JP3428428B2 - Negative electrode for non-aqueous electrolyte battery and method for producing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a negative electrode for a non-aqueous electrolyte battery.

[0002]

2. Description of the Related Art Today, lithium metal is used as a negative electrode active material, and LiClO ₄ , LiBF ₄ , LiAs are used in organic solvents such as propylene carbonate, γ-butyrolactone, dimethoxyethane, tetrahydrofuran, and dioxolane.
A non-aqueous electrolyte battery using an electrolytic solution in which a salt such as F ₆ , LiPF ₆ , LiCF ₃ SO ₃ or the like is dissolved has a high energy density, and is therefore a primary battery for small electronic devices such as electronic timepieces and cameras. Used in batteries. It is also expected as a secondary battery for portable devices such as mobile phones, portable personal computers, and video movies.

When this type of non-aqueous electrolyte battery is used as a primary battery, lithium metal has a high chemical reactivity and easily reacts with an electrolytic solution component to form a passivation film on the surface of the negative electrode. The reaction is suppressed and the storage characteristics are good.

[0004]

However, when this is used as a secondary battery, dendritic, acicular, fibril-like lithium metal deposits, so-called dendrites, are remarkably generated on the negative electrode surface during charging. To do. This is because the deposition location of lithium metal ions on the surface of the negative electrode is localized due to the formation of a passive film and the crystallographic and morphological nonuniformity of the reaction surface. Such dendrites are formed during charging, and in the subsequent discharging process, the dendrites are partially dissolved and fragmented. At this time, it becomes impossible to dissolve all the lithium metal deposited during charging,
As a result, there is a problem that the charge / discharge efficiency is significantly reduced. Further, when the dendrite grows without being fragmented, there is a problem that an internal short circuit occurs between the negative electrode and the positive electrode, and the charge / discharge cycle life is shortened.

The present invention is intended to solve such problems, and an object thereof is to provide a highly reliable non-aqueous electrolyte battery which suppresses the generation of dendrites and has a long cycle life.

[0006]

According to the present invention, in a sheet using lithium as an active material, X of a (200) crystal plane obtained with respect to incident X-rays from a direction normal to the surface of the sheet.
The line reflection peak intensity is 50% or more of the total of the reflection peak intensities obtained from the incident X-rays, and a film having a substance of rock salt type crystal structure is arranged on the surface of the sheet. A negative electrode for a water electrolyte battery.

At this time, it is effective that the film having the substance of rock salt type crystal structure has a structure in which 50% or more of specific crystal planes are oriented on the sheet surface.

Further, it is desirable that the orientation plane of the film having the substance of rock salt type crystal structure is the (100) crystal face of the rock salt type crystal structure.

The lattice constant a of the film containing the substance of rock salt type crystal structure is 4.46 <a <5.45.

Further, it is desirable that the lattice constant a of the film containing the substance of rock salt type crystal structure is 4.91 <a <5.01.

Further, it is desirable that the film containing the substance of rock salt type crystal structure contains a halide of lithium.

Further, the lithium halide is Li
It is preferably Cl. In addition, LiCl, LiB
It is useful to have a solid solution of at least one selected from r and LiI and LiF as a film component.

At this time, the solid solution is composed of LiCl and LiF.
A solid solution with is desirable. Further, the negative electrode for a non-aqueous electrolyte battery of the present invention, a sheet using lithium as an active material,
It can be prepared by immersing in an electrolytic solution containing chlorine molecules or chlorine ions.

At this time, it is useful to prepare a solution containing chlorine molecules or chlorine ions by adding an organic solvent in which chlorine gas is blown or by blowing chlorine gas in a solution containing an organic solvent.

Further, the organic solvent is preferably dimethoxyethane. Further, the negative electrode for a non-aqueous electrolyte battery of the present invention comprises a sheet having lithium as an active material, at least one selected from (chlorine molecule, chlorine ion, bromine molecule, bromine ion, iodine molecule, iodine ion), and (fluorine It can be prepared by immersing in an electrolytic solution containing at least one selected from the group consisting of molecules and fluorine ions.

Further, it can be manufactured by immersing a sheet containing lithium as an active material in an electrolytic solution in which LiPF ₆ and LiClO ₄ are dissolved.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION In order to suppress the generation of dendrites of lithium metal, it is desirable to repeatedly carry out energetically uniform deposition and dissolution reaction. For that purpose, the uniformity of the crystal structure of the lithium metal itself, and the uniformity of the surface reaction and the surface coating on the surface where the reaction occurs are required.

