JP5676886B2 - Non-aqueous secondary battery positive electrode and non-aqueous secondary battery using the same - Google Patents
Non-aqueous secondary battery positive electrode and non-aqueous secondary battery using the same Download PDFInfo
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Description
本発明は、非水系二次電池に関し、特に非水系二次電池用電極に関するものである。 The present invention relates to a non-aqueous secondary battery, and particularly relates to a non-aqueous secondary battery electrode.
近年、携帯電話、ノート型パソコン、デジタルビデオカメラ、デジタルカメラに代表される携帯機器用小型二次電池の分野では、小型化及び高容量化のニーズに応えるべく、９０年代初頭より、ニッケルカドミウム電池に続き、新型電池としてニッケル水素電池、リチウム二次電池の開発が進展し、２００Ｗｈ／ｌ以上の体積エネルギー密度を有する電池が市販されている。特にリチウムイオン電池は、３５０Ｗｈ／ｌ、形状によっては５００Ｗｈ／ｌを超える体積エネルギー密度を有するタイプも上市し、その市場を飛躍的に延ばしてきた。 In recent years, nickel cadmium batteries have been used since the early 90's to meet the needs for miniaturization and high capacity in the field of small secondary batteries for portable devices such as mobile phones, laptop computers, digital video cameras and digital cameras. Following this, the development of nickel-metal hydride batteries and lithium secondary batteries as new batteries has progressed, and batteries having a volumetric energy density of 200 Wh / l or more are commercially available. In particular, lithium ion batteries having a volume energy density exceeding 350 Wh / l and, depending on the shape, exceeding 500 Wh / l have been put on the market, and the market has been greatly expanded.
一方、中大型蓄電デバイスの分野では、省資源を目指したエネルギーの有効利用及び地球環境問題の観点から、深夜電力貯蔵及び太陽光発電の電力貯蔵を目的とした家庭用分散型蓄電システム、電気自動車、ハイブリッド車向けの蓄電システム等が注目を集めている。上記の蓄電システムでは、多数の二次電池や電気二重層キャパシタを直列及び、あるいは並列に接続し、組電池として用いるのが常であり、要求される寿命は、小型携帯機器用の５年程度に比べ１０年以上と長い場合が多い。 On the other hand, in the field of medium- and large-sized power storage devices, from the viewpoints of effective use of energy aiming at resource saving and global environmental problems, a distributed power storage system for home use for the purpose of midnight power storage and solar power generation, electric vehicles In addition, power storage systems for hybrid vehicles are attracting attention. In the above power storage system, a large number of secondary batteries and electric double layer capacitors are usually connected in series and in parallel, and used as an assembled battery, and the required life is about 5 years for small portable devices. In many cases, it is longer than 10 years.
その中でも、最近では、原油価格上昇に伴いガソリン価格が高騰する中、低燃費であり、環境に優しい車としてハイブリッド車の開発が加速され、ハイブリッド車用として、安全且つ高出力、高エネルギー密度、長寿命を有する中大型蓄電デバイスが希求されている。 Among them, recently, the development of hybrid vehicles as fuel-efficient and environmentally friendly vehicles has accelerated as gasoline prices soared as crude oil prices rose, and for hybrid vehicles, safe and high output, high energy density, There is a need for medium- and large-sized electricity storage devices having a long life.
前記ハイブリッド車に代表されるエネルギー回生を含む蓄電用途においては、蓄電デバイスが充放電時に短時間で大きな電力を出し入れすることが可能な特性を所持する必要がある。 In power storage applications including energy regeneration typified by the hybrid vehicle, it is necessary for the power storage device to have characteristics that allow large power to be taken in and out in a short time during charging and discharging.
リチウム二次電池用正極活物質には、主として４Ｖ程度の電池電圧を示し且つ高容量を有するリチウム遷移金属酸化物が用いられる。これまで出力・容量を特性改善したリチウム二次電池を提供することを目的とし、リチウム遷移金属酸化物と導電性高分子から成る複合化正極の検討が行われてきた。 As the positive electrode active material for a lithium secondary battery, a lithium transition metal oxide that mainly exhibits a battery voltage of about 4 V and has a high capacity is used. So far, a composite positive electrode composed of a lithium transition metal oxide and a conductive polymer has been studied for the purpose of providing a lithium secondary battery with improved output and capacity characteristics.
遷移金属酸化物に導電性高分子を複合化する手法として、化学重合法から得られる有機溶媒に不溶な導電性高分子粉末の混合、化学重合法より得られる有機溶媒に可溶な導電性高分子の混合、電解重合法により電解酸化膜を形成させるという手法が検討されてきた。 As a method of compounding a conductive polymer with a transition metal oxide, mixing a conductive polymer powder insoluble in an organic solvent obtained by a chemical polymerization method, a highly conductive material soluble in an organic solvent obtained by a chemical polymerization method Techniques for forming an electrolytic oxide film by molecular mixing and electrolytic polymerization have been studied.
例えば、化学重合法から作製された導電性高分子粉末の混合系は、特開平６−６８８６６号のバナジン酸リチウムに対して導電性高分子（ポリアニリン、ポリピロール等）を５〜５０重量部混合することによる活物質利用率の向上が挙げられる。この混合または重合された導電性高分子が電極中で導電材且つ活物質として機能するため、電池容量の増加が得られる。詳しくは、ポリピロール未添加系のバナジン酸リチウム正極活物質の利用率が８７％であるのと比べ、バナジン酸リチウムに対し１０重量部のポリピロールを混合することで、混合電極系でのバナジン酸リチウム正極活物質利用率が１２６％に増加する。 For example, in a mixed system of conductive polymer powder prepared by chemical polymerization, 5 to 50 parts by weight of conductive polymer (polyaniline, polypyrrole, etc.) is mixed with lithium vanadate disclosed in JP-A-6-68866. The improvement of the active material utilization rate by this is mentioned. Since the mixed or polymerized conductive polymer functions as a conductive material and an active material in the electrode, an increase in battery capacity can be obtained. Specifically, compared to the utilization rate of the polypyrrole-free lithium vanadate positive electrode active material being 87%, lithium vanadate in the mixed electrode system is obtained by mixing 10 parts by weight of polypyrrole with lithium vanadate. The positive electrode active material utilization rate increases to 126%.
また、特開２００１−３５１６３４号では、化学重合法により作製したポリアニリン、ポリピロールを混合または活物質表面に修飾する手法が検討されており、リチウムマンガン系酸化物にポリアニリン０．４重量部以上且つポリピロールを０．０１〜３．０重量部混合、または０．０１〜３．０重量部のポリピロールをリチウムマンガン系酸化物表面に修飾し且つポリアニリンを０．４重量部以上混合した正極電極を用いることで、未添加系電極と比べ放電容量が増加する。この効果は、ポリピロールが３Ｖ以下の電位領域においても電子伝導性を確保できるため、主に３Ｖ域での放電容量を増加させる。
詳しくは、リチウムマンガン系酸化物に対しポリアニリンを０．５５重量部、ポリピロールを０．５５重量部混合した電池では、４Ｖ域：１０３％、３Ｖ域：１２７％の放電容量を示し、ポリアニリン０．５５重量部、ポリピロール２.２３重量部混合すると４Ｖ域：１０４％、３Ｖ域：１０８％の放電容量を示す。リチウムマンガン酸化物正極に対し、ポリピロール５．５６重量部混合すると放電容量が４Ｖ域：１０２％、３Ｖ域：９２％を示す。
リチウムマンガン系酸化物にポリピロールを修飾した場合、リチウムマンガン系酸化物に対しポリピロールを１．２１重量部修飾したセルでは、放電容量が４Ｖ域：１０４％、３Ｖ域：１１２％となり、ポリピロール２．３０重量部を修飾したセルでは、放電容量が４Ｖ域：１０５％、３Ｖ域：１０４％となる。
Japanese Patent Application Laid-Open No. 2001-351634 discusses a method of mixing or modifying the surface of an active material with polyaniline and polypyrrole produced by chemical polymerization. The lithium manganese-based oxide contains polyaniline at least 0.4 part by weight and polypyrrole. A positive electrode in which 0.01 to 3.0 parts by weight of polypyrrole is mixed, or 0.01 to 3.0 parts by weight of polypyrrole is modified on the surface of a lithium manganese oxide and polyaniline is mixed in an amount of 0.4 parts by weight or more. Thus, the discharge capacity is increased as compared with the non-added electrode. This effect can increase the discharge capacity mainly in the 3V region because the electron conductivity can be secured even in the potential region of 3V or less of polypyrrole.
Specifically, a battery in which 0.55 parts by weight of polyaniline and 0.55 parts by weight of polypyrrole are mixed with a lithium manganese-based oxide exhibits a discharge capacity of 4 V region: 103%, 3 V region: 127%. When mixed with 55 parts by weight and 2.23 parts by weight of polypyrrole, a discharge capacity of 4 V region: 104% and 3 V region: 108% is exhibited. When the lithium manganese oxide positive electrode is mixed with 5.56 parts by weight of polypyrrole, the discharge capacity is 4 V region: 102%, 3 V region: 92%.
In the case where polypyrrole is modified to lithium manganese-based oxide, the discharge capacity becomes 4V region: 104%, 3V region: 112% in a cell in which 1.21 parts by weight of polypyrrole is modified with respect to lithium manganese-based oxide. In the cell modified with 30 parts by weight, the discharge capacity is 4V region: 105%, 3V region: 104%.
