JP2009146712A - Negative electrode structure, lithium ion secondary battery, and manufacturing method for negative electrode structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lithium ion secondary battery capable of preventing the whole battery from expanding by expansion of a negative electrode active material layer upon charging without lessening charging capacity. <P>SOLUTION: An insulating layer 12 having a plurality of openings is arranged on a collector 11, and the collector 11 and the negative electrode active material layer 13 are electrically connected with each other in the vicinity of the opening via a conductive plug 16. A recessed section is formed on a surface opposite to a connection section. A separator 3 and a positive electrode 2 are arranged on the negative electrode active material layer 13. In the negative electrode active material layer 13, lithium ions are localized in the vicinity of the opening upon charging, and a localized section of the lithium ions is expanded. Thus, expansion of the whole battery is prevented by making the expansion to be absorbed with the recessed section on the negative electrode active material layer 13. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a negative electrode structure used for a lithium ion secondary battery, a lithium ion secondary battery, and a method for producing the negative electrode structure.

  The negative electrode of the lithium ion secondary battery undergoes volume change because lithium (Li) is stored and released with respect to the negative electrode active material during charge and discharge.

  Conventionally, in order to avoid the influence due to the volume change of such a negative electrode active material, a plurality of columnar convex portions are provided on a current collector made of a metal that does not alloy with lithium, and the negative electrode active material is provided only on the convex portions. There is a technology formed (Patent Document 1).

According to this technique, since the negative electrode active material formed in a columnar shape exists only on the convex portion of the current collector, even if the volume of the negative electrode active material changes, the volume change can be absorbed by the surrounding space. It is supposed to be possible.
JP 2007-012421 A

  However, in the conventional technique, since the negative electrode active material is formed in a columnar shape with a space between them, there is a problem that the amount of active material is reduced and the charging capacity is reduced by the amount of space formed around the column.

  The objective of this invention is providing the negative electrode structure which can suppress the influence of the volume change of the negative electrode active material at the time of charging / discharging, without accompanying the reduction of structural charge capacity. Moreover, it is providing the lithium ion secondary battery which suppressed the volume change at the time of charging / discharging by using this negative electrode structure. Furthermore, it is providing the manufacturing method of the negative electrode structure which suppressed the volume change at the time of charging / discharging.

  In order to solve the above problems, a negative electrode structure of the present invention includes a current collector, an insulating layer provided on the current collector and having a plurality of openings, and a negative electrode active material layer formed thereon And have. The negative electrode active material layer is electrically connected to the current collector at the opening, and is integrally provided up to the insulating layer.

  Moreover, the lithium ion secondary battery of this invention for solving the said subject has a negative electrode using the said negative electrode structure, has a separator which touches this negative electrode, and a positive electrode which touches a separator.

  Moreover, the manufacturing method of the negative electrode structure of this invention for solving the said subject forms an insulating layer on a collector, and forms the several opening part which a collector exposes to the insulating layer. Thereafter, a negative electrode active material layer is formed on the insulating layer including the inside of the opening.

  According to the negative electrode structure of the present invention, it is possible to localize lithium ions at the time of charge and discharge and to change the volume of the negative electrode active material only to that portion. Therefore, it is possible to suppress the volume change from affecting the entire negative electrode active material.

  According to the lithium ion secondary battery of the present invention, lithium ions during charge / discharge can be localized in the negative electrode, and the volume change of the negative electrode active material can be limited to that portion. Therefore, the volume change to the whole battery is suppressed.

  According to the method for producing a negative electrode structure of the present invention, a structure for localizing lithium ions during charge / discharge can be easily formed.

  The best mode for carrying out the present invention will be described below with reference to the drawings. In the present invention and the description, unless otherwise specified, when the insulating layer is provided in direct contact with the insulating layer, the insulating layer is separated from the insulating layer or the insulating layer via another member. Includes both of the above cases.

(Embodiment 1)
FIG. 1 is a cross-sectional view showing the structure of a lithium ion secondary battery to which the present invention is applied.

  The lithium ion secondary battery includes a negative electrode 1, a positive electrode 2, and a separator 3 sandwiched between the negative electrode 1 and the positive electrode 2. The negative electrode active material layer in the negative electrode 1, the positive electrode active material layer in the positive electrode 2, and the separator 3 are impregnated with an electrolytic solution (electrolyte) (not shown). Here, a negative electrode structure to which the present invention is applied is used for the negative electrode 1. This negative electrode structure will be described later.

  The positive electrode 2 includes a current collector 21 and a positive electrode active material layer 22.

  The current collector 21 of the positive electrode is made of a metal foil (or thin plate) such as copper, aluminium, nickel, stainless steel, for example.

