JP4497622B2 - Anode material for lithium secondary battery - Google Patents
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- JP4497622B2 JP4497622B2 JP2000039104A JP2000039104A JP4497622B2 JP 4497622 B2 JP4497622 B2 JP 4497622B2 JP 2000039104 A JP2000039104 A JP 2000039104A JP 2000039104 A JP2000039104 A JP 2000039104A JP 4497622 B2 JP4497622 B2 JP 4497622B2
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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Description
【０００１】
【発明の属する技術分野】
本発明は、高エネルギー密度と高出力とを兼ね備えたリチウム系二次電池用負極材料に関する。
【０００２】
【従来の技術】
近年、地球環境の保全および省資源を目指したエネルギーの有効利用の観点から、深夜電力貯蔵システム、太陽光発電技術に基づく家庭用分散型蓄電システム、電気自動車用の蓄電システムなどが注目を集めている。
【０００３】
これらの蓄電システムにおける第一の要求事項は、用いられる電池のエネルギー密度が高いことである。この様な要求に対応すべく、リチウム電池電力貯蔵技術研究組合（LIBES）などにより、高エネルギー密度電池の有力候補として、リチウムイオン電池の開発が精力的に進められている。
【０００４】
第二の要求事項は、電池の出力特性が安定していることである。例えば、高効率エンジンと蓄電システムとの組み合わせ（例えば、ハイブリッド電気自動車）、或いは燃料電池と蓄電システムとの組み合わせ（例えば、燃料電池自動車）において、エンジン或いは燃料電池が最大効率で運転するためには、一定出力での運転が必須であり、負荷側の出力変動或いはエネルギー回生に対応するために、蓄電システムにおける高出力放電特性および/または高率充電受け入れ特性が要求されている。
【０００５】
現在、高出力蓄電デバイスとしては、電極に活性炭を用いた電気二重層キャパシタがあり、2ｋW/lを超える出力特性を有する大型キャパシタが開発されている。しかしながら、そのエネルギー密度は1〜5Wh/ｌ程度に過ぎないので、単独で上述の蓄電システムを構成することは難しい。
【０００６】
一方、現在ハイブリッド電気自動車で採用されているニッケル水素電池は、2kW/l以上の高出力を実現し、かつ160Wh/l程度のエネルギー密度を有している。しかしながら、そのエネルギー密度をより一層高めるとともに、高温での安定性をさらに改善させることにより、信頼性をより一層向上させるための研究が精力的に進められている。
【０００７】
また、リチウムイオン電池においても、高出力化への研究が進められている。例えば、DOD50%において3kW/lを超える高出力のリチウムイオン電池が開発されているが、そのエネルギー密度は100Wh/l以下であり、リチウムイオン電池の最大の特徴である高エネルギー密度を敢えて抑制した設計となっている。
【０００８】
上記の様に高出力(2kW/l以上)と高エネルギー密度（180Wｈ/ｌ以上）とを兼ね備えた電池の実用化が強く要望されているが、現在のところ、この技術的要求に応える電池は、開発されていない。特に、高エネルギー密度化における高いポテンシャルを有するリチウム系二次電池は、エネルギー密度250〜300Wｈ/ｌにおいて、その出力は1kW/l以下であり、高エネルギー密度と高出力との同時達成は、難しい。
【０００９】
高エネルギー密度と高出力との同時達成のためには、負極材料、正極材料、電解液などの各種の電池構成材料からの多面的なアプローチが必要である。例えば、リチウムイオン電池を作製するに際し、負極材料として公知の黒鉛系材料、炭素材料などを使用する場合には、例えば5分レベルの急速な放電（4000mA/gの電流密度）において、その容量は1時間レベルの放電（300mA/gの電流密度）時に比べて著しく低下する。従って、高エネルギー密度と高出力とを兼ね備えたリチウム系二次電池開発のためには、大きなブレークスルーが必要である。
【００１０】
また、高出力用デバイスであるキャパシタに用いられる活性炭は、一般的に比表面積が1000m2/g以上である。この様なキャパシタ用活性炭にリチウムイオンをドーピングする場合には、その効率が著しく低いこと、また、電極化時の密度も低いことなどの理由により、この様な活性炭をリチウム二次電池に用いることは、難しかった。
【００１１】
【発明が解決しようとする課題】
従って、本発明は、高エネルギー密度を有する高出力リチウム系二次電池用負極材料を提供することを目的とする。
【００１２】
本発明は、さらに、高エネルギー密度を有し、かつ高率充電受け入れが可能な高出力リチウム系二次電池用負極材料を提供することをも目的とする。
【００１３】
【課題を解決する手段】
本発明者は、上記のごとき従来技術の問題点を問題点に留意しつつ、研究を進めた結果、特定の物性を備えた炭素系材料がリチウム二次電池用負極材料として優れた機能を発揮することを見出し、本発明を完成するに至った。
【００１４】
すなわち、本発明は、下記のリチウム二次電池用負極材料を提供する。
１．BET法による比表面積が20〜1000m2/gである炭素系材料からなり、初期効率30％以上、4000mA/gの速度での放電において300mAh/g以上の容量を有することを特徴とするリチウム系二次電池用負極材料。
２．前記炭素系材料が、アモルファス系材料である上記項１に記載のリチウム系二次電池用負極材料。
３．前記炭素系材料が、炭素粒子表面を炭素質材料で被覆した積層材料である上記項１に記載のリチウム系二次電池負極材料。
