JP2017168198A - Method for manufacturing positive electrode active material - Google Patents
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Abstract
Description
本発明は、正極活物質の製造方法に関する。 The present invention relates to a method for producing a positive electrode active material.
リチウム二次電池（リチウムイオン二次電池）は、近年、パソコンや携帯端末等のいわゆるポータブル電源や車両駆動用電源として用いられている。特に、軽量で高エネルギー密度が得られるリチウム二次電池（リチウムイオン二次電池）は、電気自動車、ハイブリッド自動車等の車両の駆動用高出力電源として、その重要性がますます高まっている。 In recent years, lithium secondary batteries (lithium ion secondary batteries) have been used as so-called portable power sources such as personal computers and portable terminals and power sources for driving vehicles. In particular, lithium secondary batteries (lithium ion secondary batteries) that are lightweight and have high energy density are increasingly important as high-output power sources for driving vehicles such as electric vehicles and hybrid vehicles.
リチウム二次電池に用いられる正極活物質の代表例として、リチウム（Ｌｉ）と少なくとも一種の遷移金属元素とを含む複合酸化物（以下、リチウム遷移金属酸化物ともいう。）が挙げられる。また、このような正極活物質の形態の一例として、殻部と、その内部に形成された中空部とを有する中空構造の正極活物質が挙げられる。
このような中空構造の正極活物質の製造方法の一例として、特許文献１には、リチウム遷移金属酸化物を構成する遷移金属元素の少なくとも一つを含む水性溶液から遷移金属水酸化物を生成する水酸化物生成工程と、得られた遷移金属水酸化物とリチウム化合物とを混合する工程と、該混合物を焼成する工程と、を含む製造方法であって、上記水酸化物生成工程が、上記水性溶液から遷移金属水酸化物粒子を析出させる核生成段階と、該析出した遷移金属水酸化物粒子を成長させる粒子成長段階とを含む方法が記載されている。
As a typical example of a positive electrode active material used for a lithium secondary battery, a composite oxide containing lithium (Li) and at least one transition metal element (hereinafter also referred to as lithium transition metal oxide) can be given. Moreover, as an example of the form of such a positive electrode active material, a positive electrode active material having a hollow structure having a shell portion and a hollow portion formed therein can be cited.
As an example of a method for producing such a positive electrode active material having a hollow structure,
ところで、上記特許文献１に例示される中空構造の正極活物質の製造方法において、上記核生成段階および粒子成長段階の条件によっては、上記水酸化物生成工程によって得られる遷移金属水酸化物の粒子径にばらつきが生じる（即ち、粒度分布が広い）場合があった。粒子径のばらつきが大きい遷移金属水酸化物と上記リン酸化合物とを混合して焼成すると、得られる焼成物（典型的には正極活物質）の粒子径にばらつきが生じやすいだけでなく、粒子径の異なる複数の正極活物質が凝集した凝集体が形成される場合があった。
ここで、粒子径が不均一な正極活物質は、該正極活物質を用いた電池の電池特性が低下しがち（例えば反応抵抗が増大しがち）である。このため、粒子径のばらつきが少ない正極活物質の提供が求められる。
By the way, in the manufacturing method of the positive electrode active material having a hollow structure exemplified in
Here, the positive electrode active material having a non-uniform particle size tends to deteriorate the battery characteristics of a battery using the positive electrode active material (for example, the reaction resistance tends to increase). For this reason, provision of the positive electrode active material with little dispersion | variation in a particle diameter is calculated | required.
なお、正極活物質の粒子径を調整する目的で、上記焼成工程により得られた焼成物に対して解砕や篩い分けを行うことが考えられる。しかし、上記凝集体を含む焼成物に対して解砕を行うと、該解砕によって該凝集物が不規則に砕けてしまい、解砕後の粒子径がより不均一になる場合があった。また、上記粒子径がばらついた焼成物に対して篩い分けを行うと、所定の粒子径の範囲外に篩い分けられた焼成物（正極活物質）の存在により歩留りが低下しがちであった。 In addition, for the purpose of adjusting the particle diameter of the positive electrode active material, it is conceivable to crush or screen the fired product obtained by the firing process. However, when the fired product containing the aggregate is crushed, the aggregate may be crushed irregularly by the pulverization, and the particle size after pulverization may become more uneven. In addition, when sieving is performed on the fired product having a variation in the particle diameter, the yield tends to decrease due to the presence of the fired product (positive electrode active material) screened out of a predetermined particle size range.
本発明は、かかる点に鑑みてなされたものであり、その主な目的は、粒子径のばらつきが少ない正極活物質の製造方法であって、該正極活物質を高い歩留りで製造し得る方法を提供することである。 The present invention has been made in view of such points, and its main object is a method for producing a positive electrode active material with little variation in particle diameter, and a method capable of producing the positive electrode active material with a high yield. Is to provide.
上記の目的を実現すべく、本発明によると、リチウム遷移金属酸化物の一次粒子が複数集合した二次粒子と、その内側に形成された中空部とを有する中空構造の正極活物質の製造方法が提供される。かかる正極活物質の製造方法は、以下の（ｉ）〜（ｉｉｉ）の工程を包含する。即ち、ここに開示される正極活物質の製造方法は、
（ｉ）上記リチウム遷移金属酸化物を構成する遷移金属元素の少なくとも一つを含む水性溶液から、遷移金属水酸化物を生成させる水酸化物生成工程；
（ｉｉ）上記遷移金属水酸化物とリチウム化合物とを混合して未焼成の混合物を調製する混合工程；および、
（ｉｉｉ）上記混合物を焼成して上記正極活物質粒子を得る焼成工程；
を包含する。そして、ここで開示される正極活物質の製造方法において、上記（ｉ）水酸化物生成工程は、（１）上記水性溶液をアルカリ性条件に調整した反応液から上記遷移金属水酸化物を析出させる核生成段階と、（２）上記核生成段階において析出した遷移金属水酸化物を含む反応液を、粒子径が所定の大きさ以上の遷移金属水酸化物を含む沈降部分と、上澄み部分とに分離する沈降分離段階と、（３）上記沈降部分に含まれる上記遷移金属水酸化物を、上記核生成段階よりもｐＨの低いアルカリ性条件下において成長させる粒子成長段階と、を含み、上記（２）沈降分離段階において分離した上澄み部分は、上記（１）の核生成段階の上記反応液中に供給される。
In order to achieve the above object, according to the present invention, a method for producing a positive electrode active material having a hollow structure having secondary particles in which a plurality of primary particles of a lithium transition metal oxide are aggregated and a hollow portion formed inside thereof. Is provided. Such a method for producing a positive electrode active material includes the following steps (i) to (iii). That is, the manufacturing method of the positive electrode active material disclosed here is:
(I) a hydroxide generation step of generating a transition metal hydroxide from an aqueous solution containing at least one transition metal element constituting the lithium transition metal oxide;
(Ii) a mixing step of mixing the transition metal hydroxide and the lithium compound to prepare an unfired mixture; and
(Iii) a firing step of firing the mixture to obtain the positive electrode active material particles;
Is included. And in the manufacturing method of the positive electrode active material disclosed here, the (i) hydroxide generation step comprises (1) depositing the transition metal hydroxide from a reaction solution prepared by adjusting the aqueous solution to alkaline conditions. A reaction liquid containing a transition metal hydroxide precipitated in the nucleation stage and (2) a precipitation part containing a transition metal hydroxide having a particle size of a predetermined size or more and a supernatant part. And (3) a particle growth stage in which the transition metal hydroxide contained in the sedimentation part is grown under alkaline conditions having a pH lower than that of the nucleation stage. ) The supernatant part separated in the sedimentation separation step is supplied into the reaction solution in the nucleation step (1).
