JP2012204281A - Composite metal oxide, positive electrode active material for lithium secondary battery, positive electrode for lithium secondary battery, and lithium secondary battery - Google Patents
Composite metal oxide, positive electrode active material for lithium secondary battery, positive electrode for lithium secondary battery, and lithium secondary battery Download PDFInfo
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Abstract
Description
本発明は、複合金属酸化物、リチウム二次電池用正極活物質、リチウム二次電池用正極、及びリチウム二次電池に関する。 The present invention relates to a composite metal oxide, a positive electrode active material for a lithium secondary battery, a positive electrode for a lithium secondary battery, and a lithium secondary battery.
リチウム二次電池は小型、軽量でありながら高電圧でかつ高エネルギー密度を有し、携帯電話、ノート型パーソナルコンピュータ、デジタルカメラ等の情報、通信機器の端末機等の電源に使用され、急速に需要が拡大している。また、環境や資源問題から電気自動車用の電源としても注目されている。 Lithium rechargeable batteries are small and light but have high voltage and high energy density. They are used for power supplies for mobile phones, notebook personal computers, digital cameras, etc., and terminals for communication devices. Demand is expanding. It is also attracting attention as a power source for electric vehicles due to environmental and resource issues.
リチウム二次電池に用いられる正極活物質として、層状構造のマンガン酸リチウムが知られている。層状構造のマンガン酸リチウムは、その理論放電容量が２８６Ａｈ／ｋｇであり、スピネル構造のマンガン酸リチウムの理論放電容量と比較して大きいため、リチウム二次電池の有効な正極活物質となり得ると考えられていた。 As a positive electrode active material used in a lithium secondary battery, lithium manganate having a layered structure is known. The layered structure lithium manganate has a theoretical discharge capacity of 286 Ah / kg, which is larger than the theoretical discharge capacity of the spinel structure lithium manganate, and is considered to be an effective cathode active material for lithium secondary batteries. It was done.
層状構造のマンガン酸リチウムは、一般的に、その製造自体が困難であるが、製造可能な層状構造のマンガン酸リチウムとして、Ｏ３型層状構造のマンガン酸リチウムが知られている（例えば、特許文献１参照）。 Lithium manganate having a layered structure is generally difficult to produce itself, but lithium manganate having an O3 type layered structure is known as a lithium manganate having a layered structure that can be produced (for example, Patent Documents). 1).
しかし、Ｏ３型層状構造のマンガン酸リチウムから構成される正極活物質を用いたリチウム二次電池を充放電させると、リチウムのマンガン層への混入又はマンガンのリチウム層への混入により、マンガン酸リチウムは、Ｏ３型層状構造からより安定なスピネル構造に転移する。この転移により、リチウム二次電池の放電容量は大きく低下する。 However, when a lithium secondary battery using a positive electrode active material composed of a lithium manganate having an O3 type layered structure is charged / discharged, lithium manganate is mixed due to lithium mixed into the manganese layer or manganese mixed into the lithium layer. Transition from an O3 type layered structure to a more stable spinel structure. This transition greatly reduces the discharge capacity of the lithium secondary battery.
そこで、リチウム二次電池に使用するマンガン酸リチウムとして、Ｏ２型層状構造のマンガン酸リチウムが開示されている（特許文献２）。 Thus, lithium manganate having an O2 type layered structure has been disclosed as lithium manganate used in the lithium secondary battery (Patent Document 2).
特許文献２によれば、Ｏ２型層状構造は非常に安定な構造であり、充放電による構造変化を生じないため、Ｏ２型層状構造を有するマンガン酸リチウムを用いて製造した正極活物質を有するリチウム二次電池は電池性能が高いとされている。
According to
しかし、特許文献２に記載の安定なＯ２型層状構造を有するマンガン酸リチウムを、正極活物質として用いても、安定して高い放電容量を示すリチウム二次電池を得ることは困難である。
However, even when lithium manganate having a
本発明は、以上の課題を解決するためになされたものであり、その目的は、リチウム二次電池の電池性能を向上させる複合金属酸化物、当該複合金属酸化物の製造方法、当該複合金属酸化物から構成される正極活物質、当該正極活物質を備えたリチウム二次電池用正極、及び当該リチウム二次電池用正極を備えたリチウム二次電池を提供することにある。 The present invention has been made in order to solve the above-described problems, and its purpose is to provide a composite metal oxide that improves battery performance of a lithium secondary battery, a method for producing the composite metal oxide, and the composite metal oxide. It is providing the positive electrode active material comprised from the thing, the positive electrode for lithium secondary batteries provided with the said positive electrode active material, and the lithium secondary battery provided with the said positive electrode for lithium secondary batteries.
本発明者らは、上記課題を解決するために鋭意研究を重ねた。その結果、下記式（Ｉ）で表され、Ｏ２構造を有する酸化物から構成される複合金属酸化物を、リチウム二次電池の正極活物質として用いた場合に、リチウム二次電池の電池性能が向上することを見出し、本発明を完成するに至った。より具体的には本発明は以下のものを提供する。 The inventors of the present invention have made extensive studies to solve the above problems. As a result, when a composite metal oxide represented by the following formula (I) and composed of an oxide having an O2 structure is used as a positive electrode active material of a lithium secondary battery, the battery performance of the lithium secondary battery is As a result, the present invention has been completed. More specifically, the present invention provides the following.
（１） 下記式（Ｉ）で表され、Ｏ２構造を有する酸化物から構成される複合金属酸化物。
Ｌｉｘ｛（ＬｉｙＭｎ１−ｙ）ｚＭ１−ｚ｝Ｏ２・・・（Ｉ）
（式（Ｉ）中のｘは２／３を超え１未満であり、ｙは０を超え１／３未満であり、ｚは０．２以上１以下であり、ＭはＭｎ、Ｃｏ及びＮｉからなる群より選択される少なくとも一種である。）
(1) A composite metal oxide represented by the following formula (I) and composed of an oxide having an O2 structure.
Li x {(Li y Mn 1−y ) z M 1−z } O 2 (I)
(X in formula (I) is more than 2/3 and less than 1, y is more than 0 and less than 1/3, z is 0.2 or more and 1 or less, and M is from Mn, Co and Ni. At least one selected from the group consisting of:
（２） 前記ｚは１である（１）に記載の複合金属酸化物。 (2) The composite metal oxide according to (1), wherein z is 1.
（３） （１）又は（２）に記載の複合金属酸化物の製造方法であって、ナトリウム化合物と、マンガン化合物と、リチウム化合物との混合物を焼成して前駆体を製造する前駆体製造工程と、前記前駆体と、リチウムを含有する溶融塩又はリチウム化合物を含有する有機溶媒とを混合し、前記前駆体が含有するナトリウムと、前記溶融塩が含有するリチウムとをイオン交換させるイオン交換工程と、を有する複合金属酸化物の製造方法。 (3) A method for producing a composite metal oxide according to (1) or (2), wherein a precursor is produced by firing a mixture of a sodium compound, a manganese compound and a lithium compound. An ion exchange step of ion-exchange of sodium contained in the precursor and lithium contained in the molten salt by mixing the precursor and a molten salt containing lithium or an organic solvent containing a lithium compound And a method for producing a composite metal oxide.
