JP4028738B2 - Positive electrode active material for non-aqueous secondary battery, method for producing the same, and non-aqueous secondary battery - Google Patents

Description

【００７５】
Ｘ線回折測定の結果、実施例１〜５のＸ線回折パターンは全て同じ特徴を有していた。即ち、回折角が１７°から２０°の範囲内に回折角の差が０．１°から０．３°となる２本の回折ピークを有し、かつ回折角が４３°から４６°の範囲内に回折角の差が０．３°から０．６°となる２本の回折ピークを有していた。また、上記実施例１〜５のＸ線回折パターンから、本発明に用いる複合酸化物は、リチウム複合酸化物（ＬｉＮｉ_(1-y)/2Ｍｎ_(1-y)/2Ｃｏ_yＯ₂、ただし、ｙはおよそ０．３〜０．４）とコバルト酸リチウム（ＬｉＣｏＯ₂）の２つの相で構成されていることが確認された。これは、上記実施例１〜５のＸ線回折パターンのピークが、単一相のリチウム複合酸化物（ＬｉＮｉ_(1-y)/2Ｍｎ_(1-y)/2Ｃｏ_yＯ₂、ただし、ｙはおよそ０．３〜０．４）およびコバルト酸リチウム（ＬｉＣｏＯ₂）のピークとほぼ一致することによる。
【００７６】
ただし、実施例１〜５のＸ線回折パターンの回折角が４３°から４６°の範囲内にある２本の回折ピークの半価幅は、これらが単独で存在する場合よりも大きく、その値は０．２°以上であり、更に低角度側の回折ピークの半価幅の方が高角度側の回折ピークの半価幅より大きく、低角度側の回折ピークがよりブロードであることが確認された。このことから、本発明に用いる複合酸化物は、組成および格子定数の異なる２つの相が相互に関係し合っていることがわかった。
【００７７】
また、実施例１〜５において複合酸化物全体としての組成が変化しているにもかかわらず、これらの回折ピークの位置はほとんど変化せず、ピーク強度のみが変化していることから、これらの複合酸化物を構成するリチウム複合酸化物およびコバルト酸リチウムは、実施例１〜５のいずれもほぼ同じ組成となっており、その量比が変化することにより、複合酸化物全体としての組成が変化しているものと推定された。
【００７８】
さらに、実施例３の複合酸化物に対し、走査型電子顕微鏡（ＳＥＭ）での形態観察および電子線プローブマイクロアナライザー（ＥＰＭＡ）での元素分析を行い、組成の異なる２種類の粒子が互いに接合し、接続一体化された複合粒子を形成していることを確認した。このような粒子形態をとることにより、電子伝導性の高いコバルト酸リチウムが、Ｎｉ、Ｍｎ、Ｃｏを含有する電子伝導性に劣る複数のリチウム複合酸化物粒子を結びつけ、粒子間に電子伝導パスが巧く形成されるのである。
【００７９】
一方、比較例１〜３のＸ線回折パターンは単一相の層状構造を示しており、回折角が１７°から２０°の範囲内および回折角が４３°から４６°の範囲内には、それぞれ回折ピークが１本のみ存在していた。また、リチウム複合酸化物とコバルト酸リチウムの混合物である比較例４では、上記範囲にそれぞれ２本ずつの回折ピークが存在していたが、上記実施例のものに比べて半価幅が小さく、低角度側の回折ピークもシャープであった。
【００８０】
次に、上記実施例１〜５、比較例１〜４及び参考例１の複合酸化物を用い、以下に示す方法により非水二次電池を作製した。
【００８１】
先ず、バインダーとしてのポリフッ化ビニリデン２０質量部に、Ｎ−メチル−２−ピロリドンを２５０質量部加え、６０℃に加熱してポリフッ化ビニリデンをＮ−メチル−２−ピロリドンに溶解させ、バインダー溶液を調製した。このバインダー溶液に上記複合酸化物を正極活物質として４５０質量部加え、更に導電助剤としてカーボンブラック５質量部とグラファイト２５質量部を加え、攪拌してスラリー状の塗料を調製した。この塗料を厚さ２０μｍのアルミニウム箔の両面に均一に塗布して乾燥した後、ローラープレス機により加圧成形し、次いで裁断して、平均厚さ１９０μｍ、縦５４ｍｍ、横４８３ｍｍの帯状の正極を作製した。
【００８２】
上記のようにして作製した正極と、リチウム箔よりなる負極を用い、各電極との間に厚さ２５μｍの微孔性ポリエチレンフィルムからなるセパレータを配置した。続いて、エチレンカーボネートとエチルメチルカーボネートとの体積比１：３の混合溶媒にＬｉＰＦ₆を１．０ｍｏｌ／ｄｍ³の濃度で溶解させた非水溶液を電解液とし、正極活物質の評価のためにリチウムの参照電極を配置して、非水二次電池とした。
【００８３】
次に、上記非水二次電池を用いて負荷特性を評価するため、電極の面積に対する電流密度を０．５ｍＡ／ｃｍ²として、室温で４．３Ｖまで充電後、異なる電流密度で３．０Ｖまで放電させた。その結果を、電流密度０．５ｍＡ／ｃｍ²で放電した時の放電容量を１００％として、電流密度を１、２、４、６ｍＡ／ｃｍ²と上げた時の容量維持率（％）として表２に示す。
【００８４】
【表２】

【００８５】
表２から明らかなように、実施例１〜５は、電流密度を上げたときの容量維持率（放電効率）が、比較例１〜４に比べて高いことがわかる。電流密度６ｍＡ／ｃｍ²での容量維持率を見ると、比較例１〜３が６５〜６６％である。これは、参考例１の複合酸化物よりも高い放電効率であるが、実用的な値ではない。また、実施例１〜５は電流密度６ｍＡ／ｃｍ²で放電しても期待通り８６％以上の容量維持率を示した。これは、ニッケル、マンガン、コバルトから構成されるリチウム複合酸化物とコバルトを主に含んだコバルト複合酸化物との二相が共存することによって、高い電流密度での放電効率が飛躍的に向上したものと考えられる。更に、実施例１〜５の容量維持率から、正極活物質中のコバルト含有量が増えるにしたがって、その放電効率が向上することがわかる。しかし、実施例５と比較例１との比較からわかるように、この放電効率の飛躍的な向上は、単にコバルト含有量の増加によるものではなく、上記のリチウム複合酸化物とコバルト複合酸化物とを共存させるという本発明によって達成されたものと考えられる。
【００８６】
また、ＬｉＮｉ_0.33Ｍｎ_0.33Ｃｏ_0.33Ｏ₂で表されるリチウム複合酸化物（比較例２）とコバルト酸リチウム（参考例２）とを混合させた比較例４の材料では、高い電子伝導性を有するコバルト酸リチウムを混合させるだけである程度は放電効率が向上することがわかる。しかし、Ｎｉ、ＭｎおよびＣｏの比率が比較例４と同じである実施例３との比較から明らかなように、本発明の構造の正極活物質を用いることにより、より効果的に放電効率を上げることができる。
【００８７】
【発明の効果】
以上説明したように、正極活物質として、Ｎｉ及びＭｎを含有するリチウム複合酸化物粒子を複数含み、前記リチウム複合酸化物粒子の表面にコバルト複合酸化物粒子が固着され、前記コバルト複合酸化物粒子により前記複数のリチウム複合酸化物粒子が接続一体化されてなる複合粒子を用いることにより、負荷特性に優れ、かつ高容量で、充放電サイクルに対する耐久性に優れた非水二次電池を提供することができる。
【図面の簡単な説明】
【図１】本発明の正極活物質を構成する複合粒子の概念図である。
【図２】実施例３の複合酸化物のＸ線回折パターンを示す図である。
【図３】実施例５の複合酸化物のＸ線回折パターンを示す図である。
【図４】比較例１の複合酸化物のＸ線回折パターンを示す図である。
【図５】比較例２の複合酸化物のＸ線回折パターンを示す図である。
【図６】実施例３、実施例５、比較例１及び比較例２の複合酸化物の回折角が１７°から２０°の範囲のＸ線回折パターンを示す図である。
【図７】実施例３、実施例５、比較例１及び比較例２の複合酸化物の回折角が４３°から４６°の範囲のＸ線回折パターンを示す図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a non-aqueous secondary battery using a lithium composite oxide as an active material for a positive electrode.
