JP2018156931A - Negative electrode for lithium ion secondary battery and lithium ion secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a negative electrode for a lithium secondary battery which suppresses precipitation of Li and has excellent input/output characteristics and a lithium ion secondary battery using the same.SOLUTION: A negative electrode for a lithium ion secondary battery according to the present invention includes a current collector 32 and a negative electrode active material layer 34 provided on the current collector 32, the negative electrode active material layer 34 contains carbon particles, the degree of graphitization of the carbon particles is 1.0 or more and 1.5 or less, the degree of orientation of the carbon particles is 50 or more and 150 or less, the degree of graphitization is a ratio (P101/P100) between the peak intensity P101 of the (101) plane and the peak intensity P100 of the (100) plane in an X-ray diffraction pattern, and the degree of orientation is a ratio (P002/P110) between the peak intensity P002 of the (002) plane and the peak intensity P110 of the (110) plane in the X-ray diffraction pattern.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a negative electrode for a lithium ion secondary battery and a lithium ion secondary battery.

  Lithium ion secondary batteries are lighter and have a higher capacity than nickel cadmium batteries and nickel metal hydride batteries, and are widely used as power sources for portable electronic devices. Lithium ion secondary batteries are also promising candidates as power sources for hybrid vehicles and electric vehicles. The demand for miniaturization and high functionality of portable electronic devices and high capacity of power supplies for automobiles is increasing year by year, and further increase in capacity of lithium ion batteries is expected.

  In general, graphite is used as a negative electrode active material of a lithium ion secondary battery. However, the theoretical capacity of graphite is 372 mAh / g, and a battery of about 350 mAh / g has already been used in a battery that has been put into practical use. Therefore, in order to obtain a nonaqueous electrolyte secondary battery having a sufficient capacity as an energy source for future high-performance portable devices, it is necessary to further increase the capacity.

  Furthermore, in recent years, in addition to higher capacities, rapid charging characteristics have been improved to improve convenience, and rapid charging / discharging due to the development of new uses for lithium-ion secondary batteries such as power tools and cordless home appliances. Requests are also increasing.

  When fast charging is performed, a large current is required. When the Li ion moving speed exceeds the Li ion accepting performance of graphite, Li metal is deposited on the negative electrode surface, which deteriorates the performance and safety of the lithium ion secondary battery. There's a problem.

  In order to solve this problem, for example, Patent Document 1 proposes to control the pore volume of carbon particles and the interlayer distance of graphite particles, and Patent Document 2 proposes to define the density and structure of electrodes. .

Japanese Patent Laying-Open No. 2015-181116 JP2015-122340A

  However, the inventions disclosed in Patent Documents 1 and 2 do not provide sufficient input / output characteristics.

  The present invention has been made in view of the above problems, and an object thereof is to provide a negative electrode for a lithium secondary battery that suppresses Li precipitation and has excellent input / output characteristics, and a lithium ion secondary battery using the same. To do.

In order to solve the above problems, the following means are provided.
(1) The negative electrode for lithium ion secondary batteries which concerns on 1 aspect of this invention is equipped with a collector and the negative electrode active material layer provided on the said collector, and the said negative electrode active material layer is carbon particle. And the degree of graphitization of the carbon particles is 1.0 or more and 1.5 or less, and the degree of orientation of the carbon particles is 50 or more and 150 or less; The ratio (P101 / P100) between the peak intensity P101 of the (101) plane and the peak intensity P100 of the (100) plane in the diffraction pattern, and the degree of orientation is the peak of the (002) plane in the X-ray diffraction pattern. This is the ratio (P002 / P110) between the intensity P002 and the peak intensity P110 of the (110) plane.

(2) In the above aspect, the crystallite size (crystallite diameter) Lc004 in the C-axis direction in the X-ray diffraction pattern of the carbon particles may be 300 to 600 mm.

(3) In the above aspect, the R value of the carbon particles may be 0.05 or more and 1.0 or less.
Here, R value, the ratio of the intensity of a peak in the range of the peak intensity (I _D) and 1580～1620Cm ^-1 in the range of 1300～1400Cm ^-1 as measured by Raman spectroscopy spectra (I _G) ( I _D / I _G ).

(4) In the above aspect, the negative electrode active material layer has at least one peak in a pore diameter range of 0.1 μm or more and 10 μm or less in a pore diameter distribution curve obtained by a mercury intrusion method, and the pore diameter is The cumulative pore volume in the range of 0.1 μm or more and 10 μm or less may be 0.06 cc / g or more.

(5) The lithium ion secondary battery which concerns on 1 aspect of this invention is equipped with the negative electrode for lithium ion secondary batteries which concerns on the said aspect, a positive electrode, and electrolyte.

The negative electrode for a lithium ion secondary battery of the present invention can be used for a lithium ion secondary battery in which the precipitation of Li is suppressed and the input / output characteristics are excellent.
The lithium ion secondary battery of the present invention is excellent in input / output characteristics because precipitation of Li is suppressed.

It is a cross-sectional schematic diagram of the lithium ion secondary battery concerning this embodiment.

  Hereinafter, the present embodiment will be described in detail with appropriate reference to the drawings. In the drawings used in the following description, in order to make the characteristics of the present invention easier to understand, there are cases where the characteristic parts are enlarged for the sake of convenience, and the dimensional ratios of the respective components are different from actual ones. is there. The materials, dimensions, and the like exemplified in the following description are merely examples, and the present invention is not limited to these, and can be implemented with appropriate modifications within the scope of the effects of the present invention.

[Lithium ion secondary battery]
FIG. 1 is a schematic cross-sectional view of a lithium ion secondary battery according to this embodiment.
A lithium ion secondary battery 100 shown in FIG. 1 mainly includes a laminated body 40, a case 50 that accommodates the laminated body 40 in a sealed state, and a pair of leads 60 and 62 connected to the laminated body 40. Although not shown, the electrolyte solution is housed in the case 50 together with the laminate 40.

  The stacked body 40 is configured such that the positive electrode 20 and the negative electrode 30 are disposed to face each other with the separator 10 interposed therebetween. The positive electrode 20 is obtained by providing a positive electrode active material layer 24 on a plate-like (film-like) positive electrode current collector 22. The negative electrode 30 is obtained by providing a negative electrode active material layer 34 on a plate-like (film-like) negative electrode current collector 32.

  The positive electrode active material layer 24 and the negative electrode active material layer 34 are in contact with both sides of the separator 10. Leads 62 and 60 are connected to the ends of the positive electrode current collector 22 and the negative electrode current collector 32, respectively, and the ends of the leads 60 and 62 extend to the outside of the case 50. In FIG. 1, the case 50 has one laminated body 40 in the case 50, but a plurality of laminated bodies 40 may be laminated.

