JP4734707B2 - Non-aqueous electrolyte battery - Google Patents

Description

【００８２】
表１から、実施例１の非水電解液二次電池では、初期電池容量が高く、−１０℃環境下における電池容量維持率が高いことがわかる。
【００８３】
これに対し、比較例１の非水電解質二次電池は、初期電池容量が低く、−１０℃環境下における電池容量維持率も低いことがわかる。また、比較例２の非水電解液二次電池は、−１０℃環境下における電池容量が改善されているが、初期電池容量が低いことがわかる。また、比較例３の非水電解液二次電池は、初期電池容量が高いが、−１０℃環境下における電池容量維持率が低いことがわかる。
【００８４】
従って、非水電解液二次電池は、負極活物質、繊維状炭素およびカーボンブラックとからなる負極材料を含有する負極を備えることにより、低温環境下で充放電する場合であっても、充放電特性に優れ、高い電池容量を有することがわかる。
【００８５】
＜実験２＞
実験２では、負極材料中に含有させるカーボンブラックの含有量を一定とし、繊維状炭素の含有量を変化させた場合の電池特性を評価した。
【００８６】
実施例２〜実施例６、比較例４〜比較例６
カーボンブラックの含有量を０．５重量％とし、負極活物質および繊維状炭素の含有量を表２に示すようにして調製した負極材料を用いること以外は実施例１と同様にして非水電解液二次電池を作製した。
【００８７】
以上のようにして作製した実施例２〜実施例６、比較例４〜比較例６の非水電解液二次電池について、初期電池容量および−１０℃環境下における電池容量維持率を、上述した方法と同様にして測定した。
【００８８】
以上の測定結果を、負極材料中における繊維状炭素及びカーボンブラックの含有量、ａ／ｂと合わせて表２に示す。
【００８９】
【表２】

【００９０】
表２より、負極材料中に繊維状炭素が０．１重量％含有されている比較例４の非水電解液二次電池は、負極材料中に繊維状炭素が含有されていない比較例２（表１）の非水電解液二次電池と比較すると、初期電池容量が高く、−１０℃環境下における電池容量維持率も向上していることがわかる。
【００９１】
また、負極材料中に繊維状炭素が１０重量％含有されている実施例６の非水電解液二次電池は、負極材料中に繊維状炭素が２０重量％含有されている比較例６の非水電解液二次電池と比較すると、初期電池容量がより高く、−１０℃環境下における電池容量がより高いことがわかる。
【００９２】
従って、非水電解液二次電池では、繊維状炭素が負極材料中に０．１重量％以上、１０重量％以下の範囲で含有されていると、負極では本来の容量を十分に引き出すことができ、高い電池容量が実現されることがわかる。
【００９３】
＜実験３＞
実験３では、負極材料中に含有させる繊維状炭素の含有量を一定とし、カーボンブラックの含有量を変化させた場合の電池特性を評価した。
【００９４】
実施例７〜実施例１１、比較例７〜比較例９
繊維状炭素の含有量を１．０重量％とし、負極活物質およびカーボンブラックの含有量を表３に示すようにして調製した負極材料を用いること以外は実施例１と同様にして非水電解液二次電池を作製した。
【００９５】
以上のようにして作製した実施例７〜実施例１１、比較例７〜比較例９の非水電解液二次電池について、初期電池容量および−１０℃環境下における電池容量維持率を、上述した方法と同様にして測定した。
【００９６】
以上の測定結果を、負極材料中における繊維状炭素及びカーボンブラックの含有量、ａ／ｂと合わせて表３に示す。
【００９７】
【表３】

【００９８】
表３より、負極材料中にカーボンブラックが０．０２重量％含有されている比較例８の非水電解液二次電池は、負極材料中にカーボンブラックが０．０１重量％含有されている比較例７の非水電解液二次電池と比較すると、同程度に良好な初期電池容量を有しているとともに、−１０℃環境下における電池容量維持率がより向上していることがわかる。
【００９９】
また、負極材料中にカーボンブラックが２．０重量％含有されている実施例１１の非水電解液二次電池は、負極材料中にカーボンブラックが３．０重量％含有されている比較例９の非水電解液二次電池と比較すると、同程度に良好な−１０℃環境下における電池容量維持率を有しているとともに、初期電池容量がより高いことがわかる。
【０１００】
従って、非水電解液二次電池は、カーボンブラックが負極材料中に０．０２重量％以上、２重量％以下の範囲で含有されていると、例えば−１０℃という低温環境下で充放電された場合であっても、良好な充放電特性を有し、高い電池容量を有することがわかる。
【０１０１】
ここで、繊維状炭素とカーボンブラックとの重量比、すなわちａ／ｂについて考察する。ａ／ｂが２０である実施例６を、ａ／ｂが３０である比較例６およびａ／ｂが１００である比較例７と比較すると、実施例６は−１０℃環境下における容量維持率がより高いことがわかる。
【０１０２】
また、ａ／ｂが０．５である実施例１１を、ａ／ｂが０．２である比較例４およびａ／ｂが０．３３である比較例９と比較すると実施例１１は初期電池容量がより高いことがわかる。
【０１０３】
したがって、繊維状炭素とカーボンブラックとの重量比を０．５以上、２０以下の範囲とすることにより、負極活物質粒界の導電性を高める作用と、負極に電解液を保持する作用とを両立して得ることができ、極めて電池特性に優れる非水電解液二次電池を得られることがわかる。
【０１０４】
【発明の効果】
以上の説明からも明らかなように、本発明に係る非水電解質電池は、正極と、負極活物質の黒鉛と繊維状炭素とカーボンブラックとからなる負極材料を有する負極と、非水電解液とを備え、負極材料は、黒鉛が８９．５重量％以上、９９．０重量％以下の範囲で含有され、繊維状炭素が０．５重量％以上、１０重量％以下の範囲で含有され、カーボンブラックが０．１重量％以上、２重量％以下の範囲で含有され、繊維状炭素とカーボンブラックとの重量比が、０．５以上、２０以下の範囲であり、繊維状炭素のアスペクト比が１０以上であるので、低温環境下で充放電をされた場合でも、良好な充放電特性を有し、高容量である。
【図面の簡単な説明】
【図１】 円筒型の非水電解液二次電池の一構成例を示す断面図である。
【符号の説明】
１ 非水電解液二次電池、２ 負極、３ 正極、４ セパレータ、５ 電池缶、６ 負極集電体、７ 正極集電体、８ 絶縁板、９ 負極リード、１０ 正極リード、１１ 電池蓋、１２ 絶縁封口ガスケット、１３ 安全弁装置、１４ＰＴＣ素子[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a nonaqueous electrolyte battery including a positive electrode, a negative electrode containing a negative electrode active material, and an electrolyte.