本発明者らの検討によると、上記粒子成長段階に持ち込まれる遷移金属水酸化物の粒子径のばらつきを少なくすることで、上記水酸化物生成工程において生成される遷移金属水酸化物（即ち、上記粒子成長段階を経て得られる遷移金属水酸化物）の粒子径のばらつきを少なくし得ることを確認した。即ち、上記正極活物質の製造方法によると、粒子径のばらつきが少ない正極活物質を製造することができる。
ここで、上記核生成段階において遷移金属水酸化物の析出反応を継続する時間が長いほど、大きな粒子径の遷移金属水酸化物を得ることができる。即ち、上記沈降分離段階において分離した上澄み液を上記核生成段階の上記反応液中に供給することで、該上澄み部分に含まれていた遷移金属水酸化物（典型的には粒子径が所定の大きさに満たない遷移金属水酸化物）から所定の粒子径以上の遷移金属水酸化物（典型的には、上記沈降部分に含まれ得る粒子径の遷移金属水酸化物）を生成することができる。これにより、高い歩留りで、粒子径のばらつきが少ない正極活物質を製造することができる。
According to the study by the present inventors, the transition metal hydroxide produced in the hydroxide production step (i.e., by reducing the variation in the particle diameter of the transition metal hydroxide brought into the particle growth stage (i.e., It was confirmed that variation in the particle diameter of the transition metal hydroxide obtained through the particle growth stage can be reduced. That is, according to the method for producing a positive electrode active material, it is possible to produce a positive electrode active material with little variation in particle diameter.
Here, the longer the time during which the transition metal hydroxide precipitation reaction is continued in the nucleation stage, the larger the transition metal hydroxide can be obtained. That is, by supplying the supernatant liquid separated in the sedimentation separation stage into the reaction liquid in the nucleation stage, the transition metal hydroxide (typically having a predetermined particle size) contained in the supernatant portion. A transition metal hydroxide having a particle size larger than a predetermined particle size (typically a transition metal hydroxide having a particle size that can be included in the sedimentation portion) is produced from a transition metal hydroxide that is less than the size). it can. Thereby, it is possible to produce a positive electrode active material with a high yield and a small variation in particle diameter.
以下、適宜図面を参照しながら、本発明の好適な一実施形態について説明する。なお、本明細書において特に言及している事項以外の事柄であって本発明の実施に必要な事柄は、当該分野における従来技術に基づく当業者の設計事項として把握され得る。本発明は、本明細書に開示されている内容と当該分野における技術常識とに基づいて実施することができる。 Hereinafter, a preferred embodiment of the present invention will be described with reference to the drawings as appropriate. Note that matters other than matters specifically mentioned in the present specification and necessary for the implementation of the present invention can be grasped as design matters of those skilled in the art based on the prior art in this field. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field.
ここに開示される正極活物質は、各種のリチウム二次電池（リチウムイオン二次電池）用の正極、該正極を構成要素とする種々のリチウム二次電池（リチウムイオン二次電池）等に適用され得る。液状の非水電解質（すなわち非水電解液）を備えたリチウム二次電池への適用が特に好ましい。 The positive electrode active material disclosed herein is applied to positive electrodes for various lithium secondary batteries (lithium ion secondary batteries), various lithium secondary batteries (lithium ion secondary batteries) having the positive electrode as a constituent element, and the like. Can be done. Application to a lithium secondary battery including a liquid non-aqueous electrolyte (that is, a non-aqueous electrolyte) is particularly preferable.
ここに開示される正極活物質の材質は、リチウムを可逆的に吸蔵および放出可能な各種のリチウム遷移金属酸化物であり得る。例えば、一般的なリチウム二次電池の正極に用いられる層状構造のリチウム遷移金属酸化物、スピネル構造のリチウム遷移金属酸化物等であり得る。層状構造のリチウム遷移金属酸化物としては、上記遷移金属として少なくともニッケルを含む酸化物（ニッケル含有リチウム複合酸化物）、少なくともコバルトを含む酸化物、少なくともマンガンを含む酸化物等が例示される。 The material of the positive electrode active material disclosed herein can be various lithium transition metal oxides capable of reversibly inserting and extracting lithium. For example, it may be a lithium transition metal oxide having a layered structure or a lithium transition metal oxide having a spinel structure used for a positive electrode of a general lithium secondary battery. Examples of the lithium transition metal oxide having a layered structure include oxides containing at least nickel as the transition metal (nickel-containing lithium composite oxide), oxides containing at least cobalt, and oxides containing at least manganese.
ここに開示される正極活物質の好ましい組成として、下記一般式（Ｉ）：
Ｌｉ1+mＮｉpＣｏqＭｎrＭ１ sＯ2 （Ｉ）；
で表される層状Ｎｉ含有Ｌｉ酸化物が例示される。ここで、上記式（Ｉ）において、例えば、Ｍ１は、Ａｌ，Ｃｒ，Ｆｅ，Ｖ，Ｍｇ，Ｔｉ，Ｚｒ，Ｎｂ，Ｍｏ，Ｔａ，Ｗ，Ｃｕ，Ｚｎ，Ｇａ，Ｉｎ，Ｓｎ，ＬａおよびＣｅからなる群から選択される一種または二種以上であり、０≦ｍ≦０．２、０．１≦ｐ≦０．９、０≦ｑ≦０．５、０≦ｒ≦０．５、０≦ｓ≦０．０２、ｐ＋ｑ＋ｒ＋ｓ＝１であり得る。好ましい一態様では、０≦ｓ＜ｐであり、ｓが実質的に０（すなわち、Ｍ１を実質的に含有しない酸化物）であってもよい。また、より好ましい一態様として、ｐ×ｑ×ｒ≠０であるＬｉＮｉＣｏＭｎ酸化物が挙げられる。
As a preferred composition of the positive electrode active material disclosed herein, the following general formula (I):
Li 1 + m Ni p Co q Mn r M 1 s O 2 (I);
A layered Ni-containing Li oxide represented by Here, in the above formula (I), for example, M 1 is Al, Cr, Fe, V, Mg, Ti, Zr, Nb, Mo, Ta, W, Cu, Zn, Ga, In, Sn, La and One or more selected from the group consisting of Ce, 0 ≦ m ≦ 0.2, 0.1 ≦ p ≦ 0.9, 0 ≦ q ≦ 0.5, 0 ≦ r ≦ 0.5, 0 ≦ s ≦ 0.02 and p + q + r + s = 1. In a preferred embodiment, 0 ≦ s <p, and s may be substantially 0 (that is, an oxide that does not substantially contain M 1 ). As a more preferred embodiment, a LiNiCoMn oxide in which p × q × r ≠ 0 is given.
