JP5153189B2 - Method for producing lithium ion secondary battery positive electrode material - Google Patents

Method for producing lithium ion secondary battery positive electrode material Download PDF

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JP5153189B2
JP5153189B2 JP2007095790A JP2007095790A JP5153189B2 JP 5153189 B2 JP5153189 B2 JP 5153189B2 JP 2007095790 A JP2007095790 A JP 2007095790A JP 2007095790 A JP2007095790 A JP 2007095790A JP 5153189 B2 JP5153189 B2 JP 5153189B2
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義孝 濱中
優一 高梨
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Mitsui Engineering and Shipbuilding Co Ltd
Mitsui E&S Holdings Co Ltd
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Description

本発明は、リチウムイオン二次電池正極材料の製造方法に関する。   The present invention relates to a method for producing a lithium ion secondary battery positive electrode material.

金属リチウム電池、リチウムイオン電池、リチウムポリマー電池等に代表される二次電池の正極材料としては、コバルト酸リチウム（ＬｉＣｏＯ２）、マンガン酸リチウム（ＬｉＭｎＯ２）、ニッケル酸リチウム（ＬｉＮｉＯ２）、リン酸鉄リチウム（ＬｉＦｅＰＯ４）等のリチウム遷移金属が挙げられる。現在用いられている正極材料としては、コバルト酸リチウムが主流であるが、オリビン型結晶構造を持つリン酸鉄リチウムは、かなり大きい理論容量（１７０ｍＡｈ／ｇ）と比較的高い起電力（対Ｌｉ／Ｌｉ＋負極にて約３.４〜３.５Ｖ）を有し、しかも資源的に豊富な鉄・リン等からなり、安価に製造できると考えられるため、次世代の有力な正極材料候補と期待されている。 As positive electrode materials of secondary batteries represented by metal lithium batteries, lithium ion batteries, lithium polymer batteries, etc., lithium cobaltate (LiCoO 2 ), lithium manganate (LiMnO 2 ), lithium nickelate (LiNiO 2 ), phosphorus Examples thereof include lithium transition metals such as lithium iron oxide (LiFePO 4 ). As the positive electrode material currently used, lithium cobaltate is the mainstream, but lithium iron phosphate having an olivine type crystal structure has a considerably large theoretical capacity (170 mAh / g) and a relatively high electromotive force (vs. Li / Li + negative electrode is about 3.4-3.5V), and it is considered that it can be manufactured at low cost because it is made of resource-rich iron, phosphorus, etc. Has been.

また、同正極系は、他の多くの正極系、例えば現行正極のコバルト酸リチウム［ＬｉＣｏＯ２］等とは異なり、電極酸化還元の全過程を通じて、Ｌｉの充満した還元態（放電状態）のＬｉＦｅ（II）ＰＯ４、及びＬｉの完全に脱離した酸化態（充電状態）Ｆｅ（III）ＰＯ４の２相のみが常に存在する２相平衡状態をとり［即ち、例えばＬｉ0.5（Ｆｅ2＋ 0.5Ｆｅ3＋ 0.5）ＰＯ４などの中間状態は相としてはとり得ない］、その結果、充放電電圧が常に一定に保たれるために充放電状態の管理が容易であるという興味深い性質を有する。 Further, the positive electrode system is different from many other positive electrode systems, for example, lithium cobaltate [LiCoO 2 ] of the current positive electrode, and in the entire process of electrode oxidation reduction, LiFe in a reduced state (discharge state) filled with Li is used. It takes a two-phase equilibrium state in which only two phases of (II) PO 4 and Li completely deoxidized (charged state) Fe (III) PO 4 always exist [ie, Li 0.5 (Fe 2+ 0.5 An intermediate state such as Fe 3+ 0.5 ) PO 4 cannot be taken as a phase]. As a result, since the charge / discharge voltage is always kept constant, the charge / discharge state is easily managed.

ここで、前記リン酸鉄リチウム（ＬｉＦｅＰＯ４）は、例えば、シュウ酸鉄（II）［（ＦｅＣ２Ｏ４）・２Ｈ２Ｏ］、リン酸水素二アンモニウム［（ＮＨ４）２ＨＰＯ４］、水酸化リチウム一水和物［ＬｉＯＨ・Ｈ２Ｏ］等の原料を焼成することによって製造される（例えば、特許文献１および特許文献２）。 Here, the lithium iron phosphate (LiFePO 4 ) includes, for example, iron (II) oxalate [(FeC 2 O 4 ) · 2H 2 O], diammonium hydrogen phosphate [(NH 4 ) 2 HPO 4 ], It is manufactured by firing raw materials such as lithium hydroxide monohydrate [LiOH.H 2 O] (for example, Patent Document 1 and Patent Document 2).

原料であるシュウ酸鉄（II）［（ＦｅＣ２Ｏ４）・２Ｈ２Ｏ］、リン酸水素二アンモニウム［（ＮＨ４）２ＨＰＯ４］、水酸化リチウム一水和物［ＬｉＯＨ・Ｈ２Ｏ］等は、例えばエタノールを加えて粉砕・混合し、減圧下で乾燥した後、焼成される。この焼成工程により、リン酸鉄リチウムを合成することができる。 Iron (II) oxalate [(FeC 2 O 4 ) · 2H 2 O], diammonium hydrogen phosphate [(NH 4 ) 2 HPO 4 ], lithium hydroxide monohydrate [LiOH · H 2 O] ], For example, is added with ethanol, pulverized and mixed, dried under reduced pressure, and then baked. Through this firing step, lithium iron phosphate can be synthesized.

前記焼成は、温度を５００〜８００℃程度（好ましくは６００〜７００℃程度）の高温域まで昇温し、４〜２４時間程度かけて行うことができる。また、低温域から高温域まで昇温する間に、３００〜４５０℃程度（中温域）まで昇温して１〜６時間程度加熱を行う予備的な焼成工程を含ませたり、焼成工程を２つに分け、先に３００〜４５０℃程度（中温域）にて仮焼成を行い、一旦外部に仮焼成物を取り出して擂潰した後に５００〜８００℃程度（好ましくは６００〜７００℃程度）にて本焼成を行うこともできる。この場合、得られる正極材料のリン酸鉄リチウムの均一性が一層向上し、より高い２次電池性能が得られる。   The calcination can be performed over about 4 to 24 hours by raising the temperature to a high temperature range of about 500 to 800 ° C. (preferably about 600 to 700 ° C.). In addition, a preliminary baking step of heating to about 300 to 450 ° C. (medium temperature range) and heating for about 1 to 6 hours while the temperature is raised from the low temperature range to the high temperature range is included. First, pre-baking is performed at about 300 to 450 ° C. (medium temperature range), and the pre-baked product is taken out and crushed to about 500 to 800 ° C. (preferably about 600 to 700 ° C.). The main baking can also be performed. In this case, the uniformity of the obtained lithium iron phosphate of the positive electrode material is further improved, and higher secondary battery performance is obtained.

正極材料であるリン酸鉄リチウムは、コバルト酸リチウム等に比べて導電率が低いが、特許文献１および特許文献２においては、原料中に導電性炭素や導電性炭素前駆物質（加熱分解により導電性炭素を生じ得る物質）を添加して焼成し、リン酸鉄リチウム粒子の表面に炭素を析出させることによって、導電性を改善している。   Lithium iron phosphate, which is a positive electrode material, has a lower electrical conductivity than lithium cobaltate or the like. However, in Patent Document 1 and Patent Document 2, conductive carbon or conductive carbon precursor (conducted by thermal decomposition) is contained in the raw material. A substance capable of producing a conductive carbon) is added and baked to deposit carbon on the surface of the lithium iron phosphate particles, thereby improving the conductivity.

また、特許文献３には、焼成工程における合成原料の反応性を高めるため、焼成工程前の原料を混合、粉砕（ミリング）し、その原料混合物を所定の密度に圧縮する圧縮工程を行った後、焼成工程を行う方法が開示されている。
特開２００３−１５７８４５号公報 特開２００４−６３３８６号公報 特開２００２−１１７８４８号公報 In Patent Document 3, in order to increase the reactivity of the synthetic raw material in the firing step, the raw material before the firing step is mixed and pulverized (milled), and then the compression step of compressing the raw material mixture to a predetermined density is performed. A method of performing a firing step is disclosed.
JP 2003-157845 A JP 2004-63386 A JP 2002-117848 A

ここで、焼成前に原料に対して行う粉砕・混合・乾燥等の前処理や、焼成工程を２つに分け、仮焼成および本焼成を行う場合に、仮焼成後の原料に対して行う擂潰によって、前記原料、または仮焼成後の原料は微粒子化され嵩高くなる。焼成炉に導入できる原料の量はその嵩高さによって制限され、一度にそれほど多くの量を焼成できないのが現状である。   Here, the pretreatment such as pulverization, mixing, and drying performed on the raw material before firing, and the firing step are divided into two, and the preliminary firing and main firing are performed on the raw material after temporary firing. By crushing, the raw material or the raw material after provisional baking is made fine and bulky. The amount of the raw material that can be introduced into the firing furnace is limited by its bulkiness, and the present situation is that a large amount cannot be fired at once.

特に、仮焼成後の原料に、前記導電性炭素や導電性炭素前駆物質（加熱分解により導電性炭素を生じ得る物質）を添加した場合には、当該導電性炭素や導電性炭素前駆物質を加えたことによっても全体の嵩が増える場合が多いため、本焼成時に炉内に導入される被焼成物（仮焼成後の原料＋導電性炭素および／または導電性炭素前駆物質）が焼成炉の許容限界量になるように、仮焼成時に炉内に導入される原料を少なめに調整する必要があった。   In particular, when the conductive carbon or conductive carbon precursor (substance that can generate conductive carbon by thermal decomposition) is added to the raw material after the pre-baking, the conductive carbon or conductive carbon precursor is added. As a result, the overall bulk often increases, so that the material to be fired (the raw material after pre-firing + conductive carbon and / or conductive carbon precursor) introduced into the furnace during the main firing is acceptable for the firing furnace. It was necessary to adjust the amount of raw material introduced into the furnace at the time of pre-firing so as to be the limit amount.

本発明の課題は、仮焼成後の原料の擂潰処理によって原料が微粒子化されることによる嵩高さや、仮焼成後の原料に導電性炭素や導電性炭素前駆物質を添加することにより本焼成時における被焼成物が増加することなどに鑑み、被焼成物を圧縮することによって焼成炉に導入する被焼成物の量を増加させ、一度に焼成可能な被焼成物の量を増やし、効率よくリチウムイオン二次電池正極材料を製造する方法を提供することにある。   The problem of the present invention is that the bulk of the raw material is converted into fine particles by the crushing treatment of the raw material after the pre-firing, or the addition of conductive carbon or a conductive carbon precursor to the raw material after the pre-firing In view of the increase in the number of objects to be fired, the amount of the object to be fired introduced into the firing furnace is increased by compressing the object to be fired. It is providing the method of manufacturing an ion secondary battery positive electrode material.

本発明の第１の態様に係るリチウムイオン二次電池正極材料の製造方法の発明は、原料を焼成してリン酸鉄リチウム系正極材料を製造するリチウムイオン二次電池正極材料の製造方法において、焼成過程は、常温から３００℃ないし４５０℃に至る第一段階と、常温から焼成完了温度に至る第二段階と、を含み、前記第一段階の焼成によって生成する一次粒子が凝集して形成される二次粒子の集合物を所定のかさ密度に圧縮した後、前記第二段階の焼成を行うことを特徴とするものである。   Invention of the manufacturing method of the lithium ion secondary battery positive electrode material which concerns on the 1st aspect of this invention is a manufacturing method of the lithium ion secondary battery positive electrode material which bakes a raw material and manufactures lithium iron phosphate type positive electrode material, The firing process includes a first stage from room temperature to 300 ° C. to 450 ° C. and a second stage from room temperature to the firing completion temperature, and the primary particles generated by the firing of the first stage are formed by aggregation. After the secondary particle aggregate is compressed to a predetermined bulk density, the second stage firing is performed.

本発明製造方法は、原料を焼成してリン酸鉄リチウム系正極材料を製造する方法であり、その焼成過程は、常温から３００℃ないし４５０℃に至る第一段階と、常温から焼成完了温度に至る第二段階と、の二段階で行われる。前記第一段階の焼成によって生成する焼成生成物は粒状体であり、その粒は一次粒子が凝集して形成される二次粒子である。すなわち、前記焼成生成物は一次粒子が凝集して形成される二次粒子の集合物である。   The production method of the present invention is a method of firing a raw material to produce a lithium iron phosphate-based positive electrode material, and the firing process is from the first stage from room temperature to 300 ° C. to 450 ° C., and from the room temperature to the firing completion temperature. This is done in two stages: the second stage. The fired product produced by the first stage firing is a granular body, and the grains are secondary particles formed by aggregation of primary particles. That is, the fired product is an aggregate of secondary particles formed by aggregation of primary particles.

本発明によれば、第一段階の焼成によって生成する、組成の大半が既にリン酸鉄リチウム系正極活物質となった微細な一次粒子が凝集して形成される二次粒子の集合物を所定のかさ密度に圧縮した後、前記第二段階の焼成を行うので、第一段階の焼成によって生成した焼成生成物（以下、第一段階焼成生成物と記すことがある）が減容化され、第二段階の焼成を行う焼成炉等の焼成装置に高密度の第一段階焼成生成物を導入することが可能となり、第二段階の焼成において焼成することができる第一段階焼成生成物量が増加し、第二段階の焼成を効率よく行うことができる。   According to the present invention, an aggregate of secondary particles formed by agglomeration of fine primary particles, most of which are already formed by lithium iron phosphate based positive electrode active material, produced by the first stage firing is predetermined. Since the second stage firing is performed after compression to the bulk density, the fired product generated by the first stage firing (hereinafter sometimes referred to as the first stage fired product) is reduced in volume, It becomes possible to introduce a high-density first stage firing product into a firing apparatus such as a firing furnace that performs the second stage firing, and the amount of the first stage firing product that can be fired in the second stage firing is increased. In addition, the second stage firing can be performed efficiently.

また、本発明における「所定のかさ密度」とは、前記二次粒子の集合物において、前記一次粒子が凝集して形成される二次粒子同士の空隙を減少させることによってその減容化が達成され、しかも第二段階の焼成後に生じる正極材料の一次粒子が、第二段階の焼成過程で一体化・粒径増大することを促進しないような状態のかさ密度である。   The “predetermined bulk density” in the present invention means that the volume reduction is achieved by reducing the voids between the secondary particles formed by aggregation of the primary particles in the aggregate of the secondary particles. In addition, the bulk density of the positive electrode material generated after the second stage firing does not promote the integration and particle size increase in the second stage firing process.

