JP4529445B2 - Negative electrode material for lithium ion secondary battery and lithium ion secondary battery - Google Patents

Description

  The present invention relates to a negative electrode material for a lithium ion secondary battery and a lithium ion secondary battery having high battery energy density that exhibits high input / output performance in a wide SOC range.

  Lithium ion secondary batteries are lighter and have higher output characteristics than other nickel metal hydride secondary batteries and lead acid batteries, and have recently attracted attention as high-power supplies for electric vehicles and hybrid electric vehicles. . As a power source for a hybrid electric vehicle, a lithium ion secondary battery with a high energy density that balances input / output performance, expresses high input / output performance in a wide SOC range, and expresses the high input / output performance. Is required.

  In general, carbon-based negative electrode active materials of lithium ion secondary batteries are roughly classified into graphite-based and amorphous carbon. Graphite has a structure in which hexagonal network surfaces of carbon atoms are regularly stacked. Lithium ion insertion and desorption reactions proceed from the end of the stacked hexagonal network surface, and lithium ions are inserted between the layers of the hexagonal network surface. The As lithium ions are inserted between the layers of the hexagonal mesh surface, graphite develops a stable potential. Further, the irreversible capacity of graphite can be made smaller than that of amorphous carbon. Therefore, in a lithium ion secondary battery using a graphite-based material as a negative electrode active material, it is easy to obtain a high energy density lithium ion secondary battery in which the battery voltage is stable and the fluctuation of input / output characteristics due to the SOC is small. On the other hand, since the insertion and desorption reactions of lithium ions proceed only at the end of the hexagonal network surface, there is a problem that the input / output values themselves are extremely low.

  On the other hand, amorphous carbon has irregular hexagonal network surface or no network structure, and lithium ion insertion and desorption reactions proceed on the entire surface of the particle. Therefore, the resistance of lithium ion insertion and desorption reactions is low, and it is easy to obtain a high-input / output lithium ion secondary battery, but the structure is irregular, so the irreversible capacity is large, and the potential fluctuation with respect to the amount of lithium ion insertion Therefore, there is a problem that input / output characteristics vary greatly due to the SOC of the battery.

  Therefore, to realize a lithium ion secondary battery with a high battery energy density that balances the above-mentioned input / output performance, expresses high input / output performance in a wide SOC range, and expresses the high input / output performance. It was an extremely difficult technical issue.

  As such a lithium ion secondary battery oriented to high input / output performance in a wide SOC range, for example, Patent Document 1 listed below has lithium nickelate in which a part of nickel is replaced with another element in the positive electrode, and the negative electrode Discloses a lithium ion secondary battery using graphite satisfying 60 ≦ Lc ≦ 100 nm. However, in terms of input / output performance and energy density, the performance is not always sufficient.

Further, in Patent Document 2 below, lithium ions having an input and output fluctuation of 20% or less from SOC 25% to 80% using a positive electrode having an olivine structure of the general formula LiMPO ₄ (M = 2 divalent element) are used. There is a disclosure of a secondary battery. However, this lithium ion secondary battery has a significantly lower output performance than its input performance, and is not necessarily desirable as a power source for a hybrid electric vehicle that requires a balance between input and output performance. Moreover, in patent document 2, there is no prescription | regulation about negative electrode material.

JP 2000-260480 A JP 2003-36889 A

  An object of the present invention is to provide a lithium ion secondary battery having a high battery energy density that balances input / output performance, expresses high input / output performance in a wide SOC range, and expresses the high input / output performance.

  The lithium ion secondary battery of the present invention regulates the output at the time of input and output. Specifically, the input density per electrode group weight and the output density per electrode group weight that expresses 2000 W / kg or more. Is a lithium ion secondary battery having a capacity density of 20 Ah / kg or more.

