JP4940530B2 - Cathode active material for non-aqueous electrolyte secondary battery - Google Patents

Description

【００９３】
なお式中のＤは結晶子の大きさ（Å）、Ｋはシェラー定数（βを積分幅より算出した場合はＫ＝１．０５）、λはＸ線源の波長（ＣｕＫα１＝１．５４０５６２Å）、βは結晶子の大きさによる回折線の広がりの幅（ｒａｄｉａｎ）、θは回折角２θ／２（ｄｅｇｒｅｅ）を示す。
【００９４】
（リチウムイオン二次電池の作製）
ポリフッ化ビニリデン５重量部を含有したノルマルメチルピロリドン溶液に正極活物質であるリチウム遷移金属複合酸化物粉末９０重量部、導電剤として炭素粉末５重量部とを加え、混練してペーストを調製し、これをドクターブレード法にてアルミニウム極板に塗布し、乾燥して正極板とする。また負極活物質に炭素材料を用いて同様にして銅極板に塗布し、負極板を作製する。セパレーターに多孔性プロピレンフィルムを用い、電解液としてエチレンカーボネイト：ジエチルカーボネイト＝１：１（体積比）の混合溶媒にＬiＰＦ_６を１ｍｏｌ／ｌの濃度で溶解した溶液を用いてリチウムイオン二次電池を作製する。本実施例では正極板、負極板、セパレータを薄いシート状に成形し、これらを巻回し、金属ラミネート樹脂フィルムの電池ケースに収納し、ラミネート型電池とする。
【００９６】
（極板密度の測定）
正極活物質であるリチウム遷移金属複合酸化物粉末９５重量部及びポリフッ化ビニリデン５重量部を含有したノルマルメチルピロリドン溶液とを混練してペーストを調製し、これをドクターブレード法にてアルミニウム極板に塗布し、乾燥して正極板とする。正極板を所定の大きさ（２×２．５ｃｍ）に裁断した後、一軸プレス機にて極板を加圧し、加圧後の極板の厚さと重量から極板密度を得る。
【００９７】
（ドライアウトの評価）
正極活物質であるリチウム遷移金属複合酸化物粉末９５重量部及びポリフッ化ビニリデン５重量部を含有したノルマルメチルピロリドン溶液とを混練してペーストを調製し、これをドクターブレード法にてアルミニウム極板に塗布し、乾燥して正極板とする。正極を所定の大きさに裁断した後一軸プレス機にて極板を加圧し、加圧後の正極板をガラス容器に入れてアルゴンボックス内でプロピレンカーボネート液に浸す。３分間真空にしてプロピレンカーボネート液を正極板に浸透させた後、アルゴンボックスから正極板を取り出し、正極板の時間毎の重量を量る。時間毎の正極板の重量から最初の正極板の重量を引いて、プロピレンカーボネート液の減少量を計算する。プロピレンカーボネートの減少量が多ければ、電解液の移動が容易であることになり、ドライアウトが防止できると判断できる。プロピレンカーボネートの減少量が少なければ、電解液の移動が困難であり、ドライアウトが生じやすいと判断できる。
【００９８】
結果を表１、図１に示す。粒度分布を図３に示す。
【００９９】
〔実施例２〕
所定の組成比のマンガンイオンとマグネシウムイオンを含む水溶液中に炭酸水素ナトリウム水溶液を加え、マンガンとマグネシウムを共沈させ、共沈物を得た。
得られた共沈物を濾過、水洗後、乾燥したのち、第１の共沈物はそのままにし、第２の共沈物にはオルトホウ酸を２００ｐｐｍ混合した。第１の共沈物は、炭酸リチウムを所定の組成比となるように混合し、大気雰囲気中にて、９３０℃の温度で１２時間焼成を行った。第２の共沈物は、炭酸リチウムを所定の組成比となるように混合し、大気雰囲気中にて、９３０℃の温度で１２時間焼成を行った。こうして第１の粒度分布を有し一次粒子径が４μｍのリチウム遷移金属複合酸化物と、第２の粒度分布を有し一次粒子径が１５μｍの範囲にあるリチウム遷移金属複合酸化物を得た。
第１の粒度分布を有し一次粒子径が４μｍのリチウム遷移金属複合酸化物からなる第１の粒子群を選択し、第２の粒度分布を有し一次粒子径が１５μｍの範囲にあるリチウム遷移金属複合酸化物からなる第２の粒子群からなる第２の粒子群を選択し、選択された第１の粒子群と第２の粒子群を混合した。第２の粒子群であるリチウム遷移金属複合酸化物の第１の粒子群であるリチウム遷移金属複合酸化物と第２の粒子群であるリチウム遷移金属複合酸化物の合計に対する混合割合は、７０重量％とし、第１の粒子群であるリチウム遷移金属複合酸化物の第１の粒子群であるリチウム遷移金属複合酸化物と第２の粒子群であるリチウム遷移金属複合酸化物の合計に対する混合割合は、３０重量％とした。こうしてＬｉ_{１．０７３}Ｍｎ_{１．９１５}Ｍｇ_０．０１Ｂ_{０．００２３}Ｏ_４が得られた。
【０１００】
粒度分布を図４に示す。
【０１０１】
〔実施例３〕
所定の組成比のマンガンイオンとマグネシウムイオンを含む水溶液中に炭酸水素ナトリウム水溶液を加え、マンガンとマグネシウムを共沈させ、共沈物を得た。
得られた共沈物を濾過、水洗後、乾燥したのち、第１の共沈物はそのままにし、第２の共沈物にはオルトホウ酸を１００ｐｐｍ混合した。第１の共沈物は、炭酸リチウムを所定の組成比となるように混合し、大気雰囲気中にて、９３０℃の温度で１２時間焼成を行った。第２の共沈物は、炭酸リチウムを所定の組成比となるように混合し、大気雰囲気中にて、９３０℃の温度で１２時間焼成を行った。こうして第１の粒度分布を有し一次粒子径が４μｍのリチウム遷移金属複合酸化物と、第２の粒度分布を有し一次粒子径が８μｍの範囲にあるリチウム遷移金属複合酸化物を得た。
第１の粒度分布を有し一次粒子径が４μｍのリチウム遷移金属複合酸化物からなる第１の粒子群を選択し、第２の粒度分布を有し一次粒子径が８μｍの範囲にあるリチウム遷移金属複合酸化物からなる第２の粒子群からなる第２の粒子群を選択し、選択された第１の粒子群と第２の粒子群を混合した。第２の粒子群であるリチウム遷移金属複合酸化物の第１の粒子群であるリチウム遷移金属複合酸化物と第２の粒子群であるリチウム遷移金属複合酸化物の合計に対する混合割合は、７０重量％とし、第１の粒子群であるリチウム遷移金属複合酸化物の第１の粒子群であるリチウム遷移金属複合酸化物と第２の粒子群であるリチウム遷移金属複合酸化物の合計に対する混合割合は、３０重量％とした。こうしてＬｉ_{１．０７３}Ｍｎ_{１．９１６}Ｍｇ_０．０１Ｂ_{０．００１２}Ｏ_４が得られた。
【０１０２】
以下、実施例１と同様にして非水電解液二次電池用正極活物質の評価を行った。結果を表１、図１に示す。粒度分布を図５に示す。
【０１０３】
〔実施例４〕
所定の組成比のマンガンイオンとマグネシウムイオンを含む水溶液中に炭酸水素ナトリウム水溶液を加え、マンガンとマグネシウムを共沈させ、共沈物を得た。
得られた共沈物を濾過、水洗後、乾燥したのち、第１の共沈物はそのままにし、第２の共沈物にはオルトホウ酸を３００ｐｐｍ混合した。第１の共沈物は、炭酸リチウムを所定の組成比となるように混合し、大気雰囲気中にて、９３０℃の温度で１２時間焼成を行った。第２の共沈物は、炭酸リチウムを所定の組成比となるように混合し、大気雰囲気中にて、９３０℃の温度で１２時間焼成を行った。こうして第１の粒度分布を有し一次粒子径が４μｍのリチウム遷移金属複合酸化物と、第２の粒度分布を有し一次粒子径が２０μｍの範囲にあるリチウム遷移金属複合酸化物を得た。
第１の粒度分布を有し一次粒子径が４μｍのリチウム遷移金属複合酸化物からなる第１の粒子群を選択し、第２の粒度分布を有し一次粒子径が２０μｍの範囲にあるリチウム遷移金属複合酸化物からなる第２の粒子群からなる第２の粒子群を選択し、選択された第１の粒子群と第２の粒子群を混合した。第２の粒子群であるリチウム遷移金属複合酸化物の第１の粒子群であるリチウム遷移金属複合酸化物と第２の粒子群であるリチウム遷移金属複合酸化物の合計に対する混合割合は、６０重量％とし、第１の粒子群であるリチウム遷移金属複合酸化物の第１の粒子群であるリチウム遷移金属複合酸化物と第２の粒子群であるリチウム遷移金属複合酸化物の合計に対する混合割合は、４０重量％とした。こうしてＬｉ_{１．０７２}Ｍｎ_{１．９１５}Ｍｇ_０．０１Ｂ_{０．００３}Ｏ_４が得られた。
【０１０４】
粒度分布を図６に示す。
【０１０５】
〔比較例１〕
所定の組成比のマンガンイオンとマグネシウムイオンを含む水溶液中に炭酸水素ナトリウム水溶液を加え、マンガンとマグネシウムを共沈させ、共沈物を得た。
得られた共沈物を濾過、水洗後、乾燥したのち、炭酸リチウムを所定の組成比となるように混合し、大気雰囲気中にて９３０℃で１２時間焼成した。そして乳鉢にて粉砕しＬｉ_{１．０７３}Ｍｎ_{１．９１７}Ｍｇ_０．０１Ｏ_４が得られた。
【０１０６】
以下、実施例１と同様にして非水電解液二次電池用正極活物質の評価を行った。結果を表１、図１に示す。粒度分布を図７に示す。
【０１１１】
表１及び図１から明らかなように、本発明の非水電解液二次電池用正極活物質は、極板密度が比較例１に比べて向上していることがわかる。またドライアウトも防止できていることがわかる。
【０１１２】
これに対して、比較例１は、極板密度が本発明の非水電解液二次電池用正極活物質に比べて劣っている。また、ドライアウトも防止できていない。
【０１１３】
【表１】

【０１１４】
また実施例１、実施例２および実施例３において、それぞれ第１の粒子群であるリチウム遷移金属複合酸化物と第２の粒子群であるリチウム遷移金属複合酸化物の混合割合を変化させて、変化させたときの極板密度を測定した。結果を表２〜表４、図２に示す。
【０１１５】
【表２】

【０１１６】
【表３】

【０１１７】
【表４】

【０１１８】
この結果から、第２の粒子群であるリチウム遷移金属複合酸化物の第１の粒子群であるリチウム遷移金属複合酸化物と第２の粒子群であるリチウム遷移金属複合酸化物の合計に対する混合割合は、６０重量％〜７０重量％であり、第１の粒子群であるリチウム遷移金属複合酸化物の第１の粒子群であるリチウム遷移金属複合酸化物と第２の粒子群であるリチウム遷移金属複合酸化物の合計に対する混合割合は、３０重量％〜４０重量％であることがより好ましいことがわかる。
【０１２９】
以上に説明したように、本発明の非水電解液二次電池用正極活物質は、極板密度が向上するとともにドライアウトを防止することができ優れた電池特性を有する。したがって、本発明の非水電解液二次電池用正極活物質は、リチウムイオン二次電池等の非水電解液二次電池に好適に用いられる。
【図面の簡単な説明】
【図１】プレス圧の変化に伴う極板密度の変化を示す図である。
【図２】第１の粒子群であるリチウム遷移金属複合酸化物と第２の粒子群であるリチウム遷移金属複合酸化物の混合割合の変化に伴う極板密度の変化を示す図である。
【図３】実施例１の粒度分布を示す図である。
【図４】実施例２の粒度分布を示す図である。
【図５】実施例３の粒度分布を示す図である。
【図６】実施例４の粒度分布を示す図である。
【図７】比較例１の粒度分布を示す図である。
【図８】比較例２の粒度分布を示す図である。
【図９】比較例３の粒度分布を示す図である。
【図１０】スピネル構造のリチウム遷移金属複合酸化物を示す図である。
【図１１】活物質の結着模式図である。
【図１２】円筒型電池の断面図である。
【図１３】コイン型電池の構造を示す図である。
【図１４】角型電池の構造を示す図である。
【符号の説明】
１…８ａサイト
２…３２ｅサイト
３…１６ｄサイト
４…結着剤
５…活物質
１１…負極
１２…集電体
１３…正極
１４…セパレーター
２１…第１の粒度分布
２２…第２の粒度分布[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a non-aqueous electrolyte secondary battery and a positive electrode active material thereof, in particular, a lithium transition metal composite oxide having a spinel structure. For example, it is used for mobile phones, personal computers, and electric vehicles.
