JP2004227790A - Positive electrode active material for nonaqueous electrolyte solution secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positive electrode active material for a nonaqueous electrolyte solution secondary battery having superior battery characteristics even in a far severer use environment. <P>SOLUTION: In the positive electrode active material for the nonaqueous electrolyte secondary battery composed of at least lithium transition metal complex oxide of a spinel structure, a heat generation starting temperature by a differential scanning calorimetry of the lithium transition metal complex oxide is 220°C or more, a calorific value by the differential scanning calorimetry of the lithium transition metal complex oxide is 700 to 900 mJ/mg. The absolute value of the difference between the heat generation starting temperature and the heat generation termination temperature by the differential scanning calorimetry of the lithium transition metal complex oxide is preferably 13°C or more. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００３１】
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。
【００３２】
本発明に係るリチウム遷移金属複合酸化物の（４００）結晶子径は、好ましくは８００〜９６０Åである。（４００）結晶子を、この範囲に規定することにより、優れたサイクル充放電特性を維持したまま過充電特性、熱安定性および安全性に優れた非水電解液二次電池用正極活物質を得ることができる。
【００３３】
本発明に係るリチウム遷移金属複合酸化物の単位格子の格子定数は、好ましくは８．２１６〜８．２２８Åである。この範囲に規定することにより、正極活物質比容量、サイクル充放電特性を損なうことなく、優れた過充電特性、熱安定性および安全性の非水電解液二次電池用正極活物質を得ることができる。
【００３４】
本発明に係るリチウム遷移金属複合酸化物は、好適には一般式がＬｉ_１＋ａＭｎ_２−ａＯ_４＋ｆ（ａは０．０５＜ａ≦０．１５を満たす数を表し、ｆは−０．５≦ｆ≦０．５を満たす数を表す。）で表される。一般式がＬｉ_１＋ａＭｎ_２−ａＯ_４＋ｆ（ａは０．０５＜ａ≦０．１５を満たす数を表し、ｆは−０．５≦ｆ≦０．５を満たす数を表す。）で表されるリチウム遷移金属複合酸化物であることにより、携帯電話や電動工具等に用いられる非常に優れた過充電特性、熱安定性および安全性を有する非水電解液二次電池用正極活物質を得ることができる。
【００３５】
リチウムの組成比は（１＋ａ）によって表される。化学量論組成比よりも過剰量のリチウムはａで表され、０．０５＜ａ≦０．１５である。好ましくは０．０７≦ａ≦０．１３である。過充電特性、熱安定性が著しく向上する。リチウムの組成比が１．０５以下であるなら過充電特性、熱安定性および安全性が著しく低下するため好ましくない。またａ＞０．１５では、正極活物質比容量の低下が顕著に現れるため好ましくない。
【００３６】
（非水電解液二次電池用正極活物質の製造方法）
次に、本発明に係る非水電解液二次電池用正極活物質（Ｌｉ_１．０７Ｍｇ_０．０１Ｍｎ_１．９３Ｂ_{０．００５}Ｏ_４）の製造方法を説明するが、本製造方法に限定されない。
【００３７】
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、共沈物を得る。
【００３８】
マンガン源は特に限定されない。基本的には水溶液を作りうる塩であればいずれも使用可能である。例えば塩化マンガン、ヨウ化マンガン、硫酸マンガン、硝酸マンガン等が用いられる。好適には、ＭｎＳＯ_４、ＭｎＣｌ_２等が用いられる。
【００３９】
マグネシウム源は特に限定されない。基本的には水溶液を作りうる塩であればいずれも使用可能である。例えば塩化マグネシウム、ヨウ化マグネシウム、過塩素酸マグネシウム、硫酸マグネシウム、硝酸マグネシウム等が用いられる。好適には、ＭｇＳＯ_４、Ｍｇ（ＮＯ_３）_２等が用いられる。
【００４０】
また、炭酸水素ナトリウム水溶液を加えているが、これに限られるわけではなく、水酸化ナトリウム水溶液、水酸化カリウム水溶液、水酸化リチウム水溶液等のアルカリ溶液であればよい。
【００４１】
次に、得られる共沈物を濾過、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、空気中または弱酸化雰囲気にて、８００〜９００℃の温度で８〜１４時間焼成を行い、本発明に係るリチウム遷移金属複合酸化物を合成する。
【００４２】
共沈物と混合するものは炭酸リチウムに限定されない。基本的にはリチウム化合物であればいずれも使用可能である。例えばフッ化リチウム、塩化リチウム、臭化リチウム、ヨウ化リチウム、酸化リチウム、過酸化リチウム、水酸化リチウム等が用いられる。好適にはＬｉ_２ＣＯ_３、ＬｉＯＨ、ＬｉＯＨ・Ｈ_２Ｏ、Ｌｉ_２Ｏ、ＬｉＣｌ、ＬｉＮＯ_３、Ｌｉ_２ＳＯ_４、ＬｉＨＣＯ_３、Ｌｉ（ＣＨ_３ＣＯＯ）等が用いられる。
【００４３】
共沈物と混合するものはオルトホウ酸に限定されない。基本的にはホウ素化合物であればいずれも使用可能である。例えば、ホウ化物、酸化ホウ素、リン酸ホウ素等が用いられる。好適には、Ｂ_２Ｏ_３（融点４６０℃）、Ｈ_３ＢＯ_３（分解温度１７３℃）が用いられる。
【００４４】
共沈物、リチウム化合物とともに、硫黄含有化合物、ハロゲン元素を含む化合物、等を混合してもよい。
