JP2003272621A - Negative electrode material for lithium secondary battery and negative electrode sheet manufactured from it - Google Patents
Negative electrode material for lithium secondary battery and negative electrode sheet manufactured from itInfo
- Publication number
- JP2003272621A JP2003272621A JP2002071919A JP2002071919A JP2003272621A JP 2003272621 A JP2003272621 A JP 2003272621A JP 2002071919 A JP2002071919 A JP 2002071919A JP 2002071919 A JP2002071919 A JP 2002071919A JP 2003272621 A JP2003272621 A JP 2003272621A
- Authority
- JP
- Japan
- Prior art keywords
- negative electrode
- secondary battery
- lithium secondary
- graphite
- electrode material
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Classifications
-
- 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
Landscapes
- Secondary Cells (AREA)
- Battery Electrode And Active Subsutance (AREA)
- Carbon And Carbon Compounds (AREA)
Abstract
Description
【0001】[0001]
【発明の属する技術分野】本発明は、リチウム二次電池
用負極材料及びそれから製造された負極シートに関す
る。詳しくは本発明は、充電受入性が高く、かつ電極の
膨れの少ないリチウム二次電池用負極材料及びそれから
製造された負極シートに関する。TECHNICAL FIELD The present invention relates to a negative electrode material for a lithium secondary battery and a negative electrode sheet produced from the same. More specifically, the present invention relates to a negative electrode material for a lithium secondary battery, which has a high charge acceptability and a small electrode swelling, and a negative electrode sheet produced from the same.
【0002】[0002]
【従来の技術】近年、電子機器の小型化に伴い二次電池
の高容量化が望まれている。そのためニッケル・カドミ
ウム二次電池、ニッケル・水素二次電池に比べ、よりエ
ネルギー密度の高いリチウム二次電池(又はリチウムイ
オン二次電池)が注目されている。2. Description of the Related Art In recent years, with the miniaturization of electronic devices, there has been a demand for higher capacity secondary batteries. Therefore, a lithium secondary battery (or a lithium ion secondary battery) having a higher energy density than the nickel-cadmium secondary battery and the nickel-hydrogen secondary battery has been receiving attention.
【0003】その負極材料としては、最初にリチウム金
属を用いることが試みられたが、充放電を繰り返すうち
にデンドライト状のリチウムが析出し、セパレータを貫
通して正極にまで達し、短絡して発火事故を起こす可能
性があることが判明した。そのため、現在では、充放電
過程における非水溶媒の出入りを層間で行ない、リチウ
ム金属の析出を防止することのできる炭素材料を負極材
料として使用することが注目されている。Attempts were initially made to use lithium metal as the negative electrode material, but dendrite-like lithium was deposited during repeated charging and discharging, penetrated through the separator to the positive electrode, and short-circuited and ignited. It turned out to be an accident. Therefore, at present, attention is paid to the use of a carbon material as a negative electrode material, which allows a non-aqueous solvent to move in and out between layers during a charge / discharge process and prevent the precipitation of lithium metal.
【0004】この炭素材料としては、特開昭57−20
8079号公報に、黒鉛材料を使用することが提案され
ている。特に、結晶性のよい黒鉛をリチウム二次電池用
の炭素負極材料として用いると、黒鉛のリチウム吸蔵の
理論容量である372mAh/gに近い容量が得られ、
材料として好ましいことは知られている。一方、黒鉛材
料よりも結晶性の低い、いわゆる非晶質炭素材料を用い
ると黒鉛材料よりも重量当たりで高容量を得られること
が知られているが、これらの材料は、Liに対する電位
が高く、正極との電位差が取りにくいという欠点があ
る。また、真密度が黒鉛より小さいので、体積当たりの
容量が低くなるという欠点があった。更に、一般に粒子
が堅いので、電極成形性に欠け、従って電極密度を向上
させにくいという問題もあった。An example of this carbon material is Japanese Patent Laid-Open No. 57-20.
In 8079, it is proposed to use a graphite material. In particular, when graphite having good crystallinity is used as a carbon negative electrode material for a lithium secondary battery, a capacity close to 372 mAh / g, which is the theoretical capacity of graphite for occluding lithium, is obtained.
It is known that it is preferable as a material. On the other hand, it is known that when a so-called amorphous carbon material, which has lower crystallinity than the graphite material, is used, a higher capacity per weight can be obtained than the graphite material, but these materials have a high potential for Li. However, there is a drawback that it is difficult to obtain a potential difference from the positive electrode. Further, since the true density is smaller than that of graphite, there is a drawback that the capacity per volume is low. Further, since the particles are generally hard, there is a problem that the electrode formability is poor and therefore it is difficult to improve the electrode density.
【0005】また、リチウム二次電池の一形態として、
これが角型であるものは、充放電時に生じる電極の膨れ
などにより、筐体が膨れるという現象が報告されてい
る。最初からこの膨れを考慮して電池体積を設計する
と、筐体の厚みを必然的に薄くせざるを得ず、電池容量
の低下を招くことになる。As one form of the lithium secondary battery,
It has been reported that the rectangular shape of the case causes the case to swell due to the swelling of the electrodes that occurs during charging and discharging. If the battery volume is designed in consideration of this swelling from the beginning, the thickness of the housing is inevitably made thin, resulting in a decrease in battery capacity.
【0006】[0006]
【発明が解決しようとする課題】本発明の課題は、非晶
質炭素材料を用いた場合に比較して、リチウム充放電時
の電位の変化がLiの電位に近く、かつ充放電による電
位ヒステリシスを持たないので、正極電位との差を取り
やすい負極材料でありながら、高容量で、Liの充電受
入性が高く、かつ電極の膨れも少ないことで、角型電池
用としても好適なリチウム二次電池用負極材料を提供す
ることである。An object of the present invention is to compare the potential change during lithium charging / discharging to the Li potential and to obtain a potential hysteresis due to charging / discharging, as compared with the case of using an amorphous carbon material. Since it is a negative electrode material that is easy to take a difference from the positive electrode potential, it has a high capacity, high charge acceptability for Li, and little electrode swelling, making it a suitable lithium battery for prismatic batteries. It is to provide a negative electrode material for a secondary battery.
【0007】[0007]
【課題を解決するための手段】本発明者らは、上記課題
を解決するため鋭意検討を重ねた結果、特定の炭素質材
料が上記課題を解決することを見出して本発明に到達し
た。即ち本発明の要旨は、黒鉛系炭素質物に該黒鉛系炭
素質物より結晶性の劣る炭素質物を被着させた構造を有
する粉体状の負極材料であって、該負極材料と結着剤と
から作製されたリチウム二次電池用負極の抵抗(R)
が、6.5ohm以下、負極/電解液界面の二重層容量
(Cdl)が、7.0x10-4F以上、10x10-4F
未満の範囲にあることを特徴とするリチウム二次電池用
負極材料、に存する。As a result of intensive studies to solve the above problems, the present inventors have found that a specific carbonaceous material solves the above problems and arrived at the present invention. That is, the gist of the present invention is a powdery negative electrode material having a structure in which a carbonaceous material of which crystallinity is inferior to the graphite-based carbonaceous material is adhered to the graphite-based carbonaceous material, the negative-electrode material and a binder. Resistance (R) of negative electrode for lithium secondary battery prepared from
But, 6.5Ohm hereinafter, anode / electrolyte double layer capacity of the interface (Cdl) has, 7.0x10 -4 F or higher, 10x10 -4 F
It exists in the negative electrode material for lithium secondary batteries characterized by being in the range below.
【0008】また本発明の他の要旨は、黒鉛系炭素質物
に該黒鉛系炭素質物より結晶性の劣る炭素質物を被着さ
せた構造を有する粉体状の負極材料であって、該負極材
料と結着剤とから作製されたリチウム二次電池用負極の
抵抗(R)が、6.5ohm以下、負極/電解液界面の
二重層容量(Cdl)が、7.0x10-4F以上、10
x10-4F未満の範囲にあるものに、結着剤を加えてシ
ート状に成形してなることを特徴とするリチウム二次電
池用負極シート、に存する。Another aspect of the present invention is a powdery negative electrode material having a structure in which a carbonaceous material having a crystallinity lower than that of the graphite-based carbonaceous material is adhered to the graphite-based carbonaceous material. The resistance (R) of the negative electrode for a lithium secondary battery, which was prepared from the above and a binder, was 6.5 ohm or less, and the double layer capacity (Cdl) at the negative electrode / electrolyte interface was 7.0 × 10 −4 F or more, 10
A negative electrode sheet for a lithium secondary battery, which is characterized in that it is formed into a sheet by adding a binder to a material in the range of less than x10 -4 F.
【0009】[0009]
【発明の実施の形態】以下、本発明の実施の形態につき
詳細を述べる。本発明のリチウム二次電池用負極材料
は、黒鉛系炭素質物に該黒鉛系炭素質物より結晶性の劣
る炭素質物を被着させた構造を有する粉体状の負極材料
であって、特定の物性を有するものである。BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below. The negative electrode material for a lithium secondary battery of the present invention is a powdery negative electrode material having a structure in which a carbonaceous material having a crystallinity lower than that of the graphite-based carbonaceous material is adhered to the graphite-based carbonaceous material, which has specific physical properties. Is to have.