このような所定のかさ密度に制御して前記二次粒子の集合物を圧縮することにより、過度な圧縮によって、一次粒子同士が凝集し過ぎることを防止するとともに、第一段階焼成生成物の減容化を図ることができる。   By compressing the aggregate of secondary particles while controlling to such a predetermined bulk density, it is possible to prevent the primary particles from aggregating excessively due to excessive compression and to reduce the first-stage baked product. It can be easy to understand.

本発明の第２の態様に係るリチウムイオン二次電池正極材料の製造方法の発明は、原料を焼成してリン酸鉄リチウム系正極材料を製造するリチウムイオン二次電池正極材料の製造方法において、焼成過程は、常温から３００℃ないし４５０℃に至る第一段階と、常温から焼成完了温度に至る第二段階と、を含み、前記第一段階の焼成によって生成する一次粒子が凝集して形成される二次粒子の集合物に、加熱分解により導電性炭素を生じ得る物質を添加、混合した混合粒子の集合物を、所定のかさ密度に圧縮した後、前記第二段階の焼成を行うことを特徴とするものである。   Invention of the manufacturing method of the lithium ion secondary battery positive electrode material which concerns on the 2nd aspect of this invention is the manufacturing method of the lithium ion secondary battery positive electrode material which bakes a raw material and manufactures lithium iron phosphate type positive electrode material, The firing process includes a first stage from room temperature to 300 ° C. to 450 ° C. and a second stage from room temperature to the firing completion temperature, and the primary particles generated by the firing of the first stage are formed by aggregation. After adding a substance capable of generating conductive carbon by thermal decomposition to the aggregate of secondary particles, the mixed aggregate of mixed particles is compressed to a predetermined bulk density, and then the second stage firing is performed. It is a feature.

加熱分解により導電性炭素を生じ得る物質（以下、「導電性炭素前駆物質」と記すことがある）を、第一段階焼成生成物に添加して第二段階の焼成を行うことにより、加熱分解により導電性炭素を生じ得る物質が、焼成中に原料の分解により生成するガスにより発泡することを防ぐことができる。その結果、融解状態にある該物質がより均一に正極材料の表面に溶融状態で広がり、より均一に熱分解炭素を析出させることができる。このため、得られる正極材料の表面導電性がさらに良好になり、また接触が強固に安定化される。   A substance capable of generating conductive carbon by thermal decomposition (hereinafter sometimes referred to as “conductive carbon precursor”) is added to the first stage baking product and subjected to the second stage baking. Thus, it is possible to prevent a substance capable of generating conductive carbon from being foamed by a gas generated by decomposition of the raw material during firing. As a result, the substance in the molten state spreads more uniformly on the surface of the positive electrode material in a molten state, and pyrolytic carbon can be deposited more uniformly. For this reason, the surface conductivity of the positive electrode material obtained is further improved, and the contact is firmly stabilized.

前記二次粒子の集合物に、前記導電性炭素前駆物質を添加すると、当該導電性炭素前駆物質を添加した分、第二段階の焼成に供する被焼成物の嵩が増加する。   When the conductive carbon precursor is added to the aggregate of secondary particles, the volume of the object to be fired to be subjected to the second-stage firing increases by the amount of the addition of the conductive carbon precursor.

本発明によれば、前記二次粒子の集合物に、加熱分解により導電性炭素を生じ得る物質を第一段階焼成生成物に添加、混合した混合粒子の集合物を、所定のかさ密度に圧縮した後、前記第二段階の焼成を行うので、第１の態様と同様に、過度な圧縮によって、一次粒子同士が凝集し過ぎることを防止できるとともに、前記集合物と前記導電性炭素前駆物質との混合粒子の集合物の減容化を図ることができる。   According to the present invention, a substance that can generate conductive carbon by thermal decomposition is added to the aggregate of secondary particles, and the aggregate of mixed particles mixed and mixed to the first-stage baked product is compressed to a predetermined bulk density. Then, since the second stage baking is performed, the primary particles can be prevented from being excessively aggregated by excessive compression, as in the first aspect, and the aggregate and the conductive carbon precursor The volume of the aggregate of the mixed particles can be reduced.

本発明の第３の態様に係るリチウムイオン二次電池正極材料の製造方法の発明は、第２の態様に記載された二次電池正極材料の製造方法において、前記一次粒子の粒径は５０〜１００ｎｍであり、前記加熱分解により導電性炭素を生じ得る物質は、軟化温度８０℃から３５０℃の範囲にあり、加熱分解による減量開始温度が３５０℃から４５０℃の範囲にあり、かつ、５００℃から８００℃の加熱分解・焼成により導電性炭素を析出し得る物質であり、前記所定のかさ密度は、０．６〜０．９ｇ／ｃｍ３であることを特徴とするものである。 The method for producing a positive electrode material for a lithium ion secondary battery according to a third aspect of the present invention is the method for producing a positive electrode material for a secondary battery described in the second aspect, wherein the primary particles have a particle size of 50 to 50. The substance having a thickness of 100 nm and capable of generating conductive carbon by the thermal decomposition has a softening temperature in the range of 80 ° C. to 350 ° C., a weight loss starting temperature in the range of 350 ° C. to 450 ° C., and 500 ° C. From 800 to 800 ° C., it is a substance capable of precipitating conductive carbon by thermal decomposition and firing, and the predetermined bulk density is 0.6 to 0.9 g / cm 3 .

前記導電性炭素を析出し得る物質としては、ビチューメン類（特に石炭ピッチ）及び糖類が好ましい。   As the substance capable of depositing the conductive carbon, bitumen (especially coal pitch) and saccharide are preferable.

本発明製造方法により製造されたリン酸鉄リチウム系正極材料は、適宜カーボンブラック等の導電性助剤と共にアルミニウム箔などの集電体にバインダーによって結着されて、リチウムイオン二次電池の正極として用いられ、高いリチウムイオン電池性能を得るためには、リン酸鉄リチウム系正極材料及び導電性助剤はバインダー中に高度に分散することが求められる。   The lithium iron phosphate-based positive electrode material produced by the production method of the present invention is appropriately bound to a current collector such as an aluminum foil together with a conductive auxiliary agent such as carbon black by a binder, and used as a positive electrode of a lithium ion secondary battery. In order to obtain high lithium ion battery performance, the lithium iron phosphate-based positive electrode material and the conductive auxiliary are required to be highly dispersed in the binder.

本発明によれば、第一段階の焼成によって生成する一次粒子の粒径が１００〜５００ｎｍである場合に、前記二次粒子の集合物と前記導電性炭素を析出し得る物質の混合粒子の集合物のかさ密度を０．６〜０．９ｇ／ｃｍ３に制御することによって、過度な圧縮によって、前記一次粒子が凝集し過ぎることを防止することができる。 According to the present invention, when the primary particles produced by the first stage firing have a particle size of 100 to 500 nm, the aggregate of secondary particles and the aggregate of mixed particles of substances capable of depositing the conductive carbon By controlling the bulk density of the product to 0.6 to 0.9 g / cm 3 , it is possible to prevent the primary particles from aggregating excessively due to excessive compression.

更に、前記二次粒子の集合物と前記導電性炭素を析出し得る物質の混合粒子の集合物は減容化されているので、第二段階の焼成を行う焼成炉等の焼成装置に導入できる前記混合粒子の集合物の量が増加し、第二段階の焼成を効率よく行うことができる。   Furthermore, since the volume of the aggregate of secondary particles and the aggregate of mixed particles of substances capable of depositing conductive carbon are reduced, it can be introduced into a firing apparatus such as a firing furnace that performs the second stage firing. The amount of the aggregate of the mixed particles increases, and the second stage firing can be performed efficiently.

次に、具体例を挙げて、本発明を更に詳細に説明するが、本発明はこれらによって制約されるものではない。
まず本発明製造方法によって製造されるリン酸鉄リチウム系正極材料について説明する。 Next, the present invention will be described in more detail with specific examples, but the present invention is not limited by these.
First, the lithium iron phosphate-based positive electrode material produced by the production method of the present invention will be described.

＜リン酸鉄リチウム系正極材料＞
本発明において、リン酸鉄リチウム系正極材料とは、例えば、一般式Ｌｉ１−ｎｙ（ＭａｘＭｂｙＦｅ１−ｘ−ｙ）ＰＯ４で表され、オリビン型結晶構造を有し、前記式中のＭａ、ＭｂはＦｅを置換しうる金属元素であり、前記Ｍａは価数が２の元素であり、且つ元素周期表において２族、１１族、１２族に属する金属元素の群から選ばれる１種以上の金属元素であり、前記Ｍｂは価数が３以上の元素であり、且つ元素周期表において３族、４族、５族、６族、１３族、１４族に属する金属元素の群から選ばれる１種以上の金属元素であり、各置換量である前記ｘとｙは、０≦ｘ、ｙ≦０．０５の数であり、前記ｎは前記Ｍｂの平均価数をｆとして、ｎ＝ｆ−２である。特に、前記Ｍａは、カドミウム（Ｃｄ）、マグネシウム（Ｍｇ）、コバルト（Ｃｏ）、ニッケル（Ｎｉ）、ストロンチウム（Ｓｒ）、カルシウム（Ｃａ）、銅（Ｃｕ）、亜鉛（Ｚｎ）の群から選ばれる１種以上の金属元素であり、前記Ｍｂは、ニオブ（Ｎｂ）、タングステン（Ｗ）、マンガン（Ｍｎ）、スカンジウム（Ｓｃ）、イットリウム（Ｙ）、チタン（Ｔｉ）、バナジウム（Ｖ）、クロム（Ｃｒ）、モリブデン（Ｍｏ）、アルミニウム（Ａｌ）、インジウム（Ｉｎ）、スズ（Ｓｎ）よりなる群から選ばれる１種以上の金属元素である。 <Lithium iron phosphate positive electrode material>
In the present invention, the lithium iron phosphate-based cathode material, for example, is represented by the general formula Li 1-ny (Ma x Mb y Fe 1-x-y) PO 4, has an olivine-type crystal structure, the formula Ma and Mb therein are metal elements that can substitute for Fe, and Ma is an element having a valence of 2 and is selected from the group of metal elements belonging to Groups 2, 11, and 12 in the Periodic Table of Elements. A group of metal elements that are one or more metal elements, and Mb is an element having a valence of 3 or more, and belongs to Group 3, 4, 5, 6, 13, and 14 in the periodic table. Wherein x and y, which are substitution amounts, are numbers of 0 ≦ x and y ≦ 0.05, and n is an average valence of Mb, f. n = f−2. In particular, the Ma is selected from the group consisting of cadmium (Cd), magnesium (Mg), cobalt (Co), nickel (Ni), strontium (Sr), calcium (Ca), copper (Cu), and zinc (Zn). One or more metal elements, and the Mb is niobium (Nb), tungsten (W), manganese (Mn), scandium (Sc), yttrium (Y), titanium (Ti), vanadium (V), chromium ( One or more metal elements selected from the group consisting of Cr), molybdenum (Mo), aluminum (Al), indium (In), and tin (Sn).

ｘ、ｙが０でない時、この正極材料中において、異種金属元素Ｍａ、ＭｂはＦｅの一部を置換した形で入っている。Ｍａは価数が２であり、このＭａのＦｅに対する置換量ｘの置換導入によって、充電（酸化）状態においてＬｉがｘだけ残存するオリビン型結晶構造を実現する。Ｍａは２＋の酸化状態だけを安定してとるものがよい。また、Ｍｂは価数が３以上であり、このＭｂのＦｅに対する置換量ｙの置換導入によって、Ｍｂの価数をｆとして、放電（還元）状態においてＬｉがＦｅに対してｎｙ（ただし、ｎ＝ｆ−２）だけ欠損になるオリビン型結晶構造を実現する。   When x and y are not 0, different metal elements Ma and Mb are contained in the positive electrode material in a form in which a part of Fe is substituted. Ma has a valence of 2, and by introducing substitution of this substitution amount x of Ma with Fe, an olivine-type crystal structure in which only Li remains in the charged (oxidized) state is realized. It is preferable that Ma takes only the 2+ oxidation state stably. In addition, Mb has a valence of 3 or more. By introducing substitution of the substitution amount y of Mb to Fe, the valence of Mb is set to f, and Li is ny (but n = F-2) to realize an olivine type crystal structure that is deficient.

以上の正極材料の原型となる活物質であるＬｉＦｅＰＯ４は、結晶骨格構造［結晶点群ＰＮＭＡ（オリビン型）、同ＰＢＮＭなどの構造をとり、いずれも正極活物質となり得るが、前者が一般的である］が電気化学的酸化還元によってほとんど変化しないため、繰返し充放電が可能なアルカリ金属系二次電池用の正極材料として用いることができる。正極材料としては、これらの物質のそのままの状態は放電状態に相当し、電解質との界面での電気化学的酸化によって、アルカリ金属Ｌｉの脱ドープを伴いながら中心金属元素Ｆｅが酸化され、充電状態になる。充電状態から電気化学的還元を受けると、アルカリ金属Ｌｉの再ドープを伴いながら中心金属元素Ｆｅが還元され、元の放電状態に戻る。 LiFePO 4 , which is an active material serving as a prototype of the above positive electrode material, has a crystal skeleton structure [structure such as crystal point group PNMA (olivine type), PBNM, etc., and any of them can be a positive electrode active material. However, since it hardly changes due to electrochemical oxidation and reduction, it can be used as a positive electrode material for an alkali metal secondary battery that can be repeatedly charged and discharged. As the positive electrode material, the state of these substances as they are corresponds to the discharge state, and the central metal element Fe is oxidized with the undoping of the alkali metal Li by the electrochemical oxidation at the interface with the electrolyte, and the charged state become. When subjected to electrochemical reduction from the charged state, the central metal element Fe is reduced while re-doping with the alkali metal Li and returns to the original discharged state.

当該正極材料の結晶１次粒子の粒径は３００ｎｍ以下であり、１００ｎｍ以下がより好ましい。本発明の正極材料の好ましい形態においては、前記結晶１次粒子の表面に導電性炭素の析出物が存在する。正極材料表面への導電性炭素の析出は、後述するように加熱分解により導電性炭素を生じ得る物質（導電性炭素前駆物質）を焼成過程で添加することにより行われる。   The crystal primary particles of the positive electrode material have a particle size of 300 nm or less, and more preferably 100 nm or less. In a preferred embodiment of the positive electrode material of the present invention, conductive carbon deposits are present on the surfaces of the primary crystal particles. The conductive carbon is deposited on the surface of the positive electrode material by adding a substance (conductive carbon precursor) capable of generating conductive carbon by thermal decomposition during the firing process, as will be described later.

