JP3809662B2 - Non-aqueous secondary battery - Google Patents

Description

とする。結果を表４の１に示す。放電容量比Ａ、Ｂとも良好であり、大電流あるいは低温での使用時においても良好な特性が得られることがわかる。
【００５３】
参考例２
α−Ａｌ₂ Ｏ₃ （平均粒径１μｍ）８０重量％、鱗片状黒鉛１０重量％、結着剤としてポリフッ化ビニリデン４重量％を混合し、分散剤としてカルボキシメチルセルロース１重量％を加え、水を媒体として混練してスラリーを作製し、これを負極シート１と同様の塗布シート上に塗設して保護層を形成した。これを保護層１とする。参考例１と同様の方法で電極シートを作製し、円筒型電池を作製した。これを電池番号２とする。参考例１と同様の充放電試験を行った。さらに、同様な電池を３００個作製し、１ｍＡ／ｃｍ² で４．１Ｖまで充電した後、６０℃にて３週間の保存試験を行った。このとき開路電圧の低下率が０．８Ｖ以上であったものの本数の割合を不良発生率とする。それぞれの結果を表４の１に示す。放電容量比Ａ、Ｂともに良好である上に、不良発生率が極めて小さい。
【００５４】
参考例３
α−Ａｌ₂ Ｏ₃ （平均粒径１μｍ）９５重量％、結着剤としてポリフッ化ビニリデン４重量％を混合し、分散剤としてカルボキシメチルセルロース１重量％を加え、水を媒体として混練してスラリーを作製し、これを正極シート１と同様の塗布シート上に塗設して保護層を形成した。これを保護層２とする。参考例１と同様の方法で電極シートを作製し、円筒型電池を作製した。これを電池番号３とする。試験結果を表４の１に示す。放電容量比、不良発生率ともに極めて良好である。
【００５５】
参考例４
負極シート１及び正極シート１作製時にカレンダープレス機プレス圧を調整して、負極合剤及び正極合剤中の空隙率を夫々２２％及び３１％とした。参考例１と同様の方法で電極シートを作製し、円筒型電池を作製した。これを電池番号４とする。試験結果を表４の１に示す。放電容量比、不良発生率ともに極めて良好である。
【００５６】
実施例１〜３、参考例５〜２２
表１に示す負極材料、表２に示す正極活物質、表３に示す電解質を使用し、表４の１〜表４の３に示す空隙率に調整して参考例１と同様に電池番号５〜２５を作製した。ここで保護層３は保護層２におけるα−Ａｌ₂ Ｏ₃ （平均粒径１μｍ）のかわりにＴｉＯ₂ 粉末（平均粒径１μｍ）を使用したものである。試験結果を表４の１〜表４の３に示す。放電容量比、不良発生率ともに極めて良好である。
なお、実施例１〜３は、それぞれ、電池番号５，１４，２５である。
【００５７】
比較例
表１に示す負極材料、表２に示す正極活物質、表３の１〜表３の２に示す電解質を使用し、表４の３に示す空隙率に調整して実施例１と同様に電池番号２６〜３３を作製した。試験結果を表４の３に示す。全般に放電容量比Ａ、Ｂが劣り、大電流あるいは低温のもとで十分な放電容量を得ることができない。またその傾向が製造得率、安全性を向上させるため、保護層を付与した場合、合剤中の空隙率を上げた場合に著しい。
【００５８】
【表１】

