JP2015153496A - Method for manufacturing carbonaceous substance-coated graphite particles for lithium ion secondary battery negative electrodes, lithium ion secondary battery negative electrode, and lithium ion secondary battery - Google Patents
Method for manufacturing carbonaceous substance-coated graphite particles for lithium ion secondary battery negative electrodes, lithium ion secondary battery negative electrode, and lithium ion secondary battery Download PDFInfo
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Abstract
Description
本発明は、リチウムイオン二次電池負極用の炭素質被覆黒鉛粒子の製造方法、リチウムイオン二次電池負極及びリチウムイオン二次電池に関する。 The present invention relates to a method for producing carbon-coated graphite particles for a lithium ion secondary battery negative electrode, a lithium ion secondary battery negative electrode, and a lithium ion secondary battery.
リチウムイオン二次電池は携帯電子機器に広く搭載されており、今後はハイブリッド自動車や電気自動車への利用も期待される。このような状況の中で、リチウムイオン二次電池には一層の高容量、高速充放電特性、サイクル特性が要求されている。
リチウムイオン二次電池は、負極、正極および非水電解質を主たる構成要素としており、リチウムイオンが放電過程および充電過程で負極と正極との間を移動することで二次電池として作用する。現在、上記負極材料には黒鉛が広く用いられている。黒鉛は天然黒鉛と人造黒鉛に大別される。天然黒鉛は結晶性が高く容量が高いという利点を有するが、鱗片形状ゆえ電極内で粒子が一方向に配向してしまい、高速充放電特性やサイクル特性に劣るという欠点があった。
これを補うために、鱗片形状の黒鉛を球状に加工し、さらに表面被覆処理を施した材料が多く提案されている。球状化された天然黒鉛の表面には電解液との反応性が高いエッジ面が少なからず露出しており、被覆の目的はそのエッジ面を封止し、副反応を抑制することである。近年、携帯機器の大型化などにともない電池のさらなる高エネルギー密度化が求められており、それにともない負極に対してもさらなる高密度化が求められている。しかしながら従来の被覆天然黒鉛においては前記被覆層の強度が十分ではなく、高密度化によって被覆層に割れや亀裂などを生じてしまい、結果として初期効率やサイクル特性などが低下してしまうという問題があった。
一方、特許文献１には、天然黒鉛球状化粒子および／または天然黒鉛塊状化粒子が加圧処理された加圧黒鉛粒子の表面に炭化物からなる被覆層が形成されていることを特徴とするリチウムイオン二次電池用黒鉛材料、並びに、該リチウムイオン二次電池用黒鉛材料の製造方法であって、天然黒鉛球状化粒子および／または天然黒鉛塊状化粒子を加圧処理して加圧黒鉛粒子を得る加圧工程；得られた加圧黒鉛粒子を炭素物質前駆体により被覆した後、熱処理して炭素被覆する被覆工程；を有することを特徴とするリチウムイオン二次電池用黒鉛材料の製造方法が開示されている。
Lithium ion secondary batteries are widely used in portable electronic devices and are expected to be used in hybrid and electric vehicles. Under such circumstances, lithium ion secondary batteries are required to have higher capacity, faster charge / discharge characteristics, and cycle characteristics.
The lithium ion secondary battery has a negative electrode, a positive electrode, and a non-aqueous electrolyte as main components, and acts as a secondary battery by moving lithium ions between the negative electrode and the positive electrode during a discharging process and a charging process. Currently, graphite is widely used as the negative electrode material. Graphite is roughly classified into natural graphite and artificial graphite. Natural graphite has the advantage of high crystallinity and high capacity, but due to the scale shape, the particles are oriented in one direction within the electrode, resulting in inferior high-speed charge / discharge characteristics and cycle characteristics.
In order to compensate for this, many materials have been proposed in which scaly graphite is processed into a spherical shape and surface-treated. The surface of the spheroidized natural graphite has an exposed edge surface that is highly reactive with the electrolytic solution. The purpose of coating is to seal the edge surface and suppress side reactions. In recent years, with the increase in the size of portable devices, there has been a demand for further increase in energy density of batteries, and accordingly, further increase in density has been required for negative electrodes. However, in the conventional coated natural graphite, the strength of the coating layer is not sufficient, and cracking or cracking occurs in the coating layer due to high density, and as a result, the initial efficiency, cycle characteristics, etc. are deteriorated. there were.
On the other hand, in Patent Document 1, a lithium is characterized in that a coating layer made of carbide is formed on the surface of pressurized graphite particles obtained by pressurizing natural graphite spheroidized particles and / or natural graphite agglomerated particles. A graphite material for an ion secondary battery, and a method for producing the graphite material for a lithium ion secondary battery, wherein natural graphite spheroidized particles and / or natural graphite agglomerated particles are subjected to pressure treatment, A method for producing a graphite material for a lithium ion secondary battery, comprising: a pressing step to obtain; a coating step in which the obtained pressurized graphite particles are coated with a carbon material precursor and then heat-treated to coat the carbon. It is disclosed.
しかしながら、例えば特許文献１のようにまず球状化等の黒鉛粒子を加圧処理を行う場合、球状化等の黒鉛粒子を金型に挿入して加圧処理をすると、金型の隙間から球状化黒鉛粒子等が噴出して歩留まりが低下すると共に作業環境も良くないことを本発明者らは見出した。
よって、本発明は、生産性に優れ、作業環境を良好とすることができる、リチウムイオン二次電池負極用の炭素質被覆黒鉛粒子の製造方法、リチウムイオン二次電池負極及びリチウムイオン二次電池の提供を目的とする。
However, when the graphite particles such as spheroidizing are first subjected to pressure treatment as in Patent Document 1, for example, if the graphite particles such as spheroidizing are inserted into the mold and subjected to the pressure treatment, the particles are spheroidized from the gap between the molds. The present inventors have found that graphite particles and the like are ejected to reduce the yield and the working environment is not good.
Accordingly, the present invention provides a method for producing carbon-coated graphite particles for a negative electrode of a lithium ion secondary battery, a lithium ion secondary battery negative electrode, and a lithium ion secondary battery, which are excellent in productivity and can improve the working environment. The purpose is to provide.
上述のような問題を解決すべく鋭意検討した結果、本発明者らは、球状等の黒鉛粒子を予め炭素質前駆体で被覆した後に加圧処理を行う場合、球状等の黒鉛粒子が金型の隙間から噴出しがなく生産性に優れ、作業環境を低下させることがないことを見出し、本発明を完成させた。
すなわち、本発明は、以下のリチウムイオン二次電池負極用の炭素質被覆黒鉛粒子の製造方法、リチウムイオン二次電池負極及びリチウムイオン二次電池を提供する。
As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that when graphite particles such as spheres are coated with a carbonaceous precursor in advance and pressure treatment is performed, the graphite particles such as spheres are molds. The present invention has been completed by discovering that there is no ejection from the gap between the two and that the productivity is excellent and the working environment is not lowered.
That is, the present invention provides the following method for producing carbon-coated graphite particles for a lithium ion secondary battery negative electrode, a lithium ion secondary battery negative electrode, and a lithium ion secondary battery.
１． 球状及び／又は楕円体状の黒鉛粒子と炭素質前駆体とを混合して、前記黒鉛粒子の表面の少なくとも一部に前記炭素質前駆体を被覆する、混合・被覆工程と、
前記混合・被覆工程で得られた黒鉛粒子を加圧する加圧処理工程と、
前記加圧処理工程で得られた黒鉛粒子を焼成して、前記炭素質前駆体を炭素質とし、前記球状及び／又は楕円体状の黒鉛粒子の表面の少なくとも一部に前記炭素質を被覆した炭素質被覆黒鉛粒子を得る焼成工程とを有する、リチウムイオン二次電池負極用の炭素質被覆黒鉛粒子の製造方法。
２． 上記１に記載の炭素質被覆黒鉛粒子の製造方法で得られた炭素質被覆黒鉛粒子を含有する、リチウムイオン二次電池負極材料。
３． 上記２に記載のリチウムイオン二次電池負極材料を含有する、リチウムイオン二次電池負極。
４． 上記３に記載のリチウムイオン二次電池負極を有するリチウムイオン二次電池。
1. Mixing and coating step of mixing spherical and / or ellipsoidal graphite particles and a carbonaceous precursor, and coating the carbonaceous precursor on at least a part of the surface of the graphite particles;
A pressure treatment step of pressurizing the graphite particles obtained in the mixing / coating step;
The graphite particles obtained in the pressure treatment step are fired to make the carbonaceous precursor carbonaceous, and the carbonaceous material is coated on at least a part of the surface of the spherical and / or ellipsoidal graphite particles. The manufacturing method of the carbonaceous covering graphite particle for lithium ion secondary battery negative electrodes which has a baking process which obtains a carbonaceous covering graphite particle.
2. A negative electrode material for a lithium ion secondary battery, comprising carbonaceous coated graphite particles obtained by the method for producing carbonaceous coated graphite particles described in 1 above.
3. A lithium ion secondary battery negative electrode comprising the lithium ion secondary battery negative electrode material described in 2 above.
4). 4. A lithium ion secondary battery having the lithium ion secondary battery negative electrode according to 3 above.
本発明の炭素質被覆黒鉛粒子の製造方法（本発明の製造方法）は、生産性に優れ、作業環境を良好とすることができる。 The method for producing carbonaceous coated graphite particles of the present invention (production method of the present invention) is excellent in productivity and can improve the working environment.
以下、本発明をより具体的に説明する。
まず、本発明の製造方法は、
球状及び／又は楕円体状の黒鉛粒子と炭素質前駆体とを混合して、前記黒鉛粒子の表面の少なくとも一部に前記炭素質前駆体を被覆する、混合・被覆工程と、
前記混合・被覆工程で得られた黒鉛粒子を加圧する加圧処理工程と、
前記加圧処理工程で得られた黒鉛粒子を焼成して、前記炭素質前駆体を炭素質とし、前記球状及び／又は楕円体状の黒鉛粒子の表面の少なくとも一部に前記炭素質を被覆した炭素質被覆黒鉛粒子を得る焼成工程とを有する、リチウムイオン二次電池負極用の炭素質被覆黒鉛粒子の製造方法である。
Hereinafter, the present invention will be described more specifically.