４．炭素粒子を炭素質材料被膜形成物質との共存下に加熱することにより、炭素粒子表面に炭素質材料被覆層を形成させることを特徴とするリチウム系二次電池用負極材料の製造方法。
５．前記炭素粒子が、アモルファス系材料粒子である上記項４に記載のリチウム系二次電池用負極材料の製造方法。
６．前記炭素粒子が、活性炭粒子である上記項５に記載のリチウム系二次電池用負極材料の製造方法。
７．加熱温度が、500〜1500℃である上記項４〜６のいずれかに記載のリチウム系二次電池用負極材料の製造方法。
【００１５】
【発明の実施の形態】
以下、本発明の実施の形態につき詳細に説明する。
【００１６】
本発明におけるリチウム系二次電池用負極材料は、BET法による比表面積が20〜1000m2/gである炭素系材料からなり、初期効率30％以上、4000mA/gの速度での放電において300mAh/g以上の容量を有することを特徴とする。
【００１７】
本発明によるリチウム系二次電池用負極材料は、BET法による比表面積が、50〜800m2/gの炭素質材料であることがより好ましく、100〜600m2/gの炭素質材料であることがさらに好ましい。比表面積が小さすぎる場合には、充分な出力が得られない。これに対し、比表面積が大きすぎる場合には、リチウムイオンの初期充放電効率が著しく低下するとともに、該負極材料を用いた電極の密度が低下して、体積あたりの容量が減少する。また、該負極材料から電解質へのリチウムイオンの移動速度を高めるためには、電解質が活物質内部まで充分に進入できる必要があり、そのためには、特に細孔直径100〜10Åの細孔量に適切にコントロールすることが好ましい。
【００１８】
本発明におけるリチウム系二次電池用負極材料は、上記の特性ないし構造を有している限り、特に限定されるものではないが、活物質内でのリチウムイオンの移動を考慮すると、アモルファス状炭素材料であることがより好ましい。アモルファス状炭素材料は、黒鉛などの結晶性材料に比べ、その充放電曲線がなだらかであるため、リチウムをより高率で充放電することが可能である点でも、より好適である。
【００１９】
本発明のリチウム系二次電池用負極材料の容量は、通常300mAh/g以上であり、より好ましくは400mAh/g以上であり、特に好ましくは500mAh/g以上である。従来技術においては、リチウムイオン電池の負極活物質としては、200〜300mAh/g程度の材料を使用するのが一般的である。しかしながら、高出力電池を得るためには、後述の様に電解液を保持する負極の気孔率を(負極材料自体の気孔率と成形された負極中の負極材料粒子間隙に起因する気孔率の総和)が35％〜60％程度となるように設定することが好ましく、活物質容量が300mAh/g以下の場合には、電極体積当たりの容量が一般的なリチウムイオン電池に比して小さくなるので、電池のエネルギー密度が低下する。
【００２０】
上記要件を満足する好適なリチウム系二次電池用負極材料としては、アモルファス状炭素(非晶質炭素、ポリアセン系物質など)の炭素系材料が挙げられる。
【００２１】
本発明のリチウム系二次電池用負極材料としては、核となる炭素粒子(核炭素粒子)表面に炭素質材料(非晶質炭素、ポリアセン系物質など)を被覆することにより得られ、比表面積が20〜1000m2/g程度の炭素質材料(積層粒子材料)が特に好ましい。
【００２２】
負極材料として積層粒子材料を使用する場合には、核炭素粒子として、比表面積100m2/g以上の活性炭、木炭、ポリアセン系物質などが使用される。核炭素粒子の比表面積は、600ｍ2/g以上程度であることがより好ましい。また、被覆材料としては、非晶質炭素、ポリアセン系物質などが例示される。
【００２３】
この様な核炭素粒子(以下「活性炭」をもって代表させる)と被覆層とからなる積層粒子材料は、例えば、以下の様にして製造することができる。すなわち、平均粒径1〜500μm程度(より好ましくは1〜50μm)の活性炭を、フェノール樹脂、ポリパラフェニレン、ポリフェニレンスルフィド、メソカーボンマイクロビーズ、ピッチ系繊維、コークスなどの共存下に熱処理することによりその表面に被覆層を形成させるか、或いは熱処理により被覆層を形成しうる炭素前駆体(それ自身液状である有機物質ならびに有機溶媒に溶解し得る有機物質；タール、ピッチ、合成樹脂など)を予め活性炭表面にコーティングした後、熱処理するか、或いは気相での熱処理により被覆層を形成し得るキシレン、ベンゼンなどの炭化水素を含む不活性雰囲気中で活性炭を熱処理するなどの手法により、得られる。活性炭としては、得られる積層粒子材料が所望の特性を発揮する限り、その原料などに特に制限はなく、石油系、石炭系、植物系、高分子系などの各種の原料から得られた市販品を使用することができる。熱処理温度は、活性炭表面を非晶質炭素、ポリアセン系物質などのアモルファス系炭素質材料により被覆するために、500℃〜1500℃程度の温度で行うことが好ましく、特に400〜800℃程度の熱処理により、活性炭表面をポリアセン系物質により被覆することが好ましい。ポリアセンによる被覆層を備えた積層粒子材料は、リチウムをドープした状態において、150℃程度の温度における電解液との反応による発熱が少ないので、安全性の観点から公的である。
【００２４】
材料粒子としての活性炭表面を被覆する炭素質材料の量は、原料とする活性炭の構造(細孔直径、気孔率など)応じて適宜決定すれば良く、特に限定されるものではないが、通常活性炭重量を基準として10〜80％程度である。
【００２５】
本発明のリチウム系二次電池用負極材料は、公知の手法により負極に成型した後、電池の構成材料として使用される。
【００２６】
例えば、本発明の負極材料を使用する電極は、公知の電極製造技術により、結着剤である樹脂の有機溶剤溶液を用いて、負極材料を集電体である金属上に塗着し、乾燥し、必要に応じてプレスすることにより、得られる。
【００２７】