[0002]
[Prior art]
  Due to remarkable progress in electronic technology, electronic devices are becoming smaller and lighter one after another. In connection with this, the battery used as the power supply of various electronic devices is requested | required of size reduction, weight reduction, and high energy density.
[0003]
  Currently, aqueous batteries such as lead batteries and nickel / cadmium batteries are mainly used as batteries that are generally used. Although these batteries have the minimum required cycle characteristics, it is difficult to achieve a desired battery weight and improve energy density.
[0004]
  Therefore, LiCoO having a high discharge voltage as a positive electrode active material.₂A non-aqueous electrolyte battery using a lithium-containing composite oxide represented by the above and using lithium or a lithium alloy as a negative electrode material has been proposed.
[0005]
  A non-aqueous electrolyte secondary battery using lithium or a lithium alloy as a negative electrode material has excellent self-discharge and light weight, but with the progress of a charge / discharge cycle, lithium is discharged from the negative electrode. It has the disadvantage that the crystal grows in a dendritic form and reaches the positive electrode, causing a short circuit inside the battery. For this reason, practical quick charge / discharge cannot be performed in a non-aqueous electrolyte battery using lithium or a lithium alloy as the negative electrode material.
[0006]
  In view of this, a non-aqueous electrolyte battery, a so-called lithium ion battery, has been proposed in which a carbon material or the like is used as a negative electrode active material and lithium doping / dedoping reaction between negative electrode material layers is used for the negative electrode reaction. Lithium ion batteries have the advantage that lithium does not deposit on the negative electrode as the charge / discharge cycle progresses, and exhibits good cycle characteristics. Because of such advantages, research and development of lithium ion batteries have been actively conducted and put into practical use.
[0007]
[Problems to be solved by the invention]
  In recent years, lithium ion batteries are sometimes used as power sources for driving electronic devices used not only in a normal temperature environment but also in a low temperature environment. However, when a conventional lithium ion battery is charged / discharged in a low temperature environment, the diffusion of lithium ions in the negative electrode is delayed, and the internal resistance may increase to cause polarization. For this reason, when a lithium ion battery is charged / discharged in a low-temperature environment, there is a problem that charge / discharge characteristics are deteriorated and a desired battery capacity is not realized.
[0008]
  Moreover, the negative electrode active material entangled in the binder which is an insulator exists in the negative electrode of a lithium ion battery. Since the negative electrode active material entangled with the binder is electrically isolated, it cannot contribute to the charge / discharge reaction. For this reason, in the negative electrode, the original capacity cannot be drawn out sufficiently, and there is a problem that the original energy density cannot be drawn out sufficiently as a lithium ion battery.
[0009]
  The present invention has been proposed in view of such conventional circumstances, and provides a nonaqueous electrolyte battery having good charge / discharge characteristics and high battery capacity even when charged and discharged in a low temperature environment. For the purpose.
[0010]
[Means for Solving the Problems]
  To achieve the above object, a nonaqueous electrolyte battery according to the present invention includes a positive electrode containing a positive electrode active material capable of doping / dedoping lithium, and a negative electrode active material capable of doping / dedoping lithium.Of graphiteA negative electrode containing a negative electrode material composed of fibrous carbon and carbon black, and a non-aqueous electrolyte,Graphite is contained in the range of 89.5 wt% or more and 99.0 wt% or less,Fibrous carbonIs 0. Carbon black is contained in the range of 5 wt% to 10 wt%Is 0. 1% by weight or more, 2. 0It is contained in a range of not more than% by weight, the weight ratio of fibrous carbon to carbon black is in the range of 0.5 or more and 20 or less, and the aspect ratio of the fibrous carbon is 10 or more.
[0011]
  In the nonaqueous electrolyte battery according to the present invention configured as described above, fibrous carbon is interposed between the particles of the negative electrode active material, and the conductivity of the negative electrode active material grain boundary is enhanced. Thereby, even if all the negative electrode active materials present in the negative electrode are entangled with the binder, for example, they are not electrically isolated and contribute to the charge / discharge reaction.
[0012]
  In addition, carbon black is interposed between the negative electrode active material and the fibrous carbon to enhance the electrolyte retention in the negative electrode. As a result, even when the nonaqueous electrolyte battery is charged / discharged in a low temperature environment, in the negative electrode, ion conduction in the limited voids existing between the particles of the negative electrode active material is accelerated, and the lithium ion doping is performed. / The dedoping reaction is performed smoothly, the internal resistance is reduced, and polarization is prevented.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
  Hereinafter, the nonaqueous electrolyte battery according to the present invention will be described in detail with reference to the drawings.
[0014]
  A non-aqueous electrolyte secondary battery 1 to which the present invention is applied is a so-called lithium ion secondary battery. As shown in FIG. 1, a strip-shaped negative electrode 2 and a strip-shaped positive electrode 3 are stacked with a separator 4 interposed therebetween. A spiral electrode body wound in the direction is loaded into the battery can 5, and a non-aqueous electrolyte is injected into the battery can 5.
[0015]
  The negative electrode 2 is prepared by mixing a negative electrode mixture prepared by mixing a negative electrode material containing a negative electrode active material that can be doped / undoped, a negative electrode material composed of fibrous carbon and carbon black, and a binder. 6 was applied and dried.
