JP5326340B2 - Negative electrode for secondary battery, secondary battery and electronic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a secondary battery capable of improving a cycle characteristic. <P>SOLUTION: This secondary battery is provided with an electrolyte along with a positive electrode 21 and a negative electrode 22, wherein a separator 23 arranged between the positive electrode 21 and the negative electrode 22 is impregnated with the electrolyte. The negative electrode 22 has projections 22C on negative electrode active material layers 22B formed on a negative electrode collector 22A. The distal end of the projection 22C is brought into a state cut into the separator 23. Even when charge and discharge are repeated, deformation of the negative electrode collector 22A and separation of the negative electrode active material layer 22B are prevented, and structural stability of the negative electrode 22 is improved. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

BACKGROUND 1. Technical Field The present invention relates, with rechargeable battery negative electrode having a negative electrode active material layer on an anode current collector, with the negative pole of its positive electrode, a secondary battery having a separator and an electrolyte, and the secondary battery About.

  In recent years, portable electronic devices such as a video camera, a digital still camera, a mobile phone, and a laptop computer have been widely used, and there is a strong demand for miniaturization, weight reduction, and long life. Accordingly, as a power source, development of a battery, in particular, a secondary battery that is lightweight and capable of obtaining a high energy density is in progress.

  Among them, secondary batteries (so-called lithium ion secondary batteries) that use the insertion and release of lithium (Li) for charge / discharge reactions are widely put into practical use because they have higher energy density than lead batteries and nickel cadmium batteries. ing. This lithium ion secondary battery includes an electrolyte solution together with a positive electrode and a negative electrode, and the negative electrode has a negative electrode active material layer on a negative electrode current collector.

  Carbon materials such as graphite are widely used as the negative electrode active material included in the negative electrode active material layer of the lithium ion secondary battery. In addition, recently, there has been a demand for further improvement in battery capacity as portable electronic devices become more sophisticated and multifunctional, so that silicon (Si) or tin (Sn) can be used instead of carbon materials. It is being considered. This is because the theoretical capacity of silicon (4199 mAh / g) and the theoretical capacity of tin (994 mAh / g) are much larger than the theoretical capacity of graphite (372 mAh / g), so that a significant improvement in battery capacity can be expected.

  However, in this lithium ion secondary battery, the negative electrode active material expands and contracts during insertion and extraction of lithium during charge and discharge, and thus the negative electrode active material layer is peeled off or the negative electrode current collector is deformed. There are things to do. This phenomenon becomes prominent when silicon having a high theoretical capacity is used as the negative electrode active material, and the cycle characteristics, which are important characteristics of the secondary battery, are likely to deteriorate.

  Therefore, in order to improve this problem, various ideas have been made regarding a method for forming a negative electrode active material layer containing silicon. For example, a negative electrode active material containing silicon is deposited on a negative electrode current collector in a columnar shape or a particle shape by a vapor phase method, and the negative electrode active material is expanded by providing a predetermined distance from an adjacent columnar or particulate negative electrode active material. There has been proposed a technique for relieving the stress caused by (for example, see Patent Documents 1 to 3).

Note that when forming the negative electrode active material layer by a vapor phase method, the negative electrode active material droplets from the deposition source may adhere as protrusions (so-called splash) to the surface of the negative electrode active material layer. There is a problem that the separator separating the anode and the negative electrode is pierced and a short circuit is likely to occur. For this reason, a manufacturing method in which the protrusion is shaved or crushed is also known (see, for example, Patent Documents 4 and 5).
JP 2002-279974 A JP 2006-155957 A Japanese Patent Application No. 2006-155960 JP 2006-278270 A JP 2008-004281 A

  However, as described above, various studies have been made, but sufficient cycle characteristics have not been obtained, and further improvements are desired. In addition, recent portable electronic devices are becoming smaller, higher performance, and more multifunctional, and their power consumption tends to increase. Therefore, charging and discharging of secondary batteries are frequently repeated, resulting in more cycle characteristics. The situation is likely to decline. For this reason, further improvement is required regarding the cycle characteristics of the secondary battery.

The present invention has been made in view of such problems, and an object of the present invention is to provide a negative electrode for a secondary battery , a secondary battery, and an electronic device capable of improving cycle characteristics.

The negative electrode for a secondary battery of the present invention includes a negative electrode current collector and a negative electrode active material layer having a plurality of negative electrode active material particles and provided on the negative electrode current collector. The negative electrode active material layer grows in the thickness direction of the negative electrode active material layer from the surface of the body and is connected to the negative electrode current collector, and in the vicinity of the vertex of the negative electrode active material particles in the thickness direction of the negative electrode active material layer, the negative electrode width than the particle size of the active material particles is provided with a plurality of small conical projections, the anode active material particles and protrusions, simple substance of silicon, see contains at least one of alloys and compounds, the projections The width is 0.06 μm or more and 4 μm or less, and the height of the protrusion is 0.04 μm or more and 8.5 μm or less, and the protrusion bites into the separator . Here, the “protrusion” means a protrusion protruding from the surface of the negative electrode active material layer. The “width” of the protrusion refers to the maximum diameter of the interface between the negative electrode active material layer surface and the protrusion.

A secondary battery according to the present invention includes a positive electrode and a negative electrode that are disposed to face each other with a separator interposed therebetween, and an electrolyte solution that includes a solvent and an electrolyte salt. The negative electrode includes a negative electrode current collector and a plurality of negative electrode active material particles. And a negative electrode active material layer provided on the negative electrode current collector, wherein the negative electrode active material particles grow from the surface of the negative electrode current collector in the thickness direction of the negative electrode active material layer, and the negative electrode current collector A plurality of conical protrusions having a width smaller than the particle diameter of the negative electrode active material particles are provided in the vicinity of the apex of the negative electrode active material particles in the thickness direction of the negative electrode active material layer. active material particles and protrusions, simple substance of silicon, see contains at least one of alloys and compounds, together with the width of the protrusion is less 4μm least 0.06 .mu.m, the height of the projection is 0.04μm or 8.5μm The protrusion is not eaten by the separator. It is those that are crowded.

Electronic device of the present invention is provided with a secondary battery of the present invention.

The negative electrode for secondary battery of the present invention, by having a plurality of protrusions on the surface of the anode active material layer, when used in a secondary battery provided with a separator separating the positive electrode and the negative electrode, its projections physical Acts as a resistor. That is, the negative electrode active material layer and the separator are integrated or in close contact. As a result, stress due to expansion and contraction of the negative electrode active material layer caused by insertion and extraction of the electrode reactant is alleviated by the separator. Therefore, peeling of the negative electrode active material layer and deformation of the negative electrode current collector are suppressed. Therefore, the secondary battery including the separator with the anode for a secondary battery of the invention, and the electronic apparatus including the secondary battery, the discharge capacity even after repeated charge and discharge can be maintained.

According to the negative electrode for a secondary battery of the present invention, a plurality of conical protrusions having a width smaller than the particle diameter of the negative electrode active material particles are provided near the apex of the negative electrode active material particles, and the negative electrode active material The particles and protrusions contain at least one of silicon simple substance, alloy and compound . Further, the width of the protrusion is 0.06 μm to 4 μm, the height of the protrusion is 0.04 μm to 8.5 μm, and the protrusion bites into the separator. As a result, when this negative electrode is used in a secondary battery equipped with a separator, even if the electrode reactant is occluded and released, the negative electrode active material layer is prevented from expanding and contracting, and structural stability is improved. To do. Therefore, according to the secondary battery provided with the separator together with the negative electrode for secondary battery of the present invention, and the electronic device provided with the secondary battery, cycle characteristics can be improved.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a cross-sectional configuration of a negative electrode according to an embodiment of the present invention. This negative electrode is used for, for example, an electrochemical device such as a secondary battery, and includes a negative electrode current collector 1 having a pair of surfaces, a negative electrode active material layer 2 provided on the negative electrode current collector 1, and And a protrusion 3 provided on the surface of the negative electrode active material layer 2. The negative electrode active material layer 2 may be provided on both sides of the negative electrode current collector 1 or may be provided only on one side. The same applies to the protrusion 3. In the following, the case where lithium is used as the electrode reactant that is occluded and released in the negative electrode will be described.

  The negative electrode current collector 1 is preferably made of a metal material having good electrochemical stability, electrical conductivity, and mechanical strength. Examples of such a metal material include copper, nickel, and stainless steel, and copper is preferable. This is because high electrical conductivity can be obtained.

  In particular, the metal material described above preferably contains one or more metal elements that do not form an intermetallic compound with lithium. When lithium and an intermetallic compound are formed, current collecting performance is reduced because it is easily affected by stress due to expansion and contraction of the negative electrode active material layer 2 during operation of the electrochemical device (for example, during charging and discharging of the secondary battery). This is because there is a possibility that the negative electrode active material layer 2 may be separated from the negative electrode current collector 1. Examples of such metal elements include copper (Cu), nickel (Ni), titanium (Ti), iron (Fe), and chromium (Cr).

  In addition, the metal material described above preferably contains any one or more of metal elements that are alloyed with the negative electrode active material layer 2. This is because the adhesion between the negative electrode current collector 1 and the negative electrode active material layer 2 is improved, so that the negative electrode active material layer 2 is difficult to peel from the negative electrode current collector 1. Examples of the metal element that does not form an intermetallic compound with lithium and alloyed with the negative electrode active material layer 2 include, for example, copper, nickel, or iron when the negative electrode active material layer 2 contains silicon as the negative electrode active material. Is mentioned. These metal elements are also preferable from the viewpoints of strength and conductivity.

  The negative electrode current collector 1 may have a single layer structure or a multilayer structure. When the negative electrode current collector 1 has a multilayer structure, for example, a layer adjacent to the negative electrode active material layer 2 is made of a metal material alloyed therewith, and a non-adjacent layer is made of another metal material. preferable.

  The surface of the negative electrode current collector 1 is preferably roughened. This is because the adhesion between the negative electrode current collector 1 and the negative electrode active material layer 2 is improved by a so-called anchor effect. In this case, the surface of the negative electrode current collector 1 may be roughened at least in a region facing the negative electrode active material layer 2. Examples of the roughening method include a method of forming fine particles by electrolytic treatment. This electrolytic treatment is a method of forming irregularities by forming fine particles on the surface of the negative electrode current collector 1 by an electrolytic method in an electrolytic bath. The copper foil produced by the electrolytic method including the copper foil roughened by this electrolytic treatment is generally called “electrolytic copper foil”.

  The negative electrode active material layer 2 contains one or more negative electrode materials capable of inserting and extracting lithium as a negative electrode active material. The negative electrode active material layer 2 may contain other materials such as a conductive agent or a binder as necessary.

  Examples of the negative electrode material capable of inserting and extracting lithium include materials capable of inserting and extracting lithium and having at least one of a metal element and a metalloid element as a constituent element. . This is because a high energy density can be obtained. Such a negative electrode material may be a single element or an alloy or a compound of a metal element or a metalloid element, and may have one or two or more phases thereof at least in part.

  In addition, the “alloy” mentioned here includes an alloy containing one or more metal elements and one or more metalloid elements in addition to an alloy composed of two or more metal elements. Further, the “alloy” may contain a nonmetallic element. This structure includes a solid solution, a eutectic (eutectic mixture), an intermetallic compound, or one in which two or more of them coexist.

  Examples of the metal element or metalloid element described above include a metal element or metalloid element capable of forming an alloy with lithium. Specifically, magnesium (Mg), boron (B), aluminum (Al), gallium (Ga), indium (In), silicon (Si), germanium (Ge), tin (Sn), lead (Pb), Examples thereof include bismuth (Bi), cadmium (Cd), silver (Ag), zinc (Zn), hafnium (Hf), zirconium (Zr), yttrium (Y), palladium (Pd), and platinum (Pt). Among these, at least one of silicon and tin is preferable, and silicon is more preferable. This is because a high energy density can be obtained because the ability to occlude and release lithium is large.

  Examples of the negative electrode material having at least one of silicon and tin include at least a part of a simple substance, an alloy or a compound of silicon, a simple substance, an alloy or a compound of tin, or one or two or more phases thereof. The material which has in is mentioned. These may be single and multiple types may be mixed.

Examples of the silicon alloy include tin, nickel, copper, iron, cobalt (Co), manganese (Mn), zinc, indium, silver, titanium, germanium, bismuth and antimony (second constituent elements other than silicon). And those having at least one of the group consisting of Ab) and chromium. Examples of the silicon compound include those having oxygen (O) or carbon (C), and may have the second constituent element described above in addition to silicon. Examples of silicon alloys or compounds include SiB ₄ , SiB ₆ , Mg ₂ Si, Ni ₂ Si, TiSi ₂ , MoSi ₂ , CoSi ₂ , NiSi ₂ , CaSi ₂ , CrSi ₂ , Cu ₅ Si, FeSi ₂ , MnSi. ₂ , NbSi ₂ , TaSi ₂ , VSi ₂ , WSi ₂ , ZnSi ₂ , SiC, Si ₃ N ₄ , Si ₂ N ₂ O, SiO _v (0 <v ≦ 2) or LiSiO.

As an alloy of tin, for example, as a second constituent element other than tin, among the group consisting of silicon, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony and chromium The thing which has at least 1 sort (s) of these is mentioned. Examples of the tin compound include those having oxygen or carbon, and may contain the above-described second constituent element in addition to tin. Examples of tin alloys or compounds include SnO _w (0 <w ≦ 2), SnSiO ₃ , LiSnO, Mg ₂ Sn, and the like.

  In particular, as the negative electrode material having at least one of silicon and tin, for example, a material having tin and the second constituent element in addition to tin as the first constituent element is preferable. The second constituent element is cobalt, iron, magnesium, titanium, vanadium (V), chromium, manganese, nickel, copper, zinc, gallium, zirconium, niobium (Nb), molybdenum (Mo), silver, indium, cerium ( Ce), hafnium, tantalum (Ta), tungsten (W), bismuth and silicon. The third constituent element is at least one selected from the group consisting of boron, carbon, aluminum, and phosphorus (P). This is because the inclusion of the second and third constituent elements improves the cycle characteristics when the negative electrode is used in an electrochemical device such as a secondary battery.

  Among them, tin, cobalt and carbon are included as constituent elements, the carbon content is 9.9 mass% or more and 29.7 mass% or less, and the ratio of cobalt to the total of tin and cobalt (Co / (Sn + Co)) is 30. An SnCoC-containing material having a mass% of 70% by mass or less is preferable. This is because a high energy density can be obtained in such a composition range.

  This SnCoC-containing material may further contain other constituent elements as necessary. As other constituent elements, for example, silicon, iron, nickel, chromium, indium, niobium, germanium, titanium, molybdenum, aluminum, phosphorus, gallium, bismuth, and the like are preferable, and two or more of them may be included. Good. This is because a higher effect can be obtained.

  The SnCoC-containing material has a phase containing tin, cobalt, and carbon, and the phase is preferably a low crystalline or amorphous phase. This phase is a reaction phase capable of reacting with lithium, whereby excellent cycle characteristics can be obtained. The half-value width of the diffraction peak obtained by X-ray diffraction of this phase is 1.0 ° or more at a diffraction angle 2θ when CuKα ray is used as the specific X-ray and the drawing speed is 1 ° / min. Is preferred. This is because lithium is more smoothly inserted and extracted, and the reactivity with the electrolytic solution is reduced when the negative electrode is used in an electrochemical device such as a secondary battery equipped with the electrolytic solution.

