JP5272492B2 - Negative electrode material for non-aqueous electrolyte secondary battery and method for producing the same, and negative electrode for non-aqueous electrolyte secondary battery and non-aqueous electrolyte secondary battery - Google Patents
Negative electrode material for non-aqueous electrolyte secondary battery and method for producing the same, and negative electrode for non-aqueous electrolyte secondary battery and non-aqueous electrolyte secondary battery Download PDFInfo
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本発明は、リチウムイオン二次電池等の非水電解質二次電池用の負極材、この負極材を用いた非水電解質二次電池用負極及び非水電解質二次電池に関するものである。 The present invention relates to a negative electrode material for a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery, a negative electrode for a non-aqueous electrolyte secondary battery using the negative electrode material, and a non-aqueous electrolyte secondary battery.
近年、携帯型の電子機器、通信機器等の著しい発展に伴い、経済性と機器の小型化、軽量化の観点から、高エネルギー密度の非水電解質二次電池が強く要望されている。従来、この種の非水電解質二次電池の高容量化策として、例えば、負極材料にB、Ti、V、Mn、Co、Fe、Ni、Cr、Nb、Mo等の酸化物及びそれらの複合酸化物を用いる方法(特許文献1:特許第3008228号公報、特許文献2:特許第3242751号公報等参照)、熔湯急冷したM100-xSix(x≧50at%,M=Ni,Fe,Co,Mn)を負極材として適用する方法(特許文献3:特許第3846661号公報参照)、負極材料に酸化珪素を用いる方法(特許文献4:特許第2997741号公報)、負極材料にSi2N2O、Ge2N2O及びSn2N2Oを用いる方法(特許文献5:特許第3918311号公報)等が提案されている。 In recent years, with the remarkable development of portable electronic devices, communication devices, etc., there is a strong demand for non-aqueous electrolyte secondary batteries with high energy density from the viewpoints of economy and downsizing and weight reduction of devices. Conventionally, as a measure for increasing the capacity of this type of non-aqueous electrolyte secondary battery, for example, negative electrode materials such as oxides such as B, Ti, V, Mn, Co, Fe, Ni, Cr, Nb, and Mo and composites thereof A method using an oxide (see Patent Document 1: Japanese Patent No. 3008228, Patent Document 2: Japanese Patent No. 3242751, etc.) M 100-x Si x (x ≧ 50 at%, M = Ni, Fe) , Co, Mn) as a negative electrode material (see Patent Document 3: Japanese Patent No. 3,846,661), a method using silicon oxide as a negative electrode material (Patent Document 4: Japanese Patent No. 2,997,741), and Si 2 as a negative electrode material. A method using N 2 O, Ge 2 N 2 O and Sn 2 N 2 O (Patent Document 5: Japanese Patent No. 3918311) has been proposed.
珪素は、現在実用化されている炭素材料の理論容量372mAh/gより遙かに高い理論容量4200mAh/gを示すことから、電池の小型化と高容量化において最も期待される材料である。珪素はその製法により結晶構造の異なった種々の形態が知られている。例えば、単結晶珪素を負極活物質の支持体として使用したリチウムイオン二次電池が提案されており(特許文献6:特許第2964732号公報)、単結晶珪素、多結晶珪素及び非晶質珪素のLixSi(但し、xは0〜5)なるリチウム合金を使用したリチウムイオン二次電池が提案されており(特許文献7:特許第3079343号公報)、特に非晶質珪素を用いたLixSiが好ましく、モノシランをプラズマ分解した非晶質珪素で被覆した結晶性珪素の粉砕物が例示されている。しかしながら、この場合においては、実施例にあるように珪素分は30部、導電剤としてのグラファイトを55部使用しており、珪素の電池容量を十分発揮させることができなかった。 Silicon shows the theoretical capacity of 4200 mAh / g, which is far higher than the theoretical capacity of 372 mAh / g of the carbon material currently in practical use, and is the most expected material for battery miniaturization and high capacity. Various forms of silicon having different crystal structures are known depending on the production method. For example, a lithium ion secondary battery using single crystal silicon as a support for a negative electrode active material has been proposed (Patent Document 6: Japanese Patent No. 2964732), and includes single crystal silicon, polycrystalline silicon, and amorphous silicon. A lithium ion secondary battery using a lithium alloy of Li x Si (where x is 0 to 5) has been proposed (Patent Document 7: Japanese Patent No. 3079343), and particularly Li x using amorphous silicon. Si is preferable, and a pulverized product of crystalline silicon coated with amorphous silicon obtained by plasma decomposition of monosilane is exemplified. However, in this case, as in the example, 30 parts of silicon and 55 parts of graphite as a conductive agent were used, and the battery capacity of silicon could not be fully exhibited.
また、負極材に導電性を付与する目的として、酸化珪素を例とする金属酸化物と黒鉛とをメカニカルアロイング後、炭化処理する方法(特許文献8:特開2000−243396号公報)、Si粒子表面を化学蒸着法により炭素層で被覆する方法(特許文献9:特開2000−215887号公報)、酸化珪素粒子表面を化学蒸着法により炭素層で被覆する方法(特許文献10:特開2002−42806号公報)が提案されている。しかしながら、粒子表面に炭素層を設けることによって導電性を改善することはできるが、珪素負極の克服すべき課題である充放電に伴う大きな体積変化の緩和、これに伴う集電性の劣化とサイクル特性低下を防止することはできなかった。 Further, for the purpose of imparting conductivity to the negative electrode material, a method of mechanically alloying a metal oxide such as silicon oxide and graphite, followed by carbonization treatment (Patent Document 8: JP 2000-243396 A), Si A method in which the particle surface is coated with a carbon layer by chemical vapor deposition (Patent Document 9: Japanese Patent Laid-Open No. 2000-215887), and a method in which the surface of silicon oxide particles is coated with a carbon layer by chemical vapor deposition (Patent Document 10: Japanese Patent Laid-Open No. 2002-2002). -42806). However, the conductivity can be improved by providing a carbon layer on the particle surface, but the large volume change accompanying charging / discharging, which is a problem to be overcome by the silicon negative electrode, is mitigated, and the current collecting deterioration and cycle are associated with this. The characteristic deterioration could not be prevented.
このため近年では、珪素の電池容量利用率を制限して体積膨張を抑制する方法(特許文献9:特開2000−215887号公報、特許文献11:特開2000−173596号公報、特許文献12:特許第3291260号公報、特許文献13:特開2005−317309号公報)あるいは多結晶粒子の粒界を体積変化の緩衝帯とする方法としてアルミナを添加した珪素融液を急冷する技術(特許文献14:特開2003−109590号公報)、α,β−FeSi2の混相多結晶体からなる多結晶粒子(特許文献15:特開2004−185991号公報)、単結晶珪素インゴットの高温塑性加工(特許文献16:特開2004−303593号公報)が提案されている。 For this reason, in recent years, methods for suppressing the volume expansion by limiting the battery capacity utilization rate of silicon (Patent Document 9: JP 2000-215887 A, Patent Document 11: JP 2000-173596 A, Patent Document 12: Japanese Patent No. 3291260, Patent Document 13: Japanese Patent Application Laid-Open No. 2005-317309, or a technique of rapidly cooling a silicon melt to which alumina is added as a method of using a grain boundary of a polycrystalline particle as a buffer zone for volume change (Patent Document 14) : JP-A-2003-109590), polycrystalline particles made of α, β-FeSi 2 mixed phase polycrystal (Patent Document 15: JP-A-2004-185991), high-temperature plastic working of single-crystal silicon ingot (patent) Document 16: Japanese Patent Laid-Open No. 2004-303593) has been proposed.
珪素活物質の積層構造を工夫することで体積膨張を緩和する方法も提案されており、例えば珪素負極を2層に配置する方法(特許文献17:特開2005−190902号公報)、炭素や他金属及び酸化物で被覆あるいはカプセル化して粒子の崩落を抑制する方法(特許文献18:特開2005−235589号公報、特許文献19:特開2006−216374号公報、特許文献20:特開2006−236684号公報、特許文献21:特開2006−339092号公報、特許文献22:特許第3622629号公報、特許文献23:特開2002−75351号公報、特許文献24:特許第3622631号公報)等が開示されている。また、集電体に直接珪素を気相成長させる方法において、成長方向を制御することで体積膨張によるサイクル特性の低下を抑制する方法も提案されている(特許文献25:特開2006−338996号公報)。 A method of reducing volume expansion by devising a laminated structure of a silicon active material has also been proposed. For example, a method of disposing a silicon negative electrode in two layers (Patent Document 17: JP-A-2005-190902), carbon and others Method of suppressing collapse of particles by coating or encapsulating with metal and oxide (Patent Document 18: JP-A-2005-235589, Patent Document 19: JP-A-2006-216374, Patent Document 20: JP-A-2006) No. 236684, Patent Document 21: Japanese Patent Laid-Open No. 2006-339092, Patent Document 22: Japanese Patent No. 3622629, Patent Document 23: Japanese Patent Laid-Open No. 2002-75351, Patent Document 24: Japanese Patent No. 3622631) and the like. It is disclosed. In addition, in a method in which silicon is directly vapor-grown on a current collector, a method of suppressing a decrease in cycle characteristics due to volume expansion by controlling the growth direction has also been proposed (Patent Document 25: Japanese Patent Application Laid-Open No. 2006-338996). Publication).
しかしながら、珪素表面を炭素被覆して導電化したり非晶質金属層で被覆したりする等して負極材のサイクル特性を高めるという方法では、珪素本来の電池容量の半分程度を発揮できるにすぎず、さらなる高容量化が求められていた。また、結晶粒界を持つ多結晶珪素では、提案された方法では冷却速度の制御が困難であり、安定した物性を再現することが難しかった。 However, the method of improving the cycle characteristics of the negative electrode material by, for example, coating the silicon surface with carbon to make it conductive or coating with an amorphous metal layer can only exhibit about half of the original battery capacity of silicon. Therefore, further increase in capacity has been demanded. In addition, with polycrystalline silicon having crystal grain boundaries, it is difficult to control the cooling rate by the proposed method, and it is difficult to reproduce stable physical properties.
一方、酸化珪素はSiOx(ただし、xは酸化被膜のため理論値の1よりわずかに大きい)と表記することができるが、X線回折による分析では数nm〜数十nm程度のアモルファスシリコンがシリカ中に微分散している構造をとっている。このため、電池容量は珪素と比較して小さいものの炭素と比較すれば質量あたりで5〜6倍と高く、さらには体積膨張も小さく、負極活物質として使用しやすいと考えられていた。しかしながら、酸化珪素は不可逆容量が大きく、初期効率が70%程度と非常に低いため実際に電池を作製した場合では正極の電池容量を過剰に必要とし、活物質あたり5〜6倍の容量増加分に見合うだけの電池容量の増加を期待することができなかった。 On the other hand, silicon oxide can be expressed as SiOx (where x is slightly larger than the theoretical value 1 because it is an oxide film), but amorphous silicon of about several nanometers to several tens of nanometers is analyzed by X-ray diffraction. It has a finely dispersed structure. For this reason, although the battery capacity is small compared to silicon, the battery capacity is 5-6 times higher than the mass, and further, the volume expansion is small. However, silicon oxide has a large irreversible capacity, and the initial efficiency is very low at about 70%. Therefore, when a battery is actually manufactured, the battery capacity of the positive electrode is excessively required, and the capacity increase by 5 to 6 times per active material. The battery capacity could not be expected to increase to meet
酸化珪素の実用上の問題点は著しく初期効率が低い点にあり、これを解決する手段としては不可逆容量分を補充する方法、不可逆容量を抑制する方法が挙げられる。たとえばLi金属をあらかじめドープすることで、不可逆容量分を補う方法が有効であることが報告されている。しかしながら、Li金属をドープするためには負極活物質表面にLi箔を貼り付ける方法(特許文献26:特開平11−086847号公報)、及び負極活物質表面にLi蒸着する方法(特許文献27:特開2007−122992号公報)等が開示されている。しかしながら、Li箔の貼り付けでは酸化珪素負極の初期効率に見合ったLi薄体の入手が困難、かつ高コストであり、Li蒸気による蒸着は製造工程が複雑となって実用的でない等の問題があった。 A practical problem of silicon oxide is that the initial efficiency is remarkably low, and means for solving this include a method of replenishing the irreversible capacity and a method of suppressing the irreversible capacity. For example, it has been reported that a method for compensating for the irreversible capacity by doping Li metal in advance is effective. However, in order to dope Li metal, a method of attaching Li foil to the surface of the negative electrode active material (Patent Document 26: Japanese Patent Laid-Open No. 11-0868847) and a method of depositing Li on the surface of the negative electrode active material (Patent Document 27: JP, 2007-122992, A) and the like are disclosed. However, it is difficult to obtain a Li thin body corresponding to the initial efficiency of the silicon oxide negative electrode by attaching Li foil, and the cost is high, and vapor deposition using Li vapor is not practical due to complicated manufacturing process. there were.
