JPWO2004023589A1 - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

According to the present invention, there is provided a non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode containing a carbonaceous material capable of occluding and releasing lithium ions, and a non-aqueous electrolyte containing a non-aqueous solvent, And a sultone compound having at least one double bond in the ring, and the carbonaceous material has a specific surface area of 1.5 m 2 / g or more and 10 m 2 / g or less by BET method, and 0.336 nm in powder X-ray diffraction measurement. Peaks derived from the following interplanar spacing d002 appear, and peaks are detected at diffraction angles 2θ of 42.8 ° to 44.0 ° and 45.5 ° to 46.6 ° in X-ray diffraction measurement using CuKα rays, In addition, a non-aqueous electrolyte secondary battery including a graphite material having an R value measured by Raman spectrum of 0.3 or more in terms of intensity ratio and 1 or more in terms of area ratio is provided.

Description

  The present invention relates to a non-aqueous electrolyte secondary battery.

In recent years, electronic devices such as mobile communication devices, notebook computers, palmtop computers, integrated video cameras, portable CD (MD) players, cordless telephones, etc. have been reduced in size and weight. As a power source, a battery having a small size and a large capacity is particularly demanded.
Examples of batteries that are widely used as power sources for these electronic devices include primary batteries such as alkaline manganese batteries, and secondary batteries such as nickel cadmium batteries and lead storage batteries. Among them, the non-aqueous electrolyte secondary battery using a lithium composite oxide for the positive electrode and a carbonaceous material capable of occluding and releasing lithium ions for the negative electrode is small and light, has a high unit cell voltage, and has a high energy density. Has been attracting attention.
In the negative electrode, lithium or a lithium alloy can be used instead of the carbonaceous material. However, in that case, by repeating the charging / discharging operation of the secondary battery, lithium dissolution / deposition is repeated, so that a so-called dendrite that grows in a needle shape is formed, and the dendrite penetrates through the separator. There are problems such as the possibility of short circuit. On the other hand, in a negative electrode containing a carbonaceous material, dendrite formation is less likely to occur than in a negative electrode containing lithium or a lithium alloy. Further, by using a graphite material, the negative electrode capacity can be brought close to the theoretical capacity of 372 mAh / g, and a high-capacity lithium ion secondary battery can be realized. However, graphite materials are highly active against many of the non-aqueous electrolytes used in lithium ion secondary batteries, and cause decomposition of the non-aqueous electrolytes along with desorption due to peeling of the materials themselves. There is a problem that discharge efficiency, discharge capacity, and cycle characteristics are lowered.

An object of the present invention is to provide a nonaqueous electrolyte secondary battery that simultaneously satisfies initial charge / discharge efficiency, discharge capacity, and cycle characteristics.
According to the present invention, a nonaqueous electrolyte secondary battery comprising a positive electrode, a negative electrode including a carbonaceous material capable of occluding and releasing lithium ions, and a nonaqueous electrolyte including a nonaqueous solvent,
The non-aqueous solvent contains a sultone compound having at least one double bond in the ring,
The carbonaceous material has a specific surface area by the BET method of 1.5 m ² / g or more and 10 m ² / g or less, and a peak derived from an interplanar spacing d ₀₀₂ of 0.336 nm or less appears in a powder X-ray diffraction measurement. In the X-ray diffraction measurement using this, peaks are detected at diffraction angles 2θ of 42.8 ° to 44.0 ° and 45.5 ° to 46.6 °, and the R value by Raman spectrum measurement is 0.3 in terms of intensity ratio. As described above, a nonaqueous electrolyte secondary battery including a graphite material having an area ratio of 1 or more is provided.
Further, according to the present invention, there is provided a nonaqueous electrolyte secondary battery comprising a positive electrode, a negative electrode including a carbonaceous material capable of occluding and releasing lithium ions, and a nonaqueous electrolyte including a nonaqueous solvent,
The non-aqueous solvent contains a sultone compound having at least one double bond in the ring,
The carbonaceous material has a specific surface area measured by the BET method of 1.5 m ² / g or more and 10 m ² / g or less, and a peak derived from an interplanar spacing d ₀₀₂ of 0.336 nm or less appears in powder X-ray diffraction measurement. Provided is a nonaqueous electrolyte secondary battery including a graphite material having a crystal structure and having an R value by an intensity ratio of 0.3 or more and an area ratio of 1 or more by Raman spectrum measurement.

FIG. 1 is a perspective view showing a thin nonaqueous electrolyte secondary battery which is an example of a nonaqueous electrolyte secondary battery according to the present invention.
FIG. 2 is a partial cross-sectional view of the thin nonaqueous electrolyte secondary battery of FIG. 1 cut along the line II-II.
FIG. 3 is a partial cross-sectional view showing a cylindrical nonaqueous electrolyte secondary battery which is an example of the nonaqueous electrolyte secondary battery according to the present invention.
4 is a schematic diagram showing a diffraction pattern obtained by X-ray diffraction measurement using CuKα rays for the graphite material of the nonaqueous electrolyte secondary battery of Example 1. FIG.
FIG. 5 is a characteristic diagram showing a ¹ HNMR spectrum of PRS contained in the nonaqueous electrolyte of the nonaqueous electrolyte secondary battery of Example 1.

