JP2007048464A - Lithium ion secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lithium ion secondary battery having high charge discharge cycle characteristics at high temperature. <P>SOLUTION: In the lithium ion secondary battery having a positive electrode containing a positive active material, a negative electrode having a negative active material, and a nonaqueous electrolyte prepared by dissolving an electrolyte in an organic solvent, the positive active material contains a composite oxide represented by general formula (1) Li<SB>1+x</SB>(Ni<SB>1/3±δ1</SB>Co<SB>1/3±δ2</SB>Mn<SB>1/3±δ3</SB>)<SB>1-x</SB>O<SB>2</SB>as the main component, the negative active material contains a carbon material as the main component. The nonaqueous electrolyte contains at least an anionic compound represented by general formula (2). In the formula (2), M represents a transition metal, a group III element, a group IV element, or a group V element in the periodic table, and b represents 1-3, m represents 0-8, and q represents 0 or 1. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a lithium ion secondary battery using insertion / extraction of lithium ions.

  Lithium ion secondary batteries that use an aprotic solvent as the electrolyte solution are superior in that the withstand voltage is high and the energy density is high compared to, for example, nickel-metal hydride batteries and lead storage batteries that use a protic solvent as the electrolyte solution. It has the characteristics. Therefore, the lithium ion secondary battery is promising as a battery for hybrid vehicles and electric vehicles.

The lithium ion secondary battery generally uses a lithium composite oxide as a positive electrode active material, a carbon material as a negative electrode active material, and a nonaqueous electrolytic solution in which an electrolyte is dissolved in an aprotic solvent as an electrolytic solution. Composed. Specifically, for example, LiCoO ₂ , LiNiO ₂ , and LiMn ₂ O ₄ are used as the positive electrode active material, and natural graphite, artificial graphite, coke, and the like are used as the negative electrode active material. As the non-aqueous electrolyte, for example, a solution in which LiPF ₆ , LiBF ₄ or the like is used as a supporting salt and the supporting salt is dissolved in ethylene carbonate (EC) or diethylene carbonate (DEC) is used.

In particular, in a lithium ion secondary battery used for a power source for a hybrid vehicle or an electric vehicle that requires mass productivity, as a positive electrode active material, lithium such as LiNiO ₂ containing Ni which is relatively abundant as a main component. Nickel composite oxide is used. However, a positive electrode active material made of LiNiO ₂ or the like has a problem in safety because it may release oxygen during a full charge and cause a chemical reaction with the electrolytic solution.
Therefore, LiNi _1-x Al _x O ₂ , LiNi _1-xy Co _y Al _x O ₂ , LiNi _1-xy Co _y Mn _x O _2, etc., in which Ni is replaced with a metal element M (M = Al, Co, Mn), etc. The positive electrode active material which consists of is developed (refer nonpatent literature 1 and 2). By using such a compound, release of oxygen can be suppressed and safety can be improved.

  However, even if a lithium ion secondary battery is manufactured using the positive electrode active material shown in Non-Patent Documents 1 and 2, the lithium ion secondary battery is charged and discharged in a high-temperature environment of about 60 ° C., for example. There was a problem that the charge / discharge capacity decreased when repeated. Moreover, the lithium ion secondary battery used for such a positive electrode active material has a problem in that when the charge / discharge cycle is repeated at a high temperature, the internal resistance of the battery is significantly increased.

  In addition, as a characteristic of the on-vehicle battery, even if charging / discharging is repeated from a low temperature environment of about −30 ° C. to a high temperature environment of about 60 ° C., in addition to small capacity deterioration, the increase in internal resistance of the battery is small Required. Therefore, a lithium ion secondary battery excellent in charge / discharge cycle characteristics at a high temperature is particularly required for a vehicle-mounted battery.

T. Ohzuku et al., Journal of The Electrochemical Society, USA, The Electrochemical Society, The Electronic Chemical. 1995, 142, p. 4033-p. 4039 T. Ohzuku et al., Journal of Power Sources, Elsevier, Netherlands, 2003, 119-121, p. 171-174

  The present invention has been made in view of such conventional problems, and provides a lithium ion secondary battery capable of exhibiting a high discharge capacity and maintaining a high output even when repeatedly charged and discharged in a high temperature environment. It is something to try.

｛但し、Ｍは、遷移金属、周期律表のIII族、IV族、又はV族元素、ｂは１〜３、ｍは１〜４、ｎは０〜８、ｑは０又は１をそれぞれ表し、Ｒ¹は、Ｃ₁〜Ｃ₁₀のアルキレン、Ｃ₁〜Ｃ₁₀のハロゲン化アルキレン、Ｃ₆〜Ｃ₂₀のアリーレン、又はＣ₆〜Ｃ₂₀のハロゲン化アリーレン（これらのアルキレン及びアリーレンはその構造中に置換基、ヘテロ原子を持ってもよく、またｍ個存在するＲ¹はそれぞれが結合してもよい。）、Ｒ²は、ハロゲン、Ｃ₁〜Ｃ₁₀のアルキル、Ｃ₁〜Ｃ₁₀のハロゲン化アルキル、Ｃ₆〜Ｃ₂₀のアリール、Ｃ₆〜Ｃ₂₀のハロゲン化アリール、又はＸ³Ｒ³（これらのアルキル及びアリールはその構造中に置換基、ヘテロ原子を持ってもよく、またｎ個存在するＲ²はそれぞれが結合して環を形成してもよい。）、Ｘ¹、Ｘ²、Ｘ³は、Ｏ、Ｓ、又はＮＲ⁴、Ｒ³、Ｒ⁴は、それぞれが独立で、水素、Ｃ₁〜Ｃ₁₀のアルキル、Ｃ₁〜Ｃ₁₀のハロゲン化アルキル、Ｃ₆〜Ｃ₂₀のアリール、Ｃ₆〜Ｃ₂₀のハロゲン化アリールをそれぞれ示す（これらのアルキル及びアリールはその構造中に置換基、ヘテロ原子を持ってもよく、また複数個存在するＲ³、Ｒ⁴はそれぞれが結合して環を形成してもよい。）。｝ The present invention relates to a lithium ion secondary battery having a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, and a non-aqueous electrolyte obtained by dissolving an electrolyte in an organic solvent.
The positive electrode active material has the general formula (1) Li _{1 + x} (Ni _{1/3 ± δ1} Co _{1/3 ± δ2} Mn _{1/3 ± δ3} ) _1-x O ₂ (where −0.1 ≦ x ≦ 0. 2, 0 ≦ δ1 ≦ 0.1, 0 ≦ δ2 ≦ 0.1, 0 ≦ δ3 ≦ 0.1), a Li layer made of Li ions, an O layer made of oxide ions, Ni, Co , And a composite oxide having a crystal structure in which transition metal layers made of Mn are stacked as a main component,
The negative electrode active material is mainly composed of a carbon material,
The nonaqueous electrolytic solution is a lithium ion secondary battery characterized in that it contains at least an anionic compound represented by the following general formula (2).

