JP2000243398A - Lithium secondary battery negative electrode material and its manufacture, lithium secondary battery negative electrode and lithium secondary battery - Google Patents
Lithium secondary battery negative electrode material and its manufacture, lithium secondary battery negative electrode and lithium secondary batteryInfo
- Publication number
- JP2000243398A JP2000243398A JP11045512A JP4551299A JP2000243398A JP 2000243398 A JP2000243398 A JP 2000243398A JP 11045512 A JP11045512 A JP 11045512A JP 4551299 A JP4551299 A JP 4551299A JP 2000243398 A JP2000243398 A JP 2000243398A
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- Prior art keywords
- negative electrode
- secondary battery
- lithium secondary
- electrode material
- pitch
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Classifications
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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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- Working-Up Tar And Pitch (AREA)
- Secondary Cells (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
Description
【０００１】[0001]
【発明が属する技術分野】本発明は、電池用負極材料、
特に、リチウム二次電池用負極材料に関する。The present invention relates to a negative electrode material for a battery,
In particular, it relates to a negative electrode material for a lithium secondary battery.
【０００２】[0002]
【従来の技術とその課題】携帯電話や携帯用情報機器
（例えば、所謂電子手帳や携帯用パーソナルコンピュー
ター）などに代表される携帯用電子機器類の小型化・軽
量化が目覚しく進展しつつある今日では、そのような携
帯用電気機器類を駆動するための小型で軽量な二次電池
の開発が要望されている。このような背景の下、小型に
構成でき、しかも高エネルギー密度を有するリチウム二
次電池が注目を集めており、その開発が盛んに行われて
いる。2. Description of the Related Art Today, portable electronic devices represented by mobile phones and portable information devices (for example, so-called electronic notebooks and portable personal computers) are being remarkably reduced in size and weight. Therefore, development of a small and lightweight secondary battery for driving such portable electric devices is demanded. Under such a background, a lithium secondary battery that can be configured in a small size and has a high energy density has attracted attention and has been actively developed.
【０００３】一般的なリチウム二次電池は、負極活物質
として箔状のリチウムを、正極活物質として金属カルコ
ゲン化物や金属酸化物を、また、電解液として非プロト
ン性有機溶媒に種々の塩を溶解させたものをそれぞれ用
いている。ところが、このようなリチウム二次電池は、
充放電を繰り返すに従って、負極に樹枝状リチウム（デ
ンドライト）が生成し、これが正極と負極との間の短絡
を引き起こすことになるため、充放電のサイクル寿命が
短いという欠点を有している。[0003] A general lithium secondary battery comprises a foil-like lithium as a negative electrode active material, a metal chalcogenide or a metal oxide as a positive electrode active material, and various salts in an aprotic organic solvent as an electrolyte. Dissolved ones are used. However, such a lithium secondary battery is
As charge and discharge are repeated, dendritic lithium (dendrite) is generated on the negative electrode, which causes a short circuit between the positive electrode and the negative electrode, and thus has a disadvantage that the charge and discharge cycle life is short.
【０００４】一方、デンドライトを生成し易い箔状のリ
チウムに代えて、アルミニウム、鉛、カドミウムまたは
インジウムを含む可融性リチウム合金を負極材料として
用い、充電時にリチウム合金を析出させ、放電時にリチ
ウム合金からリチウムを溶解させるように構成したリチ
ウム二次電池が提案されている（例えば、米国特許第４
００２４９２号参照）。しかし、このような二次電池
は、デンドライトの生成は抑制できるものの、負極の加
工性に劣り、また、充放電サイクルを繰り返すに従っ
て、或いは深い充放電を実施した場合に、負極において
合金の偏析が生じ易く、結果的にサイクル特性を長期間
安定に維持するのは困難である。[0004] On the other hand, a fusible lithium alloy containing aluminum, lead, cadmium or indium is used as a negative electrode material instead of foil-like lithium, which easily generates dendrite. There has been proposed a lithium secondary battery configured to dissolve lithium from U.S. Pat.
002492). However, although such a secondary battery can suppress the generation of dendrite, the workability of the negative electrode is inferior, and the segregation of the alloy in the negative electrode occurs as the charge / discharge cycle is repeated or when deep charge / discharge is performed. As a result, it is difficult to maintain the cycle characteristics stably for a long period of time.
【０００５】そこで、上述のような不具合を解消でき、
サイクル特性および安全性に優れたリチウム二次電池を
実現可能な負極材料として、リチウムイオンの出入り、
すなわち挿入・脱離が可能な炭素材料からなるものが数
多く提案されており、実用化されつつある。ここで、炭
素材料からなるリチウム二次電池用の負極材料は、主と
して、１，０００℃程度で焼成された炭素系のものと、
２，０００℃を超える温度で焼成された黒鉛系のものと
の２種類に分類することができるが、炭素系の負極材料
は、リチウムイオンの放出に伴う電位の変化が大きく、
安定なリチウム二次電池を構成し難いという欠点があ
る。これに対し、黒鉛系の負極材料は、このような電位
の変化が小さく、安定なリチウム二次電池を構成可能で
あるため、炭素系の負極材料に比べて有利であり、リチ
ウム二次電池用の負極材料として主流になりつつある。Therefore, the above-mentioned problems can be solved.
As a negative electrode material that can realize a lithium secondary battery with excellent cycle characteristics and safety,
That is, many carbon materials that can be inserted and desorbed have been proposed and are being put to practical use. Here, the negative electrode material for a lithium secondary battery made of a carbon material is mainly a carbon-based material fired at about 1,000 ° C.,
Graphite-based materials fired at a temperature exceeding 2,000 ° C can be classified into two types. Carbon-based negative electrode materials have a large change in potential due to release of lithium ions,
There is a disadvantage that it is difficult to construct a stable lithium secondary battery. On the other hand, the graphite-based negative electrode material is advantageous in comparison with the carbon-based negative electrode material because such a change in potential is small and a stable lithium secondary battery can be formed. Is becoming the mainstream as a negative electrode material.
