JP3637690B2 - Non-aqueous electrolyte secondary battery - Google Patents
Non-aqueous electrolyte secondary battery Download PDFInfo
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- JP3637690B2 JP3637690B2 JP22093996A JP22093996A JP3637690B2 JP 3637690 B2 JP3637690 B2 JP 3637690B2 JP 22093996 A JP22093996 A JP 22093996A JP 22093996 A JP22093996 A JP 22093996A JP 3637690 B2 JP3637690 B2 JP 3637690B2
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- JP
- Japan
- Prior art keywords
- lithium
- aqueous electrolyte
- electrolyte secondary
- negative electrode
- secondary battery
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- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Description
【0001】
【発明の属する技術分野】
本発明は、非水電解液二次電池の、特に負極材料の改良に関するものである。
【0002】
【従来の技術】
非水電解液二次電池は、小型、軽量で、かつ高エネルギー密度を有するため、機器のポータブル化、コードレス化が進む中で、その期待は高まっている。
【0003】
従来、非水電解液二次電池用の正極活物質としてLiCoO2、LiNiO2などのリチウム含有金属酸化物が提案されている。一方、負極としては金属リチウム、リチウム合金、リチウムイオンを吸蔵・放出することのできる黒鉛材料などが提案され、一部実用化されている。
【0004】
【発明が解決しようとする課題】
しかしながら、従来の金属リチウムを用いた負極では、充電時において極板表面に金属リチウムが針状結晶となって析出し、この針状結晶がセパレ−タを突き破って、正極と接触して内部短絡を起こすことがあった。この問題を解決するために、黒鉛材料を負極に用いる検討がなされているがこの場合には、炭素は理論的にC6Li(炭素原子6個に対してLi原子1個)までLiイオンを吸蔵すると言われており、これ以上の高容量化が困難であった。
【0005】
本発明は、このような課題を解決するもので、負極の表面で金属リチウムが針状に析出することを防止するとともに、充電時に一般式C6Liで規定される絶対容量を越えることのできる非水電解液二次電池用負極材料を提供するものである。
【0006】
【課題を解決するための手段】
これらの課題を解決するために、本発明の非水電解液二次電池は、
一般式LixMSi2O7(2≦x≦4、MはV,Mn,Crのいずれか少なくとも1種以上)で表されるリチウム−シリコン酸化物を用いるものである。
【0007】
【発明の実施の形態】
本発明は請求項1記載のように、一般式LixMSi2O7(2≦x≦4、MはV,Mn,Crのいずれか少なくとも1種以上)で表されるリチウム−シリコン酸化物を用いるものであり、シリコン酸化物の安定した構造体(例えばSi2O7やSiO3などの単一ユニット)の中に混合原子価制御が可能な元素、3d遷移金属元素を取り込み、リチウムイオンの吸蔵・放出時の酸化還元を行うものである。
【0008】
これらのリチウム−シリコン酸化物は、量論組成比の酸化リチウムと二酸化シリコン、所定量のCr3O4あるいはCr2O3のクロム酸化物、Mn3O4あるいはMn2O3のマンガン酸化物とをセラミック容器において一緒に950℃で溶解させて得られる。雰囲気は通常はキャリアガスとしてのアルゴンと反応性ガスとして酸素10%混入された混合ガスをフローさせて得られる。バナジウムをドープする時はバナジウム自身の昇華温度が低いため、予めシリコンとバナジウムの複合酸化物を得て酸化リチウムと混合の後、同様の方法で得るかあるいは、先にリチウム−バナジウム酸化物を得て、次いでこれと二酸化シリコンを600℃で反応を行わせて前駆体を一度形成し、その後に900℃前後で反応させるかいずれかの方法でも得られる。
【0009】
なお、上記の例でAlを添加した場合には、Al自身が3価を取り易く、事実上Liの吸蔵・放出において原子価を補償する化学種はない。
【0010】