＜リン酸鉄リチウム系正極材料の製造方法の概要＞
リン酸鉄リチウム系正極材料は、原型となる正極活物質ＬｉＦｅＰＯ４の原料となる物質のみ、または正極活物質の原料となる物質と、前記式中のＦｅを置換しうる価数が２の元素であり且つ元素周期表において２族、１１族、１２族に属する金属元素の群から選ばれる１種以上の金属元素Ｍａを含む化合物と、前記式中のＦｅを置換しうる価数が３以上の元素であり且つ元素周期表において３族、４族、５族、６族、１３族、１４族に属する金属元素の群から選ばれる１種以上の金属元素Ｍｂを含む化合物と、を混合して得られる焼成前駆体を、所定温度、所定時間、所定雰囲気で焼成することにより、一般式Ｌｉ１−ｎｙ（ＭａｘＭｂｙＦｅ１−ｘ−ｙ）ＰＯ４で表され、オリビン型結晶構造を有し、各置換量である前記ｘとｙは、０≦ｘ、ｙ≦０．０５の数であり、前記ｎは前記Ｍｂの平均価数をｆとして、ｎ＝ｆ−２である結晶１次粒子として得ることができる。 <Outline of manufacturing method of lithium iron phosphate positive electrode material>
The lithium iron phosphate-based positive electrode material is an element having a valence of 2 capable of substituting only the material serving as the raw material of the positive electrode active material LiFePO 4 as a prototype or the material serving as the raw material of the positive electrode active material with Fe in the above formula And a compound containing one or more metal elements Ma selected from the group of metal elements belonging to Groups 2, 11, and 12 in the periodic table, and a valence capable of substituting Fe in the above formula is 3 or more And a compound containing one or more metal elements Mb selected from the group of metal elements belonging to Group 3, Group 4, Group 5, Group 6, Group 13, Group 14 in the periodic table of elements. The calcination precursor thus obtained is calcined at a predetermined temperature and for a predetermined atmosphere in a predetermined atmosphere, and is represented by the general formula Li 1-ny (Max x M b y Fe 1-xy ) PO 4 , and has an olivine type crystal structure And x and y, which are the respective substitution amounts, , 0 ≦ x, y ≦ 0.05, and n can be obtained as crystalline primary particles where n = f−2, where f is the average valence of Mb.

また、リン酸鉄リチウム系正極材料の表面に、導電性炭素を析出させた炭素析出正極材料は、炭素析出のない場合よりもさらに高い充放電特性を示すことが可能となる。該炭素析出正極材料の製造は、例えば、前記と同様に正極活物質の原料となる物質のみ、または正極活物質の原料となる物質に前記Ｍａおよび／またはＭｂの有機酸塩、ハロゲン化物、硝酸塩、アルコキシド等の化合物を添加し、例えば擂潰混合等して焼成前駆体を得た後、一旦３００〜４５０℃にて数時間（例えば５時間程度）かけて第一段階の焼成（仮焼成）をした後、炉より取り出し、その仮焼成物に対して、導電性炭素前駆物質、例えば、石炭ピッチなどのビチューメン類、またはデキストリンなどの糖類を所定量添加、擂潰・混合し、さらに数時間乃至１日程度、所定雰囲気で第二段階の焼成（本焼成）することにより行うことができる。Ｍａ、Ｍｂの化合物としては、塩化物等のハロゲン化物が好ましい。   Moreover, the carbon deposition positive electrode material in which conductive carbon is deposited on the surface of the lithium iron phosphate-based positive electrode material can exhibit higher charge / discharge characteristics than the case without carbon deposition. The carbon-deposited positive electrode material is produced, for example, in the same manner as described above by using only the material that is a raw material for the positive electrode active material, or the organic acid salt, halide, and nitrate of Ma and / or Mb as the material that is the raw material for the positive electrode active material Then, after adding a compound such as alkoxide and obtaining a calcined precursor by, for example, crushing and mixing, first-stage calcining (preliminary calcining) at 300 to 450 ° C. for several hours (for example, about 5 hours) After removing from the furnace, a predetermined amount of conductive carbon precursor, for example, bitumens such as coal pitch, or sugars such as dextrin is added to the calcined product, and the mixture is crushed and mixed for several hours. It can be carried out by firing in the second stage (main firing) in a predetermined atmosphere for about 1 day. As the compounds of Ma and Mb, halides such as chloride are preferable.

導電性炭素前駆物質の添加タイミングが相違する上記二通りの方法の中では、前者（導電性炭素前駆物質を仮焼成後に添加する）の方がより高い充放電特性を持つ炭素析出正極材料が得られる場合が多いので好ましい。従って、以下では前者を中心に説明を行うが、後者（導電性炭素前駆物質を仮焼成前に添加する）においても、焼成前駆体の調製、焼成条件の選定等は前者に準じて行うことが可能である。   Among the above two methods in which the timing of addition of the conductive carbon precursor is different, the former (adding the conductive carbon precursor after provisional firing) provides a carbon deposition cathode material having higher charge / discharge characteristics. It is preferable because it is often used. Therefore, in the following description, the former will be mainly described, but in the latter (the conductive carbon precursor is added before the preliminary calcination), the preparation of the calcination precursor, the selection of the calcination conditions, etc. may be performed in accordance with the former. Is possible.

＜正極活物質ＬｉｎＦｅＰＯ４の原料＞
以下では、正極活物質ＬｉＦｅＰＯ４として一般的なオリビン型構造を有するものについて説明する。このオリビン型ＬｉＦｅＰＯ４の原料の中で、リチウム導入用の原料としては、例えばＬｉＯＨ等の水酸化物、Ｌｉ２ＣＯ３等の炭酸塩や炭酸水素塩、ＬｉＣｌ等の塩化物を含むハロゲン化物、ＬｉＮＯ３等の硝酸塩、その他有機酸塩等のＬｉのみ目的の正極材料中に残留するようなＬｉ含有分解揮発性化合物が用いられる。また、Ｌｉ３ＰＯ４、Ｌｉ２ＨＰＯ４、ＬｉＨ２ＰＯ４等の燐酸塩や燐酸水素塩を用いることもできる。 <Raw material of the positive electrode active material Li n FePO 4>
The following describes those having the general olivine structure as a positive electrode active material LiFePO 4. Among the raw materials of this olivine type LiFePO 4, as a raw material for introducing lithium, for example, a hydroxide containing a hydroxide such as LiOH, a carbonate such as Li 2 CO 3, a bicarbonate, a chloride such as LiCl, A Li-containing decomposition volatile compound is used in which only Li such as nitrate such as LiNO 3 or other organic acid salt remains in the target positive electrode material. Moreover, phosphates and hydrogen phosphates such as Li 3 PO 4 , Li 2 HPO 4 , and LiH 2 PO 4 can also be used.

また、鉄導入用の原料としては、例えば水酸化物、炭酸塩や炭酸水素塩、塩化物等のハロゲン化物、硝酸塩、その他、Ｆｅのみが目的の正極材料中に残留するような分解揮発性化合物（例えば、シュウ酸塩や酢酸塩等の有機酸塩、アセチルアセトン錯体類や、メタロセン錯体等の有機錯体など）のほか、燐酸塩や燐酸水素塩を用いることもできる。   Examples of the raw material for introducing iron include hydroxides, carbonates, hydrogen carbonates, halides such as chlorides, nitrates, and other decomposition volatile compounds in which only Fe remains in the target positive electrode material. In addition to (for example, organic acid salts such as oxalate and acetate, acetylacetone complexes, and organic complexes such as metallocene complexes), phosphates and hydrogen phosphates can also be used.

また、燐酸導入用の原料としては、例えば、無水燐酸Ｐ２Ｏ５、燐酸Ｈ３ＰＯ４、および燐酸イオンのみ正極材料中に残留するような分解揮発性燐酸塩や燐酸水素塩［例えば、（ＮＨ４）２ＨＰＯ４、ＮＨ４Ｈ２ＰＯ４、（ＮＨ４）３ＰＯ４等のアンモニウム塩］を用いることができる。 Examples of the raw material for introducing phosphoric acid include, for example, phosphoric anhydride P 2 O 5 , phosphoric acid H 3 PO 4 , and decomposition volatile phosphates and hydrogen phosphates in which only phosphate ions remain in the positive electrode material [for example, ( NH 4 ) 2 HPO 4 , NH 4 H 2 PO 4 , ammonium salts such as (NH 4 ) 3 PO 4 ] can be used.

これらの原料において、目的の正極材料中に残存した場合に好ましくない元素や物質を含む場合には、これらが焼成中に分解・揮発することが必要である。また、原料には燐酸イオン以外の不揮発性オキソ酸塩等を用いるべきでないことは言うまでもない。なお、これらにおいては、その水和物を用いる場合もあるが［例えば、ＬｉＯＨ・Ｈ２Ｏ、Ｆｅ３（ＰＯ４）２・８Ｈ２Ｏ等］、上記においては水和物としての表記は全て省略している。 When these raw materials contain elements or substances that are not desirable when remaining in the target positive electrode material, it is necessary that these materials decompose and volatilize during firing. Needless to say, non-volatile oxoacid salts other than phosphate ions should not be used as raw materials. In these cases, hydrates may be used [for example, LiOH.H 2 O, Fe 3 (PO 4 ) 2 · 8H 2 O, etc.]. Omitted.

＜鉄導入用の原料として、金属鉄を用いる場合＞
鉄導入用の原料として、上記のような鉄化合物ではなく、例えば、安価で入手が容易な１次原料である金属鉄を用いることができる。金属鉄は、２００μｍ以下、好ましくは１００μｍ以下の粒径のものを用いる。この場合、正極材料の原料として、金属鉄に、溶液中でリン酸イオンを遊離する化合物およびリチウム源となる化合物を水とともに組み合わせて使用することができる。ここで、原料中のリン：鉄：リチウムのモル比を１：１：１となるように調整することにより、焼成過程での不純物の生成と正極材料への混入を極力抑えることができる。 <When using metallic iron as a raw material for introducing iron>
As a raw material for introducing iron, for example, metallic iron that is a primary raw material that is inexpensive and easily available can be used instead of the iron compound as described above. Metallic iron having a particle size of 200 μm or less, preferably 100 μm or less is used. In this case, as a raw material for the positive electrode material, metallic iron, a compound that liberates phosphate ions in a solution, and a compound that becomes a lithium source can be used in combination with water. Here, by adjusting the molar ratio of phosphorus: iron: lithium in the raw material to be 1: 1: 1, it is possible to minimize the generation of impurities and the mixing into the positive electrode material during the firing process.

金属鉄と組み合わせて使用可能な「溶液中でリン酸イオンを遊離する化合物」としては、例えば、リン酸Ｈ３ＰＯ４、五酸化リンＰＯ５、リン酸二水素アンモニウムＮＨ４Ｈ２ＰＯ４、リン酸水素二アンモニウム（ＮＨ４）２ＨＰＯ４等を用いることができる。これらの中でも、鉄を溶解する段階で比較的強い酸性下に保つことができるものとして、リン酸、五酸化リン、リン酸二水素アンモニウムが好ましい。これらには市販の試薬を利用できるが、原料としてリン酸を用いる場合には、化学量論的に厳密を期するために予め滴定により純度を正確に求め、ファクターを算出しておくことが好ましい。 Examples of the “compound that releases phosphate ions in a solution” that can be used in combination with metallic iron include, for example, phosphate H 3 PO 4 , phosphorus pentoxide PO 5 , ammonium dihydrogen phosphate NH 4 H 2 PO 4 , Diammonium hydrogen phosphate (NH 4 ) 2 HPO 4 or the like can be used. Among these, phosphoric acid, phosphorus pentoxide, and ammonium dihydrogen phosphate are preferred as those that can be kept under relatively strong acidity at the stage of dissolving iron. Commercially available reagents can be used for these, but when phosphoric acid is used as a raw material, it is preferable to calculate the factor in advance by accurately obtaining the purity by titration in order to ensure strict stoichiometry. .

また、金属鉄と組み合わせて使用可能な「リチウム源となる化合物」としては、焼成後にＬｉのみ目的の正極材料中に残留するような化合物（前記Ｌｉ含有分解揮発性化合物）を選択することが好ましく、例えば水酸化リチウムＬｉＯＨ等の水酸化物、炭酸リチウムＬｉ２ＣＯ３等の炭酸塩のほか、Ｌｉの有機酸塩等もＬｉ含有分解揮発性化合物として使用できる。なお、これらにおいては、その水和物を用いることも可能である（例えば、ＬｉＯＨ・Ｈ２Ｏ等）。 Further, as the “compound as a lithium source” that can be used in combination with metallic iron, it is preferable to select a compound (the Li-containing decomposition volatile compound) in which only Li remains in the target positive electrode material after firing. For example, in addition to hydroxides such as lithium hydroxide LiOH and carbonates such as lithium carbonate Li 2 CO 3 , organic salts of Li can be used as Li-containing decomposition volatile compounds. In these, the hydrate can also be used (for example, LiOH.H 2 O).

＜金属ハロゲン化物＞
Ｆｅを置換しうる２価の金属元素の原料として、元素周期表において２族、７族、９族、１０族、１１族、１２族に属する金属元素の群から選ばれる１種以上の金属元素のハロゲン化物（本明細書において「金属ハロゲン化物」と記すことがある。）を用いることが好ましい。金属ハロゲン化物としては、例えば、塩化物、臭化物、ヨウ化物等が挙げられる（これらの水和物の形態のものも含む）。なお、他の化合物であってもよいことは勿論である。 <Metal halide>
As a raw material of a divalent metal element capable of substituting Fe, one or more metal elements selected from the group of metal elements belonging to Group 2, Group 7, Group 9, Group 10, Group 11 and Group 12 in the periodic table It is preferable to use a halide of (which may be referred to as “metal halide” in the present specification). Examples of the metal halide include chloride, bromide, iodide and the like (including those in the form of these hydrates). Of course, other compounds may be used.

Ｆｅを置換しうる３価以上の金属元素の原料としても、且つ元素周期表において３族、４族、５族、６族、７族、１３族、１４族に属する金属元素の群から選ばれる１種以上の金属元素のハロゲン化物（本明細書において「金属ハロゲン化物」と記すことがある。）を用いることが好ましい。   It is selected from the group of metal elements belonging to Group 3, Group 4, Group 5, Group 6, Group 7, Group 13 and Group 14 as a raw material of a trivalent or higher valent metal element capable of substituting Fe. It is preferable to use one or more metal element halides (may be referred to as “metal halide” in this specification).

