WO2021010085A1 - Secondary battery - Google Patents

Abstract

A secondary battery according to the present invention is provided with: a positive electrode which contains a positive electrode active material that absorbs and desorbs lithium, and which achieves a positive electrode adsorption/desorption capacity when lithium is absorbed and desorbed at the positive electrode active material; a negative electrode which comprises a negative electrode collector, a base layer that is provided on the negative electrode collector and contains a carbon material, and a negative electrode active material layer that is provided on the base layer and contains a negative electrode active material which absorbs and desorbs lithium and contains a carbon-based active material and a silicon-based active material, said negative electrode active material achieving a negative electrode adsorption/desorption capacity, which is lower than the positive electrode adsorption/desorption capacity, when lithium is absorbed and desorbed at the negative electrode active material; and an electrolyte solution.

Description

Rechargeable battery

This technology relates to a secondary battery equipped with an electrolytic solution together with a positive electrode and a negative electrode that occlude and release lithium.

Due to the widespread use of various electronic devices such as mobile phones, the development of secondary batteries is underway as a power source that is compact and lightweight and can obtain high energy density. This secondary battery includes an electrolytic solution together with a positive electrode and a negative electrode. Since the configuration of the secondary battery affects the battery characteristics, various studies have been made on the configuration of the secondary battery.

Specifically, in order to improve the charge / discharge cycle characteristics, in a secondary battery in which the positive electrode and the negative electrode each occlude and release lithium, the capacity of the negative electrode obtained when the lithium is occluded and released is the capacity of the positive electrode. Is set to be smaller than (see, for example, Patent Document 1).

Further, in order to reduce the internal resistance, a carbon coat layer is inserted between the current collector and the active material in the electrode (see, for example, Patent Document 2). In this case, the surface of the carbon coat layer on the side in contact with the active material is provided with irregularities due to the carbon material.

Japanese Patent No. 3965384 JP-A-2015-088333

Various studies have been made to improve the battery characteristics of secondary batteries, but there is room for improvement because the battery characteristics are still insufficient.

This technology was made in view of such problems, and its purpose is to provide a secondary battery capable of obtaining excellent battery characteristics.

The secondary battery of the embodiment of the present technology contains a positive electrode active material that stores and releases lithium, and a positive electrode that obtains a positive electrode storage and release capacity when lithium is stored and released in the positive electrode active material, and a negative electrode current collection. The body, a base layer provided on the negative electrode current collector and containing a carbon material, and a negative electrode active material provided on the base layer and storing and releasing lithium, and the negative electrode active material is carbon-based. A negative electrode containing an active material and a silicon-based active material, and a negative electrode active material layer in which the negative electrode storage / release capacity obtained when lithium is stored and released in the negative electrode active material is smaller than the positive electrode storage / release capacity, and an electrolytic solution. It is equipped with.

Here, "carbon material" is a general term for materials containing carbon as a constituent element. The "carbon-based active material" is a general term for materials (active materials) capable of occluding and releasing lithium and containing carbon as a constituent element. The "silicon-based active material" is a general term for materials (active materials) capable of occluding and releasing lithium and containing silicon as a constituent element. However, materials corresponding to "silicon-based active materials" shall be excluded from "carbon-based active materials".

According to the secondary battery of one embodiment of the present technology, the negative electrode includes a negative electrode current collector, a base layer containing a carbon material, and a negative electrode active material layer containing a carbon-based active material and a silicon-based active material. Since the negative electrode storage / discharge capacity of the negative electrode is smaller than the positive electrode storage / discharge capacity of the positive electrode, excellent battery characteristics can be obtained.

Note that the effect of the present technology is not necessarily limited to the effect described here, and may be any effect of a series of effects related to the present technology described later.

It is a perspective view which shows the structure of the secondary battery (laminate film type) in one Embodiment of this technique. It is sectional drawing which shows the structure of the wound electrode body shown in FIG. It is a top view which shows each structure of the positive electrode and the negative electrode shown in FIG. It is sectional drawing which shows the structure of another secondary battery (cylindrical type) in one Embodiment of this technique. It is a perspective view which shows the structure of the secondary battery (laminate film type) of the modification 1. FIG. It is sectional drawing which shows the structure of the laminated electrode body shown in FIG. It is a block diagram which shows the structure of the application example (battery pack: cell) of a secondary battery. It is a block diagram which shows the structure of application example (battery pack: assembled battery) of a secondary battery. It is a block diagram which shows the structure of the application example (electric vehicle) of a secondary battery. It is sectional drawing which shows the structure of the secondary battery (coin type) for a test.

Hereinafter, one embodiment of the present technology will be described in detail with reference to the drawings. The order of explanation is as follows.

1. 1. Secondary battery 1-1. Laminate film type 1-1-1. Configuration 1-1-2. Operation (operation principle)
1-1-3. Manufacturing method 1-1-4. Action and effect 1-2. Cylindrical type 1-2-1. Configuration 1-2-2. Operation (operation principle)
1-2-3. Manufacturing method 1-2-4. Action and effect 2. Modification example 3. Applications of secondary batteries 3-1. Battery pack (cell)
3-2. Battery pack (assembled battery)
3-3. Electric vehicle 3-4. Other

<1. Rechargeable battery ＞
First, a secondary battery according to an embodiment of the present technology will be described.

The secondary battery described here is a secondary battery in which the battery capacity can be obtained by utilizing the occlusion and release of lithium and the battery capacity can be obtained by utilizing the precipitation and dissolution of lithium, and the electrolytic solution together with the positive electrode and the negative electrode. It has. In this secondary battery, lithium is occluded in an ionic state and released in an ionic state. Further, in a secondary battery, lithium is precipitated in a metallic state and dissolved in an ionic state. The detailed operating principle (charging / discharging principle) of the secondary battery will be described later.

<1-1. Laminate film type>
First, a laminated film type secondary battery using a flexible or flexible film 20 as an exterior member for accommodating a battery element will be described.

<1-1-1. Configuration>
FIG. 1 shows a perspective configuration of a laminated film type secondary battery. FIG. 2 shows the cross-sectional configuration of the wound electrode body 10 shown in FIG. FIG. 3 shows the planar configurations of the positive electrode 11 and the negative electrode 12 shown in FIG.

However, FIG. 1 shows a state in which the wound electrode body 10 and the film 20 are separated from each other. FIG. 2 shows only a part of the wound electrode body 10. FIG. 3 shows a state in which the positive electrode 11 and the negative electrode 12 are separated from each other.

In this secondary battery, as shown in FIG. 1, a winding type battery element (winding electrode body 10) is housed inside a bag-shaped film 20, and a positive electrode lead is housed in the winding electrode body 10. 14 and the negative electrode lead 15 are connected. Each of the positive electrode lead 14 and the negative electrode lead 15 is led out in the same direction from the inside to the outside of the film 20.

[the film]
The film 20 is a single film-like member that can be folded in the direction of the arrow R (dashed line) shown in FIG. The film 20 is provided with a recessed portion 20U (so-called deep drawing portion) for accommodating the wound electrode body 10.

Specifically, the film 20 is a three-layer laminated film in which a fusion layer, a metal layer, and a surface protection layer are laminated in this order from the inside, and when the film 20 is folded, it is among the fusion layers. The outer peripheral edges of the film are fused to each other. The fused layer contains a polymer compound such as polypropylene. The metal layer contains a metallic material such as aluminum. The surface protective layer contains a polymer compound such as nylon. However, since the number of layers of the film 20 which is a laminated film is not limited to three, it may be one layer, two layers, or four or more layers.

The adhesion film 21 is inserted between the film 20 and the positive electrode lead 14, and the adhesion film 22 is inserted between the film 20 and the negative electrode lead 15. The adhesion films 21 and 22 are members for preventing the intrusion of outside air, and include any one or more of a polyolefin resin having adhesion to each of the positive electrode lead 14 and the negative electrode lead 15. There is. The polyolefin resin is polyethylene, polypropylene, modified polyethylene, modified polypropylene and the like. However, one or both of the adhesion films 21 and 22 may be omitted.

[Wound electrode body]
As shown in FIGS. 1 and 2, the wound electrode body 10 includes a positive electrode 11, a negative electrode 12, a separator 13, and an electrolytic solution which is a liquid electrolyte. The wound electrode body 10 is a structure in which a positive electrode 11 and a negative electrode 12 are laminated with each other via a separator 13, and then the positive electrode 11, the negative electrode 12 and the separator 13 are wound. The electrolytic solution is impregnated in each of the positive electrode 11, the negative electrode 12, and the separator 13.

[Positive electrode]
As shown in FIG. 2, the positive electrode 11 includes a positive electrode current collector 11A and two positive electrode active material layers 11B provided on both sides of the positive electrode current collector 11A. However, the positive electrode active material layer 11B may be provided on only one side of the positive electrode current collector 11A.

(Positive current collector)
The positive electrode current collector 11A contains any one or more of conductive materials such as aluminum, nickel and stainless steel.

(Positive electrode active material layer)
The positive electrode active material layer 11B contains any one or more of the positive electrode active materials that occlude and release lithium, that is, materials that can occlude and release lithium in an ionic state. However, the positive electrode active material layer 11B may further contain a positive electrode binder, a positive electrode conductive agent, and the like.

(Positive electrode active material)
The type of the positive electrode active material is not particularly limited, but is a lithium-containing compound such as a lithium-containing transition metal compound. This lithium-containing transition metal compound contains one or more kinds of transition metal elements together with lithium, and may further contain one kind or two or more kinds of other elements. The type of the other element is not particularly limited as long as it is an arbitrary element (excluding the transition metal element). Among them, the other elements are preferably elements belonging to groups 2 to 15 in the long periodic table. The lithium-containing transition metal compound may be an oxide, a phosphoric acid compound, a silicic acid compound, a boric acid compound, or the like.