このようにLi2SiO3,LiAl(SiO3)2,Li6Si2O7,Li8SiO6,LiAlSiO4などのようなリチウム含有シリコン酸化物は、シリコン元素の原子価が4価で酸化物自体が安定化しており、電気化学的酸化還元反応に対する可逆容量を高めることが困難であった。
【0011】
本発明はV,Mn,Crのいずれか少なくとも1種以上を添加することにより、負極材料を高容量化し、高容量の非水電解液二次電池を提供することができる。
【0012】
【実施例】
以下、図面と共に本発明の実施例を説明する。
図1に本発明の負極を評価するための評価用電池の縦断面図を示す。図1において、1は耐有機電解液性のステンレス鋼板を加工した電池ケース、2は同材料の封口板、3は同材料の集電体で、電池ケース1の内面にスポット溶接されている。4は金属リチウムで、封口板2の内部に圧着されている。
【0013】
5は負極で、Li2CrSi2O7 (真比重は3.9〜4.0g/cm3)90重量部に対し、結着剤としてポリフッ化ビニリデン10重量部を混合して合剤を得てこの合剤の所定量を集電体3の上に成形し、これを150℃で減圧乾燥した。6は微孔性のポリプロピレン樹脂製セパレ−タ、7はポリプロピレン樹脂製絶縁ガスケットである。電解液は炭酸エチレン、1、3−ジメトキシエタンの等体積混合溶媒に溶質として過塩素酸リチウムを1モル/リットルの濃度で溶解して用いた。この電池の寸法は直径20mm、電池総高1.6mmとし、これを本発明の電池Aとした。
【0014】
負極は、充電することにより電気化学的にリチウムイオンを挿入し、一般式 Li4CrSi207となる。したがって、一般式LixCrSi2O7(2≦x≦4)のx値は充電によって2から4までの範囲で変化し、放電においてはその逆の反応を可逆的に起こすことが可能である。また、例えば正極にLiCoO2を用いた電池として組み立てた場合においても同様に可逆な充放電反応が上記範囲内において可能である。
【0015】
次に、Li2MnSi2O7、Li2VSi207の組成比を有するリチウム−シリコン酸化物を負極に用いた以外は本発明と同様の電池を作製し、これらを本発明の電池B,Cとした。これらの電池に対して電流密度1.0mA/cm2として、電圧2.0Vから0Vの範囲で充放電試験を行った。
【0016】
その結果、いずれもほぼ同様の平均充電電位0.7Vで約220mAh/g、平均放電電位0.82Vで約215mAh/gの特性が得られ、黒鉛負極の理論容量372mAh/gより重量あたりの比容量は下回る特性になったが、真比重のデータを基に体積あたりに換算すると 850mAh/cc程度の比容量が得られ、黒鉛系の780mAh/cc(真比重を2.1g/cm3として算出)を上回る高容量な特性が得られた。
【0017】
本実施例では、V、Mn、Crをそれぞれ含むリチウムーシリコン酸化物の例を示したが、これらを1種以上含むものでも同様な効果が得られた。
【0018】
また、Feの場合はFe自身のレドックスが2価〜4価が困難であるため、x=3が材料設計上の限度である。Mnド−プの時と同一の条件で例えばFe3O4を用いて合成し、充放電特性を検討したところLi3Fe2O7の組成のものは平均充電電位0.3Vで約125mAh/g(500mAh/cc)、平均放電電位0.4Vで約120mAh/g(480mAh/cc)の特性が得られ、単位重量あたりの比容量は可動リチウム量が1であるため他の遷移金属元素を含むシリコン酸化物ほど大きくはないが、作動電位は卑な領域にあるという特徴を有している。
【0019】
なお、Li2SiO3,LiAl(SiO3)2,Li6Si2O7,Li8SiO6,LiAlSiO4などのようなリチウム−シリコン酸化物も同様の充放電特性を検討したが、いずれも可逆容量は770mAh/cc程度となり、グラファイトを大幅に越える高容量のものは得られなかった。
【0020】
なお、本発明における効果は、LiNiO2,LiMn2O4などの正極活物質、その他のリチウム電池用有機電解液に対しても同様に効果がある。
【0021】
【発明の効果】
以上のように、本発明では一般式LixMSi2O7(2≦x≦4、MはV,Mn,Crのいずれか少なくとも1種以上)で表される3d遷移金属を含むリチウム−シリコン酸化物を用いるので、高容量を有し、さらに充放電反応に伴う電極表面上の針状結晶を抑えることができる非水電解液二次電池を提供できる。
【図面の簡単な説明】
【図1】本発明の電池の縦断面図
【符号の説明】
1 電池ケ−ス
2 封口板
3 集電体
4 金属リチウム
5 負極
6 セパレ−タ
7 ガスケット[0001]
BACKGROUND OF THE INVENTION
The present invention relates to improvements in non-aqueous electrolyte secondary batteries, particularly negative electrode materials.