【００５９】
【表２】

【００６０】
【表３】

【００６１】
【表４】

【００６２】
【表５】

【００６３】
【表６】

【００６４】
【表７】

【００６５】
【発明の効果】
本発明のように、リチウムを吸蔵放出できる正極と負極およびリチウム塩を含む非水電解質を電池容器に収納してなる非水二次電池において、該非水電解質がジメチルカーボネート、エチルメチルカーボネート、プロピオン酸メチル、プロピオン酸エチルから選ばれる少なくとも１種のエステル類およびエチレンカーボネートを少なくとも含有する混合溶媒にフッ素を含むリチウム塩を溶解した非水電解質を用いることによって、より大電流での使用に耐え、より広い温度範囲での使用に耐えうる非水二次電池を得ることができる。
【図面の簡単な説明】
【図１】実施例に使用した円筒型電池の断面図を示したものである。
【符号の説明】
８ 正極シート
９ 負極シート
１０ セパレーター
１１ 電池缶
１２ 電池蓋
１３ ガスケット
１４ 安全弁[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a non-aqueous secondary battery with improved charge / discharge characteristics such as discharge potential, discharge capacity, and charge / discharge cycle life, and productivity and safety.
[0002]
[Prior art]
Non-aqueous secondary batteries using lithium have been extensively developed because of their high capacity. These lithium secondary batteries are usually composed of a positive electrode and a negative electrode containing a material capable of reversibly occluding and releasing lithium, a non-aqueous electrolyte containing a lithium salt, and a separator. As the non-aqueous electrolyte, as shown in JP-A-3-295178, JP-A-5-234619, JP-A-6-84543, LiPF is used as a mixed solvent of a cyclic ester and a chain ester.₆It is said that a solution in which an electrolyte such as is dissolved is preferable in terms of discharge capacity and cycleability. As these lithium secondary batteries expand their application range, those that can withstand use at higher currents and those that can withstand use in a wider temperature range have come to be demanded. On the other hand, these non-aqueous secondary batteries have a problem that a sufficient capacity cannot be obtained when they are used under a large current or a low temperature in order to ensure safety and productivity.
The cause of poor productivity of the non-aqueous secondary battery, particularly the manufacturing yield, is largely due to defects caused by internal short circuits. The occurrence of an internal short circuit due to the destruction of the separator occurs when the electrode mixture expands and contracts because the active material expands and contracts as the battery is charged and discharged. This can be prevented by ensuring a certain space in the mixture. However, according to this method, the electrical conductivity between the current collector / mixture or between the active material / conductive agent in the mixture deteriorates, increasing the internal resistance of the battery, which is sufficient for use at higher currents and lower temperatures. The problem that it was not possible to obtain a sufficient discharge capacity occurred.
In addition, the occurrence of an internal short circuit due to the destruction of the separator is caused by the unevenness due to protrusions on the electrode surface, scratches on the electrode surface that occur during the process from electrode transportation to battery assembly, and unevenness due to partial dropout, etc. It is presumed that it is caused by destroying the separator directly when it is wound, or by subtle sliding at the time of winding, or by breaking the separator due to uneven pressure. Therefore, the present inventors are effective to provide a protective layer on either or both of the positive electrode and the negative electrode, as shown in the specification of Japanese Patent Application No. 7-174661, and the installation of the protective layer is a manufacturing yield. It has been found that safety is improved as well. However, the installation of these protective layers also increases the distance between the positive and negative electrode plates, which increases the internal resistance of the battery, making it impossible to obtain sufficient discharge capacity when used at higher currents and lower temperatures. was there.
[0003]
[Problems to be solved by the invention]
An object of the present invention is to obtain a non-aqueous secondary battery that can withstand use at a larger current and withstand use in a wider temperature range while ensuring the safety and productivity of the battery.
[0004]
[Means for Solving the Problems]
An object of the present invention is a nonaqueous secondary battery in which a nonaqueous electrolyte containing a positive electrode and a negative electrode capable of occluding and releasing lithium and a lithium salt is housed in a battery container, wherein the nonaqueous electrolyte is dimethyl carbonate, ethyl methyl carbonate, Use of a non-aqueous electrolyte in which a lithium salt containing fluorine is dissolved in a mixed solvent containing at least one ester selected from methyl propionate, ethyl propionate, methyl methoxyacetate and ethyl methoxyacetate and ethylene carbonate Achieved by the feature non-aqueous secondary battery.
[0005]
  That is, the present invention is a nonaqueous secondary battery having the following features (1) to (12).
(1) A nonaqueous secondary battery in which a positive electrode and a negative electrode capable of occluding and releasing lithium and a nonaqueous electrolyte containing a lithium salt are housed in a battery container,NegativeThe porosity in the mixture constituting the electrode is 10% or more and 45% or less, and the non-aqueous electrolyte is composed of dimethyl carbonate, ethyl methyl carbonate, methyl propionate, ethyl propionate, methyl methoxyacetate and ethyl methoxyacetate LiPF so that the concentration is 0.6 M or more and 1.5 M or less in a mixed solvent containing at least one ester selected from₆And LiBF_FourOn the surface of the negative electrode mixture layer, carbon black such as thermal black, furnace black, channel black, and lamp black, natural graphite such as scaly graphite, scaly graphite, earthy graphite, A non-aqueous secondary battery comprising at least one protective layer containing a conductive carbon material that is at least one selected from artificial graphite and carbon fiber.
(2) The protective layer on the surface of the negative electrode mixture layer contains at least one insulating particle selected from carbides, silicides, nitrides, sulfides, and oxides of metal or nonmetallic elements. The non-aqueous secondary battery according to (1), characterized in that it is characterized in that
(3) The insulating particles are SiC, AlN, BN, BP, Al₂O_Three, BaO, BeO, CaO, K₂O, Na₂O, InO, MgO, SiO₂, SrO, ZrO_FourTiO₂The nonaqueous secondary battery according to (2), which is at least one selected from
(4) The active material constituting the negative electrode is mainly composed of a complex oxide and / or a complex chalcogenide containing at least one of group 1 element, group 2 element, group 3 element and halogen element in the periodic table. The nonaqueous secondary battery according to any one of (1) to (3) above,
(5) The nonaqueous secondary battery according to any one of (1) to (4) above, wherein a porosity in the mixture constituting the positive electrode is 18% or more and 35% or less.
(6) The nonaqueous secondary battery according to any one of (1) to (5) above, wherein a porosity in the mixture constituting the negative electrode is 18% or more and 35% or less.
(7The nonaqueous electrolyte contains at least one ester selected from the group consisting of dimethyl carbonate, ethyl methyl carbonate, methyl propionate, ethyl propionate, methyl methoxyacetate and ethyl methoxyacetate, and ethylene carbonate and diethyl carbonate. From the above (1) characterized by6The nonaqueous secondary battery according to any one of the above.
(8) A total of 10% by volume or more of at least one ester selected from the group consisting of dimethyl carbonate, ethyl methyl carbonate, methyl propionate, ethyl propionate, methyl methoxyacetate and ethyl methoxyacetate in the solvent constituting the nonaqueous electrolyte From the above (1) characterized by containing 90% by volume or less (7The nonaqueous secondary battery according to any one of the above.
[0006]
(9The above-mentioned (1) to (1), wherein the solvent constituting the nonaqueous electrolyte contains at least one ester selected from dimethyl carbonate and ethyl methyl carbonate.8The nonaqueous secondary battery according to any one of the above.
(10(1) to (1) above, wherein the active material constituting the positive electrode is a lithium-containing transition metal oxide.9The nonaqueous secondary battery according to any one of the above.
[0007]
In the present invention, by using 10 to 45% of the porosity in the mixture constituting the positive electrode and the negative electrode as described above, and using a specific mixed solvent (requires the use of ethylene carbonate) as a non-aqueous electrolyte. Charge / discharge characteristics such as discharge potential, discharge capacity and charge / discharge cycle life, productivity and safety are improved, especially withstands the use of higher currents and has the superior effect of withstanding use over a wider temperature range. A non-aqueous secondary battery is provided.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of the present invention are as follows, but these are only examples, and it is not necessary to limit them.
The mixed solvent used in the non-aqueous electrolyte of the present invention contains at least one ester selected from dimethyl carbonate, ethyl methyl carbonate, methyl propionate, ethyl propionate, methyl methoxyacetate and ethyl methoxyacetate and ethylene carbonate. Preferably, it contains at least one ester selected from dimethyl carbonate, ethyl methyl carbonate, methyl methoxyacetate, and ethyl methoxyacetate and ethylene carbonate, more preferably dimethyl carbonate and ethylene carbonate. It contains. When these are used, when a space of 10% to 45% is provided in the positive electrode and / or negative electrode mixture, sufficient capacity can be obtained at a large discharge current and low temperature while ensuring productivity and safety. I found out.
Furthermore, it has been found that a sufficient capacity can be secured under a large discharge current and low temperature even when a protective layer is provided on the positive electrode and / or the negative electrode in order to improve productivity and safety. These can increase the dielectric constant of the electrolyte and lower the liquid viscosity at low temperatures, so that when used under high loads, when used under low temperatures, especially when conduction between the active material and current collector is not sufficient, It is presumed that the movement of lithium ions in the electrolyte and the transfer of electrons are performed smoothly when the distance between the positive and negative electrode plates is increased.
[0009]
The mixed solvent may further contain any organic solvent, chain carbonates such as diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, isopropyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, Chain esters such as methyl malonate, ethyl malonate, methyl succinate, ethyl succinate, methyl 3-methoxypropionate, ethyl 3-methoxypropionate, propylene carbonate, 1,2-butylene carbonate, 2,3- Cyclic carbonates such as butylene carbonate, 1,2-pentene carbonate, 2,3-pentene carbonate, cyclic esters such as β-butyrolactone, γ-butyrolactone, γ-valerolactone, δ-valerolactone, dimethoxyethane Can contain from ethers such as diethoxyethane and the like, preferably contains diethyl carbonate.
[0010]
Examples of the preferred mixed solvent used in the electrolyte of the present invention include 5% by volume or more and less than 60% by volume of ethylene carbonate, and a total of 5% by volume or more and less than 95% by volume of dimethyl carbonate, ethyl methyl carbonate, methyl propionate, propionic acid. It is a mixed solvent with at least one ester selected from ethyl, methyl methoxyacetate, and ethyl methoxyacetate.
More preferable examples include 10% by volume or more and less than 55% by volume of ethylene carbonate, and a total of 15% by volume or more and less than 90% by volume of dimethyl carbonate, ethyl methyl carbonate, methyl propionate, ethyl propionate, methyl methoxyacetate, ethyl ethoxy acetate. It is a mixed solvent with at least one ester selected from