"Negative electrode"
The negative electrode 30 includes a negative electrode current collector 32 and a negative electrode active material layer 34 provided on the negative electrode current collector 32.

(Negative electrode current collector)
The negative electrode current collector 32 may be a conductive plate material, and for example, a thin metal plate of copper or nickel foil can be used. The negative electrode current collector 32 is preferably not alloyed with lithium, and copper is particularly preferable. The thickness of the negative electrode current collector 32 is preferably 6 μm or more and 30 μm or less.

(Negative electrode active material layer)
The negative electrode active material layer 34 has a negative electrode active material and a negative electrode binder, and has a conductive material as necessary.

(Negative electrode active material)
The negative electrode active material is made of carbon particles, and the carbon particles have a graphitization degree of 1.0 or more and 1.5 or less and an orientation degree of 50 or more and 150 or less. Here, in this specification, the graphitization degree is a ratio (P101 / P100) between the peak intensity P101 of the (101) plane and the peak intensity P100 of the (100) plane in the X-ray diffraction pattern, and the orientation The degree is a ratio (P002 / P110) between the peak intensity P002 on the (002) plane and the peak intensity P110 on the (110) plane in the X-ray diffraction pattern.
According to this configuration, it is possible to suppress the deposition of Li and obtain a negative electrode for a lithium ion secondary battery having excellent input / output characteristics.
The reason for this is not necessarily clear, but it is due to the improved acceptability of Li ions due to the interaction between the moderately turbulent structure of the carbon particles and the presence of moderately random insertion sites of Li ions. it is conceivable that.
The negative electrode active material may contain substances other than the carbon particles as long as the effects of the present invention are achieved.

The degree of graphitization (P101 / P100) represents the degree of regular arrangement of the hexagonal network plane of carbon. The larger this value, the less the disordered layer structure, and the more regularly arranged the hexagonal network plane of carbon. Yes. In other words, the larger this value, the greater the proportion of carbon hexagonal network planes arranged at equal intervals parallel to the c-axis direction.
The degree of orientation (P002 / P110) represents the orientation of the graphite crystal with respect to the negative electrode surface. The smaller this value, the less the carbon hexagonal network plane is oriented with respect to the negative electrode surface. It shows that the hexagonal network plane of carbon is oriented in a direction parallel to the negative electrode surface.
Here, the peak intensity P110 is derived from the ab axis direction of the graphite crystal, and the peak intensity P002 is derived from the c axis direction.

The crystallite size Lc004 in the c-axis direction in the X-ray diffraction pattern of the carbon particles is preferably from 300 to 600 mm.
With this configuration, the input / output characteristics are further improved. This is presumed to be because the number of Li ion receiving sites increases due to this configuration.

The R value of the carbon particles is preferably 0.05 or more and 1.0 or less.
Here, the R value, the ratio of the intensity of a peak in the range of the peak intensity (I _D) and 1580～1620Cm ^-1 in the range of 1300～1400Cm ^-1 as measured by Raman spectroscopy spectra (I _G) (I _D / I _G ). Peak of I _G is a peak attributed to a hexagonal lattice in the vibration of carbon atoms in the graphite structure, the peak of the I _D is a peak due to carbon atoms with dangling bonds, such as amorphous carbon.
With this configuration, the input / output characteristics are further improved. This is presumably because the balance between the amorphous portion and the graphite portion is moderated by such a configuration.

(Negative electrode conductive material)
Examples of the conductive material include carbon powder such as carbon black, carbon nanotube, carbon material, fine metal powder such as copper, nickel, stainless steel and iron, a mixture of carbon material and fine metal powder, and conductive oxide such as ITO. It is done. Among these, carbon powders such as acetylene black and ethylene black are particularly preferable. In the case where sufficient conductivity can be ensured with only the negative electrode active material, the lithium ion secondary battery 100 may not include a conductive material.

(Negative electrode binder)
The binder bonds the active materials to each other and bonds the active material to the negative electrode current collector 32. The binder is not particularly limited as long as the above-described bonding is possible. For example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene- Perfluoroalkyl vinyl ether copolymer (PFA), ethylene-tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), ethylene-chlorotrifluoroethylene copolymer (ECTFE), polyvinyl fluoride (PVF) ) And the like.

  In addition to the above, as the binder, for example, vinylidene fluoride-hexafluoropropylene-based fluororubber (VDF-HFP-based fluororubber), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene-based fluororubber (VDF-HFP-) TFE fluorine rubber), vinylidene fluoride-pentafluoropropylene fluorine rubber (VDF-PFP fluorine rubber), vinylidene fluoride-pentafluoropropylene-tetrafluoroethylene fluorine rubber (VDF-PFP-TFE fluorine rubber), Vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene fluoro rubber (VDF-PFMVE-TFE fluoro rubber), vinylidene fluoride-chlorotrifluoroethylene fluoro rubber The containing rubbers (VDF-CTFE-based fluorine rubber) vinylidene fluoride-based fluorine rubbers such as may be used.

Alternatively, an electron conductive conductive polymer or an ion conductive conductive polymer may be used as the binder. Examples of the electron conductive conductive polymer include polyacetylene. In this case, since the binder also functions as a conductive material, it is not necessary to add a conductive material. As the ion-conductive conductive polymer, for example, those having ion conductivity such as lithium ion can be used. For example, polymer compounds (polyether-based polymer compounds such as polyethylene oxide and polypropylene oxide) , Polyphosphazene, etc.) and a lithium salt such as LiClO ₄ , LiBF ₄ , LiPF ₆ , or an alkali metal salt mainly composed of lithium, and the like. Examples of the polymerization initiator used for the combination include a photopolymerization initiator or a thermal polymerization initiator that is compatible with the above-described monomer.

  In addition, for example, cellulose, styrene / butadiene rubber, ethylene / propylene rubber, polyimide resin, polyamideimide resin, acrylic resin, or the like may be used as the binder.

The negative electrode active material layer has at least one peak in the pore diameter range of 0.1 μm to 10 μm in the pore diameter distribution curve obtained by mercury porosimetry, and the pore diameter is in the range of 0.1 μm to 10 μm. The cumulative pore volume in is preferably 0.06 cc / g or more. Further, the cumulative pore volume in the range where the pore diameter is 0.1 μm or more and 10 μm or less is preferably 0.15 cc / g or less.
Here, the cumulative pore volume is a pore diameter distribution curve or a pore diameter distribution graph in which a horizontal axis is a pore diameter (μm) and a vertical axis is a pore volume (cc / g). It means the total pore volume obtained by integrating the pore volume.
With this configuration, the input / output characteristics are further improved. This is presumably because this structure increased the number of pores through which Li ions diffused in the negative electrode and improved the acceptability of Li ions.