First, the production method of the present invention includes:
Mixing and coating step of mixing spherical and / or ellipsoidal graphite particles and a carbonaceous precursor, and coating the carbonaceous precursor on at least a part of the surface of the graphite particles;
A pressure treatment step of pressurizing the graphite particles obtained in the mixing / coating step;
The graphite particles obtained in the pressure treatment step are fired to make the carbonaceous precursor carbonaceous, and the carbonaceous material is coated on at least a part of the surface of the spherical and / or ellipsoidal graphite particles. It is a manufacturing method of the carbonaceous covering graphite particle for lithium ion secondary battery negative electrodes which has a baking process which obtains carbonaceous covering graphite particle.
本発明の製造方法において、加圧処理工程において使用される黒鉛粒子は、加圧処理工程の前にあらかじめ混合・被覆工程において球状及び／又は楕円体状の黒鉛粒子（これを原料黒鉛粒子ともいう。）と炭素質前駆体とを混合し、炭素質前駆体が原料黒鉛粒子の表面の少なくとも一部を被覆することによって得られる。炭素質前駆体が原料黒鉛粒子の表面の少なくとも一部を被覆することによって、原料黒鉛粒子の表面のぬれが高くなり原料黒鉛粒子の滑りが防止され、これによって加圧処理工程において、混合・被覆工程で得られた黒鉛粒子を、投入する際に発塵が発生せず、及び／又は、当該黒鉛粒子が噴出することがなく、生産性に優れ、作業環境を良好とすることができると考えられる。上記メカニズムは本発明者の推測であり、メカニズムがほかのものであっても本発明の範囲内である。 In the production method of the present invention, the graphite particles used in the pressure treatment step are spherical and / or ellipsoidal graphite particles (this is also referred to as raw graphite particles) in the mixing / coating step before the pressure treatment step. .) And a carbonaceous precursor, and the carbonaceous precursor is obtained by covering at least part of the surface of the raw graphite particles. By covering at least a part of the surface of the raw graphite particles with the carbonaceous precursor, wetting of the raw graphite particles is increased and the raw graphite particles are prevented from slipping. When graphite particles obtained in the process are added, no dust is generated and / or the graphite particles are not ejected, and it is considered that the productivity can be improved and the working environment can be improved. It is done. The above mechanism is the inventor's guess, and other mechanisms are within the scope of the present invention.
１．炭素質被覆黒鉛粒子の原料
〔球状及び／又は楕円体状の黒鉛粒子：炭素質被覆黒鉛粒子の芯材〕
本発明において使用される球状及び／又は楕円体状の黒鉛粒子（炭素質被覆黒鉛粒子の芯材となる。）は、球状及び／又は楕円体状の平均粒径１〜５０μｍの黒鉛粒子であることが好ましく、より好ましくは平均アスペクト比５以下、平均粒径５〜３０μｍの範囲である黒鉛粒子である。また、平均アスペクト比２以下であることが好ましい。平均比表面積は１０ｍ2／ｇ以下であることが好ましく、８ｍ2／ｇ以下であることがより好ましい。
1. Raw material of carbonaceous coated graphite particles [spherical and / or ellipsoidal graphite particles: core material of carbonaceous coated graphite particles]
The spherical and / or ellipsoidal graphite particles used in the present invention (the core material of the carbonaceous coated graphite particles) are spherical and / or ellipsoidal graphite particles having an average particle diameter of 1 to 50 μm. More preferably, graphite particles having an average aspect ratio of 5 or less and an average particle size in the range of 5 to 30 μm are preferred. The average aspect ratio is preferably 2 or less. The average specific surface area is preferably 10 m 2 / g or less, and more preferably 8 m 2 / g or less.
球状及び／又は楕円体状の黒鉛粒子として、例えば、球状及び／又は楕円体状に加工された黒鉛粒子を使用することができ、具体的には例えば球状及び／又は楕円体状に加工された天然黒鉛粒子が挙げられる。
市販品の球状及び／又は楕円体状の天然黒鉛粒子を用いることもできる。また、球状または楕円体状以外の形状の天然黒鉛、例えば鱗片状の天然黒鉛粒子を、機械的外力で造粒球状化して球状及び／又は楕円体状の黒鉛粒子を製造することができる。球状及び／又は楕円体状に加工する方法は、例えば、接着剤や樹脂などの造粒助剤の共存下で複数の鱗片状黒鉛を混合する方法、複数の鱗片状の黒鉛に接着剤を用いずに機械的外力を加える方法、両者の併用などが挙げられる。しかし、造粒助剤を用いずに機械的外力を加えて球状に造粒する方法が最も好ましい。機械的外力とは、機械的に粉砕および造粒することであり、鱗片状黒鉛を造粒して球状化することができる。鱗片状黒鉛の粉砕装置としては、例えば、加圧ニーダー、二本ロールなどの混練機、回転ボールミル、カウンタジェットミル（ホソカワミクロン（株）製）、カレントジェット（日清エンジニアリング（株）製）などの粉砕装置が使用可能である。
As the spherical and / or ellipsoidal graphite particles, for example, spherical and / or ellipsoidal processed graphite particles can be used, specifically, for example, spherical and / or ellipsoidal processed particles. Examples include natural graphite particles.
Commercially available spherical and / or ellipsoidal natural graphite particles can also be used. In addition, spherical and / or ellipsoidal graphite particles can be produced by granulating and spheroidizing natural graphite having a shape other than spherical or ellipsoidal shape, for example, scale-like natural graphite particles by mechanical external force. The method of processing into a spherical shape and / or an ellipsoidal shape is, for example, a method in which a plurality of scaly graphites are mixed in the presence of a granulating aid such as an adhesive or a resin, and an adhesive is used for a plurality of scaly graphites. A method of applying a mechanical external force without using them, and a combination of both. However, the most preferable method is to apply a mechanical external force to granulate into a spherical shape without using a granulating aid. The mechanical external force is mechanically pulverizing and granulating, and scaly graphite can be granulated and spheroidized. Examples of the flaky graphite crusher include a pressure kneader, a kneader such as a two-roll mill, a rotating ball mill, a counter jet mill (manufactured by Hosokawa Micron Corporation), a current jet (manufactured by Nisshin Engineering Co., Ltd.), and the like. A grinding device can be used.
上記粉砕品は、その表面が鋭角な部分を有する場合もあるが、このようなときは粉砕品を造粒球状化して使用しても良い。粉砕品の造粒球状化装置としては、例えば、ＧＲＡＮＵＲＥＸ（フロイント産業（株）製）、ニューグラマシン（（株）セイシン企業）、アグロマスター（ホソカワミクロン（株）製）などの造粒機、ハイブリダイゼーション（（株）奈良機械製作所製）、メカノマイクロス（（株）奈良機械製作所製）、メカノフュージョンシステム（ホソカワミクロン（株）製）などのせん断圧縮加工装置が使用可能である。 The pulverized product may have an acute-angled surface. In such a case, the pulverized product may be granulated and used. Examples of granulated spheroidizers for pulverized products include granulators such as GRANUREX (manufactured by Freund Sangyo Co., Ltd.), Newgra Machine (manufactured by Seisin Co., Ltd.), Agromaster (manufactured by Hosokawa Micron Co., Ltd.), and hybridization. Shear compression processing apparatuses such as (manufactured by Nara Machinery Co., Ltd.), mechanomicros (manufactured by Nara Machinery Co., Ltd.), and mechanofusion system (manufactured by Hosokawa Micron Co., Ltd.) can be used.
本発明において用いられる、球状及び／又は楕円体状の黒鉛粒子について、そのＸ線回折の測定値であるＬｃは４０ｎｍ以上、Ｌａは４０ｎｍ以上が好ましい。ここで、Ｌｃは黒鉛構造のｃ軸方向の結晶子の大きさＬｃ（００２）、Ｌａはａ軸方向の結晶子の大きさＬａ（１１０）である。また、ｄ００２が０．３３７ｎｍ以下であるのが好ましく、アルゴンレーザーを用いたラマン分光法により測定した１３６０ｃｍ−１ピーク強度（Ｉ１３６０）と１５８０ｃｍ−１ピーク強度（Ｉ１５８０）の比Ｉ１３６０／Ｉ１５８０（Ｒ値）が０．０６〜０．３０、および１５８０ｃｍ−１バンドの半値幅が１０〜６０であるのが好ましい。 Regarding the spherical and / or ellipsoidal graphite particles used in the present invention, Lc, which is a measured value of X-ray diffraction, is preferably 40 nm or more, and La is preferably 40 nm or more. Here, Lc is the crystallite size Lc (002) in the c-axis direction of the graphite structure, and La is the crystallite size La (110) in the a-axis direction. Further, d002 is preferably 0.337 nm or less, and the ratio I 1360 / I of 1360 cm −1 peak intensity (I 1360 ) and 1580 cm −1 peak intensity (I 1580 ) measured by Raman spectroscopy using an argon laser. It is preferable that 1580 (R value) is 0.06 to 0.30, and the half width of 1580 cm −1 band is 10 to 60.