（４） （１）又は（２）に記載の金属複合酸化物から構成されるリチウム二次電池用正極活物質。 (4) A positive electrode active material for a lithium secondary battery comprising the metal composite oxide according to (1) or (2).
（５） （４）に記載の正極活物質を備えたリチウム二次電池用正極。 (5) A positive electrode for a lithium secondary battery, comprising the positive electrode active material according to (4).
（６） （５）に記載のリチウム二次電池用正極を備えたリチウム二次電池。 (6) A lithium secondary battery comprising the lithium secondary battery positive electrode according to (5).
本発明の複合金属酸化物から構成されるリチウム二次電池用正極活物質を備えたリチウム二次電池は、安定して高い放電容量を示す。 The lithium secondary battery provided with the positive electrode active material for a lithium secondary battery composed of the composite metal oxide of the present invention stably exhibits a high discharge capacity.
以下、本発明の実施形態について詳細に説明する。なお、本発明は以下の実施形態に限定されない。 Hereinafter, embodiments of the present invention will be described in detail. In addition, this invention is not limited to the following embodiment.
＜複合金属酸化物＞
本発明の複合金属酸化物は、下記式（Ｉ）で表される組成を有し、Ｏ２構造を有する酸化物から構成される。ここで、複合金属酸化物が下記式（Ｉ）の組成を有することは、遷移金属層にＬｉが含まれる超格子構造を、複合金属酸化物が有することを意味する。
Ｌｉｘ｛（ＬｉｙＭｎ１−ｙ）ｚＭ１−ｚ｝Ｏ２・・・（Ｉ）
（式（Ｉ）中のｘは２／３を超え１未満であり、ｙは０を超え１／３未満であり、ｚは０．２以上１以下であり、ＭはＭｎ、Ｃｏ及びＮｉからなる群より選択される少なくとも一種である。）
<Composite metal oxide>
The composite metal oxide of the present invention has a composition represented by the following formula (I) and is composed of an oxide having an O2 structure. Here, the composite metal oxide having the composition of the following formula (I) means that the composite metal oxide has a superlattice structure in which Li is contained in the transition metal layer.
Li x {(Li y Mn 1−y ) z M 1−z } O 2 (I)
(X in formula (I) is more than 2/3 and less than 1, y is more than 0 and less than 1/3, z is 0.2 or more and 1 or less, and M is from Mn, Co and Ni. At least one selected from the group consisting of:
本発明の複合金属酸化物をリチウム二次電池の正極活物質に用いると、酸素の脱離を伴う複合金属酸化物の構造変化によって、リチウム二次電池の電池性能が向上する。電池性能を大きく向上させるｘの範囲は０．７以上０．９５以下であり、ｙの範囲は０．１以上０．３以下であり、ｚの範囲は０．２以上０．５以下である。 When the composite metal oxide of the present invention is used for the positive electrode active material of a lithium secondary battery, the battery performance of the lithium secondary battery is improved by the structural change of the composite metal oxide accompanied by the desorption of oxygen. The range of x that greatly improves battery performance is 0.7 or more and 0.95 or less, the range of y is 0.1 or more and 0.3 or less, and the range of z is 0.2 or more and 0.5 or less. .
ここで、ｘ、ｙ、ｚの値は、原料の使用量、製造条件等を調整することで調整することができる。詳細は後述する。 Here, the values of x, y, and z can be adjusted by adjusting the amount of raw material used, manufacturing conditions, and the like. Details will be described later.
複合金属酸化物がＯ２構造を有する酸化物であるか否かは、Ｘ線回析により確認することができる。具体的には実施例に記載の方法で確認することができる。 Whether or not the composite metal oxide is an oxide having an O2 structure can be confirmed by X-ray diffraction. Specifically, it can confirm by the method as described in an Example.
本発明の複合金属酸化物は、Ｏ２構造を有する酸化物から構成されるが、本発明の効果を害さない限り他の成分が含まれていてもよい。 The composite metal oxide of the present invention is composed of an oxide having an O2 structure, but may contain other components as long as the effects of the present invention are not impaired.
また、上記の構造変化後に、Ｏ２構造を有する本発明の複合金属酸化物から構造変化した複合金属酸化物であることを、Ｘ線回析測定を用いて確認することができる。 Moreover, it can confirm using X-ray diffraction measurement that it is the composite metal oxide which changed the structure from the composite metal oxide of this invention which has O2 structure after said structure change.
＜複合金属酸化物の製造方法＞
本発明の複合金属酸化物は、前駆体であるＮａｘ｛（ＬｉｙＭｎ１−ｙ）ｚＭ１−ｚ｝Ｏ２（ｘは２／３を超え１未満であり、ｙは０を超え１／３未満であり、ｚは０．２以上１以下であり、ＭはＭｎ、Ｃｏ及びＮｉからなる群より選択される少なくとも一種である。）に、リチウムを含有する溶融塩中やリチウム化合物を含有する有機溶媒中でイオン交換処理を施すことにより、本発明の複合金属酸化物であるＬｉｘ｛（ＬｉｙＭｎ１−ｙ）ｚＭ１−ｚ｝Ｏ２（ｘは２／３を超え１未満であり、ｙは０を超え１／３未満であり、ｚは０．２以上１以下である）を製造することができる。
<Method for producing composite metal oxide>
Mixed metal oxide of the present invention, Na x {(Li y Mn 1-y) z M 1-z} O 2 (x is the precursor is less than 1 exceed 2/3, y is greater than 0 Less than 1/3, z is 0.2 or more and 1 or less, and M is at least one selected from the group consisting of Mn, Co and Ni.) In a molten salt containing lithium or a lithium compound By performing an ion exchange treatment in an organic solvent containing Li x {(Li y Mn 1-y ) z M 1-z } O 2 (x is 2/3) which is the composite metal oxide of the present invention. And y is greater than 0 and less than 1/3, and z is 0.2 or more and 1 or less.
上記前駆体であるＮａｘ｛（ＬｉｙＭｎ１−ｙ）ｚＭ１−ｚ｝Ｏ２は、ナトリウム化合物、マンガン化合物、リチウム化合物、ニッケル化合物、コバルト化合物を原料として作製される。ｘ、ｙ、ｚは原料の混合比を調整することで、調整することができる。 Na x {(Li y Mn 1-y ) z M 1-z } O 2 as the precursor is produced using a sodium compound, a manganese compound, a lithium compound, a nickel compound, and a cobalt compound as raw materials. x, y, and z can be adjusted by adjusting the mixing ratio of the raw materials.
