JPH07201317A - Lithium ion secondary battery - Google Patents

Abstract

PURPOSE:To provide a lithium ion secondary battery with high capacity, high initial charging and discharging efficiency, and excellent reversibility of lithium ion absorption-desorption reaction. CONSTITUTION:A lithium ion secondary battery is a battery provided with a positive electrode 4, a negative electrode 6 containing a carbonaceous substance which absorbs and desorbs lithium ion, and a nonaqueous electrolytic solution. The carbonaceous substance has 0.355-0.375nm average plane distance (d002) computed from a peak corresponding to the (002) plane of a graphite structure and analyzed by x-ray diffraction and 0.85 or less peak intensity ratio (R=IP2/IP1) wherein the IP2 and IP1 stand for the peak intensity near 1350cm<-1> and in a range from 1500cm<-1> to 1700cm<-1>, respectively, by Raman spectrometry with argon laser light with 514.5nm wavelength.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithium ion secondary battery, and more particularly to a lithium ion secondary battery having improved non-aqueous electrolyte and exhibiting excellent battery characteristics.

[0002]

2. Description of the Related Art In recent years, non-aqueous electrolyte batteries using lithium as a negative electrode active material have been attracting attention as high energy density batteries. For example, manganese dioxide (Mn
A primary battery using O ₂ ), carbon fluoride [(CF ₂ ) _n ], thionyl chloride (SOCl ₂ ) or the like is already widely used as a power source for calculators, watches, and backup batteries for memories.

Further, in recent years, with the miniaturization and weight reduction of various electronic devices such as VTRs and communication devices, there is an increasing demand for high energy density secondary batteries as their power sources. In response to such demands, research on lithium secondary batteries using lithium as a negative electrode active material has been actively conducted.

Lithium secondary batteries use lithium as the negative electrode active material and use propylene carbonate (PC) and 1,2-dimethoxyethane (DM) as lithium ion conductive electrolytes.
E), γ-butyrolactone (γ-BL), tetrahydrofuran (THF) or the like in a non-aqueous solvent such as LiClO ₄ and Li.
A non-aqueous electrolyte solution or a lithium ion conductive solid electrolyte in which a lithium salt such as BF ₄ or LiAsF ₆ is dissolved is used, and TiS ₂ , MoS ₂ , V ₂ O ₅ , V
A structure using a compound that undergoes a topochemical reaction with lithium such as ₆ O ₁₃ and MnO ₂ has been studied.

However, the lithium secondary battery having the above structure has not yet been put into practical use. The main reason for this is that the charging / discharging efficiency is low and the number of times charging / discharging is possible (cycle life) is short. It is considered that this is largely due to the deterioration of lithium due to the reaction between the negative electrode lithium and the non-aqueous electrolyte. That is, the lithium dissolved in the non-aqueous electrolyte as lithium ions during discharge is
When it precipitates from the non-aqueous electrolyte solution during charging, it reacts with the non-aqueous solvent contained in the electrolyte solution to partially inactivate the surface. As a result, when charging / discharging is repeated, lithium deposits in a dendritic (dendritic) or small spherical shape, and further, lithium is separated from the current collector of the negative electrode.

In view of the above, a lithium secondary battery provided with a negative electrode containing a carbonaceous material that absorbs and releases lithium such as coke, a resin fired body, carbon fiber, and pyrolysis vapor-phase carbon has been proposed. ing. The lithium secondary battery including the negative electrode can suppress the reaction between lithium and the non-aqueous electrolyte, and further suppress the dendrite deposition to improve the deterioration of the negative electrode characteristics. However, since the negative electrode has a small amount of lithium ion absorption / desorption, it has a negative electrode specific capacity (mA
When h / g · mA / cm ³ ) is small and the lithium ion storage amount is large, that is, when the charge capacity is large, phenomena such as deterioration of the carbonaceous material structure occur, and charge / discharge performance, cycle efficiency, There was a problem that the life was shortened.