特開２００３−１６８４３６号では、化学重合法により得られる可溶性ポリアニリンを用いた検討がされており、リチウム電池用正極の活物質表面の少なくとも一部をポリアニリンで被覆し、そのキャパシタ材料としての機能を利用することで、低温での短時間出力特性に優れた電池を得ている。
詳しくは、リチウム遷移金属酸化物に対し、還元状態のポリアニリンを５．５重量部混合すると、ポリアニリン未添加系と比べ、−３０℃、ＳＯＣ４０％条件下での出力密度が高くなる（ポリアニリン未添加系２５℃の出力密度を１．０とした場合、出力密度比：１．６以上）。但し、電極中でのポリアニリンの酸化度指数が０．７以上となると−３０℃での出力密度比は高くなるが、２５℃での出力密度比が低下する。酸化度指数が０．７以下であれば、２５℃での出力密度比を低下させることなく−３０℃での出力密度比を向上させることが可能となっている。
In JP-A-2003-168436, studies have been made using a soluble polyaniline obtained by a chemical polymerization method, and at least a part of the active material surface of a positive electrode for a lithium battery is covered with polyaniline, and the function as a capacitor material is provided. By using it, a battery having excellent short-time output characteristics at a low temperature is obtained.
Specifically, when 5.5 parts by weight of polyaniline in a reduced state is mixed with lithium transition metal oxide, the output density under the conditions of -30 ° C. and SOC 40% is increased as compared with the polyaniline non-added system (no polyaniline added). When the power density at 25 ° C. is 1.0, the power density ratio is 1.6 or more. However, when the oxidation index of polyaniline in the electrode is 0.7 or more, the power density ratio at −30 ° C. increases, but the power density ratio at 25 ° C. decreases. If the oxidation index is 0.7 or less, it is possible to improve the power density ratio at −30 ° C. without reducing the power density ratio at 25 ° C.
特開２００３−１６８４３７号では、活物質と活物質表面を被覆していないＮＭＰに不溶な導電性高分子を混在させた電極を用いたリチウム電池が開示されている。詳しくは、正極電極の導電材として、ＮＭＰに不溶なポリアニリンを複合化させたカーボンを用いることで、室温での出力特性と低温での短時間出力特性に優れた電池となっている。この時、電極中のポリアニリン比率は、活物質に対して５．５重量部であり、出力特性は、ポリアニリン未添加系２５℃の出力密度を１．０とした場合、−３０℃、ＳＯＣ４０％条件下での出力密度比が２．２３、２５℃、ＳＯＣ６０％条件下での出力密度比が１．０５となり、室温での出力密度比を低下させることなく、−３０℃での出力密度比を向上させることが可能となっている。 Japanese Patent Application Laid-Open No. 2003-168437 discloses a lithium battery using an electrode in which an active material is mixed with an insoluble conductive polymer in NMP that does not cover the surface of the active material. Specifically, by using carbon in which polyaniline insoluble in NMP is used as the conductive material for the positive electrode, the battery has excellent output characteristics at room temperature and short-time output characteristics at low temperatures. At this time, the polyaniline ratio in the electrode is 5.5 parts by weight with respect to the active material, and the output characteristics are −30 ° C. and SOC 40% when the output density of the polyaniline-free system at 25 ° C. is 1.0. The output density ratio under the conditions is 2.23, 25 ° C., the output density ratio under the SOC 60% condition is 1.05, and the output density ratio at −30 ° C. is not reduced without reducing the output density ratio at room temperature. It is possible to improve.
特開平８−１３８６４９号では、少なくとも正極の一部を、１〜２０重量部の導電性高分子（ポリアニリン、ポリピロール）電解酸化膜で覆うことで、初期容量のロスが解消され且つサイクル寿命特性等が安定した正極性能が得られる。この導電性高分子電解酸化膜が、正極に対して１重量部以下であると容量増加の効果が小さく、２０重量部以上であると正極電極が脆くなりひび割れてしまう。詳しくは、ポリピロールを添加しない電池では、初期効率が５８．２％に対し、ポリピロールを添加した電池の初期効率が８２．０％と２３．８％効率が上昇し、高い容量が得られている。 In JP-A-8-138649, at least a part of the positive electrode is covered with 1 to 20 parts by weight of a conductive polymer (polyaniline, polypyrrole) electrolytic oxide film, so that loss of initial capacity is eliminated and cycle life characteristics, etc. However, stable positive electrode performance can be obtained. If this conductive polymer electrolytic oxide film is 1 part by weight or less with respect to the positive electrode, the effect of increasing the capacity is small, and if it is 20 parts by weight or more, the positive electrode becomes brittle and cracks. Specifically, in the battery not added with polypyrrole, the initial efficiency of the battery added with polypyrrole is 82.0% and the efficiency of 23.8% is increased, and a high capacity is obtained. .
これまで、化学重合法、電解重合法により作製された導電性高分子を混合、被覆という種々の手法でリチウム二次電池用正極に複合化する検討がされており、室温における活物質の利用率向上及び電池の低抵抗化、低温条件下における短時間（１０秒間）の出力特性向上等の効果が確認されている。 So far, various studies have been conducted to mix and coat conductive polymers prepared by chemical polymerization and electropolymerization methods into a positive electrode for lithium secondary batteries, and the utilization rate of active materials at room temperature. Effects such as improvement, reduction of battery resistance, and improvement of output characteristics in a short time (10 seconds) under low temperature conditions have been confirmed.
上記効果を得るための手法の一つとして、化学重合法で作製した導電性高分子を電極中に混合あるいは導電性材料や活物質自身の表面に被覆させたものが知られている。 As one of the techniques for obtaining the above-mentioned effect, there is known a technique in which a conductive polymer produced by a chemical polymerization method is mixed in an electrode or coated on the surface of the conductive material or the active material itself.
しかし、上記方法で室温における容量改善効果（活物質利用率向上）を得るためには、導電性高分子を活物質として利用し、且つ電極の電子伝導性を改善させるといった観点から、導電性高分子複合量をある程度増加させる必要がある。この場合、電極中に真比重の低い導電性高分子が活物質粒子や導電材同士の接触界面に存在することとなるため、電極密度の低下に伴い電池のエネルギー密度が低下する。 However, in order to obtain a capacity improvement effect at room temperature (improvement of active material utilization) by the above method, from the viewpoint of using a conductive polymer as an active material and improving the electron conductivity of the electrode, it is possible to increase the conductivity. It is necessary to increase the molecular complex amount to some extent. In this case, since the conductive polymer having a low true specific gravity exists in the electrode at the contact interface between the active material particles and the conductive material, the energy density of the battery decreases as the electrode density decreases.
また、導電性高分子複合化の効果の例として、低温（−３０℃）環境下における、短時間（１０秒間）での出力特性向上効果が確認されているが、この効果を得るためには、電極中の導電性高分子複合量が少なくとも５重量部程度は必要である。しかしながらこの場合、短時間（１０秒）の低抵抗化には有効であるが、全体としての放電容量（１０秒以降の放電特性）が低下してしまうという課題があった。 In addition, as an example of the effect of conducting polymer composite, an effect of improving output characteristics in a short time (10 seconds) in a low temperature (−30 ° C.) environment has been confirmed. The amount of the conductive polymer complex in the electrode is required to be at least about 5 parts by weight. However, in this case, although effective for reducing the resistance in a short time (10 seconds), there is a problem that the overall discharge capacity (discharge characteristics after 10 seconds) is lowered.
この様な上記効果を得るための化学重合法から得られる導電性高分子は、有機溶媒に対し不溶性と可溶性のものをそれぞれ用いた検討がされている。中でも可溶性のものを用いた場合、被覆された導電性高分子自身の分子量が低いため、電解液等の有機溶媒への溶解により、電池性能の信頼性が低下するという問題があった。 As the conductive polymer obtained from the chemical polymerization method for obtaining such an effect, studies have been made using insoluble and soluble polymers in organic solvents. Among them, when a soluble one is used, the coated conductive polymer itself has a low molecular weight, so that there is a problem that the reliability of the battery performance is lowered due to dissolution in an organic solvent such as an electrolytic solution.
また、電解重合法にて導電性高分子膜を電極中に直接形成させることで、室温の初期充放電効率の改善効果が確認されているが、この系では低温での高容量化及び低抵抗化の効果について何ら記載がない。この様な電解重合法により得られる導電性高分子膜の場合、正極に対し１重量部以上複合化することで、室温での容量改善効果は得られるが、低温条件下では抵抗が高くなり、放電特性が低下してしまうという問題がある。 Moreover, the effect of improving the initial charge / discharge efficiency at room temperature has been confirmed by directly forming a conductive polymer film in the electrode by electrolytic polymerization, but this system has a higher capacity and lower resistance at lower temperatures. There is no description about the effect of conversion. In the case of a conductive polymer film obtained by such an electropolymerization method, a capacity improvement effect at room temperature can be obtained by compounding 1 part by weight or more with respect to the positive electrode, but the resistance becomes high under low temperature conditions, There is a problem that the discharge characteristics are deteriorated.
この様に、前記従来技術においては、室温での容量改善または低温での短時間出力特性の向上のどちらの効果を得る場合でも、正極中への導電性高分子複合量は少なくとも１重量部以上必要とされており、より高い効果を得るためには電極中の導電性高分子複合量を増加させる必要があるとされてきた。また、その一方でこれら従来技術では、いずれの手法を用いた場合でも、低温での放電容量維持率を低下させてしまうという大きな課題を残してきた。 As described above, in the prior art, the composite amount of the conductive polymer in the positive electrode is at least 1 part by weight or more in any case of obtaining the effect of improving the capacity at room temperature or improving the output characteristics for a short time at low temperature. In order to obtain a higher effect, it has been necessary to increase the amount of the conductive polymer composite in the electrode. On the other hand, these conventional techniques have left a big problem of reducing the discharge capacity maintenance rate at a low temperature, regardless of which method is used.
