JP2019021418A - Controller and control method of nonaqueous electrolyte secondary battery, nonaqueous electrolyte secondary battery system having the controller, and method for manufacturing nonaqueous electrolyte secondary battery - Google Patents

Abstract

To provide means for suppressing the worsening of the cycle durability of a high-capacity and high-density nonaqueous electrolyte secondary battery which uses a solid solution positive electrode active material having a predetermined structure and a silicon-containing negative electrode active material.SOLUTION: In an embodiment of the present invention, in an activation process (a process for causing re-organization of a crystal structure by performing a charging process on a power-generating element) when manufacturing a high-capacity and high-density nonaqueous electrolyte secondary battery which uses a solid solution positive electrode active material and a silicon-containing negative electrode active material, the charging process is controlled so that a value of SOC of the power-generating element does not exceed an upper limit of SOC previously set from the relation between SOC of the power-generating element and a gas generation amount. In another embodiment of the invention, when using a high-capacity and high-density nonaqueous electrolyte secondary battery which uses a solid solution positive electrode active material and a silicon-containing negative electrode active material, the charge/discharge of a power-generating element is controlled so that the value of SOC of the power-generating element does not exceed an upper limit of SOC previously set from the relation between SOC of the power-generating element and a gas generation amount.SELECTED DRAWING: Figure 3B

Description

  The present invention relates to a control device and a control method for a nonaqueous electrolyte secondary battery, a nonaqueous electrolyte secondary battery system having the control device, and a method for manufacturing a nonaqueous electrolyte secondary battery. The non-aqueous electrolyte secondary battery according to the present invention is used, for example, as a driving power source or auxiliary power source for motors of vehicles such as electric vehicles, fuel cell vehicles, and hybrid electric vehicles.

  In recent years, in order to cope with global warming, reduction of the amount of carbon dioxide is eagerly desired. In the automobile industry, there is a great expectation for reducing carbon dioxide emissions by introducing electric vehicles (EV) and hybrid electric vehicles (HEV). Electric devices such as secondary batteries for motor drive that hold the key to their practical application. Is being actively developed.

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

  Generally, a lithium ion secondary battery includes a positive electrode in which a positive electrode active material or the like is applied to both surfaces of a positive electrode current collector using a binder, and a negative electrode in which a negative electrode active material or the like is applied to both surfaces of a negative electrode current collector using a binder. However, it has the structure connected through an electrolyte layer and accommodated in a battery case.

Conventionally, carbon / graphite-based materials that are advantageous in terms of charge / discharge cycle life and cost have been used for negative electrodes of lithium ion secondary batteries. However, since carbon / graphite-based negative electrode materials are charged / discharged by occlusion / release of lithium ions into / from graphite crystals, the charge / discharge capacity of the theoretical capacity 372 mAh / g or more obtained from LiC ₆ which is the maximum lithium-introduced compound. There is a disadvantage that cannot be obtained. For this reason, it is difficult to obtain a capacity and energy density that satisfy the practical use level of the vehicle application with the carbon / graphite negative electrode material.

In contrast, a battery using a silicon-containing negative electrode active material such as a SiO _x (0 <x <2) material that forms a compound with Li or an alloy-based material containing silicon is a conventional carbon / graphite negative electrode material. Therefore, it is expected as a negative electrode material for vehicle use. For example, in a silicon oxide having a chemical composition represented by SiO _x , when viewed microscopically, Si (single crystal nanoparticles) and amorphous SiO ₂ exist in phase separation.

On the other hand, as an effort to increase the energy density of the positive electrode material, xLi ₂ MnO _3- (1-x) LiMe′O ₂ (wherein Me ′ represents Co, Mn, Ni, Cr, etc.) as a layered compound Attempts have been made to use a solid solution as a positive electrode active material. In this solid solution positive electrode active material, a part of Li is replaced by a transition metal and has a Li-excess crystal structure. When high-voltage charging is performed on the solid solution positive electrode active material, activation due to reorganization of the crystal structure (change from a layered structure (Li ₂ MnO ₃ ) to a spinel structure (LiMn ₂ O ₄ )) occurs. High capacity can be achieved.

  However, in such a solid solution positive electrode active material, oxygen gas is released due to a change in crystal structure during charging, and the battery is swollen by oxygen gas when actually used as a positive electrode active material of a lithium ion secondary battery. It is a problem. Further, when oxygen gas is generated, there is a problem that sufficient charge / discharge characteristics cannot be exhibited.

For such a problem, a technique described in Patent Document 1 has been proposed. Specifically, the technique described in Patent Document 1 is such that xLi ₂ MnO ₃ — (1-x) LiMn _a Co _b Ni _C O ₂ (where 0.2 ≦ x ≦ 0.5, 0.3 ≦ a ≦ 0.5, 0.1 ≦ b ≦ 0.3, 0.3 ≦ c ≦ 0.5, a + b + c = 1), at least part of the surface of the solid solution other than Mn, Co, and Ni These are coated with an oxide of a transition metal or a lithium salt of an oxide. Thus, a high-capacity solid solution positive electrode active material in which generation of oxygen gas during charging is suppressed is provided.

JP 2012-129166 A

  In a battery with a small capacity, it is possible to suppress a decrease in discharge capacity by mitigating the influence of the generation of oxygen gas during charging to some extent by the technique described in Patent Document 1. However, as a result of further investigation by the present inventors, for example, in a battery having a high capacity and high density (small battery volume per battery capacity) that can be used as a driving power source for an electric vehicle or the like, oxygen is charged during charging. It has been found that when gas is generated, the discharge capacity decreases (cycle durability decreases) as the number of cycles increases.

  Therefore, an object of the present invention is to provide a means capable of suppressing a decrease in cycle durability of a high-capacity and high-density nonaqueous electrolyte secondary battery using a solid solution positive electrode active material and a silicon-containing negative electrode active material.

  In one embodiment of the present invention, an activation treatment (containing a solid solution positive electrode active material to be activated) is produced when manufacturing a high-capacity and high-density nonaqueous electrolyte secondary battery using a solid solution positive electrode active material and a silicon-containing negative electrode active material. In the process of causing restructuring of the crystal structure by performing a charging process on the power generation element), the value of the charge state of the power generation element is set in advance from the relationship between the charge state of the power generation element and the amount of gas generated The said subject is solved by controlling the said charging process so that the upper limit of a state may not be exceeded.

  In another embodiment of the present invention, when using a high-capacity and high-density non-aqueous electrolyte secondary battery using a solid solution positive electrode active material and a silicon-containing negative electrode active material, the value of the state of charge of the power generation element is: The above problem is solved by controlling charging / discharging of the power generation element so as not to exceed the preset upper limit value of the charging state from the relationship between the charging state of the power generation element and the amount of gas generated.

  In the present invention, a high-capacity and high-density nonaqueous electrolyte secondary battery using a solid solution positive electrode active material and a silicon-containing negative electrode active material is manufactured so as to be in a charged state with a small amount of gas generation or use. For this reason, the capacity | capacitance fall by the oxidation of the negative electrode resulting from gas generation and the imbalance of A / C ratio are prevented, and the fall of the cycle durability of the said battery can be suppressed.

A flat (non-bipolar) non-aqueous electrolyte secondary battery, which is an example of a non-aqueous electrolyte secondary battery that is manufactured by the manufacturing method according to the present invention and is a control target of the control method and control device according to the present invention, FIG. It is sectional drawing which follows the IIA-IIA line | wire of FIG. It is sectional drawing which follows the IIB-IIB line | wire of FIG. It is a block diagram which shows the structure containing the control apparatus for implementing especially an activation process among the manufacturing methods of the nonaqueous electrolyte secondary battery which concerns on one Embodiment of this invention. The relationship between the charge state (positive electrode capacity), which is the basis for setting the upper limit value of the charge state stored in the control device (particularly the storage unit) of FIG. 3A, the positive electrode potential (●), and the oxygen gas generation amount (◯) It is a figure which shows an example. It is a block diagram which shows the electric vehicle carrying the nonaqueous electrolyte secondary battery which concerns on one Embodiment of this invention. 5 is a graph plotting discharge capacities in each cycle of a cycle durability test for Example 3 and Comparative Example 3. FIG. “The value of the ratio of the battery volume (the product of the projected area of the battery including the battery outer casing and the thickness of the battery) to the rated capacity of the battery is 10 cm ³ / Ah or less, and the rated capacity is 3 Ah or more. It is the graph which plotted the discharge capacity in each cycle of a cycle durability test when the same comparative experiment (cycle durability test) as FIG. 5A was performed using a battery other than “battery”.

  Hereinafter, although the form for implementing this invention is demonstrated in detail, this invention is not restrict | limited only to the following forms. In addition, the dimensional ratios in the drawings are exaggerated for convenience of explanation, and may differ from actual ratios.

  The present invention includes a positive electrode containing an activated solid solution positive electrode active material, a negative electrode containing a silicon-containing negative electrode active material, and an electrolyte layer containing a non-aqueous electrolyte interposed between the positive electrode and the negative electrode. The present invention relates to a method for manufacturing a nonaqueous electrolyte secondary battery having a power generation element, a control method, and a control device.

<Configuration example of non-aqueous electrolyte secondary battery>
FIG. 1 shows a flat (non-bipolar) non-aqueous electrolyte that is an example of a non-aqueous electrolyte secondary battery that is manufactured by the manufacturing method according to the present invention and is a control target of the control method and control apparatus according to the present invention. It is a top view which shows a secondary battery (henceforth only a "stacked battery"). 2A is a cross-sectional view taken along line IIA-IIA in FIG. 2B is a cross-sectional view taken along the line IIB-IIB in FIG. Examples of the nonaqueous electrolyte secondary battery (stacked battery) 10 include a lithium secondary battery such as a lithium ion secondary battery. However, the nonaqueous electrolyte secondary battery shown below is an example of a nonaqueous electrolyte secondary battery that is manufactured by the manufacturing method according to the present invention and is a control target of the control method and the control device according to the present invention. Nonaqueous electrolyte secondary batteries having a structure other than the above are also included in the technical scope of the present invention.

  As shown in FIG. 1, the stacked battery 10 of the present embodiment has a structure in which a substantially rectangular power generation element 21 in which a charge / discharge reaction actually proceeds is sealed inside a battery exterior body 29 that is an exterior body. Have. Here, the power generation element 21 has a configuration in which a positive electrode, an electrolyte layer 17, and a negative electrode are stacked. The positive electrode has a structure in which the positive electrode active material layers 15 are disposed on both surfaces of the positive electrode current collector 12. The negative electrode has a structure in which the negative electrode active material layer 13 is disposed on both surfaces of the negative electrode current collector 11. Specifically, the negative electrode, the electrolyte layer, and the positive electrode are laminated in this order so that one positive electrode active material layer 15 and the negative electrode active material layer 13 adjacent thereto face each other with the electrolyte layer 17 therebetween. . Thereby, the adjacent positive electrode, electrolyte layer, and negative electrode constitute one unit cell layer 19. Therefore, it can be said that the stacked battery 10 shown in FIG. 1 has a configuration in which a plurality of single battery layers 19 are stacked and electrically connected in parallel.