一方、LiドープによらずにSiの質量割合を高めることで初期効率を増加させる方法が開示されている。ひとつには珪素粉末を酸化珪素粉末に添加して酸化珪素の質量割合を減少させる方法であり(特許文献28:特許第3982230号公報)、他方では酸化珪素の製造段階において珪素蒸気を同時に発生、析出することで珪素と酸化珪素の混合固体を得る方法である(特許文献29:特開2007−290919号公報)。しかしながら、珪素は酸化珪素と比較して高い初期効率と電池容量を併せ持つが、充電時に400%もの体積膨張率を示す活物質であり、酸化珪素と炭素材料の混合物に添加する場合であっても、酸化珪素の体積膨張率を維持することができないうえ、結果的に炭素材料を20質量%以上添加して電池容量が1000mAh/gに抑えることが必要であった。一方、珪素と酸化珪素の蒸気を同時に発生させて混合固体を得る方法では、珪素の蒸気圧が低いことから2000℃を超える高温での製造工程を必要とし、作業上問題があった。 On the other hand, a method for increasing the initial efficiency by increasing the mass ratio of Si irrespective of Li doping is disclosed. One is a method in which silicon powder is added to silicon oxide powder to reduce the mass ratio of silicon oxide (Patent Document 28: Japanese Patent No. 3982230). On the other hand, silicon vapor is simultaneously generated in the production stage of silicon oxide. This is a method of obtaining a mixed solid of silicon and silicon oxide by precipitation (Patent Document 29: JP 2007-290919 A). However, silicon has both high initial efficiency and battery capacity compared to silicon oxide, but is an active material that exhibits a volume expansion coefficient of 400% during charging, and even when added to a mixture of silicon oxide and carbon material. In addition, the volume expansion coefficient of silicon oxide cannot be maintained, and as a result, it was necessary to add 20% by mass or more of a carbon material to suppress the battery capacity to 1000 mAh / g. On the other hand, the method of obtaining a mixed solid by simultaneously generating vapors of silicon and silicon oxide requires a manufacturing process at a high temperature exceeding 2000 ° C. because the vapor pressure of silicon is low, and has a problem in operation.
以上のように珪素系活物質は金属単体及びその酸化物であってもそれぞれ解決課題を有しており、実用上問題となっていた。十分にLiの吸蔵、放出に伴う体積変化の抑制、粒子の割れによる微粉化や集電体からの剥離による導電性の低下を緩和することが可能であり、大量生産が可能で、コスト的に有利であって、かつ携帯電話用等の特に繰り返しのサイクル特性を重要視される用途に適応することが可能な負極活物質が望まれていた。 As described above, even if the silicon-based active material is a single metal or its oxide, each has a problem to be solved, which has been a problem in practical use. It is possible to sufficiently suppress the volume change due to insertion and extraction of Li, to reduce pulverization due to particle cracking, and to reduce the decrease in conductivity due to peeling from the current collector. There has been a demand for a negative electrode active material that is advantageous and can be applied to applications in which repetitive cycle characteristics are particularly important, such as for mobile phones.
本発明は、酸化珪素の高い電池容量と充電後の低い体積膨張率を維持しつつ、初期充放電効率が高く、サイクル特性に優れた非水電解質二次電池負極用として有効な負極材、ならびにこの負極材を用いた非水電解質二次電池負極、非水電解質二次電池を提供することを目的とする。 The present invention is a negative electrode material that is effective for a negative electrode of a nonaqueous electrolyte secondary battery having high initial charge / discharge efficiency and excellent cycle characteristics, while maintaining a high battery capacity of silicon oxide and a low volume expansion rate after charging, and It aims at providing the nonaqueous electrolyte secondary battery negative electrode and nonaqueous electrolyte secondary battery which used this negative electrode material.
本発明者らは炭素材料の電池容量を上回り、充電後の体積膨張が小さく、かつ酸化珪素の欠点である初期充放電効率の低さを克服し、初期充放電効率が高い活物質について検討した。その結果、特定の黒鉛皮膜を有する特定の被覆酸化珪素粒子と、珪素粒子1〜50質量%とを共に活物質として用いることで、上記課題が解決されることを見出した。つまり、本願発明の特定の黒鉛被覆された酸化珪素に珪素を添加すると、一般の珪素に見られるような400%を超えるような充電後の体積膨張は観測されず、ほぼ酸化珪素と同程度の体積膨張率を維持することがわかった。このため体積当たりの電池容量が増加するほか、導電剤の添加や被覆によって導電性を向上させることができる上、黒鉛を被覆することで導電性が向上し、初期充放電効率が高くなると共に、負極材に結着剤1〜20質量%を配合することにより、充放電による膨張・収縮が繰り返されても負極材の破壊・粉化が防止でき、電極自体の導電性が低下せず、この負極材を非水電解質二次電池として用いた場合、サイクル特性が良好な非水電解質二次電池が得られることを見出し、本発明をなすに至ったものである。 The present inventors have studied an active material having a high initial charge / discharge efficiency that exceeds the battery capacity of the carbon material, has a small volume expansion after charge, overcomes the low initial charge / discharge efficiency, which is a drawback of silicon oxide, and the like. . As a result, it has been found that the above problems can be solved by using both specific coated silicon oxide particles having a specific graphite film and 1 to 50% by mass of silicon particles as active materials. That is, when silicon is added to the specific graphite-coated silicon oxide of the present invention, the volume expansion after charging as observed in general silicon exceeding 400% is not observed, and is almost the same as that of silicon oxide. It was found that the volume expansion rate was maintained. For this reason, the battery capacity per volume is increased, the conductivity can be improved by adding or coating a conductive agent, and the conductivity is improved by coating graphite, and the initial charge / discharge efficiency is increased, By blending 1 to 20% by mass of the binder into the negative electrode material, the negative electrode material can be prevented from being destroyed or pulverized even if the expansion and contraction due to charge and discharge are repeated, and the conductivity of the electrode itself does not decrease. It has been found that when a negative electrode material is used as a nonaqueous electrolyte secondary battery, a nonaqueous electrolyte secondary battery with good cycle characteristics can be obtained, and the present invention has been made.
従って、本発明は下記発明を提供する。
[1].酸化珪素粒子の表面を黒鉛皮膜で被覆した被覆酸化珪素粒子(A1)及び珪素粒子(A2)からなる活物質(A)と、結着剤(B)1〜20質量%とを含有する非水電解質二次電池用負極材であって、
上記被覆酸化珪素粒子(A1)の黒鉛皮膜が、ラマンスペクトル分析において、1330cm-1と1580cm-1に散乱ピークを有し、それらの強度比I1330/I1580が1.5<I1330/I1580<3.0であり、かつ被覆酸化珪素粒子(A1)の固体NMR(29Si−DDMAS)測定において、−110ppm付近を中心とするブロードなシグナル面積と−84ppm付近のシグナル面積との比S-84/S-110が0.5<S-84/S-110<1.1であり、活物質(A)中の被覆酸化珪素粒子(A1)の割合が70〜95質量%であり、珪素粒子(A2)の割合が5〜30質量%であることを特徴とする非水電解質二次電池用負極材。
[2].酸化珪素粒子が、二酸化珪素と金属珪素との混合物を減圧下1000〜1500℃に加熱して得られる酸化珪素ガスを、500〜1100℃で析出させたものである[1]記載の非水電解質二次電池用負極材。
[3].珪素粒子(A2)が、その表面が黒鉛皮膜で被覆された被覆珪素粒子である[1]又は[2]記載の非水電解質二次電池用負極材。
[4].結着剤(B)がポリイミド樹脂であることを特徴とする[1]、[2]又は[3]記載の非水電解質二次電池用負極材。
[5].下記工程(I)及び(II)を含む[1]記載の非水電解質二次電池用負極材の製造方法。
(I)酸化珪素粒子を、有機物ガス及び/又は蒸気中、50〜30000Paの減圧下、600〜1100℃で化学蒸着することにより表面を黒鉛皮膜で被覆し、被覆酸化珪素粒子(A1)を調製する工程、
(II)工程(I)で得られた被覆酸化珪素粒子(A1)、珪素粒子(A2)、及び結着剤(B)を混合し、非水電解質二次電池用負極材を調製する工程。
[6].工程(I)から非水電解質二次電池用負極材が得られる全工程において、酸化珪素粒子及び被覆酸化珪素粒子が1100℃以下の雰囲気下である[5]記載の非水電解質二次電池用負極材の製造方法。
[7].[1]〜[4]のいずれかに記載の非水電解質二次電池用負極材を含む負極であって、充電後の体積が充電前の2倍未満であることを特徴とする非水電解質二次電池用負極。
[8].[7]記載の非水電解質二次電池用負極、正極、セパレーター及び非水電解質を備えた非水電解質二次電池。
[9].非水電解質二次電池がリチウムイオン二次電池であることを特徴とする[8]記載の非水電解質二次電池。
Accordingly, the present invention provides the following inventions.
[1]. Non-water containing active material (A) composed of coated silicon oxide particles (A1) and silicon particles (A2) whose surfaces are coated with a graphite film, and binder (B) 1 to 20% by mass A negative electrode material for an electrolyte secondary battery,
Graphite coating of the coated silicon oxide particles (A1) is, in the Raman spectrum analysis, have a scattering peak at 1330 cm -1 and 1580 cm -1, their intensity ratio I 1330 / I 1580 is 1.5 <I 1330 / I In the solid state NMR ( 29 Si-DDMAS) measurement of the coated silicon oxide particles (A1) with 1580 <3.0, the ratio S between the broad signal area centered around −110 ppm and the signal area around −84 ppm −84 / S −110 is 0.5 <S −84 / S −110 <1.1, the ratio of the coated silicon oxide particles (A1) in the active material (A) is 70 to 95% by mass, A negative electrode material for a nonaqueous electrolyte secondary battery, wherein the ratio of silicon particles (A2) is 5 to 30 % by mass.
[2]. The nonaqueous electrolyte according to [1], wherein the silicon oxide particles are formed by depositing silicon oxide gas obtained by heating a mixture of silicon dioxide and metal silicon at 1000 to 1500 ° C. under reduced pressure at 500 to 1100 ° C. Secondary battery negative electrode material.
[3]. The negative electrode material for a nonaqueous electrolyte secondary battery according to [1] or [2], wherein the silicon particles (A2) are coated silicon particles whose surfaces are coated with a graphite film.
[4]. The negative electrode material for a nonaqueous electrolyte secondary battery according to [1], [2] or [3], wherein the binder (B) is a polyimide resin.
[5]. The manufacturing method of the negative electrode material for nonaqueous electrolyte secondary batteries as described in [1] including following process (I) and (II).
(I) The silicon oxide particles are chemically vapor-deposited at 600 to 1100 ° C. under reduced pressure of 50 to 30000 Pa in an organic gas and / or vapor to prepare a coated silicon oxide particle (A1). The process of
(II) A step of mixing the coated silicon oxide particles (A1), the silicon particles (A2), and the binder (B) obtained in step (I) to prepare a negative electrode material for a nonaqueous electrolyte secondary battery.
[6]. In all steps in which the negative electrode material for a nonaqueous electrolyte secondary battery is obtained from step (I), the silicon oxide particles and the coated silicon oxide particles are in an atmosphere of 1100 ° C. or lower [5] Manufacturing method of negative electrode material.
[7]. [1] - a negative electrode containing a negative electrode material for a nonaqueous electrolyte secondary battery according to any one of [4], non, wherein the volume after charging is less than 2 times the previous charging Negative electrode for water electrolyte secondary battery.
[8]. [7] A nonaqueous electrolyte secondary battery comprising the negative electrode for a nonaqueous electrolyte secondary battery, a positive electrode, a separator, and a nonaqueous electrolyte.
[9]. The nonaqueous electrolyte secondary battery according to [8], wherein the nonaqueous electrolyte secondary battery is a lithium ion secondary battery.
本発明で得られた非水電解質二次電池用負極材を用いることで、高い電池容量と充電後の低い体積膨張率を維持しつつ、高い初期充放電効率を有し、サイクル特性に優れた非水電解質二次電池を得ることができる。 By using the negative electrode material for a non-aqueous electrolyte secondary battery obtained in the present invention, it has high initial charge / discharge efficiency and excellent cycle characteristics while maintaining a high battery capacity and a low volume expansion after charging. A nonaqueous electrolyte secondary battery can be obtained.