ナトリウム化合物とは、ナトリウムを含有するものであれば特に制限されず、例えばＮａ２Ｏ、Ｎａ２Ｏ２等の酸化物、Ｎａ２ＣＯ３、ＮａＮＯ３等の塩類、ＮａＯＨ等の水酸化物等である。これらの中でも、特にＮａ２ＣＯ３等が好ましい。なお、ナトリウム化合物は一種を単独で使用してもよく、二種以上を併用してもよい。 The sodium compound is not particularly limited as long as it contains sodium, for example, oxides such as Na 2 O and Na 2 O 2 , salts such as Na 2 CO 3 and NaNO 3 , hydroxides such as NaOH, etc. It is. Among these, Na 2 CO 3 is particularly preferable. In addition, a sodium compound may be used individually by 1 type, and may use 2 or more types together.
マンガン化合物とは、マンガンを含有するものであれば特に制限されず、例えばＭｎ３Ｏ４、Ｍｎ２Ｏ３、ＭｎＯ２等の酸化物、ＭｎＣＯ３、ＭｎＣｌ２等の塩類、Ｍｎ（ＯＨ）２等の水酸化物、ＭｎＯＯＨ等の酸化水酸化物等である。これらの中でも、特にＭｎ２Ｏ３、ＭｎＯ２等が好ましい。なお、マンガン化合物は一種を単独で使用してもよく、二種以上を併用してもよい。 The manganese compound is not particularly limited as long as it contains manganese. For example, oxides such as Mn 3 O 4 , Mn 2 O 3 and MnO 2 , salts such as MnCO 3 and MnCl 2 , Mn (OH) 2 And hydroxides such as MnOOH. Among these, Mn 2 O 3 , MnO 2 and the like are particularly preferable. In addition, a manganese compound may be used individually by 1 type, and may use 2 or more types together.
リチウム化合物とは、リチウムを含有するものであれば特に制限されず、例えば、リチウム化合物としては、Ｌｉ２ＣＯ３、ＬｉＮＯ３、ＬｉＮＯ２、ＬｉＯＨ、ＬｉＯＨ・Ｈ２Ｏ、ＬｉＨ、ＬｉＦ、ＬｉＣｌ、ＬｉＢｒ、ＬｉＩ、ＣＨ３ＯＯＬｉ、Ｌｉ２Ｏ、Ｌｉ２ＳＯ４、ジカルボン酸Ｌｉ、クエン酸Ｌｉ、脂肪酸Ｌｉ、アルキルリチウム等が挙げられる。これらの中でもＬｉ２ＣＯ３の使用が好ましい。なお、リチウム化合物は一種を単独で使用してもよく、二種以上を併用してもよい。 The lithium compound is not particularly limited as long as it contains lithium. For example, as the lithium compound, Li 2 CO 3 , LiNO 3 , LiNO 2 , LiOH, LiOH · H 2 O, LiH, LiF, LiCl, Examples include LiBr, LiI, CH 3 OOLi, Li 2 O, Li 2 SO 4 , dicarboxylic acid Li, citric acid Li, fatty acid Li, and alkyl lithium. Among these, the use of Li 2 CO 3 is preferable. In addition, a lithium compound may be used individually by 1 type, and may use 2 or more types together.
ニッケル化合物とは、ニッケルを含有するものであれば特に制限されず、例えば、Ｎｉ（ＯＨ）２、ＮｉＯ、ＮｉＯＯＨ、ＮｉＣＯ３、２ＮｉＣＯ３・３Ｎｉ（ＯＨ）２・４Ｈ２Ｏ、ＮｉＣ２Ｏ４・２Ｈ２Ｏ、Ｎｉ（ＮＯ３）２・６Ｈ２Ｏ、ＮｉＳＯ４、ＮｉＳＯ４・６Ｈ２Ｏ、脂肪酸ニッケル、ニッケルハロゲン化物等である。なお、ニッケル化合物は一種を単独で使用してもよく、二種以上を併用してもよい。 The nickel compound is not particularly limited as long as it contains nickel. For example, Ni (OH) 2 , NiO, NiOOH, NiCO 3 , 2NiCO 3 .3Ni (OH) 2 .4H 2 O, NiC 2 O 4 2H 2 O, Ni (NO 3 ) 2 .6H 2 O, NiSO 4 , NiSO 4 .6H 2 O, fatty acid nickel, nickel halide and the like. In addition, a nickel compound may be used individually by 1 type, and may use 2 or more types together.
コバルト化合物とは、コバルトを含有するものであれば特に制限されず、例えば、Ｃｏ（ＯＨ）２、ＣｏＯＯＨ、ＣｏＯ、Ｃｏ２Ｏ３、Ｃｏ３Ｏ４、Ｃｏ（ＯＣＯＣＨ３）２・４Ｈ２Ｏ、ＣｏＣｌ２、Ｃｏ（ＮＯ３）２・６Ｈ２Ｏ、Ｃｏ（ＳＯ４）２・７Ｈ２Ｏ、ＣｏＣＯ３等である。なお、コバルト化合物は一種を単独で使用してもよく、二種以上を併用してもよい。 The cobalt compound is not particularly limited as long as it contains cobalt. For example, Co (OH) 2 , CoOOH, CoO, Co 2 O 3 , Co 3 O 4 , Co (OCOCH 3 ) 2 .4H 2 O , CoCl 2 , Co (NO 3 ) 2 .6H 2 O, Co (SO 4 ) 2 .7H 2 O, CoCO 3, and the like. In addition, a cobalt compound may be used individually by 1 type, and may use 2 or more types together.
上記原料を含む混合物を調製する。ナトリウム化合物、リチウム化合物、マンガン化合物及びＭを含む化合物の混合割合は、モル比で、Ｎａが０．６〜０．９、Ｌｉが０．１〜０．３、Ｍｎが０．７〜０．９、Ｍが０．２〜０．９になるように混合割合を調整することが好ましい。 A mixture containing the raw materials is prepared. The mixing ratio of the sodium compound, the lithium compound, the manganese compound and the compound containing M is a molar ratio of Na of 0.6 to 0.9, Li of 0.1 to 0.3, and Mn of 0.7 to 0.00. 9. It is preferable to adjust the mixing ratio so that M is 0.2 to 0.9.
また、原料の混合方法は、これらを均一に混合できる限り特に限定されず、例えばミキサー等の公知の混合機を用いて、湿式又は乾式で混合すれば良い。また、マンガン、ニッケル、コバルト等の複合水酸化物、炭酸塩も利用可能である。 Moreover, the mixing method of a raw material is not specifically limited as long as these can be mixed uniformly, For example, what is necessary is just to mix by a wet or dry type using well-known mixers, such as a mixer. In addition, composite hydroxides such as manganese, nickel and cobalt, and carbonates can also be used.