化１において、Ｃ_ｍＨ_ｎは直鎖状の炭化水素基で、ｍとｎは、２ｍ＞ｎを満たす２以上の整数である。
環内に二重結合を有するスルトン化合物は、負極との還元反応の際に二重結合が開いて重合反応が起こり、ガス発生を伴うことなく負極表面に緻密な保護皮膜を形成することができる。この際、ＥＣ及びＰＣが存在していると、リチウムイオン透過性に優れる緻密な保護被膜を形成することができる。
スルトン化合物の中でも好ましいのは、スルトン化合物Ａのうちｍ＝３、ｎ＝４である化合物、即ち１，３−プロペンスルトン（ＰＲＳ）、または、ｍ＝４、ｎ＝６である化合物、即ち１，４−ブチレンスルトン（ＢＴＳ）である。これら化合物に由来する保護被膜は、黒鉛質材料中のＬｉ^＋と非水電解質との接触による副反応を抑制する効果が最も高いからである。スルトン化合物としては、１，３−プロペンスルトン（ＰＲＳ）あるいは１，４−ブチレンスルトン（ＢＴＳ）を単独で用いても、これらＰＲＳとＢＴＳを併用しても良い。
スルトン化合物の比率は、１０重量％以下にすることが望ましい。これは、スルトン化合物の比率が１０重量％を超えると、保護被膜のリチウムイオン透過性が低下して負極のインピーダンスが増大し、充分な容量や充放電効率を得られない可能性がある。更に、電極の設計容量を維持し、初期充放電効率を高く保つためには、スルトン化合物の割合は４重量％以下であることが望ましい。また、保護被膜の形成量を十分に確保するためには、スルトン化合物の比率を最低でも０．０１重量％確保することが望ましい。更に、スルトン化合物の比率が０．１重量％以上あれば、保護被膜による初充電時のガス発生を抑制するなどの保護機能を充分なものにすることができる。
非水溶媒中には、スルトン化合物の他に、他の溶媒を含有させることが好ましい。他の溶媒としては、例えば、エチレンカーボネート（ＥＣ）やプロピレンカーボネート（ＰＣ）のような環状カーボネート、鎖状カーボネート｛例えば、メチルエチルカーボネート（ＭＥＣ）、ジエチルカーボネート（ＤＥＣ）、ジメチルカーボネート（ＤＭＣ）｝、γ−ブチロラクトン（ＧＢＬ）、ビニレンカーボネート（ＶＣ）、ビニルエチレンカーボネート（ＶＥＣ）、フェニルエチレンカーボネート（ｐｈＥＣ）、γ−バレロラクトン（ＶＬ）、プロピオン酸メチル（ＭＰ）、プロピオン酸エチル（ＥＰ）、２−メチルフラン（２Ｍｅ−Ｆ）、フラン（Ｆ）、チオフェン（ＴＩＯＰ）、カテコールカーボネート（ＣＡＴＣ）、エチレンサルファイト（ＥＳ）、１２−クラウン−４（Ｃｒｏｗｎ）、テトラエチレングリコールジメチルエーテル（Ｅｔｈｅｒ）等を挙げることができる。他の溶媒の種類は、１種類または２種類以上にすることができる。
中でも、ビニレンカーボネートは、炭素質物のリチウムイオン透過性を大きく低下させずに、保護皮膜の緻密性を高めることができるため、初期充放電効率と放電容量とサイクル寿命とをさらに向上することができる。
非水溶媒中のビニレンカーボネートの重量比率は、１０重量％以下の範囲内にすることが望ましい。これは、ビニレンカーボネートの重量比率を１０重量％よりも多くすると、負極表面の保護皮膜のリチウムイオン透過性が低下するため、初期充放電効率、放電容量またはサイクル寿命が大幅に損なわれる可能性があるからである。ビニレンカーボネートの重量比率のさらに好ましい範囲は、０．０１〜５重量％である。
非水溶媒の好ましい組成としては、（Ｉ）環状カーボネートと、γ−ブチロラクトン（ＧＢＬ）と、スルトン化合物とを含む非水溶媒、（ＩＩ）ＥＣと、少なくともＭＥＣを含む鎖状カーボネートと、スルトン化合物とを含む非水溶媒、（ＩＩＩ）少なくともＥＣ及びＰＣを含む環状カーボネートと、スルトン化合物と、ＧＢＬとを含む非水溶媒、（ＩＶ）少なくともＥＣ及びＰＣを含む環状カーボネートと、スルトン化合物とを含む非水溶媒等を挙げることができる。
非水溶媒（Ｉ）の環状カーボネートには、ＥＣが含まれていることが好ましく、ＥＣと併せてＰＣが含有されているとなお好ましい。非水溶媒（Ｉ）によると、二次電池の高温貯蔵特性とサイクル寿命をさらに向上することができる。この非水溶媒（Ｉ）にさらにビニレンカーボネート（ＶＣ）を添加すると、二次電池の低温放電特性も改善することができる。
非水溶媒（ＩＩ）の鎖状カーボネートには、メチルエチルカーボネート（ＭＥＣ）が必須成分として含まれ、ＭＥＣのみを鎖状カーボネートとして用いても、ＭＥＣに他の鎖状カーボネートを併用しても良い。非水溶媒（ＩＩ）によると、初充電時のガス発生を抑制することができると共に、低温放電特性とサイクル寿命を向上することができる。
ＭＥＣと併用する他の鎖状カーボネートは凝固点が低く、かつ粘度の低いものが望ましい。さらに、分子量の比較的小さい溶媒が望ましい。これは低温での放電特性が良好になるためである。他の鎖状カーボネートとしては、ジエチルカーボネート（ＤＥＣ）及びジメチルカーボネート（ＤＭＣ）のうちの少なくとも一方が好ましい。特に、優れた充放電サイクル特性を得る観点からは、ＭＥＣとＤＥＣを含む鎖状カーボートが好ましく、一方、優れた低温放電特性を得る観点からは、ＭＥＣとＤＭＣを含む鎖状カーボネートが望ましい。
非水溶媒（ＩＩ）にさらにビニレンカーボネート（ＶＣ）を添加すると、二次電池のサイクル寿命をさらに改善することができる。
非水溶媒（ＩＩＩ）は、二次電池の初充電時のガス発生量を少なくすることができ、同時に、高温貯蔵特性を向上することができる。非水溶媒（ＩＩ）にさらにビニレンカーボネート（ＶＣ）を添加すると、二次電池の高温貯蔵特性をさらに改善することができる。
非水溶媒（ＩＶ）は、初充電時のガス発生量を抑制することができると共に、初充放電効率を向上することができる。非水溶媒（ＩＶ）にさらにビニレンカーボネート（ＶＣ）を添加すると、初充放電効率をさらに向上することができる。
非水溶媒に溶解される電解質としては、例えば、過塩素酸リチウム（ＬｉＣｌＯ_４）、六フッ化リン酸リチウム（ＬｉＰＦ_６）、四フッ化ホウ酸リチウム（ＬｉＢＦ_４）、六フッ化砒素リチウム（ＬｉＡｓＦ_６）、トリフルオロメタスルホン酸リチウム（ＬｉＣＦ_３ＳＯ_３）、ビストリフルオロメチルスルホニルイミドリチウム［（ＬｉＮ（ＣＦ_３ＳＯ_２）_２］、ＬｉＮ（Ｃ_２Ｆ_５ＳＯ_２）_２などのリチウム塩を挙げることができる。使用する電解質の種類は、１種類または２種類以上にすることができる。
中でも、ＬｉＰＦ_６あるいはＬｉＢＦ_４を含むものが好ましい。また、（ＬｉＮ（ＣＦ_３ＳＯ_２）_２およびＬｉＮ（Ｃ_２Ｆ_５ＳＯ_２）_２のうち少なくとも一方からなるイミド塩と、ＬｉＢＦ_４及びＬｉＰＦ_６のうち少なくともいずれか一方からなる塩とを含有する混合塩Ａか、あるいはＬｉＢＦ_４及びＬｉＰＦ_６を含有する混合塩Ｂを用いると、高温でのサイクル寿命をより向上することができる。また、電解質の熱安定性が向上されるため、高温環境下で貯蔵時の自己放電による電圧低下を抑えることができる。
前記電解質の前記非水溶媒に対する溶解量は、０．５〜２．５モル／Ｌとすることが望ましい。さらに好ましい範囲は、１〜２．５モル／Ｌである。
前記液状非水電解質には、セパレータとの濡れ性を良くするために、トリオクチルフォスフェート（ＴＯＰ）のような界面活性剤を含有させることが望ましい。界面活性剤の添加量は、３％以下が好ましく、さらには０．１〜１％の範囲内にすることが好ましい。
前記液状非水電解質の量は、電池単位容量１００ｍＡｈ当たり０．２〜０．６ｇにすることが好ましい。液状非水電解質量のより好ましい範囲は、０．２５〜０．５５ｇ／１００ｍＡｈである。
６）容器（収納容器）
容器の形状は、例えば、有底円筒形、有底矩形筒型、袋状、カップ状等にすることができる。
この容器は、例えば、樹脂層を含むシート、金属板、金属フィルム等から形成することができる。
前記シートに含まれる樹脂層は、例えば、ポリオレフィン、ポリアミド類から構成することができる。
前記金属板及び前記金属フィルムは、例えば、鉄、ステンレス、アルミニウムから形成することができる。
容器の厚さ（容器の壁の厚さ）は、０．３ｍｍ以下にすることが望ましい。これは、厚さが０．３ｍｍより厚いと、高い重量エネルギー密度及び体積エネルギー密度を得られ難くなるからである。容器の厚さの好ましい範囲は、０．２５ｍｍ以下で、更に好ましい範囲は０．１５ｍｍ以下で、最も好ましい範囲は０．１２ｍｍ以下である。また、厚さが０．０５ｍｍより薄いと、変形や破損し易くなることから、容器の厚さの下限値は０．０５ｍｍにすることが好ましい。
本発明に係る非水電解質二次電池の一例である薄型リチウムイオン二次電池と円筒型リチウムイオン二次電池を図１〜図３を参照して詳細に説明する。
図１は、本発明に係わる非水電解質二次電池の一例である薄型リチウムイオン二次電池を示す斜視図、図２は図１の非水電解質二次電池の要部拡大断面図で、図３は本発明に係る非水電解質二次電池の一例である円筒形非水電解質二次電池を示す部分切欠斜視図である。
まず、薄型リチウムイオン二次電池を図１，２を参照して説明する。
図１に示すように、長箱型のカップ状をなす容器本体１内には、電極群２が収納されている。電極群２は、正極３と、負極４と、正極３と負極４の間に配置されるセパレータ５を含む積層物が偏平形状に捲回された構造を有する。非水電解質は、電極群２に保持されている。容器本体１の縁の一部は幅広になっており、蓋板６として機能する。容器本体１と蓋板６は、それぞれ、ラミネートフィルムから構成される。このラミネートフィルムは、外部保護層７と、熱可塑性樹脂を含有する内部保護層８と、外部保護層７と内部保護層８の間に配置される金属層９とを含む。容器本体１には蓋体６が内部保護層８の熱可塑性樹脂を用いてヒートシールによって固定され、それにより容器内に電極群２が密封される。正極３には正極タブ１０が接続され、負極４には負極タブ１１が接続され、それぞれ容器の外部に引き出されて、正極端子及び負極端子の役割を果たす。
次いで、円筒形リチウムイオン二次電池を図３を参照して説明する。
ステンレスからなる有底円筒状の容器２１は、底部に絶縁体２２が配置されている。電極群２３は、前記容器２１に収納されている。前記電極群２３は、正極２４、セパレータ２５、負極２６及びセパレータ２５を積層した帯状物を前記セパレータ２５が外側に位置するように渦巻き状に捲回した構造になっている。
前記容器２１内には、非水電解液が収容されている。中央部が開口された絶縁紙２７は、前記容器２１内の前記電極群２３の上方に配置されている。絶縁封口板２８は、前記容器２１の上部開口部に配置され、かつ前記上部開口部付近を内側にかしめ加工することにより前記封口板２８は前記容器２１に固定されている。正極端子２９は、前記絶縁封口板２８の中央に嵌合されている。正極リード３０の一端は、前記正極２４に、他端は前記正極端子２９にそれぞれ接続されている。前記負極２６は、図示しない負極リードを介して負極端子である前記容器２１に接続されている。
以上説明した本発明に係る非水電解質二次電池は、正極と、リチウムイオンを吸蔵・放出可能な炭素質物を含む負極と、非水溶媒を含む非水電解質とを具備した非水電解質二次電池であり、
前記非水溶媒は、環内に少なくとも一つの二重結合を有するスルトン化合物を含み、かつ前記炭素質物のＢＥＴ法による比表面積は、１．５ｍ^２／ｇ以上、１０ｍ^２／ｇ以下の範囲内であることを特徴とするものである。
このように比表面積の大きな炭素質物を用いることによって、前記スルトン化合物の反応性を最適化することができるため、初充放電効率、放電容量及びサイクル寿命を同時に満足する二次電池を実現することができる。
この炭素質物のうち、粉末Ｘ線回折測定において０．３３６ｎｍ以下の面間隔ｄ_００２に由来するピークが現れるか、もしくは、ＣｕＫα線を用いるＸ線回折測定において回折角２θが４２．８°〜４４．０°と４５．５°〜４６．６°にピークが現れるものは、スルトン化合物の分解反応を促進することができるため、共存する溶媒との副反応を抑えつつ、保護皮膜を形成することができる。従って、二次電池の初充放電効率と放電容量をさらに向上することができる。
また、炭素質物のラマンスペクトル測定によるＲ値を強度比で０．３以上、面積比で１．０以上にすることによって、スルトン化合物以外の溶媒（特にプロピレンカーボネート）の分解反応を抑えることができるため、二次電池の初充放電効率をさらに向上することができる。
特に、前記炭素質物として、比表面積が１．５ｍ^２／ｇ以上１０ｍ^２／ｇ以下で、粉末Ｘ線回折測定において０．３３６ｎｍ以下の面間隔ｄ_００２に由来するピークが現れ、ラマンスペクトル測定によるＲ値が強度比で０．３以上かつ面積比で１以上で、さらにＣｕＫα線を用いるＸ線回折測定において回折角２θが４２．８°〜４４．０°と４５．５°〜４６．６°にピークが検出されるあるいは菱面体晶系構造を持つ黒鉛質材料を用いることによって、二次電池の充放電サイクル寿命をさらに向上することができる。
すなわち、面間隔、比表面積及びＲ値が前述した範囲で、かつ前述した回折ピークまたは菱面体晶系構造を有する黒鉛質材料は、スルトン化合物と優先的に反応して負極表面にリチウムイオン透過性を損なうことなく保護皮膜を均一に形成することができる。スルトン化合物との反応が優先的に生じることと初充電時から緻密な保護皮膜が形成されることから、ＰＣのような環状カーボネートの分解反応を抑えることができ、初充電時のガス発生量を少なくすることができる。その結果、初充放電効率を高くすることができるため、放電容量と充放電サイクル寿命をさらに向上することができる。
以下、本発明の実施例を前述した図面を参照して詳細に説明する。Hereinafter, an example of the nonaqueous electrolyte secondary battery according to the present invention will be described.
The non-aqueous electrolyte secondary battery includes a container, an electrode group that is housed in the container and includes a positive electrode and a negative electrode, and a non-aqueous electrolyte that is held in the electrode group and includes a non-aqueous solvent. .
The non-aqueous solvent contains a sultone compound having at least one double bond in the ring, and the specific surface area of the carbonaceous material by the BET method is 1.5 m. ² / G or more, 10m ² / G or less.
A sultone compound having at least one double bond in the ring can form a protective film on the surface of the carbonaceous material. As in the present invention, the specific surface area of the carbonaceous material by the BET method is 1.5 m. ² / G or more, 10m ² / G or less can increase the uniformity of the distribution of the protective film formed on the surface of the carbonaceous material, and suppress the protective film from inhibiting the lithium intercalation reaction related to charge / discharge. Therefore, it is possible to provide a non-aqueous electrolyte secondary battery that simultaneously satisfies initial charge / discharge efficiency, discharge capacity, and cycle characteristics.
Hereinafter, the electrode group, the positive electrode, the negative electrode, the separator, the nonaqueous electrolyte, and the container will be described.
1) Electrode group
For example, (i) the positive electrode and the negative electrode are wound in a flat shape or a spiral shape with a separator interposed therebetween, or (ii) the positive electrode and the negative electrode are wound in a spiral shape with a separator interposed therebetween. Rotating and then compressing in the radial direction, or (iii) bending the positive electrode and negative electrode one or more times with a separator between them, or (iv) laminating the positive electrode and negative electrode with a separator interposed therebetween It is produced by.
The electrode group need not be pressed, but may be pressed to increase the integrated strength of the positive electrode, the negative electrode, and the separator. It is also possible to heat at the time of pressing.
2) Positive electrode
The positive electrode includes a current collector and a positive electrode layer that is supported on one or both sides of the current collector and includes an active material.
The positive electrode layer includes a positive electrode active material, a binder, and a conductive agent.
Examples of the positive electrode active material include various oxides such as manganese dioxide, lithium manganese composite oxide, lithium-containing nickel oxide, lithium-containing cobalt oxide, lithium-containing nickel cobalt oxide, lithium-containing iron oxide, and lithium. Examples thereof include vanadium oxide and chalcogen compounds such as titanium disulfide and molybdenum disulfide. Among them, lithium-containing cobalt oxide (for example, LiCoO ₂ ), Lithium-containing nickel cobalt oxide (eg, LiNi _0.8 Co _0.2 O ₂ ), Lithium manganese composite oxide (for example, LiMn ₂ O ₄ LiMnO ₂ ) Is preferable because a high voltage can be obtained. As the positive electrode active material, one kind of oxide may be used alone, or two or more kinds of oxides may be mixed and used.
Examples of the conductive agent include acetylene black, carbon black, and graphite.
The binder has a function of holding the active material on the current collector and connecting the active materials to each other. Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), polyethersulfone, ethylene-propylene-diene copolymer (EPDM), and styrene-butadiene rubber (SBR). be able to.
The blending ratio of the positive electrode active material, the conductive agent and the binder is preferably in the range of 80 to 95% by weight of the positive electrode active material, 3 to 20% by weight of the conductive agent, and 2 to 7% by weight of the binder.
As the current collector, a conductive substrate having a porous structure or a non-porous conductive substrate can be used. These conductive substrates can be formed from, for example, aluminum, stainless steel, or nickel.
The positive electrode is produced, for example, by suspending a conductive agent and a binder in an appropriate solvent in a positive electrode active material, applying the suspension to a current collector, drying it, and applying a press.
3) Negative electrode
The negative electrode includes a current collector and a negative electrode layer carried on one side or both sides of the current collector.
The negative electrode layer includes a carbonaceous material that occludes / releases lithium ions and a binder.
The specific surface area of the carbonaceous material by the BET method is 1.5 m. ² / G or more, 10m ² / G or less. That is, the specific surface area is 1.5 m. ² If it is less than / g, since the protective film derived from the sultone compound acts as a resistance component against the lithium intercalation reaction, the discharge capacity of the secondary battery decreases. On the other hand, the specific surface area is 10 m ² If it exceeds / g, the uniformity of the distribution of the protective film is lowered, so that the initial charge / discharge efficiency, discharge capacity, and charge / discharge cycle life of the secondary battery are lowered. Specific surface area of 1.5-10m ² Since the protective film made of the cyclic sultone compound can be made uniform and thin by making it within the range of / g, lithium intercalation while suppressing side reactions due to contact between the nonaqueous electrolyte and the negative electrode active material Can be performed efficiently. A more preferable range of the specific surface area is 1.5 to 10 m. ² / G, and a more preferable range is 1.5 to 6 m. ² / G.
The carbonaceous material has an interplanar spacing d of 0.336 nm or less in powder X-ray diffraction measurement. ₀₀₂ It is preferable that a peak derived from is appeared. That is, the interplanar spacing d of 0.336 nm or less in powder X-ray diffraction measurement ₀₀₂ According to the carbonaceous material in which the peak derived from is not detected, the decomposition reaction of the non-aqueous solvent other than the sultone compound occurs, which may reduce the discharge capacity or the cycle life. Interplanar spacing d of 0.336 nm or less in powder X-ray diffraction measurement ₀₀₂ The carbonaceous material in which the peak derived from the sultone compound can narrow the decomposition potential width of the sultone compound, so that the sultone compound can be selectively decomposed during the initial charge to form a protective film and protected by the sultone compound. The film formation reaction rate can be increased. As a result, the charge / discharge cycle life of the secondary battery can be further improved. Also, the surface spacing d ₀₀₂ Is the interplanar spacing d of the (002) plane in a perfect graphite crystal. ₀₀₂ That is, it is preferable to set it to 0.3354 nm. The carbonaceous material has a surface spacing d exceeding 0.336 nm. ₀₀₂ A peak derived from may be detected.
