JP6735660B2 - Negative electrode active material for lithium ion secondary battery, method for producing the same, negative electrode and battery - Google Patents
Negative electrode active material for lithium ion secondary battery, method for producing the same, negative electrode and battery Download PDFInfo
- Publication number
- JP6735660B2 JP6735660B2 JP2016240767A JP2016240767A JP6735660B2 JP 6735660 B2 JP6735660 B2 JP 6735660B2 JP 2016240767 A JP2016240767 A JP 2016240767A JP 2016240767 A JP2016240767 A JP 2016240767A JP 6735660 B2 JP6735660 B2 JP 6735660B2
- Authority
- JP
- Japan
- Prior art keywords
- negative electrode
- active material
- electrode active
- secondary battery
- lithium ion
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
- 239000007773 negative electrode material Substances 0.000 title claims description 151
- 229910001416 lithium ion Inorganic materials 0.000 title claims description 84
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims description 60
- 238000004519 manufacturing process Methods 0.000 title claims description 25
- 239000010949 copper Substances 0.000 claims description 80
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 56
- 239000010703 silicon Substances 0.000 claims description 56
- 229910052710 silicon Inorganic materials 0.000 claims description 55
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 51
- 229910052802 copper Inorganic materials 0.000 claims description 49
- 239000000203 mixture Substances 0.000 claims description 40
- 238000000034 method Methods 0.000 claims description 37
- 239000002994 raw material Substances 0.000 claims description 32
- QPLDLSVMHZLSFG-UHFFFAOYSA-N Copper oxide Chemical compound [Cu]=O QPLDLSVMHZLSFG-UHFFFAOYSA-N 0.000 claims description 29
- 238000010298 pulverizing process Methods 0.000 claims description 24
- 238000002441 X-ray diffraction Methods 0.000 claims description 23
- 238000005259 measurement Methods 0.000 claims description 18
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 17
- 239000005751 Copper oxide Substances 0.000 claims description 16
- 229910000431 copper oxide Inorganic materials 0.000 claims description 16
- 229910001868 water Inorganic materials 0.000 claims description 16
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims description 12
- 229910052744 lithium Inorganic materials 0.000 claims description 12
- 229910052760 oxygen Inorganic materials 0.000 claims description 12
- LIVNPJMFVYWSIS-UHFFFAOYSA-N silicon monoxide Chemical compound [Si-]#[O+] LIVNPJMFVYWSIS-UHFFFAOYSA-N 0.000 claims description 12
- 238000004833 X-ray photoelectron spectroscopy Methods 0.000 claims description 10
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 10
- FUJCRWPEOMXPAD-UHFFFAOYSA-N lithium oxide Chemical compound [Li+].[Li+].[O-2] FUJCRWPEOMXPAD-UHFFFAOYSA-N 0.000 claims description 10
- 229910001947 lithium oxide Inorganic materials 0.000 claims description 10
- 239000001301 oxygen Substances 0.000 claims description 10
- 239000000470 constituent Substances 0.000 claims description 9
- 239000011856 silicon-based particle Substances 0.000 claims description 7
- -1 lithium ion ion Chemical class 0.000 claims description 6
- 239000011255 nonaqueous electrolyte Substances 0.000 claims description 6
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 5
- 229910021417 amorphous silicon Inorganic materials 0.000 claims description 4
- 238000002050 diffraction method Methods 0.000 claims description 2
- 208000028659 discharge Diseases 0.000 description 50
- 239000000843 powder Substances 0.000 description 15
- 238000012360 testing method Methods 0.000 description 14
- 238000011156 evaluation Methods 0.000 description 12
- 239000007858 starting material Substances 0.000 description 10
- 229910052814 silicon oxide Inorganic materials 0.000 description 8
- 230000000052 comparative effect Effects 0.000 description 7
- 239000002245 particle Substances 0.000 description 7
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 6
- 210000004027 cell Anatomy 0.000 description 6
- 238000000227 grinding Methods 0.000 description 6
- 238000002156 mixing Methods 0.000 description 6
- 239000011149 active material Substances 0.000 description 5
- XUCJHNOBJLKZNU-UHFFFAOYSA-M dilithium;hydroxide Chemical compound [Li+].[Li+].[OH-] XUCJHNOBJLKZNU-UHFFFAOYSA-M 0.000 description 5
- 238000007599 discharging Methods 0.000 description 5
- 238000002149 energy-dispersive X-ray emission spectroscopy Methods 0.000 description 5
- 230000014759 maintenance of location Effects 0.000 description 5
- 230000003647 oxidation Effects 0.000 description 5
- 238000007254 oxidation reaction Methods 0.000 description 5
- 239000000126 substance Substances 0.000 description 5
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 4
- 239000013078 crystal Substances 0.000 description 4
- 230000006872 improvement Effects 0.000 description 4
- 239000002002 slurry Substances 0.000 description 4
- 238000001228 spectrum Methods 0.000 description 4
- 239000011230 binding agent Substances 0.000 description 3
- 230000008859 change Effects 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 239000013081 microcrystal Substances 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 238000000926 separation method Methods 0.000 description 3
- 239000000243 solution Substances 0.000 description 3
- 239000002904 solvent Substances 0.000 description 3
- 238000003756 stirring Methods 0.000 description 3
- 239000000758 substrate Substances 0.000 description 3
- JJLJMEJHUUYSSY-UHFFFAOYSA-L Copper hydroxide Chemical compound [OH-].[OH-].[Cu+2] JJLJMEJHUUYSSY-UHFFFAOYSA-L 0.000 description 2
- 239000005750 Copper hydroxide Substances 0.000 description 2
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 230000004913 activation Effects 0.000 description 2
- 239000007864 aqueous solution Substances 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 238000007796 conventional method Methods 0.000 description 2
- 239000011889 copper foil Substances 0.000 description 2
- 229910001956 copper hydroxide Inorganic materials 0.000 description 2
- 239000010410 layer Substances 0.000 description 2
- 150000002642 lithium compounds Chemical class 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000007774 positive electrode material Substances 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 238000001878 scanning electron micrograph Methods 0.000 description 2
- 150000003377 silicon compounds Chemical class 0.000 description 2
- 238000004611 spectroscopical analysis 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
- 229910012851 LiCoO 2 Inorganic materials 0.000 description 1
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- 229910000676 Si alloy Inorganic materials 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 238000000026 X-ray photoelectron spectrum Methods 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 230000001133 acceleration Effects 0.000 description 1
- 239000006230 acetylene black Substances 0.000 description 1
- 238000005275 alloying Methods 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 239000011324 bead Substances 0.000 description 1
- 239000003575 carbonaceous material Substances 0.000 description 1
- 239000003638 chemical reducing agent Substances 0.000 description 1
- 238000005229 chemical vapour deposition Methods 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 238000013329 compounding Methods 0.000 description 1
- 229910021419 crystalline silicon Inorganic materials 0.000 description 1
- 210000001787 dendrite Anatomy 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 description 1
- 239000012153 distilled water Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
- 239000003792 electrolyte Substances 0.000 description 1
- 239000010419 fine particle Substances 0.000 description 1
- 238000010304 firing Methods 0.000 description 1
- 239000011888 foil Substances 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- JEGUKCSWCFPDGT-UHFFFAOYSA-N h2o hydrate Chemical compound O.O JEGUKCSWCFPDGT-UHFFFAOYSA-N 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000002354 inductively-coupled plasma atomic emission spectroscopy Methods 0.000 description 1
- 238000010884 ion-beam technique Methods 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 239000011259 mixed solution Substances 0.000 description 1
- 229910021421 monocrystalline silicon Inorganic materials 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 229910017604 nitric acid Inorganic materials 0.000 description 1
- 239000012299 nitrogen atmosphere Substances 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 229920001721 polyimide Polymers 0.000 description 1
- 239000009719 polyimide resin Substances 0.000 description 1
- 238000004080 punching Methods 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000001223 reverse osmosis Methods 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 238000010008 shearing Methods 0.000 description 1
- 239000002356 single layer Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000000992 sputter etching Methods 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 239000002966 varnish Substances 0.000 description 1
Classifications
-
- 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
Landscapes
- Secondary Cells (AREA)
- Battery Electrode And Active Subsutance (AREA)
Description
本発明はリチウムイオン二次電池等の二次電池用の負極活物質に関するものであり、特にケイ素、銅、リチウム、酸素を主要な構成元素とする二次電池用負極活物質およびその製造方法、並びに、その負極活物質を用いた二次電池用負極およびその負極を用いた二次電池に関する。 The present invention relates to a negative electrode active material for a secondary battery such as a lithium-ion secondary battery, and in particular, a negative electrode active material for a secondary battery having silicon, copper, lithium and oxygen as main constituent elements and a method for producing the same. In addition, the present invention relates to a negative electrode for a secondary battery using the negative electrode active material and a secondary battery using the negative electrode.
近年、携帯型の電子機器、通信機器等の著しい発展に伴い、経済性と機器の小型化、軽量化の観点から、高エネルギー密度のリチウムイオン二次電池が強く要望されている。従来、この種のリチウムイオン二次電池の高容量化の方策として、正極および正極活物質の改善、負極および負極活物質の改善等、様々な方法が検討されている。負極および負極活物質の改善として、負極活物質にケイ素（シリコン、Ｓｉ）またはケイ素化合物を用いる方法が検討されている。ケイ素は現在実用化されている炭素材料の理論容量３７２ｍＡｈ／ｇより遙かに高い理論容量４２００ｍＡｈ／ｇを示すことから、電池の小型化と高容量化において期待が大きい材料である。また、ケイ素はリチウムと合金化することが可能なため、充放電時のデンドライト発生による内部短絡が起こらない負極材として優れた特長を持っている。 In recent years, with the remarkable development of portable electronic devices, communication devices, and the like, there has been a strong demand for a high energy density lithium ion secondary battery from the viewpoints of economy and reduction in size and weight of the device. Conventionally, various methods such as improvement of a positive electrode and a positive electrode active material and improvement of a negative electrode and a negative electrode active material have been studied as measures for increasing the capacity of this type of lithium ion secondary battery. As a method for improving the negative electrode and the negative electrode active material, a method of using silicon (silicon, Si) or a silicon compound for the negative electrode active material has been studied. Since silicon has a theoretical capacity of 4200 mAh/g, which is much higher than the theoretical capacity of 372 mAh/g of carbon materials currently in practical use, silicon is a material that is expected to be small in size and has high capacity. In addition, since silicon can be alloyed with lithium, it has an excellent feature as a negative electrode material that does not cause an internal short circuit due to dendrite generation during charge/discharge.
