JP2018125086A - Negative electrode material for storage battery, negative electrode for storage battery, and storage battery - Google Patents

Negative electrode material for storage battery, negative electrode for storage battery, and storage battery Download PDF

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JP2018125086A
JP2018125086A JP2017014457A JP2017014457A JP2018125086A JP 2018125086 A JP2018125086 A JP 2018125086A JP 2017014457 A JP2017014457 A JP 2017014457A JP 2017014457 A JP2017014457 A JP 2017014457A JP 2018125086 A JP2018125086 A JP 2018125086A
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寺師　吉健
Yoshitake Terashi
吉健 寺師
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Kyocera Corp
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Abstract

PROBLEM TO BE SOLVED: To provide a negative electrode material for a storage battery, a negative electrode for a storage battery, and a storage battery, which are capable of suppressing a decrease in charge/discharge performance.SOLUTION: A negative electrode material for a storage battery according to an embodiment includes a silicon particle. The silicon particle contains one or more trace elements selected from the element group consisting of iron, nickel, and sodium. The content of the element group is 62 mg/kg or less in total.SELECTED DRAWING: None

Description

開示の実施形態は、蓄電池用負極材料、蓄電池用負極および蓄電池に関する。   The disclosed embodiments relate to a negative electrode material for a storage battery, a negative electrode for a storage battery, and a storage battery.

従来、正極と負極との間を電解液中に含まれるリチウムイオンが移動するリチウムイオン二次電池が知られている。リチウムイオン二次電池は、充電時にはリチウムイオンを吸蔵し、放電時にはリチウムイオンを放出する負極活物質層を備える蓄電池である。   Conventionally, a lithium ion secondary battery in which lithium ions contained in an electrolyte move between a positive electrode and a negative electrode is known. A lithium ion secondary battery is a storage battery including a negative electrode active material layer that occludes lithium ions during charging and releases lithium ions during discharging.

負極活物質層としてはグラファイトなどの炭素系材料を適用したものが広く採用されている。近年、電池容量をさらに増大させるために、グラファイトよりもリチウムイオンの吸蔵能力が高いケイ素系材料を単独で使用し、あるいは併用した負極活物質層を備えるリチウムイオン二次電池が検討されている（例えば、特許文献１参照）。   As the negative electrode active material layer, a layer using a carbon-based material such as graphite is widely used. In recent years, in order to further increase the battery capacity, lithium ion secondary batteries having a negative electrode active material layer using a silicon-based material having a higher lithium ion storage capacity than graphite alone or in combination have been studied ( For example, see Patent Document 1).

特開２０１４−１９１９２７号公報JP 2014-191927 A

しかしながら、ケイ素系材料を負極活物質層に適用したリチウムイオン二次電池では、依然としてリチウムイオンの吸蔵と放出に伴う体積変化の繰り返しにより充放電性能が低下するサイクル劣化が起こりやすいという懸念があった。   However, in a lithium ion secondary battery in which a silicon-based material is applied to the negative electrode active material layer, there is still a concern that cycle deterioration in which charge / discharge performance deteriorates due to repeated volume changes associated with insertion and extraction of lithium ions is likely to occur. .

実施形態の一態様は、上記に鑑みてなされたものであって、充放電性能の低下を抑制することができる蓄電池用負極材料、蓄電池用負極および蓄電池を提供することを目的とする。   One embodiment of the present invention has been made in view of the above, and an object thereof is to provide a negative electrode material for a storage battery, a negative electrode for a storage battery, and a storage battery that can suppress a decrease in charge / discharge performance.

実施形態の一態様に係る蓄電池用負極材料は、シリコン粒子を含む。シリコン粒子は、鉄、ニッケルおよびナトリウムからなる元素群から選択される１種以上の微量元素を含有する。前記元素群の含有量は合計で６２ｍｇ／ｋｇ以下である。   The negative electrode material for a storage battery according to one aspect of the embodiment includes silicon particles. The silicon particles contain one or more trace elements selected from the element group consisting of iron, nickel, and sodium. The total content of the element group is 62 mg / kg or less.

実施形態の一態様の蓄電池用負極材料、蓄電池用負極および蓄電池によれば、充放電性能の低下を抑制することができる。   According to the negative electrode material for a storage battery, the negative electrode for a storage battery, and the storage battery of one aspect of the embodiment, it is possible to suppress a decrease in charge / discharge performance.

図１は、実施形態に係る蓄電池の概略を示す図である。Drawing 1 is a figure showing the outline of the storage battery concerning an embodiment.

以下、本願の開示する蓄電池用負極材料、蓄電池用負極および蓄電池の実施形態を詳細に説明する。なお、以下に示す実施形態によりこの発明が限定されるものではない。   Hereinafter, embodiments of a negative electrode material for a storage battery, a negative electrode for a storage battery, and a storage battery disclosed in the present application will be described in detail. In addition, this invention is not limited by embodiment shown below.