  The contents of the negative electrode active material, the conductive material, and the binder in the negative electrode active material layer 34 are not particularly limited. The constituent ratio of the negative electrode active material in the negative electrode active material layer 34 is preferably 80% or more and 99% or less, and more preferably 90% or more and 98% or less by mass ratio. The constituent ratio of the conductive material in the negative electrode active material layer 34 is preferably 0% or more and 20% or less by mass ratio, and the constituent ratio of the binder in the negative electrode active material layer 34 is 1% or more and 10% or less by mass ratio. It is preferable that

  By making content of a negative electrode active material and a binder into the said range, it can prevent that the quantity of a binder is too small and it becomes impossible to form a strong negative electrode active material layer. In addition, the amount of the binder that does not contribute to the electric capacity increases, and the tendency that it is difficult to obtain a sufficient volume energy density can be suppressed.

"Positive electrode"
The positive electrode 20 includes a positive electrode current collector 22 and a positive electrode active material layer 24 provided on the positive electrode current collector 22.

(Positive electrode current collector)
The positive electrode current collector 22 may be a conductive plate material, and for example, a thin metal plate of aluminum, copper, or nickel foil can be used.

(Positive electrode active material layer)
The positive electrode active material used for the positive electrode active material layer 24 includes lithium ion occlusion and release, lithium ion desorption and insertion (intercalation), or counter ions (for example, PF ⁶⁻ ) of lithium ions and lithium ions. An electrode active material capable of reversibly proceeding doping and dedoping can be used.

For example, lithium cobalt oxide (LiCoO _2), lithium nickelate (LiNiO _2), lithium manganate (LiMnO _2), lithium manganese spinel (LiMn ₂ O _4), and the general _{formula: LiNi x Co y Mn z M} a2 ( x + y + z + a = 1, 0 ≦ x <1, 0 ≦ y <1, 0 ≦ z <1, 0 ≦ a <1, M is one or more selected from Al, Mg, Nb, Ti, Cu, Zn, and Cr Element)), lithium vanadium compound (LiV ₂ O ₅ ), olivine-type LiMPO ₄ (where M is selected from Co, Ni, Mn, Fe, Mg, Nb, Ti, Al, Zr) are shown one or more elements or VO), lithium titanate _{(Li 4 Ti 5 O 12)} , LiNi x Co y Al z O 2 (0.9 <x + y + z <1 1) a composite metal oxide such as polyacetylene, polyaniline, polypyrrole, polythiophene, and the like polyacene.

(Positive electrode conductive material)
Examples of the conductive material include carbon powder such as carbon black, carbon nanotube, carbon material, fine metal powder such as copper, nickel, stainless steel and iron, a mixture of carbon material and fine metal powder, and conductive oxide such as ITO. . Among these, carbon materials such as carbon black are preferable. In the case where sufficient conductivity can be ensured only by the positive electrode active material, the lithium ion secondary battery 100 may not include a conductive material.

(Positive electrode binder)
The binder used for the positive electrode can be the same as that for the negative electrode.

  The constituent ratio of the positive electrode active material in the positive electrode active material layer 24 is preferably 80% or more and 90% or less by mass ratio. The constituent ratio of the conductive material in the positive electrode active material layer 24 is preferably 0.5% or more and 10% or less by mass ratio, and the constituent ratio of the binder in the positive electrode active material layer 24 is 0.5% by mass ratio. It is preferable that it is 10% or less.

"Separator"
The separator 10 only needs to be formed of an electrically insulating porous structure, for example, a single layer of a film made of polyethylene, polypropylene, or polyolefin, a stretched film of a laminate or a mixture of the above resins, or cellulose, polyester, and Examples thereof include a fiber nonwoven fabric made of at least one constituent material selected from the group consisting of polypropylene.

"Electrolyte"
As the electrolytic solution, an electrolyte solution containing lithium salt (electrolyte aqueous solution, electrolyte solution using an organic solvent) can be used. However, since the electrolytic aqueous solution has a low decomposition voltage electrochemically, the withstand voltage during charging is limited to be low. Therefore, an electrolyte solution (nonaqueous electrolyte solution) using an organic solvent is preferable.

  The nonaqueous electrolytic solution has an electrolyte dissolved in a nonaqueous solvent, and may contain a cyclic carbonate and a chain carbonate as a nonaqueous solvent.

  As cyclic carbonate, what can solvate electrolyte can be used. For example, ethylene carbonate, propylene carbonate, butylene carbonate, and the like can be used.

  The chain carbonate can reduce the viscosity of the cyclic carbonate. Examples thereof include diethyl carbonate, dimethyl carbonate, and ethyl methyl carbonate. In addition, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, γ-butyrolactone, 1,2-dimethoxyethane, 1,2-diethoxyethane, and the like may be mixed and used.

  The ratio of the cyclic carbonate and the chain carbonate in the non-aqueous solvent is preferably 1: 9 to 1: 1 by volume.

Examples of the electrolyte include LiPF ₆ , LiClO ₄ , LiBF ₄ , LiCF ₃ SO ₃ , LiCF ₃ CF ₂ SO ₃ , LiC (CF ₃ SO ₂ ) ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (CF ₃ CF _{2 SO 2) 2, LiN (} CF 3 SO 2) (C 4 F 9 SO 2), LiN (CF 3 CF 2 CO) 2, lithium salts such as LiBOB can be used. In addition, these lithium salts may be used individually by 1 type, and may use 2 or more types together. In particular, LiPF ₆ is preferably included from the viewpoint of the degree of ionization.

When LiPF ₆ is dissolved in a non-aqueous solvent, the concentration of the electrolyte in the non-aqueous electrolyte is preferably adjusted to 0.5 to 2.0 mol / L. When the concentration of the electrolyte is 0.5 mol / L or more, the lithium ion concentration of the nonaqueous electrolytic solution can be sufficiently secured, and a sufficient capacity can be easily obtained during charging and discharging. Moreover, by suppressing the electrolyte concentration to within 2.0 mol / L, it is possible to suppress an increase in the viscosity of the non-aqueous electrolyte, to sufficiently secure the mobility of lithium ions, and to obtain a sufficient capacity during charging and discharging. It becomes easy.

Even when LiPF ₆ is mixed with another electrolyte, the lithium ion concentration in the non-aqueous electrolyte is preferably adjusted to 0.5 to 2.0 mol / L, and the lithium ion concentration from LiPF ₆ is 50 mol%. More preferably, it is contained.

"Case"
The case 50 seals the laminated body 40 and the electrolytic solution therein. The case 50 is not particularly limited as long as it can suppress leakage of the electrolytic solution to the outside and entry of moisture and the like into the lithium ion secondary battery 100 from the outside.