例えば、特開平５−０７４４６３号公報（特許文献１）には、単結晶ケイ素を負極活物質の支持体として使用したリチウムイオン二次電池が開示されている。また、負極材に導電性を付与することを目的として、特開２０００−２４３３９６号公報（特許文献２）には、酸化ケイ素と黒鉛とをメカニカルアロイングした後、炭化処理する技術が、特開２０００−２１５８８７号公報（特許文献３）には、ケイ素粒子表面を化学蒸着法により炭素層で被覆する技術が、それぞれ開示されている。これらの従来技術の場合、ケイ素粒子表面に炭素層を設けることにより、負極材の導電性を改善することは可能であるが、充放電に伴う大きな体積変化に起因するケイ素負極活物質の低いサイクル特性という課題を解決することはできなかった。
ケイ素はリチウムと合金化した場合、体積が最大４倍程度に膨張する。そのため、充放電サイクルを繰り返すと、ケイ素粒子内に大きな内部歪が生じ、ケイ素粒子が微粉化することによりサイクル特性が低下すると考えられている。ケイ素負極活物質のもつ低いサイクル特性という課題を解決するために、様々な方法が検討されている。特開２００４−３３５２７１号公報（特許文献４）には、ケイ素とチタン、ニッケル、銅等の金属をボールミルでメカニカルアロイし、負極活物質を得る技術が開示されている。特開２０１０−２４４７６７号公報（特許文献５）には、ケイ素粒子と銅粒子を乾式アトライタで処理して、負極活物質を得る技術が開示されている。特開２０１２−１１３９４５号公報（特許文献６）には、ケイ素の粗粉をビーズミルで破砕し、引き続き導電性基材粉として銅粉を加え、せん断応力を加えることにより凝集体を得る技術が開示されている。しかし、これらの技術を用いても、負極活物質単位質量あたりの電池容量やサイクル特性等の、負極活物質に起因する電池特性の改良は現時点では十分とは言えなかった。特開２０１５−６５１４６号公報（特許文献７）、特開２０１６−３５８２５公報（特許文献８）には、ケイ素と酸化銅（２）を粉砕手段に投入し粉砕処理を行うことにより、電池容量やサイクル特性が改善された負極活物質が得られる技術が開示されている。
For example, JP-A-5-074463 (Patent Document 1) discloses a lithium ion secondary battery using single crystal silicon as a support for a negative electrode active material. Further, for the purpose of imparting conductivity to the negative electrode material, Japanese Patent Application Laid-Open No. 2000-243396 (Patent Document 2) discloses a technique in which silicon oxide and graphite are mechanically alloyed and then carbonized. Japanese Patent Laid-Open No. 2000-215887 (Patent Document 3) discloses a technique of coating the surface of silicon particles with a carbon layer by a chemical vapor deposition method. In the case of these conventional techniques, by providing a carbon layer on the surface of silicon particles, it is possible to improve the conductivity of the negative electrode material, but a low cycle of the silicon negative electrode active material due to a large volume change due to charge and discharge. We could not solve the problem of characteristics.
When alloyed with lithium, silicon expands up to about 4 times in volume. Therefore, it is considered that when the charge/discharge cycle is repeated, a large internal strain is generated in the silicon particles and the silicon particles are pulverized to deteriorate the cycle characteristics. Various methods have been studied in order to solve the problem of the low cycle characteristics of the silicon negative electrode active material. Japanese Unexamined Patent Application Publication No. 2004-335271 (Patent Document 4) discloses a technique of mechanically alloying silicon and a metal such as titanium, nickel, or copper with a ball mill to obtain a negative electrode active material. Japanese Unexamined Patent Publication No. 2010-244767 (Patent Document 5) discloses a technique of treating silicon particles and copper particles with a dry attritor to obtain a negative electrode active material. Japanese Unexamined Patent Application Publication No. 2012-113945 (Patent Document 6) discloses a technique in which coarse powder of silicon is crushed by a bead mill, copper powder is subsequently added as a conductive base material powder, and shear stress is applied to obtain an aggregate. Has been done. However, even if these techniques are used, at present, the improvement of the battery characteristics due to the negative electrode active material such as the battery capacity per unit mass of the negative electrode active material and the cycle characteristics cannot be said to be sufficient. In JP-A-2015-65146 (Patent Document 7) and JP-A-2016-35825 (Patent Document 8), the battery capacity and the A technique for obtaining a negative electrode active material with improved cycle characteristics is disclosed.
ケイ素またはケイ素化合物を用いる負極活物質は、その高い理論容量から、電池の小型化と高容量化において期待が大きく、負極活物質単位質量あたりの電池容量とサイクル特性を同時に一定以上の水準にすることが求められていた。特許文献７および８の技術は、電池容量とサイクル特性を同時に一定以上の水準にするこという点では改善されたが、本発明者らが検討した結果、急速充放電をおこなった場合、サイクル特性が大きく損なわれることが分かった。ケイ素を用いた負極活物質を使用した二次電池が広く使用されるためには、急速充放電をおこなった場合のサイクル特性を向上する必要性が高い。本発明で解決しようとする課題は、急速充放電をおこなった場合のサイクル特性が良好であり、かつ、リチウムイオン二次電池用負極活物資として実用可能な程度に大きな電池容量を持つ負極活物質およびその製造方法を提供することである。また、この負極活物質を用いた負極および二次電池、およびこれらの製造方法を提供することである。 Due to its high theoretical capacity, negative electrode active materials using silicon or silicon compounds are highly expected in battery miniaturization and high capacity, and the battery capacity per unit mass of the negative electrode active material and the cycle characteristics are simultaneously at a certain level or higher. Was required. The techniques of Patent Documents 7 and 8 have been improved in that the battery capacity and the cycle characteristics are simultaneously set to a certain level or higher, but as a result of the study by the present inventors, the cycle characteristics are improved when the rapid charge/discharge is performed. Was found to be greatly impaired. In order for a secondary battery using a negative electrode active material using silicon to be widely used, it is highly necessary to improve the cycle characteristics when performing rapid charge/discharge. The problem to be solved by the present invention is a negative electrode active material having good cycle characteristics when subjected to rapid charge and discharge, and having a battery capacity large enough to be practically used as a negative electrode active material for a lithium ion secondary battery. And a method for manufacturing the same. Another object of the present invention is to provide a negative electrode and a secondary battery using this negative electrode active material, and a method for producing them.
本発明者らが鋭意検討した結果、ケイ素と銅原料と酸化リチウム（Ｌｉ2Ｏ）を粉砕手段に投入し粉砕処理を行うと同時に、粉砕物を混合することにより、ケイ素、銅、リチウム、酸素を主要な構成元素とする二次電池用負極活物質得られ、この本発明の二次電池用負極活物質は、急速充放電をおこなった場合でもサイクル特性が良好であり、リチウムイオン二次電池用負極活物資として実用可能な程度に大きな電池容量を持つ負極活物質であることを見出し、本発明を完成するに至った。前記銅原料は、金属銅（すなわち銅（０））、酸化銅（２）のうちの１種まだはこれらの混合物である。なお、酸化銅のあとのカッコ内の数字は、酸化数を表すもので、本来、ローマ数字で表記すべきものである。 As a result of diligent studies by the present inventors, silicon, copper raw material, and lithium oxide (Li 2 O) are put into a pulverizing means to perform a pulverizing process, and at the same time, a pulverized product is mixed to obtain silicon, copper, lithium, and oxygen. A negative electrode active material for a secondary battery containing as a main constituent element is obtained. The negative electrode active material for a secondary battery of the present invention has good cycle characteristics even when subjected to rapid charge/discharge, and a lithium ion secondary battery The present invention has been completed by finding that it is a negative electrode active material having a battery capacity as large as practicable as a negative electrode active material for use. The copper raw material is one of metallic copper (that is, copper (0)) and copper oxide (2), or a mixture thereof. The number in parentheses after the copper oxide represents the oxidation number and should be originally written in Roman numerals.
上記の目的を達成するために、本発明は、以下を提供する。すなわち、
ケイ素、銅、リチウムおよび酸素を主要な構成元素とするリチウムイオン二次電池用負極活物質であって、Ｃｕ3ＳｉおよびＸ回折法（ＸＲＤ）により測定される平均結晶子径（Ｄx）が５０ｎｍ以下、好ましくは３０ｎｍ以下でのケイ素粒子を含み、かつ、モル比で示される元素組成比Ｃｕ／（Ｓｉ＋Ｃｕ+Ｌｉ＋Ｏ）およびＯ／（Ｓｉ＋Ｃｕ+Ｌｉ＋Ｏ）が０.０２〜０.２０であり、モル比で示される元素組成比Ｌｉ／（Ｓｉ＋Ｃｕ+Ｌｉ＋Ｏ）が０.０２〜０.３０、好ましくは０.０３〜０.１５であり、ＸＲＤの測定結果から算出されるピーク強度比（Ｃｕ3Ｓｉ／Ｓｉ）が０.０５から１.０であるリチウムイオン二次電池用負極活物質が提供される。
このリチウムイオン二次電池用負極活物質は、非晶質のケイ素酸化物を含むものであって良く、その場合は、Ｘ線光電子分光分析法（ＸＰＳ）の測定結果から算出される負極活物質のピーク面積比（ＳｉＯx／Ｓｉ（０））が０.０６〜０.７２であっても良い。
また、このリチウムイオン二次電池用負極活物質は、モル比で示される元素組成比Ｌｉ／（Ｓｉ＋Ｃｕ＋Ｌｉ+Ｏ）が０.０２〜０.２であっても構わない。
また、本発明においては、前記のリチウムイオン二次電池用負極活物質の製造方法として、ケイ素と銅原料と酸化リチウムを粉砕手段中に投入し、粉砕する工程を含む、リチウムイオン二次電池用負極活物質の製造方法が提供される。このリチウムイオン二次電池用負極活物質の製造方法においては、銅原料として金属銅または酸化銅（２）の何れを用いても良く、粉砕手段にさらに水を投入しても良い。
本発明により得られるリチウムイオン二次電池用負極活物質を用いてリチウムイオン二次電池用負極が、またそのリチウムイオン二次電池用負極を用いてリチウムイオン二次電池を製造することができる。
In order to achieve the above-mentioned object, the present invention provides the following. That is,
A negative electrode active material for a lithium ion secondary battery containing silicon, copper, lithium and oxygen as main constituent elements, which has an average crystallite diameter (D x ) measured by Cu 3 Si and an X diffraction method (XRD). Includes silicon particles of 50 nm or less, preferably 30 nm or less, and the elemental composition ratio Cu/(Si+Cu+Li+O) and O/(Si+Cu+Li+O) shown by the molar ratio is 0.02 to 0.20, The elemental composition ratio Li/(Si+Cu+Li+O) represented by the molar ratio is 0.02 to 0.30, preferably 0.03 to 0.15, and the peak intensity ratio (Cu 3 Provided is a negative electrode active material for a lithium-ion secondary battery having a Si/Si ratio of 0.05 to 1.0.