The positive electrode active material layer 22 has a composition that occludes ions during discharging and releases ions during charging. A preferable example is a lithium-transition metal composite oxide that is a composite oxide of a transition metal and lithium. Specifically, as an active material, for example, spinel manganese-based (LiMn ₂ O ₄ ), ternary layered oxide-based (Li (Mn, Co, Ni) O ₂ ), olivine-based (LiFePO ₄ ), silicate It is preferable to use a system (Li ₂ FeSiO ₄ ), a layered oxide system (Li (Co and / or Ni) O ₂ ), or the like. The positive electrode active material layer 22 is obtained by forming these active materials into a powder form, mixing with a base material (binder) to form a slurry, and applying this to a metal foil of a current collector, followed by drying or press forming. . As the substrate, for example, a fluororesin such as polyvinylidene fluoride (PVDF), hexafluoropropylene (HFP), polytetrafluoroethylene (PTEF), or a copolymer of these fluororesins can be used.

  The separator 3 is made of a polyolefin-based material. Examples thereof include polyolefin resins such as a microporous polyethylene film, a microporous polypropylene film, and a microporous ethylene-propylene copolymer film, and porous films or nonwoven fabrics such as aramid, polyimide, and cellulose, and laminates thereof. The separator 3 is impregnated with an electrolyte solution.

For example, a non-aqueous electrolyte is used as the electrolyte. The nonaqueous electrolytic solution is prepared by dissolving an electrolyte in a nonaqueous solvent. Examples of the non-aqueous solvent include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), γ-butyrolactone (γ -BL), sulfolane, acetonitrile, 1,2-dimethoxyethane, 1,3-dimethoxypropane, dimethyl ether, tetrahydrofuran (THF), 2-methyltetrahydrofuran and the like. Nonaqueous solvents may be used alone or in combination of two or more. Examples of the electrolyte include lithium perchlorate (LiClO ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium boron tetrafluoride (LiBF ₄ ), lithium hexafluoroarsenide (LiAsF ₆ ), and lithium trifluoromethanesulfonate. Examples include lithium salts such as (LiCF ₃ SO ₃ ) and bistrifluoromethylsulfonylimide lithium [LiN (CF ₃ SO ₃ ) ₂ ]. The amount of the electrolyte dissolved in the non-aqueous solvent is usually about 0.2 mol / L to 2 mol / L.

  Examples of the polymer that holds the nonaqueous electrolytic solution include a polyethylene oxide derivative, a polypropylene oxide derivative, a polymer containing the derivative, a copolymer of vinylidene fluoride (VdF) and hexafluoropropylene (HFP), and the like.

  In addition, if the material of these positive electrodes 2 and the separator 3 are used for the lithium ion secondary battery, when implementing this invention, it will not specifically limit. Therefore, materials other than the exemplified materials can be used.

  On the other hand, the negative electrode 1 is an application of the negative electrode structure of the present invention.

  FIG. 2 is a perspective view for explaining the structure of the negative electrode 1 in this embodiment, and FIG. 3 is a sectional view of the same.

  The negative electrode 1 includes a current collector 11, an insulating layer 12, and a negative electrode active material layer 13. The current collector 11 and the negative electrode active material layer 13 are electrically connected only at a plurality of openings 15 provided in the insulating layer 12. A conductive plug 16 bonded to the current collector 11 is formed in the opening 15. The negative electrode active material layer 13 is bonded to the conductive plug 16 and is electrically connected to the current collector 11.

  The conductive plug 16 is formed to be thinner than the insulating layer 12. Therefore, the negative electrode active material layer 13 has a shape in which the surface opposite to the surface bonded to the conductive plug is recessed at the position where the opening 15 is present (represented recess 17 in the figure). That is, when viewed in cross section, the concave portion 17 is formed on the surface side in contact with the separator 3.

  However, in the negative electrode active material layer 13, a portion in the opening 15 and a portion on the insulating layer 12 are integrally formed. Therefore, if the negative electrode active material layer 13 falls too deeply into the opening 15, it is not preferable because the negative electrode active material layer 13 is cut at the step of the opening 15. Therefore, the depth of the opening 15 (that is, the thickness of the insulating layer 12) and the thickness of the conductive plug 16 are adjusted so that the negative electrode active material layer 13 is not cut at the step of the opening 15.

  Specifically, the depth to the conductive plug 16 in the opening 15 is determined when the conductive film 51 at the time of forming the conductive plug 16 remains on the insulating layer 12 (described later in detail) (the thickness of the insulating layer 12). Thickness + thickness of conductive film 51) −thickness of conductive film 51. Therefore, it is preferable that the thickness of the insulating layer 12 <the thickness of the negative electrode active material layer 13. Accordingly, since the thickness of the negative electrode active material layer 13 is sufficient, the negative electrode active material layer 13 in which the portion in the opening 15 and the portion on the insulating layer 12 are integrated can be easily formed.

