With the Rigaku D/MAX-2200/PC, an XRD pattern is carried out on the cathode active material. Looking at the diffraction peaks of the sintered product, except for peaks corresponding to LiNi0 1Fe0 9PO4 and MnTiNb2Os, there is no new peak or feature which indicates that the LiNi0 1Fe0 9PO4 and MnTiNb2Os exist in two phases and that no new compound is created. Accordingly, this demonstrates that the process described above provides a cathode active material having LiNi0 1Fe0 9PO4 / MnTiNb2Os / C in a mixed crystal form. EXAMPLE I l
According to the disclosed method of "The Preparation and Performance of Lithium Battery Cathode Active Material LiNi0 1 Fe0 9PO4" (THE CHINESE JOURNAL OF NONFERROUS METALS, VOLUME 16, ISSUE 4 (Apr. 2006)) to prepare LiCo0 OiFeo 99PO4. Mix Li2CO3, FeC2O4-2H2O, NH4H2PO4 and CoO in a molar ratio to the stoichiometry of LiCo0 OiFeo 99PO4. Grind the mixture in a ball mill with ethanol for 5 hours, remove and dry at room temperature. And then heat in an argon atmosphere at 320 0C for 7 hours; continue sintering the product for 24 hours at 700 0C to provide LiCo0 QiFe0 99PO4. The steps are similar to those used in Example 1, with the difference being that the LiCoo oiFeo 99PO4 substitutes the LiFePO4 to provide a LiCoo oiFeo 99PO4 / MnTiNb2Og / C mixed crystal cathode active material.
With the Rigaku D/MAX-2200/PC, an XRD pattern is carried out on the cathode active material. Looking at the diffraction peaks of the sintered product, except for peaks corresponding to LiCoo oiFeo 99PO4 and MnTiNb2Og, there is no new peak or feature which indicates that the LiCoo oiFeo 99PO4 and MnTiNb2Os exist in two phases and that no new compound is created. Accordingly, this demonstrates that the process described above provides a cathode active material having LiCoo oiFeo 99PO4 / MnTiNb2Og / C in a mixed crystal form. EXAMPLE 12
According to the disclosed method of "The Preparation and Performance of Lithium Battery Cathode Active Material LiNi0 IFe0 9PO4" (THE CHINESE JOURNAL OF NONFERROUS METALS, VOLUME 16, ISSUE 4 (Apr. 2006)) to prepare LiMn0 02Fe0 98PO4. Mix Li2CO3, FeC2O4-2H2O, NH4H2PO4 and MnCO3 in a molar ratio to the stoichiometry of LiMn0 02Fe0 9sPO4. Grind the mixture in a ball mill with ethanol for 5 hours, remove and dry at room temperature. And then heat in an argon atmosphere at 320 0C for 7 hours; continue sintering the product for 24 hours at 700 0C to provide LiMn0 02Fe0 98PO4. The steps are similar to those used in Example 1, with the difference being that the LiMn0 02Fe0 9sPO4 substitutes the LiFePO4 to provide a LiMn0 02Fe0 9sPO4 / MnTiNb2Os / C mixed crystal cathode active material.
With the Rigaku D/MAX-2200/PC, an XRD pattern is carried out on the cathode active material. Looking at the diffraction peaks of the sintered product, except for peaks corresponding to LiMn0 02Fe0 9sPO4 and MnTiNb2Og, there is no new peak or feature which indicates that the LiMn0 02Fe0 9SPO4 and MnTiNb2Os exist in two phases and that no new compound is created. Accordingly, this demonstrates that the process described above provides a cathode active material having LiMn0 02Fe0 9sPO4 / MnTiNb2Os / C in a mixed crystal form. EXAMPLE 13
According to the disclosed method of "The Preparation and Performance of Lithium Battery Cathode Active Material LiNi0 IFe0 9PO4" (THE CHINESE JOURNAL OF NONFERROUS METALS, VOLUME 16, ISSUE 4 (Apr. 2006)) to prepare LiMg0 03Fe0 97PO4. Mix Li2CO3, FeC2O4-2H2O, NH4H2PO4 and MgO in a molar ratio to the stoichiometry of LiMg0 03Fe0 97PO4. Grind the mixture in a ball mill with ethanol for 5 hours, remove and dry at room temperature. And then heat in an argon atmosphere at 320 0C for 7 hours; and continue sintering the product for 24 hours at 700 0C to provide LiMg0 03Fe0 97PO4. The steps are similar to those used in Example 1, with the difference being that the LiMg0 03Fe0 97PO4 substitutes the LiFePO4 to provide a LiNi0 1Fe0 9PO4 / MnTiNb2Os / C mixed crystal cathode active material.
