JP5963398B2 - Method for producing positive electrode active material for secondary battery - Google Patents
Method for producing positive electrode active material for secondary battery Download PDFInfo
- Publication number
- JP5963398B2 JP5963398B2 JP2011085944A JP2011085944A JP5963398B2 JP 5963398 B2 JP5963398 B2 JP 5963398B2 JP 2011085944 A JP2011085944 A JP 2011085944A JP 2011085944 A JP2011085944 A JP 2011085944A JP 5963398 B2 JP5963398 B2 JP 5963398B2
- Authority
- JP
- Japan
- Prior art keywords
- positive electrode
- active material
- electrode active
- lithium
- secondary battery
- 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.)
- Expired - Fee Related
Links
- 239000007774 positive electrode material Substances 0.000 title claims description 116
- 238000004519 manufacturing process Methods 0.000 title claims description 22
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 claims description 47
- 239000013078 crystal Substances 0.000 claims description 45
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 22
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims description 19
- 229910052744 lithium Inorganic materials 0.000 claims description 19
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims description 16
- 239000002243 precursor Substances 0.000 claims description 15
- 239000000725 suspension Substances 0.000 claims description 14
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 14
- 239000007864 aqueous solution Substances 0.000 claims description 13
- 238000003756 stirring Methods 0.000 claims description 13
- 238000000034 method Methods 0.000 claims description 12
- 229910052742 iron Inorganic materials 0.000 claims description 9
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims description 8
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 8
- 239000001301 oxygen Substances 0.000 claims description 8
- 229910052760 oxygen Inorganic materials 0.000 claims description 8
- 239000012298 atmosphere Substances 0.000 claims description 6
- 238000010438 heat treatment Methods 0.000 claims description 6
- 239000007789 gas Substances 0.000 claims description 4
- 238000002360 preparation method Methods 0.000 claims 1
- 230000002194 synthesizing effect Effects 0.000 claims 1
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 54
- 229910001416 lithium ion Inorganic materials 0.000 description 54
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 description 21
- 239000011800 void material Substances 0.000 description 21
- 239000002245 particle Substances 0.000 description 20
- 239000011149 active material Substances 0.000 description 17
- 239000000463 material Substances 0.000 description 15
- 239000008151 electrolyte solution Substances 0.000 description 14
- LFVGISIMTYGQHF-UHFFFAOYSA-N ammonium dihydrogen phosphate Chemical compound [NH4+].OP(O)([O-])=O LFVGISIMTYGQHF-UHFFFAOYSA-N 0.000 description 12
- 229910000387 ammonium dihydrogen phosphate Inorganic materials 0.000 description 12
- 235000019837 monoammonium phosphate Nutrition 0.000 description 12
- 239000007773 negative electrode material Substances 0.000 description 12
- 239000011164 primary particle Substances 0.000 description 11
- NMCUIPGRVMDVDB-UHFFFAOYSA-L iron dichloride Chemical compound Cl[Fe]Cl NMCUIPGRVMDVDB-UHFFFAOYSA-L 0.000 description 10
- 238000001027 hydrothermal synthesis Methods 0.000 description 9
- -1 polytetrafluoroethylene Polymers 0.000 description 9
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 8
- PQVSTLUFSYVLTO-UHFFFAOYSA-N ethyl n-ethoxycarbonylcarbamate Chemical compound CCOC(=O)NC(=O)OCC PQVSTLUFSYVLTO-UHFFFAOYSA-N 0.000 description 8
- GLXDVVHUTZTUQK-UHFFFAOYSA-M lithium hydroxide monohydrate Substances [Li+].O.[OH-] GLXDVVHUTZTUQK-UHFFFAOYSA-M 0.000 description 8
- 229940040692 lithium hydroxide monohydrate Drugs 0.000 description 8
- 238000001878 scanning electron micrograph Methods 0.000 description 8
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- 238000002485 combustion reaction Methods 0.000 description 7
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- WYURNTSHIVDZCO-UHFFFAOYSA-N Tetrahydrofuran Chemical compound C1CCOC1 WYURNTSHIVDZCO-UHFFFAOYSA-N 0.000 description 2
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- 239000004020 conductor Substances 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 239000010949 copper Substances 0.000 description 2
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 description 2
- VUPKGFBOKBGHFZ-UHFFFAOYSA-N dipropyl carbonate Chemical compound CCCOC(=O)OCCC VUPKGFBOKBGHFZ-UHFFFAOYSA-N 0.000 description 2
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- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 description 2
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- 229910052732 germanium Inorganic materials 0.000 description 2
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- IIPYXGDZVMZOAP-UHFFFAOYSA-N lithium nitrate Chemical compound [Li+].[O-][N+]([O-])=O IIPYXGDZVMZOAP-UHFFFAOYSA-N 0.000 description 2
- 229910003002 lithium salt Inorganic materials 0.000 description 2
- 159000000002 lithium salts Chemical class 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
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- BDAGIHXWWSANSR-UHFFFAOYSA-N methanoic acid Natural products OC=O BDAGIHXWWSANSR-UHFFFAOYSA-N 0.000 description 2
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- BHPQYMZQTOCNFJ-UHFFFAOYSA-N Calcium cation Chemical compound [Ca+2] BHPQYMZQTOCNFJ-UHFFFAOYSA-N 0.000 description 1
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- WQZGKKKJIJFFOK-GASJEMHNSA-N Glucose Natural products OC[C@H]1OC(O)[C@H](O)[C@@H](O)[C@@H]1O WQZGKKKJIJFFOK-GASJEMHNSA-N 0.000 description 1
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- 238000003917 TEM image Methods 0.000 description 1
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- VEPSWGHMGZQCIN-UHFFFAOYSA-H ferric oxalate Chemical compound [Fe+3].[Fe+3].[O-]C(=O)C([O-])=O.[O-]C(=O)C([O-])=O.[O-]C(=O)C([O-])=O VEPSWGHMGZQCIN-UHFFFAOYSA-H 0.000 description 1
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- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 description 1
- SURQXAFEQWPFPV-UHFFFAOYSA-L iron(2+) sulfate heptahydrate Chemical compound O.O.O.O.O.O.O.[Fe+2].[O-]S([O-])(=O)=O SURQXAFEQWPFPV-UHFFFAOYSA-L 0.000 description 1
- LEAMSPPOALICQN-UHFFFAOYSA-H iron(2+);diphosphate;octahydrate Chemical compound O.O.O.O.O.O.O.O.[Fe+2].[Fe+2].[Fe+2].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O LEAMSPPOALICQN-UHFFFAOYSA-H 0.000 description 1
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- MHCFAGZWMAWTNR-UHFFFAOYSA-M lithium perchlorate Chemical compound [Li+].[O-]Cl(=O)(=O)=O MHCFAGZWMAWTNR-UHFFFAOYSA-M 0.000 description 1
- 229910001386 lithium phosphate Inorganic materials 0.000 description 1
- SNKMVYBWZDHJHE-UHFFFAOYSA-M lithium;dihydrogen phosphate Chemical compound [Li+].OP(O)([O-])=O SNKMVYBWZDHJHE-UHFFFAOYSA-M 0.000 description 1
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- 125000002496 methyl group Chemical group [H]C([H])([H])* 0.000 description 1
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- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 1
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- SUKJFIGYRHOWBL-UHFFFAOYSA-N sodium hypochlorite Chemical compound [Na+].Cl[O-] SUKJFIGYRHOWBL-UHFFFAOYSA-N 0.000 description 1
- 229910001415 sodium ion Inorganic materials 0.000 description 1
- BAZAXWOYCMUHIX-UHFFFAOYSA-M sodium perchlorate Chemical compound [Na+].[O-]Cl(=O)(=O)=O BAZAXWOYCMUHIX-UHFFFAOYSA-M 0.000 description 1
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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
- Battery Electrode And Active Subsutance (AREA)
Description
本発明は、リチウムイオン二次電池用の正極活物質、およびその作製方法に関する。また、リチウムイオン二次電池に関する。 The present invention relates to a positive electrode active material for a lithium ion secondary battery and a manufacturing method thereof. The present invention also relates to a lithium ion secondary battery.
環境問題への関心が高まるなか、ハイブリッド自動車用電源等に使用できる二次電池や電気二重層キャパシタなどの蓄電装置の開発が盛んである。その候補として、エネルギー性能の高いリチウムイオン二次電池やリチウムイオンキャパシタが注目されている。リチウムイオン二次電池は、小型でも大容量の電気を蓄えられるため、携帯電話やノート型パーソナルコンピュータなどの携帯情報端末には既に搭載され、製品の小型化などに一役買っている。 Amid growing interest in environmental issues, the development of power storage devices such as secondary batteries and electric double layer capacitors that can be used for power sources for hybrid vehicles and the like has been actively developed. As the candidates, lithium ion secondary batteries and lithium ion capacitors with high energy performance are attracting attention. Lithium-ion secondary batteries can store large amounts of electricity even when they are small, so they are already installed in portable information terminals such as mobile phones and notebook personal computers, and play a role in miniaturization of products.
二次電池及び電気二重層キャパシタの基本構成は、正極と負極との間に電解質を介在させた構成を有する。正極及び負極としては、それぞれ、集電体と、集電体上に設けられた活物質と、を有する構成が知られている。例えばリチウムイオン二次電池は、リチウムイオンを挿入及び脱離することができる材料を活物質として用いる。 The basic configuration of the secondary battery and the electric double layer capacitor has a configuration in which an electrolyte is interposed between the positive electrode and the negative electrode. As the positive electrode and the negative electrode, a configuration having a current collector and an active material provided on the current collector is known. For example, a lithium ion secondary battery uses a material capable of inserting and extracting lithium ions as an active material.
リチウムイオン二次電池の特性を向上させるため、様々な面からのアプローチが図られている。例えばリチウムイオン二次電池用正極活物質の検討もその一つである。 Various approaches have been taken to improve the characteristics of lithium ion secondary batteries. For example, examination of a positive electrode active material for a lithium ion secondary battery is one of them.
