JP5095883B2 - Non-aqueous electrolyte secondary battery additive and non-aqueous electrolyte secondary battery - Google Patents

Description

但し、一般式（１）において、Ｒ¹、Ｒ²、及び、Ｒ³は、一価の置換基又はハロゲン元素を表し、少なくともいずれかはフッ素を含む。Ｘは、炭素、ケイ素、ゲルマニウム、スズ、窒素、リン、ヒ素、アンチモン、ビスマス、酸素、イオウ、セレン、テルル、及び、ポロニウムからなる群より選ばれる元素の少なくとも１種を含む置換基を表す。Ｙ¹、Ｙ²、及び、Ｙ³は、２価の連結基、２価の元素、又は、単結合を表す。
【００２４】
一般式（２）
（ＰＮＲ⁴ ₂）_n
但し、一般式（２）において、Ｒ⁴は、一価の置換基又はハロゲン元素を表す。該一般式（２）における全Ｒ⁴のうち少なくとも１つはアリーロキシル基を含む。ｎは３〜４である。
【００２５】
前記一般式（１）において、Ｒ¹、Ｒ²、及び、Ｒ³としては、高温特性の観点から、一価の置換基又はハロゲン元素であって、少なくともいずれかがフッ素を含む必要がある。
Ｒ¹、Ｒ²、及び、Ｒ³で表される一価の置換基としては、アルコキシ基、アルキル基、カルボキシル基、アシル基、アリール基、アリーロキシル基等が挙げられ、高温特性及び低粘度化の点で、アルコキシ基、アリーロキシル基が好ましい。これらの置換基は、フッ素のほか、塩素等のハロゲン元素を含んでいてもよい。
【００２６】
前記アルコキシ基としては、例えばメトキシ基、エトキシ基、プロポキシ基、ブトキシ基、フェノキシ基等や、メトキシエトキシ基、メトキシエトキシエトキシ基等のアルコキシ置換アルコキシ基等が挙げられる。これらの中でも、Ｒ¹〜Ｒ³としては、総てがメトキシ基、エトキシ基、メトキシエトキシ基、メトキシエトキシエトキシ基等が好適である。又、低粘度・高誘電率の観点からは、総てがメトキシ基又はエトキシ基が特に好適であり、高温特性の観点からは、メトキシ基が特に好適である。
【００２７】
前記アリーロキシル基としては、フェノキシ基、ナフチロキシ基、アントラセノキシ基等の芳香族置換基が挙げられ、これらの中でも、高温特性の点で、フェノキシ基等が好適である。
【００２８】
前記アルキル基としては、メチル基、エチル基、プロピル基、ブチル基、ペンチル基等が挙げられる。
前記アシル基としては、ホルミル基、アセチル基、プロピオニル基、ブチリル基、イソブチリル基、バレリル基等が挙げられる。
前記アリール基としては、フェニル基、トリル基、ナフチル基等が挙げられる。
前記一価の置換基としては、高温特性の点で、特にトリフルオロメトキシ基、フェノキシ基等が好ましい。
Ｒ¹とＲ²とは、Ｒ¹とＲ³とは、及び、Ｒ²とＲ³とは、互いに結合して環を形成していてもよい。
【００２９】
Ｒ¹、Ｒ²、及び、Ｒ³で表されるハロゲン元素としては、例えば、フッ素、塩素等が好適に挙げられ、特に高温特性の点でフッ素が好ましい。
【００３０】
一般式（１）において、Ｙ¹、Ｙ²、及び、Ｙ³で表される基としては、例えば、ＣＨ₂基のほか、酸素、硫黄、セレン、窒素、ホウ素、アルミニウム、スカンジウム、ガリウム、イットリウム、インジウム、ランタン、タリウム、炭素、ケイ素、チタン、スズ、ゲルマニウム、ジルコニウム、鉛、リン、バナジウム、ヒ素、ニオブ、アンチモン、タンタル、ビスマス、クロム、モリブデン、テルル、ポロニウム、タングステン、鉄、コバルト、ニッケル等の元素を含む基が挙げられ、これらの中でも、ＣＨ₂基、及び、酸素、硫黄、セレン、窒素の元素を含む基等が好ましく、硫黄、セレンの元素を含むのが特に好ましい。Ｙ¹〜Ｙ³は、総て同一種類でもよく、いくつかが互いに異なる種類でもよい。
【００３１】
一般式（１）において、Ｘとしては、有害性、環境等への配慮の観点からは、炭素、ケイ素、窒素、リン、酸素、及び、イオウからなる群から選ばれる元素の少なくとも１種を含む置換基が好ましく、以下の一般式（３）で表される構造を有する置換基がより好ましい。
【００３２】
一般式（３）
【化４】

【００３３】
但し、一般式（３）において、Ｒ⁵〜Ｒ⁹は、一価の置換基又はハロゲン元素を表す。Ｙ⁵〜Ｙ⁹は、２価の連結基、２価の元素、又は単結合を表し、Ｚは２価の基又は２価の元素を表す。
【００３４】
一般式（３）において、Ｒ⁵〜Ｒ⁹としては、一般式（１）におけるＲ¹〜Ｒ³で述べたのと同様の一価の置換基又はハロゲン元素がいずれも好適に挙げられ、少なくともいずれかがフッ素を含むのが好ましい。又、これらは、同一置換基内において、それぞれ同一の種類でもよく、いくつかが互いに異なる種類でもよい。Ｒ⁵とＲ⁶とは、及び、Ｒ⁸とＲ⁹とは、互いに結合して環を形成していてもよい。
一般式（３）において、Ｙ⁵〜Ｙ⁹で表される基としては、一般式（１）におけるＹ¹〜Ｙ³で述べたのと同様の２価の連結基又は２価の基等が挙げられ、同様に、硫黄、セレンの元素を含む基である場合には、非水電解液の発火・引火の危険性が低減するため特に好ましい。これらは、同一置換基内において、それぞれ同一の種類でもよく、いくつかが互いに異なる種類でもよい。
【００３５】
一般式（３）において、Ｚとしては、例えば、ＣＨ₂基、ＣＨＲ（Ｒは、アルキル基、アルコキシル基、フェニル基等を表す。以下同様。）基、ＮＲ基のほか、酸素、硫黄、セレン、ホウ素、アルミニウム、スカンジウム、ガリウム、イットリウム、インジウム、ランタン、タリウム、炭素、ケイ素、チタン、スズ、ゲルマニウム、ジルコニウム、鉛、リン、バナジウム、ヒ素、ニオブ、アンチモン、タンタル、ビスマス、クロム、モリブデン、テルル、ポロニウム、タングステン、鉄、コバルト、ニッケル等の元素を含む基等が挙げられ、これらの中でも、ＣＨ₂基、ＣＨＲ基、ＮＲ基のほか、酸素、硫黄、セレンの元素を含むのが好ましい。特に、硫黄、セレンの元素を含む場合には、非水電解液の発火・引火の危険性が低減するため好ましい。
【００３６】
一般式（３）において、置換基としては、特に効果的に発火・引火の危険性を低減し得る点で、置換基（Ａ）で表されるようなリンを含む置換基が特に好ましい。また、置換基が、置換基（Ｂ）で表されるようなイオウを含む置換基である場合には、非水電解液の小界面抵抗化の点で特に好ましい。
【００３７】
前記一般式（２）において、Ｒ⁴としては、高温特性の観点から、エトキシ基又はフェノキシ基であって、該一般式（２）における全Ｒ⁴のうちの少なくとも１つはフェノキシ基である必要がある。
【００３８】
Ｒ⁴で表される一価の置換基としては、アリーロキシル基、アルコキシ基、アルキル基、カルボキシル基、アシル基、アリール基等が挙げられ、高温特性及び低粘度化の点で、アリーロキシル基等が特に好ましい。Ｒ⁴で表される一価の置換基は、更に他の置換基（フッ素を除く）で置換されていてもよく、又、互いに結合して環を形成していてもよい。前記アリーロキシル基、アルコキシ基、アルキル基、カルボキシル基、アシル基、アリール基としては、前記一般式（１）におけるＲ¹〜Ｒ³で述べたのと同様のものがいずれも好適に挙げられる。
Ｒ⁴で表されるハロゲン元素としては、例えば、フッ素、塩素等が好適に挙げられ、特に高温特性の点でフッ素が好ましい。
前記一般式（２）において、ｎとしては、特に３が好ましい。
ｎが、４を超えると、非水電解液の粘度が上昇し、良好な高温特性が得られないことが多い。
【００３９】
前記一般式（１）又は（２）における各置換基を適宜選択することにより、より好適な粘度、混合に適する溶解性等を有する非水電解液の合成が可能となる。これらのホスファゼン誘導体は、１種単独で使用してもよく、２種以上を併用してもよい。
【００４０】
前記ホスファゼン誘導体としては、前記一般式（１）においては、その分子構造中に、前記フッ素以外にも、塩素、臭素等のハロゲン元素を含む置換基を有するのが好ましく、前記一般式（２）においては、その分子構造中に、フッ素を除くハロゲン元素（塩素、臭素等）を含む置換基を有するのが好ましい。これらの場合には、前記ホスファゼン誘導体から誘導されるハロゲンガスによって、ホスファゼン誘導体の含有量が少量でも、より効果的に自己消火性ないし難燃性を発現させることが可能となる。
尚、置換基にハロゲン元素を含む化合物においては、ハロゲンラジカルの発生が問題となることがあるが、これらのホスファゼン誘導体は、分子構造中のリン元素がハロゲンラジカルを捕促し、安定なハロゲン化リンを形成するため、このような問題は発生しない。
【００４１】
前記ハロゲン元素のこれらのホスファゼン誘導体における含有量としては、２〜８０重量％が好ましく、２〜６０重量％がより好ましく、２〜５０重量％が更に好ましい。
前記含有量が、２重量％未満では、前記ハロゲン元素を含有させる効果が十分に現れないことがある一方、８０重量％を超えると、粘度が高くなるため、非水電解液に添加した際にその導電率が低下することがある。
【００４２】
前記ホスファゼン誘導体の引火点としては、特に制限はないが、発火の抑制等の点から、１００℃以上が好ましく、１５０℃以上がより好ましい。
【００４３】
前記本発明の非水電解液二次電池用添加剤の添加量としては、後述の本発明の非水電解液二次電池におけるホスファゼン誘導体の含有量の好ましい数値範囲に相当する量が好適である。前記添加量を前記数値範囲内の値に調整することにより、非水電解液の自己消火性ないし難燃性、耐劣化性、高温特性等の本発明の効果を好適に付与できる。
【００４４】
以上説明した本発明の非水電解液二次電池用添加剤によれば、非水電解液二次電池に添加することにより、電池として必要な電池特性等を維持しつつ、自己消火性ないし難燃性に優れ、耐劣化性に優れ、非水電解液の界面抵抗が低く、低温特性に優れ、かつ、高温特性に優れた非水電解液二次電池を作製可能な非水電解液二次電池用添加剤を提供することができる。
【００４５】
［非水電解液二次電池］
前記本発明の非水電解液二次電池は、正極と、負極と、非水電解液と、を有し、必要に応じてその他の部材を有する。
【００４６】
−正極−
前記正極の材料としては、特に制限はなく、公知の正極材料から適宜選択して使用できる。例えば、Ｖ₂Ｏ₅、Ｖ₆Ｏ₁₃、ＭｎＯ₂、ＭｏＯ₃、ＬｉＣｏＯ₂、ＬｉＮｉＯ₂、ＬｉＭｎ₂Ｏ₄等の金属酸化物、ＴｉＳ₂、ＭｏＳ₂等の金属硫化物、ポリアニリン等の導電性ポリマー等が好適に挙げられ、これらの中でも、高容量で安全性が高く電解液の濡れ性に優れる点で、ＬｉＣｏＯ₂、ＬｉＮｉＯ₂、ＬｉＭｎ₂Ｏ₄が特に好適である。これらの材料は、１種単独で使用してもよく、２種以上を併用してもよい。
【００４７】
前記正極の形状としては、特に制限はなく、電極として公知の形状の中から適宜選択することができる。例えば、シート状、円柱形状、板状形状、スパイラル形状等が挙げられる。
【００４８】
−負極−
前記負極は、例えば、リチウム又はリチウムイオン等を吸蔵・放出可能である。従ってその材料としては、例えば、リチウム又はリチウムイオン等を吸蔵・放出可能であれば特に制限はなく、公知の負極材料から適宜選択して使用できる。
