JP4086653B2 - Lithium battery and manufacturing method thereof - Google Patents

Description

【００６７】
表１に示すように、負極材料として黒鉛（Ｃ）を用いた比較例１〜比較例３の電池では、初期放電効率がいずれも０％であった。これに対し、電池組み立て時の負極材料としてアルミニウム（Ａｌ）またはリチウム−アルミニウム合金（Ｌｉ−Ａｌ）を用いた実施例１ａ〜実施例３ｂの電池では、３０％〜６０％の初期放電効率であった。
【００６８】
また、表１に示すように、電池組み立て時の負極材料がアルミニウム（Ａｌ）である実施例１ａ、実施例２ａ、実施例３ａの電池では、初期充放電効率が５０％〜６０％であった。これに対し、電池組み立て時における負極材料がリチウム−アルミニウム合金（Ｌｉ−Ａｌ）である実施例１ｂ、実施例２ｂ、実施例３ｂの電池のそれは、３０％〜４０％であった。
【００６９】
このことから、結晶構造が逆ホタル石型であるリチウム含有多価金属酸化物を正極活物質として用いた電池では、電池組み立て時の負極材料として、アルミニウム（Ａｌ）などの、リチウムを吸蔵できる非リチウム金属を使用することにより、特に優れた充放電特性が得られることがわかった。
【００７０】
これに対し、一般的な正極活物質（ＬｉＭｎＯ₂）を用い、かつ電池組み立て時における負極材料をアルミニウムとした比較例４の電池では、初期充電容量が０．０２ｍＡｈであり、初期充放電効率が０％であった。
【００７１】
これらのことから、一般的な正極活物質（ＬｉＭｎＯ₂）を正極活物質とした場合においては、電池組み立て時の負極材料をアルミニウム（Ａｌ）とすると、顕著に低い初期充放電特性しか得られないことがわかった。
【００７２】
さらに、結晶構造が逆ホタル石型であるリチウム含有多価金属酸化物である、Ｌｉ₆ＣｏＯ₄ 、Ｌｉ₅ＦｅＯ₄、Ｌｉ₆ＭｎＯ₄からなる群では、電池組み立て時の負極材料がアルミニウム（Ａｌ）、リチウム−アルミニウム合金（Ｌｉ−Ａｌ）のどちらであっても、Ｌｉ₆ＣｏＯ₄を含む正極活物質の使用により一層優れた充放電特性が得られることがわかった。
【００７３】
なお、負極材料として黒鉛を用いた比較例１〜比較例３において、初期放電効率が０％となったのは、対極リチウム基準でのアルミニウムの電位が約０．３Ｖであるのに対し、黒鉛のそれは約０．１５Ｖと低いため、電池電圧３Ｖでの充電であると、正極の充電深度が浅くなるためと考えられる。
【００７４】
また、電池組み立て当初からリチウムアルミニウム合金を用いた実施例１ｂ、実施例２ｂ、実施例３ｂよりも、電池内でアルミニウムとリチウムとを合金化した実施例１ａ、実施例２ａ、実施例３ａの方が高い初期充放電効率を示したのは、電池内で非リチウム金属の合金化を行うと、充放電に好都合な性状のリチウム合金が得られるが、電池外で金属板を重ね合わせる手段により合金化を行うと、表面に亀裂が生じる等して、電池内でのような好適な性状の合金が得られないためであると考えられる。
【００７５】
（その他の事項）
本明細書でいう電池外装体とは、発電要素を密封する要素を意味しており、上記実施の形態においては負極缶４と正極缶５とがパッキング８を介在させて組み合わされたものが電池外装体に相当する。
【００７６】
本明細書でいう金属系負極活物質とは、リチウムと合金化し得る非リチウム金属また非リチウム合金、またはリチウム合金を意味しており、リチウムと合金化し得る金属としては、アルミニウム（Ａｌ）、すず（Ｓｎ）、インジウム（Ｉｎ）、亜鉛（Ｚｎ）、鉛（Ｐｂ）、ガリウム（Ｇａ）、マグネシウム（Ｍｇ）、カリウム（Ｋ）、ナトリウム（Ｎａ）、カルシウム（Ｃａ）、ストロンチウム（Ｓｒ）、シリコン（Ｓｉ）、カドミウム（Ｃｄ）ビスマス（Ｂｉ）、バリウム（Ｂａ）等が例示できる。
【００７７】
本発明においては、電池組み立て部材としてリチウムと合金化し得る物質層とリチウムと合金化しない物質層とを含むクラッド材からなる負極缶（負極を兼ねる負極缶）を用いることができ、この方法によると、初期充放電特性に優れたリチウム電池を作業性よく製造することができる。ここで、リチウムと合金化しない物質層としては、例えばステンレス鋼、チタン（Ｔｉ）、ニッケル（Ｎｉ）、クロム（Ｃｒ）、銅（Ｃｕ）、鉄（Ｆｅ）、銀（Ａｇ）、金（Ａｕ）、タングステン（Ｗ）、白金（Ｐｔ）、モリブデン（Ｍｏ）等からなる層があげられる。
【００７８】
【発明の効果】
以上説明したように、本発明によると、正極活物質として、結晶構造が逆ホタル石型であるリチウム含有多価金属酸化物を用い、負極活物質として金属系活物質用いるが、この構成であると、初期充放電容量の大きいリチウム電池、特に２〜３Ｖで好適に充放電することのできる電池容量の大きなリチウム電池を実現することができる。このような本発明にかかるリチウム電池は、例えばＣＭＯＳやＳ−ＲＡＭ等の必要な保持電圧を単一の電池で賄えるので、電子機器用のメモリバックアップ電源として有用である。
【００７９】
また、負極材料としてリチウム金属やリチウム合金を用いないで、リチウム合金を負極活物質とするリチウム電池を製造することのできる本発明製造方法によると、電池の製造作業を通常の環境下で行うことができ、しかも素電池に対して行う充電操作により好適なリチウム合金負極を作製できる。よって、本発明製造方法によると、初期放電容量が大きく、サイクル特性に優れたリチウム電池を低コストでもって提供することができる。
【図面の簡単な説明】
【図１】本発明の一例である扁平形リチウム電池の矢状断面の模式図である。
【図２】本発明で用いるリチウム含有多価金属酸化物が有する逆ホタル石型結晶構造の模式図である。
【符号の説明】
１：負極
２：正極
３：セパレータ
４：負極缶
５：正極缶
６：負極集電体
７：正極集電体
８：絶縁パッキング
９：リチウムサイト
１０：四面体サイト[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a lithium battery using a metal-based active material for a negative electrode, and more particularly to improvement of its initial discharge characteristics.
[0002]
[Prior art]
A lithium battery including a positive electrode capable of occluding lithium, a negative electrode made of lithium metal or a lithium alloy, and a non-aqueous electrolyte is expected as a battery having a high electromotive force and a large capacity. However, since lithium is extremely reactive, the manufacture of this type of battery requires special considerations in terms of safety and quality, especially lithium metal in dry rooms that are highly dehumidified. It is necessary to handle in special facilities such as. For this reason, when metallic lithium is used, although the battery capacity can be increased, the manufacturing cost is increased, and the finished battery also has problems such as an internal short circuit caused by acicular metallic lithium deposition.