本発明者は、上記の様な従来技術の問題点に留意しつつ研究を進めた結果、非水系二次電池用正極である遷移金属酸化物及び導電材、バインダーから構成される正極電極に対し、電解重合法を用いて膜状の導電性高分子を簡便且つ１重量部以下の微量で正極活物質及び導電材表面に被覆させた形態とすることで、室温における電池性能を損なうことなく、低温においても低抵抗且つ高容量を有する正極を用いた非水系二次電池を構築することが可能となり、上記課題を解決できることを見出し、本発明に至った。 As a result of conducting research while paying attention to the problems of the prior art as described above, the present inventor has developed a positive electrode composed of a transition metal oxide, a conductive material, and a binder, which is a positive electrode for a non-aqueous secondary battery. In addition, by forming a film-like conductive polymer on the surface of the positive electrode active material and the conductive material in a small amount of 1 part by weight or less using an electrolytic polymerization method, without impairing battery performance at room temperature, It became possible to construct a non-aqueous secondary battery using a positive electrode having low resistance and high capacity even at low temperatures, and found that the above problems could be solved, leading to the present invention.
本発明は、上記実情に鑑みてなされたものであり、非水系二次電池用正極において、電解重合法を用いて導電性高分子を正極活物質に対し１重量部以下の微量で、活物質及び導電材表面に膜状で被覆させることにより、室温における電池特性を損なうことなく、低温においても低抵抗且つ高容量を有する正極を提供することが可能となっている。 The present invention has been made in view of the above circumstances, and in a positive electrode for a non-aqueous secondary battery, an electroactive polymer is used in a trace amount of 1 part by weight or less with respect to the positive electrode active material using an electrolytic polymerization method. Further, by covering the surface of the conductive material with a film, it is possible to provide a positive electrode having a low resistance and a high capacity even at a low temperature without impairing battery characteristics at room temperature.
すなわち本発明は、以下の構成からなることを特徴とし、上記課題を解決するものである。 That is, the present invention is characterized by having the following configuration and solves the above problems.
〔１〕リチウムイオンをドープ・脱ドープ可能な正極活物質を含む正極において、正極活物質に対し、電解重合法により０．０１〜０．７重量部の導電性高分子が複合化され、−３０℃の条件下において導電性高分子が複合化されていないものに比較して低抵抗且つ高容量を有することを特徴とする非水系二次電池用正極。 [1] In a positive electrode including a positive electrode active material that can be doped / undoped with lithium ions, 0.01 to 0.7 parts by weight of a conductive polymer is compounded by an electrolytic polymerization method with respect to the positive electrode active material , A positive electrode for a non-aqueous secondary battery, characterized by having a low resistance and a high capacity as compared with those in which a conductive polymer is not complexed at -30 ° C.
〔２〕導電性高分子膜を複合化させる正極は、正極活物質と導電性材料を含むことを特徴とする前記〔１〕に記載の非水系二次電池用正極。 [2] The positive electrode for a non-aqueous secondary battery according to [1], wherein the positive electrode that combines the conductive polymer film includes a positive electrode active material and a conductive material.
〔３〕前記導電性高分子複合化前の前記正極は、電極電気伝導度が少なくとも1×１０-３Ｓ／ｃｍ以上であることを特徴とする前記〔１〕または〔２〕に記載の非水系二次電池用正極。 [3] The non-electrode according to [1] or [2], wherein the positive electrode before the conductive polymer composite has an electrode electrical conductivity of at least 1 × 10 −3 S / cm or more. Positive electrode for water-based secondary batteries.
〔４〕複合化させる導電性高分子膜がポリアニリンであることを特徴とする前記〔１〕〜〔３〕のいずれかに記載の非水系二次電池用正極。 [4] The positive electrode for a non-aqueous secondary battery according to any one of [1] to [3], wherein the conductive polymer film to be combined is polyaniline.
〔５〕前記〔１〕〜〔４〕のいずれかに記載されている非水系二次電池用正極を正極とする非水系二次電池。 [5] A nonaqueous secondary battery having the positive electrode for a nonaqueous secondary battery described in any one of [1] to [4] as a positive electrode.
本発明により高い電極電気伝導度を有する導電性高分子複合正極が得られ、且つその非水系二次電池用正極を用いることで、低温において低抵抗且つ高容量な非水系二次電池を構築可能な効果を奏する。
特に、導電性高分子複合化前の正極の電極電気伝導度を少なくとも1×１０-３Ｓ／ｃｍ以上にすることにより、蓄電デバイスが充放電時に短時間で大きな電力を出し入れすることが可能な特性を所持し、電池容量Ｃ（Ａｈ）の１０倍（Ｃ（Ａ）×１０）もの電流で充放電させることが可能となり、ハイブリッド車に代表されるエネルギー回生を含む蓄電用途となる非水系二次電池を提供することができる。
Conductive polymer composite positive electrode having high electrode electrical conductivity can be obtained by the present invention, and non-aqueous secondary battery with low resistance and high capacity can be constructed at low temperature by using the positive electrode for non-aqueous secondary battery. Has an effect.
In particular, by setting the electrode electrical conductivity of the positive electrode before the composite of the conductive polymer to at least 1 × 10 −3 S / cm or more, the electricity storage device can take in and out a large amount of power in a short time during charging and discharging. It has the characteristics and can be charged and discharged with a current 10 times as large as the battery capacity C (Ah) (C (A) x 10). A secondary battery can be provided.
本発明の一実施形態について、説明すれば以下のとおりである。本発明における非水系二次電池用正極は、リチウムイオンをドープ・脱ドープ可能な正極活物質と導電性材料、バインダーから構成された正極に対し、電解重合法を用いて０．０１〜０．７重量部の導電性高分子膜を複合化させた正極である。 One embodiment of the present invention will be described as follows. The positive electrode for a non-aqueous secondary battery in the present invention is 0.01 to 0.00% by electrolytic polymerization on a positive electrode composed of a positive electrode active material that can be doped / dedoped with lithium ions, a conductive material, and a binder. This is a positive electrode in which 7 parts by weight of a conductive polymer film is combined.
前記構成の正極とすることで低温条件下において低抵抗且つ高容量な非水系二次電池を得ることが可能となる。導電性高分子はセル内に各種モノマーを添加し、電解重合法により直接正極へ複合化させることとなる。このとき、導電性高分子モノマーの重合反応は、電極内の正極活物質、導電性材料の粒子表面で起こり、結果として活物質、導電材表面を導電性高分子膜で被覆した形態となる。 By using the positive electrode having the above-described configuration, it is possible to obtain a non-aqueous secondary battery having low resistance and high capacity under low temperature conditions. The conductive polymer is compounded directly to the positive electrode by adding various monomers in the cell and electrolytic polymerization. At this time, the polymerization reaction of the conductive polymer monomer occurs on the surface of the particles of the positive electrode active material and the conductive material in the electrode, and as a result, the active material and the surface of the conductive material are covered with the conductive polymer film.
正極中の導電性高分子複合量は０．７重量部以下で所望の効果が得られるが、更に０．５重量部以下ではより高い効果が得られる。これは、電解重合法で得られる導電性高分子が、正極内の活物質粒子及び導電材粒子とで構成されるマトリックスに、その活物質と導電材の接合状態を切断することなく、薄膜状に被覆することが可能となるからである。この様にして得られる導電性高分子膜は、少なくとも３５ｎｍ以下の薄膜状で被覆されていることが望ましく、２５ｎｍ以下ならより高い効果が得られる。しかし、導電性高分子の複合量が０．０１重量部以下になると所望の効果が得にくくなる。これは、導電性高分子膜の厚さが０．５ｎｍ以下と非常に薄くなるため、正極活物質と導電材、バインダー等の電極構成材料の全体を被覆した形で形成させることが困難となり、結果として活物質と導電材、導電性高分子との連続的な伝導経路が形成されにくく、所望の効果を得ることが困難となる。また、化学重合法の場合では、あらかじめ活物質粒子の表面に形成させた後に導電材、バインダーと混合または、電極作製時に粉末状で得られた導電性高分子を混合することとなる。そのため、活物質と導電材に対する導電性高分子の接触状態が電解重合法で得られる膜状の場合と異なり、活物質、導電材と導電性高分子との連続的な伝導経路を確保することが困難となるため、所望の効果が得にくくなる。 A desired effect can be obtained when the composite amount of the conductive polymer in the positive electrode is 0.7 parts by weight or less, but a higher effect is obtained when the amount is 0.5 parts by weight or less. This is because the conductive polymer obtained by the electropolymerization method is formed into a thin film without cutting the bonding state of the active material and the conductive material into the matrix composed of the active material particles and the conductive material particles in the positive electrode. This is because it can be coated. The conductive polymer film thus obtained is desirably coated with a thin film of at least 35 nm or less, and if it is 25 nm or less, a higher effect can be obtained. However, when the composite amount of the conductive polymer is 0.01 parts by weight or less, it is difficult to obtain a desired effect. This is because the thickness of the conductive polymer film is very thin, 0.5 nm or less, and it is difficult to form the positive electrode active material, the conductive material, and the entire electrode constituent material such as a binder, As a result, it is difficult to form a continuous conduction path between the active material, the conductive material, and the conductive polymer, and it is difficult to obtain a desired effect. In the case of the chemical polymerization method, the conductive material and the binder are mixed with the conductive material and the binder after being formed in advance on the surface of the active material particles, or the conductive polymer obtained in the powder form at the time of electrode preparation is mixed. Therefore, unlike the film-like case where the contact state of the conductive polymer with the active material and the conductive material is obtained by the electrolytic polymerization method, a continuous conduction path between the active material, the conductive material and the conductive polymer is ensured. Therefore, it becomes difficult to obtain a desired effect.