【0010】ここで「被着」とは、ある材料からなる核
材の表面の少なくとも一部に他の材料からなる被覆相を
形成させることを意味し、該被覆相の形成が該核材に対
して外部から供給された材料の付着によるか、或いは該
核材の表面部の材料の変質によるかは問わない。
[黒鉛系炭素質物]本発明において核材として用いられ
る黒鉛系炭素質物とは、高結晶性の黒鉛系炭素質物を指
し、好ましくはX線広角回折法による(002)面の面
間隔(d002)が3.37Å未満の黒鉛系炭素質物を
用いる。The term "deposition" as used herein means that a coating phase made of another material is formed on at least a part of the surface of the core material made of a certain material. On the other hand, it does not matter whether it is due to the adhesion of the material supplied from the outside or the deterioration of the material of the surface portion of the core material. [Graphite-based carbonaceous material] The graphite-based carbonaceous material used as the core material in the present invention refers to a highly crystalline graphite-based carbonaceous material, preferably the interplanar spacing (d002) of the (002) plane by X-ray wide angle diffraction method. A graphite-based carbonaceous material having a value of less than 3.37Å is used.
【0011】黒鉛系炭素質物の具体例としては、天然黒
鉛、人造黒鉛、又はこれらの機械的粉砕品、再熱処理
品、膨張黒鉛の再熱処理品、或いはこれらの黒鉛の高純
度精製品から選ばれる粉体が好ましい。上記人造黒鉛の
具体例としては、コールタールピッチ、石炭系重質油、
常圧残油、石油系重質油、芳香族炭化水素、窒素含有環
状化合物、硫黄含有環状化合物、ポリフェニレン、ポリ
塩化ビニル、ポリビニルアルコール、ポリアクリロニト
リル、ポリビニルブチラール、各種天然高分子、ポリフ
ェニレンサルファイド、ポリフェニレンオキシド、フル
フリルアルコール樹脂、フェノール−ホルムアルデヒド
樹脂、イミド樹脂等から選ばれる1種以上の有機物質
を、通常、2500℃以上、3200℃以下程度の焼成
温度で黒鉛化したものを、適当な粉砕手段で粉化したも
のが好ましい。Specific examples of the graphite-based carbonaceous material include natural graphite, artificial graphite, mechanically crushed products thereof, reheated products, reheated products of expanded graphite, and highly purified products of these graphites. Powder is preferred. Specific examples of the artificial graphite, coal tar pitch, coal-based heavy oil,
Atmospheric residual oil, heavy petroleum oil, aromatic hydrocarbons, nitrogen-containing cyclic compounds, sulfur-containing cyclic compounds, polyphenylene, polyvinyl chloride, polyvinyl alcohol, polyacrylonitrile, polyvinyl butyral, various natural polymers, polyphenylene sulfide, polyphenylene Suitable crushing means is obtained by graphitizing one or more kinds of organic substances selected from oxides, furfuryl alcohol resins, phenol-formaldehyde resins, imide resins, etc. at a firing temperature of usually 2500 ° C. or higher and 3200 ° C. or lower. It is preferable that the powder is powdered.
【0012】[黒鉛系炭素質物より結晶性の劣る炭素質
物]上記の黒鉛系炭素質物からなる核材の表面に被覆相
を形成させるための「黒鉛系炭素質物より結晶性の劣る
炭素質物」としては、核材の黒鉛系炭素質物より結晶性
の劣る種々の炭素質物を用いることができ、通常、X線
広角回折法による(002)面の面間隔(d002)が
3.37Å以上を示すような結晶性の低い各種炭素質物
を用いる。[Carbonaceous material having crystallinity inferior to that of graphite-based carbonaceous material] As a "carbonaceous material having crystallinity inferior to that of graphite-based carbonaceous material" for forming a coating phase on the surface of the core material made of the above-mentioned graphite-based carbonaceous material Can use various carbonaceous materials that are inferior in crystallinity to the graphite-based carbonaceous material of the core material. Normally, the interplanar spacing (d002) of the (002) plane by the X-ray wide angle diffraction method is 3.37Å or more. Various carbonaceous materials with low crystallinity are used.
【0013】上記「黒鉛系炭素質物より結晶性の劣る炭
素質物」からなる被覆相の形成は、黒鉛系炭素質物から
なる核材の表面部の変質、核材の外部から供給された結
晶性の劣る炭素質物からなる材料の付着、或いは核材の
外部から供給された各種材料の付着及び結晶性の劣る炭
素質物への変質、等の種々の形態で達成される。その詳
細は次項において詳述する。The formation of the coating phase composed of the above-mentioned "carbonaceous material having a crystallinity inferior to that of the graphite-based carbonaceous material" is caused by the alteration of the surface portion of the core material made of the graphite-based carbonaceous material This can be achieved in various forms such as adhesion of a material composed of an inferior carbonaceous material, adhesion of various materials supplied from the outside of the core material, and conversion into a carbonaceous material having inferior crystallinity. The details will be described in the next section.
【0014】[リチウム二次電池用負極材料]本発明の
リチウム二次電池用負極材料は、黒鉛系炭素質物に該黒
鉛系炭素質物より結晶性の劣る炭素質物を被着させた構
造、即ち黒鉛系炭素質物からなる核材の表面の少なくと
も一部に該黒鉛系炭素質物より結晶性の劣る炭素質物か
らなる被覆相を形成させた構造、を有する粉体状の負極
材料である。[Negative Electrode Material for Lithium Secondary Battery] The negative electrode material for a lithium secondary battery of the present invention has a structure in which a carbonaceous material having a crystallinity lower than that of the graphite-based carbonaceous material is adhered, that is, graphite. A powdery negative electrode material having a structure in which a coating phase made of a carbonaceous material having crystallinity lower than that of the graphite-based carbonaceous material is formed on at least a part of the surface of a core material made of a carbonaceous material.
【0015】上記リチウム二次電池用負極材料におけ
る、黒鉛系炭素質物と、該黒鉛系炭素質物より結晶性の
劣る炭素質物との割合は、重量比で通常、99/1〜5
0/50、好ましくは98/2〜95/5、更に好まし
くは98/2〜96/4である。結晶性の劣る炭素質物
の量が少なすぎると被覆の効果が薄く、逆に多すぎると
負極容量の低下を招く。The ratio of the graphite-based carbonaceous material and the carbonaceous material having inferior crystallinity to the graphite-based carbonaceous material in the above-mentioned lithium secondary battery negative electrode material is usually 99/1 to 5 by weight.
It is 0/50, preferably 98/2 to 95/5, and more preferably 98/2 to 96/4. If the amount of carbonaceous material having poor crystallinity is too small, the effect of coating is small, and if it is too large, the capacity of the negative electrode is reduced.
【0016】前記の通り、黒鉛系炭素質物にこれより結
晶性の劣る炭素質物を被着させる方法、即ち黒鉛系炭素
質物の表面にこれより結晶性の劣る炭素質物からなる被
覆相を形成させる方法、は多様であるが、代表的な方法
は次の通りである。
黒鉛系炭素質物を機械的又は化学的に処理して、そ
の表面部の黒鉛系炭素質物をより結晶性の劣る炭素質物
に変質させる方法。As described above, a method of depositing a carbonaceous material having a crystallinity less than that on the graphite-based carbonaceous material, that is, a method of forming a coating phase made of a carbonaceous material having a lesser crystallinity on the surface of the graphite-based carbonaceous material. , Are various, but typical methods are as follows. A method of mechanically or chemically treating a graphite-based carbonaceous material to transform the surface of the graphite-based carbonaceous material into a carbonaceous material having poorer crystallinity.
【0017】 X線広角回折法による(002)面の
面間隔(d002)が3.37Å以上を示すような結晶
性の低い土状黒鉛や鱗状黒鉛、これらの粉砕物、好まし
くはレーザー回折法で得られる平均粒径d50が5μm
以下、更に好ましくは1μm以下、最も好ましくは0.
5μm以下となるように微粉砕した粉体、を黒鉛系炭素
質物の表面に、必要により適当な粉体結着剤を用いて、
結着させる方法。[0017] Soil-like graphite or scaly graphite having low crystallinity such that the interplanar spacing (d002) of the (002) plane by X-ray wide-angle diffraction is 3.37 Å or more, a crushed product of these, preferably laser diffraction Obtained average particle size d50 is 5 μm
Or less, more preferably 1 μm or less, and most preferably 0.
A finely pulverized powder having a particle size of 5 μm or less is used on the surface of the graphite-based carbonaceous material, if necessary, by using an appropriate powder binder,
How to bind.