例えばリチウムを含む材料、具体的には、リチウム金属自体、リチウムと、アルミニウム、インジウム、鉛、又は、亜鉛等との合金、リチウムをドープした黒鉛等の炭素材料等が好適に挙げられ、これらの中でも安全性がより高い点で黒鉛等の炭素材料が好ましい。これらの材料は、１種単独で使用してもよく、２種以上を併用してもよい。
前記負極の形状としては、特に制限はなく、前記正極の形状と同様の公知の形状から適宜選択することができる。
【００４９】
−非水電解液−
前記非水電解液は、前記本発明の非水電解液二次電池用添加剤及び支持塩を含有し、必要に応じてその他の成分を含有する。
【００５０】
−−支持塩−−
前記支持塩としては、例えば、リチウムイオンのイオン源となる支持塩等が好ましい。
前記リチウムイオンのイオン源としては、特に制限はないが、例えば、ＬｉＣｌＯ₄、ＬｉＢＦ₄、ＬｉＰＦ₆、ＬｉＣＦ₃ＳＯ₃、及び、ＬｉＡｓＦ₆、ＬｉＣ４Ｆ₉ＳＯ₃、Ｌｉ（ＣＦ₃ＳＯ₂）₂Ｎ、Ｌｉ（Ｃ₂Ｆ₅ＳＯ₂）₂Ｎ等のリチウム塩が好適に挙げられる。これらは、１種単独で使用してもよく、２種以上を併用してもよい。
【００５１】
前記支持塩の前記非水電解液に対する配合量としては、前記非水電解液（溶媒成分）１ｋｇに対し、０．２〜１モルが好ましく、０．５〜１モルがより好ましい。
前記配合量が、０．２モル未満の場合には、非水電解液の充分な導電性を確保することができず、電池の充放電特性に支障をきたすことがある一方、１モルを超える場合には、非水電解液の粘度が上昇し、前記リチウムイオン等の充分な移動度が確保できないため、前述と同様に非水電解液の充分な導電性を確保できず、電池の充放電特性に支障をきたすことがある。
【００５２】
＜高温特性、自己消化性ないし難燃性、耐劣化性＞
前記非水電解液における前記ホスファゼン誘導体の含有量としては、該ホスファゼン誘導体を含有することにより得られる効果によって、非水電解液に好適に「高温特性」を付与し得る第１の含有量、非水電解液に好適に「自己消火性」を付与し得る第２の含有量、非水電解液に好適に「難燃性」を付与し得る第３の含有量、及び、非水電解液に好適に「耐劣化性」を付与し得る第４の含有量の４通りの含有量が挙げられる。
【００５３】
前記「高温特性」の観点からは、前記ホスファゼン誘導体の前記非水電解液における第１の含有量としては、１〜７０体積％が好ましく、１〜５０体積％がより好ましく、３〜３０体積％が更に好ましい。
前記含有量が、前記数値範囲外では、得られる非水電解液二次電池の高温特性が良好でないことがある。
尚、前記「高温特性」は、下記の容量残存率、高温放電特性、及び、安全性のそれぞれを評価しこれらを総合的に評価した。
【００５４】
＜＜容量残存率の測定・評価＞＞
本発明の非水電解液二次電池を７０℃条件下で１０日間放置した後、非水電解液の容量を測定し、放置前の容量と比較して容量残存率を算出し評価した。
＜＜高温放電特性の測定・評価＞＞
本発明の非水電解液二次電池を７０℃条件下で１０日間放置後、５０サイクルまで充放電を繰り返した際の放電容量を、放置前において測定した放電容量と比較し、下記式（１）より放電容量残存率を算出し高温放電特性の評価とした。
式（１）：放電容量残存率＝
１０日間放置後の放電容量／放置前の放電容量×１００（％）
＜＜安全性の評価＞＞
本発明の非水電解液二次電池を７０℃条件下で１０日間放置し電池の破裂・発火等の有無を目視にて観察し、又室温で充放電試験を行うことによって安全性の評価とした。
【００５５】
前記「自己消火性」の観点からは、前記ホスファゼン誘導体の非水電解液における第２の含有量としては、２０体積％以上が好ましく、自己消火性と高温特性とを高度に両立する観点からは、２０〜７０体積％がより好ましく、２０〜５０体積％が更に好ましく、２０〜３０体積％が特に好ましい。
前記含有量が、２０体積％未満では、非水電解液に十分な「自己消火性」を発現させ得ないことがある。
尚、本発明において、「自己消火性」とは、下記「自己消火性の評価方法」において、着火した炎が２５〜１００ｍｍラインで消火し、かつ、落下物にも着火が認められない状態となる性質をいう。
【００５６】
前記「難燃性」の観点からは、前記ホスファゼン誘導体の非水電解液における第３の含有量としては、３０体積％以上が好ましく、難燃性と高温特性とを高度に両立する観点からは、３０〜７０体積％がより好ましく、３０〜５０体積％が更に好ましい。
前記含有量が３０体積％以上であれば、非水電解液に十分な「難燃性」を発現させることが可能となる。
尚、本発明において、「難燃性」とは、下記「難燃性の評価方法」において、着火した炎が２５ｍｍラインまで到達せず、かつ、落下物にも着火が認められない状態となる性質をいう。
【００５７】
＜＜自己消火性・難燃性の評価方法＞＞
前記自己消火性・難燃性の評価は、ＵＬ（アンダーライティングラボラトリー）規格のＵＬ９４ＨＢ法をアレンジした方法を用い、大気環境下において着火した炎の燃焼挙動を測定・評価した。その際、着火性、燃焼性、炭化物の生成、二次着火時の現象についても観察した。具体的には、ＵＬ試験基準に基づき、不燃性石英ファイバーに１．０ｍｌの各種電解液を染み込ませ、１２７ｍｍ×１２．７ｍｍの試験片を作製して行った。
【００５８】
前記「自己消火性ないし難燃性」の観点から、前記非水電解液としては、前記ホスファゼン誘導体、ＬｉＰＦ₆、エチレンカーボネート及び／又はプロピレンカーボネートを含む場合、及び、前記ホスファゼン誘導体、ＬｉＣＦ₃ＳＯ₃、プロピレンカーボネートを含む場合、が特に好ましい。これらの場合には、前述の記載にかかわらず、前記含有量が少量であっても、優れた自己消火性ないし難燃性の効果を有する。即ち、ホスファゼン誘導体の非水電解液における含有量としては、自己消火性を発現させるためには、１．５〜２．５体積％が好ましく、難燃性を発現させるためには、２．５体積％を超える量が好ましい。また、難燃性と高温特性とを高度に両立する観点からは、２．５体積％を超え７０体積％以下がより好ましく、２．５体積％を超え５０体積％以下が更に好ましく、２．５体積％を超え３０体積％以下が特に好ましい。
【００５９】
前記「耐劣化性」の観点からは、前記ホスファゼン誘導体の前記非水電解液における第４の含有量としては、２体積％以上が好ましく、２．５体積％を超えるのがより好ましく、３体積％以上７５体積％未満が更に好ましく、耐劣化性と高温特性とを高度に両立する観点からは、第４の含有量の数値範囲のいずれかの下限値を下限値とし、第１の含有量の数値範囲のいずれかの上限値を上限値とする数値範囲が好ましい。
前記含有量が、前記数値範囲内であれば、好適に劣化を抑制することができる。
尚、本発明において、「劣化」とは、前記支持塩（例えば、リチウム塩）の分解をいい、該劣化防止の効果を下記「安定性の評価方法」により評価した。
【００６０】
＜＜安定性の評価方法＞＞
（１）先ず、支持塩を含む非水電解液を調製後、水分率を測定する。次に、高速液体クロマトグラフィー（イオンクロマトグラフィー）により、非水電解液中の弗化水素の濃度を測定する。更に、目視により非水電解液の色調を観察した後、充放電試験により充放電容量を算出する。
（２）上記非水電解液を２ヶ月間グローブボックス内で放置した後、再び、水分率、弗化水素の濃度を測定し、色調を観察し、充放電容量を算出し、得られた数値の変化により安定性を評価する。
【００６１】
−−その他の成分−−
前記その他の成分としては、非プロトン性有機溶媒が特に好ましい。
前記非プロトン性有機溶媒は、安全性の点から、前記非水電解液に含有させるのが好適である。即ち、非水電解液に、非プロトン性有機溶媒が含有されていれば、前記負極の材料と反応することなく高い安全性を得ることができる。また、前記非水電解液の低粘度化が可能であり、容易に非水電解液二次電池としての最適なイオン導電性を達成することができる。
【００６２】
前記非プロトン性有機溶媒としては、特に制限はないが、前記非水電解液の低粘度化の点で、エーテル化合物やエステル化合物等が挙げられる。具体的には、１，２−ジメトキシエタン、テトラヒドロフラン、ジメチルカーボネート、ジエチルカーボネート、ジフェニルカーボネート、エチレンカーボネート、プロピレンカーボネート、γ−ブチロラクトン、γ−バレロラクトン、メチルエチルカーボネート、等が好適に挙げられる。これらの中でも、エチレンカーボネート、プロピレンカーボネート、γ−ブチロラクトン等の環状エステル化合物、１、２−ジメトキシエタン、ジメチルカーボネート、エチルメチルカーボネート、ジエチルカーボネート等の鎖状エステル化合物等が好適である。特に、環状のエステル化合物は、比誘電率が高くリチウム塩等の溶解性に優れる点で、鎖状のエステル化合物は、低粘度であるため、非水電解液の低粘度化の点で好適である。これらは１種単独で使用してもよく、２種以上を併用してもよいが、２種以上を併用するのが好適である。
【００６３】
前記非プロトン性有機溶媒の２５℃における粘度としては、特に制限はないが、１０ｍＰａ・ｓ（１０ｃＰ）以下が好ましく、５ｍＰａ・ｓ（５ｃＰ）以下がより好ましい。
【００６４】
−その他の部材−
前記その他の部材としては、非水電解液二次電池において、正負極間に、両極の接触による電流の短絡を防止する役割で介在させるセパレーターが挙げられる。
前記セパレーターの材質としては、両極の接触を確実に防止し得、かつ、電解液を通したり含んだりできる材料、例えば、ポリテトラフルオロエチレン、ポリプロピレン、ポリエチレン等の合成樹脂製の不織布、薄層フィルム等が好適に挙げられる。これらの中でも、厚さ２０〜５０μｍ程度のポリプロピレン又はポリエチレン製の微孔性フィルムが特に好適である。
【００６５】
前記セパレーターのほか、前記その他の部材としては、通常電池に使用されている公知の各部材が好適に挙げられる。
【００６６】
本発明の非水電解液二次電池の形態としては、特に制限はなく、コインタイプ、ボタンタイプ、ペーパータイプ、角型又はスパイラル構造の円筒型電池等、種々の公知の形態が好適に挙げられる。
前記スパイラル構造の場合、例えば、シート状の正極を作製して集電体を挟み、これに、負極（シート状）を重ね合わせて巻き上げる等により非水電解液二次電池を作製することができる。
【００６７】
以上説明した本発明の非水電解液二次電池は、前記本発明の非水電解液二次電池用添加剤を含有するため、自己消火性ないし難燃性に優れ、耐劣化性に優れ、非水電解液の界面抵抗が低く、低温特性に優れ、かつ、高温特性に優れる。
【００６８】
【実施例】
以下、実施例と比較例を示し、本発明を具体的に説明するが、本発明は下記の実施例に何ら限定されるものではない。
（実施例１）
［非水電解液の調製］
ジエチルカーボネートとエチレンカーボネートとの混合溶媒（混合比（体積比）：ジエチルカーボネート／エチレンカーボネート＝１／１）（非プロトン性有機溶媒）７０ｍｌに、環状ホスファゼン誘導体（前記一般式（２）において、Ｒ⁴がフェノキシ基であり、ｎが３である化合物（非水電解液二次電池用添加剤））３０ｍｌを添加（１体積％）し、更に、ＬｉＢＦ₄（支持塩）を０．７５モル／ｋｇの濃度で溶解させ、非水電解液を調製した。
【００６９】
＜自己消火性ないし難燃性の評価＞
得られた非水電解液について、前述の「自己消火性・難燃性の評価方法」と同様にして、下記に示すように評価を行った。結果を表１に示す。
【００７０】
＜＜難燃性の評価＞＞
着火した炎が、装置の２５ｍｍラインまで到達せず、かつ網からの落下物にも着火が認められなかった場合を難燃性ありと評価した。
＜＜自己消火性の評価＞＞
着火した炎が、２５〜１００ｍｍラインの間で消火し、かつ、網落下からの落下物にも着火が認められなかった場合を自己消火性ありと評価した。
＜＜燃焼性の評価＞＞
着火した炎が、１００ｍｍラインを超えた場合を燃焼性ありと評価した。
【００７１】
＜劣化の評価＞
得られた非水電解液について、前述の「安定性の評価方法」と同様に、非水電解液調製直後及び２ヶ月間グローブボックス内で放置後の水分率（ｐｐｍ）、弗化水素濃度（ｐｐｍ）、充放電容量（ｍＡｈ／ｇ）を測定・算出し、劣化の評価を行った。この時、充放電容量（ｍＡｈ／ｇ）は、重量既知の正極又は前述の負極を用いて充放電曲線を測定し、得られた充電量、放電量を用いた電極の重量で除することにより求めた。また、非水電解液調製直後及び２ヶ月間グローブボックス内で放置後の非水電解液の色調変化を目視により観察した。結果を表１に示す。
【００７２】
［非水電解液二次電池の作製］
化学式ＬｉＣｏＯ₂で表されるコバルト酸化物を正極活物質として用い、ＬｉＣｏＯ₂１００部に対して、アセチレンブラック（導電助剤）を１０部、テフロンバインダー（結着樹脂）を１０部添加し、有機溶媒（酢酸エチルとエタノールとの５０／５０体積％混合溶媒）で混練した後、ロール圧延により厚さ１００μｍ、幅４０ｍｍの薄層状の正極シートを作製した。
その後、得られた正極シート２枚を用いて、表面に導電性接着剤を塗布した、厚さ２５μｍのアルミニウム箔（集電体）を挟み込み、これに厚さ２５μｍのセパレーター（微孔性フィルム：ポリプロピレン性）を介在させ、厚さ１５０μｍのリチウム金属箔を重ね合わせて巻き上げ、円筒型電極を作製した。該円筒型電極の正極長さは約２６０ｍｍであった。
【００７３】
前記円筒型電極に、前記非水電解液を注入して封口し、単三型リチウム電池を作製した。
【００７４】
＜電池特性等の測定・評価＞
得られた電池について、２０℃において、初期の電池特性（電圧、内部抵抗）を測定・評価した後、下記評価の方法により、充放電サイクル性能を測定・評価した。これらの結果を表１に示す。
【００７５】
＜＜充放電サイクル性能の評価＞＞
上限電圧４．５Ｖ、下限電圧３．０Ｖ、放電電流１００ｍＡ、充電電流５０ｍＡの条件で、５０サイクルまで充放電を繰り返した。この時の充放電の容量を、初期における充放電の容量と比較し、５０サイクル後の容量減少率を算出した。合計３本の電池について、同様に測定・算出し、これらの平均値をとり、充放電サイクル性能の評価とした。
【００７６】
＜低温特性の評価（低温放電容量の測定）＞
得られた電池について、放電時の温度を、低温（−１０℃、−２０℃）とした外は、前記「充放電サイクル性能の評価」と同様の条件で、５０サイクルまで充放電を繰り返した。この時の低温における放電容量を、２０℃において測定した放電容量と比較し、下記式（２）より放電容量残存率を算出した。合計３本の電池について、同様に測定・算出し、これらの平均値をとり、低温特性の評価とした。結果を表１に示す。
式（２）：放電容量残存率＝
低温放電容量／放電容量（２０℃）×１００（％）
【００７７】
＜高温特性の評価＞
＜＜容量減少率の測定・評価＞＞
得られた電池を７０℃条件下で１０日間放置した後、非水電解液の容量を測定し、放置前の容量と比較して容量減少率を算出した。
＜＜高温放電特性の測定・評価＞＞
得られた電池を７０℃条件下で１０日間放置後、５０サイクルまで充放電を繰り返した際の放電容量を、放置前において測定した放電容量と比較し、前述の式（１）より放電容量減少率を算出した。上記と同様に、合計３本の電池について測定・算出し、これらの平均値をとり高温放電特性の評価とした。
＜＜安全性の評価＞＞
得られた電池を７０℃条件下で１０日間放置し電池の破裂・発火等の有無を目視にて観察し、又室温で充放電試験を行うことによって安全性の評価とした。
以上の評価結果を表１に示す。
【００７８】
（実施例２）
実施例１の「非水電解液の調製」において、ジエチルカーボネートとエチレンカーボネートとの混合溶媒を８０ｍｌとし、環状ホスファゼン誘導体を２０ｍｌ（２０体積％）としたほかは、実施例１と同様に非水電解液を調製し、自己消火性ないし難燃性、耐劣化性の評価を行った。また、実施例１と同様にして非水電解液二次電池を作製し、初期の電池特性（電圧、内部抵抗）、充放電サイクル性能、低温特性、及び、高温特性をそれぞれ測定・評価した。結果を表１に示す。
【００７９】
（実施例３）
実施例１の「非水電解液の調製」において、ジエチルカーボネートとエチレンカーボネートとの混合溶媒を２５ｍｌとし、環状ホスファゼン誘導体を７５ｍｌ（７５体積％）としたほかは、実施例１と同様に非水電解液を調製し、自己消火性ないし難燃性、耐劣化性の評価を行った。また、実施例１と同様にして非水電解液二次電池を作製し、初期の電池特性（電圧、内部抵抗）、充放電サイクル性能、低温特性、及び、高温特性をそれぞれ測定・評価した。結果を表１に示す。
【００８０】
（実施例４）
実施例１の「非水電解液の調製」において、ジエチルカーボネートとエチレンカーボネートとの混合溶媒を９８ｍｌとし、環状ホスファゼン誘導体を２ｍｌ（２体積％）とし、支持塩をＬｉＰＦ₆に代えたほかは、実施例１と同様に非水電解液を調製し、自己消火性ないし難燃性、耐劣化性の評価を行った。また、実施例１と同様にして非水電解液二次電池を作製し、初期の電池特性（電圧、内部抵抗）、充放電サイクル性能、低温特性、及び、高温特性をそれぞれ測定・評価した。結果を表１に示す。
【００８１】
（実施例５）
実施例１の「非水電解液の調製」において、ジエチルカーボネートとエチレンカーボネートとの混合溶媒を９７ｍｌに変え、環状ホスファゼン誘導体を３ｍｌ（３体積％）とし、支持塩をＬｉＰＦ₆に代えたほかは、実施例１と同様に非水電解液を調製し、実施例１と同様に自己消火性ないし難燃性の評価、耐劣化性の評価を行った。
また、実施例１と同様にして非水電解液二次電池を作製し、初期の電池特性（電圧、内部抵抗）、充放電サイクル性能、低温特性、及び、高温特性をそれぞれ測定・評価した。結果を表１に示す。
【００８２】
（実施例６）
実施例１の「非水電解液の調製」において、環状ホスファゼン誘導体（前記一般式（２）において、Ｒ⁴がフェノキシ基であり、ｎが３である化合物（非水電解液二次電池用添加剤）を、環状ホスファゼン誘導体（前記一般式（２）においてｎが４であって、Ｒ⁴のうちの２つがフェノキシ基であって６つがエトキシ基である化合物（非水電解液二次電池用添加剤））に代えたほかは、実施例１と同様に非水電解液を調製し、実施例１と同様に自己消火性ないし難燃性の評価、耐劣化性の評価を行った。
また、実施例１と同様にして非水電解液二次電池を作製し、初期の電池特性（電圧、内部抵抗）、充放電サイクル性能、低温特性、及び、高温特性をそれぞれ測定・評価した。結果を表１に示す。
【００８３】
（比較例１）
実施例１の「非水電解液の調製」において、環状ホスファゼン誘導体を環状ホスファゼン誘導体（前記一般式（２）において、Ｒ⁴が塩素を含むメトキシ基であり、ｎが５である化合物（メトキシ基に対する塩素のモル比（メトキシ基／塩素）が２／４、３／３及び４／２である化合物の混合物）に代えたほかは、実施例１と同様に非水電解液を調製し、実施例１と同様に自己消火性ないし難燃性の評価、耐劣化性の評価を行った。
また、実施例１と同様にして非水電解液二次電池を作製し、初期の電池特性（電圧、内部抵抗）、充放電サイクル性能、低温特性、及び、高温特性をそれぞれ測定・評価した。結果を表１に示す。
【００８４】
【表１】

【００８５】
【発明の効果】
本発明によれば、非水電解液二次電池に添加することにより、電池として必要な電池特性等を維持しつつ、自己消火性ないし難燃性に優れ、耐劣化性に優れ、非水電解液の界面抵抗が低く、低温特性に優れ、かつ、高温特性に優れた非水電解液二次電池を作製可能な非水電解液二次電池用添加剤、及び、該非水電解液二次電池用添加剤を含有し、自己消火性ないし難燃性に優れ、耐劣化性に優れ、非水電解液の界面抵抗が低く、低温特性に優れ、かつ、高温特性に優れた非水電解液二次電池を提供することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention is excellent in self-extinguishing properties or flame retardancy, excellent in deterioration resistance, and excellent in high temperature properties while maintaining the same battery capacity as the conventional nonaqueous electrolyte secondary battery. The present invention relates to a non-aqueous electrolyte secondary battery.
[0002]
[Prior art]
Conventionally, nickel-cadmium batteries have been mainly used as memory backups for AV and information devices such as personal computers and VTRs, and secondary batteries for their drive power sources. In recent years, non-aqueous electrolyte secondary batteries have attracted a great deal of attention as an alternative to nickel-cadmium batteries because they have the advantages of high voltage and high energy density and have excellent self-discharge characteristics. Some of them have been commercialized. For example, more than half of notebook computers and mobile phones are driven by non-aqueous electrolyte secondary batteries.
[0003]
In these non-aqueous electrolyte secondary batteries, carbon is frequently used as a material for forming the negative electrode. For the purpose of reducing the danger and increasing the driving voltage when lithium is generated on the surface, various types of carbon are used. An organic solvent is used as the electrolyte.
In addition, since non-aqueous electrolyte secondary batteries for cameras use alkali metals (particularly lithium metals and lithium alloys) as negative electrode materials, the electrolytes are usually ester-based organic solvents, etc. An aprotic organic solvent is used.
[0004]
However, although these nonaqueous electrolyte secondary batteries have high performance, they have the following problems in safety.
First, when an alkali metal (particularly lithium metal or lithium alloy) used as a negative electrode material for a non-aqueous electrolyte secondary battery is used, the alkali metal is very highly active against moisture. For example, when the sealing of the battery is incomplete and moisture enters, there is a problem that the negative electrode material and water react with each other to generate hydrogen or ignite.
[0005]
In addition, since lithium metal has a low melting point (about 170 ° C.), if a large current suddenly flows during a short circuit or the like, the battery may generate abnormal heat and cause a very dangerous situation such as melting of the battery. was there.
Further, as the battery generates heat, the above-mentioned electrolyte based on the organic solvent is vaporized and decomposed to generate gas, and the generated gas causes explosion and ignition of the battery.
[0006]
In order to solve the above problem, for example, in a cylindrical battery, when the temperature rises when the battery is short-circuited or overcharged and the pressure inside the battery rises, the safety valve is activated and the electrode terminal is broken at the same time. A technology has been proposed in which a battery is provided with a mechanism for preventing an excessive current exceeding a predetermined amount from flowing in a cylindrical battery (Nikkan Kogyo Shimbun, "Electronic Technology", Vol. 39, No. 9, 1997).
[0007]
However, it is not reliable that the mechanism always operates normally. If the mechanism does not operate normally, there is a problem because heat generation due to excessive current increases and a dangerous state such as ignition may occur.
[0008]
In order to solve the above-mentioned problem, it is not a safety measure by providing ancillary parts such as a safety valve as described above, but development of a non-aqueous electrolyte secondary battery having fundamentally high safety is required. .
[0009]
In particular, in regions and periods where the temperature is high, it is necessary to maintain excellent battery characteristics for a long time even under high temperature conditions, and a nonaqueous electrolyte secondary battery excellent in high temperature characteristics is required.
[0010]
[Problems to be solved by the invention]
An object of the present invention is to solve the above-described conventional problems, meet various requirements, and achieve the following objects. That is, the present invention, when added to a non-aqueous electrolyte secondary battery, maintains the battery characteristics and the like necessary for the battery, is excellent in self-extinguishing properties or flame retardancy, excellent in deterioration resistance, non-aqueous electrolysis Non-aqueous electrolyte secondary battery additive capable of producing a non-aqueous electrolyte secondary battery having low liquid interface resistance, excellent low-temperature characteristics, and excellent high-temperature characteristics, and the non-aqueous electrolyte secondary battery Non-aqueous electrolyte with excellent self-extinguishing properties or flame retardancy, excellent deterioration resistance, low non-aqueous electrolyte interface resistance, low-temperature characteristics, and high-temperature characteristics An object is to provide a secondary battery.
[0011]
[Means for Solving the Problems]
  Means for solving the problems are as follows. That is,
  <1> The following generalformula(Represented by 2)RingA non-aqueous electrolyte secondary battery additive comprising at least a phosphazene derivative.
[0013]
oneGeneral formula (2)
  (PNR^Four ₂)_n
  However, in the general formula (2), R^FourIs a monovalentEthoxy group or phenoxy groupRepresents. Total R in the general formula (2)^FourAt least one ofPhenoxyContains groups. n is 3-4.
  <2> The phosphazene derivative is all R in the above (2).⁴Is an additive for a non-aqueous electrolyte secondary battery according to <1>, wherein n is a phenoxy group and n is 3.
  <3> In the phosphazene derivative, n in the above (2) is 4, and all R⁴2 is an additive for non-aqueous electrolyte secondary batteries according to the above <1>, wherein two are phenoxy groups and six are ethoxy groups.
[0014]
  <4> Positive electrode, negative electrode, <1>~ <3>And a non-aqueous electrolyte containing the additive for a non-aqueous electrolyte secondary battery and a supporting salt as described in 1. above.
  <5> In non-aqueous electrolyteRingThe content of the phosphazene derivative is2% by volume or more 30volume%Less thanSaid <4> Is a nonaqueous electrolyte secondary battery.
  <6> In non-aqueous electrolyteRingThe content of the phosphazene derivative isMore than 2.5 volume% and 30 volume% or lessSaid <4> Is a nonaqueous electrolyte secondary battery.
[0015]
<7> The above <wherein the non-aqueous electrolyte contains an aprotic organic solvent4The nonaqueous electrolyte secondary battery according to any one of <6> to <6>.
[0016]
  <8> The nonaqueous electrolyte secondary battery according to <7>, wherein the aprotic organic solvent contains a cyclic or chain ester compound.
  <9> Non-aqueous electrolyte is LiPF as supporting salt₆Ethylene carbonate and / or propylene carbonate as an aprotic organic solventIncludeAbove<7>It is a non-aqueous electrolyte secondary battery as described in above.
[0017]
  <10> Non-aqueous electrolyte is LiCF as supporting salt_ThreeSO_ThreePropylene carbonate as an aprotic organic solventIncludingMu<7>It is a non-aqueous electrolyte secondary battery as described in above.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
  Hereinafter, the present invention will be described in detail.
[Additives for non-aqueous electrolyte secondary batteries]
  The additive for non-aqueous electrolyte secondary battery of the present invention,The ring represented by the following general formula (2)Contains phosphazene derivatives and other components as required.
[0019]
-Phosphazene derivatives-
The reason why the phosphazene derivative is contained in the additive for non-aqueous electrolyte secondary batteries of the present invention is as follows.
Conventional non-aqueous electrolytes based on aprotic organic solvents used in non-aqueous electrolyte secondary batteries have a large current that suddenly flows during a short circuit, etc. In addition, gas is generated by vaporization and decomposition, or the battery is ruptured and ignited by the generated gas and heat.
On the other hand, by adding the additive for a non-aqueous electrolyte secondary battery of the present invention containing a phosphazene derivative to these conventional non-aqueous electrolytes, by the action of nitrogen gas and halogen gas derived from the phosphazene derivative. The non-aqueous electrolyte is imparted with excellent self-extinguishing properties or flame retardancy, and it is possible to reduce the risk as described above. Moreover, since phosphorus has the effect | action which suppresses the chain decomposition of the polymeric material which comprises a battery, it can provide self-extinguishing property thru | or flame retardance effectively.
[0020]
Furthermore, in a conventional non-aqueous electrolyte secondary battery, for example, an ester-based electrolyte used as an electrolyte, for example, LiPF which is a supporting salt₆Lithium ion source such as salt, etc., is LiF and PF over time_FivePF generated by decomposition into_FiveGas and generated PF_FiveIt is considered that corrosion proceeds and deteriorates due to hydrogen fluoride gas generated by further reaction of the gas with water or the like. That is, the conductivity of the non-aqueous electrolyte is lowered and the electrode material is deteriorated by the generated hydrogen fluoride gas.
On the other hand, the phosphazene derivative is, for example, the LiPF.₆This contributes to stabilization by suppressing decomposition of the lithium ion source. Therefore, by adding a phosphazene derivative to a conventional non-aqueous electrolyte, the decomposition reaction of the non-aqueous electrolyte is suppressed, and corrosion and deterioration can be suppressed.
[0021]
Furthermore, it becomes possible to impart excellent high temperature characteristics to the non-aqueous electrolyte, and the decomposition of the non-aqueous electrolyte when used at high temperatures is prevented. For this reason, even if it is used for a long time at a high temperature, the amount of the non-aqueous electrolyte does not decrease, the discharge characteristics do not deteriorate, and the generation of gas accompanying decomposition does not occur. There is no risk of rupture.
[0022]
The phosphazene derivative is represented by the following general formula (1) or (2).
General formula (1)
[0023]
[Chemical Formula 3]

However, in the general formula (1), R¹, R²And R^ThreeRepresents a monovalent substituent or a halogen element, and at least one of them contains fluorine. X represents a substituent containing at least one element selected from the group consisting of carbon, silicon, germanium, tin, nitrogen, phosphorus, arsenic, antimony, bismuth, oxygen, sulfur, selenium, tellurium, and polonium. Y¹, Y²And Y^ThreeRepresents a divalent linking group, a divalent element, or a single bond.
[0024]
General formula (2)
  (PNR^Four ₂)_n
  However, in the general formula (2), R^FourRepresents a monovalent substituent or a halogen element. Total R in the general formula (2)^FourAt least one ofAllyloxylContains groups. n is 3-4.
[0025]
  In the general formula (1), R¹, R²And R^ThreeFrom the viewpoint of high temperature characteristics, it is a monovalent substituent or a halogen element, and at least one of them must contain fluorine.
  R¹, R²And R^ThreeAs the monovalent substituent represented by the following, an alkoxy group, an alkyl group, a carboxyl group, an acyl group, an aryl group,AllyloxylGroups, etc., in terms of high temperature characteristics and low viscosity, alkoxy groups,AllyloxylGroups are preferred. These substituents may contain a halogen element such as chlorine in addition to fluorine.
[0026]
Examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, a butoxy group, a phenoxy group, and an alkoxy-substituted alkoxy group such as a methoxyethoxy group and a methoxyethoxyethoxy group. Among these, R¹~ R^ThreeAs for all, methoxy group, ethoxy group, methoxyethoxy group, methoxyethoxyethoxy group and the like are preferable. Further, from the viewpoint of low viscosity and high dielectric constant, all are preferably methoxy groups or ethoxy groups, and from the viewpoint of high temperature characteristics, methoxy groups are particularly preferable.
[0027]
  AboveAllyloxylExamples of the group include aromatic substituents such as a phenoxy group, a naphthyloxy group, and an anthracenoxy group. Among these, a phenoxy group and the like are preferable from the viewpoint of high temperature characteristics.
[0028]
Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, and a pentyl group.
Examples of the acyl group include formyl group, acetyl group, propionyl group, butyryl group, isobutyryl group, valeryl group and the like.
Examples of the aryl group include a phenyl group, a tolyl group, and a naphthyl group.
As the monovalent substituent, a trifluoromethoxy group, a phenoxy group, and the like are particularly preferable in terms of high temperature characteristics.
R¹And R²And R¹And R^ThreeAnd R²And R^ThreeAnd may be bonded to each other to form a ring.
[0029]
R¹, R²And R^ThreeAs the halogen element represented by, for example, fluorine, chlorine and the like are preferably mentioned, and fluorine is particularly preferable from the viewpoint of high temperature characteristics.
[0030]
In general formula (1), Y¹, Y²And Y^ThreeAs the group represented by, for example, CH₂In addition to groups, oxygen, sulfur, selenium, nitrogen, boron, aluminum, scandium, gallium, yttrium, indium, lanthanum, thallium, carbon, silicon, titanium, tin, germanium, zirconium, lead, phosphorus, vanadium, arsenic, niobium, Examples include groups containing elements such as antimony, tantalum, bismuth, chromium, molybdenum, tellurium, polonium, tungsten, iron, cobalt, nickel, and among these, CH₂A group and a group containing oxygen, sulfur, selenium, and nitrogen elements are preferable, and a sulfur and selenium element is particularly preferable. Y¹~ Y^ThreeAll may be the same type, or some may be different types.
[0031]
In the general formula (1), X includes at least one element selected from the group consisting of carbon, silicon, nitrogen, phosphorus, oxygen, and sulfur from the viewpoint of consideration of toxicity, environment, and the like. A substituent is preferable, and a substituent having a structure represented by the following general formula (3) is more preferable.
[0032]
General formula (3)
[Formula 4]

[0033]
However, in the general formula (3), R^Five~ R⁹Represents a monovalent substituent or a halogen element. Y^Five~ Y⁹Represents a divalent linking group, a divalent element, or a single bond, and Z represents a divalent group or a divalent element.
[0034]
In the general formula (3), R^Five~ R⁹As R in the general formula (1)¹~ R^ThreeAny of the same monovalent substituents and halogen elements as mentioned in the above are preferably mentioned, and at least one of them preferably contains fluorine. Moreover, these may be the same kind in the same substituent, and some may be different kinds. R^FiveAnd R⁶And R⁸And R⁹And may be bonded to each other to form a ring.
In general formula (3), Y^Five~ Y⁹As a group represented by Y in General Formula (1),¹~ Y^ThreeThe same divalent linking group or divalent group as mentioned in the above can be mentioned. Similarly, in the case of a group containing sulfur and selenium elements, the risk of ignition and ignition of non-aqueous electrolyte Is particularly preferred because of a reduction in These may be the same type in the same substituent, or some of them may be different from each other.
[0035]
In the general formula (3), as Z, for example, CH₂Group, CHR (R represents an alkyl group, an alkoxyl group, a phenyl group, etc.) group, NR group, oxygen, sulfur, selenium, boron, aluminum, scandium, gallium, yttrium, indium, lanthanum, Contains elements such as thallium, carbon, silicon, titanium, tin, germanium, zirconium, lead, phosphorus, vanadium, arsenic, niobium, antimony, tantalum, bismuth, chromium, molybdenum, tellurium, polonium, tungsten, iron, cobalt, nickel Group, etc., among these, CH₂In addition to the group, the CHR group, and the NR group, oxygen, sulfur, and selenium elements are preferably included. In particular, when an element such as sulfur or selenium is included, it is preferable because the risk of ignition and ignition of the non-aqueous electrolyte is reduced.
[0036]
In the general formula (3), as the substituent, a substituent containing phosphorus as represented by the substituent (A) is particularly preferable in that the risk of ignition / flammability can be particularly effectively reduced. In addition, when the substituent is a substituent containing sulfur as represented by the substituent (B), it is particularly preferable in terms of reducing the interfacial resistance of the nonaqueous electrolytic solution.
[0037]
  In the general formula (2), R^FourFrom the viewpoint of high temperature characteristics,Ethoxy group or phenoxy groupAnd all R in the general formula (2)^FourAt least one ofPhenoxyMust be a group.
[0038]
  R^FourAs the monovalent substituent represented byAllyloxylGroup, alkoxy group, alkyl group, carboxyl group, acyl group, aryl group and the like, and in terms of high temperature characteristics and low viscosity,AllyloxylGroups and the like are particularly preferred. R^FourThe monovalent substituent represented by may be further substituted with another substituent (excluding fluorine), or may be bonded to each other to form a ring. AboveAllyloxylExamples of the group, alkoxy group, alkyl group, carboxyl group, acyl group, and aryl group include R in the general formula (1).¹~ R^ThreeAny of those described in the above can be preferably mentioned.
  R^FourAs the halogen element represented by, for example, fluorine, chlorine and the like are preferably mentioned, and fluorine is particularly preferable from the viewpoint of high temperature characteristics.
  In the general formula (2), 3 is particularly preferable as n.
  When n exceeds 4, the viscosity of the non-aqueous electrolyte increases, and good high temperature characteristics are often not obtained.
[0039]
By appropriately selecting each substituent in the general formula (1) or (2), it is possible to synthesize a nonaqueous electrolytic solution having a more suitable viscosity, solubility suitable for mixing, and the like. These phosphazene derivatives may be used alone or in combination of two or more.
[0040]
In the general formula (1), the phosphazene derivative preferably has a substituent containing a halogen element such as chlorine and bromine in addition to the fluorine in the molecular structure. In the method, it is preferable that the molecular structure has a substituent containing a halogen element (such as chlorine or bromine) excluding fluorine. In these cases, the halogen gas derived from the phosphazene derivative can exhibit self-extinguishing properties or flame retardance more effectively even if the content of the phosphazene derivative is small.
In compounds containing a halogen element as a substituent, generation of halogen radicals may be a problem. However, these phosphazene derivatives have stable phosphorus halides because the phosphorus element in the molecular structure promotes halogen radicals. Therefore, such a problem does not occur.
[0041]
The content of the halogen element in these phosphazene derivatives is preferably 2 to 80% by weight, more preferably 2 to 60% by weight, and still more preferably 2 to 50% by weight.
When the content is less than 2% by weight, the effect of containing the halogen element may not be sufficiently exhibited. On the other hand, when the content exceeds 80% by weight, the viscosity increases. Its conductivity may decrease.
[0042]
The flash point of the phosphazene derivative is not particularly limited, but is preferably 100 ° C. or higher and more preferably 150 ° C. or higher from the viewpoint of suppressing ignition.
[0043]
As the addition amount of the additive for non-aqueous electrolyte secondary battery of the present invention, an amount corresponding to a preferable numerical range of the content of the phosphazene derivative in the non-aqueous electrolyte secondary battery of the present invention described later is suitable. . By adjusting the addition amount to a value within the numerical range, the effects of the present invention such as self-extinguishing property or flame retardancy, deterioration resistance, and high temperature characteristics of the non-aqueous electrolyte can be suitably imparted.
[0044]
According to the additive for a non-aqueous electrolyte secondary battery of the present invention described above, by adding to the non-aqueous electrolyte secondary battery, the self-extinguishing property or difficulty is maintained while maintaining the battery characteristics necessary for the battery. Nonaqueous electrolyte secondary that can produce nonaqueous electrolyte secondary batteries with excellent flammability, excellent degradation resistance, low interface resistance of nonaqueous electrolyte, excellent low temperature characteristics, and excellent high temperature characteristics An additive for a battery can be provided.
[0045]
[Nonaqueous electrolyte secondary battery]
The non-aqueous electrolyte secondary battery of the present invention has a positive electrode, a negative electrode, and a non-aqueous electrolyte, and has other members as necessary.
[0046]
-Positive electrode-
The positive electrode material is not particularly limited and can be appropriately selected from known positive electrode materials. For example, V₂O_Five, V₆O₁₃, MnO₂, MoO_ThreeLiCoO₂, LiNiO₂, LiMn₂O_FourMetal oxide such as TiS₂, MoS₂Preferred examples include metal sulfides such as polyaniline, and the like. Among these, LiCoO is preferred because of its high capacity, high safety, and excellent electrolyte wettability.₂, LiNiO₂, LiMn₂O_FourIs particularly preferred. These materials may be used alone or in combination of two or more.
[0047]
There is no restriction | limiting in particular as a shape of the said positive electrode, It can select suitably from well-known shapes as an electrode. For example, a sheet shape, a columnar shape, a plate shape, a spiral shape, and the like can be given.
[0048]
-Negative electrode-
The negative electrode can occlude and release, for example, lithium or lithium ions. Therefore, the material is not particularly limited as long as, for example, lithium or lithium ions can be occluded / released, and can be appropriately selected from known negative electrode materials.
For example, a material containing lithium, specifically, lithium metal itself, an alloy of lithium with aluminum, indium, lead, or zinc, a carbon material such as graphite doped with lithium, etc. are preferably mentioned. Among them, a carbon material such as graphite is preferable in terms of higher safety. These materials may be used alone or in combination of two or more.
There is no restriction | limiting in particular as a shape of the said negative electrode, It can select suitably from the well-known shape similar to the shape of the said positive electrode.
[0049]
-Non-aqueous electrolyte-
The non-aqueous electrolyte contains the non-aqueous electrolyte secondary battery additive of the present invention and a supporting salt, and contains other components as necessary.
[0050]
--Supported salt--
As the supporting salt, for example, a supporting salt serving as an ion source of lithium ions is preferable.
The lithium ion ion source is not particularly limited, but for example, LiClO._Four, LiBF_Four, LiPF₆, LiCF_ThreeSO_ThreeAnd LiAsF₆, LiC4F₉SO_Three, Li (CF_ThreeSO₂)₂N, Li (C₂F_FiveSO₂)₂Preferable examples include lithium salts such as N. These may be used alone or in combination of two or more.
[0051]
As a compounding quantity with respect to the said non-aqueous electrolyte of the said support salt, 0.2-1 mol is preferable with respect to 1 kg of the said non-aqueous electrolyte (solvent component), and 0.5-1 mol is more preferable.
When the blending amount is less than 0.2 mol, sufficient conductivity of the non-aqueous electrolyte cannot be ensured, which may hinder the charge / discharge characteristics of the battery, while exceeding 1 mol. In this case, the viscosity of the non-aqueous electrolyte is increased, and sufficient mobility of the lithium ions and the like cannot be ensured. May interfere with properties.
[0052]
<High temperature characteristics, self-digestibility or flame retardancy, deterioration resistance>
The content of the phosphazene derivative in the non-aqueous electrolyte is a first content that can suitably impart “high temperature characteristics” to the non-aqueous electrolyte due to the effect obtained by containing the phosphazene derivative, A second content that can suitably impart “self-extinguishing” to the water electrolyte, a third content that can suitably impart “flame retardant” to the non-aqueous electrolyte, and a non-aqueous electrolyte There are four possible contents of the fourth content that can suitably impart “deterioration resistance”.
[0053]
From the viewpoint of the “high temperature characteristics”, the first content of the phosphazene derivative in the nonaqueous electrolytic solution is preferably 1 to 70% by volume, more preferably 1 to 50% by volume, and 3 to 30% by volume. Is more preferable.
When the content is outside the numerical range, the high temperature characteristics of the obtained non-aqueous electrolyte secondary battery may not be good.
The “high temperature characteristics” were evaluated by comprehensively evaluating each of the following capacity remaining rate, high temperature discharge characteristics, and safety.
[0054]
<< Measurement and evaluation of remaining capacity >>
The non-aqueous electrolyte secondary battery of the present invention was allowed to stand at 70 ° C. for 10 days, then the capacity of the non-aqueous electrolyte was measured, and the capacity remaining rate was calculated and evaluated in comparison with the capacity before leaving.
<< Measurement and evaluation of high-temperature discharge characteristics >>
The discharge capacity when the non-aqueous electrolyte secondary battery of the present invention was allowed to stand for 10 days at 70 ° C. and then repeatedly charged and discharged up to 50 cycles was compared with the discharge capacity measured before leaving, and the following formula (1 ) To calculate the residual capacity of discharge capacity and evaluate the high temperature discharge characteristics.
Equation (1): discharge capacity remaining rate =
Discharge capacity after standing for 10 days / Discharge capacity before leaving x100 (%)
<< Safety evaluation >>
The non-aqueous electrolyte secondary battery of the present invention is allowed to stand for 10 days at 70 ° C. and visually observed for the presence or absence of rupture / ignition of the battery, and by conducting a charge / discharge test at room temperature, did.
[0055]
From the viewpoint of the “self-extinguishing property”, the second content of the phosphazene derivative in the nonaqueous electrolytic solution is preferably 20% by volume or more, and from the viewpoint of achieving both high self-extinguishing properties and high temperature characteristics. 20-70 volume% is more preferable, 20-50 volume% is still more preferable, and 20-30 volume% is especially preferable.
If the content is less than 20% by volume, sufficient “self-extinguishing” may not be achieved in the non-aqueous electrolyte.
In the present invention, “self-extinguishing” means that in the following “Self-extinguishing evaluation method”, the ignited flame extinguishes in the 25 to 100 mm line, and the fallen object is not ignited. The property which becomes.
[0056]
From the viewpoint of the “flame retardant”, the third content of the phosphazene derivative in the non-aqueous electrolyte is preferably 30% by volume or more, and from the viewpoint of highly achieving both flame retardancy and high temperature characteristics. 30-70 volume% is more preferable, and 30-50 volume% is still more preferable.
When the content is 30% by volume or more, sufficient “flame retardant” can be expressed in the non-aqueous electrolyte.
In the present invention, “flame retardant” means that in the following “flame retardant evaluation method”, the ignited flame does not reach the 25 mm line and the fallen object is not ignited. Refers to nature.
[0057]
<< Self-extinguishing / flame retardant evaluation method >>
The self-extinguishing / flame retardant evaluation was performed by measuring / evaluating the combustion behavior of a flame ignited in an atmospheric environment using a method of arranging UL94HB method of UL (Underwriting Laboratory) standard. At that time, ignitability, combustibility, formation of carbides, and secondary ignition phenomena were also observed. Specifically, based on the UL test standard, 1.0 ml of various electrolytes were impregnated into the nonflammable quartz fiber to prepare a 127 mm × 12.7 mm test piece.
[0058]
From the viewpoint of the “self-extinguishing property or flame retardancy”, the non-aqueous electrolyte includes the phosphazene derivative, LiPF.₆, Ethylene carbonate and / or propylene carbonate, and the phosphazene derivative, LiCF_ThreeSO_ThreeWhen propylene carbonate is contained, it is particularly preferable. In these cases, regardless of the above description, even if the content is small, it has an excellent self-extinguishing or flame-retardant effect. That is, the content of the phosphazene derivative in the non-aqueous electrolyte is preferably 1.5 to 2.5% by volume for exhibiting self-extinguishing properties, and 2.5% for exhibiting flame retardancy. An amount exceeding volume% is preferred. Further, from the viewpoint of achieving both high flame retardancy and high temperature characteristics, it is preferably more than 2.5% by volume and 70% by volume or less, more preferably more than 2.5% by volume and 50% by volume or less. More than 5 volume% and 30 volume% or less are especially preferable.
[0059]
From the viewpoint of the “deterioration resistance”, the fourth content of the phosphazene derivative in the non-aqueous electrolyte is preferably 2% by volume or more, more preferably more than 2.5% by volume, and 3% by volume. % Or more and less than 75% by volume is more preferable, and from the viewpoint of achieving both high resistance to deterioration and high temperature characteristics, the lower limit of any of the numerical ranges of the fourth content is set as the lower limit, and the first content A numerical range in which any upper limit value in the numerical range is set as the upper limit value is preferable.
If the content is within the numerical range, the deterioration can be suitably suppressed.
In the present invention, “deterioration” means decomposition of the supporting salt (for example, lithium salt), and the effect of preventing the deterioration was evaluated by the following “stability evaluation method”.
[0060]
<< Stability Evaluation Method >>
(1) First, after preparing a nonaqueous electrolytic solution containing a supporting salt, the moisture content is measured. Next, the concentration of hydrogen fluoride in the non-aqueous electrolyte is measured by high performance liquid chromatography (ion chromatography). Furthermore, after visually observing the color tone of the non-aqueous electrolyte, the charge / discharge capacity is calculated by a charge / discharge test.
(2) After leaving the non-aqueous electrolyte in a glove box for 2 months, the moisture content and the concentration of hydrogen fluoride were measured again, the color tone was observed, the charge / discharge capacity was calculated, and the numerical value obtained The stability is evaluated by the change of.
[0061]
-Other ingredients-
As the other components, an aprotic organic solvent is particularly preferable.
The aprotic organic solvent is preferably contained in the non-aqueous electrolyte from the viewpoint of safety. That is, if the non-aqueous electrolyte contains an aprotic organic solvent, high safety can be obtained without reacting with the negative electrode material. Moreover, the viscosity of the non-aqueous electrolyte can be lowered, and the optimum ionic conductivity as a non-aqueous electrolyte secondary battery can be easily achieved.
[0062]
The aprotic organic solvent is not particularly limited, and examples thereof include ether compounds and ester compounds from the viewpoint of reducing the viscosity of the nonaqueous electrolytic solution. Specifically, 1,2-dimethoxyethane, tetrahydrofuran, dimethyl carbonate, diethyl carbonate, diphenyl carbonate, ethylene carbonate, propylene carbonate, γ-butyrolactone, γ-valerolactone, methyl ethyl carbonate, and the like are preferable. Among these, cyclic ester compounds such as ethylene carbonate, propylene carbonate, and γ-butyrolactone, and chain ester compounds such as 1,2-dimethoxyethane, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate are preferable. In particular, the cyclic ester compound has a high relative dielectric constant and is excellent in the solubility of lithium salts and the like, and the chain ester compound has a low viscosity, which is preferable in terms of reducing the viscosity of the non-aqueous electrolyte. is there. These may be used individually by 1 type, may use 2 or more types together, but it is suitable to use 2 or more types together.
[0063]
The viscosity of the aprotic organic solvent at 25 ° C. is not particularly limited, but is preferably 10 mPa · s (10 cP) or less, and more preferably 5 mPa · s (5 cP) or less.
[0064]
-Other components-
Examples of the other member include a separator that is interposed between positive and negative electrodes in a non-aqueous electrolyte secondary battery in order to prevent a short circuit of current due to contact between both electrodes.
As the material of the separator, a material that can reliably prevent contact between both electrodes and that can pass or contain an electrolyte, for example, a non-woven fabric made of a synthetic resin such as polytetrafluoroethylene, polypropylene, polyethylene, or a thin layer film Etc. are preferable. Among these, a microporous film made of polypropylene or polyethylene having a thickness of about 20 to 50 μm is particularly suitable.
[0065]
In addition to the separator, examples of the other members include well-known members usually used in batteries.
[0066]
There is no restriction | limiting in particular as a form of the non-aqueous electrolyte secondary battery of this invention, Various well-known forms, such as a coin type, a button type, a paper type, a cylindrical battery of a square type or a spiral structure, are mentioned suitably. .
In the case of the spiral structure, for example, a non-aqueous electrolyte secondary battery can be manufactured by preparing a sheet-like positive electrode, sandwiching a current collector, and stacking and winding up a negative electrode (sheet-like) on the current collector. .
[0067]
Since the non-aqueous electrolyte secondary battery of the present invention described above contains the additive for non-aqueous electrolyte secondary batteries of the present invention, it is excellent in self-extinguishing property or flame retardancy, excellent in deterioration resistance, Non-aqueous electrolyte has low interface resistance, excellent low-temperature characteristics, and excellent high-temperature characteristics.
[0068]
【Example】
EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not limited to the following Example at all.
Example 1
[Preparation of non-aqueous electrolyte]
To 70 ml of a mixed solvent of diethyl carbonate and ethylene carbonate (mixing ratio (volume ratio): diethyl carbonate / ethylene carbonate = 1/1) (aprotic organic solvent), a cyclic phosphazene derivative (in the general formula (2), R^FourIs a phenoxy group and a compound in which n is 3 (additive for non-aqueous electrolyte secondary battery) is added (1% by volume), and LiBF is further added._Four(Supporting salt) was dissolved at a concentration of 0.75 mol / kg to prepare a non-aqueous electrolyte.
[0069]
<Evaluation of self-extinguishing or flame retardancy>
The obtained nonaqueous electrolytic solution was evaluated as described below in the same manner as in the above-mentioned “Self-extinguishing / flame retardant evaluation method”. The results are shown in Table 1.
[0070]
<< Evaluation of flame retardancy >>
The case where the ignited flame did not reach the 25 mm line of the device and the ignition of the fallen object from the net was not recognized as flame retardant.
<< Self-extinguishing evaluation >>
When the ignited flame was extinguished between 25 and 100 mm line, and the ignition was not recognized even for the fallen object from the net dropping, it was evaluated as having self-extinguishing properties.
<< Evaluation of flammability >>
The case where the ignited flame exceeded the 100 mm line was evaluated as combustible.
[0071]
<Evaluation of deterioration>
About the obtained non-aqueous electrolyte, like the above-mentioned “stability evaluation method”, the moisture content (ppm) immediately after preparation of the non-aqueous electrolyte and left in the glove box for 2 months, the hydrogen fluoride concentration ( ppm), charge / discharge capacity (mAh / g) was measured and calculated, and deterioration was evaluated. At this time, the charge / discharge capacity (mAh / g) is obtained by measuring a charge / discharge curve using a positive electrode having a known weight or the above-described negative electrode and dividing the obtained charge amount and discharge amount by the weight of the electrode. Asked. Moreover, the color tone change of the non-aqueous electrolyte was observed visually after the non-aqueous electrolyte was prepared and after being left in the glove box for 2 months. The results are shown in Table 1.
[0072]
[Preparation of non-aqueous electrolyte secondary battery]
Chemical formula LiCoO₂LiCoO is used as a positive electrode active material.₂To 100 parts, 10 parts of acetylene black (conducting aid) and 10 parts of Teflon binder (binder resin) were added and kneaded with an organic solvent (50/50% by volume mixed solvent of ethyl acetate and ethanol). Thereafter, a thin layered positive electrode sheet having a thickness of 100 μm and a width of 40 mm was produced by roll rolling.
Then, using the obtained two positive electrode sheets, a 25 μm thick aluminum foil (current collector) having a conductive adhesive applied on the surface was sandwiched, and a 25 μm thick separator (microporous film: A cylindrical electrode was manufactured by interposing and winding up a lithium metal foil having a thickness of 150 μm with a polypropylene property interposed therebetween. The cylindrical electrode had a positive electrode length of about 260 mm.