上記正極活物質は、殻部とその内部に形成された中空部（空洞部）とを有する中空構造の粒子形態をなす。このような中空構造の粒子と対比されるものとして、一般的な多孔質構造の粒子が挙げられる。ここで多孔質構造とは、実体のある部分と空隙部分とが粒子全体にわたって混在している構造（スポンジ状構造）を指す。ここに開示される中空構造の正極活物質粒子は、実体のある部分が殻部に偏っており、上記中空部にまとまった空間が確保されているという点で、上記多孔質構造の正極活物質粒子とは、構造上、明らかに区別されるものである。 The positive electrode active material is in the form of particles having a hollow structure having a shell portion and a hollow portion (cavity portion) formed therein. A particle having a general porous structure can be cited as a contrast with such a hollow structure particle. Here, the porous structure refers to a structure (sponge-like structure) in which a substantial part and a void part are mixed over the entire particle. The positive electrode active material particles having a hollow structure disclosed herein are positive electrode active materials having a porous structure in that the substantial portion is biased toward the shell portion and a space is secured in the hollow portion. Particles are clearly distinguished in structure.
このような正極活物質の平均粒径（二次粒径）は特に限定されないが、例えば、２μｍ〜２０μｍ（好ましくは２μｍ〜１０μｍ、より好ましくは４μｍ〜８μｍ）程度とすることができる。
なお、本明細書中において「平均粒径」とは、特記しない場合、レーザ散乱・回折法に
基づく粒度分布測定装置に基づいて測定した粒度分布から導き出せるメジアン径（５０％
体積平均粒子径；以下「Ｄ５０」と表記することもある。）をいう。
The average particle size (secondary particle size) of such a positive electrode active material is not particularly limited, and can be, for example, about 2 μm to 20 μm (preferably 2 μm to 10 μm, more preferably 4 μm to 8 μm).
In the present specification, the “average particle diameter” means a median diameter (50%) that can be derived from a particle size distribution measured based on a particle size distribution measuring apparatus based on a laser scattering / diffraction method unless otherwise specified.
Volume average particle diameter; hereinafter sometimes referred to as “D50”. ).
ここで開示する正極活物質の製造方法は、図１に示すように、水酸化物生成工程（Ｓ１０）、混合工程（Ｓ２０）、焼成工程（Ｓ３０）を包含する。以下に各工程について説明する。
なお、以下の説明では、かかる正極活物質の製造方法の一実施態様について、層状のＬｉＮｉＣｏＭｎ酸化物からなる中空構造の正極活物質を製造する場合を例として詳しく説明するが、この製造方法の適用対象をかかる組成の正極活物質に限定する意図ではない。
The manufacturing method of the positive electrode active material disclosed here includes a hydroxide generation step (S10), a mixing step (S20), and a firing step (S30) as shown in FIG. Each step will be described below.
In the following description, one embodiment of a method for producing such a positive electrode active material will be described in detail by taking as an example the case of producing a positive electrode active material having a hollow structure made of a layered LiNiCoMn oxide. The object is not intended to be limited to the positive electrode active material having such a composition.
まず、水酸化物生成工程（Ｓ１０）について説明する。かかる工程は、上記リチウム遷移金属酸化物（ここではＬｉＮｉＣｏＭｎ酸化物）を構成する遷移金属元素の少なくとも一つを含む水性溶液から、遷移金属水酸化物を生成させることを包含する。具体的には、上記水性溶液をアルカリ性条件に調整した反応液から上記遷移金属水酸化物を析出させる核生成段階（Ｓ１２）と、上記核生成段階において析出した遷移金属水酸化物を含む反応液を、粒子径が所定の大きさ以上の遷移金属水酸化物を含む沈降部分と、上澄み部分とに分離する沈降分離段階（Ｓ１４）と、上記沈降部分に含まれる上記遷移金属水酸化物を、上記核生成段階よりもｐＨの低いアルカリ性条件下において成長させる粒子成長段階（Ｓ１６）と、を含む。 First, a hydroxide production | generation process (S10) is demonstrated. This step includes generating a transition metal hydroxide from an aqueous solution containing at least one transition metal element constituting the lithium transition metal oxide (here, LiNiCoMn oxide). Specifically, a nucleation step (S12) for precipitating the transition metal hydroxide from the reaction solution prepared by adjusting the aqueous solution to alkaline conditions, and a reaction solution containing the transition metal hydroxide precipitated in the nucleation step Is separated into a sedimentation part containing a transition metal hydroxide having a particle size of a predetermined size or more and a supernatant part (S14), and the transition metal hydroxide contained in the sedimentation part, A particle growth step (S16) of growing under alkaline conditions having a pH lower than that of the nucleation step.
上記核生成段階（Ｓ１２）において、上記遷移金属を含む水性溶液を構成する溶媒（水性溶媒）は、典型的には水であり、水を主成分とする混合溶媒（例えば水と低級アルコールとの混合溶媒）であってもよい。上記遷移金属化合物を含む水性溶液（以下、「遷移金属溶液」ともいう。）は、製造目的たる活物質を構成するリチウム遷移金属酸化物の組成に応じて、該リチウム遷移金属酸化物を構成する遷移金属元素（ここではＮｉ，ＣｏおよびＭｎ）の少なくとも一つ（好ましくは全部）を含む。例えば、水性溶媒中にＮｉイオン，ＣｏイオンおよびＭｎイオンを供給し得る一種または二種以上の化合物を含む遷移金属溶液を使用する。これらの金属イオン源となる化合物としては、該金属の硫酸塩、硝酸塩、塩化物等を適宜採用することができる。例えば、水性溶媒（好ましくは水）に硫酸ニッケル、硫酸コバルトおよび硫酸マンガンが溶解した組成の遷移金属溶液を使用し得る。 In the nucleation step (S12), the solvent (aqueous solvent) constituting the aqueous solution containing the transition metal is typically water, and a mixed solvent containing water as a main component (for example, water and a lower alcohol). Mixed solvent). The aqueous solution containing the transition metal compound (hereinafter also referred to as “transition metal solution”) constitutes the lithium transition metal oxide according to the composition of the lithium transition metal oxide constituting the active material to be produced. It contains at least one (preferably all) transition metal elements (here, Ni, Co and Mn). For example, a transition metal solution containing one or more compounds that can supply Ni ions, Co ions, and Mn ions in an aqueous solvent is used. As the metal ion source compound, sulfates, nitrates, chlorides, and the like of the metals can be appropriately employed. For example, a transition metal solution having a composition in which nickel sulfate, cobalt sulfate and manganese sulfate are dissolved in an aqueous solvent (preferably water) may be used.
