JP2012119093A - Positive electrode active material for nonaqueous electrolyte secondary battery and manufacturing method thereof, and nonaqueous electrolyte secondary battery using positive electrode active material - Google Patents

Positive electrode active material for nonaqueous electrolyte secondary battery and manufacturing method thereof, and nonaqueous electrolyte secondary battery using positive electrode active material Download PDF

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JP2012119093A
JP2012119093A JP2010265520A JP2010265520A JP2012119093A JP 2012119093 A JP2012119093 A JP 2012119093A JP 2010265520 A JP2010265520 A JP 2010265520A JP 2010265520 A JP2010265520 A JP 2010265520A JP 2012119093 A JP2012119093 A JP 2012119093A
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JP5973128B2 (en
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Ryuichi Kuzuo
竜一 葛尾
Atsushi Fukui
篤 福井
Hiromasa Toya
広将 戸屋
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Sumitomo Metal Mining Co Ltd
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Abstract

PROBLEM TO BE SOLVED: To provide a positive electrode active material which has a good thermal stability and a high charge and discharge capacity when used as a positive electrode material of a nonaqueous electrolyte secondary battery.SOLUTION: There is provided a method for manufacturing a lithium nickel composite oxide expressed by the general formula, LiNiMO, where x meets the requirement (4-Z)x≥0.75 when the average valence of Ni is denoted by Z, and M represents at least one kind of additional element such that the average valence of M as a whole is 3.375 or more. The method comprises: (1)a crystallization step for adding an alkali solution to a mixed aqueous solution of Ni salt and M salt to obtain a composite hydroxide NiM(OH); (2) a calcination step for mixing the composite hydroxide with lithium compound such that the molar ratio of Li/(Ni+M) is 1.00 to 1.15, and calcining the resultant mixture at a temperature between 700°C or more and 1000°C or less; and (3) a water-washing step for washing a resultant lithium nickel composite oxide by water.

Description

本発明は、非水系電解質二次電池、より具体的にはリチウムイオン二次電池と、その正極材料として用いられる非水系電解質二次電池用正極活物質およびその製造方法に関する。   The present invention relates to a non-aqueous electrolyte secondary battery, more specifically, a lithium ion secondary battery, a positive electrode active material for a non-aqueous electrolyte secondary battery used as a positive electrode material thereof, and a method for producing the same.

近年、携帯電話やノート型パソコンなどの携帯電子機器の普及にともなって、高いエネルギ密度を有する小型で軽量な二次電池の開発が進められている。さらに最近では、電力貯蔵用途や、ハイブリッドカーおよび電気自動車用の電源として、大型の二次電池の研究開発もなされるようになってきている。   In recent years, with the widespread use of portable electronic devices such as mobile phones and laptop computers, development of small and lightweight secondary batteries having high energy density has been promoted. More recently, research and development of large-sized secondary batteries have also been made for power storage applications and as power sources for hybrid cars and electric vehicles.

このような用途に有用な二次電池として、非水系電解質二次電池の一種であるリチウムイオン二次電池がある。現在、リチウムイオン二次電池においては、その負極材料としてグラファイトなどのカーボン材料を、その正極材料としてリチウム金属複合酸化物からなる正極活物質をそれぞれ用いたものが、開発の主流となっている。これらの材料はいずれも、リチウム（Ｌｉ）を脱離および挿入することが可能である。   As a secondary battery useful for such applications, there is a lithium ion secondary battery which is a kind of non-aqueous electrolyte secondary battery. Currently, lithium ion secondary batteries are mainly developed using a carbon material such as graphite as the negative electrode material and a positive electrode active material made of a lithium metal composite oxide as the positive electrode material. Any of these materials can desorb and insert lithium (Li).

正極活物質であるリチウム金属複合酸化物としては、リチウムコバルト複合酸化物（ＬｉＣｏＯ2など）、リチウムマンガン複合酸化物（ＬｉＭｎＯ2など）、およびリチウムニッケル複合酸化物（ＬｉＮｉＯ2など）が用いられている。 As the lithium metal composite oxide that is a positive electrode active material, lithium cobalt composite oxide (LiCoO 2 etc.), lithium manganese composite oxide (LiMnO 2 etc.), and lithium nickel composite oxide (LiNiO 2 etc.) are used. Yes.

このうち、リチウムコバルト複合酸化物は、その合成が比較的容易であり、４Ｖ級の高い電圧が得られることから、高いエネルギ密度を有する電池材料として期待されている。このため、その実用化のために、優れた初期容量特性やサイクル特性を得るための研究開発が盛んに行われている。   Among these, the lithium cobalt composite oxide is expected to be a battery material having a high energy density because its synthesis is relatively easy and a high voltage of 4V class can be obtained. For this reason, research and development for obtaining excellent initial capacity characteristics and cycle characteristics has been actively conducted for practical use.

しかしながら、リチウムコバルト複合酸化物は、主原料であるコバルト化合物が高価であるため、電池のコストアップの原因となっている。特に、リチウムイオン二次電池を、携帯機器用の小型電池だけでなく、電力貯蔵用、ハイブリッドカー用、電気自動車用の大型二次電池にまでその適用を広げることが期待されているが、より安価なリチウムイオン二次電池の製造を可能とする正極材料を提供できれば、広範な分野への波及効果があると考えられる。   However, the lithium cobalt composite oxide is a cause of the cost increase of the battery because the cobalt compound as the main raw material is expensive. In particular, lithium ion secondary batteries are expected to be used not only for small batteries for portable devices but also for large-sized secondary batteries for power storage, hybrid cars, and electric vehicles. If a positive electrode material capable of manufacturing an inexpensive lithium ion secondary battery can be provided, it is considered that there is a ripple effect in a wide range of fields.

このような観点から、リチウムコバルト複合酸化物に代替する正極活物質として、コバルト（Ｃｏ）より安価な材料であるニッケル（Ｎｉ）やマンガン（Ｍｎ）を用いる、リチウムニッケル複合酸化物やリチウムマンガン複合酸化物が着目されている。   From this point of view, nickel (Ni) and manganese (Mn), which are cheaper materials than cobalt (Co), are used as a positive electrode active material that replaces lithium cobalt composite oxide. Oxides are drawing attention.

このうち、リチウムマンガン複合酸化物は、熱安定性（発火などについての安全性）に優れているが、理論容量がリチウムコバルト複合酸化物の半分程度しかないため、年々高まるリチウムイオン二次電池の高容量化への要求に応えることができないという問題がある。また、４５℃以上では、自己放電が激しく、充放電寿命が低下するという問題もある。   Among these, lithium manganese composite oxide is excellent in thermal stability (safety with respect to ignition, etc.), but its theoretical capacity is only about half that of lithium cobalt composite oxide. There is a problem that it cannot meet the demand for higher capacity. Moreover, at 45 degreeC or more, there exists a problem that self-discharge is intense and a charge / discharge lifetime falls.

これに対して、リチウムニッケル複合酸化物は、リチウムコバルト複合酸化物とほぼ同様の理論容量を有し、かつ、やや低い電池電圧を示す。このため、電解液の酸化による分解が問題になりにくく、より高容量が期待できるため、その研究開発も活発に行われている。   On the other hand, the lithium nickel composite oxide has almost the same theoretical capacity as the lithium cobalt composite oxide and exhibits a slightly lower battery voltage. For this reason, decomposition due to oxidation of the electrolytic solution is less likely to be a problem, and higher capacity can be expected. Therefore, research and development is actively conducted.

ただし、Ｎｉを他の添加元素で置換せずに、純粋にＮｉのみで構成したリチウムニッケル複合酸化物を正極材料として用いてリチウムイオン二次電池を作製した場合、リチウムコバルト複合酸化物を正極活物質として用いた場合に比べて、サイクル特性に劣るという問題とともに、高温環境下での使用や保存により比較的電池性能を損ないやすいという問題がある。   However, when a lithium-ion secondary battery is produced using a lithium-nickel composite oxide composed purely of Ni as a positive electrode material without replacing Ni with other additive elements, the lithium cobalt composite oxide is used as the positive electrode active material. In addition to the problem that the cycle characteristics are inferior to the case of using as a substance, there are problems that battery performance is relatively easily lost due to use and storage in a high temperature environment.

リチウムニッケル複合酸化物に関するこのような問題の解決を図るために、たとえば、特許文献１では、高温環境下での使用や保存によっても良好な電池性能を維持することを目的として、フッ素を添加した、ＬｉwＮｉxＣｏyＢzＯ2（０．０５≦ｗ≦１．１０、０．５≦ｘ≦０．９９５、０．００５≦ｚ≦０．２０、ｘ＋ｙ＋ｚ＝１）で表されるリチウムニッケル複合酸化物が提案されている。 In order to solve such a problem related to the lithium nickel composite oxide, for example, in Patent Document 1, fluorine is added for the purpose of maintaining good battery performance even when used and stored in a high temperature environment. Li w Ni x Co y B z O 2 (0.05 ≦ w ≦ 1.10, 0.5 ≦ x ≦ 0.995, 0.005 ≦ z ≦ 0.20, x + y + z = 1) Lithium nickel composite oxides have been proposed.

また、特許文献２では、自己放電特性やサイクル特性を向上させることを目的として、ＮｉとＣｏの一部を他の添加元素Ｍで置換した、ＬｉxＮｉaＣｏbＭcＯ2（０．８≦ｘ≦１．２、０．０１≦ａ≦０．９９、０．０１≦ｂ≦０．９９、０．０１≦ｃ≦０．３、０．８≦ａ＋ｂ＋ｃ≦１．２、ＭはＡｌ、Ｖ、Ｍｎ、Ｆｅ、ＣｕおよびＺｎから選ばれる少なくとも１種の添加元素）で表されるリチウムニッケル複合酸化物が提案されている。 In Patent Document 2, Li x Ni a Co b M c O 2 (0...) In which a part of Ni and Co is substituted with another additive element M for the purpose of improving self-discharge characteristics and cycle characteristics. 8 ≦ x ≦ 1.2, 0.01 ≦ a ≦ 0.99, 0.01 ≦ b ≦ 0.99, 0.01 ≦ c ≦ 0.3, 0.8 ≦ a + b + c ≦ 1.2, M is There has been proposed a lithium nickel composite oxide represented by at least one additive element selected from Al, V, Mn, Fe, Cu and Zn.

通常、これらのリチウムニッケル複合酸化物は、原料であるリチウム化合物、ニッケル化合物、その他の金属化合物を混合し、所定温度で焼成することにより得られる。   Usually, these lithium nickel composite oxides are obtained by mixing lithium compounds, nickel compounds, and other metal compounds as raw materials and firing them at a predetermined temperature.

しかしながら、このような従来のリチウムニッケル複合酸化物は、リチウムコバルト複合酸化物と比べて充電容量、放電容量ともに高く、サイクル特性も改善されているが、満充電状態で高温環境下に放置しておくと、リチウムコバルト複合酸化物に比べて低い温度から酸素放出を伴う分解が始まり、その結果、これを用いた電池の内部圧力が上昇して、最悪の場合、電池が破損する危険を有している。また、放出された酸素が、電解液の燃焼を引き起こし、電池の温度が急激に上昇してしまうといった危険性もはらんでいる。   However, such a conventional lithium nickel composite oxide has higher charge capacity and discharge capacity and improved cycle characteristics compared to lithium cobalt composite oxide, but it is left in a high temperature environment in a fully charged state. If this occurs, the decomposition with oxygen release starts at a lower temperature than lithium cobalt composite oxide, and as a result, the internal pressure of the battery using this increases, and in the worst case, there is a risk of the battery being damaged. ing. In addition, there is a risk that the released oxygen causes the electrolyte to burn and the temperature of the battery rapidly increases.

これに対して、たとえば、特許文献３では、熱安定性を向上させることを目的として、添加元素Ｍの添加により結晶構造を安定化させた、ＬｉaＭbＮｉcＣｏdＯe（ＭはＡｌ、Ｍｎ、Ｓｎ、Ｉｎ、Ｆｅ、Ｖ、Ｃｕ、Ｍｇ、Ｔｉ、ＺｎおよびＭｏからなる群から選ばれる少なくとも１種の金属であり、かつ０＜ａ＜１．３、０．０２≦ｂ≦０．５、０．０２≦ｄ／ｃ＋ｄ≦０．９、１．８＜ｅ＜２．２の範囲であって、さらにｂ＋ｃ＋ｄ＝１である）で表されるリチウム含有複合酸化物が提案されている。 On the other hand, for example, in Patent Document 3, Li a M b Ni c Co d O e (M is a crystal structure stabilized by adding an additional element M for the purpose of improving thermal stability. It is at least one metal selected from the group consisting of Al, Mn, Sn, In, Fe, V, Cu, Mg, Ti, Zn and Mo, and 0 <a <1.3, 0.02 ≦ b ≦ 0.5, 0.02 ≦ d / c + d ≦ 0.9, 1.8 <e <2.2, and b + c + d = 1) is further proposed. ing.

現在、このような添加元素Ｍとして、特にアルミニウム（Ａｌ）を選択した場合、ＮｉからＡｌへの置換量を多くすると、正極活物質の分解反応は抑えられ、熱安定性が向上することが確かめられている。しかしながら、十分な安定性を確保するのに有効なＡｌ量でＮｉを置換すると、充放電反応にともなう酸化還元反応に寄与するＮｉの量が減少するため、電池性能として最も重要である初期容量が大きく低下してしまうという問題が生ずる。   At present, when aluminum (Al) is selected as the additive element M, it is confirmed that increasing the amount of substitution from Ni to Al suppresses the decomposition reaction of the positive electrode active material and improves the thermal stability. It has been. However, if Ni is replaced with an amount of Al effective to ensure sufficient stability, the amount of Ni contributing to the oxidation-reduction reaction accompanying the charge / discharge reaction decreases, so the initial capacity, which is the most important for battery performance, is reduced. There arises a problem that it is greatly reduced.

さらに、熱安定性と高い充放電容量を両立させることを目的として、たとえば、特許文献４では、ＬｉＮｉxＭ1-xＯ2（ただし、式中のｘは、Ｎｉの平均価数をＺとしたときに、（４−Ｚ）ｘ≧０．７５を満たし、式中のＭは、Ｍ全体としての平均価数が３価以上となる少なくとも１種の添加元素を表す）で表されるリチウムニッケル複合酸化物が提案されている。なお、特許文献４では、リチウムニッケル複合酸化物の結晶構造的な安定を図るために、好ましくは、最初に共沈法によりＮｉと添加元素Ｍの複合水酸化物を得て、この複合水酸化物とリチウム化合物とを混合し、所定温度で焼成する製造方法をとることが開示されている。このリチウムニッケル複合酸化物の粉末を正極材料として用いた非水系電解質二次電池では、Ｌｉ0.25ＮｉxＭ1-xＯ2なる組成まで充電したときに、４価のＮｉのモル数がＮｉとＭを合わせたモル数の６０％以下となって、その熱的安定性が改善されている。しかしながら、その充放電容量については十分とはいえず、さらなる改善が望まれている。 Furthermore, for the purpose of achieving both thermal stability and high charge / discharge capacity, for example, in Patent Document 4, LiNi x M 1-x O 2 (where x is the average valence of Ni and Z (4-Z) x ≧ 0.75, and M in the formula represents at least one additive element having an average valence of 3 or more as a whole. Nickel composite oxides have been proposed. In Patent Document 4, in order to stabilize the crystal structure of the lithium nickel composite oxide, preferably, a composite hydroxide of Ni and an additive element M is first obtained by coprecipitation, and this composite hydroxide is obtained. It is disclosed to take a manufacturing method in which a product and a lithium compound are mixed and fired at a predetermined temperature. In a non-aqueous electrolyte secondary battery using this lithium nickel composite oxide powder as a positive electrode material, when charged to a composition of Li 0.25 Ni x M 1-x O 2 , the number of moles of tetravalent Ni is Ni and It becomes 60% or less of the total number of moles of M, and its thermal stability is improved. However, the charge / discharge capacity is not sufficient, and further improvement is desired.