Specific examples of oxides are LiNiO ₂ , LiCoO ₂ , LiCo _0.98 Al _0.01 Mg _0.01 O ₂ , LiNi _0.5 Co _0.2 Mn _0.3 O ₂ , LiNi _0.8 Co _0.15 Al _0.05 O ₂ , LiNi _0.33 Co _0.33 Mn _0.33 O ₂ , Li _1.2 Mn _0.52 Co _0.175 Ni _0.1 O ₂ , Li _1.15 (Mn _0.65 Ni _0.22 Co _0.13 ) O ₂ and Li Mn ₂ O ₄ . Specific examples of the phosphoric acid compound include LiFePO ₄ , LiMnPO ₄ , LiFe _0.5 Mn _0.5 PO _4, and LiFe _0.3 Mn _0.7 PO ₄ .

(Positive electrode binder)
The positive electrode binder contains any one or more of synthetic rubber, polymer compounds, and the like. Synthetic rubbers include styrene-butadiene rubbers, fluororubbers and ethylene propylene dienes. Polymer compounds include polyvinylidene fluoride, polyimide and carboxymethyl cellulose.

(Positive electrode conductive agent)
The positive electrode conductive agent contains any one or more of the conductive materials such as carbon material. The carbon materials include graphite, carbon black, acetylene black and ketjen black. However, the positive electrode conductive agent may be a metal material, a conductive polymer, or the like as long as it has conductivity.

On both sides of the positive electrode current collector 11A, the positive electrode active material layer 11B is provided on a part of the positive electrode current collector 11A. Therefore, the portion of the positive electrode current collector 11A where the positive electrode active material layer 11B is not provided is not covered by the positive electrode active material layer 11B and is exposed.

Specifically, as shown in FIG. 3, the positive electrode current collector 11A extends in the longitudinal direction (X-axis direction) and includes a covering portion 11AX and a pair of uncovered portions 11AY. The covering portion 11AX is located at the central portion of the positive electrode current collector 11A in the longitudinal direction, and is a portion where the positive electrode active material layer 11B is formed. The pair of uncoated portions 11AY are located at one end and the other end of the positive electrode current collector 11A in the longitudinal direction, and are portions where the positive electrode active material layer 11B is not formed. As a result, the coated portion 11AX is covered with the positive electrode active material layer 11B, whereas the pair of uncoated portions 11ZY are not covered with the positive electrode active material layer 11B and are exposed. In FIG. 3, the positive electrode active material layer 11B is lightly shaded.

[Negative electrode]
As shown in FIG. 2, the negative electrode 12 is provided on the negative electrode current collector 12A, the base layer 12B provided on the negative electrode current collector 12A (both sides), and on the base layer 12B (surface). It contains the negative electrode active material layer 12C obtained. However, each of the base layer 12B and the negative electrode active material layer 12C may be provided on only one side of the negative electrode current collector 12A.

(Negative electrode current collector)
The negative electrode current collector 12A contains any one or more of conductive materials such as copper, aluminum, nickel and stainless steel.

(Underground layer)
The base layer 12B is interposed between the negative electrode current collector 12A and the negative electrode active material layer 12C. The base layer 12B improves the adhesion of the negative electrode active material layer 12C to the negative electrode current collector 12A while ensuring the conductivity between the negative electrode current collector 12A and the negative electrode active material layer 12C. As a result, the negative electrode current collector 12A and the negative electrode active material layer 12C are electrically connected to each other, and the negative electrode active material layer 12C is less likely to be separated from the negative electrode current collector 12A during charging and discharging.

In particular, as will be described later, the negative electrode active material layer 12C is formed by a coating method, that is, the negative electrode active material layer 12C is formed on the surface of the base layer 12B by using a negative electrode mixture slurry containing a negative electrode binder together with the negative electrode active material. In the case of forming the above, the adhesion of the negative electrode active material layer 12C to the base layer 12B is dramatically improved rather than the adhesion of the negative electrode active material layer 12C to the negative electrode current collector 12A. This is because the adhesion of the negative electrode binder to the base layer 12B is significantly higher than the adhesion of the negative electrode binder to the negative electrode current collector 12A. As a result, the negative electrode active material layer 12C is significantly less likely to be separated from the negative electrode current collector 12A during charging and discharging.

This base layer 12B contains any one or more of the carbon materials. As described above, the carbon material described here is a general term for materials containing carbon as a constituent element. However, the base layer 12B may further contain a base binder or the like. The details regarding the base binder are the same as the details regarding the negative electrode binder described later.

Specific examples of carbon materials are carbon black, acetylene black, ketjen black, and the like. This is because the adhesion of the negative electrode active material layer 12C to the negative electrode current collector 12A is sufficiently high.

This carbon material is a powder (plural particles). In this case, the BET specific surface area of the plurality of particulate carbon materials is not particularly limited, but is preferably 30 m ² / g to 300 m ² / g. This is because the adhesion of the negative electrode active material layer 12C to the negative electrode current collector 12A is further improved, so that the negative electrode active material layer 12C is more difficult to peel off from the negative electrode current collector 12A.

Specifically, if the BET specific surface area is smaller than 30 m ² / g, the unevenness provided on the surface of the base layer 12B is too small, so that the adhesion of the base layer 12B to the negative electrode active material layer 12C may decrease. .. On the other hand, if the BET specific surface area is larger than 300 m ² / g, the unevenness provided on the surface of the base layer 12B is too large, so that the adhesion of the base layer 12B to the negative electrode current collector 12A may decrease. On the other hand, when the BET specific surface area is 30 m ² / g to 300 m ² / g, the adhesion of the base layer 12B to each of the negative electrode current collector 12A and the negative electrode active material layer 12C is ensured. The negative electrode active material layer 12C is remarkably difficult to be separated from the negative electrode current collector 12A by using the stratum 12B.

The crystallinity of the carbon material is not particularly limited. Above all, the carbon material preferably has low crystallinity. This is because the amount of lithium intercalated (reaction amount) with respect to the base layer 12B is reduced, so that even if the base layer 12B is used, lithium can be easily and stably occluded and released in the negative electrode active material layer 12C.

Specifically, a Raman spectrum (Raman shift (cm ^-1 ) on the horizontal axis and spectral intensity on the vertical axis) is obtained by analyzing the carbon material using Raman spectroscopy. In this case, the peak intensity IG of the G band is detected near 1580 cm ^-1, as measured with a peak intensity ID of D band is detected near 1360 cm ^-1, the ratio of the peak intensity ID for the peak intensity IG ( Peak intensity ratio) ID / IG is preferably 1.0 or more.

When investigating the above-mentioned BET specific surface area and peak intensity ratio ID / IG, it is necessary to recover the carbon material from the secondary battery in order to perform measurement and analysis using the carbon material. In this case, first, the negative electrode 12 is taken out by disassembling the secondary battery. Subsequently, the base layer 12B is taken out by disassembling the negative electrode 12. In this case, the base layer 12B is peeled off from each of the negative electrode current collector 12A and the negative electrode active material layer 12C. Finally, the base layer 12B is put into the organic solvent, and then the organic solvent is stirred. As a result, the soluble component (base binder and the like) in the base layer 12B is dissolved, so that the insoluble component (carbon material) in the base layer 12B is recovered. The type of the organic solvent is not particularly limited as long as it can dissolve a soluble component such as a base binder.

(Negative electrode active material layer)
The negative electrode active material layer 12C contains any one or more of negative electrode active materials that occlude and release lithium, that is, materials that can occlude and release lithium in an ionic state. However, the negative electrode active material layer 12C may further contain a negative electrode binder, a negative electrode conductive agent, and the like. The details regarding each of the negative electrode binder and the negative electrode conductive agent are the same as the details regarding each of the positive electrode binder and the positive electrode conductive agent described above.

(Negative electrode active material)
The negative electrode active material contains two types of materials (carbon-based active material and silicon-based active material) capable of occluding and releasing lithium in an ionic state. As described above, the carbon-based active material is a general term for materials (active materials) capable of occluding and releasing lithium and containing carbon as a constituent element. As described above, the silicon-based active material is a general term for materials (active materials) that can occlude and release lithium and also contain silicon as a constituent element, and can form an alloy with the lithium. However, materials corresponding to silicon-based active materials shall be excluded from carbon-based active materials.

The negative electrode active material contains a carbon-based active material and a silicon-based active material because the negative electrode 12 (negative electrode active material layer 12C) expands and contracts during charging and discharging while ensuring a high theoretical capacity (battery capacity). This is because it is suppressed.

Specifically, the carbon-based active material has the advantage that it does not easily expand and contract during charging and discharging, but has the concern that the theoretical capacity is low. On the other hand, the silicon-based active material has an advantage of having a high theoretical capacity, but has a concern that it easily expands and contracts during charging and discharging. Therefore, by using the carbon-based active material and the silicon-based active material in combination, the carbon-based active material suppresses the expansion and contraction of the negative electrode active material layer 12C during charging and discharging, while the silicon-based active material has a higher battery capacity. can get.

Specifically, the carbon-based active material contains any one or more of graphitizable carbon, non-graphitizable carbon, and graphite. This graphite may be natural graphite, artificial graphite, or both. Above all, the carbon-based active material preferably contains graphite. This is because a sufficient battery capacity can be stably obtained.

The silicon-based active material may be a simple substance of silicon, an alloy of silicon, a compound of silicon, or a mixture of two or more of them. Specifically, the silicon-based active materials are SiB ₄ , SiB ₆ , Mg ₂ Si, Ni ₂ Si, TiSi ₂ , MoSi ₂ , CoSi ₂ , NiSi ₂ , CaSi ₂ , CrSi ₂ , Cu ₅ Si, FeSi ₂ , MnSi ₂ , NbSi ₂ , TaSi ₂ , VSi ₂ , WSi ₂ , ZnSi ₂ , SiC, Si ₃ N ₄ , Si ₂ N ₂ O, SiO _x (0 <x ≦ 2), LiSiO, SnO _w (0 <w ≦) 2), SnSiO ₃ , LiSnO, Mg ₂ Sn, and the like, or any one or more of them are contained.