[0007]

An object of the present invention is to provide a lithium ion secondary battery having a high capacity and excellent reversibility of lithium ion storage / release reaction by improving the carbonaceous material constituting the negative electrode. It is what

[0008]

A lithium ion secondary battery according to the present invention is a lithium ion secondary battery comprising a positive electrode, a negative electrode containing a carbonaceous material that absorbs and releases lithium ions, and a non-aqueous electrolyte. In the secondary battery, the carbonaceous material has an average interplanar spacing (d ₀₀₂ ) of 0.355 to 0.0.3, which is directly obtained by the half-width center point method from the peak corresponding to the (002) plane of the graphite structure which appears by X-ray diffraction. 375n
m and a Raman spectrum analysis using an argon laser beam with a wavelength of 514.5 nm, 1500 cm ^-1 to 1
Peak in the range of 700 cm ^-1 - click height strength (IP ₁₎ peak in the vicinity of 1350 cm ^-1 for - the value of the ratio of the click height strength _{(IP 2) (R = IP} 2 / IP 1) is 0.85 or less It is characterized by being.

Another lithium ion secondary battery according to the present invention is a lithium ion secondary battery comprising a positive electrode, a negative electrode containing a carbonaceous material that absorbs and releases lithium ions, and a non-aqueous electrolyte. The material is 3000 ° C in advance
It is characterized by being obtained by acid treatment of powder of coke, spherical carbon body, carbon fiber or carbon black produced by carbonizing at the following temperature.

Hereinafter, a lithium ion secondary battery (for example, a cylindrical lithium ion secondary battery) according to the present invention will be described in detail with reference to FIG. For example, a bottomed cylindrical container 1 made of stainless steel has an insulator 2 arranged at the bottom. The electrode group 3 is housed in the container 1. The electrode group 3 has a structure in which a band-shaped material in which a positive electrode 4, a separator 5 and a negative electrode 6 are laminated in this order is spirally wound so that the negative electrode 6 is located outside. The separator 5 is made of, for example, a synthetic resin non-woven fabric, a polyethylene porous film, or a polypropylene porous film.

An electrolytic solution is contained in the container 1. The insulating paper 7 having a central opening is placed above the electrode group 3 in the container 1. The insulating sealing plate 8 is
The sealing plate 8 is arranged in the upper opening of the container 1 and the vicinity of the upper opening is caulked inward.
Is liquid-tightly fixed to the container 1. The positive electrode terminal 9 is
It is fitted in the center of the insulating sealing plate 8. Positive electrode lead
One end of the battery 10 is connected to the positive electrode 4 and the other end is connected to the positive electrode terminal 9
Respectively connected to. The negative electrode 6 is connected to the container 1, which is a negative electrode terminal, via a negative electrode lead (not shown).

Next, the constitutions of the positive electrode 4, the negative electrode 6 and the non-aqueous electrolyte will be specifically described. 1) Configuration of Positive Electrode 4 The positive electrode 4 is produced, for example, by suspending a conductive agent and a binder in an active material in an appropriate solvent, applying the suspension on a current collector, and drying the suspension to form a thin plate. To be done.

It is preferable that the active material is a metal compound mainly containing at least one metal selected from the group consisting of cobalt, nickel, manganese, vanadium, titanium, molybdenum and iron, and containing lithium. Examples of the metal compound include manganese dioxide, lithium manganese oxide, lithium-containing nickel oxide,
Examples thereof include a lithium-containing cobalt compound, a lithium-containing nickel cobalt oxide, a lithium-containing vanadium oxide, and a lithium-containing chalcogen compound such as titanium disulfide or molybdenum disulfide. Among these metal compounds, lithium cobalt oxide (LiCoO
₂ ), lithium nickel oxide (LiNiO ₂ ), lithium manganese oxide (LiMn ₂ O ₄ , LiMnO ₂ )
Is preferable because a high voltage of 4 V can be obtained.

Examples of the conductive agent include acetylene black, carbon black, graphite and the like. Examples of the binder include polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVD).
E), ethylene-propylene-diene copolymer (EPD
M), styrene-butadiene rubber (SBR) and the like can be used.

The current collector has a thickness of 10 to 10, for example.
It is preferable to use 40 μm aluminum foil, stainless steel foil, nickel foil, or the like. 2) Configuration of Negative Electrode 6 For the negative electrode 6, for example, a carbonaceous material that occludes and releases lithium ions is suspended in a suitable solvent together with a binder, and the suspension is applied to a current collector and dried to form a thin plate. It is produced by In particular, the carbonaceous material is preferably contained in the range of 5 to ²⁰ mg / cm ² in the state where the negative electrode 6 is manufactured.

Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), ethylene-propylene-diene copolymer (EPDM), styrene-butadiene rubber (SBR),
Carboxymethyl cellulose (CMC) or the like can be used.

The current collector has a thickness of 5 to 20, for example.
It is preferable to use copper foil, stainless steel foil, nickel foil or the like having a thickness of μm. As the carbonaceous material, those described below are used.

The carbonaceous material used in the lithium-ion secondary battery comprises a crystallite part composed of several layers of parallel carbon mesh planes.
In addition, from a single mesh plane that does not form parallel layers and unorganized carbon (carbon having an aliphatic chain structure, carbon attached to the periphery of an aromatic, carbon participating in a crosslinked structure between crystallites, etc.) It is composed and is generally called amorphous carbon. As an index that defines the average structure of these amorphous carbons, there is an average interplanar spacing (d ₀₀₂ ) determined from a powder X-ray diffraction spectrum. Here, the defined average interplanar spacing is a value calculated by the half-width midpoint method from the measurement diagram subjected to only the smoothing process and the separation process of the peak spread by the Kα ₂ line. The structure of the carbonaceous material suitable as the negative electrode has an average interplanar spacing (d ₀₀₂ ) of 0.355 to 0.
375 nm. The average surface spacing (d ₀₀₂ ) is 0.3.
The carbonaceous material having a wavelength of 55 to 0.375 nm contributes to the absorption and desorption of lithium ions not only in the crystallite portion but also in the amorphous portion.

The reason why the average interplanar spacing (d ₀₀₂ ) of the carbonaceous material is defined in the above range is as follows. The average surface spacing (d ₀₀₂ ) is 0.355 to 0.37.
If it deviates from the range of 5 nm, the amount of lithium ions stored / released in the carbonaceous material decreases, and the true density further decreases, so that the specific capacity of the secondary battery containing the carbonaceous material decreases.
Further, when the average surface spacing (d ₀₀₂ ) is less than 0.355 nm, the decomposition of the non-aqueous solvent and the charge / discharge rate characteristics deteriorate. More preferable average interplanar spacing (d ₀₀₂ ) of the carbonaceous material
Is in the range of 0.356 to 0.370 nm.

The carbonaceous material has a crystallite length Lc in the c-axis direction of 2 determined by Scherrer's equation from the above measurement diagram.
0 nm or less, more preferably 10 nm or less, further preferably 5 nm or less, most preferably 3 nm or less,
The crystallite length La in the a-axis direction is preferably 50 nm or less, more preferably 20 nm or less, further preferably 10 nm or less, and most preferably 5 nm or less.

Further, as a measure of the abundance ratio of the crystallite and the amorphous material constituting the carbonaceous material, an argon laser (wavelength 5
There is a Raman spectrum of the carbonaceous substance measured using 14.5 nm) as a light source. Raman spectrum measured for the carbonaceous material has a peak derived from the layered structure of the carbon hexagonal plane that appears in the range of 1500～1700Cm ^-1, derived from amorphous or disordered film structure appears in the vicinity of 1350 cm ^-1 There is a peak to do. The carbonaceous material has peak in the range of 1500cm ^-1 ~1700cm ^-1 - 1350cm against click as determined from the height strength (IP ₁₎
The ratio of strength (IP ₂ ) (R = IP ₂ / IP ₁ ) obtained from the peak height near ⁻¹ has a value of 0.85 or less.
The lithium-ion secondary battery including the negative electrode containing such a carbonaceous material has improved charge / discharge efficiency and cycle characteristics.

The ratio of IP ₂ / IP ₁ of the carbonaceous material is 0.
When it exceeds 85, the charging / discharging efficiency and cycle characteristics of the lithium ion secondary battery including the negative electrode containing the carbonaceous material cannot be improved. More preferable IP ₂ / I of the carbonaceous material
The ratio of P ₁ is in the range of 0.5 to 0.85. Further, the carbonaceous material has a true density of 1.8 g / cm ³ or more.
Therefore, the specific capacity of the lithium secondary battery provided with the negative electrode containing such a carbonaceous material is increased.