  For example, as the case 50, as shown in FIG. 1, a metal laminate film in which a metal foil 52 is coated with a polymer film 54 from both sides can be used. For example, an aluminum foil can be used as the metal foil 52 and a film such as polypropylene can be used as the polymer film 54. For example, the material of the outer polymer film 54 is preferably a polymer having a high melting point, such as polyethylene terephthalate (PET) or polyamide, and the material of the inner polymer film 54 is polyethylene (PE) or polypropylene (PP). Etc. are preferred.

"Lead"
The leads 60 and 62 are made of a conductive material such as aluminum. Then, the leads 60 and 62 are respectively welded to the positive electrode current collector 22 and the negative electrode current collector 32 by a known method, and a separator is provided between the positive electrode active material layer 24 of the positive electrode 20 and the negative electrode active material layer 34 of the negative electrode 30. 10 is inserted into the case 50 together with the electrolyte, and the entrance of the case 50 is sealed.

"Production method of negative electrode"
The manufacturing method of the negative electrode of this invention has a crystal distortion provision process, a regraphitization process, and an orientation degree adjustment process. Further, an R value adjustment step and a cumulative pore volume adjustment step may be performed. As long as the negative electrode which has the effect of this invention can be manufactured, you may have another process.
The crystal strain imparting step is a step of introducing strain or a disordered layer into the crystal structure of the pulverized graphite particles by pulverizing and classifying natural graphite or artificial graphite and then performing a mechanochemical treatment or the like.
The regraphitization step is a step of adjusting the degree of graphitization by annealing and regraphitizing the particles after the crystal strain imparting step in a temperature range of 2400 ° C to 3200 ° C. That is, the degree of graphitization is adjusted by adjusting the conditions of the two steps of the crystal strain imparting step and the regraphitization step. The crystal strain imparting step and the regraphitization step may be collectively referred to as a graphitization degree adjusting step.
In the orientation degree adjusting step, a negative electrode active material layer containing carbon particles whose degree of graphitization is adjusted in the crystal strain imparting step and the regraphitization step is formed on the current collector, and then subjected to pressurization or the like. The degree of orientation of graphite crystals in the material layer is adjusted.

The mechanism for adjusting the degree of graphitization is considered as follows.
In the re-graphitization step, the particles are annealed at 2400 ° C. to 3200 ° C. to re-graphitize the particles into which crystal strain or a disordered layer has been introduced in the crystal strain imparting step. Crystallization proceeds more rapidly in the crystallite than in the crystal inside the particle. As a result, the crystallites arranged on the particle surface impose a spatial restriction on the growth of crystallites inside the particles. If the crystallites grow freely, the hexagonal planes of carbon are arranged at equal intervals parallel to the c-axis direction. However, if there is a spatial limitation, the regularity of stacking of the hexagonal planes of carbon is It will be disturbed. Thus, the degree of the disorder, that is, the degree of graphitization, depends on the conditions of the crystal strain imparting step and the re-graphitization step. That is, the degree of graphitization can be adjusted by a combination of the conditions for the crystal strain imparting step and the regraphitization step. In this specification, adjusting the conditions of the graphitization degree adjusting process means adjusting a combination of the conditions of the crystal distortion imparting process and the regraphitizing process.

(Crushing process)
In the pulverization step, natural graphite or artificial graphite is pulverized.
The pulverization step is preferably performed in order to refine graphite and control the crystallite diameter.
For the pulverization step, a commonly used pulverization apparatus can be used. For example, a vibration ball mill, an ultra fine mill, a jet mill, or the like can be used. The pulverization step may be performed after graphitization or before.

(Classification process)
The particles after pulverization are classified. Classification can be performed using an air classifier or the like. Alternatively, classification may be performed through a sieve.

(Crystal strain application process)
In the crystal strain imparting step, strain or a turbulent layer is introduced into the crystal structure of the pulverized graphite particles by performing a mechanochemical treatment or the like. The mechanochemical treatment imparts impact, friction, shear stress and the like to the particles in addition to compressive stress, shear stress, compressive stress and shear stress. The mechanical energy given by these stresses produces an effect called a mechanochemical phenomenon. In order to cause a mechanochemical phenomenon in the particles, an apparatus capable of simultaneously applying stress such as shearing, compression, and collision may be used, and the structure and principle of the apparatus are not particularly limited. For example, there are ball type kneaders such as a rotary ball mill, mechanofusion (manufactured by Hosokawa Micron), nobilta (manufactured by Hosokawa Micron), and the like.
The crystal strain imparting step can be performed using, for example, mechanofusion (manufactured by Hosokawa Micron), and the work amount (kW · h) represented by the product of the load (kW) applied to the rotating rotor and the processing time (h). ) To adjust the crystal distortion. As a result of intensive studies, the inventor has found that the work amount and the degree of graphitization are correlated. Based on this knowledge, it discovered that a graphitization degree could be adjusted with a crystal distortion provision process and a regraphitization process.
Here, the mechano-fusion (manufactured by Hosokawa Micron) has a configuration in which a rotating rotor and a press head are attached in a cylindrical chamber, and the rotating rotor rotates at high speed. A powder material is pressed between a press head and a rotor installed in the chamber to cause a shearing force, and pulverization, granulation, surface modification, and the like are performed. The processing conditions include the rotational speed of the rotary rotor, the load applied to the rotary rotor, the processing time, the amount of powder filling, and the like. By changing these conditions, the processing result can be changed. As a result of diligent research, the present inventor has changed the energy acting on the powder material mainly by the load applied to the rotating rotor and its processing time, thereby changing the degree of turbulence and crystal distortion, and the degree of graphitization. Found that it can be adjusted. Hereinafter, the work amount (kW · h) represented by the product of the load (kW) applied to the rotating rotor and the processing time (h) may be referred to as powder processing conditions. As the powder processing conditions increase, the degree of graphitization decreases. The load applied to the rotary rotor can be adjusted by the rotational speed of the rotary rotor, the filling rate of the graphite raw material, and the like.

(Re-graphitization process)
In the crystal strain imparting step, the raw material used in the regraphitization step is pretreated for adjusting the degree of graphitization. Therefore, in the re-graphitization process, carbon particles with an adjusted graphitization degree can be obtained simply by adjusting the annealing temperature condition of the normal graphitization process using the graphitization raw material. Here, the “carbon particles whose degree of graphitization is adjusted” is close to the graphite particles when the degree of graphitization is high, and in this specification, including the case where the degree of graphitization is not high. It calls it as follows.
Annealing in the re-graphitization step can be said to be a treatment in which the disordered crystal structure caused by pulverization or powder treatment is brought closer to the graphite structure again. As the annealing temperature increases, the degree of graphitization increases. It is considered that the annealing time has little effect on the degree of graphitization. This is because when the temperature is close to 3000 ° C., it takes a very long time to raise and cool, and therefore the influence of the temperature itself is much greater than the influence of time.

