JP2002184400A - Lithium secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithium secondary battery with high capacity which can estimate the duration of discharge. SOLUTION: The lithium secondary battery comprises a nonaqueous electrolyte containing lithium salt as an electrolytic salt, a positive electrode having lithium-containing metal oxide as an electrolyte, and a negative electrode, using a compound, containing metal element which can be oxidized and deoxidized in the oxide of lithium, and becoming amorphous after an electrochemical treatment by means of preliminary charge and discharge, as an activator, or, the lithium secondary battery comprises a nonaqueous electrolyte containing lithium salt as an electrolytic salt, a positive electrode, using a compound, containing metal element which can be oxidized and deoxidized in the oxide of lithium, and becoming amorphous after an electrochemical treatment by means of preliminary charge and discharge, as an activator, and a negative electrode. It is recommendable to use vanadium as a metal element which can be oxidized and deoxidized, and it is recommendable to make the titanium oxide contain tungsten as an additive, in order to promote the solid solution of the metal element which can be oxidized and deoxidized, into titanium oxide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a lithium secondary battery.

[0002]

2. Description of the Related Art In recent years, with the development of portable electronic devices such as mobile phones and notebook computers and the practical use of electric vehicles, secondary batteries of small size, light weight and high capacity have been required. .

As a battery that meets such demands, a lithium secondary battery has attracted attention and is being studied worldwide. As a negative electrode active material for this lithium secondary battery, a lithium-containing metal oxide such as lithium titanate is used as disclosed in Japanese Patent Application Laid-Open No. 06-275263.

[0004]

However, the capacity of a lithium-containing metal oxide such as lithium titanate, which is a negative electrode active material for a lithium secondary battery, is 150 to 200.
Since the discharge capacity is about mAh / g, it is difficult to expect a higher capacity, and the discharge voltage suddenly drops at the end of discharge, thereby ending the discharge. The problem was that it was difficult.

The present invention solves the above-mentioned problems of the prior art, develops an electrode material having a high capacity and capable of predicting a discharge time, and uses the electrode material as an active material of the electrode to increase the capacity. It is an object of the present invention to provide a lithium secondary battery which has a predictable discharge time.

[0006]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, produced a negative electrode using a compound containing a redox metal element in titanium oxide. Then, in the negative electrode, a non-aqueous electrolyte containing a lithium salt as an electrolyte salt, and a battery system using a positive electrode containing a lithium-containing metal oxide as an active material, the titanium oxide can be redox-reduced into the titanium oxide. By subjecting the compound containing a metal element to electrochemical treatment by pre-charging and discharging, the compound containing a redox metal element in the titanium oxide is doped and dedoped with amorphous lithium ions. It has been found that a high capacity negative electrode active material can be obtained.

That is, for example, a compound containing a redox metal element in the titanium oxide is used as an active material to form a negative electrode, and the negative electrode is used as a non-aqueous system containing a lithium salt as an electrolyte salt. When an electrolytic solution is used in combination with a positive electrode having a lithium-containing metal oxide as an active material and subjected to electrochemical treatment by preliminary charge and discharge, a compound in which lithium ions contain a redox-reducible metal element in the titanium oxide The compound containing a metal element that can be oxidized and reduced in the titanium oxide becomes a negative electrode active material having high electrochemical reversibility, and since it becomes amorphous, lithium ions enter and exit. It is considered that the discharge capacity is easily increased to the inside of the structure, and the discharge capacity is increased and the capacity is increased as is clear from the data of the examples described later. That.

Further, a compound containing a redox metal element in the titanium oxide is used to prepare a positive electrode, and a non-aqueous electrolytic solution containing a lithium salt as an electrolyte salt is mixed with a carbon material, for example. When used in combination with a negative electrode having an active material as the active material and subjected to electrochemical treatment by preliminary charge and discharge, lithium ions are incorporated into the titanium oxide in the compound containing a redox-reducible metal element in the same manner as described above. The compound containing a redox metal element in the titanium oxide becomes a positive electrode active material having high electrochemical reversibility and becomes amorphous. It is thought that the capacity will be higher than that performed easily.