次いで、混合物を焼成する。焼成温度は、混合物の組成等に応じて適宜設定することができるが、通常は６５０〜１１００℃程度、好ましくは７５０〜９５０℃とすればよい。また、焼成雰囲気も特に限定的ではないが、通常は酸化性雰囲気又は大気中で実施すれば良い。焼成時間は、焼成温度等に応じて適宜変更することができる。 The mixture is then fired. The firing temperature can be appropriately set according to the composition of the mixture, but is usually about 650 to 1100 ° C., preferably 750 to 950 ° C. Also, the firing atmosphere is not particularly limited, but usually it may be carried out in an oxidizing atmosphere or air. The firing time can be appropriately changed according to the firing temperature and the like.
次いで、焼成物を冷却する。冷却方法は特に限定されないが、通常は自然放冷（炉内放冷）又は徐冷すれば良い。 Next, the fired product is cooled. The cooling method is not particularly limited, but it may be naturally cooled (cooled in the furnace) or gradually cooled.
必要に応じて焼成物を公知の方法で粉砕し、さらに上記の焼成工程を実施しても良い。すなわち、上記混合物の焼成、徐冷及び粉砕を２回以上繰り返して実施してもよい。なお、粉砕の程度は、焼成温度等に応じて適宜調節すればよい。 If necessary, the fired product may be pulverized by a known method, and the firing process described above may be performed. That is, the above mixture may be fired, slowly cooled and pulverized twice or more. Note that the degree of pulverization may be adjusted as appropriate according to the firing temperature and the like.
上記の工程により、目的とする前駆体であるＮａｘ｛（ＬｉｙＭｎ１−ｙ）ｚＭ１−ｚ｝Ｏ２で表される結晶材料を得ることができる。 Through the above steps, a crystal material represented by Na x {(Li y Mn 1-y ) z M 1-z } O 2 which is a target precursor can be obtained.
上記前駆体を粉砕し、粉砕された前駆体を、リチウムを含む溶融塩又はリチウム化合物を含む有機溶媒に分散させながらイオン交換処理を施す。 The precursor is pulverized, and the pulverized precursor is subjected to an ion exchange treatment while being dispersed in a molten salt containing lithium or an organic solvent containing a lithium compound.
リチウムを含む溶融塩としては、硝酸リチウム、塩化リチウム、臭化リチウム、ヨウ化リチウム等の低温で溶融する塩類を用いることができる。また、溶融塩には２種以上の塩類が含まれていてもよい。 As the molten salt containing lithium, salts that melt at a low temperature such as lithium nitrate, lithium chloride, lithium bromide, and lithium iodide can be used. The molten salt may contain two or more kinds of salts.
また、リチウム化合物としては、リチウムの炭酸塩、リチウムの酢酸塩、リチウムの硝酸塩、リチウムのシュウ酸塩、リチウムのハロゲン化物、ブチルリチウム等を単独又は必要に応じて２種以上を組み合わせて使用することができる。また、有機溶媒としては、ヘキサノール、エトキシエタノール等の高級アルコール、ジエチレングルコールモノエチルエーテル等のエーテル、もしくは沸点が１４０℃以上の有機溶剤が、作業性が良好である点で好ましい。これらは単独又は必要に応じて２種以上組み合わせて用いられる。 Further, as the lithium compound, lithium carbonate, lithium acetate, lithium nitrate, lithium oxalate, lithium halide, butyllithium, etc. are used alone or in combination of two or more as required. be able to. As the organic solvent, higher alcohols such as hexanol and ethoxyethanol, ethers such as diethylene glycol monoethyl ether, or organic solvents having a boiling point of 140 ° C. or higher are preferable from the viewpoint of good workability. These may be used alone or in combination of two or more as required.
また、前駆体と溶融塩又は有機溶媒との混合比は、特に限定されないが、リチウムとナトリウムのモル比（リチウムのモル数／ナトリウムのモル数）が０．０２以上０．５以下であることが好ましい。 Further, the mixing ratio of the precursor and the molten salt or the organic solvent is not particularly limited, but the molar ratio of lithium to sodium (number of moles of lithium / number of moles of sodium) is 0.02 or more and 0.5 or less. Is preferred.
イオン交換処理の処理温度は、特に限定されないが、０℃以上３００℃以下が好ましい。イオン交換処理の処理温度が２００℃以上の場合は、前駆体中のほぼ全てのナトリウムがリチウムに交換される。一方、イオン交換処理の処理温度が３００℃以下の場合には不可逆な相変化を起こさないという理由で好ましい。 The treatment temperature of the ion exchange treatment is not particularly limited, but is preferably 0 ° C. or higher and 300 ° C. or lower. When the ion exchange treatment temperature is 200 ° C. or higher, almost all sodium in the precursor is exchanged for lithium. On the other hand, when the ion exchange treatment temperature is 300 ° C. or lower, it is preferable because an irreversible phase change does not occur.
イオン交換処理の処理時間は、特に限定されないが１時間以上４８時間以下が好ましい。処理時間が６時間以上であればイオン交換が十分に進行するという理由で好ましく、処理時間が４８時間以下であれば不可逆な相変化を起こさないという理由で好ましい。 The treatment time for the ion exchange treatment is not particularly limited, but is preferably 1 hour or more and 48 hours or less. A treatment time of 6 hours or longer is preferred for the reason that ion exchange proceeds sufficiently, and a treatment time of 48 hours or shorter is preferred for not causing irreversible phase changes.
上記のイオン交換処理後、得られた生成物を、蒸留水でよく洗浄した後、メタノール、エタノールで洗浄後、乾燥させることによって、目的とするＬｉｘ｛（ＬｉｙＭｎ１−ｙ）ｚＭ１−ｚ｝Ｏ２（式（Ｉ）中のｘは２／３を超え１未満であり、ｙは０を超え１／３未満であり、ｚは０．２以上１以下であり、ＭはＭｎ、Ｃｏ及びＮｉからなる群より選択される少なくとも一種である。）が得られる。ここで、洗浄方法、乾燥方法については、特に制限されず、通常の方法が用いられる。 After the above-described ion exchange treatment, the obtained product is thoroughly washed with distilled water, then washed with methanol and ethanol, and then dried to obtain the target Li x {(Li y Mn 1-y ) z M 1-z } O 2 (x in formula (I) is more than 2/3 and less than 1, y is more than 0 and less than 1/3, z is 0.2 or more and 1 or less, and M is At least one selected from the group consisting of Mn, Co and Ni). Here, the washing method and the drying method are not particularly limited, and ordinary methods are used.
＜リチウム二次電池＞
本発明のリチウム二次電池は、上記複合金属酸化物から構成される正極活物質を有する正極と、リチウムイオンを吸蔵及び脱離することができる負極と、電解質とを備える。
<Lithium secondary battery>
The lithium secondary battery of this invention is equipped with the positive electrode which has the positive electrode active material comprised from the said composite metal oxide, the negative electrode which can occlude and desorb lithium ion, and an electrolyte.