まず、実施形態に係る蓄電池の構成について、図１を用いて説明する。図１は、実施形態に係る蓄電池の概略を示す断面図である。以下では、蓄電池の一例としてリチウムイオン二次電池を例に挙げて説明する。   First, the structure of the storage battery according to the embodiment will be described with reference to FIG. Drawing 1 is a sectional view showing the outline of the storage battery concerning an embodiment. Hereinafter, a lithium ion secondary battery will be described as an example of a storage battery.

図１に示すリチウムイオン二次電池（以下、「リチウム二次電池」とも称する）１は、リチウムイオン二次電池用正極（以下、「正極」とも称する）４と、リチウムイオン二次電池用負極（以下、「負極」とも称する）９と、セパレータ１１と、絶縁材１２と、電解質１３とを備える。   A lithium ion secondary battery (hereinafter also referred to as “lithium secondary battery”) 1 shown in FIG. 1 includes a positive electrode for lithium ion secondary battery (hereinafter also referred to as “positive electrode”) 4 and a negative electrode for lithium ion secondary battery. (Hereinafter also referred to as “negative electrode”) 9, a separator 11, an insulating material 12, and an electrolyte 13.

正極４は、正極集電体２と正極活物質層３とを備える。正極集電体２は、正極端子を兼ねた正極缶５と電気的に接続されている。正極集電体２としては、例えば、アルミニウムを用いることができる。   The positive electrode 4 includes a positive electrode current collector 2 and a positive electrode active material layer 3. The positive electrode current collector 2 is electrically connected to a positive electrode can 5 that also serves as a positive electrode terminal. As the positive electrode current collector 2, for example, aluminum can be used.

また、正極活物質層３としては、例えば、リチウムコバルト複合酸化物、リチウムマンガン複合酸化物、リチウムニッケル複合酸化物、リチウムニッケルコバルト複合酸化物、リチウムバナジウム複合酸化物などを用いることができる。また、正極活物質層３は、必要に応じて導電助剤その他の添加剤を含んでもよい。   Moreover, as the positive electrode active material layer 3, for example, lithium cobalt composite oxide, lithium manganese composite oxide, lithium nickel composite oxide, lithium nickel cobalt composite oxide, lithium vanadium composite oxide, or the like can be used. Moreover, the positive electrode active material layer 3 may contain a conductive support agent and other additives as needed.

負極９は、負極集電体（以下、「集電体」とも称する）６と、集電体６上に配置された負極活物質層（以下、「活物質層」とも称する）７とを備える。負極９は、正極４よりも電位の低い電極である。   The negative electrode 9 includes a negative electrode current collector (hereinafter also referred to as “current collector”) 6 and a negative electrode active material layer (hereinafter also referred to as “active material layer”) 7 disposed on the current collector 6. . The negative electrode 9 is an electrode having a lower potential than the positive electrode 4.

集電体６は、負極端子を兼ねた負極缶１０と電気的に接続されている。集電体６としては、例えば、銅、ニッケル、チタン、ステンレス鋼などを用いることができる。   The current collector 6 is electrically connected to a negative electrode can 10 that also serves as a negative electrode terminal. As the current collector 6, for example, copper, nickel, titanium, stainless steel, or the like can be used.

活物質層７は、負極活物質を含むシリコン粒子８を含む。シリコン粒子８は、鉄、ニッケルおよびナトリウムからなる元素群から選択される１種以上の微量元素を含有する。シリコン粒子８中におけるこれらの元素群の含有量は、合計で６２ｍｇ／ｋｇ以下である。このように活物質層７が特定の微量元素を含有するシリコン粒子８を含むことで充放電性能の低下を抑制することができる理由としては、次のようなことが推定されている。   The active material layer 7 includes silicon particles 8 including a negative electrode active material. The silicon particles 8 contain one or more trace elements selected from the element group consisting of iron, nickel, and sodium. The total content of these element groups in the silicon particles 8 is 62 mg / kg or less. As described above, it is estimated that the reason why the active material layer 7 can suppress the deterioration of the charge / discharge performance by including the silicon particles 8 containing a specific trace element is as follows.

