JP2014191925A - Cathode active material for lithium ion battery, cathode for lithium ion battery, and lithium ion battery - Google Patents
Cathode active material for lithium ion battery, cathode for lithium ion battery, and lithium ion battery Download PDFInfo
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- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 55
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 55
- 239000006182 cathode active material Substances 0.000 title abstract 5
- 239000002245 particle Substances 0.000 claims abstract description 51
- 238000006073 displacement reaction Methods 0.000 claims abstract description 32
- 239000000203 mixture Substances 0.000 claims abstract description 28
- 229910052751 metal Inorganic materials 0.000 claims abstract description 27
- 239000002184 metal Substances 0.000 claims abstract description 27
- 239000011163 secondary particle Substances 0.000 claims abstract description 19
- 229910003460 diamond Inorganic materials 0.000 claims abstract description 8
- 239000010432 diamond Substances 0.000 claims abstract description 8
- 238000003825 pressing Methods 0.000 claims abstract description 6
- 239000007774 positive electrode material Substances 0.000 claims description 72
- 238000012669 compression test Methods 0.000 claims description 19
- 229910052748 manganese Inorganic materials 0.000 claims description 8
- 229910052782 aluminium Inorganic materials 0.000 claims description 6
- 229910052802 copper Inorganic materials 0.000 claims description 4
- 229910052749 magnesium Inorganic materials 0.000 claims description 4
- 229910052725 zinc Inorganic materials 0.000 claims description 4
- 229910052726 zirconium Inorganic materials 0.000 claims description 4
- 229910014211 My O Inorganic materials 0.000 claims description 3
- 238000005336 cracking Methods 0.000 abstract description 6
- 238000004519 manufacturing process Methods 0.000 abstract description 5
- 239000011248 coating agent Substances 0.000 abstract description 4
- 238000000576 coating method Methods 0.000 abstract description 4
- 238000011068 loading method Methods 0.000 abstract description 2
- 229910013282 LiNiMO Inorganic materials 0.000 abstract 1
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 15
- 238000010304 firing Methods 0.000 description 15
- 229910052744 lithium Inorganic materials 0.000 description 15
- 239000011164 primary particle Substances 0.000 description 7
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 6
- 230000000052 comparative effect Effects 0.000 description 6
- 238000011156 evaluation Methods 0.000 description 6
- 239000000463 material Substances 0.000 description 6
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 5
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 5
- 229910052760 oxygen Inorganic materials 0.000 description 5
- 239000001301 oxygen Substances 0.000 description 5
- 239000000843 powder Substances 0.000 description 5
- 239000002243 precursor Substances 0.000 description 5
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 4
- 239000011230 binding agent Substances 0.000 description 4
- QHGJSLXSVXVKHZ-UHFFFAOYSA-N dilithium;dioxido(dioxo)manganese Chemical compound [Li+].[Li+].[O-][Mn]([O-])(=O)=O QHGJSLXSVXVKHZ-UHFFFAOYSA-N 0.000 description 4
- 238000007599 discharging Methods 0.000 description 4
- 238000000034 method Methods 0.000 description 4
- 239000002994 raw material Substances 0.000 description 4
- 229910012851 LiCoO 2 Inorganic materials 0.000 description 3
- 229910015643 LiMn 2 O 4 Inorganic materials 0.000 description 3
- 229910013290 LiNiO 2 Inorganic materials 0.000 description 3
- 229910002651 NO3 Inorganic materials 0.000 description 3
- 230000002776 aggregation Effects 0.000 description 3
- 230000006835 compression Effects 0.000 description 3
- 238000007906 compression Methods 0.000 description 3
- 238000001816 cooling Methods 0.000 description 3
- 239000010419 fine particle Substances 0.000 description 3
- 239000011888 foil Substances 0.000 description 3
- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical compound [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 description 3
- 239000002244 precipitate Substances 0.000 description 3
- 239000012266 salt solution Substances 0.000 description 3
- 150000003839 salts Chemical class 0.000 description 3
- 238000005406 washing Methods 0.000 description 3
- QTBSBXVTEAMEQO-UHFFFAOYSA-M Acetate Chemical compound CC([O-])=O QTBSBXVTEAMEQO-UHFFFAOYSA-M 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 2
- 238000005054 agglomeration Methods 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 239000002482 conductive additive Substances 0.000 description 2
- 239000004020 conductor Substances 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 229910052808 lithium carbonate Inorganic materials 0.000 description 2
- 150000002642 lithium compounds Chemical class 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 239000002002 slurry Substances 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-L sulfate group Chemical group S(=O)(=O)([O-])[O-] QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 2
- 229910052723 transition metal Inorganic materials 0.000 description 2
- 229910000314 transition metal oxide Inorganic materials 0.000 description 2
- 150000003624 transition metals Chemical class 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 229910001290 LiPF6 Inorganic materials 0.000 description 1
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 1
- 229910006020 NiCoAl Inorganic materials 0.000 description 1
- 229910005800 NiMnCo Inorganic materials 0.000 description 1
- 239000011149 active material Substances 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 229910017052 cobalt Inorganic materials 0.000 description 1
- 239000010941 cobalt Substances 0.000 description 1
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000002950 deficient Effects 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 239000003792 electrolyte Substances 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000009616 inductively coupled plasma Methods 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 229910000625 lithium cobalt oxide Inorganic materials 0.000 description 1
- 229910003002 lithium salt Inorganic materials 0.000 description 1
- 159000000002 lithium salts Chemical class 0.000 description 1
- BFZPBUKRYWOWDV-UHFFFAOYSA-N lithium;oxido(oxo)cobalt Chemical compound [Li+].[O-][Co]=O BFZPBUKRYWOWDV-UHFFFAOYSA-N 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- FGHSTPNOXKDLKU-UHFFFAOYSA-N nitric acid;hydrate Chemical compound O.O[N+]([O-])=O FGHSTPNOXKDLKU-UHFFFAOYSA-N 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 239000007800 oxidant agent Substances 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 230000008707 rearrangement Effects 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
- H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
- H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/021—Physical characteristics, e.g. porosity, surface area
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Inorganic Chemistry (AREA)
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- Manufacturing & Machinery (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
Description
本発明は、リチウムイオン電池用正極活物質、リチウムイオン電池用正極、及び、リチウムイオン電池に関する。 The present invention relates to a positive electrode active material for a lithium ion battery, a positive electrode for a lithium ion battery, and a lithium ion battery.
