JP6332258B2 - Lithium ion secondary battery, negative electrode for lithium ion secondary battery, battery pack, electric vehicle, power storage system, electric tool and electronic device - Google Patents

Description

  The present technology includes a negative electrode for a lithium ion secondary battery including a negative electrode active material capable of occluding and releasing lithium ions, a lithium ion secondary battery using the negative electrode, a battery pack using the secondary battery, an electric vehicle, and electric power. The present invention relates to a storage system, a power tool, and an electronic device.

  In recent years, electronic devices typified by mobile phones or personal digital assistants (PDAs) have become widespread, and further downsizing, weight reduction, and long life have been strongly demanded. Accordingly, as a power source, development of a battery, in particular, a secondary battery that is small and lightweight and capable of obtaining a high energy density is in progress. In recent years, the secondary battery is not limited to the above-described electronic devices, but includes a battery pack, an electric vehicle such as an electric vehicle, a power storage system such as a household power server, or a variety of electric tools such as an electric drill. Application to applications is also being studied.

  As secondary batteries, those using various charging / discharging principles have been widely proposed, and among them, lithium ion secondary batteries using occlusion / release of lithium ions are considered promising. This is because higher energy density can be obtained than lead batteries and nickel cadmium batteries.

  A lithium ion secondary battery includes an electrolyte solution together with a positive electrode and a negative electrode, and the negative electrode includes a negative electrode active material capable of occluding and releasing lithium ions. As the negative electrode active material, a carbon material such as graphite is widely used, but recently, since further improvement in battery capacity is required, the use of Si has been studied. This is because the theoretical capacity of Si (4199 mAh / g) is much larger than the theoretical capacity of graphite (372 mAh / g), so that significant improvement in battery capacity can be expected.

  However, when Si is used as the negative electrode active material, the negative electrode active material violently expands and contracts during charge and discharge, and therefore, the negative electrode active material is easily cracked mainly in the vicinity of the surface layer. When the negative electrode active material is cracked, a highly reactive new surface (active surface) is generated, and the surface area (reaction area) of the negative electrode active material is increased. As a result, a decomposition reaction of the electrolytic solution occurs on the new surface, and the electrolytic solution is consumed to form a coating derived from the electrolytic solution on the new surface, so that battery characteristics such as cycle characteristics are likely to deteriorate.

  Therefore, various studies have been made on the configuration of lithium ion secondary batteries in order to improve battery characteristics such as cycle characteristics.

Specifically, in order to improve cycle characteristics and safety, Si and amorphous SiO ₂ are simultaneously deposited using a sputtering method (see, for example, Patent Document 1). In order to obtain excellent battery capacity and safety performance, an electron conductive material layer (carbon material) is provided on the surface of the SiO _x particles (see, for example, Patent Document 2). In order to improve the high-rate charge / discharge characteristics and cycle characteristics, the negative electrode active material layer is formed so as to contain Si and O and to increase the oxygen ratio on the side closer to the negative electrode current collector (for example, Patent Document 3). reference.). In order to improve cycle characteristics, the negative electrode active material layer contains Si and O, the total average oxygen content is 40 atomic% or less, and the average oxygen content is increased on the side closer to the negative electrode current collector. (For example, refer to Patent Document 4). In this case, the difference between the average oxygen content on the side close to the negative electrode current collector and the average oxygen content on the side far from the negative electrode current collector is 4 atomic% to 30 atomic%.

Further, in order to improve the initial charge / discharge characteristics and the like, a nanocomposite containing Si phase, SiO ₂ and _MyO metal oxide is used (for example, see Patent Document 5). In order to improve cycle characteristics, powdery SiO _x (0.8 ≦ x ≦ 1.5, particle size range = 1 μm to 50 μm) and a carbonaceous material are mixed, and 800 ° C. to 1600 ° C. × 3 hours. Baked for ˜12 hours (see, for example, Patent Document 6). In order to shorten the initial charge time, a negative electrode active material represented by Li _a SiO _x (0.5 ≦ a−x ≦ 1.1 and 0.2 ≦ x ≦ 1.2) is used (for example, (See Patent Document 7). In this case, Li is deposited on an active material precursor containing Si and O. In order to improve the charge / discharge cycle characteristics, the molar ratio of the O amount to the Si amount in the negative electrode active material body is 0.1 to 1.2, and the Si amount in the vicinity of the interface between the negative electrode active material body and the current collector The composition of SiO _x is controlled so that the difference between the maximum value and the minimum value of the molar ratio of the amount of O to is 0.4 or less (see, for example, Patent Document 8). In order to improve the load characteristics, a Li-containing porous metal oxide (Li _x SiO: 2.1 ≦ x ≦ 4) is used (for example, refer to Patent Document 9).

Furthermore, in order to improve charge / discharge cycle characteristics, a hydrophobized layer such as a silane compound or a siloxane compound is formed on a thin film containing Si (see, for example, Patent Document 10). In order to improve cycle characteristics, a conductive powder in which the surface of SiO _x (0.5 ≦ x <1.6) is coated with a graphite film is used (see, for example, Patent Document 11). In this case, with a broad peak appears at 1330 cm ^-1 and 1580 cm ^-1 in the Raman shift of the Raman spectra for graphite coating, their intensity ratio I ₁₃₃₀ / I ₁₅₈₀ and _{1.5 <I 1330 / I 1580 <} 3 It is said. In order to improve battery capacity and cycle characteristics, a powder containing 1% by mass to 30% by mass of particles having a structure in which Si microcrystals (crystal size = 1 nm to 500 nm) are dispersed in SiO ₂ is used. (For example, refer to Patent Document 12). In this case, in the particle size distribution by the laser diffraction / scattering particle size distribution measurement method, the cumulative 90% diameter (D90) of the powder is 50 μm or less and the particle diameter of the particles is less than 2 μm. In order to improve cycle characteristics, SiO _x (0.3 ≦ x ≦ 1.6) is used, and the electrode unit is pressurized at 3 kgf / cm ² or more during charge / discharge (see, for example, Patent Document 13). . In order to improve overcharge characteristics, overdischarge characteristics, and the like, an Si oxide having an Si / O atomic ratio of 1: y (0 <y <2) is used (see, for example, Patent Document 14). ).

  In addition, in order to accumulate or release a large amount of lithium ions electrochemically, an amorphous metal oxide is provided on the surface of primary particles such as Si (see, for example, Patent Document 15). The Gibbs free energy at the time of metal oxidation for forming this metal oxide is smaller than the Gibbs free energy at the time of oxidation of Si or the like. In order to achieve high capacity, high efficiency, high operating voltage, and long life, it has been proposed to use a negative electrode material in which the oxidation number of Si atoms satisfies a predetermined condition (see, for example, Patent Document 16). The negative electrode material includes Si having an oxidation number of 0, a Si compound having a Si atom having an oxidation number of +4, and a Si lower oxide having an oxidation number of greater than 0 and less than +4.

JP 2001-185127 A JP 2002-042806 A JP 2006-164955 A JP 2006-114454 A JP 2009-070825 A JP 2008-282819 A International Publication No. 2007/010922 Pamphlet JP 2008-251369 A JP 2008-177346 A JP 2007-234255 A JP 2009-212074 A JP 2009-205950 A JP 2009-076373 A Japanese Patent No. 2,997,741 JP 2009-164104 A JP 2005-183264 A

  Electronic devices and the like are becoming more sophisticated and multifunctional, and their use frequency is increasing. Therefore, lithium ion secondary batteries tend to be charged and discharged frequently. Therefore, further improvement is desired for the battery characteristics of the lithium ion secondary battery.

  The present technology has been made in view of such problems, and the purpose thereof is a negative electrode for a lithium ion secondary battery, a lithium ion secondary battery, a battery pack, an electric vehicle, and an electric power storage capable of obtaining excellent battery characteristics. It is to provide a system, a power tool, and an electronic device.

The negative electrode for a lithium ion secondary battery of the present technology includes an active material, and the active material can occlude and release lithium ions, and a covering portion provided on at least a part of the surface of the core portion, Is included. The core part includes Si and O and at least one element M2 of Fe and Al as constituent elements, and the ratio of M2 to Si and O (M2 / (Si + O)) is 1 atom% to 50 atoms %. Covering parts are Si, O, Li, C, Mg, Al, Ca, Ti, Cr, Mn, Fe, Co, Ni, Cu, Ge, Zr, Mo, Ag, Sn, Ba, W, Ta, Na and it viewed including as constituent elements and at least one element M1 of the K, the atomic ratio of O to the Si y (O / Si) is 0.5 ≦ y ≦ 1.8. Moreover, the lithium ion secondary battery of this technique is equipped with electrolyte solution with a positive electrode and a negative electrode, and the negative electrode contains the active material similar to the negative electrode for lithium ion secondary batteries mentioned above. Furthermore, the battery pack, the electric vehicle, the power storage system, the electric tool, or the electronic device of the present technology uses the above-described lithium ion secondary battery of the present technology.

According to the negative electrode for a lithium ion secondary battery or the lithium ion secondary battery of the present technology, the active material of the negative electrode has a coating portion on the surface of the core portion , and the core portion includes an element M2 such as Si, O, and Fe. As a constituent element, and the ratio of M2 to Si and O (M2 / (Si + O)) is 1 atomic% to 50 atomic%, and the covering part contains Si, O, and an element M1 such as Li as constituent elements. At the same time, the atomic ratio y (O / Si) of O to Si is 0.5 ≦ y ≦ 1.8. Therefore, excellent battery characteristics can be obtained. Moreover, the same effect can be acquired also with the battery pack using the lithium ion secondary battery of this technique, an electric vehicle, an electric power storage system, an electric tool, or an electronic device.

It is sectional drawing showing the structure of the negative electrode for lithium ion secondary batteries of one Embodiment of this technique. It is a scanning electron microscope (SEM) photograph showing the cross-sectional structure of a negative electrode active material. It is sectional drawing showing the structure of the lithium ion secondary battery (square shape) of one Embodiment of this technique. It is sectional drawing along the IV-IV line of the lithium ion secondary battery shown in FIG. FIG. 5 is a plan view schematically illustrating the configuration of a positive electrode and a negative electrode illustrated in FIG. 4. It is sectional drawing showing the structure of the lithium ion secondary battery (cylindrical type) of one Embodiment of this technique. It is sectional drawing which expands and represents a part of winding electrode body shown in FIG. It is a disassembled perspective view showing the structure of the lithium ion secondary battery (laminate film type) of one Embodiment of this technique. It is sectional drawing along the IX-IX line of the winding electrode body shown in FIG. It is a block diagram showing the structure of the example of application (battery pack) of a lithium ion secondary battery. It is a block diagram showing the structure of the example of application (electric vehicle) of a lithium ion secondary battery. It is a block diagram showing the structure of the application example (electric power storage system) of a lithium ion secondary battery. It is a block diagram showing the structure of the example of application (electric tool) of a lithium ion secondary battery.

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

1. 1. Negative electrode for lithium ion secondary battery Lithium ion secondary battery 2-1. Square type 2-2. Cylindrical type 2-3. Laminate film type 3. Use of lithium ion secondary battery 3-1. Battery pack 3-2. Electric vehicle 3-3. Electric power storage system 3-4. Electric tool

<1. Negative electrode for lithium ion secondary battery>
FIG. 1 illustrates a cross-sectional configuration of a negative electrode for a lithium ion secondary battery (hereinafter simply referred to as “negative electrode”) according to an embodiment of the present technology. FIG. 2 is an SEM photograph showing a cross-sectional structure of an active material (negative electrode active material) included in the negative electrode.

[Overall structure of negative electrode]
For example, the negative electrode has a negative electrode active material layer 2 on a negative electrode current collector 1 as shown in FIG. In this negative electrode, the negative electrode active material layer 2 may be provided on both surfaces of the negative electrode current collector 1, or may be provided on only one surface. However, the negative electrode current collector 1 may not be provided.

[Negative electrode current collector]
The negative electrode current collector 1 is formed of, for example, a conductive material that is excellent in electrochemical stability, electrical conductivity, and mechanical strength. Such a conductive material is, for example, Cu, Ni or stainless steel. Among these, a material that does not form an intermetallic compound with Li and is alloyed with the negative electrode active material layer 2 is preferable.

  The negative electrode current collector 1 preferably contains C and S as constituent elements. This is because the physical strength of the negative electrode current collector 1 is improved, so that the negative electrode current collector 1 is hardly deformed even when the negative electrode active material layer 2 expands and contracts during charge and discharge. Such a negative electrode current collector 1 is, for example, a metal foil doped with C and S. The contents of C and S are not particularly limited, but it is preferable that both are 100 ppm or less. This is because a higher effect can be obtained.

  The surface of the negative electrode current collector 1 may be roughened or may not be roughened. The non-roughened negative electrode current collector 1 is, for example, a rolled metal foil, and the roughened negative electrode current collector 1 is, for example, a metal foil that has been subjected to electrolytic treatment or sandblasting. The electrolytic treatment is a method of forming irregularities by forming fine particles on the surface of a metal foil or the like using an electrolytic method in an electrolytic bath. A metal foil produced by an electrolytic method is generally called an electrolytic foil (for example, an electrolytic Cu foil).

  Especially, it is preferable that the surface of the negative electrode collector 1 is roughened. This is because the anchor effect improves the adhesion of the negative electrode active material layer 2 to the negative electrode current collector 1. The surface roughness (for example, ten-point average roughness Rz) of the negative electrode current collector 1 is not particularly limited, but is preferably as large as possible in order to improve the adhesion of the negative electrode active material layer 2 by the anchor effect. However, if the surface roughness is too large, the adhesion of the negative electrode active material layer 2 may be lowered.

