JP3702481B2 - Acicular manganese complex oxide, method for producing the same, and use thereof - Google Patents

Description

【００８４】
また、結晶軸の長さは、各化合物のＸ線回折測定データから、ＷＰＰＤ法( Ｗｈｏｌｅ−Ｐｏｗｄｅｒ−Ｐａｔｔｅｒｎ Ｄｅｃｏｍｐｏｓｉｔｉｏｎ Ｍｅｔｈｏｄ) によって、決定した。
【００８５】
さらに、組成分析はＩＣＰ発光分析法で測定した。
【００８６】
［マンガン複合酸化物の製造］
実施例１
（ＬｉＣｏ_0.1 Ｍｎ_1.9 Ｏ₄ の製造）
実施例１として、ＬｉＣｏ_0.1 Ｍｎ_1.9 Ｏ₄ を、以下の方法により製造した。
硝酸リチウム（試薬特級）と、短軸径が１μｍ以下、長軸径が５μｍ以下、高さが１μｍ以下の相当径を有する、針状粒子からなるγ−ＭｎＯＯＨ（東ソー株式会社製）と硝酸コバルト６水和物（試薬特級）をモル比でＬｉ：Ｍｎ：Ｃｏが１：１．９：０．１になるように混合した後、大気中で４５０℃の温度で２４時間、焼成した。
【００８７】
次に、これを室温まで降温した後に、乳鉢で粉砕、混合した後、大気中で６５０℃の温度で２４時間、焼成した。
【００８８】
得られた化合物のＸ線回折パターンを図２に、粒子構造の観察結果を図３に、化学分析結果、結晶軸の長さ、及びＢＥＴ比表面積の測定結果を表１に示した。
【００８９】
【表１】

【００９０】
解析の結果、得られた化合物は、短軸径が５μｍ以下、長軸径が１０μｍ以下、高さが５μｍ以下の相当径を有する針状粒子からなり、結晶軸の長さが８．２１７オングストローム、ＢＥＴ比表面積６．５ｍ² ／ｇの、ＬｉＣｏ_0.1 Ｍｎ_{1. 9
O3.9} で表される、スピネル構造のマンガン複合酸化物であることが分った。
【００９１】
実施例２
（ＬｉＣｏ_0.2 Ｍｎ_1.8 Ｏ₄ の製造）
実施例２として、モル比でＬｉ：Ｍｎ：Ｃｏが１：１．８：０．２になるように混合した以外は、実施例１と同様にして製造を行った。
【００９２】
解析の結果、得られた化合物は、短軸径が５μｍ以下、長軸径が１０μｍ以下、高さが５μｍ以下の相当径を有する針状粒子からなる、スピネル構造のマンガン複合酸化物であった。
【００９３】
化学分析結果、結晶軸の長さ、及びＢＥＴ比表面積の測定結果を表１に示した。
【００９４】
実施例３
（ＬｉＣｏ_0.3 Ｍｎ_1.7 Ｏ₄ の製造）
実施例３として、マンガン原料に、短軸径が１μｍ以下、長軸径が５μｍ以下、高さが１μｍ以下の相当径を有する、針状粒子からなるβ−ＭｎＯ₂ を用いて、モル比でＬｉ：Ｍｎ：Ｃｏが１：１．７：０．３になるように混合し、第２の焼成温度を７５０℃にして、実施例１と同様にして製造を行った。
【００９５】
なお、針状粒子からなるβ−ＭｎＯ₂ は以下の方法で作成した。
【００９６】
短軸径が１μｍ以下、長軸径が５μｍ以下、高さが１μｍ以下の相当径を有する、針状粒子からなるγ−ＭｎＯＯＨ( 東ソー株式会社製) の１００ｇと濃硝酸（比重＝１．３）１０ミリリットルとを混合し、２００℃の温度で８時間熱処理を行った。生成物を乳鉢で解砕し、熱水洗した。Ｘ線回折測定から、この生成物はβ−ＭｎＯ₂ であると同定された。さらに、粒子構造の観察の結果、短軸径が１μｍ以下、長軸径が５μｍ以下、高さが１μｍ以下の相当径を有する、針状粒子であった。
【００９７】
製造したマンガン複合酸化物の解析の結果、得られた化合物は、短軸径が５μｍ以下、長軸径が１０μｍ以下、高さが５μｍ以下の相当径を有する針状粒子からなる、スピネル構造のマンガン複合酸化物であった。
【００９８】
化学分析結果、結晶軸の長さ、及びＢＥＴ比表面積の測定結果を表１に示した。
【００９９】
実施例４
（ＬｉＮｉ_0.1 Ｍｎ_0.9 Ｏ₄ の製造）
実施例４として、ＬｉＮｉ_0.1 Ｍｎ_1.9 Ｏ₄ を、以下の方法により製造した。
硝酸リチウム（試薬特級）と、短軸径が１μｍ以下、長軸径が５μｍ以下、高さが１μｍ以下の相当径を有する、針状粒子からなるγ−ＭｎＯＯＨ（東ソー株式会社製）と硝酸ニッケル６水和物（試薬特級）をモル比でＬｉ：Ｍｎ：Ｎｉが１：１．９：０．１になるように混合した後、大気中で４５０℃の温度で２４時間、焼成した。
【０１００】
次に、これを室温まで降温した後に、乳鉢で粉砕、混合した後、大気中で６５０℃の温度で２４時間、焼成した。
【０１０１】
得られた化合物のＸ線回折パターンを図２に、粒子構造の観察結果を図４に、化学分析結果、結晶軸の長さ、及びＢＥＴ比表面積の測定結果を表１に示した。
解析の結果、得られた化合物は、短軸径が５μｍ以下、長軸径が１０μｍ以下、高さが５μｍ以下の相当径を有する針状粒子からなり、結晶軸の長さが８．２２８オングストローム、ＢＥＴ比表面積６．３ｍ² ／ｇの、ＬｉＮｉ_0.1 Ｍｎ_1.9O4.0 で表される、スピネル構造のマンガン複合酸化物であることが分った。
【０１０２】
実施例５
（ＬｉＮｉ_0.3 Ｍｎ_1.7 Ｏ₄ の製造）
実施例５として、モル比でＬｉ：Ｍｎ：Ｎｉが１：１．７：０．３になるように混合した以外は、実施例４と同様にして製造を行った。
【０１０３】
解析の結果、得られた化合物は、短軸径が５μｍ以下、長軸径が１０μｍ以下、高さが５μｍ以下の相当径を有する針状粒子からなる、スピネル構造のマンガン複合酸化物であった。
【０１０４】
化学分析結果、結晶軸の長さ、及びＢＥＴ比表面積の測定結果を表１に示した。
【０１０５】
実施例６
（ＬｉＦｅ_0.1 Ｍｎ_1.9 Ｏ₄ の製造)
実施例６として、ＬｉＦｅ_0.1 Ｍｎ_1.9 Ｏ₄ を、以下の方法により製造した。
硝酸リチウム( 試薬特級) と、短軸径が１μｍ以下、長軸径が５μｍ以下、高さが１μｍ以下の相当径を有する、針状粒子からなるβ−ＭｎＯ₂ と硝酸鉄の９水和物（試薬特級）をモル比でＬｉ：Ｍｎ：Ｆｅが１：１．９：０．１になるように混合した後、大気中で４５０℃の温度で２４時間、焼成した。
【０１０６】
次に、これを室温まで降温した後に、乳鉢で粉砕、混合した後、大気中で８５０℃の温度で２４時間、焼成した。
【０１０７】
得られた化合物のＸ線回折パターンを図２に、粒子構造の観察結果を図５に、化学分析結果、結晶軸の長さ、及びＢＥＴ比表面積の測定結果を表１に示した。
解析の結果、得られた化合物は、短軸径が５μｍ以下、長軸径が１０μｍ以下、高さが５μｍ以下の相当径を有する針状粒子からなり、結晶軸の長さが８．２０７オングストローム、ＢＥＴ比表面積７．２ｍ² ／ｇの、ＬｉＦｅ_0.1 Ｍｎ_{1. 9O4} で表される、スピネル構造のマンガン複合酸化物であることが分った。
【０１０８】
実施例７
（ＬｉＣｒ_0.2 Ｍｎ_1.9 Ｏ₄ の製造）
実施例７として、ＬｉＣｒ_0.2 Ｍｎ_1.8 Ｏ₄ を、以下の方法により製造した。
硝酸リチウム( 試薬特級) と、短軸径が１μｍ以下、長軸径が５μｍ以下、高さが１μｍ以下の相当径を有する、針状粒子からなるβ−ＭｎＯ2 と硝酸クロムの９水和物（試薬特級）をモル比でＬｉ：Ｍｎ：Ｃｒが１：１．８：０．２になるように混合した後、大気中で４５０℃の温度で２４時間、焼成した。