Among them, the silicon-based active material preferably contains silicon oxide represented by SiO _x (0 <x ≦ 2), and more preferably contains SiO. This is because the irreversible capacity is reduced, so that a high battery capacity can be stably obtained.

The mixing ratio (weight ratio) of the carbon-based active material and the silicon-based active material is not particularly limited. Above all, the mixing ratio of the carbon-based active material is preferably larger than the mixing ratio of the silicon-based active material. Since the proportion of carbon-based active material that does not easily expand and contract during charging and discharging is larger than the proportion of silicon-based active material that easily expands and contracts during charging and discharging, the entire negative electrode active material expands and contracts during charging and discharging. This is because it becomes difficult to shrink.

On both sides of the negative electrode current collector 12A, the negative electrode active material layer 12C is provided on the entire negative electrode current collector 12A. Therefore, the entire negative electrode current collector 12A is not exposed and is covered with the negative electrode active material layer 12C.

Specifically, as shown in FIG. 3, the negative electrode current collector 12A extends in the longitudinal direction (X-axis direction), and the negative electrode active material layer 12C includes a pair of non-opposing portions 12CZ. There is. The pair of non-opposing portions 12CZ are portions facing the pair of uncovered portions 11AY. That is, since the pair of non-opposing portions 12CZ are portions that do not face the positive electrode active material layer 11B, they are not involved in the charge / discharge reaction. In FIG. 3, the negative electrode active material layer 12C is darkly shaded.

When the BET specific surface area of the carbon material described above is examined ex post facto, that is, after the secondary battery is completed (in use), it is shown in FIG. 3 as a negative electrode active material layer 12C for recovering the carbon material. It is preferable to use the non-opposing portion 12CZ. This is because the non-opposing portion 12CZ hardly participates in the charge / discharge reaction, so that the state of the carbon material (BET specific surface area) is easily maintained as it was when the negative electrode 12 was formed without being affected by the charge / discharge reaction. As a result, the BET specific surface area of the carbon material can be examined stably and with good reproducibility even when the secondary battery has been used.

For the same reason, it is preferable to use the non-opposing portion 12CZ even when examining the peak intensity ratio ID / IG of the carbon material described above.

[Separator]
As shown in FIG. 2, the separator 13 is interposed between the positive electrode 11 and the negative electrode 12. The separator 13 is an insulating porous film that allows lithium to pass through while preventing a short circuit due to contact between the positive electrode 11 and the negative electrode 12, and may be a single-layer film composed of one type of porous film. It may be a multilayer film in which more than one kind of porous film is laminated on each other. This porous membrane contains any one or more of polymer compounds such as polytetrafluoroethylene, polypropylene and polyethylene.

[Electrolytic solution]
The electrolyte contains a solvent and an electrolyte salt. The type of the solvent may be only one type or two or more types, and the type of the electrolyte salt may be only one type or two or more types.

(solvent)
The solvent contains a non-aqueous solvent (organic solvent), and the electrolytic solution containing the non-aqueous solvent is a so-called non-aqueous electrolytic solution.

Non-aqueous solvents are esters, ethers, and the like, and more specifically, carbonic acid ester compounds, carboxylic acid ester compounds, lactone compounds, and the like.

Carbonate ester compounds include cyclic carbonates and chain carbonates. Cyclic carbonates include ethylene carbonate and propylene carbonate, and chain carbonates include dimethyl carbonate, diethyl carbonate and methyl ethyl carbonate. Carboxylate ester compounds include ethyl acetate, ethyl propionate and ethyl trimethyl acetate. Lactone compounds include γ-butyrolactone and γ-valerolactone. Ethers include 1,2-dimethoxyethane, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane and the like, in addition to the above-mentioned lactone compounds.

The non-aqueous solvent is an unsaturated cyclic carbonate ester, a halogenated carbonate ester, a sulfonic acid ester, a phosphoric acid ester, an acid anhydride, a nitrile compound, an isocyanate compound, or the like. This is because the chemical stability of the electrolytic solution is improved.

Specifically, the unsaturated cyclic carbonate is vinylene carbonate, vinyl acetate ethylene, methylene carbonate, or the like. Halogenated carbonic acid esters include ethylene fluorocarbonate and ethylene difluorocarbonate. The sulfonic acid ester is 1,3-propane sultone or the like. The phosphoric acid ester is trimethyl phosphate or the like. Acid anhydrides include cyclic carboxylic acid anhydrides, cyclic disulfonic acid anhydrides and cyclic carboxylic acid sulfonic acid anhydrides. Cyclic carboxylic acid anhydrides include succinic anhydride, glutaric anhydride and maleic anhydride. Cyclic disulfonic acid anhydrides include ethanedisulfonic anhydride and propanedisulfonic anhydride. Cyclic carboxylic acid sulfonic acid anhydrides include sulfobenzoic acid anhydride, sulfopropionic anhydride and sulfobutyric anhydride. Nitrile compounds include acetonitrile and succinonitrile. The isocyanate compound is hexamethylene diisocyanate or the like.

(Electrolyte salt)
The electrolyte salt is any one or more of light metal salts such as lithium salt. This lithium salt includes lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium trifluoromethanesulfonate (LiCF ₃ SO ₃ ), and bis (fluorosulfonyl) imide lithium (LiN (FSO)). ₂ ) ₂ ), bis (trifluoromethanesulfonyl) imidelithium (LiN (CF ₃ SO ₂ ) ₂ ), lithium tris (trifluoromethanesulfonyl) methide (LiC (CF ₃ SO ₂ ) ₃ ) and bis (oxalate) lithium borate (LiB (C ₂ O ₄ ) ₂ ) and the like. The content of the electrolyte salt is not particularly limited, but is 0.3 mol / kg to 3.0 mol / kg with respect to the solvent. This is because high ionic conductivity can be obtained.

[Positive lead and negative electrode lead]
The positive electrode lead 14 is connected to the positive electrode 11 (positive electrode current collector 11A), and the negative electrode lead 15 is connected to the negative electrode 12 (negative electrode current collector 12A). The positive electrode lead 14 contains any one or more of the conductive materials such as aluminum, and the negative electrode lead 15 is any one of the conductive materials such as copper, nickel and stainless steel. Includes type or two or more types. The shapes of the positive electrode lead 14 and the negative electrode lead 15 are thin plate-like and mesh-like, respectively.

<1-1-2. Operation (operation principle)>
This secondary battery operates by proceeding with a charge / discharge reaction based on the operating principle described below.

[Operating principle]
As described above, the positive electrode 11 contains a positive electrode active material that occludes and releases lithium, and the negative electrode 12 contains a negative electrode active material that occludes and releases lithium. As a result, in the positive electrode 11, a capacity (positive electrode occlusion / release capacity) is obtained when lithium is occluded and released in the positive electrode active material, and in the negative electrode 12, a capacity (negative electrode) is obtained when lithium is occluded and released in the negative electrode active material. (Occlusion release capacity) is obtained.

However, by adjusting the relationship between the amount of the positive electrode active material and the amount of the negative electrode active material, the negative electrode storage / release capacity is set to be smaller than the positive electrode storage / discharge capacity. As a result, when the charge / discharge reaction proceeds, lithium is deposited on the surface of the negative electrode 12 in a state where the open circuit voltage (that is, the battery voltage) is lower than the overcharge voltage.

The overcharge voltage described here is the open circuit voltage when the secondary battery reaches the overcharge state, and is one of the guidelines set by the Japan Storage Battery Industry Association (Battery Industry Association), "Lithium Ion". It means a voltage higher than the open circuit voltage of a “fully charged” secondary battery described (defined) on page 6 of the “Guidelines for Secondary Battery Safety Evaluation Criteria” (SBA G1101). In other words, it means a voltage higher than the open circuit voltage after being charged using the charging method, the standard charging method, or the recommended charging method used in determining the nominal capacity of each secondary battery.

More specifically, when the charge / discharge reaction is advanced, the battery is fully charged when the open circuit voltage reaches the upper limit voltage, and lithium is deposited in a part of the range where the open circuit voltage is 0 V to the upper limit voltage. To do. This upper limit voltage is an upper limit value of a voltage capable of advancing a normal charging reaction, and is determined according to the type of positive electrode active material. The place where lithium is deposited is not particularly limited, but is the surface of a negative electrode active material that occludes and releases lithium.

Therefore, the battery capacity, that is, the total capacity of the negative electrode 12, is the capacity obtained when lithium is occluded and released in the above-mentioned negative electrode active material and the capacity obtained when lithium is deposited and dissolved in the negative electrode 12 ( It is the sum of the negative electrode precipitation and dissolution capacity).

The total capacity of the negative electrode 12 is represented by the sum of the negative electrode occlusion / release capacity and the negative electrode precipitation / dissolution capacity. That is, it is a high energy density that the battery capacity can be obtained by utilizing the lithium occlusion / release phenomenon and the lithium precipitation / dissolution phenomenon. This is because the cycle characteristics and the quick charge characteristics are improved at the same time.

In this case, firstly, the negative electrode active material capable of occluding and releasing lithium generally has a large surface property, so that when lithium is deposited, it is present on the surface of the negative electrode active material. Lithium is likely to be deposited uniformly. Secondly, when a negative electrode active material capable of storing and releasing lithium is used, lithium is deposited not only on the surface of the negative electrode active material but also between a plurality of negative electrode active materials (gap). The volume change of the negative electrode active material layer 12C (the entire negative electrode active material) is reduced. Thirdly, the precipitation and dissolution of lithium by the negative electrode active material capable of occluding and releasing lithium also contributes to the charge / discharge capacity, so that the amount of lithium precipitation (and the amount of lithium precipitation (and) can be obtained in spite of the high battery capacity. The amount of dissolution) is reduced. Fourth, since lithium is occluded in the negative electrode active material which can occlude and release lithium in the initial stage of charging, rapid charging becomes possible.

