JP2017188245A - Positive electrode active material for nonaqueous electrolyte secondary battery, lithium secondary battery, and method for manufacturing positive electrode active material for nonaqueous electrolyte secondary battery - Google Patents
Positive electrode active material for nonaqueous electrolyte secondary battery, lithium secondary battery, and method for manufacturing positive electrode active material for nonaqueous electrolyte secondary battery Download PDFInfo
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- JP2017188245A JP2017188245A JP2016074969A JP2016074969A JP2017188245A JP 2017188245 A JP2017188245 A JP 2017188245A JP 2016074969 A JP2016074969 A JP 2016074969A JP 2016074969 A JP2016074969 A JP 2016074969A JP 2017188245 A JP2017188245 A JP 2017188245A
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- Prior art keywords
- positive electrode
- active material
- electrode active
- secondary battery
- electrolyte secondary
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- 239000007774 positive electrode material Substances 0.000 title claims abstract description 48
- 239000011255 nonaqueous electrolyte Substances 0.000 title claims abstract description 33
- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 26
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- 238000004519 manufacturing process Methods 0.000 title claims description 14
- 238000000034 method Methods 0.000 title claims description 11
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims abstract description 55
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- 238000007254 oxidation reaction Methods 0.000 claims abstract description 35
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- 229910001428 transition metal ion Inorganic materials 0.000 claims abstract description 26
- 229910021437 lithium-transition metal oxide Inorganic materials 0.000 claims abstract description 23
- 238000004448 titration Methods 0.000 claims abstract description 19
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 claims abstract description 15
- 230000033116 oxidation-reduction process Effects 0.000 claims abstract description 14
- 229910052596 spinel Inorganic materials 0.000 claims abstract description 7
- 239000011029 spinel Substances 0.000 claims abstract description 7
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- UOGMEBQRZBEZQT-UHFFFAOYSA-L manganese(2+);diacetate Chemical compound [Mn+2].CC([O-])=O.CC([O-])=O UOGMEBQRZBEZQT-UHFFFAOYSA-L 0.000 description 1
- MIVBAHRSNUNMPP-UHFFFAOYSA-N manganese(2+);dinitrate Chemical compound [Mn+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O MIVBAHRSNUNMPP-UHFFFAOYSA-N 0.000 description 1
- 229910000016 manganese(II) carbonate Inorganic materials 0.000 description 1
- XMWCXZJXESXBBY-UHFFFAOYSA-L manganese(ii) carbonate Chemical compound [Mn+2].[O-]C([O-])=O XMWCXZJXESXBBY-UHFFFAOYSA-L 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910021645 metal ion Inorganic materials 0.000 description 1
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 1
- 239000011812 mixed powder Substances 0.000 description 1
- 239000012046 mixed solvent Substances 0.000 description 1
- 239000000178 monomer Substances 0.000 description 1
- UUIQMZJEGPQKFD-UHFFFAOYSA-N n-butyric acid methyl ester Natural products CCCC(=O)OC UUIQMZJEGPQKFD-UHFFFAOYSA-N 0.000 description 1
- 239000011331 needle coke Substances 0.000 description 1
- 229940078494 nickel acetate Drugs 0.000 description 1
- BFDHFSHZJLFAMC-UHFFFAOYSA-L nickel(ii) hydroxide Chemical compound [OH-].[OH-].[Ni+2] BFDHFSHZJLFAMC-UHFFFAOYSA-L 0.000 description 1
- KBJMLQFLOWQJNF-UHFFFAOYSA-N nickel(ii) nitrate Chemical compound [Ni+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O KBJMLQFLOWQJNF-UHFFFAOYSA-N 0.000 description 1
- 229920000620 organic polymer Polymers 0.000 description 1
- 239000005518 polymer electrolyte Substances 0.000 description 1
- 229920005672 polyolefin resin Polymers 0.000 description 1
- 229920000069 polyphenylene sulfide Polymers 0.000 description 1
- FJWLWIRHZOHPIY-UHFFFAOYSA-N potassium;hydroiodide Chemical compound [K].I FJWLWIRHZOHPIY-UHFFFAOYSA-N 0.000 description 1
- RUOJZAUFBMNUDX-UHFFFAOYSA-N propylene carbonate Chemical compound CC1COC(=O)O1 RUOJZAUFBMNUDX-UHFFFAOYSA-N 0.000 description 1
- 239000002296 pyrolytic carbon Substances 0.000 description 1
- HNJBEVLQSNELDL-UHFFFAOYSA-N pyrrolidin-2-one Chemical compound O=C1CCCN1 HNJBEVLQSNELDL-UHFFFAOYSA-N 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 229920003048 styrene butadiene rubber Polymers 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 229920005608 sulfonated EPDM Polymers 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- 229920002994 synthetic fiber Polymers 0.000 description 1
- 229920005992 thermoplastic resin Polymers 0.000 description 1
- 150000003606 tin compounds Chemical class 0.000 description 1
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 1
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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Abstract
Description
本発明は、非水電解質二次電池用正極活物質、リチウム二次電池及び非水電解質二次電池用正極活物質の製造方法に関する。 The present invention relates to a positive electrode active material for a nonaqueous electrolyte secondary battery, a lithium secondary battery, and a method for producing a positive electrode active material for a nonaqueous electrolyte secondary battery.
従来、非水電解質二次電池用正極活物質としては、一般式Ｌｉ［ＮｉyＭｎ2-(a+b)-y-zＬｉaＴｉbＭz］Ｏ4（但し、ＭはＡｌ、Ｍｇ、Ｆｅ及びＣｏのうち１以上であり、０≦ｚ≦０．３、０．３≦ｙ＜０．６、ａ＞０、ｂ＞０、２≦ｂ／ａ≦８）が提案されている（例えば、特許文献１参照）。この活物質５Ｖ級のスピネルにおいて、高温サイクル中のガス発生量を抑えることができるとしている。 Conventionally, as a positive electrode active material for a non-aqueous electrolyte secondary battery, a general formula Li [Ni y Mn 2- (a + b) -yz Li a Ti b M z ] O 4 (where M is Al, Mg, Fe) And 1 or more of Co and 0 ≦ z ≦ 0.3, 0.3 ≦ y <0.6, a> 0, b> 0, 2 ≦ b / a ≦ 8) (for example, , See Patent Document 1). In this active material 5V-class spinel, the amount of gas generated during the high-temperature cycle can be suppressed.
しかしながら、上述の特許文献１の正極活物質では、高温サイクル中のガス発生量を抑えることができるとしているが、活物質の酸化状態などは考慮されておらず、まだ、高温耐久特性が十分とはいえなかった。またこのような活物質は、低温特性も要求されるが、例えば、−１０℃以下などの低温での出力特性については検討されていなかった。 However, in the positive electrode active material of Patent Document 1 described above, it is said that the amount of gas generated during a high-temperature cycle can be suppressed, but the oxidation state of the active material is not considered, and the high-temperature durability characteristics are still sufficient. I could not say. Such an active material is also required to have low-temperature characteristics, but output characteristics at low temperatures such as −10 ° C. or less have not been studied.
本発明は、このような課題に鑑みなされたものであり、低温での出力特性及び高温での耐久性をより向上することができる非水電解質二次電池用正極活物質、リチウム二次電池及び非水電解質二次電池用正極活物質の製造方法を提供することを主目的とする。 The present invention has been made in view of such a problem, and is capable of further improving the output characteristics at low temperatures and the durability at high temperatures, a positive electrode active material for a non-aqueous electrolyte secondary battery, a lithium secondary battery, and The main object is to provide a method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery.
上述した目的を達成するために鋭意研究したところ、本発明者らは、ニッケル元素およびマンガン元素を含むリチウム遷移金属酸化物の遷移金属の平均酸化数を所定の範囲に調整すると、低温での出力特性及び高温での耐久性をより向上することができることを見いだし、本発明を完成するに至った。 As a result of diligent research to achieve the above-described object, the present inventors have found that when the average oxidation number of the transition metal of the lithium transition metal oxide containing nickel element and manganese element is adjusted within a predetermined range, the output at low temperature is achieved. It has been found that the characteristics and durability at high temperatures can be further improved, and the present invention has been completed.
即ち、本発明の非水電解質二次電池用正極活物質は、
ニッケル元素およびマンガン元素を含みスピネル型構造を有しヨウ素を用いた酸化還元滴定法で算出した遷移金属イオンの平均酸化数が３．４９以上３．５５以下の範囲のリチウム遷移金属酸化物である。
That is, the positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention is
It is a lithium transition metal oxide containing a nickel element and a manganese element, having a spinel structure, and having an average oxidation number of transition metal ions calculated by oxidation-reduction titration using iodine in a range of 3.49 to 3.55 .
本発明のリチウム二次電池は、
上述した非水電解質二次電池用正極活物質を含有する正極と、
負極活物質を含有する負極と、
前記正極と前記負極との間に介在しリチウムイオンを伝導するイオン伝導媒体と、
を備えたものである。
The lithium secondary battery of the present invention is
A positive electrode containing the positive electrode active material for a non-aqueous electrolyte secondary battery described above;
A negative electrode containing a negative electrode active material;
An ion conductive medium that is interposed between the positive electrode and the negative electrode and conducts lithium ions;
It is equipped with.