(R value adjustment process)
The R value of the carbon particles can be adjusted by performing a surface treatment. This is because the R value is considered as an index indicating the crystal growth state on the surface of the graphite material. In general, the larger the R value, the less developed the crystal. Therefore, as the R value adjusting step, for example, an organic compound layer is formed on the surface of the carbon particles, and the organic compound layer is subjected to a heat treatment step. The R value is adjusted depending on the conditions of this step (mainly the amount of the organic compound and the heat treatment temperature). Adjust the value. In order to form the organic compound layer on the surface of the carbon particles, for example, spraying can be performed by a method such as spray drying.
As the organic compound, at least one selected from the group consisting of petroleum pitch, coal pitch, phenol resin, polyvinyl alcohol resin, furan resin, cellulose resin, polystyrene resin, polyimide resin, epoxy resin, and organic acid compound is used. be able to.
The heat treatment temperature of the organic compound is preferably 200 ° C. or higher and 2000 ° C. or lower, more preferably 400 ° C. or higher and 1500 ° C. or lower, and further preferably 500 ° C. or higher and 1200 ° C. or lower. If the heat treatment temperature is too low, carbonization of the organic compound may not be sufficiently completed, and hydrogen and oxygen may remain. Hydrogen or oxygen remaining in the negative electrode active material may adversely affect battery characteristics. On the other hand, if the heat treatment temperature is too high, crystallization proceeds too much and the degree of graphitization does not fall within a predetermined range. If the crystallization of the surface-treated portion proceeds, the charging characteristics may be deteriorated.

(Orientation degree adjustment process)
In order to increase the capacity density, the negative electrode of the lithium ion secondary battery is densified by pressing the active material coated on the current collector. Deformation is adjusted so that the crystallites in the graphite particles are oriented in a direction parallel to the current collector.

(Cumulative pore volume adjustment process)
As the cumulative pore volume adjusting step, for example, the particle size distribution of the carbon particles can be adjusted.
The particle size distribution can be adjusted using, for example, an airflow classifier, and fine particles and coarse particles can be cut in an arbitrary range to adjust the particle size distribution. For example, if the fine powder and coarse particles are not cut so much, the particle size distribution becomes broad, and if much fine powder and coarse particles are cut, the particle size distribution becomes sharp. When the particle size distribution is broad, the cumulative pore size volume of the negative electrode active material layer tends to decrease, and when the particle size distribution is sharp, the cumulative pore size volume of the negative electrode active material layer tends to increase.

(Measurement of graphitization degree and crystallite size (crystallite diameter) in the C-axis direction)
The graphitization degree of the carbon particles whose degree of graphitization is adjusted by the graphitization degree adjustment step is determined by the X-ray diffraction method using the peak intensity P101 of the (101) plane and the peak intensity P100 of the (100) plane in the X-ray diffraction pattern. (P101 / P100).
The crystallite size Lc004 in the C-axis direction can be calculated based on the half-value width of the peak on the (004) plane in the X-ray diffraction pattern using the X-ray diffraction method.
The graphitization degree was determined by performing X-ray diffraction after forming a negative electrode active material layer on the negative electrode current collector, and peak intensity P101 attributed to the (101) plane of carbon particles and peak intensity P100 attributed to the (100) plane. Can also be obtained by taking the ratio. Also, the crystallite size Lc004 in the C-axis direction is calculated based on the peak attributed to the (004) plane of the carbon particles by performing X-ray diffraction after forming the negative electrode active material layer on the negative electrode current collector. You can also.

(Measurement of R value)
The R value can be obtained from, for example, a D band peak intensity (I _D ) and a G band peak intensity (I _G ) measured using a commercially available Raman spectrometer.

(Measurement of orientation)
The degree of orientation of the carbon particles whose degree of orientation has been adjusted in the degree of orientation adjustment step is determined by the ratio between the peak intensity P101 of the (101) plane and the peak intensity P100 of the (100) plane in the X-ray diffraction pattern. (P101 / P100).
The degree of orientation is obtained by performing X-ray diffraction after forming the negative electrode active material layer on the negative electrode current collector.

[Method for producing lithium ion secondary battery]
Next, with respect to the method of manufacturing the lithium ion secondary battery 100, from the step of producing a negative electrode using a negative electrode active material (carbon particles having a adjusted graphitization degree) obtained by performing a graphitization degree adjustment step, This will be specifically described.

  The obtained negative electrode active material, binder and solvent are mixed to prepare a coating material. A conductive material may be further added as necessary. As the solvent, for example, water, N-methyl-2-pyrrolidone, N, N-dimethylformamide or the like can be used. The constituent ratio of the negative electrode active material, the conductive material, and the binder is preferably 80 wt% to 90 wt%: 0.1 wt% to 10 wt%: 0.1 wt% to 10 wt% by mass ratio. These mass ratios are adjusted so as to be 100 wt% as a whole.

  The mixing method of these components constituting the paint is not particularly limited, and the mixing order is not particularly limited. The paint is applied to the negative electrode current collector 32. There is no restriction | limiting in particular as an application | coating method, The method employ | adopted when producing an electrode normally can be used. Examples thereof include a slit die coating method and a doctor blade method. Similarly, the positive electrode paint is applied on the positive electrode current collector 22 for the positive electrode.

  Subsequently, the solvent in the paint applied on the positive electrode current collector 22 and the negative electrode current collector 32 is removed. The removal method is not particularly limited. For example, the positive electrode current collector 22 and the negative electrode current collector 32 to which the paint is applied may be dried in an atmosphere of 80 ° C. to 150 ° C.

Then, a positive electrode is manufactured by performing a press treatment with a roll press device or the like in a state where the positive electrode active material layer 24 is formed on the positive electrode current collector 22 in this way.
On the other hand, in a state where the negative electrode active material layer 34 is formed on the negative electrode current collector 32, a negative electrode is produced by performing a press treatment so that the degree of orientation is 50 to 150.

  Next, the positive electrode 20 having the positive electrode active material layer 24, the negative electrode 30 having the negative electrode active material layer 34, the separator 10 interposed between the positive electrode and the negative electrode, and the electrolytic solution are sealed in a case 50.

  For example, the positive electrode 20, the negative electrode 30, and the separator 10 are stacked, and the positive electrode 20 and the negative electrode 30 are heated and pressed with a press tool from a direction perpendicular to the stacking direction, and the positive electrode 20, the separator 10, and the negative electrode 30. Adhere. For example, the laminated body 40 is put into a bag-like case 50 prepared in advance.

  Finally, the lithium ion secondary battery is manufactured by injecting the electrolytic solution into the case 50. Instead of injecting the electrolytic solution into the case, the laminate 40 may be impregnated with the electrolytic solution.

