Electrodes, batteries, and battery packs

Abstract

According to an embodiment, an electrode is provided which includes an active material-containing layer, and the active material-containing layer contains an active material, a first conductive agent, and a second conductive agent. The integrated intensity I D of the D band of the first conductive agent in the Raman spectrum G and the integrated intensity I D of the G band G has a ratio I D / I G of 0.5 < I D / I G < 2, and for the second conductive agent, 0 < I D / I G < 0.5. In the constituent material mapping image obtained by Raman spectroscopy for the active material-containing layer, the occupied area S1 of the first conductive agent relative to the occupied area Sa of the active material satisfies 0.1 < S1 / Sa < 1.0, the occupied area S2 of the second conductive agent relative to the occupied area Sa of the active material satisfies 0.8 < S2 / Sa < 10, the distance between the centers of gravity R1 of the first conductive agent relative to the distance between the centers of gravity Ra of the active material satisfies 1.0 < R1 / Ra < 1.5, the distance between the centers of gravity R2 of the second conductive agent relative to the distance between the centers of gravity Ra of the active material satisfies 0.5 < R2 / Ra < 1.0, and the relationship R1 > R2 > R1-2 is satisfied for R1, R2, and the distance between the centers of gravity R1-2 between the first conductive agent and the second conductive agent.

Description

Technical Field

[0001] Embodiments of the present invention relate to electrodes, batteries, and battery packs. Background Technology

[0002] Secondary batteries, including non-aqueous electrolyte secondary batteries such as lithium-ion batteries, have been widely adopted not only in electronic devices such as mobile phones but also in vehicles such as hybrid and electric vehicles. These applications demand higher capacity, longer lifespan, and improved output performance.

[0003] Graphite is generally used as the negative electrode active material in non-aqueous electrolyte batteries. Graphite forms LiC6 by intercalating Li, exhibiting a theoretical capacity of 372 mAh / g. Furthermore, graphite has a reaction potential relative to Li (the potential at which the Li intercalation-deintercalation reaction occurs) of 0.1 V (vs. Li / Li). + The reaction occurs at a potential of approximately 0.5V (vs. Li / Li), thus, by using a graphite anode, a battery with high output and high energy density can be obtained. However, the Li intercalation reaction potential of graphite is close to the Li deposition potential, making lithium dendrites prone to deposition due to overvoltage. Since dendrites penetrate the separator and cause internal short circuits, batteries using graphite anodes suffer from low safety. Furthermore, graphite stretches and contracts along the c-axis during Li intercalation and deintercalation, resulting in significant structural degradation. As other anode active materials for non-aqueous electrolyte batteries, if used at a reaction potential of 0.5V (vs. Li / Li),... + Compounds that react at high potentials above 0.5, such as spinel-type lithium titanate (Li4Ti5O4). 12 This process can suppress the precipitation of lithium dendrites. As a result, it is known to avoid hazards such as short circuits, self-discharge, and fire, and to produce batteries with excellent lifespan performance.

[0004] As a positive electrode active material for non-aqueous electrolyte batteries, lithium nickel cobalt manganese oxide (LiCoMnO4) offers high capacity and excellent performance. Compared to batteries using graphite-based negative electrodes, conventional batteries using LiCoMnO4 as the positive electrode and LiTitanium oxide as the negative electrode exhibit superior characteristics such as rapid charge / discharge performance, long lifespan, and low-temperature performance. However, there is room for improvement in the positive electrode active material, particularly regarding lifespan performance. During charge / discharge cycles, irreversible changes occur in the LiCoMnO4 particles at the positive electrode, leading to deterioration structures such as particle fragmentation and rock-salt-type structures. Consequently, each cycle results in a decrease in capacity or an increase in resistance. Conventional LiCoMnO4 typically forms a polycrystalline system of secondary particles composed of finely shaped primary particles. When using such an active material as the positive electrode, especially during high-potential charge / discharge cycles, oxidation reactions between the positive electrode and the electrolyte are easily induced, leading to issues such as gas generation and a significant increase in resistance.

[0005] Conversely, by using active materials such as single-crystal systems with small specific surface areas in the positive electrode, side reactions between the active material and the electrolyte can be reduced. However, on the other hand, if the specific surface area decreases, the contact between the active material and the conductive agent decreases, resulting in the electrode interior being divided into parts where current can easily flow and parts where current cannot flow, which may lead to localized degradation of the active material.

[0006] Furthermore, in lithium secondary electrodes obtained using conventional lithium-containing metal oxides as active materials, carbon or similar conductive agents are added to maintain conductive pathways between the active materials in the electrode. If the conductive agent is not properly dispersed among the active materials in the electrode, it may aggregate, forming conductive pathways only within itself. Compared to the active materials, current tends to flow more easily through these aggregates, resulting in uneven current distribution. Alternatively, the aggregated conductive agent may reduce the compressibility during electrode fabrication, or weaken the adhesion between the active material layer and the current collector, all of which can cause problems.

[0007] Existing technical documents Patent documents Patent Document 1: International Publication No. 2016 / 068258 Patent Document 2: Japanese Patent Application Publication No. 2019-3946 Patent Document 3: International Publication No. 2023 / 131987 Summary of the Invention

[0008] The problem that the invention aims to solve The purpose of this invention is to provide an electrode capable of achieving a battery with low resistance and excellent lifespan performance, a battery having the electrode, and a battery pack having the battery.

[0009] Methods for solving problems According to an embodiment, an electrode is provided, comprising an active material layer containing an active material, a first conductive agent, and a second conductive agent. The Raman spectrum obtained by Raman spectroscopy for the active material layer shows a value corresponding to the first conductive agent at 1350±10 cm⁻¹. -1 The integral intensity I of the D-band that appears at the location D With at 1590±10cm -1 The integral intensity I of the G-band that appears at the location G The ratio of I D / I G At 0.5 D / I G Within the range of <2. The ratio I in the Raman spectrum for the second conductive agent. D / I G In 0 D / I G ​​In the range of <0.5. In the constituent material mapping image obtained by Raman spectroscopy for the active material layer-containing part, the ratio S1 / Sa of the occupied area S1 of the first conductive agent to the occupied area Sa of the active material is within the range of 0.1 < S1 / Sa < 1.0. In the constituent material mapping image, the ratio S2 / Sa of the occupied area S2 of the second conductive agent to the occupied area Sa of the active material is within the range of 0.8 < S2 / Sa < 10. In the constituent material mapping image, the ratio R1 / Ra of the distance between the centers of gravity R1 of the first conductive agent to the distance between the centers of gravity Ra of the active material is within the range of 1.0 < R1 / Ra < 1.5. In the constituent material mapping image, the ratio R2 / Ra of the distance between the centers of gravity R2 of the second conductive agent to the distance between the centers of gravity Ra of the active material is within the range of 0.5 < R2 / Ra < 1.0. In the constituent material mapping image, the distance between the centers of gravity R1 of the first conductive agent, the distance between the centers of gravity R2 of the second conductive agent, and the distance between the centers of gravity R1-2 between the first conductive agent and the second conductive agent satisfy the relationship R1 > R2 > R1-2.

[0010] According to another embodiment, a battery is provided, which includes the electrode and an electrolyte.

[0011] According to still another embodiment, a battery pack is provided, which includes the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a top view schematically showing an electrode of an example of an embodiment.

[0013] Figure 2 is a cross-sectional view schematically showing an electrode of an example of an embodiment.

[0014] Figure 3 is a conceptual diagram showing a constituent material mapping image obtained by Raman spectroscopy for the active material layer-containing part of an electrode of an example of an embodiment.

[0015] Figure 4 is a conceptual diagram showing a constituent material mapping image obtained by Raman spectroscopy for the active material layer-containing part of an example of a conventional electrode.

[0016] Figure 5 is a conceptual diagram showing a method for calculating the distance between centers of gravity in a constituent material mapping image obtained by Raman spectroscopy.

[0017] Figure 6 is a conceptual diagram showing a method for calculating the distance between centers of gravity in a constituent material mapping image obtained by Raman spectroscopy.

[0018] Figure 7 is a conceptual diagram showing a method for calculating the distance between centers of gravity in a constituent material mapping image obtained by Raman spectroscopy.

[0019] Figure 8 This is a conceptual diagram representing the method for calculating the distance between centroids in a material mapping image obtained by Raman spectroscopy.

[0020] Figure 9 This is a graph showing the distribution of the distance between the centers of gravity of the active material layer in an example of a conventional electrode.

[0021] Figure 10 This is a graph showing the distribution of the distance between the centroids of the active material layers of an electrode in an example of an embodiment.

[0022] Figure 11 This is a cross-sectional view of a battery cut along the thickness direction, representing one example of an implementation.

[0023] Figure 12 yes Figure 11 An enlarged sectional view of part A.

[0024] Figure 13 This is a partial cross-sectional perspective view of the battery, which is another example of the implementation method.

[0025] Figure 14 This is an exploded perspective view of a battery pack, representing one example of an implementation method.

[0026] Figure 15 It means Figure 14 The diagram shows a block diagram of the battery pack circuit. Detailed Implementation

[0027] One method for improving lifetime performance in the past was increasing the conductivity dose. If the conductivity dose is too low, it is difficult to maintain electrical contact between the electrode components, represented by the active material, resulting in increased resistance of the electrode. On the other hand, if the conductivity dose is excessively increased, it can easily cause the conductive agent to aggregate. As a result, current can easily flow only in areas of low resistance, leading to localized degradation of the active material and a decrease in lifetime performance.

[0028] In lithium-ion battery cathodes using conventional lithium-metal composite compounds as positive electrode active materials, a small specific surface area is sometimes used to improve cathode lifespan performance. However, when using active materials with small specific surface areas, not only is it difficult to achieve electrical contact between the positive electrode active material and the conductive agent, but the electrical contact is also easily lost due to the expansion and contraction of the cathode during battery charging and discharging. In such cathodes, current preferentially flows through the areas where the contact between the active material and the conductive agent remains good, potentially causing a localized increase in the positive electrode potential. Therefore, there is a tendency for increased resistance and significant gas generation to occur due to the degradation of the positive electrode active material in the areas with higher positive electrode potentials.

[0029] Therefore, particle shape control and coating application are used to suppress the degradation of active materials. However, regardless of shape or surface condition, a large specific surface area of ​​the cathode increases side reactions, leading to increased resistance, while a small specific surface area may cause localized degradation as described above. Therefore, these measures do not fundamentally solve the degradation problem of active materials.

[0030] Hereinafter, embodiments will be described with reference to the accompanying drawings. Furthermore, common structures will be labeled with the same reference numerals in the embodiments, and repeated descriptions will be omitted.

[0031] In addition, the figures are schematic diagrams used to facilitate the explanation and understanding of the embodiments. Their shapes, sizes, proportions, etc. may differ from the actual devices, but they can be appropriately modified with reference to the following description and known techniques.

[0032] (First Implementation) According to a first embodiment, an electrode is provided. This electrode includes an active material layer containing an active material, a first conductive agent, and a second conductive agent. In a Raman spectrum obtained by measuring the active material layer using Raman spectroscopy, both the first and second conductive agents exhibit a wavelength at 1350 ± 10 cm⁻¹. -1 The D-band appears at 1590±10cm -1 The G band appears at [location]. The integrated intensity I of the D band in the Raman spectrum for the first conductive agent. D Integral intensity I of G-band G The ratio of I D / I G At 0.5 D / I G Within the range of <2. The ratio I in the Raman spectrum for the second conductive agent. D / I G In 0 D / I G ​​Within the range of <0.5. In the constituent material mapping image obtained by Raman spectroscopy for the layer containing the active material, the ratio S1 / Sa of the occupied area S1 of the first conductive agent to the occupied area Sa of the active material is within the range of 0.1 < S1 / Sa < 1.0. In the constituent material mapping image, the ratio S2 / Sa of the occupied area S2 of the second conductive agent to the occupied area Sa of the active material is within the range of 0.8 < S2 / Sa < 10. In the constituent material mapping image, the ratio R1 / Ra of the distance between the centers of gravity R1 of the first conductive agent to the distance between the centers of gravity Ra of the active material is within the range of 1.0 < R1 / Ra < 1.5. In the constituent material mapping image, the ratio R2 / Ra of the distance between the centers of gravity R2 of the second conductive agent to the distance between the centers of gravity Ra of the active material is within the range of 0.5 < R2 / Ra < 1.0. In the constituent material mapping image, the distance between the centers of gravity R1 of the first conductive agent, the distance between the centers of gravity R2 of the second conductive agent, and the distance between the centers of gravity R1-2 between the first conductive agent and the second conductive agent satisfy the relationship R1 > R2 > R1-2.