本発明によるリチウム系二次電池用負極材料あるいはこのリチウム系二次電池用負極材料を用いた電極中には、あらかじめリチウムをドープしておくことができる。リチウムをドープしておくことにより、電池の初期効率、容量および出力特性を制御することが可能である。
【００２８】
【発明の効果】
本発明によるリチウム系二次電池用負極材料は、初期効率30％以上、好ましくは50％以上であり、4000mA/gの速度での放電で300mAh/g以上、好ましくは、400mAh/g以上である。この値は、例えば、上述の方法で得られる本発明のリチウム系二次電池用負極材料を用いた電極において測定可能である。BET法による比表面積が20〜1000m2/gの炭素質材料においても、上記の初期効率および容量を達成し得ない場合には、高エネルギー密度と高出力とを兼ね備えたリチウム系二次電池を得ることはできない。
【００２９】
【実施例】
以下、本発明の実施例を示し、本発明をさらに具体的に説明する。
実施例１
市販のピッチ系活性炭(粒径10μm；比表面積2000m2/ｇ)5gをステンレスメッシュ製の籠に入れ、等方性ピッチ(軟化点：270℃)10gを入れたセラミック製皿の上に置き、小型円筒炉（炉心管内径100mm）を用いて加熱処理を行った。加熱処理は、窒素雰囲気下で行い、窒素流量は0.5ｌ/minとした。加熱処理は、被加熱処理物を700℃まで昇温し、同温度で4時間保持し、続いて自然冷却により、60℃まで冷却した後、炉から取り出した。
【００３０】
得られた炭素質材料被覆活性炭は、原料ピッチ系活性炭に比して、重量が50％程度増加しており、BET法による比表面積（測定使用機：ユアサアイオニクス社製「NOVA1200」）の測定を行ったところ、550m2/gであった。
【００３１】
次いで、上記で得られた炭素質材料被覆活性炭100重量部、アセチレンブラック10重量部およびPVdF (ポリフッ化ビニリデン)10重量部とNMP(N-メチルピロリドン)200重量部とを混合して、スラリーを得た。次いで、該スラリーを厚さ14μmの銅箔の片面に塗布し、乾燥し、プレスして、厚さ60μmの電極を得た。得られた電極密度は、1.01g/ccであった。
【００３２】
上記で得られた電極を作用極とし、金属リチウムを対極および参照極とし、エチレンカーボネートとメチルエチルカーボネートを3：7重量比で混合した溶媒に1mol/lの濃度にLiPF6を溶解した溶液を電解液として、アルゴンドライボックス中で電気化学セルを作成した。リチウムのドーピングは、まずリチウム電位に対して1mVになるまで活物質重量に対して100mA/gの速度で行い、さらにリチウム電位に対して1mVの定電圧を20時間印可して、ドーピングを終了した。次いで、活物質重量に対し100mA/gの速度でリチウム電位に対して2Ｖまで脱ドーピングを行ったところ、放電容量605mAh/g、初期効率56％の値を得た。
【００３３】
次に、充電速度および放電速度を変化させて、容量測定を行った。すなわち、4000mA/gの放電あるいは5分（リチウム電位に対して1mVになるまで活物質重量に対して4000mA/gの速度で行い、更にリチウム電位に対して1mVの定電圧を印可して、総充電時間を5分間とした）の充電において、400mAh/g以上の容量が得られた。
比較例１
市販のピッチ系活性炭(粒径10μm；比表面積2000m2/ｇ)100重量部、アセチレンブラック10重量部およびPVdF10重量部とNMP300重量部とを混合して、スラリーを得た後、該スラリーを厚さ14μmの銅箔の片面に塗布し、乾燥し、プレスして、厚さ60μmの電極を得た。得られた電極の密度は、0.61g/ccであった。
【００３４】
上記で得られた電極を作用極とし、金属リチウムを対極および参照極とし、エチレンカーボネートとメチルエチルカーボネートを3：7重量比で混合した溶媒に1mol/lの濃度にLiPF6を溶解した溶液を電解液として、アルゴンドライボックス中で電気化学セルを作成した。リチウムのドーピングは、まずリチウム電位に対して1mVになるまで活物質重量に対して100mA/gの速度で行い、さらにリチウム電位に対して1mVの定電圧を20時間印可して、ドーピングを終了した。次いで、活物質重量に対し100mA/gの速度でリチウム電位に対して2Ｖまで脱ドーピングを行ったところ、放電容量502mAh/g、初期効率12％の値を得た。
【００３５】
炭素質材料粒子としての活性炭に対する被覆層の形成を行なうことなく、活性炭をそのまま負極材料として使用する場合には、初期効率が著しく低く、また、電極密度が低いことが明らかである。従って、この負極材料(活性炭そのもの)を用いて、高エネルギー密度のリチウム系二次電池を得ることは難しい。
比較例２
天然黒鉛(粒径6μm：比表面積2.3m2/ｇ)を100重量部、アセチレンブラック3重量部およびPVdF10重量部とNMP300重量部とを混合して、スラリーを得た。該スラリーを厚さ14μmの銅箔の片面に塗布し、乾燥し、プレスすることにより、厚さ60μmの電極を得た。得られた電極の密度は、1.38g/ccであった。
【００３６】
上記で得られた電極を作用極とし、金属リチウムを対極および参照極とし、エチレンカーボネートとメチルエチルカーボネートを3：7重量比で混合した溶媒に1mol/lの濃度にLiPF6を溶解した溶液を電解液として、アルゴンドライボックス中で電気化学セルを作成した。リチウムのドーピングは、まずリチウム電位に対して1mVになるまで活物質重量に対して100mA/gの速度で行い、さらにリチウム電位に対して1mVの定電圧を20時間印可して、ドーピングを終了した。次いで、活物質重量に対し100mA/gの速度でリチウム電位に対して2Vまで脱ドーピングを行ったところ、放電容量350mAh/g、初期効率83％の値を得た。
【００３７】
次いで、実施例１と同様にして、充電速度および放電速度を変化させて、容量測定を行った。
【００３８】
4000mA/gの放電あるいは5分の充電において、その容量は50mAh/g以下と実施例１に比べて、著しく低かった。
【００３９】