[0002]
[Prior art]
Non-aqueous electrolyte secondary batteries are small, light, and have a high energy density. Therefore, their expectations are increasing as devices become more portable and cordless.
[0003]
Conventionally, lithium-containing metal oxides such as LiCoO 2 and LiNiO 2 have been proposed as positive electrode active materials for non-aqueous electrolyte secondary batteries. On the other hand, as a negative electrode, metallic lithium, a lithium alloy, a graphite material capable of inserting and extracting lithium ions, and the like have been proposed and partially put into practical use.
[0004]
[Problems to be solved by the invention]
However, in the conventional negative electrode using metallic lithium, during charging, metallic lithium is deposited as acicular crystals on the surface of the electrode plate, and these acicular crystals break through the separator and come into contact with the positive electrode to cause an internal short circuit. There was a case. In order to solve this problem, studies have been made to use a graphite material for the negative electrode. In this case, however, carbon is theoretically limited to C 6 Li (1 Li atom for 6 carbon atoms). It is said to occlude, and it was difficult to increase the capacity beyond this.
[0005]
The present invention solves such a problem, and prevents lithium metal from accumulating on the surface of the negative electrode and can exceed the absolute capacity defined by the general formula C 6 Li during charging. A negative electrode material for a non-aqueous electrolyte secondary battery is provided.
[0006]
[Means for Solving the Problems]
In order to solve these problems, the non-aqueous electrolyte secondary battery of the present invention is
A lithium-silicon oxide represented by the general formula LixMSi 2 O 7 (2 ≦ x ≦ 4, M is at least one of V, Mn, and Cr) is used.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
The present invention uses a lithium-silicon oxide represented by the general formula LixMSi 2 O 7 (2 ≦ x ≦ 4, where M is at least one of V, Mn, and Cr). Incorporating lithium ion ions by incorporating 3d transition metal elements into a stable structure of silicon oxide (for example, a single unit such as Si 2 O 7 or SiO 3 ) that can control mixed valences・ Reduces redox during release.
[0008]
These lithium-silicon oxides include a stoichiometric lithium oxide and silicon dioxide, a predetermined amount of Cr 3 O 4 or Cr 2 O 3 chromium oxide, Mn 3 O 4 or Mn 2 O 3 manganese oxide. Are melted together at 950 ° C. in a ceramic container. The atmosphere is usually obtained by flowing argon as a carrier gas and a mixed gas mixed with 10% oxygen as a reactive gas. When vanadium is doped, the sublimation temperature of vanadium itself is low. Therefore, after obtaining a composite oxide of silicon and vanadium in advance and mixing with lithium oxide, it can be obtained in the same manner, or lithium-vanadium oxide can be obtained first. Then, this is reacted with silicon dioxide at 600 ° C. to form a precursor once, and then reacted at around 900 ° C. to obtain either method.
[0009]
In addition, when Al is added in the above example, Al itself is easily trivalent, and there is virtually no chemical species that compensates the valence in the insertion and release of Li.
[0010]
Thus, lithium-containing silicon oxides such as Li 2 SiO 3 , LiAl (SiO 3 ) 2 , Li 6 Si 2 O 7 , Li 8 SiO 6 , LiAlSiO 4, etc. are oxidized with a valence of silicon element of 4 valences. The product itself was stabilized, and it was difficult to increase the reversible capacity for the electrochemical redox reaction.
[0011]
The present invention can increase the capacity of the negative electrode material by adding at least one of V, Mn, and Cr, and provide a high-capacity nonaqueous electrolyte secondary battery.
[0012]
【Example】
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows a longitudinal sectional view of an evaluation battery for evaluating the negative electrode of the present invention. In FIG. 1, 1 is a battery case obtained by processing an organic electrolyte resistant stainless steel plate, 2 is a sealing plate of the same material, 3 is a current collector of the same material, and is spot-welded to the inner surface of the battery case 1. 4 is metallic lithium, and is pressure-bonded inside the sealing plate 2.
[0013]
5 is a negative electrode, and a mixture is obtained by mixing 10 parts by weight of polyvinylidene fluoride as a binder with respect to 90 parts by weight of Li 2 CrSi 2 O 7 (true specific gravity is 3.9 to 4.0 g / cm 3 ). A predetermined amount of the mixture was formed on the
[0014]
The negative electrode is electrochemically inserting lithium ions by charging, the general formula Li 4 CrSi 2 0 7. Therefore, the x value of the general formula Li x CrSi 2 O 7 (2 ≦ x ≦ 4) changes in the range from 2 to 4 by charging, and the reverse reaction can occur reversibly in discharging. . Further, for example, even when assembled as a battery using LiCoO 2 for the positive electrode, a reversible charge / discharge reaction is possible within the above range.