[0033] The electrode of the embodiment can be an electrode for a battery. As a battery that can include this electrode, for example, secondary batteries such as lithium-ion secondary batteries can be cited. The secondary battery includes a non-aqueous electrolyte secondary battery containing a non-aqueous electrolyte. This electrode can be, for example, a positive electrode for a battery.

[0034] The electrode satisfying the above constitution is an electrode that uses an active material and multiple conductive agents with different physical properties. Specifically, it is an electrode in which the conductive agent is uniformly dispersed by controlling the shape, addition amount, and dispersion method of the conductive agent. For this electrode, even if it contains an active material with a large capacity but a large deterioration caused by structural changes at high potentials, or an active material with a small side reaction but large particle size and small specific surface area that is not conducive to electrical contact, the disadvantages of these active materials can be eliminated, and the life performance of the battery can be significantly improved.

[0035] For example, carbon black such as acetylene black commonly used as a conductive agent exhibits conductivity based on percolation theory. Therefore, the particle size of carbon black is small and the specific surface area is large, and it is preferably constructed into a developed agglomerate structure. However, in an electrode using an active material with a small specific surface area, in order to form and maintain a conductive network between the active materials, the amount of carbon black required for electrical contact increases. In this case, the aggregation between carbon blacks becomes easy to occur, and the morphology of carbon black changes from an agglomerate structure suitable for exhibiting conductivity to an aggregate structure. If there are aggregates, the area with a resistance smaller than that of the active material becomes larger, and the current preferentially flows through this area. As a result, by promoting the charge-discharge reaction of the active material near the aggregates, the positive electrode potential rises, leading to local deterioration of the active material and a reduction in life performance.

[0036] Therefore, highly crystalline materials with large particle size and high orientation, primarily flake graphite which contributes little to conductivity, are added and appropriately positioned between the carbon black and the active material. This allows for the formation and maintenance of a good conductive network.

[0037] The high integrated intensity of the D-band in carbon black, caused by structural disorder, is due to... D with I G The ratio satisfies 0.5 D / I G The relationship is <2.0. That is, an example of the first conductive agent includes carbon black. Furthermore, the integrated intensity of the G-band caused by the layered structure of highly crystalline carbon is large, therefore I D with I G The ratio satisfies 0 D / I G The relationship is <0.5. Such highly crystalline carbon is an example of a second conductive agent, containing the aforementioned flake graphite. Thus, the two can be distinguished by Raman spectroscopy. Furthermore, metal oxides such as lithium-nickel-cobalt-manganese composite oxides do not possess D-bands or G-bands. Therefore, in the Raman spectrum containing the active material layer, by binarizing and overlaying these three phases separately, a mapping image of the constituting material can be obtained.

[0038] ​​In addition, according to the mixing ratios of these first and second conductive agents with different physical properties, the occupied areas of the respective phases on the material mapping image will change. Therefore, based on the ratios of the occupied areas of the active material, the first conductive agent, and the second conductive agent obtained by image analysis of the material mapping image, it is possible to confirm whether the conductive agent is contained in an appropriate mixing ratio. When the occupied areas of the active material, the first conductive agent, and the second conductive agent are set as Sa, S1, and S2 respectively, for the electrode of the embodiment, the relationships of 0.1 < S1 / Sa < 1.0 and 0.8 < S2 / Sa < 10 are satisfied, thereby suppressing the formation of agglomerates of the first conductive agent (such as carbon black), and the dispersion of the second conductive agent (such as highly crystalline carbon) becomes good. Therefore, the resistance of the electrode can be reduced, and the life performance of the battery can be improved. Moreover, since the dispersion state between the conductive agents in the active material layer is controlled, the first conductive agent can maintain the good aggregate structure of the above-mentioned carbon black, and the second conductive agent (such as highly crystalline carbon) forms the conductive network of the entire electrode. Therefore, this electrode can improve the life performance of the electrode by suppressing the deterioration caused by the charge-discharge cycle. Specifically, with the mutual positional relationships in which the distances Ra, R1, and R2 between the respective centers of gravity between the active materials, between the first conductive agents, and between the second conductive agents, and the distance R1-2 between the centers of gravity between the first conductive agent and the second conductive agent in the material mapping image respectively satisfy the relationships of 1.0 < R1 / Ra < 1.5, 0.5 < R2 / Ra < 1.0, and R1 > R2 > R1-2, these three phases are dispersedly arranged in the active material-containing layer, so that the electrode can achieve the above-mentioned effects.

[0039] Regarding this electrode, for the active material-containing layer, the occupancy area ratios obtained from the constituent material mapping images determined by measuring the cross-section by Raman spectroscopy satisfy the relationships of 0.1 < S1 / Sa < 1.0 and 0.8 < S2 / Sa < 10, respectively, thereby reducing the resistance and suppressing current unevenness. The presence ratio of the conductive agent contributing to conductivity is reflected in the occupancy area of the conductive agent in the cross-section of the active material-containing layer. That is, the ratio of the occupancy area of the conductive agent to the occupancy area of the active material is an index indicating the electrical contact in the electrode. If 0.1 > S1 / Sa or S1 / Sa > 1.0, the first conductive agent such as carbon black may be present过少 or in excess. In this case, sufficient conductivity cannot be obtained, or the generation of current unevenness due to the formation of agglomerates becomes significant. In addition, if 0.8 > S2 / Sa or S2 / Sa > 10, the second conductive agent (highly crystalline carbon) may be present过少 or in excess. In the case where the highly crystalline carbon is过少, the formation of the target conductive network cannot be carried out, and thus the above effects do not appear. On the contrary, in the case where the highly crystalline carbon is in excess, the function of the first conductive agent that electrically connects each particle to each other cannot be fully exerted, and thus local deterioration of the active material occurs. More preferably, the relationships of S1 / Sa < 0.8 and 2.0 < S2 / Sa < 4.0 are satisfied, respectively. Regarding an electrode having a preferred occupancy area ratio, in which the first conductive agent reliably exists between the active materials and the second conductive agent exists in a manner crossing them, the effect of improving the life performance can be obtained more significantly.

[0040] It should be noted that the Chinese characters "过少" in the original text seem to be incorrect or incomplete expressions. I translated them as "过少" as there is no clear correct form provided. If this is a misspelling or an incomplete word, it may affect the overall understanding of the content.The distance between the centers of gravity obtained from the constituent material mapping images determined by Raman spectroscopy of the cross-section of the active material layer is such that the active material, the first conductive agent, and the second conductive agent are dispersed in a mutual positional relationship satisfying the relationships of 1.0 < R1 / Ra < 1.5, 0.5 < R2 / Ra < 1.0, and R1 > R2 > R1 - 2. Thus, an electrode with excellent life performance can be obtained. If only the occupied area is simply considered, in the case of poor dispersion and deviation, it may not be possible to bring about performance improvement. If 1.0 > R1 / Ra or R1 / Ra > 1.5, the first conductive agent with high conductivity may be present过少 or in excess around the active material. In the case of过少, the charge-discharge reaction may not occur充分, and in the case of excess, current may flow more easily compared to other active materials, resulting in local deterioration. If 0.5 > R2 / Ra or R2 / Ra > 1.0, the second conductive agent may be present过少 or in excess around the active material. In the case of过少, the formation of the conductive network inside the electrode may become insufficient, and in the case of excess, there may be insufficient first conductive agent required for conduction between particles, and it may not be possible to sufficiently cause the charge-discharge reaction. If R1 < R2 or R1 - 2 < R2, the first conductive agent with high conductivity may be present in excess. In this case, current may flow more easily in the nearby active material than in other active materials, resulting in local deterioration. In the case of R2 < R1 - 2 or R1 < R1 - 2, the first conductive agent and the second conductive agent may be present in independent regions. In this case, the mutual or complementary effects between the conductive agents cannot be obtained, and it may not be possible to obtain the effect of improving the life performance.

[0041] The active material layer preferably contains a lithium nickel cobalt manganese composite oxide represented by the formula Li a Ni (1-b-c-d) Co b Mn c M d O2 as the active material. Each subscript in the formula is within the ranges of 1 ≤ a ≤ 1.2, 0 ≤ b ≤ 0.4, 0 ≤ c ≤ 0.4, and 0 ≤ d ≤ 0.1. M contains at least one selected from the group consisting of Fe, Cu, Ti, Mg, Al, W, Y, B, Mo, Nb, Zn, Sn, Zr, Ga, and V.

[0042] It should be noted that there are some unclear or incorrect expressions in the original text (such as "过少" which is not a proper English word in this context), and the translation is made as accurately as possible based on the overall meaning.The active material can have an average primary particle size of 2 μm or more and 7 μm or less. In an active material layer, by setting the primary particle size of the active material particles to 2 μm or more and 7 μm or less, the battery's lifespan performance can be improved. By setting the primary particle size to 2 μm or more, the specific surface area of ​​the electrode is reduced, which can decrease the impact of side reactions between the electrode and the electrolyte on lifespan performance. Furthermore, by setting the primary particle size to 7 μm or less, the diffusion of lithium ions within the solid state of the particles becomes more uniform, suppressing localized structural degradation and improving lifespan performance. More preferably, the primary particle size is set to 3 μm or more and 4.5 μm or less. This more preferred range easily prevents the aggregation or isolation of primary particles and easily satisfies the required center-of-gravity distance.

[0043] The specific surface area of ​​the active material, determined by nitrogen adsorption-desorption, is preferably 0.5 m². 2 / g or more and 1.0m 2 Within the range of / g or less. Specific surface area is 0.5m². 2 At concentrations above a certain level (e.g.), the penetration of the electrolyte solution into the layer containing the active material is promoted, resulting in improved output performance and lifespan. The specific surface area is 1.0 m². 2 At concentrations below a certain level, the contact between the active material and the conductive agent increases, further reducing resistance and improving high-current output performance. Additionally, the mechanical stability of the electrode increases.

[0044] The electrode may include a current collector. The current collector may be, for example, in the shape of a foil, a strip, or a plate. An active material layer may be disposed on at least one main surface of the current collector. That is, the current collector may have the active material layer on one side or both sides. The current collector may include a portion of its surface that does not have the active material layer. This portion may function as a current collector tab. Alternatively, the electrode may also include a current collector tab disposed separately from the current collector.

[0045] In addition to containing active materials and conductive agents, the active material layer may also contain a binder. The binder can be incorporated to bond the dispersed active materials and conductive agents, and to bond the active materials and conductive agents to the current collector.

[0046] Material Next, the active material layer of the electrode in the first embodiment and the materials that can be used in the current collector that the electrode can contain will be described.

[0047] <Contains active substance layer> The density of the active substance layer is preferably 2.0 g / cm³. 3 Above and below 4.0 g / cm³ 3In electrodes with densities within the aforementioned range, the contact between the active material and the conductive agent is enhanced, thus enabling the formation of a better conductive network and equalizing the resistance within the active material layer. Therefore, batteries with excellent lifespan performance can be fabricated using such electrodes. For example, if the density is 2.0 g / cm³... 3 The above improvements enhance the contact between the active material and the first and second conductive agents, resulting in more uniform resistance within the active material layer and improved battery life. Furthermore, the mechanical stability of the electrodes is enhanced. (If the density is less than 4.0 g / cm³...) 3 This promotes the penetration of the electrolyte solution into the layer containing the active material, thus improving lifespan performance. A more preferred value is 3.20 g / cm³. 3 Above and less than 3.50 g / cm 3 The density is higher. Within a more preferred range, the resistance equalization effect is greater, and the local degradation of active materials is reduced, thus enabling batteries with longer lifespans.

[0048] As described above, the active material layer may contain an active material, a conductive agent, and a binder, in addition to the active material and the conductive agent. The preferred proportions of the active material, conductive agent, and binder in the active material layer are: active material 63% by mass or more and 99% by mass or less, conductive agent 0.5% by mass or more and 36% by mass or less, and binder 0.5% by mass or more and 17% by mass or less. The proportion of the conductive agent is the total proportion of the first conductive agent and the second conductive agent. The content of the first and second conductive agents in the active material layer is preferably the same. Specifically, the mass ratio of the first and second conductive agents to the active material layer can be 0.0025 or more and 0.18 or less, respectively.

[0049] <Active Substances> As described above, the active material layer may contain lithium nickel cobalt manganese composite oxides (e.g., Li). a Ni (1-b-c-d) Co b Mn c M dO2; wherein 1≤a≤1.2, 0≤b≤0.4, 0≤c≤0.4, and 0≤d≤0.1; M comprises at least one selected from the group consisting of Fe, Cu, Ti, Mg, Al, W, Y, B, Mo, Nb, Zn, Sn, Zr, Ga, and V. Other compounds may also be used as active materials, but it is preferred to include at least the lithium nickel cobalt manganese composite oxide as an active material. Furthermore, it is more preferable to include an active material containing the lithium nickel cobalt manganese composite oxide and having an average primary particle size of 2 μm or more and 7 μm or less. For example, the lithium nickel cobalt manganese composite oxide may be used as the first active material, and a second active material other than the first active material may be further included in the active material layer. Of course, the first active material may be used alone, or it may be used without the first active material but containing one or more second active materials.