The carbonaceous material desirably has peaks detected at diffraction angles 2θ of 42.8 ° to 44.0 ° and 45.5 ° to 46.6 ° in X-ray diffraction measurement using CuKα rays. Since such a carbonaceous material has a rhombohedral structure, the decomposition potential width of the sultone compound can be narrowed, and the decomposition reaction of other solvents other than the sultone compound can be suppressed. The cycle life of the secondary battery can be further improved. In particular, it has a rhombohedral structure and has an interplanar spacing d of 0.336 nm or less in powder X-ray diffraction measurement. ₀₀₂ The carbonaceous material in which the peak derived from the carbonaceous material can increase the effect of promoting the formation of a protective film derived from the sultone compound and the effect of suppressing the decomposition reaction of the non-aqueous solvent other than the sultone compound. The initial charge / discharge efficiency and discharge capacity of the battery can be further improved.
(A) Interplanar spacing d of 0.336 nm or less in powder X-ray diffraction measurement ₀₀₂ As a carbonaceous material in which a peak derived from (b) has a rhombohedral structure, or satisfies both conditions (a) and (b), for example, (a) and (b) Natural graphite that satisfies at least one of the conditions can be used. Such carbonaceous materials are, for example, subjected to heat treatment at 2800 to 3000 ° C. on coke, pitch, thermosetting resin or the like, or added with coke, pitch, thermosetting resin, etc. to natural graphite. It can be obtained by heat treatment.
The carbonaceous material desirably has an R value by Raman spectrum measurement of 0.3 or more in intensity ratio and 1 or more in area ratio. Such a carbonaceous material can make part or all of the surface a low crystalline structure while maintaining the specific surface area and the internal graphite structure. As a result, since the decomposition reaction of propylene carbonate (PC) can be suppressed, the initial charge / discharge efficiency when using a non-aqueous solvent containing PC can be improved, and both the discharge capacity and the cycle life are excellent. A secondary battery can be realized. Further, when the strength ratio is larger than 1.5 and the area ratio is larger than 4.0, the ratio of the low crystalline structure region in the carbonaceous material is increased, so that the decomposition reaction of the solvent other than the sultone compound is promoted. There is a risk. Therefore, it is desirable to set the upper limit of the intensity ratio to 1.5 and the upper limit of the area ratio to 4.0. A more preferable range of the intensity ratio is 0.3 to 1.5, and a more preferable range of the area ratio is 1.0 to 3.0.
A carbonaceous material having an R value by Raman spectrum measurement of 0.3 or more in intensity ratio and 1 or more in area ratio is produced, for example, by the method described below. That is, carbonaceous material such as coke, pitch, thermosetting resin, or carbon precursor is mixed with natural graphite in liquid form or pulverized and then molded into a graphite material, and then 2500 ° C. or less in an inert atmosphere. It can be obtained by heat treatment at a temperature of Further, a material obtained by performing chemical vapor deposition using benzene, toluene or the like as a graphite material and depositing a carbon layer having low crystallinity on the surface may be used.
Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), ethylene-propylene-diene copolymer (EPDM), styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), and the like. Can be used.
The blending ratio of the carbonaceous material and the binder is preferably in the range of 90 to 98% by weight of the carbonaceous material and 2 to 20% by weight of the binder.
As the current collector, a conductive substrate having a porous structure or a non-porous conductive substrate can be used. These conductive substrates can be formed from, for example, copper, stainless steel, or nickel.
The negative electrode is, for example, kneaded with a carbonaceous material that occludes / releases lithium ions and a binder in the presence of a solvent, and the resulting suspension is applied to a current collector and dried, followed by a desired pressure. It is produced by pressing once or multistage pressing 2-5 times.
4) Separator
As this separator, a microporous film, a woven fabric, a non-woven fabric, a laminate of the same material or different materials among these can be used. Examples of the material for forming the separator include polyethylene, polypropylene, ethylene-propylene copolymer, and ethylene-butene copolymer. As a material for forming the separator, one type or two or more types selected from the types described above can be used.
The thickness of the separator is preferably 30 μm or less, and more preferably 25 μm or less. Moreover, it is preferable that the lower limit of thickness is 5 micrometers, and a more preferable lower limit is 8 micrometers.
The separator preferably has a heat shrinkage rate of 20% or less at 120 ° C. for 1 hour. The heat shrinkage rate is more preferably 15% or less.
The separator preferably has a porosity in the range of 30 to 60%. A more preferable range of the porosity is 35 to 50%.
The separator has an air permeability of 600 seconds / 100 cm. ³ The following is preferable. Air permeability is 100cm ³ Means the time (seconds) required for the air to pass through the separator. The upper limit of air permeability is 500 seconds / 100cm ³ More preferably. The lower limit of the air permeability is 50 seconds / 100 cm. ³ The lower limit is more preferably 80 seconds / 100 cm. ³ It is.
The width of the separator is desirably wider than the width of the positive electrode and the negative electrode. By adopting such a configuration, it is possible to prevent the positive electrode and the negative electrode from coming into direct contact without a separator.
5) Non-aqueous electrolyte
As the non-aqueous electrolyte, one having a substantially liquid or gel-like form can be used. The gel-like non-aqueous electrolyte can reduce the risk of the non-aqueous electrolyte leaking to the outside when the container is damaged by some external force. On the other hand, the liquid non-aqueous electrolyte can have higher ionic conductivity than the gel non-aqueous electrolyte, so the capacity when the non-aqueous electrolyte secondary battery is discharged with a large current and the capacity when discharged at a low temperature. Capacity can be improved.
The nonaqueous electrolyte is prepared, for example, by the method described in (I) to (VI) below.
(I) A nonaqueous electrolyte is obtained by dissolving an electrolyte (for example, a lithium salt) in the nonaqueous solvent described above (liquid nonaqueous electrolyte).
(II) An organic polymer compound and a lithium salt are dissolved in a solvent to prepare a polymer solution. Next, this polymer solution is applied or impregnated into an electrode (at least one of a positive electrode and a negative electrode), a separator, or both an electrode and a separator, and the solvent is evaporated to cast. Next, an electrode group is obtained by interposing a separator between the positive electrode and the negative electrode. This is accommodated in a container, and a non-aqueous electrolyte is injected and held in a cast polymer film to obtain a secondary battery including a gel-like non-aqueous electrolyte.
(III) In the method (II) described above, a crosslinked polymer may be used instead of the organic polymer compound. For example, (a) a prepolymer solution is prepared from a compound having a crosslinkable functional group, a lithium salt, and a solvent, and this is used as an electrode (at least one of a positive electrode and a negative electrode), a separator, or an electrode and a separator. After applying or impregnating both, the compound having a crosslinkable functional group is crosslinked. Next, an electrode group is obtained by interposing a separator between the positive electrode and the negative electrode. The crosslinking step may be performed before or after the solvent is volatilized, and may be crosslinked while the solvent is volatilized in the case of crosslinking by heating. Alternatively, (b) after applying or impregnating the prepolymer solution to the electrode (at least one of the positive electrode and the negative electrode), the separator, or both of the electrode and the separator, the positive electrode and the negative electrode are interposed between them. An electrode group is obtained. Thereafter, a crosslinking step can be performed.
The method for crosslinking is not particularly limited, but heat polymerization or photopolymerization with ultraviolet rays is preferable from the viewpoint of simplicity of the apparatus and cost. When crosslinking is performed by heating or ultraviolet irradiation, it is necessary to add a polymerization initiator suitable for the polymerization method to the prepolymer solution. Moreover, a polymerization initiator is not restricted to one type, You may mix and use 2 or more types.
(IV) An organic polymer compound and a lithium salt are directly dissolved in a nonaqueous electrolytic solution to obtain a gel electrolyte. This gel electrolyte is applied or impregnated into an electrode (at least one of a positive electrode and a negative electrode), a separator, or both of the electrode and the separator, and then a separator is interposed between the positive electrode and the negative electrode to obtain an electrode group. Thus, a secondary battery provided with a gel-like nonaqueous electrolyte is obtained.
(V) In the method (IV) described above, a crosslinked polymer can be used instead of the organic polymer compound. For example, a pregel solution is prepared from a compound having a crosslinkable functional group, a lithium salt, and an electrolytic solution, and this is applied to an electrode (at least one of a positive electrode and a negative electrode), a separator, or both an electrode and a separator. Alternatively, after impregnation, a compound having a crosslinkable functional group is crosslinked. This crosslinking step may be performed before or after the electrode group is manufactured.
The method for crosslinking is not particularly limited, but heat polymerization or photopolymerization with ultraviolet rays is preferable from the viewpoint of simplicity of the apparatus and cost. When crosslinking is performed by heating or ultraviolet irradiation, it is necessary to add a polymerization initiator suitable for the polymerization method to the pregel solution. Moreover, a polymerization initiator is not restricted to one type, You may mix and use 2 or more types.
(VI) An electrode group in which a separator is interposed between a positive electrode and a negative electrode is accommodated in a container. Next, after impregnating the electrode group with the gel-like nonaqueous electrolyte of (IV) described above, the container is sealed to obtain a secondary battery including the gel-like nonaqueous electrolyte. Alternatively, after the electrode group is impregnated with the pregel solution of (V), the pregel solution is crosslinked before or after sealing the container to obtain a secondary battery having a gel-like nonaqueous electrolyte.
Examples of the organic polymer compounds in (II) and (IV) described above include polymers having a backbone of alkylene oxide such as polyethylene oxide and polypropylene oxide or derivatives thereof; vinylidene fluoride, propylene hexafluoride, tetrafluoroethylene , Perfluoroalkyl vinyl ether, or a copolymer thereof; a polyacrylate polymer having polyacrylonitrile or polyacrylonitrile as a main component and a copolymer with methyl acrylate, vinyl pyrrolidone, vinyl acetate, or the like; a polyether polymer Polycarbonate-based polymers; polyacrylonitrile-based polymers; polyethylene terephthalate, polybutylene terephthalate or their derivatives as skeletons, such as ethyl methacrylate, styrene, vinyl acetate Polyester polymer is a copolymer of; fluororesin; polyolefin resins; polyether resins; and a copolymer of two or more thereof; and the like. In addition, a prepolymer solution (III) and a pregel solution (V) can be prepared from monomers and oligomers that are precursors of these polymers.
The present invention is characterized in that the above-mentioned electrolyte contains a sultone compound having at least one double bond in the ring.
Here, as the sultone compound having at least one double bond in the ring, the sultone compound A represented by the general formula shown in the following chemical formula 1 or at least one H of the sultone compound A is substituted with a hydrocarbon group. Sultone compound B can be used. In the present application, sultone compound A or sultone compound B may be used alone, or both sultone compound A and sultone compound B may be used.