Moreover, the negative electrode active material for lithium ion secondary batteries of the present invention is a graphite material that simultaneously satisfies the following conditions (1) to (4). (1) Average particle size of at 3μm or 15μm or less, a peak in the range of the peak intensity (I _D) and 1580～1620Cm ^-1 in the range of 1300～1400Cm ^-1 measured in (2) Raman spectrum The R value (I _D / I _G ), which is the intensity ratio of the intensity (I _G ), is 0.2 or more and 0.4 or less, and (3) the half width Δ value of the peak in the range of 1300 to 1400 cm ⁻¹ is 40 cm ^-1 or more 100 cm ^-1 or less, (4) the intensity ratio of the peak intensity of the (110) plane in X-ray diffraction _{(I (110))} and (004) plane peak intensity _{(I (004))} X The value (I ₍₁₁₀₎ / I ₍₀₀₄₎ ) is 0.1 or more and 0.45 or less. In addition, these measured values are prescribed | regulated by what was measured not in the negative electrode plate but in the powder state.

  According to the present invention, it is possible to realize a lithium ion secondary battery having a high battery energy density that balances the input / output performance, exhibits high input / output performance in a wide SOC range, and exhibits the high input / output performance. That is, it is possible to realize a lithium ion secondary battery in which fluctuations in output performance and input performance due to the state of charge (SOC) of the battery are small, the output performance and input performance are balanced, and the input / output values are high. Thus, for example, when used as a power source for a hybrid electric vehicle, even if the SOC due to the use of the vehicle fluctuates, the high input / output performance does not fluctuate, and a hybrid electric vehicle that is easy to control and has a high performance can be realized.

  In the lithium ion secondary battery of the present invention, a graphite material having an average particle size of 3 μm or more and 15 μm or less is used as the negative electrode active material. When the average particle diameter exceeds 15 μm, the diffusion distance of Li from the surface of the negative electrode active material to the inside becomes long, and the input / output characteristics are deteriorated. On the other hand, if the average particle size is less than 3 μm, the proportion of fine particles on the order of submicrons inevitably increases, and as a result, there is an increase in particles that do not have electronic contact with each other, that is, do not function as an active material. The output characteristics are degraded.

In addition, the lithium ion secondary battery of the present invention uses a graphite material having an R value ( _ID / _IG ) of a Raman spectrum of 0.2 or more and 0.4 or less as a negative electrode active material. Peak in the range of 1580～1620Cm ^-1 as measured by Raman spectroscopy spectra is intended to indicate a regular stacking of the hexagonal plane of graphite, the peak in the range of 1300～1400Cm ^-1 lamination of hexagonal network It shows an amorphous bond having no disorder or π electrons. Thus, R value is the intensity ratio of the peak intensity (I _G) with a peak intensity in the range of 1300～1400Cm ^-1 and (I _D) in the range of ^{_{1580~1620cm -1 (I D / I G}} ) is graphite This is a measure of the crystallinity of the material. When the R value is less than 0.2, the graphite crystallinity is high and the input / output characteristics are deteriorated. When the R value is more than 0.4, the crystallinity is low, and the voltage change with respect to the SOC of the battery is large. The battery energy density that expresses is reduced.

And a lithium ion secondary battery of the present invention, graphite half width Δ value of the peak in the range of 1300～1400Cm ^-1 as measured by Raman spectroscopy spectra is 40 cm ^-1 or more 100 cm ^-1 or less as an anode active material Use materials.

A peak in the range of 1300 to 1400 cm ⁻¹ is considered to indicate disorder in the hexagonal network stacking and amorphous bonding, and the above Δ value is considered to increase as the degree of disorder in the stacking increases. It is done. Here, when the Δ value is less than 40 cm ⁻¹ , the disorder of the stack necessary for proceeding the insertion / extraction reaction of lithium ions with lower resistance is small, and the input / output characteristics are deteriorated. When the Δ value exceeds 100 cm ⁻¹ , the structural disturbance is large, the irreversible capacity increases, and at the same time, the voltage change with respect to the SOC increases, so that the battery energy density that expresses high input / output performance decreases.

In addition, the lithium ion secondary battery of the present invention is a negative electrode active material having an intensity ratio between the peak intensity (I ₍₁₁₀₎ ) of the ₍₁₁₀ ) plane and the peak intensity (I ₍₀₀₄₎ ) of the (004) plane in X-ray diffraction. A graphite material having an X value (I ₍₁₁₀₎ / I ₍₀₀₄₎ ) of 0.1 or more and 0.45 or less is used.