[0050] As secondary active materials, various oxides can be cited, such as lithium cobalt composite oxides (e.g., LiCoO2), manganese dioxide, lithium manganese composite oxides (e.g., LiMn2O4, LiMnO2), lithium nickel composite oxides (e.g., LiNiO2), and lithium nickel cobalt composite oxides (e.g., LiNi). 0.8 Co 0.2 O2), lithium iron oxides, lithium vanadium oxides, titanium disulfide, molybdenum disulfide, and other chalcogenides, etc. The electrode may contain one of these compounds as a second active material, or it may contain two or more of these compounds as a second active material.

[0051] The proportion of the first active substance in the total mass of the active substance contained in the active substance layer is preferably 75% by mass or more and 100% by mass or less, more preferably 80% by mass or more and 100% by mass or less.

[0052] The active substance can, for example, have a particle shape. That is, the active substance layer can contain particles of the active substance. The active substance particles can be primary particles, or a mixture of primary and secondary particles.

[0053] In the active material particles, it is preferable to have a higher proportion of primary particles and a lower proportion of secondary particles. The internal conductivity of secondary particles (within the hollow structure) is poor. By eliminating the presence of primary particles within them, the active material particles can achieve good contact with the conductive agent, thereby further reducing resistance.

[0054] As described above, it is preferable to break down the agglomeration of secondary particles of the active material. On the other hand, it is preferable not to further pulverize the primary particles of the active material, but to maintain the particle size at 2 μm or larger. By not breaking the primary particles of the active material, an active material with a good crystalline structure can be obtained, maintaining good lifetime performance. By making the average particle size of the active material 2 μm or larger, the specific surface area of ​​the electrode can be reduced, minimizing the impact of side reactions between the electrode and the electrolyte on lifetime performance. Furthermore, by making the average particle size 7 μm or smaller, uniform intrasolid diffusion of lithium ions within the particles can be achieved, further improving lifetime performance.

[0055] <Conductive agent> As a conductive agent, it comprises at least a first conductive agent and a second conductive agent, wherein the first conductive agent is present in a Raman spectrum obtained by Raman spectroscopy at 1350±10 cm⁻¹. -1 The integral intensity I of the D-band that appears at the location D With at 1590±10cm -1 The integral intensity I of the G-band that appears at the location G The ratio of I D / I G At 0.5 D / I G Carbon materials in the range <2, the second conductive agent is more than I D / I G In 0 D / I G Carbon materials in the range of <0.5. Generally speaking, the first conductive agent is a carbon material with low graphitization, and the second conductive agent is a carbon material with high crystallinity and high graphitization.

[0056] Specific examples of primary conductive agents include carbon blacks such as acetylene black, Ketjen black, and furnace black. Specific examples of secondary conductive agents include graphite, graphene, single-layer carbon nanotubes, and double-layer carbon nanotubes. Multilayer carbon nanotubes, depending on the manufacturing method, are more conductive than I... D / I G ​​The value can be below 0.5 or above 0.5. It should be noted that the role of carbon nanotubes within the active material layer varies depending on their length. Short carbon nanotubes can exhibit conductivity based on percolation theory, similar to carbon black, and can form aggregate structures. Long carbon nanotubes can form conductive networks, similar to flake graphite. Furthermore, highly oriented materials such as highly oriented graphite are preferred as the second conductive agent. For example, regarding graphite, in addition to highly oriented flake graphite, there is also spherical graphite with reduced orientation. Natural graphite is flake graphite. Spherical graphite is graphite obtained through spheroidization treatment. Each active material layer contains at least one first conductive agent and one second conductive agent. The active material layer can contain conductive agents in combinations of one first conductive agent and two or more second conductive agents, or combinations of two or more first conductive agents and one second conductive agent. Additionally, the active material layer can contain two or more first conductive agents and two or more second conductive agents.

[0057] The first conductive agent may, for example, have a particle shape. From the viewpoint of forming an aggregate structure, it is preferable that the average particle size (primary particle size) of the first conductive agent is small. Therefore, the average particle size of the first conductive agent is preferably 100 nm or less. For example, it is preferable to add acetylene black, which has excellent conductivity and an average particle size in the range of 20 nm or more and 100 nm or less, as the first conductive agent. A more preferred range for the average particle size of the first conductive agent is 30 nm or more and 70 nm or less.

[0058] The second conductive agent may, for example, have a scaly shape. While the second conductive agent can form a conductive network by having a large particle size, from the viewpoint of ensuring easy dispersibility in its positional relationship with the active material and the first conductive agent, it is preferable that the average particle size of the second conductive agent is 10 μm or less. More preferably, the average particle size of the second conductive agent is 1 μm or less.

[0059] The particle size of the first and second conductive agents mentioned here refers to the diameter of the equivalent circle, that is, the diameter of the sphere when the conductive agent particles are assumed to be spheres of the same volume or with the same cross-sectional area, as will be described later.

[0060] The mass ratio of the first conductive agent and the second conductive agent to the active material is preferably 0.18 or less. That is, relative to 100 parts by mass of the active material, it is preferable to include 18 parts by mass of the first conductive agent and 18 parts by mass of the second conductive agent.

[0061] <Adhesive> Materials containing fluorine atoms in their molecules are preferred as binders due to their excellent oxidation resistance and improved lifespan. Examples of such binders include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), and fluoropolymers. Other binders include styrene-butadiene rubber, acrylic resins and their copolymers, polyacrylic acid, and polyacrylonitrile. The active material layer may contain one or more of these binders.

[0062] <Current collector> As a current collector, metal foil or alloy foil can be used, for example. Examples of metal foils include aluminum foil, stainless steel foil, and nickel foil. Examples of alloy foils include aluminum alloys, copper alloys, and nickel alloys.

[0063] Next, specific examples of the electrodes of the first embodiment will be described with reference to the accompanying drawings.

[0064] Figure 1 This is a partial cross-sectional top view schematically illustrating an example of an electrode in an embodiment. Here, as an example of an electrode, an example positive electrode is illustrated. Figure 2 This is a cross-sectional view that roughly represents an example of the electrode.

[0065] Figure 1 and Figure 2 The illustrated positive electrode 3 includes a positive current collector 3a and a layer 3b containing a positive active material disposed on the surface of the positive current collector 3a. The layer 3b containing the positive active material is supported on the main surface of the positive current collector 3a. In the illustrated example, the layer 3b containing the positive active material is disposed on one main surface of the positive current collector 3a, but it is also possible to dispose of the layer 3b containing the positive active material on both the front and back surfaces of the positive current collector 3a.

[0066] Additionally, the positive current collector 3a includes a portion of its surface where the layer containing the positive active material 3b is not disposed. This portion functions, for example, as a positive current collector tab 3c. In the illustrated example, the positive current collector tab 3c is a narrow portion with a width narrower than the layer containing the positive active material 3b. The width of the positive current collector tab 3c can be narrower than the width of the layer containing the positive active material 3b, or it can be the same as the width of the layer containing the positive active material 3b. Alternatively, instead of using the positive current collector tab 3c as part of the positive current collector 3a, a separately disposed conductive component can be electrically connected to the positive electrode 3 and used as an electrode current collector tab (positive current collector tab).

[0067] The layer 3b containing the positive electrode active material includes at least the positive electrode active material 300, a first conductive agent 301, and a second conductive agent 302. Although not illustrated, the layer 3b may further include a binder. The first conductive agent 301 is distributed to fill the gaps between the particles of the positive electrode active material 300, forming conductive pathways between the particles of the positive electrode active material 300. The first conductive agent 301, having a particle shape, is concentrated in a portion of the gaps between the positive electrode active materials 300, thereby forming an aggregate structure. The second conductive agent 302, having a scale shape, is dispersed in a manner that connects the aggregate structures of the first conductive agent 301 to each other, thereby forming a conductive network within the layer 3b containing the positive electrode active material.

[0068] Production method The electrodes of the first embodiment can be manufactured, for example, by the following method.

[0069] An active material, a first conductive agent, a second conductive agent, and an optional binder are added to a suitable solvent to obtain a mixture. The first and second conductive agents are stirred separately in powder form, then mixed and stirred again before being added to the solvent. This reduces the difference in dispersion between the first and second conductive agents. Alternatively, other materials are added to the solvent, followed by the stirred mixture of the first and second conductive agents. Here, an optional dispersant can be used to improve the dispersibility of each conductive agent and the dispersibility between them. Furthermore, the order in which the conductive agents are added can be varied depending on the type of conductive agent used. By controlling the process, the distance between the centers of gravity in the cross-section of the electrode after fabrication can be controlled.

[0070] Next, the obtained mixture is fed into a mixer. In this mixer, the mixture is stirred to obtain a slurry. Furthermore, during the stirring process, by reducing the rotation speed of the mixer, a slurry that adequately maintains the conductive network of the conductive agent can be obtained. Conversely, by increasing the rotation speed of the mixer, a slurry with good dispersion of the active material can be obtained. By using slurries obtained through such controlled stirring, the area occupied by each component and the distance between their centers of gravity in the cross-section of the fabricated electrode can be controlled. Additionally, by increasing the rotation speed of the mixer, the active material and conductive agent particles can be pulverized, thereby increasing the specific surface area of ​​the fabricated electrode. The stirring mechanism in the mixer can also be varied depending on the type of conductive agent used.

[0071] The thus obtained slurry is coated on both the front and back surfaces or on a single surface of the current collector. At this time, a portion of the current collector where no slurry is coated on any surface may remain. Then, the coating film is dried and pressed. At this time, by increasing the pressing load, the electrode density can be increased, and after further increasing the electrode density, there is a tendency to easily fabricate an electrode with good electrical contact and excellent capacity. The increase in the pressing load can not only change the electrode density but also change the distance between the centers of gravity of the respective components in the cross-section of the fabricated electrode. For example, depending on the shape or strength of the active material, if the pressing load is large, crushing or fragmentation may occur, so the occupied area Sa of the active material in the cross-section will increase or the distance between the centers of gravity Ra will become shorter. In addition, the high-orientation high-crystalline carbon material has a large expansion in the planar direction, so by changing the pressing load, the cross-sectional area of this material when observed from the cross-section can be changed. Therefore, for the highly crystalline second conductive agent with high orientation, if the pressing load is large, the occupied area S2 in the cross-section tends to become smaller.

[0072] In this way, an electrode can be fabricated.

[0073] For example, by adjusting parameters such as the selection and mixing ratio of the types of the active material, conductive agent, and binder, the particle diameters of the respective particles of the active material and conductive agent, the conditions for stirring (dispersing) the mixture, and the pressing conditions, etc., the occupied area and the distance between the centers of gravity in the mapping image of the active material-containing layer can be adjusted to the ranges described above. For example, for each of the active material, the first conductive agent, and the second conductive agent, after increasing the mixing ratio or the particle diameter, the respective occupied areas Sa, S1, and S2 tend to become higher. In addition, for each component, after increasing the mixing ratio or the particle diameter respectively, the respective distances between the centers of gravity Ra, R1, and R2 tend to become shorter. However, for the active material-containing layer containing the active material and the first and second conductive agents, if the dispersion state of the respective components of the active material-containing layer is not adjusted so as to satisfy the relationship of the ratio of the occupied areas 0.1 < S1 / Sa < 1.0 and 0.8 < S2 / Sa < 10 in the constituent material mapping image obtained by Raman spectroscopy, and the relationship of the distances between the centers of gravity 1.0 < R1 / Ra < 1.5, 0.5 < R2 / Ra < 1.0, and R1 > R2 > R1 - 2, the electrode of the first embodiment cannot be fabricated.

[0074] For example, in the mixing process, by changing the order in which the active material, the first conductive agent, and the second conductive agent are added to the solvent, the dispersion state will change according to the differences in solubility parameters of the dispersing solvent and the binder. Furthermore, as mentioned above, the stirring intensity in the stirring process affects the distance between the centers of gravity and the area occupied by the active material and the conductive agent in the resulting electrode. Moreover, regarding the pressing load, for electrodes with extremely high or low density produced by over-pressing or under-pressing, not only does the electrode density deviate from the preferred range, but the ratio of their respective areas of occupation and the ratio of their distance between centers of gravity also tend to deviate from the values ​​within the specified range. Therefore, it is clear that the above relationships cannot be unintentionally satisfied.

[0075] Specific examples of electrode fabrication will be described in the embodiments later in the text.