〔炭素質前駆体〕
本発明において、炭素質被覆黒鉛粒子の芯材である球状及び／又は楕円体状の黒鉛粒子に対して、炭素質前駆体が使用される。また、例えば後述する製造方法によって炭素質前駆体を原料黒鉛粒子に被覆することができる。本発明において用いられる炭素質前駆体としては、黒鉛に比べて結晶性が低く、黒鉛化するために必要とされる高温処理をしても黒鉛結晶とはなりえない炭素材であるタールピッチ類および／または樹脂類が例示される。具体的には、重質油、特にはタールピッチ類としては、コールタール、タール軽油、タール中油、タール重油、ナフタリン油、アントラセン油、コールタールピッチ、ピッチ油、メソフェーズピッチ、酸素架橋石油ピッチ、ヘビーオイルなどが挙げられる。樹脂類としては、ポリビニルアルコール、ポリアクリル酸などの熱可塑性樹脂、フェノール樹脂、フラン樹脂などの熱硬化性樹脂が例示される。好ましくは樹脂類を含まず、タールピッチ類のみとするとコスト的に有利である。炭素質前駆体は上記に例示したいかなるものを用いてもよいが、コールタールピッチを炭素質前駆体全量中の８０質量％以上含むものが特に好ましい。
[Carbonaceous precursor]
In the present invention, a carbonaceous precursor is used for spherical and / or ellipsoidal graphite particles which are the core material of carbonaceous coated graphite particles. Further, for example, the carbonaceous precursor can be coated on the raw graphite particles by a manufacturing method described later. As the carbonaceous precursor used in the present invention, tar pitches which are carbon materials which are low in crystallinity as compared with graphite and cannot be converted into graphite crystals even when subjected to high-temperature treatment required for graphitization. And / or resins. Specifically, as heavy oils, particularly tar pitches, coal tar, tar light oil, tar medium oil, tar heavy oil, naphthalene oil, anthracene oil, coal tar pitch, pitch oil, mesophase pitch, oxygen-crosslinked petroleum pitch, Examples include heavy oil. Examples of the resins include thermoplastic resins such as polyvinyl alcohol and polyacrylic acid, and thermosetting resins such as phenol resins and furan resins. It is advantageous in terms of cost if only tar pitches are used without containing resins. Any of the carbonaceous precursors exemplified above may be used, but those containing coal tar pitch of 80% by mass or more in the total amount of the carbonaceous precursor are particularly preferable.
２．炭素質被覆黒鉛粒子の製造方法
〔混合・被覆工程〕
混合・被覆工程において、球状及び／又は楕円体状の黒鉛粒子と炭素質前駆体とを混合して、前記黒鉛粒子の表面の少なくとも一部に前記炭素質前駆体を被覆する。
混合は、球状及び／又は楕円体状の黒鉛粒子の表面の少なくとも一部に炭素質前駆体を被覆できる方法であれば、いかなる方法を用いてもよい。例えば二軸式のニーダーなどが例示される。
好ましくは固体の原料黒鉛粒子と固体または半固体（粘調液状を含む）の炭素質前駆体とを混合する。炭素質前駆体としての重質油は、常温で固体である。炭素質前駆体としてタール軽油、タール中油等の液体を溶媒として混合した場合には２００℃以下程度の温度で予め溶媒を揮発させて次の加圧処理工程を行うのが好ましい。
混合比率は最終製品（炭素質被覆材料）の比率で黒鉛粒子が７０〜９９質量％、炭素質１〜３０質量％の範囲となるように原料を混合するのが好ましい。よって、混合・被覆工程において使用される炭素質前駆体の量は、原料黒鉛粒子及び炭素質前駆体の合計１００質量部に対して、１〜３０質量部であるのが好ましく、１〜２０質量部であるのがより好ましい。
混合は後述する加熱工程のための昇温工程とともに行っても良い。加熱混合の方法は特に限定されないが、ヒーターや熱媒などの加熱機構を有する二軸式のニーダーなどが例示される。混合処理の際、炭素質または黒鉛質の繊維、非晶質ハードカーボンなどの炭素質前駆体材料、有機材料、無機材料、金属材料を加えてもよい。加熱温度は２０〜２００℃とすることができる。
混合・被覆工程で得られる黒鉛粒子は、原料黒鉛粒子の表面の少なくとも一部又は全部に炭素質前駆体を被覆することができる。
混合・被覆工程後、加圧処理工程前に、酸化性又は非酸化性雰囲気中、３００℃以上７００℃未満の温度範囲で、炭素質前駆体で被覆された黒鉛粒子を焼成してもよい。
2. Method for producing carbon-coated graphite particles [mixing / coating process]
In the mixing / coating step, spherical and / or ellipsoidal graphite particles and a carbonaceous precursor are mixed to coat at least a part of the surface of the graphite particles with the carbonaceous precursor.
Any method may be used for mixing as long as the carbonaceous precursor can be coated on at least a part of the surface of the spherical and / or ellipsoidal graphite particles. For example, a biaxial kneader is exemplified.
Preferably, solid raw material graphite particles and a solid or semi-solid (including viscous liquid) carbonaceous precursor are mixed. Heavy oil as a carbonaceous precursor is solid at room temperature. When a liquid such as tar light oil or tar middle oil as a carbonaceous precursor is mixed as a solvent, it is preferable to volatilize the solvent in advance at a temperature of about 200 ° C. or lower to perform the next pressure treatment step.
It is preferable to mix the raw materials so that the mixing ratio of the final product (carbonaceous coating material) is in the range of 70 to 99% by mass of graphite particles and 1 to 30% by mass of carbonaceous. Therefore, the amount of the carbonaceous precursor used in the mixing / coating step is preferably 1 to 30 parts by mass, and 1 to 20 parts by mass with respect to 100 parts by mass in total of the raw graphite particles and the carbonaceous precursor. More preferably, it is part.
You may perform mixing with the temperature rising process for the heating process mentioned later. The heating and mixing method is not particularly limited, and examples thereof include a biaxial kneader having a heating mechanism such as a heater and a heat medium. During the mixing process, carbonaceous or graphite fibers, carbonaceous precursor materials such as amorphous hard carbon, organic materials, inorganic materials, and metal materials may be added. The heating temperature can be 20 to 200 ° C.
The graphite particles obtained in the mixing / coating step can coat the carbonaceous precursor on at least part or all of the surface of the raw graphite particles.
After the mixing / coating step and before the pressure treatment step, the graphite particles coated with the carbonaceous precursor may be fired in an oxidizing or non-oxidizing atmosphere in a temperature range of 300 ° C. or higher and lower than 700 ° C.
〔加圧処理工程〕
前記炭素質前駆体を被覆した黒鉛粒子（又は上述のとおり当該加圧処理工程前に焼成した場合は当該焼成工程後に得られた黒鉛粒子）を加圧処理する方法は特に限定されず、異方的または等方的のいずれの処理でもよい。例えば異方的な処理としては金型プレスやロールプレスなど、等方的な処理としては冷間静水圧プレスや熱間等方性プレスなどが挙げられる。加圧処理で固着を生じた場合などは、必要に応じて、プレスのあとに解砕工程を導入してもよい。加圧処理の際、炭素質または黒鉛質の繊維、非晶質ハードカーボンなどの炭素質前駆体材料、有機材料、無機材料、金属材料を加えてもよい。
加圧処理工程における圧力は、１〜５００ＭＰａが好ましく、２０〜２００ＭＰａがより好ましい。加圧処理工程において線圧は、０．１〜５ｔｏｎ／ｃｍが好ましく、０．５〜３ｔｏｎ／ｃｍがより好ましい。
[Pressure treatment process]
The method of pressure-treating the graphite particles coated with the carbonaceous precursor (or the graphite particles obtained after the firing step when fired before the pressure-treating step as described above) is not particularly limited, and is anisotropic. Either a target or an isotropic process may be used. For example, the anisotropic treatment includes a die press and a roll press, and the isotropic treatment includes a cold isostatic press and a hot isotropic press. In the case where fixation is caused by the pressure treatment, a crushing step may be introduced after the pressing, if necessary. During the pressure treatment, carbonaceous or graphite fibers, carbonaceous precursor materials such as amorphous hard carbon, organic materials, inorganic materials, and metal materials may be added.
The pressure in the pressure treatment process is preferably 1 to 500 MPa, and more preferably 20 to 200 MPa. In the pressure treatment step, the linear pressure is preferably 0.1 to 5 ton / cm, and more preferably 0.5 to 3 ton / cm.
〔焼成工程〕
焼成工程において、加圧処理工程で得られた黒鉛粒子を７００〜２０００℃で焼成することができる。焼成処理の方法は特に限定されないが、攪拌しながら焼成するのが好ましく、ロータリーキルンを使用することが、均質な焼成ができるので好ましい。焼成温度は最終的に到達する温度が前記範囲内であれば、複数段階で熱処理を行ってもよい。雰囲気は酸化性または非酸化性のいずれであってもよく、段階ごとに両者を使い分けてもよい。非酸化雰囲気は、アルゴン、ヘリウム、窒素等が例示できる。
[Baking process]
In the firing step, the graphite particles obtained in the pressure treatment step can be fired at 700 to 2000 ° C. The method for the baking treatment is not particularly limited, but baking is preferably performed while stirring, and the use of a rotary kiln is preferable because homogeneous baking can be performed. As long as the final temperature reaches the firing temperature, the heat treatment may be performed in a plurality of stages. The atmosphere may be oxidizing or non-oxidizing, and both may be used properly at each stage. Examples of the non-oxidizing atmosphere include argon, helium, and nitrogen.