[Negative electrode active material layer]
As shown in FIG. 2, the negative electrode active material layer 2 includes a plurality of particulate negative electrode active materials 200 capable of occluding and releasing lithium ions, and further, if necessary, a negative electrode binder or a negative electrode conductive material. Other materials such as agents may be included.

  The negative electrode active material 200 includes a core part 201 capable of occluding and releasing lithium ions, and a covering part 202 provided on the core part 201. The state in which the core portion 201 is covered with the covering portion 202 in this way can be confirmed by SEM observation as shown in FIG.

[Core]
The composition of the core part 201 is not particularly limited as long as lithium ions can be occluded and released. Especially, it is preferable that the core part 201 contains at least one of Si and Sn as a structural element. This is because a high energy density can be obtained. The core portion 201 may be a simple substance of Si, a compound of Si, an alloy of Si, or one containing two or more of them. The same applies to Sn, which may be any of a simple substance, a compound, or an alloy. Note that “single substance” is a simple substance in a general sense (may contain a small amount of impurities (elements other than oxygen)) and does not necessarily mean 100% purity.

An alloy of Si includes, for example, one or more elements such as Sn, Ni, Cu, Fe, Co, Mn, Zn, In, Ag, Ti, Ge, Bi, Sb, and Cr together with Si. Contains. The Si compound contains, for example, one or more elements such as C or O together with Si. Note that the Si compound may contain, for example, any one or two or more of the series of elements described for the Si alloy. Examples of the Si alloy or compound include SiB ₄ , SiB ₆ , Mg ₂ Si, Ni ₂ Si, TiSi ₂ , MoSi ₂ , CoSi ₂ , NiSi ₂ , CaSi ₂ , CrSi ₂ , Cu ₅ Si, FeSi ₂ , MnSi _2. NbSi ₂ , TaSi ₂ , VSi ₂ , WSi ₂ , ZnSi ₂ , SiC, Si ₃ N ₄ , Si ₂ N ₂ O, SiO _v (0 <v ≦ 2), LiSiO, or the like.

For example, the alloy of Sn includes any one element or two or more elements such as Si, Ni, Cu, Fe, Co, Mn, Zn, In, Ag, Ti, Ge, Bi, Sb, and Cr together with Sn. Contains. The compound of Sn contains, for example, any one kind or two or more kinds of elements such as C or O together with Sn. The Sn compound may contain, for example, any one or more of the series of elements described for the Sn alloy. Examples of the alloy or compound of Sn include SnO _w (0 <w ≦ 2), SnSiO ₃ , LiSnO, Mg ₂ Sn, SnCo, SnCoTi, or SnFeCo.

  Especially, the core part 201 contains, for example, Si and O as constituent elements, and the atomic ratio x (O / Si) of O to Si is preferably 0 ≦ x <0.5. Compared with the case where the atomic ratio x is out of the range (0.5 ≦ x), the core part 201 easily absorbs and releases lithium ions during charge and discharge, and the irreversible capacity decreases, so that a high battery capacity is obtained. Because it is.

As is apparent from the composition (atomic ratio x), the material for forming the core portion 201 may be a simple substance of Si (x = 0) or SiO _x (0 <x <0.5). However, x is preferably as small as possible, and more preferably x = 0 (Si simple substance). This is because a higher energy density can be obtained. Moreover, since deterioration of the core part 201 is suppressed, the discharge capacity is unlikely to decrease from the initial stage of the charge / discharge cycle.

  The core portion 201 may be crystalline (highly crystalline), low crystalline or noncrystalline, but is preferably highly crystalline or low crystalline, more preferably highly crystalline. preferable. This is because the core part 201 easily occludes and releases lithium ions during charging / discharging, so that a high battery capacity and the like can be obtained. Moreover, it is because the core part 201 becomes difficult to expand / contract at the time of charging / discharging. In particular, in the core portion 201, the half width (2θ) of the diffraction peak due to the (111) crystal plane of silicon obtained by X-ray diffraction is 20 ° or less, and the crystallites due to the (111) crystal plane The size is preferably 10 nm or more. This is because a higher effect can be obtained.

  Moreover, the median diameter of the core part 201 is not particularly limited, but is preferably 0.3 μm to 20 μm. This is because the core part 201 easily absorbs and releases lithium ions during charging and discharging, and the core part 201 is difficult to break. Specifically, when the median diameter is smaller than 0.3 μm, the total surface area of the core portion 201 becomes too large, and thus there is a possibility that expansion and contraction are likely to occur during charge / discharge. On the other hand, if the median diameter is larger than 20 μm, the core part 201 may be easily broken during charging and discharging.

  In addition, the core part 201 may contain any 1 type or 2 types or more of other elements (except Si and Sn) as a structural element with Si and Sn.

  Specifically, the core part 201 preferably includes at least one element M2 of Fe and Al as a constituent element. However, the ratio of M2 to Si and O (M2 / (Si + O)) is preferably 0.01 atomic% to 50 atomic%. This is because the electrical resistance of the core part 201 is lowered and the diffusibility of lithium ions is improved.

  In the core part 201, M2 may exist separately from Si and O (in a free state), or may form an alloy or a compound with at least one of Si and O. The composition of the core part 201 including M2 (such as the M2 bonding state) can be confirmed by EDX, for example. These combined states and confirmation methods are the same for M3 and M4 described later.

  Especially, it is preferable that the core part 201 contains Al. This is because the core portion 201 is low crystallized, so that the core portion 201 is less likely to expand and contract during charging and discharging, and lithium ion diffusibility is further improved. In the core portion 201 containing Al, the half-value width (2θ) of the diffraction peak due to the (111) crystal plane of Si obtained by X-ray diffraction is preferably 0.6 ° or more. The crystallite size resulting from the above (111) crystal plane is preferably 90 nm or less. When examining the half width, it is preferable to analyze the core portion 201 after dissolving and removing the covering portion 202 with HF or the like.

  Specifically, when the core part 201 does not contain Al and the core part 201 is highly crystalline, the core part 201 easily expands and contracts during charge and discharge. On the other hand, when the core part 201 contains Al, the core part 201 hardly expands and contracts during charge and discharge without depending on whether the core part 201 has high crystallinity or low crystallinity. Become. In this case, when the core part 201 has low crystallinity, not only the expansion and contraction of the core part 201 is suppressed, but also the diffusibility of lithium ions is improved.

Moreover, it is preferable that the core part 201 contains at least one element M3 of Cr and Ni as a constituent element. However, the ratio of M3 to Si and O (M3 / (Si + O)) is preferably 1 atomic% to 50 atomic%. Even in this case, the electrical resistance of the core portion 201 is lowered and the diffusibility of lithium ions is improved .

  In addition, the core portion 201 includes B, Mg, Ca, Ti, V, Mn, Co, Cu, Ge, Y, Zr, Mo, Ag, In, Sn, Sb, Ta, W, Pb, La, Ce, and Pr. It is preferable that at least one element M4 of Nd and Nd is included as a constituent element. However, the ratio of M4 to Si and O (M4 / (Si + O)) is preferably 0.01 atomic% to 30 atomic%. Even in this case, the electrical resistance of the core portion 201 is lowered and the diffusibility of lithium ions is improved.

[Coating]
The covering portion 202 is provided on at least a part of the surface of the core portion 201. For this reason, the coating | coated part 202 may coat | cover only a part of surface of the core part 201, and may coat | cover all. In the former case, the covering portion 202 may cover the surface of the core portion 201 while being scattered at a plurality of locations.

  The covering portion 202 contains, together with Si and O, an element M1 that can form an alloy with Si as a constituent element. This element M1 is Li, C, Mg, Al, Ca, Ti, Cr, Mn, Fe, Co, Ni, Cu, Ge, Zr, Mo, Ag, Sn, Ba, W, Ta, Na, and K. At least one of the following. However, the atomic ratio y (O / Si) of O to Si is 0.5 ≦ y ≦ 1.8, preferably 0.7 ≦ y ≦ 1.3, and more preferably y = 1.2. . This is because the protective function of the covering portion 202 described below is effectively exhibited.

  The deterioration of the negative electrode active material 200 when the charge / discharge is repeated as compared with the case where the atomic ratio y is within the above range (y <0.5 or y> 1.8). This is because it is suppressed. This is because the core part 201 is chemically and physically protected by the covering part 202 while ensuring the entry and exit of lithium ions in the core part 201.

  Specifically, when the covering portion 202 is interposed between the core portion 201 and the electrolytic solution, the highly reactive core portion 201 is less likely to come into contact with the electrolytic solution, so that the decomposition reaction of the electrolytic solution is suppressed. In this case, if the covering portion 202 is formed of the same material as the core portion 201 (a material containing common Si as a constituent element), the adhesion of the covering portion 202 to the core portion 201 is also increased.

  In addition, since the covering portion 202 has flexibility (a property of being easily deformed), even when the core portion 201 expands and contracts during charge and discharge, the covering portion 202 easily expands and contracts (extends and contracts) following the expansion and contraction. Thereby, even if the core part 201 expands and contracts, the covering part 202 is hardly damaged (ruptured or the like), so that the covering state of the core part 201 by the covering part 202 is maintained even after repeated charge and discharge. Therefore, even if the core part 201 is cracked during charging and discharging, the new surface is difficult to be exposed, and the new surface is difficult to come into contact with the electrolytic solution, so that the decomposition reaction of the electrolytic solution is suppressed.

  The reason why the covering portion 202 contains M1 together with Si and O is that the compound of Si, O, and M1 (Si-M1-O) is contained in the covering portion 202 when the atomic ratio y is within the above-described range. It is because it becomes easy to form. As a result, the irreversible capacity decreases and the electrical resistance of the negative electrode active material 200 decreases. In addition, in the coating | coated part 202, at least one part of M1 should just form Si-M1-O. This is because the above-described advantages can be obtained even in this case. The remaining M1 may exist as a free simple substance, may form an alloy with Si, or may form a compound with O.

Specifically, the bonding state (valence) of Si atoms to O atoms in the covering portion 202 is 0 valence (Si ⁰⁺ ), 1 valence (Si ¹⁺ ), 2 valence (Si ²⁺ ), 3 valence. Five types of (Si ³⁺ ) and tetravalent (Si ⁴⁺ ) are known. The presence or absence of Si atoms in each bonded state and their abundance ratio (atomic ratio) can be confirmed by analyzing the covering portion 202 by XPS, for example. When the outermost layer of the covering portion 202 is unintentionally oxidized (SiO ₂ is formed), it is preferable to analyze after dissolving and removing SiO ₂ with HF or the like.

  When Si-M1-O is formed in the covering portion 202, among the 0-valent to 4-valent bonded states, an irreversible capacity is easily generated during charge / discharge, and a high-resistance tetravalent abundance ratio is relative. To decrease. Thereby, even if the covering portion 202 is provided on the surface of the core portion 201, an irreversible capacity is hardly generated due to the presence of the covering portion 202, and the electric resistance of the covering portion 202 is reduced.

  The ratio of M1 to Si and O (M1 / (Si + O)) is not particularly limited, but is preferably 50 atomic percent or less, and more preferably 20 atomic percent or less. This is because a series of advantages by the above-described covering portion 202 can be obtained while suppressing a decrease in battery capacity due to the presence of M1.

  Note that, like the core portion 201, the covering portion 202 is preferably capable of occluding and releasing lithium ions. This is because the core portion 201 is more likely to occlude and release lithium ions because the covering portion 202 is less likely to prevent occlusion and release of lithium ions.

  The covering portion 202 is preferably non-crystalline (amorphous) or low-crystalline. Since lithium ions are more easily diffused than when crystalline (highly crystalline), even if the surface of the core part 201 is covered with the covering part 202, the core part 201 smoothly occludes lithium ions. It is because it becomes easy to discharge.

  Especially, it is preferable that the coating | coated part 202 is non-crystalline. This is because the flexibility of the covering portion 202 is improved, and it becomes easier to follow the expansion and contraction of the core portion 201 during charging and discharging. In addition, since the covering portion 202 is difficult to trap lithium ions, it is difficult for the lithium ions to enter and exit from the core portion 201.

  “Low crystallinity” means that the material for forming the covering portion 202 includes both an amorphous region and a crystalline region, and is different from “noncrystalline” including only an amorphous region. In order to confirm whether or not the covering portion 202 has low crystallinity, the covering portion 202 may be observed with, for example, a high angle scattering dark field scanning transmission electron microscope (HAADF STEM). If it can be confirmed from the TEM photograph that a non-crystalline region and a crystalline region are mixed, the covering portion 202 has low crystallinity. Note that in the case where a non-crystalline region and a crystalline region are mixed, the crystalline region is observed as a region (crystal grain) having a granular contour. Since a stripe pattern (crystal lattice stripe) due to crystallinity is observed inside the crystal grain, the crystal grain can be identified from the amorphous region.

  Further, the covering portion 202 may be a single layer or a multilayer, but among them, a multilayer is preferable. This is because even if the core part 201 expands and contracts during charging and discharging, the covering part 202 is not easily damaged. Specifically, in the single-layer covering portion 202, the internal stress of the covering portion 202 is difficult to be relieved depending on the thickness thereof, so that the covering portion 202 is damaged (cracked) due to the influence of the core portion 201 that has expanded and contracted during charging and discharging. And may peel off). On the other hand, in the multi-layer covering portion 202, the minute gap generated between the layers functions as a stress relaxation gap, so that the internal stress is relieved, so that the covering portion 202 is not easily damaged.