With the Rigaku D/MAX-2200/PC, an XRD pattern is carried out on the cathode active material. Looking at the diffraction peaks of the sintered product, except for peaks corresponding to LiMg0 03Fe0 97PO4 and MnTiNb2Og, there is no new peak or feature which indicates that the LiMg0 03Fe0 97PO4 and MnTiNb2Og exist in two phases and that no new compound is created. Accordingly, this demonstrates that the process described above provides a cathode active material having LiMg0 03Fe0 97PO4 / MnTiNb2Og / C in a mixed crystal form. EXAMPLE 14
According to the disclosed method of "The Preparation and Performance of Lithium Battery Cathode Active Material LiNi0 1 Fe0 9PO4" (THE CHINESE JOURNAL OF NONFERROUS METALS, VOLUME 16, ISSUE 4 (Apr. 2006)) to prepare LiCa0 05Fe0 95PO4. Mix Li2CO3, FeC2O4-2H2O, NH4H2PO4 and CaO in a molar ratio to the stoichiometry of LiCa0 05Fe0 9sPO4. Grind the mixture in a ball mill with ethanol for 5 hours, remove and dry at room temperature. And then heat in an argon atmosphere at 320 0C for 7 hours; and continue sintering the product for 24 hours at 700 0C to provide LiCa0 05Fe0 95PO4. The steps are similar to those used in Example 1, with the difference being that the LiCao 05Fe0 95PO4 substitutes the LiFePO4 to provide a LiCao 05Fe0 95PO4 / MnTiNb2Og / C mixed crystal cathode active material.
With the Rigaku D/MAX-2200/PC, an XRD pattern is carried out on the cathode active material. Looking at the diffraction peaks of the sintered product, except for peaks corresponding to LiCao 05Fe0 95PO4 and MnTiNb2Og, there is no new peak or feature which indicates that the LiCao 05Fe0 95PO4 and MnTiNb2Os exist in two phases and that no new compound is created. Accordingly, this demonstrates that the process described above provides a cathode active material having LiCao 05Fe0 95PO4 / MnTiNb2Os / C in a mixed crystal form. EXAMPLE 15
According to the disclosed method of "The Preparation and Performance of Lithium Battery Cathode Active Material LiNi0 IFe0 9PO4" (THE CHINESE JOURNAL OF NONFERROUS METALS, VOLUME 16, ISSUE 4 (Apr. 2006)) to prepare LiZn0 07Fe0 93PO4. Mix Li2CO3, FeC2O4-2H2O, NH4H2PO4 and ZnCO3 in a molar ratio to the stoichiometry Of LiZn0 07Fe0 93PO4. Grind the mixture in a ball mill with ethanol for 5 hours, remove and dry at room temperature. And then heat in an argon atmosphere at 320 0C for 7 hours; continue sintering the product for 24 hours at 700 0C to provide LiZn0 07Fe0 93PO4. The steps are similar to those used in Example 1, with the difference being that the LiZn0 07Fe0 93PO4 substitutes the LiFePO4 to provide a LiZn0 07Fe0 93PO4 / MnTiNb2Os / C mixed crystal cathode active material.
With the Rigaku D/MAX-2200/PC, an XRD pattern is carried out on the cathode active material. Looking at the diffraction peaks of the sintered product, except for peaks corresponding to LiZn0 07Fe0 93PO4 and MnTiNb2Os, there is no new peak or feature which indicates that the LiZn0 07Fe0 93PO4 and MnTiNb2Os exist in two phases and that no new compound is created. Accordingly, this demonstrates that the process described above provides a cathode active material having LiZn0 07Fe0 93PO4 / MnTiNb2Os / C in a mixed crystal form. COMPARATIVE EXAMPLE Rl
Example B of U.S. Patent Application No. 2007/0207385 provides a cathode material with LiFePO4 to ZnAlO2 with a molar ratio of 1 : 0.04 and carbon additive to provide a total carbon content of 5 % by weight in the final product. The ZnAlO2 and carbon additive are coated on the exterior surfaces of the LiFePO4 to provide a cathode active material having LiFePO4 / ZnAlO2 / C.
CONDUCTIVITIES OF EXAMPLES 1-15 AND COMPARATIVE EXAMPLE Rl
At 25 0C, separately take each cathode active materials of Examples 1-15 and Comparative example Rl, and apply 30 MPa of pressure to provide a cylinder. Measure the height (X), diameter (d) and resistance (R) of each cylinder. Use the following formula to calculate the electrical conductivity (σ) for each sample:
Electrical conductivity σ = 4 x 1 1 (π R x d2)
The electrical conductivities of Examples 1-15 and Comparative example Rl are shown in Table 1.