[0002]
[Prior art]
Non-aqueous electrolyte secondary batteries are characterized by higher operating voltage and higher energy density than conventional nickel cadmium secondary batteries, and are widely used as power sources for electronic devices. As the positive electrode active material of this non-aqueous electrolyte secondary battery, LiCoO₂, LiNiO₂, LiMn₂O₄And lithium transition metal composite oxides represented by
[0003]
Among them, LiMn₂O₄Since manganese, which is a constituent element, is present in a large amount as a resource, raw materials are easily available at low cost. In addition, there is a feature that the load on the environment is small. Furthermore, even if all the Li ions in the crystal are desorbed by the deintercalation reaction, the crystal structure exists stably. For this reason, LiCoO₂, LiNiO₂Compared to LiMn₂O₄The secondary battery using the battery generates little heat in an overcharged state.
[0004]
In mobile electronic devices such as mobile phones and notebook computers, so far LiMn₂O₄Sufficient battery characteristics were obtained with a non-aqueous electrolyte secondary battery using the above.
[0005]
However, at present, mobile devices such as mobile phones, notebook computers, and digital cameras have a more severe usage environment due to high functionality such as the addition of various functions and use at high and low temperatures. It has become a thing. In addition, application to power sources such as batteries for electric vehicles is expected. Under such circumstances, the conventional LiMn₂O₄In a non-aqueous electrolyte secondary battery using, sufficient battery characteristics cannot be obtained, and further improvements are required.
[0006]
[Problems to be solved by the invention]
The objective of this invention is providing the positive electrode active material for non-aqueous-electrolyte secondary batteries which has the outstanding battery characteristic also in the severer use environment. That is, an object of the present invention is to provide a positive electrode active material for a non-aqueous electrolyte secondary battery that can improve the electrode plate density and prevent dry-out during charging and discharging.
[0007]
[Means for Solving the Problems]
The positive electrode active material for a non-aqueous electrolyte secondary battery described in the present invention is a positive electrode active material for a non-aqueous electrolyte secondary battery having at least a lithium transition metal composite oxide having a spinel structure, and the lithium transition metal The composite oxide includes at least a first lithium transition metal composite oxide and a second lithium transition metal composite oxide, and the first lithium transition metal composite oxide includes an element that increases a secondary particle size, and It is smaller than the 2nd lithium transition metal complex oxide containing a compound.
[0008]
The improvement of the electrode plate density is greatly related to the improvement of the battery capacity. The electrode plate density can be improved by increasing the pressing pressure. However, when the press pressure is increased, the lithium transition metal composite oxide particles are broken, fine powder is generated, the lithium transition metal composite oxide is displaced, and dry-out of the electrolyte solution is caused. Dryout is the biggest cause of deterioration of battery characteristics. In order to prevent this dry-out, it is preferable to increase the particle size, but the large particle lithium transition metal composite oxide has a low electrode plate density. Therefore, there is a trade-off between improving the electrode plate density and preventing dryout.
[0009]
Having at least two or more types of lithium transition metal composite oxide, and at least the first lithium transition metal composite oxide being smaller than the second lithium transition metal composite oxide, the filling property to the electrode plate is improved and the electrode The plate density is improved. By containing an element and / or compound that increases the secondary particle size in the second lithium transition metal composite oxide, the size of the two or more lithium transition metal composite oxide particles can be controlled. . As a result, a positive electrode active material for a non-aqueous electrolyte secondary battery that can prevent dry-out can be obtained even if the press plate pressure is increased to improve the electrode plate density.
[0010]
The first lithium transition metal composite oxide is preferably less than the second lithium transition metal composite oxide. Since the first lithium transition metal composite oxide is smaller than the second lithium transition metal composite oxide containing an element and / or compound that increases the secondary particle size, the small particles existing between the large particles The ratio can be controlled. As a result, the electrode plate density can be improved more effectively and dry-out can be prevented.
