JP2010073349A - Lithium ion secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means that prevents the occurrence of various problems caused by expansion and contraction of an active material during discharge and charge when a silicon material is used as a negative electrode active material in a lithium ion secondary battery. <P>SOLUTION: The lithium ion secondary battery includes a battery element having at least one unit cell layer including: a positive electrode having a positive electrode active material layer containing a positive electrode active material and formed on the surface of a collector; an electrolyte layer containing an electrolyte; and a negative electrode having a negative electrode active material layer containing a negative electrode active material and formed on the surface of the collector, wherein both electrodes are layered in this order so that the positive electrode active material layer and the negative electrode active material layer face each other. In addition, the electrolyte includes a liquid electrolyte in which cations of a metallic element that is alloyed with lithium are dissolved in an organic solvent. Further, the negative electrode active material contains silicon doped with at least one kind of doping element selected from the group consisting of the elements in group XIII or group XV. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a lithium ion secondary battery. More specifically, the present invention relates to an improvement for improving the durability of lithium ions.

  In recent years, in order to cope with air pollution and global warming, reduction of the amount of carbon dioxide has been strongly desired. In the automobile industry, there is a great expectation for reducing carbon dioxide emissions by introducing electric vehicles (EV) and hybrid electric vehicles (HEV), and the development of secondary batteries for motor drive that holds the key to commercialization of these is thriving. Has been done.

  As a secondary battery for driving a motor, it is required to exhibit extremely high output characteristics and high energy density as compared with a consumer lithium ion secondary battery used in a mobile phone, a notebook personal computer, or the like. Therefore, lithium ion secondary batteries having the highest theoretical energy among all the batteries are attracting attention, and are currently being developed rapidly.

  Generally, a lithium ion secondary battery includes a positive electrode in which a positive electrode active material or the like is applied to the surface of the current collector using a binder, and a negative electrode in which a negative electrode active material or the like is applied to the surface of the current collector using a binder. It is connected via an electrolyte layer containing an electrolyte and has a configuration of being housed in a battery case.

Conventionally, as a negative electrode active material constituting a negative electrode of a lithium ion secondary battery, a carbon / graphite-based material advantageous in terms of charge / discharge cycle life and cost has been used. When a carbon / graphite-based material is used as the negative electrode active material, the charge / discharge reaction proceeds by occlusion / release of lithium ions into the graphite crystal. Due to such a mechanism limitation, when a carbon / graphite-based material is used as the negative electrode active material, a charge / discharge capacity of a theoretical capacity of 372 mAh / g or more obtained from LiC ₆ which is the maximum lithium-introduced compound cannot be obtained. There is a drawback. For this reason, it is expected that it is difficult to obtain a capacity and energy density satisfying a practical use level of a vehicle application by using a carbon / graphite-based material as a negative electrode active material.

On the other hand, in a lithium ion secondary battery, a technique using a material that can be alloyed with lithium as a negative electrode active material has been proposed (see, for example, Patent Document 1). Such a battery can achieve a high energy density as compared with a conventional carbon / graphite negative electrode material, and is expected as a vehicle battery candidate. As such a material, for example, silicon (Si) can occlude and release 4.4 mol of lithium ions per mol as shown in the following reaction formula (1) in charge and discharge. For this reason, Li ₂₂ Si ₅ has a very large theoretical capacity of about 2000 mAh / g.

Here, in the technique described in Patent Document 1, silicon, tin, or an alloy thereof is employed as the negative electrode material. As the electrolytic solution, one containing a fluorine-containing salt of a Group 2 element such as Mg (PF ₆ ) ₂ or Mg (BF ₄ ) ₂ is used. In the technique described in Patent Document 1, the side reaction in the negative electrode is suppressed by adopting such a configuration.

  By the way, since the conductivity of silicon alone is not high, when silicon is used as a negative electrode active material, a small amount of doping elements such as boron (B), aluminum (Al), and gallium (Ga) are doped into silicon alone. It has been proposed to be used as a negative electrode active material. With such a structure, silicon as the negative electrode active material becomes a semiconductor and exhibits conductivity. As a result, it can function effectively as a negative electrode active material.

However, a negative electrode active material made of a material that can be alloyed with lithium, such as silicon, has a large expansion and contraction during charge and discharge. For example, the volume expansion when lithium ions are occluded is about 1.2 times that of graphite, and about 4 times that of silicon material. When the negative electrode active material expands greatly in this way, the electrolyte solution present in the electrolyte layer penetrates into the expanded active material. As a result, there is a problem that the electrolyte solution is insufficient in the electrolyte layer and the battery capacity is reduced. There is also a problem that sufficient cycle characteristics cannot be obtained due to cracking or pulverization of the active material, peeling from the current collector, and the like.
JP 2004-296315 A

  An object of the present invention is to provide means capable of suppressing the occurrence of various problems due to expansion and contraction of an active material during charge and discharge when a silicon material is used as a negative electrode active material in a lithium ion secondary battery. With the goal.

  The present inventors have intensively studied to solve various problems caused by the expansion and contraction of the negative electrode active material. As a result, surprisingly, silicon doped with a predetermined element is used as a negative electrode active material, and an electrolyte containing a cation of a metal element that can be alloyed with lithium is included in the electrolyte. It has been found that the deterioration of the active material can be effectively suppressed and the battery capacity can be prevented from decreasing. Based on such knowledge, the present inventors have completed the present invention.

  That is, the lithium ion secondary battery of the present invention completed by the present inventors is a positive electrode in which a positive electrode active material layer containing a positive electrode active material is formed on the surface of a current collector, an electrolyte layer containing an electrolyte, At least one unit cell layer in which a negative electrode formed by forming a negative electrode active material layer containing a negative electrode active material on the surface of a current collector is laminated in this order so that the positive electrode active material layer and the negative electrode active material layer face each other A battery element having The electrolyte includes an electrolytic solution in which a cation of a metal element that can be alloyed with lithium is dissolved in an organic solvent. Furthermore, the negative electrode active material contains silicon doped with one or more doping elements selected from the group consisting of group 13 or group 15 elements in the periodic table.

  ADVANTAGE OF THE INVENTION According to this invention, in a lithium ion secondary battery, the means which can suppress generation | occurrence | production of the various problems resulting from the expansion / contraction of the active material at the time of charging / discharging at the time of using a silicon material as a negative electrode active material can be provided. .

  Hereinafter, preferred embodiments to which the present invention is applied will be described with reference to the accompanying drawings. In addition, the dimension ratio of drawing is exaggerated on account of description, and may differ from an actual ratio.

  Here, the case where the battery of the present invention is a laminated (flat) lithium ion secondary battery will be described as an example as a representative embodiment, but the technical scope of the present invention is limited to the following forms. There is no limit.

  FIG. 1 schematically shows the overall structure of a laminated lithium ion secondary battery (hereinafter also simply referred to as “lithium ion battery”), which is a typical embodiment of the lithium ion secondary battery of the present invention. FIG.