As a means for this, a lithium sheet having a uniform structure in which a (100) crystal plane in a body-centered cubic lattice crystal structure is preferentially oriented to the sheet surface is used for a sheet using lithium metal as an active material. A negative electrode having a surface film structure in which a surface film having a rock salt type crystal structure that is formed in good conformity with the atomic arrangement of the surface is formed is used for a non-aqueous electrolyte battery.

When LiCl is formed as a rock salt type crystal substance, a lithium sheet having (100) crystal planes preferentially oriented to the sheet surface is used as an electrolyte containing chlorine molecules or chlorine ions. It is made by immersing in.

Further, as a surface film of a rock salt type crystal substance having a lattice constant similar to the value of 4.96 of the superlattice period on the (100) crystal plane of lithium metal, Li was used.
At least one of Cl, LiBr, LiI and LiF
In order to form a surface film whose solid solution with is a main component of the surface film, a lithium sheet in which (100) crystal planes are preferentially oriented on the sheet surface is used as a chlorine molecule or a chlorine ion, a bromine molecule or a bromine ion. Then, a negative electrode for a non-aqueous electrolyte battery is produced by immersing in an electrolytic solution containing at least one of iodine molecules or iodine ions and fluorine molecules or fluorine ions.

The embodiments of the negative electrode for a non-aqueous electrolyte battery of the present invention will be specifically described below.

Regarding the lithium foil immediately after being obtained, CuKα
When X-ray analysis was performed using X-rays, peaks corresponding to a body-centered cubic crystal structure corresponding to Li metal (No. 150401) of JCPDS card appeared. There were no other peaks, and all showed body-centered cubic lattice type lithium metal.

However, when comparing the X-ray diffraction patterns of several samples, the intensity ratio of each peak is not constant depending on the samples, and even in the same lot of lithium foil, the crystallite orientation state in them varies considerably. Therefore, it was found that some samples had considerably low crystallinity. This is because this lithium foil is manufactured by extrusion molding,
It is considered that the crystallites were disoriented.

According to the JCPDS card (No. 150401), the following seven peaks are observed in the X-ray diffraction pattern of lithium metal as shown in FIG. That is,
110 reflections, 200 reflections, 211 reflections, 220 reflections, 3
The peaks correspond to 10 reflections, 222 reflections, and 321 reflections. Then, the peak intensity ratios thereof are 42.9%, 12.9%, 17.1%, 8.6%, 8.
It is 6%, 1.3% and 8.6%. Considering this peak intensity ratio as a standard, when the peak intensity ratio of 110 reflection peaks is 70% or more and the other reflection peaks are 50% or more, the crystallite in the lithium foil is It can be considered that the crystal planes corresponding to the respective peaks on the X-ray-irradiated plane are oriented in a fairly preferential manner.

The charging and discharging of the battery using lithium metal as the negative electrode corresponds to the precipitation and dissolution reaction of lithium. When considered microscopically, the energy required for the precipitation and dissolution of lithium should be different due to the difference in crystal planes. Therefore, when one crystal plane is preferentially oriented on the surface of the lithium metal that is the substrate, it is considered that the distribution of the energy of precipitation and dissolution of lithium is suppressed and the precipitation-dissolution reaction proceeds uniformly.

However, a surface coating is always formed on the surface of the lithium metal, and the surface coating and the surface reaction are accompanied by the reaction that does not cause a reaction obstacle to the precipitation or dissolution of lithium on the outermost surface. Only then can a homogeneous reaction proceed continuously.

That is, on the surface of a lithium sheet having a uniform crystal structure, a substance that is compatible with the surface atomic arrangement of the lithium sheet becomes a surface film, and the crystal structure is uniform inside the surface film. Is desirable. When charging / discharging cycles are repeated while always maintaining such a structure, a uniform precipitation-dissolution reaction proceeds and dendrite precipitation is suppressed.