As described above, the compound containing a redox-reducible metal element in the titanium oxide is subjected to electrochemical treatment by preliminary charging and discharging, for example, at 300 mA / g.
h, which is an active material having a large capacity per unit weight, and using it as a negative electrode active material or a positive electrode active material, a high capacity lithium secondary battery can be obtained. In addition, the discharge voltage of the compound containing a redox metal element in the titanium oxide gradually decreases in the discharge after the electrochemical treatment by the preliminary charge and discharge, so that the discharge time can be predicted. Become. Therefore, the above-mentioned problem of providing a lithium secondary battery having a high capacity and a predictable discharge time can be solved.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION In the case where a compound containing an oxidation-reduction metal element in the above-mentioned titanium oxide and becoming amorphous by electrochemical treatment by preliminary charge and discharge is used as a negative electrode active material,
As a positive electrode active material constituting the counter electrode, for example, L
lithium cobalt oxide such as iCoO ₂ , LiNiO
_2, a lithium manganese oxide such as LiMn ₂ O ₄ is preferably used, and further, a general formula LiA _x B _1-x O ₂ (where A and B are
A different element selected from the group consisting of Ti, V, Cr, Mn, Fe, CO, Ni, Cu and Al, x =
The lithium-containing metal oxide represented by 0.1 to 1) is used as a more preferable positive electrode active material.

Examples of the redox-reducible metal element contained in the titanium oxide include vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), and nickel (Ni). , Copper (Cu) or the like is used. Particularly, when vanadium is used, an electrode material having a large capacity can be obtained. The content of the redox-reducible metal element is preferably 5 to 50 mol% based on the total amount of the titanium oxide and the redox-reducible metal element. By setting the content of the redox-reducable metal element in the above range, it is possible to secure the ease of entry of the redox-reducable metal element into the titanium lattice while achieving high capacity. As the content of the redox-reducible metal element increases, the capacity also increases. However, if the content exceeds 50 mol%, the production difficulty tends to increase. 10 to 5 as the content of the metal element
0 mol% is particularly preferred. The redox metal element need not be one kind, and plural kinds of redox metal elements may be contained in the titanium oxide.
Further, in the titanium oxide, it is preferable to include, for example, tungsten or the like as an additive for promoting the solid solution of the redox-reducible metal element in the titanium oxide, and the content is preferably When the total molar ratio of titanium, a redox-reducible metal element, and a solid solution promoting additive such as tungsten in titanium oxide is 1, the molar ratio of the solid solution promoting additive such as tungsten is 0. .33-0.
It is preferably 5.

As described above, a compound containing a redox metal element in a titanium oxide becomes amorphous after electrochemical treatment by preliminary charge and discharge.
This means that the line diffraction image does not show a broad and clear crystal structure.

In the present invention, the compound containing a redox metal element in the titanium oxide is, for example, a solution containing a titanium alkoxide, a vanadium salt and a tungsten salt (for example, an ethylene glycol-nitric acid solution) is dried. By firing, it can be obtained in the form of fine particles. Further, besides the solution method as exemplified above, a coprecipitation method,
Other wet methods, such as a sol-gel method, can be employed.

Lithium ions are introduced into the compound containing a redox metal element in the titanium oxide,
In addition, the electrochemical treatment by pre-charging and discharging for making amorphous is performed, for example, at a discharge current value of 0.1 mA / cm ^{2 and} a discharge current value of 0.5 mA.
The discharge is performed by repeating the discharge at the termination of V and then the charging at the termination of 3.5 V at a charge current value of 0.1 mA / cm ² for three cycles or more. That is, by repeating the charge and discharge for 3 cycles or more, introduction of lithium ions to the compound containing a redox metal element in the titanium oxide and amorphization of the compound occur, and the charge and discharge are performed. 10
Even if the cycle is repeated about a cycle, a large decrease in capacity does not occur.

In order to obtain a compound containing a redox metal element in the titanium oxide in the form of fine particles, a titanium salt or chelate can be used in place of the titanium alkoxide as exemplified above. Further, instead of the vanadium salt or the tungsten salt, an alkoxide or chelate of vanadium or tungsten can be used. Here, as the salt of titanium, for example, titanium sulfate can be mentioned, as the alkoxide of titanium, for example, tetraisopropoxytitanium can be mentioned, and as the chelate of titanium, for example, acetylacetochelate of titanium can be mentioned. Examples of vanadium salts include triisopropoxyvanadyl, and examples of vanadium chelates include vanadium acetylacetochelate. Examples of tungsten salts include ammonium tungstate and tungsten chloride. Examples of tungsten alkoxides include pentaisopropoxytungsten. Examples of tungsten chelates include tungsten acetylacetochelate.