本発明の非水電解質二次電池用負極材は、酸化珪素粒子(A1)の表面を黒鉛皮膜で被覆した被覆酸化珪素粒子及び珪素粒子(A2)とからなる活物質(A)と、結着剤(B)1〜20質量%とを含有するものであって、上記被覆酸化珪素粒子の黒鉛皮膜が、ラマンスペクトル分析において、1330cm-1と1580cm-1に散乱ピークを有し、それらの強度比I1330/I1580が1.5<I1330/I1580<3.0であり、かつ被覆酸化珪素粒子の固体NMR(29Si−DDMAS)測定において、−110ppm付近を中心とするブロードなシグナル面積と−84ppm付近のシグナル面積との比S-84/S-110が0.5<S-84/S-110<1.1であり、活物質(A)中の珪素粒子(A2)の割合が1〜50質量であることを特徴とする非水電解質二次電池用負極材である。 A negative electrode material for a non-aqueous electrolyte secondary battery according to the present invention includes an active material (A) composed of coated silicon oxide particles and silicon particles (A2) in which the surface of silicon oxide particles (A1) is coated with a graphite film, and a binder. agent (B) it is one which contains a 1 to 20 mass%, graphite coating of the coated silicon oxide particles, in the Raman spectrum analysis, have a scattering peak at 1330 cm -1 and 1580 cm -1, their strength The ratio I 1330 / I 1580 is 1.5 <I 1330 / I 1580 <3.0, and a broad signal centered around −110 ppm in the solid state NMR ( 29 Si-DDMAS) measurement of the coated silicon oxide particles. The ratio S −84 / S −110 of the area to the signal area in the vicinity of −84 ppm is 0.5 <S −84 / S −110 <1.1, and the silicon particles (A2) in the active material (A) Non-feature characterized by a proportion of 1-50 mass A negative electrode material for electrolyte secondary battery.
[活物質(A)]
酸化珪素粒子の表面を黒鉛皮膜で被覆した被覆酸化珪素粒子(A1)と、珪素粒子(A2)とからなり、それぞれ1種単独で又は2種以上を適宜組み合わせて用いることができる。
(A1)被覆酸化珪素粒子
被覆酸化珪素粒子は、固体NMR(29Si−DDMAS)測定において、−110ppm付近を中心とする−98〜−145ppmのブロードなシグナル面積と−84ppm付近の−45〜−98ppmのシグナル面積との比S-84/S-110が、0.5<S-84/S-110<1.1であり、0.6〜1.0が好ましく、0.6〜0.8がより好ましい。なお、上記スペクトルは、アモルファス酸化珪素は−110ppm付近を中心とするブロードなピークを示すのみであるが、熱履歴によって−84ppm付近にSiのダイヤモンド結晶の特徴であるピークが検出存在する。すなわち、Siのダイヤモンド結晶に帰属されるシグナルを中心とする面積が小さい方が好ましい。このような被覆酸化珪素粒子を得るためには、上記範囲となる酸化珪素を用いる。
[Active material (A)]
It consists of the coated silicon oxide particles (A1) and the silicon particles (A2) in which the surface of the silicon oxide particles is coated with a graphite film, each of which can be used alone or in combination of two or more.
(A1) Coated silicon oxide particles Coated silicon oxide particles have a broad signal area of -98 to -145 ppm centered around -110 ppm and -45 to -84 ppm around -84 ppm in solid state NMR ( 29 Si-DDMAS) measurement. The ratio S −84 / S −110 to the signal area of 98 ppm is 0.5 <S −84 / S −110 <1.1, preferably 0.6 to 1.0, and 0.6 to 0. 8 is more preferable. In the above spectrum, amorphous silicon oxide only shows a broad peak centered around −110 ppm, but a peak characteristic of Si diamond crystal is detected near −84 ppm by thermal history. That is, it is preferable that the area centered on the signal attributed to the Si diamond crystal is small. In order to obtain such coated silicon oxide particles, silicon oxide in the above range is used.
本発明において酸化珪素とは、二酸化珪素と金属珪素との混合物を加熱して生成した酸化珪素ガスを冷却・析出して得られた非晶質珪素酸化物であり、一般式SiOxで表され、xの範囲は1.0≦x<1.6が好ましく、1.0≦x≦1.2がより好ましい。二酸化珪素と金属珪素のモル比は概ね1:1である。 In the present invention, silicon oxide is an amorphous silicon oxide obtained by cooling and precipitating silicon oxide gas generated by heating a mixture of silicon dioxide and metal silicon, and is represented by the general formula SiOx, The range of x is preferably 1.0 ≦ x <1.6, and more preferably 1.0 ≦ x ≦ 1.2. The molar ratio of silicon dioxide to metallic silicon is approximately 1: 1.
本発明に用いる酸化珪素は、例えば、二酸化珪素と金属珪素との混合物を減圧下、好適には5〜200Paで、1000〜1500℃に加熱して得られる酸化珪素ガスを、500〜1100℃で析出させることにより得ることができる。面積比を上記範囲内にするためには析出室を500〜1100℃に保つことが重要であり、好ましくは600〜950℃とするのがよい。上記の面積比であれば酸化珪素中に含まれる珪素は数nm〜数十nmのナノ粒子であって、充放電時の体積膨張が非常に小さいことから、本発明に好適に使用することができる。一方、熱履歴によって不均化が生じ上記面積比が1.1を超えると、珪素粒子が増大する傾向が見られる上、体積膨張が増大する傾向を示すためできるだけ熱履歴の進行していない酸化珪素を用いる。 The silicon oxide used in the present invention is, for example, a silicon oxide gas obtained by heating a mixture of silicon dioxide and metal silicon under reduced pressure, preferably at 5 to 200 Pa, and 1000 to 1500 ° C. at 500 to 1100 ° C. It can be obtained by precipitation. In order to make the area ratio within the above range, it is important to keep the deposition chamber at 500 to 1100 ° C., preferably 600 to 950 ° C. If the area ratio is as described above, silicon contained in silicon oxide is nanoparticles of several nm to several tens of nm, and the volume expansion at the time of charge / discharge is very small, so that it can be suitably used in the present invention. it can. On the other hand, when disproportionation occurs due to the thermal history and the area ratio exceeds 1.1, silicon particles tend to increase and the volume expansion tends to increase. Silicon is used.
酸化珪素はさらに粉砕して酸化珪素粒子とする。なお、粒子径はレーザー回折散乱式粒度分布測定法により、その粒子の全体積を100%として累積カーブを求めたとき、その累積カーブが10%、50%、90%となる点の粒子径をそれぞれ10%径、50%径、90%径(μm)として評価する。本発明においては、50%径の累積中位径D50(メジアン径)を用いた。本発明の酸化珪素粒子は、メジアン径D50が0.1〜50μmが好ましく、1〜20μmがより好ましい。メジアン径D50が小さすぎると比表面積が大きく、負極膜密度が小さくなりすぎる場合があり、メジアン径D50が大きすぎると負極膜を貫通してショートする原因となるおそれがある。 The silicon oxide is further pulverized into silicon oxide particles. The particle diameter is determined by the laser diffraction / scattering particle size distribution measurement method, and when the cumulative curve is obtained by setting the total volume of the particle to 100%, the particle diameter at the point where the cumulative curve becomes 10%, 50%, and 90%. The 10% diameter, 50% diameter, and 90% diameter (μm) are evaluated. In the present invention, a cumulative median diameter D 50 (median diameter) of 50% diameter was used. The silicon oxide particles of the present invention preferably have a median diameter D 50 of 0.1 to 50 μm, more preferably 1 to 20 μm. Median diameter D 50 is too the specific surface area is large small, sometimes negative electrode film density is too small, which may cause a short circuit through the negative electrode film when the median diameter D 50 is too large.
酸化珪素粒子を所定の粒子径とするためには、よく知られた粉砕機と分級機が用いられる。粉砕機は、例えば、ボール、ビーズ等の粉砕媒体を運動させ、その運動エネルギーによる衝撃力や摩擦力、圧縮力を利用して被砕物を粉砕するボールミル、媒体撹拌ミルや、ローラによる圧縮力を利用して粉砕を行うローラミルや、被砕物を高速で内張材に衝突もしくは粒子相互に衝突させ、その衝撃による衝撃力によって粉砕を行うジェットミルや、ハンマー、ブレード、ピン等を固設したローターの回転による衝撃力を利用して被砕物を粉砕するハンマーミル、ピンミル、ディスクミルや、剪断力を利用するコロイドミルや高圧湿式対向衝突式分散機「アルティマイザー」等が用いられる。粉砕は、湿式、乾式共に用いられる。また、粉砕後に粒度分布を整えるため、乾式分級や湿式分級もしくはふるい分け分級が用いられる。乾式分級は、主として気流を用い、分散、分離(細粒子と粗粒子の分離)、捕集(固体と気体の分離)、排出のプロセスが逐次もしくは同時に行われ、粒子相互間の干渉、粒子の形状、気流の流れの乱れ、速度分布、静電気の影響等で分級効率を低下させないように、分級をする前に前処理(水分、分散性、湿度等の調整)を行うか、使用される気流の水分や酸素濃度を調整して用いられる。また、乾式で分級機が一体となっているタイプでは、一度に粉砕、分級が行われ、所望の粒度分布とすることが可能となる。 In order to make the silicon oxide particles have a predetermined particle size, a well-known pulverizer and classifier are used. The pulverizer, for example, moves the grinding media such as balls and beads, and uses the impact force, friction force, and compression force due to the kinetic energy to pulverize the material to be crushed, the media agitation mill, and the compression force by the roller. A roller mill that uses pulverization, a jet mill that makes crushed objects collide with the lining material or collide with each other at high speed, and pulverizes by the impact force of the impact, and a rotor with a fixed hammer, blade, pin, etc. A hammer mill, a pin mill, a disk mill, a colloid mill using a shearing force, a high-pressure wet opposed collision disperser “Ultimizer”, or the like is used. For pulverization, both wet and dry processes are used. In order to adjust the particle size distribution after pulverization, dry classification, wet classification or sieving classification is used. In the dry classification, the process of dispersion, separation (separation of fine particles and coarse particles), collection (separation of solid and gas), and discharge are performed sequentially or simultaneously, mainly using air flow. Prior to classification (adjustment of moisture, dispersibility, humidity, etc.) or airflow to be used so as not to reduce the classification efficiency due to the shape, turbulence of the airflow, velocity distribution, static electricity, etc. It is used by adjusting the moisture and oxygen concentration. Further, in a dry type in which a classifier is integrated, pulverization and classification are performed at a time, and a desired particle size distribution can be obtained.
被覆酸化珪素粒子は酸化珪素粒子の表面を黒鉛皮膜で被覆したものであり、本発明においては、酸化珪素粒子の表面を皮膜する黒鉛の種類及びその割合を特定範囲にし、被覆酸化珪素粒子の黒鉛皮膜が、ラマンスペクトル分析において、1330cm-1と1580cm-1に散乱ピークを有し、それらの強度比I1330/I1580が1.5<I1330/I1580<3.0とすることが重要である。一般的に黒鉛材は三つの同素体すなわちダイヤモンド、グラファイト(黒鉛)、アモルファスカーボン(無定形炭素)に分けられる。これら黒鉛材料はそれぞれ特徴的な物性を有している。すなわち、ダイヤモンドは高強度、高密度、高絶縁性であり、グラファイトは電気伝導性に優れている。本発明では酸化珪素粒子の表面を被覆する黒鉛材として上記ダイヤモンド構造を有する黒鉛材とグラファイト構造を有する黒鉛材の割合を最適化することで上記それぞれの特徴が最適化され、結果として充放電時に伴う電極材料の膨張・収縮による電極破壊を防止でき、かつ導電ネットワークを有する負極材となし得る。 The coated silicon oxide particles are obtained by coating the surface of the silicon oxide particles with a graphite film. In the present invention, the type and ratio of graphite coating the surface of the silicon oxide particles are within a specific range, and the graphite of the coated silicon oxide particles. coating, in the Raman spectrum analysis, have a scattering peak at 1330 cm -1 and 1580 cm -1, important that their intensity ratio I 1330 / I 1580 is a 1.5 <I 1330 / I 1580 < 3.0 It is. Generally, graphite materials are divided into three allotropes, namely diamond, graphite (graphite), and amorphous carbon (amorphous carbon). Each of these graphite materials has characteristic physical properties. That is, diamond has high strength, high density, and high insulation, and graphite has excellent electrical conductivity. In the present invention, the above characteristics are optimized by optimizing the ratio of the graphite material having the diamond structure and the graphite material having the graphite structure as the graphite material covering the surface of the silicon oxide particles. Electrode destruction due to expansion and contraction of the accompanying electrode material can be prevented and a negative electrode material having a conductive network can be obtained.