  The ratio of the peak intensity of the (110) plane to the peak intensity of the (004) plane in X-ray diffraction indicates the crystal orientation of the graphite material. If the X value is small, the hexagonal network plane spreads in the network plane direction. On the other hand, if it is large, the proportion of the end portions of the laminated hexagonal mesh surfaces increases. If the X value is less than 0.1, the ratio of the hexagonal network end where the insertion / extraction reaction of lithium ions in the graphite particles proceeds is reduced, so that the input / output characteristics are reduced, and if the X value exceeds 0.45 The ratio of hexagonal mesh surface ends increases, the irreversible capacity increases, and the battery energy density that expresses high input / output performance decreases.

  In the present invention, the light diffraction method is used to determine the average particle diameter. A graphite material is dispersed in distilled water in which a small amount of a surfactant is dissolved, and this is irradiated with a laser beam having a wavelength of 633 nm, and the diffracted light of the particle is analyzed to obtain a particle size distribution. From this particle size distribution, the average particle size (D50) at a volume of 50% is determined.

Further, in order to obtain the R value and Δ value of the graphite material in the present invention, the graphite material powder is irradiated with an argon laser having a wavelength of 514.5 nm and an output of 50 W, and the Raman scattered light is measured with a spectroscope. Obtain a spectrum. Then a peak in the obtained spectrum of the baseline in the range of 1580~1620cm ^-1, to measure the height of each peak intensity of the peak in the range of 1300~1400cm ^-1, obtaining the R value. Further, the height from the baseline to the peak in the range of 1300 to 1400 cm ⁻¹ is obtained, the width of the peak at the half height is obtained, and the Δ value is obtained.

  In order to obtain the X value of the graphite material in the present invention, a reflection diffraction type powder X-ray diffraction method is used. Using Cu as a target, a graphite material powder is irradiated with CuKα rays at a tube voltage of 50 kV and a tube current of 150 mA, and diffraction lines are measured with a goniometer to obtain a powder X-ray diffraction spectrum. The height of each of the (004) plane diffraction peak with 2θ in the range of 52 to 57 ° and the (110) plane diffraction peak with 2θ in the range of 75 to 80 ° is obtained, and the X value is calculated.

  Furthermore, as a more desirable form of the lithium ion secondary battery of the present invention, the thickness of the negative electrode mixture is 20 μm or more and 40 μm or less. When the thickness of the negative electrode mixture is less than 20 μm, a large amount of lithium is inserted or released from a small active material at the time of input / output, so that the input / output performance is deteriorated. When the thickness of the negative electrode mixture exceeds 40 μm, the lithium diffusion distance in the electrolytic solution from the electrode surface to the active material inside the electrode becomes long, and the input / output performance decreases.

  The lithium ion secondary battery of the present invention preferably includes a positive electrode formed by applying a positive electrode mixture, and a negative electrode active material made of a graphite material having the above average particle diameter, R value, Δ value, and X value. An electrode group consisting of a negative electrode coated to have the above thickness and a separator, and an electrolytic solution are housed in a battery case.

  For the preparation of the positive electrode, an appropriate amount of a conductive agent such as graphite, carbon, carbon black, or carbon fiber is added to the positive electrode active material, and a binder dissolved or dispersed in an appropriate solvent is added and kneaded well. An agent slurry is prepared. As the positive electrode active material, spinel complex oxides typified by lithium cobaltate, lithium nickelate, and lithium manganate having a layered crystal structure, and elemental substitution oxides thereof can be used. A fluorine-based resin such as polyvinylidene fluoride (PVDF) can be used as the binder, and N-methyl-pyrrolidone (NMP) is used as a solvent for dissolving the resin. This positive electrode mixture slurry is applied and dried on a metal foil such as aluminum, and further applied and dried on both sides of the metal foil in the same process, and after compression molding if necessary, cut to a desired size, create.