本発明の非水電解質二次電池用正極活物質の製造方法は、
リチウム遷移金属酸化物である非水電解質二次電池用正極活物質の製造方法であって、
リチウム元素とニッケル元素とマンガン元素とを含む原料を酸化雰囲気中９００℃以上１１００℃以下の第１温度範囲で焼成する焼成処理を行ったのち、５００℃以上７００℃以下の第２温度範囲まで冷却し該第２温度範囲で５時間以上４０時間以下の時間範囲でアニールするアニール処理を行う焼成アニール工程、を含むものである。
The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention is as follows.
A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, which is a lithium transition metal oxide,
After performing a baking treatment in which a raw material containing lithium element, nickel element and manganese element is baked in an oxidizing atmosphere at a first temperature range of 900 ° C. or higher and 1100 ° C. or lower, it is cooled to a second temperature range of 500 ° C. or higher and 700 ° C. or lower. And a firing annealing step for performing an annealing treatment for annealing in the time range of 5 hours to 40 hours in the second temperature range.
本発明は、低温での出力特性及び高温での耐久性をより向上することができる。このような効果が得られる理由は、例えば、以下のように推測される。スピネル型構造を有し、少なくともニッケル元素およびマンガン元素を含むリチウム遷移金属酸化物は、９００℃以上の温度で焼成することで高結晶性の試料となる。しかし、この高温焼成過程で試料から酸素が放出され、遷移金属イオンの酸化数が減少する。この酸素欠損・低価数の酸化物は、電池性能が低いと考えられる。本発明では、この焼成温度よりも低温の５００〜７００℃でのアニール処理を施すことにより、高温で放出された酸素を再び酸化物中に吸蔵させることができ、遷移金属イオンの酸化数を制御することができる。中でも、ヨウ素を用いた酸化還元滴定法で算出した平均酸化数と低温出力特性、高温耐久性に相関関係があり、遷移金属イオンの平均酸化数を３．４９以上３．５５以下とすることで低温出力特性、高温耐久性を向上させることができるものと推察される。 The present invention can further improve the output characteristics at low temperatures and the durability at high temperatures. The reason why such an effect is obtained is estimated as follows, for example. A lithium transition metal oxide having a spinel structure and containing at least nickel and manganese elements becomes a highly crystalline sample by firing at a temperature of 900 ° C. or higher. However, oxygen is released from the sample during this high-temperature firing process, and the oxidation number of transition metal ions decreases. This oxygen deficient / low valence oxide is considered to have low battery performance. In the present invention, by performing annealing treatment at 500 to 700 ° C. lower than the firing temperature, oxygen released at high temperature can be occluded again in the oxide, and the oxidation number of transition metal ions is controlled. can do. Above all, there is a correlation between the average oxidation number calculated by the oxidation-reduction titration method using iodine, the low-temperature output characteristics, and the high-temperature durability. By setting the average oxidation number of the transition metal ions to 3.49 or more and 3.55 or less. It is assumed that the low temperature output characteristics and high temperature durability can be improved.
本発明の正極活物質は、非水電解質二次電池に用いられるものであり、スピネル型構造を有しニッケル元素およびマンガン元素を含むリチウム遷移金属酸化物である。このリチウム遷移金属酸化物は、ヨウ素を用いた酸化還元滴定法で算出した遷移金属イオンの平均酸化数が３．４９以上３．５５以下の範囲にある。遷移金属イオンの平均酸化数がこの範囲内では、−１０℃以下あるいは−３０℃などでの低温出力特性が向上すると共に、５０℃以上あるいは６０℃などでの高温耐久性が向上する。また、この遷移金属イオンの平均酸化数が３．５１以上３．５４以下の範囲では、低温出力特性及び高温耐久性を更に向上することができ、好ましい。 The positive electrode active material of the present invention is used for a non-aqueous electrolyte secondary battery, and is a lithium transition metal oxide having a spinel structure and containing nickel element and manganese element. This lithium transition metal oxide has an average oxidation number of transition metal ions calculated by an oxidation-reduction titration method using iodine in the range of 3.49 to 3.55. When the average oxidation number of the transition metal ions is within this range, the low temperature output characteristics at −10 ° C. or lower or −30 ° C. are improved, and the high temperature durability at 50 ° C. or higher or 60 ° C. is improved. Moreover, when the average oxidation number of this transition metal ion is in the range of 3.51 or more and 3.54 or less, the low temperature output characteristics and the high temperature durability can be further improved, which is preferable.
ここで、ヨウ素を用いた酸化還元滴定法について説明する。まず、試料としてのリチウム遷移金属酸化物を、誘導結合プラズマ発光分光分析法（ＩＣＰ−ＡＥＳ）を用いて組成分析を行い、試料中の遷移金属イオン量を求める。次に、このリチウム遷移金属酸化物を酸性水溶液に溶解させヨウ素カリウム溶液と混合させた場合には、正極活物質中の２価よりも高いニッケル、マンガンは、Ｎｉ2+、Ｍｎ2+に還元されると共に、還元量と等量のＩ-が酸化されてＩ2が生成する。ここで生成されたＩ2量は、デンプン溶液を指示薬としてチオ硫酸ナトリウム標準溶液（Ｎａ2Ｓ2Ｏ3）で滴定することで同定される。滴定は以下の順に実施するものとする。
（１）２００ｍＬの三角フラスコにボールフィルタを入れ、窒素ガスを３Ｌ／分で５分間置換する。
（２）三角フラスコ中にＫＩ（１００ｇ／Ｌ）溶液１０ｍＬと、ＨＣｌ（塩酸［試薬特級］と蒸留水とを体積比で１：１に混合したもの）に２０ｍＬ加える。
（３）正極活物質１００ｍｇを±０．１ｍｇで量り取る。
（４）正極活物質を三角フラスコに移し入れ、栓をして回転子で撹拌しながら７０℃で加熱して溶解させる。
（５）流水で三角フラスコを冷却後、残存酸素を除いた蒸留水を８０ｍＬ加える。
（６）０．０５ｍｏｌ／Ｌのチオ硫酸ナトリウムで溶液が褐色から薄い黄色になるまで素早く滴定する。
（７）デンプン溶液を０．５ｍＬ加えて紫色に呈色させる。
（８）続けて０．０５ｍｏｌ／Ｌのチオ硫酸ナトリウムで滴定し、紫色が消えたところを終点とし、以下の反応式に基づいて遷移金属イオンの平均酸化数を算出する。
Ｍn+＋（ｎ−２）Ｉ- → Ｍ2+＋１／２（ｎ−２）Ｉ2 …（式１）
Ｉ2＋２Ｓ2Ｏ3 → ２Ｉ-＋Ｓ4Ｏ6 2- …（式２）
平均酸化数＝Ｉ2（ｍｏｌ）／（遷移金属量（ｍｏｌ））＋２ …（式３）
Here, the oxidation-reduction titration method using iodine will be described. First, a lithium transition metal oxide as a sample is subjected to composition analysis using inductively coupled plasma emission spectroscopy (ICP-AES) to determine the amount of transition metal ions in the sample. Next, when this lithium transition metal oxide is dissolved in an acidic aqueous solution and mixed with an iodine potassium solution, nickel and manganese higher than the divalent in the positive electrode active material are reduced to Ni 2+ and Mn 2+ . At the same time, an amount of I − equal to the amount of reduction is oxidized to produce I 2 . The amount of I 2 produced here is identified by titrating with sodium thiosulfate standard solution (Na 2 S 2 O 3 ) using starch solution as an indicator. Titration shall be performed in the following order.
(1) Place a ball filter in a 200 mL Erlenmeyer flask and replace nitrogen gas with 3 L / min for 5 minutes.
(2) Add 10 mL of KI (100 g / L) solution and 20 mL of HCl (hydrochloric acid [reagent special grade] and distilled water mixed at a volume ratio of 1: 1) in an Erlenmeyer flask.
(3) Weigh out 100 mg of the positive electrode active material at ± 0.1 mg.
(4) The positive electrode active material is transferred into an Erlenmeyer flask, stoppered and heated at 70 ° C. with stirring with a rotor to dissolve.
(5) After cooling the Erlenmeyer flask with running water, 80 mL of distilled water excluding residual oxygen is added.
(6) Titrate quickly with 0.05 mol / L sodium thiosulfate until the solution turns from brown to light yellow.
(7) 0.5 mL of starch solution is added and colored purple.
(8) Subsequently, titration is performed with 0.05 mol / L sodium thiosulfate, and the point where the purple color disappears is taken as the end point, and the average oxidation number of the transition metal ion is calculated based on the following reaction formula.