Now, referring to FIG. 1, consider the (100) crystal plane of lithium metal. Since lithium metal has a body-centered cubic lattice, the (100) crystal plane has a periodic structure of a lattice in which lithium atoms are located at each vertex of a square. The lattice constant at that time is 3.51. On the other hand, when considering a square of a superlattice having a diagonal of the square as one side, its length is 4.96, which is the square root of 2. The square of this superlattice has a structure in which one lithium atom is located at the center and lithium atoms are present at each vertex. It can be seen that this structure has the same shape as the arrangement of the (100) crystal faces of the face-centered cubic lattice, and corresponds to the position of the alkali metal in the rock salt type crystal structure.

That is, by forming a surface film of a rock salt type crystal structure composed of lithium and halogen on the surface of a lithium sheet having a (100) crystal plane orientation, it is possible for lithium atoms to move from an atom to an ion without causing large atom transfer. It can be seen that the surface film can be formed by changing to.

Therefore, as an embodiment of the present invention, in a sheet using a lithium metal as an active material, the (100) crystal plane in the body-centered cubic lattice crystal structure is preferentially oriented to the sheet surface. In a lithium sheet with a structure,
A negative electrode for a non-aqueous electrolyte battery having a surface film structure formed by forming a surface film mainly composed of a substance having a rock salt type crystal structure which is formed in good conformity with the atomic arrangement on the surface is used. At that time, as the surface film of the rock salt type crystal substance, (1
00) A substance having a structure in which the crystal plane is preferentially oriented with respect to the sheet surface is desirable. Further, the rock salt type crystal substance is preferably a lithium halide.

Further, as another embodiment of the present invention,
In order to form LiCl as a rock salt type crystalline substance,
Electrolyte solution containing chlorine molecules or chlorine ions,
It is produced by immersing a lithium sheet in which the (100) crystal plane is preferentially oriented on the sheet surface. As a method of containing chlorine molecules or chlorine ions in the electrolytic solution at that time, a method of adding an organic solvent in which chlorine gas is blown into the electrolytic solution is desirable. Further, it is desirable to use dimethoxyethane as the chlorine gas-blown organic solvent.

By the way, with respect to the atomic structure of the surface, the misfit relaxation in which a different substance is formed while maintaining the lattice relaxation while maintaining the conformity, the deviation from the surface is 10%.
It is said that it is possible to some extent. That is,
Considering the above-mentioned superlattice period value of 4.96, it is considered that the above state is achieved when the lattice constant a is in the range of 4.46 <a <5.46.

Further, it can be said that when the misfit relaxation is within 1%, almost epitaxial growth has occurred, and there is almost no surface strain. The range of the lattice constant a at that time is 4.91 <a <5.01.
Becomes That is, it would be good if a surface film having a rock-salt type crystal structure and a lattice constant in the above range could be produced.

Considering only the value of the lattice constant, a substance having a rock-salt type crystal structure and a substance having an appropriate lattice constant will form a surface film with good compatibility.
Moreover, the situation is even better if the lithium halide has such a well-matched lattice constant. Now, let's consider a comparison with the above-mentioned lattice constant using a lithium halide as the rock salt type crystal structure material.
The lattice constant of LiCl is 5.14, and that of LiBr is 5.501.
3, LiF is 4.026, and LiI is 6.0. 4.
Considering 96 as the standard, the deviation of LiCl is + 3.6%, L
iBr is + 10.9%, LiF is -18.8%, LiI
Is + 21.0%. That is, in the case of these simple substances, LiCl is applicable within 10%, but LiCl
Br, LiF, and LiI are not applicable.

Therefore, in order to bring it closer to the value of 4.96 of the superlattice period with the halide of lithium, it is necessary to consider a combination of these. For example, since the lattice constant 4.96 exists between LiF and LiCl, if the VEGARD rule regarding the lattice constant is applied, Li
When F is ⅙ and LiCl is a solid solution with a distribution of 5/6, a = 4.9543, and the misfit value is -0.1%, and it is possible to form a highly consistent film. There is a nature. However, as can be seen from the phase diagram, a solid solution of LiF—LiCl cannot be produced by a normal thermal equilibrium process. However, there is a possibility that the above materials can be prepared in the case of reaction in a very limited environment only in the vicinity of the surface where the position of lithium is considerably fixed.

The above idea does not necessarily mean that LiF and LiCl
It is not limited to the combination of.
That is, if LiF shorter than 4.96 is included, Li
The required lattice constant can be obtained by combining with at least one of Cl, LiBr, and LiI.