[0011]
The positive electrode active material for a non-aqueous electrolyte secondary battery described in the present invention is a positive electrode active material for a non-aqueous electrolyte secondary battery having at least a lithium transition metal composite oxide having a spinel structure, and the lithium transition metal The composite oxide has a first lithium manganate and a second lithium manganate, and the first lithium manganate is smaller than the second lithium manganate containing boron.
[0012]
When at least two types of lithium manganate are included and at least the first lithium manganate is smaller than the second lithium manganate, the filling property of the electrode plate is improved and the electrode plate density is improved. By containing boron in the second lithium manganate, the size of the two types of lithium manganate particles can be controlled. As a result, a positive electrode active material for a non-aqueous electrolyte secondary battery that can prevent dry-out can be obtained even if the press plate pressure is increased to improve the electrode plate density.
[0013]
The first lithium manganate is preferably less than the second lithium manganate. Since the first lithium manganate is less than the second lithium manganate containing boron, the proportion of small particles existing between large particles can be controlled. As a result, the electrode plate density can be improved more effectively and dry-out can be prevented.
[0014]
The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery described in the present invention is a method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery having at least a spinel-structure lithium transition metal composite oxide. Selecting a first particle group comprising a lithium transition metal composite oxide having a first particle size distribution and a primary particle size in the range of 10 μm or less, and secondary particles larger than the first particle size distribution Selecting a second particle group comprising a lithium transition metal composite oxide having a second particle size distribution as a diameter and a primary particle diameter in the range of 8 μm to 150 μm, and the selected first particle group And a step of mixing the lithium transition metal composite oxide which is the selected second particle group and the lithium transition metal composite oxide.
[0015]
By passing through these steps, the proportion of small particles existing between large particles can be controlled. Therefore, it is possible to obtain a positive electrode active material for a non-aqueous electrolyte secondary battery that has a high electrode plate density and can prevent dryout.
[0016]
The lithium transition metal composite oxide that is the second particle group preferably contains boron. By containing boron, the size of the lithium manganate particles can be controlled. As a result, a positive electrode active material for a non-aqueous electrolyte secondary battery that can prevent dry-out can be obtained even if the press plate pressure is increased to improve the electrode plate density.
[0017]
The first particle size distribution is preferably prepared such that the secondary particle size is in the range of 1 μm to 50 μm. Non-aqueous electrolyte secondary battery that can prevent degradation of cycle charge / discharge characteristics and elution of manganese that causes dryout, and can prevent dryout even if the press plate pressure is increased to increase the electrode plate density A positive electrode active material can be obtained.
[0018]
The second particle size distribution is preferably prepared such that its secondary particle size is in the range of 8 μm to 150 μm. Non-aqueous electrolyte solution that can prevent the precipitation of lithium transition metal composite oxide particles during the preparation of the positive electrode mixture, and can prevent dry-out even if the press plate pressure is increased to increase the electrode plate density. A positive electrode active material for a secondary battery can be obtained.
[0019]
The lithium transition metal composite oxide has a general formula of Li_aMn_3-aO_{4 + f}(A represents a number satisfying 0.8 ≦ a ≦ 1.2, and f represents a number satisfying −0.5 ≦ f ≦ 0.5). A positive electrode active material for a non-aqueous electrolyte secondary battery having excellent overcharge characteristics and electrode plate density used for mobile phones and electric tools can be obtained. Furthermore, since the dry-out at the time of charging / discharging which becomes the cause of reducing a battery characteristic can be prevented, the positive electrode active material for nonaqueous electrolyte secondary batteries used for an electric vehicle is obtained.
[0020]
The mixing ratio of the lithium transition metal composite oxide which is the first particle group and the lithium transition metal composite oxide which is the second particle group of the lithium transition metal composite oxide which is the second particle group is 50% by weight to 90% by weight of the lithium transition metal composite oxide which is the first particle group of the lithium transition metal composite oxide which is the first particle group and the lithium which is the second particle group The mixing ratio with respect to the total of the transition metal composite oxides is preferably 10% by weight to 50% by weight. In this way, by controlling the proportion of small particles that can exist between large particles, it is possible to more effectively improve the electrode plate density and prevent dryout, and the positive electrode active for a non-aqueous electrolyte secondary battery. A substance can be obtained.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the positive electrode active material for a non-aqueous electrolyte secondary battery according to the present invention will be described with reference to embodiments, examples, and FIGS. However, the present invention is not limited to this embodiment, examples, and FIGS.
[0022]
(Positive electrode active material for non-aqueous electrolyte secondary battery)
The positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention comprises at least a lithium transition metal composite oxide having a spinel structure. Spinel structure is a double oxide AB₂O₄This is one of the typical crystal structure types found in type compounds (A and B are metal elements). Lithium occupies the tetrahedral site of the 8a site 1, oxygen occupies the 32e site 2, and the transition metal occupies the octahedral site of the 16d site 3.
[0023]
Examples of the lithium transition metal composite oxide having a spinel structure include lithium manganate and lithium titanate. Lithium manganate is preferable. In the case of lithium manganate, a positive electrode active material for a non-aqueous electrolyte secondary battery having excellent overcharge characteristics and electrode plate density used for mobile phones and electric tools can be obtained. Furthermore, since the dry-out at the time of charging / discharging which becomes the cause of reducing a battery characteristic can be prevented, the positive electrode active material for nonaqueous electrolyte secondary batteries used for an electric vehicle is obtained.
[0024]
The lithium transition metal composite oxide according to the present invention has at least a first lithium transition metal composite oxide and a second lithium transition metal composite oxide, and the first lithium transition metal composite oxide has a secondary It is smaller than the 2nd lithium transition metal complex oxide containing the element and / or compound which enlarges a particle diameter.
[0025]
The lithium transition metal composite oxide according to the present invention includes at least a first lithium transition metal composite oxide and a second lithium transition metal composite oxide. The first lithium transition metal composite oxide and the second lithium transition metal composite oxide may be the same or different. The first lithium transition metal composite oxide may be lithium manganate, and the second lithium transition metal composite oxide may be lithium titanate. The first lithium transition metal composite oxide may be lithium titanate, and the second lithium transition metal composite oxide may be lithium manganate. Preferably, the first lithium transition metal composite oxide is lithium manganate, and the second lithium transition metal composite oxide is also lithium manganate. At this time, a positive electrode active material for a non-aqueous electrolyte secondary battery having excellent overcharge characteristics and electrode plate density used for mobile phones and electric tools is obtained. Furthermore, since the dry-out at the time of charging / discharging which becomes the cause of reducing a battery characteristic can be prevented, the positive electrode active material for nonaqueous electrolyte secondary batteries used for an electric vehicle is obtained.
[0026]
The 1st lithium transition metal complex oxide which concerns on this invention is smaller than the 2nd lithium transition metal complex oxide containing the element and / or compound which enlarges a secondary particle diameter. As the element and / or compound for increasing the secondary particle size, boron compounds, chlorine compounds and vanadium compounds are preferable. These have an effect as a flux and can prevent dryout during charging and discharging. More preferred is a boron compound.
[0027]
The boron compound is not particularly limited. For example, boric acid, lithium borate, boride, boron oxide, boron phosphate or the like is used. Preferred are boric acid and lithium borate. The chlorine compound is not particularly limited. For example, lithium chloride, sodium chloride, hydrogen chloride, hydrochloric acid, chlorine oxide, fluorinated chlorine oxide, or the like is used. Lithium chloride and sodium chloride are preferred. The vanadium compound is not particularly limited. For example, vanadium oxide, vanadium chloride, vanadium fluoride, vanadium hydroxide, or the like is used. Vanadium oxide is preferred.
[0028]
Small means that the particle diameter or specific surface area diameter is small. The particle diameter includes a primary particle diameter and a secondary particle diameter. The secondary particle diameter includes the median diameter. Preferably, the secondary particle diameter and the median diameter are small. More preferably, the median diameter is small. General lithium transition metal composite oxide particles are composed of primary particles grown reflecting the crystal form of the lithium transition metal composite oxide, and secondary particles formed by aggregation or sintering. The diameter of such a primary particle is called a primary particle diameter, and the diameter of a secondary particle is called a secondary particle.
[0029]
The method for measuring the specific surface area diameter is not particularly limited. For example, it can be measured using a Fischer sub-sieve sizer (FSSS) by the air permeation method. The median diameter means a particle diameter at which the volume cumulative frequency of the particle size distribution of the secondary particles reaches 50%. The method for measuring the median diameter is not particularly limited. For example, the particle size distribution is measured by a laser diffraction scattering method, an integrated distribution using the logarithm of the volume-based particle diameter is obtained, and the particle diameter when occupying 50% of the entire lithium transition metal composite oxide powder, that is, oversize 50 % Particle size. The measuring method of a primary particle diameter is not specifically limited. For example, it can be measured using an image analysis method (microscope method).