  The embodiments of the present invention have been described in detail with reference to the drawings. However, the configurations and combinations of the embodiments in the embodiments are examples, and the addition and the omission of the configurations are within the scope not departing from the gist of the present invention. , Substitutions, and other changes are possible.

"Example 1"
Commercially available artificial graphite was used as a raw material, and pulverization was performed using a planetary ball mill (PM200 manufactured by Retsch) at a rotational speed of the planetary ball mill of 500 rpm. Thereafter, the particle size distribution was adjusted using an airflow classifier, and D10, D50, and D90 were set to 2 μm, 18 μm, and 42 μm, respectively. D10, D50, and D90 are respectively the particle diameter when the horizontal axis is the particle diameter and the vertical axis is the cumulative percentage particle size distribution curve, the particle diameter when the cumulative is 10% (particle diameter), the particle diameter when the cumulative ratio is 50%, 90 % Is the particle diameter.
Next, mechanochemical treatment was performed on the obtained pulverized raw material using mechanofusion (manufactured by Hosokawa Micron Corporation). That is, three forces of compressive stress, shear stress, and impact were applied. At this time, the load applied to the rotating rotor was 3 kW, the processing time was 1 hour (h), and the work amount (powder processing conditions) was 3 kW · h.
Next, the raw material pretreated using mechanofusion is filled into a graphite crucible, and is graphitized by heating at an annealing temperature of 2400 ° C. using an Atchison furnace. “Carbon particles with adjusted degree of graphitization” Was made.

The obtained negative electrode active material, acetylene black prepared as a conductive material, and polyvinylidene fluoride (PVdF) prepared as a binder were mixed to obtain a negative electrode mixture. The negative electrode active material, the conductive material, and the binder were in a mass ratio of 94: 2: 4. This negative electrode mixture was dispersed in N-methyl-2-pyrrolidone to prepare a negative electrode mixture paint. And it apply | coated so that the application quantity might be set to 6.1 mg / cm < ² > on one surface of the electrolytic copper foil of thickness 10 micrometers. After coating, the film was dried at 100 ° C., and the solvent was removed to form a negative electrode active material layer. Thereafter, the negative electrode active material layer was adjusted by a calender press apparatus with a calendar linear pressure of 300 kg / cm, and the degree of orientation was adjusted to produce a negative electrode according to Example 1.

(Production of evaluation lithium-ion secondary battery half-cell)
The produced negative electrode and a copper foil (hereinafter referred to as Li electrode) on which a Li foil was attached were alternately opposed to each other through a polypropylene separator having a thickness of 16 μm to produce a laminate. Furthermore, the negative electrode lead made from nickel was attached to the protrusion edge part of the copper foil in the side which does not provide the negative electrode active material layer in the negative electrode of a laminated body. In the Li electrode of the laminate, a nickel Li electrode lead was attached to the protruding end portion of the copper foil not provided with the Li foil by an ultrasonic welding machine.

And this closed body was inserted in the exterior body of an aluminum laminated film, and the sealing part was formed by heat-sealing except for the surrounding 1 place. A nonaqueous electrolyte solution in which EC, EMC, and DEC are mixed in a volume ratio of 3: 5: 2 and 1.5 M (mol / L) LiPF ₆ as a lithium salt is added to the exterior body. And injected. And the remaining 1 place was sealed by heat sealing, reducing pressure with a vacuum sealing machine, and the lithium ion secondary battery (half cell) which concerns on Example 1 was produced.

(Production of lithium ion secondary battery for evaluation full cell)
First, the ratio of the product of the negative electrode active material capacity and the weight per unit area calculated according to the measurement of the negative electrode active material capacity to the product of the positive electrode active material capacity and the weight per unit area is expressed by the following relational expression (2). The battery was designed by calculating the weight per unit area of the positive electrode so as to satisfy.
(Negative electrode active material capacity × weight per unit area) / (positive electrode active material capacity × weight per unit area) = 1.1 (2)

LiCoO ₂ prepared as a positive electrode active material, acetylene black prepared as a conductive material, and polyvinylidene fluoride (PVdF) prepared as a binder were mixed to obtain a positive electrode mixture. The positive electrode active material, the conductive material, and the binder were 90: 5: 5 by mass ratio. This positive electrode mixture was dispersed in N-methyl-2-pyrrolidone to prepare a positive electrode mixture paint. And it apply | coated so that it might become the calculated weight per unit area of the positive electrode on one surface of the 20-micrometer-thick aluminum foil. After application, the film was dried at 100 ° C., and the solvent was removed to form a positive electrode active material layer. Thereafter, the positive electrode active material layer was pressure-formed by a roll press to produce a positive electrode according to Example 1.

  The produced negative electrode and positive electrode were alternately laminated through a polypropylene separator having a thickness of 16 μm, and a laminate was produced by laminating three negative electrodes and two positive electrodes. Furthermore, in the negative electrode of the laminate, a negative electrode lead made of nickel was attached to the protruding end portion of the copper foil not provided with the negative electrode active material layer. Moreover, in the positive electrode of the laminated body, an aluminum positive electrode lead was attached by an ultrasonic welding machine to the protruding end portion of the aluminum foil not provided with the positive electrode active material layer.

And this closed body was inserted in the exterior body of an aluminum laminated film, and the sealing part was formed by heat-sealing except for the surrounding 1 place. A nonaqueous electrolyte solution in which EC, EMC, and DEC are mixed in a volume ratio of 3: 5: 2 and 1.5 M (mol / L) LiPF ₆ as a lithium salt is added to the exterior body. And injected. And the remaining 1 place was sealed by heat sealing, reducing pressure with a vacuum sealing machine, and the lithium ion secondary battery (full cell) which concerns on Example 1 was produced.

"Examples 2 to 9 and Comparative Examples 1 to 5"
The rotational speed of the planetary ball mill (BM) in the pulverization process, the load applied to the rotating rotor in the crystal distortion imparting process, its processing time and its work (powder processing conditions), the annealing temperature in the regraphitization process, and the orientation adjustment process The calendar linear pressure and the particle size distribution (D10, D50, and D90 particle sizes) were changed as shown in Tables 1 and 2, and negative electrodes of Examples 2 to 9 and Comparative Examples 1 to 5 were obtained. A lithium ion secondary battery was obtained in the same manner as Example 1 using the obtained negative electrode.

  While measuring the quick charge / discharge characteristic of the lithium ion secondary battery (full cell) produced in Examples 1-9 and Comparative Examples 1-5, lithium produced in Examples 1-9 and Comparative Examples 1-5 The presence or absence of Li deposition on the negative electrode of the ion secondary battery (half cell) was evaluated. The results are shown in Tables 1 and 2.