Particularly preferred examples include 10% by volume or more and less than 30% by volume of ethylene carbonate, and a total of 30% by volume or more and less than 90% by volume of dimethyl carbonate, ethyl methyl carbonate, methyl propionate, ethyl propionate, methyl methoxyacetate, methoxyacetic acid It is a mixed solvent with at least one ester selected from ethyl.
[0011]
The lithium salt used in the electrolyte of the present invention is a lithium salt containing fluorine. As a specific example, LiBF_Four, LiPF₆, LiAsF₆, LiSbF₆, LiCF_ThreeSO_Three, LiCF_ThreeCO₂However, it is not particularly limited to these compounds.
The lithium salt preferably used is LiCF_ThreeSO_Three, LiXF_n(X: B, P, As, Sb, n is 4 when X is B and 6 when X is P, As, Sb). LiXF_nIs
LiF_n+ XF_n-1→ LiXF_n
As a specific example, a Lewis acid double salt represented by the formula: LiBF_Four, LiPF₆, LiAsF₆, LiSbF₆It is.
More preferably LiBF_Four, LiPF₆, LiCF_ThreeSO_ThreeAnd particularly preferably LiPF₆, LiBF_FourAnd most preferably LiPF₆It is.
The lithium salt used in the electrolyte of the present invention can be used as a mixture. Preferably, LiPF₆And LiCF_ThreeSO_Three, LiXF_n(X: B, P, As, Sb, n is a mixture with at least one lithium salt selected from 4 when X is B and 6 when X is P, As, Sb). More preferably, LiPF₆And LiBF_Four, LiCF_ThreeSO_ThreeA mixture with at least one lithium salt selected from: Particularly preferably LiPF₆And LiBF_FourIt is mixed with.
In the present invention, the lithium salt concentration of the electrolyte is not particularly limited, but is preferably 0.2 M or more and 3 M or less, particularly preferably 0.5 M or more and 2 M or less, and most preferably 0.6 M or more and 1.5 M or less.
The amount of these electrolytes added to the battery is not particularly limited, but a necessary amount 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.
[0012]
  The positive and negative electrodes used in the nonaqueous secondary battery of the present invention can be prepared by coating a positive electrode mixture or a negative electrode mixture on a current collector. Positive and negative electrodes are mixed with a positive electrode active material or a negative electrode material, as well as an undercoat introduced for the purpose of improving the adhesion between the current collector and the mixture layer or improving the conductivity.LayeredYou may have.
  Here, in the nonaqueous secondary battery of the present invention, at least the negative electrode is formed on the surface of the negative electrode such as thermal black, furnace black, channel black, or lamp black for the purpose of mechanical protection or chemical protection of the mixture layer. It has at least one protective layer containing a conductive carbon material that is at least one selected from natural graphite such as carbon black, scaly graphite, scaly graphite, and earthy graphite, artificial graphite, and carbon fiber. The positive electrode may have a protective layer for the purpose of mechanical protection and chemical protection of the mixture layer.
  In the present invention, the protective layer comprises at least one layer, and may be composed of the same or different plural layers. These protective layers may be substantially conductive or insulating. The thickness of the protective layer is preferably 1 μm or more and 40 μm or less, more preferably 2 μm or more and 30 μm or less. These protective layers contain at least water-insoluble particles. These particles may be either conductive or insulating, and may be either organic or inorganic. These particles are preferably those having low reactivity with alkali metals, particularly lithium. The average particle size of these particles is preferably 0.01 μm or more and 20 μm or less, and more preferably 0.1 μm or more and 15 μm or less.
[0013]
  As the conductive particles, metal powder and carbon particles are preferable. The metal powder is preferably a metal having low reactivity with lithium, that is, a metal that is difficult to form a lithium alloy. Specifically, copper, nickel, iron, chromium, molybdenum, titanium, tungsten, and tantalum are preferable. As the carbon particles, a known carbon material used as a conductive material used in combination when the electrode active material is not conductive can be used. Examples of these materials include carbon black such as thermal black, furnace black, channel black, and lamp black, natural graphite such as scale-like graphite, scale-like graphite, and earth-like graphite, artificial graphite, and carbon fiber.
  As the insulating organic particles, a crosslinked latex or a fluororesin powder is preferable, and those that do not decompose or form a film are preferable. More preferred is a fine powder of Teflon.
  Insulating inorganic particles include carbides, silicides, nitrides, sulfides and oxides of metals and non-metallic elements, ChalcogenideCan be mentioned. Among carbides, silicides, and nitrides, SiC, aluminum nitride (AlN), BN, and BP are preferably highly insulating and chemically stable. In particular, SiC using BeO, Be, and BN as a sintering aid. Is particularly preferred.
  Among chalcogenides, oxides are preferable, and oxides that are not easily oxidized or reduced are preferable. These oxides include Al₂O_Three, BaO, BeO, CaO, K₂O, Na₂O, InO, MgO, SiO₂, SrO, ZrO_FourTiO₂Is preferred. These oxides may be single or complex oxides.
[0014]
The protective layer can be formed using a dispersant and a binder in addition to the water-insoluble particles. As the dispersant and binder, a dispersant and binder used when forming an electrode mixture described later can be used.
The protective layer may be applied to either the positive electrode or the negative electrode, or may be applied to both the positive electrode and the negative electrode. In addition, when the positive electrode or the negative electrode is formed by coating a mixture on both sides of the current collector, the protective layer may be coated on both sides or may be coated on only one side. Good. However, it is necessary to coat either one of the positive electrode and the negative electrode facing each other through the separator.
The coating method of the protective layer may be a sequential method in which a protective layer is sequentially coated after a mixture containing a material capable of reversibly occluding and releasing lithium on the current collector, or the mixture layer and the protective layer may be protected. A simultaneous application method in which layers are simultaneously applied may be used.
In addition to the positive electrode active material or the negative electrode material, the positive electrode or the negative electrode mixture can contain a conductive agent, a binder, a dispersant, a filler, an ionic conductive agent, a pressure enhancer, and various additives, respectively. The undercoat layer and the protective layer can contain binders, conductive agent particles, non-conductive particles, and the like.
The positive electrode active material used in the present invention may be any compound that can occlude / release light metal ions, and is particularly selected from transition metal oxides and transition metal chalcogenides. A transition metal oxide is particularly preferable, and a transition metal oxide containing lithium is particularly preferable.
[0015]
Preferred transition metals used in the present invention include Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Nb, Mo, and W. Among these transition metal compounds, manganese dioxide, five Vanadium oxide, iron oxide, molybdenum oxide, molybdenum sulfide, cobalt oxide, iron sulfide, titanium sulfide, and the like are preferable. These compounds can be used alone or in combination of two or more. Moreover, it can also be used as a transition metal oxide containing lithium.
In addition to lithium compounds and transition metal compounds, in general, Ca²⁺A compound that enhances ionic conductivity, or an amorphous network forming agent containing P, B, or Si (for example, P₂O_Five, Li_ThreePO_Four, H_ThreeBO_Three, B₂O_Three, SiO₂Etc.) and may be fired. Further, it may be fired by mixing with an alkali metal ion such as Na, K, Mg, an alkaline earth metal ion and / or a compound containing Si, Sn, Al, Ga, Ge, Ce, In, Bi, or the like. The transition metal oxide containing lithium can be synthesized, for example, by firing a mixture of a lithium compound and a transition metal compound.
[0016]
Specific examples of preferable positive electrode active materials used in the present invention include JP-A No. 61-5262, US Pat. No. 4,302,518, JP-A No. 63-299056, JP-A No. 1-294364, JP-B-4-30146, U.S. Pat. Nos. 5,240,794, 5,153,081, JP-A-4-328,258, JP-A-5-54,889, etc. It is described in. Representative compounds are shown below, but the present invention is not limited thereto.
Li_xCoO₂, Li_xNiO₂, Li_xCo_aNi_1-aO₂, Li_xCo_bV_1-bO_z, Li_xCo_bFe_1-bO_z, Li_xMn₂O_Four, Li_xMnO₂, Li_xMn₂O_Three, Li_xMn_bCo_2-bO_z, Li_xMn_bNi_2-bO_z, Li_xMn_bV_2-bO_z, Li_xMn_bFe_1-bO_z, Li_xCo_cB_1-cO₂(Where x = 0.02 to 2.2, a = 0.1 to 0.9, b = 0.8 to 0.98, c = 0.85 to 0.99, z = 1.5 to 5 ).
[0017]
The positive electrode active material used in the present invention can be synthesized by a method in which a lithium compound and a transition metal compound are mixed and fired, or by a solution reaction, and the firing method is particularly preferable.
Details for firing are described in paragraph [0035] of JP-A-6-60,867, JP-A-7-14,579, and the like, and these methods can be used. The positive electrode active material obtained by firing may be used after being washed with water, an acidic aqueous solution, an alkaline aqueous solution, or an organic solvent.
Further, as a method of chemically inserting lithium ions into the transition metal oxide, a method of synthesis by reacting lithium metal, a lithium alloy or butyl lithium with a transition metal oxide may be used.
[0018]
The average particle size of the positive electrode active material used in the present invention is not particularly limited, but is preferably 0.1 to 50 μm. The volume of particles of 0.5 to 30 μm is preferably 95% or more. More preferably, the volume occupied by a particle group having a particle size of 3 μm or less is 18% or less of the total volume, and the volume occupied by a particle group of 15 μm or more and 25 μm or less is 18% or less of the total volume. Although it does not specifically limit as a specific surface area, it is 0.01-50m in BET method²/ G is preferred, especially 0.2 m²/ G-1m²/ G is preferred. The pH of the supernatant when 5 g of the positive electrode active material is dissolved in 100 ml of distilled water is preferably 7 or more and 12 or less.
When the positive electrode active material of the present invention is obtained by firing, the firing temperature is preferably 500 to 1500 ° C, more preferably 700 to 1200 ° C, and particularly preferably 750 to 1000 ° C. The firing time is preferably 4 to 30 hours, more preferably 6 to 20 hours, and particularly preferably 6 to 15 hours.
[0019]
The negative electrode material used in the present invention may be any compound that can occlude / release light metal ions. In particular, light metals, light metal alloys, carbonaceous compounds, inorganic oxides, inorganic chalcogenides, metal complexes, and organic polymer compounds are preferable. It is preferable that the main component is a composite oxide containing one kind or a composite chalcogenide. These may be used alone or in combination. Examples include light metals and carbonaceous compounds, light metals and inorganic oxides, and combinations of light metals, carbonaceous compounds, and inorganic oxides. These negative electrode materials are preferable because they provide high capacity, high discharge potential, high safety, and high cycle effect.
[0020]