  As shown in FIG. 1, in the lithium ion battery 10 of the present embodiment, a substantially rectangular battery element (power generation element) 17 in which a charge / discharge reaction actually proceeds is sealed inside a laminate film 22 that is a battery exterior material. Has a structured. Specifically, the battery element 17 is housed and sealed by using a polymer-metal composite laminate film as a battery exterior material and joining all of its peripheral parts by thermal fusion.

  The battery element 17 includes a positive electrode in which a positive electrode active material layer 12 is formed on both surfaces of the positive electrode current collector 11 (only one side for the lowermost layer and the uppermost layer of the battery element), an electrolyte layer 13, and a negative electrode current collector 14. The negative electrode in which the negative electrode active material layer 15 is formed on both sides is laminated. Specifically, the positive electrode, the electrolyte layer 13 and the negative electrode are laminated in this order so that one positive electrode active material layer 12 and the negative electrode active material layer 15 adjacent thereto face each other with the electrolyte layer 13 therebetween. Yes.

  As a result, the adjacent positive electrode, electrolyte layer 13 and negative electrode constitute one single cell layer 16. Therefore, it can be said that the lithium ion battery 10 of the present embodiment has a configuration in which a plurality of single battery layers 16 are stacked and electrically connected in parallel. Further, on the outer periphery of the unit cell layer 16, a seal portion (insulating layer) for insulating between the adjacent positive electrode current collector 11 and negative electrode current collector 14 (not shown; see reference numeral 43 in FIG. 2) ) May be provided. The positive electrode active material layer 12 is formed on only one side of the outermost positive electrode current collector 11 a located in both outermost layers of the battery element 17. In addition, the arrangement of the positive electrode and the negative electrode is reversed from that in FIG. 1 so that the outermost negative electrode current collector is positioned in both outermost layers of the battery element 17, and the negative electrode is formed only on one side of the outermost negative electrode current collector. An active material layer may be formed.

  The positive electrode current collector 11 and the negative electrode current collector 14 are respectively attached with a positive electrode tab 18 and a negative electrode tab 19 that are electrically connected to the respective electrodes (positive electrode and negative electrode), and are laminated films so as to be sandwiched between end portions of the laminate film 22. 22 has a structure led out to the outside. The positive electrode tab 18 and the negative electrode tab 19 are attached to the positive electrode current collector 11 and the negative electrode current collector 14 of each electrode by ultrasonic welding, resistance welding or the like via the positive electrode terminal lead 20 and the negative electrode terminal lead 21 as necessary. (This form is shown in FIG. 1). However, the positive electrode current collector 11 may be extended to form the positive electrode tab 18 and may be led out from the laminate film 22. Similarly, the negative electrode current collector 14 may be extended to form a negative electrode tab 19, which may be similarly derived from the battery exterior material 22.

  FIG. 2 shows the overall structure of a bipolar stacked lithium ion secondary battery (hereinafter also simply referred to as “bipolar lithium ion battery”), which is another representative embodiment of the lithium ion secondary battery of the present invention. It is a schematic sectional drawing which represented typically.

  As shown in FIG. 2, the bipolar lithium ion battery 30 has a structure in which a substantially rectangular battery element 37 in which a charge / discharge reaction actually proceeds is sealed inside a laminate film 42 that is a battery exterior material. In the battery element 37 of the bipolar lithium ion battery 30, the electrolyte layer 35 is sandwiched between a plurality of bipolar electrodes 34 so that the positive electrode active material layer 32 and the negative electrode active material layer 33 of the adjacent bipolar electrode 34 face each other. ing. Here, the bipolar electrode 34 has a structure in which the positive electrode active material layer 32 is provided on one surface of the current collector 31 and the negative electrode active material layer 33 is provided on the other surface. That is, the bipolar lithium ion battery 30 includes a bipolar electrode 34 having a positive electrode active material layer 32 on one surface of a current collector 31 and a negative electrode active material layer 33 on the other surface via an electrolyte layer 35. A battery element 37 having a structure in which a plurality of layers are stacked.

  The adjacent positive electrode active material layer 32, electrolyte layer 35, and negative electrode active material layer 33 constitute one unit cell layer 36. Therefore, it can be said that the bipolar lithium ion battery 30 has a configuration in which the single battery layers 36 are stacked. Further, in order to prevent a liquid junction due to leakage of the electrolytic solution from the electrolyte layer 35, a seal portion (insulating layer) 43 is disposed around the unit cell layer 36. By providing the seal portion 43, the adjacent current collectors 31 can be insulated, and a short circuit due to contact between adjacent electrodes (the positive electrode active material layer 32 and the negative electrode active material layer 33) can be prevented.

  Note that the outermost layer positive electrode 34a and the outermost layer negative electrode 34b located in the outermost layer of the battery element 37 may not have a bipolar electrode structure, and the outermost layer current collector (the positive electrode side outermost current collector 31a and the negative electrode side outermost electrode). A structure in which the positive electrode active material layer 32 or the negative electrode active material layer 33 only on one side required for the outer layer current collector 31b) may be arranged. Specifically, the positive electrode active material layer 32 may be formed only on one side of the positive electrode side outermost layer current collector 31 a located in the outermost layer of the battery element 37. Similarly, the negative electrode active material layer 33 may be formed on only one surface of the negative electrode side outermost current collector 31b located in the outermost layer of the battery element 37. In the bipolar lithium ion battery 30 of the form shown in FIG. 2, the positive electrode tab 38 and the negative electrode tab 39 are provided on the positive electrode side outermost layer current collector 31a and the negative electrode side outermost layer current collector 31b, respectively. They are joined via terminal leads 41. However, the positive electrode side outermost layer current collector 31a may be extended to form a positive electrode tab 38, which may be led out from a laminate film 42 which is a battery exterior material. Similarly, the negative electrode side outermost layer current collector 31b may be extended to form a negative electrode tab 39, which may be derived from a laminate film.

  The number of stacked bipolar electrodes 34 (including electrodes 34a and 34b) can be adjusted according to a desired voltage. Further, in the bipolar lithium ion secondary battery 30, the number of stacked bipolar electrodes 34 may be reduced if a sufficient output can be ensured even if the battery is made as thin as possible. Even in the bipolar lithium ion battery 30, in order to prevent external impact and environmental degradation during use, the battery element 37 portion is sealed under reduced pressure in a battery exterior material (exterior package) such as a laminate film 42, and the positive electrode tab 38. It is preferable that the negative electrode tab 39 be taken out of the battery exterior member 42. It can be said that the basic configuration of the bipolar lithium ion battery 30 is a configuration in which a plurality of unit cell layers 36 are electrically connected in series.

  The constituent elements and the manufacturing method of the lithium ion battery 10 and the bipolar lithium ion battery 30 are basically the same except that the electrical connection form (electrode structure) in both batteries is different. . Therefore, it demonstrates below centering on each component of the above-mentioned lithium ion battery 10. FIG. However, it goes without saying that the constituent elements and the manufacturing method of the bipolar lithium ion battery 30 can be configured or manufactured by appropriately using the same constituent elements and manufacturing method.