リチウムイオン電池の正極活物質には、一般にリチウム含有遷移金属酸化物が用いられている。具体的には、コバルト酸リチウム(LiCoO2)、ニッケル酸リチウム(LiNiO2)、マンガン酸リチウム(LiMn2O4)等であり、特性改善(高容量化、サイクル特性、保存特性、内部抵抗低減、レート特性)や安全性を高めるためにこれらを複合化することが進められている。車載用やロードレベリング用といった大型用途におけるリチウムイオン電池には、これまでの携帯電話用やパソコン用とは異なった特性が求められている。 Lithium-containing transition metal oxides are generally used as positive electrode active materials for lithium ion batteries. Specifically, lithium cobaltate (LiCoO 2 ), lithium nickelate (LiNiO 2 ), lithium manganate (LiMn 2 O 4 ), etc., improved characteristics (higher capacity, cycle characteristics, storage characteristics, reduced internal resistance) In order to improve the rate characteristics and safety, it is underway to combine them. Lithium ion batteries for large-scale applications such as in-vehicle use and load leveling are required to have different characteristics from those of conventional mobile phones and personal computers.
上記のようなコバルト酸リチウム(LiCoO2)、ニッケル酸リチウム(LiNiO2)、或いは、マンガン酸リチウム(LiMn2O4)は、例えば特許文献1に開示されているように、正極活物質に用いられる代表的な材料であるが、それぞれ長所短所がある。コバルト酸リチウムは、容量及び安全性などバランスのとれた材料であるが、コバルトはレアメタルという非常に希少な金属であるため、コストが高い。ニッケル酸リチウムは、非常に電池容量を持つが、安全性に乏しい。マンガン酸リチウムは、非常に熱的安定性があるが、容量が低い等の問題が報告されている。 Lithium cobaltate (LiCoO 2 ), lithium nickelate (LiNiO 2 ), or lithium manganate (LiMn 2 O 4 ) as described above is used for the positive electrode active material as disclosed in Patent Document 1, for example. These are typical materials, but each has advantages and disadvantages. Lithium cobalt oxide is a balanced material such as capacity and safety. However, since cobalt is a rare metal called a rare metal, the cost is high. Lithium nickelate has a very high battery capacity but poor safety. Lithium manganate is very thermally stable, but problems such as low capacity have been reported.
最近になり、高容量、安全性、コストの面からNiMnCo、NiCoAlに代表される三元系の正極活物質が用いられているが、例えば、この三元系の正極活物質がニッケル比率の高いものであるような場合では、それを用いて作製されたリチウムイオン二次電池が充放電されることにより正極活物質の粒子に割れ(クラック)が生じ、これによって電池寿命の劣化が起きると云われている。また、一般に、正極活物質を、導電助剤及びバインダーと混合することで正極合剤を調製し、これをアルミニウム箔等からなる集電体の片面または両面に塗布することで正極を作製している。正極合剤を集電体に塗布するとき、正極活物質の粒子に圧がかかり粒子が弾性又は塑性変形することがある。このような正極活物質の粒子の変形により、それを用いた正極合剤の集電体への塗布性が劣化するという問題がある。 Recently, ternary positive electrode active materials represented by NiMnCo and NiCoAl have been used from the viewpoint of high capacity, safety and cost. For example, this ternary positive electrode active material has a high nickel ratio. In such a case, the lithium ion secondary battery manufactured using the battery is charged and discharged, and the positive electrode active material particles are cracked. It has been broken. In general, a positive electrode active material is mixed with a conductive additive and a binder to prepare a positive electrode mixture, and this is applied to one or both sides of a current collector made of aluminum foil or the like to produce a positive electrode. Yes. When the positive electrode mixture is applied to the current collector, the positive electrode active material particles may be pressurized, and the particles may be elastically or plastically deformed. Due to such deformation of the positive electrode active material particles, there is a problem that applicability of the positive electrode mixture using the positive electrode material to the current collector is deteriorated.
本発明は、粒子の割れが良好に抑制され、これによって電池寿命等の電池特性が良好となり、且つ、電池作製時の正極活物質を用いた正極合剤の塗布性及び定着性が良好なリチウムイオン電池用正極活物質を提供することを課題とする。 According to the present invention, the cracking of the particles is satisfactorily suppressed, thereby improving the battery characteristics such as battery life, and the good applicability and fixability of the positive electrode mixture using the positive electrode active material at the time of battery preparation. It is an object to provide a positive electrode active material for an ion battery.
