JP2004241242A - Positive electrode active material for nonaqueous electrolytic solution secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positive electrode active material for a nonaqueous electrolytic solution secondary battery having superior characteristics even under hostile using environments. <P>SOLUTION: This is a positive electrode active material for the nonaqueous electrolytic solution secondary battery having at least the lithium transition metal complex oxide of a spinel structure, and the lithium transition metal complex oxide is provided with at least a first lithium transition metal complex oxide and a second lithium transition metal complex oxide, and the first lithium transition metal complex oxide is smaller than the second lithium transition metal complex oxide containing an element and/or a compound which has a larger secondary particle diameter. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００９３】
なお式中のＤは結晶子の大きさ（Å）、Ｋはシェラー定数（βを積分幅より算出した場合はＫ＝１．０５）、λはＸ線源の波長（ＣｕＫα１＝１．５４０５６２Å）、βは結晶子の大きさによる回折線の広がりの幅（ｒａｄｉａｎ）、θは回折角２θ／２（ｄｅｇｒｅｅ）を示す。
【００９４】
（リチウムイオン二次電池の作製）
ポリフッ化ビニリデン５重量部を含有したノルマルメチルピロリドン溶液に正極活物質であるリチウム遷移金属複合酸化物粉末９０重量部、導電剤として炭素粉末５重量部とを加え、混練してペーストを調製し、これをドクターブレード法にてアルミニウム極板に塗布し、乾燥して正極板とする。また負極活物質に炭素材料を用いて同様にして銅極板に塗布し、負極板を作製する。セパレーターに多孔性プロピレンフィルムを用い、電解液としてエチレンカーボネイト：ジエチルカーボネイト＝１：１（体積比）の混合溶媒にＬｉＰＦ_６を１ｍｏｌ／ｌの濃度で溶解した溶液を用いてリチウムイオン二次電池を作製する。本実施例では正極板、負極板、セパレータを薄いシート状に成形し、これらを巻回し、金属ラミネート樹脂フィルムの電池ケースに収納し、ラミネート型電池とする。
【００９５】
（過充電特性の評価）
作製したリチウムイオン二次電池を１Ｃ（７００ｍＡ）の電流値で電池電圧４．２Ｖまで充電し、次に４．２Ｖの定電圧で１０ｍＡとなるまで充電し、満充電状態とする。満充電状態のリチウムイオン二次電池を２５〜２６℃に保たれたチャンパー内に設置し、充放電装置の電極を取り付ける。さらにリチウムイオン二次電池の中央部に測温抵抗体を取り付ける。このようにしてリチウムイオン二次電池の電池電圧、温度を記録できる状態とする。満充電状態のリチウムイオン二次電池にさらに１Ｃの一定の電流値で最大電圧１５Ｖまで充電を行い、電池の外観、表面の温度を記録する。同様に２Ｃ及び３Ｃの一定の電流値で最大電圧１５Ｖまで充電を行い、電池の外観、表面の温度を記録する。
【００９６】
（極板密度の測定）
正極活物質であるリチウム遷移金属複合酸化物粉末９５重量部及びポリフッ化ビニリデン５重量部を含有したノルマルメチルピロリドン溶液とを混練してペーストを調製し、これをドクターブレード法にてアルミニウム極板に塗布し、乾燥して正極板とする。正極板を所定の大きさ（２×２．５ｃｍ）に裁断した後、一軸プレス機にて極板を加圧し、加圧後の極板の厚さと重量から極板密度を得る。
【００９７】
（ドライアウトの評価）
正極活物質であるリチウム遷移金属複合酸化物粉末９５重量部及びポリフッ化ビニリデン５重量部を含有したノルマルメチルピロリドン溶液とを混練してペーストを調製し、これをドクターブレード法にてアルミニウム極板に塗布し、乾燥して正極板とする。正極板をガラス容器に入れてアルゴンボックス内でプロピレンカーボネート液に浸す。３分間真空にしてプロピレンカーボネート液を正極板に浸透させた後、アルゴンボックスから正極板を取り出し、正極板の時間毎の重量を量る。時間毎の正極板の重量から最初の正極板の重量を引いて、プロピレンカーボネート液の減少量を計算する。プロピレンカーボネートの減少量が多ければ、電解液の移動が容易であることになり、ドライアウトが防止できると判断できる。プロピレンカーボネートの減少量が少なければ、電解液の移動が困難であり、ドライアウトが生じやすいと判断できる。
【００９８】
結果を表１、図１に示す。粒度分布を図３に示す。
【００９９】
〔実施例２〕
所定の組成比のマンガンイオンとマグネシウムイオンを含む水溶液中に炭酸水素ナトリウム水溶液を加え、マンガンとマグネシウムを共沈させ、共沈物を得た。
得られた共沈物を濾過、水洗後、乾燥したのち、第１の共沈物はそのままにし、第２の共沈物にはオルトホウ酸を２００ｐｐｍ混合した。第１の共沈物は、炭酸リチウムを所定の組成比となるように混合し、大気雰囲気中にて、９３０℃の温度で１２時間焼成を行った。第２の共沈物は、炭酸リチウムを所定の組成比となるように混合し、大気雰囲気中にて、９３０℃の温度で１２時間焼成を行った。こうして第１の粒度分布を有し一次粒子径が４μｍのリチウム遷移金属複合酸化物と、第２の粒度分布を有し一次粒子径が１５μｍの範囲にあるリチウム遷移金属複合酸化物を得た。
第１の粒度分布を有し一次粒子径が４μｍのリチウム遷移金属複合酸化物からなる第１の粒子群を選択し、第２の粒度分布を有し一次粒子径が１５μｍの範囲にあるリチウム遷移金属複合酸化物からなる第２の粒子群からなる第２の粒子群を選択し、選択された第１の粒子群と第２の粒子群を混合した。第２の粒子群であるリチウム遷移金属複合酸化物の第１の粒子群であるリチウム遷移金属複合酸化物と第２の粒子群であるリチウム遷移金属複合酸化物の合計に対する混合割合は、７０重量％とし、第１の粒子群であるリチウム遷移金属複合酸化物の第１の粒子群であるリチウム遷移金属複合酸化物と第２の粒子群であるリチウム遷移金属複合酸化物の合計に対する混合割合は、３０重量％とした。こうしてＬｉ_{１．０７３}Ｍｎ_{１．９１５}Ｍｇ_０．０１Ｂ_{０．００２３}Ｏ_４が得られた。
【０１００】
粒度分布を図４に示す。
【０１０１】
〔実施例３〕
所定の組成比のマンガンイオンとマグネシウムイオンを含む水溶液中に炭酸水素ナトリウム水溶液を加え、マンガンとマグネシウムを共沈させ、共沈物を得た。
得られた共沈物を濾過、水洗後、乾燥したのち、第１の共沈物はそのままにし、第２の共沈物にはオルトホウ酸を１００ｐｐｍ混合した。第１の共沈物は、炭酸リチウムを所定の組成比となるように混合し、大気雰囲気中にて、９３０℃の温度で１２時間焼成を行った。第２の共沈物は、炭酸リチウムを所定の組成比となるように混合し、大気雰囲気中にて、９３０℃の温度で１２時間焼成を行った。こうして第１の粒度分布を有し一次粒子径が４μｍのリチウム遷移金属複合酸化物と、第２の粒度分布を有し一次粒子径が８μｍの範囲にあるリチウム遷移金属複合酸化物を得た。
第１の粒度分布を有し一次粒子径が４μｍのリチウム遷移金属複合酸化物からなる第１の粒子群を選択し、第２の粒度分布を有し一次粒子径が８μｍの範囲にあるリチウム遷移金属複合酸化物からなる第２の粒子群からなる第２の粒子群を選択し、選択された第１の粒子群と第２の粒子群を混合した。第２の粒子群であるリチウム遷移金属複合酸化物の第１の粒子群であるリチウム遷移金属複合酸化物と第２の粒子群であるリチウム遷移金属複合酸化物の合計に対する混合割合は、７０重量％とし、第１の粒子群であるリチウム遷移金属複合酸化物の第１の粒子群であるリチウム遷移金属複合酸化物と第２の粒子群であるリチウム遷移金属複合酸化物の合計に対する混合割合は、３０重量％とした。こうしてＬｉ_{１．０７３}Ｍｎ_{１．９１６}Ｍｇ_０．０１Ｂ_{０．００１２}Ｏ_４が得られた。
【０１０２】
以下、実施例１と同様にして非水電解液二次電池用正極活物質の評価を行った。結果を表１、図１に示す。粒度分布を図５に示す。
【０１０３】
〔実施例４〕
所定の組成比のマンガンイオンとマグネシウムイオンを含む水溶液中に炭酸水素ナトリウム水溶液を加え、マンガンとマグネシウムを共沈させ、共沈物を得た。
得られた共沈物を濾過、水洗後、乾燥したのち、第１の共沈物はそのままにし、第２の共沈物にはオルトホウ酸を３００ｐｐｍ混合した。第１の共沈物は、炭酸リチウムを所定の組成比となるように混合し、大気雰囲気中にて、９３０℃の温度で１２時間焼成を行った。第２の共沈物は、炭酸リチウムを所定の組成比となるように混合し、大気雰囲気中にて、９３０℃の温度で１２時間焼成を行った。こうして第１の粒度分布を有し一次粒子径が４μｍのリチウム遷移金属複合酸化物と、第２の粒度分布を有し一次粒子径が２０μｍの範囲にあるリチウム遷移金属複合酸化物を得た。
第１の粒度分布を有し一次粒子径が４μｍのリチウム遷移金属複合酸化物からなる第１の粒子群を選択し、第２の粒度分布を有し一次粒子径が２０μｍの範囲にあるリチウム遷移金属複合酸化物からなる第２の粒子群からなる第２の粒子群を選択し、選択された第１の粒子群と第２の粒子群を混合した。第２の粒子群であるリチウム遷移金属複合酸化物の第１の粒子群であるリチウム遷移金属複合酸化物と第２の粒子群であるリチウム遷移金属複合酸化物の合計に対する混合割合は、６０重量％とし、第１の粒子群であるリチウム遷移金属複合酸化物の第１の粒子群であるリチウム遷移金属複合酸化物と第２の粒子群であるリチウム遷移金属複合酸化物の合計に対する混合割合は、４０重量％とした。こうしてＬｉ_{１．０７２}Ｍｎ_{１．９１５}Ｍｇ_０．０１Ｂ_{０．００３}Ｏ_４が得られた。
【０１０４】
粒度分布を図６に示す。
【０１０５】
〔比較例１〕
所定の組成比のマンガンイオンとマグネシウムイオンを含む水溶液中に炭酸水素ナトリウム水溶液を加え、マンガンとマグネシウムを共沈させ、共沈物を得た。
得られた共沈物を濾過、水洗後、乾燥したのち、炭酸リチウムを所定の組成比となるように混合し、大気雰囲気中にて９３０℃で１２時間焼成した。そして乳鉢にて粉砕しＬｉ_{１．０７３}Ｍｎ_{１．９１７}Ｍｇ_０．０１Ｏ_４が得られた。
【０１０６】
以下、実施例１と同様にして非水電解液二次電池用正極活物質の評価を行った。結果を表１、図１に示す。粒度分布を図７に示す。
【０１０７】
〔比較例２〕
所定の組成比のマンガンイオンとマグネシウムイオンを含む水溶液中に炭酸水素ナトリウム水溶液を加え、マンガンとマグネシウムを共沈させ、共沈物を得た。
得られた共沈物を濾過、水洗後、乾燥したのち、炭酸リチウムとオルトホウ酸を所定の組成比となるように混合し、大気雰囲気中にて９３０℃で１２時間焼成した。そして乳鉢にて粉砕しＬｉ_{１．０７２}Ｍｎ_{１．９１３}Ｍｇ_０．０１Ｂ_{０．００５}Ｏ_４が得られた。
【０１０８】
粒度分布を図８に示す。
【０１０９】
〔比較例３〕