[motion]
At the time of charging, lithium is released from the positive electrode 11 (positive electrode active material), and the lithium is occluded in the negative electrode 12 (negative electrode active material) via the electrolytic solution. As a result, the negative electrode storage / release capacity is obtained in the negative electrode 12.

Moreover, as charging progresses further, in a state where the open circuit voltage is lower than the overcharge voltage, the charge capacity exceeds the charge capacity capacity of the negative electrode active material, so lithium begins to precipitate on the surface of the negative electrode active material. In this case, lithium continues to precipitate on the surface of the negative electrode active material until charging is completed. As a result, the negative electrode precipitation / dissolution capacity is obtained in the negative electrode 12.

At the time of discharge, lithium precipitated on the surface of the negative electrode active material is dissolved, so that the lithium is eluted in the electrolytic solution, and the lithium eluted in the electrolytic solution is occluded in the positive electrode 11 (positive electrode active material). ..

Moreover, when the discharge further progresses, the lithium stored in the negative electrode active material is released, and the lithium is occluded in the positive electrode 11 (positive electrode active material) via the electrolytic solution.

<1-1-3. Manufacturing method>
In the case of manufacturing a secondary battery, the positive electrode 11 and the negative electrode 12 are manufactured and an electrolytic solution is prepared according to the procedure described below, and then the secondary battery is assembled.

[Preparation of positive electrode]
First, the positive electrode active material is mixed with a positive electrode binder, a positive electrode conductive agent, and the like, if necessary, to obtain a positive electrode mixture. Subsequently, a paste-like positive electrode mixture slurry is prepared by adding the positive electrode mixture to a dispersion solvent such as an organic solvent. Finally, the positive electrode active material layer 11B is formed by applying the positive electrode mixture slurry on both sides of the positive electrode current collector 11A. After that, the positive electrode active material layer 11B may be compression-molded using a roll press or the like. In this case, the positive electrode active material layer 11B may be heated, or compression molding may be repeated a plurality of times. As a result, the positive electrode active material layers 11B are formed on both sides of the positive electrode current collector 11A, so that the positive electrode 11 is produced.

[Preparation of negative electrode]
First, the carbon material and, if necessary, a base binder or the like are mixed to obtain a base mixture. Subsequently, a paste-like base mixture slurry is prepared by adding the base mixture to a dispersion solvent such as an aqueous solvent. Subsequently, the base layer 12B is formed by applying the base mixture slurry on both sides of the negative electrode current collector 12A.

Subsequently, a negative electrode active material containing a carbon-based active material and a silicon-based active material is mixed with a negative electrode binder, a negative electrode conductive agent, and the like, if necessary, to obtain a negative electrode mixture. In this case, the amount of the negative electrode active material (carbon-based active material and silicon-based active material) is adjusted with respect to the amount of the positive electrode active material so that the negative electrode storage / release capacity is smaller than the positive electrode storage / discharge capacity. Subsequently, a paste-like negative electrode mixture slurry is prepared by adding the negative electrode mixture to a dispersion solvent such as an organic solvent. Finally, the negative electrode active material layer 12C is formed by applying the negative electrode mixture slurry to the surface of the base layer 12B. After that, the negative electrode active material layer 12C may be compression-molded using a roll press or the like as in the case where the positive electrode active material layer 11B is formed. As a result, the base layer 12B and the negative electrode active material layer 12C are formed on both sides of the negative electrode current collector 12A, so that the negative electrode 12 is produced.

[Preparation of electrolytic solution]
The electrolyte salt is added to a solvent such as an organic solvent. As a result, the electrolyte salt is dispersed or dissolved in the solvent, so that an electrolytic solution is prepared.

[Assembly of secondary battery]
First, the positive electrode lead 14 is connected to the positive electrode 11 (positive electrode current collector 11A) by a welding method or the like, and the negative electrode lead 15 is connected to the negative electrode 12 (negative electrode current collector 12A) by a welding method or the like. Subsequently, the positive electrode 11 and the negative electrode 12 are laminated with each other via the separator 13, and then the positive electrode 11, the negative electrode 12, and the separator 13 are wound to produce a wound body. Subsequently, the wound body is housed inside the recess 20U, the film 20 is folded, and then the outer peripheral edges of the two sides of the film 20 (fused layer) are attached to each other by using a heat fusion method or the like. By adhering, the winding body is housed inside the bag-shaped film 20. Finally, after injecting the electrolytic solution into the bag-shaped film 20, the outer peripheral edges of the remaining one side of the film 20 (fused layer) are adhered to each other by a heat fusion method or the like. In this case, the adhesive film 21 is inserted between the film 20 and the positive electrode lead 14, and the adhesive film 22 is inserted between the film 20 and the negative electrode lead 15. As a result, the wound body is impregnated with the electrolytic solution, so that the wound electrode body 10 is manufactured. Therefore, since the wound electrode body 10 is enclosed inside the bag-shaped film 20, the laminated film type secondary battery is completed.

<1-1-4. Actions and effects>
According to this laminated film type secondary battery, the negative electrode 12 contains a negative electrode current collector 12A, a base layer 12B (carbon material) and a negative electrode active material layer 12C (carbon-based active material and silicon-based active material). The negative electrode storage / release capacity of the negative electrode 12 is smaller than the positive electrode storage / release capacity of the positive electrode 11.

In this case, first, since the negative electrode active material layer 12C contains the carbon-based active material and the silicon-based active material, the negative electrode active material layer 12C expands and expands during charging and discharging while ensuring a high battery capacity. It becomes difficult to shrink. Secondly, since the base layer 12B is interposed between the negative electrode current collector 12A and the negative electrode active material layer 12C, even if the negative electrode active material layer 12C expands and contracts during charging and discharging, the negative electrode active material The layer 12C is less likely to peel off from the negative electrode current collector 12A. In this case, in particular, even if the negative electrode active material layer 12C expands violently due to the silicon-based active material reaching a state of being fully charged or higher as the charging progresses, the negative electrode active material layer 12C Is sufficiently difficult to peel off from the negative electrode current collector 12A. Thirdly, since the negative electrode storage / discharge capacity is smaller than the positive electrode storage / discharge capacity, a high energy density can be obtained and the cycle characteristics and the like can be improved. Therefore, excellent battery characteristics can be obtained.

In particular, when the BET specific surface area of a plurality of particulate carbon materials is 30 m ² / g to 300 m ² / g, the negative electrode active material layer 12C is the negative electrode current collector 12A by utilizing the base layer 12B during charging and discharging. Since it is more difficult to peel off from the surface, a higher effect can be obtained.

Further, if the peak intensity ratio ID / IG of the carbon material measured by Raman spectroscopy is 1.0 or more, lithium can be sufficiently and stably occluded in the negative electrode active material layer 12C even if the base layer 12B is used. Since it is easily released, a higher effect can be obtained.

Further, if the carbon material contains carbon black or the like, the adhesion of the negative electrode active material layer 12C to the negative electrode current collector 12A becomes sufficiently high, so that a higher effect can be obtained.

Further, if the carbon-based active material contains graphite and the silicon-based active material contains silicon oxide represented by SiO _x (0 <x ≦ 2), the irreversible capacity is reduced and the battery capacity is high. Since it can be obtained stably, a higher effect can be obtained. In this case, if the silicon-based active material contains SiO, the irreversible capacity is sufficiently reduced, so that a higher effect can be obtained.

If lithium is deposited on the surface of the negative electrode 12 when the open circuit voltage is lower than the overcharge voltage, the lithium storage and release can be utilized by using the positive electrode 11 and the negative electrode 12 that occlude and release lithium. Not only the battery capacity can be obtained, but also the precipitation and dissolution of lithium can be used to obtain the battery capacity. Therefore, a high battery capacity can be stably obtained, and a higher effect can be obtained.

Further, if the total capacity (battery capacity) of the negative electrode 12 is the sum of the negative electrode occlusion / discharge capacity and the negative electrode precipitation / dissolution capacity, a high battery capacity can be stably obtained as described above, and a higher effect can be obtained. Can be done.

<1-2. Cylindrical type>
Next, a cylindrical secondary battery using a rigid battery can 41 as an exterior member for accommodating the battery element will be described.

<1-2-1. Configuration>
FIG. 4 shows a cross-sectional configuration of a cylindrical secondary battery. In the following description, the components of the laminated film type secondary battery (FIG. 2) already described will be cited from time to time.

In this secondary battery, as shown in FIG. 4, a pair of insulating plates 42, 43 and a winding type battery element (winding electrode body 30) are provided inside the cylindrical battery can 41. A positive electrode lead 34 and a negative electrode lead 35 are connected to the wound electrode body 30.

[Battery can]
The battery can 41 has a hollow structure in which one end is closed and the other end is open, and any one or more of metal materials such as iron, aluminum and alloys thereof can be used. Includes. The surface of the battery can 41 may be plated with nickel or the like. The insulating plates 42 and 43 are arranged so as to sandwich the wound electrode body 30 with each other, and extend in a direction intersecting the winding peripheral surface of the wound electrode body 30.

A battery lid 44, a safety valve mechanism 45, and a heat-sensitive resistance element (PTC element) 46 are crimped to the open end of the battery can 41 via an insulating gasket 47. Therefore, the open end of the battery can 41 is sealed. The battery lid 44 contains the same material as the material for forming the battery can 41. The safety valve mechanism 45 and the PTC element 46 are provided inside the battery lid 44, and the safety valve mechanism 45 is electrically connected to the battery lid 44 via the PTC element 46. In this safety valve mechanism 45, when the internal pressure of the battery can 41 exceeds a certain level due to an internal short circuit, external heating, or the like, the disk plate 45A is inverted, so that the battery lid 44 and the wound electrode body 30 are electrically connected. Be disconnected. In order to prevent abnormal heat generation due to a large current, the resistance of the PTC element 46 increases as the temperature rises. Asphalt or the like may be applied to the surface of the gasket 47.