【0018】 焼成後にはリチウムイオンを吸蔵・放
出可能な結晶性の劣る炭素質物に変質し得る性質を有す
る有機物質を、黒鉛系炭素質物の表面に付着させ、これ
を焼成して結晶性の劣る炭素質物に変質させる方法。上
記各方法の中では上記の方法(以下、焼成法という)
が、簡便であり、かつ得られる効果としても優れた方法
である。After the firing, an organic substance having a property of being capable of storing and releasing lithium ions and having a property of being transformed into a carbonaceous substance having poor crystallinity is attached to the surface of the graphite-based carbonaceous substance, and this is fired to have poor crystallinity. A method of converting into a carbonaceous material. Among the above methods, the above method (hereinafter referred to as firing method)
However, it is a simple and excellent method.
【0019】上記焼成法において使用される有機物質の
具体例としては、炭素化可能な有機物質として、液相で
炭素化が進行する軟ピッチから硬ピッチまでのコールタ
ールピッチや乾留液化油などの石炭系重質油や、常圧残
油、減圧残油等の直留系重質油、原油、ナフサなどの熱
分解時に副生するエチレンタール等分解系重質油等の石
油系重質油、或いは以上のものを炭素化が進む以下の温
度で蒸留、溶媒抽出等の手段を経て固化したものが挙げ
られる。更にアセナフチレン、デカシクレン、アントラ
センなどの芳香族炭化水素、フェナジンやアクリジンな
どの窒素含有環状化合物、チオフェンなどの硫黄含有環
状化合物、30MPa以上の加圧が必要となるがアダマ
ンタンなどの多環脂環式化合物が挙げられる。また熱可
塑性高分子である、炭素化に至る過程で液相を経るビフ
ェニルやテルフェニルなどのポリフェニレン、ポリ塩化
ビニル、ポリ酢酸ビニル、ポリビニルブチラールなどの
ポリビニルエステル類、ポリビニルアルコールが挙げら
れる。また、上記各種の有機物質に適量の燐酸、ホウ
酸、塩酸などの酸類、水酸化ナトリウム等のアルカリ類
を添加したものでもよい。更にこれらのものを300〜
600℃、好ましくは300〜400℃で酸素、硫黄、
窒素、又は硼素から選ばれる元素により適度に架橋処理
したものでもよい。Specific examples of the organic substance used in the above-mentioned calcination method include carbonaceous organic substances such as coal tar pitch from soft pitch to hard pitch where carbonization proceeds in a liquid phase and dry distillation liquefied oil. Heavy oil such as coal-based heavy oil, straight-run heavy oil such as atmospheric residual oil and vacuum residual oil, and petroleum heavy oil such as crude oil and cracked heavy oil such as ethylene tar produced as a by-product during thermal decomposition of naphtha. Alternatively, the above may be solidified through a means such as distillation, solvent extraction or the like at a temperature below which carbonization proceeds. Furthermore, aromatic hydrocarbons such as acenaphthylene, decacyclene, and anthracene, nitrogen-containing cyclic compounds such as phenazine and acridine, sulfur-containing cyclic compounds such as thiophene, and polycyclic alicyclic compounds such as adamantane that require a pressure of 30 MPa or more. Is mentioned. In addition, there are thermoplastic polymers such as polyphenylene such as biphenyl and terphenyl, which undergoes a liquid phase in the process of carbonization, polyvinyl chloride such as polyvinyl chloride, polyvinyl acetate, polyvinyl butyral, and polyvinyl alcohol. Further, it is also possible to add an appropriate amount of acids such as phosphoric acid, boric acid and hydrochloric acid, and alkalis such as sodium hydroxide to the above various organic substances. Furthermore, these things
Oxygen, sulfur at 600 ° C, preferably 300-400 ° C,
It may be appropriately crosslinked with an element selected from nitrogen or boron.
【0020】上記焼成法においては、上記黒鉛系炭素質
物と上記有機物質とを混合し、焼成を行う。焼成温度
は、通常、500〜2200℃、好ましくは650〜8
50℃、更に好ましくは700〜800℃とする。焼成
温度が低すぎると導電性に劣り、充電受入性が悪化す
る。逆に高すぎると電極膨れが大きくなる。また、焼成
時に容器へ詰め込む粉体厚みは、通常1〜50cm、好
ましくは5〜20cmとし、更に焼成時の圧力は、通常
0.100〜0.400MPa、好ましくは0.101
〜0.200MPaとする。In the firing method, the graphite-based carbonaceous material and the organic substance are mixed and fired. The firing temperature is usually 500 to 2200 ° C., preferably 650 to 8
50 degreeC, More preferably, it is 700-800 degreeC. If the firing temperature is too low, the conductivity will be poor and the charge acceptance will be poor. On the contrary, if it is too high, the electrode swells more. The thickness of the powder packed in the container during firing is usually 1 to 50 cm, preferably 5 to 20 cm, and the pressure during firing is usually 0.100 to 0.400 MPa, preferably 0.101.
˜0.200 MPa.
【0021】上記焼成の後、適当な解砕、または粉砕を
行って、粒径を通常4〜40μm、好ましくは10〜3
2μm、更に好ましくは15〜30μmに調整すること
によって、本発明のリチウム二次電池用負極材料が得ら
れる。本発明のリチウム二次電池用負極材料は、後述の
[電極材料の評価方法]に記載した方法に従って、これ
と結着剤とからリチウム二次電池用負極を作製して、2
032コイン型セルを組み、複素インピーダンス測定を
行うことによって得られる、負極部分の抵抗(R)が、
6.5ohm以下、また負極と電解液との界面の二重層
容量(Cdl)が、7.0x10-4F以上、10x10
-4F未満の範囲にある必要がある。上記のような好まし
い性質の取得は、上記のような焼成温度の範囲内での焼
成温度の調整によって達成することができる。After the above firing, appropriate crushing or crushing is carried out to obtain a particle size of usually 4 to 40 μm, preferably 10 to 3
The negative electrode material for a lithium secondary battery of the present invention can be obtained by adjusting the thickness to 2 μm, more preferably 15 to 30 μm. The negative electrode material for a lithium secondary battery of the present invention is prepared by preparing a negative electrode for a lithium secondary battery from this and a binder according to the method described in [Evaluation Method of Electrode Material] below.
The resistance (R) of the negative electrode portion obtained by assembling a 032 coin cell and performing complex impedance measurement is
6.5 ohm or less, and the double layer capacity (Cdl) at the interface between the negative electrode and the electrolytic solution is 7.0 × 10 −4 F or more and 10 × 10.
Must be below -4 F. The acquisition of the preferable properties as described above can be achieved by adjusting the firing temperature within the above-mentioned firing temperature range.
【0022】また、上記リチウム二次電池用負極材料及
び該負極材料と結着剤とから作製されたリチウム二次電
池用負極について、N2ガスを用いたBET表面積の測
定を行い、得られた値から下記式(1)で計算される、
結着剤による活物質の表面被覆率Γ(%)が20〜55
%の範囲にあるのが好ましい。Further, the BET surface area was measured using N 2 gas for the negative electrode material for lithium secondary batteries and the negative electrode for lithium secondary batteries prepared from the negative electrode material and the binder, and the obtained results were obtained. Calculated from the value by the following formula (1),
The surface coverage Γ (%) of the active material with the binder is 20 to 55.
It is preferably in the range of%.
【0023】[0023]
【数2】
表面被覆率Γ=(粉体SA−負極SA)/粉体SAx100 (1)
粉体SA:リチウム二次電池用負極材料のBET表面積
負極SA:リチウム二次電池用負極のBET表面積
また、上記リチウム二次電池用負極材料のN2ガスによ
るBET表面積が2.4〜4m2/gであるのが好まし
い。## EQU00002 ## Surface coverage .GAMMA. = (Powder SA-negative electrode SA) / powder SAx100 (1) Powder SA: BET surface area of negative electrode material for lithium secondary battery Negative electrode SA: BET surface area of negative electrode for lithium secondary battery Further, the BET surface area of the negative electrode material for lithium secondary batteries by N 2 gas is preferably 2.4 to 4 m 2 / g.
【0024】また、上記リチウム二次電池用負極材料に
ついて、波長5145Åのアルゴンイオンレーザー光を
用いたラマンスペクトル分析した結果で、1570〜1
620cm-1の範囲に存在するピークの強度をIA、1
350〜1370cm-1の範囲に存在するピークの強度
をIBとしたとき、その比であるR値(=IB/IA)が
0.4を超えるものは、低抵抗な負極界面の被膜を形成
しやすいので好ましい。The results of Raman spectrum analysis of the negative electrode material for lithium secondary batteries using an argon ion laser beam having a wavelength of 5145Å show that 1570 to 1
The intensity of the peak existing in the range of 620 cm −1 is I A , 1
When the intensity of the peak existing in the range of 350 to 1370 cm −1 is I B , the ratio R value (= I B / I A ) of more than 0.4 is a film of a low resistance negative electrode interface. Are preferred because they are easy to form.