M n + + (n−2) I − → M 2+ +1/2 (n−2) I 2 (Formula 1)
I 2 + 2S 2 O 3 → 2I− + S 4 O 6 2− (Formula 2)
Average oxidation number = I 2 (mol) / (transition metal amount (mol)) + 2 (Formula 3)
このリチウム遷移金属酸化物は、一般式Ｌｉ1+zＭxＮｉ2-x-yＭｎyＯδ（但し、ＭはＦｅ及びＴｉのうち１以上であり、０≦ｘ≦０．１５、１．５≦ｙ＜２．０、０≦ｚ≦０．２５、３．９９≦δ≦４．１５を満たす）であるものとしてもよい。この範囲では、低温出力特性及び高温耐久性をより向上することができる。ここで、酸素量δは、ヨウ素を用いた酸化還元滴定法で求めたＮｉ，Ｍｎ及び元素Ｍの平均酸化数から算出した値である。この一般式において、ｘは０．２０以下であるものとしてもよく、０．１８以下であるものとしてもよい。この範囲においても、低温出力特性及び高温耐久性を向上することができる。また、ｘは０．０２５以上であることが好ましく、０．０７５以上であることがより好ましい。この一般式において、リチウム遷移金属酸化物は、元素ＭとしてＦｅ及びＴｉを等量含み、Ｆｅが０．０５≦ｘ≦０．０７５、Ｔｉが０．０５≦ｘ≦０．０７５を満たすことがより好ましい。この範囲では、低温出力特性及び高温耐久性を更に向上することができ、好ましい。 The lithium transition metal oxide represented by the general formula Li 1 + z M x Ni 2 -xy Mn y O δ ( where, M is at least one of Fe and Ti, 0 ≦ x ≦ 0.15,1.5 ≦ y <2.0, 0 ≦ z ≦ 0.25, 3.99 ≦ δ ≦ 4.15). In this range, the low temperature output characteristics and the high temperature durability can be further improved. Here, the oxygen amount δ is a value calculated from the average oxidation numbers of Ni, Mn, and element M obtained by the oxidation-reduction titration method using iodine. In this general formula, x may be 0.20 or less, or may be 0.18 or less. Even in this range, low temperature output characteristics and high temperature durability can be improved. Further, x is preferably 0.025 or more, and more preferably 0.075 or more. In this general formula, the lithium transition metal oxide contains equal amounts of Fe and Ti as the element M, Fe satisfies 0.05 ≦ x ≦ 0.075, and Ti satisfies 0.05 ≦ x ≦ 0.075. More preferred. In this range, the low temperature output characteristics and the high temperature durability can be further improved, which is preferable.
次に、本発明の非水電解質二次電池用正極活物質の製造方法について説明する。この製造方法では、（１）原料調製工程、（２）焼成アニール工程を含むものとしてもよい。なお、予め調製した原料を用意し、原料調製工程を省略してもよい。 Next, the manufacturing method of the positive electrode active material for nonaqueous electrolyte secondary batteries of this invention is demonstrated. This manufacturing method may include (1) a raw material preparation step and (2) a firing annealing step. In addition, the raw material prepared beforehand may be prepared and a raw material preparation process may be abbreviate | omitted.
（１）原料調製工程
この工程では、非水電解質二次電池用正極活物質の原料を調製する。原料は、上述したリチウム遷移金属酸化物の所望の組成に応じて加える物質及びその量を選択すればよい。
原料組成は、例えば、一般式Ｌｉ1+zＭxＮｉ2-x-yＭｎyＯ4（但し、ＭはＦｅ及びＴｉのうち１以上であり、０≦ｘ≦０．１５、１．５≦ｙ＜２．０、０＜ｚ＜０．２５を満たす）となるように、Ｌｉ，Ｎｉ，Ｍｎ及び元素Ｍを混合すればよい。遷移金属の原料は、共沈法によって合成することが好ましい。金属元素を原子レベルで均一に混合させることができ、より好適な性能が得られるからである。共沈法では、遷移金属イオンを一粒子中に共存させた前駆体を作製し、これにリチウム塩を混合するものとしてもよい。共沈法により金属イオンが均一に分布した前駆体を得る際、水溶液中に不活性ガスを通気させることにより溶存酸素を除去することが好ましい。前駆体およびリチウム塩は、水酸化物、炭酸塩、クエン酸塩などとしてもよい。前駆体の原料としては、例えば、ニッケル源として、硫酸ニッケル、硝酸ニッケル、酢酸ニッケル、水酸化ニッケル、炭酸ニッケル、塩基性炭酸ニッケル等を用いることができる。また、マンガン源として、硫酸マンガン、硝酸マンガン、酢酸マンガン、酸化マンガン、炭酸マンガン等用いることができる。鉄源として、水酸化鉄、硫酸鉄、硝酸鉄、酢酸鉄、炭酸鉄等を用いることができる。チタン源として、酸化チタン等を用いることができる。前駆体と混合するリチウム塩としては、水酸化リチウム、炭酸リチウム、硝酸リチウム、酢酸リチウム等を用いることができる。
(1) Raw material preparation process In this process, the raw material of the positive electrode active material for a nonaqueous electrolyte secondary battery is prepared. As the raw material, a substance to be added and its amount may be selected according to the desired composition of the above-described lithium transition metal oxide.
Feedstock composition, for example, the general formula Li 1 + z M x Ni 2 -xy Mn y O 4 ( where, M is at least one of Fe and Ti, 0 ≦ x ≦ 0.15,1.5 ≦ y Li, Ni, Mn, and element M may be mixed so that <2.0 and 0 <z <0.25 are satisfied. The raw material for the transition metal is preferably synthesized by a coprecipitation method. This is because metal elements can be uniformly mixed at the atomic level, and more suitable performance can be obtained. In the coprecipitation method, a precursor in which transition metal ions coexist in one particle may be prepared, and a lithium salt may be mixed with the precursor. When obtaining a precursor in which metal ions are uniformly distributed by a coprecipitation method, it is preferable to remove dissolved oxygen by passing an inert gas through an aqueous solution. The precursor and lithium salt may be hydroxides, carbonates, citrates, and the like. As a precursor raw material, for example, nickel sulfate, nickel nitrate, nickel acetate, nickel hydroxide, nickel carbonate, basic nickel carbonate, or the like can be used as a nickel source. Moreover, manganese sulfate, manganese nitrate, manganese acetate, manganese oxide, manganese carbonate, etc. can be used as a manganese source. As the iron source, iron hydroxide, iron sulfate, iron nitrate, iron acetate, iron carbonate, or the like can be used. As the titanium source, titanium oxide or the like can be used. As the lithium salt to be mixed with the precursor, lithium hydroxide, lithium carbonate, lithium nitrate, lithium acetate or the like can be used.
（２）焼成アニール工程
この工程では、上記得られた原料を焼成処理し、その後アニール処理を行う。焼成処理では、原料を酸化雰囲気中、９００℃以上１１００℃以下の第１温度範囲で焼成する。焼成時間は、例えば、５時間以上２４時間以下の範囲としてもよい。また、アニール処理は、焼成処理のあと、第１温度範囲よりも低い第２温度範囲へ温度を下げ、この温度範囲で保持するものとしてもよい。焼成処理は、高温での処理であり、結晶構造中に酸素欠損を生じることがある。アニール処理では、焼成処理により生じた酸素を補うことができ、遷移金属の平均酸化数をより好適な範囲にすることができる。第２温度範囲は、例えば、５００℃以上７００℃以下とすることができる。アニール処理時間は、５時間以上４０時間以下とする。アニール処理時間が長いとニッケルとマンガンとの規則配列が強まるなど、好ましくない。また、アニール処理時間が短いと酸素欠損を十分に補うことができない。このアニール処理時間は、１０時間以上２０時間以下の時間範囲がより好ましい。この範囲では、上述したヨウ素を用いた酸化還元滴定法による遷移金属イオンの平均酸化数をより好ましい範囲とすることができる。このような処理を経て、本発明のリチウム遷移金属酸化物を得ることができる。
(2) Firing Annealing Step In this step, the obtained raw material is fired and then annealed. In the firing treatment, the raw material is fired in an oxidizing atmosphere in a first temperature range of 900 ° C. or higher and 1100 ° C. or lower. The firing time may be, for example, in the range of 5 hours to 24 hours. In addition, the annealing treatment may be performed by lowering the temperature to a second temperature range lower than the first temperature range after the firing treatment, and maintaining the temperature range. The baking treatment is a high-temperature treatment, and oxygen deficiency may occur in the crystal structure. In the annealing treatment, oxygen generated by the firing treatment can be supplemented, and the average oxidation number of the transition metal can be set in a more suitable range. The second temperature range can be, for example, 500 ° C. or more and 700 ° C. or less. The annealing treatment time is 5 hours or more and 40 hours or less. If the annealing time is long, the ordered arrangement of nickel and manganese is increased, which is not preferable. Further, if the annealing time is short, oxygen vacancies cannot be sufficiently compensated. The annealing treatment time is more preferably in the time range from 10 hours to 20 hours. In this range, the average oxidation number of transition metal ions by the oxidation-reduction titration method using iodine described above can be made a more preferable range. Through such treatment, the lithium transition metal oxide of the present invention can be obtained.
本発明のリチウム二次電池は、リチウムイオンを吸蔵、放出する上述の非水電解質二次電池用正極活物質を有する化合物を含有する正極と、リチウムイオンを吸蔵、放出する負極活物質を含有する負極と、正極と負極との間に介在しリチウムイオンを伝導するイオン伝導媒体と、を備えている。 The lithium secondary battery of the present invention contains a positive electrode containing a compound having the above-described positive electrode active material for nonaqueous electrolyte secondary batteries that occludes and releases lithium ions, and a negative electrode active material that occludes and releases lithium ions. A negative electrode, and an ion conductive medium that is interposed between the positive electrode and the negative electrode and conducts lithium ions.
