JP7101005B2 - Manufacturing method of positive electrode active material - Google Patents
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Description
本発明は、正極活物質の製造方法、正極活物質、および全固体電池に関する。 The present invention relates to a method for producing a positive electrode active material, a positive electrode active material, and an all-solid-state battery.
リチウム二次電池は、各種二次電池の中でもエネルギー密度が高いことで知られている。しかし一般に普及しているリチウム二次電池は、電解質に可燃性の有機電解液を用いている。そのため、リチウム二次電池では、液漏れ、短絡、過充電などに対する安全対策が他の電池よりも厳しく求められている。そこで近年、電解質に酸化物系や硫化物系の固体電解質を用いた全固体電池に関する研究開発が盛んに行われている。固体電解質は、固体中でイオン伝導が可能なイオン伝導体を主体として構成される材料であり、従来のリチウム二次電池のように可燃性の有機電解液に起因する各種問題が原理的に発生しない。そして、一般的な全固体電池は層状の正極（正極層）と層状の負極（負極層）との間に層状の固体電解質（電解質層）が狭持されてなる積層電極体に集電体を形成した構造を有している。 Lithium secondary batteries are known to have a high energy density among various secondary batteries. However, widely used lithium secondary batteries use a flammable organic electrolyte as an electrolyte. Therefore, in lithium secondary batteries, safety measures against liquid leakage, short circuit, overcharge, etc. are stricter than other batteries. Therefore, in recent years, research and development on an all-solid-state battery using an oxide-based or sulfide-based solid electrolyte as an electrolyte has been actively carried out. The solid electrolyte is a material composed mainly of an ionic conductor capable of ionic conduction in a solid, and in principle, various problems caused by a flammable organic electrolyte solution like a conventional lithium secondary battery occur. do not do. In a general all-solid-state battery, a collector is placed in a laminated electrode body in which a layered solid electrolyte (electrolyte layer) is sandwiched between a layered positive electrode (positive electrode layer) and a layered negative electrode (negative electrode layer). It has a formed structure.
全固体電池の正極活物質には、ＬｉＣｏＯ２、ＬｉＭｎ２Ｏ４など、従来のリチウム二次電池用の材料を用いることができる。また、全固体電池は、可燃性の電解液を用いないことから、より高い電位差が得られ、エネルギー密度が高い全固体電池用の正極活物質についても研究されている。具体的には、一つの遷移金属に対して複数のＬｉが関与する、所謂「多電子反応」を示す正極活物質について研究されている。上記の従来の正極活物質では遷移金属に対して一つのＬｉしか関与しないが、多電子反応を示す正極活物質では、複数のＬｉがレドックス反応に寄与するため、より高電位で動作し、高容量とともに高いエネルギー密度も得られる。 As the positive electrode active material of the all-solid-state battery, a material for a conventional lithium secondary battery such as LiCoO 2 and LiMn 2 O 4 can be used. Further, since the all-solid-state battery does not use a flammable electrolytic solution, a positive electrode active material for an all-solid-state battery, which can obtain a higher potential difference and has a high energy density, is also being studied. Specifically, research is being conducted on a positive electrode active material exhibiting a so-called "multi-electron reaction" in which a plurality of Lis are involved in one transition metal. In the above-mentioned conventional positive electrode active material, only one Li is involved in the transition metal, but in the positive electrode active material showing a multi-electron reaction, since multiple Lis contribute to the redox reaction, it operates at a higher potential and is higher. High energy density can be obtained as well as capacity.
そして、以下の非特許文献１や非特許文献２には、２個のＬｉがレドックス反応に寄与する正極活物質であるＬｉ２ＦｅＰ２Ｏ７（ピロリン酸鉄リチウム）の特性などについて記載されている。以下の特許文献１には、固相法を用い、ＭをＣｏとＮｉのいずれか一方、あるいは両方として、化学式Ｌｉ２ＭＰ２Ｏ７で表される正極活物質の製造方法について記載されている。なお、負極活物質としては、酸化チタン（ＴｉＯ２）などがある。 The following Non-Patent Document 1 and Non-Patent Document 2 describe the characteristics of Li 2 FeP 2 O 7 (lithium iron pyrophosphate), which is a positive electrode active material in which two Lis contribute to the redox reaction. There is. The following Patent Document 1 describes a method for producing a positive electrode active material represented by the chemical formula Li 2 MP 2 O 7 by using a solid phase method and using M as either Co or Ni or both. .. The negative electrode active material includes titanium oxide (TiO 2 ) and the like.