［正極］
正極は集電体と、その集電体の表面に形成された正極活物質層とを有し、正極活物質層は、正極活物質、結着剤を有する。
[Positive electrode]
The positive electrode has a current collector and a positive electrode active material layer formed on the surface of the current collector, and the positive electrode active material layer has a positive electrode active material and a binder.
正極活物質層中の正極活物質の含有量は特に限定されないが、７０質量％以上９７質量％以下であることが好ましい。 Although content of the positive electrode active material in a positive electrode active material layer is not specifically limited, It is preferable that it is 70 to 97 mass%.
本発明に使用可能な結着剤としては、ポリフッ化ビニリデン（以下、ＰＶＤＦということがある。）、ポリテトラフルオロエチレン（以下、ＰＴＦＥということがある。）、四フッ化エチレン・六フッ化プロピレン・フッ化ビニリデン系共重合体、六フッ化プロピレン・フッ化ビニリデン系共重合体、四フッ化エチレン・パーフルオロビニルエーテル系共重合体等が挙げられる。これらをそれぞれ単独で用いてもよいし、二種以上を混合して用いてもよい。結着剤のその他の例示としては、例えば、デンプン、メチルセルロース、カルボキシメチルセルロース、ヒドロキシメチルセルロース、ヒドロキシエチルセルロース、ヒドロキシプロピルセルロース、カルボキシメチルヒドロキシエチルセルロース、ニトロセルロース等の多糖類及びその誘導体等が挙げられる。また、使用可能な結着剤として、無機の微粒子、例えばコロイダルシリカ等を挙げることもできる。正極活物質層中の結着剤の含有量は特に限定されないが、２質量％以上２０質量％以下であることが好ましい。 Examples of the binder usable in the present invention include polyvinylidene fluoride (hereinafter sometimes referred to as PVDF), polytetrafluoroethylene (hereinafter sometimes referred to as PTFE), tetrafluoroethylene and hexafluoropropylene. -Vinylidene fluoride copolymers, propylene hexafluoride / vinylidene fluoride copolymers, ethylene tetrafluoride / perfluorovinyl ether copolymers and the like. These may be used alone or in combination of two or more. Other examples of the binder include, for example, polysaccharides such as starch, methylcellulose, carboxymethylcellulose, hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, carboxymethylhydroxyethylcellulose, nitrocellulose, and derivatives thereof. Examples of usable binders include inorganic fine particles such as colloidal silica. Although content of the binder in a positive electrode active material layer is not specifically limited, It is preferable that they are 2 mass% or more and 20 mass% or less.
正極活物質層は、上記の正極活物質、結着剤以外の他の成分を含んでもよい。好ましい他の成分としては、導電材を挙げることができる。導電材としては、天然黒鉛、人造黒鉛、コークス類、カーボンブラック等の炭素材料等が挙げられる。また、導電材は電子伝導材料であれば特に限定されず、導電性繊維類、金属粉末類、導電性ウィスカー類、導電性金属酸化物等を使用してもよい。正極活物質層中の導電材の含有量は特に限定されないが、１質量％以上２０質量％以下であることが好ましい。 The positive electrode active material layer may contain components other than the positive electrode active material and the binder. Preferred other components include a conductive material. Examples of the conductive material include carbon materials such as natural graphite, artificial graphite, cokes, and carbon black. The conductive material is not particularly limited as long as it is an electron conductive material, and conductive fibers, metal powders, conductive whiskers, conductive metal oxides, and the like may be used. Although content of the electrically conductive material in a positive electrode active material layer is not specifically limited, It is preferable that they are 1 mass% or more and 20 mass% or less.
本発明に使用可能な集電体としては、ニッケル、アルミニウム、ステンレス（ＳＵＳ）等の導電性の材料を用いた箔、メッシュ、エキスパンドグリッド（エキスパンドメタル）、パンチドメタル等が挙げられる。メッシュの目開き、線径、メッシュ数等は、特に限定されず従来公知のものを使用できる。集電体の一般的な厚さは、１０μｍ以上４０μｍ以下である。ただし、この範囲を外れる厚さの集電体を用いてもよい。 Examples of the current collector that can be used in the present invention include foil, mesh, expanded grid (expanded metal), punched metal, and the like using a conductive material such as nickel, aluminum, and stainless steel (SUS). The mesh opening, wire diameter, number of meshes and the like are not particularly limited, and conventionally known ones can be used. The general thickness of the current collector is 10 μm or more and 40 μm or less. However, a current collector having a thickness outside this range may be used.
集電体の大きさは、電池の使用用途に応じて決定される。大型の電池に用いられる大型の電極を作製するのであれば、面積の大きな集電体が用いられる。小型の電極を作製するのであれば、面積の小さな集電体が用いられる。 The size of the current collector is determined according to the intended use of the battery. If a large electrode used for a large battery is manufactured, a current collector having a large area is used. If a small electrode is produced, a current collector with a small area is used.
正極を製造する方法としては、先ず、正極活物質層に含まれる成分と有機溶媒とを混合させて正極活物質スラリーを調製する。ここで、使用可能な有機溶媒としては、Ｎ，Ｎ−ジメチルアミノプロピリアミン、ジエチルトリアミン等のアミン系；エチレンオキシド、テトラヒドロフラン等のエーテル系；メチルエチルケトン等のケトン系；酢酸メチル等のエステル系；ジメチルアセトアミド、Ｎ−メチル−２−ピロリドン等の非プロトン性極性溶媒等が挙げられる。 As a method for producing the positive electrode, first, a component contained in the positive electrode active material layer and an organic solvent are mixed to prepare a positive electrode active material slurry. Here, usable organic solvents include amines such as N, N-dimethylaminopropylamine and diethyltriamine; ethers such as ethylene oxide and tetrahydrofuran; ketones such as methyl ethyl ketone; esters such as methyl acetate; dimethyl Examples include aprotic polar solvents such as acetamide and N-methyl-2-pyrrolidone.
次いで、上記正極活物質スラリーを正極集電体上に塗工し、乾燥後プレスする等して固着する。ここで、正極活物質スラリーを正極集電体上に塗工する方法としては、例えばスリットダイ塗工法、スクリーン塗工法、カーテン塗工法、ナイフ塗工法、グラビア塗工法、静電スプレー法等を挙げることができる。 Next, the positive electrode active material slurry is applied onto the positive electrode current collector, and dried and pressed to fix it. Here, examples of the method for coating the positive electrode active material slurry on the positive electrode current collector include a slit die coating method, a screen coating method, a curtain coating method, a knife coating method, a gravure coating method, and an electrostatic spray method. be able to.
なお、正極活物質層を、正極集電体上に形成する方法としては、上記の方法以外に、正極活物質層に含まれる成分の混合物を正極集電体上に設置し、加圧成型する方法でもよい。 As a method for forming the positive electrode active material layer on the positive electrode current collector, in addition to the above method, a mixture of components contained in the positive electrode active material layer is placed on the positive electrode current collector and pressure-molded. The method may be used.