The carbonaceous material having the above-mentioned characteristics is made of petroleum pitch, coal tar pitch, crude oil-decomposed pitch, organic resin, synthetic polymer and the like as raw materials, and 3000 ° C. or less, preferably 2000 ° C. or less, more preferably 1500 ° C. or less. It is obtained by subjecting a calcined carbonized material such as coke, spherical carbon body, carbon fiber, etc. obtained by calcining at a temperature of 10 to 50% to 200 hours in an aqueous nitric acid solution of 10 to 50%, followed by washing with water and drying. . By performing the oxidation treatment in such a nitric acid aqueous solution, a particularly easily oxidizable portion in the calcined carbonized material, that is, an amorphous portion having a collapsed structure is selectively removed. In addition to the nitric acid aqueous solution, the oxidation treatment may be oxidation with ozone or treatment with a Hummer's reagent (a concentrated sulfuric acid solution of KMnO ₄ ). When the above-mentioned reagent is used, the reaction time is about 1 to 15 hours, but the reaction selectivity is slightly lower than that of an aqueous nitric acid solution.

The absorption / desorption reaction of lithium ions in the amorphous portion is not reversible, and is considered to cause a decrease in charging efficiency and cycle characteristics. However, the carbonaceous material from which the amorphous portion has been removed is Since the secondary battery including the negative electrode containing the carbonaceous material has the above-described specific average interplanar spacing (d ₀₀₂ ) and the ratio of IP ₂ / IP ₁ , the initial charge / discharge efficiency and cycle characteristics are improved.

Further, there is a possibility that an amorphous portion in the calcined carbonized material is selectively removed by the oxidation treatment and at the same time an oxide is generated at the crystallite terminal. For this reason,
500 to 20 in an inert gas or vacuum after oxidation treatment
It is preferable to heat-treat at a temperature of 00 ° C., more preferably 500 to 15000 ° C., and further preferably 500 to 1000 ° C. to remove the surface oxide generated by the oxidation treatment or washing with water. The carbonaceous material obtained by such a treatment has an infrared spectroscopy of 3400 cm ^{−1 to} 3600 c
Around m ^-1 (-OH region) and 600 cm ^{-1 to} 1700
A peak attributed to the oxide functional group on the carbon surface does not appear in cm ^-1 (-CO region), and the content of oxygen atoms by weight element analysis is 3% or less, more preferably 2% or less, based on the total weight. It is more preferably 0.5% or less, and most preferably 0.3% or less. When the content of oxygen atoms by the weight element analysis method exceeds 5% of the whole, not the irreversible capacity due to the amorphous carbon structure but the decomposition of the solvent by the oxide layer on the surface of the carbonaceous material and charge / discharge. The reaction of the lithium ion involved in the reaction becomes remarkable, the action originally possessed by the carbon structure is not exerted, and there is a possibility that the initial cycle charge / discharge efficiency is adversely affected.

Further, the carbonaceous material obtained by the above-mentioned oxidation treatment is excellent in resistance to an acid that does not cause an intercalation reaction because the crystallite portion having a good orientation occupies most of the structure. Moreover, the weight loss is 10% for the reaction time of 150 hours in the oxidation treatment with dilute nitric acid.
Or less, more preferably 5% or less, further preferably 3%
It becomes the following.

3) Structure of Non-Aqueous Electrolyte Solution The non-aqueous electrolyte solution contained in the container 1 is prepared by dissolving an electrolyte in a non-aqueous solvent.

Examples of the non-aqueous solvent include ethylene carbonate, propylene carbonate, butylene carbonate, diethyl carbonate, γ-butyrolactone, sulfolane, acetonitrile, benzonitrile,
At least one selected from 1,2-dimethoxyethane, 1,3-dimethoxypropane, diethyl ether, tetrahydrofuran and 2-methyltetrahydrofuran can be used.

As the electrolyte contained in the non-aqueous electrolyte, for example, lithium perchlorate (LiClO ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium borofluoride (LiBF ₄ ), lithium arsenic hexafluoride ( LiAsF
₆ ), lithium trifluorometasulfonate (LiCF
₃ SO ₃ ), lithium salt (electrolyte) such as bistrifluoromethylsulfonylimide lithium [LiN (CF ₃ SO ₂ ) ₂ ] and the like. Above all, LiPE ₆ and LiB
It is preferable to use F ₄ and LiN (CF ₃ SO ₂ ) ₂ . In particular, LiN (CF ₃ SO ₂ ) ₂ is desirable because it has excellent storage characteristics and cycle performance at high temperatures (60 ° C. or higher). This is because LiN (CF ₃ SO ₂ ) ₂ has low reactivity with the positive electrode active material and has high chemical stability in the non-aqueous solvent. As the electrolyte, for example, a lithium ion conductive solid electrolyte such as a polymer solid electrolyte in which a polymer compound is combined with a lithium salt can be used. The amount of the electrolyte dissolved in the non-aqueous solvent is preferably 0.5 to 1.0 mol / l.