現在、携帯電子機器などの小型二次電池に対する高容量化の要求は年々高まる一方であり、安全性を確保するために容量を犠牲にすることは、リチウムニッケル複合酸化物を用いることによる高容量化のメリットを失うことにつながる。一方、自動車用の電源などの大型二次電池においては、高い安全性が重要な要素となることから、安全性に劣るというリチウムニッケル複合酸化物の問題点の解消は大きな課題ということができる。   Currently, the demand for higher capacity for small secondary batteries such as portable electronic devices is increasing year by year, and sacrificing capacity to ensure safety is due to the high capacity by using lithium nickel composite oxide. This leads to the loss of the benefits of conversion. On the other hand, in a large-sized secondary battery such as a power source for automobiles, high safety is an important factor. Therefore, it can be said that solving the problem of lithium nickel composite oxide that is inferior in safety is a big problem.

特開平８−４５５０９号公報JP-A-8-45509 特開平８−２１３０１５号公報Japanese Patent Laid-Open No. 8-213015 特開平５−２４２８９１号公報Japanese Patent Laid-Open No. 5-242891 特開２００６−１０７８１８号公報JP 2006-107818 A

本発明は、かかる問題点に鑑みてなされたものであって、非水系電解質二次電池の正極材料として用いた場合に、熱安定性が良好で、かつ、高い充放電容量を備える正極活物質を提供することを目的とする。   The present invention has been made in view of such problems, and when used as a positive electrode material for a non-aqueous electrolyte secondary battery, a positive electrode active material having good thermal stability and high charge / discharge capacity The purpose is to provide.

本発明の非水系電解質二次電池用正極活物質の製造方法は、Ｎｉ塩と添加元素の塩であるＭ塩との混合水溶液に、アルカリ溶液を加えて、ＮｉとＭの水酸化物を共沈させ、得られた沈殿物を濾過、水洗、乾燥して、ニッケル複合水酸化物：ＮｉxＭ1-x（ＯＨ）2を得る晶析工程と、得られたニッケル複合水酸化物：ＮｉxＭ1-x（ＯＨ）2とリチウム化合物とを、ＮｉとＭとの合計に対するＬｉのモル比：Ｌｉ／（Ｎｉ＋Ｍ）が１．００〜１．１５となるように混合し、さらに該混合物を、７００℃以上１０００℃以下の温度で焼成して、一般式：ＬｉＮｉxＭ1-xＯ2（ただし、式中のｘは、Ｎｉの平均価数をＺとしたときに、（４−Ｚ）ｘ≧０．７５を満たし、式中のＭは、Ｍ全体としての平均価数が３．３７５価以上となる少なくとも１種の添加元素を表す）で表されるリチウムニッケル複合酸化物を得る焼成工程と、得られたリチウム金属複合酸化物を水洗処理する水洗工程を有することを特徴とする。 In the method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to the present invention, an alkaline solution is added to a mixed aqueous solution of a Ni salt and an M salt, which is a salt of an additive element, and Ni and M hydroxides are combined. Precipitating, filtering, washing and drying the resulting precipitate to obtain a nickel composite hydroxide: Ni x M 1-x (OH) 2 , and the resulting nickel composite hydroxide: Ni x M 1-x (OH) 2 and a lithium compound are mixed so that the molar ratio of Li to the sum of Ni and M: Li / (Ni + M) is 1.00 to 1.15, and the mixture is further mixed. Is calcined at a temperature of 700 ° C. or more and 1000 ° C. or less, and is represented by the general formula: LiNi x M 1-x O 2 (wherein x represents the average valence of Ni when Z is (4- Z) x ≧ 0.75 is satisfied, and M in the formula is at least 1 in which the average valence of M as a whole is 3.375 or more. And a rinsing step of rinsing the obtained lithium metal composite oxide with a calcination step of obtaining a lithium nickel composite oxide represented by the following formula:

前記添加元素Ｍは、通常４価以上の価数をとる、Ｔｉ、Ｖ、Ｍｎ、Ｎｂ、Ｍｏ、Ｒｕ、ＴａおよびＷからなる群から選ばれた少なくとも１種の添加元素、または、Ｔｉ、Ｖ、Ｍｎ、Ｎｂ、Ｍｏ、Ｒｕ、ＴａおよびＷからなる群、および、通常３価以下の価数をとる、Ａｌ、Ｆｅ、Ｃｏ、Ｃｕ、Ｚｎ、Ｇａ、Ｚｒ、ＩｎおよびＳｎからなる群のそれぞれから少なくとも１種ずつ選ばれた元素であることが好ましい。   The additive element M is at least one additive element selected from the group consisting of Ti, V, Mn, Nb, Mo, Ru, Ta, and W, usually having a valence of 4 or more, or Ti, V , Mn, Nb, Mo, Ru, Ta, and W, and each group consisting of Al, Fe, Co, Cu, Zn, Ga, Zr, In, and Sn, which usually have a valence of 3 or less. It is preferable that the element is selected from at least one of them.

また、前記晶析工程の後、前記焼成工程の前に、該晶析工程で得られたニッケル複合水酸化物：ＮｉxＭ1-x（ＯＨ）2を、大気雰囲気中、８００℃未満の温度で、１時間以上の焙焼を行ってニッケル複合酸化物を得る酸化焙焼工程を設けることが好ましい。 In addition, after the crystallization step and before the firing step, the nickel composite hydroxide: Ni x M 1-x (OH) 2 obtained in the crystallization step is less than 800 ° C. in an air atmosphere. It is preferable to provide an oxidation roasting step in which the nickel composite oxide is obtained by roasting at a temperature for 1 hour or more.

さらに、前記水洗工程において、リチウムニッケル複合酸化物を、質量比で水１に対して１〜２投入してスラリーとし、３０分〜６０分間撹拌後、濾過、乾燥することが好ましい。   Furthermore, in the water washing step, it is preferable that the lithium nickel composite oxide is added to the water 1 by 1 to 2 in a mass ratio to form a slurry, stirred for 30 minutes to 60 minutes, filtered and dried.

前記リチウム化合物として、炭酸リチウム、または、水酸化リチウムもしくはその水和物を用いることが好ましく、前記晶析工程において用いるＮｉ塩とＭ塩は、硫酸塩であることが好ましい。   As the lithium compound, lithium carbonate, lithium hydroxide or a hydrate thereof is preferably used, and the Ni salt and M salt used in the crystallization step are preferably sulfates.

本発明の非水系電解質二次電池用正極活物質は、上記のいずれかの製造方法により得られる、一般式：ＬｉＮｉxＭ1-xＯ2（ただし、式中のｘは、Ｎｉの平均価数をＺとしたときに、（４−Ｚ）ｘ≧０．７５を満たし、式中のＭは、Ｍ全体としての平均価数が３．３７５価以上となる少なくとも１種の添加元素を表す）で表されるリチウムニッケル複合酸化物の粉末からなり、かつ、該粉末を正極活物質として用いた非水系電解質二次電池において、Ｌｉ0.25ＮｉxＭ1-xＯ2なる組成まで充電したときに、４価のＮｉのモル数がＮｉとＭを合わせたモル数の６０％以下となる、非水系電解質二次電池用正極活物質である。 The positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention can be obtained by any one of the above-described production methods, and has a general formula: LiNi x M 1-x O 2 (where x is an average value of Ni When the number is Z, (4-Z) x ≧ 0.75 is satisfied, and M in the formula represents at least one additive element having an average valence of M of 3.375 or more as a whole. In a non-aqueous electrolyte secondary battery using the powder as a positive electrode active material and charged to a composition of Li 0.25 Ni x M 1-x O 2 And a positive electrode active material for a non-aqueous electrolyte secondary battery in which the number of moles of tetravalent Ni is 60% or less of the number of moles of Ni and M combined.

かかる正極活物質は、２０３２型のコイン電池の正極材料として用いた場合、該２０３２型のコイン電池は、１８２ｍＡｈ／ｇ以上の初期放電容量と、示差走査熱量計を用いた測定による４００Ｊ／ｇ以下、より好ましくは３００Ｊ／ｇ以下の発熱量とを示す点にも特徴がある。   When such a positive electrode active material is used as a positive electrode material of a 2032 type coin battery, the 2032 type coin battery has an initial discharge capacity of 182 mAh / g or more and 400 J / g or less measured by using a differential scanning calorimeter. More preferably, it also has a heat generation amount of 300 J / g or less.

本発明の非水系電解質二次電池は、本発明の非水系電解質二次電池用正極活物質を正極材料として用いたものである。   The nonaqueous electrolyte secondary battery of the present invention uses the positive electrode active material for a nonaqueous electrolyte secondary battery of the present invention as a positive electrode material.

本発明により、熱安定性と充放電容量のいずれもが改善され、これら熱安定性と充放電容量とを高い水準で両立させた非水系電解質二次電池用正極活物質を得ることができる。したがって、本発明に係る非水系電解質二次電池は、携帯電子機器などの小型二次電池に対する高容量化の要求に対応でき、また、リチウムイオン二次電池を大型二次電池に用いる動きの中で、ハイブリッド自動車や電気自動車の用途に安全性を満足できる電源として用いることができ、工業的価値が非常に高いということができる。   According to the present invention, both the thermal stability and the charge / discharge capacity are improved, and a positive electrode active material for a non-aqueous electrolyte secondary battery in which the thermal stability and the charge / discharge capacity are compatible at a high level can be obtained. Therefore, the non-aqueous electrolyte secondary battery according to the present invention can meet the demand for higher capacity for small-sized secondary batteries such as portable electronic devices, and the movement of using lithium-ion secondary batteries for large-sized secondary batteries. Therefore, it can be used as a power source that can satisfy safety in applications of hybrid vehicles and electric vehicles, and it can be said that the industrial value is very high.

電池評価に用いたコイン電池を示す断面図である。It is sectional drawing which shows the coin battery used for battery evaluation.

本発明者は、リチウムニッケル複合酸化物の熱安定性と充放電容量の両立について研究した結果、Ｎｉの含有量と平均価数が特定の関係式を満たし、かつ、添加元素Ｍの平均価数が所定値以上となる場合に、充電時において熱的に不安定な４価のＮｉのモル数が、Ｎｉと添加元素Ｍを合わせたモル数の６０％以下となり、熱安定性の向上を図れること、および、リチウム化合物との混合、焼成により得られたリチウムニッケル複合酸化物を水洗することにより、充放電容量の改善を図れることを見出し、本発明を完成するに至ったものである。   As a result of studying the compatibility between the thermal stability and charge / discharge capacity of the lithium nickel composite oxide, the present inventor has found that the Ni content and the average valence satisfy a specific relational expression, and the average valence of the additive element M Is equal to or greater than a predetermined value, the number of moles of tetravalent Ni that is thermally unstable during charging is 60% or less of the total number of moles of Ni and additive element M, and thermal stability can be improved. In addition, the present inventors have found that the charge / discharge capacity can be improved by washing the lithium nickel composite oxide obtained by mixing and baking with a lithium compound with water, thereby completing the present invention.

以下、本発明の実施の形態ついて説明するが、最初に、本発明に係る非水系電解質二次電池用正極活物質について説明し、その後、非水系電解質二次電池用正極活物質の製造方法、非水系電解質二次電池の順に説明する。   Hereinafter, embodiments of the present invention will be described. First, a positive electrode active material for a non-aqueous electrolyte secondary battery according to the present invention will be described, and then a method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, The nonaqueous electrolyte secondary battery will be described in this order.

（１）非水系電解質二次電池用正極活物質
本発明に係る非水系電解質二次電池用正極活物質は、一般式：ＬｉＮｉxＭ1-xＯ2（ただし、式中のｘは、Ｎｉの平均価数をＺとしたときに、（４−Ｚ）ｘ≧０．７５を満たし、式中のＭは、Ｍ全体としての平均価数が３．３７５価以上となる少なくとも１種以上の添加元素を表す）で表されるリチウムニッケル複合酸化物の粉末からなり、かつ、該粉末を正極活物質として用いた非水系電解質二次電池においてＬｉ0.25ＮｉxＭ1-xＯ2なる組成まで充電したときに、４価のＮｉのモル数が、ＮｉとＭを合わせたモル数の６０％以下となる点に特徴がある。 (1) The positive electrode active material for a non-aqueous electrolyte secondary battery according to the positive electrode active material present invention for a nonaqueous electrolyte secondary battery has the general formula: LiNi x M 1-x O 2 ( here, x in the formula is, Ni When the average valence of Z is Z, (4-Z) x ≧ 0.75 is satisfied, and M in the formula is at least one kind of M having an average valence of 3.375 or more as a whole. And a composition of Li 0.25 Ni x M 1-x O 2 in a non-aqueous electrolyte secondary battery using the powder as a positive electrode active material. It is characterized in that when charged, the number of moles of tetravalent Ni is 60% or less of the number of moles of Ni and M combined.

まず、本発明では、Ｌｉ0.25ＮｉxＭ1-xＯ2なる組成まで充電したときに、４価のＮｉのモル数がＮｉとＭを合わせたモル数の６０％以下となることが必要である。以下、この点について説明する。 First, in the present invention, when charged to a composition of Li 0.25 Ni x M 1-x O 2 , the number of moles of tetravalent Ni needs to be 60% or less of the number of moles of Ni and M combined. is there. Hereinafter, this point will be described.

リチウムイオン二次電池の充放電反応は、正極活物質内のＬｉイオンが可逆的に出入りすることで進行する。充電によってＬｉが引き抜かれた正極活物質は高温で不安定であり、加熱すると活物質が分解して酸素を放出し、この酸素が電解液の燃焼を引き起こし、発熱反応が起こる。   The charge / discharge reaction of the lithium ion secondary battery proceeds by reversibly entering and exiting Li ions in the positive electrode active material. The positive electrode active material from which Li has been extracted by charging is unstable at high temperatures, and when heated, the active material decomposes and releases oxygen, which causes combustion of the electrolyte and an exothermic reaction.

従来、正極活物質の熱安定性の改善には、Ａｌのような酸素との共有結合性の強い元素でＮｉの一部を置換することで、充電状態の正極活物質の分解反応を抑える方法が一般的にとられている。ただし、ＮｉからＡｌへの置換量が多くなることは、充放電反応にともなう酸化還元反応に寄与するＮｉの量が減少して、充電容量の低下を招くことを意味する。このように、Ｎｉの一部をＡｌで置換した構成では、高い充放電容量と良好な熱安定性の両立が困難である。   Conventionally, in order to improve the thermal stability of the positive electrode active material, a method of suppressing the decomposition reaction of the positive electrode active material in a charged state by substituting a part of Ni with an element having strong covalent bond with oxygen such as Al Is generally taken. However, an increase in the amount of substitution from Ni to Al means that the amount of Ni that contributes to the oxidation-reduction reaction accompanying the charge / discharge reaction decreases, leading to a reduction in charge capacity. Thus, in the configuration in which a part of Ni is replaced with Al, it is difficult to achieve both high charge / discharge capacity and good thermal stability.