また、上記核生成段階（Ｓ１２）において、上記アルカリ性条件は、適当なアルカリ性水溶液を上記遷移金属溶液と混合することで実現し得る。ここで、アルカリ性水溶液は、典型的に、水性溶媒にアルカリ剤（例えば、水酸化ナトリウム、水酸化カリウム等のアルカリ金属水酸化物、アンモニア、アミン等）が溶解した水溶液である。少なくともアンモニアを含むアルカリ性水溶液の使用が好ましく、例えばアンモニアと水酸化ナトリウムとを含むアルカリ性水溶液を使用し得る。組成の異なる複数のアルカリ性水溶液（例えば、アンモニア水と、水酸化ナトリウム水溶液との二種類）を、あらかじめ混合して、あるいはそれぞれ独立した溶液として使用（典型的には、反応容器に供給）することができる。 In the nucleation step (S12), the alkaline condition can be realized by mixing an appropriate alkaline aqueous solution with the transition metal solution. Here, the alkaline aqueous solution is typically an aqueous solution in which an alkaline agent (for example, alkali metal hydroxide such as sodium hydroxide or potassium hydroxide, ammonia, amine, etc.) is dissolved in an aqueous solvent. It is preferable to use an alkaline aqueous solution containing at least ammonia. For example, an alkaline aqueous solution containing ammonia and sodium hydroxide can be used. A plurality of alkaline aqueous solutions having different compositions (for example, two types of aqueous ammonia and aqueous sodium hydroxide) are mixed in advance or used as independent solutions (typically supplied to a reaction vessel). Can do.
上記核生成段階（Ｓ１２）は、例えば、初期ｐＨが１２．０より大きい（例えば１２．５以上１３以下）程度のアルカリ性水溶液を反応槽内に用意し、この初期ｐＨを維持しつつ、該反応槽に遷移金属溶液を適切な速度で供給して撹拌混合する態様で好ましく実施することができる。このとき、上記初期ｐＨを維持するために、必要に応じて上記反応槽にアルカリ性水溶液を追加供給するとよい。
なお、本明細書中において、ｐＨの値は、液温２５℃を基準とするｐＨ値をいうものとする。また、反応液のアンモニア濃度は、例えば、イオンクロマト法、イオン電極法等により測定することができる。測定には、市販のイオンクロマトグラフ装置、電極式アンモニア計等を用いることができる。
In the nucleation step (S12), for example, an alkaline aqueous solution having an initial pH higher than 12.0 (for example, 12.5 or more and 13 or less) is prepared in the reaction tank, and the reaction is performed while maintaining the initial pH. It can implement preferably in the aspect which stirs and mixes by supplying a transition metal solution to a tank at a suitable speed | rate. At this time, in order to maintain the initial pH, an alkaline aqueous solution may be additionally supplied to the reaction vessel as necessary.
In addition, in this specification, the value of pH shall mean pH value on the basis of liquid temperature of 25 degreeC. Moreover, the ammonia concentration of the reaction solution can be measured by, for example, an ion chromatography method, an ion electrode method, or the like. For the measurement, a commercially available ion chromatograph device, an electrode type ammonia meter, or the like can be used.
核生成段階（Ｓ１２）でアンモニアを含むアルカリ性水溶液を用いる態様において、反応液中のアンモニア濃度は特に限定されないが、例えば３ｇ／Ｌ〜２５ｇ／Ｌ（好ましくは１０ｇ／Ｌ〜１５ｇ／Ｌ）程度とするとよい。上記ｐＨおよびアンモニア濃度は、上記アンモニア水の使用量と、他のアルカリ剤（典型的には他のアルカリ剤を含むアルカリ性水溶液）の使用量とを、適切にバランスさせることにより調整することができる。 In the embodiment using an alkaline aqueous solution containing ammonia in the nucleation step (S12), the ammonia concentration in the reaction solution is not particularly limited, but is, for example, about 3 g / L to 25 g / L (preferably 10 g / L to 15 g / L). Good. The pH and ammonia concentration can be adjusted by appropriately balancing the amount of ammonia water used with the amount of other alkaline agents (typically alkaline aqueous solutions containing other alkaline agents). .
次に、上記沈降分離段階（Ｓ１４）では、上記核生成段階（Ｓ１２）で遷移金属水酸化物の核（典型的には粒子状）が析出した後の反応液から、粒子径が所定の大きさ以上の遷移金属水酸化物を含む沈降部分を分離する。粒子径が大きい遷移金属水酸化物粒子は粒子径が小さい遷移金属水酸化物粒子と比較して、上記反応液中での沈降速度が速い。このため、上記核生成段階で遷移金属水酸化物の核が析出した後の反応液を沈降槽内に所定時間静置した後で、該反応液の上澄み部分と沈降部分とを分離することにより、粒子径が所定の大きさ以上の遷移金属水酸化物を含む沈降部分を好適に分離することができる。これにより、粒子径のバラつきが小さい遷移金属水酸化物粒子を得ることができる。 Next, in the sedimentation separation step (S14), the particle diameter is set to a predetermined size from the reaction solution after the transition metal hydroxide nuclei (typically particles) are precipitated in the nucleation step (S12). Separate the settled portion containing more than one transition metal hydroxide. Transition metal hydroxide particles having a large particle size have a faster sedimentation rate in the reaction solution than transition metal hydroxide particles having a small particle size. For this reason, the reaction liquid after the transition metal hydroxide nuclei precipitated in the nucleation stage is allowed to stand in a settling tank for a predetermined time, and then the supernatant part and the sedimentation part of the reaction liquid are separated. In addition, it is possible to suitably separate a sedimented portion containing a transition metal hydroxide having a particle size of a predetermined size or more. Thereby, transition metal hydroxide particles with small variations in particle diameter can be obtained.
上記沈降部分に含まれる遷移金属水酸化物の粒子径は、特に限定されず、目的の正極活物質の粒子径に応じて適宜設定すればよい。例えば、１μｍ以上（好ましくは３μｍ以上）とし得る。 The particle diameter of the transition metal hydroxide contained in the settling portion is not particularly limited, and may be set as appropriate according to the particle diameter of the target positive electrode active material. For example, it can be 1 μm or more (preferably 3 μm or more).
上記沈降分離段階（Ｓ１４）において上記核生成段階後の反応液を静置する時間は、粒子径が所定の大きさ以上の遷移金属水酸化物が沈降する（好ましくは所定の大きさよりも小さい遷移金属水酸化物は沈降しない）ことを実現し得る時間であればよい。例えば、５分以上（好ましくは５分以上１５分以下）静置することが好ましい。 In the sedimentation-separation step (S14), the time for allowing the reaction solution after the nucleation step to stand is such that the transition metal hydroxide having a particle size equal to or larger than a predetermined size is settled (preferably a transition smaller than the predetermined size) It is only necessary to be able to realize that the metal hydroxide does not settle). For example, it is preferable to stand for 5 minutes or more (preferably 5 minutes or more and 15 minutes or less).