  In the single-layer covering portion 202, Si, O, and M1 are included in the single layer. On the other hand, in the multilayer covering portion 202, a layer containing Si, O, and M1 may be laminated, or a layer containing Si and O and a layer containing M1 together with Si and O may be laminated. However, both may be mixed. Even in this case, the same effect can be obtained. Of course, the stacking order of each layer in the multilayer may be arbitrary.

Although the average thickness of this coating | coated part 202 is not specifically limited, Especially, it is preferable that it is as thin as possible, and it is more preferable that they are 1 nm-10000 nm, and also 100 nm-10000 nm. This is because the core part 201 can easily absorb and release lithium ions, and the protective function by the covering part 202 is effectively exhibited. Specifically, if the average thickness is less than 1 nm, the covering portion 202 may be difficult to protect the core portion 201. On the other hand, when the average thickness is greater than 10,000 nm, the electrical resistance is increased, and the core part 201 may be difficult to occlude and release lithium ion ions during charge and discharge. This is because when the forming material of the covering portion 202 is SiO _y , the SiO _y has a property of easily occluding lithium ions, but difficult to release the lithium ions once occluded.

  The average thickness of the covering portion 202 is calculated by the following procedure. First, as shown in FIG. 2, one negative electrode active material 200 is observed by SEM. The magnification at the time of observation is preferably such a magnification that the boundary between the core portion 201 and the covering portion 202 can be visually confirmed (determined) in order to measure the thickness T of the covering portion 202. Subsequently, after measuring the thickness T of the covering portion 202 at arbitrary 10 points, the average value (average thickness T per piece) is calculated. In this case, it is preferable to set the measurement positions so that they are widely dispersed without concentrating around a specific place as much as possible. Subsequently, the above average value calculation operation is repeated until the total number of observations by SEM reaches 100. Finally, an average value (average value of average thickness T) calculated for 100 negative electrode active materials 200 is calculated, and the average thickness of covering portion 202 is calculated. To do.

  Moreover, the average coverage of the coating part 202 with respect to the core part 201 is not particularly limited, but is preferably as large as possible, and more preferably 30% to 100%. This is because the protective function of the covering portion 202 is further improved.

  The average coverage of the covering portion 202 is calculated by the following procedure. First, as in the case of calculating the average thickness, one negative electrode active material 200 is observed by SEM. The magnification at the time of observation is preferably such a magnification that the core portion 201 can visually distinguish between the portion covered by the covering portion 202 and the portion not covered. Subsequently, the length of the portion covered with the covering portion 202 and the length of the portion not covered with the outer edge (contour) of the core portion 201 are measured. Then, the coverage ratio (coverage ratio per piece:%) = (length of the portion covered by the covering portion 202 / length of the outer edge of the core portion 201) × 100 is calculated. Subsequently, the above-described coverage calculation operation is repeated until the total number of observations by SEM reaches 100. Finally, the average value of the coverage ratio (coverage ratio per one) calculated for 100 negative electrode active materials 200 is calculated as the average coverage ratio of the covering portion 202.

The covering portion 202 is preferably adjacent to the core portion 201, but a natural oxide film (SiO ₂ ) may be interposed on the surface of the core portion 201. For example, the natural oxide film is obtained by oxidizing the vicinity of the surface layer of the core portion 201 in the air. If the core part 201 exists in the center of the negative electrode active material 200 and the covering part 202 exists outside, the presence of the natural oxide film hardly affects the functions of the core part 201 and the covering part 202.

  Here, in order to confirm that the negative electrode active material 200 includes the core portion 201 and the covering portion 202, in addition to the above-described SEM observation, for example, X-ray photoelectron spectroscopy (XPS) or energy dispersive X-ray The negative electrode active material 200 may be analyzed by an analysis method (EDX).

In this case, the composition of the core part 201 and the covering part 202 can be confirmed by measuring the oxidation degree (atomic ratio x, y) of the central part and the surface layer part of the negative electrode active material 200. In order to examine the composition of the core portion 201 covered with the covering portion 202, the covering portion 202 may be dissolved and removed with HF or the like.

A detailed procedure for measuring the degree of oxidation is, for example, as follows. First, the negative electrode active material 200 (the core portion 201 covered with the covering portion 202) is quantified using a combustion method, and the total Si amount and O amount are calculated. Subsequently, after the covering portion 202 is washed and removed with HF, the core portion 201 is quantified using a combustion method to calculate the Si amount and the O amount. Finally, the Si amount and O amount of the covering portion 202 are calculated by subtracting the Si amount and O amount of the core portion 201 from the total Si amount and O amount. Thereby, since Si amount and O amount are specified about the core part 201 and the coating | coated part 202, each oxidation degree can be specified. Instead of washing and removing the covering portion 202, the degree of oxidation may be measured using the core portion 201 that is not covered with the core portion 201 that is covered with the covering portion 202.

[Conductive part]
In particular, the negative electrode active material 200 may include a conductive portion on the surface of the covering portion 202. The conductive portion is provided on at least a part of the surface of the covering portion 202, and has a lower electrical resistance than the core portion 201 and the covering portion 202. This is because the core part 201 is less likely to come into contact with the electrolytic solution, so that the decomposition reaction of the electrolytic solution is suppressed and the electrical resistance of the negative electrode active material 200 is further reduced. This conductive part includes, for example, any one type or two or more types such as a carbon material, a metal material, or an inorganic compound. The carbon material is, for example, graphite. The metal material is, for example, Fe, Cu or Al. An example of the inorganic compound is SiO ₂ . Among these, a carbon material or a metal material is preferable, and a carbon material is more preferable. This is because the electrical resistance of the negative electrode active material 200 is further reduced. In addition, the average coverage and average thickness of the conductive portion are arbitrary, and the calculation procedure thereof is the same as that of the covering portion 202.

  The negative electrode binder contains, for example, any one kind or two or more kinds such as synthetic rubber or polymer material. Examples of the synthetic rubber include styrene butadiene rubber, fluorine rubber, and ethylene propylene diene. Examples of the polymer material include polyvinylidene fluoride, polyimide, polyamide, polyamideimide, polyacrylic acid, lithium polyacrylate, sodium polyacrylate, polymaleic acid, and copolymers thereof. In addition, the polymer material may be, for example, carboxymethyl cellulose, styrene butadiene rubber, or polyvinyl alcohol.

  The negative electrode conductive agent contains any one or more of carbon materials such as graphite, carbon black, acetylene black, and ketjen black. The negative electrode conductive agent may be a metal material or a conductive polymer as long as it is a conductive material.

  In addition, the negative electrode active material layer 2 may contain the negative electrode active material of another kind with the negative electrode active material 200 containing the above-mentioned core part 201 and the coating | coated part 202 as needed.

  Such another negative electrode active material is, for example, a carbon material. This is because the electrical resistance of the negative electrode active material layer 2 is reduced and the negative electrode active material layer 2 is less likely to expand and contract during charge and discharge. This carbon material is, for example, graphitizable carbon, non-graphitizable carbon having a (002) plane spacing of 0.37 nm or more, or graphite having a (002) plane spacing of 0.34 nm or less. . More specifically, there are pyrolytic carbons, cokes, glassy carbon fibers, organic polymer compound fired bodies, activated carbon or carbon blacks. Among these, the cokes include pitch coke, needle coke, petroleum coke and the like. The organic polymer compound fired body is obtained by firing and carbonizing a phenol resin, a furan resin, or the like at an appropriate temperature. The shape of the carbon material may be any of fibrous, spherical, granular or scale-like. In addition, the content of the carbon material in the negative electrode active material layer 2 is not particularly limited, but is preferably 60% by weight or less, and more preferably 10% by weight to 60% by weight.

  The other negative electrode active material may be a metal oxide or a polymer compound. Examples of the metal oxide include iron oxide, ruthenium oxide, and molybdenum oxide. Examples of the polymer compound include polyacetylene, polyaniline, and polypyrrole.

  The negative electrode active material layer 2 is formed by, for example, a coating method, a firing method (sintering method), or two or more kinds thereof. The application method is, for example, a method in which a negative electrode active material is mixed with a negative electrode binder and then dispersed in an organic solvent and applied. The baking method is, for example, a method in which heat treatment is performed at a temperature higher than the melting point of the negative electrode binder or the like after coating in the same procedure as the coating method. A known method can be used for the firing method. As an example, an atmosphere firing method, a reaction firing method, a hot press firing method, or the like can be given.

[Production method of negative electrode]
This negative electrode is manufactured, for example, by the following procedure. In addition, since the forming material of the negative electrode collector 1 and the negative electrode active material layer 2 has already been described in detail, the description thereof will be omitted as needed.

  First, the particulate (powder) core portion 201 having the above-described composition is obtained by using, for example, a gas atomization method, a water atomization method, a melt pulverization method, or the like.

  Subsequently, the covering portion 202 having the above-described composition is formed on the surface of the core portion 201 using, for example, a vapor phase growth method such as an evaporation method or a sputtering method. Thus, when the formation material of the coating | coated part 202 is deposited using a vapor phase growth method, the coating | coated part 202 tends to become amorphous easily. In this case, the formation material of the covering portion 202 may be deposited while being heated by induction heating, resistance heating, electron beam heating, or the like. It may be sex. The degree of low crystallinity is controlled according to conditions such as temperature and time during heating, for example. By this heat treatment, moisture in the covering portion 202 is removed and adhesion of the covering portion 202 to the core portion 201 is improved.

In particular, when the vapor phase growth method is used, not only the forming material of the covering portion 202 is heated, but also the substrate for film formation is heated, thereby forming Si-M1-O in the covering portion 202. It becomes easy. The base temperature is preferably 200 ° C. or higher and lower than 900 ° C., for example. Note that when forming the covering portion 202, the amount of oxygen atoms (O ₂ ) and hydrogen (H ₂ ) introduced into the chamber is adjusted, or the temperature of the core portion 201 is adjusted to adjust the amount of Si atoms. The abundance ratio of the bonded state to the O atom can be controlled. Thereby, since the core part 201 is coat | covered with the coating | coated part 202, the negative electrode active material 200 is obtained.

  When the negative electrode active material 200 is formed, the surface of the covering portion 202 is formed using a vapor deposition method such as a vapor deposition method, a sputtering method, a chemical vapor deposition (CVD) method, or a wet coating method. A conductive portion may be formed on the substrate.

In the case of using a vapor deposition method, for example, the conductive portion is formed by spraying steam directly on the surface of the negative electrode active material 200. In the case of using the sputtering method, for example, the conductive portion is formed using the powder sputtering method while introducing Ar gas. When using the CVD method, for example, a gas obtained by sublimating a metal chloride and a mixed gas such as H ₂ and N ₂ are mixed so that the molar ratio of the metal chloride is 0.03 to 0.3. After that, the conductive part is formed on the surface of the covering part 202 by heating to 1000 ° C. or higher. In the case of using the wet coating method, for example, an alkali solution is added to a slurry containing the negative electrode active material 200 while adding a metal-containing solution to form a metal hydroxide, followed by reduction treatment with H ₂ at 450 ° C. Then, a conductive portion is formed on the surface of the covering portion 202. When a carbon material is used as a material for forming the conductive portion, the negative electrode active material 200 is put into a chamber, an organic gas is introduced into the chamber, and then heat treatment is performed under conditions of 10,000 Pa and 1000 ° C. or higher. A conductive portion is formed on the surface of the covering portion 202 over time. The type of the organic gas is not particularly limited as long as it generates carbon by thermal decomposition, and examples thereof include methane, ethane, ethylene, acetylene, and propane.

  Subsequently, the negative electrode active material 200 and another material such as a negative electrode binder are mixed to form a negative electrode mixture, and then dissolved in a solvent such as an organic solvent to obtain a negative electrode mixture slurry. Finally, the negative electrode mixture slurry is applied to the surface of the negative electrode current collector 1 and then dried to form the negative electrode active material layer 2. Thereafter, the negative electrode active material layer 2 may be compression-molded and heated (fired) as necessary.

[Operation and effect of this embodiment]
According to this negative electrode, the negative electrode active material 200 has the coating portion 202 on the surface of the core portion 201. This covering portion 202 contains element M1 such as Li as a constituent element together with Si and O, and the atomic ratio y of O to Si is 0.5 ≦ y ≦ 1.8. As a result, the core portion 201 can easily occlude and release lithium ions, and the core portion 201 is protected by the covering portion 202 so that the new surface is not exposed during charge / discharge while maintaining the smooth occlusion / release. And since Si-MO is easy to be formed in the coating | coated part 202, it is suppressed that an irreversible capacity | capacitance arises due to presence of the coating | coated part 202, and the electrical resistance of the coating | coated part 202 falls. Therefore, it can contribute to the improvement of the performance of the lithium ion secondary battery using the negative electrode, specifically, improvement of cycle characteristics, initial charge / discharge characteristics, load characteristics, and the like.

  In particular, if the ratio of M1 to Si and O in the covering portion 202 is 50 atomic% or less, and further 20 atomic% or less, a higher effect can be obtained. Further, if the average coverage of the covering portion 202 with respect to the core portion 201 is 30% to 100%, or the average thickness of the covering portion 202 is 1 nm to 10000 nm, a higher effect can be obtained. Furthermore, if the coating | coated part 202 is a multilayer, a higher effect can be acquired.

