JP2011070976A - Lithium ion secondary battery, vehicle, and battery loading equipment - Google Patents

Lithium ion secondary battery, vehicle, and battery loading equipment Download PDF

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JP2011070976A
JP2011070976A JP2009221771A JP2009221771A JP2011070976A JP 2011070976 A JP2011070976 A JP 2011070976A JP 2009221771 A JP2009221771 A JP 2009221771A JP 2009221771 A JP2009221771 A JP 2009221771A JP 2011070976 A JP2011070976 A JP 2011070976A
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active material
negative electrode
battery
lithium ion
ion secondary
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Tatsuya Koga
達哉 古賀
Hiromoto Awano
宏基 粟野
Hiroyuki Yamaguchi
裕之 山口
Yoshio Wada
吉修 和田
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Toyota Motor Corp
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    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a lithium ion secondary battery equipped with a negative electrode plate having a negative electrode active material layer suppressing a decrease of a battery capacity involved in use, and to provide a vehicle and battery loading equipment loaded with the lithium ion secondary battery. <P>SOLUTION: The lithium ion secondary battery 1 includes a power generation element 10 formed by winding the belt-like negative electrode plate 20, a belt-like positive electrode plate 30, and a belt-like separator 50 interposed between the negative electrode plate 20 and the positive electrode plate 30 and impregnating the separator 50 with electrolyte 60, wherein the negative electrode active material layer includes belt-like end edge parts 21E respectively located at both ends in a width direction DW and a belt-like central part 21C located in the center in the width direction DW, and wherein the center part has a layer characteristic of a resistance lower than that of the end edge parts. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

本発明は、負極活物質層を有する負電極板を備えるリチウムイオン二次電池、このリチウムイオン二次電池を搭載した車両及び電池搭載機器に関する。   The present invention relates to a lithium ion secondary battery including a negative electrode plate having a negative electrode active material layer, a vehicle equipped with the lithium ion secondary battery, and a battery-equipped device.

近年、ハイブリッド自動車やノート型パソコン、ビデオカムコーダなどのポータブル電子機器の駆動用電源に、リチウムイオン二次電池が利用されている。
このようなリチウムイオン二次電池には、いずれも帯状の、負電極板と正電極板と、これらの間に介在してなるセパレータとを捲回してなり、セパレータに電解液を含浸した発電要素を備えるリチウムイオン二次電池（以下、単に電池という）が挙げられる。 In recent years, lithium ion secondary batteries have been used as power sources for driving portable electronic devices such as hybrid cars, notebook computers, and video camcorders.
In such a lithium ion secondary battery, a strip-shaped negative electrode plate, a positive electrode plate, and a separator interposed between them are wound, and the separator is impregnated with an electrolytic solution. Lithium ion secondary batteries (hereinafter simply referred to as batteries).

このような電池において、特許文献１では、さらに負極（負極活物質層）の幅方向両端部側領域（端縁部）の電極密度を、負極の幅方向中央部領域（中央部）の電極密度より高く構成することにより、電池の充放電サイクル寿命を向上させた非水電解質二次電池（リチウムイオン二次電池）が開示されている。   In such a battery, in Patent Document 1, the electrode density in the width direction both ends side region (edge portion) of the negative electrode (negative electrode active material layer) is further defined as the electrode density in the width direction central region (center portion) of the negative electrode. A non-aqueous electrolyte secondary battery (lithium ion secondary battery) is disclosed which has a higher charge / discharge cycle life by being configured higher.

特開２００５−２０９４１１号公報JP 2005-209411 A

ところで、発明者らの研究によれば、電池を繰り返し充放電した場合、負極活物質層の幅方向の両端部に位置する端縁部付近の電解液と、幅方向の中央に位置する中央部付近の電解液とのリチウムイオンの濃度を比べると、端縁部の方が中央部よりもリチウムイオンの濃度が高くなることが判ってきた。その理由としては、中央部よりも外部に近い端縁部では、充放電の際に生じる活物質層及びこれによる発電要素の膨張・収縮に伴って、電解液の溶媒が電池ケース内の外部に向けて移動しやすいためであると考えられる。
ところで、リチウムイオンの濃度が低い部位では、濃度の高い部位よりも移動できるリチウムイオンが少なく、電解液と負極活物質層とを併せた総合の電気抵抗が高く見える。従って、図１（ａ）に示すように、負極活物質層に生じる電気抵抗が中央部及び端縁部に限らず一様であったとしても、電解液と負極活物質層とを併せた総合の電気抵抗は、図１（ｂ）に示すように、中央部が端縁部に比して高く見える。
このように電解液と負極活物質層とを併せた総合の電気抵抗に高低が生じている電池をほぼ満充電まで充電して（充電末期）、負極活物質層の平均の電位（対リチウム金属電位（Ｖｖｓ．Ｌｉ／Ｌｉ+））が０Ｖに近い値（例えば、０．１Ｖ）になった場合について考える。
このような状態では、負極活物質層の電位分布は、図１（ｃ）に示すようになり、最も低い中央部では０Ｖ以下の電位になることがある。このため、中央部の表面に金属リチウムが析出してしまう虞がある。一旦析出した金属リチウムは、その後の充放電に関与しなくなるので、充放電を繰り返す等の使用に伴って、この電池の電池容量が低下してしまう。 By the way, according to the research of the inventors, when the battery is repeatedly charged and discharged, the electrolyte solution near the edge portion located at both ends in the width direction of the negative electrode active material layer and the center portion located in the center in the width direction Comparing the concentration of lithium ions with the nearby electrolyte, it has been found that the edge portion has a higher lithium ion concentration than the center portion. The reason for this is that at the edge part closer to the outside than the center part, the solvent of the electrolyte solution is exposed to the outside in the battery case as the active material layer generated during charging and discharging and the power generation element thereby expand and contract. It is thought that it is because it is easy to move toward.
By the way, in the site | part with a low density | concentration of lithium ion, there are few lithium ions which can move compared with a site | part with a high density | concentration, and the total electrical resistance which combined electrolyte solution and the negative electrode active material layer looks high. Therefore, as shown in FIG. 1 (a), even if the electrical resistance generated in the negative electrode active material layer is not limited to the central portion and the edge portion, it is a comprehensive combination of the electrolytic solution and the negative electrode active material layer. As shown in FIG. 1B, the electric resistance of the center portion appears higher than the edge portion.
In this way, the battery in which the total electric resistance including the electrolyte and the negative electrode active material layer is high or low is charged to almost full charge (at the end of charging), and the average potential of the negative electrode active material layer (with respect to lithium metal) Consider a case where the potential (Vvs. Li / Li + ) is a value close to 0 V (for example, 0.1 V).
In such a state, the potential distribution of the negative electrode active material layer is as shown in FIG. 1C, and the potential may be 0 V or less in the lowest central portion. For this reason, there exists a possibility that metallic lithium may precipitate on the surface of a center part. The metal lithium once deposited does not participate in subsequent charging / discharging, and thus the battery capacity of this battery is reduced with repeated use of charging / discharging.

これに対して、特許文献１のリチウムイオン二次電池を用いることが考えられるが、この特許文献１のリチウムイオン二次電池では、その負極活物質層の、端縁部と中央部との間で電極密度（固形分密度）を異ならせているので、充放電の際に負極活物質層に生じる膨張・収縮の程度についても、端縁部と中央部との間で異なる。つまり、電極密度が高い端縁部の方が、中央部よりも大きく膨張・収縮する。このため、例えば、端縁部と中央部との境界部分で亀裂や剥離等の不具合が生じて、電池性能が低下してしまう虞がある。   On the other hand, it is conceivable to use the lithium ion secondary battery disclosed in Patent Document 1. However, in the lithium ion secondary battery disclosed in Patent Document 1, the negative electrode active material layer is formed between the edge portion and the central portion. Therefore, the degree of expansion / contraction that occurs in the negative electrode active material layer during charge / discharge also differs between the edge portion and the central portion. That is, the edge portion having a higher electrode density expands and contracts more than the center portion. For this reason, there exists a possibility that malfunctions, such as a crack and peeling, may arise in the boundary part of an edge part and a center part, and battery performance may fall.

本発明は、かかる問題点に鑑みてなされたものであって、使用に伴う電池容量の低下を抑制した負極活物質層を有する負電極板を備えるリチウムイオン二次電池、このリチウムイオン二次電池を搭載した車両及び電池搭載機器を提供することを目的とする。   The present invention has been made in view of such problems, and a lithium ion secondary battery including a negative electrode plate having a negative electrode active material layer in which a decrease in battery capacity due to use is suppressed, and the lithium ion secondary battery An object of the present invention is to provide a vehicle equipped with a battery and a battery-equipped device.

本発明の一態様は、導電性を有する帯状の負極集電板、及び、この負極集電板上に配置されて、負極活物質粒子を含み、この負極集電板の長手方向に延びる帯状の負極活物質層を有する帯状の負電極板と、上記負電極板と対向してなる帯状の正電極板と、上記負電極板と上記正電極板との間に介在してなるセパレータと、を捲回してなり、上記セパレータにリチウムイオンを含む電解液を含浸させた発電要素を備えるリチウムイオン二次電池であって、上記負極活物質層は、上記長手方向に直交する幅方向の両端部にそれぞれ位置する帯状の端縁部と、上記幅方向の中央に位置して、上記端縁部にそれぞれ隣接する帯状の中央部と、からなり、上記中央部は、上記端縁部よりも低抵抗の層特性を有するリチウムイオン二次電池である。   One embodiment of the present invention is a strip-shaped negative electrode current collector plate having conductivity, and a strip-shaped negative electrode current collector plate disposed on the negative electrode current collector plate and including negative electrode active material particles and extending in the longitudinal direction of the negative electrode current collector plate A strip-shaped negative electrode plate having a negative electrode active material layer, a strip-shaped positive electrode plate facing the negative electrode plate, and a separator interposed between the negative electrode plate and the positive electrode plate. A lithium ion secondary battery comprising a power generation element wound and impregnated with an electrolyte solution containing lithium ions in the separator, wherein the negative electrode active material layer is formed at both ends in the width direction orthogonal to the longitudinal direction. Each of the strip-shaped end edges is located at the center in the width direction and is adjacent to each of the end edges, and the center is lower in resistance than the end edges. This is a lithium ion secondary battery having the following layer characteristics.