  In addition, although the negative electrode active material layer 13 is arrange | positioned only in the single side | surface at all the outermost layer negative electrode collectors located in both outermost layers of the electric power generation element 21, an active material layer may be provided in both surfaces. That is, instead of using a current collector dedicated to the outermost layer provided with an active material layer only on one side, a current collector having an active material layer on both sides may be used as it is as an outermost current collector. Further, by reversing the arrangement of the positive electrode and the negative electrode as compared with FIG. 1, the outermost positive electrode current collector is positioned on both outermost layers of the power generation element 21, and the outermost positive electrode current collector is disposed on one or both surfaces of the outermost layer positive electrode current collector. A positive electrode active material layer may be disposed.

  The positive electrode current collector 12 and the negative electrode current collector 11 are respectively attached with a positive electrode current collector plate 27 and a negative electrode current collector plate 25 that are electrically connected to the respective electrodes (positive electrode and negative electrode), and are sandwiched between end portions of the battery exterior body 29. In this way, it has a structure that is led out of the battery exterior body 29. The positive electrode current collector 27 and the negative electrode current collector 25 are ultrasonically welded to the positive electrode current collector 12 and the negative electrode current collector 11 of each electrode, respectively, via a positive electrode lead and a negative electrode lead (not shown) as necessary. Or resistance welding or the like.

  Further, as shown in FIG. 2B, the stacked battery 10 of the present embodiment is provided with a reference electrode (lithium metal reference electrode) 31. The reference electrode 31 is for detecting the potential of the positive electrode of the stacked battery 10 with respect to the potential of the reference electrode 31, and the lithium ion is connected to the positive electrode active material layer 15 (or the negative electrode active material layer 13). It can be moved. In other words, it is necessary to ensure ionic conductivity between the positive electrode and the negative electrode. For this reason, the reference electrode 31 of the present embodiment is sandwiched between the positive electrode active material layer 15 and the negative electrode active material layer 13, and the electrolyte layer in which lithium ions move during charge / discharge (in the separator 17 in the present embodiment). Is provided. Note that a reference electrode lead 33 is connected to the reference electrode 31, and is further taken out as a reference electrode tab 35 to the outside of the stacked battery 10 (specifically, the battery outer package 29).

[Positive electrode active material layer]
The positive electrode active material layer includes a positive electrode active material capable of occluding ions such as lithium ions during discharge and releasing ions such as lithium ions during charging. Here, as described above, the nonaqueous electrolyte secondary battery according to the present invention is a so-called high capacity and high density battery. In order to constitute such a high capacity battery, the positive electrode active material layer of the present embodiment contains an activated solid solution positive electrode active material. The solid solution positive electrode active material has a layered structure portion and a portion (layered structure Li ₂ MnO ₃ ) that changes to a spinel structure by charging or charging / discharging in a predetermined potential range. Here, although there is no restriction | limiting in particular about the specific structure of the said solid solution positive electrode active material, Preferably it consists of a solid solution lithium containing transition metal oxide. The solid solution positive electrode active material is more preferably the following chemical formula (1):
Li [Ni _a Co _b Mn _c [Li] _d ] O _z (1)
In the formula, Li represents lithium, Ni represents nickel, Co represents cobalt, Mn represents manganese, O represents oxygen, z represents the number of oxygens satisfying the valence, and a, b, c and d are 0 <a < 0.94, 0 ≦ b <0.94, 0 <c <0.94, 0.05 ≦ d ≦ 0.8, a + b + c = 1 is satisfied,
It is preferable that it has as a basic structure the solid solution lithium containing transition metal oxide which has a composition represented by these.

When such a solid solution positive electrode active material (preferably, a solid solution lithium-containing transition metal oxide) is used as a positive electrode active material of a lithium ion secondary battery, it is possible to achieve a high discharge capacity and capacity retention rate. In particular, a very high discharge capacity can be realized by changing Li ₂ MnO ₃ having a layered structure in the solid solution positive electrode active material into LiMn ₂ O ₄ having a spinel structure by an activation treatment described later. As a result, it can be suitably used as a lithium-ion secondary battery for vehicle drive power or auxiliary power. In addition to this, the present invention can be sufficiently applied to lithium ion secondary batteries for home use and portable devices.

In the formula (1), Li represents lithium, Ni represents nickel, Co represents cobalt, Mn represents manganese, O represents oxygen, z represents the number of oxygens satisfying the valence, and a, b, c and d are 0. <A <0.94, 0 ≦ b <0.94, 0 <c <0.94, 0.05 ≦ d ≦ 0.8, and a + b + c = 1 are satisfied. This has the advantage that the structure of the solid solution is sufficiently stable. Note that the oxygen number represented by z is “satisfying valence”, but this “satisfying valence” oxygen number z is a solid solution lithium-containing transition having a composition represented by chemical formula (1). When the metal oxide is a solid solution containing Li ₂ MnO ₃ and LiMe′O ₂ at a molar ratio of x: 1−x (x is 0 <x <1), a value satisfying z = 2 + x Can be obtained as In this case, d = x.

  In the solid solution lithium-containing transition metal oxide of the present embodiment, in the composition formula (1), a, b and c are 0 <a <0.9, 0 ≦ b <0.9, 0 <c <0. .9, preferably 0 <a <0.87, 0 ≦ b <0.87, and 0 <c <0.87. Further, the solid solution lithium-containing transition metal oxide of the present embodiment has a composition formula (1) as a composition that can ensure superiority from the viewpoint of energy density even if the upper limit value of the state of charge of the power generation element in the activation treatment is determined. In this case, d preferably satisfies the relationship of 0.1 ≦ d ≦ 0.8, more preferably satisfies the relationship of 0.2 ≦ d ≦ 0.7. More preferably, the relationship 2 ≦ d ≦ 0.6 is satisfied. In other words, the lithium composition (represented by 1 + d) in the composition formula (1) described above is preferably 1.1 to 1.8, more preferably 1.2 to 1.7, and still more preferably. 1.2 to 1.6.

  The solid solution positive electrode active material described above may itself be used as a positive electrode active material, or the solid solution positive electrode active material has a solid solution positive electrode active material (preferably a solid solution lithium-containing transition having a composition represented by the chemical formula (1). The metal oxide may be appropriately modified and used to such an extent that it can be confirmed to be derived from the metal oxide). Here, as the modification of the solid solution positive electrode active material, for example, the following three forms (A) to (C) are exemplified.

(A) Al, Zr, Ti, Nb, B, S, Sn, on the particle surface of the solid solution positive electrode active material (preferably a solid solution lithium-containing transition metal oxide having a composition represented by chemical formula (1)) described above. The form in which one or more elements M selected from the group consisting of W, Mo and V are present (in this case, the abundance of the element M (atomic composition molar ratio when a + b + c = 1)) is [ M] is preferably present in an amount satisfying 0.002 ≦ [M] / [a + b + c] ≦ 0.05);
(B) A form in which a coating layer made of a metal oxide or composite oxide selected from the group consisting of Al, Zr and Ti is formed on the particle surface of the solid solution positive electrode active material described above (in this case, after coating) The content of the oxide or composite oxide in the solid solution positive electrode active material is preferably 0.1 to 3.0% by weight in terms of oxide);
(C) A form in which Mn atoms contained in the above-described solid solution positive electrode active material are substituted with at least one selected from the group consisting of Ti, Zr and Nb.

The positive electrode active material layer may further include a positive electrode active material other than the predetermined solid solution positive electrode active material. Examples of such a positive electrode active material preferably include a composite oxide of lithium and a transition metal, a transition metal oxide, a transition metal sulfide, PbO ₂ , AgO, or NiOOH. Even if it mixes seeds or more, it can be used.

Examples of the composite oxide of lithium and transition metal include Li-Mn composite oxides such as LiMnO ₂ , LiMn ₂ O ₄ , and Li ₂ MnO ₃ , Li—Co composite oxides such as LiCoO ₂ , and LiNiO. ₂ , Li—Ni-based composite oxides such as Li (Ni—Co—Mn) O ₂ , Li—Fe-based composite oxides such as LiFeO ₂ , composite phosphate compounds of lithium and transition metals such as LiFePO ₄ , or Preferable examples include a composite sulfuric acid compound of lithium and a transition metal. Preferred examples of the transition metal oxide include V ₂ O ₅ , MnO ₂ , V ₂ MoO ₈ , and MoO ₃ . Preferred examples of the transition metal sulfide include TiS _{2 and} MoS ₂ . These positive electrode active materials can be used alone or in admixture of two or more.

  Depending on the purpose, the positive electrode active material layer may include any of the above-described optional components (surfactant, conductive additive, binder, electrolyte (polymer matrix, ion conductive polymer, electrolytic solution, etc.), lithium salt for increasing ion conductivity, etc. ) Can be included.

  The optional binder used for the positive electrode active material layer is not particularly limited as long as it is hydrophobic, and examples thereof include the following materials.

  Polybutylene terephthalate, polyethylene terephthalate, polyvinylidene fluoride (PVDF) (including compounds in which hydrogen atoms are substituted with other halogen elements), polyethylene, polypropylene, polymethylpentene, polybutene, polyether nitrile, polytetrafluoroethylene, Polyacrylonitrile, polyimide, polyamide, ethylene-vinyl acetate copolymer, polyvinyl chloride, styrene / butadiene rubber (SBR), ethylene / propylene / diene copolymer, styrene / butadiene / styrene block copolymer and hydrogenated products thereof , Thermoplastic polymers such as styrene / isoprene / styrene block copolymer and hydrogenated products thereof, tetrafluoroethylene / hexafluoropropylene copolymer (FEP), tetrafluoroethylene -Perfluoroalkyl vinyl ether copolymer (PFA), ethylene-tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), ethylene-chlorotrifluoroethylene copolymer (ECTFE), polyvinyl fluoride Fluorine resins such as (PVF), vinylidene fluoride-hexafluoropropylene fluorine rubber (VDF-HFP fluorine rubber), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene fluorine rubber (VDF-HFP-TFE fluorine rubber) ), Vinylidene fluoride-pentafluoropropylene-based fluororubber (VDF-PFP-based fluororubber), vinylidene fluoride-pentafluoropropylene-tetrafluoroethylene-based fluororubber (VDF-P) P-TFE fluorine rubber), vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene fluorine rubber (VDF-PFMVE-TFE fluorine rubber), vinylidene fluoride-chlorotrifluoroethylene fluorine rubber (VDF-CTFE) Vinylidene fluoride-based fluororubber such as fluororubber) and epoxy resin. Among these, polyimide, styrene / butadiene rubber, carboxymethyl cellulose, polypropylene, polytetrafluoroethylene, polyacrylonitrile, and polyamide are more preferable.