リチウムニッケル複合酸化物の熱安定性がリチウムコバルト複合酸化物やリチウムマンガン複合酸化物に比べて劣る原因は、主として高い価数のＮｉの不安定性にある。充電状態、すなわち、Ｌｉを引き抜いた状態の正極活物質は、充放電反応に寄与する元素が価数の高い状態になっているが、４価のＮｉが４価のＣｏやＭｎに比べて安定性が低い。ＮｉＯ2は、ＣｏＯ2やＭｎＯ2に比べて不安定であり、加熱によって容易に、しかも急激に酸素を放出してＮｉＯに変化する。逆にいえば、リチウムニッケル複合酸化物の充電状態で４価のＮｉ量を減らすことができれば、必然的にリチウムニッケル複合酸化物の安定性が向上することになる。 The reason why the thermal stability of the lithium nickel composite oxide is inferior to that of the lithium cobalt composite oxide or lithium manganese composite oxide is mainly due to the instability of high valence Ni. In the positive electrode active material in a charged state, that is, a state where Li is extracted, the element contributing to the charge / discharge reaction is in a high valence state, but tetravalent Ni is more stable than tetravalent Co or Mn. The nature is low. NiO 2 is unstable as compared with CoO 2 and MnO 2 , and easily and rapidly releases oxygen by heating and changes to NiO. In other words, if the amount of tetravalent Ni can be reduced in the charged state of the lithium nickel composite oxide, the stability of the lithium nickel composite oxide is necessarily improved.

本発明者は、電池を充電した際に、Ｌｉが引き抜かれた正極活物質に含まれる４価のＮｉのモル数が、ＮｉとＭを合わせたモル数の６０％以下となっていれば、熱的に不安定な４価のＮｉが減少し、結晶の安定性が改善されて、十分な熱安定性を実現できることをすでに実験的に確認している（特開２００６−１０７８１８号公報参照）。   When the present inventors charged the battery, the number of moles of tetravalent Ni contained in the positive electrode active material from which Li was extracted is 60% or less of the number of moles of Ni and M combined. It has already been experimentally confirmed that the thermally unstable tetravalent Ni is reduced, the stability of the crystal is improved, and sufficient thermal stability can be realized (see JP-A-2006-107818). .

充電後の正極活物質に含まれる４価のＮｉ量を減らすには、充電容量そのものを低く抑えることでも実現できる。たとえば、理論容量が約２８０ｍＡｈ／ｇであるＬｉＮｉＯ2において、充電容量を１６８ｍＡｈ／ｇに抑えれば、充電状態の活物質はＬｉ0.40Ｎｉ0.60 4+Ｎｉ0.40 3+Ｏ2となり、４価のＮｉ量は６０％となる。しかし、この場合、初期充放電効率が９０％程度のＬｉＮｉＯ2においては、初期放電容量が１５１ｍＡｈ／ｇ程度となり、十分な容量を有した電池とはならない。 Reducing the amount of tetravalent Ni contained in the positive electrode active material after charging can also be realized by keeping the charging capacity itself low. For example, in LiNiO 2 having a theoretical capacity of about 280 mAh / g, if the charge capacity is suppressed to 168 mAh / g, the active material in the charged state becomes Li 0.40 Ni 0.60 4+ Ni 0.40 3+ O 2 and tetravalent Ni The amount will be 60%. However, in this case, in LiNiO 2 having an initial charge / discharge efficiency of about 90%, the initial discharge capacity is about 151 mAh / g, and the battery does not have a sufficient capacity.

リチウムニッケル複合酸化物の特徴である高容量を生かすためには、７５％程度のＬｉを引き抜く必要がある。すなわち、ＬｉＮｉＯ2を高容量のものとする場合、充電状態の活物質はＬｉ0.25Ｎｉ0.75 4+Ｎｉ0.25 3+Ｏ2となり、４価のＮｉ量が６０％を超えてしまう。 In order to take advantage of the high capacity characteristic of the lithium nickel composite oxide, it is necessary to extract about 75% of Li. That is, when LiNiO 2 has a high capacity, the charged active material is Li 0.25 Ni 0.75 4+ Ni 0.25 3+ O 2 , and the amount of tetravalent Ni exceeds 60%.

このため、まず、本発明では、Ｎｉの一部を別の添加元素Ｍにより置換したリチウムニッケル複合酸化物とするとともに、一般式：ＬｉＮｉxＭ1-xＯ2で表される正極活物質において、Ｎｉの平均価数をＺとしたときに、式中のｘの範囲を（４−Ｚ）ｘ≧０．７５の関係式が満たされるようにその組成を規制している。この理由は、Ｎｉのみで充放電反応を行ったとしても７５％以上のＬｉを引き抜けるようにするためである。すなわち、充電後にＮｉがとる価数である４と充電前の平均価数Ｚとの差から導かれる、充電に伴うＮｉの電荷変化の総量が０．７５以上であれば、７５％以上のＬｉを引き抜いたことにより生じる電荷増をＮｉのみで補償することができる。 Therefore, in the present invention, first, in the positive electrode active material represented by the general formula: LiNi x M 1-x O 2 , a part of Ni is replaced with another additive element M to form a lithium nickel composite oxide. When the average valence of Ni is Z, the composition is regulated so that the relational expression (4-Z) x ≧ 0.75 is satisfied in the range of x in the formula. This is because 75% or more of Li can be pulled out even if the charge / discharge reaction is performed only with Ni. That is, if the total amount of Ni charge change accompanying charging, derived from the difference between 4 which is the valence of Ni after charging and the average valence Z before charging, is 0.75 or more, 75% or more of Li The charge increase caused by drawing out can be compensated only by Ni.

たとえば、７５％以上のＬｉを引き抜くことを可能とするためには、Ｎｉの平均価数がＺ＝３である場合には、ｘは０．７５以上必要となり、また、Ｚ＝２．７５である場合には、ｘは０．６以上、Ｚ＝２．４である場合には、ｘは０．５以上、それぞれ必要となる。   For example, in order to make it possible to extract 75% or more of Li, when the average valence of Ni is Z = 3, x needs to be 0.75 or more, and Z = 2.75. In some cases, x is 0.6 or more, and in the case of Z = 2.4, x is 0.5 or more.

このように、一般式：ＬｉＮｉxＭ1-xＯ2において、式中のｘが、（４−Ｚ）ｘ≧０．７５の関係式を満たすようにしておけば、７５％のＬｉを引き抜くことが理論上可能となる。しかしながら、さらに７５％のＬｉを引き抜いた状態でも、４価のＮｉ量が６０％以下となるようにするには、（３−Ｚ）ｘ≧０．１５の関係式を満たす必要がある。この関係式は、次のように導かれる。 Thus, in the general formula: LiNi x M 1-x O 2 , 75% of Li is extracted if x in the formula satisfies the relational expression of (4-Z) x ≧ 0.75. It is theoretically possible. However, even when 75% of Li is pulled out, the relational expression (3-Z) x ≧ 0.15 needs to be satisfied so that the amount of tetravalent Ni becomes 60% or less. This relational expression is derived as follows.

すなわち、添加元素Ｍの平均価数をＹとすると、一般式：ＬｉＮｉxＭ1-xＯ2における電荷補償の関係から、
Ｚｘ＋Ｙ（１−ｘ）＝３ ・・・（１）
となるから、
Ｙ＝（３−Ｚｘ）／（１−ｘ） ・・・（２）
である。 That is, when the average valence of the additive element M is Y, from the relationship of charge compensation in the general formula: LiNi x M 1-x O 2 ,
Zx + Y (1-x) = 3 (1)
So,
Y = (3-Zx) / (1-x) (2)
It is.

Ｌｉが７５％引き抜かれた状態では、４価のニッケル量をｐとすると、Ｌｉ0.25Ｎｉp 4+Ｎｉx-p 3+Ｍ1-x YＯ2における電荷補償の関係から、
４ｐ＋３（ｘ−ｐ）＋Ｙ（１−ｘ）＝３．７５ ・・・（３）
となるから、
ｐ＝−３ｘ−Ｙ（１−ｘ）＋３．７５ ・・・（４）
である。このｐが６０％以下になるためには、
ｐ＝−３ｘ−Ｙ（１−ｘ）＋３．７５≦０．６ ・・・（５）
であり、この式（５）に式（２）を代入すると、
（３−Ｚ）ｘ≧０．１５ ・・・（６）
の関係式が導かれる。 In a state in which Li is withdrawn 75%, the tetravalent nickel content When p, from the relationship between the charge compensation in the Li 0.25 Ni p 4+ Ni xp 3+ M 1-x Y O 2,
4p + 3 (x-p) + Y (1-x) = 3.75 (3)
So,
p = -3x-Y (1-x) +3.75 (4)
It is. In order for this p to be 60% or less,
p = -3x-Y (1-x) + 3.75 ≦ 0.6 (5)
And substituting equation (2) into equation (5),
(3-Z) x ≧ 0.15 (6)
The following relational expression is derived.

たとえば、添加元素Ｍの平均価数Ｙが３．５価とすると、式（１）よりＺ＝（３．５ｘ−０．５）／ｘとなるが、これを式（６）に代入すると、ｘ≦０．７が得られる。したがって、Ｎｉの３０％以上を添加元素Ｍで置換すれば、７５％のＬｉを引き抜けるだけの容量をもち、かつ、このときの４価のＮｉ量が６０％以下となるので、熱安定性に優れた材料となる。   For example, if the average valence Y of the additive element M is 3.5, Z = (3.5x−0.5) / x from equation (1), but if this is substituted into equation (6), x ≦ 0.7 is obtained. Therefore, if 30% or more of Ni is replaced with the additive element M, the capacity is sufficient to extract 75% of Li, and the amount of tetravalent Ni at this time is 60% or less, so that the thermal stability is improved. An excellent material.

ここで、関係式：（４−Ｚ）ｘ≧０．７５と、この関係式：（３−Ｚ）ｘ≧０．１５との関係から、Ｎｉの平均価数を示すＺは２．７５以下とする必要がある。   Here, from the relationship between the relational expression: (4-Z) x ≧ 0.75 and the relational expression: (3-Z) x ≧ 0.15, Z indicating the average valence of Ni is 2.75 or less. It is necessary to.

また、添加元素Ｍは、少なくとも１種以上の任意の添加元素でよく、２種以上の添加元素であってもよいが、７５％のＬｉを引き抜いたときの４価のＮｉの量を６０％以下に抑えるためには、式（１）〜（６）および関係式（４−Ｚ）ｘ≧０．７５から導かれるように、Ｍ全体としての平均価数Ｙを３．３７５価以上にする必要がある。Ｍ全体としての平均価数が３．３７５価未満である場合には、７５％のＬｉを引き抜いたときの４価のＮｉ量ｐが６０％以下とならない。平均価数Ｙの最小値は、次のように導かれる。   The additive element M may be at least one arbitrary additive element or two or more additive elements. The amount of tetravalent Ni when 75% of Li is extracted is 60%. In order to suppress to the following, the average valence Y as a whole M is set to 3.375 or more as derived from the formulas (1) to (6) and the relational expression (4-Z) x ≧ 0.75. There is a need. When the average valence of M as a whole is less than 3.375, the tetravalent Ni amount p when 75% of Li is extracted does not become 60% or less. The minimum value of the average valence Y is derived as follows.

すなわち、式（５）よりＹの最小値、および関係式（４−Ｚ）ｘ≧０．７５よりｘの最小値を求めると、
Ｙ≧３＋０．１５／（１−ｘ） ・・・（７）
ｘ≧０．７５／（４−Ｚ） ・・・（８）
ここで、式（１）よりＺを導くと、
Ｚ＝｛３−Ｙ（１−ｘ）｝／ｘ ・・・（９）
この式（９）を式(８)に代入してｘの最小値を求めると、
ｘ≧（３．７５―Ｙ）／（４−Ｙ） ・・・（１０）
式（７）よりｘが最小値となるとき、Ｙが最小値となるから、式（１０）から得られたｘの最小値である（３．７５―Ｙ）／（４−Ｙ）を式(７)に代入して、Ｙの最小値を求めると、
Ｙ≧３．３７５
となる。 That is, when the minimum value of Y is obtained from the expression (5) and the minimum value of x from the relational expression (4-Z) x ≧ 0.75,
Y ≧ 3 + 0.15 / (1-x) (7)
x ≧ 0.75 / (4-Z) (8)
Here, when Z is derived from the equation (1),
Z = {3-Y (1-x)} / x (9)
Substituting this equation (9) into equation (8) to find the minimum value of x,
x ≧ (3.75−Y) / (4-Y) (10)
When x is the minimum value from Equation (7), Y is the minimum value. Therefore, (3.75-Y) / (4-Y), which is the minimum value of x obtained from Equation (10), is expressed by Substituting into (7) and obtaining the minimum value of Y,
Y ≧ 3.375
It becomes.

添加元素Ｍとしては、通常４価以上の価数をとるＴｉ、Ｖ、Ｍｎ、Ｎｂ、Ｍｏ、Ｒｕ、ＴａおよびＷからなる群から選ばれた少なくとも１種が選択される。これらの４価以上の価数をとる元素を添加することでＮｉの平均価数が２．７５以下となり、７５％のＬｉを引き抜いた状態でも４価のＮｉ量を６０％以下とすることができる。さらに、電池特性改善のため、３価またはそれ以下の価数をとるＡｌ、Ｆｅ、Ｃｏ、Ｃｕ、Ｚｎ、Ｇａ、Ｚｒ、ＩｎおよびＳｎからなる群から選ばれた少なくとも１種を添加することができる。その場合には、同時に４価以上の価数をとる上記元素を添加して、添加元素Ｍ全体としての平均価数を３．３７５価以上にすれば、同様の効果が得られる。   As the additive element M, at least one selected from the group consisting of Ti, V, Mn, Nb, Mo, Ru, Ta and W, which usually has a valence of 4 or more, is selected. By adding these elements having a valence of 4 or more, the average valence of Ni becomes 2.75 or less, and even when 75% of Li is extracted, the amount of tetravalent Ni can be made 60% or less. it can. Furthermore, at least one selected from the group consisting of Al, Fe, Co, Cu, Zn, Ga, Zr, In and Sn having a valence of 3 or less may be added to improve battery characteristics. it can. In that case, the same effect can be obtained by adding the above elements having a valence of 4 or more at the same time to make the average valence of the additive element M as a whole 3.375 or more.

また、本発明の正極活物質の特徴の一つは、製造工程で表面に付着した余剰のリチウム化合物および不純物が除去されていることにある。このため、後述するように、本発明の正極活物質の製造工程においては、原料となる複合水酸化物とリチウム化合物を焼成した後に、水洗工程を設けている。焼成によって得られたリチウムニッケル複合酸化物の表面には、そのままでは余剰のリチウム化合物および不純物が付着しており、これらの付着物により、正極活物質からのＬｉイオンの挿脱が阻害され、リチウムニッケル複合酸化物が本来持っている電池特性、特に充放電容量を十分に発揮できない状態となっている。本発明の正極活物質は、焼成後の水洗によって粒子の表面に付着しているリチウム化合物などの不純物が除去されているため、結晶構造を維持したままリチウムニッケル複合酸化物が持っている充放電容量を十分に確保できる。   One of the features of the positive electrode active material of the present invention is that excess lithium compounds and impurities attached to the surface in the production process are removed. For this reason, as described later, in the manufacturing process of the positive electrode active material of the present invention, a water washing step is provided after firing the composite hydroxide and lithium compound as raw materials. On the surface of the lithium nickel composite oxide obtained by firing, surplus lithium compounds and impurities are attached as they are, and these deposits inhibit the insertion / extraction of Li ions from the positive electrode active material. The battery characteristics inherent to the composite oxide, in particular, the charge / discharge capacity cannot be fully exhibited. In the positive electrode active material of the present invention, since impurities such as lithium compounds adhering to the surface of the particles are removed by washing with water after firing, the charge / discharge of the lithium nickel composite oxide while maintaining the crystal structure Sufficient capacity can be secured.