[0016]
  As the negative electrode active material contained in the negative electrode material, a carbon material that can be doped / undoped with lithium, a crystalline material, an amorphous metal oxide, or the like is used. Examples of the carbon material include non-graphitizable carbon materials such as coke and glassy carbon, graphites of highly crystalline carbon materials with a developed crystal structure, and specifically, pyrolytic carbons, cokes, (Pitch coke, needle coke, petroleum coke, etc.), graphites, glassy carbons, organic polymer compound fired bodies (phenol resins, furan resins, etc., calcined at an appropriate temperature), carbon fibers, and Examples include activated carbon.
[0017]
  In addition, since the high-crystalline carbon material graphite has a higher true density than the non-graphitizable carbon material having low crystallinity, the negative electrode 2 using this graphite as a negative electrode material has a packing density of active materials. Higher and higher energy density batteries can be realized. Further, the non-aqueous electrolyte secondary battery 1 using the graphite as a negative electrode material has an advantage that it has a high energy density and has a flat discharge curve, so that there is no energy loss when a voltage is changed in an electronic device.
[0018]
  The fibrous carbon contained in the negative electrode material is interposed between the particles of the negative electrode active material to enhance the conductivity of the negative electrode active material grain boundary. Such fibrous carbon can be obtained by heat-treating a precursor such as a polymer spun into a fiber or pitch, or an organic vapor such as benzene directly on a substrate at a temperature of about 1000 ° C. And vapor grown carbon obtained by growing carbon crystals using iron fine particles as a catalyst.
[0019]
  When obtaining fibrous carbon by heat treatment, polyacrylonitrile, rayon, polyamide, lignin, polyvinyl alcohol, or the like can be used as the polymer precursor.
[0020]
  As pitch, distillation (vacuum distillation, atmospheric distillation, steam distillation), thermal polycondensation, extraction, chemical polycondensation from coal tar, ethylene bottom oil, tars obtained by thermal decomposition at high temperature, asphalt, etc. What is obtained by operations such as those that are produced during wood dry distillation can be used.
[0021]
  Moreover, as a starting material used as a pitch, polyvinyl chloride resin, polyvinyl acetate, polyvinyl butyrate, 3,5-dimethylphenol resin, etc. can be used.
[0022]
  During the carbonization, these coals and pitches exist in a liquid state at a maximum of about 400 ° C., and by maintaining at that temperature, the aromatic rings are condensed and polycyclic to form a laminated orientation, and then about 500 ° C. or higher. At this temperature, a solid carbon precursor, that is, semi-coke is formed. Such a process is called a liquid-phase carbonization process and is a typical process for producing graphitizable carbon.
[0023]
  Other condensed polycyclic hydrocarbon compounds such as naphthalene, phenanthrene, anthracene, triphenylene, pyrene, perylene, pentaphen, and pentacene, and other derivatives (for example, carboxylic acids, carboxylic anhydrides, carboxylic imides, etc.) or mixtures, acenaphthylene Indole, isoindole, quinoline, isoquinoline, quinoxaline, phthalazine, carbazole, acridine, phenazine, phenanthridine and other condensed heterocyclic compounds and other derivatives can also be used as raw materials for graphitizable carbon.
[0024]
  The polymer precursor and the pitch precursor are subjected to a process of infusibilization or stabilization and then heat-treated at a high temperature to become fibrous carbon.
[0025]
  The infusibilization or stabilization step is a step of oxidizing the fiber surface with acid, oxygen, ozone or the like so that the polymer or the like does not melt or undergo thermal decomposition during carbonization. At this time, the processing method is appropriately selected depending on the type of the precursor. However, it is necessary to select the processing temperature below the melting point of the precursor. Further, the treatment may be repeated a plurality of times as necessary so that the stabilization is sufficiently performed.
[0026]
  In order to obtain fibrous carbon, first, the above-described infusibilization or stabilization is applied to a polymer precursor or a pitch precursor. Next, the infusible or stabilized polymer type or pitch type precursor is carbonized at a temperature of 300 ° C. to 700 ° C. in an inert gas stream such as nitrogen, and then heated in the inert gas stream. The temperature is raised from 1 ° C. to 100 ° C. per minute up to an ultimate temperature of 900 ° C. to 1500 ° C., and calcination is performed at this ultimate temperature for a holding time of about 0 to 30 hours. Thereby, fibrous carbon is obtained. In some cases, carbonization may be omitted.
[0027]
  When fibrous carbon is obtained by a vapor phase growth method, any organic material that can be gaseous can be used as a starting material. For example, ethylene, propane, or the like that exists as a gas in a normal temperature environment, or an organic substance that can be heated and vaporized at a temperature lower than the thermal decomposition temperature can be used.
[0028]
  The vaporized organic matter is directly released into a high-temperature substrate, and thus grows as fibrous carbon. At this time, the temperature of the substrate is appropriately selected depending on the type of organic substance used as a starting material, but is preferably 400 ° C. to 1500 ° C. Further, the kind of the substrate is appropriately selected depending on the kind of the organic substance used as the starting material, and quartz, nickel and the like are preferable.
[0029]
  In addition, it is possible to promote crystal growth using a catalyst. As the catalyst, iron, nickel, a mixture thereof, or the like, a metal called a graphitization catalyst, or an oxide thereof can be used. These catalysts are appropriately selected depending on the type of organic material used as the starting material.
[0030]
  The outer shape and length of the fibrous carbon can be appropriately selected depending on the preparation conditions. For example, when a polymer-based precursor is used as a raw material, an appropriate fiber diameter and length can be obtained depending on the blow nozzle inner diameter when forming into a fiber shape, and the blow speed. In the case of the vapor phase growth method, an optimum fiber diameter can be obtained by appropriately selecting the size of a portion that becomes the nucleus of crystal growth such as a substrate and a catalyst. Further, it is possible to adjust the fiber diameter and linearity by defining the supply amount of organic materials such as ethylene and propane as raw materials.