[Wound electrode body]
The wound electrode body 30 includes a positive electrode 31, a negative electrode 32, a separator 33, and an electrolytic solution. The wound electrode body 30 is a structure in which the positive electrode 31 and the negative electrode 32 are laminated with each other via the separator 33, and then the positive electrode 31, the negative electrode 32 and the separator 33 are wound. The electrolytic solution is impregnated in each of the positive electrode 31, the negative electrode 32 and the separator 33. The positive electrode lead 34 is connected to the positive electrode 31 (positive electrode current collector 31A), and the negative electrode lead 35 is connected to the negative electrode 32 (negative electrode current collector 32A).

A center pin 36 is inserted in the space provided at the winding center of the winding electrode body 30. However, the center pin 36 may be omitted. The positive electrode lead 34 contains any one or more of the conductive materials such as aluminum, and is electrically connected to the battery lid 44 via the safety valve mechanism 45. The negative electrode lead 35 contains any one or more of conductive materials such as copper, nickel and stainless steel (SUS), and is electrically connected to the battery can 41. The shapes of the positive electrode lead 34 and the negative electrode lead 35 are thin plate-like and mesh-like.

[Positive electrode, negative electrode, separator and electrolyte layer]
As shown in FIG. 2, the positive electrode 31 includes a positive electrode current collector 31A and a positive electrode active material layer 31B, and the negative electrode 32 includes a negative electrode current collector 32A, a base layer 32B, and a negative electrode active material layer 32C. I'm out. The configurations of the positive electrode current collector 31A, the positive electrode active material layer 31B, the negative electrode current collector 32A, the base layer 32B, and the negative electrode active material layer 32C are the positive electrode current collector 11A, the positive electrode active material layer 11B, and the negative electrode current collector 12A. , The configurations of the base layer 12B and the negative electrode active material layer 12C are the same. That is, the negative electrode active material layer 32C contains a negative electrode active material (carbon-based active material and silicon-based active material). The configuration of the separator 33 is the same as that of the separator 13.

<1-2-2. Operation (operation principle)>
The operating principle and operation of the cylindrical secondary battery including the positive electrode 31 and the negative electrode 32 are the same as the operating principle and operation of the laminated film type secondary battery including the positive electrode 11 and the negative electrode 12.

That is, the negative electrode storage / release capacity of the negative electrode 32 is set to be smaller than the positive electrode storage / discharge capacity of the positive electrode 31. As a result, when the charge / discharge reaction proceeds, the negative electrode active material is in a state where the open circuit voltage is lower than the overcharge voltage, more specifically, in a part of the range where the open circuit voltage is 0 V to the upper limit voltage. Lithium is deposited on the surface of the. Therefore, the total capacity (battery capacity) of the negative electrode 12 is the sum of the negative electrode occlusion / discharge capacity and the negative electrode precipitation / dissolution capacity.

At the time of charging, lithium is released from the positive electrode 31 and the lithium is occluded in the negative electrode 32 via the electrolytic solution, so that the negative electrode storage / release capacity can be obtained in the negative electrode 32. Further, as charging progresses further, lithium is deposited on the surface of the negative electrode active material, so that the negative electrode precipitation dissolution capacity can be obtained at the negative electrode 32.

At the time of discharge, lithium precipitated on the surface of the negative electrode active material is eluted in the electrolytic solution, and the lithium is occluded in the positive electrode 31. Further, as the discharge progresses, the lithium stored in the negative electrode active material is released, and the lithium is occluded in the positive electrode 31 via the electrolytic solution.

<1-2-3. Manufacturing method>
In the case of manufacturing a secondary battery, the positive electrode 31 and the negative electrode 32 are manufactured by the procedure described below, and then the secondary battery is assembled. Since the procedure for preparing the electrolytic solution has already been described, the description thereof will be omitted here.

[Preparation of positive electrode and fabrication of negative electrode]
The positive electrode 31 is manufactured by the same procedure as the procedure for manufacturing the positive electrode 11, and the negative electrode 32 is manufactured by the same procedure as the procedure for manufacturing the negative electrode 12. That is, when the positive electrode 31 is manufactured, the positive electrode active material layers 31B are formed on both sides of the positive electrode current collector 31A, and when the negative electrode 32 is manufactured, the base layers 32B and the base layers 32B and The negative electrode active material layer 32C is formed.

[Assembly of secondary battery]
First, the positive electrode lead 34 is connected to the positive electrode 31 (positive electrode current collector 31A) by a welding method or the like, and the negative electrode lead 35 is connected to the negative electrode 32 (negative electrode current collector 32A) by a welding method or the like. Subsequently, the positive electrode 31 and the negative electrode 32 are laminated with each other via the separator 33, and then the positive electrode 31, the negative electrode 32, and the separator 33 are wound to form a wound body. Subsequently, the center pin 36 is inserted into the space provided at the winding center of the winding body.

Subsequently, in a state where the winding body is sandwiched between the pair of insulating plates 42 and 43, the winding body is stored together with the insulating plates 42 and 43 inside the battery can 41. In this case, the positive electrode lead 34 is connected to the safety valve mechanism 45 by a welding method or the like, and the negative electrode lead 35 is connected to the battery can 41 by a welding method or the like. Subsequently, the electrolytic solution is injected into the inside of the battery can 41. As a result, the positive electrode 31, the negative electrode 32, and the separator 33 are impregnated with the electrolytic solution, so that the wound electrode body 30 is formed.

Finally, by crimping the open end of the battery can 41 via the gasket 47, the battery lid 44, the safety valve mechanism 45, and the PTC element 46 are attached to the open end of the battery can 41. Therefore, since the wound electrode body 30 is enclosed inside the battery can 41, a cylindrical secondary battery is completed.

<1-2-4. Actions and effects>
According to this cylindrical secondary battery, the negative electrode 32 has the same configuration as that of the negative electrode 12, and the negative electrode storage / discharge capacity of the negative electrode 32 is smaller than the positive electrode storage / discharge capacity of the positive electrode 31. Therefore, excellent battery characteristics can be obtained for the same reason as described with respect to the laminated film type secondary battery.

Other actions and effects related to the cylindrical secondary battery are the same as those related to the laminated film type secondary battery.

<2. Modification example>
Next, a modification of the above-mentioned secondary battery will be described. The configuration of the secondary battery can be changed as appropriate as described below. However, any two or more types of modifications in the series of modifications described below may be combined with each other.

[Modification 1]
In FIGS. 1 and 2, a winding type battery element (winding electrode body 10) was used. However, as shown in FIG. 5 corresponding to FIG. 1 and FIG. 6 corresponding to FIG. 2, a laminated battery element (laminated electrode body 50) may be used instead of the wound electrode body 10.

In the laminated film type secondary battery shown in FIGS. 5 and 6, the laminated electrode body 50 (positive electrode body 50 (positive electrode body)) is used instead of the wound electrode body 10 (positive electrode body 11, negative electrode 12 and separator 13), positive electrode lead 14 and negative electrode lead 15. It has the same configuration as the laminated film type secondary battery shown in FIGS. 1 and 2 except that the 51, the negative electrode 52 and the separator 53), the positive electrode lead 54 and the negative electrode lead 55 are provided. There is.

The configurations of the positive electrode 51, the negative electrode 52, the separator 53, the positive electrode lead 54, and the negative electrode lead 55 are each of the positive electrode 11, the negative electrode 12, the separator 13, the positive electrode lead 14, and the negative electrode lead 15, except as described below. Similar to the configuration.

In the laminated electrode body 50, the positive electrode 51 and the negative electrode 52 are alternately laminated via the separator 53. The number of layers of the positive electrode 51, the negative electrode 52, and the separator 53 is not particularly limited, but here, the plurality of positive electrodes 51 and the plurality of negative electrodes 52 are laminated to each other via the plurality of separators 53. The electrolytic solution is impregnated in each of the positive electrode 51, the negative electrode 52, and the separator 53, and the structure of the electrolytic solution is as described above. The positive electrode 51 includes a positive electrode current collector 51A and a positive electrode active material layer 51B, and the negative electrode 52 includes a negative electrode current collector 52A, a base layer 52B, and a negative electrode active material layer 52C.

However, as shown in FIGS. 5 and 6, the positive electrode current collector 51A includes the protruding portion 51AT in which the positive electrode active material layer 51B is not formed, and the negative electrode current collector 52A includes the negative electrode active material layer. It includes a protrusion 52AT in which the 52C is not formed. The protruding portion 52AT is arranged at a position that does not overlap with the protruding portion 51AT. The plurality of protrusions 51AT are joined to each other to form one lead-shaped joint 51Z, and the plurality of protrusions 52AT are joined to each other to form one lead-like joint 51Z. The joint portion 52Z is formed. The positive electrode lead 54 is connected to the joint portion 51Z, and the negative electrode lead 55 is connected to the joint portion 52Z.

In the method for manufacturing the laminated film type secondary battery shown in FIGS. 5 and 6, the laminated electrode body 50 (positive electrode lead 54 and negative electrode lead 55) is used instead of the wound electrode body 10 (positive electrode lead 14 and negative electrode lead 15). The method is the same as the method for manufacturing the laminated film type secondary battery shown in FIGS. 1 and 2, except that the above is produced.