  Hereinafter, although the member which comprises the lithium ion battery of this invention is demonstrated easily, it is not restrict | limited only to the following form, A conventionally well-known form can be employ | adopted similarly.

[Current collector]
The current collectors (11, 14, 31) are made of a conductive material, and active material layers are formed on both surfaces of the current collectors to form battery electrodes, which ultimately form a battery. The size of the current collector is determined according to the intended use of the battery. For example, if it is used for a large battery that requires a high energy density, a current collector having a large area is used. There is no particular limitation on the thickness of the current collector. The thickness of the current collector is usually about 1 to 100 μm.

  There is no particular limitation on the material constituting the current collector. For example, a metal or a conductive polymer can be employed. Specifically, metal materials, such as aluminum, nickel, iron, stainless steel, titanium, copper, are mentioned, for example. In addition to these, a clad material of nickel and aluminum, a clad material of copper and aluminum, or a plating material of a combination of these metals can be preferably used. Moreover, the foil by which aluminum is coat | covered on the metal surface may be sufficient. Of these, aluminum, stainless steel, and copper are preferable from the viewpoints of electronic conductivity and battery operating potential.

[Positive electrode active material layer]
The active material layer (12, 15, 32, 33) contains an active material, and further contains other additives as necessary.

The positive electrode active material layers (12, 32) include a positive electrode active material. As the positive electrode active material, for example, LiMn ₂ O ₄ , LiCoO ₂ , LiNiO ₂ , Li (Ni—Co—Mn) O _2, and lithium-such as those in which a part of these transition metals are substituted with other elements Examples include transition metal composite oxides, lithium-transition metal phosphate compounds, and lithium-transition metal sulfate compounds. In some cases, two or more positive electrode active materials may be used in combination. Preferably, a lithium-transition metal composite oxide is used as the positive electrode active material. Of course, positive electrode active materials other than those described above may be used.

  The average particle diameter of the positive electrode active material contained in the positive electrode active material layer is not particularly limited, but is preferably 1 to 20 μm and more preferably 1 to 5 μm from the viewpoint of increasing output. However, it goes without saying that a form outside this range may be adopted. In the present specification, “particle diameter” means the maximum distance L among the distances between any two points on the contour line of the active material particles. As the value of “average particle diameter”, the average particle diameter of particles observed in several to several tens of fields using an observation means such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM). The calculated value shall be adopted.

  There is no restriction | limiting in particular about the thickness of a positive electrode active material layer, The conventionally well-known knowledge about a battery can be referred suitably. For example, the thickness of the positive electrode active material layer is about 2 to 100 μm.

[Negative electrode active material layer]
The negative electrode active material layers (15, 33) include a negative electrode active material. One of the features of the present invention is that the negative electrode active material contained in the negative electrode active material layer (15, 33) is one or more selected from the group consisting of Group 13 or Group 15 elements in the periodic table. Silicon (Si) doped with these doping elements is used.

  As described above, by using silicon (Si) as the negative electrode active material, there is an advantage that a high energy density can be achieved as compared with a carbon / graphite negative electrode material generally used conventionally.

  The element that can be doped into silicon (Si) as the negative electrode active material is a group 13 or group 15 element in the periodic table. Specifically, elements of Group 13 in the periodic table include boron (B), aluminum (Al), gallium (Ga), indium (In), and thallium (Tl). Examples of the Group 15 element in the periodic table include nitrogen (N), phosphorus (P), arsenic (As), antimony (Sb), and bismuth (Bi). Among these, from the viewpoint of providing a battery having excellent battery characteristics, B, Al, Ga, In, N, P, As, Sb, or Bi are preferable, and B, Al, Ga, or In are more preferable. Yes, particularly preferably B or Al. Only one of these doping elements may be doped alone, or two or more may be doped in combination.

Although there is no restriction | limiting in particular about the doping amount of the doping element to silicon (Si), From a viewpoint of the electroconductive improvement in a negative electrode active material layer, Preferably it is 1 * 10 < ^-20 > atoms / cm < ³ > or more, More preferably 1 × 10 ⁻¹⁸ atoms / cm ³ or more, particularly preferably 1 × 10 ⁻¹⁵ atoms / cm ³ or more.

In some cases, in addition to the doped silicon (Si) described above, carbon materials such as graphite, soft carbon, and hard carbon, metal materials, lithium-titanium composite oxides (lithium titanate: Li ₄ Ti ₅ O ₁₂ ) or other lithium-transfer metal composite oxides and other conventionally known negative electrode active materials may be used in combination.

  There is no restriction | limiting in particular about the shape of a negative electrode active material layer. As an example, the form of the thin film which consists of doped silicon (Si) mentioned above is mentioned. Although silicon (Si) is inherently low in conductivity, silicon (Si) exhibits semiconductor properties by doping silicon (Si) with the predetermined doping element and using it as a negative electrode active material. That is, the low conductivity of silicon (Si) is improved, and it can function effectively as a negative electrode active material. Therefore, a thin film made of only doped silicon as a negative electrode active material can be used as a negative electrode active material layer as it is. In such a form, the thickness of the negative electrode active material layer in the stacking direction is not particularly limited. However, from the viewpoint of providing a battery having excellent battery characteristics, the thickness is preferably 100 nm to 100 μm, more preferably 1 to 100 μm, and still more preferably 1 to 10 μm. A method for forming such a thin film will be described in detail in the section of the manufacturing method described later.

  Alternatively, the negative electrode active material layer may have the same shape as a conventional general active material layer. That is, the negative electrode active material layer includes a particulate negative electrode active material (and other negative electrode active materials as necessary) made of doped silicon (Si), and additives such as a binder and a conductive aid described later. It may be in the form of a mixture layer formed by mixing. In such a form, there is no restriction | limiting in particular about the size of the negative electrode active material particle which consists of doped silicon (Si) which is a particulate active material. However, to give an example, from the viewpoint of providing a battery having excellent battery characteristics, the average particle diameter of the particulate negative electrode active material is preferably 1 nm to 100 μm, more preferably 1 nm to 10 μm. More preferably, it is 1-500 nm.

  Examples of the additive that can be included in the positive electrode active material layer and the negative electrode active material layer include a binder, a conductive additive, an electrolyte salt (lithium salt), and an ion conductive polymer.

  Examples of the binder include polyvinylidene fluoride (PVdF), a synthetic rubber binder, and an epoxy resin.

  The conductive assistant refers to an additive that is blended in order to improve the conductivity of the positive electrode active material layer or the negative electrode active material layer. Examples of the conductive assistant include carbon materials such as carbon black such as acetylene black, graphite, and vapor grown carbon fiber. When the active material layer contains a conductive additive, an electronic network inside the active material layer is effectively formed, which can contribute to improvement of the output characteristics of the battery.

Examples of the electrolyte salt (lithium salt) include Li (C ₂ F ₅ SO ₂ ) ₂ N), LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiCF ₃ SO _{3 and the} like.

  Examples of the ion conductive polymer include polyethylene oxide (PEO) -based and polypropylene oxide (PPO) -based polymers.