  Whether or not the diffraction peak obtained by X-ray diffraction corresponds to a reaction phase capable of reacting with lithium can be easily determined by comparing X-ray diffraction charts before and after electrochemical reaction with lithium. can do. For example, if the position of the diffraction peak changes before and after the electrochemical reaction with lithium, it corresponds to a reaction phase capable of reacting with lithium. In this case, for example, a diffraction peak of a low crystalline or amorphous reaction phase is observed between 2θ = 20 ° and 50 °. This low crystalline or amorphous reaction phase contains, for example, each of the above-described constituent elements, and is considered to be mainly low-crystallized or amorphous due to carbon.

  In addition to the low crystalline or amorphous phase, the SnCoC-containing material may have a phase containing a simple substance or a part of each constituent element.

  In particular, in the SnCoC-containing material, it is preferable that at least a part of carbon as a constituent element is bonded to a metal element or a metalloid element as another constituent element. This is because aggregation or crystallization of tin or the like is suppressed.

  As a measuring method for examining the bonding state of elements, for example, X-ray photoelectron spectroscopy (XPS) can be cited. This XPS irradiates the sample surface with soft X-rays (Al-Kα ray or Mg-Kα ray is used in a commercial apparatus), and measures the kinetic energy of photoelectrons jumping out of the sample surface. To elemental composition in the region of several nanometers and the bonding state of the elements.

  The binding energy of the core orbital electrons of the element changes in a first approximation in correlation with the charge density on the element. For example, when the charge density of the carbon element decreases due to an interaction with an element present in the vicinity, the outer electrons such as 2p electrons decrease, so the 1s electron of the carbon element exerts a strong binding force from the shell. Will receive. That is, the binding energy increases as the charge density of the element decreases. In XPS, when the binding energy increases, the peak shifts to a high energy region.

  In XPS, if the peak of carbon 1s orbital (C1s) is graphite, it appears at 284.5 eV in an energy calibrated apparatus so that the peak of 4f orbital (Au4f) of gold atom is obtained at 84.0 eV. . Moreover, if it is surface contamination carbon, it will appear at 284.8 eV. On the other hand, when the charge density of the carbon element is high, for example, when it is bonded to an element more positive than carbon, the C1s peak appears in a region lower than 284.5 eV. That is, when at least a part of carbon contained in the SnCoC-containing material is bonded to a metal element or a metalloid element that is another constituent element, the peak of the synthetic wave of C1s obtained for the SnCoC-containing material is 284. Appears in a region lower than 5 eV.

  When performing XPS measurement, it is preferable that the surface is lightly sputtered with an argon ion gun attached to the XPS apparatus when the surface is covered with surface-contaminated carbon. In addition, when a negative electrode having a SnCoC-containing material to be measured is present in an electrochemical device such as a secondary battery provided with an electrolytic solution, the electrochemical device is disassembled and the negative electrode is taken out, and then dimethyl carbonate, etc. It is good to wash with a volatile solvent. This is for removing the low-volatile solvent and the electrolyte salt present on the negative electrode surface. These samplings are preferably performed under an inert atmosphere.

  In XPS measurement, for example, the peak of C1s is used to correct the energy axis of the spectrum. Usually, since surface-contaminated carbon exists on the surface of the substance, the C1s peak of the surface-contaminated carbon is set to 284.8 eV, and this is used as an energy standard. In XPS measurement, the waveform of the peak of C1s is obtained as a form including the surface contamination carbon peak and the carbon peak in the SnCoC-containing material. For example, by analyzing using commercially available software, The surface contamination carbon peak is separated from the carbon peak in the SnCoC-containing material. In the waveform analysis, the position of the main peak existing on the lowest bound energy side is used as the energy reference (284.8 eV).

  This SnCoC-containing material can be formed by, for example, a method in which a mixture obtained by mixing raw materials of each constituent element is melted in an electric furnace, a high-frequency induction furnace, an arc melting furnace or the like and then solidified. Also, various atomizing methods such as gas atomization or water atomization, methods using various mechanochemical reactions such as various roll methods, mechanical alloying methods, and mechanical milling methods may be used. Among these, a method using a mechanochemical reaction is preferable. This is because the SnCoC-containing material has a low crystalline or amorphous structure. In the method using the mechanochemical reaction, for example, a manufacturing apparatus such as a planetary ball mill or an attritor can be used.

  The raw material may be a mixture of individual constituent elements, but it is preferable to use an alloy for some of the constituent elements other than carbon. This is because, by adding carbon to such an alloy and synthesizing it by a method using a mechanical alloying method, a low crystalline or amorphous structure is obtained, and the reaction time is shortened. The raw material may be in the form of powder or a block.

  In addition to this SnCoC-containing material, an SnCoFeC-containing material having tin, cobalt, iron and carbon as constituent elements is also preferable. The composition of the SnCoFeC-containing material can be arbitrarily set. For example, as the composition when the iron content is set to be small, the carbon content is 9.9 mass% or more and 29.7 mass% or less, and the iron content is 0.3 mass% or more and 5.9 weight% %, And the ratio of cobalt to the total of tin and cobalt (Co / (Sn + Co)) is preferably 30% by mass or more and 70% by mass or less. In addition, for example, as a composition when the content of iron is set to be large, the content of carbon is 11.9 mass% or more and 29.7 mass% or less, and cobalt and iron with respect to the total of tin, cobalt, and iron The total ratio of (Co + Fe) / (Sn + Co + Fe)) is 26.4 mass% to 48.5 mass%, and the ratio of cobalt to the total of cobalt and iron (Co / (Co + Fe)) is 9.9 mass% It is preferable that it is 79.5 mass% or more. This is because a high energy density can be obtained in such a composition range. The crystallinity of the SnCoFeC-containing material, the method for measuring the bonding state of elements, the formation method, and the like are the same as those of the above-described SnCoC-containing material.

  As a negative electrode material capable of inserting and extracting lithium, a simple substance, an alloy or a compound of silicon, a simple substance, an alloy or a compound of tin, or a material having one or more phases thereof at least in part. The used negative electrode active material layer 2 is formed using, for example, a vapor phase method, a liquid phase method, a coating method, or two or more of these methods. In this case, the negative electrode current collector 1 and the negative electrode active material layer 2 are preferably alloyed at least at a part of the interface. Specifically, the constituent element of the negative electrode current collector 1 may be diffused into the negative electrode active material layer 2 at the interface between them, or the constituent element of the negative electrode active material layer 2 is diffused into the negative electrode current collector 1. These constituent elements may be diffused with each other. This is because breakage due to expansion and contraction of the negative electrode active material layer 2 during charging and discharging is suppressed, and electronic conductivity between the negative electrode current collector 1 and the negative electrode active material layer 2 is improved.

  As the vapor phase method, for example, physical deposition method or chemical deposition method, specifically, thermal spraying method, vacuum deposition method, sputtering method, ion plating method, laser ablation method, thermal chemical vapor deposition (Chemical Vapor Deposition) : CVD) method or plasma enhanced chemical vapor deposition method. As the liquid phase method, a known method such as electrolytic plating or electroless plating can be used. The coating method is, for example, a method in which a particulate negative electrode active material is mixed with a binder and then dispersed and applied in a solvent. After coating, heat treatment is performed at a temperature lower than the melting point of the binder or the like. And a method of performing a heat treatment at a temperature higher than the melting point of a binder or the like (firing method). Examples of the firing method include an atmosphere firing method, a reaction firing method, and a hot press firing method.

  In addition to the above, examples of the anode material capable of inserting and extracting lithium include a carbon material. Examples of the carbon material include graphitizable carbon, non-graphitizable carbon having a (002) plane spacing of 0.37 nm or more, and graphite having a (002) plane spacing of 0.34 nm or less. It is. More specifically, there are pyrolytic carbons, cokes, glassy carbon fibers, organic polymer compound fired bodies, activated carbon or carbon blacks. The cokes include pitch coke, needle coke, petroleum coke and the like. The organic polymer compound fired body is obtained by firing and carbonizing a phenol resin, a furan resin, or the like at an appropriate temperature. Since carbon materials undergo very little change in crystal structure due to insertion and extraction of electrode reactants, for example, when used together with other negative electrode materials, high energy density can be obtained, and the negative electrode can be used for secondary batteries, etc. When used in an electrochemical device, excellent cycle characteristics can be obtained, and it also functions as a conductive agent, which is preferable. The shape of the carbon material may be any of fibrous, spherical, granular or scale-like.

  Further, examples of the negative electrode material capable of inserting and extracting lithium include metal oxides and polymer compounds capable of inserting and extracting lithium. Examples of the metal oxide include iron oxide, ruthenium oxide, and molybdenum oxide. Examples of the polymer compound include polyacetylene, polyaniline, and polypyrrole.

  Of course, the negative electrode material capable of inserting and extracting lithium may be other than the above. Further, two or more kinds of the above series of negative electrode materials may be mixed in any combination.

  Examples of the conductive agent include carbon materials such as graphite, carbon black, acetylene black, and ketjen black. These may be single and multiple types may be mixed. Note that the conductive agent may be a metal material or a conductive polymer as long as it is a conductive material.

  Examples of the binder include synthetic rubbers such as styrene butadiene rubber, fluorine rubber or ethylene propylene diene, and polymer materials such as polyvinylidene fluoride. These may be single and multiple types may be mixed.

  The negative electrode active material made of the negative electrode material described above may have a plurality of particles. That is, the negative electrode active material layer 2 may have a plurality of negative electrode active material particles. The negative electrode active material particles can be formed by, for example, the gas phase method described above. Of course, the negative electrode active material particles may be formed by a method other than the vapor phase method.

  When the negative electrode active material particles are formed by a vapor phase method, the negative electrode active material particles may have a single layer structure formed through a single deposition process, or a plurality of deposition processes. You may have the multilayered structure formed through these. However, when the negative electrode active material particles are formed by a vapor deposition method that involves high heat during deposition, the negative electrode active material particles preferably have a multilayer structure. By performing the deposition process of the negative electrode material in a plurality of times (the negative electrode material is sequentially formed and deposited), the negative electrode current collector 1 is exposed to higher heat than when the deposition process is performed once. This is because the time required for heat treatment is shortened and it is difficult to receive thermal damage.

  The negative electrode active material particles grow, for example, from the surface of the negative electrode current collector 1 in the thickness direction of the negative electrode active material layer 2 and are connected to the negative electrode current collector 1 at the base. In this case, the negative electrode active material particles are formed by a vapor phase method, and it is preferable that the negative electrode active material particles are alloyed at least at a part of the interface with the negative electrode current collector 1 as described above. Specifically, the constituent elements of the negative electrode current collector 1 may be diffused into the negative electrode active material particles at the interface between them, or the constituent elements of the negative electrode active material particles are diffused into the negative electrode current collector 1. Alternatively, the constituent elements of both may diffuse to each other.

  When the negative electrode active material particles have silicon as a constituent element, it is preferable that the negative electrode active material particles further have oxygen. This is because expansion and contraction of the negative electrode active material layer 2 are suppressed. In this negative electrode active material layer, it is preferable that at least part of oxygen is bonded to part of silicon. In this case, the bonding state may be silicon monoxide or silicon dioxide, or another forward stable state.

  The oxygen content in the negative electrode active material particles is preferably in the range of 3 atomic% (at%) to 46.2 atomic%. This is because a higher effect can be obtained. Specifically, when the oxygen content is less than 3 atomic%, the expansion and contraction of the negative electrode active material layer 2 is not sufficiently suppressed, while when it exceeds 46.2 atomic%, the resistance increases. Because it is too much. For example, when a negative electrode is used with an electrolytic solution in an electrochemical device, a film formed by decomposition of the electrolytic solution is not included in the negative electrode active material layer 2. That is, when the oxygen content in the negative electrode active material layer 2 is calculated, oxygen in the above-described film is not included. The content of oxygen in the negative electrode active material particles is preferably 5.8 atomic% or more and 32.7 atomic% or less, particularly 9.4 atomic% or more and 24.1 atomic%. It is preferable that: This is because a higher effect can be obtained.

  The negative electrode active material particles having oxygen can be formed by continuously introducing oxygen gas into the chamber when forming the negative electrode active material particles by a vapor phase method. In particular, when a desired oxygen content cannot be obtained simply by introducing oxygen gas, a liquid (for example, water vapor) may be introduced into the chamber as an oxygen supply source.

  Further, the negative electrode active material particles having silicon as a constituent element preferably have a metal element. This is because expansion and contraction of the negative electrode active material layer 2 are suppressed. This metal element is preferably at least one member selected from the group consisting of titanium, chromium, manganese, iron, cobalt, nickel, copper, zinc, indium, silver, magnesium, aluminum, germanium, tin, bismuth, molybdenum, or antimony. . The content of the metal element in the negative electrode active material particles can be arbitrarily set. However, for example, when the negative electrode is used in a battery, if the content of the metal element is excessive, the negative electrode active material layer 2 must be thickened to obtain a desired battery capacity, and the negative electrode active material layer 2 is not practical because it easily peels off or breaks from the negative electrode current collector 1.

  The negative electrode active material particles having a metal element described above may use, for example, an evaporation source mixed with a metal element or a multi-component evaporation source when forming negative electrode active material particles by a vapor deposition method as a vapor phase method. Can be formed.

  The negative electrode active material particles having silicon as a constituent element further have an oxygen-containing region having oxygen in the thickness direction, and the oxygen content in the oxygen-containing region is the oxygen content in other regions. Higher than that. This is because expansion and contraction of the negative electrode active material layer 2 are suppressed. Regions other than this oxygen-containing region may or may not contain oxygen. Of course, when the region other than the oxygen-containing region also has oxygen, it goes without saying that the oxygen content is lower than the oxygen content in the oxygen-containing region.

  In this case, in order to further suppress the expansion and contraction of the negative electrode active material layer 2, the regions other than the oxygen-containing region also have oxygen, that is, the negative electrode active material particles are contained in the first oxygen-containing region (more Preferably, it includes a region having a low oxygen content) and a second oxygen-containing region having a higher oxygen content (region having a higher oxygen content). In this case, it is preferable that the second oxygen-containing region is sandwiched by the first oxygen-containing region, and the first oxygen-containing region and the second oxygen-containing region are alternately and repeatedly stacked. Is more preferable. This is because a higher effect can be obtained. The oxygen content in the first oxygen-containing region is preferably as low as possible, and the oxygen content in the second oxygen-containing region is the same as, for example, the content when the negative electrode active material particles include oxygen. It is.

  The negative electrode active material particles including the first oxygen-containing region and the second oxygen-containing region are, for example, intermittently introducing oxygen gas into the chamber when forming the negative electrode active material particles by a vapor phase method, It can be formed by changing the amount of oxygen gas introduced into the chamber. Of course, when a desired oxygen content cannot be obtained simply by introducing oxygen gas, a liquid (for example, water vapor) may be introduced into the chamber.