[0002]
[Prior art]
In recent years, with the development of portable electronic devices such as mobile phones and notebook computers, and the practical application of electric vehicles, secondary batteries with small size and light weight and high capacity have been required. Currently, as a high-capacity secondary battery that meets this requirement, LiCoO as a positive electrode active material₂Non-aqueous secondary batteries represented by lithium secondary batteries using a carbon-based material as a negative electrode active material have been commercialized. The lithium secondary battery is attracting attention as a power source for portable electronic devices because it has a high energy density and can be reduced in size and weight.
[0003]
LiCoO used as the positive electrode active material of this lithium secondary battery₂Is widely used as a preferred positive electrode active material because it is easy to manufacture and easy to handle. In addition, LiCoO₂Can be charged / discharged at a large current density because the electron conductivity of the lithium ion compound is high and the electron conductivity is further improved. Therefore, as a positive electrode active material for a lithium secondary battery used for a mobile phone or the like that particularly requires load characteristics at low temperatures, LiCoO₂Is mainly used. However, LiCoO₂Is manufactured using Co, which is a rare metal, as a raw material, and it is expected that resource shortages will become serious in the future. Further, since the price of cobalt itself is high and the price fluctuates greatly, it is desired to develop a cathode active material that is inexpensive and stable in supply. In addition, LiCoO₂Is used as the positive electrode active material, there is a problem in the safety of the battery in the charged state because the thermal stability of cobalt dioxide formed after charging is low.
[0004]
LiCoO for lithium secondary battery₂An alternative positive electrode active material is required to be inexpensive, have a battery capacity equivalent to or higher than that of the conventional one, and have a load characteristic equivalent to or higher than that of the conventional one. Among them, Li is a spinel type lithium manganese oxide.₂Mn_FourO₉, Li_FourMn_FiveO₁₂, LiMn₂O_FourIn particular, LiMn₂O_FourHas been actively studied since it can be charged / discharged in a voltage region around 4 V with respect to Li and has excellent thermal stability (Japanese Patent Laid-Open Nos. 6-76824 and 6 7-73883, JP-A-7-230802, JP-A-7-245106, etc.). The composition formula LiNi_1-xyCo_xM_yO₂(However, 0 ≦ x <1, 0 ≦ y ≦ 0.25, and M is an element including at least one of Al and Mn), so that lithium nickelate having a layered structure exhibits a high capacity. It has been actively studied.
[0005]
[Problems to be solved by the invention]
By the way, LiCoO₂The theoretical discharge capacity of 274 mAh / g is LiCoO when deep charge / discharge is performed.₂Causes a phase change and affects the cycle life, so that a practical discharge capacity in an actual lithium secondary battery is in the range of 125 to 140 mAh / g.
[0006]
In contrast, LiMn₂O_FourThe theoretical discharge capacity is 148 mAh / g.₂O_FourLiCoO₂In the same way as above, when a phase change occurs during charging and discharging, and when a carbon-based material is used as the negative electrode active material, the discharge capacity that can be used when the battery is actually used because the irreversible capacity of the carbon-based material is large Decreases to about 90 to 105 mAh / g. As is clear from this, LiMn₂O_FourWhen Li is used as the positive electrode active material, LiCoO₂There is a problem that the battery capacity cannot be increased as compared with the case of using as a positive electrode active material.
[0007]
LiMn₂O_FourLithium secondary batteries using as a positive electrode active material, LiMn during charging and discharging₂O_FourSince its structure is unstable, the cycle characteristics are LiCoO₂There is also a problem that it is worse than a battery.
[0008]
On the other hand, the theoretical discharge capacity of the layered lithium nickelate is 278 mAh / g, and LiCoO₂Although it is almost the same as the theoretical discharge capacity, it is a positive electrode active material having a high discharge capacity of about 160 to 200 mAh / g in the same potential region because of its low operating potential. The battery safety is reduced. Furthermore, since the tetravalence of nickel increases with charge / discharge reaction and the electron conductivity decreases, the load characteristic is LiCoO.₂There is a problem that it is inferior.
[0009]
Based on these facts, as a result of intensive studies, we have obtained the general formula Li_{1 + x + α}Ni_{(1-x-y + δ ) / 2}Mn_{(1-xy- δ ) / 2}M_yO₂(However, 0 ≦ x ≦ 0.05, −0.05 ≦ α ≦ 0.05, 0 ≦ y <0.45, −0.24 ≦ δ ≦ 0.24, and M is Ti, Cr, Fe LiCoO having a layered structure represented by LiCoO represented by one or more elements selected from the group consisting of Co, Cu, Zn, Al, Ge, and Sn)₂Invented a positive electrode active material that exhibited substantially the same discharge capacity (150 mAh / g or more) as well as excellent thermal stability and was inexpensive. However, since the positive electrode active material has a high nickel content, the load characteristics are LiCoO.₂Was inferior.
[0010]
Thus, LiMnO₂By substituting the constituent elements of lithium manganese oxide with a layered structure such as nickel and cobalt, the crystal structure is stabilized, and as a result, the capacity is increased by improving reversibility in charge and discharge, The durability can be imparted. However, since this positive electrode active material mainly uses the oxidation-reduction reaction of nickel at the time of charge / discharge, it is LiCoO like lithium nickelate.₂The load characteristics are inferior to those of the mobile phone, and improvement of the load characteristics is indispensable for application to the positive electrode active material for batteries for portable information terminals such as mobile phones.
[0011]
The present invention has been made to solve the above-described conventional problems, and an object thereof is to provide a non-aqueous secondary battery having excellent load characteristics, high capacity, and excellent durability against charge / discharge cycles. .