{However, M is a transition metal, a group III, IV or V element of the periodic table, b is 1 to 3, m is 1 to 4, n is 0 to 8, q is 0 or 1 respectively. , R ¹ is C ₁ -C ₁₀ alkylene, C ₁ -C ₁₀ halogenated alkylene, C ₆ -C ₂₀ arylene, or C ₆ -C ₂₀ halogenated arylene (the alkylene and arylene have the structure) And R ¹ may be bonded to each other.), R ² is halogen, C ₁ -C ₁₀ alkyl, C ₁ -C ₁₀ Alkyl halides, C ₆ -C ₂₀ aryls, C ₆ -C ₂₀ aryl halides, or X ³ R ³ (these alkyls and aryls may have substituents, heteroatoms in their structures, the n number R ² each may combine with each other to form a ring present.), X ^{1, 2,} X ³ is O, S, or NR ^4, R ^3, R ⁴ are, each independently, hydrogen, alkyl of C ₁ -C _10, alkyl halide C ₁ ~C _10, C ₆ ~C ₂₀ aryls and C ₆ -C ₂₀ aryl halides are shown respectively. (These alkyls and aryls may have a substituent or a hetero atom in the structure, and a plurality of R ³ and R ⁴ are respectively May combine to form a ring. }

The lithium ion secondary battery of this invention has the non-aqueous electrolyte containing the anion compound represented by the said General formula (2).
Therefore, when the lithium ion secondary battery is charged once or more, all or a part of the anion compound is decomposed, and the surface of the positive electrode or / and the negative electrode, the surface of the positive electrode active material or / and the negative electrode active material or not. Furthermore, a coating such as a low resistance and stable coating can be formed. Therefore, the lithium ion secondary battery can smoothly store and release lithium ions.
Moreover, the said covering can suppress that a high resistance film is formed on the surface of the said positive electrode active material and / or the said negative electrode active material, for example in a high temperature environment of about 60 degreeC. Therefore, an increase in internal resistance of the lithium ion secondary battery can be suppressed, and a decrease in charge / discharge cycle characteristics can be suppressed.

The above-mentioned high-resistance film is particularly likely to occur when the lithium ion secondary battery is repeatedly used, for example, at a high temperature environment of 60 ° C., etc., hindering electrode reactions and reducing output voltage, discharge capacity, and the like. sell.
In the lithium ion secondary battery of the present invention, the covering can prevent the formation of the high-resistance film. Therefore, even when repeatedly used in a high temperature environment of, for example, 60 ° C., excellent discharge capacity and output voltage can be exhibited.

In addition, the lithium ion secondary battery has a general formula (1) Li _{1 + x} (Ni _{1/3 ± δ1} Co _{1/3 ± δ2} Mn _{1/3 ± δ3} ) _1-x O ₂ (where −0.1 ≦ x ≦ 0.2, 0 ≦ δ1 ≦ 0.1, 0 ≦ δ2 ≦ 0.1, 0 ≦ δ3 ≦ 0.1), and a Li layer made of Li ions and an O layer made of oxide ions The positive electrode active material containing a composite oxide having a crystal structure in which transition metal layers made of Ni, Co, and Mn are stacked is contained.
The complex oxide represented by the general formula (1) has almost no change in lattice volume even when lithium is desorbed, and the amount of oxygen released during overcharge is small. Therefore, it is possible to suppress the positive electrode active material from expanding or contracting to cause a contact failure in the lithium ion secondary battery or a so-called thermal runaway reaction. Therefore, a decrease in discharge capacity and an increase in internal resistance of the lithium ion secondary battery can be suppressed, and a high discharge capacity and output can be exhibited even when charging and discharging are repeated.
The reason is considered as follows.
That is, in the composite oxide represented by the general formula (1), Ni ions, Co ions, and Mn ions are blended by 1/3 ± δ moles. As a result, in the composite oxide, the formal oxidation number of each ion is +2 for Ni ions, +3 for Co ions, and +4 for Mn ions, and the Ni ions, Co ions, and Mn ions are ordered in the transition metal layer. Easily arranged. Therefore, as described above, it is considered that a decrease in discharge capacity and an increase in internal resistance can be prevented.

Furthermore, in the present invention, the positive electrode active material contains the composite oxide represented by the general formula (1), the negative electrode active material contains a carbon material, and the non-aqueous electrolyte includes at least the following: The anion compound represented by the general formula (2) is contained.
Therefore, the said lithium ion secondary battery can suppress significantly the fall of the output and charging / discharging capacity when charging / discharging is repeated. That is, in the lithium ion secondary battery, as the positive electrode active material and the negative electrode active material, a combination of the specific materials as described above and a nonaqueous electrolytic solution containing the anion compound are used, whereby The resistance increase suppressing effect and the charge / discharge capacity decrease suppressing effect can be remarkably exhibited.

  As described above, according to the present invention, it is intended to provide a lithium ion secondary battery capable of exhibiting a high discharge capacity and maintaining a high output even if charging and discharging are repeatedly performed in a high temperature environment. .

Next, a preferred embodiment of the present invention will be described.
The lithium ion secondary battery of the present invention has a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, and a non-aqueous electrolyte obtained by dissolving an electrolyte in an organic solvent.
The positive electrode is, for example, a mixture of a positive electrode active material and a conductive material and a binder, and an appropriate solvent added to form a paste-like positive electrode mixture, which is a current collector made of a metal foil such as aluminum or stainless steel. It can be formed by applying and drying on the surface and compressing to increase the electrode density as necessary.

In the present invention, the positive electrode active material has the general formula (1) Li _{1 + x} (Ni _{1/3 ± δ1} Co _{1/3 ± δ2} Mn _{1/3 ± δ3} ) _1-x O ₂ (where −0.1 ≦ x ≦ 0.2, 0 ≦ δ1 ≦ 0.1, 0 ≦ δ2 ≦ 0.1, 0 ≦ δ3 ≦ 0.1), and a Li layer made of Li ions and an O layer made of oxide ions The main component is a complex oxide having a crystal structure in which transition metal layers made of Ni, Co, and Mn are stacked.
In the case of x <−0.1, the transition metal may occupy the Li site, which may reduce the battery capacity. On the other hand, when x> 0.2, an impurity phase such as Li ₂ CO ₃ or LiOH appears, which may increase the internal resistance of the lithium ion secondary battery. More preferably, 0 ≦ x ≦ 0.1.
When δ1, δ2, or δ3 exceeds 0.1, the arrangement of Ni ions, Co ions, and Mn ions tends to be random in the transition metal layer in the composite oxide. As a result, by repeating charge and discharge, the lattice volume is likely to change, and the charge and discharge capacity and output may be likely to decrease.
More preferably, 0 ≦ δ1 ≦ 0.05, 0 ≦ δ2 ≦ 0.05, and 0 ≦ δ3 ≦ 0.05. In this case, in the transition metal layer of the composite oxide, Ni ions, Co ions, and Mn ions are more easily arranged regularly, and a superlattice structure described later is easily formed.