従来技術においては、導電性高分子複合量が微量である場合、室温での高容量化や低温での短時間における出力特性向上の効果が得にくいとされており、電極内の導電性高分子複合量は少なくとも１重量部以上、もしくはそれ以上必要とされてきた。 In the prior art, when the amount of the conductive polymer complex is small, it is difficult to obtain the effect of increasing the capacity at room temperature and improving the output characteristics in a short time at low temperature. The composite amount has been required to be at least 1 part by weight or more.
本発明の様に、電解重合法により得られる導電性高分子膜を正極活物質や導電材の表面に微量且つ薄く被覆した形態を取ることで、室温での充放電特性を損なうことなく低温での低抵抗化及び高容量化の両方の効果を同時に得ることが可能となる。また、この手法では、ごく微量の導電性高分子を電極中に均一な薄膜状に形成させることが可能であるため、電極中で導電性高分子が偏在する心配がないと共に電極密度の大幅な低下による電池のエネルギー密度低下の問題も解消できる。 As in the present invention, a conductive polymer film obtained by electrolytic polymerization is coated on the surface of the positive electrode active material or conductive material in a trace amount and thinly, so that the charge and discharge characteristics at room temperature are not impaired. It is possible to simultaneously obtain the effects of both lowering the resistance and increasing the capacity. In addition, in this method, since a very small amount of conductive polymer can be formed in a uniform thin film in the electrode, there is no fear that the conductive polymer is unevenly distributed in the electrode and the electrode density is greatly increased. The problem of a decrease in the energy density of the battery due to the decrease can also be solved.
本発明における正極活物質としては、特に限定されるものではないが、例えば、リチウム複合コバルト酸化物、リチウム複合ニッケル酸化物、リチウム複合マンガン酸化物、リチウム複合バナジウム酸化物、或いはこれらの混合物、更にはこれら複合酸化物に異種金属元素を一種以上添加した系、鉄リン酸リチウム等の種々の遷移金属とポリアニオンとで形成される材料、更には、五酸化バナジウム、二酸化マンガン、二硫化モリブデン等のリチウムを吸蔵、放出可能であるがリチウムを含まない金属酸化物または硫化物を用いることも可能である。又、これらリチウム吸蔵、放出可能な金属酸化物または硫化物の粒子形態及び粒子径は、特に限定されるものではないが、例えば単分散粒子、凝集粒子、或いはこれらの混合物、更にはこれらリチウムを吸蔵、放出可能な金属酸化物または硫化物の異なる粒子径および比表面積を有する粒子の混合物を用いることが可能である。 The positive electrode active material in the present invention is not particularly limited. For example, lithium composite cobalt oxide, lithium composite nickel oxide, lithium composite manganese oxide, lithium composite vanadium oxide, or a mixture thereof, Is a system in which one or more different metal elements are added to these composite oxides, materials formed from various transition metals such as lithium iron phosphate and polyanions, and further, vanadium pentoxide, manganese dioxide, molybdenum disulfide, etc. It is also possible to use a metal oxide or sulfide that can occlude and release lithium but does not contain lithium. Further, the particle form and particle size of the metal oxides or sulfides that can occlude and release lithium are not particularly limited. For example, monodisperse particles, agglomerated particles, or a mixture thereof, and further lithium It is possible to use a mixture of particles having different particle sizes and specific surface areas of occluding and releasing metal oxides or sulfides.
上記正極活物質を用いて作製する電極構成については、特に限定されるものではなく、導電材を添加せずに正極活物質とバインダーから成る電極に導電性高分子を複合化した場合でも所望の効果は得られるが、導電材を添加し、電子伝導経路をあらかじめ形成させた正極とすることで、導電性高分子複合化の効果がより高く得られる形態となっている。 The electrode structure produced using the positive electrode active material is not particularly limited. Even when a conductive polymer is combined with an electrode composed of a positive electrode active material and a binder without adding a conductive material, a desired configuration can be obtained. Although an effect can be obtained, a conductive polymer is added to form a positive electrode in which an electron conduction path is formed in advance, so that a conductive polymer composite effect can be obtained more highly.
すなわち上記記載の正極は、導電性材料を含まない場合でも導電性高分子の複合化が可能であり、上記特性改善の効果が得られるが、カーボンブラック、アセチレンブラック等の導電性材料を電極内に混合し、あらかじめ電極内に電子伝導経路を形成させた構成にすることで導電性高分子複合化の効果がより高く得られる。 In other words, the positive electrode described above can be combined with a conductive polymer even when it does not contain a conductive material, and the effect of improving the above characteristics can be obtained. However, a conductive material such as carbon black or acetylene black is used in the electrode. In order to obtain a higher effect of conducting polymer composite, an electron conduction path is formed in the electrode in advance.
本発明の非水系二次電池に用いる正極を成形する場合、必要に応じ、導電材、バインダーを用いる。バインダーの種類は、特に限定されるものではないが、ポリフッ化ビニリデン、ポリ四フッ化エチレン等のフッ素系樹脂類、フッ素ゴム、ＳＢＲ、アクリル樹脂、ポリエチレン、ポリプロピレン等のポリオレフィン類などが例示される。バインダー量は、特に限定されないが、通常、正極活物質に対して１〜１０重量部程度添加するのが好ましい。また、導電材の種類は、特に限定されるものではないが、カーボンブラック、アセチレンブラックが例示される。導電材量は、特に限定されるものではないが、通常、正極活物質に対して１〜１５重量部程度添加され、電極密度を高くするためには、できるだけ電極内の導電材比率を減少させることが好ましい。
また、本発明の非水系二次電池に用いる正極は、塗布成形、プレス成形、ロール成形等一般的な電極成形法を用いて製造する事が可能である。
When forming the positive electrode used for the non-aqueous secondary battery of the present invention, a conductive material and a binder are used as necessary. The type of the binder is not particularly limited, and examples thereof include fluorine resins such as polyvinylidene fluoride and polytetrafluoroethylene, and polyolefins such as fluoro rubber, SBR, acrylic resin, polyethylene, and polypropylene. . The amount of the binder is not particularly limited, but it is usually preferable to add about 1 to 10 parts by weight with respect to the positive electrode active material. The type of the conductive material is not particularly limited, and examples thereof include carbon black and acetylene black. The amount of the conductive material is not particularly limited. Usually, about 1 to 15 parts by weight is added to the positive electrode active material, and in order to increase the electrode density, the ratio of the conductive material in the electrode is reduced as much as possible. It is preferable.
Moreover, the positive electrode used for the non-aqueous secondary battery of the present invention can be manufactured using a general electrode forming method such as coating, press forming, roll forming or the like.
導電性高分子膜を複合化させる前の正極を成形する方法は、所望の非水系二次電池の特性等に応じて公知の手法から適宜選択することができるが、例えば、正極活物質とバインダー、必要に応じて導電性材料を加え、その混合物にＮ−メチル−２−ピロリドン（ＮＭＰ）等の溶媒を混合してスラリーとし、これを集電体に塗布し、乾燥後、圧縮等して成形される。電極成形時の電極密度については、任意に選択することが可能であり、活物質と導電材、バインダーの混合比率により異なるが、２．０ｇ／ｃｍ３以上に成形が可能である。 The method of forming the positive electrode before the composite of the conductive polymer film can be appropriately selected from known methods depending on the desired characteristics of the nonaqueous secondary battery, etc. For example, the positive electrode active material and the binder If necessary, a conductive material is added, and the mixture is mixed with a solvent such as N-methyl-2-pyrrolidone (NMP) to form a slurry, which is applied to a current collector, dried, compressed, etc. Molded. About the electrode density at the time of electrode shaping | molding, it is possible to select arbitrarily, and although it changes with mixing ratios of an active material, a electrically conductive material, and a binder, shaping | molding is possible to 2.0 g / cm < 3 > or more.
前記にて作製される導電性材料を含む正極の電気伝導度は、特に限定されるものではないが、ハイブリッド車に代表されるエネルギー回生を含む蓄電用途においては、蓄電デバイスが充放電時に短時間で大きな電力を出し入れすることが可能な特性を所持する必要があり、電池容量Ｃ（Ａｈ）の１０倍（Ｃ（Ａ）×１０）もの電流で充放電させる場合が多く、少なくとも１０−３Ｓ／ｃｍ以上であることが好ましい。また、正極の電気伝導度は、正極活物質の種類、粒子径などにも依存するが、高ければ高いほど良く、電極内に正極活物質とそれに対する必要量の導電材（通常１〜１５重量部）を加えることで１０−３Ｓ／ｃｍ以上の電気伝導度を得ることが可能であり、その際、導電性高分子複合化の効果を、より高く発揮することが可能となる。 The electrical conductivity of the positive electrode including the conductive material produced as described above is not particularly limited. However, in power storage applications including energy regeneration typified by a hybrid vehicle, the power storage device is charged and discharged for a short time. It is necessary to possess characteristics that allow large amounts of power to be taken in and out, and is often charged and discharged with a current that is 10 times the battery capacity C (Ah) (C (A) × 10), at least 10 −3 S / Cm or more is preferable. The electrical conductivity of the positive electrode also depends on the type and particle diameter of the positive electrode active material, but the higher the better, the better the positive electrode active material and the necessary amount of conductive material (usually 1 to 15 weight) in the electrode. Part)), it is possible to obtain an electric conductivity of 10 −3 S / cm or more, and at that time, it is possible to further enhance the effect of conducting polymer composite.
上記の様な形態の正極（１０−３Ｓ／ｃｍ以上の電気伝導度を有する）に対し、導電性高分子膜を電解重合法により形成させることで、電極内部の導電性をさらに高めることが可能となり、所望の電池特性が向上する。また、この複合化により、電解重合前の電極内における導電材比率を減少させ、電極密度を高くできる可能性が高まり、電池のエネルギー密度向上にも繋がる。 For the positive electrode (having an electric conductivity of 10 −3 S / cm or more) having the above-described form, the conductivity inside the electrode can be further increased by forming a conductive polymer film by electrolytic polymerization. The desired battery characteristics are improved. In addition, this combination reduces the ratio of the conductive material in the electrode before electrolytic polymerization, increases the possibility of increasing the electrode density, and leads to an improvement in the energy density of the battery.
正極を集電体上に成形する場合には、集電体の材質などは材質の耐電圧性を考慮した上で選択すれば特に限定されず、ステンレス鋼箔、チタン箔、アルミニウム箔等が例示される。 When the positive electrode is formed on the current collector, the material of the current collector is not particularly limited as long as it is selected in consideration of the voltage resistance of the material, and examples include stainless steel foil, titanium foil, and aluminum foil. Is done.
上記正極を用いて作製したセルを用いて、電解重合法により導電性高分子を複合化させる。この電解重合法にて得られる導電性高分子膜を形成させる箇所については、特に限定されるものではなく、電極内の正極活物質、導電材いずれの表面に複合化されていてもよい。また、電解重合法にてあらかじめ正極活物質粉末に導電性高分子を複合化させ、その複合化させた活物質を用いて電極を作製することも可能であるが、上記の様に電極を成形した後に電解重合を行う方が、正極活物質、導電材及びバインダーの混合物中において、正極活物質と導電材が連続的に接続されたマトリックスに対して被覆した膜を形成させることができる。この様に、導電性高分子膜を複合化させた電極を、電池に組込むことも可能であり、作業工程を簡略化することが可能となり、より簡便となる。 A conductive polymer is compounded by an electrolytic polymerization method using a cell manufactured using the positive electrode. The location where the conductive polymer film obtained by this electrolytic polymerization method is formed is not particularly limited, and may be composited on the surface of either the positive electrode active material or the conductive material in the electrode. It is also possible to composite a conductive polymer with the positive electrode active material powder in advance by electrolytic polymerization, and to produce an electrode using the composite active material. However, the electrode is molded as described above. In the mixture of the positive electrode active material, the conductive material, and the binder, the film that covers the matrix in which the positive electrode active material and the conductive material are continuously connected can be formed by performing the electropolymerization. In this manner, an electrode in which a conductive polymer film is combined can be incorporated into a battery, and the work process can be simplified, which makes it easier.
上記作製した正極活物質、導電材、バインダーより構成される電極を用いて、セルを作製し、電解重合を行うことで正極に導電性高分子を複合化させる。 Using the electrode composed of the positive electrode active material, the conductive material, and the binder prepared as described above, a cell is prepared, and the conductive polymer is combined with the positive electrode by performing electrolytic polymerization.
導電性高分子を電解重合するセル構成を以下に示す。セル構成としては、特に限定されるものではなく、上記作製の遷移金属酸化物を正極活物質とする正極と黒鉛材料から成る負極及び非水系電解液（場合によっては、セパレータを含む）より構成された非水系二次電池内に導電性高分子モノマーを必要量添加し、電解重合を行い、導電性高分子複合正極を得ることも可能であるが、上記にて作製した正極電極と参照極、負極及び非水系電解液（場合によっては、セパレータを含む）から構成される三電極式セルを作製し、電解重合を行った後セルを解体し、導電性高分子が複合化された電極を回収し、新たに電池として組み直しても良い。また、電解重合を行うセルは、正極、負極及び非水系電解液（場合によっては、セパレータを含む）から構成される二電極式セルでも可能である。尚、三電極式及び二電極式セルの対極及び参照極に用いる金属は、特に限定されるものではなく、リチウム、銀、白金など作用極の電位変化が計測可能な金属であれば問題はない。 A cell configuration for electrolytic polymerization of a conductive polymer is shown below. The cell structure is not particularly limited, and is composed of a positive electrode using the transition metal oxide produced above as a positive electrode active material, a negative electrode composed of a graphite material, and a non-aqueous electrolyte (including a separator in some cases). It is also possible to add a necessary amount of a conductive polymer monomer in the non-aqueous secondary battery and perform electropolymerization to obtain a conductive polymer composite positive electrode, but the positive electrode and reference electrode produced above, A three-electrode cell composed of a negative electrode and a non-aqueous electrolyte (including a separator in some cases) is prepared, and after electrolytic polymerization is performed, the cell is disassembled and an electrode combined with a conductive polymer is collected. However, a new battery may be reassembled. Moreover, the cell which performs electrolytic polymerization is also possible with the two-electrode type cell comprised from a positive electrode, a negative electrode, and a non-aqueous electrolyte solution (a separator is included depending on the case). In addition, the metal used for the counter electrode and the reference electrode of the three-electrode type and two-electrode type cell is not particularly limited, and there is no problem as long as the potential change of the working electrode can be measured, such as lithium, silver, and platinum. .
上記導電性高分子の電解重合を行うセルに用いるリチウム塩を含む非水系電解液としては、例えば、ＬｉＰＦ６、ＬｉＢＦ４、ＬｉＣｌＯ４等のリチウム塩をプロピレンカーボネート、エチレンカーボネート、ジエチルカーボネート、ジメチルカーボネート、メチルエチルカーボネート、ジメトキシエタン、γ−ブチロラクトン、酢酸メチル、蟻酸メチル等の１種または２種以上からなる有機溶媒に溶解したものを用いることができる。また、電解液の電解質塩濃度は、特に限定されるものではないが、一般的に０．５〜２ｍｏｌ／ｌ程度が実用的である。電解液は、当然のことながら、水分が１００ｐｐｍ以下のものを用いることが好ましい。 Examples of the non-aqueous electrolyte solution containing a lithium salt used in a cell for performing electropolymerization of the conductive polymer include lithium salts such as LiPF 6 , LiBF 4 , and LiClO 4, such as propylene carbonate, ethylene carbonate, diethyl carbonate, and dimethyl carbonate. , Methyl ethyl carbonate, dimethoxyethane, γ-butyrolactone, methyl acetate, methyl formate and the like dissolved in one or more organic solvents can be used. The electrolyte salt concentration of the electrolytic solution is not particularly limited, but generally about 0.5 to 2 mol / l is practical. As a matter of course, it is preferable to use an electrolytic solution having a water content of 100 ppm or less.
上記電解液に対する導電性高分子モノマーの濃度は、特に限定されるものではなく、正極活物質に対する導電性高分子複合量により任意に決めることが可能であるが、一般的には０．００１〜４ｍｏｌ／ｌ程度が実用的である。しかし、０．００１ｍｏｌ／ｌ未満ではモノマー濃度が低すぎるため重合反応の進行が遅くなり、４ｍｏｌ／ｌを超えると電解質溶液に溶解し難くなる。 The concentration of the conductive polymer monomer with respect to the electrolytic solution is not particularly limited, and can be arbitrarily determined depending on the amount of the conductive polymer complex with respect to the positive electrode active material. About 4 mol / l is practical. However, if it is less than 0.001 mol / l, the monomer concentration is too low, so the progress of the polymerization reaction is slow, and if it exceeds 4 mol / l, it is difficult to dissolve in the electrolyte solution.
上記セルにおいて、正極、負極の間に絶縁、電解液保持の目的で多くの場合セパレータが配置されるが、このセパレータは、特に限定されるものではなく、ポリエチレン微多孔膜、ポリプロピレン微多孔膜、あるいはポリエチレンとポリプロピレンの積層膜、セルロース、ガラス繊維、アラミド繊維、ポリアクリルニトリル繊維等からなる織布、あるいは不織布等があり、その目的と状況に応じ、適宜決定することが可能である。一方、固体電解質系等の電解質とセパレータ両方の機能を兼ね備えた系では、セパレータを用いない場合もある。 In the above cell, a separator is often disposed between the positive electrode and the negative electrode for the purpose of insulation and electrolyte solution retention, but this separator is not particularly limited, and a polyethylene microporous film, a polypropylene microporous film, Alternatively, there are a laminated film of polyethylene and polypropylene, a woven fabric or a nonwoven fabric made of cellulose, glass fiber, aramid fiber, polyacrylonitrile fiber, and the like, which can be appropriately determined according to the purpose and situation. On the other hand, in a system having both functions of an electrolyte such as a solid electrolyte system and a separator, the separator may not be used.
本発明の非水系二次電池用正極に複合化させる導電性高分子としては、ポリアニリン、ポリパラフェニリン、ポリピロール、ポリチオフェン、ポリアズレン、ポリアセン、ポリアセチレン、ポリフェニレンスルフィド、ポリフェニレンオキシドおよびこれらの誘導体を挙げることができる。中でも、リチウム遷移金属酸化物材料を正極として用いる場合、このリチウム遷移金属酸化物の酸化還元電位と近く且つ同電位範囲内での電気伝導度が１００Ｓ／ｃｍを示すポリアニリンおよびその誘導体が望ましい。 Examples of the conductive polymer to be combined with the positive electrode for the non-aqueous secondary battery of the present invention include polyaniline, polyparaphenylin, polypyrrole, polythiophene, polyazulene, polyacene, polyacetylene, polyphenylene sulfide, polyphenylene oxide, and derivatives thereof. Can do. Above all, the case of using lithium transition metal oxide material as a positive electrode, polyaniline and its derivatives electrical conductivity indicates 10 0 S / cm in the oxidation-reduction potential and near and within the same potential range of the lithium transition metal oxide is desirable .