  Note that the oxygen content may or may not be clearly different between the first oxygen-containing region and the second oxygen-containing region. In particular, when the amount of oxygen gas introduced is continuously changed, the oxygen content may also be continuously changed. The first oxygen-containing region and the second oxygen-containing region become so-called “layers” when the oxygen gas introduction amount is changed intermittently, while the oxygen gas introduction amount is changed continuously. In this case, it becomes “layered” rather than “layer”. In the latter case, the oxygen content in the negative electrode active material particles is distributed while repeating high and low. In this case, it is preferable that the oxygen content changes stepwise or continuously between the first oxygen-containing region and the second oxygen-containing region. This is because if the oxygen content changes rapidly, the diffusibility of ions may decrease or the resistance may increase.

  A plurality of protrusions 3 are provided on the surface of the negative electrode active material layer 2 so as to protrude from the contour of the surface. As a result, when used in an electrochemical device such as a secondary battery equipped with a separator, the protrusion 3 is in a state where it has bite into the separator, that is, the state where the negative electrode and the separator are integrated, Become. For this reason, even if lithium is occluded and released, a relative positional shift in the in-plane direction between the negative electrode and the separator hardly occurs (hereinafter referred to as a spike action), and the negative electrode active material layer 2 expands and contracts. Is relaxed by the separator, and the structural stability of the negative electrode is improved. Therefore, deformation of the negative electrode current collector 1 and peeling of the negative electrode active material layer 2 are suppressed, which contributes to improvement of cycle characteristics. The protrusion 3 may be integrated with the negative electrode active material layer 2 or may be a separate body. In the case of a separate body from the negative electrode active material layer 2, the protrusion 3 is preferably fixed or fixed to the surface of the negative electrode active material layer 2. This is because a higher effect can be obtained.

  The material which comprises the processus | protrusion 3 can be set arbitrarily, may be comprised including the above-mentioned negative electrode material, and may contain materials other than negative electrode material. As a material constituting the protrusion 3, a negative electrode material is preferable. This is because the protrusion 3 has a function as a negative electrode active material, and a high capacity can be obtained as the negative electrode. Among these, a material having silicon or tin as a constituent element is preferable. This is because a higher capacity can be obtained. Examples of the material having silicon or tin as a constituent element include silicon simple substance, alloy or compound, and tin simple substance, alloy or compound. In particular, the material constituting the protrusion 3 preferably includes a material having the same composition as the negative electrode active material included in the negative electrode active material layer 2. Since the expansion / contraction rate of the negative electrode active material layer 2 and the expansion / contraction rate of the protrusion 3 when lithium is occluded and released are approximately the same, and the bonding property between the protrusion 3 and the negative electrode active material layer 2 is increased, a high effect is obtained. Because it is.

  The shape of the protrusion 3 is arbitrary as long as the above-described spike action can be obtained, and one protrusion 3 may have one or two or more tip portions. Especially, as a shape of the protrusion 3, it is preferable that the front-end | tip part is sharp, and it is more preferable that it is conical as a whole. In addition, the cone shape here represents a wide concept including a shape similar to a cone in addition to a geometric cone. This is because when the tip portion is sharp, the spike action is sufficiently exerted, and the overall shape becomes conical, so that a higher effect can be obtained.

  The protrusion 3 may have any configuration as long as the spike action as described above is exhibited. Here, the detailed structure of the negative electrode in this Embodiment is demonstrated with reference to FIGS.

  FIG. 2 shows an enlarged part of the negative electrode shown in FIG. In the negative electrode shown in FIGS. 1 and 2, the surface of the negative electrode active material layer 2 is uniformly flat. The negative electrode active material layer 2 having such a flat surface can be formed by, for example, a liquid phase method or a coating method. When the surface of the negative electrode active material layer 2 is flat, the width 3D1 of the protrusion 3 is the diameter of the interface 3A1 between the surface 2A of the negative electrode active material layer 2 and the protrusion 3 as shown in FIG. is there. The width 3D1 is the diameter of the interface 3A1 if the interface 3A1 is circular, and the maximum diameter of the interface 3A1 if the interface 3A1 is elliptical or indefinite. When the negative electrode active material layer 2 and the protrusion 3 are integrated, the width 3D1 is the maximum diameter of the constricted portion at the boundary between the surface 2A and the outline of the protrusion 3. On the other hand, the height 3H1 of the protrusion 3 is the distance between the apex of the protrusion 3 and the plane including the interface 3A1. When the interface 3A1 is a curved surface, the height 3H1 is a distance between the vertex of the protrusion 3 and a straight line passing through both ends of the width 3D1.

  Next, the case where the negative electrode active material layer 2 has a plurality of negative electrode active material particles will be described. FIG. 3 schematically shows a cross-sectional configuration of the negative electrode when the negative electrode active material layer 2 has a plurality of negative electrode active material particles, and FIG. 4 shows an enlarged part of the negative electrode shown in FIG. Yes. FIG. 5 shows an enlarged cross-sectional structure of the negative electrode. (A) is a scanning electron microscope (SEM) photograph (secondary electron image), and (B) is shown in (A). It is a schematic picture of an SEM image. FIG. 5 shows a case where a plurality of negative electrode active material particles have a single layer structure without a multilayer structure in the particles. FIG. 6 is an enlarged view of the planar structure of the negative electrode, where (A) is a SEM photograph, and (B) is a schematic picture of the SEM image shown in (A).

  The negative electrode active material layer 2 having a plurality of negative electrode active material particles 200 as shown in FIGS. 3 to 6 can be formed by, for example, a vapor phase method as described above. In the negative electrode having a plurality of negative electrode active material particles 200, the width of the protrusion 3 is smaller (narrower) than the particle diameter of the negative electrode active material particles 200. When the width of the protrusion 3 is larger (wider) than the particle diameter of the negative electrode active material particles 200, the protrusion 3 is disposed over the plurality of negative electrode active material particles 200. Therefore, when the negative electrode active material particles 200 expand and contract with the insertion and extraction of lithium, the projections 3 may break. As a result of the protrusion 3 being cracked, the width of the protrusion 3 is smaller than the particle diameter of the negative electrode active material particle 200, and the protrusion 3 does not extend over the plurality of negative electrode active material particles 200, but the upper surface of one negative electrode active material particle 200. Will be placed. That is, the width of the protrusion 3 is smaller than the average particle diameter of the negative electrode active material particles 200 and the particle diameter of the negative electrode active material particles 200 in the in-plane direction of the negative electrode active material layer 2. Further, when the protrusion 3 is cracked, part or all of the protrusion 3 may be peeled off. For this reason, as shown in FIGS. 3 to 6, the width of the protrusion 3 is previously smaller than the particle diameter of the negative electrode active material particles 200 (the particle diameter in the in-plane direction of the negative electrode active material layer 2). It is preferable that the protrusion 3 is disposed in the vicinity of the apex of the negative electrode active material particle 200.

  When the negative electrode active material layer 2 has a plurality of negative electrode active material particles, the width 3D2 of the protrusion 3 is the surface 200A of the negative electrode active material particles 200 which is the surface of the negative electrode active material layer 2 as shown in FIG. Is the maximum diameter of the interface 3A2 between the projection 3 and the same as the width 3D1. When the negative electrode active material particles 200 and the protrusions 3 are integrated, the width 3D2 is the maximum diameter of the constricted portion at the boundary between the surface 200A and the outline of the protrusions 3. On the other hand, the height 3H2 of the protrusion 3 is a distance between the vertex of the protrusion 3 and a line passing through both ends of the width 3D2.

  Note that the widths 3D1 and 3D2 and the heights 3H1 and 3H2 of the protrusions 3 can be measured by observing the negative electrode with an SEM. Further, the thickness of the negative electrode active material layer 2 is measured by observing the cross section of the negative electrode with an SEM and measuring the distance from the surface of the negative electrode current collector 1 to the surface of the negative electrode active material layer 2 (the apex of the negative electrode active material particles 200). Can be identified.

In this negative electrode, if a plurality of protrusions 3 are present on the surface of the negative electrode active material layer 2 as described above, the number and dimensions (width and height) of the protrusions 3 do not depend on the configuration of the negative electrode active material layer 2. Etc. are arbitrary. The number of protrusions 3 is preferably such that the surface density of the protrusions 3 is 0.02 pieces / μm ² or more and 2.3 pieces / μm ² or less on the surface of the negative electrode active material layer 2. This is because the spike effect is sufficiently exhibited within the range. Especially, it is preferable that this areal density is 0.02 piece / micrometer < ² > or more and 0.5 piece / micrometer < ² > or less. This is because it contributes to the improvement of cycle characteristics.

  The width (3D1, 3D2) of the protrusion 3 varies depending on the height (3H1, 3H2) and the number thereof, but is preferably 0.06 μm or more and 4 μm or less (average value). This is because a high effect can be obtained within this range. Specifically, when the width is smaller than 0.06 μm, even if the height of the protrusion 3 is high, it cannot withstand the stress generated in the negative electrode active material layer 2. Since the thickness is limited, it is considered that it is difficult to obtain a sufficient spike effect as a result. On the other hand, if the width is larger than 4 μm, the height may be set so as to cause a spike action, and the separator may be broken. If the height is set so as not to break the separator, the apex of the protrusion 3 (the tip portion) ) Is considered to be less likely to have an acute angle to the extent that it causes physical resistance (friction). Especially, it is preferable that the width | variety of the processus | protrusion 3 is 0.1 to 2.5 micrometer (average value). This is because a higher effect can be obtained.

  The height (3H1, 3H2) of the protrusion 3 depends on the width (3D1, 3D2) and number as described above, and the thickness of the separator when used in an electrochemical device such as a secondary battery equipped with a separator. It is different as long as it does not break through the separator. Among them, the height (average value) is preferably 0.04 μm or more and 8.5 μm or less. Specifically, if the height is lower than 0.04 μm, it may be difficult to obtain a spike effect, and if it is higher than 8.5 μm, it tends to break through it although it depends on the thickness of the separator. In particular, the height (average value) is preferably 0.08 μm or more and 3.2 μm or less. This is because a higher effect can be obtained. In this case, the maximum height of the protrusion 3 is preferably 12.7 μm or less, and preferably 10.1 μm or less. This is because a high effect can be obtained.

Further, when the negative electrode active material layer 2 has a plurality of negative electrode active material particles, the ratio of the surface density (N1; pieces / μm ² ) of the protrusions to the surface density (N2; pieces / μm ² ) of the negative electrode active material particles (N1 / N2) is preferably 0.05 or more and 11.5 or less. This is because a high effect can be obtained.

  Examples of the method for forming the protrusion 3 include a liquid phase method such as a dip coating method, and a vapor phase method such as a vapor deposition method, a sputtering method, or a CVD (Chemical Vapor Deposition) method. These methods may be used alone, or two or more methods may be used. Among these, it is preferable to form by a vapor phase method. This is because the shape of the protrusion 3 tends to be uniform. Examples of the method for forming the protrusions 3 by the vapor phase method include a method in which particles of a predetermined size are attached from a vapor deposition source or target, and a rotary vapor deposition method. In order to form the protrusion 3 by the rotary evaporation method, specifically, the following method is used. First, for example, the negative electrode current collector 1 provided with the negative electrode active material layer 2 is installed inside a dome-shaped support member. The support member is provided so as to cover the vapor deposition source including a predetermined projection forming material with a predetermined distance. At this time, the negative electrode current collector 1 provided with the negative electrode active material layer 2 is placed on the support member so that the surface of the negative electrode active material layer 2 is at a predetermined angle from the vertical direction with respect to the vapor deposition source. Subsequently, the material is deposited on the surface of the negative electrode active material layer 2 by irradiating the evaporation source with an electron beam while rotating the support member. At this time, the support member rotates around the vertical direction with respect to the vapor deposition source. Thereby, the protrusion 3 is formed. The protrusion 3 formed by this rotary evaporation method is likely to have a conical shape as a result of the evaporation material being deposited spirally.

  This negative electrode is manufactured, for example, by the following procedure.

  First, the negative electrode active material layer 2 is formed on both surfaces of the negative electrode current collector 1. When forming this negative electrode active material layer 2, for example, a negative electrode material is deposited on the surface of the negative electrode current collector 1 by a vapor phase method such as vapor deposition to form a plurality of negative electrode active material particles. Finally, the protrusion 3 is formed on the surface of the negative electrode active material layer 2. When forming the protrusion 3, for example, a negative electrode material is deposited on the surface of the negative electrode active material layer 2 by a vapor phase method such as an evaporation method. Thereby, the negative electrode is completed.

  According to this negative electrode, since the negative electrode active material layer 2 has a plurality of protrusions on the surface, the negative electrode active material layer 2 can be absorbed and released even when the electrode reactant is occluded and released as compared with the case where the protrusions 3 are not provided. Expansion and contraction are suppressed, deformation of the negative electrode current collector 1 and peeling of the negative electrode active material layer 2 are less likely to occur, and the structural stability of the negative electrode is improved. Therefore, when the negative electrode is used in an electrochemical device such as a secondary battery provided with a separator, the structure of the negative electrode is stably maintained even when charging and discharging are repeated, which can contribute to improvement of cycle characteristics.

  In particular, if the surface density, width, or height of the protrusions 3 is within the above-described suitable range, the cycle characteristics can be further improved. The range of the surface density and the like suitable for the protrusions 3 is the same when the negative electrode active material layer 2 has a plurality of negative electrode active material particles.

  Further, when the negative electrode active material layer 2 has a plurality of negative electrode active material particles, the ratio (N1 / N2) of the surface density (N2) of the negative electrode active material particles to the surface density (N1) of the protrusions is 0.01 or more. By setting it to 11.5 or less, a higher effect can be obtained.

  When the negative electrode active material layer 2 contains at least one of a simple substance, an alloy, and a compound of silicon as the negative electrode active material, stress due to expansion and contraction of the negative electrode active material layer 2 due to insertion and extraction of the electrode reactant Therefore, it is possible to contribute to the improvement of cycle characteristics as compared with a negative electrode including a negative electrode active material whose stress is relatively small.

  Incidentally, in Patent Document 4 (Japanese Patent Laid-Open No. 2006-278270) and Patent Document 5 (Japanese Patent Laid-Open No. 2008-004281) described in “Background Art”, vapor deposition is performed on the surface of the negative electrode active material layer formed by the vapor deposition method. It is shown that protrusions are formed on the surface of the negative electrode active material layer by so-called splash, in which the negative electrode active material scattered from the source adheres. However, when this splash occurs, the negative electrode active material layer and the negative electrode current collector are dissolved by the scattered negative electrode active material, and thus do not function as a negative electrode. For this reason, when forming a negative electrode active material layer by a vapor deposition method, it will carry out normally on the conditions which a splash does not produce. Further, even if the protrusion is formed to such an extent that it functions as a negative electrode, in Patent Documents 4 and 5, since the width of the protrusion is large and the apex is crushed or scraped, it is the same as the negative electrode of the present invention. It is considered that the action (spike action) cannot be obtained.

  Next, usage examples of the above-described negative electrode will be described. Here, taking a secondary battery as an example of an electrochemical device, the negative electrode is used as follows.

(First secondary battery)
7 and 8 show a cross-sectional configuration of the first secondary battery. FIG. 8 shows an enlarged part of the spirally wound electrode body 20 shown in FIG. The secondary battery described here is, for example, a lithium ion secondary battery in which the capacity of the negative electrode 22 is expressed based on insertion and extraction of lithium.

