JP6846734B2 - Lithium manganese spinel type crystal phase quantification method - Google Patents
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- 239000013078 crystal Substances 0.000 title claims description 90
- KLARSDUHONHPRF-UHFFFAOYSA-N [Li].[Mn] Chemical compound [Li].[Mn] KLARSDUHONHPRF-UHFFFAOYSA-N 0.000 title claims description 61
- 238000000034 method Methods 0.000 title claims description 51
- 229910052596 spinel Inorganic materials 0.000 title claims description 27
- 239000011029 spinel Substances 0.000 title claims description 27
- 238000011002 quantification Methods 0.000 title description 9
- 238000002441 X-ray diffraction Methods 0.000 claims description 31
- 239000007774 positive electrode material Substances 0.000 claims description 30
- 235000002639 sodium chloride Nutrition 0.000 claims description 27
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 claims description 26
- 239000002131 composite material Substances 0.000 claims description 26
- 239000011780 sodium chloride Substances 0.000 claims description 26
- 238000012360 testing method Methods 0.000 claims description 19
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 122
- 229910052742 iron Inorganic materials 0.000 description 46
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 27
- 239000001301 oxygen Substances 0.000 description 27
- 229910052760 oxygen Inorganic materials 0.000 description 27
- 238000004611 spectroscopical analysis Methods 0.000 description 23
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 11
- 229910001416 lithium ion Inorganic materials 0.000 description 11
- -1 iron ion Chemical class 0.000 description 10
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 description 9
- 238000001228 spectrum Methods 0.000 description 9
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 8
- 238000011156 evaluation Methods 0.000 description 6
- 239000000047 product Substances 0.000 description 6
- 239000012153 distilled water Substances 0.000 description 5
- 238000010304 firing Methods 0.000 description 5
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 5
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 4
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 4
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 4
- 150000002506 iron compounds Chemical class 0.000 description 4
- 229910052744 lithium Inorganic materials 0.000 description 4
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 4
- 229910052757 nitrogen Inorganic materials 0.000 description 4
- 230000005298 paramagnetic effect Effects 0.000 description 4
- 230000007704 transition Effects 0.000 description 4
- 229910052782 aluminium Inorganic materials 0.000 description 3
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 3
- 238000004458 analytical method Methods 0.000 description 3
- 239000007864 aqueous solution Substances 0.000 description 3
- 239000000470 constituent Substances 0.000 description 3
- 239000011572 manganese Substances 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 239000002244 precipitate Substances 0.000 description 3
- 239000011164 primary particle Substances 0.000 description 3
- 239000011435 rock Substances 0.000 description 3
- 239000000243 solution Substances 0.000 description 3
- 230000003595 spectral effect Effects 0.000 description 3
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- 229910010586 LiFeO 2 Inorganic materials 0.000 description 2
- 229910015643 LiMn 2 O 4 Inorganic materials 0.000 description 2
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 2
- 239000006230 acetylene black Substances 0.000 description 2
- 230000004913 activation Effects 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000007796 conventional method Methods 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
- PQVSTLUFSYVLTO-UHFFFAOYSA-N ethyl n-ethoxycarbonylcarbamate Chemical compound CCOC(=O)NC(=O)OCC PQVSTLUFSYVLTO-UHFFFAOYSA-N 0.000 description 2
- 239000010439 graphite Substances 0.000 description 2
- 229910002804 graphite Inorganic materials 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- VCJMYUPGQJHHFU-UHFFFAOYSA-N iron(3+);trinitrate Chemical compound [Fe+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O VCJMYUPGQJHHFU-UHFFFAOYSA-N 0.000 description 2
- GLXDVVHUTZTUQK-UHFFFAOYSA-M lithium hydroxide monohydrate Substances [Li+].O.[OH-] GLXDVVHUTZTUQK-UHFFFAOYSA-M 0.000 description 2
- 229940040692 lithium hydroxide monohydrate Drugs 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 2
- 239000004810 polytetrafluoroethylene Substances 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 239000002002 slurry Substances 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 description 1
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 1
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 description 1
- 229910012851 LiCoO 2 Inorganic materials 0.000 description 1
- 229910013190 LiMO2 Li2MnO3 Inorganic materials 0.000 description 1
- 229910013228 LiMO2-Li2MnO3 Inorganic materials 0.000 description 1
- 229910013870 LiPF 6 Inorganic materials 0.000 description 1
- 229910003286 Ni-Mn Inorganic materials 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 239000011149 active material Substances 0.000 description 1
- 230000002528 anti-freeze Effects 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 230000001351 cycling effect Effects 0.000 description 1
- QHGJSLXSVXVKHZ-UHFFFAOYSA-N dilithium;dioxido(dioxo)manganese Chemical compound [Li+].[Li+].[O-][Mn]([O-])(=O)=O QHGJSLXSVXVKHZ-UHFFFAOYSA-N 0.000 description 1
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000003792 electrolyte Substances 0.000 description 1
- 239000008151 electrolyte solution Substances 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 229910000625 lithium cobalt oxide Inorganic materials 0.000 description 1
- SWAIALBIBWIKKQ-UHFFFAOYSA-N lithium titanium Chemical compound [Li].[Ti] SWAIALBIBWIKKQ-UHFFFAOYSA-N 0.000 description 1
- BFZPBUKRYWOWDV-UHFFFAOYSA-N lithium;oxido(oxo)cobalt Chemical compound [Li+].[O-][Co]=O BFZPBUKRYWOWDV-UHFFFAOYSA-N 0.000 description 1
- VROAXDSNYPAOBJ-UHFFFAOYSA-N lithium;oxido(oxo)nickel Chemical compound [Li+].[O-][Ni]=O VROAXDSNYPAOBJ-UHFFFAOYSA-N 0.000 description 1
- 238000004020 luminiscence type Methods 0.000 description 1
- CNFDGXZLMLFIJV-UHFFFAOYSA-L manganese(II) chloride tetrahydrate Chemical compound O.O.O.O.[Cl-].[Cl-].[Mn+2] CNFDGXZLMLFIJV-UHFFFAOYSA-L 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 239000011259 mixed solution Substances 0.000 description 1
- 239000007773 negative electrode material Substances 0.000 description 1
- AOPCKOPZYFFEDA-UHFFFAOYSA-N nickel(2+);dinitrate;hexahydrate Chemical compound O.O.O.O.O.O.[Ni+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O AOPCKOPZYFFEDA-UHFFFAOYSA-N 0.000 description 1
- 239000005486 organic electrolyte Substances 0.000 description 1
- 238000000634 powder X-ray diffraction Methods 0.000 description 1
- 238000010248 power generation Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 239000012266 salt solution Substances 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 229910052814 silicon oxide Inorganic materials 0.000 description 1
- 238000010183 spectrum analysis Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000002203 sulfidic glass Substances 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
- BFKJFAAPBSQJPD-UHFFFAOYSA-N tetrafluoroethene Chemical group FC(F)=C(F)F BFKJFAAPBSQJPD-UHFFFAOYSA-N 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 229910000314 transition metal oxide Inorganic materials 0.000 description 1
- 238000009279 wet oxidation reaction Methods 0.000 description 1
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Inorganic Compounds Of Heavy Metals (AREA)
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Description
本発明は、リチウムマンガンスピネル型結晶相の定量方法に関する。 The present invention relates to a method for quantifying a lithium manganese spinel type crystal phase.