[0030]
The lithium transition metal composite oxide according to the present invention has at least a first lithium transition metal composite oxide and a second lithium transition metal composite oxide, and the first lithium transition metal composite oxide has a secondary Since the median diameter is smaller than that of the second lithium transition metal composite oxide containing an element and / or compound that increases the particle diameter, the electrode plate density can be improved and dry out can be prevented. A positive electrode active material for a non-aqueous electrolyte secondary battery with improved overcharge characteristics can be obtained.
[0031]
The first lithium transition metal composite oxide according to the present invention is preferably less than the second lithium transition metal composite oxide. Less is that the mixing ratio of the first lithium transition metal composite oxide to the total of the first lithium transition metal composite oxide and the second lithium transition metal composite oxide is that of the second lithium transition metal composite oxide. It means being less than the mixing ratio with respect to the total of the first lithium transition metal composite oxide and the second lithium transition metal composite oxide. Further, the weight of the first lithium transition metal composite oxide may be less than the weight of the second lithium transition metal composite oxide.
[0032]
The lithium transition metal composite oxide according to the present invention has a first lithium manganate and a second lithium manganate, and the first lithium manganate is more than the second lithium manganate containing boron. small.
[0033]
In the present invention, boron may be dissolved in the second lithium manganate or may be present on the surface of the lithium manganate particles. Preferably, it has a first lithium manganate and a second lithium manganate, and the first lithium manganate is smaller than the second lithium manganate having boron on the surface of the particles. It is a positive electrode active material for non-aqueous electrolyte secondary batteries. At this time, since boron improves the ease of passing electrons in lithium manganate, cycle charge / discharge characteristics and thermal stability are improved. The lithium manganate particles may be primary particles or secondary particles.
[0034]
A boron compound may be used instead of boron. The boron compound is not particularly limited. For example, boric acid, lithium borate, boride, boron oxide, boron phosphate or the like is used. Preferred are boric acid and lithium borate.
[0035]
In the present invention, the boron compound may be dissolved in the second lithium manganate or may have a boron compound on the surface of the lithium manganate particles. Preferably, the first lithium manganate and the second lithium manganate are included, and the first lithium manganate is smaller than the second lithium manganate having lithium borate on the surface of the particles. And a positive electrode active material for a non-aqueous electrolyte secondary battery. At this time, since lithium borate improves the ease of passing electrons in lithium manganate, cycle charge / discharge characteristics and thermal stability are improved. The lithium manganate particles may be primary particles or secondary particles.
[0036]
Even if boron and / or lithium borate are present on the surface of the lithium manganate particles, the effect of the present invention is exhibited. For example, even when boron and / or lithium borate is coated on the entire surface of the lithium manganate particle, boron and / or lithium borate is coated on a part of the surface of the lithium manganate particle. Even if it is carried out, cycle charge / discharge characteristics and thermal stability are improved.
[0037]
More preferably, boron and / or lithium borate is coated on the entire surface of the lithium manganate particles. In this case, it is possible to obtain a positive electrode active material for a non-aqueous electrolyte secondary battery in which not only cycle charge / discharge characteristics and thermal stability but also storage characteristics are improved.
Further, boron and / or lithium borate may be present at least on the surface of the particles. Therefore, boron and / or lithium borate may be present inside the particles.
[0038]
Whether boric acid and / or lithium borate is present on the surface of the lithium manganate particles can be analyzed by various methods. For example, analysis can be performed by Auger electron spectroscopy (AES) or X-ray photoelectron spectroscopy (XPS).
[0039]
The amount of boron contained in the second lithium manganate is preferably 50 ppm to 500 ppm with respect to the second lithium manganate. At this time, the effect of the present invention is clearly shown. Preferably it is 100 ppm-400 ppm, More preferably, it is 150 ppm-350 ppm. At this time, the electrode plate density is improved and dry-out can be prevented without deteriorating the overcharge characteristics.
[0040]
Small means that the particle diameter or specific surface area diameter is small. The particle diameter includes a primary particle diameter and a secondary particle diameter. The secondary particle diameter includes the median diameter. Preferably, the secondary particle diameter and the median diameter are small. More preferably, the median diameter is small. General lithium manganate particles are composed of primary particles grown reflecting the crystal form of lithium manganate and secondary particles formed by aggregation or sintering. The diameter of such a primary particle is called a primary particle diameter, and the diameter of a secondary particle is called a secondary particle.
[0041]
The first lithium manganate according to the present invention is preferably less than the second lithium manganate. The small amount means that the mixing ratio of the first lithium manganate to the total of the first lithium manganate and the second lithium manganate is such that the first lithium manganate and the second manganate are mixed with the second lithium manganate. It means less than the mixing ratio with respect to the total of lithium. The weight of the first lithium manganate may be less than the weight of the second lithium manganate.
[0042]
The lithium manganate according to the present invention preferably has the general formula Li_aMn_3-aO_{4 + f}(A represents a number satisfying 0.8 ≦ a ≦ 1.2, and f represents a number satisfying −0.5 ≦ f ≦ 0.5). The general formula is Li_aMn_3-aO_{4 + f}(A represents a number satisfying 0.8 ≦ a ≦ 1.2, and f represents a number satisfying −0.5 ≦ f ≦ 0.5). A positive electrode active material for a non-aqueous electrolyte secondary battery having excellent overcharge characteristics and electrode plate density used for telephones, electric tools and the like can be obtained. Furthermore, since the dry-out at the time of charging / discharging which becomes the cause of reducing a battery characteristic can be prevented, the positive electrode active material for nonaqueous electrolyte secondary batteries used for an electric vehicle is obtained.
[0043]
(Method for producing positive electrode active material for non-aqueous electrolyte secondary battery)
The method for producing a positive electrode active material for a non-aqueous electrolyte secondary battery according to the present invention includes a first particle comprising a lithium transition metal composite oxide having a first particle size distribution and a primary particle diameter of 10 μm or less. A step of selecting a group, and a second composed of a lithium transition metal composite oxide having a second particle size distribution having a larger secondary particle size than the first particle size distribution and having a primary particle size in the range of 8 μm to 150 μm. And a step of mixing a lithium transition metal composite oxide that is the selected first particle group and a lithium transition metal composite oxide that is the selected second particle group. Have.
[0044]
Hereinafter, the positive electrode active material for a non-aqueous electrolyte secondary battery according to the present invention (Li_1.072Mn_1.914Mg_0.01B_0.0035O₄The manufacturing method is not limited to the present manufacturing method except for the above steps.
[0045]
A sodium hydrogen carbonate aqueous solution is added to an aqueous solution containing manganese ions and magnesium ions having a predetermined composition ratio to coprecipitate manganese and magnesium to obtain a coprecipitate.
[0046]
The manganese source is not particularly limited. Basically, any salt that can form an aqueous solution can be used. For example, manganese chloride, manganese iodide, manganese sulfate, manganese nitrate or the like is used. Preferably, MnSO₄, MnCl₂Etc. are used.
[0047]
The magnesium source is not particularly limited. Basically, any salt that can form an aqueous solution can be used. For example, magnesium chloride, magnesium iodide, magnesium perchlorate, magnesium sulfate, magnesium nitrate and the like are used. Preferably, MgSO₄, Mg (NO₃)₂Etc. are used.
[0048]
Moreover, although the sodium hydrogencarbonate aqueous solution is added, it is not necessarily restricted to this, What is necessary is just alkaline solutions, such as sodium hydroxide aqueous solution, potassium hydroxide aqueous solution, lithium hydroxide aqueous solution.
[0049]
Next, the obtained coprecipitate is filtered, washed with water, and dried. The first coprecipitate is left as it is, and a predetermined amount of orthoboric acid is mixed with the second coprecipitate. The first coprecipitate is mixed with lithium carbonate so as to have a predetermined composition ratio, and is fired at a temperature of 800 ° C. to 1000 ° C. for 5 hours to 15 hours in air or in a weakly oxidizing atmosphere. The second coprecipitate is mixed with lithium carbonate so as to have a predetermined composition ratio, and fired in air or in a weakly oxidizing atmosphere at a temperature of 800 ° C. to 1000 ° C. for 5 hours to 15 hours. Thus, the lithium transition metal composite oxide having the first particle size distribution and the primary particle diameter in the range of 10 μm or less, and the lithium transition metal composite oxide having the second particle size distribution and the primary particle diameter in the range of 8 μm to 150 μm. Obtain an oxide. 3 to 6 show a first particle size distribution 21 and a second particle size distribution 22 in the present invention.