  The secondary battery mainly includes a wound electrode body 20 in which a positive electrode 21 and a negative electrode 22 are wound via a separator 23 inside a substantially hollow cylindrical battery can 11, a pair of insulating plates 12, 13 is stored. The battery structure including the battery can 11 is called a cylindrical type.

  The battery can 11 is made of, for example, a metal material such as iron, aluminum, or an alloy thereof, and one end thereof is closed and the other end is opened. The pair of insulating plates 12 and 13 are arranged so as to extend perpendicular to the winding peripheral surface with the winding electrode body 20 interposed therebetween.

  A battery lid 14 and a safety valve mechanism 15 and a heat sensitive resistance element (Positive Temperature Coefficient: PTC element) 16 provided inside thereof are caulked and attached to an open end portion of the battery can 11 via a gasket 17. ing. Thereby, the inside of the battery can 11 is sealed. The battery lid 14 is made of the same material as the battery can 11, for example. The safety valve mechanism 15 is electrically connected to the battery lid 14 via the heat sensitive resistance element 16. In the safety valve mechanism 15, when the internal pressure becomes a certain level or more due to an internal short circuit or external heating, the disk plate 15 </ b> A is reversed and the electric power between the battery lid 14 and the wound electrode body 20 is reversed. Connection is broken. The heat sensitive resistive element 16 limits the current by increasing the resistance according to the temperature rise, and prevents abnormal heat generation due to a large current. The gasket 17 is made of, for example, an insulating material, and asphalt is applied to the surface thereof.

  A center pin 24 may be inserted in the center of the wound electrode body 20. In this wound electrode body 20, a positive electrode lead 25 made of a metal material such as aluminum is connected to the positive electrode 21, and a negative electrode lead 26 made of a metal material such as nickel is connected to the negative electrode 22. . The positive electrode lead 25 is welded to the safety valve mechanism 15 and is electrically connected to the battery lid 14, and the negative electrode lead 26 is welded to and electrically connected to the battery can 11.

  For example, the positive electrode 21 is obtained by providing a positive electrode active material layer 21B on both surfaces of a positive electrode current collector 21A having a pair of surfaces. The positive electrode current collector 21A is made of, for example, a metal material such as aluminum, nickel, or stainless steel. The positive electrode active material layer 21B includes a positive electrode active material, and may include other materials such as the above-described binder and conductive agent as necessary.

The positive electrode active material includes one or more positive electrode materials capable of inserting and extracting lithium as an electrode reactant. As the positive electrode material, for example, a lithium-containing compound is preferable. This is because a high energy density can be obtained. Examples of the lithium-containing compound include a composite oxide containing lithium and a transition metal element, or a phosphate compound containing lithium and a transition metal element. In particular, cobalt, nickel, manganese, and iron are used as the transition metal element. Those containing at least one of the group consisting of: This is because a higher voltage can be obtained. The chemical formula is represented by, for example, Li _x M1O ₂ or Li _y M2PO ₄ . In the formula, M1 and M2 represent one or more transition metal elements. The values of x and y vary depending on the charge / discharge state of the secondary battery, and are generally 0.05 ≦ x ≦ 1.10 and 0.05 ≦ y ≦ 1.10.

Examples of the composite oxide containing lithium and a transition metal element include lithium cobalt composite oxide (Li _x CoO ₂ ), lithium nickel composite oxide (Li _x NiO ₂ ), and lithium nickel cobalt composite oxide (Li _x Ni). _(1-z) Co _z O ₂ (z <1)), lithium nickel cobalt manganese composite oxide (Li _x Ni _(1-vw) Co _v Mn _w O ₂ (v + w <1)), or spinel type structure And a lithium manganese composite oxide (LiMn ₂ O ₄ ). Among these, a complex oxide containing cobalt is preferable. This is because high capacity can be obtained and excellent cycle characteristics can be obtained. Examples of the phosphate compound containing lithium and a transition metal element include a lithium iron phosphate compound (LiFePO ₄ ) or a lithium iron manganese phosphate compound (LiFe _(1-u) Mn _u PO ₄ (u <1). ) And the like.

  In addition, examples of the positive electrode material include oxides such as titanium oxide, vanadium oxide and manganese dioxide, disulfides such as titanium disulfide and molybdenum sulfide, chalcogenides such as niobium selenide, sulfur, polyaniline or Examples also include conductive polymers such as polythiophene.

  The negative electrode 22 has the same configuration as the negative electrode described above. For example, the negative electrode active material layer 22B and the protrusion 22C are provided on both surfaces of a negative electrode current collector 22A having a pair of surfaces. The configurations of the negative electrode current collector 22A, the negative electrode active material layer 22B, and the protrusions 22C are the same as the configurations of the negative electrode current collector 1, the negative electrode active material layer 2, and the protrusions 3 in the negative electrode described above, respectively. In the negative electrode 22, the charge capacity of the negative electrode material capable of inserting and extracting lithium is preferably larger than the charge capacity of the positive electrode 21. This is because even when fully charged, the possibility that lithium is deposited as dendrites on the negative electrode 22 is reduced.

  The separator 23 separates the positive electrode 21 and the negative electrode 22 and allows lithium ions to pass through while preventing a short circuit of current due to contact between the two electrodes. The separator 23 is made of, for example, a porous film made of a synthetic resin such as polytetrafluoroethylene, polypropylene, or polyethylene, or a porous film made of ceramic, and these two or more kinds of porous films are laminated. It may be what was done. Among these, a porous film made of polyolefin is preferable because it is excellent in short-circuit preventing effect and can improve the safety of the secondary battery due to the shutdown effect. In particular, polyethylene is preferable because a shutdown effect can be obtained at 100 ° C. or higher and 160 ° C. or lower and the electrochemical stability is excellent. Polypropylene is also preferable, and other resins having chemical stability may be copolymerized with polyethylene or polypropylene, or may be blended.

  The separator 23 is impregnated with an electrolytic solution that is a liquid electrolyte. This electrolytic solution contains a solvent and an electrolyte salt dissolved in the solvent.

  The solvent contains, for example, one or more of nonaqueous solvents such as organic solvents. Examples of the non-aqueous solvent include ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, γ-butyrolactone, γ-valerolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, Methyl butyrate, methyl isobutyrate, methyl trimethylacetate, ethyl trimethylacetate, acetonitrile, glutaronitrile, adiponitrile, methoxyacetonitrile, 3-methoxypropionitrile, N, N-dimethylformamide, N-methylpyrrolidinone, N -Methyloxazolidinone, N, N'-dimethylimidazolidinone, nitromethane, nitroethane, sulfolane, trimethyl phosphate or dimethyl sulfoxide. Among these, at least one selected from the group consisting of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate is preferable. This is because excellent battery capacity, cycle characteristics and storage characteristics can be obtained. In this case, in particular, a high viscosity (high dielectric constant) solvent such as ethylene carbonate or propylene carbonate (for example, relative dielectric constant ε ≧ 30) and a low viscosity solvent such as dimethyl carbonate, ethyl methyl carbonate or diethyl carbonate (for example, A combination with (viscosity ≦ 1 mPa · s) is more preferable. This is because the dissociation property of the electrolyte salt and the ion mobility are improved, and thus higher effects can be obtained.

  This solvent preferably contains a cyclic carbonate having an unsaturated bond represented by Chemical Formulas 1 to 3. This is because high cycle characteristics can be obtained. These may be used alone or in combination.

（Ｒ１１およびＲ１２は水素基あるいはアルキル基である。）

(R11 and R12 are a hydrogen group or an alkyl group.)

（Ｒ１３〜Ｒ１６は水素基、アルキル基、ビニル基あるいはアリル基であり、それらのうちの少なくとも１つはビニル基あるいはアリル基である。）

(R13 to R16 are a hydrogen group, an alkyl group, a vinyl group or an allyl group, and at least one of them is a vinyl group or an allyl group.)

（Ｒ１７はアルキレン基である。）

(R17 is an alkylene group.)

  The cyclic ester carbonate having an unsaturated bond shown in Chemical Formula 1 is a vinylene carbonate-based compound. Examples of the vinylene carbonate compound include vinylene carbonate (1,3-dioxol-2-one), methyl vinylene carbonate (4-methyl-1,3-dioxol-2-one), and ethyl vinylene carbonate (4-ethyl). -1,3-dioxol-2-one), 4,5-dimethyl-1,3-dioxol-2-one, 4,5-diethyl-1,3-dioxol-2-one, 4-fluoro-1, Examples thereof include 3-dioxol-2-one and 4-trifluoromethyl-1,3-dioxol-2-one. Among these, vinylene carbonate is preferable. This is because it is easily available and a high effect can be obtained.

  The cyclic ester carbonate having an unsaturated bond shown in Chemical Formula 2 is a vinyl ethylene carbonate compound. Examples of the vinyl carbonate-based compound include vinyl ethylene carbonate (4-vinyl-1,3-dioxolan-2-one), 4-methyl-4-vinyl-1,3-dioxolan-2-one, and 4-ethyl. -4-vinyl-1,3-dioxolan-2-one, 4-n-propyl-4-vinyl-1,3-dioxolan-2-one, 5-methyl-4-vinyl-1,3-dioxolane-2 -One, 4,4-divinyl-1,3-dioxolan-2-one, 4,5-divinyl-1,3-dioxolan-2-one, and the like. Among these, vinyl ethylene carbonate is preferable. This is because it is easily available and a high effect can be obtained. Of course, as R13 to R16, all may be vinyl groups, all may be allyl groups, or vinyl groups and allyl groups may be mixed.

  The cyclic ester carbonate having an unsaturated bond shown in Chemical Formula 3 is a methylene ethylene carbonate compound. Examples of the methylene ethylene carbonate compound include 4-methylene-1,3-dioxolan-2-one, 4,4-dimethyl-5-methylene-1,3-dioxolan-2-one, and 4,4-diethyl-5. -Methylene-1,3-dioxolan-2-one and the like. This methylene ethylene carbonate compound may have one methylene group (compound shown in Chemical Formula 3) or two methylene groups.

  The cyclic carbonate having an unsaturated bond may be catechol carbonate having a benzene ring in addition to those shown in Chemical Formulas 1 to 3.

  The content of the cyclic carbonate having an unsaturated bond in the solvent is preferably 0.01% by weight or more and 10% by weight or less. This is because a sufficient effect can be obtained.

  The solvent contains at least one of a chain carbonate having a halogen represented by Chemical Formula 4 as a constituent element and a cyclic carbonate having a halogen represented by Chemical Formula 5 as a constituent element. preferable. This is because a stable protective film is formed on the surface of the negative electrode 22 and the decomposition reaction of the electrolytic solution is suppressed, so that the cycle characteristics are improved.

（Ｒ２１〜Ｒ２６は水素基、ハロゲン基、アルキル基あるいはハロゲン化アルキル基であり、それらのうちの少なくとも１つはハロゲン基あるいはハロゲン化アルキル基である。）

(R21 to R26 are a hydrogen group, a halogen group, an alkyl group or a halogenated alkyl group, and at least one of them is a halogen group or a halogenated alkyl group.)

（Ｒ２７〜Ｒ３０は水素基、ハロゲン基、アルキル基あるいはハロゲン化アルキル基であり、それらのうちの少なくとも１つはハロゲン基あるいはハロゲン化アルキル基である。）

(R27 to R30 are a hydrogen group, a halogen group, an alkyl group or a halogenated alkyl group, and at least one of them is a halogen group or a halogenated alkyl group.)

  In addition, R21 to R26 in Chemical formula 4 may be the same or different. The same applies to R27 to R30 in Chemical Formula 5. Although the kind of halogen is not specifically limited, For example, at least 1 type in the group which consists of a fluorine, chlorine, and a bromine is mentioned, Among these, a fluorine is preferable. This is because a high effect can be obtained. Of course, other halogens may be used.

  The number of halogens is preferably two rather than one, and may be three or more. This is because the ability to form a protective film is increased and a stronger and more stable protective film is formed, so that the decomposition reaction of the electrolytic solution is further suppressed.

  Examples of the chain carbonate having a halogen shown in Chemical Formula 4 include fluoromethyl methyl carbonate, bis (fluoromethyl) carbonate, difluoromethyl methyl carbonate, and the like. These may be single and multiple types may be mixed.

  Examples of the cyclic carbonate having a halogen shown in Chemical formula 5 include a series of compounds represented by Chemical formula 6 and Chemical formula 7. That is, 4-fluoro-1,3-dioxolan-2-one of (1) shown in Chemical formula 6, 4-chloro-1,3-dioxolan-2-one of (2), 4,5 of (3) -Difluoro-1,3-dioxolan-2-one, (4) tetrafluoro-1,3-dioxolan-2-one, (5) 4-fluoro-5-chloro-1,3-dioxolane-2-one ON, (6) 4,5-dichloro-1,3-dioxolan-2-one, (7) tetrachloro-1,3-dioxolan-2-one, (8) 4,5-bistrifluoromethyl 1,3-dioxolan-2-one, 4-trifluoromethyl-1,3-dioxolan-2-one of (9), 4,5-difluoro-4,5-dimethyl-1,3 of (10) -Dioxolan-2-one, 4-methyl-5,5 of (11) Difluoro-1,3-dioxolan-2-one, and the like 5,5-difluoro-1,3-dioxolan-2-one (12). In addition, 4-trifluoromethyl-5-fluoro-1,3-dioxolan-2-one of (1) shown in Chemical Formula 7 and 4-trifluoromethyl-5-methyl-1,3-dioxolane of (2) 2-one, 4-fluoro-4,5-dimethyl-1,3-dioxolan-2-one of (3), 4,4-difluoro-5- (1,1-difluoroethyl)-of (4) 1,3-dioxolan-2-one, 4,5-dichloro-4,5-dimethyl-1,3-dioxolan-2-one in (5), 4-ethyl-5-fluoro-1, in (6) 3-dioxolan-2-one, 4-ethyl-4,5-difluoro-1,3-dioxolan-2-one of (7), 4-ethyl-4,5,5-trifluoro-1 of (8) , 3-Dioxolan-2-one, 4-fluoro-4-methyl-1 of (9) 3-dioxolan-2-one, and the like. These may be single and multiple types may be mixed.

  Of these, 4-fluoro-1,3-dioxolan-2-one or 4,5-difluoro-1,3-dioxolan-2-one is preferred, and 4,5-difluoro-1,3-dioxolan-2-one is preferred. More preferred. In particular, 4,5-difluoro-1,3-dioxolan-2-one is preferably a trans isomer rather than a cis isomer. This is because it is easily available and a high effect can be obtained.

  The solvent may contain sultone (cyclic sulfonate ester). This sultone is, for example, propane sultone or propene sultone. These may be single and multiple types may be mixed.

  Moreover, it is preferable that the solvent contains an acid anhydride. This is because high cycle characteristics can be obtained. Examples of the acid anhydride include carboxylic acid anhydrides such as succinic acid anhydride, glutaric acid anhydride and maleic acid anhydride, disulfonic acid anhydrides such as ethanedisulfonic acid anhydride and propanedisulfonic acid anhydride, Examples thereof include anhydrides of carboxylic acid and sulfonic acid such as benzoic acid anhydride, sulfopropionic acid anhydride or sulfobutyric acid anhydride, among which sulfobenzoic acid anhydride is preferable. These may be single and multiple types may be mixed.