現在、我が国において、携帯電話、スマートフォン、ノートパソコン、タブレット型パソコン等のポータブル機器に搭載されている二次電池のほとんどは、リチウムイオン二次電池である。リチウムイオン二次電池は、今後、電気自動車、プラグインハイブリッド車等の車載用途；太陽電池、風力発電等の電力負荷平準化システム等の大型電池としても実用化されつつあり、その重要性はますます高まっている。 Currently, in Japan, most of the secondary batteries installed in portable devices such as mobile phones, smartphones, laptop computers, and tablet personal computers are lithium ion secondary batteries. Lithium-ion secondary batteries are being put to practical use in the future for in-vehicle applications such as electric vehicles and plug-in hybrid vehicles; as large batteries for power load leveling systems such as solar cells and wind power generation, and their importance is increasing. It is getting higher and higher.
現在、リチウムイオン二次電池においては、正極活物質として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)等のリチウム含有遷移金属酸化物、負極活物質としては黒鉛、チタン酸リチウム、酸化ケイ素等が使用されている。 Currently, in lithium ion secondary batteries, lithium-containing transition metal oxides such as lithium cobalt oxide (LiCoO 2 ), lithium nickel oxide (LiNiO 2 ), and lithium manganate (LiMn 2 O 4) are used as positive electrode active materials, and negative electrodes. As the active material, graphite, lithium titanate, silicon oxide and the like are used.
このようなリチウムイオン二次電池構成においては、正極活物質が唯一のリチウムイオン供給源として働き、正極活物質から可逆的に出し入れ可能なリチウムイオン量が電池として活用可能な容量となり、リチウムイオン出し入れ時の電圧が電池としての最大の電圧となる。従ってどのような正極活物質を選択するのかが電池性能を決定づけると言っても過言ではない。 In such a lithium ion secondary battery configuration, the positive electrode active material acts as the only lithium ion supply source, and the amount of lithium ions that can be reversibly taken in and out of the positive electrode active material becomes the capacity that can be used as a battery, and lithium ion is taken in and out. The voltage at the time is the maximum voltage for a battery. Therefore, it is no exaggeration to say that what kind of positive electrode active material is selected determines the battery performance.
上記課題を踏まえ、正極活物質として最近活発に検討されているのが、リチウムマンガン系複合酸化物（LiMO2-Li2MnO3、M=Ni1/2Mn1/2、Co1/3Ni1/3Mn1/3等）である（例えば、非特許文献１参照）。この材料の結晶構造は層状岩塩型結晶相であるが、サイクル経過に伴い、LiMn2O4に代表されるリチウムマンガンスピネル型結晶相に徐々に変化していくことが知られている（例えば、非特許文献２参照）。また、高容量の正極活物質となり得るリチウムマンガン系複合酸化物としては、LiFe1/2Ni1/2O2-Li2MnO3系正極活物質も知られている（例えば、特許文献１、非特許文献３参照）。
Based on the above issues, lithium manganese-based composite oxides (LiMO 2- Li 2 MnO 3 , M = Ni 1/2 Mn 1/2 , Co 1/3 Ni) have recently been actively studied as positive electrode active materials. 1/3 Mn 1/3, etc.) (see, for example, Non-Patent Document 1). The crystal structure of this material is a layered rock salt type crystal phase, but it is known that it gradually changes to a lithium manganese spinel type crystal phase represented by LiMn 2 O 4 as the cycle progresses (for example). See Non-Patent Document 2). Further, as a lithium manganese-based composite oxide that can be a high-capacity positive electrode active material, a LiFe 1/2 Ni 1/2 O 2- Li 2 MnO 3- based positive electrode active material is also known (for example,
これらの層状岩塩型結晶相からスピネル型結晶相への構造転移が、充放電サイクル時に充放電曲線の変化（4V+3Vの二段プラトー領域の出現）や放電電圧低下をもたらすと言われてきており、現時点でも変わっておらず、生成するスピネル型結晶相を定量することは、生成するスピネル型結晶相の結晶性が低いために困難である。 It has been said that the structural transition from these layered rock salt type crystal phases to spinel type crystal phases causes changes in the charge / discharge curve (appearance of a two-stage plateau region of 4V + 3V) and a decrease in discharge voltage during the charge / discharge cycle. Therefore, it has not changed even at present, and it is difficult to quantify the spinel-type crystal phase to be produced because the crystallinity of the spinel-type crystal phase to be produced is low.
さらに、充放電サイクル特性、特に充放電曲線形状の変化のない形状相似性に優れたリチウムマンガン系複合酸化物正極活物質が望まれており、そのためには、いかにスピネル型結晶相の生成を抑制できるかが鍵であるが、その前段階である簡便且つ正確なスピネル型結晶相の定量方法すら一向に見出されていない。 Further, a lithium manganese-based composite oxide positive electrode active material having excellent charge / discharge cycle characteristics, particularly shape similarity in which the charge / discharge curve shape does not change, is desired, and for that purpose, how to suppress the formation of a spinel-type crystal phase. The key is to be able to do it, but even a simple and accurate method for quantifying the spinel-type crystal phase, which is the previous step, has not been found at all.
本発明は、上記した従来技術の現状に鑑みてなされたものであり、充放電サイクル試験後に、リチウムマンガン系複合酸化物を含有する正極活物質中に存在するリチウムマンガンスピネル型結晶相を、簡便且つ正確に定量する方法を提供することを目的とする。 The present invention has been made in view of the current state of the prior art described above, and after a charge / discharge cycle test, a lithium manganese spinel-type crystal phase existing in a positive electrode active material containing a lithium manganese-based composite oxide can be easily used. Moreover, it aims at providing the method of quantifying accurately.