  The compounding ratio of the components contained in the positive electrode active material layer and the negative electrode active material layer is not particularly limited. The mixing ratio can be adjusted in consideration of the intended use of the battery (emphasis on output, importance on energy, etc.) and ion conductivity by appropriately referring to known knowledge about the lithium ion secondary battery.

[Electrolyte layer]
The electrolyte layer (13, 35) functions as a spatial partition (spacer) between the positive electrode active material layer and the negative electrode active material layer. In addition, it also has a function of holding an electrolyte that is a lithium ion transfer medium between the positive and negative electrodes during charging and discharging.

  Another feature of the present invention is that the electrolyte constituting the electrolyte layer includes an electrolytic solution in which a cation of a metal element that can be alloyed with lithium is dissolved in an organic solvent. Examples of the form of the electrolyte when the electrolyte constituting the electrolyte layer includes such an electrolyte include a liquid electrolyte and a gel electrolyte.

  The liquid electrolyte is a solution in which a lithium salt as a supporting salt is dissolved in an organic solvent as a plasticizer. That is, the liquid electrolyte is directly used as the electrolytic solution in the present invention. In the present invention, when the electrolyte constituting the electrolyte layer is a liquid electrolyte, a form in which a cation of a metal element that can be alloyed with lithium is dissolved in an organic solvent as a plasticizer in addition to the lithium salt. It becomes. On the other hand, the gel electrolyte has a configuration in which the above liquid electrolyte is injected into a matrix polymer made of an ion conductive polymer. Hereinafter, the components constituting the electrolyte of these forms will be described in detail.

  In the liquid electrolyte, the organic solvent functioning as a plasticizer is not particularly limited, and conventionally known knowledge can be appropriately referred to in the field of lithium ion secondary batteries. Examples include ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), dimethyl carbonate (DMC), methyl ethyl carbonate (MEC), butylene carbonate (BC), vinylene carbonate (VC), γ-butyrolactone. (GBL), 1,2-dimethoxyethane, dimethyl sulfoxide (DMSO), 1,3-dioxolane or derivatives thereof, formamide, dimethylformamide, acetonitrile, nitromethane, methyl formate, methyl acetate, methyl propionate, ethyl propionate, phosphorus Acid triester, trimethoxymethane, diethyl ether, 1,3-propane sultone, sulfolane, 3-methyl-2-oxazolidinone, tetrahydrofuran or derivatives thereof, and , And a 2-diethoxyethane. Here, examples of 1,3-dioxolane derivatives include 2-methyl-1,3-dioxolane. Examples of the tetrahydrofuran derivative include 2-methyltetrahydrofuran and 2-fluorotetrahydrofuran. Of these, EC, DEC, PC, DMC, and MEC are preferable, and EC and DEC are more preferable. As for these organic solvents, only 1 type may be used independently and 2 or more types may be used together. By constituting a liquid electrolyte using these organic solvents, a battery having excellent battery performance can be provided.

In the liquid electrolyte, the type of lithium salt added to the organic solvent is not particularly limited, and conventionally known knowledge can be referred to as appropriate. Examples of the lithium salt include LiPF ₆ , LiClO ₄ , LiN (CF ₃ SO ₂ ) ₂ , LiBF ₄ , LiN (CF ₃ CF ₂ SO ₂ ) ₂ , LiCl, LiBr, LiI, LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiAsF ₆ , LiSbF ₆ , LiAlCl _{4 and the} like. Among these, LiPF ₆ , LiClO ₄ , LiN (CF ₃ SO ₂ ) ₂ , LiBF ₄ , LiN (CF ₃ CF ₂ SO ₂ ) ₂ are preferable, and LiPF ₆ , LiClO ₄ , LiN (CF ₃ SO ₂ ) _{2 are} more preferable. preferable. As for these lithium salts, only 1 type may be used independently and 2 or more types may be used together. There is no restriction | limiting in particular also about the addition amount of lithium salt to an organic solvent, and conventionally well-known knowledge can be referred suitably. As an example, the lithium ion concentration in the liquid electrolyte (= electrolytic solution) may be about 1 mol / L.

As described above, in the present invention, a cation of a metal element that can be alloyed with lithium is dissolved in the organic solvent described above. Examples of metal elements that can be alloyed with lithium that can be used here include magnesium (Mg), aluminum (Al), tin (Sn), zinc (Zn), silver (Ag), lead (Pb), and germanium (Ge). ), Indium (In), vanadium (V), strontium (Sr), barium (Ba), ruthenium (Ru), rhodium (Rh), iridium (Ir), palladium (Pd), platinum (Pt), gold (Au) ), Cadmium (Cd), mercury (Hg), gallium (Ga), thallium (Tl), bismuth (Bi), and tellurium (Te). Among these, Mg, Al, Sn, Zn, Ag, Pb, Ge, In, and V are preferable from the viewpoint that the functions and effects of the present invention can be further exhibited, and more preferably Mg, Al, Sn, Zn, Ag and Pb, particularly preferably Mg, Al, Sn, and Zn. There is no particular limitation on the counter ion (anion) when these cations are dissolved in an organic solvent to form a liquid electrolyte. However, a preferable form includes a form in which the anion constituting the lithium salt described above is dissolved in an organic solvent as the counter ion of the cation. In other words, in a preferred embodiment, the liquid electrolyte has Cl ⁻ , Br ⁻ , I ⁻ , BF ₄ ⁻ , PF ₆ ⁻ , CF ₃ SO ₃ ⁻ as a counter ion of a cation of a metal element that can be alloyed with lithium. , ClO ₄ ⁻ , CF ₃ CO ₂ ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ , AlCl ₄ ⁻ , N (CF ₃ SO ₂ ) ₂ ⁻ , or N (CF ₃ CF ₂ SO ₂ ) ₂ ⁻ is there. Among these, from the viewpoint of further improving the capacity characteristics of the battery, it is preferable that an anion containing fluorine is not contained in the electrolytic solution as a counter ion, and more preferably PF ₆ ⁻ and ClO ₄ ^−. , AlCl ₄ ⁻ alone is contained as a counter ion in the electrolytic solution, and particularly preferably only ClO ₄ ⁻ is contained as a counter ion in the electrolytic solution. In addition, as said counter ion, only 1 type may be used and 2 or more types may be used together. By adopting such a configuration, it is possible to sufficiently exert the effects of the present invention while minimizing the influence on the conductivity of lithium ions, which has been conventionally required for an electrolytic solution. There is no restriction | limiting in particular also about the addition amount of the said cation to an organic solvent, as long as the effect of this invention can be exhibited. As an example, the concentration of the cation in the liquid electrolyte (= electrolytic solution) is preferably 0.01 to 2 mol / L, more preferably 0.01 to 0.5 mol / L, More preferably, it is 0.01-0.2 mol / L. When the cation concentration is within such a range, deterioration of silicon (Si) used as the negative electrode active material is effectively suppressed, and the cycle durability of the battery of the present invention can be improved.

  On the other hand, the gel electrolyte has a configuration in which an electrolytic solution is injected into a matrix polymer made of an ion conductive polymer. As the electrolytic solution, the above-described liquid electrolyte is used. Therefore, the overlapping description is omitted here.