[0003]
On the other hand, a so-called lithium ion battery using a lithium composite oxide as a positive electrode active material and a carbon material as a negative electrode active material is superior in safety to the above battery and has an electromotive force of about 4 V compared to a non-lithium battery. It is characterized by high energy density. However, even such a lithium ion battery still has problems, and battery performance cannot be sufficiently obtained. This is because a part of lithium is irreversibly taken into the carbon material at the time of charging and cannot contribute to power generation, or the crystal structure of the lithium composite oxide is broken by the detachment of lithium.
[0004]
The following Patent Documents 1 to 3 have been proposed as techniques for preventing a decrease in battery capacity due to such a cause. For example, Document 1 proposes a technique in which an inverted fluorite-type lithium-containing compound having a lower potential than the positive electrode active material and a capacity density higher than that of the positive electrode active material is contained in the positive electrode. This technique is intended to increase the battery capacity by adding the above-mentioned reverse fluorite-type lithium-containing compound to the positive electrode as an auxiliary material and supplementing lithium taken into the carbon negative electrode. Therefore, in this technique, it is necessary to properly balance the blending amount of the positive electrode active material and the auxiliary fluorite-type lithium-containing compound as an auxiliary material. Therefore, naturally, the reverse fluorite-type lithium-containing compound as an auxiliary material is required. If the amount of the compound increases so as to press the amount of the positive electrode active material, which is the main material, the battery capacity is reduced.
[0005]
[Patent Document 1]
JP-A-6-342673 (2nd page)
[Patent Document 2]
JP-A-9-59023 (2nd page)
[Patent Document 3]
JP-A-9-147863 (2nd page)
[0006]
[Problems to be solved by the invention]
The present invention is based on the above-described problems in the prior art and mainly aims to improve the initial charge / discharge capacity of a lithium battery using a metal-based negative electrode active material. A further object is to provide a battery of 2 to 3V. An object of the present invention is to provide a chargeable / dischargeable lithium battery that can be suitably used within a voltage range. Such a lithium battery according to the present invention is useful as a memory backup power source for electronic devices.
[0007]
[Means for Solving the Problems]
  To solve the above problemsIn addition,The present invention includes a positive electrode containing a lithium-containing polyvalent metal oxide having an inverted fluorite-type crystal structure as a positive electrode active material;A unit cell comprising a negative electrode containing a non-lithium metal that can occlude lithium and can be alloyed with lithium as a negative electrode active material, and a non-aqueous electrolyte is fabricated, and this unit electrode is charged for the first time to form a positive electrode Adopting a configuration in which lithium is derived from lithium and non-lithium metal that can occlude lithium to form a finished battery (this configuration is 1 Embodiment).