  The electrolyte salt includes, for example, any one or more of light metal salts such as a lithium salt. Examples of the lithium salt include lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, and lithium hexafluoroarsenate. This is because excellent battery capacity, cycle characteristics and storage characteristics can be obtained. Among these, lithium hexafluorophosphate is preferable. This is because a higher effect can be obtained because the internal resistance is lowered.

  This electrolyte salt preferably contains at least one selected from the group consisting of compounds represented by Chemical Formulas 8 to 10. This is because a higher effect can be obtained when used together with the above-described lithium hexafluorophosphate or the like. In addition, R33 in Chemical formula 8 may be the same or different. The same applies to R41 to R43 in Chemical Formula 9 and R51 and R52 in Chemical Formula 10.

（Ｘ３１は長周期型周期表における１族元素あるいは２族元素、またはアルミニウムである。Ｍ３１は遷移金属元素、または長周期型周期表における１３族元素、１４族元素あるいは１５族元素である。Ｒ３１はハロゲン基である。Ｙ３１は−（Ｏ＝）Ｃ−Ｒ３２−Ｃ（＝Ｏ）−、−（Ｏ＝）Ｃ−Ｃ（Ｒ３３）₂ −あるいは−（Ｏ＝）Ｃ−Ｃ（＝Ｏ）−である。ただし、Ｒ３２はアルキレン基、ハロゲン化アルキレン基、アリーレン基あるいはハロゲン化アリーレン基である。Ｒ３３はアルキル基、ハロゲン化アルキル基、アリール基あるいはハロゲン化アリール基である。なお、ａ３は１〜４の整数であり、ｂ３は０、２あるいは４であり、ｃ３、ｄ３、ｍ３およびｎ３は１〜３の整数である。）

(X31 is a group 1 element or group 2 element in the long-period periodic table, or aluminum. M31 is a transition metal element, or a group 13 element, group 14 element, or group 15 element in the long-period periodic table. R31 Y31 is — (O═) C—R32—C (═O) —, — (O═) C—C (R33) ₂ — or — (O═) C—C (═O) Where R32 is an alkylene group, a halogenated alkylene group, an arylene group or a halogenated arylene group, R33 is an alkyl group, a halogenated alkyl group, an aryl group or a halogenated aryl group, and a3 is (It is an integer of 1 to 4, b3 is 0, 2 or 4, and c3, d3, m3 and n3 are integers of 1 to 3.)

（Ｘ４１は長周期型周期表における１族元素あるいは２族元素である。Ｍ４１は遷移金属元素、または長周期型周期表における１３族元素、１４族元素あるいは１５族元素である。Ｙ４１は−（Ｏ＝）Ｃ−（Ｃ（Ｒ４１）₂ ）_b4−Ｃ（＝Ｏ）−、−（Ｒ４３）₂ Ｃ−（Ｃ（Ｒ４２）₂ ）_c4−Ｃ（＝Ｏ）−、−（Ｒ４３）₂ Ｃ−（Ｃ（Ｒ４２）₂ ）_c4−Ｃ（Ｒ４３）₂ −、−（Ｒ４３）₂ Ｃ−（Ｃ（Ｒ４２）₂ ）_c4−Ｓ（＝Ｏ）₂ −、−（Ｏ＝）₂ Ｓ−（Ｃ（Ｒ４２）₂ ）_d4−Ｓ（＝Ｏ）₂ −あるいは−（Ｏ＝）Ｃ−（Ｃ（Ｒ４２）₂ ）_d4−Ｓ（＝Ｏ）₂ −である。ただし、Ｒ４１およびＲ４３は水素基、アルキル基、ハロゲン基あるいはハロゲン化アルキル基であり、それぞれのうちの少なくとも１つはハロゲン基あるいはハロゲン化アルキル基である。Ｒ４２は水素基、アルキル基、ハロゲン基あるいはハロゲン化アルキル基である。なお、ａ４、ｅ４およびｎ４は１あるいは２であり、ｂ４およびｄ４は１〜４の整数であり、ｃ４は０〜４の整数であり、ｆ４およびｍ４は１〜３の整数である。）

(X41 is a group 1 element or group 2 element in the long periodic table. M41 is a transition metal element, or a group 13, element or group 15 element in the long period periodic table. Y41 is − ( O =) C- (C (R41 ) 2) b4 -C (= O) -, - (R43) 2 C- (C (R42) 2) c4 -C (= O) -, - (R43) 2 C -(C (R42) ₂ ) _c4 -C (R43) ₂ -,-(R43) ₂ C- (C (R42) ₂ ) _c4 -S (= O) ₂ -,-(O =) ₂ S- ( C (R42) ₂ ) _d4- S (= O) _2- or-(O =) C- (C (R42) ₂ ) _d4- S (= O) _2- where R41 and R43 are hydrogen groups. , An alkyl group, a halogen group or a halogenated alkyl group, at least one of each being a halogen group or a halogenated alkyl group. R42 is a hydrogen group, an alkyl group, a halogen group or a halogenated alkyl group, wherein a4, e4 and n4 are 1 or 2, b4 and d4 are integers of 1 to 4, and c4 Is an integer from 0 to 4, and f4 and m4 are integers from 1 to 3.)

（Ｘ５１は長周期型周期表における１族元素あるいは２族元素である。Ｍ５１は遷移金属元素、または長周期型周期表における１３族元素、１４族元素あるいは１５族元素である。Ｒｆはフッ素化アルキル基あるいはフッ素化アリール基であり、いずれの炭素数も１〜１０である。Ｙ５１は−（Ｏ＝）Ｃ−（Ｃ（Ｒ５１）₂ ）_d5−Ｃ（＝Ｏ）−、−（Ｒ５２）₂ Ｃ−（Ｃ（Ｒ５１）₂ ）_d5−Ｃ（＝Ｏ）−、−（Ｒ５２）₂ Ｃ−（Ｃ（Ｒ５１）₂ ）_d5−Ｃ（Ｒ５２）₂ −、−（Ｒ５２）₂ Ｃ−（Ｃ（Ｒ５１）₂ ）_d5−Ｓ（＝Ｏ）₂ −、−（Ｏ＝）₂ Ｓ−（Ｃ（Ｒ５１）₂ ）_e5−Ｓ（＝Ｏ）₂ −あるいは−（Ｏ＝）Ｃ−（Ｃ（Ｒ５１）₂ ）_e5−Ｓ（＝Ｏ）₂ −である。ただし、Ｒ５１は水素基、アルキル基、ハロゲン基あるいはハロゲン化アルキル基である。Ｒ５２は水素基、アルキル基、ハロゲン基あるいはハロゲン化アルキル基であり、そのうちの少なくとも１つはハロゲン基あるいはハロゲン化アルキル基である。なお、ａ５、ｆ５およびｎ５は１あるいは２であり、ｂ５、ｃ５およびｅ５は１〜４の整数であり、ｄ５は０〜４の整数であり、ｇ５およびｍ５は１〜３の整数である。）

(X51 is a group 1 element or group 2 element in the long-period periodic table. M51 is a transition metal element, or a group 13, element or group 15 element in the long-period periodic table. Rf is fluorinated. An alkyl group or a fluorinated aryl group, each having 1 to 10 carbon atoms Y51 is — (O═) C— (C (R51) ₂ ) _d5 —C (═O) —, — (R52); ₂ C- (C (R51) ₂ ) _d5 -C (= O)-,-(R52) ₂ C- (C (R51) ₂ ) _d5 -C (R52) ₂ -,-(R52) ₂ C- ( _{C (R51) 2) d5 -S} (= O) 2 -, - (O =) 2 S- (C (R51) 2) e5 -S (= O) 2 - or - (O =) C- (C _{(R51) 2) e5 -S (} = O) 2 -. is, however, R51 is a hydrogen group, an alkyl group, a halogen group, or a halogen Kaa R52 is a hydrogen group, an alkyl group, a halogen group or a halogenated alkyl group, at least one of which is a halogen group or a halogenated alkyl group, wherein a5, f5 and n5 are 1 or 2; B5, c5 and e5 are integers of 1 to 4, d5 is an integer of 0 to 4, and g5 and m5 are integers of 1 to 3.)

  The group 1 elements in the long-period periodic table are hydrogen, lithium, sodium, potassium, rubidium, cesium, and francium. Group 2 elements are beryllium, magnesium, calcium, strontium, barium and radium. Group 13 elements are boron, aluminum, gallium, indium and thallium. Group 14 elements are carbon, silicon, germanium, tin and lead. Group 15 elements are nitrogen, phosphorus, arsenic, antimony and bismuth.

  Examples of the compound represented by Chemical formula 8 include the compounds represented by Chemical formulas (1) to (6). Examples of the compound represented by Chemical formula 9 include the compounds represented by Chemical formulas (1) to (8). Examples of the compound represented by Chemical formula 10 include the compound represented by Chemical formula 13 and the like. It is needless to say that the compound having the structure shown in Chemical Formula 8 to Chemical Formula 10 is not limited to the compound shown in Chemical Formula 11 to Chemical Formula 13.

  Moreover, it is preferable that electrolyte salt contains at least 1 sort (s) of the group which consists of a compound represented by Chemical formula 14-Chemical formula 16. This is because a higher effect can be obtained when used together with the above-described lithium hexafluorophosphate or the like. Note that m and n in Chemical formula 14 may be the same or different. The same applies to p, q and r in Chemical formula 16.

（ｍおよびｎは１以上の整数である。）

(M and n are integers of 1 or more.)

（Ｒ６１は炭素数が２以上４以下の直鎖状あるいは分岐状のパーフルオロアルキレン基である。）

(R61 is a linear or branched perfluoroalkylene group having 2 to 4 carbon atoms.)

（ｐ、ｑおよびｒは１以上の整数である。）

(P, q and r are integers of 1 or more.)

Examples of the chain compound shown in Chemical formula 14 include bis (trifluoromethanesulfonyl) imide lithium (LiN (CF ₃ SO ₂ ) ₂ ), bis (pentafluoroethanesulfonyl) imide lithium (LiN (C ₂ F ₅ SO ₂ ) ₂ ), (trifluoromethanesulfonyl) (pentafluoroethanesulfonyl) imide lithium (LiN (CF ₃ SO ₂ ) (C ₂ F ₅ SO ₂ )), (trifluoromethanesulfonyl) (heptafluoropropanesulfonyl) imide lithium ( LiN (CF ₃ SO ₂ ) (C ₃ F ₇ SO ₂ )) or (trifluoromethanesulfonyl) (nonafluorobutanesulfonyl) imidolithium (LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ )) Can be mentioned. These may be single and multiple types may be mixed.

  Examples of the cyclic compound represented by Chemical formula 15 include a series of compounds represented by Chemical formula 17. That is, 1,2-perfluoroethanedisulfonylimide lithium of (1) shown in Chemical formula 17, 1,3-perfluoropropane disulfonylimide lithium of (2), 1,3-perfluorobutane of (3) Disulfonylimide lithium, 1,4-perfluorobutane disulfonylimide lithium of (4), and the like. These may be single and multiple types may be mixed.

Examples of the chain compound shown in Chemical formula 16 include lithium tris (trifluoromethanesulfonyl) methide (LiC (CF ₃ SO ₂ ) ₃ ).

  The content of the electrolyte salt is preferably 0.3 mol / kg or more and 3.0 mol / kg or less with respect to the solvent. This is because, outside this range, the ion conductivity may be extremely lowered.

  This secondary battery is manufactured, for example, by the following procedure.

  First, the positive electrode 21 is produced. First, a positive electrode active material, a binder, and a conductive agent are mixed to form a positive electrode mixture, and then dispersed in an organic solvent to obtain a paste-like positive electrode mixture slurry. Subsequently, the positive electrode mixture slurry is uniformly applied to both surfaces of the positive electrode current collector 21A by a doctor blade or a bar coater and dried. Finally, the positive electrode active material layer 21B is formed by compressing and molding the coating film with a roll press or the like while heating as necessary. In this case, compression molding may be repeated a plurality of times.

  Further, the negative electrode 22 is manufactured by forming the negative electrode active material layer 22B and the protrusions 22C on both surfaces of the negative electrode current collector 22A by the same procedure as the above-described negative electrode manufacturing procedure.

  Next, the wound electrode body 20 is produced using the positive electrode 21 and the negative electrode 22. First, the positive electrode lead 25 is attached to the positive electrode current collector 21A by welding or the like, and the negative electrode lead 26 is attached to the negative electrode current collector 22A by welding or the like. After that, the positive electrode 21 and the negative electrode 22 are laminated through the separator 23 and then wound in the longitudinal direction.

  The secondary battery is assembled as follows. First, the tip of the positive electrode lead 25 is welded to the safety valve mechanism 15, and the tip of the negative electrode lead 26 is welded to the battery can 11. Subsequently, the wound electrode body 20 is housed in the battery can 11 while being sandwiched between the pair of insulating plates 12 and 13. Subsequently, an electrolytic solution is injected into the battery can 11 and impregnated in the separator 23. Finally, the battery lid 14, the safety valve mechanism 15, and the heat sensitive resistance element 16 are fixed to the opening end of the battery can 11 by caulking through the gasket 17. Thereby, the secondary battery shown in FIGS. 7 and 8 is completed.

  In the secondary battery, when charged, for example, lithium ions are extracted from the positive electrode 21 and inserted in the negative electrode 22 through the electrolytic solution impregnated in the separator 23. On the other hand, when discharging is performed, for example, lithium ions are released from the negative electrode 22 and inserted into the positive electrode 21 through the electrolytic solution impregnated in the separator 23.

  According to this cylindrical secondary battery, since the negative electrode 22 has the same configuration as the above-described negative electrode, the structural stability of the negative electrode 22 is improved. Thereby, even if lithium ions are occluded and released in the negative electrode 22, deformation of the negative electrode current collector 22 </ b> A and peeling of the negative electrode active material layer 22 </ b> B are suppressed, so that cycle characteristics can be improved.

  In this case, when the negative electrode 22 contains silicon or the like (material that can occlude and release lithium and has at least one of a metal element and a metalloid element) that is advantageous for increasing the capacity, In particular, the cycle characteristics can be improved.

  Other effects relating to the secondary battery are the same as those of the above-described negative electrode.

(Secondary secondary battery)
FIG. 9 shows an exploded perspective configuration of the second secondary battery, and FIG. 10 shows an enlarged cross section along the line XX of the spirally wound electrode body 30 shown in FIG. The secondary battery is, for example, a lithium ion secondary battery, similar to the first secondary battery described above, and the positive electrode lead 31 and the negative electrode lead 32 are mainly attached to the inside of the film-shaped exterior member 40. The wound electrode body 30 is accommodated. The battery structure including the exterior member 40 is called a laminate film type.

  For example, both the positive electrode lead 31 and the negative electrode lead 32 are led out in the same direction from the inside of the exterior member 40 toward the outside. The positive electrode lead 31 is made of, for example, a metal material such as aluminum, and the negative electrode lead 32 is made of, for example, a metal material such as copper, nickel, or stainless steel. These metal materials are, for example, in a thin plate shape or a mesh shape.