上述の電池の負極活物質層は、中央部が、端縁部よりも低抵抗の層特性を有する。つまり、図２（ａ）に示すように、電解液を加味しない、負極活物質層のみに生じる電気抵抗について見ると、中央部が端縁部よりも低くされている。
そこで、この電池について充放電を繰り返し、従来と同様に、電解液のうち、幅方向の中央部付近におけるリチウムイオンの濃度が、端縁部付近よりも低くなった場合を考える。すると、電解液と負極活物質層とを併せた総合の電気抵抗は、図２（ｂ）に示したようになる。即ち、負極活物質層のうち中央部の電気抵抗を端縁部よりも低くした分、電解液と負極活物質層とを併せた総合の電気抵抗について、中央部と端縁部との間の差を小さく抑え、中央部で極端に高くなることが防止できる。
これにより、この電池に充電して、例えば、負極活物質層の平均電位が前述と同様に０．１Ｖになった場合でも、図２（ｃ）に示すように、負極活物質層の中央部の電位が０Ｖ以下になるのを防止できる。つまり、充電時に、負極活物質層に金属リチウムが析出するのを防止できる。かくして、使用に伴う電池容量の低下を抑制した電池とすることができる。 The negative electrode active material layer of the battery described above has a layer characteristic in which the central portion has a lower resistance than the edge portion. That is, as shown in FIG. 2A, when the electric resistance generated only in the negative electrode active material layer without taking the electrolytic solution into consideration is seen, the central portion is set lower than the edge portion.
Therefore, the battery is repeatedly charged and discharged, and the case where the lithium ion concentration in the vicinity of the central portion in the width direction of the electrolytic solution is lower than that in the vicinity of the edge portion, as in the conventional case. Then, the total electrical resistance combining the electrolytic solution and the negative electrode active material layer is as shown in FIG. That is, the total electrical resistance of the negative electrode active material layer combined with the electrolytic solution and the negative electrode active material layer is reduced between the central portion and the edge portion by the amount that the electrical resistance of the central portion is lower than the edge portion. The difference can be kept small and can be prevented from becoming extremely high at the center.
Thus, even when the battery is charged and, for example, the average potential of the negative electrode active material layer becomes 0.1 V as described above, as shown in FIG. Can be prevented from becoming 0 V or less. That is, metallic lithium can be prevented from being deposited on the negative electrode active material layer during charging. Thus, a battery in which a decrease in battery capacity due to use is suppressed can be obtained.

なお、各部の層特性の測定方法としては、例えば、負電極板のうち、負極活物質層の端縁部が存在する部位と中央部が存在する部位とをそれぞれ所定形状に打ち抜いて、これらを負極とする電池をそれぞれ構成し、これら負極の抵抗を交流インピーダンス法で測定する手法が挙げられる。
また、負極活物質粒子としては、例えば、鱗片状黒鉛、塊状黒鉛等の天然黒鉛や人造黒鉛の黒鉛（グラファイト）、非晶質炭素が挙げられる。 In addition, as a method for measuring the layer characteristics of each part, for example, in the negative electrode plate, the part where the edge part of the negative electrode active material layer exists and the part where the center part exist are punched into predetermined shapes, respectively, Examples include a method in which batteries for negative electrodes are configured and the resistance of these negative electrodes is measured by an AC impedance method.
Examples of the negative electrode active material particles include natural graphite such as flaky graphite and massive graphite, artificial graphite (graphite), and amorphous carbon.

さらに、上述のリチウムイオン二次電池であって、前記端縁部と前記中央部とは、固形分密度が互いに等しいリチウムイオン二次電池とすると良い。   Further, in the above-described lithium ion secondary battery, the edge portion and the central portion may be lithium ion secondary batteries having the same solid content density.

上述の電池では、端縁部及び中央部の固形分密度が互いに等しい。このため、端縁部と中央部との間で、充放電に伴う膨張・収縮の程度を同じにすることができる。従って、両者の境界部分で亀裂や剥離等の不具合の発生を防止できる。   In the above-described battery, the solid content densities of the edge portion and the central portion are equal to each other. For this reason, the degree of expansion / contraction accompanying charge / discharge can be made the same between the edge portion and the central portion. Therefore, it is possible to prevent the occurrence of defects such as cracks and peeling at the boundary between the two.

なお、固形分密度とは、端縁部（或いは中央部）における単位体積当たりの端縁部（或いは中央部）の重量をいう。なお、固形分密度は、（固形分密度）＝（端縁部（中央部）の重量）／（（端縁部（中央部）の面積）×（端縁部（中央部）の層厚））で与えられる。   In addition, solid content density means the weight of the edge part (or center part) per unit volume in an edge part (or center part). The solid density is (solid content density) = (weight of edge portion (center portion)) / ((area of edge portion (center portion)) × (layer thickness of edge portion (center portion)). ).

さらに、上述のリチウムイオン二次電池であって、前記端縁部と前記中央部とは、厚みが互いに等しく、前記負極活物質粒子のうち、上記中央部に含まれる第１活物質粒子は、その第１平均粒径が、上記端縁部に含まれる第２活物質粒子の第２平均粒径に比して小さいリチウムイオン二次電池とすると良い。   Further, in the above lithium ion secondary battery, the edge portion and the central portion have the same thickness, and among the negative electrode active material particles, the first active material particles contained in the central portion are: The first average particle size may be a lithium ion secondary battery that is smaller than the second average particle size of the second active material particles contained in the edge portion.

上述の電池では、中央部に含まれる第１活物質粒子の第１平均粒径が、端縁部に含まれる第２活物質粒子の第２平均粒径に比して小さい。ところで、粒径が小さい負極活物質粒子は、リチウムイオン或いは電子がその活物質粒子の奥（中心）にまで到達し易いので、平均粒径が小さいほど、その負極活物質粒子自身の抵抗は低くなる。従って、第１活物質粒子の方が第２活物質粒子よりも低抵抗である。その上、端縁部と中央部との固形分密度を互いに等しく、しかも端縁部と中央部とで厚みを互いに等しくした。これにより、低抵抗の第１活物質粒子を含む中央部全体の層特性も、端縁部に比べて、低抵抗とすることができる。従って、充電時に、負極活物質層に金属リチウムが析出するのを防止できる。かくして、使用に伴う電池容量の低下を確実に抑制できる電池とすることができる。
また、端縁部と中央部との固形分密度を互いに等しく、かつ、端縁部と中央部とで厚みを互いに等しくしながら、中央部における負極活物質粒子の平均粒径を端縁部に比して小さく異ならせることで、容易に中央部を端縁部よりも低抵抗の層特性にすることができる。 In the above-described battery, the first average particle diameter of the first active material particles included in the central portion is smaller than the second average particle diameter of the second active material particles included in the edge portion. By the way, since the negative electrode active material particles having a small particle size easily reach lithium ions or electrons (in the center) of the active material particles, the smaller the average particle size, the lower the resistance of the negative electrode active material particles themselves. Become. Therefore, the first active material particles have a lower resistance than the second active material particles. In addition, the solid density of the edge portion and the central portion is equal to each other, and the thickness is equal to that of the edge portion and the central portion. Thereby, the layer characteristic of the whole center part containing the 1st active material particle of low resistance can also be made low resistance compared with an edge part. Accordingly, it is possible to prevent metallic lithium from being deposited on the negative electrode active material layer during charging. Thus, a battery capable of reliably suppressing a decrease in battery capacity due to use can be provided.
Further, the average particle size of the negative electrode active material particles in the central part is set to the edge part while the solid content densities of the edge part and the central part are equal to each other and the thicknesses are equal to each other in the edge part and the central part. By making the difference smaller, the center portion can be easily made to have a layer characteristic having a lower resistance than the edge portion.

さらに、上述のいずれかのリチウムイオン二次電池であって、前記端縁部と前記中央部とは、厚みが互いに等しく、前記負極活物質粒子は黒鉛であり、上記負極活物質粒子のうち、上記中央部に含まれている第１活物質粒子は、その第１黒鉛純度が、前記端縁部に含まれている第２活物質粒子の第２黒鉛純度に比して高いリチウムイオン二次電池とすると良い。   Furthermore, in the lithium ion secondary battery described above, the edge portion and the central portion are equal in thickness to each other, the negative electrode active material particles are graphite, and among the negative electrode active material particles, The first active material particles contained in the central portion have a lithium ion secondary whose first graphite purity is higher than the second graphite purity of the second active material particles contained in the edge portion. Use batteries.

上述の電池では、負極活物質粒子に用いる黒鉛について、中央部における第１活物質粒子の第１黒鉛純度が、端縁部における第２活物質粒子の第２黒鉛純度に比して高い。ところで、黒鉛純度が高いと、黒鉛以外の不純物の割合が小さいので、黒鉛純度が高くなるに連れて、負極活物質粒子の抵抗が低くなる。従って、第１活物質粒子の方が第２活物質粒子よりも低抵抗である。その上、端縁部と中央部との固形分密度を互いに等しく、しかも端縁部と中央部とで厚みを互いに等しくした。これにより、低抵抗の第１活物質粒子を含む中央部全体の層特性も、端縁部に比べて、低抵抗とすることができる。従って、充電時に、負極活物質層に金属リチウムが析出するのを防止できる。かくして、使用に伴う電池容量の低下を確実に抑制できる電池とすることができる。
また、端縁部と中央部との固形分密度を互いに等しく、かつ、端縁部と中央部とで厚みを互いに等しくしながら、中央部における負極活物質粒子の黒鉛純度を端縁部に比して高く異ならせることで、容易に中央部を端縁部よりも低抵抗の層特性にすることができる。 In the above-described battery, for the graphite used for the negative electrode active material particles, the first graphite purity of the first active material particles at the center is higher than the second graphite purity of the second active material particles at the edge. By the way, since the ratio of impurities other than graphite is small when the graphite purity is high, the resistance of the negative electrode active material particles decreases as the graphite purity increases. Therefore, the first active material particles have a lower resistance than the second active material particles. In addition, the solid density of the edge portion and the central portion is equal to each other, and the thickness is equal to that of the edge portion and the central portion. Thereby, the layer characteristic of the whole center part containing the 1st active material particle of low resistance can also be made low resistance compared with an edge part. Accordingly, it is possible to prevent metallic lithium from being deposited on the negative electrode active material layer during charging. Thus, a battery capable of reliably suppressing a decrease in battery capacity due to use can be provided.
Further, the solid content density of the edge portion and the central portion is equal to each other, and the thickness of the edge portion and the central portion is equal to each other, while the graphite purity of the negative electrode active material particles in the central portion is compared with that of the edge portion. Thus, by making the difference high, it is possible to easily make the central portion have a layer characteristic having a resistance lower than that of the edge portion.

なお、黒鉛純度とは、負極活物質粒子における黒鉛の占める割合をいい、例えば、灰分試験（６００℃で燃焼した際の灰分の成分を分析）やＸ線回折（回折面（１０１）と（１００）との強度比を測定）により測定することができる。   The graphite purity refers to the proportion of graphite in the negative electrode active material particles. For example, ash content (analysis of ash content when burned at 600 ° C.) and X-ray diffraction (diffractive surface (101) and (100 )) To measure the intensity ratio.

或いは、本発明の他の態様は、前述のいずれかのリチウムイオン二次電池を搭載し、このリチウムイオン二次電池に蓄える電気エネルギを動力源の全部又は一部に使用する車両である。   Or the other aspect of this invention is a vehicle which mounts one of the above-mentioned lithium ion secondary batteries, and uses the electrical energy stored in this lithium ion secondary battery for all or one part of a motive power source.

上記の車両は、使用に伴う電池容量の低下を抑制できる電池を搭載しているので、安定した性能を有する車両とすることができる。   Since the above vehicle is equipped with a battery that can suppress a decrease in battery capacity due to use, the vehicle can have stable performance.

なお、車両としては、電池による電気エネルギを動力源の全部又は一部に使用する車両であれば良く、例えば、電気自動車、ハイブリッド自動車、プラグインハイブリッド自動車、ハイブリッド鉄道車両、フォークリフト、電気車いす、電動アシスト自転車、電動スクータが挙げられる。   The vehicle may be a vehicle that uses electric energy from a battery as a whole or a part of a power source. For example, an electric vehicle, a hybrid vehicle, a plug-in hybrid vehicle, a hybrid railway vehicle, a forklift, an electric wheelchair, electric Examples include assist bicycles and electric scooters.