[0076] Preferred active materials comprising the aforementioned lithium nickel cobalt manganese composite oxide and having an average primary particle size of 2 μm or more and 7 μm or less can be obtained, for example, as follows: A precursor using nickel, cobalt, and manganese sources is calcined. Here, if the calcination temperature is increased, the calcination time is extended, or the amount of a lithium source, such as lithium carbonate, is increased, particle growth is promoted compared to nucleation. Therefore, by optionally promoting particle growth, a lithium nickel cobalt manganese composite oxide with an optimized chemical composition, having a primary particle size of 2 μm or more and a nickel content ratio of at least a specified level, can be synthesized.

[0077] Electrode Measurement Various measurement methods for electrodes are described. Specifically, methods for determining the composition of the active material, methods for determining the particle size distribution and average particle size of the active material layer using laser diffraction scattering, methods for determining the specific surface area of ​​the active material using nitrogen adsorption-desorption, methods for determining the density of the active material layer, methods for obtaining Raman spectra using Raman spectroscopy, methods for image analysis of Raman spectra, and methods for determining the average particle size of the conductive agent by observation using electron microscopy are explained. As for image analysis methods for Raman spectra, methods for obtaining the mapping of the constituent materials through image analysis and methods for determining the occupied area and the distance between the centroids through image analysis are described.

[0078] When analyzing the electrodes assembled in the battery, the electrodes are removed in the following order.

[0079] First, prepare the battery to be tested. Ensure the battery has at least 80% of its rated capacity during discharge. That is, batteries that have undergone excessive degradation are not considered for testing.

[0080] Next, discharge the prepared battery until the open-circuit voltage reaches 2.0V~2.2V. Then, transfer the discharged battery to an argon-filled glove box with an internal dew point of -70°C. Cut the battery open inside the glove box. Remove the electrode assembly from the cut battery. With the removed electrode assembly containing both positive and negative leads, carefully disconnect the positive and negative leads while avoiding short-circuiting them.

[0081] Next, the electrode assembly is disassembled into a positive electrode, a negative electrode, and a diaphragm. For example, the positive electrode is selected as the electrode to be measured. The electrode thus obtained is cleaned using methyl ethyl carbonate as a solvent. For this cleaning, the disassembled components are completely immersed in methyl ethyl carbonate solvent and left in this state for 60 minutes.

[0082] After cleaning, the electrode was subjected to vacuum drying. Vacuum drying was performed at 25°C, with the pressure reduced from atmospheric pressure to above -97 kPa, and maintained at this state for 10 minutes. The electrode, after undergoing this decomposition, cleaning, and vacuum drying process, was used for the following measurements.

[0083] <Determination of the composition of active substances> By using X-ray fluorescence (XRF) to measure the surface of the electrode, the composition of the active material of the electrode can be determined.

[0084] Determination of Particle Size Distribution Using Laser Diffraction Scattering The particle size distribution of the electrode can be determined by the laser diffraction / scattering method described below.

[0085] After preparing the electrode to be measured, the active material layer is separated from the current collector using a scraper or similar tool, thereby obtaining a powdered electrode mixture sample containing the active material. Next, the powdered sample is placed into a measuring unit filled with N-methylpyrrolidone (NMP) until a measurable concentration is reached. Furthermore, the capacity of the measuring unit and the measurable concentration will vary depending on the particle size distribution measuring device.

[0086] The measuring unit containing NMP and an electrode mixture dissolved therein was irradiated with 40W ultrasound for 5 minutes. This ultrasonic irradiation broke up the aggregation of conductive agent particles and active material particles.

[0087] The ultrasonically treated measuring unit is inserted into a particle size distribution measuring device that uses laser diffraction / scattering to determine the particle size distribution. An example of a particle size distribution measuring device is the Microtrac 3100.

[0088] In this way, the particle size distribution containing the active material layer can be obtained.

[0089] Furthermore, by performing the measurement using a sample of active material particles, the particle size distribution of the active material particles can be obtained. Based on the particle size distribution of the active material particles, the average primary particle size of the active material can be determined.

[0090] The electrode mixture sample was dispersed and stirred in NMP, and the solid obtained by filtering the solvent was calcined to remove the binder and conductive agent, thereby separating the active material particles. The cumulative frequency of the particle size distribution measured using the obtained active material particles, starting from the smallest particle size, is taken as the 50% particle size (D). 50 This corresponds to the average primary particle size of the active material.

[0091] <Determination of the specific surface area of ​​active substances using nitrogen adsorption-desorption method> The specific surface area of ​​the active material obtained by nitrogen (N2) adsorption-desorption corresponds to the BET specific surface area of ​​the active material particles. The BET specific surface area refers to the specific surface area determined by the BET method, calculated using nitrogen adsorption-desorption. The analysis is carried out, for example, by the following methods.

[0092] As described above, by separating the active material layer from the current collector, a powdered electrode mixture sample containing the active material is obtained from the electrode. The obtained powdered sample is heated briefly in atmospheric air (approximately 500°C for 1 hour) to burn off unwanted components such as binder and carbon. The weight of the remaining active material sample is measured. Next, the sample is filled into the unit of the measuring apparatus. The sample placed in the measuring unit for nitrogen adsorption-desorption measurement is dried at a temperature above 120°C under a flow of N2. Then, the specific surface area is measured by the BET single-point method or the BET multi-point method. As an example of a measuring apparatus for nitrogen adsorption-desorption measurement, Quantasorb, manufactured by Quantacolme, can be cited.

[0093] <Density determination of the layer containing active substances> The density of the layer containing the active substance can be determined by the following steps.

[0094] First, the thickness of the prepared electrode is measured using a thickness gauge. Next, the electrode is punched to a size of 1cm × 1cm using a cutting machine to obtain a 1cm × 1cm sample. The weight of this sample is then measured.

[0095] Next, the active material layer is peeled off from the sample. For example, the active material layer can be peeled off by immersing the sample in N-methylpyrrolidone. Any solvent can be used as the solvent for peeling off the active material layer, as long as it does not corrode the current collector and is capable of peeling off the active material layer. The thickness and weight of the sample remaining as the current collector are then measured.

[0096] Next, the thickness of the active material layer is calculated by subtracting the thickness of the current collector from the thickness of the electrode. Additionally, the weight of the 1cm × 1cm active material layer is calculated by subtracting the weight of the current collector sample from the weight of the 1cm × 1cm sample. Finally, the density of the active material layer (unit: g / cm³) can be calculated by dividing the weight of the 1cm × 1cm active material layer by its thickness. 3 ).

[0097] <Determination using Raman spectroscopy> Next, the steps for obtaining a mapping image of the constituent material containing the active material layer using Raman spectroscopy will be explained.

[0098] (Obtaining Raman spectra) The electrode obtained by the above method is sampled. Sampling is performed at any 10 points on the electrode to be measured. At this time, it is more preferable to sample from 10 different points than to divide the sample that has been sampled at a specific point within the electrode into 10 points. In addition, in the Raman spectroscopy measurement described later, it is more preferable to perform sampling on the electrode portion with a thickness such that the entire field of view of the measurement becomes an image of the electrode cross-section, especially the cross-section containing the active material layer.

[0099] For each electrode sample obtained by sampling using the above method, it is fixed with the cross-section containing the active material layer facing the direction of the laser emitted for Raman measurement. As a specific example of the fixing method, the sample can be prepared as follows: The sample is placed in a container with its cross-section facing directly upwards, and the sample is fixed to the bottom of the container using a metal component. By allowing curable resin to flow into the container and allowing it to stand until the resin has cured, the electrode cross-section can be fixed in any orientation. Then, by mechanically cutting along a surface parallel to the bottom to expose a new cross-section, the measurement sample can be prepared in a way that allows observation of its cross-section. At this time, depending on the carbon material used, graphitization may sometimes intensify; therefore, it is necessary to reduce the energy during cutting to a level that does not affect the measurement.

[0100] The sample is fixed on the sample stage and placed into the Raman spectroscopy apparatus. For the placed sample, surface Raman spectroscopy is performed with a field of view of 50 μm × 50 μm to obtain the Raman spectrum. When obtaining the Raman spectrum, 10,000 points are measured within the 50 μm × 50 μm field of view, divided into 100 points vertically and 100 points horizontally. An example of a measuring apparatus for Raman spectroscopy measurement is the WITec α300 confocal microspectrophotometer. Measurement conditions are as follows. However, in cases where the thermal effect on the sample is significant, it is necessary to shorten the exposure time, increase the number of accumulations, or reduce the laser power. Conversely, if the obtained spectrum becomes unclear, it is necessary to extend the exposure time or increase the number of accumulations.

[0101] Exposure time: 10s or 20s Total number of times: 1 Lens magnification: 50x Measurement range: 50μm × 50μm Laser power: 5%.

[0102] (The creation of material mapping images) Next, using Raman spectra at 10,000 points, spectra were extracted from 10 randomly selected points in each high-concentration region to obtain average spectra. Multivariate analysis was performed on these average spectra to distinguish significant spectral components. For each distinguished component spectrum, the crystallinity of the active substance, the first conductive agent, and the second conductive agent was determined based on peak position, intensity, and intensity ratio. The presence ratio of each component was mapped using the obtained spectra of each constituent material and the 10,000-point Raman spectrum. It should be noted that the first and second conductive agents have D and G bands at close positions in the Raman spectrum, but the degree of overlap was calculated by fitting the spectra of the monomers, thereby distinguishing the presence of the first and second conductive agents at that point. The presence ratio of each constituent material can be represented, for example, by the different shades of color for each constituent material.

[0103] pass Figure 3 and Figure 4 The conceptual diagram shown illustrates an example of a material mapping image created from Raman spectroscopy. Figure 3 A mapped image of the active material layer of an electrode according to an example of an embodiment is shown. Figure 4 The diagram shows a mapping image of an active material layer for an example of a conventional electrode. Each image corresponds to a schematic diagram of a mapping image of the constituent materials, with white areas representing the active material 310, green areas representing the first conductive agent 311, red areas representing the second conductive agent 312, and yellow areas representing the remaining portion. Furthermore, the horizontally elongated blank bands visible at the top and bottom of each image correspond to the vertical space in the thickness direction offset from the cross-section of the active material layer.

[0104] exist Figure 3 In the mapped image of the electrode example of the illustrated embodiment, the active material 310, the first conductive agent 311, and the second conductive agent 312 are uniformly distributed within the field of view. In particular, the second conductive agent 312 is present throughout the entire area and adjacent to the active material 310, thereby forming a conductive network. Furthermore, the first conductive agent 311 is also present throughout, thereby improving the conductivity of the entire area within the active material layer. Therefore, regarding... Figure 3 In the example sample shown, charging and discharging are performed uniformly within the electrodes.

[0105] In contrast, in Figure 4 In the mapped image of the conventional electrode example shown, although there is a region where the first conductive agent 311 occupies most of the field of view and the second conductive agent 312 is adjacent to the active material 310, the second conductive agent 312 achieves a locally concentrated distribution and cannot form a conductive network. Due to the uneven distribution of the conductive agent, the distribution of the charge and discharge reaction also becomes uneven, thus causing localized degradation in the electrode.

[0106] (Determination of the area occupied and the distance between the center of gravity) The areas Sa, S1, S2 occupied by the active material, the first conductive agent, and the second conductive agent in the mapped image, and their ratios S1 / Sa and S2 / Sa, as well as the distances Ra, R1, R2 between the centers of gravity of the active material, the first conductive agent, and the second conductive agent, and their ratios R1 / Ra and R2 / Ra, can be obtained through numerical analysis of the data of the mapping of the constituent materials as described above. The distance R1-2 between the centers of gravity of the first conductive agent and the second conductive agent cannot be directly measured from the mapped data, but can be calculated by using the distances between the centers of gravity of all conductive agents that combine all first and second conductive agents, and the distances between the centers of gravity of the first conductive agents and the second conductive agents, R1 and R2. Furthermore, the measured distances Ra, R1, R2, and R1-2 represent the arithmetic mean of the distances between the centers of gravity within the mapped image.

[0107] At this point, the material mapping image used in the image analysis has an area of ​​at least 1 μm occupied by the active material, the first conductive agent, or the second conductive agent. 2 The selection is made using the above methods. The area occupied by at least one of the constituent materials—the active material, the first conductive agent, or the second conductive agent—is 1 μm. 2 The following conditions are unsuitable for measuring the area occupied and the distance between the center of gravity. A more preferred area for the positive electrode active material is 10 μm. 2 That's all.