黒鉛系材料をそのままリチウム系二次電池の負極材料として使用する場合には、所望の容量特性を得ることは、できないことが明らかである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a negative electrode material for lithium secondary batteries having both high energy density and high output.
[0002]
[Prior art]
In recent years, midnight power storage systems, home-use distributed power storage systems based on solar power generation technology, and power storage systems for electric vehicles have attracted attention from the viewpoint of the effective use of energy aimed at preserving the global environment and conserving resources. Yes.
[0003]
The first requirement in these power storage systems is that the battery used has a high energy density. In response to these demands, lithium battery power storage technology research associations (LIBES) and others are energetically developing lithium ion batteries as potential candidates for high energy density batteries.
[0004]
The second requirement is that the output characteristics of the battery are stable. For example, in order to operate an engine or a fuel cell with maximum efficiency in a combination of a high-efficiency engine and a power storage system (for example, a hybrid electric vehicle) or a combination of a fuel cell and a power storage system (for example, a fuel cell vehicle). Therefore, operation at a constant output is essential, and in order to cope with load-side output fluctuations or energy regeneration, high output discharge characteristics and / or high rate charge acceptance characteristics in the power storage system are required.
[0005]
Currently, as a high power storage device, there is an electric double layer capacitor using activated carbon as an electrode, and a large capacitor having an output characteristic exceeding 2 kW / l has been developed. However, since the energy density is only about 1 to 5 Wh / l, it is difficult to configure the above power storage system alone.
[0006]
On the other hand, nickel-metal hydride batteries currently used in hybrid electric vehicles achieve a high output of 2 kW / l or more and have an energy density of about 160 Wh / l. However, research for further improving the reliability by further increasing the energy density and further improving the stability at high temperature has been energetically advanced.
[0007]
In addition, research on higher output is also underway for lithium ion batteries. For example, a lithium ion battery with a high output exceeding 3 kW / l has been developed at a DOD of 50%, but its energy density is 100 Wh / l or less, and the high energy density, which is the biggest feature of lithium ion batteries, was intentionally suppressed. Designed.