The positive electrode active material is, for example, a mixture of Li compound and each transition metal compound of Ni, Co, and Mn at a stoichiometric ratio such that a composite oxide represented by the general formula (1) is obtained, It can synthesize | combine by baking the obtained mixed raw material in the air, oxygen, or nitrogen.
As the Li compound, lithium hydroxide, lithium nitrate, lithium carbonate, lithium sulfate, or the like can be used. Further, as each transition metal compound, Li, Co, Mn hydroxide, nitrate, carbonate, sulfate and the like can be used. More specifically, for example, there are nickel hydroxide, cobalt hydroxide, manganese hydroxide, nickel nitrate, cobalt nitrate, manganese nitrate and the like.

From the viewpoint of compatibility, it is preferable to use a hydroxide or nitrate as the Li compound and the transition metal compound.
The baking temperature is preferably 800 to 1100 ° C., for example. When the firing temperature is less than 800 ° C., the crystallinity is not sufficiently developed, and there is a possibility that desired battery characteristics cannot be obtained. On the other hand, when the temperature exceeds 1100 ° C., impurities such as a rock salt phase are generated, which may deteriorate the battery characteristics. A more preferable firing temperature is 950 ° C to 1050 ° C.
Moreover, it is preferable to perform the firing of the mixed raw material in oxygen.
In this case, Ni ions, Co ions, and Mn ions are more easily arranged regularly in the crystal lattice, and a positive electrode active material composed of the above complex oxide having excellent durability against charge / discharge cycles is obtained. Can do.

Next, it is preferable that the complex oxide has a superlattice structure.
That is, the space group of the crystal structure of the composite oxide represented by the general formula (1) is represented by R3-m, Li ions are 3b sites, Ni ions, Co ions, and Mn ions are 3a sites, and oxide ions. Occupies the 6c site, it is preferable to have a superlattice structure in which Ni ions, Co ions, and Mn ions are regularly arranged in the 3a site. At this time, the symmetry of the space group of the crystal structure of the composite oxide is lower than R3-m. Regarding the subjectivity of the space group, for example, “T. Hahn”, International Tables for Crystallography Vol. A, Kluwer Academic Publishers (Kluwer) As described in Academic Publishers, 2002, international tables are numbered from 1 to 230 in order from the least relevant (International Table Number), for example, R3 -M is No. 166. Therefore, when the composite oxide represented by the general formula (1) has a superlattice structure, the space group of the crystal structure is R3-m (No. 166). As a result, the stability of the crystal structure of the positive electrode active material is improved, and the discharge capacity and internal resistance are increased when charging and discharging are repeated. In addition, in “R3-m” indicating the above-mentioned space group, “-” is originally added on “3”, but for the convenience of preparing the specification, In the figure, it is attached to the right of “3”.

In general, the crystal structure of LiMeO ₂ (Me is Co, Ni, Co _x Ni _1-x , Co _x NiyMn _1-xy, etc.) is represented by the space group R3-m, and Li ions, Me ions, oxide ions Occupies 3a site, 3b site, and 6c site, respectively. FIG. 8 shows an image diagram of the crystal structure of LiMeO ₂ . As shown in the figure, LiMeO ₂ has a structure in which a plurality of layers made of Li ions (Li layer) 91, a layer made of Me ions (Me layer) 92, and an O layer 93 made of oxide ions are stacked. Each of the Me layer 92 and the Li layer 91 is sandwiched between O layers 93. FIG. 9 shows the Me layer 92 when the crystal structure of FIG. 8 is viewed from the direction of the arrow in the drawing. As shown in FIG. 9, in the Me layer 92, the distance between each Me ion corresponds to the lattice constant a (however, hexagonal arrangement), and the Me ion 922 and the Me ion 923 are at an angle when viewed from the central Me ion 921. γ = 120 °. A region surrounded by the central Me ion 921, Me ion 922, Me ion 923, and Me ion 924 is a unit cell 925.

In the Me layer, Me ions, that is, Ni ions, Co ions, and Mn ions can be randomly arranged as shown in FIG. 3, for example, but regularly arranged as shown in FIGS. 6 and 7, for example. You can also
The space group of the crystal structure in which Ni ions, Co ions, and Mn ions are randomly arranged as shown in FIG. 3 is represented by R3-m, and the international table number is “No. 166. In contrast, the space group of regularly arranged crystal structure as shown in FIG. 6 is represented by P3 ₁ 12, the International table numbers, No. 151. The space group of the crystal structure regularly arranged as shown in FIG. 7 is represented by P2 / c. 13
Thus, in the case of a superlattice structure in which Ni ions, Co ions, and Me ions are regularly arranged, the international table number is the international table number of a general LiMeO ₂ crystal structure, that is, No. 166. Smaller than. In this case, the stability of the crystal structure of the composite oxide represented by the above general formula (1) is further improved, and even when charging and discharging are repeated, the decrease in discharge capacity and the increase in internal resistance are further suppressed. can do.

Further, x in the general formula (1) is x = 0, and in the layered compound, Ni ions, Co ions, and Mn ions are represented by a wood notation [√3 × √3] R30 °. It forms a structure, space group superlattice structure may be a P3 ₁ 12 or P3 ₂ 12 (claim 3).
In this case, it is possible to further suppress the decrease in the discharge capacity and the increase in the internal resistance when the lithium ion secondary battery is repeatedly charged and discharged. Moreover, the initial resistance before repeating charging / discharging can be reduced.

In the composite oxide represented by the general formula (1), when x = 0, the composite oxide is Li (Ni _{1/3 ± δ1} Co _{1/3 ± δ2} Mn _{1/3 ± δ3} ) O. ₂ (where 0 ≦ δ1 ≦ 0.1, 0 ≦ δ2 ≦ 0.1, 0 ≦ δ3 ≦ 0.1). When this composite oxide forms a superlattice structure represented by wood notation [√3 × √3] R30 ° as described above, the composite oxide includes, for example, Ni ions, Mn, as shown in FIG. It has a superlattice structure in which ions and Co ions are regularly arranged on the basis of a unit lattice of √3 times. As shown in FIG. 6, when Ni ion 71 is the center, Co ions 711, 712, 713 and Mn ions 714, 715, 716 surround Ni ion 71 as the first proximity, Ni ions 721 as the second proximity, 722, 723, 724, 725, and 726 are enclosed. Similarly, with Co ions as the center, Ni ions and Mn ions surround Co ions as the first proximity, and Co ions surround the second proximity (not shown). Similarly, when Mn ions are the center, Ni and Co ions surround Mn ions as the first proximity, and Mn ions surround the second proximity (not shown).

  When Ni ions, Co ions, and Mn ions are regularly arranged as shown in FIG. 6 to form a superlattice structure, the lattice constant of the unit cell 73 of this structure is b. Compared with the unit cell 74 having the same lattice constant a as that of the structure when the superlattice structure is not used (see FIG. 9), the lattice constant b is √3 times the lattice constant a. For this reason, such a structure has a distance between the central Me ion 71 (Ni ion in FIG. 6) and the Me ion 723 (Ni ion in FIG. 6), and the central Me ion 71 and the Me ion 725 (in FIG. 6). [√3 × √3] based on the distance to (Ni ions). Further, the angle β formed by the Me ions 723 and Me ions 725 via the central Me ions 71 in the unit cell 73 is 120 °, but the unit cell 73 has a structure shifted by an angle α = 30 ° from the unit cell 74. Yes. Therefore, such a structure can be expressed as [√3 × √3] R30 ° in wood notation, √3 represents the size with respect to the unit cell 74, and R30 ° represents the unit cell 73 and the unit cell 74. The angle α formed is 30 °.