<2. Lithium ion secondary battery>
Next, a lithium ion secondary battery (hereinafter simply referred to as “secondary battery”) using the above-described negative electrode for a lithium ion secondary battery will be described.

<2-1. Square type>
3 and 4 show a cross-sectional configuration of the rectangular secondary battery, and FIG. 4 shows a cross section taken along line IV-IV shown in FIG. FIG. 5 schematically illustrates the planar configuration of the positive electrode 21 and the negative electrode 22 illustrated in FIG. 4.

[Overall structure of secondary battery]
The rectangular secondary battery is mainly one in which the battery element 20 is housed inside the battery can 11. The battery element 20 is a wound laminate in which a positive electrode 21 and a negative electrode 22 are laminated and wound via a separator 23, and has a flat shape according to the shape of the battery can 11.

  The battery can 11 is, for example, a square exterior member. As shown in FIG. 4, this rectangular exterior member has a rectangular or substantially rectangular shape (including a curve in part) in the longitudinal section, and is not only a rectangular shape but also an oval shape. This also applies to the square battery. That is, the square-shaped exterior member is a bottomed rectangular or bottomed oval shaped container-like member having a rectangular shape or a substantially rectangular (oval shape) opening formed by connecting arcs with straight lines. FIG. 4 shows a case where the battery can 11 has a rectangular cross-sectional shape.

  The battery can 11 is formed of, for example, a conductive material such as Fe, Al, or an alloy thereof, and may have a function as an electrode terminal. Among them, Fe that is harder than Al is preferable in order to suppress swelling of the battery can 11 by utilizing hardness (hardness to deform) during charge and discharge. When the battery can 11 is made of Fe, Ni or the like may be plated on the surface.

  The battery can 11 has a hollow structure in which one end is opened and the other end is closed, and is sealed by an insulating plate 12 and a battery lid 13 attached to the open end. The insulating plate 12 is provided between the battery element 20 and the battery lid 13 and is formed of an insulating material such as polypropylene. The battery lid 13 is formed of, for example, the same material as that of the battery can 11, and may have a function as an electrode terminal similarly to the battery can 11.

  A terminal plate 14 serving as a positive terminal is provided outside the battery lid 13, and the terminal plate 14 is electrically insulated from the battery lid 13 through an insulating case 16. The insulating case 16 is made of an insulating material such as polybutylene terephthalate, for example. A through hole is provided at substantially the center of the battery lid 13, and the through hole is electrically connected to the terminal plate 14 and is electrically insulated from the battery lid 13 through the gasket 17. A positive electrode pin 15 is inserted. The gasket 17 is made of, for example, an insulating material, and asphalt is applied to the surface thereof.

  In the vicinity of the periphery of the battery lid 13, a cleavage valve 18 and an injection hole 19 are provided. The cleavage valve 18 is electrically connected to the battery lid 13 and is disconnected from the battery lid 13 when the internal pressure of the battery exceeds a certain level due to an internal short circuit or heating from the outside. Is to be released. The injection hole 19 is closed by a sealing member 19A made of, for example, a stainless steel ball.

  A positive electrode lead 24 made of a conductive material such as Al is attached to an end portion (for example, an inner terminal portion) of the positive electrode 21, and Ni or the like is attached to an end portion (for example, the outer terminal portion) of the negative electrode 22. A negative electrode lead 25 made of a conductive material is attached. The positive electrode lead 24 is welded to one end of the positive electrode pin 15 and electrically connected to the terminal plate 14, and the negative electrode lead 25 is welded to the battery can 11 and electrically connected to the battery can 11. It is connected.

[Positive electrode]
The positive electrode 21 includes, for example, a positive electrode active material layer 21B on both surfaces of the positive electrode current collector 21A. However, the positive electrode active material layer 21B may be provided only on one surface of the positive electrode current collector 21A.

  The positive electrode current collector 21A is formed of a conductive material such as Al, Ni, or stainless steel, for example.

  The positive electrode active material layer 21B includes one or more positive electrode materials capable of occluding and releasing lithium ions as a positive electrode active material, and a positive electrode binder or a positive electrode conductive agent is used as necessary. Other materials may be included. In addition, the detail regarding a positive electrode binder or a positive electrode electrically conductive agent is the same as that of the negative electrode binder and negative electrode electrically conductive agent which were already demonstrated, for example.

As the positive electrode material, a Li-containing compound is preferable. This is because a high energy density can be obtained. This Li-containing compound is, for example, a composite oxide containing Li and a transition metal element as constituent elements, or a phosphate compound containing Li and a transition metal element as constituent elements. Among them, the transition metal element is preferably one or more of Co, Ni, Mn, and Fe. This is because a higher voltage can be obtained. The chemical formula thereof is represented by, for example, Li _x M11O ₂ or Li _y M12PO ₄ . In the formula, M11 and M12 represent one or more transition metal elements. The values of x and y vary depending on the charge / discharge state, but are generally 0.05 ≦ x ≦ 1.10 and 0.05 ≦ y ≦ 1.10. In particular, when the positive electrode material contains Ni or Mn, the volume stability tends to be improved.

The complex oxide containing Li and a transition metal element is, for example, Li _x CoO ₂ , Li _x NiO ₂ , or a LiNi-based complex oxide represented by the formula (1). The phosphate compound containing Li and a transition metal element is, for example, LiFePO ₄ or LiFe _1-u Mn _u PO ₄ (u <1). This is because high battery capacity is obtained and excellent cycle characteristics are also obtained. The positive electrode material may be a material other than the above. For example, a material represented by Li _x M14 _y O ₂ (M14 is NI and at least one of M13 shown in Formula (1), x> 1 and y is arbitrary). Etc.

LiNi _1-x M13 _x O ₂ (1)
(M13 is Co, Mn, Fe, Al, V, Sn, Mg, Ti, Sr, Ca, Zr, Mo, Tc, Ru, Ta, W, Re, Y, Cu, Zn, Ba, B, Cr, Si. , Ga, P, Sb and Nb, x is 0.005 <x <0.5.)

  In addition, the positive electrode material is, for example, an oxide, a disulfide, a chalcogenide, or a conductive polymer. Examples of the oxide include titanium oxide, vanadium oxide, and manganese dioxide. Examples of the disulfide include titanium disulfide and molybdenum sulfide. An example of the chalcogenide is niobium selenide. Examples of the conductive polymer include sulfur, polyaniline, and polythiophene.

[Negative electrode]
The negative electrode 22 has the same configuration as the above-described negative electrode for a lithium ion secondary battery, and includes, for example, a negative electrode active material layer 22B on both surfaces of the negative electrode current collector 22A. The configurations of the negative electrode current collector 22A and the negative electrode active material layer 22B are the same as the configurations of the negative electrode current collector 1 and the negative electrode active material layer 2, respectively. The chargeable capacity of the negative electrode material capable of occluding and releasing lithium ions is preferably larger than the discharge capacity of the positive electrode 21. This is to prevent Li metal from unintentionally precipitating during charge / discharge.

  As shown in FIG. 5, the positive electrode active material layer 21 </ b> B is provided, for example, on a part of the surface of the positive electrode current collector 21 </ b> A (for example, a central region in the longitudinal direction). On the other hand, the negative electrode active material layer 22B is provided on the entire surface of the negative electrode current collector 22A, for example. Thus, the negative electrode active material layer 22B is provided in a region (opposing region R1) facing the positive electrode active material layer 21B and a region not facing (non-facing region R2) of the negative electrode current collector 22A. In this case, in the negative electrode active material layer 22B, the portion provided in the facing region R1 is involved in charging / discharging, but the portion provided in the non-facing region R2 is hardly involved in charging / discharging. In FIG. 5, the positive electrode active material layer 21B and the negative electrode active material layer 22B are shaded.

As described above, the negative electrode active material 200 (see FIG. 2) included in the negative electrode active material layer 22B includes the core part 201 and the covering part 202. However, since the negative electrode active material layer 22B may be deformed or damaged due to expansion / contraction during charging / discharging, the formation state of the core part 201 and the covering part 202 is changed from the state when the negative electrode active material layer 22B is formed. Can vary. However, in the non-facing region R2, it is hardly affected by charging / discharging, and the formation state of the negative electrode active material layer 22B is maintained. Therefore, the presence and composition of the core portion 201 and the cover portion 202 (atomic ratio x, y), and the like percentage of M1, the set of parameters described above, to examine the anode active material layer 22B of the non-opposed region R2 Is preferred. This is because the presence / absence and composition of the core portion 201 and the covering portion 202 can be accurately and accurately examined without depending on the charge / discharge history (the presence / absence and number of times of charge / discharge).

  The maximum utilization rate of the negative electrode 22 in a fully charged state (hereinafter, simply referred to as “negative electrode utilization rate”) is not particularly limited, and can be arbitrarily set according to the ratio between the capacity of the positive electrode 21 and the capacity of the negative electrode 22. is there.

  The above-mentioned “negative electrode utilization rate” is represented by utilization rate Z (%) = (X / Y) × 100. Here, X is the amount of occlusion of lithium ions per unit area when the negative electrode 22 is fully charged, and Y is the amount of lithium ions that can be occluded electrochemically per unit area of the negative electrode 22.

The occlusion amount X can be obtained, for example, by the following procedure. First, after charging the secondary battery until it is fully charged, the secondary battery is disassembled, and a portion (inspection negative electrode) of the negative electrode 22 facing the positive electrode 21 is cut out. Subsequently, an evaluation battery using metal lithium as a counter electrode is assembled using the inspection negative electrode. Finally, after discharging the evaluation battery and measuring the discharge capacity at the first discharge, the storage capacity X is calculated by dividing the discharge capacity by the area of the inspection negative electrode. “Discharge” in this case means energization in the direction in which lithium ions are released from the inspection negative electrode. For example, until the battery voltage reaches 1.5 V at a current density of 0.1 mA / cm ^2. Discharge constant current.

On the other hand, for the amount of occlusion Y, for example, after charging the above-described discharged evaluation battery with constant current and constant voltage until the battery voltage reaches 0 V, and measuring the charge capacity, the charge capacity is divided by the area of the inspection negative electrode. calculate. “Charging” in this case means that the inspection negative electrode is energized in the direction in which lithium ions are occluded. For example, the current density is 0.1 mA / cm ² and the battery voltage is 0V. Voltage charging is performed until the current density reaches 0.02 mA / cm ² .

  Especially, it is preferable that a negative electrode utilization factor is 35%-80%. This is because excellent cycle characteristics, initial charge / discharge characteristics and load characteristics can be obtained.

[Separator]
The separator 23 separates the positive electrode 21 and the negative electrode 22 and allows lithium ions to pass through while preventing a short circuit of current due to contact between the two electrodes. The separator 23 is formed of, for example, a porous film made of synthetic resin or ceramic, and may be a laminated film in which two or more kinds of porous films are laminated. Examples of the synthetic resin include polytetrafluoroethylene, polypropylene, and polyethylene.

[Electrolyte]
The separator 23 is impregnated with an electrolytic solution that is a liquid electrolyte. This electrolytic solution is obtained by dissolving an electrolyte salt in a solvent, and may contain other materials such as additives as necessary.

  The solvent includes, for example, any one kind or two or more kinds of nonaqueous solvents such as organic solvents. Examples of the non-aqueous solvent include ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, γ-butyrolactone, γ-valerolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2 -Methyltetrahydrofuran, tetrahydropyran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, butyric acid Methyl, methyl isobutyrate, methyl trimethylacetate, ethyl trimethylacetate, acetonitrile, glutaronitrile, adiponitrile, methoxyacetonitrile, 3-methoxypropionitrile, N, N-dimethylformamide, N-methylpyrrolidinone, N-methyl Such as oxazolidinone, N, N'-dimethylimidazolidinone, nitromethane, nitroethane, sulfolane, trimethyl phosphate or dimethyl sulfoxide. This is because excellent battery capacity, cycle characteristics, storage characteristics, and the like can be obtained.

  Among these, at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate is preferable. This is because more excellent characteristics can be obtained. In this case, a high viscosity (high dielectric constant) solvent such as ethylene carbonate or propylene carbonate (for example, a relative dielectric constant ε ≧ 30) and a low viscosity solvent such as dimethyl carbonate, ethyl methyl carbonate or diethyl carbonate (for example, viscosity ≦ 1 mPas). -A combination with s) is more preferred. This is because the dissociation property of the electrolyte salt and the ion mobility are improved.

  In particular, the non-aqueous solvent preferably contains at least one of a halogenated chain carbonate ester and a halogenated cyclic carbonate ester. This is because a stable coating is formed on the surface of the negative electrode 22 during charging and discharging, and thus the decomposition reaction of the electrolytic solution is suppressed. The halogenated chain carbonate ester is a chain carbonate ester containing halogen as a constituent element (at least one hydrogen is replaced by a halogen). The halogenated cyclic carbonate is a cyclic carbonate containing halogen as a constituent element (at least one H is substituted with a halogen).

  The type of halogen is not particularly limited, but among them, F, Cl or Br is preferable, and F is more preferable. This is because an effect higher than that of other halogens can be obtained. However, the number of halogens is preferably two rather than one, and may be three or more. This is because the ability to form a protective film increases and a stronger and more stable coating is formed, so that the decomposition reaction of the electrolytic solution is further suppressed.

  Examples of the halogenated chain carbonate ester include fluoromethyl methyl carbonate, bis (fluoromethyl) carbonate, and difluoromethyl methyl carbonate. The halogenated cyclic carbonate is 4-fluoro-1,3-dioxolan-2-one or 4,5-difluoro-1,3-dioxolan-2-one. This halogenated cyclic carbonate includes geometric isomers. The content of the halogenated chain carbonate and the halogenated cyclic carbonate in the non-aqueous solvent is, for example, 0.01 wt% to 50 wt%.