Lithium is preferred as the light metal. Examples of the light metal alloy include a metal that forms an alloy with lithium or an alloy containing lithium. Al, Al—Mn, Al—Mg, Al—Sn, Al—In, and Al—Cd are particularly preferable.
The carbonaceous compound is preferably selected from natural graphite, artificial graphite, vapor-grown carbon, baked carbon of an organic substance, and the like, and includes a graphite structure. In addition to carbon, the carbonaceous compounds include different compounds such as B, P, N, S, SiC, B_FourC may be contained in an amount of 0 to 10% by weight.
As an element for forming an oxide or chalcogenide, a transition metal or a metal or a semi-metal element of Group 15 to 15 of the periodic table is preferable.
As the transition metal compound, V, Ti, Fe, Mn, Co, Ni, Zn, W, Mo alone or a composite oxide or chalcogenide is particularly preferable. As a more preferred compound, Li described in JP-A-6-44,972_pCo_qV_1-qO_r(Where p = 0.1 to 2.5, q = 0 to 1, r = 1.3 to 4.5).
[0021]
As a compound of a metal other than a transition metal or a semimetal, a group 13-15 element of the periodic table, Al, Ga, Si, Sn, Ge, Pb, Sb, Bi alone or a combination of two or more thereof An oxide consisting of chalcogenide is selected.
For example, Al₂O_Three, Ga₂O_Three, SiO, SiO₂, GeO, GeO₂, SnO, SnO₂, SnSiO_Three, PbO, PbO₂, Pb₂O_Three, Pb₂O_Four, Pb₂O_Four, Sb₂O_Three, Sb₂O_Four, Sb₂O_Five, Bi₂O_Three, Bi₂O_Four, Bi₂O_Five, SnSiO_Three, GeS, GeS₂, SnS, SnS₂, PbS, PbS₂, Sb₂S_Three, Sb₂S_Five, SnSiS_ThreeEtc. are preferable. These are also complex oxides with lithium oxide, such as Li₂GeO_Three, Li₂SnO₂It may be.
[0022]
The complex chalcogen compound and complex oxide are preferably mainly amorphous when assembled into a battery. The term “amorphous” as used herein refers to an X-ray diffraction method using CuKα rays, which has a broad scattering band having an apex from 20 ° to 40 ° as a 2θ value, and has a crystalline diffraction line. Also good. Preferably, the strongest intensity of the crystalline diffraction lines seen at 2θ values of 40 ° or more and 70 ° or less is 500 of diffraction line intensities at the apexes of broad scattering bands seen at 20 ° or more and 40 ° or less of 2θ values. It is preferably not more than twice, more preferably not more than 100 times, particularly preferably not more than 5 times, and most preferably not having a crystalline diffraction line.
[0023]
The above-mentioned composite chalcogen compound and composite oxide are composite compounds composed of transition metals and Group 15 elements from Periodic Table 13, B, Al, Ga, In, Tl, Si, Ge, Sn, Pb, P, As. , Sb and Bi are more preferably composite chalcogen compounds and composite oxides mainly composed of two or more elements. More preferred are complex oxides.
Particularly preferred are composite oxides mainly composed of two or more elements of B, Al, Si, Ge, Sn, and P.
These composite chalcogen compounds and composite oxides may contain elements from Group 1 to Group 3 of the periodic table or halogen elements mainly to modify the amorphous structure. Transition metals may also be included.
[0024]
Among the above negative electrode materials, an amorphous composite oxide mainly composed of tin is preferable, and is represented by the following general formula (1) or (2).
SnM¹ _aOt General formula (1)
Where M¹Represents two or more elements selected from Al, B, P, Si, Ge, Group 1 element, Group 2 element, Group 3 element, and halogen element of the periodic table, and a is 0.2 or more, 2 In the following numbers, t represents a number of 1 or more and 6 or less.
Sn_xT_1-xM¹ _aO_t                General formula (2)
In the formula, T represents a transition metal metal and represents V, Ti, Fe, Mn, Co, Ni, Zn, W, or Mo. x represents a number of 0.1 or more and 0.9 or less. M1, a, and t are the same as those in the general formula (1).
[0025]
Among the compounds of the general formula (1), the following compounds of the general formula (3) are more preferable.
SnM² _bO_t                    General formula (3)
Where M²Represents two or more elements selected from Al, B, P, Ge, Group 1 elements, Group 2 elements, Group 3 elements, and halogen elements in the periodic table, and b is 0.2 to 2 The number, t represents a number of 1 or more and 6 or less.
Among the compounds of the general formula (3), the following compounds of the general formula (4) are more preferable.
SnM^Three _cM^Four _dOt General formula (4) Formula
Medium, M^ThreeIs at least one of Al, B, P, Ge, M^FourRepresents at least one of group 1 element, group 2 element, group 3 element and halogen element in the periodic table, c is a number of 0.2 or more and 2 or less, and d is 0.01 or more and 1 or less. In terms of numbers, 0.2 <c + d <2, t represents a number from 1 to 6.
[0026]
The amorphous composite oxide of the present invention can employ either a firing method or a solution method, but a firing method is more preferable. In the firing method, it is preferable to obtain an amorphous composite oxide by thoroughly mixing oxides or compounds of the elements described in the general formula (1) and then firing.
As firing conditions, the temperature rise rate is preferably 5 ° C. or more and 200 ° C. or less per minute, the firing temperature is preferably 500 ° C. or more and 1500 ° C. or less, and the firing time is 1 hour. It is preferable that it is 100 hours or less. Further, the rate of temperature decrease is preferably 2 ° C. or more and 10 7 ° C. or less per minute.
The rate of temperature increase in the present invention is the average rate of temperature rise from “50% of the firing temperature (indicated in ° C.)” to “80% of the firing temperature (indicated in ° C.)”. It is the average rate of temperature drop from reaching “80% of the firing temperature (indicated in degrees Celsius)” to “50% of the firing temperature (indicated in degrees Celsius)”.
The temperature lowering may be cooled in a firing furnace, or taken out of the firing furnace and cooled, for example, in water. In addition, a super rapid cooling method such as the gun method, Hammer-Anvil method, slap method, gas atomization method, plasma spray method, centrifugal quenching method, or melt drag method described on page 217 of ceramics processing (Gihodo Publishing 1987) can also be used. Moreover, you may cool using the single roller method and the double roller method of New Glass Handbook (Maruzen 1991) p.172. In the case of a material that melts during firing, the fired product may be continuously taken out while supplying raw materials during firing. In the case of a material that melts during firing, it is preferable to stir the melt.
[0027]
The firing gas atmosphere is preferably an atmosphere having an oxygen content of 5% by volume or less, and more preferably an inert gas atmosphere. Examples of the inert gas include nitrogen, argon, helium, krypton, and xenon. The most preferred inert gas is pure argon.
[0028]
As for the average particle size of the compound shown by this invention, 0.1-60 micrometers is preferable. More specifically, it is preferable that the average particle diameter is 0.7 to 25 μm, and 60% or more of the total volume is 0.5 to 30 μm. Further, the volume occupied by the particle group having a particle size of 1 μm or less of the negative electrode active material of the present invention is 30% or less of the total volume, and the volume occupied by the particle group having a particle size of 20 μm or more is 25% or less of the total volume. Is preferred. Needless to say, the particle size of the material used does not exceed the thickness of the mixture on one side of the negative electrode.
To obtain a predetermined particle size, a well-known pulverizer or classifier is used. For example, a mortar, a ball mill, a sand mill, a vibrating ball mill, a satellite ball mill, a planetary ball mill, a swirling air flow type jet mill, a sieve, or the like is used. When pulverizing, wet pulverization in the presence of water or an organic solvent such as methanol can be performed as necessary. In order to obtain a desired particle size, classification is preferably performed. The classification method is not particularly limited, and a sieve, an air classifier, or the like can be used as necessary. Classification can be used both dry and wet.
The average particle diameter is a median diameter of primary particles, and is measured by a laser diffraction type particle size distribution measuring apparatus.
[0029]
Although the example of the negative electrode material of this invention is shown below, this invention is not limited to these.
SnAl_0.4B_0.5P_0.5K_0.1O_3.65, SnAl_0.4B_0.5P_0.5Na_0.2O_3.7, SnAl_0.4B_0.3P_0.5Rb_0.2O_3.4, SnAl_0.4B_0.5P_0.5Cs_0.1O_3.65, SnAl_0.4B_0.5P_0.5K_0.1Ge_0.05O_3.85, SnAl_0.4B_0.5P_0.5K_0.1Mg_0.1Ge_0.02O_3.83, SnAl_0.4B_0.4P_0.4O_3.2, SnAl_0.3B_0.5P_0.2O_2.7, SnAl_0.3B_0.5P_0.2O_2.7, SnAl_0.4B_0.5P_0.3Ba_0.08Mg_0.08O_3.26, SnAl_0.4B_0.4P_0.4Ba_0.08O_3.28, SnAl_0.4B_0.5P_0.5O_3.6, SnAl_0.4B_0.5P_0.5Mg_0.1O_3.7
[0030]
SnAl_0.5B_0.4P_0.5Mg_0.1F_0.2O_3.65, SnB_0.5P_0.5Li_0.1Mg_0.1F_0.2O_3.05, SnB_0.5P_0.5K_0.1Mg_0.1F_0.2O_3.05, SnB_0.5P_0.5K_0.05Mg_0.05F_0.1O_3.03, SnB_0.5P_0.5K_0.05Mg_0.1F_0.2O_3.03, SnAl_0.4B_0.5P_0.5Cs_0.1Mg_0.1F_0.2O_3.65, SnB_0.5P_0.5Cs_0.05Mg_0.05F_0.1O_3.03, SnB_0.5P_0.5Mg_0.1F_0.1O_3.05, SnB_0.5P_0.5Mg_0.1F_0.2O_Three, SnB_0.5P_0.5Mg_0.1F_0.06O_3.07, SnB_0.5P_0.5Mg_0.1F_0.14O_3.03, SnPBa_0.08O_3.58, SnPK_0.1O_3.55, SnPK_0.05Mg_0.05O_3.58, SnPCs_0.1O_3.55, SnPBa_0.08F_0.08O_3.54, SnPK_0.1Mg_0.1F_0.2O_3.55, SnPK_0.05Mg_0.05F_0.1O_3.53, SnPCs_0.1Mg_0.1F_0.2O_3.55, SnPCs_0.05Mg_0.05F_0.1O_3.53,
[0031]
Sn_1.1Al_0.4B_0.2P_0.6Ba_0.08F_0.08O_3.54, Sn_1.1Al_0.4B_0.2P_0.6Li_0.1K_0.1Ba_0.1F_0.1O_3.65, Sn_1.1Al_0.4B_0.4P_0.4Ba_0.08O_3.34, Sn_1.1Al_0.4PCs_0.05O_4.23, Sn_1.1Al_0.4PK_0.05O_4.23, Sn_1.2Al_0.5B_0.3P_0.4Cs_0.2O_3.5, Sn_1.2Al_0.4B_0.2P_0.6Ba_0.08O_3.68, Sn_1.2Al_0.4B_0.2P_0.6Ba_0.08F_0.08O_3.64, Sn_1.2Al_0.4B_0.2P_0.6Mg_0.04Ba_0.04O_3.68, Sn_1.2Al_0.4B_0.3P_0.5Ba_0.08O_3.58, Sn_1.3Al_0.3B_0.3P_0.4Na_0.2O_3.3, Sn_1.3Al_0.2B_0.4P_0.4Ca_0.2O_3.4, Sn_1.3Al_0.4B_0.4P_0.4Ba_0.2O_3.6, Sn_1.4Al_0.4PK_0.2O_4.6, Sn_1.4Al_0.2Ba_0.1PK_0.2O_4.45, Sn_1.4Al_0.2Ba_0.2PK_0.2O_4.6, Sn_1.4Al_0.4Ba_0.2PK_0.2Ba_0.1F_0.2O_4.9, Sn_1.4Al_0.4PK_0.3O_4.65, Sn_1.5Al_0.2PK_0.2O_4.4, Sn_1.5Al_0.4PK_0.1O_4.65, Sn_1.5Al_0.4PCs_0.05O_4.63, Sn_1.5Al_0.4PCs_0.05Mg_0.1F_0.2O_4.63
[0032]
SnSi_0.5Al_0.1B_0.2P_0.1Ca_0.4O_3.1, SnSi_0.4Al_0.2B_0.4O_2.7, SnSi_0.5Al_0.2B_0.1P_0.1Mg_0.1O_2.8, SnSi_0.6Al_0.2B_0.2O_2.8, SnSi_0.5Al_0.3B_0.4P_0.2O_3.55, SnSi_0.5Al_0.3B_0.4P_0.5O_4.30, SnSi_0.6Al_0.1B_0.1P_0.3O_3.25, SnSi_0.6Al_0.1B_0.1P_0.1Ba_0.2O_2.95, SnSi_0.6Al_0.1B_0.1P_0.1Ca_0.2O_2.95, SnSi_0.6Al_0.4B_0.2Mg_0.1O_3.2, SnSi_0.6Al_0.1B_0.3P_0.1O_3.05, SnSi_0.6Al_0.2Mg_0.2O_2.7, SnSi_0.6Al_0.2Ca_0.2O_2.7, SnSi_0.6Al_0.2P_0.2O_Three, SnSi_0.6B_0.2P_0.2O_Three, SnSi_0.8Al_0.2O_2.9, SnSi_0.8Al_0.3B_0.2P_0.2O_3.85, SnSi_0.8B_0.2O_2.9, SnSi_0.8Ba_0.2O_2.8, SnSi_0.8Mg_0.2O_2.8, SnSi_0.8Ca_0.2O_2.8, SnSi_0.8P_0.2O_3.1
[0033]
Sn_0.9Mn_0.3B_0.4P_0.4Ca_0.1Rb_0.1O_2.95, Sn_0.9Fe_0.3B_0.4P_0.4Ca_0.1Rb_0.1O_2.95, Sn_0.8Pb_0.2Ca_0.1P_0.9O_3.35, Sn_0.3Ge_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.
[0034]
The chemical formula of the compound obtained by firing can be calculated from an inductively coupled plasma (ICP) emission spectroscopic analysis method as a measurement method and a weight difference between powders before and after firing as a simple method.
The amount of light metal inserted into the negative electrode material of the present invention may be close to the precipitation potential of the light metal, but for example, it is preferably 50 to 700 mol%, particularly preferably 100 to 600 mol% per negative electrode material. It is preferable that the release amount be larger than the insertion amount. The light metal insertion method is preferably an electrochemical, chemical or thermal method. The electrochemical method is preferably a method in which a light metal contained in the positive electrode active material is inserted electrochemically or a method in which the light metal or an alloy thereof is directly inserted electrochemically. Chemical methods include mixing with light metals, contact, or reacting with organic metals such as butyllithium. Electrochemical methods and chemical methods are preferred. The light metal is particularly preferably lithium or lithium ion.