Furthermore, when synthesizing a compound containing a redox metal element in titanium oxide, the valence of the metal element is controlled [for example, when the metal element is titanium oxide (TiO 2)].
_In order to control the valence of the metal element to 4) to make it easy to enter into the lattice of ₂ ), it is preferable to perform firing in an inert atmosphere or a reducing atmosphere.

In the present invention, in order to produce a negative electrode using a compound containing a redox metal element in the titanium oxide, for example, a redox metal element is contained in the titanium oxide. If necessary, a negative electrode mixture is prepared by adding and mixing a conductive auxiliary agent, a binder, and the like to the compound, and the negative electrode mixture is subjected to pressure molding (or pressure molding together with the base, if necessary). Or a negative electrode mixture is dispersed in a solvent to prepare a negative electrode mixture-containing paste (in this case, when forming a negative electrode mixture-containing paste, the binder is dissolved in a solvent in advance and then the compound is mixed). The paste may be mixed with a negative electrode mixture-containing paste, applied to a substrate, dried to form a negative electrode mixture layer, and subjected to pressure molding as necessary. However, the method for manufacturing the negative electrode is not limited to the above-described example, and another method may be used.

In the preparation of the negative electrode, examples of the conductive auxiliary agent include carbon black such as acetylene black, electron conductive carbon powder such as natural graphite, artificial graphite and Ketjen black, as well as carbon fiber, metal powder and metal. Fiber or the like can be used.

As the binder, for example, a fluorine-based resin such as polytetrafluoroethylene and polyvinylidene fluoride can be used. As the base, for example, a metal mesh such as aluminum, stainless steel, titanium, and copper, punched metal, expanded metal, foam metal, foil, and the like can be used.

In the present invention, as the non-aqueous electrolyte, an organic solvent-based electrolyte obtained by dissolving an electrolyte salt such as a lithium salt in an organic solvent is mainly used. The solvent of the electrolytic solution is not particularly limited, for example,
1,2-dimethoxyethane, 1,2-diethoxyethane, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, ethyl acetate, methyl propionate, tetrahydrofuran, 2-methyl -Tetrahydrofuran, dimethyl ether, diethyl ether, 1,3-dioxolan, 4-methyl-1,3-dioxolan, ethylene glycol sulfite, etc. are used alone or as a mixture of two or more.

In preparing an electrolytic solution, as an electrolyte salt
Is, for example, LiClO_Four, LiPF ₆, LiBF_Four,
LiAsF₆, LiSbF₆, LiCF_ThreeSO_Three, Li
C_FourF ₉SO_Three, LiCF_ThreeCO_Two, Li_TwoC_TwoF
_Four(SO_Three)_Two, LiN (CF_ThreeSO_Two)_Two, LiC
(CF_ThreeSO_Two)_Three, LiC_nF_{2n + 1}SO_Three(N ≧ 2)
And the like, alone or as a mixture of two or more.
Used especially for LiPF ₆And LiC_FourF₉SO_Three
Are preferred. The concentration of the electrolyte salt in the electrolyte is
Although not particularly limited, 0.3 mol / l or more
Is preferable, and 0.4 mol / l or more is more preferable.
In addition, 1.7 mol / l or less is preferable, and 1.5 mol / l
1 or less is more preferable. In the present invention, in the electrolytic solution
Lithium salt must be contained as electrolyte salt.
However, if only lithium salt is contained in the electrolyte,
May be contained. In addition, the above electrolyte
Is gelled using a gelling agent to form a gel electrolyte.
May be used.

In the present invention, it is preferable that the separator has sufficient strength and can hold a large amount of electrolyte. From such a viewpoint, polypropylene having a thickness of 10 to 50 μm and a porosity of 30 to 70% is preferable. , A microporous film or nonwoven fabric made of polyethylene or a copolymer of ethylene and propylene is preferred.