【００４５】
硫黄含有化合物は特に限定されない。例えば硫化物、ヨウ化硫黄、硫化水素、硫酸とその塩、硫化窒素等が用いられる。好適にはＬｉ_２ＳＯ_４、ＭｎＳＯ_４、（ＮＨ_４）_２ＳＯ_４、Ａｌ_２（ＳＯ_４）_３、ＭｇＳＯ_４等が用いられる。
【００４６】
ハロゲン元素を含む化合物は特に限定されない。例えば、フッ化水素、フッ化酸素、フッ化水素酸、塩化水素、塩酸、酸化塩素、フッ化酸化塩素、酸化臭素、フルオロ硫酸臭素、ヨウ化水素、酸化ヨウ素、過ヨウ素酸等が用いられる。好適には、ＮＨ_４Ｆ、ＮＨ_４Ｃｌ、ＮＨ_４Ｂｒ、ＮＨ_４Ｉ、ＬｉＦ、ＬｉＣｌ、ＬｉＢｒ、ＬｉＩ、ＭｎＦ_２、ＭｎＣｌ_２、ＭｎＢｒ_２、ＭｎＩ_２等が用いられる。
【００４７】
焼成の温度は、好適には８００℃〜９００℃であり、また焼成の時間は８〜１４時間が好ましい。焼成温度が８００℃よりも低い場合、未反応の原料が非水電解液二次電池用正極活物質中に残留し、本発明の目的を達成できる十分な特性が得られない場合がある。また、９００℃よりも高い温度で焼成した場合、副生成物が生成しやすくなり、単位重量当たりの放電容量の低下、サイクル充放電特性の低下、動作電圧の低下を招く。焼成の時間は、８時間未満では原料混合物の粒子間の拡散反応が進行せず、目的とする非水電解液二次電池用正極活物質が得られない。また１４時間より長く焼成を行うと焼結による粗大粒子が形成され、好ましくない。
【００４８】
上記焼成により得られるリチウム遷移金属複合酸化物を乳鉢やボールミル、振動ミル、ピンミル等により粉砕する。上記方法によってリチウム遷移金属複合酸化物の（４００）結晶子径が７００〜９８０Åである本発明の非水電解液二次電池用正極活物質を得ることができる。
【００４９】
以上の製造方法を使用することにより、目的とする非水電解液二次電池用正極活物質を得ることが可能である。
【００５０】
なお、炭酸塩によるマンガンとマグネシウムの共沈により、Ｌｉ_１．０７Ｍｇ_０．０１Ｍｎ_１．９３Ｂ_{０．００５}Ｏ_４を製造したが、マンガン化合物、マグネシウム化合物を所定の組成比となるように混合し、焼成して製造してもよい。
【００５１】
（非水電解液二次電池）
本発明に係る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、リチウムイオンポリマー二次電池等の非水電解液二次電池に好適に用いられる。
【００５２】
非水電解液二次電池は、従来公知の非水電解液二次電池において、正極活物質を本発明の正極活物質とすればよく、他の構成は特に限定されない。本発明に係るリチウム遷移金属複合酸化物を主成分とする正極活物質層を備えた非水電解液二次電池であればよい。
【００５３】
正極活物質として本発明の正極活物質とともにコバルト酸リチウム及び／又はニッケル酸リチウムを用いることにより過充電特性、熱安定性、安全性だけでなく、放電容量、負荷特性、出力特性にも優れた非水電解液二次電池を得ることができる。
【００５４】
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が好ましい。前記コバルト酸リチウムは、その一部がマグネシウム、アルミニウム、カルシウム、バナジウム、チタン、クロム、マンガン、鉄、コバルト、ニッケル、銅、亜鉛、ストロンチウム、ジルコニウム、ニオブ、モリブデンおよびスズからなる群から選ばれる少なくとも１種で置換されていてもよい。
【００５５】
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が好ましい。前記ニッケル酸リチウムは、その一部がマグネシウム、アルミニウム、カルシウム、バナジウム、チタン、クロム、マンガン、鉄、コバルト、ニッケル、銅、亜鉛、ストロンチウム、ジルコニウム、ニオブ、モリブデンおよびスズからなる群から選ばれる少なくとも１種で置換されていてもよい。
【００５６】
本発明に係るリチウム遷移金属複合酸化物を主成分とする正極活物質を使用する正極は、好ましくは次のように製造される。本発明に係るリチウム遷移金属複合酸化物の粉末に、アセチレンブラック、黒鉛等のカーボン系導電剤、結着剤及び結着剤の溶媒または分散媒とを混合することにより正極合剤が形成される。前記正極合剤をスラリーまたは混練物とし、アルミニウム箔等の集電体１２に塗布又は担持し、プレス圧延して正極活物質層を集電体１２に形成する。
【００５７】
結着剤にはポリフッ化ビニリデン、ポリテトラフルオロエチレン、ポリアミドアクリル樹脂等が使用できる。
【００５８】
本発明に係るリチウム遷移金属複合酸化物は、導電剤粉末との混合性が良く、電池の内部抵抗は減少すると考えられる。このため充放電特性、特に放電容量が向上する。また結着剤と混練するときも、本発明のリチウム遷移金属複合酸化物は、流動性に優れ、また結着剤の高分子と絡まりやすく、優れた結着性を有する。さらに粗大粒子を含まず、球状であるため、作製した正極１３の塗膜面の表面は平滑性に優れる。このため正極板の塗膜面は結着性に優れ剥がれにくく、また表面が平滑で充放電に伴う塗膜面表面のリチウムイオンの出入りが均一に行われるため、サイクル充放電特性において顕著な改善が得られる。
【００５９】
例えば、負極活物質には金属リチウム、リチウム合金、又はリチウムイオンを吸蔵放出可能な化合物が使用できる。リチウム合金としては例えばＬｉＡｌ合金，ＬｉＳｎ合金，ＬｉＰｂ合金などが使用できる。リチウムイオンを吸蔵放出可能な化合物としては例えばグラファイト，黒鉛などの炭素材料が使用できる。また酸化スズ、酸化チタン等のリチウムイオンを挿入・脱離することができる酸化物を用いてもよい。
【００６０】
電解液としては作動電圧で変質、分解しない化合物であれば特に限定されず使用できる。溶媒として例えばジメトキシエタン，ジエトキシエタン，エチレンカーボネート，プロピレンカーボネート，ジメチルカーボネート，ジエチルカーボネート，エチルメチルカーボネート，メチルホルメート，γ−ブチロラクトン，２−メチルテトラヒドロフラン，ジメチルスルホキシド，スルホランなどの有機溶媒が使用でき、また前記した有機溶媒群から選ばれた２種類以上を混合して使用しても構わない。
【００６１】
電解質としては例えば過塩素酸リチウム，四フッ化ホウ酸リチウム，四フッ化リン酸リチウム，トリフルオロメタン酸リチウムなどのリチウム塩などが使用できる。上記した溶媒と電解質とを混合して電解液として使用する。ここでゲル化剤などを添加し、ゲル状として使用してもよく、また吸湿性ポリマーに吸収させて使用しても構わない。更に無機系又は有機系のリチウムイオンの導電性を有する固体電解質を使用しても構わない。
【００６２】