[0031]
  The aspect ratio, which is the ratio between the fiber length and fiber diameter of the fibrous carbon, is preferably 10 or more. When the aspect ratio is less than 10, the fibrous carbon plays a role of increasing the conductivity by connecting between the negative electrode active material particles, but on the other hand, it fills the gaps between the negative electrode active material particles and causes electrolysis in the negative electrode 2. There is a risk of reducing the liquid retention of the liquid. For this reason, as the non-aqueous electrolysis seat secondary battery 1, the low temperature load characteristic may be deteriorated. Therefore, when the aspect ratio is 10 or more, it is possible to increase the conductivity of the negative electrode active material grain boundary without reducing the liquid retention of the electrolytic solution in the negative electrode 2. The fibrous carbon refers to one having an aspect ratio of 10 or more.
[0032]
  Moreover, it is preferable that the fiber length of fibrous carbon is 0.5 micrometer or more. When the fiber length of the fibrous carbon is less than 0.5 μm, the fiber length is shorter than the distance between the negative electrode active material particles, and thus there is a possibility that the effect of increasing the conductivity of the negative electrode active material grain boundary cannot be obtained. Therefore, when the fiber length of the fibrous carbon is 0.5 μm or more, the effect of increasing the conductivity of the negative electrode active material grain boundary can be reliably obtained.
[0033]
  The fibrous carbon thus obtained is heated to an ultimate temperature of 2000 ° C. or higher, preferably 2500 ° C. or higher, with a temperature increase rate of 1 ° C. to 100 ° C. per minute in an inert gas stream. You may graphitize on this ultimate temperature on condition of holding time about 0 to 30 hours.
[0034]
  Further, the fibrous carbon may be pulverized in accordance with the thickness of the electrode, the particle size of the active material, and the like, and the fibrous carbon that has become a single fiber during spinning can be used. The pulverization of the fibrous carbon may be performed either before or after carbonization, calcination, or during the temperature raising process before graphitization.
[0035]
  The fibrous carbon is preferably contained in the negative electrode material in the range of 0.1 wt% or more and 10 wt% or less. When fibrous carbon is contained in the negative electrode material in an amount of less than 0.1% by weight, the conductivity of the negative electrode active material grain boundary may not be sufficiently increased. On the other hand, when the fibrous carbon is contained in the negative electrode material in an amount of more than 10% by weight, the amount of the negative electrode active material in the negative electrode 2 is reduced, so that the battery capacity of the nonaqueous electrolyte secondary battery 1 may be reduced. is there. Therefore, fibrous carbon is contained in the negative electrode material in the range of 0.1 wt% or more and 10 wt% or less, so that all the carbon capacity of the non-aqueous electrolyte secondary battery 1 is reduced without reducing the battery capacity. Electron conductivity can be reliably imparted to the negative electrode active material. In addition, as content of the fibrous carbon contained in negative electrode material, it is more preferable that it is the range of 0.3 weight% or more and 5 weight% or less, and 0.5 weight% or more and 2 weight% or less. The range is most preferable.
[0036]
  The carbon black contained in the negative electrode material is interposed between the negative electrode active material and the fibrous carbon to enhance the electrolyte retention in the negative electrode 2. As carbon black, raw material hydrocarbons produced by a thermal decomposition method or those produced by an incomplete combustion method are used. Examples of the thermal decomposition method include a thermal method and an acetylene decomposition method. Examples of the incomplete combustion method include a contact method, a lamp / smoke method, a gas furnace method, and an oil furnace method.
[0037]
  Examples of the carbon black produced by these production methods include acetylene black, ketjen black, thermal black, and furnace black. Of these carbon blacks, it is particularly preferable to use conductive carbon black such as acetylene black and ketjen black.
[0038]
  Carbon black DBPSuckThe amount of oil is preferably 100 ml / 100 g or more. Carbon black DBPSuckWhen the amount of oil is less than 100 ml / 100 g, the amount of electrolyte retained in the negative electrode 2 may be insufficient. DBPSuckIf a negative electrode having a desired electrolyte solution retention capacity is produced using carbon black having an oil amount of less than 100 ml / 100 g, it is necessary to add more than 2% by weight of carbon black to the negative electrode material. However, when the content of carbon black in the negative electrode material exceeds 2% by weight, the battery capacity of the non-aqueous electrolyte secondary battery 1 is reduced, as will be described in detail later. Therefore, DBPSuckBy using carbon black having an oil amount of 100 ml / 100 g or more, it is possible to increase the electrolyte solution retention capacity of the negative electrode 2 without reducing the battery capacity of the nonaqueous electrolyte secondary battery 1.
[0039]
  Moreover, it is preferable that the average particle diameter of carbon black is 0.1 micrometer or less. When the average particle size of carbon black is larger than 0.1 μm, the bulk density in the negative electrode material becomes small, and thus there is a possibility that the electrolyte solution cannot be sufficiently retained in the negative electrode 2. Therefore, when the average particle size of carbon black is 0.1 μm or less, the electrolyte solution can be sufficiently retained in the negative electrode 2.
[0040]
  This carbon black is preferably contained in the negative electrode material in a range of 0.02 wt% to 2 wt%. When carbon black is contained in the negative electrode material in an amount of less than 0.02% by weight, there is a possibility that the electrolyte solution cannot be sufficiently retained in the negative electrode 2. On the other hand, when the carbon black is contained in the negative electrode material in an amount of more than 2% by weight, the amount of the negative electrode active material in the negative electrode 2 is reduced, so that the battery capacity of the nonaqueous electrolyte secondary battery 1 may be reduced. . Therefore, when carbon black is contained in the negative electrode material in the range of 0.02 wt% or more and 2 wt% or less, it is sufficient for the negative electrode 2 without reducing the battery capacity of the nonaqueous electrolyte secondary battery 1. It is possible to retain a liquid electrolyte. The content of carbon black contained in the negative electrode material is more preferably in the range of 0.1% by weight to 1.5% by weight, more preferably 0.2% by weight to 1.0% by weight. Most preferably, it is in the range of% or less.