[0008]
As described above, there is a strong demand for practical use of a battery that has both high output (2 kW / l and above) and high energy density (180 Wh / l and above). Not developed. In particular, a lithium secondary battery having a high potential in increasing energy density has an output of 1 kW / l or less at an energy density of 250 to 300 Wh / l, and it is difficult to simultaneously achieve a high energy density and a high output. .
[0009]
In order to achieve both high energy density and high output simultaneously, a multifaceted approach from various battery constituent materials such as a negative electrode material, a positive electrode material, and an electrolytic solution is necessary. For example, when a known graphite-based material or carbon material is used as a negative electrode material when producing a lithium ion battery, for example, in a rapid discharge (current density of 4000 mA / g) at a 5-minute level, the capacity is Compared with 1 hour level discharge (300mA / g current density) Therefore, a large breakthrough is required for the development of a lithium secondary battery having both high energy density and high output.
[0010]
Moreover, the activated carbon used for the capacitor which is a high output device generally has a specific surface area of 1000 m 2 / g or more. When such capacitor activated carbon is doped with lithium ions, such an activated carbon should be used for a lithium secondary battery because of its extremely low efficiency and low density during electrode formation. Was difficult.
[0011]
[Problems to be solved by the invention]
Therefore, an object of the present invention is to provide a negative electrode material for a high-power lithium secondary battery having a high energy density.
[0012]
Another object of the present invention is to provide a negative electrode material for a high-power lithium secondary battery that has a high energy density and can accept a high rate of charge.
[0013]
[Means for solving the problems]
The present inventor conducted research while paying attention to the problems of the prior art as described above, and as a result, the carbon-based material having specific physical properties exhibited an excellent function as a negative electrode material for a lithium secondary battery. As a result, the present invention has been completed.
[0014]
That is, the present invention provides the following negative electrode material for a lithium secondary battery.
1. A lithium-based material comprising a carbon-based material having a specific surface area of 20 to 100 m 2 / g as measured by the BET method, and having an initial efficiency of 30% or more and a capacity of 300 mAh / g or more when discharged at a rate of 4000 mA / g. Negative electrode material for secondary batteries.
2. Item 2. The negative electrode material for a lithium secondary battery according to Item 1, wherein the carbon material is an amorphous material.
3. Item 2. The lithium-based secondary battery negative electrode material according to Item 1, wherein the carbon-based material is a laminated material in which the surface of carbon particles is coated with a carbonaceous material.
4). A method for producing a negative electrode material for a lithium secondary battery, wherein a carbonaceous material coating layer is formed on the surface of carbon particles by heating the carbon particles in the presence of a carbonaceous material film-forming substance.
5). Item 5. The method for producing a negative electrode material for a lithium secondary battery according to Item 4, wherein the carbon particles are amorphous material particles.
6). Item 6. The method for producing a negative electrode material for a lithium secondary battery according to Item 5, wherein the carbon particles are activated carbon particles.
7). Item 7. The method for producing a negative electrode material for a lithium secondary battery according to any one of Items 4 to 6, wherein the heating temperature is 500 to 1500 ° C.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail.
[0016]
The negative electrode material for a lithium secondary battery according to the present invention is made of a carbon-based material having a specific surface area of 20 to 100 m 2 / g according to the BET method, and has an initial efficiency of 30% or more and a discharge rate of 4000 mA / g of 300 mAh / It has a capacity of g or more.
[0017]
The negative electrode material for a lithium secondary battery according to the present invention is more preferably a carbonaceous material having a specific surface area by the BET method of 50 to 800 m 2 / g, and is a carbonaceous material of 100 to 600 m 2 / g. Is more preferable. When the specific surface area is too small, sufficient output cannot be obtained. On the other hand, when the specific surface area is too large, the initial charge / discharge efficiency of lithium ions is remarkably lowered, the density of the electrode using the negative electrode material is lowered, and the capacity per volume is reduced. In addition, in order to increase the migration rate of lithium ions from the negative electrode material to the electrolyte, the electrolyte needs to be able to sufficiently enter the active material. For this purpose, in particular, the pore volume has a pore diameter of 100 to 10 mm. It is preferable to control appropriately.
[0018]
The negative electrode material for a lithium secondary battery in the present invention is not particularly limited as long as it has the above-described characteristics or structure. However, considering the movement of lithium ions in the active material, amorphous carbon More preferably, it is a material. An amorphous carbon material is more suitable in that it can charge and discharge lithium at a higher rate because its charge / discharge curve is gentle compared to a crystalline material such as graphite.
[0019]
The capacity of the negative electrode material for a lithium secondary battery of the present invention is usually 300 mAh / g or more, more preferably 400 mAh / g or more, and particularly preferably 500 mAh / g or more. In the prior art, a material of about 200 to 300 mAh / g is generally used as the negative electrode active material of the lithium ion battery. However, in order to obtain a high-power battery, as described later, the porosity of the negative electrode holding the electrolyte (the sum of the porosity of the negative electrode material itself and the porosity of the negative electrode material particles in the formed negative electrode) ) Is preferably set to be about 35% to 60%. When the active material capacity is 300 mAh / g or less, the capacity per electrode volume is smaller than that of a general lithium ion battery. The energy density of the battery is reduced.