[0012]
[Means for Solving the Problems]
  To achieve the above object, the present inventionThen, positive electrode for non-aqueous secondary batteryNi and Mn as active materialsAt a certain ratioA plurality of lithium composite oxide particles, cobalt composite oxide particles are fixed to the surface of the lithium composite oxide particles, and the plurality of lithium composite oxide particles are connected and integrated by the cobalt composite oxide particles. Composite particlesWas applied to a non-aqueous secondary battery.It is characterized by that.
[0013]
In the above composite particles, the lithium composite oxide particles are connected by the cobalt composite oxide particles having high electron conductivity, so that the electron conductivity of the entire positive electrode active material is improved, and the non-aqueous secondary using this The load characteristics of the battery can be improved.
[0014]
  Further, in the positive electrode active material for a non-aqueous secondary battery of the present invention, the lithium composite oxide particles have the general formula Li_{1 + x + α}Ni_{(1-x-y + δ ) / 2}Mn_{(1-xy- δ ) / 2}M_yO₂(However, 0 ≦ x ≦ 0.05, −0.05 ≦ α ≦ 0.05,0 <y <0.45,-0.1≦ δ ≦0.1M is selected from the group consisting of Ti, Cr, Fe, Co, Cu, Zn, Al, Ge, and Sn., Including at least CoIt is preferable to have a composition represented by one or more elements.
[0015]
By using the lithium composite oxide particles having the above composition, it is possible to provide a non-aqueous secondary battery having a stable crystal structure, high capacity, and excellent durability against charge / discharge cycles.
[0016]
  The non-aqueous secondary battery of the present inventionCathode active materialThe cobalt composite oxide particles are preferably composed of a composite oxide in which lithium cobaltate or a part of cobalt of lithium cobaltate is substituted with another metal element. This is because lithium cobalt oxide and a composite oxide obtained by substituting a part of cobalt of lithium cobalt oxide with another metal element are excellent in electron conductivity.
[0017]
  Further, in the positive electrode active material for a non-aqueous secondary battery of the present invention, the composite particles are Ni, Mnas well asM (where M is selected from the group consisting of Ti, Cr, Fe, Co, Cu, Zn, Al, Ge, and Sn, and at least one element including Co))Containing, Ni, MnAnd MThe average atomic ratio of (1-x−y + δ) / 2: (1-xy−δ) / 2:y + z(However, 0 ≦ x ≦ 0.05, 0 <y <0.45, 0.4 <y + z <0.85, −0.24 ≦ δ ≦ 0.24). This is because, with this composition, the composite particles of the present invention can be easily formed. In particular, when the M is Co, the cobalt composite oxide particles can be reliably fixed to the surface of the lithium composite oxide particles. In addition, as the value of z increases, the proportion of the cobalt composite oxide particles increases, and the electron conductivity is improved and the load characteristics are improved. The value of y + z indicating the upper limit of the total amount is preferably less than 0.85.
[0018]
  The method for producing a positive electrode active material for a non-aqueous secondary battery according to the present invention comprises mixing a compound containing Ni and Mn as constituent elements, a compound containing Co as a constituent element, and a Li compound, and firing the mixture. Ni, Mnas well asM (where M is selected from the group consisting of Ti, Cr, Fe, Co, Cu, Zn, Al, Ge, and Sn, and at least one element including Co))Containing, Ni, MnAnd MThe average atomic ratio of (1-x−y + δ) / 2: (1-xy−δ) / 2:y + z(However, 0 ≦ x ≦ 0.05, 0 <y <0.45, 0.4 <y + z <0.85, −0.24 ≦ δ ≦ 0.24). It is characterized by.
[0019]
  Thereby, as an active material of the positive electrode, Ni,MnAnd CoA plurality of lithium composite oxide particles containing cobalt, cobalt composite oxide particles are fixed to the surface of the lithium composite oxide particles, and the plurality of lithium composite oxide particles are connected and integrated by the cobalt composite oxide particles. It is possible to reliably form composite particles.
[0020]
  The method for producing a positive electrode active material for a non-aqueous secondary battery according to the present invention includes at least one selected from a compound containing Ni and Mn as constituent elements, a compound containing Co as a constituent element, and a compound of Li. A compound ofM ′ (where M ′ is one or more elements selected from the group consisting of Ti, Cr, Fe, Co, Cu, Zn, Al, Ge, and Sn)Is preferably included as a constituent element.
[0021]
  In the method for producing a positive electrode active material for a non-aqueous secondary battery according to the present invention, the compound containing Ni and Mn as constituent elements, the compound containing Co as constituent elements, and the compound of Li are mixed. And furtherM 'A compound containing as a constituent element can also be mixed.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in more detail with reference to embodiments of the invention. The non-aqueous secondary battery of the present invention includes a positive electrode, a negative electrode, and a non-aqueous electrolyte, and includes a plurality of lithium composite oxide particles containing Ni and Mn as an active material of the positive electrode, and the lithium composite oxide particles Cobalt composite oxide particles are fixed to the surface, and composite particles in which the plurality of lithium composite oxide particles are connected and integrated by the cobalt composite oxide particles are used.
[0023]
The positive electrode active material of the present invention is composed of cobalt composite oxide particles having good electron conductivity and lithium composite oxide particles containing Ni and Mn having excellent structural stability and thermal stability. The composite particles are connected and integrated. When the positive electrode active material of the present invention is analyzed by the X-ray diffraction method, it is recognized as a mixed phase containing two hexagonal crystals having different lattice constants. Thereby, an electron conduction path between the lithium composite oxide particles is ensured by the cobalt composite oxide particles, and the electron supply to the lithium composite oxide particles containing Ni and Mn is smoothly performed, and the load characteristics Can be improved.
[0024]
This will be described using a conceptual diagram. FIG. 1 is a conceptual diagram of composite particles constituting the positive electrode active material of the present invention. In FIG. 1, the composite particles constituting the positive electrode active material of the present invention include a plurality of lithium composite oxide particles 1 containing Ni and Mn, and the cobalt composite oxide particles 2 are fixed to the surface of the lithium composite oxide particles 1. The plurality of lithium composite oxide particles 1 are connected and integrated by the cobalt composite oxide particles 2. As a result, a conductive network of cobalt composite oxide particles is formed between a plurality of lithium composite oxide particles, and even if lithium composite oxide particles with low load characteristics are used, the load characteristics of the positive electrode active material as a whole are improved. Can be achieved.
[0025]
In addition, it is most desirable that all of the positive electrode active material is the composite particle. However, lithium composite oxide particles other than the composite particles, cobalt composite oxide particles, or these two kinds of oxide particles are used as the positive electrode active material. May be contained, and a mixture with an active material other than these may be sufficient.
[0026]
In the present invention, the lithium composite oxide particles and the cobalt composite oxide particles may be primary particles or secondary particles, respectively. In order to further improve the electron conductivity, it is preferable that both the lithium composite oxide particles and the cobalt composite oxide particles are primary particles.
[0027]
The positive electrode active material of the present invention having the above structure has two diffraction peaks in the diffraction angle range of 17 ° to 20 ° in the X-ray diffraction measurement using CuKα rays, and the diffraction angle is from 43 °. There are at least two diffraction peaks in the range of 46 °, and in two diffraction peaks having a diffraction angle in the range of 43 ° to 46 °, the half-value width of the diffraction peak on the low angle side and half of the diffraction peak on the high angle side The valence width is different, and the half-value width of the diffraction peak on the low angle side is larger than the half-value width of the diffraction peak on the high angle side.