  Here, the effect | action of this negative electrode 1 (negative electrode structure) is demonstrated. FIG. 4 is an explanatory diagram for explaining the operation of the negative electrode 1 having this structure.

  In the first embodiment, the electrical connection between the negative electrode active material layer 13 and the current collector 11 is only the opening 15. For this reason, as shown in FIG. 4A, at the time of charging, lithium ions attracted to electrons from the current collector 11 are localized in the portion of the opening 15 and the lithium ion concentration in that portion becomes high. . For this reason, the negative electrode active material layer 13 expands only in the part where the lithium ions are localized, and there is almost no volume change in the other part. Moreover, in the first embodiment, the negative electrode active material layer 13 falls into the opening 15 and the side in contact with the separator 3 is recessed. For this reason, when lithium ions are localized in the opening 15 and the volume of the portion expands, the recess 17 absorbs the expansion. For this reason, the volume change as a whole battery hardly arises.

  In addition, since the area where the negative electrode active material layer 13 is in contact with the current collector 11 (here, the conductive plug 16) is small, the Hall Petch rule works and suppresses the pulverization of the active material in the negative electrode active material layer 13. In addition, the peeling between the negative electrode active material layer 13 and the current collector 11 is suppressed. Therefore, it is possible to improve the charge / discharge cycle characteristics of the lithium ion secondary battery by adopting such a connection structure.

  Further, in such a structure, a current flows through a portion where the negative electrode active material layer 13 and the current collector 11 (here, the conductive plug 16) are in contact. For this reason, it is easy to be destroyed when an overcurrent flows during charging / discharging or cycling. That is, when an overcurrent flows, this connection portion (mainly the conductive plug portion here) is destroyed, a kind of fuse function works, and no more current flows. Therefore, by taking such a structure, it is possible to prevent overcurrent in the lithium ion secondary battery.

Specifically, for example, the negative electrode active material layer 13 is made of pure silicon having a thickness of 100 (nm) (specific resistance ρ is 1 (kΩ · cm) or less), and the opening diameter of the opening 15 is the fuse function. Is 100 (nm), and the current collector 11 and the conductive plug 16 are assumed to be copper. In this case, the connection resistance at one connection portion between the negative electrode active material layer 13 and the conductive plug 16 is about 1.3 × 10 12 (Ω). Therefore, the withstand current value at one connection portion can be expressed as 1.4 × 10 ⁻⁷ / √t (A) (where t is seconds). Here, the withstand current value when t is 1 (sec) is 1.4 × 10 ⁻⁷ (A). Therefore, when a current larger than this flows in one connection portion between the negative electrode active material layer 13 and the conductive plug 16, that portion is fused.

  The above-described conditions for explaining the fuse function are merely examples. When actually manufacturing a lithium ion secondary battery, the size of each opening 15 and the number of openings 15 may be appropriately determined according to the current required to flow the entire battery. For example, when manufacturing a battery that requires a large current, the size of the opening 15 is increased or the number of the openings 15 is increased. On the other hand, if the charging / discharging current in the normal state is small, the size of the opening 15 is reduced or the number thereof is reduced so that even if an overcurrent of a slightly larger amount than that flows, it is blown immediately. Good.

  On the other hand, as shown in FIG. 4B, when the negative electrode active material layer is in contact with the entire surface of the current collector, lithium ions enter the entire negative electrode active material layer during charging. For this reason, the whole negative electrode active material layer expand | swells.

  The volume change of the negative electrode active material layer varies depending on the material. For example, in recent years, Si (4000 mAh / g) and Sn (990 mAh / g), which have been attracting attention as active materials exhibiting a high charge capacity, exhibit a volume change of about 400 to 600% due to charge and discharge. For this reason, when the negative electrode active material layer is in contact with the entire surface of the current collector, the volume change during charging / discharging causes pulverization of the active material particles, separation from the current collector, destabilization of the electrode structure, etc. Can happen.

  However, in the first embodiment, as described above, the part in which such volume change occurs is local and only occurs in a large number of openings 15. There are very few.

  Next, a preferable negative electrode material used in the present embodiment will be described.

  First, the current collector 11 is a substance having a composition that does not alloy with lithium. For example, there is no particular limitation as long as it can be used as a negative electrode side current collector of a lithium ion secondary battery, such as nickel (Ni), copper (Cu), and aluminum (Al). Further, a silicon single crystal substrate or a silicon polycrystalline substrate to which conductivity is imparted can also be used.