【０１０９】
次に、これを室温まで降温した後に、乳鉢で粉砕、混合した後、大気中で８５０℃の温度で２４時間、焼成した。
【０１１０】
得られた化合物のＸ線回折パターンを図２に、粒子構造の観察結果を図６に、化学分析結果、結晶軸の長さ、及びＢＥＴ比表面積の測定結果を表１に示した。
解析の結果、得られた化合物は、短軸径が５μｍ以下、長軸径が１０μｍ以下、高さが５μｍ以下の相当径を有する針状粒子からなり、結晶軸の長さが８．２３７オングストローム、ＢＥＴ比表面積８．２ｍ² ／ｇの、ＬｉＣｒ_0.2 Ｍｎ_1.8O4 で表される、スピネル構造のマンガン複合酸化物であることが分った。
【０１１１】
比較例１
（ＬｉＣｏ_0.2 Ｍｎ_1.8 Ｏ₄ の製造）
比較例１として、ＬｉＣｏ_0.2 Ｍｎ_1.8 Ｏ₄ を、以下の方法により製造した。
炭酸リチウム（試薬特級）と、Ｍｎ₃ Ｏ₄ （四三酸化マンガン：試薬特級) と塩基性炭酸コバルト（試薬特級）をモル比でＬｉ：Ｍｎ：Ｃｏが１：１．８：０．２になるように混合した後、大気中で９００℃の温度で１０時間、焼成した。
【０１１２】
得られた化合物のＸ線回折パターンを図２に、粒子構造の観察結果を図７に、化学分析結果、結晶軸の長さ、及びＢＥＴ比表面積の測定結果を表１に示した。
解析の結果、得られた化合物は、一辺の長さが１μｍ以上の正八面体針状粒子からなり、結晶軸の長さが８．２２２オングストローム、ＢＥＴ比表面積０．６ｍ² ／ｇの、ＬｉＣｏ_0.2 Ｍｎ_1.8 Ｏ_3.8 で表される、スピネル構造のマンガン複合酸化物であることが分った。
【０１１３】
比較例２
（ＬｉＣｏ_0.1 Ｍｎ_1.9 Ｏ₄ の製造）
比較例２として、ＬｉＣｏ_0.1 Ｍｎ_1.9 Ｏ₄ を、以下の方法により製造した。
炭酸リチウム（試薬特級）と、Ｍｎ₂ Ｏ₃ （三二酸化マンガン：試薬特級）とＣｏ₂ Ｏ₃ （三二酸化コバルト：試薬特級）をモル比でＬｉ：Ｍｎ：Ｃｏが１：１．９：０．１になるように混合した後、大気中で６５０℃の温度で６時間、焼成した。
【０１１４】
次に、これを室温まで降温した後に、乳鉢で粉砕、混合した後、大気中で８５０℃の温度で２４時間、焼成した。
【０１１５】
得られた化合物のＸ線回折パターンを図２に、粒子構造の観察結果を図８に、化学分析結果、結晶軸の長さ、及びＢＥＴ比表面積の測定結果を表１に示した。
解析の結果、得られた化合物は約０．５μｍの粒子からなり、結晶軸の長さが８．２２９オングストローム、ＢＥＴ比表面積０．７ｍ² ／ｇの、ＬｉＣｏ_0.1Mｎ_1.9 Ｏ₄ で表されるスピネル構造のマンガン複合酸化物であることが分った。
【０１１６】
［電池の構成］
実施例１〜７及び比較例１〜２で製造したマンガン複合酸化物を、導電剤のポリテトラフルオロエチレンとアセチレンブラックとの混合物（商品名：ＴＡＢ−２）を、重量比で２：１の割合で混合した。混合物の７５ｍｇを１ｔｏｎ／cm^{2 の}圧力で、２０ｍｍφのメッシュ（ＳＵＳ ３１６）上にペレット状に成型した後、２００℃で５時間、減圧乾燥処理を行った。
【０１１７】
これを、図１の３の正極に用いて、図１の５の負極にはリチウム箔( 厚さ０．２ｍｍ) から切り抜いたリチウム片を用いて、電解液にはプロピレンカーボネートに過塩素酸リチウムを１ｍｏｌ／ｄｍ³ の濃度で溶解したものを図１の４のセパレータに含浸させて、断面積２．５ｃｍ² の図１に示した電池を構成した。
【０１１８】
［電池性能の評価］
上記方法で作成した電池を用いて、１．０ｍＡ／ｃｍ² の一定電流で、電池電圧が４．５Ｖから３．５Ｖの間で充放電を繰り返した。
【０１１９】
１サイクル目の放電容量に対する５０サイクル目の放電容量の割合、即ち容量維持率を、表１に示した。
【０１２０】
実施例１〜７で製造したマンガン複合酸化物は、いずれも９５％以上の高い維持率を示したが、比較例１〜２で製造したマンガン複合酸化物は、いずれも９０％以下であった。
【０１２１】
【発明の効果】
以上述べてきたとおり、本発明者らの検討によって、針状粒子からなるγ−ＭｎＯＯＨ又は針状粒子からなるβ−ＭｎＯ2 と、リチウム化合物と、Ｎｉ，Ｃｏ，Ｆｅ，Ｃｒから選ばれる少なくとも１種類以上の金属材料との混合物を焼成することで、針状粒子からなり、結晶構造がスピネル型で、化学式ＬｉＭ_X Ｍｎ_2-XO4 （式中ＭはＮｉ，Ｃｏ，Ｆｅ，Ｃｒから選ばれる少なくとも１種類以上であり、０＜ｘ≦０．５）で表される新規なマンガン複合酸化物が合成できることを見いだし、さらに、これをリチウム二次電池の正極活物質に用いることで、従来にはない、サイクル特性の優れたマンガン系リチウム二次電池が構成できることを見いだした。
【０１２２】
リチウム二次電池正極活物質に適用可能なマンガン系正極材料を見いだしたことは、産業上有益な知見である。
【図面の簡単な説明】
【図１】実施例及び比較例で構成した電池の実施態様を示す断面図である。
【符号の説明】
１ 正極リード線
２ 正極集電用メッシュ
３ 正極
４ セパレータ
５ 負極
６ 負極集電用メッシュ
７ 負極用リード線
８ 容器
【図２】実施例１、実施例４、実施例６から７、比較例１から２で製造したマンガン複合酸化物の、Ｘ線回折図を示す図である。
【図３】実施例１で製造したマンガン複合酸化物の粒子構造を示す写真である。
【図４】実施例４で製造したマンガン複合酸化物の粒子構造を示す写真である。
【図５】実施例６で製造したマンガン複合酸化物の粒子構造を示す写真である。
【図６】実施例７で製造したマンガン複合酸化物の粒子構造を示す写真である。
【図７】比較例１で製造したマンガン複合酸化物の粒子構造を示す写真である。
【図８】比較例２で製造したマンガン複合酸化物の粒子構造を示す写真である。[0001]
[Industrial application fields]
The present invention relates to a novel manganese composite oxide, and more specifically, is composed of acicular particles, the crystal structure is spinel type, and the chemical formula LiM_xMn_2-XO_Four(Wherein M is at least one selected from Ni, Co, Fe, and Cr, and 0 <x ≦ 0.5), a method for producing the acicular manganese composite oxide, and the acicular manganese composite The present invention relates to a lithium secondary battery using an oxide as a positive electrode active material.
