JP6961338B2

JP6961338B2 - Negative electrode for non-aqueous electrolyte secondary battery and non-aqueous electrolyte secondary battery

Info

Publication number: JP6961338B2
Application number: JP2016237410A
Authority: JP
Inventors: 勝一郎澤; 耕次西田
Original assignee: Panasonic Corp; Sanyo Electric Co Ltd; Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Corp; Sanyo Electric Co Ltd; Panasonic Holdings Corp
Priority date: 2016-12-07
Filing date: 2016-12-07
Publication date: 2021-11-05
Anticipated expiration: 2036-12-07
Also published as: JP2018092857A

Description

本開示は、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。 The present disclosure relates to a negative electrode for a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery.

リチウムイオン電池等の非水電解質二次電池では、高容量化の手段として正極や負極の活物質を高密度で充填する方法が採用されている。そのため、高容量化とともに電極体内部の空間が減少するため、電解液が電極体内へ浸透しにくいという問題が顕著になる。例えば、特許文献１〜３には、電極体が挿入された電池ケース内へ注液された電解液が電極体内に速やかに浸透するように、負極合剤層の表面に複数の溝を形成した負極が開示されている。 In non-aqueous electrolyte secondary batteries such as lithium ion batteries, a method of filling the active material of the positive electrode and the negative electrode at a high density is adopted as a means for increasing the capacity. Therefore, as the capacity is increased, the space inside the electrode body is reduced, so that the problem that the electrolytic solution is difficult to permeate into the electrode body becomes remarkable. For example, in Patent Documents 1 to 3, a plurality of grooves are formed on the surface of the negative electrode mixture layer so that the electrolytic solution injected into the battery case into which the electrode body is inserted quickly permeates into the electrode body. The negative electrode is disclosed.

特開平９−２９８０５７号公報Japanese Unexamined Patent Publication No. 9-298057 特開２００８−２７６３３号公報Japanese Unexamined Patent Publication No. 2008-27633 特開２００９−５９６８６号公報Japanese Unexamined Patent Publication No. 2009-59686

確かに、特許文献１〜３に開示された負極を用いることで、注液時における電解液の電極体内への浸透性は改善される。しかし、充放電時の膨張収縮量の大きい負極活物質を用いた場合や充電後の休止時間が短い場合などにサイクル特性が十分でない場合がみられた。その原因として、充電時に膨張した電極体から押し出された電解液が電極体内へ戻るスピードが十分でないことが本発明者らにより推測された。本開示はこのような課題に鑑みてなされたものであり、サイクル特性に優れた非水電解質二次電池を提供することを目的とする。 Certainly, by using the negative electrode disclosed in Patent Documents 1 to 3, the permeability of the electrolytic solution into the electrode body at the time of injecting liquid is improved. However, there are cases where the cycle characteristics are not sufficient when a negative electrode active material having a large amount of expansion / contraction during charging / discharging is used or when the rest time after charging is short. It was speculated by the present inventors that the cause of this is that the speed at which the electrolytic solution extruded from the expanded electrode body during charging returns to the electrode body is not sufficient. The present disclosure has been made in view of such problems, and an object of the present disclosure is to provide a non-aqueous electrolyte secondary battery having excellent cycle characteristics.

本開示の一態様である非水電解質二次電池用負極は、長尺状の負極集電体と、前記負極集電体上に形成された負極合剤層とを有する非水電解質二次電池用負極であって、前記負極合剤層の表面には、前記負極集電体の幅方向に延びる複数の溝と、前記複数の溝の底部に区画されて前記負極集電体の幅方向に延びた複数の帯状領域が形成され、前記複数の帯状領域の少なくとも一つの帯状領域における前記負極合剤層の表面は、前記溝の各底部に向かって、前記負極集電体と反対側に凸となるように湾曲していることを特徴とする。 The negative electrode for a non-aqueous electrolyte secondary battery according to one aspect of the present disclosure is a non-aqueous electrolyte secondary battery having a long negative electrode current collector and a negative electrode mixture layer formed on the negative electrode current collector. On the surface of the negative electrode mixture layer, a plurality of grooves extending in the width direction of the negative electrode current collector and the bottoms of the plurality of grooves are partitioned in the width direction of the negative electrode current collector. A plurality of extended strip-shaped regions are formed, and the surface of the negative electrode mixture layer in at least one strip-shaped region of the plurality of strip-shaped regions is convex toward the bottom of each of the grooves and opposite to the negative electrode current collector. It is characterized in that it is curved so as to become.

本開示の一態様である非水電解質二次電池用負極によれば、サイクル特性に優れた非水電解質二次電池を提供することができる。 According to the negative electrode for a non-aqueous electrolyte secondary battery, which is one aspect of the present disclosure, it is possible to provide a non-aqueous electrolyte secondary battery having excellent cycle characteristics.

実施形態の一例である非水電解質二次電池の断面図である。It is sectional drawing of the non-aqueous electrolyte secondary battery which is an example of embodiment. 実施形態の一例である負極の平面図である。It is a top view of the negative electrode which is an example of an embodiment. 図２中のＡＡ線断面図である。FIG. 2 is a cross-sectional view taken along the line AA in FIG. 参考例の一例である負極の断面図である。It is sectional drawing of the negative electrode which is an example of a reference example. 実施形態の一例である負極を製造するための押圧部材を示す図である。It is a figure which shows the pressing member for manufacturing the negative electrode which is an example of an embodiment. 従来の負極（比較例１で作製した負極）の断面図である。It is sectional drawing of the conventional negative electrode (the negative electrode produced in Comparative Example 1). 図６の負極を製造するための押圧部材を示す図である。It is a figure which shows the pressing member for manufacturing the negative electrode of FIG.

上述のように、非水電解質二次電池では、充放電に伴う電極の膨張により電極体内から周囲に電解液が押し出される。特に、高容量の負極活物質を用いた場合は、充電時に負極が大きく膨張する。そして、電極体内の電解液が減少すると、電極体内で不均一な電池反応が起こる場合があり、サイクル特性の低下を招くと考えられる。 As described above, in the non-aqueous electrolyte secondary battery, the electrolytic solution is pushed out from the inside of the electrode to the surroundings due to the expansion of the electrode due to charging and discharging. In particular, when a high-capacity negative electrode active material is used, the negative electrode expands significantly during charging. Then, when the amount of the electrolytic solution in the electrode body is reduced, a non-uniform battery reaction may occur in the electrode body, which is considered to cause deterioration of the cycle characteristics.

図６は、従来の負極１００を示す断面図である。図６に例示する負極１００は、電極体内から押し出された電解液を電極体内に素早く戻すために、負極合剤層１０１の表面に形成された複数の溝１０２を有する。しかし、本発明者らの検討の結果、図６に示すような溝１０２を負極合剤層１０１の表面に形成しても、サイクル特性の改善効果は小さい、或いは殆ど得られないことが分かった。 FIG. 6 is a cross-sectional view showing a conventional negative electrode 100. The negative electrode 100 illustrated in FIG. 6 has a plurality of grooves 102 formed on the surface of the negative electrode mixture layer 101 in order to quickly return the electrolytic solution extruded from the electrode body to the electrode body. However, as a result of the studies by the present inventors, it was found that even if the groove 102 as shown in FIG. 6 is formed on the surface of the negative electrode mixture layer 101, the effect of improving the cycle characteristics is small or hardly obtained. ..

本発明者らの更なる検討の結果、負極合剤層の表面に複数の溝を形成し、複数の溝の底部に区画された帯状領域における負極合剤層の表面を負極集電体と反対側に凸となるように湾曲させることで、電池のサイクル特性が特異的に向上することが判明した。帯状領域における負極合剤層の表面を湾曲させ、溝の縁部に角ばった部分を無くすことで、溝に沿って電解液が電極体内に素早く戻りやすくなると考えられる。このため、電解液の減少に伴う不均一な電池反応が抑制され、サイクル特性が向上するものと推定される。 As a result of further studies by the present inventors, a plurality of grooves are formed on the surface of the negative electrode mixture layer, and the surface of the negative electrode mixture layer in the band-shaped region partitioned at the bottom of the plurality of grooves is opposite to that of the negative electrode current collector. It was found that the cycle characteristics of the battery were specifically improved by bending it so as to be convex to the side. It is considered that by curving the surface of the negative electrode mixture layer in the band-shaped region and eliminating the angular portion at the edge of the groove, the electrolytic solution can easily return to the inside of the electrode along the groove. Therefore, it is presumed that the non-uniform battery reaction accompanying the decrease in the electrolytic solution is suppressed and the cycle characteristics are improved.