  The thickness is preferably 5 μm or more and 500 μm or less. By using the current collector 11 having such a thickness, the battery unit cell structure can be formed very thin.

  Further, it is preferable that the surface is polished by a mechanical, electrical, chemical, or a combination thereof, and the surface roughness Ra is 100 nm or less. By reducing the surface roughness in this way, the adhesion of the insulating layer 12 is improved.

  Next, the conductive plug 16 is made of a material having a composition that does not alloy with lithium like the current collector. For example, a substance having the same composition as that of the current collector 11 is preferable, and metals such as nickel (Ni), copper (Cu), aluminum (Al), silicon single crystal, amorphous silicon, silicon polycrystal, and the like can be used. .

  As a method for forming such a conductive plug 16, for example, a general device manufacturing method in the semiconductor field can be used. Specifically, after the formation of the insulating layer 12 having a plurality of openings 15 to be described later, for example, in the case of a metal conductive plug 16, an evaporation method using resistance heating, an electron beam, an ion beam, or the like is used. The conventional vapor deposition method, sputter vapor deposition method, molecular beam epitaxy method, pulse laser vapor deposition method, MOCVD method, electroless plating method, electroplating method and the like can be used.

  In the figure, there is a thin film when the conductive plug is formed also on the insulating layer 12 (indicated by reference numeral 51). This is because the electrical connection between the opening 15 and the insulating layer 12 is broken. If so, it does not affect the battery performance at all, so it can be left as it is. However, when the conductive film formed as the conductive plug is electrically connected from the opening 15 to the insulating layer 12 after the conductive plug is formed, the conductive plug is formed on the insulating layer 12. The thin film of time is removed. In this regard, if the electroplating method is used, the current collector portion exposed from the opening 15 becomes a seed, so that a conductive film for the conductive plug 16 is formed only on that portion, and the conductive layer 16 is formed on the insulating layer 12. Is not formed.

  Similarly, when silicon such as single crystal, amorphous, or polycrystalline is used, in addition to these manufacturing methods, a CVD method or the like can also be used.

  The material state of the conductive plug 16 formed by these is not particularly limited, and may be in any state as long as it has conductivity.

  Next, the insulating layer 12 is preferably made of an organic material, an inorganic material having a high insulation property and a high chemical resistance, or a mixture or composite of these in combination. In particular, a photosensitive polyimide, a photosensitive organic resist, or an inorganic resist is used. Desirable above.

  In the case of these photosensitive materials, after applying these photosensitive materials, they are exposed and cured (baked) by photolithography using a mask, thereby forming the opening 15 having an arbitrary size and an arbitrary shape. It is possible. Further, when ultraviolet rays, lasers, or electron beams are used, the shape of the opening may be formed by direct drawing without using a mask after applying the photosensitive material. The formation method of the insulating layer itself may be a coating method such as spin coating.

  The average thickness of the insulating layer 12 is the depth from the surface of the insulating layer to the surface of the conductive plug 16 in the opening 15 (from the surface when the conductive plug-based political thin film is directly on the insulating layer 12). Is less than the average thickness of the negative electrode active material layer 13. Thereby, as described above, the negative electrode active material layer 13 can be easily integrated without being interrupted in the opening 15 and on the insulating layer 12.

The average size of the openings 15 is preferably 10 nm to 2 μm, for example. The lower limit value of 10 nm may be less than or equal to this value as long as the negative electrode active material layer 13 and the current collector 11 can be electrically connected through the opening 15 of the insulating layer 12. However, considering the manufacturing method, it is unavoidable to be about 10 nm at present. It should be noted that the thickness is preferably 100 nm or more from the viewpoint of effectively operating the fuse function. This is because if the thickness is 100 nm or less, the fuse function is too effective when a large battery such as an automobile is manufactured, and a large current may not be taken out. However, if it is a small battery, it may be less than 100 nm, and may be determined by the current desired to function as a fuse function. On the other hand, if the upper limit is 2 μm or less, even if the negative electrode active material layer 13 expands during charging / discharging, there is little influence on the surroundings. This is because the negative electrode active material layer 13 expands due to the localization of lithium ions, as already described, and therefore hardly expands in the lateral direction in the structure of this embodiment. For example, when the size of the opening is a circle having a diameter of 2 μm and the distance between the openings (the distance between the edges of adjacent openings) is 1 μm, the area of the opening and the area of the portion without the opening The ratio is about 3.14 (μm ² ): about 5.86 (μm ² ), which is about 1.87 times different. For this reason, as will be described later, although the ratio of the opening area to the area of the portion without the opening is almost twice different, the negative electrode active material layer 13 expands on the opening, although it depends on the distance between the openings. Even if it does, expansion does not spread to other parts.