[0002]
Manganese composite oxides are the material that attracts the most attention among the positive electrode active material materials for lithium secondary batteries because they are inexpensive, abundant in raw material manganese, and easy to synthesize.
[0003]
Lithium secondary batteries can theoretically constitute batteries with high energy density, so R & D aimed at higher performance, including some that have already been put into practical use as new secondary batteries that will lead the next generation Is being actively promoted.
[0004]
[Prior art]
With the widespread use of cordless devices for personal use, there is a strong demand for the development of lithium secondary batteries that are small, lightweight, and have high energy density.
[0005]
Recently, for the purpose of ensuring safety, lithium ion type using a compound capable of occluding and releasing lithium ions, such as carbonaceous materials and metal oxides, without using lithium metal or lithium alloy for the negative electrode Development of secondary batteries is actively underway. For this reason, it is necessary to use a compound containing lithium as the positive electrode active material.
[0006]
Currently, as a lithium-containing compound, LiMO has a layered structure in which the basic skeleton has a rock salt structure and lithium and transition metals are regularly arranged.₂A type oxide (where M is a transition metal) has attracted attention. Among them, lithium cobalt oxide (hereinafter referred to as LiCoO)₂Is written. ) And lithium nickel oxide (hereinafter LiNiO)₂Is written. ) Shows a battery voltage of 4V class, and research and development are being actively promoted including some practical applications.
[0007]
However, LiCoO₂With regard to the above, the fact that the cobalt raw material is expensive, LiNiO₂In regard to, the problem that synthesis is difficult has already been pointed out.
[0008]
In addition to the above two materials, a material exhibiting a 4V class battery voltage may be a spinel type lithium manganese spinel (hereinafter referred to as LiMn).₂O_FourIs written. )It has been known.
[0009]
LiMn₂O_FourIs easy to synthesize, and since the manganese raw material is abundant in resources and inexpensive, LiCoO₂And LiNiO₂It is expected as an alternative material.
[0010]
LiMn₂O_FourIs a spinel structure in which the spinel 8a site is occupied by lithium, the 16d site is occupied by manganese, and the 32e site is occupied by oxygen.
[0011]
In other words, it has a structure in which 1/8 of the tetrahedral position of cubic close-packed oxygen is occupied by lithium and 1/2 of the octahedral position is occupied by manganese.
[0012]
This LiMn₂O_FourIs used as a positive electrode active material for lithium secondary batteries, it has been clarified that there are regions that operate at a voltage of about 4V and regions that operate at a voltage of about 3V (Ogura et al., 29th Battery Discussion Meeting Abstracts, P135, 1988).
[0013]
In the region that functions at a voltage of about 4 V, LiMn₂O_FourWithout breaking the structure in a state where the lithium ions in the crystal lattice move through the lithium-occupied sites in the crystal structure via the 16c sites at the empty oxygen octahedron position and maintain the cubic structure of the original skeleton structure Incoming and outgoing reactions progress.
[0014]
On the other hand, in a region that functions at a voltage of about 3 V, LiMn₂O_FourA reaction in which lithium ions enter and exit the 16c site of the empty oxygen octahedron position in the crystal lattice with a change of the crystal structure from cubic to tetragonal.
[0015]
Of the two reactions described above, in order to construct a lithium secondary battery having a high energy density, it is important to use a region showing a voltage of about 4V.
[0016]
LiMn in the region showing a voltage of about 4V₂O_FourAs described above, the charge / discharge reaction proceeds in a state in which the cubic structure of the basic skeleton is maintained without changing the crystal system, as described above. Many proposals for application to batteries have been made so far. LiMn by these proposals₂O_FourHowever, a secondary battery having a high energy density cannot be constructed and has not yet been put into practical use.
[0017]
LiMn in the region showing a voltage of about 4V₂O_FourWhen the is functioned, the charge / discharge reaction proceeds in a state where the cubic structure is maintained, but due to the oxidation / reduction of manganese and the entry / exit of lithium ions, the crystal lattice expands and contracts slightly.
[0018]
According to the study by the present inventors, LiMn₂O_FourIs a charge / discharge cycle, that is, when the volume change due to expansion / contraction of the crystal lattice is repeated, the local crystal structure collapses, the particles become finer, and the conductivity decreases with the finer. Furthermore, the conductivity is reduced due to poor contact with the conductive additive (for example, acetylene black, graphite, etc.), and therefore the capacity is reduced due to the charge / discharge cycle.
Furthermore, when charging / discharging at a high charge / discharge rate, LiMn is observed in a region showing a voltage of about 4V₂O_FourEven if the discharge voltage is regulated so as to function, the charge / discharge is repeated, so that the utilization factor of the positive electrode active material becomes non-uniform due to a decrease in the conductivity of the positive electrode and the like, and a region showing a voltage of about 3 V in part It is considered that the reduction proceeds until the crystal structure transition occurs, the decrease in the conductivity is accelerated, and the reversibility is significantly decreased.
[0019]
For the above reasons, LiMn₂O_FourA high-performance lithium secondary battery using as a positive electrode has not yet been put into practical use.