  The exterior member 40 is made of, for example, an aluminum laminated film in which a nylon film, an aluminum foil, and a polyethylene film are bonded together in this order. The exterior member 40 has a structure in which, for example, outer edges of two rectangular aluminum laminate films are bonded to each other by fusion or an adhesive so that the polyethylene film faces the wound electrode body 30. ing.

  An adhesion film 41 is inserted between the exterior member 40 and the positive electrode lead 31 and the negative electrode lead 32 in order to prevent intrusion of outside air. The adhesion film 41 is made of a material having adhesion to the positive electrode lead 31 and the negative electrode lead 32. Examples of this type of material include polyolefin resins such as polyethylene, polypropylene, modified polyethylene, and modified polypropylene.

  In addition, the exterior member 40 may be constituted by a laminate film having another laminated structure instead of the above-described aluminum laminate film, or may be constituted by a polymer film such as polypropylene or a metal film.

  The wound electrode body 30 is wound after the positive electrode 33 and the negative electrode 34 are laminated via the separator 35 and the electrolyte 36, and the outermost peripheral portion thereof is protected by a protective tape 37.

  FIG. 11 shows an enlarged part of the spirally wound electrode body 30 shown in FIG. In the positive electrode 33, for example, a positive electrode active material layer 33B is provided on both surfaces of a positive electrode current collector 33A having a pair of surfaces. The negative electrode 34 has the same configuration as the negative electrode described above. For example, the negative electrode active material layer 34B and the protrusion 34C are provided on both surfaces of a negative electrode current collector 34A having a pair of surfaces. The configurations of the positive electrode current collector 33A, the positive electrode active material layer 33B, the negative electrode current collector 34A, the negative electrode active material layer 34B, the protrusion 34C, and the separator 35 are the same as the positive electrode current collector 21A and the positive electrode in the first secondary battery described above. The configurations of the active material layer 21B, the negative electrode current collector 22A, the negative electrode active material layer 22B, the protrusions 22C, and the separator 23 are the same.

  The electrolyte 36 is a so-called gel electrolyte that contains an electrolytic solution and a polymer compound that holds the electrolytic solution. A gel electrolyte is preferable because high ion conductivity (for example, 1 mS / cm or more at room temperature) is obtained and liquid leakage is prevented. The electrolyte 36 is preferably formed in layers between the positive electrode 33 and the negative electrode 34 and the separator 35. This is because the adhesion between the positive electrode 33 and the negative electrode 34 and the separator 35 is increased.

  Examples of the polymer compound include ether-based polymer compounds such as polyethylene oxide, a crosslinked product containing polyethylene oxide, or polypropylene oxide, and acrylate-based or ester-based polymers such as polymethyl methacrylate, polyacrylic acid, or polymethacrylic acid. Compounds, polyvinylidene fluoride, copolymers of polyvinylidene fluoride and polyhexafluoropyrene, fluorine polymer compounds such as polytetrafluoroethylene or polyhexafluoropropylene, and other materials such as polyimide, polyamide, polyamide Imide, polyethersulfone, polyaramid, carboxymethylcellulose, polyacrylonitrile, polyphosphazene, polysiloxane, polyvinyl acetate, polyvinyl alcohol Styrene - butadiene rubbers, nitrile - butadiene rubber, polystyrene, polycarbonate and the like. These may be single and multiple types may be mixed. Among these, as the polymer compound, a fluorine polymer compound such as polyvinylidene fluoride is preferable. This is because it has high redox stability and is electrochemically stable.

  The composition of the electrolytic solution is the same as the composition of the electrolytic solution in the first secondary battery. However, the solvent in this case is not only a liquid solvent but also a broad concept including those having ion conductivity capable of dissociating the electrolyte salt. Accordingly, when a polymer compound having ion conductivity is used, the polymer compound is also included in the solvent.

  Instead of the gel electrolyte 36 in which the electrolytic solution is held by the polymer compound, the electrolytic solution may be used as it is. In this case, the separator 35 is impregnated with the electrolytic solution.

  The secondary battery provided with the gel electrolyte 36 is manufactured, for example, by the following three methods.

  In the first manufacturing method, first, the positive electrode active material layer 33B is formed on both surfaces of the positive electrode current collector 33A, for example, by the same procedure as the positive electrode 21 and the negative electrode 22 in the first secondary battery described above. Thus, the negative electrode 34 is manufactured by forming the negative electrode active material layer 34B and the protrusions 34C on both surfaces of the negative electrode current collector 34A. Then, after preparing the precursor solution containing electrolyte solution, a high molecular compound, and a solvent and apply | coating to the positive electrode 33 and the negative electrode 34, the solvent is volatilized and the gel electrolyte 36 is formed. Subsequently, the positive electrode lead 31 is attached to the positive electrode 33 and the negative electrode lead 32 is attached to the negative electrode 34. Subsequently, the positive electrode 33 and the negative electrode 34 on which the electrolyte 36 is formed are stacked via the separator 35 and then wound in the longitudinal direction, and a protective tape 37 is adhered to the outermost peripheral portion to produce the wound electrode body 30. To do. Finally, for example, after the wound electrode body 30 is sandwiched between two film-shaped exterior members 40, the outer edge portions of the exterior member 40 are bonded to each other by heat fusion or the like, so that the wound electrode body 30 is Encapsulate. At this time, the adhesion film 41 is inserted between the positive electrode lead 31 and the negative electrode lead 32 and the exterior member 40. Thereby, the secondary battery shown in FIGS. 9 to 11 is completed.

  In the second manufacturing method, first, the positive electrode lead 31 is attached to the positive electrode 33 and the negative electrode lead 32 is attached to the negative electrode 34, and then the positive electrode 33 and the negative electrode 34 are stacked and wound via the separator 35. A protective tape 37 is adhered to the outer peripheral portion to produce a wound body that is a precursor of the wound electrode body 30. Subsequently, after sandwiching the wound body between the two film-shaped exterior members 40, the remaining outer peripheral edge except for the outer peripheral edge on one side is adhered by heat fusion or the like, thereby forming a bag-shaped exterior The wound body is accommodated in the member 40. Subsequently, an electrolyte composition containing an electrolytic solution, a monomer that is a raw material of the polymer compound, a polymerization initiator, and other materials such as a polymerization inhibitor as necessary is prepared to form a bag-shaped exterior member. After injecting into the inside of 40, the opening part of the exterior member 40 is sealed by heat sealing or the like. Finally, the gel electrolyte 36 is formed by thermally polymerizing the monomer to obtain a polymer compound. Thereby, the secondary battery is completed.

  In the third manufacturing method, a wound body is formed by forming a wound body in the same manner as in the second manufacturing method described above except that the separator 35 coated with the polymer compound on both sides is used first. 40 is housed inside. Examples of the polymer compound applied to the separator 35 include a polymer containing vinylidene fluoride as a component, that is, a homopolymer of vinylidene fluoride, a copolymer containing vinylidene fluoride, or a multi-component copolymer. . Specifically, polyvinylidene fluoride, binary copolymers containing vinylidene fluoride and hexafluoropropylene as components, and ternary copolymers containing vinylidene fluoride, hexafluoropropylene and chlorotrifluoroethylene as components. Such as coalescence. In addition, examples of the polymer compound include polyimide, polyamide, polyamideimide, polyethersulfone, polyaramid, and carboxymethylcellulose. In addition, the high molecular compound may contain the other 1 type, or 2 or more types of high molecular compound with the polymer which uses the above-mentioned vinylidene fluoride as a component. Subsequently, after the electrolytic solution is prepared and injected into the exterior member 40, the opening of the exterior member 40 is sealed by heat fusion or the like. Finally, the exterior member 40 is heated while being loaded, and the separator 35 is brought into close contact with the positive electrode 33 and the negative electrode 34 through the polymer compound. As a result, the electrolytic solution is impregnated into the polymer compound, and the polymer compound is gelled to form the electrolyte 36. Thus, the secondary battery is completed.

  In the third manufacturing method, the swollenness of the secondary battery is suppressed as compared with the first manufacturing method. Further, in the third manufacturing method, compared with the second manufacturing method, there are hardly any monomers or solvents that are raw materials for the polymer compound remaining in the electrolyte 36, and the formation process of the polymer compound is well controlled. Therefore, sufficient adhesion is obtained between the positive electrode 33, the negative electrode 34, the separator 35, and the electrolyte 36.

  In this secondary battery, lithium ions are occluded and released between the positive electrode 33 and the negative electrode 34 as in the first secondary battery. That is, when charged, for example, lithium ions are extracted from the positive electrode 33 and inserted in the negative electrode 34 through the electrolyte 36. On the other hand, when discharging is performed, for example, lithium ions are extracted from the negative electrode 34 and inserted into the positive electrode 33 through the electrolyte 36.

  According to this laminated film type secondary battery, since the negative electrode 34 has the same configuration as the above-described negative electrode, cycle characteristics can be improved. The effects of the secondary battery other than those described above are the same as those of the first secondary battery.

  Examples of the present invention will be described in detail.

( Experimental Examples 1-1 to 1-7)
The laminate film type secondary battery shown in FIGS. 9 to 11 was produced by the following procedure. At this time, a lithium ion secondary battery in which the capacity of the negative electrode 34 is expressed based on insertion and extraction of lithium was made.

First, the positive electrode 33 was produced. First, lithium carbonate (Li ₂ CO ₃ ) and cobalt carbonate (CoCO ₃ ) are mixed at a molar ratio of 0.5: 1, and then calcined in air at 900 ° C. for 5 hours to form a lithium cobalt composite. An oxide (LiCoO ₂ ) was obtained. Subsequently, 91 parts by mass of lithium cobalt composite oxide as a positive electrode active material, 6 parts by mass of graphite as a conductive agent, and 3 parts by mass of polyvinylidene fluoride as a binder were mixed to form a positive electrode mixture. Dispersed in methyl-2-pyrrolidone to obtain a paste-like positive electrode mixture slurry. Subsequently, the positive electrode mixture slurry was uniformly applied to both surfaces of the positive electrode current collector 33A made of a strip-shaped aluminum foil (thickness = 12 μm) by a bar coater, dried, and then compression-molded by a roll press to perform positive electrode activation. A material layer 33B was formed.

Next, the negative electrode 34 was produced. First, after preparing a negative electrode current collector 34A (thickness = 10 μm) made of a roughened electrolytic copper foil, 99% pure silicon was used as a vapor deposition source, and a straight electron beam was introduced while introducing oxygen gas. The negative electrode active material layer 34B was formed by forming a plurality of negative electrode active material particles on both surfaces of the negative electrode current collector 34A by an electron beam vapor deposition method using a vapor deposition source. When forming this negative electrode active material layer 34B, the amount of oxygen gas introduced was such that the oxygen content in the negative electrode active material particles was about 10 atomic% and the deposition rate was 100 nm / second. The thickness of the negative electrode active material layer 34B formed on one surface of the negative electrode current collector 34A was set to 7.5 μm. Subsequently, 99% pure silicon was used as a deposition source, and a plurality of protrusions 34C were formed on both surfaces of the negative electrode active material layer 34B by a rotary deposition method. When forming the protrusions 34C, the rotation speed during vapor deposition is in the range of 5 to 60 rpm so that the surface density (N1) of the protrusions 34C is as shown in Table 1 (described later) in Experimental Examples 1-1 to 1-7. Set in. With respect to the negative electrode 34, a cross section of the negative electrode active material layer 34B is cut out by a focused ion beam (FIB) method, and the oxygen content in the negative electrode active material particles is determined by Auger Electron Spectroscopy (AES). As a result, it was 9.4 atomic% (at%). This oxygen content was analyzed at five points (five negative electrode active material particles) in the cross section of the negative electrode active material layer 34B, and was taken as the average of each measured value.

Next, after mixing 4-fluoro-1,3-dioxolan-2-one (FEC) and diethyl carbonate (DEC) as a solvent, lithium hexafluorophosphate (LiPF ₆ ) is dissolved as an electrolyte salt. An electrolyte solution was prepared. At this time, the composition of the solvent (FEC: DEC) was 50:50 by weight, and the content of LiPF ₆ was 1 mol / dm ³ .

  Finally, a secondary battery was assembled using the electrolytic solution together with the positive electrode 33 and the negative electrode 34. First, the positive electrode lead 31 made of aluminum was welded to one end of the positive electrode current collector 33A, and the negative electrode lead 32 made of nickel was welded to one end of the negative electrode current collector 34A. Subsequently, the positive electrode 33, the separator 35 (thickness = 23 μm) made of a microporous polypropylene film coated with polyvinylidene fluoride (PVdF) as a polymer compound on both sides, and the negative electrode 34 were laminated in this order. After being wound in the longitudinal direction, the winding end portion was fixed with a protective tape 37 made of an adhesive tape to form a wound body that was a precursor of the wound electrode body 30. Subsequently, a laminate film (total thickness) in which a nylon film (thickness = 30 μm), an aluminum foil (thickness = 40 μm), and an unstretched polypropylene film (thickness = 30 μm) are laminated from the outside. = 100 μm), the wound body was sandwiched between the exterior members 40, and the outer edges except for one side were heat-sealed to accommodate the wound body inside the bag-shaped exterior member 40. Subsequently, an electrolytic solution was injected from the opening of the exterior member 40, and the opening of the exterior member 40 was heat-sealed and sealed in a vacuum atmosphere. Finally, the exterior member 40 is sandwiched between iron plates and heated at 70 ° C. for 3 minutes while applying a load to gel the polymer compound applied to the separator 35 to form the electrolyte 36, thereby forming a laminate film type. The secondary battery was completed. For these secondary batteries, by adjusting the thickness of the positive electrode active material layer 33B so that the charge / discharge capacity of the negative electrode 34 is larger than the charge / discharge capacity of the positive electrode 33, lithium metal is added to the negative electrode 34 during full charge. Was prevented from precipitating.

(Comparative Example 1)
A procedure similar to that of Experimental Example 1-1 was performed except that the protrusion 34C was not formed.

The surface density and particle diameter of the negative electrode active material particles for the negative electrode 34 of Experimental Examples 1-1 to 1-7 and the negative electrode of Comparative Example 1, and the surface of the protrusion 34C for the negative electrode 34 of Experimental Examples 1-1 to 1-7 When the density, width, and height were examined, the results shown in Table 1 were obtained. Further, when the cycle characteristics of the secondary batteries of Experimental Examples 1-1 to 1-7 and Comparative Example 1 were examined, the results shown in Table 1 were obtained.

The surface density of the negative electrode active material particles and the surface density of the protrusions 34C were determined by measuring the number in the range of 50 μm × 50 μm by SEM, and calculating the surface density per 1 μm ² . At this time, the ratio (N1 / N2) of the surface density (N1) of the protrusions 34C to the surface density (N2) of the negative electrode active material particles was also calculated.

  When examining the particle diameter of the negative electrode active material particles, a cross section of the negative electrode active material layer 34B was cut out by a cross section polisher, the cross section was observed by SEM, and the particle diameter in the in-plane direction of the negative electrode active material layer 34B was measured. .