  These suitable binders are excellent in heat resistance, have a very wide potential window, are stable at the positive electrode potential, and can be used for the active material layer. These binders may be used independently and may use 2 or more types together. In addition, these binders can also use what was melt | dissolved in the organic solvent in which binders are soluble, such as N-methyl-2-pyrrolidone (NMP), in a manufacture process.

  As the surfactant, known cationic surfactants, anionic surfactants, and amphoteric surfactants can be used.

  The said conductive support agent means the additive mix | blended in order to improve the electroconductivity of an active material layer. Examples of the conductive aid include carbon materials such as carbon black such as acetylene black and carbon fibers. When the positive electrode active material layer contains a conductive additive, an electronic network inside the positive electrode active material layer is effectively formed, which can contribute to the improvement of the output characteristics of the battery.

The electrolyte is preferably an electrolyte salt (lithium salt), specifically, Li (C ₂ F ₅ SO ₂ ) ₂ N, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiCF ₃ SO _{3 and the} like. It is done.

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

  In the present invention, other additives such as a conductive additive, electrolyte (polymer matrix, ion conductive polymer, electrolytic solution, etc.), lithium salt for improving ion conductivity, and the like, which can be included in the positive electrode active material layer. The blending ratio is not particularly limited. Those blending ratios can be adjusted by appropriately referring to known knowledge about non-aqueous electrolyte secondary batteries.

[Negative electrode active material layer]
The negative electrode active material layer includes a negative electrode active material that releases ions such as lithium ions during discharging and can store ions such as lithium ions during charging. Here, as described above, the nonaqueous electrolyte secondary battery according to the present invention is a so-called high capacity and high density battery. In order to constitute such a high-capacity battery, the negative electrode active material layer of the present embodiment essentially contains a silicon-containing negative electrode active material. The specific form of such a silicon-containing negative electrode active material is not particularly limited, but particularly preferably preferably contains SiOx or a silicon-containing alloy (these are also collectively referred to as “Si material”). From the viewpoint that a high-capacity negative electrode can be formed, it is more preferable that a silicon-containing alloy is essential. Moreover, in other preferable embodiment, it is more preferable that Si material is included with a carbon material, and it is further more preferable that a silicon containing alloy is included with a carbon material. Hereinafter, the Si material that is a preferable silicon-containing negative electrode active material and the carbon material that is preferably used in combination will be described in more detail.

In this specification, the Si material means SiOx (x represents the number of oxygen satisfying the valence of Si) and a silicon-containing alloy which are a mixture of amorphous SiO ₂ particles and Si particles. Only 1 type of these may be used as Si material, and 2 or more types may be used together. Hereinafter, these Si materials will be described in detail.

(SiOx)
SiOx is a mixture of amorphous SiO ₂ particles and Si particles, and x represents the number of oxygen satisfying the valence of Si. There is no restriction | limiting in particular about the specific value of x, It can set suitably.

  The SiOx may be conductive SiOx particles in which the surface of the SiOx particles is coated with a conductive substance by a mechanical surface fusion process. With such a configuration, Si in the SiOx particles can easily desorb and insert lithium ions, and the reaction in the active material can proceed more smoothly. In this case, the content of the conductive substance in the conductive SiOx particles is preferably 1 to 30% by weight, and more preferably 2 to 20% by weight.

  The average particle diameter of the SiOx may be about the same as the average particle diameter of the negative electrode active material included in the existing negative electrode active material layer 13 and is not particularly limited. From the viewpoint of increasing the output, it is preferably in the range of 1 to 20 μm. However, it is not limited at all to the above range, and it goes without saying that it may be outside the above range as long as the effects of the present embodiment can be effectively expressed. In the present specification, the “average particle diameter” refers to a volume-based median diameter (D50) obtained by a laser diffraction method. The shape of SiOx is not particularly limited, and may be spherical, elliptical, cylindrical, polygonal, scaly, indeterminate, or the like.

  The value of x can be determined by fluorescent X-ray analysis. For example, it can be determined using a fundamental parameter method in fluorescent X-ray analysis using O-Kα rays. For the fluorescent X-ray analysis, for example, RIX3000 manufactured by Rigaku Corporation can be used. As conditions for the fluorescent X-ray analysis, for example, rhodium (Rh) may be used as a target, the tube voltage may be 50 kV, and the tube current may be 50 mA. Since the x value obtained here is calculated from the intensity of the O-Kα ray detected in the measurement region on the substrate, it is an average value of the measurement region.

(Silicon-containing alloy)
The silicon-containing alloy is not particularly limited as long as it is an alloy with another metal containing silicon, and conventionally known knowledge can be appropriately referred to. Here, as preferred embodiments of the silicon-containing alloy, Si _x Ti _y Ge _z A _a , Si _x Ti _y Zn _z A _a , Si _x Ti _y Sn _z A _a , Si _x Sn _y Al _z A _a , and Si _x Sn _y V _z A _a , Si _x Sn _y C _z A _a , Si _x Zn _y V _z A _a , Si _x Zn _y Sn _z A _a , Si _x Zn _y Al _z A _a , Si _x Zn _y C _{zA a, Si x Al y C z} a a and _{Si x Al y Nb z a a} ( wherein, a is unavoidable impurities. further, x, y, z, and a represent the value of weight%, 0 <x <100, 0 <y <100, 0 <z <100, and 0 ≦ a <0.5, and x + y + z + a = 100). By using these silicon-containing alloys as the negative electrode active material, by appropriately selecting the predetermined first additive element and the predetermined second additive element, the phase transition of amorphous-crystal is suppressed during Li alloying. Thus, the cycle life can be improved. This also makes the capacity higher than that of a conventional negative electrode active material, for example, a carbon-based negative electrode active material.

(Carbon material)
The carbon material that can be used in the present invention is not particularly limited, but is graphite (graphite) that is highly crystalline carbon such as natural graphite or artificial graphite; low crystalline carbon such as soft carbon or hard carbon; ketjen black (registered) Trademark), acetylene black, channel black, lamp black, oil furnace black, thermal black, and other carbon blacks; and carbon materials such as fullerene, carbon nanotubes, carbon nanofibers, carbon nanohorns, and carbon fibrils. Of these, graphite is preferably used. There is no restriction | limiting in particular as a shape of a carbon material, A spherical shape, an ellipse shape, a column shape, a polygonal column shape, a scale shape, an indefinite shape etc. may be sufficient.

  The average particle diameter of the carbon material is not particularly limited, but is preferably 5 to 25 μm, and more preferably 5 to 10 μm. Under the present circumstances, about the ratio with the above-mentioned average particle diameter with SiOx, the average particle diameter of a carbon material may be the same as that of SiOx, or may differ, but it is preferable that it differs. In particular, the average particle size of the SiOx is more preferably smaller than the average particle size of the carbon material. When the average particle diameter of the carbon material is relatively larger than the average particle diameter of SiOx, the carbon material particles are uniformly arranged, and the structure is such that SiOx is arranged between the carbon material particles. The SiOx can be uniformly arranged inside.

  The ratio of the average particle diameter of the carbon material to the average particle diameter of SiOx (the average particle diameter of SiOx / the average particle diameter of the carbon material) is preferably 1/250 to less than 1 and preferably 1/100 to More preferably, it is 1/4.

  In the present embodiment, the use of the silicon-containing negative electrode active material as the negative electrode active material, preferably the use of the Si material, and more preferably the use of the silicon-containing alloy further increases cycle durability. In addition, it is possible to show a balanced property with high initial capacity. Moreover, these characteristics can also be improved by using these silicon-containing negative electrode active materials in combination with a carbon material.

In some cases, a negative electrode active material other than the silicon-containing negative electrode active material described above may be used in combination. Examples of the negative electrode active material that can be used in combination include lithium-transition metal composite oxides (for example, Li ₄ Ti ₅ O ₁₂ ), metal materials, lithium alloy negative electrode materials, and the like. Of course, other negative electrode active materials may be used.

  The negative electrode active material layer contains the above-described predetermined negative electrode active material, and if necessary, in order to increase the surfactant, conductive assistant, binder, electrolyte (polymer matrix, ion conductive polymer, electrolyte, etc.), and ionic conductivity. In addition, other additives such as lithium salts of For other additives such as surfactants, conductive assistants, binders, electrolytes (polymer matrix, ion conductive polymers, electrolytes, etc.), lithium salts for enhancing ion conductivity, the above-mentioned column of the positive electrode active material layer This is the same as described in.

[Electrolyte layer]
The electrolyte layer is a layer containing an electrolyte, and usually has a configuration in which a separator is impregnated with an electrolytic solution.

(Separator)
The separator has a function of holding an electrolyte and ensuring lithium ion conductivity between the positive electrode and the negative electrode, and a function as a partition wall between the positive electrode and the negative electrode.

  Examples of the separator include a porous sheet separator or a nonwoven fabric separator made of a polymer or fiber that absorbs and holds the electrolyte.

  Regardless of whether the separator is a microporous separator or a nonwoven fabric separator, it is preferable that the material has affinity with the organic electrolyte and can swell. Such a material is not particularly limited, and examples thereof include materials having cellulose, polyethylene glycol, or PVDF-HFP as a main skeleton. By swelling with the electrolytic solution, vacancies are widened, and clogging by decomposition products can be suppressed without impairing ionic conductivity. Moreover, it is desirable that the average pore diameter of the separator having such a swellable material as the main skeleton is 0.5 μm or more. With such a hole diameter, the holes are not easily blocked by the decomposition product, and the movement of ions is not easily inhibited, so that the cycle characteristics can be improved.

  As another material that can be used for the separator, for example, a microporous (microporous film) can be used as long as the separator is a porous sheet made of polymer or fiber. Specific examples of the porous sheet made of the polymer or fiber include polyolefins such as polyethylene (PE) and polypropylene (PP); a laminate in which a plurality of these are laminated (for example, three layers of PP / PE / PP) And a microporous (microporous membrane) separator made of a hydrocarbon resin such as polyimide, aramid, polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP), glass fiber, and the like.

  The thickness of the microporous (microporous membrane) separator cannot be uniquely defined because it varies depending on the intended use. For example, in applications such as secondary batteries for driving motors such as electric vehicles (EV), hybrid electric vehicles (HEV), and fuel cell vehicles (FCV), it is 4 to 60 μm in a single layer or multiple layers. Is desirable.