[0008]
As shown in FIG. 2, the lithium-containing polyvalent metal oxide having an inverted fluorite-type crystal structure is located at the center of a tetrahedron having a non-lithium metal atom as an apex (tetrahedral site 10), Lithium sites 9 in the crystal structure are substantially three-dimensionally connected, and the atomic ratio of lithium atoms to non-lithium metal atoms (5 to 6) is very large.
[0009]
The lithium-containing polyvalent metal oxide having such a structure easily releases and occludes lithium with a charge / discharge voltage of 2 to 3V. In addition, the lithium-containing polyvalent metal oxide having this structure has a small volume variation due to lithium desorption / occlusion and a stable crystal structure. Therefore, there is little deterioration of the charge / discharge characteristics due to repeated charge / discharge.
[0010]
  From the above, a lithium-containing polyvalent metal oxide having the above characteristics as a positive electrode active material,Non-lithium metal negative electrode active material that can occlude lithium and can be alloyed with lithiumAs a negative electrode active material, non-aqueous electrolyteThe lithium battery formed by first charging a unit cell havingExcellent initial charge / discharge characteristicsAndThis battery can be suitably used in the charge / discharge current region of 2 to 3V.The
[0011]
The second aspect of the present invention for solving the above problems includes a positive electrode having a positive electrode active material capable of occluding and releasing lithium, a negative electrode having a metal negative electrode active material capable of occluding lithium, In the lithium battery including an aqueous electrolyte, the positive electrode active material is mainly composed of a lithium-containing polyvalent metal oxide having an inverted fluorite-type crystal structure, and is contained in the lithium-containing polyvalent metal oxide. When the amount of metal atoms other than lithium atoms is M1, and the amount of lithium atoms contained in the positive electrode and the metal-based negative electrode is M2, the lithium battery is such that M2 / M1 is defined by Equation 1. Features.
[0012]
[7.5- (non-lithium metal oxidation number)] ≦ M2 / M1 ≦ [8.5 (non-lithium metal oxidation number)] (Equation 1)
[0013]
The technical significance of this configuration is basically the same as that of the first aspect of the invention, except that in this configuration, metal atoms other than lithium atoms contained in the lithium-containing polyvalent metal oxide are included. And the ratio of the amount of lithium atoms contained in the positive electrode and the metal-based negative electrode is regulated within a certain range, and the significance thereof is as follows.
[0014]
The lithium battery having the above configuration includes a charged battery that has been charged for the first time after battery assembly and an uncharged battery that has not been charged for the first time after battery assembly. Here, the metal-based negative electrode active material in the case of an uncharged battery in which initial charging after battery assembly is not performed is a non-lithium simple metal capable of occluding or releasing lithium, or a non-lithium alloy, Or means a lithium alloy. On the other hand, the metal-based negative electrode active material in the case where the lithium battery having the above-described configuration is a battery that has been charged for the first time after battery assembly means a lithium alloy. This is because even if the state before the first charge is a non-lithium elemental metal or a non-lithium alloy, these metals and the like are electrochemically alloyed with lithium derived from the positive electrode by the first charge / discharge.
[0015]
Incidentally, a lithium-containing polyvalent metal oxide having an inverted fluorite-type crystal structure is used as a positive electrode active material, and a non-lithium simple metal or non-lithium alloy capable of occluding lithium or a lithium alloy as a negative electrode active material In the above, the condition that the lithium contributing to charging / discharging exists without excess or deficiency is the amount of lithium that the lithium-containing polyvalent metal oxide can desorb and occlude. This condition is satisfied if the same amount of lithium as the total amount of lithium in the lithium-containing polyvalent metal oxide having an inverted fluorite-type crystal structure in a state where lithium is not detached is present in the positive and negative electrodes. Become. For example, during battery charging, a part of lithium in the lithium-containing polyvalent metal oxide having an inverted fluorite-type crystal structure is detached from the oxide and moves to the negative electrode, and thus moves to the negative electrode in the oxide. This is because the amount of lithium remaining except for the amount of lithium remaining remains, and the oxide can naturally accept the amount of all lithium transferred to the negative electrode during discharge.
[0016]
From this, if the following formula 4 is satisfied, the condition that lithium that contributes to charge / discharge exists without excess or deficiency is satisfied. The relationship between this formula 4 and the above formula 1 will be described.
[0017]
A typical example of a reverse fluorite-type lithium-containing polyvalent metal oxide is Li_FiveFeO_Four, Li₆CoO_FourThese compounds have 5-6 lithiums per non-lithium metal. The number of lithium in the oxide is determined by the oxidation number of the non-lithium metal and the number of oxygen atoms. For example, Li_FiveFeO_FourThe number (5) of lithium inside is derived by the following formula 2. The total oxidation number in this oxide is 0, the O atom is -2, the Li atom is +1, and the Fe atom is +3.
[0018]
Number of lithium = [{(Fe oxidation number: +3) × (Fe number: 1)} + {(O oxidation number: −2) × (O number: 4)}] / {(lithium oxidation) Number: +1)} × {−1} (Expression 2)
[0019]
Li₆CoO_FourThe number (6) of lithium in the lead is derived by the following formula (3). In this case, the oxidation number of Mn atoms is +2.