ここで、ダイヤモンド構造を有する黒鉛材とグラファイト構造を有する黒鉛材の割合は顕微ラマン分析(すなわち、ラマン分光分析)で得られるラマンスペクトルにより求めることができる。すなわち、ダイヤモンドはラマンシフトが1330cm-1、グラファイトはラマンシフトが1580cm-1に鋭い散乱ピークを示し、その強度比により簡易的にダイヤモンド構造を有する黒鉛材とグラファイト構造を有する黒鉛材の割合を求めることができる。 Here, the ratio between the graphite material having a diamond structure and the graphite material having a graphite structure can be obtained from a Raman spectrum obtained by microscopic Raman analysis (ie, Raman spectroscopic analysis). That is, diamond has a sharp scattering peak with a Raman shift of 1330 cm −1 and graphite with a Raman shift of 1580 cm −1 , and the ratio of the graphite material having the diamond structure and the graphite material having the graphite structure is simply determined by the intensity ratio. be able to.
本発明者らの知見では、ラマンシフトが1330cm-1の散乱ピークとラマンシフトが1580cm-1の散乱ピークの強度比I1330/I1580が1.5<I1330/I1580<3.0、好ましくは1.7<I1330/I1580<2.5の範囲の黒鉛皮膜を有する酸化珪素をリチウムイオン二次電池負極材として用いた場合、電池特性が良好なリチウムイオン二次電池が得られる。 The findings of the present inventors, an intensity ratio I 1330 / I 1580 of the scattering peak of scattering peak and the Raman shift of Raman shift 1330 cm -1 is 1580 cm -1 is 1.5 <I 1330 / I 1580 < 3.0, Preferably, when silicon oxide having a graphite film in the range of 1.7 <I 1330 / I 1580 <2.5 is used as a negative electrode material for a lithium ion secondary battery, a lithium ion secondary battery having good battery characteristics can be obtained. .
強度比I1330/I1580が1.5以下であると、グラファイト構造黒鉛材の割合が多く、膜の強度が低下することで、充放電時に伴う電極材料の膨張・収縮による電極破壊が起こり、電池容量の低下及び繰り返し使用時のサイクル性が低下する。逆に、強度比I1330/I1580が3.0以上であるとダイヤモンド構造黒鉛材の割合が大きくなり、導電性が不足し、サイクル性が低下してしまう。 If the strength ratio I 1330 / I 1580 is 1.5 or less, the ratio of the graphite-structured graphite material is large, and the strength of the film is reduced, so that electrode destruction occurs due to expansion / contraction of the electrode material during charge / discharge, The battery capacity decreases and the cycle performance during repeated use decreases. On the contrary, when the strength ratio I 1330 / I 1580 is 3.0 or more, the ratio of the diamond structure graphite material is increased, the conductivity is insufficient, and the cycle performance is lowered.
上記の強度比を有する黒鉛剤で被覆された被覆酸化珪素粒子は、例えば、酸化珪素粒子の表面を、有機物ガス及び/又は蒸気中、50〜30000Paの減圧下、600〜1100℃で化学蒸着することにより得ることができる。上記圧力は、100〜20000Paが好ましく、1000〜20000Paがより好ましい。減圧度が50Paより小さいと、ダイヤモンド構造を有する黒鉛材の割合が大きくなり、リチウムイオン二次電池負極材として用いた場合、導電性が不足し、サイクル性が低下するおそれがある。逆に30000Paより大きいと、グラファイト構造を有する黒鉛材の割合が大きくなり過ぎて、リチウムイオン二次電池負極材として用いた場合、電池容量の低下に加えてサイクル性が低下するおそれがある。上記温度は800〜1050℃がより好ましい。処理温度が600℃より低いと、長時間の処理が必要となるおそれがある。逆に1100℃より高いと、化学蒸着処理により粒子同士が融着、凝集を起こす可能性があり、凝集面で導電性皮膜が形成されず、リチウムイオン二次電池負極材として用いた場合、サイクル性能が低下するおそれがある。また、酸化珪素の不均化反応が進行し、上記固体NMRでのシグナル比が1.1を超えるおそれがある。なお、処理時間は目的とする黒鉛被覆量、処理温度、有機物ガスの濃度(流速)や導入量等によって適宜選定されるが、通常、1〜10時間、特に2〜7時間程度が経済的にも効率的である。 The coated silicon oxide particles coated with the graphite agent having the above strength ratio are, for example, chemically vapor-deposited on the surface of the silicon oxide particles at 600 to 1100 ° C. under reduced pressure of 50 to 30000 Pa in an organic gas and / or vapor. Can be obtained. The pressure is preferably 100 to 20000 Pa, more preferably 1000 to 20000 Pa. When the degree of vacuum is less than 50 Pa, the proportion of the graphite material having a diamond structure increases, and when used as a negative electrode material for a lithium ion secondary battery, the conductivity is insufficient and the cycle performance may be reduced. On the other hand, if it is higher than 30000 Pa, the ratio of the graphite material having a graphite structure becomes too large, and when used as a negative electrode material for a lithium ion secondary battery, there is a possibility that the cycle performance may be lowered in addition to the reduction in battery capacity. As for the said temperature, 800-1050 degreeC is more preferable. When the processing temperature is lower than 600 ° C., a long-time processing may be required. On the other hand, if the temperature is higher than 1100 ° C., particles may be fused and aggregated by chemical vapor deposition, and a conductive film is not formed on the agglomerated surface, and when used as a negative electrode material for a lithium ion secondary battery, Performance may be reduced. Further, the disproportionation reaction of silicon oxide proceeds, and the signal ratio in the solid state NMR may exceed 1.1. The treatment time is appropriately selected according to the target graphite coating amount, treatment temperature, concentration (flow rate) of organic gas, introduction amount, etc., but usually 1 to 10 hours, particularly about 2 to 7 hours is economical. Is also efficient.
黒鉛被覆量は特に限定されないが、被覆酸化珪素粒子中に1〜50質量%が好ましく、5〜20質量%がより好ましい。炭素量が多いと酸化珪素の特徴である高い電池容量を減じるおそれがあり、一方、少ないと炭素被覆にばらつきが出るとともに、十分な伝導性を得ることができないおそれがある。 The graphite coating amount is not particularly limited, but is preferably 1 to 50% by mass and more preferably 5 to 20% by mass in the coated silicon oxide particles. If the amount of carbon is large, the high battery capacity that is characteristic of silicon oxide may be reduced. On the other hand, if the amount of carbon is small, the carbon coating may vary, and sufficient conductivity may not be obtained.
本発明における有機物ガスを発生する原料として用いられる有機物としては、特に非酸性雰囲気下において、上記熱処理温度で熱分解して炭素(黒鉛)を生成し得るものが選択され、例えば、メタン、エタン、エチレン、アセチレン、プロパン、ブタン、ブテン、ペンタン、イソブタン、ヘキサン等の炭化水素の単独又は混合物、ベンゼン、トルエン、キシレン、スチレン、エチルベンゼン、ジフェニルメタン、ナフタレン、フェノール、クレゾール、ニトロベンゼン、クロルベンゼン、インデン、クマロン、ピリジン、アントラセン、フェナントレン等の1環〜3環の芳香族炭化水素又はこれらの混合物が挙げられる。また、タール蒸留工程で得られるガス軽油、クレオソート油、アントラセン油、ナフサ分解タール油も単独又は混合物も用いることができる。 As an organic substance used as a raw material for generating an organic gas in the present invention, an organic substance that can be thermally decomposed at the above heat treatment temperature to generate carbon (graphite) is selected, particularly in a non-acidic atmosphere. For example, methane, ethane, A single or mixture of hydrocarbons such as ethylene, acetylene, propane, butane, butene, pentane, isobutane, hexane, benzene, toluene, xylene, styrene, ethylbenzene, diphenylmethane, naphthalene, phenol, cresol, nitrobenzene, chlorobenzene, indene, coumarone , Pyridine, anthracene, phenanthrene, and the like, and monocyclic to tricyclic aromatic hydrocarbons or a mixture thereof. In addition, gas gas oil, creosote oil, anthracene oil, and naphtha cracked tar oil obtained in the tar distillation step can be used alone or as a mixture.
被覆酸化珪素粒子の平均粒子径は酸化珪素粒子と同様0.1〜50μmが好ましく、1〜20μmがより好ましい。なお、平均粒子径は酸化珪素粒子と同様のレーザー回折散乱式粒度分布測定法による値である。 The average particle diameter of the coated silicon oxide particles is preferably from 0.1 to 50 μm, more preferably from 1 to 20 μm, like the silicon oxide particles. The average particle diameter is a value obtained by a laser diffraction / scattering particle size distribution measurement method similar to that for silicon oxide particles.
本発明の活物質中における被覆酸化珪素粒子の配合量は50〜99質量%が好ましく、70〜95質量%がより好ましく、70〜90質量%がさらに好ましい。 The blending amount of the coated silicon oxide particles in the active material of the present invention is preferably 50 to 99% by mass, more preferably 70 to 95% by mass, and further preferably 70 to 90% by mass.
(A2)珪素粒子
珪素には結晶性の違いにより単結晶珪素、多結晶珪素、非晶質珪素又は純度の違いにより金属珪素と呼ばれるケミカルグレード珪素、冶金グレード珪素が知られている。単結晶珪素は半導体で使用される規則性を持った結晶であり、多結晶珪素は、部分的な規則性を持っている結晶である。一方、非晶質珪素は、Si原子がほとんど規則性をもたない配列をしており、網目構造をとっている点で異なるが、加熱エージングすることにより非晶質珪素を多結晶珪素とすることができる。
(A2) Silicon particles As the silicon, there are known single-crystal silicon, polycrystalline silicon, amorphous silicon due to the difference in crystallinity, and chemical grade silicon and metallurgical grade silicon called metal silicon due to differences in purity. Single crystal silicon is a crystal having regularity used in a semiconductor, and polycrystalline silicon is a crystal having partial regularity. Amorphous silicon, on the other hand, differs in that the Si atoms are arranged with little regularity and have a network structure, but amorphous silicon is made polycrystalline silicon by heat aging. be able to.
本発明の珪素粒子は上記いずれの珪素であってもよく、1種単独で又は2種以上を適宜組み合わせて用いることができる。純度が高い単結晶珪素あるいは多結晶珪素が好ましく、比較的価格の安い多結晶珪素が好ましい。また、金属珪素を溶融し、一方向凝固によって不純物を偏折させ純度を向上させる方法で製造した多結晶珪素又は溶融金属珪素を急冷することで多結晶珪素を得る方法もあり、これらはモノシランやクロロシランから製造される多結晶珪素より安価であることが多く、好適に使用することができる。また、純度の低いケミカルグレード珪素であっても、酸処理を行うことで不純物であるアルミニウム、鉄、カルシウム等が溶出除去することができるためより安価な原料として使用することができる。 The silicon particles of the present invention may be any of the above silicons, and may be used alone or in combination of two or more. Single crystal silicon or polycrystalline silicon with high purity is preferable, and polycrystalline silicon with relatively low price is preferable. There is also a method of obtaining polycrystalline silicon by rapidly cooling polycrystalline silicon or molten metal silicon produced by melting metal silicon and deflecting impurities by unidirectional solidification to improve purity. It is often cheaper than polycrystalline silicon produced from chlorosilane, and can be suitably used. Moreover, even chemical grade silicon with low purity can be used as a cheaper raw material because aluminum, iron, calcium, and the like, which are impurities, can be eluted and removed by acid treatment.
珪素粒子は酸化珪素粒子と同様に炭素蒸着されているものであってもよく、炭素蒸着することにより、導電性が向上し、サイクル特性及び電池容量の向上が期待できる。黒鉛被覆量は特に限定されないが、被覆珪素粒子中に0.1〜20質量%が好ましく、1〜10質量%がより好ましい。 The silicon particles may be carbon-deposited in the same manner as the silicon oxide particles, and by conducting carbon deposition, the conductivity is improved, and the cycle characteristics and battery capacity can be expected to be improved. Although the graphite coating amount is not particularly limited, it is preferably 0.1 to 20% by mass in the coated silicon particles, and more preferably 1 to 10% by mass.
珪素粒子は所望の粒子径に粉砕されて使用される。粉砕方法は酸化珪素と同様に行うことができるが、その粒子径はメジアン径D50が0.1〜50μmが好ましく、0.1〜10μmがより好ましい。珪素粒子の粒子径が大きすぎると体積膨張が増加するおそれがある。なお、測定法は酸化珪素粒子と同様である。 Silicon particles are used after being pulverized to a desired particle size. The pulverization method can be carried out in the same manner as silicon oxide, but the particle diameter is preferably 0.1 to 50 μm, more preferably 0.1 to 10 μm in median diameter D 50 . If the particle diameter of the silicon particles is too large, the volume expansion may increase. The measurement method is the same as that for silicon oxide particles.
本発明の活物質中の珪素粒子の配合量は1〜50質量%であり、5〜30質量%が好ましく、10〜30質量%がより好ましい。活物質中の珪素粒子の配合量が1質量%未満であると初期効率向上の効果が見られず、一方、50質量%を超えると、充電後の低い体積膨張率を維持することが困難となる。 The compounding quantity of the silicon particle in the active material of this invention is 1-50 mass%, 5-30 mass% is preferable and 10-30 mass% is more preferable. Amount of the silicon particles in the active material is not observed the effect of the initial efficiency is less than 1 wt%, whereas, it is difficult to maintain more than 50 wt%, the low expansion coefficient after charging It becomes.