本発明の正極活物質のさらなる熱安定性の改善を図るためには、好ましくは、その製造工程における、晶析工程後、焼成工程前に酸化焙焼工程をさらに備えて、その結晶性をさらに高めるようにする。酸化焙焼により、充放電容量を低下させることなく、熱安定性をさらに改善することが可能となる。   In order to further improve the thermal stability of the positive electrode active material of the present invention, it is preferable to further include an oxidative roasting step after the crystallization step and before the firing step in the production process, and further improve the crystallinity. Try to increase. Oxidation roasting makes it possible to further improve the thermal stability without reducing the charge / discharge capacity.

本発明の正極活物質は、タップ密度を１．５ｇ／ｃｍ3以上、比表面積が０．２〜２ｍ2／ｇ、平均粒子径が３〜２０μｍであることが好ましい。これらの特性を有することで、非水系電解質二次電池用正極活物質としてより好ましいものとなる。本発明の正極活物質は、後述する製造方法の製造条件を制御することで、容易にこれらの特性を得ることができる。 The positive electrode active material of the present invention preferably has a tap density of 1.5 g / cm 3 or more, a specific surface area of 0.2 to 2 m 2 / g, and an average particle diameter of 3 to 20 μm. By having these characteristics, it becomes more preferable as a positive electrode active material for a non-aqueous electrolyte secondary battery. The positive electrode active material of the present invention can easily obtain these characteristics by controlling the production conditions of the production method described later.

（２）非水系電解質二次電池用正極活物質の製造方法
本発明の製造方法は、Ｎｉ塩と添加元素の塩であるＭ塩との混合水溶液にアルカリ溶液を加えて、ＮｉとＭの水酸化物を共沈させ、得られた沈殿物を濾過、水洗、乾燥して、ニッケル複合水酸化物：ＮｉxＭ1-x（ＯＨ）2を得る晶析工程と、得られたニッケル複合水酸化物とリチウム化合物とを、ＮｉとＭとの合計に対するＬｉのモル比：Ｌｉ／（Ｎｉ＋Ｍ）が１．００〜１．１５となるように混合し、さらに該混合物を７００℃以上１０００℃以下の温度で焼成して、一般式：ＬｉＮｉxＭ1-xＯ2（ただし、式中のｘは、Ｎｉの平均価数をＺとしたときに、（４−Ｚ）ｘ≧０．７５を満たし、式中のＭは、Ｍ全体としての平均価数が３．３７５価以上となる少なくとも１種の添加元素を表す）で表されるリチウムニッケル複合酸化物を得る焼成工程と、得られたリチウムニッケル複合酸化物を水洗処理する水洗工程を有することを特徴とする。 (2) Method for Producing Positive Electrode Active Material for Nonaqueous Electrolyte Secondary Battery In the production method of the present invention, an alkaline solution is added to a mixed aqueous solution of Ni salt and M salt which is a salt of an additive element, and Ni and M water are added. A crystallization step for coprecipitation of oxides, filtration, washing and drying of the resulting precipitate to obtain nickel composite hydroxide: Ni x M 1-x (OH) 2 , and obtained nickel composite water The oxide and the lithium compound were mixed such that the molar ratio of Li to the total of Ni and M: Li / (Ni + M) was 1.00 to 1.15, and the mixture was 700 ° C. or higher and 1000 ° C. or lower. The general formula: LiNi x M 1-x O 2 (where x is (4-Z) x ≧ 0.75 when the average valence of Ni is Z) And M in the formula is at least one additive element whose average valence as a whole is 3.375 or more And a rinsing step of rinsing the obtained lithium nickel composite oxide with water.

（２−ａ）晶析工程
本発明の製造方法は、得られる正極活物質に関して、充電状態においても４価のＮｉのモル数をＮｉとＭを合わせたモル数の６０％以下に規制することにより、結晶性を維持し、熱安定性を改善しようとするものである。したがって、結晶性を維持し、熱安定性を改善するという効果を十分に発揮させるためには、Ｎｉと添加元素Ｍを均一に固溶させることが重要になる。Ｎｉと添加元素Ｍの固溶が不均一であると、場所によってＮｉの価数にばらつきが生じ、得られた正極活物質が優れた熱安定性を発揮できなくなるためである。 (2-a) Crystallization step The production method of the present invention regulates the number of moles of tetravalent Ni to 60% or less of the total number of moles of Ni and M even in a charged state with respect to the obtained positive electrode active material. Therefore, it is intended to maintain the crystallinity and improve the thermal stability. Therefore, in order to sufficiently exhibit the effects of maintaining the crystallinity and improving the thermal stability, it is important to uniformly dissolve Ni and the additive element M. This is because if the solid solution of Ni and the additive element M is non-uniform, the valence of Ni varies depending on the location, and the obtained positive electrode active material cannot exhibit excellent thermal stability.

Ｎｉと添加元素Ｍが均一に固溶するように合成するには、原料段階でＮｉと添加元素Ｍが均一に固溶したニッケル複合水酸化物、もしくはニッケル複合酸化物を用いることが好ましい。したがって、本発明においては、Ｎｉ塩とＭ塩の混合水溶液を中和してＮｉとＭの水酸化物を共沈させ、得られた沈殿物を濾過、水洗、乾燥するという、晶析工程を経ることにより、Ｎｉと添加元素Ｍが原子レベルで均一に固溶したニッケル複合水酸化物：ＮｉxＭ1-x（ＯＨ）2を得ることができる。 In order to synthesize Ni and additive element M so that they are uniformly dissolved, it is preferable to use nickel composite hydroxide or nickel composite oxide in which Ni and additive element M are uniformly dissolved in the raw material stage. Therefore, in the present invention, the crystallization process of neutralizing a mixed aqueous solution of Ni salt and M salt to coprecipitate Ni and M hydroxide, and filtering, washing, and drying the resulting precipitate. By passing, nickel composite hydroxide: Ni x M 1-x (OH) 2 in which Ni and additive element M are uniformly dissolved at the atomic level can be obtained.

本発明の晶析工程には、通常の中和共沈殿法を適用できる。たとえば、Ｎｉ塩とＭ塩の混合水溶液の温度を、３０℃以上６０℃以下、好ましくは４０℃以上５０℃以下に保持し、ｐＨを１０〜１３の範囲、好ましくは１１〜１２の範囲に保持するようにアルカリ溶液を添加しながら、共沈殿させ、得られた沈殿物を濾過し、水洗すればよい。   A normal neutralization coprecipitation method can be applied to the crystallization process of the present invention. For example, the temperature of the mixed aqueous solution of Ni salt and M salt is kept at 30 ° C. or more and 60 ° C. or less, preferably 40 ° C. or more and 50 ° C. or less, and the pH is kept in the range of 10-13, preferably 11-12. In this way, coprecipitation is performed while adding an alkaline solution, and the resulting precipitate is filtered and washed with water.

ここで、混合水溶液の温度が３０℃未満では、混合水溶液における塩の溶解度が低く塩濃度が低いため、複合水酸化物の結晶が十分に成長しない。また、混合水溶液の温度が６０℃を超えると、結晶核の発生が多く微細な粒子が多くなるため、複合水酸化物の粒子が高密度とならない。   Here, when the temperature of the mixed aqueous solution is less than 30 ° C., the solubility of the salt in the mixed aqueous solution is low and the salt concentration is low, so that the crystals of the composite hydroxide do not grow sufficiently. Further, when the temperature of the mixed aqueous solution exceeds 60 ° C., the generation of crystal nuclei increases and the number of fine particles increases, so that the composite hydroxide particles do not become dense.

また、混合水溶液のｐＨは、１０〜１３の範囲に保持されるように制御することが好ましい。ｐＨが１０未満では、複合水酸化物の粒子が粗大になり、ｐＨが１３を超えると複合水酸化物の晶析速度が速くなり、微細な粒子が多くなってしまう。微細な粒子が多過ぎると、これらが焼結して凝集粉を生じてしまうという問題がある。   Moreover, it is preferable to control so that pH of mixed aqueous solution may be hold | maintained in the range of 10-13. When the pH is less than 10, the composite hydroxide particles become coarse, and when the pH exceeds 13, the crystallization rate of the composite hydroxide increases and the number of fine particles increases. When there are too many fine particles, there exists a problem that these will sinter and will produce agglomerated powder.

混合水溶液のｐＨをアルカリ溶液の添加により制御するが、このためのアルカリ溶液は、特に限定されず、たとえば、水酸化ナトリウムまたは水酸化カリウムなどのアルカリ金属水酸化物水溶液を用いることができる。アルカリ金属水酸化物を、直接、混合水溶液に添加することもできるが、ｐＨ制御の容易さから、これを水溶液として添加することが好ましい。アルカリ溶液の添加方法も、特に限定されず、混合水溶液を十分に攪拌しながら、定量ポンプなど、流量制御が可能なポンプで、ｐＨを１０〜１３の範囲に保持するように添加すればよい。   The pH of the mixed aqueous solution is controlled by adding an alkaline solution, and the alkaline solution for this purpose is not particularly limited. For example, an aqueous alkali metal hydroxide solution such as sodium hydroxide or potassium hydroxide can be used. The alkali metal hydroxide can be added directly to the mixed aqueous solution, but it is preferable to add it as an aqueous solution because of easy pH control. The addition method of the alkaline solution is not particularly limited, and the alkali solution may be added so as to maintain the pH in the range of 10 to 13 with a pump capable of controlling the flow rate such as a metering pump while sufficiently stirring the mixed aqueous solution.

さらに、本発明の晶析工程においては、必要に応じて錯化剤を用いることができる。錯化剤を用いることで、Ｎｉ塩とＭ塩の混合水溶液中での溶解度を大きくして、複合水酸化物の結晶を十分に成長させることができる。錯化剤は、特に限定されず、水溶液中でＮｉおよび添加元素Ｍと結合して錯体を形成可能であればよい。たとえば、アンモニウムイオン供給体（アンモニア、硫酸アンモニウム、塩化アンモニウム、炭酸アンモニウム、フッ化アンモニウムなど）、エチレンジアミン四酢酸、ニトリト三酢酸、ウラシル二酢酸およびグリシンがあげられる。なお、Ｎｉ塩とＭ塩の混合水溶液に添加するとｐＨが上昇する錯化剤は、中和時に前記アルカリ溶液とともに混合水溶液に添加することが好ましい。   Furthermore, in the crystallization step of the present invention, a complexing agent can be used as necessary. By using a complexing agent, the solubility in a mixed aqueous solution of Ni salt and M salt can be increased, and crystals of the composite hydroxide can be sufficiently grown. The complexing agent is not particularly limited as long as it can form a complex by binding with Ni and additive element M in an aqueous solution. Examples include ammonium ion donors (ammonia, ammonium sulfate, ammonium chloride, ammonium carbonate, ammonium fluoride, etc.), ethylenediaminetetraacetic acid, nitritotriacetic acid, uracil diacetic acid, and glycine. In addition, it is preferable to add the complexing agent which raises pH when added to the mixed aqueous solution of Ni salt and M salt to the mixed aqueous solution together with the alkaline solution at the time of neutralization.

また、前記混合水溶液の塩濃度は、Ｎｉ塩とＭ塩の合計で１〜２ｍｏｌ／Ｌ、特に１．５〜２．０ｍｏｌ／Ｌとすることが好ましい。混合水溶液の塩濃度が１ｍｏｌ／Ｌ未満であると、塩濃度が低すぎて、複合水酸化物の結晶が十分に成長しない。一方、混合水溶液の塩濃度が２ｍｏｌ／Ｌを超えると、常温での飽和濃度を超えるため、結晶が再析出して配管を詰まらせるなどの危険がある上、結晶核の発生が多く微細な粒子が多くなってしまう。   Moreover, it is preferable that the salt concentration of the said mixed aqueous solution shall be 1-2 mol / L in total of Ni salt and M salt, especially 1.5-2.0 mol / L. If the salt concentration of the mixed aqueous solution is less than 1 mol / L, the salt concentration is too low and the composite hydroxide crystals do not grow sufficiently. On the other hand, if the salt concentration of the mixed aqueous solution exceeds 2 mol / L, the saturated concentration at room temperature is exceeded, so there is a risk of crystals re-depositing and clogging the piping, and there are many crystal nuclei and fine particles. Will increase.

このような本発明の晶析工程に用いるＮｉ塩とＭ塩は、特に限定されず、たとえば、硫酸塩、硝酸塩、塩化物ニッケルなどがあげられる。また、この中でも不純物の混入が少ない硫酸塩を用いることが好ましい。   The Ni salt and M salt used in such a crystallization step of the present invention are not particularly limited, and examples thereof include sulfate, nitrate, nickel chloride and the like. Of these, it is preferable to use a sulfate with less impurities.

晶析工程における反応方式は、特に限定されるものではなく、通常用いられる、バッチ方式、あるいはオーバーフローパイプを備えた反応槽に原料を供給して連続的に生成粒子を採取できる連続方式のいずれも採用することできる。   The reaction method in the crystallization step is not particularly limited, and any of the commonly used batch method or continuous method that can continuously collect the generated particles by supplying raw materials to a reaction vessel equipped with an overflow pipe. Can be adopted.

共沈殿によって得られた複合水酸化物を、濾過した後、水洗する。濾過は、通常用いられる方法でよく、たとえば、遠心機、吸引濾過機を用いて行うことができる。また、水洗は、通常行われる方法でよく、ニッケル複合水酸化物に含まれる余剰の塩基および非還元性錯化剤を除去できればよい。水洗で用いる水としては、不純物混入防止のため、可能な限り不純物含有量の少ない水を用いることが好ましい。   The composite hydroxide obtained by coprecipitation is filtered and washed with water. Filtration may be a commonly used method, and can be performed using, for example, a centrifuge or a suction filter. The washing with water may be performed by a usual method as long as the excess base and the non-reducing complexing agent contained in the nickel composite hydroxide can be removed. As water used in the water washing, it is preferable to use water having as little impurity content as possible in order to prevent contamination with impurities.

（２−ｂ）酸化焙焼工程
酸化焙焼工程は、前記晶析工程で得られたニッケル複合水酸化物：ＮｉxＭ1-x（ＯＨ）2を、後工程である焼成工程の前に、大気雰囲気中で８００℃未満の温度で１時間以上の焙焼を行って、ニッケル複合酸化物：ＮｉxＭ1-x（ＯＨ）2を得る工程である。 (2-b) Oxidation roasting step In the oxidation roasting step, the nickel composite hydroxide: Ni x M 1-x (OH) 2 obtained in the crystallization step is subjected to a post-step calcining step. In this step, the nickel composite oxide: Ni x M 1-x (OH) 2 is obtained by roasting in an air atmosphere at a temperature of less than 800 ° C. for 1 hour or longer.