  As a material used for the nonwoven fabric separator, cotton, rayon, acetate, nylon, polyester; polyolefin such as PP and PE; polyimide, aramid, etc. can be used, and these may be used alone or in combination.

  The bulk density of the nonwoven fabric is not particularly limited as long as sufficient battery characteristics can be obtained by the impregnated polymer gel electrolyte. Furthermore, the thickness of the nonwoven fabric separator may be the same as that of the electrolyte layer, preferably 5 to 200 μm, particularly preferably 10 to 100 μm.

(Electrolytes)
The electrolyte that infiltrates the separator is not particularly limited, but a liquid electrolyte or a gel polymer electrolyte is used. By using the gel polymer electrolyte, the distance between the electrodes is stabilized, the occurrence of polarization is suppressed, and the durability (cycle characteristics) is improved.

The liquid electrolyte functions as a lithium ion carrier. The liquid electrolyte constituting the electrolytic solution layer has a form in which a lithium salt as a supporting salt is dissolved in an organic solvent as a plasticizer. Examples of the organic solvent to be used include carbonates such as ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate, and the like. You may mix and use. As the lithium _{salt, Li (CF 3 SO 2)} 2 N, Li (C 2 F 5 SO 2) 2 N, LiPF 6, LiBF 4, LiClO 4, LiAsF 6, LiTaF such 6, LiCF ₃ SO ₃ A compound that can be added to the active material layer of the electrode can be similarly employed. The liquid electrolyte may further contain additives other than the components described above. Specific examples of such compounds include, for example, vinylene carbonate, methyl vinylene carbonate, dimethyl vinylene carbonate, phenyl vinylene carbonate, diphenyl vinylene carbonate, ethyl vinylene carbonate, diethyl vinylene carbonate, vinyl ethylene carbonate, 1,2-divinyl ethylene carbonate. 1-methyl-1-vinylethylene carbonate, 1-methyl-2-vinylethylene carbonate, 1-ethyl-1-vinylethylene carbonate, 1-ethyl-2-vinylethylene carbonate, vinylvinylene carbonate, allylethylene carbonate, vinyl Oxymethyl ethylene carbonate, allyloxymethyl ethylene carbonate, acryloxymethyl ethylene carbonate, methacrylate Oxy methylethylene carbonate, ethynyl ethylene carbonate, propargyl carbonate, ethynyloxy methylethylene carbonate, propargyloxy ethylene carbonate, methylene carbonate, etc. 1,1-dimethyl-2-methylene-ethylene carbonate. Among these, vinylene carbonate, methyl vinylene carbonate, and vinyl ethylene carbonate are preferable, and vinylene carbonate and vinyl ethylene carbonate are more preferable. These cyclic carbonates may be used alone or in combination of two or more.

  The gel polymer electrolyte has a configuration in which the liquid electrolyte is injected into a matrix polymer (host polymer) made of an ion conductive polymer. Using a gel polymer electrolyte as the electrolyte is superior in that the fluidity of the electrolyte is lost and it is easy to block the ion conductivity between the layers. Examples of the ion conductive polymer used as the matrix polymer (host polymer) include polyethylene oxide (PEO), polypropylene oxide (PPO), polyethylene glycol (PEG), polyacrylonitrile (PAN), polyvinylidene fluoride-hexafluoropropylene ( PVdF-HEP), poly (methyl methacrylate (PMMA), and copolymers thereof.

  The matrix polymer of gel electrolyte can express excellent mechanical strength by forming a crosslinked structure. In order to form a crosslinked structure, thermal polymerization, ultraviolet polymerization, radiation polymerization, electron beam polymerization, etc. are performed on a polymerizable polymer (for example, PEO or PPO) for forming a polymer electrolyte using an appropriate polymerization initiator. A polymerization treatment may be performed.

[Current collector]
There is no particular limitation on the material constituting the current collector, but a metal is preferably used.

  Specifically, examples of the metal include aluminum, nickel, iron, stainless steel, titanium, copper, and other alloys. In addition to these, a clad material of nickel and aluminum, a clad material of copper and aluminum, or a plating material of a combination of these metals can be preferably used. Moreover, the foil by which aluminum is coat | covered on the metal surface may be sufficient. Of these, aluminum, stainless steel, and copper are preferable from the viewpoints of electronic conductivity and battery operating potential.

  The size of the current collector is determined according to the intended use of the battery. For example, if it is used for a large battery that requires a high energy density, a current collector having a large area is used. There is no particular limitation on the thickness of the current collector. The thickness of the current collector is usually about 1 to 100 μm.

[Positive electrode current collector and negative electrode current collector]
The material which comprises a current collector plate (25, 27) is not restrict | limited in particular, The well-known highly electroconductive material conventionally used as a current collector plate for lithium ion secondary batteries can be used. As a constituent material of the current collector plate, for example, metal materials such as aluminum, copper, titanium, nickel, stainless steel (SUS), and alloys thereof are preferable. From the viewpoint of light weight, corrosion resistance, and high conductivity, aluminum and copper are more preferable, and aluminum is particularly preferable. In addition, the same material may be used for the positive electrode current collecting plate 27 and the negative electrode current collecting plate 25, and different materials may be used.

[Positive lead and negative lead]
Although not shown, the current collector and the current collector plate may be electrically connected via a positive electrode lead or a negative electrode lead. As a constituent material of the positive electrode and the negative electrode lead, materials used in known lithium ion secondary batteries can be similarly employed. In addition, heat-shrinkable heat-shrinkable parts are removed from the exterior so that they do not affect products (for example, automobile parts, especially electronic devices) by touching peripheral devices or wiring and causing leakage. It is preferable to coat with a tube or the like.

[Reference electrode]
Examples of the material constituting the reference electrode 31 include Li metal and Sn—Li alloy. The reference electrode 31 of the present embodiment may be formed by coating or pasting the material constituting the reference electrode 31 on the tip portion of the reference electrode terminal lead 33. In a form in which the reference electrode 31 is coated, there is a form in which tin is plated on the tip of a nickel thin wire that becomes the reference electrode terminal lead 33 and this is reduced in a lithium electrolyte and used as the Li-plated reference electrode 31. Although it can illustrate, it is not restrict | limited to these. The reference electrode 31 only needs to be large enough to measure the potential with high accuracy. The smallest possible reference electrode 31 between the positive electrode active material layer 15 and the negative electrode active material layer 13 so as not to affect the battery reaction. It is preferable to put in.

  The reference electrode terminal lead 33 connects the reference electrode 31 and the reference electrode tab 35. Therefore, it is necessary to be electrically insulated from the positive electrode active material layer 15 and the negative electrode active material layer 13, and a part of the reference electrode terminal lead 33 is electronically separated from the positive electrode active material layer 15 and the negative electrode active material layer 13. It can be placed inside an insulated electrolyte layer (separator 17). Note that the reference electrode terminal lead 33 does not function as the reference electrode 31 but may function as a terminal lead for extracting the potential of the reference electrode 31 to the outside. From the above, examples of the material constituting the reference electrode terminal lead 33 include Ni metal, stainless steel, and Fe metal.

  The reference electrode tab 35 is bonded between the laminate sheets constituting the battery exterior body 29 and is taken out of the stacked battery 10. With such a structure, it is possible to prevent external impact and environmental degradation during use. In particular, when used in a battery system for an electric vehicle, it is preferable to have a certain thickness so that the portion of the reference electrode tab 33 taken out of the battery by an external impact is not broken. As the reference electrode tab 35, the same material and thickness as the electrode current collector plates 27 and 25 can be cut into a predetermined width as necessary. As a material which comprises the reference electrode tab 35, metal materials, such as aluminum, copper, titanium, nickel, stainless steel (SUS), these alloys, are preferable, for example. Further, the reference electrode tab 35 may be taken out of the stacked battery 10 from the side different from the electrode current collector plates 27 and 25 as shown in FIG. 1 or from the same side.

[Battery exterior]
As the battery outer case 29, a known metal can case can be used, and a bag-like case using a laminate film containing aluminum that can cover the power generation element can be used. For example, a laminate film having a three-layer structure in which PP, aluminum, and nylon are laminated in this order can be used as the laminate film, but the laminate film is not limited thereto. A laminate film is desirable from the viewpoint that it is excellent in high output and cooling performance, and can be suitably used for a battery for large equipment for EV and HEV. Moreover, since the group pressure to the electric power generation element applied from the outside can be adjusted easily and it is easy to adjust to the desired electrolyte layer thickness, the exterior body is more preferably an aluminate laminate.

[Cell size]
As shown in FIG. 1 and FIGS. 2A and 2B, the laminated battery 10 has a rectangular flat shape, and a positive current collector 27 and a negative current collector for taking out power from both sides thereof. The plate 25 is pulled out. The power generation element 21 is wrapped by a battery outer body 29 of the stacked battery 10, and the periphery thereof is heat-sealed. The power generation element 21 is in a state in which the positive electrode current collector plate 27 and the negative electrode current collector plate 25 are pulled out to the outside. It is sealed with.

  The battery structure in which the power generation element is covered with an exterior body has recently been demanded for a large-sized battery in automobile applications and the like, and therefore the negative electrode active material layer has a rectangular shape (rectangular shape). The length of the short side is preferably 100 mm or more. Such a large battery can be used for vehicle applications. Here, the length of the short side of the negative electrode active material layer refers to the side having the shortest length among the electrodes. The upper limit of the length of the short side of the battery structure is not particularly limited, but is usually 400 mm or less. Furthermore, the aspect ratio of the rectangular electrode is preferably 1 to 3, and more preferably 1 to 2. The electrode aspect ratio is defined as the aspect ratio of the rectangular positive electrode active material layer. It is preferable to set the aspect ratio in such a range because the gas generated during charging can be discharged uniformly in the surface direction. As a result, cycle durability (discharge capacity maintenance rate) when used for a long period of time can be improved.

Further, as a viewpoint of a high energy density battery different from the viewpoint of the physical size of the electrode, in the nonaqueous electrolyte secondary battery according to the present invention, the battery has a high density due to the relationship between the battery volume and the battery capacity. It is stipulated that Specifically, in the nonaqueous electrolyte secondary battery according to the present invention, the value of the ratio of the battery volume (product of the projected area of the battery including the battery outer package and the thickness of the battery) to the rated capacity is 10 cm ³ / Ah. It is as follows. The rated capacity of the nonaqueous electrolyte secondary battery according to the present invention is 3 Ah or more. This large battery has a large battery capacity per unit volume, in other words, a small battery volume per unit capacity (ratio of battery volume to rated capacity) (10 cm ³ / Ah or less) and a battery capacity (rated capacity). Is defined as having a large value (3 Ah or more).

When the value of the ratio of the battery volume to the rated capacity (the product of the projected area and thickness of the battery including the battery outer casing) exceeds 10 cm ³ / Ah, as described above, the problem to be solved by the present invention is essentially the above. Therefore, it can be said that there is no need to apply the solution. Further, when the rated capacity is less than 3 Ah, the capacity is small, so that the problem to be solved by the present invention does not occur, and it is insufficient for a large-sized battery.

The upper limit of the ratio of the battery volume (product of the projected area and thickness of the battery including the battery outer package) to the rated capacity is preferably 8 cm ³ / Ah or less. On the other hand, the lower limit of the ratio of the battery volume to the rated capacity (the product of the projected area and thickness of the battery including the battery outer package) is not particularly limited, but may be 2 cm ³ / Ah or more, Preferably, it is 3 cm ³ / Ah or more. The rated capacity is preferably 5 Ah or more, more preferably 10 Ah or more, further preferably 15 Ah or more, particularly preferably 20 Ah or more, and particularly preferably 25 Ah or more. Only when the battery has such a high capacity and high density, the problem of a decrease in the cycle durability of the nonaqueous electrolyte secondary battery becomes obvious due to the generation of oxygen gas from the solid solution positive electrode active material. On the other hand, in a battery having a high capacity and a low density as described above, such as a conventional consumer battery, even if oxygen gas is generated from the solid solution positive electrode active material, the cycle of the nonaqueous electrolyte secondary battery associated therewith There is no decrease in durability.

  The rated capacity of the nonaqueous electrolyte secondary battery is obtained as follows.

(Measurement method of rated capacity)
The rated capacity of the test battery is measured by the following procedures 1 to 5 at a temperature of 25 ° C. and a voltage range of 3.0 V to 4.15 V after injecting the electrolytic solution and then standing for about 10 hours. The

  Procedure 1: After reaching 4.15 V with a constant current charge of 0.1 C, pause for 5 minutes.

  Procedure 2: After Procedure 1, charge for 1.5 hours by constant voltage charging and rest for 5 minutes.

  Procedure 3: After reaching 3.0 V by constant current discharge of 0.1 C, discharge at constant voltage discharge for 2 hours, and then rest for 10 seconds.

  Procedure 4: After reaching 4.1V by constant current charging at 0.1 C, charge for 2.5 hours by constant voltage charging, and then rest for 10 seconds.

  Procedure 5: After reaching 3.0 V by 0.1 C constant current discharge, discharge by constant voltage discharge for 2 hours, and then stop for 10 seconds.

  Rated capacity: The discharge capacity (CCCV discharge capacity) in the discharge from the constant current discharge to the constant voltage discharge in the procedure 5 is defined as the rated capacity.

  The battery volume is determined by the product of the projected area and thickness of the battery including the battery outer package. Among these, regarding the projected area of the battery including the battery outer casing, the projected area of the six batteries of the front, back, right side, left side, plane, and bottom can be obtained. Usually, this is the projected area of the battery on the flat or bottom surface when the battery is placed in the most stable state on the flat plate. Moreover, the thickness of the battery including the battery outer package is measured at the time of full charge. In addition, the thickness of the battery including the battery outer package is measured at eight or more locations in consideration of variations depending on the measurement locations, and is averaged. For example, in the examples to be described later, the thickness of the battery including the battery outer casing is measured at a point where the two diagonal lines of the power generation element are divided into 5 parts (9 points in total) or in the vicinity thereof, did.

<< Method for Manufacturing Nonaqueous Electrolyte Secondary Battery >>
One embodiment of the present invention relates to a method for manufacturing a nonaqueous electrolyte secondary battery. Here, in the method for manufacturing a non-aqueous electrolyte secondary battery according to this embodiment, when manufacturing a high-capacity and high-density non-aqueous electrolyte secondary battery using the solid solution positive electrode active material and the silicon-containing negative electrode active material. The power generation element containing the solid solution positive electrode active material to be activated is subjected to an activation process (charging process). This activation treatment (charging treatment) causes reorganization of the solid solution cathode active material (change from a layered structure (Li ₂ MnO ₃ ) to a spinel structure (LiMn ₂ O ₄ )), thereby causing a solid solution cathode High capacity of the active material can be achieved. Thus, the solid solution positive electrode active material whose capacity has been increased through the activation treatment is referred to as an “activated solid solution positive electrode active material” in the present specification. In addition, about the manufacturing process before performing an activation process, the conventionally well-known knowledge regarding manufacture of a nonaqueous electrolyte secondary battery can be referred suitably.

  In the method for manufacturing a non-aqueous electrolyte secondary battery according to this embodiment, in order to perform the activation treatment of the solid solution positive electrode active material, after the cell is configured, the power generation element containing the solid solution positive electrode active material to be activated is charged. What is necessary is just to give a process (or charging / discharging process). At this time, as for specific conditions necessary to cause reorganization of the crystal structure (such as the lower limit value of the charging state of the power generation element necessary for the reorganization of the crystal structure), conventionally known knowledge is appropriately used. Reference can be made. As an example, the charging process (or charging / discharging process) is performed until the maximum potential of the positive electrode in the power generation element charged by the charging process is 4.3 V or more with respect to the lithium metal counter electrode. It is done. The “solid solution cathode active material to be activated” is not particularly limited as long as it is a solid solution cathode active material that has room for reorganization of the crystal structure by the activation treatment, and is an active material that has not been activated at all. It may be an active material that has already been subjected to some activation treatment.

  Here, the present inventors have studied a non-aqueous electrolyte secondary battery using the solid solution positive electrode active material as described above for the positive electrode, and have found a new problem. That is, when such a solid solution positive electrode active material is applied to a battery having a high capacity and a high density (small battery volume per battery capacity), cycle durability is reduced due to generation of oxygen gas from the positive electrode active material. It turns out that there is a case to do.

  In order to solve such problems, the present inventors have conducted intensive studies. As a result, the upper limit value of the state of charge in the charging process (or charge / discharge process) in the activation process is defined, and the charging process (activation process) is performed on the power generation element so as not to exceed the upper limit value. We found that the problem could be solved. In the prior art, there has been no recognition that oxygen gas is generated in the high charge state region. For this reason, from the viewpoint of increasing the capacity of the solid solution positive electrode active material as much as possible, it has been common to perform the activation treatment beyond the charged state of the upper limit value at which oxygen gas is generated. The above-mentioned solution means obtained by the present inventors is contrary to such common sense in the prior art. That is, in the method for manufacturing a nonaqueous electrolyte secondary battery according to the present embodiment, in the activation process, the value of the charging state of the power generation element is set in advance from the relationship between the charging state of the power generation element and the amount of gas generated. The charging process (or charging / discharging process) in the activation process is controlled so as not to exceed the upper limit value of the state. By performing such control, oxidation of the negative electrode due to generation of oxygen gas from the solid solution positive electrode active material is prevented. As a result, even if the charge / discharge capacity of the treatment is somewhat sacrificed, the capacity decrease and the A / C ratio imbalance caused by the oxidation of the negative electrode are prevented, and finally the decrease in the cycle durability of the battery is suppressed. It can be done. In particular, in a preferred embodiment, when the value of the charging state of the power generation element reaches the predetermined upper limit value in the activation process, the charging process in the activation process is terminated. By adopting such a configuration, it is possible to perform an activation process so that the generation of oxygen gas can be suppressed to a minimum and a capacity as high as possible can be expressed.

  FIG. 3A is a block diagram showing a configuration including a control device for performing an activation process, among other methods of manufacturing a nonaqueous electrolyte secondary battery according to an embodiment of the present invention. FIG. 3B shows the state of charge (positive electrode capacity), the positive electrode potential (●), and the amount of oxygen gas generated (◯) as a basis for setting the upper limit value of the state of charge stored in the control device (particularly the storage unit) of FIG. FIG.

  As shown in FIG. 3A, the control device for a nonaqueous electrolyte secondary battery according to the present embodiment includes a solid solution positive electrode included in the above-described stacked battery 10 (including a power generation element containing a solid solution positive electrode active material to be activated). When the activation process is performed on the active material, the charging device 200 is controlled. And this control apparatus is provided with the control part 100, the current sensor 110, and the voltage sensor 120 as a structure for controlling the charging device 200. FIG.

  The control unit 100 according to the present embodiment controls a charging process (or a charging / discharging process) in an activation process of the power generating element 21 constituting the stacked battery 10 by controlling the charging device 200. The control unit 100 includes a control unit such as a CPU or MPU, and a storage unit such as a ROM or a RAM. The control unit 100 is configured to charge / discharge current flowing through the stacked battery 10 detected by the current sensor 110 (= charge / discharge current flowing through the power generation element 21) or terminal voltage of the stacked battery 10 detected by the voltage sensor 120 (= Based on the terminal voltage of the power generation element 21, the charging and discharging of the power generation element 21 are controlled and the charge state of the power generation element 21, specifically, the SOC value (State of Charge) is calculated. In the present embodiment, the control unit 100 uses a current sensor to measure the current flowing through the stacked battery 10 (current flowing through the power generating element 21) in order to execute the manufacturing method of the stacked battery 10 including the activation process described below. Detect at 110. In addition, the control unit 100 detects the terminal voltage of the stacked battery 10 (= terminal voltage of the power generation element 21) with the voltage sensor 120.

  A storage unit (not shown) included in the control unit 100 according to the present embodiment stores in advance an upper limit value of a charging state when charging the power generation element 21. The control unit 100 executes an activation process (charging process or charging / discharging process) so as not to exceed the upper limit value.

Here, the upper limit value of the state of charge is set as follows. That is, a specific example will be described in detail in the section of the embodiment, but when the present inventors have verified, the state of charge of the stacked battery 10 (= the state of charge of the power generation element 21 (positive electrode capacity)) and the generation of oxygen gas The relationship with the quantity is as shown in the graph indicated by a circle in FIG. 3B. That confirms the oxygen gas generation amount of the lithium ion secondary battery has been charged to the various volumes, the amount of oxygen gas is rapidly increased by the positive electrode capacity C ₁ in the boundary. On the other hand, the relationship between the state of charge of the stacked battery 10 (= the state of charge of the power generation element 21 (positive electrode capacity)) and the positive electrode potential (potential with respect to the lithium metal counter electrode) is as shown by the graph indicated by the mark ● in FIG. . Therefore, in the graph of charge state (positive electrode capacity) -oxygen gas generation amount, the positive electrode potential E _MAX corresponding to the charge state (positive electrode capacity C ₁ ) in which the generation amount of oxygen gas rapidly increases is set as the upper limit value of the charge state. If the positive electrode potential E does not exceed the upper limit value E _MAX in the charging process or the charging / discharging process for the activation process, generation of oxygen gas from the solid solution positive electrode active material constituting the positive electrode of the power generation element 21 is prevented. can do. As a result, it is possible to effectively prevent a decrease in cycle durability due to the generation of oxygen gas. The upper limit value of the power generation element (positive electrode capacity) for carrying out the control of the present invention is various, such as the type and blending amount of the solid solution cathode active material used, other materials and blending amounts included in each active material layer It may vary depending on the factors. However, by performing a preliminary study as shown in FIG. 3B, it is possible to recursively determine the upper limit value of the power generation element (positive electrode capacity) for carrying out the control of the present invention. This upper limit value (positive electrode potential E _MAX corresponding to a charged state (positive electrode capacity C ₁ ) in which the amount of oxygen gas generation increases rapidly) is, for example, the differential in the positive electrode capacity-gas generation amount graph shown in FIG. 3B. The positive electrode capacity at the point where the coefficient (the limit value of ΔC → 0 for ΔA / ΔC when the capacity is C and the gas generation amount is A) is 200 or more is C1, and the corresponding positive electrode potential is E _MAX Can be determined.

On the other hand, according to what the present inventors have estimated, it is considered that the upper limit value of the power generation element (positive electrode capacity) for performing the control of the present invention can be calculated a priori. That is, in the crystal structure of the lithium-containing transition metal oxide constituting the solid solution positive electrode active material, lithium ions are preferentially released from the 3b site and the 4h site at the initial stage of charging during the activation treatment. Then, if the charging process is continued thereafter, lithium ions are also released from the 2c site, resulting in a decrease in orbital interaction between Li (2b) -O-Li (2c), and oxygen atoms becoming molecular oxygen ( The inventors presume that O ₂ ) is released outside the crystal structure. Accordingly, in the crystal structure of the lithium-containing transition metal oxide constituting the solid solution positive electrode active material, lithium existing at 3b site and 4h site among all sites (3b, 4h, 2b, 2c) where lithium ions can exist. It is considered that the generation of oxygen gas can be prevented by performing the charging process during the activation process so that only ions are released. Here, for example, in the lithium-containing transition metal oxide having the composition represented by the chemical formula (1) described above, the composition ratio of lithium is represented by (1 + d). In the present specification, of the (1 + d) moles of lithium, the amount of lithium released by the activation process (charging process) (that is, contributing to charging) is referred to as “lithium utilization amount”. To do. If the amount of lithium used is equal to or less than the amount of lithium present at the 3b site and the 4h site, the generation of oxygen gas is considered to be prevented. Therefore, based on this, the power generation element (positive electrode capacity) for carrying out the control of the present invention so that the amount of lithium used in the activation process (charging process) is equal to or less than the amount of lithium existing in the 3b site and the 4h site. ) Can be calculated.

Here, for the calculation of the general state of charge SOC, the voltage sensor 120 uses the open circuit voltage of the stacked battery 10 (= the power generation element 21) (the voltage across the terminals of the stacked battery 10 in the no-load state). Can do. However, the generation of oxygen gas from the solid solution positive electrode active material constituting the positive electrode of the stacked battery 10 (that is, the power generation element 21) is due to the structural change of the active material due to the release of lithium ions from the solid solution positive electrode active material in the charged state. Arise. Therefore, in the control for suppressing the generation of oxygen gas as in the present embodiment, it is preferable to control so as not to exceed the upper limit value E _MAX of the positive electrode potential using the reference electrode 31 that measures the positive electrode potential E described above. . Here, the current sensor 110 and the voltage sensor 120 illustrated in FIG. 3A and the reference electrode 31 illustrated in FIG. 2B and the like function as a charge state detection sensor.

  The case where the control of the present invention is applied to the activation process of the solid solution positive electrode active material in the method for manufacturing the nonaqueous electrolyte secondary battery according to one embodiment of the present invention has been described above. However, the control of the present invention is also applicable when the nonaqueous electrolyte secondary battery is used (during operation). That is, the present invention is also applied to a charging process (or a charging / discharging process) when using a non-aqueous electrolyte secondary battery manufactured through the activation process described above (the positive electrode contains an activated solid solution positive electrode active material). The control of the invention is applicable. Below, the control at the time of use (during driving | operation) of the nonaqueous electrolyte secondary battery which concerns on this invention mounted in the electric vehicle is demonstrated.

  FIG. 4 is a block diagram showing an electric vehicle equipped with a nonaqueous electrolyte secondary battery according to an embodiment of the present invention.

  As illustrated in FIG. 4, the electric vehicle 300 according to the present embodiment includes the above-described stacked battery 10, the above-described control device (including the control unit 100, the current sensor 110, and the voltage sensor 120), the inverter 310, And a motor 320. The control unit 100, the current sensor 110, and the voltage sensor 120 have the same configurations as the control unit 100, the current sensor 110, and the voltage sensor 120 illustrated in FIG. Note that the electric vehicle 300 shown in FIG. 4 includes the stacked battery 10 and the control device described above, and thus can be said to be a nonaqueous electrolyte secondary battery system.

  The inverter 310 converts the DC power generated by the stacked battery 10 into AC power and applies the AC power to the motor 320, and drives the motor 320 to run the electric vehicle 300. The inverter 310 converts regenerative power, which is AC power generated by the motor 320 during braking of the electric vehicle 300, into DC power and applies it to the stacked battery 10 to charge the stacked battery 10.

Thus, when the stacked battery 10 is charged by the regenerative power generated by the motor 320, the control of the present invention can be applied. That is, in the present embodiment, the control unit 100 controls the charging process (or charging / discharging process) using regenerative power when the stacked battery 10 is used (when the electric vehicle 300 is running) in the same manner as described above. Specifically, in the graph of charge state (positive electrode capacity) -oxygen gas generation amount shown in FIG. 3B, the positive electrode potential E _MAX corresponding to the charge state (positive electrode capacity C ₁ ) in which the generation amount of oxygen gas rapidly increases is charged. If the positive electrode potential E is set as the upper limit value of the state so that the positive electrode potential E does not exceed the upper limit value E _MAX in the charging process (or charge / discharge process) by regenerative power, the solid solution positive electrode active material constituting the positive electrode of the power generation element 21 Generation of oxygen gas can be prevented. As a result, it is possible to effectively prevent a decrease in cycle durability due to the generation of oxygen gas. Of course, also in the control as in the present embodiment, it is preferable to control so as not to exceed the upper limit value E _MAX of the positive electrode potential using the reference electrode 31 that measures the positive electrode potential E, as described above. With this configuration, it is possible to use as much regenerative power as possible for charging the power generating element 21 while suppressing generation of oxygen gas to a minimum.

  In the above description, the application example of the control of the present invention when the stacked battery 10 is used has been described by taking the control of the charging process by the regenerative power when the electric vehicle is running as an example. However, the control of the present invention can be applied to normal charging processing of the stacked battery 10 using a charging device, for example.

  The effects of the present invention will be described using the following examples and comparative examples. However, the technical scope of the present invention is not limited only to the following examples.

[Example 1]
(Preparation of positive electrode sample)
As a positive electrode active material, a lithium-containing transition metal oxide, which is a solid solution containing Li ₂ MnO ₃ and LiNi _0.375 Co _0.375 Mn _0.25 O _{2 in} a molar ratio of 1: 9, is a conventionally known composite. Prepared using the carbonate method. The composition formula of this lithium-containing transition metal oxide is:
Li [Ni _0.3375 Co _0.3375 Mn _0.325 [Li] _0.1 ] O _2.1
Met. When this is applied to the chemical formula (1), z = 2.1 (the number of oxygen satisfying the valence), a = b = 0.3375, c = 0.325, d = 0.1, and a + b + c = 1. .

  90 parts by mass of the solid solution positive electrode active material (lithium-containing transition metal oxide) prepared in this way, 1 part by mass of flake graphite and 4 parts by mass of acetylene black as a conductive assistant, and polyvinylidene fluoride (PVDF) as a binder 5 parts by mass and 74 parts by mass of N-methyl-2-pyrrolidone (NMP) as a viscosity adjusting solvent were prepared. And 5 mass parts of PVDF was melt | dissolved in 50 mass parts of NMP, and the binder solution was prepared. Next, 1 part by mass of flake graphite and 4 parts by mass of acetylene black (total 5 parts by mass) and 90 parts by mass of a solid solution positive electrode active material (lithium-containing transition metal oxide) are added to 60 parts by mass of the binder solution. The mixture was kneaded with a planetary mixer (manufactured by Primics, Hibismix 2P-03 type), and then 24 parts by weight of NMP was added to the kneaded product to obtain a positive electrode active material slurry (solid content concentration 60 mass%).

Thereafter, the positive electrode active material slurry was applied to one side of a 20 μm-thick (sheet-like) aluminum current collector foil as a current collector using a bar coater (the mass of the positive electrode active material layer after drying was approximately 3.5 mg / cm ² ). Applied). Subsequently, the current collector foil coated with the positive electrode active material slurry was dried on a hot plate (120 ° C. to 130 ° C., drying time 10 minutes) to form a positive electrode active material layer. By this drying treatment, the amount of NMP remaining in the positive electrode active material layer was set to 0.02% by mass or less. In this way, a sheet-like positive electrode was obtained.

Next, the sheet-like positive electrode is subjected to compression molding using a roller press and cut, and the mass of the positive electrode active material layer on one side is about 3.5 mg / cm ² , the thickness is about 50 μm, and the density is 2.70 g / cm ^2. Adjusted to cm ³ .

Thereafter, the sheet-like positive electrode was dried in a vacuum drying furnace. After installing the sheet-like positive electrode inside the drying furnace, the pressure in the room was reduced (100 mmHg (1.33 × 10 ⁴ Pa)) at room temperature (25 ° C.) to remove the air in the drying furnace. Subsequently, while flowing nitrogen gas (100 cm ³ / min), the temperature was raised to 120 ° C. at 10 ° C./min, the pressure was reduced again at 120 ° C., and nitrogen was maintained in the furnace for 12 hours. The temperature was lowered. In this way, a positive electrode sample was completed.

(Production of gas generation measurement cell)
A microporous membrane made of polypropylene (PP) prepared as a separator by cutting out the positive electrode sample prepared above and placing it in a piezoelectric AE sensor (manufactured by Vallen system, VS900-M) so that the positive electrode active material layer is exposed. (Thickness 25 μm) and lithium metal foil (thickness 200 μm) as a negative electrode were laminated in this order. Next, the electrolyte solution (ethylene carbonate (EC) and diethyl carbonate (DEC) was mixed at a ratio of EC: DEC = 1: 2 (volume ratio) in an organic solvent, and the concentration of LiPF ₆ as a supporting salt was 1 M (mol). / L)) was injected using a syringe and sealed to complete a gas generation measurement cell.

(Activation treatment for gas generation measurement cell)
The gas generation measurement cell prepared above is placed in a thermostatic chamber (25 ° C.) to adjust the temperature, and in that state, a charge / discharge tester: HJ0501SM8A (made by Hokuto Denko Co., Ltd.) is used for gas generation measurement. The cell was charged once. In this charging process, charging is performed up to 4.8 V by a constant current method with a charging current of 0.1 C, and then charging is performed until the charging capacity of the positive electrode is 320 mAh / g by a constant voltage method of 4.8 V. It was. Here, the current density of 1 C refers to a current value at which the discharge ends when a cell having a nominal capacity value a [Ah] is discharged at a constant current for 1 hour. In this case, 1 C = a [A].

  In this charging process, the terminal voltage (open circuit voltage) between the positive and negative electrodes of the gas generation measurement cell was monitored over time using a voltage sensor. Further, the gas generation event inside the gas generation measurement cell was also monitored over time by operating the piezoelectric AE sensor. From these results, the charge state (positive electrode capacity) of the gas generation measurement cell used in this example is plotted on the horizontal axis, and the positive electrode potential (●) and oxygen gas generation amount (oxygen gas generation event) with respect to metallic lithium ( (Circle) was plotted on the vertical axis | shaft, and the graph shown to FIG. 3B was obtained. As shown in FIG. 3B, it can be seen that the oxygen gas generation event (oxygen gas generation amount) rapidly increases with the positive electrode capacity at 294 mAh / g as a boundary. It can also be seen that a positive electrode capacity of 294 mAh / g corresponds to 4.68 V as a positive electrode potential with respect to lithium metal. Therefore, these positive electrode capacities (or positive electrode potentials) are set as upper limit values, and the activation treatment (charging treatment) of the solid solution positive electrode active material is performed so as not to exceed the upper limit value. It was shown that generation can be sufficiently suppressed. In addition, even during normal use of a battery including the positive electrode used here, the positive electrode capacity (or positive electrode potential) obtained above is set as the upper limit value, and the power generation element of the battery is set so as not to exceed this value. It was also shown that the generation of oxygen gas during the charging process can be sufficiently suppressed by performing the charging process.

(Preparation of negative electrode sample)
As a silicon-containing negative electrode active material, a silicon-containing alloy having a composition of Si ₆₅ Sn ₅ Ti ₃₀ (composition ratio is mass ratio) was produced by the following method.

  Specifically, using a stirring ball mill device C-01M manufactured by ZOZ, Germany, 1920 g of zirconia pulverized balls (φ5 mm) and 1 g of carbon (SGL) were put into a SUS pulverized pot, and then at 1000 rpm for 10 minutes. A pre-grinding process was performed. Thereafter, 100 g of each alloy raw material powder (high-purity metal Si ingot (5N), high-purity Ti wire (3N), high-purity Sn plate (3N)) is added and alloyed at 1500 rpm for 5 hours (alloying) Treatment), and then pulverized at 400 rpm for 1 hour to obtain a silicon-containing alloy (negative electrode active material). In the stirring ball mill apparatus used in this example, the revolution radius rs = 0.070 [m], the rotation radius rpl = 0 [m], and the rotation speed rpm = 1500 [times / minute]. The force is calculated as Gnl = 176.0 [G]. Moreover, the average particle diameter (D50) of the obtained silicon-containing alloy (negative electrode active material) powder was 5.4 μm.

80 parts by mass of the silicon-containing negative electrode active material (Si ₆₅ Sn ₅ Ti ₃₀ powder) prepared in this way, 5 parts by mass of acetylene black as a conductive additive, and 15 parts by mass of polyamideimide as a binder were mixed. N-methyl-2-pyrrolidone was dispersed in an appropriate amount to obtain a negative electrode active material slurry. Next, the obtained negative electrode active material slurry was uniformly applied to one side of a negative electrode current collector made of copper foil (thickness: 15 μm) so that the thickness of the negative electrode active material layer was 30 μm, and was subjected to vacuum for 24 hours. A negative electrode sample was obtained by drying.

(Production of test laminate cell)
The positive electrode sample obtained above was cut out so that the active material layer area was 2.5 cm long and 2.0 cm wide, and the two current collectors were faced to each other so that the uncoated surface (aluminum current collector) The current collector portion was spot welded together with the surface not coated with the foil slurry. This formed the positive electrode which has a positive electrode active material layer on both surfaces of the two-ply current collector foil with which the outer peripheral part was integrated by spot welding. Thereafter, an aluminum positive electrode tab (positive electrode current collector plate) was further welded to the current collector portion to form a positive electrode. That is, the positive electrode has a configuration in which a positive electrode active material layer is formed on both surfaces of the current collector foil.

  On the other hand, the negative electrode sample obtained above was cut out to have an active material layer area of 2.7 cm in length and 2.2 cm in width, and then a negative electrode tab of electrolytic copper was further welded to the current collector portion to form a negative electrode. Formed. That is, the negative electrode sample has a configuration in which a negative electrode active material layer is formed on one side of a current collector.

A laminated power generation element consisting of five layers with a porous polypropylene separator (length 3.0 cm × width 2.5 cm, thickness 25 μm, porosity 55%) between the negative electrode and the positive electrode welded with these tabs Was made. The configuration of the laminated power generation element was a configuration of negative electrode (single side) / separator / positive electrode (both sides) / separator / negative electrode (single side). Next, both sides of the power generation element were sandwiched with an aluminum laminate film exterior material (length 3.5 cm × width 3.5 cm), and the above power generation element was accommodated by thermocompression sealing at three sides. After injecting 0.8 cm ³ of the same electrolyte solution into the power generation element (in the case of the above five-layer configuration, a two-cell configuration and an injection amount of 0.4 cm ³ per cell), the remaining one side was Temporary sealing was performed by thermocompression bonding to produce a test laminate cell. In order to sufficiently permeate the electrolytic solution into the electrode pores, the electrolyte was held at 25 ° C. for 24 hours while being pressurized at a surface pressure of 0.5 MPa.

(Charging process for power generation elements (activation process))
In this example, the charge state of the power generation element corresponding to a positive electrode capacity of 4.94 mAh / g (positive electrode potential for lithium metal: 4.68 V) is set as an upper limit value by preliminary examination using the above-described gas generation measurement cell. It has been found that the generation of oxygen gas from the power generation element (particularly, the solid solution positive electrode active material) can be suppressed by performing the activation treatment so as not to exceed the upper limit. Therefore, in this example, the activation treatment was performed on the test cell manufactured as described above until the positive electrode capacity was 294 mAh / g (the positive electrode potential with respect to lithium metal was 4.68 V).

  Specifically, first, at 25 ° C., the battery was charged at 0.05 C for 4 hours (SOC approximately 20%) by a constant current charging method. Next, after charging to 4.45 V at a 0.1 C rate at 25 ° C., the charging was stopped, and the state (SOC about 70%) was maintained for about 2 days (48 hours) (aging process). Next, one side temporarily sealed by thermocompression bonding was opened, gas was removed at 10 ± 3 hPa for 5 minutes, and then thermocompression bonding was performed again to perform temporary sealing. Further, pressurization with a roller (surface pressure 0.5 ± 0.1 MPa) was performed, and the electrode and the separator were sufficiently adhered.

  Thereafter, as an activation process, charging was performed up to 4.68 V by a constant current method with a charging current of 0.1 C so as not to exceed the upper limit value of the charging state of the power generating element described above. And after making it rest for 10 minutes, the activation process was performed by discharging to 2.0V by the constant current system of the charging current of 0.1C. The theoretical amount of lithium used during charging in the activation process in this example was calculated to be 0.941.

  Further, from the volume change of the test laminate cell before and after the activation treatment, the amount of oxygen gas generated before and after the activation treatment was measured by the Archimedes method. The results are shown in Table 1 below.

(Cycle durability evaluation)
Cycle durability evaluation was performed about the test cell which performed the activation process above. Specifically, under a room temperature condition, after charging until the battery voltage reaches 4.5 V with a charging current of 0.1 C, a constant current constant voltage charging method of holding for about 1 to 1.5 hours, Then, a constant current method was used in which the battery was discharged at a discharge current of 0.1 C until the battery voltage reached 2.0V. This cycle was repeated 50 times, and the ratio of the discharge capacity at the 50th cycle to the discharge capacity at the 1st cycle was evaluated as “capacity maintenance ratio (%)”. The results are shown in Table 1 below:
Capacity retention rate (%) = 50th cycle discharge capacity / first cycle discharge capacity × 100
It should be noted that the value of the charge capacity and discharge capacity in the first cycle, the value of the rated capacity of the test laminate cell, and the battery volume with respect to the rated capacity of the test laminate cell (the projected area of the battery including the battery case and the thickness of the battery) Table 1 below also shows the value of the ratio of the product to the product.

[Example 2]
As a positive electrode active material, a lithium-containing transition metal oxide, which is a solid solution containing Li ₂ MnO ₃ and LiNi _0.375 Co _0.375 Mn _0.25 O _{2 in} a molar ratio of 3: 7, is a conventionally known composite. Prepared using the carbonate method. The composition formula of this lithium-containing transition metal oxide is:
Li [Ni _0.2625 Co _0.2625 Mn _0.475 [Li] _0.3 ] O _2.3
Met. When this is applied to the chemical formula (1), z = 2.3 (the number of oxygen satisfying the valence), a = b = 0.2625, c = 0.475, d = 0.3, and a + b + c = 1. .

  A cell for measuring gas generation was prepared by the same method as in Example 1 except that the positive electrode active material thus obtained was used, and the amount of oxygen gas generated from the solid solution positive electrode active material was drastically increased. The upper limit value of the increasing charging state of the positive electrode was examined.

  Next, a test laminate cell was prepared in the same manner as in Example 1 except that the positive electrode active material obtained in this example was used, and the activation treatment and measurement of the amount of oxygen gas generated at that time were performed. In addition, cycle durability was evaluated. The results are shown in Table 1 below. The theoretical amount of lithium used during charging in the activation process in this example was calculated to be 1.057.

[Example 3]
As a positive electrode active material, a lithium-containing transition metal oxide, which is a solid solution containing Li ₂ MnO ₃ and LiNi _0.375 Co _0.375 Mn _0.25 O _{2 in} a molar ratio of 5: 5, is a conventionally known composite. Prepared using the carbonate method. The composition formula of this lithium-containing transition metal oxide is:
Li [Ni _0.1875 Co _0.1875 Mn _0.625 [Li] _0.5 ] O _2.5
Met. When this is applied to the chemical formula (1), z = 2.5 (the number of oxygen satisfying the valence), a = b = 0.1875, c = 0.625, d = 0.5, and a + b + c = 1. .

  A cell for measuring gas generation was prepared by the same method as in Example 1 except that the positive electrode active material thus obtained was used, and the amount of oxygen gas generated from the solid solution positive electrode active material was drastically increased. The upper limit value of the increasing charging state of the positive electrode was examined.

  Next, a test laminate cell was prepared in the same manner as in Example 1 except that the positive electrode active material obtained in this example was used, and the activation treatment and measurement of the amount of oxygen gas generated at that time were performed. In addition, cycle durability was evaluated. The results are shown in Table 1 below. In addition, the theoretical lithium usage amount at the time of charging in the activation process in this example was calculated as 1.088.

[Example 4]
As a positive electrode active material, a lithium-containing transition metal oxide, which is a solid solution containing Li ₂ MnO ₃ and LiNi _0.375 Co _0.375 Mn _0.25 O _{2 in} a molar ratio of 7: 3, is a conventionally known composite. Prepared using the carbonate method. The composition formula of this lithium-containing transition metal oxide is:
Li [Ni _0.1125 Co _0.1125 Mn _0.775 [Li] _0.7 ] O _2.7
Met. When this is applied to the chemical formula (1), z = 2.7 (the number of oxygen satisfying the valence), a = b = 0.1125, c = 0.775, d = 0.7, and a + b + c = 1. .

  A cell for measuring gas generation was prepared by the same method as in Example 1 except that the positive electrode active material thus obtained was used, and the amount of oxygen gas generated from the solid solution positive electrode active material was drastically increased. The upper limit value of the increasing charging state of the positive electrode was examined.

  Next, a test laminate cell was prepared in the same manner as in Example 1 except that the positive electrode active material obtained in this example was used, and the activation treatment and measurement of the amount of oxygen gas generated at that time were performed. In addition, cycle durability was evaluated. The results are shown in Table 1 below. The theoretical amount of lithium used during charging in the activation process in this example was calculated to be 1.057.

[Comparative Example 1]
During the charging process in the activation process, charging was performed until the charging state exceeded the upper limit value of the charging state of the power generation element described above. Specifically, the activation process (charging process) was performed so that the theoretical lithium usage during charging in the activation process was 1.093. Other than that, a test laminate cell was prepared in the same manner as in Example 1 described above, and an activation treatment, measurement of the amount of oxygen gas generated at that time, and cycle durability evaluation were performed. The results are shown in Table 1 below.

[Comparative Example 2]
During the charging process in the activation process, charging was performed until the charging state exceeded the upper limit value of the charging state of the power generation element described above. Specifically, the activation process (charging process) was performed so that the theoretical lithium usage during charging in the activation process was 1.154. Other than that, a test laminate cell was prepared in the same manner as in Example 2 described above, and the activation treatment, measurement of the amount of oxygen gas generated at that time, and cycle durability evaluation were performed. The results are shown in Table 1 below.

[Comparative Example 3]
During the charging process in the activation process, charging was performed until the charging state exceeded the upper limit value of the charging state of the power generation element described above. Specifically, the activation process (charging process) was performed so that the theoretical lithium usage during charging in the activation process was 1.176. Other than that, a test laminate cell was prepared in the same manner as in Example 3 described above, and the activation treatment, measurement of the amount of oxygen gas generated at that time, and cycle durability evaluation were performed. The results are shown in Table 1 below.

[Comparative Example 4]
During the charging process in the activation process, charging was performed until the charging state exceeded the upper limit value of the charging state of the power generation element described above. Specifically, the activation process (charging process) was performed such that the theoretical lithium usage during charging in the activation process was 1.150. Other than that, a test laminate cell was prepared in the same manner as in Example 4 described above, and activation treatment, measurement of the amount of oxygen gas generated at that time, and cycle durability evaluation were performed. The results are shown in Table 1 below.

  As can be seen from the results shown in Table 1, in Examples 1 to 4, the control of the present invention was applied to the activation treatment (charging treatment) of the solid solution positive electrode active material during the production of the lithium ion secondary battery. It can be seen that the generation of oxygen gas during the activation treatment was suppressed, and that the cycle durability of the battery was also greatly improved. On the other hand, in Comparative Examples 1 to 4 in which the control of the present invention was not applied, a large amount of oxygen gas was generated during the activation process, and the cycle durability of the battery was greatly reduced thereby. Recognize.

Here, the graph which plotted the discharge capacity in each cycle of a cycle durability test about Example 3 and Comparative Example 3 which were mentioned above is shown to FIG. 5A. As shown in FIG. 5A, as in Example 3 and Comparative Example 3 described above, a high-capacity and high-density battery (battery volume relative to the rated capacity of the battery (the projected area of the battery including the battery outer casing, the thickness of the battery, Battery) having a ratio value of 10 cm ³ / Ah or less and a rated capacity of 3 Ah or more) when the control of the present invention is performed (Example 3) and when not performed ( It can be seen that there is a large difference in cycle durability with Comparative Example 3).

On the other hand, a high-capacity and high-density battery as described above (the ratio of the battery volume (the product of the projected area of the battery including the battery casing and the thickness of the battery) to the rated capacity of the battery is 10 cm ³ / Ah or less. And a discharge capacity in each cycle of the cycle durability test when a comparative experiment (cycle durability test) similar to FIG. 5A is performed using a battery that is not a battery having a rated capacity of 3 Ah or more. A graph in which is plotted is shown in FIG. 5B. As shown in FIG. 5B, in a battery that does not satisfy the condition of “high capacity and high density”, there is almost no difference in cycle durability between when the control of the present invention is performed and when it is not performed. I can't understand.

  From the above, the non-aqueous electrolyte secondary battery manufacturing method, control method, control device, and non-aqueous electrolyte secondary battery system according to the present invention is a high-capacity and high-density battery including a solid solution positive electrode active material in the positive electrode. It can be seen that this can solve a peculiar problem (reduction in cycle durability due to generation of oxygen gas in a high potential state).

10 stacked battery,
11 negative electrode current collector,
12 positive electrode current collector,
13 negative electrode active material layer,
15 positive electrode active material layer,
17 electrolyte layer,
19 cell layer,
21 power generation elements,
25 negative electrode current collector plate (negative electrode tab),
27 positive current collector (positive electrode tab),
29 Battery exterior body,
31 reference electrode,
33 Reference electrode terminal lead,
35 reference electrode tab,
100 control unit,
110 current sensor,
120 voltage sensor,
200 charger,
300 electric car,
310 inverter,
320 Motor.

Claims (8)

A power generation element comprising: a positive electrode containing an activated solid solution positive electrode active material; a negative electrode containing a silicon-containing negative electrode active material; and an electrolyte layer containing a non-aqueous electrolyte interposed between the positive electrode and the negative electrode. A method for controlling a non-aqueous electrolyte secondary battery comprising:
The ratio of the battery volume (the product of the projected area of the battery including the battery outer casing and the thickness of the battery) to the rated capacity of the non-aqueous electrolyte secondary battery is 10 cm ³ / Ah or less, and the rated capacity Is 3Ah or more,
A non-aqueous electrolyte that controls charging / discharging of the power generation element so that a value of a charge state of the power generation element does not exceed an upper limit value of a charge state set in advance from a relationship between a charge state of the power generation element and a gas generation amount Secondary battery control method.   The method for controlling a non-aqueous electrolyte secondary battery according to claim 1, wherein charging of the power generation element is terminated when a value of a state of charge of the power generation element reaches the upper limit value during charging of the power generation element. A control device for a non-aqueous electrolyte secondary battery used in the method for controlling a non-aqueous electrolyte secondary battery according to claim 1 or 2,
A storage unit that stores an upper limit value of a preset charging state from a relationship between a charging state of the power generation element and a gas generation amount;
A charge state detection sensor for detecting a charge state of the power generation element;
A control unit that controls charging / discharging of the power generation element so that the value of the detected state of charge does not exceed the upper limit;
A control device for a non-aqueous electrolyte secondary battery. A positive electrode containing an activated solid solution positive electrode active material, a negative electrode containing a silicon-containing negative electrode active material, and an electrolyte layer containing a non-aqueous electrolyte interposed between the positive electrode and the negative electrode. A non-aqueous electrolyte secondary having a ratio of the battery volume (product of the projected area of the battery including the battery outer package and the thickness of the battery) to 10 cm ³ / Ah or less and the rated capacity being 3 Ah or more Battery,
A control device for a non-aqueous electrolyte secondary battery according to claim 3,
A non-aqueous electrolyte secondary battery system. The solid solution positive electrode active material has the following chemical formula (1):
Li [Ni _a Co _b Mn _c [Li] _d ] O _z (1)
In the formula, Li represents lithium, Ni represents nickel, Co represents cobalt, Mn represents manganese, O represents oxygen, z represents the number of oxygens satisfying the valence, and a, b, c and d are 0 <a < 0.94, 0 ≦ b <0.94, 0 <c <0.94, 0.05 ≦ d ≦ 0.8, a + b + c = 1 is satisfied,
The nonaqueous electrolyte secondary battery system of Claim 4 which has a solid solution lithium containing transition metal oxide which has a composition represented by these as a basic structure.   The non-aqueous electrolyte secondary battery system according to claim 4, wherein the silicon-containing negative electrode active material includes a silicon-containing alloy. A power generation element comprising: a positive electrode containing an activated solid solution positive electrode active material; a negative electrode containing a silicon-containing negative electrode active material; and an electrolyte layer containing a non-aqueous electrolyte interposed between the positive electrode and the negative electrode. A method for producing a non-aqueous electrolyte secondary battery comprising:
The ratio of the battery volume (the product of the projected area of the battery including the battery outer casing and the thickness of the battery) to the rated capacity of the non-aqueous electrolyte secondary battery is 10 cm ³ / Ah or less, and the rated capacity Is 3Ah or more,
The solid solution positive electrode is obtained by changing a layered structure of Li ₂ MnO ₃ to a spinel structure of LiMn ₂ O ₄ in the solid solution positive electrode active material by charging the power generation element containing the solid solution positive electrode active material to be activated. Including activating the active material,
In the activation process, the charging process is controlled so that a value of a charging state of the power generation element does not exceed a preset upper limit value of a charging state from a relationship between a charging state of the power generation element and a gas generation amount. A method for producing a non-aqueous electrolyte secondary battery, further comprising:   The method for manufacturing a nonaqueous electrolyte secondary battery according to claim 7, wherein, in the activation process, when the value of the state of charge of the power generation element reaches the upper limit value, the charge process in the activation process is terminated. .