[0073]
The non-aqueous electrolyte was injected into the cylindrical electrode and sealed to produce an AA lithium battery.
[0074]
<Measurement and evaluation of battery characteristics>
About the obtained battery, after measuring and evaluating initial battery characteristics (voltage, internal resistance) at 20 ° C., charge / discharge cycle performance was measured and evaluated by the following evaluation method. These results are shown in Table 1.
[0075]
<< Evaluation of charge / discharge cycle performance >>
Charging / discharging was repeated up to 50 cycles under the conditions of an upper limit voltage of 4.5 V, a lower limit voltage of 3.0 V, a discharge current of 100 mA, and a charge current of 50 mA. The charge / discharge capacity at this time was compared with the charge / discharge capacity in the initial stage, and the capacity decrease rate after 50 cycles was calculated. A total of three batteries were measured and calculated in the same manner, and the average value of these was taken to evaluate the charge / discharge cycle performance.
[0076]
<Evaluation of low temperature characteristics (measurement of low temperature discharge capacity)>
The obtained battery was repeatedly charged and discharged up to 50 cycles under the same conditions as in the above “Evaluation of charge / discharge cycle performance” except that the temperature during discharge was low (−10 ° C., −20 ° C.). . The discharge capacity at low temperature at this time was compared with the discharge capacity measured at 20 ° C., and the discharge capacity remaining rate was calculated from the following formula (2). A total of three batteries were measured and calculated in the same manner, and the average of these was taken to evaluate the low temperature characteristics. The results are shown in Table 1.
Equation (2): discharge capacity remaining rate =
Low temperature discharge capacity / discharge capacity (20 ° C) x 100 (%)
[0077]
<Evaluation of high temperature characteristics>
<< Measurement / Evaluation of Capacity Reduction Rate >>
The obtained battery was allowed to stand at 70 ° C. for 10 days, and then the capacity of the non-aqueous electrolyte was measured, and the capacity reduction rate was calculated in comparison with the capacity before standing.
<< Measurement and evaluation of high-temperature discharge characteristics >>
The obtained battery was allowed to stand for 10 days at 70 ° C., and then the discharge capacity when charging / discharging was repeated up to 50 cycles was compared with the discharge capacity measured before leaving, and the discharge capacity was reduced from the above equation (1). The rate was calculated. In the same manner as described above, a total of three batteries were measured and calculated, and the average value of these was taken as the evaluation of the high temperature discharge characteristics.
<< Safety evaluation >>
The obtained battery was allowed to stand at 70 ° C. for 10 days and visually observed for the presence or absence of rupture / ignition of the battery, and a charge / discharge test was conducted at room temperature to evaluate safety.
The above evaluation results are shown in Table 1.
[0078]
(Example 2)
In Example 1 “Preparation of non-aqueous electrolyte”, non-aqueous electrolyte was the same as Example 1 except that the mixed solvent of diethyl carbonate and ethylene carbonate was 80 ml and the cyclic phosphazene derivative was 20 ml (20% by volume). An electrolytic solution was prepared and evaluated for self-extinguishing properties, flame retardancy, and deterioration resistance. In addition, a non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1, and initial battery characteristics (voltage, internal resistance), charge / discharge cycle performance, low temperature characteristics, and high temperature characteristics were measured and evaluated. The results are shown in Table 1.
[0079]
(Example 3)
In Example 1 “Preparation of non-aqueous electrolyte”, non-aqueous electrolyte was the same as Example 1, except that the mixed solvent of diethyl carbonate and ethylene carbonate was 25 ml and the cyclic phosphazene derivative was 75 ml (75% by volume). An electrolytic solution was prepared and evaluated for self-extinguishing properties, flame retardancy, and deterioration resistance. In addition, a non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1, and initial battery characteristics (voltage, internal resistance), charge / discharge cycle performance, low temperature characteristics, and high temperature characteristics were measured and evaluated. The results are shown in Table 1.
[0080]
Example 4
In “Preparation of Nonaqueous Electrolyte” in Example 1, the mixed solvent of diethyl carbonate and ethylene carbonate was 98 ml, the cyclic phosphazene derivative was 2 ml (2% by volume), and the supporting salt was LiPF.₆A nonaqueous electrolytic solution was prepared in the same manner as in Example 1 except that the self-extinguishing property, flame retardancy, and deterioration resistance were evaluated. In addition, a non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1, and initial battery characteristics (voltage, internal resistance), charge / discharge cycle performance, low temperature characteristics, and high temperature characteristics were measured and evaluated. The results are shown in Table 1.
[0081]
(Example 5)
In “Preparation of Nonaqueous Electrolyte” in Example 1, the mixed solvent of diethyl carbonate and ethylene carbonate was changed to 97 ml, the cyclic phosphazene derivative was changed to 3 ml (3% by volume), and the supporting salt was LiPF.₆A nonaqueous electrolyte solution was prepared in the same manner as in Example 1 except that the self-extinguishing property or flame retardancy and deterioration resistance were evaluated in the same manner as in Example 1.
In addition, a non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1, and initial battery characteristics (voltage, internal resistance), charge / discharge cycle performance, low temperature characteristics, and high temperature characteristics were measured and evaluated. The results are shown in Table 1.
[0082]
(Example 6)
In “Preparation of Nonaqueous Electrolyte” in Example 1, a cyclic phosphazene derivative (in the general formula (2), R^FourIs a phenoxy group, and n is 3 (additive for nonaqueous electrolyte secondary battery), a cyclic phosphazene derivative (wherein n is 4 in the general formula (2), R^FourA non-aqueous electrolyte was prepared in the same manner as in Example 1, except that two of them were replaced with a compound (non-aqueous electrolyte secondary battery additive) in which two were phenoxy groups and six were ethoxy groups, In the same manner as in Example 1, self-extinguishing properties or flame resistance properties and deterioration resistance properties were evaluated.
In addition, a non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1, and initial battery characteristics (voltage, internal resistance), charge / discharge cycle performance, low temperature characteristics, and high temperature characteristics were measured and evaluated. The results are shown in Table 1.
[0083]
(Comparative Example 1)
In “Preparation of Nonaqueous Electrolyte” in Example 1, the cyclic phosphazene derivative was converted to a cyclic phosphazene derivative (in the general formula (2), R^FourIs a methoxy group containing chlorine and n is 5 (mixture of compounds having a molar ratio of chlorine to methoxy group (methoxy group / chlorine) of 2/4, 3/3 and 4/2) Other than that, a non-aqueous electrolyte solution was prepared in the same manner as in Example 1, and self-extinguishing property or flame retardancy and deterioration resistance were evaluated in the same manner as in Example 1.
In addition, a non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1, and initial battery characteristics (voltage, internal resistance), charge / discharge cycle performance, low temperature characteristics, and high temperature characteristics were measured and evaluated. The results are shown in Table 1.
[0084]
[Table 1]

[0085]
【Effect of the invention】
According to the present invention, by adding to a non-aqueous electrolyte secondary battery, while maintaining the battery characteristics and the like necessary for the battery, it is excellent in self-extinguishing property or flame retardancy, excellent in deterioration resistance, non-aqueous electrolysis Non-aqueous electrolyte secondary battery additive capable of producing a non-aqueous electrolyte secondary battery having low liquid interface resistance, excellent low-temperature characteristics, and excellent high-temperature characteristics, and the non-aqueous electrolyte secondary battery Non-aqueous electrolyte with excellent self-extinguishing properties or flame retardancy, excellent deterioration resistance, low non-aqueous electrolyte interface resistance, low-temperature characteristics, and high-temperature characteristics A secondary battery can be provided.

Claims (10)

A non-aqueous electrolyte secondary battery additive comprising at least a cyclic phosphazene derivative represented by the following general formula (2).
General formula (2)
(PNR ⁴ ₂ ) _n
However, in the general formula (2), R ⁴ represents an ethoxy group or phenoxy group. At least one of all R ⁴ in the general formula (2) includes a phenoxy group . n is 3-4. 2. The additive for a non-aqueous electrolyte secondary battery according to claim 1, wherein in the cyclic phosphazene derivative, all R ⁴ in the general formula (2) are phenoxy groups and n is 3. 3. 2. The non-aqueous electrolyte secondary battery according to claim 1, wherein the cyclic phosphazene derivative has n of 4 in the general formula (2), 2 out of all R ⁴ are phenoxy groups and 6 are ethoxy groups. Additives.   A non-aqueous electrolyte comprising: a positive electrode; a negative electrode; a supporting salt; and a non-aqueous electrolyte containing the additive for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 3. Electrolyte secondary battery.   The non-aqueous electrolyte secondary battery according to claim 4, wherein the content of the cyclic phosphazene derivative in the non-aqueous electrolyte is 2% by volume or more and 30% by volume or less.   5. The non-aqueous electrolyte secondary battery according to claim 4, wherein the content of the cyclic phosphazene derivative in the non-aqueous electrolyte is more than 2.5 volume% and 30 volume% or less.   The nonaqueous electrolyte secondary battery according to claim 4, wherein the nonaqueous electrolyte contains an aprotic organic solvent.   The non-aqueous electrolyte secondary battery according to claim 7, wherein the aprotic organic solvent contains a cyclic or chain ester compound. The non-aqueous electrolyte secondary battery according to claim 7, wherein the non-aqueous electrolyte contains LiPF ₆ as a supporting salt and ethylene carbonate and / or propylene carbonate as an aprotic organic solvent. The nonaqueous electrolyte secondary battery according to claim 7, wherein the nonaqueous electrolyte contains LiCF ₃ SO ₃ as a supporting salt and propylene carbonate as an aprotic organic solvent.