Therefore, in another embodiment of the present invention, a solid solution of at least one of LiCl, LiBr, and LiI and LiF is a main component as a substance having a rock salt type crystal structure and a controlled lattice constant. In order to form a surface film, a lithium sheet having (100) crystal planes preferentially oriented on the sheet surface is prepared from at least one of chlorine molecule or chlorine ion, bromine molecule or bromine ion, iodine molecule or iodine ion. And a molecule of fluorine or fluorine ions are soaked in an electrolytic solution to prepare a negative electrode for a non-aqueous electrolyte battery.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, all the following processes were performed in argon gas atmosphere.

Example 1 As an active material, a thickness of 10
A lithium foil having a thickness of 0 μm and a width of 22 mm was used. This lithium foil was cut into a square shape having a side of 22 mm, folded into 1/16, and then pressed at a pressure of 250 kg / cm ² for 10 seconds using a steel jig having a mirror-polished surface. The obtained lithium foil was folded again and pressed in the same manner. Then, the operation of pressing the lithium foil as it is for 10 seconds at a pressure of 200 kg / cm ² without folding was repeated twice. That is, the pressing process was performed on the lithium foil four times in total. By performing this operation, the thickness of the lithium foil was about 100 μm, which was the same level as at the beginning.
The surface of the prepared lithium foil had a dull metallic luster, but in comparison with this, the lithium foil subjected to this pressing treatment,
It had a very bright metallic luster surface.

This lithium foil was subjected to X-ray analysis using CuKα rays. The results are shown in Fig. 2. Figure 2
As can be seen from the above, the intensity of the diffraction peak of 200 reflection was very high in the obtained diffraction pattern, and the peak intensity of 200 reflection accounted for about 91% of the sum of the peak intensities of all the obtained diffraction peaks. Such preferential orientation of the 200 reflection peak could be observed over the entire lithium foil subjected to the pressing treatment.

In such a lithium foil, the surface of the lithium foil has a very preferential orientation to the (100) crystal plane. Since the surface has a very bright metallic luster, the surface film seems to be thin.

First, in order to confirm that a film having a rock salt type crystal structure can be formed on the surface of this lithium foil, the following electrolytic solution was prepared and a (100) crystal plane oriented lithium foil was immersed in it. did.

In order to form a LiCl film, it was decided to use an organic solvent in which chlorine gas was blown into a normally used electrolytic solution as the electrolytic solution. First, 100
Chlorine gas flow rate of 10 cc / m in ml of dimethoxyethane
It was blown in for 1 minute to prepare a chlorine gas blown organic solvent. Then, this chlorine gas-blown dimethoxyethane was mixed with ethylene carbonate and diethyl carbonate (volume ratio 1: LiClO _{4 at} a ratio of 1 mol / liter).
The solution dissolved in the mixed solvent of 1) was added at a rate of 5 ml / L.

After dipping the (100) crystal plane oriented lithium foil described above in this electrolyte for 3 days, an X-ray analysis was performed using CuKα rays in order to investigate the structure of the surface.
The results are shown in Fig. 3. As can be seen from FIG. 3, 2θ
It can be seen that a very large diffraction peak of 200 reflection of lithium is observed in the vicinity of 52 °, and a diffraction peak of 110 reflection exists in the vicinity of 2θ of 36 ° with a slight broadening. These peaks are present at the same positions as in FIG.

However, when 2θ is in the vicinity of 35 degrees, as shown in FIG.
A peak that did not exist was observed in J.
According to the CPDS card (number 40664), LiCl
It was found that this corresponds to the diffraction peak of 200 reflections of.
At this time, the surface of the lithium metal was in a state where the degree of gloss of the lithium surface when pressed was almost unchanged by visual observation. That is, it is considered that the surface coating itself is very thin. Nevertheless, the fact that the diffraction peak of 200 reflection could be confirmed means that the surface film itself has a high preferential orientation to the (100) crystal plane in the rock salt type crystal structure. That is, by immersing a (100) crystal plane oriented lithium foil having a body-centered cubic lattice crystal structure in an electrolytic solution containing a chlorine-containing organic solvent, the surface of the (100) crystal plane having a rock salt type crystal structure is preferentially applied. Oriented LiC
It was found that 1 l of the surface coating was formed.

Therefore, 1 mol / mol of (100) crystal plane oriented lithium foil and dimethoxyethane blown with chlorine gas are used.
A flat type non-aqueous electrolyte secondary battery shown in FIG. 4 was produced using an electrolytic solution added at a rate of 5 ml / L to a mixed solvent of liter LiClO ₄ (ethylene carbonate, diethyl carbonate 1). The manufacturing procedure will be described with reference to FIG.