[0020]
As a method for solving this problem, a method of substituting a part of manganese with another element has been proposed.
[0021]
For example, in JP-A-3-219571 and JP-A-4-160769, Li is obtained by substituting a part of manganese with at least one of Co, Cr, and Fe._XM_YMn_(2-Y)O_Four(0.85 ≦ x ≦ 1.15, 0.02 ≦ y ≦ 0.5) is proposed.
[0022]
In these proposals, by replacing a part of manganese with Co, Cr, and Fe, the lattice constant is reduced and the crystal structure is strengthened, so that the crystal structure is destroyed, that is, the discharge capacity is reduced. The purpose is to prevent.
[0023]
However, strengthening the crystal structure reduces the flexibility of the volume change of the crystal lattice due to the charge / discharge reaction, and although the deterioration rate can be reduced, the discharge capacity still decreases. Is difficult to prevent.
[0024]
Furthermore, in all of these proposals, the synthesis is performed at 900 ° C., and the particles of the compound obtained at this temperature are large. Therefore, when used as a positive electrode active material, the particles are easily refined by charge / discharge. Therefore, the capacity is likely to decrease.
[0025]
On the other hand, in JP-A-5-36412, LiA in which a part of manganese is substituted with at least one of Fe and Cr._XMn_(2-X)O_Four(0.1 ≦ x ≦ 0.4), and in the case of Fe, heat treatment is proposed at a temperature of 650 ° C. to 800 ° C., and in the case of Cr, heat treatment is performed at a temperature of 650 ° C. to 850 ° C.
[0026]
However, in this proposal, the manganese raw material is Mn₂O_ThreeAccording to the study by the present inventors, Mn₂O_ThreeWhen the synthesis is carried out at a temperature of 650 ° C. or higher, the particle size of the resulting compound is large, and the particles are easily refined by charge / discharge, and the capacity is likely to decrease.
[0027]
As described above, LiMn, which has been proposed so far₂O_FourA compound obtained by substituting a part of manganese with other elements has insufficient cycle characteristics when used as a positive electrode active material of a lithium secondary battery, and has not been put into practical use so far.
[0028]
On the other hand, with the widespread use of cordless devices for personal use, there is a strong demand for development of lithium secondary batteries that are small, light, and have high energy density.
[0029]
To date, LiCoO has been used as the positive electrode active material.₂Ion-type lithium secondary batteries using a carbonaceous material for the negative electrode and a non-aqueous electrolyte for the electrolyte have been put into practical use, but they are widely used as consumer power sources and on-site power storage power sources. In order to make it popular, development of a cheaper and more stable lithium secondary battery is desired.
[0030]
[Problems to be solved by the invention]
The object of the present invention is to provide a novel LiMn₂O_FourProposing a compound in which a part of manganese is substituted with another element and a method for producing the same, and further providing a manganese-based lithium secondary battery having excellent cycle characteristics using this compound as a positive electrode active material .
[0031]
[Means for Solving the Problems]
As a result of intensive studies aimed at solving the above-mentioned problems, the present inventors have found that γ-MnOOH composed of acicular particles or β-MnO composed of acicular particles.₂And a mixture of a lithium compound and at least one metal material selected from Ni, Co, Fe, and Cr to form needle-like particles, the crystal structure is spinel, and the chemical formula LiM_XMn_2-XO_FourIt has been found that a novel manganese composite oxide represented by (wherein M is at least one selected from Ni, Co, Fe, Cr and 0 <x ≦ 0.5) can be synthesized. Furthermore, by using this as a positive electrode active material for a lithium secondary battery, it has been found that a manganese-based lithium secondary battery with excellent cycle characteristics, which has not been heretofore, can be constructed, and the present invention has been completed.
[0032]
[Action]
Hereinafter, the present invention will be specifically described.
[0033]
The chemical formula LiM of the present invention_XMn_2-XO_Four(Wherein M is at least one selected from Ni, Co, Fe, and Cr, and 0 <x ≦ 0.5), the manganese composite oxide represented by the tetrahedral position of cubic close-packed oxygen This is a manganese composite oxide having a spinel structure in which 1/8 is occupied by lithium and 1/2 of the octahedral position is occupied by manganese and at least one metal selected from Ni, Co, Fe, and Cr.
[0034]
The manganese composite oxide of the present invention has a LiMn whose diffraction peak position is shifted to the high angle side.₂O_FourSimilar X-ray diffraction patterns are shown. That is, the crystal lattice is LiMn_2O4This is a smaller manganese composite oxide.
[0035]
According to the inventors' investigation, depending on the valence and ion size of the substituted metal, LiMn₂O_FourIt becomes a manganese complex oxide having a smaller crystal lattice.
[0036]
When a part of manganese is substituted with Ni, the stable phase as an oxide of Ni is NiO. Therefore, Ni substitutes a part of manganese as +2 valence, and +3 valent manganese in the compound becomes +4 valence. Oxidation causes shrinkage of the crystal lattice.
[0037]
When substituted with Co, the stable phase as an oxide of Co is CoO or Co._ThreeO_{Four so}For this reason, a part of Co is replaced with a part of manganese as +2 or +3. In the case of substitution as +2 valence, the effect is obtained when +3 valence manganese is oxidized to +4 valence, and in the case of substitution as +3 valence, the effect of substitution with Co having a smaller ionic radius than manganese, In both mixed types, crystal lattice shrinkage occurs.
[0038]
When substituted with Fe and Cr, the stable phase as an oxide is Fe₂O_ThreeAnd Cr₂O_ThreeTherefore, each of them is substituted with a part of manganese as +3 valence. Shrinkage of the crystal lattice occurs due to the effect of substitution with Fe and Cr having an ionic radius smaller than that of manganese.
[0039]
Due to the above effects, the crystal lattice becomes LiMn.₂O_FourIt will be smaller.
[0040]
Furthermore, from the above, the rate of crystal lattice shrinkage due to the amount of substitution varies depending on the type of metal material to be substituted and the amount of substitution.
[0041]
In addition to Ni, Co, Fe, and Cr, there are metals with smaller ionic radii than manganese and metals that form +2 valent and stable oxides, but if the ionic radius is too small, they penetrate into the lithium site. In addition, even if it is +2 valence, if the ion radius is too large, the substitution reaction is unlikely to occur. Therefore, Ni, Co, Fe, and Cr proposed this time are considered to be the most excellent substitution metals.
[0042]
The manganese composite oxide of the present invention has a crystal lattice of LiMn₂O_FourAlthough it is a smaller compound, it is considered that the following effects can be obtained by reducing the crystal lattice.
Substituting a part of manganese with at least one of Ni, Co, Fe, and Cr basically reduces the amount of trivalent manganese in the compound. When functioning at a voltage of about 4 V, By reducing the amount of manganese involved in the oxidation-reduction reaction, in other words, by limiting the amount of charge / discharge reaction, it is considered that the amount of expansion / contraction of the crystal lattice is reduced and the cycle characteristics are improved.