[0035]
The negative electrode material of the present invention can contain various elements. For example, it may contain dopants of lanthanoid metals (Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg) and various compounds that increase electron conductivity (for example, compounds of Sb, In, and Nb). . The amount of the compound to be added is preferably 0 to 5 mol%.
[0036]
The surface of the positive electrode active material or negative electrode material of the oxide used in the present invention can be coated with an oxide having a chemical formula different from that of the positive electrode active material or negative electrode material used. The surface oxide is preferably an oxide containing a compound that dissolves both acidic and alkaline. Furthermore, a metal oxide having high electron conductivity is preferable. For example, PbO₂,
Fe₂O_Three, SnO₂, In₂O₂, ZnO, or these oxides or dopants (for example, oxides having different valences such as metals and halogen elements) are preferably included. Particularly preferably, SiO₂, SnO₂, Fe₂O_ThreeZnO, PbO₂It is.
The amount of the surface-treated metal oxide is based on the positive electrode active material or the negative electrode material.
0.1 to 10% by weight is preferred. Moreover, 0.2 to 5 weight% is especially preferable, and 0.3 to 3 weight% is the most preferable.
[0037]
In addition, the surface of the positive electrode active material or the negative electrode material can be modified. For example, the surface of the metal oxide may be treated with an esterifying agent, treated with a chelating agent, treated with a conductive polymer, polyethylene oxide, or the like.
In addition, the surface of the negative electrode material can be modified. For example, the treatment may be performed by providing an ion conductive polymer or a polyacetylene layer. Further, the positive electrode active material and the negative electrode material may be subjected to a purification step such as washing with water.
[0038]
As the electrode mixture, a conductive agent, a binder, a filler, a dispersant, an ionic conductive agent, a pressure enhancer, and other various additives can be used.
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. Carbon black such as natural graphite (scale-like graphite, scale-like graphite, earth-like graphite), graphite such as artificial graphite, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, etc. , Conductive fibers such as carbon fibers and metal fibers, metal powders such as copper, nickel, aluminum and silver, conductive whiskers such as zinc oxide and potassium titanate, conductive metal oxides such as titanium oxide or An organic conductive material such as a polyphenylene derivative or the like can be contained alone or as a mixture thereof. Among these conductive agents, acetylene black and a combination of graphite and acetylene black are particularly preferable. When preparing an aqueous dispersion, it is preferable to use a conductive agent previously dispersed in water.
Although the addition amount of a electrically conductive agent is not specifically limited, 1 to 50 weight% is preferable and especially 1 to 30 weight% is preferable. In the case of carbon or graphite, 2 to 15% by weight is particularly preferable.
[0039]
As the binder, one or a mixture of polysaccharides, thermoplastic resins, and polymers having rubber elasticity can be used. Preferred examples include starch, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, regenerated cellulose, diacetyl cellulose, polyvinyl chloride, polyvinyl pyrrolidone, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, and ethylene-propylene-diene terpolymer. Mention may be made of (EPDM), sulfonated EPDM, styrene butadiene rubber, polybutadiene, fluororubber and polyethylene oxide. Moreover, when using the compound containing a functional group which reacts with lithium like a polysaccharide, it is preferable to add the compound like an isocyanate group and to deactivate the functional group, for example. The amount of the binder added is not particularly limited, but is preferably 1 to 50% by weight, and particularly preferably 2 to 30% by weight. The distribution of the binder in the mixture may be uniform or non-uniform. A preferable binder in the present invention is a polymer having a decomposition temperature of 300 ° C. or higher. For example, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA) , Vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer (ETFE resin), polychlorotrifluoroethylene (PCTFE), vinylidene fluoride- Pentafluoropropylene copolymer, propylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer (ECTFE), vinylidene fluoride-hexafluoropropylene Tetrafluoroethylene copolymer, vinylidene fluoride - perfluoromethylvinylether - can be exemplified tetrafluoroethylene copolymer.
[0040]
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.
As the ionic conductive agent, those known as inorganic and organic solid electrolytes can be used, and details are described in the section of the electrolytic solution. A pressure enhancer is a compound that increases the internal pressure described later, and carbonate is a typical example.
As the electrolyte, the following solid electrolyte can be used in combination with the above electrolytic solution. The solid electrolyte is classified into an inorganic solid electrolyte and an organic solid electrolyte.
Well-known inorganic solid electrolytes include Li nitrides, halides, oxyacid salts, and the like. Among them, Li_ThreeN, LiI, Li_FiveNI₂, Li_ThreeN-LiI-LiOH, Li_FourSiO_Four, Li_FourSiO_Four-LiI-LiOH, x Li_ThreePO_Four− (1-x) Li_FourSiO_Four, Li₂SiS_ThreeIn addition, phosphorus sulfide compounds are effective.
[0041]
In the organic solid electrolyte, a polyethylene oxide derivative or a polymer containing the derivative, a polypropylene oxide derivative or a polymer containing the derivative, a polymer containing an ion dissociation group, a mixture of a polymer containing an ion dissociation group and the above aprotic electrolyte, phosphoric acid A polymer matrix material containing an ester polymer and an aprotic polar solvent is effective. Furthermore, there is a method of adding polyacrylonitrile to the electrolytic solution. A method of using an inorganic and organic solid electrolyte in combination is also known.
Further, other compounds may be added to the electrolyte for the purpose of improving discharge and charge / discharge characteristics. For example, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivative, sulfur, quinoneimine dye, N-substituted oxazolidinone and N, N'-substituted imidazolidinone, ethylene glycol dialkyl ether , Quaternary ammonium salt, polyethylene glycol, pyrrole, 2-methoxyethanol, AlCl_Three, Conductive polymer electrode active material monomers, triethylenephosphoramide, trialkylphosphine, morpholine, aryl compounds having a carbonyl group, crown ethers such as 12-crown-4, hexamethylphosphoric triamide and 4-alkyl Examples thereof include morpholine, bicyclic tertiary amine, oil, quaternary phosphonium salt, and tertiary sulfonium salt.
[0042]
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. In addition, carbon dioxide gas can be included in the electrolyte in order to make it suitable for high-temperature storage.
Further, the mixture of the positive electrode and the negative electrode can contain an electrolytic solution or an electrolyte. For example, a method in which the ion conductive polymer, nitromethane, or an electrolytic solution is included is known.
As the separator, an insulating microporous thin film having a large ion permeability and a predetermined mechanical strength is used. Moreover, it is preferable to have a function of closing the hole at 80 ° C. or higher and increasing the resistance. Sheets and nonwoven fabrics made from olefin polymers such as polypropylene and / or polyethylene or glass fibers are used because of their organic solvent resistance and hydrophobicity. As the pore diameter of the separator, a range generally used as a battery separator is used. For example, 0.01 to 10 μm is used. The thickness of the separator is generally used within the range of battery separators. For example, 5 to 300 μm is used. In the production of the separator, after the synthesis of the polymer, the pores may be formed by a dry method, a stretching method, a solution, a solvent removing method, or a combination thereof.
[0043]
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, carbon, and the like as materials for the positive electrode, a material obtained by treating the surface of aluminum or stainless steel with carbon, nickel, titanium, or silver is used. In particular, aluminum or an aluminum alloy is preferable. For the negative electrode, in addition to stainless steel, nickel, copper, titanium, aluminum, carbon, etc., the surface of copper or stainless steel treated with carbon, nickel, titanium or silver, Al-Cd alloy, etc. are used. It is done. In particular, copper or a copper alloy is preferable. Oxidizing the surface of these materials is also used. Further, it is desirable to make the current collector surface uneven by surface treatment. 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. Although thickness is not specifically limited, Although a thing of 1-500 micrometers is used, Preferably it is 5-40 micrometers, More preferably, it is 8-30 micrometers.
[0044]
The battery shape can be applied to any of coins, buttons, sheets, cylinders, flats, corners, etc.
When the shape of the battery is a coin or button, the positive electrode active material or the negative electrode material mixture is mainly used after being compressed into a pellet shape. The thickness and diameter of the pellet are determined by the size of the battery. Moreover, when the shape of the battery is a sheet, cylinder, or corner, the positive electrode active material or the negative electrode material mixture is mainly used after being applied (coated), dried and compressed on the current collector. As a coating method, a general method can be used. Examples thereof include a reverse roll method, a direct roll method, a blade method, a knife method, an extrusion method, a curtain method, a gravure method, a bar method, a dip method, and a squeeze method. Of these, blade method, knife method and extrusion method are preferred. The application is preferably performed at a speed of 0.1 to 100 m / min. Under the present circumstances, the surface state of a favorable coating layer can be obtained by selecting the said application | coating method according to the solution physical property and dryness of a mixture. The application may be performed one side at a time or simultaneously on both sides. The application may be continuous, intermittent, or striped. The thickness, length and width of the coating layer are determined by the size of the battery, but the thickness of the coating layer on one side is preferably 1 to 2000 μm in a compressed state after drying. 10-500 micrometers is more preferable, and 20-250 micrometers is especially preferable.
[0045]
As a method for drying or dehydrating pellets and sheets, a generally adopted method can be used. In particular, it is preferable to use hot air, vacuum, infrared rays, far infrared rays, electron beams and low-humidity air alone or in combination. The temperature is preferably in the range of 80 to 350 ° C, particularly preferably in the range of 100 to 250 ° C. The water content is preferably 2000 ppm or less for the entire battery, and preferably 500 ppm or less for each of the positive electrode mixture, the negative electrode mixture, and the electrolyte in terms of cycleability.