  For the preparation of the negative electrode, the graphite material having the above average particle diameter, R value, Δ value, and X value is used as the negative electrode active material. An appropriate amount of a conductive agent such as carbon black, acetylene black, or carbon fiber is added to the negative electrode active material, and, for example, PVDF dissolved in NMP is added as a binder to the negative electrode active material and kneaded well to prepare a negative electrode mixture slurry. This negative electrode mixture slurry is applied and dried on a metal foil such as copper, and further applied and dried on both sides of the metal foil in the same process, and after compression molding, cut into a desired size to produce a negative electrode. The thickness of the prepared negative electrode mixture is desirably 20 μm or more and 40 μm or less, and the coating amount of the mixture and the pressure at the time of compression molding are adjusted so as to obtain a desired thickness.

  When producing a cylindrical battery, it is as follows. As a mechanism for electrically insulating the obtained positive electrode and negative electrode from each other, a separator made of a porous insulating film having a thickness of 15 to 50 μm is sandwiched between the positive electrode and the negative electrode, and this is wound into a cylindrical shape. An electrode group is prepared and inserted into a battery container made of SUS or aluminum. As a separator that can be used, a resin porous insulating film such as polyethylene (PE) or polypropylene (PP) can be used.

  A nonaqueous electrolyte solution in which a lithium salt for electrochemically bonding the positive electrode and the negative electrode is dissolved in a nonaqueous solvent in a working container in dry air or an inert gas atmosphere is injected into the battery container, and the container is sealed. Battery.

Lithium salt supplies lithium ions that move in the electrolyte by charging and discharging the battery, and LiClO ₄ , LiCF ₃ SO ₃ , LiPF ₆ , LiBF ₄ , LiAsF _6, etc. may be used alone or in combination. it can. As an organic solvent, it is desirable to have a linear or cyclic carbonate as a main component, and esters, ethers and the like can be mixed therewith. Examples of carbonates include ethylene carbonate (EC), propylene carbonate, butylene carbonate, dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate, diethyl carbonate, and the like. A nonaqueous solvent in which these are used alone or in combination is used.

  Further, in order to obtain a square battery, it is as follows. The application of the positive electrode and the negative electrode is the same as that for producing the cylindrical battery. In order to produce a prismatic battery, an electrode group is produced around a square center pin. As in the case of the cylindrical battery, the battery can is sealed after storing it in a battery container and injecting an electrolyte. Moreover, the laminated body laminated | stacked in order of a separator, a positive electrode, a separator, a negative electrode, and a separator can also be used instead of an electrode group.

  Hereinafter, the present invention will be described using examples and comparative examples.

[Example 1]
The 18650 cylindrical lithium ion secondary battery (battery 1), (battery 2), (battery 3), and (battery 4) of Example 1 of the present invention were produced as follows. First, a positive electrode was produced. As a positive electrode active material, lithium cobaltate having a particle diameter of 7 μm was dissolved in NMP in 8% by weight of lithium cobaltate, 8% by weight of flaky graphite and 1.5% by weight of acetylene black as a conductive agent, and 5% by weight of PVDF as a binder in advance. The solution was added and further mixed to prepare a positive electrode mixture slurry. This slurry was applied to a 20 μm thick aluminum foil (positive electrode current collector) substantially uniformly and evenly, and then dried at a temperature of 80 ° C., followed by coating and drying on both sides of the aluminum foil in the same procedure. Thereafter, it was compression molded by a roll press machine, cut into a predetermined size, and a lead piece made of aluminum foil for taking out electric current was welded to produce a positive electrode.