  Moreover, it is preferable that the nonaqueous solvent contains unsaturated carbon bond cyclic ester carbonate. This is because a stable coating is formed on the surface of the negative electrode 22 during charging and discharging, and thus the decomposition reaction of the electrolytic solution is suppressed. An unsaturated carbon bond cyclic ester carbonate is a cyclic ester carbonate containing one or more unsaturated carbon bonds (in which an unsaturated carbon bond is introduced at any position). Examples of the unsaturated carbon-bonded cyclic ester carbonate include vinylene carbonate and vinyl ethylene carbonate. The content of the unsaturated carbon bond cyclic carbonate in the nonaqueous solvent is, for example, 0.01% by weight to 10% by weight.

  The non-aqueous solvent preferably contains sultone (cyclic sulfonic acid ester). This is because the chemical stability of the electrolytic solution is improved. The sultone is, for example, propane sultone or propene sultone. The content of sultone in the non-aqueous solvent is, for example, 0.5% by weight to 5% by weight.

  Further, the non-aqueous solvent preferably contains an acid anhydride. This is because the chemical stability of the electrolytic solution is improved. Examples of the acid anhydride include carboxylic acid anhydride, disulfonic acid anhydride, and carboxylic acid sulfonic acid anhydride. Examples of the carboxylic acid anhydride include succinic anhydride, glutaric anhydride, and maleic anhydride. Examples of the disulfonic anhydride include ethanedisulfonic anhydride and propanedisulfonic anhydride. Examples of the carboxylic acid sulfonic acid anhydride include anhydrous sulfobenzoic acid, anhydrous sulfopropionic acid, and anhydrous sulfobutyric acid. The content of the acid anhydride in the nonaqueous solvent is, for example, 0.5% by weight to 5% by weight.

The electrolyte salt includes, for example, any one or more of light metal salts such as Li salt. Examples of the Li salt include LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiB (C ₆ H ₅ ) ₄ , LiCH ₃ SO ₃ , LiCF ₃ SO ₃ , LiAlCl ₄ , Li ₂ SiF ₆ , LiCl or LiBr. There may be other types of Li salts. This is because excellent battery capacity, cycle characteristics, storage characteristics, and the like can be obtained.

Among them, one or more of LiPF ₆ , LiBF ₄ , LiClO ₄ and LiAsF ₆ are preferable, LiPF ₆ or LiBF ₄ is preferable, and LiPF ₆ is more preferable. This is because the internal resistance is reduced, so that more excellent characteristics can be obtained.

  The content of the electrolyte salt is preferably 0.3 mol / kg or more and 3.0 mol / kg or less with respect to the solvent. This is because high ionic conductivity is obtained.

[Operation of secondary battery]
In this rectangular secondary battery, for example, lithium ions released from the positive electrode 21 during charging are occluded in the negative electrode 22 via the electrolytic solution, and lithium ions released from the negative electrode 22 during discharging pass through the electrolytic solution. And occluded by the positive electrode 21.

[Method for producing secondary battery]
This secondary battery is manufactured by the following procedure, for example.

  First, the positive electrode 21 is produced. First, a positive electrode active material and, if necessary, a positive electrode binder and a positive electrode conductive agent are mixed to form a positive electrode mixture, which is then dispersed in an organic solvent or the like to obtain a paste-like positive electrode mixture slurry. Subsequently, the positive electrode mixture slurry is applied to the positive electrode current collector 21A using a coating device such as a doctor blade or a bar coater, and then dried to form the positive electrode active material layer 21B. Finally, the positive electrode active material layer 21B is compression-molded using a roll press or the like while being heated as necessary. In this case, compression molding may be repeated a plurality of times.

  Next, the negative electrode active material layer 22 </ b> B is formed on the negative electrode current collector 22 </ b> A by the same production procedure as the above-described negative electrode for a lithium ion secondary battery to produce the negative electrode 22.

  Next, the battery element 20 is produced. First, the positive electrode lead 24 is attached to the positive electrode current collector 21A and the negative electrode lead 25 is attached to the negative electrode current collector 22A by a welding method or the like. Then, after laminating the positive electrode 21 and the negative electrode 22 via the separator 23, they are wound in the longitudinal direction. Finally, the wound body is molded so as to have a flat shape.

  Finally, the secondary battery is assembled. First, after storing the battery element 20 in the battery can 11, the insulating plate 12 is placed on the battery element 20. Subsequently, the positive electrode lead 24 is attached to the positive electrode pin 15 and the negative electrode lead 25 is attached to the battery can 11 by a welding method or the like. In this case, the battery lid 13 is fixed to the open end of the battery can 11 by a laser welding method or the like. Finally, after injecting the electrolyte into the battery can 11 from the injection hole 19 and impregnating the separator 23, the injection hole 19 is closed with a sealing member 19A.

[Operation and effect of secondary battery]
According to this rectangular secondary battery, since the negative electrode 22 has the same configuration as the above-described negative electrode for a lithium ion secondary battery, the same action can be obtained. Therefore, excellent battery characteristics such as cycle characteristics, initial charge / discharge characteristics, and load characteristics can be obtained. Other effects are the same as those of the negative electrode for a lithium ion secondary battery.

<2-2. Cylindrical type>
6 and 7 show a cross-sectional configuration of the cylindrical secondary battery. In FIG. 7, a part of the spirally wound electrode body 40 shown in FIG. 6 is enlarged. In the following, the constituent elements of the already-described prismatic secondary battery are referred to as needed.

[Configuration of secondary battery]
The cylindrical secondary battery mainly includes a wound electrode body 40 and a pair of insulating plates 32 and 33 in a substantially hollow cylindrical battery can 31. The wound electrode body 40 is a wound laminated body in which a positive electrode 41 and a negative electrode 42 are laminated and wound via a separator 43.

  The battery can 31 has a hollow structure in which one end is closed and the other end is opened. For example, the battery can 31 is formed of the same material as the battery can 11. The pair of insulating plates 32 and 33 are disposed so as to sandwich the wound electrode body 40 from above and below and to extend perpendicularly to the wound peripheral surface.

  A battery lid 34, a safety valve mechanism 35, and a heat sensitive resistance element (PTC element) 36 are caulked through a gasket 37 at the open end of the battery can 31, and the battery can 31 is sealed. The battery lid 34 is formed of the same material as the battery can 31, for example. The safety valve mechanism 35 and the thermal resistance element 36 are provided inside the battery lid 34, and the safety valve mechanism 35 is electrically connected to the battery lid 34 via the thermal resistance element 36. In this safety valve mechanism 35, when the internal pressure becomes a certain level or more due to an internal short circuit or heating from the outside, the disk plate 35A is reversed and the electric power between the battery lid 34 and the wound electrode body 40 is reversed. Connection is cut off. The heat-sensitive resistance element 36 prevents abnormal heat generation caused by a large current by increasing resistance in response to a temperature rise. The gasket 37 is made of, for example, an insulating material, and asphalt may be applied to the surface thereof.

  A center pin 44 may be inserted in the center of the wound electrode body 40. A positive electrode lead 45 formed of a conductive material such as Al is connected to the positive electrode 41, and a negative electrode lead 46 formed of a conductive material such as Ni is connected to the negative electrode 42. The positive electrode lead 45 is welded to the safety valve mechanism 35 and electrically connected to the battery lid 34, and the negative electrode lead 46 is welded to the battery can 31 and electrically connected thereto.

The positive electrode 41 has, for example, a positive electrode active material layer 41B on both surfaces of the positive electrode current collector 41A. The negative electrode 42 has the same configuration as the above-described negative electrode for a lithium ion secondary battery. For example, the negative electrode 42 has a negative electrode active material layer 42B on both surfaces of the negative electrode current collector 42A. The configurations of the positive electrode current collector 41A, the positive electrode active material layer 41B, the negative electrode current collector 42A, the negative electrode active material layer 42B, and the separator 43 are the positive electrode current collector 21A, the positive electrode active material layer 21B, the negative electrode current collector 22A, and the negative electrode, respectively. The configurations of the active material layer 22B and the separator 23 are the same. The composition of the electrolytic solution impregnated in the separator 43 is the same as the composition of the electrolytic solution in the square secondary battery.

[Operation of secondary battery]
In this cylindrical secondary battery, for example, lithium ions released from the positive electrode 41 during charging are occluded in the negative electrode 42 via the electrolytic solution, and lithium ions released from the negative electrode 42 during discharging pass through the electrolytic solution. And occluded by the positive electrode 41.

[Method for producing secondary battery]
This cylindrical secondary battery is manufactured, for example, by the following procedure. First, for example, the positive electrode active material layer 41B is formed on both surfaces of the positive electrode current collector 41A to produce the positive electrode 41 by the same production procedure as that of the positive electrode 21 and the negative electrode 22, and the negative electrode is formed on both surfaces of the negative electrode current collector 42A. The active material layer 42B is formed to produce the negative electrode 42. Subsequently, the positive electrode lead 45 is attached to the positive electrode 41 and the negative electrode lead 46 is attached to the negative electrode 42 by a welding method or the like. Subsequently, the positive electrode 41 and the negative electrode 42 are stacked and wound through the separator 43 to produce the wound electrode body 40, and then the center pin 44 is inserted into the winding center. Subsequently, the wound electrode body 40 is accommodated in the battery can 31 while being sandwiched between the pair of insulating plates 32 and 33. In this case, the positive electrode lead 45 is attached to the safety valve mechanism 35 and the tip of the negative electrode lead 46 is attached to the battery can 31 by welding or the like. Subsequently, an electrolytic solution is injected into the battery can 31 and impregnated in the separator 43. Finally, after attaching the battery lid 34, the safety valve mechanism 35, and the heat sensitive resistance element 36 to the opening end of the battery can 31, they are crimped via the gasket 37.

[Operation and effect of secondary battery]
In this cylindrical secondary battery, since the negative electrode 42 has the same configuration as the above-described negative electrode for a lithium ion secondary battery, the same effect as that of the square secondary battery can be obtained.

<2-3. Laminate film type>
FIG. 8 shows an exploded perspective configuration of the laminated film type secondary battery, and FIG. 9 is an enlarged cross section taken along line IX-IX of the spirally wound electrode body 50 shown in FIG.

[Configuration of secondary battery]
The laminated film type secondary battery is mainly one in which a wound electrode body 50 is housed inside a film-shaped exterior member 60. The wound electrode body 50 is a wound laminated body in which a positive electrode 53 and a negative electrode 54 are laminated and wound via a separator 55 and an electrolyte layer 56. A positive electrode lead 51 is attached to the positive electrode 53, and a negative electrode lead 52 is attached to the negative electrode 54. The outermost peripheral portion of the wound electrode body 50 is protected by a protective tape 57.

  The positive electrode lead 51 and the negative electrode lead 52 are led out in the same direction from the inside of the exterior member 60 to the outside, for example. The positive electrode lead 51 is formed of, for example, a conductive material such as Al, and the negative electrode lead 52 is formed of, for example, a conductive material such as Cu, Ni, or stainless steel. These materials have, for example, a thin plate shape or a mesh shape.

  The exterior member 60 is, for example, a laminate film in which a fusion layer, a metal layer, and a surface protective layer are laminated in this order. In this laminate film, for example, the outer peripheral edge portions of the fusion layers of the two films are bonded together by an adhesive or the like so that the fusion layer faces the wound electrode body 50. The fusing layer is, for example, a film of polyethylene or polypropylene. The metal layer is, for example, an Al foil. The surface protective layer is, for example, a film such as nylon or polyethylene terephthalate.

  Especially, as the exterior member 60, an aluminum laminated film in which a polyethylene film, an aluminum foil, and a nylon film are laminated in this order is preferable. However, the exterior member 60 may be a laminate film having another laminated structure, a polymer film such as polypropylene, or a metal film.

  An adhesion film 61 is inserted between the exterior member 60 and the positive electrode lead 51 and the negative electrode lead 52 to prevent the outside air from entering. The adhesion film 61 is formed of a material having adhesion to the positive electrode lead 51 and the negative electrode lead 52. Such a material is, for example, a polyolefin resin such as polyethylene, polypropylene, modified polyethylene, or modified polypropylene.

  The positive electrode 53 has, for example, a positive electrode active material layer 53B on both surfaces of the positive electrode current collector 53A. The negative electrode 54 has the same configuration as the above-described negative electrode for a lithium ion secondary battery. For example, the negative electrode 54 has negative electrode active material layers 54B on both surfaces of the negative electrode current collector 54A. The configurations of the positive electrode current collector 53A, the positive electrode active material layer 53B, the negative electrode current collector 54A, and the negative electrode active material layer 54B are respectively the positive electrode current collector 21A, the positive electrode active material layer 21B, the negative electrode current collector 22A, and the negative electrode active material layer. The configuration is the same as 22B. The configuration of the separator 55 is the same as the configuration of the separator 23.

  The electrolyte layer 56 is one in which an electrolytic solution is held by a polymer compound, and may contain other materials such as additives as necessary. The electrolyte layer 56 is a so-called gel electrolyte. A gel electrolyte is preferable because high ion conductivity (for example, 1 mS / cm or more at room temperature) is obtained and leakage of the electrolyte is prevented.