正極活物質の検討の一つとして、材料からのアプローチがある。正極活物質の材料として、リン酸鉄リチウム（ＬｉＦｅＰＯ４）が注目されている。リン酸鉄リチウムは、コバルト（Ｃｏ）等と比較して非常に安価な鉄を用いていること、Ｆｅ２＋／Ｆｅ３＋の酸化還元を伴う材料としては高電位（約３．５Ｖ）を示すこと、サイクル特性が良好であること、理論容量が約１７０ｍＡｈｇ−１であり、エネルギー密度にして従来のコバルト酸リチウム（ＬｉＣｏＯ２）、ニッケル酸リチウム（ＬｉＮｉＯ２）といった材料を上回ること、等の利点がある。 One of the examinations of the positive electrode active material is a material approach. As a positive electrode active material, lithium iron phosphate (LiFePO 4 ) has attracted attention. Lithium iron phosphate uses iron that is very cheap compared to cobalt (Co) and the like, and shows a high potential (about 3.5 V) as a material accompanied by Fe 2+ / Fe 3+ redox. The cycle characteristics are good, the theoretical capacity is about 170 mAhg −1 , and the energy density exceeds the conventional materials such as lithium cobaltate (LiCoO 2 ) and lithium nickelate (LiNiO 2 ). is there.
しかしながら、リン酸鉄リチウムは、リチウムの拡散が一次元的であり遅いことと、低い電子伝導性のために、出力（電力）を高めにくいという問題点がある。そこで、リン酸鉄リチウムと電解液との接触面積を大きくすることで高出力とするべく、リン酸鉄リチウム結晶の微粒子化により比表面積の拡大を図る方法が多数報告されている。 However, lithium iron phosphate has a problem in that it is difficult to increase output (electric power) due to one-dimensional and slow diffusion of lithium and low electronic conductivity. Therefore, many methods have been reported to increase the specific surface area by making fine particles of lithium iron phosphate crystals in order to increase the contact area between the lithium iron phosphate and the electrolytic solution to increase the output.
例えば非特許文献１では、水熱法を用いたリン酸鉄リチウム結晶の合成において、空気中よりも窒素雰囲気で合成する方がリン酸鉄リチウム結晶の粒径が小さくなることが報告されている。また、非特許文献２では、水熱法を用いたリン酸鉄リチウム結晶の合成において、前駆体を含む水のｐＨがリン酸鉄リチウム結晶の粒径に影響することが報告されている。 For example, Non-Patent Document 1 reports that in the synthesis of lithium iron phosphate crystals using a hydrothermal method, the particle size of lithium iron phosphate crystals is smaller when synthesized in a nitrogen atmosphere than in air. . Non-Patent Document 2 reports that in the synthesis of lithium iron phosphate crystals using a hydrothermal method, the pH of the water containing the precursor affects the particle size of the lithium iron phosphate crystals.
また正極活物質の比表面積を大きくする他の例として、正極活物質に、一次粒子と、その一次粒子が多数集合した二次粒子を用いる方法が報告されている。例えば特許文献１に記載の正極活物質は、コバルト酸リチウムの小結晶である一次粒子と、その一次粒子が多数集合した二次粒子を有するため、正極活物質の比表面積が大きくなり、正極活物質と電解液との接触面積が大きくなっている。 As another example of increasing the specific surface area of the positive electrode active material, a method using primary particles and secondary particles in which a large number of primary particles are aggregated as the positive electrode active material has been reported. For example, since the positive electrode active material described in Patent Document 1 includes primary particles that are small crystals of lithium cobaltate and secondary particles in which a large number of primary particles are aggregated, the specific surface area of the positive electrode active material is increased, and the positive electrode active material is increased. The contact area between the substance and the electrolyte is increased.
上述のように正極活物質の検討の成果はあるものの、近年の環境問題への関心の高まりの中、より出力の高いリチウムイオン二次電池用正極活物質が要求されている。 As described above, although positive electrode active materials have been studied, a positive electrode active material for a lithium ion secondary battery with higher output has been demanded in recent years due to increasing interest in environmental problems.
そこで、本発明の一態様は、より比表面積の大きなリン酸鉄リチウムを含む正極活物質を提供することを目的の一とする。また、本発明の一態様は、該正極活物質を用いることで、正極活物質と電解液との接触面積を大きくし、より高出力なリン酸鉄リチウムを含むリチウムイオン二次電池を提供することを目的の一とする。 In view of this, an object of one embodiment of the present invention is to provide a positive electrode active material containing lithium iron phosphate having a larger specific surface area. Another embodiment of the present invention provides a lithium ion secondary battery including lithium iron phosphate with higher output by using the positive electrode active material so as to increase a contact area between the positive electrode active material and the electrolytic solution. One of the purposes.
上記目的を達成するために本発明の一態様では、正極活物質に用いるリン酸鉄リチウム結晶の一次粒子として、内部に空隙を有し、空隙に開口を有する結晶を用いることに着眼した。内部に空隙を有する結晶を用いることで、結晶の比表面積が大きくなり、正極活物質と電解液との接触面積を大きくすることができる。正極活物質と電解液との接触面積を大きくすることで、リチウムイオン二次電池の出力を高くすることができる。 In order to achieve the above object, one embodiment of the present invention has focused on using a crystal having a void inside and an opening in the void as the primary particles of lithium iron phosphate crystal used for the positive electrode active material. By using a crystal having voids inside, the specific surface area of the crystal is increased, and the contact area between the positive electrode active material and the electrolytic solution can be increased. By increasing the contact area between the positive electrode active material and the electrolytic solution, the output of the lithium ion secondary battery can be increased.
本発明の一態様は、外形が直方体で、内部に空隙を有し、空隙の開口を直方体の側面に有するリン酸鉄リチウムの結晶を、一次粒子として含む、二次電池用の正極活物質である。 One embodiment of the present invention is a positive electrode active material for a secondary battery including, as a primary particle, a lithium iron phosphate crystal having a rectangular parallelepiped outer shape, a void inside, and a void opening on a side surface of the rectangular solid. is there.
また、直方体のそれぞれの辺は２０ｎｍ以上５μｍ以下とすることができる。 Each side of the rectangular parallelepiped can be 20 nm or more and 5 μm or less.
また、本発明の別の一態様は、上記の正極活物質を含む正極、正極に対応して設けられた負極、および電解質を有する二次電池である。 Another embodiment of the present invention is a secondary battery including a positive electrode including the positive electrode active material, a negative electrode provided corresponding to the positive electrode, and an electrolyte.
また、本発明の別の一態様は、リン酸鉄リチウムを含む正極活物質の製造方法であって、リン酸鉄リチウムの前駆体を含む懸濁液を、酸素を含む雰囲気中で攪拌したのち、加熱および加圧を行う工程を含む、二次電池用正極活物質の作製方法である。 Another embodiment of the present invention is a method for producing a positive electrode active material containing lithium iron phosphate, wherein a suspension containing a precursor of lithium iron phosphate is stirred in an atmosphere containing oxygen. , A method for producing a positive electrode active material for a secondary battery, including a step of heating and pressurizing.
本発明の一態様により、より比表面積の大きなリン酸鉄リチウムを含む正極活物質を提供することが可能となる。また、該正極活物質を用いることで、正極活物質と電解液との接触面積を大きくし、より高出力なリン酸鉄リチウムを含むリチウムイオン二次電池を提供することが可能となる。 According to one embodiment of the present invention, a positive electrode active material containing lithium iron phosphate having a larger specific surface area can be provided. In addition, by using the positive electrode active material, it is possible to increase the contact area between the positive electrode active material and the electrolytic solution and to provide a lithium ion secondary battery containing lithium iron phosphate with higher output.
以下、実施の形態について、図面を用いて詳細に説明する。但し、発明は以下に示す実施の形態の記載内容に限定されず、本明細書などにおいて開示する発明の趣旨から逸脱することなく形態および詳細を様々に変更し得ることは当業者にとって自明である。また、異なる実施の形態に係る構成は、適宜組み合わせて実施することが可能である。なお、以下に説明する発明の構成において、同一部分または同様な機能を有する部分には同一の符号を用い、その繰り返しの説明は省略する。 Hereinafter, embodiments will be described in detail with reference to the drawings. However, the present invention is not limited to the description of the embodiments described below, and it is obvious to those skilled in the art that modes and details can be variously changed without departing from the spirit of the invention disclosed in this specification and the like. . In addition, structures according to different embodiments can be implemented in appropriate combination. Note that in the structures of the invention described below, the same portions or portions having similar functions are denoted by the same reference numerals, and repetitive description thereof is omitted.
なお、図面などにおいて示す各構成の、位置、大きさ、範囲などは、理解の簡単のため、実際の位置、大きさ、範囲などを表していない場合がある。このため、開示する発明は、必ずしも、図面などに開示された位置、大きさ、範囲などに限定されない。 Note that the position, size, range, and the like of each component illustrated in the drawings and the like may not represent the actual position, size, range, or the like for easy understanding. Therefore, the disclosed invention is not necessarily limited to the position, size, range, or the like disclosed in the drawings and the like.
なお、本明細書にて用いる第１、第２、第３といった序数を用いた用語は、構成要素を識別するために便宜上付したものであり、その数を限定するものではない。 In addition, the term using the ordinal numbers such as first, second, and third used in this specification is given for convenience in order to identify the constituent elements, and the number is not limited.
（実施の形態１）
本実施の形態では、本発明の一態様である正極活物質とその作製方法について、図１および図２を用いて説明する。
(Embodiment 1)
In this embodiment, a positive electrode active material which is one embodiment of the present invention and a manufacturing method thereof will be described with reference to FIGS.
＜正極活物質＞
まず、本発明の一態様である正極活物質について説明する。図１（Ａ）および（Ｂ）に本発明の一態様である正極活物質１００の模式図を示す。正極活物質１００は、リン酸鉄リチウムの結晶であり、内部に空隙を有し、該空隙が開口している一次粒子である。
<Positive electrode active material>
First, the positive electrode active material which is one embodiment of the present invention is described. 1A and 1B are schematic views of a positive electrode active material 100 which is one embodiment of the present invention. The positive electrode active material 100 is a crystal of lithium iron phosphate and is a primary particle having a void inside and opening the void.