以下、実施形態の一例として、円筒形の金属製ケースを備えた円筒形電池である非水電解質二次電池１０を例示するが、本開示の非水電解質二次電池はこれに限定されない。本開示の非水電解質二次電池は、例えば角形の金属製ケースを備えた角形電池、樹脂製シートからなる外装体を備えたラミネート電池などであってもよい。 Hereinafter, as an example of the embodiment, the non-aqueous electrolyte secondary battery 10 which is a cylindrical battery provided with a cylindrical metal case will be illustrated, but the non-aqueous electrolyte secondary battery of the present disclosure is not limited thereto. The non-aqueous electrolyte secondary battery of the present disclosure may be, for example, a square battery having a square metal case, a laminated battery having an exterior body made of a resin sheet, or the like.

図１は、非水電解質二次電池１０の断面図である。図１に例示するように、非水電解質二次電池１０は、巻回構造を有する電極体１４と、非水電解質（図示せず）とを備える。電極体１４は、正極１１と、負極１２と、セパレータ１３とを有し、正極１１と負極１２がセパレータ１３を介して渦巻状に巻回されてなる。以下では、電極体１４の軸方向一方側を「上」、軸方向他方側を「下」という場合がある。 FIG. 1 is a cross-sectional view of the non-aqueous electrolyte secondary battery 10. As illustrated in FIG. 1, the non-aqueous electrolyte secondary battery 10 includes an electrode body 14 having a wound structure and a non-aqueous electrolyte (not shown). The electrode body 14 has a positive electrode 11, a negative electrode 12, and a separator 13, and the positive electrode 11 and the negative electrode 12 are spirally wound via the separator 13. In the following, one side in the axial direction of the electrode body 14 may be referred to as “upper”, and the other side in the axial direction may be referred to as “lower”.

非水電解質は、非水溶媒と、非水溶媒に溶解又は分散した電解質塩とを含む。非水溶媒には、例えばエステル類、エーテル類、ニトリル類、アミド類、及びこれらの２種以上の混合溶媒等を用いることができる。非水溶媒は、これら溶媒の水素の少なくとも一部をフッ素等のハロゲン原子で置換したハロゲン置換体を含有していてもよい。 The non-aqueous electrolyte includes a non-aqueous solvent and an electrolyte salt dissolved or dispersed in the non-aqueous solvent. As the non-aqueous solvent, for example, esters, ethers, nitriles, amides, and a mixed solvent of two or more of these can be used. The non-aqueous solvent may contain a halogen substituent in which at least a part of hydrogen in these solvents is substituted with a halogen atom such as fluorine.

電極体１４を構成する正極１１、負極１２、及びセパレータ１３は、いずれも長尺状に形成されている。これら各部材は、渦巻状に巻回されることで電極体１４の径方向に交互に積層された状態となる。電極体１４において、各電極の長手方向が巻回方向となり、各電極の幅方向が軸方向となる。正極１１と正極端子とを電気的に接続する正極リード１９は、例えば正極１１の長手方向中央部に接続され、電極群の上端から延出している。負極１２と負極端子とを電気的に接続する負極リード２０は、例えば負極１２の長手方向端部に接続され、電極群の下端から延出している。 The positive electrode 11, the negative electrode 12, and the separator 13 constituting the electrode body 14 are all formed in a long shape. Each of these members is spirally wound so that the electrode body 14 is alternately laminated in the radial direction. In the electrode body 14, the longitudinal direction of each electrode is the winding direction, and the width direction of each electrode is the axial direction. The positive electrode lead 19 that electrically connects the positive electrode 11 and the positive electrode terminal is connected to, for example, the central portion in the longitudinal direction of the positive electrode 11 and extends from the upper end of the electrode group. The negative electrode lead 20 that electrically connects the negative electrode 12 and the negative electrode terminal is connected to, for example, the longitudinal end of the negative electrode 12 and extends from the lower end of the electrode group.

図１に示す例では、ケース本体１５と封口体１６によって、電極体１４及び非水電解質を収容する金属製の電池ケースが構成されている。電極体１４の上下には、絶縁板１７，１８がそれぞれ設けられる。正極リード１９は絶縁板１７の貫通孔を通って封口体１６側に延び、封口体１６の底板であるフィルタ２２の下面に溶接される。非水電解質二次電池１０では、フィルタ２２と電気的に接続された封口体１６のキャップ２６が正極端子となる。他方、負極リード２０はケース本体１５の底部側に延び、ケース本体１５の底部内面に溶接される。非水電解質二次電池１０では、ケース本体１５が負極端子となる。 In the example shown in FIG. 1, the case body 15 and the sealing body 16 constitute a metal battery case that houses the electrode body 14 and the non-aqueous electrolyte. Insulating plates 17 and 18 are provided above and below the electrode body 14, respectively. The positive electrode lead 19 extends to the sealing body 16 side through the through hole of the insulating plate 17 and is welded to the lower surface of the filter 22 which is the bottom plate of the sealing body 16. In the non-aqueous electrolyte secondary battery 10, the cap 26 of the sealing body 16 electrically connected to the filter 22 serves as the positive electrode terminal. On the other hand, the negative electrode lead 20 extends toward the bottom of the case body 15 and is welded to the inner surface of the bottom of the case body 15. In the non-aqueous electrolyte secondary battery 10, the case body 15 serves as a negative electrode terminal.

ケース本体１５は、有底円筒形状の金属製容器である。ケース本体１５と封口体１６の間にはガスケット２７が設けられ、電池ケース内の密閉性が確保されている。ケース本体１５は、例えば側面部を外側からプレスして形成された、封口体１６を支持する張り出し部２１を有する。張り出し部２１は、ケース本体１５の周方向に沿って環状に形成されることが好ましく、その上面で封口体１６を支持する。 The case body 15 is a bottomed cylindrical metal container. A gasket 27 is provided between the case body 15 and the sealing body 16 to ensure the airtightness inside the battery case. The case body 15 has, for example, an overhanging portion 21 that supports the sealing body 16 formed by pressing a side surface portion from the outside. The overhanging portion 21 is preferably formed in an annular shape along the circumferential direction of the case body 15, and the sealing body 16 is supported on the upper surface thereof.

封口体１６は、電極体１４側から順に、フィルタ２２、下弁体２３、絶縁部材２４、上弁体２５、及びキャップ２６が積層された構造を有する。封口体１６を構成する各部材は、例えば円板形状又はリング形状を有し、絶縁部材２４を除く各部材は互いに電気的に接続されている。下弁体２３と上弁体２５は各々の中央部で互いに接続され、各々の周縁部の間には絶縁部材２４が介在している。下弁体２３には通気孔が設けられているため、異常発熱で電池の内圧が上昇すると、上弁体２５がキャップ２６側に膨れて下弁体２３から離れることにより両者の電気的接続が遮断される。さらに内圧が上昇すると、上弁体２５が破断し、キャップ２６の開口部からガスが排出される。 The sealing body 16 has a structure in which a filter 22, a lower valve body 23, an insulating member 24, an upper valve body 25, and a cap 26 are laminated in this order from the electrode body 14 side. Each member constituting the sealing body 16 has, for example, a disk shape or a ring shape, and each member except the insulating member 24 is electrically connected to each other. The lower valve body 23 and the upper valve body 25 are connected to each other at the central portion thereof, and an insulating member 24 is interposed between the peripheral portions thereof. Since the lower valve body 23 is provided with a ventilation hole, when the internal pressure of the battery rises due to abnormal heat generation, the upper valve body 25 swells toward the cap 26 side and separates from the lower valve body 23, so that the electrical connection between the two is established. It is blocked. When the internal pressure further rises, the upper valve body 25 breaks and gas is discharged from the opening of the cap 26.