[0050]
If the primary particle size exceeds 10 μm with the first particle size distribution, the difference between small particles and large particles becomes small, which is not preferable. Preferably, it has the first particle size distribution and the primary particle size is 2 μm to 8 μm. If the second particle size distribution and the primary particle size is smaller than 8 μm or larger than 150 μm, it becomes difficult to maintain the balance between the small particles and the large particles. Since sedimentation occurs, it is not preferable. Preferably, the lithium transition metal composite oxide has a second particle size distribution and a primary particle size in the range of 10 μm to 80 μm.
[0051]
What is mixed with the coprecipitate is not limited to lithium carbonate. Basically, any lithium compound can be used. For example, lithium fluoride, lithium chloride, lithium bromide, lithium iodide, lithium oxide, lithium peroxide, lithium hydroxide, or the like is used. Preferably Li₂CO₃, LiOH, LiOH · H₂O, Li₂O, LiCl, LiNO₃, Li₂SO₄, LiHCO₃, Li (CH₃COO) or the like is used.
[0052]
You may mix a sulfur containing compound, the compound containing a halogen element, etc. with a coprecipitate and a lithium compound.
[0053]
The sulfur-containing compound is not particularly limited. For example, sulfide, sulfur iodide, hydrogen sulfide, sulfuric acid and its salt, nitrogen sulfide and the like are used. Preferably Li₂SO₄, MnSO₄, (NH₄)₂SO₄, Al₂(SO₄)₃, MgSO₄Etc. are used.
[0054]
The compound containing a halogen element is not particularly limited. For example, hydrogen fluoride, oxygen fluoride, hydrofluoric acid, hydrogen chloride, hydrochloric acid, chlorine oxide, fluorinated chlorine oxide, bromine oxide, bromine fluorosulfate, hydrogen iodide, iodine oxide, periodic acid and the like are used. Preferably, NH₄F, NH₄Cl, NH₄Br, NH₄I, LiF, LiCl, LiBr, LiI, MnF₂, MnCl₂, MnBr₂, MnI₂Etc. are used.
[0055]
The firing temperature is preferably 850 ° C. to 950 ° C., and the firing time is preferably 8 to 14 hours. When the firing temperature is lower than 800 ° C., unreacted raw materials may remain in the positive electrode active material for a non-aqueous electrolyte secondary battery, and sufficient characteristics that can achieve the object of the present invention may not be obtained. Further, when baked at a temperature higher than 1000 ° C., a by-product is likely to be generated, resulting in a decrease in discharge capacity per unit weight, a decrease in cycle charge / discharge characteristics, and a decrease in operating voltage. When the firing time is less than 5 hours, the diffusion reaction between the particles of the raw material mixture does not proceed, and the target positive electrode active material for a non-aqueous electrolyte secondary battery cannot be obtained. In addition, firing for longer than 15 hours is not preferable because coarse particles are formed by sintering.
[0056]
A first particle group made of a lithium transition metal composite oxide having a first particle size distribution and a primary particle size in the range of 10 μm or less is selected, and a second particle size larger than the first particle size distribution is obtained. A second particle group consisting of a second particle group consisting of a lithium transition metal complex oxide having a particle size distribution of 2 and a primary particle diameter in the range of 8 μm to 150 μm, and the selected first particle group And the second particle group are mixed.
[0057]
The lithium transition metal composite oxide which is the second particle group preferably contains boron. In the present invention, boron may be dissolved in the lithium transition metal composite oxide that is the second particle group, or boron may be present on the surface of the lithium transition metal composite oxide particles. If the surface of the particles of the lithium transition metal composite oxide that is the second particle group has boron, boron improves the ease of passing electrons in the lithium transition metal composite oxide, High load characteristics are improved. The particles of the lithium transition metal composite oxide may be primary particles or secondary particles.
[0058]
A boron compound may be used instead of boron. The boron compound is not particularly limited. For example, boric acid, lithium borate, boride, boron oxide, boron phosphate or the like is used. Preferred are boric acid and lithium borate.
[0059]
In the present invention, the boron compound may be dissolved in the lithium transition metal composite oxide as the second particle group, or may have a boron compound on the surface of the lithium transition metal composite oxide particles. It is preferable to have lithium borate on the surface of the particles of the lithium transition metal composite oxide that is the second particle group. At this time, since lithium borate improves the ease of passing electrons in the lithium transition metal composite oxide, cycle charge / discharge characteristics and high load characteristics are improved. The particles of the lithium transition metal composite oxide may be primary particles or secondary particles.
[0060]
Even if boron and / or lithium borate are present on the surface of the lithium transition metal composite oxide particles, the effects of the present invention are exhibited. For example, even when boron and / or lithium borate is coated on the entire surface of the lithium transition metal composite oxide particles, boron and / or lithium borate is used as the lithium transition metal composite oxide particles. Even when the surface is partially covered, the cycle charge / discharge characteristics and thermal stability are improved.
[0061]
More preferably, boron and / or lithium borate is coated over the entire surface of the lithium transition metal composite oxide particles. In this case, it is possible to obtain a positive electrode active material for a non-aqueous electrolyte secondary battery in which not only cycle charge / discharge characteristics and thermal stability but also storage characteristics are improved.
Further, boron and / or lithium borate may be present at least on the surface of the particles. Therefore, boron and / or lithium borate may be present inside the particles.
[0062]
Whether boric acid and / or lithium borate is present on the surface of the lithium transition metal composite oxide particles can be analyzed by various methods. For example, analysis can be performed by Auger electron spectroscopy (AES) or X-ray photoelectron spectroscopy (XPS).
[0063]
The amount of boron contained in the lithium transition metal composite oxide that is the second particle group is preferably 50 ppm to 500 ppm with respect to the lithium transition metal composite oxide that is the second particle group. At this time, the effect of the present invention is clearly shown. Preferably it is 100 ppm-400 ppm, More preferably, it is 150 ppm-350 ppm. At this time, the electrode plate density is improved and dry-out can be prevented without deteriorating the overcharge characteristics.
[0064]
The first particle size distribution is preferably prepared such that the secondary particle size is in the range of 1 μm to 50 μm. If the secondary particle diameter is smaller than 1 μm, the specific surface area of the lithium transition metal composite oxide increases, and manganese elution that causes deterioration of cycle charge / discharge characteristics and dryout occurs. If the secondary particle diameter is larger than 50 μm, it cannot contribute to mixing with large particles as small particles, and is not effective in achieving the object of the present invention. More preferably, the secondary particle size of the first particle size distribution is adjusted in the range of 1 μm to 30 μm.
[0065]
The second particle size distribution is preferably prepared such that the secondary particle size is in the range of 8 μm to 150 μm. If the secondary particle size is smaller than 8 μm, it is impossible to contribute to mixing with small particles as large particles, which is not effective for achieving the object of the present invention. If the secondary particle diameter is larger than 150 μm, precipitation of lithium transition metal composite oxide particles during production of the positive electrode mixture occurs, which is not preferable. More preferably, the secondary particle size of the second particle size distribution is adjusted in the range of 10 μm to 50 μm.
[0066]
The lithium transition metal composite oxide has a general formula of Li_aM_bMn_3-a-bA_gX_cB_dS_eD_hO_{4 + f}(M represents aluminum and / or magnesium, A represents at least one selected from the group consisting of titanium, zirconium and hafnium, X represents at least one selected from the group consisting of fluorine, chlorine, bromine and iodine, B Represents boron, S represents sulfur, D represents sodium and / or calcium, a represents a number satisfying 0.8 ≦ a ≦ 1.2, and b represents a number satisfying 0 ≦ b ≦ 0.2. C represents a number satisfying 0 ≦ c ≦ 0.05, d represents a number satisfying 0 ≦ d ≦ 0.02, e represents a number satisfying 0 ≦ e ≦ 0.1, and f represents -0.5 ≦ f ≦ 0.5, g represents a number satisfying 0 ≦ g ≦ 0.1, and h represents a number satisfying 0 ≦ h ≦ 0.015. It is preferable.