[0020]
Number of lithium = [{(Co oxidation number: +2) × (Co number: 1)} + {(O oxidation number: −2) × (O number: 4)}] / {(lithium oxidation Number: +1)} × {−1} (Expression 3)
[0021]
From the above formula 2 or formula 3, when the amount of metal atoms other than lithium atoms in the lithium-containing polyvalent metal oxide having an inverted fluorite-type crystal structure is M1, and the amount of lithium atoms is M2 ′, the atomic ratio M2 ′ It is easily understood that / M1 can be expressed by the following equation (4).
[0022]
M2 '/ M1 = {8- (oxidation number of non-lithium metal)} (Expression 4)
[0023]
Here, as described above, lithium in the lithium-containing polyvalent metal oxide that is the positive electrode active material moves to the negative electrode side during charging and is taken into the metal negative electrode active material, and from the metal negative electrode active material during discharge. It separates and moves to the positive electrode side, and is taken into the crystal structure of the reverse fluorite-type lithium-containing polyvalent metal oxide. Therefore, when all of the lithium that directly contributes to power generation in the battery is lithium derived from the reverse fluorite-type lithium-containing polyvalent metal oxide, the total amount of lithium in the positive electrode and the negative electrode is positive at the beginning of battery assembly. This is equivalent to the amount of lithium contained in the lithium-containing polyvalent metal oxide used as the active material.
[0024]
Therefore, by measuring the total amount of lithium atoms (M2) in the positive electrode and the negative electrode and measuring the amount (M1) of non-lithium metal atoms derived from the lithium-containing polyvalent metal oxide in the positive electrode, Equivalent atomic ratios will be sought, which also indirectly proves that the oxide has an inverted fluorite-type crystal structure.
[0025]
However, in a practical battery, a part of lithium derived from a lithium-containing polyvalent metal oxide is detached from the system while going back and forth between positive and negative electrodes according to charge and discharge. Further, the lithium-containing polyvalent metal oxide as a raw material may contain impurities that are not inverted fluorite-type structures, and may be slightly deviated from the stoichiometric ratio. According to the experience of the present inventors, such a fluctuation range is about ± 0.5. Therefore, if the above equation 4 is rewritten by incorporating this fluctuation range, the above equation 1 is obtained.
[0026]
That is, when the positive electrode active material has a lithium-containing polyvalent metal oxide having an inverted fluorite-type crystal structure as a main component and satisfies the above-mentioned formula 1, the battery has a necessary and sufficient width. The condition that the lithium that contributes to the discharge exists without excess or deficiency is satisfied. Therefore, according to the second aspect of the present invention, a lithium battery excellent in initial charge / discharge characteristics is realized.
[0027]
In the second aspect of the present invention, the lithium-containing polyvalent metal oxide further comprises Li₆CoO_Four , Li_FiveFeO_Four, Li₆MnO_FourThe metal-based negative electrode active material is a non-lithium metal that can be alloyed with lithium.
[0028]
Li₆CoO_Four , Li_FiveFeO_Four, Li₆MnO_FourHas a stable crystal structure and can smoothly occlude and release lithium. Therefore, these compounds are used as a positive electrode active material, and a non-lithium metal that can be alloyed with lithium is used as a negative electrode active material. In the case of a battery, the non-lithium metal can be easily made into a lithium alloy by the initial charge performed on the battery, and thereby a practical battery having a large initial discharge capacity can be realized easily.
[0029]
  In the second aspect of the present invention, the lithium-containing polyvalent metal oxide further comprises Li₆CoO_Four, Li_FiveFeO_Four, Li₆MnO_FourOne or more compounds selected from the group consisting of:
  The metal-based negative electrode active material isAn alloy of non-lithium metal and lithium derived from the lithium-containing polyvalent metal oxide,It can be set as the structure.
[0030]
This configuration describes the practical battery after the initial charge in the above description. As described above, in the present invention, the amount M1 of metal atoms other than lithium atoms contained in the lithium-containing polyvalent metal oxide and the amount M2 of lithium atoms contained in the positive electrode and the metal-based negative electrode are as follows. , Is defined by equation (1). When the amount of lithium in the positive and negative electrodes is regulated in this way, the amount of lithium extracted from the lithium-containing polyvalent metal oxide can be kept within an appropriate range, and a sufficient amount of lithium can be supplied to the negative electrode. Therefore, alloying of a non-lithium metal and lithium suitably proceeds in the negative electrode by the first charge. Therefore, according to this configuration, a practical lithium battery having a large initial charge capacity and excellent cycle characteristics can be easily realized.