[0043]
Furthermore, according to the study by the present inventors, by replacing a part of manganese with at least one of Ni, Co, Fe, and Cr, a compound having a uniformly developed crystal structure is obtained. Even when charging / discharging at a rate, the charge / discharge reaction proceeds uniformly throughout the active material, and if the discharge voltage is regulated so that it functions in a region showing a voltage of about 4V, the region showing a voltage of about 3V is reached. It will function reversibly without a reduction reaction.
[0044]
The size of the crystal lattice is preferably less than 8.24 angstroms, and more specifically, less than 8.24 angstroms and more preferably 8.10 angstroms or more.
[0045]
This is because when the crystal lattice size is 8.24 angstroms or more, when used as the positive electrode active material of a lithium secondary battery, the crystal lattice expands and contracts due to charge / discharge, and the collapse of the crystal structure is promoted. To do.
[0046]
On the other hand, if the crystal lattice is less than 8.24 angstroms, the expansion / contraction of the crystal lattice accompanying charge / discharge is reduced, and the cycle characteristics are improved.
[0047]
If the crystal lattice becomes too small, it becomes difficult for lithium to diffuse into the solid phase, and therefore, the crystal lattice is easily broken along with charge and discharge.
[0048]
According to the study by the present inventors, it was found that when a high-power type lithium secondary battery is configured, 8.10 angstroms or more is preferable.
[0049]
The substitution amount at the time of substitution with at least one of Ni, Co, Fe, and Cr is expressed by the chemical formula LiM._XMn_2-XO_FourThe value of x in the case of being expressed by the formula is required to be 0 or more and 0.5 or less, and more specifically 0.05 or more and 0.2 or less is more preferable.
[0050]
This is because when the value of x exceeds 0.5, as described above, the crystal lattice of the resulting compound becomes too small, and the synthesis of the spinel single-phase compound becomes difficult.
[0051]
When a high-capacity lithium secondary battery is configured, it is more preferable that the value of x is 0.05 or more and 0.2 or less because it is necessary to achieve both charge / discharge capacity and cycle characteristics.
[0052]
The chemical formula LiM of the present invention_XMn_2-XO_Four(In the formula, M is at least one selected from Ni, Co, Fe, and Cr, and 0 <x ≦ 0.5), and the manganese composite oxide represented by acicular particle form is essential. And
[0053]
Although details are unknown, since it is acicular particles, when used as the positive electrode active material of a lithium secondary battery, it becomes easier to absorb the expansion and contraction of the crystal lattice accompanying charge and discharge between the particles, It is considered that the decrease in conductivity due to poor contact can be suppressed.
[0054]
The particle shape is not particularly limited as long as it is needle-like, but more specifically, needle-like particles having an equivalent diameter having a minor axis diameter of 5 μm or less, a major axis diameter of 10 μm or less, and a height of 5 μm or less are more preferable.
[0055]
When acicular particles having a short axis diameter of 5 μm or less, a major axis diameter of 10 μm or less, and a height of 5 μm or less are used as the positive electrode active material of a lithium secondary battery, Shrinkage is more easily absorbed between particles.
[0056]
Incidentally, the equivalent diameter used by the present inventors is a definition of Heywood in which one particle is stably placed on a horizontal plane and the shape of the particle is displayed with the lengths of three orthogonal axes. (See Yasuo Arai, Powder Material Chemistry, Bafukan).
[0057]
The chemical formula LiM of the present invention_XMn_2-XO_Four(Wherein M is at least one selected from Ni, Co, Fe, and Cr, and 0 <x ≦ 0.5), the size of the surface area of the manganese composite oxide is not particularly limited.₂The value of BET specific surface area by gas adsorption method is 5m²/ G or more, more specifically 5 m²/ M or more 10m²/ G or less is more preferable.
[0058]
BET specific surface area is 5m²/ G or more of the compound used as the positive electrode active material of the lithium secondary battery improves the contact with the conductive additive and the electrolytic solution, and even when charging / discharging at a high charge / discharge rate, the charge / discharge reaction is performed throughout the active material. Thus, a secondary battery having a high capacity type and excellent cycle characteristics can be constructed.
[0059]
Considering the filling property as the positive electrode active material, the value of the BET specific surface area is 10 m.²By limiting to / g or less, the filling property as the positive electrode material can be maintained, and a high-capacity type secondary battery can be configured.
[0060]
In the method for producing a manganese composite oxide of the present invention, acicular γ-MnOOH or acicular β-MnO₂It is essential to use as a manganese source.
[0061]
Γ-MnOOH composed of acicular particles or β-MnO composed of acicular particles₂By using as a manganese source, the reaction proceeds uniformly, particle growth is remarkably suppressed, and a manganese composite oxide having a uniform composition can be synthesized.
[0062]
Although details of the mechanism of this reaction are not clear, it is considered as follows.
Γ-MnOOH composed of acicular particles used in the present invention is easily transferred to β-type manganese dioxide having a rutile crystal structure at a temperature of about 300 ° C. or higher in the presence of oxygen. Since this transition occurs easily and quickly, the particle shape remains acicular particles.
[0063]
Manganese dioxide having a β-type crystal structure has a (1 × 1) channel structure, and since a diffusion path to the inside of the lithium crystal is secured, the reaction is easy when reacted with a lithium compound. It is thought to progress. Further, although the reason is unknown, it is considered that since the particle shape is needle-shaped, the composite with the metal material easily proceeds, and a manganese composite oxide having a uniform composition is easily generated.
[0064]
Regarding the thermal phase transition of manganese oxide that occurs during firing, the change from the rutile structure to the spinel skeleton structure is very rapid. M.M. (Revue De Chimi Mineral vol. 21, 55 (1984)), it is considered that the reaction proceeds easily from this.
[0065]
In addition, since the reaction is easy to proceed, the growth of the particles due to the compositional deviation of manganese, metal, and lithium on the particle surface and inside is suppressed, and the reaction is performed while maintaining the needle-like particle shape of the starting manganese species. It is thought to go forward.
[0066]
From the synergistic effect described above, it is considered that a manganese composite oxide having a uniform particle shape and a uniform composition is easily generated.
[0067]
Β-MnO made of acicular particles as starting manganese raw material₂Even when γ is used, the same effect as that in the case of using γ-MnOOH composed of acicular particles is observed, and a manganese composite oxide having a uniform particle shape and a uniform composition is generated.
[0068]
In the case where γ-MnOOH or β-MnO2 composed of needle-like particles having a short axis diameter of 1 μm or less, a major axis diameter of 5 μm or less, and a height of 1 μm or less is used as a manganese starting material, Further, the reaction is easy to proceed, and it becomes possible to synthesize a manganese composite oxide composed of needle-like particles having a short axis diameter of 5 μm or less, a long axis diameter of 10 μm or less, and a height of 5 μm or less. As described above, when this manganese composite oxide is used as the positive electrode active material of a lithium secondary battery, a battery with more excellent cycle characteristics can be configured, which is more preferable.