  Examples of the ion conductive polymer used as the matrix polymer include polyethylene oxide (PEO), polypropylene oxide (PPO), polyethylene glycol (PEG), polyacrylonitrile (PAN), polymethacrylic acid ester, polyvinylidene fluoride (PVdF), Examples thereof include a copolymer of polyvinylidene fluoride and hexafluoropropylene (PVdF-HFP), poly (methyl methacrylate) (PMMA), and a copolymer thereof. In these polymers, lithium salts can be dissolved well. Especially, it is preferable that PEO, PPO or these copolymers, or PVdF-HFP is used as a matrix polymer.

  In addition, the content rate in particular of electrolyte solution (components other than a matrix polymer) in a gel electrolyte is not restrict | limited. From the viewpoint of ionic conductivity and the like, it may be about several mass% to 98 mass%, preferably 80 mass% or more. Moreover, the matrix polymer of gel electrolyte can express the outstanding mechanical strength by forming a crosslinked structure. In order to form a crosslinked structure, a polymerization process such as thermal polymerization, ultraviolet polymerization, radiation polymerization, or electron beam polymerization may be performed on a matrix polymer (for example, PEO or PPO) using an appropriate polymerization initiator.

  In the present invention in which the electrolyte layer is composed of a liquid electrolyte or a gel electrolyte, a separator may be used for the electrolyte layer. Specific examples of the separator include a microporous film made of polyolefin such as polyethylene or polypropylene.

[Seal part]
The seal portion 43 is a member specific to the bipolar secondary battery, and is disposed on the peripheral portion of the single cell layer 36 for the purpose of preventing leakage of the electrolyte layer 35. In addition to this, it is possible to prevent current collectors adjacent in the battery from coming into contact with each other and a short circuit due to a slight unevenness at the end of the laminated electrode. In the form shown in FIG. 1, the seal portion 43 is disposed on the peripheral portion of the unit cell layer 35 so as to be sandwiched between the current collector 31 and the electrolyte layer 35. Examples of the constituent material of the seal portion 43 include polyolefin resins such as PE and PP, epoxy resins, rubber, and polyimide. Of these, polyolefin resins are preferred from the viewpoints of corrosion resistance, chemical resistance, film-forming properties, economy, and the like.

[Positive electrode and negative electrode tab]
In the battery (10, 30), the tabs (the positive electrode tabs (18, 38) and the negative electrode tabs (19, 39)) electrically connected to the current collector are external materials for the purpose of taking out the current outside the battery. The laminate film (22, 42) is taken out from the outside.

  The material which comprises a tab in particular is not restrict | limited, The well-known highly electroconductive material conventionally used as a tab for lithium ion secondary batteries can be used. As a constituent material of a tab, metal materials, such as aluminum, copper, titanium, nickel, stainless steel (SUS), these alloys, are preferable, for example. From the viewpoint of light weight, corrosion resistance, and high conductivity, aluminum and copper are more preferable, and aluminum is particularly preferable. Note that the same material may be used for the positive electrode tab and the negative electrode tab, or different materials may be used. In the bipolar lithium ion battery 30, the outermost layer current collector (31a, 31b) may be extended to form a tab, or a separately prepared tab is connected to the outermost layer current collector as shown in FIG. May be.

[Positive electrode and negative electrode lead]
In the bipolar lithium ion battery 30 shown in FIG. 2, the current collector is electrically connected to the tab via the positive electrode lead 40 and the negative electrode lead 41. However, when the outermost layer current collector (31a, 31b) is extended as a tab as described above, the positive electrode and the negative electrode lead may not be used.

  As a material for the positive electrode and the negative electrode lead, a lead used in a known lithium ion battery can be used. In addition, the parts removed from the battery exterior material should be heat-insulating so that they do not affect products (for example, automobile parts, especially electronic devices) by touching peripheral devices or wiring and causing leakage. It is preferable to coat with a heat shrinkable tube or the like.

[Exterior material]
A conventionally known metal can case can be used as the exterior material. In addition, battery elements (17, 37) may be packed using a laminate film 22 as shown in FIG. 1 or 2 as an exterior material. For example, the laminate film 22 may be configured as a three-layer structure in which PP, aluminum, and nylon are laminated in this order.

[Appearance structure of lithium ion secondary battery]
FIG. 3 is a perspective view showing the appearance of a stacked flat battery which is a typical embodiment of the lithium ion secondary battery according to the present invention.

  As shown in FIG. 3, the stacked flat lithium ion secondary battery 50 has a rectangular flat shape, and a positive electrode tab 58 and a negative electrode tab 59 for extracting power from both sides thereof. Has been pulled out. The battery element 57 is wrapped by a laminate film 52 that is a battery exterior material, and the periphery thereof is heat-sealed. The battery element 57 is sealed with the positive electrode tab 58 and the negative electrode tab 59 pulled out to the outside. . Here, the battery element 57 corresponds to the battery elements (17, 37) of the battery (10, 30) shown in FIGS. 1 and 2 described above. That is, the battery element 57 is formed by laminating a plurality of single battery layers (16, 36) composed of positive electrodes (12, 32), electrolyte layers (13, 35), and negative electrodes (15, 33).

  The shape of the lithium ion secondary battery of the present invention is not limited to the stacked flat shape as shown in FIGS. The wound lithium ion secondary battery may have a cylindrical shape, or may have a shape that is a flattened rectangular shape by deforming such a cylindrical shape. . In the cylindrical shape, there is no particular limitation such as using a laminate film or a conventional cylindrical can (metal can) as the exterior material.

  Moreover, there is no restriction | limiting in particular also regarding extraction of the tab (58, 59) shown in FIG. For example, the positive electrode tab 58 and the negative electrode tab 59 may be pulled out from the same side, or the positive electrode tab 58 and the negative electrode tab 59 may be divided into a plurality of parts and taken out from each side. Further, in a wound type lithium ion battery, instead of a tab, for example, a terminal may be formed using a cylindrical can (metal can).

(Production method)
There is no restriction | limiting in particular about the manufacturing method of the lithium ion battery of this invention. Silicon (Si) doped with a predetermined doping element may be used as a negative electrode active material, and an electrolytic solution in which a cation of a metal element that can be alloyed with lithium is dissolved in an organic solvent may be used as an electrolyte. Conventionally known knowledge can be appropriately referred to for other specific forms.

  When the shape of the negative electrode active material layer is the above-described thin film made of doped silicon (Si), the negative electrode collects doped silicon (Si) as the negative electrode active material by a vapor deposition process. It can be formed by vapor deposition on the body. There is no restriction | limiting in particular about the specific form of such a vapor-phase film-forming process, A conventionally well-known method can be employ | adopted suitably. As an example, a vacuum deposition method, a sputtering method (for example, RF sputtering method), a chemical vapor deposition (CVD) method, etc. can be illustrated. According to such a method, the negative electrode active material layer having a uniform thickness can be formed by a simple method.