Next, a negative electrode was produced. As the negative electrode active material, graphite A having an average particle diameter of 3.2 μm in (Battery 1), graphite B having an average particle diameter of 15 μm in (Battery 2), graphite C having an average particle diameter of 11 μm in (Battery 3), (battery 1) In 4), graphite D having an average particle size of 9.3 μm was used. The intensity ratio R of the peak in the range of peak and 1580～1620Cm ^-1 in the range of 1300～1400Cm ^-1 by Raman spectroscopy, and the half width Δ value of the peak in the range of 1300～1400Cm ^-1 is graphite In the material A, the R value is 0.25 and the Δ value is 42 cm ⁻¹ , in the graphite material B, the R value is 0.20 and the Δ value is 51 cm ⁻¹ , and in the graphite material C, the R value is 0.40 and the Δ value is 98 cm ⁻¹ . In the material D, the R value was 0.34 and the Δ value was 63 cm ⁻¹ . The intensity ratio X value (I ₍₁₁₀₎ / I ₍₀₀₄₎ ) between the peak intensity (I ₍₁₁₀₎ ) of the ₍₁₁₀₎ plane and the peak intensity (I ₍₀₀₄₎ ) of the (004) plane is graphitic. It was 0.42 for material A, 0.18 for graphite material B, 0.25 for graphite material C, and 0.11 for graphite material D. A negative electrode mixture slurry was prepared by adding and mixing a solution prepared by dissolving 4% by weight of acetylene black as a conductive agent and 92% by weight of an active material in advance in 4% by weight of PVDF in NMP. This slurry was applied substantially uniformly and evenly on both sides of a rolled copper foil (negative electrode current collector) having a thickness of 15 μm in the same procedure as the positive electrode. After coating, it was compression molded by a roll press, cut to a predetermined size, and a nickel foil lead piece was welded to produce a negative electrode. The thickness of the negative electrode mixture was adjusted to 30 μm.

  As shown in FIG. 1, a cylindrical battery having a length of 65 mm and a diameter of 18 mm was produced using the produced positive electrode and negative electrode. The produced positive electrode 11 and negative electrode 12 were wound with a microporous polypropylene separator 13 having a thickness of 25 μm interposed therebetween to produce an electrode group, and the weight of the electrode group was measured. The electrode group was inserted into a battery can 14 made of SUS, the negative electrode lead piece 15 was welded to the bottom of the can, and the positive electrode lead piece 17 was welded to the sealing lid portion 16 also serving as a positive electrode current terminal. After injecting the electrolyte into the battery can, the sealing lid portion 16 to which the positive electrode terminal was attached was caulked and sealed to the battery can 14 via the packing 18 to obtain a cylindrical battery. As the non-aqueous electrolyte, a solution obtained by dissolving 1 mol / liter of LiPF6 in a mixed solvent of EC, DMC, and DEC in a volume ratio of 1: 1: 1 was used.

(Measurement of capacity density and input / output density)
The capacity density and input / output density of each battery of Example 1 were measured as follows.
First, the rated capacity of the battery was measured. The manufactured lithium ion secondary battery was charged and discharged three times at 20 ° C., and the third discharge capacity was determined as the rated capacity of the battery. The charging conditions were constant current and constant voltage charging with a charging current equivalent to 0.33 C and an upper limit voltage of 4.1 V for 4 hours. The discharge conditions were a constant current discharge with a discharge voltage corresponding to 0.33 C and a lower limit voltage of 3.0 V.

The output was then measured. First, constant current / constant voltage charging was performed for 4 hours at an upper limit voltage of 4.1 V with a current corresponding to 0.33 C to obtain a SOC of 100%. Next, 20% of the rated capacity was discharged and the SOC was 80%. Next, the discharge current was discharged at 1 C for 10 seconds, the open circuit voltage (V (D) ₀ ) before discharge and the voltage (V (D) ₁₀ ) at the _10th discharge were measured, and the difference between them (V (D) ) A voltage drop (ΔV (D)) of _0−V (D) ₁₀ ) was obtained. Thereafter, charging corresponding to the discharged amount of electricity was performed, and the discharge current was sequentially changed to 5C and 10C to similarly determine the voltage drop (ΔV). Extrapolating the voltage drop (ΔV (D)) with respect to the discharge current value, the maximum current value (I (D) _MAX ) is calculated when it is assumed that the discharge end voltage reaches 3.0 V in 10 seconds, and I (D) _MAX The output at SOC 80% is obtained by multiplying 3.0V by 3.0V. Similarly, outputs of SOC 60%, SOC 40%, and SOC 20% were sequentially measured.