[0031]
[7.5- (non-lithium metal oxidation number)] ≦ M2 / M1 ≦ [8.5 (non-lithium metal oxidation number)] (Equation 1)
[0032]
  Moreover, the manufacturing method of the lithium battery concerning this invention for solving the said subject is positive electrode preparation which produces the positive electrode which has a lithium containing polyvalent metal oxide whose crystal structure is a reverse fluorite type as a positive electrode active material. A battery exterior body comprising: a process; a negative electrode preparation process for preparing a negative electrode having a non-lithium metal capable of occluding lithium; an electrode body in which the positive electrode and the negative electrode are opposed to each other with a separator interposed therebetween; A cell assembly process to be housed and sealed,ElementaryBy charging the unit cell after battery assembly, lithium derived from the lithium-containing polyvalent metal oxide and, Produced in the negative electrode production processIn the negative electrodeSaidAnd an alloying step of alloying non-lithium metal in the negative electrode.
[0033]
In this configuration, lithium metal that reacts violently with moisture in the air or highly reactive lithium alloy is not used as a raw material, so it is possible to manufacture a lithium battery safely without using a special facility such as a dry room. it can. Further, in this configuration, by first charging the sealed unit cell, a lithium alloy as a negative electrode active material is produced. In this battery, a lithium alloy as a negative electrode active material is produced electrochemically in the battery. If it is a method, the lithium alloy negative electrode of the property convenient for performing charging / discharging reaction can be produced. As already explained, since the lithium alloy has a lower oxidation-reduction potential than non-lithium metals and other known negative electrode materials, in combination with the above-mentioned advantageous properties, the manufacturing method of this configuration has a large electromotive force. High capacity batteries can be manufactured safely and at low cost.
[0034]
In the method for producing a lithium battery according to the present invention, the lithium-containing polyvalent metal oxide further comprises Li₆CoO_Four , Li_FiveFeO_Four, Li₆MnO_FourIt can be set as the structure which is 1 or more compounds chosen from the group which consists of, and the said non-lithium metal is aluminum.
[0035]
As mentioned above, Li₆CoO_Four , Li_FiveFeO_Four, Li₆MnO_FourHas excellent crystal structure stability and can smoothly occlude and release lithium. On the other hand, aluminum has the characteristics that it can be easily alloyed with lithium and can form a film on the alloy surface that has ionic conductivity and suppresses the reaction between the alloy and the nonaqueous solvent. Therefore, when a battery is constituted by combining these substances, a lithium battery having a large initial discharge capacity and excellent cycle characteristics can be manufactured with high productivity.
[0036]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described with reference to the drawings, taking a flat lithium battery as an example. FIG. 1 is a cross-sectional view showing the configuration of this battery.
[0037]
As shown in FIG. 1, this battery has a flat outer appearance and has a battery outer can (positive electrode can) 5, and in the positive electrode can 5, a positive electrode 2, a negative electrode 1, and both electrodes The electrode body comprised from the separator 3 which spaces apart is accommodated. The separator 3 is impregnated with an electrolytic solution. A negative electrode current collector 6 and a positive electrode current collector 7 are interposed between the negative electrode can 4, the positive electrode can 5, and the electrode body. The openings of the negative electrode can 4 and the positive electrode can 5 are sealed by caulking and fixing via a ring-shaped insulating packing 8.
[0038]
A lithium battery having the above structure was produced as follows.
[0039]
[Production of positive electrode]
Lithium oxide (Li₂O) and cobalt oxide (CoO) were mixed at a molar ratio of 3: 1 and then heat-treated (fired) at 700 ° C. for 12 hours in a nitrogen stream to obtain Li as a positive electrode active material.₆CoO_FourWas prepared.
[0040]
Li₆CoO_Four(Powder), carbon black (powder) as a conductive agent, and fluororesin (powder) as a binder were mixed at a mass ratio of 84: 15: 1 to prepare a positive electrode mixture. This positive electrode mixture was cast into a disk shape and dried in vacuum at 250 ° C. for 2 hours to produce a positive electrode having a diameter of 2 mm, a thickness of 0.6 mm, and a mass of 5 mg.
[0041]
Here, only the lithium-containing polyvalent metal oxide having a reverse fluorite-type crystal structure is used as the positive electrode active material, but lithium-containing metal oxides other than the reverse fluorite-type can also be included. The compounding ratio of substances other than the inverted fluorite-type crystal structure is preferably 25% by mass or less based on the total active material. This is because if the compounding ratio of the other oxides is increased too much, suitable properties of the reverse fluorite-type lithium-containing polyvalent metal oxide are diluted.
[0042]
(Production of negative electrode)
An aluminum foil was punched into a disk shape to produce a negative electrode having a diameter of 2 mm, a thickness of 0.02 mm, and a mass of 0.2 mg.
[0043]
[Preparation of non-aqueous electrolyte]
In a solvent in which propylene carbonate (PC) and diethylene glycol dimethyl ether (DDE) were mixed at a volume ratio of 10:90 (1013 hPa, volume ratio at 25 ° C.), lithium trifluoromethanesulfonate imide {LiN (CF_ThreeSO₂)₂} Was dissolved at a rate of 1 mol / l to prepare a non-aqueous electrolyte.