The positive electrode current collector 2 made of expanded metal made of titanium was placed in the positive electrode can 1, and both were spot-welded. A positive electrode mixture containing a mixture of LiCoO ₂ powder, carbon black and polyethylene tetrafluoride powder was filled in a predetermined amount above the positive electrode current collector 2 and pressed to form the positive electrode 3.

A negative electrode 6 made of a disk-shaped lithium foil subjected to the above-mentioned pressing treatment was pressure-bonded to a sealing plate 5 to which a negative electrode current collector 4 made of expanded metal made of nickel was spot-welded in advance.

After arranging the separator 7 made of a polypropylene porous film above the positive electrode 3, the electrolytic solution is injected into the positive electrode can 1, and the sealing plate 5 is opened through the gasket 8 to open the positive electrode can 1. Then, the flat type non-aqueous electrolyte secondary battery was assembled by fitting the parts.

As a comparative example, a similar non-aqueous electrolyte secondary battery was assembled by using the lithium foil that had not been subjected to any treatment as a negative electrode, as it was obtained. Ten such batteries were produced for each of the example and the comparative example.

With respect to these batteries, under the environment of 20 ° C., at the current density of ² mA / cm ² , the discharge lower limit voltage was 2.
A charging / discharging cycle test was performed at 0 V and an upper limit charging voltage of 3.5 V to determine the cycle life. However, the cycle life was defined as the life when the discharge capacity became half of the first cycle, and when an internal short circuit due to a dendrite occurred during the charge / discharge cycle, the cycle life was defined as that cycle.

The results are shown in Table 1. The values of cycle life in the table are average values ± σ.

[0053]

[Table 1]

As shown in Table 1, the battery of Example 1 using (100) crystal plane oriented lithium and an electrolytic solution containing chlorine gas blown in organic solvent was compared with Comparative Example 1 in charge / discharge cycle life. It turns out that is long. Further, it can be seen that the battery of Example 1 has reduced variations as compared with the battery of Comparative Example 1.

This is because the lithium halide (LiCl in this case) having a rock-salt type crystal structure is formed as a surface film of the (100) crystal plane oriented lithium with good compatibility, so that the lithium is electrochemically dissolved. It is considered that this is the result of the charge and discharge cycle being performed very efficiently because the reaction of the precipitation and the deposition proceeded smoothly and the dendrite precipitation and the isolation due to the cleavage of lithium during the dissolution were reduced. Further, it can be seen that the cycle life is improved and the variation is reduced, and the accuracy is improved.

Therefore, a lithium sheet having a (100) crystal plane preferentially oriented and an electrolytic solution containing a chlorine gas blown organic solvent were assembled into a battery to form a LiCl surface coating on the surface of a lithium foil. It can be seen that the charging / discharging is performed by using to increase the charging / discharging cycle life and improve the accuracy.

In this example, LiCl was used as the rock salt type crystal substance of the surface coating, but the same effect can be obtained by forming the surface coating of LiF, LiBr, LiI by the same method. It was

Example 2 Example 1 was used as the active material.
The same lithium foil having a thickness of 100 μm and a width of 22 mm was used. Then, the same pressing process as in Example 1 was performed on this lithium foil. With this pressing process, the first embodiment
Similarly to the above, a preferential orientation of the (100) crystal plane of lithium was observed.

Subsequently, as in Example 1, first, LiF and LiCl having a rock salt type crystal structure were formed on the surface of the lithium foil.
In order to confirm that the solid solution film of (1) can be prepared with matching lattice constants, the following electrolytic solution was prepared, and (1
00) It was decided to immerse the crystal plane oriented lithium foil.

LiPF ₆ and LiClO ₄ were dissolved at a ratio of 1:30 in a mixed solvent of ethylene carbonate and diethyl carbonate (volume ratio 1: 1) at a concentration of 1 mol / liter and used as an electrolytic solution. . In this case, the ratio of the number of fluorine atoms to the number of chlorine atoms is 1: 5. After dipping the (100) crystal plane oriented lithium foil described above in this electrolytic solution for 3 days, the structure of the surface was X-rayed using CuKα rays.
Line analysis was performed. The results are shown in Fig. 5.