正極は、例えば正極活物質と導電材と結着材とを混合し、適当な溶剤を加えてペースト状の正極合材としたものを、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てもよい。正極は、上述したリチウムニッケルマンガン複合酸化物を正極活物質として含有する。導電材は、正極の電池性能に悪影響を及ぼさない電子伝導性材料であれば特に限定されず、例えば、天然黒鉛（鱗状黒鉛、鱗片状黒鉛）や人造黒鉛などの黒鉛、アセチレンブラック、カーボンブラック、ケッチェンブラック、カーボンウィスカ、ニードルコークス、炭素繊維、金属（銅、ニッケル、アルミニウム、銀、金など）などの１種又は２種以上を混合したものを用いることができる。これらの中で、導電材としては、電子伝導性及び塗工性の観点より、カーボンブラック及びアセチレンブラックが好ましい。結着材は、活物質粒子及び導電材粒子を繋ぎ止める役割を果たすものであり、例えば、ポリテトラフルオロエチレン（ＰＴＦＥ）、ポリフッ化ビニリデン（ＰＶＤＦ）、フッ素ゴム等の含フッ素樹脂、或いはポリプロピレン、ポリエチレン等の熱可塑性樹脂、エチレンプロピレンジエンモノマー（ＥＰＤＭ）ゴム、スルホン化ＥＰＤＭゴム、天然ブチルゴム（ＮＢＲ）等を単独で、あるいは２種以上の混合物として用いることができる。また、水系バインダーであるセルロース系やスチレンブタジエンゴム（ＳＢＲ）の水分散体等を用いることもできる。集電体としては、アルミニウム、チタン、ステンレス鋼、ニッケル、鉄、焼成炭素、導電性高分子、導電性ガラスなどのほか、接着性、導電性及び耐酸化性向上の目的で、アルミニウムや銅などの表面をカーボン、ニッケル、チタンや銀などで処理したものを用いることができる。集電体の厚さは、例えば１〜５００μｍのものが用いられる。 For example, the positive electrode is prepared by mixing a positive electrode active material, a conductive material, and a binder, adding a suitable solvent to form a paste-like positive electrode mixture, applying and drying on the surface of the current collector, and if necessary You may compress and form in order to raise an electrode density. The positive electrode contains the above-described lithium nickel manganese composite oxide as a positive electrode active material. The conductive material is not particularly limited as long as it is an electron conductive material that does not adversely affect the battery performance of the positive electrode. For example, graphite such as natural graphite (scale-like graphite, scale-like graphite) or artificial graphite, acetylene black, carbon black, What mixed 1 type (s) or 2 or more types, such as ketjen black, carbon whisker, needle coke, carbon fiber, metal (copper, nickel, aluminum, silver, gold, etc.) can be used. Among these, as the conductive material, carbon black and acetylene black are preferable from the viewpoints of electron conductivity and coatability. The binder serves to bind the active material particles and the conductive material particles. For example, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), fluorine-containing resin such as fluorine rubber, or polypropylene, Thermoplastic resins such as polyethylene, ethylene propylene diene monomer (EPDM) rubber, sulfonated EPDM rubber, natural butyl rubber (NBR) and the like can be used alone or as a mixture of two or more. In addition, an aqueous dispersion of cellulose or styrene butadiene rubber (SBR), which is an aqueous binder, can also be used. Current collectors include aluminum, titanium, stainless steel, nickel, iron, calcined carbon, conductive polymer, conductive glass, and aluminum, copper, etc. for the purpose of improving adhesion, conductivity, and oxidation resistance. A surface treated with carbon, nickel, titanium, silver or the like can be used. The thickness of the current collector is, for example, 1 to 500 μm.
負極は、例えば負極活物質と結着材とを混合し、適当な溶剤を加えてペースト状の負極合材としたものを、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てもよい。負極活物質としては、例えば、リチウム、リチウム合金、スズ化合物などの無機化合物、リチウムイオンを吸蔵・放出可能な炭素質材料、リチウムチタン複合酸化物、導電性ポリマーなどが挙げられるが、このうち炭素質材料が安全性の面から見て好ましい。この炭素質材料は、特に限定されるものではないが、コークス類、ガラス状炭素類、グラファイト類、難黒鉛化性炭素類、熱分解炭素類、炭素繊維などが挙げられる。このうち、人造黒鉛、天然黒鉛などのグラファイト類が、金属リチウムに近い作動電位を有し、高い作動電圧での充放電が可能であり電解質塩としてリチウム塩を使用した場合に自己放電を抑え、且つ充電時における不可逆容量を少なくできるため、好ましい。また、負極に用いられる導電材、結着材、溶剤などは、それぞれ正極で例示したものを用いることができる。負極の集電体には、銅、ニッケル、ステンレス鋼、チタン、アルミニウム、焼成炭素、導電性高分子、導電性ガラス、Ａｌ−Ｃｄ合金などのほか、接着性、導電性及び耐還元性向上の目的で、例えば銅などの表面をカーボン、ニッケル、チタンや銀などで処理したものも用いることができる。これらについては、表面を酸化処理することも可能である。集電体の形状は、正極と同様のものを用いることができる。 For the negative electrode, for example, a negative electrode active material and a binder are mixed, an appropriate solvent is added to form a paste-like negative electrode mixture, which is applied to the surface of the current collector and dried, and the electrode density is adjusted as necessary. You may compress and form in order to raise. Examples of the negative electrode active material include inorganic compounds such as lithium, lithium alloys, and tin compounds, carbonaceous materials that can occlude and release lithium ions, lithium titanium composite oxides, and conductive polymers. A quality material is preferable from the viewpoint of safety. The carbonaceous material is not particularly limited, and examples thereof include cokes, glassy carbons, graphites, non-graphitizable carbons, pyrolytic carbons, and carbon fibers. Of these, graphites such as artificial graphite and natural graphite have an operating potential close to that of metallic lithium, can be charged and discharged at a high operating voltage, and suppresses self-discharge when a lithium salt is used as an electrolyte salt. In addition, it is preferable because the irreversible capacity during charging can be reduced. In addition, as the conductive material, binder, solvent, and the like used for the negative electrode, those exemplified for the positive electrode can be used. The negative electrode current collector includes copper, nickel, stainless steel, titanium, aluminum, calcined carbon, conductive polymer, conductive glass, Al-Cd alloy, etc., as well as improved adhesion, conductivity and reduction resistance. For the purpose, for example, a copper surface treated with carbon, nickel, titanium, silver or the like can be used. For these, the surface can be oxidized. The shape of the current collector can be the same as that of the positive electrode.
イオン伝導媒体は、リチウムを含む支持塩と、非水系の溶媒とを含むものとしてもよい。非水電解液の溶媒としては、カーボネート類、エステル類、エーテル類、ニトリル類、フラン類、スルホラン類及びジオキソラン類などが挙げられ、これらを単独又は混合して用いることができる。具体的には、カーボネート類としてエチレンカーボネートやプロピレンカーボネート、ビニレンカーボネート、ブチレンカーボネート、クロロエチレンカーボネートなどの環状カーボネート類や、ジメチルカーボネート、エチルメチルカーボネート、ジエチルカーボネート、エチル−ｎ−ブチルカーボネート、メチル−ｔ−ブチルカーボネート、ジ−ｉ−プロピルカーボネート、ｔ−ブチル−ｉ−プロピルカーボネートなどの鎖状カーボネート類、γ−ブチルラクトン、γ−バレロラクトンなどの環状エステル類、ギ酸メチル、酢酸メチル、酢酸エチル、酪酸メチルなどの鎖状エステル類、ジメトキシエタン、エトキシメトキシエタン、ジエトキシエタンなどのエーテル類、アセトニトリル、ベンゾニトリルなどのニトリル類、テトラヒドロフラン、メチルテトラヒドロフラン、などのフラン類、スルホラン、テトラメチルスルホランなどのスルホラン類、１，３−ジオキソラン、メチルジオキソランなどのジオキソラン類などが挙げられる。このうち、環状カーボネート類と鎖状カーボネート類との組み合わせが好ましい。この組み合わせによると、充放電の繰り返しでの電池特性を表すサイクル特性が優れているばかりでなく、電解液の粘度、得られる電池の電気容量、電池出力などをバランスの取れたものとすることができる。 The ion conductive medium may include a supporting salt containing lithium and a non-aqueous solvent. Examples of the solvent for the nonaqueous electrolytic solution include carbonates, esters, ethers, nitriles, furans, sulfolanes and dioxolanes, and these can be used alone or in combination. Specifically, as carbonates, cyclic carbonates such as ethylene carbonate, propylene carbonate, vinylene carbonate, butylene carbonate, chloroethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethyl-n-butyl carbonate, methyl-t -Chain carbonates such as butyl carbonate, di-i-propyl carbonate, t-butyl-i-propyl carbonate, cyclic esters such as γ-butyllactone and γ-valerolactone, methyl formate, methyl acetate, ethyl acetate, Chain esters such as methyl butyrate, ethers such as dimethoxyethane, ethoxymethoxyethane, and diethoxyethane; nitriles such as acetonitrile and benzonitrile; Examples include furans such as lan, methyltetrahydrofuran, sulfolanes such as sulfolane and tetramethylsulfolane, and dioxolanes such as 1,3-dioxolane and methyldioxolane. Among these, the combination of cyclic carbonates and chain carbonates is preferable. According to this combination, not only the cycle characteristics representing the battery characteristics in repeated charge and discharge are excellent, but also the viscosity of the electrolyte, the electric capacity of the obtained battery, the battery output, etc. should be balanced. it can.