The distance between adjacent openings is preferably such that the distance between the edges of adjacent openings is 1 μm or more. For example, when silicon is used as the negative electrode active material layer, the diffusion coefficient of lithium in silicon is said to be about 10 ⁻¹⁰ to 10 ⁻¹² cm ² / sec. For example, from the larger value of 10 ⁻¹⁰ cm ² / sec, even if charging is continued for 10 hours, the diffusion amount is about 0.036 μm ² . Accordingly, if the adjacent openings are separated by 1 μm or more, even if the negative electrode active material layer 13 expands, the expanded portion of the negative electrode active material layer 13 is pressed between the adjacent openings and the entire negative electrode is raised. There is no such thing. In addition, since such a value changes also with the member to be used etc., it should just adjust suitably and is not limited.

  There is no particular limitation on the upper limit value of the interval between adjacent openings. However, the number of openings is set based on the amount of current allowed for the battery (if the number of openings is large, a large amount of current can flow), and the number of openings is arranged with an interval of 1 μm or more. You can do it.

  In addition, the shape (pattern) of the opening 15 can be various shapes other than a circle. FIG. 5 is a drawing showing an example of an opening shape. As illustrated, the shape of the opening 15 may be a circle, a polygon such as a triangle, a quadrangle, a pentagon, a hexagon and an octagon, a line-shaped groove (a plurality of lines), or a cross. Various patterns such as intersecting groove forms may be used. In the case of these various patterns, for the above reason, the size of each pattern is such that the smallest (narrow) portion of each pattern is about 10 nm and the largest (widest) portion is about 1 μm. It is preferable to make it.

  Next, as long as the negative electrode active material layer 13 is an active material that is alloyed with lithium, it can be used as long as it is normally used for a lithium ion secondary battery. Among them, carbon (C) exhibiting a high theoretical charge capacity (theoretical charge capacity (hereinafter the same): 372 (mAh / g)), silicon (Si) (4000 (mAh / g)), tin (Sn) (990 (mAh) / G)) is preferred. In particular, silicon (Si) is a more preferable material because of its large theoretical charge capacity. By using these substances as electrode materials, the charge capacity is high, and by adopting the connection structure of the first embodiment, it is possible to obtain a lithium ion secondary battery electrode with good cycle characteristics and high safety.

  In these active materials, for example, the conductivity of the negative electrode active material layer 13 can be controlled by adding impurities such as boron (B), antimony (Sb), phosphorus (P), and arsenic (As). it can. Note that the concentration of these impurities may be adjusted as appropriate in accordance with the application form. Thereby, the electrical conductivity of the negative electrode active material layer 13 can be controlled, various fuse functions can be provided, and the reaction rate with lithium can also be controlled. And thereby, the safety | security and charging / discharging speed | rate of a lithium ion secondary battery can be improved.

  As a method for forming the negative electrode active material layer 13, any device manufacturing method in the semiconductor field can be used. For example, a vapor deposition method using resistance heating, a vapor deposition method using an electron beam or an ion beam, a sputter vapor deposition method, a molecular beam epitaxy method, a pulse laser vapor deposition method, an electroless plating method, electroplating, or the like can be used.

  More specifically, in the case of silicon, sputtering deposition, CVD, vacuum deposition, pulsed laser deposition, molecular beam epitaxy, electron beam deposition, ion beam deposition, electroless plating, etc. are used. sell.

  In the case of tin, a vacuum deposition method, a CVD method, an electroless plating method, a sputter deposition method, a pulse laser deposition method, a molecular beam epitaxy method, an electron beam deposition method, an ion beam deposition method, an electroplating method, or the like can be used.

  In the case of carbon, a sputter deposition method, a CVD method, a vacuum deposition method (by energizing a carbon rod), a pulse laser deposition method, a molecular beam epitaxy method, or the like can be used. In addition, although carbon depends on the size of the opening, if the inside of the opening can be sufficiently filled, the graphite is formed into fine particles, mixed with the base material, applied and dried to form the negative electrode active material layer 13. Also good.

  The material states of the negative electrode active material layer 13 by these manufacturing methods are an amorphous state, a single crystal state, and a polycrystalline state. By making these crystalline states, charge / discharge characteristics are improved.

  The average thickness of the negative electrode active material layer 13 is desirably 500 nm or less, and the lower limit of the thickness is not particularly limited as long as the lithium ion from the positive electrode 2 side can be sufficiently retained as a lithium ion secondary battery.

  Next, an example of the manufacturing method of this negative electrode 1 is demonstrated. FIG. 6 is a cross-sectional view illustrating the method for manufacturing the negative electrode 1 separately for each process.