[0069]
The γ-MnOOH composed of acicular particles used in the present invention is, for example, a method reported by Owen Bricker, that is, manganese hydroxide (Mn (OH)₂) Hydrogen peroxide (H₂O₂) (The American Mineralologist vol. 50, p. 1296 (1965)), K. The method reported by Matsuki et al. (Electrochimica Actavol. 31, p. 13 (1986)), that is, at a temperature of 20 ° C. or lower, manganese sulfate (MnSO_Four) And hydrogen peroxide mixture with ammonia (NH_FourOH) can be obtained.
[0070]
Β-MnO composed of acicular particles used in the present invention₂Can be produced using the method disclosed in JP-A-63-30323.
[0071]
It is composed of needle-shaped particles of the present invention and has a crystal structure of spinel type, chemical formula LiM_XMn_2-XO_Four(Wherein M is at least one selected from Ni, Co, Fe, and Cr, and 0 <x ≦ 0.5), the lithium material used for producing the acicular manganese composite oxide is lithium and Any lithium compound may be used. For example, lithium metal, lithium hydroxide, lithium oxide, lithium carbonate, lithium iodide, lithium nitrate, lithium oxalate, alkyl lithium, etc. are exemplified, preferably those that melt at a temperature of 500 ° C. or less, In particular, lithium nitrate is more preferable.
[0072]
It is composed of needle-shaped particles of the present invention and has a crystal structure of spinel type, chemical formula LiM_xMn_2-XO_Four(Wherein M is at least one selected from Ni, Co, Fe and Cr, and 0 <X ≦ 0.5), the metal material used for producing the acicular manganese composite oxide is a metal and Any metal compound may be used as long as it is a metal compound. Examples include metals, metal hydroxides, metal oxides, metal carbonates, metal nitrates, organometallic complexes, etc., preferably those that melt at a temperature of 500 ° C. or less, Particularly preferred are metal nitrates.
[0073]
Needle-like γ-MnOOH or needle-like β-MnO₂And lithium compounds, Ni,
The method for mixing at least one metal material selected from Co, Fe, and Cr is not particularly limited, and may be mixed in a solid phase and / or a liquid phase. For example, the above raw material powder is mixed in a dry and / or wet manner, or acicular γ-MnOOH or acicular β-MnO2 is added to a solution in which a lithium compound and a metal material are dissolved and / or suspended. And a method of mixing by stirring.
[0074]
Needle-like γ-MnOOH or needle-like β-MnO₂The method of firing the manganese composite oxide for firing a mixture of at least one metal material selected from Ni, Co, Fe, and Cr is not particularly limited. In addition, after the first heat treatment is performed at a temperature of 500 ° C. or lower in oxygen, the second heat treatment is preferably performed at a temperature higher than 500 ° C. and lower than 850 ° C.
[0075]
According to the study by the present inventors, the complexing reaction proceeds on the low temperature side at 500 ° C., and the development of the spinel structure occurs on the high temperature side. Therefore, a manganese composite oxide having a more uniform composition and having a developed spinel structure can be synthesized by first carrying out a complexing reaction sufficiently in the first heat treatment and then performing a crystal growth reaction in the second heat treatment. Furthermore, the complexing reaction is further promoted by performing the first heat treatment in the atmosphere and / or oxygen.
[0076]
Note that, when the second heat treatment is performed at a temperature exceeding 850 ° C., particle growth and manganese reduction reaction are likely to occur.
[0077]
In addition, although it does not restrict | limit in particular regarding baking time, 10 hours or more are preferable for both 1st heat processing and 2nd heat processing.
[0078]
As the negative electrode of the lithium secondary battery of the present invention, lithium metal, a lithium alloy, or a compound capable of occluding and releasing lithium can be used. Examples of the lithium alloy include a lithium / tin alloy, a lithium / aluminum alloy, and a lithium / lead alloy. Examples of compounds capable of occluding and releasing lithium include carbonaceous materials such as graphite and graphite, FeO, Fe₂O_Three, Fe_ThreeO_FourIron oxide such as CoO, Co₂O_Three, Co_ThreeO_FourAn oxide such as cobalt oxide is exemplified.
[0079]
The electrolyte of the lithium secondary battery of the present invention is not particularly limited, and examples thereof include carbonates such as propylene carbonate and diethyl carbonate, sulfolanes such as sulfolane and dimethyl sulfoxide, lactones such as γ-butyrolactone, and dimethoxyethane. Dissolve at least one lithium salt such as lithium perchlorate, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium trifluoromethanesulfonate in at least one organic solvent such as ethers Inorganic or organic lithium ion conductive solid electrolytes can be used. The battery shown in FIG. 1 was constructed using the manganese composite oxide positive electrode active material obtained in the present invention.
[0080]
In the figure, 1: lead wire for positive electrode, 2: mesh for positive electrode current collector, 3: positive electrode, 4: separator, 5: negative electrode, 6: mesh for negative electrode current collector, 7: lead wire for negative electrode, 8: container, Indicates.
[0081]
Examples are shown below as specific examples of the present invention, but the present invention is not limited to these examples.
[0082]
【Example】
In addition, the X-ray-diffraction measurement in the Example and comparative example of this invention, observation of a particle structure, and the measurement of a specific surface area were performed with the following method.
[0083]

[0084]
Further, the length of the crystal axis was determined from the X-ray diffraction measurement data of each compound by the WPPD method (Whole-Powder-Pattern Decomposition Method).
[0085]
Furthermore, composition analysis was measured by ICP emission spectrometry.
[0086]
[Manufacture of manganese composite oxide]
Example 1
(LiCo_0.1Mn_1.9O_FourManufacturing of)
As Example 1, LiCo_0.1Mn_1.9O_FourWas produced by the following method.
Lithium nitrate (special grade reagent), γ-MnOOH (manufactured by Tosoh Corporation) and cobalt nitrate having an equivalent diameter of a minor axis diameter of 1 μm or less, a major axis diameter of 5 μm or less, and a height of 1 μm or less Hexahydrate (special reagent grade) was mixed at a molar ratio of Li: Mn: Co of 1: 1.9: 0.1, and then calcined in the atmosphere at a temperature of 450 ° C. for 24 hours.
[0087]
Next, this was cooled to room temperature, pulverized and mixed in a mortar, and then baked in the atmosphere at a temperature of 650 ° C. for 24 hours.
[0088]
The X-ray diffraction pattern of the obtained compound is shown in FIG. 2, the observation result of the particle structure is shown in FIG. 3, and the chemical analysis result, the length of the crystal axis, and the measurement result of the BET specific surface area are shown in Table 1.
[0089]
[Table 1]

[0090]
As a result of the analysis, the obtained compound was composed of needle-like particles having a short axis diameter of 5 μm or less, a long axis diameter of 10 μm or less, and a height of 5 μm or less, and the crystal axis length was 8.217 angstroms. , BET specific surface area 6.5m²/ G LiCo_0.1Mn_{1. 9
O3.9}It was found that this is a manganese composite oxide having a spinel structure represented by
[0091]
Example 2
(LiCo_0.2Mn_1.8O_FourManufacturing of)
As Example 2, production was carried out in the same manner as in Example 1 except that Li: Mn: Co was mixed at a molar ratio of 1: 1.8: 0.2.