焼成条件は、均一に被覆できるという観点から、混合・被覆工程と、３００℃以上から７００℃未満の範囲での第１の焼成工程（第１の焼成工程は空気中で行ってもよい。）と、加圧処理工程と、７００℃〜２２００℃の範囲での第２の焼成工程（第２の焼成工程は非酸化性雰囲気中で行うことができる。）をこの順番で組み合わせることが好ましい。各焼成時間は５分〜３０時間が好ましい。また昇温時および焼成時の温度プロファイルとしては、直線的な昇温、一定間隔で温度をホールドする段階的な昇温などの様々な形態をとることが可能である。
本発明の製造方法は、焼成後に粉砕工程を含まないのが好ましい。
また焼成処理の前に、異種の黒鉛材料同士を、付着、埋設、複合して用いても良い。炭素質または黒鉛質の繊維、非晶質ハードカーボンなどの炭素質前駆体材料、有機材料、無機材料、金属材料を芯材の黒鉛粒子に付着、埋設、複合してから用いてもよい。
The firing conditions are a mixing / coating step and a first firing step in the range of 300 ° C. or more to less than 700 ° C. (the first firing step may be performed in air) from the viewpoint that uniform coating is possible. It is preferable to combine the pressure treatment step and the second baking step in the range of 700 ° C. to 2200 ° C. (the second baking step can be performed in a non-oxidizing atmosphere) in this order. Each firing time is preferably 5 minutes to 30 hours. Further, the temperature profile at the time of temperature rise and firing can take various forms such as a linear temperature rise and a stepwise temperature rise in which the temperature is held at a constant interval.
The production method of the present invention preferably does not include a pulverization step after firing.
Further, different types of graphite materials may be attached, embedded, or combined before firing. Carbonaceous or graphite fibers, carbonaceous precursor materials such as amorphous hard carbon, organic materials, inorganic materials, and metal materials may be attached to, embedded in, or combined with the graphite particles of the core material.
３．炭素質被覆黒鉛粒子
本発明の製造方法によって製造される炭素質被覆黒鉛粒子に含まれる炭素質の割合は、炭素質被覆黒鉛粒子中の１〜３０質量％であるのが好ましい。炭素質の割合が１質量％未満の場合は、活性な黒鉛エッヂ面を完全に被覆することが難しくなり、初期充放電効率が低下することがある。一方、３０質量％を越える場合には、相対的に放電容量の低い炭素材の割合が多すぎて、炭素質被覆黒鉛粒子の放電容量が低下することがある。また、炭素質を形成するための原料（熱硬化性樹脂類やタールピッチ類）の割合が多い場合、混合・被覆工程やその後の焼成工程（熱処理工程）において、粒子が融着しやすく、最終的に得られる炭素質被覆黒鉛粒子の炭素質層の一部に割れや剥離を生じ、初期充放電効率の低下を生じることがある。炭素質被覆黒鉛粒子に含まれる炭素質の割合は、炭素質被覆黒鉛粒子中の、特に１〜２０質量％、さらには１〜１０質量％であることが好ましい。なお、炭素質の含有量は炭素質被覆黒鉛粒子全体の平均として上記範囲内にあればよい。個々の粒子全てが上記範囲内にある必要はなく、上記範囲以外の粒子を一部含んでいてもよい。
3. Carbonaceous coated graphite particles The proportion of carbonaceous material contained in the carbonaceous coated graphite particles produced by the production method of the present invention is preferably 1 to 30% by mass in the carbonaceous coated graphite particles. When the carbonaceous content is less than 1% by mass, it becomes difficult to completely cover the active graphite edge surface, and the initial charge / discharge efficiency may be lowered. On the other hand, if it exceeds 30% by mass, the proportion of the carbon material having a relatively low discharge capacity may be too high, and the discharge capacity of the carbonaceous coated graphite particles may decrease. In addition, when the ratio of raw materials (thermosetting resins and tar pitches) for forming carbonaceous material is large, the particles are likely to be fused in the mixing / coating process and the subsequent firing process (heat treatment process). In some cases, a part of the carbonaceous layer of the carbonaceous coated graphite particles obtained may be cracked or peeled off, resulting in a decrease in initial charge / discharge efficiency. The carbonaceous ratio contained in the carbonaceous coated graphite particles is preferably 1 to 20% by mass, more preferably 1 to 10% by mass in the carbonaceous coated graphite particles. In addition, carbon content should just exist in the said range as an average of the whole carbonaceous covering graphite particle. It is not necessary that all the individual particles are within the above range, and some particles outside the above range may be included.
最終製品である炭素質被覆黒鉛粒子の平均粒子径は１〜５０μｍの範囲であることが好ましく、５〜３０μｍの範囲であることがさらに好ましい。ＢＥＴ法により測定した比表面積は５．０ｍ2／ｇ以下であることが好ましく、３．０ｍ2／ｇ以下であることがさらに好ましい。
また、上記炭素質被覆黒鉛粒子が、アルゴンレーザーを用いたラマン分光法により測定した１３６０ｃｍ−１ピーク強度（Ｉ１３６０）と１５８０ｃｍ−１ピーク強度（Ｉ１５８０）の比Ｉ１３６０／Ｉ１５８０（Ｒ値）が黒鉛のＲ値より大きく、０．０５〜０．８０であることが好ましい。
本発明の製造方法によって製造された炭素質被覆黒鉛粒子は、例えば、リチウムイオン二次電池負極材料として使用することができる。
The average particle diameter of the carbon-coated graphite particles as the final product is preferably in the range of 1 to 50 μm, and more preferably in the range of 5 to 30 μm. The specific surface area measured by the BET method is preferably 5.0 m 2 / g or less, and more preferably 3.0 m 2 / g or less.
Further, the carbon-coated graphite particles had a ratio I 1360 / I 1580 (R value) of 1360 cm −1 peak intensity (I 1360 ) and 1580 cm −1 peak intensity (I 1580 ) measured by Raman spectroscopy using an argon laser. ) Is larger than the R value of graphite and is preferably 0.05 to 0.80.
The carbonaceous coated graphite particles produced by the production method of the present invention can be used as, for example, a lithium ion secondary battery negative electrode material.
本発明のリチウムイオン二次電池負極材料について以下に説明する。
本発明のリチウムイオン二次電池負極材料は、本発明の炭素質被覆黒鉛粒子の製造方法で得られた炭素質被覆黒鉛粒子を含有する、リチウムイオン二次電池負極材料である。
炭素質被覆黒鉛粒子は、本発明の炭素質被覆黒鉛粒子の製造方法で得られた炭素質被覆黒鉛粒子であれば特に制限されない。
The lithium ion secondary battery negative electrode material of the present invention will be described below.
The lithium ion secondary battery negative electrode material of the present invention is a lithium ion secondary battery negative electrode material containing carbonaceous coated graphite particles obtained by the method for producing carbonaceous coated graphite particles of the present invention.
The carbonaceous coated graphite particles are not particularly limited as long as they are carbonaceous coated graphite particles obtained by the method for producing carbonaceous coated graphite particles of the present invention.
〔負極〕
本発明はまた、上記の本発明の負極材料を含有するリチウムイオン二次電池用負極であり、また該負極を有するリチウムイオン二次電池である。
本発明のリチウムイオン二次電池用の負極は、例えば通常の負極の成形方法に準じて作製されうるが、化学的、電気化学的に安定な負極を得ることができる方法であれば何ら制限されない。負極の作製時には、本発明の負極材料に結合剤を加えて、予め調製した負極合剤を用いることが好ましい。結合剤としては、電解質に対して、化学的および電気化学的に安定性を示すものが好ましく、例えば、ポリテトラフルオロエチレン、ポリフッ化ビニリデンなどのフッ素系樹脂粉末、ポリエチレン、ポリビニルアルコールなどの樹脂粉末、カルボキシメチルセルロースなどが用いられる。これらを併用することもできる。結合剤は、通常、負極合剤の全量中の１〜２０質量％程度の割合で用いられる。
[Negative electrode]
The present invention is also a negative electrode for a lithium ion secondary battery containing the negative electrode material of the present invention, and a lithium ion secondary battery having the negative electrode.
The negative electrode for a lithium ion secondary battery of the present invention can be produced, for example, according to a normal negative electrode molding method, but is not limited as long as it is a method capable of obtaining a chemically and electrochemically stable negative electrode. . When preparing the negative electrode, it is preferable to use a negative electrode mixture prepared in advance by adding a binder to the negative electrode material of the present invention. As the binder, those showing chemical and electrochemical stability with respect to the electrolyte are preferable. For example, fluorine-based resin powders such as polytetrafluoroethylene and polyvinylidene fluoride, and resin powders such as polyethylene and polyvinyl alcohol Carboxymethyl cellulose and the like are used. These can also be used together. A binder is normally used in the ratio of about 1-20 mass% in the whole quantity of a negative electrode mixture.
より具体的には、例えば、まず、本発明の負極材料を分級などにより所望の粒度に調整し、これを結合剤と混合して得た混合物を溶剤に分散させ、ペースト状にして負極合剤を調製することができる。すなわち、例えば、本発明の負極材料と、結合剤を、水、イソピロピルアルコール、Ｎ−メチルピロリドン、ジメチルホルムアミドなどの溶剤と混合して得たスラリーを、公知の攪拌機、混合機、混練機、ニーダーなどを用いて攪拌混合して、ペーストを調製することができる。該ペーストを、集電材の片面または両面に塗布し、乾燥すれば、負極合剤層が均一かつ強固に接着した負極が得られる。負極合剤層の膜厚は１０〜２００μｍとすることができ、好ましくは２０〜１００μｍである。
また、本発明の負極は、本発明の負極材料と、ポリエチレン、ポリビニルアルコールなどの樹脂粉末を乾式混合し、金型内でホットプレス成型して作製することもできる。
負極合剤層を形成した後、プレス加圧などの圧着を行うと、負極合剤層と集電体との接着強度をより高めることができる。
負極の作製に用いる集電体の形状としては、特に限定されることはないが、例えば、箔状、メッシュ、エキスパンドメタルなどの網状などが挙げられる。集電材の材質としては、銅、ステンレス、ニッケルなどが好ましい。集電体の厚みは、箔状の場合で５〜２０μｍ程度であるのが好ましい。
なお、本発明の負極は、本発明の目的を損なわない範囲で、異種の黒鉛質材料、非晶質ハードカーボンなどの炭素質材料、有機物、金属、金属化合物などを混合しても、内包しても、被覆しても、または積層してもよい。
More specifically, for example, first, the negative electrode material of the present invention is adjusted to a desired particle size by classification or the like, and a mixture obtained by mixing this with a binder is dispersed in a solvent to form a paste to form a negative electrode mixture. Can be prepared. That is, for example, a slurry obtained by mixing the negative electrode material of the present invention and a binder with a solvent such as water, isopropyl alcohol, N-methylpyrrolidone, and dimethylformamide is used as a known stirrer, mixer, kneader. The paste can be prepared by stirring and mixing using a kneader or the like. When the paste is applied to one or both sides of the current collector and dried, a negative electrode in which the negative electrode mixture layer is uniformly and firmly bonded is obtained. The film thickness of the negative electrode mixture layer can be 10 to 200 μm, and preferably 20 to 100 μm.