  First, as shown in FIG. 6A, a photosensitive material that becomes the insulating layer 12 is applied on the current collector 11. Subsequently, openings 15 having a predetermined pattern are formed in the photosensitive material. The method for forming the insulating layer 12 and the opening 15 is as described above.

  Next, as shown in FIG. 6B, a conductive film that becomes the conductive plug 16 is formed on the insulating layer 12. The method for forming the conductive plug 16 is as described above. In the figure, the conductive film 51 is also formed on the insulating layer 12, but the conductive film 51 is left as it is so as not to be electrically connected to the conductive plug 16 formed in the opening 15. .

  Next, as shown in FIG. 6C, the negative electrode active material layer 13 is formed on the insulating layer 12 (on the conductive thin film 51 and the conductive plug 16 on the insulating layer 12). The method for forming the negative electrode active material layer 13 is as described above. At this time, the negative electrode active material layer 13 is formed indented by the depth of the step from the surface of the conductive plug 16 to the surface of the conductive thin film 51 on the insulating layer 12. This indentation becomes a recess 17.

  According to the first embodiment described above, as the negative electrode 1, the negative electrode active material layer 13 and the current collector 11 are electrically connected only at the opening 15 of the insulating layer 12 provided on the current collector 11. . As a result, lithium ions are localized in the portion during charging and discharging. For this reason, since the volume change of the negative electrode active material layer 13 occurs only in this portion, the volume change of the negative electrode active material layer 13 as a whole is not necessary or very small. Further, since the negative electrode active material layer 13 is formed so as to enter into the opening 15, the surface of the negative electrode active material layer 13 opposite to the opening 15 (side in contact with the separator 3) is recessed. For this reason, at the time of charging / discharging, this recessed part 17 part can expand | swell and can absorb expansion | swelling of the negative electrode active material layer 13. In addition, since the negative electrode active material layer 13 is integrally formed by the portion in the opening 15 and the portion on the insulating layer 12, even if there is a recess 17, the negative electrode active material is not reduced accordingly. Therefore, the charging capacity is not reduced.

  Further, in the manufacturing method of the first embodiment, the negative electrode active material layer 13 having such a recess 17 is automatically formed only by sequentially forming the insulating layer 12 and the conductive plug 16 on the current collector 11. Can be formed. Further, by using the conductive plug 16, the depth of the opening 15 is adjusted, and the current collector and the negative electrode active material layer are securely connected in a state where the negative electrode active material layer 13 is integrated. can do. That is, it is possible to prevent the negative electrode active material layer 13 from being cut at the step portion due to the opening 15 becoming too deep.

  Further, the current collector 11 and the negative electrode active material layer 13 are connected only at the opening 15. For this reason, when an overcurrent flows, this minute connection portion is easily cut off, so that no more current flows.

  In the first embodiment, a larger charge capacity can be obtained by using carbon, silicon, or tin as the negative electrode active material layer 13.

  Further, the negative electrode active material layer 13 is further added with at least one element selected from the group consisting of boron, antimony, phosphorus, and arsenic as an impurity for controlling electrical conductivity. The electrical conductivity of the battery can be increased to enable rapid charging.

  And the lithium ion secondary battery using this negative electrode 1 has a small volume change at the time of charging / discharging as a whole. Therefore, since unstable factors such as internal electrode peeling are eliminated, durability is improved and a charge / discharge cycle is also improved.

(Embodiment 2)
FIG. 7 is a cross-sectional view for explaining the negative electrode 1 (negative electrode structure) in the second embodiment.

  The negative electrode 1 according to the second embodiment is obtained by providing an ohmic contact layer 18 between the conductive plug 16 and the negative electrode active material layer 13. Since the other configuration and the configuration of the lithium ion secondary battery using the negative electrode 1 are the same as those of the first embodiment, the description thereof is omitted. In addition, since the second embodiment has the same effects as those of the first embodiment, the description of the same points is omitted.

  Carbon, silicon, and tin used as the negative electrode active material layer 13 have properties as semiconductors. Therefore, a Schottky barrier is formed when the negative electrode active material layer 13 made of these directly contacts the metal conductive plug 16. The barrier height (energy barrier height) varies depending on the materials of the negative electrode active material layer 13 and the conductive plug 16.

  Therefore, in the second embodiment, in order to eliminate (or reduce) the influence of this Schottky barrier, an ohmic contact layer 18 is provided at this connection portion.

  In the semiconductor device process, the Schottky barrier is eliminated by performing a sintering process after forming a metal film on a film of silicon or the like. However, when a resin material is used as the insulating layer 12, it cannot withstand high-temperature heat treatment that allows sintering, and therefore, in the second embodiment, an ohmic contact layer 18 is separately provided.