本発明者らは、上記した目的を達成すべく鋭意研究を重ねてきた。その結果、汎用的な評価法であるX線回折法を用い、特定のピーク位置にてカーブフィッティングを行うことにより、層状岩塩型結晶相から生成するスピネル型結晶相を高精度に見積もることが可能なことを見出した。また、本発明者らは、正極活物質が鉄を含むリチウムマンガン複合酸化物である場合には、57Feメスバウワ分光法を適用することによっても、X線回折法と同様にスピネル型結晶相を高精度に見積もることが可能なことを見出した。本発明者らは、このような知見に基づき、さらに研究を重ね、本発明を完成した。即ち、本発明は、以下の構成を包含する。
項１．充放電サイクル試験後に、リチウムマンガン系複合酸化物を含有する正極活物質中に存在するリチウムマンガンスピネル型結晶相を定量する方法であって、
前記充放電サイクル試験後の正極活物質を、CuKα線を用いたX線回折計において2θ= 61〜66°の範囲を測定し、得られたX線回折パターンを3つのピークでプロファイルフィッティングを行い、高角側2本のピークと低角側1本のピークとの面積比を算出する工程
を備える、方法。
項２．前記高角側2本のピークが六方晶層状岩塩型結晶相のピークであり、前記低角側1本のピークがリチウムマンガンスピネル型結晶相のピークである、項１に記載の方法。
項３．前記プロファイルフィッティングの前に、得られたX線回折パターンのバックグラウンドを除去する工程を備える、項１又は２に記載の方法。
項４．さらに、
前記充放電サイクル試験後の正極活物質を、57Feメスバウワ分光スペクトルを測定し、得られた常磁性ダブレットピークを2成分の対称性ダブレットでプロファイルフィッティングを行い、酸素4配位位置の3価鉄イオン成分と、酸素6配位位置の3価鉄イオン成分との面積比を算出する工程
を備える、項１〜３のいずれか1項に記載の方法。
項５．前記リチウムマンガン系複合酸化物が、鉄を含む、項４に記載の方法。
項６．充放電試験前に、前記正極活物質中に、さらに、57Feをエンリッチさせた鉄化合物を含有させる、項４又は５に記載の方法。
項７．前記酸素4配位位置の3価鉄イオン成分がリチウムマンガンスピネル型結晶相中の8a位置の3価鉄成分であり、前記酸素6配位位置の3価鉄イオン成分がリチウムマンガンスピネル型結晶相中の16d位置の3価鉄成分及び層状岩塩型結晶相中の3a及び3b位置の3価鉄成分である、項４〜６のいずれか1項に記載の方法。
項８．前記57Feメスバウワ分光スペクトルを±3.0mm/s以上の速度範囲で測定する、項４〜７のいずれか1項に記載の方法。
項９．充放電サイクル試験後に、リチウムマンガン系複合酸化物を含有する正極活物質中に存在するリチウムマンガンスピネル型結晶相を定量する方法であって、
前記充放電サイクル試験後の正極活物質を、57Feメスバウワ分光スペクトルを測定し、得られた常磁性ダブレットピークを2成分の対称性ダブレットでプロファイルフィッティングを行い、酸素4配位位置の3価鉄イオン成分と、酸素6配位位置の3価鉄イオン成分との面積比を算出する工程
を備える、方法。
項１０．前記リチウムマンガン系複合酸化物が、鉄を含む、項９に記載の方法。
項１１．充放電試験前に、前記正極活物質中に、さらに、57Feをエンリッチさせた鉄化合物を含有させる、項９又は１０に記載の方法。
項１２．前記酸素4配位位置の3価鉄イオン成分がリチウムマンガンスピネル型結晶相中の8a位置の3価鉄成分であり、前記酸素6配位位置の3価鉄イオン成分がリチウムマンガンスピネル型結晶相中の16d位置の3価鉄成分及び層状岩塩型結晶相中の3a及び3b位置の3価鉄成分である、項９〜１１のいずれか1項に記載の方法。
項１３．前記57Feメスバウワ分光スペクトルを±3.0mm/s以上の速度範囲で測定する、項９〜１２のいずれか1項に記載の方法。
The present inventors have carried out diligent research to achieve the above-mentioned object. As a result, it is possible to estimate the spinel-type crystal phase generated from the layered rock salt-type crystal phase with high accuracy by performing curve fitting at a specific peak position using the X-ray diffraction method, which is a general-purpose evaluation method. I found something. In addition, when the positive electrode active material is a lithium manganese composite oxide containing iron, the present inventors can also apply 57 Fe Mesbauwa spectroscopy to obtain a spinel-type crystal phase in the same manner as in the X-ray diffraction method. We found that it is possible to estimate with high accuracy. Based on such findings, the present inventors have further studied and completed the present invention. That is, the present invention includes the following configurations.
The positive electrode active material after the charge / discharge cycle test was measured in the range of 2θ = 61 to 66 ° with an X-ray diffractometer using CuKα rays, and the obtained X-ray diffraction pattern was profile-fitted with three peaks. , A method comprising the step of calculating the area ratio of two peaks on the high angle side and one peak on the low angle side.
Item 4. further,
The positive electrode active material after the charge / discharge cycle test was measured with a 57 Fe female bower spectral spectrum, and the obtained paramagnetic doublet peak was profile-fitted with a two-component symmetric doublet to perform profile fitting of the trivalent iron at the oxygen 4-coordination position. Item 6. The method according to any one of
Item 5. Item 4. The method according to Item 4, wherein the lithium manganese-based composite oxide contains iron.
Item 6. Item 4. The method according to Item 4 or 5 , wherein an iron compound enriched with 57 Fe is further contained in the positive electrode active material before the charge / discharge test.
Item 7. The trivalent iron ion component at the oxygen 4-coordination position is the trivalent iron component at the 8a position in the lithium manganese spinel-type crystal phase, and the trivalent iron ion component at the oxygen 6-coordination position is the lithium manganese spinel-type crystal phase. Item 6. The method according to any one of Items 4 to 6, wherein the trivalent iron component at the 16d position and the trivalent iron component at the 3a and 3b positions in the layered rock salt type crystal phase.
Item 8. Item 6. The method according to any one of Items 4 to 7, wherein the 57 Fe Mesbauer spectroscopic spectrum is measured in a speed range of ± 3.0 mm / s or more.
Item 9. A method for quantifying the lithium manganese spinel-type crystal phase present in the positive electrode active material containing a lithium manganese-based composite oxide after a charge / discharge cycle test.
The positive electrode active material after the charge / discharge cycle test was measured with a 57 Fe female bower spectral spectrum, and the obtained paramagnetic doublet peak was profile-fitted with a two-component symmetric doublet to perform profile fitting of the trivalent iron at the oxygen 4-coordination position. A method comprising the step of calculating the area ratio of the ionic component to the trivalent iron ionic component at the oxygen hexacoordinate position.
Item 12. The trivalent iron ion component at the oxygen 4-coordination position is the trivalent iron component at the 8a position in the lithium manganese spinel-type crystal phase, and the trivalent iron ion component at the oxygen 6-coordination position is the lithium manganese spinel-type crystal phase. Item 6. The method according to any one of Items 9 to 11, wherein the trivalent iron component at the 16d position and the trivalent iron component at the 3a and 3b positions in the layered rock salt type crystal phase.
Item 13. Item 6. The method according to any one of Items 9 to 12, wherein the 57 Fe Mesbauer spectroscopic spectrum is measured in a speed range of ± 3.0 mm / s or more.