[0044]
[Production of battery body]
A negative electrode can 4 with a negative electrode current collector 6 (stainless steel plate (SUS304)) and a positive electrode can 5 with a positive electrode current collector 7 (stainless steel plate (SUS304)) were prepared. The negative electrode 1 was placed on the negative electrode current collector 6, and a separator 3 made of a non-woven fabric made of polyphenylene sulfide (PPS) was placed on the negative electrode 1. The electrolytic solution was poured into the separator 3. Thereafter, the positive electrode 2 was placed on the separator 3, and the positive electrode can 5 was covered thereon. Further, the positive electrode can 5 and the negative electrode can 4 were caulked and sealed through an insulating packing 8 to produce a lithium battery having an outer diameter of 4 mm and a thickness of 1.4 mm.
[0045]
This battery was charged for the first time under the condition of constant current charging until it reached 3.0 V with a charging current of 20 μA, to produce a charged practical battery.
[0046]
Next, the practical battery is disassembled, the positive electrode active material and the negative electrode active material are collected, and the amount M1 of metal atoms other than lithium atoms contained in the lithium-containing polyvalent metal oxide that is the positive electrode active material; The amount M2 of lithium atoms in the lithium-containing polyvalent metal oxide and the negative electrode active material was measured, and M2 / M1 was calculated. As a result, M2 / M1 = 5.9, and it was confirmed that the following condition 1 was satisfied.
[0047]
[7.5- (non-lithium metal oxidation number)] ≦ M2 / M1 ≦ [8.5 (non-lithium metal oxidation number)] (Equation 1)
[0048]
The amount of each atom was measured using an inductively coupled plasma emission spectrometer (ICP: Inductively Coupled Plasma Atomic Emission Spectrometer) manufactured by Seiko Instruments Inc. (SPS1700HVR).
[0049]
The contents of the present invention will be described in more detail based on examples and comparative examples. Of course, the present invention is not limited to the following examples.
[0050]
Example 1a
As Example 1a, a lithium battery manufactured by a method similar to the method described in the above embodiment was used.
[0051]
(Example 1b)
Instead of the aluminum negative electrode used in the battery of Example 1a, an electrochemically produced lithium-aluminum alloy (Li / Al = 1/2) having a thickness of 0.03 mm was punched into a disk shape having a diameter of 2.0 mm. A lithium battery was produced in the same manner as in Example 1a except that the negative electrode was used.
[0052]
The lithium-aluminum alloy was produced by a method of superposing and alloying a lithium plate having a thickness of 0.01 mm and an aluminum plate having a thickness of 0.02 mm under completely dehumidified conditions.
[0053]
Example 2a
Li as the positive electrode active material used in the battery of Example 1a₆CoO_FourInstead of lithium oxide (Li₂Li) prepared by mixing O) and iron oxide (FeO) at a molar ratio of 5: 2 and then heat-treating (baking) at 800 ° C. for 12 hours in a nitrogen stream._FiveFeO_FourA lithium battery was produced in the same manner as in Example 1a except that was used.
[0054]
(Example 2b)
Example 2a was used except that instead of the aluminum negative electrode used in the battery of Example 2a, a negative electrode obtained by punching an electrochemically produced lithium-aluminum alloy (Li / Al = 1/2) into a disk shape was used. In the same manner as in Example 1, a lithium battery was produced in the same manner as in Example 1b.
[0055]
Example 3a
Li as the positive electrode active material used in the battery of Example 1a₆CoO_FourInstead of lithium oxide (Li₂Li) prepared by mixing O) and manganese oxide (MnO) at a molar ratio of 3: 1 and then heat-treating (baking) at 950 ° C. for 12 hours in an air current of 99% nitrogen + 1% hydrogen._FiveFeO_FourA lithium battery was produced in the same manner as in Example 1a except that was used.
[0056]
(Example 3b)
A lithium battery was produced in the same manner as in Example 3a, except that an anode produced by punching an electrochemically produced lithium-aluminum alloy into a disk shape was used instead of the aluminum anode used in the battery of Example 3a. did.
[0057]
(Comparative Example 1)
Instead of the aluminum metal negative electrode used in the battery of Example 1a, a negative electrode mixture prepared by mixing graphite powder and a fluororesin (powder) as a binder at a mass ratio of 95: 5 was molded into a disk shape. A lithium battery was produced in the same manner as in Example 1a, except that a negative electrode produced by drying at 150 ° C. for 2 hours in a vacuum was used.
[0058]
(Comparative Example 2)
Instead of the aluminum metal negative electrode used in the battery of Example 2a, a negative electrode mixture in which graphite powder and a fluororesin (powder) as a binder were mixed at a mass ratio of 95: 5 was molded into a disk shape. A lithium battery was produced in the same manner as in Example 2a, except that a negative electrode produced by drying at 150 ° C. for 2 hours in a vacuum was used.
[0059]
(Comparative Example 3)
Instead of the aluminum metal negative electrode used in the battery of Example 3a, a negative electrode mixture in which graphite powder and a fluororesin (powder) as a binder were mixed at a mass ratio of 95: 5 was molded into a disk shape. A lithium battery was produced in the same manner as in Example 3a, except that a negative electrode produced by drying at 150 ° C. for 2 hours in a vacuum was used.