所定の組成比のマンガンイオンとマグネシウムイオンを含む水溶液中に炭酸水素ナトリウム水溶液を加え、マンガンとマグネシウムを共沈させ、所定の二次粒子径の共沈物を得た。
得られた共沈物を濾過、水洗後、乾燥したのち、炭酸リチウムとオルトホウ酸を所定の組成比となるように混合し、大気雰囲気中にて９３０℃で１２時間焼成した。これを第１のリチウム遷移金属複合酸化物とした。一次粒子径は０．７μｍであった。
所定の組成比のマンガンイオンとマグネシウムイオンを含む水溶液中に炭酸水素ナトリウム水溶液を加え、マンガンとマグネシウムを共沈させ、所定の二次粒子径の共沈物を得た。
得られた共沈物を濾過、水洗後、乾燥したのち、炭酸リチウムとオルトホウ酸を所定の組成比となるように混合し、第１のリチウム遷移金属複合酸化物より大きな所定の粒径になるように大気雰囲気中にて９３０℃で１２時間焼成した。これを第２のリチウム遷移金属複合酸化物とした。一次粒子径は０．７μｍであった。
こうして得られた２種のリチウム遷移金属複合酸化物を、第２のリチウム遷移金属複合酸化物の第１のリチウム遷移金属複合酸化物と第２のリチウム遷移金属複合酸化物の合計に対する混合割合は、７０重量％とし、第１のリチウム遷移金属複合酸化物の第１のリチウム遷移金属複合酸化物と第２のリチウム遷移金属複合酸化物の合計に対する混合割合は、３０重量％として混合した。こうしてＬｉ_{１．０７２}Ｍｎ_{１．９１３}Ｍｇ_０．０１Ｂ_{０．００５}Ｏ_４が得られた。
【０１１０】
粒度分布を図９に示す。
【０１１１】
表１及び図１から明らかなように、本発明の非水電解液二次電池用正極活物質は、極板密度が比較例１に比べて向上していることがわかる。またドライアウトも防止できていることがわかる。さらに過充電特性も向上していることがわかる。
【０１１２】
これに対して、比較例１は、極板密度、過充電特性が本発明の非水電解液二次電池用正極活物質に比べて劣っている。また、ドライアウトも防止できていない。
【０１１３】
【表１】

【０１１４】
また実施例１、実施例２および実施例３において、それぞれ第１の粒子群であるリチウム遷移金属複合酸化物と第２の粒子群であるリチウム遷移金属複合酸化物の混合割合を変化させて、変化させたときの極板密度を測定した。結果を表２〜表４、図２に示す。
【０１１５】
【表２】

【０１１６】
【表３】

【０１１７】
【表４】

【０１１８】
この結果から、第２の粒子群であるリチウム遷移金属複合酸化物の第１の粒子群であるリチウム遷移金属複合酸化物と第２の粒子群であるリチウム遷移金属複合酸化物の合計に対する混合割合は、６０重量％〜７０重量％であり、第１の粒子群であるリチウム遷移金属複合酸化物の第１の粒子群であるリチウム遷移金属複合酸化物と第２の粒子群であるリチウム遷移金属複合酸化物の合計に対する混合割合は、３０重量％〜４０重量％であることがより好ましいことがわかる。
【０１１９】
前記各実施の形態から把握できる請求項記載以外の技術思想（発明）について、以下にその効果とともに記載する。
【０１２０】
（１）請求項１乃至請求項４のいずれかに記載の発明において、前記リチウム遷移金属複合酸化物は、アルミニウム及び／又はマグネシウムが含まれる非水電解液二次電池用正極活物質である。アルミニウム及び／又はマグネシウムを加えることで、本発明の特性を損なわずに、サイクル充放電特性が向上する。アルミニウム及び／又はマグネシウムを加えることで、結晶構造の安定化を図ることができると考えられる。
【０１２１】
（２）請求項１乃至請求項４及び（１）のいずれかに記載の発明において、前記リチウム遷移金属複合酸化物は、さらにチタン、ジルコニウム、ハフニウムからなる群から選ばれる少なくとも１種が含まれる非水電解液二次電池用正極活物質である。チタン、ジルコニウム、ハフニウムからなる群から選ばれる少なくとも１種が含まれることで本発明の特性を損なわずに、インピーダンスを低減することができる。チタン、ジルコニウム、ハフニウムからなる群から選ばれる少なくとも１種が含まれることで格子定数が上昇し、粒子内のリチウムイオンの易動度は上昇すると考えられる。
【０１２２】
（３）請求項１乃至請求項４及び（１）又は（２）のいずれかに記載の発明において、前記リチウム遷移金属複合酸化物は、さらに硫黄が含まれる非水電解液二次電池用正極活物質である。本発明の構成元素である硫黄により、リチウムイオンの移動抵抗が低減し、本発明の特性を損なわずに、正極板の抵抗が低減すると考えられる。
【０１２３】
（４）請求項１乃至請求項４及び（１）乃至（３）のいずれかに記載の発明において、前記リチウム遷移金属複合酸化物は、さらにフッ素、塩素、臭素およびヨウ素からなる群から選ばれる少なくとも１種が含まれる非水電解液二次電池用正極活物質である。ハロゲン元素を加えることで粒子性状を改善する効果を示すと考えられる。ハロゲン元素がない場合に比べて、結晶性に優れ、比表面積が小さく、粗大粒子を含まず、かつ球状で、粒子径の揃ったリチウム遷移金属複合酸化物が得られると考えられる。またハロゲン元素は粒子表面に偏析し、本発明の特性を損なわずに、ハロゲン元素がない場合に比べてリチウム遷移金属複合酸化物表面のインピーダンスの低減を図ることができると考えられる。さらにハロゲン元素がない場合に比べてリチウム遷移金属複合酸化物の粒子表面と電解液との界面におけるリチウムイオンの移動抵抗が低減すると考えられる。
【０１２４】
（５）請求項１乃至請求項４及び（１）乃至（４）のいずれかに記載の発明において、前記リチウム遷移金属複合酸化物は、さらにナトリウム及び／又はカルシウムが含まれる非水電解液二次電池用正極活物質である。ナトリウム、カルシウムはリチウム遷移金属複合酸化物粒子の一部、もしくは全面を覆い電解質との反応性を制御するため、本発明の特性を損なわずに、電池膨張率を大幅に低下すると考えられる。ナトリウム、カルシウムはリチウムに比べ充放電容量を減少させる効果が少ないため、効果を上乗せし、さらに電池膨張率を低下させることができる。
【０１２５】
（６）請求項１乃至請求項４及び（１）乃至（５）のいずれかに記載の発明において、前記リチウム遷移金属複合酸化物は、一般式がＬｉ_ａＭ_ｂＭｎ_{３−ａ−ｂ}Ａ_ｇＸ_ｃＢ_ｄＳ_ｅＤ_ｈＯ_４＋ｆ（Ｍはアルミニウム及び／又はマグネシウム、Ａはチタン、ジルコニウムおよびハフニウムからなる群から選ばれる少なくとも１種を表し、Ｘはフッ素、塩素、臭素およびヨウ素からなる群から選ばれる少なくとも１種を表し、Ｂはホウ素を表し、Ｓは硫黄を表し、Ｄはナトリウム及び／又はカルシウムを表し、ａは０．８≦ａ≦１．２を満たす数を表し、ｂは０＜ｂ≦０．２を満たす数を表し、ｃは０≦ｃ≦０．０５を満たす数を表し、ｄは０≦ｄ≦０．０２を満たす数を表し、ｅは０＜ｅ≦０．１を満たす数を表し、ｆは−０．５≦ｆ≦０．５を満たす数を表し、ｇは０＜ｇ≦０．１を満たす数を表し、ｈは０≦ｈ＜０．０１５を満たす数を表す。）で表される非水電解液二次電池用正極活物質である。この場合、本発明の特性を損なわずに、優れたサイクル充放電特性と保存特性の向上が実現でき、電池の膨れの抑制が可能となる。
【０１２６】
（７）請求項１乃至請求項４及び（１）乃至（６）のいずれかに記載の発明において、前記リチウム遷移金属複合酸化物の比表面積が０．２〜１．２ｍ^２／ｇである非水電解液二次電池用正極活物質である。このように規格化することでさらに優れた電池特性が得られる。
【０１２７】
（８）請求項１乃至請求項４及び（１）乃至（７）のいずれかに記載の発明において、前記リチウム遷移金属複合酸化物は、１μｍ以下の粒子が１体積％以下である非水電解液二次電池用正極活物質である。こうすることで本願発明の特性を損なわずに、電池膨張率が低減できる。
【０１２８】
（９）正極、負極、セパレータおよび非水電解液を有する非水電解液二次電池であって、下記Ｉを正極の正極活物質として、下記ＩＩを負極の負極活物質として用いることを特徴とする非水電解液二次電池である。
Ｉ：請求項１乃至請求項４及び（１）乃至（８）のいずれかに記載の非水電解液二次電池用正極活物質に用いられるリチウム遷移金属複合酸化物と、
一般式がＬｉ_１＋ｘＣｏＯ_２（ｘは−０．５≦ｘ≦０．５を満たす数を表す。）で表されるコバルト酸リチウム及び／又は一般式がＬｉ_１＋ｘＮｉＯ_２（ｘは−０．５≦ｘ≦０．５を満たす数を表す。）で表されるニッケル酸リチウムを、
前記リチウム遷移金属複合酸化物の重量をＡとし、前記コバルト酸リチウム及び／又は前記ニッケル酸リチウムの重量をＢとした場合に０．２≦Ｂ／（Ａ＋Ｂ）≦０．８の範囲になるように混合する非水電解液二次電池用正極活物質。
ＩＩ：金属リチウム、リチウム合金およびリチウムイオンを吸蔵放出可能な化合物からなる群から選ばれる少なくとも１種からなる非水電解液二次電池用負極活物質。
この非水電解液二次電池は、極板密度、ドライアウトの防止および過充電特性だけでなく、放電容量、サイクル充放電特性、負荷特性、出力特性にも優れている。正極活物質は、０．４≦Ｂ／（Ａ＋Ｂ）≦０．６の範囲になるように混合することが好ましい。０．４≦Ｂ／（Ａ＋Ｂ）≦０．６の範囲であれば、極板密度、ドライアウトの防止および過充電特性の向上だけでなく、サイクル充放電特性、負荷特性および出力特性の向上が著しいからである。負極活物質に用いられるリチウムイオンを吸蔵放出可能な化合物としては、アルカリ金属及び／又はアルカリ土類金属を含むスピネル構造からなる一般式がＬｉ_ａＴｉ_ｂＯ_４＋ｃ（ａは０．８≦ａ≦１．５を満たす数を表し、ｂは１．５≦ｂ≦２．２を満たす数を表し、ｃは−０．５≦ｃ≦０．５を満たす数を表す。）で表される非水電解液二次電池用負極活物質が好ましい。このとき極板密度、ドライアウトの防止および過充電特性だけでなく、サイクル充放電特性が非常に向上した非水電解液二次電池を得ることができる。
【０１２９】
【発明の効果】
以上に説明したように、本発明の非水電解液二次電池用正極活物質は、極板密度が向上するとともにドライアウトを防止することができ優れた電池特性を有する。さらに過充電特性にも優れる。したがって、本発明の非水電解液二次電池用正極活物質は、リチウムイオン二次電池等の非水電解液二次電池に好適に用いられる。
【図面の簡単な説明】
【図１】プレス圧の変化に伴う極板密度の変化を示す図である。
【図２】第１の粒子群であるリチウム遷移金属複合酸化物と第２の粒子群であるリチウム遷移金属複合酸化物の混合割合の変化に伴う極板密度の変化を示す図である。
【図３】実施例１の粒度分布を示す図である。
【図４】実施例２の粒度分布を示す図である。
【図５】実施例３の粒度分布を示す図である。
【図６】実施例４の粒度分布を示す図である。
【図７】比較例１の粒度分布を示す図である。
【図８】比較例２の粒度分布を示す図である。
【図９】比較例３の粒度分布を示す図である。
【図１０】スピネル構造のリチウム遷移金属複合酸化物を示す図である。
【図１１】活物質の結着模式図である。
【図１２】円筒型電池の断面図である。
【図１３】コイン型電池の構造を示す図である。
【図１４】角型電池の構造を示す図である。
【符号の説明】
１…８ａサイト
２…３２ｅサイト
３…１６ｄサイト
４…結着剤
５…活物質
１１…負極
１２…集電体
１３…正極
１４…セパレーター
２１…第１の粒度分布
２２…第２の粒度分布[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a nonaqueous electrolyte secondary battery and a positive electrode active material thereof, particularly a lithium transition metal composite oxide having a spinel structure. For example, it is used for mobile phones, personal computers, and electric vehicles.