[Battery]
A plurality of lithium ion secondary batteries of the present invention can be connected to form an assembled battery. Specifically, at least two or more are used, and are configured by serialization, parallelization, or both. Capacitance and voltage can be freely adjusted by paralleling in series. Further, by using the lithium ion secondary battery of the present invention, an assembled battery having excellent cycle durability and high long-term reliability can be provided. In the assembled battery of the present invention, the non-bipolar lithium ion secondary battery and the bipolar lithium ion secondary battery of the present invention are used, and a plurality of them are connected in series, in parallel, or in series and in parallel. An assembled battery can also be configured in combination.

  FIG. 4 is an external view of a typical embodiment of the assembled battery according to the present invention. 4A is a plan view of the assembled battery, FIG. 4B is a front view of the assembled battery, and FIG. 4C is a side view of the assembled battery.

  As shown in FIG. 4, in the assembled battery 300 according to the present invention, first, a plurality of lithium ion secondary batteries of the present invention are connected in series or in parallel to form a small assembled battery 250 that can be attached and detached. Yes. The assembled battery 300 is configured by further connecting a plurality of these detachable small assembled batteries 250 in series or in parallel. With such a configuration, the assembled battery 300 having a large capacity and a large output suitable for a vehicle driving power source and an auxiliary power source that require high energy density and high power density can be obtained. The small assembled batteries 250 that can be attached and detached are connected to each other using an electrical connection means such as a bus bar, and are stacked in a plurality of stages using a connection jig 310. How many non-bipolar or bipolar lithium ion secondary batteries are connected to produce the assembled battery 250, and how many assembled batteries 250 are stacked to produce the assembled battery 300 are mounted. What is necessary is just to determine according to the battery capacity and output of a vehicle (electric vehicle).

[vehicle]
The lithium ion secondary battery and the assembled battery of the present invention can be used as a power source for driving a vehicle. The secondary battery or the assembled battery of the present invention may be, for example, a hybrid vehicle, a fuel cell vehicle, an electric vehicle (all are four-wheeled vehicles (commercial vehicles such as passenger cars, trucks, buses, light vehicles, etc.) as well as two-wheeled vehicles. (Including motorcycles and tricycles). Thereby, a long-life and highly reliable automobile can be provided. However, the application is not limited to automobiles. For example, if it is another vehicle, it can be applied to various power sources for moving bodies such as trains, and it can be used for mounting uninterruptible power supplies and the like. It can also be used as a power source.

  FIG. 5 is a conceptual diagram of an electric vehicle 400 equipped with the assembled battery 300 of the present invention. As shown in FIG. 5, in order to mount the assembled battery 300 on the electric vehicle 400, the battery pack 300 is mounted under the seat at the center of the vehicle body of the electric vehicle 400. This is because if it is installed under the seat, the interior space and the trunk room can be widened. The place where the assembled battery 300 is mounted is not limited to the position under the seat, but may be a lower part of the rear trunk room or an engine room in front of the vehicle. The electric vehicle 400 using the assembled battery 300 as described above has excellent durability and can exhibit a sufficient output even when used for a long time.

  The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments, and various modifications, omissions, and additions can be made by those skilled in the art.

  Hereinafter, although the effect by this invention is demonstrated using an Example and a comparative example, the technical scope of this invention is not limited to these Examples.

<Example 1-1>
(Preparation of negative electrode)
A circular nickel foil (thickness 20 μm, diameter 16 mm) was prepared as a negative electrode current collector. A negative electrode active material layer (thickness: 100 nm) made of P-type silicon (p-Si) is formed on one surface of the negative electrode current collector by RF sputtering using boron-doped silicon as a target, Produced. Sputtering was performed under the condition of a degree of vacuum of 3.0 × 10 ⁻³ Pa without heating the current collector. Secondary ion mass spectrometry showed that the amount of boron in the negative electrode active material layer was about 1 × 10 ⁻¹⁸ atoms / cm ³ .

(Preparation of electrolyte)
An electrolyte solution was prepared by adding LiPF ₆ as an electrolyte salt and Mg (ClO ₄ ) ₂ as an additive to an equal volume mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) as an organic solvent. . At this time, the concentration of LiPF ₆ in the electrolytic solution is 1 mol / L, to adjust the amount of the additive as Li / Mg molar ratio is 10.

(Production of battery)
The electrolyte layer prepared above was immersed in a separately prepared polyolefin separator (thickness 20 μm) to prepare an electrolyte layer. The negative electrode produced above and a positive electrode made of a separately prepared circular metal lithium foil (thickness 250 μm, diameter 16 mm, affixed to a stainless steel disk) so that the negative electrode active material layer faces the positive electrode side The electrolyte layer produced above was sandwiched. The laminate thus obtained was placed inside a battery can (made of SUS304) and sealed to complete a lithium ion secondary battery.

<Example 1-2>
A lithium ion secondary battery was fabricated in the same manner as in Example 1-1 described above, except that Mg (PF ₆ ) ₂ was used as an additive.

<Example 1-3>
By using the same method as in Example 1-1 described above except that Zn (ClO ₄ ) ₂ was used as the additive and the additive amount was adjusted so that the Li / Zn molar ratio was 10. A secondary battery was produced.

<Example 1-4>
Lithium ions were obtained in the same manner as in Example 1-1, except that Al (ClO ₄ ) ₂ was used as the additive and the additive amount was adjusted so that the Li / Al molar ratio was 10. A secondary battery was produced.

<Example 1-5>
Lithium ions were obtained in the same manner as in Example 1-1, except that Sn (ClO ₄ ) ₂ was used as the additive and the additive amount was adjusted so that the Li / Sn molar ratio was 10. A secondary battery was produced.

<Comparative Example 1-1>
A lithium ion secondary battery was produced in the same manner as in Example 1-1 described above, except that no additive was added to the electrolytic solution.

<Comparative Example 1-2>
Except that Ca (ClO ₄ ) ₂ was used as an additive and the additive amount was adjusted so that the Li / Ca molar ratio was 10, lithium ions were obtained in the same manner as in Example 1-1 described above. A secondary battery was produced. Ca (calcium) is a metal element that does not alloy with lithium.

<Charge / discharge cycle test (1)>
The charge / discharge cycle test (1) was performed on the lithium ion secondary batteries prepared in Examples 1-1 to 1-5 and Comparative Examples 1-1 and 1-2.

  Specifically, charging was performed until the battery voltage reached 0.01 V under a constant current constant voltage condition of 1 C rate, and discharging was performed until the battery voltage reached 2 V under a constant current condition of 1 C rate. This charge / discharge cycle was repeated 90 cycles, and the subsequent discharge capacity was measured. The results are shown in Table 1 below. In Comparative Example 1-2, since the discharge capacity was lower than 100 mAh / g at the end of 50 cycles, the subsequent charge / discharge was not performed.

  From the results shown in Table 1, the use of doped silicon as a negative electrode active material and the use of a liquid electrolyte in which ions of an element that can be alloyed with lithium are dissolved in an organic solvent results in a high discharge capacity after 90 cycles. Can be maintained. That is, according to the present invention, a means capable of effectively improving cycle durability in a lithium ion secondary battery can be provided.