正極材料の原料に添加される金属ハロゲン化物の例を以下に示す（これらの中には水和物もあるが、水和物としての標記は省略する）。ここで、金属ハロゲン化物の中では塩化物が比較的安価で入手しやすく有利である。   Examples of metal halides added to the raw material of the positive electrode material are shown below (some of these also include hydrates, but the titles as hydrates are omitted). Here, among metal halides, chloride is relatively inexpensive and easily available, which is advantageous.

これらの金属ハロゲン化物の添加量は、前記各置換量である前記ｘとｙが、０≦ｘ、ｙ≦０．０５の数となり、且つ後述の組成条件を満たすように調整する。また、金属ハロゲン化物を添加した正極材料の焼成前駆体を焼成する際に、該金属ハロゲン化物の種類に応じて、例えば炭素、水素等の還元剤、酸素等の酸化剤、および／または塩素、ホスゲン等の第３成分を共存させることによって、より好適な条件で異種金属元素複合化正極材料を形成できる場合がある。また、焼成前駆体製造または仮焼成の際に、例えば他の物質と混合することにより、金属ハロゲン化物を生成するような条件の下では、これらの金属やその酸化物等を複合化の原料として使用することも可能である。
以上のハロゲン化物の他に、上述の金属元素の有機酸塩、硝酸塩、アセチルアセトナト錯体、金属アルコキシド、金属フェノキシド等も用いることが可能である。 The addition amount of these metal halides is adjusted so that the substitution amounts x and y are 0 ≦ x and y ≦ 0.05, and the compositional condition described later is satisfied. Further, when firing the firing precursor of the positive electrode material to which the metal halide is added, depending on the type of the metal halide, for example, a reducing agent such as carbon and hydrogen, an oxidizing agent such as oxygen, and / or chlorine, By allowing the third component such as phosgene to coexist, it may be possible to form the dissimilar metal element composite cathode material under more suitable conditions. In addition, during the production of the calcining precursor or the preliminary calcining, for example, under conditions such as mixing with other substances to form a metal halide, these metals and their oxides are used as raw materials for compounding. It is also possible to use it.
In addition to the above halides, organic acid salts, nitrates, acetylacetonato complexes, metal alkoxides, metal phenoxides, and the like of the above metal elements can be used.

＜導電性炭素前駆物質＞
導電性炭素前駆物質としては、例えば、ビチューメン類（いわゆるアスファルト；石炭や石油スラッジから得られるピッチ類を含む）、糖類、スチレン−ジビニルベンゼン共重合体、ＡＢＳ樹脂、フェノール樹脂、その他芳香族基を有する架橋高分子などが挙げられる。 <Conductive carbon precursor>
Examples of conductive carbon precursors include bitumens (so-called asphalt; including pitches obtained from coal and petroleum sludge), sugars, styrene-divinylbenzene copolymers, ABS resins, phenol resins, and other aromatic groups. And a crosslinked polymer.

これらの中でも、ビチューメン類（特に、精製された、いわゆる石炭ピッチ）および糖類が好ましい。これらのビチューメン類や糖類は加熱分解によって導電性炭素を生じて正極材料に導電性を付与する。特に、精製された石炭ピッチは、非常に安価であり、かつ焼成中に融解して焼成中の原料粒子の表面に均一に広がり、また熱分解過程を経て比較的低温（６５０℃〜８００℃）での焼成後、高い導電性を発現する炭素析出物となる。   Among these, bitumens (especially purified so-called coal pitch) and saccharides are preferable. These bitumens and saccharides produce conductive carbon by thermal decomposition and impart conductivity to the positive electrode material. In particular, the refined coal pitch is very inexpensive, melts during firing, spreads uniformly on the surface of the raw material particles being fired, and undergoes a thermal decomposition process at a relatively low temperature (650 ° C. to 800 ° C.). After firing at, carbon precipitates exhibiting high conductivity are obtained.

また、糖類の場合は、糖類に含まれる多くの水酸基が原料および生じた正極材料粒子表面に強く相互作用することにより、結晶成長抑制作用も併せ持つため、糖類を用いることによって、より優れた結晶成長抑制効果と導電性付与効果を得ることができるからである。   In the case of saccharides, since many hydroxyl groups contained in the saccharide strongly interact with the raw material and the surface of the resulting positive electrode material particles, it also has an effect of suppressing crystal growth. This is because the suppressing effect and the conductivity imparting effect can be obtained.

精製石炭ピッチとしては、軟化温度が８０℃から３５０℃の範囲内にあり、熱分解による減量開始温度が３５０℃から４５０℃の範囲内にあり、５００℃以上８００℃以下までの加熱分解・焼成により、導電性炭素を生成するものが好適に用いられる。正極性能をより高めるためには、軟化温度が２００℃〜３００℃の範囲内にある精製石炭ピッチがより好ましい。また、精製石炭ピッチに含有される不純物は、正極性能に悪影響を与えることがないものが良いことは言うまでもないが、特に灰分が５０００ｐｐｍ以下であることが好ましい。   Refined coal pitch has a softening temperature in the range of 80 ° C to 350 ° C, a weight loss starting temperature in the range of 350 ° C to 450 ° C, and thermal decomposition / firing from 500 ° C to 800 ° C. Thus, those that generate conductive carbon are preferably used. In order to further improve the positive electrode performance, a refined coal pitch having a softening temperature in the range of 200 ° C to 300 ° C is more preferable. Needless to say, the impurities contained in the refined coal pitch should not adversely affect the positive electrode performance, but the ash content is particularly preferably 5000 ppm or less.

糖類としては、２５０℃以上５００℃未満の温度域において分解を起こし、かつ１５０℃から前記温度域までの昇温過程において一度は少なくとも部分的に融液状態をとり、さらに５００℃以上８００℃以下までの加熱分解・焼成によって導電性炭素を生成する糖類が特に好ましい。かかる特定の性質を有する糖類は、融解により加熱反応中の正極材料粒子の表面に好適にコートされ、加熱分解後は生じた正極材料粒子表面に導電性炭素を良好に析出するとともに、この過程で上記したように結晶成長を抑制するからである。また、上記糖類は加熱分解によって、該糖類の焼成前の乾燥重量に対し、少なくとも１５重量％以上、好ましくは２０重量％以上の導電性炭素を生じ得るものがよい。これは、生じる導電性炭素の量的な管理を容易にするためである。以上のような性質を有する糖類としては、例えばデキストリンなどのオリゴ糖や、可溶性でんぷん、加熱により融解しやすい架橋の少ないでんぷん（例えば５０％以上のアミロースを含むでんぷん）等の高分子多糖類が挙げられる。   As the saccharide, decomposition occurs in a temperature range of 250 ° C. or more and less than 500 ° C., and at least partially takes a melt state once in the temperature rising process from 150 ° C. to the temperature range, and further 500 ° C. or more and 800 ° C. or less. Particularly preferred are saccharides that produce conductive carbon by thermal decomposition and calcination. The saccharide having such specific properties is suitably coated on the surface of the positive electrode material particles during the heating reaction by melting, and after the thermal decomposition, the conductive carbon is favorably deposited on the surface of the generated positive electrode material particles. This is because crystal growth is suppressed as described above. The saccharide should be capable of producing at least 15% by weight, preferably 20% by weight or more of conductive carbon based on the dry weight of the saccharide before baking, by thermal decomposition. This is to facilitate the quantitative management of the conductive carbon produced. Examples of the saccharide having the above properties include high-molecular polysaccharides such as oligosaccharides such as dextrin, soluble starch, and starch with low cross-linking that is easily melted by heating (for example, starch containing 50% or more amylose). It is done.

＜焼成前駆体の調製＞
焼成前駆体は、前記したように、前述の正極材料の原料となる物質のみ、または２価と３価以上の異種金属元素Ｍａ、Ｍｂのハロゲン化物を、正極材料の原料となる物質に添加したものを、例えば、遊星ボールミル、揺動または回転式の粉体混合機等を用いて乾燥状態で１時間〜１日程度混合する方法（以下、「乾式混合」と記す）、または例えばアルコール類、ケトン類、テトラヒドロフランなどの有機溶媒、または水等の溶媒もしくは分散媒とともに正極材料の原料に添加され、湿式で例えば１時間〜１日程度、混合・擂潰後、乾燥する方法(以下、「湿式混合」と記す）によって焼成前駆体となる。 <Preparation of firing precursor>
As described above, the firing precursor is obtained by adding only the above-described material for the positive electrode material, or the divalent and trivalent or higher dissimilar metal elements Ma and Mb to the material for the positive electrode material. For example, using a planetary ball mill, a rocking or rotating powder mixer, etc., for 1 hour to 1 day in a dry state (hereinafter referred to as “dry mixing”), or for example alcohols, A method of adding to a raw material of the positive electrode material together with an organic solvent such as ketones, tetrahydrofuran, or a solvent or dispersion medium such as water, and mixing, crushing, and drying in a wet process, for example, for about 1 hour to 1 day (hereinafter referred to as “wet process”). It becomes a calcined precursor by “mixing”).

前記した金属ハロゲン化物のうち、例えば五塩化モリブデン（ＭｏＣｌ５）、四塩化チタン（ＴｉＣｌ４）、三塩化バナジウム（ＶＣｌ３）等は常温においても空気中で極めて不安定であり、塩素、塩化水素などを放出しながら分解しやすい。また、水分やアルコール類と容易に反応して水酸化物や金属アルコキシドを生じる。これらの不安定な金属ハロゲン化物を正極材料の混合原料に添加し、湿式混合する場合は、その過程で水酸化物や金属アルコキシド等を生じる反応を経ることにより、異種金属元素複合化正極の焼成前駆体が得られる。これを焼成して得られるＭｏ、Ｔｉ、Ｖ等の金属複合化リン酸鉄リチウム正極材料は、金属複合化を行わない同正極材料に比べれば高いレート特性を示し、正極性能向上に対する効果が認められる上に、ＬｉＦｅＰＯ４の理論容量１７０ｍＡｈ／ｇに近い容量をも維持し得る。 Among the above-mentioned metal halides, for example, molybdenum pentachloride (MoCl 5 ), titanium tetrachloride (TiCl 4 ), vanadium trichloride (VCl 3 ), etc. are extremely unstable in the air even at room temperature. It is easy to disassemble while releasing. In addition, it easily reacts with moisture and alcohols to produce hydroxides and metal alkoxides. When these unstable metal halides are added to the mixed raw material of the positive electrode material and wet-mixed, the dissimilar metal element composite positive electrode is fired through a reaction that generates a hydroxide, a metal alkoxide, or the like in the process. A precursor is obtained. The metal composite lithium iron phosphate positive electrode material such as Mo, Ti, V, etc. obtained by firing this shows higher rate characteristics than the same positive electrode material without metal composite, and the effect on positive electrode performance improvement is recognized. In addition, a capacity close to the theoretical capacity of 170 mAh / g of LiFePO 4 can be maintained.

しかし、乾燥した正極材料の混合原料にこれらの金属ハロゲン化物を直接添加し、乾式混合によって得た焼成前駆体を焼成して得られる金属複合化リン酸鉄リチウム正極材料は、前記湿式混合の場合の金属複合化正極材料と比較すると、さらに良好なレート特性と理論容量に迫る大きな容量を示すことから、これらを使用することがより好ましい。   However, the metal composite lithium iron phosphate positive electrode material obtained by directly adding these metal halides to the mixed raw material of the positive electrode material and calcining the calcined precursor obtained by dry mixing is used in the case of the above wet mixing. Compared with the metal composite positive electrode material, it shows more excellent rate characteristics and a large capacity approaching the theoretical capacity. Therefore, it is more preferable to use these.

一方、前出の金属ハロゲン化物のうち、例えば三塩化クロム（水和物を含む）、二塩化銅、塩化亜鉛、塩化インジウム四水和物、二塩化スズ、四塩化スズ等のように、空気中や水中で分解・脱塩素を起すことがないものを用いる場合は、湿式混合、乾式混合のいずれによっても高い性能の正極材料を生じ得る正極前駆体が得られる。また、これらの安定な金属ハロゲン化物の場合、正極材料の原料自体の粉砕混合と該金属ハロゲン化物の添加混合の２つの工程を兼ねて、正極材料の各原料の仕込み時に一緒に該金属ハロゲン化物を添加し、前記原料と共に粉砕、混合することによっても好適な焼成前駆体が得られる。この際、アルコールや水等を加え、湿式にて粉砕・混合を行うことも何ら問題なく可能である。一般に、湿式粉砕・混合によれば、いっそう均一、細粒で組成の安定した焼成前駆体が得られる。   On the other hand, among the above metal halides, for example, chromium trichloride (including hydrate), copper dichloride, zinc chloride, indium chloride tetrahydrate, tin dichloride, tin tetrachloride, etc., air In the case of using a material that does not cause decomposition / dechlorination in or in water, a positive electrode precursor capable of producing a positive electrode material with high performance can be obtained by either wet mixing or dry mixing. Further, in the case of these stable metal halides, the metal halide can be used together with the two steps of pulverizing and mixing the raw material of the positive electrode material and adding and mixing the metal halide together with the charging of each raw material of the positive electrode material. A suitable calcined precursor can also be obtained by adding, pulverizing and mixing together with the raw materials. At this time, it is possible to add alcohol, water, or the like and perform pulverization / mixing in a wet manner without any problem. In general, by wet pulverization / mixing, a more uniform, fine-grained and stable composition precursor can be obtained.