ところで、全固体電池には、焼結体からなる積層電極体を備えたバルク焼結型と呼ばれるものがよく知られている。バルク型の全固体電池では、積層電極体を、例えば、周知のグリーンシート法を用いて作製することができる。グリーンシート法を用いた積層電極体の作製方法の一例を示すと、まず、正極活物質と固体電解質を含むスラリー状の正極層材料、負極活物質と固体電解質を含むスラリー状の負極層材料、および固体電解質を含むスラリー状の固体電解質層材料をそれぞれシート状のグリーンシートに成形し、固体電解質層材料からなるグリーンシート（以下、電解質層シートとも言う）を正極層材料からなるグリーンシート（以下、正極層シートとも言う）と負極層材料からなるグリーンシート（以下、負極層シートとも言う）とで挟持して得た積層体を圧着し、その圧着後の積層体を焼成する。それによって焼結体である積層電極体が完成する。 By the way, as an all-solid-state battery, a so-called bulk sintered type having a laminated electrode body made of a sintered body is well known. In the bulk type all-solid-state battery, the laminated electrode body can be manufactured by using, for example, a well-known green sheet method. To show an example of a method for producing a laminated electrode body using the green sheet method, first, a slurry-like positive electrode layer material containing a positive electrode active material and a solid electrolyte, a slurry-like negative electrode layer material containing a negative electrode active material and a solid electrolyte, and a slurry-like negative electrode layer material. The slurry-like solid electrolyte layer material containing the solid electrolyte is formed into a sheet-shaped green sheet, and the green sheet made of the solid electrolyte layer material (hereinafter, also referred to as the electrolyte layer sheet) is formed into the green sheet made of the positive electrode layer material (hereinafter referred to as the positive electrode layer material). , Also referred to as a positive electrode layer sheet) and a green sheet made of a negative electrode layer material (hereinafter, also referred to as a negative electrode layer sheet) are crimped to obtain a laminated body, and the crimped laminated body is fired. As a result, a laminated electrode body which is a sintered body is completed.
各層のグリーンシートを作製する方法としては、周知のドクターブレード法がある。ドクターブレード法では、無機酸化物などのセラミックス粉体にバインダ（ポリビニルアルコール(ＰＶＡ)、ポリビニルブチラール(ＰＶＢ)、ポリフッ化ビニリレン(ＰＶＤＦ)、アクリル、エチルメチルセルロースなど）および溶剤（無水アルコールなど）を混合して得たスラリーを塗布工程あるいは印刷工程により薄板状に成形してグリーンシートを作製する。そしてスラリーに含ませるセラミック粉体として正極活物質、固体電解質、および負極活物質のそれぞれの粉体を用いる。 As a method for producing a green sheet for each layer, there is a well-known doctor blade method. In the doctor blade method, a binder (polyvinyl alcohol (PVA), polyvinyl butyral (PVB), polyvinylylene polyfluoride (PVDF), acrylic, ethyl methyl cellulose, etc.) and a solvent (anhydrous alcohol, etc.) are mixed with ceramic powder such as an inorganic oxide. The slurry thus obtained is formed into a thin plate by a coating step or a printing step to prepare a green sheet. Then, as the ceramic powder to be contained in the slurry, each powder of the positive electrode active material, the solid electrolyte, and the negative electrode active material is used.
上述したように、ＭをＣｏあるいはＮｉのいずれか、あるいは両方として、化学式Ｌｉ２ＭＰ２Ｏ７で表される正極活物質は、２個のＬｉイオンがレドックス反応に寄与し、高いエネルギー密度を有するものである。しかしながら、この正極活物質を用いた全固体電池を実用化するためには、異相を含まない純度の高いＬｉ２ＭＰ２Ｏ７を得る必要がある。そして、上記特許文献１には、異相を含まないＬｉ２ＭＰ２Ｏ７を得るための正極活物質の製造方法について記載されている。 As described above, in the positive electrode active material represented by the chemical formula Li 2 MP 2 O 7 , where M is either Co or Ni, or both, two Li ions contribute to the redox reaction, resulting in a high energy density. It has. However, in order to put an all-solid-state battery using this positive electrode active material into practical use, it is necessary to obtain a high-purity Li 2 MP 2 O 7 that does not contain different phases. Further, Patent Document 1 describes a method for producing a positive electrode active material for obtaining Li 2 MP 2 O 7 containing no different phase.