上記セルに対して、定電流または定電圧にて充電（酸化反応）し、導電性高分子を電解重合することで、正極活物質及び導電材表面に膜状で被覆させた正極を作製する。この時、電解重合法にて得られる導電性高分子複合量の制御方法については特に限定されないが、セル内の電解液に添加するモノマー濃度もしくは充電時の電気量により制御が可能である。又、電解重合を行う際の充電方法についても特に限定されず、定電流、定電圧の単独または定電流と定電圧の併用いずれの方法でも複合化が可能である。 The cell is charged (oxidation reaction) at a constant current or a constant voltage, and a conductive polymer is electrolytically polymerized to produce a positive electrode in which the surface of the positive electrode active material and the conductive material is coated with a film. At this time, the method for controlling the amount of the conductive polymer composite obtained by the electrolytic polymerization method is not particularly limited, but it can be controlled by the concentration of the monomer added to the electrolytic solution in the cell or the amount of electricity at the time of charging. Further, the charging method for carrying out the electropolymerization is not particularly limited, and it can be combined by any method of constant current, constant voltage alone or a combination of constant current and constant voltage.
導電性高分子の電解重合は、導電性高分子モノマーが酸化重合される電圧範囲内であれば、いずれの電圧で行うことも可能であるが、導電性高分子モノマーが重合される電圧範囲の上限に近づくにつれ、導電性高分子の生成速度を速めることとなり、電極内における導電性高分子の形成される箇所に偏りが生じてしまう可能性がある。そのため、電極内に均一且つ薄膜状で導電性高分子を形成させたい場合は、導電性高分子モノマーが重合される電圧範囲の上限電圧を少し下げた電圧範囲で電解重合を行うことが望ましい。 The electropolymerization of the conductive polymer can be carried out at any voltage as long as it is within the voltage range in which the conductive polymer monomer is oxidatively polymerized. As the upper limit is approached, the generation rate of the conductive polymer is increased, and there is a possibility that the portion where the conductive polymer is formed in the electrode is biased. Therefore, when it is desired to form the conductive polymer in a uniform and thin film shape in the electrode, it is desirable to perform electrolytic polymerization in a voltage range in which the upper limit voltage of the voltage range in which the conductive polymer monomer is polymerized is slightly lowered.
導電性高分子を高い電圧範囲で電解重合すると生成速度が速いため、重合度の低い導電性高分子が重合され、機械的強度が低い場合がある。重合度の低い導電性高分子である場合、充放電サイクルと共に電解液中に複合化された導電性高分子が溶解してしまい、電池の信頼性が損なわれる危険性がある。そのため、比較的低い電圧範囲且つ低電流密度で重合することにより、電極内に均一で且つ重合度の高い導電性高分子を複合化することが必要である。 When a conductive polymer is electrolytically polymerized in a high voltage range, the production rate is fast, and therefore a conductive polymer having a low degree of polymerization is polymerized and the mechanical strength may be low. In the case of a conductive polymer having a low degree of polymerization, there is a risk that the conductive polymer combined in the electrolyte solution is dissolved together with the charge / discharge cycle, and the reliability of the battery is impaired. For this reason, it is necessary to combine a conductive polymer that is uniform and has a high degree of polymerization in the electrode by polymerization in a relatively low voltage range and low current density.
上記の様な条件で、電解重合した導電性高分子膜を、正極活物質に対し０．８重量部以上複合化した場合、低温条件下での抵抗が高くなり放電特性が低下する。正極活物質に対する導電性高分子複合量が、０．７重量部以下で所望の効果が得られ、更に０．５重量部以下ならより高い効果が得られる。上記電解重合法より得られる導電性高分子膜の被覆箇所は何ら限定されるものでなく、電極中の正極活物質、導電材いずれの表面を被覆していても良い。この時の導電性高分子膜の複合量は、元素分析より測定される構成元素の量から算出され、正極活物質に対する比が０．７重量部以下となれば、所望の効果を得ることが可能な形態となる。
一方、導電性高分子膜の複合量が正極活物質に対し０．０１重量部以下となると、導電性高分子膜が薄くなりすぎるため、活物質と導電材、導電性高分子との連続的な伝導経路を形成させることが困難となり、所望の効果が得にくくなる。この様にして得られる導電性高分子膜の厚さは、０．７重量部でおよそ３５ｎｍ、０．５重量部でおよそ２５ｎｍの薄膜状であると予想される。しかし、複合量が０．０１重量部以下では、およそ０．５ｎｍ以下と非常に薄くなりすぎるため、活物質と導電材、導電性高分子との連続的な伝導経路が形成されにくく、所望の効果が得にくくなる。一方、正極活物質に対して０．８重量部以上複合化した場合、形成される膜がおよそ４０ｎｍ以上となり、複合化した導電性高分子膜が逆に正極活物質からのＬｉ＋の拡散を阻害し、低温での放電特性が低下してしまう。
When the electropolymerized conductive polymer film is combined in an amount of 0.8 parts by weight or more with respect to the positive electrode active material under the above conditions, the resistance under low temperature conditions increases and the discharge characteristics deteriorate. A desired effect is obtained when the amount of the conductive polymer composite with respect to the positive electrode active material is 0.7 parts by weight or less, and a higher effect is obtained when the amount is 0.5 parts by weight or less. The coating location of the conductive polymer film obtained by the electrolytic polymerization method is not limited at all, and the surface of either the positive electrode active material or the conductive material in the electrode may be coated. The composite amount of the conductive polymer film at this time is calculated from the amount of constituent elements measured by elemental analysis, and if the ratio to the positive electrode active material is 0.7 parts by weight or less, a desired effect can be obtained. Possible form.
On the other hand, when the composite amount of the conductive polymer film is 0.01 parts by weight or less with respect to the positive electrode active material, the conductive polymer film becomes too thin, so that the active material, the conductive material, and the conductive polymer continuously It becomes difficult to form a simple conduction path, and it becomes difficult to obtain a desired effect. The conductive polymer film thus obtained is expected to have a thickness of about 35 nm at 0.7 parts by weight and about 25 nm at 0.5 parts by weight. However, when the composite amount is 0.01 parts by weight or less, it becomes too thin at about 0.5 nm or less, so that it is difficult to form a continuous conduction path between the active material, the conductive material, and the conductive polymer. It becomes difficult to obtain the effect. On the other hand, when 0.8 parts by weight or more is combined with the positive electrode active material, the formed film becomes approximately 40 nm or more, and the composite conductive polymer film conversely diffuses Li + from the positive electrode active material. This hinders discharge characteristics at low temperatures.
電解重合法にて導電性高分子を複合化した電極は、非水系溶媒中で重合処理を行うため、複合化された正極は有機溶媒で洗浄後乾燥させて使用、あるいは未乾燥のまま使用しても非水系二次電池用正極として用いることが可能である。 Electrode polymerized electrodes composed of conductive polymers are polymerized in a non-aqueous solvent, so the composite positive electrode can be used after washing with an organic solvent and drying, or it can be used undried. However, it can be used as a positive electrode for a non-aqueous secondary battery.
本発明の非水系二次電池は、前記の導電性高分子膜が複合化された正極、負極、セパレータからなる２層以上の電極が積層された電極積層体を電池容器内に収容した構成となる。 The non-aqueous secondary battery of the present invention has a configuration in which an electrode laminate in which two or more electrodes composed of a positive electrode, a negative electrode, and a separator in which the conductive polymer film is combined is laminated is contained in a battery container. Become.
本発明に用いる負極活物質としては、リチウム系の負極材料であれば特に限定されるものではないが、リチウムドープ及び脱ドープ可能な材料であることが、安全性、サイクル寿命等の信頼性が向上するため、好ましい。リチウムドープ及び脱ドープ可能な材料としては、公知のリチウムイオン電池材料として使用されている黒鉛系物質、炭素系物質、錫酸化物系、ケイ素系酸化物等の金属酸化物等が挙げられる。 The negative electrode active material used in the present invention is not particularly limited as long as it is a lithium-based negative electrode material. However, a lithium-doped and dedopeable material has safety and reliability such as cycle life. Since it improves, it is preferable. Examples of materials that can be doped with lithium and dedope include metal oxides such as graphite-based materials, carbon-based materials, tin oxide-based materials, and silicon-based oxides that are used as known lithium ion battery materials.
本発明の非水系二次電池は、リチウム塩が非水溶媒に溶解されてなる非水系電解液を用いる。本発明において用いる非水系電解液としては、リチウム塩を含む非水系電解液を用いることが可能であり、正極材料の種類、負極材料の性状、充電電圧などの使用条件などに対応して、適宜決定される。リチウム塩を含む非水系電解液としては、例えば、ＬｉＰＦ６、ＬｉＢＦ４、ＬｉＣｌＯ４等のリチウム塩をプロピレンカーボネート、エチレンカーボネート、ジエチルカーボネート、ジメチルカーボネート、メチルエチルカーボネート、ジメトキシエタン、γ−ブチロラクトン、酢酸メチル、蟻酸メチル等の１種または２種以上からなる有機溶媒に溶解したものを用いることができる。また、電解液の電解質塩濃度は、特に限定されるものではないが、一般的に０．５〜２ｍｏｌ／ｌ程度が実用的である。電解液は、当然のことながら、水分が１００ｐｐｍ以下のものを用いることが好ましい。 The non-aqueous secondary battery of the present invention uses a non-aqueous electrolyte solution in which a lithium salt is dissolved in a non-aqueous solvent. As the non-aqueous electrolyte solution used in the present invention, a non-aqueous electrolyte solution containing a lithium salt can be used. According to the use conditions such as the type of the positive electrode material, the property of the negative electrode material, the charging voltage, etc. It is determined. Examples of the non-aqueous electrolyte containing a lithium salt include lithium salts such as LiPF 6 , LiBF 4 , LiClO 4 , propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, dimethoxyethane, γ-butyrolactone, acetic acid. What was melt | dissolved in the organic solvent which consists of 1 type, or 2 or more types, such as methyl and methyl formate, can be used. The electrolyte salt concentration of the electrolytic solution is not particularly limited, but generally about 0.5 to 2 mol / l is practical. As a matter of course, it is preferable to use an electrolytic solution having a water content of 100 ppm or less.