In chemical formula 1, C _m H _n Is a linear hydrocarbon group, and m and n are integers of 2 or more satisfying 2m> n.
A sultone compound having a double bond in the ring can form a dense protective film on the surface of the negative electrode without gas generation due to a double bond opening during a reduction reaction with the negative electrode to cause a polymerization reaction. . At this time, if EC and PC are present, a dense protective film excellent in lithium ion permeability can be formed.
Among the sultone compounds, a compound in which sultone compound A has m = 3 and n = 4, that is, 1,3-propene sultone (PRS), or a compound in which m = 4 and n = 6, that is, 1 , 4-butylene sultone (BTS). The protective coating derived from these compounds is Li ⁺ This is because the effect of suppressing the side reaction due to the contact of the non-aqueous electrolyte is the highest. As the sultone compound, 1,3-propene sultone (PRS) or 1,4-butylene sultone (BTS) may be used alone, or these PRS and BTS may be used in combination.
The ratio of the sultone compound is desirably 10% by weight or less. This is because if the ratio of the sultone compound exceeds 10% by weight, the lithium ion permeability of the protective film is lowered, the impedance of the negative electrode is increased, and sufficient capacity and charge / discharge efficiency may not be obtained. Furthermore, in order to maintain the design capacity of the electrode and keep the initial charge / discharge efficiency high, the ratio of the sultone compound is desirably 4% by weight or less. In order to ensure a sufficient amount of the protective coating, it is desirable to ensure a sultone compound ratio of at least 0.01% by weight. Furthermore, if the ratio of the sultone compound is 0.1% by weight or more, a protective function such as suppression of gas generation during the initial charge by the protective coating can be made sufficient.
In the non-aqueous solvent, it is preferable to contain other solvent in addition to the sultone compound. Other solvents include, for example, cyclic carbonates such as ethylene carbonate (EC) and propylene carbonate (PC), chain carbonates {eg, methyl ethyl carbonate (MEC), diethyl carbonate (DEC), dimethyl carbonate (DMC)} , Γ-butyrolactone (GBL), vinylene carbonate (VC), vinyl ethylene carbonate (VEC), phenyl ethylene carbonate (phEC), γ-valerolactone (VL), methyl propionate (MP), ethyl propionate (EP), 2-methylfuran (2Me-F), furan (F), thiophene (TIOP), catechol carbonate (CATC), ethylene sulfite (ES), 12-crown-4 (Crown), tetraethylene glycol dimethyl ester And the like. The type of the other solvent can be one type or two or more types.
Among them, vinylene carbonate can further improve the initial charge / discharge efficiency, the discharge capacity, and the cycle life because the denseness of the protective film can be improved without significantly reducing the lithium ion permeability of the carbonaceous material. .
The weight ratio of vinylene carbonate in the non-aqueous solvent is desirably within the range of 10% by weight or less. This is because if the weight ratio of vinylene carbonate is more than 10% by weight, the lithium ion permeability of the protective film on the negative electrode surface is lowered, so that the initial charge / discharge efficiency, the discharge capacity or the cycle life may be greatly impaired. Because there is. A more preferable range of the weight ratio of vinylene carbonate is 0.01 to 5% by weight.
Preferred compositions of the non-aqueous solvent include (I) a non-aqueous solvent containing a cyclic carbonate, γ-butyrolactone (GBL), and a sultone compound, (II) EC, a chain carbonate containing at least MEC, and a sultone compound (III) a non-aqueous solvent containing at least EC and PC, a non-aqueous solvent containing at least EC and PC, and (IV) a cyclic carbonate containing at least EC and PC, and a sultone compound. Nonaqueous solvents can be mentioned.
The cyclic carbonate of the non-aqueous solvent (I) preferably contains EC, and more preferably contains PC together with EC. According to the nonaqueous solvent (I), the high-temperature storage characteristics and cycle life of the secondary battery can be further improved. When vinylene carbonate (VC) is further added to the nonaqueous solvent (I), the low-temperature discharge characteristics of the secondary battery can also be improved.
The chain carbonate of the non-aqueous solvent (II) contains methyl ethyl carbonate (MEC) as an essential component, and only MEC may be used as the chain carbonate or other chain carbonate may be used in combination with MEC. . According to the non-aqueous solvent (II), gas generation at the time of initial charge can be suppressed, and low-temperature discharge characteristics and cycle life can be improved.
Other chain carbonates used in combination with MEC are preferably those having a low freezing point and a low viscosity. Furthermore, a solvent having a relatively low molecular weight is desirable. This is because the discharge characteristics at low temperature are improved. The other chain carbonate is preferably at least one of diethyl carbonate (DEC) and dimethyl carbonate (DMC). In particular, a chain carboard containing MEC and DEC is preferable from the viewpoint of obtaining excellent charge / discharge cycle characteristics, while a chain carbonate containing MEC and DMC is desirable from the viewpoint of obtaining excellent low temperature discharge characteristics.
If vinylene carbonate (VC) is further added to the nonaqueous solvent (II), the cycle life of the secondary battery can be further improved.
The non-aqueous solvent (III) can reduce the amount of gas generated when the secondary battery is initially charged, and at the same time can improve the high-temperature storage characteristics. When vinylene carbonate (VC) is further added to the nonaqueous solvent (II), the high-temperature storage characteristics of the secondary battery can be further improved.
The non-aqueous solvent (IV) can suppress the amount of gas generated at the time of initial charge, and can improve the initial charge / discharge efficiency. When vinylene carbonate (VC) is further added to the nonaqueous solvent (IV), the initial charge / discharge efficiency can be further improved.
Examples of the electrolyte dissolved in the nonaqueous solvent include lithium perchlorate (LiClO). ₄ ), Lithium hexafluorophosphate (LiPF) ₆ ), Lithium tetrafluoroborate (LiBF) ₄ ), Lithium hexafluoroarsenide (LiAsF) ₆ ), Lithium trifluorometasulfonate (LiCF) ₃ SO ₃ ), Bistrifluoromethylsulfonylimide lithium [(LiN (CF ₃ SO ₂ ) ₂ ], LiN (C ₂ F ₅ SO ₂ ) ₂ And lithium salts. The type of electrolyte used can be one type or two or more types.
Among them, LiPF ₆ Or LiBF ₄ The thing containing is preferable. Also, (LiN (CF ₃ SO ₂ ) ₂ And LiN (C ₂ F ₅ SO ₂ ) ₂ An imide salt comprising at least one of LiBF and LiBF ₄ And LiPF ₆ A mixed salt A containing a salt consisting of at least one of LiBF or LiBF ₄ And LiPF ₆ When the mixed salt B containing is used, the cycle life at a high temperature can be further improved. In addition, since the thermal stability of the electrolyte is improved, voltage drop due to self-discharge during storage in a high temperature environment can be suppressed.
The amount of the electrolyte dissolved in the non-aqueous solvent is preferably 0.5 to 2.5 mol / L. A more preferable range is 1 to 2.5 mol / L.
The liquid non-aqueous electrolyte preferably contains a surfactant such as trioctyl phosphate (TOP) in order to improve the wettability with the separator. The addition amount of the surfactant is preferably 3% or less, and more preferably in the range of 0.1 to 1%.
The amount of the liquid non-aqueous electrolyte is preferably 0.2 to 0.6 g per 100 mAh of battery unit capacity. A more preferable range of the liquid nonaqueous electrolytic mass is 0.25 to 0.55 g / 100 mAh.
6) Container (storage container)
The shape of the container can be, for example, a bottomed cylindrical shape, a bottomed rectangular tube shape, a bag shape, a cup shape, or the like.
This container can be formed from, for example, a sheet including a resin layer, a metal plate, a metal film, or the like.
The resin layer contained in the sheet can be composed of, for example, polyolefin or polyamide.
The metal plate and the metal film can be formed of, for example, iron, stainless steel, or aluminum.
The thickness of the container (the thickness of the container wall) is desirably 0.3 mm or less. This is because if the thickness is greater than 0.3 mm, it is difficult to obtain a high weight energy density and volume energy density. A preferable range of the thickness of the container is 0.25 mm or less, a more preferable range is 0.15 mm or less, and a most preferable range is 0.12 mm or less. Moreover, since it will become easy to deform | transform and break when thickness is thinner than 0.05 mm, it is preferable that the lower limit of the thickness of a container shall be 0.05 mm.
A thin lithium ion secondary battery and a cylindrical lithium ion secondary battery, which are examples of the nonaqueous electrolyte secondary battery according to the present invention, will be described in detail with reference to FIGS.
FIG. 1 is a perspective view showing a thin lithium ion secondary battery which is an example of a nonaqueous electrolyte secondary battery according to the present invention, and FIG. 2 is an enlarged cross-sectional view of a main part of the nonaqueous electrolyte secondary battery of FIG. 3 is a partially cutaway perspective view showing a cylindrical nonaqueous electrolyte secondary battery which is an example of the nonaqueous electrolyte secondary battery according to the present invention.
First, a thin lithium ion secondary battery will be described with reference to FIGS.
As shown in FIG. 1, an electrode group 2 is accommodated in a container body 1 having a long box-like cup shape. The electrode group 2 has a structure in which a laminate including a positive electrode 3, a negative electrode 4, and a separator 5 disposed between the positive electrode 3 and the negative electrode 4 is wound into a flat shape. The nonaqueous electrolyte is held in the electrode group 2. A part of the edge of the container body 1 is wide and functions as the lid plate 6. The container body 1 and the cover plate 6 are each composed of a laminate film. The laminate film includes an external protective layer 7, an internal protective layer 8 containing a thermoplastic resin, and a metal layer 9 disposed between the external protective layer 7 and the internal protective layer 8. A lid 6 is fixed to the container body 1 by heat sealing using a thermoplastic resin of the inner protective layer 8, whereby the electrode group 2 is sealed in the container. A positive electrode tab 10 is connected to the positive electrode 3, and a negative electrode tab 11 is connected to the negative electrode 4, and each is pulled out of the container and serves as a positive electrode terminal and a negative electrode terminal.
Next, a cylindrical lithium ion secondary battery will be described with reference to FIG.
A bottomed cylindrical container 21 made of stainless steel has an insulator 22 disposed at the bottom. The electrode group 23 is accommodated in the container 21. The electrode group 23 has a structure in which a belt-like material in which a positive electrode 24, a separator 25, a negative electrode 26, and a separator 25 are laminated is wound in a spiral shape so that the separator 25 is located outside.
A nonaqueous electrolytic solution is accommodated in the container 21. An insulating paper 27 having an opening at the center is disposed above the electrode group 23 in the container 21. The insulating sealing plate 28 is disposed in the upper opening of the container 21, and the sealing plate 28 is fixed to the container 21 by caulking the vicinity of the upper opening. The positive terminal 29 is fitted in the center of the insulating sealing plate 28. One end of the positive electrode lead 30 is connected to the positive electrode 24, and the other end is connected to the positive electrode terminal 29. The negative electrode 26 is connected to the container 21 which is a negative electrode terminal through a negative electrode lead (not shown).
The non-aqueous electrolyte secondary battery according to the present invention described above includes a positive electrode, a negative electrode including a carbonaceous material capable of inserting and extracting lithium ions, and a non-aqueous electrolyte secondary battery including a non-aqueous electrolyte including a non-aqueous solvent. Battery,
The non-aqueous solvent contains a sultone compound having at least one double bond in the ring, and the specific surface area of the carbonaceous material by the BET method is 1.5 m. ² / G or more, 10m ² / G or less.
By using a carbonaceous material having a large specific surface area in this way, the reactivity of the sultone compound can be optimized, and thus a secondary battery that simultaneously satisfies initial charge / discharge efficiency, discharge capacity, and cycle life can be realized. Can do.
Among these carbonaceous materials, the interplanar spacing d of 0.336 nm or less in powder X-ray diffraction measurement ₀₀₂ Or the peaks at diffraction angles 2θ of 42.8 ° to 44.0 ° and 45.5 ° to 46.6 ° in X-ray diffraction measurement using CuKα rays Since the decomposition reaction of the compound can be promoted, the protective film can be formed while suppressing the side reaction with the coexisting solvent. Therefore, the initial charge / discharge efficiency and discharge capacity of the secondary battery can be further improved.
In addition, the decomposition reaction of solvents other than sultone compounds (particularly propylene carbonate) can be suppressed by setting the R value by the Raman spectrum measurement of the carbonaceous material to 0.3 or more in intensity ratio and 1.0 or more in area ratio. Therefore, the initial charge / discharge efficiency of the secondary battery can be further improved.
In particular, the carbonaceous material has a specific surface area of 1.5 m. ² / G or more 10m ² / G or less and a surface spacing d of 0.336 nm or less in powder X-ray diffraction measurement ₀₀₂ In the X-ray diffraction measurement using CuKα rays, the diffraction angle 2θ is 42.8 ° to 44.44. By using a graphitic material in which peaks are detected at 0 ° and 45.5 ° to 46.6 ° or a rhombohedral structure is used, the charge / discharge cycle life of the secondary battery can be further improved.
That is, the graphite material having the interplanar spacing, specific surface area, and R value in the above-described range and having the above-described diffraction peak or rhombohedral structure reacts preferentially with the sultone compound and allows lithium ion permeability to the negative electrode surface. The protective film can be formed uniformly without impairing the above. Since the reaction with the sultone compound occurs preferentially and a dense protective film is formed from the initial charge, the decomposition reaction of the cyclic carbonate such as PC can be suppressed, and the amount of gas generated at the initial charge can be reduced. Can be reduced. As a result, since the initial charge / discharge efficiency can be increased, the discharge capacity and the charge / discharge cycle life can be further improved.
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings described above.