しかしながら、特許文献１に記載の製造方法では、製造した正極活物質の結晶相を、Ｘ線回折装置を用いた測定（ＸＲＤ測定）によって調べており、ＸＲＤ測定では、測定限界に近い微量の異相が含まれている可能性もある。そして、特許文献１に記載の製造方法で作製した正極活物質をより詳しく調べてみたところ、極めて微少ではあるが、ＸＲＤ測定における回折パターンに、異相を示すピークがあった。また、特許文献１に記載の製造方法では、６５０℃以上の焼成温度で２０時間以上の時間を掛けて正極活物質を焼結させていた。そのため、焼成炉内の温度を焼成温度まで昇温させ、その温度を長時間維持するために、多大なエネルギーコストが掛かっていた。 However, in the production method described in Patent Document 1, the crystal phase of the produced positive electrode active material is investigated by measurement using an X-ray diffractometer (XRD measurement), and in XRD measurement, a trace amount of different phase close to the measurement limit is investigated. May be included. Then, when the positive electrode active material produced by the production method described in Patent Document 1 was examined in more detail, there was a peak showing a different phase in the diffraction pattern in the XRD measurement, although it was extremely small. Further, in the production method described in Patent Document 1, the positive electrode active material is sintered at a firing temperature of 650 ° C. or higher for 20 hours or longer. Therefore, in order to raise the temperature in the firing furnace to the firing temperature and maintain the temperature for a long time, a large energy cost is required.
なお、固相法で作製される正極活物質から、目的とする化合物の結晶相以外の異相のみを取り除くことが極めて難しい。そのため、極めて純度の高い正極活物質を得るためには、製造方法を改良する以外に手段がない。しかし、現状では、その製造方法も存在しない。液相法や気相法など、固相法以外にも正極活物質を作製する方法はあるが、これらの方法でも、異相をほとんど含まない正極活物質を作製することは難しい。そして、固相法以外の正極活物質の製造方法は、製造工程が複雑であり、製造コストが嵩む。 It is extremely difficult to remove only the heterogeneous phase other than the crystalline phase of the target compound from the positive electrode active material produced by the solid phase method. Therefore, in order to obtain an extremely high-purity positive electrode active material, there is no means other than improving the production method. However, at present, there is no manufacturing method for this. Although there are methods for producing a positive electrode active material other than the solid phase method such as the liquid phase method and the gas phase method, it is difficult to produce a positive electrode active material containing almost no heterogeneous phase even with these methods. Further, in the method for producing a positive electrode active material other than the solid phase method, the manufacturing process is complicated and the manufacturing cost is high.
そこで、本発明は、固相法を用い、ＭをＣｏあるいはＮｉのいずれか、あるいは両方として、化学式Ｌｉ２ＭＰ２Ｏ７で表される正極活物質を極めて高い純度で製造するための方法、当該方法によって作製されてＬｉ２ＭＰ２Ｏ７の純度が極めて高い正極活物質、およびこの正極活物質を用いた全固体電池を提供することを目的としている。 Therefore, the present invention is a method for producing a positive electrode active material represented by the chemical formula Li 2 MP 2 O 7 with extremely high purity by using the solid-state method and using M as either Co or Ni or both. It is an object of the present invention to provide a positive electrode active material having extremely high purity of Li 2 MP 2 O 7 produced by the above method, and an all-solid-state battery using the positive electrode active material.
上記目的を達成するための本発明の一態様は、正極活物質の製造方法であって、
ＭをＣｏあるいはＮｉのいずれか、あるいは両方として、化学式Ｌｉ２ＭＰ２Ｏ７で表される化合物の原料を混合する原料混合ステップと、
前記原料混合ステップにより混合された前記原料を３００℃以上４００℃以下の温度で仮焼成する仮焼成ステップと、
前記仮焼成ステップにより得た粉体材料を、平均粒子径が０．３μｍ以下となるように粉砕する粉砕ステップと、
前記粉砕ステップ後の粉体材料を６２０℃以上６４０℃以下の温度で焼成して、当該粉体材料を焼結させる焼成ステップと、
を含むことを特徴とする正極活物質の製造方法としている。
One aspect of the present invention for achieving the above object is a method for producing a positive electrode active material.