[0030]

EXAMPLES The present invention will now be described in detail with reference to the cylindrical lithium ion secondary battery shown in FIG. Example 1 First, 80% by weight of lithium cobalt oxide powder, 15% by weight of acetylene black and 5% by weight of polytetrafluoroethylene powder were mixed and formed into a sheet, which was then pressure-bonded to an expanded metal as a current collector to form a positive electrode. Was produced.

Further, the mesophase spherules separated by heat treatment from coal tar pitch were placed in an argon stream at 75
It was baked at 0 ° C. for 2 hours. The obtained fired carbonized product is 50
% Aqueous nitric acid solution at a temperature of 50 ° C. for 80 hours, the residue was washed with water, dried and further heat-treated at 600 ° C. for 2 hours in an argon stream to produce a carbonaceous material.

The obtained carbonaceous material had d ₀₀₂ of 0.358 nm, La of 1.3 nm and wavelength of 51 according to powder X-ray diffraction.
4.5nm of Arugonre - in The Raman spectrum analysis using a range of 1500cm ^-1 ~1700cm ^-1 peak - click intensity (IP ₁₎ in the vicinity of 1350 cm ^-1 for peak - the ratio of the click intensity (IP ₂₎ ( R = IP ₂ / IP ₁₎ was 0.8. In addition, the carbonaceous material has a wavelength of around 3500 cm ^-1 (-OH region) and 1700 in infrared spectroscopy.
The peak attributed to the oxide functional group on the carbon surface does not appear in cm ^-1 (-CO region), the oxygen atom content by gravimetric elemental analysis is 0.18% by weight, and the concentration is 15%.
The weight loss after reacting for 150 hours in dilute nitric acid at 5% was 5% by weight or less.

Next, 96.7% by weight of the carbonaceous material was mixed with 2% by weight of an ethylene-propylene copolymer, and this was coated on a stainless steel foil as a current collector in an amount of 10 mg / cm ² , and dried. A negative electrode was produced.

The positive electrode, the separator made of a polypropylene porous film, and the negative electrode were laminated in this order, and then spirally wound so that the negative electrode was located outside, to prepare an electrode group.

Further, lithium hexafluorophosphate (LiPF ₆ ) as an electrolyte was added to a mixed solvent of ethylene carbonate, propylene carbonate and 1,2-dimethoxyethane (mixing volume ratio 25:25:50) A non-aqueous electrolyte was prepared by dissolving 0 mol / l.

The electrode group and the electrolytic solution were respectively housed in a bottomed cylindrical container made of stainless steel to assemble the aforementioned cylindrical lithium ion secondary battery shown in FIG. Example 2 The cylindrical lithium ion secondary battery shown in FIG. 1 was assembled in the same configuration as in Example 1 except that the carbonaceous material shown below was used.

First, mesophen obtained from petroleum pitch
Spitchy carbon fiber was fired at 900 ° C. The resulting calcined carbonized product is reacted with the Hammer's reagent at a temperature of 50 ° C. for 2 hours, the residue is washed with water, dried and further heat-treated at 600 ° C. for 2 hours in an argon stream to obtain carbon. A quality product was manufactured.

The obtained carbonaceous material had d ₀₀₂ of 0.359 nm, La of 1.5 nm, and wavelength of 51 according to powder X-ray diffraction.
4.5nm of Arugonre - in The Raman spectrum analysis using a range of 1500cm ^-1 ~1700cm ^-1 peak - click intensity (IP ₁₎ in the vicinity of 1350 cm ^-1 for peak - the ratio of the click intensity (IP ₂₎ ( R = IP ₂ / IP ₁₎ was 0.82. In addition, the carbonaceous material has an infrared spectroscopy of around 3500 cm ^-1 (-OH region) and 170
A peak attributed to the oxide functional group on the carbon surface did not appear at 0 cm ^-1 (-CO region), and the content of oxygen atoms by gravimetric elemental analysis was 0.08% by weight. Under the same conditions as above, the weight loss in dilute nitric acid was 5% by weight or less, and it had excellent acid resistance.