本発明者は、リチウムイオン二次電池が充放電されることによる正極活物質の粒子内の割れの発生を抑制するため、及び、正極合剤の塗布性及び定着性を向上させるために、正極活物質の粒子の強度に着目し、さらに踏み込んで検討し、単なる強度ではなく、正極活物質の粒子1単位の硬度、すなわち、微小圧縮硬度を所定範囲に制御することが、充放電後の粒子の割れの低減、及び、正極合剤塗布時の正極活物質の粒子の変形の抑制に非常に有効であることを見出した。また、正極活物質の組成を所定の組成とし、正極活物質の粒子径が均一とすることで、より一層、これらの特性が良好となることを見出した。 In order to suppress the occurrence of cracks in the particles of the positive electrode active material due to charging / discharging of the lithium ion secondary battery, and to improve the coating property and fixing property of the positive electrode mixture, Focusing on the strength of the particles of the active material, further study, it is possible to control the hardness of one unit particle of the positive electrode active material, that is, the fine compression hardness within a predetermined range, not just the strength, after charging and discharging. It was found that this method is very effective in reducing cracking and suppressing deformation of the positive electrode active material particles during application of the positive electrode mixture. Further, the inventors have found that these characteristics are further improved by setting the composition of the positive electrode active material to a predetermined composition and making the particle diameter of the positive electrode active material uniform.
上記知見を基礎にして完成した本発明は一側面において、組成式:LixNi1-yMyO2+α
(前記式において、Mは金属であり、0.9≦x≦1.2であり、0<y≦0.7であり、−0.1≦α≦0.1である。)
で表され、平均粒子径D50が7μm以上12μm以下であり、微小圧縮試験において、正極活物質の2次粒子の1粒子にダイヤモンド製の圧子によって負荷速度2.67mN/秒で設定荷重49mNまで負荷した時の平均機械強度が10MPa以上60MPa以下、且つ、粒子に圧子が当接して押圧を開始する位置から圧裂した位置までの圧子の移動距離を変位としたときの平均変位が0.2μm以上1μm以下であるリチウムイオン電池用正極活物質である。
In one aspect, the present invention completed based on the above knowledge has a composition formula: Li x Ni 1- y My O 2 + α
(In the above formula, M is a metal, 0.9 ≦ x ≦ 1.2, 0 <y ≦ 0.7, and −0.1 ≦ α ≦ 0.1.)
The average particle diameter D50 is 7 μm or more and 12 μm or less, and in a micro compression test, one particle of the secondary particles of the positive electrode active material is loaded to a set load of 49 mN at a load speed of 2.67 mN / sec with a diamond indenter. The average mechanical strength is 10 MPa or more and 60 MPa or less, and the average displacement is 0.2 μm or more when the movement distance of the indenter from the position where the indenter comes into contact with the particle to start pressing is the displacement It is a positive electrode active material for a lithium ion battery having a size of 1 μm or less.
本発明に係るリチウムイオン電池用正極活物質は一実施形態において、より良い前記平均機械強度が15MP以上60MP以下である。 In one embodiment, the positive electrode active material for a lithium ion battery according to the present invention has a better average mechanical strength of 15 MP or more and 60 MP or less.
本発明に係るリチウムイオン電池用正極活物質は別の一実施形態において、前記Mが、Mn、Co、Cu、Al、Zn、Mg及びZrから選択される1種以上である。 In another embodiment of the positive electrode active material for a lithium ion battery according to the present invention, the M is at least one selected from Mn, Co, Cu, Al, Zn, Mg, and Zr.
本発明に係るリチウムイオン電池用正極活物質は更に別の一実施形態において、前記Mが、Mn及びCoから選択される1種以上である。 In still another embodiment of the positive electrode active material for a lithium ion battery according to the present invention, the M is at least one selected from Mn and Co.
本発明に係るリチウムイオン電池用正極活物質は更に別の一実施形態において、前記平均機械強度及び平均変位が、微小圧縮試験において、正極活物質の2次粒子の1粒子にダイヤモンド製の圧子によって負荷速度2.67mN/秒未満で設定荷重49mNまで負荷した時のものである。 In another embodiment of the positive electrode active material for a lithium ion battery according to the present invention, the average mechanical strength and average displacement are determined by a diamond indenter on one of the secondary particles of the positive electrode active material in a micro compression test. When the load speed is less than 2.67 mN / sec and the set load is 49 mN.
本発明は、別の一側面において、本発明に係るリチウムイオン電池用正極活物質を用いたリチウムイオン電池用正極である。 In another aspect, the present invention is a positive electrode for a lithium ion battery using the positive electrode active material for a lithium ion battery according to the present invention.
本発明は、更に別の一側面において、本発明に係るリチウムイオン電池用正極を用いたリチウムイオン電池である。 In still another aspect, the present invention is a lithium ion battery using the positive electrode for a lithium ion battery according to the present invention.
本発明によれば、粒子の割れが良好に抑制され、これによって電池寿命等の電池特性が良好となり、且つ、電池作製時の正極活物質を用いた正極合剤の塗布性及び定着性が良好なリチウムイオン電池用正極活物質を提供することができる。 According to the present invention, the cracking of the particles is satisfactorily suppressed, thereby improving the battery characteristics such as the battery life, and the coating property and fixing property of the positive electrode mixture using the positive electrode active material at the time of battery production are good. A positive electrode active material for a lithium ion battery can be provided.
