JP3994238B2 - Nonaqueous electrolyte lithium secondary battery - Google Patents

Description

【００３６】
表１の結果から、本発明に記載する表面導電材料被覆を施した金属酸化物系負極材料を負極の合剤層中に含有するリチウムイオン二次電池が、ハイレート放電効率と容量の点において優れた性能を示すことがわかる。なお、本発明のリチウムイオン二次電池は、Ｃ−１と炭素被覆したＡ−３、およびＣ−１と銅被覆したＡ−３の組み合わせの場合、室温での充放電のサイクル寿命として、それぞれ１００サイクル当たり９５％および９２％の放電容量維持率を示した。
【００３７】
【発明の効果】
リチウム含有遷移金属複合酸化物からなる正極材料、リチウムを挿入可能な金属酸化物からなる負極材料と、非水電解質によって構成され、負極の金属酸化物粒子が、金属複合酸化物からなる粒子の表面に導電性の無機材料の薄膜が被覆された複合粒子であることを特徴とするリチウムイオン非水電解質二次電池を用いることにより、電池容量とハイレート放電特性を向上する事ができる。
【図面の簡単な説明】
【図１】実施例で作製したシリンダー型二次電池の断面図を示したものである。
【符号の説明】
１ 負極端子を兼ねる電池缶
２ 巻回電極群（正極、セパレーター、負極）
３ 上部絶縁板
４ 正極リード
５ ガスケット
６ 正極端子を兼ねる電池蓋
６１ 圧力感応弁体
６２ 電流遮断体
６３ ＰＴＣ素子[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a high capacity type lithium ion non-aqueous electrolyte secondary battery in which the discharge capacity of a metal oxide negative electrode is improved.
[0002]
[Prior art]
Lithium secondary batteries that use lithium and lithium alloys as the negative electrode active material have the advantage that the negative electrode has a high capacity density, but the safety problem due to the deposition of metallic lithium (dendritic generation) and the decrease in cycle life caused by this Is a practical obstacle. In order to improve this, various carbonaceous materials have been developed as materials for reversibly intercalating lithium in the ionic state to the negative electrode, and lithium-containing oxides that can reversibly insert and release lithium ions are also used as the positive electrode active material. In combination with materials, so-called rocking chair type lithium ion secondary batteries have been developed and are currently mass-produced as general-purpose 4V class secondary batteries. As the positive electrode active material, LiCoO₂LiCo_1-xNi_xO₂, LiNiO₂, LiMn₂O_FourIn particular, LiCoO disclosed in JP-A-55-136131 is used.₂Is 3.5 Vvs. This is advantageous in that it has a high capacity in addition to a high charge / discharge potential higher than Li. In addition, LiMn is advantageous because it has a large amount of raw material supply compared to Co and is low in cost and excellent in safety.₂O_FourJapanese Patent Application Laid-Open Nos. 3-147276 and 4-123769 have proposed secondary batteries using as a positive electrode material.
Examples of the carbonaceous material used as the negative electrode active material include graphitic carbon material, pitch coke, fibrous carbon, and high-capacity soft carbon fired at a low temperature. Carbon materials generally have a bulk specific gravity of 2.20. Since it is relatively small as follows, it is difficult to design a high capacity per battery volume when it is used at a lithium insertion capacity (372 mAh / g) up to the stoichiometric limit. Therefore, as a negative electrode material capable of inserting lithium having a high capacity density exceeding that of a carbonaceous material, JP-A-6-60867, 7-220721, 7-122274, and 7-288123 disclose composite oxidation mainly composed of tin oxide. An amorphous active material made of a material is disclosed.
As the battery material increases in capacity as described above, the current density at the time of discharge use increases, and it becomes increasingly important that the battery capacity can be kept high even when using a high current (high rate). Conventionally, when a metal oxide or the like is used as a lithium insertion compound in the negative electrode, the conductivity inherent to the metal oxide is not sufficient, so the addition of a conductive material and the combined use to perform uniform insertion of lithium ions during high-rate charging Is essential. As the conductive material, acetylene black or graphitic carbon is generally used. When an electrode mixture is prepared by mixing these powders with active material particles, the substantial content of the negative electrode active material in the mixture layer (filling degree) As a result, the capacity per volume of the negative electrode coating layer decreases, leading to a decrease in battery capacity. In order to maximize the capacity of the oxide negative electrode material, a technique for coexisting the conductive material with the active material particles efficiently is required.
[0003]
[Problems to be solved by the invention]
An object of the present invention is to provide a high capacity type lithium ion non-aqueous electrolyte secondary battery that solves the above-described problems, improves the usage of the conductive agent, and has excellent charge / discharge characteristics, particularly high rate discharge capacity. .
[0004]
[Means for Solving the Problems]
  The above-described problems are solved in a positive electrode made of a lithium-containing transition metal composite oxide, a negative electrode containing metal oxide particles into which lithium can be inserted, and a lithium ion non-aqueous electrolyte secondary battery made of a non-aqueous electrolyte. The metal oxide particles contained in the active material layer are composite particles in which the surface of particles made of a metal composite oxide is coated with a thin film of a conductive inorganic material, on the negative electrode active material layerContains aluminum oxideA lithium ion non-aqueous electrolyte secondary battery characterized by being a negative electrode with a protective layer formed has been solved.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
  Although the preferable form of this invention is enumerated below, this invention is not limited to these.
(1) In a positive electrode made of a lithium-containing transition metal composite oxide, a negative electrode containing metal oxide particles into which lithium can be inserted, and a lithium ion non-aqueous electrolyte secondary battery made of a non-aqueous electrolyte, the negative electrode active material of the negative electrode The metal oxide particles contained in the layer are composite particles in which a thin film of a conductive inorganic material is coated on the surface of a particle made of a metal composite oxide, on the negative electrode active material layerContains aluminum oxideA lithium ion non-aqueous electrolyte secondary battery, which is a negative electrode on which a protective layer is formed.