本明細書において、一次粒子とは、単一の核から発生した粒子を言う。または、凝集していない粒子を言う。また、二次粒子とは一次粒子が凝集したものを言う。また本明細書において、活物質とはキャリアであるイオンの挿入及び脱離に関わる物質を指し、グルコースを用いた炭素層などを含むものではない。よって、例えば、活物質の導電率を表す時には、活物質自身の導電率を指し、表面に形成された炭素層を含む活物質層の導電率を意味するものではない。 In the present specification, primary particles refer to particles generated from a single nucleus. Or the particle | grains which are not aggregated. The secondary particles are those in which primary particles are aggregated. In this specification, an active material refers to a material related to insertion and desorption of ions serving as carriers, and does not include a carbon layer using glucose or the like. Thus, for example, when expressing the conductivity of the active material, it refers to the conductivity of the active material itself, and does not mean the conductivity of the active material layer including the carbon layer formed on the surface.
正極活物質１００について、結晶の粒子の外径をｄとする。結晶が球でなく、たとえば図１（Ａ）および（Ｂ）のように略直方体の場合、それぞれの辺をｄ１、ｄ２、ｄ３とする。ｄ１、ｄ２、ｄ３は、たとえば２０ｎｍ以上５μｍ以下である。また、略直方体の各面のうち、もっとも面積の大きい面を底面とし、それ以外の面を側面とする。また、正極活物質１００について、結晶部分と内部空隙部分をあわせた体積を、見かけの体積Ｖ１００とする。すなわち図１の場合、正極活物質１００の見かけの体積Ｖ１００は、ｄ１×ｄ２×ｄ３で表される。 In the positive electrode active material 100, the outer diameter of the crystal particles is d. When the crystal is not a sphere and is a substantially rectangular parallelepiped as shown in FIGS. 1A and 1B, for example, the sides are d1, d2, and d3. d1, d2, and d3 are 20 nm or more and 5 μm or less, for example. Moreover, let the surface with the largest area among each surface of a substantially rectangular parallelepiped be a bottom surface, and let other surfaces be side surfaces. Also, the positive electrode active material 100, the volume of combined crystalline portion and internal void portion, the apparent volume V 100. That is, in the case of FIG. 1, the apparent volume V 100 of the positive electrode active material 100 is represented by d1 × d2 × d3.
図１（Ａ）および（Ｂ）の正極活物質１００は結晶上部の側面に内部空隙の開口を有するが、開口の場所と大きさは限定されない。また、図１の正極活物質１００は略直方体であるが、正極活物質１００は内部空隙を有する結晶であればよく、例えば略直方体から角がとれて丸みを帯びた、内部空隙を有する形状であってもよい。また、図１の正極活物質１００の開口の形状は四角形であるが、例えば開口の形状は略円形であってもよい。 Although the positive electrode active material 100 in FIGS. 1A and 1B has an opening of an internal void on the side surface of the upper part of the crystal, the location and size of the opening are not limited. Further, the positive electrode active material 100 in FIG. 1 is a substantially rectangular parallelepiped, but the positive electrode active material 100 only needs to be a crystal having an internal void. For example, the positive electrode active material 100 has a shape having an internal void that is rounded from a substantially rectangular parallelepiped. There may be. Moreover, although the shape of the opening of the positive electrode active material 100 in FIG. 1 is a quadrangle, for example, the shape of the opening may be a substantially circular shape.
正極活物質１００は内部空隙を有し、該空隙が開口しているため、同じ見かけの体積を持つ球状の粒子よりも比表面積が大きくなる。なお本明細書において、比表面積とは、単位質量あたりの表面積を言う。 Since the positive electrode active material 100 has internal voids and the voids are open, the specific surface area is larger than spherical particles having the same apparent volume. In the present specification, the specific surface area refers to the surface area per unit mass.
たとえば、リン酸鉄リチウムは固相法により合成すると略球状の粒子が得られることが知られている。そこで、球状の粒子の例として、図２のようなリン酸鉄リチウムの粒子を想定し、粒子の直径を２ｒとする。球状のリン酸鉄リチウムの粒子である正極活物質１５０について、粒子の見かけの体積Ｖ１５０は、（４／３）πｒ３で表される。 For example, when lithium iron phosphate is synthesized by a solid phase method, it is known that substantially spherical particles can be obtained. Thus, as an example of spherical particles, a lithium iron phosphate particle as shown in FIG. 2 is assumed, and the particle diameter is 2r. Regarding the positive electrode active material 150 that is spherical lithium iron phosphate particles, the apparent volume V 150 of the particles is represented by (4/3) πr 3 .
上述のように、内部空隙を有する正極活物質１００の見かけの体積Ｖ１００と、球状の正極活物質１５０の見かけの体積Ｖ１５０が等しいとき、正極活物質１００の比表面積Ｓ１００の方が、正極活物質１５０の比表面積Ｓ１５０よりも大きい。すなわち、Ｖ１００＝Ｖ１５０のとき、Ｓ１００＞Ｓ１５０になる。 As described above, when the apparent volume V 100 of the positive electrode active material 100 having internal voids and the apparent volume V 150 of the spherical positive electrode active material 150 are equal, the specific surface area S 100 of the positive electrode active material 100 is larger than the specific surface area S 150 of the positive electrode active material 150. That is, when V 100 = V 150 , S 100 > S 150 .
このように、正極活物質として内部空隙を有し、該空隙が開口しているリン酸鉄リチウムの結晶を用いることで、比表面積を大きくすることができる。比表面積の大きな正極活物質を用いることで、正極活物質と電解液の接触面積が大きくなり、リチウムイオン電池の出力を大きくすることができる。 Thus, the specific surface area can be increased by using a lithium iron phosphate crystal having an internal void as the positive electrode active material and opening the void. By using a positive electrode active material having a large specific surface area, the contact area between the positive electrode active material and the electrolytic solution is increased, and the output of the lithium ion battery can be increased.
＜正極活物質の作製方法＞
次に、正極活物質１００の作製方法について説明する。
<Method for producing positive electrode active material>
Next, a method for manufacturing the positive electrode active material 100 will be described.
正極活物質１００であるリン酸鉄リチウム結晶の合成の原料には、リチウム源として、水酸化リチウム一水和物（ＬｉＯＨ・Ｈ２Ｏ）、無水水酸化リチウム（ＬｉＯＨ）、炭酸リチウム（Ｌｉ２ＣＯ３）、酸化リチウム（Ｌｉ２Ｏ）、硝酸リチウム（ＬｉＮＯ３）、リン酸二水素リチウム（ＬｉＨ２ＰＯ４）、酢酸リチウム（ＣＨ３ＣＯＯＬｉ）、リン酸リチウム（Ｌｉ３ＰＯ４）などを用いることができる。 The raw material for the synthesis of the lithium iron phosphate crystal that is the positive electrode active material 100 includes lithium hydroxide monohydrate (LiOH.H 2 O), anhydrous lithium hydroxide (LiOH), lithium carbonate (Li 2 ) as a lithium source. CO 3 ), lithium oxide (Li 2 O), lithium nitrate (LiNO 3 ), lithium dihydrogen phosphate (LiH 2 PO 4 ), lithium acetate (CH 3 COOLi), lithium phosphate (Li 3 PO 4 ), or the like may be used. it can.
また、鉄源として、塩化鉄（ＩＩ）四水和物（ＦｅＣｌ２・４Ｈ２Ｏ）、硫酸鉄（ＩＩ）七水和物（ＦｅＳＯ４・７Ｈ２Ｏ）、リン酸鉄（ＩＩ）八水和物（Ｆｅ３（ＰＯ４）２・８Ｈ２Ｏ）、酢酸鉄（ＩＩ）（Ｆｅ（ＣＨ３ＣＯＯ）２）、シュウ酸鉄（ＩＩ）（ＦｅＣ２Ｏ４）、硫酸鉄（ＩＩ）（ＦｅＳＯ４）などを用いることができる。 Further, as an iron source, iron (II) chloride tetrahydrate (FeCl 2 .4H 2 O), iron (II) sulfate heptahydrate (FeSO 4 .7H 2 O), iron (II) phosphate octahydrate ( Fe 3 (PO 4) 2 · 8H 2 O), iron acetate (II) (Fe (CH 3 COO) 2), iron oxalate (II) (FeC 2 O 4 ), iron sulfate (II) (FeSO 4) Etc. can be used.
また、リン酸源として、リン酸二水素アンモニウム（ＮＨ４Ｈ２ＰＯ４）、リン酸水素二アンモニウム（（ＮＨ４）２ＨＰＯ４）、リン酸（Ｈ３ＰＯ４）などを用いることができる。 In addition, ammonium dihydrogen phosphate (NH 4 H 2 PO 4 ), diammonium hydrogen phosphate ((NH 4 ) 2 HPO 4 ), phosphoric acid (H 3 PO 4 ), and the like can be used as the phosphoric acid source.
本実施の形態では、リチウム源として水酸化リチウム一水和物を、鉄源として塩化鉄（ＩＩ）四水和物を、リン酸源としてリン酸二水素アンモニウムを用いることとする。 In this embodiment, lithium hydroxide monohydrate is used as the lithium source, iron (II) chloride tetrahydrate is used as the iron source, and ammonium dihydrogen phosphate is used as the phosphoric acid source.
次に、リチウム源、鉄源、およびリン酸源の原料をそれぞれ秤量する。本実施の形態では、水酸化リチウム一水和物：塩化鉄（ＩＩ）四水和物：リン酸二水素アンモニウム＝２：１：１（ｍｏｌ比）となるよう、それぞれを秤量することとする。 Next, the raw materials for the lithium source, iron source, and phosphate source are weighed. In the present embodiment, lithium hydroxide monohydrate: iron (II) chloride tetrahydrate: ammonium dihydrogen phosphate = 2: 1: 1 (molar ratio) are weighed. .