  As the crystal structure (superlattice structure) of the composite oxide represented by the general formula (1), for example, X-ray diffraction measurement (XRD), electron beam diffraction measurement (TEM), neutron diffraction measurement (ND), or the like was used. It can be determined by crystal structure analysis.

  Further, the conductive material is for ensuring the electrical conductivity of the positive electrode. For example, one or more carbon powder materials such as carbon black, acetylene black, natural graphite, artificial graphite, and cokes are used. Can be used.

The binder serves to bind the active material particles and the conductive material particles. For example, a fluorine-containing resin such as polytetrafluoroethylene, polyvinylidene fluoride, or fluororubber, or a thermoplastic resin such as polypropylene or polyethylene. Etc. can be used. In addition, an aqueous dispersion of a cellulose-based or styrene-butadiene rubber that is an aqueous binder can also be used.
As a solvent for dispersing these active material, conductive material, and binder, for example, an organic solvent such as N-methyl-2-pyrrolidone can be used.

  Next, the negative electrode is prepared by mixing a negative electrode active material with a binder, adding a suitable solvent as a dispersing agent to form a slurry, applying the slurry to the surface of a metal foil current collector such as copper, and drying. Then, it can be formed by pressing. Similarly to the positive electrode, a fluorine-containing resin such as polyvinylidene fluoride can be used as a binder to be mixed with the negative electrode active material, and an organic solvent such as N-methyl-2-pyrrolidone can be used as a solvent.

In the present invention, the negative electrode active material contains a carbon-based material as a main component.
Examples of the carbon-based material include natural or artificial graphite, mesocarbon microbeads (MCMB), mesophase pitch-based carbon fiber and a mixture thereof, vapor-grown carbonized fiber, a fired organic compound such as phenol resin, coke, and the like. The powdery body etc. are mentioned. Further, non-graphitizable carbon (hard carbon), graphitizable carbon (soft carbon), and the like can also be used.

Next, the non-aqueous electrolyte contains the anionic compound represented by the general formula (2).
In the said General formula (2), the valence b of an anion is 1-3. When b is larger than 3, the crystal lattice energy of the salt of the anionic compound is increased, so that it is difficult to form the anionic compound by dissolving the salt of the anionic compound in the nonaqueous electrolytic solution. Therefore, b = 1 is most preferable.
For the same reason, the valence of the cation constituting the salt of the anionic compound is preferably 1 to 3, and most preferably the valence of the cation is 1. Examples of such cations include lithium ions, sodium ions, rubidium ions, cesium ions, potassium ions, tetraalkylammonium ions, and protons.

  In addition, the anion compound represented by the general formula (2) has an ionic metal complex structure, and M as the center is a transition metal, a group III, group IV, or group V element of the periodic table. Chosen from.

In the non-aqueous electrolyte, the electrolyte compound composed of the anion compound and the cation represented by the general formula (2) is ionized, and M in the general formula (2) is Al, B, V, Ti, Si, Zr, Ge, Sn, Cu, Y, Zn, Ga, Nb, Ta, Bi, P, As, Sc, Hf, or Sb, and the cation is at least Li ⁺ or Na ⁺ One is preferable (claim 4).
In this case, the nonaqueous electrolytic solution containing the anionic compound can be easily prepared by dissolving the electrolytic compound in the nonaqueous electrolytic solution. In this case, the anion compound or the electrolyte compound can be easily synthesized.

  More preferably, M in the general formula (2) is Al, B, or P. In this case, in addition to facilitating the synthesis of the anion compound or the electrolyte compound, the toxicity can be lowered, and the production cost can be reduced.

In addition to the electrolyte compound composed of the anion compound and the cation represented by the general formula (2), another electrolyte is added to the non-aqueous electrolyte as the electrolyte. Is preferably 2 to 80% by weight based on the total electrolytic mass (Claim 5).
When the amount of the electrolyte compound added is less than 2% by weight, the internal resistance of the lithium ion secondary battery may increase due to repeated charge and discharge. The reason for this is considered that the anion compound does not sufficiently form a coating such as a coating on the surface of the positive electrode or / and the negative electrode, or on the surface of the positive electrode active material or / and the negative electrode active material. . Moreover, when the addition amount of the said electrolyte compound exceeds 80 weight%, there exists a possibility that the initial stage discharge capacity of a lithium ion secondary battery may fall. The reason for this is considered to be that the thickness of the covering becomes unnecessarily thick.

The non-aqueous electrolyte solution, as other electrolytes other than the above electrolyte _{compounds, LiPF 6, LiClO 4, LiBF} 4, LiAsF 6, or it is preferable that at least one member selected from LiSbF ₆ is added (Claim 6).
In this case, since LiPF ₆ , LiClO ₄ , LiBF ₄ , LiAsF ₆ , or LiSbF ₆ has a relatively high ionic conductivity and is electrochemically stable, a lithium ion secondary battery having a high charge / discharge capacity is obtained. Obtainable.

Next, the ligand part of the anionic compound (ionic metal complex) will be described.
Hereinafter, in the present specification, in the general formula (2), an organic or inorganic part bonded to M is referred to as a ligand.

R ¹ in the general formula (2) is selected from C _{1 to} C ₁₀ alkylene, C _{1 to} C ₁₀ halogenated alkylene, C _{6 to} C ₂₀ arylene, or C _{6 to} C ₂₀ halogenated arylene. It consists of things. These alkylene and arylene may have a substituent or a hetero atom in the structure. Specifically, instead of hydrogen on alkylene and arylene, halogen, chain or cyclic alkyl group, aryl group, alkenyl group, alkoxy group, aryloxy group, sulfonyl group, amino group, cyano group, carbonyl group, acyl Examples thereof include a group, an amide group, a hydroxyl group, and a structure in which nitrogen, sulfur, or oxygen is introduced instead of carbon on alkylene and arylene.
Furthermore, when a plurality of R ¹ are present (when q = 1 and m = 2 to 4), each may be bonded, and examples thereof include a ligand such as ethylenediaminetetraacetic acid.

R ² is selected from halogen, C ₁ -C ₁₀ alkyl, C ₁ -C ₁₀ alkyl halide, C ₆ -C ₂₀ aryl, C ₆ -C ₂₀ aryl halide, or X ³ R ³ It consists of things. Similarly to R ¹ , alkyl or aryl may have a substituent or a heteroatom in the structure, and when there are a plurality of R ² (when n = 2 to 8), each R ² is They may combine to form a ring.
Preferably, R ² is an electron-withdrawing group, particularly fluorine. In this case, the solubility and dissociation degree of the salt of the anionic compound can be improved, and the effect of improving the ionic conductivity can be obtained. Furthermore, in this case, the oxidation resistance is improved, thereby preventing the occurrence of side reactions.