The negative electrode active material for a lithium ion secondary battery may contain an amorphous silicon oxide, and in that case, the negative electrode active material calculated from the measurement result of X-ray photoelectron spectroscopy (XPS). The peak area ratio (SiO x /Si(0)) may be 0.06 to 0.72.
The negative electrode active material for a lithium ion secondary battery may have an element composition ratio Li/(Si+Cu+Li+O) represented by a molar ratio of 0.02 to 0.2.
Further, in the present invention, as a method for producing the negative electrode active material for a lithium ion secondary battery, including a step of introducing silicon and a copper raw material and lithium oxide into a pulverizing means, and pulverizing, for a lithium ion secondary battery A method for manufacturing a negative electrode active material is provided. In this method for producing a negative electrode active material for a lithium ion secondary battery, either copper metal or copper oxide (2) may be used as a copper raw material, and water may be further added to the pulverizing means.
The negative electrode active material for a lithium ion secondary battery obtained by the present invention can be used to manufacture a negative electrode for a lithium ion secondary battery, and the negative electrode for a lithium ion secondary battery can be used to manufacture a lithium ion secondary battery.
以上、本発明においては、ケイ素と銅原料と酸化リチウム（Ｌｉ2Ｏ）を粉砕処理すると同時に粉砕物を混合することにより、ケイ素、銅、リチウムおよび酸素を主要な構成元素とするリチウムイオン二次電池用負極活物質が得ることができる。また、粉砕処理をおこなう際に前記物質に水を添加することができる。この二次電池用負極活物質は、急速充放電をおこなった場合でもサイクル特性が良好であり、かつ、リチウムイオン二次電池用負極活物資として実用可能な程度に大きな電池容量を持つ。また、その負極活物質を用いたリチウムイオン二次電池用負極およびリチウムイオン二次電池を得ることが出来る。 As described above, in the present invention, the lithium ion secondary containing silicon, copper, lithium and oxygen as main constituent elements is obtained by pulverizing the silicon, the copper raw material and the lithium oxide (Li 2 O) and mixing the pulverized material at the same time. A negative electrode active material for batteries can be obtained. In addition, water can be added to the substance when performing the crushing treatment. The negative electrode active material for a secondary battery has good cycle characteristics even when subjected to rapid charge/discharge, and has a battery capacity large enough to be practically used as a negative electrode active material for a lithium ion secondary battery. Further, a negative electrode for a lithium ion secondary battery and a lithium ion secondary battery using the negative electrode active material can be obtained.
［負極活物質］
本発明のリチウムイオン二次電池用負極活物質は、原料であるケイ素と銅原料と酸化リチウム（Ｌｉ2Ｏ）とを、公知の粉砕手段中で粉砕処理を行うと同時に、粉砕された原料を混合することにより得られる。粉砕手段への原料投入のタイミングは、使用する原料の大きさに依存し、必ずしも同時に投入することを要さないが、原料物質を同時に投入することが好ましい。前記銅原料は、金属銅（すなわち銅（０））、酸化銅（２）のうちの１種またはこれらの混合物とすることが好ましい。また、前記原料に加えて、水を粉砕手段に投入してもよい。
[Negative electrode active material]
The negative electrode active material for a lithium ion secondary battery of the present invention is a raw material silicon, a copper raw material and lithium oxide (Li 2 O) are pulverized in a known pulverizing means, and at the same time, the pulverized raw material is Obtained by mixing. The timing of feeding the raw materials to the crushing means depends on the size of the raw materials used and does not necessarily need to be fed simultaneously, but it is preferable to feed the raw materials at the same time. The copper raw material is preferably one of metallic copper (that is, copper (0)) and copper oxide (2) or a mixture thereof. In addition to the above raw materials, water may be added to the crushing means.
粉砕、混合処理する前の銅原料についてのＸ線回折（ＸＲＤ）パターンでは銅原料の種類に応じて酸化銅（２）または金属銅に対応するピークが観察されるが、各実施例により得られた負極活物質のＸＲＤパターンには、酸化銅（２）または金属銅に対応するピークは認められず、２θが４４.８°付近にピークが認められ、これはＣｕ3Ｓｉが存在することを示している。また、ケイ素に対応するピークの半値幅が、粉砕処理により増大しており、粉砕処理によりケイ素が微結晶化してケイ素の結晶子径が小さくなっていることが判る。なお、後述する様に、本明細書における２θの値は、Ｘ線源としてＣｕ管球を用いた場合の値である。
図１に、後述する実施例１において得られた負極活物質について、Ｘ線光電子分光分析法（ＸＰＳ）により得られた、ケイ素の２ｐピークのスペクトルを示す。Ｓｉ２ｐスペクトル中には金属状態のケイ素（Ｓｉ（０））に対応するピーク以外に、酸化状態の異なる複数の酸化物に対応するピークが観察され、低級酸化物を含むケイ素の酸化物、すなわちＳｉＯx（ただし０＜ｘ＜２）が存在していることが判る。すなわち、粉砕処理中、ケイ素は還元剤として作用し、酸化銅（２）、酸化リチウム、水のいずれか1つ以上に含まれる酸素の一部または全部を奪って、ケイ素自体は酸化したものと考えられる。Ｓｉ（０）、ＳｉＯxに対応するピークをピーク分離し、分子をＳｉＯｘに対応する各ピークの面積の和、分母をＳｉ（０）に対応するピークの面積としたピーク面積比（ＳｉＯx／Ｓｉ（０））は、０.０６〜０.７２であることが好ましい。従来技術であるＳｉ（０）と金属銅を粉砕処理して得られる負極活物質と比較すると、特許文献７、８に記載の負極活物質は、サイクル特性が向上している。本発明者らは、このサイクル特性の向上には、負極活物質中にＳｉＯｘが存在していることが貢献していると考えている。
In the X-ray diffraction (XRD) pattern of the copper raw material before the crushing and mixing treatment, peaks corresponding to copper oxide (2) or metallic copper are observed depending on the type of the copper raw material. In the XRD pattern of the negative electrode active material, no peak corresponding to copper oxide (2) or metallic copper was observed, and a peak was observed near 2θ of 44.8°, which indicates that Cu 3 Si is present. Showing. Further, it can be seen that the full width at half maximum of the peak corresponding to silicon is increased by the pulverization treatment, and the pulverization treatment microcrystallizes the silicon to reduce the crystallite diameter of silicon. As will be described later, the value of 2θ in this specification is a value when a Cu tube is used as the X-ray source.
FIG. 1 shows a 2p peak spectrum of silicon obtained by X-ray photoelectron spectroscopy (XPS) for the negative electrode active material obtained in Example 1 described later. In the Si2p spectrum, peaks corresponding to a plurality of oxides having different oxidation states were observed in addition to the peak corresponding to silicon (Si(0)) in a metal state, and silicon oxides including lower oxides, that is, SiO It can be seen that x (where 0<x<2) exists. That is, during the pulverization process, silicon acts as a reducing agent and deprives some or all of oxygen contained in at least one of copper oxide (2), lithium oxide and water, and silicon itself is oxidized. Conceivable. Si (0), and the peak separation of the peaks corresponding to SiO x, the sum of the areas of the peaks corresponding to molecules SiOx, denominator Si (0) peak area ratio as the area of the corresponding peak (SiO x / Si(0)) is preferably 0.06 to 0.72. Compared with a negative electrode active material obtained by pulverizing Si(0) and metallic copper, which is a conventional technique, the negative electrode active materials described in Patent Documents 7 and 8 have improved cycle characteristics. The present inventors believe that the presence of SiOx in the negative electrode active material contributes to the improvement of the cycle characteristics.
特許文献７、８に記載されているケイ素と酸化銅（２）に対してせん断力を加えることにより得られる負極活物質と比較して、本発明の負極活物質が、急速充放電をおこなった場合のサイクル特性が良好である理由は現時点で特定できていないが、本発明者らは、以下のように推定している。本発明の負極活物質は、ケイ素および酸化銅、またはケイ素と金属銅と水とを粉砕して得られた負極活物質に、さらに、それ自身は負極活物質の必須構成元素ではないリチウムを構成元素に有するリチウム化合物を含有することに特徴がある。詳細な機構はわかっていないが、このリチウム化合物を含有することにより、負極活物質中の電子やリチウムイオンの移動度が高くなり、結果として、高速充放電に伴う大きな体積変化に起因するケイ素負極活物質のサイクル特性の劣化が生じにくくなっていると考えられる。 Compared with the negative electrode active material obtained by applying a shearing force to silicon and copper oxide (2) described in Patent Documents 7 and 8, the negative electrode active material of the present invention was subjected to rapid charge/discharge. The reason why the cycle characteristics in this case are good has not been identified yet, but the present inventors presume as follows. The negative electrode active material of the present invention is a negative electrode active material obtained by pulverizing silicon and copper oxide, or silicon, metallic copper and water, and further comprises lithium which is not an essential constituent element of the negative electrode active material. It is characterized by containing a lithium compound contained in the element. Although the detailed mechanism is not known, by containing this lithium compound, the mobility of electrons and lithium ions in the negative electrode active material becomes high, and as a result, the silicon negative electrode caused by a large volume change accompanying high-speed charge and discharge. It is considered that the cycle characteristics of the active material are less likely to deteriorate.
本発明の負極活物質に含まれるＣｕ3Ｓｉは、ＸＲＤの測定結果から後述する方法で得られるピーク強度比（Ｃｕ3Ｓｉ／Ｓｉ）が０.０５〜１.０の範囲であることが好ましい。ピーク強度比（Ｃｕ3Ｓｉ／Ｓｉ）が０.０５未満の場合には、サイクル特性が十分向上しない場合があり、１.０を超える場合には、負極活物質に含まれる結晶性のＳｉの割合が少なくなり、初期放電容量が十分得られない場合があり、ピーク強度比（Ｃｕ3Ｓｉ／Ｓｉ）は、０.０５〜０.５の範囲であることが更に好ましく、０.０５〜０.３の範囲であることが一層好ましい。本発明の電極活物質の複合体には、処理中に形態が変化しなかった銅原料である酸化銅（２）または金属銅の微粒子が極少量含まれることも考えられるが、その存在自体は特に問題とならない。
ケイ素結晶を微細化すると、ケイ素微結晶の体積変動の絶対値が小さくなるため、リチウムイオンの吸放出に伴うケイ素微結晶の体積変化に基づく電池特性の劣化を抑制する観点から、ケイ素結晶をより微細化することが好ましいと考えられる。
本発明において得られるリチウムイオン二次電池用負極活物質中に含まれるケイ素微結晶の平均粒子径は、後述するＸ線回折法（ＸＲＤ）により測定される平均結晶子径（Ｄx）で５０ｎｍ以下が好ましく、より良好なサイクル特性（容量維持率）を得るためには３０ｎｍ以下であることがさらに好ましい。結晶子径が５０ｎｍを超える場合には、サイクル特性が十分向上しない場合があるので、好ましくない。Ｄxの下限は特に限定されないが、粉砕処理によって１ｎｍ未満にすることは困難であり、現実的には１ｎｍ以上となる。
For Cu 3 Si contained in the negative electrode active material of the present invention, it is preferable that the peak intensity ratio (Cu 3 Si/Si) obtained by the method described later from the measurement result of XRD is in the range of 0.05 to 1.0. .. If the peak intensity ratio (Cu 3 Si/Si) is less than 0.05, the cycle characteristics may not be sufficiently improved, and if it exceeds 1.0, the crystalline Si content in the negative electrode active material may be reduced. The ratio may decrease and the initial discharge capacity may not be sufficiently obtained, and the peak intensity ratio (Cu 3 Si/Si) is more preferably in the range of 0.05 to 0.5, and 0.05 to 0. The range of 0.3 is more preferable. It is possible that the composite of the electrode active material of the present invention contains a very small amount of fine particles of copper oxide (2) which is a copper raw material whose shape is not changed during the treatment, or metallic copper, but the existence itself is present. No particular problem.