[0067]
The mixing ratio of the lithium transition metal composite oxide which is the first particle group and the lithium transition metal composite oxide which is the second particle group of the lithium transition metal composite oxide which is the second particle group is 50 wt. % To 90% by weight of the lithium transition metal composite oxide that is the first particle group of the lithium transition metal composite oxide that is the first particle group and the lithium transition metal composite oxide that is the second particle group. The mixing ratio relative to the total is preferably 10% by weight to 50% by weight. If the mixing ratio is not within this range, the electrode plate density cannot be increased efficiently. When the mixing ratio of small particles is large, the surface of the electrode plate is crushed by the press at the time of electrode plate production, making it difficult for the electrolyte to enter and exit, resulting in dryout. More preferably, the mixing ratio of the lithium transition metal composite oxide that is the first particle group of the lithium transition metal composite oxide that is the second particle group and the total of the lithium transition metal composite oxide that is the second particle group Is 55% by weight to 75% by weight, and the lithium transition metal composite oxide that is the first particle group of the lithium transition metal composite oxide that is the first particle group and the lithium transition metal that is the second particle group The mixing ratio with respect to the total of the composite oxide is 25% by weight to 45% by weight.
[0068]
You may grind | pulverize the lithium transition metal complex oxide obtained by the said baking with a mortar, a ball mill, a vibration mill, a pin mill, etc. Specific surface area of 0.2 m by the above method²/G-1.2m²/ G of the positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention can be obtained.
[0069]
By using the above manufacturing method, it is possible to obtain a target positive electrode active material for a non-aqueous electrolyte secondary battery.
[0070]
In addition, by coprecipitation of manganese and magnesium with carbonate, Li_1.072Mn_1.914Mg_0.01B_0.0035O₄However, a manganese compound and a magnesium compound may be mixed so as to have a predetermined composition ratio and fired.
[0071]
(Non-aqueous electrolyte secondary battery)
The positive electrode active material for a non-aqueous electrolyte secondary battery according to the present invention is suitably used for non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries and lithium ion polymer secondary batteries.
[0072]
The non-aqueous electrolyte secondary battery may be a conventionally known non-aqueous electrolyte secondary battery in which the positive electrode active material may be the positive electrode active material of the present invention, and other configurations are not particularly limited. Any non-aqueous electrolyte secondary battery including a positive electrode active material layer mainly composed of the lithium transition metal composite oxide according to the present invention may be used.
[0073]
By using lithium cobaltate and / or lithium nickelate together with the positive electrode active material of the present invention as a positive electrode active material, not only overcharge characteristics, thermal stability and safety, but also excellent discharge capacity, load characteristics, and output characteristics A nonaqueous electrolyte secondary battery can be obtained.
[0074]
The general formula is Li_{1 + x}CoO₂Lithium cobaltate represented by (x represents a number satisfying −0.5 ≦ x ≦ 0.5) is preferable. The lithium cobaltate is at least a part selected from the group consisting of magnesium, aluminum, calcium, vanadium, titanium, chromium, manganese, iron, cobalt, nickel, copper, zinc, strontium, zirconium, niobium, molybdenum and tin. It may be substituted with one kind.
[0075]
The general formula is Li_{1 + x}NiO₂Lithium nickelate represented by (x represents a number satisfying −0.5 ≦ x ≦ 0.5) is preferable. The lithium nickelate is at least a part selected from the group consisting of magnesium, aluminum, calcium, vanadium, titanium, chromium, manganese, iron, cobalt, nickel, copper, zinc, strontium, zirconium, niobium, molybdenum and tin. It may be substituted with one kind.
[0076]
The positive electrode using the positive electrode active material mainly composed of the lithium transition metal composite oxide according to the present invention is preferably produced as follows. A positive electrode mixture is formed by mixing the lithium transition metal composite oxide powder according to the present invention with a carbon-based conductive agent such as acetylene black or graphite, a binder, and a solvent or dispersion medium of the binder. . The positive electrode mixture is made into a slurry or a kneaded material, applied or supported on a current collector 12 such as an aluminum foil, and press-rolled to form a positive electrode active material layer on the current collector 12.
[0077]
As the binder, polyvinylidene fluoride, polytetrafluoroethylene, polyamide acrylic resin, or the like can be used.
[0078]
It is considered that the lithium transition metal composite oxide according to the present invention has good mixing properties with the conductive agent powder, and the internal resistance of the battery is reduced. For this reason, the charge / discharge characteristics, particularly the discharge capacity, are improved. Further, when kneaded with the binder, the lithium transition metal composite oxide of the present invention is excellent in fluidity, easily entangled with the polymer of the binder, and has excellent binding properties. Furthermore, since it is spherical without containing coarse particles, the surface of the coating film surface of the produced positive electrode 13 is excellent in smoothness. For this reason, the coating surface of the positive electrode plate has excellent binding properties and is not easily peeled off, and the surface is smooth and the lithium ion on and off of the coating surface due to charging / discharging is uniformly performed, so the cycle charge / discharge characteristics are remarkably improved. Is obtained.
[0079]
For example, as the negative electrode active material, metallic lithium, a lithium alloy, or a compound capable of occluding and releasing lithium ions can be used. As the lithium alloy, for example, a LiAl alloy, a LiSn alloy, a LiPb alloy, or the like can be used. As a compound capable of occluding and releasing lithium ions, carbon materials such as graphite and graphite can be used. Further, an oxide capable of inserting / extracting lithium ions such as tin oxide and titanium oxide may be used.
[0080]
The electrolyte solution is not particularly limited as long as it is a compound that does not change or decompose at the operating voltage. Examples of solvents that can be used include organic solvents such as dimethoxyethane, diethoxyethane, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl formate, γ-butyrolactone, 2-methyltetrahydrofuran, dimethyl sulfoxide, and sulfolane. In addition, two or more kinds selected from the above-mentioned organic solvent group may be mixed and used.
[0081]
Examples of the electrolyte that can be used include lithium salts such as lithium perchlorate, lithium tetrafluoroborate, lithium tetrafluorophosphate, and lithium trifluoromethanoate. The above solvent and electrolyte are mixed and used as an electrolytic solution. Here, a gelling agent or the like may be added and used as a gel, or may be used after being absorbed in a hygroscopic polymer. Further, a solid electrolyte having conductivity of inorganic or organic lithium ions may be used.
[0082]
Furthermore, as the separator 14, a porous film made of polyethylene, polypropylene, or the like can be used. Using the positive electrode active material for a non-aqueous electrolyte secondary battery according to the present invention, the negative electrode active material, the electrolytic solution, and the separator, a non-aqueous electrolyte secondary battery is obtained in accordance with a conventional method. Thereby, the outstanding battery characteristic which was not able to be achieved conventionally is realizable.
[0083]
Further, a strip-shaped positive electrode configured by forming a positive electrode active material layer using the positive electrode active material for a non-aqueous electrolyte secondary battery according to the present invention as a positive electrode active material on both surfaces of the strip-shaped positive electrode current collector, Each of the negative electrode active material layers includes a negative electrode active material layer formed on each side of the negative electrode current collector, and each of the negative electrode active material layers is laminated in a state where the positive electrode and the negative electrode are stacked with a band separator. By winding, a spiral wound body in which a strip separator is interposed between the strip-shaped positive electrode and the strip-shaped negative electrode can be formed into a non-aqueous electrolyte secondary battery. With this configuration, the manufacturing process is simple, the positive electrode active material layer and the negative electrode active material layer are not easily cracked or peeled off from the strip separator, the battery capacity can be increased, and the energy density can be increased. . In particular, the positive electrode active material for a non-aqueous electrolyte secondary battery according to the present invention has a high electrode plate density and excellent filling properties, and is easily compatible with a binder. Therefore, the positive electrode has a high charge / discharge capacity and excellent binding properties and surface smoothness, so that the positive electrode active material layer can be prevented from being cracked or peeled off.
[0084]
The shape of the nonaqueous electrolyte secondary battery may be a cylindrical shape, a coin shape, a square shape, or the like.
[0085]
(Applications for non-aqueous electrolyte secondary batteries)
The application of the non-aqueous electrolyte secondary battery using the positive electrode active material for a non-aqueous electrolyte secondary battery according to the present invention is not particularly limited. For example, notebook computers, pen input computers, pocket computers, notebook word processors, pocket word processors, electronic book players, mobile phones, cordless phones, electronic notebooks, calculators, LCD TVs, electric shavers, electric tools, electronic translators, car phones , Portable printer, transceiver, pager, handy terminal, portable copy, voice input device, memory card, backup power supply, tape recorder, radio, headphone stereo, handy cleaner, portable CD, video movie, navigation system, etc. Can be used. Also lighting equipment, air conditioner, TV, stereo, water heater, refrigerator, oven microwave, dishwasher, washing machine, dryer, game machine, toy, road conditioner, medical equipment, automobile, electric car, golf cart, electric cart It can be used as a power source for power storage systems. It can also be used for civilian use, military use, and space use.