As a pressing method for pellets and sheets, a generally adopted method can be used, and a die pressing method and a calendar pressing method are particularly preferable. The press pressure is not particularly limited, but is 0.2 to 3 t / cm.²Is preferred. By securing a certain space in the mixture, expansion and contraction of the mixture due to expansion and contraction of the active material accompanying charge / discharge can be prevented. At this time, it is possible in terms of safety and productivity because it is possible to prevent the occurrence of an internal short circuit caused by the separator destruction due to the mixture expansion. Therefore, it is preferable that the mixture is not excessively compressed by the press. On the other hand, if the compression of the mixture is extremely insufficient, conduction between the current collector and the mixture or between the active materials in the mixture is no longer possible. The preferable porosity in a preferable mixture varies depending on the constituent materials, but is usually 10% or more and 45% or less, and more preferably 18% or more and 35% or less. The porosity of the mixture can be measured by a mercury intrusion method, for example, using a pore sizer 9310 type (trade name, manufactured by Shimadzu Corporation).
The press speed of the calendar press method is preferably 0.1 to 50 m / min. The pressing temperature is preferably room temperature to 200 ° C. The ratio of the width of the positive electrode sheet to the negative electrode sheet is preferably 0.9 to 1.1. In particular, 0.95-1.0 is preferable. The content ratio of the positive electrode active material and the negative electrode material varies depending on the compound type and the mixture formulation, and thus cannot be limited, but can be set to an optimal value from the viewpoint of capacity, cycle performance, and safety.
[0046]
After the mixture sheet and the separator are overlapped with each other, the sheets are rolled, folded, inserted into the can, the can and the sheet are electrically connected, the electrolyte is injected, and the sealing plate is attached. To form a battery can. At this time, the safety valve can be used as a sealing plate. In addition to the safety valve, various conventionally known safety elements may be provided. For example, a fuse, bimetal, PTC element, or the like is used as the overcurrent prevention element. In addition to the safety valve, as a countermeasure against the increase in internal pressure of the battery can, a method of cutting the battery can, a method of cracking the gasket, a method of cracking the sealing plate, or a method of cutting the lead plate can be used. Further, the charger may be provided with a protection circuit incorporating a countermeasure against overcharge or overdischarge, or may be connected independently. In addition, as a measure against overcharging, a method of cutting off current by increasing the battery internal pressure can be provided. At this time, a compound for increasing the internal pressure can be contained in the mixture, the protective layer, or the electrolyte. As a compound for increasing the internal pressure, Li₂CO_Three, LiHCO_Three, Na₂CO_ThreeNaHCO_Three, CaCO_Three, MgCO_ThreeAnd carbonates.
For the can and lead plate, a metal or alloy having electrical conductivity can be used. For example, metals such as iron, nickel, titanium, chromium, molybdenum, copper, and aluminum, or alloys thereof are used. As a method for welding the cap, the can, the sheet, and the lead plate, a known method (eg, direct current or alternating current electric welding, laser welding, ultrasonic welding) can be used. As the sealing agent for sealing, a conventionally known compound or mixture such as asphalt can be used.
[0047]
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 sub-notebook computer pen input computer, a pocket (palmtop) computer, a notebook type Word processor, pocket word processor, electronic book player, mobile phone, cordless phone, pager, handy terminal, mobile fax, mobile copy, mobile printer, headphone stereo, video movie, LCD TV, handy cleaner, portable CD, minidisc, electricity Shavers, electronic translators, car phones, transceivers, power tools, electronic notebooks, calculators, memory cards, tape recorders, radios, backup power supplies, memory cards, etc. Others for consumer use include automobiles, electric vehicles, motors, lighting equipment, toys, game equipment, road conditioners, irons, watches, strobes, cameras, medical equipment (such as pacemakers, hearing aids, shoulder grinders). Furthermore, it can be used for various military use and space use. Moreover, it can also combine with another secondary battery, a solar cell, or a primary battery.
[0048]
The preferred combination of the present invention is preferably a combination of the above-described chemical materials and preferred battery components._xCoO₂, Li_xNiO₂, Li_xMnO₂, Li_xMn₂O_Four(Wherein x = 0.05 to 1.2) and at least one compound selected from acetylene black as a conductive agent. The positive electrode current collector is made of stainless steel or aluminum and has a net, sheet, foil, or lath shape. As a negative electrode material, lithium metal, lithium alloy (Li-Al), carbonaceous compound, oxide (LiCoVO)_Four, SnO₂, SnO, SiO, GeO₂, GeO, SnSiO_Three, SnSi_0.3Al_0.1B_0.2P_0.3O_3.2), Sulfide (TiS₂, SnS₂, SnS, GeS₂, GeS) and the like are preferably used. The negative electrode current collector is made of stainless steel or copper and has the shape of a net, sheet, foil, lath or the like. In the mixture used together with the positive electrode active material or the negative electrode material, a carbon material such as acetylene black or graphite may be mixed as an electron conductive agent. As the binder, fluorine-containing thermoplastic compounds such as polyvinylidene fluoride and polyfluoroethylene, polymers containing acrylic acid, elastomers such as styrene butadiene rubber and ethylene propylene terpolymer can be used alone or in combination. The porosity in the mixture of the positive electrode and / or the negative electrode is 10% or more and 45% or less. Further, as an electrolytic solution, ethylene carbonate, and also a combination of cyclic and non-cyclic carbonates such as dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate or ester compounds such as methyl propionate and ethyl propionate, and LiPF as a supporting electrolyte₆Including LIBF_Four, LiCF_ThreeSO_ThreeIt is preferable to use a mixture of lithium salts such as. Further, as the separator, polypropylene or polyethylene alone or a combination thereof is preferable. The form of the battery may be any of coins, buttons, cylinders, flats and squares. It is preferable that the battery is provided with means (eg, an internal pressure relief type safety valve, a current cutoff type safety valve, a separator that increases resistance at high temperatures) that can ensure safety against malfunction.
[0049]
【Example】
Hereinafter, the present invention will be described in more detail with reference to specific examples. However, the present invention is not limited to the examples unless it exceeds the gist of the invention.
The following compounds were used as the negative electrode material and the positive electrode active material, respectively.
(Negative electrode material)
Negative electrode material 1: SnGe_0.1B_0.5P_0.58Mg_0.1K_0.1O_3.35
Negative electrode material 2: SnAl_0.5B_0.4P_0.5Mg_0.1F_0.2O_3.65
Negative electrode material 3: Sn_1.0Si_0.8P_0.2O_3.1
Negative electrode material 4: Sn_0.9Al_0.5P_0.5B_0.5K_0.1O_3.7
Negative electrode material 5: SnSi_0.6Al_0.3B_0.3P_0.2O_3.6
Negative electrode material 6: SnAl_0.4B_0.5P_0.5Cs_0.1O_3.65
(Synthesis example of negative electrode material)
Negative electrode material 1; 6.7 g of tin monoxide, 10.3 g of tin pyrophosphate, 1.7 g of diboron trioxide, 0.7 g of potassium carbonate, 0.4 g of magnesium oxide, and 1.0 g of germanium dioxide were dry mixed and made of alumina. Place in a crucible, raise the temperature to 1000 ° C. at 15 ° C./min in an argon atmosphere, calcinate at 1100 ° C. for 12 hours, cool to 10 ° C./min to room temperature, collect the material taken out from the kiln, It is crushed. An X-ray diffraction method using an average particle size of 4.5 μm and CuKα rays has a broad peak with a peak at around 28 ° with a 2θ value, and a crystalline diffraction line with a 2θ value between 40 ° and 70 ° Was not seen.
Similarly to the above, the anode materials 2 to 6 were mixed, calcined, and pulverized with stoichiometric amounts of raw materials to obtain the above compounds.
(Positive electrode active material)
Cathode active material 1: LiCoO₂
Cathode active material 2: LiMn₂O_Four
Cathode active material 3: LiNiO₂
[0050]
Reference example 1
  80% by weight of negative electrode material 1, 15% by weight of flake graphite, 4% by weight of polyvinylidene fluoride as a binder, 1% by weight of carboxymethylcellulose as a dispersant, and kneading with water as a medium to produce a slurry did. The slurry was applied on both sides of a copper foil having a thickness of 18 μm by an extrusion method, dried, compression-molded with a calender press machine, and cut into a predetermined width and length to produce a strip-shaped negative electrode sheet. This is a negative electrode sheet 1. The thickness of the negative electrode sheet 1 was 80 μm, and the porosity in the negative electrode mixture was 22%.
  94% by weight of the positive electrode active material 1 and 3% by weight of acetylene black were mixed, and an aqueous dispersion (solid concentration 50% by weight) of a copolymer of 2-ethylhexyl acrylate, acrylic acid and acrylonitrile was used as a binder. 2% by weight and 1% by weight of carboxymethylcellulose as a dispersant were added and kneaded using water as a medium to prepare a slurry. The slurry was applied to both surfaces of an aluminum foil having a thickness of 18 μm by an extrusion method, dried, compression-molded with a calendar press machine, and cut into a predetermined width and length to produce a belt-like positive electrode sheet. This is a positive electrode sheet 1. The thickness of the positive electrode sheet 1 was 260 μm, and the porosity in the positive electrode mixture was 21%.
[0051]
Nickel and aluminum lead plates were spot welded to the respective end portions of the negative electrode sheet 1 and the positive electrode sheet 1, and then dehydrated and dried for 2 hours while being heated to 150 ° C in dry air having a dew point of -40 ° C or lower.
Furthermore, a dehydrated and dried positive electrode sheet (8), a microporous polypropylene film separator, a dehydrated and dried negative electrode sheet (9), and a separator (10) were laminated in this order, and this was wound in a spiral shape with a rewinder.
The wound body was housed in a nickel-plated iron-bottomed cylindrical battery can (11) that also serves as a negative electrode terminal. Furthermore, the electrolyte 1 shown in Table 1 was injected into the battery can as the electrolyte. A battery lid (12) having a positive electrode terminal was caulked through a gasket (13) to produce a cylindrical battery. The positive electrode terminal (12) was connected to the positive electrode sheet (8) and the battery can (11) was previously connected to the negative electrode sheet (9) by a lead terminal. FIG. 1 shows a cross section of the obtained cylindrical battery. (14) is a safety valve. The battery produced as described above is designated as battery number 1. The charge / discharge conditions are a charge voltage of 4.1 V, a discharge voltage of 2.8 V, and a charge current of 1 mA / cm.²Discharge current 1 mA / cm²Or 5 mA / cm²As a result, a charge / discharge test was conducted. The environmental temperature during charging was 25 ° C., and the environmental temperature during discharging was 25 ° C. and 0 ° C.
[0052]
[Expression 1]