上記沈降分離段階（Ｓ１４）において、上記反応液から沈降部分と上澄み部分を分離する手法は特に限定されない。典型的には、所定の時間静置した反応液が収容された容器（沈降槽）を転動（所謂、デカンテーション）して上澄み部分を除去することにより、上記沈降部分を残渣として分離することができる。上記反応液から分離（除去）される上澄み部分の割合は、沈降部分に所定の粒子径以上の遷移金属水酸化物が含まれることを実現し得る限りにおいて、特に限定されない。例えば、反応液の体積を１００体積％とした場合に、３０体積％以上８０体積％以下（好ましくは４０体積％以上７０体積％以下、例えば凡そ５０体積％）に相当する部分を上澄み部分として分離することが好ましい。 In the sedimentation separation step (S14), the method for separating the sedimentation portion and the supernatant portion from the reaction solution is not particularly limited. Typically, the settling portion is separated as a residue by rolling (so-called decantation) a container (settling tank) containing the reaction liquid that has been allowed to stand for a predetermined time to remove the supernatant portion. Can do. The ratio of the supernatant portion separated (removed) from the reaction solution is not particularly limited as long as it is possible to realize that the settled portion contains a transition metal hydroxide having a predetermined particle diameter or more. For example, when the volume of the reaction solution is 100% by volume, a part corresponding to 30% to 80% by volume (preferably 40% to 70% by volume, for example, about 50% by volume) is separated as a supernatant part. It is preferable to do.
なお、上記沈降分離段階（Ｓ１４）において分離された上澄み部分は、上記核生成段階の反応液に供給される。これにより、該上澄み部分に含まれていた遷移金属水酸化物（典型的には粒子径が所定の大きさに満たない遷移金属水酸化物）から所定の粒子径以上の遷移金属水酸化物（典型的には、沈降分離段階において沈降部分に含有される粒子径の遷移金属水酸化物）を生成することができる。なお、上記上澄み部分は、上記核生成段階の反応液中に一度に供給してもよいが、適切な速度で一定量ずつ供給することが好ましい。 The supernatant portion separated in the sedimentation separation step (S14) is supplied to the reaction liquid in the nucleation step. Thereby, a transition metal hydroxide (typically a transition metal hydroxide having a particle size of less than a predetermined size) contained in the supernatant portion to a transition metal hydroxide having a predetermined particle size or more ( Typically, a transition metal hydroxide having a particle size contained in the sedimentation portion in the sedimentation step can be produced. In addition, although the said supernatant part may be supplied at once in the reaction liquid of the said nucleation stage, it is preferable to supply a fixed amount at a suitable speed | rate.
上記粒子成長段階（Ｓ１６）では、上記沈降分離段階（Ｓ１４）で分離した沈降部分に含まれる遷移金属水酸化物を、好ましくは該核生成段階よりも低ｐＨ域（例えば０．１以上、典型的には０．５〜１．５程度低いｐＨ域）のアルカリ性条件下で成長させる。例えば、ｐＨ１２．０以下（典型的にはｐＨ１０．０以上１２．０以下、例えばｐＨ１１．５以上１２．０以下）で粒子成長させるとよい。この粒子成長段階を経て得られる遷移金属水酸化物（前駆体水酸化物）は、典型的には、該水酸化物粒子の外表面部の密度に比べて、該粒子の内部の密度が低い構造を有する。アンモニアを含むアルカリ性水溶液を用いる態様において、かかる構造の遷移金属水酸化物を安定して得るためには、該粒子成長段階における液中アンモニア濃度を高くしすぎない（低く抑える）ことが肝要である。このことによって、上記遷移金属水酸化物の析出速度が速くなり、中空構造の正極活物質粒子の形成に適した前駆体水酸化物を効果的に生成させ得る。なお、遷移金属水酸化物の析出速度は、例えば、反応液に供給される遷移金属溶液に含まれる遷移金属イオンの合計モル数に対して、反応液の液相中に含まれる遷移金属イオンの合計モル数（合計イオン濃度）の推移を調べることにより把握され得る。 In the particle growth stage (S16), the transition metal hydroxide contained in the sedimentation part separated in the sedimentation-separation stage (S14) is preferably at a lower pH range (for example, 0.1 or more, typically, the nucleation stage). Specifically, it is grown under alkaline conditions (pH range as low as about 0.5 to 1.5). For example, the particles may be grown at a pH of 12.0 or less (typically pH 10.0 to 12.0, for example, pH 11.5 to 12.0). The transition metal hydroxide (precursor hydroxide) obtained through this particle growth stage typically has a lower density inside the particle than the density of the outer surface portion of the hydroxide particle. It has a structure. In an embodiment using an alkaline aqueous solution containing ammonia, in order to stably obtain the transition metal hydroxide having such a structure, it is important not to make the ammonia concentration in the liquid too high (to keep it low) in the particle growth stage. . By this, the precipitation rate of the said transition metal hydroxide becomes quick, and the precursor hydroxide suitable for formation of the positive electrode active material particle of a hollow structure can be produced | generated effectively. In addition, the precipitation rate of the transition metal hydroxide is, for example, the transition metal ions contained in the liquid phase of the reaction liquid with respect to the total number of moles of transition metal ions contained in the transition metal solution supplied to the reaction liquid. It can be grasped by examining the transition of the total number of moles (total ion concentration).
粒子成長段階におけるアンモニア濃度は、例えば３ｇ／Ｌ〜２５ｇ／Ｌ（好ましくは１０ｇ／Ｌ〜１５ｇ／Ｌ）程度とするとよい。粒子成長段階における液中アンモニア濃度は、核生成段階におけるアンモニア濃度と概ね同程度としてもよく、核生成段階におけるアンモニア濃度より低くしてもよい。上記ｐＨおよびＮＨ４ ＋濃度は、核生成段階と同様にして調整することができる。 The ammonia concentration in the particle growth stage may be, for example, about 3 g / L to 25 g / L (preferably 10 g / L to 15 g / L). The ammonia concentration in the liquid in the particle growth stage may be approximately the same as the ammonia concentration in the nucleation stage, or may be lower than the ammonia concentration in the nucleation stage. The pH and NH 4 + concentration can be adjusted in the same manner as in the nucleation stage.