[0108] The method for determining the centroid distance R1-2 between the first conductive agent and the second conductive agent is explained with reference to the attached diagram. Figures 5 to 8 This conceptually illustrates a method for determining the distance between the centroids of a first and second conductive agent in a mapped image. In these figures, for ease of understanding, only the first and second conductive agents are conceptually shown, omitting the active material. Numerical analysis of the mapped data, such as... Figure 5 As shown, the distances R211, R212, and R213 between the centroids of the first conductive agents 210 can be directly measured, and as... Figure 6 The distances R221, R222, and R223 between the centroids of the second conductive agents 220 are directly measured. However, for Figure 7 The distance between the centroids R231 to R239 between the first conductive agent 210 and the second conductive agent 220, as shown, cannot be directly measured using numerical analysis based on mapping data. However, if the first conductive agent 210 and the second conductive agent 220 are not distinguished and are considered to belong to the same group, they can be directly measured. Figure 8 The distance between the centers of gravity of the first conductive agent 210 relative to each other, the second conductive agent 220 relative to each other, and the distance between the centers of gravity of the first conductive agent 210 and the second conductive agent 220, as shown. Therefore, as Figure 8 As shown, the distance between the centers of gravity of all conductive agents was measured by subtracting... Figure 5 and Figure 6 The distances R211, R12, R13, R221, R222, and R223 between the centers of gravity of the first conductive agent 210 and the second conductive agent 220, respectively, can be determined according to... Figure 7 R239 is calculated by using the distance R231 between the centroids of the first conductive agent 210 and the second conductive agent 220 shown.

[0109] Here is an example of the measurement results of the distance between the centers of gravity. First, Figure 9 as well as Figure 10 The diagram shows the distribution of frequencies representing the distance between each centroid, representing the frequency distribution of the pair. Figure 3 as well as Figure 4 The graph shown is a chart of the distances between centroids obtained from the mapped image. Figure 9 It is aimed at Figure 4 The graph shown is a diagram of the distance between the centroids obtained from previous electrode examples. Figure 10 It is aimed at Figure 3The graph shows the inter-centrifugal distances calculated from the electrode examples of the illustrated embodiments. In any graph, the dashed line Da represents the frequency distribution (histogram) of the inter-centrifugal distances of the active materials, and the integral area under this curve is equal to the average inter-centrifugal distance Ra between the active materials in each mapped image. The integral area under the dashed line D1 corresponding to the first conductive agent is equal to the average inter-centrifugal distance R1 between the first conductive agents in the mapped image. The integral area under the solid line D2 corresponding to the second conductive agent is equal to the average inter-centrifugal distance R2 between the second conductive agents in the mapped image. The integral area under the single-dotted dashed line D12, which represents the frequency distribution of the inter-centrifugal distance between the first and second conductive agents, is equal to the average inter-centrifugal distance R12 between the first and second conductive agents in the mapped image.

[0110] will with Figure 10 The data on the distances between centroids corresponding to the distribution shown are summarized in Table 1 below.

[0111] Table 1

[0112] (Verification of measurement and analysis results) Through the aforementioned measurements and analyses, Raman spectra, average spectra, multivariate analysis results, material mapping images, and the area occupied and centroid distance of each constituent material can be obtained for 10 specimens used in the test. When the values ​​of 3 or more specimens out of the 10 specimens are within the aforementioned range and satisfy the aforementioned relationships, the corresponding electrode is effective in improving the lifespan performance of the battery. More preferably, 6 or more specimens are used, at which point a high effect can be obtained.

[0113] In addition, in the test results or analysis results, test samples that cannot distinguish between active substances, first conductive agents and second conductive agents, or do not contain any of the active substances, first conductive agents and second conductive agents, are judged to be unable to be effectively measured or analyzed, and are not included in the 10 samples.

[0114] <Determination of the average particle size of conductive agents> The average particle size of each conductive agent can be determined, for example, by observing the cross-section during Raman spectroscopy using a transmission electron microscope (TEM). Alternatively, the active material layer can be peeled off from the removed electrode, sampled by dispersing it in a solvent such as ethanol, and then observed using TEM. Furthermore, due to the observed shape, the interplanar spacing d of the graphene (002) surface... 002 The value of d varies depending on the conductive agent, thus allowing for differentiation of different types of conductive agents through electron microscopy. For example, the higher the graphitic content, the greater the interfacial spacing d. 002Becomes a value closer to 0.335 nm. By comparing the constituent material mapping image obtained by Raman spectroscopy and the TEM image, it is also possible to confirm correspondence with the first conductive agent and the second conductive agent within the TEM image, respectively.

[0115] For each of various conductive agents, as the particle diameters of 30 randomly selected particles, for example, the equivalent circle diameter is calculated by image analysis using the image analysis software "Particle Analysis" ver. 3.5 manufactured by Nippon Steel Technology Co., Ltd., and the average value of the obtained equivalent circle diameters is taken as the average particle diameter. Additionally, the average particle diameter is typically the diameter of a sphere when the particle is assumed to have the same volume or the same cross-sectional area. However, in image analysis, care should be taken not to calculate the equivalent circle diameter of aggregates such as aggregates or agglomerates.

[0116] The electrode of the first embodiment includes an active material-containing layer containing at least an active material, a first conductive agent, and a second conductive agent. The first conductive agent is the integral intensity I of the D band obtained by Raman spectroscopy D and the integral intensity I of the G band G The ratio I D / I G For materials within the range of 0.5 < I D / I G < 2, in the second conductive agent, for the ratio I D / I G For materials within the range of 0 < I D / I G < 0.5, in the constituent material mapping image obtained by Raman spectroscopy for the active material-containing layer, the occupied area Sa of the active material and the distance Ra from the center of gravity, the occupied area S1 of the first conductive agent and the distance R1 from the center of gravity, the occupied area S2 of the second conductive agent and the distance R2 from the center of gravity, and the distance R1-2 between the centers of gravity of the first conductive agent and the second conductive agent satisfy the relationships of 0.1 < S1 / Sa < 1.0, 0.8 < S2 / Sa < 10, 1.0 < R1 / Ra < 1.5, 0.5 < R2 / Ra < 1.0, and R1 > R2 > R1-2. This electrode can achieve a battery with excellent life performance having a small resistance, an excellent capacity retention rate, and suppressed resistance increase.

[0117] (Second Embodiment) According to the second embodiment, a battery is provided. The battery includes the electrode of the first embodiment and an electrolyte. As described above, the electrode of the first embodiment can achieve a battery with excellent life performance. Therefore, the battery of the second embodiment can have excellent life performance.

[0118] This battery may include a positive electrode and a negative electrode. The battery may include the electrode of the first embodiment as the positive electrode.

[0119] The battery can also be further equipped with a separator disposed between the positive and negative electrodes. The positive electrode, negative electrode, and separator can constitute an electrode assembly. The electrolyte can be retained in the electrode assembly.

[0120] In addition, the battery can be further equipped with an outer packaging component that houses the electrode assembly and electrolyte.

[0121] Furthermore, the battery may further include a positive terminal electrically connected to the positive electrode and a negative terminal electrically connected to the negative electrode. Each electrode terminal may be connected, for example, to a current collector tab of the target electrode. At least a portion of the positive terminal and at least a portion of the negative terminal may extend outward from the outer packaging component.

[0122] The battery can be, for example, a lithium-ion secondary battery. Alternatively, the battery may include a non-aqueous electrolyte battery containing a non-aqueous electrolyte as the electrolyte.

[0123] The following provides a detailed description of the positive electrode, negative electrode, electrolyte, separator, outer packaging components, positive terminal, and negative terminal.

[0124] (1) Positive electrode The positive electrode includes a positive current collector and a layer containing positive active material (positive electrode binder layer) supported on one side or both sides of the positive current collector. The layer containing positive active material includes positive active material, conductive agent and binder.

[0125] The positive electrode can be the electrode of the first embodiment. Regarding the form of the positive electrode, the positive current collector, the positive active material, and the layer containing the positive active material are respectively equivalent to the current collector, the active material, and the layer containing the active material of the electrode of the first embodiment. The electrode of the first embodiment has been described in detail above, therefore the description of the positive electrode here is omitted.

[0126] (2) Negative electrode The negative electrode comprises a negative electrode current collector and a layer containing negative electrode active material (negative electrode binder layer) supported on one side or both sides of the negative electrode current collector. The layer containing negative electrode active material contains negative electrode active material. In addition to the negative electrode active material, the layer may also contain a conductive agent and a binder. A conductive agent may be incorporated to improve current collection performance and suppress the contact resistance between the negative electrode active material and the negative electrode current collector. A binder may be incorporated to bond the dispersed negative electrode active material to each other and to bond the negative electrode active material to the negative electrode current collector.

[0127] Material The following describes materials that can be used in the negative electrode active material layer and the negative electrode current collector.

[0128] <Contains a layer of negative electrode active material> The preferred proportions of the negative electrode active material, conductive agent, and binder in the negative electrode active material layer are within the following ranges: negative electrode active material 70% by mass or more and 96% by mass or less, conductive agent 2% by mass or more and 28% by mass or less, and binder 2% by mass or more and 28% by mass or less. By setting the amount of conductive agent to 2% by mass or more, the current collection performance of the negative electrode active material layer can be improved, and excellent high-current performance and low-temperature performance are expected. In addition, by setting the amount of binder to 2% by mass or more, the adhesion between the negative electrode active material layer and the current collector becomes sufficient, and excellent cycle performance is expected.

[0129] On the other hand, from the viewpoint of high capacity, the conductive agent and the binder are preferably 28% by mass or less.

[0130] <Negative Electrode Active Material> The negative electrode preferably contains components capable of operating at 0.4V (vs. Li / Li). + A negative electrode active material that allows lithium ion insertion and extraction at potentials above a certain threshold. In the second embodiment of the battery, the deposition of lithium caused by charging and discharging can be suppressed. Therefore, such a battery exhibits superior fast charge / discharge performance.

[0131] As capable of operating at 0.4V (vs. Li / Li + Anode active materials that allow lithium-ion insertion and extraction at potentials above a certain level include, for example, Li. 4+x Ti5O 12 Lithium titanate with a spinel-type crystal structure (x varies within the range of -1 ≤ x ≤ 3 through charge-discharge reactions) and Lithium titanate with an orthorhombic manganese oxide-type crystal structure are represented by (x varies within the range of -1 ≤ x ≤ 3) 2+x Ti3O7 (where x varies within the range of -1 ≤ x ≤ 3 through charge-discharge reactions), and metal composite oxides containing Ti and at least one element selected from the group consisting of P, V, Sn, Cu, Ni, and Fe, are examples. Examples of metal composite oxides containing Ti and at least one element selected from the group consisting of P, V, Sn, Cu, Ni, and Fe include TiO2-P2O5, TiO2-V2O5, TiO2-P2O5-SnO2, and TiO2-P2O5-MeO (where Me is at least one element selected from the group consisting of Cu, Ni, and Fe). These metal composite oxides transform into lithium-titanium composite oxides through lithium intercalation during charging. Among lithium-titanium composite oxides, spinel-type lithium titanate exhibits excellent cycle performance and is preferred.

[0132] The negative electrode can contain other active materials, such as carbonaceous materials and metal compounds.

[0133] Examples of carbonaceous materials include natural graphite, synthetic graphite, coke, vapor-grown carbon fibers, mesophase pitch-based carbon fibers, spherical carbon, and resin-fired carbon. More preferred carbonaceous materials include vapor-grown carbon fibers, mesophase pitch-based carbon fibers, and spherical carbon. Preferably, the carbonaceous material has a surface spacing d002 of 0.34 nm or less for the (002) planes as measured by X-ray diffraction.

[0134] As metal compounds, metal sulfides, metal nitrides, etc., can be used. As metal sulfides, examples include titanium sulfide such as TiS2, molybdenum sulfide such as MoS2, and FeS, FeS2, and Li. x Iron sulfides such as FeS2 (0≤x≤2) can be used. As metal nitrides, lithium cobalt nitrides (e.g., Li) can be used. x Co y N; 0 <x<4、0<y<0.5)。

[0135] In addition to the lithium-titanium composite oxides mentioned above, other lithium-titanium composite oxides, such as monoclinic niobium titanium oxides and orthorhombic titanium-containing composite oxides, may also be included as negative electrode active materials.

[0136] As an example of the monoclinic niobium titanium oxide, Li can be cited as an example. a Ti 1-x M1 x Nb 2-y M2 y O 7+δ The compound is represented by M1, which is selected from at least one of the group consisting of Zr, Si, and Sn. M2 is selected from at least one of the group consisting of V, Ta, and Bi. The subscripts in the composition formula are 0 ≤ a ≤ 5, 0 ≤ x < 1, 0 ≤ y < 2, and -0.3 ≤ δ ≤ 0.3. As a specific example of a monoclinic niobium titanium oxide, Li can be cited. a Nb2TiO7 (0≤a≤5).

[0137] Other examples of monoclinic niobium titanium oxides include those made from Li a Ti 1-x M3 x+y Nb 2-y O 7-δ The compound is indicated by M3. Here, M3 is at least one selected from the group consisting of Mg, Fe, Ni, Co, W, Ta, and Mo. The subscripts in the composition formula are 0 ≤ a ≤ 5, 0 ≤ x < 1, 0 ≤ y < 2, and -0.3 ≤ δ ≤ 0.3.