すなわち、導電性が低く、それ自体では電極材料として使用できない高純度シリコンに、上記した微量元素を含有させることで、シリコン粒子８自体に導電性が付与され、負極材料としての使用が可能となる。また、導電性の向上により、シリコン粒子８を含む活物質層７における局所的なリチウムの吸蔵・放出が抑制され、シリコン粒子８全体での均一的なリチウムの吸蔵・放出が可能となる。このため、リチウムイオンの吸蔵と放出の繰り返しによる活物質層７の構造の変化に伴うサイクル劣化を抑制することができる。なお、微量元素として上記した元素群のうち、ニッケルは、リチウムとの反応性・親和性が高く、活物質へのリチウムの吸着を促進するため、特に好ましい。   That is, by adding the above-mentioned trace elements to high-purity silicon that has low conductivity and cannot be used as an electrode material by itself, conductivity is imparted to the silicon particle 8 itself, and it can be used as a negative electrode material. . Further, due to the improvement in conductivity, local lithium occlusion / release in the active material layer 7 including the silicon particles 8 is suppressed, and uniform lithium occlusion / release in the entire silicon particles 8 becomes possible. For this reason, cycle deterioration accompanying the change in the structure of the active material layer 7 due to repeated insertion and extraction of lithium ions can be suppressed. Note that among the element groups described above as a trace element, nickel is particularly preferable because nickel has high reactivity and affinity with lithium and promotes adsorption of lithium to the active material.

ここで、シリコン粒子８は、微量元素として鉄を含有する場合、５０ｐｐｍ以上、すなわち５０ｍｇ／ｋｇ以下であることが好ましく、より好ましくは１ｍｇ／ｋｇ以上３０ｍｇ／ｋｇである。鉄の含有量が５０ｍｇ／ｋｇを超えると、鉄が電解質１３中に不純物として溶解し、電解質１３の劣化が促進される懸念がある。   Here, when the silicon particle 8 contains iron as a trace element, it is preferably 50 ppm or more, that is, 50 mg / kg or less, more preferably 1 mg / kg or more and 30 mg / kg. When the iron content exceeds 50 mg / kg, iron is dissolved as an impurity in the electrolyte 13 and there is a concern that deterioration of the electrolyte 13 is promoted.

また、シリコン粒子８は、微量元素としてニッケルを含有する場合、２ｍｇ／ｋｇ以下であることが好ましく、より好ましくは０．５ｍｇ／ｋｇ以上１ｍｇ／ｋｇである。ニッケルの含有量が２ｍｇ／ｋｇを超えると、ニッケルが電解質１３中に不純物として溶解し、電解質１３の劣化が促進される懸念がある。   Moreover, when the silicon particle 8 contains nickel as a trace element, it is preferable that it is 2 mg / kg or less, More preferably, it is 0.5 mg / kg or more and 1 mg / kg. If the nickel content exceeds 2 mg / kg, nickel is dissolved as an impurity in the electrolyte 13, and there is a concern that deterioration of the electrolyte 13 is promoted.

また、シリコン粒子８は、微量元素としてナトリウムを含有する場合、１０ｍｇ／ｋｇ以下であることが好ましく、より好ましくは１ｍｇ／ｋｇ以上５ｍｇ／ｋｇである。ナトリウムの含有量が１０ｍｇ／ｋｇを超えると、ナトリウムが電解質１３中に不純物として溶解し、電解質１３の劣化が促進される懸念がある。   Moreover, when the silicon particle 8 contains sodium as a trace element, it is preferable that it is 10 mg / kg or less, More preferably, it is 1 mg / kg or more and 5 mg / kg. When the content of sodium exceeds 10 mg / kg, sodium is dissolved as an impurity in the electrolyte 13 and there is a concern that deterioration of the electrolyte 13 is promoted.

また、シリコン粒子８は、好ましくは９５質量％以上、より好ましくは９９質量％以上９９．９質量％以下のケイ素を含有する。ケイ素の含有量が９５質量％未満だと、リチウム二次電池１の電池容量が十分に得られないことがある。   Further, the silicon particles 8 preferably contain 95% by mass or more, more preferably 99% by mass or more and 99.9% by mass or less of silicon. If the silicon content is less than 95% by mass, the battery capacity of the lithium secondary battery 1 may not be sufficiently obtained.

また、シリコン粒子８のうち好ましくは９５体積％以上、より好ましくは９７体積％以上９９．９体積％以下が０．１μｍ以上５μｍ以下の直径を有する。このように９５体積％以上のシリコン粒子８が０．１μｍ以上５μｍ以下の直径を有することにより、充放電に応じたリチウムイオンの吸蔵と放出を適切に行うことができる。   Further, among the silicon particles 8, preferably 95 volume% or more, more preferably 97 volume% or more and 99.9 volume% or less has a diameter of 0.1 μm or more and 5 μm or less. Thus, when 95 volume% or more of silicon particles 8 have a diameter of 0.1 μm or more and 5 μm or less, insertion and extraction of lithium ions according to charge / discharge can be performed appropriately.

また、シリコン粒子８の平均粒子径は、例えば、１μｍ以上３μｍ以下とすることができる。また、活物質層７の厚みｔ１は、例えば１００μｍ以下、より好ましくは１μｍ以上３０μｍ以下とすることができる。ただし、シリコン粒子８の平均粒子径や活物質層７の厚みｔ１は、これに限らず、例えば所望するリチウム二次電池１の性能や形状等に応じて適宜変更することができる。   Moreover, the average particle diameter of the silicon particles 8 can be set to 1 μm or more and 3 μm or less, for example. Moreover, the thickness t1 of the active material layer 7 can be, for example, 100 μm or less, more preferably 1 μm or more and 30 μm or less. However, the average particle diameter of the silicon particles 8 and the thickness t1 of the active material layer 7 are not limited thereto, and can be appropriately changed according to, for example, the desired performance and shape of the lithium secondary battery 1.