次に、秤量したリチウム源、鉄源、およびリン酸源の原料をそれぞれ水に溶解し、リチウム水溶液、鉄水溶液、リン酸水溶液を調製する。ここで用いる水を、あらかじめ窒素でバブリングしてもよい。水を窒素でバブリングすることで、水中の溶存酸素を低減し、溶存酸素による副生成物を低減することができる。本実施の形態では、水酸化リチウム一水和物、塩化鉄（ＩＩ）四水和物、およびリン酸二水素アンモニウムを、それぞれあらかじめ窒素でバブリングした水に溶解することとする。 Next, the weighed lithium source, iron source, and phosphoric acid source raw materials are each dissolved in water to prepare a lithium aqueous solution, an iron aqueous solution, and a phosphoric acid aqueous solution. The water used here may be previously bubbled with nitrogen. By bubbling water with nitrogen, dissolved oxygen in the water can be reduced, and by-products due to dissolved oxygen can be reduced. In this embodiment, lithium hydroxide monohydrate, iron (II) chloride tetrahydrate, and ammonium dihydrogen phosphate are each dissolved in water previously bubbled with nitrogen.
次に、リン酸水溶液を攪拌しながら、リチウム水溶液を徐々に加える。攪拌は空気中、または酸素を含む雰囲気中で行うことが好ましい。発明者の試行錯誤の結果、酸素を含まない雰囲気中で攪拌を行うと、後の工程で内部空隙を有する結晶を合成できないことが明らかとなっているためである。本実施の形態では、空気中、室温でリン酸二水素アンモニウム水溶液を攪拌しながら、水酸化リチウム水溶液を徐々に加えることとする。 Next, the lithium aqueous solution is gradually added while stirring the phosphoric acid aqueous solution. Stirring is preferably performed in air or in an atmosphere containing oxygen. As a result of the inventor's trial and error, it is clear that if the stirring is performed in an oxygen-free atmosphere, crystals having internal voids cannot be synthesized in a later step. In the present embodiment, the aqueous lithium hydroxide solution is gradually added while stirring the aqueous ammonium dihydrogen phosphate solution at room temperature in the air.
次に、鉄水溶液を攪拌しながら、上記のリン酸とリチウムの水溶液を徐々に加え、リン酸鉄リチウムの前駆体を含む懸濁液を調製する。攪拌は空気中、または酸素を含む雰囲気中で行うことが好ましい。発明者の試行錯誤の結果、酸素を含まない雰囲気中で攪拌を行うと、後の工程で内部空隙を有する結晶を合成できないことが明らかとなっているためである。本実施の形態では、空気中、室温で塩化鉄（ＩＩ）水溶液を攪拌しながら、リン酸二水素アンモニウムと水酸化リチウムの水溶液を徐々に加え、リン酸鉄リチウムの前駆体を含む懸濁液を調製することとする。 Next, the aqueous solution of phosphoric acid and lithium is gradually added while stirring the aqueous iron solution to prepare a suspension containing a precursor of lithium iron phosphate. Stirring is preferably performed in air or in an atmosphere containing oxygen. As a result of the inventor's trial and error, it is clear that if the stirring is performed in an oxygen-free atmosphere, crystals having internal voids cannot be synthesized in a later step. In the present embodiment, an aqueous solution of ammonium dihydrogen phosphate and lithium hydroxide is gradually added while stirring an iron (II) chloride aqueous solution at room temperature in the air, and a suspension containing a precursor of lithium iron phosphate Will be prepared.
また、リン酸鉄リチウムの前駆体を含む懸濁液を調製した後、空気または酸素を含む気体でバブリングを行ってもよい。バブリングの時間は、たとえば空気でバブリングする場合１５分以上１時間以下が好ましい。 Further, after preparing a suspension containing a precursor of lithium iron phosphate, bubbling may be performed with a gas containing air or oxygen. The bubbling time is preferably 15 minutes or more and 1 hour or less when bubbling with air, for example.
次に、上記の前駆体を含む懸濁液に、加熱および加圧処理を行う（すなわち、水熱法により合成をする）。加熱および加圧処理は、たとえば１００℃以上水の臨界温度以下、０．１ＭＰａ以上水の臨界圧力以下、１時間以上で行うことができる。水熱法による合成には、１００℃以上の水と大気圧以上の圧力が必要であり、また１時間以下の加熱および加圧処理では、内部空隙を有する結晶を合成できないことが明らかとなっているためである。本実施の形態では、約１５０℃、約０．５ＭＰａで１６時間処理することとする。加熱および加圧処理により、前駆体を含む懸濁液から内部空隙を有するリン酸鉄リチウムの結晶を合成することができる。 Next, the suspension containing the precursor is subjected to heat and pressure treatment (that is, synthesized by a hydrothermal method). The heating and pressurizing treatment can be performed, for example, at 100 ° C. or higher and the critical temperature of water or lower, 0.1 MPa or higher and the critical pressure of water or lower for 1 hour or longer. It is clear that the synthesis by the hydrothermal method requires water of 100 ° C. or higher and a pressure of atmospheric pressure or higher, and that heating and pressurizing treatment for 1 hour or less cannot synthesize crystals having internal voids. Because it is. In this embodiment, the treatment is performed at about 150 ° C. and about 0.5 MPa for 16 hours. By heating and pressurizing treatment, crystals of lithium iron phosphate having internal voids can be synthesized from the suspension containing the precursor.
反応後、得られた固形物を水で洗浄してから濾過を行い、得られた固形物を正極活物質１００とする。このようにして、正極活物質１００として略直方体の内部空隙を有し、該空隙が開口しているリン酸鉄リチウムの結晶を作製することができる。 After the reaction, the obtained solid is washed with water and then filtered, and the obtained solid is used as the positive electrode active material 100. In this way, a crystal of lithium iron phosphate having a substantially rectangular parallelepiped internal void as the positive electrode active material 100 and opening the void can be produced.
（実施の形態２）
本実施の形態では、実施の形態１に記載の正極活物質１００を用いた正極およびリチウムイオン二次電池について説明する。正極の概要を図３（Ａ）に、リチウムイオン二次電池の概要を図３（Ｂ）に示す。
(Embodiment 2)
In this embodiment, a positive electrode and a lithium ion secondary battery using the positive electrode active material 100 described in Embodiment 1 will be described. FIG. 3A shows an outline of the positive electrode, and FIG. 3B shows an outline of the lithium ion secondary battery.
＜正極＞
まず、リチウムイオン二次電池の正極について、図３（Ａ）を用いて説明する。図３（Ａ）に示す正極２０２は、正極集電体２００と正極活物質層２０１を含む。
<Positive electrode>
First, a positive electrode of a lithium ion secondary battery will be described with reference to FIG. A positive electrode 202 illustrated in FIG. 3A includes a positive electrode current collector 200 and a positive electrode active material layer 201.
正極集電体２００としては、アルミニウム、ステンレス等の導電性の高い材料を用いることができる。正極集電体２００は、箔状、板状、網状等の形状を適宜用いることができる。 As the positive electrode current collector 200, a highly conductive material such as aluminum or stainless steel can be used. The positive electrode current collector 200 can have a foil shape, a plate shape, a net shape, or the like as appropriate.
正極活物質層２０１は、実施の形態１で示した内部空隙を有し、該空隙が開口しているリン酸鉄リチウムの結晶である正極活物質１００を含む。なお、正極活物質層２０１として機能するすべてのリン酸鉄リチウムが、実施の形態１で示した正極活物質１００である必要はない。正極活物質層２０１に、例えば内部空隙のないリン酸鉄リチウムが含まれていてもよい。 The positive electrode active material layer 201 includes the positive electrode active material 100 which has the internal voids described in Embodiment 1 and is a crystal of lithium iron phosphate in which the voids are open. Note that all the lithium iron phosphates functioning as the positive electrode active material layer 201 do not need to be the positive electrode active material 100 described in Embodiment 1. The positive electrode active material layer 201 may contain, for example, lithium iron phosphate without an internal void.
次に正極２０２の作製方法について説明する。まず、正極活物質１００に導電助剤やバインダ、溶媒を加えてペースト状に調合する。 Next, a method for manufacturing the positive electrode 202 will be described. First, a conductive additive, a binder, and a solvent are added to the positive electrode active material 100 to prepare a paste.
導電助剤とは、活物質間の導電性を助ける物質であり、離れている活物質の間に充填され、活物質同士の導通をとる材料である。導電助剤は、その材料自身が電子導電体であり、電池装置内で他の物質と化学変化を起こさないものであればよい。例えば、黒鉛、炭素繊維、カーボンブラック、アセチレンブラック、ＶＧＣＦ（商標登録）などの炭素系材料、銅、ニッケル、アルミニウムもしくは銀など金属材料またはこれらの混合物の粉末や繊維などがそれに該当する。 The conductive assistant is a substance that helps conductivity between the active materials, and is a material that is filled between the active materials that are separated from each other to establish conduction between the active materials. The conductive assistant may be any material as long as the material itself is an electronic conductor and does not cause a chemical change with other substances in the battery device. Examples thereof include carbon-based materials such as graphite, carbon fiber, carbon black, acetylene black, and VGCF (registered trademark), metal materials such as copper, nickel, aluminum, and silver, or powders and fibers of a mixture thereof.
バインダとしては、澱粉、ポリビニルアルコール、カルボキシメチルセルロース、ヒドロキシプロピルセルロース、再生セルロース、ジアセチルセルロース、ポリビニルクロリド、ポリビニルピロリドン、ポリテトラフルオロエチレン、ポリフッ化ビニリデン、ポリエチレン、ポリプロピレン、ＥＰＤＭ（Ｅｔｈｙｌｅｎｅ Ｐｒｏｐｙｌｅｎｅ Ｄｉｅｎｅ Ｍｏｎｏｍｅｒ）、スルホン化ＥＰＤＭ、スチレンブタジエンゴム、ブタジエンゴム、フッ素ゴムもしくはポリエチレンオキシドなどの多糖類、熱可塑性樹脂またはゴム弾性を有するポリマーなどがある。 Examples of the binder include starch, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, regenerated cellulose, diacetyl cellulose, polyvinyl chloride, polyvinyl pyrrolidone, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, EPDM (Ethylene Propylene Diene Monomer), and sulfone. EPDM, styrene butadiene rubber, butadiene rubber, polysaccharides such as fluoro rubber or polyethylene oxide, thermoplastic resins, polymers having rubber elasticity, and the like.