(リチウムイオン電池用正極活物質の構成)
本発明のリチウムイオン電池用正極活物質の材料としては、一般的なリチウムイオン電池用正極用の正極活物質として有用な化合物を広く用いることができるが、特に、コバルト酸リチウム(LiCoO2)、ニッケル酸リチウム(LiNiO2)、マンガン酸リチウム(LiMn2O4)等のリチウム含有遷移金属酸化物を用いるのが好ましい。このような材料を用いて作製される本発明のリチウムイオン電池用正極活物質は、
組成式:LixNi1-yMyO2+α
(前記式において、Mは金属であり、0.9≦x≦1.2であり、0<y≦0.7であり、−0.1≦α≦0.1である。)
で表される。
また、Mは、好ましくはMn、Co、Cu、Al、Zn、Mg及びZrから選択される1種以上であり、より好ましくはMn及びCoから選択される1種以上である。
(Configuration of positive electrode active material for lithium ion battery)
As a material of the positive electrode active material for lithium ion batteries of the present invention, compounds useful as a positive electrode active material for general positive electrodes for lithium ion batteries can be widely used. In particular, lithium cobaltate (LiCoO 2 ), It is preferable to use lithium-containing transition metal oxides such as lithium nickelate (LiNiO 2 ) and lithium manganate (LiMn 2 O 4 ). The positive electrode active material for a lithium ion battery of the present invention produced using such a material is
Composition formula: Li x Ni 1- y My O 2 + α
(In the above formula, M is a metal, 0.9 ≦ x ≦ 1.2, 0 <y ≦ 0.7, and −0.1 ≦ α ≦ 0.1.)
It is represented by
M is preferably at least one selected from Mn, Co, Cu, Al, Zn, Mg and Zr, more preferably at least one selected from Mn and Co.
本発明のリチウムイオン電池用正極活物質は、一次粒子、一次粒子が凝集して形成された二次粒子、又は、一次粒子及び二次粒子の混合物で構成されている。これらの一次粒子、一次粒子が凝集して形成された二次粒子、又は、一次粒子及び二次粒子の混合物の平均粒子径D50は7μm以上12μm以下である。平均粒子径D50が7μm以上12μm以下であれば、ばらつきが抑制された粉体となり、リチウムイオン電池の電極作製時の正極活物質を含んだ正極合剤の均一な塗布が可能となり、さらに電極組成のばらつきを抑制することができる。このため、リチウムイオン電池に用いたときにレート特性及びサイクル特性等の電池特性が良好となる。平均粒子径D50は、好ましくは7μm以上9μm以下である。 The positive electrode active material for a lithium ion battery of the present invention is composed of primary particles, secondary particles formed by aggregation of primary particles, or a mixture of primary particles and secondary particles. The average particle diameter D50 of these primary particles, secondary particles formed by agglomeration of primary particles, or a mixture of primary particles and secondary particles is 7 μm or more and 12 μm or less. If the average particle diameter D50 is 7 μm or more and 12 μm or less, it becomes a powder in which variation is suppressed, and it becomes possible to uniformly apply a positive electrode mixture containing a positive electrode active material at the time of preparing an electrode of a lithium ion battery. Can be suppressed. For this reason, when used in a lithium ion battery, battery characteristics such as rate characteristics and cycle characteristics are improved. The average particle diameter D50 is preferably 7 μm or more and 9 μm or less.
本発明に係る微小圧縮試験は、微小圧縮試験装置を用いて行うことができる。微小圧縮試験装置は、試験対象となる粒子を載せる平台と、平台に乗せた粒子を押圧して圧縮するための、例えば50〜500μm径の押圧面を有する、ダイヤモンド製の圧子とを備えている。微小圧縮試験装置は、電磁力によって例えば9.8〜4903mNの負荷を圧子から粒子へかけることが可能であり、これによって、例えば1〜500μm径の粒子を1粒ずつ、すなわち1粒子ずつ圧縮することができる。試料については、顕微鏡により正極活物質の2次粒子であることを確認し、これを測定対象の粒子とする。本発明のリチウムイオン電池用正極活物質は、微小圧縮試験において、正極活物質の2次粒子の1粒子に、負荷速度2.67mN/秒で設定荷重49mNを負荷した時の平均機械強度が10MPa以上60MPa以下、且つ、平均変位が0.2μm以上1μm以下である。本発明に係る微小圧縮試験では、試験対象とする正極活物質の2次粒子を数十〜数百粒採取し、これを1粒子ずつ試験して上記機械強度及び変位を測定し、測定結果の平均値を求めてそれぞれ平均機械強度及び平均変位とする。粒子に負荷速度2.67mN/秒で設定荷重49mNまで負荷して粒子を圧縮変位させていき、変位が急激に増加したポイント(圧縮に要する試験力が一定となるポイント)を粒子が圧裂したポイントと判定し、当該ポイントにおける機械強度及び変位を求める。
すなわち、変位は微小圧縮試験装置の圧子の移動距離を示し、より具体的には、平台に乗せた粒子に圧子が当接して押圧を開始する位置から、粒子を圧縮変位させていき、変位が急激に増加した位置(圧裂した位置)までの圧子の移動距離で求められる。
また、機械強度(CS)は、JIS R 1639−5より、下記式(1)で求める。
CS(MPa)=2.48×P/πd2 (1)
〔P:試験力(N)、d:粒子径(nm)〕
正極活物質の2次粒子は、微小な粒子(一次粒子)が集合してなるものであるため、微小圧縮試験装置において、荷重を急激に加えると、急な変形等が生じてしまい、目的とする正極活物質の平均機械強度及び平均変位を正確に測定することが困難となる。そこで、本発明では、正極活物質の2次粒子の1粒子に、負荷速度2.67mN/秒というゆっくりとした速度で荷重を負荷することにより、正確な平均機械強度及び平均変位を測定している。また、本発明のリチウムイオン電池用正極活物質の平均機械強度及び平均変位は、微小圧縮試験において、正極活物質の2次粒子の1粒子にダイヤモンド製の圧子によって負荷速度2.67mN/秒未満で設定荷重49mNまで負荷した時のものであってもよい。なお、本発明にて上記平均機械強度及び平均変位の範囲であると確認できた最小の負荷速度は0.446mN/秒であった。
正極活物質の2次粒子の1粒子の上記機械強度が10MPa以上60MPa以下で、且つ、平均変位が0.2μm以上1μm以下であれば、リチウムイオン二次電池が充放電されることによる正極活物質の粒子内の割れの発生が抑制される。また、このような正極活物質を用いた正極合剤の塗布性及び定着性が向上する。上記機械強度が10MPa未満であれば、正極活物質の強度が不足し、充放電後の粒子の割れが増大する。また、上記機械強度が60MPaを超えると、AS樹脂のように硬質になり、かえって割れやすいという問題が生じる(衝撃強度が弱い)可能性がある。上記変位が0.2μm未満であれば、正極活物質の強度が不足し、充放電後の粒子の割れが増大する。また、上記変位が1μmを超えると、軟質な粒子であり、焼成および焼結が不十分であり、ぐずぐずとつぶれて破壊強度が得られないなど結晶性の不良なものが生じている可能性がある。本発明は、正極活物質全体の強度ではなく、さらに踏み込んで検討され、正極活物質の粒子1単位の機械強度及び変位を上記範囲に制御することが、充放電後の粒子の割れの低減、及び、正極合剤塗布時の正極活物質の粒子の変形の抑制に非常に有効であるという知見に基づくものである。このように二次粒子の1粒子の機械強度及び変位を制御することで、結晶性及び電池特性が良好な正極材活物質を作製することが可能となる。平均機械強度は好ましくは10MPa以上60MPa以下であり、平均機械強度は好ましくは15MPa以上60MPa以下である。
The micro compression test according to the present invention can be performed using a micro compression test apparatus. The micro-compression test apparatus includes a flat table on which particles to be tested are placed, and a diamond indenter having a pressing surface with a diameter of, for example, 50 to 500 μm for pressing and compressing the particles placed on the flat table. . The micro-compression test apparatus can apply a load of, for example, 9.8 to 4903 mN from the indenter to the particles by electromagnetic force, thereby compressing particles having a diameter of, for example, 1 to 500 μm one by one, that is, one particle at a time. be able to. About a sample, it confirms that it is a secondary particle of a positive electrode active material with a microscope, and makes this a particle | grain of measuring object. The positive electrode active material for a lithium ion battery of the present invention has an average mechanical strength of 10 MPa when a set load of 49 mN is applied to one of the secondary particles of the positive electrode active material at a load speed of 2.67 mN / sec in a micro compression test. The average displacement is not less than 0.2 μm and not more than 1 μm. In the micro-compression test according to the present invention, several tens to several hundreds of secondary particles of the positive electrode active material to be tested are collected and tested one by one to measure the mechanical strength and displacement. The average value is obtained and set as the average mechanical strength and average displacement, respectively. The particle was compressed and displaced by loading the particle at a load speed of 2.67 mN / sec up to a set load of 49 mN, and the particle crushed at the point where the displacement increased rapidly (the point at which the test force required for compression becomes constant). The point is determined, and the mechanical strength and displacement at the point are obtained.
That is, the displacement indicates the moving distance of the indenter of the micro-compression test apparatus. More specifically, the particle is compressed and displaced from the position where the indenter comes into contact with the particle placed on the flat base and starts pressing, and the displacement is It is obtained from the distance of movement of the indenter to the position where it suddenly increased (the position where the crushing occurred).
Moreover, mechanical strength (CS) is calculated | required by following formula (1) from JISR1639-5.
CS (MPa) = 2.48 × P / πd 2 (1)
[P: test force (N), d: particle size (nm)]
Since the secondary particles of the positive electrode active material are formed by agglomeration of fine particles (primary particles), if a load is applied suddenly in a micro compression test apparatus, sudden deformation or the like occurs. It becomes difficult to accurately measure the average mechanical strength and average displacement of the positive electrode active material. Therefore, in the present invention, an accurate average mechanical strength and average displacement are measured by applying a load to one of the secondary particles of the positive electrode active material at a slow speed of 2.67 mN / sec. Yes. The average mechanical strength and average displacement of the positive electrode active material for a lithium ion battery of the present invention are less than 2.67 mN / sec with a diamond indenter applied to one secondary particle of the positive electrode active material in a micro compression test. It may be the one when a set load of 49 mN is applied. In the present invention, the minimum load speed that could be confirmed to be within the range of the average mechanical strength and the average displacement was 0.446 mN / sec.
When the mechanical strength of one of the secondary particles of the positive electrode active material is 10 MPa or more and 60 MPa or less and the average displacement is 0.2 μm or more and 1 μm or less, the positive electrode active due to charging / discharging of the lithium ion secondary battery is performed. Generation of cracks in the particles of the substance is suppressed. Moreover, the applicability | paintability and fixing property of a positive mix using such a positive electrode active material improve. When the mechanical strength is less than 10 MPa, the strength of the positive electrode active material is insufficient and cracking of the particles after charge / discharge increases. On the other hand, when the mechanical strength exceeds 60 MPa, there is a possibility that the material becomes hard like an AS resin and easily breaks (impact strength is weak). If the said displacement is less than 0.2 micrometer, the intensity | strength of a positive electrode active material will run short, and the crack of the particle | grains after charging / discharging will increase. Further, if the displacement exceeds 1 μm, the particles are soft, the firing and sintering are insufficient, and there is a possibility that a defective crystallinity such as crushing and failure strength cannot be obtained. is there. The present invention is not the strength of the entire positive electrode active material, but is further studied and controlling the mechanical strength and displacement of one unit of the positive electrode active material particles within the above range reduces the cracking of the particles after charge and discharge, And it is based on the knowledge that it is very effective for suppression of the deformation | transformation of the particle | grains of the positive electrode active material at the time of positive electrode mixture application | coating. In this way, by controlling the mechanical strength and displacement of one secondary particle, it is possible to produce a positive electrode active material having good crystallinity and battery characteristics. The average mechanical strength is preferably 10 MPa or more and 60 MPa or less, and the average mechanical strength is preferably 15 MPa or more and 60 MPa or less.