  When examining the width and height of the protrusion 34C, first, the SEM stage was measured three times for each protrusion 34C in the range of 50 μm × 50 μm, and the average of the width and height of each protrusion 34C was measured. It was height. Subsequently, the average of the width and height of each protrusion 34C within the range was calculated, and the values were taken as the values of the width and height of the protrusion 34C in the negative electrode 34.

When examining the cycle characteristics, charging and discharging was performed for 2 cycles in an atmosphere at 23 ° C., and the discharge capacity was measured. Subsequently, charging and discharging were performed in the same atmosphere until the total number of cycles reached 100 cycles, and the discharge capacity was measured. After that, the discharge capacity retention ratio (%) = (discharge capacity at the 100th cycle / discharge capacity at the second cycle) × 100 was calculated. In this case, the charge / discharge conditions for one cycle are charging at a constant current density of ² mA / cm ² until the battery voltage reaches 4.2 V, and at a constant voltage of 4.2 V, the current density is 0.05 mA / cm ^2. Then, the battery was discharged at a constant current density of ² mA / cm ² until the battery voltage reached 2.5V.

The procedures and conditions for examining the surface density of the negative electrode active material particles described above, the surface density of the protrusions 34C, and the cycle characteristics are the same for the subsequent series of experimental examples and comparative examples.

As shown in Table 1, in Experimental Examples 1-1 to 1-7 in which the protrusions 34C were formed, the discharge capacity retention rate was higher than in Comparative Example 1 in which the protrusions 34C were not formed. In this case, the width of the protrusion 34C in the negative electrode 34 used in Experimental Examples 1-1 to 1-7 is smaller than the particle diameter in the in-plane direction of the negative electrode active material particles, and is 1.7 μm to 2.3 μm. The height was 2.1 μm to 2.2 μm. This result indicates that deformation of the negative electrode current collector 34A and peeling of the negative electrode active material layer 34B were suppressed by forming the protrusion 34C. That is, the protrusion 34C bites into the separator 35 and the electrolyte 36, and the negative electrode 34 is integrated with the separator 35 through the electrolyte 36, and the stress due to expansion and contraction of the negative electrode active material layer 34B during charge / discharge is spiked. It is considered that the structural stability of the negative electrode 34 is improved.

When attention is paid to the surface density N1 of the protrusion 34C, the discharge capacity retention rate increases when the surface density N1 is 0.002 pieces / μm ² or more and 2.46 pieces / μm ² or less, and 0.02 pieces μm ² or more. The discharge capacity retention rate was significantly increased at 2.26 / μm ² or less, and the discharge capacity retention rate was at a maximum at 0.02 / μm ^{2 to} 0.49 / μm ² . In this case, the discharge capacity retention ratio was high when the ratio of the surface density of the protrusions 34C to the negative electrode active material particles (N1 / N2) was 0.01 or more and 12.3 or less.

Therefore, in the secondary battery described above, when the negative electrode 34 contains silicon (electron beam evaporation method) as the negative electrode active material, the particle size of the negative electrode active material particles in the in-plane direction on the surface of the negative electrode active material 34B. It was confirmed that by providing a plurality of protrusions 34C having a smaller width, the cycle characteristics are improved without depending on the surface density of the protrusions 34C. In this case, in particular, a high effect is obtained when the surface density of the protrusions 34C is 0.002 pieces / μm ² or more and 2.46 pieces / μm ² or less, and 0.02 pieces μm ² or more and 2.26. It was confirmed that a higher effect can be obtained by the number of particles / μm ² or less. It was also confirmed that a high effect was obtained when the ratio (N1 / N2) of the surface density of the protrusions 34C to the negative electrode active material particles was 0.01 or more and 12.3 or less.

( Experimental examples 2-1 to 2-8)
The projection 34C as shown in Table 2, except that the surface density was formed by changing the width and height, was formed by the same process as Experimental Example 1-1.

For the secondary batteries of Examples 2-1 to 2-8, the surface density and the like of the negative electrode active material particle surface density, and the like and the protrusion 34C of the anode 34, and the cycle characteristics were examined, the results shown in Table 2 was gotten. In Table 2, the results of Comparative Example 1 are also shown.

As shown in Table 2, even when the width of the protrusion 34C was 3.1 μm to 3.6 μm and the height was 7.4 μm to 7.6 μm, the same result as the result of Table 1 was obtained. . That is, in Experimental Examples 2-1 to 2-8 in which the protrusions 34C were formed, the discharge capacity retention rate was higher than that in Comparative Example 1 in which the protrusions 34C were not formed. In this case, when the surface density N1 of the protrusion 34C is 0.01 / μm ² or more and 2.29 / μm ² or less, the discharge capacity retention rate becomes high, and 0.02 μm ² or more and 0.42 / μm ^{2. At 2} or less, the discharge capacity retention rate showed a maximum value. The ratio of the surface density of the protrusions 34C to the negative electrode active material particles (N1 / N2) was higher than 0.05 to 11.5, and the discharge capacity retention rate was high.

Therefore, in the secondary battery described above, when the negative electrode 34 contains silicon (electron beam evaporation method) as the negative electrode active material, the particle size of the negative electrode active material particles in the in-plane direction on the surface of the negative electrode active material 34B. It was confirmed that by providing a plurality of protrusions 34C having a smaller width, the cycle characteristics were improved without depending on the surface density, width and height of the protrusions 34C. In this case, when the surface density of the protrusions 34C is 0.01 piece / μm ² or more and 2.29 piece / μm ² or less, a high effect is obtained, and 0.02 piece μm ² or more and 0.42 piece / piece. It was confirmed that a higher effect can be obtained when the thickness is not more than μm ² . It was also confirmed that a high effect was obtained when the ratio (N1 / N2) of the surface density of the protrusions 34C to the negative electrode active material particles was 0.01 or more and 11.5 or less.

From the results of Table 1 and Table 2 above, when the surface density of the protrusions 34C is 0.02 pieces / μm ² or more and 2.3 pieces / μm ² or less, the cycle characteristics are further improved, and 0.02 pieces μm. It was confirmed that the cycle characteristics were particularly improved by being ² or more and 0.5 / μm ² or less.

( Experimental examples 3-1 to 3-7)
As shown in Table 3, the same procedure as in Experimental Example 1-3 was performed, except that the protrusion 34C was formed by changing the width and height.

For the secondary batteries of Examples 3-1 to 3-7, the surface density and the like of the negative electrode active material particle surface density, and the like and the protrusion 34C of the anode 34, and the cycle characteristics were examined, the results shown in Table 3 was gotten. Table 3 also shows the results of examining the maximum height of the negative electrode 34C used in the secondary batteries of Experimental Examples 3-1 to 3-7. Note that when the cycle characteristics of a plurality of secondary batteries were examined under the same conditions as in Experimental Example 3-7, they were shorted with a probability of 67%. For this reason, Table 3 shows the results of the cycle characteristics for those not short-circuited. Table 3 also shows the results of Experimental Examples 1-3 and 2-5 and Comparative Example 1.

As shown in Table 3, even when the width (average value) of the protrusion 34C is 0.06 μm to 4.0 μm and the height (average value) is 0.04 μm to 8.5 μm, Table 1 and Table 2 The results similar to those shown in the above were obtained. That is, in Experimental Examples 3-1 to 3-7 in which the protrusions 34C were formed, the discharge capacity retention rate was higher than in Comparative Example 1 in which the protrusions 34C were not formed. In this case, when paying attention to the width and height of the protrusion 34C, the discharge capacity retention rate increases when the width is 0.06 μm or more and 4.0 μm or less, and the discharge capacity retention rate is 0.1 μm or more and 2.5 μm or less. It became high. Further, when the height (average value) of the protrusion 34C was 0.04 μm or more and 8.5 μm or less, the discharge capacity retention ratio increased, and when the height of the projection 34C was 0.08 μm or more and 3.2 μm or less, the discharge capacity retention ratio showed a maximum value.

  Therefore, in the secondary battery described above, when the negative electrode 34 contains silicon (electron beam evaporation method) as the negative electrode active material, the particle size of the negative electrode active material particles in the in-plane direction on the surface of the negative electrode active material 34B. It was confirmed that by providing a plurality of protrusions 34C having a smaller width, the cycle characteristics are improved without depending on the width and height of the protrusions 34C. In this case, it was confirmed that a high effect can be obtained when the width of the protrusion 34C is 0.06 μm or more and 4.0 μm or less. In addition, when the height (average value) of the protrusion 34C was 8.5 μm (maximum height; 12.7 μm), it was short-circuited with a probability of 67%, but the thickness of the separator 35 and the electrolyte 36 should be adjusted. Therefore, it is considered that the short circuit can be prevented. Therefore, a high effect is obtained when the height (average value) of the protrusion 34C is 0.04 μm or more and 8.5 μm or less, and a particularly high effect is obtained when the height is 0.08 μm or more and 3.2 μm or less. It was also confirmed.

( Experimental examples 4-1 to 4-6)
Experimental example, except that the amount of oxygen gas introduced was changed when forming the negative electrode active material layer 34B by the electron beam evaporation method, and the oxygen content in the negative electrode active material particles was as shown in Table 4 below. The same procedure as in 1-3 was performed.

(Comparative Examples 2-1 to 2-6)
The same procedure as in Experimental Examples 4-1 to 4-6 was performed except that the protrusion 34C was not formed.

Regarding the secondary batteries of Experimental Examples 4-1 to 4-6 and Comparative Examples 2-1 to 2-6, the surface density of the negative electrode active material particles in the negative electrode 34, the surface density of the protrusions 34C, and the like, and the cycle characteristics are as follows. When examined, the results shown in Table 4 were obtained. In Table 4, the results of Experimental Example 1-3 and Comparative Example 1 are also shown.

As shown in Table 4, the same results as those shown in Table 1 were obtained even when the oxygen content in the negative electrode active material particles was 3 at% to 46.2 at%. That is, in Experimental Examples 4-1 to 4-6 in which the protrusions 34C were formed, the discharge capacity retention ratio was not formed compared to Comparative Examples 2-1 to 2-6 in which the oxygen content in the negative electrode active material particles was the same. Was high. In this case, when the oxygen content in the negative electrode active material particles is 3 at% or more and 46.2 at% or less, the discharge capacity maintenance ratio is high, and when the oxygen content is 5.8 at% or more and 32.7 at% or less, the discharge capacity maintenance ratio is greatly increased. It became high and showed the maximum value within the range.

  Therefore, in the secondary battery described above, when the negative electrode 34 contains silicon (electron beam evaporation method) as the negative electrode active material, the particle size of the negative electrode active material particles in the in-plane direction on the surface of the negative electrode active material 34B. It was confirmed that by providing the plurality of protrusions 34C having a width smaller than that, the cycle characteristics are improved without depending on the oxygen content in the negative electrode active material particles. In this case, in particular, a high effect can be obtained by setting the oxygen content in the negative electrode active material particles to 3 atomic% or more and 46.2 atomic% or less, and 5.8 atomic% or more and 32.7. It was confirmed that a higher effect can be obtained by setting the number of atoms to not more than%.

( Experimental example 5-1)
When forming the negative electrode active material layer 34B, the same procedure as in Experimental Example 1-3 was performed except that the negative electrode active material layer 34B was formed by the RF magnetron sputtering method instead of the electron beam evaporation method. When forming the negative electrode active material layer 34B by sputtering, the amount of oxygen gas introduced was such that the oxygen content in the negative electrode active material particles was 9.4 at%, and the deposition rate was 0.5 nm / second. . The thickness of the negative electrode active material layer 34B formed on one surface of the negative electrode current collector 34A was set to 7.5 μm.

( Experimental example 5-2)
When the negative electrode active material layer 34B was formed, the same procedure as in Experimental Example 1-3 was performed except that the negative electrode active material layer 34B was formed by the CVD method instead of the electron beam evaporation method. When the negative electrode active material layer 34B is formed by the CVD method, the amount of oxygen gas introduced is set so that the oxygen content in the negative electrode active material particles is 9.4 at%, and the raw material and the excitation gas are silane (SiH ₄ ) And argon (Ar), and the deposition rate and substrate temperature were 1.5 nm / second and 200 ° C., respectively. The thickness of the negative electrode active material layer 34B formed on one surface of the negative electrode current collector 34A was set to 7.5 μm.

(Comparative Examples 3-1 and 3-2)
A procedure similar to that of Experimental Example 5-1 or 5-2 was performed, except that the protrusion 34C was not formed.

Regarding the secondary batteries of these Experimental Examples 5-1 and 5-2 and Comparative Examples 3-1 and 3-2, the surface density of the negative electrode active material particles in the negative electrode 34, the surface density of the protrusions 34C, etc. When examined, the results shown in Table 5 were obtained. In Table 5, the results of Experimental Example 1-3 and Comparative Example 1 are also shown.

As shown in Table 5, when the negative electrode active material layer 34B was formed by the sputtering method or the CVD method, the same results as those in Table 1 were obtained. That is, in the experimental examples 5-1 and 5-2 in which the protrusions 34C are formed, the discharge capacity maintenance rate is not formed as compared with the comparative examples 3-1 and 3-2 in which the formation method of the negative electrode active material layer 34B is the same. It became high.

  Therefore, in the secondary battery described above, when the negative electrode 34 contains silicon as the negative electrode active material, the negative electrode active material particles in the in-plane direction are formed on the surface of the negative electrode active material layer 34B formed by the vapor phase method. It was confirmed that providing a plurality of protrusions 34C having a width smaller than the diameter improves the cycle characteristics without depending on the formation method of the negative electrode active material layer 34B.

( Experimental example 6)
When the negative electrode active material layer 34B was formed, the same procedure as in Experimental Example 1-3 was performed except that the negative electrode active material layer 34B was formed by a coating method instead of the electron beam evaporation method. When the negative electrode active material layer 34B is formed by a coating method, first, as the negative electrode active material, silicon powder having an average particle size of 5 μm and a polyamic acid solution (N, N-dimethylacetamide (DMAC) + N-methyl-2-pyrrolidone) are used. ) Was mixed at a weight ratio of silicon powder to DMAC (silicon powder: DMAC) of 80:20, and N-methyl-2-pyrrolidone was further added to form a negative electrode mixture slurry. After that, the negative electrode mixture slurry is uniformly applied to the negative electrode current collector 34A made of copper foil (18 μm thick) using a coating apparatus, dried, pressurized, and heated at 400 ° C. for 12 hours in a vacuum atmosphere. did. The thickness of the negative electrode active material layer 34B formed on one surface of the negative electrode current collector 34A was set to 7.5 μm. When the oxygen content of the negative electrode active material layer 34B thus formed was analyzed in the same manner, it was 7.0 atomic%.

(Comparative Example 4)
The same procedure as in Experimental Example 6 was performed except that the protrusion 34C was not formed.

For the secondary batteries of Experimental Example 6 and Comparative Example 4, the surface density and the like of the negative electrode active material particles in the negative electrode 34 and the surface density of the protrusions 34C and the cycle characteristics were examined. The results shown in Table 6 were obtained. It was. In Table 6, the results of Experimental Example 1-3 and Comparative Example 1 are also shown.