<Preparation of positive electrode>
First, 90% by weight of lithium cobalt oxide (Li _x CoO ₂ ; X is 0 <X ≦ 1) powder, 5% by weight of acetylene black and 5% by weight of polyvinylidene fluoride (PVdF) dimethylformamide (DMF) solution was added and mixed to prepare a slurry. The slurry was applied to both sides of a current collector made of an aluminum foil having a thickness of 15 μm, then dried and pressed to produce a positive electrode having a structure in which the positive electrode layer was supported on both sides of the current collector. The thickness of the positive electrode layer was 60 μm per side.
<Production of negative electrode>
In powder X-ray diffraction, a peak derived from the (002) plane spacing (d ₀₀₂ ) of 0.3358 nm was detected, and the diffraction angle 2θ was 43.35 ° (P ₄ ) in X-ray diffraction measurement using CuKα rays. And natural graphite having a peak at 46.19 ° (P ₅ ) was prepared. FIG. 4 shows the results of X-ray diffraction measurement using CuKα rays of the graphite material used in Example 1. In addition, the space _| interval d002 of (002) plane is the value calculated | required by the half value width midpoint method from the powder X-ray diffraction spectrum. At this time, scattering correction such as Lorentz scattering was not performed.
The natural graphite was spheroidized and then subjected to chemical vapor deposition at 1000 ° C. under a benzene / N ₂ stream to obtain a graphite material.
With respect to this graphite material, the specific surface area by the BET method and the Raman R value were measured by the method described below, and the results are shown in Table 1 below.
(Measurement of specific surface area by BET method)
As a measuring device, a product name manufactured by Yuasa Ionics used Kantasorb. The sample amount was set to around 0.5 g, and the sample was deaerated at 120 ° C. for 15 minutes as a pretreatment.
(Measurement of R value)
Peak separation is performed on the Raman spectrum of the graphite material, and D (A1g): peak derived from the disorder of the graphite structure near 1360 cm ⁻¹ , D ′ (A1g): the disorder of the graphite structure near 1620 cm ⁻¹ Derived peak, D: Peak derived from disorder of graphite structure of amorphous carbon, G (E2g): Peak derived from graphite structure in the vicinity of 1580 cm ⁻¹ , G: Peak derived from graphite structure of amorphous carbon were obtained.
Calculating the intensity of each peak, intensity and I _D the sum of the intensity of a peak derived from the D-band, the ratio of I _G the sum of the intensity of a peak derived from the G band (I D _{/ I G)} The ratio is shown in Table 1 below. Also, the area of each peak is calculated, and the ratio of the sum of the peak area values derived from the _D band to the sum of the peak area values derived from the G band, S _G (S _D / S Table 1 below shows _G ) as an area ratio.
A slurry was prepared by mixing 95% by weight of the obtained graphite material powder and 5% by weight of a polyvinylidene fluoride (PVdF) dimethylformamide (DMF) solution. The slurry was applied to both surfaces of a current collector made of a copper foil having a thickness of 12 μm, dried, and pressed to prepare a negative electrode having a structure in which the negative electrode layer was supported on the current collector. The thickness of the negative electrode layer was 55 μm per side.
<Separator>
A separator made of a microporous polyethylene film having a thickness of 25 μm was prepared.
<Preparation of non-aqueous electrolyte>
2% by weight of 1,3-propene sultone (PRS) with respect to a mixed solution in which ethylene carbonate (EC) and γ-butyrolactone (GBL) are mixed at a volume ratio (EC: GBL) of 35:65, A non-aqueous solvent was prepared by adding 1% by weight of vinylene carbonate (VC) and 0.5% by weight of trioctyl phosphate (TOP). A liquid non-aqueous electrolyte was prepared by dissolving lithium tetrafluoroborate (LiBF ₄ ) in the obtained non-aqueous solvent so as to have a concentration of 1.5 mol / L.
<Production of electrode group>
After the positive electrode lead made of a strip-shaped aluminum foil (thickness 100 μm) is ultrasonically welded to the positive electrode current collector, and the negative electrode lead made of a strip-shaped nickel foil (thickness 100 μm) is ultrasonically welded to the negative electrode current collector The positive electrode and the negative electrode were spirally wound through the separator therebetween, and then formed into a flat shape to produce an electrode group.
A laminate film having a thickness of 100 μm in which both surfaces of an aluminum foil were covered with polyethylene was formed into a rectangular cup shape by a press machine, and the electrode group was housed in the obtained container.
Next, the electrode group in the container was vacuum dried at 80 ° C. for 12 hours to remove moisture contained in the electrode group and the laminate film.
After injecting the liquid non-aqueous electrolyte into the electrode group in the container so that the amount per battery capacity 1Ah is 4.8 g and sealing by heat sealing, the structure shown in FIGS. A thin non-aqueous electrolyte secondary battery having a thickness of 3.6 mm, a width of 35 mm, a height of 62 mm, and a nominal capacity of 0.65 Ah was assembled.
The following treatment was applied to the non-aqueous electrolyte secondary battery as an initial charge / discharge process. First, constant current / constant voltage charging was performed for 15 hours at room temperature to 4.2 V at 0.2C. Then, it discharged to 3.0V at 0.2C at room temperature, and manufactured the nonaqueous electrolyte secondary battery.
Here, 1C is a current value necessary for discharging the nominal capacity (Ah) in one hour. Therefore, 0.2 C is a current value necessary for discharging the nominal capacity (Ah) in 5 hours.