支持塩は、例えば、ＬｉＰＦ6、ＬｉＢＦ4、ＬｉＡｓＦ6、ＬｉＣＦ3ＳＯ3、ＬｉＮ（ＣＦ3ＳＯ2）2、ＬｉＣ（ＣＦ3ＳＯ2）3、ＬｉＳｂＦ6、ＬｉＳｉＦ6、ＬｉＡｌＦ4、ＬｉＳＣＮ、ＬｉＣｌＯ4、ＬｉＣｌ、ＬｉＦ、ＬｉＢｒ、ＬｉＩ、ＬｉＡｌＣｌ4などが挙げられる。このうち、ＬｉＰＦ6、ＬｉＢＦ4、ＬｉＡｓＦ6、ＬｉＣｌＯ4などの無機塩、及びＬｉＣＦ3ＳＯ3、ＬｉＮ（ＣＦ3ＳＯ2）2、ＬｉＣ（ＣＦ3ＳＯ2）3などの有機塩からなる群より選ばれる１種又は２種以上の塩を組み合わせて用いることが電気特性の点から見て好ましい。この支持塩は、非水電解液中の濃度が０．１ｍｏｌ／Ｌ以上５ｍｏｌ／Ｌ以下であることが好ましく、０．５ｍｏｌ／Ｌ以上２ｍｏｌ／Ｌ以下であることがより好ましい。支持塩を溶解する濃度が０．１ｍｏｌ／Ｌ以上では、十分な電流密度を得ることができ、５ｍｏｌ／Ｌ以下では、電解液をより安定させることができる。 Examples of the supporting salt include LiPF 6 , LiBF 4 , LiAsF 6 , LiCF 3 SO 3 , LiN (CF 3 SO 2 ) 2 , LiC (CF 3 SO 2 ) 3 , LiSbF 6 , LiSiF 6 , LiAlF 4 , LiSCN, LiClO. 4 , LiCl, LiF, LiBr, LiI, LiAlCl 4 and the like. Among these, from the group consisting of inorganic salts such as LiPF 6 , LiBF 4 , LiAsF 6 , LiClO 4 , and organic salts such as LiCF 3 SO 3 , LiN (CF 3 SO 2 ) 2 , LiC (CF 3 SO 2 ) 3. It is preferable from the viewpoint of electrical characteristics to use a combination of one or two or more selected salts. The supporting salt preferably has a concentration in the non-aqueous electrolyte of 0.1 mol / L or more and 5 mol / L or less, and more preferably 0.5 mol / L or more and 2 mol / L or less. When the concentration for dissolving the supporting salt is 0.1 mol / L or more, a sufficient current density can be obtained, and when it is 5 mol / L or less, the electrolytic solution can be made more stable.
また、液状のイオン伝導媒体の代わりに、固体のイオン伝導性ポリマーをイオン伝導媒体として用いることもできる。イオン伝導性ポリマーとしては、例えば、アクリロニトリル、エチレンオキシド、プロピレンオキシド、メチルメタクリレート、ビニルアセテート、ビニルピロリドン、フッ化ビニリデンなどのポリマーと支持塩とで構成されるポリマーゲルを用いることができる。更に、イオン伝導性ポリマーと非水系電解液とを組み合わせて用いることもできる。また、イオン伝導媒体としては、イオン伝導性ポリマーのほか、無機固体電解質あるいは有機ポリマー電解質と無機固体電解質の混合材料、若しくは有機バインダーによって結着された無機固体粉末などを利用することができる。 Further, instead of the liquid ion conducting medium, a solid ion conducting polymer may be used as the ion conducting medium. As the ion conductive polymer, for example, a polymer gel composed of a polymer such as acrylonitrile, ethylene oxide, propylene oxide, methyl methacrylate, vinyl acetate, vinyl pyrrolidone, vinylidene fluoride and a supporting salt can be used. Further, an ion conductive polymer and a non-aqueous electrolyte can be used in combination. In addition to the ion conductive polymer, an inorganic solid electrolyte, a mixed material of an organic polymer electrolyte and an inorganic solid electrolyte, an inorganic solid powder bound by an organic binder, or the like can be used as the ion conductive medium.
本発明のリチウム二次電池は、負極と正極との間にセパレータを備えていてもよい。セパレータとしては、リチウム二次電池の使用範囲に耐えうる組成であれば特に限定されないが、例えば、ポリプロピレン製不織布やポリフェニレンスルフィド製不織布などの高分子不織布、ポリエチレンやポリプロピレンなどのオレフィン系樹脂の薄い微多孔膜が挙げられる。これらは単独で用いてもよいし、複数を混合して用いてもよい。 The lithium secondary battery of the present invention may include a separator between the negative electrode and the positive electrode. The separator is not particularly limited as long as it has a composition that can withstand the range of use of the lithium secondary battery. For example, a polymer nonwoven fabric such as a polypropylene nonwoven fabric or a polyphenylene sulfide nonwoven fabric, or a thin fine olefin resin such as polyethylene or polypropylene is used. A porous membrane is mentioned. These may be used alone or in combination.
本発明のリチウム二次電池の形状は、特に限定されないが、例えばコイン型、ボタン型、シート型、積層型、円筒型、偏平型、角型などが挙げられる。また、電気自動車等に用いる大型のものなどに適用してもよい。図１は、本発明のリチウム二次電池１０の一例を示す模式図である。このリチウム二次電池１０は、集電体１１に正極活物質１２を形成した正極シート１３と、集電体１４の表面に負極活物質１７を形成した負極シート１８と、正極シート１３と負極シート１８との間に設けられたセパレータ１９と、正極シート１３と負極シート１８の間を満たす非水電解液２０と、を備えたものである。このリチウム二次電池１０では、正極シート１３と負極シート１８との間にセパレータ１９を挟み、これらを捲回して円筒ケース２２に挿入し、正極シート１３に接続された正極端子２４と負極シートに接続された負極端子２６とを配設して形成されている。このリチウム二次電池１０は、ヨウ素を用いた酸化還元滴定法で算出した遷移金属イオンの平均酸化数が３．４９以上３．５５以下の範囲のリチウム遷移金属酸化物を含む正極活物質１２を備える。
The shape of the lithium secondary battery of the present invention is not particularly limited, and examples thereof include a coin type, a button type, a sheet type, a laminated type, a cylindrical type, a flat type, and a square type. Moreover, you may apply to the large sized thing etc. which are used for an electric vehicle etc. FIG. 1 is a schematic diagram showing an example of a lithium
以上詳述した非水電解質二次電池用正極活物質、その製造方法及びリチウム二次電池
では、低温での出力特性及び高温での耐久性をより向上することができる。このような効果が得られる理由は、例えば、以下のように推測される。スピネル型構造を有し、ニッケル元素およびマンガン元素を含むリチウム遷移金属酸化物は、９００℃以上の温度で焼成することで高結晶性の試料となる。しかし、この高温焼成過程で試料から酸素が放出され、遷移金属イオンの酸化数が減少する。この酸素欠損・低価数の酸化物は、電池性能が低いと考えられる。ここで、この焼成温度よりも低温の５００〜７００℃でのアニール処理を施すことにより、高温で放出された酸素を再び酸化物中に吸蔵させることができ、遷移金属イオンの酸化数を制御することができる。中でも、ヨウ素を用いた酸化還元滴定法で算出した平均酸化数と低温出力特性、高温耐久性に相関関係があり、遷移金属イオンの平均酸化数を３．４９以上３．５５以下とすることで低温出力特性、高温耐久性を向上させることができると考えられる。
In the positive electrode active material for a non-aqueous electrolyte secondary battery, the manufacturing method thereof, and the lithium secondary battery described in detail above, the output characteristics at a low temperature and the durability at a high temperature can be further improved. The reason why such an effect is obtained is estimated as follows, for example. A lithium transition metal oxide having a spinel structure and containing a nickel element and a manganese element becomes a highly crystalline sample by firing at a temperature of 900 ° C. or higher. However, oxygen is released from the sample during this high-temperature firing process, and the oxidation number of transition metal ions decreases. This oxygen deficient / low valence oxide is considered to have low battery performance. Here, by performing an annealing process at 500 to 700 ° C. lower than the firing temperature, oxygen released at a high temperature can be occluded again in the oxide, and the oxidation number of the transition metal ions is controlled. be able to. Above all, there is a correlation between the average oxidation number calculated by the oxidation-reduction titration method using iodine, the low-temperature output characteristics, and the high-temperature durability. By setting the average oxidation number of the transition metal ions to 3.49 or more and 3.55 or less. It is thought that low temperature output characteristics and high temperature durability can be improved.