[0086]
Hereinafter, although the Example is given and demonstrated about the positive electrode active material for nonaqueous electrolyte secondary batteries which concerns on this invention, it is not limited to this Example.
[0087]
【Example】
[Example 1]
A sodium hydrogen carbonate aqueous solution was added to an aqueous solution containing manganese ions and magnesium ions having a predetermined composition ratio to coprecipitate manganese and magnesium to obtain a coprecipitate.
The obtained coprecipitate was filtered, washed with water and dried, and then the first coprecipitate was left as it was, and the second coprecipitate was mixed with 300 ppm of orthoboric acid. The first coprecipitate was mixed with lithium carbonate so as to have a predetermined composition ratio, and baked in an air atmosphere at a temperature of 930 ° C. for 12 hours. The second coprecipitate was mixed with lithium carbonate so as to have a predetermined composition ratio, and baked in an air atmosphere at a temperature of 930 ° C. for 12 hours. Thus, a lithium transition metal composite oxide having a first particle size distribution and a primary particle diameter of 4 μm and a lithium transition metal composite oxide having a second particle size distribution and a primary particle diameter of 20 μm were obtained.
Lithium transition having a first particle size distribution and a first particle group made of a lithium transition metal composite oxide having a primary particle size of 4 μm and a second particle size distribution having a primary particle size of 20 μm A second particle group composed of a second particle group composed of a metal composite oxide was selected, and the selected first particle group and second particle group were mixed. The mixing ratio of the lithium transition metal composite oxide that is the first particle group of the lithium transition metal composite oxide that is the second particle group and the lithium transition metal composite oxide that is the second particle group is 70 wt%. %, And the mixing ratio with respect to the total of the lithium transition metal composite oxide that is the first particle group and the lithium transition metal composite oxide that is the second particle group of the lithium transition metal composite oxide that is the first particle group is 30% by weight. Thus Li_1.072Mn_1.914Mg_0.01B_0.0035O₄was gotten.
[0088]
(Evaluation of positive electrode active material for non-aqueous electrolyte secondary battery)
The positive electrode active material for a non-aqueous electrolyte secondary battery according to the present invention performs composition analysis, specific surface area, and particle size distribution measurement by the following methods. In addition, a test battery is prepared and evaluated.
[0089]
(Composition analysis)
A predetermined amount of a positive electrode active material for a non-aqueous electrolyte secondary battery is dissolved in nitric acid, and the content of each constituent element other than halogen elements and oxygen is quantified by plasma emission spectroscopy (ICP) analysis. A predetermined amount of the positive electrode active material for a non-aqueous electrolyte secondary battery is added to pure water and stirred to obtain a supernatant aqueous solution. The halogen element in the supernatant aqueous solution is quantified by an ion meter using an anion selective electrode as an indicator electrode.
[0090]
(Powder evaluation)
The specific surface area of the positive electrode active material for a non-aqueous electrolyte secondary battery is measured by a constant pressure BET adsorption method using nitrogen gas. The median diameter is obtained by measuring the particle size distribution by the laser diffraction scattering method, obtaining an integrated distribution using the logarithm of the volume-based particle diameter, and the particle diameter when occupying 50% of the entire lithium transition metal composite oxide powder, Measure as particle size with 50% oversize. The primary particle size is measured using an image analysis method (microscope method).
[0091]
(Measurement of crystallite diameter)
Measurement is performed using RINT2500V manufactured by Rigaku Denki Co., Ltd. CuKα1 is used as the X-ray source, and the X-ray diffraction pattern is measured at a tube current of 100 mA and a tube voltage of 40 kV. It is calculated by the Scherrer formula expressed by the following formula from the diffraction peak due to the (400) plane.
[0092]
[Expression 1]

[0093]
In the equation, D is the crystallite size (Å), K is the Scherrer constant (K = 1.05 when β is calculated from the integral width), and λ is the wavelength of the X-ray source (CuKα1 = 1.540562Å). , Β is the width (radian) of the diffraction line spread depending on the crystallite size, and θ is the diffraction angle 2θ / 2 (degree).
[0094]
(Production of lithium ion secondary battery)
To a normal methylpyrrolidone solution containing 5 parts by weight of polyvinylidene fluoride, 90 parts by weight of lithium transition metal composite oxide powder as a positive electrode active material and 5 parts by weight of carbon powder as a conductive agent were added and kneaded to prepare a paste. This is applied to an aluminum electrode plate by a doctor blade method and dried to obtain a positive electrode plate. Similarly, a carbon material is used as the negative electrode active material and applied to the copper electrode plate to produce a negative electrode plate. A porous propylene film is used as a separator, and LiPF is used as a mixed solvent of ethylene carbonate: diethyl carbonate = 1: 1 (volume ratio) as an electrolytic solution.₆A lithium ion secondary battery is manufactured using a solution in which is dissolved at a concentration of 1 mol / l. In this embodiment, a positive electrode plate, a negative electrode plate, and a separator are formed into a thin sheet, wound, and stored in a battery case of a metal laminate resin film to obtain a laminate type battery.
[0096]
(Measurement of electrode plate density)
A paste was prepared by kneading 95 parts by weight of a lithium transition metal composite oxide powder, which is a positive electrode active material, and a normal methylpyrrolidone solution containing 5 parts by weight of polyvinylidene fluoride, and this was applied to an aluminum electrode plate by a doctor blade method. It is applied and dried to form a positive electrode plate. After the positive electrode plate is cut into a predetermined size (2 × 2.5 cm), the electrode plate is pressed with a uniaxial press, and the electrode plate density is obtained from the thickness and weight of the electrode plate after pressurization.
[0097]
  (Dry out evaluation)
  A paste was prepared by kneading 95 parts by weight of a lithium transition metal composite oxide powder, which is a positive electrode active material, and a normal methylpyrrolidone solution containing 5 parts by weight of polyvinylidene fluoride, and this was applied to an aluminum electrode plate by a doctor blade method. It is applied and dried to form a positive electrode plate.After cutting the positive electrode to a predetermined size, press the electrode plate with a uniaxial press,The positive electrode plate is placed in a glass container and immersed in a propylene carbonate solution in an argon box. After making a vacuum for 3 minutes to allow the propylene carbonate solution to penetrate into the positive electrode plate, the positive electrode plate is taken out from the argon box and the positive electrode plate is weighed every hour. The amount of decrease in the propylene carbonate solution is calculated by subtracting the weight of the first positive electrode plate from the weight of the positive electrode plate per hour. If the amount of decrease in propylene carbonate is large, it is easy to move the electrolyte, and it can be determined that dryout can be prevented. If the amount of decrease in propylene carbonate is small, it can be determined that the electrolyte solution is difficult to move and that dryout is likely to occur.
[0098]
The results are shown in Table 1 and FIG. The particle size distribution is shown in FIG.
[0099]
[Example 2]
A sodium hydrogen carbonate aqueous solution was added to an aqueous solution containing manganese ions and magnesium ions having a predetermined composition ratio to coprecipitate manganese and magnesium to obtain a coprecipitate.
The obtained coprecipitate was filtered, washed with water, and dried. Then, the first coprecipitate was left as it was, and 200 ppm of orthoboric acid was mixed with the second coprecipitate. The first coprecipitate was mixed with lithium carbonate so as to have a predetermined composition ratio, and baked in an air atmosphere at a temperature of 930 ° C. for 12 hours. The second coprecipitate was mixed with lithium carbonate so as to have a predetermined composition ratio, and baked in an air atmosphere at a temperature of 930 ° C. for 12 hours. Thus, a lithium transition metal composite oxide having a first particle size distribution and a primary particle size of 4 μm and a lithium transition metal composite oxide having a second particle size distribution and a primary particle size of 15 μm were obtained.
Lithium transition having a first particle size distribution and a first particle group made of a lithium transition metal composite oxide having a primary particle size of 4 μm and a second particle size distribution having a primary particle size of 15 μm A second particle group composed of a second particle group composed of a metal composite oxide was selected, and the selected first particle group and second particle group were mixed. The mixing ratio of the lithium transition metal composite oxide that is the first particle group of the lithium transition metal composite oxide that is the second particle group and the lithium transition metal composite oxide that is the second particle group is 70 wt%. %, And the mixing ratio with respect to the total of the lithium transition metal composite oxide that is the first particle group and the lithium transition metal composite oxide that is the second particle group of the lithium transition metal composite oxide that is the first particle group is 30% by weight. Thus Li_1.073Mn_1.915Mg_0.01B_0.0023O₄was gotten.