反応液に含まれるＮｉイオン，ＣｏイオンおよびＭｎイオンの合計モル数（合計イオン濃度）は、核生成段階および粒子成長段階を通じて、例えば凡そ０．５モル／Ｌ〜２．５モル／Ｌ（通常は凡そ１．０モル／Ｌ〜２．２モル／Ｌ）とすることが好ましい。かかる濃度が維持されるように、遷移金属水酸化物の析出速度に合わせて遷移金属溶液を補充（典型的には連続供給）するとよい。反応液に含まれるＮｉイオン，ＣｏイオンおよびＭｎイオンの量は、目的物たる正極活物質の組成（すなわち、該正極活物質を構成するＬｉＮｉＣｏＭｎ酸化物におけるＮｉ，Ｃｏ，Ｍｎのモル比）に対応する量比とすることが好ましい。
好適な一形態では、このようにして生成した遷移金属水酸化物粒子（ここでは、Ｎｉ，ＣｏおよびＭｎを含む複合水酸化物粒子）は、晶析終了後、反応液から分離し、洗浄（典型的には水洗）して乾燥させる。
The total number of moles (total ion concentration) of Ni ions, Co ions and Mn ions contained in the reaction solution is, for example, about 0.5 mol / L to 2.5 mol / L (usually through the nucleation stage and the particle growth stage) Is preferably about 1.0 mol / L to 2.2 mol / L). In order to maintain such a concentration, the transition metal solution may be replenished (typically continuously supplied) in accordance with the precipitation rate of the transition metal hydroxide. The amounts of Ni ions, Co ions, and Mn ions contained in the reaction solution correspond to the composition of the positive electrode active material that is the target (that is, the molar ratio of Ni, Co, and Mn in the LiNiCoMn oxide constituting the positive electrode active material). It is preferable to set the quantity ratio.
In a preferred embodiment, the transition metal hydroxide particles thus produced (here, composite hydroxide particles containing Ni, Co and Mn) are separated from the reaction solution after crystallization, and washed ( Typically washed with water) and dried.
次に、混合工程（Ｓ２０）について説明する。かかる工程は、上記水酸化物生成工程（Ｓ１０）において生成された遷移金属水酸化物と、リチウム化合物とを所望の量比で混合して未焼成の混合物を調製することを包含する。この混合工程では、典型的には、目的物たる正極活物質の組成（すなわち、該正極活物質を構成するＬｉＮｉＣｏＭｎ酸化物におけるＬｉ，Ｎｉ，Ｃｏ，Ｍｎのモル比）に対応する量比で、Ｌｉ化合物と遷移金属水酸化物とを混合する。上記リチウム化合物としては、加熱により溶解し、酸化物となり得るＬｉ化合物、例えば炭酸リチウム，水酸化リチウム等を好ましく用いることができる。 Next, the mixing step (S20) will be described. This step includes preparing the unfired mixture by mixing the transition metal hydroxide generated in the hydroxide generation step (S10) and the lithium compound in a desired quantitative ratio. In this mixing step, typically, the quantitative ratio corresponding to the composition of the positive electrode active material that is the target (that is, the molar ratio of Li, Ni, Co, Mn in the LiNiCoMn oxide constituting the positive electrode active material) Li compound and transition metal hydroxide are mixed. As the lithium compound, Li compounds that can be dissolved by heating and become oxides, such as lithium carbonate and lithium hydroxide, can be preferably used.
次に、焼成工程（Ｓ３０）について説明する。かかる工程は、上記混合工程（Ｓ２０）にて得られた混合物を焼成してリチウム遷移金属酸化物（即ち、正極活物質）を生成することを包含する。この焼成工程における焼成温度は、例えば、最高焼成温度が７００℃〜１１００℃（好ましくは８００℃〜１１００℃、より好ましくは９００℃〜１０００℃）の範囲とすればよい。 Next, the firing step (S30) will be described. This step includes firing the mixture obtained in the mixing step (S20) to produce a lithium transition metal oxide (ie, positive electrode active material). The firing temperature in this firing step may be, for example, a range where the maximum firing temperature is 700 ° C. to 1100 ° C. (preferably 800 ° C. to 1100 ° C., more preferably 900 ° C. to 1000 ° C.).
ここで開示される正極活物質の製造方法によると、粒子径のばらつきが少ない正極活物質を高い歩留りで製造することができる。このため、かかる製造方法により得られる正極活物質によると、正極活物質の粒子径のバラつきに起因した電池特性の低下（典型的には、反応抵抗の増大）を低減することができる。従って、かかる正極活物質は、各種用途の非水電解質二次電池（典型的にはリチウム二次電池）の正極活物質として利用可能であるが、このような性質を活かして、例えば、車両に搭載される駆動用電源に用いられる非水電解質二次電池の正極活物質として好適に用いることができる。車両の種類は特に限定されないが、例えばプラグインハイブリッド自動車（ＰＨＶ）、ハイブリッド自動車（ＨＶ）、電気自動車（ＥＶ）、電気トラック、原動機付自転車、電動アシスト自転車、電動車いす、電気鉄道等が挙げられる。
また、かかる正極活物質を用いることで、優れた電池性能の非水電解質二次電池、或いは当該非水電解質二次電池を好ましくは動力源として備えた車両を提供することが可能である。
According to the method for producing a positive electrode active material disclosed herein, a positive electrode active material with little variation in particle diameter can be produced with a high yield. For this reason, according to the positive electrode active material obtained by such a manufacturing method, it is possible to reduce a decrease in battery characteristics (typically an increase in reaction resistance) due to a variation in the particle diameter of the positive electrode active material. Accordingly, such a positive electrode active material can be used as a positive electrode active material for non-aqueous electrolyte secondary batteries (typically lithium secondary batteries) for various applications. It can be suitably used as a positive electrode active material of a non-aqueous electrolyte secondary battery used for a driving power source to be mounted. The type of vehicle is not particularly limited, and examples include plug-in hybrid vehicles (PHV), hybrid vehicles (HV), electric vehicles (EV), electric trucks, motorbikes, electric assist bicycles, electric wheelchairs, electric railways, and the like. .
In addition, by using such a positive electrode active material, it is possible to provide a non-aqueous electrolyte secondary battery having excellent battery performance or a vehicle preferably including the non-aqueous electrolyte secondary battery as a power source.
以下、本発明に関するいくつかの実施例を説明するが、本発明をかかる具体例に示すものに限定することを意図したものではない。 Several examples relating to the present invention will be described below, but the present invention is not intended to be limited to the specific examples.
＜例１＞
反応槽内にイオン交換水を入れ、攪拌しつつ窒素ガスを流通させて、反応槽内を非酸化性雰囲気に調整した。次いで、水酸化ナトリウム水溶液とアンモニア水とを、液温２５℃を基準として測定するｐＨがｐＨ１２．５〜ｐＨ１３．０となり且つ液中ＮＨ４ ＋濃度が１０ｇ／Ｌ〜１５ｇ／Ｌとなるように加えた。
また、硫酸ニッケル、硫酸コバルトおよび硫酸マンガンを、Ｎｉ：Ｃｏ：Ｍｎのモル比が０．３３：０．３３：０．３３となり且つこれら金属元素の合計モル濃度が１．５モル／Ｌ〜３．０モル／Ｌとなるように水に溶解させて、混合水溶液を調整した。
<Example 1>
Ion exchange water was put into the reaction vessel, and nitrogen gas was circulated while stirring to adjust the inside of the reaction vessel to a non-oxidizing atmosphere. Next, the pH of the aqueous solution of sodium hydroxide and aqueous ammonia measured with a liquid temperature of 25 ° C. as a reference is pH 12.5 to pH 13.0, and the NH 4 + concentration in the liquid is 10 g / L to 15 g / L. added.