[0041]
  The negative electrode material contains fibrous carbon and carbon black as described above, but the ratio between the content of fibrous carbon and the content of carbon black, that is, the weight ratio of fibrous carbon and carbon black. Is preferably 0.5 or more and 20 or less. If the weight ratio of fibrous carbon is below this range, the conductivity may be insufficient. On the other hand, when the weight ratio of carbon black is less than this range, there is a possibility that the function of holding the electrolytic solution in the negative electrode 2 cannot be sufficiently obtained. Therefore, when the weight ratio of fibrous carbon to carbon black is 0.5 or more and 20 or less, both the effect of increasing the conductivity of the grain boundary of the negative electrode active material and the function of holding the electrolyte in the negative electrode 2 are achieved. Can be obtained. The weight ratio of fibrous carbon to carbon black is more preferably 1.0 or more and 10 or less, and most preferably 1.5 or more and 6 or less.
[0042]
  As a binder contained in the negative electrode 2, the well-known binder normally used for the negative mix of this kind of battery can be used. Moreover, you may add a well-known additive etc. to a negative electrode mixture as needed.
[0043]
  The positive electrode 3 is obtained by applying a positive electrode mixture containing a positive electrode active material and a binder onto the positive electrode current collector 7 and drying it.
[0044]
  The positive electrode active material may be any conventionally known positive electrode material that can be doped / undoped with lithium and contains a sufficient amount of lithium. Specifically, the general formula LiM_xO_y(However, 1 <x ≦ 2, 2 <y ≦ 4, and M contains at least one of Co, Ni, Mn, Fe, Al, V, and Ti.) It is preferable to use a composite metal oxide composed of a transition metal and an intercalation compound containing lithium.
[0045]
  As the binder contained in the positive electrode 3, a known binder that is usually used in a positive electrode mixture of this type of battery can be used. Moreover, you may add a well-known additive etc. to a positive electrode mixture as needed.
[0046]
  A non-aqueous electrolyte is one in which an electrolyte is dissolved in a non-aqueous solvent.
[0047]
  As the non-aqueous solvent, ethylene carbonate (hereinafter referred to as EC), which has a relatively high dielectric constant and is not easily decomposed by graphite constituting the negative electrode, is used as a main solvent. In particular, when a graphite material is used for the negative electrode, it is preferable to use EC as a main solvent, but it is also possible to use a compound in which a hydrogen atom of EC is substituted with a halogen element.
[0048]
  Moreover, although it is reactive with graphite material like PC, by substituting a part of the EC as the main solvent or a compound in which the hydrogen atom of EC is substituted with a halogen element with a second component solvent Better properties can be obtained.
[0049]
  Examples of the second component solvent include propylene carbonate, butylene carbonate, vinylene carbonate, 1,2-dimethoxyethane, 1,2-diethoxymethane, γ-butyrolactone, valerolactone, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3- Examples include dioxolane, 4-methyl-1,3-dioxolane, sulfolane, methyl sulfolane and the like.
[0050]
  Furthermore, it is preferable to use a low-viscosity solvent in combination with the non-aqueous solvent to improve electrical conductivity and improve current characteristics, and to reduce the reactivity with lithium metal and improve safety.
[0051]
  Examples of the low-viscosity solvents include symmetrical or asymmetric chain carbonates such as diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, and methyl propyl carbonate, carboxylic acid esters such as methyl propionate and ethyl propionate, trimethyl phosphate, Phosphate esters such as triethyl phosphate can be used. These low-viscosity solvents may be used alone or in combination of two or more.
[0052]
  The electrolyte is not particularly limited as long as it is a lithium salt that dissolves in a non-aqueous solvent and exhibits ionic conductivity. For example, LiPF₆LiClO₄, LiAsF₆, LiBF₄, LiB (C₆H₅)₄, LiCH₃SO₃, CF₃SO₃Li, LiCl, LiN (CnC_{2n + 1}SO₂)₂LiBr or the like can be used. In particular, LiPF as the electrolyte₆Is preferably used. These electrolytes may be used alone or in combination of two or more.
[0053]
  As a material of the battery can 5, Fe, Ni, stainless steel, Al, Ti, or the like can be used. The battery can 5 may be plated in order to prevent corrosion due to an electrochemical non-aqueous electrolyte accompanying charging / discharging of the battery.
[0054]
  When producing the non-aqueous electrolyte secondary battery 1 configured as described above, first, the strip-shaped negative electrode 2 and the strip-shaped positive electrode 3 obtained as described above are made of, for example, a microporous polypropylene film. After stacking through the separator 4, a spiral electrode body is produced by winding a number of times in the longitudinal direction.
[0055]
  Next, the electrode body is housed in an iron battery can 5 having an insulating plate 8 inserted in the bottom and nickel-plated on the inside. In order to collect current from the negative electrode 2, one end of the negative electrode lead 9 made of, for example, nickel is pressed against the negative electrode 2 and the other end is welded to the battery can 5. As a result, the battery can 5 is electrically connected to the negative electrode 2 and becomes an external negative electrode of the non-aqueous electrolyte secondary battery 1. In order to collect current from the positive electrode 3, one end of a positive electrode lead 10 made of, for example, aluminum is attached to the positive electrode 3, and the other end is electrically connected to the battery lid 11 through a thin plate for current interruption. This thin plate for current interruption interrupts current according to the battery internal pressure. As a result, the battery lid 11 is electrically connected to the positive electrode 3 and serves as the external positive electrode of the nonaqueous electrolyte secondary battery 1.
[0056]
  Then, after injecting a non-aqueous electrolyte prepared by dissolving an electrolyte in a non-aqueous solvent into the battery can 5, the battery can 5 is caulked through an insulating sealing gasket 12 coated with asphalt. The cylindrical nonaqueous electrolyte secondary battery 1 with the lid 11 fixed thereto is produced.