本発明によれば、充放電サイクル試験後に、リチウムマンガン系複合酸化物を含有する正極活物質中に存在するリチウムマンガンスピネル型結晶相を簡便且つ高精度に定量することができる。本発明の定量方法を正極活物質の開発に活用することにより、充放電サイクル経過時に起こる、層状岩塩型結晶相からスピネル型結晶相への構造相転移を抑制する手法が見出だされ、結果として長寿命のリチウムイオン二次電池を開発できることが期待される。 According to the present invention, after the charge / discharge cycle test, the lithium manganese spinel-type crystal phase present in the positive electrode active material containing the lithium manganese-based composite oxide can be easily and highly accurately quantified. By utilizing the quantification method of the present invention for the development of the positive electrode active material, a method for suppressing the structural phase transition from the layered rock salt type crystal phase to the spinel type crystal phase that occurs during the charge / discharge cycle has been found. It is expected that a long-life lithium-ion secondary battery can be developed.
以下、本発明の定量方法を詳細に説明する。本発明において、充放電サイクル試験後に、リチウムマンガン系複合酸化物を含有する正極活物質中に存在するリチウムマンガンスピネル型結晶相を定量するには、(1) X線回折法及び(2) 57Feメスバウワ分光法の2種類を採用することができる。 Hereinafter, the quantification method of the present invention will be described in detail. In the present invention, in order to quantify the lithium manganese spinel type crystal phase present in the positive electrode active material containing the lithium manganese-based composite oxide after the charge / discharge cycle test, (1) X-ray diffraction method and (2) 57 Two types of Fe Mesbauwa spectroscopy can be adopted.
両分析法ともに、公知の方法により得られたリチウムイオン二次電池であれば特に限定なく使用することができる。すなわち、正極材料としてリチウムマンガン系複合酸化物を用い、負極材料として公知の金属リチウム、黒鉛系材料、リチウムチタンスピネル型結晶相等を使用し、電解質として有機電解液、硫化物固体電解質等を用い、さらにその他の公知の電池構成要素を使用して、常法に従って、リチウムイオン二次電池を組み立てることができる。 Both analytical methods can be used without particular limitation as long as they are lithium ion secondary batteries obtained by a known method. That is, a lithium manganese-based composite oxide is used as the positive electrode material, a known metallic lithium, a graphite-based material, a lithium titanium spinel-type crystal phase or the like is used as the negative electrode material, and an organic electrolyte, a sulfide solid electrolyte or the like is used as the electrolyte. Yet other known battery components can be used to assemble a lithium ion secondary battery according to conventional methods.
１．X線回折法
X線回折法による本発明の定量方法は、充放電サイクル試験後に、リチウムマンガン系複合酸化物を含有する正極活物質中に存在するリチウムマンガンスピネル型結晶相を定量する方法であって、前記充放電サイクル試験後の正極活物質を、CuKα線を用いたX線回折計において2θ= 61〜66°の範囲を測定し、得られたX線回折パターンを3つのピークでプロファイルフィッティングを行い、高角側2本のピークと低角側1本のピークとの面積比を算出する工程を備える。
1. 1. X-ray diffraction method
The quantification method of the present invention by the X-ray diffraction method is a method for quantifying the lithium manganese spinel type crystal phase present in the positive electrode active material containing the lithium manganese-based composite oxide after the charge / discharge cycle test, and is the above-mentioned charging method. The positive electrode active material after the discharge cycle test was measured in the range of 2θ = 61 to 66 ° with an X-ray diffractometer using CuKα rays, and the obtained X-ray diffraction pattern was profile-fitted with three peaks to achieve a high angle. A step of calculating the area ratio between the two peaks on the side and the one peak on the low angle side is provided.
X線回折法による本発明の定量方法は、リチウムマンガン系複合酸化物が有する元素の種類に依存せず、リチウムマンガン系複合酸化物からなる正極活物質から生成するリチウムマンガンスピネル型結晶相を定量することができる。例えば、構成成分としてLi2MnO3を含むリチウムマンガン系複合酸化物を対象に測定することができる。 The quantification method of the present invention by the X-ray diffraction method quantifies the lithium manganese spinel type crystal phase generated from the positive electrode active material composed of the lithium manganese-based composite oxide, regardless of the type of the element possessed by the lithium manganese-based composite oxide. can do. For example, a lithium manganese-based composite oxide containing Li 2 MnO 3 as a constituent can be measured.
一般的に、層状岩塩型結晶相とリチウムマンガンスピネル型結晶相とは類似のX線回折パターンを示すため、両者のピークは比較的近い位置に存在する。X線回折法において、角度分解能は高角側（2θ=90°に近い側）に近いほど高くなるが、ピーク強度が弱くなるため、解析する角度範囲の選択は重要である。本発明では、例えば図１に示されるように、CuKα線を用いたX線回折計において2θ= 61〜66°の範囲（例えば、61〜66°の範囲、61〜65°の範囲、62〜66°の範囲、62〜65°の範囲等）を測定し、プロファイルフィッティングを行う。また、測定の精度を向上させるため、プロファイルフィッティングの前に、得られたX線回折パターンのバックグラウンドを常法により除去することが好ましい。 In general, the layered rock salt type crystal phase and the lithium manganese spinel type crystal phase show similar X-ray diffraction patterns, so that the peaks of both are relatively close to each other. In the X-ray diffraction method, the angular resolution increases as it approaches the higher angle side (the side closer to 2θ = 90 °), but the peak intensity becomes weaker, so it is important to select the angle range to be analyzed. In the present invention, for example, as shown in FIG. 1, in an X-ray diffractometer using CuKα rays, the range of 2θ = 61 to 66 ° (for example, the range of 61 to 66 °, the range of 61 to 65 °, 62 to Measure the range of 66 °, the range of 62 to 65 °, etc.) and perform profile fitting. Further, in order to improve the accuracy of measurement, it is preferable to remove the background of the obtained X-ray diffraction pattern by a conventional method before profile fitting.
図１に示されるように、充放電サイクル試験後のリチウムマンガン系複合酸化物の実測のX線回折パターンは、3つのピーク成分、つまり、低角側からリチウムマンガンスピネル型結晶相の440ピーク、層状岩塩型結晶相の018ピーク、層状岩塩型結晶相の110ピークからなる。この傾向は、リチウムマンガン系複合酸化物が有する元素の種類や含有量、充放電サイクル試験の条件等にほとんど影響されない。リチウムマンガンスピネル型結晶相の存在比は、全面積中のリチウムマンガンスピネル型結晶相の440ピークの割合を算出することによって見積もることができる。プロファイルフィッティングの解析プログラムは、市販のものを用いることができ、特に制限されない。また、用いるピークのプロファイル関数もGaussian関数等、X線回折パターンに適度に適合するものであれば特に制限されない。 As shown in FIG. 1, the actually measured X-ray diffraction pattern of the lithium manganese-based composite oxide after the charge / discharge cycle test has three peak components, that is, 440 peaks of the lithium manganese spinel type crystal phase from the low angle side. It consists of 018 peaks of the layered rock salt type crystal phase and 110 peaks of the layered rock salt type crystal phase. This tendency is hardly affected by the type and content of elements contained in the lithium manganese-based composite oxide, the conditions of the charge / discharge cycle test, and the like. The abundance ratio of the lithium manganese spinel type crystal phase can be estimated by calculating the ratio of 440 peaks of the lithium manganese spinel type crystal phase in the total area. A commercially available profile fitting analysis program can be used, and is not particularly limited. Further, the profile function of the peak to be used is not particularly limited as long as it appropriately matches the X-ray diffraction pattern such as the Gaussian function.