[0028]
  The composite particles constituting the positive electrode active material of the present invention include Ni, Mnas well asM (where M is selected from the group consisting of Ti, Cr, Fe, Co, Cu, Zn, Al, Ge, and Sn, and at least one element including Co))Containing, Ni, MnAnd MThe average atomic ratio of (1-x−y + δ) / 2: (1-xy−δ) / 2:y + z(However, the one having a composition represented by 0 ≦ x ≦ 0.05, 0 <y <0.45, 0.4 <y + z <0.85, −0.24 ≦ δ ≦ 0.24) is used. can do. In particular, it is preferable that M is Co.
[0029]
  The lithium composite oxide particles constituting the composite particles include a general formula Li_{1 + x + α}Ni_{(1-x-y + δ ) / 2}Mn_{(1-xy- δ ) / 2}M_yO₂(However, 0 ≦ x ≦ 0.05, −0.05 ≦ α ≦ 0.05,0 <y <0.45,-0.1≦ δ ≦0.1M is selected from the group consisting of Ti, Cr, Fe, Co, Cu, Zn, Al, Ge, and Sn., Including at least CoThose having a composition represented by (one or more elements) are preferred. The lithium composite oxide particles have a layered structure.
[0030]
The lithium composite oxide particles having the above composition having a layered structure are selected for the following reason. That is, in lithium manganese oxide, it is known that when the proportion of trivalent Mn increases, the crystal structure becomes unstable due to the yarn-teller effect. Therefore, the inventors have made LiMnO in order to achieve stabilization of the crystal structure.₂On the other hand, as a composition containing excessive Li, the average valence of Mn is increased, or LiMnO₂It was considered effective to replace Mn with an element that can stably form a layered lithium composite oxide, such as Co or Ni, and the amount ratio of Li, the type and amount ratio of the substitution element were examined in detail. .
[0031]
  As a result, the general formula Li_{1 + x}Ni_{(1-x) / 2}Mn_{(1-x) / 2}O₂The amount ratio of Ni and Mn represented by (0 ≦ x ≦ 0.05) is (1-x) / 2: (1-x) / 2, that is, 1: 1, and the decrease in Ni and Mn ( Based on a composition in which Li is excessive by the sum (x) of x / 2), the amount ratio of Ni and Mn is δ / 2 (-0.1≦ δ ≦0.1), The Li amount ratio is α (−0.05 ≦ α ≦ 0.05), and Ni and Mn are each y / 2 (0 <y <0.45) M (M is selected from the group consisting of Ti, Cr, Fe, Co, Cu, Zn, Al, Ge and Sn), Including at least CoComposition substituted with one or more elements), ie, the general formula Li_{1 + x + α}Ni_{(1-x-y + δ ) / 2}Mn_{(1-xy- δ ) / 2}M_yO₂(However, 0 ≦ x ≦ 0.05, −0.05 ≦ α ≦ 0.05,0 <y <0.45, −0.1 ≦ δ ≦ 0.1, and M is selected from the group consisting of Ti, Cr, Fe, Co, Cu, Zn, Al, Ge, and Sn., Including at least CoIt was found that in the composition range represented by one or more elements), the layered crystal structure was stabilized, and a lithium composite oxide excellent in charge / discharge reversibility and durability against charge / discharge cycles was obtained.
[0032]
  As a result of further detailed study, it was found that a lithium composite oxide having particularly excellent characteristics can be obtained in the vicinity of a composition in which the quantity ratio of Ni, Mn and M is 1: 1: 1. That is, the general formula Li_{1 + x + α}Ni_{(1-x-y + δ ) / 2}Mn_{(1-xy- δ ) / 2}M_yO₂In the composition range of 0.2 <y <0.45 with y = 1/3 as the centerIs preferably used in the present invention.
[0033]
As the cobalt composite oxide particles having an effect of imparting electron conductivity in the positive electrode active material of the present invention, lithium cobaltate or a composite oxide obtained by substituting a part of cobalt of lithium cobaltate with another metal element is used. Can do. All of these are excellent in electronic conductivity and also function as a positive electrode active material. Ti, Mn, Ni, Fe, Al, Ge, Sn, etc. can be used as a metal element that replaces cobalt of lithium cobalt oxide. The substitution amount is desirably 25 mol% or less.
[0034]
  Next, the manufacturing method of the said composite particle which is a positive electrode active material of this invention is demonstrated. As a method for producing the composite particles, simply mixing and firing a Li compound, a Mn compound, a Ni compound, and the like includes a plurality of lithium composite oxide particles containing Ni and Mn of the present invention, and the lithium It is difficult to synthesize composite particles in which cobalt composite oxide particles are fixed to the surface of the composite oxide particles, and the plurality of lithium composite oxide particles are connected and integrated by the cobalt composite oxide particles. This is because the diffusion rate of Ni, Mn, etc. is slow in the solid, so that it is difficult to uniformly diffuse them in the synthesis reaction, and the element is not uniformly distributed in the generated lithium composite oxide. Conceivable. Accordingly, as a result of detailed studies on the method for synthesizing the composite particles of the present invention, the present inventors have made use of a reaction system in which phase separation occurs spontaneously for a lithium composite oxide having a layered structure. It came to be able to manufacture the composite particle which has the structure of invention. That is, the general formula Li_{1 + x + α}Ni_{(1-x-y + δ ) / 2}Mn_{(1-xy- δ ) / 2}Co_yO₂(However, 0 ≦ x ≦ 0.05, −0.05 ≦ α ≦ 0.05,0 <y <0.45,-0.1≦ δ ≦0.1By using the solid solution limit of the lithium composite oxide having a layered structure represented by) and adding excessive Co thereto, the lithium composite oxide particles and the cobalt composite oxide particles having a layered structure are separated from each other. In addition, the composite particle in which cobalt composite oxide particles are unevenly distributed on the surface of the lithium composite oxide particles, and the cobalt composite oxide is firmly bonded between the lithium composite oxide particles. Was invented.
[0035]
  As described above, the composite particles of the present invention are prepared by separately preparing a compound containing Ni and Mn as constituent elements, a compound containing Co as a constituent element, and a Li compound separately, and mixing them. It can be manufactured by firing. The composition and blending amount of each compound are determined as follows.as well asM (where M is selected from the group consisting of Ti, Cr, Fe, Co, Cu, Zn, Al, Ge, and Sn, and at least one element including Co))Containing, Ni, MnAnd MThe average atomic ratio of (1-x−y + δ) / 2: (1-xy−δ) / 2:y + z(However, adjustments are made so that 0 ≦ x ≦ 0.05, 0 <y <0.45, 0.4 <y + z <0.85, −0.24 ≦ δ ≦ 0.24). Thereby, the composite particle which has the structure of this invention can be manufactured reliably.
[0036]
  In the above manufacturing method,Said M ′Needs to be included in a compound containing Ni and Mn as constituent elements, or / and a compound containing Co as constituent elements, or / and a compound of Li.M 'May be prepared and mixed.
