JP6045879B2 - Sn alloy powder used as a raw material of the negative electrode active material of a lithium ion secondary battery, and its manufacturing method. - Google Patents
Sn alloy powder used as a raw material of the negative electrode active material of a lithium ion secondary battery, and its manufacturing method. Download PDFInfo
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Description
本発明は、放電容量、サイクル寿命に優れるリチウムイオン二次電池負極活物質の原料に用いるＳｎ合金粉末およびその製造方法に関する。 The present invention relates to a Sn alloy powder used as a raw material for a negative electrode active material of a lithium ion secondary battery having excellent discharge capacity and cycle life, and a method for producing the same.
近年、カメラ一体型ＶＴＲ（ビデオテープレコーダー）、携帯電話、ノートパソコンなどのポータブル電子機器が多く登場し、その小型化および軽量化が図られている。それに伴い、それらの電子機器のポータブル電源として用いられている電池、特に二次電池についてエネルギー密度の向上が強く要請されている。このような要求に応える二次電池としては、従来より、リチウムイオンの二次電池が実用化されている。 In recent years, many portable electronic devices such as a camera-integrated VTR (video tape recorder), a mobile phone, and a laptop computer have appeared, and their size and weight have been reduced. Accordingly, there is a strong demand for an improvement in energy density of batteries used as portable power sources for such electronic devices, particularly secondary batteries. Conventionally, lithium ion secondary batteries have been put to practical use as secondary batteries that meet such requirements.
しかしながら、近年の携帯用機器の高性能化に伴い、二次電池の容量に対する要求はさらに強いものとなっている。このような要求に応える二次電池として、リチウム金属などの軽金属をそのまま負極活物質として用いることが提案されている。この電池では、充電過程において負極に軽金属がデンドライト状に析出しやすくなり、デンドライトの先端で電流密度が非常に高くなる。このため、非水電解液の分離などによりサイクル寿命が低下したり、また、過度にデンドライトが成長して電池の内部短絡が発生したりするという問題があった。 However, with the recent improvement in performance of portable devices, the demand for the capacity of the secondary battery has become stronger. As a secondary battery that meets such requirements, it has been proposed to use a light metal such as lithium metal as a negative electrode active material as it is. In this battery, light metal tends to precipitate in a dendrite state on the negative electrode during the charging process, and the current density becomes very high at the end of the dendrite. For this reason, there has been a problem that the cycle life is reduced due to separation of the non-aqueous electrolyte, or the dendrite grows excessively and an internal short circuit of the battery occurs.
これに対し、種々の合金材料などを負極活物質として用いることが提案されている。例えば、珪素合金、Ｓｎ−Ｎｉ合金、Ｌｉ−Ａｌ−Ｓｎ合金、Ｓｎ−Ｚｎ合金、Ｐ−Ｓｎ合金、Ｓｎ−Ｃｕ合金等が提案されている。しかし、これらの合金材料を用いた場合においても、十分なサイクル特性は得られず、合金材料における高容量負極の特徴を十分に活かしきれていないのが実状である。 On the other hand, using various alloy materials etc. as a negative electrode active material is proposed. For example, silicon alloys, Sn—Ni alloys, Li—Al—Sn alloys, Sn—Zn alloys, P—Sn alloys, Sn—Cu alloys and the like have been proposed. However, even when these alloy materials are used, sufficient cycle characteristics cannot be obtained, and the fact is that the characteristics of the high-capacity negative electrode in the alloy materials are not fully utilized.
このような課題に対し、例えば、特開２００６−２４５１７号公報（特許文献１）には、Ｃｏ−Ｓｎ系合金に種々の元素を添加した合金が提案されている。また、特開２００６−２３６８３５号公報（特許文献２）には、Ｆｅ，Ｎｉ，Ｃｏのうち少なくとも１つの元素とＳｎを含む合金が提案されている。さらに、特開２００８−６６０２５号公報（特許文献３）にも同類の合金が提案されている。 In response to such a problem, for example, Japanese Patent Application Laid-Open No. 2006-24517 (Patent Document 1) proposes an alloy in which various elements are added to a Co—Sn alloy. Japanese Patent Laid-Open No. 2006-236835 (Patent Document 2) proposes an alloy containing Sn, at least one of Fe, Ni, and Co. Furthermore, a similar alloy is also proposed in Japanese Patent Application Laid-Open No. 2008-66025 (Patent Document 3).