正極活物質の原料物質として金属鉄を用いる場合は、溶液中でリン酸イオンを遊離する化合物と、水と、金属鉄とを混合し金属鉄を溶解した後、炭酸リチウム、水酸化リチウムまたはその水和物などのＬｉ含有分解揮発性化合物を添加し、生じた反応生成物を単独で焼成前駆体とするか、またはこれに前記金属ハロゲン化物を添加し、上記と同様に乾式混合または湿式混合することにより、焼成前駆体が得られる。この場合、正極活物質の原料としての金属鉄の溶解に際しては、まず、リン酸などの、溶液中でリン酸イオンを遊離する化合物と金属鉄と水を混合し、擂潰や加熱（還流など）して鉄を反応させる。ここで擂潰操作は、溶液中の金属鉄にせん断力を加え、表面を更新させることにより金属鉄を溶解させる目的で行うものであり、これにより正極材料の収率を向上させ得る。擂潰は、自動擂潰機、ボールミル、ビーズミルなどを用い、擂潰装置の効率にもよるが、例えば３０分から１０時間程度の時間をかけて行うことが好ましい。さらに、完全に金属鉄の溶解反応を進行させるには、超音波照射を行うことも効果がある。   When metallic iron is used as a raw material for the positive electrode active material, a compound that liberates phosphate ions in water, water, and metallic iron are mixed to dissolve metallic iron, and then lithium carbonate, lithium hydroxide, or the like Li-containing decomposition volatile compound such as hydrate is added, and the resulting reaction product is used alone as a firing precursor, or the metal halide is added thereto, and dry mixing or wet mixing is performed in the same manner as above. By doing so, a calcined precursor is obtained. In this case, when dissolving metallic iron as a raw material of the positive electrode active material, first, a compound such as phosphoric acid, which liberates phosphate ions in a solution, metallic iron and water are mixed, and then crushed or heated (such as reflux). ) To react iron. Here, the crushing operation is performed for the purpose of dissolving the metallic iron by applying a shearing force to the metallic iron in the solution and renewing the surface, thereby improving the yield of the positive electrode material. Crushing is preferably carried out using an automatic crusher, a ball mill, a bead mill, etc., depending on the efficiency of the crushing apparatus, for example, taking about 30 minutes to 10 hours. Furthermore, it is also effective to perform ultrasonic irradiation in order to advance the dissolution reaction of metallic iron completely.

また、加熱操作により、金属鉄の還元溶解反応が促進されるので、正極材料の収率を向上させ得る。加熱は、鉄の酸化を回避するため、例えば不活性ガス中での還流などにより実施することが好ましい。還流では、比較的大型化が困難な機械的微粉砕操作が不要になるため、大量生産を行う上で特に有利であると考えられる。また、金属鉄を溶解させる際には、シュウ酸や塩酸などの揮発性の酸を添加して酸濃度を上たり、あるいは、酸素（空気でもよい）、過酸化水素、ハロゲン（臭素、塩素など）、もしくは次亜塩素酸、さらし粉などのハロゲン酸化物等の揮発性の酸化剤を共存させることができる。また、酸化能と酸性を兼ね備えた揮発性酸である硝酸を添加することも効果がある。   Moreover, since the reduction dissolution reaction of metallic iron is promoted by the heating operation, the yield of the positive electrode material can be improved. Heating is preferably performed, for example, by refluxing in an inert gas in order to avoid iron oxidation. Refluxing is considered to be particularly advantageous in mass production because mechanical pulverization operations that are relatively difficult to increase in size are unnecessary. When dissolving metallic iron, volatile acids such as oxalic acid and hydrochloric acid are added to increase the acid concentration, or oxygen (may be air), hydrogen peroxide, halogen (bromine, chlorine, etc.) ), Or volatile oxidizing agents such as hypochlorous acid and halogen oxides such as bleaching powder can coexist. It is also effective to add nitric acid, which is a volatile acid having both oxidation ability and acidity.

さらに、以上において、５０℃〜８０℃程度に加熱して反応させるとより効果的である。また、上記揮発性酸、酸化剤等は金属鉄から鉄(II)イオンへの酸化に対し等量以下となる量で作用させることが好ましい。これにより、金属鉄のリン酸等の溶液への溶解反応を促進させることが可能となる一方で、これらの揮発性酸、酸化剤等は焼成過程で除去されるため正極材料中には残存しない。   Furthermore, in the above, it is more effective when heated to about 50 to 80 ° C. for reaction. The volatile acid, the oxidizing agent, etc. are preferably allowed to act in an amount that is equal to or less than the equivalent amount for the oxidation of metallic iron to iron (II) ions. This makes it possible to accelerate the dissolution reaction of metallic iron in a solution such as phosphoric acid, but these volatile acids, oxidants, and the like are removed in the firing process and thus do not remain in the positive electrode material. .

以上のように、擂潰操作や加熱操作後により鉄を溶解させた溶液にリチウム源としての水酸化リチウム等を添加する。リチウム源を添加した後も、必要に応じてさらに粉砕、擂潰を行うことが好ましい。さらに、金属ハロゲン化物を添加した後においても、擂潰・混合を行うことにより焼成前駆体が得られる。   As described above, lithium hydroxide or the like as a lithium source is added to a solution in which iron is dissolved by a crushing operation or a heating operation. Even after the lithium source is added, it is preferable to further crush and crush as necessary. Furthermore, even after the metal halide is added, a calcined precursor can be obtained by crushing and mixing.

＜焼成の概要＞
正極材料の原料のみ、またはこれと金属ハロゲン化物とを上記のように混合して得られた焼成前駆体に対して、焼成を行う。焼成は、一般に採用されるような３００〜９００℃に至る焼成過程において、適切な温度範囲及び時間を選んで実施することができる。また、焼成は、酸化態不純物の生成防止や、残存する酸化態不純物の還元を促すため、酸素ガス不存在下で行うことが好ましい。 <Outline of firing>
Firing is performed on the calcining precursor obtained by mixing the raw material of the positive electrode material alone or the metal halide as described above. Firing can be carried out by selecting an appropriate temperature range and time in the firing process up to 300 to 900 ° C. as generally employed. In addition, the firing is preferably performed in the absence of oxygen gas in order to promote the generation of oxidized impurities and the reduction of remaining oxidized impurities.

本発明製造方法において、焼成は、一連の昇温およびこれに引き続く温度保持過程の一回のみにより実施することも可能であるが、第一段階のより低温域での焼成過程（通例常温〜３００ないし４５０℃の温度範囲；以下、「仮焼成」と記すことがある）、および第二段階のより高温域での焼成過程［通例常温〜焼成完了温度（５００℃ないし８００℃程度）；以下、「本焼成」と記すことがある］の２段階に分けて行うことが好ましい。   In the production method of the present invention, the firing can be carried out by only one series of temperature rise and subsequent temperature holding process, but the firing process in the lower temperature region of the first stage (usually normal temperature to 300 ° C). Or a temperature range of 450 ° C .; hereinafter referred to as “temporary firing”), and a firing process in a higher temperature range of the second stage [usually normal temperature to firing completion temperature (about 500 ° C. to 800 ° C.); It is preferable to carry out in two stages of “may be described as“ main firing ”].

仮焼成においては、正極材料の原料が加熱により最終的な正極材料に至る中間的な状態まで反応し、その際、多くの場合は熱分解によるガス発生を伴う。仮焼成の終了温度としては、発生ガスの大部分が放出し終わり、かつ最終生成物の正極材料に至る反応が完全には進行しない温度（すなわち、より高温域での第二段階の本焼成時に正極材料中の構成元素の再拡散・均一化が起こる余地を残した温度）が選択される（ただしこの時、組成の大半は既にリン酸鉄リチウム系正極活物質となっている）。   In the pre-baking, the raw material of the positive electrode material reacts to an intermediate state that reaches the final positive electrode material by heating, and in this case, gas generation is often caused by thermal decomposition. The temperature at which the calcining is finished is a temperature at which most of the generated gas has been released and the reaction leading to the positive electrode material of the final product does not proceed completely (that is, during the second stage of the main calcination at a higher temperature range). The temperature that leaves room for re-diffusion / homogenization of the constituent elements in the positive electrode material is selected (however, most of the composition is already a lithium iron phosphate-based positive electrode active material).

仮焼成に続く本焼成では、構成元素の再拡散・均一化が起こるとともに、正極材料への反応が完了し、しかも焼結などによる結晶成長を極力防げるような温度域まで昇温および温度保持がなされる。   In the main firing following the pre-firing, the constituent elements are re-diffusioned and made uniform, the reaction to the positive electrode material is completed, and the temperature is raised and maintained to a temperature range that prevents crystal growth due to sintering as much as possible. Made.

また、前記した炭素析出正極材料を製造する場合は、第一段階の焼成を行い、該第一段階の焼成後の生成物に、導電性炭素前駆物質を添加した後、第二段階の焼成を行うことにより、得られる正極材料の性能をより向上させることができる。導電性炭素前駆物質、特に加熱により融解する石炭ピッチや糖類を用いる場合は、仮焼成前の原料に添加することも可能であるが（この場合でも相応の正極性能向上効果が得られる）、仮焼成後の原料（既に原料からのガス発生の大半が終了し、中間生成物となった状態）に添加し、本焼成を行うことがより好ましい。つまり、焼成過程における仮焼成と本焼成との間に、原料への導電性炭素前駆物質の添加工程を設けることになる。これにより、加熱により融解・熱分解する石炭ピッチや糖類等の物質が、原料から発生するガスにより発泡することを防ぎ、より均一に正極材料の表面に溶融状態で広がり、より均一に熱分解炭素を析出させることができる。   In addition, when producing the above-described carbon deposited positive electrode material, the first stage firing is performed, and after adding the conductive carbon precursor to the product after the first stage firing, the second stage firing is performed. By performing, the performance of the positive electrode material obtained can be further improved. When using conductive carbon precursors, especially coal pitch or saccharide that melts by heating, it can be added to the raw material before pre-firing (even in this case, a corresponding positive electrode performance improvement effect can be obtained). It is more preferable to add to the raw material after firing (a state where most of the gas generation from the raw material has already been completed and become an intermediate product) and perform the main firing. That is, a step of adding a conductive carbon precursor to the raw material is provided between the preliminary firing and the main firing in the firing process. This prevents substances such as coal pitch and saccharides that are melted and pyrolyzed by heating from being foamed by the gas generated from the raw material, spread more uniformly in the molten state on the surface of the positive electrode material, and more uniformly pyrolytic carbon. Can be deposited.

これは以下の理由による。
すなわち、仮焼成において原料の分解により発生するガスの大半が放出されてしまう結果、本焼成ではガスの発生が殆ど起こらず、仮焼成後のタイミングで導電性炭素前駆物質を添加することにより、均一な導電性炭素の析出が可能になる。このため、得られる正極材料の表面導電性がさらに良好になり、また接触が強固に安定化される。なお、前述のように仮焼成前の原料に導電性炭素前駆物質を添加しても、比較的高い充放電特性の炭素析出−複合化正極材料を得ることができる。しかし、この方法による正極材料は、前記の仮焼成後に導電性炭素前駆物質を添加して得られる正極材料に比べると性能の点で及ばない。これは、仮焼成中に原料から旺盛に発生するガスにより、融解状態で未だ完全には熱分解していない導電性炭素前駆物質が発泡し、均一な析出が妨げられる場合があるほか、異種金属元素の複合化に好ましくない影響を与える可能性があるためと考えられる。 This is due to the following reason.
That is, most of the gas generated by decomposition of the raw material in the pre-firing is released. As a result, almost no gas is generated in the main firing. By adding the conductive carbon precursor at the timing after the pre-firing, uniform It is possible to deposit conductive carbon. For this reason, the surface conductivity of the positive electrode material obtained is further improved, and the contact is firmly stabilized. As described above, even when a conductive carbon precursor is added to the raw material before pre-firing, a carbon deposition-composite positive electrode material having relatively high charge / discharge characteristics can be obtained. However, the positive electrode material obtained by this method is less in terms of performance than the positive electrode material obtained by adding a conductive carbon precursor after the preliminary calcination. This is because the gas generated vigorously from the raw material during pre-firing may cause the conductive carbon precursor, which has not yet been completely pyrolyzed in the molten state, to foam, preventing uniform precipitation, and dissimilar metals. This is thought to be because it may adversely affect elemental composition.

焼成は、所定量の水素や水分（水、水蒸気等）を継続的に炉内に不活性ガスとともに供給しながら行うことも可能であり、このようにすることによって水素や水分を添加しない場合より高い充放電特性の炭素析出正極材料が得られる場合もある。この場合は、例えば、焼成過程の全時間に渡って、または特に５００℃以下から焼成完了までの温度、好ましくは４００℃以下から焼成完了までの温度、より好ましくは３００℃以下から焼成完了までの焼成温度において、水素や水分を添加することができる。なお、気体である水素や水蒸気を「添加する」ことには、水素等のガスの存在下（つまり、水素雰囲気下等）で焼成を行うことが含まれる。   Firing can also be performed while continuously supplying a predetermined amount of hydrogen and moisture (water, water vapor, etc.) together with an inert gas into the furnace, and in this way, hydrogen and moisture are not added. In some cases, a carbon-deposited positive electrode material having high charge / discharge characteristics can be obtained. In this case, for example, over the entire time of the firing process, or in particular, a temperature from 500 ° C. or less to the completion of firing, preferably a temperature from 400 ° C. or less to the completion of firing, more preferably from 300 ° C. or less to the completion of firing. Hydrogen or moisture can be added at the firing temperature. Note that “adding” gaseous hydrogen or water vapor includes firing in the presence of a gas such as hydrogen (ie, in a hydrogen atmosphere).

＜焼成条件（導電性炭素の析出を行わない場合）＞
焼成前駆体を焼成する条件（特に焼成温度、焼成時間）は、注意して設定する必要がある。
すなわち、複合化正極材料の反応完結・安定化のためには焼成温度は高い方が良いが、導電性炭素の析出を行わない場合は、焼成温度が高すぎると燒結・結晶成長しすぎ、充放電のレート特性を著しく低下させる場合がある。このため、焼成温度は約６００〜７００℃、好ましくは約６５０〜７００℃の範囲とし、例えば、Ｎ２、Ａｒなどの不活性ガス中で焼成する。この際、前記したように水素（加熱分解により水素を生成する水分を含む）を添加することによって、正極材料の性能が向上することがある。 <Baking conditions (when conductive carbon is not deposited)>
The conditions for firing the firing precursor (particularly the firing temperature and firing time) must be set with care.
In other words, a higher firing temperature is better for the reaction completion and stabilization of the composite positive electrode material. However, when conductive carbon is not deposited, if the firing temperature is too high, sintering and crystal growth will occur, resulting in higher charge. The rate characteristics of the discharge may be significantly reduced. For this reason, the firing temperature is in the range of about 600 to 700 ° C., preferably about 650 to 700 ° C., for example, in an inert gas such as N 2 or Ar. At this time, as described above, the performance of the positive electrode material may be improved by adding hydrogen (including moisture that generates hydrogen by thermal decomposition).