[0020]
Suitable examples of the negative electrode material for a lithium secondary battery that satisfies the above requirements include carbon materials such as amorphous carbon (amorphous carbon, polyacene materials, etc.).
[0021]
The negative electrode material for a lithium secondary battery of the present invention is obtained by coating a carbonaceous material (amorphous carbon, polyacene, etc.) on the surface of carbon particles (nuclear carbon particles) as a core, and has a specific surface area. Is particularly preferably a carbonaceous material (laminated particle material) having a particle size of about 20 to 1000 m 2 / g.
[0022]
When a laminated particle material is used as the negative electrode material, activated carbon, charcoal, polyacene-based material or the like having a specific surface area of 100 m 2 / g or more is used as the core carbon particle. The specific surface area of the nuclear carbon particles is more preferably about 600 m 2 / g or more. Examples of the coating material include amorphous carbon and polyacene-based substances.
[0023]
A laminated particle material composed of such nuclear carbon particles (hereinafter represented by “activated carbon”) and a coating layer can be produced, for example, as follows. That is, by heat-treating activated carbon having an average particle size of about 1 to 500 μm (more preferably 1 to 50 μm) in the presence of phenol resin, polyparaphenylene, polyphenylene sulfide, mesocarbon microbeads, pitch fibers, coke, etc. A carbon precursor (an organic substance that is liquid itself and an organic substance that can be dissolved in an organic solvent; tar, pitch, synthetic resin, etc.) that can form a coating layer on the surface or that can be formed by heat treatment is pre-loaded. After coating on the surface of the activated carbon, heat treatment is performed, or the activated carbon is heat treated in an inert atmosphere containing hydrocarbons such as xylene and benzene that can form a coating layer by heat treatment in a gas phase. As the activated carbon, as long as the obtained laminated particle material exhibits desired characteristics, there are no particular restrictions on its raw materials, and commercial products obtained from various raw materials such as petroleum-based, coal-based, plant-based, and polymer-based materials. Can be used. The heat treatment temperature is preferably about 500 to 1500 ° C., particularly about 400 to 800 ° C. in order to coat the activated carbon surface with amorphous carbonaceous material such as amorphous carbon or polyacene. Thus, it is preferable to coat the activated carbon surface with a polyacene-based material. A laminated particle material provided with a polyacene coating layer is public from the viewpoint of safety because it generates little heat due to reaction with an electrolyte at a temperature of about 150 ° C. in a lithium-doped state.
[0024]
The amount of the carbonaceous material covering the activated carbon surface as material particles may be appropriately determined according to the structure (pore diameter, porosity, etc.) of the activated carbon used as a raw material, and is not particularly limited, but is usually activated carbon About 10 to 80% based on weight.
[0025]
The negative electrode material for a lithium secondary battery of the present invention is used as a constituent material of a battery after being formed into a negative electrode by a known method.
[0026]
For example, an electrode using the negative electrode material of the present invention is coated with a negative electrode material on a metal as a current collector using an organic solvent solution of a resin as a binder by a known electrode manufacturing technique and dried. It is obtained by pressing as necessary.
[0027]
The negative electrode material for lithium secondary batteries according to the present invention or the electrode using this negative electrode material for lithium secondary batteries can be doped with lithium in advance. By doping with lithium, it is possible to control the initial efficiency, capacity, and output characteristics of the battery.
[0028]
【The invention's effect】
The negative electrode material for a lithium secondary battery according to the present invention has an initial efficiency of 30% or more, preferably 50% or more, and 300mAh / g or more, preferably 400mAh / g or more when discharged at a rate of 4000mA / g. . This value can be measured, for example, in an electrode using the negative electrode material for a lithium secondary battery of the present invention obtained by the above-described method. Even in the case of a carbonaceous material having a specific surface area of 20 to 1000 m 2 / g according to the BET method, if the above initial efficiency and capacity cannot be achieved, a lithium-based secondary battery having both high energy density and high output is required. I can't get it.
[0029]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples.
Example 1
Place 5 g of commercially available pitch-based activated carbon (particle size 10 μm; specific surface area 2000 m 2 / g) in a stainless steel mesh basket and place it on a ceramic dish with 10 g of isotropic pitch (softening point: 270 ° C.) Heat treatment was performed using a small cylindrical furnace (core tube inner diameter 100 mm). The heat treatment was performed in a nitrogen atmosphere, and the nitrogen flow rate was 0.5 l / min. In the heat treatment, the object to be heated was heated to 700 ° C., held at the same temperature for 4 hours, subsequently cooled to 60 ° C. by natural cooling, and then taken out from the furnace.
[0030]
The obtained carbonaceous material-coated activated carbon has a weight increase of about 50% compared to the raw material pitch-based activated carbon, and the specific surface area (measurement machine: Yuasa Ionics "NOVA1200") is measured by the BET method. The result was 550 m 2 / g.