なお、本発明は上述した実施形態に何ら限定されることはなく、本発明の技術的範囲に属する限り種々の態様で実施し得ることはいうまでもない。 It should be noted that the present invention is not limited to the above-described embodiment, and it goes without saying that the present invention can be implemented in various modes as long as it belongs to the technical scope of the present invention.
以下には、本発明のリチウム二次電池を具体的に作製した例を実験例として説明する。なお、実験例３〜１５が実施例に相当し、実験例１、２が比較例に相当する。 Below, the example which produced the lithium secondary battery of this invention concretely is demonstrated as an experiment example. Experimental examples 3 to 15 correspond to examples, and experimental examples 1 and 2 correspond to comparative examples.
［実験例１］
予め不活性ガスを通気させて溶存酸素を取り除いたイオン交換水に硫酸ニッケル、硫酸マンガンをＮｉ，Ｍｎの各元素が０．２５：０．７５のモル比となるように溶解させ、これら金属元素の合計モル濃度が２ｍｏｌ／Ｌとなるように混合水溶液を調製した。一方、同様に溶存酸素を取り除いたイオン交換水を用いて、２ｍｏｌ／Ｌの水酸化ナトリウム水溶液と、０．３５２ｍｏｌ／Ｌのアンモニア水をそれぞれ調製した。溶存酸素を取り除いたイオン交換水を槽内温度５０℃に設定された反応槽に入れ、８００ｒｐｍで撹拌させた状態で水酸化ナトリウム水溶液を滴下して液温２５℃を基準としたときにｐＨが１２となるように溶液を調製した。反応槽に上記混合水溶液、水酸化ナトリウム水溶液及びアンモニア水をｐＨ１２に制御しつつ加え、共沈生成物の複合水酸化物を得た。水酸化ナトリウム水溶液のみを適宜加えてｐＨを１２に保ち、２時間撹拌を継続した。その後、６０℃で１２時間静置することで複合水酸化物を粒子成長させた。反応終了後、複合水酸化物をろ過、水洗して取り出し、１２０℃のオーブン内で一晩乾燥させて複合水酸化物の粉末試料を得た。得られた複合水酸化物粉末と、水酸化リチウム粉末とをリチウムのモル数Ｍｌと遷移金属（Ｎｉ、Ｍｎ）の総モル数Ｍｍとのモル比Ｍｌ／Ｍｍが０．５５となるようにこれらを混合した。この混合粉末を６ＭＰａの圧力で直径２ｃｍ、厚さ５ｍｍのペレットに加圧成形し、空気雰囲気の電気炉中、１０００℃の温度まで１０℃／分で昇温し、その温度で１２時間焼成することにより、目的の試料を得た。焼成後、ヒータの電源を切り、自然放冷した。８時間後、炉内温度が１００℃以下となっていることを確認してペレットを取り出した。得られたものを実験例１の正極活物質とした。
[Experimental Example 1]
These metal elements are prepared by dissolving nickel sulfate and manganese sulfate in ion exchange water in which an inert gas is previously passed through to remove dissolved oxygen so that each element of Ni and Mn has a molar ratio of 0.25: 0.75. A mixed aqueous solution was prepared so that the total molar concentration of was 2 mol / L. On the other hand, 2 mol / L sodium hydroxide aqueous solution and 0.352 mol / L ammonia water were prepared using ion-exchanged water from which dissolved oxygen was similarly removed. When ion-exchanged water from which dissolved oxygen has been removed is placed in a reaction tank set at a tank temperature of 50 ° C. and stirred at 800 rpm, an aqueous solution of sodium hydroxide is added dropwise to adjust the pH to 25 ° C. as a reference. A solution was prepared to be 12. The above mixed aqueous solution, aqueous sodium hydroxide solution and aqueous ammonia were added to the reaction vessel while controlling the pH to 12, thereby obtaining a composite hydroxide of a coprecipitation product. Only aqueous sodium hydroxide was added as appropriate to maintain the pH at 12, and stirring was continued for 2 hours. Thereafter, the composite hydroxide was allowed to grow at 60 ° C. for 12 hours to grow particles. After completion of the reaction, the composite hydroxide was filtered, washed with water and taken out, and dried overnight in an oven at 120 ° C. to obtain a composite hydroxide powder sample. The obtained composite hydroxide powder and lithium hydroxide powder were mixed so that the molar ratio Ml / Mm between the molar number Ml of lithium and the total molar number Mm of transition metals (Ni, Mn) was 0.55. Were mixed. This mixed powder is pressure-molded into a pellet having a diameter of 2 cm and a thickness of 5 mm at a pressure of 6 MPa, heated at a temperature of 10 ° C./min up to a temperature of 1000 ° C. in an electric furnace in an air atmosphere, and fired at that temperature for 12 hours. Thus, a target sample was obtained. After firing, the heater was turned off and allowed to cool naturally. After 8 hours, it was confirmed that the furnace temperature was 100 ° C. or less, and the pellets were taken out. The obtained product was used as the positive electrode active material of Experimental Example 1.
（ヨウ素を用いた酸化還元滴定法）
誘導結合プラズマ発光分光分析法（ＩＣＰ−ＡＥＳ）を用いてリチウム遷移金属酸化物の組成分析を行い、試料中の遷移金属イオン量を求めた。このリチウム遷移金属酸化物を酸性水溶液に溶解させ、ヨウ素カリウム溶液と混合させた場合には、リチウム遷移金属酸化物中の２価よりも高いニッケル、マンガンは、Ｎｉ2+、Ｍｎ2+に還元されると共に、還元量と等量のＩ-が酸化されてＩ2が生成する。ここで生成されたＩ2量は、デンプン溶液を指示薬としてチオ硫酸ナトリウム標準溶液（Ｎａ2Ｓ2Ｏ3）で滴定することで同定される。滴定は以下の順に実施した。
（１）２００ｍＬの三角フラスコにボールフィルタを入れ、窒素ガスを３Ｌ／分で５分間置換した。
（２）三角フラスコ中にＫＩ（１００ｇ／Ｌ）溶液１０ｍＬと、ＨＣｌ（塩酸［試薬特級］と蒸留水とを体積比で１：１に混合したもの）に２０ｍＬ加えた。
（３）正極活物質１００ｍｇを±０．１ｍｇで量り取った。
（４）正極活物質を三角フラスコに移し入れ、栓をして回転子で撹拌しながら７０℃で加熱して溶解させた。
（５）流水で三角フラスコを冷却後、残存酸素を除いた蒸留水を８０ｍＬ加えた。
（６）０．０５ｍｏｌ／Ｌのチオ硫酸ナトリウムで溶液が褐色から薄い黄色になるまで素早く滴定した。
（７）デンプン溶液を０．５ｍＬ加えて紫色に呈色させた。
（８）続けて０．０５ｍｏｌ／Ｌのチオ硫酸ナトリウムで滴定し、紫色が消えたところを終点とし、以下の反応式に基づいて遷移金属イオンの平均酸化数を算出した。
Ｍn+＋（ｎ−２）Ｉ- → Ｍ2+＋１／２（ｎ−２）Ｉ2
Ｉ2＋２Ｓ2Ｏ3 → ２Ｉ-＋Ｓ4Ｏ6 2-
平均酸化数＝Ｉ2（ｍｏｌ）／（遷移金属量（ｍｏｌ））＋２
(Redox titration method using iodine)
Composition analysis of the lithium transition metal oxide was performed using inductively coupled plasma emission spectroscopy (ICP-AES) to determine the amount of transition metal ions in the sample. When this lithium transition metal oxide is dissolved in an acidic aqueous solution and mixed with potassium iodine solution, nickel and manganese higher than the divalent lithium transition metal oxide are reduced to Ni 2+ and Mn 2+ . At the same time, an amount of I − equal to the amount of reduction is oxidized to produce I 2 . The amount of I 2 produced here is identified by titrating with sodium thiosulfate standard solution (Na 2 S 2 O 3 ) using starch solution as an indicator. Titration was performed in the following order.
(1) A ball filter was placed in a 200 mL Erlenmeyer flask, and nitrogen gas was replaced with 3 L / min for 5 minutes.
(2) In an Erlenmeyer flask, 20 mL of KI (100 g / L) solution and 20 mL of HCl (hydrochloric acid [reagent special grade] and distilled water mixed at a volume ratio of 1: 1) were added.
(3) 100 mg of the positive electrode active material was weighed at ± 0.1 mg.
(4) The positive electrode active material was transferred into an Erlenmeyer flask, capped, heated and dissolved at 70 ° C. while stirring with a rotor.
(5) After cooling the Erlenmeyer flask with running water, 80 mL of distilled water excluding residual oxygen was added.
(6) The solution was quickly titrated with 0.05 mol / L sodium thiosulfate until the solution turned from brown to light yellow.
(7) 0.5 mL of starch solution was added to give a purple color.
(8) Subsequently, titration with 0.05 mol / L sodium thiosulfate was performed, and the point where the purple color disappeared was taken as the end point, and the average oxidation number of transition metal ions was calculated based on the following reaction formula.