X ¹ , X ² , and X ³ are each independently O, S, or NR ⁴ , and the ligand is bonded to M through these heteroatoms. Here, it is not impossible to combine other than O, S, and N, but the synthesis becomes very complicated. As a feature of the compound represented by the general formula (2), there is binding to M by X ¹ and X ² in the same in the ligand, these ligands form a M and chelate structure . The constant q in this ligand is 0 or 1. When q = 0, the chelate ring becomes a five-membered ring, and the complex structure of the anionic compound is stabilized. Therefore, in this case, it is possible to prevent side reactions other than the formation of the coating.

R ³ and R ⁴ are each independently hydrogen, C _{1 to} C ₁₀ alkyl, C _{1 to} C ₁₀ alkyl halide, C _{6 to} C ₂₀ aryl, or C _{6 to} C ₂₀ aryl halide. These alkyls and aryls may have a substituent or a heteroatom in the structure, and when a plurality of R ³ and R ⁴ are present, each may be bonded to form a ring. .

The constants m and n related to the number of ligands described above are determined by the type of M at the center, and m is 1 to 4 and n is 0 to 8.
It in ^{R 1, R 2, R 3} , R 4 described above, C ₁ -C ₁₀ indicates 1 to 10 carbon atoms, C ₆ -C ₂₀ is 6 to 20 carbon atoms Indicates.

As the anion compound represented by the general formula (2), it is preferable to use one or more types represented by the following formulas (3) to (6) (claim 7).
In this case, the solubility and dissociation degree of the salt of the anionic compound can be improved, and the ionic conductivity of the non-aqueous electrolyte can be improved. Furthermore, in this case, oxidation resistance can be improved.

As the anionic compound, it is preferable to use a compound represented by the above formula (5) (claim 8).
In this case, the anionic compound can exert the above-described excellent effect of suppressing the increase in internal resistance and the effect of improving the charge / discharge cycle characteristics even with a small amount of addition. That is, in this case, a higher characteristic improvement effect can be obtained with respect to the addition rate of the anionic compound.

As a method for synthesizing the anion compound, for example, in the case of a compound represented by the following formula (3), LiBF ₄ and 2 moles of lithium alkoxide are reacted in a non-aqueous solvent, and then oxalic acid is added. Then, there is a method of substituting alkoxide bonded to boron with oxalic acid. In this case, a lithium salt of a compound represented by the following formula (3) can be obtained.

  As the organic solvent for dissolving the anionic compound and the electrolyte, an aprotic organic solvent can be used. As such an organic solvent, for example, a mixed solvent composed of one or more selected from cyclic carbonate, chain carbonate, cyclic ester, cyclic ether, chain ether, and the like can be used.

  Here, examples of the cyclic carbonate include ethylene carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate. Examples of the chain carbonate include dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate. Examples of the cyclic ester carbonate include gamma butyrolactone and gamma valerolactone. Examples of the cyclic ether include tetrahydrofuran and 2-methyltetrahydrofuran. Examples of the chain ether include dimethoxyethane and ethylene glycol dimethyl ether. As the organic solvent, any one of these can be used alone, or two or more kinds can be mixed and used.

  In addition, the anion compound contained in the non-aqueous electrolytic solution is obtained by charging the lithium ion secondary battery one or more times, whereby all or part of the anion compound is decomposed, and the positive electrode or / and the A coating such as a film can be formed by coating the surface of the negative electrode or the surface of the positive electrode active material or / and the negative electrode active material. The coating can be detected by, for example, X-ray photoelectron spectroscopy (XPS) or IR analysis.

  The lithium ion secondary battery mainly comprises the positive electrode and the negative electrode, a separator sandwiched between the positive electrode and the negative electrode, and the non-aqueous electrolyte that moves lithium between the positive electrode and the negative electrode. Can be configured as an element.

As said separator, a positive electrode and a negative electrode are isolate | separated and nonaqueous electrolyte solution is hold | maintained, For example, thin microporous films, such as polyethylene and a polypropylene, etc. can be used.
Examples of the shape of the lithium ion secondary battery include a paper type, a coin type, a cylindrical type, and a square type. As said battery case which accommodates a positive electrode, a negative electrode, and a non-aqueous electrolyte, the thing corresponding to these shapes can be used.

Example 1
Next, an embodiment of the present invention will be described with reference to FIGS.
As shown in FIG. 1, the lithium ion secondary battery 1 of this example includes a positive electrode 2, a negative electrode 3, and a nonaqueous electrolytic solution obtained by dissolving an electrolyte in an organic solvent. The positive electrode 2 has a general formula (1) Li _{1 + x} (Ni _{1/3 ± δ1} Co _{1/3 ± δ2} Mn _{1/3 ± δ3} ) _1-x O ₂ (where −0.1 ≦ x ≦ 0.2, 0 ≦ δ1 ≦ 0.1, 0 ≦ δ2 ≦ 0.1, 0 ≦ δ3 ≦ 0.1), and as shown in FIG. 2, a Li layer 251 made of Li ions and an O layer made of oxide ions A composite oxide 25 having a crystal structure in which 252 and a transition metal layer 253 made of Ni, Co, and Mn are stacked is contained as a positive electrode active material. The negative electrode 3 contains a carbon material as a negative electrode active material. The nonaqueous electrolytic solution contains an anionic compound represented by the following formula (5).

Hereinafter, the lithium ion secondary battery 1 of this example will be described in detail with reference to FIG.
As shown in FIG. 1, the lithium ion secondary battery 1 of this example includes a positive electrode 2, a negative electrode 3, a separator 4, a gasket 59, a battery case 6, and the like. The battery case 6 is a 18650-type cylindrical battery case, and includes a cap 63 and an outer can 65. In the battery case 6, a sheet-like positive electrode 2 and a negative electrode 3 are arranged in a wound state together with a separator 4 sandwiched between the positive electrode 2 and the negative electrode 3.
A gasket 59 is disposed inside the cap 63 of the battery case 6, and a non-aqueous electrolyte is injected into the battery case 6.

The positive electrode 2 contains a composite oxide represented by Li (Ni _0.43 Co _0.33 Mn _0.24 ) O ₂ as a positive electrode active material. A schematic diagram of the crystal structure of this composite oxide is shown in FIG.
As shown in FIG. 2, the composite oxide 25 includes a Li layer 251 made of Li ions, an O layer 252 made of oxide ions, and a transition metal layer 253 made of Ni ions, Co ions, and Mn ions. It has a crystal structure. In the transition metal layer 253, as shown in FIG. 3, Ni ions, Co ions, and Mn ions are irregularly arranged.