[0138] As an example of orthorhombic titanium-containing composite oxides, one could cite Li... 2+a M4 2-x Ti6-y M5 z O 14+σ The compound is indicated by M4. Here, M4 is at least one selected from the group consisting of Sr, Ba, Ca, Mg, Na, Cs, Rb, and K. M5 is at least one selected from the group consisting of Zr, Sn, V, Nb, Ta, Mo, W, Y, Fe, Co, Cr, Mn, Ni, and Al. The subscripts in the compositional formula are 0 ≤ a ≤ 6, 0 ≤ x < 2, 0 ≤ y < 6, 0 ≤ z < 6, and -0.5 ≤ σ ≤ 0.5. As a specific example of an orthorhombic titanium-containing composite oxide, Li can be cited. 2+a Na2Ti6O 14 (0≤a≤6).

[0139] One of the active substances can be included in the negative electrode as a negative electrode active substance, or two or more of the active substances can be included in the negative electrode as negative electrode active substances.

[0140] <Conductive agent> Examples of conductive agents include carbonaceous materials such as acetylene black, carbon black, graphite, carbon nanofibers, and carbon nanotubes. These carbonaceous materials can be used alone or in combination.

[0141] <Adhesive> Examples of adhesives include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluoropolymers, and styrene-butadiene rubber (SBR). Additionally, carboxymethyl cellulose (CMC), polyimide, and polyamide can also be used as adhesives. These adhesives can be used alone or in combination.

[0142] <Negative Electrode Current Collector> As the negative electrode current collector, an electrochemically stable material can be used at the potential where the lithium-ion insertion-deintercalation reaction of the negative electrode active material occurs. The negative electrode current collector is preferably a metal foil composed of at least one selected from copper, nickel, stainless steel, and aluminum, or an aluminum alloy foil containing at least one selected from the group consisting of Mg, Ti, Zn, Mn, Fe, Cu, and Si.

[0143] The shape of the negative electrode current collector can vary depending on the intended use of the battery.

[0144] The negative electrode current collector may consist of a portion of its surface that does not support a layer containing the negative electrode active material. This portion can function as a negative electrode current collector tab. Alternatively, the negative electrode may also include current collector tabs that are separate from the negative electrode current collector.

[0145] <Production Method> The negative electrode can be made, for example, by the following method.

[0146] First, a slurry for making a negative electrode is prepared by suspending the negative electrode active material, binder, and optionally conductive agent in a suitable solvent. A common solvent, such as N-methylpyrrolidone, is used as the solvent. The resulting slurry is coated onto a negative electrode current collector. By drying the coated slurry and pressing it, a negative electrode containing a negative electrode current collector and a layer of negative electrode active material formed on the current collector can be obtained. Alternatively, the negative electrode active material, binder, and optionally conductive agent can be formed into granules and used as the layer of negative electrode active material.

[0147] (3) Diaphragm As a diaphragm, an electrically insulating material is used. There are no particular limitations as long as it is insulating, but the diaphragm can be, for example, a porous membrane or nonwoven fabric made of polymers such as polyolefins, cellulose, polyethylene terephthalate, and vinylon. The diaphragm can be made of one material, or two or more materials can be used in combination.

[0148] (4) Electrolytes Examples of electrolytes include liquid non-aqueous electrolytes prepared by dissolving electrolyte salts (solutes) in non-aqueous solvents, and gel-like non-aqueous electrolytes formed by combining liquid non-aqueous electrolytes with polymer materials.

[0149] Examples of lithium salts that can be cited as electrolyte salts include lithium perchlorate (LiClO4), lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), lithium hexalithium antimonyate (LiSbF6), lithium difluorophosphate (LiPO2F2), lithium trifluoromethanesulfonate (LiCF3SO3; commonly known as LiTFS), lithium bis(trifluoromethanesulfonamide) {Li(CF3SO2)2N; commonly known as LiTFSI}, lithium bis(pentafluoroethanesulfonamide) {Li(C2F5SO2)2N; commonly known as LiBETI}, lithium bis(oxalateborate) {LiB(C2O4)2; commonly known as LiBOB}, and lithium difluoro(trifluoro-2-oxide-2-trifluoro-methylpropionate(2-)-O,O)borate {LiBF2OCOOC(CF3)2; commonly known as LiBF2(HHIB)}. These electrolyte salts can be used alone or in combination of two or more. Among them, LiPF6 and LiBF4 are particularly preferred.

[0150] The electrolyte salt is preferably dissolved in a non-aqueous solvent at a concentration between 1 mol / L and 3 mol / L. Electrolyte salt concentrations within this range can suppress the increase in viscosity caused by rising electrolyte salt concentrations and further improve performance under high load currents.

[0151] Examples of non-aqueous solvents include cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC), and vinylene carbonate (VC); chain carbonates such as dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and dipropyl carbonate (DPC); cyclic ethers such as tetrahydrofuran (THF) and 2-methyl tetrahydrofuran (2-MeTHF); and 1,2-dimethoxyethane. Chain ethers such as ethane (DME); cyclic esters such as γ-butyrolactone (BL); chain esters such as methyl acetate, ethyl acetate, methyl propionate, and ethyl propionate; 1,3-dioxolane; acetonitrile (AN); sulfolane (SL); and other organic solvents. These organic solvents can be used alone or in mixtures of two or more. Non-aqueous solvents containing cyclic carbonates and / or chain carbonates are preferred.

[0152] Examples of polymeric materials used in gel-like non-aqueous electrolytes include polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), and polyethylene oxide (PEO).

[0153] (5) Outer packaging components The outer packaging component can be formed from a laminated film or made of a metal container. Alternatively, resin containers made of polyolefin resin, polyvinyl chloride resin, polystyrene resin, acrylic resin, phenolic resin, polyphenylene resin, fluorinated resin, etc., can also be used for the outer packaging component. When using a metal container, the lid can be an integral part of the container or a separate component. The wall thickness of the metal container is preferably 3 mm or less, more preferably 0.5 mm or less.

[0154] Examples of shapes for outer packaging components include flat (thin), square, cylindrical, coin-shaped, button-shaped, sheet-shaped, and stacked types. These outer packaging components can be used for small batteries in portable electronic devices, as well as for large batteries in two-wheeled or four-wheeled automobiles.

[0155] The wall thickness of the laminated film outer packaging component is preferably 0.5 mm or less. Examples of laminated films include multilayer films comprising a resin layer and a metal layer disposed between the resin layers. For weight reduction, the metal layer is preferably aluminum foil or aluminum alloy foil. The resin layer can be, for example, a film made of polymer materials such as polypropylene (PP), polyethylene (PE), nylon, or polyethylene terephthalate (PET). The laminated film can be sealed by heat welding to form the shape of the outer packaging component.

[0156] The metal container is made of aluminum or an aluminum alloy. Preferably, the aluminum alloy contains elements such as magnesium, zinc, and silicon. In the case of aluminum or aluminum alloy containing transition metals such as iron, copper, nickel, and chromium, the content of these metals is preferably less than 100 ppm.

[0157] Reference Figure 11 and Figure 12 Here is an example illustrating the battery. Figure 11 The flat battery shown comprises a flat, wound electrode assembly 1, an outer packaging component 2, a positive terminal 7, a negative terminal 6, and an electrolyte (not shown). The outer packaging component 2 is a pouch-shaped outer packaging component made of laminated film. The wound electrode assembly 1 is housed within the outer packaging component 2. Figure 12 As shown, the wound electrode assembly 1 includes a positive electrode 3, a negative electrode 4, and a separator 5. It is formed by winding the stacked material from the outside in the order of negative electrode 4, separator 5, positive electrode 3, and separator 5 into a vortex shape and then pressing it into shape.

[0158] The positive electrode 3 includes a positive current collector 3a and a layer 3b containing positive active material. The layer 3b contains positive active material. The layer 3b is formed on both sides of the positive current collector 3a. The negative electrode 4 includes a negative current collector 4a and a layer 4b containing negative active material. The layer 4b contains negative active material. In the outermost portion of the negative electrode 4, the layer 4b is formed only on one side of the inner surface of the negative current collector 4a. In other portions of the negative electrode 4, the layer 4b is formed on both sides of the negative current collector 4a.

[0159] like Figure 11As shown, near the outer periphery of the wound electrode assembly 1, the positive terminal 7 is connected to the positive electrode 3. Additionally, the negative terminal 6 is connected to the outermost negative electrode 4. Both the positive terminal 7 and the negative terminal 6 extend outwards through the opening in the outer packaging component 2.

[0160] The battery is not limited to the aforementioned. Figure 11 and Figure 12 The structure shown, for example, can be set as Figure 13 The structure shown.

[0161] exist Figure 13 In the square battery shown, the wound electrode assembly 11 is housed within a bottomed rectangular cylindrical metal container 12, which serves as the outer packaging component. A rectangular cap 13 is welded to the opening of the container 12. The flat wound electrode assembly 11 may, for example, have the same shape as the referenced... Figure 11 and Figure 12 The structure is the same as that of the wound electrode assembly 1, which has been described.

[0162] One end of the negative current collector tab 14 is electrically connected to the negative current collector, and the other end is electrically connected to the negative terminal 15. The negative terminal 15 is fixed to the rectangular cover 13 by an airtight seal with glass material 16 sandwiched between it. One end of the positive current collector tab 17 is electrically connected to the positive current collector, and the other end is electrically connected to the positive terminal 18 fixed to the rectangular cover 13.

[0163] The negative current collector tab 14 is made of materials such as aluminum or aluminum alloys containing elements such as Mg, Ti, Zn, Mn, Fe, Cu, and Si. To reduce the contact resistance with the negative current collector, the negative current collector tab 14 is preferably made of the same material as the negative current collector.

[0164] The positive current collector tab 17 is made of materials such as aluminum or aluminum alloys containing elements such as Mg, Ti, Zn, Mn, Fe, Cu, and Si. To reduce the contact resistance with the positive current collector, the positive current collector tab 17 is preferably made of the same material as the positive current collector.

[0165] It should be noted that the battery illustrated uses a wound electrode assembly, which is formed by winding the separator together with the positive and negative electrodes. However, a stacked electrode assembly, in which the positive and negative electrodes are alternately layered with the separator in between, can also be used. Alternatively, the electrode assembly can have other structures.

[0166] The battery of the second embodiment includes the electrodes of the first embodiment. Therefore, the battery has excellent capacity retention, suppressed resistance rise, and excellent lifespan performance.

[0167] (Third Implementation) According to a third embodiment, a battery pack is provided. This battery pack includes the battery of the second embodiment.

[0168] The battery pack of the third embodiment may include one or more batteries (single cells) as described in the second embodiment previously. Multiple batteries in such a battery pack may also be connected in series or parallel to form a battery array. Such a battery pack may include multiple battery arrays.

[0169] Next, an example of a battery pack according to the third embodiment will be described with reference to the accompanying drawings.

[0170] Figure 14 This is an exploded perspective view of a battery pack, which is an example of a second embodiment. Figure 15 It is shown Figure 14 A block diagram of the battery pack circuit.

[0171] Figure 14 and Figure 15 The battery pack 20 shown includes multiple individual cells 21. Each individual cell 21 can be a reference cell. Figure 13 A flat battery is an example of one of the second embodiments described.

[0172] Multiple individual cells 21 are stacked such that their outwardly extending negative terminals 51 and positive terminals 61 are aligned in the same direction and secured with adhesive tape 22, thereby forming a battery pack 23. Figure 15 As shown, these individual cells 21 are electrically connected in series with each other.

[0173] The printed wiring substrate 24 is arranged side-by-side with the negative terminal 51 and positive terminal 61 of the single cell 21. For example... Figure 15 As shown, a thermistor 25, a protection circuit 26, and a terminal 27 for powering external devices are mounted on the printed circuit board 24. Additionally, an insulating plate (not shown) is mounted on the surface of the printed circuit board 24 opposite to the battery pack 23 to prevent unnecessary connections with the wiring of the battery pack 23.

[0174] The positive terminal lead 28 is connected to the bottom positive terminal 61 of the battery pack 23, and its front end is inserted into the positive terminal connector 29 of the printed circuit board 24 for electrical connection. The negative terminal lead 30 is connected to the top negative terminal 51 of the battery pack 23, and its front end is inserted into the negative terminal connector 31 of the printed circuit board 24 for electrical connection. These connectors 29 and 31 are connected to the protection circuit 26 through wirings 32 and 33 formed on the printed circuit board 24.