[0092]
As a result of analysis, the obtained compound was a manganese composite oxide having a spinel structure composed of needle-like particles having a short axis diameter of 5 μm or less, a long axis diameter of 10 μm or less, and a height of 5 μm or less. .
[0093]
The results of chemical analysis, crystal axis length, and BET specific surface area are shown in Table 1.
[0094]
Example 3
(LiCo_0.3Mn_1.7O_FourManufacturing of)
As Example 3, β-MnO made of acicular particles having an equivalent diameter of a minor axis diameter of 1 μm or less, a major axis diameter of 5 μm or less, and a height of 1 μm or less is used as a manganese raw material.₂The mixture was mixed so that the molar ratio of Li: Mn: Co was 1: 1.7: 0.3, the second baking temperature was 750 ° C., and the production was performed in the same manner as in Example 1. It was.
[0095]
Note that β-MnO composed of acicular particles₂Was created by the following method.
[0096]
100 g of γ-MnOOH (manufactured by Tosoh Corporation) consisting of acicular particles having a short axis diameter of 1 μm or less, a long axis diameter of 5 μm or less, and a height of 1 μm or less and concentrated nitric acid (specific gravity = 1.3) ) 10 ml was mixed and heat-treated at a temperature of 200 ° C. for 8 hours. The product was crushed in a mortar and washed with hot water. From X-ray diffraction measurements, this product is β-MnO.₂Was identified. Furthermore, as a result of observing the particle structure, it was an acicular particle having a short axis diameter of 1 μm or less, a long axis diameter of 5 μm or less, and a height of 1 μm or less.
[0097]
As a result of analysis of the manufactured manganese composite oxide, the obtained compound has a spinel structure composed of needle-like particles having a short axis diameter of 5 μm or less, a long axis diameter of 10 μm or less, and a height of 5 μm or less. It was a manganese composite oxide.
[0098]
The results of chemical analysis, crystal axis length, and BET specific surface area are shown in Table 1.
[0099]
Example 4
(LiNi_0.1Mn_0.9O_FourManufacturing of)
As Example 4, LiNi_0.1Mn_1.9O_FourWas produced by the following method.
Lithium nitrate (special grade reagent), γ-MnOOH (manufactured by Tosoh Corporation) and nickel nitrate having an equivalent diameter with a minor axis diameter of 1 μm or less, a major axis diameter of 5 μm or less, and a height of 1 μm or less Hexahydrate (special grade reagent) was mixed at a molar ratio of Li: Mn: Ni of 1: 1.9: 0.1, and then calcined in the atmosphere at a temperature of 450 ° C. for 24 hours.
[0100]
Next, this was cooled to room temperature, pulverized and mixed in a mortar, and then baked in the atmosphere at a temperature of 650 ° C. for 24 hours.
[0101]
The X-ray diffraction pattern of the obtained compound is shown in FIG. 2, the observation result of the particle structure is shown in FIG. 4, and the chemical analysis result, the length of the crystal axis, and the measurement result of the BET specific surface area are shown in Table 1.
As a result of analysis, the obtained compound was composed of needle-like particles having a short axis diameter of 5 μm or less, a long axis diameter of 10 μm or less, and a height of 5 μm or less, and the crystal axis length was 8.228 angstroms. , BET specific surface area 6.3m²/ G LiNi_0.1Mn_1.9O4.0It was found that this is a manganese composite oxide having a spinel structure represented by
[0102]
Example 5
(LiNi_0.3Mn_1.7O_FourManufacturing of)
As Example 5, it manufactured like Example 4 except having mixed so that Li: Mn: Ni might be set to 1: 1.7: 0.3 by molar ratio.
[0103]
As a result of analysis, the obtained compound was a manganese composite oxide having a spinel structure composed of needle-like particles having a short axis diameter of 5 μm or less, a long axis diameter of 10 μm or less, and a height of 5 μm or less. .
[0104]
The results of chemical analysis, crystal axis length, and BET specific surface area are shown in Table 1.
[0105]
Example 6
(LiFe_0.1Mn_1.9O_FourManufacturing of)
As Example 6, LiFe_0.1Mn_1.9O_FourWas produced by the following method.
Β-MnO composed of needle-shaped particles having lithium nitrate (special grade reagent) and an equivalent diameter having a minor axis diameter of 1 μm or less, a major axis diameter of 5 μm or less, and a height of 1 μm or less₂And iron nitrate nonahydrate (special grade reagent) are mixed so that the molar ratio of Li: Mn: Fe is 1: 1.9: 0.1, and then is 24 hours at a temperature of 450 ° C. in the atmosphere. Baked.
[0106]
Next, this was cooled to room temperature, pulverized and mixed in a mortar, and then baked in the atmosphere at a temperature of 850 ° C. for 24 hours.
[0107]
The X-ray diffraction pattern of the obtained compound is shown in FIG. 2, the observation result of the particle structure is shown in FIG. 5, and the chemical analysis result, the length of the crystal axis, and the measurement result of the BET specific surface area are shown in Table 1.
As a result of analysis, the obtained compound is composed of needle-like particles having a short axis diameter of 5 μm or less, a long axis diameter of 10 μm or less, and a height of 5 μm or less, and the crystal axis length is 8.207 angstroms. , BET specific surface area 7.2m²/ G LiFe_0.1Mn_{1. 9O4}It was found that this is a manganese composite oxide having a spinel structure represented by
[0108]
Example 7
(LiCr_0.2Mn_1.9O_FourManufacturing of)
As Example 7, LiCr_0.2Mn_1.8O_FourWas produced by the following method.
Lithium nitrate (special grade reagent) and β-MnO2 consisting of acicular particles with a minor axis diameter of 1 μm or less, a major axis diameter of 5 μm or less, and a height of 1 μm or less, and chromium nitrate nonahydrate ( The reagent special grade was mixed at a molar ratio of Li: Mn: Cr of 1: 1.8: 0.2, and then calcined in the atmosphere at a temperature of 450 ° C. for 24 hours.
[0109]
Next, this was cooled to room temperature, pulverized and mixed in a mortar, and then baked in the atmosphere at a temperature of 850 ° C. for 24 hours.
[0110]
The X-ray diffraction pattern of the obtained compound is shown in FIG. 2, the observation result of the particle structure is shown in FIG. 6, and the chemical analysis result, the length of the crystal axis, and the measurement result of the BET specific surface area are shown in Table 1.
As a result of analysis, the obtained compound was composed of needle-like particles having a short axis diameter of 5 μm or less, a long axis diameter of 10 μm or less, and a height of 5 μm or less, and the crystal axis length was 8.237 angstroms. , BET specific surface area 8.2m²/ G LiCr_0.2Mn_1.8O4It was found that this is a manganese composite oxide having a spinel structure represented by
[0111]
Comparative Example 1
(LiCo_0.2Mn_1.8O_FourManufacturing of)
As Comparative Example 1, LiCo_0.2Mn_1.8O_FourWas produced by the following method.
Lithium carbonate (special grade reagent) and Mn_ThreeO_Four(Trimanganese tetraoxide: special reagent grade) and basic cobalt carbonate (special reagent grade) were mixed at a molar ratio of Li: Mn: Co of 1: 1.8: 0.2, and then 900 ° C. in the atmosphere. Baked at a temperature of 10 hours.