M n + + (n−2) I − → M 2+ +1/2 (n−2) I 2
I 2 + 2S 2 O 3 → 2I− + S 4 O 6 2−
Average oxidation number = I 2 (mol) / (transition metal amount (mol)) + 2
（電池作製）
上記合成材料を正極活物質として用い、正極活物質を８５質量％、導電材としてカーボンブラックを１０質量％、結着材としてポリフッ化ビニリデンを５質量％混合し、分散材としてＮ−メチル−２−ピロリドンを適量添加、分散してスラリー状合材とした。このスラリー状合材を２０μｍ厚のアルミニウム箔集電体の両面に均一に塗布し、加熱乾燥させて塗布シートを作製した。その後塗布シートをロールプレスに通して高密度化させ、５２ｍｍ幅×４５０ｍｍ長さの形状に切り出して正極電極とした。負極活物質として黒鉛を９５質量％、結着剤としてポリフッ化ビニリデンを５質量％混合し、正極と同様にスラリー状合材とした。このスラリー状合材を１０μｍ厚の銅箔集電体の両面に均一に塗布し、加熱乾燥させて塗布シートを作製した。その後塗布シートをロールプレスに通して高密度化させ、５４ｍｍ幅×５００ｍｍ長さの形状に切り出して負極電極とした。上記の正極シートと負極シートを５６ｍｍ幅で２５μｍ厚のポリエチレン製セパレータを挟んで捲回し、ロール状電極体を作製した。この電極体を１８６５０型円筒ケースに挿入し、非水電解液を含侵させた後に密閉して円筒型リチウム二次電池を作製した。非水電解液には、エチレンカーボネート、ジメチルカーボネート、エチルメチルカーボネートを体積％で３０／４０／３０の割合で混合した混合溶媒に、ＬｉＰＦ6を１Ｍの濃度で溶解させたものを用いた。
(Battery production)
The above synthetic material is used as a positive electrode active material, 85% by mass of the positive electrode active material, 10% by mass of carbon black as a conductive material, 5% by mass of polyvinylidene fluoride as a binder, and N-methyl-2 as a dispersion material. -An appropriate amount of pyrrolidone was added and dispersed to form a slurry composite. This slurry-like composite material was uniformly applied to both surfaces of an aluminum foil current collector having a thickness of 20 μm and dried by heating to prepare a coated sheet. Thereafter, the coated sheet was passed through a roll press to be densified, and cut into a shape of 52 mm width × 450 mm length to obtain a positive electrode. 95% by mass of graphite as a negative electrode active material and 5% by mass of polyvinylidene fluoride as a binder were mixed to obtain a slurry-like composite material in the same manner as the positive electrode. This slurry-like composite material was uniformly applied to both surfaces of a 10 μm thick copper foil current collector and dried by heating to prepare a coated sheet. Thereafter, the coated sheet was passed through a roll press to increase the density, and cut into a 54 mm wide × 500 mm long shape to obtain a negative electrode. The positive electrode sheet and the negative electrode sheet were wound with a polyethylene separator having a width of 56 mm and a thickness of 25 μm interposed therebetween, and a rolled electrode body was produced. This electrode body was inserted into a 18650 type cylindrical case, impregnated with a non-aqueous electrolyte, and then sealed to produce a cylindrical lithium secondary battery. As the non-aqueous electrolyte, a solution obtained by dissolving LiPF 6 at a concentration of 1M in a mixed solvent in which ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate were mixed at a volume ratio of 30/40/30 was used.
（電池の−３０℃出力評価：低温出力特性）
低温出力評価は、−３０℃において電池容量の５０％（ＳＯＣ＝５０％）に調整した後、種々の電流値で電流を流し、２秒後の電池電圧を測定した。流した電流と電圧を直線補間し、２秒後の電圧が３．０Ｖになる電流値を求め、その電流と電圧の積を低温出力特性とした。電池の低温出力特性は、（各実験例の低温出力特性〔Ｗ〕）／（実験例１の低温出力特性〔Ｗ〕)に基づいて、実験例１の電池出力特性で規格化した。
(Battery -30 ° C output evaluation: low temperature output characteristics)
For low-temperature output evaluation, after adjusting the battery capacity to 50% (SOC = 50%) at −30 ° C., current was passed at various current values, and the battery voltage after 2 seconds was measured. The applied current and voltage were linearly interpolated to obtain a current value at which the voltage after 2 seconds becomes 3.0 V, and the product of the current and voltage was defined as a low temperature output characteristic. The low-temperature output characteristics of the battery were normalized by the battery output characteristics of Experimental Example 1 based on (Low-temperature output characteristics [W] of each Experimental Example) / (Low-temperature output characteristics of Experimental Example 1 [W]).
（電池の６０℃充放電サイクル試験：高温耐久性試験）
電池の高温充放電サイクル評価は、６０℃の温度条件下、２Ｃレートの定電流で充電上限電圧５．１Ｖまで充電し、放電下限電圧３．０Ｖまで放電を行う充放電を１サイクルとし、このサイクルを５００サイクル行った。サイクルごとにそれぞれのリチウム二次電池について放電容量を測定した。電池の高温耐久試験の容量維持率は、（５００サイクル後の放電容量／初期放電容量×１００％）という式を用いて計算した。また、容量維持率は、（各実験例の容量維持率〔％〕）／（実験例１の容量維持率〔％〕）に基づいて、実験例１の容量維持率で規格化した。
(Battery 60 ° C charge / discharge cycle test: high temperature durability test)
The high-temperature charge / discharge cycle evaluation of the battery is performed by charging / discharging up to a charge upper limit voltage of 5.1V at a constant current of 2C rate under a temperature condition of 60 ° C. 500 cycles were performed. The discharge capacity of each lithium secondary battery was measured for each cycle. The capacity retention rate in the high-temperature durability test of the battery was calculated using the formula (discharge capacity after 500 cycles / initial discharge capacity × 100%). The capacity retention rate was normalized by the capacity retention rate of Experimental Example 1 based on (Capacity Maintenance Rate [%] of each Experimental Example) / (Capacity Maintenance Rate [%] of Experimental Example 1).
［実験例２〜９］
実験例１で合成した正極活物質の焼成処理と同様に、１０００℃、１２時間の焼成処理を行った。その後、自然放冷で７００℃まで冷却させ、その温度で７２時間保持し、アニールさせた。得られた正極活物質を実験例２とした。また、アニール処理を表１に示した条件で行った以外は実験例２と同様に作製した正極活物質を実験例３〜９とした。
[Experimental Examples 2 to 9]
Similarly to the baking treatment of the positive electrode active material synthesized in Experimental Example 1, the baking treatment was performed at 1000 ° C. for 12 hours. Then, it was naturally cooled to 700 ° C., held at that temperature for 72 hours, and annealed. The obtained positive electrode active material was set as Experimental Example 2. In addition, Experimental Examples 3 to 9 were made as positive electrode active materials prepared in the same manner as in Experimental Example 2 except that the annealing treatment was performed under the conditions shown in Table 1.
［実験例１０〜１５］
正極活物質の合成原料としてニッケルマンガンの複合水酸化物に加えて、ニッケルマンガンイオンに対して鉄イオンを２．５ｍｏｌ％、チタンイオンを２．５ｍｏｌ％となるようにＦｅＯＯＨ、アナターゼ型ＴｉＯ2を混合し、遷移金属原料粉末を得た以外は実験例９と同様の工程を経て得られた正極活物質を実験例１０とした。なお、実験例１０では、遷移金属イオンの平均酸化数は、Ｎｉ，Ｍｎ，Ｆｅイオンの平均として求めた。また、原料組成を表２に示した条件で行った以外は実験例１０と同様に作製した正極活物質を実験例１１〜１５とした。
[Experimental Examples 10 to 15]
In addition to nickel manganese composite hydroxide as a raw material for the synthesis of the positive electrode active material, FeOOH and anatase TiO 2 are added so that the iron ion is 2.5 mol% and the titanium ion is 2.5 mol% with respect to the nickel manganese ion. The positive electrode active material obtained through the same steps as in Experimental Example 9 was obtained as Experimental Example 10 except that the transition metal raw material powder was obtained by mixing. In Experimental Example 10, the average oxidation number of transition metal ions was determined as the average of Ni, Mn, and Fe ions. Moreover, the positive electrode active material produced similarly to Experimental example 10 was made into Experimental Examples 11-15 except having performed the raw material composition on the conditions shown in Table 2.