前記晶析工程により得られたニッケル複合水酸化物を、そのままリチウム化合物と混合して焼成しても、リチウムニッケル複合酸化物を得ることはできるが、一度、大気雰囲気中、８００℃未満の温度で、１時間以上の焙焼を行い、ニッケル複合酸化物としてからリチウム化合物と混合して焼成すると、リチウムニッケル複合酸化物の結晶性がよくなり、充放電容量を低下させることなく、熱安定性がより改善する。   Even if the nickel composite hydroxide obtained by the crystallization step is directly mixed with a lithium compound and fired, a lithium nickel composite oxide can be obtained, but once in the atmosphere, a temperature of less than 800 ° C. Then, after baking for 1 hour or more and mixing with a lithium compound after baking as a nickel composite oxide, the crystallinity of the lithium nickel composite oxide is improved, and the thermal stability is reduced without reducing the charge / discharge capacity. Will be improved.

焙焼温度は、８００℃未満であることが好ましく、より好ましくは３００℃以上７５０℃未満である。焙焼温度が８００℃以上では、複合酸化物の粒子間で焼結が生じて粒子が粗大化し、充放電容量が低下する場合がある。特に、焙焼温度を７５０℃未満とすることにより、充電状態の活物質における４価のＮｉ量の制限と結晶性の向上により、高次元で充放電容量と熱安定性の両立が可能となる。焙焼温度の下限は、特に限定されないが、３００℃未満の温度が低い場合には水酸化物から酸化物への転換が十分に行われず、酸化焙焼の効果を十分に得られないことがある。   The roasting temperature is preferably less than 800 ° C, more preferably 300 ° C or more and less than 750 ° C. When the roasting temperature is 800 ° C. or higher, sintering may occur between the composite oxide particles, the particles may become coarse, and the charge / discharge capacity may decrease. In particular, by setting the roasting temperature to less than 750 ° C., it is possible to achieve both charge / discharge capacity and thermal stability at a high level by limiting the amount of tetravalent Ni in the charged active material and improving the crystallinity. . The lower limit of the roasting temperature is not particularly limited, but when the temperature below 300 ° C. is low, the conversion from hydroxide to oxide is not sufficiently performed, and the effect of oxidative roasting may not be sufficiently obtained. is there.

酸化焙焼時間は、１時間以上が好ましく、より好ましくは３〜１５時間とする。１時間未満では、水酸化物から酸化物への転換が十分に行われない場合があり、また、３時間未満では、結晶性が向上せず、熱安定性が十分に得られない場合がある。   The oxidation roasting time is preferably 1 hour or longer, more preferably 3 to 15 hours. If the time is less than 1 hour, the conversion from hydroxide to oxide may not be sufficiently performed. If the time is less than 3 hours, the crystallinity may not be improved and sufficient thermal stability may not be obtained. .

また、酸化焙焼工程では、含有水分を除去するため、酸化焙焼に際して、最初に焙焼温度よりも低い温度で、かつ２５０℃以上５５０℃以下の温度で少なくとも１時間以上、より好ましくは１〜５時間程度、保持して仮焼することが好ましい。仮焼することで、含有水分を除去することができ、水酸化物から酸化物への転換を十分に行うことができる。   Further, in the oxidation roasting step, in order to remove the contained moisture, at the time of the oxidation roasting, first at a temperature lower than the roasting temperature and at a temperature of 250 ° C. or higher and 550 ° C. or lower for at least 1 hour, more preferably 1 It is preferable to hold and calcine for about 5 hours. By calcination, the contained water can be removed, and the conversion from hydroxide to oxide can be sufficiently performed.

また、酸化焙焼の雰囲気は、大気雰囲気とすることができるが、酸化焙焼が可能な雰囲気であれば、特に問題なく他の酸化性雰囲気を用いることもできる。   The atmosphere for oxidation roasting can be an air atmosphere, but other oxidizing atmospheres can be used without any particular problem as long as the atmosphere can be oxidized roasting.

酸化焙焼に用いる炉は、特に限定されるものではなく、空気気流中で加熱できるものであればよいが、ガス発生のない電気炉が好ましく、バッチ式あるいは連続式の炉を用いることができる。   The furnace used for oxidation roasting is not particularly limited as long as it can be heated in an air stream, but an electric furnace without gas generation is preferable, and a batch type or continuous type furnace can be used. .

（２−ｃ）焼成工程
焼成工程では、晶析工程で得られたニッケル複合水酸化物：ＮｉxＭ1-x（ＯＨ）2、あるいは酸化焙焼工程で得られたニッケル複合酸化物：ＮｉxＭ1-xＯ2と、リチウム化合物とを、Ｎｉと添加元素Ｍとの合計に対するＬｉのモル比Ｌｉ／（Ｎｉ＋Ｍ）が１．００〜１．１５となるように混合し、さらに該混合物を７００℃以上１０００℃以下の温度で熱処理して焼成することで、一般式：ＬｉＮｉxＭ1-xＯ2（ただし、式中のｘは、Ｎｉの平均価数をＺとしたときに、（４−Ｚ）ｘ≧０．７５を満たし、式中のＭは、Ｍ全体としての平均価数が３．３７５価以上となる少なくとも１種の添加元素を表す）で表されるリチウムニッケル複合酸化物を得る。 (2-c) Firing step In the firing step, nickel composite hydroxide obtained in the crystallization step: Ni x M 1-x (OH) 2 , or nickel composite oxide obtained in the oxidation roasting step: Ni x M 1-x O 2 and a lithium compound are mixed so that the molar ratio Li / (Ni + M) of Li to the sum of Ni and additive element M is 1.00 to 1.15, and the mixture Is calcined at a temperature of 700 ° C. or higher and 1000 ° C. or lower and fired to obtain a general formula: LiNi x M 1-x O 2 (where x is the average valence of Ni when Z is Z (4-Z) satisfying x ≧ 0.75, and M in the formula represents at least one additive element having an average valence of M as a whole of 3.375 or more) Obtain an oxide.

Ｎｉと添加元素Ｍとの合計に対するＬｉのモル比Ｌｉ／（Ｎｉ＋Ｍ）が、１．００〜１．１５となるように、ニッケル複合水酸化物もしくはニッケル複合酸化物と、リチウム化合物とを混合することで、結晶性に優れた、すなわち熱安定性が高く、充放電容量が大きいリチウムニッケル複合酸化物を得られる。Ｌｉの原子数が少なく、Ｌｉ／（Ｎｉ＋Ｍ）が１．００未満の場合、後工程で水洗を行っても、得られる正極活物質を用いた非水系電解質二次電池の充放電容量が十分に得られない。また、Ｌｉの原子数が多く、Ｌｉ／（Ｎｉ＋Ｍ）が１．１５を超えると、後工程で水洗を行っても、正極活物質表面に余剰リチウムが残存し、非水系電解質二次電池の充放電容量が十分に得られない。また、これを正極活物質として用いると、電池の充電時にガスを多量に発生するばかりでなく、高ｐＨを示す粉末であるため、電極作製時に使用する有機溶剤などの材料と反応してスラリーがゲル化し、不具合を起こす要因となる。   A nickel composite hydroxide or nickel composite oxide and a lithium compound are mixed so that a molar ratio Li / (Ni + M) of Li to the sum of Ni and additive element M is 1.00 to 1.15. Thus, a lithium nickel composite oxide having excellent crystallinity, that is, high thermal stability and large charge / discharge capacity can be obtained. When the number of Li atoms is small and Li / (Ni + M) is less than 1.00, the charge / discharge capacity of the non-aqueous electrolyte secondary battery using the positive electrode active material obtained is sufficiently high even if washing is performed in a subsequent step. I can't get it. Further, when the number of Li atoms is large and Li / (Ni + M) exceeds 1.15, excess lithium remains on the surface of the positive electrode active material even after washing with water in a subsequent process, and the non-aqueous electrolyte secondary battery is charged. A sufficient discharge capacity cannot be obtained. In addition, when this is used as the positive electrode active material, it not only generates a large amount of gas when charging the battery, but also exhibits a high pH, so that it reacts with a material such as an organic solvent used at the time of electrode preparation to produce a slurry. Gelates and causes trouble.

前記リチウム化合物の種類は、特に限定されるものではなく、入手が容易であり、かつ、取扱いも容易なものが好ましい。炭酸リチウム、または水酸化リチウムもしくはその水和物が好適に用いられる。その他、硝酸リチウムや硫酸リチウムなども用いることができる。   The kind of the lithium compound is not particularly limited and is preferably easily available and easy to handle. Lithium carbonate, lithium hydroxide or a hydrate thereof is preferably used. In addition, lithium nitrate, lithium sulfate, or the like can also be used.

ニッケル複合水酸化物もしくはニッケル複合酸化物とリチウム化合物は、焼成する前にこれらを十分混合しておくことが好ましい。混合には、一般的な混合機を使用することができ、たとえば、シェーカーミキサやレーディゲミキサ、ジュリアミキサ、Ｖブレンダなどを用いて、ニッケル複合酸化物もしくはニッケル複合酸化物の形骸が破壊されない程度に、これらとリチウム化合物とを十分に混合することができる。   It is preferable that the nickel composite hydroxide or the nickel composite oxide and the lithium compound are sufficiently mixed before firing. For mixing, a general mixer can be used. For example, using a shaker mixer, a Laedige mixer, a Julia mixer, a V blender or the like, the nickel composite oxide or the nickel composite oxide is not destroyed. These and the lithium compound can be sufficiently mixed.

十分に混合した前記混合物を７００℃以上１０００℃以下、好ましくは７３０℃以上８００℃以下の温度で焼成することによって、一般式：ＬｉＮｉxＭ1-xＯ2（ただし、式中のｘは、Ｎｉの平均価数をＺとしたときに、（４−Ｚ）ｘ≧０．７５を満たし、式中のＭは、Ｍ全体としての平均価数が３．３７５価以上となる少なくとも１種の添加元素を表す）で表されるリチウムニッケル複合酸化物、すなわちＬｉとＮｉと添加元素Ｍの複合酸化物を得ることができる。 By firing the sufficiently mixed mixture at a temperature of 700 ° C. or higher and 1000 ° C. or lower, preferably 730 ° C. or higher and 800 ° C. or lower, the general formula: LiNi x M 1-x O 2 (where x is When the average valence of Ni is Z, (4-Z) x ≧ 0.75 is satisfied, and M in the formula is at least one kind of M having an average valence of 3.375 or more as a whole. Lithium-nickel composite oxide represented by an additive element), that is, a composite oxide of Li, Ni, and additive element M can be obtained.

焼成温度が７００℃未満であると、前記複合酸化物粒子中へのＬｉの拡散が十分でなく、余剰のＬｉと未反応の前記複合酸化物が残るため、結晶性が低下するとともに、水洗後も十分な充放電容量を得ることができない。また、１０００℃を超えるとリチウムニッケル複合酸化物粒子間で焼結が生じて粒子が粗大となってしまう。   When the firing temperature is less than 700 ° C., the diffusion of Li into the composite oxide particles is not sufficient, and the excess Li and the unreacted composite oxide remain, so that the crystallinity is lowered and after washing with water However, sufficient charge / discharge capacity cannot be obtained. Moreover, when it exceeds 1000 degreeC, sintering will arise between lithium nickel complex oxide particles, and particle | grains will become coarse.

焼成時間は、少なくとも１時間以上とすることが好ましく、より好ましくは１０〜１５時間とする。１時間未満では、リチウムニッケル複合酸化物の生成が十分に行われず、十分な結晶性が得られないことがある。   The firing time is preferably at least 1 hour, more preferably 10 to 15 hours. If it is less than 1 hour, the lithium nickel composite oxide is not sufficiently produced, and sufficient crystallinity may not be obtained.

焼成工程では、焼成に際して、最初に４５０℃以上５５０℃以下の温度で、少なくとも１時間、より好ましくは１〜５時間程度、保持して仮焼し、引き続いて焼成することが好ましい。リチウム化合物の融点付近で保持することにより、リチウムの拡散を十分に行い、より均一なリチウムニッケル複合酸化物を得ることができる。   In the firing step, it is preferable that the firing is first carried out at a temperature of 450 ° C. or more and 550 ° C. or less for at least 1 hour, more preferably about 1 to 5 hours, followed by calcination, followed by firing. By holding near the melting point of the lithium compound, lithium can be sufficiently diffused to obtain a more uniform lithium-nickel composite oxide.

焼成時の雰囲気は、特に限定されず、前記混合物を十分に酸化させてリチウムニッケル複合酸化物を生成することのできる酸化性雰囲気であればよいが、十分な結晶性を得るために、酸素含有量が２０体積％以上である酸化性雰囲気とすることが好ましく、酸素含有量が８０体積％以上である酸素雰囲気とすることがより好ましい。   The atmosphere at the time of firing is not particularly limited as long as it is an oxidizing atmosphere that can sufficiently oxidize the mixture to produce a lithium nickel composite oxide. The oxidizing atmosphere is preferably 20% by volume or more, and more preferably the oxygen atmosphere is 80% by volume or more.

焼成に用いる炉は、特に限定されるものではなく、十分に雰囲気ガスを流せる状態で加熱できるものであればよいが、ガス発生のない電気炉が好ましく、バッチ式あるいは連続式の炉を用いることができる。   The furnace used for firing is not particularly limited as long as it can be heated in a state in which an atmosphere gas can sufficiently flow, but an electric furnace without gas generation is preferable, and a batch type or continuous type furnace is used. Can do.

（２−ｄ）水洗工程
水洗工程は、焼成工程で得られたリチウムニッケル複合酸化物を水洗処理して、非水系電解質二次電池用正極活物質を得る工程である。上述のように焼成工程で得られたリチウムニッケル複合酸化物の表面には、余剰のリチウムなどが付着しており、水洗によって余剰リチウムを除去する水洗工程は、十分な特性を持った正極活物質を得るために、本発明の製造方法において特に重要な工程である。 (2-d) Water washing step The water washing step is a step of obtaining a positive electrode active material for a non-aqueous electrolyte secondary battery by subjecting the lithium nickel composite oxide obtained in the firing step to a water washing treatment. As described above, excess lithium or the like is attached to the surface of the lithium nickel composite oxide obtained in the firing step, and the water washing step of removing the excess lithium by washing with water has a positive active material with sufficient characteristics. This is a particularly important step in the production method of the present invention.

水洗工程においては、前記リチウムニッケル複合酸化物を、質量比で水１に対して１〜２投入してスラリーとし、３０分〜６０分間撹拌後、濾過、乾燥することが好ましい。リチウムニッケル複合酸化物が水１に対して質量比で１未満であると、リチウムニッケル複合酸化物粒子から過剰にリチウムが溶出し、正極活物質の性能が悪化してしまうことがある。一方、リチウムニッケル複合酸化物が水１に対して質量比で２を超えると、スラリーの粘度が高すぎて、均一撹拌が難しくなり、余剰リチウムを十分に除去できないことがある。   In the water washing step, it is preferable that the lithium nickel composite oxide is added to the water 1 by 1 to 2 in a mass ratio to form a slurry, stirred for 30 minutes to 60 minutes, filtered and dried. When the lithium nickel composite oxide is less than 1 in terms of mass ratio with respect to water 1, lithium is eluted excessively from the lithium nickel composite oxide particles, and the performance of the positive electrode active material may deteriorate. On the other hand, if the lithium nickel composite oxide exceeds 2 in terms of mass ratio with respect to water 1, the viscosity of the slurry is too high, making uniform stirring difficult, and excessive lithium may not be removed sufficiently.

前記撹拌時間が３０分間未満であると、撹拌が均一にならず、余剰リチウムを十分に除去できないことがある。また、６０分間より長くても、リチウムの溶出はある程度で飽和するため、無駄に長時間を要することになるだけである。   If the stirring time is less than 30 minutes, stirring may not be uniform and excess lithium may not be sufficiently removed. Further, even if the time is longer than 60 minutes, the elution of lithium is saturated to some extent, and therefore it takes only a long time.