【0025】[リチウム二次電池用負極]次に本発明の
リチウム二次電池用負極材料を用いてリチウム二次電池
用負極シート、或いはリチウム二次電池用負極を製造す
る方法について説明する。負極の製造方法は、上記本発
明のリチウム二次電池用負極材料を負極の成分として含
む限り、特に限定されず、従来公知の種々の方法が採用
可能である。例えば、リチウム二次電池用負極材料に結
着剤及び溶媒等を加えてスラリー状とし、銅箔等の金属
製の集電体基板に上記スラリーを塗布・乾燥して負極シ
ートを形成させることで負極とする。銅箔の代わりにニ
ッケル箔やステンレス箔を用いてもよい。また、上記負
極材料をそのままロール成形、圧縮成形等の方法で負極
シートの形状に成形することもできる。[Negative Electrode for Lithium Secondary Battery] Next, a method for producing a negative electrode sheet for a lithium secondary battery or a negative electrode for a lithium secondary battery using the negative electrode material for a lithium secondary battery of the present invention will be described. The method for producing the negative electrode is not particularly limited as long as it contains the negative electrode material for a lithium secondary battery of the present invention as a component of the negative electrode, and various conventionally known methods can be adopted. For example, by adding a binder, a solvent and the like to a negative electrode material for a lithium secondary battery to form a slurry, and coating and drying the slurry on a metal current collector substrate such as a copper foil to form a negative electrode sheet. The negative electrode. Nickel foil or stainless steel foil may be used instead of the copper foil. Further, the negative electrode material can be directly molded into a negative electrode sheet shape by a method such as roll molding or compression molding.
【0026】上記結着剤としては、溶媒に対して安定
な、ポリエチレン、ポリプロピレン、ポリエチレンテレ
フタレート、芳香族ポリアミド、セルロース等の樹脂系
高分子、スチレン・ブタジエンゴム、イソプレンゴム、
ブタジエンゴム、エチレン・プロピレンゴム等のゴム状
高分子、スチレン・ブタジエン・スチレンブロック共重
合体、その水素添加物、スチレン・エチレン・ブタジエ
ン・スチレン共重合体、スチレン・イソプレン・スチレ
ンブロック共重合体、その水素添加物等の熱可塑性エラ
ストマー状高分子、シンジオタクチック−1,2−ポリ
ブタジエン、エチレン・酢酸ビニル共重合体、プロピレ
ン・α−オレフィン(炭素数2〜12)共重合体等の軟
質樹脂状高分子、メチルセルロース、カルボキシメチル
セルロース、ポリビニルアルコール、ポリビニルブチラ
ール、これらのポリマーのホルマール化物、などを用い
ることができる。ここに、ポリフッ化ビニリデン、ポリ
テトラフルオロエチレンなどのフッ素系結着剤を更に適
量添加してもよい。アルカリ金属イオン、特にリチウム
イオンのイオン伝導性を有する有機高分子組成物を更に
混合してもよいが、電極の賦形性を損なわないように注
意が必要である。Examples of the binder include solvent-stable resin polymers such as polyethylene, polypropylene, polyethylene terephthalate, aromatic polyamide and cellulose, styrene-butadiene rubber, isoprene rubber,
Rubber-like polymers such as butadiene rubber and ethylene / propylene rubber, styrene / butadiene / styrene block copolymers, hydrogenated products thereof, styrene / ethylene / butadiene / styrene copolymers, styrene / isoprene / styrene block copolymers, Soft resins such as thermoplastic elastomeric polymers such as hydrogenated products, syndiotactic-1,2-polybutadiene, ethylene / vinyl acetate copolymers, propylene / α-olefin (C2-12) copolymers, etc. Polymers, methyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, polyvinyl butyral, formalized products of these polymers, and the like can be used. A suitable amount of a fluorine-based binder such as polyvinylidene fluoride or polytetrafluoroethylene may be added to this. An organic polymer composition having an ionic conductivity of alkali metal ions, especially lithium ions may be further mixed, but care must be taken so as not to impair the shapeability of the electrode.
【0027】リチウム二次電池用負極を製造する際のリ
チウム二次電池用負極材料と上記結着剤との混合形態は
特に限定されず、各種の形態をとることができる。即
ち、両者の粒子が混合した形態、繊維状の結着剤が炭素
質物の粒子に絡み合う形で混合した形態、または結着剤
の層が炭素質物の粒子表面に付着した形態などが挙げら
れる。炭素質物と結着剤との混合割合は、炭素質物に対
して、通常0.1〜30重量%、好ましくは、0.5〜
10重量%、より好ましくは0.5〜5重量%である。
結着剤の量が多すぎると、電極の内部抵抗が大きくな
り、逆に少なすぎると集電体と炭素質粉体との結着性に
劣る。The form of mixing the negative electrode material for a lithium secondary battery and the above-mentioned binder when producing the negative electrode for a lithium secondary battery is not particularly limited, and various forms can be adopted. That is, a form in which both particles are mixed, a form in which a fibrous binder is mixed with particles of a carbonaceous material so as to be entangled with each other, or a form in which a layer of the binder is attached to the surface of the particles of the carbonaceous material can be mentioned. The mixing ratio of the carbonaceous material and the binder is usually 0.1 to 30% by weight, preferably 0.5 to 30% by weight based on the carbonaceous material.
It is 10% by weight, more preferably 0.5 to 5% by weight.
When the amount of the binder is too large, the internal resistance of the electrode becomes large, and when it is too small, the binding property between the current collector and the carbonaceous powder is poor.
【0028】また、負極の作製時に、適当な導電剤を添
加してもよい。導電剤の例としては、アセチレンブラッ
ク、ファーネスブラック、ケッチェンブラックなどのカ
ーボンブラックや平均粒径が1μm以下のニッケル、銅
などの金属パウダーが挙げられる。上記のように、リチ
ウム二次電池用負極材料と適当な粉体結着剤とを混合
し、その量を調整することで、Liの挿入に好ましい表
面積を持つ電極を作製することができる。更に低抵抗の
負極界面の被膜形成が可能なため、Liの充電受入性に
好ましい影響を与えることができる。また、被膜が均一
にできるため、表面被膜由来の電極膨れが少ない。従っ
て、本発明のリチウム二次電池用負極材料は、例えば、
角型電池用負極材料として好適である。A suitable conductive agent may be added when the negative electrode is produced. Examples of the conductive agent include carbon black such as acetylene black, furnace black, and Ketjen black, and metal powder such as nickel and copper having an average particle diameter of 1 μm or less. As described above, by mixing the negative electrode material for a lithium secondary battery and a suitable powder binder and adjusting the amount thereof, an electrode having a surface area preferable for Li insertion can be manufactured. Further, since it is possible to form a coating film on the negative electrode interface having a low resistance, it is possible to positively affect the charge acceptability of Li. Further, since the coating can be made uniform, the electrode swelling due to the surface coating is small. Therefore, the lithium secondary battery negative electrode material of the present invention, for example,
It is suitable as a negative electrode material for prismatic batteries.
【0029】更に、本発明のリチウム二次電池用負極材
料は、その構成要素として黒鉛系炭素質物を用いるた
め、サイクル時の可逆容量も大きく、かつ非晶質炭素の
ようにLiに対し高電位をとることもなく、正極と共に
電池に組んだときのセル電圧を確保しやすいため、高容
量化にも役立つ。
[電解液]本発明のリチウム二次電池用負極材料と結着
剤とから作製されたリチウム二次電池用負極を電池とし
て用いる場合の電解液は有機溶媒及び電解質から構成さ
れる。Furthermore, the negative electrode material for a lithium secondary battery of the present invention uses a graphite-based carbonaceous material as its constituent element, and therefore has a large reversible capacity during cycling and has a high potential with respect to Li like amorphous carbon. Since it is easy to secure the cell voltage when assembled in a battery together with the positive electrode, it is also useful for increasing the capacity. [Electrolytic Solution] When the negative electrode for a lithium secondary battery produced from the negative electrode material for a lithium secondary battery of the present invention and a binder is used as a battery, the electrolytic solution is composed of an organic solvent and an electrolyte.
【0030】上記有機溶媒としては、例えばエチレンカ
ーボネート等の環状カーボネート、ジエチルカーボネー
ト、ジメチルカーボネート、エチルメチルカーボネート
等の鎖状カーボネート、1,2−ジメトキシエタン、テ
トラヒドロフラン、2−メチルテトラヒドロフラン、
1,3−ジオキソラン等のエーテル類、スルホランなど
が挙げられる。これら有機溶媒中にビニレンカーボネー
ト、ビニルエチレンカーボネート、メチルフェニルカー
ボネート、エチレンサルファイド、プロピレンサルファ
イド、1,3−プロパンスルトン、1,4−ブタンスル
トン、或いはマレイン酸無水物、コハク酸無水物等の酸
無水物から選ばれるいわゆる皮膜形成剤を添加してもよ
い。皮膜形成剤の添加量は通常10重量%以下、好まし
くは8重量%以下、より好ましくは5重量%以下、さら
に好ましくは2重量%以下である。皮膜形成剤の添加量
が多すぎると初期不可逆容量の増加や低温特性、レート
特性の低下等、他の電池特性に悪影響を及ぼす恐れがあ
る。Examples of the organic solvent include cyclic carbonates such as ethylene carbonate, chain carbonates such as diethyl carbonate, dimethyl carbonate and ethylmethyl carbonate, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran,
Examples include ethers such as 1,3-dioxolane, sulfolane and the like. In these organic solvents, vinylene carbonate, vinyl ethylene carbonate, methylphenyl carbonate, ethylene sulfide, propylene sulfide, 1,3-propane sultone, 1,4-butane sultone, or acid anhydrides such as maleic anhydride and succinic anhydride. A so-called film forming agent selected from the above may be added. The addition amount of the film forming agent is usually 10% by weight or less, preferably 8% by weight or less, more preferably 5% by weight or less, and further preferably 2% by weight or less. If the amount of the film-forming agent added is too large, it may adversely affect other battery characteristics such as an increase in initial irreversible capacity, deterioration of low temperature characteristics and rate characteristics.