また、シリコン粒子８は、上記した微量元素のほか、さらにリンを含有してもよい。シリコン粒子８がリンを含有すると、シリコン中におけるリンの拡散濃度が高いため、本来は絶縁物であるシリコンの導電性をより高めることができる。かかる場合、リンの含有量は０．８ｍｇ／ｋｇ以下であることが好ましく、より好ましくは０．２ｍｇ／ｋｇ以上０．６ｍｇ／ｋｇである。ただし、リンの含有量が０．８ｍｇ／ｋｇを超えると、リンが電解質１３中に不純物として溶解し、電解質１３の劣化が促進される懸念がある。   Further, the silicon particles 8 may further contain phosphorus in addition to the trace elements described above. When the silicon particles 8 contain phosphorus, since the diffusion concentration of phosphorus in silicon is high, the conductivity of silicon, which is originally an insulator, can be further increased. In such a case, the phosphorus content is preferably 0.8 mg / kg or less, more preferably 0.2 mg / kg or more and 0.6 mg / kg. However, when the phosphorus content exceeds 0.8 mg / kg, phosphorus is dissolved as an impurity in the electrolyte 13, and there is a concern that deterioration of the electrolyte 13 is promoted.

また、シリコン粒子８は、上記した微量元素のほか、さらにホウ素を含有してもよい。シリコン粒子８がホウ素を含有すると、シリコン中におけるホウ素の拡散濃度が高いため、本来は絶縁物であるシリコンの導電性をより高めることができる。かかる場合、ホウ素の含有量は０．２ｍｇ／ｋｇ以下であることが好ましく、より好ましくは０．０５ｍｇ／ｋｇ以上０．１ｍｇ／ｋｇである。ホウ素の含有量が０．２ｍｇ／ｋｇを超えると、ホウ素が電解質１３中に不純物として溶解し、電解質１３の劣化が促進される懸念がある。   Further, the silicon particles 8 may further contain boron in addition to the trace elements described above. When the silicon particles 8 contain boron, since the diffusion concentration of boron in the silicon is high, the conductivity of silicon, which is originally an insulator, can be further increased. In such a case, the boron content is preferably 0.2 mg / kg or less, more preferably 0.05 mg / kg or more and 0.1 mg / kg. When the boron content exceeds 0.2 mg / kg, boron is dissolved as an impurity in the electrolyte 13 and there is a concern that deterioration of the electrolyte 13 is promoted.

また、シリコン粒子８は、上記した微量元素のほか、さらにカルシウムを含有してもよい。シリコン粒子８がカルシウムを含有すると、シリコン粒子８の機械的強度が高まり、電極としての保持力を高めることができる。かかる場合、カルシウムの含有量は１０ｍｇ／ｋｇ以下であることが好ましく、より好ましくは１ｍｇ／ｋｇ以上５ｍｇ／ｋｇである。カルシウムの含有量が１０ｍｇ／ｋｇを超えると、カルシウムが電解質１３中に不純物として溶解し、電解質１３の劣化が促進される懸念がある。   The silicon particles 8 may further contain calcium in addition to the trace elements described above. When the silicon particles 8 contain calcium, the mechanical strength of the silicon particles 8 increases, and the holding power as an electrode can be increased. In such a case, the calcium content is preferably 10 mg / kg or less, more preferably 1 mg / kg or more and 5 mg / kg. When the calcium content exceeds 10 mg / kg, there is a concern that calcium is dissolved as an impurity in the electrolyte 13 and deterioration of the electrolyte 13 is promoted.

また、活物質層７は、バインダや、導電性を付与するための炭素粒子その他の導電助剤をさらに含んでもよい。ここで、活物質層７に含まれるシリコン粒子８の粒子径や含有量は、厚さ方向に切断した活物質層７のＳＥＭ（Scanning Electron Microscope）画像に基づいて計測される。   The active material layer 7 may further include a binder, carbon particles for imparting conductivity, and other conductive aids. Here, the particle diameter and content of the silicon particles 8 included in the active material layer 7 are measured based on an SEM (Scanning Electron Microscope) image of the active material layer 7 cut in the thickness direction.