更にセパレーター１４としてポリエチレン製、ポリプロピレン製等の多孔性膜等が使用できる。本発明に係る非水電解液二次電池用正極活物質、上記した負極活物質、電解液、セパレーターを用いて定法に従い非水電解液二次電池とする。これにより従来達成できなかった優れた電池特性が実現できる。
【００６３】
また、本発明に係る非水電解液二次電池用正極活物質を正極活物質として用いた正極活物質層を帯状正極集電体の両面にそれぞれ形成することにより構成した帯状正極と、上記の負極活物質層の負極活物質層を帯状負極集電体の両面にそれぞれ形成することにより構成した帯状負極とをそれぞれ具備し、帯状正極と帯状負極とを帯状セパレータを介して積層した状態で多数回巻回することにより帯状正極と帯状負極との間に帯状セパレータが介在している渦巻型の巻回体を構成して非水電解液二次電池とすることができる。このように構成することで、製造工程が簡単であるとともに、正極活物質層および負極活物質層の割れや帯状セパレータからの剥離を生じ難く、電池容量を大きく、エネルギー密度を高くすることができる。特に本発明に係る非水電解液二次電池用正極活物質は、充填性に優れ、かつ結合材となじみやすい。そのため高い充放電容量を有し、かつ結着性、表面の平滑性に優れた正極になるため、さらに正極活物質層の割れや剥がれを防ぐことができる。
【００６４】
非水電解液二次電池の形状としては、円筒型でも、コイン型でも、角型等でもよい。
【００６５】
（非水電解液二次電池の用途）
本発明に係る非水電解液二次電池用正極活物質を用いた非水電解液二次電池の用途は特に限定されない。例えばノートパソコン、ペン入力パソコン、ポケットパソコン、ノート型ワープロ、ポケットワープロ、電子ブックプレーヤ、携帯電話、コードレスフォン子機、電子手帳、電卓、液晶テレビ、電気シェーバ、電動工具、電子翻訳機、自動車電話、携帯プリンタ、トランシーバ、ページャ、ハンディターミナル、携帯コピー、音声入力機器、メモリカード、バックアップ電源、テープレコーダ、ラジオ、ヘッドホンステレオ、ハンディクリーナ、ポータブルＣＤ、ビデオムービ、ナビゲーションシステムなどの機器用の電源に用いることができる。また照明機器、エアコン、テレビ、ステレオ、温水器、冷蔵庫、オーブン電子レンジ、食器洗い器、洗濯機、乾燥器、ゲーム機器、玩具、ロードコンディショナ、医療機器、自動車、電気自動車、ゴルフカート、電動カート、電力貯蔵システムなどの電源として使用することができる。また、民生用の他、軍需用、宇宙用としても使用することができる。
【００６６】
以下、本発明に係る非水電解液二次電池用正極活物質について実施例を挙げて説明するが、この実施例に限定されるものではない。
【００６７】
【実施例】
〔実施例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、オルトホウ酸とを所定の組成比となるように混合し、大気雰囲気中にて約８００℃で約１０時間焼成した。そして乳鉢にて粉砕しＬｉ_１．０７Ｍｇ_０．０１Ｍｎ_１．９３Ｂ_{０．００５}Ｏ_４が得られた。
【００６８】
（非水電解液二次電池用正極活物質の評価）
本発明に係る非水電解液二次電池用正極活物質は、以下の方法により組成分析、比表面積、粒度分布の測定を行う。また試験電池を作製し、各評価を行う。
【００６９】
（組成分析）
所定量の非水電解液二次電池用正極活物質を硝酸に溶解し、プラズマ発光分光（ＩＣＰ）分析法により、ハロゲン元素、酸素以外の各構成元素の含有量の定量を行う。また所定量の非水電解液二次電池用正極活物質を純水に投入して撹拌し、上澄み水溶液を得る。アニオン選択性電極を指示電極に用いたイオンメーターにより、上澄み水溶液中のハロゲン元素を定量する。
【００７０】
（粉末の評価）
非水電解液二次電池用正極活物質の比表面積は、窒素ガスを用いた定圧式ＢＥＴ吸着法により測定する。
【００７１】
（結晶子径の測定）
理学電気（株）社製のＲＩＮＴ２５００Ｖを用いて測定する。Ｘ線源にはＣｕＫα１を用い、管電流１００ｍＡ、管電圧４０ｋＶにてＸ線回折パターンを測定する。（１０４）面に起因する回折ピークより以下の式で表されるシェラーの式によって算出される。
【００７２】
【数２】

【００７３】
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。
【００７４】
（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マンガン複合酸化物粉末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。
【００７５】
（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。
【００７６】
（熱安定性の評価）
正極活物質粉末９０重量部と導電剤としてのカーボン５重量部と、ＰＶＤＦ（ポリフッ化ビニリデン）５重量部とを混練してペーストを調製する。得られたペーストを正極集電体に塗布し、試験用二次電池を作製し、定電流による充放電を行いなじませる。その後、試験用二次電池を一定電流の下で電池電圧が４．３Ｖになるまで充電を行う。充電が完了した後、試験用二次電池から正極を取り出し、試験用二次電池に使用した電解液に含まれる一成分の溶液で洗浄し、真空乾燥後、正極から正極活物質を削り取る。アルミニウムセルに、エチレンカーボネートと、正極から削り取った正極活物質を０．４０：１．０の重量比で入れ、示差走査熱量を昇温速度５℃／ｍｉｎで測定する。
【００７７】
結果を表１、図１に示す。
【００７８】
〔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、炭酸リチウム、オルトホウ酸とを所定の組成比となるように混合し、大気雰囲気中にて約８００℃で約１０時間焼成した。そして乳鉢にて粉砕しＬｉ_１．１１Ｍｇ_０．０１Ｍｎ_１．８９Ｂ_{０．００５}Ｏ４が得られた。
【００７９】
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。
【００８０】
〔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、炭酸リチウム、オルトホウ酸とを所定の組成比となるように混合し、大気雰囲気中にて約８００℃で約１０時間焼成した。そして乳鉢にて粉砕しＬｉ_１．１３Ｍｇ_０．０１Ｍｎ_１．８７Ｂ_{０．００５}Ｏ_４が得られた。
【００８１】
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。
【００８２】
〔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、オルトホウ酸とを所定の組成比となるように混合し、大気雰囲気中にて約８００℃で約１０時間焼成した。そして乳鉢にて粉砕しＬｉ_１．０５Ｍｇ_０．０１Ｍｎ_１．９５Ｂ_{０．００５}Ｏ_４が得られた。