[0015]
Next, a battery similar to the present invention was prepared except that lithium-silicon oxide having a composition ratio of Li 2 MnSi 2 O 7 and Li 2 VSi 2 0 7 was used for the negative electrode, and these were produced as the battery B of the present invention. , C. A charge / discharge test was performed on these batteries at a current density of 1.0 mA / cm 2 in a voltage range of 2.0 V to 0 V.
[0016]
As a result, characteristics of approximately 220 mAh / g at an average charge potential of 0.7 V and approximately 215 mAh / g at an average discharge potential of 0.82 V were obtained, and the ratio per weight was calculated from the theoretical capacity of 372 mAh / g of the graphite negative electrode. Although the capacity was lower, when converted to volume based on the data of true specific gravity, a specific capacity of about 850 mAh / cc was obtained. Graphite-based 780 mAh / cc (calculated with true specific gravity of 2.1 g / cm 3) ) And higher capacity characteristics were obtained.
[0017]
In this example, an example of lithium-silicon oxide containing V, Mn, and Cr was shown, but the same effect was obtained even when one or more of these were included.
[0018]
Further, in the case of Fe, since the redox of Fe itself is difficult to be bivalent to tetravalent, x = 3 is a limit in material design. For example, Fe 3 O 4 was synthesized under the same conditions as in the case of Mn doping and the charge / discharge characteristics were examined. The composition of Li 3 Fe 2 O 7 had an average charge potential of 0.3 V and was about 125 mAh / g (500 mAh / cc), an average discharge potential of 0.4 V, and a characteristic of about 120 mAh / g (480 mAh / cc) is obtained. Since the specific capacity per unit weight is 1, the amount of movable lithium is 1, so that other transition metal elements can be used. Although it is not as large as the silicon oxide containing, it has the feature that the operating potential is in a base region.
[0019]
Although lithium-silicon oxides such as Li 2 SiO 3 , LiAl (SiO 3 ) 2 , Li 6 Si 2 O 7 , Li 8 SiO 6 , LiAlSiO 4 have been studied for the same charge / discharge characteristics, all The reversible capacity was about 770 mAh / cc, and a high capacity significantly exceeding graphite was not obtained.
[0020]
Note that the effectiveness of the present invention, there is a positive electrode active material, similarly effective against organic electrolytic solution for other lithium batteries such as LiNiO 2, LiMn 2 O 4.
[0021]
【The invention's effect】
As described above, in the present invention, a lithium-silicon oxide containing a 3d transition metal represented by the general formula LixMSi 2 O 7 (2 ≦ x ≦ 4, where M is at least one of V, Mn, and Cr) Therefore, it is possible to provide a non-aqueous electrolyte secondary battery that has a high capacity and can suppress needle-like crystals on the electrode surface accompanying charge / discharge reactions.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a battery according to the present invention.
1 Battery Case 2
Claims (1)
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JP22093996A JP3637690B2 (en) | 1996-08-22 | 1996-08-22 | Non-aqueous electrolyte secondary battery |
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JP22093996A JP3637690B2 (en) | 1996-08-22 | 1996-08-22 | Non-aqueous electrolyte secondary battery |
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JP3637690B2 true JP3637690B2 (en) | 2005-04-13 |
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US11264614B2 (en) | 2018-02-01 | 2022-03-01 | Thermal Ceramics Uk Limited | Energy storage device and ionic conducting composition for use therein |
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FR2864348B1 (en) * | 2003-12-18 | 2006-03-10 | Commissariat Energie Atomique | LITHIUM ACCUMULATOR HAVING BOTH ELECTRICAL POTENTIAL AND HIGH LTHIUM INSERTION CAPABILITY. |
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JP7116518B1 (en) * | 2022-03-03 | 2022-08-10 | 日本重化学工業株式会社 | Negative electrode active material for lithium ion secondary battery, manufacturing method thereof, and negative electrode for lithium ion secondary battery |
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US11264614B2 (en) | 2018-02-01 | 2022-03-01 | Thermal Ceramics Uk Limited | Energy storage device and ionic conducting composition for use therein |
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