［負極］
負極は集電体と、その集電体の表面に形成された負極活物質層とを有し、負極活物質層は負極活物質及び結着剤を有する。また、負極として、リチウム金属又はリチウム合金等のリチウムイオンを吸蔵・脱離可能な金属又は合金を使用してもよい。
[Negative electrode]
The negative electrode has a current collector and a negative electrode active material layer formed on the surface of the current collector, and the negative electrode active material layer has a negative electrode active material and a binder. Moreover, you may use the metal or alloy which can occlude / desorb lithium ions, such as lithium metal or a lithium alloy, as a negative electrode.
負極活物質としては、例えば、ナトリウムイオンを吸蔵・脱離することのできる天然黒鉛、人造黒鉛、コークス類、ハードカーボン、カーボンブラック、熱分解炭素類、炭素繊維、有機高分子化合物焼成体等の炭素材料が挙げられる。炭素材料の形状としては、例えば天然黒鉛のような薄片状、メソカーボンマイクロビーズのような球状、黒鉛化炭素繊維のような繊維状、又は微粉末の凝集体等のいずれでもよい。ここで、炭素材料は、導電材としての役割を果たす場合もある。 Examples of the negative electrode active material include natural graphite capable of inserting and extracting sodium ions, artificial graphite, cokes, hard carbon, carbon black, pyrolytic carbons, carbon fibers, and fired organic polymer compounds. Examples thereof include carbon materials. The shape of the carbon material may be any of a flake shape such as natural graphite, a spherical shape such as mesocarbon microbeads, a fibrous shape such as graphitized carbon fiber, or an aggregate of fine powder. Here, the carbon material may play a role as a conductive material.
負極活物質層中の負極活物質の含有量は特に限定されないが、７０質量％以上９７質量％以下であることが好ましい。 Although content of the negative electrode active material in a negative electrode active material layer is not specifically limited, It is preferable that it is 70 to 97 mass%.
結着剤としては、正極に使用可能なものと同様のものが使用可能であるため、これらについては説明を省略する。また、負極活物質層には、負極活物質、結着剤以外の成分が含まれていてもよい。好ましい他の成分としては、正極活物質層と同様に導電材を挙げることができる。 As the binder, the same binders that can be used for the positive electrode can be used, and thus the description thereof will be omitted. In addition, the negative electrode active material layer may contain components other than the negative electrode active material and the binder. As other preferable components, a conductive material can be used as in the positive electrode active material layer.
集電体としては、ニッケル、銅、ステンレス（ＳＵＳ）等の導電性の材料を用いる。集電体は正極用の集電体と同様に、箔、メッシュ、エキスパンドグリッド（エキスパンドメタル）、パンチドメタル等から構成される。 As the current collector, a conductive material such as nickel, copper, and stainless steel (SUS) is used. The current collector is composed of a foil, a mesh, an expanded grid (expanded metal), a punched metal, and the like, like the current collector for the positive electrode.
また、負極活物質層を集電体上に形成する方法としては、正極活物質層を集電体上に形成する方法と同様の方法を採用することができる。 As a method for forming the negative electrode active material layer on the current collector, a method similar to the method for forming the positive electrode active material layer on the current collector can be employed.
［電解質］
電解質は、非水電解質とリチウム塩とから構成される。非水電解質としては、非水電解液、有機固体電解質、無機固体電解質が用いられる。非水電解液としては、非プロトン性有機溶媒を使用することができる。また、複数種類の非プロトン性有機溶媒を併用してもよい。
[Electrolytes]
The electrolyte is composed of a non-aqueous electrolyte and a lithium salt. As the non-aqueous electrolyte, a non-aqueous electrolyte, an organic solid electrolyte, or an inorganic solid electrolyte is used. An aprotic organic solvent can be used as the non-aqueous electrolyte. A plurality of types of aprotic organic solvents may be used in combination.
有機固体電解質としては、イオン性解離基を含むポリマー、イオン性解離基を含むポリマーと上記非水電解液の混合物等が挙げられる。 Examples of the organic solid electrolyte include a polymer containing an ionic dissociation group, a mixture of a polymer containing an ionic dissociation group and the nonaqueous electrolytic solution, and the like.
無機固体電解質としては、Ｌｉの窒化物、ハロゲン化物、酸素酸塩、硫化物等を用いることができる。 As the inorganic solid electrolyte, a nitride, halide, oxyacid salt, sulfide, or the like of Li can be used.
リチウム塩としては、上記非水電解質に溶解するものが用いられ、例えば、ＬｉＣｌ、ＬｉＢｒ、ＬｉＩ、ＬｉＣｌＯ４、ＬｉＢＦ４、ＬｉＢ１０Ｃｌ１０、ＬｉＰＦ６、ＬｉＣＦ３ＳＯ３、ＬｉＣＦ３ＣＯ２、ＬｉＡｓＦ６、ＬｉＳｂＦ６、ＬｉＢ１０Ｃｌ１０、ＬｉＡｌＣｌ４、ＣＨ３ＳＯ３Ｌｉ、ＣＦ３ＳＯ３Ｌｉ、（ＣＦ３ＳＯ２）２ＮＬｉ、クロロボランリチウム、低級脂肪族カルボン酸リチウム、四フェニルホウ酸リチウム、イミド類等の１種又は２種以上を混合した塩が挙げられる。 As the lithium salt, those dissolved in the non-aqueous electrolyte are used. For example, LiCl, LiBr, LiI, LiClO 4 , LiBF 4 , LiB 10 Cl 10 , LiPF 6 , LiCF 3 SO 3 , LiCF 3 CO 2 , LiAsF 6 , LiSbF 6 , LiB 10 Cl 10 , LiAlCl 4 , CH 3 SO 3 Li, CF 3 SO 3 Li, (CF 3 SO 2 ) 2 NLi, lithium chloroborane, lithium lower aliphatic carboxylate, lithium tetraphenylborate, Examples thereof include a salt obtained by mixing one or more imides.
また、非水電解質には、放電、充電特性、難燃性を改良する目的で、添加物を配合してもよい。 Moreover, you may mix | blend an additive with a nonaqueous electrolyte in order to improve discharge, a charge characteristic, and a flame retardance.
本発明に係るリチウム二次電池は、電池性能、特にサイクル特性に優れたリチウム二次電池であり、電池の形状はボタン、シート、シリンダー、角、コイン型等いずれの形状であってもよい。 The lithium secondary battery according to the present invention is a lithium secondary battery excellent in battery performance, particularly in cycle characteristics, and the shape of the battery may be any shape such as a button, a sheet, a cylinder, a corner, or a coin type.