When the silicon crystal is miniaturized, the absolute value of the volume fluctuation of the silicon microcrystal becomes small. Therefore, from the viewpoint of suppressing the deterioration of the battery characteristics due to the volume change of the silicon microcrystal accompanying the absorption and release of lithium ions, the silicon crystal is more preferable. It is considered preferable to reduce the size.
The average particle size of the silicon microcrystals contained in the negative electrode active material for a lithium ion secondary battery obtained in the present invention is 50 nm in the average crystallite size (D x ) measured by the X-ray diffraction method (XRD) described later. The following is preferable, and 30 nm or less is more preferable in order to obtain better cycle characteristics (capacity retention rate). If the crystallite size exceeds 50 nm, the cycle characteristics may not be sufficiently improved, which is not preferable. The lower limit of D x is not particularly limited, but it is difficult to reduce it to less than 1 nm by pulverization, and it is actually 1 nm or more.
本発明のリチウムイオン二次電池用負極活物質は、ケイ素、銅、リチウム、酸素を主要な構成元素とするものであり、これらの元素のモル比で示される元素組成比Ｃｕ／（Ｓｉ＋Ｃｕ＋Ｌｉ＋Ｏ）およびＯ／（Ｓｉ＋Ｃｕ＋Ｌｉ＋Ｏ）は、サイクル特性と活物質単位質量あたりの容量を同時に高くする観点から、それぞれ０.０２〜０.２０の範囲内であることが好ましい。これらの元素組成比としては、０.０３〜０.１５であることがさらに好ましく、０.０４〜０.１２であることがより好ましい。前記元素組成比が、０.０２未満の場合には、サイクル特性が十分向上しない場合があり、前記元素組成比が、０.２０を超える場合には、活物質単位質量あたりの電池容量が小さくなる場合があるので好ましくない。本発明のリチウムイオン二次電池用負極活物質のモル比で示される元素組成比Ｌｉ／（Ｓｉ＋Ｃｕ＋Ｌｉ＋Ｏ）が、０.０２〜０.３０の範囲内であることが好ましい。前記元素組成比が、０.０２未満の場合には、その負極活物質を使用して製造したリチウムイオン二次電池に対して急速充放電をおこなった場合のサイクル特性が十分に向上しない場合がある。前記元素組成比が、０.３０を超える場合には、活物質単位質量あたりの電池容量が小さくなる場合があるので好ましくない。元素組成比Ｌｉ／（Ｓｉ＋Ｃｕ＋Ｌｉ＋Ｏ）は、０.０２〜０.２の範囲内であることが更に好ましい。これらの元素組成比の値は、原料の配合比率を変化させることにより制御することができる。尚、本発明では、負極活物質の元素組成比とは、負極活物質に対して充電操作をおこなう前の状態での負極活物質の元素組成比を指す。
本発明の負極活物質に、ケイ素、銅、リチウム、酸素以外の構成元素を含む物質が混入していても、その混入量が一定以下であれば、本発明の効果を奏することが可能である。前記のケイ素、銅、リチウムおよび酸素を主要な構成元素とするリチウムイオン二次電池用負極活物質とは、負極活物質中のケイ素、銅、リチウムおよび酸素の含有量が合計で８０質量％以上であることを意味する。前記含有量は、９０質量％以上が好ましく、９５質量％以上が更に好ましい。
The negative electrode active material for a lithium ion secondary battery of the present invention contains silicon, copper, lithium and oxygen as main constituent elements, and has an elemental composition ratio Cu/(Si+Cu+Li+O) and a molar ratio of these elements. From the viewpoint of simultaneously increasing the cycle characteristics and the capacity per unit mass of the active material, O/(Si+Cu+Li+O) is preferably within the range of 0.02 to 0.20. The composition ratio of these elements is more preferably 0.03 to 0.15, and further preferably 0.04 to 0.12. When the elemental composition ratio is less than 0.02, the cycle characteristics may not be sufficiently improved, and when the elemental composition ratio exceeds 0.20, the battery capacity per unit mass of the active material is small. It is not preferable because it may occur. The elemental composition ratio Li/(Si+Cu+Li+O) represented by the molar ratio of the negative electrode active material for a lithium ion secondary battery of the present invention is preferably in the range of 0.02 to 0.30. When the elemental composition ratio is less than 0.02, the cycle characteristics may not be sufficiently improved when the lithium ion secondary battery manufactured using the negative electrode active material is subjected to rapid charge/discharge. is there. If the elemental composition ratio exceeds 0.30, the battery capacity per unit mass of the active material may decrease, which is not preferable. The elemental composition ratio Li/(Si+Cu+Li+O) is more preferably in the range of 0.02 to 0.2. The values of these elemental composition ratios can be controlled by changing the mixing ratio of the raw materials. In the present invention, the elemental composition ratio of the negative electrode active material refers to the elemental composition ratio of the negative electrode active material before the negative electrode active material is charged.
Even if a substance containing a constituent element other than silicon, copper, lithium, and oxygen is mixed in the negative electrode active material of the present invention, the effect of the present invention can be obtained as long as the mixed amount is not more than a certain amount. .. The negative electrode active material for a lithium ion secondary battery containing silicon, copper, lithium and oxygen as main constituent elements has a total content of silicon, copper, lithium and oxygen of 80% by mass or more in the negative electrode active material. Means that. The content is preferably 90% by mass or more, and more preferably 95% by mass or more.
［出発物質］
ケイ素
本発明のリチウムイオン二次電池用負極活物質の製造に用いられる出発物質のケイ素としては、ケイ素からなるものであればその形態は特に問わない。市販のシリコン基板（単結晶、多結晶）、原料用多結晶や非晶質ケイ素を始めとした純ケイ素以外に、ケイ素合金も用いることができる。本発明の負極活物質の製造方法には、粉砕手段による粉砕のステップが含まれるので、出発物質のケイ素の大きさは特に規定するものではないが、作業性の観点から、１ｍｍ以下とすることが好ましい。
酸化銅（２）
出発物質の酸化銅（２）としては、市販の酸化銅（２）粉等、いかなるものでも用いることができる。
金属銅
出発物質の金属銅としては、市販の金属銅粉等を用いることができる。なお、金属銅の表面に水酸化銅または酸化銅が生成することもあるが、それらを含めて金属銅と称する。本発明の負極活物質の製造方法には、粉砕手段による粉砕のステップが含まれるので、出発物質の金属銅の大きさは特に規定するものではないが、作業性の観点から、１ｍｍ以下の粉状とすることが好ましい。
酸化リチウム
出発原料の酸化リチウム（Ｌｉ2Ｏ）としては、市販の酸化リチウム粉等を用いることができる。
水
水の純度については、特に規定しないが、不純物低減の観点から、イオン交換水、逆浸透水、蒸留水などの、純度の高い水を用いることが好ましい。粉砕手段に投入する水の量が過剰であると、得られる粉砕処理して得られる負極活物質の元素組成比Ｏ／（Ｓｉ＋Ｃｕ＋Ｌｉ＋Ｏ）が大きくなりすぎることがある。具体的には、銅原料として金属銅のみを用いる場合には、ケイ素に対する水の質量比（Ｈ2Ｏ／Ｓｉ）は、０.５以下が好ましく、０.２以下が更に好ましい。
[Starting material]
Silicon As the starting material silicon used in the production of the negative electrode active material for a lithium ion secondary battery of the present invention, the form is not particularly limited as long as it is composed of silicon. Besides pure silicon such as commercially available silicon substrates (single crystal, polycrystal), raw material polycrystal, and amorphous silicon, silicon alloys can be used. Since the method for producing the negative electrode active material of the present invention includes a step of pulverization by a pulverizing means, the size of the starting material silicon is not particularly specified, but from the viewpoint of workability, it should be 1 mm or less. Is preferred.
Copper oxide (2)
As the starting material copper (2) oxide, any commercially available copper (2) oxide powder or the like can be used.
Metallic Copper Commercially available metallic copper powder or the like can be used as the metallic copper as the starting material. In addition, although copper hydroxide or copper oxide may be generated on the surface of the metallic copper, the copper hydroxide and the copper oxide are collectively referred to as metallic copper. Since the method for producing the negative electrode active material of the present invention includes a step of pulverizing by a pulverizing means, the size of the metallic copper as a starting material is not particularly specified, but from the viewpoint of workability, a powder having a particle size of 1 mm or less is used. It is preferable to have a shape.
Lithium Oxide As lithium oxide (Li 2 O) as a starting material, commercially available lithium oxide powder or the like can be used.
Water Purity of water is not particularly specified, but from the viewpoint of reducing impurities, it is preferable to use highly pure water such as ion-exchanged water, reverse osmosis water, and distilled water. If the amount of water introduced into the pulverizing means is excessive, the element composition ratio O/(Si+Cu+Li+O) of the obtained negative electrode active material obtained by the pulverization treatment may become too large. Specifically, when only metallic copper is used as the copper raw material, the mass ratio of water to silicon (H 2 O/Si) is preferably 0.5 or less, and more preferably 0.2 or less.