これらの合金はリチウムイオン電池負極用材料として優れた特性を示すが、合金溶湯を凝固させて作製した場合、様々な構成相が生成することがこれら従来例に記載されており、この構成相を制御することにより高い充放電特性が得られる。特許文献２では熱処理によりＣｏ3Ｓｎ2などの化合物を消失させる方法が提案され、また、特許文献３では２種類の合金粉末の混合粉末とすることで構成相の制御を行なっている。 These alloys exhibit excellent properties as lithium ion battery negative electrode materials, but it is described in these conventional examples that various constituent phases are formed when the molten alloy is solidified. High charge / discharge characteristics can be obtained by controlling. Patent Document 2 proposes a method for eliminating a compound such as Co 3 Sn 2 by heat treatment, and Patent Document 3 controls the constituent phases by using a mixed powder of two types of alloy powders.
特に、特許文献３に示されている通り、Ｓｎ相が有害な相として知られている。さらに発明者が提案した特開２０１２−１３４１０５号公報（特許文献４）は低温で熱処理することにより、本合金系の凝固体に生成する２種類の非平衡相のうち、Ｓｎ相を消失させる一方でＣｏ3Ｓｎ2相は残存させ微細組織を実現したものである。なお、熱処理条件は特許文献１の実施例では４５０℃、２４ｈ、特許文献２の実施例では５００℃、１２ｈと高温、長時間であり、これらの条件は主に非平衡相であるＳｎとＣｏ3Ｓｎ2を消失させて平衡相の均質化された組織とすることが目的である。 In particular, as shown in Patent Document 3, the Sn phase is known as a harmful phase. Furthermore, Japanese Patent Laid-Open No. 2012-134105 proposed by the inventor (Patent Document 4) is one in which the Sn phase disappears among the two types of nonequilibrium phases generated in the solidified body of this alloy system by heat treatment at a low temperature. Thus, the Co 3 Sn 2 phase is left to realize a fine structure. The heat treatment conditions are 450 ° C. and 24 h in the example of Patent Document 1 and high temperature and long time of 500 ° C. and 12 h in the example of Patent Document 2, and these conditions are mainly Sn and Co which are non-equilibrium phases. The purpose is to eliminate 3 Sn 2 to obtain a homogenized structure of the equilibrium phase.
一方、特許文献４は熱処理温度を１００℃を超え２２０℃未満とすることで、Ｓｎ相を消失させるとともにＣｏ3Ｓｎ2相を残存させ、さらにＣｏＳｎ相に対するＣｏＳｎ2相の生成量を制御し、放電容量とサイクル寿命の両立を図っている。
しかしながら、近年、さらに放電容量アップの要求が高く、特許文献４の材料を用いても十分な放電容量が十分でない場合が出てきた。そこで本発明は、特許文献４からさらに改良を加え、わずかなサイクル寿命の劣化に留めた上で、放電容量を増加させる技術である。
However, in recent years, there has been a demand for further increase in discharge capacity, and there have been cases where sufficient discharge capacity is not sufficient even when the material of Patent Document 4 is used. Therefore, the present invention is a technique for further increasing the discharge capacity after adding further improvements from Patent Document 4 and maintaining only a slight deterioration in cycle life.
上述したような問題を解消するために、発明者らは鋭意開発を進めた結果、放電容量が高く、サイクル寿命に優れるリチウムイオン二次電池負極活物質の原料として用いるＳｎ合金粉末およびその製造方法を提供するものである。すなわち、本発明では、合金成分としてＴｉ，Ｚｒ量を特許文献４の低濃度領域に限定するとともに、Ｃｏ，Ｆｅ量をＴｉ，Ｚｒ量と対応させた狭い濃度域に限定しており、さらに熱処理温度として特許文献４よりも高温とすることでＣｏＳｎ相に対するＣｏＳｎ2相の生成量を特許文献４より大幅に増加させることにより、更なる放電容量の増加を実現したものである。 In order to solve the problems as described above, the inventors have made extensive developments, and as a result, Sn alloy powder used as a raw material for a negative electrode active material of a lithium ion secondary battery having high discharge capacity and excellent cycle life, and a method for producing the same Is to provide. That is, in the present invention, the Ti and Zr amounts as alloy components are limited to the low concentration region of Patent Document 4, and the Co and Fe amounts are limited to a narrow concentration region corresponding to the Ti and Zr amounts. By increasing the temperature of the CoSn 2 phase with respect to the CoSn phase to a temperature higher than that of Patent Document 4, the discharge capacity can be further increased.