焼成時間はおよそ数時間乃至３日程度が目安となるが、異種金属元素Ｍａ、Ｍｂによる置換複合化を行う際は、６５０〜７００℃程度の焼成温度の場合、１０時間程度以下の焼成時間では得られる正極材料中での異種金属元素の固溶の均一性が不足し、１０数サイクルの充放電経過後に充放電異常が起こり、急激に性能が劣化する場合があるため、焼成時間を１〜２日（２４時間〜４８時間）確保するのが良い。この放電異常は、例えば異種金属元素がＭｏの場合に起こることが確認されており、サイクル数経過と共に次第に電池内部抵抗が増大し、さらには放電の途中で充放電容量対電圧曲線が不連続な２段波になるという異常な挙動であり、その原因は明らかではないが、充放電中のＬｉ＋イオンの出入りに伴い、局在していた異種金属元素化学種の凝集・相分離／偏析が引起されてＬｉ＋イオンの移動が阻害されるものと現段階では推定している。 The firing time is about several hours to about 3 days, but when performing substitution composite with different metal elements Ma and Mb, when the firing temperature is about 650 to 700 ° C., the firing time is about 10 hours or less. Since the uniformity of the solid solution of different metal elements in the obtained positive electrode material is insufficient, charging / discharging abnormality occurs after 10 or more cycles of charging / discharging, and the performance may deteriorate rapidly. It is good to secure 2 days (24 hours to 48 hours). This discharge abnormality has been confirmed to occur when, for example, the foreign metal element is Mo, and the internal resistance of the battery gradually increases as the number of cycles elapses. Further, the charge / discharge capacity versus voltage curve is discontinuous during the discharge. Although it is an abnormal behavior of becoming a two-stage wave, the cause is not clear, but with the entry and exit of Li + ions during charge and discharge, the dissociation / phase separation / segregation of the dissimilar metal element species was localized. It is presumed at this stage that it is induced to inhibit the movement of Li + ions.

一方、異種金属元素としてＭｏを用いた場合においても、７００℃以上の焼成温度ではこのような異常挙動はみられなくなる。しかし、急速に正極材料の焼成・結晶成長が進み、電池性能が低下するため、焼成時間は１０時間より短い適切な時間を選ぶべきである。良好な条件で得られた異種金属元素複合化ＬｉＦｅＰＯ４正極材料を組込んだ金属Ｌｉ負極コイン電池は、後述の実施例に記すように、充放電電流密度０.５ｍＡ／ｃｍ２にて理論容量（約１７０ｍＡｈ／ｇ）に近い常温充放電容量と良好な充放電サイクル特性を示す。 On the other hand, even when Mo is used as the dissimilar metal element, such abnormal behavior is not observed at a firing temperature of 700 ° C. or higher. However, since firing and crystal growth of the positive electrode material rapidly progress and battery performance deteriorates, an appropriate firing time shorter than 10 hours should be selected. A metal Li negative electrode coin battery incorporating a heterogeneous metal element composite LiFePO 4 positive electrode material obtained under good conditions has a theoretical capacity at a charge / discharge current density of 0.5 mA / cm 2 as described in Examples below. It shows a room temperature charge / discharge capacity close to (about 170 mAh / g) and good charge / discharge cycle characteristics.

なお、正極材料のより良好な均一性を得るために、第一段階の焼成（仮焼成）と第二段階の焼成（本焼成過程）の間に、仮焼成物を十分に粉砕混合した後、前述の所定温度における第二段階の本焼成を行うことも好ましい。   In addition, in order to obtain better uniformity of the positive electrode material, between the first stage firing (preliminary firing) and the second stage firing (main firing process), the temporary fired product is sufficiently pulverized and mixed, It is also preferable to perform the second stage main firing at the predetermined temperature.

＜焼成条件（導電性炭素の析出を行う場合）＞
導電性炭素析出を行う場合も本焼成の温度は非常に重要であり、前述の炭素析出のない場合に比べ、高い温度（例えば７５０℃〜８５０℃）とすることが好ましい。異種金属元素Ｍａ、Ｍｂによる置換を行う際は、焼成温度が高い場合は正極材料中の異種金属元素（Ｍａ、Ｍｂ）分布の均一性が不足することが少ないため、１０時間程度以下の焼成時間が選ばれる。異種金属元素（Ｍａ、Ｍｂ）とＬｉＦｅＰＯ４との複合化正極材料に石炭ピッチなどのビチューメン類、またはデキストリン等の糖類由来の導電性熱分解炭素を析出させた炭素析出−複合化正極材料を製造する場合、本焼成温度が約７５０℃以下であると、得られる正極材料のサイクル充放電において、サイクル数経過に伴う電池内部抵抗の増大及び充放電容量対電圧曲線の２段波化という、炭素析出させない異種金属元素複合化正極材料の場合と同様の異常挙動が出現し、性能劣化が進む場合がある。 <Baking conditions (when conducting conductive carbon is deposited)>
Also when conducting carbon deposition, the temperature of the main calcination is very important, and it is preferable to set the temperature higher (for example, 750 ° C. to 850 ° C.) than the case where there is no carbon deposition. When replacing with different metal elements Ma and Mb, if the firing temperature is high, the uniformity of the distribution of different metal elements (Ma, Mb) in the positive electrode material is rarely insufficient, and the firing time is about 10 hours or less. Is selected. Manufactures a carbon deposition-composite cathode material in which conductive pyrolytic carbon derived from bitumens such as coal pitch or saccharides such as dextrin is deposited on a composite cathode material of different metal elements (Ma, Mb) and LiFePO 4 When the main firing temperature is about 750 ° C. or less, in the cycle charge / discharge of the obtained positive electrode material, the increase in battery internal resistance with the passage of the number of cycles and the two-stage wave shape of the charge / discharge capacity vs. voltage curve Abnormal behavior similar to that in the case of a heterogeneous metal element composite positive electrode material that does not precipitate may appear and performance degradation may progress.

しかし、不活性ガス中で、約７５０℃を超える温度、例えば７７５℃で本焼成した炭素析出−複合化正極材料ではこのような異常挙動は見られなくなる。これは、比較的高い本焼成温度を採用することによって異種金属元素の分布が均一化・安定化されたためと推定される。後述の実施例で示すように、このようにして得られた異種金属元素／炭素／ＬｉＦｅＰＯ４複合化正極を組込んだ金属Ｌｉ負極電池は、理論容量１７０ｍＡｈ／ｇに近い常温充放電容量を示し、しかもサイクル寿命、レート特性が共に格段に改善されることが判った。 However, such an abnormal behavior is not observed in a carbon deposition-composite positive electrode material that is finally fired at a temperature exceeding about 750 ° C., for example, 775 ° C., in an inert gas. This is presumably because the distribution of dissimilar metal elements was made uniform and stabilized by adopting a relatively high main firing temperature. As shown in the examples described later, the metal Li negative electrode battery incorporating the thus obtained heterogeneous metal element / carbon / LiFePO 4 composite positive electrode exhibits a room temperature charge / discharge capacity close to a theoretical capacity of 170 mAh / g. Moreover, it has been found that both the cycle life and the rate characteristics are remarkably improved.

なおここで、炭素を析出させなかった場合と異なり、該炭素析出正極材料の場合は、例えば、７７５℃という高温で焼成を行っても容量減少などの性能低下はほとんど起こらない。これは、導電性炭素析出によって材質の導電性が向上する上に、析出させた導電性炭素が障害となって焼成・結晶成長を抑制するために正極材料の粒径増大が起こりにくく、Ｌｉイオンの正極材料粒子内における移動が容易であるためと考えられる。従って、かかる焼成条件で製造された該炭素析出正極材料は、きわめて高い性能と安定性を両立できる。なお、およそ８５０℃以上の温度で本焼成を行うと、活物質ＬｉＦｅＰＯ４の分解が起こり、組成の変動などをもたらす上に焼結を引起す場合があるため、７７５〜８００℃付近の温度にて焼成することが好ましい。 Here, unlike the case where no carbon is deposited, in the case of the carbon deposited positive electrode material, for example, even when firing at a high temperature of 775 ° C., performance degradation such as capacity reduction hardly occurs. This is because the conductivity of the material is improved by the conductive carbon deposition, and the deposited conductive carbon becomes an obstacle to suppress firing and crystal growth, so that the particle size of the positive electrode material is hardly increased. This is considered to be due to the easy movement in the positive electrode material particles. Therefore, the carbon deposited positive electrode material produced under such firing conditions can achieve both extremely high performance and stability. In addition, if the main calcination is performed at a temperature of about 850 ° C. or higher, the active material LiFePO 4 is decomposed, which may cause a change in composition and the like, and may cause sintering. And firing.

導電性炭素の析出量は、異種金属元素複合化正極材料の１次結晶粒子サイズによっても異なるが、同正極材料及び導電性炭素の合計重量に対し、約０.５〜５重量％の範囲が好ましい。特に、正極材料の１次結晶粒子サイズが５０〜１００ｎｍ程度の場合は約２．５〜５重量％、１５０〜３００ｎｍ程度の場合は約１〜２重量％程度となるようにすることが望ましい。これより析出量が少ない場合は導電性付与の効果が低下し、また多すぎる場合は正極材料の結晶子表面においてＬｉ＋イオンの出入りの障害となりやすく、共に充放電性能を低下させる傾向がある。好適な量の炭素を析出させるためには、その前駆体となる石炭ピッチなどのビチューメン類、及び／またはデキストリン等の糖類について、前記したようにあらかじめ熱分解炭化の際の減量率を求めておき、それに従って該炭素前駆体の添加量を決めることが好ましい。 The amount of conductive carbon deposited varies depending on the primary crystal particle size of the positive electrode material composited with different metal elements, but is in the range of about 0.5 to 5% by weight with respect to the total weight of the positive electrode material and conductive carbon. preferable. In particular, it is desirable that when the primary crystal particle size of the positive electrode material is about 50 to 100 nm, it is about 2.5 to 5% by weight, and about 150 to 300 nm is about 1 to 2% by weight. When the amount of precipitation is less than this, the effect of imparting conductivity is reduced, and when it is too much, Li + ions are liable to enter and exit on the crystallite surface of the positive electrode material, and both tend to lower the charge / discharge performance. In order to deposit a suitable amount of carbon, as described above, the weight loss rate at the time of pyrolytic carbonization is obtained in advance for bitumens such as coal pitch and / or saccharides such as dextrin as precursors thereof. Accordingly, it is preferable to determine the amount of the carbon precursor added accordingly.

＜原料の圧縮の概要＞
本発明製造方法では、前記焼成過程の前の原料を圧縮し、減容化した後に焼成を行う。このことによって、焼成を行う焼成炉等の焼成装置に高密度の原料を導入することが可能となり、一度の焼成工程によって多くの原料を焼成することができる。原料の圧縮には、金型プレス機、ロールプレス機、ローラーコンパクター等の機械的な外圧により圧縮する公知の圧縮装置を用いることができる。 <Outline of raw material compression>
In the production method of the present invention, the raw material before the firing process is compressed and reduced in volume, and then fired. This makes it possible to introduce a high-density raw material into a baking apparatus such as a baking furnace that performs baking, and it is possible to burn a large number of raw materials in a single baking step. For the compression of the raw material, a known compression device that compresses by a mechanical external pressure such as a die press, a roll press, or a roller compactor can be used.

第一段階の焼成（仮焼成）と第二段階の焼成（本焼成）の二段階の焼成を行い、第一段階の焼成によって、一次粒子が凝集して形成される二次粒子の集合物を形成する場合には、前記二次粒子の集合物を圧縮して所定のかさ密度に制御する。第一段階の焼成後の焼成生成物の一次粒子の粒径は５０ｎｍ〜１００ｎｍであることが望ましい。   The first stage firing (preliminary firing) and the second stage firing (main firing) are performed in two stages. By the first stage firing, an aggregate of secondary particles formed by aggregation of primary particles is obtained. In the case of forming, the aggregate of secondary particles is compressed and controlled to a predetermined bulk density. The primary particle size of the fired product after the first stage firing is desirably 50 nm to 100 nm.

前記「所定のかさ密度」は、前記二次粒子の集合物において、前記一次粒子が凝集して形成される二次粒子同士の空隙を減少させることによってその減容化が達成され、しかも第二段階の焼成後に生じる正極材料の一次粒子が、第二段階の焼成過程で一体化・粒径増大することを促進しないような状態のかさ密度である。   The “predetermined bulk density” is achieved by reducing the voids between the secondary particles formed by agglomeration of the primary particles in the aggregate of the secondary particles, and the second volume density is reduced. The bulk density is such that the primary particles of the positive electrode material generated after the stage firing do not promote integration and particle size increase in the second stage firing process.

このような所定のかさ密度に制御して前記二次粒子の集合物を圧縮することにより、過度な圧縮によって、一次粒子同士が凝集し過ぎることを防止するとともに、前記集合物の減容化を図ることができる。   By controlling the aggregate of the secondary particles by controlling to such a predetermined bulk density, it is possible to prevent the primary particles from aggregating excessively due to excessive compression, and to reduce the volume of the aggregate. Can be planned.

更に、炭素析出正極材料を製造する場合には、第一段階の焼成を行い、該第一段階の焼成によって生成する一次粒子が凝集して形成された二次粒子の集合物に、石炭ピッチ等の導電性炭素前駆物質を添加した後に第二段階の焼成を行う。   Furthermore, in the case of producing a carbon deposition positive electrode material, the first stage firing is performed, and the aggregate of secondary particles formed by aggregation of the primary particles generated by the first stage firing is combined with coal pitch or the like. After the addition of the conductive carbon precursor, the second stage firing is performed.

前記二次粒子の集合物に前記導電性炭素前駆物質を添加すると、当該導電性炭素前駆物質を添加した分、第二段階の焼成に供する被焼成物の嵩が増加する。したがって、前記二次粒子の集合物に導電性炭素前駆物質を添加する場合には、前記二次粒子の集合物と導電性炭素前駆物質の混合粒子の集合物を圧縮して減容化し、続いて本焼成を行うことが望ましい。   When the conductive carbon precursor is added to the aggregate of secondary particles, the volume of the object to be fired to be subjected to the second stage firing is increased by the amount of the addition of the conductive carbon precursor. Therefore, when a conductive carbon precursor is added to the aggregate of secondary particles, the volume of the mixed aggregate of the secondary particles and the conductive carbon precursor is compressed to reduce the volume. It is desirable to perform the main firing.

前記一次粒子の粒径が５０〜１００ｎｍであり、前記導電性炭素前駆物質として軟化温度８０℃から３５０℃の範囲にあり、加熱分解による減量開始温度が３５０℃から４５０℃の範囲にあり、かつ、５００℃から８００℃の加熱分解・焼成により導電性炭素を析出し得る物質を添加する場合には、前記所定のかさ密度が０．６〜０．９ｇ／ｃｍ３になるように圧縮を制御することが望ましい。その理由を以下に説明する。 The primary particles have a particle size of 50 to 100 nm, the conductive carbon precursor has a softening temperature in the range of 80 ° C. to 350 ° C., the weight loss starting temperature due to thermal decomposition is in the range of 350 ° C. to 450 ° C., and When adding a substance capable of precipitating conductive carbon by thermal decomposition / firing at 500 ° C. to 800 ° C., the compression is controlled so that the predetermined bulk density is 0.6 to 0.9 g / cm 3. It is desirable to do. The reason will be described below.