  The ohmic contact layer 18 forms a conductive metal oxide, a conductive organic material, carbon (C), hafnium (Hf), antimony (Sb), or the like imparted with conductivity. As a formation method, any device manufacturing method in the semiconductor field can be used. For example, molecular beam epitaxy is preferable for conductive metal oxides, conductive organic substances, and carbon (C) imparted with conductivity. For metals such as hafnium (Hf) and antimony (Sb), vapor deposition using resistance heating, vapor deposition using electron beam or ion beam, sputter vapor deposition, molecular beam epitaxy, pulsed laser vapor deposition, An electrolytic plating method, an electroplating method, or the like can be used.

  It is sufficient that the ohmic contact layer 18 has a thickness of several nm to 1 μm. However, even if it becomes thicker than that, there is no particular problem as long as the opening 15 is not thick enough to be buried. This is because the negative electrode active material layer 13 is integrated in the opening and on the insulating layer 12. Specifically, when the conductive film 51 at the time of forming the conductive plug 16 and the thin film 52 at the time of forming the ohmic contact layer 18 are left on the insulating layer 12, the opening depth is (the thickness of the insulating layer 12). + Thickness of conductive film 51 + thickness of thin film 52) − (thickness of conductive film 51 + thin film 52). Therefore, it is preferable that the thickness of the insulating layer 12 <the thickness of the negative electrode active material layer 13. Accordingly, since the thickness of the negative electrode active material layer 13 is sufficient, the negative electrode active material layer 13 in which the portion in the opening 15 and the portion on the insulating layer 12 are integrated can be easily formed.

  In such a manufacturing method of the second embodiment, after the formation of the conductive plug 16, only the step of forming the ohmic contact layer 18 is added, and the other steps may be the same as those of the first embodiment.

  As described above, in the second embodiment, the ohmic contact layer 18 is provided at the connection portion between the conductive plug 16 and the negative electrode active material layer 13. This eliminates (or reduces) the energy barrier caused by the Schottky barrier between the conductive plug 16 and the negative electrode active material layer 13 and eliminates (or reduces) unnecessary resistance components in the battery. it can. Therefore, it becomes easy to charge quickly. In addition, the ohmic contact layer 18 can alleviate a difference in physical properties between the metal and the negative electrode active material layer 13 that is a semiconductor, for example, inconsistency due to a composition, an electronic state, a crystal structure, and the like.

(Embodiment 3)
FIG. 8 is a cross-sectional view for explaining the negative electrode 1 (negative electrode structure) of the third embodiment.

  In the third embodiment, the conductive plug 16 between the current collector 11 and the negative electrode active material layer 13 in the opening 15 in the first embodiment is omitted. That is, the negative electrode active material layer 13 is directly connected to the current collector 11 in the opening 15.

  Even if the conductive plug 16 is omitted in this way, the negative electrode active material layer 13 is connected to the current collector 11 only in the opening 15, so that the same actions and effects as in the first embodiment can be obtained.

  Also in this case, in order for the negative electrode active material layer 13 to be connected to the current collector 11 only in the opening 15 and to be integrated up to the insulating layer 12, the thickness of the negative electrode active material layer 13 is set to the insulating layer. It is preferable to make it thicker than 12.

  By omitting the conductive plug 16 in this way, the manufacturing process can be shortened accordingly. In addition, also in the third embodiment, similar to the first embodiment, it is possible to obtain effects such as a volume change mitigating action and a fuse function during charging and discharging.

(Embodiment 4)
FIG. 9 is a cross-sectional view for explaining the negative electrode 1 (negative electrode structure) of the fourth embodiment.

  In the fourth embodiment, when the conductive plug 16 is omitted, an ohmic contact layer 18 is provided between the current collector 11 and the negative electrode active material layer 13. Since other members, functions, and operations are the same as those in the third embodiment, description thereof is omitted.

  This is because the Schottky barrier generated by the material of the current collector 11 and the negative electrode active material layer 13 is eliminated (or reduced) as described in the second embodiment. Therefore, by providing the ohmic contact layer 18 between the current collector 11 and the negative electrode active material layer 13 as in the fourth embodiment, the Schottky between the metal current collector 11 and the negative electrode active material layer 13 made of a semiconductor is provided. The electric conductivity inside the battery can be improved by eliminating (reducing) the barrier.

  Although the embodiment to which the present invention is applied has been described above, the present invention is not limited to the above-described embodiment.