(リチウムイオン電池用正極及びそれを用いたリチウムイオン電池の構成)
本発明の実施形態に係るリチウムイオン電池用正極は、例えば、上述の構成のリチウムイオン電池用正極活物質と、導電助剤と、バインダーとを混合して調製した正極合剤をアルミニウム箔等からなる集電体の片面または両面に設けた構造を有している。また、本発明の実施形態に係るリチウムイオン電池は、このような構成のリチウムイオン電池用正極を備えている。
(Configuration of positive electrode for lithium ion battery and lithium ion battery using the same)
The positive electrode for a lithium ion battery according to an embodiment of the present invention includes, for example, a positive electrode mixture prepared by mixing a positive electrode active material for a lithium ion battery having the above-described configuration, a conductive additive, and a binder from an aluminum foil or the like. The current collector has a structure provided on one side or both sides. Moreover, the lithium ion battery which concerns on embodiment of this invention is equipped with the positive electrode for lithium ion batteries of such a structure.
(リチウムイオン電池用正極活物質の製造方法)
次に、本発明の実施形態に係るリチウムイオン電池用正極活物質の製造方法について詳細に説明する。
まず、金属塩溶液を作製する。当該金属は、Ni及び金属Mである。金属Mとしては、好ましくはMn、Co、Cu、Al、Zn、Mg及びZrから選択される1種以上であり、より好ましくはMn及びCoから選択される1種以上である。また、金属塩は硫酸塩、塩化物、硝酸塩、酢酸塩等であり、特に硝酸塩が好ましい。これは、焼成原料中に不純物として混入してもそのまま焼成できるため洗浄工程が省けることと、硝酸塩が酸化剤として機能し、焼成原料中の金属の酸化を促進する働きがあるためである。金属塩に含まれる各金属は、所望のモル比率となるように調整しておく。これにより、正極活物質中の各金属のモル比率が決定する。
(Method for producing positive electrode active material for lithium ion battery)
Next, the manufacturing method of the positive electrode active material for lithium ion batteries which concerns on embodiment of this invention is demonstrated in detail.
First, a metal salt solution is prepared. The metals are Ni and metal M. The metal M is preferably at least one selected from Mn, Co, Cu, Al, Zn, Mg and Zr, more preferably at least one selected from Mn and Co. The metal salt is sulfate, chloride, nitrate, acetate, etc., and nitrate is particularly preferable. This is because even if it is mixed as an impurity in the firing raw material, it can be fired as it is, so that the washing step can be omitted, and nitrate functions as an oxidant, and promotes the oxidation of the metal in the firing raw material. Each metal contained in the metal salt is adjusted so as to have a desired molar ratio. Thereby, the molar ratio of each metal in the positive electrode active material is determined.
次に、炭酸リチウムを純水に懸濁させ、その後、上記金属の金属塩溶液を投入して金属炭酸塩スラリーを作製する。このとき、スラリー中に微小粒のリチウム含有炭酸塩が析出する。なお、金属塩として硫酸塩や塩化物等熱処理時にそのリチウム化合物が反応しない場合は飽和炭酸リチウム溶液で洗浄した後、濾別する。硝酸塩や酢酸塩のように、そのリチウム化合物が熱処理中にリチウム原料として反応する場合は洗浄せず、そのまま濾別し、乾燥することにより焼成前駆体として用いることができる。
次に、濾別したリチウム含有炭酸塩を乾燥することにより、リチウム塩の複合体(リチウムイオン電池正極材用前駆体)の粉末を得る。
Next, lithium carbonate is suspended in pure water, and then the metal salt solution of the metal is added to prepare a metal carbonate slurry. At this time, fine particles of lithium-containing carbonate precipitate in the slurry. If the lithium compound does not react during heat treatment such as sulfate or chloride as a metal salt, it is washed with a saturated lithium carbonate solution and then filtered off. When the lithium compound reacts as a lithium raw material during the heat treatment, such as nitrate or acetate, it can be used as a calcined precursor by washing and drying as it is without washing.
Next, the lithium-containing carbonate separated by filtration is dried to obtain a lithium salt composite (precursor for lithium ion battery positive electrode material) powder.