以下、図２及び図３を適宜参照しながら、電極体１４の各構成要素（正極１１、負極１２、セパレータ１３）について、特に負極１２について詳説する。 Hereinafter, each component (positive electrode 11, negative electrode 12, separator 13) of the electrode body 14 will be described in detail with reference to FIGS. 2 and 3, particularly the negative electrode 12.

［正極］
正極１１は、長尺状の正極集電体１１ａと、正極集電体１１ａ上に形成された正極合剤層１１ｂとを有する。正極集電体１１ａは、例えば５μｍ〜２０μｍの厚みを有し、幅が略一定の帯状体である。正極集電体１１ａには、アルミニウムなどの正極１１の電位範囲で安定な金属の箔、当該金属を表層に配置したフィルム等を用いることができる。正極合剤層１１ｂは、例えば正極活物質、導電剤、及び樹脂バインダーを含む。正極１１は、例えば正極集電体１１ａの両面に正極活物質、導電剤、及び樹脂バインダー等を含む正極合剤スラリーを塗布し、塗膜を乾燥させた後、圧縮して正極合剤層１１ｂを集電体の両面に形成することにより作製できる。 [Positive electrode]
The positive electrode 11 has a long positive electrode current collector 11a and a positive electrode mixture layer 11b formed on the positive electrode current collector 11a. The positive electrode current collector 11a is, for example, a strip-shaped body having a thickness of 5 μm to 20 μm and a substantially constant width. As the positive electrode current collector 11a, a metal foil stable in the potential range of the positive electrode 11 such as aluminum, a film in which the metal is arranged on the surface layer, or the like can be used. The positive electrode mixture layer 11b contains, for example, a positive electrode active material, a conductive agent, and a resin binder. For the positive electrode 11, for example, a positive electrode mixture slurry containing a positive electrode active material, a conductive agent, a resin binder, and the like is applied to both surfaces of the positive electrode current collector 11a, the coating film is dried, and then compressed to compress the positive electrode mixture layer 11b. Can be produced by forming on both sides of the current collector.

正極合剤層１１ｂは、例えば正極リード１９が溶接される部分及びそのちょうど反対側に位置する部分を除く正極集電体１１ａの両面の全域に形成されている。正極合剤層１１ｂの厚みは、特に限定されないが、好ましくは正極集電体１１ａの片側で４０μｍ〜８０μｍである。正極合剤層１１ｂに含まれる正極活物質としては、Ｎｉ、Ｃｏ、Ｍｎ等の遷移金属元素を含有するリチウム含有遷移金属１４酸化物が例示できる。リチウム含有遷移金属酸化物は、特に限定されないが、一般式Ｌｉ_1+xＭＯ₂（式中、−０．２＜ｘ≦０．２、ＭはＮｉ、Ｃｏ、Ｍｎ、Ａｌの少なくとも１種を含む）で表される複合酸化物であることが好ましい。 The positive electrode mixture layer 11b is formed on the entire surface of both sides of the positive electrode current collector 11a except for a portion where the positive electrode lead 19 is welded and a portion located on the opposite side thereof, for example. The thickness of the positive electrode mixture layer 11b is not particularly limited, but is preferably 40 μm to 80 μm on one side of the positive electrode current collector 11a. Examples of the positive electrode active material contained in the positive electrode mixture layer 11b include lithium-containing transition metal 14 oxides containing transition metal elements such as Ni, Co, and Mn. The lithium-containing transition metal oxide is not particularly limited, but the general formula Li _{1 + x} MO ₂ (in the formula, −0.2 <x ≦ 0.2, M is at least one of Ni, Co, Mn, and Al). It is preferably a composite oxide represented by).

正極合剤層１１ｂに含まれる導電剤としては、カーボンブラック、アセチレンブラック、ケッチェンブラック、黒鉛等の炭素材料が例示できる。正極合剤層１１ｂに含まれる樹脂バインダーとしては、ポリテトラフルオロエチレン（ＰＴＦＥ）、ポリフッ化ビニリデン（ＰＶｄＦ）等のフッ素樹脂、ポリアクリロニトリル（ＰＡＮ）、ポリイミド樹脂、アクリル樹脂、ポリオレフィン樹脂などが例示できる。これらの樹脂と、カルボキシメチルセルロース（ＣＭＣ）又はその塩等のセルロース誘導体、ポリエチレンオキシド（ＰＥＯ）等が併用されてもよい。 Examples of the conductive agent contained in the positive electrode mixture layer 11b include carbon materials such as carbon black, acetylene black, ketjen black, and graphite. Examples of the resin binder contained in the positive electrode mixture layer 11b include fluororesins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide resins, acrylic resins, and polyolefin resins. .. These resins may be used in combination with cellulose derivatives such as carboxymethyl cellulose (CMC) or salts thereof, polyethylene oxide (PEO) and the like.

［負極］
負極１２は、長尺状の負極集電体３０と、負極集電体３０上に形成された負極合剤層３１とを有する。負極集電体３０は、例えば５μｍ〜２０μｍの厚みを有し、幅が略一定の帯状体である。負極集電体３０には、銅などの負極１２の電位範囲で安定な金属の箔、当該金属を表層に配置したフィルム等を用いることができる。負極合剤層３１は、例えば負極活物質、及び樹脂バインダーを含む。負極１２は、例えば負極集電体３０の両面に負極活物質、樹脂バインダー等を含む負極合剤スラリーを塗布し、塗膜を乾燥させた後、圧縮して負極合剤層３１を集電体の両面に形成することにより作製できる。詳しくは後述するが、負極合剤層３１の圧縮は、例えば２回行われ、２回目の圧縮工程で溝３２が形成される。 [Negative electrode]
The negative electrode 12 has a long negative electrode current collector 30 and a negative electrode mixture layer 31 formed on the negative electrode current collector 30. The negative electrode current collector 30 is, for example, a strip-shaped body having a thickness of 5 μm to 20 μm and a substantially constant width. For the negative electrode current collector 30, a metal foil stable in the potential range of the negative electrode 12 such as copper, a film in which the metal is arranged on the surface layer, or the like can be used. The negative electrode mixture layer 31 contains, for example, a negative electrode active material and a resin binder. For the negative electrode 12, for example, a negative electrode mixture slurry containing a negative electrode active material, a resin binder, and the like is applied to both sides of the negative electrode current collector 30, the coating film is dried, and then compressed to form the negative electrode mixture layer 31. It can be produced by forming on both sides of. As will be described in detail later, the negative electrode mixture layer 31 is compressed twice, for example, and the groove 32 is formed in the second compression step.

負極合剤層３１は、例えば負極リード２０が溶接される部分及びそのちょうど反対側に位置する部分を除く負極集電体３０の両面の全域に形成されている。負極合剤層３１の厚みは特に限定されないが、好ましくは負極集電体３０の片側において最も厚い部分の厚みＴ₃₁は４０μｍ〜８０μｍである。負極合剤層３１に含まれる負極活物質としては、リチウムイオンを可逆的に吸蔵、放出できるものであれば特に限定されず、例えば天然黒鉛、人造黒鉛等の炭素材料、ケイ素（Ｓｉ）、錫（Ｓｎ）等のリチウムと合金化する金属、又はＳｉ、Ｓｎ等の金属元素を含む酸化物などを用いることができる。 The negative electrode mixture layer 31 is formed on both sides of the negative electrode current collector 30 except for a portion where the negative electrode lead 20 is welded and a portion located on the opposite side thereof, for example. The thickness of the negative electrode mixture layer 31 is not particularly limited, but preferably the thickness T ₃₁ of the thickest portion on one side of the negative electrode current collector 30 is 40 μm to 80 μm. The negative electrode active material contained in the negative electrode mixture layer 31 is not particularly limited as long as it can reversibly occlude and release lithium ions, for example, carbon materials such as natural graphite and artificial graphite, silicon (Si), and tin. A metal alloying with lithium such as (Sn) or an oxide containing a metal element such as Si or Sn can be used.