［粉砕手段］
本発明のリチウムイオン二次電池用負極活物質の製造方法においては、ケイ素と銅原料と酸化リチウム（Ｌｉ2Ｏ）と場合によっては水とを粉砕すると同時に混合するために、粉砕手段を用いる。粉砕手段としては、振動ミル、ボールミル等の公知の粉砕手段のいずれを用いても構わない。なお、使用する原料の大きさが大幅に異なるときは、最初に大きいほうの原料を粉砕し、その後残りの原料を投入し、粉砕と同時に混合処理しても構わない。粉砕メディアも、特に限定されないが、ジルコニアボール等を用いることができる。粉砕手段に、秤量した出発物質のケイ素と酸化銅（２）、またはケイ素と銅と水とを入れ、撹拌しながら出発物質を粉砕することにより、本発明の負極活物質を得ることができる。なお、出発原料、粉砕メディアとともに撹拌用溶媒を粉砕手段に投入して粉砕することもできる。撹拌用溶媒には非極性の有機溶媒を用いることが出来る。また、粉砕手段でケイ素と酸化銅（２）と酸化リチウム、またはケイ素と銅と酸化リチウムと水を入れる容器は、得られる負極活物質の元素組成比（Ｏ／（Ｓｉ＋Ｃｕ＋Ｌｉ+Ｏ））の制御性を向上するために密封できる構造とすることができる。
前記粉砕処理の際、回転数、振動数、処理時間等の粉砕処理の適切な条件範囲は、原料投入量、装置仕様、粉砕メディア等の条件により変化するので適宜設定すればよい。粉砕メディアを用いて粉砕処理をおこなった場合、粉砕処理後に、ふるい等を用いて粉砕メディアを除去して、本発明の負極活物質を得る。
[Crushing means]
In the method for producing a negative electrode active material for a lithium ion secondary battery according to the present invention, a pulverizing means is used for pulverizing silicon, a copper raw material, lithium oxide (Li 2 O) and, in some cases, water and simultaneously mixing them. As the crushing means, any known crushing means such as a vibration mill or a ball mill may be used. When the sizes of the raw materials to be used are significantly different, the larger raw material may be crushed first, and then the remaining raw materials may be charged, and the crushing and the mixing treatment may be simultaneously performed. The grinding medium is not particularly limited, but zirconia balls or the like can be used. The negative electrode active material of the present invention can be obtained by adding weighed starting materials of silicon and copper oxide (2) or silicon, copper and water to a grinding means and grinding the starting materials while stirring. The starting material and the grinding medium may be mixed with a stirring solvent in a grinding means for grinding. A nonpolar organic solvent can be used as the stirring solvent. Further, a container for containing silicon, copper oxide (2) and lithium oxide, or silicon, copper, lithium oxide and water by a crushing means controls the elemental composition ratio (O/(Si+Cu+Li+O)) of the obtained negative electrode active material. The structure can be hermetically sealed to improve the property.
At the time of the crushing process, an appropriate range of conditions for the crushing process such as the number of revolutions, the number of vibrations, and the processing time varies depending on the conditions such as the amount of raw material input, the device specifications, the crushing media, etc. When the crushing treatment is performed using a crushing medium, the crushing medium is removed using a sieve or the like after the crushing treatment to obtain the negative electrode active material of the present invention.
［リチウムイオン二次電池用負極］
本発明の負極活物質を用いて、公知の方法により、リチウムイオン二次電池用負極を作製することができる。例えば、前記負極活物質に適当なバインダ（結着剤）を混合し、必要に応じて導電性の向上のために適当な導電性粉末を混合する。この混合物にバインダが溶解する溶媒を加え、必要に応じて公知の撹拌機により十分に撹拌してスラリー状にする。この負極活物質を含むスラリーを、ドクターブレードなどを用いて圧延銅箔などの電極基板（集電体）に塗布し、乾燥した後、必要に応じてロール圧延などによって圧密化して、非水電解質二次電池用負極を作製することができる。
[Negative electrode for lithium-ion secondary battery]
A negative electrode for a lithium ion secondary battery can be produced by a known method using the negative electrode active material of the present invention. For example, a suitable binder (binder) is mixed with the negative electrode active material, and if necessary, a suitable conductive powder is added to improve conductivity. A solvent in which a binder is dissolved is added to this mixture, and if necessary, sufficiently stirred by a known stirrer to form a slurry. A slurry containing this negative electrode active material is applied to an electrode substrate (current collector) such as a rolled copper foil using a doctor blade, etc., dried, and then, if necessary, compacted by roll rolling or the like to obtain a non-aqueous electrolyte. A negative electrode for a secondary battery can be manufactured.
［リチウムイオン二次電池］
前述のようにして製造された負極を用いてリチウムイオン二次電池を組立てることが出来るが、他の非水電解質二次電池を作製することも可能である。リチウムイオン二次電池は、基本構造として負極、正極、セパレータおよび非水系の電解質を含んでおり、前述の手順により作製された負極と、公知の正極、セパレータおよび電解質を用いて、リチウムイオン二次電池を組立てることができる。
[Lithium-ion secondary battery]
A lithium ion secondary battery can be assembled using the negative electrode manufactured as described above, but other non-aqueous electrolyte secondary batteries can also be manufactured. The lithium ion secondary battery includes a negative electrode, a positive electrode, a separator and a non-aqueous electrolyte as a basic structure, and a negative electrode produced by the above-mentioned procedure and a known positive electrode, separator and electrolyte are used to form a lithium ion secondary battery. Batteries can be assembled.
［評価用電池の製造方法］
本発明により得られるリチウムイオン二次電池負極活物質の性能評価は、以下の手順で行った。
得られた粉末（負極活物質）１.０質量部にアセチレンブラック０.１４質量部と宇部興産（株）製ポリイミド樹脂（商標名：Ｕ−ワニスＡ、固形分１８質量％）１.５６質量部およびN-メチルピロリドン１.２８質量部を加え、撹拌してスラリーを得た。このスラリーを５０μｍのドクターブレードを使用して厚さ１０μｍの銅箔（負極集電体）に塗布し、窒素雰囲気中、７０℃で２０分乾燥後、６５０℃で３時間真空焼成した。焼成後に１９.６ＭＰａ（２００ｋｇｆ／ｃｍ2）で加圧をおこなった後、１.５ｃｍ2に打ち抜き、負極成型体とした。
評価用電池は、以下の手順で作製した。正極材料としてＬｉＣｏＯ2を活物質とし、正極集電体には、アルミ箔を用いた単層シート（宝泉（株）製）を用いた。非水電解質溶液には、エチレンカーボネート、ジエチルカーボネートおよびジメチルカーボネートの６０：２５：１５（体積比）混合液に、六フッ化リン酸リチウムを１ｍｏｌ／Ｌの濃度で溶解した非水電解質溶液を用い、セパレータに厚さ５０μｍのポリエチレン製微多孔質フィルムを用いてコイン型リチウムイオン二次電池を作製した。得られた評価用電池を用いて、負極成型体の初回充放電効率及びサイクル特性を評価した。
[Method for manufacturing evaluation battery]
The performance evaluation of the lithium ion secondary battery negative electrode active material obtained by the present invention was performed by the following procedure.
0.14 parts by mass of acetylene black and 1.06 parts by mass of polyimide resin (trade name: U-varnish A, solid content 18% by mass) manufactured by Ube Industries, Ltd. in 1.0 parts by mass of the obtained powder (negative electrode active material). Parts and 1.28 parts by mass of N-methylpyrrolidone were added and stirred to obtain a slurry. This slurry was applied to a 10 μm thick copper foil (negative electrode current collector) using a 50 μm doctor blade, dried in a nitrogen atmosphere at 70° C. for 20 minutes, and then vacuum-baked at 650° C. for 3 hours. After firing, pressure was applied at 19.6 MPa (200 kgf/cm 2 ) and punching to 1.5 cm 2 was performed to obtain a negative electrode molded body.
The evaluation battery was manufactured by the following procedure. As a positive electrode material, LiCoO 2 was used as an active material, and as the positive electrode current collector, a single layer sheet (manufactured by Hosen Co., Ltd.) using aluminum foil was used. As the non-aqueous electrolyte solution, a non-aqueous electrolyte solution prepared by dissolving lithium hexafluorophosphate at a concentration of 1 mol/L in a 60:25:15 (volume ratio) mixed solution of ethylene carbonate, diethyl carbonate and dimethyl carbonate was used. A coin-type lithium-ion secondary battery was produced by using a polyethylene microporous film having a thickness of 50 μm for the separator. Using the obtained battery for evaluation, the initial charge/discharge efficiency and cycle characteristics of the molded negative electrode were evaluated.
［電池容量、サイクル特性評価方法］
作製した評価用リチウムイオン二次電池は、室温で３時間放置した後、充放電装置（（株）北斗電工製）を用い以下の方法で活性化充放電処理を行った。テストセルの電圧が４.２Ｖに達するまで０.０１ｍＡ定電流で充電を行い、電圧が４.２Ｖに達した後は、セル電圧を４.２Ｖで一定に保つように電流を調整して充電を行い、電流の値が１μＡを下回った時点で充電を終了した。充電終了後、放電を０.０１ｍＡ定電流で行い、セル電圧が１.６Ｖを下回った時点で放電を終了した。
活性化充放電処理を行った後、充放電装置（（株）北斗電工製）を用いテストセルの電圧が４.２Ｖに達するまで表１に示す充放電レートとなる電流（定電流）で充電を行い、４.２Ｖに達した後は、セル電圧を４.２Ｖで一定に保つように電流を調整して充電をおこない、電流値が１０μＡを下回った時点で充電を終了した。放電は表１に示す充放電レートとなる電流（定電流）で行い、セル電圧が１.６Ｖを下回った時点で放電を終了し、放電容量を求めた。この充放電および放電容量測定の操作（充放電試験）を３０回繰り返し、評価用リチウムイオン二次電池の３０サイクルの充放電試験を行った。各サイクルにおける充放電レートの値を表１に示す。
具体的には、実施例１、２および比較例１、２では、１回目から５回目の充放電試験の定電流値が充放電レート０.０５Ｃとなるような定電流値で充放電試験を行い、６回目以降３０回目まではそれぞれ表１に示す充放電レート０.０５Ｃとなるような定電流値で充放電試験を行った。最終の３０回目の充放電レート０.０５Ｃは、１回目から５回目の充放電試験の充放電レートと同じである。実施例３および４では、１回目から３０回目まで全て、充放電試験の定電流値が充放電レート１.０Ｃとなるような定電流値で充放電試験を実施した。
[Battery capacity, cycle characteristics evaluation method]
The produced lithium-ion secondary battery for evaluation was left at room temperature for 3 hours and then subjected to activation charge/discharge treatment by the following method using a charge/discharge device (manufactured by Hokuto Denko KK). Charge with 0.01mA constant current until the voltage of the test cell reaches 4.2V. After the voltage reaches 4.2V, adjust the current to keep the cell voltage at 4.2V and charge. The charging was terminated when the current value fell below 1 μA. After the completion of charging, discharging was performed at a constant current of 0.01 mA, and the discharging was completed when the cell voltage fell below 1.6V.