また、活物質層７に含まれるシリコン粒子８が含有する各種微量元素の含有量は、試料としてシリコン粒子８または活物質層７を用意し、例えば、蛍光Ｘ線分析、波長分散型Ｘ線分光分析（ＷＤＳ）、グロー放電質量分析（ＧＤＭＳ）、ＩＣＰ（Inductively Coupled Plasma）発光分光分析（ＩＣＰ−ＡＥＳ）、ＩＣＰ質量分析（ＩＣＰ−ＭＳ）などを用いた元素分析に基づいて測定される。   The content of various trace elements contained in the silicon particles 8 contained in the active material layer 7 is prepared by preparing the silicon particles 8 or the active material layer 7 as a sample, for example, fluorescent X-ray analysis, wavelength dispersion X-ray spectroscopy. It is measured based on elemental analysis using analysis (WDS), glow discharge mass spectrometry (GDMS), ICP (Inductively Coupled Plasma) emission spectroscopic analysis (ICP-AES), ICP mass spectrometry (ICP-MS) and the like.

セパレータ１１は、正極４と負極９との間に配置され、正極４および負極９を区画する。セパレータ１１としては、例えば、有機樹脂繊維または無機繊維の不織布、セラミックス製の多孔質材料、ポリエチレンやポリプロピレンその他のポリオレフィンなどを用いることができる。   The separator 11 is disposed between the positive electrode 4 and the negative electrode 9 and partitions the positive electrode 4 and the negative electrode 9. As the separator 11, for example, a nonwoven fabric of organic resin fibers or inorganic fibers, a porous material made of ceramics, polyethylene, polypropylene, or other polyolefins can be used.

絶縁材１２は、正極缶５と負極缶１０との間に配置され、正極缶５と負極缶１０との短絡を防止するとともに内部に封入した電解質１３の漏出を防止する。絶縁材１２としては、耐電解液性を有する絶縁性材料、例えば、ポリプロピレンや、フッ素樹脂またはフッ素ゴムなどのフッ素系材料を用いることができる。   The insulating material 12 is disposed between the positive electrode can 5 and the negative electrode can 10 to prevent a short circuit between the positive electrode can 5 and the negative electrode can 10 and to prevent leakage of the electrolyte 13 enclosed therein. As the insulating material 12, an insulating material having an electrolytic solution resistance, for example, a fluorine-based material such as polypropylene, fluorine resin, or fluorine rubber can be used.

電解質１３は、有機溶媒と、リチウムイオン源であるリチウム塩とを含む非水電解質である。有機溶媒は、高誘電率を有し、低粘性、低蒸気圧のものが好ましい。このような有機溶媒としては、例えば、エチレンカーボネート、プロピレンカーボネート、ブチレンカーボネート、γ−ブチロラクトン、スルホラン、１，２−ジメトキシエタン、１，３−ジメトキシプロパン、ジメチルエーテル、テトラヒドロフラン、２−メチルテトラヒドロフラン、メチルエチルカーボネート、ジメチルカーボネート、ジエチルカーボネートなどから選ばれる１種もしくは２種以上を混合したものを用いることができる。また、電解質１３は、有機溶媒としてビニレンカーボネートおよびフルオロエチレンカーボネートのうち一方または両方を含むと、サイクル特性向上の観点から特に好ましい。   The electrolyte 13 is a nonaqueous electrolyte containing an organic solvent and a lithium salt that is a lithium ion source. The organic solvent preferably has a high dielectric constant, low viscosity and low vapor pressure. Examples of such organic solvents include ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, sulfolane, 1,2-dimethoxyethane, 1,3-dimethoxypropane, dimethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, and methylethyl. What mixed 1 type, or 2 or more types chosen from carbonate, dimethyl carbonate, diethyl carbonate, etc. can be used. In addition, it is particularly preferable that the electrolyte 13 includes one or both of vinylene carbonate and fluoroethylene carbonate as an organic solvent from the viewpoint of improving cycle characteristics.

また、リチウム塩としては、例えば、ＬｉＣｌＯ４、ＬｉＢＦ４、ＬｉＰＦ６、ＬｉＣＦ３ＳＯ３、ＬｉＮ(ＣＦ３ＳＯ２)２、ＬｉＮ(Ｃ２Ｆ５ＳＯ２)２などを用いることができる。電解質１３は、必要に応じて、過充電防止、難燃性の付与等を目的とした添加剤を含んでもよい。 Examples of the lithium salt, LiClO 4, LiBF 4, LiPF 6, LiCF 3 SO 3, LiN (CF 3 SO 2) 2, LiN (C 2 F 5 SO 2) 2 or the like can be used. The electrolyte 13 may include an additive for the purpose of preventing overcharge, imparting flame retardancy, and the like, if necessary.

また、電解質１３は、流動性を有する電解液であってもよく、例えばポリマーでゲル化して流動性を低減させたゲル電解質であってもよい。   Further, the electrolyte 13 may be an electrolytic solution having fluidity, for example, a gel electrolyte that is gelled with a polymer to reduce fluidity.