When producing the laminated electrode body 50, first, the positive electrode 51 in which the positive electrode active material layers 51B are formed on both sides of the positive electrode current collector 51A (excluding the protruding portion 51AT) and the negative electrode current collector 52A (protruding) After producing the negative electrode 52 in which the base layer 52B and the negative electrode active material layer 52C are formed on both sides of the portion 52AT), the plurality of positive electrodes 51 and the plurality of negative electrodes 52 are laminated with each other via the plurality of separators 53. As a result, a laminated body is formed. Subsequently, the joint portion 51Z is formed by joining the plurality of projecting portions 51AT to each other by using a welding method or the like, and the joining portion 52Z is formed by joining the plurality of projecting portions 52AT to each other by using a welding method or the like. To form. Subsequently, the positive electrode lead 54 is connected to the protruding portion 51AT by using a welding method or the like, and the negative electrode lead 55 is connected to the protruding portion 52AT by using a welding method or the like. Finally, the electrolytic solution is injected into the bag-shaped film 20 in which the laminate is housed, and then the film 20 is sealed. As a result, the laminated body is impregnated with the electrolytic solution, so that the laminated electrode body 50 is produced.

Even when the laminated electrode body 50 is used, the same effect as when the wound electrode body 10 is used can be obtained. Although not specifically shown here, a laminated battery element (laminated electrode body 50) may be applied to the cylindrical secondary batteries shown in FIGS. 2 and 4.

[Modification 2]
In the laminated film type secondary battery shown in FIGS. 5 and 6, the number of positive electrode leads 54 and the number of negative electrode leads 55 are not particularly limited. That is, the number of positive electrode leads 54 is not limited to one, and may be two or more, and the number of negative electrode leads 55 is not limited to one, and may be two or more. The same effect can be obtained even when the number of positive electrode leads 54 and the number of negative electrode leads 55 are changed. Although not specifically shown here, the number of positive electrode leads 34 and the number of negative electrode leads 35 may be changed in the cylindrical secondary batteries shown in FIGS. 2 and 4.

[Modification 3]
In the laminated film type secondary battery shown in FIGS. 1 and 2, a separator 13 which is a porous film was used. However, although not specifically shown here, a laminated separator containing a polymer compound layer may be used instead of the separator 13 which is a porous film.

Specifically, the laminated type separator includes the above-mentioned porous film base material layer and the polymer compound layer provided on one side or both sides of the base material layer. This is because the adhesion of the separator to each of the positive electrode 11 and the negative electrode 12 is improved, so that the positional deviation of the wound electrode body 10 is less likely to occur. As a result, the secondary battery is less likely to swell even if a decomposition reaction of the electrolytic solution occurs. The polymer compound layer contains a polymer compound such as polyvinylidene fluoride. This is because it has excellent physical strength and is electrochemically stable.

Note that one or both of the base material layer and the polymer compound layer may contain any one or more of a plurality of inorganic particles and a plurality of resin particles. This is because the heat resistance and safety of the secondary battery are improved because a plurality of inorganic particles and the like dissipate heat when the secondary battery generates heat. The type of the inorganic particles is not particularly limited, and includes aluminum oxide (alumina), aluminum nitride, boehmite, silicon oxide (silica), titanium oxide (titania), magnesium oxide (magnesia), and zirconium oxide (zirconia).

When producing a laminated separator, a precursor solution containing a polymer compound, an organic solvent, etc. is prepared, and then the precursor solution is applied to one or both sides of the base material layer.

Even when this laminated separator is used, lithium can move between the positive electrode 11 and the negative electrode 12, so that the same effect can be obtained. A laminated separator may be applied to the cylindrical secondary battery shown in FIGS. 2 and 4.

[Modification example 4]
In the laminated film type secondary battery shown in FIGS. 1 and 2, an electrolytic solution which is a liquid electrolyte was used. However, although not specifically shown here, an electrolyte layer, which is a gel-like electrolyte, may be used instead of the electrolytic solution.

In the wound electrode body 10 using the electrolyte layer, the positive electrode 11 and the negative electrode 12 are laminated with each other via the separator 13 and the electrolyte layer, and then the positive electrode 11, the negative electrode 12, the separator 13 and the electrolyte layer are wound. .. This electrolyte layer is interposed between the positive electrode 11 and the separator 13 and is interposed between the negative electrode 12 and the separator 13.

Specifically, the electrolyte layer contains a polymer compound together with the electrolytic solution, and the electrolytic solution is held by the polymer compound in the electrolyte layer. The composition of the electrolytic solution is as described above. The polymer compound contains polyvinylidene fluoride and the like. When forming the electrolyte layer, a precursor solution containing an electrolytic solution, a polymer compound, an organic solvent and the like is prepared, and then the precursor solution is applied to both the positive electrode 11 and the negative electrode 12.

Even when this electrolyte layer is used, the same effect can be obtained because lithium can move between the positive electrode 11 and the negative electrode 12 via the electrolyte layer. The electrolyte layer may be applied to the cylindrical secondary battery shown in FIGS. 2 and 4.

<3. Applications for secondary batteries>
Next, the application (application example) of the above-mentioned secondary battery will be described.

Secondary batteries are mainly used for machines, devices, appliances, devices and systems (aggregates of multiple devices, etc.) in which the secondary battery can be used as a power source for driving or a power storage source for storing power. If so, it is not particularly limited. The secondary battery used as a power source may be a main power source or an auxiliary power source. The main power source is a power source that is preferentially used regardless of the presence or absence of another power source. The auxiliary power supply may be a power supply used in place of the main power supply, or may be a power supply that can be switched from the main power supply as needed. When a secondary battery is used as an auxiliary power source, the type of main power source is not limited to the secondary battery.

Specific examples of applications for secondary batteries are as follows. Electronic devices (including portable electronic devices) such as video cameras, digital still cameras, mobile phones, laptop computers, cordless phones, headphone stereos, portable radios, portable TVs and portable information terminals. It is a portable living appliance such as an electric shaver. A storage device such as a backup power supply and a memory card. Electric tools such as electric drills and electric saws. It is a battery pack that is installed in notebook computers as a removable power source. Medical electronic devices such as pacemakers and hearing aids. It is an electric vehicle such as an electric vehicle (including a hybrid vehicle). It is a power storage system such as a household battery system that stores power in case of an emergency. The battery structure of the secondary battery may be the above-mentioned laminated film type or cylindrical type, or may be another battery structure other than these. Further, a plurality of secondary batteries may be used as the battery pack, the battery module, and the like.

Above all, it is effective that the battery pack and the battery module are applied to relatively large equipment such as electric vehicles, electric power storage systems and electric tools. As the battery pack, as will be described later, a single battery or an assembled battery may be used. The electric vehicle is a vehicle that operates (runs) using a secondary battery as a driving power source, and may be a vehicle (hybrid vehicle or the like) that also has a drive source other than the secondary battery as described above. A power storage system is a system that uses a secondary battery as a power storage source. In a household electric power storage system, since electric power is stored in a secondary battery which is an electric power storage source, it is possible to use the electric power for household electric products and the like.

Here, some application examples of the secondary battery will be specifically described. The configuration of the application example described below is just an example, and can be changed as appropriate. The type of the secondary battery used in the following application examples is not particularly limited, and may be a laminated film type or a cylindrical type.

<3-1. Battery pack (cell) ＞
FIG. 7 shows a block configuration of a battery pack using a cell. The battery pack described here is a simple battery pack (so-called soft pack) using one secondary battery, and is mounted on an electronic device represented by a smartphone.

As shown in FIG. 7, this battery pack includes a power supply 61 and a circuit board 62. The circuit board 62 is connected to the power supply 61 and includes a positive electrode terminal 63, a negative electrode terminal 64, and a temperature detection terminal (so-called T terminal) 65.

The power supply 61 includes one secondary battery. In this secondary battery, the positive electrode lead is connected to the positive electrode terminal 63, and the negative electrode lead is connected to the negative electrode terminal 64. Since this power supply 61 can be connected to the outside via the positive electrode terminal 63 and the negative electrode terminal 64, it can be charged and discharged through the positive electrode terminal 63 and the negative electrode terminal 64. The circuit board 62 includes a control unit 66, a switch 67, a PTC element 68, and a temperature detection unit 69. However, the PTC element 68 may be omitted.

The control unit 66 includes a central processing unit (CPU: Central Processing Unit), a memory, and the like, and controls the operation of the entire battery pack. The control unit 66 detects and controls the usage state of the power supply 61 as needed.

When the battery voltage of the power supply 61 (secondary battery) reaches the overcharge detection voltage or the overdischarge detection voltage, the control unit 66 disconnects the switch 67 so that the charging current does not flow in the current path of the power supply 61. To do so. Further, when a large current flows during charging or discharging, the control unit 66 cuts off the charging current by disconnecting the switch 67. The overcharge detection voltage and the overdischarge detection voltage are not particularly limited. As an example, the overcharge detection voltage is 4.2V ± 0.05V, and the overdischarge detection voltage is 2.4V ± 0.1V.

The switch 67 includes a charge control switch, a discharge control switch, a charging diode, a discharging diode, and the like, and switches whether or not the power supply 61 is connected to an external device according to an instruction from the control unit 66. This switch 67 includes a field effect transistor (MOSFET: Metal-Oxide-Semiconductor Field-Effect Transistor) using a metal oxide semiconductor, and the charge / discharge current is detected based on the ON resistance of the switch 67. ..

The temperature detection unit 69 includes a temperature detection element such as a thermistor, measures the temperature of the power supply 61 using the temperature detection terminal 65, and outputs the measurement result of the temperature to the control unit 66. The temperature measurement result measured by the temperature detection unit 69 is used when the control unit 66 performs charge / discharge control when abnormal heat generation occurs, or when the control unit 66 performs correction processing when calculating the remaining capacity.

<3-2. Battery pack (assembled battery)>
FIG. 8 shows a block configuration of a battery pack using an assembled battery. In the following description, the components of the battery pack (FIG. 7) using a cell will be quoted from time to time.

As shown in FIG. 8, this battery pack includes a positive electrode terminal 81 and a negative electrode terminal 82. Specifically, the battery pack contains a control unit 71, a power supply 72, a switch 73, a current measurement unit 74, a temperature detection unit 75, a voltage detection unit 76, and a switch control unit inside the housing 70. It includes 77, a memory 78, a temperature detection element 79, and a current detection resistor 80.