その発明の要旨とするところは、
（１）原子％（ただし、ピーク強度比の％を除く）で、
Ｔｉ，Ｚｒの１種または２種を２．０％を超え５．０％未満含み、Ｃｏ，Ｆｅの１種または２種を下記式（１）を満たす範囲で含み、残部Ｓｎおよび不可避的不純物からなり、Ｘ線回折によるＡＳｎ［１１０］ピークに対するＡＳｎ2［２１１］ピークの強度比が５００％以上３０００％以下、ＡＳｎ［１１０］ピークに対するＳｎ［１０１］ピークの強度比が１０％以下（０％を含む）、ＡＳｎ［１１０］ピークに対するＡ3Ｓｎ2［１０２］ピークの強度比が１０％以上１００％以下であることを特徴とするリチウムイオン電池負極活物質の原料として用いるＳｎ合金粉末。
ただし、Ａは、Ｃｏ，Ｆｅの１種または２種である。
０．３５≦［（Ｃｏ＋Ｆｅ）−２（Ｔｉ＋Ｚｒ）］／［１００−４（Ｔｉ＋Ｚｒ）］≦０．４５ ・・・（１）
The gist of the invention is that
(1) Atomic% (excluding% of peak intensity ratio)
1 type or 2 types of Ti and Zr are included more than 2.0% and less than 5.0%, 1 type or 2 types of Co and Fe are included within the range satisfying the following formula (1), the remaining Sn and inevitable impurities The intensity ratio of the ASn 2 [211] peak to the ASn [110] peak by X-ray diffraction is 500% or more and 3000% or less, and the intensity ratio of the Sn [101] peak to the ASn [110] peak is 10% or less (0 % including), ASn [110] Sn alloy powder used as a raw material of the lithium ion battery negative electrode active material, characterized in that a 3 Sn 2 [102] peak intensity ratio of the relative peak is less than 100% to 10%.
However, A is 1 type or 2 types of Co and Fe.
0.35≤ [(Co + Fe) -2 (Ti + Zr)] / [100-4 (Ti + Zr)] ≤0.45 (1)
（２）前記（１）に記載の組成の合金溶湯を凝固させた後、２５０〜４００℃の温度で熱処理することを特徴とするリチウムイオン電池負極活物質の原料として用いるＳｎ合金粉末の製造方法にある。 (2) A method for producing an Sn alloy powder used as a raw material for a negative electrode active material for a lithium ion battery, comprising solidifying the molten alloy having the composition described in (1) and then heat-treating the molten alloy at a temperature of 250 to 400 ° C. It is in.
以上述べたように、本発明により放電容量が高く、サイクル寿命に優れるリチウムイオン二次電池負極活物質の原料として用いるＳｎ合金粉末およびその製造方法を提供できるものである。 As described above, the present invention can provide an Sn alloy powder used as a raw material for a negative electrode active material of a lithium ion secondary battery having a high discharge capacity and excellent cycle life, and a method for producing the same.
以下、本発明についての限定理由について述べる。
Ｔｉ，Ｚｒの１種または２種を２．０％を超え５．０％未満
本発明合金において、Ｔｉ，Ｚｒは主にＡ2ＢＳｎ（ＢはＴｉおよび／またはＺｒ）を生成する元素であり、これらの元素が２．０％以下ではサイクル寿命が劣化し、５．０％以上では放電容量が劣化する。好ましくは、２．５％以上５％未満、より好ましくは３．０％以上４．８％以下である。
Hereinafter, the reasons for limitation of the present invention will be described.
One or two of Ti and Zr are more than 2.0% and less than 5.0%. In the alloy of the present invention, Ti and Zr are elements that mainly generate A 2 BSn (B is Ti and / or Zr). When these elements are 2.0% or less, the cycle life is deteriorated, and when they are 5.0% or more, the discharge capacity is deteriorated. Preferably, it is 2.5% or more and less than 5%, more preferably 3.0% or more and 4.8% or less.