As can be seen from FIG. 5, a very large diffraction peak of 200 reflection of lithium was observed near 2θ of 52 °, and a diffraction peak of 110 reflection was broad and present as a small peak near 36 ° of 2θ. You can see that These peaks are present at the same positions as in FIG. However, a peak that did not exist in FIGS. 2 and 3 was observed on the high-angle side in the vicinity of the 110 reflection peak, which could not be confirmed by the JCPDS card, but by the calculation shown below, LiF and LiCl It is presumed that it is the (100) crystal plane of the solid solution.

LiF JCPDS card (number 4085
7) and LiCl JCPDS card (No. 40664)
According to the data, the (200) peak of LiF has a d value of 2.01.
2θ exists at 44.99 degrees in 3 and LiCl (20
It can be seen that the 0) peak has a d value of 2.57 and a 2θ of 34.88 degrees. LiF is 1/6 and LiCl is 5 /
When LiF and LiCl form a solid solution at a ratio of 6, VEG
If the ARD rule is followed, the lattice constant will be 4.9543 and the d value will be half, 2.477, in the (200) crystal plane. At this d value, the wavelength of CuKα ray is 1.5405
The peak of 200 reflection of the solid solution of LiCl and LiF appears at 2θ of 36.23 degrees. In addition, the glossiness of the lithium metal surface at the time of pressing was almost the same as that of Example 1 at the time of pressing. That is, as in the case of Example 1, the surface film is very thin and (100)
It is considered that the preferential orientation to the crystal plane is high.

That is, it was found that LiF and LiCl form a solid solution, and a surface film in which the (100) crystal face of the rock salt type crystal structure is preferentially oriented is formed. Although the crystal structure in this case has not been analyzed in detail, one of the halogens in which the lithium ion exists in the face-centered cubic position of the rock-salt type crystal structure and is surrounded by six coordinations is the F ion. And, it seems that it has a structure in which five are Cl ions. Since the small F ions are evenly present at 1/6 in the large Cl ion radius, the lattice constant becomes smaller on average, and VEGARD
It is considered that the value is in accordance with the rule. Normally, as can be seen from the phase diagram, a solid solution cannot be produced by a process of thermal equilibrium, but it is in a very limited situation that it is only near the surface and depends on the state of the crystal plane of the substrate. It seems that a solid solution of LiCl could be produced.

Therefore, a mixed salt of (100) crystal plane oriented lithium foil and (LiPF ₆ : LiClO ₄ = 1: 30) was added to 1 part.
A flat type non-aqueous electrolyte secondary battery shown in FIG. 4 was produced in the same manner as in Example 1 using a mixed solvent of ethylene carbonate and diethyl carbonate (volume ratio 1: 1) contained at a ratio of mol / liter.

As a comparative example, a similar non-aqueous electrolyte secondary battery was assembled by using a lithium foil which had not been treated and was used as a negative electrode. In this manner, 10 batteries of the example and 10 batteries of the comparative example were produced, and the same charge and discharge test as in example 1 was performed.

The results are shown in Table 2. The values of cycle life in the table are average values ± σ.

[0067]

[Table 2]

From Table 2, an electrolyte solution containing (100) crystallographically oriented lithium and a mixed salt in which the mixing ratio of two salts of LiPF ₆ and LiClO ₄ was 1:30 in the above order was used. It can be seen that the battery of Example 2 thus obtained has a longer charge / discharge cycle life and the variation thereof is reduced as compared with Comparative Example 2.

This is a halide of lithium having a rock salt type crystal structure (in this case, a solid solution of LiF and LiCl).
However, since it has a structure formed in a highly conforming state such that the lattice constant is almost the same as the surface film of (100) crystal plane oriented lithium, the reaction of electrochemical dissolution or precipitation of lithium is smooth. It is considered that this is a result of a very efficient charge / discharge cycle, since dendrite precipitation and isolation due to cleavage of lithium during dissolution were reduced. Further, it can be seen that the cycle life is improved and the variation is reduced, and the accuracy is improved.

It is also understood that the battery of Example 2 has a longer life than the battery of Example 1.
This is because the reaction of precipitation dissolution proceeds more uniformly by using a surface film with almost no deviation in lattice constant,
This is probably because the effect of suppressing the dendrite precipitation was exhibited and the charge / discharge efficiency was improved.