The power supply 72 includes an assembled battery in which two or more secondary batteries are connected to each other, and the connection form of the two or more secondary batteries is not particularly limited. Therefore, the connection method may be in series, in parallel, or a mixed type of both. As an example, the power supply 72 includes six secondary batteries connected to each other so as to be in two parallels and three series.

The configuration of the control unit 71, the switch 73, the temperature detection unit 75, and the temperature detection element 79 is the same as the configuration of the control unit 66, the switch 67, and the temperature detection unit 69 (temperature detection element). The current measuring unit 74 measures the current using the current detection resistor 80, and outputs the measurement result of the current to the control unit 71. The voltage detection unit 76 measures the battery voltage of the power source 72 (secondary battery) and supplies the measurement result of the analog-to-digital converted voltage to the control unit 71.

The switch control unit 77 controls the operation of the switch 73 according to the signals input from the current measurement unit 74 and the voltage detection unit 76. When the battery voltage reaches the overcharge detection voltage or the overdischarge detection voltage, the switch control unit 77 disconnects the switch 73 (charge control switch) so that the charge current does not flow in the current path of the power supply 72. .. As a result, in the power supply 72, only discharging is possible through the discharging diode, or only charging is possible through the charging diode. Further, the switch control unit 77 cuts off the charging current or the discharging current when a large current flows during charging or discharging.

By omitting the switch control unit 77, the control unit 71 may also function as the switch control unit 77. The overcharge detection voltage and the overdischarge detection voltage are not particularly limited, but are the same as those described for the battery pack using a cell.

The memory 78 includes an EEPROM (Electrically Erasable Programmable Read-Only Memory) which is a non-volatile memory, and the memory 78 includes a numerical value calculated by the control unit 71 and a secondary battery measured in the manufacturing process. Information (initial resistance, full charge capacity, remaining capacity, etc.) is stored.

The positive electrode terminal 81 and the negative electrode terminal 82 are terminals connected to an external device (such as a notebook personal computer) that operates using the battery pack and an external device (such as a charger) that is used to charge the battery pack. is there. The power supply 72 (secondary battery) can be charged and discharged via the positive electrode terminal 81 and the negative electrode terminal 82.

<3-3. Electric vehicle>
FIG. 9 shows a block configuration of a hybrid vehicle which is an example of an electric vehicle. As shown in FIG. 9, this electric vehicle includes a control unit 84, an engine 85, a power supply 86, a motor 87, a differential device 88, a generator 89, and a transmission 90 inside the housing 83. It also includes a clutch 91, inverters 92 and 93, and various sensors 94. Further, the electric vehicle includes a front wheel drive shaft 95 and a pair of front wheels 96 connected to the differential device 88 and the transmission 90, and a rear wheel drive shaft 97 and a pair of rear wheels 98.

This electric vehicle can run using either one of the engine 85 and the motor 87 as a drive source. The engine 85 is a main power source such as a gasoline engine. When the engine 85 is used as a power source, the driving force (rotational force) of the engine 85 is transmitted to the front wheels 96 and the rear wheels 98 via the differential device 88, the transmission 90, and the clutch 91, which are the driving units. Since the rotational force of the engine 85 is transmitted to the generator 89, the generator 89 uses the rotational force to generate AC power, and the AC power is converted into DC power via the inverter 93. Therefore, the DC power is stored in the power source 86. On the other hand, when the motor 87, which is a conversion unit, is used as a power source, the electric power (DC power) supplied from the power source 86 is converted into AC power via the inverter 92, and the AC power is used to convert the motor. 87 is driven. The driving force (rotational force) converted from the electric power by the motor 87 is transmitted to the front wheels 96 and the rear wheels 98 via the differential device 88, the transmission 90, and the clutch 91, which are the driving units.

When the electric vehicle decelerates through the braking mechanism, the resistance force at the time of deceleration is transmitted to the motor 87 as a rotational force. Therefore, the motor 87 may generate AC power by using the rotational force. Since this AC power is converted into DC power via the inverter 92, the DC regenerative power is stored in the power supply 86.

The control unit 84 includes a CPU and the like, and controls the operation of the entire electric vehicle. The power supply 86 includes one or more secondary batteries and is connected to an external power source. In this case, the power supply 86 may store electric power by being supplied with electric power from an external power source. The various sensors 94 are used to control the rotation speed of the engine 85 and to control the opening degree (throttle opening degree) of the throttle valve. The various sensors 94 include any one type or two or more types of a speed sensor, an acceleration sensor, an engine speed sensor, and the like.

Although the case where the electric vehicle is a hybrid vehicle is taken as an example, the electric vehicle may be a vehicle (electric vehicle) that operates using only the power supply 86 and the motor 87 without using the engine 85.

<3-4. Others>
Although not specifically shown here, other application examples can be considered as application examples of the secondary battery.

Specifically, the secondary battery is applicable to the power storage system. This power storage system includes a control unit, a power source including one or more secondary batteries, a smart meter, and a power hub inside a house such as a general house or a commercial building.

The power supply is connected to electrical equipment such as a refrigerator installed inside the house, and can also be connected to an electric vehicle such as a hybrid vehicle parked outside the house. In addition, the power supply is connected to a private power generator such as a solar power generator installed in a house via a power hub, and is also connected to a centralized power system such as an external thermal power plant via a smart meter and a power hub. Has been done.

Alternatively, the secondary battery can be applied to electric tools such as electric drills and electric saws. This power tool includes a control unit and a power supply including one or more secondary batteries inside a housing to which a movable portion such as a drill portion and a saw blade portion is attached.

An embodiment of this technology will be described.

(Experimental Examples 1-1 to 1-5)
FIG. 10 shows a cross-sectional configuration of a secondary battery (coin type) for testing. Here, after producing a coin-type secondary battery, the battery characteristics of the secondary battery were evaluated.

In the coin-type secondary battery, as shown in FIG. 10, the test pole 101 is housed inside the outer cup 104, and the counter electrode 103 is housed inside the outer can 102. The test pole 101 and the counter electrode 103 are laminated to each other via the separator 105, and the outer can 102 and the outer cup 104 are crimped to each other via the gasket 106. The electrolytic solution is impregnated in each of the test electrode 101, the counter electrode 103 and the separator 105.

[Making secondary batteries]
First, a secondary battery was manufactured by the procedure described below.

(Preparation of test pole)
Here, a negative electrode was produced as a test electrode 101. First, 98 parts by mass of a carbon material (carbon black, peak intensity ratio ID / IG = 1.1) and 2 parts by mass of a base binder (1 part by mass of styrene butadiene rubber and 1 part by mass of carboxymethyl cellulose) are mixed. As a result, it was used as a base mixture. The BET specific surface area (m ² / g) of this carbon material is as shown in Table 1. Subsequently, a base mixture was added to an aqueous solvent (pure water), and then the aqueous solvent was stirred to prepare a paste-like base mixture slurry. Subsequently, the undercoat mixture slurry was applied to both sides of the negative electrode current collector (copper foil, thickness = 15 μm) using a coating device, and then the undercoat mixture slurry was dried to form an underlayer.

Subsequently, 90 parts by mass of the negative electrode active material (70 parts by mass of graphite which is a carbon-based active material and 20 parts by mass of silicon oxide (SiO) which is a silicon-based active material) and 90 parts by mass of a negative electrode binder (1 part by mass of styrene butadiene rubber and). A negative electrode mixture was prepared by mixing 2 parts by mass of carboxymethyl cellulose (1 part by mass) and 8 parts by mass of a negative electrode conductive agent (carbon black). Subsequently, the negative electrode mixture was added to the aqueous solvent (pure water), and then the aqueous solvent was stirred to prepare a paste-like negative electrode mixture slurry. Subsequently, a negative electrode mixture slurry was applied to the surface of the base layer using a coating device, and then the negative electrode mixture slurry was dried to form a negative electrode active material layer.

Finally, the negative electrode current collector on which the base layer and the negative electrode active material layer were formed was punched into a disk shape (outer diameter = 16 mm), and then the negative electrode active material layer was compression-molded using a uniaxial hydraulic press. As a result, a test electrode 101, which is a negative electrode, was produced. However, when the test electrode 101 is produced, the negative electrode storage / release capacity is increased by adjusting the amount of the negative electrode active material (carbon-based active material and silicon-based active material) with respect to the amount of the positive electrode active material. I made it smaller than the capacity.

For comparison, the test electrode 101 was prepared by the same procedure except that the base layer was not formed. Further, for comparison, the test electrode 101 was prepared by the same procedure except that only one of the carbon-based active material and the silicon-based active material was used as the negative electrode active material. Further, for comparison, the test electrode 101 was prepared by the same procedure except that the base layer was not formed and only the carbon-based active material was used as the negative electrode active material.

(Making the opposite pole)
Here, a positive electrode was produced as the counter electrode 103. First, by mixing 95 parts by mass of the positive electrode active material (lithium cobalt oxide (LiCoO ₂ )), 3 parts by mass of the positive electrode binder (vinylidene fluoride), and 2 parts by mass of the positive electrode conductive agent (carbon black). , Positive electrode mixture. Subsequently, a positive electrode mixture was added to an organic solvent (N-methyl-2-pyrrolidone), and then the organic solvent was stirred to obtain a paste-like positive electrode mixture slurry. Subsequently, a positive electrode mixture slurry is applied to both sides of the positive electrode current collector (aluminum foil, thickness = 15 μm) using a coating device, and then the positive electrode mixture slurry is dried to form a positive electrode active material layer. did. Finally, the positive electrode current collector on which the positive electrode active material layer was formed was punched into a disk shape (outer diameter = 15 mm), and then the positive electrode active material layer was compression molded using a roll press machine. As a result, the counter electrode 103, which is a positive electrode, was produced.