The input was then measured. After the output measurement, a constant current discharge with a lower limit voltage of 3.0 V was performed with a discharge current corresponding to 0.33 C to obtain a SOC of 0%. Next, 20% of the rated capacity was charged and the SOC was 20%. Next, the charging current is charged at 1 C for 10 seconds, the open circuit voltage (V (C) ₀ ) before charging and the voltage (V (C) ₁₀ ) at the _10th charging time are measured, and the difference between them (V (C) ) A voltage increase (ΔV (C)) of _10−V (C) ₀ ) was determined. Thereafter, discharging corresponding to the charged amount of electricity was performed, and the charging current was sequentially changed to 5C and 10C to similarly determine the voltage increase (ΔV (C)). Extrapolating the voltage rise (ΔV (C)) with respect to the charging current value, the maximum current value (I (C) _MAX ) is calculated when it is assumed that the end-of-charge voltage is 4.1 V in 10 seconds, and I (C) _MAX Multiplied by 4.1V was used as the input at SOC 20%. Similarly, inputs of SOC 40%, SOC 60%, and SOC 80% were sequentially measured.

  Based on the measured weight of the electrode group, the rated capacity of the battery, and the input and output at each SOC, the capacity density at which the input density and the output density were both 2000 W / kg or more was calculated. The vertical axis represents the output density, which is the quotient of the output electrode group weight in each SOC, and the input density, which is the quotient of the input electrode group weight in each SOC. The horizontal axis represents the capacity density which is the quotient of the weight of the electrode group of capacity. The capacity density in each SOC was calculated by setting the capacity density in the rated capacity as 100% SOC, and the values of the input density and the output density in each SOC were plotted to obtain the relationship between the input density and the output density with respect to the capacity density. Finally, the capacity density at which both the input density and the output density were 2000 W / kg or more was calculated from this relationship.

  Table 1 shows the capacity density at which the average particle diameter, R value, Δ value, X value, and input / output density of the graphite used for the negative electrode are all 2000 W / kg or more for each battery of Example 1. As shown in Table 1, the capacity density of (Battery 1) is 21.0 Ah / kg, the capacity density of (Battery 2) is 21.3 Ah / kg, the capacity density of (Battery 3) is 22.4 Ah / kg, (Battery 4) The volume density of was 21.8 Ah / kg. The capacity densities at which the input / output densities of the batteries of Example 1 were both 2000 W / kg or more were all 20 Ah / kg or more, which was superior to the batteries of Comparative Examples described later.

Comparative example

  The 18650 cylindrical lithium ion secondary battery (Comparative Battery 1), (Comparative Battery 2), (Comparative Battery 3), and (Comparative Battery 4) of Comparative Example 1 were produced as follows.

As the negative electrode active material, graphite E having an average particle diameter of 20 μm in (Comparative Battery 1), graphite F having an average particle diameter of 2.5 μm in (Comparative Battery 2), and graphite G having an average particle diameter of 9 μm in (Comparative Battery 3). In (Comparative Battery 4), graphite H having an average particle size of 14 μm was used. The R value of graphite E is 0.26, Δ value is 50 cm ⁻¹ , X value is 0.31, R value of graphite F is 0.23, Δ value is 46 cm ⁻¹ , X value is 0.25, R value of graphite G is 0.16, Δ value Was 35 cm ⁻¹ , the X value was 0.15, the R value of graphite H was 0.45, the Δ value was 103 cm ⁻¹ , and the X value was 0.48. A lithium ion secondary battery was produced in the same manner as in Example 1 except for the above.

  Table 1 shows the capacity density at which the average particle diameter, R value, Δ value, X value, and input / output density of the graphite used for the negative electrode are each 2000 W / kg or more for each battery of the comparative example. The capacity density of (Comparative Battery 1) was 8.6 Ah / kg, the capacity density of (Comparative Battery 2) was 6.3 Ah / kg, and the capacity density of (Comparative Battery 4) was 18.1 Ah / kg. In (Comparative Battery 3), there was no SOC area where the input / output density was 2000 W / kg. As for the output density of each battery of the comparative example, the capacity density at which the input / output density is 2000 W / kg or more is less than 20 Ah / kg, and the characteristics are inferior to those of the battery of the example.