Examples 2-5

  A thin nonaqueous electrolyte secondary battery was manufactured in the same manner as described in Example 1 except that the composition of the nonaqueous solvent and the type and concentration of the electrolyte were changed as shown in Table 1 below.

In powder X-ray diffraction, a peak derived from the (002) plane spacing (d ₀₀₂ ) of 0.3358 nm was detected, and in the X-ray diffraction measurement using CuKα rays, the diffraction angle 2θ was 43.35 ° and 46.19. Natural graphite with a peak at ° was molded to obtain a graphite material.
This graphite material was measured for specific surface area and Raman R value by the BET method in the same manner as described in Example 1 above, and the results are shown in Table 1 below.
A negative electrode was produced in the same manner as described in Example 1 except that such a graphite material was used.
Further, 2% by weight of 1,3-propene sultone (PRS) and trioctyl phosphate are mixed with a mixed solution in which ethylene carbonate (EC) and propylene carbonate (PC) are mixed at a volume ratio of 50:50. (TOP) was added at 0.5 wt% to prepare a non-aqueous solvent. A liquid nonaqueous electrolyte was prepared by dissolving lithium hexafluorophosphate (LiPF ₆ ) in the obtained nonaqueous solvent so that the concentration thereof was 1 mol / L.
A thin nonaqueous electrolyte secondary battery was produced in the same manner as described in Example 1 except that the obtained negative electrode and nonaqueous electrolyte were used.