"Examples 10 to 17"
In Example 10, a 0.1% sodium carboxymethylcellulose (CMC) solution was sprayed on the carbon particles obtained under the same conditions as in Example 9 so that the amount of adhesion was 4% with respect to the weight of the carbon particles. . Subsequently, the carbon particles obtained by heat-treating the carbon particles with CMC attached thereto at 1000 ° C. in an inert atmosphere were used, except that carbon particles (surface-treated carbon particles) were used. A negative electrode was obtained under the same conditions as in Example 9.
Examples 11 to 17 differ from Example 10 only in that the adhesion amount with respect to the weight of the carbon particles of the 0.1% CMC solution is different.

"Examples 18 to 20"
Example 18 uses a gas stream classifier for the carbon particles obtained under the same conditions as in Example 9, and the particle size distribution (D10, D50 and D90 particle diameters) is D10, D50 and D90 particle diameters. Are adjusted to 4 μm, 17 μm, and 32 μm, respectively.
Examples 19 and 20 differ from Example 18 only in the adjustment of the particle size distribution.

"Examples 21 to 24"
In Examples 21 to 24, the crystallite diameter was adjusted by changing the planetary BM grinding conditions of the carbon particle conditions used in Example 4. This is an example in which the parameters of the degree of graphitization and the degree of orientation were fixed and the crystallite diameter was moved.

  In Example 25, a 0.1% sodium carboxymethyl cellulose (CMC) solution was sprayed on the carbon particles obtained in Example 6 so that the amount of adhesion was 8% with respect to the weight of the carbon particles. Next, carbon particles to which CMC was attached were heat-treated at 1000 ° C. in an inert atmosphere to obtain carbon particles (surface-treated carbon particles), and different from Example 6 in that classification treatment was performed. Other than that, a negative electrode was obtained under the same conditions as in Example 6.

(Measurement of negative electrode active material capacity)
The negative electrode active material capacity was measured using a secondary battery charge / discharge test apparatus. The voltage range was 5 mV to 1.5 V, the negative electrode active material weight was 1 C = 340 mAh / g, and constant current-constant voltage charging was performed with 0.1 C charging. Then, constant current discharge was performed with 0.1 C discharge. The lithium ion secondary batteries (half cells) produced in Examples 1 to 9 and Comparative Examples 1 to 5 measured the negative electrode active material capacity (mAh / g) per weight under the above conditions.
Note that 1C is a current value at which charging / discharging is completed in just one hour after constant current charging or constant current discharging of a battery cell having a nominal capacity value.

(Measurement of quick charge characteristics)
The quick charge characteristics of the produced lithium ion secondary battery (full cell) were measured using a secondary battery charge / discharge test apparatus. The voltage range was 3.0V to 4.2V, and 1C = 355 mAh per full cell design capacity, and the 3C capacity maintenance rate (%) was evaluated. Here, the 3C capacity maintenance rate is a ratio of the charging capacity at the time of 3C constant current charging with respect to the 0.2C charging amount based on the constant current-constant voltage charging capacity at the time of 0.2C charging. It is represented by
3C capacity maintenance rate (%) = (charging capacity at the time of 3C constant current charging) / (constant current at the time of 0.2C charging−constant voltage charging capacity) × 100 (1)

  The higher the capacity retention rate, the better the quick charge characteristics. The lithium ion secondary batteries (full cells) produced in Examples 1 to 9 and Comparative Examples 1 to 5 were subjected to a quick charge test under the above conditions, and the quick charge characteristics were evaluated.

(Evaluation of lithium deposition on the negative electrode)
About the produced lithium ion secondary battery (half cell), it charged with the charge rate of 1.5C. Then, it decomposed | disassembled in 5 degreeC environment and the presence or absence of lithium precipitation was confirmed visually.

(Measurement of graphitization degree, orientation degree, and crystallite size in the C-axis direction)
The degree of graphitization, the degree of orientation, and the crystallite are obtained from an X-ray diffraction pattern obtained using an X-ray diffractometer (Ultima IV manufactured by RIGAKU, X-ray source: CuKα). That is, the degree of graphitization is obtained as the ratio (P101 / P100) of the peak intensity P101 of the (101) plane and the peak intensity P100 of the (100) plane in the X-ray diffraction pattern, and the degree of orientation is the ratio in the X-ray diffraction pattern. Obtained as a ratio (P002 / P110) between the peak intensity P002 of the (002) plane and the peak intensity P110 of the (110) plane, the crystallite size Lc004 in the C-axis direction is the peak of the (004) plane in the X-ray diffraction pattern. It is calculated based on the half width of.
When evaluating the degree of orientation, the peak intensity of the (004) plane may be used instead of the peak intensity of the (002) plane, but the peak intensity of the (004) plane is compared with the peak intensity of the (002) plane. Results in variations. The present inventor was able to complete the present invention by using the peak intensity of the (002) plane instead of the peak intensity of the (004) plane.

(Measurement of R value)
Raman spectroscopy uses NRS-7100 manufactured by JASCO Corporation, uses an argon laser with a wavelength of 532 nm, adjusts to an irradiation intensity of 1 mW or less using a dimmer, and measures a Raman scattering spectrum at an excitation wavelength of 532 nm. R values were obtained.

(Measurement of cumulative pore volume)
The pore distribution of the prepared negative electrode active material layer was measured by mercury porosimetry using a mercury porosimeter, and the pore diameter distribution curve with the horizontal axis representing the pore diameter (μm) and the vertical axis representing the pore volume (cc / g). Got. From the obtained pore diameter distribution curve, it is confirmed that the pore diameter has at least one peak in the range of 0.1 μm or more and 10 μm or less, and the cumulative pore volume in the range of the pore diameter of 0.1 μm or more and 10 μm or less is calculated. Obtained.

From Table 1 and Table 2, in all data of Example 1-9 and Comparative Example 1-5, when the calender linear pressure is 300 kg / cm, the degree of orientation is about 40-50 (Example 1, Comparative Example 1). The degree of orientation becomes higher as it becomes larger. At 700 kg / cm, the degree of orientation is about 150 (Example 9). At 900 kg / cm, the degree of orientation is about 160 (Comparative Example 4). I know that there is. Moreover, when compared with Example 4 and Comparative Example 4, the load applied to the rotary rotor and the processing time thereof are the same, and the same graphitization degree is obtained reflecting this, but the calendar linear pressure is implemented. Reflecting that Example 4 is 400 kg / cm and Comparative Example 4 is 900 kg / cm, the degree of orientation is 72 in Example 4 and 162 in Comparative Example 4. As described above, the degree of orientation can be adjusted by adjusting the calender linear pressure.
In the case of the production conditions of the present embodiment, the calender linear pressure may be adjusted in the range of about 300 to 700 in order to bring the degree of orientation of the carbon particles into the range of 50 to 150.