活物質(A)の配合量は、負極材中に50〜98質量%が好ましく、75〜96質量%がより好ましく、80〜96質量%がさらに好ましい。 The amount of the active material (A) is preferably 50 to 98 wt% in the negative electrode material, more preferably 75 to 96 wt%, more preferably 80 to 96 wt%.
[結着剤(B)]
本発明に用いられる結着剤としては、ポリイミド樹脂が好ましく、芳香族ポリイミド樹脂がより好ましい。結着剤としてポリイミド樹脂を用いることによって、集電体との密着性に優れ、また初期充放電効率が高く、充放電時の体積変化が緩和されて繰り返しによるサイクル特性及び効率が良好な非水電解質二次電池が得られる。また、芳香族ポリイミド樹脂は耐溶剤性に優れ、集電体からの剥離や活物質の分離を抑制することができる。なお、結着剤は1種単独で又は2種以上を適宜組み合わせて用いることができる。
[Binder (B)]
As a binder used for this invention, a polyimide resin is preferable and an aromatic polyimide resin is more preferable. By using a polyimide resin as a binder, non-water is excellent in adhesion to the current collector, high in initial charge / discharge efficiency, relaxed in volume change during charge / discharge, and has good cycle characteristics and efficiency due to repetition. An electrolyte secondary battery is obtained. In addition, the aromatic polyimide resin is excellent in solvent resistance and can suppress separation from the current collector and separation of the active material. In addition, a binder can be used individually by 1 type or in combination of 2 or more types as appropriate.
芳香族ポリイミド樹脂は、一般に有機溶剤に対して難溶性であり、特に電解液に対して膨潤あるいは溶解しないことが必要であり、一般的に高沸点の有機溶剤、例えばクレゾール等に溶解するのみである。従って、電極ペーストの作製には、ポリイミドの前駆体であって、種々の有機溶剤、例えばジメチルホルムアミド、ジメチルアセトアミド、N−メチルピロリドン、酢酸エチル、アセトン、メチルエチルケトン、メチルイソブチルケトン、ジオキソランに比較的易溶であるポリアミック酸の状態で添加し、300℃以上の温度で長時間加熱処理することにより、脱水、イミド化させて結着剤とするとよい。 Aromatic polyimide resins are generally poorly soluble in organic solvents, and in particular need not swell or dissolve in the electrolyte, and generally only dissolve in high-boiling organic solvents such as cresol. is there. Therefore, the electrode paste is a precursor of polyimide and relatively easy to use in various organic solvents such as dimethylformamide, dimethylacetamide, N-methylpyrrolidone, ethyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, and dioxolane. It is good to add in the state of the melted polyamic acid and heat-treat at a temperature of 300 ° C. or higher for a long time, thereby dehydrating and imidizing to form a binder.
この場合、芳香族ポリイミド樹脂としては、テトラカルボン酸二無水物とジアミンより構成される基本骨格を有するが、具体例としては、ピロメリット酸二無水物、ベンゾフェノンテトラカルボン酸二無水物及びビフェニルテトラカルボン酸二無水物等の芳香族テトラカルボン酸二無水物、シクロブタンテトラカルボン酸二無水物、シクロペンタンテトラカルボン酸二無水物及びシクロヘキサンテトラカルボン酸二無水物等の脂環式テトラカルボン酸二無水物、ブタンテトラカルボン酸二無水物等の脂肪族テトラカルボン酸二無水物等が挙げられ、1種単独で又は2種以上を適宜組み合わせて用いることができる。 In this case, the aromatic polyimide resin has a basic skeleton composed of tetracarboxylic dianhydride and diamine. Specific examples thereof include pyromellitic dianhydride, benzophenone tetracarboxylic dianhydride and biphenyltetra. Arocyclic tetracarboxylic dianhydrides such as aromatic tetracarboxylic dianhydrides such as carboxylic dianhydrides, cyclobutane tetracarboxylic dianhydrides, cyclopentane tetracarboxylic dianhydrides and cyclohexane tetracarboxylic dianhydrides And aliphatic tetracarboxylic dianhydrides such as butanetetracarboxylic dianhydride can be used alone or in combination of two or more.
また、ジアミンとしては、p−フェニレンジアミン、m−フェニレンジアミン、4,4’−ジアミノジフェニルメタン、4,4’−ジアミノジフェニルエーテル、2,2’−ジアミノジフェニルプロパン、4,4’−ジアミノジフェニルスルホン、4,4’−ジアミノベンゾフェノン、2,3−ジアミノナフタレン、1,3−ビス(4−アミノフェノキシ)ベンゼン、1,4−ビス(4−アミノフェノキシ)ベンゼン、4,4’−ジ(4−アミノフェノキシ)ジフェニルスルホン、2,2’−ビス[4−(4−アミノフェノキシ)フェニル]プロパン等の芳香族ジアミン、脂環式ジアミン、脂肪族ジアミン等が挙げられ、1種単独で又は2種以上を適宜組み合わせて用いることができる。 Examples of the diamine include p-phenylenediamine, m-phenylenediamine, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenyl ether, 2,2′-diaminodiphenylpropane, 4,4′-diaminodiphenylsulfone, 4,4′-diaminobenzophenone, 2,3-diaminonaphthalene, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 4,4′-di (4- Aminophenoxy) diphenyl sulfone, aromatic diamines such as 2,2′-bis [4- (4-aminophenoxy) phenyl] propane, alicyclic diamines, aliphatic diamines, and the like are included, one kind alone or two kinds The above can be used in appropriate combination.
ポリアミック酸中間体の合成方法としては、通常は溶液重合法が用いられる。溶液重合法に使用される溶剤としては、N,N’−ジメチルホルムアミド、N,N’−ジメチルアセトアミド、N−メチル−2−ピロリドン、N−メチルカプロラクタム、ジメチルスルホキシド、テトラメチル尿素、ピリジン、ジメチルスルホン、ヘキサメチルホスホルアミド及びブチロラクトン等が挙げられ、1種単独で又は2種以上を適宜組み合わせて用いることができる。 As a method for synthesizing the polyamic acid intermediate, a solution polymerization method is usually used. Solvents used in the solution polymerization method include N, N′-dimethylformamide, N, N′-dimethylacetamide, N-methyl-2-pyrrolidone, N-methylcaprolactam, dimethyl sulfoxide, tetramethylurea, pyridine, dimethyl Examples include sulfone, hexamethylphosphoramide, and butyrolactone, which can be used alone or in appropriate combination of two or more.
反応温度は、通常、−20〜150℃の範囲内であるが、−5〜100℃の範囲が好ましい。さらに、ポリアミック酸中間体をポリイミド樹脂に転化するには、通常は、加熱により脱水閉環する方法がとられる。この加熱脱水閉環温度は140〜400℃、好ましくは150〜250℃の任意の温度を選択できる。この脱水閉環に要する時間は、上記反応温度にもよるが30秒間〜10時間、好ましくは5分間〜5時間が適当である。 The reaction temperature is usually in the range of −20 to 150 ° C., preferably in the range of −5 to 100 ° C. Furthermore, in order to convert the polyamic acid intermediate into a polyimide resin, a method of dehydrating and ring-closing by heating is usually employed. The heating and dehydration ring-closing temperature can be selected from 140 to 400 ° C, preferably 150 to 250 ° C. The time required for this dehydration and ring closure is 30 seconds to 10 hours, preferably 5 minutes to 5 hours, although it depends on the reaction temperature.
このようなポリイミド樹脂としては、ポリイミド樹脂粉末のほか、ポリイミド前駆体のN−メチルピロリドン溶液等が入手できるが、例えば、U−ワニスA、U−ワニスS、UIP−R、UIP−S(宇部興産(株)製)やKAYAFLEX KPI−121(日本化薬(株)製)、リカコートSN−20、PN−20、EN−20(新日本理化(株)製)が挙げられる。 Examples of such polyimide resin include polyimide resin powder and N-methylpyrrolidone solution of a polyimide precursor. For example, U-varnish A, U-varnish S, UIP-R, UIP-S (Ube) Kosan Co., Ltd.), KAYAFLEX KPI-121 (Nippon Kayaku Co., Ltd.), Rika Coat SN-20, PN-20, EN-20 (Shin Nihon Rika Co., Ltd.).
上記結着剤の配合量は、負極材中に1〜20質量%であり、3〜15質量%が好ましい。結着剤が少なすぎると負極活物質が分離し、多すぎると空隙率が減少して絶縁膜が厚くなり、Liイオンの移動を阻害する場合がある。 The amount of the binder is 1 to 20 mass% in the negative electrode material is preferably 3 to 15 mass%. When the amount of the binder is too small, the negative electrode active material is separated. When the amount is too large, the porosity is decreased and the insulating film becomes thick, which may inhibit the movement of Li ions.
[非水電解質二次電池用負極材]
非水電解質二次電池用負極材は、被覆酸化珪素粒子(A1)及び珪素粒子(A2)とからなる活物質(A)と、結着剤(B)1〜20質量%とを含有する非水電解質二次電池用負極材であって、被覆酸化珪素粒子(A1)、珪素粒子(A2)、及び結着剤(B)を混合することにより得ることができる。被覆酸化珪素粒子と珪素粒子との混合物を、予め水又はN−メチル−2−ピロリドン等の溶剤に分散させた後、結着剤を配合してもよい。なお、本発明においては、酸化珪素粒子から負極材が得られるまでの全工程において、酸化珪素粒子及び被覆酸化珪素粒子が1100℃以下、好ましくは1050℃以下の雰囲気下であることが好ましい。
[Negative electrode material for non-aqueous electrolyte secondary battery]
The negative electrode material for a non-aqueous electrolyte secondary battery contains an active material (A) composed of coated silicon oxide particles (A1) and silicon particles (A2), and a binder (B) of 1 to 20% by mass. A negative electrode material for a water electrolyte secondary battery, which can be obtained by mixing coated silicon oxide particles (A1), silicon particles (A2), and a binder (B). A mixture of the coated silicon oxide particles and the silicon particles may be previously dispersed in water or a solvent such as N-methyl-2-pyrrolidone, and then a binder may be blended. In the present invention, it is preferable that the silicon oxide particles and the coated silicon oxide particles are in an atmosphere of 1100 ° C. or lower, preferably 1050 ° C. or lower, in all steps from obtaining the negative electrode material from the silicon oxide particles.
負極材には、上記成分以外に黒鉛等の導電剤を添加することができる。この場合、導電剤の種類は特に限定されず、構成された電池において、分解や変質を起こさない電子伝導性の材料であればよい。具体的にはAl、Ti、Fe、Ni、Cu、Zn、Ag、SnSi等の金属粉末や金属繊維、天然黒鉛、人造黒鉛、各種のコークス粉末、メソフェーズ炭素、気相成長炭素繊維、ピッチ系炭素繊維、PAN系炭素繊維、各種の樹脂焼成体等の黒鉛等を用いることができる。これらの導電剤は、予め水又はN−メチル−2−ピロリドン等の溶剤の分散物を作製し、添加することで、珪素粒子に均一に付着、分散した電極ペーストを作製することができることから、上記溶剤分散物として添加することが好ましい。なお、導電剤は上記溶剤に公知の界面活性剤を用いて分散を行うことができる。また、導電剤に用いる溶剤は、結着剤に用いる溶剤と同一のものであることが望ましい。 In addition to the above components, a conductive agent such as graphite can be added to the negative electrode material. In this case, the kind of the conductive agent is not particularly limited as long as it is an electron conductive material that does not cause decomposition or alteration in the configured battery. Specifically, metal powder and metal fibers such as Al, Ti, Fe, Ni, Cu, Zn, Ag, SnSi, natural graphite, artificial graphite, various coke powders, mesophase carbon, vapor grown carbon fiber, pitch-based carbon Fiber, PAN-based carbon fiber, graphite such as various resin fired bodies, and the like can be used. Since these conductive agents are prepared by adding a dispersion of water or a solvent such as N-methyl-2-pyrrolidone in advance, an electrode paste uniformly attached and dispersed on silicon particles can be prepared. It is preferable to add as the solvent dispersion. The conductive agent can be dispersed in the solvent using a known surfactant. The solvent used for the conductive agent is preferably the same as the solvent used for the binder.