Ｃｏ，Ｆｅの１種または２種を式（１）を満たす範囲で含む
本発明合金において、Ｃｏ，Ｆｅは、Ａ2ＢＳｎ、ＡＳｎ、ＡＳｎ2、Ａ3Ｓｎ2を形成する元素である。ここで、Ｔｉおよび／またはＺｒは添加した全量がＡ2ＢＳｎを生成し、その余剰分のＣｏ，Ｆｅ，ＳｎがＡＳｎ、ＡＳｎ2、Ａ3Ｓｎ2を生成する。したがって、ＡＳｎ、ＡＳｎ2、Ａ3Ｓｎ2の生成量の比率には、Ｃｏ，Ｆｅ，Ｓｎの余剰分における（Ｃｏ＋Ｆｅ）／（Ｃｏ＋Ｆｅ＋Ｓｎ）の比率が大きく影響し、これが放電容量とサイクル寿命に大きな影響を与える。
In the alloy of the present invention containing one or two of Co and Fe in a range satisfying the formula (1), Co and Fe are elements that form A 2 BSn, ASn, ASn 2 , and A 3 Sn 2 . Here, the total amount of Ti and / or Zr produces A 2 BSn, and the excess Co, Fe, and Sn produce ASn, ASn 2 , and A 3 Sn 2 . Therefore, the ratio of (Co + Fe) / (Co + Fe + Sn) in the excess of Co, Fe, and Sn greatly affects the ratio of the generation amount of ASn, ASn 2 , and A 3 Sn 2 , and this greatly affects the discharge capacity and cycle life. Influence.
また、余剰分のＣｏ，Ｆｅの合計は［Ｃｏ＋Ｆｅ−２（Ｔｉ＋Ｚｒ）］、余剰分のＳｎは［Ｓｎ−（Ｔｉ＋Ｚｒ）］＝［（１００−Ｃｏ−Ｆｅ−Ｔｉ−Ｚｒ）−（Ｔｉ＋Ｚｒ）］＝［１００−Ｃｏ−Ｆｅ−２（Ｔｉ＋Ｚｒ）］で与えられる。すなわち、Ａ2ＢＳｎの量論比から、この化合物を形成するＡ元素（Ｃｏおよび／またはＦｅ）の合計量はＢ元素（Ｔｉおよび／またはＺｒ）の合計量の２倍であり、この化合物を形成するＳｎ元素はＢ元素の合計量と同じになるため、合金全体の添加量から、これらを差し引いた量がそれぞれの余剰分となる。 Further, the sum of excess Co and Fe is [Co + Fe-2 (Ti + Zr)], and the excess Sn is [Sn- (Ti + Zr)] = [(100-Co-Fe-Ti-Zr)-(Ti + Zr)]. = [100-Co-Fe-2 (Ti + Zr)]. That is, from the stoichiometric ratio of A 2 BSn, the total amount of element A (Co and / or Fe) forming this compound is twice the total amount of element B (Ti and / or Zr). Since the Sn element to be formed is the same as the total amount of the B element, the amount obtained by subtracting these from the added amount of the entire alloy is the surplus amount.
したがって、上述の余剰分における（Ｃｏ＋Ｆｅ）／（Ｃｏ＋Ｆｅ＋Ｓｎ）の比率は、［（Ｃｏ＋Ｆｅ）−２（Ｔｉ＋Ｚｒ）］／［１００−４（Ｔｉ＋Ｚｒ）］となり、これが式（１）の中辺である。ここで、余剰分における（Ｃｏ＋Ｆｅ）／（Ｃｏ＋Ｆｅ＋Ｓｎ）の比率が０．３５以上０．４５以下の範囲で放電容量とサイクル寿命を両立することができる。この比率が０．３５未満ではサイクル寿命が劣化し、０．４５を超えると放電容量が劣化する。 Therefore, the ratio of (Co + Fe) / (Co + Fe + Sn) in the above-described surplus is [(Co + Fe) −2 (Ti + Zr)] / [100−4 (Ti + Zr)], which is the middle side of the formula (1). Here, when the ratio of (Co + Fe) / (Co + Fe + Sn) in the surplus is in the range of 0.35 to 0.45, both the discharge capacity and the cycle life can be achieved. When this ratio is less than 0.35, the cycle life is deteriorated, and when it exceeds 0.45, the discharge capacity is deteriorated.