前記濾過および乾燥としては、通常の方法を用いることができ、たとえば、濾過では吸引濾過、遠心分離などを用いることができ、乾燥では大気乾燥、真空乾燥を用いることができる。   For the filtration and drying, ordinary methods can be used. For example, suction filtration, centrifugation, etc. can be used for filtration, and air drying or vacuum drying can be used for drying.

以上のような、晶析工程、酸化焙焼工程、焼成工程、水洗工程を有する本発明の製造方法によって、熱安定性と充放電容量のいずれもが改善され、これら熱安定性と充放電容量とを高い水準で両立させた、本発明の正極活物質を得ることができる。   As described above, both the thermal stability and the charge / discharge capacity are improved by the production method of the present invention having the crystallization process, the oxidation roasting process, the firing process, and the water washing process. Can be obtained at a high level, and the positive electrode active material of the present invention can be obtained.

（３）非水系電解質二次電池
本発明の非水系電解質二次電池は、正極、負極、非水電解液など、一般の非水系電解質二次電池と同様の構成要素から構成される。なお、以下で説明する実施形態は例示に過ぎず、本発明の非水系電解質二次電池を、当業者の知識に基づいて種々の変更、改良を施した形態でも実施することができる。また、本発明の非水系電解質二次電池は、その用途を特に限定されるものではない。 (3) Non-aqueous electrolyte secondary battery The non-aqueous electrolyte secondary battery of the present invention is composed of the same components as a general non-aqueous electrolyte secondary battery, such as a positive electrode, a negative electrode, and a non-aqueous electrolyte. The embodiment described below is merely an example, and the nonaqueous electrolyte secondary battery of the present invention can be implemented in various modifications and improvements based on the knowledge of those skilled in the art. Moreover, the use of the nonaqueous electrolyte secondary battery of the present invention is not particularly limited.

（３−ａ）正極
まず、正極を形成する正極合材およびこれを構成する各正極材料について説明する。正極は、正極活物質、導電材および結着剤を含んだ正極合材から形成されるが、このうちの正極活物質には上述した本発明の正極活物質が適用されるため、その説明は省略する。 (3-a) Positive Electrode First, the positive electrode mixture forming the positive electrode and each positive electrode material constituting the positive electrode mixture will be described. The positive electrode is formed from a positive electrode mixture containing a positive electrode active material, a conductive material, and a binder, and since the positive electrode active material of the present invention described above is applied to the positive electrode active material, the description thereof is Omitted.

導電材は、正極の電気伝導性を確保する役割を果たすもので、たとえば、カーボンブラック、アセチレンブラック、黒鉛などの炭素物質粉状体の１種または２種以上を混合したものを用いることができる。   The conductive material plays a role of ensuring the electrical conductivity of the positive electrode, and for example, a material obtained by mixing one or more carbon material powders such as carbon black, acetylene black, and graphite can be used. .

結着剤は、活物質粒子をつなぎ止める役割を果たすもので、たとえば、ポリテトラフルオロエチレン、ポリフッ化ビニリデン、フッ素ゴムなどのフッ素樹脂、ポリプロピレン、ポリエチレンなどの熱可塑性樹脂などを用いることができる。必要に応じて、正極活物質、導電材、活性炭を分散させ、結着剤を溶解するための溶剤を、正極合材に添加する。このような溶剤としては、具体的にはＮ−メチル−２−ピロリドンなどの有機溶剤を用いることができる。   The binder plays a role of holding the active material particles, and for example, a fluororesin such as polytetrafluoroethylene, polyvinylidene fluoride, and fluororubber, and a thermoplastic resin such as polypropylene and polyethylene can be used. If necessary, a positive electrode active material, a conductive material, and activated carbon are dispersed, and a solvent for dissolving the binder is added to the positive electrode mixture. Specifically, an organic solvent such as N-methyl-2-pyrrolidone can be used as such a solvent.

また、正極合材には、電気二重層の容量を増加させるために活性炭を添加することができる。   In addition, activated carbon can be added to the positive electrode mixture in order to increase the capacity of the electric double layer.

このような構成を有する正極は、次のようにして作製する。まず、粉末状の正極活物質、導電材および結着剤を混合し、さらに必要に応じて活性炭、粘度調整などの目的の溶剤を添加し、これを混練して正極合材ペーストを作製する。正極合材中のそれぞれの混合比も、リチウムイオン二次電池の性能を決定する重要な要素となる。溶剤を除いた正極合材の固形分の全質量を１００質量％とした場合、一般のリチウムイオン二次電池の正極と同様、それぞれ、正極活物質の含有量を６０〜９５質量％、導電材の含有量を１〜２０質量％、結着剤の含有量を１〜２０質量％とすることが望ましい。次いで、得られた正極合材ペーストを、たとえば、アルミニウム箔製の集電体の表面に塗布し、乾燥して溶剤を飛散させる。必要に応じて、電極密度を高めるために、ロールプレスなどによって加圧することもある。このようにして、シート状の正極を作製することができる。シート状の正極は、目的とする電池に応じて適当な大きさに裁断などし、電池の作製に供することができる。   The positive electrode having such a configuration is manufactured as follows. First, a powdered positive electrode active material, a conductive material, and a binder are mixed, and if necessary, a target solvent such as activated carbon and viscosity adjustment is added and kneaded to prepare a positive electrode mixture paste. Each mixing ratio in the positive electrode composite material is also an important factor that determines the performance of the lithium ion secondary battery. When the total mass of the solid content of the positive electrode mixture excluding the solvent is 100% by mass, the content of the positive electrode active material is 60 to 95% by mass, as in the case of the positive electrode of a general lithium ion secondary battery. The content of is preferably 1 to 20% by mass and the content of the binder is preferably 1 to 20% by mass. Next, the obtained positive electrode mixture paste is applied to the surface of a current collector made of aluminum foil, for example, and dried to disperse the solvent. If necessary, pressurization may be performed by a roll press or the like to increase the electrode density. In this way, a sheet-like positive electrode can be produced. The sheet-like positive electrode can be cut into an appropriate size according to the target battery and used for battery production.

（３−ｂ）負極
負極には、金属リチウム、リチウム合金など、あるいは、リチウムイオンを吸蔵および脱離できる負極活物質に、結着剤を混合し、適当な溶剤を加えてペースト状にした負極合材を、銅などの金属箔集電体の表面に塗布、乾燥し、必要に応じて電極密度を高めるべく圧縮して形成したものを使用する。 (3-b) Negative electrode A negative electrode made of metal lithium, lithium alloy, or the like, or a negative electrode active material capable of inserting and extracting lithium ions, mixed with a binder, and added with a suitable solvent to form a paste. The composite material is applied to the surface of a metal foil current collector such as copper, dried, and compressed to increase the electrode density as necessary.

負極活物質としては、たとえば、天然黒鉛、人造黒鉛、フェノール樹脂などの有機化合物焼成体、コークスなどの炭素物質の粉状体を用いることができる。この場合、負極結着剤としては、正極同様、ポリフッ化ビニリデンなどの含フッ素樹脂などを用いることができ、これら活物質および結着剤を分散させる溶剤としてはＮ−メチル−２−ピロリドンなどの有機溶剤を用いることができる。   As the negative electrode active material, for example, natural graphite, artificial graphite, an organic compound fired body such as phenol resin, and a powdery body of carbon material such as coke can be used. In this case, as the negative electrode binder, a fluorine-containing resin such as polyvinylidene fluoride can be used as in the positive electrode, and the active material and the solvent for dispersing the binder include N-methyl-2-pyrrolidone. Organic solvents can be used.

（３−ｃ）セパレータ
正極と負極との間に、セパレータを挟み込んで配置する。セパレータは、正極と負極とを分離し電解質を保持するものであり、ポリエチレン、ポリプロピレンなどの薄い膜で、微少な孔を多数有する膜を用いることができる。 (3-c) Separator A separator is interposed between the positive electrode and the negative electrode. The separator separates the positive electrode and the negative electrode and retains the electrolyte, and a thin film such as polyethylene or polypropylene and a film having many minute holes can be used.

（３−ｄ）非水系電解液
非水系電解液は、支持塩としてのリチウム塩を有機溶媒に溶解したものである。 (3-d) Non-aqueous electrolyte The non-aqueous electrolyte is obtained by dissolving a lithium salt as a supporting salt in an organic solvent.

有機溶媒としては、エチレンカーボネート、プロピレンカーボネート、ブチレンカーボネート、トリフルオロプロピレンカーボネートなどの環状カーボネート、また、ジエチルカーボネート、ジメチルカーボネート、エチルメチルカーボネート、ジプロピルカーボネートなどの鎖状カーボネート、さらに、テトラヒドロフラン、２−メチルテトラヒドロフラン、ジメトキシエタンなどのエーテル化合物、エチルメチルスルホン、ブタンスルトンなどの硫黄化合物、リン酸トリエチル、リン酸トリオクチルなどのリン化合物などからなる群から選ばれる１種を単独で、あるいは２種以上を混合して用いることができる。   Examples of the organic solvent include cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, and trifluoropropylene carbonate, chain carbonates such as diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, and dipropyl carbonate, and tetrahydrofuran, 2- 1 type selected from the group consisting of ether compounds such as methyltetrahydrofuran and dimethoxyethane, sulfur compounds such as ethylmethylsulfone and butanesultone, phosphorus compounds such as triethyl phosphate and trioctyl phosphate, or a mixture of two or more. Can be used.

支持塩としてのリチウム塩としては、ＬｉＰＦ6、ＬｉＢＦ4、ＬｉＣｌＯ4、ＬｉＡｓＦ6、ＬｉＮ（ＣＦ3ＳＯ2）2など、およびそれらの複合塩を用いることができる。 As the lithium salt as the supporting salt, LiPF 6 , LiBF 4 , LiClO 4 , LiAsF 6 , LiN (CF 3 SO 2 ) 2 , and complex salts thereof can be used.

さらに、非水系電解液は、ラジカル補足剤、界面活性剤および難燃剤などを含んでいてもよい。   Furthermore, the non-aqueous electrolyte solution may contain a radical scavenger, a surfactant, a flame retardant, and the like.

（３−ｅ）電池の形状、構成
以上のように説明してきた正極、負極、セパレータおよび非水系電解液で構成される、本発明に係る非水系電解質二次電池の形状は、円筒型、積層型など、種々のものとすることができる。 (3-e) Shape and configuration of battery The shape of the non-aqueous electrolyte secondary battery according to the present invention, which is composed of the positive electrode, the negative electrode, the separator, and the non-aqueous electrolyte described above, is cylindrical, laminated Various types such as a mold can be used.

いずれの形状をとる場合であっても、正極および負極を、セパレータを介して積層させて電極体とし、この電極体に前記非水系電解液を含浸させる。また、正極集電体と外部に通ずる正極端子との間、並びに負極集電体と外部に通ずる負極端子との間を、集電用リードなどを用いてそれぞれ接続する。そして、以上のように構成したものを電池ケース内に密閉して、非水系電解質二次電池を完成させることができる。   In any case, the positive electrode and the negative electrode are laminated via a separator to form an electrode body, and the electrode body is impregnated with the non-aqueous electrolyte solution. Further, the positive electrode current collector and the positive electrode terminal communicating with the outside, and the negative electrode current collector and the negative electrode terminal communicating with the outside are connected using a current collecting lead or the like. And what was comprised as mentioned above can be sealed in a battery case, and a non-aqueous electrolyte secondary battery can be completed.

（実施例１）
リチウムニッケル複合酸化物：ＬｉＮｉxＭ1-xＯ2において、添加元素ＭをＣｏおよびＭｎとして、Ｎｉ全原子数の２０原子％をＣｏに置換し、２０原子％をＭｎに置換した、ＬｉＮｉ0.60Ｃｏ0.20Ｍｎ0.20Ｏ2（ｘ＝０．６０に相当）を合成した。このとき、ＣｏとＭｎからなる添加元素Ｍの平均価数はＹ＝３．５であり、Ｎｉの平均価数は、Ｚ＝２．６６７となり、（４−Ｚ）ｘ＝０．８０となる。また、Ｌｉ0.25ＮｉxＭ1-xＯ2なる組成まで充電したときに、電荷増をＮｉのみで補償するとしても、４価のＮｉのモル数は、ＮｉとＣｏとＭｎを合わせたモル数の５５％となる。 Example 1
Lithium nickel complex oxide: In LiNi x M 1-x O 2 , the added element M as Co and Mn, replacing 20 atomic% of Ni the total number of atoms in Co, was replaced 20 atomic percent Mn, LiNi 0.60 Co 0.20 Mn 0.20 O 2 (corresponding to x = 0.60) was synthesized. At this time, the average valence of the additive element M composed of Co and Mn is Y = 3.5, the average valence of Ni is Z = 2.667, and (4-Z) x = 0.80. . In addition, when charging to a composition of Li 0.25 Ni x M 1-x O 2 , even if the charge increase is compensated only by Ni, the number of moles of tetravalent Ni is the number of moles of Ni, Co and Mn combined. Of 55%.

本例では、以上のようなＬｉＮｉ0.60Ｃｏ0.20Ｍｎ0.20Ｏ2を合成するために、まず、ＮｉとＣｏとＭｎのモル比が６０：２０：２０で固溶しているニッケル複合水酸化物を次のようにして得た。すなわち、硫酸ニッケル、硫酸コバルトおよび硫酸マンガンの混合水溶液を、その塩濃度が２ｍｏｌ／Ｌとなるように調製し、温度を５０℃に保持し、水酸化ナトリウムを添加して、ｐＨを１１〜１２の範囲に維持しつつ、共沈により沈殿物を得て、得られた沈殿物を乾燥することによりニッケル複合水酸化物を得た。 In this example, in order to synthesize LiNi 0.60 Co 0.20 Mn 0.20 O 2 as described above, first, a nickel composite hydroxide in which the molar ratio of Ni, Co, and Mn is 60:20:20 is dissolved. Obtained as follows. That is, a mixed aqueous solution of nickel sulfate, cobalt sulfate and manganese sulfate was prepared so that the salt concentration was 2 mol / L, the temperature was maintained at 50 ° C., sodium hydroxide was added, and the pH was adjusted to 11-12. While maintaining the above range, a precipitate was obtained by coprecipitation, and the resulting precipitate was dried to obtain a nickel composite hydroxide.

得られたニッケル複合水酸化物は、１μｍ以下の一次粒子が複数集合した二次粒子からなっていた。   The obtained nickel composite hydroxide consisted of secondary particles in which a plurality of primary particles of 1 μm or less were assembled.

得られたニッケル複合水酸化物と、ジェットミルで粉砕した市販の水酸化リチウム一水和物（ケメタル社製）とを、ＬｉとＮｉ、Ｃｏ、Ｍｎの合計とのモル比：Ｌｉ／（Ｎｉ＋Ｃｏ＋Ｍｎ）が１．０５となるように秤量した後、球状の二次粒子の形骸が維持される程度の強さでシェーカーミキサを用いて十分に混合した。   The obtained nickel composite hydroxide and a commercially available lithium hydroxide monohydrate (manufactured by Kemetal Co., Ltd.) pulverized with a jet mill, the molar ratio of Li to the total of Ni, Co and Mn: Li / (Ni + Co + Mn ) Was adjusted to 1.05, and then sufficiently mixed using a shaker mixer at such a strength that the shape of spherical secondary particles was maintained.