The negative electrode 3 contains MCMB (manufactured by Osaka Gas, graphitized mesocarbon microbeads) as a negative electrode active material.
The positive electrode 2 and the negative electrode 3 are respectively provided with a positive electrode current collecting lead 23 and a negative electrode current collecting lead 33 by welding. The positive electrode current collector lead 23 is connected to the positive electrode current collector tab 235 disposed on the cap 63 side by welding. Further, the negative electrode current collecting lead 33 is connected by welding to a negative electrode current collecting tab 335 disposed on the bottom of the outer can 65.

In addition, the non-aqueous electrolytic solution was prepared by mixing a lithium salt of an anionic compound represented by the above formula (5) (LiPF ₂ (C ₂ O ₄ ) in an organic solvent obtained by mixing ethylene carbonate and diethyl carbonate at a volume ratio of 30:70. ₂ ) (hereinafter referred to as LPFO as appropriate) and LiPF ₆ are added as electrolytes and injected into the battery case 6.

Next, the manufacturing method of the lithium ion secondary battery 1 of this example will be described with reference to FIGS.
First, Li (Ni _0.43 Co _0.33 Mn _0.24 ) O ₂ as a positive electrode active material is synthesized as follows.
That is, first, lithium hydroxide (LiOH.H ₂ O), nickel hydroxide (Ni (OH) ₂ ), cobalt hydroxide (Co (OH) ₂ ), and manganese hydroxide (Mn (OH) ₂ ) are prepared. did. Next, lithium hydroxide, nickel hydroxide, cobalt hydroxide, and manganese hydroxide are mixed in a molar ratio of Li: Ni: Co: Mn of 1.01: 0.43: 0.33: 0. A mixed raw material was obtained by mixing at a mixing ratio of 24.
Next, this mixed raw material is fired at a temperature of 1000 ° C. in an oxygen atmosphere and is made of Li (Ni _0.43 Co _0.33 Mn _0.24 ) O ₂ , and has a structure in which a Li layer 251, an O layer 252 and a transition metal layer 253 are stacked. A composite oxide was obtained (see FIG. 2). This is designated as Sample E1.

Next, crystal structure analysis of the sample E1 by electron beam diffraction measurement (TEM) was performed. FIG. 4 shows an ED (Electron Diffraction) pattern of the sample E1 obtained as a result.
FIG. 4 shows an ED pattern when the transition metal layer of the sample E1 is observed from the c-axis direction. In FIG. 4, the Miller index of each spot is shown. In FIG. 4, a cross mark on the white circle at the center indicates that an electron beam is irradiated from the top to the bottom of the paper in a direction perpendicular to the paper (c-axis direction). Arrows a and b indicate the a-axis and b-axis in the reciprocal lattice space, respectively.

  FIG. 4 shows that the sample E1 has a crystal structure represented by the space group R3-m. The crystal structure of the sample E1 belongs to International Table No. (International Table No.) No. 166. Based on the ED pattern of FIG. 4, the arrangement pattern of Ni ions, Co ions, and Mn ions in the transition metal layer of the composite oxide of sample E1 can be determined. This arrangement pattern is shown in FIG. As known from the figure, in the sample E1, Ni ions, Co ions, and Mn ions in the transition metal layer are irregularly arranged.

Next, using the sample E1 as a positive electrode active material, a lithium ion secondary battery 1 is manufactured as shown in FIG.
First, the sample E1 as a positive electrode active material, carbon black as a conductive material, and polyvinylidene fluoride as a binder are mixed, and an appropriate amount of N-methyl-2-pyrrolidone is added and dispersed as a dispersant. A slurry-like positive electrode mixture was obtained. The mixing ratio of the positive electrode active material, the conductive material, and the binder was, by weight ratio, positive electrode active material: conductive material: binder = 85: 10: 5.

Next, the positive electrode mixture obtained as described above was applied to both sides of an aluminum foil current collector having a thickness of 20 μm and dried. Then, it densified with the roll press, cut out in the shape of 52 mm width x 450 mm length, and produced the sheet-like positive electrode 2. In addition, the adhesion amount of the positive electrode active material was about 7 mg / cm ² per side.

  On the other hand, in producing the negative electrode 3, first, MCMB (manufactured by Osaka Gas, graphitized mesocarbon microbeads) was prepared as a negative electrode active material. This negative electrode active material and polyvinylidene fluoride as a binder were mixed, an appropriate amount of N-methyl-2-pyrrolidone was added as a dispersing agent, and dispersed to obtain a slurry-like negative electrode mixture. The mixing ratio of the negative electrode active material and the binder was a weight ratio of negative electrode active material: binder = 95: 5.

Next, the negative electrode mixture obtained as described above was applied to the surface of a copper foil current collector having a thickness of 10 μm and dried. Then, it densified with the roll press, cut out into the shape of 54 mm width x 500 mm length, and produced the sheet-like negative electrode 3. In addition, the adhesion amount of the negative electrode active material was about 4 mg / cm ² per side.

Further, in an organic solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) are mixed at a volume ratio of 3: 7, LiPF ₆ and LPFO at a weight ratio of LiPF ₆ : LPFO = 0.95: 0.05 The non-aqueous electrolyte was prepared by adding the mixed supporting salt so mixed to a concentration of 1M.

  Next, as shown in FIG. 1, a positive electrode current collecting lead 23 and a negative electrode current collecting lead 33 were welded to the sheet-like positive electrode 2 and negative electrode 3 obtained as described above, respectively. The positive electrode 2 and the negative electrode 3 were wound in a state where a polyethylene separator 4 having a width of 56 mm and a thickness of 25 μm was sandwiched between them, and a roll-shaped electrode body was produced.

  Subsequently, the roll-shaped electrode body was inserted into an 18650-type cylindrical battery case 6 including an outer can 65 and a cap 63. At this time, the positive electrode current collecting lead 23 is welded to the positive electrode current collecting tab 235 disposed on the cap 63 side of the battery case 6 and the negative electrode current collecting lead 335 is disposed on the negative electrode current collecting tab 335 disposed on the bottom of the outer can 65. 33 was connected by welding.

  Next, the battery case 6 was impregnated with the non-aqueous electrolyte prepared as described above. A gasket 59 is disposed inside the cap 63, and the cap 63 is disposed in the opening of the outer can 65. Subsequently, the battery case 6 was sealed by caulking the cap 63, and the lithium ion secondary battery 1 was manufactured. This was designated as battery E1.

(Example 2)
In this example, a lithium ion secondary battery is manufactured using a positive electrode active material having a different crystal structure from that of Example 1. The lithium ion secondary battery of this example has Li (Ni
_0.33 Co _0.33 Mn _0.34 ) It was prepared in the same manner as in Example 1 except that it contained a complex oxide represented by O ₂ .

In producing the lithium ion secondary battery of this example, first, as in Example 1, lithium hydroxide (LiOH.H ₂ O), nickel hydroxide (Ni (OH) ₂ ), cobalt hydroxide (Co (OH) ₂ ) and manganese hydroxide (Mn (OH) ₂ ) were prepared. Next, lithium hydroxide, nickel hydroxide, cobalt hydroxide, and manganese hydroxide are mixed in a molar ratio of Li: Ni: Co: Mn of 1.01: 0.33: 0.33: 0. A mixed raw material was obtained by mixing at a mixing ratio of 34.
Subsequently, the mixed raw material was fired in an oxygen atmosphere at a temperature 1000 ° C., to obtain a _{Li (Ni 0.33 Co 0.33 Mn 0.34} ) composite oxide consisting of O _2. This is designated as Sample E2.