[0031]
Next, 100 parts by weight of the carbonaceous material-coated activated carbon obtained above, 10 parts by weight of acetylene black, 10 parts by weight of PVdF (polyvinylidene fluoride), and 200 parts by weight of NMP (N-methylpyrrolidone) were mixed to prepare a slurry. Obtained. Next, the slurry was applied to one side of a copper foil having a thickness of 14 μm, dried and pressed to obtain an electrode having a thickness of 60 μm. The obtained electrode density was 1.01 g / cc.
[0032]
A solution in which LiPF 6 was dissolved at a concentration of 1 mol / l in a solvent in which ethylene carbonate and methyl ethyl carbonate were mixed at a weight ratio of 3: 7 was used with the electrode obtained above as a working electrode, metallic lithium as a counter electrode and a reference electrode. As an electrolyte, an electrochemical cell was prepared in an argon dry box. Lithium doping was first performed at a rate of 100 mA / g with respect to the weight of the active material until 1 mV with respect to the lithium potential, and then a constant voltage of 1 mV with respect to the lithium potential was applied for 20 hours to complete the doping. . Subsequently, when dedoping was performed up to 2 V with respect to the lithium potential at a rate of 100 mA / g with respect to the weight of the active material, a discharge capacity of 605 mAh / g and an initial efficiency of 56% were obtained.
[0033]
Next, the capacity measurement was performed by changing the charge rate and the discharge rate. That is, discharge at 4000 mA / g or 5 minutes (at a rate of 4000 mA / g with respect to the active material weight until 1 mV with respect to the lithium potential, and then apply a constant voltage of 1 mV with respect to the lithium potential, A capacity of 400 mAh / g or more was obtained during charging (with a charging time of 5 minutes).
Comparative Example 1
100 parts by weight of commercially available pitch-based activated carbon (particle size 10 μm; specific surface area 2000 m 2 / g), 10 parts by weight of acetylene black, 10 parts by weight of PVdF and 300 parts by weight of NMP were obtained to obtain a slurry. It was applied to one side of a 14 μm thick copper foil, dried and pressed to obtain an electrode having a thickness of 60 μm. The density of the obtained electrode was 0.61 g / cc.
[0034]
A solution in which LiPF 6 was dissolved at a concentration of 1 mol / l in a solvent in which ethylene carbonate and methyl ethyl carbonate were mixed at a weight ratio of 3: 7 was used with the electrode obtained above as a working electrode, metallic lithium as a counter electrode and a reference electrode. As an electrolyte, an electrochemical cell was prepared in an argon dry box. Lithium doping was first performed at a rate of 100 mA / g with respect to the weight of the active material until 1 mV with respect to the lithium potential, and then a constant voltage of 1 mV with respect to the lithium potential was applied for 20 hours to complete the doping. . Subsequently, when dedoping was performed up to 2 V with respect to the lithium potential at a rate of 100 mA / g with respect to the weight of the active material, a discharge capacity of 502 mAh / g and an initial efficiency of 12% were obtained.
[0035]
When the activated carbon is used as the negative electrode material as it is without forming a coating layer on the activated carbon as the carbonaceous material particles, it is clear that the initial efficiency is remarkably low and the electrode density is low. Therefore, it is difficult to obtain a high energy density lithium secondary battery using this negative electrode material (activated carbon itself).
Comparative Example 2
100 parts by weight of natural graphite (particle size 6 μm: specific surface area 2.3 m 2 / g), 3 parts by weight of acetylene black, 10 parts by weight of PVdF and 300 parts by weight of NMP were mixed to obtain a slurry. The slurry was applied to one side of a 14 μm thick copper foil, dried and pressed to obtain an electrode having a thickness of 60 μm. The density of the obtained electrode was 1.38 g / cc.
[0036]
A solution in which LiPF 6 was dissolved at a concentration of 1 mol / l in a solvent in which ethylene carbonate and methyl ethyl carbonate were mixed at a weight ratio of 3: 7 was used with the electrode obtained above as a working electrode, metallic lithium as a counter electrode and a reference electrode. As an electrolyte, an electrochemical cell was prepared in an argon dry box. Lithium doping was first performed at a rate of 100 mA / g with respect to the weight of the active material until 1 mV with respect to the lithium potential, and then a constant voltage of 1 mV with respect to the lithium potential was applied for 20 hours to complete the doping. . Next, when dedoping was performed up to 2 V with respect to the lithium potential at a rate of 100 mA / g with respect to the weight of the active material, a discharge capacity of 350 mAh / g and an initial efficiency of 83% were obtained.
[0037]
Next, in the same manner as in Example 1, the capacity measurement was performed while changing the charge rate and the discharge rate.
[0038]
When discharged at 4000 mA / g or charged for 5 minutes, the capacity was 50 mAh / g or less, which was significantly lower than that of Example 1.