２． 57 Feメスバウワ分光法
57Feメスバウワ分光法による本発明の定量方法は、充放電サイクル試験後に、リチウムマンガン系複合酸化物を含有する正極活物質中に存在するリチウムマンガンスピネル型結晶相を定量する方法であって、前記充放電サイクル試験後の正極活物質を、57Feメスバウワ分光スペクトルを測定し、得られた常磁性ダブレットピークを2成分の対称性ダブレットでプロファイルフィッティングを行い、酸素4配位位置の3価鉄イオン成分と、酸素6配位位置の3価鉄イオン成分との面積比を算出する工程を備える。
2. 57 Fe Mesbauwa spectroscopy
57 The quantification method of the present invention by Fe Mesbauwa spectroscopy is a method for quantifying the lithium manganese spinel type crystal phase present in the positive electrode active material containing the lithium manganese-based composite oxide after the charge / discharge cycle test. The positive electrode active material after the charge / discharge cycle test was measured by 57 Fe Mesbauwa spectral spectrum, and the obtained paramagnetic doublet peak was profile-fitted with a two-component symmetric doublet, and the trivalent iron ion at the oxygen 4-coordination position was performed. A step of calculating the area ratio of the component and the trivalent iron ion component at the oxygen 6-coordination position is provided.
57Feメスバウワ分光法は、Feイオンの価数や酸素配位数に依存する異性体シフト値の変化を利用している。このため、57Feメスバウワ分光法による本発明の定量方法を採用するには、リチウムマンガン系複合酸化物の構成元素として鉄（鉄イオン）が含まれている必要がある。例えば、構成成分としてLiFeO2及びLi2MnO3を含むリチウムマンガン系複合酸化物を対象に測定することができる。ただし、鉄（鉄イオン）が含まれていないリチウムマンガン系複合酸化物であっても、57Feをエンリッチさせた鉄化合物（酸化鉄等）を用いて、電気化学的評価に支障がない程度（リチウムマンガン系複合酸化物中のLi量に対して5モル%以下程度）に材料系に導入することにより、定量が可能である。 57 Fe Mesbauwa spectroscopy utilizes changes in isomer shift values that depend on the valence of Fe ions and the oxygen coordination number. Therefore, in order to adopt the quantification method of the present invention by 57 Fe Mesbauwa spectroscopy, iron (iron ion) must be contained as a constituent element of the lithium manganese-based composite oxide. For example, a lithium manganese-based composite oxide containing LiFeO 2 and Li 2 MnO 3 as constituents can be measured. However, even if it is a lithium manganese-based composite oxide that does not contain iron (iron ion) , using an iron compound (iron oxide, etc.) enriched with 57 Fe does not interfere with the electrochemical evaluation (to the extent that it does not interfere with the electrochemical evaluation). Quantification is possible by introducing into the material system (about 5 mol% or less with respect to the amount of Li in the lithium manganese-based composite oxide).
図２に典型的な57Feメスバウワ分光法によるスペクトル解析の結果を示す。57Feメスバウワ分光スペクトルは非対称ダブレット（常磁性ダブレットピーク）であり、異性体シフト値の異なる2つの対称性ダブレット成分で帰属される。異性体シフト値はダブレットの中心値の0速度からのずれに相当する。黒色破線の成分が酸素6配位のダブレット成分であり、リチウムマンガンスピネル型結晶相（16d位置）と層状岩塩型結晶相内（3a及び3b位置）の6配位3価鉄成分である。灰色のダブレット成分がリチウムマンガンスピネル型結晶相内酸素4配位位置（8a位置）の3価鉄成分である。層状岩塩型結晶相内にも6c位置と言われる酸素4配位位置が存在するが、この成分は層状岩塩型結晶相のみの57Feメスバウワ分光スペクトルにおいて検出されないため、灰色のダブレット成分はリチウムマンガンスピネル型結晶相内酸素4配位位置（8a位置）の3価鉄成分を示している。したがって、リチウムマンガンスピネル型結晶相存在比は、全成分中の酸素4配位位置（8a位置）の鉄成分の割合に相当する。57Feメスバウワ分光法の場合、ドップラー速度範囲を適切に選択することが好ましい。なお、ドップラー速度はガンマ線のエネルギーに相当し、目的のスペクトルを精度よく取得するためには適切に選択することが好ましい。具体的には、ドップラー速度範囲は、±3.0mm/s以上が好ましく、±3.0〜5.0mm/sがより好ましく、±3.0〜4.0mm/sがさらに好ましい。 FIG. 2 shows the results of spectral analysis by 57 Fe Mesbauwa spectroscopy, which is typical. 57 Fe The Mesbauer spectroscopic spectrum is an asymmetric doublet (paramagnetic doublet peak) and is assigned by two symmetric doublet components with different isomer shift values. The isomer shift value corresponds to the deviation of the center value of the doublet from the 0 velocity. The component of the black dashed line is the doublet component of oxygen 6-coordination, and the 6-coordinated trivalent iron component in the lithium manganese spinel type crystal phase (16d position) and the layered rock salt type crystal phase (3a and 3b positions). The gray doublet component is the trivalent iron component at the oxygen 4-coordination position (8a position) in the lithium manganese spinel type crystal phase. The oxygen 4-coordination position, which is said to be the 6c position, also exists in the layered rock salt type crystal phase, but since this component is not detected in the 57 Fe Mesbauwa spectroscopic spectrum of only the layered rock salt type crystal phase, the gray doublet component is lithium manganese. The trivalent iron component at the oxygen 4-coordination position (8a position) in the spinel-type crystal phase is shown. Therefore, the lithium manganese spinel-type crystal phase abundance ratio corresponds to the ratio of the iron component at the oxygen 4-coordination position (8a position) in all the components. For 57 Fe Mesbauer spectroscopy, it is preferable to select the Doppler velocity range appropriately. The Doppler velocity corresponds to the energy of gamma rays, and it is preferable to select it appropriately in order to accurately acquire the target spectrum. Specifically, the Doppler speed range is preferably ± 3.0 mm / s or more, more preferably ± 3.0 to 5.0 mm / s, and even more preferably ± 3.0 to 4.0 mm / s.