或いは、本発明の他の態様は、前述のいずれかのリチウムイオン二次電池を搭載し、このリチウムイオン二次電池に蓄える電気エネルギをエネルギ源の全部又は一部に使用する電池搭載機器である。   Alternatively, another aspect of the present invention is a battery-equipped device in which any of the above-described lithium ion secondary batteries is mounted and the electric energy stored in the lithium ion secondary battery is used for all or part of the energy source. .

上記の電池搭載機器は、使用に伴う電池容量の低下を抑制できる電池を搭載しているので、安定した性能を有する電池搭載機器とすることができる。   Since the battery-equipped device is equipped with a battery that can suppress a decrease in battery capacity due to use, it can be a battery-equipped device having stable performance.

なお、電池搭載機器としては、電池を搭載し、これをエネルギ源の全部又は一部に使用する機器であれば良く、例えば、パーソナルコンピュータ、携帯電話、電池駆動の電動工具、無停電電源装置など、電池で駆動される各種の家電製品、オフィス機器、産業機器が挙げられる。   In addition, as a battery mounting apparatus, what is necessary is just an apparatus which mounts a battery and uses this for all or one part of an energy source, for example, a personal computer, a mobile telephone, a battery-powered electric tool, an uninterruptible power supply, etc. And various home appliances driven by batteries, office equipment, and industrial equipment.

従来の電池の説明図であり、（ａ）は負極活物質層の各部位における電気抵抗の大きさを示すグラフ、（ｂ）は電解液と負極活物質層とを併せた総合の電気抵抗の各部位における大きさを示すグラフ、（ｃ）は充電末期における負極活物質層の電位を示すグラフである。It is explanatory drawing of the conventional battery, (a) is a graph which shows the magnitude | size of the electrical resistance in each site | part of a negative electrode active material layer, (b) is the total electrical resistance which combined electrolyte solution and the negative electrode active material layer. The graph which shows the magnitude | size in each site | part, (c) is a graph which shows the electric potential of the negative electrode active material layer in the charge end stage. 実施形態１，変形形態１にかかる電池の説明図であり、（ａ）は負極活物質層の各部位における電気抵抗の大きさを示すグラフ、（ｂ）は電解液と負極活物質層とを併せた総合の電気抵抗の各部位における大きさを示すグラフ、（ｃ）は充電末期における負極活物質層の電位を示すグラフである。It is explanatory drawing of the battery concerning Embodiment 1, modification 1, (a) is a graph which shows the magnitude | size of the electrical resistance in each site | part of a negative electrode active material layer, (b) is electrolyte solution and a negative electrode active material layer. The graph which shows the magnitude | size in each site | part of the combined electric resistance combined, (c) is a graph which shows the electric potential of the negative electrode active material layer in the charge end stage. 実施形態１，変形形態１にかかる電池の斜視図である。2 is a perspective view of a battery according to Embodiment 1 and Modification 1. FIG. 実施形態１，変形形態１の正電極板の斜視図である。It is a perspective view of the positive electrode plate of Embodiment 1 and Modification 1. 実施形態１，変形形態１の負電極板の斜視図である。It is a perspective view of the negative electrode plate of Embodiment 1 and Modification 1. 実施形態１，変形形態１の負電極板の製造工程の説明図である。It is explanatory drawing of the manufacturing process of the negative electrode plate of Embodiment 1, modification 1. FIG. 実施形態２にかかる車両の説明図である。It is explanatory drawing of the vehicle concerning Embodiment 2. FIG. 実施形態３にかかる電池搭載機器の説明図である。It is explanatory drawing of the battery mounting apparatus concerning Embodiment 3. FIG.

（実施形態１）
次に、本発明の実施形態１について、図面を参照しつつ説明する。
まず、本実施形態１にかかる電池１について、図３を参照して説明する。
この電池１は、帯状の負電極板２０と、帯状の正電極板３０と、負電極板２０と正電極板３０との間に介在させた帯状のセパレータ５０とを捲回し、このセパレータ５０に電解液６０を含浸させた発電要素１０を備えるリチウムイオン二次電池である（図３参照）。この電池１は、発電要素１０を電池ケース８０に収容してなる。 (Embodiment 1)
Next, Embodiment 1 of the present invention will be described with reference to the drawings.
First, the battery 1 according to the first embodiment will be described with reference to FIG.
The battery 1 is formed by winding a strip-shaped negative electrode plate 20, a strip-shaped positive electrode plate 30, and a strip-shaped separator 50 interposed between the negative electrode plate 20 and the positive electrode plate 30. It is a lithium ion secondary battery provided with the electric power generation element 10 impregnated with the electrolyte solution 60 (refer FIG. 3). The battery 1 includes a power generation element 10 accommodated in a battery case 80.

この電池ケース８０は、共にアルミニウム製の電池ケース本体８１及び封口蓋８２を有する。このうち電池ケース本体８１は有底矩形箱形であり、この電池ケース８０と発電要素１０との間には、樹脂からなり、箱状に折り曲げた絶縁フィルム（図示しない）が介在させてある。また、封口蓋８２は矩形板状であり、電池ケース本体８１の開口を閉塞して、この電池ケース本体８１に溶接されている。この封口蓋８２には、発電要素１０と接続している正極集電部材９１及び負極集電部材９２のうち、それぞれ先端に位置する正極端子部９１Ａ及び負極端子部９２Ａが貫通しており、図３中、上方に向く蓋表面８２ａから突出している。これら正極端子部９１Ａ及び負極端子部９２Ａと封口蓋８２との間には、それぞれ絶縁性の樹脂からなる絶縁部材９５が介在し、互いを絶縁している。さらに、この封口蓋８２には矩形板状の安全弁９７も封着されている。   The battery case 80 has a battery case body 81 and a sealing lid 82 both made of aluminum. Among these, the battery case main body 81 has a bottomed rectangular box shape, and an insulating film (not shown) made of resin and bent into a box shape is interposed between the battery case 80 and the power generation element 10. The sealing lid 82 has a rectangular plate shape, closes the opening of the battery case body 81, and is welded to the battery case body 81. Of the positive electrode current collecting member 91 and the negative electrode current collecting member 92 connected to the power generation element 10, the positive electrode terminal portion 91 </ b> A and the negative electrode terminal portion 92 </ b> A located at the tips of the sealing lid 82 pass through, respectively. 3 protrudes from the lid surface 82a facing upward. Insulating members 95 made of insulating resin are interposed between the positive electrode terminal portion 91A and the negative electrode terminal portion 92A and the sealing lid 82 to insulate each other. Further, a rectangular plate-shaped safety valve 97 is also sealed on the sealing lid 82.

また、電解液６０は、エチレンカーボネート（ＥＣ）とエチルメチルカーボネート（ＥＭＣ）とを、体積比でＥＣ：ＥＭＣ＝３：７に調整した混合有機溶媒に、溶質としてＬｉＰＦ6を添加し、リチウムイオンを１ｍｏｌ／ｌの濃度とした非水電解液である。 In addition, the electrolytic solution 60 is obtained by adding LiPF 6 as a solute to a mixed organic solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are adjusted to EC: EMC = 3: 7 by volume ratio, and lithium ion Is a non-aqueous electrolyte having a concentration of 1 mol / l.

また、発電要素１０は、帯状の負電極板２０及び正電極板３０が、帯状のセパレータ５０を介して扁平形状に捲回されてなる捲回型の形態である（図３参照）。なお、この発電要素１０の負電極板２０及び正電極板３０はそれぞれ、クランク状に屈曲した板状の負極集電部材９２又は正極集電部材９１と接合している（図３参照）。このうち、多孔性のポリプロピレンからなる帯状のセパレータ５０は、正電極板３０と負電極板２０との間に介在して、これらを離間させている。このセパレータ５０には、全体に上述した電解液６０が含浸させてある。   The power generation element 10 has a wound-type configuration in which a strip-shaped negative electrode plate 20 and a positive electrode plate 30 are wound into a flat shape via a strip-shaped separator 50 (see FIG. 3). The negative electrode plate 20 and the positive electrode plate 30 of the power generation element 10 are joined to a plate-like negative electrode current collecting member 92 or positive electrode current collecting member 91 bent in a crank shape (see FIG. 3). Among these, the strip-shaped separator 50 made of porous polypropylene is interposed between the positive electrode plate 30 and the negative electrode plate 20 to separate them. The separator 50 is entirely impregnated with the electrolytic solution 60 described above.

また、正電極板３０は、図４に示すように、長手方向ＤＬに延びる帯状で、導電性のアルミニウムからなるアルミ箔３８と、このアルミ箔３８の主面上にそれぞれ帯状に形成された２つの正極活物質層３１，３１とを有している。
この正極活物質層３１は、ＬｉＣｏＯ2からなる正極活物質粒子３４、カーボンブラックからなる導電材３５、及び、ポリフッ化ビニリデン（ＰＶＤＦ）からなる結着材３６を含む（図４参照）。なお、正極活物質層３１内における、これらの重量比を、正極活物質粒子３４：導電材３５：結着材３６＝８５：５：１０とした。また、この正極活物質層３１の層厚Ｔ３１を２６μｍとした。 Further, as shown in FIG. 4, the positive electrode plate 30 has a strip shape extending in the longitudinal direction DL, and an aluminum foil 38 made of conductive aluminum, and two strips formed on the main surface of the aluminum foil 38. Two positive electrode active material layers 31, 31.
The positive electrode active material layer 31 includes positive electrode active material particles 34 made of LiCoO 2 , a conductive material 35 made of carbon black, and a binder 36 made of polyvinylidene fluoride (PVDF) (see FIG. 4). The weight ratio in the positive electrode active material layer 31 was set to positive electrode active material particles 34: conductive material 35: binder 36 = 85: 5: 10. The layer thickness T31 of the positive electrode active material layer 31 was set to 26 μm.

また、負電極板２０は、図５に示すように、長手方向ＤＬに延びる帯状で、導電性の銅からなる銅箔２８と、この銅箔２８の主面上にそれぞれ帯状に形成された２つの負極活物質層２１，２１とを有している。
このうち負極活物質層２１は、黒鉛からなる負極活物質粒子（次述する第１活物質粒子２４Ｃ，第２活物質粒子２４Ｅ）、及び、ＰＶＤＦからなる結着材（図示しない）を含む。 Further, as shown in FIG. 5, the negative electrode plate 20 has a strip shape extending in the longitudinal direction DL, and a copper foil 28 made of conductive copper and 2 formed on the main surface of the copper foil 28 in a strip shape. Two negative electrode active material layers 21, 21.
Among these, the negative electrode active material layer 21 includes negative electrode active material particles (first active material particles 24C and second active material particles 24E described below) made of graphite, and a binder (not shown) made of PVDF.