この混合物２０ｇを、５ｃｍ×１２ｃｍ×３ｃｍのマグネシア製の焼成容器に挿入し、密閉式電気炉を用いて、流量３Ｌ／ｍｉｎの１００％酸素気流中、５００℃で、２時間、仮焼した後、昇温速度５℃／ｍｉｎで９００℃まで昇温し、１０時間焼成した後、室温まで炉冷した。   After 20 g of this mixture was inserted into a 5 cm × 12 cm × 3 cm magnesia firing container and calcined at 500 ° C. for 2 hours in a 100% oxygen stream with a flow rate of 3 L / min using a sealed electric furnace. The temperature was raised to 900 ° C. at a heating rate of 5 ° C./min, baked for 10 hours, and then cooled to room temperature.

得られたリチウムニッケル複合酸化物を質量比で水１に対して１．５投入してスラリーとし、３０分間撹拌後、濾過、乾燥して正極活物質を得た。   The obtained lithium nickel composite oxide was added at a mass ratio of 1.5 to water 1 to form a slurry, stirred for 30 minutes, filtered and dried to obtain a positive electrode active material.

得られた正極活物質をＸ線回折で分析したところ、六方晶系の層状構造を有した正極活物質（ＬｉＮｉ0.60Ｃｏ0.20Ｍｎ0.20Ｏ2）であった。粒度分布測定装置（日機装株式会社製、マイクロトラック）で測定した平均粒子径は、９．６μｍであった。 When the obtained positive electrode active material was analyzed by X-ray diffraction, it was a positive electrode active material (LiNi 0.60 Co 0.20 Mn 0.20 O 2 ) having a hexagonal layered structure. The average particle diameter measured with a particle size distribution measuring apparatus (manufactured by Nikkiso Co., Ltd., Microtrac) was 9.6 μm.

得られた正極活物質の初期容量評価は、以下のようにして行った。正極活物質粉末７０質量％にアセチレンブラック２０質量％およびＰＴＦＥ１０質量％を混合し、ここから１５０ｍｇを取り出してペレットを作製し正極とした。   The initial capacity evaluation of the obtained positive electrode active material was performed as follows. 70% by mass of the positive electrode active material powder was mixed with 20% by mass of acetylene black and 10% by mass of PTFE, and 150 mg was taken out from this to produce a pellet to obtain a positive electrode.

負極としてリチウム金属を用い、電解液には１ｍｏｌ／ＬのＬｉＣｌＯ4を支持塩とするエチレンカーボネート（ＥＣ）とジエチルカーボネート（ＤＥＣ）の等量混合溶液（富山薬品工業株式会社製）を用いた。そして、露点が−８０℃に管理されたＡｒ雰囲気のグローブボックス中で、図１に断面図を示すような、正極缶（５）中の正極（１）、負極缶（６）中の負極（２）、電解液含浸のセパレータ（３）、ガスケット（４）から構成される、２０３２型のコイン電池（Ｂ）を作製した。 Lithium metal was used as the negative electrode, and an equivalent mixed solution of ethylene carbonate (EC) and diethyl carbonate (DEC) (made by Toyama Pharmaceutical Co., Ltd.) using 1 mol / L LiClO 4 as a supporting salt was used as the electrolyte. And in the glove box of Ar atmosphere where the dew point was controlled at -80 ° C., the positive electrode (1) in the positive electrode can (5) and the negative electrode in the negative electrode can (6) (see FIG. 1) 2) A 2032 type coin battery (B) composed of an electrolyte-impregnated separator (3) and a gasket (4) was produced.

作製した電池は２４時間程度放置し、開回路電圧ＯＣＶ（Open Circuit Voltage）が安定した後、正極に対する電流密度を０．５ｍＡ／ｃｍ2として、カットオフ電圧４．３Ｖまで充電して初期充電容量とし、１時間の休止後にカットオフ電圧３．０Ｖまで放電したときの容量を初期放電容量とした。 The prepared battery is left for about 24 hours, and after the open circuit voltage OCV (Open Circuit Voltage) is stabilized, the current density with respect to the positive electrode is set to 0.5 mA / cm 2 and charged to a cutoff voltage of 4.3 V to obtain an initial charge capacity. The capacity when discharging to a cut-off voltage of 3.0 V after a one hour rest was defined as the initial discharge capacity.

正極の安全性の評価は、前述と同様な方法で作製した２０３２型のコイン電池をカットオフ電圧４．５Ｖまで定電流定電圧（ＣＣＣＶ）方式で充電した後、短絡しないように注意しながら解体して正極を取り出した。この電極を３．０ｍｇ計り取り、電解液を１．３ｍｇ加えて、アルミニウム製測定容器に封入し、示差走査熱量計（ＤＳＣ）（株式会社リガク製）を用いて、昇温速度１０℃／ｍｉｎで室温から４００℃まで発熱挙動を測定した。   The safety of the positive electrode is evaluated by charging a 2032 type coin battery manufactured by the same method as described above to a cut-off voltage of 4.5V using the constant current / constant voltage (CCCV) method, and then disassembling with care so as not to cause a short circuit. Then, the positive electrode was taken out. 3.0 mg of this electrode is measured, 1.3 mg of the electrolytic solution is added, sealed in an aluminum measuring container, and the temperature rising rate is 10 ° C./min using a differential scanning calorimeter (DSC) (manufactured by Rigaku Corporation). The exothermic behavior was measured from room temperature to 400 ° C.

電池評価によって得られた初期放電容量とＤＳＣ測定から得られた正極の発熱量を表２に示す。   Table 2 shows the initial discharge capacity obtained by battery evaluation and the calorific value of the positive electrode obtained from DSC measurement.

（実施例２）
水酸化リチウム一水和物との混合前に、ニッケル複合水酸化物を、大気雰囲気中、３００℃で、２時間、仮焼した後、７００℃で、１０時間、酸化焙焼したこと以外は、実施例１と同様にして正極活物質を得た。 (Example 2)
Before mixing with lithium hydroxide monohydrate, the nickel composite hydroxide was calcined in air at 300 ° C. for 2 hours and then oxidized and roasted at 700 ° C. for 10 hours. In the same manner as in Example 1, a positive electrode active material was obtained.

得られた正極活物質をＸ線回折で分析したところ、六方晶系の層状構造を有した正極活物質（ＬｉＮｉ0.60Ｃｏ0.20Ｍｎ0.20Ｏ2）であった。また、その平均粒子径は９．８μｍであった。 When the obtained positive electrode active material was analyzed by X-ray diffraction, it was a positive electrode active material (LiNi 0.60 Co 0.20 Mn 0.20 O 2 ) having a hexagonal layered structure. Moreover, the average particle diameter was 9.8 micrometers.

得られた正極活物質の初期放電容量の評価は実施例１と同様に行い、得られた初期放電容量とＤＳＣ測定から得られた正極の発熱量を表２に示す。   Evaluation of the initial discharge capacity of the obtained positive electrode active material was performed in the same manner as in Example 1. Table 2 shows the obtained initial discharge capacity and the calorific value of the positive electrode obtained from the DSC measurement.

（実施例３）
水酸化リチウム一水和物との混合前に、ニッケル複合水酸化物を、大気雰囲気中、３００℃で、２時間、仮焼した後、７００℃で、１０時間、酸化焙焼したこと、焼成温度を７８０℃で焼成したこと以外は、実施例１と同様にして正極活物質を得た。 (Example 3)
Before mixing with lithium hydroxide monohydrate, the nickel composite hydroxide was calcined at 300 ° C. for 2 hours in the atmosphere and then oxidized and roasted at 700 ° C. for 10 hours. A positive electrode active material was obtained in the same manner as in Example 1 except that the temperature was baked at 780 ° C.

得られた正極活物質をＸ線回折で分析したところ、六方晶系の層状構造を有した正極活物質（ＬｉＮｉ0.60Ｃｏ0.20Ｍｎ0.20Ｏ2）であった。また、その平均粒子径は９．７μｍであった。 When the obtained positive electrode active material was analyzed by X-ray diffraction, it was a positive electrode active material (LiNi 0.60 Co 0.20 Mn 0.20 O 2 ) having a hexagonal layered structure. Moreover, the average particle diameter was 9.7 micrometers.

得られた正極活物質の初期放電容量の評価は実施例１と同様に行い、得られた初期放電容量とＤＳＣ測定から得られた正極の発熱量を表２に示す。   Evaluation of the initial discharge capacity of the obtained positive electrode active material was performed in the same manner as in Example 1. Table 2 shows the obtained initial discharge capacity and the calorific value of the positive electrode obtained from the DSC measurement.

（実施例４）
水酸化リチウム一水和物との混合前に、ニッケル複合水酸化物を、大気雰囲気中、３００℃で、２時間、仮焼した後、７００℃で、１０時間、酸化焙焼したこと、焼成温度を７５０℃で焼成したこと以外は、実施例１と同様にして正極活物質を得た。 Example 4
Before mixing with lithium hydroxide monohydrate, the nickel composite hydroxide was calcined at 300 ° C. for 2 hours in the atmosphere and then oxidized and roasted at 700 ° C. for 10 hours. A positive electrode active material was obtained in the same manner as in Example 1 except that the temperature was baked at 750 ° C.

得られた正極活物質をＸ線回折で分析したところ、六方晶系の層状構造を有した正極活物質（ＬｉＮｉ0.60Ｃｏ0.20Ｍｎ0.20Ｏ2）であった。また、その平均粒子径は９．６μｍであった。 When the obtained positive electrode active material was analyzed by X-ray diffraction, it was a positive electrode active material (LiNi 0.60 Co 0.20 Mn 0.20 O 2 ) having a hexagonal layered structure. Moreover, the average particle diameter was 9.6 micrometers.

得られた正極活物質の初期放電容量の評価は実施例１と同様に行い、得られた初期放電容量とＤＳＣ測定から得られた正極の発熱量を表２に示す。   Evaluation of the initial discharge capacity of the obtained positive electrode active material was performed in the same manner as in Example 1. Table 2 shows the obtained initial discharge capacity and the calorific value of the positive electrode obtained from the DSC measurement.

（比較例１）
リチウムニッケル複合酸化物（ＬｉＮｉxＭ1-xＯ2）において、添加元素ＭをＣｏおよびＭｎとして、Ｎｉ全原子数の１０原子％をＣｏに置換し、１０原子％をＭｎに置換した、ＬｉＮｉ0.80Ｃｏ0.10Ｍｎ0.10Ｏ2（ｘ＝０．８０に相当）を合成した。このときのＣｏとＭｎからなる添加元素Ｍの平均価数はＹ＝３．５であり、Ｎｉの平均価数Ｚ＝２．８７５となり、（４−Ｚ）ｘ＝０．９０となる。また、Ｌｉ0.25ＮｉxＭ1-xＯ2なる組成まで充電したときに、電荷増をＮｉのみで補償するとしても、４価のＮｉのモル数はＮｉとＣｏとＭｎを合わせたモル数の６５％となる。 (Comparative Example 1)
In the lithium nickel composite oxide (LiNi x M 1-x O 2 ), the additive element M is Co and Mn, and 10 atomic% of the total number of Ni atoms is replaced with Co, and 10 atomic% is replaced with Mn. 0.80 Co 0.10 Mn 0.10 O 2 (corresponding to x = 0.80) was synthesized. At this time, the average valence of the additive element M composed of Co and Mn is Y = 3.5, the average valence Z of Ni is 2.875, and (4-Z) x = 0.90. In addition, when charging to a composition of Li 0.25 Ni x M 1-x O 2 , even if the charge increase is compensated only by Ni, the number of moles of tetravalent Ni is the number of moles of Ni, Co, and Mn combined. 65%.

本例では、以上のようなＬｉＮｉ0.80Ｃｏ0.10Ｍｎ0.10Ｏ2を合成するために、ＮｉとＣｏとＭｎのモル比が８０：１０：１０（ｘ＝０．８０に相当）となるように混合水溶液を調製したこと、焼成温度を８００℃としたこと以外は、実施例１と同様にして正極活物質を得た。 In this example, in order to synthesize LiNi 0.80 Co 0.10 Mn 0.10 O 2 as described above, mixing was performed so that the molar ratio of Ni, Co, and Mn was 80:10:10 (corresponding to x = 0.80). A positive electrode active material was obtained in the same manner as in Example 1 except that an aqueous solution was prepared and the firing temperature was 800 ° C.

得られた正極活物質をＸ線回折で分析したところ、六方晶系の層状構造を有した正極活物質（ＬｉＮｉ0.80Ｃｏ0.10Ｍｎ0.10Ｏ2）であった。また、その平均粒子径は１０．３μｍであった。 When the obtained positive electrode active material was analyzed by X-ray diffraction, it was a positive electrode active material (LiNi 0.80 Co 0.10 Mn 0.10 O 2 ) having a hexagonal layered structure. The average particle size was 10.3 μm.

得られた正極活物質の初期放電容量の評価は実施例１と同様に行い、得られた初期放電容量とＤＳＣ測定から得られた正極の発熱量を表２に示す。   Evaluation of the initial discharge capacity of the obtained positive electrode active material was performed in the same manner as in Example 1. Table 2 shows the obtained initial discharge capacity and the calorific value of the positive electrode obtained from the DSC measurement.

（比較例２）
リチウムニッケル複合酸化物（ＬｉＮｉxＭ1-xＯ2）において、添加元素ＭをＣｏおよびＭｎとして、Ｎｉ全原子数の３３原子％をＣｏに置換し、３３原子％をＭｎに置換した、ＬｉＮｉ0.34Ｃｏ0.33Ｍｎ0.33Ｏ2（ｘ＝０．３４に相当）を合成した。このときのＣｏとＭｎからなる添加元素Ｍの平均価数はＹ＝３．５であり、Ｎｉの平均価数Ｚ＝２．０００となり、（４−Ｚ）ｘ＝０．６８となる。したがって、電荷増をＮｉのみで補償する場合、Ｌｉ0.25ＮｉxＭ1-xＯ2となる組成まで充電することはできない。満充電時の４価のＮｉのモル数はＮｉとＣｏとＭｎを合わせたモル数の３３％となる。 (Comparative Example 2)
In the lithium nickel composite oxide (LiNi x M 1-x O 2 ), the additive element M is Co and Mn, 33 atomic% of the total number of Ni atoms is replaced with Co, and 33 atomic% is replaced with Mn. 0.34 Co 0.33 Mn 0.33 O 2 (corresponding to x = 0.34) was synthesized. At this time, the average valence of the additive element M composed of Co and Mn is Y = 3.5, the average valence Z of Ni is 2.000, and (4-Z) x = 0.68. Therefore, when the charge increase is compensated only by Ni, it is not possible to charge the composition to Li 0.25 Ni x M 1-x O 2 . The number of moles of tetravalent Ni at full charge is 33% of the number of moles of Ni, Co and Mn.

本例では、以上のようなＬｉＮｉ0.34Ｃｏ0.33Ｍｎ0.33Ｏ2を合成するために、ＮｉとＣｏとＭｎのモル比が３４：３３：３３（ｘ＝０．３４に相当）となるように混合水溶液を調製したこと以外は、実施例１と同様にして正極活物質を得た。 In this example, in order to synthesize LiNi 0.34 Co 0.33 Mn 0.33 O 2 as described above, mixing was performed so that the molar ratio of Ni, Co, and Mn was 34:33:33 (corresponding to x = 0.34). A positive electrode active material was obtained in the same manner as in Example 1 except that an aqueous solution was prepared.