負極活物質の好適な例としては、黒鉛、ＳｉＯ_xで表される酸化ケイ素が挙げられる。負極合剤層３１は、負極活物質として、黒鉛又はＳｉＯ_xで表される酸化ケイ素のいずれか一方を含んでいてもよく、両方を含んでいてもよい。黒鉛と当該酸化ケイ素が併用される場合、黒鉛と当該酸化ケイ素の質量比は、例えば９９：１〜８０：２０であり、好ましくは９７：３〜９０：１０である。 Preferable examples of the negative electrode active material include graphite and silicon oxide represented by _{SiO x.} The negative electrode mixture layer 31 may contain either graphite or silicon oxide represented by _{SiO x} as the negative electrode active material, or may contain both. When graphite and the silicon oxide are used in combination, the mass ratio of graphite and the silicon oxide is, for example, 99: 1 to 80:20, preferably 97: 3 to 90:10.

ＳｉＯ_xで表される酸化ケイ素は、例えば非晶質のＳｉＯ₂マトリックス中にＳｉの微粒子が分散した構造を有する。好適な酸化ケイ素の一例は、ＳｉＯ_x（０．５≦ｘ≦１．６）である。ＳｉＯ_xで表される酸化ケイ素は、Ｌｉ_2yＳｉＯ_(2+y)（０＜ｙ＜２）で表されるリチウムシリケートを含有していてもよく、リチウムシリケート相中にＳｉの微粒子が分散した構造を有していてもよい。 Silicon oxide represented by SiO _x has a structure in which fine particles of Si are dispersed in, for example, an amorphous SiO _{2 matrix.} An example of a suitable silicon oxide is SiO _x (0.5 ≦ x ≦ 1.6). Silicon oxide represented by SiO _x _{may contain lithium silicate represented by Li 2y} SiO _{(2 + y)} (0 <y <2), and Si fine particles are dispersed in the lithium silicate phase. It may have a structure.

ＳｉＯ_xで表される酸化ケイ素の粒子表面には、酸化ケイ素よりも導電性の高い材料で構成される導電被膜が形成されていることが好ましい。導電被膜を構成する材料としては、炭素材料、金属、及び金属化合物から選択される少なくとも１種であることが好ましい。中でも、炭素材料を用いることが特に好ましい。炭素被膜は、例えばＳｉＯ_x粒子の質量に対して０．５〜１０質量％で形成される。 It is preferable that a conductive film made of a material having a higher conductivity than silicon oxide is formed on the surface of silicon oxide particles represented by SiO _x. The material constituting the conductive coating is preferably at least one selected from a carbon material, a metal, and a metal compound. Above all, it is particularly preferable to use a carbon material. The carbon film is formed, for example, at 0.5 to 10% by mass with respect to the mass of _{SiO x particles.}

負極合剤層３１に含まれる樹脂バインダーには、正極の場合と同様に、フッ素樹脂、ＰＡＮ、ポリイミド樹脂、アクリル樹脂、ポリオレフィン樹脂等を用いることができる。水系溶媒を用いて合剤スラリーを調製する場合は、ＣＭＣ又はその塩、スチレン−ブタジエンゴム（ＳＢＲ）、ポリアクリル酸（ＰＡＡ）又はその塩、ポリビニルアルコールなどを用いることが好ましい。 As the resin binder contained in the negative electrode mixture layer 31, a fluororesin, a PAN, a polyimide resin, an acrylic resin, a polyolefin resin or the like can be used as in the case of the positive electrode. When preparing a mixture slurry using an aqueous solvent, it is preferable to use CMC or a salt thereof, styrene-butadiene rubber (SBR), polyacrylic acid (PAA) or a salt thereof, polyvinyl alcohol, or the like.

図２及び図３に例示するように、負極合剤層３１の表面には、負極集電体３０の幅方向に延びる複数の溝３２が形成されている。また、負極合剤層３１には、溝３２の底部３３に区画されて負極集電体３０の幅方向に延びた複数の帯状領域３４が形成されている。そして、帯状領域３４における負極合剤層３１の表面は、各溝３２の底部３３に向かって、負極集電体３０と反対側に凸となるように湾曲している。つまり、負極合剤層３１では、溝縁部３５が丸みを帯びており、溝縁部３５に角が存在しない。これにより、充電により電極体１４が膨張している場合でも、溝３２に沿って電解液が電極体１４内へ浸透しやすくなる。少なくとも一つの帯状領域３４における負極合剤層３１の表面が各溝３２の底部３３に向かって湾曲していれば本開示の効果が発揮されるように作用する。しかし、全ての帯状領域３４における負極合剤層３１の表面が溝３２の底部３３に向かって湾曲していることが好ましい。 As illustrated in FIGS. 2 and 3, a plurality of grooves 32 extending in the width direction of the negative electrode current collector 30 are formed on the surface of the negative electrode mixture layer 31. Further, the negative electrode mixture layer 31 is formed with a plurality of band-shaped regions 34 partitioned by the bottom 33 of the groove 32 and extending in the width direction of the negative electrode current collector 30. The surface of the negative electrode mixture layer 31 in the band-shaped region 34 is curved toward the bottom 33 of each groove 32 so as to be convex on the side opposite to the negative electrode current collector 30. That is, in the negative electrode mixture layer 31, the groove edge portion 35 is rounded, and the groove edge portion 35 has no corners. As a result, even when the electrode body 14 is expanded by charging, the electrolytic solution easily permeates into the electrode body 14 along the groove 32. If the surface of the negative electrode mixture layer 31 in at least one band-shaped region 34 is curved toward the bottom 33 of each groove 32, the effect of the present disclosure is exerted. However, it is preferable that the surface of the negative electrode mixture layer 31 in all the band-shaped regions 34 is curved toward the bottom 33 of the groove 32.

本実施形態では、負極集電体３０の両面に形成された各負極合剤層３１に複数の溝３２がそれぞれ形成されている。各負極合剤層３１において溝３２の本数が同じであり、各負極合剤層３１の溝３２は互いに略同じ間隔、幅、深さで形成され、負極１２の厚み方向に重なっているが、各負極合剤層３１で溝３２の本数は異なっていてもよい。また、各負極合剤層３１の溝３２の間隔、幅、深さは互いに異なっていてもよく、各溝３２は負極１２の厚み方向に重なっていなくてもよい。 In the present embodiment, a plurality of grooves 32 are formed in each of the negative electrode mixture layers 31 formed on both sides of the negative electrode current collector 30. The number of grooves 32 in each negative electrode mixture layer 31 is the same, and the grooves 32 in each negative electrode mixture layer 31 are formed at substantially the same spacing, width, and depth, and overlap in the thickness direction of the negative electrode 12. The number of grooves 32 may be different in each negative electrode mixture layer 31. Further, the intervals, widths, and depths of the grooves 32 of each negative electrode mixture layer 31 may be different from each other, and the grooves 32 may not overlap in the thickness direction of the negative electrode 12.

複数の溝３２は、例えば負極合剤層３１の幅方向両端から幅方向中央部の近傍までそれぞれ形成されていてもよいが、好ましくは負極合剤層３１の全幅にわたって形成される（本実施形態では、負極集電体３０の全幅にわたって形成される）。溝３２は、負極集電体３０の幅方向に対して傾斜していてもよいが、好ましくは幅方向と略平行に形成される。また、各溝３２は互いに略平行に形成されていることが好ましい。 The plurality of grooves 32 may be formed, for example, from both ends in the width direction of the negative electrode mixture layer 31 to the vicinity of the central portion in the width direction, but are preferably formed over the entire width of the negative electrode mixture layer 31 (the present embodiment). Then, it is formed over the entire width of the negative electrode current collector 30). The groove 32 may be inclined with respect to the width direction of the negative electrode current collector 30, but is preferably formed substantially parallel to the width direction. Further, it is preferable that the grooves 32 are formed substantially parallel to each other.