In graphite X-ray diffraction, artificial graphite in which a peak derived from an interplanar spacing (d ₀₀₂ ) of (002) plane of 0.3358 nm is detected and a peak derived from rhombohedral system is not detected is formed into a graphite material. Got.
This graphite material was measured for specific surface area and Raman R value by the BET method in the same manner as described in Example 1 above, and the results are shown in Table 1 below.
A negative electrode was produced in the same manner as described in Example 1 except that such a graphite material was used.
A liquid nonaqueous electrolyte was prepared in the same manner as described in Example 6 above.
A thin nonaqueous electrolyte secondary battery was produced in the same manner as described in Example 1 except that the obtained negative electrode and nonaqueous electrolyte were used.

A spherical artificial graphite material is prepared in which a peak derived from the (002) plane spacing (d ₀₀₂ ) of 0.3362 nm in powder X-ray diffraction is detected and a peak derived from the rhombohedral system is not detected. The graphite material was measured for the specific surface area and Raman R value by the BET method in the same manner as described in Example 1 above, and the results are shown in Table 1 below.
A negative electrode was produced in the same manner as described in Example 1 except that such a graphite material was used.
A liquid nonaqueous electrolyte was prepared in the same manner as described in Example 6 above.
A thin nonaqueous electrolyte secondary battery was produced in the same manner as described in Example 1 except that the obtained negative electrode and nonaqueous electrolyte were used.

Examples 9-11

表１〜表２から明らかなように、ＢＥＴ法による比表面積が１．５ｍ^２／ｇ以上、１０ｍ^２／ｇ以下の範囲内である炭素質物を用いる実施例１〜１１の二次電池は、初充放電効率、放電容量および３００サイクル時の容量維持率のいずれもが優れていることがわかる。中でも、粉末Ｘ線回折測定において０．３３６ｎｍ以下の面間隔ｄ_００２に由来するピークが現れ、菱面体晶系構造を有し、かつラマンスペクトル測定によるＲ値が強度比で０．３以上、面積比で１以上である黒鉛質材料と、ＥＣ、ＰＲＳ及びＶＣを含有する非水電解質とを用いる実施例２〜４の二次電池は、放電容量と３００サイクル時の容量維持率の双方が最も高くなった。
これに対し、ＢＥＴ法による比表面積が１．５ｍ^２／ｇ未満の炭素質物を用いる比較例１〜３の二次電池は、放電容量と３００サイクル時の容量維持率のいずれもが低くなり、比較例３に至っては、充放電反応を行えなかった。また、比較例４の二次電池は、３００サイクル時の容量維持率が高いものの、放電容量が低かった。
また、実施例１〜５，９〜１１の二次電池では、５０サイクル時の容量維持率が９０％以上と高いのに対し、実施例６〜８の二次電池では、５０サイクル時の容量維持率が９０％に満たなかった。主な原因は以下に説明するものであると考えられる。
実施例６の二次電池では、表面の黒鉛化度が高いため、ＰＲＳの分解の他にＰＣのような環状カーボネートの分解反応を生じ、初期のサイクルに伴って負極表面の保護皮膜の抵抗が高くなり、容量が急激に低下したことから、５０サイクル目の容量維持率が低くなった。
一方、実施例７，８の二次電池では、菱面体晶系構造を持たない黒鉛質材料を用いているため、ＰＲＳの分解反応が優先的に進行せず、初期のサイクルに伴って負極表面の保護皮膜の抵抗が高くなり、容量が急激に低下したことから、５０サイクル目の容量維持率が低くなった。
（ＰＲＳとＶＣの検出方法）
また、実施例１の二次電池について、前記初充放電工程後、５時間以上回路を開放して十分に電位を落ち着かせた後、Ａｒ濃度が９９．９％以上、かつ露点が−５０℃以下のグローブボックス内で分解し、電極群を取り出した。前記電極群を遠沈管につめ、ジメチルスルホキシド（ＤＭＳＯ）−ｄ_６を加えて密封し、前記グローブボックスより取り出し、遠心分離を行った。その後、前記グローブボックス内で、前記遠沈管から前記電解液と前記ＤＭＳＯ−ｄ_６の混合溶液を採取した。前記混合溶媒を５ｍｍφのＮＭＲ用試料管に０．５ｍｌ程度入れ、ＮＭＲ測定を行った。前記ＮＭＲ測定に用いた装置は日本電子株式会社製ＪＮＭ−ＬＡ４００ＷＢであり、観測核は^１Ｈ、観測周波数は４００ＭＨｚ、ジメチルスルホキシド（ＤＭＳＯ）−ｄ_６中に僅かに含まれる残余プロトン信号を内部基準として利用した（２．５ｐｐｍ）。測定温度は２５℃とした。^１ＨＮＭＲスペクトルではＥＣに対応するピークが４．５ｐｐｍ付近、ＶＣに対応するピークが７．７ｐｐｍ付近に観測された。一方、ＰＲＳに対応するピークが、図５に示すスペクトルのように５．１ｐｐｍ付近（Ｐ_１）、７．０５ｐｐｍ付近（Ｐ_２）及び７．２ｐｐｍ付近（Ｐ_３）に観測された。これらの結果から、初充放電工程後の実施例１の二次電池に存在する非水溶媒中にＶＣとＰＲＳが含まれていることを確認できた。
また、観測周波数を１００ＭＨｚとし、ジメチルスルホキシド（ＤＭＳＯ）−ｄ_６（３９．５ｐｐｍ）を内部基準物質として^１３ＣＮＭＲ測定を行ったところ、ＥＣに対応するピークが６６ｐｐｍ付近、ＶＣに対応するピークが１３３ｐｐｍ付近、ＰＲＳに対応するピークが７４ｐｐｍ付近と１２４ｐｐｍ付近と１４０ｐｐｍ付近に観測され、この結果からも、初充放電工程後の実施例１の二次電池に存在する非水溶媒中にＶＣとＰＲＳが含まれていることを確認できた。
さらに、^１ＨＮＭＲスペクトルにおいて、ＥＣのＮＭＲ積分強度に対するＶＣのＮＭＲ積分強度の比と、ＥＣのＮＭＲ積分強度に対するＰＲＳのＮＭＲ積分強度の比を求めたところ、非水溶媒全体に対するＶＣの割合、ＰＲＳの割合がいずれも二次電池組立て前より減少していることを確認することができた。
なお、本発明は、上記の実施例に止まるものではなく、他の種類の正極・負極・セパレータ・容器の組合わせにおいても同様に適用可能である。また、上記の実施例のようなラミネートフィルムから容器を形成した非水電解質二次電池以外にも、円筒形や角形の容器を有する二次電池においても本発明は適用可能である。A thin nonaqueous electrolyte secondary battery was produced in the same manner as described in Example 1 except that the parameters of the graphite material and the composition of the nonaqueous electrolyte were set as shown in Table 1 below.
In addition, the graphite material used in Examples 9-11 was produced by the method described below.
For Example 9, the same natural graphite as described in Example 1 was pitch coated, and then fired at 1500 ° C. to obtain a graphite material.
For Example 10, in the powder X-ray diffraction, a peak derived from the (002) plane spacing (d ₀₀₂ ) of 0.3356 nm was detected, and in the X-ray diffraction measurement using CuKα ray, the diffraction angle 2θ was 43. Natural graphite having peaks at 35 ° (P ₄ ) and 46.19 ° (P ₅ ) was prepared.
The natural graphite was spheroidized and then subjected to chemical vapor deposition at 1000 ° C. under a benzene / N ₂ stream to obtain a graphite material.
In Example 11, natural graphite similar to that described in Example 10 was spheroidized, pitch-coated, and fired at 1000 ° C. to obtain a graphite material.
(Comparative Example 1)
Spherical artificial graphite in which a peak derived from a (002) plane spacing (d ₀₀₂ ) of 0.3365 nm in powder X-ray diffraction was prepared, and this artificial graphite was explained in Example 1 described above. Similarly, the specific surface area by the BET method and the Raman R value were measured, and the results are shown in Table 1 below.
A negative electrode was produced in the same manner as described in Example 1 except that such artificial graphite was used.
In addition, 1,3-propene sultone (PRS) is added to the mixed solution in which ethylene carbonate (EC) and methyl ethyl carbonate (MEC) are mixed so that the volume ratio (EC: MEC) is 35:65. 5 wt% and vinylene carbonate (VC) 0.5 wt% were added to prepare a non-aqueous solvent. A liquid nonaqueous electrolyte was prepared by dissolving lithium hexafluorophosphate (LiPF ₆ ) in the obtained nonaqueous solvent so that the concentration thereof was 1 mol / L.
A thin nonaqueous electrolyte secondary battery was produced in the same manner as described in Example 1 except that the obtained negative electrode and nonaqueous electrolyte were used.
(Comparative Examples 2-3)
A thin nonaqueous electrolyte secondary battery was manufactured in the same manner as described in Comparative Example 1 except that the composition of the nonaqueous solvent and the type and concentration of the electrolyte were changed as shown in Table 2 below.
(Comparative Example 4)
A thin nonaqueous electrolyte secondary battery having the same configuration as described in Comparative Example 1 was manufactured except that the specific surface area of the carbonaceous material by the BET method was changed as shown in Table 2 below.
(Comparative Example 5)
In powder X-ray diffraction, a peak derived from the (002) plane spacing (d ₀₀₂ ) of 0.3358 nm was detected, and in the X-ray diffraction measurement using CuKα rays, the diffraction angle 2θ was 43.35 ° and 46.19. Natural graphite having a peak at ° was prepared as a graphite material.
This graphite material was measured for specific surface area and Raman R value by the BET method in the same manner as described in Example 1 above, and the results are shown in Table 1 below.
Except for using such a graphite material, a negative electrode was produced in the same manner as described in Example 1 described above, and a thin structure having the same configuration as that described in Example 1 was used using this negative electrode. A non-aqueous electrolyte secondary battery was manufactured.
For the obtained secondary batteries of Examples 1 to 11 and Comparative Examples 1 to 5, initial charge / discharge efficiency, battery capacity, and charge / discharge cycle characteristics were evaluated under the conditions described below, and the results are shown in Tables 1 to 2 below. Shown in
(Initial charge / discharge efficiency)
For each secondary battery, the initial charge / discharge efficiency was evaluated by conducting a charge / discharge test with a charge / discharge rate of 0.2 C, a charge termination voltage of 4.2 V, and a discharge cut voltage of 3.0 V in an environment of 20 ° C. The results are shown in Tables 1 and 2 below.
(Battery capacity)
The discharge capacity at a discharge cut voltage of 3.0 V at the time of initial charge / discharge was compared as the battery capacity, and the results are shown in Tables 1 and 2 below.
(Charge / discharge cycle characteristics)
Each secondary battery was subjected to a charge / discharge test at a charge / discharge rate of 1 C, a charge end voltage of 4.2 V, and a discharge end voltage of 3.0 V, and repeated 50 times and 300 times in a 20 ° C. environment. The discharge capacity retention rate (the capacity of the first discharge is 100%) was determined, and the results are shown in Tables 1 and 2 below.