【００８３】
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。
【００８４】
表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、発熱開始温度は比較例１に比べて低いものの、発熱量は小さく熱安定性が優れていることがわかる。また過充電特性も向上していることがわかる。さらに安全性も優れていることがわかる。このような非常に熱安定性、過充電特性および安全性に優れた非水電解液二次電池用正極活物質は、携帯電話、電動工具等に好適に用いられる。
【００８５】
これに対して、比較例１は、発熱開始温度は高いものの発熱量は大きく熱安定性が劣っている。また、過充電特性、安全性も、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。
【００８６】
【表１】

【００８７】
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。
【００８８】
（１）請求項１乃至請求項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、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、本願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。
【００８９】
（２）請求項１乃至請求項５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願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。
【００９０】
（３）請求項１乃至請求項５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、さらにホウ素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ホウ素は、焼成のときに原料混合物中のリチウムと反応し、リチウム、ホウ素、酸素からなる化合物を形成する。この化合物は融剤（フラックス）として作用するため、リチウム遷移金属複合酸化物は、結晶成長が促進し、結晶性が高まり、かつ粒子径の大きなリチウム遷移金属複合酸化物が得られると考えられる。またホウ素がない場合に比べて自己放電が抑制されるため、本願発明の特性を損なわずに、保存特性が向上すると考えられる。
【００９１】
（４）請求項１乃至請求項５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、本願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。
【００９２】
（５）請求項１乃至請求項５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、本願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。
【００９３】
（６）請求項１乃至請求項５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、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、本願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。
【００９４】
（７）請求項１乃至請求項５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は、一般式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０．０５＜ａ≦０．１５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、本願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。
【００９５】
（８）請求項１乃至請求項５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。
【００９６】
（９）請求項１乃至請求項５及び（１）乃至（８）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。
【００９７】
（１０）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５及び（１）乃至（９）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≦Ｂ／（Ａ＋Ｂ）＜０．０５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、過充電特性、熱安定性、安全性だけでなく、放電容量、負荷特性、出力特性にも優れている。正極活物質は、０≦Ｂ／（Ａ＋Ｂ）＜０．０５の範囲になるように混合することが好ましい。Ｂ／（Ａ＋Ｂ）≧０．０５の範囲では、過充電特性、熱安定性、安全性が劣化するため好ましくない。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。このとき過充電特性、熱安定性、安全性だけでなく、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。
【００９８】
【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、過充電特性、熱安定性及び安全性等の電池特性に優れる。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】示差走査熱量測定図である。
【図２】層状構造のリチウム遷移金属複合酸化物を示す図である。
【図３】活物質の結着模式図である。
【図４】円筒型電池の断面図である。
【図５】コイン型電池の構造を示す図である。
【図６】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[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 having excellent battery characteristics such as overcharge characteristics, thermal stability, and safety.