ＡＳｎ［１１０］ピークに対するＡＳｎ2［２１１］ピークの強度比が５００％以上３０００％以下
本発明合金において、ＡＳｎ相とＡＳｎ2相はいずれもＬｉを吸蔵し充放電に寄与する相であるが、ＡＳｎ相は放電容量は比較的低く、サイクル寿命は比較的優れると考えられ、一方、ＡＳｎ2相は放電容量は比較的高く、サイクル寿命は比較的劣ると考えられる。この２相のバランスを一定範囲とすることにより放電容量とサイクル寿命が両立できる。
The intensity ratio of the ASn 2 [211] peak to the ASn [110] peak is 500% or more and 3000% or less. In the present invention alloy, both the ASn phase and the ASn 2 phase occlude Li and contribute to charge and discharge. The ASn phase is considered to have a relatively low discharge capacity and a relatively good cycle life, while the ASn 2 phase is considered to have a relatively high discharge capacity and a relatively poor cycle life. By keeping the balance of the two phases within a certain range, both the discharge capacity and the cycle life can be achieved.
ＡＳｎ［１１０］ピークに対するＡＳｎ2［２１１］ピークの強度比が５００％未満では、ＡＳｎ2相が少ないため放電容量に劣り、３０００％を超えるとＡＳｎ相が少ないためサイクル寿命に劣る。好ましくは６００％以上２５００％以下、より好ましくは７００％以上２０００％以下である。 When the intensity ratio of the ASn 2 [211] peak to the ASn [110] peak is less than 500%, the ASn 2 phase is small and the discharge capacity is inferior, and when it exceeds 3000%, the ASn phase is small and the cycle life is inferior. Preferably they are 600% or more and 2500% or less, More preferably, they are 700% or more and 2000% or less.
ＡＳｎ［１１０］ピークに対するＳｎ［１０１］ピークの強度比が１０％以下（０％を含む）
本発明合金において、Ｓｎ相は充放電に寄与するもののサイクル寿命を劣化させてしまう。１０％を超えるとサイクル寿命が劣化する。好ましくは５％以下、より好ましくは０％である。
The intensity ratio of Sn [101] peak to ASn [110] peak is 10% or less (including 0%)
In the alloy of the present invention, the Sn phase contributes to charging / discharging but deteriorates the cycle life. If it exceeds 10%, the cycle life is deteriorated. Preferably it is 5% or less, More preferably, it is 0%.
ＡＳｎ［１１０］ピークに対するＡ3Ｓｎ2［１０２］ピークの強度比が１０％以上１００％以下
本発明合金において、Ａ3Ｓｎ2相は放電容量はほとんどないもののサイクル寿命を改善する効果があるとともに、この相を消失させるとミクロ組織が著しく粗大化し、サイクル寿命を劣化させる。１０％未満ではサイクル寿命が劣化し、１００％を超えると放電容量が低下してしまう。好ましくは２０％以上９０％以下、より好ましくは４０％以上８０％以下である。
The intensity ratio of the A 3 Sn 2 [102] peak to the ASn [110] peak is 10% or more and 100% or less. In the alloy of the present invention, the A 3 Sn 2 phase has an effect of improving the cycle life although there is almost no discharge capacity. When this phase disappears, the microstructure becomes extremely coarse and the cycle life is deteriorated. If it is less than 10%, the cycle life is deteriorated, and if it exceeds 100%, the discharge capacity is lowered. Preferably they are 20% or more and 90% or less, More preferably, they are 40% or more and 80% or less.