【０００６】ところが、黒鉛系の負極材料は、リチウム
イオンや電解液と反応し易く、その結果として理論容量
値が３７２Ａｈ／ｋｇであるものの、実際の容量は３２
０Ａｈ／ｋｇ程度に低下してしまい、初期効率が通常は
８５％未満である。負極材料の初期効率は、リチウム二
次電池を小型にかつ安価に構成する上での重要なパラメ
ーターである。すなわち、負極材料の初期効率が低い場
合は、より多くの正極材料が必要となるため、リチウム
二次電池が高価になり、同時にそのような多くの正極材
料をパッキングする必要性からリチウム二次電池が必然
的に大型化してしまう。However, the graphite-based negative electrode material easily reacts with lithium ions and an electrolytic solution. As a result, although the theoretical capacity value is 372 Ah / kg, the actual capacity is 32 Ah / kg.
It is reduced to about 0 Ah / kg, and the initial efficiency is usually less than 85%. The initial efficiency of the negative electrode material is an important parameter in configuring a lithium secondary battery to be small and inexpensive. That is, when the initial efficiency of the negative electrode material is low, more positive electrode material is required, so that the lithium secondary battery becomes expensive, and at the same time, the need to pack such a large number of positive electrode materials makes the lithium secondary battery Inevitably increases in size.
【０００７】そのため、黒鉛系材料の表面にピッチやタ
ールなどの固体或いは液体有機物によるコーティング層
を配置し、それによって当該黒鉛系材料からなる負極材
料とリチウムイオンや電解液との反応を抑制する試みが
なされている。しかし、このコーティング層は、黒鉛系
材料と電解液等との反応を抑制することはできるもの
の、同時に充放電時のリチウムイオンの通過を阻止する
ことになるため、初期効率および容量の低下を却って招
くことになる。Therefore, an attempt is made to arrange a coating layer made of a solid or liquid organic substance such as pitch or tar on the surface of a graphite material, thereby suppressing the reaction between the negative electrode material made of the graphite material and lithium ions or an electrolyte. Has been made. However, although this coating layer can suppress the reaction between the graphite-based material and the electrolytic solution, etc., it also prevents the passage of lithium ions at the time of charging / discharging. Will be invited.
【０００８】本発明の目的は、高い初期効率および容量
を有するリチウム二次電池用負極材料を実現することに
ある。An object of the present invention is to realize a negative electrode material for a lithium secondary battery having high initial efficiency and capacity.
【０００９】[0009]
【課題を解決するための手段】本発明に係るリチウム二
次電池用負極材料は、黒鉛系炭素材料を、軟化点が１５
０〜３００℃のピッチの熱分解生成物を含む雰囲気下に
おいて熱処理する工程を経て得られるものである。The negative electrode material for a lithium secondary battery according to the present invention comprises a graphite-based carbon material having a softening point of 15%.
It is obtained through a step of heat treatment in an atmosphere containing a pyrolysis product having a pitch of 0 to 300 ° C.
【００１０】このリチウム二次電池用負極材料におい
て、黒鉛系炭素材料は、通常、Ｘ線回折法により得られ
る（００２）面の平均面間隔ｄ００２が０．３４０ｎｍ
以下のものである。また、ピッチは、例えば、下記の式
（１）で示される芳香族指数（ｆａ）が０．６０〜０．
９８のものである。In this negative electrode material for a lithium secondary battery, the graphite-based carbon material usually has an average spacing d002 of the (002) plane obtained by the X-ray diffraction method of 0.340 nm.
These are: The pitch is, for example, such that the aromatic index (fa) represented by the following formula (1) is 0.60-0.
98.
【００１１】[0011]
【数２】 (Equation 2)
【００１２】なお、このようなピッチは、例えば石炭系
ピッチである。さらに、熱処理は、例えば、不活性雰囲
気および還元性雰囲気のうちの１つの雰囲気の常圧下に
おける６００〜１，３００℃の温度による処理である。
このようなリチウム二次電池用負極材料は、熱処理後の
黒鉛系炭素材料の重量増加率が例えば５％未満である。[0012] Such a pitch is, for example, a coal-based pitch. Further, the heat treatment is, for example, a treatment at a temperature of 600 to 1,300 ° C. under normal pressure in one of an inert atmosphere and a reducing atmosphere.
In such a negative electrode material for a lithium secondary battery, the weight increase rate of the graphite-based carbon material after the heat treatment is, for example, less than 5%.
【００１３】また、このようなリチウム二次電池用負極
材料は、通常、放電容量が少なくとも３３０ｍＡｈ／ｇ
でありかつ初期効率が少なくとも８５％である。Such a negative electrode material for a lithium secondary battery usually has a discharge capacity of at least 330 mAh / g.
And the initial efficiency is at least 85%.
【００１４】本発明に係るリチウム二次電池用負極材料
の製造方法は、黒鉛系炭素材料と軟化点が１５０〜３０
０℃のピッチとを同じ閉空間内に別々に配置する工程
と、当該閉空間内の温度をピッチの熱分解温度以上に高
めるための工程とを含んでいる。In the method for producing a negative electrode material for a lithium secondary battery according to the present invention, the graphite-based carbon material has a softening point of 150 to 30.
The method includes a step of separately arranging the pitch of 0 ° C. in the same closed space, and a step of increasing the temperature in the closed space to a temperature higher than the thermal decomposition temperature of the pitch.