Figure imgf000026_0001
Table 1. Electrical conductivities of samples at 25 0C.
From Table 1, it can be observed that the cathode active materials of the present embodiments can achieve electrical conductivity up to 1.8 S / cm measured by a Siemens per Centimeter. By contrast, the cathode active material of Comparative example Rl, obtained by known publication having ZnAlO2 and carbon additives coated on the surfaces of LiFePO4, achieves electrical conductivity of 2.6 x 10"6 S / cm while the cathode active material of Example A7, having similar composition to that of Comparative example Rl but provides by the presently disclosed method, achieves electrical conductivity of 0.5 S / cm, the latter being 19,000 times more electrically conductive.
TESTINGS OF EXAMPLES 1-15 AND COMPARATIVE EXAMPLE Rl (1) Battery preparation
(a) Cathode active material
Separately combine 90 grams of each of the composite cathode materials from Examples 1-15 and Comparative example Rl with 5 grams of polyvinylidene fluoride (PVDF) binder and 5 grams of acetylene black to 50 grams of
N-methylpyrrolidone (NMP). Place in a vacuum mixer to mix into uniform slurry.
Apply a coating with a thickness of about 20 microns on both sides of an aluminum foil, dry at 1500C, roll and cut into a size of 540 x 43.5 mm2 to provide about 5.2 grams of cathode active material.
(b) Anode active material
Combine 90 grams of natural graphite with 5 grams of polyvinylidene fluoride (PVDF) binder and 5 grams of conductive carbon black to 100 grams of N-methylpyrrolidone (NMP). Place in a vacuum mixer to mix into uniform slurry. Apply a coating of about 12 microns thick to both sides of a copper foil, dry at 900C, roll and crop to a size of 500 x 44 mm2 to provide about 3.8 grams of anode active material.
(c) Battery assembly Separately wind each of the cathode and anode active materials with polypropylene film into a lithium secondary battery core, followed by dissolving one mole of LiPF6 in a mixture of non-aqueous electrolyte solvent EC/EMC/DEC to provide a ratio of 1 : 1 : 1, inject and seal the electrolyte having a capacity of 3.8 g/Ah into the battery to provide separate lithium secondary batteries Al -Al 5 (Examplesl-15) and ACl (Comparative example Rl) for testing.
PERFORMANCE TESTINGS OF BATTERIES Al -Al 5 and ACl
Separately place each of batteries Al -Al 5 and ACl on the testing cabinet. At 25 0C, charge each battery at a current of 0.5 C with a voltage limit of 3.8 V and set the battery aside for 20 minutes. Using a current of 0.5 C, discharge the battery from 3.8 V to 2.5 V and record the discharge capacity as the battery's initial discharge capacity. The following equation is used to calculate the battery's specific discharge capacity. The test results for batteries Al -Al 5 and ACl are shown in Table 2.
Specific discharge capacity = Initial discharge capacity (milliampere hour) / weight of cathode active material (grams)
The process as described above is repeated: charge the battery, set it aside, and discharge each battery for 500 cycles. Record the battery's discharge capacity and use the following equation to calculate the battery's ability to maintain discharge capacity after 500 cycles. The higher the maintenance rate, the better the performance of the battery in maintaining its discharge capacity. The test results for batteries Al -Al 5 and ACl are shown in Table 2.
Capacity maintenance rate = (Discharge capacity after nth cycle / initial discharge capacity ) x 100 %
Figure imgf000028_0001
TABLE 2. Electrical testing results for batteries Al -Al 5 and ACl .
From Table 2, it can be observed that the cathode active materials according to Examples 1-15 of the presently disclosed invention are able to achieve better electrical performance than Comparative example Rl . Specifically, the cathode active materials of batteries Al -Al 5 are able to achieve specific discharge capacity of at least 123 mAh/g at 0.5 C and maintain greater than 95 % discharge capacity after 500 cycles.
Additionally, the cathode active material of Comparative example Rl achieved specific discharge capacity of 112 mAh/g and maintained 90.12 % discharge capacity after 500 cycles while cathode active material of Example 7, having similar composition to that of Comparative example Rl but provided by the presently disclosed method, achieved specific discharge capacity of 126 mAh/g and maintained 96.44 % discharge capacity after 500 cycles. Accordingly, the cathode active materials for lithium secondary batteries and methods of manufacturing the same according to the presently disclosed embodiments are able to provide superior electrical performance, e.g., higher electrical conductivity, discharge capacity and discharge capacity maintenance or retention rate.