[0002]
[Prior art]
Non-aqueous electrolyte secondary batteries are characterized by higher operating voltage and higher energy density than conventional nickel cadmium secondary batteries and the like, and are widely used as power sources for electronic devices. LiCoO is used as a positive electrode active material of the nonaqueous electrolyte secondary battery. ₂ , LiNiO ₂ , LiMn ₂ O ₄ And lithium transition metal composite oxides.
[0003]
Above all, LiMn ₂ O ₄ Since manganese which is a constituent element is present in a large amount as a resource, raw materials are easily available at low cost. Also, there is a feature that the load on the environment is small. Furthermore, even if all the Li ions in the crystal are desorbed by the deintercalation reaction, the crystal structure is stably present. For this reason, LiCoO ₂ , LiNiO ₂ Compared to LiMn ₂ O ₄ Rechargeable batteries generate less heat in an overcharged state.
[0004]
In mobile electronic devices such as mobile phones and notebook computers, LiMn ₂ O ₄ Sufficient battery characteristics have been obtained with a non-aqueous electrolyte secondary battery using.
[0005]
However, at present, mobile devices such as mobile phones, notebook computers, digital cameras, and the like have more severe usage environments due to higher functions such as being provided with various functions and use at high and low temperatures. It has become something. Further, application to a power supply such as a battery for an electric vehicle is expected. Under such circumstances, the conventional LiMn ₂ O ₄ In non-aqueous electrolyte secondary batteries using, a sufficient battery characteristic cannot be obtained, and further improvement is required.
[0006]
[Problems to be solved by the invention]
An object of the present invention is to provide a positive electrode active material for a non-aqueous electrolyte secondary battery having excellent battery characteristics even in a more severe use environment. That is, an object of the present invention is to provide a positive electrode active material for a non-aqueous electrolyte secondary battery, which has an improved electrode plate density and can prevent dryout during charge and discharge.
[0007]
[Means for Solving the Problems]
The positive electrode active material for a non-aqueous electrolyte secondary battery described in the present invention is a positive electrode active material for a non-aqueous electrolyte secondary battery having at least a spinel-structured lithium transition metal composite oxide, wherein the lithium transition metal The composite oxide has at least a first lithium transition metal composite oxide and a second lithium transition metal composite oxide, and the first lithium transition metal composite oxide has an element that increases the secondary particle diameter and And / or smaller than the second lithium transition metal composite oxide containing the compound.
[0008]
Improvement in electrode plate density is greatly related to improvement in battery capacity. The electrode plate density can be improved by increasing the pressing pressure. However, when the press pressure is increased, the particles of the lithium transition metal composite oxide are broken, fine powder is generated, the lithium transition metal composite oxide is shifted, and dry-out of the electrolyte is caused. Dryout is the biggest cause of deterioration of battery characteristics. To prevent this dry-out, it is preferable to increase the particle size. However, the lithium-transition metal composite oxide having large particles has a low electrode density. Therefore, there is a trade-off between increasing the electrode plate density and preventing dryout.
[0009]
It has at least two or more lithium transition metal composite oxides, and at least the first lithium transition metal composite oxide is smaller than the second lithium transition metal composite oxide. The board density is improved. When the second lithium transition metal composite oxide contains an element and / or compound that increases the secondary particle diameter, the size of two or more lithium transition metal composite oxide particles can be controlled. . As a result, a positive electrode active material for a non-aqueous electrolyte secondary battery that can prevent dry-out even when the electrode pressure is increased by increasing the pressing pressure can be obtained.
[0010]
It is preferable that the first lithium transition metal composite oxide is smaller than the second lithium transition metal composite oxide. Since the first lithium transition metal composite oxide is smaller than the second lithium transition metal composite oxide containing the element and / or the compound that increases the secondary particle diameter, the amount of the small particles existing between the large particles is reduced. The ratio can be controlled. Thereby, it is possible to more effectively increase the electrode plate density and prevent dryout.
[0011]
The positive electrode active material for a non-aqueous electrolyte secondary battery described in the present invention is a positive electrode active material for a non-aqueous electrolyte secondary battery having at least a spinel-structured lithium transition metal composite oxide, wherein the lithium transition metal The composite oxide has a first lithium manganate and a second lithium manganate, and the first lithium manganate is smaller than the second lithium manganate containing boron.
[0012]
By having at least two kinds of lithium manganate and at least the first lithium manganate being smaller than the second lithium manganate, the filling property to the electrode plate is improved and the electrode plate density is improved. By containing boron in the second lithium manganate, the size of the particles of the two lithium manganates can be controlled. As a result, a positive electrode active material for a non-aqueous electrolyte secondary battery that can prevent dry-out even when the electrode pressure is increased by increasing the pressing pressure can be obtained.
[0013]
It is preferable that the first lithium manganate is smaller than the second lithium manganate. When the amount of the first lithium manganate is smaller than that of the second lithium manganate containing boron, the ratio of the small particles existing between the large particles can be controlled. Thereby, it is possible to more effectively increase the electrode plate density and prevent dryout.
[0014]
The method for producing a positive electrode active material for a nonaqueous electrolyte secondary battery described in the present invention is a method for producing a positive electrode active material for a nonaqueous electrolyte secondary battery having at least a lithium transition metal composite oxide having a spinel structure. Selecting a first particle group comprising a lithium-transition metal composite oxide having a first particle size distribution and a primary particle size in a range of 10 μm or less; and secondary particles larger than the first particle size distribution. Selecting a second particle group made of a lithium transition metal composite oxide having a second particle size distribution having a primary particle diameter in the range of 8 μm to 150 μm, and the selected first particle group And mixing a lithium transition metal composite oxide as the selected second particle group with a lithium transition metal composite oxide.
[0015]
Through these steps, the ratio of small particles existing between large particles can be controlled. Therefore, it is possible to obtain a positive electrode active material for a non-aqueous electrolyte secondary battery having a high electrode plate density and capable of preventing dryout.
[0016]
The lithium transition metal composite oxide as the second particle group preferably contains boron. By containing boron, the size of the lithium manganate particles can be controlled. As a result, a positive electrode active material for a non-aqueous electrolyte secondary battery that can prevent dry-out even when the electrode pressure is increased by increasing the pressing pressure can be obtained.
[0017]
The first particle size distribution is preferably adjusted so that the secondary particle diameter is in the range of 1 μm to 50 μm. Non-aqueous electrolyte secondary battery that can prevent manganese elution that causes deterioration of cycle charge / discharge characteristics and dryout, and can prevent dryout even if the press plate density is increased by increasing the press pressure The positive electrode active material for use can be obtained.
[0018]
The second particle size distribution is preferably adjusted so that the secondary particle size is in the range of 8 μm to 150 μm. A non-aqueous electrolyte solution that can prevent sedimentation of lithium transition metal composite oxide particles during the preparation of the positive electrode mixture, and can prevent dryout even if the pressing pressure is increased to increase the electrode plate density. A positive electrode active material for a secondary battery can be obtained.
[0019]
The lithium transition metal composite oxide has a general formula of Li _a Mn _3-a O _{4 + f} (A represents a number satisfying 0.8 ≦ a ≦ 1.2, and f represents a number satisfying −0.5 ≦ f ≦ 0.5). A positive electrode active material for a non-aqueous electrolyte secondary battery having excellent overcharge characteristics and electrode plate density used for a mobile phone, a power tool, and the like can be obtained. Furthermore, since dry-out at the time of charging and discharging, which causes deterioration of battery characteristics, can be prevented, an excellent positive electrode active material for a non-aqueous electrolyte secondary battery used for electric vehicles can be obtained.
[0020]
The mixing ratio of the lithium transition metal composite oxide of the second particle group to the total of the lithium transition metal composite oxide of the first particle group and the lithium transition metal composite oxide of the second particle group is as follows: , 50% by weight to 90% by weight, wherein the lithium transition metal composite oxide as the first particle group and the lithium transition metal composite oxide as the second particle group of the lithium transition metal composite oxide as the first particle group The mixing ratio based on the total of the transition metal composite oxides is preferably 10% by weight to 50% by weight. By controlling the ratio of the small particles that can exist between the large particles in this manner, the electrode density can be more effectively improved, and the positive electrode active material for a nonaqueous electrolyte secondary battery can prevent dryout. Substance can be obtained.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the positive electrode active material for a non-aqueous electrolyte secondary battery according to the present invention will be described with reference to embodiments, examples, and FIGS. However, the present invention is not limited to this embodiment, examples and FIGS.
[0022]
(Positive electrode active material for non-aqueous electrolyte secondary batteries)
The positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention comprises at least a lithium transition metal composite oxide having a spinel structure. Spinel structure is a complex oxide of AB ₂ O ₄ Is one of the typical crystal structure types found in the type compounds (A and B are metal elements). Lithium occupies the tetrahedral site at 8a site 1, oxygen occupies 32e site 2, and transition metal occupies the octahedral site at 16d site 3.
[0023]
Examples of the lithium transition metal composite oxide having a spinel structure include lithium manganate and lithium titanate. Preferred is lithium manganate. In the case of lithium manganate, a positive electrode active material for a non-aqueous electrolyte secondary battery having excellent overcharge characteristics and an electrode plate density used for a mobile phone, a power tool, and the like can be obtained. Furthermore, since dry-out at the time of charging and discharging, which causes deterioration of battery characteristics, can be prevented, an excellent positive electrode active material for a non-aqueous electrolyte secondary battery used for electric vehicles can be obtained.
[0024]
The lithium transition metal composite oxide according to the present invention has at least a first lithium transition metal composite oxide and a second lithium transition metal composite oxide, and the first lithium transition metal composite oxide is secondary. It is smaller than the second lithium transition metal composite oxide containing an element and / or compound that increases the particle size.