[0175] Thermistor 25 detects the temperature of the individual cell 21, and this detection signal is sent to protection circuit 26. Protection circuit 26 can, under specified conditions, block the positive-side wiring 34a and negative-side wiring 34b between protection circuit 26 and terminal 27 for powering external devices. An example of the specified conditions is, for example, when the detected temperature of thermistor 25 reaches or exceeds a specified temperature. Other examples of the specified conditions include detecting overcharging, over-discharging, or overcurrent of the individual cell 21. This overcharging detection is performed on each individual cell 21 or the entire battery pack 23. When detecting each individual cell 21, the battery voltage, positive electrode potential, or negative electrode potential can be detected. In the latter case, a lithium electrode used as a reference electrode is inserted into each individual cell 21. Figure 14 as well as Figure 15 In the case of battery pack 20, each individual battery 21 is connected to wiring 35 for voltage detection. Detection signals are sent to protection circuit 26 through these wirings 35.

[0176] Protective sheets 36 made of rubber or resin are provided on the three sides of the battery pack 23, excluding the protruding sides of the positive terminal 61 and the negative terminal 51.

[0177] The battery pack 23, along with each protective sheet 36 and the printed circuit board 24, is housed within a storage container 37. Specifically, protective sheets 36 are disposed on the two inner sides along the long side and the inner side along the short side of the storage container 37, and the printed circuit board 24 is disposed on the inner side opposite to the short side. The battery pack 23 is located within the space enclosed by the protective sheets 36 and the printed circuit board 24. A cover 38 is attached to the upper surface of the storage container 37.

[0178] Alternatively, heat shrinkable tape can be used instead of adhesive tape 22 to secure the battery pack 23. In this case, protective tabs are placed on both sides of the battery pack, and the heat shrinkable tape is wrapped around it to heat shrink and secure the battery pack.

[0179] exist Figure 14 and Figure 15 The diagram shows a method of connecting individual cells 21 in series, but they can also be connected in parallel to increase battery capacity. Furthermore, assembled battery packs can also be connected in series and / or in parallel.

[0180] Furthermore, the form of such a battery pack can be appropriately modified depending on the application. The preferred application is one where good cycle performance is desired when drawing high current. Specific applications include powering digital cameras, two- to four-wheeled hybrid electric vehicles, two- to four-wheeled electric vehicles, and electric bicycles. This type of battery pack is particularly suitable for automotive applications.

[0181] The battery pack of the third embodiment includes the battery of the second embodiment. Therefore, such a battery pack has excellent capacity retention, suppressed resistance rise, and excellent lifespan performance.

[0182] Example The following examples illustrate the invention in more detail, but the invention is not limited to the embodiments described below, as long as they do not exceed the spirit of the invention.

[0183] (Example 1) <The Making of the Positive Electrode> A lithium nickel cobalt manganese composite oxide (LiNi) with an average primary particle size of 3.7 μm was prepared as the positive electrode active material. 0.8 Co 0.1 Mn 0.1 O2, acetylene black as the first conductive agent, graphite as the second conductive agent, and polyvinylidene fluoride (PVdF) as the binder. The prepared materials, with the first and second conductive agents respectively in powder form, were stirred using a mixer capable of both rotation and revolution, then mixed and stirred again. Other materials were added to N-methylpyrrolidone (NMP), followed by the stirred conductive agent. By mixing the NMP solution containing the prepared materials, a slurry for positive electrode fabrication with the materials suspended in NMP was obtained. The slurry for positive electrode fabrication was then dispersed. Zirconia beads of 2 mm in diameter were added to the slurry. The material is evenly dispersed by using a mixer that can rotate on its own axis and revolve around the sun.

[0184] The mass ratios of the positive electrode active material, the first conductive agent, the second conductive agent, and the binder added to NMP were set to 100 parts by mass, 5 parts by mass, 5 parts by mass, and 5 parts by mass, respectively.

[0185] The obtained slurry is coated on both sides of a 12μm thick aluminum foil (current collector) with a strip shape and dried. After a pressing process, a positive electrode with active material layers on the current collector and both sides is fabricated.

[0186] <Making the Negative Electrode> Prepare spinel-type lithium titanate Li4Ti5O 12 Graphite was used as the negative electrode active material, graphite as the conductive agent, and PVdF as the binder. The prepared material was suspended in N-methylpyrrolidone to obtain a slurry for negative electrode fabrication. The mass ratios of the negative electrode active material, conductive agent, and binder added to N-methylpyrrolidone were set to 95% by mass, 2.5% by mass, and 2.5% by mass, respectively. The prepared negative electrode fabrication slurry was coated on both sides of a 12 μm thick aluminum foil (current collector) with a strip shape and dried. The negative electrode was then fabricated through a pressing process.

[0187] <Electrode Assembly Fabrication> The positive and negative electrodes, fabricated as described above, are overlapped with a separator sandwiched between them. A cellulose separator with a thickness of 14 μm and a width of 85 mm is used as the separator. The resulting laminate is wound around an axis extending along the short sides of the positive and negative current collectors. The wound positive, negative, and separator are hot-pressed at 80°C and fixed with insulating tape. This yields a wound electrode assembly comprising a positive electrode, a negative electrode, and a separator located between the positive and negative electrodes.

[0188] <Preparation of Non-Aqueous Electrolytes> A non-aqueous solvent was prepared by mixing propylene carbonate (PC) and diethyl carbonate (DEC) in a 1:1 volume ratio. A non-aqueous electrolyte was prepared by dissolving lithium hexafluorophosphate (LiPF6) in the obtained non-aqueous solvent at a concentration of 1.0 mol / L.

[0189] <Battery Assembly> The electrode assembly, shaped into a flat form as described above, is inserted into a metal can made of an aluminum plate with a thickness of 0.5 mm. The opening of the metal can is sealed with a sealing plate, and the electrode assembly is housed inside the metal can, which serves as the outer packaging component. The non-aqueous electrolyte prepared as described above is injected into the container through an electrolyte injection port provided on the sealing plate. Next, a flat non-aqueous electrolyte battery is fabricated by welding a sealing cap around the periphery of the electrolyte injection port.

[0190] (Examples 2-3, Comparative Examples 1-6) In Examples 2-3 and Comparative Examples 1-6, based on Example 1, the average particle size of the positive electrode active material, the first conductive agent, and the second conductive agent were changed as shown in Table 2. The mass fraction of each conductive agent, the dispersion conditions of the slurry for positive electrode fabrication, and the pressing load of the active material layer were also adjusted. The design of the positive electrode active material layer was changed to the design shown in Tables 2 and 3. Otherwise, the battery was fabricated using the same method as in Example 1. As shown in Tables 2 and 3, the specific surface area and electrode density obtained by the nitrogen adsorption-desorption method (BET method), the occupied areas S1 and S2 of the first and second conductive agents in the material mapping image obtained by the Raman spectroscopy, the occupied area Sa of the positive electrode active material, the distance between the centroids R1 and R2 of the first and second conductive agents, the distance between the centroids R1-2 between each conductive agent, and the distance between the centroids Ra of the positive electrode active material were adjusted.

[0191] Table 2 below summarizes the designs of the positive electrode active material layer in each embodiment and comparative example. As designs of the active material layer, the average primary particle size of the positive electrode active material particles and the specific surface area determined by the nitrogen adsorption-desorption method (BET method) are shown, as well as the average particle size of the first conductive agent and its mass ratio relative to the positive electrode active material, the average particle size of the second conductive agent and its mass ratio relative to the positive electrode active material, and the density determined by the method.

[0192] Table 3 below summarizes the analysis results of the Raman spectroscopy-obtained material mapping images of the constituent materials containing the positive electrode active material layer in each embodiment and comparative example. As a result of the image analysis, the occupied areas S1 and S2 of the first and second conductive agents, the occupied area Sa of the positive electrode active material, the ratio of occupied areas S1 / Sa and S2 / Sa, the centroid distances R1 and R2 of the first and second conductive agents, the centroid distances R1-2 between each conductive agent, the centroid distance Ra of the positive electrode active material, and the ratios of the centroid distances R1 / Ra and R2 / Ra are shown.

[0193] Table 2

[0194] Table 3

[0195] <Determination of volume resistivity of layer containing active material> The volume resistivity (unit: Ω·cm) of the active material layer of the positive electrode is measured as follows. The electrode is removed from the battery using the method described in the <Electrode Measurement Methods> section, and samples are taken from the removed electrode.

[0196] Sampling was performed as follows: A smooth section of the surface containing the active material layer was selected, and a sample was cut out at a size of 10cm × 10cm. The cut electrode sample was placed statically in the electrode resistance measuring device without bending, and the volume resistivity of the active material layer was measured by pressing the electrode probe. The electrode resistance measuring device used was a HIOKI RM2610 electrode resistance measuring system. The measurement was performed in potentiometric measurement + calculation mode, with the resistance range set to Auto and the number of repetitions set to 30. In this mode, the potential obtained by simulation using a virtual model was repeatedly calculated while changing the resistance value used in the virtual model until the difference between the potential distribution obtained when a constant current flows through the surface of the electrode being measured—that is, the measured potential—became small. The volume resistivity was calculated from the resistance value where the difference between the model and the measured value was sufficiently small.

[0197] <Cyclic Test> For each battery manufactured, a cycle test was performed as described below.

[0198] First, charge the battery at 25°C until it reaches 50% State of Charge (SOC). Then, leave it in standby mode for 1 hour and record the Open Circuit Voltage (OCV). Next, discharge the battery at a 10C current and measure the voltage drop. Subtract the OCV from the voltage drop at 10C discharge, and divide the result by the value obtained at 10C discharge current to obtain the battery's discharge resistance (unit: mΩ).

[0199] Next, the battery was charged at 3C rate to 100% State of Charge (SOC) at 65°C and discharged at 3C rate to 0% SOC for 700 cycles. The discharge capacity was measured during the discharge of the first and 700th cycles.

[0200] After 700 discharge cycles, the battery's discharge resistance was measured again.

[0201] Based on the discharge capacity of the 1st and 700th cycles, the capacity retention rate is calculated using the following formula: Capacity retention rate (unit: %) = [Discharge capacity of the 700th cycle / Discharge capacity of the 1st cycle] × 100%. Additionally, based on the discharge resistance values ​​before and after 700 charge-discharge cycles, the resistance rise rate is calculated using the following formula: Resistance rise rate (unit: %) = [Discharge resistance value after the cycle / Discharge resistance value before the cycle] × 100%. The calculated results are shown in Table 4 below.

[0202] Table 4

[0203] As can be seen from Table 4, the batteries fabricated in Examples 1 to 3 exhibited low electrode resistivity and achieved excellent capacity retention. On the other hand, it was found that for Comparative Examples 1 to 6, the volume resistivity of the positive electrode, the capacity retention of the battery, and the suppression of resistance increase were all inferior to those of Examples 1 to 3. This is because, in Examples 1 to 3, in the constituent material mapping image obtained by Raman spectroscopy, the ratios of the occupied areas S1 and S2 of the first conductive agent and the second conductive agent to the occupied area Sa of the active material satisfied 0.1 < S1 / Sa < 1.0 and 0.8 < S2 / Sa < 10, and in the constituent material mapping image, the ratios of the distances between the centers of gravity R1 and R2 of the first conductive agent and the second conductive agent to the distance between the centers of gravity Ra of the active material satisfied 1.0 < R1 / Ra < 1.5 and 0.5 < R2 / Ra < 1.0. Furthermore, a positive electrode active material layer having a relationship of R1 > R2 > R1-2 between the distances R1 and R2 between the centers of gravity of the first conductive agent and the second conductive agent and the distance R1-2 between the centers of gravity between the first conductive agent and the second conductive agent was obtained, which could appropriately control the ratio and positional relationship between each conductive agent and the active material to make the conductive network between particles in the positive electrode active material layer and the entire positive electrode active material layer good.

[0204] On the other hand, the batteries of Comparative Examples 1 to 6 did not satisfy at least one of the above conditions in the positive electrode active material layer, and as a result, the volume resistivity of the positive electrode active material layer, the capacity retention of the battery, and the suppression of resistance increase were all inferior to those of Examples 1 to 3. That is, a conductive path for the entire positive electrode active material layer could not be formed, so that the electrode resistivity could not be suppressed to a low level, and thus the local deterioration of the active material could not be suppressed, and as a result, excellent results in both capacity retention and suppression of resistance increase could not be obtained.