A raw material mixing step of mixing the raw materials of the compound represented by the chemical formula Li 2 MP 2 O 7 with M as Co, Ni, or both.
A temporary firing step in which the raw materials mixed by the raw material mixing step are temporarily fired at a temperature of 300 ° C. or higher and 400 ° C. or lower,
A pulverization step of pulverizing the powder material obtained by the temporary firing step so that the average particle size is 0.3 μm or less, and a pulverization step.
A firing step in which the powder material after the crushing step is fired at a temperature of 620 ° C. or higher and 640 ° C. or lower to sinter the powder material.
It is a method for producing a positive electrode active material, which is characterized by containing.
前記化合物が、Ｌｉ２ＣｏＰ２Ｏ７である正極活物質の製造方法とすることもでき、当該製造方法は、原料混合ステップにおいて、前記原料として、（ＮＨ４）２ＨＰＯ４、Ｌｉ２ＣＯ３、ＣｏＣ２Ｏ４を用いることとしてもよい。 The compound can also be a method for producing a positive electrode active material in which Li 2 CoP 2 O 7 is used, and the production method uses (NH 4 ) 2 HPO 4 , Li 2 CO 3 as the raw material in the raw material mixing step. , CoC 2 O 4 may be used.
本発明によれば、固相法を用い、ＭをＣｏあるいはＮｉのいずれか、あるいは両方として、化学式Ｌｉ２ＭＰ２Ｏ７で表される正極活物質を極めて高い純度で製造するための方法が提供される。そして、当該方法によって作製された正極活物質は、高いエネルギー密度を有し、当該正極活物質を用いた全固体電池は、高電圧で動作し、大きな容量を有するものとなる。なお、その他の効果については以下の記載で明らかにする。 According to the present invention, there is a method for producing a positive electrode active material represented by the chemical formula Li 2 MP 2 O 7 with extremely high purity by using the solid phase method and using M as Co or Ni or both. Provided. The positive electrode active material produced by the method has a high energy density, and the all-solid-state battery using the positive electrode active material operates at a high voltage and has a large capacity. Other effects will be clarified in the following description.
＝＝＝実施例＝＝＝
本発明の実施例に係る正極活物質の製造方法として、化学式Ｌｉ２ＭＰ２Ｏ７における遷移金属ＭをＣｏとしたＬｉ２ＣｏＰ２Ｏ７を作製する手順を挙げる。そして、実施例に係る方法で作製された正極活物質の特性を評価するために、同じ原料を用いつつ、製造条件が異なる各種正極活物質をサンプルとして作製した。
=== Example ===
As a method for producing a positive electrode active material according to an embodiment of the present invention, a procedure for producing Li 2 CoP 2 O 7 in which the transition metal M in the chemical formula Li 2 MP 2 O 7 is Co is given. Then, in order to evaluate the characteristics of the positive electrode active material produced by the method according to the example, various positive electrode active materials having different production conditions were prepared as samples while using the same raw materials.
図１に、本発明の実施例に係る正極活物質の製造方法の手順を示した。まず、Ｌｉ２ＣｏＰ２Ｏ７の原料として（ＮＨ４）２ＨＰＯ４、Ｌｉ２ＣＯ３、ＣｏＣ２Ｏ４・２Ｈ２Ｏを使用し、この原料を秤量する（ｓ１）。そして、Ｌｉ２ＣｏＰ２Ｏ７の原料を、ボールミルを用いて湿式混合する（ｓ２）。湿式混合によって得た原料の混合物をアルミナるつぼに入れ、大気雰囲気中で、原料の混合物が焼結する温度より低い温度で仮焼成する（ｓ３）。仮焼成工程（ｓ３）における温度は、正極活物質に限らず、固相法でセラミック粉を作製する場合では、一般的に３００℃～４００℃の温度である。ここでは３５０℃の温度で２時間掛けて仮焼成した。 FIG. 1 shows a procedure for producing a positive electrode active material according to an embodiment of the present invention. First, (NH 4 ) 2 HPO 4 , Li 2 CO 3 , and CoC 2 O 4.2H 2 O are used as raw materials for Li 2 CoP 2 O 7 , and the raw materials are weighed (s1). Then, the raw materials of Li 2 CoP 2 O 7 are wet-mixed using a ball mill (s2). The mixture of raw materials obtained by wet mixing is placed in an alumina crucible and calcined in an air atmosphere at a temperature lower than the temperature at which the mixture of raw materials is sintered (s3). The temperature in the temporary firing step (s3) is not limited to the positive electrode active material, and is generally 300 ° C. to 400 ° C. when the ceramic powder is produced by the solid phase method. Here, it was calcined at a temperature of 350 ° C. for 2 hours.