Examples of the polymer compound include polyacrylonitrile, polyvinylidene fluoride, polytetrafluoroethylene, polyhexafluoropropylene, polyethylene oxide, polypropylene oxide, polyphosphazene, polysiloxane, polyvinyl fluoride, polyvinyl acetate, polyvinyl alcohol, polymethacryl. Contains one or more of methyl acid, polyacrylic acid, polymethacrylic acid, styrene-butadiene rubber, nitrile-butadiene rubber, polystyrene, polycarbonate, or a copolymer of vinylidene fluoride and hexafluoropyrene It is out. It is. Among them, a copolymer of polyvinylidene fluoride or vinylidene fluoride and hexafluoropropylene pyrene are preferable. This is because it is electrochemically stable.

  The composition of the electrolytic solution is, for example, the same as the composition of the electrolytic solution in a square secondary battery. However, in the electrolyte layer 56 which is a gel electrolyte, the solvent of the electrolytic solution is a wide concept including not only a liquid solvent but also a material having ion conductivity capable of dissociating the electrolyte salt. For this reason, when using the high molecular compound which has ion conductivity, the high molecular compound is also contained in a solvent.

  Instead of the gel electrolyte layer 56, an electrolytic solution may be used. In this case, the separator 55 is impregnated with the electrolytic solution.

[Operation of secondary battery]
In this laminated film type secondary battery, for example, lithium ions released from the positive electrode 53 during charging are occluded in the negative electrode 54 via the electrolyte layer 56, and lithium ions released from the negative electrode 54 during discharge are stored in the electrolyte layer. It is occluded in the positive electrode 53 through 56.

[Method for producing secondary battery]
The laminate film type secondary battery provided with the gel electrolyte layer 56 is manufactured, for example, by the following three types of procedures.

  In the first procedure, first, the positive electrode 53 and the negative electrode 54 are manufactured by the same manufacturing procedure as that of the positive electrode 21 and the negative electrode 22. In this case, the positive electrode active material layer 53B is formed on both surfaces of the positive electrode current collector 53A to produce the positive electrode 53, and the negative electrode active material layer 54B is formed on both surfaces of the negative electrode current collector 54A to produce the negative electrode 54. To do. Subsequently, after preparing a precursor solution containing an electrolytic solution, a polymer compound, an organic solvent, and the like, the precursor solution is applied to the positive electrode 53 and the negative electrode 54 to form a gel electrolyte layer 56. Subsequently, the positive electrode lead 51 is attached to the positive electrode current collector 53A by a welding method or the like, and the negative electrode lead 52 is attached to the negative electrode current collector 54A. Subsequently, the positive electrode 53 and the negative electrode 54 on which the electrolyte layer 56 is formed are stacked and wound via a separator 55 to produce a wound electrode body 50, and then a protective tape 57 is bonded to the outermost periphery. Finally, after sandwiching the wound electrode body 50 between the two film-like exterior members 60, the outer peripheral edges of the exterior member 60 are bonded to each other by a heat-sealing method or the like. The rotating electrode body 50 is enclosed. In this case, the adhesion film 61 is inserted between the positive electrode lead 51 and the negative electrode lead 52 and the exterior member 60.

  In the second procedure, first, the positive electrode lead 51 is attached to the positive electrode 53 and the negative electrode lead 52 is attached to the negative electrode 54. Subsequently, the positive electrode 53 and the negative electrode 54 are stacked and wound through the separator 55 to produce a wound body that is a precursor of the wound electrode body 50, and then a protective tape 57 is bonded to the outermost peripheral portion thereof. Let Subsequently, after sandwiching the wound body between the two film-like exterior members 60, the remaining outer peripheral edge portion excluding the outer peripheral edge portion on one side is adhered by a heat-sealing method or the like to form a bag-like The wound body is accommodated in the exterior member 60. Subsequently, an electrolyte composition containing an electrolytic solution, a monomer that is a raw material of the polymer compound, a polymerization initiator, and other materials such as a polymerization inhibitor as necessary is prepared to form a bag-shaped exterior member. After the injection into the interior of the 60, the opening of the exterior member 60 is sealed by a heat fusion method or the like. Finally, the monomer is thermally polymerized to obtain a polymer compound, and the gel electrolyte layer 56 is formed.

  In the third procedure, first, a wound body is prepared in the interior of the bag-shaped exterior member 60 in the same manner as in the second procedure described above except that the separator 55 coated with the polymer compound on both sides is used. Store. Examples of the polymer compound applied to the separator 55 include a polymer (such as a homopolymer, a copolymer, or a multi-component copolymer) containing vinylidene fluoride as a component. Specifically, a binary copolymer comprising polyvinylidene fluoride, vinylidene fluoride and hexafluoropropylene as components, or a ternary copolymer comprising vinylidene fluoride, hexafluoropropylene and chlorotrifluoroethylene as components. Etc. In addition to the polymer containing vinylidene fluoride as a component, one or more other polymer compounds may be used. Subsequently, after the electrolytic solution is prepared and injected into the exterior member 60, the opening of the exterior member 60 is sealed by a heat fusion method or the like. Finally, the exterior member 60 is heated while applying a load, and the separator 55 is brought into close contact with the positive electrode 53 and the negative electrode 54 through the polymer compound. Thereby, since the electrolytic solution is impregnated into the polymer compound, the polymer compound is gelled to form the electrolyte layer 56.

  In this third procedure, battery swelling is suppressed more than in the first procedure. In addition, since the monomer or organic solvent, which is a raw material of the polymer compound, hardly remains in the electrolyte layer 56 as compared with the second procedure, the formation process of the polymer compound is controlled well. For this reason, sufficient adhesion is obtained between the positive electrode 53, the negative electrode 54 and the separator 55 and the electrolyte layer 56.

[Operation and effect of secondary battery]
In this laminated film type secondary battery, since the negative electrode 54 has the same configuration as the above-described negative electrode for lithium ion secondary battery, the same effect as that of the square type secondary battery can be obtained.

<3. Applications of lithium ion secondary batteries>
Next, application examples of the above-described lithium ion secondary battery will be described.

  Applications of lithium ion secondary batteries include machines, devices, instruments, devices, or systems (collections of multiple devices) that can be used as a power source for driving or a power storage source for storing power. If there is, it will not be specifically limited. When a lithium ion secondary battery is used as a power source, it may be a main power source (a power source that is used preferentially) or an auxiliary power source (a power source that is used in place of or switched from the main power source). . The type of the main power source is not limited to the lithium ion secondary battery.

  Examples of the use of the lithium ion secondary battery include the following uses. It is a portable electronic device such as a video camera, a digital still camera, a mobile phone, a notebook computer, a cordless phone, a headphone stereo, a portable radio, a portable TV, or a portable information terminal. It is a portable living device such as an electric shaver. A storage device such as a backup power supply or a memory card. An electric tool such as an electric drill or an electric saw. A battery pack used as a power source for a notebook computer or the like. Medical electronic devices such as pacemakers or hearing aids. An electric vehicle such as an electric vehicle (including a hybrid vehicle). It is an electric power storage system such as a home battery system that stores electric power in case of an emergency. Of course, applications other than those described above may be used.

  Among these, it is effective that the lithium ion secondary battery is applied to a battery pack, an electric vehicle, an electric power storage system, an electric tool, an electronic device, or the like. This is because, since excellent battery characteristics are required, the characteristics can be effectively improved by using the lithium ion secondary battery of the present technology. The battery pack is a power source using a lithium ion secondary battery, and is a so-called assembled battery or the like. The electric vehicle is a vehicle that operates (runs) using a lithium ion secondary battery as a driving power source, and may be an automobile (such as a hybrid automobile) provided with a driving source other than the lithium ion secondary battery as described above. . The power storage system is a system that uses a lithium ion secondary battery as a power storage source. For example, in a household power storage system, power is stored in a lithium ion secondary battery, which is a power storage source, and the power is consumed as needed, so that household electrical products can be used. Become. An electric power tool is a tool in which a movable part (for example, a drill etc.) moves, using a lithium ion secondary battery as a drive power source. An electronic device is a device that exhibits various functions by using a lithium ion secondary battery as a driving power source.

  Here, some application examples of the lithium ion secondary battery will be specifically described. In addition, since the structure of each application example demonstrated below is an example to the last, it can change suitably.

<3-1. Battery Pack>
FIG. 10 shows a block configuration of the battery pack. For example, as shown in FIG. 10, the battery pack includes a control unit 61, a power source 62, a switch unit 63, a current measurement unit 64, a temperature, and the like inside a housing 60 formed of a plastic material or the like. A detection unit 65, a voltage detection unit 66, a switch control unit 67, a memory 68, a temperature detection element 69, a current detection resistor 70, a positive electrode terminal 71, and a negative electrode terminal 72 are provided.

  The control unit 61 controls the operation of the entire battery pack (including the usage state of the power supply 62), and includes, for example, a central processing unit (CPU). The power source 62 includes one or more lithium ion secondary batteries. The power source 62 is, for example, an assembled battery including two or more lithium ion secondary batteries, and the connection form thereof may be in series, in parallel, or a mixture of both. For example, the power source 62 includes six lithium ion secondary batteries connected in two parallel three series.

  The switch unit 63 switches the usage state of the power source 62 (whether or not the power source 62 can be connected to an external device) according to an instruction from the control unit 61. The switch unit 63 includes, for example, a charge control switch, a discharge control switch, a charging diode, a discharging diode, and the like. The charge control switch and the discharge control switch are semiconductor switches such as a field effect transistor (MOSFET) using a metal oxide semiconductor, for example.

  The current measurement unit 64 measures current using the current detection resistor 70 and outputs the measurement result to the control unit 61. The temperature detection unit 65 measures the temperature using the temperature detection element 69 and outputs the measurement result to the control unit 61. This temperature measurement result is used, for example, when the control unit 61 performs charge / discharge control during abnormal heat generation, or when the control unit 61 performs correction processing when calculating the remaining capacity. The voltage detector 66 measures the voltage of the lithium ion secondary battery in the power source 62, converts the measured voltage from analog to digital (A / D), and supplies the converted voltage to the controller 61.

The switch control unit 67 controls the operation of the switch unit 63 according to signals input from the current measurement unit 64 and the voltage measurement unit 66.

For example, when the battery voltage reaches the overcharge detection voltage, the switch control unit 67 disconnects the switch unit 63 (charge control switch) and controls the charging current not to flow through the current path of the power source 62. It is like that. As a result, the power source 62 can only discharge through the discharging diode. The switch control unit 67 is configured to cut off the charging current when a large current flows during charging, for example.

The switch control unit 67 controls the switch unit 63 (discharge control switch) so that no discharge current flows in the current path of the power source 62 when the battery voltage reaches the overdischarge detection voltage, for example. It is supposed to be. As a result, the power source 62 can only be charged via the charging diode. For example, the switch control unit 67 is configured to cut off the discharge current when a large current flows during discharging.

  In the lithium ion secondary battery, for example, the overcharge detection voltage is 4.20 V ± 0.05 V, and the overdischarge detection voltage is 2.4 V ± 0.1 V.

The memory 68 is, for example, an EEPROM that is a nonvolatile memory. In the memory 68, for example, numerical values calculated by the control unit 61 and information (for example, internal resistance in an initial state) of the lithium ion secondary battery measured in the manufacturing process stage are stored. If the full charge capacity of the lithium ion secondary battery is stored in the memory 68, the control unit 61 can grasp information such as the remaining capacity.

  The temperature detection element 69 measures the temperature of the power supply 62 and outputs the measurement result to the control unit 61, and is, for example, a thermistor.

  The positive electrode terminal 71 and the negative electrode terminal 72 are connected to an external device (for example, a notebook personal computer) operated using a battery pack or an external device (for example, a charger) used to charge the battery pack. Terminal. Charging / discharging of the power source 62 is performed via the positive terminal 71 and the negative terminal 72.

<3-2. Electric vehicle>
FIG. 11 shows a block configuration of a hybrid vehicle which is an example of an electric vehicle. For example, as shown in FIG. 11, the electric vehicle includes a control unit 74, an engine 75, a power source 76, a drive motor 77, and a differential device 78 in a metal housing 73. , A generator 79, a transmission 80 and a clutch 81, inverters 82 and 83, and various sensors 84. In addition, the electric vehicle includes, for example, a front wheel drive shaft 85 and a front wheel 86 connected to the differential device 78 and the transmission 80, and a rear wheel drive shaft 87 and a rear wheel 88.

  This electric vehicle can run using either the engine 75 or the motor 77 as a drive source. The engine 75 is a main power source, such as a gasoline engine. When the engine 75 is used as a power source, the driving force (rotational force) of the engine 75 is transmitted to the front wheels 86 or the rear wheels 88 via, for example, a differential device 78 that is a driving unit, a transmission 80, and a clutch 81. The rotational force of the engine 75 is also transmitted to the generator 79. The generator 79 generates AC power by the rotational force, and the AC power is converted into DC power via the inverter 83 and stored in the power source 76. Is done. On the other hand, when the motor 77 serving as a conversion unit is used as a power source, the power (DC power) supplied from the power source 76 is converted into AC power via the inverter 82, and the motor 77 is driven by the AC power. The driving force (rotational force) converted from electric power by the motor 77 is transmitted to the front wheels 86 or the rear wheels 88 via, for example, a differential device 78, a transmission 80, and a clutch 81, which are driving units.

  When the electric vehicle is decelerated by a braking mechanism (not shown), the resistance force at the time of deceleration may be transmitted as a rotational force to the motor 77, and the motor 77 may generate AC power by the rotational force. This AC power is preferably converted into DC power via the inverter 82, and the DC regenerative power is preferably stored in the power source 76.