[0025]
The lithium transition metal composite oxide according to the present invention has at least a first lithium transition metal composite oxide and a second lithium transition metal composite oxide. The first lithium transition metal composite oxide and the second lithium transition metal composite oxide may be the same or different. The first lithium transition metal composite oxide may be lithium manganate, and the second lithium transition metal composite oxide may be lithium titanate. The first lithium transition metal composite oxide may be lithium titanate, and the second lithium transition metal composite oxide may be lithium manganate. Preferably, the first lithium transition metal composite oxide is lithium manganate, and the second lithium transition metal composite oxide is also lithium manganate. At this time, a positive electrode active material for a non-aqueous electrolyte secondary battery having excellent overcharge characteristics and electrode plate density used for a mobile phone, a power tool, and the like can be obtained. Furthermore, since dry-out at the time of charging and discharging, which causes deterioration of battery characteristics, can be prevented, an excellent positive electrode active material for a non-aqueous electrolyte secondary battery used for electric vehicles can be obtained.
[0026]
The first lithium transition metal composite oxide according to the present invention is smaller than the second lithium transition metal composite oxide containing an element and / or compound that increases the secondary particle diameter. Elements and / or compounds that increase the secondary particle diameter are preferably boron compounds, chlorine compounds, and vanadium compounds. These have an effect as a flux and can prevent dryout during charge / discharge. More preferably, it is a boron compound.
[0027]
The boron compound is not particularly limited. For example, boric acid, lithium borate, boride, boron oxide, boron phosphate and the like are used. Preferably, boric acid and lithium borate. The chlorine compound is not particularly limited. For example, lithium chloride, sodium chloride, hydrogen chloride, hydrochloric acid, chlorine oxide, chlorine fluoride oxide and the like are used. Preferably, they are lithium chloride and sodium chloride. The vanadium compound is not particularly limited. For example, vanadium oxide, vanadium chloride, vanadium fluoride, vanadium hydroxide, or the like is used. Preferably, it is vanadium oxide.
[0028]
Small means that the particle diameter or specific surface area diameter is small. The particle diameter includes a primary particle diameter and a secondary particle diameter. The secondary particle size includes the median size. Preferably, the secondary particle diameter and the median diameter are small. More preferably, the median diameter is small. A typical lithium transition metal composite oxide particle is composed of primary particles grown by reflecting the crystal form of the lithium transition metal composite oxide, and secondary particles formed by agglomeration or sintering. The diameter of such primary particles is called primary particle diameter, and the diameter of secondary particles is called secondary particle.
[0029]
The method for measuring the specific surface area diameter is not particularly limited. For example, it can be measured using a Fisher sub-sieve sizer (FSSS) by an air permeation method. The median diameter means a particle diameter at which the volume cumulative frequency of the particle size distribution of the secondary particles reaches 50%. The method for measuring the median diameter is not particularly limited. For example, a particle size distribution is measured by a laser diffraction scattering method, an integrated distribution is calculated using a logarithm of a particle size on a volume basis, and a particle size when occupying 50% of the whole lithium transition metal composite oxide powder, ie, oversize 50 % Can be measured. The method for measuring the primary particle diameter is not particularly limited. For example, it can be measured using an image analysis method (microscope method).
[0030]
The lithium transition metal composite oxide according to the present invention has at least a first lithium transition metal composite oxide and a second lithium transition metal composite oxide, and the first lithium transition metal composite oxide is secondary. Since the median diameter is smaller than that of the second lithium transition metal composite oxide containing the element and / or the compound that increases the particle diameter, the electrode density can be improved and dryout can be prevented. A positive electrode active material for a non-aqueous electrolyte secondary battery having improved overcharge characteristics can be obtained.
[0031]
The first lithium transition metal composite oxide according to the present invention is preferably less than the second lithium transition metal composite oxide. The small amount means that the mixing ratio of the first lithium transition metal composite oxide to the total of the first lithium transition metal composite oxide and the second lithium transition metal composite oxide is smaller than that of the second lithium transition metal composite oxide. It means that the mixing ratio is smaller than the mixing ratio to the total of the first lithium transition metal composite oxide and the second lithium transition metal composite oxide. Further, the weight of the first lithium transition metal composite oxide may be smaller than the weight of the second lithium transition metal composite oxide.
[0032]
The lithium transition metal composite oxide according to the present invention has a first lithium manganate and a second lithium manganate, and the first lithium manganate is higher than the second lithium manganate containing boron. small.
[0033]
In the present invention, boron may be dissolved in the second lithium manganate or may have boron on the surface of the lithium manganate particles. Preferably, it has a first lithium manganate and a second lithium manganate, and the first lithium manganate is smaller than the second lithium manganate having boron on the surface of the particles. It is a positive electrode active material for non-aqueous electrolyte secondary batteries. At this time, the boron improves the passage of electrons in the lithium manganate, so that the cycle charge / discharge characteristics and the thermal stability are improved. The lithium manganate particles may be primary particles or secondary particles.
[0034]
A boron compound may be used instead of boron. The boron compound is not particularly limited. For example, boric acid, lithium borate, boride, boron oxide, boron phosphate and the like are used. Preferably, boric acid and lithium borate.
[0035]
In the present invention, the boron compound may be dissolved in the second lithium manganate or may have the boron compound on the surface of the lithium manganate particles. Preferably, it has a first lithium manganate and a second lithium manganate, and the first lithium manganate is smaller than the second lithium manganate having lithium borate on the surface of the particles. Is a positive electrode active material for a non-aqueous electrolyte secondary battery. At this time, the lithium borate improves the passage of electrons in the lithium manganate, so that the cycle charge / discharge characteristics and the thermal stability are improved. The lithium manganate particles may be primary particles or secondary particles.
[0036]
Boron and / or lithium borate exerts the effects of the present invention regardless of the form of lithium manganate particles present on the surface of the particles. For example, even when boron and / or lithium borate is coated on the entire surface of the lithium manganate particles, boron and / or lithium borate covers a part of the surface of the lithium manganate particles. Even in the case where it is performed, the cycle charge / discharge characteristics and the thermal stability are improved.
[0037]
More preferably, boron and / or lithium borate is coated on the entire surface of the lithium manganate particles. In this case, it is possible to obtain a positive electrode active material for a non-aqueous electrolyte secondary battery having improved storage characteristics as well as cycle charge / discharge characteristics and thermal stability.
Further, boron and / or lithium borate may be present at least on the surface of the particles. Therefore, boron and / or lithium borate may be present inside the particles.
[0038]
Whether boric acid and / or lithium borate is present on the surface of lithium manganate particles can be analyzed by various methods. For example, it can be analyzed by Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS).
[0039]
The amount of boron contained in the second lithium manganate is preferably 50 ppm to 500 ppm based on the second lithium manganate. At this time, the effect of the present invention is clearly shown. Preferably it is 100 ppm-400 ppm, More preferably, it is 150 ppm-350 ppm. At this time, the density of the electrode plate can be improved without lowering the overcharge characteristics, and dryout can be prevented.
[0040]
Small means that the particle diameter or specific surface area diameter is small. The particle diameter includes a primary particle diameter and a secondary particle diameter. The secondary particle size includes the median size. Preferably, the secondary particle diameter and the median diameter are small. More preferably, the median diameter is small. General lithium manganate particles are composed of primary particles that have been grown to reflect the crystal form of lithium manganate, and secondary particles formed by agglomeration or sintering. The diameter of such primary particles is called primary particle diameter, and the diameter of secondary particles is called secondary particle.
[0041]
The first lithium manganate according to the present invention is preferably less than the second lithium manganate. The small amount means that the mixing ratio of the first lithium manganate to the total of the first lithium manganate and the second lithium manganate is such that the first lithium manganate and the second lithium manganate of the second lithium manganate are mixed. It means that it is less than the mixing ratio with respect to the total of lithium. Further, the weight of the first lithium manganate may be smaller than the weight of the second lithium manganate.
[0042]
The lithium manganate according to the present invention preferably has the general formula Li _a Mn _3-a O _{4 + f} (A represents a number satisfying 0.8 ≦ a ≦ 1.2, and f represents a number satisfying −0.5 ≦ f ≦ 0.5.) The general formula is Li _a Mn _3-a O _{4 + f} (A represents a number that satisfies 0.8 ≦ a ≦ 1.2, and f represents a number that satisfies −0.5 ≦ f ≦ 0.5). A positive electrode active material for a non-aqueous electrolyte secondary battery having excellent overcharge characteristics and electrode plate density used for telephones, power tools, and the like can be obtained. Furthermore, since dry-out at the time of charging and discharging, which causes deterioration of battery characteristics, can be prevented, an excellent positive electrode active material for a non-aqueous electrolyte secondary battery used for electric vehicles can be obtained.
[0043]
(Method of producing positive electrode active material for non-aqueous electrolyte secondary battery)
The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to the present invention includes a first particle comprising a lithium transition metal composite oxide having a first particle size distribution and a primary particle diameter in a range of 10 μm or less. A step of selecting a group, and a second particle comprising a lithium transition metal composite oxide having a second particle size distribution having a secondary particle size larger than the first particle size distribution and having a primary particle size in a range of 8 μm to 150 μm. And a step of mixing the lithium transition metal composite oxide as the selected first particle group and the lithium transition metal composite oxide as the selected second particle group. Have.
[0044]
Hereinafter, the positive electrode active material for a nonaqueous electrolyte secondary battery according to the present invention (Li _1.072 Mn _1.914 Mg _0.01 B _0.0035 O ₄ ) Will be described, but the present invention is not limited to this method except for the above steps.
[0045]
An aqueous solution of sodium bicarbonate is added to an aqueous solution containing manganese ions and magnesium ions having a predetermined composition ratio to coprecipitate manganese and magnesium to obtain a coprecipitate.
[0046]
The manganese source is not particularly limited. Basically, any salt that can form an aqueous solution can be used. For example, manganese chloride, manganese iodide, manganese sulfate, manganese nitrate and the like are used. Preferably, MnSO ₄ , MnCl ₂ Are used.
[0047]
The magnesium source is not particularly limited. Basically, any salt that can form an aqueous solution can be used. For example, magnesium chloride, magnesium iodide, magnesium perchlorate, magnesium sulfate, magnesium nitrate and the like are used. Preferably, MgSO ₄ , Mg (NO ₃ ) ₂ Are used.
[0048]
Further, although the aqueous solution of sodium hydrogen carbonate is added, the invention is not limited to this, and an alkaline solution such as an aqueous solution of sodium hydroxide, an aqueous solution of potassium hydroxide, or an aqueous solution of lithium hydroxide may be used.
[0049]
Next, the obtained coprecipitate is filtered, washed with water, and dried. Then, the first coprecipitate is left as it is, and a predetermined amount of orthoboric acid is mixed with the second coprecipitate. The first coprecipitate is mixed with lithium carbonate so as to have a predetermined composition ratio, and baked in air or a weakly oxidizing atmosphere at a temperature of 800 ° C. to 1000 ° C. for 5 hours to 15 hours. The second coprecipitate is mixed with lithium carbonate so as to have a predetermined composition ratio, and calcined in air or a weakly oxidizing atmosphere at a temperature of 800 ° C to 1000 ° C for 5 hours to 15 hours. Thus, a lithium transition metal composite oxide having a first particle size distribution and a primary particle size in a range of 10 μm or less, and a lithium transition metal composite oxide having a second particle size distribution and a primary particle size in a range of 8 μm to 150 μm Obtain the oxide. 3 to 6 show a first particle size distribution 21 and a second particle size distribution 22 in the present invention.
[0050]
If the primary particles have the first particle size distribution and exceed 10 μm, the difference between small particles and large particles becomes small, which is not preferable. Preferably, it has a first particle size distribution and has a primary particle size of 2 μm to 8 μm. If it has the second particle size distribution and the primary particle diameter is smaller than 8 μm or larger than 150 μm, it becomes difficult to maintain the balance between small particles and large particles, and the particles of the lithium transition metal composite oxide during the preparation of the cathode mixture It is not preferable because sedimentation occurs. Preferably, it is a lithium transition metal composite oxide having a second particle size distribution and having a primary particle size in a range of 10 μm to 80 μm.
[0051]
What is mixed with the coprecipitate is not limited to lithium carbonate. Basically, any lithium compound can be used. For example, lithium fluoride, lithium chloride, lithium bromide, lithium iodide, lithium oxide, lithium peroxide, lithium hydroxide and the like are used. Preferably Li ₂ CO ₃ , LiOH, LiOH.H ₂ O, Li ₂ O, LiCl, LiNO ₃ , Li ₂ SO ₄ , LiHCO ₃ , Li (CH ₃ COO) or the like.
[0052]
A sulfur-containing compound, a compound containing a halogen element, and the like may be mixed together with the coprecipitate and the lithium compound.
[0053]
The sulfur-containing compound is not particularly limited. For example, sulfide, sulfur iodide, hydrogen sulfide, sulfuric acid and its salts, nitrogen sulfide and the like are used. Preferably Li ₂ SO ₄ , MnSO ₄ , (NH ₄ ) ₂ SO ₄ , Al ₂ (SO ₄ ) ₃ , MgSO ₄ Are used.
[0054]
The compound containing a halogen element is not particularly limited. For example, hydrogen fluoride, oxygen fluoride, hydrofluoric acid, hydrogen chloride, hydrochloric acid, chlorine oxide, chlorine fluoride oxide, bromine oxide, bromine fluorosulfate, hydrogen iodide, iodine oxide, periodic acid and the like are used. Preferably, NH ₄ F, NH ₄ Cl, NH ₄ Br, NH ₄ I, LiF, LiCl, LiBr, LiI, MnF ₂ , MnCl ₂ , MnBr ₂ , MnI ₂ Are used.
[0055]
The firing temperature is preferably 850 ° C. to 950 ° C., and the firing time is preferably 8 to 14 hours. If the firing temperature is lower than 800 ° C., unreacted raw materials may remain in the positive electrode active material for a non-aqueous electrolyte secondary battery, and sufficient characteristics for achieving the object of the present invention may not be obtained. Further, when firing at a temperature higher than 1000 ° C., by-products are easily generated, which causes a decrease in discharge capacity per unit weight, a decrease in cycle charge / discharge characteristics, and a decrease in operating voltage. If the firing time is less than 5 hours, the diffusion reaction between the particles of the raw material mixture does not proceed, and the desired positive electrode active material for a non-aqueous electrolyte secondary battery cannot be obtained. If the firing is performed for more than 15 hours, coarse particles are formed by sintering, which is not preferable.
[0056]
A first particle group comprising a lithium transition metal composite oxide having a first particle size distribution and a primary particle size in a range of 10 μm or less is selected, and a second particle group having a secondary particle size larger than the first particle size distribution is selected. A second particle group consisting of a lithium transition metal composite oxide having a particle size distribution of 2 and a primary particle diameter in the range of 8 μm to 150 μm, and a selected first particle group And the second group of particles.
[0057]
The lithium transition metal composite oxide as the second particle group preferably contains boron. In the present invention, boron may be dissolved in the lithium transition metal composite oxide, which is the second particle group, or may have boron on the surface of the lithium transition metal composite oxide particles. If the surface of the particles of the lithium transition metal composite oxide, which is the second particle group, has boron, the boron improves the passage of electrons in the lithium transition metal composite oxide, so that the cycle charge and discharge characteristics, High load characteristics are improved. The particles of the lithium transition metal composite oxide may be primary particles or secondary particles.
[0058]
A boron compound may be used instead of boron. The boron compound is not particularly limited. For example, boric acid, lithium borate, boride, boron oxide, boron phosphate and the like are used. Preferably, boric acid and lithium borate.
[0059]
In the present invention, the boron compound may be dissolved in the lithium transition metal composite oxide, which is the second particle group, or may have the boron compound on the surface of the lithium transition metal composite oxide particles. The particles of the lithium transition metal composite oxide, which is the second particle group, preferably have lithium borate on the surface. At this time, since lithium borate improves the ease of passing electrons in the lithium transition metal composite oxide, cycle charge / discharge characteristics and high load characteristics are improved. The particles of the lithium transition metal composite oxide may be primary particles or secondary particles.
[0060]
Boron and / or lithium borate can exert the effects of the present invention regardless of the form of lithium transition metal composite oxide particles present on the surface of the particles. For example, even when boron and / or lithium borate is coated on the entire surface of the particles of the lithium transition metal composite oxide, boron and / or lithium borate may Even when a part of the surface is covered, the cycle charge / discharge characteristics and the thermal stability are improved.
[0061]
More preferably, the case where boron and / or lithium borate is coated on the entire surface of the particles of the lithium transition metal composite oxide. In this case, it is possible to obtain a positive electrode active material for a non-aqueous electrolyte secondary battery having improved storage characteristics as well as cycle charge / discharge characteristics and thermal stability.
Further, boron and / or lithium borate may be present at least on the surface of the particles. Therefore, boron and / or lithium borate may be present inside the particles.
[0062]
Whether boric acid and / or lithium borate is present on the surface of the lithium transition metal composite oxide particles can be analyzed by various methods. For example, it can be analyzed by Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS).
[0063]
The amount of boron contained in the lithium transition metal composite oxide as the second particle group is preferably 50 ppm to 500 ppm based on the lithium transition metal composite oxide as the second particle group. At this time, the effect of the present invention is clearly shown. Preferably it is 100 ppm-400 ppm, More preferably, it is 150 ppm-350 ppm. At this time, the density of the electrode plate can be improved without lowering the overcharge characteristics, and dryout can be prevented.
[0064]
The first particle size distribution is preferably adjusted so that the secondary particle diameter is in the range of 1 μm to 50 μm. When the secondary particle size is smaller than 1 μm, the specific surface area of the lithium transition metal composite oxide increases, and manganese elution causing deterioration in cycle charge / discharge characteristics and dryout occurs. If the secondary particle diameter is larger than 50 μm, it cannot contribute to mixing with the large particles as small particles, which is not effective for achieving the object of the present invention. More preferably, the secondary particle diameter of the first particle size distribution is adjusted in the range of 1 μm to 30 μm.
[0065]
The second particle size distribution is preferably adjusted so that the secondary particle size is in the range of 8 μm to 150 μm. If the secondary particle diameter is smaller than 8 μm, it cannot contribute to mixing with the small particles as a large particle, which is not effective in achieving the object of the present invention. If the secondary particle size is larger than 150 μm, sedimentation of lithium transition metal composite oxide particles during the preparation of the positive electrode mixture is not preferred. More preferably, the secondary particle size of the second particle size distribution is adjusted in the range of 10 μm to 50 μm.
[0066]
The lithium transition metal composite oxide has a general formula of Li _a M _b Mn _3-ab A _g X _c B _d S _e D _h O _{4 + f} (M represents aluminum and / or magnesium; A represents at least one selected from the group consisting of titanium, zirconium and hafnium; X represents at least one selected from the group consisting of fluorine, chlorine, bromine and iodine; Represents boron, S represents sulfur, D represents sodium and / or calcium, a represents a number satisfying 0.8 ≦ a ≦ 1.2, and b represents a number satisfying 0 ≦ b ≦ 0.2. Represents a number satisfying 0 ≦ c ≦ 0.05, d represents a number satisfying 0 ≦ d ≦ 0.02, e represents a number satisfying 0 ≦ e ≦ 0.1, and f represents a number satisfying 0 ≦ e ≦ 0.1. Represents a number satisfying −0.5 ≦ f ≦ 0.5, g represents a number satisfying 0 ≦ g ≦ 0.1, and h represents a number satisfying 0 ≦ h ≦ 0.015.) Is preferred.
[0067]
The mixing ratio of the lithium transition metal composite oxide as the first particle group and the lithium transition metal composite oxide as the second particle group of the lithium transition metal composite oxide as the second particle group was 50 weight%. % To 90% by weight of the lithium transition metal composite oxide as the first particle group and the lithium transition metal composite oxide as the second particle group. The mixing ratio with respect to the total is preferably from 10% by weight to 50% by weight. If the mixing ratio is not in this range, it is not possible to efficiently increase the electrode plate density. When the mixing ratio of the small particles is large, the surface of the electrode plate is crushed by the pressing at the time of manufacturing the electrode plate, so that it is difficult to enter and exit the electrolytic solution, and dry-out occurs. More preferably, the mixing ratio of the lithium transition metal composite oxide as the first particle group and the lithium transition metal composite oxide as the second particle group in the lithium transition metal composite oxide as the second particle group Is from 55% by weight to 75% by weight, and the lithium transition metal composite oxide as the first particle group and the lithium transition metal as the second particle group of the lithium transition metal composite oxide as the first particle group The mixing ratio with respect to the total of the composite oxides is from 25% by weight to 45% by weight.
[0068]
The lithium transition metal composite oxide obtained by the above calcination may be pulverized by a mortar, a ball mill, a vibration mill, a pin mill, or the like. 0.2m specific surface area by the above method ² /G~1.2m ² / G of the positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention.
[0069]
By using the above manufacturing method, it is possible to obtain a desired positive electrode active material for a non-aqueous electrolyte secondary battery.
[0070]
The coprecipitation of manganese and magnesium with carbonates resulted in Li _1.072 Mn _1.914 Mg _0.01 B _0.0035 O ₄ Was manufactured, but a manganese compound and a magnesium compound may be mixed so as to have a predetermined composition ratio and fired.
[0071]
(Non-aqueous electrolyte secondary battery)
The positive electrode active material for a non-aqueous electrolyte secondary battery according to the present invention is suitably used for a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery and a lithium ion polymer secondary battery.
[0072]
The nonaqueous electrolyte secondary battery may be any of the conventionally known nonaqueous electrolyte secondary batteries, in which the positive electrode active material is the positive electrode active material of the present invention, and other configurations are not particularly limited. Any non-aqueous electrolyte secondary battery including the positive electrode active material layer containing the lithium transition metal composite oxide according to the present invention as a main component may be used.
[0073]
By using lithium cobaltate and / or lithium nickelate together with the positive electrode active material of the present invention as a positive electrode active material, not only overcharge characteristics, thermal stability and safety but also excellent discharge capacity, load characteristics and output characteristics are obtained. A non-aqueous electrolyte secondary battery can be obtained.
[0074]
The general formula is Li _{1 + x} CoO ₂ (X represents a number that satisfies -0.5 ≦ x ≦ 0.5). The lithium cobaltate has at least a part thereof selected from the group consisting of magnesium, aluminum, calcium, vanadium, titanium, chromium, manganese, iron, cobalt, nickel, copper, zinc, strontium, zirconium, niobium, molybdenum and tin. It may be substituted by one kind.
[0075]
The general formula is Li _{1 + x} NiO ₂ (X represents a number satisfying -0.5≤x≤0.5.) Lithium nickelate is preferred. The lithium nickelate has at least a part thereof selected from the group consisting of magnesium, aluminum, calcium, vanadium, titanium, chromium, manganese, iron, cobalt, nickel, copper, zinc, strontium, zirconium, niobium, molybdenum and tin. It may be substituted by one kind.
[0076]
The positive electrode using the positive electrode active material mainly containing the lithium transition metal composite oxide according to the present invention is preferably manufactured as follows. The positive electrode mixture is formed by mixing the lithium transition metal composite oxide powder according to the present invention with a carbon-based conductive agent such as acetylene black and graphite, a binder and a solvent or a dispersion medium of the binder. . The positive electrode mixture is formed into a slurry or a kneaded material, which is applied or supported on a current collector 12 such as an aluminum foil, and is press-rolled to form a positive electrode active material layer on the current collector 12.
[0077]
As the binder, polyvinylidene fluoride, polytetrafluoroethylene, polyamide acrylic resin or the like can be used.
[0078]
It is considered that the lithium transition metal composite oxide according to the present invention has good mixing properties with the conductive agent powder, and the internal resistance of the battery is reduced. For this reason, the charge / discharge characteristics, particularly the discharge capacity, are improved. Also, when kneaded with a binder, the lithium transition metal composite oxide of the present invention has excellent fluidity, easily entangles with a polymer of the binder, and has excellent binding properties. Further, since it is spherical without containing coarse particles, the surface of the coating surface of the produced positive electrode 13 is excellent in smoothness. As a result, the coating surface of the positive electrode plate has excellent binding properties and is difficult to peel off, and the surface is smooth and lithium ions enter and exit uniformly on the coating film surface during charge and discharge, so there is a marked improvement in cycle charge and discharge characteristics. Is obtained.
[0079]
For example, as the negative electrode active material, metal lithium, a lithium alloy, or a compound capable of inserting and extracting lithium ions can be used. As the lithium alloy, for example, a LiAl alloy, a LiSn alloy, a LiPb alloy or the like can be used. As the compound capable of inserting and extracting lithium ions, for example, a carbon material such as graphite and graphite can be used. Further, an oxide such as tin oxide or titanium oxide which can insert and remove lithium ions may be used.
[0080]
The electrolyte can be used without any particular limitation as long as it is a compound that does not deteriorate or decompose at the operating voltage. As the solvent, for example, organic solvents such as dimethoxyethane, diethoxyethane, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl formate, γ-butyrolactone, 2-methyltetrahydrofuran, dimethyl sulfoxide, and sulfolane can be used. Alternatively, two or more kinds selected from the above-mentioned organic solvent group may be used as a mixture.
[0081]
As the electrolyte, for example, lithium salts such as lithium perchlorate, lithium tetrafluoroborate, lithium tetrafluorophosphate, and lithium trifluoromethane can be used. The above-mentioned solvent and electrolyte are mixed and used as an electrolyte. Here, a gelling agent or the like may be added and used as a gel, or it may be used after being absorbed by a hygroscopic polymer. Further, a solid electrolyte having inorganic or organic lithium ion conductivity may be used.
[0082]
Further, as the separator 14, a porous film made of polyethylene, polypropylene, or the like can be used. A non-aqueous electrolyte secondary battery is prepared according to a standard method using the positive electrode active material for a non-aqueous electrolyte secondary battery according to the present invention, the above-described negative electrode active material, electrolyte, and separator. Thereby, excellent battery characteristics that could not be achieved conventionally can be realized.
[0083]
Further, a band-shaped positive electrode constituted by forming a positive electrode active material layer using a positive electrode active material for a nonaqueous electrolyte secondary battery according to the present invention as a positive electrode active material on both surfaces of a band-shaped positive electrode current collector, A strip-shaped negative electrode constituted by forming a negative electrode active material layer of the negative electrode active material layer on each side of the strip-shaped negative electrode current collector is provided, and a large number of strip-shaped positive electrodes and strip-shaped negative electrodes are stacked via a strip-shaped separator. By winding, a spiral wound body in which a band-shaped separator is interposed between the band-shaped positive electrode and the band-shaped negative electrode can be formed to obtain a nonaqueous electrolyte secondary battery. With this configuration, the manufacturing process is simple, cracking of the positive electrode active material layer and the negative electrode active material layer and separation from the strip-shaped separator are less likely to occur, and the battery capacity can be increased and the energy density can be increased. . In particular, the positive electrode active material for a non-aqueous electrolyte secondary battery according to the present invention has a high electrode plate density, excellent filling properties, and is easily compatible with a binder. Therefore, a positive electrode having a high charge / discharge capacity, and excellent in binding property and surface smoothness can be further prevented from cracking or peeling of the positive electrode active material layer.
[0084]
The shape of the nonaqueous electrolyte secondary battery may be a cylindrical shape, a coin shape, a square shape, or the like.
[0085]
(Applications of non-aqueous electrolyte secondary batteries)
The use of the nonaqueous electrolyte secondary battery using the positive electrode active material for a nonaqueous electrolyte secondary battery according to the present invention is not particularly limited. For example, notebook PC, pen input PC, pocket PC, notebook word processor, pocket word processor, e-book player, mobile phone, cordless phone handset, electronic notebook, calculator, LCD TV, electric shaver, electric tool, electronic translator, car phone , Portable printer, transceiver, pager, handy terminal, portable copy, voice input device, memory card, backup power supply, tape recorder, radio, headphone stereo, handy cleaner, portable CD, video movie, navigation system, etc. Can be used. Lighting equipment, air conditioners, televisions, stereos, water heaters, refrigerators, oven microwaves, dishwashers, washing machines, dryers, game machines, toys, road conditioners, medical equipment, automobiles, electric vehicles, golf carts, electric carts , Can be used as a power source for power storage systems and the like. It can also be used for civilian use, military use, and space use.
[0086]
Hereinafter, the positive electrode active material for a non-aqueous electrolyte secondary battery according to the present invention will be described with reference to examples, but the present invention is not limited to these examples.
[0087]
【Example】
[Example 1]
An aqueous solution of sodium hydrogen carbonate was added to an aqueous solution containing manganese ions and magnesium ions having a predetermined composition ratio to coprecipitate manganese and magnesium to obtain a coprecipitate.
The obtained coprecipitate was filtered, washed with water and dried, and then the first coprecipitate was left as it was, and the second coprecipitate was mixed with 300 ppm of orthoboric acid. The first coprecipitate was mixed with lithium carbonate so as to have a predetermined composition ratio, and baked in an air atmosphere at a temperature of 930 ° C. for 12 hours. The second coprecipitate was mixed with lithium carbonate so as to have a predetermined composition ratio, and baked in an air atmosphere at a temperature of 930 ° C. for 12 hours. Thus, a lithium transition metal composite oxide having a first particle size distribution and a primary particle size of 4 μm and a lithium transition metal composite oxide having a second particle size distribution and a primary particle size in a range of 20 μm were obtained.
A first particle group comprising a lithium transition metal composite oxide having a first particle size distribution and a primary particle size of 4 μm is selected, and a lithium transition material having a second particle size distribution and a primary particle size in a range of 20 μm is selected. A second particle group consisting of a second particle group consisting of a metal composite oxide was selected, and the selected first particle group and second particle group were mixed. The mixing ratio of the lithium transition metal composite oxide as the first particle group and the lithium transition metal composite oxide as the second particle group of the lithium transition metal composite oxide as the second particle group was 70% by weight. %, And the mixing ratio of the lithium transition metal composite oxide as the first particle group to the total of the lithium transition metal composite oxide as the first particle group and the lithium transition metal composite oxide as the second particle group is , 30% by weight. Thus Li _1.072 Mn _1.914 Mg _0.01 B _0.0035 O ₄ was gotten.
[0088]
(Evaluation of positive electrode active material for non-aqueous electrolyte secondary battery)
The positive electrode active material for a non-aqueous electrolyte secondary battery according to the present invention is subjected to composition analysis, specific surface area measurement and particle size distribution measurement by the following methods. In addition, a test battery is prepared and each evaluation is performed.
[0089]
(Composition analysis)
A predetermined amount of the positive electrode active material for a non-aqueous electrolyte secondary battery is dissolved in nitric acid, and the contents of each of the constituent elements other than the halogen element and oxygen are quantified by plasma emission spectroscopy (ICP) analysis. Further, a predetermined amount of the positive electrode active material for a non-aqueous electrolyte secondary battery is charged into pure water and stirred to obtain a supernatant aqueous solution. The halogen element in the supernatant aqueous solution is quantified by an ion meter using an anion-selective electrode as an indicator electrode.
[0090]
(Evaluation of powder)
The specific surface area of the positive electrode active material for a nonaqueous electrolyte secondary battery is measured by a constant pressure BET adsorption method using nitrogen gas. The median diameter is obtained by measuring the particle size distribution by a laser diffraction scattering method, obtaining an integrated distribution using the logarithm of the volume-based particle diameter, and determining the particle diameter when occupying 50% of the entire lithium transition metal composite oxide powder, that is, It is measured as a particle size of 50% oversize. The measurement of the primary particle diameter is measured by using an image analysis method (microscope method).
[0091]
(Measurement of crystallite diameter)
The measurement is performed using RINT2500V manufactured by Rigaku Corporation. Using CuKα1 as an X-ray source, an X-ray diffraction pattern is measured at a tube current of 100 mA and a tube voltage of 40 kV. It is calculated from the diffraction peak caused by the (400) plane by Scherrer's formula represented by the following formula.
[0092]
(Equation 1)

[0093]
In the formula, D is the crystallite size (Å), K is the Scherrer constant (K = 1.05 when β is calculated from the integration width), and λ is the wavelength of the X-ray source (CuKα1 = 1.540562Å). , Β indicate the width (radian) of the spread of the diffraction line depending on the crystallite size, and θ indicates the diffraction angle 2θ / 2 (degree).
[0094]
(Production of lithium ion secondary battery)
To a normal methylpyrrolidone solution containing 5 parts by weight of polyvinylidene fluoride, 90 parts by weight of lithium transition metal composite oxide powder as a positive electrode active material and 5 parts by weight of carbon powder as a conductive agent were added, and kneaded to prepare a paste. This is applied to an aluminum electrode plate by a doctor blade method, and dried to obtain a positive electrode plate. In addition, a carbon material is used as a negative electrode active material, and the same is applied to a copper electrode plate to produce a negative electrode plate. Using a porous propylene film as a separator, LiPF in a mixed solvent of ethylene carbonate: diethyl carbonate = 1: 1 (volume ratio) as an electrolytic solution ₆ Is dissolved at a concentration of 1 mol / l to produce a lithium ion secondary battery. In this embodiment, a positive electrode plate, a negative electrode plate, and a separator are formed into a thin sheet shape, wound, and housed in a battery case made of a metal laminated resin film to obtain a laminated battery.
[0095]
(Evaluation of overcharge characteristics)
The produced lithium ion secondary battery is charged to a battery voltage of 4.2 V at a current value of 1 C (700 mA), and then charged at a constant voltage of 4.2 V until the battery voltage reaches 10 mA, thereby obtaining a fully charged state. A fully charged lithium ion secondary battery is placed in a champ maintained at 25 to 26 ° C., and an electrode of a charge / discharge device is attached. Further, a resistance temperature detector is attached to the center of the lithium ion secondary battery. In this way, the battery voltage and temperature of the lithium ion secondary battery can be recorded. The fully charged lithium ion secondary battery is further charged at a constant current value of 1 C up to a maximum voltage of 15 V, and the appearance and surface temperature of the battery are recorded. Similarly, the battery is charged to a maximum voltage of 15 V at a constant current value of 2 C and 3 C, and the appearance and surface temperature of the battery are recorded.
[0096]
(Measurement of electrode density)
A paste is prepared by kneading 95 parts by weight of a lithium transition metal composite oxide powder as a positive electrode active material and a normal methylpyrrolidone solution containing 5 parts by weight of polyvinylidene fluoride, and the paste is prepared on an aluminum electrode plate by a doctor blade method. It is applied and dried to obtain a positive electrode plate. After cutting the positive electrode plate into a predetermined size (2 × 2.5 cm), the electrode plate is pressed with a uniaxial press, and the electrode plate density is obtained from the thickness and weight of the pressed electrode plate.
[0097]
(Evaluation of dryout)
A paste is prepared by kneading 95 parts by weight of a lithium transition metal composite oxide powder as a positive electrode active material and a normal methylpyrrolidone solution containing 5 parts by weight of polyvinylidene fluoride, and the paste is prepared on an aluminum electrode plate by a doctor blade method. It is applied and dried to obtain a positive electrode plate. The positive electrode plate is placed in a glass container and immersed in a propylene carbonate solution in an argon box. After vacuuming for 3 minutes and allowing the propylene carbonate solution to permeate the positive electrode plate, the positive electrode plate is taken out of the argon box, and the positive electrode plate is weighed every hour. The weight of the positive electrode plate per hour is subtracted from the weight of the first positive electrode plate to calculate the reduction amount of the propylene carbonate solution. If the amount of propylene carbonate reduced is large, it can be determined that the electrolyte solution can be easily moved, and that dryout can be prevented. If the amount of decrease in propylene carbonate is small, it can be determined that the electrolyte solution is difficult to move and dryout is likely to occur.
[0098]
The results are shown in Table 1 and FIG. The particle size distribution is shown in FIG.
[0099]
[Example 2]
An aqueous solution of sodium hydrogen carbonate was added to an aqueous solution containing manganese ions and magnesium ions having a predetermined composition ratio to coprecipitate manganese and magnesium to obtain a coprecipitate.
After the obtained coprecipitate was filtered, washed with water and dried, the first coprecipitate was left as it was, and the second coprecipitate was mixed with 200 ppm of orthoboric acid. The first coprecipitate was mixed with lithium carbonate so as to have a predetermined composition ratio, and baked in an air atmosphere at a temperature of 930 ° C. for 12 hours. The second coprecipitate was mixed with lithium carbonate so as to have a predetermined composition ratio, and baked in an air atmosphere at a temperature of 930 ° C. for 12 hours. Thus, a lithium transition metal composite oxide having a first particle size distribution and a primary particle size of 4 μm and a lithium transition metal composite oxide having a second particle size distribution and a primary particle size in a range of 15 μm were obtained.
A first particle group comprising a lithium transition metal composite oxide having a first particle size distribution and a primary particle size of 4 μm is selected, and a lithium transition material having a second particle size distribution and a primary particle size in a range of 15 μm is selected. A second particle group consisting of a second particle group consisting of a metal composite oxide was selected, and the selected first particle group and second particle group were mixed. The mixing ratio of the lithium transition metal composite oxide as the first particle group and the lithium transition metal composite oxide as the second particle group of the lithium transition metal composite oxide as the second particle group was 70% by weight. %, And the mixing ratio of the lithium transition metal composite oxide as the first particle group to the total of the lithium transition metal composite oxide as the first particle group and the lithium transition metal composite oxide as the second particle group is , 30% by weight. Thus Li _1.073 Mn _1.915 Mg _0.01 B _0.0023 O ₄ was gotten.
[0100]
The particle size distribution is shown in FIG.
[0101]
[Example 3]
An aqueous solution of sodium hydrogen carbonate was added to an aqueous solution containing manganese ions and magnesium ions having a predetermined composition ratio to coprecipitate manganese and magnesium to obtain a coprecipitate.
The obtained coprecipitate was filtered, washed with water, and dried. Then, the first coprecipitate was left as it was, and the second coprecipitate was mixed with 100 ppm of orthoboric acid. The first coprecipitate was mixed with lithium carbonate so as to have a predetermined composition ratio, and baked in an air atmosphere at a temperature of 930 ° C. for 12 hours. The second coprecipitate was mixed with lithium carbonate so as to have a predetermined composition ratio, and baked in an air atmosphere at a temperature of 930 ° C. for 12 hours. Thus, a lithium transition metal composite oxide having a first particle size distribution and a primary particle size of 4 μm and a lithium transition metal composite oxide having a second particle size distribution and a primary particle size in a range of 8 μm were obtained.
A first particle group comprising a lithium transition metal composite oxide having a first particle size distribution and a primary particle size of 4 μm is selected, and a lithium transition material having a second particle size distribution and a primary particle size in a range of 8 μm is selected. A second particle group consisting of a second particle group consisting of a metal composite oxide was selected, and the selected first particle group and second particle group were mixed. The mixing ratio of the lithium transition metal composite oxide as the first particle group and the lithium transition metal composite oxide as the second particle group of the lithium transition metal composite oxide as the second particle group was 70% by weight. %, And the mixing ratio of the lithium transition metal composite oxide as the first particle group to the total of the lithium transition metal composite oxide as the first particle group and the lithium transition metal composite oxide as the second particle group is , 30% by weight. Thus Li _1.073 Mn _1.916 Mg _0.01 B _0.0012 O ₄ was gotten.
[0102]
Hereinafter, the positive electrode active material for a non-aqueous electrolyte secondary battery was evaluated in the same manner as in Example 1. The results are shown in Table 1 and FIG. The particle size distribution is shown in FIG.
[0103]
[Example 4]
An aqueous solution of sodium hydrogen carbonate was added to an aqueous solution containing manganese ions and magnesium ions having a predetermined composition ratio to coprecipitate manganese and magnesium to obtain a coprecipitate.
The obtained coprecipitate was filtered, washed with water and dried, and then the first coprecipitate was left as it was, and the second coprecipitate was mixed with 300 ppm of orthoboric acid. The first coprecipitate was mixed with lithium carbonate so as to have a predetermined composition ratio, and baked in an air atmosphere at a temperature of 930 ° C. for 12 hours. The second coprecipitate was mixed with lithium carbonate so as to have a predetermined composition ratio, and baked in an air atmosphere at a temperature of 930 ° C. for 12 hours. Thus, a lithium transition metal composite oxide having a first particle size distribution and a primary particle size of 4 μm and a lithium transition metal composite oxide having a second particle size distribution and a primary particle size in a range of 20 μm were obtained.
A first particle group comprising a lithium transition metal composite oxide having a first particle size distribution and a primary particle size of 4 μm is selected, and a lithium transition material having a second particle size distribution and a primary particle size in a range of 20 μm is selected. A second particle group consisting of a second particle group consisting of a metal composite oxide was selected, and the selected first particle group and second particle group were mixed. The mixing ratio of the lithium transition metal composite oxide as the first particle group and the lithium transition metal composite oxide as the second particle group of the lithium transition metal composite oxide as the second particle group is 60 weight%. %, And a mixing ratio of the lithium transition metal composite oxide as the first particle group to the total of the lithium transition metal composite oxide as the first particle group and the lithium transition metal composite oxide as the second particle group is , 40% by weight. Thus Li _1.072 Mn _1.915 Mg _0.01 B _0.003 O ₄ was gotten.
[0104]
FIG. 6 shows the particle size distribution.
[0105]
[Comparative Example 1]
An aqueous solution of sodium hydrogen carbonate was added to an aqueous solution containing manganese ions and magnesium ions having a predetermined composition ratio to coprecipitate manganese and magnesium to obtain a coprecipitate.
The obtained coprecipitate was filtered, washed with water, dried, and then mixed with lithium carbonate so as to have a predetermined composition ratio, and calcined at 930 ° C. for 12 hours in an air atmosphere. And crushed in a mortar and Li _1.073 Mn _1.917 Mg _0.01 O ₄ was gotten.
[0106]
Hereinafter, the positive electrode active material for a non-aqueous electrolyte secondary battery was evaluated in the same manner as in Example 1. The results are shown in Table 1 and FIG. FIG. 7 shows the particle size distribution.
[0107]
[Comparative Example 2]
An aqueous solution of sodium hydrogen carbonate was added to an aqueous solution containing manganese ions and magnesium ions having a predetermined composition ratio to coprecipitate manganese and magnesium to obtain a coprecipitate.
The obtained coprecipitate was filtered, washed with water, dried, then mixed with lithium carbonate and orthoboric acid so as to have a predetermined composition ratio, and calcined at 930 ° C. for 12 hours in an air atmosphere. And crushed in a mortar and Li _1.072 Mn _1.913 Mg _0.01 B _0.005 O ₄ was gotten.
[0108]
FIG. 8 shows the particle size distribution.
[0109]
[Comparative Example 3]
An aqueous solution of sodium bicarbonate was added to an aqueous solution containing manganese ions and magnesium ions having a predetermined composition ratio, and manganese and magnesium were coprecipitated to obtain a coprecipitate having a predetermined secondary particle diameter.
The obtained coprecipitate was filtered, washed with water, dried, then mixed with lithium carbonate and orthoboric acid so as to have a predetermined composition ratio, and calcined at 930 ° C. for 12 hours in an air atmosphere. This was used as the first lithium transition metal composite oxide. The primary particle size was 0.7 μm.
An aqueous solution of sodium bicarbonate was added to an aqueous solution containing manganese ions and magnesium ions having a predetermined composition ratio, and manganese and magnesium were coprecipitated to obtain a coprecipitate having a predetermined secondary particle diameter.
The obtained coprecipitate is filtered, washed with water, dried, and then mixed with lithium carbonate and orthoboric acid so as to have a predetermined composition ratio to have a predetermined particle size larger than that of the first lithium transition metal composite oxide. In the air atmosphere at 930 ° C. for 12 hours. This was used as a second lithium transition metal composite oxide. The primary particle size was 0.7 μm.
The mixing ratio of the two kinds of lithium transition metal composite oxides thus obtained to the total of the first lithium transition metal composite oxide of the second lithium transition metal composite oxide and the second lithium transition metal composite oxide is , 70% by weight, and the mixing ratio of the first lithium transition metal composite oxide to the total of the first lithium transition metal composite oxide and the second lithium transition metal composite oxide was 30% by weight. Thus Li _1.072 Mn _1.913 Mg _0.01 B _0.005 O ₄ was gotten.
[0110]
FIG. 9 shows the particle size distribution.
[0111]
As is clear from Table 1 and FIG. 1, the positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention has an improved electrode density compared to Comparative Example 1. It can also be seen that dryout was also prevented. Further, it can be seen that the overcharge characteristics are also improved.
[0112]
On the other hand, Comparative Example 1 is inferior in the electrode plate density and the overcharge characteristic to the positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention. Also, dryout has not been prevented.
[0113]
[Table 1]

[0114]
In Examples 1, 2, and 3, the mixing ratio of the lithium transition metal composite oxide as the first particle group and the lithium transition metal composite oxide as the second particle group was changed, The electrode plate density when changing was measured. The results are shown in Tables 2 to 4 and FIG.
[0115]
[Table 2]

[0116]
[Table 3]

[0117]
[Table 4]

[0118]
From these results, the mixing ratio of the lithium transition metal composite oxide as the second particle group to the total of the lithium transition metal composite oxide as the first particle group and the lithium transition metal composite oxide as the second particle group Is 60% by weight to 70% by weight, and a lithium transition metal composite oxide as a first particle group and a lithium transition metal as a second particle group of a lithium transition metal composite oxide as a first particle group It can be seen that the mixing ratio with respect to the total of the composite oxides is more preferably 30% by weight to 40% by weight.
[0119]
The technical ideas (inventions) other than those described in the claims that can be grasped from the above embodiments will be described below together with their effects.