＜実施例１＞
炭酸ナトリウム（Ｎａ２ＣＯ３：和光純薬工業株式会社製：純度９９．８％）、酸化マンガン（ＩＶ）（ＭｎＯ２：株式会社高純度化学研究所製：純度９９．９％）、及び炭酸リチウム（Ｌｉ２ＣＯ３：関東化学株式会社製：純度９９．０％）を、Ｎａ：Ｍｎ：Ｌｉのモル比が５／６：７／９：２／９となるように秤量し、メノウ乳鉢で０．５時間にわたって混合して金属含有化合物の混合物を得た。得られた混合物を、アルミナボートに充填し、電気炉を用いて空気雰囲気において７００℃で１２時間の条件で焼成した。焼成物を冷却することで前駆体であるＮａ５／６（Ｌｉ２／９Ｍｎ７／９）Ｏ２を得た。
<Example 1>
Sodium carbonate (Na 2 CO 3 : manufactured by Wako Pure Chemical Industries, Ltd .: purity 99.8%), manganese (IV) oxide (MnO 2 : manufactured by Kojundo Chemical Laboratory Co., Ltd .: purity 99.9%), and carbonic acid Lithium (Li 2 CO 3 : manufactured by Kanto Chemical Co., Inc .: purity 99.0%) was weighed so that the molar ratio of Na: Mn: Li was 5/6: 7/9: 2/9, and an agate mortar For 0.5 hour to obtain a mixture of metal-containing compounds. The obtained mixture was filled in an alumina boat and baked in an air atmosphere at 700 ° C. for 12 hours using an electric furnace. By cooling the fired product, Na 5/6 (Li 2/9 Mn 7/9 ) O 2 as a precursor was obtained.
上記前駆体と溶融塩（硝酸リチウム（８８％）及び塩化リチウム（１２％）の混合物）とを、１：３０（質量比）で混合し、処理温度２８０℃、処理時間２時間の条件でイオン交換処理を行い、得られた固体を蒸留水、アセトンで洗浄することで、本発明の複合金属酸化物を得た。 The above precursor and molten salt (mixture of lithium nitrate (88%) and lithium chloride (12%)) were mixed at 1:30 (mass ratio) and ionized under the conditions of a processing temperature of 280 ° C. and a processing time of 2 hours. The composite metal oxide of the present invention was obtained by performing an exchange treatment and washing the resulting solid with distilled water and acetone.
上記実施例１の複合金属酸化物からなる正極活物質、導電材としてのアセチレンブラック、及び結着剤としてのポリビリニデンフルオライドを、正極活物質：導電材：結着剤＝８：１：１（質量比）の組成となるようにそれぞれ秤量した。その後、先ず、正極活物質と導電材をメノウ乳鉢で十分に混合し、この混合物に、Ｎ−メチルピロリドンを加えて引き続き均一になるように混合し、混合物をスラリー化した。次いで、得られた正極活物質スラリーを、集電体である厚さ２０μｍのアルミ箔上に、アプリケータを用いて８０μｍの厚さで塗布し、これを乾燥機に入れ、Ｎ−メチルピロリドンを除去させながら、十分に乾燥することによって電極シートを得た。この電極シートを電極打ち抜き機で直径１．０ｃｍに打ち抜いた後、ハンドプレスにて十分に圧着し、正極を得た。 A positive electrode active material composed of the composite metal oxide of Example 1 above, acetylene black as a conductive material, and polybilinidene fluoride as a binder were used as positive electrode active material: conductive material: binder = 8: 1. : 1 (mass ratio), each was weighed. Then, first, the positive electrode active material and the conductive material were sufficiently mixed in an agate mortar, and N-methylpyrrolidone was added to the mixture, and the mixture was then mixed uniformly to make a slurry. Next, the obtained positive electrode active material slurry was applied to an aluminum foil having a thickness of 20 μm, which is a current collector, with a thickness of 80 μm using an applicator. While being removed, the electrode sheet was obtained by sufficiently drying. This electrode sheet was punched out to a diameter of 1.0 cm with an electrode punching machine, and then sufficiently pressed with a hand press to obtain a positive electrode.
負極として、直径１０ｍｍ×厚み１ｍｍの金属リチウム箔を用いた。 As the negative electrode, a metal lithium foil having a diameter of 10 mm and a thickness of 1 mm was used.
作用極に上記の負極を、対極に正極を使用して、実施例１のコイン型リチウム二次電池（以下、単に「実施例１のリチウム二次電池」という場合がある。）を作製した。電解液としては、１Ｍの電解質塩（ＬｉＰＦ６）を非水溶媒（エチレンカーボネート：ジメチルカーボネート＝１：１）に溶解させたものを用いた。また、リチウム二次電池の作製はアルゴンを満たしたグローブボックス中にて行った。 Using the negative electrode as a working electrode and the positive electrode as a counter electrode, a coin-type lithium secondary battery of Example 1 (hereinafter sometimes simply referred to as “lithium secondary battery of Example 1”) was produced. As the electrolytic solution, a 1M electrolyte salt (LiPF 6 ) dissolved in a non-aqueous solvent (ethylene carbonate: dimethyl carbonate = 1: 1) was used. The lithium secondary battery was produced in a glove box filled with argon.
＜比較例１＞
Ｎａｘ｛（ＬｉｙＭｎ１−ｙ）ｚＭ１−ｚ｝Ｏ２で記述される組成としてｘの値が１に近くｙの値が０．２以下の場合でＯ３構造が安定相となる。また焼成温度が６００℃以下の場合も同様である。またｘの値が０．６の場合、ｙ＝０．２の組成において、Ｐ３構造が安定相となる。
<Comparative Example 1>
The composition described by Na x {(Li y Mn 1−y ) z M 1−z } O 2 has a stable phase when the value of x is close to 1 and the value of y is 0.2 or less. . The same applies when the firing temperature is 600 ° C. or lower. When the value of x is 0.6, the P3 structure becomes a stable phase in the composition of y = 0.2.
＜評価１＞
実施例１の複合金属酸化物、実施例１の複合金属酸化物を製造するための前駆体について、粉末Ｘ線回折測定を行った。測定は、リガク製の粉末Ｘ線回折測定装置ＭｕｌｔｉＦｌｅｘを用いて、以下の条件で行った。測定結果を図１に示した。
Ｘ線：ＣｕＫα
電圧−電流：３０ｋＶ−２０ｍＡ
測定角度範囲：２θ＝１０〜７０°
ステップ：０．０１°
スキャンスピード：１°／分
<
The composite metal oxide of Example 1 and the precursor for producing the composite metal oxide of Example 1 were subjected to powder X-ray diffraction measurement. The measurement was performed under the following conditions using a Rigaku powder X-ray diffraction measurement device MultiFlex. The measurement results are shown in FIG.