上述のピーク強度比は、全てＡＳｎ［１１０］のピーク強度を１００％とした百分率で示しており、例えばピーク強度比２００％の場合、ＡＳｎ［１１０］の２倍の高さであることを示す。また、ＡはＣｏ，Ｆｅの１種または２種を示すものであり、例えばＡＳｎは、ＣｏＳｎや（Ｃｏ，Ｆｅ）Ｓｎなどを示す。なお、上述したＡＳｎの［１１０］、ＡＳｎ2の［２１１］、Ｓｎの［１０１］、Ａ3Ｓｎ2［１０２］のおおよそのｄ値を示すと、それぞれ、２．６４、２．５３、２．７９、２．０９Åである。 The above-described peak intensity ratios are all expressed as a percentage with the peak intensity of ASn [110] as 100%. For example, when the peak intensity ratio is 200%, the peak intensity ratio is twice as high as ASn [110]. . A represents one or two of Co and Fe. For example, ASn represents CoSn, (Co, Fe) Sn, and the like. The approximate d values of the above-mentioned ASn [110], ASn 2 [211], Sn [101], and A 3 Sn 2 [102] are 2.64, 2.53, 2 and 2, respectively. 79, 2.09 mm.
熱処理温度を２５０〜４００℃
本発明方法において、請求項１に記載のＳｎ系合金粉末を、２００〜４５０℃の温度で熱処理することにより、ＡＳｎ相に対するＡＳｎ2 相の生成量を増加させ、更なる放電容量の増加を図るものである。しかし、２５０℃未満ではその効果が十分でなく、また、４００℃を超えると非平衡相であるＳｎとＡ3 Ｓｎ2 を消失させて平衡相の均質化の目的を得ることに留まり、放電容量は増加するもののサイクル寿命が劣化することから、その範囲を２００〜４００℃とした。
Heat treatment temperature is 250-400 ° C
In the method of the present invention, the Sn-based alloy powder according to claim 1 is heat-treated at a temperature of 200 to 450 ° C., thereby increasing the generation amount of the ASn 2 phase with respect to the ASn phase and further increasing the discharge capacity. Is. However, if the temperature is less than 250 ° C., the effect is not sufficient, and if it exceeds 400 ° C., the non-equilibrium phase Sn and A 3 Sn 2 are lost and the purpose of homogenization of the equilibrium phase is obtained. However, the cycle life is deteriorated, but the range is set to 200 to 400 ° C.
以下、本発明について実施例によって具体的に説明する。
表１に示す組成のＳｎ系合金をガスアトマイズ法もしくは単ロール法により作製した。ガスアトマイズは、溶解量１０００ｇの母材をアルミナ性耐火坩堝中で、Ａｒ雰囲気にて誘導溶解し、坩堝下部の細孔ノズルより溶湯を出湯した。出湯直後に窒素ガスによりアトマイズした。単ロール法は直径約１ｍｍの小孔の空いた石英管中で、あらかじめアーク溶解法で作製した３０ｇの母材をＡｒ雰囲気で誘導溶解し、溶解直後に直径３００ｍｍの銅ロール上に出湯した。なお、ロール回転数は１５００ｒｐｍとした。この急冷薄帯を１ｍｍ程度の長さに切断し粉末状とした。
Hereinafter, the present invention will be specifically described with reference to examples.
Sn-based alloys having the compositions shown in Table 1 were produced by a gas atomization method or a single roll method. In the gas atomization, a base material having a dissolution amount of 1000 g was induction-melted in an alumina-type refractory crucible in an Ar atmosphere, and the molten metal was discharged from a pore nozzle at the bottom of the crucible. Atomized with nitrogen gas immediately after tapping. In the single roll method, in a quartz tube with a small hole having a diameter of about 1 mm, 30 g of a base material prepared in advance by an arc melting method was induction-melted in an Ar atmosphere, and immediately after melting, the hot water was discharged onto a copper roll having a diameter of 300 mm. The roll rotation speed was 1500 rpm. The quenched ribbon was cut into a powder form by cutting to a length of about 1 mm.