[0205] Specifically, in Comparative Example 1, the occupied areas of each conductive agent were within the above range, but regarding the distance between the centers of gravity, R1 / Ra was small and R2 / Ra was large, both outside the above range. In addition, the distance of R2 was greater than R1. In Comparative Example 1, the volume resistivity of the positive electrode was high, the capacity retention of the battery was low, and the resistance increase rate was high compared with Examples 1 to 3. The ratio of the conductive agent in the active material layer was appropriate, but the positional relationship was inappropriate, and the formation of the conductive network in the positive electrode and the conductivity between particles could not be achieved. As a result, it was found that even when observed with a positive electrode monomer, the resistance was large, and furthermore, due to the uneven distribution of the reaction, the resistance increase deteriorated with the charge-discharge cycle. Specifically, from the small R1 / Ra, it can be seen that the first conductive agent with high conductivity exists excessively around the active material, the volume resistance of the electrode becomes small, current unevenness is likely to occur, and the local deterioration of the active material is aggravated. In addition, according to the large R2 / Ra, the second conductive agent is less near the active material and the first conductive agent, and a conductive path for the entire active material layer cannot be formed, and the local deterioration of the active material cannot be suppressed.

[0206] Although the area occupied in Comparative Example 2 is also within the range, R1 / Ra is smaller in terms of the distance between the centers of gravity, and the distance of R2 is greater than that of R1. Regarding Comparative Example 2, although the volume resistivity of the positive electrode and the increase in battery resistance are relatively low, the capacity retention rate of the battery is lower than that of Comparative Example 1. That is, although the ratio of the conductive agent in the active material layer is appropriate, the positional relationship of the first conductive agent is inappropriate. From the R2 / Ra within the aforementioned range, it can be seen that the conductive pathway formed by the second conductive agent is well formed. However, from the small R1 / Ra, it can be seen that the highly conductive first conductive agent is excessively present around the active material. As a result, the utilization rate of the active material near the first conductive agent is locally high, accompanied by localized deterioration of the positive electrode during charge-discharge cycles and a worsening of the capacity retention rate due to the deviation in utilization rate.

[0207] In Comparative Example 3, regarding the occupied area, S1 / Sa becomes larger and falls outside the range. Regarding the distance between the centers of gravity, similar to Comparative Example 1, R1 / Ra is small, R2 / Ra is large, and the distance of R2 is greater than that of R1. In Comparative Example 3, compared to Comparative Example 1, the volume resistivity of the positive electrode is higher, and compared to Comparative Example 1, the capacity retention rate of the battery is lower, and the resistance rise suppression is higher. In Comparative Example 3, as shown by the large S1 / Sa, the amount of the first conductive agent is excessive, thus exacerbating the formation of agglomerates; as shown by the small R1 / Ra, these agglomerates are located near the active material. Furthermore, as shown by the large R2 / Ra, a conductive path formed by the second conductive agent cannot be formed. As a result, the conductivity cannot be improved as a whole layer containing the active material; instead, the current unevenness caused by the excessive concentration of the first conductive agent near the active material becomes significant, and the localized deterioration of the active material is exacerbated.

[0208] In Comparative Example 4, regarding the occupied area, S1 / Sa becomes smaller and falls outside the range. Regarding the distance between centroids, both R1 / Ra and R2 / Ra become larger and fall outside the range. In Comparative Example 4, the volume resistivity of the positive electrode is high, the capacity retention rate of the battery is low, and the rate of increase in resistance is significantly high. The small S1 / Sa indicates that the proportion of the highly conductive first conductive agent is small, and the large R1 / Ra and R2 / Ra indicate that each conductive agent is scarce near the active material. Therefore, it can be seen that not only is it impossible to form a conductive path throughout the active material layer, but the conductivity is also not locally improved. As a result, even in areas where current is uneven and a large current flows, the resistance is not small, thus exacerbating the local degradation of the active material.

[0209] In Comparative Example 5, regarding the occupied area, S2 / Sa becomes larger and is outside the range. Regarding the distance between the centers of gravity, both R1 / Ra and R2 / Ra become larger, and the distance of R1-2 is greater than R2. In Comparative Example 5, the volume resistivity of the positive electrode is high, the capacity retention rate of the battery is low, and the resistance increase rate is quite high. From the relatively large S2 / Sa, it can be seen that the proportion of the second conductive agent is excessive. From the relatively large R1 / Ra and R2 / Ra, it can be seen that each conductive agent is less near the active material. Therefore, it can be known that the local deterioration of the active material in the active material-containing layer is aggravated thereby.

[0210] In Comparative Example 6, the occupied area is within the range, but R1 / Ra becomes larger and is outside the range. In Comparative Example 6, the volume resistivity of the positive electrode is significantly high, the capacity retention rate of the battery is low, and the resistance increase rate is higher than that in Comparative Example 4. From the relatively large R1 / Ra, it can be seen that the first conductive agent is less near the active material and the first conductive agent. Therefore, it can be known that the current required for the charge-discharge reaction cannot be transmitted to the active material, the resistance increases, and the deterioration of the active material is aggravated.

[0211] According to one or more of the above-described embodiments and examples, an electrode is provided. The electrode includes an active material-containing layer, and the active material-containing layer contains an active material, the integrated intensity I of the D band in the Raman spectrum D and the integrated intensity I of the G band G The ratio I D / I G is 0.5 < I D / I G < 2 for the first conductive agent, and 0 < I D / I G < 0.5 for the second conductive agent. In the constituent material mapping image of the active material-containing layer obtained by Raman spectroscopy, the occupied area S1 of the first conductive agent, the occupied area S2 of the second conductive agent, and the occupied area Sa of the active material satisfy the relationships of 0.1 < S1 / Sa < 1.0 and 0.8 < S2 / Sa < 10. In the constituent material mapping image, the distance between the centers of gravity R1 of the first conductive agent, the distance between the centers of gravity R2 of the second conductive agent, the distance between the centers of gravity Ra of the active material, and the distance between the centers of gravity R1-2 between the first conductive agent and the second conductive agent satisfy the relationships of 1.0 < R1 / Ra < 1.5, 0.5 < R2 / Ra < 1.0, and R1 > R2 > R1-2. The electrode can provide a battery and a battery pack with low resistance and excellent life performance.

[0212] Several embodiments of the present invention have been described, but these embodiments are presented as examples and are not intended to limit the scope of the invention. These new embodiments can be implemented in various other ways, and various omissions, substitutions, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope or gist of the invention, and are also included in the scope of the invention described in the claims and its equivalents.

[0213] Hereinafter, several embodiments of the present invention will be described incidentally.

[0214] [1] An electrode comprising an active material-containing layer, the active material-containing layer containing an active material, a first conductive agent, and a second conductive agent, Regarding the integral intensity I of the D band that appears at 1350 ± 10 cm for the first conductive agent in the Raman spectrum obtained for the active material-containing layer -1 at D and the integral intensity I of the G band that appears at 1590 ± 10 cm -1 at G the ratio I D / I G is within the range of 0.5 < I D / I G < 2, and regarding the second conductive agent, the ratio I D / I G is within the range of 0 < I D / I G < 0.5. In the constituent material mapping image obtained by Raman spectroscopy for the active material-containing layer, the ratio S1 / Sa of the occupied area S1 of the first conductive agent to the occupied area Sa of the active material is within the range of 0.1 < S1 / Sa < 1.0, and the ratio S2 / Sa of the occupied area S2 of the second conductive agent to the occupied area Sa of the active material is within the range of 0.8 < S2 / Sa < 10. In the constituent material mapping image, the ratio R1 / Ra of the center-of-gravity distance R1 of the first conductive agent to the center-of-gravity distance Ra of the active material is within the range of 1.0 < R1 / Ra < 1.5, the ratio R2 / Ra of the center-of-gravity distance R2 of the second conductive agent to the center-of-gravity distance Ra of the active material is within the range of 0.5 < R2 / Ra < 1.0, and the center-of-gravity distance R1 of the first conductive agent, the center-of-gravity distance R2 of the second conductive agent, and the center-of-gravity distance R1-2 between the first conductive agent and the second conductive agent satisfy the relationship R1 > R2 > R1-2.

[0215] [2] The electrode according to [1], wherein the active material is composed of Li a Ni(1-b-c-d) Co b Mn c M d O2 represents 1≤a≤1.2, 0≤b≤0.4, 0≤c≤0.4 and 0≤d≤0.1, M comprises a compound containing at least one selected from the group consisting of Fe, Cu, Ti, Mg, Al, W, Y, B, Mo, Nb, Zn, Sn, Zr, Ga and V, and the active material has an average primary particle size of 2 μm or more and 7 μm or less.

[0216] [3] According to the electrode described in [1] or [2], wherein the specific surface area of ​​the active material obtained by nitrogen adsorption-desorption method is 0.5 m². 2 / g or more and 1.0m 2 / g or less.

[0217] [4] The electrode according to any one of [1] to [3], wherein the average particle size of the first conductive agent is less than 100 nm, the average particle size of the second conductive agent is less than 10 μm, and the mass ratio of the first conductive agent and the second conductive agent to the active material is less than 0.18.

[0218] [5] The electrode according to any one of [1] to [4], wherein the density of the active material layer is 2.0 g / cm³. 3 Above and below 4.0 g / cm³ 3 .

[0219] [6] A battery comprising any one of [1] to [5] electrodes and an electrolyte.

[0220] [7] A battery pack comprising the battery described in [6].

[0221] Explanation of reference numerals in the attached figures 1 Electrode assembly, 2 Outer packaging components, 3 Positive electrode, 3a Positive current collector, 3b Positive active material layer, 4 Negative electrode, 4a Negative current collector, 4b Negative active material layer, 5 Separator, 6 Negative terminal, 7 Positive terminal, 11 Electrode assembly, 12 Container, 13 Rectangular cover, 14 Negative current collector tab, 16 Glass material, 17 Positive current collector tab, 18 Positive terminal, 20 Battery pack, 21 Single cell, 22 Adhesive tape, 23 Battery assembly, 24 Printed circuit board, 25 Thermistor, 26 Protection circuit, 27 Terminal for powering external devices, 28 Positive side lead, 29 Positive side connector, 30 Negative side lead, 31 Negative side connector, 32 Wiring, 33 Wiring, 34a Positive side wiring, 34b Negative side wiring, 35 Wiring, 36 Protective plate, 37 Storage container, 38 Lid, 51 Negative terminal, 61 Positive terminal, 300 Positive active material, 301 First conductive agent, 302 Second conductive agent.

Claims

1. An electrode having an active material-containing layer, the active material-containing layer containing an active material, a first conductive agent, and a second conductive agent. The Raman spectrum obtained by Raman spectroscopy for the active material layer, specifically the Raman spectrum for the first conductive agent, is located at 1350±10 cm⁻¹. -1 The integral intensity I of the D-band that appears at the location D With at 1590±10cm -1 The integral intensity I of the G-band that appears at the location G The ratio of I D / I G At 0.5 D / I G Within the range of <2, the ratio I for the second conductive agent D / I G In 0 D / I G Within the range of <0.5,​​ In a constituent material mapping image obtained by Raman spectroscopy for the active material-containing layer, the ratio S1 / Sa of the occupied area S1 of the first conductive agent to the occupied area Sa of the active material is in the range of 0.1 < S1 / Sa < 1.0, and the ratio S2 / Sa of the occupied area S2 of the second conductive agent to the occupied area Sa of the active material is in the range of 0.8 < S2 / Sa < 10. In the constituent material mapping image, the ratio R1 / Ra of the distance between the centers of gravity R1 of the first conductive agent to the distance between the centers of gravity Ra of the active material is in the range of 1.0 < R1 / Ra < 1.5, the ratio R2 / Ra of the distance between the centers of gravity R2 of the second conductive agent to the distance between the centers of gravity Ra of the active material is in the range of 0.5 < R2 / Ra < 1.0, and the distance between the centers of gravity R1 of the first conductive agent, the distance between the centers of gravity R2 of the second conductive agent, and the distance between the centers of gravity R1-2 between the first conductive agent and the second conductive agent satisfy the relationship R1 > R2 > R1-2.

2. The electrode according to claim 1, wherein, The active substance is composed of Li a Ni (1-b-c-d) Co b Mn c M d O2 represents 1≤a≤1.2, 0≤b≤0.4, 0≤c≤0.4 and 0≤d≤0.1, M comprises a compound containing at least one selected from the group consisting of Fe, Cu, Ti, Mg, Al, W, Y, B, Mo, Nb, Zn, Sn, Zr, Ga and V, and the active material has an average primary particle size of 2 μm or more and 7 μm or less.

3. The electrode according to claim 1 or 2, wherein, The specific surface area of ​​the active material obtained by nitrogen adsorption-desorption method is 0.5 m². 2 / g or more and 1.0m 2 / g or less.

4. The electrode according to claim 1 or 2, wherein, The average particle size of the first conductive agent is 100 nm or less, the average particle size of the second conductive agent is 10 μm or less, and the mass ratio of each of the first conductive agent and the second conductive agent to the active material is 0.18 or less.

5. The electrode according to claim 1 or 2, wherein, The density of the active material layer is 2.0 g / cm³. 3 Above and below 4.0 g / cm³ 3 .

6. A battery having the electrode according to claim 1 or 2 and an electrolyte.

7. A battery pack having the battery according to claim 6.

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