Further, nickel sulfate, cobalt sulfate, and manganese sulfate have a molar ratio of Ni: Co: Mn of 0.33: 0.33: 0.33, and the total molar concentration of these metal elements is 1.5 mol / L to 3 A mixed aqueous solution was prepared by dissolving in water to a concentration of 0.0 mol / L.
上記混合水溶液を４ｍＬ／ｍｉｎ〜６ｍＬ／ｍｉｎの速度で上記反応槽内に供給するとともに、ＮａＯＨ水溶液とアンモニア水とを供給し、反応液をｐＨ１２．５〜ｐＨ１３．０、ＮＨ４ ＋濃度１０ｇ／Ｌ〜１５ｇ／Ｌに制御した。このとき、上記反応槽中の反応液は５００〜６００ｒｐｍの回転数で攪拌した。上記混合水溶液、ＮａＯＨ水溶液およびアンモニア水の反応槽への供給と攪拌を、上記混合水溶液の供給開始から最大２時間継続し、上記反応液からＮｉＣｏＭｎ複合水酸化物を晶析させた（核生成段階）。 The mixture solution is supplied to the reaction vessel at a rate of 4mL / min~6mL / min, supplying the NaOH aqueous solution and aqueous ammonia, the reaction solution pH12.5~pH13.0, NH 4 + concentration 10 g / Controlled to L-15 g / L. At this time, the reaction solution in the reaction vessel was stirred at a rotational speed of 500 to 600 rpm. The supply and stirring of the mixed aqueous solution, NaOH aqueous solution and ammonia water to the reaction tank were continued for up to 2 hours from the start of the supply of the mixed aqueous solution, and NiCoMn composite hydroxide was crystallized from the reaction solution (nucleation stage) ).
次いで、上記攪拌を中止し、反応液を５分〜１５分静置した。そして、かかる静置後の反応液の４０体積％〜７０体積％に相当する上澄み部分をデカンテーションにより除去し、沈降部分と上澄み部分とを分離した（沈降分離段階）。なお、分離した上澄み液は、上記核生成段階の反応槽中に供給した。 Next, the stirring was stopped and the reaction solution was allowed to stand for 5 to 15 minutes. And the supernatant part corresponding to 40 volume%-70 volume% of this reaction liquid after this standing was removed by decantation, and the sedimentation part and the supernatant part were isolate | separated (precipitation separation step). The separated supernatant was supplied into the reaction tank in the nucleation stage.
次いで、上記沈降部分を水（脱イオン水）で希釈し、上記核生成段階を実施した反応槽とは別の反応槽内に入れた。かかる反応槽内に、上記混合水溶液を４ｍＬ／ｍｉｎ〜６ｍＬ／ｍｉｎの速度で供給するとともに、ＮａＯＨ水溶液およびアンモニア水を供給し、反応液をｐＨ１１．５〜ｐＨ１２．０且つＮＨ４ ＋濃度１０ｇ／Ｌ〜１５ｇ／Ｌに制御する操作を２時間〜４時間継続してＮｉＣｏＭｎ複合水酸化物粒子を成長させた（粒子成長段階）。このとき、上記反応槽中の反応液は５００〜６００ｒｐｍの回転数で攪拌した。
その後、生成物を反応槽から取り出し、水洗して乾燥（２４時間の真空乾燥、または大気雰囲気下での１２０℃１２時間以上の乾燥）させた。このようにして、Ｎｉ0.33Ｃｏ0.33Ｍｎ0.33（ＯＨ）2+α（ここで、式中のαは０≦α≦０．５である。）で表わされる組成のＮｉＣｏＭｎ複合水酸化物粒子を得た。
Subsequently, the sedimentation part was diluted with water (deionized water) and placed in a reaction tank different from the reaction tank in which the nucleation step was performed. In the reaction tank, the mixed aqueous solution is supplied at a rate of 4 mL / min to 6 mL / min, an aqueous NaOH solution and aqueous ammonia are supplied, and the reaction solution is adjusted to pH 11.5 to pH 12.0 and NH 4 + concentration 10 g / min. The operation of controlling L to 15 g / L was continued for 2 to 4 hours to grow NiCoMn composite hydroxide particles (particle growth stage). At this time, the reaction solution in the reaction vessel was stirred at a rotational speed of 500 to 600 rpm.
Thereafter, the product was taken out of the reaction vessel, washed with water and dried (24 hours of vacuum drying or drying at 120 ° C. for 12 hours or more in an air atmosphere). In this way, NiCoMn composite hydroxide particles having a composition represented by Ni 0.33 Co 0.33 Mn 0.33 (OH) 2 + α (where α is 0 ≦ α ≦ 0.5) are obtained. It was.
次いで、リチウム源としてのＬｉ2ＣＯ3と上記ＮｉＣｏＭｎ複合水酸化物粒子とを、リチウムのモル数（ＭLi）と上記複合水酸化物を構成するＮｉ，ＣｏおよびＭｎの総モル数（ＭMe）との比（ＭLi：ＭMe）が１．１４：１〜１．２０：１となるように混合した。この混合物を９００℃〜１０００℃で１２時間焼成した。その後、焼成物を解砕し、篩分けを行った。このようにして、ＬｉＮｉＣｏＭｎ酸化物からなる中空構造の正極活物質を得た。 Next, Li 2 CO 3 as the lithium source and the NiCoMn composite hydroxide particles are combined into the number of moles of lithium (M Li ) and the total number of moles of Ni, Co and Mn constituting the composite hydroxide (M Me ) And the ratio (M Li : M Me ) to 1.14: 1 to 1.20: 1. This mixture was calcined at 900 ° C. to 1000 ° C. for 12 hours. Thereafter, the fired product was crushed and sieved. In this way, a positive electrode active material having a hollow structure made of LiNiCoMn oxide was obtained.
＜例２＞
上記沈降分離段階を行わない以外は上記例１と同様の材料およびプロセスにて、例２に係る正極活物質を作製した。
<Example 2>
A positive electrode active material according to Example 2 was produced using the same materials and processes as in Example 1 except that the sedimentation step was not performed.