なお、負極活物質層２１は、図５に示すように、長手方向ＤＬに直交する幅方向ＤＷ（図５中、左上から右下方向）の両端部にそれぞれ位置し、長手方向ＤＬに延びる帯状の２つの端縁部２１Ｅ，２１Ｅと、幅方向ＤＷの中央に位置して、端縁部２１Ｅ，２１Ｅにそれぞれ隣接する帯状の中央部２１Ｃとからなる。
このうち端縁部２１Ｅは、第２平均粒径ＲＥが１７．２μｍの黒鉛からなる第２活物質粒子２４Ｅを含む。また、この端縁部２１Ｅの第２層厚ＴＥは３２μｍ、端縁部２１Ｅの固形分密度は１．４ｇ／ｃｍ3である。
一方、中央部２１Ｃは、第１平均粒径ＲＣが、第２平均粒径ＲＥに比して小さな３．２μｍの黒鉛からなる第１活物質粒子２４Ｃを含む。また、この中央部２１Ｃの第１層厚ＴＣは３２μｍであり、端縁部２１Ｅの第２層厚ＴＥと等しい。また、この中央部２１Ｃの固形分密度は１．４ｇ／ｃｍ3であり、端縁部２１Ｅの固形分密度と等しい。 As shown in FIG. 5, the negative electrode active material layer 21 is located at both ends in the width direction DW (upper left to lower right in FIG. 5) perpendicular to the longitudinal direction DL, and extends in the longitudinal direction DL. The two edge portions 21E and 21E, and a belt-like central portion 21C that is located in the center of the width direction DW and is adjacent to the edge portions 21E and 21E, respectively.
Among these, the edge part 21E contains the 2nd active material particle 24E which consists of graphite whose 2nd average particle diameter RE is 17.2 micrometers. The second layer thickness TE of the edge portion 21E is 32 μm, and the solid density of the edge portion 21E is 1.4 g / cm 3 .
On the other hand, the central portion 21C includes first active material particles 24C made of graphite having a first average particle size RC smaller than the second average particle size RE and 3.2 μm. Further, the first layer thickness TC of the central portion 21C is 32 μm, which is equal to the second layer thickness TE of the edge portion 21E. Further, the solid content density of the central portion 21C is 1.4 g / cm 3 , which is equal to the solid content density of the edge portion 21E.

ところで、本発明者らは、上述した電池１の電池特性（容量維持率）を評価すべく、電池１と同様の正極活物質層、負極活物質層、セパレータ及び電解液６０を用いた円筒形状の試料電池１を用意し、評価を行った。
具体的には、ＬｉＣｏＯ2からなる正極活物質粒子３４、カーボンブラックからなる導電材３５、及び、ＰＶＤＦからなる結着材３６を、重量比で正極活物質粒子３４：導電材３５：結着材３６＝８５：５：１０となるように混合した。この混合物の中に、分散材としてＮ−メチル−２−ピロリドン（ＮＭＰ）を適量添加し、ペースト状の正極ペーストを作製した。この正極ペーストをアルミ箔の両主面に塗布し、乾燥させた後、ロールプレスで高密度化して、正極活物質層を作製した。
作製した正極活物質層は、アルミ箔と共に、５２ｍｍ×７２０ｍｍの形状に切断し（このうち、正極活物質層を担持した部位の寸法は５２ｍｍ×６８０ｍｍ）、正電極板とした。 By the way, in order to evaluate the battery characteristics (capacity maintenance ratio) of the battery 1 described above, the present inventors have a cylindrical shape using the same positive electrode active material layer, negative electrode active material layer, separator, and electrolytic solution 60 as the battery 1. Sample battery 1 was prepared and evaluated.
Specifically, the positive electrode active material particles 34 made of LiCoO 2 , the conductive material 35 made of carbon black, and the binder 36 made of PVDF are, in weight ratio, positive electrode active material particles 34: conductive material 35: binder. It mixed so that it might become 36 = 85: 5: 10. An appropriate amount of N-methyl-2-pyrrolidone (NMP) was added to the mixture as a dispersing material to prepare a paste-like positive electrode paste. The positive electrode paste was applied to both main surfaces of the aluminum foil, dried, and then densified with a roll press to prepare a positive electrode active material layer.
The produced positive electrode active material layer was cut into a shape of 52 mm × 720 mm together with the aluminum foil (among these, the dimension of the portion carrying the positive electrode active material layer was 52 mm × 680 mm) to obtain a positive electrode plate.

また一方で、第１平均粒径ＲＣ（＝３．２μｍ）の第１活物質粒子２４Ｃ、及び、ＰＶＤＦからなる結着材（図示しない）を、重量比で第１活物質粒子２４Ｃ：結着材＝９０：１０となるように混合した。この混合物の中に、分散材のＮＭＰを適量添加し、ペースト状の第１負極ペースト２１ＣＰを作製した。同様にして、第２平均粒径ＲＥ（＝１７．２μｍ）の第２活物質粒子２４Ｅ、及び、ＰＶＤＦからなる結着材（図示しない）を、重量比で第２活物質粒子２４Ｅ：結着材＝９０：１０となるように混合し、第２負極ペースト２１ＥＰを作製した。   On the other hand, the first active material particles 24C having the first average particle diameter RC (= 3.2 μm) and the binder (not shown) made of PVDF are mixed in a weight ratio. It mixed so that it might become material = 90: 10. An appropriate amount of NMP as a dispersion material was added to this mixture to prepare a paste-like first negative electrode paste 21CP. Similarly, a second active material particle 24E having a second average particle diameter RE (= 17.2 μm) and a binder (not shown) made of PVDF are mixed in a weight ratio. The mixture was mixed so that the material = 90: 10, and the second negative electrode paste 21EP was produced.

これら第１負極ペースト２１ＣＰ及び第２負極ペースト２１ＥＰを銅箔ＣＦに塗布した。具体的には、図６に示すダイコータＤＣを用いて、第１負極ペースト２１ＣＰ及び第２負極ペースト２１ＥＰを、長手方向ＤＬに延びる帯状の銅箔ＣＦの両主面に塗布した。   The first negative electrode paste 21CP and the second negative electrode paste 21EP were applied to the copper foil CF. Specifically, using the die coater DC shown in FIG. 6, the first negative electrode paste 21CP and the second negative electrode paste 21EP were applied to both main surfaces of the strip-shaped copper foil CF extending in the longitudinal direction DL.

このダイコータＤＣは、各ペースト２１ＣＰ，２１ＥＰを内部に貯留するペースト貯留部ＤＣＴと、このペースト貯留部ＤＣＴの各ペースト２１ＣＰ，２１ＥＰを銅箔ＣＦに向けて連続的に吐出する吐出口ＤＣＳとを有する。
このうち、ペースト貯留部ＤＣＴは、内部の２箇所で板状の仕切り板ＰＴ，ＰＴに仕切られ、銅箔ＣＦの幅方向ＤＷの一方の端側に位置する第１貯留部ＤＣＴ１、他方の端側に位置する第３貯留部ＤＣＴ３、及び、幅方向の中央に位置する第２貯留部ＤＣＴ２の３つに分かれている。第２貯留部ＤＣＴ２には、第１負極ペースト２１ＣＰが、第１貯留部ＤＣＴ１及び第３貯留部ＤＣＴ３には、第２負極ペースト２１ＥＰが、それぞれ貯留されている。
また、吐出口ＤＣＳは、スリット状で幅方向ＤＷに平行に開口している。この吐出口ＤＣＳもまた、ペースト貯留部ＤＣＴと同様、２つの仕切り板ＰＴ，ＰＴに仕切られており、第１貯留部ＤＣＴ１に対応した第１吐出口ＤＣＳ１、第２貯留部ＤＣＴ２に対応した第２吐出口ＤＣＳ２、及び、第３貯留部ＤＣＴ３に対応した第３吐出口ＤＣＳ３の３つに分かれている。 This die coater DC has a paste storage part DCT for storing the pastes 21CP and 21EP therein, and a discharge port DCS for continuously discharging the pastes 21CP and 21EP of the paste storage part DCT toward the copper foil CF. .
Among these, the paste storage part DCT is divided into plate-like partition plates PT, PT at two locations inside, the first storage part DCT1 located on one end side in the width direction DW of the copper foil CF, the other end The third reservoir DCT3 located on the side and the second reservoir DCT2 located in the center in the width direction are divided into three. The first negative electrode paste 21CP is stored in the second storage part DCT2, and the second negative electrode paste 21EP is stored in the first storage part DCT1 and the third storage part DCT3, respectively.
Further, the discharge port DCS is slit-shaped and opened in parallel with the width direction DW. The discharge port DCS is also divided into two partition plates PT and PT, similar to the paste storage portion DCT, and the first discharge port DCS1 corresponding to the first storage portion DCT1 and the second storage portion DCT2 corresponding to the second storage portion DCT2. The two discharge ports DCS2 and the third discharge port DCS3 corresponding to the third reservoir DCT3 are divided into three.

このようなダイコータＤＣを用いて、幅方向ＤＷに、第２負極ペースト２１ＥＰ、第１負極ペースト２１ＣＰ及び第２負極ペースト２１ＥＰの順序に並ぶよう、吐出口ＤＣＳを通じて各ペーストを銅箔ＣＦに向けて塗布した。   Using such a die coater DC, each paste is directed to the copper foil CF through the discharge port DCS so that the second negative electrode paste 21EP, the first negative electrode paste 21CP, and the second negative electrode paste 21EP are arranged in the width direction DW in this order. Applied.

銅箔ＣＦ上に塗布した第１負極ペースト２１ＣＰ及び第２負極ペースト２１ＥＰを乾燥させた後、ロールプレスで高密度化して、幅方向ＤＷの両端部にそれぞれ位置する帯状の２つの端縁部と、幅方向ＤＷの中央に位置して、端縁部にそれぞれ隣接する帯状の中央部とからなる負極活物質層を作製した。なお、この負極活物質層の層厚は、中央部、端縁部にかかわらず、３２μｍで一定である。
作製した負極活物質層は、銅箔と共に、５５ｍｍ×７４０ｍｍの形状に切断し（このうち、正極活物質層を担持した部位の寸法は５５ｍｍ×７２０ｍｍ）、負電極板とした。なお、幅方向ＤＷの、中央部の寸法は２５ｍｍ、端縁部（１つ分）の寸法は１５ｍｍである。また、中央部及び端縁部の固形分密度は互いに等しい。 The first negative electrode paste 21CP and the second negative electrode paste 21EP applied on the copper foil CF are dried and then densified by a roll press to have two strip-shaped edge portions respectively positioned at both ends in the width direction DW Then, a negative electrode active material layer was produced, which was located at the center in the width direction DW and was composed of a strip-shaped center portion adjacent to the edge portion. In addition, the layer thickness of this negative electrode active material layer is constant at 32 μm regardless of the central portion and the edge portion.
The produced negative electrode active material layer was cut into a shape of 55 mm × 740 mm together with the copper foil (among these, the size of the portion carrying the positive electrode active material layer was 55 mm × 720 mm) to obtain a negative electrode plate. In the width direction DW, the dimension of the central part is 25 mm, and the dimension of the edge part (for one) is 15 mm. Moreover, the solid content density of a center part and an edge part is mutually equal.

なお、上述した負電極板における中央部及び端縁部の抵抗値を別途測定した。
具体的には、作製した負電極板の、中央部及び端縁部をそれぞれ円形に打ち抜き、対極に用いる金属リチウムと共にコイン型セルを作製し、このセルの交流インピーダンスを測定した。その測定結果から得られたナイキストプロットの円弧の径を比較して、各部位における抵抗値とした。
以上より、中央部の抵抗値は７．５Ω、端縁部の抵抗値は１４．０Ωであり、中央部が端縁部に比べて低抵抗の層特性を有していることが判る。 In addition, the resistance value of the center part and edge part in the negative electrode plate mentioned above was measured separately.
Specifically, the center part and the edge part of the produced negative electrode plate were each punched out into a circle, a coin-type cell was produced together with metallic lithium used for the counter electrode, and the AC impedance of this cell was measured. The Nyquist plot arc diameters obtained from the measurement results were compared to determine the resistance value at each part.
From the above, it can be seen that the resistance value of the central portion is 7.5Ω and the resistance value of the edge portion is 14.0Ω, and the central portion has a low resistance layer characteristic compared to the edge portion.