電極用材料として用いられる正極活物質１００、導電助剤、及びバインダは、それぞれ８０〜９６重量％、２〜１０重量％、２〜１０重量％の割合で、且つ全体で１００重量％になるように混合する。更に、電極用材料、導電助剤、及びバインダの混合物と同体積程度の有機溶媒を混合し、これらが有機溶媒に懸濁している状態にする。なお、電極用材料、導電助剤、バインダが有機溶媒に懸濁している状態にしたものを、スラリーと呼ぶ。有機溶媒としては、Ｎメチル−２ピロリドンや乳酸エステルなどがある。成膜した時の活物質および導電助剤の密着性が弱い時にはバインダを多くし、活物質の抵抗が高い時には導電助剤を多くするなどして、活物質、導電助剤、バインダの割合を適宜調整するとよい。 The positive electrode active material 100, the conductive additive, and the binder used as the electrode material are 80 to 96% by weight, 2 to 10% by weight, 2 to 10% by weight, and 100% by weight as a whole. To mix. Further, an organic solvent having the same volume as that of the mixture of the electrode material, the conductive additive and the binder is mixed, and these are suspended in the organic solvent. In addition, what made the material for electrodes, the conductive support agent, and the binder suspended in the organic solvent is called slurry. Examples of the organic solvent include N-methyl-2-pyrrolidone and lactic acid ester. When the adhesion between the active material and the conductive auxiliary agent is weak, increase the binder, and when the active material resistance is high, increase the conductive auxiliary agent to increase the ratio of the active material, conductive auxiliary agent and binder. It is good to adjust appropriately.
ここでは、正極集電体２００としてアルミ箔を用い、その上にスラリーを滴下してキャスト法により薄く広げた後、ロールプレス器で更に延伸し、厚みを均等にした後、真空乾燥（１０Ｐａ以下）や加熱乾燥（１５０〜２８０℃）して、正極集電体２００上に正極活物質層２０１を形成する。正極活物質層２０１の厚さは、２０〜１００μｍの間で所望の厚さを選択する。クラックや剥離が生じないように、正極活物質層２０１の厚さを適宜調整することが好ましい。さらには、電池の形態にもよるが、平板状だけでなく、筒状に丸めた時に、正極活物質層２０１にクラックや剥離が生じないようにすることが好ましい。 Here, an aluminum foil is used as the positive electrode current collector 200, a slurry is dropped on the positive electrode current collector 200, and the slurry is spread thinly by a casting method. Further, the film is further stretched by a roll press to equalize the thickness, and then vacuum-dried (10 Pa or less) ) Or heat drying (150 to 280 ° C.) to form the positive electrode active material layer 201 on the positive electrode current collector 200. A desired thickness of the positive electrode active material layer 201 is selected between 20 and 100 μm. It is preferable to adjust the thickness of the positive electrode active material layer 201 as appropriate so that cracks and peeling do not occur. Furthermore, although depending on the form of the battery, it is preferable that the positive electrode active material layer 201 is not cracked or peeled when rolled into a cylindrical shape as well as a flat shape.
このようにして、正極２０２を作製することができる。 In this manner, the positive electrode 202 can be manufactured.
＜リチウムイオン二次電池＞
次に、上記の正極２０２を有するリチウムイオン二次電池について、図３（Ｂ）を用いて説明する。図３（Ｂ）に示すリチウムイオン二次電池は、正極２０２、負極２０７、及びセパレータ２１０を外部と隔絶する筐体２２０の中に設置し、筐体２２０中に電解液２１１が充填されている。また、正極２０２及び負極２０７との間にセパレータ２１０を有する。
<Lithium ion secondary battery>
Next, a lithium ion secondary battery including the above positive electrode 202 will be described with reference to FIG. In the lithium ion secondary battery illustrated in FIG. 3B, the positive electrode 202, the negative electrode 207, and the separator 210 are installed in a housing 220 that is isolated from the outside, and the housing 220 is filled with an electrolytic solution 211. . In addition, a separator 210 is provided between the positive electrode 202 and the negative electrode 207.
正極集電体２００には第１の電極２２１が、負極集電体２０５には第２の電極２２２が接続されており、第１の電極２２１及び第２の電極２２２より、充電や放電が行われる。また、正極活物質層２０１及びセパレータ２１０の間と負極活物質層２０６及びセパレータ２１０との間とはそれぞれは一定間隔をおいて示しているが、これに限らず、正極活物質層２０１及びセパレータ２１０と負極活物質層２０６及びセパレータ２１０とはそれぞれが接していても構わない。また、正極２０２及び負極２０７は間にセパレータ２１０を配置した状態で筒状に丸めても構わない。 A first electrode 221 is connected to the positive electrode current collector 200, and a second electrode 222 is connected to the negative electrode current collector 205. Charging and discharging are performed from the first electrode 221 and the second electrode 222. Is called. Further, the positive electrode active material layer 201 and the separator 210 and the negative electrode active material layer 206 and the separator 210 are shown at regular intervals, but the present invention is not limited thereto. 210, the negative electrode active material layer 206, and the separator 210 may be in contact with each other. Further, the positive electrode 202 and the negative electrode 207 may be rounded into a cylindrical shape with the separator 210 interposed therebetween.
正極集電体２００上に正極活物質層２０１が形成されている。正極活物質層２０１には、上述のように実施の形態１で作製した正極活物質１００が含まれている。一方、負極集電体２０５の上には負極活物質層２０６が形成されている。負極２０７は、負極活物質層２０６と、それが形成された負極集電体２０５を含む。 A positive electrode active material layer 201 is formed on the positive electrode current collector 200. The positive electrode active material layer 201 includes the positive electrode active material 100 manufactured in Embodiment 1 as described above. On the other hand, a negative electrode active material layer 206 is formed on the negative electrode current collector 205. The negative electrode 207 includes a negative electrode active material layer 206 and a negative electrode current collector 205 on which the negative electrode active material layer 206 is formed.
負極集電体２０５としては、銅、ステンレス、鉄、ニッケル等の導電性の高い材料を用いることができる。 As the negative electrode current collector 205, a highly conductive material such as copper, stainless steel, iron, or nickel can be used.
負極活物質層２０６としては、リチウム、アルミニウム、黒鉛、シリコン、ゲルマニウムなどが用いられる。負極集電体２０５上に、塗布法、スパッタ法、蒸着法などにより負極活物質層２０６を形成してもよいし、それぞれの材料を単体で負極活物質層２０６として用いてもよい。黒鉛と比較すると、ゲルマニウム、シリコン、リチウム、アルミニウムの理論リチウム吸蔵容量が大きい。吸蔵容量が大きいと小面積でも十分に充放電が可能であり、負極として機能するため、コストの節減及び二次電池の小型化につながる。ただし、シリコンなどはリチウム吸蔵により体積が４倍程度まで増えるために、材料自身が脆くなる事や爆発する危険性などにも十分に気をつける必要がある。 As the negative electrode active material layer 206, lithium, aluminum, graphite, silicon, germanium, or the like is used. The negative electrode active material layer 206 may be formed over the negative electrode current collector 205 by a coating method, a sputtering method, a vapor deposition method, or the like, or each material may be used alone as the negative electrode active material layer 206. Compared to graphite, the theoretical lithium storage capacity of germanium, silicon, lithium, and aluminum is large. When the storage capacity is large, charge and discharge can be sufficiently performed even in a small area, and the negative electrode functions as a negative electrode, which leads to cost savings and downsizing of the secondary battery. However, since the volume of silicon and the like increases by about 4 times due to occlusion of lithium, it is necessary to pay sufficient attention to the danger of the material itself becoming brittle or exploding.
電解質は、液体の電解質である電解液や、固体の電解質である固体電解質を用いればよい。電解液は、キャリアイオンであるアルカリ金属イオン、アルカリ土類金属イオンを含み、このキャリアイオンが電気伝導を担っている。アルカリ金属イオンとしては、例えば、リチウムイオン、ナトリウムイオン、若しくはカリウムイオンがある。アルカリ土類金属イオンとしては、例えばベリリウムイオン、マグネシウムイオン、カルシウムイオン、ストロンチウムイオン、若しくはバリウムイオンがある。 As the electrolyte, an electrolytic solution that is a liquid electrolyte or a solid electrolyte that is a solid electrolyte may be used. The electrolytic solution contains alkali metal ions and alkaline earth metal ions which are carrier ions, and the carrier ions are responsible for electrical conduction. Examples of alkali metal ions include lithium ions, sodium ions, and potassium ions. Examples of alkaline earth metal ions include beryllium ions, magnesium ions, calcium ions, strontium ions, or barium ions.
電解液２１１は、例えば溶媒と、その溶媒に溶解するリチウム塩またはナトリウム塩とから構成されている。リチウム塩としては、例えば、塩化リチウム（ＬｉＣｌ）、フッ化リチウム（ＬｉＦ）、過塩素酸リチウム（ＬｉＣｌＯ４）、硼弗化リチウム（ＬｉＢＦ４）、ＬｉＡｓＦ６、ＬｉＰＦ６、Ｌｉ（Ｃ２Ｆ５ＳＯ２）２Ｎ等がある。ナトリウム塩としては、例えば、塩化ナトリウム（ＮａＣｌ）、フッ化ナトリウム（ＮａＦ）、過塩素酸ナトリウム（ＮａＣｌＯ４）、硼弗化ナトリウム（ＮａＢＦ４）等がある。 The electrolytic solution 211 is composed of, for example, a solvent and a lithium salt or a sodium salt dissolved in the solvent. Examples of the lithium salt include lithium chloride (LiCl), lithium fluoride (LiF), lithium perchlorate (LiClO 4 ), lithium borofluoride (LiBF 4 ), LiAsF 6 , LiPF 6 , Li (C 2 F 5 SO 2 ) 2 N and the like. Examples of the sodium salt include sodium chloride (NaCl), sodium fluoride (NaF), sodium perchlorate (NaClO 4 ), sodium borofluoride (NaBF 4 ), and the like.