【0031】上記電解質としては、例えばLiCl
O4、LiPF6、LiBF4、LiCF3SO3、LiA
sF6、LiCl、LiBr、Liトリフルオロメタン
スルホンイミド等の塩が挙げられる。電解質の濃度は有
機溶媒中、0.5〜2.0M程度とする。これらの電解
液を更に有機高分子化合物に含ませ、ゲル状またはゴム
状或いは固体シート状としたものを用いてもよい。その
ような場合には骨材となる有機高分子化合物の分量を除
いた有機溶媒のみの組成で上記組成を議論する。上記有
機高分子化合物の具体例としては、ポリエチレンオキシ
ド、ポリプロピレンオキシド等のポリエーテル系高分子
化合物、これらポリエーテル系高分子化合物の架橋体高
分子、ポリビニルアルコール、ポリビニルブチラール、
これらの不溶化物、ポリエピクロルヒドリン、ポリホス
ファゼン、ポリシロキサン、ポリビニルピロリドン、ポ
リビニリデンカーボネート、ポリアクリロニトリルが挙
げられる。また、ポリ(ω−メトキシオリゴオキシエチ
レンメタクリレート)、ポリ(ω−メトキシオリゴオキ
シエチレンメタクリレート−co−メチルメタクリレー
ト)等のポリマー共重合体も使用可能である。Examples of the electrolyte include LiCl
O 4 , LiPF 6 , LiBF 4 , LiCF 3 SO 3 , LiA
Examples thereof include salts of sF 6 , LiCl, LiBr, Li trifluoromethanesulfonimide, and the like. The concentration of the electrolyte is about 0.5 to 2.0 M in the organic solvent. A gel-like, rubber-like, or solid sheet-like material may be used by further incorporating these electrolytic solutions into an organic polymer compound. In such a case, the above composition will be discussed with the composition of only the organic solvent excluding the amount of the organic polymer compound serving as the aggregate. Specific examples of the organic polymer compound, polyethylene oxide, polyether polymer compounds such as polypropylene oxide, cross-linked polymers of these polyether polymer compounds, polyvinyl alcohol, polyvinyl butyral,
Examples thereof include insolubilized products, polyepichlorohydrin, polyphosphazene, polysiloxane, polyvinylpyrrolidone, polyvinylidene carbonate and polyacrylonitrile. Further, polymer copolymers such as poly (ω-methoxy oligooxyethylene methacrylate) and poly (ω-methoxy oligooxyethylene methacrylate-co-methyl methacrylate) can also be used.
【0032】また、リチウムイオン等のアルカリ金属カ
チオンの導電体である高分子固体電解質を用いることも
でき、その例としては、上記ポリエーテル系高分子化合
物にLi塩を溶解させたものや、ポリエーテル末端水酸
基がアルコキシドに置換されているポリマーなどが挙げ
られる。
[リチウム二次電池用正極]リチウム二次電池を構成す
るための正極体の材料は、特に限定されないが、上記リ
チウム二次電池用負極と組み合わせて使用するための標
準的なものとしては、LiCoO2をアセチレンブラッ
クなどの導電材及びポリフッ化ビニリデンなどと混合
し、アルミニウム箔上に塗布、乾燥し、プレスを施した
ものが挙げられる。その他、一般にリチウムイオンなど
のアルカリ金属カチオンを充放電時に吸蔵、放出するこ
とのできる金属カルコゲン化合物からなることが好まし
い。そのような金属カルコゲン化合物としては、バナジ
ウムの酸化物、バナジウムの硫化物、モリブデンの酸化
物、モリブデンの硫化物、マンガンの酸化物、クロムの
酸化物、チタンの酸化物、チタンの硫化物及びこれらの
複合酸化物、複合硫化物等が挙げられる。好ましくは、
Cr3O8、V2O5、V5O13、VO2、Cr2O5、MnO
2、TiO2、MoV2O8、TiS2、V2S5、Cr0.25
V0.75S2、Cr0.5V0.5S2等である。また、LiMY
2(Mは、Co、Ni等の遷移金属、YはO、S等のカ
ルコゲン元素)、LiM2Y4(MはMn、YはO)、W
O3等の酸化物、CuS、Fe0.25V0.75S2、Na0.1
CrS2等の硫化物、NiPS3、FePS3等のリン・
硫黄化合物、VSe2、NbSe3等のセレン化合物等を
用いることもできる。It is also possible to use a polymer solid electrolyte which is a conductor of an alkali metal cation such as lithium ion. Examples thereof include those obtained by dissolving a Li salt in the above polyether polymer compound, Examples thereof include polymers in which the ether terminal hydroxyl group is substituted with an alkoxide. [Positive Electrode for Lithium Secondary Battery] The material of the positive electrode body for constituting the lithium secondary battery is not particularly limited, but LiCoO 2 is a standard material for use in combination with the negative electrode for the lithium secondary battery. 2 is mixed with a conductive material such as acetylene black, polyvinylidene fluoride, etc., coated on an aluminum foil, dried, and pressed. In addition, in general, it is preferably composed of a metal chalcogen compound capable of inserting and extracting an alkali metal cation such as lithium ion during charge and discharge. Such metal chalcogen compounds include vanadium oxide, vanadium sulfide, molybdenum oxide, molybdenum sulfide, manganese oxide, chromium oxide, titanium oxide, titanium sulfide, and these. Complex oxides, complex sulfides, and the like. Preferably,
Cr 3 O 8, V 2 O 5, V 5 O 13, VO 2, Cr 2 O 5, MnO
2 , TiO 2 , MoV 2 O 8 , TiS 2 , V 2 S 5 , Cr 0.25
V 0.75 S 2 , Cr 0.5 V 0.5 S 2 and the like. In addition, LiMY
2 (M is a transition metal such as Co and Ni, Y is a chalcogen element such as O and S), LiM 2 Y 4 (M is Mn, Y is O), W
O 3 and other oxides, CuS, Fe 0.25 V 0.75 S 2 , Na 0.1
Sulfides such as CrS 2 and phosphorus such as NiPS 3 and FePS 3
Sulfur compounds, selenium compounds such as VSe 2 and NbSe 3 can also be used.
【0033】上記の化合物を、前記の負極の製造法と同
様の手法で、結着剤と混合し、集電体上に塗布、乾燥し
て正極板とする。
[リチウム二次電池]上記のようにして作製した負極
板、正極板及び電解液を、その他の電池構成要素である
セパレータ、ガスケット、集電体、封口板、セルケース
等と組み合わせてリチウム二次電池を構成する。作製可
能な電池は筒型、角型、コイン型等特に限定されるもの
ではないが、基本的にはセル床板上に集電体と負極材料
とを乗せ、その上に電解液とセパレータを、更に負極と
正極を対向させ、ガスケット、封口板と共にかしめて二
次電池とする。The above compound is mixed with a binder, coated on a current collector, and dried to form a positive electrode plate in the same manner as in the method for producing the negative electrode. [Lithium secondary battery] A lithium secondary battery is prepared by combining the negative electrode plate, the positive electrode plate and the electrolytic solution produced as described above with other battery components such as a separator, a gasket, a current collector, a sealing plate and a cell case. Configure the battery. Batteries that can be manufactured are not particularly limited, such as a cylinder type, a prismatic type, and a coin type, but basically, a current collector and a negative electrode material are placed on a cell floor plate, and an electrolytic solution and a separator are placed thereon. Further, the negative electrode and the positive electrode are opposed to each other, and they are caulked together with the gasket and the sealing plate to form a secondary battery.
【0034】電解液を保持するセパレータは、一般的に
保液性に優れた材料であり、例えば、ポリオレフィン系
樹脂の不織布や多孔性フィルムなどを使用して、上記電
解液を含浸させる。The separator holding the electrolytic solution is generally a material having excellent liquid retaining properties, and is impregnated with the electrolytic solution using, for example, a nonwoven fabric of polyolefin resin or a porous film.