導電剤の配合量の上限は負極材中に50質量%以下(負極材あたりの電池容量は概ね1000mAH/g以上となる)が好ましく、1〜30質量%がより好ましく、1〜10質量%がさらに好ましい。導電剤量が少ないと、負極材の導電性に乏しい場合があり、初期抵抗が高くなる傾向がある。一方、導電剤量の増加は電池容量の低下につながるおそれがある。 The upper limit of the amount of the conductive agent is preferably 50% by mass or less in the negative electrode material (the battery capacity per negative electrode material is approximately 1000 mAH / g or more), more preferably 1 to 30% by mass, and more preferably 1 to 10% by mass. Further preferred. When the amount of the conductive agent is small, the conductivity of the negative electrode material may be poor and the initial resistance tends to be high. On the other hand, an increase in the amount of conductive agent may lead to a decrease in battery capacity.
また、上記ポリイミド樹脂結着剤の他に、粘度調整剤としてカルボキシメチルセルロース、ポリアクリル酸ソーダ、その他のアクリル系ポリマー又は脂肪酸エステル等を添加してもよい。 In addition to the polyimide resin binder, carboxymethyl cellulose, polyacrylic acid soda, other acrylic polymers or fatty acid esters may be added as a viscosity modifier.
[負極]
本発明の非水電解質二次電池負極材は、例えば以下のように負極(成型体)とすることができる。上記活物質(A)と、結着剤(B)と、必要に応じて導電剤と、その他の添加剤とに、N−メチルピロリドン又は水等の結着剤の溶解、分散に適した溶剤を混練してペースト状の合剤とし、この合剤を集電体のシートに塗布する。この場合、集電体としては、銅箔、ニッケル箔等、通常、負極の集電体として使用されている材料であれば、特に厚さ、表面処理の制限なく使用することができる。なお、合剤をシート状に成形する成形方法は特に限定されず、公知の方法を用いることができる。本発明の負極材を含む負極は、充電後の体積が充電前の2倍未満が好ましく、1.0〜1.8倍がより好ましく、1.0〜1.6倍がさらに好ましい。このような充電後の体積膨張の少ない負極は、本発明の負極材を用いることで達成することができる。なお、本発明において充電後の体積(V2)が充電前の体積(V1)の2倍未満、つまり(V2)/(V1)が2未満となる場合の測定条件は、実施例で記載の条件である。
[Negative electrode]
The negative electrode material of the nonaqueous electrolyte secondary battery of the present invention can be made into a negative electrode (molded body) as follows, for example. A solvent suitable for dissolving and dispersing the binder such as N-methylpyrrolidone or water in the active material (A), the binder (B), if necessary, a conductive agent and other additives. Are mixed into a paste-like mixture, and this mixture is applied to the sheet of the current collector. In this case, as the current collector, any material that is usually used as a negative electrode current collector, such as a copper foil or a nickel foil, can be used without any particular limitation on thickness and surface treatment. In addition, the shaping | molding method which shape | molds a mixture into a sheet form is not specifically limited, A well-known method can be used. Negative electrode containing a negative electrode material of the present invention is preferably less than two times of charging before volume after charging, more preferably 1.0 to 1.8 times, more preferably 1.0 to 1.6 times. Negative little volume expansion after such charging can be achieved by using the negative electrode material of the present invention. The measurement conditions when less than twice the volume after charging in the present invention (V2) GaTakashi electrostatic previous volume (V1), that is the (V2) / (V1) is less than 2, described in Example This is the condition.
[非水電解質二次電池]
このようにして得られた負極(成型体)を用いることにより、非水電解質二次電池用負極、正極、セパレーター及び非水電解質を備えた非水電解質二次電池を製造することができ、特にリチウムイオン二次電池とすると好適である。非水電解質二次電池は、上記負極材を用いる点に特徴を有し、その他の正極、セパレーター、非水電解質溶液等の材料及び電池形状等は限定されない。
[Nonaqueous electrolyte secondary battery]
By using the negative electrode (molded body) thus obtained, a non-aqueous electrolyte secondary battery including a negative electrode for a non-aqueous electrolyte secondary battery, a positive electrode, a separator, and a non-aqueous electrolyte can be manufactured. A lithium ion secondary battery is preferable. The nonaqueous electrolyte secondary battery is characterized in that the negative electrode material is used, and other materials such as the positive electrode, the separator, and the nonaqueous electrolyte solution, the battery shape, and the like are not limited.
正極活物質としては、リチウムイオンを吸蔵及び離脱することが可能な酸化物あるいは硫化物等が挙げられ、1種単独で又は2種以上を適宜組み合わせて用いることができる。具体的には、TiS2、MoS2、NbS2、ZrS2、VS2、V2O5、MoO3、Mg(V3O8)2等のリチウムを含有しない金属硫化物もしくは酸化物、又はリチウム及びリチウムを含有するリチウム複合酸化物等が挙げられ、NbSe2等の複合金属等も用いられる。中でも、エネルギー密度を高くするには、LipMetO2を主体とするリチウム複合酸化物が好ましい。なお、Metは、コバルト、ニッケル、鉄及びマンガンのうちの1種以上が好ましく、pは、通常、0.05≦p≦1.10の範囲内の値である。このようなリチウム複合酸化物の具体例としては、層構造を持つLiCoO2、LiNiO2、LiFeO2、LiqNirCo1-rO2(但し、q及びrの値は電池の充放電状態によって異なり、通常、0<q<1、0.7<r≦1)、スピネル構造のLiMn2O4及び斜方晶LiMnO2等が挙げられる。さらに高電圧対応型として置換スピネルマンガン化合物としてLiMetsMn1-sO4(0<s<1)も使用されており、この場合のMetはチタン、クロム、鉄、コバルト、ニッケル、銅及び亜鉛等が挙げられる。 Examples of the positive electrode active material include oxides or sulfides capable of inserting and extracting lithium ions, and these can be used singly or in appropriate combination of two or more. Specifically, TiS 2 , MoS 2 , NbS 2 , ZrS 2 , VS 2 , V 2 O 5 , MoO 3, Mg (V 3 O 8 ) 2 or other metal sulfide or oxide not containing lithium, or Examples thereof include lithium and lithium composite oxides containing lithium, and composite metals such as NbSe 2 are also used. Among these, in order to increase the energy density, a lithium composite oxide mainly composed of Li p MetO 2 is preferable. Met is preferably one or more of cobalt, nickel, iron and manganese, and p is usually a value in the range of 0.05 ≦ p ≦ 1.10. Specific examples of the lithium composite oxide, LiCoO 2, LiNiO 2, LiFeO 2, Li q Ni r Co 1-r O 2 ( where, the values of q and r is a charge-discharge state of the battery having the layer structure Usually, 0 <q <1, 0.7 <r ≦ 1), spinel-structured LiMn 2 O 4, orthorhombic LiMnO 2, and the like. Furthermore, LiMet s Mn 1-s O 4 (0 <s <1) is also used as a substituted spinel manganese compound for high voltage applications, where Met is titanium, chromium, iron, cobalt, nickel, copper and zinc. Etc.
なお、上記のリチウム複合酸化物は、例えば、リチウムの炭酸塩、硝酸塩、酸化物あるいは水酸化物と、遷移金属の炭酸塩、硝酸塩、酸化物あるいは水酸化物とを所望の組成に応じて粉砕混合し、酸素雰囲気中において600〜1,000℃の範囲内の温度で焼成することにより調製することができる。 The lithium composite oxide is obtained by, for example, grinding lithium carbonate, nitrate, oxide or hydroxide, and transition metal carbonate, nitrate, oxide or hydroxide according to a desired composition. It can prepare by mixing and baking at the temperature within the range of 600-1,000 degreeC in oxygen atmosphere.
さらに、正極活物質としては有機物も使用することができる。例示すると、ポリアセチレン、ポリピロール、ポリパラフェニレン、ポリアニリン、ポリチオフェン、ポリアセン、ポリスルフィド化合物等である。 Furthermore, an organic substance can also be used as the positive electrode active material. Illustrative examples include polyacetylene, polypyrrole, polyparaphenylene, polyaniline, polythiophene, polyacene, polysulfide compounds and the like.
以上の正極活物質は負極合材に使用した導電剤や結着剤と共に混練して集電体に塗布され、公知の方法により正極(成型体)とすることができる。 The above positive electrode active material is kneaded together with the conductive agent and binder used for the negative electrode mixture and applied to the current collector, and can be formed into a positive electrode (molded body) by a known method.
正極と負極の間に用いられるセパレーターは電解液に対して安定であり、保液性に優れていれば特に制限はないが、一般的にはポリエチレン、ポリプロピレン等のポリオレフィン及びこれらの共重合体やアラミド樹脂等の多孔質シート又は不織布が挙げられる。これらは単層あるいは多層に重ね合わせて使用してもよく、表面に金属酸化物等のセラミックスを積層してもよい。また、多孔質ガラス、セラミックス等も使用される。 The separator used between the positive electrode and the negative electrode is not particularly limited as long as it is stable with respect to the electrolytic solution and has excellent liquid retention, but in general, polyolefins such as polyethylene and polypropylene, copolymers thereof, Examples thereof include a porous sheet such as an aramid resin or a nonwoven fabric. These may be used as a single layer or multiple layers, and ceramics such as metal oxide may be laminated on the surface. Moreover, porous glass, ceramics, etc. are also used.
非水電解質としては電解質塩及び非水溶媒を含む非水電解質溶液が挙げられる。電解質塩としては、例えば、軽金属塩が挙げられる。軽金属塩にはリチウム塩、ナトリウム塩、カリウム塩等のアルカリ金属塩、マグネシウム塩、カルシウム塩等のアルカリ土類金属塩、アルミニウム塩等が挙げられ、目的に応じて1種単独で又は2種以上を適宜組み合わせて用いることができる。例えば、リチウム塩であれば、LiBF4、LiClO4、LiPF6、LiAsF6、CF3SO3Li、(CF3SO2)2NLi、C4F9SO3Li、CF3CO2Li、(CF3CO2)2NLi、C6F5SO3Li、C8F17SO3Li、(C2F5SO2)2NLi、(C4F9SO2)(CF3SO2)NLi、(FSO2C6F4)(CF3SO2)NLi、((CF3)2CHOSO2)2NLi、(CF3SO2)3CLi、(3,5−(CF3)2C6F3)4BLi、LiCF3、LiAlCl4あるいはC4BO8Liが挙げられる。 Examples of the non-aqueous electrolyte include a non-aqueous electrolyte solution containing an electrolyte salt and a non-aqueous solvent. Examples of the electrolyte salt include light metal salts. Examples of the light metal salts include alkali metal salts such as lithium salts, sodium salts, and potassium salts, alkaline earth metal salts such as magnesium salts and calcium salts, and aluminum salts. Can be used in appropriate combination. For example, in the case of a lithium salt, LiBF 4 , LiClO 4 , LiPF 6 , LiAsF 6 , CF 3 SO 3 Li, (CF 3 SO 2 ) 2 NLi, C 4 F 9 SO 3 Li, CF 3 CO 2 Li, ( CF 3 CO 2 ) 2 NLi, C 6 F 5 SO 3 Li, C 8 F 17 SO 3 Li, (C 2 F 5 SO 2 ) 2 NLi, (C 4 F 9 SO 2 ) (CF 3 SO 2 ) NLi , (FSO 2 C 6 F 4 ) (CF 3 SO 2 ) NLi, ((CF 3 ) 2 CHOSO 2 ) 2 NLi, (CF 3 SO 2 ) 3 CLi, (3,5- (CF 3 ) 2 C 6 F 3 ) 4 BLi, LiCF 3 , LiAlCl 4 or C 4 BO 8 Li.
非水電解質溶液中における電解質塩の濃度は、電気伝導度の点から、0.5〜2.0mol/Lが好ましい。なお、この電解質の温度25℃における導電率は0.01S/cm以上であることが好ましく、電解質塩の種類あるいはその濃度により調整される。 The concentration of the electrolyte salt in the nonaqueous electrolyte solution is preferably 0.5 to 2.0 mol / L from the viewpoint of electrical conductivity. The conductivity of the electrolyte at 25 ° C. is preferably 0.01 S / cm or more, and is adjusted according to the type of electrolyte salt or its concentration.
さらに、非水電解質溶液には、必要に応じて各種添加剤を添加してもよい。例えば、サイクル寿命向上を目的としたビニレンカーボネート、メチルビニレンカーボネート、エチルビニレンカーボネート、4−ビニルエチレンカーボネート等や、過充電防止を目的としたビフェニル、アルキルビフェニル、シクロヘキシルベンゼン、t−ブチルベンゼン、ジフェニルエーテル、ベンゾフラン等や、脱酸や脱水を目的とした各種カーボネート化合物、各種カルボン酸無水物、各種含窒素及び含硫黄化合物が挙げられる。 Furthermore, you may add various additives to a nonaqueous electrolyte solution as needed. For example, vinylene carbonate, methyl vinylene carbonate, ethyl vinylene carbonate, 4-vinylethylene carbonate and the like for the purpose of improving cycle life, biphenyl, alkylbiphenyl, cyclohexylbenzene, t-butylbenzene, diphenyl ether for the purpose of preventing overcharge, Examples include benzofuran, various carbonate compounds for the purpose of deoxidation and dehydration, various carboxylic acid anhydrides, various nitrogen-containing compounds, and sulfur-containing compounds.