[Example 2]
The 18650 cylindrical lithium ion secondary battery (battery 5), (battery 6), (battery 7), and (battery 8) of Example 2 of the present invention were produced as follows.

  In (Battery 5), graphite A was used as the negative electrode active material, and the negative electrode mixture thickness was 15 μm. In (Battery 6), graphite B was used, and the thickness of the negative electrode mixture was 20 μm. In (Battery 7), graphite B was used, and the thickness of the negative electrode mixture was 40 μm. In (Battery 8), graphite B was used, and the negative electrode mixture thickness was 45 μm. The positive electrode thickness of each battery was prepared in the same manner as the thickness ratio of the positive electrode to the negative electrode in Example 1 by adjusting the coating amount of the positive electrode. A lithium ion secondary battery was produced in the same manner as in Example 1 except for the above.

  Table 2 shows the capacity density at which the type of graphite used in the negative electrode, the thickness of the negative electrode mixture, and the input / output density of each battery of Example 2 are 2000 W / kg or more. As shown in Table 2, the capacity density of (Battery 5) is 20.3 Ah / kg, the capacity density of (Battery 6) is 22.1 Ah / kg, the capacity density of (Battery 7) is 21.0 Ah / kg, (Battery 8) The volume density of was 20.1 Ah / kg. The capacity densities at which the input / output densities of the batteries of Example 2 were both 2000 W / kg or more were all 20 Ah / kg or more, which was superior to the battery of the comparative example. The capacity densities of the batteries (Battery 5) and (Battery 8) were inferior to those of the other examples.

The schematic diagram which shows an example of the cylindrical lithium ion secondary battery of this invention

Explanation of symbols

11: positive electrode, 12: negative electrode, 13: separator, 14: battery can, 15: negative electrode lead piece, 16: lid, 17: positive electrode lead piece, 18: packing, 19: insulating plate.

Claims (3)

(1) is an average particle diameter of at 3μm or 15μm or less, and (2) the peak intensity in the range of 1300～1400Cm ^-1 as measured by Raman spectroscopy and _{(I D)} in the range of 1580～1620Cm ^-1 R value (I _D / I _G ) which is an intensity ratio of peak intensity (I _G ) is 0.2 or more and 0.4 or less, and (3) half width Δ of a peak in the range of 1300 to 1400 cm ⁻¹ value is at 40 cm ^-1 or more 100 cm ^-1 or less, and (4) of the peak intensity of the X-ray diffraction (110) plane _{(I (110))} and (004) plane peak intensity _{(I (004))} A negative electrode material for a lithium ion secondary battery, which is made of a graphite material that simultaneously satisfies the condition that the strength ratio X value (I ₍₁₁₀₎ / I ₍₀₀₄₎ ) is 0.1 or more and 0.45 or less. Lithium having a positive electrode formed by applying a positive electrode mixture containing a positive electrode active material, a negative electrode formed by applying a negative electrode mixture containing a negative electrode active material, an electrode group consisting of separators, and an electrolyte In the ion secondary battery, the negative electrode active material has (1) an average particle diameter of 3 μm or more and 15 μm or less, and (2) a peak intensity in a range of 1300 to 1400 cm ⁻¹ measured by a Raman spectrum ( R value (I _D / I _G ), which is an intensity ratio of peak intensity (I _G ) in the range of I _D ) and 1580 to 1620 cm ⁻¹ , is 0.2 or more and 0.4 or less, (3) 1300 half width Δ value of the peak in the range of 1400 cm ^-1 is not more than 40 cm ^-1 or more 100 cm ^-1, (4) the peak intensity of the X-ray diffraction (110) plane _{(I (110))} with (004) plane the strength of the peak intensity _{(I (004))} The ratio X values _{(I (110) / I (} 004)) is a lithium ion secondary battery, which is a graphite material that simultaneously satisfies 0.1 0.45 requirements. 3. The lithium ion secondary battery according to claim 2 , wherein the negative electrode mixture has a thickness of 20 μm or more and 40 μm or less.

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