Example 3 The cylindrical lithium ion secondary battery shown in FIG. 1 was assembled in the same configuration as in Example 1 except that the carbonaceous material shown below was used.

First, the mesophase spherules separated by heat treatment from coal tar pitch were placed in an argon stream at 75
It was baked at 0 ° C. for 2 hours. The obtained fired carbonized product is 50
% Aqueous nitric acid solution at a temperature of 50 ° C. for 80 hours, and the residue was washed with water and dried to produce a carbonaceous material.

The obtained carbonaceous material had d ₀₀₂ of 0.358 nm, La of 1.3 nm and wavelength of 51 according to powder X-ray diffraction.
4.5nm of Arugonre - in The Raman spectrum analysis using a range of 1500cm ^-1 ~1700cm ^-1 peak - click intensity (IP ₁₎ in the vicinity of 1350 cm ^-1 for peak - the ratio of the click intensity (IP ₂₎ ( R = IP ₂ / IP ₁₎ was 0.8. In addition, the carbonaceous material has a wavelength of around 3500 cm ^-1 (-OH region) and 1700 in infrared spectroscopy.
A broad peak attributed to the oxide functional group on the carbon surface was observed in cm ^-1 (-CO region), and the oxygen atom content determined by gravimetric elemental analysis was 5% by weight of the whole.
Furthermore, the weight loss in dilute nitric acid under the same conditions as in Example 1 was 5% by weight or less.

Comparative Example 1 The cylindrical lithium ion secondary battery shown in FIG. 1 was assembled in the same configuration as in Example 1 except that the carbonaceous material shown below was used.

A carbonaceous material was produced by calcining the mesophase spheres separated from the coal tar pitch by heat treatment in an argon stream at 750 ° C. for 2 hours. The obtained carbonaceous material had a d ₀₀₂ of 0.36 by powder X-ray diffraction.
1 in Raman spectrum analysis using argon laser light of 3 nm, La 1.3 nm, wavelength 514.5 nm
Peak in the range of 500cm ^-1 ~1700cm ^-1 - click intensity (I
Peak strength (IP) around 1350 cm ^{-1 with} respect to P ₁ )
The ratio of _{2) (R = IP 2 /} IP 1) was 0.95.
In addition, the carbonaceous material is 3500 cm in infrared spectroscopy.
^-1 (-OH region) and 1700 cm ^-1 (-CO region), peaks attributable to oxide functional groups on the carbon surface did not appear, and the oxygen atom content by gravimetric elemental analysis was 0. Although it was 12% by weight, a weight reduction of 30% by weight was observed when the reaction was carried out in dilute nitric acid under the same conditions as in Example 1.

Comparative Example 2 The cylindrical lithium ion secondary battery shown in FIG. 1 was assembled in the same structure as in Example 1 except that the carbonaceous material shown below was used.

A carbonaceous material was produced by firing mesophase pitch carbon fiber obtained from petroleum pitch at 900 ° C. The obtained carbonaceous material had d ₀₀₂ of 0.361 nm, La of 1.5 nm and wavelength of 51 according to powder X-ray diffraction.
4.5nm of Arugonre - in The Raman spectrum analysis using a range of 1500cm ^-1 ~1700cm ^-1 peak - click intensity (IP ₁₎ in the vicinity of 1350 cm ^-1 for peak - the ratio of the click intensity (IP ₂₎ ( R = IP ₂ / IP ₁₎ was 1.22. In addition, the carbonaceous material has an infrared spectroscopy of around 3500 cm ^-1 (-OH region) and 170
A peak attributed to the oxide functional group on the carbon surface did not appear at 0 cm ^-1 (-CO region), and the oxygen atom content by gravimetric elemental analysis was 0.08% by weight, but When reacted in nitric acid under the same conditions as in Example 1, 20
A weight loss of wt% was seen.

Comparative Example 3 The cylindrical lithium ion secondary battery shown in FIG. 1 was assembled in the same configuration as in Example 1 except that the carbonaceous material shown below was used.