X-ray: CuKα
Voltage-current: 30kV-20mA
Measurement angle range: 2θ = 10 to 70 °
Step: 0.01 °
Scan speed: 1 ° / min
図１より、２θ＝２１度の位置に超格子回折線のピークが確認できることから、マンガン層にリチウムが混入しており、マンガン層におけるマンガンとリチウムとのモル比が２：７（Ｌｉ：Ｍｎ）であるＰ２構造を有することが確認された。 From FIG. 1, since the peak of the superlattice diffraction line can be confirmed at a position of 2θ = 21 degrees, lithium is mixed in the manganese layer, and the molar ratio of manganese to lithium in the manganese layer is 2: 7 (Li: Mn ) Was confirmed to have a P2 structure.
図１より、２θ＝３８度の位置に（０１１）回折線のピークが確認できることから、実施例１の複合金属酸化物がＯ２型構造であることが確認された。
From FIG. 1, since the peak of the (011) diffraction line can be confirmed at a position of 2θ = 38 degrees, it was confirmed that the composite metal oxide of Example 1 has an
図１より、前駆体の測定結果と複合金属酸化物の測定結果との比較から、Ｐ２構造がＯ２構造へと相変化しているという理由で、前駆体のナトリウムがリチウムに交換されていることが確認された。 From the comparison of the measurement results of the precursor and the measurement results of the composite metal oxide, it can be seen from FIG. 1 that the sodium of the precursor is replaced with lithium because the P2 structure has changed to the O2 structure. Was confirmed.
＜評価２＞
実施例１のリチウム二次電池の充放電評価を行った。各電極に対して電流密度が１５ｍＡ／ｇの電流になるように設定し、４．８Ｖ（充電電圧）まで定電流充電を行った。充電後、各電極に対して電流密度が１５ｍＡ／ｇの電流になるように設定し、２．０Ｖ（放電電圧）まで定電流放電を行った。この充放電を１９サイクル行い、サイクル数と放電容量との関係を図２（ａ）に示した。なお、評価１の充放電は、温度２５℃の条件下で行った。
<
The charge / discharge evaluation of the lithium secondary battery of Example 1 was performed. The current density was set to 15 mA / g for each electrode, and constant current charging was performed up to 4.8 V (charging voltage). After charging, each electrode was set to have a current density of 15 mA / g, and constant current discharge was performed up to 2.0 V (discharge voltage). This charge / discharge was performed 19 cycles, and the relationship between the number of cycles and the discharge capacity is shown in FIG. The charge / discharge of
充電電圧を４．４Ｖに変更した以外は、上記と同様の方法で、実施例１のリチウム二次電池の充放電評価を行った。サイクル数と充放電容量との関係を図２（ｂ）に示した。 The charge / discharge evaluation of the lithium secondary battery of Example 1 was performed in the same manner as described above except that the charge voltage was changed to 4.4V. The relationship between the number of cycles and the charge / discharge capacity is shown in FIG.
図２（ａ）、（ｂ）の結果から、充電電圧が４．８Ｖの場合には、１６０〜２００ｍＡｈ／ｇ程度の高い放電容量を、２０サイクル以上維持できることが確認された。一方、充電電圧が４．４Ｖの場合には、サイクル安定性を有するものの、８０ｍＡｈ／ｇ程度の放電容量であることが確認された。 From the results shown in FIGS. 2A and 2B, it was confirmed that a high discharge capacity of about 160 to 200 mAh / g can be maintained for 20 cycles or more when the charging voltage is 4.8V. On the other hand, when the charging voltage is 4.4 V, it has been confirmed that although it has cycle stability, it has a discharge capacity of about 80 mAh / g.
＜評価３＞
上記の充放電評価を微分容量曲線から評価した。先ず、評価２における充電電圧４．８Ｖの条件の充放電曲線から、１サイクル目、２サイクル目、５サイクル目及び１０サイクル目の微分容量曲線を求めた。これらの微分容量曲線を図３に示した。
<
The above charge / discharge evaluation was evaluated from the differential capacity curve. First, differential charge curves for the first cycle, the second cycle, the fifth cycle, and the 10th cycle were obtained from the charge / discharge curve under the condition of the charging voltage of 4.8 V in
図３から、１サイクル目の微分容量曲線の４．５Ｖ付近で、放電容量が非常に大きくなることが確認された。この４．５Ｖ付近の挙動から、複合金属酸化物の構造変化が生じていると考えられる。また、２サイクル目以降で３．０Ｖ付近、４．０Ｖ付近に新たな放電容量が観測された。この放電容量は、構造変化によって生じたものと考えられる。 From FIG. 3, it was confirmed that the discharge capacity becomes very large around 4.5 V of the differential capacity curve at the first cycle. From the behavior around 4.5 V, it is considered that the structural change of the composite metal oxide occurs. In addition, a new discharge capacity was observed near 3.0V and 4.0V after the second cycle. This discharge capacity is considered to be caused by the structural change.
＜評価４＞
上記の微分容量曲線から確認された複合金属酸化物の構造変化をＸ線光電子分光法という方法で評価した。評価結果から酸素の還元生成物が確認されたことから、上記の構造変化は、複合金属酸化物から酸素が脱離する構造変化であることが確認された。
<
The structural change of the composite metal oxide confirmed from the differential capacity curve was evaluated by a method called X-ray photoelectron spectroscopy. Since the reduction product of oxygen was confirmed from the evaluation results, it was confirmed that the above structural change was a structural change in which oxygen was released from the composite metal oxide.
Claims (6)
Ｌｉｘ｛（ＬｉｙＭｎ１−ｙ）ｚＭ１−ｚ｝Ｏ２・・・（Ｉ）
（式（Ｉ）中のｘは２／３を超え１未満であり、ｙは０を超え１／３未満であり、ｚは０．２以上１以下であり、ＭはＭｎ、Ｃｏ及びＮｉからなる群より選択される少なくとも一種である。） A composite metal oxide represented by the following formula (I) and composed of an oxide having an O2 structure.
Li x {(Li y Mn 1−y ) z M 1−z } O 2 (I)
(X in formula (I) is more than 2/3 and less than 1, y is more than 0 and less than 1/3, z is 0.2 or more and 1 or less, and M is from Mn, Co and Ni. At least one selected from the group consisting of:
ナトリウム化合物と、マンガン化合物と、リチウム化合物との混合物を焼成して前駆体を製造する前駆体製造工程と、
前記前駆体と、リチウムを含有する溶融塩又はリチウム化合物を含有する有機溶媒とを混合し、前記前駆体が含有するナトリウムと、前記溶融塩が含有するリチウムとをイオン交換させるイオン交換工程と、を有する複合金属酸化物の製造方法。 A method for producing a composite metal oxide according to claim 1 or 2,
A precursor production step of producing a precursor by firing a mixture of a sodium compound, a manganese compound, and a lithium compound;
An ion exchange step of mixing the precursor and a molten salt containing lithium or an organic solvent containing a lithium compound, and ion-exchanging sodium contained in the precursor and lithium contained in the molten salt; The manufacturing method of the composite metal oxide which has this.
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