次に、仮焼成によって得た粉体状の混合物を粉砕し、粉体材料の平均粒子径を調整した（ｓ４）。このとき、サンプルに応じて平均粒子径（以下、粒子径とも言う）を変えた。なお、この粉砕工程（ｓ４）では、粒子径を６．０μｍ以下にする場合は、遊星ボールミルを用いた。また、粉砕工程（ｓ４）を省略したサンプルも作製した。そして、粉砕後の混合物を、大気雰囲気中で焼成し、焼結体を得た（ｓ５）。このとき、サンプルに応じて焼成温度を変えた。焼成時間については１０時間とした。また、焼成工程（ｓ５）では、焼成炉内に大気組成のガスを流さずに試料である粉体を焼成した。最後に、メノウ乳鉢を用いて焼結体を粉砕し、その粉砕後のサンプルの特性を評価した。 Next, the powdery mixture obtained by calcination was crushed to adjust the average particle size of the powder material (s4). At this time, the average particle size (hereinafter, also referred to as particle size) was changed according to the sample. In this crushing step (s4), a planetary ball mill was used when the particle size was 6.0 μm or less. In addition, a sample in which the crushing step (s4) was omitted was also prepared. Then, the pulverized mixture was fired in an air atmosphere to obtain a sintered body (s5). At this time, the firing temperature was changed according to the sample. The firing time was 10 hours. Further, in the firing step (s5), the powder as a sample was fired without flowing a gas having an atmospheric composition into the firing furnace. Finally, the sintered body was crushed using an agate mortar and the characteristics of the crushed sample were evaluated.
＝＝＝特性評価＝＝＝
＜ＸＲＤ測定＞
粉砕工程（ｓ４）における平均粒子径や、焼成工程（ｓ５）における焼成条件が異なる各種サンプルに対し、ＸＲＤ測定を行い、各サンプルに含まれる化合物の生成状態を調べた。図２に各サンプルの作製条件とＸＲＤ測定の結果とを示した。図２では、各サンプルに結晶として含まれている化合物の種類が作製条件別にプロットされている。図中では、結晶相において主相となるＬｉ２ＣｏＰ２Ｏ７が白丸でプロットされており、異相であるＬｉ４Ｐ２Ｏ１０、ＬｉＣＯ２Ｐ３Ｏ１０、Ｌｉ６Ｃｏ５（Ｐ２Ｏ７）４、およびＬｉＣｏＰＯ４が、それぞれ、菱形、黒塗り四角、バツ、および黒塗り三角の各図形でプロットされている。また、同じ温度で焼成されたサンプル同士が、破線で示された一つの矩形領域内にプロットされており、粉砕工程（ｓ４）において同じ粒子径に調整されたサンプル同士が、点線で示された一つの矩形領域内にプロットされている。なお、粒子径６μｍのサンプルは、粉砕工程（ｓ４）を省略したサンプルである。
=== Characteristic evaluation ===
<XRD measurement>
XRD measurements were performed on various samples having different average particle diameters in the pulverization step (s4) and firing conditions in the firing step (s5), and the formation state of the compounds contained in each sample was investigated. FIG. 2 shows the preparation conditions of each sample and the results of XRD measurement. In FIG. 2, the types of compounds contained as crystals in each sample are plotted according to the production conditions. In the figure, Li 2 CoP 2 O 7 which is the main phase in the crystal phase is plotted with white circles, and Li 4 P 2 O 10 and Li CO 2 P 3 O 10 and Li 6 Co 5 (P 2 O) which are different phases are plotted. 7 ) 4 , and LiCoPO 4 are plotted as diamonds, black squares, crosses, and black triangles, respectively. Further, the samples fired at the same temperature are plotted in one rectangular region shown by the broken line, and the samples adjusted to the same particle size in the pulverization step (s4) are shown by the dotted line. It is plotted in one rectangular area. The sample having a particle size of 6 μm is a sample in which the pulverization step (s4) is omitted.