[0037]
Here, as the compound containing Ni and Mn as constituent elements, for example, a coprecipitation compound containing Ni and Mn, a hydrothermally synthesized compound, a mechanically synthesized compound and a compound obtained by heat-treating them are used. Ni_0.5Mn_0.5(OH)₂NiMn₂O_Four, Ni_0.5Mn_0.5An oxide or hydroxide of Ni and Mn such as OOH can be preferably used.
[0038]
  As described above, a compound containing Ni and Mn as constituent elements, a compound containing Co as a constituent element, a compound of Li,M 'The composite particles of the present invention can also be obtained by mixing and baking with a compound containing as a constituent element, but if possible, Ni and Mn and furtherM 'It is preferable to use a composite compound containing. In addition, Ni, Mn andM 'The composition ratio may be appropriately selected according to the composition of the target composite particles.
[0039]
As the compound containing Co as a constituent element, cobalt carbonate, cobalt hydroxide, cobalt oxide, or the like can be used.
[0040]
As the Li compound, various lithium salts can be used, for example, lithium hydroxide monohydrate, lithium nitrate, lithium carbonate, lithium acetate, lithium bromide, lithium chloride, lithium citrate, fluorine. Lithium iodide, lithium iodide, lithium lactate, lithium oxalate, lithium phosphate, lithium pyruvate, lithium sulfate, lithium oxide, etc. can be used. Among them, carbon dioxide, nitrogen oxide, sulfur oxide, etc. Lithium hydroxide monohydrate is preferably used because it does not generate harmful substances that adversely affect the environment.
[0041]
The compound containing Ni and Mn as constituent elements, the compound containing Co as constituent elements, the compound of Li and the like are mixed at a composition ratio according to the composition of the target composite particles of the present invention. For example, the mixture Can be synthesized in an atmosphere containing oxygen at about 700 to 1100 ° C. for 1 to 24 hours to synthesize the composite particles of the present invention.
[0042]
As the heat treatment in the firing, rather than raising the temperature to a predetermined temperature at once, it is heated to a temperature lower than the firing temperature (about 250 to 850 ° C.) and preheated by holding at that temperature. It is preferable to raise the temperature to a predetermined firing temperature to advance the reaction. This is because, in the production process of the composite oxide of the present invention, a reaction between the compound of Li and a compound containing Ni and Mn as constituent elements occurs stepwise, and finally the lithium composite oxidation via the intermediate product. It is because it is thought that a thing produces | generates. Here, when the temperature is raised to the firing temperature all at once, the Li compound and the compound containing Ni and Mn as constituent elements partially react to the final stage, and the resulting lithium composite oxide is not yet formed. There is a risk that the reaction of the reactants may be hindered or the uniformity of the composition may be impaired. In order to shorten the time required for the reaction process and obtain a homogeneous composite oxide, it is effective to perform heating stepwise. The preheating time is not particularly limited, but is usually about 0.5 to 30 hours.
[0043]
In the step of firing the mixture, the dry-mixed mixture may be used as it is, but the mixture is dispersed in a solvent such as ethanol to form a slurry, and mixed for about 30 to 60 minutes with a planetary ball mill or the like. It is preferable to fire the dried product since the homogeneity of the synthesized compound can be further increased.
[0044]
The atmosphere for the heat treatment may be performed in an atmosphere containing oxygen, for example, in air, in a mixed atmosphere of an inert gas such as argon, helium, or nitrogen and oxygen gas, or in oxygen gas. The proportion of oxygen in the atmosphere is preferably 10 to 100% by volume.
[0045]
The gas flow rate is 1 dm / 100 g of the mixture.^Three/ Min or more, preferably 1 to 5 dm^Three/ Min is more preferable. When the gas flow rate is small, that is, when the gas flow rate is slow, the reaction proceeds non-uniformly and Mn₂O_ThreeOr Li₂MnO_ThreeImpurities such as are easily generated.
[0046]
Other than the above positive electrode active material, the non-aqueous secondary battery of the present invention can be produced, for example, as follows.
[0047]
The positive electrode is obtained by mixing the positive electrode active material with a conductive auxiliary agent such as flake graphite or acetylene black and a binder such as polytetrafluoroethylene or polyvinylidene fluoride if necessary. It is produced by molding the mixture by an appropriate means.
[0048]
As the active material of the negative electrode facing the positive electrode, lithium or a lithium-containing compound is usually used. As the lithium-containing compound, an element capable of forming an alloy with lithium such as Li-Al alloy, Li-Pb alloy, Li-In alloy, Li-Ga alloy, or lithium, such as Si, Sn, Mg-Si alloy, or the like The alloy is mentioned. In addition to oxide-based materials such as Sn oxide and Si oxide, carbonaceous materials such as graphite and fibrous carbon, lithium-containing composite nitrides, and the like can also be used.
[0049]
The negative electrode is produced by adding and mixing a binder, a conductive additive or the like to the negative electrode active material, if necessary, and mixing the obtained negative electrode mixture by an appropriate means, as in the case of the positive electrode. The
[0050]
The positive electrode or negative electrode forming means may be formed by pressure forming a positive electrode mixture or a negative electrode mixture, or coating the positive electrode mixture or the negative electrode mixture into a paste or slurry with water or other appropriate solvent. Various means can be employed, such as applying or impregnating the coating material to a substrate that also serves as a current collector and then drying to form a coating film integrated with the substrate.
[0051]
Here, as a substrate that also serves as a current collector, for example, a metal net such as aluminum, stainless steel, titanium, copper, punching metal, expanded metal, foam metal, metal foil, etc. can be used. A method of forming a coating film of a mixture on a metal foil as a base and pressurizing it to form a sheet-like positive electrode or negative electrode is preferably used.
[0052]
As the non-aqueous electrolyte in the non-aqueous secondary battery of the present invention, an organic solvent-based liquid electrolyte (electrolytic solution) in which an electrolyte is dissolved in an organic solvent, a polymer electrolyte in which the electrolytic solution is held in a polymer, or the like is used. be able to.
[0053]
The organic solvent contained in the electrolytic solution or polymer electrolyte is not particularly limited, but it preferably contains a chain ester from the viewpoint of load characteristics. Examples of such chain esters include chain COO-bonds such as dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), ethyl acetate (EA), and methyl propionate (MP). An organic solvent having These chain esters can be used singly or in combination of two or more, and in order to improve the low temperature characteristics, these chain esters occupy 50% by volume or more in the total organic solvent. It is more preferable that the chain ester occupies 65% by volume or more in the total organic solvent, and it is most preferable that 75% by volume or more is occupied.
[0054]
However, as an organic solvent, an ester having a high dielectric constant (an ester having a dielectric constant of 30 or more) is used in combination with the chain ester in order to improve battery capacity rather than using only the chain ester. It is preferable. Specific examples of the ester having a high dielectric constant include, for example, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene carbonate (VC), γ-butyrolactone (γ-BL), ethylene glycol sal A phyto (EGS) etc. are mentioned, The thing of cyclic structures, such as ethylene carbonate and propylene carbonate, is especially preferable. Such an ester having a high dielectric constant is preferably contained in an amount of 10% by volume or more, particularly 20% by volume or more in the total organic solvent from the viewpoint of discharge capacity. Moreover, from the point of coexistence with a load characteristic, 40 volume% or less is preferable and 25 volume% or less is more preferable.