The negative electrode of the present invention can also be produced by dry-mixing the negative electrode material of the present invention and resin powders such as polyethylene and polyvinyl alcohol and hot pressing in a mold.
When the negative electrode mixture layer is formed and then pressure bonding such as pressurization is performed, the adhesive strength between the negative electrode mixture layer and the current collector can be further increased.
The shape of the current collector used for producing the negative electrode is not particularly limited, and examples thereof include a foil shape, a mesh shape, and a net shape such as expanded metal. The material for the current collector is preferably copper, stainless steel, nickel or the like. The thickness of the current collector is preferably about 5 to 20 μm in the case of a foil.
It should be noted that the negative electrode of the present invention can be included even if different types of graphite materials, carbonaceous materials such as amorphous hard carbon, organic substances, metals, metal compounds, and the like are mixed within a range that does not impair the object of the present invention. Alternatively, it may be coated or laminated.
〔正極〕
本発明のリチウム二次電池に用いる正極は、例えば正極材料と結合剤および導電剤よりなる正極合剤を集電体の表面に塗布することにより形成することができる。正極の材料（正極活物質）は、充分量のリチウムを吸蔵／離脱し得るものを選択するのが好ましく、例えば、リチウム含有遷移金属酸化物、遷移金属カルコゲン化物、バナジウム酸化物およびそのリチウム化合物などのリチウム含有化合物、一般式ＭＸＭｏ6Ｓ8-Y（式中Ｍは少なくとも一種の遷移金属元素であり、Ｘは０≦Ｘ≦４、Ｙは０≦Ｙ≦１の範囲の数値である）で表されるシェブレル相化合物、活性炭、活性炭素繊維などである。バナジウム酸化物は、例えば、Ｖ２Ｏ５、Ｖ６Ｏ１３、Ｖ２Ｏ４、Ｖ３Ｏ８で示されるものである。
[Positive electrode]
The positive electrode used in the lithium secondary battery of the present invention can be formed, for example, by applying a positive electrode mixture comprising a positive electrode material, a binder and a conductive agent to the surface of the current collector. The positive electrode material (positive electrode active material) is preferably selected from materials that can occlude / release a sufficient amount of lithium, such as lithium-containing transition metal oxides, transition metal chalcogenides, vanadium oxides, and lithium compounds thereof. Lithium-containing compound of general formula M X Mo 6 S 8-Y (wherein M is at least one transition metal element, X is a value in the range of 0 ≦ X ≦ 4, Y is 0 ≦ Y ≦ 1) ) Represented by a chevrel phase compound, activated carbon, activated carbon fiber and the like. Vanadium oxide, for example, those represented by V 2 O 5, V 6 O 13, V 2 O 4, V 3 O 8.
リチウム含有遷移金属酸化物は、リチウムと遷移金属との複合酸化物であり、リチウムと２種類以上の遷移金属を固溶したものであってもよい。複合酸化物は単独で使用しても、２種類以上を組合わせて使用してもよい。リチウム含有遷移金属酸化物は、具体的には例えば、ＬｉＭ１ １−Ｘ Ｍ２ ＸＯ２（式中Ｍ１、Ｍ２は少なくとも一種の遷移金属元素であり、Ｘは０≦Ｘ≦１の範囲の数値である）、またはＬｉＭ１ １−ＹＭ２ ＹＯ４（式中Ｍ１、Ｍ２は少なくとも一種の遷移金属元素であり、Ｙは０≦Ｙ≦１の範囲の数値である）で示される。
Ｍ1、Ｍ2で示される遷移金属元素は、例えば、Ｃｏ、Ｎｉ、Ｍｎ、Ｃｒ、Ｔｉ、Ｖ、Ｆｅ、Ｚｎ、Ａｌ、Ｉｎ、Ｓｎなどであり、好ましいのはＣｏ、Ｆｅ、Ｍｎ、Ｔｉ、Ｃｒ、Ｖ、Ａｌなどである。好ましい具体例は、ＬｉＣｏＯ２、ＬｉＮｉＯ２、ＬｉＭｎＯ２、ＬｉＮｉ０．９Ｃｏ０．１Ｏ２、ＬｉＮｉ０．５Ｃｏ０．５Ｏ２などである。
The lithium-containing transition metal oxide is a composite oxide of lithium and a transition metal, and may be a solid solution of lithium and two or more transition metals. The composite oxide may be used alone or in combination of two or more. Specifically, the lithium-containing transition metal oxide is, for example, LiM 1 1-X M 2 X O 2 (wherein M 1 and M 2 are at least one transition metal element, and X is 0 ≦ X ≦ 1) LiM 1 1-Y M 2 Y O 4 (wherein M 1 and M 2 are at least one transition metal element, and Y is a numerical value in the range of 0 ≦ Y ≦ 1). Indicated by
Transition metal elements represented by M 1 and M 2 are, for example, Co, Ni, Mn, Cr, Ti, V, Fe, Zn, Al, In, Sn, etc., preferably Co, Fe, Mn, Ti , Cr, V, Al and the like. Preferred examples include LiCoO 2 , LiNiO 2 , LiMnO 2 , LiNi 0.9 Co 0.1 O 2 , LiNi 0.5 Co 0.5 O 2 , and the like.
リチウム含有遷移金属酸化物は、例えば、リチウム、遷移金属の酸化物、水酸化物、塩類等を出発原料とし、これら出発原料を所望の金属酸化物の組成に応じて混合し、酸素雰囲気下６００〜１０００℃の温度で焼成することにより得ることができる。
正極活物質は、前記化合物を単独で使用しても２種類以上併用してもよい。例えば、正極中に炭酸リチウム等の炭素塩を添加することができる。また、正極を形成するに際しては、従来公知の導電剤や結着剤などの各種添加剤を適宜に使用することができる。
Examples of the lithium-containing transition metal oxide include lithium, transition metal oxides, hydroxides, salts, and the like as starting materials, and these starting materials are mixed in accordance with the composition of the desired metal oxide, and are mixed under an oxygen atmosphere. It can be obtained by firing at a temperature of ˜1000 ° C.
The positive electrode active material may be used alone or in combination of two or more. For example, a carbon salt such as lithium carbonate can be added to the positive electrode. Moreover, when forming a positive electrode, conventionally well-known various additives, such as a electrically conductive agent and a binder, can be used suitably.
［正極の製造］
正極は、例えば、前記正極材料、結合剤、および正極に導電性を付与するための導電剤よりなる正極合剤を、集電体の両面に塗布して正極合剤層を形成して作製されうる。結合剤としては、負極の作製に使用されるものと同じものが使用可能である。導電剤としては、例えば、黒鉛化物、カーボンブラックなど公知のものが使用される。
集電体の形状は特に限定されないが、例えば、箔状またはメッシュ、エキスパンドメタル等の網状等のものが用いられる。集電体の材質は、例えば、アルミニウム、ステンレス、ニッケル等が挙げられる。その厚さは１０〜４０μｍのものが好適である。
正極も負極と同様に、正極合剤を溶剤中に分散させペースト状にし、このペースト状の正極合剤を集電体に塗布、乾燥して正極合剤層を形成してもよく、正極合剤層を形成した後、さらにプレス加圧等の圧着を行ってもよい。これにより正極合剤層が均一且つ強固に集電材に接着される。
[Production of positive electrode]
The positive electrode is produced, for example, by applying a positive electrode mixture composed of the positive electrode material, the binder, and a conductive agent for imparting conductivity to the positive electrode on both surfaces of the current collector to form a positive electrode mixture layer. sell. As the binder, the same one as that used for producing the negative electrode can be used. As the conductive agent, for example, known materials such as graphitized materials and carbon black are used.
The shape of the current collector is not particularly limited, and for example, a foil shape or a net shape such as a mesh or expanded metal is used. Examples of the material of the current collector include aluminum, stainless steel, nickel, and the like. The thickness is preferably 10 to 40 μm.
Similarly to the negative electrode, the positive electrode mixture may be formed in a paste by dispersing the positive electrode mixture in a solvent, and the paste-like positive electrode mixture may be applied to a current collector and dried to form a positive electrode mixture layer. After forming the agent layer, pressure bonding such as press pressing may be further performed. As a result, the positive electrode mixture layer is uniformly and firmly bonded to the current collector.