図２に示したように、結晶相において主相となるＬｉ２ＣｏＰ２Ｏ７は、全ての作製条件で生成されることが確認できた。しかし、多くの作製条件で異相の生成も確認された。そして、粒子径が０．３μｍで、焼成温度が６２０℃と６４０℃の条件では、異相の生成を確認することができなかった。また、各サンプルのＸＲＤ測定結果から、焼成温度が適正（６２０℃、６４０℃）であっても、粒子径が０．５μｍ以上であると異相が生成され易いことがわかった。これは、粒子径が大きいと、焼成工程において、粉体材料中の各粒子に均一に熱が拡散せず異相が生成され易くなると考えることができる。すなわち、焼成温度が適正で、粒子径が０．３μｍ以下であれば、十分に熱が拡散されて異相が発生し難くなる。また、粒子径が０．３μｍであっても、焼成温度が適正温度の範囲外である場合では、LｉＣｏＰ２Ｏ７以外の結晶相が焼結したものと考えることができる。 As shown in FIG. 2, it was confirmed that Li 2 CoP 2 O 7 , which is the main phase in the crystal phase, is produced under all the production conditions. However, the formation of heterogeneous phases was also confirmed under many production conditions. The formation of different phases could not be confirmed under the conditions of a particle size of 0.3 μm and firing temperatures of 620 ° C and 640 ° C. Further, from the XRD measurement results of each sample, it was found that even if the firing temperature is appropriate (620 ° C., 640 ° C.), a different phase is likely to be generated when the particle size is 0.5 μm or more. It can be considered that when the particle size is large, heat is not uniformly diffused to each particle in the powder material in the firing step, and a different phase is likely to be generated. That is, if the firing temperature is appropriate and the particle size is 0.3 μm or less, heat is sufficiently diffused and different phases are less likely to occur. Further, even if the particle size is 0.3 μm, if the firing temperature is out of the proper temperature range, it can be considered that the crystal phases other than LiCoP 2 O 7 are sintered.
したがって、LｉＣｏＰ２Ｏ７の純度が極めて高い正極活物質を作製するためには、焼成工程（ｓ５）前の粉砕工程（ｓ４）において、仮焼成工程（ｓ３）によって得た粉体材料を、粒子径が０．３μｍ以下となるように粉砕し、焼成工程（ｓ５）において、焼成温度を６２０℃以上６４０℃以下とすればよい。なお、粒子径の下限は、粉砕工程（ｓ４）に用いられるボールミルなどの粉砕装置の性能に依存する。 Therefore, in order to produce a positive electrode active material having extremely high purity of LiCoP 2 O 7 , the powder material obtained by the temporary firing step (s3) in the crushing step (s4) before the firing step (s5) is used as particles. It may be crushed so as to have a diameter of 0.3 μm or less, and the firing temperature may be set to 620 ° C. or higher and 640 ° C. or lower in the firing step (s5). The lower limit of the particle size depends on the performance of a crushing device such as a ball mill used in the crushing step (s4).
焼成工程（ｓ５）における焼成時間については、粉体材料を焼結させることができれば、時間は特に問わない。本実施例では、１０時間であったが、焼結させることができれば、それより短くてもよい。焼成時間を長くする場合では、温度が一定であれば、一度ある結晶相として焼結した化合物が他の結晶相になることはほとんどない。 The firing time in the firing step (s5) is not particularly limited as long as the powder material can be sintered. In this example, it was 10 hours, but it may be shorter if it can be sintered. When the firing time is lengthened, if the temperature is constant, the compound once sintered as one crystal phase rarely becomes another crystal phase.