[0060]
(Comparative Example 4)
Li as the positive electrode active material used in the battery of Example 1a₆CoO_FourInstead of manganese dioxide (MnO₂) Manganese trioxide (Mn) obtained by heat treatment in air at 700 ° C.₂O_Three) And lithium hydroxide (LiOH) in a molar ratio of 1: 2 and prepared by heat treatment (firing) at 700 ° C. for 4 hours in the atmosphere.₂LiMnO prepared by mixing O) and manganese oxide (MnO) at a molar ratio of 3: 1 and then heat-treating (baking) at 950 ° C. for 12 hours in a stream of nitrogen 99% + hydrogen 1%.₂A lithium battery was produced in the same manner as in Example 1a except that was used.
[0061]
In order to investigate the relationship between the initial charge / discharge capacity of the battery and the positive electrode active material or the negative electrode material at the time of battery assembly, the following charge / discharge characteristic tests were performed using the batteries of Examples 1a to 3b and Comparative Examples 1 to 4. It was.
[0062]
[Charge / discharge characteristics test]
Each battery was charged with a constant current at a charging current of 20 μA until reaching 3.0 V, and the initial charge capacity was calculated from the charging time. Then, constant current discharge was performed until the voltage reached 2.0 V with a discharge current of 20 μA, and the initial discharge capacity was calculated from the discharge time.
[0063]
Furthermore, from the initial charge capacity and the initial discharge capacity, the initial charge / discharge efficiency (%) of each battery was determined according to the following formula 5.
[0064]
Initial charge / discharge efficiency (%) = [(initial discharge capacity) / (initial charge capacity)] × 100 (Equation 5)
[0065]
The results of this charge / discharge characteristic test are shown in Table 1 below.
[0066]
[Table 1]

[0067]
As shown in Table 1, in the batteries of Comparative Examples 1 to 3 using graphite (C) as the negative electrode material, the initial discharge efficiency was 0%. In contrast, the batteries of Examples 1a to 3b using aluminum (Al) or lithium-aluminum alloy (Li-Al) as the negative electrode material during battery assembly had an initial discharge efficiency of 30% to 60%. It was.
[0068]
Moreover, as shown in Table 1, in the batteries of Example 1a, Example 2a, and Example 3a in which the negative electrode material at the time of battery assembly was aluminum (Al), the initial charge / discharge efficiency was 50% to 60%. . On the other hand, those of the batteries of Example 1b, Example 2b, and Example 3b in which the negative electrode material at the time of battery assembly was a lithium-aluminum alloy (Li-Al) was 30% to 40%.
[0069]
Therefore, in a battery using a lithium-containing polyvalent metal oxide having an inverted fluorite-type crystal structure as a positive electrode active material, it is possible to occlude lithium, such as aluminum (Al), as a negative electrode material during battery assembly. It has been found that particularly excellent charge / discharge characteristics can be obtained by using lithium metal.
[0070]
In contrast, a general positive electrode active material (LiMnO₂In the battery of Comparative Example 4 in which the negative electrode material at the time of battery assembly was aluminum, the initial charge capacity was 0.02 mAh, and the initial charge / discharge efficiency was 0%.
[0071]
From these, a general positive electrode active material (LiMnO₂) Was used as the positive electrode active material, it was found that if the negative electrode material at the time of battery assembly was aluminum (Al), only significantly low initial charge / discharge characteristics were obtained.
[0072]
Furthermore, Li is a lithium-containing polyvalent metal oxide whose crystal structure is an inverted fluorite type,₆CoO_Four , Li_FiveFeO_Four, Li₆MnO_FourIn the group consisting of Li, the negative electrode material during battery assembly is either aluminum (Al) or lithium-aluminum alloy (Li-Al).₆CoO_FourIt has been found that a more excellent charge / discharge characteristic can be obtained by using a positive electrode active material containing.
[0073]
In Comparative Examples 1 to 3 using graphite as the negative electrode material, the initial discharge efficiency was 0% because the potential of aluminum on the basis of the counter lithium was about 0.3 V, whereas graphite Since it is as low as about 0.15 V, it is considered that the charging depth of the positive electrode becomes shallow when charging at a battery voltage of 3 V.
[0074]
In addition, Examples 1a, 2a, and 3a in which aluminum and lithium are alloyed in the battery are used in comparison with Examples 1b, 2b, and 3b that use a lithium aluminum alloy from the beginning of battery assembly. However, the high initial charge / discharge efficiency was achieved by alloying non-lithium metal in the battery to obtain a lithium alloy with favorable properties for charge / discharge. This is considered to be because an alloy having a suitable property as in a battery cannot be obtained due to cracking on the surface.
[0075]
(Other matters)
The battery exterior body in the present specification means an element that seals the power generation element, and in the above embodiment, a battery in which the negative electrode can 4 and the positive electrode can 5 are combined with the packing 8 interposed therebetween. Corresponds to the exterior body.