A carbonaceous material was produced by calcining the mesophase spheres separated from the coal tar pitch by heat treatment in air at 750 ° C. for 2 hours. The obtained carbonaceous material had a d ₀₀₂ by powder X-ray diffraction of 0.363 nm,
Ar laser with La of 1.3 nm and wavelength of 514.5 nm
1500c in Raman spectrum analysis using the light
m ^-1 peak in the range of ～1700Cm ^-1 - click intensity (IP ₁₎ in the vicinity of 1350 cm ^-1 for peak - the ratio of the click intensity _{(IP 2) (R = IP} 2 / IP 1) was 1.03 . In addition, the carbonaceous material is 1700 cm ^-1 (-C in infrared spectroscopy.
In the (O region), a peak attributed to the oxide functional group on the carbon surface was observed. Further, the content of oxygen atoms by weight elemental analysis was 5% by weight of the whole, and a weight reduction of 35% by weight was observed when the reaction was carried out in dilute nitric acid under the same conditions as in Example 1.

The obtained Examples 1 to 3 and Comparative Examples 1 to 1
For the lithium-ion secondary battery of No. 3, charging current 150
Charge to 4.2V with mA and 150mA to 2.5V
The initial charging / discharging efficiency of each battery was measured by repeatedly performing charging / discharging for discharging with the current. The result is shown in FIG.

Further, the present Examples 1 to 3 and Comparative Examples 1 to 3
Regarding the lithium ion secondary battery of _{No. 3} , the relationship between the R (IP ₂ / IP ₁ ) value of the carbonaceous material contained in the negative electrode and the charge / discharge efficiency at the second cycle was measured. The result is shown in FIG.

As is clear from FIGS. 2 and 3, the lithium ions of Examples 1 to 3 provided with the negative electrode containing the carbonaceous material having a specific d ₀₀₂ and R (IP ₂ / IP ₁ ) value of 0.85 or less. It can be seen that the secondary batteries have higher initial charge / discharge efficiency than the batteries of Comparative Examples 1 to 3 and excellent reversibility of the lithium ion storage / release reaction by the negative electrode containing the specific carbonaceous material.

In addition, although the example applied to the cylindrical lithium secondary battery has been described in the above embodiment, the present invention can be similarly applied to the rectangular lithium secondary battery. Further, the electrode group housed in the battery container is not limited to the spiral shape, and a plurality of positive electrodes, separators and negative electrodes may be laminated in this order.

[0052]

As described above, according to the present invention, it is possible to provide a lithium ion secondary battery having a high capacity, a high initial charge / discharge efficiency, and an excellent reversibility of the absorption / desorption reaction of lithium ions.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view showing a cylindrical lithium secondary battery according to the present invention.

FIG. 2 is a characteristic diagram showing the relationship between the number of cycles and the charge / discharge efficiency in the lithium ion secondary batteries of Examples 1 to 3 and Comparative Examples 1 to 3 of the present invention.

FIG. 3 is a graph showing the R (IP ₂ / IP ₁ ) value of the carbonaceous material contained in the negative electrode of the lithium ion secondary batteries of Examples 1 to 3 and Comparative Examples 1 to 3 of the present invention, and the charge / discharge efficiency at the second cycle. FIG.

[Explanation of symbols]

1 ... Container, 3 ... Electrode group, 4 ... Positive electrode, 6 ... Negative electrode, 8 ... Sealing plate.

Claims (2)

[Claims] 1. A lithium ion secondary battery comprising a positive electrode, a negative electrode containing a carbonaceous material that absorbs and releases lithium ions, and a non-aqueous electrolyte, wherein the carbonaceous material has a graphite structure that appears by X-ray diffraction. (0
02) Mean spacing obtained from the corresponding peak surface (d ₀₀₂₎ is at 0.355～0.375Nm, and wavelength 514.5nm Arugonre - 1500cm ^-1 ~1700cm in the Raman spectrum analysis using laser light ^{- 1} in the range of Pi - 1350 cm for click height strength (IP ₁₎
Ratio of peak height strength (IP ₂ ) near ^-1 (R = IP ₂ /
IP ₁ ) has a value of 0.85 or less, a lithium ion secondary battery. 2. A lithium ion secondary battery comprising a positive electrode, a negative electrode containing a carbonaceous material that absorbs and releases lithium ions, and a non-aqueous electrolyte, wherein the carbonaceous material is carbon at a temperature of 3000 ° C. or lower in advance. A lithium-ion secondary battery, which is obtained by acid-treating powder of coke, spherical carbon body, carbon fiber or carbon black produced by liquefying.