[0055]
Examples of the solvent that can be used in addition to the ester having a high dielectric constant include 1,2-dimethoxyethane (1,2-DME), 1,3-dioxolane (1,3-DO), and tetrahydrofuran (THF). , 2-methyl-tetrahydrofuran (2-Me-THF), diethyl ether (DEE) and the like. In addition, amine imide organic solvents, sulfur-containing or fluorine-containing organic solvents, and the like can also be used.
[0056]
Examples of the electrolyte dissolved in the organic solvent include LiClO._Four, LiPF₆, LiBF_Four, LiAsF₆, LiSbF₆, LiCF_ThreeSO_Three, LiC_FourF₉SO_Three, LiCF_ThreeCO₂, Li₂C₂F_Four(SO_Three)₂, LiN (CF_ThreeSO₂)₂, LiC (CF_ThreeSO₂)_Three, LiC_nF_{2n + 1}SO_Three(N ≧ 2) etc. are used alone or in combination of two or more. Among them, LiPF that provides good charge / discharge characteristics₆And LiC_FourF₉SO_ThreeEtc. are preferably used. The concentration of the electrolyte in the electrolytic solution is not particularly limited, but is 0.3 to 1.7 mol / dm.^ThreeIn particular, 0.4 to 1.5 mol / dm^ThreeThe degree is preferred.
[0057]
Moreover, in order to improve the safety | security and storage characteristic of a battery, you may make the non-aqueous electrolyte contain an aromatic additive. As the aromatic additive, benzenes having an alkyl group such as cyclohexylbenzene and t-butylbenzene, or fluorobenzenes are preferably used.
[0058]
As the separator, a separator having sufficient strength and capable of holding a large amount of electrolyte is preferable. From such a viewpoint, the separator is made of polypropylene, polyethylene, propylene having a thickness of 10 to 50 μm and a porosity of 30 to 70%. A microporous film or a nonwoven fabric made of a copolymer with ethylene is preferably used.
[0059]
【Example】
Examples of the present invention will be described below. However, this invention is not limited only to those Examples.
[0060]
Example 1
In the reaction vessel, 2% by mass of ammonia water whose pH was adjusted to about 12 by adding sodium hydroxide was prepared, and while stirring this strongly, nickel sulfate and manganese nitrate were each added at 1 mol / dm.^Three46cm of mixed aqueous solution each containing^ThreePer minute, and 25% by mass of ammonia water is 3.3 cm.^ThreeNi / Mn coprecipitated compound was formed by adding dropwise using a metering pump at a rate of / min. At this time, the temperature of the reaction solution is maintained at 50 ° C., and 3.2 mol / dm so that the pH of the reaction solution is maintained around 12.^ThreeA sodium hydroxide aqueous solution having a concentration of was dropped at the same time. Further, during the reaction, 1 dm of nitrogen gas is used so that the atmosphere of the reaction solution becomes an inert atmosphere.^ThreePurged at a rate of / min.
[0061]
The obtained product was washed with water, filtered and dried to obtain a hydroxide containing Ni and Mn at a ratio of 1: 1, 0.03 mol of this hydroxide, 0.07 mol of cobalt hydroxide, and 0.0. 1 mol of LiOH · H₂O was weighed, and the mixture was dispersed in ethanol to form a slurry, which was then mixed for 40 minutes with a planetary ball mill and dried at room temperature to prepare a mixture. The mixture is then placed in an alumina crucible and 1 dm^ThreeThe composite oxide was synthesized by heating to 800 ° C. in an air stream / min, maintaining the temperature for 2 hours for preheating, and further raising the temperature to 1000 ° C. and firing for 12 hours. The synthesized oxide was pulverized in a mortar and stored as a powder in a desiccator.
[0062]
When the composition of the oxide powder was measured with an atomic absorption spectrometer, the atomic ratio of Ni, Mn and Co was found to be 0.33: 0.33: 1.54 on average.
[0063]
(Example 2)
0.035 mol of hydroxide containing Ni and Mn in a ratio of 1: 1 synthesized in the same manner as in Example 1, 0.065 mol of cobalt hydroxide, 0.1 mol of LiOH.H₂O was weighed and a composite oxide having an average atomic ratio of Ni, Mn and Co of 0.33: 0.33: 1.23 was synthesized in the same manner as in Example 1.
[0064]
(Example 3)
0.04 mol of hydroxide containing Ni and Mn in a ratio of 1: 1 synthesized in the same manner as in Example 1, 0.06 mol of cobalt hydroxide, 0.1 mol of LiOH.H₂O was weighed, and a composite oxide having an average atomic ratio of Ni, Mn and Co of 0.33: 0.33: 0.99 was synthesized in the same manner as in Example 1 below.
[0065]
Example 4
0.045 mol of hydroxide containing Ni and Mn in a ratio of 1: 1 synthesized in the same manner as in Example 1, 0.055 mol of cobalt hydroxide, 0.1 mol of LiOH.H₂O was weighed, and a composite oxide having an average atomic ratio of Ni, Mn and Co of 0.33: 0.33: 0.81 was synthesized in the same manner as in Example 1 below.
[0066]
(Example 5)
0.05 mol of hydroxide containing Ni and Mn in a ratio of 1: 1 synthesized in the same manner as in Example 1, 0.05 mol of cobalt hydroxide, 0.1 mol of LiOH.H₂O was weighed, and a composite oxide having an average atomic ratio of Ni, Mn and Co of 0.33: 0.33: 0.66 was synthesized in the same manner as in Example 1 below.
[0067]
(Comparative Example 1)
0.06 mol of hydroxide containing Ni and Mn in a ratio of 1: 1 synthesized in the same manner as in Example 1, 0.04 mol of cobalt hydroxide, 0.1 mol of LiOH.H₂O is weighed, and Li is the same as in Example 1 below._1.0Ni_0.30Mn_0.30Co_0.40O₂A composite oxide represented by the following formula was synthesized.
[0068]
(Comparative Example 2)
0.067 mol of hydroxide containing Ni and Mn in a ratio of 1: 1 synthesized in the same manner as in Example 1, 0.033 mol of cobalt hydroxide, 0.1 mol of LiOH.H₂O is weighed, and Li is the same as in Example 1 below._1.0Ni_0.33Mn_0.33Co_0.33O₂A composite oxide represented by the following formula was synthesized.
[0069]
(Comparative Example 3)
0.16 mol of hydroxide containing Ni and Mn in a ratio of 5: 3 synthesized in the same manner as in Example 1, 0.04 mol of cobalt hydroxide, 0.20 mol of LiOH.H₂O is weighed, and Li is the same as in Example 1 below._1.0Ni_0.50Mn_0.31Co_0.19O₂A composite oxide represented by the following formula was synthesized.