[0112]
The X-ray diffraction pattern of the obtained compound is shown in FIG. 2, the observation result of the particle structure is shown in FIG. 7, and the chemical analysis result, the length of the crystal axis, and the measurement result of the BET specific surface area are shown in Table 1.
As a result of analysis, the obtained compound was composed of octahedral needle-like particles having a side length of 1 μm or more, a crystal axis length of 8.222 angstroms, and a BET specific surface area of 0.6 m.²/ G LiCo_0.2Mn_1.8O_3.8It was found that this is a manganese composite oxide having a spinel structure represented by
[0113]
Comparative Example 2
(LiCo_0.1Mn_1.9O_FourManufacturing of)
As Comparative Example 2, LiCo_0.1Mn_1.9O_FourWas produced by the following method.
Lithium carbonate (special grade reagent) and Mn₂O_Three(Manganese sesquioxide: reagent grade) and Co₂O_Three(Cobalt sesquioxide: special grade reagent) was mixed at a molar ratio of Li: Mn: Co of 1: 1.9: 0.1, and then fired in the atmosphere at a temperature of 650 ° C. for 6 hours.
[0114]
Next, this was cooled to room temperature, pulverized and mixed in a mortar, and then baked in the atmosphere at a temperature of 850 ° C. for 24 hours.
[0115]
The X-ray diffraction pattern of the obtained compound is shown in FIG. 2, the observation result of the particle structure is shown in FIG. 8, and the chemical analysis result, the length of the crystal axis, and the measurement result of the BET specific surface area are shown in Table 1.
As a result of analysis, the obtained compound was composed of particles of about 0.5 μm, the crystal axis length was 8.229 angstroms, and the BET specific surface area was 0.7 m.²/ G LiCo_0.1Mn_1.9O_FourIt was found that the manganese composite oxide has a spinel structure represented by
[0116]
[Battery configuration]
A mixture (trade name: TAB-2) of polytetrafluoroethylene and acetylene black as a conductive agent was used for the manganese composite oxides produced in Examples 1 to 7 and Comparative Examples 1 and 2 at a weight ratio of 2: 1. Mixed in proportion. 75 mg of the mixture is 1 ton / cm^{2 of}After forming into a pellet on a 20 mmφ mesh (SUS 316) with pressure, a vacuum drying treatment was performed at 200 ° C. for 5 hours.
[0117]
This was used for the positive electrode 3 in FIG. 1, and for the negative electrode 5 in FIG. 1, a lithium piece cut out from a lithium foil (thickness 0.2 mm) was used. As the electrolyte, propylene carbonate and lithium perchlorate were used. 1 mol / dm^Three1 is impregnated with the separator 4 in FIG.²The battery shown in FIG. 1 was constructed.
[0118]
[Evaluation of battery performance]
Using the battery prepared by the above method, 1.0 mA / cm²The battery voltage was repeated between 4.5V and 3.5V at a constant current of.
[0119]
Table 1 shows the ratio of the discharge capacity at the 50th cycle to the discharge capacity at the 1st cycle, that is, the capacity retention rate.
[0120]
The manganese composite oxides manufactured in Examples 1 to 7 all showed a high maintenance rate of 95% or more, but the manganese composite oxides manufactured in Comparative Examples 1 to 2 were all 90% or less. .
[0121]
【The invention's effect】
As described above, according to the study by the present inventors, at least one kind selected from γ-MnOOH consisting of acicular particles or β-MnO2 consisting of acicular particles, a lithium compound, and Ni, Co, Fe, Cr. By firing a mixture with the above metal materials, it consists of acicular particles, the crystal structure is spinel type, chemical formula LiM_XMn_2-XO4(Wherein M is at least one selected from Ni, Co, Fe, and Cr, and 0 <x ≦ 0.5), and it was found that a novel manganese composite oxide represented by It has been found that by using it as a positive electrode active material for a lithium secondary battery, it is possible to construct a manganese-based lithium secondary battery having an unprecedented excellent cycle characteristics.
[0122]
The discovery of a manganese-based positive electrode material applicable to a positive electrode active material for a lithium secondary battery is an industrially useful finding.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an embodiment of a battery configured in examples and comparative examples.
[Explanation of symbols]
1 Positive lead wire
2 Positive electrode current collector mesh
3 Positive electrode
4 Separator
5 Negative electrode
6 Negative electrode current collector mesh
7 Lead wire for negative electrode
8 containers
2 is a diagram showing X-ray diffraction patterns of manganese composite oxides produced in Example 1, Example 4, Examples 6 to 7, and Comparative Examples 1 and 2. FIG.
3 is a photograph showing the particle structure of the manganese composite oxide produced in Example 1. FIG.
4 is a photograph showing the particle structure of a manganese composite oxide produced in Example 4. FIG.
5 is a photograph showing the particle structure of the manganese composite oxide produced in Example 6. FIG.
6 is a photograph showing the particle structure of a manganese composite oxide produced in Example 7. FIG.
7 is a photograph showing the particle structure of the manganese composite oxide produced in Comparative Example 1. FIG.
8 is a photograph showing the particle structure of a manganese composite oxide produced in Comparative Example 2. FIG.

Claims (9)

It consists of acicular particles and has a crystal structure of spinel type, chemical formula LiM _x Mn _{2 -X} O ₄ (wherein M is at least one selected from Ni, Co, Fe, Cr, 0 <x ≦ 0. 5) Acicular manganese composite oxide represented by The acicular manganese composite oxide according to claim 1, wherein the BET specific surface area of the acicular manganese composite oxide is 5 m ² / g or more and 10 m ² / g or less. The needle according to claim 1, wherein a mixture of γ-MnOOH composed of acicular particles, a lithium compound, and at least one metal material selected from Ni, Co, Fe, and Cr is fired. Of producing a manganese complex oxide. Wherein the firing of claim 3, the first in the air, after performing at 500 ° C. below the temperature, to claim 3, characterized in that the second baking at temperatures below 850 ° C. 500 ° C. or higher Manufacturing method of manganese composite oxide. The needle according to claim 1, wherein a mixture of β-MnO ₂ composed of acicular particles, a lithium compound, and at least one metal material selected from Ni, Co, Fe, and Cr is fired. Method for producing a manganese complex oxide. The firing according to claim 5 is performed at a temperature of 500 ° C. or higher and 850 ° C. or lower after first performing in the air and / or oxygen at a temperature of 500 ° C. or lower. The method for producing acicular manganese composite oxide. The method for producing acicular manganese composite oxide according to claim 3, wherein the lithium compound is lithium nitrate. The method for producing acicular manganese composite oxide according to claim 3, wherein the metal material of Ni, Co, Fe, and Cr is nitrate. Lithium, a lithium alloy, or a compound capable of occluding and releasing lithium is used as a negative electrode active material, a nonaqueous electrolyte is used as an electrolyte, and the acicular manganese composite oxide according to claim 1 is used as a positive electrode active material. Next battery.

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