(2)The protective layer contains graphite and aluminum oxideThe lithium ion non-aqueous electrolyte secondary battery according to Item 1, wherein
(3) Item 1 is characterized in that the conductive inorganic material is a carbonaceous material.Or 2A lithium ion non-aqueous electrolyte secondary battery according to 1.
(4) The lithium ion nonaqueous electrolyte secondary battery according to item 1, wherein the conductive inorganic material is a metal.
(5) The lithium ion nonaqueous electrolyte secondary battery according to item 1, wherein the conductive inorganic material is a metal coated on the surface of metal oxide particles by an electroless plating method.
(6) The conductive inorganic material is one or more metals selected from Cu, Ag, Ni, Au, Pt, Al, Mg, Ti, Zn, Sn, In, W, and Pb, or these metals and Li Item 6. The lithium ion non-aqueous electrolyte secondary battery according to Item 4 or 5, wherein
(7) The lithium ion nonaqueous electrolyte secondary battery according to any one of Items 1 to 6, wherein the surface coverage of the conductive inorganic material is 20% or more and 100% or less.
(8) The lithium ion nonaqueous electrolyte 2 according to any one of Items 1 to 7, wherein the surface coverage of the conductive inorganic material is 0.01% by weight or more and 15% by weight or less with respect to the metal oxide particles. Next battery.
(9) The lithium metal or lithium alloy is further deposited on the protective layer.Or 2The lithium ion nonaqueous electrolyte secondary battery as described.
(10) Items 1 to 3, wherein the metal oxide is a composite oxide mainly containing tin and having an amorphous structure.9The lithium ion nonaqueous electrolyte secondary battery according to any one of the above.
[0006]
Hereinafter, the present invention will be described in detail.
The lithium ion non-aqueous electrolyte secondary battery of the present invention has a basic configuration comprising a positive electrode active material, a metal oxide-based negative electrode material and a non-aqueous electrolyte containing a lithium salt, compared with a conventional lithium battery using a carbon material negative electrode. And high capacity. A negative electrode material made of a metal oxide is responsible for the high capacity, and a metal composite oxide mainly containing tin oxide is particularly preferably used as the negative electrode material. This negative electrode material is activated by electrochemically inserting (intercalating) lithium ions into the metal composite oxide as an active material precursor in the battery. As the positive electrode active material, a high potential type lithium-containing metal composite oxide represented by lithium cobaltate and lithium manganate is used. These positive electrode active materials together with the lithium-containing non-aqueous electrolyte serve as a supply source of lithium ions to the negative electrode to constitute a rocking chair type secondary battery.
[0007]
The positive electrode and the negative electrode of the present invention are composed of a current collector (generally a metal support) and an active material mixture layer coated thereon, that is, a conductive layer containing an active material powder. Among these, in the mixture layer of the negative electrode, in the present invention, the conductive material made of an inorganic material is used in a state of being coated as a thin film on the surface of the negative electrode material particles made of a metal oxide. Rather than the conventional method of mixing negative electrode particles and conductive agent particles, the first method is to coat the negative electrode particles with a minimum amount of conductive material effective for imparting conductivity between the negative electrode particles as in the present invention. The capacity per volume of the negative electrode can be increased by minimizing the amount of the conductive agent used. Second, the negative electrode particles are mechanically separated from the conductive material matrix during the lithium insertion / release cycle of the negative electrode particles. The problem that the internal resistance of the battery increases increases, and the cycle life of the battery can be improved.
In the present invention, coating includes not only covering the entire particle but also partially covering it. In the case of partially covering, the case of adhering is also included.
For the above purpose, one of the preferred conductive materials to be coated on the surface of the negative electrode particles in the present invention is represented by graphitized carbons, fibrous carbon, pitch coke, glassy carbon, carbon black, fluorinated carbon, or the like. A crystalline or amorphous carbonaceous material. As a method of coating these carbon materials as a thin film on the surface of negative electrode particles, for example, 1) a method of coating carbon particles by attaching them in gas or liquid by electrostatic attraction on electrically charged particles; 3) A method of depositing a carbon thin film on the negative electrode particles by vacuum deposition. 3) A negative electrode particle whose surface has been modified or coated with a carbon-containing compound is heated at high temperature in a reducing gas to carbonize the compound to form a film. Chemical methods such as methods can be used. Among the carbonaceous materials to be coated, carbon black represented by graphite carbon and acetylene black is particularly preferable.
[0008]
Another type used as a conductive material that coats the surface of the negative electrode particles is a metal material. Among metal materials, preferred are one or more metals selected from Cu, Ag, Ni, Au, Pt, Al, Mg, Ti, Zn, Sn, In, W, and Pb, or a combination of these metals and Li. An alloy is used. Of these, Cu, Ag, Ni, Al, and Sn are particularly preferable. When an alloy of these metals and Li is used as the surface conductive film, the alloy may be formed during the electrochemical insertion of Li ions into the negative electrode particles inside the battery.
As a method for forming a thin film of these metal materials on the surface of the negative electrode particle, for example, 1) a method of forming a thin film by depositing metal on the particle surface in a solution in the presence of metal ions and a reducing agent by electroless plating 2) A method of forming a metal thin film on the negative electrode particles by a vacuum deposition method or a sputtering method. 3) Thermal decomposition or redox of negative electrode particles in which metal-containing compounds (mainly organometallic compounds) are surface-modified or adhered. A method of forming a thin film by depositing a metal on particles by a chemical reaction such as decomposition (chemical decomposition method) can be used.
Among these, particularly preferable methods are an electroless plating method and a chemical decomposition method.
In electroless plating of powder, metal ions are used as a metal raw material, the metal ions are reduced in the presence of a reducing agent and a complexing agent under stirring in a solution in which the powder is dispersed, and the metal is deposited on the powder surface. It is a method of plating. The reaction method is roughly divided into a batch method and a dropping method.
The electroless copper plating is described in, for example, Japanese Patent Publication No. 4-53949 and Japanese Patent Laid-Open No. 2-153076. Copper sulfate as a copper raw material, EDTA as a complexing agent, formaldehyde as a reducing agent, and sulfuric acid in which a powder subjected to surface activation pretreatment is dispersed under conditions of a liquid temperature of 40 to 90 ° C. and pH 8 to 11 A reducing agent is dropped into an aqueous solution of copper and EDTA while stirring to allow the plating reaction to proceed.
In the case of nickel plating, for example, nickel sulfate can be used as the nickel source, malic acid, succinic acid as the complexing agent, and sodium hypophosphite as the reducing agent, and the reaction can proceed at pH 5-8.
For the purpose of silver plating, for example, as shown in JP-A-63-79975 and JP-A-2-173272, when using a non-cyan plating bath, silver nitrate is used as a silver raw material, ethylenediamine is used as a complexing agent, Using glutamic acid, Rochelle salt as the reducing agent, and tin chloride (SnCl) in the pH range of 9-13.₂) Can be plated on the particles activated in step (1).
[0009]
In the present invention, the carbon material or the metal material coated on the negative electrode particles as the conductive material is 0.01 to 0.01% of the total weight of the metal oxide particles in the mixture layer containing the metal oxide particles of the negative electrode material. It is added at a content of 15% by weight, and the preferred addition amount is in the range of 0.1 to 7% by weight, more preferably in the range of 1 to 5% by weight. In addition to the conductive material coated on these particles, the conductive material particles can be further mixed with the binder in the mixture layer.
In the present invention, the ratio of the conductive inorganic material covering the surface of the negative electrode particle (surface coverage) is that the Li ion at the interface between the particle and the electrolyte is increased while increasing the electron conductivity of the surface of the particle group. For the purpose of not impairing the permeability of the film, it is preferably 20% or more and 100% or less, and more preferably 40% or more and 90% or less.
[0010]
A preferred positive electrode active material in the present invention is a lithium-containing transition metal oxide. One of them is Li_xMO₂ (Where M = Co, Mn, Ni, V, and transition metal including at least one selected from Fe), x = 0.3 to 1.2). Particularly preferred is an active material having a layered structure mainly composed of an oxide of cobalt or nickel. M may be a solid solution of different kinds of elements, and examples of the solid solution element include Ti, Ge, Zr, Cr, Fe, Sn, Al, B, and Ga other than the above M. As these positive electrode active materials, Li_xCoO₂, Li_xNiO₂, Li_xMnO₂, Li_xCo_aNi_1-aO₂, Li_xCo_bFe_1-bO₂(Where x = 0.02 to 1.2, a = 0.1 to 0.9, b = 0.8 to 0.98).
[0011]
Another used as the positive electrode active material is A [B₂ ] O_Four Type LiMn with spinel structure₂ O_Four It is a system oxide.
LiMn₂ O_Four As a preferred oxide, LiMn₂ O_Four, Li_xMn_cCo_2-cO_Four, Li_xMn_cNi_2-cO_Four , Li_xMn_cV_2-cO_Four , Li_xMn_cFe_2-cO_Four (Where x = 0.02 to 1.2, c = 1.6 to 1.96).
Furthermore, the general formula Li_{1 + x}[Mn_2-y] O_Four(0 <x <1.7, 0 ≦ y <0.7) or Li_1-x[Mn_2-y] O_FourA compound having a non-stoichiometric composition and a structure containing a defect as shown by (0 <x <1.0, 0 ≦ y <0.5) is also included. Examples of these compounds include Li_Four Mn_Five O₁₂Alternatively, Li [Li_1/3Mn_5/3] O_Four , Li_Four Mn_Four O₉LiMnO₂ Or Li₂ Mn₂ O_Four , Li₂ MnO_Three , Li_Five Mn_Four O₉, Li_Four Mn_Five O₁₂, Li₂Mn_FourO₉And the like are also included within the range of the above general formula (the structural formula includes those represented by an integer multiple or a decimal multiple of the general formula).
[0012]
These positive electrode active materials can be synthesized by a solid phase reaction method in which a lithium compound and a transition metal compound are mixed and fired, or a solution reaction such as a sol-gel reaction or a precipitation method. When using the solid phase reaction method by baking, the baking temperature should just be a temperature at which a part of raw material compound used as a positive electrode active material raw material decomposes | disassembles and fuse | melts, and is 600-1000 degreeC normally.
The average particle size of the positive electrode active material is preferably from 0.1 to 50 μm, particularly preferably from 1 to 9.5 μm. The preferred specific surface area of the positive electrode active material is 0.1 m²/ M larger than 5g²/ G or less, particularly preferably 0.1 m²Larger than 3g / g²/ G or less.
[0013]
The metal species of the metal oxide of the negative electrode used in the secondary battery of the present invention is not particularly limited, but oxides or complex oxides of elements from Group 3 to Group 15 of the periodic table are usually used, preferably Oxides or complex oxides of elements from Group 3 to Group 7 and Group 13 to 15 are used.
In order to ensure the battery performance of the object of the present invention, a preferable metal oxide for the negative electrode is a composite oxide mainly containing tin and containing an amorphous structure.
A preferable form of the composite oxide mainly containing tin and containing an amorphous structure is mainly composed of tin oxide, and the periodic table includes Group 1, Group 2, Group 13, Group 14, Group 15, and transition metal. And a composite oxide containing an amorphous structure containing at least one selected from halogen elements.
Particularly preferred composite oxides for the negative electrode are those represented by the general formula Sn._xM¹ _1-xM² _yO_z(M¹Is one or more selected from Mn, Fe, Pb and Ge,²Represents two or more elements selected from Al, B, P, Si, Periodic Table Group 1, Group 2, Group 3, and halogen elements, and 0 <x ≦ 1, 0.1 ≦ y ≦ 3 , 1 ≦ z ≦ 8), an amorphous composite oxide obtained by inserting lithium into an amorphous lithium-occlusion negative electrode active material precursor. In the above negative electrode active material precursor, Sn and M¹Is a functional element involved in electrochemical insertion and release of lithium ions.²Is an element constituting a matrix effective for amorphization of the composite oxide.
[0014]
The negative electrode active material precursor composite oxide includes an amorphous structure in the structure or is amorphous. The complex oxide of the present invention includes an amorphous structure. Specifically, the X-ray diffraction method using CuKα rays is a diffraction scattering band having a broad apex that is weak in intensity from 20 ° to 40 ° as a 2θ value. In this broad scattering band, a crystalline diffraction line may be included. This crystalline diffraction line is a reflection of a slightly ordered structure in the amorphous structure. More preferably, when a crystalline diffraction line is observed at a 2θ value of 40 ° or more and 70 ° or less, the strongest intensity of the crystalline diffraction lines is observed at a 2θ value of 20 ° or more and 40 ° or less. The intensity of the diffraction line at the apex of the broad scattering band is preferably 500 times or less, more preferably 100 times or less, particularly preferably 5 times or less, and most preferably no crystalline diffraction line. .
[0015]
Below, the preferable example of the metal complex oxide used for the negative electrode active material precursor of this invention is shown.
PbO
PbSiO_Three
SnSiO_Three
PbSi_0.5B_0.2P_0.2O_1.85
PbK_0.1Si_0.8P_0.2O_1.95
FeK_0.1Si_0.8P_0.2O_1.95
MnB_0.5P_0.5O_Three
GeSi_0.5B_0.2P_0.2O_1.85
SnSi_0.8P_0.2O_3.1
SnSi_0.5B_0.2P_0.2O_1.85
SnSi_0.8B_0.2O_2.9
SnSi_0.8Al_0.2O_2.9
SnSi_0.6Al_0.1B_0.2O_1.65
SnSi_0.3Al_0.1P_0.6O_2.25
SnSi_0.4B_0.2P_0.4O_2.1
SnSi_0.6Al_0.1B_0.5O_2.1
SnB_0.5P_0.5O_Three
SnK_0.2PO_3.6,
SnRb_0.2P_0.8O_3.2
SnBa_0.1P_1.45O_4.5
SnLa_0.1P_0.9O_3.4
SnNa_0.1B_0.45O_1.75
SnLi_0.2B_0.5P_0.5O_3.1
SnCs_0.1B_0.4P_0.4O_2.65
SnBa_0.1B_0.4P_0.4O_2.7
SnCa_0.1Al_0.15B_0.45P_0.55O_3.9,
SnY_0.1B_0.6P_0.6O_3.55
SnRb_0.2B_0.3P_0.4O_2.55
SnCs_0.2B_0.3P_0.4O_2.55
SnCs_0.1B_0.4P_0.4O_2.65
SnK_0.1Cs_0.1B_0.4P_0.4O_2.7
SnBa_0.1Cs_0.1B_0.4P_0.4O_2.75
SnMg_0.1K_0.1B_0.4P_0.4O_2.75
SnCa_0.1K_0.1B_0.4P_0.5O_Three
SnBa_0.1K_0.1Al_0.1B_0.3P_0.4O_2.75
SnMg_0.1Cs_0.1Al_0.1B_0.3P_0.4O_2.75
SnCa_0.1K_0.1Al_0.1B_0.3P_0.4O_2.75
SnMg_0.1Rb_0.1Al_0.1B_0.3P_0.4O_2.75
SnCa_0.1B_0.2P_0.2F_0.2O_2.6
SnMg_0.1Cs_0.1B_0.4P_0.4F_0.2O_3.3
Sn_0.5Mn_0.5Mg_0.1B_0.9O_2.45
Sn_0.5Mn_0.5Ca_0.1P_0.9O_3.35
Sn_0.5Ge_0.5Mg_0.1P_0.9O_3.35
Sn_0.5Fe_0.5Ba_0.1P_0.9O_3.35
Sn_0.8Fe_0.2Ca_0.1P_0.9O_3.35
Sn_0.3Fe_0.7Ba_0.1P_0.9O_3.35
Sn_0.9Mn_0.1Mg_0.1P_0.9O_3.35
Sn_0.2Mn_0.8Mg_0.1P_0.9O_3.35
Sn_0.7Pb_0.3Ca_0.1P_0.9O_3.35
Sn_0.2Ge_0.8Ba_0.1P_0.9O_3.35
Sn_1.0Al_0.1B_0.5P_0.5O_3.15
Sn_1.0Cs_0.1Al_0.4B_0.5P_0.5O_3.65
Sn_1.0Cs_0.1B_0.5P_0.5O_3.05
Sn_1.0Cs_0.1Ge_0.05B_0.5P_0.5O_3.15
Sn_1.0Cs_0.1Ge_0.05Al_0.3B_0.5P_0.5O_3.60
[0016]
Examples of the negative electrode active material that can be used together with the negative electrode material synthesized by the method of the present invention in the production of a secondary battery include lithium metal, the above lithium alloy, and the like, and a carbonaceous compound that can occlude and release lithium ions or lithium metal. (For example, JP-A-58-209,864, 61-214,417, 62-88,269, 62-216,170, 63-13,282, 63-24,555, 63- 121,247, 63-121,257, 63-155,568, 63-276,873, 63-314,821, JP-A-1-204,361, 1-221,859, 1- 274, 360). The purpose of the combined use of the lithium metal and the lithium alloy is to insert lithium ions in the battery, and does not use a dissolution and precipitation reaction of lithium metal or the like as the battery reaction.
[0017]
A conductive agent, a binder, a filler, or the like can be added to the electrode mixture of the positive electrode and the negative electrode. In addition to the conductive agent used for coating the particle surface, a conductive agent can be supplementarily added to the negative electrode mixture. The conductive agent may be anything as long as it is an electron conductive material that does not cause a chemical change in the constructed battery. Usually, natural graphite (scale-like graphite, scale-like graphite, earth-like graphite, etc.), artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber or metal (copper, nickel, aluminum, silver (JP-A-63-148)) , 554) etc.) Conductive materials such as powder, metal fibers or polyphenylene derivatives (Japanese Patent Laid-Open No. 59-20,971) can be included as one kind or a mixture thereof. The combined use of graphite and acetylene black is particularly preferred. The addition amount is not particularly limited, but is preferably 1 to 50% by weight, particularly preferably 2 to 30% by weight. In the case of carbon or graphite, 2 to 15% by weight is particularly preferable.
[0018]
The binder is usually starch, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, regenerated cellulose, diacetyl cellulose, polyvinyl chloride, polyvinyl pyrrolidone, tetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, ethylene-propylene-di. Enter polymers (EPDM), sulfonated EPDM, styrene butadiene rubber, polybutadiene, fluororubber, polyethylene oxide and other polysaccharides, thermoplastic resins, rubber elastic polymers and the like are used as one kind or a mixture thereof. The addition amount of the binder is preferably 2 to 30% by weight. Any filler can be used as long as it is a fibrous material that does not cause a chemical change in the constructed battery. Usually, olefin polymers such as polypropylene and polyethylene, fibers such as glass and carbon are used. Although the addition amount of a filler is not specifically limited, 0 to 30 weight% is preferable.
[0019]
Non-aqueous electrolytes used for the production of secondary batteries include propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethylsulfate. Foxoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphoric acid triester (JP 60-23973), trimethoxymethane (JP 61- 4,170), dioxolane derivatives (Japanese Patent Laid-Open Nos. 62-15771, 62-22,372, 62-108,474), sulfolane (Japanese Patent Laid-Open No. 62-31,959), 3-methyl-2- Oxazolidinone ( No. 62-44,961), propylene carbonate derivatives (JP-A 62-290,069, 62-290,071), tetrahydrofuran derivatives (JP-A 63-32,872), diethyl ether (JP-A 63) -62,166), 1,3-propane sultone (Japanese Patent Laid-Open No. Sho 63-102,173) and a mixture of at least one aprotic organic solvent and a lithium salt soluble in the solvent, such as LiClO_Four, LiBF₆, LiPF₆, LiCF_ThreeSO_Three, LiCF_ThreeCO₂, LiAsF₆, LiSbF₆, LiB_TenCl_Ten(JP-A 57-74,974), lower aliphatic lithium carboxylate (JP-A 60-41,773), LiAlCl_FourLiCl, LiBr, LiI (JP 60-247,265), lithium chloroborane (JP 61-165,957), lithium tetraphenylborate (JP 61-214,376), LiOSO₂C_nF_{2n + 1}(N is a positive integer of 6 or less), LiN (SO₂ C_nF_{2n + 1}) (SO₂ C_mF_{2m + 1}) Imide salt (m and n are each a positive integer of 6 or less), LiN (SO₂ C_pF_{2p + 1}) (SO₂ C_qF_{2q + 1}) (SO₂ C_rF_{2r + 1}) And the like (p, q, and r are each a positive integer of 6 or less). Among them, LiCF is added to a mixed solution of propylene carbonate or ethylene carbonate and 1,2-dimethoxyethane and / or diethyl carbonate._ThreeSO_ThreeLiClO_Four, LiBF_FourAnd / or LiPF₆The amount of these electrolytes preferably added to the battery is not particularly limited, but can be used depending on the amount of the positive electrode active material and the negative electrode active material and the size of the battery. The volume ratio of the solvent is not particularly limited, but is 0.4 / 0.6 to 0.6 / 0.4 in the case of a mixed solution of propylene carbonate or ethylene carbonate and 1,2-dimethoxyethane and / or diethyl carbonate. (The mixing ratio when both 1,2-dimethoxyethane and diethyl carbonate are used is preferably 0.4 / 0.6 to 0.6 / 0.4). The concentration of the supporting electrolyte is not particularly limited, but is preferably 0.2 to 3 mol per liter of the electrolytic solution.
[0020]
In addition to the electrolytic solution, the following organic solid electrolyte can also be used. For example, a polyethylene oxide derivative or a polymer containing the derivative (Japanese Patent Laid-Open No. 63-135,447), a polypropylene oxide derivative or a polymer containing the derivative, a polymer containing an ionic dissociation group (Japanese Patent Laid-Open Nos. 62-254,302 and 62- 254,303, 63-193,954), a mixture of a polymer containing an ion dissociation group and the above aprotic electrolyte (US Pat. Nos. 4,792,504, 4,830,939, JP-A-62-22). , 375, 62-22, 376, 63-22, 375, 63-22, 776, JP-A-1-95,117), and phosphate ester polymers (JP-A-61-256,573). is there. Furthermore, there is a method of adding polyacrylonitrile to the electrolytic solution (Japanese Patent Laid-Open No. 62-278,774). In addition, a method using an inorganic and organic solid electrolyte in combination (Japanese Patent Laid-Open No. 60-1,768) is also known.
[0021]
As a separator used for the secondary battery, an insulating thin film having a large ion permeability and a predetermined mechanical strength is used. Sheets and non-woven fabrics made from olefin polymers such as polypropylene, glass fibers or polyethylene are used because of their organic solvent resistance and hydrophobicity. A range useful for batteries is generally used as the pore diameter of the separator. For example, 0.01 to 10 μm is used. The thickness of the separator is generally used in the battery range. For example, 5 to 300 μm is used.
When a solid electrolyte such as a polymer is used as the electrolyte, the solid electrolyte may also serve as a separator.
[0022]
For the purpose of improving charge / discharge characteristics, it is known to add the following compounds to the electrolyte. For example, pyridine (JP 49-108,525), triethyl phosphite (JP 47-4,376), triethanolamine (JP 52-72,425), cyclic ether (JP 57-57). 152, 684), ethylene diamine (JP 58-87,777), n-glyme (JP 58-87,778), hexaphosphoric triamide (JP 58-87,779), nitrobenzene derivatives (JP 58-214,281), sulfur (JP 59-8,280), quinoneimine dyes (JP 59-68,184), N-substituted oxazolidinones and N, N'-substituted imidazolidinones (JP No. 59-154,778), ethylene glycol dialkyl ether (JP 59-205,167), quaternary ammonium salt (JP 60-30,065) Polyethylene glycol (JP 60-41,773), pyrrole (JP 60-79,677), 2-methoxyethanol (JP 60-89,075), aluminum trichloride (JP 61-88) , 466), monomers of conductive polymer electrode active materials (JP 61-161,673), triethylenephosphonamide (JP 61-208,758), trialkylphosphine (JP 62-80,976). ), Morpholine (JP 62-80,977), aryl compounds having a carbonyl group (JP 62-86,673), hexamethylphosphoric triamide and 4-alkylmorpholine (JP 62-62). 217,575), bicyclic tertiary amines (JP 62-217,578), oils (JP 62-287,580), quaternary phosphoniu. Salt (JP-63-121,268), and a tertiary sulfonium salt (JP 63-121,269).
In order to make the electrolyte nonflammable, a halogen-containing solvent such as carbon tetrachloride or ethylene trifluoride chloride can be contained in the electrolyte (Japanese Patent Laid-Open No. 48-36,632). In addition, carbon dioxide gas can be included in the electrolytic solution to make it suitable for high-temperature storage (Japanese Patent Laid-Open No. 59-134,567).
[0023]
The current collector of the electrode active material may be anything as long as it is an electronic conductor that does not cause a chemical change in the constructed battery. For example, in addition to stainless steel, nickel, aluminum, titanium, calcined carbon, etc. as materials for the positive electrode, the surface of aluminum or stainless steel is treated with carbon, nickel, titanium, or silver. In addition to stainless steel, nickel, copper, titanium, aluminum, calcined carbon, etc., the surface of copper or stainless steel treated with carbon, nickel, titanium or silver), Al—Cd alloy, or the like is used. Oxidizing the surface of these materials is also used. As the shape, a film, a sheet, a net, a punched product, a lath body, a porous body, a foamed body, a molded body of a fiber group, and the like are used in addition to the foil. The thickness is not particularly limited, but a thickness of 5 to 100 μm is used.
[0024]
The battery shape can be applied to any of coins, buttons, sheets, cylinders, and corners. In coins and buttons, a mixture of a positive electrode active material and a negative electrode active material is used after being pressed into a pellet shape. In the sheet, cylinder, and corner, the positive electrode active material and the negative electrode active material mixture are applied onto a current collector, dried, dehydrated, and pressed. The coating thickness is determined by the size of the battery, and is preferably 10 to 500 μm in a compressed state after drying.
The use of the non-aqueous secondary battery of the present invention is not particularly limited. For example, when mounted on an electronic device, a color notebook computer, a monochrome notebook computer, a pen input personal computer pocket (palmtop) personal computer, a notebook word processor, a pocket word processor , Electronic book player, mobile phone, cordless phone, pager, handy terminal, mobile fax, mobile copy, mobile printer, headphones stereo video movie, LCD TV, handy cleaner, portable CD, mini desk, electric shaver, electronic translation Machine, car phone, transceiver, power tool, electronic notebook, calculator, memory card, tape recorder, radio, backup power supply, memory card, etc. Others for consumer use include automobiles, electric vehicle motors, lighting equipment, toys, game equipment, road conditioners, irons, watches, strobes, cameras, medical equipment (pacemakers, hearing aids, shoulder grinders, etc.). Furthermore, it can be used for various military use and space use. It can also be combined with solar cells.
[0025]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples of battery production. However, the scope of the present invention is not limited to these examples as long as the gist of the invention is not exceeded.
[0026]
Example
[Synthesis example of negative electrode material, melt firing method]
SnO 67.4g, B₂O_Three  17.4g, Sn₂P₂O₇  102.8 g was mixed, sufficiently ground and mixed in an automatic mortar, then set in an alumina crucible and fired at 1000 ° C. for 10 hours in an argon gas atmosphere. After firing, it is rapidly cooled at a rate of 100 ° C./min, and a yellow transparent glassy negative electrode material SnB_0.5P_0.5O_Three(Compound A-1) was obtained. When X-ray diffraction of the active material was measured, it showed a broad diffraction band in the region of 2θ = 20-35 ° under Cu-α radiation, but a sharp diffraction line attributed to the crystal structure was detected. Thus, the active material structure was found to be amorphous (amorphous).
In addition, Si raw material is SiO₂Or Al as the Al raw material₂O_ThreeThe following A-2 and 3 amorphous negative electrode materials were synthesized by firing at 1200 ° C. for 10 hours under an argon gas atmosphere.
SnSiO_Three(Compound A-2)
Sn_0.8Si_0.5B_0.3P_0.2Al_0.1O_3.70(Compound A-3)
A-1 to A-3 were all pulverized into amorphous particles having an average particle diameter of 7 μm using a jet mill. The specific surface area of these particles by the BET method is 0.7 to 1.2 m.²/ G.
[0027]
[Surface coating of negative electrode material particles with conductive material]
The surfaces of the negative electrode material particles A-1 to A-3 were coated with carbon and copper by the following method.
(1) Coating of carbon: After the negative electrode particle powder was dried in vacuum at 150 ° C. for 5 hours, 10^-FiveThe powder was stirred by placing it on a tray at the bottom in a Pascal vacuum evaporator. The carbon electrode of the vapor deposition raw material was energized and heated red, and carbon was vapor deposited on the powder being stirred. The amount of deposition was controlled by changing the amount of the deposition source and the deposition time (energization time). The amount of carbon deposited per 100 g of powder measured from the difference in weight of the powder before and after deposition was 3 g. Further, the carbon surface coverage evaluated from the scanning electron micrograph of the particles was 50%.
For comparison, a sample was prepared in which the deposition amount and the surface coverage were changed to 0.3 g and 10% per 100 g, respectively.
(2) Copper coating: 100 g of negative electrode particle powder was added to pH 3 SnCl₂After dispersing in 1000 cc of aqueous solution and adsorbing Sn ions, the powder is filtered and washed with water, then PdCl₂Soaked in a hydrochloric acid (pH 4) aqueous solution containing 0.02 g of Pd²⁺Was adsorbed to perform surface activation treatment.
CuSO as a copper raw material_Four・ 5H₂60 g of negative electrode particles obtained by applying the above activation treatment to 1000 cc of an aqueous NaOH solution (pH 10) containing 20 g of O, 1.2 equivalents of EDTA · 4Na as a complexing agent with respect to copper and 2 equivalents of formaldehyde with respect to copper. After dispersing and maintaining the water temperature at 65 ° C. to start the plating reaction, the pH of the reaction solution was controlled to 8.5, and then the plating reaction was carried out for 3 hours to plate copper on the particle surfaces. The powder was filtered, washed with water, and dried at 150 ° C. for 24 hours. The copper surface coverage evaluated from the scanning electron micrographs of the particles was 60%.
As a comparison, a sample was prepared in which the amount of copper raw material was reduced, the amount of plating was reduced, and the surface coverage was changed to 35%.
[0028]
[Example of preparation of positive electrode active material]
LiCoO₂(Compound C-1) was synthesized by the following method. Co_ThreeO_Four, Co₂O_ThreeThe mixture was mixed with lithium carbonate so that the Li / Co molar ratio was 1.05, and calcined in air at 600 ° C. for 4 hours and further at 880 ° C. for 8 hours. Particles obtained as a result of grinding the fired product with an automatic mortar have a median diameter of 6 μm and a BET specific surface area of 0.5 m.²/ G and LiCoO by X-ray diffraction₂Was identified. This active material gave a pH of 10.5 in water dispersion.
[0029]
Further, as a positive electrode active material, lithium manganese cobalt composite oxide Li_1.05Mn_1.95Co_0.05O_Four(C-2) was synthesized by the following method.
Particle size 0.5-30 μm (including primary particles and secondary particles), BET surface area 40-70 m²/ G chemically synthesized manganese dioxide (CMD, each containing 1% by weight or less of Mn as an impurity)₂O_ThreeAnd Mn_ThreeO_FourAnd 3 wt% or less of sulfate and water, 0.5 wt% or less of Na, K, and Ca), lithium hydroxide pulverized to an average particle size of 1 to 10 μm, and cobalt carbonate in the above chemical formula After mixing at stoichiometric ratio, the mixture was heat-treated at 600 ° C. for 4 hours, and then calcined in air for 18 hours with changing temperature conditions in the range of 650 ° C. to 750 ° C. As a result of gradually cooling the final fired product to room temperature and pulverizing, the obtained particles had an average median diameter of 0.5 μm of primary particles and a particle size of secondary particles of 10 μm as measured by laser particle size distribution measurement. . BET surface area is 2m²/ G. As a result of identifying the structure and composition by ICP and X-ray diffraction, the fired product was a spinel crystal type Li_1.05Mn_1.95Co_0.05O_FourThe half-width of the diffraction peak at 2θ = 36 in the X-ray diffraction using Cu-α rays is about 0.3, and the intensity is 27% of the peak at 2θ = 18.6. It was. The lattice constant of the a axis of the crystal was 8.22A. In addition, a small amount of LiMnO is contained in the fired product.₂It was also found that was mixed. As a result of dispersing 5 g of this fired product in 100 cc of pure water and measuring the pH, it was 8.0.
[0030]
[Production example of electrode mixture sheet]
A mixture comprising 93% by weight of a negative electrode active material precursor coated with a conductive material, 2% by weight of acetylene black as an auxiliary conductive agent, 4% by weight of an aqueous dispersion of styrene-butadiene rubber as a binder and 1% by weight of carboxymethylcellulose. Water was added to the mixture and kneaded at 10,000 rpm for 10 minutes or more with a homogenizer to prepare a negative electrode mixture slurry. The obtained slurry was applied to both sides of a 18 μm thick copper film to prepare a negative electrode sheet. As a result of drying and pressing the coated sheet, the coating amount of the dry film was approximately 65 g / m.²The thickness of the coating film was approximately 27 μm.
Next, a protective layer (average thickness of 5 μm) made of a 1: 4 (weight ratio) mixture of scaly graphite and aluminum oxide is applied to the surface of the active material layer of the negative electrode sheet, and the active material precursor is applied. A prepared negative electrode sheet with a surface protective layer was produced.
[0031]
A mixture comprising 90% by weight of the positive electrode active material compound C-1 as a positive electrode mixture, 6% by weight of acetylene black, 3% by weight of an aqueous dispersion of polytetrafluoroethylene and 1% by weight of sodium polyacrylate as a binder. Water was added to and kneaded, and the resulting slurry was applied to both sides of an aluminum film having a thickness of 30 μm to produce a positive electrode sheet. As a result of drying and pressing the coated sheet, the coating amount of the dry film was 285 g / m.²The thickness of the coating film was about 100 μm.
Similarly, a positive electrode coated sheet was prepared using Compound C-2 as a positive electrode active material. The coating amount of the dry film is 340 g / m²The thickness of the coating film was 120 μm.
[0032]
[Production example of cylinder type battery]
Surfaces of both surfaces of a negative electrode sheet obtained by cutting a metal Li foil having a thickness of 35 μm into pieces having a width of 5 mm and a length of 37 mm and applying the negative electrode active material precursors A-1 to 3 in dry air having a dew point of −60 ° C. It was adhered on the protective layer using a pressure roller at regular intervals of 2 mm. The amount of Li attached to the negative electrode sheet was approximately 110 mg as a weight.
The positive electrode sheet was cut to a width of 35 mm, the negative electrode sheet was cut to a width of 37 mm, and aluminum and nickel lead plates were spot welded to the ends of the sheet, respectively. Dehydrated and dried at 2 ° C. for 2 hours. As shown in the cross-sectional view of the battery in FIG. 1, the positive electrode sheet after dehydration and drying, the porous polyethylene film as the separator, the negative electrode sheet after dehydration and drying, and the separator are laminated in this order, and then spirally formed by a wrapping machine. I wound it. This wound electrode group (2) was housed in an iron-bottomed cylindrical battery can (1) (also serving as a negative electrode terminal) plated with nickel. 1 mol / liter LiPF as electrolyte in this battery can₆(A 2: 2: 6 (volume ratio) mixture of ethylene carbonate, butylene carbonate, and dimethyl carbonate) was injected.