And The results are shown in 1 of Table 4. It can be seen that the discharge capacity ratios A and B are both good, and good characteristics can be obtained even when used at a large current or low temperature.
[0053]
Reference example 2
  α-Al₂O_Three(Average particle size 1 μm) 80% by weight, flake graphite 10% by weight, 4% by weight polyvinylidene fluoride as a binder, 1% by weight carboxymethylcellulose as a dispersant, kneaded with water as a medium, and slurry This was coated on the same application sheet as the negative electrode sheet 1 to form a protective layer. This is designated as protective layer 1.Reference example 1An electrode sheet was prepared in the same manner as described above to prepare a cylindrical battery. This is designated as battery number 2.Reference example 1The same charge / discharge test was conducted. Furthermore, 300 similar batteries were produced and 1 mA / cm.²After charging to 4.1 V, a storage test was conducted at 60 ° C. for 3 weeks. At this time, although the rate of decrease in the open circuit voltage is 0.8 V or more, the ratio of the number is the defect occurrence rate. Each result is shown in 1 of Table 4. The discharge capacity ratios A and B are both good, and the defect rate is extremely small.
[0054]
Reference example 3
  α-Al₂O_Three(Average particle size 1 μm) 95% by weight, 4% by weight of polyvinylidene fluoride as a binder, 1% by weight of carboxymethyl cellulose as a dispersant, kneaded with water as a medium to produce a slurry, A protective layer was formed by coating on the same application sheet as the sheet 1. This is designated as protective layer 2.Reference example 1An electrode sheet was prepared in the same manner as described above to prepare a cylindrical battery. This is battery number 3. The test results are shown in 1 of Table 4. Both the discharge capacity ratio and the defect occurrence rate are extremely good.
[0055]
Reference example 4
  When the negative electrode sheet 1 and the positive electrode sheet 1 were prepared, the calender press machine press pressure was adjusted so that the porosity in the negative electrode mixture and the positive electrode mixture was 22% and 31%, respectively.Reference example 1An electrode sheet was prepared in the same manner as described above to prepare a cylindrical battery. This is designated as battery number 4. The test results are shown in 1 of Table 4. Both the discharge capacity ratio and the defect occurrence rate are extremely good.
[0056]
Examples 1-3, Reference Examples 5-22
  Using the negative electrode material shown in Table 1, the positive electrode active material shown in Table 2, and the electrolyte shown in Table 3, the porosity shown in 3 of Table 4 to 1 of Table 4 was adjusted.Reference example 1Battery numbers 5 to 25 were produced in the same manner as described above. Here, the protective layer 3 is α-Al in the protective layer 2.₂O_ThreeTiO instead of (average particle size 1μm)₂A powder (average particle size: 1 μm) is used. The test results are shown in Table 4 to 1 in Table 4. Both the discharge capacity ratio and the defect occurrence rate are extremely good.
  In addition, Examples 1-3 are battery numbers 5, 14, and 25, respectively.
[0057]
Comparative example
Using the negative electrode material shown in Table 1, the positive electrode active material shown in Table 2, the electrolyte shown in 1 through Table 3 in Table 3, and adjusting the porosity shown in 3 in Table 4, the battery as in Example 1 Numbers 26-33 were produced. The test results are shown in 3 of Table 4. In general, the discharge capacity ratios A and B are inferior, and a sufficient discharge capacity cannot be obtained under a large current or low temperature. Moreover, since the tendency improves a manufacturing yield and safety | security, when a protective layer is provided, it is remarkable when the porosity in a mixture is raised.
[0058]
[Table 1]