電解液２１１の溶媒として、環状カーボネート類（例えば、エチレンカーボネート（以下、ＥＣと略す）、プロピレンカーボネート（ＰＣ）、ブチレンカーボネート（ＢＣ）、およびビニレンカーボネート（ＶＣ）など）、非環状カーボネート類（ジメチルカーボネート（ＤＭＣ）、ジエチルカーボネート（ＤＥＣ）、エチルメチルカーボネート（ＥＭＣ）、メチルプロピルカーボネート（ＭＰＣ）、メチルイソブチルカーボネート（ＭＩＢＣ）、およびジプロピルカーボネート（ＤＰＣ）など）、脂肪族カルボン酸エステル類（ギ酸メチル、酢酸メチル、プロピオン酸メチル、およびプロピオン酸エチルなど）、非環状エーテル類（γ−ブチロラクトン等のγ−ラクトン類、１，２−ジメトキシエタン（ＤＭＥ）、１，２−ジエトキシエタン（ＤＥＥ）、およびエトキシメトキシエタン（ＥＭＥ）等）、環状エーテル類（テトラヒドロフラン、２−メチルテトラヒドロフラン等）、環状スルホン（スルホランなど）、アルキルリン酸エステル（ジメチルスルホキシド、１，３−ジオキソラン等やリン酸トリメチル、リン酸トリエチル、およびリン酸トリオクチルなど）やそのフッ化物があり、これらの一種または二種以上を混合して使用する。 As a solvent for the electrolytic solution 211, cyclic carbonates (for example, ethylene carbonate (hereinafter abbreviated as EC), propylene carbonate (PC), butylene carbonate (BC), vinylene carbonate (VC), etc.), acyclic carbonates (dimethyl) Carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl propyl carbonate (MPC), methyl isobutyl carbonate (MIBC), dipropyl carbonate (DPC), etc.), aliphatic carboxylic acid esters (formic acid) Methyl, methyl acetate, methyl propionate, and ethyl propionate), acyclic ethers (γ-lactones such as γ-butyrolactone, 1,2-dimethoxyethane (DME), 1,2-diethoxyethane (DEE), ethoxymethoxyethane (EME, etc.), cyclic ethers (tetrahydrofuran, 2-methyltetrahydrofuran, etc.), cyclic sulfones (sulfolane, etc.), alkyl phosphate esters (dimethyl sulfoxide, 1,3-dioxolane, etc., phosphorus Trimethyl acid, triethyl phosphate, trioctyl phosphate, etc.) and fluorides thereof, and these are used alone or in combination.
セパレータ２１０として、紙、不織布、ガラス繊維、あるいは、ナイロン（ポリアミド）、ビニロン（ビナロンともいう）（ポリビニルアルコール系繊維）、ポリエステル、アクリル、ポリオレフィン、ポリウレタンといった合成繊維等を用いればよい。ただし、上記した電解液２１１に溶解しない材料を選ぶ必要がある。 As the separator 210, paper, nonwoven fabric, glass fiber, or synthetic fiber such as nylon (polyamide), vinylon (also referred to as vinylon) (polyvinyl alcohol fiber), polyester, acrylic, polyolefin, polyurethane, or the like may be used. However, it is necessary to select a material that does not dissolve in the electrolytic solution 211 described above.
より具体的には、セパレータ２１０の材料として、例えば、フッ素系ポリマ−、ポリエチレンオキシド、ポリプロピレンオキシド等のポリエーテル、ポリエチレン、ポリプロピレン等のポリオレフィン、ポリアクリロニトリル、ポリ塩化ビニリデン、ポリメチルメタクリレート、ポリメチルアクリレート、ポリビニルアルコール、ポリメタクリロニトリル、ポリビニルアセテート、ポリビニルピロリドン、ポリエチレンイミン、ポリブタジエン、ポリスチレン、ポリイソプレン、ポリウレタン系高分子およびこれらの誘導体、セルロース、紙、不織布から選ばれる一種を単独で、または二種以上を組み合せて用いることができる。 More specifically, as the material of the separator 210, for example, fluoropolymer, polyether such as polyethylene oxide and polypropylene oxide, polyolefin such as polyethylene and polypropylene, polyacrylonitrile, polyvinylidene chloride, polymethyl methacrylate, polymethyl acrylate , Polyvinyl alcohol, polymethacrylonitrile, polyvinyl acetate, polyvinyl pyrrolidone, polyethyleneimine, polybutadiene, polystyrene, polyisoprene, polyurethane polymers and derivatives thereof, cellulose, paper, nonwoven fabric, alone or in combination A combination of the above can be used.
上記に示すリチウムイオン二次電池に充電をする時には、第１の電極２２１に正極端子、第２の電極２２２に負極端子を接続する。正極２０２からは電子が第１の電極２２１を介して奪われ、第２の電極２２２を通じて負極２０７に移動する。加えて、正極からはリチウムイオンが正極活物質層２０１中の活物質から溶出し、セパレータ２１０を通過して負極２０７に達し、負極活物質層２０６内の活物質に取り込まれる。当該領域でリチウムイオン及び電子が合体して、負極活物質層２０６に吸蔵される。同時に正極活物質層２０１では、活物質から電子が放出され、活物質に含まれる金属Ｍの酸化反応が生じる。 When charging the lithium ion secondary battery described above, the positive electrode terminal is connected to the first electrode 221 and the negative electrode terminal is connected to the second electrode 222. Electrons are taken from the positive electrode 202 through the first electrode 221 and move to the negative electrode 207 through the second electrode 222. In addition, lithium ions are eluted from the active material in the positive electrode active material layer 201 from the positive electrode, pass through the separator 210, reach the negative electrode 207, and are taken into the active material in the negative electrode active material layer 206. In the region, lithium ions and electrons are combined and occluded in the negative electrode active material layer 206. At the same time, in the positive electrode active material layer 201, electrons are emitted from the active material, and an oxidation reaction of the metal M contained in the active material occurs.
放電する時には、負極２０７では、負極活物質層２０６がリチウムをイオンとして放出し、第２の電極２２２に電子が送り込まれる。リチウムイオンはセパレータ２１０を通過して、正極活物質層２０１に達し、正極活物質層２０１中の活物質に取り込まれる。その時には、負極２０７からの電子も正極２０２に到達し、金属Ｍの還元反応が生じる。 At the time of discharging, in the negative electrode 207, the negative electrode active material layer 206 releases lithium as ions, and electrons are sent to the second electrode 222. The lithium ions pass through the separator 210, reach the positive electrode active material layer 201, and are taken into the active material in the positive electrode active material layer 201. At that time, electrons from the negative electrode 207 also reach the positive electrode 202, and a reduction reaction of the metal M occurs.
以上のようにして作製したリチウムイオン二次電池は、内部空隙を有し、該空隙が開口しているリン酸鉄リチウムの結晶を正極活物質として有している。このリン酸鉄リチウムの結晶は比表面積が大きいため、電解液との接触面積が大きくなり、本実施の形態で得られるリチウムイオン二次電池を、出力の大きなリチウムイオン二次電池とすることができる。 The lithium ion secondary battery produced as described above has an internal void, and has, as a positive electrode active material, a crystal of lithium iron phosphate in which the void is open. Since the crystal of lithium iron phosphate has a large specific surface area, the contact area with the electrolytic solution becomes large, and the lithium ion secondary battery obtained in this embodiment can be a lithium ion secondary battery with high output. it can.
以上、本実施の形態に示す構成、方法などは、他の実施の形態に示す構成、方法などと適宜組み合わせて用いることができる。 The structures, methods, and the like described in this embodiment can be combined as appropriate with any of the structures, methods, and the like described in the other embodiments.
（実施の形態３）
本実施の形態では、実施の形態２に記載のリチウムイオン二次電池の応用形態について説明する。
(Embodiment 3)
In this embodiment, an application mode of the lithium ion secondary battery described in Embodiment 2 will be described.
実施の形態２で説明したリチウムイオン二次電池は、電気自動車、ハイブリッド自動車、建設機械、作業車、鉄道用電気車両、カート、車椅子、自転車等の電気推進車両に用いることができる。また、無停電電源装置（Ｕｎｉｎｔｅｒｒｕｐｔｉｂｌｅ Ｐｏｗｅｒ Ｓｕｐｐｌｙ，ＵＰＳ）、デジタルカメラやビデオカメラ等のカメラ、携帯電話、デジタルフォトフレーム、携帯電話機（携帯電話、携帯電話装置ともいう）、携帯型ゲーム機、携帯情報端末、音響再生装置等の電子機器に用いることができる。 The lithium ion secondary battery described in Embodiment 2 can be used for an electric propulsion vehicle such as an electric vehicle, a hybrid vehicle, a construction machine, a work vehicle, a railway electric vehicle, a cart, a wheelchair, and a bicycle. Uninterruptible power supply (UPS), cameras such as digital cameras and video cameras, mobile phones, digital photo frames, mobile phones (also referred to as mobile phones and mobile phone devices), portable game machines, mobile information It can be used for electronic devices such as terminals and sound reproducing devices.
図４（Ａ）は、電気自動車３００の一例を示している。電気自動車３００には、リチウムイオン二次電池３０１が搭載されている。リチウムイオン二次電池３０１の電力は、制御回路３０２により出力が調整されて、駆動装置３０４に供給される。制御回路３０２は、コンピュータ３０３によって制御される。 FIG. 4A illustrates an example of the electric vehicle 300. A lithium ion secondary battery 301 is mounted on the electric vehicle 300. The output of the power of the lithium ion secondary battery 301 is adjusted by the control circuit 302 and supplied to the driving device 304. The control circuit 302 is controlled by the computer 303.
駆動装置３０４は、直流電動機若しくは交流電動機単体、又は電動機と内燃機関と、を組み合わせて構成される。コンピュータ３０３は、電気自動車３００の運転者の操作情報（加速、減圧、停止など）や走行時の情報（登坂や下坂等の情報、駆動輪にかかる負荷情報など）の入力情報に基づき、制御回路３０２に制御信号を出力する。制御回路３０２は、コンピュータ３０３の制御信号により、リチウムイオン二次電池３０１から供給される電気エネルギーを調整して駆動装置３０４の出力を制御する。交流電動機を搭載している場合は、直流を交流に変換するインバータも内蔵される。 The driving device 304 is configured by a DC motor or an AC motor alone, or a combination of an electric motor and an internal combustion engine. The computer 303 is a control circuit based on input information such as operation information (acceleration, decompression, stop, etc.) of the driver of the electric vehicle 300 and information at the time of travel (information such as climbing or downhill, load information applied to driving wheels) A control signal is output to 302. The control circuit 302 controls the output of the driving device 304 by adjusting the electrical energy supplied from the lithium ion secondary battery 301 according to the control signal of the computer 303. If an AC motor is installed, an inverter that converts DC to AC is also built-in.