[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 comprising at least a lithium transition metal composite oxide having a spinel structure, wherein the lithium transition metal composite oxide An exothermic onset temperature of the product by differential scanning calorimetry is 220 ° C. or higher, and a calorific value of the lithium transition metal composite oxide by differential scanning calorimetry is 700 to 900 mJ / mg.
[0008]
When the exothermic onset temperature by differential scanning calorimetry is lower than 220 ° C., the exothermic onset temperature of the lithium-transition metal composite oxide having a layered structure is equivalent to that of the present invention, and the object of the present invention is to improve the thermal stability and safety. I can't. If the calorific value by differential scanning calorimetry is smaller than 700 mJ / mg, the capacity of the positive electrode active material per unit active material (specific capacity of the positive electrode active material (mAh / g)) is not preferable. On the other hand, if the calorific value by differential scanning calorimetry is larger than 900 mJ / mg, thermal stability is lacking. When a non-aqueous electrolyte secondary battery is assembled using such a positive electrode active material for a non-aqueous electrolyte secondary battery composed of a lithium transition metal composite oxide, the temperature in an overcharged state increases sharply. Therefore, heat release due to the operation of the safety valve of the non-aqueous electrolyte secondary battery cannot be made in time, resulting in lack of overcharge characteristics and safety.
[0009]
It is preferable that the absolute value of the difference between the heat generation start temperature and the heat generation end temperature of the lithium transition metal composite oxide measured by differential scanning calorimetry is 13 ° C. or more.
[0010]
If the absolute value of the difference between the heat generation start temperature and the heat generation end temperature according to the differential scanning calorimetry is smaller than 13 ° C., the lithium transition metal composite oxide generates heat rapidly. Therefore, it lacks thermal stability. When a non-aqueous electrolyte secondary battery is assembled using such a positive electrode active material for a non-aqueous electrolyte secondary battery composed of a lithium transition metal composite oxide, the temperature in an overcharged state increases sharply. Therefore, heat release due to the operation of the safety valve of the non-aqueous electrolyte secondary battery cannot be made in time, resulting in lack of overcharge characteristics and safety.
[0011]
The lithium transition metal composite oxide preferably has a (400) crystallite diameter of 700 to 980 °.
[0012]
If the (400) crystallite diameter is smaller than 700 °, the crystal structure is distorted to some extent, and the lithium-transition metal composite oxide generates heat slowly, which results in overcharge characteristics, thermal stability and safety. Is preferred. However, the cycle charge / discharge characteristics deteriorate due to the collapse of the crystal structure, which is not preferable. On the other hand, when the (400) crystallite diameter is larger than 980 °, the lithium transition metal composite oxide generates heat rapidly. Therefore, it lacks thermal stability. When a non-aqueous electrolyte secondary battery is assembled using such a positive electrode active material for a non-aqueous electrolyte secondary battery composed of a lithium transition metal composite oxide, the temperature in an overcharged state increases sharply. Therefore, heat release due to the operation of the safety valve of the non-aqueous electrolyte secondary battery cannot be made in time, resulting in lack of overcharge characteristics and safety.
[0013]
The unit cell of the lithium transition metal composite oxide preferably has a lattice constant of 8.214 to 8.230 °.
[0014]
When the lattice constant of the unit cell of the lithium transition metal composite oxide is smaller than 8.214 °, the specific capacity of the positive electrode active material becomes small, which is not preferable. On the other hand, when the lattice constant of the unit cell is larger than 8.230 °, thermal stability is lacking. When a non-aqueous electrolyte secondary battery is assembled using such a positive electrode active material for a non-aqueous electrolyte secondary battery composed of a lithium transition metal composite oxide, the temperature in an overcharged state increases sharply. Therefore, heat release due to the operation of the safety valve of the non-aqueous electrolyte secondary battery cannot be made in time, resulting in lack of overcharge characteristics and safety.
[0015]
The lithium transition metal composite oxide has a general formula of Li _{1 + a} Mn _2-a O _{4 + f} (A represents a number satisfying 0.05 <a ≦ 0.15, and f represents a number satisfying −0.5 ≦ f ≦ 0.5).
[0016]
In the above general formula, a is preferably a number satisfying 0.05 <a ≦ 0.15. If a is greater than 0.15, Li ₂ MnO ₃ Is not preferable because the specific capacity of the positive electrode active material is reduced due to the presence of the like. When a is 0.05 or less, heat generation of the lithium transition metal composite oxide occurs rapidly. Therefore, it lacks thermal stability. When a non-aqueous electrolyte secondary battery is assembled using such a positive electrode active material for a non-aqueous electrolyte secondary battery composed of a lithium transition metal composite oxide, the temperature in an overcharged state increases sharply. Therefore, heat release due to the operation of the safety valve of the non-aqueous electrolyte secondary battery cannot be made in time, resulting in lack of overcharge characteristics and safety.