なお、リチウム二次電池１の形状は角型、円筒型、ボタン型、コイン型、扁平型など、用途に応じていかなるものであってもよい。また、正極缶５および負極缶１０に代えて、正極端子および負極端子を備える絶縁性の容器を用いたリチウム二次電池１としてもよい。さらに、リチウム二次電池１の電極構造は、一対の正極４および負極９を有する単層構造に限らず、複数の正極４および負極９を有する積層構造であってもよい。   The shape of the lithium secondary battery 1 may be any shape such as a square shape, a cylindrical shape, a button shape, a coin shape, and a flat shape. Instead of the positive electrode can 5 and the negative electrode can 10, a lithium secondary battery 1 using an insulating container including a positive electrode terminal and a negative electrode terminal may be used. Furthermore, the electrode structure of the lithium secondary battery 1 is not limited to a single layer structure having a pair of positive electrodes 4 and negative electrodes 9, and may be a laminated structure having a plurality of positive electrodes 4 and negative electrodes 9.

以上、本発明の実施形態について説明したが、本発明は上記実施形態に限定されるものではなく、その趣旨を逸脱しない限りにおいて種々の変更が可能である。   The embodiment of the present invention has been described above, but the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

例えば、蓄電池の種類は上記したリチウム二次電池１に限らず、例えば硫黄電池（シリコン−硫黄電池）や次世代リチウム電池（全固体リチウム二次電池、高容量の正極材料を用いたリチウム二次電池など）、ナトリウム二次電池など、電極や電解質の構成が異なる電池であってもよい。すなわち、シリコン粒子８は、リチウム二次電池１の活物質層７に用いられる負極材料に限らず、さまざまな蓄電池用負極材料として利用することができる。   For example, the type of the storage battery is not limited to the lithium secondary battery 1 described above, and for example, a sulfur battery (silicon-sulfur battery) or a next generation lithium battery (all-solid lithium secondary battery, lithium secondary using a high-capacity positive electrode material). Battery), a secondary battery such as a sodium secondary battery, and the like, which have different electrode and electrolyte configurations. That is, the silicon particles 8 are not limited to the negative electrode material used for the active material layer 7 of the lithium secondary battery 1 but can be used as various negative electrodes for storage batteries.

（実施例１）
［負極塗工液の調製］
シリコン粉末（「シリコン粒子８」に対応、平均粒子径５μｍ、純度９９．９質量％）７５質量％、導電助剤（アセチレンブラック）１０質量％、バインダ（ＰＶＤＦ（ポリフッ化ビニリデン））１５質量％を、溶剤（ＮＭＰ（Ｎ−メチルピロリドン））と混合攪拌し、固形分６５％の負極塗工液を調製した。 Example 1
[Preparation of negative electrode coating solution]
Silicon powder (corresponding to “silicon particles 8”, average particle diameter 5 μm, purity 99.9% by mass) 75% by mass, conductive additive (acetylene black) 10% by mass, binder (PVDF (polyvinylidene fluoride)) 15% by mass Was mixed and stirred with a solvent (NMP (N-methylpyrrolidone)) to prepare a negative electrode coating liquid having a solid content of 65%.

［負極シートの作製］
４０ｍｍ×３５ｍｍ×３０μｍの銅箔（「集電体６」に対応）上に負極塗工液を塗工し、３０ｍｍ×３５ｍｍ×１５μｍの活物質層７を調製した。 [Preparation of negative electrode sheet]
A negative electrode coating solution was applied onto a 40 mm × 35 mm × 30 μm copper foil (corresponding to “current collector 6”) to prepare an active material layer 7 of 30 mm × 35 mm × 15 μm.

[充放電試験用セル（ハーフセル）の作製]
上記のように作製した負極９、セパレータ１１および対極を順に積層したハーフセルを２組用意し、これらを直列に接続したものを電解質１３とともにアルミラミネートフィルムに収納し、試験用セルとした。なお、セパレータ１１として、厚さ２０μｍのポリエチレンを、対極として、厚さ３０μｍのリチウム箔をそれぞれ使用した。また、電解質１３として、エチレンカーボネートとジエチルカーボネートを体積比で１：１の割合で混合した溶媒に１Ｍの濃度となるようにＬｉＰＦ６を溶解させた電解液を使用した。 [Production of charge / discharge test cell (half cell)]
Two sets of half cells in which the negative electrode 9, the separator 11, and the counter electrode prepared as described above were sequentially laminated were prepared, and those connected in series were accommodated in an aluminum laminate film together with the electrolyte 13 to obtain a test cell. The separator 11 was made of polyethylene having a thickness of 20 μm, and the counter electrode was made of lithium foil having a thickness of 30 μm. Further, as the electrolyte 13, an electrolytic solution in which LiPF 6 was dissolved so as to have a concentration of 1M in a solvent in which ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 1: 1 was used.