第一段階の焼成によって生成する一次粒子が凝集して形成される二次粒子の集合物中に添加した前記導電性炭素前駆物質が、第二段階の焼成によって加熱分解することにより、前記一次粒子の表面には導電性炭素の層が形成される。   The conductive carbon precursor added to the aggregate of secondary particles formed by agglomeration of the primary particles produced by the first stage firing is thermally decomposed by the second stage firing, whereby the primary particles A conductive carbon layer is formed on the surface.

また、本発明製造方法により製造されたリン酸鉄リチウム系正極材料は、適宜カーボンブラック等の導電性助剤と共にアルミニウム箔などの集電体にバインダーによって結着されて、リチウムイオン二次電池の正極として用いられ、高いリチウムイオン電池性能を得るためには、リン酸鉄リチウム系正極材料及び導電性助剤はバインダー中に高度に分散することが求められる。   Further, the lithium iron phosphate-based positive electrode material produced by the production method of the present invention is appropriately bound to a current collector such as an aluminum foil together with a conductive auxiliary agent such as carbon black by a binder, and the lithium ion secondary battery In order to be used as a positive electrode and obtain high lithium ion battery performance, the lithium iron phosphate-based positive electrode material and the conductive auxiliary are required to be highly dispersed in the binder.

しかし、前記二次粒子の集合物と前記導電性炭素前駆物質との混合粒子の集合物に対して過度の圧縮を行うと、第二段階の焼成中に前記リン酸鉄リチウム系化合物の表面に形成される導電性炭素によって一次粒子が固く包含され、電池作製時に電解液が十分浸透できずにＬｉイオン移動が妨げられてしまう問題がある。   However, if excessive compression is performed on the aggregate of mixed particles of the aggregate of secondary particles and the conductive carbon precursor, the surface of the lithium iron phosphate compound is applied during the second stage firing. There is a problem that the primary particles are tightly included by the formed conductive carbon, and the electrolytic solution cannot sufficiently permeate at the time of battery fabrication, and Li ion migration is hindered.

二次粒子の集合物と導電性炭素前駆物質の混合粒子の集合物のかさ密度を０．６〜０．９ｇ／ｃｍ３に制御すると、前記混合粒子の集合物において、前記二次粒子同士の空隙を減少させることによってその減容化が達成され、前記問題が回避できる。 When the bulk density of the aggregate of secondary particles and the aggregate of conductive carbon precursor particles is controlled to 0.6 to 0.9 g / cm 3 , the secondary particles By reducing the gap, the volume reduction is achieved, and the above problem can be avoided.

更に、前記二次粒子の集合物と導電性炭素前駆物質の混合粒子の集合物は減容化されているので、第二段階の焼成を行う焼成炉等の焼成装置に導入できる前記混合粒子の集合物の量が増加し、第二段階の焼成を効率よく行うことができる。   Furthermore, since the aggregate of the mixed particles of the secondary particles and the conductive carbon precursor is reduced in volume, the mixed particles that can be introduced into a baking apparatus such as a baking furnace that performs the second stage baking are used. The amount of aggregate increases, and the second stage firing can be performed efficiently.

［異種金属元素としてモリブデン（Ｍｏ）を複合化させたＬｉＦｅＰＯ４正極材料の製造方法］
図１は、本発明にかかるリン酸鉄リチウム系正極材料の製造方法の一例を示すフロー図であり、異種金属元素としてモリブデン（Ｍｏ）を複合化させたＬｉＦｅＰＯ４正極材料の製造方法を示すものである。また、加熱分解により導電性炭素を生じ得る物質としては精製石炭ピッチを添加した。フロー図に基づいて異種金属元素としてモリブデン（Ｍｏ）を複合化させたＬｉＦｅＰＯ４正極材料の製造方法を説明する。 [Method for producing LiFePO 4 positive electrode material in which molybdenum (Mo) is compounded as a different metal element]
FIG. 1 is a flowchart showing an example of a method for producing a lithium iron phosphate positive electrode material according to the present invention, showing a method for producing a LiFePO 4 positive electrode material in which molybdenum (Mo) is compounded as a different metal element. It is. Moreover, refined coal pitch was added as a substance which can produce conductive carbon by thermal decomposition. A method for producing a LiFePO 4 positive electrode material in which molybdenum (Mo) is compounded as a different metal element will be described based on a flow diagram.

１．原料混合・粉砕
正極活物質ＬｉｎＦｅＰＯ４の原料として、リチウム導入用の原料としてＬｉＯＨ・Ｈ２Ｏ、鉄導入用の原料としてＦｅＣ２Ｏ４・２Ｈ２Ｏ、燐酸導入用の原料としてＮＨ４Ｈ２ＰＯ４の三種の原料を混合する。これら三種の原料を所定量［Ｌｉ：Ｆｅ：Ｐ＝０．９９：１：１（モル比）］混合・粉砕し、三種原料混合物を調製した。 1. Mixing and grinding of raw materials As raw materials for the positive electrode active material Li n FePO 4 , LiOH · H 2 O as a raw material for introducing lithium, FeC 2 O 4 · 2H 2 O as a raw material for introducing iron, and NH 4 as a raw material for introducing phosphoric acid Three raw materials of H 2 PO 4 are mixed. These three kinds of raw materials were mixed and pulverized in a predetermined amount [Li: Fe: P = 0.99: 1: 1 (molar ratio)] to prepare a three kinds of raw material mixture.

２．塩化モリブデン添加・混合
前記三種原料混合物に対し、リン（Ｐ）に対して１ｍｏｌ％のＭｏＣｌ５を添加・混合して粒径調整を行い、焼成前駆体を得た。 2. Addition and mixing of molybdenum chloride 1 mol% of MoCl 5 with respect to phosphorus (P) was added to and mixed with the three raw material mixtures to adjust the particle size, thereby obtaining a calcined precursor.

３．第一段階の焼成（仮焼成）
前記焼成前駆体に対し、純Ｎ２ガスを通気しながら４００℃にて１０時間、第一段階の焼成（仮焼成）を行った。 3. First stage firing (temporary firing)
The firing precursor was subjected to first-stage firing (temporary firing) at 400 ° C. for 10 hours while flowing pure N 2 gas.

４．石炭ピッチの混合
一旦取出した第一段階焼成生成物（一次粒子径：５０〜１００ｎｍ）に、約７重量％の軟化温度２５０℃の精製石炭ピッチを加え、混合粉砕機にて混合・粉砕し、第一段階焼成生成物と精製石炭ピッチの混合粒子の集合物（以下、石炭ピッチ混合物と記すことがある）を得た。 4). Mixing of coal pitch To the first stage baked product (primary particle size: 50 to 100 nm) once taken out, about 7% by weight of refined coal pitch with a softening temperature of 250 ° C. is added and mixed and pulverized by a mixing pulverizer. An aggregate of mixed particles of the first-stage fired product and the refined coal pitch (hereinafter sometimes referred to as a coal pitch mixture) was obtained.

５．石炭ピッチ混合物の圧縮
石炭ピッチ混合物の圧縮は、図２および図３のような圧縮器１を用いて行った。
図３に示すように、石炭ピッチ混合物６をプレス容器２に移し、蓋状おもり３を載せることによって圧力をかけて圧縮をした。荷重をかけるためのおもりの重さは、蓋状おもり３にリング状おもり４を追加して載せることによって変えることができる。おもりを載せて荷重をかける際には、前記圧縮器１を超音波振動機のような振動装置（図示せず）に載せて振動させてエア抜き部５から石炭ピッチ混合物６中の空気を追い出し、プレス容器２中の石炭ピッチ混合物６に対して荷重が均一にかかるようにした。 5. Compression of the coal pitch mixture The compression of the coal pitch mixture was performed using the compressor 1 as shown in FIGS.
As shown in FIG. 3, the coal pitch mixture 6 was transferred to the press vessel 2 and compressed by applying pressure by placing a lid-like weight 3. The weight of the weight for applying the load can be changed by adding a ring-shaped weight 4 to the lid-shaped weight 3. When applying a load with a weight, the compressor 1 is placed on a vibration device (not shown) such as an ultrasonic vibrator and vibrated to expel air in the coal pitch mixture 6 from the air vent 5. The load was uniformly applied to the coal pitch mixture 6 in the press vessel 2.

６．第二段階の焼成（本焼成）
圧縮された前記石炭ピッチ混合物６に対し、純Ｎ２ガスを通気しながら、７８０℃にて１０時間、第二段階の焼成（本焼成）を行った（ガスは昇温開始から焼成放冷後まで流通しつづけた）。以上により最終生成物を得た。 6). Second stage firing (main firing)
The compressed coal pitch mixture 6 was subjected to second-stage firing (main firing) at 780 ° C. for 10 hours while passing pure N 2 gas (the gas was fired and allowed to cool from the start of heating). To continue to distribute). Thus, the final product was obtained.

［実施例］
図１のフロー図によって説明した異種金属元素としてモリブデン（Ｍｏ）を複合化させたＬｉＦｅＰＯ４正極材料の製造方法において、前記「５．石炭ピッチ混合物の圧縮」における圧縮条件を変え、その条件によって製造された正極材料を用いて作製した二次電池の性能評価を行い、前記圧縮条件の検討を行った。 [Example]
In the method for producing a LiFePO 4 positive electrode material in which molybdenum (Mo) is compounded as a different metal element described with reference to the flow chart of FIG. 1, the compression conditions in “5. Compression of coal pitch mixture” are changed, and the production is performed according to the conditions. The performance of a secondary battery manufactured using the prepared positive electrode material was evaluated, and the compression conditions were examined.

前記圧縮条件は、プレス容器に移した第一段階焼成生成物と精製石炭ピッチの混合粒子の集合物の上に載せる蓋状のおもりの重量を変えることによって調整した。前記「１．原料混合・粉砕」〜「３．第一段階の焼成（仮焼成）」によって得られる第一段階焼成生成物の一次粒子の粒径は、５０〜１００ｎｍである。   The compression conditions were adjusted by changing the weight of the lid-like weight placed on the aggregate of the mixed particles of the first stage baked product and refined coal pitch transferred to the press vessel. The primary particle size of the first stage fired product obtained by the above-mentioned “1. Raw material mixing / pulverization” to “3. First stage firing (temporary firing)” is 50 to 100 nm.

「４．石炭ピッチの混合」までの工程を１バッチで行い、表１に示す重量のおもりを載せて圧縮を行う実施例１〜実施例３および比較例２のＬｉＦｅＰＯ４正極材料を、図１の「７．石炭ピッチ混合物の圧縮」以降のフローに示す製造方法によって合成した。実施例１〜実施例３および比較例２の圧縮は、それぞれ石炭ピッチ混合物１７７ｇに対して行ったものである。圧縮を行わない比較例１は、「４．石炭ピッチの混合」の次に「６．第二段階の焼成（本焼成）」を行ったものである。 The LiFePO 4 positive electrode materials of Examples 1 to 3 and Comparative Example 2 in which the steps up to “4. Coal pitch mixing” are performed in one batch and the weights shown in Table 1 are loaded and compressed are shown in FIG. Of “7. Compression of coal pitch mixture” and subsequent manufacturing methods shown in the flow. The compression in Examples 1 to 3 and Comparative Example 2 was performed on 177 g of the coal pitch mixture. In Comparative Example 1 in which compression is not performed, “6. Second stage firing (main firing)” is performed after “4. Coal pitch mixing”.

表１には、圧縮に用いたおもり重量（ｇ）の他、圧縮前かさ密度（ｇ／ｃｍ３）、圧縮後かさ密度（ｇ／ｃｍ３）、圧縮率（％）、および製造効率（％）を示す。圧縮前かさ密度（ｇ／ｃｍ３）、圧縮後かさ密度（ｇ／ｃｍ３）、圧縮率（％）、および製造効率（％）の計算方法は、図２および図３に示す圧縮器のプレス容器２および蓋状おもり３の寸法に基いて下記の式により算出した。 Table 1 shows weight weight (g) used for compression, bulk density before compression (g / cm 3 ), bulk density after compression (g / cm 3 ), compression rate (%), and production efficiency (%). ). The calculation method of the bulk density before compression (g / cm 3 ), the bulk density after compression (g / cm 3 ), the compression ratio (%), and the production efficiency (%) is shown in FIG. 2 and FIG. Based on the dimensions of the container 2 and the lid-like weight 3, the following formula was used.

《かさ密度》
かさ密度(ｇ／ｃｍ３)＝石炭ピッチ混合物重量(ｇ)／石炭ピッチ混合物体積(ｃｍ３)
石炭ピッチ混合物体積＝（プレス容器内径半径）２×円周率×Ｌ２
Ｌ２＝プレス容器内深さ（6.0ｃｍ）−［蓋状おもり高さ（5.0ｃｍ）−Ｌ１］
圧縮前の石炭ピッチ混合物体積に対するかさ密度が圧縮前かさ密度であり、圧縮後の石炭ピッチ混合物体積に対するかさ密度が圧縮後かさ密度である。 << bulk density >>
Bulk density (g / cm 3 ) = Coal pitch mixture weight (g) / Coal pitch mixture volume (cm 3 )
Coal pitch mixture volume = (inner radius of press vessel) 2 x Circumference x L2
L2 = depth in press container (6.0 cm) − [height of lid weight (5.0 cm) −L1]
The bulk density with respect to the coal pitch mixture volume before compression is the bulk density before compression, and the bulk density with respect to the coal pitch mixture volume after compression is the bulk density after compression.

《圧縮率》
圧縮率（％）＝［１−（圧縮前かさ密度／圧縮後かさ密度）］×１００ 《Compression rate》
Compression rate (%) = [1− (bulk density before compression / bulk density after compression)] × 100

《製造効率》
製造効率（％）＝（圧縮後かさ密度／圧縮前かさ密度）×１００ 《Production efficiency》
Production efficiency (%) = (bulk density after compression / bulk density before compression) × 100

Figure 0005153189
Figure 0005153189

表１に示されるように、おもりの荷重による圧縮を行うことによって、石炭ピッチ混合物は高度に減容化され、圧縮後かさ密度は圧縮前かさ密度よりも大きくなっている。おもりの重量を増加させると圧縮率は高まり、本焼成時に焼成装置に導入することができる石炭ピッチ混合物の量が増加するので製造効率が高まる。圧縮を行わない比較例１の製造効率に比して、実施例１〜実施例３の製造効率は約１．３６〜２．５１倍にまで高められていると言える。   As shown in Table 1, by compressing with a weight load, the coal pitch mixture is highly reduced in volume, and the post-compression bulk density is greater than the pre-compression bulk density. Increasing the weight of the weight increases the compressibility and increases the production efficiency because the amount of coal pitch mixture that can be introduced into the firing apparatus during the main firing is increased. It can be said that the production efficiency of Examples 1 to 3 is increased to about 1.36 to 2.51 times that of Comparative Example 1 in which compression is not performed.