57Feメスバウワ分光法は、ガンマ線を用いた透過法の分光法なので、電極状態の試料をアルミニウムラミネートに封じた状態（大気非暴露）でも測定可能である。ただし、アルミニウム内に鉄成分が含まれるので、アルミニウムラミネートのみを測定しておき、実測データからその鉄成分を差し引くことが好ましい。前述したように57Feメスバウワ分光法は鉄成分のみを検出する方法なので、リチウムマンガン複合酸化物中にLiFeO2成分等の鉄成分が含まれていることが必要である。鉄イオン濃度は特に限定されないが、S/Nの良いスペクトルを得るためには、Li以外の全金属中に鉄が10モル%以上含まれていることが必要である。なお、それ以下の濃度であっても、試料中に57Feをエンリッチさせた鉄化合物（57Feをエンリッチさせた酸化鉄等）を、全量の0.1〜5モル%程度含ませることで測定することができる。 57 Fe Mesbauwa spectroscopy is a transmission method spectroscopy using gamma rays, so it can be measured even when the sample in the electrode state is sealed in an aluminum laminate (not exposed to the atmosphere). However, since aluminum contains an iron component, it is preferable to measure only the aluminum laminate and subtract the iron component from the measured data. As mentioned above, since 57 Fe Mesbauwa spectroscopy is a method for detecting only the iron component, it is necessary that the lithium manganese composite oxide contains an iron component such as LiFeO 2 component. The iron ion concentration is not particularly limited, but in order to obtain a good spectrum of S / N, it is necessary that all metals other than Li contain 10 mol% or more of iron. Incidentally, it is also a less concentration, be measured by the iron compound is enriched with 57 Fe in the sample (57 Fe iron oxide was enriched etc.), included about 0.1 to 5 mole% of the total amount Can be done.
以下、実施例及び比較例を示し、本発明の特徴とするところを一層明確にするが、本発明は以下の実施例に限定されるものではない。 Hereinafter, examples and comparative examples will be shown to further clarify the features of the present invention, but the present invention is not limited to the following examples.
［実施例1］
硝酸鉄(III)9水和物10.10g、硝酸ニッケル(II)6水和物7.27g、塩化マンガン(II)4水和物39.58g（全量0.25mol、Fe: Ni: Mnモル比1: 1: 8）を500mLの蒸留水に加え完全に溶解させて金属塩水溶液を得た。別のビーカーに水酸化リチウム1水和物50gを秤量し、蒸留水500mLを添加して撹拌しつつ溶解後、150mLのエタノールを加えて不凍化した水酸化リチウム溶液を作製した。この水酸化リチウム水溶液をチタン製ビーカーに入れ、-10℃に保たれた恒温槽内に静置した。次いでこの水酸化リチウム水溶液に、上記金属塩水溶液を約3時間かけて徐々に滴下し、Fe-Ni-Mn沈殿物（共沈物）を形成させた。反応液が完全にアルカリ性になっていることを確認し、撹拌下に共沈物を含む反応液に、室温で2日間酸素を吹き込んで湿式酸化処理して、沈殿を熟成させた。
[Example 1]
10.10 g of iron (III) nitrate 9 hydrate, 7.27 g of nickel (II) nitrate hexahydrate, 39.58 g of manganese (II) chloride tetrahydrate (total amount 0.25 mol, Fe: Ni: Mn molar ratio 1: 1) : 8) was added to 500 mL of distilled water and completely dissolved to obtain an aqueous metal salt solution. 50 g of lithium hydroxide monohydrate was weighed in another beaker, 500 mL of distilled water was added and dissolved while stirring, and then 150 mL of ethanol was added to prepare an antifreeze lithium hydroxide solution. This lithium hydroxide aqueous solution was placed in a titanium beaker and allowed to stand in a constant temperature bath kept at -10 ° C. Next, the above metal salt aqueous solution was gradually added dropwise to the lithium hydroxide aqueous solution over about 3 hours to form a Fe-Ni-Mn precipitate (coprecipitate). After confirming that the reaction solution was completely alkaline, oxygen was blown into the reaction solution containing the coprecipitate under stirring for 2 days at room temperature for wet oxidation treatment, and the precipitate was aged.
得られた沈殿物を蒸留水で洗浄して濾別し、蒸留水200mLで溶解させた0.50mol水酸化リチウム1水和物20.98gとミキサー混合し、均一なスラリーを形成させた。スラリーをテトラフルオロエチレン製シャーレに移し、50℃で2日間乾燥後、粉砕して焼成用原料を作製した。 The obtained precipitate was washed with distilled water, filtered off, and mixed with 20.98 g of 0.50 mol lithium hydroxide monohydrate dissolved in 200 mL of distilled water with a mixer to form a uniform slurry. The slurry was transferred to a tetrafluoroethylene petri dish, dried at 50 ° C. for 2 days, and then pulverized to prepare a raw material for firing.
次いで得られた粉末を、空気気流下、1時間かけて850℃まで昇温し、その温度で5時間保持後、炉中で室温付近まで冷却した。電気炉から焼成物を取り出し、焼成物を蒸留水で水洗し、濾過し、乾燥してXRD評価及び化学分析（ICP発光分析）を行い、仕込み遷移金属比と一致したリチウムマンガン系複合酸化物（単斜晶層状岩塩型結晶相）を粉末状生成物として単相で得た。 Next, the obtained powder was heated to 850 ° C. over 1 hour under an air stream, held at that temperature for 5 hours, and then cooled to near room temperature in a furnace. The calcined product is taken out from the electric furnace, the calcined product is washed with distilled water, filtered, dried, and subjected to XRD evaluation and chemical analysis (ICP luminescence analysis). (Monoclinic layered rock salt type crystal phase) was obtained as a powdery product in a single phase.
生成物の走査型電子顕微鏡（SEM）写真を図３に示す。図３より、一次粒子径が0.1〜0.5μmの粒子より構成されていることがわかる。 A scanning electron microscope (SEM) photograph of the product is shown in FIG. From FIG. 3, it can be seen that the particles are composed of particles having a primary particle diameter of 0.1 to 0.5 μm.