In the case where a compound containing a redox metal element in the titanium oxide and becoming amorphous after electrochemical treatment by preliminary charge and discharge is used as a positive electrode active material,
As the active material of the negative electrode constituting the counter electrode, for example, lithium, lithium alloy or graphite, pyrolytic carbons, cokes, glassy carbons, fired bodies of organic polymer compounds,
Carbon materials such as mesocarbon microbeads, carbon fiber, and activated carbon are used. Then, in order to prepare a positive electrode using a compound containing a redox metal element in the titanium oxide and becoming amorphous after electrochemical treatment by preliminary charge and discharge as a positive electrode active material, the negative electrode is prepared. This can be performed in substantially the same manner as in the case of For example, the same conductive assistants and binders as in the case of the negative electrode can be used.Also, when pressing the positive electrode mixture or applying the positive electrode mixture-containing paste to the substrate, drying, etc. In producing the negative electrode, the same means as pressure molding of the negative electrode mixture, application of the negative electrode mixture-containing paste to the substrate, and drying can be employed.

[0024]

Embodiments of the present invention will be described below. However, the following embodiments are merely examples for carrying out the present invention, and do not limit the present invention.

Example 1 Ethylene glycol and nitric acid (nitrate having a concentration of 16 mol / l)
Acid) at a volume ratio of 9: 1.
Respectively, using a titanium compound [TiO (C _TwoH_Five)
_Four] And a tungsten compound [5 (NH_Four) O ・
12 WO_Three・ 5H_TwoO] solution and a vanadium compound
(NH_ThreeVO_Four) Was prepared. Preparation of the above solution
Use nitric acid only for ethylene glycol
When used as a solvent, the tungsten compound and
Nitric acid mixed with solvent because it does not dissolve with Na compounds
This is to increase the solubility by doing so. The above solution
The liquid is charged with titanium, tungsten and vanadium.
Ratio (molar ratio, the same applies to the following composition ratio) is T
i: W: V = 5: 5: 5, titanium, tungsten and
The total concentration of the three components, including Na, is 0.1 mol
/ L and mix the solution at 200 ° C for 12 hours.
Evaporate to dryness to obtain a powder.

Next, the evaporated and dried powder thus obtained was calcined at 700 ° C. for 30 minutes in an inert atmosphere of argon. The calcined powder thus obtained contains vanadium as a redox-reducible metal element in titanium oxide, and contains tungsten as an additive that promotes the solid solution of vanadium in titanium oxide. It is configured.

Next, the calcined powder, an aqueous dispersion of acetylene black as a conductive additive, and an aqueous dispersion of polytetrafluoroethylene as a binder were adjusted to have a solid content of 79: 10: 1 by weight. After mixing to prepare a negative electrode mixture-containing paste, the obtained negative electrode mixture-containing paste is applied to a substrate made of a platinum net, dried to form a negative electrode mixture layer, and then pressed and molded by a press to form a negative electrode mixture. Was prepared.

On the other hand, the positive electrode was manufactured as follows using LiCoO ₂ as an active material. That is, LiCo
Scaly graphite is added to O ₂ as a conductive additive in a ratio of 100: 6 by weight and mixed, and the obtained mixture is prepared by previously dissolving polyvinylidene fluoride in N-methyl-2-pyrrolidone. Mix with the solution
A paste containing the positive electrode mixture was prepared. The obtained positive electrode mixture-containing paste was applied to a substrate made of aluminum foil, dried to form a positive electrode mixture layer, and then press-molded with a press to produce a positive electrode.

As the electrolytic solution, 1 mol / l of LiPF ₆ dissolved in propylene carbonate was used, and a model cell was assembled by attaching aluminum leads to the negative electrode and the positive electrode.

With respect to this model cell, 0.1 mA / c
0.5 V discharge at m ² discharge current value, then 0.1
Charging at 3.5 V was repeated for 3 cycles at a charging current value of mA / cm ² , which was used as an electrochemical treatment by pre-charging and discharging.

The structural analysis of the negative electrode active material after the electrochemical treatment by the preliminary charge and discharge was performed by X-ray diffraction. The figure shows the results together with the X-ray diffraction results of the fired powder (that is, the fired powder in the state of being a source of the above-mentioned negative electrode active material and not being subjected to electrochemical treatment by negative electrode conversion or preliminary charge and discharge). It is shown in FIG.