上述の正電極板と負電極板との間に、ポリプロピレン製のセパレータを介在させて積層し、これら正電極板、負電極板及びセパレータを捲回して、捲回型の発電要素を作製した。この発電要素を１８６５０型円筒ケースに挿入し、電解液６０をその中に注入した後、封止して試料電池１を製造した。   A laminate made of polypropylene was interposed between the positive electrode plate and the negative electrode plate, and the positive electrode plate, the negative electrode plate and the separator were wound to produce a wound power generation element. The power generation element was inserted into a 18650 type cylindrical case, and the electrolytic solution 60 was injected therein, and then sealed to manufacture the sample battery 1.

まず、上述の試料電池１のうち、製造して間もない新品（初期）のものの電池容量について測定した。具体的には、まず、２５℃の温度環境下で、試料電池１について、３．０〜４．１Ｖの電圧範囲で定電流充電及び定電流放電（共に０．１０Ａ）を、１組の充放電を１サイクルとして３サイクル繰り返した（コンディショニング）。続いて、１．０Ａの電流値で、４．１Ｖまで充電し、その後、２５℃の温度環境下で、その電圧を保ちつつ電流値を徐々に低下させ、９０分間保持した（定電流−定電圧充電）。さらに、２５℃の温度環境下で、０．３３Ａの電流値で３．０Ｖとなるまで定電流放電を行い、放電した電池容量を測定した。なお、このときの電池容量を初期容量（１Ｃ）とした。   First, among the sample batteries 1 described above, the battery capacity of a new (initial) battery that was just manufactured was measured. Specifically, first, in a temperature environment of 25 ° C., the sample battery 1 was charged with a set of constant current charge and constant current discharge (both 0.10 A) in a voltage range of 3.0 to 4.1 V. The discharge was repeated for 3 cycles (conditioning). Subsequently, the battery was charged to 4.1 V at a current value of 1.0 A, and then gradually decreased while maintaining the voltage in a temperature environment of 25 ° C. and held for 90 minutes (constant current-constant). Voltage charging). Further, under a temperature environment of 25 ° C., constant current discharge was performed until the current value of 0.33 A reached 3.0 V, and the discharged battery capacity was measured. The battery capacity at this time was defined as the initial capacity (1C).

上述の測定を行った試料電池１について、６０℃の温度環境下で、３．０〜４．１Ｖの電圧範囲で定電流による充放電（電流値は２Ｃ）を繰り返すサイクル試験を実施した。具体的には、１組の充放電を１サイクルとして、５００サイクルを連続して繰り返した。
その後、試料電池１の電池容量を、上述と同様にして測定した。そして、サイクル試験後における試料電池１の容量維持率を算出した。この容量維持率は、サイクル試験後の電池容量の値を、サイクル試験前の、初期の初期容量で割ったものである。 About the sample battery 1 which performed the above-mentioned measurement, the cycle test which repeats charging / discharging by a constant current (current value is 2C) was performed in the voltage range of 3.0-4.1V in a 60 degreeC temperature environment. Specifically, 500 cycles were repeated continuously, with one set of charging / discharging as one cycle.
Thereafter, the battery capacity of the sample battery 1 was measured in the same manner as described above. Then, the capacity retention rate of the sample battery 1 after the cycle test was calculated. This capacity maintenance ratio is obtained by dividing the value of the battery capacity after the cycle test by the initial initial capacity before the cycle test.

この試料電池１と同様にして、比較例である比較電池Ｃ１，Ｃ２も製作し、これらの電池特性についての電池特性（容量維持率）を、試料電池１と同様に行った。
なお、比較電池Ｃ１は、負極活物質層が第１平均粒径ＲＣの第１活物質粒子２４Ｃのみを含む、即ち、中央部及び端縁部が共に第１活物質粒子２４Ｃのみを含む点で試料電池１と異なる。また、比較電池Ｃ２は、負極活物質層が第２平均粒径ＲＥの第２活物質粒子２４Ｅのみを含む、即ち、中央部及び端縁部が共に第２活物質粒子２４Ｅのみを含む点で試料電池１と異なる。
これら試料電池１及び比較電池Ｃ１，Ｃ２の各負極活物質層の構成、及び、容量維持率を表１に示す。 Comparative batteries C1 and C2, which are comparative examples, were also manufactured in the same manner as the sample battery 1, and the battery characteristics (capacity retention ratio) for these battery characteristics were the same as those of the sample battery 1.
Note that the comparative battery C1 is such that the negative electrode active material layer includes only the first active material particles 24C having the first average particle diameter RC, that is, both the central portion and the edge include only the first active material particles 24C. Different from the sample battery 1. Further, the comparative battery C2 is such that the negative electrode active material layer includes only the second active material particles 24E having the second average particle diameter RE, that is, the center portion and the edge portion include only the second active material particles 24E. Different from the sample battery 1.
Table 1 shows the configurations and capacity retention ratios of the negative electrode active material layers of the sample battery 1 and the comparative batteries C1 and C2.

Figure 2011070976
Figure 2011070976

表１によれば、中央部が第１活物質粒子２４Ｃを、端縁部が第２活物質粒子２４Ｅをそれぞれ含む試料電池１の容量維持率は、負極活物質層が第１活物質粒子２４Ｃのみ、或いは、第２活物質粒子２４Ｅのみを含む各比較電池Ｃ１，Ｃ２よりも高い。このことから、負極活物質層全体に１種類の負極活物質粒子（第１活物質粒子２４Ｃ，第２活物質粒子２４Ｅ）を含む電池よりも、負極活物質層の端縁部に第２活物質粒子２４Ｅを、中央部に第２活物質粒子２４Ｅよりも平均粒径の小さな第１活物質粒子２４Ｃを含む電池の方が、その電池の容量維持率を高くできることが判る。   According to Table 1, the capacity retention rate of the sample battery 1 including the first active material particles 24C at the center and the second active material particles 24E at the edge is determined by the negative active material layer as the first active material particles 24C. Or the comparison batteries C1 and C2 including only the second active material particles 24E. From this, the second active material layer has the second active material layer at the edge portion of the negative electrode active material layer, rather than the battery including one type of negative electrode active material particles (first active material particles 24C, second active material particles 24E) in the entire negative electrode active material layer. It can be seen that a battery including the first active material particles 24C having the average particle diameter smaller than the second active material particles 24E in the center can increase the capacity retention rate of the battery.

このようになる理由は以下であると考えられる。即ち、粒径が小さい負極活物質粒子は、リチウムイオン或いは電子がその活物質粒子の奥（中心）にまで到達し易いので、平均粒径が小さいほど、その負極活物質粒子自身の抵抗は低くなる。従って、第２平均粒径ＲＥ（＝１７．２μｍ）よりも小さな第１平均粒径ＲＣ（＝３．２μｍ）の第１活物質粒子２４Ｃの方が第２活物質粒子２４Ｅよりも低抵抗である。その上、端縁部と中央部との固形分密度を互いに等しく、しかも端縁部と中央部とで厚みを互いに等しくした。これにより、低抵抗の第１活物質粒子２４Ｃを含む中央部全体の層特性も、端縁部に比べて、低抵抗とすることができる。   The reason for this is considered as follows. That is, since the negative electrode active material particles having a small particle diameter easily reach lithium ions or electrons to the back (center) of the active material particles, the smaller the average particle diameter, the lower the resistance of the negative electrode active material particles themselves. Become. Accordingly, the first active material particles 24C having the first average particle size RC (= 3.2 μm) smaller than the second average particle size RE (= 17.2 μm) have lower resistance than the second active material particles 24E. is there. In addition, the solid density of the edge portion and the central portion is equal to each other, and the thickness is equal to that of the edge portion and the central portion. Thereby, the layer characteristics of the entire central portion including the low-resistance first active material particles 24 </ b> C can also be made lower resistance than the edge portion.

上述の試料電池１、及び、これと同様の正極活物質層３１、負極活物質層２１、セパレータ５０及び電解液６０を用いた電池１について、充放電を繰り返すと、従来と同様、電解液６０のうち、中央部２１Ｃ付近でのリチウムイオンの濃度が、端縁部２１Ｅ付近の濃度よりも低くなる。ところで、本実施形態１では、図２（ａ）に示すように、負極活物質層２１のうち、中央部２１Ｃが、端縁部２１Ｅよりも低抵抗の層特性を有する。このため、この試料電池１，電池１では、電解液と負極活物質層とを併せた総合の電気抵抗が、図２（ｂ）のようになる。即ち、中央部２１Ｃの電気抵抗を端縁部２１Ｅよりも低くした分、電解液と負極活物質層とを併せた総合の電気抵抗について、中央部２１Ｃと端縁部２１Ｅとの間の差を小さく抑え、中央部２１Ｃで極端に高くなることが防止できる。
これにより、この試料電池１，電池１に充電して、例えば、負極活物質層２１の平均電位が０．１Ｖになった場合でも、図２（ｃ）に示すように、負極活物質層２１の中央部２１Ｃの電位が０Ｖ（ｖｓ．Ｌｉ／Ｌｉ+）以下になるのを防止できる。つまり、充電時に、負極活物質層２１に金属リチウムが析出するのを防止できる。かくして、使用に伴う電池容量の低下を抑制した試料電池１，電池１とすることができる。 When the above-described sample battery 1 and the battery 1 using the same positive electrode active material layer 31, negative electrode active material layer 21, separator 50, and electrolytic solution 60 are repeatedly charged and discharged, the electrolytic solution 60 is the same as before. Of these, the concentration of lithium ions in the vicinity of the central portion 21C is lower than the concentration in the vicinity of the edge portion 21E. By the way, in this Embodiment 1, as shown to Fig.2 (a), the center part 21C has the layer characteristic of resistance lower than the edge part 21E among the negative electrode active material layers 21. FIG. For this reason, in the sample battery 1 and the battery 1, the total electric resistance combining the electrolytic solution and the negative electrode active material layer is as shown in FIG. That is, the difference between the central portion 21C and the end edge portion 21E is obtained with respect to the total electric resistance of the electrolyte solution and the negative electrode active material layer by the amount that the electric resistance of the central portion 21C is lower than that of the end edge portion 21E. It can be kept small and can be prevented from becoming extremely high at the central portion 21C.
Thus, even when the sample battery 1 and the battery 1 are charged and the average potential of the negative electrode active material layer 21 becomes 0.1 V, for example, as shown in FIG. It is possible to prevent the potential of the central portion 21C of the battery from becoming 0 V (vs. Li / Li + ) or less. That is, it is possible to prevent metallic lithium from being deposited on the negative electrode active material layer 21 during charging. Thus, it can be set as the sample battery 1 and the battery 1 which suppressed the fall of the battery capacity accompanying use.

また、試料電池１及び電池１では、端縁部２１Ｅ及び中央部２１Ｃの固形分密度が互いに等しい。
前述した特許文献１の電池のように、端縁部２１Ｅと中央部２１Ｃとの間で固形分密度が異なる電池では、充放電の際に負極活物質層に生じる膨張・収縮の程度が、端縁部と中央部との間で異なってしまう。これに対し、上述の試料電池１及び電池１では、端縁部２１Ｅと中央部２１Ｃとの間で、充放電に伴う膨張・収縮の程度を同じにすることができる。従って、両者の境界部分で亀裂や剥離等の不具合の発生を防止できる。 Moreover, in the sample battery 1 and the battery 1, the solid content density of the edge part 21E and the center part 21C is mutually equal.
As in the battery of Patent Document 1 described above, in a battery in which the solid density is different between the edge portion 21E and the central portion 21C, the degree of expansion / contraction that occurs in the negative electrode active material layer during charge / discharge is limited. It will be different between the edge and the center. On the other hand, in the sample battery 1 and the battery 1 described above, the degree of expansion / contraction associated with charge / discharge can be made the same between the edge portion 21E and the central portion 21C. Therefore, it is possible to prevent the occurrence of defects such as cracks and peeling at the boundary between the two.

また、試料電池１及び電池１では、中央部２１Ｃの第１活物質粒子２４Ｃの第１平均粒径ＲＣが、端縁部２１Ｅに含まれる第２活物質粒子２４Ｅの第２平均粒径ＲＥに比して小さい。これにより、低抵抗の第１活物質粒子２４Ｃを含む中央部２１Ｃ全体の層特性を、端縁部２１Ｅに比べて、低抵抗とすることができる。従って、使用に伴う電池容量の低下を確実に抑制できる電池とすることができる。
また、端縁部２１Ｅと中央部２１Ｃとの固形分密度を互いに等しく、かつ、端縁部２１Ｅと中央部２１Ｃとで厚みＴＥ，ＴＣを互いに等しくしながら、中央部２１Ｃにおける負極活物質粒子（第１活物質粒子２４Ｃ）の平均粒径ＲＣを、端縁部２１Ｅに比して小さく異ならせることで、容易に中央部２１Ｃを端縁部２１Ｅよりも低抵抗の層特性にすることができる。 Moreover, in the sample battery 1 and the battery 1, the first average particle diameter RC of the first active material particles 24C in the central portion 21C is changed to the second average particle diameter RE of the second active material particles 24E included in the edge portion 21E. Smaller than that. Thereby, the layer characteristics of the entire central portion 21C including the low-resistance first active material particles 24C can be made lower resistance than the edge portion 21E. Therefore, it can be set as the battery which can suppress reliably the fall of the battery capacity accompanying use.
Further, the negative electrode active material particles (in the central portion 21C (with the same solid content density in the end portion 21E and the central portion 21C) and in the end portion 21E and the central portion 21C with the same thickness TE and TC). By making the average particle size RC of the first active material particles 24C) smaller than that of the edge portion 21E, the central portion 21C can be easily made to have lower resistance layer characteristics than the edge portion 21E. .

次に、本実施形態１にかかる電池１の製造方法について説明する。
まず、試料電池１とほぼ同様にして、発電要素１０を作製する。具体的には、前述した正極活物質粒子３４、導電材３５及び結着材３６を、重量比で正極活物質粒子３４：導電材３５：結着材３６＝８５：５：１０となるように混合した。この混合物の中に、分散材を適量添加し、ペースト状の正極ペーストを作製した。この正極ペーストを公知の手法で、帯状のアルミ箔の両主面に塗布し、乾燥させた後、ロールプレスで高密度化して、正極活物質層を作製し、帯状の正電極板３０ができあがる（図４参照）。 Next, a method for manufacturing the battery 1 according to the first embodiment will be described.
First, the power generation element 10 is produced in substantially the same manner as the sample battery 1. Specifically, the positive electrode active material particles 34, the conductive material 35, and the binder 36 described above are in a weight ratio such that the positive electrode active material particles 34: the conductive material 35: the binder 36 = 85: 5: 10. Mixed. An appropriate amount of a dispersing agent was added to the mixture to prepare a paste-like positive electrode paste. This positive electrode paste is applied to both main surfaces of a strip-shaped aluminum foil by a known method, dried, and then densified with a roll press to produce a positive electrode active material layer, and a strip-shaped positive electrode plate 30 is completed. (See FIG. 4).

また一方で、前述した第１負極ペースト２１ＣＰ及び第２負極ペースト２１ＥＰを作製した。これら第１負極ペースト２１ＣＰ，第２負極ペースト２１ＥＰを、前述したダイコータＤＣを用いて（図６参照）、帯状の銅箔２８の両主面に塗布し、乾燥させた後、ロールプレスで高密度化して、負極活物質層２１を作製し、負電極板２０ができあがる（図５参照）。
上述のように作製した正電極板３０と負電極板２０との間に、セパレータ５０を介在させて捲回し、発電要素１０とする。 On the other hand, the first negative electrode paste 21CP and the second negative electrode paste 21EP described above were produced. The first negative electrode paste 21CP and the second negative electrode paste 21EP are applied to both main surfaces of the strip-shaped copper foil 28 using the above-described die coater DC (see FIG. 6), dried, and then high-density by a roll press. Thus, the negative electrode active material layer 21 is produced, and the negative electrode plate 20 is completed (see FIG. 5).
A power generation element 10 is obtained by winding the separator 50 between the positive electrode plate 30 and the negative electrode plate 20 produced as described above.

その後は、正電極板３０（アルミ箔３８）及び負電極板２０（銅箔２８）にそれぞれ正極集電部材９１及び負極集電部材９２を溶接し、電池ケース本体８１に挿入し、前述した電解液６０を注入後、封口蓋８２で電池ケース本体８１を溶接で封口する。かくして、電池１が完成する（図３参照）。   Thereafter, the positive electrode current collecting member 91 and the negative electrode current collecting member 92 are respectively welded to the positive electrode plate 30 (aluminum foil 38) and the negative electrode plate 20 (copper foil 28), inserted into the battery case body 81, and the above-described electrolysis. After injecting the liquid 60, the battery case body 81 is sealed with a sealing lid 82 by welding. Thus, the battery 1 is completed (see FIG. 3).

（変形形態１）
次に、本発明の変形形態１にかかる電池１０１について、図３〜６を参照しつつ説明する。
本変形形態１は、負極活物質層のうち、中央部に含まれる第１活物質粒子、及び、端縁部に含まれる第２活物質粒子が、前述の実施形態１と異なり、それ以外は同様である。
そこで、実施形態１と異なる点を中心に説明し、同様の部分の説明は省略または簡略化する。なお、同様の部分については同様の作用効果を生じる。また、同内容のものには同番号を付して説明する。 (Modification 1)
Next, the battery 101 according to the first modification of the present invention will be described with reference to FIGS.
In the first modification, the first active material particles included in the central portion and the second active material particles included in the edge portion of the negative electrode active material layer are different from those in the first embodiment, and other than that, It is the same.
Therefore, differences from the first embodiment will be mainly described, and description of similar parts will be omitted or simplified. In addition, about the same part, the same effect is produced. In addition, the same contents are described with the same numbers.

本変形形態１にかかる電池１０１は、帯状の負電極板１２０と、実施形態１の電池１と同様の正電極板３０及びセパレータ５０とを捲回してなり、このセパレータ５０に電解液６０を含浸した発電要素１１０を備えるリチウムイオン二次電池である（図３参照）。   A battery 101 according to the first modification is formed by winding a strip-shaped negative electrode plate 120, a positive electrode plate 30 and a separator 50 similar to those of the battery 1 of the first embodiment, and impregnating the separator 50 with an electrolytic solution 60. It is a lithium ion secondary battery provided with the electric power generation element 110 (refer FIG. 3).

このうち、負電極板１２０は、図５に示すように、前述の銅箔２８と、この銅箔２８の主面上にそれぞれ形成された２つの負極活物質層１２１，１２１とを有している。
このうち負極活物質層１２１は、黒鉛からなる負極活物質粒子（次述する第１活物質粒子１２４Ｃ，第２活物質粒子１２４Ｅ）、及び、ＰＶＤＦからなる結着材（図示しない）を含む。 Among these, as shown in FIG. 5, the negative electrode plate 120 includes the above-described copper foil 28 and two negative electrode active material layers 121 and 121 respectively formed on the main surface of the copper foil 28. Yes.
Among these, the negative electrode active material layer 121 includes negative electrode active material particles (first active material particles 124C and second active material particles 124E described below) made of graphite, and a binder (not shown) made of PVDF.

なお、負極活物質層１２１は、実施形態１と同様に、帯状の２つの端縁部１２１Ｅ，１２１Ｅと、幅方向ＤＷの中央に位置して、端縁部１２１Ｅ，１２１Ｅにそれぞれ隣接する帯状の中央部１２１Ｃとからなる（図５参照）。
このうち端縁部１２１Ｅは、天然黒鉛からなる第２活物質粒子１２４Ｅを含む。なお、この端縁部１２１Ｅの第２層厚ＴＥは３２μｍ、固形分密度は１．４ｇ／ｃｍ3である。
また、中央部１２１Ｃは、人造黒鉛からなる第１活物質粒子１２４Ｃを含む。また、この中央部１２１Ｃの第１層厚ＴＣは３２μｍであり、端縁部１２１Ｅの第２層厚ＴＥと等しい。また、この中央部１２１Ｃの固形分密度は１．４ｇ／ｃｍ3であり、端縁部１２１Ｅの固形分密度と等しい。
なお、人造黒鉛からなる第１活物質粒子１２４Ｃの黒鉛純度（第１黒鉛純度ＫＣ）が、天然黒鉛からなる第２活物質粒子１２４Ｅの黒鉛純度（第２黒鉛純度ＫＥ）に比して高くしてある。 As in the first embodiment, the negative electrode active material layer 121 has two strip-shaped end edge portions 121E and 121E and a strip-like shape that is located at the center in the width direction DW and is adjacent to the end edge portions 121E and 121E, respectively. It consists of a central part 121C (see FIG. 5).
Among these, the edge part 121E contains the 2nd active material particle 124E which consists of natural graphite. The edge layer 121E has a second layer thickness TE of 32 μm and a solid content density of 1.4 g / cm 3 .
The central portion 121C includes first active material particles 124C made of artificial graphite. Further, the first layer thickness TC of the central portion 121C is 32 μm, which is equal to the second layer thickness TE of the edge portion 121E. Moreover, the solid content density of this center part 121C is 1.4 g / cm < 3 >, and is equal to the solid content density of the edge part 121E.
The graphite purity (first graphite purity KC) of the first active material particles 124C made of artificial graphite is made higher than the graphite purity (second graphite purity KE) of the second active material particles 124E made of natural graphite. It is.

ところで、本発明者らは、実施形態１と同様にして、電池１０１の電池特性（容量維持率）を評価すべく、電池１と同様の正極活物質層、負極活物質層、セパレータ及び電解液６０を用いた円筒形状の試料電池１０１を用意し、評価を行った。
具体的には、第１黒鉛純度ＫＣの第１活物質粒子１２４Ｃ、及び、ＰＶＤＦからなる結着材（図示しない）を、重量比で第１活物質粒子１２４Ｃ：結着材＝９０：１０となるように混合した。この混合物の中に、分散材のＮＭＰを適量添加し、ペースト状の第１負極ペースト１２１ＣＰを作製した。同様にして、第２黒鉛純度ＫＥの第２活物質粒子１２４Ｅ、及び、ＰＶＤＦからなる結着材（図示しない）を、重量比で第２活物質粒子１２４Ｅ：結着材＝９０：１０となるように混合し、第２負極ペースト１２１ＥＰを作製した。 By the way, in order to evaluate the battery characteristics (capacity retention ratio) of the battery 101, the present inventors have the same positive electrode active material layer, negative electrode active material layer, separator, and electrolytic solution as the battery 1 in the same manner as in the first embodiment. A cylindrical sample battery 101 using 60 was prepared and evaluated.
Specifically, a first active material particle 124C having a first graphite purity KC and a binder (not shown) made of PVDF are expressed by weight ratio of the first active material particle 124C: the binder = 90: 10. It mixed so that it might become. A proper amount of NMP as a dispersion material was added to the mixture to prepare a paste-like first negative electrode paste 121CP. Similarly, the second active material particles 124E having the second graphite purity KE and the binder (not shown) made of PVDF are second active material particles 124E: binder = 90: 10 in weight ratio. Thus, the second negative electrode paste 121EP was produced.

これら第１負極ペースト１２１ＣＰ及び第２負極ペースト１２１ＥＰを、実施形態１と同様の、図６に示すダイコータＤＣを用いて、長手方向ＤＬに延びる帯状の銅箔ＣＦの両主面に塗布した。   These first negative electrode paste 121CP and second negative electrode paste 121EP were applied to both main surfaces of the strip-shaped copper foil CF extending in the longitudinal direction DL using the die coater DC shown in FIG.

銅箔ＣＦ上に塗布した第１負極ペースト１２１ＣＰ及び第２負極ペースト１２１ＥＰを乾燥させた後、ロールプレスで高密度化して、幅方向ＤＷの両端部にそれぞれ位置する帯状の２つの端縁部と、幅方向ＤＷの中央に位置して、端縁部にそれぞれ隣接する帯状の中央部とからなる負極活物質層を作製した。なお、この負極活物質層の層厚は、中央部、端縁部にかかわらず、３２μｍで一定である。
作製した負極活物質層は、銅箔と共に、５５ｍｍ×７４０ｍｍの形状に切断し（このうち、正極活物質層を担持した部位の寸法は５５ｍｍ×７２０ｍｍ）、負電極板とした。なお、幅方向ＤＷの、中央部の寸法は２５ｍｍ、端縁部（１つ分）の寸法は１５ｍｍである。また、中央部及び端縁部の固形分密度は互いに等しい。 The first negative electrode paste 121CP and the second negative electrode paste 121EP applied on the copper foil CF are dried and then densified by a roll press to have two strip-shaped edge portions respectively positioned at both ends in the width direction DW Then, a negative electrode active material layer was produced, which was located at the center in the width direction DW and was composed of a strip-shaped center portion adjacent to the edge portion. In addition, the layer thickness of this negative electrode active material layer is constant at 32 μm regardless of the central portion and the edge portion.
The produced negative electrode active material layer was cut into a shape of 55 mm × 740 mm together with the copper foil (among these, the size of the portion carrying the positive electrode active material layer was 55 mm × 720 mm) to obtain a negative electrode plate. In the width direction DW, the dimension of the central part is 25 mm, and the dimension of the edge part (for one) is 15 mm. Moreover, the solid content density of a center part and an edge part is mutually equal.

なお、上述した負電極板における中央部及び端縁部の抵抗値を、実施形態１と同様に測定したところ、中央部の抵抗値は８．０Ω、端縁部の抵抗値は１４．２Ωであり、中央部が端縁部に比べて低抵抗の層特性を有していることが判った。   In addition, when the resistance value of the center part and edge part in the negative electrode plate mentioned above was measured similarly to Embodiment 1, the resistance value of the center part is 8.0Ω, and the resistance value of the edge part is 14.2Ω. In other words, it has been found that the central portion has a low resistance layer characteristic as compared with the edge portion.

上述の負電極板と、実施形態１の試料電池１と同様の正電極板との間に、試料電池１と同様のセパレータを介在させて積層し、これら正電極板、負電極板及びセパレータを捲回して、捲回型の発電要素を作製し、その後も試料電池１と同様にして試料電池１０１を製造した。   The negative electrode plate described above and the positive electrode plate similar to the sample battery 1 of Embodiment 1 are stacked with the same separator as the sample battery 1 interposed therebetween, and the positive electrode plate, the negative electrode plate, and the separator are stacked. Winding to produce a wound type power generation element, and thereafter, the sample battery 101 was manufactured in the same manner as the sample battery 1.

上述の試料電池１０１について、実施形態１の試料電池１と同様、初期のものの電池容量について測定した。その後、実施形態１の試料電池１と同様のサイクル試験を実施した。
さらに、サイクル試験後における試料電池１０１の電池容量を、再度測定した。そして、サイクル試験後における試料電池１０１の容量維持率を算出した。 Regarding the sample battery 101 described above, the battery capacity of the initial one was measured in the same manner as the sample battery 1 of the first embodiment. Thereafter, a cycle test similar to that of the sample battery 1 of Embodiment 1 was performed.
Furthermore, the battery capacity of the sample battery 101 after the cycle test was measured again. Then, the capacity maintenance rate of the sample battery 101 after the cycle test was calculated.

この試料電池１０１と同様にして、比較例である比較電池Ｃ３，Ｃ４も製作し、これらの電池特性についての電池特性（容量維持率）を、試料電池１０１と同様に行った。
なお、比較電池Ｃ３は、負極活物質層が第１黒鉛純度ＫＣの第１活物質粒子１２４Ｃのみを含む、即ち、中央部及び端縁部が共に第１活物質粒子１２４Ｃのみを含む点で試料電池１０１と異なる。また、比較電池Ｃ４は、負極活物質層が第２黒鉛純度ＫＥの第２活物質粒子１２４Ｅのみを含む、即ち、中央部及び端縁部が共に第２活物質粒子１２４Ｅのみを含む点で試料電池１０１と異なる。
これら試料電池１０１及び比較電池Ｃ３，Ｃ４の各負極活物質層の構成、及び、容量維持率を表２に示す。 Comparative batteries C3 and C4, which are comparative examples, were also manufactured in the same manner as the sample battery 101, and the battery characteristics (capacity maintenance ratio) for these battery characteristics were the same as those of the sample battery 101.
The comparative battery C3 is a sample in that the negative electrode active material layer includes only the first active material particles 124C having the first graphite purity KC, that is, both the central portion and the edge include only the first active material particles 124C. Different from battery 101. Further, the comparative battery C4 is a sample in that the negative electrode active material layer includes only the second active material particles 124E having the second graphite purity KE, that is, the center portion and the edge portion both include only the second active material particles 124E. Different from battery 101.
Table 2 shows the configurations and capacity retention ratios of the negative electrode active material layers of the sample battery 101 and the comparative batteries C3 and C4.

Figure 2011070976
Figure 2011070976

表２によれば、中央部が第１活物質粒子１２４Ｃを、端縁部が第２活物質粒子１２４Ｅをそれぞれ含む試料電池１０１の容量維持率は、負極活物質層が第１活物質粒子１２４Ｃのみ、或いは、第２活物質粒子１２４Ｅのみを含む各比較電池Ｃ３，Ｃ４よりも高い。このことから、負極活物質層全体に１種類の負極活物質粒子（第１活物質粒子１２４Ｃ，第２活物質粒子１２４Ｅ）を含む電池よりも、負極活物質層の端縁部に第２活物質粒子１２４Ｅを、中央部に第２活物質粒子１２４Ｅよりも黒鉛純度の高い第１活物質粒子１２４Ｃを含む電池の方が、その電池の容量維持率を高くできることが判る。   According to Table 2, the capacity retention rate of the sample battery 101 including the first active material particles 124C in the central portion and the second active material particles 124E in the edge portion is as follows. The negative electrode active material layer has the first active material particles 124C in the negative electrode active material layer. Or the comparison batteries C3 and C4 including only the second active material particles 124E. Therefore, the second active material layer has a second active material layer at the edge portion of the negative electrode active material layer rather than a battery in which the entire negative electrode active material layer includes one type of negative electrode active material particles (first active material particles 124C and second active material particles 124E). It can be seen that a battery including the material particles 124E in the center and the first active material particles 124C having higher graphite purity than the second active material particles 124E can increase the capacity retention rate of the battery.

このようになる理由は以下であると考えられる。即ち、黒鉛純度が高い負極活物質粒子では、黒鉛以外の不純物の割合が小さいので、黒鉛純度が高くなるに連れて、負極活物質粒子の抵抗は低くなる。従って、黒鉛純度の高い第１活物質粒子１２４Ｃの方が第２活物質粒子１２４Ｅよりも低抵抗である。その上、端縁部と中央部との固形分密度を互いに等しく、しかも端縁部と中央部とで厚みを互いに等しくした。これにより、低抵抗の第１活物質粒子１２４Ｃを含む中央部全体の層特性も、端縁部に比べて、低抵抗とすることができる。   The reason for this is considered as follows. That is, in the negative electrode active material particles having a high graphite purity, since the ratio of impurities other than graphite is small, the resistance of the negative electrode active material particles decreases as the graphite purity increases. Therefore, the first active material particles 124C having a higher graphite purity have a lower resistance than the second active material particles 124E. In addition, the solid density of the edge portion and the central portion is equal to each other, and the thickness is equal to that of the edge portion and the central portion. Thereby, the layer characteristics of the entire central portion including the low-resistance first active material particles 124 </ b> C can also be made lower resistance than the edge portion.

以上より、試料電池１０１、及び、これと同様の正極活物質層３１、負極活物質層１２１、セパレータ５０及び電解液６０を用いた電池１０１では、負極活物質粒子１２４Ｃ，１２４Ｅに用いる黒鉛について、中央部１２１Ｃにおける第１活物質粒子１２４Ｃの第１黒鉛純度ＫＣが、端縁部１２１Ｅにおける第２活物質粒子１２４Ｅの第２黒鉛純度ＫＥに比して高い。これにより、低抵抗の第１活物質粒子１２４Ｃを含む中央部１２１Ｃ全体の層特性も、端縁部１２１Ｅに比べて、低抵抗とすることができる。従って、実施形態１と同様、充電時に、負極活物質層に金属リチウムが析出するのを防止できる。かくして、使用に伴う電池容量の低下を確実に抑制できる電池とすることができる。
また、端縁部１２１Ｅと中央部１２１Ｃとの固形分密度を互いに等しく、かつ、端縁部１２１Ｅと中央部１２１Ｃとで厚みＴＥ，ＴＣを互いに等しくしながら、中央部１２１Ｃにおける負極活物質粒子（第１活物質粒子１２４Ｃ）の第１黒鉛純度ＫＣを端縁部１２１Ｅに比して高く異ならせることで、容易に中央部１２１Ｃを端縁部１２１Ｅよりも低抵抗の層特性にすることができる。 From the above, in the battery 101 using the sample battery 101 and the same positive electrode active material layer 31, negative electrode active material layer 121, separator 50, and electrolytic solution 60, graphite used for the negative electrode active material particles 124C and 124E is as follows. The first graphite purity KC of the first active material particles 124C in the central portion 121C is higher than the second graphite purity KE of the second active material particles 124E in the edge portion 121E. As a result, the layer characteristics of the entire central portion 121C including the low-resistance first active material particles 124C can also be reduced compared to the edge portion 121E. Therefore, similarly to Embodiment 1, it is possible to prevent metallic lithium from being deposited on the negative electrode active material layer during charging. Thus, a battery capable of reliably suppressing a decrease in battery capacity due to use can be provided.
Moreover, while the solid content densities of the edge part 121E and the central part 121C are equal to each other, and the thicknesses TE and TC are equal to each other in the edge part 121E and the central part 121C, the negative electrode active material particles ( By making the first graphite purity KC of the first active material particles 124C) higher than that of the edge portion 121E, the central portion 121C can be easily made to have lower resistance layer characteristics than the edge portion 121E. .