【0035】[0035]
【実施例】次に実施例により本発明の具体的態様を更に
詳細に説明するが、本発明はこれらの例によって限定さ
れるものではない。
[電極材料の評価方法]負極材料中の結晶性の劣る炭素質物の含有量
焼成法においては、黒鉛系炭素質物の表面に有機物質を
付着させ焼成することによって生成される炭素質物が結
晶性の劣る炭素質物を構成するので、この焼成操作によ
る重量の増加、即ち残炭率によって結晶性の劣る炭素質
物の量を定量した。EXAMPLES Specific examples of the present invention will now be described in more detail with reference to Examples, but the present invention is not limited to these Examples. [Evaluation Method of Electrode Material ] In the firing method for the content of carbonaceous material having poor crystallinity in the negative electrode material, the carbonaceous material produced by adhering an organic substance to the surface of the graphite-based carbonaceous material and firing it is crystalline. Since an inferior carbonaceous material is constituted, the amount of carbonaceous material having inferior crystallinity was quantified by the increase in weight due to this firing operation, that is, the residual carbon ratio.
【0036】ラマンスペクトル測定
日本分光製、NR−1800により行い、波長5145
Åのアルゴンイオンレーザー光を、30mWの強度で照
射した。ここでは1570〜1620cm-1の範囲に存
在するピークの強度および、1350〜1370cm-1
の範囲に存在するピークの強度を測定し、これらから得
られるラマンR値を求めた。 Raman spectrum measurement NR-1800 manufactured by JASCO Corporation, wavelength 5145
The Å argon ion laser beam was irradiated at an intensity of 30 mW. Here the peaks present in the range of 1570~1620Cm -1 strength and, 1350 -1
The intensity of the peak existing in the range was measured, and the Raman R value obtained from them was determined.
【0037】結着剤による活物質の表面被覆率
負極材料及び負極について、N2ガスを用いたBET1
点法によりBET表面積の測定を行った。なお、電極の
表面積は、電極密度を調整する前のものとした。得られ
たBET表面積の値から下記式(1)で、結着剤による
活物質の表面被覆率Γ(%)を算出した。 Surface Coverage of Active Material with Binder For the negative electrode material and the negative electrode, BET1 using N 2 gas was used.
The BET surface area was measured by the dot method. The surface area of the electrode was that before the electrode density was adjusted. From the value of the obtained BET surface area, the surface coverage Γ (%) of the active material with the binder was calculated by the following formula (1).
【0038】[0038]
【数3】
表面被覆率Γ=(粉体SA−負極SA)/粉体SAx100 (1)
粉体SA:リチウム二次電池用負極材料のBET表面積
負極SA:リチウム二次電池用負極のBET表面積電気化学的評価のためのサンプルの作製
負極材料粉体10gに対し、粉体結着剤としてカルボキ
シメチルセルロース1重量%、及びスチレン・ブタジエ
ンゴム1重量%を加えたものをキーエンス製ハイブリッ
ドミキサーで3分間撹拌し、スラリーを得た。このスラ
リーを銅箔上に塗布し、110℃で予備乾燥を行った。
集電体上に負極材料粉体が10±0.1mg/cm2付
着するようにした。乾燥後、電極密度を1.5±0.0
3g/cm3に調整し、負極シートとした。更に150
℃で真空減圧乾燥を施して負極とした。## EQU00003 ## Surface coverage .GAMMA. = (Powder SA-negative electrode SA) / powder SAx100 (1) Powder SA: BET surface area of negative electrode material for lithium secondary battery Negative electrode SA: BET surface area of negative electrode for lithium secondary battery Preparation of sample for electrochemical evaluation To 10 g of the negative electrode material powder, 1% by weight of carboxymethyl cellulose and 1% by weight of styrene-butadiene rubber as a powder binder were added, and the mixture was mixed for 3 minutes with a Keyence hybrid mixer. Stir to obtain a slurry. This slurry was applied on a copper foil and pre-dried at 110 ° C.
10 ± 0.1 mg / cm 2 of the negative electrode material powder was made to adhere to the current collector. After drying, the electrode density is 1.5 ± 0.0
The negative electrode sheet was adjusted to 3 g / cm 3 . Further 150
It was vacuum dried at 0 ° C. to obtain a negative electrode.
【0039】溶質としてLiPF6を1mol/Lにな
るように溶解させたエチレンカーボネート及びエチルメ
チルカーボネート(1:1)を含む電解液を用い、セパ
レータ(多孔性ポリエチレンフィルム製)を介してLi
CoO2を対極とした2032コイン型セルを組んだ。複素インピーダンス測定
上記2032コイン型セルについて、24時間測定前休
止をおいた後、0.6mA/cm2の電流値で、極間電
位差が4.2Vになるまで充電を行い、極間電位差が
3.0Vになるまで放電した。この充放電を室温で6回
行った後、7回目の4.2V充電時に10-2〜105H
zの周波数帯で複素インピーダンス測定を行い、負極部
分の抵抗(R)と、負極/電解液界面の二重層容量(C
dl)を測定した。この際、正極や低周波部分の因子の
影響を避ける為に、負極の被膜抵抗成分として現れる円
弧の一部を外挿し、上記パラメータの数値を求めた。各
数値はコイン型セル3個の結果の平均値とした。An electrolytic solution containing ethylene carbonate and ethyl methyl carbonate (1: 1) in which LiPF 6 was dissolved as a solute to 1 mol / L was used, and Li was added through a separator (made of a porous polyethylene film).
A 2032 coin type cell having CoO 2 as a counter electrode was assembled. Complex Impedance Measurement After the 2032 coin cell was paused for 24 hours before measurement, it was charged at a current value of 0.6 mA / cm 2 until the potential difference between electrodes reached 4.2 V, and the potential difference between electrodes was 3%. It discharged until it became 0.0V. After carrying out this charging and discharging 6 times at room temperature, 10 -2 to 10 5 H was obtained at the 7th 4.2V charging.
Complex impedance measurement was performed in the z frequency band, and the resistance (R) of the negative electrode portion and the double layer capacitance (C
dl) was measured. At this time, in order to avoid the influence of the factors of the positive electrode and the low frequency part, a part of the arc appearing as the film resistance component of the negative electrode was extrapolated to obtain the numerical values of the above parameters. Each numerical value was an average value of the results of three coin type cells.
【0040】電極の膨れ
負極、電解液及びセパレータに上記と同じものを、対極
にリチウム金属を用いて2016コイン型セルを組み、
上記と同様の5回目の充放電の後に電池を解体し、負極
を取り出し、マイクロメータ(ミツトヨ製)で電極厚み
を測定した。充放電前と5回目放電後の電極厚みの差か
ら、電極の膨張率を下記式(2)で算出し、電極膨れを
求めた。なお、放電は電流密度0.33mA/cm2で
極間電位差が1.5Vになるまで行った。 Electrode swelling A 2016 coin type cell was assembled by using the same as above for the negative electrode, the electrolytic solution and the separator, and using lithium metal for the counter electrode.
The battery was disassembled after the fifth charge and discharge similar to the above, the negative electrode was taken out, and the electrode thickness was measured with a micrometer (manufactured by Mitutoyo). The expansion coefficient of the electrode was calculated by the following formula (2) from the difference between the electrode thickness before charge and discharge and after the fifth discharge, and the electrode swelling was obtained. The discharge was performed at a current density of 0.33 mA / cm 2 until the potential difference between the electrodes reached 1.5V.
【0041】[0041]
【数4】
電極の膨張率(%)=(5回目放電後電極厚み−充放電前電極厚み)
/充放電前電極厚み×100 (2)充電受入性
電極膨れの場合と同様にコイン型セルを組み立て、電流
密度0.16mA/cm2で極間電位差が0Vになるま
で充電を行い、電流密度0.33mA/cm2で極間電
位差が1.5Vになるまで放電した。この充放電過程を
2回繰り返した後、1.6mA/cm2で0Vになるま
で充電を行い、充電容量を測定した。結果はコイン型セ
ル4個の結果の平均値で評価した。これから、高電流密
度時のLi充電受入性が推測可能である。本測定ではリ
チウムを対極とした半電池評価としたが、LiCoO2
の様な正極材料を用いた場合も同様の効果が期待でき
る。## EQU00004 ## Expansion coefficient of electrode (%) = (electrode thickness after fifth discharge-electrode thickness before charge / discharge) / electrode thickness before charge / discharge × 100 (2) Charge-accepting electrode Coin-shaped cell as in the case of electrode swelling the assembly was charged at a current density of 0.16 mA / cm 2 until the interelectrode potential difference becomes to 0V, and was discharged at a current density of 0.33 mA / cm 2 until the interelectrode potential difference becomes 1.5V. After repeating this charging / discharging process twice, the battery was charged to 0 V at 1.6 mA / cm 2 and the charging capacity was measured. The result was evaluated by the average value of the results of four coin cells. From this, the Li charge acceptability at high current density can be estimated. In the present measurement was half-cell evaluation as the counter electrode of lithium, LiCoO 2
Similar effects can be expected when the above positive electrode material is used.