[0039]
When the graphite material is used as it is as a negative electrode material for a lithium secondary battery, it is apparent that desired capacity characteristics cannot be obtained.
Claims (5)
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| JP4288465B2 (en) * | 2000-11-17 | 2009-07-01 | 株式会社Ｋｒｉ | Non-aqueous lithium secondary battery |
| CN101100296B (en) | 2002-11-13 | 2012-07-18 | 昭和电工株式会社 | Active carbon, production method thereof and polarizable electrode |
| JP4611082B2 (en) * | 2005-03-31 | 2011-01-12 | ダイハツ工業株式会社 | Electrochemical capacitor |
| US7862897B2 (en) * | 2006-01-27 | 2011-01-04 | Carbon Ceramics Company, Llc | Biphasic nanoporous vitreous carbon material and method of making the same |
| JP2011081960A (en) * | 2009-10-05 | 2011-04-21 | Kri Inc | Nonaqueous secondary battery |
| EP2693537B1 (en) | 2011-05-23 | 2017-12-06 | LG Chem, Ltd. | High energy density lithium secondary battery having enhanced energy density characteristic |
| CN103518277B (en) | 2011-05-23 | 2016-03-23 | 株式会社Lg化学 | The height with the power density properties of enhancing exports lithium secondary battery |
| JP2014513409A (en) | 2011-05-23 | 2014-05-29 | エルジー ケム． エルティーディ． | High power lithium secondary battery with improved power density characteristics |
| WO2012161479A2 (en) | 2011-05-23 | 2012-11-29 | 주식회사 엘지화학 | High output lithium secondary battery having enhanced output density characteristic |
| WO2012161476A2 (en) | 2011-05-23 | 2012-11-29 | 주식회사 엘지화학 | High energy density lithium secondary battery having enhanced energy density characteristic |
| KR101336076B1 (en) | 2011-05-23 | 2013-12-03 | 주식회사 엘지화학 | Lithium Secondary Battery of High Power Property with Improved High Power Density |
| WO2013009078A2 (en) | 2011-07-13 | 2013-01-17 | 주식회사 엘지화학 | High-energy lithium secondary battery having improved energy density characteristics |
| EP2930728B1 (en) | 2012-12-06 | 2020-02-05 | Asahi Kasei Kabushiki Kaisha | Nonaqueous lithium storage element |
| WO2015080253A1 (en) | 2013-11-29 | 2015-06-04 | 旭化成株式会社 | Lithium ion capacitor |
| JP6453560B2 (en) * | 2014-06-03 | 2019-01-16 | 旭化成株式会社 | Negative electrode for non-aqueous lithium storage element and non-aqueous lithium storage element using the same |
| TWI565654B (en) * | 2014-08-08 | 2017-01-11 | Kureha Corp | Production method of carbonaceous material for negative electrode of nonaqueous electrolyte secondary battery and carbonaceous material for negative electrode of nonaqueous electrolyte secondary battery |
| TWI599092B (en) | 2014-08-08 | 2017-09-11 | Kureha Corp | Non-Aqueous Electrolyte Secondary Battery Negative Carbonaceous Material |
| TWI604655B (en) * | 2014-08-08 | 2017-11-01 | Kureha Corp | Non-aqueous electrolyte secondary battery negative carbonaceous material |
| US10403447B2 (en) | 2016-01-22 | 2019-09-03 | Asahi Kasei Kabushiki Kaisha | Nonaqueous lithium storage element |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS63218160A (en) * | 1987-03-06 | 1988-09-12 | Kanebo Ltd | Organic electrolyte cell |
| JPS63226019A (en) * | 1987-03-13 | 1988-09-20 | 松下電器産業株式会社 | Manufacture of polarizing electrode |
| JPH0967112A (en) * | 1995-08-31 | 1997-03-11 | Kyocera Corp | Solid activated carbon and its production |
| JPH10233206A (en) * | 1997-02-17 | 1998-09-02 | Asahi Chem Ind Co Ltd | Nonaqueous electrolyte secondary battery |
| JPH10287412A (en) * | 1997-04-15 | 1998-10-27 | Kyocera Corp | Solid active carbon |
-
2000
- 2000-02-17 JP JP2000039104A patent/JP4497622B2/en not_active Expired - Lifetime
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS63218160A (en) * | 1987-03-06 | 1988-09-12 | Kanebo Ltd | Organic electrolyte cell |
| JPS63226019A (en) * | 1987-03-13 | 1988-09-20 | 松下電器産業株式会社 | Manufacture of polarizing electrode |
| JPH0967112A (en) * | 1995-08-31 | 1997-03-11 | Kyocera Corp | Solid activated carbon and its production |
| JPH10233206A (en) * | 1997-02-17 | 1998-09-02 | Asahi Chem Ind Co Ltd | Nonaqueous electrolyte secondary battery |
| JPH10287412A (en) * | 1997-04-15 | 1998-10-27 | Kyocera Corp | Solid active carbon |
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