複数の溝３２の負極集電体３０の長手方向の間隔Ｐ₃₂は、例えば各底部３３の負極集電体３０の長手方向に垂直な中心線αを基準として１５０μｍ〜２５０μｍである（図２参照）。溝３２の間隔Ｐ₃₂は、１５０μｍ〜２００μｍがより好ましい。各間隔Ｐ₃₂は、不規則であってもよいが、好ましくは略一定である。各溝３２の幅Ｗ₃₂（図２参照）は、例えば５μｍ〜１５μｍである。なお、幅Ｗ₃₂とは溝３２の底部３３の幅である。図３に示す例では、溝３２の底部３３が略平坦に形成されているが、底部３３は負極集電体３０側に凸となるように湾曲、又はＶ字状となるように突出していてもよい。その場合は湾曲部又は突出部の幅が溝の幅Ｗ₃₂に一致する。各溝３２の幅Ｗ₃₂は互いに異なっていてもよいが、好ましくは略同じである。 _{The distance P 32 in} the longitudinal direction of the negative electrode current collectors 30 of the plurality of grooves 32 is, for example, 150 μm to 250 μm with respect to the center line α perpendicular to the longitudinal direction of the negative electrode current collectors 30 of each bottom 33 (see FIG. 2). ). The spacing P _{32 of the} grooves 32 is more preferably 150 μm to 200 μm. Each interval P ₃₂ may be irregular, but is preferably substantially constant. The width W ₃₂ (see FIG. 2) of each groove 32 is, for example, 5 μm to 15 μm. The width W ₃₂ is the width of the bottom 33 of the groove 32. In the example shown in FIG. 3, the bottom 33 of the groove 32 is formed substantially flat, but the bottom 33 is curved so as to be convex toward the negative electrode current collector 30 or protrudes so as to be V-shaped. May be good. In that case, the width of the curved portion or the protruding portion _{matches the width W 32} of the groove. The widths W ₃₂ of each groove 32 may be different from each other, but are preferably substantially the same.

各溝３２の深さＤ₃₂（図３参照）は、例えば７μｍ〜２０μｍである。ここで、深さＤ₃₂とは、負極合剤層３１の厚みが最も厚い部分の表面から溝３２の最深部までの負極１２の厚み方向に沿った長さである。各溝３２の深さＤ₃₂は、例えば負極合剤層３１の最も厚い部分の厚みＴ₃₁に対して５％〜４０％となる。各溝３２の深さＤ₃₂は互いに異なっていてもよいが、好ましくは略同じである。 The depth D ₃₂ (see FIG. 3) of each groove 32 is, for example, 7 μm to 20 μm. Here, the depth D ₃₂ is the length along the thickness direction of the negative electrode 12 from the surface of the thickest portion of the negative electrode mixture layer 31 to the deepest portion of the groove 32. The depth D ₃₂ of each groove 32, is 5% to 40% relative to the thickness T ₃₁ of the thickest portion of the example the negative electrode mixture layer 31. The depth D ₃₂ of each groove 32 may be different but are preferably substantially the same.

帯状領域３４は、負極集電体３０の長手方向に並んで形成されている。図３に示す例では、帯状領域３４における負極合剤層３１の表面が、当該領域の全幅にわたって負極集電体３０と反対側に凸となるように湾曲している。即ち、帯状領域３４における負極合剤層３１の表面全体が湾曲しており、負極１２を長手方向に切断した断面において帯状領域３４における負極合剤層３１の表面は緩やかな曲線となっている。 The band-shaped regions 34 are formed side by side in the longitudinal direction of the negative electrode current collector 30. In the example shown in FIG. 3, the surface of the negative electrode mixture layer 31 in the band-shaped region 34 is curved so as to be convex on the opposite side to the negative electrode current collector 30 over the entire width of the region. That is, the entire surface of the negative electrode mixture layer 31 in the band-shaped region 34 is curved, and the surface of the negative electrode mixture layer 31 in the band-shaped region 34 is a gentle curve in the cross section obtained by cutting the negative electrode 12 in the longitudinal direction.

各帯状領域３４は、当該領域の幅方向両端部から略等距離の位置、即ち帯状領域３４の幅方向中央部が頂部となるように湾曲していることが好ましい。つまり、帯状領域３４の厚みは、幅方向両端部から幅方向中央部に近づくほど厚くなる。換言すると、負極合剤層３１は、帯状領域３４の幅方向中央部から当該領域の両側に形成された各溝３２の底部３３に向かって次第に厚みが薄くなっている。溝縁部３５には角が存在せず、溝３２が形成された部分のみで負極合剤層３１の厚みが急峻に減少するような表面形状を有さない。 It is preferable that each band-shaped region 34 is curved so as to be at a position substantially equidistant from both ends in the width direction of the region, that is, the central portion in the width direction of the band-shaped region 34 is the top. That is, the thickness of the strip-shaped region 34 becomes thicker as it approaches the central portion in the width direction from both ends in the width direction. In other words, the negative electrode mixture layer 31 gradually becomes thinner from the central portion in the width direction of the strip-shaped region 34 toward the bottom 33 of each groove 32 formed on both sides of the region. The groove edge portion 35 has no corners and does not have a surface shape such that the thickness of the negative electrode mixture layer 31 sharply decreases only in the portion where the groove 32 is formed.

負極合剤層３１は、例えば帯状領域３４における負極合剤層３１の密度と、底部領域３５における負極合剤層３１の密度との差が５％以内である。ここで、底部領域３５とは、各溝３２の底部３３と負極集電体３０の間に位置する領域である。図６に例示するような溝１０２を形成した場合は、底部領域１０６で他の領域よりも負極合剤層１０１の密度が高くなりやすいが、帯状領域３４の表面を緩やかな曲面状とすることで、底部領域３５における密度の上昇を抑制できる。負極合剤層３１の密度を均一化することは、充電により膨張した電極体内への電解液の浸透を容易にするとともに不均一な電池反応を抑制し、サイクル特性の向上に寄与する。 In the negative electrode mixture layer 31, for example, the difference between the density of the negative electrode mixture layer 31 in the band-shaped region 34 and the density of the negative electrode mixture layer 31 in the bottom region 35 is within 5%. Here, the bottom region 35 is a region located between the bottom 33 of each groove 32 and the negative electrode current collector 30. When the groove 102 as illustrated in FIG. 6 is formed, the density of the negative electrode mixture layer 101 tends to be higher in the bottom region 106 than in the other regions, but the surface of the band-shaped region 34 should have a gentle curved surface. Therefore, the increase in density in the bottom region 35 can be suppressed. Making the density of the negative electrode mixture layer 31 uniform facilitates the permeation of the electrolytic solution into the electrode body expanded by charging, suppresses the non-uniform battery reaction, and contributes to the improvement of the cycle characteristics.

図４に示す例では、負極合剤層３１Ｘの表面が、各帯状領域３４Ｘの幅方向両端部の近傍のみで負極集電体３０と反対側に凸となるように湾曲している。図４に例示する負極１２Ｘでは、各溝３２Ｘの底部３３Ｘが略平坦である。また、溝縁部３５Ｘが湾曲し、溝縁部３５Ｘに角が存在しない点で、負極１２と共通する。他方、帯状領域３４Ｘは、幅方向中央部が湾曲しておらず、その表面が略平坦である点で、負極１２の帯状領域３４と異なる。なお、溝３２Ｘの寸法等は、負極１２の溝３２と同様とすることができる。 In the example shown in FIG. 4, the surface of the negative electrode mixture layer 31X is curved so as to be convex on the opposite side to the negative electrode current collector 30 only in the vicinity of both ends in the width direction of each band-shaped region 34X. In the negative electrode 12X illustrated in FIG. 4, the bottom portion 33X of each groove 32X is substantially flat. Further, it is common with the negative electrode 12 in that the groove edge portion 35X is curved and the groove edge portion 35X has no corner. On the other hand, the strip-shaped region 34X is different from the strip-shaped region 34 of the negative electrode 12 in that the central portion in the width direction is not curved and the surface thereof is substantially flat. The dimensions of the groove 32X and the like can be the same as those of the groove 32 of the negative electrode 12.

図５は、負極合剤層３１の表面に複数の溝３２を形成するための押圧部材５０を示す。複数の溝３２は、表面に凹凸を有さないローラ等の押圧部材で負極合剤層３１を圧縮した後、図５に例示する押圧部材５０を用いて負極合剤層３１を再度圧縮することにより形成される。押圧部材５０の表面には、複数の凸部５１が形成されている。各凸部５１は、互いに略一定の間隔をあけて、各凸部５１が並ぶ方向と直交する方向に細長く形成されている。そして、各凸部５１の両側には表面が緩やかに湾曲した凹部５２が形成されている。押圧部材５０は、例えば負極合剤層３１に当接する表面に複数の凸部５１と、複数の凹部５２とが形成されたローラである。 FIG. 5 shows a pressing member 50 for forming a plurality of grooves 32 on the surface of the negative electrode mixture layer 31. In the plurality of grooves 32, the negative electrode mixture layer 31 is compressed by a pressing member such as a roller having no unevenness on the surface, and then the negative electrode mixture layer 31 is compressed again by using the pressing member 50 illustrated in FIG. Is formed by. A plurality of convex portions 51 are formed on the surface of the pressing member 50. The convex portions 51 are formed elongated in a direction orthogonal to the direction in which the convex portions 51 are lined up at a substantially constant interval from each other. The concave portions 52 having a gently curved surface are formed on both sides of each convex portion 51. The pressing member 50 is, for example, a roller in which a plurality of convex portions 51 and a plurality of concave portions 52 are formed on a surface that abuts on the negative electrode mixture layer 31.

負極合剤層３１は、凸部５１によって圧縮された部分に溝３２となり、凹部５２によって圧縮された部分が帯状領域３４となる。図５に示す例では、凸部５１の先端が略平坦であるため、溝３２の底部３３が略平坦となる。そして、凹部５２の表面は、上述のように湾曲しているので、帯状領域３４における負極合剤層３１の表面全体が負極集電体３０と反対側に凸となるように湾曲した形状となる。なお、凹部５２の表面形状を変更することで、図４に例示する帯状領域３４Ｘを形成することができる。 The negative electrode mixture layer 31 has a groove 32 in a portion compressed by the convex portion 51, and a strip-shaped region 34 in a portion compressed by the concave portion 52. In the example shown in FIG. 5, since the tip of the convex portion 51 is substantially flat, the bottom portion 33 of the groove 32 is substantially flat. Since the surface of the recess 52 is curved as described above, the entire surface of the negative electrode mixture layer 31 in the band-shaped region 34 is curved so as to be convex on the opposite side to the negative electrode current collector 30. .. By changing the surface shape of the recess 52, the band-shaped region 34X illustrated in FIG. 4 can be formed.

［セパレータ］
セパレータ１３には、イオン透過性及び絶縁性を有する多孔性シートが用いられる。多孔性シートの具体例としては、微多孔薄膜、織布、不織布等が挙げられる。セパレータ１３の材質としては、ポリエチレン、ポリプロピレン等のオレフィン樹脂、セルロースなどが好適である。セパレータ１３は、単層構造、積層構造のいずれであってもよい。セパレータ１３の表面には、耐熱性材料を含む耐熱層が形成されていてもよい。 [Separator]
As the separator 13, a porous sheet having ion permeability and insulating property is used. Specific examples of the porous sheet include a microporous thin film, a woven fabric, and a non-woven fabric. As the material of the separator 13, olefin resin such as polyethylene and polypropylene, cellulose and the like are suitable. The separator 13 may have either a single-layer structure or a laminated structure. A heat-resistant layer containing a heat-resistant material may be formed on the surface of the separator 13.

以下、実施例により本開示をさらに説明するが、本開示はこれらの実施例に限定されるものではない。 Hereinafter, the present disclosure will be further described with reference to Examples, but the present disclosure is not limited to these Examples.

＜実施例１＞
［正極の作製］
リチウムニッケル複合酸化物を９８質量部と、導電性炭素粉末を１質量部と、ポリフッ化ビニリデンを１質量部と、適量のＮ−メチル−２−ピロリドン（ＮＭＰ）とを混合して、正極合剤スラリーを調製した。次に、正極合剤スラリーを厚み１５μｍのアルミニウム箔からなる正極集電体の両面にそれぞれ塗布し、塗膜を乾燥させた後、塗膜を圧縮して正極合剤層を形成した。正極合剤層が両面に形成された集電体を所定の電極サイズに切断し、集電体の表面が露出した部分にアルミニウム製リードを接続して正極を得た。正極の厚みは、正極合剤層が集電体の両面に形成された部分で１４３μｍであった。 <Example 1>
[Preparation of positive electrode]
98 parts by mass of lithium nickel composite oxide, 1 part by mass of conductive carbon powder, 1 part by mass of polyvinylidene fluoride, and an appropriate amount of N-methyl-2-pyrrolidone (NMP) are mixed to form a positive electrode. An agent slurry was prepared. Next, the positive electrode mixture slurry was applied to both sides of the positive electrode current collector made of aluminum foil having a thickness of 15 μm, the coating film was dried, and then the coating film was compressed to form the positive electrode mixture layer. A current collector having a positive electrode mixture layer formed on both sides was cut into a predetermined electrode size, and an aluminum lead was connected to a portion where the surface of the current collector was exposed to obtain a positive electrode. The thickness of the positive electrode was 143 μm at the portion where the positive electrode mixture layer was formed on both sides of the current collector.

［負極の作製］
黒鉛粉末を９８質量部と、スチレンブタジエンゴムを１質量部と、カルボキシメチルセルロースを１質量部とを混合し、さらに水を適量加えて、負極合剤スラリーを調製した。次に、負極合剤スラリーを厚み１０μｍの銅箔からなる負極集電体の両面にそれぞれ塗布し、塗膜を乾燥させた後、塗膜を圧縮して負極合剤層を形成した。このときの負極合剤層の密度は、１．６ｇ／ｃｃであった。 [Preparation of negative electrode]
98 parts by mass of graphite powder, 1 part by mass of styrene-butadiene rubber, and 1 part by mass of carboxymethyl cellulose were mixed, and an appropriate amount of water was added to prepare a negative electrode mixture slurry. Next, the negative electrode mixture slurry was applied to both sides of the negative electrode current collector made of copper foil having a thickness of 10 μm, the coating film was dried, and then the coating film was compressed to form the negative electrode mixture layer. The density of the negative electrode mixture layer at this time was 1.6 g / cc.

次に、図５に示すような表面形状を有するエンボスロール（凸部５１の頂点の幅：１０μｍ、凸部５１同士の間隔：２００μｍ）を用いて負極合剤層を圧縮し、負極合剤層の表面に複数の溝を形成した。各溝は、幅：１０μｍ、深さ：１０μｍ、間隔：２００μｍで、負極集電体の全幅にわたって形成され、各溝の間には集電体と反対側に凸となるように表面が湾曲した複数の帯状領域が形成された。帯状領域は表面全体が緩やかに湾曲し、溝に沿った縁部に角は存在しない。帯状領域及び底部領域における負極合剤層の密度は、いずれも１．６ｇ／ｃｃであった。 Next, the negative electrode mixture layer is compressed using an embossed roll having a surface shape as shown in FIG. 5 (width of the apex of the convex portion 51: 10 μm, distance between the convex portions 51: 200 μm), and the negative electrode mixture layer is used. Multiple grooves were formed on the surface of the. Each groove had a width of 10 μm, a depth of 10 μm, and an interval of 200 μm, and was formed over the entire width of the negative electrode current collector, and the surface was curved so as to be convex on the opposite side of the current collector between the grooves. Multiple strips were formed. The entire surface of the band-shaped region is gently curved, and there are no corners at the edges along the grooves. The density of the negative electrode mixture layer in the band-shaped region and the bottom region was 1.6 g / cc.