非水溶媒としては、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−ブチロラクトン等の非プロトン性高誘電率溶媒や、ジメチルカーボネート、エチルメチルカーボネート、ジエチルカーボネート、メチルプロピルカーボネート、ジプロピルカーボネート、ジエチルエーテル、テトラヒドロフラン、1,2−ジメトキシエタン、1,2−ジエトキシエタン、1,3−ジオキソラン、スルホラン、メチルスルホラン、アセトニトリル、プロピオニトリル、アニソール、メチルアセテート等の酢酸エステル類あるいはプロピオン酸エステル類等の非プロトン性低粘度溶媒が挙げられる。これらの非プロトン性高誘電率溶媒と非プロトン性低粘度溶媒を適当な混合比で併用することが望ましい。さらには、イミダゾリウム、アンモニウム、及びピリジニウム型のカチオンを用いたイオン液体を使用することができる。対アニオンは特に限定されるものではないが、BF4 -、PF6 -、(CF3SO2)2N-等が挙げられる。イオン液体は前述の非水電解液溶媒と混合して使用することが可能である。 As non-aqueous solvent, aprotic high dielectric constant solvent such as ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl propyl carbonate, dipropyl carbonate, diethyl ether, Acetic acid esters such as tetrahydrofuran, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1,3-dioxolane, sulfolane, methylsulfolane, acetonitrile, propionitrile, anisole, methyl acetate, or propionic acid esters Examples include aprotic low viscosity solvents. It is desirable to use these aprotic high dielectric constant solvents and aprotic low viscosity solvents in combination at an appropriate mixing ratio. Furthermore, ionic liquids using imidazolium, ammonium, and pyridinium type cations can be used. The counter anion is not particularly limited, and examples thereof include BF 4 − , PF 6 − , (CF 3 SO 2 ) 2 N − and the like. The ionic liquid can be used by mixing with the non-aqueous electrolyte solvent described above.
また、非水電解質として、固体電解質、ゲル電解質等も用いることができ、シリコーンゲル、シリコーンポリエーテルゲル、アクリルゲル、シリコーンアクリルゲル、アクリロニトリルゲル、ポリ(ビニリデンフルオライド)等を高分子材料として含有することが可能である。なお、これらは予め重合していてもよく、注液後重合してもよい。これらは1種単独で又は2種以上を適宜組み合わせて用いることができる。 In addition, solid electrolytes, gel electrolytes, etc. can be used as non-aqueous electrolytes, and silicone polymers, silicone polyether gels, acrylic gels, silicone acrylic gels, acrylonitrile gels, poly (vinylidene fluoride), etc. are contained as polymer materials. Is possible. These may be polymerized in advance or may be polymerized after injection. These can be used individually by 1 type or in combination of 2 or more types.
非水電解質二次電池の形状は任意であり、特に制限はない。一般的にはコイン形状に打ち抜いた電極とセパレーターを積層したコインタイプ、電極シートとセパレーターをスパイラル状に捲回した角型あるいは円筒型等の電池が挙げられる。 The shape of the nonaqueous electrolyte secondary battery is arbitrary and is not particularly limited. In general, a coin type battery in which an electrode punched into a coin shape and a separator are stacked, and a square type or cylindrical type battery in which an electrode sheet and a separator are wound in a spiral shape are included.
以下、製造例、実施例及び比較例を示し、本発明を具体的に説明するが、本発明は下記の実施例に制限されるものではない。下記の例において組成の「%」は質量%を示し、粒子径はレーザー光回折法による粒度分布測定装置によって測定したメジアン径D50を示す。 EXAMPLES Hereinafter, although a manufacture example, an Example, and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example. In the following examples, “%” of the composition indicates mass%, and the particle diameter indicates the median diameter D 50 measured by a particle size distribution measuring apparatus by a laser light diffraction method.
[調製例1:被覆酸化珪素粒子1]
二酸化珪素粒子(BET比表面積=200m2/g)とケミカルグレード金属珪素粒子(BET比表面積=4m2/g)を等モルの割合で混合した混合粒子を、1350℃、10Paの高温減圧雰囲気で熱処理し、発生した酸化珪素ガスを800℃に保持したSUS製基体に析出させた。次にこの析出物を回収した後、ジョークラッシャーで粗砕した。この粗砕物をジェットミル(ホソカワミクロン社製AFG−100)を用いて分級機の回転数9000rpmにて粉砕し、D50=7.6μm、D90=11.9μmの酸化珪素粒子(SiOx:x=1.02)をサイクロンにて回収した。得られた粒子の固体NMR(29Si−DDMAS)を測定したところ、−110ppm付近を中心とするブロードな二酸化珪素のシグナル面積と−84ppm付近のダイヤモンド構造珪素のシグナル面積との比(S-84/S-110)は0.69であった。
さらに、得られた酸化珪素粒子を横型加熱炉にて、油回転式真空ポンプを作動させながら1000℃/2000Paの条件で、CH4ガスを0.5NL/min流入し、5時間の黒鉛被覆処理を行った。運転終了後冷却し黒色粒子を回収した。
得られた黒色粒子は、平均粒子径が8.2μm、炭素量が5%(黒色粒子中)である導電性粒子であった。この粒子について、固体NMR(29Si−DDMAS)測定したところ(図1参照)、−110ppm付近を中心とするブロードな二酸化珪素のシグナル面積と−84ppm付近のダイヤモンド構造珪素のシグナル面積との比(S-84/S-110)は0.69であり、顕微ラマン分析を行った結果(図4参照)、ラマンシフトが1330cm-1と1580cm-1付近にスペクトルを有しており、強度比I1330/I1580は2.0であった。
[Preparation Example 1: Coated silicon oxide particles 1]
Mixed particles in which silicon dioxide particles (BET specific surface area = 200 m 2 / g) and chemical grade metal silicon particles (BET specific surface area = 4 m 2 / g) are mixed at an equimolar ratio are mixed at 1350 ° C. and 10 Pa in a high temperature reduced pressure atmosphere. After heat treatment, the generated silicon oxide gas was deposited on a SUS substrate maintained at 800 ° C. Next, this precipitate was collected and then roughly crushed with a jaw crusher. The coarsely pulverized product was pulverized using a jet mill (AFG-100 manufactured by Hosokawa Micron Corporation) at a rotational speed of 9000 rpm of a classifier, and silicon oxide particles having a D 50 = 7.6 μm and D 90 = 11.9 μm (SiOx: x = 1.02) was recovered in a cyclone. When solid-state NMR ( 29 Si-DDMAS) of the obtained particles was measured, the ratio of the signal area of broad silicon dioxide centered around −110 ppm to the signal area of diamond structure silicon around −84 ppm (S −84 / S −110 ) was 0.69.
Furthermore, in the resulting silicon oxide particles a horizontal furnace, at 1000 ° C. / 2000 Pa conditions while operating the oil-rotary vacuum pump, a CH 4 gas flow 0.5 NL / min, graphite coating treatment of 5 hours Went. After the operation, the system was cooled and black particles were collected.
The obtained black particles were conductive particles having an average particle diameter of 8.2 μm and a carbon content of 5% (in the black particles). When this particle was measured by solid-state NMR ( 29 Si-DDMAS) (see FIG. 1), the ratio of the signal area of broad silicon dioxide centered around −110 ppm to the signal area of diamond structure silicon around −84 ppm ( S -84 / S -110) is 0.69, as a result of Raman analysis (see FIG. 4) has a spectrum in the vicinity of Raman shift 1330 cm -1 and 1580 cm -1, the intensity ratio I 1330 / I 1580 was 2.0.
[比較調製例1:被覆酸化珪素粒子2]
調製例1で用いた酸化珪素粒子を、油回転式真空ポンプを作動せず、常圧下(Ar/CH4=2.0/0.5NL/min混合ガス流入)、1150℃で黒鉛被覆処理を行った他は、調製例1と同様な方法で黒色粒子を得た。得られた黒色粒子は、平均粒子径が8.5μm、炭素量が5%(黒色粒子中)である導電性粒子であった。この粒子について、固体NMR(29Si−DDMAS)を測定したところ(図2参照)、−110ppm付近を中心とするブロードな二酸化珪素のシグナル面積と−84ppm付近のダイヤモンド構造珪素のシグナル面積との比(S-84/S-110)は1.21であり、顕微ラマン分析を行った結果(図4参照)、ラマンシフトが1330cm-1と1580cm-1付近にスペクトルを有しており、強度比I1330/I1580は1.4であった。
[Comparative Preparation Example 1: Coated silicon oxide particles 2]
The silicon oxide particles used in Preparation Example 1 were subjected to graphite coating treatment at 1150 ° C. under normal pressure (Ar / CH 4 = 2.0 / 0.5 NL / min mixed gas inflow) without operating the oil rotary vacuum pump. Otherwise, black particles were obtained in the same manner as in Preparation Example 1. The obtained black particles were conductive particles having an average particle diameter of 8.5 μm and a carbon content of 5% (in the black particles). The solid NMR ( 29 Si-DDMAS) of this particle was measured (see FIG. 2). The ratio between the signal area of broad silicon dioxide centered around −110 ppm and the signal area of diamond structure silicon around −84 ppm. (S −84 / S −110 ) is 1.21, and as a result of microscopic Raman analysis (see FIG. 4), the Raman shift has spectra near 1330 cm −1 and 1580 cm −1 , and the intensity ratio I 1330 / I 1580 was 1.4.
[比較調製例2:被覆酸化珪素粒子3]
調製例1で用いた酸化珪素粒子を、油回転式真空ポンプに加えメカニカルブスターポンプを作動しつつ、30Paの減圧下で黒鉛被覆処理を行った他は、実施例1と同様な方法で黒色粒子を得た。得られた黒色粒子は、平均粒子径が8.5μm、炭素量が4.5%(黒色粒子中)である導電性粒子であった。この粒子について、固体NMR(29Si−DDMAS)を測定したところ(図3参照)、−110ppm付近を中心とするブロードな二酸化珪素のシグナル面積と−84ppm付近のダイヤモンド構造珪素のシグナル面積との比(S-84/S-110)は0.69であり、顕微ラマン分析を行った結果(図4参照)、ラマンスペクトルは、ラマンシフトが1330cm-1と1580cm-1付近にスペクトルを有しており、強度比I1330/I1580は3.8であった。
[Comparative Preparation Example 2: Coated silicon oxide particles 3]
The black particles were prepared in the same manner as in Example 1 except that the silicon oxide particles used in Preparation Example 1 were added to the oil rotary vacuum pump and the mechanical booster pump was operated and the graphite coating treatment was performed under a reduced pressure of 30 Pa. Got. The obtained black particles were conductive particles having an average particle diameter of 8.5 μm and a carbon content of 4.5% (in the black particles). The solid NMR ( 29 Si-DDMAS) of this particle was measured (see FIG. 3), and the ratio of the broad silicon dioxide signal area centered around −110 ppm to the diamond structured silicon signal area around −84 ppm. (S -84 / S -110) is 0.69, (see Fig. 4) results of Raman analysis, Raman spectrum, the Raman shift has a spectrum in the vicinity of 1330 cm -1 and 1580 cm -1 The intensity ratio I 1330 / I 1580 was 3.8.
[珪素粒子1の作製]
金属珪素塊(ELKEM製)をジェットミル(ホソカワミクロン社製AFG−100)を用いて分級機の回転数7,200rpmにて粉砕した後、分級機(日清エンジニアリング社製TC−15)にて分級することで、D50=6.1μmの珪素粒子を得た。
[Preparation of silicon particles 1]
Metallic silicon lump (ELKEM) is pulverized using a jet mill (AFG-100 manufactured by Hosokawa Micron Corporation) at a rotational speed of a classifier of 7,200 rpm, and then classified by a classifier (TC-15 manufactured by Nisshin Engineering Co., Ltd.). As a result, silicon particles having D 50 = 6.1 μm were obtained.
[珪素粒子2の作製]
トリクロロシランの1,100℃での熱分解によって製造された多結晶珪素塊をジョークラッシャーで破砕したものをジェットミル(ホソカワミクロン社製AFG−100)を用いて分級機の回転数7,200rpmにて粉砕した後、分級機(日清エンジニアリング社製TC−15)にて分級し、D50=5.5μmの多結晶珪素粒子を得た。
[Preparation of silicon particles 2]
A polycrystalline silicon lump produced by pyrolysis of trichlorosilane at 1,100 ° C. is crushed with a jaw crusher using a jet mill (AFG-100 manufactured by Hosokawa Micron Corporation) at a rotational speed of 7,200 rpm of a classifier. After pulverization, classification was performed with a classifier (TC-15 manufactured by Nissin Engineering Co., Ltd.) to obtain polycrystalline silicon particles having D 50 = 5.5 μm.