以上より、本実施例に係る正極活物質の製造方法では、６２０℃以上６４０℃以下の低い温度で粉体材料を焼結させることができ、焼成工程（ｓ５）に要するエネルギーコストを抑制することが可能となる。さらに、本実施例に係る正極活物質の製造方法では、焼成工程（ｓ５）を大気雰囲気で行っており、不活性ガス雰囲気での焼成が不要である。また、焼成炉内に大気を含むガスを導入するための設備や工程も不要である。本実施例に係る正極活物質の製造方法は、製造工程が簡素な固相法であり、基本的に、液相法や気相法などの他の製造方法よりも製造コストを抑制することができる。 From the above, in the method for producing a positive electrode active material according to the present embodiment, the powder material can be sintered at a low temperature of 620 ° C. or higher and 640 ° C. or lower, and the energy cost required for the firing step (s5) can be suppressed. Is possible. Further, in the method for producing a positive electrode active material according to the present embodiment, the firing step (s5) is performed in an atmospheric atmosphere, and firing in an inert gas atmosphere is unnecessary. In addition, there is no need for equipment or processes for introducing gas containing air into the firing furnace. The method for producing a positive electrode active material according to this embodiment is a solid phase method having a simple manufacturing process, and basically, the manufacturing cost can be suppressed as compared with other manufacturing methods such as a liquid phase method and a gas phase method. can.
＜リートベルト解析＞
図２に示したＸＲＤ測定結果において、平均粒子径を０．３μｍとし、焼成工程（ｓ５）において、焼成温度を６２０℃、または６４０℃としたサンプル（以下、実施例のサンプルとも言う）は、Ｌｉ２ＣｏＰ２Ｏ７の純度が高い正極活物質であった。少なくとも、ＸＲＤ測定では、異相の含有率は測定限界以下であった。そこで、次に、本実施例の製造方法によって作製された正極活物質中のＬｉ２ＣｏＰ２Ｏ７の純度をより詳しく調べるために、実施例のサンプルに対するＸＲＤ測定によって得られた回折パターンを、リートベルト法を用いて解析した。その結果、実施例のサンプルに含まれている異相の割合は、最大でも１ｗｔ％～２ｗｔ％であり、実施例のサンプルは、Ｌｉ２ＣｏＰ２Ｏ７の純度が極めて高い正極活物質であることが実証された。言い換えれば、Ｌｉ２ＣｏＰ２Ｏ７を含む粉体状の正極活物質に対するＸＲＤ測定結果を、リートベルト法を用いて解析した際に、異相が２ｗｔ％以下であれば、その正極活物質は、本実施例に係る方法で製造されたものである可能性が高いと言える。また、粉体材料からなる正極活物質を用いて作製される全固体電池は、上述したバルク型であることから、バルク型の全固体電池の正極層に含まれる正極活物質中のＬｉ２ＣｏＰ２Ｏ７の含有率が９８ｗｔ％以上であれば、やはり、その全固体電池に用いた正極活物質も本実施例の方法で作製されたものである可能性が高い。
<Rietveld analysis>
In the XRD measurement results shown in FIG. 2, a sample having an average particle size of 0.3 μm and a firing temperature of 620 ° C. or 640 ° C. in the firing step (s5) (hereinafter, also referred to as a sample of an example) is It was a positive electrode active material having a high purity of Li 2 CoP 2 O 7 . At least, in the XRD measurement, the content of the heterogeneous phase was below the measurement limit. Therefore, next, in order to investigate the purity of Li 2 CoP 2 O 7 in the positive electrode active material produced by the production method of this example in more detail, the diffraction pattern obtained by the XRD measurement with respect to the sample of the example was used. The analysis was performed using the Rietveld method. As a result, the ratio of the heterogeneous phase contained in the sample of the example is 1 wt% to 2 wt% at the maximum, and the sample of the example is a positive electrode active material having extremely high purity of Li 2 CoP 2 O 7 . Was demonstrated. In other words, when the XRD measurement results for the powdery positive electrode active material containing Li 2 CoP 2 O 7 are analyzed using the Rietveld method, if the heterogeneous phase is 2 wt% or less, the positive electrode active material is It can be said that it is highly possible that the product was manufactured by the method according to this embodiment. Further, since the all-solid-state battery manufactured by using the positive electrode active material made of a powder material is the bulk type described above, Li 2 CoP in the positive electrode active material contained in the positive electrode layer of the bulk type all-solid-state battery. If the content of 2O 7 is 98 wt% or more, it is highly possible that the positive electrode active material used in the all-solid-state battery is also produced by the method of this example.