  The control unit 74 controls the operation of the entire electric vehicle, and includes, for example, a CPU. The power source 76 includes one or more lithium ion secondary batteries. The power source 76 may be connected to an external power source and can store power by receiving power supply from the external power source. The various sensors 84 are used, for example, to control the rotational speed of the engine 75 or to control the opening (throttle opening) of a throttle valve (not shown). The various sensors 84 include, for example, a speed sensor, an acceleration sensor, an engine speed sensor, and the like.

  In the above description, the hybrid vehicle is described as the electric vehicle. However, the electric vehicle may be a vehicle (electric vehicle) that operates using only the power source 76 and the motor 77 without using the engine 75.

<3-3. Power storage system>
FIG. 12 shows a block configuration of the power storage system. This power storage system includes, for example, a control unit 90, a power source 91, a smart meter 92, and a power hub 93 in a house 89 such as a general house or a commercial building as shown in FIG. Yes.

  Here, the power source 91 is connected to, for example, an electric device 94 installed inside the house 89 and can be connected to an electric vehicle 96 stopped outside the house 89. The power source 91 is connected to, for example, a private generator 95 installed in a house 89 via a power hub 93 and can be connected to an external centralized power system 97 via the smart meter 92 and the power hub 93. It has become.

  Note that the electric device 94 includes one or more home appliances such as a refrigerator, an air conditioner, a television, or a water heater. The private power generator 95 is, for example, one type or two or more types such as a solar power generator or a wind power generator. The electric vehicle 96 is, for example, one type or two or more types such as an electric vehicle, an electric motorcycle, or a hybrid vehicle. The centralized power system 97 is, for example, one type or two or more types such as a thermal power plant, a nuclear power plant, a hydroelectric power plant, or a wind power plant.

  The control unit 90 controls the operation of the entire power storage system (including the usage state of the power supply 91), and includes, for example, a CPU. The power source 91 includes one or two or more lithium ion secondary batteries. The smart meter 92 is, for example, a network-compatible power meter installed in a house 89 on the power demand side, and can communicate with the power supply side. Accordingly, for example, the smart meter 92 controls the balance between supply and demand in the house 89 while communicating with the outside as necessary, thereby enabling efficient and stable energy supply.

In this power storage system, for example, power is accumulated in the power source 91 from the centralized power system 97 that is an external power source via the smart meter 92 and the power hub 93, and from the private power generator 95 that is an independent power source via the power hub 93. Thus, electric power is accumulated in the power source 91. The electric power stored in the power supply 91 is supplied to the electric device 94 or the electric vehicle 96 as required according to an instruction from the control unit 90 , so that the electric device 94 can be operated and the electric vehicle 96 is operated. Can be charged. In other words, the power storage system is a system that makes it possible to store and supply power in the house 89 using the power source 91.

  The power stored in the power supply 91 can be used arbitrarily. For this reason, for example, power is stored in the power source 91 from the centralized power system 97 at midnight when the amount of electricity used is low, and the power stored in the power source 91 is used during the day when the amount of electricity used is high. it can.

  The power storage system described above may be installed for each house (one household), or may be installed for each of a plurality of houses (multiple households).

<3-4. Electric tool>
FIG. 13 shows a block configuration of the electric power tool. For example, as shown in FIG. 13, the electric power tool is an electric drill, and includes a control unit 99 and a power source 100 inside a tool main body 98 formed of a plastic material or the like. For example, a drill portion 101 which is a movable portion is attached to the tool body 98 so as to be operable (rotatable).

  The control part 99 controls operation | movement (including the use condition of the power supply 100) of the whole electric tool, and contains CPU etc., for example. The power supply 100 includes one or more lithium ion secondary batteries. This controlled object 99 is moved by supplying electric power from the power supply 100 to the drill unit 101 as necessary in accordance with operation of an operation switch (not shown).

  Examples of the present technology will be described in detail.

(Examples 1-1 to 1-9)
The laminate film type secondary battery shown in FIGS. 8 and 9 was produced by the following procedure.

First, the positive electrode 53 was produced. First, 91 parts by mass of a positive electrode active material (LiCoO ₂ ), 6 parts by mass of a positive electrode conductive agent (graphite), and 3 parts by mass of a positive electrode binder (polyvinylidene fluoride: PVDF) were mixed to obtain a positive electrode mixture. Subsequently, the positive electrode mixture was dispersed in an organic solvent (N-methyl-2-pyrrolidone: NMP) to obtain a paste-like positive electrode mixture slurry. Subsequently, the positive electrode mixture slurry was applied to both surfaces of the positive electrode current collector 53A using a coating apparatus and then dried to form the positive electrode active material layer 53B. As the positive electrode current collector 53A, a strip-shaped Al foil (thickness = 12 μm) was used. Finally, the positive electrode active material layer 53B was compression molded using a roll press. Note that the thickness of the positive electrode active material layer 53B was adjusted so that Li metal did not precipitate on the negative electrode 54 during full charge.

Next, the negative electrode 54 was produced. First, after obtaining a core part (SiO _x ) using a gas atomizing method, a single-layer covering part (SiO _y + M1 (Ni)) was formed on the surface of the core part using a powder vapor deposition method. The composition (atomic ratio x, y and ratio (M1 / (Si + O))) of the core part and the covering part is as shown in Table 1. In this case, the half width of the core portion was 0.6 °, the crystallite size was 90 nm, the median diameter was 4 μm, the average thickness of the coating portion was 200 nm, and the average coverage was 70%.

In the case of obtaining the core portion, the composition (atomic ratio x) was controlled by adjusting the amount of oxygen introduced during the melting and solidification of the raw material (Si). When forming the covering portion, the SiO _y powder and the metal powder M1 are co-evaporated, and the composition (atomic ratio y) is controlled by adjusting the amount of O ₂ or H ₂ introduced during the deposition of the raw materials. The ratio (M1 / (Si + O)) was controlled by adjusting the input power. In the powder vapor deposition method, a deflection type electron beam vapor deposition source is used, the median diameter of the raw material Si powder = 0.2 μm to 30 μm, the deposition rate = 2 nm / second, and the pressure using a turbo molecular pump = 1 × 10 ^−3. A vacuum state of Pa was set.

  Subsequently, the negative electrode active material and the negative electrode binder precursor were mixed at a dry weight ratio of 90:10, and then diluted with NMP to obtain a paste-like negative electrode mixture slurry. In this case, polyamic acid containing NMP and N, N-dimethylacetamide (DMAC) was used. Subsequently, the negative electrode mixture slurry was applied to both surfaces of the negative electrode current collector 54A using a coating apparatus, and then dried. As the negative electrode current collector 54A, a rolled Cu foil (thickness = 15 μm, ten-point average roughness Rz <0.5 μm) was used. Finally, in order to enhance the binding property, the coating film was hot-pressed and then baked in a vacuum atmosphere at 400 ° C. for 1 hour. Thereby, since the negative electrode binder (polyamideimide) was formed, the negative electrode active material layer 54B containing a negative electrode active material and a negative electrode binder was formed. Note that the thickness of the negative electrode active material layer 54B was adjusted so that the negative electrode utilization rate was 65%.

Next, an electrolyte salt (LiPF ₆ ) was dissolved in a solvent (ethylene carbonate (EC) and diethyl carbonate (DEC)) to prepare an electrolyte solution. In this case, the composition of the solvent was EC: DEC = 50: 50 by weight, and the content of the electrolyte salt was 1 mol / kg with respect to the solvent.

  Finally, a secondary battery was assembled. First, the positive electrode lead 51 made of Al was welded to one end of the positive electrode current collector 53A, and the negative electrode lead 52 made of Ni was welded to one end of the negative electrode current collector 54A. Subsequently, the positive electrode 53, the separator 55, the negative electrode 54, and the separator 55 are stacked in this order, and then wound in the longitudinal direction to form a wound body that is a precursor of the wound electrode body 50, and then the winding ends. The part was fixed with protective tape 57 (adhesive tape). In this case, a laminated film (thickness = 20 μm) in which a film mainly composed of porous polyethylene was sandwiched between films mainly composed of porous polypropylene was used as the separator 55. Subsequently, after sandwiching the wound body between the exterior members 60, the outer peripheral edge portions except for one side were heat-sealed, and the wound body was housed inside the bag-shaped exterior member 60. In this case, an aluminum laminate film in which a nylon film (thickness = 30 μm), an Al foil (thickness = 40 μm) and an unstretched polypropylene film (thickness = 30 μm) were laminated as the exterior member 60 was used. . Subsequently, the electrolytic solution was injected from the opening of the exterior member 60 and impregnated in the separator 55 to produce the wound electrode body 50. Finally, the opening of the exterior member 60 was heat-sealed and sealed in a vacuum atmosphere.

  When the cycle characteristics, initial charge / discharge characteristics, and load characteristics of the secondary battery were examined, the results shown in Table 1 were obtained.

In examining the cycle characteristics, first, in order to stabilize the battery state, the battery was charged and discharged for one cycle in an atmosphere at 23 ° C., and then charged and discharged again to measure the discharge capacity. Subsequently, charging and discharging were performed until the total number of cycles reached 100 cycles, and the discharge capacity was measured. Finally, cycle maintenance ratio (%) = (discharge capacity at the 100th cycle / discharge capacity at the second cycle) × 100 was calculated. During charging, charging was performed at a constant current density of 3 mA / cm ² until the voltage reached 4.2 V, and then charging was performed at a constant voltage of 4.2 V until the current density reached 0.3 mA / cm ² . During discharging, discharging was performed at a constant current density of 3 mA / cm ² until the voltage reached 2.5V.

  When investigating the initial charge / discharge characteristics, first, one cycle charge / discharge was performed to stabilize the battery state. Then, after charging again and measuring a charge capacity, it discharged and measured the discharge capacity. Finally, initial efficiency (%) = (discharge capacity / charge capacity) × 100 was calculated. The atmospheric temperature and the charge / discharge conditions were the same as in the case where the cycle characteristics were examined.

When examining the load characteristics, first, charging and discharging were performed for one cycle in order to stabilize the battery state. Subsequently, after the discharge capacity was measured by performing a second cycle of charging and discharging, the discharge capacity was measured by performing the charging and discharging of the third cycle. Finally, load retention ratio (%) = (discharge capacity at the third cycle / discharge capacity at the second cycle) × 100 was calculated. Except that the current density at the second cycle discharge was 0.2 mA / cm ² and the current density at the third cycle discharge was changed to 1 mA / cm ² , the ambient temperature and charge / discharge conditions were examined for cycle characteristics. Same as the case.

  When the covering portion (Si + O + Ni) is formed on the surface of the core portion (Si + O), the initial efficiency and load maintenance are higher than when the covering portion is not formed and when the covering portion does not contain Ni. While maintaining the rate, the cycle maintenance rate increased significantly.

  Specifically, when the covering portion (Si + O) is formed on the surface of the core portion (Si + O), the cycle retention ratio is remarkably increased as compared with the case where the covering portion is not formed, but the initial efficiency and the load retention ratio are increased. Will decrease. On the other hand, when the covering portion (Si + O + Ni) is formed on the surface of the core portion (Si + O), the initial efficiency exceeding 80% and the load maintenance ratio exceeding 90% are compared with the case where the covering portion is not formed. As a result, the cycle maintenance rate was further increased. Thus, the advantageous tendency that the cycle maintenance ratio is further increased while the decrease in the initial efficiency and the load maintenance ratio is suppressed to a minimum is a specific tendency obtained only by the formation of the covering portion (Si + O + Ni).

  In particular, when the covering portion (Si + O + Ni) was formed, a decrease in battery capacity was suppressed when the ratio of M1 was 50 atomic% or less, and thus a high battery capacity was obtained. In this case, a higher battery capacity was obtained when the proportion of M1 was 20 atomic% or less.

(Experimental examples 2-1 to 2-94)
Except for changing the type and combination of M1 as shown in Tables 2 to 7, secondary batteries were fabricated in the same procedure as in Experimental Examples 1-1 to 1-7, and various characteristics were examined. In this case, each metal powder M1 was used for co-evaporation with SiO _y powder.

  Even if the type and combination of M1 were changed, similar to the results in Table 1, high cycle retention ratio, initial efficiency, and load retention ratio were obtained.

(Experimental examples 3-1 to 3-7)
As shown in Table 8, secondary batteries were fabricated in the same procedure as in Experimental Examples 1-1 to 1-7, except that the composition (atomic ratio y) of the covering portion was changed, and various characteristics were examined. . In this case, the atomic ratio y was controlled by adjusting the oxygen introduction amount when the raw material (Si) was melted and solidified.

  When the atomic ratio y was 0.5 ≦ y ≦ 1.5, a high cycle retention rate was obtained.

(Experimental examples 4-1 to 4-9, 5-1 to 5-10)
As shown in Table 9 and Table 10, secondary batteries were fabricated in the same manner as in Experimental Examples 1-1 to 1-7, except that the average coverage and average thickness of the covering portions were changed. The characteristics were investigated. In this case, when forming the coating portion, the average power was controlled by changing the input power and the deposition time, and the average thickness was controlled by changing the deposition rate and the deposition time.

  When the average coverage was 30% or more and the average thickness was 1 nm to 10000 nm, a high cycle retention rate was obtained.