次に、所定の大きさの容量を有する焼成容器を準備し、この焼成容器にリチウムイオン電池正極材用前駆体の粉末を充填する。次に、リチウムイオン電池正極材用前駆体の粉末が充填された焼成容器を、焼成炉へ移設し、焼成を行う。焼成は、昇温工程においては140〜170℃/hの昇温レートで850〜1000℃まで加熱し、続いて当該温度で所定時間保持する。降温工程においては、当該保持温度から300℃までは70〜90℃/hの降温レートで冷却し、さらにその際に空気を10m3/h以上、或いは、酸素を10m3/h以上の供給量で供給する。このような焼成条件により、昇温工程では均一に熱が入り、粒子同士の熱の伝導性が良好となる。また、降温工程では適度な降温レートで所定温度まで冷却し、且つ、適切な空気や酸素の供給によって、遷移金属層内の原子の再配列や遷移金属層の積層欠陥、酸素欠陥等の生成のような構造的変化が促進され、二次粒子の平均機械強度を10MPa以上60MPa以下、平均変位を0.2μm以上1μm以下に制御することができる。
また、101〜202KPaでの加圧下で焼成を行うと、さらに組成中の酸素量が増加するため、好ましい。
本発明のリチウムイオン電池用正極活物質の製造方法において、焼成温度を高くすることで結晶化を促進し、平均粒子径D50を7μm以上12μm以下に制御する。
Next, a firing container having a predetermined capacity is prepared, and this firing container is filled with a precursor powder for a lithium ion battery positive electrode material. Next, the firing container filled with the precursor powder for the lithium ion battery positive electrode material is transferred to a firing furnace and fired. Firing is heated to 850 to 1000 ° C. at a temperature rising rate of 140 to 170 ° C./h in the temperature raising step, and then held at the temperature for a predetermined time. In the temperature lowering process, cooling from the holding temperature to 300 ° C. is performed at a temperature decreasing rate of 70 to 90 ° C./h, and at that time, the supply amount of air is 10 m 3 / h or more, or oxygen is 10 m 3 / h or more. Supply with. Due to such firing conditions, heat is uniformly input in the temperature raising step, and the heat conductivity between the particles is improved. Also, in the temperature lowering process, cooling to a predetermined temperature at an appropriate temperature lowering rate, and by supplying appropriate air and oxygen, the rearrangement of atoms in the transition metal layer, stacking faults in the transition metal layer, generation of oxygen defects, etc. Such structural change is promoted, and the average mechanical strength of the secondary particles can be controlled to 10 MPa to 60 MPa and the average displacement can be controlled to 0.2 μm to 1 μm.
Further, it is preferable to perform baking under pressure of 101 to 202 KPa because the amount of oxygen in the composition further increases.
In the method for producing a positive electrode active material for a lithium ion battery of the present invention, crystallization is promoted by increasing the firing temperature, and the average particle diameter D50 is controlled to 7 μm or more and 12 μm or less.
以下、本発明及びその利点をより良く理解するための実施例を提供するが、本発明はこれらの実施例に限られるものではない。 Examples for better understanding of the present invention and its advantages are provided below, but the present invention is not limited to these examples.
(実施例1〜11)
まず、所定の投入量の炭酸リチウムを純水3.2リットルに懸濁させた後、金属塩溶液を4.8リットル投入した。ここで、金属塩溶液は、各金属の硝酸塩の水和物を、各金属が表1に記載の組成比になるように調整し、また全金属モル数が14モルになるように調整した。
この処理により溶液中に微小粒のリチウム含有炭酸塩が析出したが、この析出物を、フィルタープレスを使用して濾別した。
続いて、析出物を乾燥してリチウム含有炭酸塩(リチウムイオン電池正極材用前駆体)を得た。
次に、焼成容器を準備し、この焼成容器内にリチウム含有炭酸塩を充填した。次に、表2に示すような焼成条件により焼成を行った。続いて室温まで冷却した後、解砕してリチウムイオン二次電池正極材の粉末を得た。
(Examples 1 to 11)
First, after a predetermined amount of lithium carbonate was suspended in 3.2 liters of pure water, 4.8 liters of metal salt solution was charged. Here, the nitrate hydrate of each metal was adjusted so that each metal might become the composition ratio of Table 1, and the total metal mole number might be set to 14 mol.
By this treatment, fine particles of lithium-containing carbonate were precipitated in the solution, and this precipitate was filtered off using a filter press.
Subsequently, the precipitate was dried to obtain a lithium-containing carbonate (a precursor for a lithium ion battery positive electrode material).
Next, a firing container was prepared, and this firing container was filled with a lithium-containing carbonate. Next, firing was performed under the firing conditions shown in Table 2. Subsequently, after cooling to room temperature, it was crushed to obtain a powder of a positive electrode material for a lithium ion secondary battery.
(比較例1〜3)
比較例1〜3として、原料の各金属を表1に示すような組成とし、表2に示すような焼成条件により焼成を行い、実施例1〜11と同様の処理を行った。
(Comparative Examples 1-3)
As Comparative Examples 1 to 3, each metal of the raw material had a composition as shown in Table 1, fired under the firing conditions as shown in Table 2, and the same treatment as in Examples 1 to 11 was performed.
(評価)
−正極材組成の評価−
各正極材中の金属含有量は、誘導結合プラズマ発光分光分析装置(ICP−OES)で測定し、各金属の組成比(モル比)を算出した。各金属の組成比は、表1に記載の通りであることを確認した。また、酸素含有量はLECO法で測定しαを算出した。
(Evaluation)
-Evaluation of composition of positive electrode material-
The metal content in each positive electrode material was measured with an inductively coupled plasma optical emission spectrometer (ICP-OES), and the composition ratio (molar ratio) of each metal was calculated. It was confirmed that the composition ratio of each metal was as shown in Table 1. The oxygen content was measured by the LECO method and α was calculated.
−平均粒子径D50の評価−
粒子断面をFIBにより切り出し、そのままエスエスアイ・ナノテクノロジー社製のFIB装置(SMI3050SE)を用いてSIM像を取得した。当該SIM像上の任意の直線上に存在する粒子のみの定方向径を測定することにより、平均粒子径D50を算出した。
-Evaluation of average particle diameter D50-
A particle cross section was cut out by FIB, and a SIM image was obtained as it was using an FIB apparatus (SMI3050SE) manufactured by SSI Nanotechnology. The average particle diameter D50 was calculated by measuring the constant direction diameter of only the particles existing on an arbitrary straight line on the SIM image.