（結果と考察）
表１に、実験例１〜９のアニール処理条件、平均酸化数、組成、低温出力特性、高温耐久性試験の結果をまとめて示す。実験例１〜９は、一般式ＬｉＮｉ0.50Ｍｎ1.50Ｏδのδが、それぞれ３．９８５、４．０５５、３．９９０、４．０００、４．０４５、４．０５０、４．０１０、４．０２２及び４．０４０であった。なお、一般式の酸素量δは、ヨウ素を用いた酸化還元滴定法で求めたＮｉ，Ｍｎの平均酸化数から算出した値である。表１に示すように、ヨウ素を用いた酸化還元滴定法で算出した遷移金属イオンの平均酸化数が３．４９以上３．５５以下の範囲では、実験例１に対して低温出力特性が１．０５倍以上、高温耐久性が１．２０倍以上を示し、それぞれの特性が向上することがわかった。特に、平均酸化数が３．５１以上３．５４以下の範囲では、更にこれらの特性が高く良好であることがわかった。この理由は、例えば以下のように推察された。正極活物質は、９００℃以上の温度で焼成することで高結晶とすることができる。しかし、得られた活物質（実験例１）は、高温耐久試験での材料劣化が激しくなるとともに低温出力特性が低かった。これは、試料の高温焼成中に酸素が放出され、酸素欠損の生成とともに遷移金属イオンの価数が低下し、この酸素欠損及び低価数により、電池性能の低下が生じると考えられた。一方、焼成温度よりも低温の６００〜７００℃でアニール処理を施すと、例えば、構造内へ酸素を再吸蔵させることができ、酸素欠損を減少させて遷移金属イオンの平均酸化数を上昇させることができると推察された。このとき、実験例２のようにアニール時間を長くしてしまうと、酸素欠損が減少するだけでなくニッケルとマンガンの構造内で規則配列するようになり、充放電反応メカニズムがそれまでの一相反応から二相反応へと変化し、その結果、低温出力特性が低下し、高温耐久性も低下する。これらの関係から、アニール時間を調整し、ヨウ素を用いた酸化還元滴定法で算出した遷移金属イオンの平均酸化数を３．４９以上３．５５以下とすることで低温出力特性、高温耐久性が向上し、３．５１以上３．５４以下とすることでさらに向上させることができることが明らかとなった。
(Results and discussion)
Table 1 summarizes the annealing treatment conditions, average oxidation number, composition, low-temperature output characteristics, and high-temperature durability test results of Experimental Examples 1 to 9. In Experimental Examples 1 to 9, δ of the general formula LiNi 0.50 Mn 1.50 O δ is 3.985, 4.055, 3.990, 4.0000, 4.045, 4.050, 4.010, 4. 022 and 4.040. The oxygen amount δ in the general formula is a value calculated from the average oxidation numbers of Ni and Mn obtained by the oxidation-reduction titration method using iodine. As shown in Table 1, when the average oxidation number of transition metal ions calculated by the oxidation-reduction titration method using iodine is in the range of 3.49 to 3.55, the low-temperature output characteristics are 1. It was found that the characteristics were improved by 05 times or more and high-temperature durability was 1.20 times or more. In particular, when the average oxidation number is in the range of 3.51 or more and 3.54 or less, it was found that these characteristics are higher and better. This reason was guessed as follows, for example. The positive electrode active material can be made highly crystalline by firing at a temperature of 900 ° C. or higher. However, the obtained active material (Experimental Example 1) showed severe deterioration of the material in the high temperature durability test and low low temperature output characteristics. It was considered that oxygen was released during the high-temperature firing of the sample, and the valence of transition metal ions was reduced with the generation of oxygen vacancies, and the battery performance was reduced due to the oxygen vacancies and the low valence. On the other hand, when annealing is performed at 600 to 700 ° C., which is lower than the firing temperature, for example, oxygen can be re-occluded into the structure, and oxygen vacancies can be reduced to increase the average oxidation number of transition metal ions. It was inferred that At this time, if the annealing time is increased as in Experiment 2, not only the oxygen deficiency is reduced, but also the nickel and manganese structures are regularly arranged, and the charge / discharge reaction mechanism is one phase until then. It changes from a reaction to a two-phase reaction, and as a result, the low-temperature output characteristics are lowered and the high-temperature durability is also lowered. From these relationships, by adjusting the annealing time and setting the average oxidation number of transition metal ions calculated by the oxidation-reduction titration method using iodine to be 3.49 or more and 3.55 or less, low temperature output characteristics and high temperature durability can be obtained. It became clear that it can improve further by setting it as 3.51 or more and 3.54 or less.
表２に、実験例１０〜１５のＦｅ，Ｔｉの原料組成、平均酸化数、組成、低温出力特性、高温耐久性試験の結果をまとめて示す。実験例１０〜１５は、一般式ＬｉＭxＮｉ2-x-yＭｎyＯδのδが、それぞれ４．０３７、４．０４２、４．０４７、４．０４７、４．０４０及び４．０３３であった。ここでの酸素量δは、ヨウ素を用いた酸化還元滴定法で求めたＮｉ，Ｍｎ及びＦｅの平均酸化数、及びＴｉの価数から算出した値である。表２に示すように、Ｆｅ、Ｔｉが含まれることにより、低温出力特性や高温耐久性をより向上することができることがわかった。特に、Ｆｅ、Ｔｉが等モル量含まれ、かつ０．０５〜０．０７５の範囲で添加された実験例１１、１２では、実験例１に対して低温出力特性が１．３０倍以上、高温耐久性が１．７０倍以上を示し、それぞれの特性が極めて向上することがわかった。この理由は、例えば、Ｆｅ、Ｔｉが等モル量含まれると、構造内でＦｅＴｉＯ3に近い状態が形成され、これが遷移金属イオンの配列様式を最適化させるとともに、界面反応の向上効果を示すためであると推察された。ＦｅとＴｉが等量から外れた場合には余分のＦｅもしくはＴｉイオンが構造内に混入するため、十分な性能向上効果が得られないと考えられた。Ｆｅ，Ｔｉの含有量がＦｅ０．０５Ｔｉ０．０５〜Ｆｅ０．０７５Ｔｉ０．０７５の範囲で含まれる場合に、特に優れた特性を示すのは、例えばＦｅ及びＴｉが少ないと界面反応向上効果を示さず、Ｆｅ及びＴｉが過剰に存在すると抵抗層として働き性能低下するためであると推察された。 Table 2 summarizes the results of Fe, Ti raw material compositions, average oxidation numbers, compositions, low-temperature output characteristics, and high-temperature durability tests of Experimental Examples 10 to 15. Experimental Examples 10 to 15, [delta] of the general formula LiM x Ni 2-xy Mn y O δ is, were respectively 4.037,4.042,4.047,4.047,4.040 and 4.033 . Here, the amount of oxygen δ is a value calculated from the average oxidation number of Ni, Mn, and Fe obtained by the oxidation-reduction titration method using iodine, and the valence of Ti. As shown in Table 2, it was found that the inclusion of Fe and Ti can further improve the low temperature output characteristics and the high temperature durability. In particular, in Experimental Examples 11 and 12 in which equimolar amounts of Fe and Ti are contained and added in the range of 0.05 to 0.075, the low-temperature output characteristics are 1.30 times higher than that of Experimental Example 1, and the high temperature It was found that the durability was 1.70 times or more, and the respective characteristics were remarkably improved. This is because, for example, when equimolar amounts of Fe and Ti are contained, a state close to FeTiO 3 is formed in the structure, which optimizes the arrangement pattern of transition metal ions and shows the effect of improving the interfacial reaction. It was guessed that. When Fe and Ti deviated from the same amount, extra Fe or Ti ions were mixed in the structure, and it was considered that a sufficient performance improvement effect could not be obtained. When the content of Fe and Ti is included in the range of Fe0.05Ti0.05 to Fe0.075Ti0.075, particularly excellent characteristics are exhibited, for example, when the amount of Fe and Ti is small, the interfacial reaction improving effect is not exhibited. It was inferred that when Fe and Ti were present excessively, they acted as a resistance layer and the performance deteriorated.
なお、本発明は上述した実施例に何ら限定されることはなく、本発明の技術的範囲に属する限り種々の態様で実施し得ることはいうまでもない。 In addition, this invention is not limited to the Example mentioned above at all, and as long as it belongs to the technical scope of this invention, it cannot be overemphasized that it can implement with a various aspect.
１０ リチウム二次電池、１１ 集電体、１２ 正極活物質、１３ 正極シート、１４ 集電体、１７ 負極活物質、１８ 負極シート、１９ セパレータ、２０ 非水電解液、２２ 円筒ケース、２４ 正極端子、２６ 負極端子。
DESCRIPTION OF
Claims (9)
負極活物質を含有する負極と、
前記正極と前記負極との間に介在しリチウムイオンを伝導するイオン伝導媒体と、
を備えたリチウム二次電池。 A positive electrode containing the positive electrode active material for a nonaqueous electrolyte secondary battery according to any one of claims 1 to 4,
A negative electrode containing a negative electrode active material;
An ion conductive medium that is interposed between the positive electrode and the negative electrode and conducts lithium ions;
Rechargeable lithium battery.
リチウム元素とニッケル元素とマンガン元素とを含む原料を酸化雰囲気中９００℃以上１１００℃以下の第１温度範囲で焼成する焼成処理を行ったのち、５００℃以上７００℃以下の第２温度範囲まで冷却し該第２温度範囲で５時間以上４０時間以下の時間範囲でアニールするアニール処理を行う焼成アニール工程、を含む、非水電解質二次電池用正極活物質の製造方法。 A method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery, which is a lithium transition metal oxide,
After performing a baking treatment in which a raw material containing lithium element, nickel element and manganese element is baked in an oxidizing atmosphere at a first temperature range of 900 ° C. or higher and 1100 ° C. or lower, it is cooled to a second temperature range of 500 ° C. or higher and 700 ° C. or lower. And a baking annealing step of performing an annealing treatment for annealing in the second temperature range for a time range of 5 hours or more and 40 hours or less, and a method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery.
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