[充放電試験]
充放電装置として、北斗電工製ＨＪ１００１ＳＤ８を使用した。また、充電を８００ｍＡ／ｇの定電流で充電電圧が５ｍＶに到達するまで行い、放電を８００ｍＡ／ｇの定電流で放電電圧が１５００ｍＶに到達するまで行う１サイクルを、１０分間の休止を挟みながら３００サイクルまで繰り返し行った。１サイクル後の充放電容量（初期容量）と、１００サイクル後、３００サイクル後の充放電容量および容量維持率を、シリコン粒子８に対する微量元素、ケイ素および任意成分（リン（Ｐ）、ホウ素（Ｂ）、カルシウム（Ｃａ））の含有量とともに表１にまとめて示す。 [Charge / discharge test]
As a charging / discharging device, HJ1001SD8 manufactured by Hokuto Denko was used. Also, charging is performed at a constant current of 800 mA / g until the charging voltage reaches 5 mV, and discharging is performed at a constant current of 800 mA / g until the discharging voltage reaches 1500 mV, with a pause of 10 minutes. Repeated up to 300 cycles. The charge / discharge capacity (initial capacity) after one cycle, the charge / discharge capacity and capacity retention rate after 100 cycles, and after 300 cycles are shown as follows: trace elements, silicon and optional components (phosphorus (P), boron (B ) And calcium (Ca)) together with the content of Table 1.

（実施例２）
微量元素、ケイ素および任意成分の含有量が異なるシリコン粒子８を適用し、さらに電解質１３用の溶媒として、エチレンカーボネートおよびジエチルカーボネートを体積比で１：１の割合で混合したもの１００質量部と、ビニレンカーボネートおよびフルオロエチレンカーボネートを体積比で１：１の割合で混合したもの６質量部とを混合したものを使用したことを除き、実施例１と同様に負極９および試験用セルを作製し、充放電試験を行った。用いたシリコン粒子８に対する微量元素、ケイ素および任意成分の含有量を、充放電試験の結果とともに表１にまとめて示す。 (Example 2)
Applying silicon particles 8 having different contents of trace elements, silicon and optional components, and further 100 parts by mass of ethylene carbonate and diethyl carbonate mixed at a volume ratio of 1: 1 as a solvent for electrolyte 13; A negative electrode 9 and a test cell were prepared in the same manner as in Example 1 except that 6 parts by mass of vinylene carbonate and fluoroethylene carbonate mixed at a volume ratio of 1: 1 were used. A charge / discharge test was conducted. The contents of trace elements, silicon and optional components with respect to the used silicon particles 8 are shown in Table 1 together with the results of the charge / discharge test.

（実施例３〜４）
微量元素、ケイ素および任意成分の含有量が異なるシリコン粒子８を適用したことを除き、実施例１と同様に負極９および試験用セルを作製し、充放電試験を行った。用いたシリコン粒子８に対する微量元素、ケイ素および任意成分の含有量を、充放電試験の結果とともに表１にまとめて示す。なお、シリコン粒子８中の微量元素、ケイ素および任意成分の含有量は、ＧＤＭＳを用いて、試料を陰極としてアルゴン雰囲気下でグロー放電を発生させ、プラズマ内で試料表面をスパッタし、イオン化された構成元素を質量分析計で測定した。具体的には、ケイ素および微量元素を含む目的元素のイオン強度比を相対感度係数で補正して得られた半定量値を各元素の含有量とした。 (Examples 3 to 4)
A negative electrode 9 and a test cell were produced in the same manner as in Example 1 except that silicon particles 8 having different contents of trace elements, silicon, and optional components were applied, and a charge / discharge test was performed. The contents of trace elements, silicon and optional components with respect to the used silicon particles 8 are shown in Table 1 together with the results of the charge / discharge test. The contents of the trace elements, silicon, and optional components in the silicon particles 8 were ionized by using GDMS, generating a glow discharge in an argon atmosphere using the sample as a cathode, and sputtering the sample surface in plasma. The constituent elements were measured with a mass spectrometer. Specifically, the semi-quantitative value obtained by correcting the ionic strength ratio of the target element including silicon and trace elements with the relative sensitivity coefficient was defined as the content of each element.

Figure 2018125086
Figure 2018125086

さらなる効果や変形例は、当業者によって容易に導き出すことができる。このため、本発明のより広範な態様は、以上のように表しかつ記述した特定の詳細および代表的な実施形態に限定されるものではない。したがって、添付の特許請求の範囲およびその均等物によって定義される総括的な発明の概念の精神または範囲から逸脱することなく、様々な変更が可能である。   Further effects and modifications can be easily derived by those skilled in the art. Thus, the broader aspects of the present invention are not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications can be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.