[0120]
(1) In the invention according to any one of claims 1 to 4, the lithium transition metal composite oxide is a positive electrode active material for a non-aqueous electrolyte secondary battery containing aluminum and / or magnesium. By adding aluminum and / or magnesium, the cycle charge / discharge characteristics are improved without impairing the characteristics of the present invention. It is thought that the crystal structure can be stabilized by adding aluminum and / or magnesium.
[0121]
(2) In the invention according to any one of claims 1 to 4 and (1), the lithium transition metal composite oxide further includes at least one selected from the group consisting of titanium, zirconium, and hafnium. It is a positive electrode active material for non-aqueous electrolyte secondary batteries. By including at least one selected from the group consisting of titanium, zirconium, and hafnium, the impedance can be reduced without impairing the characteristics of the present invention. It is considered that when at least one selected from the group consisting of titanium, zirconium, and hafnium is included, the lattice constant increases, and the mobility of lithium ions in the particles increases.
[0122]
(3) In the invention according to any one of claims 1 to 4 and (1) or (2), the lithium transition metal composite oxide further contains sulfur, and the positive electrode for a nonaqueous electrolyte secondary battery is further included. Active material. It is considered that sulfur, which is a constituent element of the present invention, reduces the migration resistance of lithium ions and reduces the resistance of the positive electrode plate without impairing the characteristics of the present invention.
[0123]
(4) In the invention according to any one of claims 1 to 4 and (1) to (3), the lithium transition metal composite oxide is further selected from the group consisting of fluorine, chlorine, bromine and iodine. A positive electrode active material for a non-aqueous electrolyte secondary battery containing at least one kind. It is considered that the effect of improving the particle properties is exhibited by adding a halogen element. It is considered that a lithium-transition metal composite oxide having excellent crystallinity, a small specific surface area, containing no coarse particles, having a spherical shape, and a uniform particle size is obtained as compared with a case where there is no halogen element. Further, it is considered that the halogen element segregates on the particle surface, and the impedance of the lithium transition metal composite oxide surface can be reduced as compared with the case where there is no halogen element, without impairing the characteristics of the present invention. Furthermore, it is considered that the migration resistance of lithium ions at the interface between the particle surface of the lithium transition metal composite oxide and the electrolytic solution is reduced as compared with the case where there is no halogen element.
[0124]
(5) In the invention according to any one of claims 1 to 4 and (1) to (4), the lithium transition metal composite oxide is a non-aqueous electrolyte solution further containing sodium and / or calcium. It is a positive electrode active material for secondary batteries. Since sodium and calcium cover a part or the whole of the lithium transition metal composite oxide particles and control the reactivity with the electrolyte, it is considered that the expansion coefficient of the battery is significantly reduced without impairing the characteristics of the present invention. Sodium and calcium have less effect of reducing the charge / discharge capacity than lithium, so that the effect can be added and the battery expansion coefficient can be further reduced.
[0125]
(6) In the invention according to any one of claims 1 to 4 and (1) to (5), the lithium transition metal composite oxide has a general formula of Li _a M _b Mn _3-ab A _g X _c B _d S _e D _h O _{4 + f} (M represents aluminum and / or magnesium, A represents at least one selected from the group consisting of titanium, zirconium and hafnium, X represents at least one selected from the group consisting of fluorine, chlorine, bromine and iodine; Represents boron, S represents sulfur, D represents sodium and / or calcium, a represents a number satisfying 0.8 ≦ a ≦ 1.2, and b represents a number satisfying 0 <b ≦ 0.2. Represents a number satisfying 0 ≦ c ≦ 0.05, d represents a number satisfying 0 ≦ d ≦ 0.02, e represents a number satisfying 0 <e ≦ 0.1, and f represents a number satisfying 0 <e ≦ 0.1. Represents a number satisfying −0.5 ≦ f ≦ 0.5, g represents a number satisfying 0 <g ≦ 0.1, and h represents a number satisfying 0 ≦ h <0.015.) It is a positive electrode active material for non-aqueous electrolyte secondary batteries. In this case, excellent cycle charge / discharge characteristics and improved storage characteristics can be realized without impairing the characteristics of the present invention, and swelling of the battery can be suppressed.
[0126]
(7) In the invention according to any one of claims 1 to 4 and (1) to (6), the specific surface area of the lithium transition metal composite oxide is 0.2 to 1.2 m. ² / G of the positive electrode active material for a non-aqueous electrolyte secondary battery. By such standardization, more excellent battery characteristics can be obtained.
[0127]
(8) In the invention according to any one of claims 1 to 4 and (1) to (7), the lithium transition metal composite oxide is a nonaqueous electrolyte in which particles of 1 μm or less are 1% by volume or less. It is a positive electrode active material for a liquid secondary battery. By doing so, the battery expansion coefficient can be reduced without impairing the characteristics of the present invention.
[0128]
(9) A nonaqueous electrolyte secondary battery including a positive electrode, a negative electrode, a separator, and a nonaqueous electrolyte, wherein I is used as a positive electrode active material of the positive electrode and II is used as a negative electrode active material of the negative electrode. Non-aqueous electrolyte secondary battery.
I: a lithium transition metal composite oxide used for the positive electrode active material for a nonaqueous electrolyte secondary battery according to any one of claims 1 to 4 and (1) to (8);
The general formula is Li _{1 + x} CoO ₂ (X represents a number that satisfies -0.5 ≦ x ≦ 0.5) and / or the general formula is Li _{1 + x} NiO ₂ (X represents a number satisfying −0.5 ≦ x ≦ 0.5).
When the weight of the lithium transition metal composite oxide is A and the weight of the lithium cobaltate and / or the lithium nickelate is B, the range is 0.2 ≦ B / (A + B) ≦ 0.8. Positive electrode active material for non-aqueous electrolyte secondary batteries mixed with water.
II: A negative electrode active material for a non-aqueous electrolyte secondary battery comprising at least one selected from the group consisting of lithium metal, a lithium alloy, and a compound capable of inserting and extracting lithium ions.
This nonaqueous electrolyte secondary battery is excellent not only in electrode density, prevention of dryout and overcharge characteristics, but also in discharge capacity, cycle charge / discharge characteristics, load characteristics, and output characteristics. It is preferable that the positive electrode active materials be mixed so that the range of 0.4 ≦ B / (A + B) ≦ 0.6 is satisfied. In the range of 0.4 ≦ B / (A + B) ≦ 0.6, not only the electrode plate density, prevention of dryout and improvement of overcharge characteristics, but also improvement of cycle charge / discharge characteristics, load characteristics and output characteristics are achieved. This is because it is remarkable. As the compound capable of inserting and extracting lithium ions used for the negative electrode active material, a general formula having a spinel structure containing an alkali metal and / or an alkaline earth metal is represented by Li _a Ti _b O _{4 + c} (A represents a number satisfying 0.8 ≦ a ≦ 1.5, b represents a number satisfying 1.5 ≦ b ≦ 2.2, and c represents a number satisfying −0.5 ≦ c ≦ 0.5 The negative electrode active material for a non-aqueous electrolyte secondary battery represented by the following formula is preferable. At this time, it is possible to obtain a non-aqueous electrolyte secondary battery in which not only the electrode plate density, prevention of dryout and overcharge characteristics but also cycle charge / discharge characteristics are significantly improved.
[0129]
【The invention's effect】
As described above, the positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention has excellent electrode characteristics that can improve the electrode plate density and prevent dryout. Furthermore, it has excellent overcharge characteristics. Therefore, the positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention is suitably used for a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery.
[Brief description of the drawings]
FIG. 1 is a diagram showing a change in electrode density with a change in press pressure.
FIG. 2 is a diagram showing a change in electrode density with a change in a mixing ratio of a lithium transition metal composite oxide as a first particle group and a lithium transition metal composite oxide as a second particle group.
FIG. 3 is a view showing a particle size distribution of Example 1.
FIG. 4 is a view showing a particle size distribution of Example 2.
FIG. 5 is a view showing a particle size distribution of Example 3.
FIG. 6 is a diagram showing a particle size distribution of Example 4.
FIG. 7 is a diagram showing a particle size distribution of Comparative Example 1.
FIG. 8 is a view showing a particle size distribution of Comparative Example 2.
FIG. 9 is a view showing a particle size distribution of Comparative Example 3.
FIG. 10 is a diagram showing a lithium transition metal composite oxide having a spinel structure.
FIG. 11 is a schematic diagram showing binding of an active material.
FIG. 12 is a sectional view of a cylindrical battery.
FIG. 13 is a view showing a structure of a coin-type battery.
FIG. 14 is a diagram showing a structure of a prismatic battery.
[Explanation of symbols]
1… 8a site
2 ... 32e site
3… 16d site
4: Binder
5 Active material
11 ... negative electrode
12 ... current collector
13 ... Positive electrode
14 ... Separator
21: First particle size distribution
22 Second particle size distribution

Claims (10)

A positive electrode active material for a non-aqueous electrolyte secondary battery having at least a lithium transition metal composite oxide having a spinel structure,
The lithium transition metal composite oxide has at least a first lithium transition metal composite oxide and a second lithium transition metal composite oxide,
The first lithium transition metal composite oxide is smaller than the second lithium transition metal composite oxide containing an element and / or compound that increases the secondary particle diameter. Cathode active material for batteries. The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein the first lithium transition metal composite oxide is smaller than the second lithium transition metal composite oxide. A positive electrode active material for a non-aqueous electrolyte secondary battery having at least a lithium transition metal composite oxide having a spinel structure,
The lithium transition metal composite oxide has a first lithium manganate and a second lithium manganate,
The positive electrode active material for a non-aqueous electrolyte secondary battery, wherein the first lithium manganate is smaller than the second lithium manganate containing boron. The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 3, wherein the first lithium manganate is smaller than the second lithium manganate. A method for producing a positive electrode active material for a nonaqueous electrolyte secondary battery having at least a lithium transition metal composite oxide having a spinel structure,
Selecting a first particle group consisting of a lithium transition metal composite oxide having a first particle size distribution and a primary particle size in a range of 10 μm or less;
A step of selecting a second particle group composed of a lithium transition metal composite oxide having a second particle size distribution having a secondary particle size larger than the first particle size distribution and having a primary particle size in a range of 8 μm to 150 μm. When,
Mixing a lithium transition metal composite oxide that is the selected first particle group and a lithium transition metal composite oxide that is the selected second particle group;
A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, comprising: The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 5, wherein the lithium transition metal composite oxide as the second particle group contains boron. The production of the positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 5, wherein the first particle size distribution has a secondary particle diameter adjusted in a range of 1 μm to 50 μm. Method. The positive electrode active material for a non-aqueous electrolyte secondary battery according to at least one of claims 5 to 7, wherein the second particle size distribution has a secondary particle size adjusted in a range of 8 µm to 150 µm. The method of manufacturing the substance. The lithium transition metal composite oxide is represented by the general formula is _{Li a Mn 3-a O 4} + f (a is a number satisfying 0.8 ≦ a ≦ 1.2, f is -0.5 ≦ f ≦ 0.5 The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to at least one of claims 5 to 8, which is a number satisfying the following. The mixing ratio of the lithium transition metal composite oxide of the first particle group and the lithium transition metal composite oxide of the second particle group of the lithium transition metal composite oxide as the second particle group is , 50% by weight to 90% by weight, and the lithium transition metal composite oxide of the first particle group and the lithium transition metal composite oxide of the second particle group. The production of the positive electrode active material for a nonaqueous electrolyte secondary battery according to at least one of claims 5 to 9, wherein a mixing ratio of the transition metal composite oxide to the total is 10 wt% to 50 wt%. Method.

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