生成物20mgをアセチレンブラック（AB）5mgと混合後、0.5mgのポリテトラフルオロエチレン（PTFE）で結着させ、錠剤正極を得た。錠剤正極は120℃で一晩真空乾燥後グロ−ブボックス（GB）に導入し、一晩放置の後にコイン電池化した。負極には金属リチウムを、電解液には1M LiPF6を溶解させた炭酸エチレンと炭酸ジメチルの混合溶液を用いた。コイン電池は段階充電法で活性化した。なお、段階充電法とは、容量又は電位規制充電により充放電サイクルさせ、以後充電容量を徐々に大きく（又は充電電位を徐々に高く）しながら数回に分けてサイクルさせ、最終的に目的の電位範囲でサイクルさせる方法を意味する。具体的には、定電流（正極粉末重量あたり40mA/g）で充電容量を80mAh/gに制限して2.00Vまで放電後40mAh/g刻みで徐々に充電容量を上げて充放電を繰り返し4サイクル目に200mAh/gまで充電後放電し、5サイクル目に容量規制なしで4.8Vまで充電後放電して活性化した六方晶層状岩塩型結晶相を得た。その後、電位範囲を2.00-4.80Vに制限して29サイクル充放電し、放電後GB内で電池を解体して錠剤正極を取り出し、炭酸ジエチルで洗浄及びGB内で放置することにより乾燥後、大気非暴露で測定可能な試料ホルダ内に取り付け、GBより取り出し、粉末X線回折及び57Feメスバウワ分光評価を行った。 20 mg of the product was mixed with 5 mg of acetylene black (AB) and then bound with 0.5 mg of polytetrafluoroethylene (PTFE) to obtain a tablet positive electrode. The positive electrode of the tablet was vacuum-dried at 120 ° C. overnight, introduced into a globe box (GB), left overnight, and then converted into a coin battery. Metallic lithium was used for the negative electrode, and a mixed solution of ethylene carbonate and dimethyl carbonate in which 1M LiPF 6 was dissolved was used as the electrolytic solution. The coin battery was activated by the stepwise charging method. In the stepwise charging method, a charge / discharge cycle is performed by capacity or potential regulated charging, and then the charging capacity is gradually increased (or the charging potential is gradually increased) and the cycle is divided into several times to finally achieve the desired purpose. It means a method of cycling in a potential range. Specifically, the charging capacity is limited to 80mAh / g with a constant current (40mA / g per positive electrode powder weight), discharged to 2.00V, and then gradually increased in 40mAh / g increments to repeat charging and discharging for 4 cycles. The eyes were charged to 200 mAh / g and then discharged, and in the 5th cycle, they were charged to 4.8 V and then discharged to obtain an activated hexagonal layered rock salt type crystal phase. After that, the potential range is limited to 2.00-4.80V and charged / discharged for 29 cycles. After discharging, the battery is disassembled in GB, the positive electrode of the tablet is taken out, washed with diethyl carbonate and left in GB to dry, and then in the air. The sample was placed in a sample holder that could be measured without exposure, taken out from GB, and subjected to powder X-ray diffraction and 57 Fe female bower spectroscopic evaluation.
図１にX線回折評価結果を示す。回折パターンは3つのピーク（スピネル型結晶相1本、層状岩塩型結晶相2本）の重ね合わせでフィットできた。各ピークの面積比、スピネル型結晶相存在量の結果を表１に示す。表１から、スピネル型結晶相の存在比は22.3質量%と見積もることができた。 FIG. 1 shows the X-ray diffraction evaluation results. The diffraction pattern could be fitted by superimposing three peaks (one spinel-type crystal phase and two layered rock salt-type crystal phases). Table 1 shows the results of the area ratio of each peak and the abundance of spinel-type crystal phase. From Table 1, the abundance ratio of the spinel-type crystal phase could be estimated to be 22.3% by mass.
次に、57Feメスバウワ分光の結果を図２に示す。異性体シフトが+0.27mm/sの酸素4配位3価鉄成分と、異性体シフトが+0.34mm/sの酸素6配位3価鉄成分との重ね合わせでフィッティングできた。 57 Feメスバウワ分光法により得られる酸素4配位3価鉄成分及び酸素6配位3価鉄成分の面積比を表２に示す。表２から、スピネル型結晶相中の8a位置の3価鉄成分は49.3質量%と見積もることができた。 Next, the result of 57 Fe Mesbauwa spectroscopy is shown in FIG. Fitting was possible by superimposing an oxygen tetracoordinated trivalent iron component having an isomer shift of +0.27 mm / s and an oxygen hexacoordinated trivalent iron component having an isomer shift of +0.34 mm / s. 57 Fe Mesubauwa spectroscopy by oxygen tetracoordinate obtained trivalent iron component and oxygen 6-coordinated 3 area ratio of ferrous components shown in Table 2. From Table 2, the trivalent iron component at the 8a position in the spinel-type crystal phase could be estimated to be 49.3% by mass.
［実施例2］
最終焼成条件を大気から窒素に変更したこと以外は実施例1と同様に単斜晶層状岩塩型結晶相の試料作製を行った。得られたX線回折データを図４及び表１に示す。窒素中焼成を行うことにより、スピネル型結晶相の存在比が大幅に下がっていることがわかる。次に、57Feメスバウワ分光法の結果を図５及び表２に示す。異性体シフトが+0.21mm/sの酸素4配位3価鉄成分と、異性体シフトが+0.35mm/sの酸素6配位3価鉄成分との重ね合わせでフィッティングできた。面積比を表２に示す。面積比よりスピネル型結晶相中の8a位置の3価鉄成分は27.2質量％と見積もることができ、X線回折の結果と同様に窒素中焼成により低下していることがわかった。また、生成物の走査型電子顕微鏡（SEM）写真を図６に示す。実施例1に比べて明らかに一次粒子が大きくなっていることがわかり、粒成長が層状岩塩型結晶相−スピネル型結晶相転移を抑制する効果があることが分かった。
[Example 2]
A sample of the monoclinic layered rock salt type crystal phase was prepared in the same manner as in Example 1 except that the final firing condition was changed from the atmosphere to nitrogen. The obtained X-ray diffraction data are shown in FIG. 4 and Table 1. It can be seen that the abundance ratio of the spinel-type crystal phase is significantly reduced by firing in nitrogen. Next, the results of 57 Fe Mesbauwa spectroscopy are shown in FIG. 5 and Table 2. Fitting was possible by superimposing an oxygen tetracoordinated trivalent iron component having an isomer shift of +0.21 mm / s and an oxygen hexacoordinated trivalent iron component having an isomer shift of +0.35 mm / s. The area ratio is shown in Table 2. From the area ratio, the trivalent iron component at the 8a position in the spinel-type crystal phase could be estimated to be 27.2% by mass, and it was found that it was reduced by firing in nitrogen as in the result of X-ray diffraction. A scanning electron microscope (SEM) photograph of the product is also shown in FIG. It was found that the primary particles were clearly larger than in Example 1, and that the grain growth had the effect of suppressing the layered rock salt type crystal phase-spinel type crystal phase transition.