〔非水電解質〕
本発明のリチウムイオン二次電池に用いられる非水電解質としては、通常の非水電解液に使用される電解質塩である、ＬｉＰＦ６、ＬｉＢＦ４、ＬｉＡｓＦ６、ＬｉＣｌＯ４、ＬｉＢ（Ｃ６Ｈ５）、ＬｉＣｌ、ＬｉＢｒ、ＬｉＣＦ３ＳＯ３、ＬｉＣＨ３ＳＯ３、ＬｉＮ（ＣＦ３ＳＯ２）２、ＬｉＣ（ＣＦ３ＳＯ２）３、ＬｉＮ（ＣＦ３ＣＨ２ＯＳＯ２）２、ＬｉＮ（ＣＦ３ＣＦ２ＯＳＯ２）２、ＬｉＮ（ＨＣＦ２ＣＦ２ＣＨ２ＯＳＯ２）２、ＬｉＮ（（ＣＦ３）２ＣＨＯＳＯ２）２、ＬｉＢ［｛Ｃ６Ｈ３（ＣＦ３）２｝］４、ＬｉＡｌＣｌ４、ＬｉＳｉＦ６などのリチウム塩を用いることができる。酸化安定性の点からは、特に、ＬｉＰＦ６、ＬｉＢＦ４が好ましい。
電解液中の電解質塩濃度は０．１〜５ｍｏｌ／Ｌが好ましく、０．５〜３．０ｍｏｌ／Ｌがより好ましい。
非水電解質は液状の非水電解質としてもよく、固体電解質またはゲル電解質などの高分子電解質としてもよい。前者の場合、非水電解質電池は、いわゆるリチウムイオン二次電池として構成され、後者の場合は、非水電解質電池は高分子固体電解質、高分子ゲル電解質電池などの高分子電解質電池として構成される。
非水電解質液を調製するための溶媒としては、例えば、エチレンカーボネート、プロピレンカーボネート、ジメチルカーボネート、ジエチルカーボネートなどのカーボネート、１、１−または１、２−ジメトキシエタン、１、２−ジエトキシエタン、テトラヒドロフラン、２−メチルテトラヒドロフラン、γ−ブチロラクトン、１、３−ジオキソラン、４−メチル−１、３−ジオキソラン、アニソール、ジエチルエーテルなどのエーテル、スルホラン、メチルスルホランなどのチオエーテル、アセトニトリル、クロロニトリル、プロピオニトリルなどのニトリル、ホウ酸トリメチル、ケイ酸テトラメチル、ニトロメタン、ジメチルホルムアミド、Ｎ−メチルピロリドン、酢酸エチル、トリメチルオルトホルメート、ニトロベンゼン、塩化ベンゾイル、臭化ベンゾイル、テトラヒドロチオフェン、ジメチルスルホキシド、３−メチル−２−オキサゾリドン、エチレングリコール、ジメチルサルファイトなどの非プロトン性有機溶媒などを用いることができる。
非水電解質を高分子固体電解質または高分子ゲル電解質などの高分子電解質とする場合には、マトリクスとして可塑剤（非水電解液）でゲル化された高分子を用いることが好ましい。前記マトリクスを構成する高分子としては、ポリエチレンオキサイドやその架橋体などのエーテル系高分子化合物、ポリメタクリレート系高分子化合物、ポリアクリレート系高分子化合物、ポリビニリデンフルオライドやビニリデンフルオライド−ヘキサフルオロプロピレン共重合体などのフッ素系高分子化合物などを用いることが特に好ましい。
前記高分子固体電解質または高分子ゲル電解質には、可塑剤が配合されるが、該可塑剤としては、前記の電解質塩や非水溶媒が使用可能である。高分子ゲル電解質の場合、可塑剤である非水電解液中の電解質塩濃度は０．１〜５ｍｏｌ／Ｌが好ましく、０．５〜２．０ｍｏｌ／Ｌがより好ましい。
[Non-aqueous electrolyte]
The non-aqueous electrolyte used in the lithium ion secondary battery of the present invention, an electrolyte salt used in the conventional non-aqueous electrolyte, LiPF 6, LiBF 4, LiAsF 6, LiClO 4, LiB (C 6 H 5 ), LiCl, LiBr, LiCF 3 SO 3 , LiCH 3 SO 3 , LiN (CF 3 SO 2 ) 2 , LiC (CF 3 SO 2 ) 3 , LiN (CF 3 CH 2 OSO 2 ) 2 , LiN (CF 3 CF 2 OSO 2) 2, LiN ( HCF 2 CF 2 CH 2 OSO 2) 2, LiN ((CF 3) 2 CHOSO 2) 2, LiB [{C 6 H 3 (CF 3) 2}] 4, LiAlCl 4, Lithium salts such as LiSiF 6 can be used. From the viewpoint of oxidation stability, LiPF 6 and LiBF 4 are particularly preferable.
The electrolyte salt concentration in the electrolytic solution is preferably 0.1 to 5 mol / L, and more preferably 0.5 to 3.0 mol / L.
The non-aqueous electrolyte may be a liquid non-aqueous electrolyte or a polymer electrolyte such as a solid electrolyte or a gel electrolyte. In the former case, the non-aqueous electrolyte battery is configured as a so-called lithium ion secondary battery, and in the latter case, the non-aqueous electrolyte battery is configured as a polymer electrolyte battery such as a polymer solid electrolyte or a polymer gel electrolyte battery. .
Examples of the solvent for preparing the non-aqueous electrolyte include carbonates such as ethylene carbonate, propylene carbonate, dimethyl carbonate, and diethyl carbonate, 1,1- or 1,2-dimethoxyethane, 1,2-diethoxyethane, Tetrahydrofuran, 2-methyltetrahydrofuran, γ-butyrolactone, 1,3-dioxolane, 4-methyl-1,3-dioxolane, ethers such as anisole and diethyl ether, thioethers such as sulfolane and methylsulfolane, acetonitrile, chloronitrile, propio Nitriles such as nitriles, trimethyl borate, tetramethyl silicate, nitromethane, dimethylformamide, N-methylpyrrolidone, ethyl acetate, trimethylorthoformate, nitrobenzene, benzoyl chloride Yl, benzoyl bromide, tetrahydrothiophene, dimethyl sulfoxide, 3-methyl-2-oxazolidone, ethylene glycol, aprotic organic solvents such as dimethyl sulfite may be used.
When the non-aqueous electrolyte is a polymer electrolyte such as a polymer solid electrolyte or a polymer gel electrolyte, it is preferable to use a polymer gelled with a plasticizer (non-aqueous electrolyte) as a matrix. Examples of the polymer constituting the matrix include ether-based polymer compounds such as polyethylene oxide and cross-linked products thereof, polymethacrylate-based polymer compounds, polyacrylate-based polymer compounds, polyvinylidene fluoride, and vinylidene fluoride-hexafluoropropylene. It is particularly preferable to use a fluorine-based polymer compound such as a copolymer.
The polymer solid electrolyte or polymer gel electrolyte is mixed with a plasticizer, and as the plasticizer, the electrolyte salt and the non-aqueous solvent can be used. In the case of a polymer gel electrolyte, the concentration of the electrolyte salt in the nonaqueous electrolytic solution that is a plasticizer is preferably 0.1 to 5 mol / L, and more preferably 0.5 to 2.0 mol / L.
高分子固体電解質の作製方法は特に限定されないが、例えば、マトリクスを構成する高分子化合物、リチウム塩および非水溶媒（可塑剤）を混合し、加熱して高分子化合物を溶融する方法、有機溶剤に高分子化合物、リチウム塩、および非水溶媒（可塑剤）を溶解させた後、混合用有機溶剤を蒸発させる方法、重合性モノマー、リチウム塩および非水溶媒（可塑剤）を混合し、混合物に紫外線、電子線または分子線などを照射して、重合性モノマーを重合させ、ポリマーを得る方法などを挙げることができる。
ここで、前記固体電解質中の非水溶媒（可塑剤）の割合は１０〜９０質量％が好ましく、３０〜８０質量％がより好ましい。１０質量％未満であると導電率が低くなり、９０質量％を超えると機械的強度が弱くなり、成膜しにくくなることがある。
The method for producing the polymer solid electrolyte is not particularly limited. For example, a method of mixing a polymer compound constituting a matrix, a lithium salt, and a nonaqueous solvent (plasticizer) and heating to melt the polymer compound, an organic solvent A method in which a polymer compound, a lithium salt, and a non-aqueous solvent (plasticizer) are dissolved in, and an organic solvent for mixing is evaporated, a polymerizable monomer, a lithium salt, and a non-aqueous solvent (plasticizer) are mixed, and the mixture is mixed Examples thereof include a method of polymerizing a polymerizable monomer by irradiating an ultraviolet ray, an electron beam, a molecular beam or the like to obtain a polymer.
Here, the ratio of the non-aqueous solvent (plasticizer) in the solid electrolyte is preferably 10 to 90% by mass, and more preferably 30 to 80% by mass. If it is less than 10% by mass, the electrical conductivity will be low, and if it exceeds 90% by mass, the mechanical strength will be weak and it may be difficult to form a film.
〔セパレータ〕
本発明のリチウムイオン二次電池においては、セパレータを使用することもできる。セパレータの材質は特に限定されるものではないが、例えば、織布、不織布、合成樹脂製微多孔膜などを用いることができる。前記セパレータの材質としては、合成樹脂製微多孔膜が好適であるが、なかでもポリオレフィン系微多孔膜が、厚さ、膜強度、膜抵抗の面で好適である。具体的には、ポリエチレンおよびポリプロピレン製微多孔膜、またはこれらを複合した微多孔膜等が好適である。
[Separator]
In the lithium ion secondary battery of the present invention, a separator can also be used. Although the material of a separator is not specifically limited, For example, a woven fabric, a nonwoven fabric, a synthetic resin microporous film, etc. can be used. As a material for the separator, a microporous membrane made of synthetic resin is suitable. Among them, a polyolefin microporous membrane is suitable in terms of thickness, membrane strength, and membrane resistance. Specifically, polyethylene and polypropylene microporous membranes, or microporous membranes composed of these are suitable.
〔リチウムイオン二次電池の製造〕
本発明のリチウムイオン二次電池は、上述した構成の負極、正極および非水電解質を、例えば、負極、非水電解質、正極の順で積層し、電池の外装材内に収容することで構成される。さらに、負極と正極の外側に非水電解質を配するようにしてもよい。
また、本発明のリチウムイオン二次電池の構造は特に限定されず、その形状、形態についても特に限定されるものではなく、用途、搭載機器、要求される充放電容量などに応じて、円筒型、角型、コイン型、ボタン型などの中から任意に選択することができる。より安全性の高い密閉型非水電解液電池を得るためには、過充電などの異常時に電池内圧上昇を感知して電流を遮断させる手段を備えたものを用いることが好ましい。
リチウムイオン二次電池が高分子固体電解質電池や高分子ゲル電解質電池の場合には、ラミネートフィルムに封入した構造とすることもできる。
[Manufacture of lithium ion secondary batteries]
The lithium ion secondary battery of the present invention is configured by laminating the negative electrode, the positive electrode, and the nonaqueous electrolyte having the above-described configuration in the order of, for example, the negative electrode, the nonaqueous electrolyte, and the positive electrode, and accommodating the laminate in the battery exterior material. The Further, a non-aqueous electrolyte may be disposed outside the negative electrode and the positive electrode.