(Experimental examples 6-1 to 6-5)
As shown in Table 11, secondary batteries were produced in the same procedure as in Experimental Examples 1-1 to 1-7 except that the layer structure of the covering portion was changed, and various characteristics were examined. In this case, the covering portion was formed in multiple layers by performing the covering portion forming process in two steps. Moreover, the bonding state in the coating part was controlled by changing the base temperature at the time of co-evaporation when the coating part was formed.

  When the coating part was multi-layered, the cycle maintenance rate increased more. Moreover, when SiNiO was formed in the coating part, initial efficiency and load efficiency increased more.

(Experimental examples 7-1 to 7-5)
As shown in Table 12, secondary batteries were fabricated in the same procedure as in Experimental Examples 1-1 to 1-7, except that the core composition (atomic ratio x) was changed, and various characteristics were examined. . In this case, the atomic ratio x was controlled by adjusting the amount of oxygen introduced when the raw material (Si) was melted and solidified.

  When the atomic ratio x was 0 ≦ x <0.5, the cycle maintenance ratio and the initial efficiency were further increased.

(Experimental examples 8-1 to 8-3)
As shown in Table 13, secondary batteries were fabricated in the same procedure as in Experimental Examples 1-1 to 1-7 except that the material of the core portion was changed, and various characteristics were examined. As a material for forming the core portion, an Sn alloy was used.

  Even when the material of the core part was changed to a simple substance or an alloy of Sn, a high cycle retention rate, initial efficiency and load retention rate were obtained.

(Experimental examples 9-1 to 9-14)
As shown in Table 14, a secondary battery was fabricated in the same procedure as in Experimental Examples 1-1 to 1-7, except that the core portion contained the element M2 (Fe or the like), and various characteristics were examined. It was. In this case, a core part was obtained by a gas atomizing method using SiO _x powder and metal powder M2 (Al, etc.) as raw materials.

  When M2 was contained in the core part, the cycle retention rate was further increased. In this case, a higher battery capacity was obtained when the proportion of M2 was 0.01 atomic% to 50 atomic%.

(Experimental examples 10-1 to 10-60)
As shown in Table 15 to Table 17, two procedures were performed in the same manner as in Experimental Examples 1-1 to 1-7, except that the core portion contained the element M3 (Cr or the like) or the element M4 (B or the like). Next batteries were fabricated and various characteristics were examined. In this case, a core portion was obtained by a gas atomizing method using SiO _x powder and metal powder M3 or the like (Cr or the like) as raw materials.

  When M3 or M4 was contained in the core part, the cycle retention rate was further increased. In this case, a higher battery capacity was obtained when the proportion of M3 was 1 atomic percent to 50 atomic percent and the proportion of M4 was 0.01 atomic percent to 30 atomic percent.

(Experimental examples 11-1 to 11-8)
As shown in Table 18, secondary batteries were produced in the same procedure as in Experimental Examples 1-1 to 1-7, and various characteristics were examined, except that a conductive part was formed on the surface of the covering part. In this case, the conductive portion was formed by the same procedure as that for forming the covering portion. The average thickness and average coverage of the conductive part are as shown in Table 18.

  Better results were obtained when the conductive part was formed.

(Experimental examples 12-1 to 12-6)
As shown in Table 19, secondary batteries were fabricated in the same procedure as in Experimental Examples 1-1 to 1-7, except that the median diameter of the core portion was changed, and various characteristics were examined.

  When the median diameter of the core portion was 0.3 μm to 20 μm, a high cycle retention rate and initial efficiency were obtained, and a high battery capacity was also obtained.

(Experimental Examples 13-1 to 13-18)
As shown in Table 20, secondary batteries were prepared in the same procedure as in Experimental Examples 1-1 to 1-7, except that the type of the negative electrode binder was changed, and various characteristics were examined. In this case, polyimide (PI), polyvinylidene fluoride (PVDF), polyamide (PA), polyacrylic acid (PAA), lithium polyacrylate (PAAL) or carbonized polyimide (carbonized PI) is used as the negative electrode binder. Using. When PAA or PAAL was used, a negative electrode mixture slurry was prepared using a 17% by volume aqueous solution in which they were dissolved, and the negative electrode active material layer 54B was formed without firing after hot pressing.

  Even when the type of the negative electrode binder was changed, a high cycle retention rate, initial efficiency and load retention rate were obtained.

(Experimental examples 14-1 to 14-12)
As shown in Table 21, secondary batteries were prepared in the same manner as in Experimental Examples 1-1 to 1-7, except that the type of the positive electrode active material was changed, and various characteristics were examined.

  Even when the type of the positive electrode active material was changed, a high cycle retention rate, initial efficiency and load retention rate were obtained.

  From the results of Tables 1 to 21, it was confirmed that high cycle characteristics, initial charge / discharge characteristics, and load characteristics can be obtained when the negative electrode active material includes a coating portion having a predetermined composition on the surface of the core portion.

  As described above, the present technology has been described with reference to the embodiment and the examples, but the present technology is not limited to the aspect described in them, and various modifications can be made. For example, although the case where the capacity of the negative electrode is expressed by occlusion / release of lithium ions has been described, the present invention is not necessarily limited thereto. The present technology can also be applied to a case where the capacity of the negative electrode includes a capacity due to insertion and extraction of lithium ions and a capacity due to precipitation dissolution of Li metal, and is expressed by the sum of these capacities. In this case, a negative electrode material capable of inserting and extracting lithium ions is used as the negative electrode active material, and the chargeable capacity of the negative electrode material is set to be smaller than the discharge capacity of the positive electrode.

  Moreover, although the case where the battery structure is a square shape, a cylindrical shape, or a laminate film type and the battery element has a winding structure has been described, the present invention is not necessarily limited thereto. The present technology can also be applied when the battery structure is a square type or a button type, or when the battery element has a laminated structure or the like.

  DESCRIPTION OF SYMBOLS 1,42A, 54A ... Negative electrode collector, 2, 42B, 54B ... Negative electrode active material layer, 22, 42, 54 ... Negative electrode, 20 ... Battery element, 21, 41, 53 ... Positive electrode, 21A, 22A, 41A, 53A ... positive electrode current collector, 21B, 22B, 41B, 53B ... positive electrode active material layer, 23, 43, 55 ... separator, 40, 50 ... wound electrode body, 56 ... electrolyte layer, 60 ... exterior member, 200 ... negative electrode active Substance, 201 ... core part, 202 ... covering part.

Claims (16)

A positive electrode, a negative electrode containing an active material, and an electrolyte solution,
The active material includes a core part capable of occluding and releasing lithium ions, and a covering part provided on at least a part of the surface of the core part,
The core part includes Si and O and at least one element M2 of Fe and Al as constituent elements, and the ratio of M2 to Si and O (M2 / (Si + O)) is 1 atomic% to 50 Atomic percent,
The covering portion includes Si and O, Li, C, Mg, Al, Ca, Ti, Cr, Mn, Fe, Co, Ni, Cu, Ge, Zr, Mo, Ag, Sn, Ba, W, Ta, It includes at least one element M1 of Na and K as a constituent element, and an atomic ratio y (O / Si) of O to Si is 0.5 ≦ y ≦ 1.8.
Lithium ion secondary battery. The ratio of M1 to Si and O (M1 / (Si + O)) is 50 atomic% or less.
The lithium ion secondary battery according to claim 1. At least a portion of M1 is bonded to at least one of Si and O;
The lithium ion secondary battery according to claim 1 or claim 2. The covering portion includes a compound of Si, O, and M1,
The lithium ion secondary battery according to claim 3. The average coverage of the covering portion relative to the core portion is 30% to 100%.
The lithium ion secondary battery according to any one of claims 1 to 4. The average thickness of the covering portion is 1 nm to 10000 nm.
The lithium ion secondary battery according to any one of claims 1 to 5. The covering portion is multilayer.
The lithium ion secondary battery according to any one of claims 1 to 6. In the core portion , the atomic ratio x (O / Si) of O to Si is 0 < x <0.5.
The lithium ion secondary battery according to any one of claims 1 to 7 . The median diameter of the core portion is 0.3 μm to 20 μm.
The lithium ion secondary battery according to any one of claims 1 to 8 . The negative electrode active material includes a conductive portion that is provided on at least a part of the surface of the covering portion and has a lower electrical resistance than the core portion and the covering portion.
The lithium ion secondary battery according to any one of claims 1 to 9 . Including an active material, the active material including a core part capable of occluding and releasing lithium ions, and a covering part provided on at least a part of the surface of the core part,
The core part includes Si and O and at least one element M2 of Fe and Al as constituent elements, and the ratio of M2 to Si and O (M2 / (Si + O)) is 1 atomic% to 50 Atomic percent,
The covering portion includes Si and O, Li, C, Mg, Al, Ca, Ti, Cr, Mn, Fe, Co, Ni, Cu, Ge, Zr, Mo, Ag, Sn, Ba, W, Ta, It includes at least one element M1 of Na and K as a constituent element, and an atomic ratio y (O / Si) of O to Si is 0.5 ≦ y ≦ 1.8.
Negative electrode for lithium ion secondary battery. A lithium ion secondary battery;
A control unit for controlling the use state of the lithium ion secondary battery;
A switch unit for switching the usage state of the lithium ion secondary battery according to an instruction of the control unit,
The lithium ion secondary battery includes a positive electrode, a negative electrode containing an active material, and an electrolyte solution.
The active material includes a core part capable of occluding and releasing lithium ions, and a covering part provided on at least a part of the surface of the core part,
The core part includes Si and O and at least one element M2 of Fe and Al as constituent elements, and the ratio of M2 to Si and O (M2 / (Si + O)) is 1 atomic% to 50 Atomic percent,
The covering portion includes Si and O, Li, C, Mg, Al, Ca, Ti, Cr, Mn, Fe, Co, Ni, Cu, Ge, Zr, Mo, Ag, Sn, Ba, W, Ta, It includes at least one element M1 of Na and K as a constituent element, and an atomic ratio y (O / Si) of O to Si is 0.5 ≦ y ≦ 1.8.
Battery pack. A lithium ion secondary battery;
A converter that converts electric power supplied from the lithium ion secondary battery into driving force;
A drive unit that drives according to the driving force;
A control unit for controlling a use state of the lithium ion secondary battery,
The lithium ion secondary battery includes a positive electrode, a negative electrode containing an active material, and an electrolyte solution.
The active material includes a core part capable of occluding and releasing lithium ions, and a covering part provided on at least a part of the surface of the core part,
The core part includes Si and O and at least one element M2 of Fe and Al as constituent elements, and the ratio of M2 to Si and O (M2 / (Si + O)) is 1 atomic% to 50 Atomic percent,
The covering portion includes Si and O, Li, C, Mg, Al, Ca, Ti, Cr, Mn, Fe, Co, Ni, Cu, Ge, Zr, Mo, Ag, Sn, Ba, W, Ta, It includes at least one element M1 of Na and K as a constituent element, and an atomic ratio y (O / Si) of O to Si is 0.5 ≦ y ≦ 1.8.
Electric vehicle. A lithium ion secondary battery;
One or more electrical devices;
A controller that controls power supply from the lithium ion secondary battery to the electrical device,
The lithium ion secondary battery includes a positive electrode, a negative electrode containing an active material, and an electrolyte solution.
The active material includes a core part capable of occluding and releasing lithium ions, and a covering part provided on at least a part of the surface of the core part,
The core part includes Si and O and at least one element M2 of Fe and Al as constituent elements, and the ratio of M2 to Si and O (M2 / (Si + O)) is 1 atomic% to 50 Atomic percent,
The covering portion includes Si and O, Li, C, Mg, Al, Ca, Ti, Cr, Mn, Fe, Co, Ni, Cu, Ge, Zr, Mo, Ag, Sn, Ba, W, Ta, It includes at least one element M1 of Na and K as a constituent element, and an atomic ratio y (O / Si) of O to Si is 0.5 ≦ y ≦ 1.8.
Power storage system. A lithium ion secondary battery;
A movable part supplied with electric power from the lithium ion secondary battery,
The lithium ion secondary battery includes a positive electrode, a negative electrode containing an active material, and an electrolyte solution.
The active material includes a core part capable of occluding and releasing lithium ions, and a covering part provided on at least a part of the surface of the core part,
The core part includes Si and O and at least one element M2 of Fe and Al as constituent elements, and the ratio of M2 to Si and O (M2 / (Si + O)) is 1 atomic% to 50 Atomic percent,
The covering portion includes Si and O, Li, C, Mg, Al, Ca, Ti, Cr, Mn, Fe, Co, Ni, Cu, Ge, Zr, Mo, Ag, Sn, Ba, W, Ta, It includes at least one element M1 of Na and K as a constituent element, and an atomic ratio y (O / Si) of O to Si is 0.5 ≦ y ≦ 1.8.
Electric tool. Equipped with a lithium ion secondary battery, powered by the lithium ion secondary battery,
The lithium ion secondary battery includes a positive electrode, a negative electrode containing an active material, and an electrolyte solution.
The active material includes a core part capable of occluding and releasing lithium ions, and a covering part provided on at least a part of the surface of the core part,
The core part includes Si and O and at least one element M2 of Fe and Al as constituent elements, and the ratio of M2 to Si and O (M2 / (Si + O)) is 1 atomic% to 50 Atomic percent,
The covering portion includes Si and O, Li, C, Mg, Al, Ca, Ti, Cr, Mn, Fe, Co, Ni, Cu, Ge, Zr, Mo, Ag, Sn, Ba, W, Ta, It includes at least one element M1 of Na and K as a constituent element, and an atomic ratio y (O / Si) of O to Si is 0.5 ≦ y ≦ 1.8.
Electronics.

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