［実施例3］
活性化後、サイクル時の電位範囲のうちの上限電位を4.80Vから4.60Vに変更したこと以外は、実施例1と同様に試料作製を行った。得られたX線回折データを図７及び表１に示す。上限電圧を4.80Vから4.60Vに変更することにより、実施例1に比べてスピネル型結晶相含有量が22.3質量%から16.4質量%に下がっていることがわかる。次に、57Feメスバウワ分光法の結果を図８及び表２に示す。異性体シフトが+0.28mm/sの酸素4配位3価鉄成分と、異性体シフトが+0.33mm/sの酸素6配位3価鉄成分との重ね合わせでフィッティングできた。面積比を表２に示す。面積比よりスピネル型結晶相中の8a位置の3価鉄成分は31.2質量%と見積もることができ、X線回折の結果と同様に4.60Vに上限電圧を下げることによりスピネル型結晶相含有量が低下していることが分かった。
[Example 3]
After activation, samples were prepared in the same manner as in Example 1 except that the upper limit potential in the potential range during the cycle was changed from 4.80 V to 4.60 V. The obtained X-ray diffraction data are shown in FIG. 7 and Table 1. By changing the upper limit voltage from 4.80V to 4.60V, it can be seen that the spinel-type crystal phase content is reduced from 22.3% by mass to 16.4% by mass as compared with Example 1. Next, the results of 57 Fe Mesbauwa spectroscopy are shown in FIG. 8 and Table 2. Fitting was possible by superimposing an oxygen tetracoordinated trivalent iron component having an isomer shift of +0.28 mm / s and an oxygen hexacoordinated trivalent iron component having an isomer shift of +0.33 mm / s. The area ratio is shown in Table 2. From the area ratio, the trivalent iron component at the 8a position in the spinel-type crystal phase can be estimated to be 31.2% by mass, and the spinel-type crystal phase content can be increased by lowering the upper limit voltage to 4.60 V, similar to the result of X-ray diffraction. It turned out to be declining.
［実施例4］
活性化後、サイクル時の電位範囲のうちの上限電位を4.80Vから4.60Vに変更したこと以外は、実施例2と同様に試料作製を行った。得られたX線回折データを図９及び表１に示す。上限電圧を4.80Vから4.60Vに変更することにより、実施例2に比べてスピネル型結晶相含有量が13.2質量%から8.1質量%に下がっていることがわかる。次に、57Feメスバウワ分光法の結果を図１０及び表２に示す。異性体シフトが+0.20mm/sの酸素4配位3価鉄成分と、異性体シフトが+0.33mm/sの酸素6配位3価鉄成分との重ね合わせでフィッティングできた。面積比を表２に示す。面積比よりスピネル型結晶相中の8a位置の3価鉄成分は13.0質量%と見積もることができ、X線回折の結果と同様に4.60Vに上限電圧を下げることによりスピネル型結晶相含有量が低下していることが分かった。すなわち、窒素中焼成により一次粒子径を増大させ、上限電圧を4.60V以下に下げることにより、層状岩塩型結晶相−スピネル型結晶相転移が抑制できることがわかった。
[Example 4]
After activation, samples were prepared in the same manner as in Example 2 except that the upper limit potential in the potential range during the cycle was changed from 4.80 V to 4.60 V. The obtained X-ray diffraction data are shown in FIG. 9 and Table 1. By changing the upper limit voltage from 4.80V to 4.60V, it can be seen that the spinel-type crystal phase content is reduced from 13.2% by mass to 8.1% by mass as compared with Example 2. Next, the results of 57 Fe Mesbauwa spectroscopy are shown in FIG. 10 and Table 2. Fitting was possible by superimposing an oxygen tetracoordinated trivalent iron component having an isomer shift of +0.20 mm / s and an oxygen hexacoordinated trivalent iron component having an isomer shift of +0.33 mm / s. The area ratio is shown in Table 2. From the area ratio, the trivalent iron component at the 8a position in the spinel-type crystal phase can be estimated to be 13.0% by mass, and the spinel-type crystal phase content can be increased by lowering the upper limit voltage to 4.60 V, similar to the result of X-ray diffraction. It turned out to be declining. That is, it was found that the layered rock salt type crystal phase-spinel type crystal phase transition can be suppressed by increasing the primary particle size by firing in nitrogen and lowering the upper limit voltage to 4.60 V or less.
最後に、実施例1〜4の試料に対して、X線回折測定の結果と、57Feメスバウワ分光結果の関連性を図１１に示す。両者には良好な相関関係が成立し、57Feメスバウワ分光法を用いてもX線回折測定とほぼ同様のスピネル型結晶相含有量を定量することができることが明らかである。 Finally, FIG. 11 shows the relationship between the X-ray diffraction measurement results and the 57 Fe Mesbauwa spectroscopic results for the samples of Examples 1 to 4. A good correlation was established between the two, and it is clear that the spinel-type crystal phase content can be quantified by using 57 Fe Mesbauer spectroscopy, which is almost the same as the X-ray diffraction measurement.
以上の実施例から明らかなように、層状岩塩型結晶相リチウムマンガン系複合酸化物正極材料のサイクル試験中に生成するスピネル型結晶相は、X線回折データのプロファイルフィッティングにより定量可能であり、試料中にFeイオンが含まれていれば、57Feメスバウワ分光法によっても定量可能である。本手法を用いることにより、層状岩塩型結晶相−スピネル型結晶相転移抑制技術開発が加速することが明らかである。 As is clear from the above examples, the spinel-type crystal phase generated during the cycle test of the layered rock salt-type crystal phase lithium manganese-based composite oxide positive electrode material can be quantified by profile fitting of the X-ray diffraction data, and is a sample. If Fe ions are contained in it, it can be quantified by 57 Fe Mesbauwa spectroscopy. It is clear that the use of this method accelerates the development of layered rock salt type crystal phase-spinel type crystal phase transition suppression technology.
本発明の定量方法は、例えば、小型民生用、車載用、定置用等のリチウムイオン二次電池の正極活物質から生成するリチウムマンガンスピネル型結晶相を定量することができる。 The quantification method of the present invention can, for example, quantify the lithium manganese spinel-type crystal phase produced from the positive electrode active material of a lithium ion secondary battery for small consumer use, in-vehicle use, stationary use, and the like.
Claims (2)
前記充放電サイクル試験後の正極活物質を、CuKα線を用いたX線回折計において2θ= 61〜66°の範囲を測定し、得られたX線回折パターンを3つのピークでプロファイルフィッティングを行い、高角側2本のピークと低角側1本のピークとの面積比を算出する工程
を備え、前記高角側2本のピークが六方晶層状岩塩型結晶相のピークであり、前記低角側1本のピークがリチウムマンガンスピネル型結晶相のピークである、方法。 A method for quantifying the lithium manganese spinel-type crystal phase present in the positive electrode active material containing a lithium manganese-based composite oxide after a charge / discharge cycle test.
The positive electrode active material after the charge / discharge cycle test was measured in the range of 2θ = 61 to 66 ° with an X-ray diffractometer using CuKα rays, and the obtained X-ray diffraction pattern was profile-fitted at three peaks. , The step of calculating the area ratio between the two peaks on the high angle side and the one peak on the low angle side is provided, and the two peaks on the high angle side are the peaks of the hexagonal layered rock salt type crystal phase, and the two peaks on the low angle side are the peaks of the low angle side. The method in which one peak is the peak of the lithium manganese spinel type crystal phase.
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