本発明の非水系二次電池において、正極、負極の間に絶縁、電解液保持の目的で多くの場合セパレータが配置されるが、このセパレータは、特に限定されるものではなく、ポリエチレン微多孔膜、ポリプロピレン微多孔膜、あるいはポリエチレンとポリプロピレンの積層膜、セルロース、ガラス繊維、アラミド繊維、ポリアクリルニトリル繊維等からなる織布、あるいは不織布などがあり、その目的と状況に応じ、適宜決定することが可能である。一方、固体電解質系等の電解質とセパレータ両方の機能を兼ね備えた系では、セパレータを用いない場合もある。 In the nonaqueous secondary battery of the present invention, a separator is often disposed between the positive electrode and the negative electrode for the purpose of insulation and electrolyte solution retention, but this separator is not particularly limited, and is a polyethylene microporous membrane. , Polypropylene microporous film, polyethylene and polypropylene laminated film, cellulose, glass fiber, aramid fiber, polyacrylonitrile fiber, woven fabric or non-woven fabric, etc., which can be determined appropriately according to the purpose and situation Is possible. On the other hand, in a system having both functions of an electrolyte such as a solid electrolyte system and a separator, the separator may not be used.
本発明の非水系二次電池の形状は特に限定されるものではなく、コイン型、円筒型、角型、フィルム型等、その目的に応じ、適宜決定することが可能である。 The shape of the non-aqueous secondary battery of the present invention is not particularly limited, and can be appropriately determined according to the purpose, such as a coin type, a cylindrical type, a square type, a film type, and the like.
以下に、実施例を示し、本発明の特徴とするところをさらに明確にするが、本発明は、実施例により何ら限定されるものではない。 Hereinafter, examples will be shown to further clarify the features of the present invention, but the present invention is not limited to the examples.
以下、本発明の実施例及び比較例を挙げてさらに具体的に説明する。 Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples.
まず、正極活物質としてＬiＣｏＯ２、導電材であるアセチレンブラックとを乾式混合した。バインダーであるポリフッ化ビニリデン（ＰＶｄＦ）を溶解させたＮ−メチル−２−ピロリドン（ＮＭＰ）中に、得られた混合物を均一に分散させて、スラリーを調製した。この時、スラリー中の固形分重量比は、活物質が９１重量部、導電材が４重量部、バインダーが５重量部となるよう調整した。
次いで、スラリーを集電体となる厚さ２０μｍのアルミニウム箔に７．５ｍｇ／ｃｍ２±３％（１.０ｍＡｈ／ｃｍ２）となるよう塗布し、１２０℃で１０分乾燥した。その後、前記Ａｌ箔上の電極層をその密度が２．８〜３．０ｇ／ｃｍ３となるようロールプレスで成形後、直径１７ｍｍの円形に打ち抜き、その後１５０℃で真空乾燥させ、正極を得た。
First, LiCoO 2 as a positive electrode active material and acetylene black as a conductive material were dry mixed. The obtained mixture was uniformly dispersed in N-methyl-2-pyrrolidone (NMP) in which polyvinylidene fluoride (PVdF) as a binder was dissolved to prepare a slurry. At this time, the solid content weight ratio in the slurry was adjusted so that the active material was 91 parts by weight, the conductive material was 4 parts by weight, and the binder was 5 parts by weight.
Next, the slurry was applied to an aluminum foil having a thickness of 20 μm serving as a current collector so as to be 7.5 mg / cm 2 ± 3% (1.0 mAh / cm 2 ), and dried at 120 ° C. for 10 minutes. Thereafter, the electrode layer on the Al foil is molded by a roll press so that the density is 2.8 to 3.0 g / cm 3 , punched into a circle having a diameter of 17 mm, and then vacuum dried at 150 ° C. to obtain a positive electrode. It was.
正極へのポリアニリン複合化は、上記工程にて得られたＬｉＣｏＯ２正極を用いてセルを作製し、電解重合法にて行った。 Polyaniline complexing to the positive electrode was performed by electrolytic polymerization using a LiCoO 2 positive electrode obtained in the above step.
セル構成は、作用極に上記作製正極を用い、参照極、対極には厚さ２００μｍの金属リチウム箔、電解液には、１ｍｏｌ／ｌ−ＬｉＰＦ６、エチレンカーボネートとエチルメチルカーボネート（体積比３０：７０）に、アニリンモノマーを２ｍｏｌ／ｌの濃度になるよう加えたものを用いた。セパレータには、ガラス不織布：厚さ４００μｍとポリエチレン製微多孔膜：厚さ２０μｍとを重ね合わせて用いた。 In the cell configuration, the above-described positive electrode was used as the working electrode, the metal lithium foil with a thickness of 200 μm was used as the reference electrode and the counter electrode, and 1 mol / l-LiPF 6 , ethylene carbonate and ethyl methyl carbonate (volume ratio 30: 70) to which aniline monomer was added to a concentration of 2 mol / l was used. For the separator, glass nonwoven fabric: 400 μm thick and polyethylene microporous film: 20 μm thick were used in an overlapping manner.
上記作製したセルを３．３Ｖ（ｖｓ．Ｌｉ＋／Ｌｉ）まで電流密度０.１０ｍＡ/ｃｍ２で定電流充電を行い、その後定電圧充電することによりポリアニリンの電解重合を行った。また、セルの電気量が０．５ｍＡｈ、１．０ｍＡｈ、２．０ｍＡｈに達したところで電解重合を終了し、ポリアニリン複合量の異なる正極を作製した。電解重合が終了した後、電極をセルから取り出し、有機溶媒（ジエチルカーボネート）で洗浄し、１００℃で真空乾燥させ、ポリアニリン複合正極を得た。 The produced cell was charged with a constant current up to 3.3 V (vs. Li + / Li) at a current density of 0.10 mA / cm 2 , and then charged with a constant voltage to perform electropolymerization of polyaniline. In addition, when the amount of electricity in the cell reached 0.5 mAh, 1.0 mAh, and 2.0 mAh, the electropolymerization was terminated, and positive electrodes with different amounts of polyaniline were produced. After the completion of the electropolymerization, the electrode was taken out from the cell, washed with an organic solvent (diethyl carbonate), and vacuum dried at 100 ° C. to obtain a polyaniline composite positive electrode.
例２〜４の正極中のポリアニリン複合量を確認するため、化学分析を行い、Ｃ、Ｈ、Ｎ含有率を確認した。化学分析には、ＰＥＲＫＩＮ ＥＬＭＥＲ社製、ＳＥＲＩＥＳII ＣＨＮＳ／Ｏ Ａｎａｌｙｚｅｒ２４００を用いた。その結果を下記表１に示す。 In order to confirm the amount of polyaniline complex in the positive electrodes of Examples 2 to 4, chemical analysis was performed to confirm the C, H, and N contents. For chemical analysis, SERIES II CHNS / O Analyzer 2400 manufactured by PERKIN ELMER was used. The results are shown in Table 1 below.
前記表より、例２〜４のポリアニリンを複合化した電極では、重合電気量の増加に伴いＣ、Ｈ、Ｎ含有量が増加することが確認できた。 From the said table | surface, it has confirmed that C, H, and N content increased with the increase in the amount of superposition | polymerization in the electrode which compounded the polyaniline of Examples 2-4.
上記化学分析の結果より正極電極中のポリアニリン比率を算出した。例１〜４のサンプルの正極組成及び活物質に対するポリアニリン比率（重量百分率表示）を下記表２に示す。 The polyaniline ratio in the positive electrode was calculated from the result of the chemical analysis. Table 2 below shows the positive electrode composition of the samples of Examples 1 to 4 and the polyaniline ratio (expressed in weight percentage) with respect to the active material.
上記作製電極を正極とし、負極には厚さ２００μｍの金属リチウム箔、電解液には、１ｍｏｌ/ｌ−ＬｉＰＦ６、エチレンカーボネートとエチルメチルカーボネート（体積比３０：７０）、セパレータにはガラス不織布：厚さ４００μｍとポリエチレン製微多孔膜：厚さ２０μｍとを重ね合わせたものを用いて二電極式セルを作製した。 The produced electrode is a positive electrode, the negative electrode is a metal lithium foil having a thickness of 200 μm, the electrolyte is 1 mol / l-LiPF 6 , ethylene carbonate and ethyl methyl carbonate (volume ratio 30:70), and the separator is a glass nonwoven fabric: A two-electrode cell was prepared using a laminate of 400 μm thickness and polyethylene microporous membrane: 20 μm thickness.
以上の工程で作製したセルを以下に示す試験条件にて初期特性を評価した。 The initial characteristics of the cell produced by the above steps were evaluated under the test conditions shown below.
２５℃におけるセルの初期充放電容量を測定した。初期充放電容量は、０．２０ｍＡ/ｃｍ２の定電流で４．２Ｖまで充電し、続いて０．２０ｍＡ/ｃｍ２の定電流で３．０Ｖまで放電して求めた。初期充放電特性結果を下記表３に示す。 The initial charge / discharge capacity of the cell at 25 ° C. was measured. Initial charge-discharge capacity, and charged to 4.2V at a constant current of 0.20mA / cm 2, followed by a constant current of 0.20mA / cm 2 was determined by discharged to 3.0 V. The initial charge / discharge characteristic results are shown in Table 3 below.