【0042】実施例1
機械粉砕により平均粒径25μmにした天然黒鉛粒子1
5重量部と石油系ピッチ1重量部とを、大気中、70℃
でミキサーを使用して均一混合した。得られた混合物を
上面が開放された容器に10cmの厚みで詰め、回分式
加熱炉で不活性雰囲気下にて600℃で1時間熱処理し
た。冷却後、得られた混合物焼成体を20cm厚みに詰
め直し、圧力0.103MPaに調整した不活性雰囲気
下にて更に800℃で1時間熱処理した。冷却後、得ら
れた焼成体を解砕、篩い分けし、中心粒径d50が25
μmのサンプル粉体とした。残炭率から計算される黒鉛
より結晶性の劣る炭素質物の含有量は、粉体全体を10
0重量%とした時、1.2重量%であった。また、ラマ
ン分光の結果から計算されたR値は0.35であった。
本粉体のBET表面積は、3.7m2/gであり、表面
被覆率Γは33%であった。電気化学的評価から得られ
た負極の抵抗は4.9ohmであり、負極/電解液界面
の二重層容量は9.6×10-4Fであった。また、充電
受入性は125mAh/gであり、電極膨れは13%で
あった。Example 1 Natural graphite particles 1 having an average particle size of 25 μm obtained by mechanical grinding
5 parts by weight and 1 part by weight of petroleum-based pitch in air at 70 ° C.
Using a mixer, mixed uniformly. The obtained mixture was packed in a container having an open top with a thickness of 10 cm, and heat-treated at 600 ° C. for 1 hour in an inert atmosphere in a batch heating furnace. After cooling, the obtained fired mixture was repacked to a thickness of 20 cm and further heat-treated at 800 ° C. for 1 hour in an inert atmosphere adjusted to a pressure of 0.103 MPa. After cooling, the obtained fired body was crushed and sieved, and the central particle diameter d50 was 25.
A sample powder of μm was used. The content of carbonaceous material, which has a crystallinity inferior to that of graphite, calculated from the residual carbon ratio is 10
When it was 0% by weight, it was 1.2% by weight. The R value calculated from the results of Raman spectroscopy was 0.35.
The BET surface area of this powder was 3.7 m 2 / g, and the surface coverage Γ was 33%. The resistance of the negative electrode obtained from the electrochemical evaluation was 4.9 ohm, and the double-layer capacity at the negative electrode / electrolyte interface was 9.6 × 10 −4 F. The charge acceptability was 125 mAh / g, and the electrode swelling was 13%.
【0043】実施例2
原料の黒鉛と石油系ピッチの割合をそれぞれ3重量部、
1重量部に変えたこと以外は実施例1と同様に混合し、
600℃で1時間熱処理した。冷却後、得られた混合物
焼成体を20cm厚みに詰め直し、圧力0.153MP
aに調整した不活性雰囲気下にて更に700℃で1時間
熱処理した。冷却後、得られた焼成体を解砕、篩い分け
し、中心粒径d50が25μmのサンプル粉体とした。
残炭率から計算される黒鉛より結晶性の劣る炭素質物の
含有量は、粉体全体を100重量%とした時、6.3重
量%であった。また、ラマン分光の結果から計算された
R値は0.57であった。本粉体のBET表面積は、
2.9m2/gであり、表面被覆率Γは21%であっ
た。電気化学的評価から得られた負極の抵抗は5.9o
hmであり、負極/電解液界面の二重層容量は8.2×
10-4Fであった。また、充電受入性は111mAh/
gであり、電極膨れは15%であった。Example 2 3 parts by weight of graphite as a raw material and 3 parts by weight of petroleum-based pitch, respectively.
Mix as in Example 1 except changing to 1 part by weight,
It heat-processed at 600 degreeC for 1 hour. After cooling, the resulting mixture fired body was repacked to a thickness of 20 cm, and the pressure was 0.153 MP.
It was further heat-treated at 700 ° C. for 1 hour in an inert atmosphere adjusted to a. After cooling, the obtained fired body was crushed and sieved to obtain a sample powder having a median particle diameter d50 of 25 μm.
The content of the carbonaceous material having a crystallinity inferior to that of graphite calculated from the residual carbon ratio was 6.3% by weight when the entire powder was taken as 100% by weight. The R value calculated from the results of Raman spectroscopy was 0.57. The BET surface area of this powder is
It was 2.9 m 2 / g, and the surface coverage Γ was 21%. The resistance of the negative electrode obtained from the electrochemical evaluation was 5.9 o.
hm and the double layer capacity at the negative electrode / electrolyte interface is 8.2 ×
It was 10 -4 F. In addition, the charge acceptance is 111 mAh /
The electrode swelling was 15%.
【0044】実施例3
原料の黒鉛と石油系ピッチの割合をそれぞれ5重量部、
1重量部に変えたこと以外は、実施例2と同様に混合
し、熱処理した。冷却後、得られた焼成体を解砕、篩い
分けし、中心粒径d50が25μmのサンプル粉体とし
た。残炭率から計算される黒鉛より結晶性の劣る炭素質
物の含有量は、粉体全体を100重量%とした時、4.
4重量%であった。また、ラマン分光の結果から計算さ
れたR値は0.52であった。本粉体のBET表面積
は、2.9m2/gであり、表面被覆率Γは31%であ
った。電気化学的評価から得られた負極の抵抗は5.4
ohmであり、負極/電解液界面の二重層容量は9.1
×10-4Fであった。また、充電受入性は115mAh
/gであり、電極膨れは13%であった。Example 3 5 parts by weight of the raw material graphite and 5 parts by weight of petroleum pitch, respectively.
Mixing and heat treatment were performed in the same manner as in Example 2 except that the amount was changed to 1 part by weight. After cooling, the obtained fired body was crushed and sieved to obtain a sample powder having a median particle diameter d50 of 25 μm. The content of the carbonaceous material having a crystallinity inferior to that of graphite calculated from the residual carbon ratio is 4.
It was 4% by weight. The R value calculated from the results of Raman spectroscopy was 0.52. The BET surface area of this powder was 2.9 m 2 / g, and the surface coverage Γ was 31%. The negative electrode resistance obtained from the electrochemical evaluation was 5.4.
ohm and the double layer capacity at the negative electrode / electrolyte interface is 9.1.
It was × 10 -4 F. Charge acceptability is 115 mAh
/ G, and the electrode swelling was 13%.
【0045】比較例1
原料の黒鉛と石油系ピッチの割合をそれぞれ3重量部、
1重量部とし、大気中、70℃でミキサーを使用して均
一混合した。得られた混合物を上面が開放された容器に
40cmの厚みで詰め、回分式加熱炉で不活性雰囲気下
にて600℃で1時間熱処理した。冷却後、得られた混
合物焼成体を更に、圧力0.103MPaに調整した不
活性雰囲気下にて1300℃で1時間熱処理した。冷却
後、得られた焼成体を解砕、篩い分けし、中心粒径d5
0が25μmのサンプル粉体とした。残炭率から計算さ
れる黒鉛より結晶性の劣る炭素質物の含有量は、粉体全
体を100重量%とした時6.0重量%であった。ま
た、ラマン分光の結果から計算されたR値は0.35で
あった。本粉体のBET表面積は、2.3m2/gであ
り、表面被覆率Γは18%であった。電気化学的評価か
ら得られた負極の抵抗は6.8ohmであり、負極/電
解液界面の二重層容量は7.1×10- 4Fであった。
また、充電受入性は83mAh/gであり、電極膨れは
19%であった。Comparative Example 1 3 parts by weight of graphite as a raw material and 3 parts by weight of petroleum pitch, respectively.
1 part by weight and uniformly mixed at 70 ° C. in the air using a mixer. The obtained mixture was packed in a container having an open top with a thickness of 40 cm, and heat-treated at 600 ° C. for 1 hour in an inert atmosphere in a batch heating furnace. After cooling, the obtained mixture fired body was further heat-treated at 1300 ° C. for 1 hour in an inert atmosphere adjusted to a pressure of 0.103 MPa. After cooling, the obtained fired product was crushed and sieved to obtain a median particle diameter d5.
0 was 25 μm sample powder. The content of the carbonaceous material, which was inferior in crystallinity to graphite and was calculated from the residual coal rate, was 6.0% by weight when the entire powder was 100% by weight. The R value calculated from the results of Raman spectroscopy was 0.35. The BET surface area of this powder was 2.3 m 2 / g, and the surface coverage Γ was 18%. Resistance of the negative electrode obtained from the electrochemical evaluation is 6.8Ohm, the double layer capacity of the anode / electrolyte interface 7.1 × 10 - was 4 F.
The charge acceptability was 83 mAh / g, and the electrode swelling was 19%.