これらのガスアトマイズと急冷薄帯による粉末を所定の温度で２時間熱処理し、負極活物質の原料として用いるＳｎ合金粉末を得た。熱処理はいずれも真空中で実施した。これらについてＸ線回折を行なった。更に、これらの原料粉末を遊星ボールミルにて粉砕し、２５μｍ以下に分級し充放電用の供試粉末を得た。遊星ボールミルにはステンレス製の容器と直径１０ｍｍのボールを用い、３００ｒｐｍで４時間粉砕した。これら供試粉末について充放電評価を行なった。以下、充放電評価の方法について説明する。 These powders of gas atomization and quenching ribbon were heat-treated at a predetermined temperature for 2 hours to obtain Sn alloy powder used as a raw material for the negative electrode active material. All heat treatments were performed in vacuum. These were subjected to X-ray diffraction. Further, these raw material powders were pulverized with a planetary ball mill and classified to 25 μm or less to obtain test powders for charging and discharging. For the planetary ball mill, a stainless steel container and a ball having a diameter of 10 mm were used and pulverized at 300 rpm for 4 hours. These sample powders were evaluated for charge and discharge. Hereinafter, the method of charge / discharge evaluation will be described.
供試粉末：市販の人造黒鉛粉末：アセチレンブラック：バインダー（スチレンブタジエンラバー）：カルロキシメチルセルロースを４５：４０：５：５：５の比率で混合、混錬し、スラリーを得た。このスラリーを銅箔に塗布、乾燥させ、直径約１０ｍｍに打ち抜き、これを金型でプレスしたものを負極として用いた。対極にＬｉ金属を用いたコイン型セルにて充放電評価を行なった。電解液はエチレンカーボネートとジメチルカーボネートの１：１混合溶媒中に、ＬｉＰＦ6を１Ｍ濃度電解質として添加したものを用いた。 Test powder: Commercially available artificial graphite powder: Acetylene black: Binder (styrene butadiene rubber): Carboxymethyl cellulose was mixed and kneaded at a ratio of 45: 40: 5: 5: 5 to obtain a slurry. This slurry was applied to a copper foil, dried, punched out to a diameter of about 10 mm, and pressed with a mold, and used as a negative electrode. Charge / discharge evaluation was performed in a coin-type cell using Li metal as a counter electrode. The electrolytic solution used was a mixture of ethylene carbonate and dimethyl carbonate in a 1: 1 mixed solvent with LiPF 6 added as a 1M concentration electrolyte.
このセルを用い、電流値１ｍＡで充電した後、電流値１ｍＡで参照極に対して−１．２Ｖになるまで放電を行なった。この時、黒鉛材料の放電容量を差し引いて、供試粉末の放電容量を評価した。また、この充放電を１サイクルとし、５０サイクル目の放電容量を１サイクル目の放電容量に対する割合（％）で示し、評価した。 Using this cell, the battery was charged at a current value of 1 mA and then discharged at a current value of 1 mA until −1.2 V with respect to the reference electrode. At this time, the discharge capacity of the graphite powder was subtracted to evaluate the discharge capacity of the test powder. Further, this charge / discharge was defined as one cycle, and the discharge capacity at the 50th cycle was expressed as a percentage (%) with respect to the discharge capacity at the first cycle.
比較例Ｎｏ．１３は式（１）の値が低く、ピーク比（１）および（２）が大きく、ピーク比（３）が小さいためサイクル寿命に劣る。比較例Ｎｏ．１４は式（１）の値が低く、ピーク比（３）が小さいためサイクル寿命に劣る。比較例Ｎｏ．１５は式（１）の値が高く、ピーク比（３）が高いため放電容量に劣る。比較例Ｎｏ．１６は式（１）の値が高く、ピーク比（１）が小さく、ピーク比（３）が大きいため放電容量に劣る。 Comparative Example No. 13 is inferior in cycle life because the value of the formula (1) is low, the peak ratios (1) and (2) are large, and the peak ratio (3) is small. Comparative Example No. No. 14 is inferior in cycle life because the value of the formula (1) is low and the peak ratio (3) is small. Comparative Example No. 15 is inferior in discharge capacity because the value of the formula (1) is high and the peak ratio (3) is high. Comparative Example No. No. 16 is inferior in discharge capacity because the value of equation (1) is high, the peak ratio (1) is small, and the peak ratio (3) is large.