【００１５】本発明のリチウム二次電池用負極は、集電
体と、集電体上に配置された本発明のリチウム二次電池
用負極材料とバインダーとを含む活物質層とを備えてい
る。活物質層は、密度が少なくとも１．４ｇ／ｃｍ3、
放電容量が少なくとも３３０ｍＡｈ／ｇおよび初期効率
が少なくとも８５％である。本発明のリチウム二次電池
は、本発明に係る上述の各種のリチウム二次電池用負極
材料を含む負極を備えたものである。The negative electrode for a lithium secondary battery of the present invention includes a current collector, and an active material layer disposed on the current collector and containing the negative electrode material for a lithium secondary battery of the present invention and a binder. . The active material layer has a density of at least 1.4 g / cm 3 ,
The discharge capacity is at least 330 mAh / g and the initial efficiency is at least 85%. The lithium secondary battery of the present invention includes a negative electrode including the above-described various negative electrode materials for a lithium secondary battery according to the present invention.
【００１６】[0016]
【発明の実施の形態】本発明のリチウム二次電池用負極
材料で用いられる黒鉛系炭素材料は、黒鉛として一般に
理解される範疇に入る炭素材料であれば特に限定される
ものではないが、例えば、天然黒鉛、人造黒鉛、並びに
メソカーボンマイクロビーズ、メソフェーズピッチ粉
末、等方性ピッチ粉末および樹脂炭などの炭素前駆体を
焼成して黒鉛化したものなどを挙げることができる。な
お、これらの黒鉛系炭素材料は、２種以上のものが併用
されてもよい。BEST MODE FOR CARRYING OUT THE INVENTION The graphite-based carbon material used in the negative electrode material for a lithium secondary battery of the present invention is not particularly limited as long as it is a carbon material falling within a category generally understood as graphite. And natural graphite, artificial graphite, and mesocarbon microbeads, mesophase pitch powder, isotropic pitch powder, and carbonized carbon precursors such as resin charcoal and the like, and the like. In addition, two or more of these graphite-based carbon materials may be used in combination.
【００１７】なお、本発明で用いられる黒鉛系炭素材料
として特に好ましいものは、Ｘ線回折法により得られる
（００２）面の平均面間隔ｄ００２が０．３４０ｎｍ以
下のもの、特に、０．３３５ｎｍ以上０．３４０ｎｍ以
下のものである。Particularly preferred as the graphite-based carbon material used in the present invention are those having an average spacing d002 of (002) planes obtained by the X-ray diffraction method of 0.340 nm or less, particularly 0.335 nm or more. It is 0.340 nm or less.
【００１８】上述の黒鉛系炭素材料の形状・形態は特に
限定されるものではなく、鱗片状、塊状、繊維状、ウイ
スカー状、球状および破砕状などの各種のものである。
また、このような黒鉛系炭素材料の平均粒径は、通常、
１〜５０μｍ程度が好ましい。なお、黒鉛系炭素材料
は、２種以上の形状・形態のものの混合物であってもよ
い。The shape and form of the above-mentioned graphite-based carbon material are not particularly limited, and may be various types such as flake, lump, fibrous, whisker, spherical and crushed.
The average particle size of such a graphite-based carbon material is usually
It is preferably about 1 to 50 μm. The graphite-based carbon material may be a mixture of two or more types and shapes.
【００１９】本発明で用いられる上述のような黒鉛系炭
素材料は、炭素前駆体を１，０００℃程度の比較的低温
で焼成することにより得られる炭素材料とは異なり、通
常、リチウム二次電池において用いられる電解質、例え
ば、非プロトン性有機溶媒と塩とを含む電解液やリチウ
ムイオンに対する活性点、すなわち、当該電解液と反応
して電解液を分解したり、充放電時に移動するリチウム
イオンと反応する活性点を部分的に有している。この活
性点は、詳細が明らかではないが、一般には、黒鉛系炭
素材料の外側に配向している、結晶子の端面（ｅｄｇｅ
ｐｌａｎｅ）であると理解されている。The above-mentioned graphite-based carbon material used in the present invention is different from a carbon material obtained by firing a carbon precursor at a relatively low temperature of about 1,000 ° C., and is usually a lithium secondary battery. In the electrolyte used in, for example, an active point for an electrolyte or lithium ions containing an aprotic organic solvent and a salt, that is, the electrolyte reacts with the electrolyte and decomposes the electrolyte, or lithium ions that move during charge and discharge. It partially has active sites to react. Although the details of the active site are not clear, generally, the active site is oriented to the outside of the graphite-based carbon material.
plane).
【００２０】なお、上述の電解液を構成する非プロトン
性有機溶媒としては、例えば、エチレンカーボネート、
プロピレンカーボネート、ブチレンカーボネート、ジメ
チルカーボネート、ジエチルカーボネート、メチルエチ
ルカーボネートおよびγ−ブチロラクトンなどのエステ
ル類、テトラヒドロフランや２−メチルテトラヒドロフ
ランなどのフラン類、ジオキソラン、ジエチルエーテ
ル、ジメトキシエタン、ジエトキシエタンおよびメトキ
シエトキシエタンなどのエーテル類、ジメチルスルホキ
シド、スルホラン、メチルスルホラン、アセトニトリ
ル、ギ酸メチル並びに酢酸メチルなどを挙げることがで
きる。これらの有機溶媒は、２種以上が混合して用いら
れていてもよい。一方、このような非プロトン性有機溶
媒に溶解される塩は、例えば、過塩素酸リチウム、ホウ
フッ化リチウム、６フッ化りん酸リチウム、６フッ化砒
酸リチウム、トリフルオロメタンスルホン酸リチウム、
ハロゲン化リチウムおよび塩化アルミン酸リチウムなど
のリチウム塩である。これらの塩は、２種以上が同時に
溶解されていてもよい。The aprotic organic solvent constituting the above-mentioned electrolyte includes, for example, ethylene carbonate,
Esters such as propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate and γ-butyrolactone, furans such as tetrahydrofuran and 2-methyltetrahydrofuran, dioxolane, diethyl ether, dimethoxyethane, diethoxyethane and methoxyethoxyethane And ethers such as dimethyl sulfoxide, sulfolane, methyl sulfolane, acetonitrile, methyl formate and methyl acetate. These organic solvents may be used as a mixture of two or more. On the other hand, salts dissolved in such aprotic organic solvents include, for example, lithium perchlorate, lithium borofluoride, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium trifluoromethanesulfonate,
Lithium salts such as lithium halide and lithium chloroaluminate. Two or more of these salts may be dissolved simultaneously.