続いて、溝付きの負極合剤層が両面に形成された集電体を所定の電極サイズに切断し、集電体の表面が露出した部分にニッケル製リードを接続して負極を得た。負極の厚みは、負極合剤層が集電体の両面に形成された部分であって、帯状領域の頂部に対応する部分で１６０μｍであった。 Subsequently, a current collector having grooved negative electrode mixture layers formed on both sides was cut to a predetermined electrode size, and a nickel lead was connected to a portion where the surface of the current collector was exposed to obtain a negative electrode. The thickness of the negative electrode was 160 μm at the portion where the negative electrode mixture layer was formed on both sides of the current collector and corresponding to the top of the band-shaped region.

［非水電解液の調製］
アルゴン雰囲気下で、エチレンカーボネート（ＥＣ）と、ジメチルカーボネート（ＤＭＣ）とを、３：７の体積比で混合した。当該混合溶媒に、１モル／Ｌの濃度になるようにＬｉＰＦ₆を溶解させて非水電解液を調製した。 [Preparation of non-aqueous electrolyte solution]
Ethylene carbonate (EC) and dimethyl carbonate (DMC) were mixed in an argon atmosphere at a volume ratio of 3: 7. A non-aqueous electrolyte solution was prepared by dissolving _{LiPF 6} in the mixed solvent so as to have a concentration of 1 mol / L.

［電池の作製］
上記正極と上記負極を、厚み２０μｍのポリエチレン製微多孔膜からなるセパレータを介して渦巻き状に巻回することで巻回型の電極体を作製した。当該電極体を、２５℃、１気圧の窒素雰囲気下で有底円筒形状の電池ケース本体に収容し、上記非水電解液を注入した後、ガスケット及び封口体により電池ケース本体の開口部を封口して、円筒形非水電解質二次電池を作製した。 [Battery production]
A wound electrode body was produced by spirally winding the positive electrode and the negative electrode through a separator made of a polyethylene microporous film having a thickness of 20 μm. The electrode body is housed in a bottomed cylindrical battery case body under a nitrogen atmosphere of 25 ° C. and 1 atmosphere, and after injecting the non-aqueous electrolyte solution, the opening of the battery case body is sealed with a gasket and a sealing body. Then, a cylindrical non-aqueous electrolyte secondary battery was produced.

＜実施例２＞
負極活物質として、黒鉛を９３質量部と、ＳｉＯ_x（ｘ＝１）で表される酸化ケイ素を７質量部とを混合したものを用いたこと以外は、実施例１と同様にして非水電解質二次電池を作製した。 <Example 2>
As the negative electrode active material, non-aqueous material was used in the same manner as in Example 1 except that a mixture of 93 parts by mass of graphite and _{7 parts by mass of silicon oxide represented by SiO x (x = 1) was used.} An electrolyte secondary battery was manufactured.

＜比較例１＞
図７に示すような表面形状を有するエンボスロール（凸部１１１の頂点の幅：１０μｍ、凸部１１１同士の間隔：２００μｍ）を用いて負極合剤層を圧縮し、負極合剤層の表面に複数の溝を形成した以外は、実施例１と同様にして負極及び電池を作製した。各溝は、幅：１０μｍ、深さ：１０μｍ、間隔：２００μｍで、負極集電体の全幅にわたって形成された。各溝の間には表面が略平坦な複数の帯状領域が形成され、溝に沿った縁部には角が形成された。帯状領域における負極合剤層の密度は１．６ｇ／ｃｃ、底部領域における負極合剤層の密度は１．６５ｇ／ｃｃであった。 <Comparative example 1>
The negative electrode mixture layer is compressed using an embossed roll having a surface shape as shown in FIG. 7 (width of vertices of convex portions 111: 10 μm, distance between convex portions 111: 200 μm), and the surface of the negative electrode mixture layer is formed. A negative electrode and a battery were produced in the same manner as in Example 1 except that a plurality of grooves were formed. Each groove was formed over the entire width of the negative electrode current collector with a width of 10 μm, a depth of 10 μm, and an interval of 200 μm. A plurality of strip-shaped regions having a substantially flat surface were formed between the grooves, and corners were formed at the edges along the grooves. The density of the negative electrode mixture layer in the band-shaped region was 1.6 g / cc, and the density of the negative electrode mixture layer in the bottom region was 1.65 g / cc.

＜比較例２＞
エンボスロールを用いた負極合剤層の圧縮を行わず、負極合剤層の表面に溝を形成しなかったこと以外は、実施例１と同様にして負極及び電池を作製した。 <Comparative example 2>
A negative electrode and a battery were produced in the same manner as in Example 1 except that the negative electrode mixture layer was not compressed using embossed rolls and no grooves were formed on the surface of the negative electrode mixture layer.

＜比較例３＞
負極活物質として、黒鉛を９３質量部と、ＳｉＯ_x（ｘ＝１）で表される酸化ケイ素を７質量部とを混合したものを用いたこと以外は、比較例１と同様にして非水電解質二次電池を作製した。 <Comparative example 3>
Non-aqueous in the same manner as in Comparative Example 1 except that a mixture of 93 parts by mass of graphite and _{7 parts by mass of silicon oxide represented by SiO x (x = 1) was used as the negative electrode active material.} An electrolyte secondary battery was manufactured.

＜比較例４＞
負極活物質として、黒鉛を９３質量部と、ＳｉＯ_x（ｘ＝１）で表される酸化ケイ素を７質量部とを混合したものを用いたこと以外は、比較例２と同様にして非水電解質二次電池を作製した。 <Comparative example 4>
Non-aqueous in the same manner as in Comparative Example 2 except that a mixture of 93 parts by mass of graphite and _{7 parts by mass of silicon oxide represented by SiO x (x = 1) was used as the negative electrode active material.} An electrolyte secondary battery was manufactured.

上記各非水電解質二次電池について以下の方法で性能評価を行い、評価結果を表１に示した。表１には、当該評価結果と共に、負極活物質、充電時における電極体の膨張率、及び負極合剤層の表面に形成された溝の寸法等を示す。 The performance of each of the above non-aqueous electrolyte secondary batteries was evaluated by the following method, and the evaluation results are shown in Table 1. Table 1 shows the negative electrode active material, the expansion coefficient of the electrode body during charging, the dimensions of the grooves formed on the surface of the negative electrode mixture layer, and the like, as well as the evaluation results.

［サイクル特性の評価］
２５℃の温度条件下において、１Ｃの定電流で電池電圧が４．２Ｖになるまで充電した後、４．２Ｖの定電圧で終止電流が０．０２Ｃになるまで充電した。１分間休止した後、１Ｃの定電流で電池電圧が２．５Ｖになるまで放電を行い、１分間休止した。この充放電サイクルを５００サイクル繰り返し、１サイクル目の放電容量に対する５００サイクル目の放電容量の比率（容量維持率）を求めた。なお、表１に示す実施例２及び各比較例の電池の容量維持率は、実施例１の電池の容量維持率を１００としたときの値である。 [Evaluation of cycle characteristics]
Under the temperature condition of 25 ° C., the battery was charged with a constant current of 1 C until the battery voltage became 4.2 V, and then charged with a constant voltage of 4.2 V until the final current became 0.02 C. After resting for 1 minute, the battery was discharged with a constant current of 1C until the battery voltage became 2.5V, and then rested for 1 minute. This charge / discharge cycle was repeated for 500 cycles, and the ratio of the discharge capacity at the 500th cycle (capacity retention rate) to the discharge capacity at the first cycle was determined. The battery capacity retention rate of Example 2 and each Comparative Example shown in Table 1 is a value when the capacity retention rate of the battery of Example 1 is 100.