<Example 2>
A lithium ion secondary battery was fabricated in the same manner as in Example 1-1 described above except that the thickness of the negative electrode active material layer made of P-type silicon (p-Si) was 1000 nm.

<Comparative example 2>
A lithium ion secondary battery was produced in the same manner as in Example 2 except that no additive was added to the electrolytic solution.

<Charge / discharge cycle test (2)>
About the lithium ion secondary battery produced in said Example 2 and Comparative Example 2, the charging / discharging cycle test (2) was done by the method similar to the said charging / discharging cycle test (1). However, in the test (2), the charge / discharge cycle was repeated 50 cycles, and the discharge capacity after 5 cycles and after 50 cycles was measured. The results are shown in Table 2 below.

  In general, when silicon (Si) is used as the negative electrode active material, the deterioration of the active material due to expansion and contraction during charge / discharge becomes more prominent as the size of the active material increases (thicker). In test (2), the thickness of the active material layer was set to 10 times that of Example 1, and a charge / discharge cycle test was performed under conditions where deterioration due to expansion and contraction is more likely to occur.

  As a result, from the results shown in Table 2, the discharge capacity after 5 cycles and after 50 cycles can be obtained by adopting the configuration of the present invention even under conditions where the active material is more likely to deteriorate (the active material layer is thick). It is shown that it can be controlled to a high value.

<Various analyzes>
Various analyzes were performed on the negative electrode active material layers of Example 1-1 and Comparative Example 1-1 after completion of the above-described charge / discharge cycle test (1).

(SEM observation)
The surface state of the negative electrode active material layer was observed using a scanning electron microscope (SEM). Specifically, SEM (VE-7800) manufactured by Keyence Corporation was used, and the acceleration voltage of the electron beam was set to 2 kV, and the surface of the negative electrode active material layer was observed.

  The result of the above analysis is shown in FIG. Fig.6 (a) is the photograph which observed the surface state of the negative electrode active material layer of the battery produced by the comparative example 1-1. FIG.6 (b) is the photograph which observed the surface state of the negative electrode active material layer of the battery produced in Example 1-1. For each of FIGS. 6A and 6B, the upper photo was taken at 500x magnification, and the lower photo was taken at 3300x magnification.

  From the results shown in FIG. 6 (a), the surface of the p-Si thin film, which is the negative electrode active material layer of Comparative Example 1-1, is finely cracked, and the deterioration of the active material due to expansion / contraction during charge / discharge is significant. It can be seen that it is expressed. On the other hand, the surface of the p-Si thin film, which is the negative electrode active material layer of Example 1-1, maintained a smooth state despite the charge / discharge cycle test. This is considered to be the reason why a high discharge capacity was maintained even after 90 cycles as compared with the comparative example.

(TEM observation)
The cross-sectional state near the surface of the negative electrode active material layer was observed using a transmission electron microscope (TEM). In addition, the said observation was similarly performed beforehand about the negative electrode active material layer before performing a charging / discharging cycle test. Specifically, first, carbon and platinum were each formed by sputtering to a thickness of 10 nm on each negative electrode active material layer (p-Si thin film), and then covered with a resin to form a protective layer. . Next, the obtained laminate was made into an ultrathin film by using a focused ion beam processing apparatus (manufactured by Seiko Instruments Inc., SMI19200) with an acceleration voltage of 30 kV to prepare a measurement sample. About the obtained measurement sample, TEM (Tecnai G2 F20) made from FEI company was used, the acceleration voltage was 200 kV, and the cross-sectional state of the surface vicinity of a negative electrode active material layer was observed.

  The results of the above analysis are shown in FIG. Fig.7 (a) is the photograph which observed the cross-sectional state of the negative electrode active material layer before performing a charging / discharging cycle test. FIG.7 (b) is the photograph which observed the cross-sectional state of the negative electrode active material layer after the charging / discharging cycle test of the battery produced by the comparative example 1-1. FIG.7 (c) is the photograph which observed the cross-sectional state of the negative electrode active material layer after the charging / discharging cycle test of the battery produced in Example 1-1.

  From the results shown in FIG. 7A, it can be seen that the p-Si thin film as the negative electrode active material layer was formed as a uniform and flat continuous body before the charge / discharge cycle test. Then, from the comparison between FIG. 7B and FIG. 7A, in Comparative Example 1-1, vacancies exist at the interface between the current collector and the active material layer due to the charge / discharge cycle, and p -It turns out that the negative electrode active material layer which consists of Si thin films is in the state disturbed violently. On the other hand, in Example 1-1, even after the charge / discharge cycle, the generation of vacancies at the interface between the current collector and the active material layer was slight, and the surface of the active material layer was relatively It can be seen that the flat state is maintained.

(AES analysis)
The element distribution in the depth direction from the surface of the negative electrode active material layer was evaluated by Auger electron spectroscopy (AES method). Specifically, the elemental distribution in the depth direction from the surface of the negative electrode active material layer after the end of the charge / discharge cycle test was evaluated using a field emission Auger electron spectrometer (Model-680, manufactured by PHI). . At this time, the analysis was performed with the electron beam acceleration voltage of 10 kV, the ion gun acceleration voltage of 3 kV, and the sputtering rate of 19 nm / min.

  The results of the above analysis are shown in FIG. Fig.8 (a) is an evaluation result about the negative electrode active material layer after the charging / discharging cycle test of the battery produced by the comparative example 1-1. FIG.8 (b) is an evaluation result about the negative electrode active material layer after the charging / discharging cycle test of the battery produced in Example 1-1.

  From the results shown in FIG. 8A, it can be seen that in Comparative Example 1-1, the proportion of silicon in the p-Si thin film constituting the negative electrode active material layer after the charge / discharge cycle decreases as the depth increases. This is consistent with the results of TEM observation described above, and indicates that silicon is lost due to deterioration due to charge and discharge. On the other hand, from the results shown in FIG. 8B, in Example 1-1, no significant change was observed in the ratio of silicon in the depth direction even after the charge / discharge cycle. This indicates that in Example 1-1, the negative electrode active material layer (p-Si thin film) was relatively less deteriorated due to charging and discharging.

(XPS analysis)
As shown in Table 1 above, when Mg (ClO ₄ ) ₂ was used as an additive (Example 1-1), Mg (PF ₆ ) ₂ was used as an additive (Example 1-2). ), The discharge capacity after 90 cycles was maintained at a higher value. In order to search for the cause, for the batteries produced in Example 1-1 and Example 1-2 after the end of the charge / discharge cycle test, the bonding state of each element on the surface of the negative electrode active material layer was determined by X-ray photoelectron spectroscopy. Evaluation was performed by an analytical method (XPS method). Specifically, the combined state of each element on the surface of the negative electrode active material layer after the charge / discharge cycle test was evaluated using a composite surface analyzer (manufactured by PHI, ESCA-5600). At this time, monochromatic Al-Kα was used as the X-ray source, the photoelectron extraction angle was 45 degrees, and the measurement depth was 4 nm.