After performing the activation charge/discharge treatment, charge using a charge/discharge device (manufactured by Hokuto Denko Co., Ltd.) with a current (constant current) that gives the charge/discharge rate shown in Table 1 until the voltage of the test cell reaches 4.2V. After reaching 4.2 V, the current was adjusted by adjusting the current so as to keep the cell voltage at 4.2 V constant, and the charging was terminated when the current value fell below 10 μA. The discharge was carried out at a current (constant current) that resulted in the charge/discharge rate shown in Table 1, and the discharge was terminated when the cell voltage fell below 1.6 V, and the discharge capacity was determined. This operation of charging/discharging and measuring the discharge capacity (charging/discharging test) was repeated 30 times to perform a 30-cycle charging/discharging test of the evaluation lithium ion secondary battery. Table 1 shows the values of the charge/discharge rate in each cycle.
Specifically, in Examples 1 and 2 and Comparative Examples 1 and 2, the charge and discharge test was performed at a constant current value such that the constant current value of the first to fifth charge and discharge tests was a charge and discharge rate of 0.05C. The 6th to 30th tests were performed at constant current values such that the charge/discharge rates shown in Table 1 were 0.05C. The final 30th charge/discharge rate of 0.05C is the same as the charge/discharge rate of the 1st to 5th charge/discharge tests. In Examples 3 and 4, the charge-discharge test was performed from the first to the 30th times at a constant current value such that the constant-current value of the charge-discharge test was 1.0 C.
［負極活物質の元素組成比測定方法］
得られた負極活物質中のＬｉ含有量は、以下の方法で求めた。負極活物質をフッ化水素酸と硝酸の混酸水溶液で溶解して負極活物質溶解液を得て、その負極活物質溶解液をＩＣＰ−ＡＥＳ法（ＩＣＰ発光分光分析法）で負極活物質溶解液のＬｉ濃度を測定した。前記Ｌｉ濃度と負極活物質溶解液の質量から、負極活物質中に含有されているＬｉの質量（Ａ）を求めた。混酸水溶液で溶解した負極活物質の質量（Ｂ）として、（Ａ）／（Ｂ）を負極活物質中のＬｉ含有率とし、この値を負極活物質の元素組成質量比（Ｌｉ／（Ｓｉ＋Ｃｕ＋Ｌｉ＋Ｏ））とした。
得られた負極活物質のＳｉ、Ｃｕ、Ｏの元素組成比は、走査型電子顕微鏡（Ｈｉｔａｃｈｉ ＳＵ−８０００）および電子顕微鏡用エネルギー分散型Ｘ線分析システム（サーモフィッシャーサイエンティフィック社製ＮＯＲＡＮ Ｓｙｓｔｅｍ ７、ＮＳＳ３１２Ｅ）を用いて、以下の方法で測定した。測定領域を２００μｍ×２００μｍとし、加速電圧１０ｋＶで、試料の異なる１０箇所について、Ｓｉ、Ｃｕ、Ｏの元素組成質量比を測定し、得られた１０個の測定値の平均値から元素組成質量比（Ｓｉ／（Ｓｉ＋Ｃｕ＋Ｏ）、Ｏ／（Ｓｉ＋Ｃｕ＋Ｏ）、Ｃｕ／（Ｓｉ＋Ｃｕ＋Ｏ））を計算した。これらの元素組成質量比の値に、（１−（Ｌｉ／（Ｓｉ＋Ｃｕ＋Ｌｉ＋Ｏ））の値を掛けた数値をそれぞれ、負極活物質の元素組成質量比（Ｓｉ／（Ｓｉ＋Ｃｕ＋Ｌｉ+Ｏ）、Ｏ／（Ｓｉ＋Ｃｕ＋Ｌｉ+Ｏ）、Ｃｕ／（Ｓｉ＋Ｃｕ＋Ｌｉ+Ｏ））とした。これら４つの負極活物質の元素組成質量比から、モル比で示される元素組成比（Ｓｉ／（Ｓｉ＋Ｃｕ＋Ｌｉ+Ｏ）、Ｏ／（Ｓｉ＋Ｃｕ＋Ｌｉ+Ｏ）、Ｃｕ／（Ｓｉ＋Ｃｕ＋Ｌｉ+Ｏ））を計算した。
[Method for measuring elemental composition ratio of negative electrode active material]
The Li content in the obtained negative electrode active material was determined by the following method. The negative electrode active material is dissolved in a mixed acid aqueous solution of hydrofluoric acid and nitric acid to obtain a negative electrode active material solution, and the negative electrode active material solution is subjected to the ICP-AES method (ICP emission spectroscopic analysis method). Was measured for Li concentration. The mass (A) of Li contained in the negative electrode active material was determined from the Li concentration and the mass of the negative electrode active material solution. As the mass (B) of the negative electrode active material dissolved in the mixed acid aqueous solution, (A)/(B) was defined as the Li content in the negative electrode active material, and this value was used as the element composition mass ratio (Li/(Si+Cu+Li+O)). ).
The element composition ratios of Si, Cu, and O of the obtained negative electrode active material are the energy dispersive X-ray analysis system for a scanning electron microscope (Hitachi SU-8000) and an electron microscope (NORAN System 7 manufactured by Thermo Fisher Scientific Co., Ltd.). , NSS312E), and the following method was used. The measurement area was set to 200 μm×200 μm, the acceleration voltage was 10 kV, and the element composition mass ratios of Si, Cu, and O were measured at 10 different locations of the sample, and the element composition mass ratio was calculated from the average value of the 10 measured values obtained. (Si/(Si+Cu+O), O/(Si+Cu+O), Cu/(Si+Cu+O)) was calculated. Numerical values obtained by multiplying the values of these elemental composition mass ratios by the value of (1-(Li/(Si+Cu+Li+O)) are respectively the elemental composition mass ratios (Si/(Si+Cu+Li+O), O/(Si+Cu+Li) of the negative electrode active material. +O), Cu/(Si+Cu+Li+O)) From the element composition mass ratios of these four negative electrode active materials, the element composition ratios (Si/(Si+Cu+Li+O) and O/(Si+Cu+Li+) represented by molar ratios are obtained. O), Cu/(Si+Cu+Li+O)) were calculated.
［負極活物質のＸ線回折評価方法］
得られた負極活物質について、Ｘ線回折装置（株式会社リガク製、ＲＩＮＴ−２０００）によりＣｕ線源（４０ｋＶ／２０ｍＡ）の条件で測定して、Ｘ線回折（ＸＲＤ）の評価をおこない、Ｘ線回折パターンを得た。
ＸＲＤの測定結果からＳｉの平均結晶子径（Ｄx）を算出する場合には、Ｘ線回折パターンから得られたＳｉ相の（１１１）面の半値幅βを用いて、Ｓｃｈｅｒｒｅｒの式 Ｄ＝（Ｋ・λ）／（β・ｃｏｓθ）を用いて結晶子径（Ｄx）を算出した。なお、Ｓｃｈｅｒｒｅｒの式において、Ｄは結晶子径（ｎｍ）、λは測定Ｘ線波長（ｎｍ）、βは結晶子による回折幅の広がり（半値幅、ラジアン）、θは回折角のブラッグ角、ＫはＳｃｈｅｒｒｅｒ定数を示し、この式中の測定Ｘ線波長λを０.１５４ｎｍ、Ｓｃｈｅｒｒｅｒ定数Ｋを０.９とした。
ＸＲＤの測定結果から、分子をＣｕ3Ｓｉに対応するピーク高さ、分母をＳｉに対応するピーク高さとしたピーク強度比（Ｃｕ3Ｓｉ／Ｓｉ）を以下の方法で算出した。Ｃｕ3に対応するピーク高さは、２θが４４.８°付近にピークがあるＣｕ3Ｓｉに対応するピークと２θが４７.４°付近にピークがあるＳｉに対応するピークをピーク分離し、ピーク分離の結果得られた２θが４４.８°付近にピークがあるプロファイルのピーク高さをＣｕ3Ｓｉに対応するピーク高さとし、
２θが２８.４°付近にピークがあるピークの高さをＳｉに対応するピーク高さとして、これらのピーク高さからピーク強度比（Ｃｕ3Ｓｉ／Ｓｉ）を算出した。
[X-Ray Diffraction Evaluation Method for Negative Electrode Active Material]
The obtained negative electrode active material was measured by an X-ray diffractometer (Rigaku Corporation, RINT-2000) under the condition of a Cu radiation source (40 kV/20 mA), and X-ray diffraction (XRD) was evaluated. A line diffraction pattern was obtained.
When calculating the average crystallite diameter (D x ) of Si from the measurement result of XRD, the half-value width β of the (111) plane of the Si phase obtained from the X-ray diffraction pattern is used, and Scherrer's formula D= The crystallite diameter (D x ) was calculated using (K·λ)/(β·cos θ). In the Scherrer's equation, D is the crystallite diameter (nm), λ is the measured X-ray wavelength (nm), β is the spread of the diffraction width due to the crystallite (half-width, radian), θ is the Bragg angle of the diffraction angle, K represents the Scherrer constant, and the measured X-ray wavelength λ in this formula was 0.154 nm, and the Scherrer constant K was 0.9.
From the XRD measurement results, the peak intensity ratio (Cu 3 Si/Si) in which the numerator is the peak height corresponding to Cu 3 Si and the denominator is the peak height corresponding to Si was calculated by the following method. The peak height corresponding to Cu 3 is such that a peak corresponding to Cu 3 Si having a peak at 2θ of about 44.8° and a peak corresponding to Si having a peak at 2θ of about 47.4° are peak-separated, The peak height of the profile having a peak at 2θ of 44.8° obtained as a result of peak separation is defined as the peak height corresponding to Cu 3 Si,
The peak intensity ratio (Cu 3 Si/Si) was calculated from these peak heights with the height of the peak having a peak near 2θ of 28.4° as the peak height corresponding to Si.