Therefore, a battery was assembled using an electrolytic solution containing a chlorine gas blown organic solvent, and L was formed on the surface of the lithium foil.
It can be seen that the charge and discharge cycle life is extended and the accuracy is improved by performing the charge and discharge using the negative electrode having the iCl surface coating.

Therefore, the (100) crystal plane is preferentially oriented.
Lithium sheet and LiPF ₆And LiClO_FourOf 2
Assemble the battery using the electrolyte containing mixed salt of
Surface coating of solid solution of LiF and LiCl on the surface of thium
Charge and discharge using the prepared negative electrode
We see that cycle life is extended and accuracy is improved.
It

In Examples 1 and 2, LiCoO ₂ was used as the positive electrode, but LCoO ₂ was used as the other positive electrode.
Layered oxides such as iNiO ₂ and LiMnO ₂ , LiMn ₂
Spinel type oxides such as O ₄ ; V type oxides such as V ₂ O ₅ ; T
A material such as iS ₂ may be used.

[0074]

As described above, according to the present invention, a lithium metal active material sheet having a (100) crystal plane preferentially oriented has a rock salt type crystal structure on the surface thereof. By forming a surface film structure containing a substance as a main component, it became possible to carry out a uniform precipitation-dissolution reaction, that is, charge and discharge of the battery. Furthermore, the dendrite deposition reaction of lithium metal, which is an active material, was suppressed, and the effect of improving the cycle life of the battery and improving the accuracy could be obtained.

[Brief description of drawings]

FIG. 1 is a schematic view of a (100) crystal plane of lithium metal for explaining one embodiment of the present invention.

FIG. 2 is an X-ray diffraction diagram of a pressure-treated lithium foil used for a battery negative electrode according to an example of the present invention.

FIG. 3 is an X-ray diffraction diagram of a surface-treated lithium foil used for a battery negative electrode according to an example of the present invention.

FIG. 4 is a vertical cross-sectional view of a flat type non-aqueous electrolyte secondary battery used in an example of one example of the present invention.

FIG. 5 is an X-ray diffraction diagram of a surface-treated lithium foil used for a battery negative electrode according to an example of the present invention.

FIG. 6 is a view showing an intensity ratio of X-ray diffraction of lithium metal shown in a conventional document.

[Explanation of symbols]

1 positive electrode can 2 Positive electrode current collector 3 positive electrode 4 Negative electrode current collector 5 Seal plate 6 lithium foil 7 separator 8 gasket

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toyoguchi ▲ Yoshi ▼ No. 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) Reference JP 10-12218 (JP, A) 7-302617 (JP, A) JP 7-296851 (JP, A) JP 58-142771 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01M 4 / 00-4/04 H01M 4/36-4/62 H01M 10/40

Claims (5)

(57) [Claims] 1. A sheet using lithium as an active material, with respect to incident X-rays from a direction normal to the surface of the sheet.
X-ray reflection of the (200) crystal plane of the lithium obtained
The peak intensity is the reflection peak intensity obtained from the incident X-ray.
50% or more of the sum of the total degrees , and the lithium has a lattice constant a of 4.91 <a <5.01 on the surface of the sheet.
The negative electrode for a non-aqueous electrolyte battery is characterized in that a film having a substance of rock salt type crystal structure in which the (100) crystal plane is oriented by 50% or more is formed. 2. A coating LiCl, LiBr, at least one and, for a nonaqueous electrolyte battery negative electrode according to claim 1, characterized by having a solid solution of LiF selected from LiI. 3. The negative electrode for a non-aqueous electrolyte battery according to claim 2, wherein the solid solution is a solid solution of LiCl and LiF. 4. The non-aqueous electrolyte battery negative electrode according to claim 2 or 3, wherein a sheet containing lithium as an active material is used (chlorine molecule, chlorine ion, bromine molecule, bromine ion, iodine molecule,
A method for producing a negative electrode for a non-aqueous electrolyte battery, which is prepared by immersing in an electrolytic solution containing at least one selected from (iodine ion) and at least one selected from (fluorine molecule, fluorine ion) . 5. The negative electrode for a non-aqueous electrolyte battery according to claim 3, wherein a sheet containing lithium as an active material is used as LiPF ₆ and L.
method for producing a negative electrode for a nonaqueous electrolyte battery you characterized in that to produce by immersion in an electrolyte solution prepared by dissolving and iClO _4.