As shown in FIG. 1, the X-ray diffraction image of the fired powder (in FIG. 1, the X-ray diffraction image shown on the upper side is the X-ray diffraction image of the fired powder) , About 25 °, about 36 °, and about 52 °, indicating that the powder after calcination is crystalline. The X-ray diffraction image of the negative electrode active material after that (in FIG. 1, the X-ray diffraction image shown on the lower side is the X-ray diffraction image of the negative electrode active material after electrochemical treatment by preliminary charge and discharge) In addition, there was substantially no peak other than the peak of the platinum substrate (consisting of a platinum network), indicating that the negative electrode active material after the electrochemical treatment by preliminary charge and discharge was amorphous.

Comparative Example 1 A model cell was prepared in the same manner as in Example 1, except that lithium titanate oxide (Li _1.33 Ti _1.66 O ₂ ) was used as the negative electrode active material instead of the negative electrode active material of Example 1. Produced.

Next, charge and discharge tests were performed on the model cells of Example 1 and Comparative Example 1. The conditions of this charge / discharge test were as follows: at 25 ° C., a charge / discharge current value of 0.1 mA;
The charge end voltage was 3.5 V and the discharge end voltage was 0.5 V.
After repeating this charge / discharge cycle 10 times, the capacity was measured. Table 1 shows the results.

[0035]

[Table 1]

As shown in Table 1, the model cell of Example 1 has a larger capacity and a higher capacity lithium secondary battery than the model cell of Comparative Example 1 using lithium titanate oxide as the negative electrode active material. This indicated that a battery could be obtained.

In the first embodiment, the characteristics are shown in the model cell. However, the lithium secondary battery of the present invention has the effect of having a high capacity and a predictable discharge time even in a mounted battery. Things. To show an example when the lithium secondary battery of the present invention is a mounted battery, for example,
The structure is as shown in FIG. In FIG. 2, 1 is the positive electrode, 2 is the negative electrode, and these positive electrodes 1
A separator 3 made of a polypropylene non-woven fabric is disposed between the anode and the negative electrode 2. However, in FIG. 2, in order to avoid complication, the aluminum foil and the platinum net used as the base in the production of the positive electrode 1 and the negative electrode 2 are not shown, and the positive electrode 1 and the negative electrode 2 are shown as having a single structure. I have. The positive electrode 1, the negative electrode 2, the separator 3, and the electrolytic solution are sealed in a space formed by a stainless steel positive electrode can 4, a stainless steel negative electrode can 5, and a polypropylene insulating packing 6. However, FIG. 2 shows only an example of the structure of the lithium secondary battery, and the present invention is applicable not only to the coin-shaped battery described above but also to any battery such as a cylindrical or rectangular battery. Is what you can do.

Example 2 In Example 2, an example in which a compound containing a redox metal element in titanium oxide and becoming amorphous after electrochemical treatment by preliminary charging and discharging is used for a positive electrode will be described. .

Ethylene glycol and nitric acid (concentration: 16 m
ol / l nitric acid) at a volume ratio of 9: 1.
Each of the titanium compounds [TiO 2
(C _TwoH_Five)_Four] And a tungsten compound [5
(NH_Four) O ・ 12WO_Three・ 5H_TwoO] solution and banana
Indium compound (NH_ThreeVO_Four) Was prepared. So
Then, the above solution is mixed with titanium (Ti) and tungsten
(W) and vanadium (V) charge composition ratio (molar ratio)
Ti: W: V = 5: 5: 5, titanium and tungsten
The total concentration of the three components including vanadium is 0.1mo
1 / l, and the resulting mixed solution is 200
Evaporated to dryness at 12 ° C. for 12 hours to obtain a powder.

Next, the above-mentioned evaporated and dried powder was fired at 700 ° C. for 30 minutes in an inert atmosphere of argon. The calcined powder thus obtained contains vanadium as a redox-reducible metal element in titanium oxide, and contains tungsten as an additive that promotes the solid solution of vanadium in titanium oxide. It is configured.

Next, the above-mentioned calcined powder, acetylene black as a conductive additive, and an aqueous dispersion of polytetrafluoroethylene as a binder are each in a weight ratio of 79: 10: 1 in terms of solid content. To prepare a positive electrode mixture-containing paste, apply the obtained positive electrode mixture-containing paste on a platinum net, dry to form a positive electrode mixture layer, and press-mold with a press to form a positive electrode. Produced.