Moreover, from Table 1 and Table 2, when the rotational speed of the planetary ball mill is 500 rpm, the crystallite diameter (crystallite size) is 230 to 301 (Examples 1-3 and Comparative Examples 1 and 4). When the rotation speed is 400 rpm, the crystallite diameter is 432 to 492 (Example 4-5), and when the rotation speed is 300 rpm, the crystallite diameter is 527 to 612 ( Example 6-8, Comparative Example 5) When the rotational speed is 250 rpm, it can be seen that the crystallite diameter is 629 to 665 (Example 9, Comparative Example 2-3). As described above, the crystallite diameter can be adjusted by the rotational speed of the planetary ball mill.
In the case of the production conditions of this example, in order to make the crystallite diameter (crystallite size) of the carbon particles in the range of 300 to 600, the rotational speed of the planetary ball mill may be adjusted in the range of about 250 to 500 rpm.

Moreover, in Table 1 and Table 2, based on Examples 1-9, the work amount (powder processing conditions) represented by the product of the load (kW) applied to the rotating rotor and the processing time (h) is 3 kW. It can be seen that the graphitization degree simply increases from 1.01 to 1.49 as h decreases to 0.3 kW · h. At this time, as the powder processing condition is reduced from 3 kW · h to 0.3 kW · h, the annealing temperature is increased from 2400 ° C. to 3200 ° C. Based on Examples 1-9, the degree of graphitization is 1.0-1 by adjusting the annealing temperature in the range of 2400 ° C.-3200 ° C. with the powder processing conditions in the range of 0.3-3 kW · h. .5 range. Here, in order to set the powder processing conditions in the range of 0.3 to 3 kW · h, the load applied to the rotating rotor is set in the range of 1.2 to 3 kW, and the processing time is set in the range of 0.25 hours to 1 hour. be able to.
On the other hand, based on Comparative Example 1, when the powder processing condition is 3.5 kW · h, even when the annealing temperature is 2800 ° C., the degree of graphitization only rises to 0.9, and 1.0-1 Cannot be in the range of .5. Further, based on Comparative Examples 2, 3 and 5, when the powder processing condition is 0.2 kW · h or 0.25 kW · h, if the annealing temperature is 3300 ° C., the degree of graphitization is 1.6. As a result, it cannot be in the range of 1.0 to 1.5. In Comparative Examples 2 and 5, although the load applied to the rotating rotor and the processing time thereof are different, the powder processing condition which is the product of them is also 0.25 kW · h, and the degree of graphitization reflects this. It is considered that the same value of 1.6 was obtained.

In Comparative Examples 1 to 5, the 3C capacity maintenance rate is 73% or less, whereas in Examples 1 to 9 using the negative electrode according to the present invention, the 3C capacity maintenance rate is 82% or more and rapid charging is performed. It was found that the characteristics were good. Further, in Comparative Examples 1 to 5, lithium deposition was observed on the negative electrode, whereas in Examples 1 to 9, lithium deposition was not observed on the negative electrode.
Among Examples 1 to 9, Examples 3 to 8 have a 3C capacity maintenance rate of 90% or more. By setting the degree of graphitization to 1.1 to 1.35 and the degree of orientation to 64 to 122, there is no lithium deposition on the negative electrode, and the 3C capacity retention rate can be 90% or more.

When Example 9 is compared with Examples 10 to 17, even when the degree of graphitization is 1.49, the degree of orientation is 149, and the crystallite diameter Lc004 exceeds 600%, the R value is 0.05 or more and 1.0. It can be seen that the discharge rate characteristics can be set to 90% or more when set to the following.
Further, when Example 9 is compared with Examples 18 to 20, even when the degree of graphitization is 1.49, the degree of orientation is 149, the crystallite diameter Lc004 exceeds 600%, and the R value is 0.05, It can be seen that when the cumulative pore volume is 0.06 cc / g or more, the discharge rate characteristic can be 90% or more.
When Example 4 is compared with Examples 21 to 24, the degree of graphitization is 1.15, the degree of orientation is 72, the R value is 0.02, and the cumulative pore volume is 0.05 cc / g. It can be seen that the discharge rate characteristics can be adjusted from 81% to 93% by adjusting only the crystallite diameter Lc004.
In Example 25, the highest discharge characteristic rate of 95% was obtained.
Based on the results shown in Tables 1 and 2, the parameters of degree of graphitization, degree of orientation, crystallite diameter, R value, and cumulative pore volume can be adjusted independently and combined as an appropriate range for each parameter. Thus, it is possible to provide a negative electrode for a lithium secondary battery excellent in input / output characteristics and a lithium ion secondary battery using the same while suppressing the precipitation of Li.

DESCRIPTION OF SYMBOLS 10 ... Separator, 20 ... Positive electrode, 22 ... Positive electrode collector, 24 ... Positive electrode active material layer, 30 ... Negative electrode, 32 ... Negative electrode collector, 34 ... Negative electrode active material layer, 36 ... Negative electrode active material, 40 ... Laminate 50 ... Case, 60, 62 ... Lead, 100 ... Lithium ion secondary battery

Claims (5)

A current collector, and a negative electrode active material layer provided on the current collector,
The negative electrode active material layer includes carbon particles,
The degree of graphitization of the carbon particles is 1.0 or more and 1.5 or less, and
A negative electrode for a lithium ion secondary battery, wherein the orientation degree of the carbon particles is 50 or more and 150 or less;
Here, the graphitization degree is a ratio (P101 / P100) between the peak intensity P101 of the (101) plane and the peak intensity P100 of the (100) plane in the X-ray diffraction pattern, and the degree of orientation is X This is the ratio (P002 / P110) between the peak intensity P002 on the (002) plane and the peak intensity P110 on the (110) plane in the line diffraction pattern.   2. The negative electrode for a lithium ion secondary battery according to claim 1, wherein a crystallite size Lc004 in the C-axis direction in the X-ray diffraction pattern of the carbon particles is 300 to 600 mm. The negative electrode for a lithium ion secondary battery according to claim 1, wherein the R value of the carbon particles is 0.05 or more and 1.0 or less;
Here, R value, the ratio of the intensity of a peak in the range of the peak intensity (I _D) and 1580～1620Cm ^-1 in the range of 1300～1400Cm ^-1 as measured by Raman spectroscopy spectra (I _G) ( I _D / I _G ). The negative electrode active material layer has at least one peak in a pore diameter range of 0.1 μm or more and 10 μm or less in a pore diameter distribution curve obtained by a mercury intrusion method,
The negative electrode for a lithium ion secondary battery according to any one of claims 1 to 3, wherein the cumulative pore volume in the range of the pore diameter of 0.1 µm or more and 10 µm or less is 0.06 cc / g or more.   The lithium ion secondary battery provided with the negative electrode for lithium ion secondary batteries as described in any one of Claims 1-4, a positive electrode, and electrolyte.

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