１ リチウムイオン二次電池（リチウム二次電池）
２ 正極集電体
３ 正極活物質層
４ リチウムイオン二次電池用正極（正極）
５ 正極缶
６ 負極集電体（集電体）
７ 負極活物質層（活物質層）
８ シリコン粒子
９ リチウムイオン二次電池用負極（負極）
１０ 負極缶
１１ セパレータ
１２ 絶縁材
１３ 電解質 1 Lithium ion secondary battery (lithium secondary battery)
2 Positive electrode current collector 3 Positive electrode active material layer 4 Positive electrode for lithium ion secondary battery (positive electrode)
5 Positive electrode can 6 Negative electrode current collector (current collector)
7 Negative electrode active material layer (active material layer)
8 Silicon particles 9 Negative electrode (negative electrode) for lithium ion secondary battery
10 Negative electrode can 11 Separator 12 Insulating material 13 Electrolyte

Claims (13)

鉄、ニッケルおよびナトリウムからなる元素群から選択される１種以上の微量元素を含有し、前記元素群の含有量が合計で６２ｍｇ／ｋｇ以下であるシリコン粒子を含むこと
を特徴とする蓄電池用負極材料。 A negative electrode for a storage battery comprising one or more trace elements selected from an element group consisting of iron, nickel and sodium, and containing silicon particles having a total content of 62 mg / kg or less. material. 前記シリコン粒子は、５０ｍｇ／ｋｇ以下の鉄を含有することを特徴とする請求項１に記載の蓄電池用負極材料。   The negative electrode material for a storage battery according to claim 1, wherein the silicon particles contain 50 mg / kg or less of iron. 前記シリコン粒子は、２ｍｇ／ｋｇ以下のニッケルを含有することを特徴とする請求項１または２に記載の蓄電池用負極材料。   The negative electrode material for a storage battery according to claim 1 or 2, wherein the silicon particles contain 2 mg / kg or less of nickel. 前記シリコン粒子は、１０ｍｇ／ｋｇ以下のナトリウムを含有することを特徴とする請求項１〜３のいずれか１つに記載の蓄電池用負極材料。   The negative electrode material for a storage battery according to any one of claims 1 to 3, wherein the silicon particles contain 10 mg / kg or less of sodium. 前記シリコン粒子は、９５質量％以上のケイ素を含有することを特徴とする請求項１〜４のいずれか１つに記載の蓄電池用負極材料。   The negative electrode material for a storage battery according to any one of claims 1 to 4, wherein the silicon particles contain 95% by mass or more of silicon. 前記シリコン粒子は、０．８ｍｇ／ｋｇ以下のリンをさらに含有することを特徴とする請求項１〜５のいずれか１つに記載の蓄電池用負極材料。   The negative electrode material for a storage battery according to any one of claims 1 to 5, wherein the silicon particles further contain 0.8 mg / kg or less of phosphorus. 前記シリコン粒子は、０．２ｍｇ／ｋｇ以下のホウ素をさらに含有することを特徴とする請求項１〜６のいずれか１つに記載の蓄電池用負極材料。   The negative electrode material for a storage battery according to any one of claims 1 to 6, wherein the silicon particles further contain 0.2 mg / kg or less of boron. 前記シリコン粒子は、１０ｍｇ／ｋｇ以下のカルシウムをさらに含有することを特徴とする請求項１〜７のいずれか１つに記載の蓄電池用負極材料。   The negative electrode material for a storage battery according to any one of claims 1 to 7, wherein the silicon particles further contain 10 mg / kg or less of calcium. 前記シリコン粒子のうち９５体積％以上が０．１μｍ以上５μｍ以下の直径を有することを特徴とする請求項１〜８のいずれか１つに記載の蓄電池用負極材料。   The negative electrode material for a storage battery according to any one of claims 1 to 8, wherein 95% by volume or more of the silicon particles have a diameter of 0.1 µm or more and 5 µm or less. 集電体と、前記集電体上に配置された活物質層とを備え、
前記活物質層は、請求項１〜９のいずれか１つに記載の蓄電池用負極材料を含むことを特徴とする蓄電池用負極。 A current collector, and an active material layer disposed on the current collector,
The said active material layer contains the negative electrode material for storage batteries as described in any one of Claims 1-9, The negative electrode for storage batteries characterized by the above-mentioned. 電解質を挟んで互いに向かい合う正極および負極を備え、
前記負極は、請求項１０に記載の蓄電池用負極であることを特徴とする蓄電池。 Provided with a positive electrode and a negative electrode facing each other across the electrolyte,
The said negative electrode is a negative electrode for storage batteries of Claim 10, The storage battery characterized by the above-mentioned. 前記電解質は、リチウムイオンを含有することを特徴とする請求項１１に記載の蓄電池。   The storage battery according to claim 11, wherein the electrolyte contains lithium ions. 前記電解質は、ビニレンカーボネートおよびフルオロエチレンカーボネートのうち一方または両方を含むことを特徴とする請求項１２に記載の蓄電池。   The storage battery according to claim 12, wherein the electrolyte contains one or both of vinylene carbonate and fluoroethylene carbonate.
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