[0100]
The particle size distribution is shown in FIG.
[0101]
Example 3
A sodium hydrogen carbonate aqueous solution was added to an aqueous solution containing manganese ions and magnesium ions having a predetermined composition ratio to coprecipitate manganese and magnesium to obtain a coprecipitate.
The obtained coprecipitate was filtered, washed with water, and dried. Then, the first coprecipitate was left as it was, and the second coprecipitate was mixed with 100 ppm of orthoboric acid. The first coprecipitate was mixed with lithium carbonate so as to have a predetermined composition ratio, and baked in an air atmosphere at a temperature of 930 ° C. for 12 hours. The second coprecipitate was mixed with lithium carbonate so as to have a predetermined composition ratio, and baked in an air atmosphere at a temperature of 930 ° C. for 12 hours. Thus, a lithium transition metal composite oxide having a first particle size distribution and a primary particle size of 4 μm and a lithium transition metal composite oxide having a second particle size distribution and a primary particle size of 8 μm were obtained.
Lithium transition having a first particle size distribution and a first particle group made of a lithium transition metal composite oxide having a primary particle size of 4 μm and a second particle size distribution having a primary particle size of 8 μm A second particle group composed of a second particle group composed of a metal composite oxide was selected, and the selected first particle group and second particle group were mixed. The mixing ratio of the lithium transition metal composite oxide that is the first particle group of the lithium transition metal composite oxide that is the second particle group and the lithium transition metal composite oxide that is the second particle group is 70 wt%. %, And the mixing ratio with respect to the total of the lithium transition metal composite oxide that is the first particle group and the lithium transition metal composite oxide that is the second particle group of the lithium transition metal composite oxide that is the first particle group is 30% by weight. Thus Li_1.073Mn_1.916Mg_0.01B_0.0012O₄was gotten.
[0102]
Hereinafter, the positive electrode active material for the nonaqueous electrolyte secondary battery was evaluated in the same manner as in Example 1. The results are shown in Table 1 and FIG. The particle size distribution is shown in FIG.
[0103]
Example 4
A sodium hydrogen carbonate aqueous solution was added to an aqueous solution containing manganese ions and magnesium ions having a predetermined composition ratio to coprecipitate manganese and magnesium to obtain a coprecipitate.
The obtained coprecipitate was filtered, washed with water and dried, and then the first coprecipitate was left as it was, and the second coprecipitate was mixed with 300 ppm of orthoboric acid. The first coprecipitate was mixed with lithium carbonate so as to have a predetermined composition ratio, and baked in an air atmosphere at a temperature of 930 ° C. for 12 hours. The second coprecipitate was mixed with lithium carbonate so as to have a predetermined composition ratio, and baked in an air atmosphere at a temperature of 930 ° C. for 12 hours. Thus, a lithium transition metal composite oxide having a first particle size distribution and a primary particle diameter of 4 μm and a lithium transition metal composite oxide having a second particle size distribution and a primary particle diameter of 20 μm were obtained.
Lithium transition having a first particle size distribution and a first particle group made of a lithium transition metal composite oxide having a primary particle size of 4 μm and a second particle size distribution having a primary particle size of 20 μm A second particle group composed of a second particle group composed of a metal composite oxide was selected, and the selected first particle group and second particle group were mixed. The mixing ratio of the lithium transition metal composite oxide that is the first particle group of the lithium transition metal composite oxide that is the second particle group and the lithium transition metal composite oxide that is the second particle group is 60% by weight. %, And the mixing ratio with respect to the total of the lithium transition metal composite oxide that is the first particle group and the lithium transition metal composite oxide that is the second particle group of the lithium transition metal composite oxide that is the first particle group is 40% by weight. Thus Li_1.072Mn_1.915Mg_0.01B_0.003O₄was gotten.
[0104]
The particle size distribution is shown in FIG.
[0105]
[Comparative Example 1]
A sodium hydrogen carbonate aqueous solution was added to an aqueous solution containing manganese ions and magnesium ions having a predetermined composition ratio to coprecipitate manganese and magnesium to obtain a coprecipitate.
The obtained coprecipitate was filtered, washed with water, dried, mixed with lithium carbonate so as to have a predetermined composition ratio, and calcined at 930 ° C. for 12 hours in an air atmosphere. And pulverize in a mortar_1.073Mn_1.917Mg_0.01O₄was gotten.
[0106]
Hereinafter, the positive electrode active material for the nonaqueous electrolyte secondary battery was evaluated in the same manner as in Example 1. The results are shown in Table 1 and FIG. The particle size distribution is shown in FIG.
[0111]
  As is apparent from Table 1 and FIG. 1, it can be seen that the positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention has an improved electrode plate density as compared with Comparative Example 1. I also know that it can prevent dryoutThe
[0112]
  On the other hand, Comparative Example 1 is an electrode plate denseDegreeIt is inferior to the positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention. In addition, dryout cannot be prevented.
[0113]
[Table 1]

[0114]
In Example 1, Example 2 and Example 3, the mixing ratio of the lithium transition metal composite oxide which is the first particle group and the lithium transition metal composite oxide which is the second particle group is changed, The electrode plate density was measured when it was changed. The results are shown in Tables 2 to 4 and FIG.
[0115]
[Table 2]

[0116]
[Table 3]

[0117]
[Table 4]

[0118]
From this result, the mixing ratio with respect to the sum total of the lithium transition metal composite oxide which is the first particle group and the lithium transition metal composite oxide which is the second particle group of the lithium transition metal composite oxide which is the second particle group Is 60 wt% to 70 wt%, and the lithium transition metal composite oxide that is the first particle group of the lithium transition metal composite oxide that is the first particle group and the lithium transition metal that is the second particle group It can be seen that the mixing ratio relative to the total of the composite oxides is more preferably 30% by weight to 40% by weight.
[0129]
  As described above, the positive electrode active material for a non-aqueous electrolyte secondary battery according to the present invention has excellent battery characteristics that can improve the electrode plate density and prevent dryout.. ShiTherefore, the positive electrode active material for a non-aqueous electrolyte secondary battery of the present invention is suitably used for a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery.
[Brief description of the drawings]
FIG. 1 is a graph showing changes in electrode plate density accompanying changes in press pressure.
FIG. 2 is a graph showing changes in electrode plate density accompanying changes in the mixing ratio of a lithium transition metal composite oxide that is a first particle group and a lithium transition metal composite oxide that is a second particle group.
3 is a graph showing the particle size distribution of Example 1. FIG.
4 is a graph showing the particle size distribution of Example 2. FIG.
5 is a graph showing the particle size distribution of Example 3. FIG.
6 is a graph showing the particle size distribution of Example 4. FIG.
7 is a graph showing the particle size distribution of Comparative Example 1. FIG.
8 is a graph showing the particle size distribution of Comparative Example 2. FIG.
9 is a graph showing the particle size distribution of Comparative Example 3. FIG.
FIG. 10 is a diagram showing a lithium transition metal composite oxide having a spinel structure.
FIG. 11 is a schematic view of binding of active materials.
FIG. 12 is a cross-sectional view of a cylindrical battery.
FIG. 13 is a diagram showing a structure of a coin-type battery.
FIG. 14 is a diagram showing a structure of a prismatic battery.
[Explanation of symbols]
1 ... 8a site
2 ... 32e site
3 ... 16d site
4 ... Binder
5 ... Active material
11 ... Negative electrode
12 ... current collector
13 ... Positive electrode
14 ... Separator
21 ... 1st particle size distribution
22 ... second particle size distribution

Claims (2)

A positive electrode active material for a non-aqueous electrolyte secondary battery having at least a lithium transition metal composite oxide having a spinel structure,
The lithium transition metal composite oxide has a first lithium manganate having a primary particle diameter of 2 μm to 8 μm and a second lithium manganate having a primary particle diameter of 8 μm to 150 μm ,
The primary particle diameter of said 1st lithium manganate is smaller than the primary particle diameter of the 2nd lithium manganate containing 50 ppm-500 ppm of boron, The positive electrode active material for nonaqueous electrolyte secondary batteries characterized by the above-mentioned. The mixing ratio (% by weight) of the first lithium manganate to the total of the first lithium manganate and the second lithium manganate is such that the second lithium manganate and the first lithium manganate 2. The positive electrode active material for a non-aqueous electrolyte secondary battery according to claim 1, wherein the amount is less than a mixing ratio (% by weight) with respect to a total amount of the second lithium manganate.

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