Next, the crystal structure analysis of the sample E2 by electron beam diffraction measurement (TEM) was performed. The ED pattern of the sample E2 obtained as a result is shown in FIG.
FIG. 5 shows an ED pattern when the sample E2 is observed from the c-axis direction. In FIG. 5, the same Miller index of the spot as that of the sample E1 of Example 1 is shown. In FIG. 5, the central cross mark on the white circle indicates that the electron beam was irradiated from the top to the bottom in the direction perpendicular to the paper surface (c-axis direction). Arrows a and b indicate the a-axis and b-axis in the reciprocal lattice space, respectively.

From FIG. 5, it can be seen that the sample E2 has a superlattice structure represented by the space group P3 ₁ 12. The crystal structure of Sample E2 belongs to International Table No. 151 (International Table No.). Moreover, in the electron beam diffraction of the sample E2, an extra spot was observed compared with the said sample E1 of the crystal structure represented by space group R3-m.

Based on the ED pattern of FIG. 5, the arrangement pattern of Ni ions, Co ions, and Mn ions in the transition metal layer of the composite oxide of sample E2 can be determined. This arrangement pattern is shown in FIG.
As is known from FIG. 6, in the sample E2, Ni ions, Co ions, and Mn ions in the transition metal layer are regularly arranged. As shown in the figure, in the transition metal layer of the sample E2, Ni ions, Mn ions, and Co ions are regularly arranged on the basis of √3 times the unit cell 73, and the angle α = 30. °. Therefore, the crystal structure of the sample E2 is represented by [√3 × √3] R30 ° in terms of wood.

Next, a lithium ion secondary battery was produced in the same manner as in Example 1 using the sample E2 as a positive electrode active material. This is referred to as a battery E2.
The battery E2 was produced in the same manner as the battery E1 of Example 1 except that the sample E2 was used as the positive electrode active material.

(Example 3)
In this example, a lithium ion secondary battery is manufactured using a positive electrode active material having a crystal structure different from that of Example 1 and Example 2. The lithium ion secondary battery of this example was fabricated in the same manner as in Example 1 except that the positive electrode active material contained a composite oxide represented by Li (Ni _0.33 Co _0.33 Mn _0.34 ) O ₂ . Is.

In manufacturing a lithium ion secondary battery of the present embodiment, first, in the same manner as in Example 1, lithium hydroxide (LiOH · H ₂ O), nickel hydroxide (Ni (OH) _2), cobalt hydroxide (Co (OH) ₂ ) and manganese hydroxide (Mn (OH) ₂ ) were prepared. Next, lithium hydroxide, nickel hydroxide, cobalt hydroxide, and manganese hydroxide are mixed in a molar ratio of Li: Ni: Co: Mn of 1.01: 0.33: 0.33: 0. A mixed raw material was obtained by mixing at a mixing ratio of 34.
Next, this mixed raw material was fired in an oxygen atmosphere at a temperature of 850 ° C. to obtain a composite oxide composed of Li (Ni _0.33 Co _0.33 Mn _0.34 ) O ₂ . This is designated as Sample E3.

Next, as in Example 1, when the crystal structure analysis by electron beam diffraction measurement (TEM) was performed on the sample E3, the sample E3 had a superlattice structure represented by the space group P2 / c. I found out. The crystal structure of Sample E3 belongs to International Table No. 13 (International Table No.).
Similarly to Example 1, the arrangement pattern of Ni ions, Co ions, and Mn ions in the transition metal layer of the composite oxide of sample E3 was determined from the result of electron beam diffraction of sample E3. This arrangement pattern is shown in FIG. As known from the figure, in the sample E3, the Ni ions, Co ions, and Mn ions in the transition metal layer were regularly arranged so as to be linearly arranged.

Next, a lithium ion secondary battery was produced in the same manner as in Example 1 using the sample E3 as a positive electrode active material. This is designated as battery E3.
Battery E3 was produced in the same manner as Battery E1 of Example 1 except that Sample E3 was used as the positive electrode active material.

(Comparative example)
In this example, three types of lithium containing no anionic compound in the non-aqueous electrolyte are used for comparison of the lithium ion secondary batteries (battery E1 to battery E3) prepared in Examples 1 to 3. Ion secondary batteries (battery C1 to battery C3) were produced.
In manufacturing the battery C1, firstly, a non-aqueous electrolyte of ethylene carbonate (EC) and diethyl carbonate (DEC) 3: the mixed organic solvent at 7 volume ratio of the LiPF _6, to a concentration of 1M In addition, a non-aqueous electrolyte was prepared.
Subsequently, the lithium ion secondary battery was produced like Example 1 using the said sample E1 similar to Example 1 as a positive electrode active material. This is designated as battery C1.

The battery C2 is the battery of Example 1 except that the non-aqueous electrolyte similar to the battery C1 is used as the electrolyte and the sample E2 similar to Example 2 is used as the positive electrode active material. It was produced in the same manner as E1.
The battery C3 was the same as the battery of Example 1 except that the nonaqueous electrolytic solution similar to the battery C1 was used as the electrolytic solution, and the sample E3 similar to that of Example 3 was used as the positive electrode active material. It was produced in the same manner as E1.

(Experimental example)
Next, for each of the six types of batteries (battery E1 to battery E3 and battery C1 to battery C3) prepared in Examples 1 to 3 and the comparative example, the following charge / discharge cycle test is performed in a high temperature environment of 60 ° C. The capacity retention rate, initial IV resistance (initial internal resistance), and resistance increase rate (internal resistance increase rate) were examined.

"Initial IV resistance"
Each battery was adjusted to a battery capacity of 50% (SOC = 50%), and a battery voltage after 10 seconds after applying a current of 0.12A, 0.4A, 1.2A, 2.4A, 4.8A. Was measured. The current and voltage passed through each battery were linearly approximated, and the initial resistance was determined from the slope. The initial resistance value of each battery was calculated as a relative value when the value of the battery E2 was 1. That is, the result of the initial resistance of each battery was expressed as a value normalized with respect to the value of the battery E2. The results are shown in Table 1.

"Charge / discharge cycle test"
Under the temperature condition of 60 ° C., which is regarded as the upper limit of the actual use temperature range of the battery, each battery is charged to a charging upper limit voltage of 4.1 V with a constant current of 2.0 mA / cm ² , and then a current density of 2 Charge / discharge for discharging to a discharge lower limit voltage of 3 V at a constant current of 0.0 mA / cm ^{2 was} defined as one cycle, and this cycle was performed for a total of 500 cycles.