[0017]
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 the embodiments, examples, and FIGS.
[0018]
(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.
[0019]
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, thermal stability, and safety used for a mobile phone, a power tool, and the like can be obtained.
[0020]
The exothermic onset temperature of the lithium transition metal composite oxide according to the present invention by differential scanning calorimetry is 220 ° C. or higher. The calorific value of the lithium transition metal composite oxide according to the present invention as measured by differential scanning calorimetry is 700 to 900 mJ / mg.
[0021]
Differential scanning calorimetry is a method of measuring the difference in energy input between a substance and a reference substance as a function of temperature while changing the temperature of the substance and the reference substance by a program. The differential scanning calorimetry of the lithium transition metal composite oxide according to the present invention is specifically performed by preparing a measurement sample as follows.
[0022]
A paste is prepared by kneading 90 parts by weight of the positive electrode active material powder, 5 parts by weight of carbon as a conductive agent, and 5 parts by weight of PVDF (polyvinylidene fluoride). The obtained paste is applied to a positive electrode current collector to produce a test secondary battery, which is charged and discharged with a constant current to make it familiar. Thereafter, the test secondary battery is charged under a constant current until the battery voltage becomes 4.3 V. After the charging is completed, the positive electrode is taken out of the test secondary battery, washed with a one-component solution contained in the electrolytic solution used for the test secondary battery, vacuum-dried, and then the positive electrode active material is scraped off the positive electrode. Ethylene carbonate and the positive electrode active material scraped from the positive electrode are put into an aluminum cell at a weight ratio of 0.40: 1.0, and the differential scanning calorific value is measured at a heating rate of 5 ° C./min.
[0023]
In the differential scanning calorimetry diagram measured in this way, as shown in FIG. 1, the calorific value does not change even if the temperature rises in a low temperature part, but the calorific value greatly increases above a certain temperature. The temperature A at this time is defined as a heat generation start temperature. Then, when the temperature exceeds a certain temperature, the calorific value does not change again. The temperature B at this time is defined as the heat generation end temperature. The calorific value by differential scanning calorimetry is calculated from the peak area.
[0024]
The calorific value of the lithium transition metal composite oxide according to the present invention by differential scanning calorimetry is preferably 720 to 880 mJ / mg. By defining within this range, it is possible to obtain a positive electrode active material for a non-aqueous electrolyte secondary battery having excellent overcharge characteristics, thermal stability and safety without impairing the specific capacity of the positive electrode active material and the cycle charge / discharge characteristics. Can be.
[0025]
The absolute value of the difference between the exothermic start temperature and the exothermic end temperature by differential scanning calorimetry of the lithium transition metal composite oxide according to the present invention is preferably 13 ° C. or more.
[0026]
The absolute value of the difference between the exothermic onset temperature and the exothermic end temperature by differential scanning calorimetry of the lithium transition metal composite oxide according to the present invention is preferably 13 to 25 ° C. If the absolute value of the difference between the heat generation start temperature and the heat generation end temperature by differential scanning calorimetry is greater than 25 ° C., the specific capacity of the positive electrode active material is undesirably small.
[0027]
The (400) crystallite diameter of the lithium transition metal composite oxide according to the present invention is preferably from 700 to 980 °.
[0028]
The crystallite diameter is the maximum set considered to be a single crystal. The larger the crystallite diameter, the better the crystallinity and the less distortion of the crystal structure. By using the (400) crystallite diameter, the degree of regular arrangement of the unit cells can be determined. Specifically, the (400) crystallite diameter is measured as follows.
[0029]
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 in a range of 2θ = 43.2 to 44.8 °. It is calculated from the diffraction peak caused by the (400) plane by Scherrer's formula represented by the following formula.
[0030]
(Equation 1)

[0031]
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).
[0032]
The (400) crystallite diameter of the lithium transition metal composite oxide according to the present invention is preferably 800 to 960 °. By defining the (400) crystallite in this range, a positive electrode active material for a non-aqueous electrolyte secondary battery having excellent overcharge characteristics, thermal stability and safety while maintaining excellent cycle charge / discharge characteristics can be obtained. Obtainable.
[0033]
The unit cell of the lithium transition metal composite oxide according to the present invention preferably has a lattice constant of 8.216 to 8.228 °. By defining the content in this range, it is possible to obtain a positive electrode active material for a non-aqueous electrolyte secondary battery having excellent overcharge characteristics, heat stability and safety without impairing the specific capacity of the positive electrode active material and the cycle charge / discharge characteristics. Can be.
[0034]
The lithium transition metal composite oxide according to the present invention preferably has a general formula of Li _{1 + a} Mn _2-a O _{4 + f} (A represents a number satisfying 0.05 <a ≦ 0.15, and f represents a number satisfying −0.5 ≦ f ≦ 0.5). The general formula is Li _{1 + a} Mn _2-a O _{4 + f} (A represents a number that satisfies 0.05 <a ≦ 0.15, and f represents a number that satisfies −0.5 ≦ f ≦ 0.5). Accordingly, it is possible to obtain a positive electrode active material for a non-aqueous electrolyte secondary battery having extremely excellent overcharge characteristics, thermal stability, and safety used for a mobile phone, a power tool, and the like.