In addition, the structure of the lithium ion secondary battery of the present invention is not particularly limited, and the shape and form thereof are not particularly limited, and are cylindrical, depending on the application, mounted equipment, required charge / discharge capacity, and the like. , Square shape, coin shape, button shape, and the like. In order to obtain a sealed nonaqueous electrolyte battery with higher safety, it is preferable to use a battery equipped with means for detecting an increase in the internal pressure of the battery and shutting off the current when an abnormality such as overcharging occurs.
In the case where the lithium ion secondary battery is a polymer solid electrolyte battery or a polymer gel electrolyte battery, a structure in which the lithium ion secondary battery is enclosed in a laminate film may be used.
次に本発明を実施例により具体的に説明するが、本発明はこれら実施例に限定されるものではない。また以下の実施例および比較例では、添付の図１に示す評価電池（単極評価用のボタン型二次電池。添付の図１に示す評価電池については後述する。）を作製して、これを用いて電池特性の評価をした。実電池は、本発明の概念に基づき、例えば公知の方法に準じて作製することができる。 EXAMPLES Next, although an Example demonstrates this invention concretely, this invention is not limited to these Examples. Further, in the following examples and comparative examples, an evaluation battery shown in FIG. 1 (button-type secondary battery for single electrode evaluation. The evaluation battery shown in FIG. 1 will be described later) is prepared. Was used to evaluate battery characteristics. Based on the concept of the present invention, the actual battery can be manufactured, for example, according to a known method.
（実施例１）
［負極材料の作製］
平均粒子径２０μmの球状に加工された天然黒鉛粒子１００質量部に対して、コールタールピッチ（残炭率５０％）のタール中油溶液を、固形分比率が１５質量部となるように添加し、二軸ニーダーで１５０℃に加熱して６０分混合した（混合・被覆工程）。得られた混合物を、ロータリーキルンを用い、空気５Ｌ／分の流通下３１０℃で３時間の一段階目の熱処理を行った（焼成工程：第１段階）。次いでこの熱処理物を、加圧処理の方法として金型成形機を用い２５℃、５０ＭＰａの条件下で異方的に加圧処理したのち解砕し（加圧処理工程）、管状炉を用い窒素２Ｌ／分の流通下１３００℃で３時間の二段階目の熱処理を行った（焼成工程：第２段階）。第２段階の焼成工程後に最終製品（炭素質被覆材料）を得た。
Example 1
[Production of negative electrode material]
To 100 parts by mass of natural graphite particles processed into a spherical shape with an average particle diameter of 20 μm, a tar-in-oil solution of coal tar pitch (residual carbon ratio 50%) is added so that the solid content ratio is 15 parts by mass, The mixture was heated to 150 ° C. with a biaxial kneader and mixed for 60 minutes (mixing / coating step). The obtained mixture was subjected to a first heat treatment for 3 hours at 310 ° C. under a flow of 5 L / min using a rotary kiln (firing step: first step). Next, this heat-treated product was anisotropically pressurized under a condition of 25 ° C. and 50 MPa using a die molding machine as a pressure treatment method, and then crushed (pressure treatment step), and then nitrogenized using a tube furnace. The second stage heat treatment was performed for 3 hours at 1300 ° C. under a flow of 2 L / min (firing step: second stage). The final product (carbonaceous coating material) was obtained after the second stage baking process.
［負極合剤ペーストの作製］
上述のとおり製造された負極材料（炭素質被覆材料）９５質量％と、ポリフッ化ビニリデン５質量％をＮ−メチルピロリドン中に入れ、ホモミキサーを用いて２０００ｒｐｍで３０分間攪拌混合し、有機溶剤系負極合剤（負極合剤ペースト）を調製した。
[Preparation of negative electrode mixture paste]
95% by mass of the negative electrode material (carbonaceous coating material) produced as described above and 5% by mass of polyvinylidene fluoride are placed in N-methylpyrrolidone, and stirred and mixed at 2000 rpm for 30 minutes using a homomixer. A negative electrode mixture (negative electrode mixture paste) was prepared.
［作用電極（負極）の作製］
上述のとおり製造された負極合剤ペーストを銅箔に均一な厚さで塗布し、真空中９０℃で溶剤を揮発させ、乾燥し、負極合剤層をハンドプレスによって加圧した。銅箔と負極合剤層を直径１５．５ｍｍの円柱状に打抜いて、集電体と、該集電体に密着した負極合剤とからなる作用電極（負極）を作製した。
[Production of working electrode (negative electrode)]
The negative electrode mixture paste produced as described above was applied to a copper foil with a uniform thickness, the solvent was evaporated at 90 ° C. in a vacuum, and the negative electrode mixture layer was pressed by a hand press. The copper foil and the negative electrode mixture layer were punched into a cylindrical shape having a diameter of 15.5 mm to prepare a working electrode (negative electrode) composed of a current collector and a negative electrode mixture adhered to the current collector.
［対極（正極）の作製］
リチウム金属箔をニッケルネットに押付け、直径１５．５ｍｍの円形状に打抜いて、ニッケルネットからなる集電体と、この集電体に密着したリチウム金属箔（厚み０．５ｍｍ）からなる対極（正極）を作製した。
[Production of counter electrode (positive electrode)]
A lithium metal foil is pressed against a nickel net and punched into a circular shape with a diameter of 15.5 mm. A current collector made of nickel net and a counter electrode made of a lithium metal foil (thickness 0.5 mm) in close contact with the current collector ( Positive electrode) was prepared.
［電解液、セパレータ］
エチレンカーボネート５０体積％−プロピレンカーボネート５０体積％の混合溶剤に、ＬｉＰＦ6を１ｍｏｌ／ｋｇとなる濃度で溶解させ、非水電解液を調製した。得られた非水電解液をポリプロピレン多孔質体（厚み２０μｍ）に含浸させ、電解液が含浸したセパレータを作製した。
[Electrolyte, separator]
LiPF 6 was dissolved at a concentration of 1 mol / kg in a mixed solvent of 50% by volume of ethylene carbonate and 50% by volume of propylene carbonate to prepare a nonaqueous electrolytic solution. The obtained nonaqueous electrolytic solution was impregnated into a polypropylene porous body (thickness 20 μm) to produce a separator impregnated with the electrolytic solution.
［評価（黒鉛粒子の噴出又は発塵の有無）］
＜混合・被覆工程で得られた黒鉛粒子の加圧処理工程における噴出又は発塵の有無＞
加圧処理工程において、各実施例等の加圧処理の方法で、混合・被覆工程で得られた黒鉛粒子が噴出または発塵したかを以下のとおり確認した。結果を表１に示す。
・加圧処理の方法として金型成形機を用いた場合、金型から混合・被覆工程で得られた黒鉛粒子が噴出したかどうか
・加圧処理の方法としてロールプレスを用いた場合、混合・被覆工程で得られた黒鉛粒子をロールに投入する際に発塵が生じたかどうか
・加圧処理の方法として冷間静水圧プレスを用いた場合、混合・被覆工程で得られた黒鉛粒子を加圧用ラバーに投入する際に発塵が生じたかどうか
[Evaluation (whether graphite particles are ejected or dust is generated)]
<Presence / absence of ejection or dust generation in the pressure treatment process of the graphite particles obtained in the mixing / coating process>
In the pressurization process, whether the graphite particles obtained in the mixing / coating process were ejected or dusted by the pressurization process of each example or the like was confirmed as follows. The results are shown in Table 1.
・ When using a mold molding machine as a pressure treatment method, whether graphite particles obtained in the mixing / coating process were ejected from the mold ・ When using a roll press as a pressure treatment method, mixing ・Whether or not dust was generated when the graphite particles obtained in the coating process were put into a roll. ・ When a cold isostatic press was used as the pressure treatment method, the graphite particles obtained in the mixing / coating process were added. Whether dust was generated when thrown into the pressure rubber
［評価電池の作製］
評価電池として図１に示す評価電池（ボタン型二次電池）を作製した。図１は本発明のリチウムイオン二次電池負極の電池特性を評価するために使用された評価電池の概略を示す断面図である。
図１において、外装カップ１と外装缶３とを、その周縁部において絶縁ガスケット６を介在させ、両周縁部（図示せず。）をかしめて密閉した。その内部に外装缶３の内面から順に、ニッケルネットからなる集電体７ａ、リチウム箔よりなる円筒状の対極（正極）４、電解液が含浸されたセパレータ５、負極材料２、銅箔からなる集電体７ｂが積層された電池系である。負極材料２は集電体７ｂに付着する。
図１に示す評価電池は、電解液を含浸させたセパレータ５を、集電体７ｂに付着した負極材料２と集電体７ａに密着した対極４との間に挟んで積層した後、集電体７ｂを外装カップ１内に収容し、対極４を外装缶３内に収容して、外装カップ１と外装缶３とを合わせ、さらに、外装カップ１と外装缶３との周縁部に絶縁ガスケット６を介在させ、両周縁部（図示せず。）をかしめて密閉して作製した。
[Production of evaluation battery]
The evaluation battery (button type secondary battery) shown in FIG. 1 was produced as the evaluation battery. FIG. 1 is a cross-sectional view showing an outline of an evaluation battery used for evaluating battery characteristics of a negative electrode of a lithium ion secondary battery of the present invention.