Of the analysis results obtained by the XPS method, the state analysis result of magnesium 1s electrons (Mg1s) is shown in FIG. According to the results shown in FIG. 9, the graph corresponding to Example 1-2 (additive = Mg (PF ₆ ) ₂ ) corresponds to Example 1-1 (additive = Mg (ClO ₄ ) ₂ ). Compared with, it has shifted to the high energy side. This indicates that Mg is more bonded to an element having a high electron-withdrawing property such as F on the surface of the negative electrode active material layer (p-Si thin film) of the battery manufactured in Example 1-2. As a result, it is considered that the difference in discharge capacity as shown in Table 1 may have been brought about. Therefore, an alloy with lithium containing no fluorine as a counter ion of the cation of the metal element capable of anions (eg, ClO ₄ ^- ions) By adopting, believed to be effective in improving the cycle durability.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic cross-sectional view schematically showing the overall structure of a laminated lithium ion secondary battery that is a typical embodiment of a lithium ion secondary battery of the present invention and is not a bipolar type. It is the schematic sectional drawing which represented typically the whole structure of the bipolar | stacked laminated lithium ion secondary battery which is other typical embodiment of the lithium ion secondary battery of this invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view illustrating an appearance of a stacked flat battery which is a typical embodiment of a lithium ion secondary battery according to the present invention. It is an external view of typical embodiment of the assembled battery which concerns on this invention. 4A is a plan view of the assembled battery, FIG. 4B is a front view of the assembled battery, and FIG. 4C is a side view of the assembled battery. It is a conceptual diagram of the electric vehicle 400 carrying the assembled battery 300 of this invention. It is a photograph which shows the analysis result of SEM observation in an Example. Fig.6 (a) is the photograph which observed the surface state of the negative electrode active material layer of the battery produced by the comparative example 1-1. FIG.6 (b) is the photograph which observed the surface state of the negative electrode active material layer of the battery produced in Example 1-1. It is a photograph which shows the analysis result of TEM observation in an Example. Fig.7 (a) is the photograph which observed the cross-sectional state of the negative electrode active material layer before performing a charging / discharging cycle test. FIG.7 (b) is the photograph which observed the cross-sectional state of the negative electrode active material layer after the charging / discharging cycle test of the battery produced by the comparative example 1-1. FIG.7 (c) is the photograph which observed the cross-sectional state of the negative electrode active material layer after the charging / discharging cycle test of the battery produced in Example 1-1. It is a graph which shows the result of AES analysis in an example. Fig.8 (a) is an evaluation result about the negative electrode active material layer after the charging / discharging cycle test of the battery produced by the comparative example 1-1. FIG.8 (b) is an evaluation result about the negative electrode active material layer after the charging / discharging cycle test of the battery produced in Example 1-1. It is a graph which shows the state analysis result of the 1s electron (Mg1s) of magnesium among the analysis results by the XPS method in an Example.

Explanation of symbols

10 Lithium ion secondary battery,
11 positive electrode current collector,
11a Outermost layer positive electrode current collector,
12, 32 positive electrode active material layer,
13, 35 electrolyte layer,
14 negative electrode current collector,
15, 33 negative electrode active material layer,
16, 36 cell layer,
17, 37, 57 battery element,
18, 38, 58 positive electrode tab,
19, 39, 59 negative electrode tab,
20, 40 Positive terminal lead,
21, 41 Negative terminal lead,
22, 42, 52 Laminated film,
30 Bipolar lithium ion secondary battery,
31 current collector,
31a positive electrode side outermost layer current collector,
31b negative electrode side outermost layer current collector,
34 Bipolar electrode,
34a, 34b The electrode located in the outermost layer,
43 Sealing part (insulating layer),
50 lithium ion secondary battery,
250 small battery pack,
300 battery packs,
310 connection jig,
400 Electric car.

Claims (10)

A positive electrode in which a positive electrode active material layer containing a positive electrode active material is formed on the surface of a current collector, an electrolyte layer containing an electrolyte, and a negative electrode active material layer containing a negative electrode active material on the surface of the current collector A negative electrode is a lithium ion secondary battery including a battery element having at least one single battery layer laminated in this order so that the positive electrode active material layer and the negative electrode active material layer face each other,
The electrolyte includes an electrolytic solution in which a cation of a metal element that can be alloyed with lithium is dissolved in an organic solvent,
A lithium ion secondary battery in which the negative electrode active material contains silicon doped with one or more doping elements selected from the group consisting of group 13 or group 15 elements in the periodic table.   The metal element cation that can be alloyed with lithium is a cation of one or more elements selected from the group consisting of magnesium, aluminum, tin, zinc, silver, lead, germanium, indium, and vanadium. The lithium ion secondary battery according to claim 1.   The lithium according to claim 1 or 2, wherein the doping element is one or more elements selected from the group consisting of boron, aluminum, gallium, indium, nitrogen, phosphorus, arsenic, antimony, and bismuth. Ion secondary battery.   The lithium ion secondary according to any one of claims 1 to 3, wherein the negative electrode is formed by depositing the negative electrode active material on a surface of a current collector by a vapor deposition process. battery.   The lithium ion secondary battery according to claim 4, wherein a thickness of the active material layer in the stacking direction is 100 nm to 100 μm.   The negative electrode active material is a particulate active material having an average particle diameter of 1 nm to 100 µm, and the negative electrode active material layer includes the particulate active material, a binder, and a conductive additive. 2. The lithium ion secondary battery according to item 1. The electrolyte solution contains Cl ⁻ , Br ⁻ , I ⁻ , BF ₄ ⁻ , PF ₆ ⁻ , CF ₃ SO ₃ ⁻ , ClO ₄ ⁻ , CF ₃ as counter ions of a cation of a metal element that can be alloyed with lithium. _{^{CO 2 -, AsF 6 -,}} SbF 6 -, AlCl 4 -, N (CF 3 SO 2) 2 -, and _{N (CF 3 CF 2 SO 2} ) 2 - 1 kind or 2 kinds selected from the group consisting of The lithium ion secondary battery according to any one of claims 1 to 6, wherein the above anions are dissolved.   The organic solvent is propylene carbonate, ethylene carbonate, butylene carbonate, vinylene carbonate, γ-butyrolactone, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, 1,2-dimethoxyethane, dimethyl sulfoxide, 1,3-dioxolane or a derivative thereof, Formamide, dimethylformamide, acetonitrile, nitromethane, methyl formate, methyl acetate, methyl propionate, ethyl propionate, phosphate triester, trimethoxymethane, diethyl ether, 1,3-propane sultone, sulfolane, 3-methyl-2- 2. One or more selected from the group consisting of oxazolidinone, tetrahydrofuran or derivatives thereof, and 1,2-diethoxyethane. Lithium-ion secondary battery according to any one of 7.   The assembled battery using the lithium ion secondary battery of any one of Claims 1-8.   The vehicle which mounts the lithium ion secondary battery of any one of Claims 1-8, or the assembled battery of Claim 9 as a drive power supply.