表１に示すように、実施例１の電池は、比較例１，２の電池と比べて、サイクル特性に優れる。比較例１，２の電池ではサイクル特性に差がなく、比較例１の負極合剤層の表面に形成された溝はサイクル特性に寄与しないことが分かった。つまり、充電時における電極体の膨張率が１２０％である場合は、溝縁部に角が存在するような溝を形成してもサイクル特性の改善効果がなく、溝縁部に角が存在しない溝を形成した場合にのみ、サイクル特性が改善される。 As shown in Table 1, the battery of Example 1 is superior in cycle characteristics to the batteries of Comparative Examples 1 and 2. It was found that there was no difference in the cycle characteristics between the batteries of Comparative Examples 1 and 2, and that the grooves formed on the surface of the negative electrode mixture layer of Comparative Example 1 did not contribute to the cycle characteristics. That is, when the expansion coefficient of the electrode body at the time of charging is 120%, there is no effect of improving the cycle characteristics even if a groove having a corner exists at the groove edge portion, and there is no corner at the groove edge portion. Cycle characteristics are improved only when grooves are formed.

一方、充電時における電極体の膨張率が１５０％である場合は、負極合剤層の表面に溝が形成されていない比較例４の電池においてサイクル特性が大きく低下した。この場合は、溝縁部に角が存在するような溝であっても、これを負極合剤層の表面に形成することで（比較例３）、サイクル特性の改善効果が見られる。さらに、実施例２の電池では、比較例３の電池よりもサイクル特性が大きく向上し、実施例１の電池と同等以上のサイクル特性が得られた。 On the other hand, when the expansion coefficient of the electrode body at the time of charging was 150%, the cycle characteristics were significantly deteriorated in the battery of Comparative Example 4 in which the groove was not formed on the surface of the negative electrode mixture layer. In this case, even if the groove has an angle at the groove edge, the effect of improving the cycle characteristics can be seen by forming the groove on the surface of the negative electrode mixture layer (Comparative Example 3). Further, the battery of Example 2 has significantly improved cycle characteristics as compared with the battery of Comparative Example 3, and the cycle characteristics equal to or higher than those of the battery of Example 1 have been obtained.

以上のように、溝縁部に角が存在しない溝が負極合剤層の表面に形成された負極を用いることにより、サイクル特性に優れた非水電解質二次電池が得られる。特に、非水電解質二次電池が充放電に伴う体積変化が大きな電極体を備える場合に、サイクル特性の改善効果が顕著に現れる。 As described above, by using the negative electrode in which the groove having no corner at the groove edge portion is formed on the surface of the negative electrode mixture layer, a non-aqueous electrolyte secondary battery having excellent cycle characteristics can be obtained. In particular, when the non-aqueous electrolyte secondary battery includes an electrode body having a large volume change due to charging / discharging, the effect of improving the cycle characteristics is remarkably exhibited.

１０非水電解質二次電池、１１正極、１２，１２Ｘ負極、１３セパレータ、１４電極体、１５ケース本体、１６封口体、１７，１８絶縁板、１９正極リード、２０負極リード、２１張り出し部、２２フィルタ、２３下弁体、２４絶縁部材、２５上弁体、２６キャップ、２７ガスケット、３０負極集電体、３１，３１Ｘ負極合剤層、３２，３２Ｘ溝、３３，３３Ｘ底部、３４，３４Ｘ帯状領域、３５，３５Ｘ溝縁部、３６底部領域、５０押圧部材、５１凸部、５２凹部、１００負極、１０１負極合剤層、１０２溝、１０６底部領域、１１０押圧部材、１１１凸部、１１２凹部、α 中心線 10 Non-aqueous electrolyte secondary battery, 11 positive electrode, 12, 12X negative electrode, 13 separator, 14 electrode body, 15 case body, 16 sealing body, 17, 18 insulating plate, 19 positive electrode lead, 20 negative electrode lead, 21 overhang, 22 Filter, 23 lower valve body, 24 insulating member, 25 upper valve body, 26 cap, 27 gasket, 30 negative electrode current collector, 31, 31X negative electrode mixture layer, 32, 32X groove, 33, 33X bottom, 34, 34X strip Region, 35, 35X groove edge, 36 bottom region, 50 pressing member, 51 convex, 52 concave, 100 negative electrode, 101 negative electrode mixture layer, 102 groove, 106 bottom region, 110 pressing member, 111 convex, 112 concave , Α Center line

Claims

長尺状の負極集電体と、前記負極集電体上に形成された負極合剤層とを有する非水電解質二次電池用負極であって、
前記負極合剤層の表面には、前記負極集電体の幅方向に延びる複数の溝と、前記複数の溝の底部に区画されて前記負極集電体の幅方向に延びた複数の帯状領域が形成され、
前記複数の帯状領域の少なくとも一つの帯状領域における前記負極合剤層の表面は、当該領域の全幅にわたって、前記負極集電体と反対側に凸となるように湾曲しており、
前記少なくとも一つの帯状領域の前記負極合剤層の厚みは、当該領域の幅方向両端部から当該領域の幅方向中央部に近づくほど厚くなっている、非水電解質二次電池用負極。 A negative electrode for a non-aqueous electrolyte secondary battery having a long negative electrode current collector and a negative electrode mixture layer formed on the negative electrode current collector.
On the surface of the negative electrode mixture layer, a plurality of grooves extending in the width direction of the negative electrode current collector and a plurality of strip-shaped regions partitioned at the bottom of the plurality of grooves and extending in the width direction of the negative electrode current collector. Is formed,
At least one surface of said at strip area anode mixture layer of said plurality of band-like regions, over the entire width of the region is curved to be convex on the negative electrode current collector opposite,
A negative electrode for a non-aqueous electrolyte secondary battery , wherein the thickness of the negative electrode mixture layer in the at least one band-shaped region becomes thicker from both ends in the width direction of the region toward the center in the width direction of the region.

前記複数の溝の各底部と前記負極集電体の間に位置する底部領域の前記負極合剤層の密度と、前記帯状領域の前記負極合剤層の密度との差は、５％以内である、請求項１に記載の非水電解質二次電池用負極。 The difference between the density of the negative electrode mixture layer in the bottom region located between each bottom of the plurality of grooves and the negative electrode current collector and the density of the negative electrode mixture layer in the band-shaped region is within 5%. The negative electrode for a non-aqueous electrolyte secondary battery according to claim 1.

前記負極合剤層は、ＳｉＯ_ｘ（０．５≦ｘ≦１．６）で表される酸化ケイ素を含む、請求項１又は２に記載の非水電解質二次電池用負極。 The negative electrode for a non-aqueous electrolyte secondary battery according to claim 1 or 2 , wherein the negative electrode mixture layer contains silicon oxide represented by _{SiO x} (0.5 ≦ x ≦ 1.6).

前記複数の溝は、前記負極合剤層の全幅にわたって形成されている、請求項１〜３のいずれか１項に記載の非水電解質二次電池用負極。 The negative electrode for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 3 , wherein the plurality of grooves are formed over the entire width of the negative electrode mixture layer.

前記複数の溝の前記負極集電体の長手方向の間隔は、前記複数の溝の各底部の前記負極集電体の長手方向に垂直な中心線を基準として１５０μｍ〜２５０μｍである、請求項１〜４のいずれか１項に記載の非水電解質二次電池用負極。 The distance between the plurality of grooves in the longitudinal direction of the negative electrode current collector is 150 μm to 250 μm with respect to a center line perpendicular to the longitudinal direction of the negative electrode current collector at the bottom of each of the plurality of grooves. The negative electrode for a non-aqueous electrolyte secondary battery according to any one of 4 to 4.

前記複数の溝の各底部の幅は５μｍ〜１５μｍであり、前記各溝の深さは７μｍ〜２０μｍである、請求項１〜５のいずれか１項に記載の非水電解質二次電池用負極。 The negative electrode for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 5 , wherein the width of each bottom of the plurality of grooves is 5 μm to 15 μm, and the depth of each groove is 7 μm to 20 μm. ..

請求項１〜６のいずれか１項に記載の負極と、正極と、セパレータと、前記負極及び前記正極が前記セパレータを介して渦巻状に巻回された巻回型の電極体と、非水電解質とを備える、非水電解質二次電池。 The negative electrode, the positive electrode, the separator, the negative electrode and the positive electrode in which the negative electrode and the positive electrode are spirally wound via the separator, and a non-water type electrode body according to any one of claims 1 to 6. A non-aqueous electrolyte secondary battery with an electrolyte.