[0057]
  The nonaqueous electrolyte secondary battery 1 includes a safety valve device 13 for venting the gas inside when the pressure inside the battery becomes higher than a predetermined value, and a PTC element 14 for preventing the temperature inside the battery from rising. Is provided.
[0058]
  In the non-aqueous electrolyte secondary battery 1 manufactured as described above, in the negative electrode 2, the fibrous carbon contained in the negative electrode material is interposed between the particles of the negative electrode active material, and the conductivity of the negative electrode active material grain boundary is Therefore, even if the negative electrode active material is entangled in the binder which is an insulator, it is not electrically isolated and can contribute to the charge / discharge reaction. Therefore, in the non-aqueous electrolyte secondary battery 1, the negative electrode 2 can draw out its original capacity.
[0059]
  Further, in the negative electrode 2, the carbon black contained in the negative electrode material is interposed between the negative electrode active material and the fibrous carbon, and improves the liquid retention of the electrolyte in the negative electrode 2. Thus, ion conduction in the limited voids present in the metal becomes faster, and the lithium ion doping / dedoping reaction is performed more smoothly. Thereby, in the non-aqueous electrolyte secondary battery 1, the internal resistance is further reduced, and polarization is reliably prevented.
[0060]
  Therefore, even if the nonaqueous electrolyte secondary battery 1 including the negative electrode 2 containing the negative electrode material composed of the negative electrode active material, fibrous carbon, and carbon black is repeatedly charged / discharged in a low temperature environment, for example, good charge / discharge Characteristics and high battery capacity.
[0061]
  The nonaqueous electrolyte battery according to the present invention is not limited to the nonaqueous electrolyte secondary battery 1 using a nonaqueous electrolyte as an electrolyte as described above, and a solid electrolyte or a gel electrolyte is used as an electrolyte. It is also possible to apply to a primary battery. In the nonaqueous electrolyte battery according to the present invention, the shape thereof is not particularly limited, such as a cylindrical shape, a rectangular shape, a coin shape, and a button shape, and may be any size such as a thin shape and a large size.
[0062]
【Example】
  Hereinafter, the nonaqueous electrolyte battery according to the present invention will be described based on specific experimental results. Here, a plurality of non-aqueous electrolyte secondary batteries were produced as examples and comparative examples.
[0063]
  <Experiment 1>
  In Experiment 1, the difference in capacity of the nonaqueous electrolyte secondary battery due to the difference in the negative electrode material was evaluated.
[0064]
  Example 1
  (Production of negative electrode)
  The negative electrode active material was adjusted as shown below. First, 30 parts by weight of coal tar pitch as a binder was added to 100 parts by weight of coal-based coke as a filler, mixed at about 100 ° C., and then compression molded to obtain a precursor of a carbon molded body. . Next, the precursor is heat treated at 1000 ° C. or lower to form a carbon molded body, impregnated with a binder pitch melted at 200 ° C. or lower, and further heat treated at 1000 ° C. or lower. Repeated times. Subsequently, this carbon molded body was heat-treated in an inert atmosphere at a temperature of 2700 ° C. to obtain a graphitized molded body. The graphitized molded body was pulverized and classified to obtain a negative electrode active material sample powder.
[0065]
  As a result of X-ray diffraction measurement of this graphitized molded body, the (002) plane spacing was 0.337 nm, and the C-axis crystallite thickness calculated from the (002) diffraction line was 50. It was 0 nm. Moreover, the true density by the pycnometer method which uses butanol as a solvent is 2.23 g / cm.³The bulk density is 0.83 g / cm³The specific surface area by the Brunauer Emmettteller method is 4.4 m.²/ G. The average particle size of the particle size distribution by laser diffraction method is 31.2 μm, the cumulative 10% particle size is 12.3 μm, the cumulative 50% particle size is 29.5 μm, and the cumulative 90% particle size is 53. The average value of the fracture strength of the graphite particles is 7.1 kgf / mm.³Met.
[0066]
  Next, 98.5% by weight of the negative electrode active material sample powder, 1.0% by weight of fibrous carbon (trade name: VGCF, manufactured by Showa Denko KK), and 0.5% by weight of acetylene black as carbon black A negative electrode material was prepared by mixing. The fibrous carbon is an average fiberDiameterIs 0.2 μm, the average fiber length is 10 μm, and the aspect ratio is 50.
[0067]
  Furthermore, 90 parts by weight of the negative electrode material and 10 parts by weight of polyvinylidene fluoride as a binder were mixed to prepare a negative electrode mixture, which was then dispersed in N-methylpyrrolidone to form a negative electrode mixture slurry. . Then, the negative electrode mixture slurry was uniformly applied on a strip-shaped negative electrode current collector, dried, compression-molded at a constant pressure, and then slitted to produce a strip-shaped negative electrode. As the negative electrode current collector, a strip-shaped copper foil having a thickness of 10 μm was used.
[0068]
  [Production of positive electrode]
  A positive electrode active material was prepared as follows. First, 0.5 mol of lithium carbonate and 1 mol of cobalt carbonate are mixed and calcined in air at a temperature of 900 ° C. for 5 hours to obtain LiCoO₂Was synthesized. In addition, X-ray diffraction measurement was performed on the obtained material, and a peak was recorded in the LiCoO registered in the JCPDS file.₂It was confirmed that it matches the data of.
[0069]
  Next, LiCoO₂LiCoO with a cumulative 50% particle size of 15 μm obtained by laser diffraction₂After making powder, this LiCoO₂A mixed powder was prepared by mixing 95% by weight of the powder and 5% by weight of the lithium carbonate powder. Then, 91 parts by weight of the mixed powder, 6 parts by weight of flake graphite as a conductive agent, and 3 parts by weight of polyvinylidene fluoride as a binder were prepared to prepare a positive electrode mixture, and then N-methylpyrrolidone. The mixture was dispersed in a positive electrode mixture slurry.