Although the invention has been described in detail with reference to several embodiments, additional variations and modifications exist within the scope and spirit of the invention as described and defined in the following claims.

Claims

WHAT IS CLAIMED IS:
1. A cathode active material comprising a mixed crystal, the mixed crystal having: a first crystalline substance having one or more members with following general formulas LixM'y(XO4)z, LiM5XO5, LiM5XO6 and LiM5X2O7, wherein: 0<x/z<l and O≤y/z≤l .l;
M5 is an element selected from a group consisting of Na, Mn, Fe, Co, Ni, Ti, V, Y, Mg, Ca, Nb and Zn; X is an element selected from a group consisting of P, S, As, Mo and W; and a second crystalline substance having one or more members with a general formula of AaMbNcOd, wherein:
A, M and N are different metals selected from groups HA, IIIA, IVA, VA, IB, HB, IIIB, IVB, VB, VIB, VIIB and VIII of the periodic table; 0<a<6, 0<b<6, 0<c<6 and 0<d<12; and a and b cannot both be zero at the same time.
2. The material according to claim 1, wherein the cathode active material has electrical conductivity of 0.01 to 10 S/cm at 25 0C.
3. The material according to claim 2 wherein the cathode active material has electrical conductivity of 0.1 to 2 S/cm at 25 0C.
4. The material according to claim 1, wherein the first crystalline substance and the second crystalline substance has a molar ratio of 1 to 0.01-0.05.
5. The material according to claim 1, wherein M5 includes element Fe and one or more members selected form the group consisting of Mn, Co, Ni, Ti, Y, Mg, Ca and Zn, and wherein the amount of Fe is from 90 % to 100 % by molar.
6. The material according to claim 1, wherein the first crystalline substance includes one or more members selected from the group consisting of LiFePO4, LiMnPO4, LiCoPO4, Li3Fe2(PO4)3, LiTi2(PO4),, Li3V2(PO4),, Li2NaV2(PO4),, Li099Yo OiFePO4, LiR1FeI-1PO4, LiTiPO5, LiVMoO6, LiVWO6, LiVP2O7 and LiFeAs2O7 wherein 0<i<0.1, R is one or more members selected from elements Mn, Co, Ni, Ti, Mg, Ca and Zn; and wherein the second crystalline substance includes one or more members selected from the group consisting of Bi4Ti3Oi2, CuNb2Oo, MnTaO4, FeWO4, ZnZrNb2O8, NiNb2O6, NiZrNb2O8, FeTiNb2O8, MnTiNb2O8, MgSnNb2O8, ZnTa2O6, Cu0 85Zn0 15Nb2O6, YBa3Ti2O85, Zr0 75Ti075Sn05O4, HfTiO4 and MgNb2O6.
7. The material according to claim 6, wherein the first crystalline substance includes one or more members selected from the group consisting of LiFePO4, Li0 99 Yo 01FePO4 and LiR1FeI-1PO4 wherein 0<i<0.1, R is one or more members selected from elements Mn, Co, Ni, Ti, Mg, Ca and Zn.
8. The material according to claim 1, wherein the mixed crystal further comprising carbon which is 1-5 % of the mixed crystal by weight.
9. A lithium ion secondary battery comprising a battery shell, electrodes and electrolyte with the electrodes and electrolyte being sealed within the battery shell, the electrodes having wounded or stacked cathode, anode and divider film, the cathode further comprising the cathode active material according to claim 1.
10. A rechargeable battery, including an anode, an electrolyte and a cathode made from cathode active material according to claim 1.
PCT/CN2009/074769 2008-11-05 2009-11-03 Cathode active material, lithium ion secondary battery and rechargable battery having the same Ceased WO2010051746A1 (en)

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CN200810173652 2008-11-05
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US12/316,165 US8062559B2 (en) 2008-02-29 2008-12-09 Composite compound with mixed crystalline structure
US12/316,180 2008-12-09
US12/316,180 US8057711B2 (en) 2008-02-29 2008-12-09 Composite compound with mixed crystalline structure
US12/316,165 2008-12-09
CN2008101892388A CN101478042B (en) 2008-11-05 2008-12-26 Positive pole active substance, positive pole and battery
CN200810189235.4 2008-12-26
CN200810189233A CN101740749A (en) 2008-11-06 2008-12-26 Method for preparing anode active substance, anode active substance, anode and battery
CN200810189238.8 2008-12-26
CN2008101892354A CN101740750B (en) 2008-11-05 2008-12-26 Method for preparing anode active substance, anode active substance, anode and battery
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