[珪素粒子3の作製]
珪素粒子2を横型加熱炉にて、メタンガス通気下で1100℃/1000Pa、平均滞留時間約2時間の条件で熱CVDを行った。運転終了後、冷却し黒色粒子を回収した。
得られた黒色粒子は、平均粒子径=6.3μm、炭素量2質量%(黒色粒子中)の導電性粒子であった。
[Preparation of silicon particles 3]
The silicon particles 2 were subjected to thermal CVD in a horizontal heating furnace under the conditions of 1100 ° C./1000 Pa and average residence time of about 2 hours under methane gas flow. After the operation, the system was cooled and black particles were collected.
The obtained black particles were conductive particles having an average particle size = 6.3 μm and a carbon content of 2% by mass (in the black particles).
[実施例1〜5、比較例1〜3]
上記例で得られた被覆酸化珪素粒子と珪素粒子との混合物をN−メチルピロリドンで希釈した。これに結着剤としてポリイミド樹脂(固形分18.1%)を加え、スラリーとした。このスラリーを厚さ12μmの銅箔に50μmのドクターブレードを使用して塗布し、200℃で2時間減圧乾燥後、60℃のローラープレスにより電極を加圧成形し、最終的には2cm2に打ち抜き、負極成型体を得た。負極材中の固形分組成を表1に示す。
[Examples 1-5, Comparative Examples 1-3]
The mixture of coated silicon oxide particles and silicon particles obtained in the above example was diluted with N-methylpyrrolidone. A polyimide resin (solid content: 18.1%) was added as a binder to the resulting slurry. This slurry was applied to a copper foil with a thickness of 12 μm using a 50 μm doctor blade, dried under reduced pressure at 200 ° C. for 2 hours, and then pressure-formed with a roller press at 60 ° C., and finally to 2 cm 2 . Punched to obtain a molded negative electrode. The solid content composition in the negative electrode material is shown in Table 1.
<電池特性>
負極材の有用性を確認するため、下記方法で充放電容量及び体積膨張率の測定を行った。上記で得られた負極成型体、対極にリチウム箔を使用し、非水電解質としてリチウムビス(トリフルオロメタンスルホニル)イミドをエチレンカーボネートとジエチルカーボネートの1/1(体積比)混合液に1mol/Lの濃度で溶解した非水電解質溶液を用い、セパレーターに厚さ30μmのポリエチレン製微多孔質フィルムを用いた評価用リチウムイオン二次電池を各6個作製した。
<Battery characteristics>
In order to confirm the usefulness of the negative electrode material, the charge / discharge capacity and the volume expansion coefficient were measured by the following methods. Lithium foil was used for the negative electrode molded body obtained above and the counter electrode, and lithium bis (trifluoromethanesulfonyl) imide was used as a nonaqueous electrolyte in a 1 mol / L mixed solution of ethylene carbonate and diethyl carbonate (1 mol / L). Six lithium ion secondary batteries for evaluation each using a non-aqueous electrolyte solution dissolved at a concentration and a microporous polyethylene film having a thickness of 30 μm as a separator were prepared.
作製したリチウムイオン二次電池は、一晩室温で放置した後、2個は放置後直ちに解体して厚み測定を行い、電解液膨潤状態での膜厚を測定し、体積を求めた(V1)。なお、電解液及び充電によるリチウム増加量は含まないものとした。次の2個は二次電池充放電試験装置((株)ナガノ製)を用い、リチウムイオン二次電池の電圧が5mVに達するまで0.05cの定電流で充電を行い、5mVに達した後は、セル電圧を5mVに保つように電流を減少させて充電を行った。そして、電流値が0.02cを下回った時点で充電を終了した。なお、cは負極の理論容量を1時間で充電する電流値であり、1c=15mAである。充電終了後、リチウムイオン二次電池を解体し、厚みを測定することで充電時の体積を求めた(V2)、上記V1とV2の結果から、V2/V1により充電後の体積変化倍率を算出した。残りの2個は上記の方法で充電を行った後、1500mVに達するまで0.05cの定電流で放電を行うことで、充放電容量を算出し、初回充放電効率(%)を求めた。なお、充放電容量は結着剤を除いた活物質あたりの容量であり、初回充放電効率(%)は充電容量に対する放電容量の百分率(放電容量/充電容量×100)で示した。結果を表1に示す。 The prepared lithium ion secondary battery was left overnight at room temperature, and then two were disassembled immediately after being left to measure the thickness, and the thickness was measured in the electrolyte swelling state to determine the volume (V1). . Note that the amount of increase in lithium due to the electrolyte and charging was not included. The next two batteries were charged with a constant current of 0.05 c until the voltage of the lithium ion secondary battery reached 5 mV using a secondary battery charge / discharge test device (manufactured by Nagano Co., Ltd.), and after reaching 5 mV Were charged by decreasing the current so as to keep the cell voltage at 5 mV. And charge was complete | finished when the electric current value fell below 0.02c. Note that c is a current value for charging the theoretical capacity of the negative electrode in one hour, and 1c = 15 mA. After completion of charging, the lithium ion secondary battery was disassembled, and the volume during charging was obtained by measuring the thickness (V2). From the results of V1 and V2, the volume change magnification after charging was calculated by V2 / V1. did. The remaining two were charged by the above method, and then discharged at a constant current of 0.05 c until reaching 1500 mV, thereby calculating the charge / discharge capacity and obtaining the initial charge / discharge efficiency (%). The charge / discharge capacity is the capacity per active material excluding the binder, and the initial charge / discharge efficiency (%) is expressed as a percentage of the discharge capacity with respect to the charge capacity (discharge capacity / charge capacity × 100). The results are shown in Table 1.
調製例1、比較調製例1,2を使用した実施例1及び比較例1,2の負極材を比較すると本発明の負極材が容量及び放電効率が同等であっても、充電後の体積変化倍率が低かった。また、本発明の負極材である実施例1〜5は珪素粒子を活物質として配合しない比較例3と比較すると、初回充放電効率が向上しており、充放電容量の増加が認められた。一方、充放電容量の増加にもかかわらず体積変化倍率はほとんど変化していない。 Comparing the negative electrode materials of Example 1 and Comparative Examples 1 and 2 using Preparation Example 1 and Comparative Preparation Examples 1 and 2, even if the negative electrode material of the present invention has the same capacity and discharge efficiency, the volume change after charging The magnification was low. Moreover, compared with the comparative example 3 which does not mix | blend a silicon particle as an active material, Example 1-5 which is a negative electrode material of this invention has improved the first time charge / discharge efficiency, and the increase in charge / discharge capacity was recognized. On the other hand, despite the increase in charge / discharge capacity, the volume change magnification has hardly changed.
<サイクル特性の確認>
実施例1と比較例1〜3の負極材を用いて、上記方法で負極成型体を作製した。得られた負極成型体のサイクル特性を評価するために、正極材料としてLiCoO2を活物質とし、集電体としてアルミ箔を用いた単層シート(パイオニクス(株)製、商品名;ピオクセル C−100)を用いた。非水電解質は六フッ化リン酸リチウムをエチレンカーボネートとジエチルカーボネートの1/1(体積比)混合液に1mol/Lの濃度で溶解した非水電解質溶液を用い、セパレーターに厚さ30μmのポリエチレン製微多孔質フィルムを用いたコイン型リチウムイオン二次電池を作製した。
<Check cycle characteristics>
Using the negative electrode materials of Example 1 and Comparative Examples 1 to 3, a negative electrode molded body was produced by the above method. In order to evaluate the cycle characteristics of the obtained molded negative electrode, a single-layer sheet using LiCoO 2 as an active material as a positive electrode material and aluminum foil as a current collector (trade name: Pioxel C-, manufactured by Pionics Corporation) 100) was used. The non-aqueous electrolyte uses a non-aqueous electrolyte solution in which lithium hexafluorophosphate is dissolved in a 1/1 (volume ratio) mixture of ethylene carbonate and diethyl carbonate at a concentration of 1 mol / L, and the separator is made of polyethylene having a thickness of 30 μm. A coin-type lithium ion secondary battery using a microporous film was produced.
作製したコイン型リチウムイオン二次電池は、二晩室温で放置した後、二次電池充放電試験装置((株)ナガノ製)を用い、テストセルの電圧が4.2Vに達するまで1.2mA(正極基準で0.25c)の定電流で充電を行い、4.2Vに達した後は、セル電圧を4.2Vに保つように電流を減少させて充電を行った。そして、電流値が0.3mAを下回った時点で充電を終了した。放電は0.6mAの定電流で行い、セル電圧が2.5Vに達した時点で放電を終了し、放電容量を求めた。これを50サイクル継続した。初回放電容量に対する50サイクル目の放電容量の百分率(50サイクル目の放電容量/初回放電容量×100)を放電容量維持率(%)として算出した。結果を表2に示す。比較例1〜3に対して実施例1は初期効率及び電池容量の増加にもかかわらず、珪素粒子を添加する前とほとんど同等のサイクル特性を示しており、比較例1及び2の被覆酸化珪素粒子を用いた場合よりも良好な値を示した。 The produced coin-type lithium ion secondary battery was allowed to stand at room temperature for two nights, and then used a secondary battery charge / discharge test apparatus (manufactured by Nagano Co., Ltd.), and 1.2 mA until the test cell voltage reached 4.2V. The battery was charged with a constant current of 0.25c (positive electrode reference), and after reaching 4.2V, the battery was charged by decreasing the current so as to keep the cell voltage at 4.2V. The charging was terminated when the current value was less than 0.3 mA. The discharge was performed at a constant current of 0.6 mA, and when the cell voltage reached 2.5 V, the discharge was terminated and the discharge capacity was determined. This was continued for 50 cycles. The percentage of the discharge capacity at the 50th cycle with respect to the initial discharge capacity (discharge capacity at the 50th cycle / initial discharge capacity × 100) was calculated as the discharge capacity retention rate (%). The results are shown in Table 2. In contrast to Comparative Examples 1 to 3, Example 1 shows almost the same cycle characteristics as before the addition of silicon particles, despite the increase in initial efficiency and battery capacity, and the coated silicon oxide of Comparative Examples 1 and 2 Better values were obtained than when particles were used.
Claims (9)
上記被覆酸化珪素粒子(A1)の黒鉛皮膜が、ラマンスペクトル分析において、1330cm-1と1580cm-1に散乱ピークを有し、それらの強度比I1330/I1580が1.5<I1330/I1580<3.0であり、かつ被覆酸化珪素粒子(A1)の固体NMR(29Si−DDMAS)測定において、−110ppm付近を中心とするブロードなシグナル面積と−84ppm付近のシグナル面積との比S-84/S-110が0.5<S-84/S-110<1.1であり、活物質(A)中の被覆酸化珪素粒子(A1)の割合が70〜95質量%であり、珪素粒子(A2)の割合が5〜30質量%であることを特徴とする非水電解質二次電池用負極材。 Non-water containing active material (A) composed of coated silicon oxide particles (A1) and silicon particles (A2) whose surfaces are coated with a graphite film, and binder (B) 1 to 20% by mass A negative electrode material for an electrolyte secondary battery,
Graphite coating of the coated silicon oxide particles (A1) is, in the Raman spectrum analysis, have a scattering peak at 1330 cm -1 and 1580 cm -1, their intensity ratio I 1330 / I 1580 is 1.5 <I 1330 / I In the solid state NMR ( 29 Si-DDMAS) measurement of the coated silicon oxide particles (A1) with 1580 <3.0, the ratio S between the broad signal area centered around −110 ppm and the signal area around −84 ppm −84 / S −110 is 0.5 <S −84 / S −110 <1.1, the ratio of the coated silicon oxide particles (A1) in the active material (A) is 70 to 95% by mass, A negative electrode material for a nonaqueous electrolyte secondary battery, wherein the ratio of silicon particles (A2) is 5 to 30 % by mass.
(I)酸化珪素粒子を、有機物ガス及び/又は蒸気中、50〜30000Paの減圧下、600〜1100℃で化学蒸着することにより表面を黒鉛皮膜で被覆し、被覆酸化珪素粒子(A1)を調製する工程、
(II)工程(I)で得られた被覆酸化珪素粒子(A1)、珪素粒子(A2)、及び結着剤(B)を混合し、非水電解質二次電池用負極材を調製する工程。 The manufacturing method of the negative electrode material for nonaqueous electrolyte secondary batteries of Claim 1 including following process (I) and (II).
(I) The silicon oxide particles are chemically vapor-deposited at 600 to 1100 ° C. under reduced pressure of 50 to 30000 Pa in an organic gas and / or vapor to prepare a coated silicon oxide particle (A1). The process of
(II) A step of mixing the coated silicon oxide particles (A1), the silicon particles (A2), and the binder (B) obtained in step (I) to prepare a negative electrode material for a nonaqueous electrolyte secondary battery.
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