A battery lid (6) having a positive terminal was caulked through a gasket (5) to produce a cylindrical battery having a diameter of 14 mm and a height of 50 mm. The positive electrode terminal (6) is connected to the positive electrode sheet, the battery can (1) is connected to the negative electrode sheet in advance by a lead terminal, and the pressure-sensitive valve element (61), current interrupter (62), A PTC element (63) was provided.
As described above, C-1 and C-2 as positive electrode active materials and A-1 to A-3 as negative electrode active material precursors coated with a surface conductive material were selected and combined.
[0033]
The battery produced as described above is a battery precursor in which the process of electrochemically inserting lithium on the coating sheet protective layer into the negative electrode active material precursor is not completed. Therefore, an operation for converting the battery precursor into a negative electrode active material by inserting lithium into the negative electrode active material precursor and making the battery precursor a chargeable / discharge cycleable secondary battery was performed as follows.
The battery precursor was allowed to stand at room temperature for 12 hours, precharged for 1 hour under a constant current of 0.1 A, and then aged at 50 ° C. for 10 days. In this aging step, it was confirmed that Li supported on the negative electrode was almost dissolved and inserted into the negative electrode active material precursor.
2 mA / cm for activation of this battery²The battery was charged to 4.2 V at room temperature. Further, the battery was kept at 55 ° C. in a charged state, and aging was performed for 3 days.
These batteries were repeatedly charged and discharged with a constant current under the conditions of a charge end voltage of 4.2 V (open circuit voltage (OCV)) and a discharge end voltage of 2.8 V (circuit voltage), and were cycled. At this time, the battery is 2 mA / cm.²After charging at a current density (equivalent to 0.2 C in this battery), 10 mA / cm²The capacity (Ah) given by the discharge current (equivalent to 1.0 C in this battery) and 2 mA / cm²The ratio of the capacity given by the discharge current of (0.2C) was determined and evaluated as the high rate discharge efficiency (%) (where 1C represents the value of the current corresponding to discharging the nominal capacity of the battery in 1 hour) ).
[0034]
Table 1 shows the measured high-rate efficiency and the capacity at high current discharge of 1 C under the conditions in which the combination of the positive electrode active material and the negative electrode material was changed for the above lithium ion secondary battery.
[0035]

[0036]
From the results in Table 1, the lithium ion secondary battery containing the metal oxide negative electrode material coated with the surface conductive material described in the present invention in the negative electrode mixture layer is excellent in terms of high rate discharge efficiency and capacity. It can be seen that the performance is high. In addition, in the case of the combination of C-1 and carbon-coated A-3, and C-1 and copper-coated A-3, the lithium ion secondary battery of the present invention has a charge / discharge cycle life at room temperature, Discharge capacity maintenance ratios of 95% and 92% per 100 cycles were shown.
[0037]
【The invention's effect】
A positive electrode material made of a lithium-containing transition metal composite oxide, a negative electrode material made of a metal oxide into which lithium can be inserted, and a nonaqueous electrolyte, and the metal oxide particles of the negative electrode are surfaces of particles made of the metal composite oxide By using a lithium ion non-aqueous electrolyte secondary battery characterized in that it is a composite particle coated with a thin film of a conductive inorganic material, battery capacity and high rate discharge characteristics can be improved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a cylinder type secondary battery manufactured in an example.
[Explanation of symbols]
1 Battery can also serves as a negative terminal
2 wound electrode group (positive electrode, separator, negative electrode)
3 Upper insulation plate
4 Positive lead
5 Gasket
6 Battery cover that also serves as a positive terminal
61 Pressure sensitive valve
62 Current interrupter
63 PTC element

Claims (10)

In a negative electrode active material layer of a negative electrode comprising a positive electrode comprising a lithium-containing transition metal composite oxide, a negative electrode comprising metal oxide particles capable of inserting lithium and a non-aqueous electrolyte, and a non-aqueous electrolyte. The metal oxide particles are composite particles in which the surface of particles made of a metal composite oxide is coated with a thin film of a conductive inorganic material, and a protective layer containing aluminum oxide is formed on the anode active material layer A lithium ion non-aqueous electrolyte secondary battery characterized by being a negative electrode. The lithium ion nonaqueous electrolyte secondary battery according to claim 1 , wherein the protective layer contains graphite and aluminum oxide . The lithium ion nonaqueous electrolyte secondary battery according to claim 1 or 2 , wherein the conductive inorganic material is a carbonaceous material.   The lithium ion nonaqueous electrolyte secondary battery according to claim 1, wherein the conductive inorganic material is a metal.   2. The lithium ion non-aqueous electrolyte secondary battery according to claim 1, wherein the conductive inorganic material is a metal coated on the surface of metal oxide particles by an electroless plating method.   The conductive inorganic material is one or more metals selected from Cu, Ag, Ni, Au, Pt, Al, Mg, Ti, Zn, Sn, In, W, and Pb, or an alloy of these metals and Li The lithium ion non-aqueous electrolyte secondary battery according to claim 4 or 5, wherein:   The lithium ion non-aqueous electrolyte secondary battery according to any one of claims 1 to 6, wherein the surface coverage of the conductive inorganic material is 20% or more and 100% or less.   The lithium ion nonaqueous electrolyte secondary battery according to any one of claims 1 to 7, wherein the surface coverage of the conductive inorganic material is 0.01 wt% or more and 15 wt% or less with respect to the metal oxide particles. . 3. The lithium ion non-aqueous electrolyte secondary battery according to claim 1, wherein lithium metal or a lithium alloy is further adhered on the protective layer. Lithium ion nonaqueous electrolyte secondary battery according to any one of claims 1 to 9, characterized in that the metal oxide is a composite oxide containing an amorphous structure containing mainly tin.

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