［負極活物質のＸ線光電子分光分析評価方法］
負極活物質のＸ線光電子分光分析評評価は、Ｘ線源としてモノクロメーターにより単色化されたＡｌＫα線を用い、測定領域φ０.６２ｍｍ、光電子の取り出し角度４５°の条件で測定を行った。測定前に、試料表面をシリコン基板が１００ｎｍの深さでエッチングされる条件でＡｒスパッタエッチングをおこなった。Ｓｉ２ｐスペクトル中には金属状態のケイ素（Ｓｉ（０））に対応するピーク以外に、高結合エネルギー側にシフトした複数のピークが観察された。この高結合エネルギー側にシフトした複数のピークは酸化状態の異なる複数の酸化物（低級酸化物を含むケイ素の酸化物、すなわちＳｉＯx（ただし０＜ｘ＜２））に対応するピークと判断される。Ｓｉ（０）、ＳｉＯxに対応するピークをピーク分離し、分子をＳｉＯxに対応する各ピークの面積の和、分母をＳｉ（０）に対応するピークの面積としたピーク面積比（ＳｉＯx／Ｓｉ（Ｏ））を算出した。
[Method of evaluating negative electrode active material by X-ray photoelectron spectroscopy]
The X-ray photoelectron spectroscopic analysis evaluation of the negative electrode active material was carried out by using AlKα rays monochromated by a monochromator as an X-ray source under the conditions of a measurement area φ0.62 mm and a photoelectron take-out angle of 45°. Before the measurement, Ar sputter etching was performed on the sample surface under the condition that the silicon substrate was etched to a depth of 100 nm. In the Si2p spectrum, in addition to the peak corresponding to silicon (Si(0)) in the metallic state, a plurality of peaks shifted to the high binding energy side were observed. The peaks shifted to the high binding energy side are judged to be the peaks corresponding to the oxides having different oxidation states (silicon oxides including lower oxides, that is, SiO x (where 0<x<2)). It Si (0), the peak corresponding to the SiO x to peak separation, the sum of the areas of the peaks corresponding to molecules SiO x, the peak area ratio as the area of the peak corresponding to the denominator to Si (0) (SiO x /Si(O)) was calculated.
［実施例１］
平均粒径が５μｍである粒状Ｓｉ（高純度化学研究所製、純度９９.９％）１.８０６ｇと、粒状Ｃｕ（高純度化学研究所製、純度９９.９質量％、平均粒径５μｍ）０.２１４ｇと、酸化リチウム粉（販売元和光純薬工業、販売元コード１２７−０６０６２）０.１９４ｇと、直径１５ｍｍのジルコニアボール７個を粉砕ポット（ステンレス製、容量４５ｃｍ3）に入れ密封した。この粉砕ポットを遊星ボールミル（Ｆｒｉｔｓｃｈ社製、Ｐｕｌｖｅｒｉｓｅｔｔｅ−７）にセットし、回転速度６００ｒｐｍの条件で、３時間粉砕処理を実施した。粉砕ポットの内容物から、ジルコニアボールを分離し、負極活物質を得た。粉砕処理をした原料の量（仕込み量）から計算した元素組成比、得られた負極活物質のＸＲＤのＳｉ（１１１）ピークの半値幅および結晶子径、ピーク強度比（Ｃｕ3Ｓｉ／Ｓｉ）を表２に示し、ＸＰＳ測定結果を図１に、走査型電子顕微鏡（ＳＥＭ）写真を図２に、ＸＲＤ測定結果を図３（ａ）にそれぞれ示す。なお、図２のＳＥＭ写真において、下部右側に示す縦の白線１１本全体で示す幅が５μｍである。
実施例１で得られた負極活物質のＸＰＳスペクトル中のＳｉ２ｐピーク（図１）は、酸化数０〜４に対応する５つのピークに分離することができた。このことは、得られた負極活物質には酸化数の異なるＳｉ酸化物が存在していることを示している。なお、ここで実施例２〜４で得られた負極活物質についてのＸＰＳ測定結果は図示しないが、同様のスペクトルが得られている。実施例１〜４で得られた負極活物質のピーク面積比（ＳｉＯx／Ｓｉ（０））は、いずれも０.１〜０.６の範囲内であった。
実施例１により得られた負極活物質のＸＲＤパターン（図３（ａ））には、２θが４４.８°付近にピークが認められ、当該負極活物質中にＣｕ3Ｓｉが存在することが判る。なお、後述する実施例２〜４で得られた負極活物質のＸＲＤパターン（図３（ｂ）〜（ｄ））においても、θが４４.８°付近にピークが観察され、本発明により得られる負極活物質中がＣｕ3Ｓｉを含むことが判る。
前述した負極活物質の元素組成比測定方法により計算した実施例１〜４で得られた負極活物質のモル比で示される元素組成比の値は、各元素とも表１に記載の原料配合量から算出した元素組成比の０.９倍から１.１倍の範囲内であり、請求項１および請求項５に規定する各元素の元素組成比の範囲内であった。
得られた負極活物質の圧紛体を作製し、その圧粉体を集束イオンビーム（ＦＩＢ）加工装置を用いて切断し、その圧粉体切断面について調べた。圧粉体切断面を走査型電子顕微鏡で観察した走査型電子顕微鏡写真を図４に示す。また、圧粉体切断面を透過電子顕微鏡の走査モード（ＳＴＥＭ）で観察したＳＴＥＭ写真を図５に示す。また、圧粉体切断面をＳＴＥＭ−ＥＤＸで測定した結果を図６に示す。ここで、図４のＳＥＭ写真において、下部右側に示す縦の白線１１本全体で示す幅が５００ｎｍであり、図５（ｂ）のそれは１０ｎｍである。図５（ａ）および図６（ａ）、（ｂ）については、図中に縮尺を示してある。
図５（ｂ）は、ＳＴＥＭ−ＥＤＸ測定で、Ｓｉが多く存在する部分を高倍率で撮影したＳＴＥＭ写真である。金属状態のＳｉは良好な結晶性を示すが、このＳＴＥＭ写真には、間隔が３.１ｎｍ程度の縞模様が認められる領域が点在し、その縞模様が認められる領域以外の領域では、規則的な模様が観察されなかった。このことは、実施例１で得られた負極活物質中には、結晶性のよい金属状態のＳｉが点在するとともに、同時に結晶格子の乱れた非晶質なＳｉも存在していることが考えられる。
[Example 1]
1.806 g of granular Si (manufactured by Kojundo Chemical Laboratory, purity 99.9%) having an average particle size of 5 μm and granular Cu (manufactured by Kojundo Chemical Laboratory, purity 99.9% by mass, average particle size 5 μm) 0.214 g, lithium oxide powder (Wako Pure Chemical Industries, Ltd., vendor code 127-06062) 0.194 g, and 7 zirconia balls with a diameter of 15 mm were put in a crushing pot (stainless steel, capacity 45 cm 3 ) and sealed. .. This crushing pot was set in a planetary ball mill (Pulverisette-7 manufactured by Fritsch), and crushing treatment was carried out for 3 hours under the condition of a rotation speed of 600 rpm. Zirconia balls were separated from the contents of the crushing pot to obtain a negative electrode active material. Elemental composition ratio calculated from the amount (feeding amount) of pulverized raw material, half-width of Si(111) peak and crystallite diameter of XRD of the obtained negative electrode active material, peak intensity ratio (Cu 3 Si/Si) Is shown in Table 2, the XPS measurement result is shown in FIG. 1, the scanning electron microscope (SEM) photograph is shown in FIG. 2, and the XRD measurement result is shown in FIG. 3(a). In the SEM photograph of FIG. 2, the width of the 11 vertical white lines shown on the lower right side as a whole is 5 μm.
The Si2p peak (FIG. 1) in the XPS spectrum of the negative electrode active material obtained in Example 1 could be separated into five peaks corresponding to oxidation numbers 0 to 4. This indicates that Si oxides having different oxidation numbers are present in the obtained negative electrode active material. The XPS measurement results of the negative electrode active materials obtained in Examples 2 to 4 are not shown here, but similar spectra are obtained. The peak area ratios (SiO x /Si(0)) of the negative electrode active materials obtained in Examples 1 to 4 were all in the range of 0.1 to 0.6.
In the XRD pattern (FIG. 3(a)) of the negative electrode active material obtained in Example 1, a peak was observed at 2θ of around 44.8°, and Cu 3 Si was present in the negative electrode active material. I understand. In addition, in the XRD patterns (FIGS. 3B to 3D) of the negative electrode active materials obtained in Examples 2 to 4 described later, a peak was observed around θ of 44.8°, which was obtained by the present invention. It can be seen that the obtained negative electrode active material contains Cu 3 Si.
The values of the elemental composition ratios shown by the molar ratios of the negative electrode active materials obtained in Examples 1 to 4 calculated by the above-described method for measuring the elemental composition ratio of the negative electrode active material are the raw material compounding amounts shown in Table 1 for each element. It was within the range of 0.9 times to 1.1 times the elemental composition ratio calculated from the above, and within the range of the elemental composition ratio of each element defined in claim 1 and claim 5.
A powder compact of the obtained negative electrode active material was produced, the powder compact was cut using a focused ion beam (FIB) processing device, and the cut surface of the powder compact was examined. A scanning electron micrograph of the green compact cut surface observed with a scanning electron microscope is shown in FIG. Moreover, the STEM photograph which observed the green compact cut surface in the scanning mode (STEM) of the transmission electron microscope is shown in FIG. Moreover, the result of having measured the green compact cut surface by STEM-EDX is shown in FIG. Here, in the SEM photograph of FIG. 4, the width indicated by the entire 11 vertical white lines shown on the lower right side is 500 nm, and that of FIG. 5B is 10 nm. 5(a), 6(a), and 6(b), the scale is shown in the figure.
FIG. 5B is a STEM photograph obtained by STEM-EDX measurement, in which a portion where a large amount of Si exists is photographed at high magnification. Si in the metallic state shows good crystallinity, but in this STEM photograph, there are scattered regions with a stripe pattern with an interval of about 3.1 nm, and in regions other than the region where the stripe pattern is observed, regularity is observed. No pattern was observed. This means that in the negative electrode active material obtained in Example 1, Si in a metallic state with good crystallinity is scattered, and at the same time, amorphous Si having a disordered crystal lattice is also present. Conceivable.
得られた負極活物質を用い、前述の手順で評価用電池を作製し、負極活物質の性能を評価した。充放電試験の結果を表２および図７に示す。表２では、１サイクル目の充放電における放電容量を初期放電容量とし、この初期放電容量に対する２５サイクル目の放電容量の比率を２５サイクル目容量維持率（％）として、この初期放電容量に対する３０サイクル目の放電容量の比率を３０サイクル目容量維持率（％）として示した。ここで、充放電容量は、負極活物質の単位質量あたりの容量を示す。なお、表１には、実施例２〜４および比較例１および２についての結果も併せて示す。図７では、実施例１〜４および比較例１、２についての各サイクル数と各サイクル数における放電容量の関係を示した。
図７の結果から、本実施例により得られた負極活物質は、急速充放電を多数回繰り返しても、高い充放電容量（容量維持率）を示すことが判る。
Using the obtained negative electrode active material, a battery for evaluation was prepared by the procedure described above, and the performance of the negative electrode active material was evaluated. The results of the charge/discharge test are shown in Table 2 and FIG. 7. In Table 2, the discharge capacity in the first cycle of charge and discharge is defined as the initial discharge capacity, and the ratio of the discharge capacity of the 25th cycle to the initial discharge capacity is defined as the 25th cycle capacity retention rate (%). The discharge capacity ratio at the cycle is shown as the capacity retention rate (%) at the 30th cycle. Here, the charge/discharge capacity indicates the capacity per unit mass of the negative electrode active material. In addition, Table 1 also shows the results of Examples 2 to 4 and Comparative Examples 1 and 2. FIG. 7 shows the relationship between each cycle number and the discharge capacity at each cycle number for Examples 1 to 4 and Comparative Examples 1 and 2.