前表の充放電結果より、ＬｉＣｏＯ２正極電極にポリアニリンを０．３４重量部複合化した電極を用いたセル（例２）の２５℃での放電容量は、ポリアニリン複合化無し（例１）の１０４％であり、０．６９重量部複合化した電極を用いたセル（例３）は１０４％、０．８６重量部複合化したセル（例４）は１００％であった。また、同表記載のＷｈ放電エネルギーで見た場合も、例１と比較して例２：１０４％、例３：１０４％、例４：１００％の放電エネルギーであり、いずれのセルにおいても同等の特性が得られた。 From the charge / discharge results in the previous table, the discharge capacity at 25 ° C. of the cell using the electrode obtained by combining 0.34 parts by weight of polyaniline with the LiCoO 2 positive electrode (Example 2) is not polyaniline combined (Example 1). The cell using the electrode combined with 0.69 parts by weight (Example 3) was 104%, and the cell combined with 0.86 parts by weight (Example 4) was 100%. Also, when viewed in terms of the Wh discharge energy described in the same table, the discharge energy of Example 2: 104%, Example 3: 104%, and Example 4: 100% compared to Example 1 is the same in all cells. The characteristics were obtained.
−３０℃での放電容量の測定は、室温で０．２ｍＡ／ｃｍ２の定電流で充電を行い、セルをＳＯＣ（Ｓｔａｔｅ ｏｆ ｃｈａｒｇｅ）６０％に調整した。ＳＯＣ６０％に調整したセルを、−３０℃に保たれた恒温槽に３時間保持し、セルの作動下限電圧を３.０Ｖとし、０．２ｍＡ/ｃｍ２の定電流で放電を行った。この測定より、−３０℃でのＡｈ放電容量、Ｗｈ放電エネルギーおよび直流抵抗（１０秒抵抗）を算出した。この直流抵抗は、放電開始から１０秒後のΔＥと電流値よりオームの法則を用いて算出した。 The discharge capacity at −30 ° C. was charged at a constant current of 0.2 mA / cm 2 at room temperature, and the cell was adjusted to 60% SOC (State of charge). The cell adjusted to SOC 60% was held in a thermostat kept at −30 ° C. for 3 hours, the cell operating lower limit voltage was 3.0 V, and discharge was performed at a constant current of 0.2 mA / cm 2 . From this measurement, the Ah discharge capacity at -30 ° C., the Wh discharge energy, and the DC resistance (10-second resistance) were calculated. This direct current resistance was calculated by using Ohm's law from ΔE and current value 10 seconds after the start of discharge.
例１〜４の−３０℃、ＳＯＣ６０％での直流抵抗値を下記表４に示す。 The direct current resistance values of Examples 1 to 4 at −30 ° C. and SOC 60% are shown in Table 4 below.
表４より、ポリアニリン複合化無しのセル（例１）の抵抗を基準とすると、ポリアニリンが複合化された例２（複合量０．３４重量部）のセルの抵抗が７６％、例３（複合量０．６９重量部）が８２％であり、−３０℃、ＳＯＣ６０％の１０秒抵抗が改善された。一方、例４（複合量０．８６重量部）のセルの抵抗は、複合化無しのセル（例１）の１２２％と抵抗が増加した。 From Table 4, based on the resistance of the cell without polyaniline complex (Example 1), the resistance of the cell of Example 2 (composite amount 0.34 parts by weight) in which polyaniline was complexed was 76%, and Example 3 (composite). The amount was 0.69 parts by weight), and the resistance for 10 seconds at −30 ° C. and SOC 60% was improved. On the other hand, the resistance of the cell of Example 4 (composite amount 0.86 parts by weight) increased to 122% of that of the non-complexed cell (Example 1).
例１〜４のＳＯＣ６０％、−３０℃での放電容量及び放電エネルギーを下記表５に示す。 Table 5 below shows the discharge capacity and discharge energy at 60% SOC and -30 ° C of Examples 1 to 4.
ＬｉＣｏＯ２に対しポリアニリンを０．３４重量部複合化した電極のセル（例２）では、Ａｈ放電容量が１１６％、Ｗｈ放電エネルギーが１１８％であった。ポリアニリンを０．６９重量部複合化した電極のセル（例３）では、Ａｈ放電容量が１０６％、Ｗｈ放電エネルギーが１０７％であった。一方、ポリアニリンを０．８６重量部複合化した電極のセル（例４）は、Ａｈ放電容量が３６％、Ｗｈ放電エネルギーが３５％であった。
ＬｉＣｏＯ2電極にポリアニリンを０．３４、０．６９重量部複合化させた電極を用いたセルでは、−３０℃、ＳＯＣ６０％状態でのＡｈ放電容量及びＷｈ放電エネルギーが複合化無しのセルと比べ改善される。一方、複合量が０．８６重量部となると複合化無しのセルと比べてもＡｈ放電容量及びＷｈ放電エネルギーが低くなる。
In the electrode cell (Example 2) in which 0.34 parts by weight of polyaniline was combined with LiCoO 2 , the Ah discharge capacity was 116%, and the Wh discharge energy was 118%. In the electrode cell (Example 3) in which 0.69 parts by weight of polyaniline was combined, the Ah discharge capacity was 106% and the Wh discharge energy was 107%. On the other hand, an electrode cell (Example 4) in which 0.86 parts by weight of polyaniline was combined had an Ah discharge capacity of 36% and a Wh discharge energy of 35%.
In the cell using the electrode in which 0.34 and 0.69 parts by weight of polyaniline are combined with the LiCoO 2 electrode, the Ah discharge capacity and the Wh discharge energy at -30 ° C. and SOC 60% are compared with the cell without the combination. Improved. On the other hand, when the composite amount is 0.86 parts by weight, the Ah discharge capacity and the Wh discharge energy are lowered even when compared with a cell without composite.
例１〜４のＳＯＣ６０％、−３０℃での放電曲線を図１に示す。 The discharge curves at 60% SOC and −30 ° C. of Examples 1 to 4 are shown in FIG.
ＬｉＣｏＯ２電極にポリアニリンを複合化した電極を用いた例２（０．３４重量部）、例３（０．６９重量部）のセルは複合化無しのセル（例１）と比べ放電作動電圧が高い。また、例１のセルは、放電開始直後の電圧降下が大きく、放電作動電圧が、およそ３.３５Ｖ付近であるのに対し、ポリアニリン複合化電極を用いたセルでは、例２が３．４７Ｖ、例３が３．４３Ｖと、電圧降下が緩やかであると共に、その後も高い電圧を維持して放電していることがわかる。一方、例４（０．８６重量部）のセルは、およそ３．２Ｖ付近と放電開始後の電圧降下が大きく、例１及び例２、３と比べ低い電圧範囲で放電していることがわかる。 The cells of Example 2 (0.34 parts by weight) and Example 3 (0.69 parts by weight) using an electrode in which polyaniline was combined with an LiCoO 2 electrode had a discharge operating voltage as compared with a cell without combination (Example 1). high. Further, the cell of Example 1 has a large voltage drop immediately after the start of discharge, and the discharge operating voltage is about 3.35V, whereas in the cell using the polyaniline composite electrode, Example 2 has 3.47V, It can be seen that Example 3 is 3.43 V, the voltage drop is gradual, and the discharge continues while maintaining a high voltage. On the other hand, the cell of Example 4 (0.86 parts by weight) has a large voltage drop after the start of discharge at around 3.2 V, and it can be seen that the cell is discharged in a lower voltage range than Examples 1, 2 and 3. .
以上の結果より、電解重合法を用いて正極電極にポリアニリンを複合化することで、低温（−３０℃）における放電特性改善効果を確認した。 From the above results, the effect of improving discharge characteristics at low temperatures (−30 ° C.) was confirmed by combining polyaniline with the positive electrode using an electrolytic polymerization method.
例２〜４いずれの電極においても、ＬｉＣｏＯ2に対してポリアニリン複合量が１％以下であった。中でも−３０℃環境下におけるＡｈ放電容量及びＷｈ放電エネルギーが最も改善された例２は、ポリアニリン複合量が０．３４重量部であった。複合量が増加するに伴い−３０℃でのＡｈ放電容量及びＷｈ放電エネルギー改善効果が小さくなることが確認できた。一方、ポリアニリン複合量が０．８６重量部では、複合化無し（例１）と比べＡｈ放電容量及びＷｈ放電エネルギーが低下することが確認できた。−３０℃における放電特性改善の効果を得るためには、少なくともポリアニリン複合量が０．７重量部以下であることが必要であり、改善効果を更に向上させるには、より微量に複合化させることが望ましい。 In any of the electrodes of Examples 2 to 4, the polyaniline complex amount was 1% or less with respect to LiCoO 2 . In particular, in Example 2 in which the Ah discharge capacity and Wh discharge energy in the -30 ° C environment were most improved, the polyaniline complex amount was 0.34 parts by weight. It was confirmed that the effect of improving the Ah discharge capacity and Wh discharge energy at −30 ° C. became smaller as the composite amount increased. On the other hand, when the polyaniline complex amount was 0.86 parts by weight, it was confirmed that the Ah discharge capacity and the Wh discharge energy were reduced as compared with the case where no complex was made (Example 1). In order to obtain the effect of improving the discharge characteristics at −30 ° C., it is necessary that at least the polyaniline complex amount is 0.7 parts by weight or less. Is desirable.
本発明により、正極活物質に対するポリアニリン複合量が０．７重量部以下の微量であると、低温での放電エネルギーが高い二次電池の提供が可能となる。 According to the present invention, when the polyaniline complex amount with respect to the positive electrode active material is a very small amount of 0.7 parts by weight or less, it is possible to provide a secondary battery having high discharge energy at a low temperature.
ハイブリッド電気自動車、瞬時停電バックアップ等の大電流負荷用途に向けた、最先端蓄電デバイスである非水系二次電池用正極に関し、低温条件下において低抵抗且つ高容量な非水系二次電池を提供する。 Providing non-aqueous secondary batteries with low resistance and high capacity under low temperature conditions for positive electrodes for non-aqueous secondary batteries, which are cutting-edge storage devices for high-current load applications such as hybrid electric vehicles and instantaneous power outages .
Claims (5)
The non-aqueous secondary battery which uses the positive electrode for non-aqueous secondary batteries as described in any one of Claims 1-4 as a positive electrode.
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