比較例Ｎｏ．１７，１８はＴｉとＺｒの合計量が少ないため、サイクル寿命に劣る。比較例Ｎｏ．１９，２０はＴｉとＺｒの合計量が多いため、放電容量に劣る。比較例Ｎｏ．２１，２２はピーク比（１）が低いため、放電容量に劣る。比較例Ｎｏ．２３はピーク比（３）が低いためサイクル寿命に劣る。比較例Ｎｏ．２４はピーク比（１）および（２）が大きく、ピーク比（３）が小さいためサイクル寿命に劣る。 Comparative Example No. 17 and 18 are inferior in cycle life because the total amount of Ti and Zr is small. Comparative Example No. 19 and 20 are inferior in discharge capacity because the total amount of Ti and Zr is large. Comparative Example No. Since 21 and 22 have a low peak ratio (1), they are inferior in discharge capacity. Comparative Example No. Since No. 23 has a low peak ratio (3), the cycle life is inferior. Comparative Example No. 24 is inferior in cycle life because the peak ratios (1) and (2) are large and the peak ratio (3) is small.
以上述べたように、本発明では、合金成分として、Ｔｉ、Ｚｒ量を限定するとともに、Ｃｏ、Ｆｅ量をＴｉ、Ｚｒ量と対応させた狭い濃度域に限定し、さらに熱処理温度を従来より高温とすることでＡＳｎ相に対するＡＳｎ2 相の生成量を大幅に増加させることにより、更なる放電容量の増加を実現させることを可能としたものである。このようにして製造された放電容量が高く、サイクル寿命に優れたリチウム二次電池活物質の原料として用いるＳｎ合金粉末であり、これをそのまま負極活物質として用いることが出来るとともに、一般的な粉砕加工で粒度などを調整したうえで負極活物質として用いることも出来る極めて優れた効果を奏するものである。
特許出願人 山陽特殊製鋼株式会社
代理人 弁理士 椎 名 彊
As described above, in the present invention, the amount of Ti and Zr are limited as alloy components, the amount of Co and Fe is limited to a narrow concentration range corresponding to the amount of Ti and Zr, and the heat treatment temperature is higher than before. Thus, it is possible to realize a further increase in the discharge capacity by greatly increasing the generation amount of the ASn 2 phase with respect to the ASn phase. The Sn alloy powder used as a raw material for the lithium secondary battery active material having a high discharge capacity and excellent cycle life thus produced can be used as a negative electrode active material as it is, and is generally pulverized. It has an extremely excellent effect that can be used as a negative electrode active material after adjusting the particle size and the like by processing.
Patent Applicant Sanyo Special Steel Co., Ltd.
Attorney: Attorney Shiina
Claims (2)
Ｔｉ，Ｚｒの１種または２種を２．０％を超え５．０％未満含み、Ｃｏ，Ｆｅの１種または２種を下記式（１）を満たす範囲で含み、残部Ｓｎおよび不可避的不純物からなり、Ｘ線回折によるＡＳｎ［１１０］ピークに対するＡＳｎ2［２１１］ピークの強度比が５００％以上３０００％以下、ＡＳｎ［１１０］ピークに対するＳｎ［１０１］ピークの強度比が１０％以下（０％を含む）、ＡＳｎ［１１０］ピークに対するＡ3Ｓｎ2［１０２］ピークの強度比が１０％以上１００％以下であることを特徴とするリチウムイオン電池負極活物質の原料として用いるＳｎ合金粉末。
ただし、Ａは、Ｃｏ，Ｆｅの１種または２種である。
０．３５≦［（Ｃｏ＋Ｆｅ）−２（Ｔｉ＋Ｚｒ）］／［１００−４（Ｔｉ＋Ｚｒ）］≦０．４５ ・・・（１） Atomic% (excluding% of peak intensity ratio)
1 type or 2 types of Ti and Zr are included more than 2.0% and less than 5.0%, 1 type or 2 types of Co and Fe are included within the range satisfying the following formula (1), the remaining Sn and inevitable impurities The intensity ratio of the ASn 2 [211] peak to the ASn [110] peak by X-ray diffraction is 500% or more and 3000% or less, and the intensity ratio of the Sn [101] peak to the ASn [110] peak is 10% or less (0 % including), ASn [110] Sn alloy powder used as a raw material of the lithium ion battery negative electrode active material, characterized in that a 3 Sn 2 [102] peak intensity ratio of the relative peak is less than 100% to 10%.
However, A is 1 type or 2 types of Co and Fe.
0.35≤ [(Co + Fe) -2 (Ti + Zr)] / [100-4 (Ti + Zr)] ≤0.45 (1)
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