【００２１】一方、本発明で用いられるピッチは、公知
の各種のピッチであり、軟化点が１５０〜３００℃の範
囲であれば特に限定されるものではない。但し、本発明
で用いるピッチは、軟化点がこのような範囲でありかつ
下記の式（１）で示される芳香族指数（ｆａ）が０．６
０〜０．９８のものが好ましい。芳香族指数がこの範囲
外の場合は、却って容量および初期効率の低下を招くお
それがある。On the other hand, the pitch used in the present invention is various known pitches, and is not particularly limited as long as the softening point is in the range of 150 to 300 ° C. However, the pitch used in the present invention has a softening point in such a range and an aromatic index (fa) represented by the following formula (1) of 0.6.
Those having 0 to 0.98 are preferred. When the aromatic index is out of this range, the capacity and the initial efficiency may be reduced.
【００２２】[0022]
【数３】 (Equation 3)
【００２３】因みに、上述のような軟化点を有しかつ芳
香族指数が上述の範囲にあるピッチとしては、例えば、
石炭系等方性ピッチなどの石炭系ピッチおよび石油系等
方性ピッチなどの石油系ピッチを挙げることができる
が、本発明では石炭系ピッチ、特に石炭系等方性ピッチ
を用いるのが好ましい。なお、本発明では、２種以上の
ピッチが併用されてもよい。Incidentally, the pitch having the above-mentioned softening point and the aromatic index in the above-mentioned range includes, for example,
Coal-based pitch such as coal-based isotropic pitch and petroleum-based pitch such as petroleum-based isotropic pitch can be mentioned. In the present invention, coal-based pitch, particularly coal-based isotropic pitch, is preferably used. In the present invention, two or more pitches may be used in combination.
【００２４】本発明のリチウム二次電池用負極材料は、
上述のような黒鉛系炭素材料を、上述のようなピッチの
熱分解生成物を含む、通常は窒素やアルゴンなどの不活
性雰囲気下または水素混合気体などの還元性雰囲気下に
おいて熱処理することにより得られるものである。The negative electrode material for a lithium secondary battery of the present invention comprises:
The graphite-based carbon material as described above is obtained by heat treatment under an inert atmosphere containing a pyrolysis product of the pitch as described above, usually in an inert atmosphere such as nitrogen or argon, or in a reducing atmosphere such as a hydrogen mixed gas. It is something that can be done.
【００２５】ここでの熱処理方法としては、例えば、
加熱炉などの閉空間内に黒鉛系炭素材料を配置し、加熱
炉内にピッチの熱分解生成物を含む不活性ガスまたは還
元性ガスを導入しつつ黒鉛系炭素材料を加熱処理する方
法、および加熱炉などの閉空間内に黒鉛系炭素材料と
上述のようなピッチとを別々に配置し、両者を同時に加
熱する方法などを採用することができる。As the heat treatment method here, for example,
A method of arranging a graphite-based carbon material in a closed space such as a heating furnace, and heating the graphite-based carbon material while introducing an inert gas or a reducing gas containing a pyrolysis product of pitch into the heating furnace, and A method in which the graphite-based carbon material and the pitch as described above are separately arranged in a closed space such as a heating furnace and both are heated simultaneously can be adopted.
【００２６】このような熱処理時における、加熱炉など
の閉空間内の不活性雰囲気または還元性雰囲気中に含ま
れるピッチの熱分解生成物の濃度は、通常、処理する黒
鉛系炭素材料の量や熱処理時間に応じて適宜設定するこ
とができる。During such heat treatment, the concentration of the pyrolysis products of the pitch contained in an inert atmosphere or a reducing atmosphere in a closed space such as a heating furnace usually depends on the amount of the graphite-based carbon material to be treated and It can be set appropriately according to the heat treatment time.
【００２７】なお、熱処理方法として上述のの方法を
採用する場合は、加熱炉などの閉空間内に配置するピッ
チの量を、上述のような熱分解生成物濃度を達成するた
めに必要な量に設定する。When the above-described method is adopted as the heat treatment method, the amount of the pitch arranged in a closed space such as a heating furnace is adjusted to the amount necessary to achieve the above-mentioned concentration of the pyrolysis products. Set to.
【００２８】また、熱処理は、常圧で実施するのが好ま
しく、またその際の設定温度は、通常、６００〜１，３
００℃に設定するのが好ましく、９００〜１，２００℃
に設定するのがより好ましい。設定温度が６００℃未満
の場合は、黒鉛系炭素材料と熱分解生成物とが十分に反
応せず、結果的にリチウムイオンや電解液と反応しにく
い負極材料が得られにくくなる。逆に、１，３００℃を
超える場合は、容量および初期効率の低下を招くおそれ
がある。なお、熱処理方法として上述のの方法を採用
する場合、設定温度は、上述の範囲でありかつピッチの
熱分解温度以上（例えば石炭系ピッチを用いる場合は、
石炭系ピッチの熱分解温度以上）に設定する。The heat treatment is preferably carried out at normal pressure, and the temperature set at that time is usually from 600 to 1,3.