[0035]
The composition ratio of lithium is represented by (1 + a). Lithium in excess of the stoichiometric composition ratio is represented by a, and 0.05 <a ≦ 0.15. Preferably, 0.07 ≦ a ≦ 0.13. Overcharge characteristics and thermal stability are significantly improved. If the composition ratio of lithium is 1.05 or less, it is not preferable because the overcharge characteristics, thermal stability, and safety are significantly reduced. When a> 0.15, the specific capacity of the positive electrode active material is significantly reduced, which is not preferable.
[0036]
(Method of producing positive electrode active material for non-aqueous electrolyte secondary battery)
Next, the positive electrode active material for a nonaqueous electrolyte secondary battery (Li _1.07 Mg _0.01 Mn _1.93 B _0.005 O ₄ ) Will be described, but the present invention is not limited to this method.
[0037]
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.
[0038]
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.
[0039]
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.
[0040]
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.
[0041]
Next, 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, and in air or a weakly oxidizing atmosphere, at a temperature of 800 to 900 ° C. For 8 to 14 hours to synthesize the lithium transition metal composite oxide according to the present invention.
[0042]
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.
[0043]
What is mixed with the coprecipitate is not limited to orthoboric acid. Basically, any boron compound can be used. For example, boride, boron oxide, boron phosphate and the like are used. Preferably, B ₂ O ₃ (Melting point 460 ° C), H ₃ BO ₃ (Decomposition temperature 173 ° C.) is used.
[0044]
A sulfur-containing compound, a compound containing a halogen element, and the like may be mixed together with the coprecipitate and the lithium compound.
[0045]
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.
[0046]
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.
[0047]
The firing temperature is preferably 800 ° C. to 900 ° 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 900 ° 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 calcination time is less than 8 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 14 hours, coarse particles are formed by sintering, which is not preferable.
[0048]
The lithium transition metal composite oxide obtained by the above calcination is pulverized with a mortar, a ball mill, a vibration mill, a pin mill or the like. The positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention, in which the lithium transition metal composite oxide has a (400) crystallite diameter of 700 to 980 ° by the above method, can be obtained.
[0049]
By using the above manufacturing method, it is possible to obtain a desired positive electrode active material for a non-aqueous electrolyte secondary battery.
[0050]
The coprecipitation of manganese and magnesium with carbonates resulted in Li _1.07 Mg _0.01 Mn _1.93 B _0.005 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.
[0051]
(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.
[0052]
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.
[0053]
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.
[0054]
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.
[0055]
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.
[0056]
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.
[0057]
As the binder, polyvinylidene fluoride, polytetrafluoroethylene, polyamide acrylic resin or the like can be used.
[0058]
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.
[0059]
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.
[0060]
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.
[0061]
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.
[0062]
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.
[0063]
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 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.
[0064]
The shape of the nonaqueous electrolyte secondary battery may be a cylindrical shape, a coin shape, a square shape, or the like.
[0065]
(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.
[0066]
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.
[0067]
【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, dried, then mixed with lithium carbonate and orthoboric acid so as to have a predetermined composition ratio, and calcined in an air atmosphere at about 800 ° C. for about 10 hours. And crushed in a mortar and Li _1.07 Mg _0.01 Mn _1.93 B _0.005 O ₄ was gotten.
[0068]
(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.
[0069]
(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.
[0070]
(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.
[0071]
(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 (104) plane by Scherrer's formula expressed by the following formula.
[0072]
(Equation 2)

[0073]
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).
[0074]
(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 manganese 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. 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.
[0075]
(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.
[0076]
(Evaluation of thermal stability)
A paste is prepared by kneading 90 parts by weight of the positive electrode active material powder, 5 parts by weight of carbon as a conductive agent, and 5 parts by weight of PVDF (polyvinylidene fluoride). The obtained paste is applied to a positive electrode current collector to produce a test secondary battery, which is charged and discharged with a constant current to make it familiar. Thereafter, the test secondary battery is charged under a constant current until the battery voltage becomes 4.3 V. After the charging is completed, the positive electrode is taken out of the test secondary battery, washed with a one-component solution contained in the electrolytic solution used for the test secondary battery, vacuum-dried, and then the positive electrode active material is scraped off the positive electrode. Ethylene carbonate and the positive electrode active material scraped from the positive electrode are put into an aluminum cell at a weight ratio of 0.40: 1.0, and the differential scanning calorific value is measured at a heating rate of 5 ° C./min.
[0077]
The results are shown in Table 1 and FIG.
[0078]
[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 in an air atmosphere at about 800 ° C. for about 10 hours. And crushed in a mortar and Li _1.11 Mg _0.01 Mn _1.89 B _0.005 O4 was obtained.
[0079]
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.
[0080]
[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, dried, then mixed with lithium carbonate and orthoboric acid so as to have a predetermined composition ratio, and calcined in an air atmosphere at about 800 ° C. for about 10 hours. And crushed in a mortar and Li _1.13 Mg _0.01 Mn _1.87 B _0.005 O ₄ was gotten.
[0081]
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.