実施の形態２で説明したリチウムイオン二次電池を、リチウムイオン二次電池３０１として用いることができる。リチウムイオン二次電池３０１は、プラグイン技術による外部からの電力供給により充電することができる。実施の形態２で説明したリチウムイオン二次電池を用いることで、出力を向上させることができる。 The lithium ion secondary battery described in Embodiment 2 can be used as the lithium ion secondary battery 301. The lithium ion secondary battery 301 can be charged by supplying power from the outside by plug-in technology. By using the lithium ion secondary battery described in Embodiment 2, the output can be improved.
図４（Ｂ）は、内燃機関動力と電気動力を組み合わせたハイブリッド型の建築機械３１０の一例を示している。建築機械３１０には、電気動力の供給源としてリチウムイオン二次電池３１１が搭載されている。リチウムイオン二次電池３１１は、インバータ３１４を介して電気モーター３１５および内燃機関モーター３１３と接続されている。内燃機関モーター３１３は内燃機関３１２と接続されている。建築機械３１０は、動作の減速時に電気モーター３１５による回生ブレーキをかけることで、電力をリチウムイオン二次電池３１１に蓄えることができる。 FIG. 4B shows an example of a hybrid type construction machine 310 that combines internal combustion engine power and electric power. The building machine 310 is equipped with a lithium ion secondary battery 311 as a source of electric power. The lithium ion secondary battery 311 is connected to the electric motor 315 and the internal combustion engine motor 313 via the inverter 314. The internal combustion engine motor 313 is connected to the internal combustion engine 312. The construction machine 310 can store electric power in the lithium ion secondary battery 311 by applying a regenerative brake by the electric motor 315 when the operation is decelerated.
実施の形態２で説明したリチウムイオン二次電池を、リチウムイオン二次電池３１１として用いることができる。実施の形態２で説明したリチウムイオン二次電池を用いることで、出力を向上させることができる。 The lithium ion secondary battery described in Embodiment 2 can be used as the lithium ion secondary battery 311. By using the lithium ion secondary battery described in Embodiment 2, the output can be improved.
なお、電気推進車両が鉄道用電気車両の場合、架線や導電軌条からの電力供給により充電をすることができる。 When the electric propulsion vehicle is a railway electric vehicle, charging can be performed by supplying power from an overhead wire or a conductive rail.
図４（Ｃ）および（Ｄ）は無停電電源装置の回路図である。図４（Ｃ）は、常時商用方式の無停電電源装置３２０であり、充電回路３２２、リチウムイオン二次電池３２１、インバータ３２３、リレー３２４を含む。図４（Ｄ）は常時インバータ方式の無停電電源装置３３０であり、整流回路３３２、充電回路３３１、リチウムイオン二次電池３３３、インバータ３３４を含む。 4C and 4D are circuit diagrams of the uninterruptible power supply. FIG. 4C illustrates a continuous commercial uninterruptible power supply 320 that includes a charging circuit 322, a lithium ion secondary battery 321, an inverter 323, and a relay 324. FIG. 4D illustrates an always-inverter-type uninterruptible power supply 330 including a rectifier circuit 332, a charging circuit 331, a lithium ion secondary battery 333, and an inverter 334.
実施の形態２で説明したリチウムイオン二次電池をリチウムイオン二次電池３２１、３３３として用いることができる。実施の形態２で説明したリチウムイオン二次電池を用いることで、出力を向上させることができる。 The lithium ion secondary battery described in Embodiment 2 can be used as the lithium ion secondary batteries 321 and 333. By using the lithium ion secondary battery described in Embodiment 2, the output can be improved.
本実施の形態は、他の実施の形態と組み合わせて実施することが可能である。 This embodiment can be implemented in combination with any of the other embodiments.
本実施例では、本発明の一態様である正極活物質１００の作製方法の一例とＸＲＤ解析、形状、粒径および比表面積について、図５乃至図７を用いて説明する。 In this example, an example of a method for manufacturing the positive electrode active material 100 which is one embodiment of the present invention, and XRD analysis, shape, particle diameter, and specific surface area will be described with reference to FIGS.
＜正極活物質の作製方法＞
まず、本発明の一態様である正極活物質の作製方法について説明する。
<Method for producing positive electrode active material>
First, a method for manufacturing a positive electrode active material which is one embodiment of the present invention is described.
本実施例では、正極活物質１００であるリン酸鉄リチウムの合成の原料として、水酸化リチウム一水和物（ＬｉＯＨ・Ｈ２Ｏ）、塩化鉄（ＩＩ）四水和物（ＦｅＣｌ２・４Ｈ２Ｏ）、およびリン酸二水素アンモニウム（ＮＨ４Ｈ２ＰＯ４）を用いた。 In this example, lithium hydroxide monohydrate (LiOH.H 2 O), iron (II) chloride tetrahydrate (FeCl 2 .4H) are used as raw materials for the synthesis of lithium iron phosphate, which is the positive electrode active material 100. 2 O) and ammonium dihydrogen phosphate (NH 4 H 2 PO 4 ).
まず、水酸化リチウム一水和物：塩化鉄（ＩＩ）四水和物：リン酸二水素アンモニウム＝２：１：１（ｍｏｌ比）となるよう、本実施例では水酸化リチウム一水和物を１．６７ｇ、塩化鉄（ＩＩ）四水和物を３．９７ｇ、リン酸二水素アンモニウムを２．３０ｇ、それぞれ秤量した。 First, in this example, lithium hydroxide monohydrate is lithium hydroxide monohydrate: iron (II) chloride tetrahydrate: ammonium dihydrogen phosphate = 2: 1: 1 (mol ratio). 1.67 g, iron (II) chloride tetrahydrate 3.97 g, and ammonium dihydrogen phosphate 2.30 g were weighed.
次に、秤量した水酸化リチウム一水和物、塩化鉄（ＩＩ）四水和物、およびリン酸二水素アンモニウムを、それぞれ、あらかじめ窒素でバブリングした水約３０ｍｌに溶解させた。 Next, weighed lithium hydroxide monohydrate, iron (II) chloride tetrahydrate, and ammonium dihydrogen phosphate were each dissolved in about 30 ml of water previously bubbled with nitrogen.
次に、リン酸二水素アンモニウム水溶液をスターラーで攪拌しながら、水酸化リチウム水溶液を徐々に加えた。攪拌は空気中で行った。その結果、白色沈殿が生成した。 Next, the lithium hydroxide aqueous solution was gradually added while stirring the ammonium dihydrogen phosphate aqueous solution with a stirrer. Stirring was performed in air. As a result, a white precipitate was formed.
次に、塩化鉄（ＩＩ）水溶液をスターラーで攪拌しながら、上記のリン酸二水素アンモニウムと水酸化リチウムの水溶液を徐々に加え、リン酸鉄リチウムの前駆体を含む懸濁液を調整した。攪拌は空気中で行った。その結果、緑白色沈殿が生成した。 Next, the aqueous solution of ammonium dihydrogen phosphate and lithium hydroxide was gradually added while stirring the aqueous iron (II) chloride solution with a stirrer to prepare a suspension containing a precursor of lithium iron phosphate. Stirring was performed in air. As a result, a greenish white precipitate was formed.
次に、上記の前駆体を含む懸濁液を、フッ素樹脂内筒を有する水熱合成用反応容器（ミニリアクターＭＳ型 ＭＳ２００−Ｃ（オーエムラボテック社製））に入れ、約１５０℃、約０．５ＭＰａで１６時間、水熱反応させた。 Next, the suspension containing the above precursor is put into a reaction vessel for hydrothermal synthesis (minireactor MS type MS200-C (manufactured by OM Labotech)) having a fluororesin inner cylinder, and about 150 ° C., about 0 The hydrothermal reaction was carried out at 5 MPa for 16 hours.
反応後、得られた固形物を純水で１０回程度洗浄してから濾過を行い、得られた固形物を正極活物質１００として回収した。 After the reaction, the obtained solid was washed about 10 times with pure water and filtered, and the obtained solid was recovered as the positive electrode active material 100.
＜正極活物質のＸＲＤ解析＞
上記の作製方法によって得られた正極活物質１００のＸＲＤ解析（Ｘ線結晶構造解析）を行った。図５にその結果を示す。横軸は回折角（２θ）、縦軸は回折強度である。図５の結果から、正極活物質１００はオリビン型構造のリン酸鉄リチウムの結晶であること示された。
<XRD analysis of positive electrode active material>
An XRD analysis (X-ray crystal structure analysis) of the positive electrode active material 100 obtained by the above manufacturing method was performed. FIG. 5 shows the result. The horizontal axis represents the diffraction angle (2θ), and the vertical axis represents the diffraction intensity. From the result of FIG. 5, it was shown that the positive electrode active material 100 was a crystal of lithium iron phosphate having an olivine structure.
＜正極活物質の透過型電子顕微鏡観察＞
上記の作製方法によって得られた正極活物質１００の透過型電子顕微鏡による観察を行った。図６にその結果を示す。観察には、Ｈ−９０００ＮＡＲ（日立ハイテクノロジーズ製）を用い、加速電圧２００ｋＶ、総合倍率２０５，０００倍（倍率精度±１０％）で行った。正極活物質１００のうち、結晶の欠陥もしくは結晶方位の変化に起因すると考えられる濃淡の変化は一部に限られ、ほとんどの部分は同一の結晶方位を有していた。図６の結果から、正極活物質１００のほとんどの部分は単結晶のリン酸鉄リチウムであることが示された。
<Transmission electron microscope observation of positive electrode active material>
The positive electrode active material 100 obtained by the above production method was observed with a transmission electron microscope. The result is shown in FIG. The observation was performed using H-9000NAR (manufactured by Hitachi High-Technologies) at an acceleration voltage of 200 kV and a total magnification of 205,000 times (magnification accuracy ± 10%). In the positive electrode active material 100, the change in light and shade considered to be caused by a crystal defect or a change in crystal orientation was limited to a part, and most parts had the same crystal orientation. From the result of FIG. 6, it was shown that most part of the positive electrode active material 100 is single-crystal lithium iron phosphate.