Preferably set to 00 ° C, 900 to 1200 ° C
Is more preferably set to. When the set temperature is lower than 600 ° C., the graphite-based carbon material and the pyrolysis product do not sufficiently react with each other, and as a result, it is difficult to obtain a negative electrode material that does not easily react with lithium ions or an electrolytic solution. Conversely, if the temperature exceeds 1,300 ° C., the capacity and the initial efficiency may be reduced. In addition, when the above-described method is adopted as the heat treatment method, the set temperature is in the above-described range and is equal to or higher than the thermal decomposition temperature of the pitch (for example, when using coal-based pitch,
Above the thermal decomposition temperature of coal-based pitch).
【００２９】本発明のリチウム二次電池用負極材料は、
上述のような製造工程を経て得られるものであるため、
黒鉛系炭素材料の表面全体が炭素質材料からなるコーテ
ィング層により被覆されている従来のものとは異なり、
黒鉛系炭素材料の主として活性点が選択的にピッチの熱
分解生成物と反応し、電解液やリチウムイオンに対して
不活性化されている。すなわち、この負極材料は、黒鉛
系炭素材料の主として活性点部分が選択的に上述のピッ
チの熱分解生成物によるコーティング層により被覆され
ているものと考えられる。The negative electrode material for a lithium secondary battery of the present invention comprises:
Because it is obtained through the above manufacturing process,
Unlike the conventional one in which the entire surface of the graphite-based carbon material is covered with a coating layer made of a carbonaceous material,
The active site of the graphite-based carbon material mainly reacts selectively with the thermal decomposition product of the pitch and is inactivated with respect to the electrolytic solution and lithium ions. That is, in the negative electrode material, it is considered that the active site portion of the graphite-based carbon material is mainly selectively covered with the coating layer of the above-described pitch pyrolysis product.
【００３０】本発明のリチウム二次電池用負極材料は、
このように黒鉛系炭素材料の主として活性点が選択的に
処理されているもの、すなわち、黒鉛系炭素材料の表面
が部分的に処理されているものであるため、通常、熱処
理前の黒鉛系炭素材料の重量を基準とした場合の重量増
加率が多くても５％（すなわち５％未満）、好ましい場
合は多くても１％（すなわち１％未満）である。The negative electrode material for a lithium secondary battery of the present invention comprises:
As described above, the active site of the graphite-based carbon material is mainly selectively treated, that is, the surface of the graphite-based carbon material is partially treated. The rate of weight gain, based on the weight of the material, is at most 5% (ie, less than 5%), and is preferably at most 1% (ie, less than 1%).
【００３１】本発明のリチウム二次電池用負極材料は、
上述のような電解液やリチウムイオンと反応しにくく、
電解液を分解したり、充放電に関与するリチウムイオン
を捕捉しにくいと共にそれ自体も電解液との反応による
破壊を受け難い。また、黒鉛系炭素材料の表面が部分的
にしか処理されていないので、充放電時のリチウムイオ
ンの通過を安定に確保することができ、容量が従来のも
のに比べて対理論容量比で大幅に低下しにくく、また、
初期効率も従来のものに比べて高い。より具体的には、
本発明の負極材料は、少なくとも３３０ｍＡｈ／ｇの放
電容量および少なくとも８５％の初期効率を達成するこ
とができる。The negative electrode material for a lithium secondary battery of the present invention comprises:
It is difficult to react with the electrolyte and lithium ions as described above,
It is difficult to decompose the electrolytic solution or to capture lithium ions involved in charge and discharge, and it is also less susceptible to destruction by a reaction with the electrolytic solution. In addition, since the surface of the graphite-based carbon material is only partially treated, the passage of lithium ions during charging and discharging can be ensured stably, and the capacity is significantly higher than the conventional one at a theoretical capacity ratio. Less likely to fall,
The initial efficiency is also higher than the conventional one. More specifically,
The negative electrode material of the present invention can achieve a discharge capacity of at least 330 mAh / g and an initial efficiency of at least 85%.
【００３２】本発明のリチウム二次電池用負極は、集電
体と、その上に配置された活物質層とを主に備えてい
る。集電体は、銅などの金属からなる、例えば箔状の部
材であり、また、活物質層は、本発明のリチウム二次電
池用負極材料とバインダーとを含んでいる。このような
リチウム二次電池用負極を形成する場合は、本発明のリ
チウム二次電池用負極材料をフッ素系ポリマー、ポリオ
レフィン系ポリマーまたは合成ゴムなどの公知のバイン
ダーと混合してペースト状にし、そのペーストを金属製
等の集電体上に塗布して活物質層を形成する。The negative electrode for a lithium secondary battery according to the present invention mainly includes a current collector and an active material layer disposed thereon. The current collector is, for example, a foil-shaped member made of a metal such as copper, and the active material layer contains the negative electrode material for a lithium secondary battery of the present invention and a binder. When forming such a negative electrode for a lithium secondary battery, the negative electrode material for a lithium secondary battery of the present invention is mixed with a known binder such as a fluorine-based polymer, a polyolefin-based polymer or synthetic rubber to form a paste, and the paste is formed. The paste is applied on a current collector made of metal or the like to form an active material layer.
【００３３】活物質層は、通常、単位面積当たりの容量
を確保するために、加圧されて密度が高められるが、本
発明のリチウム二次電池用負極は、活物質層の密度が
１．４ｇ／ｃｍ3以上に高められた場合であっても、容
量および初期効率の低下が起こり難い。従って、このリ
チウム二次電池用負極は、密度を少なくとも１．４ｇ／
ｃｍ3に維持しつつ、少なくとも３３０ｍＡｈ／ｇの放
電容量および少なくとも８５％の初期効率を達成するこ
とができる。The active material layer is usually pressed to increase its density in order to secure a capacity per unit area. However, in the negative electrode for a lithium secondary battery of the present invention, the active material layer has a density of 1. Even when it is increased to 4 g / cm 3 or more, the capacity and the initial efficiency hardly decrease. Accordingly, the negative electrode for a lithium secondary battery has a density of at least 1.4 g /
While maintaining at cm 3 , a discharge capacity of at least 330 mAh / g and an initial efficiency of at least 85% can be achieved.
【００３４】本発明のリチウム二次電池は、正極、負
極、電解質およびこれらを収納するための容器を主に備
えている。ここで、正極は、リチウムを含有する酸化
物、例えば、ＬｉＣｏＯ2と公知のバインダーとを混合
してペースト状にしたもの（活物質）を金属製などの集
電体上に塗布したものであり、また、負極は、本発明に
係る上述の負極材料を用いて形成されたものである。さ
らに、電解質は、上述のような非プロトン性有機溶媒に
塩を溶解した電解液であって正極と負極との間に配置さ
れており、例えば、正極と負極との短絡を防止するため
の不織布等からなるセパレーターに含浸されて保持され
ている。The lithium secondary battery of the present invention mainly comprises a positive electrode, a negative electrode, an electrolyte and a container for accommodating them. Here, the positive electrode is obtained by applying an oxide containing lithium, for example, LiCoO 2 and a known binder to form a paste (active material) on a current collector made of metal or the like. The negative electrode is formed by using the above-described negative electrode material according to the present invention. Further, the electrolyte is an electrolytic solution obtained by dissolving a salt in an aprotic organic solvent as described above, and is disposed between the positive electrode and the negative electrode.For example, a nonwoven fabric for preventing a short circuit between the positive electrode and the negative electrode Etc., and is held by being impregnated.
【００３５】このような本発明のリチウム二次電池は、
負極に本発明の負極材料を用いているため、負極の容量
および初期効率が高く、正極の活物質量を抑制すること
ができる。このため、このリチウム二次電池は、多量の
正極活物質を収容するための大型の容器を用いる必要が
ないので、従来のものに比べて小型化することができか
つ容量が大きく、また、負極が電解液と反応しにくいた
め安全性が高い。The lithium secondary battery of the present invention has the following features.
Since the negative electrode material of the present invention is used for the negative electrode, the capacity and the initial efficiency of the negative electrode are high, and the amount of the active material of the positive electrode can be suppressed. For this reason, this lithium secondary battery does not need to use a large container for accommodating a large amount of the positive electrode active material, so that it can be downsized and has a large capacity as compared with the conventional one. Is highly safe because it does not easily react with the electrolyte.
【００３６】なお、本発明のリチウム二次電池は、上述
の電解液に代えて、公知の無機固体電解質や高分子固体
電解質などの他の電解質を用いた場合も同様に実施する
ことができる。It should be noted that the lithium secondary battery of the present invention can be similarly implemented when other known electrolytes such as an inorganic solid electrolyte and a solid polymer electrolyte are used in place of the above-mentioned electrolyte.
【００３７】[0037]
【実施例】実施例１〜４ 表１に示す人造黒鉛と石炭系等方性ピッチとを炭化炉内
に別々に配置した。ここでは、炭化炉内に配置されたメ
ッシュ上に人造黒鉛を載置し、また、当該メッシュ下に
人造黒鉛と等重量の石炭系等方性ピッチを入れたトレー
を配置した。そして、炭化炉内を窒素ガスで満たした
後、炭化炉内の温度を３００℃／時の昇温速度で１，１
００℃まで高めて人造黒鉛を熱処理し、リチウム二次電
池用負極材料を得た。なお、熱処理後の人造黒鉛の重量
増加率は表１に示す通りである。EXAMPLES Examples 1 to 4 Artificial graphite and coal-based isotropic pitch shown in Table 1 were separately placed in a carbonization furnace. Here, artificial graphite was placed on a mesh placed in the carbonization furnace, and a tray containing a coal-based isotropic pitch having the same weight as the artificial graphite was placed under the mesh. Then, after filling the inside of the carbonization furnace with nitrogen gas, the temperature in the carbonization furnace was raised to 1,1 at a rate of 300 ° C / hour.
The temperature was raised to 00 ° C., and the artificial graphite was heat-treated to obtain a negative electrode material for a lithium secondary battery. The weight increase rate of the artificial graphite after the heat treatment is as shown in Table 1.
【００３８】得られた負極材料、ポリフッ化ビニリデン
樹脂およびＮ−メチルピロリドン溶媒を混合してペース
トを調製した。このペーストを、厚さが２５μｍの銅箔
上に１×１ｃｍの面積で厚さ１２０〜１５０μｍになる
ようドクターブレードを用いて塗布した後に乾燥し、活
物質層を形成した。このようにして得られた活物質層を
ロールプレス機を用いて圧縮し、各実施例について活物
質層の密度が異なる２種類のリチウム二次電池用負極を
得た。The obtained negative electrode material, polyvinylidene fluoride resin and N-methylpyrrolidone solvent were mixed to prepare a paste. The paste was applied on a copper foil having a thickness of 25 μm with a doctor blade so as to have an area of 1 × 1 cm and a thickness of 120 to 150 μm, followed by drying to form an active material layer. The active material layer thus obtained was compressed using a roll press machine to obtain two types of negative electrodes for lithium secondary batteries having different active material layer densities in each example.
【００３９】得られたリチウム二次電池用負極の充放電
特性を調べた。ここでは、先ず、参照極および対極とし
てリチウム箔を用い、また、電解液として１Ｍの過塩素
酸リチウムを電解質として含むエチレンカーボネート：
ジエチレンカーボネート＝１：１溶液を用いたセルを作
成した。そして、このセルを１ｍＡ／ｃｍ2で１ｍＶま
で定電流充電し、１ｍＶに到達したところで１ｍＶの定
電位充電に切り替え、充電時間が合計で１２時間になっ
たところで充電を終了した。次に、充電されたセルを、
１ｍＡ／ｃｍ2で１．２Ｖまで定電流放電した。このよ
うな一連の充放電過程より判明した、各実施例で得られ
たリチウム二次電池用負極材料の充電容量、放電容量お
よび初期効率は表１に示す通りである。The charge / discharge characteristics of the obtained negative electrode for a lithium secondary battery were examined. Here, first, a lithium foil is used as a reference electrode and a counter electrode, and ethylene carbonate containing 1 M lithium perchlorate as an electrolyte as an electrolyte:
A cell was prepared using a 1: 1 solution of diethylene carbonate. Then, the cell was charged at a constant current of 1 mA / cm 2 up to 1 mV. When the cell reached 1 mV, switching to 1 mV constant potential charging was performed. When the charging time reached 12 hours in total, charging was terminated. Next, the charged cell is
The battery was discharged at a constant current of 1.2 mA at 1 mA / cm 2 . Table 1 shows the charge capacity, discharge capacity, and initial efficiency of the negative electrode material for a lithium secondary battery obtained in each example, which were found from such a series of charge / discharge processes.
【００４０】実施例５〜７ 石炭系等方性ピッチに代えて石油系等方性ピッチを用い
た点を除いて実施例１〜４の場合と同様に各実施例につ
いて活物質層の密度が異なる２種類のリチウム二次電池
用負極を作成し、この負極の充電容量、放電容量および
初期効率を実施例１〜４の場合と同様にして評価した。
結果を表１に示す。 Examples 5 to 7 The density of the active material layer for each example was the same as in Examples 1 to 4 except that petroleum isotropic pitch was used instead of coal-based isotropic pitch. Two different types of negative electrodes for lithium secondary batteries were prepared, and the charge capacity, discharge capacity, and initial efficiency of the negative electrodes were evaluated in the same manner as in Examples 1 to 4.
Table 1 shows the results.
【００４１】比較例１ 実施例３で用いたものと同じ人造黒鉛を熱処理せずにそ
のまま用いて実施例１〜４と同様に活物質層の密度が異
なる２種類のリチウム二次電池用負極を作成し、この負
極の充電容量、放電容量および初期効率を実施例１〜４
の場合と同様にして評価した。結果を表１に示す。COMPARATIVE EXAMPLE 1 Two kinds of negative electrodes for lithium secondary batteries having different active material layer densities were produced in the same manner as in Examples 1 to 4 by using the same artificial graphite as used in Example 3 without heat treatment. Then, the charge capacity, discharge capacity and initial efficiency of this negative electrode were measured in Examples 1 to 4.
The evaluation was performed in the same manner as in the above case. Table 1 shows the results.
【００４２】[0042]
【表１】 [Table 1]
【００４３】[0043]
【発明の効果】本発明のリチウム二次電池用負極材料
は、黒鉛系炭素材料を上述のようなピッチの熱分解生成
物を含む雰囲気下で熱処理したものであるため、従来の
リチウム二次電池用の黒鉛系負極材料に比べて容量およ
び初期効率が高い。The negative electrode material for a lithium secondary battery according to the present invention is obtained by heat-treating a graphite-based carbon material in an atmosphere containing the above-described thermal decomposition products of pitch. Capacity and initial efficiency are higher than graphite-based negative electrode materials for use.
【００４４】また、本発明に係るリチウム二次電池用負
極材料の製造方法は、黒鉛系炭素材料を上述のようなピ
ッチの熱分解生成物を含む雰囲気下で熱処理しているた
め、従来のリチウム二次電池用の黒鉛系負極材料に比べ
て容量および初期効率が高いリチウム二次電池用負極材
料を実現することができる。In the method for producing a negative electrode material for a lithium secondary battery according to the present invention, since the graphite-based carbon material is heat-treated in an atmosphere containing the above-described pitch pyrolysis products, the conventional lithium A negative electrode material for a lithium secondary battery having higher capacity and higher initial efficiency than a graphite-based negative electrode material for a secondary battery can be realized.
【００４５】さらに、本発明のリチウム二次電池用負極
は、本発明の負極材料を用いているため、活物質層の密
度を高めた場合であっても容量および初期効率が低下し
にくい。Further, since the negative electrode for a lithium secondary battery of the present invention uses the negative electrode material of the present invention, the capacity and the initial efficiency are not easily reduced even when the density of the active material layer is increased.
【００４６】さらに、本発明のリチウム二次電池は、容
量および初期効率が高い上述の負極材料を用いているた
め、容量を高めつつ小型化することができ、また、負極
が電解液と反応しにくいため安全性が高い。Further, since the lithium secondary battery of the present invention uses the above-described negative electrode material having high capacity and high initial efficiency, the lithium secondary battery can be reduced in size while increasing the capacity, and the negative electrode reacts with the electrolyte. High safety because it is difficult.
───────────────────────────────────────────────────── フロントページの続き (72)発明者 竹崎 和弘 大阪府大阪市中央区平野町四丁目１番２号 大阪瓦斯株式会社内 Ｆターム(参考） 4G046 EA02 EA05 EB02 EB04 EC02 EC05 EC06 4H058 DA01 DA02 DA13 EA12 EA45 GA16 HA06 HA13 5H003 AA02 AA04 BA01 BB01 BC01 BC06 BD00 BD01 BD03 BD04 BD05 5H014 AA01 BB01 EE08 HH00 HH01 HH04 HH08 5H029 AJ03 AJ05 AK03 AL07 AM03 AM04 AM05 AM06 AM07 CJ02 CJ28 DJ16 DJ17 HJ00 HJ01 HJ08 HJ13 HJ14 HJ15 HJ19 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuhiro Takezaki 4-1-2, Hirano-cho, Chuo-ku, Osaka-shi, Osaka F-term in Osaka Gas Co., Ltd. (reference) 4G046 EA02 EA05 EB02 EB04 EC02 EC05 EC06 4H058 DA01 DA02 DA13 EA12 EA45 GA16 HA06 HA13 5H003 AA02 AA04 BA01 BB01 BC01 BC06 BD00 BD01 BD03 BD04 BD05 5H014 AA01 BB01 EE08 HH00 HH01 HH04 HH08 5H029 AJ03 AJ05 AK03 AL07 AM03 AM04 AM05 AM06 AM07 CJ02 HJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJJHJJ
Claims (10)
０℃のピッチの熱分解生成物を含む雰囲気下において熱
処理する工程を経て得られるリチウム二次電池用負極材
料。1. A graphite-based carbon material having a softening point of 150 to 30.
A negative electrode material for a lithium secondary battery obtained through a heat treatment step in an atmosphere containing a pyrolysis product at a pitch of 0 ° C.
得られる（００２）面の平均面間隔ｄ００２が０．３４
０ｎｍ以下である、請求項１に記載のリチウム二次電池
用負極材料。2. The graphite-based carbon material has an average spacing d002 of (002) plane obtained by an X-ray diffraction method of 0.34.
The negative electrode material for a lithium secondary battery according to claim 1, which has a thickness of 0 nm or less.
香族指数（ｆａ）が０．６０〜０．９８である、請求項
１または２に記載のリチウム二次電池用負極材料。 【数１】 3. The negative electrode material for a lithium secondary battery according to claim 1, wherein the pitch has an aromatic index (fa) represented by the following formula (1) of 0.60 to 0.98. (Equation 1)
３に記載のリチウム二次電池用負極材料。4. The negative electrode material for a lithium secondary battery according to claim 3, wherein the pitch is a coal-based pitch.
雰囲気のうちの１つの雰囲気の常圧下における６００〜
１，３００℃の温度による処理である、請求項１、２、
３または４に記載のリチウム二次電池用負極材料。5. The method according to claim 1, wherein the heat treatment is performed under a normal pressure of one of an inert atmosphere and a reducing atmosphere.
The treatment at a temperature of 1,300 ° C.
5. The negative electrode material for a lithium secondary battery according to 3 or 4.
増加率が５％未満である、請求項１、２、３、４または
５に記載のリチウム二次電池用負極材料。6. The negative electrode material for a lithium secondary battery according to claim 1, wherein the rate of weight increase of the graphite-based carbon material after the heat treatment is less than 5%.
ありかつ初期効率が少なくとも８５％である、請求項
１、２、３、４、５または６に記載のリチウム二次電池
用負極材料。7. The negative electrode material for a lithium secondary battery according to claim 1, which has a discharge capacity of at least 330 mAh / g and an initial efficiency of at least 85%.
０℃のピッチとを同じ閉空間内に別々に配置する工程
と、 前記閉空間内の温度を前記ピッチの熱分解温度以上に高
めるための工程と、を含むリチウム二次電池用負極材料
の製造方法。8. A graphite-based carbon material having a softening point of 150 to 30.
Production of a negative electrode material for a lithium secondary battery, comprising: a step of separately disposing a pitch of 0 ° C. in the same closed space; and a step of increasing the temperature in the closed space to the pyrolysis temperature of the pitch or more. Method.
チウム二次電池用負極材料とバインダーとを含む活物質
層とを備え、 前記活物質層は、密度が少なくとも１．４ｇ／ｃｍ3、
放電容量が少なくとも３３０ｍＡｈ／ｇおよび初期効率
が少なくとも８５％である、リチウム二次電池用負極。9. An active material comprising: a current collector; and an active material layer disposed on the current collector, the active material layer including the negative electrode material for a lithium secondary battery according to claim 1 and a binder. The layer has a density of at least 1.4 g / cm 3 ,
A negative electrode for a lithium secondary battery having a discharge capacity of at least 330 mAh / g and an initial efficiency of at least 85%.
ウム二次電池用負極材料を含む負極を備えたリチウム二
次電池。10. A lithium secondary battery provided with a negative electrode comprising the negative electrode material for a lithium secondary battery according to claim 1.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2011034152A1 (en) * | 2009-09-18 | 2011-03-24 | Ｊｘ日鉱日石エネルギー株式会社 | Negative electrode carbon material for lithium secondary battery and method for manufacturing same |
| JP2012038900A (en) * | 2010-08-06 | 2012-02-23 | Jm Energy Corp | Lithium ion capacitor |
-
1999
- 1999-02-23 JP JP04551299A patent/JP3886285B2/en not_active Expired - Fee Related
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2011034152A1 (en) * | 2009-09-18 | 2011-03-24 | Ｊｘ日鉱日石エネルギー株式会社 | Negative electrode carbon material for lithium secondary battery and method for manufacturing same |
| US8617508B2 (en) | 2009-09-18 | 2013-12-31 | Jx Nippon Oil & Energy Corporation | Carbon material for negative electrode of lithium secondary battery and method for producing the same |
| JP2012038900A (en) * | 2010-08-06 | 2012-02-23 | Jm Energy Corp | Lithium ion capacitor |
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| Publication number | Publication date |
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