An aluminum lead was attached to the positive electrode, metallic lithium was used as a counter electrode, and LiPF ₆ was added to propylene carbonate in an amount of 1.0 m in the same manner as in Example 1 for the electrolytic solution.
ol / l was dissolved, a model cell was assembled, and the model cell was discharged at a discharge current value of 0.1 mA / cm ² at 0.5 V termination and a charge current value of 0.1 mA / cm ^2. The charge at 3.5 V termination was repeated for three cycles, and the discharge capacity at the third cycle was measured.
mAh / g, and the average voltage during discharge was 1.5 V.

FIG. 3 shows the charge / discharge characteristics of the positive electrode during the above charge / discharge. In FIG. 3, the horizontal axis represents the capacity (mAh), and the vertical axis represents the positive electrode potential with respect to lithium. In FIG. 3, this is simply represented by “positive electrode potential (V)”. As shown in FIG. 3, the initial cycle (that is, the first cycle)
The positive electrode has poor charge / discharge capacity and poor reversibility because the charge capacity and discharge capacity are not equal, and the polarization is large.However, as the number of cycles increases, the charge capacity and discharge capacity become equal, the electrochemical reversibility increases, and the polarization decreases. You can see that it goes. This is because the structure of the initial positive electrode active material is crystalline, and it is difficult to charge and discharge because the structure does not contain lithium ions.
It is considered that the electrochemical treatment by pre-charging and discharging changes the structure to amorphous, facilitates the entrance and exit of lithium ions, reduces polarization, and improves electrochemical reversibility. .

Further, as is apparent from the discharge curve at the third cycle in FIG. 3, since the voltage of the amorphous positive electrode of Example 2 gradually decreases during discharge, it is necessary to predict the discharge time. It can be seen that is possible.

In the first embodiment, LiCoO ₂ was used as the lithium-containing metal oxide as the positive electrode active material. Instead, LiNiO ₂ , LiMn ₂ O ₄ , or the general formula LiA _x B _{1 -x} O ₂ (where A and B are
A different element selected from the group consisting of Ti, V, Cr, Mn, Fe, CO, Ni, Co and Al, x =
Similar results are obtained when the lithium-containing metal oxides represented by 0.1 to 1) are used. Of course, the same result can be obtained by using an electrolytic solution other than those described above.

[0046]

As described above, according to the present invention,
A lithium secondary battery having a high capacity and a predictable discharge time can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing an X-ray diffraction image of a negative electrode active material of Example 1 and a fired powder before electrochemical treatment by preliminary charging and discharging thereof.

FIG. 2 is a partial cross-sectional view showing one example of a lithium secondary battery according to the present invention.

FIG. 3 is a diagram showing charge / discharge characteristics of a positive electrode in a third charge / discharge cycle of the battery of Example 2.

[Explanation of symbols]

 1 positive electrode 2 negative electrode 3 separator

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Ryu Nagai 1-88 Ushitora, Ibaraki-shi, Osaka Prefecture F-term within Hitachi Maxell, Ltd. 5H029 AJ03 AK02 AK03 AL02 AL03 AL06 AL07 AL08 AL12 AL16 AM03 AM04 AM05 AM07 BJ03 BJ12 CJ14 CJ16 CJ28 DJ18 5H050 AA08 BA16 BA17 CA02 CA07 CA08 CA09 CB02 CB03 CB07 CB08 CB09 CB12 FA02 FA19 GA15 GA18 GA27

Claims (4)

[Claims] 1. A non-aqueous electrolytic solution containing a lithium salt as an electrolyte salt, a positive electrode containing a lithium-containing metal oxide as an active material, and a preliminary charge and discharge containing a redox metal element in titanium oxide A lithium secondary battery comprising a negative electrode containing, as an active material, a compound that becomes amorphous after electrochemical treatment of the lithium secondary battery. 2. A non-aqueous electrolytic solution containing a lithium salt as an electrolyte salt and a compound containing a redox metal element in titanium oxide and becoming amorphous after electrochemical treatment by preliminary charge and discharge. A lithium secondary battery having a positive electrode as a substance and a negative electrode. 3. The lithium secondary battery according to claim 1, wherein the redox-reducible metal element is vanadium. 4. The lithium secondary battery according to claim 1, further comprising tungsten as an additive for promoting the solid solution of a redox metal element in the titanium oxide.