[0076]
The metal-based negative electrode active material in the present specification means a non-lithium metal that can be alloyed with lithium, a non-lithium alloy, or a lithium alloy. Examples of the metal that can be alloyed with lithium include aluminum (Al), tin. (Sn), indium (In), zinc (Zn), lead (Pb), gallium (Ga), magnesium (Mg), potassium (K), sodium (Na), calcium (Ca), strontium (Sr), silicon (Si), cadmium (Cd) bismuth (Bi), barium (Ba), etc. can be illustrated.
[0077]
In the present invention, a negative electrode can made of a clad material including a material layer that can be alloyed with lithium and a material layer that is not alloyed with lithium can be used as a battery assembly member. A lithium battery excellent in initial charge / discharge characteristics can be manufactured with good workability. Here, as the material layer not alloyed with lithium, for example, stainless steel, titanium (Ti), nickel (Ni), chromium (Cr), copper (Cu), iron (Fe), silver (Ag), gold (Au ), Tungsten (W), platinum (Pt), molybdenum (Mo), and the like.
[0078]
【The invention's effect】
As described above, according to the present invention, a lithium-containing polyvalent metal oxide having an inverted fluorite type crystal structure is used as the positive electrode active material, and a metal-based active material is used as the negative electrode active material. Thus, a lithium battery having a large initial charge / discharge capacity, particularly a lithium battery having a large battery capacity capable of being suitably charged / discharged at 2 to 3 V can be realized. Such a lithium battery according to the present invention can be used as a memory backup power source for electronic equipment because a single battery can provide a necessary holding voltage such as CMOS or S-RAM.
[0079]
Moreover, according to the manufacturing method of the present invention, which can manufacture a lithium battery using a lithium alloy as a negative electrode active material without using lithium metal or a lithium alloy as a negative electrode material, the battery manufacturing operation is performed under a normal environment. In addition, a suitable lithium alloy negative electrode can be produced by a charging operation performed on the unit cell. Therefore, according to the production method of the present invention, a lithium battery having a large initial discharge capacity and excellent cycle characteristics can be provided at low cost.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of a sagittal cross section of a flat lithium battery as an example of the present invention.
FIG. 2 is a schematic diagram of an inverted fluorite-type crystal structure possessed by a lithium-containing polyvalent metal oxide used in the present invention.
[Explanation of symbols]
1: Negative electrode
2: Positive electrode
3: Separator
4: Negative electrode can
5: Positive electrode can
6: Negative electrode current collector
7: Positive electrode current collector
8: Insulation packing
9: Lithium site
10: Tetrahedral site

Claims (5)

In a lithium battery comprising a positive electrode having a positive electrode active material capable of occluding and releasing lithium, a negative electrode having a metal negative electrode active material capable of occluding lithium, and a non-aqueous electrolyte,
  The positive electrode active material is mainly composed of a lithium-containing polyvalent metal oxide having an inverted fluorite-type crystal structure,
  When the amount of metal atoms other than lithium atoms contained in the lithium-containing polyvalent metal oxide is M1, and the amount of lithium atoms contained in the positive electrode and the metal-based negative electrode is M2, M2 / M1 Is defined by Equation 1,
  The lithium battery characterized by the above-mentioned.
  [Equation 1]
[ 7.5- (non-lithium metal oxidation number) ≦ M2 / M1 ≦ 8.5- (non-lithium metal oxidation number) ] ... (Equation 1) The lithium-containing polyvalent metal oxide is Li ₆ CoO _Four , Li _Five FeO _Four , Li ₆ MnO _Four One or more compounds selected from the group consisting of:
  The metal-based negative electrode active material is a non-lithium metal that can be alloyed with lithium.
  The lithium battery according to claim 1. The lithium-containing polyvalent metal oxide is Li ₆ CoO _Four , Li _Five FeO _Four , Li ₆ MnO _Four One or more compounds selected from the group consisting of:
  The metal-based negative electrode active material is an alloy of non-lithium metal and lithium derived from the lithium-containing polyvalent metal oxide,
  The lithium battery according to claim 1. As a positive electrode active material, a positive electrode preparation step of preparing a positive electrode having a lithium-containing polyvalent metal oxide having a crystal structure of an inverted fluorite type,
  A negative electrode manufacturing step of manufacturing a negative electrode having a non-lithium metal capable of occluding lithium;
  A unit cell assembly step of housing and sealing an electrode body in which the positive electrode and the negative electrode are opposed to each other via a separator, and a non-aqueous electrolyte in a battery exterior body;
  Alloying in which the lithium-containing polyvalent metal oxide-derived lithium and the non-lithium metal in the negative electrode prepared in the negative electrode preparation step are alloyed in the negative electrode by charging the unit cell after assembly. Process,
  A method for producing a lithium battery, comprising: The lithium-containing polyvalent metal oxide is Li ₆ CoO _Four , Li _Five FeO _Four , Li ₆ MnO _Four One or more compounds selected from the group consisting of:
  The non-lithium metal is aluminum;
  The method for producing a lithium battery according to claim 4.

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