[0070]
  Then, the positive electrode mixture slurry is uniformly applied to a band-shaped aluminum foil having a thickness of 20 μm to be a positive electrode current collector, dried, compression-molded at a constant pressure, and slitted, thereby forming a band-shaped positive electrode. Produced.
[0071]
  [Production of battery]
  After laminating the strip-shaped negative electrode and the strip-shaped positive electrode prepared as described above in order of the negative electrode, the separator 4, the positive electrode, and the separator 4 through the separator 4 having a thickness of 25 μm and made of a microporous polyethylene film. A spiral electrode body having an outer diameter of 18 mm was produced by winding a number of times.
[0072]
  Next, this electrode body was stored in an iron battery can plated with nickel. Insulating plates are provided on the upper and lower surfaces of the electrode body, the aluminum positive electrode lead is led out from the positive electrode current collector and welded to the battery lid, and the nickel negative electrode lead is led out from the negative electrode current collector to obtain a battery can. Welded to.
[0073]
  Then, LiBF is added to a solution in which ethylene carbonate and dimethyl carbonate are mixed 1: 1 in a battery can.₄An electrolyte solution in which 1 mol / l was dissolved was injected. Next, the battery can was caulked through an insulating sealing gasket whose surface was coated with asphalt, thereby fixing the safety valve device having a current interruption mechanism, the PTC element, and the battery lid, and maintaining airtightness in the battery.
[0074]
  As described above, a cylindrical nonaqueous electrolyte secondary battery having a diameter of 18 mm and a height of 65 mm was produced.
[0075]
  Comparative Example 1
  A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that a negative electrode material consisting only of the negative electrode active material was used.
[0076]
  Comparative Example 2
  A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that a negative electrode material obtained by mixing 99.5% by weight of the negative electrode active material and 0.5% by weight of carbon black was used. .
[0077]
  Comparative Example 3
  A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that a negative electrode material obtained by mixing 99.0% by weight of the negative electrode active material and 1.0% by weight of fibrous carbon was used. did.
[0078]
  For the non-aqueous electrolyte secondary batteries of Example 1 and Comparative Examples 1 to 3 manufactured as described above, first, in a 23 ° C. environment, the charging current is 0.5 A, and the end voltage is 4 The battery was charged with constant current for 4 hours up to 2V. Then, in a 23 ° C. environment, a constant current discharge was performed with a discharge current of 0.5 A and a final voltage of 2.75 V, and the initial battery capacity was measured.
[0079]
  Next, under a 23 ° C. environment, constant current charging was performed for 2.5 hours with a charging current of 1.0 A and a final voltage of 4.2 V. Then, in a -10 degreeC environment, the discharge current was set to 1.0A, the constant current discharge to a final voltage of 2.75V was performed, and the battery capacity in a -10 degreeC environment was measured. And the ratio of the battery capacity in -10 degreeC environment with respect to initial stage battery capacity was calculated | required, and the ratio was made into the battery capacity maintenance rate in -10 degreeC environment.
[0080]
  The above measurement results are shown in Table 1 together with the contents of fibrous carbon and carbon black in the negative electrode material. In Table 1, the fibrous carbon content is a weight%, the carbon black content is b weight%, and the weight ratio of the fibrous carbon to carbon black is represented by a / b.
[0081]
[Table 1]

[0082]
  From Table 1, it can be seen that the non-aqueous electrolyte secondary battery of Example 1 has a high initial battery capacity and a high battery capacity retention rate in an environment of −10 ° C.
[0083]
  On the other hand, it can be seen that the nonaqueous electrolyte secondary battery of Comparative Example 1 has a low initial battery capacity and a low battery capacity retention rate in a -10 ° C environment. Moreover, although the battery capacity in the non-aqueous-electrolyte secondary battery of the comparative example 2 is improved in -10 degreeC environment, it turns out that initial stage battery capacity is low. Moreover, although the non-aqueous-electrolyte secondary battery of the comparative example 3 has high initial battery capacity, it turns out that the battery capacity maintenance factor in -10 degreeC environment is low.
[0084]
  Therefore, the non-aqueous electrolyte secondary battery includes a negative electrode containing a negative electrode material composed of a negative electrode active material, fibrous carbon, and carbon black, so that charge / discharge can be performed even when charging / discharging in a low temperature environment. It can be seen that it has excellent characteristics and a high battery capacity.
[0085]
  <Experiment 2>
  In Experiment 2, the battery characteristics were evaluated when the content of carbon black contained in the negative electrode material was constant and the content of fibrous carbon was changed.
[0086]
  Example 2 to Example 6, Comparative Example 4 to Comparative Example 6
  Non-aqueous electrolysis in the same manner as in Example 1 except that the content of carbon black is 0.5% by weight and the negative electrode material prepared as shown in Table 2 is used for the negative electrode active material and the fibrous carbon content. A liquid secondary battery was produced.
[0087]
  Produced as aboveExample 2 to Example 6, Comparative Example 4 to Comparative Example 6With respect to the nonaqueous electrolyte secondary battery, the initial battery capacity and the battery capacity retention rate under the environment of −10 ° C. were measured in the same manner as described above.
[0088]
  The above measurement results are shown in Table 2 together with the content of fibrous carbon and carbon black in the negative electrode material, and a / b.
[0089]
[Table 2]

[0090]
  From Table 2, 0.1% by weight of fibrous carbon is contained in the negative electrode material.Comparative Example 4Compared with the nonaqueous electrolyte secondary battery of Comparative Example 2 (Table 1) in which the fibrous carbon is not contained in the negative electrode material, the nonaqueous electrolyte secondary battery has a high initial battery capacity of −10 ° C. It can be seen that the battery capacity retention rate in the environment is also improved.
[0091]
  Also, an example in which 10% by weight of fibrous carbon is contained in the negative electrode material6In the non-aqueous electrolyte secondary battery, 20% by weight of fibrous carbon is contained in the negative electrode material.Comparative Example 6As compared with the non-aqueous electrolyte secondary battery, it can be seen that the initial battery capacity is higher and the battery capacity in a -10 ° C environment is higher.