[0070]
(Comparative Example 4)
The composite oxide synthesized in Comparative Example 2 and LiCoO₂The powder was simply mixed at a molar ratio of 0.6: 0.4 so as to obtain the same composition as in Example 3 as a whole to prepare a mixture.
[0071]
(Reference Example 1)
0.16 mol of nickel hydroxide, 0.04 mol of cobalt hydroxide, and 0.2 mol of lithium hydroxide were mixed in the same manner as in Example 1 and calcined in oxygen at 650 ° C. for 12 hours. Crush and mix and fire again in oxygen at 850 ° C. for 12 hours._0.80Co_0.20O₂A composite oxide represented by the following formula was synthesized.
[0072]
(Reference Example 2)
0.20 mol of cobalt hydroxide and 0.20 mol of LiOH.H₂O was weighed, and LiCoO was performed in the same manner as in Example 1 below.₂A lithium cobaltate represented by the following formula was synthesized.
[0073]
The composite oxides of Examples 1 to 5, Comparative Examples 1 to 4, and Reference Examples 1 and 2 were subjected to X-ray diffraction measurement using CuKα rays. The results are shown in Table 1. Of these, the X-ray diffraction patterns of Example 3, Example 5, Comparative Example 1 and Comparative Example 2 are shown in FIGS.
[0074]
[Table 1]

[0075]
As a result of the X-ray diffraction measurement, the X-ray diffraction patterns of Examples 1 to 5 all had the same characteristics. That is, it has two diffraction peaks with a diffraction angle difference of 0.1 ° to 0.3 ° within a diffraction angle range of 17 ° to 20 °, and a diffraction angle range of 43 ° to 46 °. It had two diffraction peaks in which the difference in diffraction angle was 0.3 ° to 0.6 °. Further, from the X-ray diffraction patterns of Examples 1 to 5, the composite oxide used in the present invention is lithium composite oxide (LiNi_{(1-y) / 2}Mn_{(1-y) / 2}Co_yO₂However, y is approximately 0.3 to 0.4) and lithium cobalt oxide (LiCoO₂It was confirmed that it was composed of two phases. This is because the peak of the X-ray diffraction pattern of Examples 1 to 5 is a single-phase lithium composite oxide (LiNi_{(1-y) / 2}Mn_{(1-y) / 2}Co_yO₂Where y is approximately 0.3 to 0.4) and lithium cobaltate (LiCoO₂) Due to almost coincident with the peak.
[0076]
However, the half-value widths of the two diffraction peaks in which the diffraction angles of the X-ray diffraction patterns of Examples 1 to 5 are in the range of 43 ° to 46 ° are larger than those in the case where these exist alone, and the value Is 0.2 ° or more, and the half-width of the diffraction peak on the low angle side is larger than the half-width of the diffraction peak on the high angle side, and the diffraction peak on the low angle side is broader. It was. From this, it was found that in the composite oxide used in the present invention, two phases having different compositions and lattice constants are related to each other.
[0077]
Further, although the composition of the composite oxide as a whole in Examples 1 to 5 was changed, the positions of these diffraction peaks were hardly changed, and only the peak intensity was changed. The lithium composite oxide and lithium cobaltate constituting the composite oxide have almost the same composition in each of Examples 1 to 5, and the composition ratio of the composite oxide as a whole changes as the amount ratio changes. It was estimated that
[0078]
Further, morphological observation with a scanning electron microscope (SEM) and elemental analysis with an electron probe microanalyzer (EPMA) were performed on the composite oxide of Example 3, and two kinds of particles having different compositions were bonded to each other. It was confirmed that composite particles integrated with each other were formed. By taking such a particle form, lithium cobaltate having high electron conductivity binds a plurality of lithium composite oxide particles having inferior electron conductivity containing Ni, Mn, and Co, and an electron conduction path is formed between the particles. Skillfully formed.
[0079]
On the other hand, the X-ray diffraction patterns of Comparative Examples 1 to 3 show a single-phase layered structure. The diffraction angle is in the range of 17 ° to 20 ° and the diffraction angle is in the range of 43 ° to 46 °. There was only one diffraction peak for each. Moreover, in Comparative Example 4 which is a mixture of lithium composite oxide and lithium cobaltate, there were two diffraction peaks each in the above range, but the half width was smaller than that of the above Example, The diffraction peak on the low angle side was also sharp.
[0080]
Next, using the composite oxides of Examples 1 to 5, Comparative Examples 1 to 4, and Reference Example 1, non-aqueous secondary batteries were produced by the method described below.
[0081]
First, 250 parts by mass of N-methyl-2-pyrrolidone is added to 20 parts by mass of polyvinylidene fluoride as a binder and heated to 60 ° C. to dissolve the polyvinylidene fluoride in N-methyl-2-pyrrolidone. Prepared. 450 parts by mass of the composite oxide as a positive electrode active material was added to the binder solution, and 5 parts by mass of carbon black and 25 parts by mass of graphite were further added as a conductive assistant, and stirred to prepare a slurry-like paint. This paint is uniformly applied to both sides of an aluminum foil having a thickness of 20 μm and dried, and then subjected to pressure molding with a roller press, and then cut to form a strip-like positive electrode having an average thickness of 190 μm, a length of 54 mm, and a width of 483 mm. Produced.
[0082]
A separator made of a microporous polyethylene film having a thickness of 25 μm was disposed between each positive electrode using the positive electrode produced as described above and a negative electrode made of lithium foil. Subsequently, LiPF was added to a mixed solvent of ethylene carbonate and ethyl methyl carbonate in a volume ratio of 1: 3.₆1.0 mol / dm^ThreeA non-aqueous secondary battery was prepared by using a non-aqueous solution dissolved at a concentration of 1 as an electrolytic solution and arranging a lithium reference electrode for evaluation of the positive electrode active material.
[0083]
Next, in order to evaluate load characteristics using the non-aqueous secondary battery, the current density with respect to the area of the electrode is 0.5 mA / cm.²As follows, after charging to 4.3 V at room temperature, it was discharged to 3.0 V at different current densities. The result is obtained as a current density of 0.5 mA / cm.²When the discharge capacity is 100%, the current density is 1, 2, 4, 6 mA / cm.²Table 2 shows the capacity retention rate (%).
[0084]
[Table 2]

[0085]
As is clear from Table 2, Examples 1 to 5 show that the capacity retention rate (discharge efficiency) when the current density is increased is higher than that of Comparative Examples 1 to 4. Current density 6mA / cm²When the capacity maintenance rate at is seen, Comparative Examples 1 to 3 are 65 to 66%. This is higher discharge efficiency than the composite oxide of Reference Example 1, but is not a practical value. In Examples 1 to 5, the current density is 6 mA / cm.²Even after discharging, the capacity retention rate was 86% or more as expected. This is because the discharge efficiency at a high current density has been greatly improved by the coexistence of two phases of a lithium composite oxide composed of nickel, manganese and cobalt and a cobalt composite oxide mainly containing cobalt. It is considered a thing. Furthermore, it can be seen from the capacity retention rates of Examples 1 to 5 that the discharge efficiency improves as the cobalt content in the positive electrode active material increases. However, as can be seen from the comparison between Example 5 and Comparative Example 1, this dramatic improvement in discharge efficiency is not simply due to an increase in the cobalt content, but the lithium composite oxide and the cobalt composite oxide described above. This is considered to be achieved by the present invention of coexistence of
[0086]
LiNi_0.33Mn_0.33Co_0.33O₂In the material of Comparative Example 4 in which the lithium composite oxide represented by (Comparative Example 2) and lithium cobaltate (Reference Example 2) are mixed, to some extent, only by mixing lithium cobaltate having high electronic conductivity. It can be seen that the discharge efficiency is improved. However, as is clear from the comparison with Example 3 in which the ratios of Ni, Mn and Co are the same as those in Comparative Example 4, the discharge efficiency is more effectively increased by using the positive electrode active material having the structure of the present invention. be able to.