From the results of FIG. 7, it can be seen that the negative electrode active material obtained in this example shows a high charge/discharge capacity (capacity retention rate) even when rapid charge/discharge is repeated many times.
［実施例２］
負極活物質製造の際、粒状Ｓｉおよび酸化リチウム粉、ＣｕＯ粉（株式会社レアメタリック製、純度９９.９質量％、平均粒径１μｍ）を用い、それらの量を表２に記載の値に変更した以外は、実施例１と同様にして、負極活物質およびそれを用いた電池を作製し、評価をおこなった。粉砕処理をした原料の量（仕込み量）から計算した元素組成比、得られた負極活物質のＸＲＤのＳｉ（１１１）ピークの半値幅および結晶子径、ピーク強度比（Ｃｕ3Ｓｉ／Ｓｉ）を表２に、充放電試験の結果を図７に合せて示す。
[Example 2]
At the time of manufacturing the negative electrode active material, granular Si, lithium oxide powder, and CuO powder (manufactured by Rare Metallic Co., Ltd., purity 99.9% by mass, average particle size 1 μm) were used, and their amounts were changed to values shown in Table 2. A negative electrode active material and a battery using the same were prepared and evaluated in the same manner as in Example 1 except for the above. Elemental composition ratio calculated from the amount (feeding amount) of pulverized raw material, half-width of Si(111) peak and crystallite diameter of XRD of the obtained negative electrode active material, peak intensity ratio (Cu 3 Si/Si) Is shown in Table 2, and the results of the charge/discharge test are shown in FIG.
［実施例３、４］
負極活物質製造の際、粒状Ｓｉ、粒状Ｃｕ、酸化リチウム粉の量を表２に記載の値に変更したことと、電池容量、サイクル特性評価方法における電流値を表１の実施例３、４として記載した値としたこと以外は、実施例１と同様にして、負極活物質およびそれを用いた電池を作製し、評価をおこなった。粉砕処理をした原料の量（仕込み量）から計算した元素組成比、得られた負極活物質のＸＲＤのＳｉ（１１１）ピークの半値幅および結晶子径、ピーク強度比（Ｃｕ3Ｓｉ／Ｓｉ）を表２に、充放電試験の結果を図７に合せて示す。
[Examples 3 and 4]
At the time of manufacturing the negative electrode active material, the amounts of granular Si, granular Cu, and lithium oxide powder were changed to the values described in Table 2, and the battery capacity and the current value in the cycle characteristic evaluation method were set to Examples 3, 4 in Table 1. A negative electrode active material and a battery using the same were manufactured and evaluated in the same manner as in Example 1 except that the values described as were used. Elemental composition ratio calculated from the amount (feeding amount) of pulverized raw material, half-width of Si(111) peak and crystallite diameter of XRD of the obtained negative electrode active material, peak intensity ratio (Cu 3 Si/Si) Is shown in Table 2, and the results of the charge/discharge test are shown in FIG.
［比較例１］
負極活物質製造の際、粒状Ｓｉ、ＣｕＯ粉（株式会社レアメタリック製、純度９９.９質量％、平均粒径１μｍ）を用いて、それらの量を表２に記載の値に変更した以外は、実施例１と同様にして、負極活物質及びそれを用いた電池を作製し、評価をおこなった。
［比較例２］
負極活物質製造の際、粒状Ｓｉを用い、その量を表２に記載の値に変更した以外は、実施例１と同様にして、負極活物質及びそれを用いた電池を作製し、評価をおこなった。
比較例１および２についての粉砕処理をした原料の量（仕込み量）から計算した元素組成比、得られた負極活物質のＸＲＤのＳｉ（１１１）ピークの半値幅および結晶子径、ピーク強度比（Ｃｕ3Ｓｉ／Ｓｉ）を表２に、充放電試験の結果を図７に合せて示す。
[Comparative Example 1]
Granular Si, CuO powder (manufactured by Rare Metallic Co., Ltd., purity 99.9% by mass, average particle size 1 μm) was used during production of the negative electrode active material, and the amounts thereof were changed to the values described in Table 2. In the same manner as in Example 1, a negative electrode active material and a battery using the same were prepared and evaluated.
[Comparative example 2]
During the production of the negative electrode active material, a negative electrode active material and a battery using the same were prepared and evaluated in the same manner as in Example 1 except that granular Si was used and the amount thereof was changed to the value described in Table 2. I did it.
The elemental composition ratio calculated from the amount of the pulverized raw materials (charged amount) for Comparative Examples 1 and 2, the half width of the Si(111) peak and the crystallite diameter of the XRD of the obtained negative electrode active material, and the peak intensity ratio. (Cu 3 Si/Si) is shown in Table 2, and the result of the charge/discharge test is also shown in FIG. 7.
上述の様に、本発明の製造方法により得られた負極活物質を用いたリチウムイオン二次電池は、急速充放電をおこなった後でも高い充放電容量（容量維持率）を示し、優れた性能を示した。実施例３、４の結果は、本発明の製造方法により得られた負極活物質を用いたリチウムイオン二次電池は、高い電流値で充放電を３０回おこなった後でも高い充放電容量（容量維持率）を示した。 As described above, the lithium ion secondary battery using the negative electrode active material obtained by the production method of the present invention shows a high charge/discharge capacity (capacity retention rate) even after performing rapid charge/discharge, and has excellent performance. showed that. The results of Examples 3 and 4 show that the lithium ion secondary batteries using the negative electrode active material obtained by the production method of the present invention have a high charge/discharge capacity (capacity) even after 30 times of charge/discharge at a high current value. The maintenance rate) was shown.
Claims (13)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2016240767A JP6735660B2 (en) | 2016-12-12 | 2016-12-12 | Negative electrode active material for lithium ion secondary battery, method for producing the same, negative electrode and battery |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2016240767A JP6735660B2 (en) | 2016-12-12 | 2016-12-12 | Negative electrode active material for lithium ion secondary battery, method for producing the same, negative electrode and battery |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JP2018098018A JP2018098018A (en) | 2018-06-21 |
| JP6735660B2 true JP6735660B2 (en) | 2020-08-05 |
Family
ID=62633096
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2016240767A Active JP6735660B2 (en) | 2016-12-12 | 2016-12-12 | Negative electrode active material for lithium ion secondary battery, method for producing the same, negative electrode and battery |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP6735660B2 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112885990B (en) | 2019-11-29 | 2022-11-01 | 宁德时代新能源科技股份有限公司 | Secondary battery |
| CN111430692B (en) * | 2020-03-31 | 2022-01-18 | 北京卫蓝新能源科技有限公司 | Lithium ion battery cathode material and preparation method thereof |
-
2016
- 2016-12-12 JP JP2016240767A patent/JP6735660B2/en active Active
Also Published As
| Publication number | Publication date |
|---|---|
| JP2018098018A (en) | 2018-06-21 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JP7427156B2 (en) | Lithium nickelate-based positive electrode active material particles and method for producing the same, and non-aqueous electrolyte secondary battery | |
| KR101587671B1 (en) | Lithium iron phosphate powder manufacturing method, olivine structured lithium iron phosphate powder, cathode sheet using said lithium iron phosphate powder, and non-aqueous solvent secondary battery | |
| JP5558482B2 (en) | Secondary battery electrode active material and method for producing the same | |
| Park et al. | Stibnite (Sb 2 S 3) and its amorphous composite as dual electrodes for rechargeable lithium batteries | |
| KR101562686B1 (en) | Oxycobalt hydroxide particulate powder and manufacturing method therefor, as well as lithium cobaltate particulate powder, manufacturing method therefor, and non-aqueous electrolyte secondary battery using the same | |
| JP6328888B2 (en) | Nanoscale ion storage materials consisting of amorphous and partially amorphous | |
| CN107408689B (en) | Positive electrode active material for nonaqueous electrolyte secondary battery and secondary battery | |
| KR20160065028A (en) | Anode active material for lithium secondary battery and lithium secondary battery including the same | |
| JP2010135314A (en) | Negative electrode material for nonaqueous secondary battery | |
| WO2014129096A1 (en) | Lithium-ion secondary battery and manufacturing method therefor | |
| KR20110118790A (en) | Carbon material for lithium ion secondary batteries | |
| US20230352665A1 (en) | Porous silicon-based carbon composite, method for preparing same, and negative electrode active material comprising same | |
| Park et al. | Co–Sb intermetallic compounds and their disproportionated nanocomposites as high-performance anodes for rechargeable Li-ion batteries | |
| CN111628161A (en) | Negative electrode active material | |
| US12021188B2 (en) | Sulfide solid electrolyte, method for producing sulfide solid electrolyte, electrode, and all solid state battery | |
| JP2011132095A (en) | Method for producing olivine-type compound particle powder, and nonaqueous electrolyte secondary battery | |
| JP6307317B2 (en) | Negative electrode active material for lithium ion secondary battery, method for producing the same, negative electrode and battery | |
| JP6376884B2 (en) | Negative electrode active material for lithium ion secondary battery, method for producing the same, negative electrode and battery | |
| WO2018156355A1 (en) | Core-shell electrochemically active particles with modified microstructure and use for secondary battery electrodes | |
| CN106030866B (en) | Negative electrode active material, negative electrode, and battery | |
| WO2021193662A1 (en) | Composite active material for lithium secondary battery, electrode composition for lithium secondary battery, lithium secondary battery electrode, and method for manufacturing composite active material for lithium secondary battery | |
| JP6735660B2 (en) | Negative electrode active material for lithium ion secondary battery, method for producing the same, negative electrode and battery | |
| US10256464B2 (en) | Method for producing negative electrode active material for lithium ion secondary battery | |
| KR102569385B1 (en) | Negative Electrode Material for Secondary Battery | |
| KR100968583B1 (en) | Electrochemical cell |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| A621 | Written request for application examination |
Free format text: JAPANESE INTERMEDIATE CODE: A621 Effective date: 20191030 |
|
| A977 | Report on retrieval |
Free format text: JAPANESE INTERMEDIATE CODE: A971007 Effective date: 20200630 |
|
| TRDD | Decision of grant or rejection written | ||
| A01 | Written decision to grant a patent or to grant a registration (utility model) |
Free format text: JAPANESE INTERMEDIATE CODE: A01 Effective date: 20200707 |
|
| A61 | First payment of annual fees (during grant procedure) |
Free format text: JAPANESE INTERMEDIATE CODE: A61 Effective date: 20200714 |
|
| R150 | Certificate of patent or registration of utility model |
Ref document number: 6735660 Country of ref document: JP Free format text: JAPANESE INTERMEDIATE CODE: R150 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |