WO2017183653A1 - Material for positive electrodes - Google Patents

Abstract

Provided is a novel material for positive electrodes, which is capable of serving as a positive electrode active material. A material for positive electrodes, which is characterized by containing Li_aM_bD_cO_d (wherein 4 < a < 7, (b + c) = 1, 0.9 ≤ b ≤ 1, 0 ≤ c ≤ 0.1 and 3 < d < 5 are satisfied; M represents at least one transition metal; and D represents a dopant element) and Li_eO_f (wherein 0 < e and 0 < f are satisfied).

Description

Positive electrode material

The present invention relates to a positive electrode material.

It is known that various materials are used for the positive electrode active material of the secondary battery, and a material that can be a high-capacity positive electrode active material is being sought.

For example, layered rock salt structures such as LiCoO ₂ and LiNiO ₂ are widely known as high-capacity positive electrode active materials. Patent Document 1 describes that the active material capacity of LiNi _0.80 Co _0.15 Al _0.05 O ₂ in the range of 4.2 V to 2.5 V was 188 mAh / g.

Patent Document 2 _discloses that a positive electrode active material obtained by fluorine treatment of Li (Li _0.2 Ni _0.137 Co _0.125 Mn _0.538 ) O ₂ is about 250 mAh / g in the range of 4.8V to 2.5V. It was described that the initial capacity of was shown.

In Patent Document 3, Li _1.03 Ni _0.75 Co _0.20 Al _0.05 O ₂ showed an initial capacity of about 210 to 220 mAh / g in the range of 4.35 V to 2.5 V. Is described.

Patent Document 4 describes a solid solution obtained by mechanochemical reaction between Li ₂ O and Co ₃ O ₄ , CoO, LiCoO ₂ , MnO ₂ , Fe ₂ O ₃ , NiO or MoO _3. That the solid solution can function as a positive electrode active material, and that some of these solid solutions showed an initial capacity of about 280 mAh / g. On the other hand, Patent Document 4 describes that charging and discharging were impossible with Li ₂ O alone.

JP 2013-114848 A JP 2014-75177 A JP 2014-22127 A JP2015-107890A

Investigators in the technical field of secondary batteries have eagerly promoted research, and as a result, various materials that can have a high capacity have been provided. However, a new material that can be used as a positive electrode active material is demanded by the industry.

The present invention has been made in view of such circumstances, and an object thereof is to provide a new material that can be a positive electrode active material.

The present inventor has directed a material that can be a higher-capacity positive electrode active material. Here, if the material contains a lot of lithium per unit mass, the capacity is theoretically high. However, as described in Patent Document 4, it is impossible to charge and discharge with Li ₂ O alone containing a large amount of lithium per unit mass. Therefore, the present inventor examined whether or not there is a substance capable of activating Li ₂ O that can function lithium of Li ₂ O as a charge carrier. Then, was subjected to a mixture of Li ₂ O and _Li 6 CoO ₄ as a cathode material was found that lithium Li ₂ O in the mixture functions as a charge carrier. The present invention has been completed based on such knowledge of the present inventors.

Positive electrode material of the present _{invention, Li a M b D c O} d ( although, 4 <a <7, b + c = 1,0.9 ≦ b ≦ 1,0 ≦ c ≦ 0.1,3 <d <5 M is at least one transition metal, D is a doping element), and Li _e O _f (where 0 <e, 0 <f is satisfied). Features.

The positive electrode material of the present invention functions as a positive electrode active material and exhibits a suitable capacity.

3 is a powder X-ray diffraction chart of positive electrode materials of Example 2-1, Example 3-1, and Example 5-1. 4 is a powder X-ray diffraction chart of positive electrode materials of Example 1-2, Example 2-2, and Example 3-2. It is a powder X-ray diffraction chart of the Li 2 _O powder used in Examples and Comparative Examples. _{3 is} a powder X-ray diffraction chart of Li ₆ CoO ₄ powder used in Examples 1-1 to 5-1 and Comparative Example 1. FIG. 6 is a graph showing results of charge / discharge capacities of lithium ion secondary batteries of Example 1-1 to Example 5-1 and Comparative Example 1 in Evaluation Example 2. 7 is a graph showing the results of charge / discharge capacities of lithium ion secondary batteries of Example 1-2 to Example 5-2 in Evaluation Example 2. 6 is an initial discharge capacity chart of Example 1-1 and Comparative Example 1 in Evaluation Example 2. It is a charging / discharging curve of Example 4-1 in Evaluation Example 3. It is a charging / discharging curve of Example 4-2 in Evaluation Example 3. It is a charging / discharging curve of Example 4-3 in Evaluation Example 3. It is a charging / discharging curve of Example 8-1 in Evaluation Example 4.

The best mode for carrying out the present invention will be described below. Unless otherwise specified, the numerical range “x to y” described in this specification includes the lower limit x and the upper limit y. The numerical range can be configured by arbitrarily combining these upper limit value and lower limit value and the numerical values listed in the examples. Furthermore, numerical values arbitrarily selected from the numerical value range can be used as upper and lower numerical values.

Positive electrode material of the present _{invention, Li a M b D c O} d ( although, 4 <a <7, b + c = 1,0.9 ≦ b ≦ 1,0 ≦ c ≦ 0.1,3 <d <5 M is at least one transition metal, D is a doping element), and Li _e O _f (where 0 <e, 0 <f is satisfied). Features.

In Li _a M _b D _c O _d , a preferably satisfies 4.5 ≦ a ≦ 6.5, more preferably 5 ≦ a ≦ 6. M is preferably at least one of Co, Fe and Mn. d preferably satisfies 3.5 ≦ d ≦ 4.5, and more preferably satisfies 3.8 ≦ d ≦ 4.2.

Li _{a Mb} D _c O _d is preferably one exhibiting an inverted fluorite-type crystal structure. D is a doping element, Cu, Zn, Ca, Mg, Zr, S, Si, Li, Na, K, Al, Ti, P, Ga, Ge, V, Mo, Nb, W, La, Hf, It is at least one element selected from Rf and F. Due to the presence and D, changes to the bonding state of oxygen atoms in the reverse fluorite crystal _{occurs, Li a M b D c O} d is likely to improve the efficiency of activating the Li _e O _f.

Li _a M _b D _c O Examples of _{d, Li 6 CoO 4, Li} 5 FeO 4, Li 6 MnO 4, Li 6 (Co x, Mn 1-x) O 4, Li 6-x (Co 1- _{x, Fe x) O 4,} Li 6-x (Mn 1-x, the _{Fe x) O 4, Li 5} Fe 0.95 Al 0.05 O 4, Li 5 Fe 0.98 Al 0.02 O 4 It can be illustrated.

Li _{a Mb} D _c O _d is preferably in a powder state. Examples of suitable average particle diameter of Li _{a Mb} D _c O _d include 0.1 to 50 μm, 0.5 to 30 μm, and 1 to 20 μm. In addition, the average particle diameter in this specification means D50 when measured with a general laser diffraction type particle size distribution measuring apparatus.

In li _e O _f, the case of e = 2, f is preferably satisfied 0 <f ≦ 3, more preferably satisfies 0 <f ≦ 2, more preferably satisfies 1 ≦ f ≦ 2. Wherein the Li _e O _f may include, for example, by a number of lithium released from Li 2 _O, those oxygen and some lithium is present. From the relationship between the valence electrons of Li and the valence electrons of oxygen, it is reasonable that e and f satisfy e ≦ 2 × f. However, since the unshared electron pair of oxygen has a coordination ability to lithium ions, For example, it can be assumed that an unshared electron pair of oxygen in a chemical structure of Li—O—Li is coordinated with another lithium ion to become Li ₃ O. Then, it is considered that e and f may satisfy 2 × f <e <3 × f.

Specific examples of the _{Li e O f, Li 2 O} , may be exemplified _Li 2 _{O 2} and LiO _2. Li _e O _f is crystalline if they exhibit a structure of a 4-coordinate or 6-coordinate Li to oxygen atom, it can be utilized regardless of the amorphous, preferably those exhibiting reverse fluorite type crystal structure, especially Moreover, the thing of a powder state is preferable. Suitable average particle diameter of the _{Li e O f, 0.1 ~ 50μm} , 0.5 ~ 30μm, can be exemplified 1 ~ 20 [mu] m.

Here, the action mechanism at the time of charging of the positive electrode material of the present invention will be considered taking a mixture of Li ₆ CoO ₄ and Li ₂ O as an example.

First, basic research as a trigger for the present invention will be described. The present inventor has investigated the redox reaction during charging / discharging of Li ₆ CoO ₄ , which is known to exhibit a reversible charging / discharging reaction, by transmission electron microscope-electron energy loss spectroscopy (TEM-EELS) and radiation. Detailed analysis using an X-ray absorption fine structure (XAFS) analysis method using optical X-rays was performed. As a result, significant energy changes were observed at the Co-L2,3 absorption edge in the TEM-EELS analysis and the Co-K absorption edge in the XAFS analysis, which show the change in the valence of cobalt during charging and discharging of Li ₆ CoO _4. It was only during the first charge reaction and was not observed after the first discharge reaction. After the initial discharge reaction, it was confirmed that the Co-K absorption edge of XAFS showed a slightly reversible shape change. On the other hand, the shape change of the OK absorption edge in the TEM-EELS analysis showing the energy change of 2p orbit of oxygen was reversibly observed during the charge / discharge reaction after the first discharge. That is, it is considered that the reversible charge / discharge reaction of Li ₆ CoO ₄ is expressed mainly by the movement of oxygen electrons, not Co. Furthermore, Co is considered to have a role of assisting the movement of oxygen electrons during the charge / discharge reaction.

Given the results of the basic research, the positive electrode material of the present invention, in the initial charging process, _firstly, with the lithium ions Li 6 CoO ₄ is _disengaged, Co in Li 6 CoO ₄ is activatable oxygen Presumed to change to the state. Next, one electron is released from the 2p orbit of oxygen activated by Co. Here, the activation of oxygen by Co is not only oxygen in the _Li 6 CoO _4, since the span via its interface to the Li ₂ O in contact with Li 6 CoO _4, the extraction of lithium ions in the Li ₂ O Estimated to prompt. When a part of the mechanism of action is shown in the reaction formula, it is estimated as follows.

Li ₆ Co ²⁺ O ₄ → Li ₅ Co ³⁺ O ₄ + Li ⁺ + e ⁻
Li ₅ Co ³⁺ O ₄ + Li ₂ O ⇔ [Li ₄ Co ³⁺ O ₄ ^· (LiO ^· )] + 2Li ⁺ + 2e ⁻

When a part of the reversible mechanism of action is shown by a microscopic reaction equation, it is estimated as follows.
^{Co 3+ -O-Li ⇔ Co 3+} -O · + Li + + e -
O—Co ³⁺ + Li ₂ O ⇔ [O—Co—O ^· —Li] + Li ⁺ + e ⁻

_Therefore, it can be said that Li _a M _b D c _{O d} while still allowing the positive electrode active material, a trigger compound for the functioning of the _Li e _{O f} as the positive electrode active material. Further, the positive electrode material of the present _invention, the interface between the Li _a M _b D c _{O d} and _Li e _{O f} is the time of withdrawal and storage of the lithium ion, is believed to function as a passage for lithium ions.

In terms of _capacity, the amount of Li _a M _b D c _{O d} and _Li e _{O f,} based on the total mass of Li _a M _b D c _{O d} and _{Li e O f, Li a M} b D c O _d is preferably present within a range of 20 to 99% by mass, more preferably within a range of 40 to 97% by mass, and even more preferably within a range of 50 to 96% by mass, It is particularly preferred that it is present in the range of ~ 95% by weight. The _molar ratio of Li _a M _b D c _{O d} and _Li e _{O f} is 20: 80-90: 10 are preferred, 30: 70-85: 15, more preferably, 35: 65-80: 20 and more A ratio of 50:50 to 70:30 is particularly preferable.

Production of a positive electrode material of the present invention _may be mixed with Li _a M _b D c _{O d} powder and _Li e _{O f} powder. Mixing using a mortar may be used, and mixing may be performed using a known mixer. As the mixer, a stirring mixer such as a V-type mixer, a W-type mixer, a ribbon-type mixer, or a drum mixer may be used, or a ball mill, a jet mill, a hammer mill, a pin mill, a disk mill, a turbo mill, or the like. A pulverizing mixer may be used.

The mixing speed and mixing time may be appropriately determined as appropriate. _However, Li _a M _b D c _{O d} and _Li e _{O f} it is not appropriate to mix excessive to disappear, using an analytical device such as X-ray powder _{diffractometer,} Li _a M _{b D} c O while confirming the presence of _d and Li _e O _f, preferably determined mixing rate and mixing time. Since the capacity of the positive electrode material of the present invention can vary depending on the mixing speed and mixing time, the mixing speed and mixing time should be appropriately determined in order to produce the positive electrode material of the present invention showing an appropriate capacity. Is preferred. Examples of the mixing speed include a ball mill rotational speed of 200 to 1500 rpm, 300 to 1000 rpm, and 400 to 800 rpm. Further, for example, the mixing time when a ball mill is used can be exemplified by 5 to 30 hours and 10 to 25 hours. Furthermore, as mixing conditions, after mixing at the first mixing speed V ₁ , mixing may be performed at the second mixing speed V ₂ . Here, from the viewpoint of increasing the capacity, it is preferable to satisfy V ₁ <V ₂ .

Further, the positive electrode material of the present invention may contain a lithium salt selected from Li ₂ CO ₃ , LiPF ₆ , Li ₃ PO ₄ , and LiBF ₄ . From the results of Evaluation Example 4 to be described later, these lithium salts, the effect of Li _a M _b D _c O _d as a trigger compound for causing a Li _e O _f as the positive electrode active material, suitably assist and increase It is suggested that there is an effect, and it is also suggested that the lithium salt itself can act as an active material.

The blending amount of the lithium salt in the positive electrode material of the present invention is preferably 1 to 50% by mass, more preferably 3 to 30% by mass, and even more preferably 5 to 20% by mass. _Also, the _{Li a M b D c O d} , the relationship between the molar ratio of the total amount of _Li e _{O f} and lithium salts, 20:80 to 90:10 is preferred, 30: 70: to 85: 15 Gayori Preferably, 35:65 to 80:20 is more preferable, and 50:50 to 70:30 is particularly preferable. Lithium salt with respect to the total amount of _Li e _{O f} and lithium salts, preferably 20 to 80 mass%, more preferably 30 to 70 mass%, or preferably 10 to 70 mol%, more preferably from 10 to It should be blended at 60 mol%.

Production of a positive electrode material of the present invention containing a lithium salt _may be mixed with Li _a M _b D c _{O d} powder and _Li e _{O f} powder and a lithium salt. About the detail of the mixing method, each condition in manufacture of the positive electrode material of this invention mentioned above is used.

Hereinafter, the positive electrode including the positive electrode material of the present invention is referred to as the positive electrode of the present invention.

The positive electrode of the present invention includes a positive electrode active material layer containing the positive electrode material of the present invention and a current collector. The positive electrode active material layer is formed on the current collector.

The positive electrode active material layer may contain a known positive electrode active material in addition to the positive electrode material of the present invention. In addition, a conductive additive, a binder, or the like may be added to the positive electrode active material layer. The blending amount of the positive electrode material of the present invention in the positive electrode active material layer is preferably in the range of 30 to 99% by mass, more preferably in the range of 40 to 95% by mass, and still more preferably in the range of 45 to 90% by mass. .

Conductive aid is added to increase the conductivity of the electrode. Therefore, the conductive auxiliary agent may be added arbitrarily when the electrode conductivity is insufficient, and may not be added when the electrode conductivity is sufficiently excellent. The conductive auxiliary agent may be a chemically inert electronic conductor, and examples thereof include carbon black, graphite, vapor grown carbon fiber (Vapor Grown Carbon Fiber), and various metal particles. . Examples of carbon black include acetylene black, ketjen black (registered trademark), furnace black, and channel black. These conductive assistants can be added to the positive electrode active material layer alone or in combination of two or more.

The shape of the conductive auxiliary agent is not particularly limited, but it is preferable that the average particle diameter is small in view of its role. The average particle diameter of the conductive auxiliary agent is preferably 5 μm or less, more preferably in the range of 0.01 to 3 μm, further preferably in the range of 0.05 to 2 μm, and in the range of 0.1 to 1 μm. Particularly preferred.

The blending amount of the conductive additive in the positive electrode active material layer is preferably in the range of 0.5 to 50% by mass, more preferably in the range of 1 to 45% by mass, and particularly in the range of 2 to 40% by mass. preferable.

The binder serves to bind the positive electrode material and the conductive additive of the present invention to the surface of the current collector. Examples of the binder include fluorine-containing resins such as polyvinylidene fluoride, polytetrafluoroethylene, and fluororubber, thermoplastic resins such as polypropylene and polyethylene, imide resins such as polyimide and polyamideimide, and alkoxysilyl group-containing resins. be able to. Moreover, you may employ | adopt the polymer which has a hydrophilic group as a binder. Examples of the hydrophilic group of the polymer having a hydrophilic group include a carboxyl group, a sulfo group, a silanol group, an amino group, a hydroxyl group, and a phosphate group. Specific examples of the polymer having a hydrophilic group include polyacrylic acid, carboxymethylcellulose, polymethacrylic acid, and poly (p-styrenesulfonic acid).

The amount of the binder in the positive electrode active material layer is preferably in the range of 0.5 to 20% by mass, more preferably in the range of 1 to 15% by mass, and particularly in the range of 2 to 10% by mass. preferable. If the blending amount of the binder is too small, the moldability of the positive electrode active material layer may be lowered. Moreover, when there are too many compounding quantities of a binder, since the quantity of the positive electrode active material in a positive electrode active material layer reduces, it is unpreferable.

In the positive electrode active material layer, additives other than the conductive additive and the binder may be appropriately mixed in appropriate amounts.

The current collector refers to a chemically inert electronic conductor that keeps a current flowing through an electrode during discharge or charging of a lithium ion secondary battery. As the current collector, at least one selected from silver, copper, gold, aluminum, magnesium, tungsten, cobalt, zinc, nickel, iron, platinum, tin, indium, titanium, ruthenium, tantalum, chromium, molybdenum, and stainless steel Examples of such a metal material can be given. The current collector may be covered with a known protective layer.

The current collector can take the form of a mesh, foil, sheet, film, wire, rod or the like. Therefore, as the current collector, for example, a mesh-like metal, or a metal foil such as a copper foil, a nickel foil, an aluminum foil, or a stainless steel foil can be suitably used. When the current collector is in the form of a mesh, foil, sheet, or film, the thickness is preferably in the range of 10 μm to 100 μm.

In order to form the positive electrode active material layer on the surface of the current collector, a conventionally known method such as a roll coating method, a die coating method, a dip coating method, a doctor blade method, a spray coating method, or a curtain coating method is used. The positive electrode material of the present invention may be applied to the surface of the electric body. Specifically, a slurry containing the positive electrode material of the present invention, a solvent, and, if necessary, a binder and a conductive additive is prepared, and the slurry is applied to the surface of the current collector and then dried. Examples of the solvent include N-methyl-2-pyrrolidone (hereinafter sometimes abbreviated as NMP), methanol, and methyl isobutyl ketone. In order to increase the electrode density, the dried product may be compressed. In addition, the positive electrode material of the present invention, a binder, and, if necessary, a positive electrode mixture containing a conductive additive are prepared, and the positive electrode mixture is pressure-bonded to the current collector, so that the surface of the current collector is A positive electrode active material layer may be formed.

In the positive electrode production method of the present invention, the Li _a M _b D _c O _d and the Li _e O process to _f were mixed mixture, the production method comprising the steps of placing the mixture on the current collector of the positive electrode It can be grasped that there is.

Regarding the conductive additive, the Li _a M _b D _c O _d and subsequently the Li _e O _f mixing step of the mixture, and mixed by adding a conductive additive to the mixture, the material for the positive electrode It is preferable to provide the process of obtaining a containing mixture. Due to this manufacturing method, the capacity of the positive electrode provided with the positive electrode material of the present invention may increase. In the step of obtaining the positive electrode material-containing mixture, it is preferable to employ a mixer having the same performance as the mixer used in the production of the positive electrode material of the present invention. Examples of such mixers include stirring mixers such as V-type mixers, W-type mixers, ribbon-type mixers and drum mixers, and pulverizing and mixing such as ball mills, jet mills, hammer mills, pin mills, disk mills, and turbo mills. The machine can be exemplified. What is necessary is just to determine suitably about the suitable mixing conditions in the process of obtaining the material containing mixture for positive electrodes. Examples of the mixing speed include, for example, 100 to 1000 rpm, 150 to 600 rpm, and 200 to 400 rpm as the rotation speed of the ball mill. Further, for example, the mixing time when using a ball mill may be 0.1 to 5 hours, 0.3 to 3 hours.

The positive electrode material-containing mixture thus obtained, and a slurry containing a binder and / or a solvent as necessary are prepared, and the slurry is applied to the surface of the current collector and then dried to collect the current. A positive electrode active material layer can be formed on the surface of the body. Alternatively, a positive electrode active material layer may be formed on the surface of the current collector by preparing a positive electrode mixture containing a positive electrode material-containing mixture and a binder and then pressing the positive electrode mixture to the current collector. . *

Hereinafter, the lithium ion secondary battery provided with the positive electrode of the present invention is referred to as the lithium ion secondary battery of the present invention.

The lithium ion secondary battery of the present invention may be an open air battery in which oxygen is part of the positive electrode active material, but from the viewpoint of the chemical stability of Li _{a Mb} D _c O _d A lithium ion secondary battery that is not a battery, that is, a sealed lithium ion secondary battery in which oxygen is not taken in and out is preferable. If it is a sealed lithium ion secondary battery, mixing of moisture and the like can be suppressed.

In the case of an air battery, it is known that oxygen functions as a positive electrode active material, and as a result, Li ₂ O ₂ and Li ₂ O are formed. In the above-mentioned Patent Document 4, it is assumed that Li ₂ O alone could not be charged / discharged in the case of a sealed lithium ion secondary battery.

The lithium ion secondary battery of the present invention includes the positive electrode, the negative electrode, the separator and the electrolytic solution of the present invention as battery components.

The negative electrode has a current collector and a negative electrode active material layer bound to the surface of the current collector. The negative electrode active material layer includes a negative electrode active material and, if necessary, a binder and / or a conductive aid. As the current collector, the binder, and the conductive additive, those described for the positive electrode may be adopted. Further, styrene-butadiene rubber may be employed as a binder for the negative electrode active material layer.

Examples of the negative electrode active material include a carbon-based material capable of inserting and extracting lithium, an element that can be alloyed with lithium, a compound having an element that can be alloyed with lithium, a polymer material, and the like.

Examples of the carbon-based material include non-graphitizable carbon, natural graphite, artificial graphite, coke, graphite, glassy carbon, organic polymer compound fired body, carbon fiber, activated carbon, or carbon black. Here, the organic polymer compound fired body refers to a material obtained by firing and carbonizing a polymer material such as phenols and furans at an appropriate temperature.

Specifically, elements that can be alloyed with lithium include Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, Ti, Ag, Zn, Cd, Al, Ga, In, Si. , Ge, Sn, Pb, Sb, Bi can be exemplified, and Si or Sn is particularly preferable.

Specific examples of the compound having an element that can be alloyed with lithium include ZnLiAl, AlSb, SiB ₄ , SiB ₆ , Mg ₂ Si, Mg ₂ Sn, Ni ₂ Si, TiSi ₂ , MoSi ₂ , CoSi ₂ , NiSi ₂ , _{CaSi 2, CrSi 2, Cu 5} Si, FeSi 2, MnSi 2, NbSi 2, TaSi 2, VSi 2, WSi 2, ZnSi 2, SiC, Si 3 N 4, Si 2 N 2 O, SiO v (0 <v ≦ 2), SnO _w (0 <w ≦ 2), SnSiO ₃ , LiSiO or LiSnO can be exemplified, and SiO _x (0.3 ≦ x ≦ 1.6) is particularly preferable. In addition, examples of the compound having an element capable of alloying with lithium include tin compounds such as tin alloys (Cu—Sn alloy, Co—Sn alloy, etc.).

Specific examples of the polymer material include polyacetylene and polypyrrole.

Also, a method of synthesizing a layered silicon compound mainly composed of polysilane obtained by reacting CaSi ₂ and acid to remove Ca as a negative electrode active material, and releasing the hydrogen by heating the layered silicon compound at 300 ° C. or higher. The silicon material manufactured by can be mentioned. The silicon material has a structure in which a plurality of plate-like silicon bodies are laminated in the thickness direction. This structure can be confirmed by observation with a scanning electron microscope or the like. In consideration of using the silicon material as an active material of a lithium ion secondary battery, the plate-like silicon body has a thickness in the range of 10 nm to 100 nm for efficient insertion and removal reaction of lithium ions. Are preferable, and those in the range of 20 nm to 50 nm are more preferable. The length of the plate-like silicon body in the major axis direction is preferably in the range of 0.1 μm to 50 μm. Further, the plate-like silicon body preferably has a (length in the long axis direction) / (thickness) range of 2 to 1000.

The silicon material preferably contains amorphous silicon and / or silicon crystallites. The size of the silicon crystallite is preferably in the range of 0.5 nm to 300 nm, more preferably in the range of 1 nm to 100 nm, still more preferably in the range of 1 nm to 50 nm, and particularly preferably in the range of 1 nm to 10 nm. The size of the silicon crystallite is calculated from the Scherrer equation using X-ray diffraction measurement (XRD measurement) on the silicon material and using the half-value width of the diffraction peak on the Si (111) surface of the obtained XRD chart. Is done.

As a preferable particle size distribution of the silicon material when measured with a general laser diffraction particle size distribution analyzer, it can be exemplified that the average particle diameter (D50) is in the range of 1 to 30 μm, more preferably the average particle It can be exemplified that the diameter (D50) is in the range of 1 to 10 μm.

If necessary, the negative electrode active material may be carbon coated.

The separator separates the positive electrode and the negative electrode and allows lithium ions to pass while preventing a short circuit due to contact between the two electrodes. Examples of the separator include a porous film using one or more synthetic resins such as polytetrafluoroethylene, polypropylene, and polyethylene, or a ceramic porous film.

The electrolytic solution contains a nonaqueous solvent and an electrolyte dissolved in the nonaqueous solvent.

As the non-aqueous solvent, cyclic carbonates, cyclic esters, chain carbonates, chain esters, ethers and the like can be used. Examples of the cyclic carbonate include ethylene carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate, and examples of the cyclic ester include gamma butyrolactone, 2-methyl-gamma butyrolactone, acetyl-gamma butyrolactone, and gamma valerolactone. Examples of the chain carbonate include dimethyl carbonate, diethyl carbonate, dibutyl carbonate, dipropyl carbonate, and ethyl methyl carbonate. Examples of the chain ester include propionic acid alkyl ester, malonic acid dialkyl ester, and acetic acid alkyl ester. Examples of ethers include tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, 1,2-diethoxyethane, and 1,2-dibutoxyethane. Further, as the solvent, a solvent in which a part or all of hydrogen constituting the chemical structure of the above specific solvent is substituted with fluorine may be employed. These nonaqueous solvents may be used alone or in combination with the electrolyte.

Examples of the electrolyte include lithium salts such as LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , and LiN (CF ₃ SO ₂ ) ₂ .

As an electrolytic solution, 0.5 mol / l to 1.7 mol of a lithium salt such as LiClO ₄ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO _{3 in} a nonaqueous solvent such as ethylene carbonate, dimethyl carbonate, propylene carbonate, and diethyl carbonate. A solution dissolved at a concentration of about 1 / l can be exemplified.

As a method for producing the lithium ion secondary battery of the present invention, it is only necessary to have a step of arranging the positive electrode of the present invention. Hereinafter, the specific manufacturing method of the lithium ion secondary battery of this invention is illustrated. A separator is sandwiched between the positive electrode and the negative electrode to form an electrode body. The electrode body may be either a stacked type in which the positive electrode, the separator and the negative electrode are stacked, or a wound type in which the positive electrode, the separator and the negative electrode are sandwiched. After connecting the positive electrode current collector and the negative electrode current collector to the positive electrode terminal and the negative electrode terminal connected to the outside using a current collecting lead or the like, an electrolytic solution is added to the electrode body, and the lithium of the present invention It is preferable to use an ion secondary battery.

The lithium ion secondary battery of the present invention can be mounted on a vehicle. Since a lithium ion secondary battery maintains a large charge / discharge capacity and has excellent cycle performance, a vehicle equipped with the lithium ion secondary battery is a high-performance vehicle.

The vehicle may be a vehicle that uses electric energy from a battery as a whole or a part of a power source. For example, an electric vehicle, a hybrid vehicle, a plug-in hybrid vehicle, a hybrid railway vehicle, an electric forklift, an electric wheelchair, and an electric assist. Bicycles and electric motorcycles are examples.

As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment. The present invention can be implemented in various forms without departing from the gist of the present invention, with modifications and improvements that can be made by those skilled in the art.

Hereinafter, various specific examples will be shown to describe the present invention more specifically. The present invention is not limited to these specific examples.

Example 1-1
64.7 parts by mass of Li ₆ CoO ₄ powder and 35.3 parts by mass of Li ₂ O powder were mixed using a ball mill at 500 rpm for 14.5 hours to produce a positive electrode material of Example 1-1. .

5 parts by weight of the positive electrode material of Example 1-1, 4 parts by weight of acetylene black as a conductive auxiliary agent, and 1 part by weight of polytetrafluoroethylene as a binder were mixed in an agate mortar, processed into a clay shape, and mixed with the positive electrode Got. Mesh-like aluminum was prepared as a current collector, and a positive electrode mixture was pressure-bonded thereto to obtain a positive electrode of Example 1-1. All operations were performed in a glove box with a water concentration of 1 ppm or less, which was purged with argon gas.

Lithium foil was prepared and used as a negative electrode. As a separator, a glass filter (Hoechst Celanese) and celgard 2400 (Polypore Corporation), which is a single-layer polypropylene, were prepared. It was also prepared an electrolyte solution obtained by dissolving LiPF ₆ at 1 mol / L in a solvent obtained by mixing ethylene carbonate 3 parts by volume and diethyl carbonate 7 parts by volume. Two types of separators were sandwiched between the negative electrode and the positive electrode of Example 1-1 in this order: negative electrode, glass filter, celgard 2400, and positive electrode of Example 1-1 to form an electrode body. This electrode body was accommodated in a coin-type battery case CR2032 (Hosen Co., Ltd.), and an electrolyte was further injected to obtain a sealed coin-type battery. This was designated as the lithium ion secondary battery of Example 1-1.

Example 2-1
Except for using 78.6 parts by mass of Li ₆ CoO ₄ powder and 21.4 parts by mass of Li ₂ O powder, the positive electrode material and positive electrode of Example 2-1 were prepared in the same manner as in Example 1-1. And the lithium ion secondary battery was manufactured.

Example 3-1
Except for using 84.6 parts by mass of Li ₆ CoO ₄ powder and 15.4 parts by mass of Li ₂ O powder, the positive electrode material and positive electrode of Example 3-1 were prepared in the same manner as in Example 1-1. And the lithium ion secondary battery was manufactured.

Example 4-1
Except for using 89.5 parts by mass of Li ₆ CoO ₄ powder and 10.5 parts by mass of Li ₂ O powder, the positive electrode material and positive electrode of Example 4-1 were prepared in the same manner as in Example 1-1. And the lithium ion secondary battery was manufactured.

Example 5-1
Except for using 94.3 parts by mass of Li ₆ CoO ₄ powder and 5.7 parts by mass of Li ₂ O powder, the positive electrode material and positive electrode of Example 5-1 were prepared in the same manner as in Example 1-1. And the lithium ion secondary battery was manufactured.

Example 1-2
The positive electrode material, positive electrode, and lithium of Example 1-2 were prepared in the same manner as in Example 1-1, except that after mixing for 14.5 hours at 500 rpm using a ball mill, mixing was further performed for 5 hours at 600 rpm. An ion secondary battery was manufactured.

(Example 2-2)
The positive electrode material, positive electrode and lithium of Example 2-2 were prepared in the same manner as in Example 2-1, except that after mixing for 14.5 hours at 500 rpm using a ball mill, mixing was further performed for 5 hours at 600 rpm. An ion secondary battery was manufactured.

(Example 3-2)
The positive electrode material, positive electrode, and lithium of Example 3-2 were mixed in the same manner as in Example 3-1, except that mixing was performed at 500 rpm for 14.5 hours using a ball mill, and then mixing was performed at 600 rpm for 5 hours. An ion secondary battery was manufactured.

(Example 4-2)
The positive electrode material, positive electrode, and lithium of Example 4-2 were mixed in the same manner as in Example 4-1, except that mixing was performed at 500 rpm for 14.5 hours using a ball mill, and then mixing was performed at 600 rpm for 5 hours. An ion secondary battery was manufactured.

(Example 5-2)
The positive electrode material, positive electrode, and lithium of Example 5-2 were prepared in the same manner as in Example 5-1, except that mixing was performed at 500 rpm for 14.5 hours using a ball mill, followed by addition of 600 rpm for 5 hours. An ion secondary battery was manufactured.

Example 6-1
Example 6- In the same manner as in Example 1-1, except that 82.3 parts by mass of Li ₅ FeO ₄ powder and 17.7 parts by mass of Li ₂ O powder were used as raw materials for the positive electrode material. 1 positive electrode material, positive electrode and lithium ion secondary battery were produced.

Example 7-1
The positive electrode material of Example 7-1 was used in the same manner as in Example 1-1, except that 89 parts by mass of Li ₆ MnO ₄ powder and 11 parts by mass of Li ₂ O powder were used as raw materials for the positive electrode material. Materials, positive electrodes and lithium ion secondary batteries were manufactured.

(Example 6-2)
Example 6- In the same manner as in Example 1-2, except that 82.3 parts by mass of Li ₅ FeO ₄ powder and 17.7 parts by mass of Li ₂ O powder were used as raw materials for the positive electrode material. 2 positive electrode materials, a positive electrode, and a lithium ion secondary battery were manufactured.

(Example 7-2)
The positive electrode material of Example 7-2 was prepared in the same manner as in Example 1-2, except that 89 parts by mass of Li ₆ MnO ₄ powder and 11 parts by mass of Li ₂ O powder were used as raw materials for the positive electrode material. Materials, positive electrodes and lithium ion secondary batteries were manufactured.

(Comparative Example 1)
A positive electrode material, a positive electrode, and a lithium ion secondary battery of Comparative Example 1 were produced in the same manner as in Example 1-1, except that the Li ₆ CoO ₄ powder itself was used as the positive electrode material.

(Comparative Example 2)
The same method as in Example 1-1 was used except that 84.5 parts by mass of Li ₂ FeSiO ₄ powder and 15.5 parts by mass of Li ₂ O powder were used as raw materials for the positive electrode material. A positive electrode material, a positive electrode, and a lithium ion secondary battery were manufactured.

(Comparative Example 3)
Except that 84.5 parts by mass of Li ₂ FeSiO ₄ powder and 15.5 parts by mass of Li ₂ O powder were used as raw materials for the positive electrode material, the same method as in Example 1-2 was used. A positive electrode material, a positive electrode, and a lithium ion secondary battery were manufactured.

A list of positive electrode materials of Examples and Comparative Examples is shown in Table 1.

(Evaluation example 1)
Used as the positive electrode material of Example 2-1, Example 3-1, Example 5-1, Example 1-2, Example 2-2, and Example 3-2, and each example and comparative example The raw material materials of Li ₂ O powder and Li ₆ CoO ₄ powder were subjected to powder X-ray diffraction analysis using synchrotron radiation as a light source. FIG. 1 shows a powder X-ray diffraction chart of the positive electrode materials of Example 2-1, Example 3-1, and Example 5-1, and FIG. 2 shows Example 1-2, Example 2-2, and 3 shows a powder X-ray diffraction chart of a positive electrode material of Example 3-2. Further, FIG. 3 shows a powder X-ray diffraction chart of Li ₆ CoO ₄ powder, and FIG. 4 shows a powder X-ray diffraction chart of Li ₂ O powder. For all evaluations, X-ray energy was measured under the condition of 12.4 keV. The horizontal axis of FIGS. 1 to 4 is 2θ, and the vertical axis is intensity.

From both diffraction charts of FIGS. 1 and 2, a peak derived from Li ₆ CoO ₄ having an inverted fluorite-type crystal structure represented by the space group P4 ₂ / nmc in FIG. 3 (mainly around 2θ = 12 °). , Peaks observed near 15 °, 21 °, and 23 °), and peaks derived from Li ₂ O having an inverted fluorite-type crystal structure represented by the space group Fm-3m in FIG. 4 ( The peaks observed mainly at around 2θ = 21 ° to 22 ° and around 35 ° to 36 °) were observed. Note that “−3” in the space group represents 3 with an overline.

The diffraction charts of Example 2-1 and Example 1-2 suggested the presence of LiCoO ₂ represented by the space group Fd-3m. Note that a general crystal structure of LiCoO ₂ is represented by a space group R-3m.

(Evaluation example 2)
With respect to the lithium ion secondary batteries of Examples and Comparative Examples, charging and discharging cycles were repeated by charging to 3.5 V and discharging to 1.5 V under a constant current of 13.5 mA / g. All evaluations were performed in a thermostatic chamber controlled at 25 ° C.
Table 2 shows a list of initial discharge capacities of the positive electrode materials of Examples and Comparative Examples in Evaluation Example 2.

It was confirmed that all of the lithium ion secondary batteries of Examples were suitably charged and discharged. On the other hand, the lithium ion secondary batteries of Comparative Example 2 and Comparative Example 3 were unable to perform desired charge / discharge. From these results, it can be said that Li ₂ O operates as a positive electrode active material when used in combination with a specific compound. Further, as shown in the examples, by using Li ₆ CoO ₄ , Li ₅ FeO ₄ or Li ₆ MnO ₄ , the positive electrode material of the present invention performed a desired operation as a positive electrode active material. _{Li a M b D c O d} ( provided that includes a compound of satisfying 4 <a <7, b + c = 1,0.9 ≦ b ≦ 1,0 ≦ c ≦ 0.1,3 <d <5 M is at least one kind of transition metal, and D is a doping element).

FIG. 5 and FIG. 6 show the results of the charge / discharge capacities of the lithium ion secondary batteries of Examples 1-1 to 5-2 and Comparative Example 1. 5 and 6, “Dchg Cap.” Means discharge capacity, and “Chg Cap.” Means charge capacity. Note that the capacity observed at the time of the first charge includes not only the capacity associated with the originally desired movement of Li ions but also a large amount of electrochemical capacity generated in the process of activating oxygen. Therefore, it was determined that the capacity observed during the first charge should be treated as different from the battery capacity realized in the present invention, and the capacity after the first discharge was defined as the battery capacity in the product of the present invention. In FIGS. 5 and 6, the result of the initial charge capacity is omitted.

As described in Patent Document 4, charging and discharging does not occur with Li ₂ O alone. And from the results of FIGS. 5 and 6, it can be seen that the positive electrode material of the present invention exhibited a charge / discharge capacity that can be generated by Li ₆ CoO ₄ alone. That is, in the positive electrode material made of a mixture of Li ₆ CoO ₄ and Li ₂ O, it can be seen that Li ₂ O lithium also contributed to charging and discharging.

When the charging / discharging curve of the Example was observed, the flat state existed in two steps in each curve. The two-stage flat state was observed in each of the charge / discharge curves because the lithium ions were separated from Li ₆ CoO ₄ and Li ₂ O at different timings as the charge / discharge progressed, and the lithium ions were Occluded at separate timings suggests that Li ₆ CoO ₄ and Li ₂ O were formed at separate timings.

5 and 6, it can be seen that Example 2-1 to Example 5-1 and Example 1-2 to Example 5-2 showed initial discharge capacities of 200 mAh / g or more. In particular, Example 2-1, Example 4-1, Example 1-2, Example 2-2, Example 4-2, and Example 5-2 showed initial discharge capacities of 300 mAh / g or more. Is worthy of special mention. Furthermore, the initial discharge capacity of Example 4-2 and Example 5-2 showed a capacity of about 400 mAh / g or more, and the initial discharge capacity of Example 1-2 was a capacity of 600 mAh / g or more. It is surprising to show that.

In Example 1-1, in which the mass mixing ratio of Li ₆ CoO ₄ is 64.7%, the capacity is about 110 mAh / g, and the capacity of Comparative Example 1 in which the mixing ratio of Li ₆ CoO ₄ is 100%. Although it was about 118 mAh / g, the difference was noticeable when the discharge curves were compared. FIG. 7 shows initial discharge curves of Comparative Example 1 and Example 1-1. In particular, in the reaction between 2.6 V and 3.0 V, it can be understood that in Example 1-1, a capacity expressed by utilizing O electrons of Li ₂ O is added. That is, it can be said that Example 1-1 has a completely different charging / discharging mechanism that Comparative Example 1 does not have, and the above-described lithium ions are occluded at different timings, and Li ₆ CoO ₄ and Li ₂ O are separated. It can be said that the effect produced by Example 1-1 is remarkable. In all of Examples 1-1 to 5-2, and Examples 6 and 7, the characteristics of the above-described discharge curve were confirmed, and it is considered that the capacity due to the activation of Li ₂ O was developed. .

Further, Examples 2-1 to 5-1 and Examples 1-2 to 5-2 show a charge / discharge capacity of about 200 mAh / g or more even after repeated charge / discharge. . In particular, Example 3-1 to Example 5-1, Example 2-2 to Example 5-2 are advantageous in that the difference between the charge / discharge capacity after the second time and the initial discharge capacity is small. It can be said. This is due to differences in the mixing ratio of Li ₂ O and the trigger substance and the ball milling conditions suggested by the powder X-ray diffraction results of FIGS. It is expected to be related to what was recognized, but the details are not yet known.

(Example 4-3)
5 parts by mass of the positive electrode material of Example 4-2 and 4 parts by mass of acetylene black as a conductive auxiliary agent were mixed at 300 rpm for 0.5 hour using a ball mill, and the positive electrode of Example 4-3 A material-containing mixture was prepared. 1 part by mass of polytetrafluoroethylene as a binder was added to the positive electrode material-containing mixture of Example 4-3, mixed in an agate mortar, processed into a clay, and a positive electrode mixture was obtained. Mesh-like aluminum was prepared as a current collector, and a positive electrode mixture was pressure-bonded thereto to obtain a positive electrode of Example 4-3. All operations were performed in a glove box with a water concentration of 1 ppm or less, which was purged with argon gas.
Thereafter, a lithium ion secondary battery of Example 4-3 was produced in the same manner as in Example 4-1.

(Evaluation example 3)
The lithium ion secondary batteries of Example 4-1, Example 4-2, and Example 4-3 are charged to 3.5 V and discharged to 1.5 V under a constant current of 13.5 mA / g. And charging / discharging was performed. Evaluation was carried out in a thermostat controlled at 25 ° C.
The charge / discharge curve in the lithium ion secondary battery of Example 4-1 is shown in FIG. 8, the charge / discharge curve in the lithium ion secondary battery of Example 4-2 is shown in FIG. 9, and the lithium ion in Example 4-3 A charge / discharge curve in the secondary battery is shown in FIG. In FIG. 8, FIG. 9 and FIG. 10, “1cyc CHG” means a charging curve, and “1cyc DCHG” means a discharging curve.

From FIG. 8, FIG. 9 and FIG. 10, it can be seen that the discharge capacity in the lithium ion secondary battery of Example 4-3 is significantly larger than the discharge capacity in Example 4-1 and Example 4-2. . That is, it can be said that the positive electrode of Example 4-3 has a large capacity and a high energy density. From this result, the carbon-based conductive aids such as acetylene black, the effect of Li _a M _b D _c O _d as a trigger compound for causing a Li _e O _f as the positive electrode active material, suitably auxiliary and increased It is suggested that there is an effect to do. And it can be said that this effect is more clearly demonstrated by processing the positive electrode material and the conductive additive of the present invention under stronger mixing conditions.

Example 8-1
Li ₆ CoO ₄ powder, the Li ₂ O powder and _Li 2 CO ₃ powder, using a ball mill, and mixed for 14.5 hours at 500 rpm, further, add 5 hours mixing at 600 rpm, Example 8-1 The positive electrode material was manufactured. The molar ratio of Li ₆ CoO ₄ powder, Li ₂ O powder, and Li ₂ CO ₃ powder in the positive electrode material of Example 8-1 was 66:17:17, and the mass ratio was 86: 4: 10.

5 parts by mass of the positive electrode material of Example 8-1 and 4 parts by mass of acetylene black as a conductive auxiliary agent were mixed at 300 rpm for 0.5 hour using a ball mill, and the positive electrode of Example 8-1 A material-containing mixture was prepared. 1 part by mass of polytetrafluoroethylene as a binder was added to the positive electrode material-containing mixture of Example 8-1 and mixed in an agate mortar and processed into a clay to obtain a positive electrode mixture. A mesh-like aluminum was prepared as a current collector, and a positive electrode mixture was pressure-bonded thereto to obtain a positive electrode of Example 8-1. All operations were performed in a glove box with a water concentration of 1 ppm or less, which was purged with argon gas.
Thereafter, a lithium ion secondary battery of Example 8-1 was produced in the same manner as in Example 1-1.

(Example 8-2)
Except for using LiPF ₆ powder in place of Li ₂ CO ₃ powder, the same procedure as in Example 8-1 was used to produce the positive electrode material, positive electrode material-containing mixture, positive electrode, and lithium ion A secondary battery was manufactured. The molar ratio of Li ₆ CoO ₄ powder, Li ₂ O powder and LiPF ₆ powder in the positive electrode material of Example 8-2 is 53: 41: 6, and the mass ratio is 80: 11: 9.

(Example 8-3)
The positive electrode material, positive electrode material-containing mixture, positive electrode, and lithium in Example 8-3 were prepared in the same manner as in Example 8-1, except that Li ₃ PO ₄ powder was used instead of Li ₂ CO ₃ powder. An ion secondary battery was manufactured. The molar ratio of the Li ₆ CoO ₄ powder, the Li ₂ O powder and the Li ₃ PO ₄ powder in the positive electrode material of Example 8-3 is 58: 33: 9, and the mass ratio is 82: 9: 9.

(Example 8-4)
Except for using LiBF ₄ powder in place of Li ₂ CO ₃ powder, the same procedure as in Example 8-1 was performed, and the positive electrode material, positive electrode material-containing mixture, positive electrode, and lithium ion secondary battery of Example 8-4 were used. A secondary battery was manufactured. The molar ratio of Li ₆ CoO ₄ powder, Li ₂ O powder and LiBF ₄ powder in the positive electrode material of Example 8-4 is 60:28:11, and the mass ratio is 84: 7: 9.

(Evaluation example 4)
The lithium ion secondary batteries of Examples 8-1 to 8-4 were charged to 3.5 V and discharged to 1.5 V under a constant current of 13.5 mA / g. It was. Evaluation was carried out in a thermostat controlled at 25 ° C.
As a result, all of the lithium ion secondary batteries of Examples 8-1 to 8-4 showed significantly larger discharge capacities than the initial discharge capacities of Comparative Example 1 (see Table 2). .

FIG. 11 shows a charge / discharge curve of the lithium ion secondary battery of Example 8-1. In FIG. 11, “1cyc CHG” means a charging curve, and “1cyc DCHG” means a discharging curve. From FIG. 11, the initial discharge capacity of the lithium ion secondary battery of Example 8-1 was 458.3 mAh / g. The initial discharge capacity of the lithium ion secondary battery of Example 8-2 was 446.6 mAh / g, and the initial discharge capacity of the lithium ion secondary battery of Example 8-3 was 432.3 mAh / g, Example 8- The initial discharge capacity of the lithium ion secondary battery 4 was 418.7 mAh / g. These initial discharge capacities are remarkably larger than the initial discharge capacities of Comparative Example 1, and even when compared with the initial discharge capacities of Examples 1-1 to 7-2, It can be said that there is.

These _results, the lithium salt selected from _{Li 2 CO 3, LiPF 6,} Li 3 PO 4, LiBF 4 is, _Li e _{O Li} a of _f as a trigger compound to function as a positive electrode active material _M b D It is suggested that there is an effect of suitably assisting and increasing the action of _c O _d . Moreover, it is suggested that said lithium salt itself is acting as an active material from the value of the discharge capacity shown in FIG. 10 and the shape of the discharge curve.

Claims (12)

1. Li _a M _b D _c O _d (where 4 <a <7, b + c = 1, 0.9 ≦ b ≦ 1, 0 ≦ c ≦ 0.1, 3 <d <5. M is at least 1) A positive electrode characterized by containing a transition metal of a seed, D is a doping element, and Li _e O _f (where 0 <e, 0 <f is satisfied).
2. Li _a M _b D _c O with respect to the total mass of the _d and _li e _{O f,} the positive electrode according to claim 1 containing Li _a M _b D c _{O d} in the range of 20 to 99 mass%.
3. The positive electrode according to claim 1, wherein the Li _{a Mb} D _c O _d has an inverted fluorite-type crystal structure.
4. The positive electrode according to any one of claims 1 to 3, wherein the M is at least one of Co, Fe, and Mn.
5. The _Li e _{O f} is, Li ₂ O or _Li 2 _{O 2} as a positive electrode according to any one of claims 1 to 4.
6. The positive electrode according to claim 1, further comprising a lithium salt selected from Li ₂ CO ₃ , LiPF ₆ , Li ₃ PO ₄ and LiBF ₄ .
7. A lithium ion secondary battery comprising the positive electrode according to any one of claims 1 to 6.
8. The _Li a _M b _D c _{O d} and the _Li e _{O f} mixing step of the mixture,
   Disposing the mixture on a positive electrode current collector;
   The method for producing a positive electrode according to any one of claims 1 to 6, comprising:
9. The _Li a _M b _D c _{O d} and mixing the _Li e _{O f,} the step of further conductive additive were added and the mixture,
   Disposing the mixture on a positive electrode current collector;
   The method for producing a positive electrode according to any one of claims 1 to 6, comprising:
10. A method for producing a lithium ion secondary battery, comprising a step of arranging a positive electrode produced by the production method according to claim 8 or 9.
11. Li _a M _b D _c O _d (where 4 <a <7, b + c = 1, 0.9 ≦ b ≦ 1, 0 ≦ c ≦ 0.1, 3 <d <5. M is at least 1) A positive electrode material comprising: a seed transition metal, D is a doping element, and Li _e O _f (where 0 <e, 0 <f is satisfied).
12. Li _a M _b D _c O _d (where 4 <a <7, b + c = 1, 0.9 ≦ b ≦ 1, 0 ≦ c ≦ 0.1, 3 <d <5. M is at least 1) species of the transition metal .D is doping element.) and, _Li e _{O f} (although, 0 <e, 0 <satisfies f. _{a), Li 2 CO 3, LiPF} 6, Li 3 PO 4 And a lithium salt selected from LiBF ₄ .

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