＝＝＝その他の実施例＝＝＝
Ｌｉ２ＣｏＰ２Ｏ７の原料は、上記実施例において用いたものに限らない。本発明の実施例に係る正極活物質の製造方法は、固相法であることから、目的とする化合物の化学式に含まれる元素が揃うのであれば、様々な原料を採用することができる。例えば、上記実施例では、ＬｉやＣｏの起源となる原料としてＬｉＮＯ３やＣｏＣＯ３などを用いることができる。
=== Other Examples ===
The raw material of Li 2 CoP 2 O 7 is not limited to that used in the above examples. Since the method for producing the positive electrode active material according to the embodiment of the present invention is a solid phase method, various raw materials can be adopted as long as the elements contained in the chemical formula of the target compound are available. For example, in the above embodiment, LiNO 3 or CoCO 3 can be used as a raw material that is the origin of Li or Co.
また、Ｌｉ２ＣｏＰ２Ｏ７とＬｉ２ＮｉＰ２Ｏ７とは特性が近似しており、本発明の実施例に係る正極活物質の製造方法は、Ｌｉ２ＣｏＰ２Ｏ７に限らず、Ｌｉ２ＣｏＰ２Ｏ７に含まれるＣｏの全部あるいは一部をＮｉに置換した、化学式Ｌｉ２ＭＰ２Ｏ７で表される化合物（Ｍは、ＣｏとＮｉのいずれか、あるいは両方）にも適用できる。 Further, the characteristics of Li 2 CoP 2 O 7 and Li 2 NiP 2 O 7 are similar to each other, and the method for producing the positive electrode active material according to the embodiment of the present invention is not limited to Li 2 CoP 2 O 7 . 2 It can also be applied to a compound represented by the chemical formula Li 2 MP 2 O 7 in which all or part of Co contained in CoP 2 O 7 is replaced with Ni (M is either Co or Ni, or both). ..
本発明の実施例に係る方法で作製された正極活物質は、全固体電池用の正極活物質として特に有用であるが、充放電反応にＬｉイオンを用いるリチウム二次電池であれば、全固体電池に限らず適用可能である。 The positive electrode active material produced by the method according to the embodiment of the present invention is particularly useful as a positive electrode active material for an all-solid-state battery, but if it is a lithium secondary battery that uses Li ions for a charge / discharge reaction, it is an all-solid-state battery. It is applicable not only to batteries.
ｓ１ 秤量工程、ｓ２ 混合工程、ｓ３ 仮焼成工程、ｓ４ 粉砕工程、ｓ５ 焼成工程
s1 weighing process, s2 mixing process, s3 temporary firing process, s4 crushing process, s5 firing process
Claims (3)
ＭをＣｏあるいはＮｉのいずれか、あるいは両方として、化学式Ｌｉ２ＭＰ２Ｏ７で表される化合物の原料を混合する原料混合ステップと、
前記原料混合ステップにより混合された前記原料を３００℃以上４００℃以下の温度で仮焼成する仮焼成ステップと、
前記仮焼成ステップにより得た粉体材料を、平均粒子径が０．３μｍ以下となるように粉砕する粉砕ステップと、
前記粉砕ステップ後の粉体材料を６２０℃以上６４０℃以下の温度で焼成して、当該粉体材料を焼結させる焼成ステップと、
を含むことを特徴とする正極活物質の製造方法。 It is a method for manufacturing a positive electrode active material.
A raw material mixing step of mixing the raw materials of the compound represented by the chemical formula Li 2 MP 2 O 7 with M as Co, Ni, or both.
A temporary firing step in which the raw materials mixed by the raw material mixing step are temporarily fired at a temperature of 300 ° C. or higher and 400 ° C. or lower,
A pulverization step of pulverizing the powder material obtained by the temporary firing step so that the average particle size is 0.3 μm or less, and a pulverization step.
A firing step in which the powder material after the crushing step is fired at a temperature of 620 ° C. or higher and 640 ° C. or lower to sinter the powder material.
A method for producing a positive electrode active material, which comprises.
原料混合ステップでは、前記原料として、（ＮＨ４）２ＨＰＯ４、Ｌｉ２ＣＯ３、ＣｏＣ２Ｏ４を用いる、
ことを特徴とする正極活物質の製造方法。 The method for producing a positive electrode active material according to claim 2.
In the raw material mixing step, (NH 4 ) 2 HPO 4 , Li 2 CO 3 , and CoC 2 O 4 are used as the raw materials.
A method for producing a positive electrode active material.
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