In FIG. 1, the outer cup 1 and the outer can 3 are hermetically sealed by caulking both peripheral portions (not shown) with an insulating gasket 6 interposed at the peripheral portion. In the inside, in order from the inner surface of the outer can 3, a current collector 7 a made of nickel net, a cylindrical counter electrode (positive electrode) 4 made of lithium foil, a separator 5 impregnated with an electrolyte, a negative electrode material 2, and a copper foil It is a battery system in which the current collector 7b is laminated. The negative electrode material 2 adheres to the current collector 7b.
In the evaluation battery shown in FIG. 1, a separator 5 impregnated with an electrolyte is stacked between a negative electrode material 2 attached to a current collector 7b and a counter electrode 4 in close contact with the current collector 7a. The body 7 b is accommodated in the exterior cup 1, the counter electrode 4 is accommodated in the exterior can 3, the exterior cup 1 and the exterior can 3 are combined, and an insulating gasket is provided at the peripheral edge of the exterior cup 1 and the exterior can 3. 6 was interposed, and both peripheral portions (not shown) were caulked and sealed.
上述のとおり製造した評価電池を用いて以下の電池特性を評価した。結果を表１に示した。
［充放電試験］
回路電圧が１ｍＶに達するまで０．９ｍＡの定電流充電を行った後、回路電圧が１ｍＶに達した時点で定電圧充電に切替え、さらに電流値が２０μＡになるその間の通電量から充電容量（単位：ｍＡｈ／ｇ）を求めた。その後、１０分間休止した。次に０．９ｍＡの電流値で、回路電圧が１．５Ｖに達するまで定電流放電を行い、この間の通電量から放電容量（単位：ｍＡｈ／ｇ）を求めた。これを第１サイクルとした。
初回充放電効率は次式（１）から計算した。
初回充放電効率（％）＝１００×（（第１サイクルの充電容量−第１サイクルの放電容量）／第１サイクルの放電容量）・・・（１）
また、上記の充放電を１００回繰返し、得られた放電容量から次式（２）を用いてサイクル特性を計算した。
サイクル特性（％）＝１００×（第１００サイクルの放電容量／第１サイクルの放電容量）・・・（２）
なおこの試験では、リチウムイオンを負極材料に吸蔵する過程を充電、負極材料からリチウムイオンが脱離する過程を放電とした。
The following battery characteristics were evaluated using the evaluation battery manufactured as described above. The results are shown in Table 1.
[Charge / discharge test]
After constant current charging of 0.9 mA until the circuit voltage reaches 1 mV, switching to constant voltage charging is performed when the circuit voltage reaches 1 mV, and further, the charging capacity (unit: : MAh / g). Then, it rested for 10 minutes. Next, constant current discharge was performed at a current value of 0.9 mA until the circuit voltage reached 1.5 V, and the discharge capacity (unit: mAh / g) was determined from the amount of electricity supplied during this period. This was the first cycle.
The initial charge / discharge efficiency was calculated from the following equation (1).
Initial charge / discharge efficiency (%) = 100 × ((first cycle charge capacity−first cycle discharge capacity) / first cycle discharge capacity) (1)
Moreover, said charging / discharging was repeated 100 times, and the cycle characteristics were calculated from the obtained discharge capacity using the following equation (2).
Cycle characteristics (%) = 100 × (100th cycle discharge capacity / first cycle discharge capacity) (2)
In this test, the process of occluding lithium ions in the negative electrode material was charged, and the process of detaching lithium ions from the negative electrode material was discharge.
（実施例２）
実施例１において、加圧処理の方法を金型成形機からロールプレスに変更し、線圧１ｔｏｎ／ｃｍとなるように加圧する以外は、実施例１と同様にして、炭素質被覆黒鉛粒子（被覆天然黒鉛材料）を製造し、評価した。
(Example 2)
In Example 1, the method of the pressure treatment was changed from the die molding machine to the roll press, and the carbonaceous coated graphite particles ( Coated natural graphite material) was produced and evaluated.
（実施例３）
実施例１において、加圧処理の方法を金型成形機から冷間静水圧プレスに変更し、５０ＭＰａを等方的に加圧する以外は、実施例１と同様にして、炭素質被覆黒鉛粒子（被覆天然黒鉛材料）を製造し、評価した。
(Example 3)
In Example 1, the method of the pressure treatment was changed from the mold molding machine to the cold isostatic press, and the carbonaceous coated graphite particles ( Coated natural graphite material) was produced and evaluated.
（実施例４）
実施例２において、加圧処理のタイミングを混練直後とする以外は、実施例１と同様にして、炭素質被覆黒鉛粒子（被覆天然黒鉛材料）を製造し、評価した。
Example 4
In Example 2, carbonaceous coated graphite particles (coated natural graphite material) were produced and evaluated in the same manner as in Example 1 except that the timing of the pressure treatment was immediately after kneading.
（比較例１）
実施例１において、加圧処理工程を行わない以外は、実施例１と同様にして、被覆天然黒鉛材料を製造し、評価した。
(Comparative Example 1)
In Example 1, a coated natural graphite material was produced and evaluated in the same manner as in Example 1 except that the pressure treatment step was not performed.
（比較例２）
［負極材料の作製］
平均粒子径２０μｍの球状に加工された天然黒鉛粒子を冷間静水圧プレスで５０ＭＰａを等方的に加圧処理した。黒鉛粒子を加圧用ラバーに投入する際に発塵が生じた。
上記のとおり加圧処理して製造された天然黒鉛粒子１００質量部に対して、コールタールピッチ（残炭率５０％）のタール中油溶液を、固形分比率が１５質量部となるように添加し、二軸ニーダーで１５０℃に加熱して６０分混合した。
得られた混合物を、ロータリーキルンを用い、空気５Ｌ／分の流通下５００℃で３時間の一段階目の熱処理を行った。
次いでこの熱処理物を、管状炉を用い窒素２Ｌ／分の流通下１３００℃で３時間の二段階目の熱処理を行うことで最終製品（炭素質被覆材料）を得た。
実施例１と同様にして評価電池を製造しその電池特性を評価した。結果を表１に示す。
(Comparative Example 2)
[Production of negative electrode material]
Natural graphite particles processed into a spherical shape with an average particle diameter of 20 μm were subjected to an isotropic pressure treatment of 50 MPa with a cold isostatic press. Dust generation occurred when the graphite particles were put into the pressure rubber.
To 100 parts by mass of natural graphite particles produced by pressure treatment as described above, a tar-in-oil solution of coal tar pitch (residual carbon ratio 50%) is added so that the solid content ratio is 15 parts by mass. The mixture was heated to 150 ° C. with a biaxial kneader and mixed for 60 minutes.
The obtained mixture was heat-treated in the first stage for 3 hours at 500 ° C. under a flow of 5 L / min using a rotary kiln.
Next, this heat-treated product was subjected to a second-stage heat treatment at 1300 ° C. for 3 hours under a flow of 2 L / min of nitrogen using a tubular furnace to obtain a final product (carbonaceous coating material).
Evaluation batteries were produced in the same manner as in Example 1, and the battery characteristics were evaluated. The results are shown in Table 1.
表１に示す結果から明らかなように、加圧処理工程を有さない比較例１は初回充放電効率が低かった。球状の黒鉛粒子を加圧処理した後に、混合・被覆、焼成した比較例２は黒鉛粒子を加圧用ラバーに投入する際に発塵が生じた。
これに対して、実施例１〜４は加圧処理工程の際原料が噴出や発塵を生じることはなく生産性に優れ、作業環境を良好とすることができる。
As is clear from the results shown in Table 1, Comparative Example 1 having no pressure treatment step had a low initial charge / discharge efficiency. In Comparative Example 2 in which spherical graphite particles were subjected to pressure treatment, mixed, coated, and fired, dust was generated when the graphite particles were charged into the pressure rubber.
On the other hand, in Examples 1 to 4, the raw material does not spout or generate dust during the pressure treatment process, and is excellent in productivity and can improve the working environment.
本発明の炭素質被覆黒鉛粒子の製造方法（本発明の製造方法）は、生産性に優れ、作業環境を良好とすることができる。 The method for producing carbonaceous coated graphite particles of the present invention (production method of the present invention) is excellent in productivity and can improve the working environment.
１ 外装カップ
２ 負極材料
３ 外装缶
４ 対極
５ セパレータ
６ 絶縁ガスケット
７ａ、７ｂ 集電体
DESCRIPTION OF SYMBOLS 1 Exterior cup 2 Negative electrode material 3 Exterior can 4 Counter electrode 5 Separator 6 Insulation gasket 7a, 7b Current collector
Claims (4)
前記混合・被覆工程で得られた黒鉛粒子を加圧する加圧処理工程と、
前記加圧処理工程で得られた黒鉛粒子を焼成して、前記炭素質前駆体を炭素質とし、前記球状及び／又は楕円体状の黒鉛粒子の表面の少なくとも一部に前記炭素質を被覆した炭素質被覆黒鉛粒子を得る焼成工程とを有する、リチウムイオン二次電池負極用の炭素質被覆黒鉛粒子の製造方法。 Mixing and coating step of mixing spherical and / or ellipsoidal graphite particles and a carbonaceous precursor, and coating the carbonaceous precursor on at least a part of the surface of the graphite particles;
A pressure treatment step of pressurizing the graphite particles obtained in the mixing / coating step;
The graphite particles obtained in the pressure treatment step are fired to make the carbonaceous precursor carbonaceous, and the carbonaceous material is coated on at least a part of the surface of the spherical and / or ellipsoidal graphite particles. The manufacturing method of the carbonaceous covering graphite particle for lithium ion secondary battery negative electrodes which has a baking process which obtains a carbonaceous covering graphite particle.
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| JP2020087916A (en) * | 2018-11-20 | 2020-06-04 | Ｊｆｅケミカル株式会社 | Production method of carbonaceous coated graphite particle |
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