【0046】比較例2
原料の黒鉛と石油系ピッチの割合をそれぞれ1重量部、
2.3重量部とし、大気中、80℃でミキサーを使用し
て均一混合した。得られた混合物を上面が開放された容
器に40cmの厚みで詰め、回分式加熱炉で不活性雰囲
気下にて600℃で1時間熱処理した。冷却後、得られ
た混合物を更に、圧力0.103MPaに調整した不活
性雰囲気下にて1200℃で1時間熱処理した。R値は
0.71であった。本粉体のBET表面積は、1.5m
2/gであり、表面被覆率Γは57%であった。電気化
学的評価から得られた被膜抵抗は5.0ohmであり、
負極/電解液界面の二重層容量は1.1×10-3Fであ
った。また、充電受入性は55mAh/gであり、電極
膨れは25%であった。Comparative Example 2 The ratio of the raw material graphite to the petroleum pitch was 1 part by weight,
The amount was 2.3 parts by weight, and uniform mixing was performed in the air at 80 ° C. using a mixer. The obtained mixture was packed in a container having an open top with a thickness of 40 cm, and heat-treated at 600 ° C. for 1 hour in an inert atmosphere in a batch heating furnace. After cooling, the obtained mixture was further heat-treated at 1200 ° C. for 1 hour in an inert atmosphere adjusted to a pressure of 0.103 MPa. The R value was 0.71. The BET surface area of this powder is 1.5m
2 / g, and the surface coverage Γ was 57%. The film resistance obtained from the electrochemical evaluation is 5.0 ohm,
The double layer capacity at the negative electrode / electrolyte interface was 1.1 × 10 −3 F. The charge acceptability was 55 mAh / g, and the electrode swelling was 25%.
【0047】[0047]
【発明の効果】本発明によれば、充電受入性が高く、か
つ電極の膨れの少ないリチウム二次電池用負極材料及び
負極シートを得ることができる。EFFECTS OF THE INVENTION According to the present invention, a negative electrode material and a negative electrode sheet for a lithium secondary battery, which have high charge acceptance and less swelling of electrodes, can be obtained.
───────────────────────────────────────────────────── フロントページの続き (72)発明者 鎌田 富行 茨城県稲敷郡阿見町中央八丁目3番1号 三菱化学株式会社内 (72)発明者 岡西 健悟 香川県坂出市番の州町1番地 三菱化学株 式会社内 (72)発明者 石原 正司 茨城県稲敷郡阿見町中央八丁目3番1号 三菱化学株式会社内 Fターム(参考) 4G146 AA01 AA02 AA19 AB01 AD24 AD25 BA02 BA12 BA13 BA18 BA21 BA22 BA24 BC02 BC33A BC34A BC34B 5H029 AJ02 AJ03 AK02 AK03 AK05 AL06 AL07 AL18 AM03 AM04 AM05 AM07 AM16 CJ08 CJ22 DJ16 HJ07 HJ13 HJ19 HJ20 5H050 AA02 AA08 BA17 CA02 CA05 CA08 CA11 CB07 CB08 FA17 FA18 GA10 GA22 HA07 HA19 ─────────────────────────────────────────────────── ─── Continued front page (72) Inventor Tomiyuki Kamata 3-3-1 Chuo 8-chome, Ami Town, Inashiki District, Ibaraki Prefecture Within Mitsubishi Chemical Corporation (72) Inventor Kengo Okani 1 Kyushu Town, Sakaide City, Kagawa Prefecture Mitsubishi Chemical Corporation Inside the company (72) Inventor Shoji Ishihara 3-3-1 Chuo 8-chome, Ami Town, Inashiki District, Ibaraki Prefecture Within Mitsubishi Chemical Corporation F-term (reference) 4G146 AA01 AA02 AA19 AB01 AD24 AD25 BA02 BA12 BA13 BA18 BA21 BA22 BA24 BC02 BC33A BC34A BC34B 5H029 AJ02 AJ03 AK02 AK03 AK05 AL06 AL07 AL18 AM03 AM04 AM05 AM07 AM16 CJ08 CJ22 DJ16 HJ07 HJ13 HJ19 HJ20 5H050 AA02 AA08 BA17 CA02 CA05 CA08 CA11 CB07 CB08 FA17 FA18 GA10 GA22 HA07 HA19
Claims (4)
結晶性の劣る炭素質物を被着させた構造を有する粉体状
の負極材料であって、該負極材料と結着剤とから作製さ
れたリチウム二次電池用負極の抵抗(R)が、6.5o
hm以下、負極/電解液界面の二重層容量(Cdl)
が、7.0x10-4F以上、10x10 -4F未満の範囲
にあることを特徴とするリチウム二次電池用負極材料。1. A graphite-based carbonaceous material comprising:
Powder form with a structure in which a carbonaceous material with poor crystallinity is deposited
Which is a negative electrode material and is prepared from the negative electrode material and a binder.
The negative electrode resistance (R) for the rechargeable lithium secondary battery was 6.5 o.
hm or less, negative electrode / electrolyte interface double layer capacity (Cdl)
But 7.0x10-FourF or higher, 10x10 -FourRange less than F
A negative electrode material for a lithium secondary battery, characterized in that
材料と結着剤とから作製されたリチウム二次電池用負極
について、N2ガスを用いたBET表面積の測定を行
い、得られた値から下記式(1)で計算される、結着剤
による活物質の表面被覆率Γ(%)が、20〜55%の
範囲にある、請求項1に記載のリチウム二次電池用負極
材料。 【数1】 表面被覆率Γ=(粉体SA−負極SA)/粉体SAx100 (1) 粉体SA:リチウム二次電池用負極材料のBET表面積 負極SA:リチウム二次電池用負極のBET表面積2. A value obtained by measuring the BET surface area using N 2 gas for a negative electrode material for a lithium secondary battery and a negative electrode for a lithium secondary battery prepared from the negative electrode material and a binder. The negative electrode material for a lithium secondary battery according to claim 1, wherein the surface coverage Γ (%) of the active material with the binder calculated from the following formula (1) is in the range of 20 to 55%. ## EQU00001 ## Surface coverage .GAMMA. = (Powder SA-negative electrode SA) / powder SAx100 (1) Powder SA: BET surface area of negative electrode material for lithium secondary battery Negative electrode SA: BET surface area of negative electrode for lithium secondary battery
によるBET表面積が2.4〜4m2/gである、請求
項1又は2に記載のリチウム二次電池用負極材料。3. The negative electrode material for a lithium secondary battery according to claim 1, wherein the negative electrode material for a lithium secondary battery has a BET surface area by N 2 gas of 2.4 to 4 m 2 / g.
結晶性の劣る炭素質物を被着させた構造を有する粉体状
の負極材料であって、該負極材料と結着剤とから作製さ
れたリチウム二次電池用負極の抵抗(R)が、6.5o
hm以下、負極/電解液界面の二重層容量(Cdl)
が、7.0x10-4F以上、10x10 -4F未満の範囲
にあるものに、結着剤を加えてシート状に成形してなる
ことを特徴とするリチウム二次電池用負極シート。4. A graphite-based carbonaceous material comprising:
Powder form with a structure in which a carbonaceous material with poor crystallinity is deposited
Which is a negative electrode material and is prepared from the negative electrode material and a binder.
The negative electrode resistance (R) for the rechargeable lithium secondary battery was 6.5 o.
hm or less, negative electrode / electrolyte interface double layer capacity (Cdl)
But 7.0x10-FourF or higher, 10x10 -FourRange less than F
It is formed into a sheet by adding a binder to the one in
A negative electrode sheet for a lithium secondary battery, which is characterized in that
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JP2005317389A (en) * | 2004-04-28 | 2005-11-10 | Sanyo Electric Co Ltd | Non-aqueous electrolyte secondary battery |
JP2007103382A (en) * | 2006-12-08 | 2007-04-19 | Mitsubishi Chemicals Corp | Negative electrode material for lithium secondary battery and negative electrode sheet manufactured of this |
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JP2005317389A (en) * | 2004-04-28 | 2005-11-10 | Sanyo Electric Co Ltd | Non-aqueous electrolyte secondary battery |
KR100759632B1 (en) | 2006-01-03 | 2007-09-17 | 엘에스전선 주식회사 | Anode material for secondary battery and secondary batteries using the same |
JP2007103382A (en) * | 2006-12-08 | 2007-04-19 | Mitsubishi Chemicals Corp | Negative electrode material for lithium secondary battery and negative electrode sheet manufactured of this |
JP4595931B2 (en) * | 2006-12-08 | 2010-12-08 | 三菱化学株式会社 | Negative electrode material for lithium secondary battery and negative electrode sheet produced therefrom |
JP2012074297A (en) * | 2010-09-29 | 2012-04-12 | Mitsubishi Chemicals Corp | Multilayer structural carbon material for nonaqueous secondary battery, negative electrode material using the same, and nonaqueous secondary battery |
JP2014010989A (en) * | 2012-06-28 | 2014-01-20 | Toyota Motor Corp | Nonaqueous electrolyte secondary battery |
WO2014003067A1 (en) * | 2012-06-28 | 2014-01-03 | トヨタ自動車株式会社 | Non-aqueous electrolyte secondary battery |
JP2015053116A (en) * | 2013-09-05 | 2015-03-19 | トヨタ自動車株式会社 | Nonaqueous electrolyte secondary battery |
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