[0087]
【The invention's effect】
As described above, the cathode composite material includes a plurality of lithium composite oxide particles containing Ni and Mn, and the cobalt composite oxide particles are fixed to the surface of the lithium composite oxide particles. By using the composite particles in which the plurality of lithium composite oxide particles are connected and integrated, a non-aqueous secondary battery having excellent load characteristics, high capacity, and excellent durability against charge / discharge cycles is provided. be able to.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram of composite particles constituting the positive electrode active material of the present invention.
2 is a view showing an X-ray diffraction pattern of a composite oxide of Example 3. FIG.
3 is a view showing an X-ray diffraction pattern of a composite oxide of Example 5. FIG.
4 is a view showing an X-ray diffraction pattern of a composite oxide of Comparative Example 1. FIG.
5 is a view showing an X-ray diffraction pattern of a composite oxide of Comparative Example 2. FIG.
6 is a diagram showing X-ray diffraction patterns in which the diffraction angles of the composite oxides of Example 3, Example 5, Comparative Example 1 and Comparative Example 2 are in the range of 17 ° to 20 °. FIG.
7 is a diagram showing X-ray diffraction patterns in which the diffraction angles of the composite oxides of Example 3, Example 5, Comparative Example 1 and Comparative Example 2 are in the range of 43 ° to 46 °. FIG.

Claims (9)

Formula _{Li 1 + x + α Ni (} 1-x-y + δ) / 2 Mn (1-xy- δ) / 2 M y O 2 ( however, 0 ≦ x ≦ 0.05, -0.05 ≦ α ≦ 0.05, 0 <y <0.45, −0.1 ≦ δ ≦ 0.1, and M is selected from the group consisting of Ti, Cr, Fe, Co, Cu, Zn, Al, Ge, and Sn. A plurality of lithium composite oxide particles having a composition represented by at least one element including Co), and lithium cobalt oxide or a part of cobalt of lithium cobalt oxide is formed on the surface of the lithium composite oxide particles. Cobalt composite oxide particles composed of composite oxides substituted with other metal elements are fixed, and the composite composite particles are formed by connecting and integrating the plurality of lithium composite oxide particles with the cobalt composite oxide particles. A positive electrode active material for a non-aqueous secondary battery.   The positive electrode active material for a non-aqueous secondary battery according to claim 1, wherein M is Co.   The positive electrode active material for a non-aqueous secondary battery according to claim 1, wherein 0.2 <y <0.45 in the general formula. The composite particles include Ni, Mn and M (where M is selected from the group consisting of Ti, Cr, Fe, Co, Cu, Zn, Al, Ge and Sn, and at least one element including Co ). And the atomic ratios of Ni, Mn, and M are averaged to (1-xy−δ) / 2: (1-xy−δ) / 2: y + z (where 0 ≦ x ≦ 0. The positive electrode active material for a non-aqueous secondary battery according to claim 1, wherein 05, 0 <y <0.45, 0.4 <y + z <0.85, −0.24 ≦ δ ≦ 0.24).   The positive electrode active material for a non-aqueous secondary battery according to claim 4, wherein the M is Co. A positive electrode active material for a non-aqueous secondary battery comprising composite particles composed of a mixed phase containing two hexagonal crystals having different lattice constants,
The hexagonal one crystal has the general formula _{Li 1 + x + α Ni (} 1-x-y + δ) / 2 Mn (1-xy- δ) / 2 M y O 2 ( however, 0 ≦ x ≦ 0.05, −0.05 ≦ α ≦ 0.05, 0 <y <0.45, −0.1 ≦ δ ≦ 0.1, and M is Ti, Cr, Fe, Co, Cu, Zn, Al, Ge, and A phase selected from the group consisting of Sn and having a composition represented by at least one element including at least Co;
The positive electrode active for a non-aqueous secondary battery, wherein the other hexagonal crystal is a phase having a composition in which lithium cobaltate or cobalt of lithium cobaltate is substituted with another metal element in a range of 25 mol% or less material. A method for producing a positive electrode active material for a non-aqueous secondary battery comprising composite particles composed of a mixed phase containing two hexagonal crystals having different lattice constants,
The hexagonal one crystal has the general formula _{Li 1 + x + α Ni (} 1-x-y + δ) / 2 Mn (1-xy- δ) / 2 M y O 2 ( however, 0 ≦ x ≦ 0.05, −0.05 ≦ α ≦ 0.05, 0 <y <0.45, −0.1 ≦ δ ≦ 0.1, and M is Ti, Cr, Fe, Co, Cu, Zn, Al, Ge, and A phase selected from the group consisting of Sn and having a composition represented by at least one element including at least Co;
The other of the hexagonal crystals is a phase having a composition in which lithium cobaltate or cobalt of lithium cobaltate is substituted with another metal element in a range of 25 mol% or less,
Calcining a composition containing an excess of Co containing the elements constituting the hexagonal crystal and exceeding the solid solubility limit of the phase represented by the general formula;
A method for producing a positive electrode active material for a non-aqueous secondary battery, wherein the mixed phase is formed by causing phase separation. A non-aqueous secondary battery comprising a positive electrode, a negative electrode and a non-aqueous electrolyte,
The said positive electrode contains the positive electrode active material for nonaqueous secondary batteries in any one of Claims 1-6, The nonaqueous secondary battery characterized by the above-mentioned. A non-aqueous secondary battery comprising a positive electrode, a negative electrode and a non-aqueous electrolyte,
The positive electrode active material includes composite particles composed of a mixed phase containing two hexagonal crystals having different lattice constants,
The hexagonal one crystal has the general formula _{Li 1 + x + α Ni (} 1-x-y + δ) / 2 Mn (1-xy- δ) / 2 M y O 2 ( however, 0 ≦ x ≦ 0.05, −0.05 ≦ α ≦ 0.05, 0 <y <0.45, −0.1 ≦ δ ≦ 0.1, and M is Ti, Cr, Fe, Co, Cu, Zn, Al, Ge, and A phase selected from the group consisting of Sn and having a composition represented by at least one element including at least Co;
The non-aqueous secondary battery, wherein the other hexagonal crystal is a phase having a composition in which lithium cobaltate or cobalt of lithium cobaltate is substituted with another metal element in a range of 25 mol% or less.

Images