  For example, in the above-described embodiments, the concave portion 17 is formed on the surface of the negative electrode active material layer 13. The concave portion 17 can be naturally obtained from the manufacturing method. The above-described embodiment is used to relieve the volume change during charging / discharging by making good use of the recess 17. However, the concave portion 17 may not be provided. That is, when the recess 17 is very shallow or not at all. Even in such a case, since the connection part between the current collector 11 and the negative electrode active material layer 13 is only a minute part in the opening 15, there is no change in that the volume change occurs only in the minute part. . On the other hand, the separator in contact with the negative electrode active material layer 13 is formed of a resin member, and is further swollen by the electrolytic solution. For this reason, the volume change in a very small portion is absorbed by their flexibility. Therefore, even when the concave portion 17 is not shallow, the volume change of the entire battery during charging / discharging can be alleviated. Further, since the fuse function is exhibited by the connection state in the minute portion, it functions even when there is no recess 17 at all.

  Furthermore, materials such as the current collector 11, the negative electrode active material layer 13, the insulating layer 12, the conductive plug 16, and the ohmic contact layer 18, and the materials such as the positive electrode 2 and the separator 3 may be other than the exemplified materials. Anything suitable for those functions can be applied.

It is sectional drawing which shows the structure of the lithium ion secondary battery of Embodiment 1 to which this invention is applied. 4 is a perspective view for explaining the structure of a negative electrode in Embodiment 1. FIG. 4 is a cross-sectional view for explaining the structure of a negative electrode in Embodiment 1. FIG. FIG. 5 is an explanatory diagram for explaining an operation of a negative electrode in the first embodiment. It is drawing which shows the example of opening part shape. FIG. 3 is a cross-sectional view illustrating the method for manufacturing a negative electrode in Embodiment 1 separately for each process. 6 is a cross-sectional view for describing a negative electrode in Embodiment 2. FIG. 6 is a cross-sectional view for explaining a negative electrode of Embodiment 3. FIG. 6 is a cross-sectional view for explaining a negative electrode of Embodiment 4. FIG.

Explanation of symbols

1 negative electrode,
2 positive electrode,
3 separator,
11 Current collector,
12 Insulating layer,
13 negative electrode active material layer,
15 opening,
16 conductive plug,
17 recess,
18 ohmic contact layer,
21 positive electrode current collector,
22 Positive electrode active material layer.

Claims (15)

A current collector,
An insulating layer provided on the current collector and having a plurality of openings;
A negative electrode active material layer electrically connected to the current collector at the opening and integrally provided up to the insulating layer;
A negative electrode structure comprising:   2. The negative electrode structure according to claim 1, wherein the negative electrode active material layer has a recess formed on a surface opposite to a surface facing the opening at the position of the opening.   The negative electrode structure according to claim 1, wherein a conductive plug that electrically connects the current collector and the negative electrode active material layer is provided in the opening.   The negative electrode structure according to claim 3, wherein a thickness of the conductive plug is thinner than a thickness of the insulating layer.   5. The negative electrode structure according to claim 3, further comprising an ohmic contact layer between the conductive plug and the negative electrode active material layer.   The negative electrode structure according to claim 1 or 2, wherein the negative electrode active material layer is in direct contact with the current collector in the opening.   The negative electrode structure according to claim 6, further comprising an ohmic contact layer between the current collector and the negative electrode active material layer in the opening.   The negative electrode structure according to claim 1, wherein the negative electrode active material layer is made of at least one selected from the group consisting of carbon, silicon, and tin.   9. The negative electrode structure according to claim 8, wherein the negative electrode active material layer contains at least one element selected from the group consisting of boron, antimony, phosphorus, and arsenic as an impurity for controlling electrical conductivity. body. A current collector,
A negative electrode active material layer provided on the current collector and having a portion where the lithium concentration is localized during charge and discharge;
A negative electrode structure having a recess in a portion where the lithium concentration of the negative electrode active material layer is localized. A negative electrode using the negative electrode structure according to any one of claims 1 to 10,
A separator in contact with the negative electrode;
A lithium ion secondary battery comprising: a positive electrode in contact with the separator. Forming an insulating layer on the current collector;
Forming a plurality of openings in the insulating layer through which the current collector is exposed;
Forming a negative electrode active material layer on the insulating layer, including within the opening;
The manufacturing method of the negative electrode structure characterized by having.   After the step of forming a plurality of openings through which the current collector is exposed in the insulating layer, a conductive film thinner than the thickness of the insulating layer is further formed on the insulating layer to make the conductive material in the opening. The method for producing a negative electrode structure according to claim 12, comprising a step of forming a plug.   14. The method of manufacturing a negative electrode structure according to claim 13, further comprising a step of forming an ohmic contact layer on the conductive plug after the step of forming the conductive plug.   13. The negative electrode structure according to claim 12, further comprising a step of forming an ohmic contact layer in the opening after forming the plurality of openings exposing the current collector in the insulating layer. Body manufacturing method.

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