−平均機械強度及び平均変位の評価−
島津製作所社製微小圧縮試験装置MCT−211を用いた微小圧縮試験を行った。微小圧縮試験は、まず、2次粒子の1粒子に対して、負荷速度:2.67mN/秒、設定荷重:49mNでダイヤモンド製の圧子によって押圧して圧縮変形させていき、変位が急激に増加したポイント(圧縮に要する試験力が一定となるポイント)を粒子が圧裂したポイントと判定し、当該ポイントにおける機械強度及び変位を求めた。
機械強度(CS)は、JIS R 1639−5より、下記式(1)で求めた。
CS(MPa)=2.48×P/πd2 (1)
〔P:試験力(N)、d:粒子径(nm)〕
このような測定を20粒子分行い、その平均値を求めた。
-Evaluation of average mechanical strength and average displacement-
A micro compression test using a micro compression test apparatus MCT-211 manufactured by Shimadzu Corporation was performed. In the micro-compression test, first, one secondary particle is pressed and deformed by a diamond indenter at a load speed of 2.67 mN / sec and a set load of 49 mN, and the displacement increases rapidly. The point (the point at which the test force required for compression becomes constant) was determined as the point at which the particles were crushed, and the mechanical strength and displacement at the point were determined.
The mechanical strength (CS) was determined by the following formula (1) from JIS R 1639-5.
CS (MPa) = 2.48 × P / πd 2 (1)
[P: test force (N), d: particle size (nm)]
Such measurement was performed for 20 particles, and the average value was obtained.
−放電容量及び充放電効率の評価−
各正極活物質と、導電材と、バインダーとを90:5:5の割合で秤量し、バインダーを有機溶媒(N−メチルピロリドン)に溶解したものに、正極活物質と導電材とを混合してスラリー化して正極合剤を作製し、これをAl箔上に塗布して乾燥後にプレスして正極とした。続いて、対極をLiとした評価用の2032型コインセルを作製し、電解液に1M−LiPF6をEC−DMC(1:1)に溶解したものを用いて、電流密度0.2Cの際の放電容量を測定した。また、充放電効率は、電池測定によって得られた初期放電容量及び初期充電容量から算出した。
これらの結果を表1〜3に示す。
-Evaluation of discharge capacity and charge / discharge efficiency-
Each positive electrode active material, a conductive material, and a binder are weighed in a ratio of 90: 5: 5, and the positive electrode active material and the conductive material are mixed in a material in which the binder is dissolved in an organic solvent (N-methylpyrrolidone). Thus, a positive electrode mixture was prepared by slurrying, applied onto an Al foil, dried and pressed to obtain a positive electrode. Subsequently, a 2032 type coin cell for evaluation with Li as the counter electrode was prepared, and a discharge at a current density of 0.2 C was performed using 1M-LiPF6 dissolved in EC-DMC (1: 1) as an electrolyte. The capacity was measured. The charge / discharge efficiency was calculated from the initial discharge capacity and the initial charge capacity obtained by battery measurement.
These results are shown in Tables 1-3.
表3より、実施例1〜11は、いずれも平均粒子径D50が7μm以上12μm以下、平均機械強度が10MPa以上60MPa以下、且つ、平均変位が0.2μm以上1μm以下であり、作製した電池の放電容量及び充放電効率が良好であった。また、正極活物質を含んだ正極合剤の集電体への塗布性も良好であった。
比較例1〜3は平均機械強度が10MPa未満であり、比較例1及び3ではさらに平均変位が1μmを超えており、いずれも作製した電池の充放電効率が不良であった。
実施例3及び比較例2の微小圧縮試験における機械強度(CS)及び変位の関係図をそれぞれ図1、2に示す。
From Table 3, Examples 1 to 11 all have an average particle diameter D50 of 7 μm to 12 μm, an average mechanical strength of 10 MPa to 60 MPa, and an average displacement of 0.2 μm to 1 μm. The discharge capacity and charge / discharge efficiency were good. Moreover, the applicability | paintability to the electrical power collector of the positive mix containing a positive electrode active material was also favorable.
In Comparative Examples 1 to 3, the average mechanical strength was less than 10 MPa, and in Comparative Examples 1 and 3, the average displacement further exceeded 1 μm, and the charge / discharge efficiency of the produced batteries was poor.
FIGS. 1 and 2 show the relationship between mechanical strength (CS) and displacement in the micro compression test of Example 3 and Comparative Example 2, respectively.
Claims (7)
(前記式において、Mは金属であり、0.9≦x≦1.2であり、0<y≦0.7であり、−0.1≦α≦0.1である。)
で表され、
平均粒子径D50が7μm以上12μm以下であり、
微小圧縮試験において、正極活物質の2次粒子の1粒子にダイヤモンド製の圧子によって負荷速度2.67mN/秒で設定荷重49mNまで負荷した時の平均機械強度が10MPa以上60MPa以下、且つ、粒子に圧子が当接して押圧を開始する位置から圧裂した位置までの圧子の移動距離を変位としたときの平均変位が0.2μm以上1μm以下であるリチウムイオン電池用正極活物質。 Composition formula: Li x Ni 1- y My O 2 + α
(In the above formula, M is a metal, 0.9 ≦ x ≦ 1.2, 0 <y ≦ 0.7, and −0.1 ≦ α ≦ 0.1.)
Represented by
The average particle diameter D50 is 7 μm or more and 12 μm or less,
In the micro-compression test, the average mechanical strength when a load of 2.67 mN / sec. To a set load of 49 mN is applied to one particle of the secondary particles of the positive electrode active material with a diamond indenter at a load speed of 2.67 mN / sec. A positive electrode active material for a lithium ion battery having an average displacement of not less than 0.2 μm and not more than 1 μm when the distance of movement of the indenter from the position where the indenter comes into contact to start pressing to the position where the indenter is crushed is defined as displacement.
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