得られた正極活物質をＸ線回折で分析したところ、六方晶系の層状構造を有した正極活物質（ＬｉＮｉ0.34Ｃｏ0.33Ｍｎ0.33Ｏ2）であった。また、その平均粒子径は１０．１μｍであった。 When the obtained positive electrode active material was analyzed by X-ray diffraction, it was a positive electrode active material (LiNi 0.34 Co 0.33 Mn 0.33 O 2 ) having a hexagonal layered structure. The average particle size was 10.1 μm.

得られた正極活物質の初期放電容量の評価は実施例１と同様に行い、得られた初期放電容量とＤＳＣ測定から得られた正極の発熱量を表２に示す。   Evaluation of the initial discharge capacity of the obtained positive electrode active material was performed in the same manner as in Example 1. Table 2 shows the obtained initial discharge capacity and the calorific value of the positive electrode obtained from the DSC measurement.

（比較例３）
水酸化リチウム一水和物との混合前に、金属複合水酸化物を大気雰囲気中にて３００℃で２時間仮焼した後、７００℃にて１０時間酸化焙焼したこと、焼成後に水洗しなかったこと以外は、実施例１と同様にして正極活物質を得た。 (Comparative Example 3)
Before mixing with lithium hydroxide monohydrate, the metal composite hydroxide was calcined in air at 300 ° C. for 2 hours, then oxidized and roasted at 700 ° C. for 10 hours, and washed after washing. A positive electrode active material was obtained in the same manner as in Example 1 except that there was not.

得られた正極活物質をＸ線回折で分析したところ、六方晶系の層状構造を有した正極活物質（ＬｉＮｉ0.60Ｃｏ0.20Ｍｎ0.20Ｏ2）であった。また、その平均粒子径は１０．２μｍであった。 When the obtained positive electrode active material was analyzed by X-ray diffraction, it was a positive electrode active material (LiNi 0.60 Co 0.20 Mn 0.20 O 2 ) having a hexagonal layered structure. Moreover, the average particle diameter was 10.2 micrometers.

得られた正極活物質の初期放電容量の評価は実施例１と同様に行い、得られた初期放電容量とＤＳＣ測定から得られた正極の発熱量を表２に示す。   Evaluation of the initial discharge capacity of the obtained positive electrode active material was performed in the same manner as in Example 1. Table 2 shows the obtained initial discharge capacity and the calorific value of the positive electrode obtained from the DSC measurement.

Figure 2012119093
Figure 2012119093

Figure 2012119093
Figure 2012119093

表１から明らかなように、実施例１〜４で合成した正極活物質は、（４−Ｚ）ｘ≧０．７５という条件を満たし、かつ、理論容量の７５％までＬｉを引き抜いたときの４価のＮｉ量がＮｉとＣｏとＭｎ全体の６０％以下であり、さらに水洗工程を経ているため、１８２ｍＡｈ／ｇ以上の高い初期放電容量を有しながら、４００Ｊ／ｇ以下の小さい発熱量となっており、高容量と高安全性の両立が実現できていることがわかる。特に、酸化焙焼を行った実施例２〜４は、発熱量がさらに改善されて、発熱量が３００Ｊ／ｇ以下に抑えられているとともに、初期放電容量も改善されていることが理解される。   As is clear from Table 1, the positive electrode active materials synthesized in Examples 1 to 4 satisfy the condition (4-Z) x ≧ 0.75, and when Li was extracted to 75% of the theoretical capacity. The amount of tetravalent Ni is 60% or less of the total of Ni, Co and Mn, and since it has undergone a water washing step, it has a high initial discharge capacity of 182 mAh / g or more and a small heating value of 400 J / g or less. It can be seen that both high capacity and high safety can be realized. In particular, it is understood that in Examples 2 to 4 where oxidation roasting was performed, the calorific value was further improved, the calorific value was suppressed to 300 J / g or less, and the initial discharge capacity was also improved. .

一方、比較例１で合成した正極活物質は、（４−Ｚ）ｘが０．７５以上という条件を満たしているので、初期放電容量は十分高いものを有しているが、４価のＮｉ量がＮｉとＣｏとＭｎ全体の６０％を超えているために、発熱量が大きく、安全性に劣る電池となっている。また、比較例２で合成した正極活物質は、４価のＮｉ量がＮｉとＣｏとＭｎ全体の６０％以下となっているために発熱量が十分小さく、安全性の高い電池となっているが、（４−Ｚ）ｘが０．７５未満であるために、十分な初期放電容量が得られていない。また、比較例３に示した正極活物質は、（４−Ｚ）ｘ≧０．７５という条件を満たし、かつ、４価のＮｉ量がＮｉとＣｏとＭｎ全体の６０％以下であるので、４００Ｊ／ｇ以下の小さい発熱量となっているが、水洗工程を経ていないため、表面残留Ｌｉ化合物が多く、十分な初期容量が得られていない。同様の工程で水洗工程を有する実施例２〜４と比較すると、初期容量も低く、発熱量がやや大きくなっていることがわかる。   On the other hand, since the positive electrode active material synthesized in Comparative Example 1 satisfies the condition that (4-Z) x is 0.75 or more, the initial discharge capacity is sufficiently high. Since the amount exceeds 60% of Ni, Co, and Mn as a whole, the battery generates a large amount of heat and is inferior in safety. Further, the positive electrode active material synthesized in Comparative Example 2 has a sufficiently low calorific value because the amount of tetravalent Ni is 60% or less of the total of Ni, Co, and Mn, and is a highly safe battery. However, since (4-Z) x is less than 0.75, a sufficient initial discharge capacity is not obtained. Further, the positive electrode active material shown in Comparative Example 3 satisfies the condition (4-Z) x ≧ 0.75, and the amount of tetravalent Ni is 60% or less of Ni, Co and Mn as a whole. Although it has a small calorific value of 400 J / g or less, it has not undergone a water washing step, so there are many surface residual Li compounds, and a sufficient initial capacity cannot be obtained. When compared with Examples 2 to 4 having a water washing step in the same step, it can be seen that the initial capacity is low and the calorific value is slightly high.

安全性に優れていながら高い初期放電容量を有しているという本発明の非水系電解質二次電池のメリットを活かすためには、常に高容量を要求される小型携帯電子機器の電源としての用途が好適である。   In order to take advantage of the non-aqueous electrolyte secondary battery of the present invention that has a high initial discharge capacity while being excellent in safety, it can be used as a power source for small portable electronic devices that always require a high capacity. Is preferred.

また、ハイブリッドカーや電気自動車の電源などの大型二次電池においては、大型化による安全性の確保の困難性ゆえ、より高度な安全性を確保するための高価な保護回路の装着が必要不可欠とされているが、本発明の非水系電解質二次電池は、優れた安全性を有しているために、安全性の確保が容易になるばかりでなく、高価な保護回路を簡略化し、より低コストにできるという点において、電気自動車などの電源としても好適である。   In addition, for large-sized secondary batteries such as power supplies for hybrid cars and electric vehicles, it is indispensable to install expensive protection circuits to ensure a higher level of safety because of the difficulty in ensuring safety due to the increase in size. However, since the non-aqueous electrolyte secondary battery of the present invention has excellent safety, not only is it easy to ensure safety, but also an expensive protection circuit is simplified and reduced. In terms of cost, it is also suitable as a power source for electric vehicles.

１ 正極
２ 負極
３ セパレータ
４ ガスケット
５ 正極缶
６ 負極缶
Ｂ コイン電池 DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Negative electrode 3 Separator 4 Gasket 5 Positive electrode can 6 Negative electrode can B Coin battery

Claims (11)

一般式：ＬｉＮｉxＭ1-xＯ2（ただし、式中のｘは、Ｎｉの平均価数をＺとしたときに、（４−Ｚ）ｘ≧０．７５を満たし、式中のＭは、Ｍ全体としての平均価数が３．３７５価以上となる少なくとも１種の添加元素を表す）で表されるリチウムニッケル複合酸化物を得るための製造方法であって、
Ｎｉ塩とＭ塩の混合水溶液にアルカリ溶液を加えて、ＮｉとＭの水酸化物を共沈させ、得られた沈殿物を濾過、水洗、乾燥して、ニッケル複合水酸化物：ＮｉxＭ1-x（ＯＨ）2を得る晶析工程と、
得られたニッケル複合水酸化物：ＮｉxＭ1-x（ＯＨ）2とリチウム化合物とを、ＮｉとＭとの合計に対するＬｉのモル比：Ｌｉ／（Ｎｉ＋Ｍ）が１．００〜１．１５となるように混合し、さらに該混合物を、７００℃以上１０００℃以下の温度で焼成して、前記リチウムニッケル複合酸化物を得る焼成工程と、
得られたリチウムニッケル複合酸化物を水洗処理する水洗工程と、
を有することを特徴とする非水系電解質二次電池用正極活物質の製造方法。 General formula: LiNi x M 1-x O 2 (wherein x satisfies (4-Z) x ≧ 0.75 when the average valence of Ni is Z, and M in the formula is The average valence of M as a whole represents at least one additional element having a valence of 3.375 or more),
An alkaline solution is added to a mixed aqueous solution of Ni salt and M salt to coprecipitate Ni and M hydroxides, and the resulting precipitate is filtered, washed with water, and dried to obtain a nickel composite hydroxide: Ni x M Crystallization step to obtain 1-x (OH) 2 ,
The obtained nickel composite hydroxide: Ni x M 1-x (OH) 2 and a lithium compound, the molar ratio of Li to the sum of Ni and M: Li / (Ni + M) is 1.00 to 1.15. And further calcining the mixture at a temperature of 700 ° C. or higher and 1000 ° C. or lower to obtain the lithium nickel composite oxide;
A water washing step of washing the obtained lithium nickel composite oxide with water;
The manufacturing method of the positive electrode active material for nonaqueous electrolyte secondary batteries characterized by having. 前記Ｍが、Ｔｉ、Ｖ、Ｍｎ、Ｎｂ、Ｍｏ、Ｒｕ、ＴａおよびＷからなる群から選ばれた少なくとも１種の添加元素、または、Ｔｉ、Ｖ、Ｍｎ、Ｎｂ、Ｍｏ、Ｒｕ、ＴａおよびＷからなる群、および、Ａｌ、Ｆｅ、Ｃｏ、Ｃｕ、Ｚｎ、Ｇａ、Ｚｒ、ＩｎおよびＳｎからなる群のそれぞれから少なくとも１種ずつ選ばれた添加元素であることを特徴とする、請求項１に記載の非水系電解質二次電池用正極活物質の製造方法。   M is at least one additive element selected from the group consisting of Ti, V, Mn, Nb, Mo, Ru, Ta and W, or Ti, V, Mn, Nb, Mo, Ru, Ta and W And an additive element selected from at least one selected from the group consisting of Al, Fe, Co, Cu, Zn, Ga, Zr, In and Sn. The manufacturing method of the positive electrode active material for non-aqueous electrolyte secondary batteries of description. 前記晶析工程の後、前記焼成工程の前に、該晶析工程で得られたニッケル複合水酸化物：ＮｉxＭ1-x（ＯＨ）2を、大気雰囲気中、８００℃未満の温度で、１時間以上の焙焼を行って複合酸化物を得る酸化焙焼工程を有することを特徴とする、請求項１または２に記載の非水系電解質二次電池用正極活物質の製造方法。 After the crystallization step and before the firing step, the nickel composite hydroxide obtained in the crystallization step: Ni x M 1-x (OH) 2 is heated in an air atmosphere at a temperature of less than 800 ° C. The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1 or 2, further comprising an oxidation roasting step of roasting for 1 hour or more to obtain a composite oxide. 前記水洗工程において、リチウムニッケル複合酸化物を、質量比で水１に対して１〜２投入してスラリーとし、３０分〜６０分間撹拌後、濾過、乾燥することを特徴とする、請求項１〜３のいずれか一項に記載の非水系電解質二次電池用正極活物質の製造方法。   In the water washing step, the lithium nickel composite oxide is added to the water 1 in a mass ratio of 1 to 2 to form a slurry, stirred for 30 minutes to 60 minutes, filtered and dried. The manufacturing method of the positive electrode active material for nonaqueous electrolyte secondary batteries as described in any one of -3. 前記リチウム化合物として、炭酸リチウムを用いたことを特徴とする、請求項１〜４のいずれかに記載の非水系電解質二次電池用正極活物質の製造方法。   The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 4, wherein lithium carbonate is used as the lithium compound. 前記リチウム化合物として、水酸化リチウムまたはその水和物を用いたことを特徴とする、請求項１〜４のいずれか一項に記載の非水系電解質二次電池用正極活物質の製造方法。   The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 4, wherein lithium hydroxide or a hydrate thereof is used as the lithium compound. 前記晶析工程において用いるＮｉ塩とＭ塩が硫酸塩であることを特徴とする、請求項１〜６のいずれか一項に記載の非水系電解質二次電池用正極活物質の製造方法。   The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 6, wherein the Ni salt and M salt used in the crystallization step are sulfates. 請求項１〜７のいずれか一項に記載の製造方法により得られ、一般式：ＬｉＮｉxＭ1-xＯ2（ただし、式中のｘは、Ｎｉの平均価数をＺとしたときに、（４−Ｚ）ｘ≧０．７５を満たし、式中のＭは、Ｍ全体としての平均価数が３．３７５価以上となる少なくとも１種の添加元素を表す）で表されるリチウムニッケル複合酸化物の粉末からなり、かつ、該粉末を正極活物質として用いた非水系電解質二次電池において、Ｌｉ0.25ＮｉxＭ1-xＯ2なる組成まで充電したときに、４価のＮｉのモル数がＮｉとＭを合わせたモル数の６０％以下となることを特徴とする、非水系電解質二次電池用正極活物質。 It is obtained by the production method according to any one of claims 1 to 7, and is represented by a general formula: LiNi x M 1-x O 2 (where x is an average valence of Ni when Z is Z) (4-Z) x ≧ 0.75, and M in the formula represents lithium nickel represented by at least one additive element having an average valence of 3.375 or more as a whole) In a non-aqueous electrolyte secondary battery comprising a composite oxide powder and using the powder as a positive electrode active material, when charged to a composition of Li 0.25 Ni x M 1-x O 2 , tetravalent Ni A positive electrode active material for a non-aqueous electrolyte secondary battery, wherein the number of moles is 60% or less of the total number of moles of Ni and M combined. 前記非水系電解質二次電池が２０３２型のコイン電池であって、該コイン電池の正極材料として用いた場合に、該２０３２型のコイン電池は、１８２ｍＡｈ／ｇ以上の初期放電容量と、示差走査熱量計を用いた測定による４００Ｊ／ｇ以下の発熱量とを示すことを特徴とする、請求項８に記載の非水系電解質二次電池用正極活物質。   When the non-aqueous electrolyte secondary battery is a 2032 type coin battery and is used as a positive electrode material of the coin battery, the 2032 type coin battery has an initial discharge capacity of 182 mAh / g or more and a differential scanning calorific value. The positive electrode active material for a nonaqueous electrolyte secondary battery according to claim 8, which exhibits a calorific value of 400 J / g or less as measured by a meter. 示差走査熱量計を用いた測定による３００Ｊ／ｇ以下の発熱量を示すことを特徴とする、請求項９に記載の非水系電解質二次電池用正極活物質。   The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 9, which exhibits a calorific value of 300 J / g or less as measured by a differential scanning calorimeter. 請求項８〜１０のいずれかに記載の正極活物質を、正極材料として用いている非水系電解質二次電池。   A non-aqueous electrolyte secondary battery using the positive electrode active material according to claim 8 as a positive electrode material.
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