＜正極活物質の形状および粒径＞
上記の作製方法によって得られた、正極活物質１００の走査型電子顕微鏡観察を行った。図７乃至図９にその走査型電子顕微鏡写真を示す。観察は、加速電圧１０ｋＶ、倍率は図７（Ａ）は１０，０００倍、図７（Ｂ）は図７（Ａ）含まれる視野で、３０，０００倍、図８（Ａ）は１０，０００倍、図８（Ｂ）は図８（Ａ）含まれる視野で、３０，０００倍、図９（Ａ）は上記と異なる視野で、３０，０００倍、図９（Ｂ）は上記と異なる視野で、３０，０００倍で行った。図７乃至図９のように、正極活物質の粒子の多くは平板状の結晶であった。また平板状の結晶の一部に開口を有し、開口から内部の空隙を観察できる粒子が多数あった。また開口の多くは、結晶の側面に形成されていた。
<Shape and particle size of positive electrode active material>
The positive electrode active material 100 obtained by the above manufacturing method was observed with a scanning electron microscope. 7 to 9 show scanning electron micrographs thereof. In the observation, the acceleration voltage is 10 kV, the magnification is 10,000 times in FIG. 7 (A), FIG. 7 (B) is the field of view included in FIG. 7 (A), 30,000 times, and FIG. 8 (A) is 10,000. 8B is a field of view included in FIG. 8A, 30,000 times, FIG. 9A is a field of view different from the above, 30,000 times, and FIG. 9B is a field of view different from the above. And performed at 30,000 times. As shown in FIGS. 7 to 9, most of the particles of the positive electrode active material were tabular crystals. In addition, there were a large number of particles having an opening in a part of the flat crystal and being able to observe the internal voids from the opening. Many of the openings were formed on the side surfaces of the crystal.
また、図７の走査型電子顕微鏡写真から、正極活物質１００の一次粒子径の平均を求めた。具体的には、図７の走査型顕微鏡写真から結晶の幅が明らかな４４個の粒子について、それぞれ幅を測定して平均し、粒径とみなした。その結果、正極活物質１００であるリン酸鉄リチウム結晶の粒子径の平均は０．９４μｍであった。 Moreover, the average of the primary particle diameter of the positive electrode active material 100 was calculated | required from the scanning electron micrograph of FIG. Specifically, the widths of 44 particles whose crystal width was clear from the scanning micrograph of FIG. 7 were measured and averaged, and regarded as the particle size. As a result, the average particle diameter of the lithium iron phosphate crystal as the positive electrode active material 100 was 0.94 μm.
＜正極活物質の比表面積＞
また、上記の作製方法によって得られた、正極活物質１００の比表面積を測定した。測定には自動比表面積・細孔分布測定装置（トライスターＩＩ３０２０（島津製作所社製））を用いた。自動比表面積・細孔分布測定装置とは、試料粒子の表面に吸着占有面積のわかったガス分子を吸着させ、ガス分子の吸着量から試料の比表面積を求める測定装置である。測定の結果、正極活物質１００の比表面積は４．２ｍ２／ｇであった。
<Specific surface area of positive electrode active material>
Further, the specific surface area of the positive electrode active material 100 obtained by the above production method was measured. For the measurement, an automatic specific surface area / pore distribution measuring device (Tristar II 3020 (manufactured by Shimadzu Corporation)) was used. The automatic specific surface area / pore distribution measuring device is a measuring device that adsorbs gas molecules whose adsorption occupation area is known on the surface of a sample particle and obtains the specific surface area of the sample from the amount of adsorption of the gas molecules. As a result of the measurement, the specific surface area of the positive electrode active material 100 was 4.2 m 2 / g.
本実施例では、本発明の一態様である正極活物質１００の作製方法の別の一例と形状について、図１０を用いて説明する。 In this example, another example and a shape of a method for manufacturing the positive electrode active material 100 which is one embodiment of the present invention will be described with reference to FIGS.
＜正極活物質の作製方法＞
実施例１の正極活物質の作製方法と同様に前駆体を含む懸濁液を調製した。その後、前駆体を含む懸濁液を、フッ素樹脂内筒を有する水熱合成用反応容器に入れてから、３０分間空気でバブリングを行った。後の工程は実施例１の正極活物質の作製方法と同様に行った。
＜正極活物質の形状＞
上記の作製方法によって得られた、正極活物質１００の走査型電子顕微鏡観察を行った。図１０にその走査型電子顕微鏡写真を示す。実施例１の図７よりも壁が薄く、孔また凹部が大きな結晶が多数観察された。また、平板状の結晶の一部に開口を有し、開口から内部の空隙を観察できる粒子があった。また開口の多くは、結晶の側面に形成されていた。
<Method for producing positive electrode active material>
A suspension containing the precursor was prepared in the same manner as in the method for producing the positive electrode active material of Example 1. Thereafter, the suspension containing the precursor was put into a reaction container for hydrothermal synthesis having a fluororesin inner cylinder, and then bubbled with air for 30 minutes. The subsequent steps were performed in the same manner as in the method for producing the positive electrode active material in Example 1.
<Shape of positive electrode active material>
The positive electrode active material 100 obtained by the above manufacturing method was observed with a scanning electron microscope. FIG. 10 shows a scanning electron micrograph thereof. Many crystals with thinner walls and larger holes or recesses than in FIG. 7 of Example 1 were observed. In addition, there was a particle having an opening in a part of the flat crystal, and an internal void could be observed from the opening. Many of the openings were formed on the side surfaces of the crystal.
本実施例では、比較例として球状の正極活物質１５０の比表面積について説明する。 In this example, the specific surface area of the spherical positive electrode active material 150 will be described as a comparative example.
＜比較例の比表面積＞
比較例の正極活物質１５０として、一次粒子径が０．９４μｍであり、図２のような内部空隙をもたない球状のリン酸鉄リチウムの結晶の表面積を計算した。計算の結果、正極活物質１５０の比表面積は１．８２ｍ２／ｇであった。
<Specific surface area of comparative example>
As the positive electrode active material 150 of the comparative example, the surface area of a spherical lithium iron phosphate crystal having a primary particle diameter of 0.94 μm and no internal voids as shown in FIG. 2 was calculated. As a result of the calculation, the specific surface area of the positive electrode active material 150 was 1.82 m 2 / g.
実施例１のＸＲＤ解析、および走査型電子顕微鏡写真から、内部空隙を有するリン酸鉄リチウムの結晶を作製できたことが示された。また、実施例１および実施例３の比較から、内部空隙を有し、該空隙に開口を有するリン酸鉄リチウムの結晶が、同じ粒径で内部空隙をもたないリン酸鉄リチウムの結晶よりも、大きな表面積を有することが示された。 From the XRD analysis and scanning electron micrograph of Example 1, it was shown that a lithium iron phosphate crystal having internal voids could be produced. Further, from the comparison between Example 1 and Example 3, the lithium iron phosphate crystal having an internal void and having an opening in the void is more than the crystal of lithium iron phosphate having the same particle size and no internal void. Was also shown to have a large surface area.
１００ 正極活物質
１５０ 正極活物質
２００ 正極集電体
２０１ 正極活物質層
２０２ 正極
２０５ 負極集電体
２０６ 負極活物質層
２０７ 負極
２１０ セパレータ
２１１ 電解液
２２０ 筐体
２２１ 電極
２２２ 電極
３００ 電気自動車
３０１ リチウムイオン二次電池
３０２ 制御回路
３０３ コンピュータ
３０４ 駆動装置
３１０ 建築機械
３１１ リチウムイオン二次電池
３１２ 内燃機関
３１３ 内燃機関モーター
３１４ インバータ
３１５ 電気モーター
３２０ 無停電電源装置
３２１ リチウムイオン二次電池
３２２ 充電回路
３２３ インバータ
３２４ リレー
３３０ 無停電電源装置
３３１ 充電回路
３３２ 整流回路
３３３ リチウムイオン二次電池
３３４ インバータ
DESCRIPTION OF SYMBOLS 100 Positive electrode active material 150 Positive electrode active material 200 Positive electrode current collector 201 Positive electrode active material layer 202 Positive electrode 205 Negative electrode current collector 206 Negative electrode active material layer 207 Negative electrode 210 Separator 211 Electrolytic solution 220 Case 221 Electrode 222 Electrode 300 Electric vehicle 301 Lithium ion Secondary battery 302 Control circuit 303 Computer 304 Drive device 310 Construction machine 311 Lithium ion secondary battery 312 Internal combustion engine 313 Internal combustion engine motor 314 Inverter 315 Electric motor 320 Uninterruptible power supply 321 Lithium ion secondary battery 322 Charging circuit 323 Inverter 324 Relay 330 Uninterruptible power supply 331 Charging circuit 332 Rectifier circuit 333 Lithium ion secondary battery 334 Inverter
Claims (2)
前記リン酸鉄リチウムの前駆体を含む懸濁液に、加熱および加圧処理を行って、リン酸鉄リチウムの結晶を合成する工程とを有し、
前記加熱および前記加圧処理は、１００℃以上水の臨界温度以下で且つ０．１ＭＰａ以上水の臨界圧力以下で行う二次電池用正極活物質の作製方法。 Adding an aqueous solution containing phosphoric acid and lithium while stirring an aqueous solution containing iron in an atmosphere containing oxygen, and preparing a suspension containing a precursor of lithium iron phosphate;
The suspension containing the precursor of the lithium iron phosphate, subjected to heat and pressure treatment, possess a step of synthesizing a lithium iron phosphate crystals,
The method for producing a positive electrode active material for a secondary battery, wherein the heating and the pressure treatment are performed at 100 ° C. or more and a critical temperature of water or less and 0.1 MPa or more and a critical pressure of water or less .
前記リン酸鉄リチウムの前駆体を含む懸濁液の調整後であって、前記加熱および加圧処理前に、前記リン酸鉄リチウムの前駆体を含む懸濁液に酸素を含む気体でバブリング処理を行う工程を有する二次電池用正極活物質の作製方法。 In claim 1 ,
After the preparation of the suspension containing the lithium iron phosphate precursor and before the heating and pressurizing treatment, the suspension containing the lithium iron phosphate precursor is bubbled with a gas containing oxygen. The manufacturing method of the positive electrode active material for secondary batteries which has the process of performing.
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