"Capacity maintenance rate"
Before and after the charge / discharge cycle test, when the discharge capacity before the charge / discharge cycle test was discharge capacity A and the discharge capacity after the charge / discharge cycle test was discharge capacity B, the capacity retention rate was calculated by the following equation (a). The results are shown in Table 1. The discharge capacity A and the discharge capacity B were measured under the conditions of a temperature of 20 ° C. and a current density of 0.2 mA / cm ² before and after the charge / discharge cycle test. Further, the discharge capacity is obtained by measuring the discharge current value (mA) and multiplying this discharge current value by the time (hr) required for discharge by the weight (g) of the positive electrode active material in the battery. It was calculated by dividing.
Capacity maintenance ratio (%) = discharge capacity B / discharge capacity A × 100 (a)

"Resistance increase rate"
Before and after the charge / discharge cycle test, each battery was adjusted to 50% of the battery capacity (SOC = 50%), and a current of 0.12A, 0.4A, 1.2A, 2.4A, 4.8A was applied to flow 10 The battery voltage after 2 seconds was measured. The applied current and voltage were linearly approximated, and IV resistance was obtained from the slope.
The resistance increase rate can be calculated by the following equation (b), where the resistance after resistance is Y and the resistance before X is the IV resistance before the charge / discharge cycle test. The results are shown in Table 1.
IV resistance increase rate (%) = (resistance Y−resistance X) × 100 / resistance X (b)

  As is known from Table 1, it can be seen that the battery E1 to the battery E3 have an improved capacity retention rate and a lower resistance increase rate than the batteries C1 to C3. Therefore, the batteries E1 to E3 can exhibit a high charge / discharge capacity and output even when charge / discharge is repeated. The improvement in the capacity retention rate and the decrease in the resistance increase rate are more remarkable when the batteries having the same positive electrode active material, that is, the battery E1 and the battery C1, the battery E2 and the battery C2, and the battery E3 and the battery C3 are compared. .

  In addition, among the batteries E1 to E3, lithium ion secondary batteries (battery E1 and battery E3) using a positive electrode active material (sample E1 and sample E2) having a superlattice structure have a very high capacity maintenance rate, Furthermore, the rate of increase in resistance was further suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. BRIEF DESCRIPTION OF THE DRAWINGS Explanatory drawing which shows the crystal structure of the positive electrode active material (sample E1) concerning Example 1. FIG. Explanatory drawing which shows the arrangement | sequence of Ni ion, Co ion, and Mn ion in the transition metal layer of positive electrode active material (sample E1) concerning Example 1. FIG. FIG. 3 is an explanatory diagram showing an ED pattern of a positive electrode active material (sample E1) according to Example 1. Explanatory drawing which shows the ED pattern of the positive electrode active material (sample E2) concerning Example 2. FIG. Explanatory drawing which shows the arrangement | sequence of Ni ion, Co ion, and Mn ion in the transition metal layer of positive electrode active material (sample E2) concerning Example 2. FIG. Explanatory drawing which shows the arrangement | sequence of Ni ion, Co ion, and Mn ion in the transition metal layer of positive electrode active material (sample E3) concerning Example 3. FIG. Explanatory view showing a crystal structure of the composite oxide represented by LiMeO _2. Explanatory diagram showing the arrangement of Me ions in Me layer of a composite oxide represented by LiMeO _2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Lithium ion secondary battery 2 Positive electrode 3 Negative electrode 4 Separator 6 Battery case

Claims (8)

In a lithium ion secondary battery having a positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, and a non-aqueous electrolyte obtained by dissolving an electrolyte in an organic solvent,
The positive electrode active material has the general formula (1) Li _{1 + x} (Ni _{1/3 ± δ1} Co _{1/3 ± δ2} Mn _{1/3 ± δ3} ) _1-x O ₂ (where −0.1 ≦ x ≦ 0. 2, 0 ≦ δ1 ≦ 0.1, 0 ≦ δ2 ≦ 0.1, 0 ≦ δ3 ≦ 0.1), a Li layer made of Li ions, an O layer made of oxide ions, Ni, Co , And a composite oxide having a crystal structure in which transition metal layers made of Mn are stacked as a main component,
The negative electrode active material is mainly composed of a carbon material,
The non-aqueous electrolyte contains at least an anionic compound represented by the following general formula (2).

{However, M is a transition metal, a group III, IV or V element of the periodic table, b is 1 to 3, m is 1 to 4, n is 0 to 8, q is 0 or 1 respectively. , R ¹ is C ₁ -C ₁₀ alkylene, C ₁ -C ₁₀ halogenated alkylene, C ₆ -C ₂₀ arylene, or C ₆ -C ₂₀ halogenated arylene (the alkylene and arylene have the structure) And R ¹ may be bonded to each other.), R ² is halogen, C ₁ -C ₁₀ alkyl, C ₁ -C ₁₀ Alkyl halides, C ₆ -C ₂₀ aryls, C ₆ -C ₂₀ aryl halides, or X ³ R ³ (these alkyls and aryls may have substituents, heteroatoms in their structures, the n number R ² each may combine with each other to form a ring present.), X ^{1, 2,} X ³ is O, S, or NR ^4, R ^3, R ⁴ are, each independently, hydrogen, alkyl of C ₁ -C _10, alkyl halide C ₁ ~C _10, C ₆ ~C ₂₀ aryls and C ₆ -C ₂₀ aryl halides are shown respectively. (These alkyls and aryls may have a substituent or a hetero atom in the structure, and a plurality of R ³ and R ⁴ are respectively May combine to form a ring. }   2. The lithium ion secondary battery according to claim 1, wherein the composite oxide has a superlattice structure. In Claim 2, x in the said General formula (1) is x = 0, and Ni ion, Co ion, and Mn ion in the said transition metal layer of the said composite oxide are a wood description [√3x√3 A lithium ion secondary battery, wherein a superlattice structure represented by R30 ° is formed, and a space group of the superlattice structure is P3 ₁ 12 or P3 ₂ 12. In any one of Claims 1-3, in the said non-aqueous electrolyte, the electrolyte compound which consists of the said anion compound represented by the said General formula (2) and a cation is ionizing, The said general formula ( M in 2) is any one of Al, B, V, Ti, Si, Zr, Ge, Sn, Cu, Y, Zn, Ga, Nb, Ta, Bi, P, As, Sc, Hf, or Sb. There, the lithium ion secondary batteries, wherein said cation is at least one of Li ⁺ or Na ^+.   In any one of Claims 1-4, in addition to the electrolyte compound which consists of the said anion compound and cation represented by the said General formula (2) as said electrolyte in the said nonaqueous electrolyte solution, An electrolyte is added, and the addition amount of the electrolyte compound is 2% by weight to 80% by weight in the total electrolytic mass. In claim 5, the non-aqueous electrolyte solution, as other electrolytes other than the above electrolyte _{compounds, LiPF 6, LiClO 4, LiBF} 4, LiAsF 6, or that one or more selected from LiSbF ₆ is added A lithium ion secondary battery characterized by the above. In any 1 item | term of Claims 1-6, 1 or more types represented by following formula (3)-(6) are used as said anion compound represented by said general formula (2). Lithium ion secondary battery.

  8. The lithium ion secondary battery according to claim 7, wherein a compound represented by the formula (5) is used as the anion compound.

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