(Preparation of electrolyte)
The electrolyte salt (lithium hexafluorophosphate) was added to the solvent (ethylene carbonate and ethylmethyl carbonate), and then the solvent was stirred. The mixing ratio (weight ratio) of the solvent was ethylene carbonate: ethyl methyl carbonate = 50:50. The content of the electrolyte salt was 1 mol / kg with respect to the solvent.

(Assembly of secondary battery)
First, the test pole 101 was housed inside the outer cup 104, and the counter electrode 103 was housed inside the outer can 102. Subsequently, the test pole 101 housed inside the outer cup 104 and the counter electrode 103 housed inside the outer can 102 were laminated with each other via the separator 105 impregnated with the electrolytic solution. As a result, a part of the electrolytic solution impregnated in the separator 105 was impregnated in each of the test electrode 101 and the counter electrode 103. Finally, the outer can 102 and the outer cup 104 were crimped to each other via the gasket 106 in a state where the test pole 101 and the counter electrode 103 were laminated with each other via the separator 105. Therefore, the test pole 101, the counter electrode 103, the separator 105, and the electrolytic solution were sealed by the outer can 102 and the outer cup 104, so that the coin-type secondary battery was completed.

[Evaluation of battery characteristics]
When the battery characteristics (cycle characteristics) of the secondary battery were evaluated, the results shown in Table 1 were obtained.

When examining the cycle characteristics, first, in order to stabilize the state of the secondary battery, the secondary battery was charged and discharged for one cycle in a room temperature environment (temperature = 23 ° C.). Subsequently, the discharge capacity of the second cycle was measured by charging and discharging the secondary battery in the same environment. Subsequently, the discharge capacity at the 100th cycle was measured by repeatedly charging and discharging the secondary battery until the number of charge / discharge cycles reached 100 cycles in the same environment. Finally, the capacity retention rate (%) = (discharge capacity in the 100th cycle / discharge capacity in the second cycle) × 100 was calculated.

At the time of charging, a constant current charge was performed until the voltage reached 4.25 V at a current of 0.5 C, and then a constant voltage charge was performed until the current reached 0.05 C at the voltage of 4.25 V. At the time of discharge, constant current discharge was performed at a current of 0.5 C until the voltage reached 3.0 V. 0.5C is a current value that can completely discharge the battery capacity (theoretical capacity) in 2 hours, and 0.05C is a current value that can completely discharge the above-mentioned battery capacity in 20 hours.

[Discussion]
As shown in Table 1, the negative electrode active material (one or both of the carbon-based active material and the silicon-based active material) was used, and the negative electrode storage / release capacity was set to be smaller than the positive electrode storage / release capacity. In the secondary battery, the battery characteristics (cycle characteristics) of the secondary battery fluctuated greatly depending on the presence or absence of the base layer.

Specifically, when only a carbon-based active material was used as the negative electrode active material (Experimental Examples 1-2, 1-3), the capacity retention rate did not change depending on the presence or absence of the underlying layer. That is, when the base layer was not formed (Experimental Example 1-2), a high capacity retention rate was obtained, and the same was also obtained when the base layer was formed (Experimental Example 1-3). A high capacity retention rate was obtained.

On the other hand, when both a carbon-based active material and a silicon-based active material are used as the negative electrode active material (Experimental Examples 1-1, 1-4), the capacity retention rate is significantly increased depending on the presence or absence of the underlying layer. Changed to. That is, when the base layer was not formed (Experimental Example 1-4), the capacity was compared with the case where only the carbon-based active material was used as the negative electrode active material (Experimental Examples 1-2, 1-3). The maintenance rate has decreased significantly. However, when the base layer was formed (Experimental Example 1-1), the capacity retention rate was significantly increased as compared with the case where the base layer was not formed (Experimental Example 1-4). In other words, when the underlayer is formed (Experimental Example 1-1), the capacity is maintained as compared with the case where only the carbon-based active material is used as the negative electrode active material (Experimental Examples 1-2, 1-3). Although the rate decreased, the decrease in the capacity retention rate was sufficiently suppressed, so that a high capacity retention rate within the permissible range was obtained.

When only a silicon-based active material was used as the negative electrode active material (Experimental Example 1-5), the capacity retention rate drastically decreased even though the base layer was formed.

From these facts, in a secondary battery in which the negative electrode storage / discharge capacity is set to be smaller than the positive electrode storage / discharge capacity, the base layer has a function of increasing the capacity retention rate, in other words, the base layer expands the negative electrode active material and The function of sufficiently suppressing the decrease in the capacity retention rate due to shrinkage cannot be obtained when only the carbon-based active material is used, and is obtained only when both the carbon-based active material and the silicon-based active material are used. Is a special advantage.

(Experimental Examples 2-1 to 2-5)
As shown in Table 2, a secondary battery was produced and the battery characteristics were evaluated by the same procedure except that the BET specific surface area of the carbon material was changed. In this case, the BET specific surface area was changed by using a plurality of types of carbon materials (carbon black) having different BET specific surface areas.

As shown in Table 2, a high capacity retention rate was obtained even when the BET specific surface area was changed (Experimental Examples 2-1 to 2-5). Above all, when the BET specific surface area of the carbon material was 30 m ² / g to 300 m ² / g (Experimental Examples 1-1, 2-2 to 2-4), the capacity retention rate was further increased.

(Experimental Examples 3-1 to 3-3)
As shown in Table 3, a secondary battery was produced and the battery characteristics were evaluated by the same procedure except that the peak intensity ratio ID / IG of the carbon material was changed. In this case, the peak intensity ratio ID / IG was changed by using a plurality of types of carbon materials (carbon black) having different peak intensity ratio IDs / IGs. This peak intensity ratio ID / IG changed according to the firing temperature during the production of carbon black.

As shown in Table 3, a high capacity retention rate was obtained even when the peak intensity ratio ID / IG was changed (Experimental Examples 3-1 to 3-3). Above all, when the peak intensity ratio ID / IG was 1.0 or more (Experimental Examples 1-1, 3-2, 3-3), the capacity retention rate was further increased.

[Summary]
From the results shown in Tables 1 to 3, the negative electrode contains a negative electrode current collector, an underlayer (carbon material) and a negative electrode active material layer (carbon-based active material and silicon-based active material), and the negative electrode is stored in the negative electrode. When the discharge capacity was smaller than the positive electrode storage and discharge capacity of the positive electrode, the cycle characteristics were improved. Therefore, excellent battery characteristics have been obtained in a secondary battery in which the battery capacity can be obtained by utilizing the lithium storage / release phenomenon and the lithium precipitation / dissolution phenomenon.

Although the present technology has been described above with reference to one embodiment and examples, the configuration of the present technology is not limited to the configurations described in one embodiment and examples, and thus can be variously modified.

Specifically, the case where a liquid electrolyte (electrolyte solution) and a gel-like electrolyte (electrolyte layer) are used has been described, but since the type of the electrolyte is not particularly limited, a solid electrolyte (solid electrolyte) is used. You may.

Further, the case where the battery structure of the secondary battery is a laminated film type, a cylindrical type, or a coin type has been described, but since the battery structure is not particularly limited, other battery structures such as a square type may be used.

Further, the case where the element structure of the battery element is a winding type or a laminated type has been described, but since the element structure of the battery element is not particularly limited, the electrodes (positive electrode and negative electrode) are folded in a zigzag pattern. Other element structures such as a folding type may be used.

Further, although the case where the electrode reactant is lithium has been described, the electrode reactant is not particularly limited. Specifically, the electrode reactant may be another alkali metal such as sodium and potassium, or an alkaline earth metal such as beryllium, magnesium and calcium. In addition, the electrode reactant may be another light metal such as aluminum.

Since the effects described in the present specification are merely examples, the effects of the present technology are not limited to the effects described in the present specification. Therefore, other effects may be obtained with respect to the present technology.

Claims (8)

1. A positive electrode containing a positive electrode active material that occludes and releases lithium, and a positive electrode that can obtain a positive electrode occlusal and release capacity when occluding and releasing lithium in the positive electrode active material
   The negative electrode activity includes a negative electrode current collector, a base layer provided on the negative electrode current collector and containing a carbon material, and a negative electrode active material provided on the base layer and storing and releasing the lithium. A negative electrode active material layer in which the material contains a carbon-based active material and a silicon-based active material, and the negative electrode storage / release capacity obtained when storing and releasing the lithium in the negative electrode active material is smaller than the positive electrode storage / release capacity. Including negative electrode and
   A rechargeable battery with an electrolyte.
2. The carbon material is in the form of a plurality of particles and is in the form of a plurality of particles.
   The BET specific surface area of the plurality of particulate carbon materials is 30 m ² / g or more and 300 m ² / g or less.
   The secondary battery according to claim 1.
3. When analyzing the carbon material using a Raman spectroscopy, to the peak intensity IG of the G band is detected near 1580 cm ^-1, the ratio ID / IG of the peak intensity ID of D band is detected near 1360 cm ^-1 is , 1.0 or more,
   The secondary battery according to claim 1 or 2.
4. The carbon material comprises at least one of carbon black, acetylene black and ketjen black.
   The secondary battery according to any one of claims 1 to 3.
5. The carbon-based active material contains graphite and contains graphite.
   The silicon-based active material contains silicon oxide represented by SiO _x (0 <x ≦ 2).
   The secondary battery according to any one of claims 1 to 4.
6. The silicon-based active material contains SiO.
   The secondary battery according to claim 5.
7. When the open circuit voltage is lower than the overcharge voltage, the lithium is deposited on the surface of the negative electrode.
   The secondary battery according to any one of claims 1 to 6.
8. The total capacity of the negative electrode is the sum of the negative electrode occlusion / release capacity and the negative electrode precipitation / dissolution capacity obtained when the lithium is precipitated and dissolved in the negative electrode.
   The secondary battery according to claim 7.

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