As shown in Table 6, even when the formation method of the negative electrode active material layer 34B was the coating method, the same result as the result of Table 1 was obtained. That is, in Experimental Example 6 in which the protrusion 34C was formed, the discharge capacity retention rate was higher than that in Comparative Example 4 in which the negative electrode active material layer 34B was formed without forming the protrusion 34C.

  Therefore, in the secondary battery described above, when the negative electrode 34 includes silicon as the negative electrode active material, a method for forming the negative electrode active material layer 34B is provided by providing a plurality of protrusions 34C on the surface of the negative electrode active material layer 34B. It was confirmed that the cycle characteristics were improved without depending on. Therefore, even when the negative electrode active material layer 34C was formed by the coating method, it was suggested that the desirable shape, surface density, width, and height of the protrusion 34C were the same as those formed by the vapor phase method.

( Experimental examples 7-1 to 7-7)
As a polymer compound, instead of PVdF, polytetrafluoroethylene (PTFE; Experimental Example 7-1), polyimide (PI; Experimental Example 7-2), polyamide (PA; Experimental Example 7-3), polyamideimide (PAI) Experimental Example 7-4), Polyethersulfone (PES; Experimental Example 7-5), Polyaramid (PAr; Experimental Example 7-6) or Carboxymethylcellulose (CMS; Experimental Example 7-7) on both sides of the separator 35 Except that it was applied, the same procedure as in Experimental Example 1-3 was performed.

(Comparative Examples 5-1 to 5-7)
Except that the protrusion 34C was not formed, the same procedure as in Experimental Examples 7-1 to 7-7 was performed.

Regarding the secondary batteries of Experimental Examples 7-1 to 7-7 and Comparative Examples 5-1 to 5-7, the surface density of the negative electrode active material particles in the negative electrode 34, the surface density of the protrusions 34C, and the like, and the cycle characteristics are as follows. When examined, the results shown in Table 7 were obtained. Table 7 also shows the results of Experimental Example 1-3 and Comparative Example 1.

As shown in Table 7, when PTFE or the like was used as the polymer compound included in the electrolyte 36, the same result as that shown in Table 1 was obtained. That is, in Experimental Examples 7-1 to 7-7 in which the protrusions 34C were formed, the discharge capacity retention rate was higher than in Comparative Examples 5-1 to 5-7 in which the protrusions 34C were not formed.

  Therefore, in the secondary battery described above, when the negative electrode 34 includes silicon as the negative electrode active material, the plurality of protrusions 34C are provided on the surface of the negative electrode active material layer 34B, so that the polymer compound included in the electrolyte 36 It was confirmed that the cycle characteristics improved without depending on the type. That is, it was confirmed that a high effect was obtained without depending on the type of the polymer compound applied to both surfaces of the separator 35.

( Experimental example 8-1)
A procedure similar to that of Experimental Example 1-3 was performed except that sulfobenzoic anhydride (SBAH) as a solvent and lithium tetrafluoroborate (LiBF ₄ ) as an electrolyte salt were added and the composition of the electrolytic solution was changed. . In this case, the content of SBAH in the electrolytic solution was 1 wt%, and the content of LiPF ₆ and LiBF ₄ and respectively 1 mol / dm ³ and 0.05 mol / dm ^3.

( Experimental example 8-2)
A procedure similar to that in Experimental Example 8-1 was performed except that propylene carbonate (PC) was added as a solvent and the composition of the electrolytic solution was changed. At this time, the composition of PC, FEC, and DEC was 20:30:50 by weight ratio (PC: FEC: DEC). Further, the content of SABH in the electrolytic solution was 1 wt%, and the content of LiPF ₆ and LiBF ₄ and respectively 1 mol / dm ³ and 0.05 mol / dm ^3.

( Experimental example 8-3)
Except that 4,5-difluoro-1,3-dioxolan-2-one (DFEC) was added as a solvent to the electrolytic solution, and the composition of the electrolytic solution was changed, the same procedure as in Experimental Example 8-2 was performed. At this time, the composition of PC, FEC, DFEC, and DEC was 30: 10: 10: 50 by weight ratio (PC: FEC: DFEC: DEC). Further, the content of SABH in the electrolytic solution was 1 wt%, and the content of LiPF ₆ and LiBF ₄ and respectively 1 mol / dm ³ and 0.05 mol / dm ^3.

( Experimental example 8-4)
A procedure similar to that in Experimental Example 8-2 was performed except that DFEC was added instead of FEC as a solvent to the electrolytic solution, and the composition of the electrolytic solution was changed. At this time, the composition of PC, DFEC, and DEC was 40:10:50 by weight ratio (PC: DFEC: DEC). The content of SABH in the electrolytic solution was 1 wt%, and the content of LiPF ₆ and LiBF ₄ and respectively 1 mol / dm ³ and 0.05 mol / dm ^3.

For the secondary batteries of Examples 8-1 to 8-4, the surface density and the like of the negative electrode active material particle surface density, and the like and the protrusion 34C of the anode 34, and the cycle characteristics were examined, the results shown in Table 8 was gotten. In Table 8, the results of Experimental Example 1-3 and Comparative Example 1 are also shown.

As shown in Table 8, when SBAH or the like was added to the electrolytic solution, the same results as those shown in Table 1 were obtained. That is, in Experimental Examples 8-1 to 8-4 in which the protrusions 34C were formed, the discharge capacity retention rate was higher than that in Comparative Example 1 in which the protrusions 34C were not formed. In this case, in Experiment Example 8-1 in which SBAH and LiBF ₄ were added to the electrolyte, the discharge capacity retention rate was higher than in Experiment Example 1-3 that did not include them, and an experiment in which PC was further added. In Example 8-2, the discharge capacity retention rate was higher than in Experimental Example 8-1 not including it. Furthermore, in Experimental Examples 8-3 and 8-4 to which DFEC was added, the discharge capacity maintenance rate was higher than in Experimental Examples 8-1 and 8-2 that did not include DFEC.

  Therefore, in the secondary battery described above, when the negative electrode 34 includes silicon as the negative electrode active material, by providing a plurality of protrusions 34C on the surface of the negative electrode active material layer 34B, it does not depend on the composition of the electrolyte 36. In addition, it was confirmed that the cycle characteristics were improved. In this case, in particular, by adding lithium tetrafluoroborate and an acid anhydride to the electrolytic solution, a higher effect can be obtained. Propylene carbonate and 4,5-difluoro-1,3-dioxolan-2-one It was confirmed that a particularly high effect can be obtained by adding.

  From the results shown in Tables 1 to 8, in the secondary battery of the present invention, by providing a plurality of protrusions on the surface of the negative electrode active material layer, the type of the negative electrode active material or the method for forming the negative electrode active material layer, It was confirmed that the cycle characteristics were improved without depending on the surface density of the protrusions or the composition of the electrolyte. That is, when the negative electrode has a plurality of protrusions on the surface of the negative electrode active material layer, the protrusions become physical resistances, and the negative electrode and the separator are not easily displaced. As a result, it was confirmed that stress due to expansion and contraction of the negative electrode active material layer during charge / discharge was relaxed, and the structural stability of the negative electrode was improved. Therefore, in the case where a material having a large stress due to expansion and contraction of the negative electrode active material layer accompanying charge / discharge, for example, a material containing silicon or tin as a constituent element is used as the negative electrode active material, It is considered that the effect of suppressing the peeling of the negative electrode active material layer is remarkably exhibited.

  The present invention has been described with reference to the embodiments and examples. However, the present invention is not limited to the embodiments described in the above embodiments and examples, and various modifications can be made. For example, the use application of the negative electrode of the present invention is not necessarily limited to the secondary battery, but may be an electrochemical device other than the secondary battery. Other applications include, for example, capacitors.

  Further, in the above-described embodiments and examples, the lithium ion secondary battery in which the capacity of the negative electrode is expressed based on insertion and extraction of lithium is described as the type of the secondary battery. However, the secondary battery is not necessarily limited to this. is not. The secondary battery of the present invention has a negative electrode material capable of occluding and releasing lithium with a smaller charge capacity than that of the positive electrode, and the negative electrode capacity is reduced by the capacity of lithium insertion and removal and lithium deposition. The present invention can be similarly applied to a secondary battery that includes a capacity that accompanies melting and is represented by the sum of the capacities.

  In the above-described embodiments and examples, the case where the electrolytic solution or the gel electrolyte in which the electrolytic solution is held in the polymer compound is used as the electrolyte of the secondary battery of the present invention has been described. The electrolyte may be used. Other electrolytes include, for example, a mixture of an ion conductive inorganic compound such as ion conductive ceramics, ion conductive glass or ionic crystal and an electrolyte, or a mixture of another inorganic compound and an electrolyte. Or a mixture of these inorganic compounds and a gel electrolyte.

  In the above-described embodiments and examples, the case where the battery structure is a cylindrical type and a laminate film type and the case where the battery element has a winding structure have been described as examples. However, the secondary battery of the present invention is described. Can be similarly applied to the case where other battery structures such as a square shape, a button shape and a coin shape are provided, and the case where the battery element has another structure such as a laminated structure.

  In the above-described embodiments and examples, the case where lithium is used as the electrode reactant has been described. However, other group 1 elements such as sodium or potassium, group 2 elements such as magnesium or calcium, aluminum, and the like Other light metals may be used. In these cases, the negative electrode material described in the above embodiment can be used as the negative electrode active material.

  Further, in the above-described embodiments and examples, the surface density, width, and height of the protrusions in the negative electrode or the secondary battery of the present invention, the ratio of the surface density between the protrusions and the negative electrode active material particles, and the negative electrode active material particles Although the appropriate range derived from the results of the examples has been described with respect to the oxygen content, the description does not completely deny the possibility that the surface density of the protrusions is outside the above range. In other words, the appropriate range described above is a particularly preferable range for obtaining the effects of the present invention, and the surface density of the protrusions may slightly deviate from the above ranges as long as the effects of the present invention are obtained.

It is sectional drawing showing the structure of the negative electrode which concerns on one embodiment of this invention. It is sectional drawing which expands and represents a part of negative electrode shown in FIG. It is sectional drawing showing the structure of the modification of the negative electrode shown in FIG. FIG. 4 is an enlarged cross-sectional view illustrating a part of the negative electrode illustrated in FIG. 3. FIG. 4 is an SEM photograph showing a cross-sectional structure of the negative electrode shown in FIG. 3 and a schematic diagram thereof. FIG. 4 is an SEM photograph showing a planar structure of the negative electrode shown in FIG. 3 and a schematic diagram thereof. It is sectional drawing showing the structure of the 1st secondary battery provided with the negative electrode which concerns on one embodiment of this invention. FIG. 8 is an enlarged cross-sectional view illustrating a part of a wound electrode body illustrated in FIG. 7. It is sectional drawing showing the structure of the 2nd secondary battery provided with the negative electrode which concerns on one embodiment of this invention. FIG. 10 is a cross-sectional view taken along line XX of the spirally wound electrode body illustrated in FIG. 9. It is sectional drawing which expands and represents a part of winding electrode body shown in FIG.

Explanation of symbols

  1, 22A, 34A ... negative electrode current collector, 2, 22B, 34B ... negative electrode active material layer, 3, 22C, 34C ... projection, 11 ... battery can, 12, 13 ... insulating plate, 14 ... battery lid, 15 ... safety valve Mechanism, 15A ... disk plate, 16 ... heat resistance element, 17 ... gasket, 20, 30 ... wound electrode body, 21, 33 ... positive electrode, 21A, 33A ... positive electrode current collector, 21B, 33B ... positive electrode active material layer , 22, 34 ... negative electrode, 23, 35 ... separator, 24 ... center pin, 25, 31 ... positive electrode lead, 26, 32 ... negative electrode lead, 36 ... electrolyte, 37 ... protective tape, 40 ... exterior member, 41 ... adhesive film 54 ... exterior can, 55 ... exterior cup, 200 ... negative electrode active material particles.

Claims (12)

A positive electrode and a negative electrode arranged opposite to each other with a separator, and an electrolyte solution containing a solvent and an electrolyte salt;
The negative electrode includes a negative electrode current collector and a negative electrode active material layer having a plurality of negative electrode active material particles and provided on the negative electrode current collector,
The negative electrode active material particles are grown in the thickness direction of the negative electrode active material layer from the surface of the negative electrode current collector, and are connected to the negative electrode current collector,
Near the apex of the negative electrode active material particles in the thickness direction of the negative electrode active material layer, a plurality of conical protrusions having a width smaller than the particle diameter of the negative electrode active material particles are provided,
The negative active material particles and the projections, viewed contains at least one of silicon simple substance, alloys and compounds,
The width of the protrusion is 0.06 μm or more and 4 μm or less, and the height of the protrusion is 0.04 μm or more and 8.5 μm or less,
The protrusion is a secondary battery that bites into the separator . The secondary battery according to claim 1, wherein a surface density of the protrusions is 0.02 pieces / μm ² or more and 2.3 pieces / μm ² or less. The secondary battery according to claim 1, wherein the surface density of the protrusions is 0.02 pieces / μm ² or more and 0.5 pieces / μm ² or less. The secondary battery according to claim 1, wherein a height of the protrusion is 0.08 μm or more and 3.2 μm or less. The ratio (N1 / N2) of the surface density (N1; pieces / μm ² ) of the protrusions to the surface density (N2; pieces / μm ² ) of the negative electrode active material particles is 0.05 to 11.5. Item 11. The secondary battery according to Item 1. The secondary battery according to claim 1, wherein the negative electrode active material layer is formed by a vapor phase method. The negative electrode active material particles have oxygen together with silicon,
The secondary battery according to claim 1, wherein a content of oxygen in the negative electrode active material particles is 3 atomic% to 46.2 atomic%. Between the separator and the positive electrode and the negative electrode, an electrolyte having a polymer compound together with the electrolytic solution,
The secondary battery according to claim 1, wherein the polymer compound is at least one of polyvinylidene fluoride, polytetrafluoroethylene, polyimide, polyamide, polyamideimide, polyethersulfone, polyaramid, and carboxymethylcellulose. The solvent contains at least one of 4-fluoro-1,3-dioxolan-2-one, 4,5-difluoro-1,3-dioxolan-2-one, and an acid anhydride,
The secondary battery according to claim 1, wherein the electrolyte salt contains at least one of lithium hexafluorophosphate (LiPF ₆ ) and lithium tetrafluoroborate (LiBF ₄ ). The secondary battery according to claim 1, wherein the protrusion includes a material having the same composition as the negative electrode active material particles. A negative electrode current collector, a negative electrode active material layer provided on the negative electrode current collector and having a plurality of negative electrode active material particles,
The negative electrode active material particles are grown in the thickness direction of the negative electrode active material layer from the surface of the negative electrode current collector, and are connected to the negative electrode current collector,
Near the apex of the negative electrode active material particles in the thickness direction of the negative electrode active material layer, a plurality of conical protrusions having a width smaller than the particle diameter of the negative electrode active material particles are provided,
The negative active material particles and the projections, viewed contains at least one of silicon simple substance, alloys and compounds,
The width of the protrusion is 0.06 μm or more and 4 μm or less, and the height of the protrusion is 0.04 μm or more and 8.5 μm or less,
The negative electrode for a secondary battery , wherein the protrusion has a bite into the separator . A secondary battery according to any one of claims 1 to 10 is provided.
Electronics.

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