また、実施例１〜実施例３、比較例１および比較例２の正極材料を用いて二次電池を作製し、その電池性能を評価した。二次電池の調製方法を以下に説明する。   Moreover, the secondary battery was produced using the positive electrode material of Example 1- Example 3, the comparative example 1, and the comparative example 2, and the battery performance was evaluated. A method for preparing the secondary battery will be described below.

＜二次電池の調製＞
前記正極材料と、導電性付与材としてのアセチレンブラック［デンカブラック（登録商標）；電気化学工業株式会社製、５０％プレス品］と、結着材としての未焼成ＰＴＦＥ（ポリテトラフルオロエチレン）粉とを重量比で７０：２５：５となるように混合・混練して、厚さ０．６ｍｍのシート状に圧延し、これを直径１．０ｃｍに打抜いたペレットを正極とした。 <Preparation of secondary battery>
The positive electrode material, acetylene black [DENKA BLACK (registered trademark); manufactured by Denki Kagaku Kogyo Co., Ltd., 50% pressed product] as a conductivity imparting material, and unfired PTFE (polytetrafluoroethylene) powder as a binder Were mixed and kneaded so as to have a weight ratio of 70: 25: 5, rolled into a sheet having a thickness of 0.6 mm, and a pellet punched out to a diameter of 1.0 cm was used as a positive electrode.

その後、ステンレス製コイン電池ケース（型番ＣＲ２０３２）に金属チタン網、金属ニッケル網をそれぞれ正負極集電体としてスポット溶接し、前記正極及び金属リチウム箔負極を多孔質ポリエチレン製隔膜（東燃化学株式会社製Ｅ−２５）を介して組入れ、電解液として１ＭのＬｉＰＦ６を溶解したジメチルカーボネート／エチレンカーボネートの１／１混合電解液（富山薬品工業株式会社製）を満たして封入し、コイン型リチウム二次電池を作製した。正負極、隔膜、電解液等の一連の電池組立ては、アルゴン置換されたグローブボックス内で行った。 Thereafter, a stainless steel coin battery case (model number CR2032) was spot welded with a metal titanium mesh and a metal nickel mesh as positive and negative current collectors, respectively, and the positive electrode and the metal lithium foil negative electrode were made of a porous polyethylene diaphragm (manufactured by Tonen Chemical Co., Ltd.). E-25), filled with and filled with a dimethyl carbonate / ethylene carbonate 1/1 mixed electrolyte solution (manufactured by Toyama Pharmaceutical Co., Ltd.) in which 1M LiPF 6 is dissolved as an electrolyte solution, and coin-type lithium secondary A battery was produced. A series of battery assemblies such as positive and negative electrodes, a diaphragm, and an electrolyte solution were performed in a glove box substituted with argon.

以上のようにして得た正極材料を組み込んだコイン型二次電池に対して、２５℃において正極ペレットの見かけ面積当たりの電流密度０．５ｍＡ／ｃｍ２にて、３．０Ｖ〜４．０Ｖの動作電圧範囲で定電流充放電を繰り返したところ、第１サイクル、第５サイクル、および第１０サイクルにおける充電容量、放電容量、第２〜１０サイクルの平均クーロン効率、および３サイクル充電後１時間のＯＣＶの値は、表２のようになった。 With respect to the coin-type secondary battery incorporating the positive electrode material obtained as described above, a current density of 0.5 mA / cm 2 per apparent area of the positive electrode pellet at 25 ° C. was 3.0 V to 4.0 V. When the constant current charge / discharge was repeated in the operating voltage range, the charge capacity, discharge capacity, average coulombic efficiency of the 2nd to 10th cycles, and 1 hour after the 3rd cycle charge in the 1st cycle, 5th cycle and 10th cycle The OCV values were as shown in Table 2.

Figure 0005153189
Figure 0005153189

実施例２（圧縮後かさ密度０．６３３ｇ／ｃｍ３）は、比較例１（圧縮無し：かさ密度０．３３４ｇ／ｃｍ３）と同等の電池性能を備えていると言える。実施例３（圧縮後かさ密度０．８３７ｇ／ｃｍ３は、第２〜１０サイクルの平均クーロン効率の値が比較例１よりも高く、充放電の繰り返しによるリチウム損失の少ない優れた性能を有していると言える。 Example 2 (after compression bulk density 0.633 g / cm 3) is, in Comparative Example 1 (Compression None: bulk density 0.334 g / cm 3) and said that with the same cell performance. Example 3 (bulk density after compression 0.837 g / cm 3 has a higher average coulomb efficiency value in the 2nd to 10th cycles than Comparative Example 1 and has excellent performance with little lithium loss due to repeated charge and discharge. It can be said that.

一方、比較例２（圧縮後かさ密度１．２５６ｇ／ｃｍ３）は、圧縮率が最も高く、正極材料の製造効率は高いものの、この正極材料を用いて作製した二次電池の電池性能は比較例１よりも劣る結果となった。これは、石炭ピッチ混合物の高圧縮により、本焼成において正極活物質ＬｉｎＦｅＰＯ４の表面に形成される導電性炭素によって一次粒子が固く包含され、電池製作時に電解液が十分浸透できずにＬｉイオン移動が妨げられたためであると推測される。また、前記実施例３においては、圧縮された仮焼成後の原料は、本焼成によって正極活物質ＬｉｎＦｅＰＯ４の表面に導電性炭素が生じて成る一次粒子構造が適切に形成され得るかさ密度に調整されており、優れた電池性能を示すものと考えられる。 On the other hand, Comparative Example 2 (bulk density after compression 1.256 g / cm 3 ) has the highest compression rate and high production efficiency of the positive electrode material, but the battery performance of the secondary battery produced using this positive electrode material is comparative. The result was inferior to Example 1. This is because primary particles are tightly contained by the conductive carbon formed on the surface of the positive electrode active material Li n FePO 4 in the main firing due to the high compression of the coal pitch mixture, and the electrolyte does not sufficiently permeate when the battery is manufactured. This is presumed to be because ion movement was hindered. Further, in the above described Example 3, starting material after calcination, which is compressed, Is either primary particle structure in which a positive electrode active material Li n conductive carbon on the surface of the FePO 4 is caused by the sintering can be suitably formed density It is considered that the battery performance is excellent.

したがって、石炭ピッチを添加して導電性炭素の析出を行うリン酸鉄リチウム系正極材料の製造過程において、一次粒子の粒径が５０〜１００ｎｍである第一段階焼成生成物に石炭ピッチの添加した後、圧縮を行う際には、その圧縮後かさ密度（ｇ／ｃｍ３）の上限はおよそ０．９ｇ／ｃｍ３に設定することが望ましい。更に、圧縮後かさ密度を０．６〜０．９ｇ／ｃｍ３の範囲に制御することによって、特に優れた電池性能を示す正極材料とすることができる。 Therefore, in the production process of the lithium iron phosphate positive electrode material in which conductive carbon is deposited by adding coal pitch, the coal pitch is added to the first stage fired product having a primary particle size of 50 to 100 nm. Thereafter, when compression is performed, the upper limit of the bulk density after compression (g / cm 3 ) is desirably set to approximately 0.9 g / cm 3 . Furthermore, it can be set as the positive electrode material which shows the especially outstanding battery performance by controlling the bulk density after compression in the range of 0.6-0.9 g / cm < 3 >.

以上、本発明を異種金属元素としてモリブデン（Ｍｏ）を複合化させ、石炭ピッチの添加によって正極材料の表面に導電性炭素を析出させたＬｉＦｅＰＯ４正極材料の製造の実施形態に関して述べたが、本発明は上記実施形態に制約されるものではなく、特許請求の範囲に記載された発明の範囲内で、他の実施形態についても適用可能である。 As described above, the present invention has been described with respect to the embodiment of manufacturing the LiFePO 4 positive electrode material in which molybdenum (Mo) is compounded as a different metal element and conductive carbon is deposited on the surface of the positive electrode material by adding coal pitch. The present invention is not limited to the above-described embodiment, and can be applied to other embodiments within the scope of the invention described in the claims.

本発明の二次電池正極材料の製造方法は、二次電池のリン酸鉄リチウム系正極材料の製造に利用が可能である。   The manufacturing method of the secondary battery positive electrode material of this invention can be utilized for manufacture of the lithium iron phosphate type positive electrode material of a secondary battery.

異種金属元素としてモリブデン（Ｍｏ）を複合化させたＬｉＦｅＰＯ４正極材料の製造方法を説明するフロー図である。Molybdenum (Mo) as the different metal elements is a flow diagram illustrating a method of manufacturing the LiFePO 4 cathode material obtained by compounding. 圧縮器の一例を示す図であり、（Ａ）はプレス容器の斜視図、（Ｂ−１）は蓋状おもりの斜視図、（Ｂ−２）は蓋状おもりの上面図、（Ｃ）はリング状おもりの斜視図である。It is a figure which shows an example of a compressor, (A) is a perspective view of a press container, (B-1) is a perspective view of a lid-shaped weight, (B-2) is a top view of a lid-shaped weight, (C) is It is a perspective view of a ring-shaped weight. 図２の圧縮器使用時の断面図である。It is sectional drawing at the time of use of the compressor of FIG.

符号の説明Explanation of symbols

１ 圧縮器、 ２ プレス容器、 ３ 蓋状おもり、
４ リング状おもり、 ５ エア抜き部、
６ 石炭ピッチ混合物（第一段階焼成生成物と精製石炭ピッチの混合粒子の集合物） 1 Compressor, 2 Press container, 3 Lid weight,
4 ring weight, 5 air vent,
6 Coal pitch mixture (aggregate of mixed particles of the first stage baked product and refined coal pitch)

Claims (4)

原料を焼成してリン酸鉄リチウム系正極材料を製造するリチウムイオン二次電池正極材料の製造方法において、
焼成過程は、常温から３００℃ないし４５０℃に至る第一段階と、常温から焼成完了温度に至る第二段階と、を含み、
前記第一段階の焼成によって生成する一次粒子が凝集して形成される二次粒子の集合物を０．６〜０．９ｇ／ｃｍ ３ とするかさ密度に圧縮した後、前記第二段階の焼成を行うことを特徴とする、リチウムイオン二次電池正極材料の製造方法。 In the method for producing a lithium ion secondary battery positive electrode material by firing a raw material to produce a lithium iron phosphate-based positive electrode material,
The firing process includes a first stage from room temperature to 300 ° C. to 450 ° C., and a second stage from room temperature to the firing completion temperature,
After compressing the aggregate of secondary particles in which primary particles produced by calcination of the first stage is formed by aggregation in bulk density to 0.6~0.9g / cm 3, the firing of the second stage The manufacturing method of the lithium ion secondary battery positive electrode material characterized by performing. 原料を焼成してリン酸鉄リチウム系正極材料を製造するリチウムイオン二次電池正極材料の製造方法において、
焼成過程は、常温から３００℃ないし４５０℃に至る第一段階と、常温から焼成完了温度に至る第二段階と、を含み、
前記第一段階の焼成によって生成する一次粒子が凝集して形成される二次粒子の集合物に、加熱分解により導電性炭素を生じ得る物質を添加、混合した混合粒子の集合物を０．６〜０．９ｇ／ｃｍ ３ とするかさ密度に圧縮した後、前記第二段階の焼成を行うことを特徴とする、リチウムイオン二次電池正極材料の製造方法。 In the method for producing a lithium ion secondary battery positive electrode material by firing a raw material to produce a lithium iron phosphate-based positive electrode material,
The firing process includes a first stage from room temperature to 300 ° C. to 450 ° C., and a second stage from room temperature to the firing completion temperature,
The aggregate of secondary particles formed by agglomeration of primary particles produced by the first stage firing is added with a substance capable of generating conductive carbon by thermal decomposition, and the aggregate of mixed particles is 0.6. after compressing the bulk density to 0.9 g / cm 3, and performs firing of the second step, method for producing a lithium ion secondary battery positive electrode material. 請求項２に記載された二次電池正極材料の製造方法において、前記加熱分解により導電性炭素を生じ得る物質は、軟化温度８０℃から３５０℃の範囲にあり、加熱分解による減量開始温度が３５０℃から４５０℃の範囲にあり、かつ、５００℃から８００℃の加熱分解・焼成により導電性炭素を析出し得る物質であることを特徴とする、リチウムイオン二次電池正極材料の製造方法。   3. The method for producing a positive electrode material for a secondary battery according to claim 2, wherein the substance capable of generating conductive carbon by thermal decomposition is in a range of a softening temperature of 80 ° C. to 350 ° C., and a weight loss start temperature by thermal decomposition is 350 ° C. A method for producing a positive electrode material for a lithium ion secondary battery, characterized in that it is a substance in a range of from 450 to 450 ° C. and capable of depositing conductive carbon by thermal decomposition and firing at 500 to 800 ° C. 請求項２に記載された二次電池正極材料の製造方法において、前記一次粒子の粒径は５０〜１００ｎｍであり、
前記加熱分解により導電性炭素を生じ得る物質は、軟化温度８０℃から３５０℃の範囲にあり、加熱分解による減量開始温度が３５０℃から４５０℃の範囲にあり、かつ、５００℃から８００℃の加熱分解・焼成により導電性炭素を析出し得る物質であり、
前記かさ密度は、０．６〜０．９ｇ／ｃｍ３であることを特徴とする、リチウムイオン二次電池正極材料の製造方法。 The method for producing a secondary battery positive electrode material according to claim 2, wherein the primary particles have a particle size of 50 to 100 nm,
The substance capable of generating conductive carbon by the thermal decomposition has a softening temperature in the range of 80 ° C. to 350 ° C., a weight loss starting temperature in the range of 350 ° C. to 450 ° C., and 500 ° C. to 800 ° C. It is a substance that can deposit conductive carbon by thermal decomposition and firing,
The said bulk density is 0.6-0.9 g / cm < 3 >, The manufacturing method of the lithium ion secondary battery positive electrode material characterized by the above-mentioned.
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