なお、電池１０１の製造方法は、実施形態１の電池１とほぼ同じであるので説明を省略する。   Note that the manufacturing method of the battery 101 is substantially the same as that of the battery 1 of the first embodiment, and a description thereof will be omitted.

（実施形態２）
本実施形態２にかかる車両２００は、前述した電池１，１０１を複数含むバッテリパック２１０を搭載したものである。具体的には、図７に示すように、車両２００は、エンジン２４０、フロントモータ２２０及びリアモータ２３０を併用して駆動するハイブリッド自動車である。この車両２００は、車体２９０、エンジン２４０、これに取り付けられたフロントモータ２２０、リアモータ２３０、ケーブル２５０、インバータ２６０、及び、矩形箱形状のバッテリパック２１０を有している。このうちバッテリパック２１０は、前述した電池１，１０１を複数収容してなる。 (Embodiment 2)
A vehicle 200 according to the second embodiment is equipped with a battery pack 210 including a plurality of the batteries 1 and 101 described above. Specifically, as shown in FIG. 7, vehicle 200 is a hybrid vehicle that is driven by using engine 240, front motor 220, and rear motor 230 in combination. The vehicle 200 includes a vehicle body 290, an engine 240, a front motor 220, a rear motor 230, a cable 250, an inverter 260, and a battery pack 210 having a rectangular box shape. Among these, the battery pack 210 contains a plurality of the above-described batteries 1 and 101.

本実施形態２にかかる車両２００は、使用に伴う電池容量の低下を抑制できる電池１，１０１を搭載しているので、安定した性能を有する車両２００とすることができる。   Since the vehicle 200 according to the second embodiment is equipped with the batteries 1 and 101 that can suppress a decrease in battery capacity due to use, the vehicle 200 having stable performance can be obtained.

（実施形態３）
また、本実施形態３のハンマードリル３００は、前述した電池１，１０１を含むバッテリパック３１０を搭載したものであり、図８に示すように、バッテリパック３１０、本体３２０を有する電池搭載機器である。なお、バッテリパック３１０はハンマードリル３００の本体３２０のうち底部３２１に可能に収容されている。 (Embodiment 3)
Further, the hammer drill 300 according to the third embodiment is mounted with the battery pack 310 including the batteries 1 and 101 described above, and is a battery-mounted device having the battery pack 310 and the main body 320 as shown in FIG. . Note that the battery pack 310 is accommodated in the bottom portion 321 of the main body 320 of the hammer drill 300.

本実施形態３にかかるハンマードリル３００は、使用に伴う電池容量の低下を抑制できる電池１，１０１を搭載しているので、安定した性能を有する電池搭載機器とすることができる。   Since the hammer drill 300 according to the third embodiment is equipped with the batteries 1 and 101 that can suppress a decrease in battery capacity due to use, a battery-equipped device having stable performance can be obtained.

以上において、本発明を実施形態１〜３及び変形形態１に即して説明したが、本発明は上記実施形態に限定されるものではなく、その要旨を逸脱しない範囲で、適宜変更して適用できることは言うまでもない。
例えば、実施形態１では粒径の異なる黒鉛を、変形形態１では黒鉛純度の異なる黒鉛を負極活物質粒子に用いたが、例えば、アスペクト比の異なる黒鉛を負極活物質粒子に用いても良い。 In the above, the present invention has been described with reference to the first to third embodiments and the first modified embodiment, but the present invention is not limited to the above-described embodiments, and can be appropriately modified and applied without departing from the gist thereof. Needless to say, you can.
For example, graphite having a different particle diameter is used for the negative electrode active material particles in Embodiment 1 and graphite having a different graphite purity is used for the negative electrode active material particles in Modification 1. For example, graphite having a different aspect ratio may be used for the negative electrode active material particles.

このような場合として、具体的には、黒鉛のうち、ほぼ球状の塊状黒鉛（アスペクト比が１．０〜１．３）と、この塊状黒鉛よりもアスペクト比が大きな鱗片状の鱗片状黒鉛（アスペクト比が２．０以上）が挙げられる。
黒鉛は六角板状結晶であるので、アスペクト比が大きな負極活物質粒子ほど、リチウムイオン或いは電子がその奥（中心）にまで到達し難い。このため、アスペクト比が大きいほど、その負極活物質粒子自身の抵抗は高くなり、逆にアスペクト比が小さいほど、その負極活物質粒子自身の抵抗は低くなる。従って、塊状黒鉛の方が鱗片状黒鉛よりも低抵抗である。
かくして、負極活物質層の中央部に含む第１活物質粒子に塊状黒鉛を、端縁部に含む第２活物質粒子に鱗片状黒鉛をそれぞれ用いた電池でも、充電時に、負極活物質層に金属リチウムが析出するのを防止できて、使用に伴う電池容量の低下を抑制できる。 As such a case, specifically, among graphite, substantially spherical massive graphite (aspect ratio is 1.0 to 1.3), and flaky graphite having an aspect ratio larger than that of massive graphite ( The aspect ratio is 2.0 or more).
Since graphite is a hexagonal plate-like crystal, the negative electrode active material particles having a larger aspect ratio are less likely to reach the back (center) of lithium ions or electrons. For this reason, the larger the aspect ratio, the higher the resistance of the negative electrode active material particle itself. Conversely, the smaller the aspect ratio, the lower the resistance of the negative electrode active material particle itself. Therefore, massive graphite has a lower resistance than flaky graphite.
Thus, even in a battery in which massive graphite is used for the first active material particles included in the central portion of the negative electrode active material layer and flaky graphite is used for the second active material particles included in the edge portion, The precipitation of metallic lithium can be prevented, and the decrease in battery capacity accompanying use can be suppressed.

１，１０１ 電池（リチウムイオン二次電池）
１０，１１０ 発電要素
２０，１２０ 負電極板
２１，１２１ 負極活物質層
２１Ｃ，１２１Ｃ 中央部
２１Ｅ，１２１Ｅ 端縁部
２４Ｃ，１２４Ｃ 第１活物質粒子（負極活物質粒子）
２４Ｅ，１２４Ｅ 第２活物質粒子（負極活物質粒子）
２８ 銅箔（負極集電板）
３０ 正電極板
５０ セパレータ
６０ 電解液
２００ 車両
３００ ハンマードリル（電池搭載機器）
ＤＬ 長手方向
ＤＷ 幅方向
ＫＣ 第１黒鉛純度
ＫＥ 第２黒鉛純度
ＲＣ 第１平均粒径
ＲＥ 第２平均粒径
ＴＣ 第１層厚（中央部の厚み）
ＴＥ 第２層厚（端縁部の厚み） 1,101 battery (lithium ion secondary battery)
10, 110 Power generation element 20, 120 Negative electrode plate 21, 121 Negative electrode active material layer 21C, 121C Central portion 21E, 121E Edge portion 24C, 124C First active material particles (negative electrode active material particles)
24E, 124E Second active material particles (negative electrode active material particles)
28 Copper foil (Negative electrode current collector)
30 Positive electrode plate 50 Separator 60 Electrolytic solution 200 Vehicle 300 Hammer drill (battery-equipped equipment)
DL Longitudinal direction DW Width direction KC 1st graphite purity KE 2nd graphite purity RC 1st average particle diameter RE 2nd average particle diameter TC 1st layer thickness (thickness of center part)
TE 2nd layer thickness (edge thickness)

Claims (6)

導電性を有する帯状の負極集電板、及び、この負極集電板上に配置されて、負極活物質粒子を含み、この負極集電板の長手方向に延びる帯状の負極活物質層を有する帯状の負電極板と、
上記負電極板と対向してなる帯状の正電極板と、
上記負電極板と上記正電極板との間に介在してなるセパレータと、を捲回してなり、
上記セパレータにリチウムイオンを含む電解液を含浸させた発電要素を備える
リチウムイオン二次電池であって、
上記負極活物質層は、
上記長手方向に直交する幅方向の両端部にそれぞれ位置する帯状の端縁部と、上記幅方向の中央に位置して、上記端縁部にそれぞれ隣接する帯状の中央部と、からなり、
上記中央部は、
上記端縁部よりも低抵抗の層特性を有する
リチウムイオン二次電池。 A strip-shaped negative electrode current collector plate having conductivity, and a band-shaped negative electrode active material layer disposed on the negative electrode current collector plate and including negative electrode active material particles and extending in the longitudinal direction of the negative electrode current collector plate Negative electrode plate of
A belt-like positive electrode plate facing the negative electrode plate;
A separator formed between the negative electrode plate and the positive electrode plate is wound,
A lithium ion secondary battery comprising a power generation element impregnated with an electrolyte containing lithium ions in the separator,
The negative electrode active material layer is
A band-shaped edge located at both ends in the width direction perpendicular to the longitudinal direction, and a band-shaped center located at the center in the width direction and adjacent to the edge, respectively.
The central part is
The lithium ion secondary battery which has a layer characteristic of resistance lower than the said edge part. 請求項１に記載のリチウムイオン二次電池であって、
前記端縁部と前記中央部とは、固形分密度が互いに等しい
リチウムイオン二次電池。 The lithium ion secondary battery according to claim 1,
The edge portion and the central portion are lithium ion secondary batteries having the same solid density. 請求項２に記載のリチウムイオン二次電池であって、
前記端縁部と前記中央部とは、厚みが互いに等しく、
前記負極活物質粒子のうち、上記中央部に含まれる第１活物質粒子は、
その第１平均粒径が、上記端縁部に含まれる第２活物質粒子の第２平均粒径に比して小さい
リチウムイオン二次電池。 The lithium ion secondary battery according to claim 2,
The edge portion and the central portion have the same thickness,
Of the negative electrode active material particles, the first active material particles contained in the central portion are:
The lithium ion secondary battery whose 1st average particle diameter is small compared with the 2nd average particle diameter of the 2nd active material particle contained in the said edge part. 請求項２又は請求項３に記載のリチウムイオン二次電池であって、
前記端縁部と前記中央部とは、厚みが互いに等しく、
前記負極活物質粒子は黒鉛であり、
上記負極活物質粒子のうち、上記中央部に含まれている第１活物質粒子は、
その第１黒鉛純度が、前記端縁部に含まれている第２活物質粒子の第２黒鉛純度に比して高い
リチウムイオン二次電池。 The lithium ion secondary battery according to claim 2 or claim 3,
The edge portion and the central portion have the same thickness,
The negative electrode active material particles are graphite,
Of the negative electrode active material particles, the first active material particles contained in the central portion are:
The lithium ion secondary battery whose 1st graphite purity is high compared with the 2nd graphite purity of the 2nd active material particle contained in the said edge part. 請求項１〜請求項４のいずれか１項に記載のリチウムイオン二次電池を搭載し、このリチウムイオン二次電池に蓄えた電気エネルギを動力源の全部又は一部に使用する車両。 A vehicle on which the lithium ion secondary battery according to any one of claims 1 to 4 is mounted and the electric energy stored in the lithium ion secondary battery is used for all or part of a power source. 請求項１〜請求項４のいずれか１項に記載のリチウムイオン二次電池を搭載し、このリチウムイオン二次電池に蓄えた電気エネルギをエネルギ源の全部又は一部に使用する電池搭載機器。 The battery mounting apparatus which mounts the lithium ion secondary battery of any one of Claims 1-4, and uses the electrical energy stored in this lithium ion secondary battery for all or one part of an energy source.
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