なお、例１および例２に係る正極活物質について、上記核生成段階を行った後の反応液中のＮｉＣｏＭｎ複合水酸化物、上記沈降分離段階で分離した沈降部分に存在するＮｉＣｏＭｎ複合水酸化物（例１のみ）、上記粒子成長段階を実施した後の反応液中のＮｉＣｏＭｎ複合水酸化物、および、上記ＬｉＮｉＣｏＭｎ酸化物の粒度分布をレーザ回析・散乱式粒度分布測定装置（Ｓｈｉｍａｚｕ ＳＡＬＤ−７５００、株式会社島津製作所製）を用いて測定した。
結果を図２〜４に示す。図２は、上記核生成段階を行った後の反応液中のＮｉＣｏＭｎ複合水酸化物の粒度分布（図中の反応液）と上記沈降分離段階で分離した沈降部分に存在するＮｉＣｏＭｎ複合水酸化物の粒度分布（図中の沈降部分）を重ねて示すグラフである。図３は、上記粒子成長段階を実施した後の例１および例２に係るＮｉＣｏＭｎ複合水酸化物の粒度分布を重ねて示すグラフである。図４は、上記例１および例２に係るＬｉＮｉＣｏＭｎ酸化物の粒度分布を重ねて示すグラフである。
In addition, regarding the positive electrode active materials according to Example 1 and Example 2, the NiCoMn composite hydroxide in the reaction solution after performing the nucleation stage, the NiCoMn composite hydroxide present in the settled portion separated in the settling separation stage (Example 1 only), NiCoMn composite hydroxide in the reaction solution after carrying out the particle growth step, and the particle size distribution of the LiNiCoMn oxide in a laser diffraction / scattering type particle size distribution analyzer (Shimazu SALD-7500) , Manufactured by Shimadzu Corporation).
The results are shown in FIGS. FIG. 2 shows the NiCoMn composite hydroxide particle size distribution in the reaction solution after the nucleation step (reaction solution in the figure) and the NiCoMn composite hydroxide present in the sedimentation part separated in the sedimentation separation step. It is a graph which overlaps and shows the particle size distribution (sedimentation part in a figure). FIG. 3 is a graph showing the particle size distribution of the NiCoMn composite hydroxide according to Example 1 and Example 2 after performing the above-described grain growth stage. FIG. 4 is a graph showing the particle size distribution of the LiNiCoMn oxide according to Examples 1 and 2 in an overlapping manner.
図２に示すように、上記核生成段階を行った後に上記沈降分離段階を行うことで、沈降部分に含まれるＮｉＣｏＭｎ複合水酸化物（遷移金属水酸化物）の粒子径のバラつきを小さくすることができることを確認した。そして、図３および図４に示すように、上記沈降分離段階で分離した沈降部分に含まれるＮｉＣｏＭｎ複合水酸化物（遷移金属水酸化物）をその後の反応に供することで、粒子径のバラつきの小さいＬｉＮｉＣｏＭｎ酸化物（正極活物質）を得られることを確認した。
また、上記沈降分離段階で分離した上澄み部分に含まれるＮｉＣｏＭｎ複合水酸化物を核生成段階に供給した以外は上記例１と同様の材料およびプロセスで作製したＬｉＮｉＣｏＭｎ酸化物（正極活物質）についても、上記例１に係る正極活物質と同様に粒子径のバラつきが小さいことを確認した。
即ち、ここで開示する技術によると、粒子径のバラつきが抑制された正極活物質を高い歩留りで（少ない原料のロスで）提供し得ることが明らかとなった。
As shown in FIG. 2, the particle size variation of the NiCoMn composite hydroxide (transition metal hydroxide) contained in the sedimentation portion is reduced by performing the sedimentation separation step after performing the nucleation step. I confirmed that I was able to. As shown in FIGS. 3 and 4, the NiCoMn composite hydroxide (transition metal hydroxide) contained in the sedimentation part separated in the sedimentation-separation step is subjected to the subsequent reaction. It was confirmed that a small LiNiCoMn oxide (positive electrode active material) can be obtained.
In addition, LiNiCoMn oxide (positive electrode active material) produced by the same material and process as in Example 1 except that the NiCoMn composite hydroxide contained in the supernatant portion separated in the sedimentation separation stage was supplied to the nucleation stage. As in the positive electrode active material according to Example 1, it was confirmed that the variation in particle diameter was small.
That is, according to the technology disclosed herein, it has been clarified that a positive electrode active material in which variation in particle diameter is suppressed can be provided with a high yield (with a small loss of raw material).
以上、本発明を詳細に説明したが、上記実施形態および実施例は例示にすぎず、ここで開示される発明には上述の具体例を様々に変形、変更したものが含まれる。 As mentioned above, although this invention was demonstrated in detail, the said embodiment and Example are only illustrations and what changed and changed the above-mentioned specific example is contained in the invention disclosed here.
Claims (1)
前記リチウム遷移金属酸化物を構成する遷移金属元素の少なくとも一つを含む水性溶液から、遷移金属水酸化物を生成させる水酸化物生成工程；
前記遷移金属水酸化物とリチウム化合物とを混合して未焼成の混合物を調製する混合工程；および、
前記混合物を焼成して前記正極活物質の粒子を得る焼成工程；
を包含し、
ここで、前記水酸化物生成工程は、
前記水性溶液をアルカリ条件に調整した反応液から前記遷移金属水酸化物を析出させる核生成段階と、
前記核生成段階において析出した遷移金属水酸化物を含む前記反応液を、粒子径が所定の大きさ以上の遷移金属水酸化物を含む沈降部分と、上澄み部分とに分離する沈降分離段階と、
前記沈降部分に含まれる前記遷移金属水酸化物を、前記核生成段階よりもｐＨの低いアルカリ性条件下において成長させる粒子成長段階と、
を含み、
前記沈降分離段階において分離した上澄み部分は、前記核生成段階の前記反応液に供給される、正極活物質の製造方法。
A method for producing a positive electrode active material having a hollow structure having secondary particles in which a plurality of primary particles of a lithium transition metal oxide are aggregated and a hollow portion formed inside the secondary particles:
A hydroxide production step of producing a transition metal hydroxide from an aqueous solution containing at least one of the transition metal elements constituting the lithium transition metal oxide;
A mixing step of mixing the transition metal hydroxide and the lithium compound to prepare an unfired mixture; and
A firing step of firing the mixture to obtain particles of the positive electrode active material;
Including
Here, the hydroxide generation step includes
A nucleation step for precipitating the transition metal hydroxide from a reaction solution prepared by adjusting the aqueous solution to an alkaline condition;
A sedimentation separation step for separating the reaction liquid containing the transition metal hydroxide precipitated in the nucleation step into a sedimented portion containing a transition metal hydroxide having a particle size of a predetermined size or more and a supernatant portion;
A particle growth stage in which the transition metal hydroxide contained in the sedimentation portion is grown under alkaline conditions having a pH lower than that of the nucleation stage;
Including
The supernatant part separated in the sedimentation separation step is supplied to the reaction solution in the nucleation step, wherein the positive electrode active material is produced.
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| JP7050071B2 (en) | 2017-11-28 | 2022-04-07 | アモイタングステンニューエナジーマテリアル（アモイ）カンパニーリミテッド | Three-way precursor material and its manufacturing method |
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