[0082]
[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, then mixed with lithium carbonate and orthoboric acid so as to have a predetermined composition ratio, and calcined in an air atmosphere at about 800 ° C. for about 10 hours. And crushed in a mortar and Li _1.05 Mg _0.01 Mn _1.95 B _0.005 O ₄ was gotten.
[0083]
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.
[0084]
As is evident from Table 1, the positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention has a lower heat generation start temperature than Comparative Example 1, but has a small heat generation and excellent thermal stability. Understand. It can also be seen that the overcharge characteristics have been improved. It can be seen that the safety is also excellent. Such a positive electrode active material for a non-aqueous electrolyte secondary battery having extremely excellent thermal stability, overcharge characteristics and safety is suitably used for mobile phones, power tools and the like.
[0085]
On the other hand, in Comparative Example 1, the heat generation start temperature is high, but the heat generation amount is large and the thermal stability is inferior. Further, the overcharge characteristics and safety are also inferior to the positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention.
[0086]
[Table 1]

[0087]
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.
[0088]
(1) In the invention according to any one of claims 1 to 5, 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.
[0089]
(2) In the invention according to any one of claims 1 to 5 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.
[0090]
(3) In the invention according to any one of claims 1 to 5 and (1) or (2), the lithium transition metal composite oxide further contains boron, and the positive electrode for a non-aqueous electrolyte secondary battery is further included. Active material. Boron, a constituent element of the present invention, reacts with lithium in the raw material mixture during firing to form a compound composed of lithium, boron, and oxygen. Since this compound acts as a flux (flux), the lithium transition metal composite oxide is considered to promote crystal growth, increase crystallinity, and obtain a lithium transition metal composite oxide having a large particle diameter. Further, since self-discharge is suppressed as compared with the case without boron, it is considered that the storage characteristics are improved without impairing the characteristics of the present invention.
[0091]
(4) The positive electrode for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 5 and (1) to (3), wherein the lithium transition metal composite oxide further contains sulfur. Active material. It is considered that the 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.
[0092]
(5) In the invention according to any one of claims 1 to 5 and (1) to (4), 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 surface of the lithium transition metal composite oxide 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.
[0093]
(6) In the invention according to any one of claims 1 to 5 and (1) to (5), the lithium transition metal composite oxide is a nonaqueous 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.
[0094]
(7) In the invention according to any one of claims 1 to 5 and (1) to (6), the lithium transition metal composite oxide is represented by a general formula 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 0.05 <a ≦ 0.15, 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 battery swelling can be suppressed.
[0095]
(8) In the invention according to any one of claims 1 to 5 and (1) to (7), 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.
[0096]
(9) In the invention according to any one of claims 1 to 5 and (1) to (8), the lithium transition metal composite oxide is a non-aqueous 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.
[0097]
(10) A non-aqueous electrolyte secondary battery having a positive electrode, a negative electrode, a separator, and a non-aqueous 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 non-aqueous electrolyte secondary battery according to any one of claims 1 to 5 and (1) to (9);
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, mixing is performed so that 0 ≦ B / (A + B) <0.05. Active material for non-aqueous electrolyte secondary batteries.
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 non-aqueous electrolyte secondary battery is excellent not only in overcharge characteristics, thermal stability and safety, but also in discharge capacity, load characteristics and output characteristics. It is preferable that the positive electrode active materials be mixed so that 0 ≦ B / (A + B) <0.05. A range of B / (A + B) ≧ 0.05 is not preferable because overcharge characteristics, thermal stability, and safety deteriorate. 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 nonaqueous electrolyte secondary battery in which not only overcharge characteristics, thermal stability, and safety but also cycle charge / discharge characteristics are significantly improved.
[0098]
【The invention's effect】
As described above, the positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention is excellent in battery characteristics such as overcharge characteristics, thermal stability, and safety. 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 differential scanning calorimetry.
FIG. 2 is a diagram showing a lithium transition metal composite oxide having a layered structure.
FIG. 3 is a schematic diagram of binding of an active material.
FIG. 4 is a sectional view of a cylindrical battery.
FIG. 5 is a view showing a structure of a coin-type battery.
FIG. 6 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

Claims (5)

In a positive electrode active material for a non-aqueous electrolyte secondary battery comprising at least a lithium transition metal composite oxide having a spinel structure,
The exothermic onset temperature of the lithium transition metal composite oxide by differential scanning calorimetry is 220 ° C. or higher,
The positive electrode active material for a non-aqueous electrolyte secondary battery, wherein a calorific value of the lithium transition metal composite oxide measured by differential scanning calorimetry is 700 to 900 mJ / mg. The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein the absolute value of the difference between the heat generation start temperature and the heat generation end temperature of the lithium transition metal composite oxide measured by differential scanning calorimetry is 13 ° C or more. The positive electrode active material for a nonaqueous electrolyte secondary battery according to claim 1, wherein the (400) crystallite diameter of the lithium transition metal composite oxide is 700 to 980 °. 4. The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein a lattice constant of a unit cell of the lithium transition metal composite oxide is 8.214 to 8.230 °. 5. material. The lithium transition metal composite oxide has a general formula of Li1 ₊ aMn2 _- aO4 _{+ f} (a represents a number satisfying 0.05 <a≤0.15, and f represents -0.5≤f≤0.5. The positive electrode active material for a nonaqueous electrolyte secondary battery according to at least one of claims 1 to 4, wherein the positive electrode active material is a number that satisfies the following.

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