[0092]
  Therefore, in the nonaqueous electrolyte secondary battery, fibrous carbon is contained in the negative electrode material in the range of 0.1 wt% to 10 wt%.PleaseAs a result, it can be seen that the negative electrode can sufficiently draw out the original capacity and realize a high battery capacity.
[0093]
  <Experiment 3>
  In Experiment 3, the battery characteristics were evaluated when the content of fibrous carbon contained in the negative electrode material was constant and the content of carbon black was changed.
[0094]
  Example 7 to Example 11, Comparative Example 7 to Comparative Example 9
  Nonaqueous electrolysis in the same manner as in Example 1 except that the content of fibrous carbon was 1.0% by weight and the negative electrode material prepared as shown in Table 3 was used with the negative electrode active material and the carbon black content. A liquid secondary battery was produced.
[0095]
  Produced as aboveExample 7 to Example 11, Comparative Example 7 to Comparative Example 9With respect to the nonaqueous electrolyte secondary battery, the initial battery capacity and the battery capacity retention rate under the environment of −10 ° C. were measured in the same manner as described above.
[0096]
  The above measurement results are shown in Table 3 together with the content of fibrous carbon and carbon black in the negative electrode material, and a / b.
[0097]
[Table 3]

[0098]
  From Table 3, 0.02% by weight of carbon black is contained in the negative electrode material.Comparative Example 8In the non-aqueous electrolyte secondary battery, 0.01% by weight of carbon black is contained in the negative electrode material.Comparative Example 7As compared with the non-aqueous electrolyte secondary battery, it can be seen that the battery capacity is maintained at the same level as the initial battery capacity and the battery capacity retention rate in the -10 ° C environment is further improved.
[0099]
  Example 1 in which 2.0% by weight of carbon black is contained in the negative electrode material1In the non-aqueous electrolyte secondary battery, 3.0% by weight of carbon black is contained in the negative electrode material.Comparative Example 9As compared with the non-aqueous electrolyte secondary battery, it can be seen that the battery capacity retention rate is as good as −10 ° C. and the initial battery capacity is higher.
[0100]
  Therefore, in the non-aqueous electrolyte secondary battery, when carbon black is contained in the negative electrode material in a range of 0.02 wt% or more and 2 wt% or less, the battery is charged / discharged in a low temperature environment of, for example, −10 ° C. Even if it is a case, it turns out that it has a favorable charge / discharge characteristic and has a high battery capacity.
[0101]
  Here, the weight ratio between fibrous carbon and carbon black, that is, a / b is considered. Example where a / b is 206A / b is 30Comparative Example 6And a / b is 100Comparative Example 7Compared with Example6It can be seen that the capacity retention rate in a -10 ° C environment is higher.
[0102]
  Example 1 in which a / b is 0.51A / b is 0.2IsComparative Example 4And a / b is 0.33Comparative Example 9Compared to Example 11Shows that the initial battery capacity is higher.
[0103]
  Therefore, by setting the weight ratio of fibrous carbon and carbon black in the range of 0.5 or more and 20 or less, the effect of increasing the conductivity of the negative electrode active material grain boundary and the effect of holding the electrolyte in the negative electrode are achieved. It can be seen that both can be obtained and a non-aqueous electrolyte secondary battery having excellent battery characteristics can be obtained.
[0104]
【The invention's effect】
  As is clear from the above description, the nonaqueous electrolyte battery according to the present invention includes a positive electrode and a negative electrode active material.Of graphiteAnd a negative electrode having a negative electrode material composed of fibrous carbon and carbon black, and a non-aqueous electrolyte,The negative electrode material contains 89.5 wt% or more and 99.0 wt% or less of graphite,Fibrous carbonIs 0. Carbon black is contained in the range of 5 wt% to 10 wt%Is 0. It is contained in the range of 1% by weight or more and 2% by weight or less, the weight ratio of fibrous carbon to carbon black is in the range of 0.5 or more and 20 or less, and the aspect ratio of the fibrous carbon is 10 or more. Therefore, even when charged and discharged in a low temperature environment, it has good charge / discharge characteristics and a high capacity.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a configuration example of a cylindrical nonaqueous electrolyte secondary battery.
[Explanation of symbols]
  1 Nonaqueous electrolyte secondary battery, 2 negative electrode, 3 positive electrode, 4 separator, 5 battery can, 6 negative electrode current collector, 7 positive electrode current collector, 8 insulating plate, 9 negative electrode lead, 10 positive electrode lead, 11 battery cover, 12 Insulation sealing gasket, 13 Safety valve device, 14PTC element

Claims (4)

A positive electrode containing a positive electrode active material capable of doping / dedoping lithium;
A negative electrode containing a negative electrode material composed of graphite , fibrous carbon, and carbon black as negative electrode active materials capable of doping / dedoping lithium; and
With a non-aqueous electrolyte,
The negative electrode material contains the graphite in an amount of 89.5 wt% or more and 99.0 wt% or less, and the fibrous carbon is 0.02 wt% or less . 5 wt% or more, is contained in an amount of 10 wt% or less, the carbon black is 0. 1 wt% or more, 2. Non-water that is contained in the range of 0 % by weight or less, the weight ratio of the fibrous carbon to the carbon black is 0.5 or more and 20 or less, and the aspect ratio of the fibrous carbon is 10 or more. Electrolyte battery.   The nonaqueous electrolyte battery according to claim 1, wherein the fibrous carbon has a fiber length of 0.5 μm. The non-aqueous electrolyte battery according to claim 1, wherein the carbon black has a DBP oil absorption of 100 ml / 100 g or more .   The nonaqueous electrolyte battery according to any one of claims 1 to 3, wherein the nonaqueous electrolytic solution is a mixed solution of ethylene carbonate and dimethyl carbonate.

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