[0059]
[Table 2]

[0060]
[Table 3]

[0061]
[Table 4]

[0062]
[Table 5]

[0063]
[Table 6]

[0064]
[Table 7]

[0065]
【The invention's effect】
As in the present invention, in a nonaqueous secondary battery in which a nonaqueous electrolyte containing a positive electrode and a negative electrode capable of occluding and releasing lithium and a lithium salt is contained in a battery container, the nonaqueous electrolyte is dimethyl carbonate, ethyl methyl carbonate, propionic acid By using a non-aqueous electrolyte in which a lithium salt containing fluorine is dissolved in a mixed solvent containing at least one ester selected from methyl and ethyl propionate and ethylene carbonate, it can withstand use at a higher current, and more A non-aqueous secondary battery that can withstand use in a wide temperature range can be obtained.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a cylindrical battery used in an example.
[Explanation of symbols]
8 Positive electrode sheet
9 Negative electrode sheet
10 Separator
11 Battery can
12 Battery cover
13 Gasket
14 Safety valve

Claims (10)

A nonaqueous secondary battery of the non-aqueous electrolyte formed by accommodating the battery case including a positive electrode and the negative electrode and a lithium salt which is capable of occluding and releasing lithium, the porosity in the material mixture constituting the positive electrode and the negative electrode 10% or more and 45% or less, and the non-aqueous electrolyte is at least one ester selected from the group consisting of dimethyl carbonate, ethyl methyl carbonate, methyl propionate, ethyl propionate, methyl methoxyacetate and ethyl methoxyacetate, and ethylene Using a non-aqueous electrolyte in which LiPF ₆ and LiBF ₄ are dissolved so that the concentration is 0.6 M or more and 1.5 M or less in a mixed solvent containing at least carbonate, on the surface of the mixture layer of the negative electrode, thermal black, Carbon black, such as furnace black, channel black, and lamp black, scaly graphite, scaly black A non-aqueous secondary battery comprising at least one protective layer containing a conductive carbon material that is at least one selected from natural graphite such as lead and earth-like graphite, artificial graphite, and carbon fiber.   The protective layer on the surface of the negative electrode mixture layer contains at least one insulating particle selected from carbides, silicides, nitrides, sulfides, and oxides of metal or nonmetallic elements. The non-aqueous secondary battery according to claim 1. The insulating particles are selected from SiC, AlN, BN, BP, Al ₂ O ₃ , BaO, BeO, CaO, K ₂ O, Na ₂ O, InO, MgO, SiO ₂ , SrO, ZrO ₄ , and TiO _2. The nonaqueous secondary battery according to claim 2, wherein the nonaqueous secondary battery is at least one kind.   The active material constituting the negative electrode is mainly composed of a composite oxide and / or a composite chalcogenide containing at least one of group 1 element, group 2 element, group 3 element and halogen element in the periodic table. The nonaqueous secondary battery according to any one of claims 1 to 3.   The nonaqueous secondary battery according to any one of claims 1 to 4, wherein a porosity of the mixture constituting the positive electrode is 18% or more and 35% or less.   The nonaqueous secondary battery according to any one of claims 1 to 5, wherein a porosity in the mixture constituting the negative electrode is 18% or more and 35% or less. The non-aqueous electrolyte contains at least one ester selected from the group consisting of dimethyl carbonate, ethyl methyl carbonate, methyl propionate, ethyl propionate, methyl methoxyacetate and ethyl methoxyacetate, and ethylene carbonate and diethyl carbonate. non-aqueous secondary battery according to claim 1, wherein 6. In the solvent constituting the nonaqueous electrolyte, a total of at least one ester selected from the group consisting of dimethyl carbonate, ethyl methyl carbonate, methyl propionate, ethyl propionate, methyl methoxyacetate and ethyl methoxyacetate is 10% by volume or more. The nonaqueous secondary battery according to any one of claims 1 to 7 , wherein the nonaqueous secondary battery is contained by volume% or less. The nonaqueous secondary battery according to any one of claims 1 to 8 , wherein the solvent constituting the nonaqueous electrolyte contains at least one ester selected from dimethyl carbonate and ethyl methyl carbonate. Active material for constituting the positive electrode, a nonaqueous secondary battery according to any one of claims 1-9, characterized in that a lithium-containing transition metal oxide.