As apparent from Tables 1 and 2, the secondary batteries of Examples 1 to 11 using carbonaceous materials having a specific surface area by the BET method in the range of 1.5 m ² / g or more and 10 m ² / g or less, It can be seen that the initial charge / discharge efficiency, the discharge capacity, and the capacity retention rate at 300 cycles are all excellent. Among them, a peak derived from an interplanar spacing d ₀₀₂ of 0.336 nm or less appears in powder X-ray diffraction measurement, has a rhombohedral structure, and an R value by an intensity ratio is 0.3 or more in terms of intensity ratio. The secondary batteries of Examples 2 to 4 using a graphite material having a ratio of 1 or more and a nonaqueous electrolyte containing EC, PRS, and VC have the highest discharge capacity and capacity retention rate at 300 cycles. It became high.
On the other hand, in the secondary batteries of Comparative Examples 1 to 3 using a carbonaceous material having a specific surface area of less than 1.5 m ² / g by the BET method, both the discharge capacity and the capacity maintenance rate at 300 cycles are low, In Comparative Example 3, the charge / discharge reaction could not be performed. In addition, the secondary battery of Comparative Example 4 had a high capacity retention rate at 300 cycles, but a low discharge capacity.
Moreover, in the secondary batteries of Examples 1 to 5 and 9 to 11, the capacity maintenance rate at 50 cycles is as high as 90% or more, whereas in the secondary batteries of Examples 6 to 8, the capacity at 50 cycles is obtained. The maintenance rate was less than 90%. The main cause is considered to be explained below.
In the secondary battery of Example 6, since the graphitization degree of the surface is high, the decomposition reaction of cyclic carbonate such as PC occurs in addition to the decomposition of PRS, and the resistance of the protective film on the negative electrode surface increases with the initial cycle. As the capacity increased and the capacity decreased rapidly, the capacity retention rate at the 50th cycle decreased.
On the other hand, in the secondary batteries of Examples 7 and 8, since the graphite material having no rhombohedral structure is used, the PRS decomposition reaction does not proceed preferentially, and the negative electrode surface is increased with the initial cycle. Since the resistance of the protective film increased and the capacity decreased rapidly, the capacity retention rate at the 50th cycle decreased.
(PRS and VC detection method)
For the secondary battery of Example 1, after the initial charge / discharge step, the circuit was opened for 5 hours or more to sufficiently settle the potential, and then the Ar concentration was 99.9% or more and the dew point was −50 ° C. It decomposed | disassembled in the following glove boxes and took out the electrode group. The electrode group was put in a centrifuge tube, dimethyl sulfoxide (DMSO) -d ₆ was added and sealed, removed from the glove box, and centrifuged. Thereafter, a mixed solution of the electrolytic solution and the DMSO-d ₆ was collected from the centrifuge tube in the glove box. About 0.5 ml of the mixed solvent was put into a 5 mmφ NMR sample tube and subjected to NMR measurement. The apparatus used for the NMR measurement is JNM-LA400WB manufactured by JEOL Ltd., the observation nucleus is ¹ H, the observation frequency is 400 MHz, and the residual proton signal slightly contained in dimethyl sulfoxide (DMSO) -d ₆ is used as an internal reference. (2.5 ppm). The measurement temperature was 25 ° C. ^{In the 1} HNMR spectrum, a peak corresponding to EC was observed near 4.5 ppm, and a peak corresponding to VC was observed near 7.7 ppm. On the other hand, peaks corresponding to PRS were observed around 5.1 ppm (P ₁ ), 7.05 ppm (P ₂ ), and 7.2 ppm (P ₃ ) as shown in the spectrum of FIG. From these results, it was confirmed that VC and PRS were contained in the nonaqueous solvent present in the secondary battery of Example 1 after the initial charge / discharge step.
Further, when ¹³ CNMR measurement was performed with an observation frequency of 100 MHz and dimethyl sulfoxide (DMSO) -d ₆ (39.5 ppm) as an internal reference substance, a peak corresponding to EC was around 66 ppm, and a peak corresponding to VC was 133 ppm. In the vicinity, peaks corresponding to PRS were observed at around 74 ppm, around 124 ppm and around 140 ppm. From this result as well, VC and PRS were found in the nonaqueous solvent present in the secondary battery of Example 1 after the initial charge / discharge process. It was confirmed that it was included.
Further, in the ¹ H NMR spectrum, the ratio of the NMR integrated intensity of the VC to the NMR integrated intensity of the EC and the ratio of the NMR integrated intensity of the PRS to the EC NMR integrated intensity were determined. It was confirmed that the ratios of both were lower than before the secondary battery assembly.
The present invention is not limited to the above-described embodiments, and can be similarly applied to other types of combinations of positive electrode, negative electrode, separator, and container. In addition to the non-aqueous electrolyte secondary battery in which the container is formed from the laminated film as in the above-described embodiment, the present invention can be applied to a secondary battery having a cylindrical or rectangular container.

  As described above in detail, according to the present invention, it is possible to provide a nonaqueous electrolyte secondary battery that simultaneously satisfies initial charge / discharge efficiency, discharge capacity, and charge / discharge cycle life.

Claims (13)

A non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode containing a carbonaceous material capable of occluding and releasing lithium ions, and a non-aqueous electrolyte containing a non-aqueous solvent,
The non-aqueous solvent contains a sultone compound having at least one double bond in the ring,
The carbonaceous material has a specific surface area by the BET method of 1.5 m ² / g or more and 10 m ² / g or less, and a peak derived from an interplanar spacing d ₀₀₂ of 0.336 nm or less appears in a powder X-ray diffraction measurement. In the X-ray diffraction measurement using this, peaks are detected at diffraction angles 2θ of 42.8 ° to 44.0 ° and 45.5 ° to 46.6 °, and the R value by Raman spectrum measurement is 0.3 in terms of intensity ratio. As mentioned above, the graphite material whose area ratio is 1 or more is included. A non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode containing a carbonaceous material capable of occluding and releasing lithium ions, and a non-aqueous electrolyte containing a non-aqueous solvent,
The non-aqueous solvent contains a sultone compound having at least one double bond in the ring,
The carbonaceous material has a specific surface area measured by the BET method of 1.5 m ² / g or more and 10 m ² / g or less, and a peak derived from an interplanar spacing d ₀₀₂ of 0.336 nm or less appears in powder X-ray diffraction measurement. It includes a graphite material having a crystal structure and an R value measured by Raman spectrum of 0.3 or more in intensity ratio and 1 or more in area ratio. The non-aqueous electrolyte secondary battery according to claim 1, wherein the specific surface area is 1.5 m ² / g or more and 6 m ² / g or less. The non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein the intensity ratio of the R value is 0.3 or more and 1.5 or less. The non-aqueous electrolyte secondary battery according to claim 1, wherein an area ratio of the R value is 1 or more and 4 or less. The non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein an area ratio of the R value is 1 or more and 3 or less. The non-aqueous electrolyte secondary battery according to claim 1, wherein the sultone compound includes at least one of 1,3-propene sultone (PRS) and 1,4-butylene sultone (BTS). The non-aqueous electrolyte secondary battery according to claim 1, wherein the non-aqueous solvent further contains vinylene carbonate (VC). The nonaqueous electrolyte secondary battery according to claim 1, wherein the nonaqueous solvent further contains a cyclic carbonate and γ-butyrolactone. The nonaqueous electrolyte secondary battery according to claim 1, wherein the nonaqueous solvent further contains ethylene carbonate and a chain carbonate containing at least methyl ethyl carbonate. The nonaqueous electrolyte secondary battery according to claim 1, wherein the nonaqueous solvent further contains a cyclic carbonate containing at least ethylene carbonate and propylene carbonate, and γ-butyrolactone. The nonaqueous electrolyte secondary battery according to claim 1 or 2, wherein the nonaqueous solvent further contains a cyclic carbonate containing at least ethylene carbonate and propylene carbonate. The non-aqueous electrolyte secondary battery according to claim 1, wherein the non-aqueous electrolyte further contains at least one lithium salt of LiPF ₆ and LiBF ₄ .

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